08 Industrial Minerals (Pages 743-806)

Industrial Minerals

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

BENEFICIATION OF UKRANIAN KAOLINS FOR CERAMIC INDUSTRY WITH FALCON GRAVITY SEPARATOR AND HYDROCYCLONE Utku Anıl Baştaş1, Mustafa Özer 1, Ozan Kökkılıç1 and Hayrünnisa Ateşok1,a 1. I.T.U. Mineral Processing Engineering, Istanbul, Turkey a. Corresponding author ([email protected])

ABSTRACT: In this study, kaolin sample which is belonging to Ukraine Vikninskaya area is prepared for ceramic industry. First of all, after communition, kaolin sample has scrubbed with Attrition Scrubber for separating over 0,5 mm sized quartz (SiO2) particles from the system as quartz concentrate. After scrubbing, enrichment tests have done with C124 diffuse-type 50 mm Mozley Hydrocyclone and Falcon Gravity Concentrator and the results were compared. In hydrocyclone tests, optimum mixing time and solid rates are determined and in Falcon tests the effect of the solid rates to the separation are optimised. Also, in parallel, with the optimal conditions, the optimum capacity is calculated for getting the best possible concentrate. The processing plants process flow chart has been created and solid water balance has calculated with the optimum conditions.

1. INTRODUCTION: Kaolinite clay with formula Si2Al2O5(OH)4, is the major mineral component of kaolin, which may usually contain quartz and mica and also, less frequently feldspar, illite, ilmenite, anatase, heamatite, bauxite, zircon, rutile, kyanite, silimanite, graphite, attapulgite, montmorillonite, and halloysite [Varga G.,2007]. Kaolin finds extensive applications in a variety of industries such as paper, paint rubber and especially in ceramics [Murray etal, 1993]. The quality of kaolins used in the ceramic industry is very important so chemical and mineralogical specifications of the kaolins should meet the following requirements; minimum 35% Al2O3 maximum 0,4 % Fe2O3 and between 4464% SiO2 for marketing to ceramic industry [Guven, 1998]. The preferred beneficiation methods of

kaolin minerals depend on the amount and nature of the mineral impurities associated to it. Although these methods are quite useful in removing impurities, they are, at the same time, costly, complicated and environmentally hazardous [Rawlings D.E.,2004]. The size classification produces different grades of kaolin with varying particle size distribution. Increase in the finer fraction can result in improved brightness due to the increase in surface area and hence more light scattering sites. During sizing, coarser (quartz) and / or denser (ilmenite, rutile etc.) impurity minerals get separated. Even small quantities of the coloring impurities in the finer fractions contaminate the clay and reduce its brightness. Hence, these impurities can be removed only by special techniques such as froth flotation, magnetic separation, oxidative/ reductive bleaching etc. Depending upon the nature and quantity of impurities (Murray et al, 1993; Jepson, 1988). 743

2. EXPERIMENTAL The physical,chemical and mineralogical properties were determined by standart methods and the chemical composition of the row ore has shown in the table. (Table 1) Table 1: The chemical composition of row ore Weight Component (%) LOI 9.06 SiO2 63.83 Al2O3 25.33 Fe2O3 0.51 TiO2 0.73 CaO 0.04 Na2O 0.16 K2O 0.26

50 slurry density were fed into the scrubber and, 1200 and 900 rpm velocities and 5, 10 and 15 min. times were adjusted as the working conditions of scrubber. And at the end of the tests optimum scrubbing time and speed and optimum particle size distributions were optimised. 2.1.1. Scrubber Tests with -20 mm Sample The sample is crushed under 20 mm with Jaw crusher and screening tests were applied to the sample and particle size distribution of the sample was determined.(Figure 2) After that, attrition scrubbing tests were done for optimising scrubbing time, scrubbing speed and slurry density of the pulp. The results were given in (Table 2).

For determining the particle size distribution of the sample screen test were done and particle size distribution curve has and d50 and d80 parameters were found as 10 and 23 mm.(Figure 1)

Figure 2: Particle size distribution curve of -20 mm sample

Figure 1:Particle size distribution of the sample 2.1. Attrition Scrubbing Tests Attrition scrubbing tests were done in Wemco attrition scrubber. The samples in -20 mm and 10 mm particle sizes and% 744

2.1.2. Tests with -10 mm sample The sample is crushed under 10 mm with Jaw crusher and screening tests were applied to the sample and particle size distribution of the sample was determined(Figure 3).After that, attrition scrubbing tests were done for optimising scrubbing time, scrubbing speed and slurry density of the pulp.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

1200 rpm was found to be optimum after the tests and the scrubbing tests were done in these constant conditions: 1200 rpm and %50 slurry density. The results of the scrubbing tests were given in (Table 3) and (Table 4).

Figure 3: Particle size distribution curve of -20 mm sample

Table 2: -20 mm sized sample attrition scrubbing test results for determining optimum mixing time. Time (min)

5

10

15

Particle Size (microns) +500 -500+106 -106+38 -38 Total +500 -500+106 -106+38 -38 Total +500 -500+106 -106+38 -38 Total

Amount (%)

Content, (%) SiO2 Al2O3

Fe2O3

Distribution, (%) SiO2 Al2O3

Fe2O3

19,2 13,6 6,8 60,4 100 17 12,6 10 60,4 100 18,7 11,4 9,4 60,5 100

97,3 91,3 62,8 46,9 63,7 98,75 95,20 66,21 47,40 64,03 99,45 96,3 55,3 45,2 62,12

0,13 0,28 0,68 0,6 0,47 0,04 0,19 0,63 0,61 0,46 0,03 0,17 0,62 0,63 0,46

29,3 19,5 6,7 44,5 100,0 26,22 18,73 10,34 44,71 100,00 29,94 17,67 8,37 44,02 100,00

5,3 8,1 9,8 76,8 100,0 1,47 5,18 13,63 79,72 100,00 1,21 4,17 12,55 82,07 100,00

0,33 4,67 24,51 37,17 24,87 0,07 2,62 22,25 36,41 24,56 0,05 1,88 21,52 36,7 24,45

0,3 2,6 6,7 90,5 100,0 0,05 1,34 9,06 89,55 100,00 0,04 0,88 8,27 90,81 100,00

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Table 3: -10 mm sized sample attrition scrubbing test results for determining optimum mixing time. Time (min)

5

10

15

Particle Size (microns) +500 -500+106 -106+38 -38 Total +500 -500+106 -106+38 -38 Total +500 -500+106 -106+38 -38 Total

Amount (%)

Content, (%) SiO2 Al2O3

Fe2O3

Distribution, (%) SiO2 Al2O3

Fe2O3

20,8 12,5 8,4 56,3 100 18,8 12,0 9,0 60,2 100,00 18,6 12,3 9,2 59,9 100,00

98,1 92,4 65,32 47,04 63,9252 99,05 95,00 64,45 47,98 64,70 99,50 96,10 55,70 44,90 62,35

0,13 0,28 0,68 0,6 0,45696 0,07 0,24 0,77 0,6 0,47 0,02 0,18 0,64 0,62 0,46

31,9 18,1 8,6 41,4 100,0 28,8 17,6 9,0 44,6 100,00 29,68 18,96 8,22 43,14 100,00

5,9 7,7 12,5 73,9 100,0 2,8 6,1 14,7 76,5 100,00 0,82 4,85 12,91 81,42 100,00

0,33 4,67 24,51 37,17 23,63794 0,26 2,65 21,65 37,52 24,90 0,04 1,86 21,54 36,72 24,21

0,3 2,5 8,7 88,5 100,0 0,2 1,3 7,8 90,7 100,00 0,03 0,94 8,18 90,84 100,00

Table 4: Attrition scrubbing test results for determining optimum mixing velocity. Velocity rpm 1200

900

Particle Size (microns) +500 -500+106 -106+38 -38 Total +500 -500+106 -106+38 -38 Total

Amount (%)

Content, (%) SiO2 Al2O3

Fe2O3

Distribution, (%) SiO2 Al2O3

Fe2O3

19,20 13,60 6,80 60,40 100,0 26,10 11,20 4,40 58,30 100,0

97,30 91,30 62,80 46,90 63,69 97,65 84,20 63,80 46,90 65,06

0,13 0,28 0,68 0,60 0,47 0,07 0,34 0,65 0,54 0,40

29,30 19,50 6,70 44,50 100,0 39,20 14,50 4,30 42,0 100,0

5,30 8,10 9,80 76,80 100,0 4,50 9,50 7,20 78,80 100,0

2.2. Classification Tests: After -20 mm sample was screened from 0,5 mm sized screen classification tests with hydrocyclone and Falcon Gravity Concentrator were done for determining optimum working conditions. 2.2.1. Hydrocyclone Tests After scrubbing and screening from 0,5 mm screen over 0,5 mm size particles were taken as quartz concentrate. Under

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0,33 4,67 24,51 37,17 24,81 1,19 10,13 24,22 37,52 24,38

0,30 2,60 6,70 90,50 100,0 1,30 4,70 4,30 89,70 100,0

0,5 mm sized sample was fed to the hydrocyclone. The parameters slurry density,feed pressure,apex and vortex diameters were optimised for determining optimum working conditions of hydrocyclone.The flowsheet of hydrocyclone tests were given in the (Figure4). And the results of hydrocyclone tests were given in (Table 5).

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

2.2.2. Beneficiation tests with Falcon Gravity Concentrator: After scrubbing and screening from 0,5 mm screen over 0,5 mm size particles were taken as quartz concentrate. Under 0,5 mm sized sample was fed to the Falcon Gravity Concentrator. The parameters slurry densityand G force were optimised for determining optimum working conditions of Falcon Gravity Concentrator.

Figure 4: Flowsheet of hydrocyclone tests

The flowsheet of Falcon Gravity Concentrator tests were given in the (Figure 5).And the results of Falcon Gravity Concentrator tests were given in (Table6). After these tests the final flow sheet was determined as in the (Figure 6).

Table5: Hydrocyclone tests results Products Amount Content, (%) (%) SiO2 Al2O3 Kaolin 65,20 46,90 37,35

Fe2O3 0,66

SiO2 48,89

Al2O3 93,20

Fe2O3 87,82

Middling

5,30

57,50

28,84

0,81

4,87

5,85

8,76

Quartz

29,50

98,08

0,85

0,09

46,26

0,96

5,42

Total

100,0

62,55

26,13

0,49

100,0

100,0

100,0

Distribution, (%)

Figure 5: Flowsheet of Falcon Gravity Concentrator tests. 747

Table 6: Falcon Gravity Concentrator test results Saolid Ratio, % 10

20

30

Products Kaolin Middling Quartz Total Kaolin Middling Quartz Total Kaolin Middling Quartz Total

Amount (%) 20,80 12,50 8,40 100,00 20,80 12,50 8,40 100,00 20,80 12,50 8,40 100,00

Content, (%) SiO2 Al2O3 98,10 0,33 92,40 4,67 65,32 24,51 63,90 23,60 98,10 0,33 92,40 4,67 65,32 24,51 64,70 24,90 98,10 0,33 92,40 4,67 65,32 24,51 62,35 24,21

3. RESULTS AND DISCUSSION 1) From the chemical and mineralogical analysis of the row sample it can be seen that the quartz content of the sample is higher for the needs of the ceramic industry. 2) After screen tests row ore’s d80= 23 mm and d50= 10 mm has determined. 3) As the results of the scrubbing tests the optimum conditions for enrichment were found like that: %50 slurry density, 1200 r.p.m. attrition speed, -20mm particle size and 5 minutes scrubbing time. 4) After attrition scrubbing +0,5 mm can be separated from the system as quartz concentrate. 5) The optimum conditions for hydrocyclone tests slurry density10%; 3,2 mm and 2,2 mm apex radius are determined. 6) From Falcon gravity separator tests it has been found that the ideal slurry density10 %. 7) It can be clearly said that the content of the quartz concentrate that is obtained from Falcon gravity concentrator is not as well as the hydrocyclone tests.The efficiency of the Falcon is not enough to get a good quality of quartz concentrate

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Fe2O3 0,13 0,28 0,68 0,45 0,13 0,28 0,68 0,47 0,13 0,28 0,68 0,46

Distribution, (%) SiO2 Al2O3 31,90 0,30 18,10 2,50 8,60 8,70 100,00 100,00 31,90 0,30 18,10 2,50 8,60 8,70 100,00 100,00 31,90 0,30 18,10 2,50 8,60 8,70 100,00 100,00

Fe2O3 5,90 7,70 12,50 100,00 5,90 7,70 12,50 100,00 5,90 7,70 12,50 100,00

but good quality of kaolin concentrate can be obtained. 4. CONCLUSION: As the results of the attrition scrubbing tests, optimum scrubbing time 5 min., %50 solid ratio and 1200 rpm scrubbing velocity were found. From hydrocyclone tests %46,90 SiO2, %37,50 Al2O3 ve % 0,66 Fe2O3 content kaolin concentrate; %98,08 SiO2, %0,85 Al2O3 ve % 0,09 Fe2O3 content quartz concentrate were obtained. From the Falcon gravity concentrator tests the content of kaolin concentrate were found %46,90 SiO2, %37,50 Al2O3and % 0,66 Fe2O3 and content of quartz concentrate %98,08 SiO2, %0,85 Al2O3and % 0,09 Fe2O3 were obtained. Also according to the results of the process flow chart 1,78 m3 water must be feed per ton ore to the process plant.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Figure 6: Flowsheet of the process plant. Acknowledgements: Authors present their special gratefulness to Eczacıbaşı Esan to reproduce chemical analysis of the samples. REFERENCES Guven, C., 1998, Investigation of beneficiation possibility of Istanbul-Sile region clays for ceramics industry, Graduation Thesis, I.U. Mining Eng. Dept. Jepson, W.B., 1998,Structural iron in kaolinites in associated ancillary Minerals, Iron in soils and clay minerals. NATO Advanced Science Institutes Series, pp. 467-536.

Murray, K.J., and Keller, W.D.,1993. Kaolins, Kaolins and Kaolins in Kaolin Genesis and Utilisation. Special publications by the Clay Mineral Society, Colorado, US pp 1-24. Rawlings, D.E., 2004. Microbially assisted dissolution of minerals and its use in the mining industry. Varga, G., 2007. The structure of kaolinite and metakaolinite. Epitoanyag, 59, 4-8.

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

INVESTIGATION OF USAGE OF ZONGULDAK ALACAAĞZI SANDSTONE IN CASTING INDUSTRY Gündüz Ateşok1,a, Feridun Boylu1, Mustafa Özer1, Fırat Burat1 and Hüseyin Baştürkcü1 Istanbul Technical University Mining Faculty, Mineral Processing Engineering Department, Maslak-İstanbul, Turkey a. Corresponding author ([email protected])

ABSTRACT: In 2013 demand of silica sand, which has a usage area in glass, casting, construction, metallurgy, electronic, and ceramic industries with silicon-ferrosilicon production, is over 4 million tons in Turkey. This demand cannot be met with running out of reserves of coastal sand and it resulted in production gap. Therefore, quartzite reserves of 6.3 billion tons, which exists in Zonguldak, Antalya, Adana, Kastamonu, Yozgat, and Denizli provinces of Turkey, have increased in importance. In this research, technological tests were performed on Zonguldak Alacaağzı sandstone, which have 700 million tons of reserves. In order to investigate the possibility of usage of this sandstone in casting industry, at first, physical and chemical properties of the sample was determined. Particle size was reduced with jaw and cone crushers. Then, scrubbing was performed on Alacaağzı sandstone sample, which has 96.8% SiO2 and 0.6% Fe2O3. After classification into size fractions, it was seen that a clay product could be obtained with 4.40% Fe2O3 content, while the sandstone contained 0.36% Fe2O3. On the other hand, the scrubbed sandstone was tested in high intensity wet magnetic separation and flotation. According to the results, flotation method gave more positive results than magnetic separation did. 96% amount of Alacaazğı sandstone was obtained with 0.24 Fe2O3. At the end of the tests, process flow sheets for both of the samples were generated. 1. INTRODUCTION Quartz naturally occurs as colorless or light-white colored and fine-grained structure. It has a hardness of 7 on the Mohs scale with 2.65 specific gravity and 17850C melting temperature [İpekoğlu, 1999]. While pure quartz crystals can be used in optic and electronic industry, quartz has areas of usage in chemistry, electric, glass, detergent, paint, ceramic, abrasive, and metallurgy industries [SPO, 2001]. On the other hand, quartz ores contain impurities, especially iron. Unless irons minerals are removed, transmission of optic fibers are obstructed, discoloration in ceramic products occurs and melting

point of refractory materials is decreased [Taxiarchou et al.1997]. In order to remove iron minerals, various physical, chemical and physico-chemical methods can be applied. As simple processes of crushing, grinding and sieving can respond, sometimes magnetic separation and/or flotation processed can be necessary [Akçıl et al., 2007]. However when the iron minerals are not able to be liberated, then, acid leaching method becomes an alternative method to obtain high-purity quartz [Loritsch ve James, 1991].

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In this study, possibility of usage of a sandstone sample in casting industry was investigated. 2. MATERIALS AND METHOD The sandstone sample was taken from Alacaağzı region of Zonguldak-Turkey. In order to determine its characterization, mineralogical analyses were performed. Polished section of the sample was examined and (Figure 1) demonstrates the iron oxide formation in the matrix. Alacaağzı sample had a magmatic origin and iron oxide mineral (probably hematite) existed in its matrix. Also, some amount of clay was observed. On the other hand, X-ray Diffraction analyses were conducted on magnetic and

non-magnetic products of the samples, in order to determine iron minerals. As is known, the mineral contents less than 2% cannot be determined by XRD. (Figure 2 and 3) demonstrate the XRD patterns of the samples; however the iron minerals could not be determined. In the study, the sample was crushed using jaw and cone crushers. d90 size of the sample was found as 0.6 mm. Following crushing, for the purpose of liberating clay material, the sample was scrubbed and classified into size fractions. Later, high intensity wet magnetic separation with Jones separator and oxide flotation were performed.

Figure 1: Iron oxide minerals formation as a result of diagenesis in the matrix

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Figure 2: XRD pattern of the non magnetic product

Figure 3: XRD pattern of the magnetic product

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3. RESULTS 3.1 Scrubbing Tests These tests aimed abrasion of the sample by scrubbing rather than grinding. Thus, formation of fine sizes could be prevented. Under the conditions of 60% solid ratio by weight and 700 rpm rotational speed, different scrubbing durations were tested. After scrubbing, the sample was decantated in three stages and clay was separated. Scrubbing tests’ results are given in (Table 1). Scrubbing+decantation tests showed that 4.9-5.1% of clay material could be separated, which provided a mechanical abrasion. Table 1: Scrubbing+decantation Scrubbing Particle Size Fraction, mm 5 min 10 min 15 min 100.0 100.0 100.0 +1.41 98.5 98.4 98.5 -1.41+1.00 96.5 96.6 96.8 -1.00+0.710 93.4 93.6 94.0 -0.710+0.500 84.3 86.3 87.4 -0.500+0.355 62.7 68.3 66.4 -0.355+0.212 20.9 27.8 27.6 -0.212+0.180 10.1 12.5 13.1 -0.180+0.125 6.7 7.7 8.0 -0.125+0.090 3.7 4.7 4.7 -0.090+0.063 2.0 2.8 2.4 -0.063 Weight accordng 95.1 95.1 94.9 to feed, % -0.125+0.106 -0.106+0.090 -0.090+0.074 -0.074+0.063 -0.063+0.045 -0.045 Weight accordng to feed, %

100.0 99.8 99.7 99.7 99.6 98.1

100.0 100.0 100.0 100.0 99.7 99.1

100.0 100.0 100.0 100.0 99.9 99.7

4.9

4.9

5.1

Chemical analyses of the products are shown in (Table 2a and 2b). Loss on ignitions was nearly 0.1%. The SiO2 754

content of the raw ore sample, which was 96.8%, increased above 99%. On the other hand, Fe2O3 content of the raw sample known as 0.72% decreased to 0.39%. Table 2a: Chemical analyses of Scrubbing+decantation tests Scrubbing SiO2, Al2O3 Fe2O3 TiO2 Duration, % % % % min 5 99.00 0.38 0.42 0.035 10 99.09 0.26 0.41 0.036 20 99.11 0.25 0.39 0.033 When the results were evaluated, in order to decrease the iron content further, flotation was decided to be performed following 10 min scrubbing and decantation. Table 2b: Chemical analyses of Scrubbing+decantation tests Scrubbing CaO MgO Na2O K2O Duration, % % % % min 5 0.01 0.00 0.00 0.05 10 0.01 0.00 0.00 0.04 20 0.01 0.00 0.00 0.04

3.2 Flotation Tests In the flotation tests, collectors of R801 and R825 were used with the amounts of varying between 100-400 kg/t. Since the collectors have frother property, there was no need to use any frother. The collectors used in a ratio of R801/R825 : 2/1. pH value was kept constant between 2.5-3.0. Collector amount, multiple stage collector addition and solid ratios were tried in the flotation tests. The results were given in (Table 3). 400 g/t collector addition in multiple stages to the scrubbed pulp of which can be adjusted above 30% solid ratios was

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

determined as the optimum flotation condition. 0.72% of Fe2O3 content in the raw ore sample was decreased to 0.4% with scrubbing and decantation. After flotation tests, this value was decreased to 0.24% Fe2O3. Besides, 99.46% SiO2 content was able to be obtained.

3.3 Wet High Intensity Magnetic Separation Tests Scrubbed and decantated pulp, which contained 0.4% Fe2O3, was fed to Jones magnetic separator at 20% solid ratios with a constant feed rate. During the test, strength of current was adjusted to different values of 1, 3 and 6.8 A.

Table 3: Scrubbing+decantation+flotation test results Solid Ratio % 20 20 20 20 28 40

Amount, g/t 150 200 250 360 250 250

28

250

20 20 20 20 28 36

150 200 250 360 200 200

28

400

Collector Add. 150 200 250 360 250 250 125+ 62.5+ 62.5 150 200 250 360 200 200 67.5 + 67.5 + 67.5 + 67.5 +130

Weight

SiO2

Al2O3

Fe2O3

% 99.2 98.8 96.6 94.9 96.6 96.6

% 99.33 99.31 99.36 99.43 99.46 99.40

% 0.23 0.23 0.24 0.23 0.19 0.22

% 0.27 0.29 0.26 0.23 0.26 0.25

% % 0.028 0.01 0.027 0.01 0.022 0.01 0.022 0.022 0.025 -

% 0.01 0.01 0.01 0.01 -

% -

% 0.04 0.04 0.04 0.04 0.03 0.04

97.6

99.44

0.18

0.27

0.026

-

0.01

-

0.03

98.8 96.2 93.7 84.5 96.3 96.6

99.20 99.24 99.31 99.28 99.21 99.29

0.22 0.22 0.23 0.23 0.24 0.23

0.32 0.29 0.25 0.29 0.32 0.29

0.03 0.025 0.024 0.023 0.034 0.023

-

0.01 0.01 0.01 0.01 0.01

0.01 -

0.04 0.04 0.04 0.04 0.04 0.04

95.8

99.40

0.19

0.24

0.025

-

-

-

0.03

While the results of the magnetic separation can be seen in (Table 4), the distributed metal balances are given in (Table 5). According to the results, Jones magnetic separator provided a decrease in Fe2O3 content, which was found as 0.3%. Under these conditions, 99.45% SiO2 was able to be obtained.

TiO2 CaO MgO Na2O K2O

When the weights and contents of the products were evaluated, it can be concluded that there was not suitable magnetic type iron minerals, which could be removed with wet high intensity magnetic separator.

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Table 4: Jones Magnetic Separation Results Weight, Fe2O3, % Products % Content Distr. Non 68.2 0.30 59.4 Magnetic Middling 8.9 0.31 8.0 Magnetic 13.0 0.34 13.0 Product-3 Magnetic 6.6 0.51 9.7 Product-2 Magnetic 3.4 0.99 9.9 Product-1 Feed 100 0.35 100 Table 5: Jones Magnetic Separation Results (Distributed) Weight, Fe2O3 Products % Content Distr. Non 90.0 0.30 80.4 magnetic Middling 6.6 0.51 9.7 Magnetic 3.4 0.99 9.9 Feed 100 0.35 100 4. CONCLUSION Primary and secondary crushing units were decided as jaw and cone crushers respectively. Since sandstone ores excavated from open pit mines can have some extent of moisture, hammer crushers are not be suitable for this process. Using flotation method, 0.24% Fe2O3 was able to be obtained with 96% efficiency from the sandstone sample, which contained 0.7% Fe2O3. With wet high intensity magnetic separation using Jones separator, 0.30% Fe2O3 was able to be obtained with 90% efficiency from the sandstone sample, which contained 0.7% Fe2O3. Either flotation or magnetic separation processes provided acceptable Fe2O3 contents. However when these processes 756

were compared, in terms of the silica sand weight and lower Fe2O3 content obtained, flotation method was thought to be better. REFERENCES Akçıl, A., Tuncuk, A, Deveci, H., 2007. An Overview of Chemical Methods Used in the Purification of Quartz. Madencilik, Vol.46, No.4, pp 3-10. İpekoğlu, B., 1999. Quartz,Quartzite, Quartz sand. Association of İstanbul Mine Exportersi, Inventory of Industrial Minerals of Turkey, pp. 102-106. Loritsch, K.B. and James, R.D., 1991. Purified Quartz and Process for Purifying Quartz. United States Patent, Patent Number: 4,983,370. Specialization Commission of Mining Reports of Development Plan-8th, 2001. Subcommission of Industrial Raw Materials, Sand Industry Raw Materials- III (Quartz sand, Quartizte, Quartz). State Planning Organization. Taxiarchou, M., Panias, D., Douni, I., Paspaliaris, I. ve Kontopoulos, A., 1997. Removal of Iron from Silica Sand by Leaching with Oxalic Acid. Hydrometallurgy, 46, 215-227.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

LEACHING OF A COMMERCIAL VERMICULITE IN H2SO4 SOLUTIONS İ.Ehsani1, E.Turianicová2, M.Baláž2 and A.Obut1,a 1. Hacettepe University, Mining Engineering Department, Ankara, Turkey 2. Institute of Geotechnics, Slovak Academy of Sciences, Košice, Slovakia a. Corresponding author ([email protected])

ABSTRACT: In this study, the leaching behaviour of a commercial vermiculite sample, in natural and heated forms, in 1 M aqueous sulphuric acid solutions at 20°C and 90°C was investigated using chemical and X-ray diffraction analyses, Fourier transform infrared spectroscopy and nitrogen adsorption measurements. Although small changes occurred in the chemical compositions and surface area values following leaching at 20°C, great reductions in the amounts of structural components, i.e. Al2O3, Fe2O3, MgO, and dramatic increases in the surface area values were observed after leaching of both samples at 90°C, indicating quantitative, but not total, dissolution of the samples. Similarly, acid leaching of natural and heated vermiculite samples at 20°C resulted only small changes in the X-ray diffraction patterns and infrared spectra, but with the increase of leaching temperature to 90°C, significant changes, i.e. the dissolution of vermiculite structures and the formation of hydrous amorphous silica phase, were observed. 1. INTRODUCTION Swelling clay minerals, such as smectites and vermiculites, exhibit differences in their layer charges, adsorptive properties, cation exchange capacities, particle sizes etc. Because of these differences, they can be used in different areas such as foundry, construction, agriculture or chemical industries either directly or after the application of different modification processes. Leaching by inorganic acids, i.e. sulphuric or hydrochloric acid, is one of the useful modification processes for these clay minerals and due to the enhanced surface and catalytic behaviour following acid leaching, they can be used as bleaching earths, as catalysts or catalyst supports, in the production of carbonless copying paper or in the preparation of pillared clays and organoclays [Komadel et al., 1990; Suquet et al., 1991; Mokaya and Jones, 1995; Breen et al., 1997; Ravichandran and Sivasankar, 1997; Londo et al., 2001; Gates et al., 2002; Jozefaciuk and Bowanko, 2002; Önal et al., 2002; Kooli, 2009; Steudel et al., 2009a].

In contrast to numerous studies related with acid leaching of smectites, the number of studies investigating the leaching behaviour of commercial vermiculites in inorganic or organic acids is low. Therefore, in this study, leaching behaviour of a commercial vermiculite, in natural and heated forms, in sulphuric acid solutions was investigated and comparative data were collected for future studies. To identify the changes caused by acid leaching, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and chemical analyses together with nitrogen adsorption measurements were performed on the natural, heated and leached vermiculite samples. 2. MATERIALS AND METHODS The natural sample used in this work is commercial micron grade Palabora (South Africa) vermiculite. According to the data supplied by the producer, 80% of the natural sample is in the size range of -0.710+0.250 mm and the fraction of -0.180 mm is maximum 10%. The natural sample contains 85-95% ‘vermiculite’,

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and phlogopite, apatite, diopside with trace amounts of dolomite and quartz are the impurities. Chemical composition of the natural sample was given in Table 1. Table 1: Chemical composition (%) of the natural vermiculite sample.

3. RESULTS AND DISCUSSION 3.1. Chemical Analyses, Surface Area Measurements and Porous Properties Some of the main chemical components and surface area values of the natural and heated samples together with their corresponding leached counterparts were presented in Table 2 and Table 3, respectively.

SiO2

Al2O3

Fe2O3

MgO

41.02

8.90

8.36

19.91

CaO

Na2O

K2O

TiO2

6.27

0.07

4.63

0.97

Table 2: Main chemical components (%) of the natural, heated and leached vermiculites.

P2O5

MnO

Cr2O3

L.O.I

Sample

SiO2

Al2O3

Fe2O3

MgO

K 2O

2.41

0.06

0.05

6.97

NV

41.02

8.90

8.36

19.91

4.63

NV-20

44.22

9.32

8.77

20.21

4.65

NV-90

64.81

4.32

5.08

10.95

2.58

HV

44.39

10.09

9.31

21.69

5.20

HV-20

45.59

9.56

9.08

21.18

4.89

HV-90

62.10

4.94

5.54

13.18

3.03

In the leaching studies, natural and heated (at 900°C, according to Turianicová et al. [2014]) vermiculite samples were used. Because surface area is one of the most important parameters in leaching studies, in this study, heated vermiculite was compared with the natural vermiculite due to its higher surface area. Sulphuric acid was selected as the leaching reagent due to its reported efficiency on dissolution [Steudel et al., 2009a]. In a representative experiment, 50 grams of natural (NV) or heated (HV) vermiculite was leached in 500 mL, 1 M aqueous H2SO4 solution either at 20°C or 90°C for 60 minutes under constant rate of stirring. Following leaching, the solid residues were separated by filtration, washed and finally dried at 105°C. The chemical compositions, XRD patterns (Rigaku with CuKα radiation, following equilibration under room atmosphere), FT-IR spectra (Bruker, by KBr pellet method), and B.E.T. surface area values (Quantachrome Instruments, by nitrogen adsorption following degas for two hours at 105°C) of the natural, heated and leached vermiculites were determined in order to observe the changes caused by acid leaching. The pore size distribution of a selected leach residue was also determined.

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Table 3: Surface area values (m2/g) of the natural, heated and leached vermiculites. NV

NV-20

NV-90

3.322

5.632

251.844

HV

HV-20

HV-90

13.963

15.429

97.950

(Table 2) showed that when the natural and heated samples were leached at 20°C (NV-20 and HV-20, respectively), there were only small changes in the values of main chemical components, indicating insignificant dissolution from the clay samples. Due to the low amounts of dissolution of the structural components, i.e. Mg, Fe and Al, the increases in the surface area values of the leached vermiculites were also low (Table 3). On the other hand, when leaching process was performed at 90°C (samples NV-90 and HV-90), the amounts of magnesium, iron and aluminum in the leach residues became approximately half of their initial

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

values, which indicated quantitative, but not total, dissolution of the clay structures in both samples. Although surface area of the heated sample is higher than the natural one, the amount of residual structural components in its leach residues were higher in comparison to the residues of the natural sample probably due to the presence of dehydrated and collapsed clay structures in the heated sample [Okada et al., 2006; Steudel et al., 2009a,b]. In the studies where micron grade South African vermiculite was used; Okada et al. [2006] were increased the surface area from 1 to 265 m2/g by leaching the natural sample in 1 M H2SO4 solution at 70°C for 60 minutes; Temuujin et al. [2003] were increased the surface area from 1.4 to 407 m2/g by leaching the natural sample in 1 M HCl solution at 80°C for 60 minutes and to 553 m2/g by leaching under same conditions for 120 minutes; and Temuujin et al. [2008] were increased the surface area again from 1.4 to 547 m2/g by leaching the heated (at 600°C) sample in 2 M HCl solution at 80°C for 120 minutes. In this study, the surface area of the natural (3.322 m2/g) and heated (at 900°C, 13.963 m2/g) micron grade South African vermiculite samples were increased to 5.632 m2/g and 15.429 m2/g by low temperature (20°C), and to 251.844 m2/g and 97.950 m2/g for high temperature (90°C) leaching in 1 M H2SO4 solution for 60 minutes, respectively (Table 3). The adsorption-desorption isotherms and pore size distribution of the leach residue HV-90 were given in Figures 1 and 2, respectively. As can be seen from Figure 1, there is a hysteresis loop which suggests the presence of mesopores in the sample. There are no micropores present in the sample. Due to the shape of the isotherm in the region of higher relative pressures, it can be said that there could

be some small amount of macropores present in the sample. The total pore volume of HV-90 was 0.1326 cm3·g-1. The presence of mesopores was confirmed by the pore size distribution study. As can be seen from Figure 2, the structure contains almost no other type of pores than mesopores with radii between 1.5 and 10 nm (the diameters between 3 and 20 nm). The measurement from adsorption isotherm confirmed the presence of so-called tensile strength effect, because the peak with maximum around 2 nm present in case of pore size distribution calculated from the desorption isotherm does not present.

Figure 1: Nitrogen adsorption/desorption isotherm for HV-90.

Figure 2: Pore size distribution for HV90.

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3.2. XRD Analyses XRD patterns of the natural and heated samples together with their leached counterparts were given in Figures 3 and 4, respectively.

NV-90

NV-20

NV

2θ(°)

Figure 3: XRD patterns of the natural vermiculite and its leach residues.

HV-90

HV-20

HV

2θ(°)

Figure 4: XRD patterns of the heated vermiculite and its leach residues. XRD pattern of the natural sample (NV in Figure 3) shows diffraction peaks at 6.22°, 7.18° and 7.48°, indicating the presence of both two- and one-water760

layer hydration states and interstratified phases [Ruiz-Conde et al., 1996; Marcos et al., 2009; Muiambo et al., 2010]. High content of potassium (see Table 1) in the natural sample in comparison to true vermiculites also indicated the presence of interstratification [Muiambo and Focke, 2012]. Very small intensity peak at 8.80° was attributed to mica impurity [Muiambo et al., 2010]. The main and single basal peak at 8.86° in XRD pattern of the heated sample indicated the existence of dehydrated and collapsed clay structures. Leaching of the natural and heated samples at 20°C in 1 M H2SO4 solution caused small changes and only insignificant differences in the peak intensities of clay structures were observed, in accord with the chemical analyses results. On the other hand, leaching of the natural sample at 90°C caused major dissolution of the vermiculite structures as observed by the disappearance of peak at 6.22° (compare NV or NV-20 with NV-90 in Figure 3). The intensities of the basal peaks were also greatly reduced and background of the pattern was increased, both suggesting amorphization by dissolution of the clay structures. Heating of the natural sample at 900°C produced dehydrated and collapsed clay structures, which resemble micas, as observed by the main peak at 8.86° (see pattern HV in Figure 4). Although the changes caused by acid leaching in the natural sample were easily observable by the analyses of XRD peaks in the related patterns, almost no changes were observed in case of the heated samples. Only very small increase was observed in the background intensity in XRD pattern of the leach residue obtained by leaching of heated vermiculite sample in 1 M H2SO4 for 60 minutes (see HV-90 in Figure 4).

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

3.2. FT-IR Analyses FT-IR spectra of the natural and heated samples together with their corresponding leached counterparts were given in Figures 5 and 6, respectively. NV

NV-20

NV-90

Wavenumber (cm-1)

Figure 5: FT-IR spectra of natural vermiculite and its leach residues. HV

HV-20

HV-90

Wavenumber (cm-1)

Figure 6: FT-IR spectra of heated vermiculite and its leach residues.

FT-IR spectrum of the natural sample shows a broad and very strong intensity absorption band at 999 cm-1 belonging to Si-O-Si and Si-O-Al vibrations. The strong intensity band (with a shoulder) centered at 457 cm-1 may be associated with Si-O-Si and Si-O-Mg. The medium intensity absorption at 1632 cm-1 is attributed to the OH bend deformation of water. The medium band observed at 687 cm-1 may be related with R-O-Si, where R=Mg, Al or Fe. The weak bands at 602, 729 and 818 cm-1 may be assigned to mixed Al-O/Si-O and hydroxyl groups [Suquet et al., 1991; Ravichandran and Sivasankar, 1997; da Fonseca et al., 2006; Steudel et al., 2009a; Chmielarz et al., 2010; Muiambo et al., 2010; Hongo et al., 2012; Muiambo and Focke, 2012]. In accord with the results of XRD analyses, low temperature acid leaching caused only small changes in the FT-IR spectra of both the natural and heated vermiculites. But, high temperature acid leaching changed the corresponding IR spectra dramatically, because of the sensitivity of FT-IR spectroscopy for detecting the possible changes (or destruction) in the crystalline structure of clay minerals following any modification process [Suquet et al., 1991]. By high temperature leaching of the natural sample, bands at 602, 687, 729 and 818 cm-1 disappeared and new absorption peaks of Si-O at 1088 (with shoulder ~1200 cm-1), 800 and 461 cm-1, and SiOH at 968 cm-1 belonging to hydrous amorphous silica phase were revealed [Pálková et al., 2003; Wypych et al., 2005; Yu et al., 2012]. This indicates the formation of hydrous amorphous silica phase by acid dissolution of the structural components from the natural and heated vermiculites. Similar changes were also observed by high temperature acid leaching of heated vermiculite sample but the effect of acid leaching is somewhat lower when compared to the natural

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sample. The absorption band at 1007 cm-1 belonging to the heated sample also indicated the higher resistance of collapsed mica like layers against acid attack, which is consistent with the results obtained by chemical and XRD analyses. 4. CONCLUSIONS In this work, the leaching behaviours of a natural and a heated vermiculite sample in 1 M H2SO4 solution at 20°C and 90°C for 60 minutes were investigated using different analyses methods. Although no or small changes occurred in chemical compositions, in XRD/FT-IR patterns and surface area values of the leach residues obtained by low temperature (20°C) acid leaching, significant reductions in the amounts of structural components, important changes in XRD and especially in FT-IR patterns and great increases in surface area values of the leach residues obtained by high temperture (90°C) acid leaching of the natural and heated vermiculites were observed. All results of the analyses methods indicated that hydrous amorphous silica phase was formed following high temperature acid leaching of the natural and heated vermiculites due to the dissolution of structural components from the clay structures. Under any leaching condition studied, the heated vermiculite showed higher resistance against acid leaching probably due to the presence of collapsed mica like layers. According to the data collected in this work, a new leaching study was initiated for determining the high temperature (90°C) acid leaching behaviour of the vermiculite samples at different sulphuric acid concentrations and for the preparation of higher surface area and purer hydrous amorphous silica phases suitable for various applications. Acknowledgements: The authors wish to acknowledge Mike Darling (Palabora Europe Ltd.) for the supply of natural

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vermiculite sample. Two of the authors (E.T. and M.B.) thanks the Slovak Grant Agency VEGA (project 2/0064/14) and the Agency for Science and Development (APVV-0189-10) for the partial support. REFERENCES Breen, C., Watson, R., Madejová, J., Komadel, P. and Klapyta, Z., 1997. Acid-activated organoclays: Preparation, characterization and catalytic activity of acid-treated tetraalkylammonium-exchanged smectites, Langmuir, 13, 6473. Chmielarz, L., Kowalczyk, A., Michalik, M., Dudek, B., Piwowarska, Z. and Matusiewicz, A., 2010. Acid-activated vermiculites and phlogopites as catalysts for the DeNOx process, Applied Clay Science, 49, 156. da Fonseca, M.G.,Wanderley, A.F., Sousa, K., Araraki, L.N.H. and Espinola, J.G.P., 2006. Interaction of aliphatic diamines with vermiculite in aqueous solution, Applied Clay Science, 32, 94. Gates, W.P., Anderson, J.S., Raven, M.D. and Churchman, G.J., 2002. Mineralogy of a bentonite from Miles, Queensland, Australia and characterisation of its acid activation products, Applied Clay Science, 20, 189. Hongo, T., Yoshino, S., Yamazaki, A., Yamasaki, A. and Satokawa, S., 2012. Mechanochemical treatment of vermiculite in vibration milling and its effect on lead(II) adsorption ability, Applied Clay Science, 70, 74. Jozefaciuk, G. and Bowanko, G., 2002. Effect of acid and alkali treatments on surface areas and adsorption energies of selected minerals, Clays and Clay Minerals, 50, 771. Komadel, P., Schmidt, D., Madejova, J. and Čičel, B., 1990. Alteration of smectites by treatments with hydrochloric acid and sodium carbonate solutions, Applied Clay Science, 5, 113. Kooli, F., 2009. Exfoliation properties of acidactivated montmorillonites and their resulting organoclays, Langmuir, 25, 724. Londo, M.G., Yang, X. and Young, R.H., 2001. Mesoporous silicoaluminate pigments for use in inkjet and carbonless paper coatings, US Patent 6274226B1. Marcos, C., Arango, Y.C. and Rodriguez, I., 2009. X-ray diffraction studies of the thermal behaviour of commercial vermiculites, Applied Clay Science, 42, 368. Mokaya, R. and Jones, W., 1995. Pillared clays and pillared acid-activated clays: A comparative study of physical, acidic, and

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

catalytic properties, Journal of Catalysis, 153, 76. Muiambo, H.F. and Focke, W.W., 2012. Ion exchanged vermiculites with lower expansion onset temperatures, Molecular Crystals and Liquid Crystals, 555, 65. Muiambo, H.F., Focke, W.W., Atanasova, M., van der Westhuizen, I. and Tiedt, L.R., 2010. Thermal properties of sodium-exchanged Palabora vermiculite, Applied Clay Science, 50, 51. Okada, K., Arimitsu, N., Kameshima, Y., Nakajima, A. and MacKenzie, K.J.D., 2006. Solid acidity of 2:1 type clay minerals activated by selective leaching, Applied Clay Science, 31, 185. Önal, M., Sarıkaya, Y., Alemdaroğlu, T. and Bozdoğan, İ., 2002. The effect of acid activation on some physicochemical properties of a bentonite, Turkish Journal of Chemistry, 26, 409. Pálková, H., Madejová, J. and Righi, D., 2003. Acid dissolution of reduced-charge Li- and Ni-montmorillonites, Clays and Clay Minerals, 51, 133. Ravichandran, J. and Sivasankar, B., 1997. Properties and catalytic activity of acidmodified montmorillonite and vermiculite, Clays and Clay Minerals, 45, 854. Ruiz-Conde, A., Ruiz-Amil, A., Pérez-Rodríguez, J.L. and Sánchez-Soto, P.J., 1996. Dehydration-rehydration in magnesium vermiculite: conversion from two-one and one-two water layer hydration states through the formation of interstratified phases, Journal of Materials Chemistry, 6, 1557. Steudel, A., Batenburg, L.F., Fischer, H.R., Weidler, P.G. and Emmerich, K., 2009a. Alteration of swelling clay minerals by acid activation, Applied Clay Science, 44, 105. Steudel, A., Batenburg, L.F., Fischer, H.R., Weidler, P.G. and Emmerich, K., 2009b. Alteration of non-swelling clay minerals and magadiite by acid activation, Applied Clay Science, 44, 95. Suquet, H., Chevalier, S., Marcilly, C. and Barthomeuf, D., 1991. Preparation of porous materials by chemical activation of the Llano vermiculite, Clay Minerals, 26, 49. Temuujin, J., Minjigmaa, A., Jadambaa, Ts., Tsend-Ayush, S. and MacKenzie, K.J.D., 2008. Porous properties of silica prepared by selective acid leaching of heat-treated vermiculite, Chemistry for Sustainable Development, 16, 221. Temuujin, J., Okada, K. and MacKenzie, K.J.D., 2003. Preparation of porous silica from vermiculite by selective leaching, Applied Clay Science, 22, 187.

Turianicová, E., Obut, A., Tuček, Ľ., Zorkovská, A., Girgin, İ., Baláž, P., Németh, Z., Matik, M. and Kupka, D., 2014. Interaction of natural and thermally processed vermiculites with gaseous carbon dioxide during mechanical activation, Applied Clay Science, 88&89, 86. Wypych, F., Adad, L.B., Mattoso, N., Marangon, A.A.S. and Schreiner, W.H., 2005. Synthesis and characterization of disordered layered silica obtained by selective leaching of octahedral sheets from chrysotile and phlogopite structures, Journal of Colloid and Interface Science, 283, 107. Yu, X.-b., Wei, C.-h., Ke, L., Wu, H.-z., Chai, X.s. and Hu, Y., 2012. Preparation of trimethylchlorosilane-modified acid vermiculites for removing diethyl phthalate from water, Journal of Colloid and Interface Science, 369, 344.

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

MECHANICALLY INDUCED CHANGES ON CRYSTAL STRUCTURE AND THERMAL BEHAVIOUR OF INDUSTRIAL MINERALS: CASE STUDIES FOR COLEMANITE, PYROPHYLLITE AND QUARTZ T. Uysal1,a, M. Şener1, H. Toptaş1, Ş. S. Karamazı1, S. Yazıcı1, Y. Eroğlu1 and M. Erdemoğlu1 1. İnönü University Department of Mining Engineering, 44280 Malatya, Turkey a. Corresponding author ([email protected])

ABSTRACT: Some advanced engineering materials like B4C, CaB6, SiC, Si3N4, Si or Al2O3 are obtained by thermal treatment methods as calcination roasting or carbothermic reduction. In this study, intensive planetary ball milling was employed to mechanically activate selected minerals such as colemanite (Ca2B6O11.5H2O), pyrophllite (Al2Si4O10(OH)2) and quartz (SiO2) in order to alter their thermal behaviour in the high temperature processes. Unmilled and milled mineral samples were then roasted to determine high temperature phases of the minerals. Minerals were also analysed using thermogravimetry. By comparing the crystal structures and thermal behaviors of the minerals investigated, the footprints of the mechanical activation were investigated. It was concluded that mechanical activation of these industrial minerals can provide more useful outputs in the production of the advanced materials at low costs.

1. INTRODUCTION Mechanical activation (MA) is a pretreatment method applied to increase the reactivity of mineral in metallurgical processes like roasting, carbothermic reduction or leaching, and performed in the new generation grinding mills where the mechanical energy is intensively transformed into mineral treated. During MA, size of the mineral particles gets finer and the formation of defects in the crystal structure occurs due to mainly the mechanical energy density [Baláž and Ebert, 1991]. Decreasing the reaction temperatures, increasing the reaction rate, preparation of water soluble compounds, necessity for less expensive reactors and shorter reaction times are some advantages of MA [Erdemoğlu, 2009]. Various enginering ceramics are manufactured generally by thermal treatment of naturally occurring minerals. Of these, colemanite (Ca2B6O11.5H2O), pyrophllite (Al2Si4O10(OH)2) and quartz

(SiO2) minerals are used as the primary raw material in the production of several advanced materials. Colemanite is the most occurring type of the boron minerals. Advanced materials such as silicon (Si), boron nitride, (BN), titanium diboride (TiB2), boron carbide (B4C) and calcium hegzaboride (CaB6) are some of the examples that have applications in the boron industry [Tekin, 1990; Şekerci, 2000; Üstün, 2002]. For instance, CaB6 is used in a variety of industrial applications, where it is known as an abrasive and deoxydation material because of its hardness and electronic properties. CaB6 was reported by Yıldız et al. (2005) to be produced from colemanite. However, direct use of colemanite is so problematic that transporting raw colemanite and removing impurities and crystal water later is expensive and energy inefficient. Thus colemanite must then undergo heat treatment before use. These compounds 765

are used in most of today's high-tech materials and are sold to 10-20 times the cost. In our country, some of these products espacially used in a variety of cutting and etching materials are imported at very high prices. Pyrophyllite is an aluminum silicate mineral with Al2Si4O10(OH)2 formula. Regarding the usage, it belongs to family of high alumina clays like kyanite, andalusite and diaspore [Cornish, 1983]. These alumina containing materials exhibit very good thermal shock resistance at high temperatures. Largely depending on this, they are used in the fabrication of alumina refractories. Investigations on pyrophyllite based refractories and ceramics have revealed some unique advantages, leading to high corrosion resistance to molten iron, steel and the slag in iron-steel works; good thermal shock resistance, low deformation under load, and good mechanical resistance in the production of ceramics. Thus, thermal treatment is very important mainly mullite (3Al2O3.2SiO2) requiring processes. Silicon is one of the most found elements in the Earth’s crust. But it is not available in the element form. It is found as compounds with oxygen in the form of quartz or silicates. One of the most important use of Si is in the solar cells. Photovoltaic cell manufacturers mostly use silicon, which can convert sunlight directly into electricity. 98% of the solar cells are from silicon. Metallurgical grade silicon is primaryly produced by high temperature treatment of high grade silica sand with a carbon source. In this present study, effects of intensive planetary ball milling on the crystal structure and thermal behaviour of selected minerals of colemanite (Ca2B6O11.5H2O), pyrophllite (Al2Si4O10(OH)2) and quartz (SiO2) were

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examined to determine whether the milling resulted in an mechanical activation or not. 2. MATERIALS and METHODS Colemanite (Ca2B6O11.5H2O) of a high grade colemanite concentrate, pyrophllite (Al2Si4O10(OH)2) hand picked from the mine and quartz (SiO2) from high grade silica sand were used. All mineral samples were dry milled in air by a planetary ball mill. 250 cm3 tungsten carbide bowl and 10 mm balls of the same material were used. Colemanite and pyrophyllite samples were milled alone, whereas silica sand was milled together with coke. To define the crystal structure of the unmilled but gently powdered for particle size reduction, and intensively milled mineral samples were analysed using Rigaku RadB model X-ray diffractometer (XRD). Thermal behavior of all samples were determined using Setaram Labsys1600 Model TGA/DTA instrument operates in argon atmosphere and up to 1600°C. 3. RESULTS and DISCUSSION For determining the effects of intensive milling on the structure of crystal colemenite, it was milled and the milled products were analysed by using XRD. Milled colemanite samples were then roasted to determine the solid phases remained. (Figure 1) shows XRD patterns of unmilled and milled, and then roasted colemanite. In the original colemanite (K00) sample, there are some calcite (CaCO3) and gypsum (CaSO4.2H2O). All other peaks belog to colemanite. As also seen from the Figure 1, intensive milling for 45 min (Sample K4-45), not completely but partially, altered the crystal structure of colemenite. At the examples subjected to mechanical activation, colemanite crystal peak intensities decreased with milling.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Accordingly, mechanical activation caused disruption of the crystal structure of this borate mineral. However, this disorder is not very clear and maybe gradual. When these samples were roasted up to 500°C it was found that colemanite‘s peaks disappeared and

almost amorphous structure occurred. It can be proposed that colemanite begin to transform into dehydrated form, maybe just calcium borate. When the temperature was increased to 800°C, new XRD peaks occurs, depending on the recrystallisation of anhydrous colemanite.

Figure 1: Comparison of XRD patterns for unmilled (K00) and 45 min milled (K4-45) colemanite samples, and of roasted at 425°, 500° and 800 °C (Symbols: ♦, calcite; ■ gypsum). Seen in (Figure 2) are TG curves for unmilled and 45 min milled colemanite samples. Thermal decomposition depending on initially loss of crystal water begins nearly but not very significantly at 337 °C and continues up to 700 °C for unmilled colemanite. At 363 °C, other strong hydrogen bonds of water molecules are broken and then borate structure is began to decompose. When the temperature is at between of 393°-400 °C, decomposition rate reaches to maximum depending on the final release of water molecules in the pores. This phenomenon causes sudden crash of the samples, known as decrepitation [Uzunoğlu, 1992; Çelik et al., 1994; Şener and Özbayoğlu, 1995]. After 700 °C, colemanite converts to sintered colemanite. It was also

demonstrated by Yıldız (2004) that colemanite loses its crystal water through endothermic reactions at 300°-460 °C and that decrepitation and decomposition of colemanite to amorphous B2O3 and CaO takes place at temperatures lower than 600 °C, and finally CaB2O4 and Ca2B6O11 appear as new crystalline boron compounds at 800 °C. When compared to TG curve of unmilled colemanite, 45 min milled colemanite losses its water at very low temperatures. Since the interval between onset and offset temperatures appears within very big interval, decrepitation of milled colemanite does not occur. In addition, decrepitation of the milled colemanite was not observed during atmospheric roasting experiments performed at isothermal conditions.

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creep of tetrahedral-octahedral layers [Pérez- Rodriguez et al., 1988]. Erdemoğlu and Sarıkaya (2002) was also reported that collectorless flotation recovery of pyrophyllite decreases with prolonged milling due to structural deformation occurred during the milling.

Figure 2: Comparison of TG curves obtained for unmilled and 45 min milled colemanite samples. (Figure 3) collectively shows XRD patterns for pyrophyllite samples which unmilled (P0, just gently milled), 45 min milled (P45), and then roasted at various temperatures. Major minerals determined in pyrophyllite samples are pyrophyllite (Al2Si4O10(OH)2), quartz (SiO2), kaolinite (Al2Si2O5(OH)4) and dickite (Al2Si2O5(OH)4). It was found that milling for 45 min significantly results in decrease mainly at the peak intensities of pyrophyllite, kaolinite and dickite. Peaks which remain after 45 min of milling fully belong to quartz. It is reported that when the milling time increases, dry milled pyrophyllite losses its original crystal structure depending on the

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In order to determine the effects of heat treatment on the thermal behaviour unmilled and milled pyrophyllite samples were roasted at different temperatures and the raosted samples were also analysed for their crystal structure. As seen in (Figure 3), peaks of pyrophyllite and kaolinite are disappeared in the unmilled sample roasted at 800°C, whereas they are not present in the milled sample even at roasting temperatures as low as 400°C. Peaks of kaolinite found in the unmilled sample disappeared at 800°C, whereas 700°C was enough for decomposition of kaolinite present in the milled pyrophyllite sample. Morover, new peaks occurred at high temperatures belonging to mullite with a nominal composition of 3Al2O3.2SiO2 are very common in the milled pyrophyllite samples roasted at temperatures as low as 400°C, when compared to those of unmilled samples.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Figure 3: Comparison of XRD patterns for unmilled (P0), 45 min milled (P45) and then roasted phyrophyllite samples. Thermograms obtained by roasting of unmilled and milled pyrophyllite at isothermal heating conditions are shown in Figure 4. It seems that pyrophyllite losses its bound water without any structural changes at temperatures between 400° and 700°C. At temperatures near to 800°C, pyrophyllite converts into a mullite-like aluminium silicate form and stays steady up to 1000°C. After this temperature, mullite-phase conversions begin and free quartz present converts into the crystobalite which is a hightemperature polymorph of quartz. It was found that intensive milling significantly changes the thermal behaviour of pyrophylite. Mass loss in 20 min of milled pyrophyllite sample begins at 400°C, whereas it is almost 500°C for unmilled sample. Besides, mass loss of unmilled pyrophyllite at 700°C was calculated as 2.5%, whereas it is 3.8% pyrophyllite sample which was milled for 60 min. Consequently, conversion of pyrophyllite into mullite shifted to low temperatures, suggesting the mechanical activation. In

the literature, it was reported that transformation in the pyrophyllite begins with the milling; milling longer than 7 min changes the thermal behaviour; according to TG curves, onset temperature at which mass loss begins decreases and endothermic reaction region shifts to occur at low temperatures [Pérez-Rodriguez and Sânchez-Soto, 1991].

Figure 4: TG curves for unmilled and milled (20, 45 and 60 min) pyrophyllite as obtained by isothermal roasting tests.

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Silicon carbide is manufactured by charbothermic roasting of high purity silica in the presence of coke: SiO2 + 3C → SiC + 2CO Metallurgical-grade silicon used for many purposes including photovoltaics is obtained from the reduction of silicon in the presence of carbon at high temperatures: SiO2 + 2C → Si + 2CO In order to determine the effect of intensive milling on the carbothermic roasting and reduction of quartz, high purity silica sand was mixed with metallurgical grade coke; milled for long periods and finally the milled mixtures roasted at 1200 °C for half a day. Unmilled, milled and roasted materials were characterised using XRD and TGA. As seen from Figure 5, XRD patterns of unmilled mixture are very simple. Since silica sand is very pure, one and only the crystal mineral phase seems as quartz. All the peaks on the patterns are belongs to quartz. Since coke is in the amorphous phase, it was not determined by XRD analysis. However, intensities of the quartz

XRD peaks decreased and peak areas enlarged gradually with prolonged miling. Milling 5 h resulted in the amorphisation of quartz in the silica sand-coke mixture. Since the presence of coke in the mixture behaved as grinding additive, 10 h of milling gave a complete amouphous material. XRD patterns for unmilled and 10 h milled silica sand-coke mixtures both which were roasted at 1200°C for 12 h were collectively shown in Figure 6. Seen on the XRD pattern of unmilled and then roasted silica sand-coke mixture is quartz with a little bit high peak intensities due to heat treatment. But, the materials including quartz in the 10 h milled mixture were completely amorphous, roasting of milled mixture at 1200 °C gave also rise to appearance of crystal quartz. But in this case, quartz is in crystobalite phase. All of the peaks reappeared belong to crystobalite quartz. It is known that quartz is in trydimite phase after 870°C and in crystobalite phase after 1470 °C. Since the crystobalite phase is obtained just at 1200 °C, this result solely suggests mechanical activation which provides phase transformation of quartz to occur at low temperatures.

Figure 5: XRD patterns of unmilled and milled (1, 5, 10 h) silica sand-coke mixtures. 770

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Figure 6: Comparison of the XRD patterns for the unmilled and 45 min milled silica sand and coke mixtures roasted at 1200°C for 12 hours in the air. This may not be resulted from gasification of carbon using O2 originated from the air to form COx gases, since TG analysis was performed in argon atmosphere. According to Sahajwalla et al. (2003), the reaction between SiO2 and C in powdery mixtures has significant rates from about 1400°C onwards in vacuum or in stream of argon. The reaction can be seen as a combination of two basic reactions: SiO2 (s, l) + C(s)  SiO (g) + CO(g) SiO(g) + 2C(s)  SiC(s) + CO(g) Figure 7: TG curves for unmilled silica sand only, unmilled and milled (1, 5 and 10 h) silica sand-coke mixtures as obtained by non-isothermal analysis in argon. Shown in (Figure 7) are TG curves for original silica sand only, unmilled and 1, 5 and 10 h milled silica sand-coke mixtures, as obtained by thermal analysis performed up to 1400 °C. On TG curve of the unmilled original silica sand only, mass loss onset temperature is about 1300°C, whereas it is about 1050 °C for the unmilled silica sand-coke mixture. It seems that milling considerably changed the mass loss starting temperature which decreases with milling time be longed from 1 to 5 h.

The reactions taking place at the carbon surface are also reported to play a role in controlling reaction kinetics. Thus it was suggested that the mass loss occurred in the 1 and 5 h milled mixtures is due to early reactions of silica and carbon to form SiO gas and to release CO. But, TG curve of the mixture milled for 10 is very different. TG pattern is similar to others up to 900°-1000°C, then the material dramatically starts to gain mass up to 1350°C and to loose its mass again with the increasing temperature up to the end of analysis limit. The mechanism causing this thermal behaviour needs further study. But what the observed is the clear effect of 771

intensive milling on the charbothermic reactions of quartz. 4. CONCLUSIONS In this study, structural and thermal alterations resulted from intensive milling of selected minerals such as colemanite, pyrophyllite and quartz were investigated, which are processed generally at very high temperatures in their metallurgy. For each of the minerals examined in this study, it was typically found by XRD analysis that intensive milling appearently alter or deform the crystal structure of the minerals, as leading to become XRD amourphous as a final point. There was a remarkable result so that quartz present in the pyrophyllite sample resists to the action of intensive milling while the quartz in the silica sand-coke mixture easily goes to become amorphous. Studies performed either at non-isothermal or isothermal heating conditions showed that, as compared to their unmilled counterparts, thermal behaviour of the intensively milled minerals significantly was altered to release their volatile content at low temperatures, mainly due to mechanical activation. Finally, it was concluded that mechanical activation may be one of the keys to develop existing technologies for manufacturing many of the high temperature processed engineering materials like oxides (Al2O3, ZrO2), nitrides (AlN, BN), borides (CaB6, TiB2), carbides (SiC, TiC, WC, B4C) at low-costs. Acknowledgement: Financial supports of İnönü University (BAPB Project Numbers: 2012/108 and 2012/14) is gratefully acknowledged. REFERENCES Baláž P., Ebert I., 1991. Oxidative leaching of mechanically activated sphalerite, Hydrometallurgy, 27, 141-150.

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Çelik, M.S., Uzunoğlu, H.A., Arslan, F., 1994. Decrepitation properties of some boron minerals, Powder Technology ,79,167– 172. Cornish, B.E. 1983. Pyrophyllite. Industrial Minerals and Rocks, SJ.Lefond (Ed.) SME Publications, s.1085-1108, New York. Erdemoğlu M., Carbothermic reduction of mechanically activated celestite, Int. J. Miner. Process. 92, 144–152, (2009). Erdemoğlu, M., Sarıkaya, M., 2002. The effect of grinding on pyrophylliye flotaion, Minerals Engineering, 15, 723-725. Pérez-Rodriguez, J.L., Madrid Sanchez Del Villar, L., Sänchez-Soto, P.J. 1988. Effects of dry grinding on pyrophyllite. Clay Minerals. 23,399. Pérez-Rodriguez, J.L., Sânchez-Soto, P.J. 1991. The Influence of the Dry Grinding on the Thermal Behavior of Pyrophyllite. Journal of Thermal Analysis. 37:1401. Sahajwalla, V., Wu, C., Khanna, R., Saha Chaudhury, N., Spink, J., 2003. Kinetic study of factors affecting in Situ reduction of silica in carbon-silica mixtures for refractories. ISIJ International, 43(9), 1309–1315. Şekerci Y., 2002. Calcium hegzaboride production. BSc Thesis. Afyon Kocatepe University, Ceramics Engineering Department, Afyon. Şener, S., Özbayoğlu, G., 1995. Separation of ulexite from colemanite by calcination, Minerals Engineering, 6, 697-704. Tekin A., 1990. High technology ceramics and developments in Turkey. Proceedings of 4th Int. Ceramics Congress, p317, İstanbul. Üstün, R., 2002. Titanium diboride production. Afyon Kocatepe University, Ceramics Engineering Department, in Turkish, Afyon. Uzunoglu, A., 1992. Decrepitation properties of the boron minerals colemanite and ulexite. Master of Science Thesis, Technical University of Istanbul, in Turkish, 1992. Yıldız, Ö., 2004. The effect of heat treatment on colemanite processing: a ceramics application, Powder Technology, 142, 7-12. Yıldız, Ö., Telle, R., Schmalzried, C., Kaiser, A., 2005. Phase transformation of transient B 4C to CaB6 during production of CaB6 from colemanite. Journal of the European Ceramic Society, 25, 3375-3381.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

OPTIMUM USE OF ZEOLITE IN THE PRODUCTION OF BLENDED CEMENT Melis Toker Derdiyok1 and Hasan Ergin1,a 1. Istanbul Technical University, Mining Engineering Department, Istanbul, Turkey a. Corresponding author ([email protected])

ABSTRACT: Cement industry is an energy-intensive process and results in large amount of CO2 emissions. This study is aimed at reducing energy consumption and the emissions by using zeolite as a substitute of clinker. Firstly, the physical, chemical and mineralogical characterization of zeolite was determined and the grinding properties of zeolite and clinker were performed in laboratory ball mill. Then, the ground zeolite which has the fineness of 5% residue on 32 micrometer sieve was substituted for clinker by 10% and 20%. The physical, chemical and mechanical analyses were conducted on produced blended cements in accordance with standards. The use of zeolite has resulted in an increase in the compressive strength at 90 days and also increase in setting time. It has also been observed that the zeolite has much easier grindability than clinker. Therefore, the use of zeolite reduces the grinding energy consumption and also emissions due to the use of less amount of clinker usage without causing any degradation of cement properties. The full results are illustrated in this article.

Production of cement is an expensive process and has adverse ecological effects. CO2, NOx, and SOx are among the hazardous emissions generated in relatively high volumes in the conventional Portland cement process.

natural zeolites in water and air filtration, pollution, and odour control, animal hygiene, aqua-culture, pond filtration, soil amendment, and as an industrial filler and dietary supplement in animal feeds [Ortega et al., 2000]. Zeolite types that have been tested so far are those most common in the sedimentary zeolite (tuff) deposits widespread all over the world, namely, clinoptilolite, mordenite, phillipsite and chabazite [Caputo et al., 2008].

Zeolites are a group of crystalline hydrated alumino silicates with unique physico-chemical properties resulting from their specific structure in which cavities or pores with strictly defined nanodimensions occur [Mozgawa et al., 2009]. The microporous crystalline structure of zeolites is able to adsorb species that have diameters that fit through surface entry channels, while larger species are excluded, giving rise to molecular sieving properties that are exploited in a wide range of commercial applications. These include the use of

Zeolite as natural pozzolan, which are materials exhibiting cementitions properties, have been widely used as substitutes for Portland cement clinker in many applications because of reductions in the production cost and CO2 emission [Kurudirek et al., 2010]. In a recent study, Uzal et al. [2012] reported that the clinoptilolite minerals of zeolite possesses a lime reactivity which is comparable to silica fume and higher than fly ash and a non-zeolitic natural pozzolan. They also concluded that the high reactivity of the clinoptilolite is

1. INTRODUCTION Cement is the biggest man-made and used material in the world with its 3.6 billion tons of annual production at 2013 [Republic of Turkey Ministry of Economy, 2014].

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attributable to its specific surface area for certain grinding method and duration as well as its reactive SiO2 content. In another study, the use of zeolite samples, where collected from İzmirFoça, Balıkesir-Bigadiç and ManisaGördes, were investigated in ceramic industry, in paper industry as filler and coater and in the cement industry as additive [Ulusoy & Albayrak, 2009]. Canpolat et al. [2004] investigated the effects of zeolite, coal bottom ash and fly ash as Portland cement replacement materials. The results shown that inclusion of zeolite up to the level of 15% resulted in an increase in compressive strength at early ages, but resulted in a decrease in compressive strength when used in combination with fly ash. Karakurt & Topçu [2012] reported that according to the results of accelerated corrosion test; concretes produced with zeolite, fly ash and ground granulated blast furnace slag in ternary composition, the corrosion were significantly reduced. In this study, the usage of zeolite was studied as clinker replacement material. The zeolite was taken from KütahyaGediz. The experiments were carried out at Nuh Cement Plant in Turkey. 2. MATERIALS & METHODOLOGY 2.1. Materials Clinker, zeolite (Z) and gypsum were used in this study. The chemical compositions of these materials determined by XRF. The results are given in Table 1. The mineralogical analysis of clinker and zeolite were also determined by DTA as the results are presented in Table 2.

Table 1: Chemical characteristics of materials used (wt. %).

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Clinker

Gypsum

Zeolite

CaO

65.91

32.4

5.81

SiO2

21.55

1.1

62.27

Al2O3

4.80

0.4

12.46

Fe2O3

3.29

0.1

1.51

MgO

1.34

0.1

5.81

SO3

0.48

44.50

0.16

K2O

0.78

0.05

3.65

Na2O

0.20

0.04

0.06

21.50

10.60

Loss on 0.28 ignition

The specific gravity was determined by Gas Pycnometer and the specific surface area was measured by Blaine equipment. Specific gravity of zeolite was found 2.24 g/cm3. Specific surface area of zeolite was measured as 7969 cm2/g. Table 2: Mineralogical characteristic of clinker and zeolite. Clinker (wt. %)

Zeolite

C3S (58.48)

Clinoptilolite Illite mica Opal-CT Feldspar Smectite Quartz

C2S (47.69) C3A (7.17) C4AF (10.00)

C: CaO, S: SiO2, A: Al2O3, F: Fe2O3

The other authors were determined morphology of zeolite by Scanning Electron Microscope (SEM). As shown in Figure 1, the particles are typically euhedral plate prism, monoclinic and its crystal size is 5-10 micrometer [Esenli & Gültekin, 2011].

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

called as reference cement. After that, the ground powders of zeolite, which has the fineness of 5% residue on 32 micron sieve, were added by 10% and 20% to the ground clinker and gypsum.

Figure 1: SEM image of zeolite. 2.1. Methodology Figure 2 shows the experimental design of investigating the usability of the zeolite as a substitute of clinker in production of blended cement. Firstly; the crushing and grinding test were performed in order to compare the grindability of the zeolite and clinker. The zeolite was crushed in a laboratory jaw crusher under the size 5 mm. Then, the comparative test for grinding properties of clinker and zeolite were carried out in a laboratory ball mill. The ball mill is 52 cm in length and 42 cm in diameter as it has a rotational speeds of 46 rev/min. The ball sizes ranging from 60 to 15 mm are in total of 215 balls. Its total weight is 58.58 kg. The particle size distributions were determined by Laser particle size analyzer. Average particle size of ground clinker was 13.70 micrometer after 60 minutes of grinding. Average particle size of ground zeolite was 7.85 micrometer after 45 minutes. Thus, it has been found as a result of grinding test, zeolites can be ground easier than clinker. In the final stage, the features of reference cement was determined that contains 95% clinker and 5% gypsum, called Portland cement (R) that is CEM I

Figure 2: Experimental processes to investigate the usability of zeolite. In experimental studies; the physical, chemical, and mechanical analysis (setting time, volume expansion, compressive strength, fineness, Blaine) were conducted on produced Blended cements in accordance with Turkish Standards that comply with European Standards. TS EN 196-3 is for setting time and volume expansion, TS EN 1966 is for Blaine and fineness, TS EN 196-1 is for compressive strength (Turkish Standard, 2000, 2002, 2009). Chemical analysis of the samples was performed using X-ray spectrometer. Setting time was determined by the Automatic Vicat apparatus. Determination of expansion of the Blended cements was carried out by the Le Chatelier’s. Fineness of Blended cements was found by using both Blaine apparatus and Air Jet Sieve. Compressive strength of Blended cements was determined in samples having dimensions of 40 mm x 40 mm x 160 mm with prismatic shape at the ages of 2, 7, 28, and 90 days.

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3. RESULTS AND DISCUSSION Blended cements recipes were labelled according to the amount of zeolite additions. The cement mix recipes are given Table 3.

The volume expansion, the fineness and the compressive strength were within the specified value in the standards. The compressive strength values of R, Z10 and Z20 are presented in Figure 3.

Table 3. Mix proportions of the cements (% mass).

Table 4: Physical characteristics of R and the cement containing zeolite (% mass).

Clinker

Zeolite

Gypsum

R

95

-

5

Z10

85

10

5

Z20

75

20

5

The physical properties of reference cement and the cements containing zeolite called blended cements are presented in Table 4. The specific gravity values were determined as the average of four measurements. The fineness of blended cements was determined using sieves of 32 micrometer and 90 micrometer. The specific gravity of the blended cements was reduced while the specific surface area was increased by the addition of zeolite. Initial and final setting times of blended cements were longer than that of reference cement R.

R

Z10

Z20

3.15

2.98

2.88

3343

5213

6063

27.2

23.7

23.0

Fineness (90 micrometer)

7.4

2.8

2.8

Initial setting time (minute)

124

173

174

Final setting time (minute)

157

227

260

Volume expansion (mm)

10

10

9

Specific gravity (g/cm3) Specific surface (cm2/g) Fineness (32 micrometer)

Figure 3: Compressive strength test results of reference cement and blended cements.

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

4. CONCLUSIONS Blended cement produced by the addition of zeolite was analyzed and their compressive strength development was compared at 2, 7, 28 and 90 days with reference cement R. The produced blended cements comply with the standards. Zeolite can be used as substitute till 20% without any quality degradation. Moreover, the use of zeolite also contributes to the compressive strength of the final product. Since the grinding energy consumption of zeolite is much less than clinker so that the usage of the zeolite provides some economic advantages as well. Acknowledgements: This research has been done in Nuh Cement Plant and was supported by Turkish Cement Manufacturers’ Association. REFERENCES Canpolat, F., Yılmaz, K., Köse, M.M., Sümer, M., yurdusev, M.A., 2004. Use of zeolite, coal bottom ash and fly ash as replacement materials in cement production, Cement and Concrete Research, Volume (34), pp. 731735. Caputo, D., Liguori, B., Colella, C., 2008. Some advances in understanding the pozzolanic activity of zeolites: The effectof zeolite structure, Cement and Concrete Composites, Volume (30), pp. 455-462. Esenli, F., Gültekin, A.H., 2011. SANTEK Mining Company–Gediz (Kütahya) Area Zeolite (Clinoptilolite) Material Characteristics, Internal Report, Istanbul Technical University, Mining Faculty Department of Geological Engineering. Hewlett, P.C. (ed), 2004. Lea’s chemistry of cement and concrete, 4th edn, Oxford: Elsevier Butterworth-Heinmann, Oxford. Karakurt, C., Topçu, I.B., 2012. Effect of blended cements with natural zeolite and industrial by-products on rebar corrosion and high temperature resistance of concrete, Construction and Building Materiaals, Volume (35), pp. 906-911.

clinoptilolite-rich natural zeolite from Turkey, Radiation Physics and Chemistry, Volume (79), pp. 1120-1126. Mozgawa, W., Krol, M., Pichor, W., 2009. Use of clinoptilolite for the immobilization of heavy metal ions and preparation of autoclaved building composites, Journal of Hazardous Materials, Volume (168), pp. 1482-1489. Ortega, E.A., Chris, C., Knight, J., Loizdou, M., (2000). Properties of alkali-activated clinoptilolite, Cement and Concrete Research, Volume (30), pp. 1641-1646. Toker, M., 2013. Enerji tüketimi ve emisyonların düşürülmesi amacıyla çimento üretiminde mineral katkıların kullanımının optimizasyonu, Optimization of the use mineral additives in cement production for reduce to energy comsumption and emissions. M.Sc. Thesis, Istanbul Technical University, Graduate School of Science, Engineering and Technology (in Turkish). Türkiye Cumhuriyeti Ekonomi Bakanlığı, 2014. Çimento Raporu, Sektör Raporları, İhracat Genel Müdürlüğü, Kimya Ürünleri ve Özel İhracat Daire Başkanlığı, Ankara (in Turkish). Türk Standardı, 2000. Çimento deney metotlarıbölüm 6: incelik tayini, TS EN 196-6, Türk Standardları Enstitüsü, Ankara (in Turkish). Türk Standardı, 2002. Çimento-deney metotlarıbölüm 3: priz süresi ve genleşme tayini, TS EN 196-3, Türk Standardları Enstitüsü, Ankara (in Turkish). Türk Standardı, 2009. Çimento deney metotlarıbölüm 1: dayanım tayini, TS EN 196-1, Türk Standardları Enstitüsü, Ankara (in Turkish). Ulusoy, G. & Albayrak, M. 2009. Foça (Izmir)Bigadic (Balıkesir) ve Gördes (Manisa) Yöresi Zeolitlerinin Mineralojik ve Teknolojik Ozellikleri, MTA Dergisi, Volume (139), pp. 61-74 (in Turkish). Uzal, B., & Turanlı, L. 2012. Blended cements containing high volume of natural zeolites: Properties, hydration and paste microstructure, Cement & Concrete Composites, Volume (34), pp. 101-109.

Kurudirek, M., Özdemir, Y., Türkmen, I., Levet, A., 2010. A study of chemical composition and radiation attenuation properties in

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

PRECONCENTRATION OF MUĞLA/KÖYCEĞİZ OLIVINES BY COMMINUTION Taki Güler1,a, Selçuk Aktürk2 and Ali Özer3 1. Muğla Sıtkı Koçman University, Department of Mining Engineering, Muğla, Turkey 2. Muğla Sıtkı Koçman University, Department of Physics, Muğla, Turkey 3. Cumhuriyet University, Department of Metallurgical and Materials Engineering, Sivas, Turkey a. Corresponding author ([email protected])

ABSTRACT: Olivine, a magnesium-iron orthosilicate, is an important raw material especially for metallurgical applications. Muğla/Köyceğiz olivines contain alteration product, lizardite, which increases loss on ignition (LOI) of olivine, an important specification for metallurgical applications. This study was performed to investigate the preconcentration possibility of olivine by comminution. Characterization of olivine was made by XRD, SEM-EDS, XRF and petrographic analyses. Mineralogical analysis exhibited that the olivine sample contains olivine, forsterite, enstatite and augite having hardnesses closer to each other, and soft lizardite. Comminution was made by jaw crusher and rod mill. Enrichment of the soft mineral (lizardite) was observed at finer size fractions. This work revealed that olivine preconcentration with low LOI value could be achieved at +38 µm size by classification after comminution. But, required chemical composition for industrial areas could not be satisfied by comminution due to the close hardness values of enstatite and augite to olivine. 1. INTRODUCTION Olivine is a naturally occurring orthosilicate mineral group in mafic and ultramafic igneous rocks. It has a nominal formula (Mg,Fe)2SiO4, and owes its name to the olive-green color. It is a solid solution of two pure end-members forsterite (Mg2SiO4) and fayalite (Fe2SiO4) [Davis, 1977; Kleiv and Thornhill, 2011; Krivolutskaya and Bryanchaninova, 2011; Wells, 1959]. Olivine has many favorable properties so that it has been preferred in many technical application areas, such as foundry sand, refractories, production of iron ore pellets, fluidized beds and abrasives. Based on the potential environmental benefits, many studies have been conducted in the last few decades to explore new possibilities of olivine applications such as CO2 sequestration, neutralization of industrial waste and acid mine drainage, treatment of heavy metal contaminated water

reserves, elimination of dissolved natural organic matter and microbial pathogens [Acar, 2003; Jolsterå, 2010; Kleiv and Thornhill, 2011; Krivolutskaya and Bryanchaninova, 2011]. Major part of mined olivine is consumed as slag conditioner where the mineral is exploited for its high magnesium content. Olivine is used to scavenge alkali carbonates and sulfates, and prevent basic slags from attacking refractory linings. It reduces viscosity while maintaining basicity. Mg content of olivine is higher than dolomite so that less material is required to meet Mg requirements [Facer, 2007]. Its loss on ignition (LOI) values is low, which means lower energy loses in endothermic reactions in blast furnaces and sintering plants, and improved thermal stability of olivine sand used for foundry purposes. One of the common application areas of olivine is casting due to health and safety advantages over free

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silica. Olivine produces a clean surface finish [Acar, 2003; Davis, 1977]. Olivine may be present as an accessory component or may make up the main rock constituent as in the dunite variety of peridotite [Kleiv and Thornhill, 2011]. Over time, olivine minerals convert to serpentines, hydrated Mgsilicate minerals, in the presence of water at elevated temperature and under pressure. Serpentines increase LOI value of olivines. So, they are particularly undesirable minerals. This bulk alteration process is named as serpentinization [Jasieniak and Smart, 2010; King, 2009]. Olivine ores, then, may contain serpentine minerals as the product of alteration process in addition to pyroxene minerals and chromite. Pyroxene (Mohs hardness between 5 and 7) and chromite (around 5.5) have hardness values much closer to that of olivine (6.5-7), but serpentine minerals (2.5-4) are reasonably soft [Acar, 2003; Davis, 1977; King, 2009]. Hardness of minerals determines the comminution characteristics of them. There is an inverse relationship between hardness and grindability: harder minerals have lower breakage rates than softer ones [Tong et al., 2013]. Concentration of readily ground soft minerals occurs at finer sizes in comminution process products. Cho and Luckie [1995] stated that the proportion of the stronger material in the coarser size fractions of the product is greater after mixing the two feed materials and grinding them than after grinding the two materials separately and mixing the products. Tong et al [2013] investigated the effect of grinding conditions on selective comminution and nickel upgrade conducted on the siliceous goethitic nickel laterite ore sample. They proposed that the grinding behavior of the majority of feed samples was non-first-

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order due to the fast breakage rate of soft minerals and the low breakage rate of hard minerals in the feed. They observed an enrichment of the soft mineral in the under-screen product by selective grinding. Velázquez et al. [2008] studied the grindability of a binary mixture of serpentine and limonite components. They found that breakage rate of the limonite–serpentine blends increased with the increase of limonite content due to the effect of hard minerals on the grinding of the soft minerals. Muğla-Köyceğiz olivines do not meet the LOI specifications for metallurgical applications due to the presence of serpentine minerals. This study was conducted to investigate the possibility for preconcentration of these reserves to obtain low LOI value olivine concentrate only by applying comminution and classification. 2. MATERIALS AND METHODS A representative ore sample was supplied from Alfa Olivin A.Ş. in Namnam region of Köyceğiz, Muğla, Turkey. Mineralogical and chemical characterization of ore sample was performed by XRD, SEM-EDS, XRF and petrographic analyses. Comminution was made by laboratory type jaw crusher and rod mill. Supplied sample having size of -20 cm was first crushed by a single-toggle Blake type jaw crusher down to -1 cm size. Finely sized fraction (-212 µm) of crushed sample was removed prior to further comminution process to avoid over-grinding. Then, sampling of jaw crusher product was performed by conning-and-quartering followed by sampling using Riffle splitter to get 700 g lots of crushed ore sample (-1cm+212µm). Each ore sample batch was ground by a laboratory type rod mill (200x300mm). Grinding time was determined as 10 minutes by preliminary

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

works. Mill load was adjusted as 40% solid. Mill speed was applied as 60% of critical speed. Classification and size analysis of crusher and mill products were performed by laboratory type (20 mm in diameter) sieves at coarser sizes (+38 µm). Finely ground (-38 µm) portion was classified by applying gravity sedimentation method. Sedimentation process was applied at 5% solid by weight in the pulp, where Stokes law is valid. One of the product specifications for metallurgical applications is LOI value. LOI variable was determined using a high-temperature furnace. Olivine sample was first dried in an oven at 50ºC for at least 2 hours, and then taken to a desiccator. Dried sample was weighed and heated in a furnace up to 900°C at a heating rate of 50°C/min, at which temperature it was calcined for 30 minutes [Kleiv and Thornhill, 2011]. Then, heating was stopped, and calcined sample was left in the furnace for cooling down to 150ºC. After cooling, sample was taken to the desiccator, where it cooled down to room temperature. Calcined sample was reweighed, and LOI value was calculated from weight loss. 3. RESULTS AND DISCUSSIONS Mineralogical and chemical characterization of olivine sample, supplied from Alfa Olivin A.Ş. in Muğla/Köyceğiz, was made by several methods. The characterization works stated that sample has ultramafic rock origin. Olivine and pyroxene (orthopyroxene and clinopyroxene) minerals were found to be major constituents in addition to chromite in minor scale as opaque phase. Such formation was defined as a rock having a harzburgite-lherzolite constituent. Chemical analysis of olivine sample stated that major elements are Mg, Si and Fe (Table 1). Such a high Mg and Si

content means that Köyceğiz olivines already meet the specifications of metallurgical use [Acar, 2003; Kleiv and Thornhill, 2011]. But, Fe2O3 content was higher than the upper limits, which is around 6.5-7% Fe2O3 for olivines as refractory raw material, and around 6.87.3% Fe2O3 for standard olivines. Moreover, total percentage of all oxides other than Mg, Si and Fe-oxides should be lower than 3%, which was around 4% in Köyceğiz olivines [Örgün and Erarslan, 2012]. Table 1: Analysis of olivine ore sample from Alfa Olivin A.Ş. Content, % MgO 47.79 SiO2 39.36 Fe2O3 8.87 Al 0.79 Ca 1.21 Cr 0.26 XRD of olivine sample shows that the main peaks are closer to those of olivine and forsterite (Figure 1). The secondary crystalline phases observed are enstatite and lizardite. Augite was hardly discriminated on the diffraction pattern. Lizardite, one of the secondary phase, was visualized especially by its highintensity line at 12.04° 2θ. Lizardite is the first mineral of the alteration product observed in the serpentinization process [Gürtekin and Albayrak, 2006]. Pure and unaltered olivine does not contain crystal water (Wells, 1959), which increases depending on the alteration rate. Presence of lizardite peaks on the XRD pattern (Figure 1) indicates serpentinization of the ore [Acar, 2003; Güney and Atak, 1997; Kleiv and Thornhill, 2011]. Then, LOI test was applied on olivine sample, and LOI was found as 1.43%. Such value means that studied olivine sample does not meet LOI 781

specification for metallurgical application areas in the present form, and needs to be concentrated. It is expected to be lower than 1% to reduce energy consumption required for endothermic reactions proceeding in the dehydration-calcination processes. Lizardite, present in the olivine ore as an alteration product, has lower hardness than olivine (Table 2) while hardnesses of other minerals constituting ore are closer to that of olivine [Acar, 2003; Davis, 1977; King, 2009]. Data given in (Table 2) shows that LOI value of sample depends only on grade of lizardite. Therefore, preconcentration was thought to be possible only applying comminution process due to reasonable difference between the hardnesses of

lizardite and other minerals constituting the ore.

Figure 1: XRD pattern of olivine sample

Table 2: Theoretical chemical composition and hardness of minerals constituting the studied olivine ore [www.mindat.org, www.webmineral.com] Elements, % Mohs Mineral Chemical Formula Hardness Mg Si Fe Ca Al Olivine (Mg,Fe)2SiO4 25,37 18,32 14,57 6,5-7,0 Forsterite Mg2SiO4 34,55 19,96 7,0 Enstatite Mg2Si2O6 24,21 27,98 5,0-6,0 Augite (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6 9,26 22,58 4,73 15,26 4,57 5,5-6,0 Lizardite Mg3Si2O5(OH)4 26,31 20,27 2,5 Crushing operation was the first stage of comminution. Sample was crushed using a laboratory type jaw crusher down to -1cm. Effect of crushing on preconcentration in certain size fractions was evaluated by chemical analysis and LOI tests (Table 3, Figure 2). Survey of (Table 3) pointed out that chemical composition of the fractions of classified sample did almost not differ from each other. Moreover, preconcentration of lizardite was not observed except the sharp increase in LOI value at finer sizes. Significantly high LOI value at the -38 µm fraction indicates selective comminution and lizardite accumulation at finer sizes. But, amount of this fraction left at negligible rate, and removal of it

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does almost not change the LOI value of coarse fraction. Then, this fraction was not separated from rod mill feed. Table 3: Chemical analysis jaw crusher product at fractions Size fraction Weight MgO µm % % +1180 77.17 48.06 -1180+212 11.76 46.31 -212+75 5.70 47.24 -75+38 4.25 47.79 -38 1.12 47.70

of classified certain size SiO2 % 39.63 38.52 38.32 38.45 38.73

Fe2O3 % 8.81 8.87 9.31 9.32 8.38

Grinding process was applied to obtain -212 µm size product. Prior to grinding,

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

finely sized fraction (-212 µm) of crusher sample was removed from mill feed by sieving to avoid over-grinding. Classification of ground olivine was performed by using test sieves at coarse sizes (+38 µm), and by applying gravity sedimentation method at fine sizes (-38 µm). (Table 4) shows the results of size analysis of ground olivine: about 20% of sample was at -38 µm, and 80% at -121 µm. LOI values given in the table pointed out that selective grinding occurred and, serpentinized portion of sample concentrated at -38 µm size fraction [Jasieniak and Smart, 2010; King, 2009]. LOI value of the -53+38 µm size fraction does not satisfy the specification for metallurgical applications, which is higher than 1%. On the other hand, the +38 µm size ground olivine was found to meet the LOI specifications whereas fine fraction (-38 µm) has significantly high crystal water.

particle size of the ground olivine. But, interesting situation was that the intensity rates of these two peaks increased at finer sizes. This result was attributed to the increase in LOI values at finer sizes, and therefore increases in the concentration of serpentinized-soft altered minerals in the finely sized fractions. Table 4. Size analysis of rod mill product, and LOI data Size CO* Weight CO* LOI fraction LOI % % % µm % 212+150 10.36 10.36 1.03 1.03 150+106 16.58 26.94 0.86 0.93 -106+75 18.37 45.31 0.84 0.89 -75+53 15.6 60.91 0.92 0.90 -53+38 18.82 79.73 1.20 0.97 -38+20 18.86 98.59 3.09 1.38 -20+5 1.18 99.77 4.56 1.41 -5 0.23 100.00 7.20 1.43 *: Cumulative Oversize

Figure 2. Variation of LOI of jaw crusher product with size distribution XRD patterns were also recorded to clarify the effect of hardness on the grindability of Köyceğiz olivines (Figure 3). As compared with the XRD pattern of raw olivine sample (Figure 1), variation at 12.04° 2θ became apparent (Figure 3). This peak belongs to lizardite [Whittaker and Zussman, 1956]. On the other hand, one of the easily detectable olivine peaks is at 36.44° 2θ. Intensity of this peak did not change noticeably depending on the

Figure 3. XRD patterns of high LOI value-finely sized ground olivine samples

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classified at (a) -38+20 µm, (b) -20+5 µm and (c) -5 µm size fractions Chemical analysis of each size fraction of the ground ore sample exhibited similar results. Data given in (Table 5) does not deviate noticeably from each other for SiO2 and MgO. Only a negligible increase in Fe2O3 content was observed in finely sized fractions. Fe content of classified rod mill product depends on the grade of olivine and augite. Hardnesses of these minerals are much closer to each other. Then, selective grinding of augite is not expected, and negligible increase in Fe2O3 content at finer sizes was not taken into consideration. Ca and Al grades of classified fractions did also verify this finding. Such a negligible variation was related with the fundamental principle of comminution: breakage rate of relatively weaker material increases. [Tong et al., 2013; Velázquez et al., 2008]. LOI value of each fraction was evaluated in relation to the hardnesses of minerals constituting the ore (Table 2): hardness of lizardite is 2.5 while olivine and pyroxene minerals have a hardness value between 5-7 [Acar, 2003; Davis, 1977; King, 2009]. Therefore, grade of lizardite increased at finer sizes as a result of reasonable difference between their hardnesses. Experimental works revealed that preconcentration of olivine is possible at coarser sizes by separating the lizardite-rich fine fraction (-38 µm) (Table 6). Although this work does not cause any significant chemical differentiation between coarse and fine fractions, significant variation in LOI data was observed.

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Table 5. Chemical composition of classified rod-mill product Size Weight MgO SiO2 Fe2O3 fraction % % % % µm -212+150 10.36 47.67 41.01 7.47 -150+106 16.58 47.68 38.90 9.63 -106+75 18.37 47.45 39.93 8.50 -75+53 15.60 48.73 39.12 8.55 -53+38 18.82 48.06 39.20 8.79 -38+20 18.86 47.41 38.63 9.62 -20+5 1.18 45.45 40.16 9.14 -5 0.23 47.00 39.61 9.75 4. CONCLUSIONS Preconcentration of Muğla/Köyceğiz olivines was investigated by comminution. Chemical and mineralogical characterization of the olivine sample revealed that the sample contained hard (olivine, forsterite, enstatite, augite) and soft (lizardite) minerals. Grade of lizardite was a measure of LOI while Fe content of the sample depended on the grades of olivine and augite. It was stated by comminutionclassification works that lizardite liberates selectively at finer sizes, and an olivine preconcentrate having low LOI could be obtained by classifying ground olivine ore. Significant Fe accumulation in the ground-classified products was not observed. End product satisfying specifications of chemical composition for industrial consumption areas could not be obtained by comminution due to closer hardnesses of enstatite, augite, forsterite and olivine minerals.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Table 6. Oxide analysis and LOI values of raw and ground-classified olivine samples Oxide, % Size fraction LOI µm % MgO SiO2 Fe2O3 Al2O3 CaO Feed 47.79 39.36 8.87 1.49 1.69 1.43 -212+38 47.86 39.30 8.94 1.47 1.65 0.97 -38 47.51 39.64 8.57 1.57 1.86 3.22 Acknowledgements: The authors acknowledge the grant (Project No: 2013/55) provided by Muğla Sıtkı Koçman University Scientific Projects Unit. REFERENCES Acar, B., 2003. Olivinin Sanayiye Yönelik Kullanım Özelliklerinin Tespiti: Çayırbağı (Konya) ve Kızıldağ (Akseki) Olivinleri. Yüksek Lisans Tezi, Selçuk Üniversitesi Fen Bilimleri Enstitüsü, Konya. Davis, E.G., 1977. Beneficiation of Olivine Foundry Sand by Differential Attrition Grinding, US Patent No.4039625, 5 p. Cho, H. and Luckie, P.T., 1995. Investigation of the Brakage Properties of Components in Mixtures Ground in a Batch Ball-and-Race Mill, Energy and Fuels, 9, 53. Facer, R.A., 2007. Industrial Mineral Opportunities in New South Wales. Geological Survey of New South Wales, Bulletin 33. Güney, A. and Atak, S., 1997. Separation of Chromite from Olivine by Anionic Collectors. Physicochemical Problems of Mineral Processing, 31, 99. Gürtekin, G. and Albayrak, M., 2006. Antigoritin Isıl Reaksiyonu: XRD, DTA-TG Çalışması, MTA Dergisi, 133, 37. Jasieniak, M. and Smart, R.C., 2010. Surface Chemical Mechanisms of Inadvertent Recovery of Chromite in UG2 Ore Flotation: Residual Layer Identification Using Statistical ToF-SIMS Analysis, International Journal of Mineral Processing, 94, 72. Jolsterå, R., 2010. Reactions at the Water-Mineral Interface of Olivine and Silicate Modified Maghemite, Luleå University of Technology, 53 p. King, R.J., 2009. Olivine Group, Geology Today, 25(5), 193. Kleiv, R.A. and Thorhnhill, M., 2011. Dry Magnetic Separation of Olivine Sand. Physicochemical Problems of Mineral Processing, 47, 213.

Krivolutskaya, N.A. and Bryanchaninova, N.I., 2011. Olivines of Igneous Rocks. Russian Journal of General Chemistry, 81(6), 1302. Örgün, Y. and Erarslan, C., 2012. 21. Yüzyılda Olivin ve Türkiye’nin Olivin Potansiyeli, Madencilik Türkiye, June, 62. Tong, L., Klein, B., Zanin, M., Quast, K., Skinner, W., Addai-Mensah, J. and Robinson, D., 2013. Stirred Milling Kinetics of Siliceous Goethitic Nickel Laterite for Selective Comminution, Minerals Engineering, 49, 109. Velázquez, A.L.C., Menéndez-Aguado, J.M., and Brown, R.L., 2008. Grindability of Lateritic Nickel Ores in Cuba. Powder Technology 182(1), 113. Wells, W.G., 1959. Olivine Uses and Beneficiation Methods. NCSU Mineral Research Laboratory Bulletin, 1(2), 1. Whittaker, E.J.W. and Zussman, J., 1956. The Characterization of Serpentine Minerals by X-Ray Diffraction, Mineralogical Magazine, 31, 107. www.mindat.org www.webmineral.com

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

PREPARATION OF STRONTIUM HEXAFERRITE POWDERS USING SrSO4 AND Fe3O4 Abdullah Obut1,a 1. Hacettepe University, Mining Engineering Department, Ankara, Turkey a. Corresponding author ([email protected])

ABSTRACT: In this study, the interaction between strontium sulphate and iron(II,III) oxide under conventional and microwave heating were investigated by X-ray diffraction/infrared analyses and magnetic measurements at Fe/Sr mole ratios of 11 and 8 in the absence and presence of sodium carbonate additive, considering the preparation of strontium hexaferrite powders. X-ray diffraction analyses showed that higher amounts of strontium hexaferrite formed by microwave heating with respect to conventional heating in the absence of sodium carbonate at both Fe/Sr mole ratios. On the other hand, in the presence of sodium carbonate, strontium hexaferrite phase was formed at both Fe/Sr mole ratios for both heating processes due to the reaction promoting effect of sodium carbonate. Magnetic measurements showed that wide coercivity values were obtained for the studied experimental conditions, and a coercivity value of 284 Oe was obtained by microwave heating at Fe/Sr mole ratio of 11 and a coercivity value of 2420 Oe was obtained by conventional heating at Fe/Sr mole ratio of 8. 1. INTRODUCTION Celestine (natural SrSO4) and strontianite (natural SrCO3) are the most important strontium minerals and only celestine is commercially mined for the production of strontium carbonate using double decomposition and black ash processes. Strontium carbonate is used in the production of glasses, in pyrotechnics, in paints, in the production of other strontium compounds, in medicine, in metallurgy and in the production of ceramic ferrite magnets [Griffiths, 1985; Hong, 1993]. Strontium iron oxides (SrFe12O19, SrFe2O4, Sr2Fe2O5 etc.) show a range of different structures/properties and in particular M-type strontium hexaferrite (SrFe12O19) is a permanent hard magnetic material and is widely used in high density recording media, in microwave devices, in motors, in loudspeakers and in other equipment due to its appropriate magnetic properties, good thermal durability, chemical stability, lower processing cost and wide availability of

the raw materials [Griffiths, 1992; Senzaki et al., 1995; Sharma et al., 2005; Rakshit et al., 2007]. In the related literature, there are several different routes, single or combinations, such as molten-flux, spray pyrolysis, glassceramic, crystallization, hydrothermal, combustion, microwave, sonochemical, sol-gel, mechanochemical, hightemperature solid-state reaction etc. for the preparation of SrFe12O19 using different initial strontium and iron compounds with or without additives. But, there are only few papers in the related literature about the preparation of strontium hexaferrite using celestine or reagent grade SrSO4 as the initial strontium source. Tombs [1974] and Mozaffari and Amighian [2002] used celestine + Na2CO3 + Fe2O3 mixture, and Routil and Barham [1969] used reagent grade SrSO4 + Na2CO3 + Fe2O3 mixture for the preparation of SrFe12O19 by conventional heating. On the other hand, Tiwary et al. [2008] used celestine + Na2CO3 + iron ore mixture for the 787

synthesis of strontium hexaferrite by mechanochemical route. Guo et al. [1997] used both reagent grade SrSO4 and celestine + Fe2O3 for SrFe12O19 synthesis by the use of conventional heating, Cochardt [1963] used complex strontium carbonate/sulphate (prepared from celestine) + Fe2O3 for the preparation of strontium hexaferrite by conventional heating, Fujita et al. [1993] used strontium carbonate (manufactured from celestine) + hematite for the synthesis of SrFe12O19 by conventional heating and Hessien et al. [2009] used SrS (obtained from celestine) + FeCl3·6H2O for SrFe12O19 formation by co-precipitation followed by conventional heating. In this study, considering the strong interaction of Fe3O4 with microwaves [Haque, 1999; Rao et al., 1999], SrFe12O19 formation conditions were investigated at Fe/Sr mole ratios of 11 and 8 using SrSO4 and Fe3O4 compounds under conventional and microwave heating in the absence and presence of sodium carbonate additive by mainly Xray diffraction (XRD) analyses. The infrared (FT-IR) spectra and magnetic properties of prepared SrFe12O19 powders were also determined. In one experiment, celestine was also directly used for comparison purposes. 2. EXPERIMENTAL 2.1. Materials In the experimental studies, reagent grade SrSO4 and reagent grade Fe3O4 were used as initial Sr and Fe sources, respectively. Reagent grade Na2CO3 was also used in selected experiments as an additive. XRD patterns of the initial Sr and Fe compounds (Figure 1) are well-matched with JCPDF No: 5-0593 (SrSO4, celestine) and JCPDF No: 19-0629 (Fe2+Fe3+2O4, magnetite), respectively. The maximum particle sizes of SrSO4

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and Fe3O4 powders were found as 30 μm and 5 μm, respectively.

Figure 1: XRD patterns of the initial compounds. 2.2. Methods The flowsheet given in Figure 2 was followed for the preparation of SrFe12O19 powders.

Figure 2: The experimental flowsheet. Firstly, initial homogeneous solid powder mixtures at Fe/Sr mole ratios of 11 and 8 were prepared in the absence and presence of sodium carbonate by hand mixing of calculated amounts of reactants in a mortar, and then the prepared mixtures were heated separately in a

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

conventional muffle furnace for 30 min at 1200°C and in a commercial microwave oven (power: 900 W, frequency: 2450 MHz) for 5 min at 100% power and immediately followed for 25 min at 50% power (total 30 min). After conventional (C) and microwave (MW) heating, the samples were hand ground in a mortar, leached in 1 M aqueous HCl solution for 2 min to remove residual salts, vacuum filtered, washed with distilled water on filter paper and finally dried at 105°C for 2 h. Then, the obtained powders were characterized by XRD (Rigaku, CuKα) analyses. FT-IR (Perkin-Elmer) spectra and magnetic properties (Quantum Design) of the powders were also determined for comparison purposes. 3. RESULTS AND DISCUSSION 3.1. XRD Analyses XRD patterns of the powders prepared at Fe/Sr mole ratio of 11 under conventional and microwave heating in the absence and presence of additive sodium carbonate were given in Figure 3.

Figure 3: XRD patterns of powders prepared at Fe/Sr mole ratio of 11. a)11-

C, b)11-MW, c)11-C-CO3, d)11-MW-CO3 and e)SrFe12O19 (JCPDF No: 33-1340). In the absence of sodium carbonate, the amount of formed SrFe12O19 is higher for the mixtures heated under microwave radiation (Figure 3b) than the mixtures heated conventionally in a muffle furnace (Figure 3a) as seen from the peaks at 2θ=32.4°, 34.2°, 37.2° and 40.4° belonging to SrFe12O19 and the peak at 2θ=33.2° belonging to Fe2O3. In XRD pattern of the powder prepared by conventional heating at Fe/Sr mole ratio of 11 in the absence of sodium carbonate (Figure 3a), iron(III) oxide (Fe2O3, JCPDF No: 33-0664) was observed to be the main phase, and SrSO4 and SrFe12O19 were observed as the minor phases. On the other hand, in the presence of additive sodium carbonate, the situation for SrFe12O19 formation is completely different due to the reaction promoting effect of sodium carbonate, which melts and fluxes inital mixture to promote SrFe12O19 formation [Tombs, 1974; Guo et al., 1997]. In the presence of sodium carbonate, for both kind of heating processes, SrFe12O19 is the only phase formed (Figure 3c-d) without Fe2O3 impurity. Although the peak positions and intensities were well-matched with the JCPDF No: 33-1340 for both powders, only three peak intensities indicated with “x” in Figure 3d (sample prepared under microwave radiation) at 2θ=23.2°, 31.1° and 55.9° differ from the intensities given in JCPDF No: 33-1340 (Figure 3e). XRD patterns (Figure 4) of the powders prepared at Fe/Sr mole ratio of 11 under microwave heating in the presence of additive sodium carbonate using celestine (maximum particle size is 75 μm) showed that other than reagent grade SrSO4, SrFe12O19 can also be prepared from natural celestine using microwave heating.

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Figure 4: XRD patterns of powders prepared at Fe/Sr mole ratio of 11 using celestine. a)11-MW-CO3 and b)SrFe12O19 (JCPDF No: 33-1340). XRD patterns of the powders prepared at Fe/Sr mole ratio of 8 under conventional and microwave heating in the absence and presence of sodium carbonate were given in Figure 5.

expected from the reaction stoichiometry, was the presence of higher intensity peaks of unreacted SrSO4. In the presence of sodium carbonate, again SrFe12O19 is the main phase formed and again peaks indicated with “x” were also observed in XRD diffraction pattern of the powder prepared at mole ratio of 8 under microwave radiation (Figure 5d), but at smaller intensities with respect to the same peaks observed in Figure 3d. 3.2. FT-IR Analyses The FT-IR spectra of powders prepared at different Fe/Sr mole ratios under conventional and microwave heating in the presence of sodium carbonate were given in Figure 6. The main peaks at 444456 cm-1, 552-554 cm-1 and 615-618 cm-1 are belong to SrFe12O19 as given in the related literature [Fang et al., 2000; Garcia et al., 2001; Sivakumar et al., 2004]. The peaks at 1448 cm-1 and 865 cm-1 shown in the spectrum of powder 8MW-CO3 are belong to SrCO3 (see also Figure 5d) [Adler and Kerr, 1963; Gadsden, 1975], which were probably formed during synthesis and/or handling before analysis.

Figure 5: XRD patterns of powders prepared at Fe/Sr mole ratio of 8. a)8-C, b)8-MW, c)8-C-CO3, d)8-MW-CO3 and e)SrFe12O19 (JCPDF No: 33-1340). In the absence of sodium carbonate, nearly same XRD patterns obtained for powders prepared at Fe/Sr mole ratio of 8 with respect to Fe/Sr mole ratio of 11 (compare Figure 3a-b with Figure 5a-b). The only observable difference, as 790

Figure 6: FT-IR spectra of a)11-C-CO3, b)8-C-CO3, c)11-MW-CO3 and d)8-MWCO3 powders. 3.3. Magnetic Properties The values of some of the magnetic properties and the magnetic hysteresis

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

loops of SrFe12O19 powders prepared in the presence of Na2CO3 were given in Table 1 and Figure 7, respectively. In the related literature, the saturation magnetization values of 74.3-92.6 emu/g have been reported for single crystal SrFe12O19 and the maximum coercivity value of ~6700 Oe (theoretical limit 7500 Oe [Chen and Chen, 2002; Sivakumar et al., 2004]) has been reported, but for polycrystalline samples, these high values were rarely approached [Hessien et al., 2008; Li and Xu, 2011]. Table 1: Magnetic properties of prepared SrFe12O19 powders. Sample 11-C-CO3 8-C-CO3 11-MW-CO3 8-MW-CO3

Max. magn. at 15 kOe (emu/g) 57.4 52.4 60.5 52.5

Rem. Coercivity magn. (Oe) (emu/g) 37.6 30.3 22.7 10.9

664 2420 284 277

Figure 7: Magnetic hysteresis loops of SrFe12O19 powders. The prepared SrFe12O19 powders have different maximum magnetization and wide coercivity values due to the differences in the preparation conditions, which create differences in purity, crystallinity, grain size and morphology [Chen and Chen, 2002; Hessien et al., 2008; Li and Xu, 2011]. Maximum magnetization values (52-60 emu/g at 15 kOe) of prepared samples are comparable

to those observed in other methods of preparations [Chen and Chen, 2001; Brito et al., 2006]. Higher coercivity and remanent magnetization values were obtained for the powders heated conventionally in a muffle furnace with respect to the powders heated under microwave radiation. Highest coercivity value (2420 Oe) obtained for the powders prepared in the presence of Na2CO3 at Fe/Sr mole ratio of 8 under conventional heating, for which the maximum magnetization, remanent magnetization and squareness ratio values are 52.4 emu/g, 30.3 emu/g and 0.578, respectively. 4. CONCLUSIONS In this study, the interaction between SrSO4 and Fe3O4 compounds under conventional and microwave heating were investigated in the absence and presence of Na2CO3 at Fe/Sr mole ratios of 11 and 8. In the absence of Na2CO3, higher amounts of SrFe12O19 phase was obtained by microwave heating when compared to conventional heating, where Fe2O3 was the main phase observed. In the presence of Na2CO3, SrFe12O19 powders prepared without formation of unwanted secondary Fe2O3 phase at both Fe/Sr mole ratios and for both kind of heating processes. Due to the differences in preparation conditions, synthesized SrFe12O19 powders have different maximum magnetization (52-60 emu/g at 15 kOe) and wide coercivity (277-2420 Oe) values. Acknowledgements: The author wishes to acknowledge Prof. Dr. Abidin Temel and Prof. Dr. Şadan Özcan, both from Hacettepe Univ., for their help during experimental work. REFERENCES Adler, H.H. and Kerr, P.F., 1963. Infrared absorption frequency trends for anhydrous normal carbonates, The American Mineralogist, 48, 124.

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Brito, P.C.A., Gomes, R.F., Duque, J.G.S., and Macêdo, M.A., 2006. SrFe12O19 prepared by the proteic sol-gel process, Physica B, 384, 91. Chen D.-H. and Chen, Y.-Y., 2001. Synthesis of strontium ferrite ultrafine particles using microemulsion processing, Journal of Colloid and Interface Science, 236, 41. Chen D.-H. and Chen, Y.-Y., 2002. Synthesis of strontium ferrite nanoparticles by coprecipitation in the presence of polyacrylic acid, Materials Research Bulletin, 37, 801. Cochardt, A.W., 1963. Ferrite Magnets, US Patent 3113927. Fang, J., Wang, J., Gan, L.-M., Ng, S.-C., Ding, J. and Liu, X., 2000. Fine strontium ferrite powders from an ethanol - based microemulsion, Journal of the American Ceramic Society, 83, 1049. Fujita, T., Ito, T. and Mayima, M., 1993. Wet blending of strontium carbonate and hematite particles for preparation of strontium ferrite magnet, International Journal of the Society of Materials Engineering for Resources, 1, 76. Gadsden, J.A., 1975. Infrared Spectra of Minerals and Related Inorganic Compounds, Butterworths. Garcia, R.M., Ruiz, E.R. and Rams, E.E., 2001. Structural characterization of low temperature synthesized SrFe12O19, Materials Letters, 50, 183. Griffiths, J., 1985. Celestite, Industrial Minerals November, 21. Griffiths, J., 1992. Celestite & strontium chemical trade, Industrial Minerals, October, 21. Guo, Z.-B., Ding, W.-P., Zhong, W., Zhang, J.-R. and Du, Y.-W., 1997. Preparation and magnetic properties of SrFe12O19 particles prepared by the salt - melt method, Journal of Magnetism and Magnetic Materials, 175, 333. Haque, K., 1999. Microwave energy for mineral treatment processes - a brief review, International Journal of Mineral Processing, 57, 1. Hessien, M.M., Rashad, M.M. and El-Barawy, K., 2008. Controlling the composition and magnetic properties of strontium hexaferrite synthesized by co-precipitation method, Journal of Magnetism and Magnetic Materials, 320, 336. Hessien, M.M., Rashad, M.M., Hassan, M.S. and El-Barawy, K., 2009. Synthesis and magnetic properties of strontium hexaferrite from celestite ore, Journal of Alloys and Compounds, 476, 373. Hong, W., 1993. Celestite & Strontianite, Industrial Minerals, June, 55.

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Li,

C.-J. and Xu, G.-R., 2011. Template preparation of strontium hexaferrite (SrFe12O19) micro/ nanostructures: Characterization, synthesis mechanism and magnetic properties, Materials Research Bulletin, 46, 119. Mozaffari, M. and Amighian, J., 2002. Direct use of celestite to prepare presintered SrFe12O19 powders, Physica B, 321, 45. Rakshit, S.K., Parida, S.C., Dash, S., Singh, Z., Sen, B.K. and Venugopal, V., 2007. Thermodynamic studies on SrFe12O19(s), SrFe2O4(s), Sr2Fe2O5(s) and Sr3Fe2O6(s), Journal of Solid State Chemistry, 180, 523. Rao, K.J., Vaidhyanathan, B., Ganguli, M. and Ramakrishnan, P.A., 1999. Synthesis of inorganic solids using microwaves, Chemistry of Materials, 11, 882. Routil, R.J. and Barham, D., 1969. Preparation of ferrimagnetic barium- and strontium- iron oxides, BaFe12O19 and SrFe12O19, Canadian Journal of Chemistry, 47, 3919. Senzaki, Y., Caruso, J., Hampden-Smith, M.J., Kodas, T.T. and Wang, L.-M., 1995. Preparation of strontium ferrite particles by spray pyrolysis, Journal of the American Ceramic Society, 78, 2973. Sharma, P., Verma, A., Sidhu, R.K. and Pandey, O.P., 2005. Process parameter selection for strontium ferrite sintered magnets using Taguchi L9 orthogonal design, Journal of Materials Processing Technology, 168, 147. Sivakumar, M., Gedanken, A., Zhong, W., Du, Y.W., Bhattacharya, D., Yeshurun, Y. and Felner, I., 2004. Nanophase formation of strontium hexaferrite fine powder by the sonochemical method using Fe(CO)5, Journal of Magnetism and Magnetic Materials, 268, 95. Tiwary, R.K., Narayan, S.P. and Pandey, O.P., 2008. Preparation of strontium hexaferrite magnets from celestite and blue dust by mechanochemical route, Journal of Mining and Metallurgy B, 44, 91. Tombs, T.L., 1974. Method of Manufacturing Ceramic Magnets Containing Strontium or Barium Ferrite, US Patent 3804767.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

THE RECYCLING AND OPTIMUM USE OF WALL TILE WASTES IN THE PRODUCTION OF CERAMIC BODY Kağan Kayacı1, Yıldız Yıldırım1, Ali Altıntaş1, Mert Kılıç1, Emrah Durgut1, Çiğdem Yiğit Pala1 and Hasan Ergin2a 1. Kaleseramik Inc., R&D Center, Çan Çanakkale, Turkey 2. Mining Engineering/Faculty of Mines, Istanbul Technical University, Turkey a. Corresponding author ([email protected])

ABSTRACT: In ceramic production, the cracked or broken tile, which are not accepted as commercial products, are around 5-8 % of total products. There are some attempts to utilize these waste materials by adding to the recipes. Currently, these wastes can only be used partly as raw materials in ceramic factories. Therefore, the huge amount of fired tiles accumulated near factories and subject to environmental problem. The aim of this work is to search the higher rate of the use in economic and technically feasible way. This paper illustrates the optimum use of wall tile waste in the production of ceramic body. The characterizations of sintered wall tile wastes were carried out by using XRF and XRD. Then the optimum grinding condition was sought by using fully instrumented laboratory ball mill. The wall tile waste is ground to the finesses of 2,0 % residue of 63 micron sieve. The ground powder was added by 10,15,20,25 and 30 % to the recipes of ceramic body composition. XRD and dilatometer, color values, water absorption and shrinkage of sintered bodies were determined. It has been concluded that the optimum use of wall tile waste can be as high as 15 % without any problem provided that readjusting the body composition especially the clay component. The use of larger amount of sintered tile waste avoids the environmental problems and considerably reduced to the production costs of raw materials. Additionally, the use of tile wastes in ceramic production provides a more stable structure as the phase transitions of tile waste was already completed. 1. INTRODUCTION Economic and demographic growth demands increasingly high indices of industrial activity, which implies two major environmental problems. Firstly, it ultimately feeds on natural nonrenewable resources that are becoming scarce and will be sooner or later depleted. Secondly, it produces increasing amounts of waste materials, which are more and more difficult to dispose [Menezes at al., 2008; Segadaes, 2006]. Millions of tons of inorganic wastes are produced every day in the world [Menezes at al., 2008]. Generally, a large part of these wastes are not recycled and the storage causes the problems in terms of the economic aspect

and the environmental pollution. Inevitably, the use of product waste gives an advantage that may provide the manufacturer a highly competitive position in the market due to economic issues involved and the opportunity of marketing products particularly emphasizing on the ecological aspect. In this way, some investigation was made to the use of the industrial waste in ceramic tile formulations [Junkes at al., 2011]. The use of granite sawing wastes in the production of ceramic bricks and tiles were also investigated [Menezes at al., 2005]. The possibility of the use of mining wastes in the production of the glasses and glass–ceramics was studied

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by some researchers [Marabini at al., 1998]. The use of granite waste, granite sawing waste and fly ashes in the production of different types of ceramic were also investigated [Hernandez at al., 2001;Vieira at al., 2004;Monteiro at al., 2004]. The ceramic industry generates a large amount of sintered tile waste which cause environmental problem. The ceramic body is prepared by using raw materials in different ratios of feldspar, kaolin and clay. The granules are produced by milling, mixing, and spray drying process. Then, it is subjected to the processes of forming, drying, bring aesthetic and finally sintering. The body which is exposed to sintering process undergoes serious changes. The sintered ceramic body has the general features as follow;  It is an inert material which completed its phase formation (mullite, anorthite, etc.),  Density of material increased due to grain growth,  Material formed a more stable structure,  Material completely lost plasticity and flow characteristics.  For these reasons, the use of sintered tile waste in body recipes will make positive changes in technical values of ceramic products. As the material has completed forming of phases, it will become more stable structure. Kaleseramik Inc. is one of the biggest ceramic tile producers in the world. The sintered tile waste continually forms because of the providing 100 % quality about the manufacture of ceramic tile. Around 21000 tons of sintered wall tile waste per year is generated in the

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Kaleseramik Factories. The aim of this research is to assess to the use of sintered wall tile waste and the determination of optimum usage rate in the production of ceramic body. 2. MATERIALS AND METHOD 2.1. Material Characterization Firstly, the currently used process for wall tiles starts with crushing-screening unit. At that part, the aim is to prepare raw materials, such as siliceous kaolin, calcite and wall tile wastes for wet grinding feed down to 1 cm particle size. In addition, clay materials are prepared at a homogenizing process plant. Secondly, the crushed raw materials and wall tile wastes are transported to silos for wet grinding in ball mills. On the other hand, clay materials are dissolved to remove from such impurities in a blunger system. These two slurries are homogenized in a mixing pool at ordered ratio and the bulk density of the final slip is 1642 g/L for wall tile. The mixing ceramic slurry is separated from iron impurities in a wet magnetic separator and sieved on a vibrating screen. The final ceramic slip is pumped to spray dryer, where ceramic granule is produced. The flow chart of the currently used process is shown in (Figure 1).

Figure 1: Currently used wall tile granule preparation system. In this research, the uses of conventional ceramic raw materials together with

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

different amount of wall tile wastes were investigated. The wall tile waste was dry ground to the finesses of 2 % residue of 63 micron sieve and the ground powder was added by 10, 15, 20, 25 and 30 % to the recipes of ceramic body composition. The chemical composition of sintered wall tile waste was obtained by XRF that was given in (Table 1). It can be observed that the wastes have high amount of SiO2 and low value of loss on ignition that shows the reaction of gas evolution finished. Table 1: Chemical composition of the sintered wall tile waste. LOIa SiO2 Al2O3 TiO2 Fe2O3 0.57 63.91 20.95 0.78 1.62 CaO MgO Na2O K2O 8.67 0.71 0.74 2.08 a: Loss of Ignition

These wastes were also analyzed by XRay diffraction to characterize the mineralogical structures. (Figure 2) shows the X-Ray Diffraction patterns of the sintered wall tile waste. The diffraction patterns of the sintered wall tile waste gives the peaks of quartz, anorthite, gehlenite and wollastonite as seen in (Figure 2).

Figure 2: X-ray diffraction patterns of the sintered wall tile waste.

2.2. Methods and Technological Tests Technological tests of wall tile wastes were also carried out to investigate the sintering behaviors. After applying the size reduction, weathering applied to reach the 6 % moisture in sample. Then, the sample was sieved through 1 mm sieve hence the granules were obtained in laboratory. The granules were pressed to having 5 cm diameter tablets at 325 kg/cm2. After that, the tablets were dried and sintered in the conditions of wall tile production that is at 1150°C, 36 minutes. After thermal treatments, the water absorption of the samples (according to the ISO 10545-3), linear shrinkage that is the difference in the length of the test specimen before and after firing (according to the ISO 10545-2) and color values were measured. Sintering behavior of the wastes was determined by sintering in the conditions of wall tile sintering conditions. The result is given in (Table 2). Table 2: Technological properties of wall tile wastes. Max. Sintering Temp. 1150 (°C) Furnace Cycle 36 (min.) Linear Shrinkage 4.47 (%) Water Absorption 15.98 (%) L 73.24 Color a 6.76 b 17.72 The similar tests were applied to the original slurry of wall tile mixture that was prepared without addition of sintered wall tile waste. Then, the body compositions were obtained by adding 10, 15, 20, 25 and 30 % of dry ground sintered wall tile waste. The slips were dried 12 hours in an oven at 110 ◦C to obtain powders suitable for shaping and breaking tests. The test specimens were 795

prepared by adding 6 % water to the dried powders in form of disk. It is followed by pressing at 325 kg/cm2. Then, the tablets dried and sintered in the conditions of wall tile at 1150, 36 minutes for investigating technological properties. The firing behavior of the materials has been studied by evaluating the water absorption, linear shrinkage and color values. The densities of slurries were determined by using a picnometer. Dilatometer was used to measure thermal expansion of sintered tablets by the heating rate of 10 °C/min till 750 °C. 3. RESULTS AND DISCUSSION 3.1. Process Parameters The different recipes prepared using different ratios of ground floor tile waste and other components as are shown in (Table 3). Table 3: The recipes of wall tile by the additions of dry ground wall tile waste (%). Dry Siliceous ground Items Calcite Clay Kaolin tile waste STD 13,5 57 36 0 W10% 13,5 49 36 10 W15% 13,5 49 36 15 W20% 13,5 49 36 20 W25% 13,5 49 36 25 W30% 13,5 49 36 30

The density and flow time of wall tile recipes which were prepared by adding different ratio of sintered wall tile waste and original body were given in (Figure 3). It is observed that the recipe prepared by addition of 15 % sintered floor tile waste has the suitable flow time value with the original one in (Figure 3). Density of W % 15 is 1745 g/lt and its flow time value is 35 second while the

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density and flow time values of original recipe are 1642 g/lt and 20 second respectively. The 35 second of flow time value is a suitable value for the process. 3.2. Product Parameters Changes of water absorption and linear shrinkage of the recipes prepared by the addition of waste and original recipe for wall tile were given (Figure 4). 17.45% water absorption and 0.32% linear shrinkage were found on the original wall tile body while 15% sintered wall tile waste body has 0.36% linear shrinkage and 16.89% water absorption values, respectively. The measured linear shrinkage and water absorption values are similar with values of the original body. The 0.36 % linear shrinkage value is suitable for the process.

Figure 3: Density and flow time changes of wall tile mixing slurry.

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

Figure 4: Linear shrinkage and water absorption changes of the original Wall tile body and recipes including waste.

Figure 5: Changes of sintered color values of the original wall tile body and bodies including waste. (Figure 5) shows the color values of wall tile bodies which were prepared by adding different ratio of sintered wall tile waste and the original body. Color values of W 15 % are L: 74.57, a: 6.93, b: 18.34 when the color values of original wall tile body are L: 75.37, a: 6.70, b: 17.64. Both recipes have the similar color values. (Figure 6) shows the X-ray diffraction patterns of the original sintered wall tile body and the sintered wall tile body contained 10%, 15%, 20%, 25% and 30% sintered tile wastes respectively. The

diffraction patterns of the original sintered wall tile body gives the peaks of quartz (SiO2), anorthite (CaAl2Si2O8), gehlenite (Ca2Al [AlSiO7]), wollastonite (CaSiO3). Also, the diffraction patterns of sintered wall tile body containing 10%, 15%, 20% wastes give the same peaks of quartz (SiO2), anorthite (CaAl2Si2O8), gehlenite (Ca2Al[AlSiO7]), wollastonite (CaSiO3). The diffraction patterns of sintered wall tile bodies containing 25% and 30% waste gave peaks of quartz (SiO2), anorthite (CaAl2Si2O8), wollastonite (CaSiO3), tridymite (SiO2), gehlenite (Ca2Al[AlSiO7]).

Figure 6: X-ray diffraction patterns of original wall tile body and sintered wall tile bodies including waste. After standard wall tile body and wall tile waste added wall tile body were sintered, the DLM analyses were also made. The results of the analysis are shown in Table 4. Thermal expansion value (α400) of original body is 67.26 x10-7K-1, the body of 15% wall tile waste added is 66.49 x10-7.K-1. It can be concluded that there is some decrement at the thermal expansion with increasing amount of sintered wall tile waste.

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Table 4: Thermal original wall tile including waste. DLM α300 (x10-7.K-1) Standard 64.8 W 10% 64.1 W 15% 63.9 W 20% 63.5 W 25% 63.6 W 30% 63.6

expansion of the recipe and recipes α400

α500

α600

67.3 66.6 66.5 66.2 66.3 66.0

70.8 70.1 70.0 69.8 69.8 69.3

81.8 80.8 80.9 80.7 80.7 79.4

The slurry densities of the compositions by the addition of the dry ground wall tile wastes provide higher slurry density than standard compositions. Therefore, the energy consumption of the spray dryer is also reduced due to the use of high slurry density. The costs of natural gas and costs of raw material in current production and at the case of 15% use of tile wastes were given in (Table 5). The optimum recipe is obtained by the use of 15% of waste according to the technological and economic criteria that is the recipe of W 15%. This recipe reduces the raw materials costs of wall tile recipe from 47.57 TL/ton to 44.83 TL/ton. Also the natural gas consumption costs of wall tile decreases from 40.23 TL/ton to 30.88 TL/ton. Table 5: Costs of natural gas and raw material in current production and at the case of 15% added tile waste. Cost of raw materials in 47.57 current production (8% wall (TL/ton) tile waste) Cost of raw materials in 44.83 the case of increased use (15% wall of tile waste (TL/ton) tile waste) The cost of natural gas in 40.23 current production (1642 g/lt) (TL/Ton) The cost of natural gas in 30.88 the case of 15% use of tile (1745 g/lt) waste (TL/ton)

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4. CONCLUSIONS In the experimental study; the slurry of original mixture of wall tile was prepared without sintered wall tile waste. Then, the body compositions were obtained by addition of dry ground sintered wall tile waste. Technological and mineralogical properties of original body and the bodies that include different amount of sintered wall tile wastes were obtained in laboratory. XRD and dilatometer analyses, color values, water absorption and shrinkage of sintered bodies were measured to compare the differences of original body and the waste added bodies. It is found that the optimum usage rate is 15% of waste for wall tile composition that is given in the recipe of W 15%. The use of waste provides substantial reduction on energy consumption and the cost of raw material supply. It also prevents the potential environmental problem caused due to the storage of the waste. Acknowledgements: This research has been done in Kaleseramik Research and Development Center that is supported by Republic of Turkey, Ministry of Science, Industry and Technology. REFERENCES Hernandez-Crespo, M. S. and Rincon, J. Ma., 2001. New porcelainized stoneware materials obtained by recycling of MSW incinerator fly ashes and granite sawing residues. Ceram. Int., 27, 713. Junkes, J.A., Carvalho, M.A., Segadães, A.M., Hotza D., 2011. Ceramic Tile Formulations from Industrial Waste. Interceram, 60. Marabini, A. M., Plescia, P., Maccari, D., Burragato, F. and Pelino, M., 1998. New materials from industrial and mining wastes: glass-ceramics and glass- and rock-woll fibre. Int. J. Miner. Process, 53, 121. Menezes, R.R., Ferreira, H. S., Neves, G. A., Lira, H. L. and Ferreira, H. C., 2005. Use of granite sawing wastes in the production of ceramic bricks and tiles. J. Eur. Ceram. Soc., 25, 1149. Menezes, R.R., Malzac Neto, H.G., Santana, L.N.L., Lira, H.L., Ferreira, H.S., Neves. G.A., 2008. Optimization of wastes content

Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

in ceramic tiles using statistical design of mixture experiments, Journal of the European Ceramic Society, 28, 3027. Monteiro, S. N., Pecanha, L. A. and Vieira, C. M. F., 2004. Reformulation of roofing tiles body with addition of granite waste from sawing operations. J. Eur. Ceram. Soc., 24, 2349. Segadaes, A.M., 2006. Use of phase diagrams to guide ceramic production from wastes. Adv. Appl. Ceram., 105, 46. Vieira, C. M. F., Soares, T. M., Sanchez, R. and Monteiro, S. N., 2004. Incorporation of granite waste in red ceramics. Mater. Sci. Eng. A, 373, 115.

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Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014

UTILIZATION OF KALECİK BENTONITE IN CASTING INDUSTRY THROUGH ACTIVATION Turan Kılınç1,a, Yakup. Cebeci2 and Mehmet S. Çelik3 1. Cumhuriyet University, Sivas, Vocational Schools, Mining Technology Program, Sivas, Turkey 2. Cumhuriyet University, Faculty of Engineering, Department of Mining Engineering,Sivas,Turkey 3. Istanbul Technical University, Faculty of Mines, Department of Mining Engineering, Istanbul, Turkey a. Corresponding author ([email protected])

ABSTRACT: Casting is one of the industrial application areas of bentonites. In this study, activation processes were investigated to improve the industrial foundry properties of Kalecik bentonite samples. In the experiments, bentonite samples taken from Çankırı district were used. Activation agent of Na2CO3 was used In different concentrations to optimize its use. The foundry properties (compactibility, wet compressive strength, dry compressive strength, splitting strength, transverse strength, wet tensile strength, gas permeability) of both raw and activated bentonites were investigated details. The foundry properties of activated bentonite were compared with those of raw bentonite. It was found that the activated bentonite showed much better foundry properties than that of raw bentonite. 1. INTRODUCTION Bentonite was suggested in 1898 by Knight for a term clay-like material with soapy properties from it is occurrence in the Fort Benton unit of Cretaceous age formation in Wyoming [Grim and Güven, 1978]. Bentonite was used in a wide range of industrial areas because it swells in water and in some organic liquid media, shows high plasticity and colloidal properties when mixed with water, exhibits high cation exchange capacity, high surface area and very good rheological properties. Activation processes for calcium or mixed bentonite are carried to improve the properties and/or appropriate properties. Various studies were conducted with Na2CO3, NaOH, Mg(OH)2, MgO, MgCl2.6H2O as activating agents to improve properties of bentonite [Szanto et al., 1967; Bleifuss, 1973; Lagaly et al., 1981; Alther, 1982; Yıldız et al., 1999; Boylu, 2013]. The most commonly used method is activation with Na2CO3. Sodium carbonate was used to improve swelling

properties and increase the viscosity. Also, Christidis (1998) stated that soda activation improves wet compressive strength and wet tensile strength and decreases permeability Mainly, the casting mold consisting of the mixture of bentonite and water are desired to protect (endurance) their shapes without becoming deformed when hot metal is spilled in it, to be with pores in a way that they will be able to provide the extraction of gases like CO2 which may occur during the casting (gas permeability) and to be removed from the metal immediately by falling into small pieces and to be easily broken after the metal gets cold [Beşün et al., 1993]. Water is added at the ratio of 1,5-8 % in the preparation of molding sand [Boylu, 2011]. The amount of water added is important in terms of the quality of casting due to the water retention quality of bentonite. For this reason, the expected utilization of bentonite is its addition in minimum amount together with

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cohesiveness at high levels and high gas permeability. This study was performed to enhance casting properties by activation of Kalecik (Çankırı) bentonite. The suitability of casting industry was investigated by various testing procedures i.e. compactability, wet and dry compressive strength, splitting strength, wet tensile strength, gas permeability on soda activation of raw bentonite samples. 2. MATERIAL AND METHOD Bentonite samples of Kalecik have been taken from the fields of bentonite companies operating in Çankırı. Chemical analysis of the raw bentonite samples used in the experiments is given in (Table 1). Table 1: Chemical analysis of Kalecik bentonite SiO2

Al2O3

Fe2O3

MgO

CaO

Na2O

K2O

LOI

(%)

(%)

(%)

(%)

(%)

(%)

(%)

(%)

53,63

13,23

5,20

2,22

7,11

2,25

1,71

14,56

2.1. Activation In this study, dry activation method was used to activate Kalecik bentonite samples. Activation is made with Na2CO3 (Merck, M=105.99 g/mol, purity of 99.9 %). The activation studies were performed at 40 % moisture similar to industrial applications. Moistening was performed by spraying water and mixing. Afterwards, Na2CO3 in powder form were added onto samples by hand mixing (respectively, by weight (dry basis) 0.5%, 1%, 2%, 3%). Activated bentonite samples were heated at ambient conditions for 15-20 days and then oven dried at 60 oC. The activated bentonite samples were ground to