LLE Experiment 2

Abstract This experiment was conducted to study the distribution coefficient of K. The separating funnel will be used for first experiment. The liquid/liquid extraction was used to carried out for second experiment.The liquid/liquid experiment allow us to demonstrate the mass bala nce and mass coefficient. In order to that, there ther e are certain formulas that will be used. The experiment These experiments required several data from the experiment like volume and concentration of titration Sodium hydroxide, flow rate of aqueous and organic phase, etc. The liquid/liquid extraction was maintained at constant flow rate for 20minutes. Then, the sample can be taken from the experiment and proceed with tit ration with sodium hydroxide. After calculated the desired based on the data, we were able to achieve the objectives of the experiment conducted. This experiment was classified as successful.

INTRODUCTION: Liquid-liquid extraction have been applied in industry started from 1930’s. This equipment have been used in industrial operation. Some of the application of liquid-liquid extraction are neutralization, purification of heat sensitive material and liquid-liquid extraction for biotechnology. In this experiment, this equipment have been used in experiment B which we need to demonstrate the mass balance that happen in the extraction column. Besides that, we also need to measure the coefficient of mass transfer with the aqueous phase as the continuous or batch medium. Liquid- liquid extraction is about transferring solute to the solvent. For experiment A, we used tit ration process to determine the distribution coefficient for the system organic solvent-Propionic Acid-Water also to show its dependence on concentration. Sodium Hydroxide also have been used when this experiment was performed. In addition, the function of liquid-liquid extraction is t o separate two immiscible the have been mixed that have unequal distribution of the component.

AIMS

The objective of experiment A is to determine the distribution coefficient for the system organic solvent –  Propionic Acid Water and to show its dependence on concentration .While experiment B is conducted for demonstrating how a mass balance is performed on the extraction column and measuring the mass transfer coefficient with the aqueous phase as the continuous medium.

Theory Experiment A The distribution coefficient, K also the defined as a ratio. The equation that have been used to determine the distribution coefficient is:

K = Concentration of solute in the extract phase Y Concentration of solute in the raffinate phase X

We assumed that the equilibrium exists between the two phase and at the low concentrations, the distribution coefficient is dependence on the concentration. Then, Y=KX. The important of K or distribution is to know the mass balance. After we know the mass balance, it is easier for us to save energy. Save energy is important in industry because it includes overall cost of  production.  Next, Titration process have been used in experiment A. First of all, the solvent or in this experiment we used deionized water or demineralization water (which ions inside the water have been removed) have been mixed with Propionic acid or organic solvent which is solution in this mixture. After that, the mixture have been allowed to be separate into two  parts which are, the raffinate phase and extract phase. Furthermore, the organic solvent with a trace of propionic acid will be take the raffinate phase, while water and propionic acid will be the extract phase. Experiment B There are all the equation involve to get the mass transfer coefficient. First of all, let: Vw = Water flow rate (l/ s) Vo = Organic solvent flow rate (l/s) X = Propionic Acid concentration in the organic phase (kg/l) Y = Propionic Acid concentration in the aqueous phase (kg/l) 1 =

Top of column

2 =

Bottom of column

Then, the mass balance: Vo (X1-X2) = Propionic Acid that have been extracted from the organic phase or raffinate  phase. Vw (Y1-0) = Propionic Acid that extracted from the aqueous phase which is extract phase. Thus, Vo (X1-X2) = Vw (Y1-0)

 Next is the equation of extraction efficiency:

Mass transfer coefficient (based on the raffinate phase) =

Rate of acid transfer (Volume of Packing)(mean driving force)

Then, log mean driving force =  x1   x 2

ln

 x1  x 2

Where, ∆x1 = Driving force at the top of the column = (X2  –  0) ∆x2 = Driving force at the bottom of the column = (X 1 - X1*) X1* is the concentration of organic phase that could be in equilibrium with concentration Y 1 that in the aqueous phase. In addition, the value of equilibrium can be known by using the distribution coefficient that have been calculated from experiment 1.

APPARATUS EXPERIMENT A 

250ml conical stoppered flask



250ml measuring cylinder



250ml separating funnel



Pipette

MATERIALS 

Sodium hydroxide solution(0.1M)



Phenolphthalein



Propionic acid

EXPERIMENT B 

Liquid liquid extraction unit



Beakers



Measuring cylinders



Conical flasks



Retort stand



Burette



Separating funnel

MATERIALS 

0.1M and 0.0025M NaOH



Phenolphthalein

PROCEDURE Experiment A : 1) A mixture of 50 ml organic solvent and 50 ml deionised water was made up in a conical flask. 2) 5 ml of propionic acid was added. 3) A stopper was placed into the flask and it had been shaken for 5 minutes. 4) Then the mixture was poured into the separating funnel and it had been left for 5 minutes and the aqueous layer had been removed. 5) Then the 100 ml of the layer had been taken and being titrated against 0.1M s odium hydroxide solution using phenolphthalein as the indicator. 6) The experiment was repeated twice for initial additions for propionic acid were 3 ml and 1ml. Experiment B : 1) 100 ml of propionic acid was added into 10 litres of the organic phase.The mixture had been mixed well to ensure an even concentration.Then the organic phase feed tank was filled with the mixture, 2) The level control to the bottom of column was switched. 3) The water feed tank was filled with 15 L of clean deionised water then the water feed  pump started while the column was filled with water at high flow rate. 4) The flowrate was reduced to 0.21 L/min as the water is above the top of packing. 5) The metering pump was started and the flowrate was se t to 0.21 L/min. 6) The extraction column was ran fo 15 minutes until steady condition was achieved. 7) Then 15 ml samples from feed,raffinate and extract stream were taken. 8) Each 10 ml sample were titrated against 0.1 M sodium hydroxide solution using  phenolphthalein as the indicator.

DISCUSSION EXPERIMENT A

For the first experiment,the distribution coefficient for the system organic solvent propionic acid – water was calculated by using the formula K=Y/X,in which Y represents the concentration (M) of propionic acid in aqueous layer while X represents the concentration of  propionic acid in organic layer.Aqueous layer is the extract of the mixture and it is the  product that contains the removed material whereas the organic layer is the raffinate,the liquid streams that remains after solutes from original liquid is removed through contact with immiscible liquid.Water acts as the solvent whilst the organic solvent-propionic acid is solution to be separated into extract and raffinate phase.Water comes in contact with the solution and the propionic acid is separated from the organic solvent.10 ml of the lower aqueous layer from the experiment was obtained and was titrated with 0.1M of NaOH solution to neutralised the acid.Hence,the concentrati on of the propionic acid from the sample can be calculated.The concentration of the propionic acid (solute) is vital for the determination of the distribution coefficient (K). From the experiment,the concentration of solute(propionic acid)is greater in aqueous layer (Y) than that of in the organic layer(X).Thus,propionic acid has great miscibility with water than in the organic solvent.For example,the concentration of propionic acid in the aqueous layer for 5ml propionic acid added is 1.68 M while for the organic layer the concentration of propionic acid is less that is only 1.32 M. Distribution coefficient (K) is defined as the ratio of the amount of solutes dissolved in two immiscible liquids at equilibrium.In this experiment,water and organic solvent were used as the immiscible liquids.From the results,the distribution coefficient (K) of the  propionic acid increased when less amount of propionic acid was added into the solution.Thus,distribution

coefficient

is

dependent

on

the

acid

concentration.At

equilibrium,Y=KX is proven. EXPERIMENT B

In experiment B,the mass transfer coefficient of propionic acid at different transfer rate and driving force was determined.The experiment was conducted at constant flow rate of aqueous phase and organic phase, 0.21 L/min.Samples were taken from the feed,raffinate and extract valves of the liquid-liquid extraction unit respectively and were titrated against 0.1M

and 0.025M NaOH solution to be neutralised.Hence,the concentration of propionic acid in each samples can be determined. Results shows that the concentration of propionic acid in the raffinate phase is greater than that of in the extract phase.These results are different as we compared with the results of experiment A.In experiment A,the concentration of propionic acid is larger in the extract  phase than in the raffinate phase.Hence,we can say that liquid-liquid extraction unit has different effect on mass balance of solutes. The mass balance of propionic acid was determined by calculating the rate of  propionic acid transfer in both raffinate and extract phase.We compare the rate of propionic acid transfer by using the formula: For 0.1 M NaOH : vo ( X 1  X 2 ) 



0.0294 mol  min



V w ( y1



0)

0.0294 mol  / min

For 0.025 M NaOH :

V 0 ( X 1  X 2 ) V w ( y1 



0.0247 mol  min





0)

0.0247 mol  / min

Hence,mass balance of propionic acid in each phase is achieved. However,different rate of acid transfer gives different mass transfer coefficient value.For example,when the rate of acid transfer is 0.0294 mol/min,the mass transfer coefficient is 0.5191 kg/min while when the rate of acid transfer is 0.0247 mol/min,the mass transfer coefficient is 0.56624 kg/min.These are due to certain conditions such driving force in top and bottom columns and different concentration of acid added.

Conclusion Based on our experiment and the result. We can conclude the experiment was succeed as we were able to achieve the objectives of the experiment. For experiment A, the concentration (M) of

 propionic acid in aqueous layer, Y proportional to the concentration of propionic acid in organic layer, X. When less amount of propionic acid was added, distr ibution coefficient (K) of the propionic acid increased. Thus, prove the equation Y=KX. For experiment B, we did achieve the aims of the experiment despite the result were the same as experimental value. This was probably because the liquid/liquid extraction giv the different e ffect on mass  balance of solutes RECOMMENDATION

For this experiment , there are some precaution steps that I want to recommend . Firstly , I suggest we should wear a lab coat wit h long hand before enter the lab and while conducting the experiment. Then, the important part is we should wear a safety cap when enter the pilot plant and while conducting the experiment to prevent any head injury .Then during taking the reading for volume NaOH used for titration,we must place our eyes perpendicular to the scale reading to get ac curate reading.Lastly while conducting the experiment, we should wear a gloves and goggles to protect our hand and eyes from any hazardous and toxic substances .Besides that, do not wear contact lens while conducting the experiment because it can easily be effect by the toxic, thus can give harmful to our eye .

References: 1)

2) 3) 4) 5) 6)

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7) Immiscible Liquids(June 2012)[online]Retrieved from: http://www.newton.dep.anl.gov/askasci/chem00/chem00600.htm 8) Fundamentals of Separation Process(n.d)[online]Retrieved from: https://noppa.aalto.fi/noppa/kurssi/ke-42.3200/materiaali/KE42_3200_03_extraction.pdf 9) College Term Papers (2014) .Liquid-Liquid Extraction.Retrieved f rom: http://www.collegetermpapers.com/TermPapers/Engineering/liquid_liquid_extraction. html 10) Robbins, L. A., "Liquid-Liquid Extraction", in Perry's Chemical Engineers' Handbook, Sixth Ed., D. Green and R. H. Perr y, McGraw Hill, New York, NY, p 511, (1984) 11) Allerton, J., "Liquid Extraction in Perforated-Plate and Packed Towers." American Institute of Chemical Engineers. 39:361-384 (1943).