Water - CHEGRP5 - homechegrp5.wikispaces.com/file/view/Group+5+Final+Lab... · Web viewThe purpose of the Liquid-Liquid Extraction lab is to determine the effect of mixing and its

Liquid-Liquid Extraction University of Illinois

Liquid-Liquid Extraction

Liquid to Liquid extractors are used in industry in order to remove unwanted solutes from one stream (organic) to a more common stream like aqueous stream in order to free up the usually desired organic

stream. Usually two counter current stream flow past each other and the solute moves from one stream to the other.

Unit Operations ChE 382 Group 5 Spring 2011 2 /02/2011Damo, Duffy, Guerrero, Hsu, Kosak, Qamar, Tyska


Final Lab Report

Unit Operations II Lab 1

February 2nd, 2011

Group 5

Andrew Duffy

Daniyal Qamar

Jeff Tyska

Bernard Hsu

Ryan Kosak

Tomi Damo

Alex Guerrero



1. Summary

The purpose of the Liquid-Liquid Extraction lab is to determine the effect of mixing and its

correlation with the system’s efficiency to remove unwanted components from a mixture. The system

works off the premise that the components involved are all immiscible with one another. In this case of

this lab there are three liquids used; acetic acid, Chevron Superla White Oil, and water. The white oil and

acetic acid are mixed together in the feed tank with a 0.5 weight percent of acid to oil, which is then

mixed through the recycle system of the pump before it is sent to be mixed with the water in the first

stage. When it is properly mixed it is then sent to the first stage and allowed to interact with the water

which is flowing countercurrent to the feed of the oil-acid mix. Throughout the three stages the acetic

acid will transfer from the oil, which is the raffinate, to the extract, water in this case. Out of each stage

two samples will be taken, one of water and one of oil, and titrated with sodium hydroxide to determine

the amount of acetic acid contained in either the extract or raffinate of that stage.

There were many errors in the performance of the lab which yielded improper data. Therefore it

is very difficult to make any definite conclusions on how the speeds of the agitators affected the overall

efficiency of removing acetic acid from the white oil. The most significant error was that 94.829% of the

acetic acid was lost, and because of this fact the rest of the data cannot definitively draw any conclusions.

From data collected for the concentrations of the acetic acid found in each stage it can be seen that most

of the acid was lost between the first and second stage. In stage one the weight percent of acetic acid in

the water was 1.160e-2 and then in the second stage that dropped to 8.880e-4 and then to 1.497e-4 in the last

stage. It is recommended that covers for all of the tanks should be kept on at all times while the process is

in operation to ensure there is no loss of the acetic acid through evaporation. Another recommendation is

to understand early on how exactly the system works because it is difficult to get the countercurrent flows

to perform properly and to ensure that the mixing is successful in transferring the acetic acid.



2. Results

The objective of this lab was to remove the acetic acid in the mineral oil by transferring the acetic

acid to a counter current water stream. This experiment used three counter current cascading stages. The

feed had roughly .05 wt% of acetic acid in oil and the water stream (solvent) had no acetic acid. The most

important trial measurements that were taken were the second trial since the oil had started to flow out of

the third stage. Concentrations of acetic acid were taken for each phase at every stage in order to

determine the effectiveness of the system. The following graph outlines general trends observed during

the trial.

Figure 1: Shows weight fraction of Acetic acid in each phase and stage.

As can be seen the weight fractions that are present at each stage are significantly lower than the

feed fraction of .05 wt%. The most notable observation is that the majority of the acetic acid was removed

from the oil during the first stage of interaction between the two streams. The fraction of acid in the oil

phase seems to have had some minimum solubility or possibly it is within the titration error. A different

test for determining acid in oil will need to be used to determine which it is. The reason for the large

discrepancy in the acetic acid concentration from stage one to two is not because of the water removal but


Extraction Data

0.000E+001.000E-032.000E-033.000E-034.000E-035.000E-036.000E-037.000E-038.000E-039.000E-03

0 1 2 3 4

Stage Number

Perc

ent w

t Ace

tic A

cid

Water PhaseOil Phase


rather evaporation. When the acid and oil were mixed and then pumped to the first stage the

concentrations went from roughly .05 wt% to .008 wt% and even more was lost as the liquids were

further pumped. It was calculated from Table 7 that around 96 % of the acid was lost to the atmosphere

rather than extracted by the water.

The overall objective of the experiment was to determine a Murphree efficiency for either phase.

This objective was not able to be completes simply because of the quality of the data. An equilibrium

composition of the acid was not able to be determined from the initial numbers that were worked within

the lab.

3. Discussion

This Liquid-Liquid Extraction experiment was concerned about the effect of the speed of

mixing on the extraction efficiency. Two trials were performed – the first trial with a moderate

agitator speed and the second with a faster speed. As the data suggests, for both trials the results

do not agree with the principle behind Liquid-Liquid Extraction that with the more mixing of the

two liquids the better the molecules are able to partition (dissolve) into the preferred solvent and

the greater the extraction given more time to separate out. The data illustrates that for both trials

the majority of the Acetic Acid was extracted from the oil to the water in the first stage, and

subsequently that the amount of Acetic Acid in water decreased from each stage thereafter. This

means that the amount of Acetic Acid extracted into water decreased with each stage. It was

reliably assumed that the longer the mixing of the liquids the better the molecules are able to

partition into the preferred solvent. As stated, the data does not agree with this for the simple fact

that the majority of Acetic Acid used between both trials evaporated. It should be noted that

between both trials almost 95% of the Acetic Acid used in this experiment evaporated to the air.

This explains the trend seen in the data, because the majority of the Acetic Acid that was



extracted into the water occurred in the first stage shortly after the Acetic Acid – Oil mixture was

added to the system. Once the liquids were allowed to mix and settle throughout the other two

stages all the mixing and time to settle out allowed the Acetic Acid to evaporate out due to

uncovered tanks. With so much Acetic Acid evaporating out it is clear that with time the amount

of Acetic Acid extracting into the water decreased with increasing evaporation as seen in the

data.

Based on the principle of Liquid-Liquid Extraction, it was a reliable assumption that with

increasing agitator speed the more the two liquids mix and the more partitioning into the

preferred solvent will occur. The second trial should show that more Acetic Acid was extracted

between the three stages because it had an overall faster agitator speed. The data instead shows

that the first stage extracted more Acetic Acid in water in every stage than the second trial. This

disagreement can be explained by the source of error caused by the agitators. The agitators did

not have a very accurate way of indicate mixing speed. Although the dials had speed markings

from 1-9, when all of the agitators were set to the same dial speed it was observed that all three

agitators were going at different speeds. The operators had to try and estimate by eye that the

three impellers were all going around the same speed each trial. It is for this reason that during

the first trial the three impellers were operating at different speeds, which is a possible

explanation for the disagreement in Acetic Acid extracted from the two trials. The lack of being

able to accurately and quantitatively measure the agitator speeds has lead to the inability to draw

accurate conclusions about the effect of the speed of mixing on the extraction efficiency. As a

result the Murphree efficiencies were not calculated. This could have been avoided by fixing the

agitator speed dials and calibrating them so they all move at the same speed when set to the same

dial speed. An alternative solution to this is obtaining a new mixer/settler system that is clear or



relatively see-through so that the tank covers don’t have to be removed to make sure the agitators

are all going at the same speed.

Furthermore, the data should show that the amount of Acetic Acid in the oil is decreasing

between each stage (meaning that the Acetic Acid is partitioning into the water), which it does

for the most part but there are a few discrepancies most likely due to the fact that the oil was not

standardized and that the tank covers were removed for a significant portion of both trials. There

are a few causes for this. One major complication of this experiment was the fact that the system

kept clogging. This not only affected the mixing between the two liquids but also required the

tank covers to be removed in order to manually fix the clogging as stated before. The drain

valves of the settling compartments were very tiny and prone to clogging. This could have been

avoided if the drain valves were increased in size to avoid clogging from all the debris that enters

in from the dirty holding tanks. Also, the Rotameter for the Acetic Acid – Oil mixture did not

indicate any oil flow rate, and it also had a large clog in it. Without knowing the flowrate of the

Oil-Acid mixture, or whether its flow was steady, it was difficult to determine the water flowrate

required for the 2:1 countercurrent flow necessary to achieve steady state. The Water Rotameter

was constantly being changed by operators of the apparatus (leading to a non–steady state

operation) and it is likely that these complications lead to some of the discrepancies observed.

Definitive conclusions that can be drawn from this lab include the fact that since Acetic Acid

is polar it will dissolve easier in water than white oil and the more mixed the liquids are, the

more Acetic Acid should be transferred to the water. Another definitive conclusion that can be

made is that the agitator speeds have a strong influence on how much the Acetic Acid will

partition out into the water as can be seen from the data obtained. A more speculative conclusion



is exactly how the agitator speeds affect the amount of Acetic Acid partitioned into the water – it

was assumed that the faster the agitator speeds the more Acetic Acid extracted into the water, but

this was proven not to be the case for this specific experiment.

4. Conclusion

The purpose of the Liquid-Liquid Extraction lab is to determine the effect of mixing and its

correlation with the system’s efficiency to remove unwanted components from a mixture. The system

works off the premise that the components involved are all immiscible with one another. In this case of

this lab there are three liquids used; acetic acid, Chevron Superla White Oil, and water. The white oil and

acetic acid are mixed together in the feed tank with a 0.5 weight percent of acid to oil, which is then

mixed through the recycle system of the pump before it is sent to be mixed with the water in the first

stage. When it is properly mixed it is then sent to the first stage and allowed to interact with the water

which is flowing countercurrent to the feed of the oil-acid mix. Throughout the three stages the acetic

acid will transfer from the oil, which is the raffinate, to the extract, water in this case. Out of each stage

two samples will be taken, one of water and one of oil, and titrated with sodium hydroxide to determine

the amount of acetic acid contained in either the extract or raffinate of that stage.

There were many errors in the performance of the lab which yielded improper data. Therefore it

is very difficult to make any definite conclusions on how the speeds of the agitators affected the overall

efficiency of removing acetic acid from the white oil. The most significant error was that 94.829% of the

acetic acid was lost, and because of this fact the rest of the data cannot definitively draw any conclusions.

From data collected for the concentrations of the acetic acid found in each stage it can be seen that most

of the acid was lost between the first and second stage. In stage one the weight percent of acetic acid in

the water was 1.160e-2 and then in the second stage that dropped to 8.880e-4 and then to 1.497e-4 in the last

stage. The concentration of acetic acid stayed relatively constant in the oil samples indicating that it was

indeed transferred from the oil to the water in the mixing stages. It is recommended that covers for all of



the tanks should be kept on at all times while the process is in operation to ensure there is no loss of the

acetic acid through evaporation. Another recommendation is to understand early on how exactly the

system works because it is difficult to get the countercurrent flows to perform properly and to ensure that

the mixing is successful in transferring the acetic acid.

5. References



6. Appendix I: Data Tabulation/Graphs

Trial 1

Comp. StageVol Sample

(mL)Vol NaOH

(mL)V(NaOH) - V(NaOH, H2O, per

wt, if needed)) Moles NaOH Moles AA

water 3 20 1 0.625 5.94E-07 5.94E-07

water 2 17 2.7 2.38125 2.26E-06 2.26E-06

water 1 20 57.2 56.825 5.40E-05 5.40E-05

oil 2 23 0.5 0.5 4.75E-07 4.75E-07

oil 1 22 0.1 0.1 9.50E-08 9.50E-08

Table 1: Acetic Acid in Extractor Trial 1

Note - 16 mL of pure water took .3 mL NaOH to standardize, oil was not standardized

Trial 2

V(NaOH) - V(NaOH, H2O, per wt, if needed)

Comp. Stage Vol Sample Vol NaOH M NaOH Moles AA

water 1 20 25 24.53125 2.33E-05 2.33E-05

oil 1 10 0.9 0.9 8.55E-07 8.55E-07

water 2 10 1.9 1.7125 1.63E-06 1.63E-06

oil 2 10 0.3 0.3 2.85E-07 2.85E-07

water 3 10 0.4 0.2125 2.02E-07 2.02E-07

oil 3 11 0.5 0.5 4.75E-07 4.75E-07

end end 10 0.6 0.6 5.70E-07 5.70E-07

Table 2: Acetic Acid in Extractor Trial 2



Molarity AA in Phase mol frac. AA wt% AA Comp.

2.97E-05 5.35E-07 1.78E-04 water

1.33E-04 2.40E-06 7.99E-04 water

2.70E-03 4.86E-05 1.62E-02 water

2.07E-05 1.46E-04 oil

4.32E-06 3.04E-05 oil

Table 3: Weight percent of AA in Oil/Water

Molarity AA in Phase mol fract. AA wt% AA Comp.

1.17E-03 2.10E-05 7.00E-03 water

8.55E-05 6.03E-04 oil

1.63E-04 2.93E-06 9.77E-04 water

2.85E-05 2.01E-04 oil

2.02E-05 3.64E-07 1.21E-04 water

4.32E-05 3.04E-04 oil

5.70E-05 3.42E-04 end

Table 4: Weight percent of AA in Oil/Water



This table shows our flowrates and the calculations that were used in the standardization of our Sodium Hydroxide:

Max Flow Rate (gpm) Actual Flow Rate (gpm)

Water1.12 0.448

Oil 1.12 0.224

Standardization of NaOH

Normalization HCL (g/L)

Molarity HCL (mol/L) Volume HCL (L)

Volume NaOH (L)

Molarity NaOH (mol/L)

12.1 0.331507 0.0003 0.1 0.000995

Table 5: Flow rates and Normalization of Acid/Base

This table shows the average concentration of Acetic Acid in both phases, and in every stage of the apparatus:

1st stage average AA wt% in water 1.160E-02

2nd stage average AA wt% in water 8.880E-04

3rd stage average AA wt% in water 1.497E-04

1st stage average AA wt% in oil 2.697E-04

2nd stage average AA wt% in oil 1.476E-04

3rd stage average AA wt% in oil 2.593E-04

Table 6: Average AA weight percents in Oil and Water



This table shows how much of the Acetic Acid was lost to the surroundings during the experiment:

Wt AA in, without evaporation, per minute = 9.34E-03lb

wt AA removed with water, per minute = 3.449E-04lb

wt AA out with oil in the final stage, per minute = 4.844E-06lb

Wt AA evaporated or lost, per minute 8.864E-03lb

% of AA evaporated or lost 94.892%

Table 7: AA recovery/loss

The following graph shows how the concentration of Acetic Acid varies in both phases as a function of stage:


Extraction Lab

0.000E+00

2.000E-03

4.000E-03

6.000E-03

8.000E-03

1.000E-02

1.200E-02

1.400E-02

0 1 2 3 4

Stage #

Perc

ent A

A in

pha

se

Water Phase (Extract)Oil Phase (Raffinate)

Figure 1: Percent AA in phases


7. Appendix II: Error Analysis

Data tables indicate that 94.892 % of all Acetic Acid was lost due to evaporation. Thus, out of the

113mL of Acetic Acid that was mixed with the oil, only about 4.44g were recovered or about 4.23mL.

There were several different factors that led to the evaporation of such a great quantity of Acetic Acid.

The system was not at steady state when the Acetic Acid was added to the oil. It was found that the initial

oil amount in the feed was not sufficient for operation. The system was then subsequently stopped, oil

and more Acetic Acid added, and then restarted. This stop-restart cycle contributed to the non-steady

state operation of the apparatus and also allowed for more error in Acetic Acid addition, since a graduated

cylinder was used to measure the amount of Acetic Acid needed for 0.5 wt%. Following the restarting of

the system, the system was still found to not be at steady state, and thus the covers on the oil feed tank

and stages were taken off. This allowed for much of the Acetic Acid to evaporate into the air. The

smell around the laboratory area was physical evidence that a great amount of Acetic Acid evaporated

during the first trial. While much of the Acetic Acid was lost to the air, there were several other factors

that would have led to skewed data for this Liquid-Liquid Extraction laboratory.

The Oil-Acid Rotameter (Equipment #12) was broken and did not indicate any type of oil flow rate.

Visually, the rotameter had a large mass clogging it. The mass seemed to contain both hair and paint

chips from the oil feed tank. Without knowing the flowrate of the Oil-Acid mixture, or whether its flow

is steady, it is very difficult to determine the water flowrate that would be needed for countercurrent flow

to achieve steady state. However, not only was the rotameter clogged, during the cleaning process of the

system, it was found that much of the hairy, paint chip-laden residue was clogging the pump and much of

it was present in the water/oil mixture in the first two stages.

The Water Rotameter (Equipment #11) was constantly being changed by operators of the apparatus,

again, this led to a non-steady state operation. However, when the Water Rotameter was not longer being

changed, it indicated a dropping flowrate, despite no one turning the valve. This drop was sporadic and

not constant, but always in a dropping fashion. To further add to the non-steady state system problem, the Unit Operations ChE 382 Group 5 Spring 2011 2 /02/2011Damo, Duffy, Guerrero, Hsu, Kosak, Qamar, Tyska


impellers on the apparatus do not have a very distinct marking pattern to indicate mixing speed.

Operators of the apparatus were led to estimate, by eye, that the three impellers were all at the same

speed. During the first trial, it was clear that the three different impellers were operating at different

speeds. This would lead to a different and difficult-to-calculate yield for each stage and contribute to the

non-steady state problem of that trial.

Other possible sources of error are in the titration, where the standardized NaOH was over 3 years

old, had molarity of 0.000994 mol/L and in the use of a graduated cylinder to measure the 0.5 wt% Acetic

Acid. The buret for titration had an error of ± 0.05mL. Regardless, none of these possible sources of

measurement errors could have contributed to the evaporative loss of 94.892% of all Acetic Acid added to

the system.



8. Appendix III: Sample Calculations

**0.3mL of NaOH was required to standardize pure tap water.

V eq=V NaOH−V sample ( 0.3mLNaOH16mLPureH2O )

V eq=1.0mL−20mL∗( 0.3mLNaOH16mLPureH 2O )=0.625mL

Where:

V eq is the equivalent volume (mL) of NaOH required to titrate the sample corrected for the naturally occurring acidity of pure tap water

V NaOH is the volume (mL)of NaOH used to titrate the sample read directly from the burette. V sample is the volume (mL) of sample that was titrated.

nNaOH=M NaOH∗V eq

nNaOH=0.00095 M∗0.625mL

1000 mLL

=5.94∗10−7moles NaOH

Where:

nNaOH is the moles NaOH required to titrate the sample corrected for the naturally occurring acidity of pure tap water

MNaOH is the Molarity (mols/L) of the NaOH used in the titration. V eq is the equivalent volume (L) of NaOH required to titrate the sample corrected for the

naturally occurring acidity of pure tap water

nAA=nNaOH

5.94∗10−7moles AA=5.94∗10−7moles NaOH

Where:

nAA is the moles of acetic acid in the titrated sample. nNaOH is the moles NaOH required to titrate the sample corrected for the naturally occurring

acidity of pure tap water



M AA=nAAV sample

M AA=5.94∗10−7moles AA

20mL

1000 mLL

=2.97∗10−5M

Where:

M AA is the Molarity (moles/L) of Acetic Acid in the sample. nAA is the moles of acetic acid in the titrated sample. V sample is the volume (mL) of sample that was titrated.

X AA=nAA

V samle∗ρMW

X AA=5.94∗10−7moles AA

20mL∗1.0 g/mL18g /mol

=5.35∗10−7

Where:

X AA is the mole fraction of Acetic Acid in the sample. nAA is the moles of acetic acid in the titrated sample. V sample is the volume (mL) of sample that was titrated. ρ is the density (g/mL) of the sample. For water samples assume that the density is that of pure

water (1.0g/mL), and for the oil samples assume the density is that of pure oil (0.853g/mL). MW is the molecular weight of the sample. For the water samples assume the weight is 18g/mol. X AA for oil samples was not calculated because of uncertainty in the molecular weight of the oil.

W=MW AA∗MAA

ρ∗100

W=60.05 g/mol∗2.97∗10−5M1.0g /mL

∗100=1.78∗10−4 %

Where:

W is the weight percent of Acetic Acid in the sample.Unit Operations ChE 382 Group 5 Spring 2011 2 /02/2011Damo, Duffy, Guerrero, Hsu, Kosak, Qamar, Tyska


ρ is the density (g/mL) of the sample. For water samples assume that the density is that of pure water (1.0g/mL), and for the oil samples assume the density is that of pure oil (0.853g/mL).

M AA is the Molarity (moles/mL) of Acetic Acid in the sample.



9. Appendix IV: Individual Team Contributions

Name: Daniyal Qamar

Section Time (hrs) Description of Work Done

1.

Name: Bernard Hsu


1.

Name: Ryan Kosak


1.

Name: Tomi Damo


1.

Name: Jeff Tyska


1.



Name: Alex Guerrero


1.

Name: Andrew Duffy


1.


Documents

Water - CHEGRP5 - homechegrp5.wikispaces.com/file/view/Group+5+Final+Lab... · Web viewThe purpose of the Liquid-Liquid Extraction lab is to determine the effect of mixing and its