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Extraction Liquid-liquid and aqueous two-phase extraction · 2019-06-09 · 2 Abstract Extraction...

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Aalto University School of Chemical Technology Master’s Programme in Chemical, Biochemical and Materials Engineering CHEM-E3140 Extraction Liquid-liquid and aqueous two-phase extraction Henna Pauliina Ahokas, 657945 Johanna Kuronen, 477167 Yingfeng Wang, 661151 Espoo, 4.12.2017
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Page 1: Extraction Liquid-liquid and aqueous two-phase extraction · 2019-06-09 · 2 Abstract Extraction is a separation method based on isolating components based on their different solubilities

Aalto University School of Chemical Technology

Master’s Programme in Chemical, Biochemical and Materials Engineering

CHEM-E3140

Extraction

Liquid-liquid and aqueous two-phase extraction

Henna Pauliina Ahokas, 657945

Johanna Kuronen, 477167

Yingfeng Wang, 661151

Espoo, 4.12.2017

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Table of contents

Abstract .................................................................................................................... 2

Background .............................................................................................................. 2

Theory ...................................................................................................................... 3

Principle ................................................................................................................ 3

Selection of solvent ............................................................................................... 6

Importance / Case study .......................................................................................... 6

Importance............................................................................................................ 6

Case study from bioprocess technology ............................................................... 7

Conclusions.............................................................................................................. 8

References ............................................................................................................. 10

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Abstract

Extraction is a separation method based on isolating components based on their

different solubilities on different solvents. Liquid-liquid extraction (LLE) is the most

widely used type of extraction, and it consists of two liquid solvent phases. These are

usually water or an aqueous phase and an organic solvent. Aqueous two-phase

extraction (ATPE) is a unique type of liquid-liquid extraction, which consists of

aqueous solutions of two polymers or a polymer and a salt. Liquid-liquid extraction is

an important separation method in traditional industries such as hydrometallurgy and

chemical processing, especially where distillation cannot be used. Aqueous two-

phase extraction is used and researched especially in the biomolecule separation and

purification because of its good features in for example protein recovery.

Background

When a compound or compounds need to be separated from a mixture to form a more

distinct product, a separation process is needed. One of these processes is extraction,

which is based on transferring components from one phase to another. It is based on

the separable compound's different solubility in different solvents. These solvents can

mix with each other only to a limited extent so that they can be separated from each

other. (Müller et. al. 2015) When the wanted compound has been extracted to the

wanted solvent, the different phases are separated from each other and the

compound-containing mixture goes through a separate process phase, for example

distillation or stripping, to separate the compound from the solvent.

One of the most important types of extraction is liquid-liquid extraction (LLE), or

solvent extraction. In LLE there are two liquid phases between which the compound

transfer takes place. Usually one of the solvents is an aqueous mixture or water and

the other is an organic liquid, for example dichloromethane or diethyl ether. (Galceran

& Puignou 2006) LLE was initially utilized in the 1930's in the petroleum industry.

Since then, it has been used widely in different fields of industry including

hydrometallurgical and pharmaceutical industries. (Law & Todd 2008)

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Aqueous two-phase extraction (ATPE) is a form of liquid-liquid extraction, but it has

unique features. In ATPE, the solvents can be aqueous solutions of two polymers or

a polymer and a salt. (Goja et. al. 2013) Commonly used ATPE systems include

polyethylene glycol (PEG) as the polymer and for example a phosphate as the salt

phase. ATPE has been used since the 1960’s and it’s mainly used in biomolecule

separation and purification, as it prevents for example protein denaturation better than

the traditional liquid-liquid extraction. (Iqbal et. al. 2016; Chethana et. al. 2006; Goja

et. al. 2013)

Theory

Principle

A liquid-liquid extraction is a technique for separating two immiscible liquids that are

used to isolate components of a mixture based on a difference in their solubilities. In

this technique, the idea is to separate a desired dissolved component from its solvent

by transferring it to another solvent. The solvent in which the compound is transferred

to is called the extract and the solvent, from which the component was transferred, is

called raffinate. The transferring is caused by solvents’ different solubilities and the

larger the difference is, the greater is the extend to which the compound is extracted.

(De Haan & Bosch 2013) However, according to Hendriks et. al. (2007) solubility can

be changed by modifying the pH-value of the solvent. The adjustment of pH to the

effective level will lead to higher selectivity. The right pH-value can be determined with

the Henderson-Hasselbalch Plot. (Hendriks et. al. 2007) Down below in figure 1 is

presented one example of the Henderson-Hasselbalch Plot. In this case recovery of

amitriptyline is highest at pH-value higher than 9.

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Figure 1. Graphical representation of the extraction recovery results of amitriptyline. (Hendriks et. al.

2007)

When the suitable solvents have been chosen and tested and the needed facilities

are designed and built, the liquid-liquid extraction process starts with a loading the

solvents into the column. Then solvents are agitated with a mixer to ensure that

solvents are thoroughly dispersed. Other than mechanical stirring, pump circulation

and air agitation can be used as well. Below is shown (fig 2) a schematic of a

mechanical mixer. Also, extractors can be used to maximize the dispersion of one

phase to another. However, emulsions may occur in over-agitating, especially with

halogenated organic phases, not often with ethers. (De Haan & Bosch 2013)

Figure 2. Mixer-settler. (De Haan & Bosch 2013)

After the agitation, the column has to be vent so that the pressure that has built up in

the column, can be let out. After venting the column, mixed solvents need to rest and

separate and then the heavier solvent is drained out of the column. If the solvent is

partially miscible with the feed, a second separation process, usually distillation, is

required to recover solvent from raffinate. Down below in figure 3 is presented the

mechanism of liquid-liquid extraction.

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Figure 3. Schematic of a principle liquid-liquid extraction process (De Haan & Bosch 2013)

Application of LLE should be considered over distillation in the following cases (De

Haan & Bosch 2013):

• Dissolved or complexed inorganic components in organic or aqueous

solutions

• Removal or recovery of components present in small concentrations

• When a high-boiling component is present in relatively small quantities in a

waste steam

• Recovery of heat-sensitive materials and processing temperatures are

needed

• Separation of a mixture according to chemical type rather than relative

volatility

• Separation of close-melting or close-boiling liquids, when there is a solubility

difference between solvents

• Mixtures that form azeotropes or exhibit low relative volatilities and distillation

cannot be used.

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There are also some ternary systems of LLE and they are often represented in a

triangular diagram. In ternary systems, the solute is miscible with the carrier as well

as the solvent. One of the disadvantages of LLE is that the necessity of a solvent

increases the complexity and therefore costs of the process grows as well. (De Haan

& Bosch 2013)

Selection of solvent

Solvents are usually chosen so, that the other phase is organic and the other one

inorganic. Therefore, high polarity compounds tend to dissolve in inorganic, aqueous

phase, whereas low polarity compounds solute in the organic phase. (De Haan &

Bosch 2013)

Reactivity with the other chemicals involved and solubility are the most important

qualities when selecting the solvent to use in liquid-liquid extraction. As well as

density, interfacial tension, resistance to thermal degradation, boiling point, viscosity

and toxicity of the chemical should be considered when selecting solvent for the

application. Also cost of the chemical will determine whether it is economically wise

to be used as a solvent. (Koch & Shiveler 2015)

The partitioning coefficient, which is the ratio of concentrations of a solute that is

distributed between two immiscible solvents at equilibrium, can be calculated from the

equation (1) shown below.

𝐸 =𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑖𝑛 𝑒𝑥𝑡𝑟𝑎𝑐𝑡 𝑝ℎ𝑎𝑠𝑒

𝑎𝑚𝑜𝑢𝑛𝑦 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑖𝑛 𝑟𝑎𝑓𝑓𝑖𝑛𝑎𝑡𝑒 𝑝ℎ𝑎𝑠𝑒= 𝐾

𝑒𝑥𝑡𝑟𝑎𝑐𝑡 𝑓𝑙𝑜𝑤

𝑟𝑎𝑓𝑓𝑖𝑛𝑎𝑡𝑒 𝑓𝑙𝑜𝑤 (1)

Importance / Case study

Importance

From a hydrometallurgical perspective, solvent extraction is exclusively used in

separation and purification of uranium and plutonium, zirconium and hafnium,

separation of cobalt and nickel, separation and purification of rare earth elements etc.,

it's greatest advantage being its ability to selectively separate out even very similar

metals. We obtain high purity single metal streams on 'stripping' out the metal value

from the 'loaded' organic. Wherein we can precipitate or deposit the metal value.

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Stripping is the opposite of extraction, transfer of mass from organic to aqueous

phase. (Wikipedia 2017)

LLE is also widely used in the production of fine organic compounds, the processing

of perfumes, the production of vegetable oils and biodiesel, and other industries. [not

verified in body] It is among the most common initial separation techniques, though

some difficulties result in extracting out closely related functional groups. (Wikipedia

2017)

Liquid-liquid extraction is an important separation technology for a wide range of

applications in the chemical process industries (CPI). Unlike distillation, which is

based on boiling point differences, extraction separates components based on their

relative solubilities in two immiscible liquids. Extraction is typically chosen over

distillation for separation applications that would not be cost-effective, or even

possible, with distillation. (Koch & Shiveler 2015)

Separation of single components from the multi-component mixture extraction of

components present in the electrolytic solutions. Common industrial application of

liquid-liquid extraction include in areas like bulk chemical industry, petroleum industry,

fine chemical industry, pharmaceutical industry, biotech industry, food industry and

hydrometallurgy. (SlideShare 2014)

Extraction processes are well suited to the petroleum industry because of the need to

separate heat-sensitive liquid feeds according to chemical type (e.g. aliphatic,

aromatic, naphthenic) rather than by molecular weight or vapor pressure. Other major

applications include the purification of antibiotics and the recovery of vegetable oils

from natural substrates. In metals processing the recovery of metals such as copper

from acidic leach liquors and the refining of uranium, plutonium and other radioactive

isotopes from spent fuel elements. Recently extraction is gaining increasing

importance as a separation technique in biotechnology.

Case study from bioprocess technology

The main objective of the present work was to study the importance of modelling

reaction and phase equilibria simultaneously with irreversible chemical reactions.

Based on the mechanism presented in the literature, libraries consisting of irreversible

reactions were constructed for the following cases: the hot water extraction of wood,

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kraft liquor impregnation into wood, lignin oxidation in oxygen delignification

conditions, and alkaline extraction of chlorine dioxide delignified pulp. (Kuitunen 2014)

OBC was further processed by partial depolymerisation of beta-glucan with acid- or

enzyme-catalysed hydrolysis at relatively low water content using a twin-screw

extruder as a bioreactor. The hydrolysed oat brans were extracted with hot water and

centrifuged to obtain a water-soluble phase and an insoluble residue. (Sibakov 2014)

In order to provide valuable information for the process up-scaling, the features that

affect the extraction (solvent and substrate properties, reaction conditions) and

equipment requirements were studied profoundly. The studies progressed by

examining the usability of the separated polymer fractions, by investigating the purity,

reactivity and integrity of the polymers. (Roselli 2017)

The results revealed that the solvation selectivity towards hemicelluloses was

governed by the molecule size of the carbohydrate polymers. Short hemicelluloses

dissolve more readily in aqueous ionic liquids, while the cellulose fraction remains

intact. Thus, the molar mass distribution (MMD) of the pulp is a decisive feature

regarding the suitability of this pulp for the IONCELL-P process. A distinct difference

in the size of hemicelluloses and cellulose allows for a more accurate tuning of the

solvent-water mixture for the selective and efficient extraction of hemicelluloses.

(Roselli 2017)

Conclusions

Liquid-liquid extraction is most beneficial in cases where complexed inorganic

components are dissolved in aqueous solutions and transferable components are

present in relatively small concentrations and quantities. LLE should also be

considered in cases where recovery of heat-sensitive materials and processing are

needed, the used mixtures form azeotropes and if separation of a mixture according

to volatility is not an option, since solvents’ melting or boiling points are close to each

other.

The common industrial application of Liquid-liquid extraction includes in the areas like

Bulk chemical industry, Petroleum industry, Fine chemical industry and

Hydrometallurgy etc. From a hydrometallurgical perspective, it's greatest advantage

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being its ability to selectively separate out even very similar metals. There are also

many case studies from bioprocess technology.

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References

Chethana, S., Nayak, C.A. & Raghavarao, K.S.M.S. 2006. Aqueous two phase

extraction for purification and concentration of betalains. Journal of Food Engineering

81(2007). P. 679-687.

De Haan, A. & Bosch, H. 2013. Liquid-liquid extraction. Industrial Separation

Processes - Fundamentals. De Gruyter. P. 111-142.

Galceran, M.T. & Puignou, L. 2006. Latest developments in the analysis of

heterocyclic amines in cooked foods. Acrylamide and Other Hazardous Compounds

in Heat-Treated Foods, Chapter 5. A volume in Woodhead Publishing Series in Food

Science, Technology and Nutrition. P. 68-116.

Goja, A.M., Yang, H., Cui, M. & Li, C. 2013. Aqueous Two-Phase Extraction Advances

for Bioseparation. J Bioprocess Biotech. 4:140.

Hendriks, G., Uges, D.R.A. & Franke, J.P. 2007. Reconsideration of sample pH

adjustment in bioanalytical liquid–liquid extraction of ionisable compounds. Journal of

Chromatography B, 853 (2007). ScienceDirect. P. 234-241.

Iqbal, M., Tao, Y., Xie, S., Zhu, Y., Chen, D., Wang, X., Huang, L., Peng, D., Sattar,

A., Shabbir, M.A.B., Hussain, H. I., Ahmed, S. & Yuan, Z. 2016. Aqueous two-phase

system (ATPS): An overview and advances in its applications. Biol Proced Online.

18:18.

Koch, J. & Shiveler, G. 2015. Design principles for Liquid-Liquid Extraction. American

Institute of Chemical Engineers. United States of America. [referred 28.11.2017]

Available: https://www.aiche.org/resources/publications/cep/2015/november/design-

principles-liquid-liquid-extraction

Kuitunen, S. 2014. Phase and reaction equilibria in the modelling of hot water

extraction, pulping and bleaching. Aalto University Publication Series, Doctoral

dissertations. 37/2014.

Law, J. D. & Todd, T. A. 2008. Liquid-Liquid Extraction Equipment. Idaho National

Laboratory (INL).

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Müller, E., Berger, R., Blass, E., Sluyts, D. & Pfennig, A. 2015. Liquid-Liquid

Extraction. Ullmann’s Academy - Encyclopedia of Industrial Chemistry. Wiley-VCH

Verlag GmbH & Co. KGaA, Weinheim.

Roselli, A. 2017. Extraction of Hemicelluloses from a Kraft Paper Pulp with an Ionic

Liquid water Mixture. Aalto University Publication Series, Doctoral dissertations.

School of Chemical Technology 153/2017. Defence date: 2017-09-22.

Sibakov, J. 2014. Processing of oat dietary fibre for improved functionality as a food

ingredient. VTT Science, Doctoral Dissertations. School of Chemical Technology 67.

Date of defence: 2014-10-31.

SlideShare. 2014. Advantages of Liquid-liquid Extraction System. LinkedIn

Corporation. [referred 1.12.2017] Available:

https://www.slideshare.net/kumarsachin3801/advantages-of-liquid-liquid-extraction-

system

Wikipedia. 2017. Liquid-liquid Extraction. [referred 1.12.2017] Available:

https://en.wikipedia.org/wiki/Liquid%E2%80%93liquid_extraction


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