Aqueous two phase extraction—an environmentally benign technique
Aqueous two-phase extraction (ATPE) is basically a liquid–liquid extraction technique employing two aqueous phases comprising either two polymers or a polymer and a salt. In addition to the other advantages it offers, ATPE is gaining increasing popularity as an environmentally benign technique because (1) it does not employ volatile organic compounds as solvents, (2) it involves phase-forming polymers that rely on the structuring properties of liquid water not only for the formation of phase systems but also for solubilizing the otherwise relatively insoluble hydrophobic solutes, (3) it exploits the remarkable properties of polymers such as polyethylene glycols, polyvinyl pyrrolidone (PVP) etc. and (4) it makes use of phase-forming components which could be recovered and recycled to a limited degree. In some modified form, ATPE is finding application in environmental remediation. ATPE is discussed by considering case studies involving extraction of enzymes for waste treatment and recovery of valuable by-products from waste, extraction of useful components of plant origin and extraction of natural colours. The scope of ATPE in the context of pollution prevention or application for environmental remediation is discussed. Advantages/limitations of ATPE are also discussed. Barriers to a widespread industrial application of ATPE are examined and possible solutions suggested.
The authors thank Dr. V Prakash, Director, CFTRI for his keen interest in aqueous two-phase separations. One of the authors RSB gratefully acknowledges CSIR, Government of India for a Senior Research Fellowship.
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