Facilitated transport of lactic acid and its ethyl eater by supported liquid membranes containing functionalized polyorganosiloxanes as carriers

The feasibility of using hydrophobic fluid organosiloxane, Me3SiO(MeSi(OR)O )(x)(Me2SiO)(y)SiMe3 polymer (containing x=4, 11 or 30 mol% of R=-(CH2)(3)N Me2 (amine); -(CH2)(2)OEt (ether); -(CH2)(5)COOEt tester); or -(CH2)(4)Me t alkyl), side-arm organofunctional groups) as integrated solvent/carrier sup ported liquid membranes (SLMs) for the recovery from aqueous phases of lact ic acid and its ethyl ester has been investigated. The carriers are capable of interacting specifically with the required product in a complex mixture . The ethyl ester of lactic acid undergoes pH driven facilitated transport through both ether and amine functionalized polyorganosiloxane/celgard K-27 3 SLMs resulting in a dramatic permeability enhancement compared with that displayed by the free acid. The pH driven facilitated flux of the ester is directly proportional to the substrate concentration, and it is also greate st at low amine and ether functional group loadings. Both amine and ether f unctionalized polyorganosiloxane/celgard SLMs were found to be stable throu ghout the duration of the experiments tup to 100 h). (C) 2000 Elsevier Scie nce B.V. All rights reserved.