Mobile Macromolecular Carriers of Ionic Substances, 2. Transport Rates and Separation of Some Divalent Cations by Poly(oxyethylene) Phosphates

Abstract

The permeation of Cu(II), Zn(II), Mn(II), Co(II), Ni(II) as facilitated by soluble macromolecular carriers (macroionophores) was investigated in a multimembrane hybrid system (MHS). The system was composed of two cation-exchange polymer membranes and an agitated bulk liquid membrane containing one of the following polymers as the transport activating component: ω-methoxy-poly(oxyethylene) phosphate (MPOEP, 1), α,ω-poly(oxyethylene) bisphosphate (POEBP, 2), and α,ω-poly(oxyethylene) bis(dimethyl phosphate) (POEBMP, 3) of various molecular mass. For comparative studies, poly(ethylene glycol)s (PEG, 4) of equivalent molecular mass (1 500–6 000), were also studied. The results have been analysed by comparing the overall metal cation fluxes, facilitation factors, and separation coefficients. It was found that compound 2 exhibits favourable carrier properties represented by the ionic fluxes as high as 2·10–11 mol/(cm2·s). This macromolecular carrier allows the achievement of transport facilitation factors ranging from 10 to 100 with respect to the system without any carrier, and from 6 to 34 with respect to the system containing an equivalent amount of PEG. The specific values depend on molecular mass of POE in 2, with a maximum at POE 2000. The mechanism of transport when mediated by the ionic macromolecular carriers 1 and 2 is probably influenced by their bifunctional character involving the cooperation between ion exchange processes and ion binding by pseudocyclic structures of poly(oxyethylene) moieties.