Pertraction of cations in a hybrid membrane system containing soluble polymeric ionophores

Abstract

A hybrid membrane system composed of two insoluble cation-exchange membranes (Nafion) and a liquid membrane in between was studied. A series of organic and aqueous liquid membranes containing soluble polymers as macromolecular ionophores (macroionophores) was prepared and tested. The pertraction (membrane-transport) characteristics of poly(ethylene glycol) and its ionizable derivatives, including as poly[poly(oxyethylene) phosphate] (PPOEP) and di-[-methoxy poly(oxyethylene)] phosphate, were measured and are discussed as dependent on the composition and molecular mass of a macroionophore. The liquid membrane composed of PPOEPs dissolved in dichloroethane combined the cation-exchange properties with neutral coordination functionalities introduced by the poly(oxyethylene) backbone of this ionophore. The overall fluxes, facilitation factors, and the membrane system selectivity were measured in the carrier-mediated pertraction of transient metal cations (Cu . In the case of an aquatic hybrid membrane system, high but nonselective ionic fluxes were observed.

Poly[poly(oxypropylene) phosphate] macroionophores for transport and separation of cations in a hybrid: Cation‐exchange polymer and liquid membrane system

“…According to Yanagida,48 PPG is a worse extractant of cations than PEG, and thus it can be expected that the role of POP units is not so clear as in the case of PEG derivatives studied before. 13,32 Nevertheless, the simple experiments discussed above demonstrate that the specific properties of POP chains are also observable in the case of pertraction processes described in this article.…”

“…Previously 13 we indicated the role of water uptake into the liquid membrane phase, the process of which was suggested to be responsible for enhancing the process of permeation with simultaneous lowering of the membrane system selectivity. We also suggested solving this problem by continuous dehydration of the organic liquid membrane by a pervaporation method.…”

“…This rather evident-to biophysicists-feature of natural systems was the inspiration for our studies, based on the assumption that high selectivity and stability of membrane systems can be attained probably in the multimembrane systems with a hierarchy of processes mimicking bacterial cell envelopes. 15 From the perspective of our previous reports concerning the properties of poly[poly(oxyethylene) phosphate]s 13,26,27,32 as the macroionophores, a natural extension of our studies was to synthesize more hydrophobic polymers such as poly[poly-(oxypropylene) phosphate]s (PPOPPs) and to test them in the pertraction of typical transient (Zn 2ϩ , Cu 2ϩ ), alkali-earth (Ca 2ϩ , Mg 2ϩ ), and alkaline (K uptake from external aqueous solutions into a liquid membrane phase, a continuous dehydration of a liquid membrane by water pervaporation method was additionally applied. According to the scheme of the system operation in Figure 1, the overall membrane system constitutes a set of very different membranes such as: a hydrophobic liquid membrane, hydrophilic polymer cation-exchange, and hydrophilic polymer pervaporation membranes.…”

“…15 In this context, the development and application of the soluble polymeric carriers (macroionophores) is a challenging problem from both a fundamental and practical point of view, as reported in a number of articles 6,16 -34 and briefly discussed in our previous report. 13 Moreover, in a number of natural cellular systems, a transported solute when reaching its destination passes and/or is separated by a series of membranes of varied properties. This rather evident-to biophysicists-feature of natural systems was the inspiration for our studies, based on the assumption that high selectivity and stability of membrane systems can be attained probably in the multimembrane systems with a hierarchy of processes mimicking bacterial cell envelopes.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The development of advanced hybrid liquid membrane systems, involving the process of pertraction (liquid membrane transport arranged as extraction-diffusion-back extraction), 14 is strongly influenced by advances in the synthesis of new reagents that would be able to recognize and react specifically and reversibly with separated substances, and thereafter, to transfer them throughout a conventional liquid or polymeric membrane by a diffusion mechanism. On the other hand, searching for new ionophores (liquid membrane carriers) is stimulated also by the biophysics of cellular transport ascribed to the crucial role of various natural ionophores in the regulation of metal cations content in living organisms.…”