Transport of platinum(IV) through supported liquid membrane (SLM) and polymeric plasticized membrane (PPM)

Plasticized polymeric membranes (PPM) are regarded as one of the solutions to overcome the instability of supported liquid membranes (SLM). The transport of platinum in chloride media through both types of membranes, SLM and PPM, containing the anion-exchange carrier Aliquat 336 is compared. Different organic compounds have been tested to act either as organic solvent in SLM or as plasticizers in PPM. Dibutylsebacate gave the highest flux value when comparing platinum fluxes across SLM, whereas a solvent with high dielectric constant, 2-nitrophenyl octyl ether (NPOE), was the most effective plasticizer in PPM. The variation of plasticizer volume added to the polymeric matrix when preparing membranes of constant CTA weight and carrier concentration, evidenced a direct relationship with the thickness of the obtained membrane, pointing out that NPOE remains in the polymer network increasing presumably the inter-chain free volume. The influence of Aliquat 336 concentration dissolved in NPOE in both types of membranes revealed differences at low carrier concentration. SLM presented an increase in flux when increasing carrier concentration while for PPM a carrier concentration higher than 50 mM is needed for achieving platinum transport. The effect of the temperature on metal flux across PPM has also been evaluated in the range 4-50 degrees C for different carrier concentrations, and it can be observed that by increasing the temperature, the platinum transport is enhanced. Moreover, CTA membranes are more selective for platinum than SLM with the same carrier. (c) 2005 Elsevier B.V. All rights reserved.