Transport and separation of arsenate and arsenite from aqueous media by supported liquid and anion-exchange membranes

Abstract

This work evaluates two different membrane-based possibilities for the transport of inorganic arsenic species in natural waters. With this purpose, a supported liquid membrane (SLM) system containing the anion-exchanger Aliquat 336 as a mobile carrier, and two different anion-exchange membranes (AEMs), a mono-anion and non-mono-anion permselective membranes, have been studied, and parameters affecting As transport have been evaluated. The effect of pH of the feed phase was investigated in all the systems setting as stripping phase a 0.1 M NaCl solution. It was observed that, in the case of SLM, As(V) was totally transported at pHs 10 and 7, whereas acidic pH such as 3 or more basic, such as 13 resulted in poorer results. This pH dependence was also observed for both AEM systems, and better results were obtained when using a non-mono-anion permselective membrane at pH 7. Moreover, the transport of As(III) was investigated under the best experimental conditions found for As(V) permeation, and different behavior was observed from SLM and AEMs. In the first case, no transport of As(III) was achieved whereas in the case of non-mono-AEM this species was transported until an equilibrium was reached. In order to demonstrate the applicability of both types of membranes, the effect of accompanying anions present in equivalent concentrations as possible interferents was investigated, and it was concluded that although the anions were co-transported with the inorganic arsenic species their presence did not affect the As removal