Extraction of multi-component system of metals from simulated and industrial effluents by liquid surfactant membranes (LSM)

Abstract

A study of metal extraction from a multi-component system was carried out by applying a liquid surfactant membrane (LSM) process. The system was an industrial effluent which contains a mixture of metallic species such as Na(I), Mn(II), Co(II), Ni(II), Fe(III) and Cr(III). Concurrently, an analogous research programme was conducted on model solutions reproducing nearly the same physical and chemical composition as the industrial feed. The main goal behind this endeavour was to elucidate the effect of impurities and other components co-existing alongside the metallic species in the industrial feed. Di-2-ethylhexyl phosphoric acid (D2EHPA) was used as a carrier with tri-n-butyl phosphate (TBP). The latter's influence on the kinetics of metal extraction occupied a major part of the investigations. It was found that an optimal composition of the extracting mixture exists (5.5 vol.% D2EHPA + 0.5 vol.% TBP) at which a maximum extraction efficiency can be achieved. It has also been revealed that, although the selectivity is relatively poor, it can be improved by varying the concentration of TBP in the membrane phase. The raffinate kinetic profiles of the simulated solutions have been shown to fit those of the industrial effluent adequately.