Selective transport-recovery of bismuth(III) by a polymer inclusion membrane containing polyvinyl chloride base polymer and bis (2-ethylhexyl)phosphoric acid

Recently, it has been shown that a polymer inclusion membrane (PIM) containing 50 wt% of polyvinyl chloride (PVC) and 50 wt% bis(2-ethylhexyl)phosphoric acid (D2EHPA) is able to extract efficiently Bi(III) from sulfate solutions. The advantages of the transport processes motivated us to evaluate the potential of the proposed PIM for the recovery of Bi(III). Efficient transport of Bi(III) was achieved by using the PIMs (14 mu m thickness, and 33.2 cm(2) surface area) from the source phase, initially contained 20 mg L-1 of Bi(III) adjusted to pH 1.3 and 0.2 mol L-1 Na2SO4, to the receiving phase (H2SO4, 2 mol L-1). It is demonstrated that the transfer is carried out by a pure diffusion process. Under selected conditions, the highest permeability coefficient and initial flux are found to be 1.08 x 10-5 m s(-1) and 1.03 x 10(-6) mol m(-2) s(-1), respectively. The investigated PIM is more stable and can be used at least for 10 successive transport experiments. A pronounced selectivity is observed for Bi(III) in the competitive transport experiments of Bi(III) from its solutions containing some other associated metals. The preliminary experiments show that a dual-PIM system significantly increases transport efficiency.