Selective extraction of vanadium(V) from sulfate solutions into a polymer inclusion membrane composed of poly(vinylidenefluoride-co-hexafluoropropylene) and Cyphos (R) IL 101

A poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP)-based PIM containing trihexyltetradecylphosphonium chloride (Cyphos (R) IL 101) as its carrier was developed for the selective extraction of V(V) from sulfate solutions. Various plasticizers/modifiers were tested and best results in terms of rate of extraction and amount extracted were obtained with 2-nitrophenyloctyl ether (NPOE). The optimal PIM composition, with respect to the same criteria was determined to be 35 wt% Cyphos (R) IL 101, 55 wt% PVDF-HFP and 10 wt% NPOE. Back-extraction of V(V) was achieved using 6 mol L-1 H2SO4. An anion exchange mechanism is proposed for the extraction of V(V) involving the formation of the complex anion VO2SO4-. The selectivity of the PIM towards V (V) was tested in the presence of Mo(VI), Al(III), Co(II), Cu(II), Fe(III), Mn(II), and Ni(II). Only Mo(VI) was co-extracted with V(V) at pH 2.3. The Mo(VI) interference was eliminated by a two-step separation procedure in which Mo(VI) was extracted at pH 1.1 which was followed by the selective extraction of V(V) at pH 2.3. The PIM was found to be stable over five extraction/back-extraction cycles.