Separation of Simulated Mixed Mo(VI) and V(V) From HNO3 and HCl Solutions by Selective Extraction and Stripping with Tri-N-Butyl Phosphate as Extractant

Abstract

Equilibrium study was carried out to determine the optimum conditions required for Mo(VI) extraction from HNO3 solutions and subsequently, simulated mixed Mo(VI), and V(V) were extracted from HNO3 (pH = 1.0) and 6.0 mol L−1 HCl solutions with TBP dissolved in n-hexane. The variation of pH (selective extraction) and selective stripping were investigated as methods of separation of Mo(VI) and V(V). The latter method was found inefficient for separations from HNO3 solutions (pH = 1.0) except supplemented with selective stripping (back-extraction with 2.0 mol L−1 H2SO4/14.5 mol L−1 NH4OH). While from 6.0 mol L−1 HCl, selective stripping was adequate to quantitatively strip in turns the Mo(VI) and V(V) co-extracted into the TBP phase. About 100% of the co-extracted V(V) from the HCl medium was stripped in a two-stage process, in contrast to a single-stage required for Mo(VI) of the same result. The selective stripping method was found to be better because an initial appreciable co-extraction had occurred prior to stripping separation. Based on analytical and spectra data, the extracted complexes from HNO3 and HCl media were formulated as ((MoO2)7–8n(VO2)2n · (NO3)16) (16–18)n- · m TBP (where n>m) and (MoO2Cl2 · VO2 Cl) · xTBP, respectively.