Separation Techniques

Biography

Biography: James O. OJo

Abstract

The extractive separation of vanadium (V) and molybdenum (VI) from 6.0 mol dm^-3 HCI in the presence of 0.1 mol dm^-3 KCI as a salting -out agent using trioctyl phosphine oxide (TOPO) IN n-heptane has been investigated. Equilibrations were performed at optimal contact time of 5 min. The V (V) and Mo (VI) ions were determined spectrophotometrically by the phosphotungstate and thiocyanate methods respectively. From their individual synthetic solutions, the effect of increasing concentration of TOPO in the range 0.013-0.065moldm^-3 to enhance a selective extraction, proved inefficient. This is because both ions were substantially extracted with percentage V(V) extraction (E%) optimized at 90.0% while Mo(VI) was 95.0%, with both observed at a concentration of 0.52 mol dm^-3  TOPO. This was reflected in the low separation factor() of the range 1.8-2.1. For the synthetic simulated mixture of the metals in 6.0 mol dm^-3 HCl, parameters such as the effect of concentration of TOPO and organic to aqueous phase volume ratio (1:1- 4:1) on the percentage of the metal extracted or stripped was examined. The optimal separation of V(V) and Mo(VI) was achieved by selective stripping with percentage of V(V) and Mo(VI) stripped (separately) after two stages being 99.0 and 99.8% respectively. In this process we used 2.0 mol dm^-3 H₂SO₄ and 14.5 mol dm^-3 NH₃ in that order, at organic to aqueous phase volume ratio (1:1 to 4:1). It decreased the percentage of the metals co-extracted and hence that available for stripping (E% of V(V) decreased from 90.0 to 75.0% and for Mo(VI) 96.0 to 57.1% for a single stage stripping. From the slope and spectral analysis , the stoichiometries of the composition of the organic phase were formulated as VO₂Cl. 2TOPO and MoO₂Cl₂. TOPO.