A novel complexation method for separation and recovery of low valence vanadium, iron and chromium from sulfuric acid solution

Abstract

Traditional methods of vanadium recovery from vanadium slag suffer from serious environmental pollution due to the residue and wastewater containing highly toxic V(V) and Cr(VI). To avoid this, a complexation method based on sodium diethyldithiocarbamate (DDTC) complexing agent was proposed to separate and recover V(IV), Fe(II), Cr(III) in the leaching solution directly prepared from vanadium slag. Firstly, the recovery effect of DDTC on metal ions was studied in the imitated solution containing V (IV), Fe (II) and Cr (III), 97.67% vanadium, 99.51% iron and 98.99% chromium were recovered, respectively. In addition, DDTC was recycled in the complexation process. After four cycles, the regeneration rate of DDTC remained above 86%. Then, this method was applied to the leaching solution of vanadium slag, and 97.38% Cr, 97.69% V, 99.66% Fe and 97.64% Mn were recovered, respectively. Chromium was recovered as Cr2O3 with purity of 97.1%. Most iron was recovered as (NH4)2Fe(SO4)2·6H2O with purity of 99.23%. Manganese and a small amount of iron were enriched in the slag, which could be used to produce manganese alloy. Vanadium was recovered as calcium salt, which could be used to produce VOSO4 electrolyte with purity greater than 99.8%. Without waste water and residue containing highly toxic V(V) and Cr(VI) produced in this new method, which provides a new strategy for cleaner comprehensive utilization of vanadium slag.