Remediation of the vanadium slag processing residue and recovery of the valuable elements

The vanadium slag processing residue (VSPR), which is a metallurgical waste produced during the vanadium extraction process from the vanadium titano-magnetite, exhibits potential environmental risk due to the toxicity of chromium in this residue. To remediate the VSPR and recover the valuable elements including iron, chromium, vanadium and titanium, a novel process, i.e., "carbothermic reduction"-"magnetic separation"-"sulfuric acid leaching"-"solvent extraction", is proposed in this work. The transfer of iron, chromium, vanadium and titanium in the novel process was theoretically and experimentally analyzed. The results demonstrate that the iron oxide can be selectively reduced via the carbothermic reduction. To minimize the loss of chromium, vanadium, and titanium in the magnetic separation, the reduction temperature is suggested to be below 1100 degrees C to inhibit the reduction of the chromium, vanadium, and titanium oxides in the spinel of (Fe,Mn)(x)(V,Cr,Ti)(3-x)O-4. Iron was concentrated in the magnetic phase while chromium, vanadium and titanium were concentrated in the non-magnetic phase after carbothermic reduction and magnetic separation. With perchloric acid as oxidizer, the spinel of (Fe,Mn)(x)(V,Cr,Ti)(3-x)O-4 in the non-magnetic phase was decomposed through sulfuric acid leaching at 160 degrees C without the generation of hexavalent chromium, and the metal elements were effectively leached. The toxicity test shows that the leaching residue is harmless. Finally, iron, titanium, vanadium, chromium could be preliminarily separated via the solvent extraction by employing D2EHPA as the extraction agent. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.