Efficient separation of V(V) and Cr(VI) in aqua by microemulsion extraction

Abstract

Separation of V(V) and Cr(VI) in aqua is intensively demanded in consideration of full resource utilization and environmental safety of vanadium extraction industry, which is however a challenge due to their highly similar chemical properties. In this work, chromium transformation is firstly conducted to convert Cr(VI) anions into Cr(III) cations that are differentiable from V(V) anions. Then, the microemulsion system of Aliquat 336/isoamyl alcohol/n-heptane/NaCl is utilized to selectively extract V(V) anions by method of microemulsion extraction and leave Cr(III) cations in the raffinate, leading to the separation of V and Cr. In optimal conditions of microemulsion extraction, the extraction efficiency of V is as high as 98.45% while that of Cr is only 4.44%, confirming the efficient separation of V and Cr in aqua. Extracted V is retrieved back to aqueous solution by stripping V-loaded microemulsion and simultaneously concentrated by 4 times with total recovery of 97.91%; Cr(III) left in the raffinate is environmentally safe and ready for direct precipitation recovery. The achieved separation of V(V) and Cr(VI) is thus not only efficient, but also beneficial to their subsequent recovery. This work has demonstrated a powerful separation method for V(V) and Cr(VI) with high separation capacity, efficiency and speed, which lays the essential foundation for the recovery and comprehensive utilization of V and Cr resources in vanadium metallurgy industry.