Selective leaching of vanadium from vanadium-molybdenum residue based on carbonation transformation at ambient temperature

Abstract

A novel process is proposed to selectively leach vanadium and separate molybdenum from the vanadium-molybdenum residue (VMR) in the weakly alkaline solution, which is built on carbonation leaching. The optimal leaching conditions of the 16 wt% sodium carbonate, leaching temperature of 25℃, leaching time of 4 h, and liquid-solid ratio of 1.5:1 mL/g were systematically researched. And the leaching efficiency of vanadium and molybdenum were 86.85% and 7.73%. The equilibrium constant K was calculated from the solubility product Ksp of the calcium-based compounds, and it was found that calcium vanadate was considerably preferred to the transformation of calcium molybdate and sodium carbonate. Calcium vanadate was simpler to dissolve than calcium molybdate, simultaneously vanadium and molybdenum were separated. XRD and XPS analysis confirmed that vanadium was leached while molybdenum remained in the leaching residue. One of the reasons why a small amount of vanadium was not leached was that calcium sulfate participated in the carbonation transformation and consumed sodium carbonate. The other reason is that part of V(III) stably existed in the (Cr, Fe)2O3 spinel. The whole process of carbonation leaching is carried out at ambient temperature, which is a process of clean separation of vanadium and molybdenum.