Mechanism of Selective Precipitation of Molybdenum from Tungstate Solution

Selective precipitation of molybdenum (Mo) is a widely utilized method for separation of Mo from tungstate solution; however, the corresponding mechanism is still unclear. The aim of the work presented herein is to investigate the effects of the reaction time, temperature, and CuS dose on the precipitation of Mo and characterize the obtained precipitates via powder x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) analyses. The results demonstrate that sulfurized molybdenum (\( {\text{MoS}}_{ 4}^{{ 2 {-}}} \)) can be selectively precipitated as NH4CuMoS4 or Cu2MoS4 on addition of CuS depending on the reaction temperature and CuS dose, and a corresponding reaction mechanism is proposed. Under the optimum conditions of CuS/Mo = 1.5, T = 35°C, and t = 8 h, up to 99% of the Mo was selectively precipitated. The present study elucidates the mechanism of Mo precipitation and provides basic and robust guidelines for separation of Mo from tungstate solution.