A new recyclable sulfurizing reagent for Mo-S complexes and separation of molybdenum from tungstate solutions

Abstract

Separation of tungsten and molybdenum has been a key technology in tungsten metallurgy. In this study, a new sulfurizing reagent of thiocyanuric acid (TTCA) was employed to sulfurized trace amount of molybdenum in ammonium tungstate solution. The effects of initial feed pH, reaction temperature and molar ratio of Mo/TTCA on complexing of Mo and S were investigated. The Mo-S complex was also characterized. The organic phase consisting of 50% (v/v) N1923 in kerosene was used to selectively extract molybdenum from a synthetic tungstate solution containing 100 g/L WO3 and 1 g/L Mo. The extraction of molybdenum reached 99.5% after a four-stage counter current extraction, leaving only 5 mg/L Mo in raffinates with a mass ratio of Mo/WO3 less than 3.3 × 10−6. More than 95% of molybdenum can be stripped from loaded organic phases using 2 mol/L NaOH solution in a single stage. The sulfurizing reagent can be recovered for sustainable reuse. Compared to conventional inorganic sulfurizing reagents, the use of organic reagent TTCA avoided the generation of toxic H2S gas.