A sustainable process for tungsten extraction from wolframite concentrate

Aiming to explore a sustainable process for tungsten extraction from wolframite concentrate, the digestion behavior and mechanism of wolframite in HCl solution at atmospheric pressure were firstly investigated in this work. The results showed that the digestion efficiency of wolframite reached 99.3% at the optimum condition: particle size of D(95) = 20 mu m, stirring intensity of 250 r/min, reaction temperature of 90 degrees C, HCl stoichiometric ratio of 3.0, liquid to solid ratio of 3:1, and duration of 4 h. In the initial stage of digestion, tungsten was mainly dissolved into HCl solution, when the tungsten dissolution reached balance, solid H2WO4 layers were formed on the particle surface. The accumulation of Fe2+ and Mn2+ in HCl solution reduced the digestion efficiency of wolframite. The process of atomization-oxidative thermal decomposition is feasible for the recovery of Fe and Mn and recycling of HCl from the mother solution of digestion. Additionally, it was showed that the digested product had an excellent leachability of tungsten in NH3 center dot H2O solution with WO3 leaching efficiency above 99.5%, and the (NH4)(2)WO4 solution was qualified for ammonium paratungstate (APT) production. The wrapping of wolframite by quartz, as well as the solid H2WO4 layers covering on wolframite particles, is a crucial factor for the incomplete digestion. This work has the potential to develop a novel technique for tungsten extraction from wolframite concentrate bypassing the alkali leaching process.