Efficient recovery of tungsten from scheelite concentrates using a sulfur-phosphorus mixed acid leaching system

In recent years, a new process for leaching scheelite concentrates with sulfur-phosphorus mixed acid has been successfully industrialized. This process suffers from the elimination of the retarding effect of calcium sulfate, the selective extraction of tungsten from the H3PW12O40-H2SO4-H3PO4 mixture solution, and the removal of introduced phosphorus. Therefore, in this paper, we investigated the inhibition measures of a calcium sulfate-blocking membrane, the selective extraction of tungsten by ion exchange, and the removal of phosphorus by the magnesium ammonium salt method. The results showed that the addition of calcium sulfate whisker seeds and a higher H3PO4 concentration inhibited spontaneous diffuse nucleation, promoted crystal growth, and avoided the formation of a dense blocking film. About 98 wt.