High effective method for separation of molybdenum from tungsten during ammonium paratungstate crystallization process

A novel method to inhibit Mo codeposition from ammonium tungstate solution during ammonium paratungstate (APT) crystallization process by control the concentration of Cl- in the solution. Based on the plentiful APT production practices, the wonderful effect of Cl- on inhibition Mo co-deposition with APT during APT crystallization process has been found out. For a special ammonium tungstate solution with given Mo concentration, there is a corresponding threshold concentration of Cl- in order to achieve high crystallization rate and low Mo content for APT production. Using this high effective method, the primary crystallization rate of the APT increases from 80% to 96% and the resultant APT is zero-grade with very low Mo concentration (&le 2 × 10-5). The APT products have perfect crystal morphology and homogenous particle size (40~50 μm). A possible mechanism of Cl- inhibiting molybdenum deposition is proposed.