Continuous running test of the solvent extraction separation of Mo and W by H2O2-complexation with TRPO/TBP

Abstract

An unusual multi-stage extraction and stripping continuous running test was carried out in a mixer-settler. The test of the solvent extraction separation of molybdenum (Mo) and tungsten (W) from ammonium tungstate solution containing high content of Mo was carried out by using a mixture of tri-alkyl phosphine oxide (TRPO) and tributyl phosphate (TBP) as extractant, hydrogen peroxide (H2O2) as complex agent and ammonium bicarbonate (NH4HCO3) solution as stripping agent. According to the effect of pH distribution and storage time on extraction and the poor phase separation of the stripping system, the improvements such as acid addition into middle one stage of extraction, 2-section countercurrent extraction and 2-section concurrent stripping were proposed in order to improve the Mo/W separation effect and phase separation property. The ammonium paratungstate (APT) product was prepared by evaporating crystallization from the 2nd-section raffinate. The continuous running test had successfully and continuously run for more than 98h. The results indicated that the system was very stable and the separation property good. The Mo/WO3 (mass ratio) in the 2nd-section raffinate was less than 1×10−4 under optimal conditions using the aqueous solution containing 110–150g/L WO3 and Mo/WO3 (mass ratio) 10%–15%. The APT product could meet the requirement of 0 grade of APT of the national standards GB/T 10116-2007 of China.