Wenjuan Guan

Precursor solution prepared by evaporation deamination complex method for solvent separation of Mo and W by H2O2-complexation

Abstract An novel method on preparation of precursor solution for solvent separation of molybdenum (Mo) and tungsten (W) by hydrogen peroxide (H 2 O 2 )-complexation from the ammonium tungstate solution containing high Mo was studied. The precursor solution was obtained via evaporation deamination and H 2 O 2 -complex transformation processes. Then it was extracted with a mixture extractant of tri-alkyl phosphine oxide (TRPO) and tributyl phosphate (TBP) to separate Mo and W. The results indicated that the evaporation deamination complex method reduced the acid consumption by more than 90% in comparison with the traditional directly acid regulation complex method. The transformation rates of W and Mo were higher than 95% and the decomposition rate of H 2 O 2 was less than 15% at a 1.8 - 1.9 times H 2 O 2 dosage, 45-50 °C, initial pH of 1.80-1.90, and transformation volume ratio of 100% for 60 min in the H 2 O 2 -complexation transformation process. The minimum extraction rate of W was 2%, the maximum extraction rate of Mo was 82.6% and the highest separation coefficient was 76.7 in a single-stage extraction.

A novel process on preparation of ammonium metatungstate solution using bipolar membrane electrodialysis

ABSTRACT An industrial (NH4)2WO4 solution was used to directly prepare ammonium metatungstate solution using bipolar membrane electrodialysis. The effects of current density, initial concentrations of NH4HCO3 and WO3 in feeds, temperature and pH of product solution on the process were investigated. A continuous running test was carried out under the optimum conditions and the results showed that the direct recovery of WO3 reached 99.97% with average current efficiency of 72.5% and power consumption of 0.877 kWh kg−1 WO3 using a feed solution containing 172.3 g L−1 WO3 and a base solution containing 1.5 mol L−1 NH4HCO3 with a current density of 700 A m−2 and a solution pH in salt compartment of 2.8 at 31°C for 600 min, indicating easy and stable operation of the bipolar membrane electrodialysis process.