Preliminary study on preparation of ammonium metatungstate from ammonium tungstate solutions using bipolar membrane electrodialysis

A novel process for the preparation of ammonium metatungstate (AMT) from industrial ammonium tungstate solutions using bipolar membrane electrodialysis (BMED) was developed. The preliminary study results showed that the BMED process can be used to effectively prepare the AMT solution from the (NH4)2WO4 solution with the current efficiency of 73.8%. The direct recovery of WO3 reached 99.5% with the power consumption only 864.3 kWh/t WO3. The obtained AMT solution can be directly used to produce the AMT crystal. The solubility of the final AMT product reached 650 g AMT per 100 g H2O at 25 °C, which meets the Chinese National Standard on the preparation of petrochemical hydrodesulfurization catalysts. The new process exhibits significant advantages including short flow sheet, low energy consumption, high recovery of WO3 and high quality of product, and environmental friendliness.