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.

RÉSUMÉ

On a utilisé une solution industrielle de (NH₄)₂WO₄ pour préparer directement une solution de métatungstate d’ammonium en utilisant l’électrodialyse à membrane bipolaire. On a examiné les effets de la densité de courant, des concentrations initiales de NH₄HCO₃ et de WO₃ dans l’alimentation, de la température et du pH de la solution produite, sur le procédé. On a effectué un essai de fonctionnement continu sous conditions optimales et les résultats ont montré que la récupération directe de WO₃ atteignait 99.97% avec un rendement moyen du courant de 72.5% et une consommation d’énergie de 0.877 kWh/kg de WO_3. On utilisait une solution d’alimentation contenant 172.3 g/L de WO₃ et une solution de base contenant 1.5 mol/L de NH₄HCO₃ avec une densité de courant de 700 A/m² et un pH de 2.8 de la solution dans le compartiment salin à 31°C pendant 600 min. Ceci indiquait une opération facile et stable du procédé d’électrodialyse à membrane bipolaire.

KEYWORDS:

• Ammonium metatungstate
• ammonium tungstate
• bipolar membrane
• electrodialysis

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Wenjuan Guan is a lecturer at the School of Metallurgy and Environment, Central South University, China. The recovery of tungsten from its mineral ores and secondary resources such as spent catalysts is one of the areas of her research work.

Guiqing Zhang is a professor at the School of Metallurgy and Environment, Central South University, China.The novel process for tungsten hydrometallurgy based on direct solvent extraction in alkaline medium is one of the areas of his reserach work.

Li Zeng is an associate professor at the School of Metallurgy and Environment, Central South University, China. The novel process for nickel hydrometallurgy based on direct solvent extraction in acidic medium is one of the areas of his research work.

Chengwei Zeng completed his master degree studies at the School of Metallurgy and Environment, Central South University, China 2 years ago. He now works as a registered EAI engineer in a domestic company.

Guanghao Shang has recently completed his PhD studies in the BMED process applied to the treatment of waste water containing trace amount of heavy metals at the School of Metallurgy and Environment, Central South University, China.

Additional information

Funding

The authors are thankful to the China Postdoctoral Science Foundation (2015M572264), the China Scholarship Council (CSC201606375041), and the innovation driven program of Central South University (2015CX001) for financial support.