Valorisation of alkali from tungsten leaching solution using diffusion dialysis and selective electrodialysis for anion-exchange membrane water electrolysis

Abstract

Currently, tungsten mining procedures discharge a large amount of alkali wastewater, necessitating the development of sustainable approaches to valorise valuable bases for further utilization. In this study, diffusion dialysis (DD) and selective electrodialysis (SED) were utilized to recycle the alkali from a simulated tungsten leaching solution; the recycling base was further subjected to anion-exchange membrane water electrolysis (AEMWE) for H2 production. The results indicate that DD is capable of recycling 0.447 mol/L NaOH base with negligible leakage of WO42−, while the SED process enables the recycling of 1.63–2.01 mol/L NaOH but contains 0.11–0.14 mol/L WO42−. The AEMWE experiment showed that the water electrolyser with SED recycling alkali had a current density of 580.26 mA·cm−2 at 1.8 V, which is much greater than 374.16 mA·cm−2 with DD treatment solution and 352.81 mA·cm−2 without any treatment. The WO42− impurities could adsorb on the surface of the catalyst, which further occupied the catalytic active site of the electrode catalyst and reduced the active specific surface area of the catalyst. This work demonstrated the ability of the SED and DD approaches to recycle alkali for hydrogen production, creating a new pathway for the valorisation of alkali from the tungsten mining industry.