Preparation of electrolyte for vanadium redox flow battery from sodium-polyvanadate precipitated wastewater

Abstract

In order to reduce pollution from wastewater and recycle the valuable metal in the vanadium precipitation process, sodium polyvanadate precipitated wastewater was utilized to prepare an electrolyte for the vanadium redox flow battery after two-stage purification via solvent extraction, which removed most of the impurities, especially Mn. The concentration of impurity ions was less than 10 ppm, as obtained by using inductively coupled plasma-optical emission spectroscopy, and the electrolyte obtained from the wastewater complied with the Chinese national standard. The method applied herein can simplify the preparation process compared to the conventional method and avoid ammonia nitrogen pollution. Electrochemical analysis showed that the properties of the prepared electrolyte were similar to those of the standard electrolyte. From the charge/discharge test, the energy efficiency and coulombic efficiency of the electrolyte reached nearly 90% of those of the standard electrolyte, which indicates that the electrolyte prepared from wastewater has the potential for commercial applications.