Utilization of waste sodium sulfate from battery chemical production in neutral electrolytic pickling

Abstract

Several industrial activities produce metal sulfates, which are controlled by strict limitations for wastewater concentrations of sulfate. One emerging area where these activities occur is the production of lithium-ion battery chemicals in which sodium sulfates are formed because of cathode precursor co-precipitation. Several solutions for sulfate removal exist, but one option is to reuse the sulfate side stream in other processes to increase circular economy and atom efficiency. In this paper, the reuse of sodium sulfate solution in a steel industry pickling solution is considered. Neutral electrolytic pickling experiments were carried out to compare the pickling behavior of the electrolyte dissolved from pure sodium sulfate and the electrolyte diluted from a side stream solution. Effect of impure electrolyte was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectrometry (EDS). Concentrations of the metal ions were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results indicated a slight increase in current efficiency with the side stream electrolyte solution, while overall the pickling behavior remained similar. This suggests that a side stream sodium sulfate solution could be used as a pickling electrolyte, reducing the need for pure reagents.