Hybrid electrochemical process and electrodialysis treatment of a rare earth extraction wastewater: Organic removal and Na2SO4 recovery

Recovery of value-added resources from rare earth extraction wastewater is a pivotal vehicle for sustainable wastewater management. In this study, a novel technology that integrated electrodialysis (ED) with electrochemical oxidation (ECO) for the sustainable extraction of Na2SO4 from rare earth extraction wastewater was presented. The impacts of operating parameters on the performance of the ED and ECO processes for rare earth extraction wastewater were investigated. Our results revealed that ECO effectively removed organics, achieving removal rates exceeding 95 % within 90 min at a pH of 3 and a current density of 30 mA/cm2. Concentration factors of up to 1.8 corresponding to energy consumption of 70.7 kWh/m3 were achieved at an operating voltage of 9 V, a volume ratio of 1:1.5 and a circulation flow rate of 600 mL/min. In addition, both ECO and ED were applied to Na2SO4 recovery from rare earth extraction wastewater under optimal parameters and a preliminary evaluation of the performance and economics of this hybrid process was undertaken. The results underscore that the hybrid ECO and ED process offers potential for Na2SO4 recovery from rare earth extraction wastewater and other mineral rich and mining tailing-like effluents alike.