Selective removal of thiosulfate from coke oven gas desulfurization wastewater by catalytic wet air oxidation with manganese-based oxide from spent ternary lithium-ion batteries

Abstract

Selective and efficient removal of thiosulfates (S₂O₃^2-) to recover high-purity and value-added thiocyanate products by fractional crystallization process is a promising route for the resource treatment of coke oven gas desulfurization wastewater. Herein, catalytic wet air oxidation (CWAO), with manganese-based oxide synthesized from spent ternary lithium-ion batteries (MnO_x-LIBs), was proposed to selectively remove S₂O₃^2- from desulfurization wastewater. 98.0 % of S₂O₃^2- is selectively removed by the MnO_x-LIBs CWAO system, which was 4.1 times that of the MnO_x CWAO system. The synergistic effect among multiple metals from spent LIBs induces the enlarged specific surface area, increased reactive sites and formation of oxygen vacancy, promoting the adsorption and activation of O₂, thereby realizing high-efficiency removal of S₂O₃^2-. The satisfactory selective removal efficiency can be maintained in the proposed system under complex environmental conditions. Notably, the proposed system is cost-effective and applicable to actual wastewater, in which 81.2 % of S₂O₃^2- is selectively removed from coke oven gas desulfurization wastewater. More importantly, compared with the typical processes, the proposed process is simpler and more environmentally-friendly. This work provides an alternative route to selectively remove S₂O₃^2- from coke oven gas desulfurization wastewater, expecting to drive the development of resource utilization of coke oven gas desulfurization wastewater.

Keywords: CWAO; Coking wastewater; Spent LIBs; Thiocyanate; Thiosulfate.