Enhanced nickel removal by N, S co-doped hierarchical porous biochar in capacitive deionization process: Performance and application

Despite the effectiveness of capacitive deionization (CDI) in removing heavy metals, several issues exist, particularly the lack of high-performance electrode materials. In this study, a hierarchical porous carbon was synthesized by combining a novel organic potassium salt as a source of N and S, and biochar derived from casuarina leaves (CL). The results revealed that the pyrolysis temperature plays a crucial role in determining the performance of materials. Owing to the synergistic effects of N and S, the etching effects of intermediates, and the appropriate pyrolysis temperature, a well-balanced structure with optimal pore distributions was achieved, facilitating the Ni2+ removal from aqueous solution with an impressive adsorption capacity of 36.86 mg g- 1. Additionally, the prepared materials demonstrated significant reactivity in CDI systems during cyclic tests and in practical applications involving electroplating wastewater, establishing their considerable potential for realworld use. Density functional theory (DFT) calculations highlighted the essential roles played by N and S in adjusting of carbon frameworks and optimizing electron density distribution. This study introduces a promising approach for designing N, S co-doped biochar materials and broadening the scope of asymmetric CDI in the treatment of electroplating wastewater.