Enhanced removal of copper ions from wastewater using small spherical Fe-N-C material via selective electro-sorption: Experiment and calculation

Abstract

In the current research, the resource recovery technology for Cu-containing wastewater from electroplating is still a difficult problem. Capacitive deionization technology (CDI) has received widespread attention for its strengths of convenient operation, low cost, and environmentally friendly. In this paper, Fe-N-C was prepared as the electrode material for the treatment of Cu-containing wastewater by capacitive deionization technology through one-pot thermal method. The optimum treatment conditions of Fe-N-C for Cu-containing wastewater were voltage equal to 1 V, pH = 5, and the inlet flow rate was 5 mL/min. The electro-adsorption capacity of a single Cu-containing solution of 400 mg/L could reach 389.4 mg/g. Meanwhile, by carrying out ion competition experiments on five cations, namely Zn2+, Na+, Mg2+, K+, and Cu2+, which demonstrated Fe-N-C had a significant selectivity for the electro-adsorption removal of Cu2+. Theoretical calculations revealed that Fe3N and Fe4N were more dominant for Cu2+ adsorption energy and more binding for competing ions in the monovalent state, but had less practical effect on Cu2+ adsorption. The morphology of the Fe-N-C was analyzed in more depth by X-ray photoelectron spectroscopy (XPS) and other characterization methods. Combined with density functional calculations, Cu would not only displace with Fe in FeXN to form a more stable CuXN structure, but also combine with FeXN to form a Cu-FeXN structure. This is conducive to accelerating the application of CDI to recover Cu2+ from heavy metal wastewater.