S, N co-doped Porous Carbon for the Effective Capacitive Deionization of Pb²⁺, Cd²⁺ and Cu²⁺ Ions: Performance and Mechanism

In this work, the soybean-derived S, N co-doped porous carbon (SNPC) was successfully synthesized via thiourea modification and KOH activation. The SNPC has a large specific surface area (2310.642 m 2 ·g −1 ), low resistance, excellent electron transfer capability and electric double layer capacitance (EDLC). The removal capacity of Pb 2+ , Cd 2+ and Cu 2+ by SNPC was 55.3, 48.0, and 5.3 mg·g −1 in 100 mg·l −1 signal solution at an operating voltage of 1.2 V, respectively. After undergoing 1000 charge and discharge cycles, the coulombic efficiency of SNPC remained consistently stable. Furthermore, even after subjecting it to 20 electro-sorption desorption experiments in a mixed solution, the removal efficiency for Pb 2+ , Cd 2+ and Cu 2+ still maintained a remarkable level of 90%. These results indicate that SNPC exhibits excellent cyclic performance and regeneration capability. The experimental results and DFT calculations demonstrate that the removal efficiencies of Pb 2+ , Cd 2+ and Cu 2+ by SNPC doped with S and N are superior to those by NPC solely doped with N. Thus, the present study offers an efficient and cost-effective material for the electro-sorption of Pb 2+ , Cd 2+ and Cu 2+ .