Selective electrosorption of silver ions from wastewater by biomass-derived N, S co-doped hierarchical porous carbon

• NSPC exhibited a high electroadsorption capacity of 480.5 mg g −1 for Ag + . • NSPC could selectively remove 100% of Ag + from a solution containing multiple metal ions. • High selectivity is due to the strong interaction between Ag + and S functional groups. • N doping accelerated the reduction of sorbed Ag + to Ag 0 . The recovery of precious silver (Ag) from wastewater, a dual pursuit of environmental sustainability and economic benefits, faces a formidable challenge in the selective extraction of Ag + ions amidst a matrix of other metal ions. To address this, we developed a novel N, S co-doped hierarchical porous carbon (NSPC) derived from a renewable precursor of Camellia oleifera shell. As the electrode material for capacitive deionization (CDI), the NSPC exhibited a high electrosorption capacity of 480.5 mg g −1 for Ag + ions under an operating voltage of 1.2 V. Owing to the strong reaction between Ag + and S functional groups and the synergistic effect from a hierarchical porous structure and N doping, the formation of Ag 2 S and elemental Ag is facilitated, and the NSPC cathode could selectively remove nearly 100 % of Ag + ions from saline water and a solution containing Ni 2+ , Co 2+ , Pb 2+ , Zn 2+ , and Fe 3+ ions. Furthermore, the NSPC cathode showed a high anti-interference ability in the presence of anions (C 10 H 14 N 2 O 8 2− , C 4 H 4 O 6 2− , C 5 H 7 O 5 COO − and HCO 3 − ) and excellent reusability until 9 cycles. The impressive results show that the biomass-derived NSPC has the potential for rapid and selective recovery of silver from wastewater and offers a solution for environmental remediation and metal resource recovery.