An insight into N,S-codoped activated carbon for the catalytic persulfate oxidation of organic pollutions in water: Effect of surface functionalization

To reveal the surface active groups on N,S co-doped activated carbon (AC) for persulfate (PS) activation, control experiments on different modified ACs treated by oxidation, single-S and single-N doping were performed. The modified ACs were characterized by N-2 adsorption/desorption, Raman spectra, Boehm titration and XPS. It was found that the N,S co-doped AC presented higher catalytic performance than that of single-element doped ACs. The corresponding methyl orange (MO) removal and COD removal in 30 min reached 99 % and 69 % under mild conditions. The significant enhancement on N,S co-doped AC can ascribe to the presence of basic groups of quinone-like O, thiophene-like S, graphitic N and pyridinic N. S dopants were more active than O-containing groups and N dopants. Quenching experiment indicated that surface bound radical oxidation process was the dominant process for MO removal. These findings provided new insights into PS activation by N,S co-doped AC with functionalized surfaces.