Activation of peroxodisulfate by Ag3PO4/N, S-doped graphene for efficient organic degradation and bacterial disinfection

Advanced peroxodisulfate (PDS)-based oxidation processes have a promising potential for water purification. In this study, Ag3PO4 coupled with nitrogen and sulfur co-doped graphene (NSG) was synthesized and, owing to its excellent visible-light utilization efficiency, Ag3PO4-NSG catalyst was used for photoactivation of PDS. Under optimal reaction conditions of 20 mg·L-1 amoxicillin (AMX), 0.2 g·L-1 Ag3PO4-NSG, and 1.25 mM PDS, the Ag3PO4-NSG/PDS/visible-light system achieved 100 % removal efficiency of AMX in 10 min; the kinetic reaction constant of this system (0.48 min−1) was 28.38 and 5.14 times higher than that of Ag3PO4-NSG/PDS and Ag3PO4-NSG/visible-light systems, respectively. This enhancement is attributed to the presence of NSG, which provides additional active sites and effectively facilitates charge transfer. Additionally, the effects of the amount of photocatalyst, initial contaminant concentration, and initial PDS concentration were investigated. Possible intermediates and degradation pathways were also investigated. The proposed system exhibited excellent degradation ability in water bodies with different water quality characteristics and in complex real water. Moreover, this system showed excellent water disinfection capability, achieving complete inactivation of Escherichia coli within 20 min, with an improvement of 3.0-log inactivation of E. coli than that by the Ag3PO4-NSG system. Based on the appropriate energy band level of Ag3PO4-NSG, the carrier separation rate was improved, and sulfate (SO4·-), hydroxyl (·OH), and superoxide (·O2–) radicals were produced for the effective degradation of AMX and inactivation of E. coli. This study contributes to the application of Ag3PO4-based photocatalyst for water purification and provides new opportunities for PDS photoactivation.