Enhanced peroxydisulfate activation by rGO/nZVI composites for efficient sulfamethoxazole degradation.

A reduced graphene oxide-supported nanoscale zero-valent iron (rGO/nZVI) composite was fabricated via an in situ liquid-phase reduction and employed to activate peroxydisulfate (PDS) for sulfamethoxazole (SMX) degradation. Characterization results indicated that rGO incorporation improved the dispersion of nZVI and increased the specific surface area and pore volume of the composite. Under the optimized conditions, the rGO/nZVI/PDS system achieved > 98% SMX removal within 10 min. The apparent rate constant was 5.6 and 13.2 times higher than those of the nZVI/PDS and PDS-alone systems, respectively. Quenching experiments and EPR results suggested the involvement of singlet oxygen (1O2) in SMX degradation, whereas freely diffusing sulfate radicals and hydroxyl radicals were not the predominant reactive species under the tested conditions. The enhanced performance of rGO/nZVI may be associated with the improved dispersion of Fe-containing sites, increased accessibility of the composite surface, and possible changes in interfacial electron-transfer processes during PDS activation. This study demonstrates the potential of rGO-supported nZVI as a PDS activator for rapid SMX removal under the tested conditions.