A photocatalysis-self-Fenton system based on NCDs@ZnIn2S4 composites at neutral pH and low amount of Fe2+ for the effective degradation of antibiotics

Photocatalysis-self-Fenton combining photocatalytic production of H 2 O 2 with Fenton reaction has been a hotspot, but the pH limitation and iron sludge production problems remain unsolved. Herein, we proposed a self-fenton system based on N-doped carbon dots modified ZnIn 2 S 4 (NCDs@ZnIn 2 S 4 ) composites that exhibits effective degradation of antibiotics under neutral pH using low amounts of Fe 2+ . The decoration of ZnIn 2 S 4 with NCDs significantly increased the surface area, visible light absorption, charge transfer ability and oxygen adsorption ability. NCDs@ZnIn 2 S 4 composites exhibited a high H 2 O 2 production rate (1528 μM g −1 •h −1 ) under visible light, which was 1.9 and 5.3 times higher than ZnIn 2 S 4 and NCDs, respectively. Meanwhile, the Fe 2+ /NCDs@ZnIn 2 S 4 system with a low concentration of Fe 2+ (1 mg/L) could remove over 95% levofloxacin and oxytetracycline within 30 min. Interestingly, the highest degradation efficiency occurred under neutral pH. Quenching experiments and analytical measurements indicated that the high catalytic performance under pH = 7 with low amounts of Fe 2+ stemmed from the higher amount of inner-generate H 2 O 2 under neutral pH and easy regeneration of Fe 2+ by photoinduced electrons for high •OH yields. Additionally, the Fe 2+ /NCDs@ZnIn 2 S 4 system exhibited high degradation performance under different water matrix and ultrahigh degradation efficiency towards levofloxacin under real sunlight irradiation. The work shows the prospects of photocatalysis-self-Fenton systems for overcoming the pH limitation and the difficulty of iron sludge separation in the purification of effluents.