A photocatalysis-self-Fenton system based on NCDs@ZnInS composites at neutral pH and low amount of Fe for the effective degradation of antibiotics.

Photocatalysis-self-Fenton combining photocatalytic production of HO 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 ZnInS (NCDs@ZnInS) composites that exhibits effective degradation of antibiotics under neutral pH using low amounts of Fe. The decoration of ZnInS with NCDs significantly increased the surface area, visible light absorption, charge transfer ability and oxygen adsorption ability. NCDs@ZnInS composites exhibited a high HO production rate (1528 μM g•h) under visible light, which was 1.9 and 5.3 times higher than ZnInS and NCDs, respectively. Meanwhile, the Fe/NCDs@ZnInS system with a low concentration of Fe(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 stemmed from the higher amount of inner-generate HO under neutral pH and easy regeneration of Fe by photoinduced electrons for high •OH yields. Additionally, the Fe/NCDs@ZnInS 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.