Synthesis of AgCl/ZIF-8/C–TiO2 heterojunction photocatalysts for enhanced degradation of levofloxacin under visible-light

The design of photocatalytic heterojunctions for the degradation of organic contaminants from wastewater under visible illumination has attracted much attention recently. Through these heterojunctions, the separation efficiency of photogenerated charges can be increased, thus enhancing photocatalytic activity. Herein, ternary heterojunctions composed of carbon-doped TiO2 (C–TiO2) decorated by Zn-zeolitic imidazole framework (ZIF-8) and AgCl have been constructed as photocatalysts by facile deposition and precipitation routes with the aim of degrading organic pollutants in water (levofloxacin (LVFX) antibiotic). The developed heterojunction structure of C–TiO2, ZIF-8, and AgCl synergistically contributed to the efficient transfer of photo-charges and prevention of their recombination, thus achieving high photocatalytic efficiency, in which 98 % of LVFX can be decomposed within 60 min under solar illumination. The outstanding performance of the AgCl/ZIF-8/C–TiO2 composite was credited to the dual heterojunctions of AgCl and C–TiO2 with ZIF-8, which decreased the degree of photogenerated carrier's recombination. Accordingly, the proposed mechanism and the photodegradation pathways have been detailedly elucidated. Also, it was confirmed through trapping experiments that •O2- and h+ were considered the most effective species in the photodegradation process. Moreover, the AgCl/ZIF-8/C–TiO2 photocatalyst system displayed remarkable photostability during successive photocatalysis.