Visible light photocatalytic abatement of tetracycline over unique Z-scheme ZnS/PI composites

In the field of pollution control, heterojunction photocatalytic materials have attracted much attention because of their good photo-generated electron-hole pair separation efficiency. ZnS in situ growth on polyimide (PI) by the solvothermal method to fabricate unique Z-scheme ZnS/PI photocatalyst. 45ZnS/PI (Mass rate of ZnS is 45%, 45ZnS/PI) exhibited the highest degradation efficiency (84%) for tetracycline (TC), which is 11 times and 8 times higher than pure PI and ZnS under visible light irradiation. After 4 cycles of degradation experiments, the degradation efficiency of the composite reached 59%. The excellent photocatalytic activity was attributed the enhanced charge separation efficiency and reduced electron-hole pair recombination efficiency aroused by the forming Z-scheme heterostructure, which affirmed by HRTEM, XPS analysis, radical trapping experiment and ESR analysis. Compared with that of pure PI and ZnS, the composite photocatalyst could produce more active species ∙O2− and h+, and exhibited high mineralization ability, good stability and recyclability simultaneously. Moreover, the possible photocatalytic degradation pathways of TC over ZnS/PI materials were studied based on HPLC-MS analysis. This work might provide some guidance for the photocatalytic degradation mechanism, and rational construction of Z-scheme heterojunctions to solve ever-increasing environmental problems.