Synthesis of a Co/Ni-MOF-74@PDI Z-scheme photocatalyst as a highly efficient photo-assisted Fenton-like catalyst for the removal of chlortetracycline hydrochloride.

Abstract

In this paper, ultra-thin nanofiber PDI was obtained by self-assembly dispersion of commercial PDINH. A novel Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material was constructed by a simple solvothermal method. XRD, SEM, TEM, FT-IR and other characterization techniques proved the successful preparation of the Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material. By degrading chlortetracycline hydrochloride, it was found that the photocatalytic activity of Co/Ni-MOF-74@PDI was much higher than that of pure Co/Ni-MOF-74 and PDI. Subsequently, Co/Ni-MOF-74@PDI was used to activate H2O2 to further improve the degradation efficiency of chlortetracycline hydrochloride. It was found that the photocatalytic performance was greatly improved after the addition of 19.6 mM H2O2 to the system, and the degradation rate of chlortetracycline hydrochloride was 87% within 90 min. The electron transfer pathway and H2O2 activation mechanism of the Co/Ni-MOF-74@PDI composite photocatalyst were proved by free radical quenching experiments, electron paramagnetic resonance analysis and X-ray electron spectroscopy. Finally, the easy exfoliation point and degradation pathway of chlortetracycline hydrochloride were studied using density functional theory, UPLC-MS and toxicity evaluation software. It was found that the main active substances were h+, ˙O2, 1O2 and ˙OH, and the toxicity of chlortetracycline hydrochloride and its intermediates was evaluated.