Synthesis of dual p-n heterojunction of NiWO4/CdS/ZIF-67 photocatalyst as a highly efficient photo-assisted fenton-like catalyst for removal of doxycycline hydrochloride

Abstract

There was no report about dual p-n junction photocatalyst activating persulfate to accelerate the photodegradation of organic pollutants until now. Therefore, there was a need to investigate dual p-n junction photocatalyst activating persulfate to accelerate photodegradation. In this paper, we synthesized a dual p-n junction photocatalyst, NiWO4/CdS/ZIF-67, which demonstrated superior degradation capabilities for doxycycline hydrochloride compared to pure NiWO4, ZIF-67 and NiWO4/CdS. NiWO4 exhibited p-type semiconductor properties, while CdS and ZIF-67 exhibited n-type semiconductor properties. By combining them into a composite photocatalyst, a conventional type II heterojunction formed at the interface of the p-n junction. This design established an internal electric field at both ends, effectively separating the photogenerated electrons and holes of each individual photocatalyst. Consequently, the photocatalytic activities of the materials were maximized. To further enhance the degradation of doxycycline hydrochloride, we employed NiWO4/CdS/ZIF-67 to activate persulfate under visible light irradiation. The results showed that the best degradation was achieved when 0.3 mmol persulfate was added with a k-value of 0.00681 min−1. We investigated the mechanism of activation of persulfate and the degradation pathway of doxycycline hydrochloride over the dual p-n heterojunction NiWO4/CdS/ZIF-67 catalysts. Additionally, we evaluated the toxicity of doxycycline hydrochloride and its intermediates using toxicity evaluation software.