A novel Z-scheme covalent triazine framework/silver phosphate (CTF/Ag3PO4) heterojunction photocatalyst: Improved adsorption, photocatalytic degradation and degradation mechanism of rifampicin

Abstract

In order to achieve a suitable covalent triazine framework (CTF) photocatalyst, it is imperative to further improve synthesis conditions of ionothermal trimerization technique. Therefore, in this study, CTF was prepared using a binary ZnCl2-NaCl molten salt mixture at 250 °C for 20 h. Furthermore, a Z-scheme CTF/silver phosphate (CTF/Ag3PO4) was prepared by facile in-situ precipitation technique for the adsorption and photocatalytic degradation of rifampicin (RIF) under visible light. The synthesized CTF, Ag3PO4, and CTF/Ag3PO4 composites were extensively characterized using various spectroscopic tools. The composites displayed improved visible light absorption, low resistance to charge transfer, and enhanced heteroatom effect (HAE) compared to pristine CTF and Ag3PO4. The CTF/Ag3PO4 composite showed improved rifampicin removal from solution. Consequently, the 0.75 % CTF/Ag3PO4 composite attained an adsorption capacity of 41.72 mg/g and 100 % degradation of RIF, which corresponded to a 3.5-fold improvement compared to pristine CTF. Its efficiency was attributed to its narrow band gap of 2.20 eV, improved surface area, and low resistance to charge transfer. Degradation product analysis revealed that rifampicin with m/z of 823 was successfully degraded to m/z of 189 within 360 min. The successful removal of RIF from influent wastewater (65.5 %) and tap water (75.5 %) samples indicates the practical application of 0.75 % CTF/Ag3PO4. The stability measurement suggests a stable 0.75 % CTF/Ag3PO4 material compared to Ag3PO4.