Defect-rich heterojunction photocatalyst originated from the removal of chloride ions and its degradation mechanism of norfloxacin

Abstract

Concentrated leachate (CL) contains typical high concentration of Cl−, and it is necessary to remove Cl− efficiently and even to achieve a high value-added product from the Cl− removal process. In this study, a Bi-contained upconversion glass–ceramic (GC) is firstly explored for ultra-efficient removal and utilization of Cl−, wherein the abundant porous structure is continuously formed in the Cl− removal process to further provide channels for the deep migration of Cl− and H+ to its inner Bi source. The high Cl− removal rates above 96% were all achieved over the best GC sample at the Cl− concentrations of 1300–13,000 mg/L, then the terminal BiOCl-based precipitates were directly collected as the near-infrared (NIR) GC photocatalysts, which possessed defect-rich heterostructure with excellent upconversion luminescence and electronic energy transmission properties. In the degradation of norfloxacin (NOR), high removal rates of 98%, 73%, and 36% were achieved under UV–Vis-NIR, Vis-NIR, and NIR irradiations. On a basis of the four possible NOR degradation pathways discussed, we found that the primary active species were attributed to O2·− and ·OH radicals under NIR and UV–Vis-NIR irradiations, respectively. Therefore, the Bi-contained GC will supply a new strategy for high-efficiency Cl− removal and value-added resource utilization.