Bi-doped ZnAl-layered double hydroxides with enhanced photocatalytic activity for ciprofloxacin degradation: the synergistic effect of Bi doping and oxygen vacancies

Abstract

In this study, a series of Bi-ZnAl-LDHs (BZA-X) enriched with oxygen vacancies (OVs) were synthesized by doping ZnAl-LDHs with different ratios of bismuth ions. The characterization results indicated that the doping of bismuth ions promotes the formation of oxygen vacancies (OVs), with the highest level of oxygen vacancies when the bismuth ions are doped at 50%. The level of oxygen vacancies is lower than that of the conduction band, which leads to a substantial increase in the separation efficiency of photogenerated carriers from BZA-X. In addition, the oxygen vacancies in BZA-X promote the adsorption of H⁺ in the reaction system, which further promotes the formation of ˙OH. The main active species ˙OH and h⁺ contributed the most to the photodegradation of CIP, and the degradation rate and the degradation kinetic constant of ciprofloxacin (CIP) for BZA-0.5 were 1.56 and 2.63 times higher than those of ZA, respectively. On this basis, a CIP transformation pathway was proposed based on the identified transformation products. This work provides a new strategy to improve the degradation of ciprofloxacin in wastewater through the synergistic effect of bismuth-doped and oxygen vacancies.