Efficient visible-light-driven photocatalysis: simultaneous degradation of multiple pollutants with bismuth oxyhalide solid solutions†

Abstract

Visible-light-driven photocatalysis is considered as a sustainable and cost-effective method for water remediation. In aquatic environments, the coexistence of multiple contaminants, such as organic and inorganic compounds, poses a potential threat to both biological organisms and human health, complicating their removal. Despite the urgent need for the development of comprehensive solutions, the research on the concurrent and simultaneous removal of multiple pollutants remains limited primarily relies on photocatalysts based on heterojunctions. To address this issue, we have prepared BiOCl_0.9I_0.1 and BiOBr_0.9I_0.1 solid solutions, exhibiting well-tailored band gaps and energetics of the conduction and valence bands, using an easy chemical precipitation approach. These synthesized materials exhibited exceptional photocatalytic efficacy under visible light, effectively removing a complex mixture of contaminants, including ciprofloxacin (CIP), methylparaben (MP), and rhodamine B (RhB), from water. Particularly noteworthy was the outstanding performance of BiOCl_0.9I_0.1, which demonstrated a complete removal of RhB within 10 min, CIP within 40 min, and an 86% degradation of MP within 40 min. This superior performance can be attributed to the materials' exceptional optical and (photo)electrochemical properties. Furthermore, the synergistic or antagonistic effects coexisting contaminants, organic matter, and inorganic ions on the photodegradation process were also investigated. Additionally, the generation of reactive oxygen species (ROS), and the elucidation of the degradation pathways were examined providing valuable insights into the intricate interplay of environmental factors that may have an influence on the photocatalytic performance. Our study shows, therefore, the high potential of BiOCl_0.9I_0.1 and BiOBr_0.9I_0.1 as promising candidates for the simultaneous removal of diverse water pollutants, offering a robust and efficient approach towards advancing water purification technologies.