In situ synthesis of Bi/Bi24O31Br10 nanosheet for enhanced photocatalytic degradation of tetracycline: Kinetics, density functional theory, and toxicity studies

Abstract

Achieving highly controlled and directional electron transfer at catalyst interface remains a persistent challenge in photocatalysis. Herein, Bi/Bi₂₄O₃₁Br₁₀ nanosheets were prepared through a simple in situ reduction method to enhance the photocatalytic degradation of tetracycline (TC). Leveraging the surface plasmon resonance (SPR) effect of metallic Bi and the marked enhancement of interfacial charge transfer and separation efficiency, the optimized Bi/Bi₂₄O₃₁Br₁₀ nanosheets exhibited significantly improved TC photodegradation performance, achieving a degradation efficiency of 80.78 % within 120 min under visible light irradiation-surpassing the performance of pristine Bi₂₄O₃₁Br₁₀ nanosheets. Notably, the Bi/Bi₂₄O₃₁Br₁₀ nanosheets demonstrated robust degradation efficiency under diverse conditions, including a broad pH range (3.0–9.0), varying TC concentrations (5–25 mg L⁻¹), different photocatalyst dosages (5–20 mg), and in the presence of common inorganic anions (e.g., Cl^-, HCO₃^-, SO₄^2-, and NO₃^-). The mineralization process and degradation pathway of TC were elucidated through active sites trapping experiments, liquid chromatography-mass spectrometry (LC-MS), three-dimensional excitation-emission matrix (3D EEM) spectroscopy, and density functional theory (DFT) calculations. Additionally, the ecotoxicity of TC and its degradation intermediates was evaluated using the Toxicity Estimation Software Tool (T.E.S.T.) and the Ecological Structure Activity Relationships (ECOSAR) model, revealing a reduction in environmental toxicity during the degradation process. This study provides valuable insights into the rational design of advanced Bi-based semiconductor photocatalysts for efficient environmental remediation.