The performance and mechanism of phosphotungstic acid-modified NiFe-LDH heterogeneous photo-Fenton catalyst for efficient degradation of tetracycline

Abstract

There is a serious risk to human health because of the misuse of tetracycline and ineffective wastewater treatment systems, which have left a lot of antibiotics in the environment. In this study, a composite catalyst of phosphotungstic acid-modified LDHs (PTA-LDHs) was synthesized using ion exchange technology, and the degradation performance for tetracycline hydrochloride (TC-HCl) in a heterogeneous photo-Fenton system was examined. Surprisingly, PTA-LDHs could completely remove TC-HCl (30 mg L⁻¹) within 40 min, and after conducting five consecutive cycles of experiments, the attenuation in the TC-HCl removal rate stayed within a mere 15%. Furthermore, the PTA-LDHs/H₂O₂/vis system maintained a removal efficiency of pollutants above 75% across various antibiotic and water quality tests, underscoring its robust performance and environmental suitability. PTA-LDHs exhibited excellent purity, and acid and alkali resistance, as well as remarkable structural stability. PTA could act as a photosensitizer, which was advantageous for extending the visible light absorption range, decreasing the bandgap width, and encouraging the migration of photogenerated carriers according to optical properties, and electrochemical tests, enhancing the catalytic performance. Free radical quenching and EPR testing indicated that the catalyst surface ·OH, and h⁺ were the main active species. Based on the experimental results and DFT calculations, possible degradation pathways and the toxicity of the intermediates of TC-HCl were proposed. In summary, a novel heterogeneous catalyst for the degradation of TC-HCl residues in water is presented.