Optimization of tetracycline antibiotic photocatalytic degradation from wastewater using a novel type-II -Fe₂O₃-CeO₂-SiO₂ heterojunction photocatalyst: Performance, pathways, mechanism insights, reaction kinetics and toxicity assessment

The photocatalytic degradation of organic pollutants, especially tetracycline (TC), poses challenges in precisely targeting and selectively breaking down specific hazardous chemical groups. Herein, a new alpha-Fe2O3-CeO2-SiO2 (FeCeS) photocatalyst was synthesized and characterized by XRD, XPS, SEM, EDS, BET, PL, and TEM analyses. It was employed to optimize operational parameters, including photocatalyst dosage, TC concentration, pH levels, and visible irradiation time, in the photodegradation process of TC via the RSM-CCD method. The results indicate that the FeCeS heterojunction had a significant degradation efficiency (95.90 %) under optimum conditions (TC concentration: 25.1 mg/L, photocatalyst dose: 0.62 g/L, visible time: 94.2 min, and pH: 4.89) with the rate of 0.05 min(-1). Additionally, a mineralization rate of >62 % was recorded for TOC, suggesting that the conversion of TC into environmentally safe compounds was successful. The degradation pathways of TC and its chemical intermediates were elucidated using HPLC/MS analysis. The results revealed the existence of two potential degradation routes. These findings offer valuable insights into the intricate mechanisms inherent in the photocatalytic process. The type-II FeCeS photocatalyst exhibits effective generation and separation of crucial reactive species, such as OH, O-2(-), and h(+), which play essential roles in the degradation of TC. The synthesized photocatalyst significantly decreased the TC solution's toxicity and improved its biodegradability, according to the toxicity evaluation. This study presents a straightforward synthesis approach and impressive mineralization capability. Additionally, the recyclability of FeCeS enhances its potential as a viable option for widespread utilization as a visible light photocatalyst in removing antibiotics from natural water sources and controlling environmental contamination.