Preparation of CeO₂-WO₃ binary heterojunction photocatalyst for sustainable tetracycline degradation: Optimization of synthesis and degradation conditions, characterization, transformation pathway, and dominant reactive species

Tetracycline (TC) is a widely utilized antibiotic recognized for its potential consequences on human health. Herein, a novel photocatalyst, CeO2-WO3 nanocomposite, was synthesized through a sufficient and cost-effective technique, and subsequently subjected to comprehensive characterization including XPS, XRD, SEM, TEM, FTIR, and BET. The optimal photocatalyst based on its performance in TC degradation was achieved at CeO2 content ranging from 5 to 25 wt. % and calcination temperature ranging from 300 to 600 degrees C, using Response Surface Methodology (RSM). The optimal synthesis condition obtained from the Design of Experiments (DoE) was CeO2 content of 16.25 wt. % and calcination temperature of 444.37 degrees C. In addition, the effect of four affecting variables, including TC concentration, pH, catalyst dose, and irradiation time was investigated and TC degradation of 94.28 % was attained at optimum conditions (i.e., TC initial concentration: 20.04 mg/L, pH: 6.88, catalyst dose: 0.19 g/L, and irradiation time: 94.90 min). The synthesized photocatalyst demonstrated a significant removal of chemical oxygen demand (COD) by 79.42 % in TC mineralization, showing notable efficacy compared to previous investigations. Hydroxyl (center dot OH) and superoxide (center dot O-2(-)) radicals were found to be robust active agents, owing to their indiscriminate oxidation capabilities through scavenger tests and ESR analysis. Additionally, LC-Mass analysis was employed to elucidate the intermediates generated during the photodegradation of TC, resulting in the formulation of a plausible degradation pathway. Overall, the CeO2-WO3 photocatalyst demonstrated commendable resistance, enduring through five cycles with minimal cerium leaching, thereby accentuating its efficacy in the decomposition of antibiotics.