Degradation of amoxicillin using CoFe₂O₄@three-dimensional TiO₂@graphene aerogels composite: kinetic, reusability, mineralization, degradation pathway, and toxicity assessment

An efficient photocatalyst, CoFe₂O₄@3D-TiO₂@GA, was developed to investigate the degradation of amoxicillin (AMX) using visible light. The nanocomposite was synthesized as a hierarchical porous graphene aerogel doped with CoFe₂O₄@three-dimensional-TiO₂. Achieving 100% removal of AMX required optimal values of solution pH ~ 3–5, initial AMX concentration of 25 mg/L, and catalyst dose of 0.5 g/L within a reaction time of 60 min. Extensive analysis was performed on the degradation mechanism and oxidation pathway. The CoFe₂O₄@3D-TiO₂@GA displayed high reusability, so that after five consecutive cycles, the AMX degradation (100–96.1%) decreased slightly. While the total mineralization of AMX reached 86% after 2 h, based on TOC, the intermediate products in the AMX solution lost their toxicity to E. coli after undergoing photocatalytic degradation. BOD₅/COD and BOD₅/TOC ratios in raw sewage were 0.73 and 0.22, respectively. After 120 min photocatalytic reaction, BOD₅/TOC and BOD₅/COD reached 1.3 and 0.77, indicating conversion of non-biological sewage to biodegradable effluent. Also, the reaction rate coefficient for the photocatalytic process at different concentrations was 7–16 times higher than that of the adsorption process. The half-life constant for the optimal concentration of 10 mg/L was 101.9 min for the adsorption process and 6.5 min for the photocatalytic process. This research found that a combination of adsorption and photocatalysis was crucial, with superoxide and hydroxyl radicals as the main reactive oxidative species. In summary, the study offers a fresh approach to creating CoFe₂O₄@3D-TiO₂@GA that could have significant promise in environmental applications driven by visible light.