Enhanced sonophotocatalytic degradation of amoxicillin antibiotics using Fe₃O₄@SiO₂/PAEDTC surrounded by MIL-101(Fe) in aquatic environment under the COVID-19 pandemic

In the conditions of corona disease, the need for antibiotics in the world has quadrupled, so it is required to remove their residues from the environment. A core–shell metal–organic framework (MOF) composed of Fe₃O₄, SiO₂, and MIL-101 was synthesized by hydrothermal method and used as a sonophotocatalyst for the amoxicillin (AMX) degradation from aqueous solution. The features of the new MOF were determined by SEM, TEM, XRD, FTIR, and BET techniques. The specific area of core–shell magnetic particles was 992 m²/g, which was indicative of its usability to adsorb pollutants and photons. Complete degradation of AMX was achieved by sonophotocatalysis process based on prepared nanocomposite at pH of 5, UV intensity of 36 W, AMX concentration of 50 mg/L, US frequency of 36 kHz, and time of 25 min. Kinetic study with pseudo-first order reaction for the decomposition of AMX showed the order of kinetic constant rate as K_{sonophotocatalytic} > K_{photocatalytic} > K_{sonocatalytic} > K_adsorption. Hydroxyl radicals (^•OH) and holes (h⁺) were respectively determined as the main species in the decomposition of AMX by performing quenching experiments. Less than an 8% reduction in AMX degradation rate was observed by the sonophotocatalytic process in the presence of prepared nanocomposite during six consecutive reaction cycles. Removal rates of TOC > 77% and BOD₅/COD ratio > 0.4 showed that AMX was converted to CO₂, H₂O, and simple degradable compounds during the sonophotocatalysis process. A toxicity study with the microbial culture of Escherichia coli (E. coli) demonstrated a lower inhibition rate in the sonophotocatalytic process compared to photolysis and photocatalytic processes. All the laboratory results proved that the Fe₃O₄@SiO₂@MIL-101(Fe) is an encouraging candidate for AMX degradation to preserve the ecosystem.