Insights into heterogeneous Fenton-like systems catalyzed by novel magnetic yolk-shell structures for the removal of acetaminophen from aquatic environments

In this study, novel magnetic yolk-shell structures (Fe3O4@SiO2 and Fe3O4@SiO2@Cu) were used as heterogeneous Fenton-like catalysts for the degradation of acetaminophen (ACTM) under different experimental conditions. Important factors that affected their catalytic performance were investigated, including catalysts dosage, oxidant concentrations, pH, ionic strength (IS), and natural organic matter (NOM). In addition, the NOM was isolated into different molecular size fractions, and their characterization and influence on ACTM degradation were examined to provide insight into NOM behavior in the system. The results showed that the degradation of ACTM was promoted with increases of the investigated Fe3O4 dosages. The degradation efficiencies were also enhanced as the H2O2 concentration increased from 5.0 to 15.0 mM, but they were decreased at a higher dosage of H2O2 (25 mM). The degradation was inhibited as the pH increased, but it was an insignificant difference when the pH increased from 5.0 to 7.0 in the case of Fe3O4@SiO2@Cu as the catalyst. Electrochemical analysis indicated that NOM at a certain concentration could enhance the electron transfer reactions. However, NOM was observed to have different effects on the two catalysts. Fe3O4@SiO(sic)2@Cu catalytic activity was accelerated when the NOM concentration was below 30.0 mg/L, and it was retarded at higher NOM concentrations, while the catalytic activity of Fe3O4@SiO2 was inhibited at all ranges of the investigated NOM concentrations. The presence of different NOM size fractions in the systems resulted in various behaviors of the catalysts in the degradation of ACTM.