Metal/sulfite systems are currently used for SO4•− generation and oxidative removal of organic contaminants. However, homogeneous metal/sulfite systems are limited because their working pHs must be acidic and metal ions cannot be separated from the bulk reaction solution. As a consequence, these drawbacks have severely limited the application of metal/sulfite systems in real conditions. To address these issues, we tested the use of copper ferrite (CuFe2O4), a ferromagnetic nanoparticle, to catalyze sulfite oxidation for the degradation of the metoprolol drug. The reaction mechanism was investigated by electron spin resonance, X-ray photoelectron spectroscopy, and radical quenching assay. The effects of pH, CuFe2O4, and sulfite dosages were also assessed. Results show that SO4•− was the primary radical responsible for metoprolol degradation. Higher pHs induced more metoprolol degradation using CuFe2O4/sulfite. Moreover, CuFe2O4 remained morphologically intact and catalytically active after four batches of recycling. Overall, our findings show that CuFe2O4/sulfite can effectively degrade water contaminants in alkali pH and withhold catalyst activity after multiple reuses, therefore addressing the issues associated with homogeneous metal/sulfite systems.
Sulfate radical Advanced oxidation process Sulfite Metoprolol Copper ferrite Pharmaceutical and personal care products (PPCPs)
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This work was supported by the Science and Technology Project of Guangdong Province (No. 2014B030301055). Comments from anonymous reviewers are also appreciated.
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