RESUMO
The design of sustainable, effective and recyclable hybrid catalysts for advanced oxidation processes is highly significant for remediation of the water environment. In this study, we synthesized magnetic Fe3O4-N-doped carbon sphere composite catalysts (Fe3O4-NCS-x) for efficient removal of tetracycline by activating peroxymonosulfate (PMS). The Fe3O4-NCS-x composite was obtained by facile hydrothermal treatment of chitosan-iron complexes followed by pyrolysis. The unique structure of N-doped carbon spheres embedded in Fe3O4 nanoparticles intensified the electron transport, consequently improving the catalytic activity via a synergistic effect. Factors influencing the catalytic activity of the Fe3O4-NCS-2 were systematically investigated. High degradation efficiency of TC-97.1% within 1 h-was achieved in this Fe3O4-NCS-2/PMS system under the optimum conditions (C0 = 20 mg L-1, catalyst dosage 0.2 g L-1, PMS concentration 2.4 mM, native pH and 25 °C). The inhibitory effect of anions in the water matrix decreased in the order Cl- > NO3- > SO42- > CH3COO- > HCO3-. The obtained results from the competitive quenching tests and electron paramagnetic resonance measurements demonstrated that singlet oxygen (1O2), a non-radical species, plays a major role in TC degradation. It is estimated that 1O2 and hydroxyl radicals (·OH) contributed â¼65.2% and â¼24.2% to TC degradation in the Fe3O4-NCS-2/PMS system, respectively. The M-H hysteresis loop of Fe3O4-NCS-2 revealed that its saturation moment is 56 emu g-1. Magnetic responsive behavior and consecutive runs confirmed that Fe3O4-NCS-2 possesses remarkable separation performance and desirable reusability. This novel magnetic Fe3O4-NCS-2 composite activator for PMS promises great potential in TC degradation.