Efficient activation of peroxymonosulfate on CuS@MIL-101(Fe) spheres featured with abundant sulfur vacancies for coumarin degradation: Performance and mechanisms

For improving the catalytic activity and recyclability of CuS in Fenton-like reaction processes, novel sulfur vacancies-enriched CuS@MIL-101(Fe) was constructed, characterized, and examined as heterogeneous catalysts for activating peroxymonosulfate (PMS) to degrade coumarin (COU). Thanks to the redox pairs of Fe3+/Fe2+, Cu+/Cu2+, S2-/S2(2-)/S-0/sulfate species, copper-iron synergistic effect and sulfur vacancies, the CuS@MIL-101 (Fe) realized a complete removal of COU (30 mu M) in 10 min with reaction rate constant of 0.577 min(-1), which was 11.1 and 17.0 times of CuS and MIL-101(Fe), respectively. The effect of various experimental conditions (i.e., initial pH, CuS@MIL-101(Fe) dosage, PMS concentration, and background anions) on COU degradation was discussed, and the stability and versatility of CuS@MIL-101(Fe) was studied as well. Radical scavenging experiments and electron paramagnetic resonance (EPR) spectroscopy identified (OH)-O-center dot and O-1(2) as the main reactive oxygen species (ROS). Finally, the possible mechanism of higher COU degradation efficiency in the CuS@MIL-101(Fe) activated PMS system and the degradation pathways were also deeply explored. Consequently, this work provided a novel insight into construction of sulfur vacancies-enriched heterogeneous catalysts for efficiently activating PMS for refractory organic pollutants elimination.