Peroxymonosulfate (PMS) activated by magnetic Fe3O4 doped carbon quantum dots (CQDs) for degradation of Rhodamine B (RhB) under visible light: DFT calculations and mechanism analysis

Currently, photo-assisted peroxymonosulfate (PMS) activation has received more and more attention in the degradation of wastewater pollutants. In this paper, the Fe3O4@CQDs magnetic nanocatalyst was successfully prepared by modifying alpha-Fe2O3, and Rhodamine B (RhB) was degraded by activating PMS under visible light. Moreover, in order to explore the reason why Fe3O4@CQDs was more beneficial to the activation of PMS than alpha-Fe2O3 at the microscopic level and reaction mechanism, the corresponding DFT calculations were performed. The results revealed that the degradation efficiency of RhB reached 98% in 35 min. Subsequently, the quenching experiments and EPR tests jointly verified that SO4 center dot(-), center dot OH, O-2 center dot(-) free radical pathway and O-1(2), h(+) non-free radical pathway participated in the degradation of RhB in the Fe3O4@CQDs + PMS + light system. The adsorption energy reached -5.247 eV with Fe3O4@CQDs adsorbed PMS by DFT calculation. The electron enrichment and charge redistribution can be apparently observed during the adsorption of PMS at Fe3O4@CQDs nanocatalyst. It was confirmed that the embedding of CQDs effectively regulated the electron transfer efficiency at the Fe3O4@CQDs interface to promote the improvement of electrical conductivity. It was more conducive to forming Fe(III) to Fe(II) cycles, and then the ability of the catalyst to activate PMS was improved.