The Pivotal Role of Selenium Vacancies in Defective FeSe2@MoO3 for Efficient Peroxymonosulfate Activation: Experimental and DFT Calculation

The presence of selenium vacancies (V-Se) inmetal selenidesenables the activation of peroxymonosulfate (PMS) for efficient waterpurification. However, the mechanisms of interactions of V-Se with PMS and organic pollutant removal are unclear. Hence, we preciselyprepared a series of FeSe2@MoO3 composites withV(Se) for effective activation of PMS for the removal ofvarious organic pollutants. The roles of V-Se are exploredvia density functional theory (DFT) calculations: (i) regulating theelectron distribution of Fe and Mo orbitals in FeSe2@MoO3 for enhancing the PMS adsorption and (ii) promoting the conversionof transition metallic redox pairs (Fe3+/Fe2+ and Mo6+/Mo5+/Mo4+). The as-preparedFeSe(2)@MoO3-8 exhibits excellent catalytic performancevia PMS activation in which nearly 100% removal efficiencies of variousorganic pollutants are achieved within 2-10 min. The quenchingexperiments, electronic spin resonance (ESR), and probe tests demonstratedthat the multiple reactive species like SO4 (& BULL;-), O-2 (& BULL;-), (OH)-O-& BULL;,and O-1(2) contributed to the removal of 2,4-D.Finally, FeSe2@MoO3-8 was attached to the polyvinylidenedifluoride (PVDF) membrane for continuous and efficient removal of2,4-D, in which the removal efficiency and total organic carbon removalefficiency of 2,4-D were > 90% and >70% within 12 h of operation.