Two-dimensional ultrathin perforated Co₃O₄ nanosheets enhanced PMS-Activated selective oxidation of organic micropollutants in environmental remediation

Here a two-dimensional (2D) ultrathin perforated Co3O4 nanosheet is rationally designed by a wet-chemical synthesis to activate peroxymonosulfate (PMS) for efficient selective oxidation. And the physicochemical properties of catalyst were investigated by series of techniques. The Co3O4 nanosheets achieved a 98.0% degradation efficiency of bisphenol A (BPA) within 30 min, showing a 4 times higher kinetic constant (0.112 min-1) and 5 times lower Co2+ leakage (6.5 mu g/L), than commercial Co3O4 microspheres. The great enhancement in catalytic performance was ascribed to the large surface area and pore diameter in porous 2D structure, as well as the strong electrostatic attraction with PMS. Moreover, the influence of several parameters such as initial pH, temperatures, humic acids and inorganic anions in the system on the remaval of BPA were systematically studied. Since sulfate radicals (SO4 center dot- ) were proved to be the primary reactive oxygen species by EPR measurements and quenching experiments, the PMS/Co3O4 nanosheets exhibits a highly selective oxidation on aromatics with electron donating groups (i.e., -OH and -CH3), while a relatively low value for organics with electronwithdrawing groups (e.g., -NO2 and -COOH). A high ionization potential threshold was determined to be greater than 9.39 eV, corresponding to a high oxidation ability to react with the organics. Finally, possible degradation pathways were proposed based on twenty intermediate products determined from mass spectrometry.