Sulfur-modified porous Co3O4 in activating peroxymonosulfate for degradation of methylene blue

A series of sulfur-modified porous Co3O4 [Sx@Co3O4, x=0.25, 0.50, 0.75, 1, where x represents the modified content of sulfur, based on the molar amount of Co(NO3)2•6H2O, the same below] via an improved oxalate-pyrolysis method with Na2S2O3 as sulfur source. The catalytic performance of the catalysts obtained in activation of peroxymonosulfate (PMS) for methylene blue (MB) degradation was then investigated, followed by evaluation on the influence of catalyst dosage, PMS concentration, reaction temperature, and common anion species on the degradation rate of MB in the Sx@Co3O4-PMS system as well as the cyclic stability of the catalyst. The results showed that the catalytic performance of Co3O4 was improved with the sulfur-modified content increased, and S1@Co3O4 exhibited the best catalytic performance among the catalysts obtained. Sulfur bonded to the surface of Co3O4 in the form of SO42–increased the specific surface area of Co3O4, the content of oxygen vacancies on the surface and the polarization of HSO5–, the combined of which enhanced the catalytic performance of Co3O4. Under the optimal reaction conditions of catalyst dosage 0.04 g/L, PMS concentration 0.6 mmol/L, reaction temperature 25 ℃, and reaction time 25 min, the degradation rate of 500 mL MB solution with a mass concentration of 10 mg/L reached 98.35% in S1@Co3O4-PMS system. S1@Co3O4 could be recycled in a simple way and the degradation ratio of MB could reach 68.57% after four consecutive cycles. The degradation of MB in S1@Co3O4-PMS system was the result of synergistic effect between free radicals (•SO4–, •OH and •O2–) and non-free radical (1O2). © 2023 Fine Chemicals. All rights reserved.