Abstract: The activated peracetic acid (PAA) advanced oxidation technology is a highly efficient and eco-friendly water pollution treatment strategy, which is expected to serve as a viable solution for addressing methylene blue contamination in water bodies. However, existing studies have primarily focused on the mechanism of PAA activation, while lacking in-depth discussions on how to improve the practical applicability of catalytic materials. This research gap has restricted the engineering application of activated PAA technology. A new type of cobalt based heterogeneous catalyst Co(x)/γ-Al2O3 was developed in this study. With an optimal impregnation time of 12 h, this catalyst enables efficient activation of PAA, achieving a removal rate of 99.6% for 10 mg/L methylene blue wastewater. Compared with the homogeneous cobalt ion (Co2+) activation system, the Co(x)/γ-Al2O3 activation system can reduce the dosage of PAA by approximately 25%. Meanwhile, this catalyst exhibits a wide pH adaptation range, strong tolerance to HCO3?, and an ultra-low metal leaching concentration of less than 10 μg/L. Its overall performance, stability, and service life are all superior to those of conventional PAA activated materials. Combined analyses of surface chemical characterization and theoretical calculations demonstrate that the catalytic activity of Co(x)/γ-Al2O3 originates from the Co2+/Co3+ cycle on the catalyst surface. The acetyl(per)oxy radicals (CH3C(O)O· and CH3C(O)OO·) generated during this process are identified as the primary reactive species responsible for degrading methylene blue. The activation of PAA mainly occurs at the Co active sites, which exhibit a high adsorption energy of 1.00 eV and a d-band center of 1.55 eV on the Co3O4 (311) plane. This characteristic enhances the adsorption of PAA on the reaction interface, facilitates charge transfer, and thereby strengthens the PAA activation capability of Co(x)/γ-Al2O3. In conclusion, the Co(x)/γ-Al2O3 catalyst provides a sustainable and highly efficient solution for the practical application of the activated PAA process in the treatment of methylene blue wastewater.

Key words: Peracetic acid activation; Cobalt based catalyst, Methylene blue wastewater, Organic radicals, Density functional theory