Al-Ov-Co active sites confined in beta zeolite enabling non-radical pathways dominated peroxymonosulfate activation...

Peroxymonosulfate (PMS) activation through non-radical pathways exhibits high efficiency and selectivity for pollutant degradation. However, the complex regulation of catalytic active centers makes the generation of ¹O₂ challenging. In this work, Beta zeolite with uniformly dispersed Al-Ov-Co active sites (Co-Beta zeolite) was synthesized via a simple impregnation method, which exhibits excellent ¹O₂ steady-state generation concentration (2.46 × 10^-11 M) at extremely low doses (0.05 g/L). Compared with the original Co₃O₄, Co-Beta zeolite displays significantly enhanced PMS activation efficiency, and the apparent reaction rate constant for degrading tetracycline hydrochloride (CTC) increases by 4.7 times. Pyridine infrared characterization confirms that cobalt ions occupy the Brønsted acid sites of the Beta zeolite and undergo proton exchange with them. Accompanied by the redistribution of electrons during the calcination process, some lattice oxygen in the material is removed to form Al-Ov-Co sites. The proportion of Co²⁺ in the Al-Ov-Co sites dramatically increases, thereby ensuring efficient activation of PMS. As PMS is adsorbed onto the Al-Ov-Co sites, the H atom of PMS directly bonds with the O atom in Co-Beta zeolite, while the O atom in PMS forms a bond with Co²⁺. After the HO and SO bonds of PMS are broken, abundant ¹O₂ is produced. In practical application evaluation, Co-Beta zeolite shows satisfactory anti-interference ability, reliable cycling stability and acceptable metal leaching. This work inspires the design of highly-dispersed Co²⁺ to promote non-radical pathways for PMS-activated water purification.