Oxygen vacancies promoted heterogeneous catalytic ozonation of atrazine by defective 4A zeolite.

The ozone activation reaction is becoming more popular with the treatment of organic pollutants, while the key to improving the efficiency heavily lies in the selection of active catalysts. In this study, we demonstrate that synthetic 4A zeolite with a high surface oxygen vacancy density and acidity exhibits excellent activity toward the ozonation process, where the removal rates of atrazine (ATZ) reached 87.5% at 6 min, and the removal rates of Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) reached 66.7% and 35.8% at 15 min, respectively. Compared with commercial 4A zeolite and synthetic 4A zeolite with acid treatment, the ozonation activities of 4A zeolites positively correlate with the surface acidity. Mechanistic investigations have identified that hydroxyl radicals are the main reactive oxygen species, and thus, the degradation pathway of ATZ is provided. Moreover, the influences of catalyst dosage, reaction temperature, pH and cycling stability on ozonation performance are systematically evaluated. (a) Schematic illustration of possible reaction mechanism of the 4A Zeolite + O3 system.(b) Removal of ATZ by catalytic ozonation with all 4A zeolites.(c) EPR for O vacancies of C-4A, S-4A, C-4A-Acid.(d) Reusability of S-4A in catalyst ozonation ATZ. [Display omitted] • A 4A zeolite with high surface acidity is controllably synthesized. • The surface acidity of 4A zeolite is enhanced by introduction of oxygen vacancies. • The designed 4A zeolite shows higher catalytic activity than purchased zeolite. • Oxygen vacancies, as Lewis acid sites, catalyze ozone to produce HO.•. • The designed catalyst shows excellent stability, and wide applicability. [ABSTRACT FROM AUTHOR]