Labile oxygen-driven catalytic ozonation via surface peroxide pathway for efficient wastewater treatment

The aluminosilicate-based heterogeneous catalysts hold great promise for industrial catalytic ozonation; however, the lack of exploration into novel active sites and mechanism studies has impeded their development. In this work, we demonstrate that labile oxygen (Olab) can be generated in mullite (mullite-Olab) by the introduction of extra Al-O4 tetrahedral units. In our experiments, mullite-Olab exhibits excellent performance in terms of catalytic ozone activation, with a degradation rate of 87.4 % within 15 min for nonbiodegradable atrazine, corresponding to a high quasi-first-order rate constant (k, 0.112 min−1), while the degradation constant is close to 0 for mullite without Olab. Operando Raman and density functional theory (DFT) simulations further reveal that Olab activates ozone via a novel surface peroxide pathway to generate surface Olab-O* species with a high oxidizing ability. The mullite-Olab is stable with an average Al3+ leaching of 0.339 ppm during cycling, meeting the effluent discharge standard of the total Al. Moreover, we achieve the kilogram synthesis of mullite-Olab, which shows promising activity in the catalytic ozonation of acrylic fiber wastewater, with the chemical oxygen demand (COD) and total organic carbon (TOC) removal rates of 46.0 %±4.8 % and 24.9 %±2.8 % for 5 cycles. This work is the first to demonstrate the role of Olab in ozone activation and provides an advanced mullite-Olab catalyst for future nonbiodegradable wastewater treatment.