Continuous-flow ozonation over modified ceramsite: implications for the degradation of cation red x-GRL

Catalytic ozonation has been widely used for refractory dye wastewater treatment due to highly reactive HO·. In this study, a kind of low-cost and environmental-friendly modified ceramsite sphere derived from pyrite cinder, silty clay and kaolin was prepared as ozonation catalyst. The degradation performances of cation red x-GRL were performed under a continuous mode. Being close to the practical treatment, continuous-flow ozonation study is vital for applying heterogeneous catalytic ozonation in wastewater treatment at a large industrial scale. Results showed that the absorption capacity of this modified ceramsite towards cation red x-GRL was confirmed to be slight. The mineralization efficiency was high, accounting for 48.0% of 200 mg/L cation red x-GRL at a constant flow rate of 0.18 L/min (hydraulic retention time = 16 min), while only 7.8% during ozonation alone. Furthermore, this novel catalytic ozonation can maintain high mineralization efficiency in a wide range of pH (3-10), which was ascribed to the synergistic catalytic performance of various oxides. The reaction mechanism is ascribed to the promotion of ·OH production from O₃ molecules' decomposition. Moreover, ozone utilization efficiency at hydraulic retention time of 16 min during catalytic ozonation was 2.0 times as high as that during ozonation alone.