Catalytic wet air oxidation of m-cresol over a surface-modified sewage sludge-derived carbonaceous catalyst
Sewage sludge-derived carbonaceous materials (SW) treated with different kinds of acids were used as catalysts for catalytic wet air oxidation (CWAO) of m-cresol. The SW catalysts were characterized by XRF, XRD, FTIR, XPS and TPD-MS. The results showed that SW treated with HNO3 (HNO3-SW) exhibited the best catalytic activity. When the initial concentration of m-cresol was 5000 mg L−1, the conversion of m-cresol reached 99.0% with HNO3-SW after 90 min at 160 °C and 0.66 MPa oxygen. Continuous experiments were carried out for 8 d to investigate the durability and catalytic performance of HNO3-SW in CWAO reaction. Some correlation was observed between the conversion of m-cresol and the content of carboxyl groups, indicating that the carboxyl group might play a key role in determining the catalytic activity of SW catalysts in CWAO reaction. Based on the intermediate products identified by GC-MS, HPLC-MS, IC and HRMS analyses, the oxidation pathways of m-cresol in CWAO were proposed.