Surface modification of sewage sludge derived carbonaceous catalyst for m-cresol catalytic wet peroxide oxidation and degradation mechanism

Abstract

Sewage sludge derived carbonaceous materials (SWs) treated with different kinds of acid were used as the catalysts for catalytic wet peroxide oxidation (CWPO) of m-cresol in batch reactor and continuous reactor, respectively. The results showed that SW treated with nitric acid (HNO₃-SW) and sulfuric acid (H₂SO₄-SW) exhibited high catalytic activity in a CWPO reaction. The conversion of m-cresol reached 100%, after CWPO reaction for 3 h at an initial pH of 7 and a temperature of 25 °C over a H₂SO₄-SW catalyst. The elements content and chemical state of SWs treated with different kinds of acids were measured by XRF, XPS and Mössbauer spectra, the results implied that ferric iron and surface functional groups might play the main role in m-cresol degradation. The intermediate oxidation products were identified by in situ NMR, GC-MS, IC and HRMS analyses. Based on a free-radical reaction mechanism, a m-cresol oxidation pathway in CWPO was proposed.