The high catalytic activity and strong stability of 3%Fe/AC catalysts for catalytic wet peroxide oxidation of m-cresol: The role of surface functional groups and FeO particles

Abstract

FeO x supported on activated carbon (AC) has been shown to be an ideal catalyst for catalytic wet peroxide oxidation (CWPO) due to its high CWPO reaction activity and stability. Although there have been some studies on the mechanism of Fe/AC catalysis in CWPO, the specific contribution of each component (surface oxygen groups and FeO x on AC) inside an Fe/AC catalyst and their corresponding reaction mechanism remain unclear, and the reaction stability of CWPO catalysts has rarely been discussed. Then the optimal CWPO catalyst in our laboratory, 3%Fe/AC, was selected. (1) By removing certain components on the AC through heat treatment, its contribution to the reaction and the corresponding reaction mechanism were investigated. With the aid of temperature-programmed desorption-mass spectrometry (TPD-MS) and the CWPO reaction, the normalized catalytic contributions of components were shown to be: 37.3% (carboxylic groups), 5.3% (anhydride), 19.3% (ether/hydroxyl), −71.4% (carbonyl groups) and 100% (FeO x ), respectively. DFT calculation and EPR analysis confirmed that carboxylic groups and Fe 2 O 3 are able to activate the H 2 O 2 to generate ·OH. (2) The catalysts at were characterized at different reaction times (0 h, 450 h, 900 h, 1350 h, and 1800 h) by TPD-MS and Mössbauer spectroscopy. Results suggested that the number of carboxylic goups gradually increased and the size of paramagnetic Fe 2 O 3 particle crystallites gradually increased as the reactions progressed. The occurrence of strong interactions between metal oxides and AC was also confirmed. Due to these effects, the strong stability of 3%Fe/AC was further improved. Therefore, the reasons for the high activity and strong stability of 3%Fe/AC in CWPO were clearly shown. We believe that this work provides an idea of the removal of cresols from wastewater into the introduction to show the potential applications of CWPO.