A mechanistic assessment of the wet air oxidation activity of MnCeO sub(x) catalyst toward toxic and refractory organic pollutants

The reactivity pattern of a model MnCeO sub(x) catalyst (Mn sub(at):Ce sub(at), 1) in the wet air oxidation (CWAO) of toxic (phenol) and refractory (acetic, oxalic and formic acids) organic pollutants has been probed, using a stirred batch reactor with continuous oxygen feeding (PO sub(2)PO sub(2), 0.9 MPa). In the range of 110-150 degree C the MnCeO sub(x) catalyst (w sub(cat)/w sub(sub), 5) shows high abatement and mineralization efficiency toward all the substrates. Parallel trends of substrate and total organic carbon (TOC) conversion prove that adsorption is the primary reaction step, while slower mineralization rates signal that surface oxidation is rate determining step (r.d.s.). Activity data in the pH range of 3-10 and straight relationships between conversion and dissociation constant (K sub(a)) signal that acids adsorption is driven by electrostatic interactions with acid sites (E sub(Ads) approximately 80 kJ/mol), while a low energetic barrier (E sub(Ads) approximately 16 kJ/mol) discloses the physical nature of phenol adsorption. A kinetic analysis of conversion-selectivity data, based on a dual-site Langmuir-Hinshelwood (L-H) mechanism, sheds light into the CWAO pattern of MnCeO sub(x) catalyst toward different classes of organic pollutants.