Screening of catalysts and effect of temperature for kinetic degradation studies of aromatic compounds during wet oxidation

Abstract

Catalytic wet air oxidation (CWO) of six model phenolic acids: syringic, vanillic, 3,4,5-trimethoxybenzoic, veratric, protocatechuic and trans-cinnamic acid present in wastewaters from olive oil mills was studied at different temperatures. Experiments completed in the presence of four commercially available catalysts, CuO-MnOx/Al2O3, CuO-ZnO/Al2O3, Fe2O3-MnOx and CuO-MnOx were compared with the ones related to various catalysts prepared in our laboratory (Ag-Ce-O, Mn-Ce-O, Mn-O, Ce-O). These catalysts showed a higher effective reduction of the total organic carbon (TOC) especially when the experiments were carried out with manganese oxide supported on ceria, an alternative and powerful catalyst to treat highly contaminated wastewaters containing phenolic compounds. Along the oxidation, acetic acid and phenol were detected and quantified by HPLC as the main intermediate species. Leaching, carbon adsorption as well as texture and morphology by SEM were analyzed and formation of whiskers at the catalyst surface was observed. Moreover, the kinetic parameters were obtained and co-oxidation of the phenolic compounds in the mixture was identified in our studies.