Manganese and Copper Catalysts for the Phenolic Wastewaters Remediation by Catalytic Wet Air Oxidation

Abstract

The catalytic wet air oxidation (CWAO) of a simulated phenolic wastewater was investigated at temperatures up to 200ºC and 15 bar of air partial pressure. Laboratorial (Mn-Ce-O 70/30 IMP, Mn-Ce-O 70/30 CP, MnCu 70/30, MnCu 50/50) and a commercial catalyst (N140: CuO-MnOx 22/50) were used to evaluate the catalytic activity in terms of Total Organic Carbon (TOC). Among the manganese/cerium and manganese/copper catalysts tested with different molar ratios, Mn-Ce-O was the most active leading to the complete mineralization after 120 min of an aqueous solution containing six representative phenolic acids. The co-oxidation effect was identified when comparing the oxidation of global phenolic mixture and the individual parent compounds' depletion. The catalyst preparation method had no significant differences in terms of catalytic activity. During the CWAO experiments, acetic acid and phenol were detected and measured by HPLC as the main reaction intermediate compounds. Concerning catalytic stability, manganese and copper catalyst revealed good properties in terms of active metal leaching to the bulk liquid as well as in the deposition of only 3.152% (W/W) of carbonaceous material on the catalyst surface for the co-precipitated Mn-Ce-O 70/30 catalyst.