Catalytic Removal of Phenolic Compounds by Ozone using Manganese and Cerium Oxides

The ozonation of a mixture of six phenolic acids present in Olive Mill Wastewaters enhanced by Manganese and Cerium oxides based catalysts was studied. The activity of MnO2, CeO2 and the bimetallic catalyst with a ratio Mn/Ce of 70/30 was studied. No significant differences were observed concerning the initial phenolic compounds degradation, however, when total organic carbon removal was studied it was observed a synergetic effect between Mn and Ce, thus the best results were obtained when the catalyst where these two metals were present was used. The increase of the calcination temperature leads to a decrease in the Bruaneur-Emmet-Teller area resulting in a inhibitory effect over the total organic carbon removal, pointing out a higher importance of the catalyst in the reaction intermediates mineralization that in the parent phenolic compounds degradation. By the comparison between the ozonation and the catalytic ozonation in the presence of the Mn-Ce-O (70/30) catalyst, a high enhancement was observed in both total phenolic content and total organic carbon. After 120 min of reaction low carbon adsorption was detected in the recovered catalyst meaning that the pollutants removal occurred by oxidation and not by adsorption to the solid phase, moreover low Mn was detected in the liquid phase confirming the stability of the catalyst in what concerns leaching behaviour of the active phase to the liquid. Therefore, Mn-Ce-O showed to be an interesting catalyst to be applied to improve the efficiency of ozonation in the treatment of phenolic wastewaters.