Mn-Fe-Mg-Ce loaded Al 2 O 3 catalyzed ozonation for mineralization of refractory organic chemicals in petroleum refinery wastewater

Abstract

Abstract There is great interest in designing a cost-efficient catalytic ozonation system for refractory wastewater treatment. A novel Mn-Fe-Mg-Ce loaded Al 2 O 3 (Mn-Fe-Mg-Ce/Al 2 O 3 ) was developed to catalytically ozonate real petroleum refinery wastewater (PRW). The loadings, calcination temperature and impregnation sequence of metals significantly influenced the catalytic performance. An optimized catalyst was consisted of 2.2% MnO, 2.2% Fe 2 O 3 , 0.9% MgO and 0.9% CeO 2 . Mg and Ce were co-impregnated and then calcinated at 550 °C, followed by Mn and Fe co-impregnation and calcination at 550 °C. Mg and Ce oxides pre-loaded on the catalyst promoted an even surface distribution of multivalent Mn (Mn 4+ , Mn 3+ and Mn 2+ ) and Fe oxides (Fe 3+ and Fe 2+ ). Such evenly distributed Mn, Fe, Mg and Ce oxides greatly facilitated the hydroxyl radical generation, thus promoted mineralization of refractory organic chemicals in PRW. The Mn-Fe-Mg-Ce/Al 2 O 3 catalyzed ozonation doubled removal of total organic carbon in PRW relative to single ozonation. About 54% polar chemicals were removed, and 60% naphthenic acids and naphthenic acid esters were eliminated, indicating a high degree of mineralization. This study illustrates a potential of Mn-Fe-Mg-Ce/Al 2 O 3 catalyzed ozonation for advanced treatment of refractory wastewaters.