Bi-metal oxide-modified flat-sheet ceramic membranes for catalytic ozonation of organic pollutants in wastewater treatment

Abstract

Ceramic membranes have a highly porous structure and a high surface area, which provide suitable support for heterogeneous catalytic oxidation. In this study, as effective catalysts for ozonation, Mg, Ce, and Mn oxides were coated by co-precipitation onto a flat-sheet ceramic membrane to produce two catalytic ceramic membranes (CCMs), namely an Mg-Ce membrane and an Mg-Mn membrane. This technique combines ceramic membrane filtration with catalytic ozonation for advanced water and wastewater treatment. The CCM characterization showed that the metal oxide catalysts were well coated on the membrane surface and inside the membrane pores. Compared with non-catalytic ozonation, catalytic ozonation with CCMs was more effective for the degradation and removal of organic pollutants, including a dye as a model pollutant in water and residual organics in secondary wastewater effluent. At the same ozone dosage for ozonation coupled with membrane filtration, the organic removal efficiency was increased from approximately 30% for the ceramic membrane without the catalyst coating to over 80% for the CCM with the catalyst coating. Membrane catalytic ozonation also resulted in effective membrane fouling control during ultrafiltration of the secondary effluent. Based on the hydroxyl (OH) quenching test, ozonation with CCMs produced more OH free radicals than ozonation alone, which led to enhanced organic degradation. Moreover, catalytic ozonation in the membrane reactor played an effective role in mitigation of membrane fouling. Ceramic membrane-based catalytic ozonation can be used for effective removal of toxic and persistent organic pollutants from water and wastewater.