A CuMn2O4/g-C3N4 catalytic ozonation membrane reactor used for water purification: Membrane fabrication and performance evaluation

Abstract

The combination of membrane filtration with catalytic ozonation was established in this study, to develop in-situ self-cleaning of membrane fouling and micropollutants degradation. Herein, a novel CuMn2O4/g-C3N4 catalytic ceramic membrane (CG/CM) was fabricated and a catalytic ozonation membrane reactor (COMR) was established. Firstly, powder catalyst CuMn2O4/g-C3N4 was synthesized under two steps and its parameters was optimized (urea (10.0 g) and CuMn2O4 (0.2 g) was combined and calcinated under 350 °C for 2.0 h) for the degradation of micropollutant benzophenone-4 (BP-4) and elimination of toxic byproduct bromate (BrO3−). Secondly, the active catalytic ceramic membrane was fabricated, where the thickness, roughness, and hydrophilicity/hydrophobicity of CuMn2O4/g-C3N4 deposition on CG/CM was adjustable by changing the number of coating procedures. As increasing the coating times, the thickness increased but the roughness and hydrophobicity decreased, which was first reported in catalytic membrane synthesis process and was favored for interface catalytic ozonation. Therefore, the obtained CG/CM showed good in-situ self-cleaning for membrane fouling, BP-4 degradation, and BrO3− elimination through interface catalytic ozonation, as sodium alginate (SA) selected as the model probe. The concentration of ozone and transmembrane pressure (TMP) showed a significant influence on the CG/CM performance. The best operation parameters were optimized as [ozone] = 20 mg/L, TMP = 0.2 bar, and cross flow velocity = 0.0845 m/s, achieving that the normalized flux recovering to 87% and more three times increasing of BP-4 degradation rate than that in sole ozonation. The better bromate elimination performance in COMR was first reported. Furthermore, the concentration effects of SA, bovine serum albumin, and BP-4 on the performance were studied. This represents a promising strategy for developing catalytic ceramic membranes coupled with catalytic ozonation for water treatment.