Preparation of ceramic membranes with small pore size, narrow pore size distribution and investigation of oil-water separation mechanism

To solve the problems of wide pore size distribution, complex preparation process, poor performance and low anti-fouling performance of commercial ceramic membrane prepared by sintering technology. In this study, the ceramic membrane (ACM-W) with small pore size (83 nm), narrow pore size distribution and high anti-fouling ability was prepared by coating the water glass (WG) + Al₂O₃ slurry on commercial Al₂O₃ ceramic membrane (ACM-0) by one-step. WG was used as an inorganic binder for bonding and pore plugging. The chemical structure of the membrane surface was characterized and analyzed. The bonding mode between WG and Al₂O₃, and the effect of WG on the surface microstructure of the membranes were investigated. The surface microstructure, pore size distribution and anti-fouling ability of membranes were revealed. The findings showed that the pore size of 83 nm accounted for 98.3 % of the ACM-W pore size distribution. The rejection for emulsified oil of 99.96 % and the flux recovery rate (FRR) of 98.7 % achieved for ACM-W, which indicated that ACM-W has excellent separation performance and anti-fouling ability. Based on the above results, combined with the size change of oil droplets before and after separation, wettability, surface charge and the cleaning process of the ACM-W, the anti-oil fouling mechanism of “charge repulsion & pore barrier” for the membrane was presented. This study introduces a novel idea for preparation of the ceramic membrane with high filtration accuracy and anti-fouling ability, and a fresh insight into the anti-fouling mechanism of ceramic membranes.