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.