Preparation of asymmetric SiC membranes with narrow pore size distribution for efficient separation of oil-in-water emulsions

Preparation of ceramic membranes with narrow pore size distribution are highly desired for the high accuracy separation, while it is rather challenging due to the randomly stacking of ceramic particles especially on macroporous supports. In this work, by screening the particle size and distribution of SiC powders to match with the pore characteristics of the SiC supports, asymmetric SiC membranes with narrow pore size distribution were successfully prepared on reaction-bonded SiC supports with multiple-peak distribution in the range of 0.1–1.5 μm. Three types of SiC powders (P1, P3 and P5) were selected and correspondingly well-dispersed ceramic slurry were formulated. Then, three types of SiC membranes (M1, M3 and M5) with tailored thickness of 20 μm were realized based on the capillary force dominated formation mechanism. Results showed that the M5 membranes presented excellent hydrophilicity (WCA<15°), narrow pore size distribution (distribution factor α < 0.88) and the highest water permeance (1476 ± 159 L m⁻² h⁻¹ bar⁻¹). Besides, it was found that the pore size of SiC membranes became smaller and more uniform with the increasing sintering temperature, originating from the surface oxidation and volume expansion of SiC particles. Three membranes (M1, M3, and M5) were used to separate 100 mg L⁻¹ of (lubricated) oil-water emulsion, and the retention rates were all greater than 90 % at a lower transmembrane pressure (TMP) of 0.5 bar, meeting the national emission standards of China. This work demonstrates the feasibility of preparing asymmetric membranes with tailored thickness and narrow pore size distribution based on the reaction-bonded SiC supports and their promising application in high-efficient oil-in-water emulsion separation.