The preparation and application of air superhydrophilic-superoleophobic SiC membrane with low adhesion to oil

Superhydrophilic-superoleophobic membranes are of great value for oil-water separation. Most studies have concentrated on the superhydrophilic-underwater superoleophobic properties of membranes. Air superhydrophilic-superoleophobic membranes feature excellent resistance to oil contamination and do not require pre-wetting with water prior to their application in oil-water separation, thus holding more promising prospects in this field. This study utilized two fluorine-containing materials, fluorosurfactant (Capstone FS-50, DuPont) and perfluorooctanoic acid sodium salt (PFOA-Na), along with TiO 2 nanoparticles, to fabricate air superhydrophilic-superoleophobic SiC (HiOo-SiC) membranes successfully. The resulting HiOo-SiC membrane displayed a lower water contact angle (4.1 °) and a higher oil contact angle (170.8 °) compared to the original SiC membrane, indicating exceptional air superhydrophilic-superoleophobic properties. Additionally, the HiOo-SiC membranes exhibited significantly lower adhesion to oil droplets than SiC membranes modified by either Capstone FS-50 or PFOA-Na alone, which is advantageous for mitigating membrane fouling and thereby improving oil-water separation performance. This attribute may be attributed to the higher surface free energy and roughness of the HiOo-SiC membrane. Furthermore, the HiOo-SiC membrane had smaller pore sizes ranging from 40 to 60 nm due to the incorporation of TiO 2 nanoparticles, which were 9 to 13.5 times smaller than those of the original SiC membrane. The small pore size, high air superhydrophilic-superoleophobic properties, and low oil adhesion of the HiOo-SiC membrane led to a notable enhancement in the oil-water separation efficiency of emulsions, increasing from 94.15% to 99.61% for edible oil-in-water emulsions and from 26.4% to 89.2% for hexadecane-in-water emulsions, demonstrating remarkable capabilities in separating oil-in-water emulsions.