Multilevel hierarchical super-hydrophobic ceramic membrane for water-in-oil emulsion separation

Hierarchical silicon nitride (Si3N4) membranes were fabricated by catalytic growth of α-Si3N4 nanowires onto the rod-like β-Si3N4 grains. Compared to the bare asymmetric structure of β-Si3N4 membranes, the average pore size reduced from 0.9 µm to 0.67 µm, while the porosity decreased slightly from 47 ± 0.6% to 45.3 ± 1.1%. Inorganic nanoparticles derived from organosilane were used to further modify the membranes. The membranes displayed super-hydrophobic characteristics with a water contact angle of 155 ± 1° due to the multilevel hierarchical structure and the -Si-CH3 low energy terminal groups. The super-hydrophobic membranes were successfully applied for the water-in-oil emulsion separation process. At various driving pressures, the water rejection of the water-in-oil emulsion was higher than 95%. This work's durable super-hydrophobic ceramic membrane has promise for the purification of a variety of oil products.