Superhydrophobic β-Sialon-mullite ceramic membranes with high performance in water treatment

Abstract

β-Sialon membranes with high mechanical strength and suitable porosity were prepared by pressureless sintering of samples obtained via phase-inversion and tape-casting and methods, and then their surface was modified with mullite whiskers through vapor-phase growth technology. Mullite whiskers, with a small diameter of ~100 nm and a high aspect ratio of ~30, were formed at the surface of the asymmetrically structured membrane. The prepared membrane exhibited high performance in separating of an aqueous emulsion of oil, (i.e. when the average diameter of the droplets of oil was 1.62 μm, oil rejection reached 94%). The mullite whiskers significantly increased the surface roughness of the membrane, leading, after surface modification, to superhydrophobicity (i.e. water contact angle was 165°), and to membrane distillation operational stability with 4% NaCl solution, containing 50 ppm humic acid, for more than 400 h. These results offer the prepared β-Sialon-mullite membranes excellent potential in the field of water treatment.