β-Sialon ceramic hollow fiber membranes with high strength and low thermal conductivity for membrane distillation

Novel microporous β-Sialon (Si6–zAlzOzN8–z, z = 1–4) ceramic hollow fiber membranes have been successfully prepared by a combined phase-inversion and sintering method. The influence of dispersant concentrations on the viscosity curve was first studied to obtain a stable precursor suspension. Different z value and sintering temperature were studied to get asymmetric hollow fibers with a good combination of high bending strength (369 MPa), suitable pore size (0.8 μm), large gas and water flux, which are suitable for membrane distillation (MD). The membranes also exhibited a much lower thermal conductivity. After modified to hydrophobic by grafting fluoroalkylsilane (FAS), the membranes were applied to vacuum membrane distillation (VMD) and direct contact membrane distillation (DCMD). They exhibited satisfactory water flux and a salt rejection rate of 99–100% for both methods. Most importantly, the permeate flux in DCMD reaches 63% of that in VMD due to the lower thermal conductivity, indicating their potential industrial applications.