Robust hydrophobic ceramic membrane for high-salinity wastewater separation via membrane distillation

Ceramic membranes with high bending strengths and chemical resistances show considerable potential for treating saline water using membrane distillation (MD) technology. However, maintaining the stability of ceramic membranes for the treatment of high-salinity wastewater is challenging. In this study, a robust asymmetrical SiC ceramic membrane composed of a SiC support and SiC separation layer was fabricated by finely tuning the preparation parameters. When the sintering temperature of the SiC support was 1300 °C, the SiC support showed a mean pore size of ∼1.5 μm and a water permeance of 10,389 L⋅m⁻²⋅h⁻¹⋅bar⁻¹. Subsequently, a SiC separation layer was constructed on the support by optimizing the preparation parameters. When the sintering temperature of the membrane layer was 1000 °C, the solid content of the membrane dispersion was 10 wt% and the dip-coating time was 3 s, the resulting SiC membranes exhibited a pore size of 0.165 μm and a remarkable water permeance of 1758 L⋅m⁻²⋅h⁻¹⋅bar⁻¹, which is higher than the values reported in the literature. After fluorination, the membranes were employed in MD processes to separate wastewater containing high salinity. The resulting SiC membranes exhibited no evident flux decline or membrane fouling when treating saline water containing the salt concentrations of 35 g⋅L⁻¹, 100 g⋅L⁻¹, and 150 g⋅L⁻¹ with a salt rejection of ∼99.99 %. Furthermore, when four different dyes (direct red, chlorazol black, titan yellow, and crystal violet) were separately added to high-salinity wastewater (100 g⋅L⁻¹), the rejection rates for both salt and dye remained above 99.99 % and 99.9 %, respectively, throughout the long MD period. This study comprehensively investigates the fabrication of robust and stable hydrophobic ceramic membranes for MD applications in high-salinity solutions.