Porous β-Sialon planar membrane with a robust polymer-derived hydrophobic ceramic surface

A novel method of fabricating an all-ceramic hydrophobic membrane is proposed. First, porous β-Sialon planar ceramic membrane was prepared by a phase inversion and sintering method. Then, the β-Sialon ceramic membrane was coated with a uniform polydimethylsiloxane (PDMS) layer through a poly-condensation reaction. Finally, through post-heat treatment in N2 atmosphere, the polymer layer was transformed into a tough hydrophobic vesicular ceramic layer with strong covalent Si-O and Si-N skeleton and Si-CH3 terminal groups in the surface. High contact angles were measured between the water and the modified hydrophobic membrane, ~140°, attributed to the presence of terminal Si-CH3 groups, which were derived from the polymer, and the micro- and nano-hierarchical lotus leaf-like structure of the surface. The high hydrophobicity was perfectly maintained after a 24 h exposure of the produced membranes to humic acid, boiling water, aqueous solution of HCl, and benzene. Membrane distillation water desalination tests were also conducted. A water flux of 14.08 l/m2h was obtained at 90 °C, while the rejection rate was over 99% over the duration of the test that lasted for more than 70 h, which supports that the produced membrane had excellent long-term stability and good recovery ability.