Polymer-derived porous SiOC ceramic membranes for efficient oil-water separation and membrane distillation

Porous SiOC ceramic membranes (PSCM), with a narrow pore size distribution, were prepared by a casting method, using a polymer liquid (polydimethylsiloxane, PDMS), as a pore-forming agent, and a pre-ceramic liquid (polysiloxane, PSO), followed by pyrolysis at 1200 degrees C in flowing Ar gas. Pore size, porosity, and N-2 and water permeation increased with increasing PDMS content in the mixture of the precursors. An oil-in-water emulsion, with an average oil diameter of 0.83 mu m was effectively separated (95% rejection rate) with membranes which had an average pore size of 0.59 mu m. PDMS was also used for membrane surface modification and the surfaces became super-hydrophobic. After modification, membranes with an average pore size of 0.95 mu m were tested in sweeping gas membrane distillation. High salt rejection of 99.9% was achieved with NaCl solution (at various concentrations, 4-16 wt%()) at several temperatures (55-85 degrees C). A stable performance was recorded for over 100 h, using 4 wt% NaCl in the feed at 75 degrees C. The produced membranes displayed clear separation and high efficiency in separation rates, which was reflected in the high permeation flux in both oil-in-water emulsion filtration and membrane distillation, attributed to the narrow pore size distribution.