Compact SiOC ceramic composite nanofiltration membranes by slow dip coating for water purification

In this work, novel silicon oxycarbide (SiOC) ceramic composite nanofiltration membranes with high performance were successfully synthesized at low sintering temperatures by gradual dip-coating approach for the first time. The slow dip-coating process facilitated improved wetting and even spreading of the precursor solution across the substrate. This controlled method ensured the formation of uniform and continuous SiOC ceramic membranes without the introduction of substantial defects or irregularities. Consequently, the systematic approach minimized the occurrence of pinholes, cracks and other structural imperfections in the SiOC ceramic membranes. The synthesis of the SiOC separation layer involved the sintering of polymeric polysilicon as precursor, which caused a lower decomposition temperature in contrast to the conventional method employing silicon carbide powder for sintering. The specific feature enabled a sharp decrease in the sintering temperature which was required for the formation of the separation layer. The prepared SiOC ceramic composite nanofiltration membranes exhibited good permeability with high rejection of dye molecules (>95%) and maintained stable water flux for at least 24 h, showing good long-term stability during cross-flow filtration. This progress provides new approach for the fabrication of compact ceramic nanofiltration membranes with low sintering temperatures, high separation efficiency and enhanced stability.