SiO2 nanoparticles modified Si3N4 hollow fiber membrane for efficient oily wastewater microfiltration

Uniform deposition of SiO2 nanoparticles (NPs) on the outer surface of Si3N4 hollow fiber membrane was achieved via sol-gel method using tetraethyl orthosilicate (TEOS) at various concentrations. The experimental results (SEM, XRD, XPS, AFM) demonstrated that the SiO2 NPs were strongly adhered to the grains of Si3N4. At highest TEOS concentration, the generated SiO2 NPs entirely covered the membrane surface resulting in the presence of a newly-formed smooth selective filtering layer. It has reduced the surface roughness and increased the surface hydrophilicity of the membrane. These features have considerably enhanced the selectivity of the membranes, especially in the case of submicron contaminants, and suppressed fouling phenomena, as recorded in filtration experiments using a stable oil-in-water emulsion. High separation performance (95% oil rejection) was achieved in SiO2-coated Si3N4 hollow fiber membrane prepared with 7.5 mol L-1 TEOS concentration.