Robust Pvdf Hollow-Fiber Membranes Modified with Inorganic Tio2 Particles for Enhanced Oil-Water Separation

Hollow-fiber (HF) membranes with high tensile strength and water permeance and composed of poly(vinylidene fluoride) (PVDF) and polysulfone (PSF) were prepared using phase inversion to enhance separation of oil-in-water (O/W) emulsions. Hydrophilic inorganic particles of titanium dioxide (TiO2) were coated onto PVDF/PSF membrane surfaces with the aid of Pluronic and polydopamine (PDA). The pore structure, hydrophilic properties, and tensile strength of HF membranes can be finely tuned by varying the TiO2 concentration in the coating solution. Pluronic or PDA-assisted TiO2 coating enhanced the adhesion between TiO2 and membrane surface as revealed by X-ray photoelectron spectroscopy and stability tests. These HF membranes achieved enhanced O/W emulsion separation in a crossflow filtration process. A Pluronic-stabilized HF membrane achieved a higher rejection rate (above 99.5%) and stable permeance (~650 Lm-2 h-1 bar-1) in a micro-sized emulsion (soybeans-in-water) at a TiO2 concentration of 0.75 wt% compared with a pristine HF membrane. Meanwhile, PDA-stabilized HF membranes exhibited 99% rejection and stable permeance of 410 Lm-2 h-1 bar-1 toward nano-sized emulsion (hexane-in-water) when the PDA@TiO2 composite concentration was 0.75 wt%, while a pristine HF membrane achieved a rejection rate of only ~90% and a permeance < 200 Lm-2 h-1 bar-1. The enhanced hydrophilicity and decorated pore structure produced by hydrophilic TiO2 with the aid of polymers (Pluronic or PDA) enhanced the separation performance of both micro- and nano-sized O/W emulsions through HF membranes