In-situ grown inorganic layer coated PVDF/PSF composite hollow fiber membranes with enhanced separation performance

Poly(vinylidene fluoride) (PVDF) membranes are widely employed for water treatment but mainly limited by their hydrophobic properties that increase the separation resistance. To make hydrophilic PVDF membranes, inorganic layer coated PVDF blend hollow fiber membranes are reported here. PVDF/polysulfone (PSF) blend hollow fiber membranes with pore size of ~110 nm were fabricated using PolarClean as a green solvent. Then, a facile and green method was employed to in-situ grow an inorganic layer (including TiO2 and Al2O3 layers) on these high strength membranes. Pluronic L61 was used as a dispersing agent to distribute the precursors in isopropanol, and enhanced adhesive strength between the polymer membrane and inorganic particles as characterized by XPS. The inorganic layers on the PVDF/PSF membrane surface both improved the mechanical strength from 7.7 MPa to 9.2 MPa and decreased the membrane roughness from ~50 nm to ~10 nm. The water permeance of the composite membranes can be finely tuned from 50 to 500 Lm−2h−1bar−1. In addition, the resulting membranes simultaneously enhanced the separation performance and anti-fouling performance characterized by bovine serum albumin (BSA) rejection behavior and flux recovery rate (FRR), respectively. The best BSA rejection and FRR of the PVDF/PSF-inorganic composite membranes reach 95% and 72.2%, respectively. The anti-fouling performance of composite membranes is mainly attributed to the decreased membrane roughness and enhanced hydrophilic properties compared with pristine PVDF/PSF membranes. Furthermore, the in-situ grown inorganic layers on the PVDF/PSF membrane surface effectively prevent foulants from blocking the pore channels as they are easily washed by the hydraulic washing method.