A double anti-fouling mechanism established by self-assembly of TiO2 on F127 chains for improving the hydrophilicity of PES membrane based on RTIPS method

Abstract

Novel polyethersulfone (PES) membranes with porous top surface and sponge-like structure based on reverse thermally induced phase separation (RTIPS) method modified by titania sol (TiO2 sol) and triblock copolymer (F127) were developed. The highlight of this work was that the self-assembly of TiO2 on F127 was obtained during the RTIPS membrane formation process. Properties of PES/TiO2/F127 membranes, which varied with TiO2 sol, F127 and coagulation water bath temperature, were investigated by cloud point, SEM, EDX, AFM, TGA, XPS, FRR, contact angle and so on. SEM morphologies revealed that homogeneous porous top surface as well as sponge-like structure appeared in the membrane prepared by RTIPS process, while dense skin surface and finger-like cross-section obtained from the membranes by NIPS method. As a result, the pure water flux, rm and porosity of the membranes by RTIPS method were higher than that by NIPS method. EDX results indicated that the agglomeration of titanium dioxide was avoided by sol gel process. The XPS data revealed that the self assembly of TiO2 on PEO segments in F127 alleviated the leakage of TiO2 from the modified membrane and then improved the hydrophilic stability of the membrane. The water contact angle illustrated that the addition of TiO2 and F127 improved the hydrophilicity of the membrane. Furthermore, the pure water flux recovery ratio of the modified membranes were higher (>79%) than that of pure PES membrane (61%). In a word, the permeability and anti-pollution performance of the PES/TiO2/F127 membrane could be improved by the addition of TiO2 sol and F127, moreover, RTIPS method was a superior method for membrane preparation.