An attempt to enhance water flux of hollow fiber polyamide composite nanofiltration membrane by the incorporation of hydrophilic and compatible PPTA/PSF microparticles

Abstract

Hollow fiber composite (HFC) nanofiltration (NF) membrane was prepared on the inner surface of porous hollow fiber polysulphone (PSF) support membrane through the interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC). Hydrophilic and compatible poly(p-phenylene terephthalamide) (PPTA)/PSF blend particles were sythesized by the in situ polycondensation and cloud-point precipitation method and embedded in the polyamide (PA) functional layer via the incorporation into PIP aqueous phase to enhnace membrane water flux. The crystal structure and size distribution of the particles were characterized by X-ray diffraction (XRD) and dynamic light scattering (DLS). The effects of blend particle content on membrane morphology, surface hydrophilicity, water permeability and separation performance were investigated through the Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis, scanning electron microscope (SEM) observation, dynamic water contact angle (WCA) and separation performance measurements. The embedding of blend particles effectively improves membrane hydrophilicity, negative charge and water flux. The modified NF membrane with a blend particle concentration of 0.5 wt% has an enhanced water flux (5.46 L.m−2.h−1.bar−1) which is increased by 57.2 % meanwhile the salt rejection of MgSO4 can be well maintained (98.1 %) at 0.7 MPa. NF membrane exhibits an excellent NF performance with a high selectivity factor of 6 for MgSO4/NaCl and a high rejection (>98 %) of the selected dyes with different charge types. Appropriate membrane cleaning can effectively recover the water flux up to 90 %. The model of interfacial polymerization process was also proposed. PPTA blend particle was proved to be an excellent modifier for the separation performance improvement of NF membrane.