Enhancing the Compatibility, Hydrophilicity and Mechanical Properties of Polysulfone Ultrafiltration Membranes with Lignocellulose Nanofibrils

Lignocellulose nanofibrils (LCN) and cellulose nanofibrils (CNF) are popular nanometer additives to improve mechanical properties and hydrophilic abilities; moreover, lignocellulose has potential as a natural adhesion promoter in fiber-reinforced composites. LCN and CNF were blended into polysulfone (PSF) to prepare ultrafiltration membranes via the phase inversion method. These additives were characterized by Fourier transform infrared spectroscopy and transmission electron microscopy, and the rheological properties such as shear viscosity and non-Newtonian fluid index of the casting solutions were analyzed using a rotational rheometer. The performance of ultrafiltration membranes was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The pure water flux, bovine serum albumin retention ratio, water contact angle, surface energy, molecular weight cut-off, pore size and mechanical properties were measured. The equilibrium contact angle of water decreased from 63.5° on the PSF membrane to 42.1° on the CNF/PSF membrane and then decreased to 33.9° on the LCN/PSF membrane when the nanometer additives content was 0.8 wt %. The results reveal that LCN and CNF were successfully combined with PSF. Moreover, the combination of LCN/PSF ultrafiltration membranes was more promising than that of CNF/PSF ultrafiltration membranes.