Preparation and performance evaluation of poly (amide-imide) and TiO_2 nanoparticles impregnated polysulfone nanofiltration membranes in the removal of humic substances

摘要

Poly (amide-imide) (PAI) and TiO_2 nanoparticles impregnated polysulfone (PSf) nanofiltration membranes with integral dense layer were prepared by phase inversion technique from a dope solution containing N-methyl-2-pyrrolidone as solvent and 1,4-dioxane as co-solvent. The prepared membranes were characterized using attenuated total reflectance-fourier transform Infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), pure water flux and contact angle technique to investigate the influence of PAI on the properties of the membranes. Low miscibility of 1,4-dioxane in the dope solution with coagulant and higher water tolerance of PAI enabled us to prepare membrane with spongy substructure and provided control over the pore size of the blend membranes. The contact angle values indicated that, the hydrophilicity of the PSf membranes was improved by the addition of PAI and TiO_2 nanoparticles due to the preferential orientation of these components towards the membrane surface. Surface energy parameters of the membrane such as surface free energy, interfacial free energy and work of adhesion were calculated. These prepared membranes were subjected to the separation of humic substances from aqueous streams and separation efficiency of blend membranes were found to be improved significantly. Antifouling property of the membranes was studied by humic acid (HA) as the model foulant. Attempts have been made to correlate the changes in the performance of the membranes with its structure. It is worth mentioning that low free energy membranes prepared by the incorporation of PAI and TiO_2 nanoparticles may be valuable for various industrial separations.