Preparation, Morphology, Performance, and Hydrophilicity Studies of Poly(amide-imide) Incorporated Cellulose Acetate Ultrafiltration Membranes

Fouling-resistant cellulose acetate (CA) membranes were prepared by the phase inversion technique using hydrophilic poly(amide-imide) (PAI) as the modification agent. 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, water content, porosity, and contact angle technique to investigate the influence of PAI on the final properties of the membranes. Intermolecular interactions between the components in blend membranes were established by ATR-FTIR, and semicrystalline nature was confirmed by XRD. SEM analysis showed that blend CA membranes have a thinner top layer and higher porosity in the sublayer. AFM surface roughness analysis data substantiate the enhanced surface porosity with an increase in PAI content, while the mean pore size decreases. The contact angle measurements indicated that the hydrophilicity of the CA membranes was improved by the addition of PAI due to the preferential orientation of functional groups towards the surface. Moreover, the surface free energy parameters of the membrane such as surface free energy, interfacial free energy, work of adhesion, and spreading coefficient were calculated. From the results, it was revealed that low interfacial free energy membranes prepared by the incorporation of PAI may be valuable in fouling-resistant industrial separations.