Preparation and characterisation of poly (amide-imide) incorporated cellulose acetate membranes for polymer enhanced ultrafiltration of metal ions

Polymeric membranes intended to use in industrial separations must maintain excellent thermal and mechanical properties over their targeted operating conditions. Therefore, cellulose acetate (CA) membranes with superior properties were prepared by phase inversion technique using high performance thermoplastic poly (amide-imide) (PAI) as the modification agent. The prepared membranes were characterised using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and mechanical analysis to understand the influence of PAI on the properties of modified membranes. The SEM analysis showed that blend CA membranes have thinner top layer and higher porosity in the sub-layer. The improvement of surface porosity with an increase in PAI content and decrease in mean pore size was substantiated by the AFM surface roughness analysis data. The modified membranes were applied for the separation of metal ions from aqueous solutions by polymer enhanced ultra filtration. Attempts have been made to correlate the changes in thermal, mechanical properties and membranes performance with morphology. It is worth mentioning that the outstanding thermal stability and separation efficiency of these membranes arising from the fine dispersion of PAI in the CA matrix obviously offers immense potential in industrial separations.