Preparation and characterization of cellulose acetate-sulfonated poly (ether imide) blend ultrafiltration membranes and their applications

Modification of polymeric membrane materials by incorporation of hydrophilicity results in membranes with low fouling behavior and high flux. Hence, polyetherimide (PEI) was functionalized by sulfonation and ultrafiltration membranes were prepared based on cellulose acetate (CA) and sulfonated poly (ether imide) (SPEI) in various blend compositions in N-methyl-2-pyrrolidone (NMP) as solvent by phase inversion technique. Prepared membranes were subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane hydraulic resistance. All CA/SPEI blend membranes had substantially higher pure water flux, water content, and reduced hydraulic resistance compared to the pure CA membrane. Further, all of these above properties varied systematically with variation of SPEI content. Studies were carried out to find the rejection and permeate flux of macromolecular proteins such as trypsin, pepsin, egg albumin (EA), and bovine serum albumin (BSA) and toxic heavy metal ions such as Cu2+, Ni2+, Zn2+, and Cd2+ using polyethyleneimine as the chelating agent. On increasing the concentration of SPEI, the rejection of proteins and metal ions decreases whereas the permeate flux has an increasing trend. The molecular weight cut-offs (MWCO) of the blend membranes were determined using protein separation studies found to vary from 20 to 69 kDa, depending on the various polymer compositions. In general it was found that CA/SPEI blend ultrafiltration membranes demonstrated better performance compared to the membranes prepared from pure cellulose acetate.