Hydrophilic surface modification of polysulfone hollow fiber membrane was performed by acrylic acid treatment.Stannic chloride was selected as the proper catalyst

and phosphoric acid as the co-catalyst.The modification conditions

such as the ratio of the reagents (acrylic acid∶catalyst=1∶0.05)

temperature (30℃) and reaction time (60 min)

were optimized based on the contact angle measurements.The grafting of carboxyl group to the membrane surface was confirmed by IR spectrum and wettability analysis

and no degradation of the modified membrane skin or framework was observed with scanning electron microscopy.The experimental results of filtrating bovine serum albumin solutions indicated that the property of resisting protein adsorption on the membrane surface for the modified membrane was much better than that for unmodified membrane.In the process of separating casein hydrolysates

the advantages of modified membrane were also shown by comparing the permeate flux and molecular mass distribution with those of unmodified membrane.