Preparation of composite UF membranes of sulfonated polysulfone coated on ceramics

Sulfonated polysulfone (SPS) was synthesized from polysulfone resin using s ulfuric anhydride-triethyl phosphate complex. The SPS was dissolved in N-me thyl-2-pyrrolidone (NMP) using LiNO3 as a swelling agent. The resultant SPS dope was casted on a glass plate. An optimum ratio of SPS, NMP and LiNO3 w as 1:5:0.2 for making an UF membrane. The solvent was evaporated for 30 min , at 338 K, and an ultrafiltration membrane was obtained by gelation in an ice-cold bath. The ceramic/SPS composite membrane was prepared by the follo wing original procedure. First, the pores of the ceramic support were plugg ed with chitosan suspension at a pH over 6. The SPS dope was thinly coated on the membrane surface, and then the membrane was gelled in an ice-cold ba th under pH 6. The chitosan suspension plugged in the pores was removed bec ause the chitosan became soluble under pH 6. Thus, the composite membrane h aving negatively charged layer was obtained without plugging the ceramic su pport pores. The composite membrane showed a high pure water flux of 39.5 x 10(-6) m(3) m(-1) s(-1) at an applied pressure of 100 kPa and a molecular weight cut-off of 20 000. (C) 1999 Elsevier Science B.V. All rights reserve d.