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Keywords:

  • polysulfone;
  • membrane;
  • fouling;
  • persulfate;
  • oxidation;
  • ESCA-XPS;
  • FT-IR

Abstract

Polysulfone (Udel P1800) ultrafiltration membranes were surface modified using potassium persulfate (K2S2O8) as a free radical source in the aqueous phase. The expected modification was hydrogen abstraction leading to hydroxylation at one or two sites on the isopropylidene linkage. Reaction time, K2S2O8 concentration, and temperature were optimized based on two criteria: (1) minimal change in pure water fluxes after surface modification and (2) reduction of adsorptive fouling with a pulp mill effluent. The pure water flux retention for an unmodified membrane was ∼20% after adsorptive fouling with the pulp mill effluent and was increased to 70% after reaction with K2S2O8. Angle-resolved XPS indicated increased oxygen and a new carbon peak consistent with an aldehyde reaction occurring in the top 3.5 nm. NMR solution analysis was inconclusive because of the low sensitivity of the experiment. Further analysis of oxidation products was carried out on finely dispersed polymer. Fourier transform infrared, internal reflection spectroscopy suggested oxidation by the formation of an aldehyde which was further oxidized to carboxylic acid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1723–1730, 2006