In a recent paper [Susanto, Ulbricht, J. Membr. Sci. 266 (2005) 132], we showed that dextran does foul polyethersulfone (PES) ultrafiltration (UF)
membranes by contact of the solution with the membrane surface without flux through the membrane. In this work, dextran fouling was visualized
using atomic force microscopy (AFM) and quantified by ATR-IR spectroscopy and by the mass balance in simultaneous diffusionâadsorption
measurements (SDAM). Good correlations have been found between the water flux reduction due to dextran adsorption and the quantitative data
for bound dextran on the PES membranes. Further, a pronounced effect of dextran size on adsorptive membrane fouling was identified. Contact
angle and zeta potential measurements with non-porous films, where solute entrapment in pores can be ruled out, gave additional clear evidence
for dextran binding on the PES surface. Complementary data for adsorption and fouling of porous membranes and non-porous films by the protein
myoglobin indicated that the larger fouling tendency for protein than for dextran is due to a higher surface coverage of PES by the adsorbed
biomacromolecule layer. Data for batch UF confirm the conclusions from the static contact experiments because significant fouling is observed
for PES membranes (more severe for myoglobin than for dextrans), while no fouling is seen for a cellulose-based UF membrane with the same
nominal cut-off. Finally, two mechanisms for the attractive PESâdextran interaction â multiple hydrogen bonding involving the SO2 groups of PES
and âsurface dehydrationâ of the relatively hydrophobic PES â are discusse
