Introduction Poly(ethersulfone) (PES) is a popular material for the manufacture of ultrafiltration and microfiltration membranes, due to its structural and chemical stability. Unfortunately, the separation performance of PES membranes often deteriorates because of membrane fouling, which is attributed to the intrinsic hydrophobic character of this material. Therefore, introduction of different polar functional groups to the PES membrane surfaces has been reported in literature by incorporation of hydrophilic polymer through blending , coating , and radiation induced-grafting . Although successful to some extent, these methods only offer random control over the resulting surface structure and may be environmentally adverse. This study presents the first successful example of environmentally benign enzyme-catalyzed grafting to PES membranes. Various phenolic acids were coupled to the membrane at room temperature using laccase in aqueous medium, and the resulting surfaces were investigated by XPS and FT-IR. The extent of modification was varied and protein repellence of the modified surfaces and membranes was measured. Materials and Methods Flat (and hollow fibre) PES membranes were incubated in 0.1 M sodium acetate buffer (pH 5) containing phenolic acids (Figure 1) and laccase from Trametes versicolor. Substrates were tested at concentrations of 0.6, 10, and 28.8 mM, respectively, and with incubation times of 0.5, 2, 8, and 24 h. After the incubation time was completed, the membranes were washed and tested further. Results and Discussion PES membranes become strongly colored upon incubation with laccase and any of the three phenolic acids. This coloration cannot be removed by washing, and is a function of grafting yield (Figure 2) which in turn depends on substrate and enzyme concentration, reaction temperature and incubation time. Please note, that the relation is not linear ,various structures were formed ranging from brushes to interlinked polymers. XPS measurements indicate the covalent attachment of new material to the membrane, which is confirmed by IRRAS studies that show the presence of carbonyl and hydroxy groups on the modified membrane. Further, protein repellence is greatly influenced (see Figure 3). Conclusions Poly(ethersulfone) membranes can be grafted with phenolic acids using laccase in water at ambient temperature, yielding stable modified membranes that show increased protein (and bacterial) repellence.
|Publication status||Published - 2013|
|Event||8th International Membrane Science & Technology Conference - |
Duration: 25 Nov 2013 → 29 Nov 2013
|Conference||8th International Membrane Science & Technology Conference|
|Period||25/11/13 → 29/11/13|