W. Richard Bowen and Nidal Hilal 4
W. Richard Bowen and Nidal Hilal 4
W. Richard Bowen and Nidal Hilal 4
- No tags were found...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
144 5. AFM AND DEvELOPMENT OF (BIO)FOULINg-REsIsTANT MEMBRANEs<br />
small pieces of membrane are necessary for experiments to be undertaken.<br />
Ultimately the direct measurements of the AFM will help to assist<br />
in the development of new membranes with more fouling-resistant properties.<br />
(Further information on ES 404 <strong>and</strong> XP 117 is given in Chapter 4.)<br />
5.3 ModIfICAtIon of MEMbrAnES<br />
The development of high-performance membranes involves the<br />
selection of a suitable material <strong>and</strong> the formation of this material into a<br />
desired membrane structure. However, it is often necessary to modify the<br />
membrane material or the structure to enhance the overall performance<br />
of the membrane. The field of membrane technology is extremely broad,<br />
<strong>and</strong> the applicability of surface modification for different types of membranes<br />
is equally diverse. Polymeric membranes of nearly every variety<br />
have been utilised in the literature as substrate for polymer modification<br />
by the addition of another polymer.<br />
There are many techniques for the attachment of polymers to membrane<br />
surfaces. Some of these techniques, such as electrochemical <strong>and</strong><br />
�-irradiation, require continuous application of current or radiation<br />
throughout the polymerisation process. Others, such as UV-initiation,<br />
electron beam deposition, plasma treatment <strong>and</strong> silanisation, create reactive<br />
sites for subsequent formation of the polymer in situ, in general by<br />
free radical polymerisation. Whole macromolecules can be incorporated<br />
either by their cross-linking within the pores or by specific attachment of<br />
polymer chains to the membrane pore surfaces. Such modification methods<br />
are commonly applied to improve various membrane properties,<br />
including improvement of their surface-fouling resistance. Rendering the<br />
membrane surface more hydrophilic is a widely used method to reduce<br />
their tendency to become fouled.<br />
Modification by photo-initiated graft polymerisation with various<br />
hydrophilic monomers has been extensively applied to vary the hydrophilicity<br />
of the membrane surface. Acrylic acid, hydroxyethyl methacrylate<br />
(HEMA), poly(ethylene glycol) derivatives <strong>and</strong> vinyl pyrolidinone are<br />
examples of such hydrophilic monomers. Improvement in membrane fouling<br />
tendency has been reached after modification with such hydrophilic<br />
monomers [16–18].<br />
5.3.1 Modification of Membranes with Quaternary<br />
Ammonium Salts<br />
Quaternary 2-dimethyl-aminoethylmethacrylate (qDMAEMA) was<br />
chosen for the modification of PES <strong>and</strong> polyvinylidene fluoride (PVDF)<br />
membranes using photo-initiated graft copolymerisation method [1, 19, 20].