>Magister Scientiae - MSc / Over the last decade polysulfone membranes have been demonstrated to be one
of the best membrane types in wastewater treatment, especially in ultrafiltration,
owing to its mechanical robustness, structural and chemical stability. Regrettably
these membranes are mostly hydrophobic by nature and therefore highly
vulnerable to fouling due to chemosorptive mechanisms. Fouling may be caused
by cake formation on the surface of the membrane or by surface assimilation of the
foulants. Many studies have been directed at improving hydrophilic properties of
polysulfone membranes by introducing different types of nanoparticle composite
such as TiO2, ZnO2, Au and Ag nanoparticles to the polymer matrix, in order to
reduce fouling potential and increase membrane performance. In the present
investigation a hydrogel material was developed by crosslinking polyvinyl alcohol
(PVA) with polysulfone (PSF), using glutaraldehyde as crosslinker. PVA has
excellent film formation, emulsifying and adhesive properties, it is highly flexible
and has high tensile strength. Introducing PVA into the PSF polymer matrix was
expected to impart its advantageous properties onto the resulting membrane and
enhance hydrophilic characteristics of the membrane. The cross linking of PVA
and PSF was controlled at three different ratios to evaluate the effect of the PSF
contribution i.e. 25:75, 50:50 and 75:25. The crosslinked polymer composites
produced three unique hydrogel materials, which were evaluated for the separation
of selected small organic molecules, under hydrodynamic conditions, using rotating
disk electrochemistry. The hydrogel thin film behaved as a chemical sensor for the
oxidation of tannic acid in aqueous solution, with negligible shift in peak potential
as a function of concentration. The nanomaterials prepared were characterised
using spectroscopic, morphological and electrochemical techniques. Hydrogel performance in the presence of analyte molecule was evaluated by hydrodynamic
voltammetry and electrochemical impedance spectroscopy.
From calibration curves based on cyclic voltammetry, hydrodynamic, macroscopic
and spectroscopic techniques, the 75% polysulfone and 25 % polyvinyl alcohol
hydrogel (75:25 PSF-PVA) presented the best performance for quantitative
detection and best sensitivity toward alginic acid and tannic acid than the
corresponding composites (50:50 and 25:75 PSF-PVA). Optical results (contact
angle) show an agreement with spectroscopic (EC) and microscopic (AFM) result.
A decrease in contact angle gives an increase in roughness and diffusion
coefficient. High surface roughness was linked to improved hydrophilicity of the
polysulfone.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/4274 |
| Date | January 2013 |
| Creators | Muya, Francis Ntumba |
| Contributors | Baker, Priscilla |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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