Abstract
M.Sc. (Nanoscience)
This study focused on the synthesis of pH responsive polyamide thin film composite
(PA TFC) membranes modified with zinc oxide (ZnO) nanoparticles and polyacrylic
acid (AA) for effective removal of Pb(II) heavy metal ions from wastewater. The
novelty of the work was based on the combination of both ZnO and AA, through an
in-situ interfacial polymerization modification method of m-phenylenediamine
(MPDA) and trimesoyl chloride (TMC). The first part of the research work was based
on the modification of PA TFC membranes with different concentration of AA
(0.00%, 0.25%, 0.50%, 0.75%, 1.00%, and 1.50%). These membranes were
characterized with different techniques such as attenuated total reflectance Fourier
transform infra-red spectroscopy (ATR-FTIR), scanning electron microscopy (SEM),
and atomic force microscopy (AFM) and thermal gravimetric analysis (TGA). AFM
results showed smoother surfaces upon increasing the AA content. Membrane
performance of the PA TFC membranes such as permeability, hydrophilicity,
swelling, ion exchange and rejection were evaluated with respect to pH. It was
observed that low pH conditions favour high permeability whilst high pH conditions
favours high rejection. This is due to the AA ionisable –COOH side chains which
tend to collapse at lower pH thereby allowing the diffusion of solutes through the
membranes and swelling at high pH thereby restricting the passage of solutes
through the membranes.
In the second part of the work, the PA TFC membranes were modified with both the
AA hydrogel and ZnO nanoparticles at different concentrations. The AA
concentration used were 1.00% and 1.50% and were constant throughout while the
ZnO concentrations were varied (0.50%, 1.00% and 1.50%). The modified
membranes were also found to exhibit high pH responsiveness in terms of
permeability, hydrophilicity and Pb(II) rejection. Characterisations such as SEM,
AFM and TGA were also carried out. AFM showed rougher surfaces upon an
increase concentration of ZnO nanoparticles...