Power, Orla (2013) Formation and Characterisation of Nanostructured Polypyrrole Films: Their Growth on Membrane Supports and Application in Heavy Metal Remediation. PhD thesis, National University of Ireland Maynooth.
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Abstract
The Millennium Development Goal to halve, by 2015, the proportion of the population
without sustainable access to safe drinking water, was met in 2010, with an additional
two billion people gaining access to improved sources of drinking water since 1990.
However in 2013, the United Nations Year of Water Cooperation, almost one in nine
people worldwide still do not have access to a secure supply of clean, contaminant free
drinking water. Although the EPA 2010 Report “Water Quality in Ireland 2007-2009”
classes 84.7% of water bodies as good, the protection of Ireland’s water resources is
paramount as an ever-increasing population requires a continuous supply of clean, safe
drinking water. The Water Quality (Dangerous Substances) Regulations, 2001, were
introduced to regulate dangerous substances, including heavy metals. These include
chromium, nickel, lead, zinc and arsenic. The natural concentrations of these metals in
water vary depending on the metal content of the surroundings, but they may also enter
the environment from a range of anthropogenic sources. Chromium for instance is often
released as a by-product of electroplating, leather tanning and pigment manufacturing
processes.
In the research described herein, a number of polypyrrole based nanomaterials were
developed and their potential for heavy metal removal was investigated. The
polypyrrole nanomaterials formed were polypyrrole nanowires on conventional
electrodes and on porous polyamide membranes; polypyrrole nanowires coated with
polypyrrole-immobile dopant films and polypyrrole-sodium alginate particles.
Characterisation of the polypyrrole nanowires indicated that these films are more
hydrophilic than polypyrrole formed in the bulk morphology. The removal of chromium
by polypyrrole nanowires polymerised on conventional electrodes and on porous
membranes was found to be initially enhanced by the application of a pre-reduction step
which ensured that the polypyrrole was in its reduced state. After one hour immersion in
an acidified chromium solution, little difference was observed between the rate of
removal of the reduced polypyrrole nanowires and the non-reduced polypyrrole
nanowires. Adsorption and spontaneous electron transport at the polymer interface were
found to be the dominant processes in the removal process. The application of a
reduction potential was found to improve the recyclability of the polypyrrole nanowires.
vii
Polypyrrole nanowires were successfully coated with films of
p-sulfonatocalix[4]arene-polypyrrole and polypyrrole doped with poly(sodium
4-styrenesulfonate). Characterisation of the thus coated nanowires suggested that the
polypyrrole-immobile dopant films improved the conjugation of the polymer. The ion
exchange properties of these coatings were examined using an electrochemical quartz
crystal microbalance. It was found that polypyrrole doped with poly(sodium
4-styrenesulfonate) exhibited cation exchange behaviour, whereas the
p-sulfonatocalix[4]arene-polypyrrole films exhibited mixed cation-anion exchange
behaviour. The pre-dominance of cation or anion exchange of the
p-sulfonatocalix[4]arene-polypyrrole films was dependent on the dopant concentration,
the scan rate, and the nature of anion and cation in solution.
Chromium removal by the polypyrrole-sodium alginate particles was examined over a
range of solution pHs and was found to be most effective at a solution pH of 1.0. While
this material was designed primarily as an adsorbent, preliminary studies at pH 1.0
indicate that 67 ± 2 percent of the Cr(VI) is reduced to Cr(III) and released back into
solution. This suggests that spontaneous electron transfer between the conducting
polymer and the Cr(VI) may be occurring. The kinetics of the adsorption process was
best described by the pseudo-second-order kinetic model and fitting to the Morris-
Weber model indicated that intraparticle diffusion may also play a role in the adsorption
process.
Item Type: | Thesis (PhD) |
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Keywords: | Formation; Characterisation; Nanostructured Polypyrrole Films; Growth; Membrane Supports; Application; Heavy Metal Remediation; |
Academic Unit: | Faculty of Science and Engineering > Chemistry |
Item ID: | 15516 |
Depositing User: | IR eTheses |
Date Deposited: | 16 Feb 2022 11:41 |
URI: | https://mu.eprints-hosting.org/id/eprint/15516 |
Use Licence: | This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here |
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