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    Formation and Characterisation of Nanostructured Polypyrrole Films: Their Growth on Membrane Supports and Application in Heavy Metal Remediation

    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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    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)
    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
      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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