Browsing by Subject "in situ"
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Item Enhanced Adsorption of Perfluoro Alkyl Substances in Groundwater; Development of a Novel In-Situ Groundwater Remediation Method(2019-03) Aly, YousofPer- and poly- fluoro alkyl substances (PFAS) are a class of highly persistent, toxic and bio-accumulative anthropogenic chemicals. Due to their wide range of application including non-stick cookware, water and stain resistant coatings, chrome plating and aqueous film forming foams (AFFF), the potential exposure pathways for humans are numerous. AFFF use and subsequent release often leads to groundwater contamination, which poses a risk for human health. Currently, there is a wide array of remediation methods capable of treating PFAS contamination. These pump and treat methods, however, face many limitations including inhibitory costs, harmful byproducts, feasibility and ease of deployment. An in place (in-situ) remediation method holds the advantage of being more cost-effective, easier to deploy and cope with post remediation. Current in-situ PFAS remediation is limited. This thesis explores the amendment of a natural soil by two cationic coagulants (polydiallyldimethylammonium chloride [PDM] and poly(epichlorohydrin-dimethyl) amine [PA]) in order to increase adsorption, and thus retention, of PFAS in groundwater, and possibly sequestering a plume. PFAS adsorption onto natural soil was increased significantly based on batch and column tests. The increase in PFAS adsorption was not due solely to increases in organic matter from the addition of adsorption enhancers. Therefore, the mechanism of PFAS-enhancer interaction was explored. 19Fluorine-NMR spectra indicated that perfluoro carboxylates (PFCAs) were strongly bound in solution when in a solution of PA and PDM. The use of a PFOS ion specific electrode (ISE) found the same result. Given that this is a proposed in-situ remediation method; the long term behavior of PFAS-enhancer binding interactions is an important question that needs answering. Weathering and biodegradation by bacteria native to natural soil were not capable of degrading PA and PDM. However, activated sludge was able to degrade enhancers. There was little PFAS release detected indicating again that PFAS are strongly bound in solution and that this binding interaction potentially reduces bioavailability of enhancers when bound with PFAS.Item Semifluorinated Polymers and Hydrophilic High Capacity Ion-Exchangers as Ion-Sensing Membranes for Measurements in Harsh Sample Conditions(2016-01) Carey, JesseThe research presented in this thesis is focused on the development and use of ion-selective electrodes (ISEs) in harsh conditions, such as measurements in organic solvents, biological media, and samples containing lipophilic ions and at high temperatures. This thesis focuses on the study of two classes of ISE membranes to overcome challenges presented by these conditions, semifluorinated polymer membranes and hydrophilic high capacity ion-exchanger (HHCIE) membranes. First, a brief overview of the working mechanism and components of ISEs, as well as the problems caused by harsh sample conditions is given. Also, included is a discussion on fluorous membrane ISEs, which show resistance to biofouling, HHCIE membranes and polymer background relevant to ISEs. Semifluorinated polymers were synthesized by attachment of fluorinated side chains to the lipophilic polymer, poly(4-vinylphenol). However, the percent conversions of these reactions are not high enough to produce polymers that are suitable for use as ISE membranes. Several semifluorinated monomers were synthesized, polymerized into semifluorinated polymers and then fabricated into ISEs. These electrodes can utilize both fluorophilic and lipophilic ionophores, allowing for a wider range of possible analyte ions then previously available to fluorous membrane ISEs. Ion-exchanger electrodes made from these polymers show a wide selectivity rage, up to 14 orders of magnitude. Study of HHCIE membranes found them to be highly resistant to the effect of Donnan failure (co-ion interference). HHCIE membranes were used to make a sensor that could monitor the concentration of NOX- species in situ during nanoparticle synthesis reactions at 150 ºC in propylene glycol. It is also shown that nitrate ions present in this reaction are reduced to nitrite. A current pulse reference electrode with a HHCIE membrane was developed which should have advantages over similar electrodes made with lipophilic membranes when measuring in biological media.