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Metal speciation by high performance liquid chromatography25 November 2014 (has links)
Ph.D. (Chemistry) / Please refer to full text to view abstract
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Lanthanide metals as potential shark deterrentsUnknown Date (has links)
Sharks comprise a large portion of bycatch in pelagic longline fisheries worldwide. Lanthanide metals have been proposed as shark repellents. This study quantified the normalized voltage of lanthanide metals in seawater and found that there was no difference in normalized voltage among the six tested metals. Temperature and salinity had a significant effect on lanthanide normalized voltage. The output at 18ºC was significantly greater than at both 12 and 24ºC. The normalized voltage was significantly greater in freshwater than brackish or seawater. The dissolution rate for the lanthanides varied from -1.6 to -0.2g/h. As the metals dissolved the voltage remained constant. In a behavioral assay, neodymium was ineffective at repelling bonnethead sharks (Sphyrna tiburo) tested individually and in groups, and lemon sharks (Negaprion brevirostris) in groups. Due to high cost, fast dissolution rates, and lack of deterrent effects, lanthanide metals are not recommended for use in mitigating shark bycatch. / by Sara M. McCutcheon. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.
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Multi-metal equilibrium sorption and transport modeling for copper, chromium, and arsenic in an iron oxide-coated sand, synthetic groundwater systemOsathaphan, Khemarath 13 June 2001 (has links)
The mixed metal compound, Chromated Copper Arsenate, or CCA, has
been widely used as a wood preservative. The metal ions in CCA,
CrO��������, Cu�����, and AsO��������, have been found in contaminated surface and subsurface
soils and groundwater nearby some wood preservative facilities and nearby wood
structures. Iron oxides are a ubiquitous soil-coating constituent and are believed to
be a main factor in controlling the transport and fate of many metals in the soil
solution. In this research, iron-oxide-coated sand (IOCS) is used as a surrogate soil
to investigate the adsorption and transport behavior of the mixed metals solution,
copper, chromate, and arsenate, in the subsurface environment.
Copper adsorption increases with increasing pH. The presence of arsenate
in the solution slightly increases, while chromate has minimal effect, on the amount
of copper adsorbed. Chromate adsorption decreases with increasing pH. With
arsenate present in solution, chromate adsorption is significantly suppressed over
the pH range studied. In contrast, the presence of copper slightly increases
chromate adsorption. Similar to chromate, arsenate adsorption decreases with
increasing pH. The presence of chromate or copper does not affect the amount of
arsenate adsorbed over the range of concentrations studied.
Two surface complexation models, the triple layer model (TLM) and the
electrostatic implicit model (EIM), were used to simulate equilibrium adsorption in
both single-metal and multi-metal systems. Simulations using the specific surface
complexation equilibrium constants derived from either the single-metal or the
multi-metal systems with both the TLM and the EIM were successful in fitting the
adsorption data in that respective single or multi-metal system.
The local equilibrium assumption using batch-derived sorption isotherm
parameters from the EIM failed to predict the copper and arsenate transport, while
it adequately described chromate transport. The breakthrough curves of all three
metals were asymmetrical and showed long-tailing behavior. This nonideal
behavior is caused by nonlinear sorption and/or non-equilibrium conditions during
transport. The two-site chemical non-equilibrium model, which accounts for the
kinetically controlled adsorption sites, was able to fit the observed breakthrough
curves for all three metals in single-metal systems. However, the model was
partially successful in predicting transport in multi-metal systems. / Graduation date: 2002
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Trace metal speciation and bioavailability in urban contaminated soilsGe, Ying, 1974- January 1999 (has links)
Urban soils are often contaminated with trace metals and the toxicity of the metals depends, in part, on their speciation in soil solutions. The objectives of this project were to estimate the metal speciation in urban soils and to evaluate the predictability of soil metal pools on plant uptake. The chemical speciation of Cd, Cu, Ni, Pb and Zn was estimated by using the Windermere Humic Aqueous Model (WHAM). In soil solutions, Cd, Ni and Zn were present mainly as free ions when the solutions were acidic and their organic complexes were dominant as the pH was over 7.5. The other two metals mostly formed complexes with organic ligands. The activities of Cd2+, Cu2+, Ni2+, Pb2+ and Zn 2+ were affected by soil pH and total soil metal burdens. All five metals were under-saturated with respect to the minerals which could potentially control the metal solubility. / Metal uptake by plants in the contaminated railway yards was generally not correlated with free, dissolved and total soil metal pools. A pot experiment demonstrated better correlations between the metal pools and the metal content in wild chicory. Multiple regression analysis showed that the metals in the leaves and roots of wild chicory could be adequately predicted by the soil total metals and soil properties such as pH and exchangeable Ca.
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Trace metal speciation and bioavailability in urban contaminated soilsGe, Ying, 1974- January 1999 (has links)
No description available.
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Trace metal and speciation analysis using ion-exchange and energy dispersive X-ray fluorescence spectrometryMenendez-Alonso, Elena January 2000 (has links)
Studies have been carried out on specific ion-exchange (Dowex 50W-X8 and Dowex 1-X8) and chelation (Chelex-100) resins, in order to determine their physical and chemical characteristics, to understand and explain their limits of function and to optimise their use as substrates in trace metal and speciation measurement by EDXRF. Structural information was obtained by scanning electron microscopy and x-ray microanalysis showing a homogeneous distribution of functional groups and retained ions on both sectioned and whole resins. Particle size experiments performed on Dowex 50W-X8 (38 - 840 µm) showed that this parameter has no effect on the relationship between intensity of fluorescence and concentration or mass of resin. Inter-element effects were not observed in the analysis of multielemental specimens prepared on ion-exchange / chelation media by EDXRF. This indicates that the proposed method has a significant advantage when compared with other methodologies. A theoretical ‘model’, based on the formation of thin films on the surface of the resin beads, has been proposed in order to link and explain the effects observed in these experiments. The use of a batch retention system has shown distinct advantages over using columns in terms of linearity, accuracy, precision, rapidity and simplicity. Parameters such as pH and ionic strength of the solution, concentration of competing ions and volume of the sample have been proven to be critical. The maximum retention capacity has been determined as 3.2, 1.1 and 0.67 mEq/g for Dowex 50W-X8, Dowex 1-X8 and Chelex-100 respectively. The optimum mass of resin for XRF analysis was found to be 0.5 g, for all resins tested. The linear range covered 4 to 5 orders of magnitude. These findings show the potential of the investigated media to overcome instrumental and sample limitations. Based on the physico-chemical information found, methodologies for three different applications of the resins to EDXRF determinations have been developed and their analytical possibilities explored. The multi-elemental determination of metals in sewage sludge digests was achieved by retaining the metals on Dowex 50W-X8 at pH 2 and Chelex-100 at pH 4. Chelex-100 allows quantitative recoveries for Cu and Zn. A wider range of elements was determined on Dowex 50W-X8, although with poorer recoveries (60 - 90%). The limits of detection were 10 - 21 µg when Dowex 50W-X8 was used and 8 - 49 µg for Chelex-100. The method was validated by the analysis of a certified material. The determination of Kβ/Kα intensity ratios for Cr and Mn species and its potential as a tool for direct elemental speciation has also been studied. A difference in Kβ/Kα between the oxidation states of the analytes was only observed during the analysis of solutions of the metal species by EDXRF at the 98% level of confidence. Finally, the speciation and preconcentration of Cr(III) and Cr(VI) in waters has been performed by retention on Dowex 50W-X8 and Dowex 1-X8 followed by EDXRF determination. Efficient recoveries and preconcentration factors of up to 500 were achieved, leading to limits of detection of 30 µg/L for Cr(VI) and 40 µg/L for Cr(III). This method is simple, fast and inexpensive, allowing quantitative recoveries in the speciation of chromium in waste waters.
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