There are a number of impurity elements present in sulphide ores that can have a deleterious effect on the properties of the final copper metal product. In this thesis, an equilibrium distribution technique was used to determine the thermodynamic behaviour of selenium and tellurium in molten slags used in copper production. Calcium ferrite based slags and copper or silver alloy were equilibrated in magnesia crucibles at temperatures of 1200 to 1400 °C and oxygen partial pressures of 10-11 to 10-0.68 atm. Under conditions typical of those employed during copper converting, the minor elements were found to enter the slag as negatively charged species. The partitioning of selenium and tellurium to the slag was greatest at high temperature, low oxygen partial pressure and at highest concentration of basic oxide (CaO or BaO). The experimentally derived data were combined with published information to calculate the selenide and telluride capacities of the slag, and also to generate fundamental thermodynamic activity data for selenium and tellurium in the slag phase. It was found that the activity coefficients of selenium and tellurium were independent of their concentration in the slag over the range studied, but were strongly dependent on the temperature, slag chemistry and oxidation state of the slag. Experiments were also designed and carried out to determine what effect the presence of iron oxide and its oxidation state has on the behaviour of selenium in the slag. A series of experiments involving iron oxide additions to a calcium aluminate slag was conducted under increasingly oxidising conditions to assess the effect of total iron on the selenide capacity as the dominant oxidation state of iron in the slag changed. It was shown that at a constant ratio of CaO:Al2O3, the selenide capacity increased with total iron in the slag. However, the effect on the selenide capacity did not appear any more significant as the Fe3+:Fe2+ ratio changed in a particular direction. 4 Another series of experiments was carried out with iron calcium silicate slags to determine the stability of phases within the slag, and how this affected the equilibrium distribution and activity coefficient of selenium in the slag. A number of solid phases were identified and their composition determined by scanning electron microscopy, energy dispersive spectroscopy and electron microprobe analysis. The composition and minor element content of the remaining liquid was calculated using a thermodynamic model. From this it was found that the capacity of the liquid slag has a region of independence against slag chemistry, before increasing strongly with increasing lime content to the calcium ferrite composition. Some of the implications of this work are discussed with reference to the practicality of adjusting the process variables in a large-scale industrial process for the purpose of managing minor element content of the molten phases. Considerations include the effect on copper recovery and rate of wear of furnace refractory materials.

Whether a global greenhouse interval is a distinct or distant future, it is important to understand the dynamics of a greenhouse system. During such intervals the oceans, in the absence of sizeable polar ice caps, flood the continental shelf. The stratification and circulation of these epicontinental seas are open to debate, because there are no Recent analogs. The carbon and oxygen stable isotope record of fossil molluscan shell from epicontinental seas has the potential to reveal their stratification and seasonal cycles. Whether a global greenhouse interval is a distinct or distant future, it is important to understand the dynamics of a greenhouse system. During such intervals the oceans, in the absence of sizeable polar ice caps, flood the continental shelf. The stratification and circulation of these epicontinental seas are open to debate, because there are no Recent analogs. The carbon and oxygen stable isotope record of fossil molluscan shell from epicontinental seas has the potential to reveal their stratification and seasonal cycles. As a study sample, mollusks from the Baculites compressus and Baculites cuneatus biozones of the Western Interior Seaway of North America were collected from three locations: Kremmling, Colorado; Trask Ranch, South Dakota; Game Ranch, South Dakota. These fossils date to the Campanian (Late Cretaceous). Taxa include ammonites, bivalves, gastropods, and nautiloids. The first part of this investigation, described in Chapter 2, investigates the degree of alteration in these specimens. Elevated concentrations of minor elements such as magnesium and strontium reveal alteration from the original aragonite and/or calcite skeletons. Concentrations of these elements obtained by ICP-OES analysis are compared within several suites of specimens: mode of preservation, shell testing location, shell color, cementation, appearance under light microscope, and appearance under scanning electron microscope. Each of these suites tests a hypothesis about optimal shell preservation. Shell was found to be preserved best in shale rather than concretions, ammonite phragmacone rather than septa, opalescent specimens rather that nonopalescent ones, and uncemented shells rather than cemented shells, especially those with second-order versus first-order cement. Salinity and temperature values were derived for the organisms in the Western Interior Seaway: while bivalves produced unusually low temperatures, the others were reasonable for an inland sea. The second part of this study, described in Chapter 3, examines the isotopic record within exemplary mollusk shells, taken perpendicular to growth lines. The data for this investigation in sclerochronology documents the dominant isotopically enigmatic bottom-water habitat of the Inoceramus, the geochemical signature of the overlying water mass inhabited by Baculites, and short-term migrations between the two water masses in the nautiloid Eutrephoceras.

Made available in DSpace on 2014-12-17T15:41:46Z (GMT). No. of bitstreams: 1 RinaLSMpdf.pdf: 3452236 bytes, checksum: 7d7e19e1df71d1563d94e1dd5d766bbb (MD5) Previous issue date: 2009-02-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The aim of this study was to quantify the presence of major and minor elements in the sediments of the Jundia?-Potengi estuary, bordering the municipalities of Maca?ba, Natal and S?o Gon?alo do Amarante in the state of Rio Grande do Norte, Brazil, considering the evidence of anthropic activity along this estuary, resulting in pollution by treated and untreated wastewaters as well as those produced by industry and shrimp farming. The assessment of the environmental status of this estuary was based on physical-chemical parameters, such as granulometry, organic matter and the major (Al, Fe, Mn and P) and minor (Cd, Cr, Cu, Ni, Pb and Zn) elements found in sediment samples. Two collections were made at 12 georeferenced points along the channel of the estuary at different times. Granulometric analysis was carried out and the percentage of organic matter was determined. The sediments were microwave digested using acid digestion and quantitative analyses of the elements Al, Fe, Cd, Cr, Cu, Mn, Ni, P, Pb and Zn were performed by inductively coupled plasma optical emission spectrometry. Sediment analysis followed the methodology proposed by US EPA 3051A for total elements analysis. The small correlation between the organic matter and the elements studied here suggests that they are of geochemical rather than anthropic origin. The analytical results obtained from the bottom sediment samples in the study area show that the concentration of elements was below the reference values for standard shales (Turekian & Wedepohl, 1961) at the vast majority of points analyzed, ruling out a possible contamination by metals / Este trabalho teve como objetivo avaliar, por meio da quantifica??o, a presen?a dos elementos maiores e menores nos sedimentos do Estu?rio Jundia?-Potengi localizado as margens dos munic?pios de Maca?ba, Natal e S?o Gon?alo do Amarante no Estado do Rio Grande do Norte, considerando as evid?ncias de atividades antr?picas ao longo deste estu?rio, no qual se destacam a polui??o por efluentes dom?sticos, tratados e sem tratamento, efluentes industriais e de carciniculturas. A avalia??o do estado ambiental desse estu?rio foi feito atrav?s da determina??o dos par?metros f?sicoqu?micos, como granulometria, mat?ria org?nica e elementos maiores, Al, Fe, Mn e P, e elementos menores, Cd, Cr, Cu, Ni, Pb e Zn em amostras de sedimento deste estu?rio. As coletas foram feitas em 12 pontos, georefer?nciados, na calha, ao longo desse estu?rio, e em duas coletas com per?odos distintos. Foram feitas as determina??es das porcentagens de mat?ria org?nica e a an?lise granulom?trica. A digest?o dos sedimentos foi feita com um aparelho de microondas por digest?o ?cida e as an?lises quantitativas dos elementos Al, Fe, Cd, Cr, Cu, Mn, Ni, P, Pb e Zn por espectrometria de emiss?o ?tica com plasma acoplado indutivamente Para a an?lise dos sedimentos tomou-se como refer?ncia a metodologia proposta pela US EPA 3051A para a an?lise dos elementos. A pequena correla??o da mat?ria org?nica com os elementos estudados neste trabalho sugere que estes n?o sejam de origem antr?pica e sim de suporte geoqu?mico. Os resultados anal?ticos apresentados pelas amostras de sedimentos de fundo para a ?rea estudada mostraram que a concentra??o dos elementos ficou abaixo dos valores de refer?ncia do folhelho padr?o de Turekian & Wedepohl (1961) na grande maioria dos pontos analisados, descaracterizando uma poss?vel contamina??o por metais