Thesis (Ph. D.)--University of Wyoming, 2005. / Title from PDF title page (viewed on March 4, 2008). Includes bibliographical references.

Thesis (PH. D.)--Columbia University. / Biographical.

Thesis (Ph.D.)--University of Virginia, 1895. / Also available online through Digital Dissertations.

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.

Thesis (M.Sc.(Physics)) --University of Limpopo, 2006 / Platinum group minerals are abundant in South Africa. Platinum is of great significance in catalytic applications and many other medical and pharmaceutical industries. Our studies of PtSb2 and PtBi2 were carried out using Density Functional Techniques, including LDA and GGA methods. We investigated the pressure dependences of lattice parameters and bond lengths of the materials. All these properties were shown to decrease with increasing pressure, in a linear fashion. Other features that were studied are the electronic properties like density of states (DOS) and optical properties to determine the type of material being studied. A set of interatomic potentials has been derived for the study of bulk and surface properties of PtSb2 using the GULP code (General Utility Lattice Program). These potentials have proved to be reliable since they reproduced bulk properties of PtSb2 such as lattice parameters and elastic constants. As there are no experimental studies on surfaces we have been able, for the first time, to calculate surface energies for the low index surfaces and found out that the most stable surface is the {100} Sb terminated one, with the energy of 0.933 J.m-2 and the least stable is the {111} Sb terminated surface with the energy of 2.586 J.m-2.

M.Sc. (Physics) / Please refer to full text to view abstract

In this dissertation, the aim was to develop a platinum specific resin to be utilized for the early removal of platinum from the industrial feed solution. Efforts were therefore directed towards the syntheses of silica based resins, with active centra, designed for platinum. The large chlorometallate ions present in the feed stream, were characterized in terms of physical parameters relevant to phase distribution, namely distortability (RD), charge density, softness (σ) etc. Matching cations for each of the types were investigated. In order to attempt the design of platinum specific resins, different structural amines were used to aminate the silicone precursor and to subsequently fix these onto the silica framework. Two different solvents namely alcohol and dmf were used in this process, resulting in two sets of resins, with different properties. The design was based on previous experience with these ions, with reference to their behaviour towards different types of cations. The platinum species, PtCl6 2- and PtCl4 2-, as well as the most important contaminants in the feed stream, were typified, bearing in mind size, charge, charge density and distortability. Different types of cationic centra, having differences in charge density, stereochemical crowding and extent of hydrophobicity, were synthesized and tested-both as solvent extractants (where possible) and silica based resins. The results indicated that, partly screened secondary ammonium cationic resin species, which could be regarded as “intermediate”, proved to be satisfactory both in their high percentage extraction for PtCl4 2- and rejection of contaminants like chlororhodates, chloroiridates(III) and FeCl4 -. It was however necessary, to work at a redox potential, where iridium(IV) in the form of IrCl6 2-, was absent. Various 2-aminoalkane resins were prepared, with variation in the length of alkane group and synthesised by the two different solvents. The latter resulted in two sets of resins with not only differing compactness, but also having significantly different properties with reference to platinum specificity, HCl effect and stripping potential. The 2-aminobutane and 2-aminoheptane resins in particular, proved to be very satisfactory platinum specific resins, both with respect to selectivity, platinum capacity and stripping potential. The various physical parameters could be applied to identify the chemical behaviour of anions and assist in the development of anion specificity for the relevant species.

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Thesis (Ph. D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 165).