No description available.

Thesis--University of Missouri, School of Mines and Metallurgy, 1885. / The entire thesis text is included in file. Phil VanFrank determined to be Philip R. VanFrank from "1874-1990 MSM-UMR Alumni Directory". Holograph [Handwritten and illustrated in entirety by author]. Title from title screen of thesis/dissertation PDF file (viewed September 24, 2008)

No description available.

No description available.

No description available.

The leaching behaviour of enargite was studied under atmospheric pressure. The kinetics of enargite dissolution appear to be extremely slow under the conditions studied using both small scale shake flasks and bench scale stirred tank reactors. An enargite concentrate and a purer mineral specimen were utilized and the effect of numerous variables including temperature, particle size, acidity, oxygen flow rate, iron addition, redox potential and pyrite addition were investigated. The initial rate of copper dissolution from enargite was relatively fast up to about 40% copper extraction but this was followed by a much slower dissolution rate. The first stage is thought to be reaction rate controlled while the latter stage appears to be diffusion controlled. The activation energy was determined to be 32 kJ/mol for the concentrate and 33 kJ/mol for the pure specimen in the temperature range of 55-85°C. In the presence of high concentrations of copper sulphate, enhanced copper recovery was observed for the pure enargite specimen. This could be the result of a change in the reaction product layer on the enargite surface and perhaps the formation of intermediate Cu2S. Previous work has shown that adding excess pyrite enhances copper extraction from enargite but these results could not be reproduced. Particle size reduction appears to be the most effective method to increase extraction rates, however only 70% copper recovery and 35% arsenic recovery was achieved after 24 hours of leaching at d80=2μm. At these reaction rates, it appears that enargite dissolution at atmospheric pressure will not be an economical process compared to other technologies such as high temperature/pressure oxidation or roasting. / Thesis (Master, Mining Engineering) -- Queen's University, 2010-05-02 23:12:46.528

The potential region in which chalcopyrite dissolves during the oxidative leaching of the mineral in ferric sulphate solutions has been established. These results have been modelled using an extended mixed-potential description of the system. The initial stages of the dissolution process have been studied using a chalcopyrite disk and a platinum ring electrode held at appropriate potentials for the detection of ferrous and cupric ions. These experiments have shown that the initial stages of oxidation of the mineral involve the formation of soluble sulphur species in addition to elemental sulphur. The ring-disk experiments are generally consistent with thiosulphate as this species. The effectof potential and various ratios of ferric to ferrous ions on the rate has been investigated by both electrochemical and chemical analysis techniques. The role of non-oxidative dissolution in the leaching of chalcopyrite has been explored and it has been shown that the initial rate of non-oxidative dissolution is significant and could exceed the oxidative rate at long leach times.

Thesis (Ph.D.)--Murdoch University, 2001. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 279-300.

M.Tech / Atomic force microscopy (AFM) has been an integral tool in bacterial studies for resolving surface structures. Novel applications of this instrument in research require the development of sample preparation techniques and improvement of existing ones. Careful selection of the scanning parameters is particularly crucial when exploring the full potential of the AFM. The objective of this study was to design sample preparation methods for AFM imaging bioleaching bacteria and optimise the scanning parameters (deflection setpoint, feedback loop and the scan rate) for contact mode (CM) imaging in air. The method should be simple, fast and cost effective. The strategy used in this study of (i) evaluation of support substrates for bacterial attachment, (ii) investigation of the effect of pH and centrifugation on cell samples during imaging. Centrifuged and noncentrifuged cell samples suspended in either deionised water (pH 7) or acidified water (pH 1.5) were tested for imaging. Mica and glass cover slips were used as potential substrates for attachment. Cells were attached to substrates for imaging by simple adsorption (‘air-drying’ method). To optimise the scanning parameters, the effect of different values of the scan rate, deflection setpoint and the feedback gains on the quality of AFM imaging was investigated. Optimisation of these parameters was found to be instrumental when imaging weakly adsorbed samples prepared by simple adsorption and ‘soft’ samples such as bacterial cells. The results obtained from these experiments were used during preparation of iron- oxidising leaching bacteria for AFM imaging. The surface morphology of iron-grown bacterial samples was investigated with contact mode AFM in air. Reproducible results obtained in each scan shown by the stability of morphological characteristics of bacterial samples indicate that (i) mica can be used successfully as a substrate for attaching cells, (ii) centrifuged bacterial samples can be easily imaged (iii) scanning with scan rate values of <0.5Hz, deflection setpoint of between 0.2-0.5V and feedback values of < 5.000V improve the image quality and can prevent deformation of the bacterial cells by the tip. Non-centrifuged samples could not be imaged, indicating that bacterial cells need to be separated from growth residues as a prerequisite for successful AFM imaging.

The leaching of goethite in solutions of perchloric, sulphuric, and hydrochloric acids and in perchloric acid in presence of sulphur dioxide has been investigated. Suspensions of goethite powder (-65, +150 mesh) were leached over a wide range of temperatures, acid concentrations and sulphur dioxide pressures. Strong solutions of hydrochloric acid leached goethite powder more rapidly than equivalent solutions of sulphuric acid, whilst at low concentrations sulphuric acid was the more active reagent. Perchloric acid was found to leach the mineral only very slowly. The rate of dissolution was found to increase with time in the early stages of leaching with all concentrations of sulphuric acid, with strong solutions of hydrochloric acid, and with perchloric acid solutions containing sulphur dioxide. This phenomenon has been correlated with changes in the surface morphology of the goethite during leaching. The rate data derived from the observed results have enabled the effects of temperature, acid type, concentration and partial pressure of sulphur dioxide on rate of leaching to be studied. A common mechanism of leaching is proposed in which protonation of the hydrated oxide surface is followed by adsorption of an anion and desorption of the ferric-anion complex. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate