Over a century of mining activities and smelting in the area of Sudbury, Ontario, Canada have resulted in the contamination of the local soils with metal(loid) bearing particulates. Minor and trace elements associated with these phases are released during their weathering. This release is therefore strongly dependent on the mineralogical and chemical character of the metal(loid) bearing phases. The metal(loid)s are then subject to transport before being attenuated through their incorporation into secondary phases. Elevated concentrations of metal(loid)s in silica rich alteration layers has recently been described for altered surfaces at the solid-water and solid-atmospheric interfaces in tailings, and in the vicinity of smelters, respectively. To determine if similar coatings occur in soils, samples were taken from areas around three major smelting centers in the area. Coated grains were extracted from these samples and individually mounted to be analysed. Particulate matter (representing primary metal(loid)-bearing phases) and coatings (secondary metal(loid)-bearing phases) were analysed using scanning electron microscopy, Raman spectroscopy, Laser-Ablation Inductively-coupled plasma mass spectroscopy, Micro-X-ray fluorescence, and X-ray photoelectron spectroscopy. The particulates were divided into three main groups: smelter-derived particles, sulfides, and nickel-oxides. Smelter derived particles contained the most elevated concentrations of metal(loid)s in their sulfide inclusions and metal(loid)-rich rims. The mobility of metal(loid)s in the identified mineral phases found within particulates mirrored the transport observed in the soil column; Zn>Cu>Ni>Pb. Once mobilized, these elements are subject to transport before being attenuated by secondary phases. Micro-coatings were found to be composed of hematite, schwertmannite, ferrihydrite, silica, and jarosite group minerals. Coatings are distinguished on the basis of their atomic Si:Fe ratios: FeOx coatings have Si:Fe <1, Si–FeOx coatings have Si:Fe between 1-10, and SiOx coatings iv have Si:Fe>10. Iron-rich coatings (FeOx) and silica-rich coatings (SiOx) have lower trace-metal concentrations than Fe-SiOx coatings. Micrometer-thick coatings are predominantly composed of hematite, schwertmannite, ferrihydrite and (amorphous) silica and contain elevated metal(loid) concentrations in the form of metal(loid)-rich phosphate minerals (mainly minerals of the jarosite group). A general model is developed that describes the formation of mineral coatings in acid soils and their important role in the uptake and retention of metal(loids). Here, micrometer-thick Fe-silica coatings form through adsorption, co-precipitation and dehydration processes involving amorphous silica and iron hydroxides. Metal(loid)-bearing phases nucleate within a gel-type matrix and are subsequently preserved during dehydration and solidification. Aluminum-rich surfaces form on mineral grains once the pH has been raised sufficiently high (pH~5-6) so as to lead to the complete removal of sulfate-bearing phases. The implications of this model are widespread in terms of the attenuation of metal(loid)s in acid soils and their retention or subsequent remobilization in recovered soils with near neutral pH.

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Thesis--University of Missouri, School of Mines and Metallurgy, 1877. / The entire thesis text is included in file. Holograph [Handwritten and illustrated in entirety by author]. Title from title screen of thesis/dissertation PDF file (viewed September 5, 2008)

Thesis (M.S.)--Rochester Institute of Technology, 1987. / Typescript. Includes bibliographical references (leaves 79-81).

Thesis (Ed.D.)--Teachers College, Columbia University, 1972. / Typescript; issued also on microfilm. Sponsor: Douglas R. McManis. Dissertation Committee: Harvey A. Levenstein. Includes bibliographical references.

M.Tech. (Chemical Engineering) / Please refer to full text to view abstract

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M. Ing. / The purpose of this study is to investigate the use of computer vision techniques to measure the electrode slip. The study investigates a potential location for camera placement in the furnace housing, as well as the use of computer vision algorithms that could be used to solve the problem. A slip measurement algorithm is then designed, implemented and tested. The implemented slip measurement algorithm is based on the manual slip measurement technique, by measuring relative electrode and slip arm displacement between the electrode and the slip arm. The algorithm uses SURF invariant features to extract the electrode features and slip arm features in one frame, and match these features to the next frame SURF. Scene calibration is then used to relate the pixel slip measurement to a metric distance measurement. The experimental results proved that there is scope for applying computer vision techniques to address the slip measurement problem, using a single HD camera. However, there is room for improvement and the recommendations and future work are also discussed.

Titania slag is a feedstock to the pigment industry, which in turn provides titania pigment to producers of everyday products like paper, cosmetics and toothpaste. Titania slag is the primary product of the pyrometallurgical process of ilmenite smelting – the other products being iron and CO gas. Titania slag is typically tapped from the furnace into blocks of approximately 20 tons. After cooling these blocks are crushed and milled to size fractions suitable for the processes of the pigment producers. These processes are broadly grouped into two types of technology: the chloride route (during which titania slag is reacted with chlorine and subsequently re oxidised thereby removing the impurities) and the sulphate route (in this process the titania slag is purified after dissolving the slag in sulphuric acid). Due to the nature of these two processes, several specifications are imposed on the quality of the titania slags. The fluidised-bed technology used in the chloride process limits the size distribution of the slag to between 106 µm and 850 µm. Ilmenite smelting industries consequently crush and mill the titania slag to below 850 µm. The fraction below 106 µm is then sold to the sulphate market. Since the coarser chloride grade product is the more valuable product, slag producers continuously strive to improve the ratio between the coarser and finer fractions. This study reports on parameters which influence the particle size distribution of titania slags and therefore the split between the coarser (more valuable) and finer (less valuable) products. Pilot-scale slag ingots were used to identify chemical and process variables which influence the yield of coarser material. The microstructure of as-cast and milled slag was examined, and indicated a role of silicate phases in the crushing behaviour. Industrial-scale slag ingots were used to test whether the roles of tapping rate and water cooling (as identified from the pilot-scale ingots) also applied under industrial conditions. A numerical method was applied to estimate the thermal conductivity of the solidified slag (from measurements on pilot-scale ingots), and to predict the cooling and solidification behaviour of industrial-scale ingots. The study concludes that the chemical composition and cooling conditions of the slag block play central roles in the final particle size distribution of the slag. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2009. / Materials Science and Metallurgical Engineering / unrestricted

No description available.