Chuquicamata mine mineralogy has been studied performing both X-Ray Diffraction (XRD) and X-RayFluorescence (XRF) to determine whether there is any influence in the thickener operations. Thetargeted minerals were the clay group because of their detrimental effect on mining operations asmodify the rheology of the suspensions. The operation stages most affected by the presence of the clayminerals are gravity separation, milling, conveyor belts, flotation and specially thickener operations. Inorder to cope with Chuquicamata production, the plant is constantly fed from a neighboring ore calledRadomiro Tomic (RT) ore, a secondary sulfide enrichment. At Chuquicamata, the thickener operatorfeedback has been pointed out that every time the concentrator plant is fed in high ratio with this so-called RT ore the mineral processing is hindered. For this reason, RT ore samples from a criticaloperation day were sent to Sweden for mineralogical analysis. In addition, flotation tailings from thethree Chuquicamata concentrator plants were also sent aimed to perform thickener pilot tests. In thismanner, it was seen if it could be possible to achieve new operational strategies in Chuquicamatathickener operations given the current Chuquicamata mineralogy and physical conditions in the flotationtailings.From the XRD analysis, the following clay minerals were identified in order of abundance: Illite>>Kaolinite>Smectite Thus, illite reached up to 23.3vol% being the highest clay amount, followed by lower case kaolinite up to2.5% and up to 1% of smectite values correspond for the RT sample. However, the clay content in theflotation tailings samples were less than expected. Also, clay Crystallinity was also assessed for its abilityto interfere negatively with the pulp rheology, and the results showed that there is a strong link amongpoor crystallized smectite clay with the semi-autogenous mill compare to those samples where themilling was performed in the traditional steel media. Along with the three clay minerals found, quartz,potassic feldspar, and plagioclase were also identified, accounting for up to 76% of the representativesample. The silicate minerals are thought to be problematic in Chuquicamata thickener operations givenits high amount, especially in <2 µm size.For the thickener tests, three types of polyacrylamide were used plus the current Chuquicamataflocculant. Prior to the sedimentation batch test, the rheology of the flocculants was measured in arange of 0.02%w/w to 1%. It was found that flocculant concentrations between 0.02 to 0.05%w/w themost suitable in terms of avoiding suspension rheology increase. After establishing suitable flocculantconcentrations solutions, these were used in the thickener pilot tests at conditions similar to thoseperformed in Chuquicamata thickener operations. Two criteria were used to analyze the bestsedimentation conditions: Initial settling rate (ISR); and Turbidimeter. At pH in a range of 11-12 and 15%solid, bridging flocculation probed to be the most suitable conditions for Chuquicamata thickeneroperations. Moreover, a polyacrylamide blend was tested aiming to achieve high sedimentationperformances. The flocculant blend reached both the highest initial sedimentations rate up to 48m/hand turbidity values below 20NTU at addition rate 5g/t and 7g/t. On the other hand, Chuquicamatacurrent flocculant only reached the highest values of 36m/h and turbidity of 40NTU at an addition rateof 5g/t. In this way, the current work established that conditions at Chuquicamata thickener operation 4can be improved by understanding the absorption process among particle-polymer and mineralogy ofthe mine.Hence, the implication of this work to Chuquicamata mine is a better knowledge of its mineralogyespecially concerned with it is believed that clay minerals are not the only mineralogical factors thatcould be hindering thickener operations in Chuquicamata. Other factors that also could be problematicare: high content of silicates; clay crystallinity, particle size and mixed clay. In addition, the improvementin the thickener sedimentation operations will bring better use of the water by increasing therecirculation towards the concentrator area in a friendly way with the environment and communitiesthat also demand water in the arid region of the Atacama Desert.

The Lowry Method of Protein Assay is an effective alternative to point count or culture methods to determine the relative abundance of microorganisms in geologic samples. Results of this project show that the outcome of the Lowry assay is not affected by the constituents of a sandstone reservoir and that a relationship exists between microbes and clay minerals. Core samples were taken from the Carter sandstone at the North Blowhorn Creek Unit in Lamar County, Alabama. Samples were chosen based on mineralogic heterogeneity. The samples were placed in an anaerobic glove bag and given nutrients to induce the growth of in situ microorganisms. Samples were then assayed. Results of the protein assays show that the Lowry Method of Protein Assay is effective in determining protein concentrations in geologic samples with varying mineralogies. The assays also indicated that samples with abundant clay minerals show the greatest amount of microbial growth.

No description available.

No description available.

<p>Bentonite clays and Fe-reducing bacteria have been independently identified as important geochemical agents possessing the ability to influence metal(loid) mobility in aqueous environments. In the context of metal(loid) immobilization, however, the interactions occurring between Fe-reducing bacteria and bentonite clays remain largely undescribed. This thesis examines the immobilization of Cu²⁺, Cd²⁺, and As⁵⁺ from aqueous solution by natural bentonite clays, and compares sorption to sterile bentonite clays with sorption in the presence of Fe-reducing bacteria. The research questions under investigation in this thesis are: 1) What are the influences of potentially metal-tolerant Fe-reducing bacteria on metal(loid) uptake by bentonite clay sorbents of varying smectite content and on the stability of bentonite clay-sorbed metal(loid)s?; and 2) Are there differences in the influence of Fe-reducing bacteria on Cd²⁺ and Cu²⁺ sorption to bentonite clays when As⁵⁺, a reducible, metabolically-available metalloid, is present in solution?</p> <p>While the influence of bacterial augmentation on Cu²⁺ sorption was negligible in these experiments, Cd²⁺ sorption was enhanced in the presence of Fe-reducing bacteria, and most profoundly, As displayed time-dependent desorption during the experimental timeframe in the presence of Fe-reducing bacteria. These results highlight the existence of potential limitations to the use of bentonite clay sorbents for metal(loid)-contaminated wastewater reclamation, identifying the microbially-vulnerable nature of metal(loid) sorption reactions. Abundant facets concerning clay-bacterial-metal(loid) interactions exist which require further characterization and experimentation to generate deeper understanding of the potential utility of, as well as limitations to, the use of clay mineral-based sorbents for the sequestration of toxic metal(loid)s from aqueous solution.</p> / Master of Science (MSc)

X-ray photoelectron spectroscopy (XPS) has been used to study the bonding of adsorbed metal cations to clay minerals. Binding energy differences of the adsorbed metal cations can be related to changes in the electron density or charge on the atom of interest. Adsorption experiments were carried out in aqueous solution at controlled pH's of 2, 4, 6, 8, and 10 for Ba²⁺, Co²⁺, Cr³⁺, adsroption on the clays kaolinite and ripidolite. Solution processes were monitored by measuring the solution concentrations of dissolved silica and the metal ions Fe³⁺, Mg²⁺, K⁺, Al³⁺, Cr³⁺, and Co²⁺ at the beginning and the end of the experiment. Atomic absorption spectroscopy was used to determine the metal ion concentrations and dissolved silica was determined spectrophotometrically as a molybdate complex. Examination of the adsorbed cation species on the clay surface by XPS indicated that the clays behaved as nucleation centers at or near the pH of precipitation of the cations. Further it was found that high spin Co²⁺ in solution became low spin Co²⁺ or formed a highly covalent bond when adsorbed on kaolinite at pH's 4, 6, and 7 and on ripidolite at pH 2 and 4. Finally, if the clay has a negatively charged surface which donates some of its charge to the positive cation, then the barium XPS data indicated that ripidolite has a greater negative surface charge than kaolinite. This idea was supported by calculations of the surface charge density from CEC and surface area data. / Master of Science

M.S.

A heavy mineral mining company (RGC Inc.) faces challenging mining and reclamation practices for its proposed operation in the Upper Coastal Plain of Virginia due to the high clay content of the deposit. The original intent of this study was to identify the mineralogy present in the proposed mining area and to determine similarities and differences among sampled pedons. Twenty-eight typical pedons were sampled throughout the profile and these samples were prepared for mineralogical analysis. The pedon comparisons were performed to determine differences due to location and geomorphic surface, and due to drainage. Statistical results were then used to relate mineralogy, together with data on pH, CEC, and particle size distribution to pedogenesis in the area. Coastal Plain soils had sandier subsurface horizons than Piedmont soils. The above-scarp soils (> 75 meters) were the most mature Coastal Plain soils and approached the kaolinitic Piedmont soils reasonably well in mineralogy and particle size distribution. Coastal Plain soils were dominated by kaolinite, HIV, and gibbsite. Wet soils were less mature in mineralogy due to the lack of weathering activity. All but the Piedmont soils contained a surface mica enrichment, believed to be eolian additions. Well-drained and moderately well-drained soils had a more mature mineralogy than somewhat poorly and poorly drained soils. Kaolinite contents increased with depth whereas HIV contents tended to be concentrated in the A horizon. Despite the large clay content, the low charge nature of all soils should limit problems associated with clay dispersion practices during the mining. The low charge nature of the soils is reinforced by low ECEC data. / Master of Science

M.S.

Marine clay deposits are characterized by very soft to soft consistencies (undrained strength 1-50 kPa), presence of saline pore solution and low-swelling clays. Besides, loss of metastable structure on disturbance, poor undrained strengths of soft clays is contributed by high water contents. Presence of saline pore solution and low-swelling clays (illite, chlorite, kaolinite) play an important role in developing metastable structure of soil sediments deposited in marine environment. The pore solution salinity regulates the “physico-chemical (A - R) stress” that in turn has significant bearing on development of the metastable structure. Metastable structure refers to edge-face, edge-edge associations in card-house arrangement of platy/elongate particles that develop during deposition. Loss of metastable structure of soft marine clays upon disturbance leads to excessive settlements and slope failures. Besides A - R forces, metastable structure of marine clays is contributed by cementation bonds, thixotropic hardening, ion leaching, formation or addition of dispersing agents and chemical weathering. Secondary compression also causes bonding of micro-structural units that increase stiffness and strength of the metastable structure. Review of literature brings out that majority of studies examining the role of physico-chemical factors on the engineering behavior of marine clays have focused on illite rich sediments. However, non-swelling clay, namely, kaolinite is also encountered in marine deposits (example, Pusan clay, Singapore clay, Sarapui soft clays). Kaolinites differ from illites in being 1:1 mineral (unit layer comprises of 1 silica sheet bonded to 1 gibbsite sheet) and having strong hydrogen bonding between unit layers. Consequently, kaolinite particles are thick (0.3 to 3 ìm thickness) with low surface area (10 to 20 m2/g). Also the hydrogen bonding between unit layers do not allow them to separate on hydration. Combination of very low isomorphous substitution (Al for Si 1 in 400), low cation exchange capacity (3 meq/100g), and low surface area, lead to negligible development of diffuse double layer repulsion forces between kaolinite particles. Strong positive edge (developed on broken bonds at particle edges from adsorption of hydrogen ions) negative face attraction between kaolinite particles, encourages flocculation of particles at range of water contents. It was therefore considered of interest to examine the engineering response of kaolinites to changes in pore solution salinity from leaching effects. The focus of the thesis is hence to gain better understanding of physico-chemical (pore solution salinity, A - R forces) and mechanical (secondary compression, loss of overburden) factors towards development of metastable structure of kaolinite clays deposited in synthetic seawater environments in the context of their compressibility and undrained strength characteristics. Laboratory experiments are performed with kaolinites that are slurry consolidated in conventional consolidometers in saline and synthetic seawater solutions. The metastable structure developed by consolidated specimens is relevant to alluvial marine sediments that contain kaolinite (example, Pusan clay, Singapore clay, Sarapui soft clays). The structure of the thesis is as follows: Chapter 1 gives an introduction to the thesis. Chapter 2 provides a detailed review of literature on the role of chemical factors (pore solution composition, A - R forces, osmotic suction) and mechanical processes (secondary compression and overconsolidation) in developing metastable structure of kaolinite specimens subjected to slurry consolidation and the consequent influence of metastable structure on compression, undrained strength and sensitivity characteristics of clay specimens. The Chapter also defines the scope and objectives of the study. Chapter 3 details the experimental program undertaken to bring out the role of chemical factors and mechanical processes in influencing the 1-dimensional compression and undrained strength characteristics of slurry consolidated kaolinites prepared in saline medium. Chapter 4 delineates the role of chloride salt solutions (sodium, magnesium and calcium) and synthetic seawater solution in contributing to the metastable structure developed by slurry consolidated kaolinites at various vertical effective stress (óv’) and the consequent influence of metastable structure on 1-dimensional compression, undrained strength and sensitivity characteristics of the clay. Chapter 5 examines influence of secondary compression on metastable structure developed by kaolinites that were slurry consolidated in 24.53 g/L sodium chloride and synthetic seawater solutions and the consequence of the developed metastable structure on undrained strength and sensitivity. The chapter also examines the consequences of secondary compression experienced by soft overconsolidated kaolinites on their undrained strength and sensitivity characteristics. Chapter 6 examines the relative influence of differential osmotic stress and electrochemical stress on the consolidation behaviour of kaolinite specimens that are slurry consolidated in sodium chloride solutions. The osmotic efficiencies (á) of kaolinite were obtained using the Fritz-Marine Membrane Model. Chapter 7 summarizes the major conclusions of the thesis.