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The use of stabilized coal combustion solid residues for artificial reef construction in Hong Kong an examination of environmental impacts /Leung, Kim-fung. January 2000 (has links)
Thesis (Ph.D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 417-523) Also available in print.
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Recovery of silver from lead/zinc flotation tailings by thiosulfate leaching /Chieng, Pau. January 2005 (has links) (PDF)
Thesis (M.Phil.) - University of Queensland, 2006. / Includes bibliography.
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Evidence of leach field seepage determined by microbial and water quality analysis /Soltren, Elisa A. January 1900 (has links)
Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 20-22). Also available via Humboldt Digital Scholar.
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Limiting copper loss from treated wood in or near aquatic environments /Mitsuhashi Gonzalez, June M. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.
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Application of microwaves in leachingMukendi, David Ngalula 14 May 2014 (has links)
M.Tech. (Extraction Metallurgy) / Please refer to full text to view abstract
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Modeling chalcopyrite leaching kineticsTrejo-Gallardo, Jaime 05 1900 (has links)
Chalcopyrite (CuFeS2) is the most abundant of the copper sulfides and also one of the
most refractory for leaching. Several processing routes have been proposed to
overcome drawbacks associated with environmental problems related to copper
extraction from this mineral. Atmospheric leaching in acidic ferric sulfate is regarded as
being particularly attractive over other hydrometallurgical systems. However, the
challenge has been to overcome the problem of slow extraction rates due to passivity
encountered at high solution potentials in this system. This highlights the need to
investigate better operating conditions to optimize copper extraction and prevent the
problem of passivation, and to develop suitable modeling tools to assess and diagnose
leaching performance.
In this work, a dissolution rate expression for chalcopyrite leaching in acidic ferric sulfate
media is proposed accounting for effects in the active and passive regions under
potentials from 415 to 550 mV (Ag/AgCl). A model of chemical speciation in the bulk
solution elucidates the idea of passivation caused by precipitation of ferric species and
their consequent adsorption onto the chalcopyrite surface. Electrochemical studies on
massive samples of chalcopyrite involving characterization and modeling of the anodic
and cathodic half-cell reactions of chalcopyrite leaching together with mixed potential
considerations lead to the development of the mathematical expression for dissolution rate.
The mathematical model was calibrated with electrochemical parameters and results
are in good agreement with real leaching data from batch tests for solution potential
regions where passivity is not observed. On the other hand, the passive region was
modeled by means of adjusting parameters related to adsorption energies of the
passivating species. Results of the model for this region deviate from real data as
potential becomes higher probably due to diffusion resistance through a layer
composed of ferric complexes. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
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The biodegradation of nepheline by Aspergillus nigerKing, Andrew January 1985 (has links)
No description available.
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Dissolution of ilemite in sulphuric acid under reducing conditions with controlled abrasionBhan, Autar Krishen January 1965 (has links)
The kinetics of dissolution of ilmenite, containing haematite, in aqueous solutions of sulphuric acid have been studied. Iron was found to leach from the mineral complex at a faster rate than titanium. The rates of solution of both iron and titanium increased, up to certain limiting values, upon abrading the mineral during leaching and were found to be related to the hydrogen ion activity of the leaching solution by a first order dependency. The results have been interpreted in terms of preferential and possibly diffusion-controlled leaching of the haematite with ilmenite being removed both by slow leaching and tearing out from the specimen surface. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
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Microbiological leaching of a zinc sulfide concentrateTorma, Arpad Emil January 1970 (has links)
The applicability of microbiological oxidation for the recovery of zinc from a high-grade zinc sulfide concentrate has been investigated using a pure strain of Thiobacillus ferrooxidans. Factors affecting the bacterial activity and consequently the rate and extent of zinc extraction were studied. These factors were: temperature, pH, nutrient and substrate concentrations, solid particle size and surface area. The effect of carbon dioxide concentration in the air supplied to the oxidation was also studied. Larger scale experiments were carried out to simulate more closely possible industrial conditions.
The optimum temperature was found to be 35°C, the optimum pH 2.3. Nutrient levels of 89 mg phosphate P/l and 636 mg ammonia N/1 were sufficient to avoid rate limitation and provide for maximum extraction,
respectively. Increasing the particle surface area, the pulp density, or the total surface per unit volume of leach liquor increased the rate of zinc extraction up to a point beyond which further increases were not effective. Increasing the carbon dioxide content of the air had a similar effect.
The larger scale experiments gave similar extraction rates to those observed in shake flasks but the extent of zinc extraction was significantly higher. The final concentration of zinc in leach solutions reached levels currently-employed in commercial electrowinning procedures. A form of the generalized logistic equation was shown to be capable of representing the complete extraction curve under a variety of experimental
conditions. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
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Oxygen transfer in a stirred tankLiu, Ming-Shen January 1969 (has links)
Microbiological leaching of sulfide minerals in fermenters is believed to have commercial potential. The oxygen transfer rate has been assumed to be one of the most important factors affecting the leach rate.
The mass-transfer rate at various solution pH's was studied by using an unsteady gassing out process. The sulfite-oxidation process was also studied in an attempt to explain the absorption mechanism.
A 7.5 inch I.D. methyl methacrylate tank with 4 baffles and a 4-inch diameter paddle type impeller were used. The impeller was driven by a motor mounted on a dynamometer which allowed measurement of the power used in agitation. All the experiments were carried out under highly turbulent
conditions and covered the liquid temperature range 25°C to 40°C.
The results showed that pH had no effect on mass-transfer coefficient.
The values of K[subscript L]a increased as temperature increased. The relationship
between K[subscript L]a, power input and superficial gas velocity was found to be of the form:
K[subscript L]a = c(HP/V)[superscript x] (V[subscript s])[superscript y]
A comparison of the K[subscript L]a observed in an unsteady gassing out process
and that in a sulfite-oxidation process showed that the interfacial
area/unit volume of liquid, a, is directly proportional to (V[subscript s])º‧⁵º which coincides with Calderbank's result. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
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