It is generally recognized that the recovery of particles from a flotation pulp is controlled by (i) the flotation rate constant and (ii) the residence time distribution of the particles. In the present work, theoretical and experimental analyses have been carried out to develop methods for predicting these parameters from first principles considerations. In order to predict the flotation rate constant, a bubble-particle interaction model has been developed using a dynamic force balance to determine the trajectory of a particle as it approaches a rising air bubble. The trajectory has been used to determine the probability of bubble-particle attachment, from which the flotation rate constant can be readily obtained. The model is unique in that it simultaneously considers the effects of hydrodynamic and surface forces on the interaction between bubbles and particles. Model predictions have been shown to be in good agreement with results from bubble-particle attachment experiments for narrowly-sized coal and silica samples. In the present work, the residence time distribution of particles in column flotation has been examined by conducting experimental tracer tests. These tests have been performed with two tracer materials to characterize mixing for both the liquid and the solids in a single system. The measured residence time distributions have shown that the assumption of equating liquid and solids residence time distributions is inappropriate, except for very small and low density particles. At larger sizes and higher densities, the correction formula advocated by Dobby and Finch (1985) has been shown to adequately predict the solids residence time. / Master of Science

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This study was aimed at recovering lithium from china clay waste using a combination of froth flotation, magnetic separation, roasting and leaching. The china clay waste produced by Goonvean Ltd contains about 0.84% Li2O and 0.36% Rb2O, present in some of the mica minerals. Among the mica minerals, zinnwaldite is the major source of lithium with smaller amounts being contributed by muscovite. The results of the flotation tests showed that the dodecylamine collector dosage had a greater effect on the recovery and grade of mica minerals to concentrate than pH over the range tested. It was found that a mica concentrate containing 1.45% Li2O, 0.55% Rb2O and 4.47% Fe2O3 could be produced at a recovery of 98.6%, 85.2% and 92.8% respectively. Mineralogical analysis of the flotation products showed that the concentrate consisted mainly of muscovite, zinnwaldite and kaolinite with minor amounts of K-feldspar and quartz. The tailing consisted of mainly quartz, K-feldspar and kaolinite with minor amounts of apatite, topaz, zinnwaldite and muscovite. Further upgrading of the concentrate was found to be possible using a wet high intensity magnetic separator producing a magnetic fraction containing 2.07% Li2O, 0.74% Rb2O and 7.42% Fe2O3 with a recovery of 73%, 67% and 77% respectively. A mineralogical analysis of the separation products showed that the magnetic fraction consisted of predominantly zinnwaldite with muscovite as the main contaminant. The non-magnetic fraction consisted of muscovite and kaolinite as the main minerals while zinnwaldite, K-feldspar and quartz were subordinate. Electron-microprobe analysis on individual mica grains have shown that zinnwaldite and muscovite contain on average a calculated Li2O content of 3.88% and 0.13% respectively. Lithium extraction from the concentrate is only possible after the lithium has been converted into a water-soluble compound. Thus, in order to convert the lithium in concentrate into a water-soluble compound, the gypsum and limestone lithium extraction methods together with the new method of using sodium sulphate were investigated. The process involved roasting a predetermined amount of lithium-mica concentrate with either gypsum, limestone or sodium sulphate at various temperatures and subsequently leaching the pulverised materials in water at 85oC. A lithium extraction efficiency of about 84% was obtained using gypsum at 1050oC while rubidium extraction was very low at 14%. It was found possible to extract about 97% Li and 16% Rb if the concentrate was roasted with sodium sulphate at 850oC. Processing the concentrate with limestone resulted in very low lithium extraction. Iron co-extraction was low in all cases. The XRD analysis of the gypsum and sodium sulphate roast-products showed that the water soluble lithium species were KLiSO4 and Li2KNa(SO4)2 respectively. Preliminary tests on the leach solution obtained by using sodium sulphate as an additive have shown that a Li2O3 product with a purity of > 90% could be produced by precipitation with sodium carbonate although more work is required to reach the industrial target of > 99%. The lithium carbonate obtained with Li2CO3 content of about 90% is still suitable for use in the glass and ceramic industries, and as feedstock for the production of high-purity lithium compounds. An economic evaluation of the proposed lithium carbonate production plant has indicated an annual rate of return on the investment before tax of 7.2%.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1990. / The static Rand gold price has put pressure on the South African gold mines to improve efficiency. Superior metallurgical performance and lower costs attributed to column flotation prompted the construction of a pilot plant (238 millimetres by 10 metres) at ERGO, an Anglo American tailings retreatment plant [Abbreviated Abstract. Open document to view full version] / MT2017

Quartz particles of various discrete particle size ranges have been methylated to varying known mounts using trimethylchlorosilane and their flotation behaviour has been assessed in a modification of the Hallimond tube. For each particle size there is a definite degree of. surface coverage below which the particles do not float. A 'flotation domain' is identified which shorvs that both coarse (-100pm) and fine (-10pm) particles require a greater degree of surface coverage to initiate flotation than do intermediate (-40pm) particles. Water contact angles have been measured on quartz plates and powders which have been methylated (under the same conditions) with trimethylchlorosilane. Both advancing and receding water contact angles measured on quartz plates as a function of degree of surface methylationare in good agreement with the angles predicted by the Cassie equation. Advancing water contact angles measured on quartz particles as a function of degree of surface methylation are also in good agreement with angles predicted by the Cassie equation up to surface coverages of'about 70%. The angles measured at higher surface coverages are less than those anticipated by the Cassie equation. The flotation behaviour of the particles has been compared with that predicted by existing flotation theories. It has been shown that coarse particle behaviour is predicted by the kinetic theory of flotation proposed by Schulze. Fine particle behaviour, however, only qualitatively agrees with Scheludko's theory of fine particle behaviour. Calculated induction times, in conjunction with observed flotation behaviour, indicate that the bubble-particle attachment process is most efficient for particles of about 38pm in diameter ander the set experimental conditions used in this study. Flotation rate trials were performed for three particle size ranges and rate constants were evaluated for the various degrees of surface coverage. It was found that the dependence of rate constant on particle size is essentially linear.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 97 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 82-87).

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

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