Surface properties of New York talc as a function of pH, polymer adsorption and electrolyte concentration
Doctoral Thesis
2007
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University of Cape Town
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Abstract
Talc is a common siliceous gangue mineral found in ore bodies beneficiated by flotation. Talc is a layered anisotropic mineral, with a mineral structure comprising of basal planes and edges. The basal planes of talc are considered completely neutral, while the edges of talc are thought to undergo a change from positive to negative at a highly acidic pH. Talc is highly floatable, requiring polymeric depressants to be added to flotation pulps in order to prevent it from entering the concentrate and reducing its grade. Various polymers such as non-ionic guar gums and anionic Carboxymethyl cellulose (CMC) depressants are employed for this purpose. However, the industrial use of these reagents is still inefficient. One of the factors affecting the performance of these polymers as depressants is the water quality of the flotation medium, specifically the concentration and type of electrolyte present. The objective of this thesis was to investigate of the surface properties and structure talc, and its effect on the adsorption mechanisms of different types of polymeric depressants in the presence of varying types of metal cations in solution in the context of mineral flotation. The surface potential of talc was investigated using rheological, titration and electron microprobe analyses. It was found that the rheological behaviour of talc is inconsistent with the premise that the talc basal planes carry no electrical charge. Furthermore, potentiometric titration measurements showed that the point of zero charge of talc does not correspond to the electrophoretic isoelectric point of talc. The discrepancy was attributed to the unsuitability of zeta potential measurements for evaluation of anisotropic plate-like minerals.
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Includes bibliographical references (p. 35-39).
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Burdukova, E. 2007. Surface properties of New York talc as a function of pH, polymer adsorption and electrolyte concentration. University of Cape Town.