A study has been conducted on the loss of phosphate ions and excessive oleic acid consumption encountered in the selective flotation of dolomite from apatite. An attempt has been made to evaluate the mechanism by which orthophosphate ions depress apatite flotation. Replacement of SO₄⁻² ions on gypsum by HFO₄⁻² ions is found to occur rapidly in solution. The presence of CaHPO₄⁻² 2H₂O on gypsum surfaces is shown using infrared reflectance spectroscopy. CaHPO₄⁻²H₂O is isomorphous with gypsum and has identical lattice parameters. Experiments show that the addition of sulfate ion to the system suppresses the reaction of orthophosphate ions with gypsum by the common ion effect. The proposed reversible reaction in the system is: CaSO₄∙2H₂O + HPO₄⁻²↼⇁ CaHPO₄ ∙2H₂O + SO₄⁻² A proposed mechanism by which orthophosphate ions selectively depress apatite flotation is shown to fit all experimental observations. Orthophosphate ions are known to be potential determining for calcite, dolomite and apatite. It is observed that in the presence of orthophosphate ions calcite and dolomite recovery is higher at pH 6.0 than at pH 8.5. Apatite and gypsum exhibit opposite behavior. It is proposed that the adsorption of strongly hydrogen bonding H₃PO⁴, H₂PO₄⁻² and HPO₄⁻² in the electrical double layer results in collector species being slow to penetrate and adsorb on the minerals. Acid attack on calcite and dolomite results in disruption of the hydrogen bonded layer and allows rapid collector adsorption. Two equally important effects of adsorbed phosphates are to decrease collector adsorption due to the large negative zeta potential generated and to impede fruitful particle-bubble interactions. Brittle froths encountered in flotation at pH 6.0 are related to condensation of surface films formed by oleic acid -sodium oleate complexes. The froth stabilizing effects of hydrophobic dolomite particles is noted. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Dolomite is a naturally abundant carbonate mineral possessing important links to economic mineral deposits, petroleum reservoirs and carbonate geochemistry, yet the geochemical conditions by which it forms remain a mystery. Abundant attempts to synthesis dolomite at temperatures below 100 °C have proved unsuccessful, forming the paradox known as the “dolomite problem”. This study demonstrates a newly developed method capable of synthesizing dolomite at temperatures as low as 60 °C. This method, involving the addition of solid phase Na2CO3 to Ca-Mg2+ cation solutions, seemingly overcomes the kinetic barriers known to inhibit dolomite formation by rapid replacement of Na2CO3. Furthermore, although previously proposed to encourage dolomite formation, the role of urea facilitating dolomite synthesis is confirmed. The addition of varying urea concentrations is found to improve the stoichiometry and cation ordering of dolomite between 50 - 80 °C, and notably, dolomite synthesis at 50 °C requires a 252 mmolal urea concentration in solution. These findings provide a foundational tool which will greatly benefit future research into answering the “dolomite problem”. Due to the inability to synthesize dolomite at low temperatures, understanding of isotope fractionation between dolomite and water has been poorly constrained. Therefore, calibrations of the dolomite-water oxygen isotope paleothermometer are scarce, relying on data from either the extrapolation of high temperature (> 100 °C) dolomite studies or protodolomite synthesized at more ambient temperatures. Provided here is a new dolomite-water oxygen isotope fractionation curve, constructed from dolomite synthesized between 50 - 80 °C. Although certain dolomite synthesized by the method developed in this study display apparent isotopic heterogeneity, a correction is applied to more closely resemble isotopic equilibrium fractionation between dolomite and water. Initial investigations into isotope effects associated with dolomite synthesis by the method developed here are promising and should strengthen the role of dolomite in carbonate geochemistry research. / Thesis / Master of Science (MSc)

Development on dolomite poses a risk due to the possible formation of instability features such as sinkholes. Most of these features are however man-induced, and the risk associated with development on dolomitic areas can be mitigated through correct management. Therefore, since the Tlokwe City Council is accountable for safe development within its jurisdiction, a Dolomite Risk Management Strategy (DRMS) should be put in place. There are several factors that contribute to the risk for development on dolomite. These factors can be catagorised into two groups that should be considered during the hazard identification process, namely physical factors that consists of geology, geohydrology and geotechnical, and anthropogenic factors that consists of existing infrastructure and development, land use planning, as well as social structure and awareness. These factors are assessed by means of a risk assessment in order to obtain a disaster risk score for different areas within the study area. Based on this score, priority focus areas can be identified, mainly for critically important further research before any development can be allowed or mitigation measures implemented. Once these research activities are completed, a DRMS can be compiled based on the guidelines set by SANS 1936, which will promote the safety of people and property when further development on dolomite takes place. Urgent and interim mitigation measures are proposed to manage the risk during further research activities. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

Development on dolomite poses a risk due to the possible formation of instability features such as sinkholes. Most of these features are however man-induced, and the risk associated with development on dolomitic areas can be mitigated through correct management. Therefore, since the Tlokwe City Council is accountable for safe development within its jurisdiction, a Dolomite Risk Management Strategy (DRMS) should be put in place. There are several factors that contribute to the risk for development on dolomite. These factors can be catagorised into two groups that should be considered during the hazard identification process, namely physical factors that consists of geology, geohydrology and geotechnical, and anthropogenic factors that consists of existing infrastructure and development, land use planning, as well as social structure and awareness. These factors are assessed by means of a risk assessment in order to obtain a disaster risk score for different areas within the study area. Based on this score, priority focus areas can be identified, mainly for critically important further research before any development can be allowed or mitigation measures implemented. Once these research activities are completed, a DRMS can be compiled based on the guidelines set by SANS 1936, which will promote the safety of people and property when further development on dolomite takes place. Urgent and interim mitigation measures are proposed to manage the risk during further research activities. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

No description available.

Thesis (M.S.)--Baylor University, 2005. / Includes bibliographical references (p. 142-147).

Thesis (M.S.)--University of South Florida, 1993. / Includes bibliographical references (leaves 87-93).

Thesis (M.S.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaf 83). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 110-116).

Thesis (M.Sc.) -- Memorial University of Newfoundland, 1985. / [10] fold. leaves in pocket. Typescript. Bibliography : leaves 257-276. Also available online.