The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
J.w.a. Kondoro - One of the best experts on this subject based on the ideXlab platform.
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Mössbauer study of vacancies in natural Pyrrhotite
Journal of Alloys and Compounds, 1999Co-Authors: J.w.a. KondoroAbstract:Abstract Mossbauer spectra corresponding to natural hexagonal and monoclinic Pyrrhotite from Lake Victoria Goldfield in Tanzania (East Africa) were recorded between room temperature and 4.2 K. There is good agreement between experiment and the literature. The Mossbauer spectra of samples of monoclinic Pyrrhotite are relatively narrow, but those corresponding to hexagonal Pyrrhotite are very broad and asymmetric due to the vacancy distribution. The intensity ratios of the inequivalent Fe sites in monoclinic Pyrrhotite are in the ratio of about 2:1:2:2 in the order of increasing hyperfine field, but those corresponding to hexagonal Pyrrhotite do not have any particular pattern due to varying at.% Fe in the analysed material which is, in turn, related to the vacancy distribution.
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Moessbauer study of natural Pyrrhotites
Applied Radiation and Isotopes, 1997Co-Authors: J.w.a. Kondoro, C.a. KiwangaAbstract:Abstract The natural Pyrrhotites from the Lake Victoria Goldfield in Tanzania have been studied by Moessbauer spectroscopy and the X-ray diffraction technique. Of the eight iron sulphide samples studied, four were found to be mostly monoclinic Pyrrhotite and the other four were found to be mostly hexagonal or intermediate Pyrrhotite. The Moessbauer spectra of both monoclinic and hexagonal Pyrrhotites were best fitted with four sextets. A discussion on the determination of the Fe-sites in the Pyrrhotites is presented.
Dee Bradshaw - One of the best experts on this subject based on the ideXlab platform.
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The mineralogy and crystallography of Pyrrhotite from selected nickel and PGE ore deposits
Economic Geology, 2010Co-Authors: Megan Becker, Johan P. R. De Villiers, Dee BradshawAbstract:The nonstoichiometric sulfide Pyrrhotite (Fe S) common to many ore deposits occurs in a variety of crystallographic forms and compositions and occasionally is also intergrown with stoichiometric troilite (FeS). In this study, the mineralogy of Pyrrhotite derived from several different nickel and PGE ore deposits in South Africa, Botswana, and Canada was examined in detail in terms of Pyrrhotite association, crystallography, and mineral chemistry. Pyrrhotite samples were subdivided into two-phase 6C Fe11S12 Pyrrhotite intergrown with2C FeS troilite, two-phase 4C Fe7S8 Pyrrhotite intergrown with 5C Fe9S10 Pyrrhotite, single-phase 5C Fe9S10 Pyrrhotite and single-phase 4C Fe7S8 Pyrrhotite. None of the Pyrrhotite samples analyzed were classified as two-phase 4C Pyrrhotite intergrown with pyrite due to the scarcity of pyrite in these samples. Average solid solution Ni contents of NC Pyrrhotite (0.75 ± 0.10 wt % Ni) in this study were found to be greater than in 4C Pyrrhotite (0.43 ± 0.10 wt % Ni), but only when the Pyrrhotite occurred as two-phase 4C Pyrrhotite intergrown with NC Pyrrhotite. For single-phase Pyrrhotite occurrences in this study, 4C Pyrrhotite was more Ni rich (up to 2 wt % Ni) than NC Pyrrhotite (0.75 ± 0.19 wt % Ni). The average atomic metal/S ratios obtained for 4C Fe7S8 Pyrrhotite was 0.869 ± 0.013 (n = 699), for 5C Fe9S10 Pyrrhotite was 0.895 ± 0.013 (n = 316) and for 6C Fe11S12 Pyrrhotite was 0.918 ± 0.017 (n = 101). The histogram comparing metal/S ratios of all the Pyrrhotite samples analyzed showed a continuum of metal/S ratios, although with frequency maxima corresponding to the ideal compositions of 4C, 5C, and 6C Pyrrhotite. The presence of the continuum however, was interpreted to be representative of nonstoichiometry in the Pyrrhotite structure.
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An impedance study of the adsorption of CuSO4 and SIBX on Pyrrhotite samples of different provenances
Minerals Engineering, 2010Co-Authors: Zafir Ekmekci, Megan Becker, Esra Bagci Tekes, Dee BradshawAbstract:Abstract The non-stoichiometric sulfide mineral Pyrrhotite (Fe (1− x ) S), common to many nickel ore deposits, occurs in differing crystallographic forms and compositions. The processing of Pyrrhotite from these ores through froth flotation is based on the surface properties of the sulfides and since Pyrrhotite is a metallic conductor, it is of interest to characterise the surface properties of Pyrrhotite with respect to its electrochemical state. In this study, a series of Pyrrhotite samples derived from Canada, South Africa, and Botswana whose mineralogy is well characterised, were used for electrochemical impedance spectroscopy (EIS). The behaviour of the different Pyrrhotite samples were compared in terms of the effect of pH (7 and 10), collector addition (SIBX) and copper activation and the results correlated with microflotation tests. The EIS results were then used to interpret and understand the differences in flotation performance of the Pyrrhotite samples under the different reagent conditions and provide some answers as to why the success of copper activation on Pyrrhotite is so variable.
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The flotation of magnetic and non-magnetic Pyrrhotite from selected nickel ore deposits
Minerals Engineering, 2010Co-Authors: Megan Becker, Johan De Villiers, Dee BradshawAbstract:The non-stoichiometric sulfide mineral Pyrrhotite (Fe(1 x)S), common to many nickel ore deposits, occurs in different crystallographic forms and compositions. A series of Pyrrhotite samples derived from Canada, South Africa and Botswana whose mineralogy is well characterised, were selected here in order to develop the relationship between mineralogy and flotation performance. Using both oxygen uptake and microflotation tests, the behaviour of the different Pyrrhotite types was compared in terms of the effect of pH and collector addition. Non-magnetic Pyrrhotite was less reactive in terms of its oxygen uptake and showed the best collectorless flotation recovery. Magnetic Pyrrhotite was more reactive and showed poor collectorless flotation performance that could be improved with the addition of xanthate collector, but only if it was not already passivated. These differences are interpreted to be a result of Pyrrhotite mineralogy. This has implications that may aid the manipulation of Pyrrhotite flotation performance in processing operations
Megan Becker - One of the best experts on this subject based on the ideXlab platform.
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A comparison of Pyrrhotite rejection and passivation in two nickel ores
Minerals Engineering, 2013Co-Authors: T. Chimbganda, Megan Becker, J.l. Broadhurst, Susan T.l. Harrison, J.-p. FranzidisAbstract:The non-stoichiometric sulfide mineral Pyrrhotite (Fe1-xS) occurs almost ubiquitously inter-grown with the principal nickel mineral, pentlandite ((Fe,Ni)9S8). During Ni processing, Pyrrhotite is generally rejected to the tailings stream by flotation to produce a low tonnage, high grade (Ni) smelter feed and reduce SO2 emissions. In this study, the effect of different Pyrrhotite flotation rejection strategies (artificial oxidation and TETA: SMBS addition) are evaluated on a magnetic (Ore A) and non-magnetic (Ore B) Pyrrhotite ore to determine if either may effectively depress and potentially passivate the Pyrrhotite surface during flotation to produce benign tailings without compromising pentlandite recovery. For both ores, the best Pyrrhotite rejection (pentlandite/Pyrrhotite recovery) was obtained using TETA: SMBS. Differences in the flotation performance of the two ores are considered more a function of BMS content, liberation and ore handling rather than a difference in sulfide passivation from the inherent Pyrrhotite mineralogy (magnetic vs non-magnetic Pyrrhotite). Pyrrhotite passivation could possibly provide a means of rendering the tailings non-reactive and thus mitigate acid rock drainage (ARD) formation.
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the relationship between the electrochemical mineralogical and flotation characteristics of Pyrrhotite samples from different ni ores
Journal of Electroanalytical Chemistry, 2010Co-Authors: Zafir Ekmekci, Megan Becker, Esra Bagci Tekes, D J BradshawAbstract:Abstract The common sulphide mineral Pyrrhotite (Fe (1− x ) S) occurs in varying crystallographic forms with each type exhibiting subtly different physical and chemical properties. Accounts in the literature suggest that the processing behaviour of magnetic and non-magnetic Pyrrhotite differ from each other in their flotation properties, although limited agreement exists in terms of which is the more reactive Pyrrhotite form. Since the flotation process is based on the surface properties of the sulphide minerals and Pyrrhotite is a metallic conductor, it is of interest to characterise the surface properties of Pyrrhotite with respect to its electrochemical state. This paper presents the results of electrochemical measurements performed on four Pyrrhotite samples which have been characterised in terms of their mineralogical characteristics and flotation performance. Pyrrhotite samples from the Phoenix, Sudbury Copper Cliff North (CCN), Sudbury Gertrude West and Nkomati nickel mines were used for electrochemical measurements. Rest potential measurements, cyclic voltammetry and electrochemical impedance spectroscopy techniques were employed to characterise electrochemical behaviour of the samples. The electrochemical results showed that non-magnetic Pyrrhotite was the least reactive towards oxidation and hence showed the best collectorless flotation performance, whereas the magnetic Pyrrhotite samples were considerably more reactive. Due to the reactivity of the magnetic Pyrrhotite samples, their collectorless flotation recovery was almost negligible due to the formation of hydrophilic ferric hydroxide species associated with the oxidation reaction. Differences in electrochemical reactivity were also noted for different magnetic Pyrrhotite samples, suggesting the dependency of Pyrrhotite reactivity on its provenance.
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The mineralogy and crystallography of Pyrrhotite from selected nickel and PGE ore deposits
Economic Geology, 2010Co-Authors: Megan Becker, Johan P. R. De Villiers, Dee BradshawAbstract:The nonstoichiometric sulfide Pyrrhotite (Fe S) common to many ore deposits occurs in a variety of crystallographic forms and compositions and occasionally is also intergrown with stoichiometric troilite (FeS). In this study, the mineralogy of Pyrrhotite derived from several different nickel and PGE ore deposits in South Africa, Botswana, and Canada was examined in detail in terms of Pyrrhotite association, crystallography, and mineral chemistry. Pyrrhotite samples were subdivided into two-phase 6C Fe11S12 Pyrrhotite intergrown with2C FeS troilite, two-phase 4C Fe7S8 Pyrrhotite intergrown with 5C Fe9S10 Pyrrhotite, single-phase 5C Fe9S10 Pyrrhotite and single-phase 4C Fe7S8 Pyrrhotite. None of the Pyrrhotite samples analyzed were classified as two-phase 4C Pyrrhotite intergrown with pyrite due to the scarcity of pyrite in these samples. Average solid solution Ni contents of NC Pyrrhotite (0.75 ± 0.10 wt % Ni) in this study were found to be greater than in 4C Pyrrhotite (0.43 ± 0.10 wt % Ni), but only when the Pyrrhotite occurred as two-phase 4C Pyrrhotite intergrown with NC Pyrrhotite. For single-phase Pyrrhotite occurrences in this study, 4C Pyrrhotite was more Ni rich (up to 2 wt % Ni) than NC Pyrrhotite (0.75 ± 0.19 wt % Ni). The average atomic metal/S ratios obtained for 4C Fe7S8 Pyrrhotite was 0.869 ± 0.013 (n = 699), for 5C Fe9S10 Pyrrhotite was 0.895 ± 0.013 (n = 316) and for 6C Fe11S12 Pyrrhotite was 0.918 ± 0.017 (n = 101). The histogram comparing metal/S ratios of all the Pyrrhotite samples analyzed showed a continuum of metal/S ratios, although with frequency maxima corresponding to the ideal compositions of 4C, 5C, and 6C Pyrrhotite. The presence of the continuum however, was interpreted to be representative of nonstoichiometry in the Pyrrhotite structure.
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An impedance study of the adsorption of CuSO4 and SIBX on Pyrrhotite samples of different provenances
Minerals Engineering, 2010Co-Authors: Zafir Ekmekci, Megan Becker, Esra Bagci Tekes, Dee BradshawAbstract:Abstract The non-stoichiometric sulfide mineral Pyrrhotite (Fe (1− x ) S), common to many nickel ore deposits, occurs in differing crystallographic forms and compositions. The processing of Pyrrhotite from these ores through froth flotation is based on the surface properties of the sulfides and since Pyrrhotite is a metallic conductor, it is of interest to characterise the surface properties of Pyrrhotite with respect to its electrochemical state. In this study, a series of Pyrrhotite samples derived from Canada, South Africa, and Botswana whose mineralogy is well characterised, were used for electrochemical impedance spectroscopy (EIS). The behaviour of the different Pyrrhotite samples were compared in terms of the effect of pH (7 and 10), collector addition (SIBX) and copper activation and the results correlated with microflotation tests. The EIS results were then used to interpret and understand the differences in flotation performance of the Pyrrhotite samples under the different reagent conditions and provide some answers as to why the success of copper activation on Pyrrhotite is so variable.
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The flotation of magnetic and non-magnetic Pyrrhotite from selected nickel ore deposits
Minerals Engineering, 2010Co-Authors: Megan Becker, Johan De Villiers, Dee BradshawAbstract:The non-stoichiometric sulfide mineral Pyrrhotite (Fe(1 x)S), common to many nickel ore deposits, occurs in different crystallographic forms and compositions. A series of Pyrrhotite samples derived from Canada, South Africa and Botswana whose mineralogy is well characterised, were selected here in order to develop the relationship between mineralogy and flotation performance. Using both oxygen uptake and microflotation tests, the behaviour of the different Pyrrhotite types was compared in terms of the effect of pH and collector addition. Non-magnetic Pyrrhotite was less reactive in terms of its oxygen uptake and showed the best collectorless flotation recovery. Magnetic Pyrrhotite was more reactive and showed poor collectorless flotation performance that could be improved with the addition of xanthate collector, but only if it was not already passivated. These differences are interpreted to be a result of Pyrrhotite mineralogy. This has implications that may aid the manipulation of Pyrrhotite flotation performance in processing operations
J. G. Dunn - One of the best experts on this subject based on the ideXlab platform.
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A comparative study of the dissolution of hexagonal and monoclinic Pyrrhotites in cyanide solution
Hydrometallurgy, 2000Co-Authors: M N Lehmann, R.m Pennifold, P. Kaur, J. G. DunnAbstract:Abstract The extent and rate of dissolution of two natural Pyrrhotite samples, one monoclinic (Fe 0.88 S) and the other hexagonal (Fe 0.90 S), were studied in alkaline cyanide solutions (pH 10). The effects of dissolved oxygen, particle size, and temperature were investigated. The extent of dissolution was followed by monitoring the dissolved sulfur levels in solution. The initial rates of dissolution were determined by fitting the conversion data to a second-order polynomial regression equation. The rate of dissolution of the monoclinic Pyrrhotite under the variety of conditions was found to be greater than that of the hexagonal Pyrrhotite. The activation energies for the oxidative dissolution of monoclinic and hexagonal Pyrrhotites were found to be 65.3 and 71.9 kJ/mol, respectively, which indicated that the initial dissolution of Pyrrhotite is under chemical control. The reduced reactivity of the hexagonal form was attributed to its greater iron content, which, during oxidation, was proposed to form a more compact iron-oxyhydroxide coating, which passivated the sulfide and made it less susceptible to cyanide ion attack. No passivation effect was evident in the case of the monoclinic Pyrrhotite.
Kan-hsi Hsiung - One of the best experts on this subject based on the ideXlab platform.
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Pyrrhotite as a tracer for denudation of the Taiwan orogen
Geochemistry Geophysics Geosystems, 2012Co-Authors: Chorng-shern Horng, Chih-an Huh, Kuo-hang Chen, Chun-hung Lin, Kai-shuan Shea, Kan-hsi HsiungAbstract:[1] The use of Pyrrhotite as an index mineral to delineate metamorphic isograds has long been proposed. However, details of the occurrence of Pyrrhotite in different metamorphic facies and its implications have rarely been explored. Here, by simple characterization of magnetic properties and mineral identification, we demonstrate that Pyrrhotite is widely distributed in low-grade metamorphic terranes of Taiwan's Central Range and in sediments derived therefrom. By coupling the distribution of Pyrrhotite in rocks with that in dated sediment strata, we have studied the denudation history of Taiwan's orogen from a source-to-sink perspective. We suggest that Pyrrhotite is a potential tracer for studying surface processes in orogens with high denudation rates similar to that in Taiwan.
