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Published in Andrzej Stokłosa, Stefan S. Kurek, Structure and Concentration of Point Defects in Selected Spinels and Simple Oxides, 2021
Andrzej Stokłosa, Stefan S. Kurek
An important magnetite from the practical point of view, but also chronologically, is the magnetite doped with manganese, in which Mn2+ ions incorporate into nodes of Fe2+ ions and in the limit case the spinel reaches the composition MnFe2O4 (jacobsite). At a higher manganese content, the spinels should be treated as hausmannite doped with iron; this will be discussed in Chapter 12. Many works concerned the range of existence of spinels (Fe1−xMnx)3±δO4, mainly at 1273 K and 1473 K, (Bergstein 1963, Bergstein and Kleinert 1964, Bulgakova and Rozanov 1970, Duquesnoy et al. 1975, Franke 1987, Franke and Dieckmann 1989, Franke and Dieckmann 1990, Komarov et al. 1965, Muan and Somiya 1962, Ono et al. 1971, Roethe et al. 1970, Schwerdtfeger and Muan 1967, Subramanian and Dieckmann 1993, Terayama et al. 1983, Wickham 1969, Yoo and Tuller 1988). The discussion and analysis of results on the range of existence of manganese ferrites and their enthalpies of formation can be found in (Kjellqvist and Selleby 2010). For the study of cation distribution in the sublattice of the spinel MnFe2O4 and (Fe1−xMnx)3±δO4, various methods were applied, mainly neutron diffraction, X-ray diffraction (Hastings and Corliss 1956, Jirak and Vratislav 1974, Murthy et al. 1971, Rieck and Driessens 1966, Sawatzky et al. 1967) and Mössbauer spectroscopy (Becker et al. 1994, Bonsdorf et al. 1997). It was found that MnFe2O4 spinel at room temperature has the structure of normal spinel. Thus, in cation sites of the sublattice with tetrahedral coordination there are Mn2+ ions. At high temperatures, there occurs an exchange of ions and change in the oxidation state, and, depending on the temperature, an equilibrium distribution of cations is set. Partial studies of the deviation from the stoichiometry in a narrow range of oxygen pressures were presented in (Bergstein 1963, Bulgakova and Rozanov 1970, Duquesnoy et al. 1975, Komarov et al. 1965, Ono et al. 1971, Roethe et al. 1970, Terayama et al. 1983, Wickham 1969, Yoo and Tuller 1988).
Nano MNO2 production from fine-grained and low-grade manganese ore using a mixture of citric acid and molasses as reductant
Published in Canadian Metallurgical Quarterly, 2023
Havvanur Ucbeyiay, Y. Ramazan Eker, Emine Ozkan
Manganese is a transition metal and is commonly found in the +2, +3 and +4 oxidation states. +3 and +5 states of manganese compounds are not very common. While about 40% of Mn ore resources are composed of carbonate minerals, 25% are composed of silicate and 20% are oxide minerals. The gangue minerals found in these ores are non-metallic minerals (compounds such as SiO2, Al2O3, CaO, MgO and other elements such as Ba, K, P, S, etc.), metallic ones (Co, Cu, Mo, Ni, As, Cu, Mo, Pb, Zn and Fe) and other impurities (H2O, CO2 and other organic substances) [2]. The choice of the enrichment method largely depends on these impurities. Since a significant portion of these resources are rich in iron, they are often referred to as ferro manganese ores. While there are minerals enriched by a magnetic separation such as hematite, goethite, magnetite in ferro manganese ores, minerals such as jacobsite and bixbit that are difficult to separate and require more chemical processing can also be found. Gravity methods have generally been used for the enrichment of siliceous ores, and industrial applications have also been made in Brazil and India. Gravity and magnetic separation methods were also applied for the enrichment of carbonate ores [2]. However, these methods lose their effectiveness in fine particles.
Microhardness-compositional relationship of Fe3O4-Mn3O4 series spinels from ferromanganese sinter and its relationship to sinter strength
Published in Mineral Processing and Extractive Metallurgy, 2023
M. J. Peterson, S. Hapugoda, J. R. Manuel
The miscibility of jacobsite and galaxite appears to be unresolved. Essene and Peacor (1983) and Brugger and Meisser (2006) found only limited miscibility between the phases. Beard and Tracy (2002), argued that the apparent miscibility gap observed by Essene and Peacor (1983) in part reflects differences in the silica activity during formation, but also may be promoted by the inclusion of other elements, such as Mg or Zn. In support of limited Mn3O4-MnAl2O4 miscibility, Gnos and Peters (1995) described opaque, but low reflectivity galaxite with ∼35% hausmannite solid solution (Al3+ replaced by Mn3+). Their observation of hausmannite with a maximum of a 7% galaxite component was ascribed to the presence of Fe.
Demonstration of dry magnetic separation to upgrade the Mn:Fe ratio of a ferromanganese ore sample
Published in Mineral Processing and Extractive Metallurgy, 2023
M. J. Peterson, R. Karadkal, V. Nunna, S. Hapugoda, P. Austin
Iron may be present in manganese deposits in the form of Fe-bearing manganese minerals such as bixbyite, jacobsite, braunite and hausmannite (e.g. in the Otsojondu and Wessels deposits in southern Africa – Buehn et al. 1992; Gutzmer and Beukes 1996). However, it may also be commonly found in the Fe oxide and oxyhydroxide minerals hematite and goethite, as well as in Fe silicates (e.g. garnet and amphibole) and Fe carbonate (e.g. siderite) minerals, depending on the local geology and the mode(s) of ore genesis.