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Manganese Particles in Freshwaters
Published in Jacques Buffle, Herman P. van Leeuwen, Environmental Particles, 2018
Richard R. De Vitre, William Davison
Mn-specific minerals are quite scarce and, in common with other transition metal minerals, often include two or more formal oxidation states. Among the more common Mn minerals are the oxides and oxyhydroxides such as pyrolusite (MnO2) and psilomelane (BaMn(II)Mn(IV)8O16(0H)4), and in near surface deposits manganite (MnOOH), braunite (Mn,Si)2O3 and hausmanite (Mn3O4). Less common manganese minerals, generally found in more reducing environments, include pyrochroite (Mn(OH)2), manganosite (MnO), and alabanite (MnS). Finally, rhodochrosite (MnC03) is found in sedimentary rocks, and as an impurity in carbonate rich ores such as calcium carbonates through ionic substitution since the charge and ionic radii of Mn2+ and Ca2+ are quite similar.
Influence Mechanisms of Additives on Coal-based Reduction of Complex Refractory Iron Ore
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Peng Gao, Wentao Zhou, Yuexin Han, Yanjun Li, Chengwen Zhang
From Table 1 and Figure 1 it can be seen that the total iron grade of the ore was 36.5%, with the main iron-bearing minerals being siderite, hematite, and magnetite. The aluminum and silicon content of the iron ore was relatively high, and the main gangue minerals were quartz and oolitic chlorite. The chemical composition of the coal was analyzed, and the results are given in Table 2. It can be seen that the test coal was a good reductant with high volatile and fixed carbon, low ash content, and harmful elemental sulfur. The CaF2, Na2CO3, and MgCO3 used as additives were analytically pure. Table 3 lists the main iron-bearing minerals in the raw ore as hematite, magnetite, and siderite. In addition, there was a certain amount of rhodochrosite (MnCO3) in the ore which could be decomposed into manganosite (MnO) when heated in a reducing atmosphere.
Gaseous Reduction of Manganese Ores: A Review and Theoretical Insight
Published in Mineral Processing and Extractive Metallurgy Review, 2020
Alireza Cheraghi, Hossein Yoozbashizadeh, Jafar Safarian
Mn oxides (either hydrated or anhydrous) can be assumed as the common minerals in the Mn-containing ore (Wellbeloved et al. 1990; Olsen et al. 2007). Thus, the stability of Mn oxides is an important matter in the reduction process. Various Mn oxides are formed according to temperature and oxygen pressure/concentration. The Mn-rich part of the Mn–O phase diagram can be calculated using FactSage software as shown in Figure 7. Different oxides of Mn are evident in the figure: pyrolusite (Mn4+ O2), hausmannite ((Mn3+)2(Mn2+) O4), bixbyite ((Mn3+)2O3), and manganosite (MnO). Table 3 shows different Mn oxides’ specifications. As Figure 7 indicates, only MnO is able to construct a solid solution (monoxide phase), and other Mn oxides show no solubility in solid state. The four allotropes of solid Mn are also observed in Figure 7. Gaseous reduction of Mn oxides is of interest for the solid state, and as the phase diagram in Figure 7 indicates, all the Mn oxides are in solid phase below 1580°C. This is where solid-state transformations of the oxides in reducing atmosphere are possible. Association of other elements such as Si in the mineral has been reported to lower the mineral melting point considerably (Anacleto et al. 2004a).
Thermodynamic modelling of decomposition processes in the Mn-O and Mn-O-H systems
Published in Canadian Metallurgical Quarterly, 2023
Initially, it would be of interest to investigate the decomposition behaviours of the various manganese oxides in the Mn-O system. The effects of the different data sets on the decomposition temperatures can be evaluated to determine if there is some agreement. Also, the impacts of variables such as temperature, gas composition and pressure can be studied. As mentioned previously, the Mn-O system consists of the following four well-established stable oxides in order of decreasing oxygen content: MnO2 (pyrolusite), Mn2O3 (bixbyite), Mn3O4 (hausmannite) and MnO (manganosite). Also, if desired Mn5O8 can be included in the equilibrium calculations.