China
Africa
Explore chapters and articles related to this topic
Mineral formation sequence in the hyperbasites of the Serovsko-Maukski ophiolite belt (the Northern Urals)
Published in Vladimir Litvinenko, Advances in Raw Material Industries for Sustainable Development Goals, 2020
R.K. Ilalova, I.V. Talovina, I.V. Vorontsovac
Infiltration-overlay minerals appeared after the formation of the weathering crust and its overlapping by precipitation from the Jurassic and Cretaceous periods. They are not connected with the destruction of hyperbasite massifs and dike rocks. Mineralized waters from lake and marsh water bodies penetrated downwards (into the upper zones of the weathering crust) and as a result of infiltration and overlaying replaced some previously formed minerals. In addition to metasomatic substitution, the minerals of this group were precipitated from cold solutions of cracks and rocks in the weathering crust. Infiltration-metasomatic chamosite was found in the weathering crust of serpentinite, which partially replaced both exogenous newly formed and endogenous relic minerals. Infiltration chamosite is distinguished by cracks and voids and belongs to the later generation. This group also includes pyrite, siderite and rhodochrosite. Pyritization and sideritization as infiltrationally superimposed processes are weaker in the weathering crust than chamositization. Pyrite in the form of crystals 0.5 mm in size is often found in the ochreous hydrogethyte mass of the upper area of the weathering crust. Siderite is in close paragenetic association with chamosite, rhodochrosite. It is observed in the form of rounded spherolite grains and clear crystalline aggregates in loose clayey chamosite rocks, cementing them.
Practical Applications: Landfills
Published in William J. Deutsch, Groundwater Geochemistry, 2020
Ferrous iron, Fe2+, dominates the next zone. It forms from the dissolution of ferrihydrite, and although it does participate in cation exchange reactions, the typical large amount of ferrous iron produced overwhelms the exchange capacity of most systems to significantly retard its movement. In the presence of high ferrous iron and carbonate concentrations, siderite (FeCO3) may form. The precipitation of this mineral usually limits the upper concentration of iron because carbonate is present in excess of the iron concentration. High dissolved levels of manganese may also be present in the iron zone; however, as conditions become more oxidizing the iron will reprecipitate as ferrihydrite [Fe(OH)3], leaving Mn(II) as the dominant, dissolved redox-sensitive species. The manganese carbonate mineral rhodochrosite (MnCO3) may form in the zones where manganese concentration is elevated. Finally, downgradient of the landfill where the plume has sufficiently mixed with fresh water or been subject to the diffusion of gases from the soil vapor, dissolved oxygen will be present at levels greater than 1 mg/L and the system will be oxic again.
Use of Wetlands for Treatment of Environmental Problems in Mining: Non-Coal-Mining Applications
Published in Donald A. Hammer, Constructed Wetlands for Wastewater Treatment, 2020
Thomas R. Wildeman, Leslie S. Laudon
If a wetland were buried, upon diagenesis, it would eventually become a bog deposit, coal, or black shale.30,34 Reviewing metals occurrence in these sediment types that have undergone early diagenesis may identify forms with long-term stability. Mineral forms of manganese, iron, and other base metals in these sediments represent the most thermodynamically stable phases of these elements. In sediments formed by chemical precipitation, the stable iron minerals are hematite (Fe2O3), pyrite, or siderite (FeCO3); stable manganese minerals are pyrolusite (MnO2) and rhodochrosite.1,30,34,35 Trace elements such as Co, Ni, Cu, Zn, Ag, Cd, Au, Hg, and U occur as sulfides, oxides, and carbonates. The same is true in lignite and coal deposits. With the possible exceptions of V and Ni, metals are not retained by the organic fraction in organic-rich reducing sediments.1,5,34
A Review of Low Grade Manganese Ore Upgradation Processes
Published in Mineral Processing and Extractive Metallurgy Review, 2020
Veerendra Singh, Tarun Chakraborty, Sunil K Tripathy
Rhodochrosite is the main manganese mineral found in the carbonate ores. These ores are first crushed into finer sizes to improve the mineral liberation and subsequently jigging, spirals, or gravity tables are employed to separate the gangue and valuable minerals. Most of the manganese carbonate minerals are found embedded evenly and require very fine grinding to achieve the mineral liberation. Sulfur, carbonaceous gangue, and Pb–Zn gangue is removed by flotation and magnetic separation process. Aplan (1985) had recovered manganese-rich concentrate from carbonate ores using dense medium separation and both the products (i.e., that sinks and floats [high silica]) had been agglomerated and used to produce ferromanganese and silico-manganese, respectively.
Magnesium salt removal from manganese electrolyte via low-temperature crystallisation
Published in Canadian Metallurgical Quarterly, 2023
Chunlin Chen, Xiaohua Peng, Xingbin Li, Chang Wei, Zhigan Deng, Minting Li, Gang Fan
Currently, manganese metal is primarily extracted using hydrometallurgical processes. Raw materials for manganese production include manganese carbonate and manganese dioxide ores in addition to manganese-rich slag from blast furnaces. In China, rhodochrosite (MnCO3) is the main raw material for manganese metal extraction. Rhodochrosite is initially leached by concentrated sulphuric acid, subsequently neutralised by air and liquid ammonia oxidation, and finally purified to remove impurities and obtain a manganese sulphate solution. Manganese metal is extracted from the manganese sulphate solution through electrolysis [1]. However, magnesium compounds, such as MgCO3, MgSiO3 and CaCO3·MgCO3, typically accompany rhodochrosite. Therefore, magnesium is inevitably introduced into the solution in the form of magnesium sulphate during the acid-leaching process, and is continuously circulated and enriched in the manganese electrolyte. Currently, the Mg2+ concentration in the industry has exceeded 30 g L–1, which is equivalent to >150 g L–1 of MgSO4 [2]. The increase in the MgSO4 content in the manganese sulphate solution severely affects the hydrometallurgical process in terms of decreasing the manganese leaching efficiency and, increasing the viscosity and density of the solution; consequently, the current efficiency is decreased and energy consumption is increased [3, 4]. Magnesium sulphate crystallises out in pipelines because the local temperature is lowered, thus hindering production [5, 6]. Moreover, the high level of magnesium sulphate affects the manganese metal quality. Therefore, magnesium sulphate concentration in the electrolyte solution must be reduced.