China
Africa
Explore chapters and articles related to this topic
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.
Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Dividing minerals into classes based on anion or anionic group is convenient because we can determine class from chemical formula. However, this classification scheme makes sense for other reasons, too. The kinds of atomic arrangements and bonding are similar within a mineral class; thus, minerals within a class often have similar physical properties, making the classes useful in mineral identification. Such would not be the case if we divided minerals into groups based on cations. For example, lime (calcium oxide), wollastonite (calcium silicate), calcite (calcium carbonate), and fluorite (calcium fluoride) all contain Ca, but have few properties in common. In contrast, the carbonate group minerals, shown in Figure 3.30, share many properties. These carbonates include calcite (calcium carbonate), dolomite (calcium magnesium carbonate), rhodochrosite (manganese carbonate), smithsonite (zinc carbonate), and cerussite (lead carbonate) They are all quite soft and dissolve in acidic water. They have good cleavage, and, when they grow as flat-sided crystals, their crystals have similar shapes.
Layer by Layer Microencapsulate Technology as Basis for Fabrication of Drug Delivery Nanosystems with Remote Controlling Properties
Published in Vladimir Torchilin, Mansoor M Amiji, Handbook of Materials for Nanomedicine, 2011
Olga A. Inozemtseva, Sergey A. Portnov, Tatyana A. Kolesnikova, Dmitry A. Gorin, Gleb B. Sukhorukov
To produce magnetite nanoparticles inside the capsules one needs to form a water-insoluble PAH/citrate complex as the first layer on the surface of the template particles. The authors of Ref. 61 used manganese carbonate particles as cores. Then multilayers of PAH/PSS were formed using the layer-by-layer technique. Hollow capsules with inner PAH/citrate layer and outer PAH/PSS layers were obtained after core dissolution. Then citrate ions could be replaced by other anions which can act as precipitating agents to form an insoluble inorganic material directly inside the polyelectrolyte capsule. Exposing the obtained PAH/citrate-PAH/PSS capsules in a solution of 0.01M sodium hydroxide resulted in the replacement of citrate ions by hydroxyl ones. After that the polyelectrolyte capsules were treated by the solution of iron salts to form magnetite nanoparticles in the capsule interior. The external PAH/PSS layers were dissolved in concentrated alkaline solution and nanocomposite microcapsules containing iron oxide nanoparticles were received. These capsules possessed higher mechanical stability in comparison with initial ones.
Development of a process to produce manganese nanomaterials from low grade ferruginous manganese ores
Published in Mineral Processing and Extractive Metallurgy, 2021
Veerendra Singh, Soobhankar Pati, Kishan Kumar
The leach liquor contains Fe as the main impurity. Since manganese has a high negative value in the electromotive series, the levels of metals with higher reduction potentials should be controlled to a low level. Most of the iron present in the solution is removed by goethite precipitation with the addition of lime to bring the pH to 2–3. Potassium and rest of iron are removed by jarosite precipitation with the addition of lime to maintain pH ranging from 4 to 6. After removal of all the impurities, for CMD production, first manganese carbonate is produced by the addition of sodium carbonate to the purified liquor. Then the raw CMD is obtained by oxidation of manganese carbonate at 500°C in the presence of oxygen for 1 h.
Synthesis and kinetic modeling of manganese carbonate precipitated from manganese sulfate solution
Published in Chemical Engineering Communications, 2022
Sajjad Ali, Yaseen Iqbal, Khizar Hussain Shah, Muhammad Fahad
Manganese carbonate (MnCO3) is a valuable product which is utilized in the manufacturing of ferrites, alloys, paints, fertilizers, dietaries, and welding electrodes (Lei et al. 2009; Pourmortazavi et al. 2012). At laboratory scale, MnCO3 can be synthesized from aqueous manganese sulfate (MnSO4) solutions. MnSO4 solutions obtained via hydrometallurgical treatment of low-grade manganese ore (LGMO) mostly contain substantial amounts of impurities, e.g., Ca2+ and Mg2+ that affect the subsequent recovery of Mn2+ due to similar chemical properties. Various purification methods such as solvent extraction, precipitation, and crystallization are employed to purify MnSO4 solutions from Ca2+ and Mg2+. Among these, crystallization of MnSO4 solutions has been proved to be relatively simpler and easier to operate; however, it is difficult to isolate MnSO4 crystals from MgSO4 crystals (Mingliang and Guanzhou 2000; Pagnanelli et al. 2004; Farrah et al. 2007). In the solvent extraction method, manganese can be separated from other metals, but high reagent costs involved in the removal of Ca and Mg ions make its use uneconomical (Cheng 2000; Pakarinen and Paatero 2011; Haghighi et al. 2015). In comparison with crystallization and solvent extraction methods, the chemical precipitation method has been reported to be relatively more appropriate for the purification of MnSO4 solutions. For example, to precipitate Ca and Mg ions, the cheap and non-hazardous precipitants such as phosphate, oxalate, fluoride, and carbonate are used (Changhong et al. 2006; Honggang and Guocai 2007; Guixiang et al. 2013). Therefore, chemical precipitation method is a cheap and green method for the purification of MnSO4. A high recovery of manganese from solutions containing multiple metals (such as Fe, Co, Ni, Zn, Ca, Mg, and Cu) by utilizing hydroxide, carbonate, or oxidative precipitation methods has already been reported in the literature (Lan-Xiang and Chang-Lun 1989; Zhang et al. 2002, 2010; Zhang and Cheng 2007). More than 90% recovery of manganese from MnSO4 solution has been recovered using Na2CO3, and this method has been reported to be highly effective, efficient, and economical (Pakarinen and Paatero 2011). Researchers have found carbonates as an ideal reactant to precipitate Mn (II) not only because of simple reaction between CO3 and Mn (II) but also the generated product is stable in composition. Several kinetic studies were reported on the removal of heavy metal ions (Freitas et al. 2008; Mohapatra et al. 2009) from aqueous solutions, but only a few studies focused on recovery of particular metal ions using precipitation (Bryson and Bijsterveld 1991). For analysis of kinetic data, several models have been reported in the literature such as surface chemical reaction, diffusion through product layer, and mixed control model (Suhaina et al. 2016). The most important parameter related to the applicability of a certain kinetic model is the activation energy. A possible change in the observed activation energy with temperature indicates a shift in the controlling mechanism of reaction.