Manganese, oxide

Transition metal oxides are also widely used electrode materials for supercapacitors [3]. They also have attracted more attention as support for the conducting-polymer electrode materials. MnO nanocrystals (a-MnO and P-MnO ) are the most used one among the metal oxides. 

Sharma et al. synthesized electrochemically the MnO -embedded PPy nanocomposite (MnO /PPy) thin-film electrodes for supercapacitors [56]. It was found that growing PPy polymer chains provided large surface area template that enabled MnO to form as nanoparticles embedding within the polymer matrix. The co-deposition of MnO and PPy had a complimentary action in which the porous PPy matrix provided high active surface area for the MnO nanoparticles and the MnO nanoparticles nucleated over polymer chains contributed to the enhanced conductivity and stability of the nanocomposite material by interlinking the PPy polymer chains. The SC of the nanocomposite thin-film electrode 

Hashmi and Upadhyaya compared the electrochemical properties of the electrochemically synthesized MnO /PPy composite electrodes, fabricated with different electrolytes, namely polymer electrolyte film (polyvinyl alcohol [PVA]-HjPO aqueous blend), aprotic liquid electrolyte (LiClO -propylene carbonate [PC]), and polymeric gel electrolyte (poly methyl methacrylate [PMMA]-ethylene carbonate [EC]-PC-NaClO ) [60]. The cell with aqueous PVA-H PO showed non-capacitive behavior owing to some reversible chemical reaction of MnO with water, while the MnO / PPy composite was found to be a suitable electrode material for redox supercapacitors with aprotic (non-aqueous) electrolytes. The solid-state supercapacitor based on the MnO /PPy composite electrodes with gel 

Owing to the rapid development of portable personal electronics, flexible electronics has attracted intense interests due to their application in varied fields, such as artificial electronic skin, roll-up displays, distributed 

The cluster molecular-orbital approach has also been successfully applied to studies of the electronic structures of manganese oxide minerals and related compounds, notably in the work of Sherman (1984) using the MS-SCF-2fa method. Calculations were performed on the clusters 

The valence-band orbitals include nonbonding oxygen orbitals such as the lt g, 6tiu, l 2u. and 5t, and those orbiteds with appreciable metal and oxygen character (2 g, 6a,g, lt2g)- The atomic compositions of the latter are given in Table 4.20 along with the compositions of the crystal-field 

SCF-Afa calculations show them to be extensively delocalized over the oxygen, interatomic, and extramolecular regions. 

XES band Transition (expt.) (calc.) (expt.) (0310.) Reference 

One-electron transition (calc.) Corresponding spectral transitions  

Albeit it is not as abundant as aluminum or iron, manganese is a key element in soil chemistry, due to its redox behavior, and is an essential nutrient for animals and plants. Manganese occurs in nature mostly as oxides, which have environmental 

There is a number of Mn minerals in soils, several of which are poorly known, because they tend to appear as small nodules of poor crystallinity or as coatings on other minerals, such as Fe oxides. Table 9.3 summarizes data for some relatively common Mn oxides the last three are, in fact, less common but are included here for reference and comparison. Manganite and hausmannite are analogues of goethite and magnetite, respectively (Kampf, Scheinost, and Schulze 1999 Dixon and White 2002). 

It is worth here to discuss further the redox behavior of manganese oxides, as they have an important role in soil chemistry. Mn(II) is oxidized in soil by diverse routes. One prominent path is microbial oxidation to Mn(IV), and several bacterial species 

Source Dixon, J.B. and White, G.N., Soil Mineralogy with Environmental Applications, Soil Science Society of America, Madison, WI, 2002. 

FIGURE 9.10 Polyhedral models of some Mn minerals (a) bimessite with divalent (Mg) ions in the interlayer (b) bimessite with monovalent (Na) ions in the interlayer—note that Na+ ions are in the center, whereas ions in bimessite are closer to one of the sheets (c) lithioporite, with an (Al, Li)-OH sheet stacked in the z direetion (d) todorokite, showing the channels containing cations surrounded by water molecules. (Reprinted from Dixon, J. B. and White, G. N., Soil Mineralogy with Environmental Applications, Soil Science Society of America, Madison, WI, 367-388, 2002, with kind permission.) 

N anomaterials have been around for hundreds of years and are typically defined as particles of size ranging from 1 to 100 nm in at least one dimension. The inorganic nanomaterial catalysts discussed here are manganese oxides and titanium dioxide. Outside the scope of this chapter are polymers, pillared clays, coordination compounds, and inorganic-organic hybrid materials such as metal-organic frameworks. 

OMS materials are also green in that they are heterogeneous catalysts. Heterogeneous catalysts do not leach into the system and are therefore completely recoverable. In addition, doping of OMS materials with iron allows separation of 

KMn8016 nH20 and has a 2 x 2 tunnel generated using CrystalMaker (CrystalMaker 

At present, titanium dioxide meets green chemistry principles, including energy efficiency and renewable feedstocks through a wide variety of heterogeneous photo- 

Selective transformations Selective styrene ring opening [103] One-pot domino process for regioselective synthesis of a-carbonyl furans [104] Tandem process for synthesis of quinoxalines [105] Atmospheric oxidation of toluene [106] Cyclohexane oxidation [107] Synthesis of imines from alcohols [108] Synthesis of 2-aminodiphenylamine [109] 9H-Fluorene oxidation [110] Dehydrogenation of ethane in the presence of C02 [111] Decomposition of methane [112] Carbon monoxide oxidation [113] 

Absorbent sample BET surfece area (m g ) Removal capacity for As (mgg ) Removal capacity for Cr (mgg- ) 

Reproduced with kind permission from Ref. [97] John Wiley Sons, Inc. 

Figu re 9.3 (a) Adsorption rate of As(V) (solid line) and Cr(VI) (dashed line) on the as-prepared a-Fe203 (b) Adsorption rate of the azo-dye Orange II on new as-prepared a-Fe203 (solid line) and regenerated a-Fe203 (dashed line). Reproduced with kind permission from Ref [97] ]ohn Wiley Sons, Inc. 

Figu re 9.5 Time profiles of methylene blue (MB) degradation. 

Hydrous rare earth oxides have been proposed as a new adsorbent for the removal of aqueous hazardous anions such as arsenate, fluoride and phosphate, because of their relatively higher adsorption capacitors [145,146]. The relatively small ionic potential and strong basicity of rare earth ions bring a strong tendency to dissociate OH groups into hydroxyl ions [147, 148]. 

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Process Chemistry. Manganese is combined with oxygen in its ores (see Table 3) and carbon is the most economical reducing agent for oxides. Therefore, the essential characteristics of manganese metallurgy is evident from examination of the interactions between manganese oxides and... 

In the presence of moist air, MnCl2 vapor decomposes into hydrochloric acid and manganese oxides. 

The mixed valent oxide Mn.O occurs in nature as the mineral hasumannite. The stmcture of this ferromagnetic material has been the subject of much dispute. Mn.O is the most stable of the manganese oxides, and is formed when any of the other oxides or hydroxides are heated in air above 940—1000°C. The oxidation of aqueous solutions of Mn (OH)2 can also lead to the formation of Mn O. ... 

Fig. 2. Hydration of the surface stmcture of manganese dioxide (2) and subsequent reactions of hydrous manganese oxide (3) showing proton transfer (4)...

Manganese Oxides. Manganese(IV) dioxide rarely corresponds to the expected stoichiometric composition of Mn02, but is more reahsticaHy represented by the formula MnO y 2 q, because invariably contains varying percentages of lower valent manganese. It also exists in a number of different crystal forms, in various states of hydration, and with a variety of contents of foreign ions. 

A thermally stable, pure todorokite has been synthesized by autoclaving a layered stmctured manganese oxide, initially generated from the reaction of MnO and Mn " under alkaline conditions. The synthetic manganese oxide molecular sieve (11) was shown to have a tunnel size, ie, diameter of 690 pm. This material was thermally stable to 500°C just as natural todorokite is (68). 

The dissolution of carbon in molten iron in the lower part of the furnace, leads to the reduction of manganese oxide (eq. 15) and some sihea (eq. 14), both in the slag, whereby the subsequent dissolution of these metals occurs in the molten iron. 

Water Dispersions. Polysulftde products are offered as aqueous dispersions (Thiokol WD-6). These are useful for applyiag protective coatings to line fuel tanks, and for concrete, wood, and ia some cases fabrics, felt, leather (qv), and paper (qv). It has been found that a stable emulsion can be made that contains both LP and manganese oxide curing agent. The emulsion can be thinned and appHed as a spray coating. After it is appHed, water evaporates and the LP cures to form a soHd mbber (13). 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

The thermistor material is usually a metal oxide, eg, manganese oxide. Dopants, eg, nickel oxide or copper oxide, may be added to obtain a variety of resistance and slope characteristics. The material is usually skitered kito a disk or bead with kitegral or attached connecting wkes. Figure 4 shows a typical series of steps ki the production of a disk thermistor. 

Variety and source Si02 (siHca ) FeO (ferrou s oxide) 3 (ferri c oxide ) AI2O3 (alumina) MgO (magnesia) CaO (lime ) MnO (manganese oxide) Na20 (sodiu m oxide) icp (potassiu m oxide) up, adsoibe d up+, combine d... 

The manganous ion [16397-91 -4] in solution then reacts with higher valent manganese oxide and zinc ions in solution to form a new phase called... 

Other Types of Portland Cements. White Portland cementis standard Type I or III Pordand cement with raw materials selected and controUed to have negligible amounts of Hon and manganese oxides, which impart the gray color. The white Pordand cement is used in decorative and architectural appHcations like precast curtain waUs, terra22o surfaces, stucco, tile grout, and decorative concrete. 

Analysis. Butenes are best characterized by their property of decolorizing both a solution of bromine in carbon tetrachloride and a cold, dilute, neutral permanganate solution (the Baeyer test). A solution of bromine in carbon tetrachloride is red the dihaUde, like the butenes, are colorless. Decoloration of the bromine solution is rapid. In the Baeyer test, a purple color is replaced by brown manganese oxide (a precipitate) and a colorless diol. These tests apply to all alkenes. 

The laterites can be divided into three general classifications (/) iron nickeliferrous limonite which contains approximately 0.8—1.5 wt % nickel. The nickel to cobalt ratios for these ores are typically 10 1 (2) high siUcon serpentinous ores that contain more than 1.5 wt % nickel and (J) a transition ore between type 1 and type 2 containing about 0.7—0.2 wt % nickel and a nickel to cobalt ratio of approximately 50 1. Laterites found in the United States (8) contain 0.5—1.2 wt % nickel and the nickel occurs as the mineral goethite. Cobalt occurs in the lateritic ore with manganese oxide at an estimated wt % of 0.06 to 0.25 (9). 

EDA reacts readily with two moles of CS2 in aqueous sodium hydroxide to form the bis sodium dithiocarbamate. When aqueous ammonia and 2inc oxide (or manganese oxide or its hydrate) is used with a basic catalyst, the 2inc (or manganese) dithiocarbamate salt is isolated. Alternatively, the disodium salt can react with ZnSO or MnSO followed by dehydration in an organic solvent to yield the same salts (48—50). 

Figure 4.6 A thin, glassy layer of predominantly manganese oxide on the internal surface of a brass condenser tube. The many white spots are pits at fractures in the manganese layer.

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