Metal oxides, hydroxides

Manufacture. The transition- and heavy-metal fluoroborates can be made from the metal, metal oxide, hydroxide, or carbonate with fluoroboric acid. Because of the difficulty ia isolating pure crystalline soflds, these fluoroborates are usually available as 40—50% solutions, M(BP. Most... 

Perchlorates. Historically, perchlorates have been produced by a three-step process (/) electrochemical production of sodium chlorate (2) electrochemical oxidation of sodium chlorate to sodium perchlorate and (4) metathesis of sodium perchlorate to other metal perchlorates. The advent of commercially produced pure perchloric acid directly from hypochlorous acid means that several metal perchlorates can be prepared by the reaction of perchloric acid and a corresponding metal oxide, hydroxide, or carbonate. 

The carboxyl group reacts with metal oxides, hydroxides, or salts to form rosin soaps or salts (resinates). The soaps of alkah metals, such as sodium and potassium, are usehil in paper sizing and as emulsifiers in mbber polymerization. 

Nanocomposites based on other nanofillers like metal oxides, hydroxides, and carbonates... 

Tolstoy, V. P. 1997. The peroxide route of the successive ionic layer deposition procedure for synthesizing nanolayers of metal oxides, hydroxides and peroxides. Thin Solid Films 307 10-13. 

Rates of reductive dissolution of transition metal oxide/hydroxide minerals are controlled by rates of surface chemical reactions under most conditions of environmental and geochemical interest. This paper examines the mechanisms of reductive dissolution through a discussion of relevant elementary reaction processes. Reductive dissolution occurs via (i) surface precursor complex formation between reductant molecules and oxide surface sites, (ii) electron transfer within this surface complex, and (iii) breakdown of the successor complex and release of dissolved metal ions. Surface speciation is an important determinant of rates of individual surface chemical reactions and overall rates of reductive dissolution. 

Transition metal oxide/hydroxides differ in their ability to oxidize organic compounds. Table I lists reduction potentials E° (for [H+]=[Me2+]=1.0M) and E (for [H+]=10 7M and [Me2+]=10 6m) for several first-row transition metals. 

Examples of electroactive NP materials discussed in the review include Ti02, Mn02, iron oxides, other metal oxides, hydroxides and oxyhydroxides and Prussian Blue. We use the term electroactive N Ps to refer to the faradaic electroactivity in such materials and to distinguish them from NPs comprised of metals (such as Au, Ag, Pt, Co, etc.) or semiconductors (such as CdS, CdSe, etc.). This distinction is based on the ability of many electroactive NPs to undergo faradaic oxidation or reduction of all of the metal (redox) centers in the NP. This is in contrast to the behavior of many metal and semiconductor NPs for which oxidation or reduction is fundamentally an interfacial, double-layer process. This deflnition is somewhat arbitrary, since the smallest metal and semiconductor NPs behave molecularly, blurring the distinction... 

We turn now to discussion of the specific types of electroactive NPs that have been described. The NPs are grouped according to the composition of the electroactive NP rather than the method of immobilization. In most cases, metal-oxide/ hydroxide/oxyhy dr oxides materials are grouped together using a formulation such as MO , to indicate the different compositions and redox states of the metals that may be described. 

Due to very high GHSV (>l(/h ), an extremely low limit of vapor pressure (<10 Pa) has been fixed as a rough criterion to match the 8000 h constraint of catalyst life in GT combustors [95]. Estimates made considering all the relevant species (metals, oxides, hydroxides, oxyhydroxides) under the oxidizing and water-containing atmosphere of GT combustors showed that Pd is able to match such a constraint up to about 1000 °C, whereas most other components (including Pt) fail [95]. 

Ligands of the NTA3" and EDTA4 type (complexones or sequestering agents, as they are sometimes called) are often able to dissolve deposits of metal oxides, hydroxides, sulfides, and carbonates because they displace solubility equilibria such as reaction 13.13 to the right by reducing the free... 

Alkali leach methods axe exemplified by the Bayer process for the preparation of pure a-A C for electrolysis (Section 17.5) from the mineral bauxite. Bauxite consists mainly of a-AlO(OH) (diaspore) and/or 7-A10(0H) (boehmite), the difference between these being essentially that the oxygen atoms form hep and ccp arrays, respectively. The chief contaminants are silica, some clay minerals, and iron(III) oxides/hydroxides, which impart a red-brown color to the mineral. Aluminum (III) is much more soluble than iron(III) or aluminosilicates in alkali, so that it can be leached out with aqueous NaOH (initially 10-15 mol L 1) at 165 °C under approximately 0.6 MPa pressure, leaving a red mud of iron (and other transition metal) oxides/hydroxides and aluminosilicates ... 

The role of transition metal oxide/hydroxide minerals such as Fe and Mn oxides in redox reactions in soils and aqueous sediments is pronounced (Stumm and Morgan, 1980 Oscarson et al., 1981a). These oxides occur widely as suspended particles in surface waters and as coatings on soils and sediments (Taylor and McKenzie, 1966). 

Reductive dissolution of transition metal oxide/hydroxide minerals can be enhanced by both organic and inorganic reductants (Stone, 1986). There are numerous examples of natural and xenobiotic organic compounds that are efficient reducers of oxides and hydroxides. Organic reductants associated with carboxyl, carbonyl, phenolic, and alcoholic functional groups of soil humic materials are one example. However, large... 

Koppers Process (44). In the Koppers "Book Keeper" process, the books are treated with submicron particles of basic metal oxides, hydroxides, or salts of calcium, magnesium, or zinc. The particles can be applied in the paper making process or to the finished paper by electrostatic transfer such as in a xerographic process, by a dispersion in a gas, or by a suspension in an inert liquid. In the case of a liquid suspension of the particles, the liquids chosen are halogenated hydrocarbons. Typical liquids include Dupont Freon Fluorocarbons such as Freon 11 (trichloromonofluoromethane),... 

Koppers "Book Keeping" Process. In view of the limitation of the Wei T o process, chemists at the Koppers Company developed a "Book Keeper" process by dispersing submicron particles of basic metal oxides, hydroxides or salts of calcium, magnesium, or zinc, in a suitable gas such as Freon or liquid medium, so that the active chemicals can be transferred and deposited electrostatically on the surface of paper. It also does not require pre-drying of books as is required for both the DEZ and Wei T o processes. The testing results appear satisfactory as shown in Table I. The major concern with this process is the distribution of the alkaline reserve on the paper. It appears the process deposits alkaline chemicals on the surface of paper and achieves surface deacidification. However, acid formed in the core of the paper is not neutralized. Koppers intends to prove the degrees of chemical penetration and neutralization of acid in the center layers by examination of the cross-section of paper by SEM. 

Metals are subject to electrochemical corrosion in the presence of water Metal atoms lose electrons to become positively charged metal ions that go into solution. These then react with other chemical species in the soil ground-water to form solid corrosion products (e.g., metal oxides, hydroxides, sulfates). It is these solid corrosion products that often form a colored matrix with soil particles around the corroding object (Cronyn 1990). The initial formation of the metal ions takes place at a site on the metal known as the anode, whereas the electrons produced consumed by another reaction with an electron acceptor (the cathode). Due to the electrical conductivity of metals the location of the anode and cathode can be at different locations on the metal surface. In the presence of water and oxygen the cathodic reaction is... 

---