Mn ?. oxidation

Hydrogenation. Gas-phase catalytic hydrogenation of succinic anhydride yields y-butyrolactone [96-48-0] (GBL), tetrahydrofiiran [109-99-9] (THF), 1,4-butanediol (BDO), or a mixture of these products, depending on the experimental conditions. Catalysts mentioned in the Hterature include copper chromites with various additives (72), copper—zinc oxides with promoters (73—75), and mthenium (76). The same products are obtained by hquid-phase hydrogenation catalysts used include Pd with various modifiers on various carriers (77—80), Ru on C (81) or Ru complexes (82,83), Rh on C (79), Cu—Co—Mn oxides (84), Co—Ni—Re oxides (85), Cu—Ti oxides (86), Ca—Mo—Ni on diatomaceous earth (87), and Mo—Ba—Re oxides (88). Chemical reduction of succinic anhydride to GBL or THF can be performed with 2-propanol in the presence of Zr02 catalyst (89,90). 

In this work a novel five-step leaching scheme for HM has been developed addressing exchangeable, acid soluble (carbonate), easily reducible (bound to Mn oxides), easily oxidizable (bound to humic and fulvic acids), and moderately reducible (bound to amorphous Ee oxides) fractions extractable by 0.05 M Ca(N03), 0.43 M CH3COOH, 0.1 M NH,OH-HCl (non-acidified), 0.1 M K/,03 (pH 11), and 0.1 M (NH4),C,04 (pH 3), respectively. The sequence of extractants was chosen according to recent studies on the selectivity of leachants toward dissolved phases of soils. 

The destruction and removal of trichloroethylene (TCE) by reaction with OXITOX , (sodium carbonate activated by Mg and Mn oxides and carbonates), proceeds through the following stoichiometric reaction ... 

Figure 15-12 is a schematic illustration of a technique known as acid volatile sulfides/ simultaneously extracted metals analysis (AVS/SEM). Briefly, a strong acid is added to a sediment sample to release the sediment-associated sulfides, acid volatile sulfides, which are analyzed by a cold-acid purge-and-trap technique (e.g., Allen et ai, 1993). The assumption shown in Fig. 15-12 is that the sulfides are present in the sediments in the form of either FeS or MeS (a metal sulfide). In a parallel analysis, metals simultaneously released with the sulfides (the simultaneously extracted metals) are also quantified, for example, by graphite furnace atomic absorption spectrometry. Metals released during the acid attack are considered to be associated with the phases operationally defined as "exchangeable," "carbonate," "Fe and Mn oxides," "FeS," and "MeS."... 

While Fe- and Mn-oxides certainly are important in the binding and transport of the trace metals in the estuarine system, organic matter appears to play a dominant role in the coagulation step. For instance, adjustment of the solution pH to values where humics normally precipitate (pH = l to 3) causes all the components (Fe and Mn, organics, and trace metals) to coagulate into filterable particles. By contrast, adjustment of the pH upward, which would normally favor precipitation of Fe- and Mn-oxides, has no effect. In view of this it is not... 

MnSOt Milliequiv. chromic acid reduced Milliequiv. Mn oxidized Fi Fe IHzR] ... 

HCHO] (MX 10 ) Equiv. of Mn oxidized Equio. of HCHO oxidized Fi F, kuCHO ku i ... 

Several types of mineralizations, massive-type stockwork mineralization and a sulfide-bearing sediment layer were described (Halbach et al., 1989). The outer portion of the massive sulfide sample (late-stage) is composed of barite, realgar, orpiment, amorphous silica and hydrous Fe-Mn oxides, small amounts of sphalerite, galena and pyrite. The central portion consists mainly of sphalerite, pyrite and galena with small... 

Gamo (1995) showed that mFe/ Mn of hydrothermal solution from sediment-hosted hydrothermal site is high (Fig. 2.40). This suggests that Mn concentration of hydrothermal solution increased by the interaction with sediments (probably dissolution of Mn-oxides and hydroxides). 

Thorium is a highly insoluble element, mainly carried in the particulate form in river waters. This is well shown by Th data for the MacKenzie river (Vigier et al. 2001) and for the Kalix river (Andersson et al. 1995 Porcelli et al. 2001) in both cases, more than 95% of Th is carried by >0.45 pm particles. An important part of this Th is included within detrital material. This is illustrated by sequential extractions performed on sediments from the Witham river (Plater et al. 1992), which show the very low amount of Th in ion-exchangeable and organic-bound fractions compared to Th in Fe-Mn oxides... 

Strong adsorption on Fe and Mn oxides and hydrous oxides Precipitation... 

A change in redox conditions (lower Eh) can partly or completely dissolve Fe and Mn oxides and liberate other coprecipitated metals. 

Arsenite can be oxidized by manganese dioxides in soils. The rate constants for the depletion of As(III) by bimessite and cryptomelane are much higher than those by pyrolusite due to the difference in the crystallinity and specific surfaces of the Mn oxides (Oscarson et al., 1983). The ability of the Mn dioxides to sorb As(III) and As(V) is related to the specific surface and the point-of-zero charge of the oxides. The one-to-one relationship between the amount of As(III) depleted and the amount of As(V) appearing in solution was reported by Oscarson and colleagues (1983). 

Soluble Exchangeable Carbonate Fe/Mn oxides Organically Residual... 

Grossman and Millet (1961) found that the free Fe-oxide concentration in noncalcareous soils was unchanged after contact with this buffer for nine weeks. Other researchers have shown that acetic acid at a concentration of 2.5% and pH 2.5 led to a partial attack of Fe and Mn oxides (Nissenbaum, 1972 Mclaren and Crawford, 1973 Tessier et al., 1979). Tessier et al. (1979) also indicated that this buffer solution at pH 5.0 was minimal in the attack of silicate minerals and sulfide. 

The cumulative sums of selected major and trace metals extracted by the two SSD procedures from representative arid-zone soils are shown in Fig. 4.6. As can be seen from the figure, the Rehovot procedure is stronger in attacking desired fractions, such as the carbonate bound, Mn oxide bound and organically bound fractions. Extraction of certain major elements, indicating selectivity, specificity and completeness of extraction of given soil components, was found to differ between the two procedures. Calcium and Mg were more completely extracted from the carbonate fraction in arid zone soils by the Rehovot procedure. Calcium and relevant trace elements bound in the carbonate fraction, which were not completely dissolved by the Bonn procedure at this step, were released at the following steps, such as the ERO, OM or RO fractions. 

Carbonate/Mobilizable, 3 Easily reducible oxide/Mn oxide, 4 Organic matter, 5 Reducible oxide/Fe oxide... 

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