Amorphous manganese hydroxide

Diphenyl Mercury Adsorption. Adsorption of DPM from seawater onto amorphous iron hydroxide, manganese oxide and bentonite clay was not detected in this study. A comparison of standard diphenyl mercury solutions in seawater with Identical solutions to which sediment phase had been added and shaken for 48 hours was routinely performed as part of the isotherm determination. There was no significant difference in the concentration of dissolved diphenyl mercury for standard. versus standard plus solid phase for any of the suspensions of amorphous, Fe(OH)-, MnO, or bentonite in seawater, implying no significant adsorption of DPM from seawater onto these phases under the concentrations studied. If lower concentrations of DPM could have been used (ppb or lower) it is possible that adsorption might have been detected. 

ELECTRON SPIN RESONANCE SPECTROSCOPY Electron spin resonance (ESR) is a technique that can also be used on aqueous samples and has been used to study the adsorption of copper, manganese, and chromium on aluminum oxides and hydroxides. Copper(II) was found to adsorb specifically on amorphous alumina and microcrystalline gibbsite forming at least one Cu-O-Al bond (McBride, 1982 McBride et al., 1984). Manganese(II) adsorbed on amorphous aluminum hydroxide was present as a hydrated outer-sphere surface complex (Micera et al., 1986). Electron spin resonance combined with electron spin-echo experiments revealed that chromium(III) was adsorbed as an outer-sphere surface complex on hydrous alumina that gradually converted to an inner-sphere surface complex over 14 days of reaction time (Karthein et al., 1991). 

Belzile, N., Chen, Y.W., Wang, Z.J., 2001. Oxidation of antimony (III) by amorphous iron and manganese oxy hydroxides. Chemical Geology, 174, 379-389. 

Oxy)(hydr)oxide compounds Nonsilicate, crystalline, or amorphous solids that contain oxide (O2-), hydroxide (OH-), or oxyhydroxide (OOH3-) as the major anion. Common cations include aluminum, iron(II), iron(III), or manganese. 

In natural anoxic environments, the major alternative oxidants are iron(III) and manga-nese(IV) oxides and hydroxides. Both are common in natural systems, as crystalline or amorphous particles or coatings on other particles. In the absence of photocatalysis, however, iron and manganese oxides are weak oxidants. As a result, they appear to react at significant rates only with phenols and anilines (45, 59-64). 

The iron hydroxide in manganese nodules cristallizes possibly as the mineral Goethite . The crystallization of Goethite is presumed to occur secondarily by drying and in the preparation of the manganese nodules. The primary iron hydroxide is amorphous. 

Hydrous manganese oxides and amorphous iron oxides were prepared in the laboratory according to the methods described by Oakley et al 3). The addition of manganese sulfate solution to a slightly basic potassium permanganate solution produces a suspension of hydrous MnO. A suspension of Fe(0H)2 is produced by simply adjusting a ferric nitrate solution to a pH of 8.0 with a dilute sodium hydroxide solution. Both suspensions were washed repeatedly with seawater and stored in seawater for several days. 

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