Manganese oxide colloidal

Manganese ions enzyme activators, 6,578 probes, 6,563 RNA polymerases activation, 6, 585 transport microbes, 6, 569 plants, 6, 572 Manganese oxide colloidal... 

The two higher energy electronic absorption bands of TAA-OL-1 are the result of quantum confinement effects that arise when the size of the particles becomes smaller than the electron-hole pair in the bulk semiconductor material. The large band-gap was corresponded to nano-particle sizes of manganese oxide. TEM images of 0,1 M TAA manganese oxide colloids were obtained [33, 34]. The particle sizes are between 30 100 nm. 

In the case of iron and manganese, most of these metals are removed from the hydrothermal fluids and converted to particulate form close to their point of entry. Some of these removals are in the form of sulfides, which fc>rm as the fluids emerge into the deep sea. The rest occurs as the fluids mix with cold, oxic, alkaline seawater, which promotes the oxidation of reduced metals. Thus, Fe (aq) and Mn (aq) are transformed into insoluble iron and manganese oxides, forming colloids and particles, the latter of which eventually settle onto the sediments. As described in the next chapter, at least some of these oxidation reactions are biologically mediated. Some of... 

The Adsorption of Aqueous Metal on Colloidal Hydrous Manganese Oxide... 

T he ability of colloidal, hydrous manganese oxides to adsorb large quantities of aqueous metal ions has been a continuing subject of study since van Bemmelen s work of 1881 (5). While certain aspects of the subject have been well established—e.g., hydrogen ions are released (or hydroxide ions adsorbed) in proportion to the quantity of metal ion adsorbed (11)—there is still confusion as to the details of the mechanism of ion adsorption. 

Cheney, M.A., J.Y. Shin, D.E. Crowley, S. Alvey, N. Malengreau, and G. Sposito (1998). Atrazine dealkylation on a manganese oxide surface. Colloid. Surf., A Physicochem. Eng. Aspects, 137 267-273. 

The most likely sources of metal ions for marine organisms are the colloidal or particulate moieties such as plankton, organic detritus, and clay minerals. The latter may be coated with iron or manganese oxides which are efficient scavengers of metals in slightly alkaline media. 

Stable colloids of nanometer-sized lamellar manganese oxides have been prepared by intercalation and self-assembly direct reduction methods. The structures, particle sizes, and optical properties of the materials have been described. Organic amine/ammonium species (TAA and DA) were used to intercalate birnessite H-OL-1 to prepare TAA-OL-1. Many kinds of structures and their formation processes were also described. The effects of organic ammonium cations and organic amines on the preparation of the manganese oxides were studied systematically. 

The UV-vis spectra of the colloids/sols of TAA-OL-1 and DA-OL-1 diluted to concentrations of 10 10 moH" manganese were measured. One strong absorption band centered at 368 nm and one weak absorption band centered at 216 nm were found for TMA-OL-1 colloids. Based on the Beer-Lambert law, the molar absorption coefficients of TMA-OL-1 colloids with Mn concentrations of 3.60 x 10 moi r were 2.41 x lo" M cm" and 1.89 x lO" M cm for the two absorption bands centered at 368 nm and 216 nm, respectively. Similar results were found for the other TAA-OL-l colloids. The molar absorption coefffcients of TAA-OL-1 colloids bectune smaller along with the longer alkyl chain TAA species intercalated into OL-1 layers. These results are similar to those of TAA manganese oxides reduced from TAA permanganate, whose UV-vis absorption peaks shift from lower to higher... 

Waite, T. D., Wrigley, I. C., and Szymczak, R. (1988) Photoassisted Dissolution of a Colloidal Manganese Oxide in the Presence of Fulvic Acid, Environ. Sci. Technol. 22, 778. 

Sienna, consisting mainly of a mixture of finely crystalline goethite and colloidal silica (Fc203 content ca. 50%), has translucent (semi-transparent) properties and as a result is particularly important in artists paints and other special fields. Raw sienna has a brown-yellow hue due its manganese oxide content (up to 1%), which changes to bright red-brown upon burning. 

Trivedi, P., and Axe, L. (1999). A comparison of strontium sorption to hydrous aluminum, iron, and manganese oxides. J. Colloid Interface Sci. 218, 554-563. 

Waite, T.D., I.C. Wrigley, and R. Szymczak. 1988. Photoassisted dissolution of a colloidal manganese oxide in the presence of fulvic acid. Environ. Sci. Technol, 22 778-785. 

Manceau A., and L. Charlet. 1992. X-ray absorption spectroscopic study of the sorption of chromium(III) at the oxide-water interface. I. Molecular mechanism of Cr(III) oxidation on manganese oxides. J. Colloid Interf. Sci. 148 425-429. 

In natural systems microbiological oxidation may offer a faster pathway, particularly at pH < 8 and low concentrations (<5 jlM) of particulate oxides. Hastings and Emerson (17) showed that sporulated cultures of marine bacillus SG-1 at pH 7.5 accelerated the oxidation of Mn(II) by a factor of 104 with respect to the abiotic catalysis on a colloidal MnOz surface. A radiotracer study of microbial Mn oxidation in a marine fjord revealed half-lives as short as 2 days (18). Perhaps microorganisms can use the entire redox cycle of manganese. A study indicates that the vegetative cells of spores that mediate Mn(II) oxidation also reduce manganese oxides (19). 

Perhaps the most comprehensive explanation of the role of hydrogenetic and diagenetic processes on manganese nodule accretion has been presented by Dymondetal (1984). On their classification, hydrogenous deposition involves the direct precipitation or accumulation of colloidal metals oxides from seawater. Strictly, this involves deposition of manganese oxides on surfaces in contact with seawater such as involved in the formation of manganese crusts. In practice, manganese nodules formed on red clays have charac-... 

Axe L, Tyson T, Trivedi P, Morrison T (2000) Local structure analysis of strontium to hydrous manganese oxide. J Colloid Interface Sci 224 408-416... 

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