Manganese oxide, adsorption hydrous

The most general feature of the adsorption behavior of metal ions at solid-aqueous solution interfaces is the abrupt rise in adsorption over a narrow pH range. This has been illustrated, for example, for manganese adsorption on glass (2), cobalt on hydrous ferric oxide (8), manganese on hydrous manganese oxide (12), protactinium on glass (14), and... 

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. 

The present study was initiated in order to obtain quantitative data on the relative adsorption potentials of metal ions in the region of the z.p.c. of hydrous manganese oxide. This information is of considerable importance in a variety of practical phenomena ranging from the mechanism of trace metal inclusion in ocean-floor manganese nodules and pisolitic manganese ores to the sorption behavior of manganese precipitates in natural water and waste systems. 

The adsorption of diphenylmercury (DPM) and phenylmercuric ion (PM) was studied on the solid phases described above (hydrous manganese oxides, amorphous iron oxides, humic acid and bentonite clay). The solid phase (5-15 mg) was added to 25-50 ml of filtered seawater yielding solid phase concentrations of approximately 100 to 400 ppm suspended matter. The concentration of seawater was also varied in order to study the variation of adsorptive behavior with changes in ionic strength. The suspension was then spiked with either DPM or PMA to yield concentrations of organometallic which varied from 0.10 to 3.5 ppm. The range in organometallic concentration used for this study was determined by the sensitivity of the detection method and the solubility of DPM and PMA in seawater. 

Adsorption and coprecipitation by hydrous iron and manganese oxides... 

Gadde. R.R. and Laitinen, H.A., Studies of heavy metal adsorption by hydrous iron and manganese oxides. Anal. Chem., 46, 2022, 1974. 

Lead enters surface water from atmospheric fallout, run-off, or wastewater. Little lead is transferred from natural minerals or leached from soil. Pb ", the stable ionic species of lead, forms complexes of low solubility with major anions in the natural environment such as the hydroxide, carbonate, sulfide, and sulfate ions, which limit solubility. Organolead complexes are formed with humic materials, which maintain lead in a bound form even at low pH. Lead is effectively removed from the water column to the sediment by adsorption to organic matter and clay minerals, precipitation as insoluble salt (the carbonate, sulfate, or sulfide) and reaction with hydrous iron, aluminum, and manganese oxides. Lead does not appear to bioconcentrate significantly in fish but does in some shellfish such as mussels. When released to the atmosphere, lead will generally occur as particulate matter and will be subject to gravitational settling. Transformation to oxides and carbonates may also occur. 

T-H Hsia, S-L Lo, C-F Lin, D-Y Lee. Characterization of arsenate adsorption on hydrous iron oxide using chemical and physical methods. CoU Surf 85 1-7, 1994. RB Robinson, GD Reed, B Frazier. Iron and manganese sequestration facilities using sodium silicate. J Am Water Works Assoc 84 77-82, 1992. 

The number of studies which utilize ionic liquid electrol54e in redox capacitor system is still small, probably due to the difficulty to reproduce the pseudo-capacitive reaction in ionic liquid media. While the principle of pseudo-capacitance of conductive polymer electrodes permits to utilize ionic liquid electrolytes, high viscosity and rather inactive ions of ionic liquid may make their pseudo-capacitive reaction slow. The combination of nanostmctured conductive polymer electrode and ionic liquid electrolyte is expected to be effective [27]. It is far difficult that ionic liquids are utilized in transition metal-based redox capacitors where proton frequently participates in the reaction mechanisms. Some anions such as thiocyanate have been reported to provide pseudo-capacitance of manganese oxide [28]. The pseudo-capacitance of hydrous ruthenium oxide is based on the adsorption of proton on the electrode surface and thus requires proton in electrolyte. Therefore ionic liquids having proton have been attempted to be utilized with ruthenium oxide electrode [29]. Recent report that 1,3-substituted imidazolium cations such as EMI promote pseudo-capacitive reaction of mthenium oxide is interesting on the viewpoint of the establishment of the pseudo-capacitive system based on chemical nature of ionic liquids [30]. 

In Skirmer, H.G.W. Fitzpatrick, R.W. (eds.) Biomineralization processes of iron and manganese. Catena Verlag, Cremhngen-Destedt, Catena Suppl. 21 75—99 Ghoneimy, H.F. Morcos.T.N. Misak, N.Z. (1997) Adsorption of Co and Zn ions on hydrous Fe(lll), Sn(lV) and mixed Fe(lll)/ Sn(IV) oxides. Part 1. Characteristics of the hydrous oxides, apparent capacity and some equilibria measurements. Colloids Surfaces A. 122 13-26... 

Arsenic is most prone to form surface complexes by adsorption on metal (mostly iron and manganese) (oxy)(hydr)oxides, followed by clays and feldspars (Lin and Puls, 2003). As discussed in Chapters 3 and 7, iron (oxy)(hydr)oxides are groups of Fe(III) Fe(II) (hydrous) oxides, (hydrous) hydroxides, and (hydrous) oxyhydroxides. Individual compounds, such as ferrihydrite, often have highly variable and... 

Finally, finely divided hydrous oxides of iron, aluminum, manganese, and silicon are the dominant sorbents in nature because they are common in soils and rivers, where they tend to coat other particles. This is the reason why numerous laboratory researchers have been studying the uptake of trace elements by adsorption on hydrous oxides (Dzomback and Morel, 1990). Partition coefficients (concentration in solid/concentration in the solution) for a number of trace elements and a great variety of surfaces have been determined. The comparison of these experimental with natural values should give information on the nature of the material on which trace elements adsorb in namral systems and allow quantitative modeling. 

Reprecipitation A drastic but effective way to minimize the effects of adsorption is reprecipitation. In this process, the filtered solid is redissolved and reprecipitated. The first precipitate ordinarily carries down only a fraction of the contaminant present in the original solvent. Thus, the solution containing the redissolved precipitate has a significantly lower contaminant concentration than the original, and even less adsorption occurs during the second precipitation. Reprecipitation adds substantially to the time required for an analysis but is often necessary for such precipitates as the hydrous oxides of iron(III) and aluminum, which have extraordinary tendencies to adsorb the hydroxides of heavy-metal cations such as zinc, cadmium, and manganese. 

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). 

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