The Effect of Nickel on the Conversion of Amorphous Iron(III) Hydroxide into more Crystalline Iron Oxides in Alkaline Media

2007 ◽  
Vol 53 (1) ◽  
pp. 73-79 ◽  
Author(s):  
R. M. Cornell ◽  
W. Schneider ◽  
R. Giovanoli
Keyword(s):  
Iron Oxides ◽  
Alkaline Media ◽  
Amorphous Iron

Balneaves: Soil Thin Sections

1992 ◽  
Vol 58 (S2) ◽  
pp. 23-25
Author(s):  
Donald Davidson
Keyword(s):  
Iron Oxides ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Random Pattern ◽  
Medium Sand ◽  
Thin Sections ◽  
Amorphous Iron ◽  
Channel Pattern ◽  
Mineral Components ◽  
Quartz Grains

1. Structure: partially accommodated channels (0.16 to 0.80mm in width) above the pan; no aggregates; fewer channels below the pan; channel pattern - straight to curved; vughs (spherical to elongate, not normally connected) 0.4 to 0.8mm in diameter and are not orientated and have random pattern: above pan channels and vughs partially connected; pellicular grain microstructure - weakly developed.2. Mineral components: coarse fraction: quartz grains range in size from silt to fine/medium sand (<lmm). One large quartz (200mm). Dominance of single and compound quartz grains; instances of biotite and plagioclase; quartz grains -angular/subangular and smooth. Fine fraction: brown, optically amorphous iron oxides, isotropic.

Tritium exchange studies on metal oxide colloidal dispersions

1977 ◽  
Vol 30 (8) ◽  
pp. 1655 ◽  
Author(s):  
DE Yates ◽  
F Grieser ◽  
R Cooper ◽  
TW Healy
Keyword(s):  
Crystal Structure ◽  
Heat Treatment ◽  
Iron Oxide ◽  
Metal Oxide ◽  
Iron Oxides ◽  
Colloidal Dispersions ◽  
Water Interface ◽  
Amorphous Iron ◽  
Tio2 Rutile ◽  
Exchange Technique

The tritium exchange technique has been used to detemine the maximum number of surface protons at the oxide-water interface for oxide colloids including silicas, TiO2 (rutile) and the iron oxides goethite, hematite and amorphous iron oxide. The effects of heat treatment, crystal structure and exchange conditions are considered and tritium exchange values for the number of surface protons are compared with values calculated from crystal structures.

Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources

2008 ◽  
Vol 59 (9) ◽  
pp. 780 ◽  
Author(s):  
Julia A. Howitt ◽  
Darren S. Baldwin ◽  
Gavin N. Rees ◽  
Barry T. Hart
Keyword(s):  
Organic Matter ◽  
Iron Oxide ◽  
Dissolved Organic Matter ◽  
Iron Oxides ◽  
Photochemical Reactions ◽  
Oxbow Lake ◽  
Photochemical Degradation ◽  
Fluorescence Excitation ◽  
Amorphous Iron ◽  
Leaf Leachate

Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.

THE EFFECTS OF ORGANIC MATTER, IRON OXIDES AND MOISTURE ON THE COLOR OF TWO AGRICULTURAL SOILS OF QUEBEC

1979 ◽  
Vol 59 (2) ◽  
pp. 191-202 ◽  
Author(s):  
S. CHOMCHAN ◽  
R. G. LEGER ◽  
G. J. F. MILLETTE
Keyword(s):  
Organic Matter ◽  
Iron Oxide ◽  
Iron Oxides ◽  
Agricultural Soils ◽  
Area Ratio ◽  
Oxide Coatings ◽  
Soil Color ◽  
Amorphous Iron ◽  
Reflectance Curve ◽  
Iron Oxide Coatings

A new spectrophotometric interpretation of the influence of organic matter, iron oxides and moisture on the soil color of the Ste-Sophie sand and the Ste-Rosalie clay is reported. The method is based on calculation of the area ratio of the reflected (area under the reflectance curve) against the absorbed (area over the reflectance curve). The higher the ratio the lighter is the soil. After treatment to remove organic matter and iron oxide coatings, both soils presented colors significantly lighter than those observed in untreated soils. Organic matter and amorphous iron oxide contributed for 78% and 64% of the color in the Ste-Sophie sand and in the Ste-Rosalie clay, respectively. Moisture tends to mask the effects of organic matter and iron oxides on soil color. Air-dried soils when compared to moistened soils were lighter in color.

scholarly journals Selectivity of Mixed Iron-Cobalt Spinels Deposited on a N,S-Doped Mesoporous Carbon Support in the Oxygen Reduction Reaction in Alkaline Media

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 820
Author(s):  
Aldona Kostuch ◽  
Joanna Gryboś ◽  
Szymon Wierzbicki ◽  
Zbigniew Sojka ◽  
Krzysztof Kruczała
Keyword(s):  
Phase Composition ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Iron Oxides ◽  
Mesoporous Carbon ◽  
Carbon Support ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Iron Cobalt ◽  
Cobalt Spinel

One of the practical efforts in the development of oxygen reduction reaction (ORR) catalysts applicable to fuel cells and metal-air batteries is focused on reducing the cost of the catalysts production. Herein, we have examined the ORR performance of cheap, non-noble metal based catalysts comprised of nanosized mixed Fe-Co spinels deposited on N,S-doped mesoporous carbon support (N,S-MPC). The effect of the chemical and phase composition of the active phase on the selectivity of catalysts in the ORR process in alkaline media was elucidated by changing the iron content. The synthesized materials were thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). Detailed S/TEM/EDX and Raman analysis of the phase composition of the synthesized ORR catalysts revealed that the dominant mixed iron-cobalt spinel is accompanied by minor fractions of bare cobalt and highly dispersed spurious iron oxides (Fe2O3 and Fe3O4). The contribution of individual phases and their degree of agglomeration on the carbon support directly influence the selectivity of the obtained catalysts. It was found that the mixed iron-cobalt spinel single phase gives rise to significant improvement of the catalyst selectivity towards the desired 4e− reaction pathway, in comparison to the reference bare cobalt spinel, whereas spurious iron oxides play a negative role for the catalyst selectivity.

scholarly journals Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

2019 ◽  
Author(s):  
Alexander I. Malov ◽  
Sergey B. Zykov
Keyword(s):  
Iron Oxides ◽  
Extraction Procedure ◽  
Retardation Factor ◽  
Uranium Isotopes ◽  
Iron Hydroxides ◽  
Carbonate Minerals ◽  
Amorphous Iron ◽  
Mineral Phases ◽  
Clay Deposits ◽  
Total Digestion

A partial extraction procedure was used to study the distribution of uranium in the mineral phases of rocks of an aquifer of sandy-clay deposits of the Vendian in the northwest of Russia. This work is a part of a research project to develop a method for combined radiocarbon and uranium-isotope dating of groundwater. Representative aliquots of each core sample were subjected to five "partial" extractions by treatment with: distilled water, low mineralized fresh natural groundwater, minopolycarboxylic acid chelating agent (0.05M EDTA), 0.5M HCl, 15M HNO3, and a total digestion, with U isotopes reported in this study for each procedure. The following mineral phases of core samples: adsorbed material, carbonate minerals, amorphous iron oxides, aluminosilicates partial digestion and a crystalline iron oxides, aluminosilicates total digestion and a clay/quartz resistate were characterized. Red-colored siltstones depleted in uranium in relatively readily soluble mineral phases. The concentration of adsorbed uranium was established in the amount of 15.8&plusmn;2.1 - 30.5&plusmn;3.9 &mu;g/kg. Carbonate minerals contain even less of this element. In iron hydroxides and the most readily soluble aluminosilicates, its concentrations are in the range 168&plusmn;24 - 212&plusmn;28 &mu;g/kg. The most insoluble fraction contains 1.65&plusmn;0.21 - 4.32&plusmn;0.45 mg/kg of uranium. In green-colored siltstones, the concentration of adsorbed uranium is much higher: 106&plusmn;14 - 364&plusmn;43 &mu;g/kg. Carbonate minerals and amorphous iron oxides contain 1.91&plusmn;0.21 - 2.34&plusmn;0.26 mg/kg of uranium. In aluminosilicates and a clay/quartz resistate, uranium concentrations are 5.6&plusmn;0.5 - 16.8&plusmn;1.4 mg/kg. Elevated values of 234U:238U activity ratio prevail in the adsorbed material and iron hydroxides. In aluminosilicates and clay/quartz resistate, the values decrease. This indicates the replacement of primary sedimentogenic uranium by secondary hydrogenic uranium adsorbed on the surface of minerals and coprecipitated with iron hydroxides. The results obtained made it possible to carry out preliminary quantitative estimates of the retardation factor and recoil loss factor of uranium in the groundwater of siltstones of the studied Vendian aquifer.

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