Surface analysis and the adsorption of Co(II) on goethite

Schenck, Catherine V.; Dillard, John G.; Murray, James

doi:10.1016/0021-9797(83)90199-6

Cited by 263 publications

(159 citation statements)

References 24 publications

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“…The Co 2p spectra of the samples Co, MnCo50, MnCo and CoMn are rather similar ( Figure S2); they consist of a Co 2p 3/2 signal at a binding energy of 780.3 eV, which is associated with the presence of Co (III). 72,73 The quantitative analysis of the O 1s peak associated with Co agrees with the presence of CoOOH or Co(OH) 2 in the outer part of the aggregates and Co 3 O 4 in the inner part. The oxygen atomic percentage of the oxide-deposited samples (>35%) is higher than that of bare CC (22.5%) (Table II); it suggests that the Mn oxide and/or Co one are attached to the carbon fibers through oxygen bonding.…”

Section: Resultssupporting

confidence: 61%

Composite Electrodes Made from Carbon Cloth as Supercapacitor Material and Manganese and Cobalt Oxide as Battery One

Aldama

Barranco

Centeno

et al. 2016

J. Electrochem. Soc.

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Mn oxide and/or Co oxide are deposited on flexible carbon cloth by a cathodic potentiodynamic procedure from their respective sulfates. In KOH electrolyte, the charge stored from reversible redox reactions of the two oxides (battery response) overlaps with the charge stored from the double layer of the carbon cloth (supercapacitor response). These charges or capacities are compared. For the electrodes having one oxide only, either Mn or Co oxide, the highest capacity is obtained for 8 wt% oxide load. To overcome this limitation, both Mn and Co oxide are simultaneously or sequentially electrodeposited on carbon cloth over a broad compositional range. The electrode capacity can reach 71 mA · h · g −1 or 0.9 mA · h · cm −2 , which are higher than the values found for the bare carbon cloth. The electrode capacity depends on the relative content of the carbon cloth and the two deposited oxides according to the rule of mixtures. The decrease of the specific surface area of the carbon cloth is discussed in relation to the deposited oxide. The high capacity retention vs current is due to the contribution of the carbon cloth substrate. The electrode cycle life is discussed on the basis of the supercapacitor response and battery one.

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Section: Resultssupporting

confidence: 61%

Composite Electrodes Made from Carbon Cloth as Supercapacitor Material and Manganese and Cobalt Oxide as Battery One

Aldama

Barranco

Centeno

et al. 2016

J. Electrochem. Soc.

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“…In a series of investigations, metal ions (Co(II), Ni(II), Cr(III), Fe(III)) sorbed to clays and oxides (kaolinite, illite, chlorite, goethite) as a function of increasing pH were studied by XPS Dillard, 1975, 1977;Koppelman et al, 1980;Dillard and Koppelman, 1982;Schenk et al, 1983). Based on changes in binding energies and peak intensities, these studies concluded that the bonding environment of the metal cation becomes "more ionic" with increasing pH.…”

Section: Spectroscopic Studies Of Sorbed Metal Ionsmentioning

confidence: 99%

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

O’Day

Parks

Brown

1994

Clays and clay miner.

127

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Abstract--X-ray absorption spectroscopy (XAS) was used to determine the local molecular environment of Co(II) surface complexes sorbed on three different kaolinites at ambient temperature and pressure in contact with an aqueous solution. Interatomic distances and types and numbers of backscattering atoms have been derived from analysis of the extended X-ray absorption fine structure (EXAFS). These data show that, at the lowest amounts of Co uptake on kaolinite (0.20--0.32 ~mol m-2), Co is surrounded by ~60 atoms at 2.04-2.08 A and a small number orAl or Si atoms (N = 0.6-1.5) at two distinct distances, 2.67-2.72 A and 3.38-3.43/~. These results indicate that Co bonds to the kaolinite surface as octahedrally coordinated, bidentate inner-sphere mononuclear complexes at low surface coverages, confirming indirect evidence from solution studies that a fraction of sorbed Co forms strongly bound complexes on kaolinite. In addition to inner-sphere complexes identified by EXAFS spectroscopy, solution studies provide evidence for the presence of weakly bound, outer-sphere Co complexes that cannot be detected directly by EXAFS. One orientation for inner-sphere complexes indicated by XAS is bidentate bonding of Co to oxygen atoms at two A1-O-Si edge sites or an A1-O-Si and AI-OH (inner hydroxyl) edge site, i.e., comersharing between Co octahedra and AI and Si potyhedra. At slightly higher surface sorption densities (0.51-0.57/~mol m-2), the presence of a small number of second-neighbor Co atoms (average Nco < 1) at 3.10-3.13/~ indicates the formation of oxy-or hydroxy-bridged, multinuclear surface complexes in addition to mononuclear complexes. At these surface coverages, Co-Co and Co-AI/Si distances derived from EXAFS are consistent with edge-sharing between Co and AI octahedra on either edges or (001) faces of the aluminol sheet in kaolinite. Multinuclear complexes form on kaolinite at low surface sorption densities equivalent to < 5% coverage by a monolayer of oxygen-ligated Co octahedra over the N2-BET surface area. These spectroscopic results have several implications for macroscopic modeling of metal ion uptake on kaolinite: 1) Primary binding sites on the kaolinite surface at low uptake are edge, non-bridging AI-OH inner hydroxyl sites and edge AI-O-Si bridging oxygen sites, not Si-OH sites typically assumed in sorption models; 2) specific adsorption of Co is via bidentate, inner-sphere complexation; and 3) at slightly higher uptake but still a small fraction of monolayer coverage, formation of Co multinuclear complexes, primarily edge-sharing with A1-OH octahedra, begins to dominate sorption.

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“…The discrepancy between the sorption being unaffected and the extraction behaviour being affected by oxygen is hard to explain. Oxidation of Co(II) to Co(III) to form CoOOH as suggested by Schenck et al (1983) could explain the lower extractability from samples exposed to oxygen but this would certainly be reflected in differences between the sorption curves. Thus the different extraction behaviour depending on the presence and absence of oxygen may simply be due to experimental error.…”

Section: Cobalt Retentionmentioning

confidence: 99%

Retention of Cobalt by Pure and Foreign-Element Associated Goethites

Bibak¹,

Gerth

Borggaard³

1995

Clays and clay miner.

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Abstract--Retention studies of the cobalt-goethite system were carried out using synthetic, star-shaped and lath-shaped pure, AI-, Cd-, Cu-and Si-associated goethites. Aluminium and Si are commonly occurring foreign elements in natural goethites. The goethites were prepared by coprecipitating Fe and the foreign element under controlled conditions and characterized by X-ray diffraction, transmission electron microscopy, specific surface area determination and 2 M HC1 extraction. The foreign-element associated goethites contained ~3, ~5 and ~9 mole % A1, ~4 mole % Cd and ~3 mole % Cu incorporated by isomorphous substitution but only ~0.4 mole % of probably occluded Si. Crystal size and shape but also number of defects and domains, and hence specific surface area, unit-cell dimensions and reactivity towards 2 M HC1, exhibited great variability among the goethites. Accordingly the amounts of Co sorbed from initially 10 -7 M Co in 0.1 M Ca(NO3)2 in relation to pH (3-8) and reaction time (2-504 h) were very different for the eight gnethites. The affinity of Co is highest for Cd-and lowest for Cu-gnethite. These samples also form the extremes regarding time-dependent sorption with Cu-goethite showing the smallest and Cd-goethite the largest increase in sorption with increasing reaction time. The Co uptake was not caused by precipitation Co(III) oxides due to Co(II) oxidation, since oxygen exclusion during sorption had no effect on the amount of Co sorbed. The amounts of sorbed Co extracted by 2 M HC1 decreased with increasing sorption time but 40--87% of sorbed Co remained unextracted after 48 h, most in Cu-goethite and least in lath-shaped pure goethite. The strong retention suggests Co uptake by diffusion into micropores and fissures resulting from structural defects and intergrowths. The diffusion coefficients range from 3.10-19 to 6.10 -17 cm2/s with the highest values for A1-and Si-associated gnethites emphasizing the importance for Co immobilization, and hence availability, of foreign-element associations in goethite.

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Surface analysis and the adsorption of Co(II) on goethite

Cited by 263 publications

References 24 publications

Composite Electrodes Made from Carbon Cloth as Supercapacitor Material and Manganese and Cobalt Oxide as Battery One

Composite Electrodes Made from Carbon Cloth as Supercapacitor Material and Manganese and Cobalt Oxide as Battery One

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

Retention of Cobalt by Pure and Foreign-Element Associated Goethites

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