Specific adsorption of sulfamate ions at the mercury/solution interface

1982 ◽  
Vol 60 (13) ◽  
pp. 1643-1647 ◽  
Author(s):  
Ernesto R. Gonzalez
Keyword(s):  
Ionic Strength ◽  
Activity Coefficient ◽  
Double Layer ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Electrostatic Model ◽  
Solution Composition ◽  
Solution Interface ◽  
Double Layer Capacity ◽  
Mercury Electrodes

The adsorption of sulfamate ions on mercury electrodes has been studied by measuring the double layer capacity in constant ionic strength solutions of composition xM NH4SO3NH2 + (1−x)M NH4F. It was found that sulfamate ions are weakly adsorbed on mercury, the amount adsorbed being significant only for x > 0.1 at positive charges on the electrode. Because of this, the properties of the inner layer were found to be strongly dependent on the adsorbed water molecules and the structure of the diffuse layer. It was determined that the adsorption of sulfamate ions can be described by an isotherm based on the electrostatic model of the double layer. The possible effects of the activity coefficient variation with solution composition are discussed.

The influence of ionic strength on the adsorption of azide ions on mercury electrodes

1986 ◽  
Vol 64 (2) ◽  
pp. 413-418 ◽  
Author(s):  
Artur J. Motheo ◽  
Ernesto R. Gonzalez ◽  
Luis A. Avaca
Keyword(s):  
Ionic Strength ◽  
Adsorption Isotherm ◽  
Double Layer ◽  
Activity Coefficients ◽  
Constant Ionic Strength ◽  
Electrostatic Model ◽  
Solution Composition ◽  
Mercury Electrodes

The adsorption of azide ions on mercury electrodes has been studied from constant ionic strength solutions of composition χ M NaN3 + (μ–χ) M NaF with μ = 0.25 and 0.5. Double layer parameters were obtained by taking into account the change in activity coefficients with solution composition. The results were analyzed together with those reported previously for μ = 0.95, recalculated to take into account the change in activity coefficients. The influence of the ionic strength on the amount adsorbed, the properties of the inner layer, and the parameters of an adsorption isotherm for azide anions are discussed in terms of the electrostatic model of the double layer.

Restricted Rotational Motion of InterlayerWaterMolecules in Vanadium Pentoxide Hydrate, V2O5·n D2O, as Studied by Deuterium NMR

2002 ◽  
Vol 57 (6-7) ◽  
pp. 419-424 ◽  
Author(s):  
Sadamu Takeda ◽  
Yuko Gotoh ◽  
Goro Maruta ◽  
Shuichi Takahara ◽  
Shigeharu Kittaka
Keyword(s):  
Double Layer ◽  
Vanadium Pentoxide ◽  
Rotational Motion ◽  
Interlayer Space ◽  
Layer Structure ◽  
Bond Distance ◽  
Adsorbed Water ◽  
Deuterium Nmr ◽  
Water Molecules ◽  
Layer Structures

The rotational behavior of the interlayer water molecules of deuterated vanadium pentoxide hydrate, V2O5.nD2O, was studied by solid-state deuterium NMR for the mono- and double-layer structures of the adsorbed water molecules. The rotational motion was anisotropic even at 355 K for both the mono- and double-layer structures. The 180° flipping motion about the C2-symmetry axis of the water molecule and the rotation around the figure axis, which makes an angle Ɵ with the C2-axis, occurred with the activation energy of (34±4) and (49±6) kJmol-1, respectively. The activation energies were almost independent of the mono- and double-layer structures of the water molecules, but the angle Ɵ made by the two axes varied from 33° for the monolayer to 25° for the double-layer at 230 K. The angle started to decrease above 250 K (e. g. the angle was 17 at 355 K for the double-layer structure). The results indicate that the average orientation of the water molecules in the two dimensional interlayer space depends on the layer structure and on the temperature. From the deuterium NMR spectrum at 130 K, the quadrupole coupling constant e2Qq/h = 240 kHz and the asymmetry parameter η= 0.12 were deduced. These values indicate the average hydrogen bond distance R(O H) = 2.0 Å for the D2O molecules in the 2D-interlayer space

Some observations on the double layer capacity at mercury electrodes

1940 ◽  
Vol 35 ◽  
pp. 128 ◽  
Author(s):  
I. M. Barclay ◽  
J. A. V. Butler
Keyword(s):  
Double Layer ◽  
Double Layer Capacity ◽  
Mercury Electrodes

Ionic Properties of Vanadium Pentoxide Gels

1988 ◽  
Vol 121 ◽  
Author(s):  
J. Livage ◽  
P. Barboux ◽  
J. C. Badot ◽  
N. Baffier
Keyword(s):  
Vanadium Pentoxide ◽  
Water Adsorption ◽  
Mixed Valence ◽  
Adsorbed Water ◽  
Water Molecules ◽  
Proton Diffusion ◽  
Hydrous Oxides ◽  
Solution Interface ◽  
Ionic Devices ◽  
Acid Aqueous Medium

ABSTRACTVanadium pentoxide gels V2O5·nH2O are actually hydrous oxides. Water adsorption and dissociation occurs at the surface of the oxide leading to negatively charged oxide particles surrounded by an acid aqueous medium. Ionic conductivity is observed, arising from proton diffusion through the water molecules. This process mainly depends on the nature of adsorbed water molecules. Proton conductivity is strongly related to the water adsorption isotherm.Ion exchange readily occurs at the oxide-solution interface when the gel is dipped into an aqueous solution of a metal chloride. New vanadium bronzes have been obtained upon heating such gels around 300° C. They exhibit interesting properties as reversible cathodes.Electrochemical insertion of Li* into the gel phase is quite easy. This is due to the very open structure of the gel and the mixed valence behavior of the vanadium oxide.Transition metal oxide gels could then be used as thin films or pressed pellets for making micro-ionic devices.

scholarly journals The adsorption of vapours on mercury III. Polar substances

1947 ◽  
Vol 190 (1020) ◽  
pp. 117-137 ◽  
Keyword(s):  
Double Layer ◽  
Adsorbed Water ◽  
Liquid Films ◽  
Heat Of Adsorption ◽  
Water Molecules ◽  
Two Dimensional ◽  
Triple Layer ◽  
Adsorption Of Water ◽  
Multilayer Formation ◽  
Low Pressures

Water, acetone and the normal alcohols from methyl to hexyl have been adsorbed on mercury. All substances gave reversible adsorption and, with the exception of water, gaseous films were formed at low pressures. Methyl and ethyl alcohols showed the adsorption of a second layer at higher pressures, the double layer having half the co-area of the original monolayer. Actone gave rise to a double layer and finally a triple layer (with one-third of the original co-area). The property of multilayer formation was thought to be one of small partially polar molecules. For the gaseous films of n -butyl, n -amyl and n -hexyl alcohols the co-areas and the thermodynamic data indicated that the molecules were lying flat on the surface. These three substances showed two-dimensional condensation to liquid films at higher pressures. This phase change was accompanied by an increase of entropy which led to a decrease of the surface-vapour pressure with rise of temperature. The large entropy and heat of adsorption of water were taken as evidence for the association of the adsorbed water molecules and this probably occurred, to some extent, with methyl alcohol as well. The heat of adsorption of acetone was smaller than expected for a substance with a large dipole moment.

scholarly journals Study of polyacrylic acid adsorption on the interface of hydroxyapatite – electrolyte solutions

2013 ◽  
Vol 12 (3) ◽  
pp. 270-278
Keyword(s):  
Ionic Strength ◽  
Layer Thickness ◽  
Double Layer ◽  
Polyacrylic Acid ◽  
Electrolyte Solutions ◽  
Effect Of Temperature ◽  
Solution Composition ◽  
Ph Values ◽  
Adsorbed Amount ◽  
Double Layer Thickness

The adsorption of polyacrylic acid (PAA) on hydroxyapatite (HAP) from HAP saturated solutions was studied in this work as a function of PAA concentration, temperature, pH and ionic strength. In all experiments, the adsorption was studied under conditions of negatively charged adsorbent and adsorbate, respectively. These conditions ensured that adsorption was not electrostatically favored. The solution composition was found to influence significantly the maximum of the adsorbed amount. In fact, the adsorption of PAA, was found to increase with ionic strength, due to the decrease of double layer thickness of HAP particles. The effect of temperature and ionic strength on the kinetics of adsorption are also reported. Adsorption isotherms obtained at 30oC were found to be Langmuirtype, while at higher temperatures they were of the Brunauer-Emmett-Teller (BET) type. The absorbed amount of PAA was found to decrease with temperature, while it increased with ionic strength. For pH values lower than 6.5, the adsorption increased while for pH between 6.5 and 9 the adsorbed amount remained almost constant.

Adsorption and Condensation of Xanthine at the Mercury/Solution Interface

1998 ◽  
Vol 63 (12) ◽  
pp. 1977-1993 ◽  
Author(s):  
Viktor Dražan ◽  
Vladimír Vetterl
Keyword(s):  
Double Layer ◽  
Electrode Surface ◽  
Lattice Gas ◽  
Standard Gibbs Energy ◽  
Mercury Electrode ◽  
Ising Lattice ◽  
Compact Layer ◽  
Solution Interface ◽  
Double Layer Capacity ◽  
Lattice Gas Models

The adsorption and two-dimensional condensation of xanthine at the mercury electrode in 0.2 and 2 M NaCl was studied by electrode double layer capacity measurements. The condensation of xanthine molecules adsorbed at the electrode was observed at pH 6.0 and 7.4, but not at 9.0. The standard Gibbs energy of adsorption, energy of lateral interactions and the surface occupied by one xanthine molecule in a compact layer were calculated from the temperature dependence of the capacity pit using the Frumkin and Ising lattice gas models. The orientation of xanthine molecules in a compact layer at the electrode surface was estimated. At higher bulk concentrations of xanthine, the double layer capacity decreases to a very low value of about 1.5 mF cm-2, which might be an indication of the formation of a xanthine multilayer at the electrode surface.

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