Adsorption of aliphatic fatty acids on aquatic interfaces.  Comparison between two model surfaces:  the mercury electrode and δ -Al2O3 colloids

Ulrich, Hans Jakob; Stumm, Werner; Ćosović, Božena

doi:10.1021/es00166a002

Cited by 81 publications

(51 citation statements)

References 5 publications

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“…The sign of r is positive for suppression, but it is negative for promotive lateral interactions like the association of fatty acids adsorbed on mercury (27).…”

Section: The Frumkin Modelmentioning

confidence: 99%

“…Thus far, the actual r values determined have suggested the effect of a variety of factors in the lateral interactions. The factors include the size and hydration state of ions, association of hydrophobic molecules, internal surfaces of oxides such as pores, crevices, and flaws, polarization of surface complexes, nano-and macropore environments around carboxyl sites, and others (27,28,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51).…”

Section: The Frumkin Modelmentioning

confidence: 99%

“…10, and the [-O -・Na + ] term is omitted in Eq. [27]. and (1:2) exchange reactions [25] and [26] can be defined by the Frumkin model [1], like…”

Section: Materials Balancementioning

confidence: 99%

“…However, steric (geometric) hindrance is very likely to affect the adsorption of cations on metal oxide because small surface protons are replaced by larger cations (26). Further, for fatty acids adsorbed on mercury the promotive lateral interaction have been suggested to be due to 2-D association, to explain deviations from the Langmuir isotherm (27).…”

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confidence: 99%

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Theorization on ion-exchange equilibria: activity of species in 2-D phases

Tamura

2004

Journal of Colloid and Interface Science

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Ion-exchange reactions are naturally occurring at soil and sediment/water interphases, determining soil fertility and water quality. These ion-exchange reactions with inorganic and organic exchangers are applied to chemical analysis, recovery of useful ions from low grade ores (potentially from sea water), water purification including the preparation of "ultra-pure" water, production of foods and medicines, therapy, and others. It is important to theorize about or to model ion-exchange reactions for quantitative explanations of ion-exchange phenomena and for efficient operation of ion-exchange processes. This paper describes the modeling of ion-exchange equilibria for hydroxyl sites on metal oxides and carboxyl sites in resins with monovalent cations (alkali metal ions), a monovalent anion (nitrate ion), and divalent heavy metal ions. However, the lateral interactions are large because of a large polarization of the ion-site pairs. When the monovalent cations are dehydrated to react with carboxyl sites in narrow resin nanopores, the bond formation is difficult because energy for dehydration is necessary. The suppressive lateral interactions here are small because of a small polarization of the dehydrated ion-site pairs that are in direct contact. Divalent heavy metal ions react with oxide hydroxyl sites by replacing their hydrated water molecules and form ion-site pairs in direct strong contact (specific adsorption). The bond formation becomes easier with increasing charge density of the ions evaluated by the charge/radius ratio, agreeing with the order of these ions to form hydroxo complexes in solution.The suppressive lateral interaction is however small for ions with large charge densities, because a strong contact bond reduces the polarization of ion-site pairs by neutralization.The properties of exchangers are functions of the molecular and pore environments around the functional groups. The acid-base nature of oxide surface-hydroxyl groups is determined by the electronegativity of surrounding lattice metal ions, and that of resin carboxyl groups by the electron repelling effect of adjacent methyl groups. Pores in oxides have diameters sufficient to accommodate hydrated ions, and the suppression is large because of repulsion from ions adsorbed on opposite pore walls (across-pore interaction). Pores in resins differentiate ions that can access or not access sites on the internal surfaces of the pores. Narrow nanopores with diameters less than those of the hydrated ions require ions to dehydrate before they can enter. The ion-exchange reactivity here is small as described above for dehydrated monovalent ions. In wide nanopores where hydrated ions can enter, the bond formation is easier, but the suppression is larger because of a larger polarization of hydrated ion-site pairs and also of the across-pore interaction.Macropores have diameters much larger than those of the hydrated ions and the bond formation is the same as that in wide nanopores, but the suppression is smaller because of the absence of t...

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“…The sign of r is positive for suppression, but it is negative for promotive lateral interactions like the association of fatty acids adsorbed on mercury (27).…”

Section: The Frumkin Modelmentioning

confidence: 99%

Section: The Frumkin Modelmentioning

confidence: 99%

“…10, and the [-O -・Na + ] term is omitted in Eq. [27]. and (1:2) exchange reactions [25] and [26] can be defined by the Frumkin model [1], like…”

Section: Materials Balancementioning

confidence: 99%

mentioning

confidence: 99%

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Theorization on ion-exchange equilibria: activity of species in 2-D phases

Tamura

2004

Journal of Colloid and Interface Science

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“…Adsorption experiment with fatty acids with an increasing chain length showed good correlation between the adsorption constant B and the octanol/water coefficient, as a measure of the hydrophobic properties. 15 Generally, adsorption on the electrode is dependent on the concentration, but also on the applied potential. Adsorption experiment with sodium oleate, 16 using three dimensional phase sensitive ac voltammetry, showed that at moderate and negative polarization of mercury electrode for the bulk concentrations below critical micellar concentration (cmc= 2 x 10 -4 M at 25C), 16 sodium oleate formed a close-packed monolayer.…”

Section: Introductionmentioning

confidence: 99%

Fractal and Voltammetric Study of Linoleic Acid Adsorption at the Mercury/Electrolyte Solution Interface

2001

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A new method, size-scaling of the hanging mercury drop electrode, is introduced and used to determine the fractal properties of the adsorbed layer and its dependence on fractional electrode coverage. Simultaneously, the adsorption process of linoleic acid at a mercury electrode surface has been studied by means of phase-sensitive ac voltammetry in 0.5 M NaCl electrolyte solution, pH 8.3, simulating seawater conditions. Three concentration domains that exhibit different fractal behavior characterize the adsorption process. In the first domain, corresponding to the fractional electrode coverage  < 0.5, the fractal dimension of the adsorbed layer D  2. Further increase in surface concentration (electrode coverage) is followed by a swift change in fractal dimension, reaching the peak value D  2.4. This indicates that, at fractional electrode coverage of 0.7 -0.8, depending on adsorption conditions, a second order phase change in the adsorbed layer of linoleic acid takes place. In the third domain, the fractal dimension rapidly decreases to D  2.0 and remains stable regardless of bulk concentration increase, reflecting formation of a rather uniform and homogenous layer of perpendicularly oriented molecules of linoleic acid. The observed changes of fractal dimension are result of restructuring of the adsorbed layer and 2 a change in the orientation of adsorbed molecules due to molecular interactions.The influence of electrode polarity on the adsorption process of linoleic acid and fractal properties of the adsorbed layer is discussed. Comparison with the apparent isotherm, obtained in a classical voltammetric way, shows that the analysis of fractal properties of the adsorbed layer provides a useful tool for studies of the adsorption process and a sensitive method for detection of phase changes.

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Voltammetric Analysis of Surface Active Substances in Natural Seawater

Ćosović

Vojvodić

1998

Electroanalysis

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The electrochemical method based on the measurement of capacitance (out of phase signal) at the hanging mercury drop electrode by using alternating-current voltammetry has been employed for the analysis of surface active substances in seawater. Such determination is of a collective parameter, i.e., all present adsorbable substances take part in adsorption on the electrode in a competitive manner. Calibration problems, sample treatment and comparison of naturally occurring surface active substances with different model substances are discussed.

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Adsorption of aliphatic fatty acids on aquatic interfaces. Comparison between two model surfaces: the mercury electrode and δ -Al2O3 colloids

Cited by 81 publications

References 5 publications

Theorization on ion-exchange equilibria: activity of species in 2-D phases

Theorization on ion-exchange equilibria: activity of species in 2-D phases

Fractal and Voltammetric Study of Linoleic Acid Adsorption at the Mercury/Electrolyte Solution Interface

Voltammetric Analysis of Surface Active Substances in Natural Seawater

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