Showing papers on "Langmuir published in 1970"

Analysis of sorption isotherms of non-homogeneous sorbents

Abstract: A theoretical isotherm to predict sorption from the vapour phase for heterogeneous sorbents has been derived from thermodynamic considerations. The predicted isotherms is a composite curve comprised of component isotherms arising from three separate processes : (a) monolayer adsorption by strongly binding sites, (b) monolayer adsorption by weakly binding sites, and (c) formation of a multilayer the extent of which is limited by the properties of the substrate. Components (a) and (b) have the form of Langmuir isotherms for monolayer adsorption at surfaces while component (c) describing the formation of a multilayer yields a modified Langmuir-type equation. In general, component (b) can be approximated by an adsorption which is linear with relative vapour pressure. For some substrates one or more of the three component isotherms may be inoperative. The composite isotherm is represented by the equation, [graphic ommitted], and has general applicability to a wide range of systems for water vapour sorption.

Ethylene Adsorption on Pt(111)

Abstract: The scattering of helium and deuterium beams has been used along with LEED to establish the cleanliness and order of a Pt surface under ultrahigh‐vacuum conditions and to study the adsorption of ethylene on the (111) face. Ethylene adsorbs irreversibly according to first‐order Langmuir kinetics with a sticking coefficient of unity, and dissociates upon adsorption into an acetylenic species which occupies four platinum sites and two mobile hydrogen atoms. At high coverages the ethylene is ordered, producing a (2 × 2) LEED pattern. Above temperatures of 200°C irreversible degradation of the adsorbate occurs. The use of both atomic scattering and LEED seems to be uniquely complimentary for the study of adsorption on clean surfaces of single crystals.

A new adsorption isotherm for phosphate in soil

Abstract: Summary Phosphate adsorption data for 24 soils showed that although the Langmuir equation gave a good fit, there was significant curvature. Of the alternative equations examined, that of Freundlich provided a better description than that of Langmuir in 22 soils, but the best fit, accounting for more than 99·8 per cent of the variation in phosphate adsorption, was given by introducing a square-root term: where y= adsorbed phosphate, c= equilibrium concentration of phosphate in solution, B, A, and D are constants. The phosphate adsorption maximum, obtained from I/B, gave values in the range 325 to 1427 μg P/g soil which were 1·39 to 2·40 times those obtained from the Langmuir equation. The inclusion of a square-root term in the Langmuir equation could be taken to imply that the soil will adsorb a little phosphate firmly, a slightly greater amount of phosphate less firmly, and so on until a limiting value is reached when all the components of the phosphate adsorption system are saturated.

A wave-interaction model for the generation of windrows

Abstract: Interactions of suitable pairs of gravity waves in a shear flow are found to give rise to aperiodic or weakly periodic secondary motions. These secondary flows resemble the ‘Langmuir vortices’ which are associated with the formation of windrows. It seems likely that such wave interactions will play a substantial part in determining the quasi-steady structure of the flow when wind blows over a water surface.

Über die spektrale Sensibilisierung von Zinkoxid: I. Sorptionsverhalten von o,o′-Dihydroxyazofarbstoffen†

Abstract: o,o′-Dihydroxyazo compounds are spectral sensitizers for the photosemiconductor properties of zinc oxide. It is shown that 1-(2-hydroxyphenylazo-)-2-naphthol (II) forms a 1:1 Zn complex on the surface of ZnO particles if adsorbed from toluene solution. With most samples of ZnO a Langmuir type adsorption isotherm is obtained. The concentration of the dye at saturation relative to the BET surface of the ZnO particles correponds to a slightly oblique edge-on arrangement of the dye molecules on the surfaces. In the case of ZnO pretreated with propionic acid and having taken up dye in excess of a monolayer, it can be shown by electron microscopy that tail-like complexes (zinc: dye ratio = 1:1) are formed, and that these complexes contain zinc which was originally on the particle surfaces.

The Adsorption of Polyvinyl Pyrrolidone on Silver Iodide Surfaces

Abstract: Adsorption isotherms for four kinds of polyvinyl pyrrolidone (PVP), having different molecular weights, on the sol particles and the powder of silver iodide at 25°C were obtained. Further, the adsorption of PVP on the sol particles was investigated by means of the electrophoresis method. All of the PVP materials give approximate adsorption isotherms of the Langmuir type, at least up to the PVP concentration of 0.4 g/l At higher concentrations, the amounts of PVP adsorbed gradually increase with the increase in the PVP concentration. The effect of the molecular weight on the PVP adsorption is not observed except for the lowest-molecular-weight material, which displays a lower adsorption. The tendency for the ζ-potential of the sol particles to increase with an increase in the PVP concentration almost coincides with that of the amount of PVP adsorbed.

The adsorption of dinonylnaphthalenesulfonates on metal oxide powders

Abstract: : The adsorption of oleophilic rust inhibitors, sodium and barium dinonylnaphthalenesulfonate, from cyclohexane solution on Nickel(III) oxide and iron(III) oxide was investigated. Rate data for adsorption of sodium dinonylnaphthalenesulfonate on nickel oxide indicate a complex mechanism of adsorption. An empirical equation was found that accurately describes the data. The log of the uncovered surface plotted against log time was linear. The extrapolated time for 50% coverage was 0.36 min. Experimentally the adsorption process was irreversible. The effect of temperature in the range of 10 to 60C on the adsorption isotherm was negligible. Adsorption isotherm data for sodium dinonylnaphthalenesulfonate were of a Langmuir type. The values of (a) indicated a more close-packed monolayer on nickel oxide than on iron oxide. The ratio of the molecules per square centimeter for the former and the latter was 1.49. The (b) values indicated a rather strong interaction at the metal oxide surfaces. Monolayer concentrations were found to be essentially the same irrespective of the salt used.

The Relationship between Adsorption Phenomena of Surface Active Agent on Carbon Black and Deposition Phenomena by Carbon Black on Textiles

Abstract: In order to investigate the effect of alkyl chain length and builder on adsorption, the adsorption isotherms of linear alkylbenzene sulfonate from aqueous solution on carbon black were determined at 30°C, The adsorption isotherms were fitted to a Langmuir type equation. The amount of saturated adsorption and equilibrium constant which characterize the adsorption were determined by Langmuir plot. The saturated amount depended upon the builder added, but did not upon alkyl chain length. On the other hand, equilibrium constant were markedly affected by alkyl chain length and the builder added. Authers also investigated the correlation between the adsorption of surface active agent on carbon black and the deposition phenomena of carbon black on textile fibers in surface active agent solution, but could not obtain a clear conclusion.

Corrosion Inhibition Study of Al-Cu-Ni Alloy in Simulated Sea-Water Environment

Abstract: A study on the inhibition of Al-Cu-Ni alloy in simulated sea-water environment was investigated using Sodium Chromate as inhibitor. The inhibitor concentration was varied as control, 0.25, 0.5, 1.0, 1.5 and 2.0 Molar. Al-Cu-Ni alloy was sand cast into cylindrical bars of 20 mm x 300 mm dimension. The corrosion of the sand-cast and treated alloys in 3.5wt% sodium chloride solution at temperatures 30 o C, 50 o C and 70 o C over 1-5 hrs was evaluated using the weight loss method. It was observed that the corrosion rate of the treated alloys decreases with increase in inhibitor concentration. The decrease in corrosion rate on addition of the inhibitor can be attributed to the adsorption of the inhibitor onto the surface of the alloy. The attachment is by physical adsorption as the values of heat of adsorption were less than -10 kJ/mol. The plots obtained were linear meaning that they obey the Langmuir and Temkin adsorption isotherms. The inhibition efficiency increases generally with increase in temperature and inhibitor concentration. KEYWORDS : inhibition, simulated sea-water, corrosion, alloy, concentration, adsorption

Adsorption of Limonene on Inorganic Powders

Abstract: In Cosmetics using powders, topnote and retention of perfume are important problems. These problems depend on adsorptive properties of odoriferous substances adsorbed on powders. Adsorption of limonene on inorganic powders that are for cosmetics such as titanium dioxide, talc, zinc oxide, calcium carbonate magnesium carbonate, and silicic acid anhydride, is measured by an adsorption measurement apparatus attached to a gas liquid partition chromatograph.Total amount of limonene adsobed on 9 kinds of inorganic powders is calculated by using Langmuir's adsorption isothermal equation subject to the continuous flow method.Irreversible adsorption is measured by pulse method, and from difference of this value and total amount of limonene adsorbed, reversible adsorption is determined.Results are as follows; 1) magnesium carbonate has the largest amount of adsorption and most of the adsorption is reveresible one, on the other hand, calctum carbonate the smallest adsorption value, 2) in the amount of irreversible adsorption of titanium dioxide, anatase has 10 times larger value than that of rutile, 3) in silicic acid anhydride, most of the adsorption is irreversible.From these results, retention of perfume of powder products and the possibility of a simple test method are discussed.