Showing papers on "Langmuir published in 1977"
TL;DR: In this paper, the solubility, permeability, and diffusion time lag for CO2, CH4, Ar, N2, and He in polycarbonate are reported at 35°C for pressures ranging from 1 atm to 20 atm.
320 citations
TL;DR: In this paper, a method of successive approximation of the Langmuir sorption constants was proposed to resolve the data for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel.
Abstract: Summary
Data for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel were resolved by a method of successive approximation of the Langmuir sorption constants. Three distinct Langmuir equations described the overall isotherm irrespective of the experimental conditions used. Free energies of sorption (ΔG) for a particular region were similar for each soil and for iron oxide gel under all experimental conditions. In contrast, the sorption maximum for each region was influenced by the sorbent and experimental conditions.
Because of the pronounced similarities in their P sorption characteristics iron oxide gel was used as a model surface for P sorption by soils. Three mechanisms for P sorption by iron oxide gel and by soils are proposed: (i) chemisorption at protonated surface sites, (ii) chemisorption by replacement of surface hydroxyls, and (iii) a more-physical sorption of P as a potential-determining ion.
224 citations
TL;DR: In this paper, the authors measured the adsorption capacity of 14 surface and 6 subsurface horizons of Illinois soils with respect to the amount of F− with release of OH− at low concentrations, and found that F− was due to amorphous aluminum oxyhydroxides which are common weathering products in these soils.
Abstract: Summary
Fourteen surface and 6 subsurface horizons of Illinois soils adsorbed significant amounts of F− with release of OH−. At low concentrations, adsorption was described by both Langmuir and Freundlich isotherms. The calculated Langmuir adsorption capacities were related to pH, clay, organic carbon, and amorphous aluminum contents.
Two soils with different gross chemical properties behaved in essentially the same manner, with adsorption maxima occuring between pH 5.5 and 6.5. The similarity between adsorption at different pH values for the soils and those for bauxite, allophane and synthesized ‘soil chlorite’, and the lack of adsorption maxima between pH 5.5 and 6.5 for pure kaolinite and montmorillonite, suggest that F− adsorption in the soils is due primarily to the presence of amorphous aluminum oxyhydroxides which are common weathering products in these soils.
117 citations
TL;DR: In this paper, the adsorption of Pb from pure Pb(NO/sub 3/)/sub 2/ solutions by Ca-montmorillonite at pH 5.00 and 25/sup 0/C was found to be sensitive to the weight of the clay sample.
Abstract: The adsorption of Pb from pure Pb(NO/sub 3/)/sub 2/ solutions by Ca-montmorillonite at pH 5.00 and 25/sup 0/C was found to be sensitive to the weight of the clay sample. This apparent sensitivity of the adsorption of Pb to the weight of the sample was attributed to Ca competition for exchange sites as determined from Pb/Ca ratios found in the solutions. Adsorption of Pb from 0.1M Ca(ClO/sub 4/)/sub 2/ solutions was substantially lower and was insensitive to the weight of the clay sample. This further supported our conclusion that adsorption of Pb was dependent on the Pb/Ca ratio. Application of the ''simple'' Langmuir equation to Pb adsorption by 0.05 and 0.10 g of clay resulted in a linear relation over the entire concentration range (0 to 1,200 ppM Pb). However, increasing nonlinearity was observed at the lower Pb concentrations when 0.50 and 1.00 g of clay were used, respectively. These Langmuir plots yielded lower adsorption maxima than maxima obtained from the two lower weights of clay and the shapes of the isotherms indicated two distinct regions of adsorption. The data were then plotted according to a ''competitive'' Langmuir equation, which successfully resolved the data for all four weights of claymore » into a single linear adsorption plot.« less
74 citations
Journal Article•
TL;DR: It was concluded that physical adsorption can account for the deposition of part but not all of the matrix in calcium oxalate stones and could explain the inhibition of growth and aggregation of calcium Oxalate crystals seen with in vitro precipitation systems.
Abstract: The adsorption of proteins and mucopolysaccharides on calcium oxalate crystals was measured by solution depletion. Anionic protein adsorption was found to be sensitive to calcium ion concentration. Adsorption of fibrinogen was anomalously large in the presence of 0.01 M Ca2+. Adsorption of cationic protein (histone) was sensitive to oxalate ion concentration. A small alteration in adsorption of protein as a result of pH or temperature change was also observed. Plots of adsorption versus concentration were interpreted in terms of a Langmuir adsorption isotherm. The derived Langmuir adsorption parameters were then used to investigate the contribution of protein, by physical adsorpti, to the quantity of matrix in urinary stones. It was concluded that physical adsorption can account for the deposition of part but not all of the matrix in calcium oxalate stones. It was also concluded that physical adsorption of mucopolysaccharides by calcium oxalate crystals could explain the inhibition of growth and aggregation of calcium oxalate crystals seen with in vitro precipitation systems. Recalculation of published data indicates that adsorption of protein on dental enamel (calcium hydroxyapatite) results in approximately the same extent of surface coverage as adsorption on calcium oxalate crystals, but protein has a much lower affinity for dental enamel than for calcium oxalate crystals.
69 citations
TL;DR: When the amount of inorganic phosphate (P) sorbed by contrasting subsoils was expressed as a fraction of the overall Langmuir sorption maximum for that soil, the sorption data plotted on essentially the same isotherm as mentioned in this paper.
Abstract: When the amount of inorganic phosphate (P) sorbed by contrasting subsoils was expressed as a fraction of the overall Langmuir sorption maximum for that soil, the sorption data plotted on essentially the same isotherm. This reflected the similarity in the Langmuir sorption constants relating
58 citations
TL;DR: In this article, a theory for the evolution of the wind drift current and of the Langmuir circulations in infinitely deep water of constant density is presented, which improves and extends a recent quasi-steady theory of Craik & Leibovich.
Abstract: A theory for the evolution of the wind drift current and of the Langmuir circulations in infinitely deep water of constant density is presented. The model improves and extends a recent quasi-steady theory of Craik & Leibovich which asserts that the Langmuir circulations arise from a nonlinear interaction between surface waves and the frictional wind drift current. In turn, the development of the wind drift should be strongly influenced by Langmuir circulations, when they are present, and the two current systems are therefore treated here as a single inseparable system driven by a prescribed wind stress and surface wave field. Mixing by the vertical motions in the Langmuir circulations is shown to yield solutions for the wind drift, obtained both analytically and numerically, which are consistent with experiments and with field observations. The model yields a streaky flow pattern with a mean motion much like a turbulent wall layer, although the model is deterministic. In particular, it is found that a ‘viscous sublayer’ joins surface water to a logarithmic ‘inertial subIayer ’ below. The scaling rules that emerge from the theory allow the surface speed of the wind drift to reach nearly full development in a matter of minutes.
53 citations
TL;DR: In this paper, the Langmuir adsorption maxima were related positively to clay and carbonate content and negatively with organic matter content of soils, and a multiple regression analysis revealed that zinc adsorment maxima can be predicted with good precision from information in soil survey reports.
Abstract: Zinc adsorption was studied in suspensions of six soils of different physicochemical characteristics in dilute ZnSO4 solutions. At low concentrations, Zn2+ adsorption was described by the Langmuir adsorption equation. The calculated Langmuir adsorption maxima were related positively to clay and carbonate content and negatively with organic matter content of soils. Multiple regression analysis revealed that zinc adsorption maxima can be predicted with good precision from information in soil survey reports.
47 citations
TL;DR: In this article, a clean Pt(100) surfaces with bulk-like 1×1 structure, or the stable, reconstructed 5×20 structure and held at 200 or 330 K were exposed to ethylene.
42 citations
TL;DR: In this article, the electrical properties of m.i.s. structures based on InP and Langmuir films have been investigated and a strongly inverted low-frequency-type C/V response occurs at about 30 Hz.
Abstract: The electrical properties of m.i.s. structures based on InP and Langmuir films have been investigated. A strongly inverted low-frequency-type C/V response occurs at about 30 Hz. Surface-state distributions have been evaluated by using both quasistatic and conductance techniques. Effective surface-state densities are found to be ~3 × 1011cm?2 eV?1 over a large fraction of the band gap.
38 citations
TL;DR: In this article, the LaB6 clean surface and its initial oxidation have been studied by UPS, XPS, and work-function measurements, and a so-called surface state has been found, with a work function of 2.4±0.1 eV.
Abstract: The LaB6 (001) clean surface and its initial oxidation have been studied by UPS, XPS, and work‐function measurements. For the clean surface, a so‐called surface state has been found, and a work function of 2.4±0.1 eV has been measured. The surface state disappears by an oxygen exposure of ∼7 langmuir (L), and the work function increases up to 4.0±0.1 eV. This initial oxidation is not a simple oxygen‐adsorption process but proceeds with the formation of a surface oxide or oxides.
TL;DR: In this paper, rate models for adsorption and desorption on a non-uniform surface are derived using the "Extent of Reaction Effect" which describes the behaviour of large systems of parallel reactions.
Abstract: Rate models for adsorption and desorption on a non-uniform surface are derived using the “Extent of Reaction Effect” which describes the behaviour of large systems of parallel reactions. When the rate models and the resulting isotherm are fitted to data taken from the literature, very good agreement is found between the fitted model and the data. The new isotherm also provides an explanation for cases where physisorption is observed to follow Langmuir's dissociative chemisorption isotherm.Extensions of our rate model are presented for the case where a precursor state exists. This approach leads to two well-established isotherms: the Freundlich isotherm and the “generalized Freundlich” isotherm proposed by Sips.
TL;DR: In this paper, the atomic absorption spectroscopy (AA) was used for solution analyses, and ESCA for detection of Ba 2+ sorbed on the crystalline surface.
TL;DR: In this paper, an explanation for the shape of adsorption envelopes found for phosphate adaption by various metallic oxides is presented. But the shape is not described.
Abstract: Summary
An explanation is put forward for the shape of adsorption envelopes found for phosphate adsorption by various metallic oxides. The equation xm= C1 (μH3PO4+μ∑anions) is proposed, where μH3pO4 is the chemical potential of undissociated H3PO4; μ∑anions is the chemical potential of all phosphate anions considered as one. component; C1 is a constant that includes influences of surface charge, chemical affinity of the metal for phosphate, specific surface area, etc., and xmis the calculated Langmuir maximum adsorption of P at each pH. The dependence of C1 on the metal present in the oxide is shown.
TL;DR: In this paper, simultaneous chemiluminescence and piezoelectric quarts crystal vacuum microbalance measurements of chemisorption rates of oxygen on deposited metal films reveal the existence of slow and fast reactions.
TL;DR: In this article, the authors used the gas chromatographic method of Cremer and Huber to investigate the adsorption isotherms on γ-alumina of hydrocarbons with up to eight carbon-atoms.
TL;DR: In this paper, the authors derived polarographic currentpotential characteristics and current-time curves for a Nernstian charge transfer O+ ne R with Langmuir or Frumkin adsorption of reactant and/or product via a mathematical procedure based on diffusion-layer approximation.
TL;DR: In this paper, the problem of determining adsorption from binary gaseous mixtures on the basis of pure-gas adorption parameters has been theoretically discussed and analyzed.
Abstract: In this paper the problem of determining adsorption from binary gaseous mixtures on the basis of pure-gas adsorption parameters has been theoretically discussed. The author analysed adsorption systems whose adsorption from pure gases is in agreement with the equation ofToth, Freundlich orLangmuir.
TL;DR: In this article, the effects of the chemical and physical properties of surface and subsurface soils of a temperate region on P sorption from solutions containing various concentrations of P were evaluated.
Abstract: Several factors affect phosphate sorption by soils. This study was conducted to evaluate the effects of the chemical and physical properties of surface and subsurface soils of a temperate region on P sorption from solutions containing various concentrations of P. Results showed that Na2S2O4‐extractable Fe and Al of surface soils were significantly correlated with P sorption from a solution containing 10, 15, or 20 ppm P. The relationships between the amounts of P sorbed and the other properties of the surface and subsurface soils studied (e.g., pH, organic C, soluble P, CEC) were influenced by use of 0.01M CaCl2 as an equilibrating solution. The values of P adsorption maxima calculated from soil‐water systems were from 1.2‐ to 2.1‐fold higher than those calculated from soil‐0.01M CaCl2 systems. But the Langmuir adsorption constants calculated from results obtained in the presence of CaCl2 were from 7‐ to 27‐fold higher than those in the absence of salt.
TL;DR: In this paper, the effect of the hydrostatic pressure exerted by bulk phases on adsorbed phases depends on the mobility of the adorbed phase and on the topographical distribution of adsorption energy.
Abstract: The effect of the hydrostatic pressure exerted by bulk phases on adsorbed phases depends on the mobility of adsorbed phase and on the topographical distribution of adsorption energy. It is shown in this paper that the Langmuir's equation applies also to adsorption of fully mobile hard discs, on heterogeneous surfaces having fully random topographical distribution of adsorption energy. The effects of the hydrostatic pressure are discussed also in the case of heterogeneous surfaces exhibiting patchwise topographical distribution of adsorption energy.
TL;DR: In this article, the ultrasonic relaxation method has been used to monitor the rates of the dynamic equilibrium between surface active agent ions, small molecules including alcohols, an aldehyde, an acid and a surfactant micelle.
Abstract: The ultrasonic relaxation method has been used to monitor the rates of the dynamic equilibrium between surface active agent ions, small molecules including alcohols, an aldehyde, an acid and a surfactant micelle. These data have been interpreted in terms of a model in which the kinetics of the exchange process are governed by the principles of the Langmuir adsorption theory. In all cases the correspondence between theory and experiment is good.
TL;DR: The Jovanovic kinetical derivation as discussed by the authors takes into account the mechanical contact between adsorbed and bulk phases in the case of the systems with localized admolecules without mutual interactions.
Abstract: In addition to the mass exchange the equilibrium bulk phase exerts a hydrostatic pressure on the adsorbed phase: this hydrostatic pressure is a source of an additional positive adsorption. The Jovanovic kinetical derivation is the first one taking into account the mechanical contact between adsorbed and bulk phases in the case of the systems with localized admolecules without mutual interactions. At a same numerical values of parameters the Jovanovic isotherm predicts a greater adsorption than the Langmuir does.
TL;DR: A detailed study showed that the transition from adsorption to total elution is very sharp and proceeds under critical conditions of pH near the pK of the SiOH groups, therefore, conditions are very favourable for the elution chromatography of viruses.
TL;DR: In this paper, a model was developed which includes Langmuir type adsorption followed by a chemical reaction for a reactor with steady input of phosphorus, which reached steady state and followed a Michaelis-Menten type equation as predicted for the catalytic process.
TL;DR: In this article, conditions for the sorption of trivalent iron in the ionic and colloidal states on silica gel impregnated with manganese dioxide from aqueous solution were studied by batch equilibrations.
TL;DR: In this paper, a quantitative treatment, coupled with critical qualitative considerations, pertaining to the study of thermodynamics of adsorption of N2 and CO2 on different graphite samples, through the evaluation of the film pressure,π as a function of temperature and pressure, is presented.
Abstract: A quantitative treatment, coupled with critical qualitative considerations, pertaining to the study of thermodynamics of adsorption of N2 and CO2 on different graphite samples, through the evaluation of the ‘film pressure’,π as a function of temperature and pressure, is presented. The . determination of the adsorbent specific surface areas is affected through the graphic manipulation of the Langmuir adsorption equation utilizing data adopted from literature, and theπ values are then computed by employing the Gibbs adsorption equation by making use of the areas under them-lnP curves. The results deduced are discussed specifically in terms of π as related to the nature of the adsorbents, the magnitude of the calculated thermodynamic functions and the specific surface areas for the individual adsorbents.
TL;DR: In this article, a batch equilibrations of copper, palladium and platinum salts with Bio-Gel P-2 yielded adsorption isotherms of the Langmuir type, and the rate-determining step in the chromatographic process was found to be the detachment of solute molecules from the functional groups of the gel.
TL;DR: In this paper, the authors investigated the stationary one-dimensional propagation of Langmuir waves trapped in a local density cavity in a plasma, where the frequency spectrum is broad as compared with the ion acoustic frequency, but their wavenumbers are comparable to the inverse scale length of the density cavity.
Abstract: Stationary one-dimensional propagation of Langmuir waves trapped in a local density cavity in a plasma is investigated for the case in which the frequency spectrum of the Langmuir waves is broad as compared with the ion acoustic frequency, but in which their wavenumbers are comparable to the inverse scale length of the density cavity Analytical solutions for the density cavity, which traps many Langmuir wave modes and which is self-consistent with the ponder-omotive potential coming from these eigenmodes, are obtained The Langmuir wave envelopes exhibit oscillations at the beat frequencies of the different eigenmodes These solutions are valid when the intensity of the trapped Langmuir waves normalized by the electron thermal energy is much greater than the electron-to-ion mass ratio
TL;DR: In this paper, the adsorption rate of surfactant ion in foam separation technique was experimentally studied, and it was found that there was a large amount of surface excess of DBS- at the liberation of bubbles from a sparger.
Abstract: The adsorption rate of surfactant ion in foam separation technique was experimentally studied. By using SDBS (sodium dodecylbenzene sulphonate) as surfactant and NaCl as coexisting salt, foam separation experiments in a continuous-flow foam column were carried out, and following facts were obtained. It was found that there was a large amount of surface excess of DBS- at the liberation of bubbles from a sparger. In a non-salt system (SDBS solution), the adsorption rate equation of Langmuir''s type could be well applied to the adsorption of DBS-, in the region of bulk concentration of DBS- in which the Langmuir adsorption isotherm can be applied. In the case of 0.17-0.19 cm of bubble diameter, surface excess of DBS- attained to an adsorption equilibrium within one second, and the apparent adsorption rate became more rapid than that in the case of 0.06-0.07 cm of bubble diameter. Moreover, the adsorption rate increased more than that in a non-salt system, by the addition of NaCl.
TL;DR: In this paper, the effects of some non-ionic surface-active substances on the potential-time curves of the reduction of hexaisothiocyanatochromate (III) on the mercury electrode have been investigated, and explained in terms of the blocking effect of adsorbed surfaceactive substance which is in equilibrium with that in the bulk of the solution by the apparent adsorption isotherm of Langmuir type.