Showing papers on "Langmuir published in 1983"
TL;DR: The adsorption of cellulase from Trichoderma viride (Meicelase CEP) on the surface of pure cellulose was studied and was found to obey apparently the Langmuir isotherm.
Abstract: The adsorption of cellulase from Trichoderma viride (Meicelase CEP) on the surface of pure cellulose was studied. The adsorption was found to obey apparently the Langmuir isotherm. From the data concering the effects of temperature and the crystallinity of cellulose on the Langmuir adsorption parameters, the characteristics of the adsorption of the individual cellulase components, namely CMCase (endoglucanase) and Avicelase (exoglucanase), were discussed. While beta-glucosidase also adsorbed on the surface of cellulose at 5 degrees C, it did not at 50 degrees C.
165 citations
TL;DR: In this paper, a nonlinear equilibrium isotherm was used to predict theoretical concentration versus time curves of dyestuffs on chitin, and the analysis was based on a computer program.
111 citations
TL;DR: In this paper, the authors investigated the role of physico-chemical factors that control the adsorption of dextrin by coal and found that the more hydrophobic demineralized coal was found to exhibit an adaption density twice the adsoption density of natural coal.
93 citations
TL;DR: The adsorption reaction reached equilibrium in about 2 hours and was irreversible as mentioned in this paper, reaching a maximum at pH 6 and a decrease below pH 6 was due to competition with protons as well as to problems inherent in surface packing of positively charged quinoline molecules.
Abstract: The adsorption isotherms of quinoline from aqueous solutions by some clays and oxides varied from the S type for silica to a form somewhat similar to the Langmuir type for montmorillonite and silica- alumina. The adsorption reaction reached equilibrium in about 2 hr and was irreversible. X-ray powder diffraction studies showed that a single layer of molecules is adsorbed on montmorillonite and that the molecules lie either flat or in an upright position depending on surface coverage. The adsorption showed high sensitivity towards pH, attaining a maximum at pH 6. The decrease below pH 6 was due to competition with protons as well as to problems inherent in surface packing of positively charged quinoline molecules. The decrease above pH 6 is probably due to more exchangeable metallic cations on the surface leading to a favored sorption of water over organic molecules.
66 citations
TL;DR: In this paper, the exchange current in a solid electrolyte concentration cell is measured potentiostatically using a reference, counter, and working electrode with oxygen partial pressure (PO2) ranging from 6 × 101 to 2 × 104 Pa, at temperatures between 600 and 1000 K.
55 citations
TL;DR: In this article, the total and external surface areas of three kinds of ZSM-5 type zeolites were determined in the usual way for adsorbents having Langmuir isotherms.
44 citations
TL;DR: In this article, a regular perturbation series method was used to solve the diffusion equation when the boundary condition is a non-linear adorption isotherm, and convergence of the power series solutions was improved by applying the Shanks transformation.
Abstract: A regular perturbation series method provides a solution to the diffusion equation when the boundary condition is a non-linear adsorption isotherm. For adsorption at the interface the Freundlich and Langmuir isotherms yield power series in the square root of time. Convergence of the power series solutions is improved by applying the Shanks transformation. The solutions are compared to limiting cases and to published numerical solutions. The results are most accurate for small time where the numerical finite difference method is least reliable.
32 citations
TL;DR: In this article, a simple model to explore the role of surface diffusion on the rate of reaction between a surface diffusing species and a set of fixed randomly distributed reactive sites is presented.
Abstract: We present a simple model to explore the role of surface diffusion on the rate of reaction between a surface diffusing species and a set of fixed randomly distributed reactive sites A Langmuir adsorption/desorption term is used to describe the influence of the bulk phase on the surface Reaction is modeled by a fast, with respect to surface diffusion, absorption on the perimeters of the reactive sites A general effective medium theory is formulated for this model and solved approximately for the rate kf and diffusion coefficient D, which characterize the transport of the reactive density on a scale large compared with intersite dimensions We find that surface diffusion can be an important contributing factor to the rate of reaction In particular, when surface diffusion is rapid relative to the Langmuir adsorption/desorption rate, the reaction rate increases strongly with increasing reactive site surface concentration relative to its value for low surface site concentration
31 citations
TL;DR: In this paper, computer simulations of the effects of Langmuir and Freundlich-type competition in binary systems under equilibrium and dynamic (time-dependent) conditions have been presented and discussed.
Abstract: Computer simulations of the effects of Langmuir and Freundlich-type competition, in binary systems under equilibrium and dynamic (time-dependent) conditions, have been presented and discussed.These simulations indicate that during competitive adsorption (for both Langmuir and Freundlich-type competi
30 citations
TL;DR: In this paper, the adsorption and desorption of hydrogen, oxygen, carbon monoxide, and ethylene on Ni(110) and Ni(100) were monitored with He•atomic beam scattering.
Abstract: The adsorption and desorption of hydrogen, oxygen, carbon monoxide, and ethylene on Ni(110) and of hydrogen on Ni(100) were monitored with He‐atomic beam scattering. The attenuation of the specular beam during gas adsorption initially shows a linear dependence on the adsorbate partial pressure and dose, which, when extrapolated, corresponds to a decrease of 100% for about one‐half a Langmuir (1 L=1.33×10−4 Pa s). This can be related to total collision cross sections of the adsorbed particles in the range of 30 to 100 A2, indicating dominance of the attractive interaction of the He atoms with adsorbates in dilute concentrations. Statistical occupation or depletion of sites in the adlayer structures suffice to explain the changes in coherent specular intensity upon adsorption and desorption processes. Near the Curie temperature of Ni (Tc=631 K), diffracted intensities of H2 and He show non‐Debye–Waller behavior in their temperature dependence. Connections to changes in carbon surface concentration and to a ...
28 citations
TL;DR: The ratio of contributions of adsorption at the second site to that at the first site increases upon increasing pore opening and may serve as a qualitative measure of the ratio of pore volume to surface area of the fine-pore adsorbent as mentioned in this paper.
TL;DR: In this paper, a greenhouse bioassy was conducted to evaluate differences in P availability to plants (Oats, Avena sativa L. cv. Korwood) due to liming and incubation treatments.
Abstract: Changes in the adsorption and availability of P in an acid, aluminous soil (surface and subsoil) were evaluated following liming to neutralize 1N KCl-exchangeable Al (minimal liming) or to pH 6.8 as determined by the SMP (Shoemaker-McLean-Pratt) buffer method. Langmuir adsorption isotherms were utilized to ascertain changes in P adsorption. A greenhouse bioassy was conducted to evaluate differences in P availability to plants (Oats, Avena sativa L. cv. Korwood) due to liming and incubation treatments. Results from these studies confirm that minimal liming is the most effective approach, from both agronomic and economic standpoints. Minimal liming optimized P uptake and minimized the P adsorption maxima (Langmuir b values). Liming by the SMP recommendation did not improve P uptake despite the application of three times as much lime, and also markedly reduced exchangeable Mg. Aging of adsorbate surfaces in the soil reduced their bonding intensity for P (Langmuir K), as did increasing soil pH. Development of ordered, less soluble Al-OH polymers with fewer nonstructural OH groups capable of ligand exchange with P is postulated as the mechanism underlying these observations. Increases in pH-dependent negative surface charge and P adsorption by free CaCO/sub 3/ may be involved. 43 references, 8 tables.
TL;DR: The theory for the EE mechanism influenced by adsorption of the intermediate (E↓E) has been developed in this article, and the resulting variation of pulse polarographic total current has been described and discussed.
TL;DR: In this paper, the authors derived the Langmuir equation for the adsorption process of divalent metal cations by Na-montmorillonite and analyzed the adaption behavior of Ca, Ni, and Cu by a montmorillonitic at pH 4 through 7.
Abstract: Adsorption behavior of Ca, Ni, and Cu by a montmorillonite at pH 4 through 7 was analyzed within a wide range of divalent cation concentrations (M2+=1.25 to 4.5 mi/liter). The data were interpreted in terms of the following Langmuir equation which was derived in assuming that the adsorption process of divalent metal cations by Na-montmorillonite does not involve more than simple ion exchange: where C=equilibrium concentration of M2+, X=amount of MH adsorbed, Xm=adsorption maximum, and K″ =an energy constant. All the figures for Ca adsorption at each pH value could be plotted on a straight line, indicating that Ca was adsorbed onto the montmorillonite by a simple ion-exchange reaction. Langmuir plots of Ni and Cu adsorption revealed that the montmorillonite surface seems to provide the heavy metal cations with three types of adsorption sites of widely different reactivities, that is, Sites I, II, and III. Adsorption onto Site I corresponded to the ion-exchange reaction and both of the divalent cat...
TL;DR: In this article, a mathematical model was developed to simulate phosphate reactions with minerals in acidic soils, where the first step of the reaction followed the kinetic version of the Langmuir adsorption isotherm and was a second-order reaction in nature.
Abstract: A mathematical model was developed to simulate phosphate reactions with minerals in acidic soils. Phosphate in solution was assumed to react with kaolinite, gibbsite, and goethite simultaneously. Each reaction had a two-step sorption mechanism, i.e., mineral + solution P ⇄ labile P ⇄ nonlabile P, where labile and nonlabile forms are defined as isotopically exchangeable and nonexchangeable, respectively. The first step of the sorption mechanism followed the kinetic version of the Langmuir adsorption isotherm and was a second-order reaction in nature. The second step of the sorption mechanism was a linear reversible kinetic equation. Seven ordinary differential equations describing the system were solved by numerical methods. The model effectively simulated the trend of phosphate reactions with soil minerals. Using the model to study the adsorption isotherm, we found that the Langmuir plot, i.e., concentration/adsorption vs. concentration, was linear when minerals had relatively homogeneous adsorption rates (or adsorption energies) and was nonlinear for widely differing rates, implying that a homogeneous surface provides a sufficient condition but not a necessary condition for a linear Langmuir plot. Simulation and analysis of a two-surface Langmuir equation supported this finding.
TL;DR: In this article, the Gibbs adsorption equation was applied to the γ vs C curves of alkylsulfonate ions at the air-aqueous solution interface to obtain the adsorbed isotherms of the Langmuir type.
TL;DR: In this paper, the adsorption of SO2 on CaO (100) at 300 K has been studied using X-ray photoelectron spectroscopy, and the surface coverage due to the SO42− species was also measured as a function of surface coverage.
TL;DR: In this article, a representative group of ferroin-type ligands and various activated carbons were screened for possible use in trace metal separations, and 2,2′-dipyridylketone-2-pyrid ylhydrazone (DPPH) and Norit A were investigated more extensively with special attention to p K a values and ionic charges of DPPH species, isotherms and Langmuir parameters for the adsorption, and to conditions and procedures optimal for analytical separations and recoveries of trace metal
01 Jan 1983
TL;DR: The interpretation of the Szyszkowski equation for a surface-tension isotherm of a solution is equivalent thermodynamically to the Langmuir adsorption and also to the Frumkin two-dimensional equation of state as discussed by the authors.
Abstract: The Szyszkowski equation for a surface-tension isotherm of a solution is equivalent thermodynamically to the Langmuir adsorption isotherm and also to the Frumkin two-dimensional equation of state. Lucassen-Reynders and van den Tempel (1964) maintained that Szyszkowski-Langmuir adsorption implies ideality of the surface phase. Reasons for disputing the uniqueness of this interpretation and a new interpretation are given.
TL;DR: In this paper, it was shown that a single non-invasive experimental observation should be sufficient to determine all these viscoelastic surface properties, including film tension and elasticity and the two associated surface viscosities.
TL;DR: Banerji et al. as mentioned in this paper proposed the activated sludge adsorption equation (ASAE), which was tested and proven by experimental data and by data obtained independently by Banerji and others.
TL;DR: This paper showed that smectite with polyvalent cations on the exchange complex readily absorbed riboflavin from aqueous solution to a limit of about 0.5 mmole/g.
Abstract: Smectite with polyvalent cations on the exchange complex readily absorbed riboflavin from aqueous solution to a limit of about 0.5 mmole/g. The shape of the adsorption isotherms was of the Langmuir type. An exception was Na+-smectite which provided an S-shaped isotherm and smaller amounts of adsorption. Ca2+-vermiculite had no interlamellar adsorption of riboflavin, suggesting that this mineral does not swell sufficiently to permit such adsorption. Adsorption isotherms, X-ray powder diffraction data, and UV-visible spectroscopic data suggest that the mechanisms of interaction between smectite and riboflavin may involve a combination of ion-dipole, charge transfer, hydrogen bonding, and physical effects.
TL;DR: The spin polarization in low-energy electron diffraction from a clean W(001) surface, as well as from a surface exposed to residual gas, has been measured with a newly-constructed compact Mott detector as discussed by the authors.
Abstract: The spin polarization in low-energy electron diffraction (LEED) from a clean W(001) surface, as well as from a surface exposed to residual gas, has been measured with a newly-constructed compact Mott detector At a particular electron energy and incident angle, exposure of a clean surface to 05 Langmuir of residual gas causes a significant polarization change, from -45% to +31% This characteristic is not inconsistent with results reported by other workers under different diffraction conditions
Journal Article•
TL;DR: In this article, the zinc adsorption in seven soils of the state of Karnataka was studied in three red soils with lower pH and cation exchange capacity (CEC) conformed to Langmuir's equation.
Abstract: Zinc adsorption was studied in seven soils of the state of Karnataka. In three red soils with lower pH and cation exchange capacity (CEC) the adsorption isotherm conformed to Langmuir's equation. In the other four soils, which were either sodic or calcareous and had higher pH, the isotherms could be resolved into two linear portions and the lower portion showed better fit to Langmuir's equation. The adsorption maxima accounted for 24 to 35.4% of the CEC in red soils, whereas in the other four the adsorption maxima pertaining to the lower linear portion correspond to 35 to 54.4% of CEC. Correlation studies showed that zinc content and uptake by tomato had a negative relationship with adsorption maxima, bonding energy coefficients and maximum buffering capacity.
TL;DR: The adsorption of O2 and CO on polycrystalline and (111) thin palladium films formed by vapor deposition has been studied by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and mass spectrometry.
TL;DR: In this article, the exchange current in a solid electrolyte concentration cell is measured potentiostatically using a reference, counter, and working electrode with oxygen partial pressure (PO2) ranging from 6 × 101 to 2 × 104 Pa, at temperatures between 600 and 1000 K.
Abstract: To investigate oxygen adsorption of Pt, the exchange current (i0) in a solid electrolyte concentration cell is measured potentiostatically using a reference, counter, and working electrode with oxygen partial pressure (PO2) ranging from 6 × 101 to 2 × 104 Pa, at temperatures between 600 and 1000 K. It is found that i0 is a function of PO2 with a maximum at a specific PO2 which depends on temperature, and the slope of the log i0vs log PO2 for a higher PO2 region is approx. 0.2 and that for a lower PO2 region is between 0.2 and 0.6. These results are explained in terms of an electrochemical reaction of oxygen dissociatively adsorbed on Pt via a two-electron mechanism. On the basis of Langmuir's adsorption isotherm, the heat of oxygen adsorption on Pt is determined to be 180 KJ mol−1.
TL;DR: In this article, the adsorption isotherms of hydroquinone, some N -substituted p -phenylenediamines, 1-phenyl-pyrazolidin-3-one, sulfite, and iodide were measured at pH = 10.5 at a stationary gold electrode.
03 Jun 1983
TL;DR: In this article, the heat of adsorption of a gas from the solid sample in continuous flow sorptometer has been determined using simple Langmuir kinetics in the dynamic equilibrium model.
TL;DR: In this paper, the interaction between oxprenolol hydrochloride and montmorillonite was studied by adsorption isotherms, x-ray diffraction and i.r. spectroscopy.
Abstract: The interaction between oxprenolol hydrochloride and montmorillonite was studied by adsorption isotherms, x-ray diffraction and i.r. spectroscopy.The adsorption isotherm fits Langmuir's equation and the maximum amount of oxprenolol adsorbed by the clay is 70 mEq/100 g of clay.The results of x-ray diffraction studies and i.r. spectroscopy reveal that the oxprenolol molecule is adsorbed into the interlayer space of the clay and that the mechanism of adsorption is cation exchange.