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  • Articles  (22)
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  • Articles  (22)
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  • Springer  (22)
  • American Geophysical Union
  • American Institute of Physics (AIP)
  • American Physical Society
  • Blackwell Publishing Ltd
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  • 2000-2004  (10)
  • 1995-1999  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Neural Network Modeling of Adsorption of Binary Vapour Mixtures (1999)
    Springer
    Adsorption 5 (1999), S. 183-192 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; activated carbon ; neural network ; ideal adsorption solution theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Three neural network models were used for prediction of adsorption equilibria of binary vapour mixtures on an activated carbon. The predictions were compared both with published experimental data and calculated values from the Ideal Adsorption Solution (IAS) model. The neural network was trained using both binary and single component experimental adsorption data. Even for a limited number of data points (about 60) the network models were capable of approximating experimental data very precisely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008977528474
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  • 2
    Electronic Resource
    Electronic Resource
    Pressure Effects in Adsorption Systems (1999)
    Springer
    Adsorption 5 (1999), S. 261-278 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; concentrated systems ; pressure transients ; flow transients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A study of the occurrence of large pressure and flow transients when a strongly adsorbed gas is fed to a column which is initially loaded with a lightly adsorbed gas is presented here. Under certain conditions, these transients can cause premature breakthrough and change the shape of the breakthrough curve. This will result in improper estimation of adsorption parameters by the dynamic column loading method and lower apparent adsorption capacity in a full scale unit. A data acquisition system was used to record the pressure and flow transients. An isothermal PDE model developed to study these transients agreed reasonably well with the nonisothermal experimental results. The PDE model predicts that pressure and flow transients will occur during step and pulse~tests conducted to obtain adsorption and mass transfer parameters by the chromatographic method. For instance, lower adsorption capacity will be realized during step tests due to lowering in column pressure. Oscillations were observed when columns are connected in series. The PDE model also predicts these oscillations. Simulations indicate that the extent of oscillations is dependent on the dead volume between columns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008955828900
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  • 3
    Electronic Resource
    Electronic Resource
    Methane Adsorption on Planar WS2 and on WS2-Fullerene and -Nanotube Containing Samples (2000)
    Springer
    Adsorption 6 (2000), S. 169-174 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; WS2 ; nanotubes and fullerenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Adsorption-desorption cycles were measured for methane on non-irradiated WS2, and on irradiated WS2 (which contained, in part, WS2 fullerenes and nanotubes). Both types of samples were further subdivided into three sets: one set received no further treatment, another set was heated under vacuum, and the last set was acid-treated and heated. The specific surface area was determined for each set; so was the presence or absence of a hysteresis loop in the adsorption-desorption cycles. The results of these two groups of measurements were correlated with the space available for adsorption. The implications of the results for the experimental determination of the dimensionality of gas adsorbed at the interior of nanotubes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008921602962
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  • 4
    Electronic Resource
    Electronic Resource
    Why Does the Linear Driving Force Model for Adsorption Kinetics Work? (2000)
    Springer
    Adsorption 6 (2000), S. 137-147 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; kinetics ; linear driving force model ; process design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008965317983
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  • 5
    Electronic Resource
    Electronic Resource
    A Grand Canonical Monte-Carlo Simulation Study of Xenon Adsorption in a Vycor-like Porous Matrix (2000)
    Springer
    Adsorption 6 (2000), S. 241-249 
    Details
    ISSN: 1572-8757
    Keywords: silical glasses ; CPG ; Vycor ; adsorption ; capillary condensation ; molecular simulation ; Monte-Carlo ; SANS ; SAXS ; fractals ; surface roughness ; Porod's law ; Gurvitch rule ; hysteresis loop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We have performed atomistic Grand Canonical Monte-Carlo (GCMC) simulations of adsorption of xenon in a Vycor-like matrix at 195 K. The disordered mesoporous network is obtained by applying a numerical 3D off-lattice reconstruction procedure to a simulation box originally containing silicon and oxygen atoms of a non-porous silica solid. In order to reduce the computational cost, we have applied a homothetic decrease of the simulation box dimensions which preserves the morphology and the topology of the pore network (the average pore dimension is then around 30 Å). The surface chemistry is obtained in a realistic fashion by saturating all dangling bonds with hydrogen atoms. Small angle scattering spectra calculated on different numerical samples have evidenced a departure from Porod's law due to surface roughness. The simulated isotherms calculated on such disordered connected porous networks, show the capillary condensation phenomenon. The shape of the adsorption curves differs from that obtained for simple pore geometries. The analysis of the adsorbed quantity distribution indicates partial molecular-film formation depending on the local surface curvature and roughness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008993328699
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  • 6
    Electronic Resource
    Electronic Resource
    The Adsorption of CHClF2 on NaY5.6 Zeolite (2000)
    Springer
    Adsorption 6 (2000), S. 259-267 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; zeolite ; chlorodifluoromethane ; adsorption structure ; H and F NMR ; chemicalshift ; relaxation time ; adsorbate mobility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The adsorption of CHClF2 on NaY5.6 zeolite has been studied by measuring the H and F NMR of the adsorbed CHClF2, focusing in particular on the measurements of the chemical shift and longitudinal relaxation time, as well as the adsorption isotherm measurements. It is possible to determine the coordination structure of the CHClF2 adsorbed on NaY5.6 zeolite by measuring the adsorption amount dependence of the chemical shift. In addition, the motional activity of the adsorbed molecules in the super cage of the zeolite is discussed on the basis of observed longitudinal relaxation times for various adsorption amounts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008997529608
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  • 7
    Electronic Resource
    Electronic Resource
    Adsorption Characteristics in Zeolite Nano-Pore Evaluated by use of Nitrogen Monoxide as a Probe Adsorbate (2000)
    Springer
    Adsorption 6 (2000), S. 251-257 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; EPR ; mordenite ; MOR ; NO ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Adsorption isotherms of nitrogen monoxide (NO) and in situ EPR spectra of adsorbed NO on mordenite zeolites (MOR) of different cation types (HM, NaM and CaM) are measured at different temperatures to elucidate the effect of the strong adsorption promoted by the enhancement of potential field in micropore of MOR (micropore filling) as well as the electrostatic interaction in MOR on NO adsorption. The NO molecules adsorb irreversibly and fill up the micropore of MOR at 201 K, above the critical temperature of NO, regardless of the kind of cation species. The NO adsorption takes place even at 273 K. In the adsorption at 273 K, the strength of electrostatic field formed by cation sites affects the adsorptivity and the order of saturation amount of adsorption (V s) corresponds to that of the electrostatic field strength. EPR results show that NO molecules strongly interact with cation sites in MOR and disproponation reaction of NO take place on CaM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008945412770
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  • 8
    Electronic Resource
    Electronic Resource
    Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)
    Springer
    Adsorption 5 (1999), S. 25-37 
    Details
    ISSN: 1572-8757
    Keywords: micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026481704926
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  • 9
    Electronic Resource
    Electronic Resource
    Equilibrium Adsorption of Light Alkanes in Silicalite-1 by the Inertial Microbalance Technique (2000)
    Springer
    Adsorption 6 (2000), S. 159-167 
    Details
    ISSN: 1572-8757
    Keywords: silicalite-1 ; adsorption ; TEOM ; alkanes ; isosteric heat ; adsorption entropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The equilibrium adsorption of the light alkanes methane, ethane, propane, n-butane, and i-butane in silicalite-1 has been investigated using the TEOM technique. Either a conventional or a dual-site Langmuir isotherm appropriately describes the equilibrium data. Good agreement with the literature data determined by other techniques indicates the TEOM is a reliable technique. The adsorption of i-butane in silicalite-1 reveals the discrete preferential molecular siting, implying a discrete-dual-structural heterogeneity for light alkanes in silicalite-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008969518892
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  • 10
    Electronic Resource
    Electronic Resource
    Thermodynamics of Copper Adsorption-Desorption by Ca-Kaolinite (2000)
    Springer
    Adsorption 6 (2000), S. 325-335 
    Details
    ISSN: 1572-8757
    Keywords: copper ; ca-koalinite ; adsorption ; desorption ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The temperature effect on Cu adsorption and desorption on kaolinite has been investigated at four temperatures (8°C, 25°C, 30°C and 40°C). The clay sample was saturated with Ca. Copper was sorbed from solutions containing eleven Cu concentrations between 0.0010 and 0.0211 M, equilibrated for 2 days. Cu adsorption decreased, but desorption increased with increasing temperature, indicating that adsorption is an exothermic process while desorption is endothermic. These conclusions are confirmed by the values of ΔH 0 estimated for adsorption and desorption. The initial copper concentration is a significant factor influencing mainly the adsorption process, which is spontaneous (ΔG 0 〈 0) only for low initial Cu concentrations. The desorption process is spontaneous for all Cu concentrations. ΔS 0 values have also been calculated. Experimental adsorption data were successfully fitted to the Freundlich isotherm and to the Gouy-Chapman model in order to express the process quantitatively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026513032260
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  • 11
    Electronic Resource
    Electronic Resource
    Static and Kinetic Studies on the Adsorption Behavior of Sulfadiazene (2000)
    Springer
    Adsorption 6 (2000), S. 349-357 
    Details
    ISSN: 1572-8757
    Keywords: sulfadiazene ; adsorption ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To investigate the nature of interactive forces between sulfadiazene molecules and alumina surface the experiments were performed for the adsorption of sulfadiazene (SD) from its aqueous sulution onto the alumina surfaces at 25 ± 0.2°C and the influence of factors such as increasing concentration of SD (4.0–20.0 × 10−3 mol cm−3), the time required for adsorption equilibrium, pH (2.0–12.0) and temperature (5–45°C) of the adsorption medium, the presence of ions like Cl−, SO2− 4 and PO3− 4 (0.01–0.30 M) and organic solvents (5% v/v) were observed on the course of adsorption of SD. Various adsorption and kinetic parameters such as adsorption coefficient, the rate constants for adsorption and desorption were also evaluated. The results of the above cited studies facilitated to formulate the mechanisms of interaction between SD and alumina surfaces. From application view point the present work may be a potential tool for an effective chromatographic separation of sulfa drugs from industrial effluents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026517117239
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  • 12
    Electronic Resource
    Electronic Resource
    Effects of Surface Oxygen of Activated Carbon on Alkaloid Adsorption: A Molecular Dynamics Simulation Study (1999)
    Springer
    Adsorption 5 (1999), S. 97-108 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; molecular simulation ; activated carbon ; surface oxygen ; alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The influence of the density and the type of surface oxygen on the adsorption of berberine alkaloid onto activated carbon was investigated using the molecular dynamics simulation method in vacuum. The carbon surface consisted of a basal plane of graphite and surface oxygen groups which were bonded on the graphite plane in a regular square array with various densities. Two types of surface oxygen groups, =O and —OH, were employed. The simulation results showed that the berberine alkaloids were favorable to be adsorbed on the negative charged carbon surfaces. It was indicated that the vdw attraction of the carbon surface to the alkaloid molecule dominates the adsorption only at the lower surface density of oxygen. It is also indicated that a good adsorptive selectivity for a certain berberine alkaloid can be obtained by controlling the density of surface oxygen. The adsorption simulation of berberine alkaloids onto activated carbon in the presence of water was also carried out by using a dome-shape molecular model for presenting the alkaloid/water/carbon system. It was found that the adsorption of berberine alkaloids on the activated carbon which has a higher density of surface oxygen was strongly inhibited by the presence of water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026479130851
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  • 13
    Electronic Resource
    Electronic Resource
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 14
    Electronic Resource
    Electronic Resource
    Impedance Spectroscopic Measurements of Pure Gas Adsorption Equilibria on Zeolites (1999)
    Springer
    Adsorption 5 (1999), S. 159-167 
    Details
    ISSN: 1572-8757
    Keywords: impedance spectroscopy ; uptake curve ; adsorption ; polarization of adsorbate ; dielectric properties of adsorbed phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Physisorption equilibria of gases on inert porous solids like activated carbon or molecular sieves can be characterized by measuring the (frequency dependent) capacitance of a capacitor filled with a sample adsorbent. This quantity strongly depends not only on the physico-chemical structure of the empty adsorbent in vacuum, but also on the permanent or induced dipole moments of the molecules adsorbed and of the fluid phase. Consequently, it should be possible to determine the excess mass being adsorbed on the internal surface of a highly porous solid by measurements of the dielectric constant. The aim of this work is to show for various pure gases and adsorbents that the change of the capacitance of an adsorption system depends on the adsorbed mass. Therefore, this effect can be used to characterize porous solids and their adsorbates and, for example, to check the state or the quality of industrial adsorbents during a process on site if calibration measurements have been taken (Staudt et al., 1994, 1998).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008969308910
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  • 15
    Electronic Resource
    Electronic Resource
    Liquid Phase Separation of Polar Hydrocarbons from Light Aromatics Using Zeolites (1999)
    Springer
    Adsorption 5 (1999), S. 399-407 
    Details
    ISSN: 1572-8757
    Keywords: zeolites ; polar compounds ; adsorption ; adsorption isotherms ; equilibrium ; liquid phase ; breakthrough curves ; acetonitrile ; acrylonitrile ; dioxane ; ZSM-5 ; MCM-22 ; Na-X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The liquid phase removal of low concentrations of polar compounds (acetonitrile, acrylonitrile and dioxane) from toluene by adsorption on zeolites reveals very high selectivity factors. Kinetic selectivity factors as high as 16,100 are observed. The selection of the zeolites (MFI, MWW and FAU type) allowed the study of the effects of varying aluminum content, the presence and absence of acidic centers and varying pore volumes. To assess the relative effectiveness of each adsorbent, both equilibrium and continuous flow, pseudo equilibrium, breakthrough experiments were conducted. The continuous flow experiments were carried out at 25 and 75°C. The zeolites H-ZSM-5, H-MCM-22 and Na-X are highly effective in removing the polar compounds from toluene to a concentration level down to less than 20 ppm (detection limit). The results obtained with the equilibrium batch experiments are confirmed by the continuous flow breakthrough experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008916917943
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  • 16
    Electronic Resource
    Electronic Resource
    Wetting-Induced Aggregation of Colloids (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 997-1008 
    Details
    ISSN: 1572-9613
    Keywords: adsorption ; aggregation ; colloids ; interfaces ; wetting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract More than two decades ago, in a seminal paper John Cahn proposed scaling arguments for the possibility of a wetting transition in two coexisting fluid phases near the critical point. Since then, Cahn's model has been tested in many fluid systems and further refined by including the real interactions between the fluid and the solid wall. A fascinating consequence of the existence of a wetting transition is the possibility for a transition from weak to strong adsorption in the homogeneous phase. The situation is further enriched in nonstandard geometries having special geometrical constraints. The subject of this review concerns one such situation, where charge-stabilized colloidal particles are suspended in the homogeneous region of a binary liquid mixture. In this case, the preferential adsorption of one of the liquid components on to the colloid surface completely modifies the stability of the particles leading to an aggregation process. Although the exact mechanism underlying the adsorption phenomenon is still debated, it is closely related to the wetting transition. Recent experimental developments concerning the static and dynamic aspects of this phenomenon are reviewed. In addition, the main findings of a theoretical model based on the adsorption-modified electrostatic interactions between the colloidal particles are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004506601807
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  • 17
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    Electronic Resource
    Removal of Sulfate, Phosphate and Colored Substances in Wastewater Effluents using Feldspar (2000)
    Springer
    Water resources management 14 (2000), S. 417-434 
    Details
    ISSN: 1573-1650
    Keywords: adsorption ; feldspar ; industrial effluent ; pollution control ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Feldspar, among many natural substances such as termitemount-clay, saw-dust, kaolinite and dolomite, offers asignificant removal ability for sulfate, phosphate, and coloredsubstances. Optimization of experimental parameters such assolution pH and flow rate reveals, that the maximum efficiency forremoval of phosphate, sulfate, and colored substances is about42, 52, and 73% respectively. X-ray diffraction, adsorptionisotherm and recovery studies suggest, that the removal processof anions occurs via ion exchange in conjunction with surfaceadsorption. Furthermore, reaction rate studies indicate thatthe removal of the selected pollutants by feldspar follows first-order kinetics. Although the percent removal, under the optimized conditions, is higher for laboratory prepared solutions, efficiency is a little less for industrial effluentsdue to interferent effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011171330097
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  • 18
    Electronic Resource
    Electronic Resource
    Fokker–Planck Equation, Molecular Friction, and Molecular Dynamics for Brownian Particle Transport near External Solid Surfaces (1999)
    Springer
    Journal of statistical physics 94 (1999), S. 557-586 
    Details
    ISSN: 1572-9613
    Keywords: Brownian particle ; Fokker–Planck equation ; adsorption ; molecular friction; force autocorrelation function ; molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Fokker–Planck (FP) equation describing the dynamics of a single Brownian particle near a fixed external surface is derived using the multiple-time-scales perturbation method, previously used by Cukier and Deutch and Nienhuis in the absence of any external surfaces, and Piasecki et al. for two Brownian spheres in a hard fluid. The FP equation includes an explicit expression for the (time-independent) particle friction tensor in terms of the force autocorrelation function and equilibrium average force on the particle by the surrounding fluid and in the presence of a fixed external surface, such as an adsorbate. The scaling and perturbation analysis given here also shows that the force autocorrelation function must decay rapidly on the zeroth-order time scale τ 0, which physically requires N Kn≪1, where N Kn is the Knudsen number (ratio of the length scale for fluid intermolecular interactions to the Brownian particle length scale). This restricts the theory given here to liquid systems where N Kn≪1. For a specified particle configuration with respect to the external surface, equilibrium canonical molecular dynamics (MD) calculations are conducted, as shown here, in order to obtain numerical values of the friction tensor from the force autocorrelation expression. Molecular dynamics computations of the friction tensor for a single spherical particle in the absence of a fixed external surface are shown to recover Stokes' law for various types of fluid molecule–particle interaction potentials. Analytical studies of the static force correlation function also demonstrate the remarkable principle of force-time parity whereby the particle friction coefficient is nearly independent of the fluid molecule–particle interaction potential. Molecular dynamics computations of the friction tensor for a single spherical particle near a fixed external spherical surface (adsorbate) demonstrate a breakdown in continuum hydrodynamic results at close particle–surface separation distances on the order of several molecular diameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004552421971
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  • 19
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    The Influence of Adsorption on PVT Measurements in the Gaseous Phase (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1711-1719 
    Details
    ISSN: 1572-9567
    Keywords: adsorption ; capillary condensation ; HFC-134a ; HFC-134a/ FC-218 mixture ; phase transition ; PVT measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract PVT measurements of 1,1,1,2-tetrafluoroethane (C2H2F4, HFC-134a) and its blend with octofluoropropane (C3F8, FC-218) have been performed in the gas phase near the dew curve. The experimental data were obtained by variable-volume and vibrating tube methods. Discrepancies in the behavior of isotherms from their classical behavior were experimentally observed. It was found that the phase transition does not go to completion at a single point of the thermodynamic surface but extends over a limited range of conditions. Obtained results are in accordance with a concept of adsorption of the vapor sample on the surface of the experimental cell. An increase in adsorption under the conditions close to condensation is caused by capillary condensation of the sample at the walls of the cell that initiates an early phase transition. The ranges of diffuse phase transitions were determined for 1,1,1,2-tetrafluoroethane as well as for its mixture with octofluoropropane at different thermodynamic parameters. The influence of selective adsorption on the change in the conditions of phase transition of the 1,1,1,2-tetrafluoroethane/octofluoropropane mixture was also experimentally studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022657929526
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  • 20
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    The Adsorption of Mixed Surfactants at the Hydrophilic Silica Surface from Aqueous Solution: Studied by Specular Neutron Reflection (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 19-34 
    Details
    ISSN: 1572-9567
    Keywords: adsorption ; hydrophilic interface ; mixed surfactants ; neutron reflectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Specular neutron reflection has been used to determine the structure and composition of the mixed ionic–non-ionic surfactants adsorbed at the hydrophilic silica solid/water interface. Measurements on two different mixed surfactant systems are reported: the cationic/nonionic mixture of hexadecyltrimethyl ammonium bromide, C16TAB, and hexaethylene glycol monododecyl ether, C12E6, and the anionic/nonionic mixture of sodium dodecyl sulfate, and C12E6. For the C16TAB–C12E6 mixture, pH is shown to have a dramatic effect on the relative affinity for adsorption of the two surfactants at the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021413810630
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  • 21
    Electronic Resource
    Electronic Resource
    Observation of a Sharp Transition in Contact Angle in the Wetting of Graphite by Solid Pb-Ni Alloys (1999)
    Springer
    Interface science 7 (1999), S. 173-180 
    Details
    ISSN: 1573-2746
    Keywords: contact angle transition ; wetting ; interfacial energy ; solid pb-Ni/graphite system ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The wetting of Pb-Ni crystals on graphite has been observed at 558 K in a Scanning Auger Microprobe. Samples were prepared so as to produce 10 μm crystals of Pb with Ni contents increasing from 0 to 0.3 wt% along one axis of the graphite substrate. In the low Ni region, the contact angle was found to decrease slowly from 119° to 98° with increasing Ni content. In the region of high Ni content, a constant contact angle of 83° was measured. In between, crystals with contact angles of 98° and 83° were observed to coexist, near the limit of solubility of Ni in Pb, indicating the presence of a first order transition in contact angle. The continuous decrease in contact angle, in the low Ni region, is due to Ni adsorption at the Pb-graphite interface, which leads to a decrease in interfacial energy. The constant contact angle in the high Ni region is associated with the precipitation of a Ni-rich phase. Various hypotheses are advanced to account for the first order transition in contact angle as a function of Ni concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008779501606
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  • 22
    Electronic Resource
    Electronic Resource
    Electrochemical and Adsorption Studies on the Formation of Poly-8-Hydroxyquinaldine Thin Films at Glassy Carbon/Electrolyte Interface (2000)
    Springer
    Interface science 8 (2000), S. 111-121 
    Details
    ISSN: 1573-2746
    Keywords: 8-hydroxyquinaldine ; electropolymerization ; adsorption ; glassy carbon ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The kinetics and thermodynamics of the electropolymerization of the chelating agent 8-hydroxyquinaldine on GCE's (Glassy Carbon Electrodes') surface from aqueous phosphate buffers are reported. Thermodynamic functions related to the adsorption of the monomer on the GCE's surfaces were determinated. No contribution from GCE surface's functional group to the electropolymerization reactions was reported. The effects of monomer concentration, pH, and temperature on the electrochemical growth of poly 8-hydroxyquinaldine were investigated. The results suggest that the propagation of the electropolymerization process takes place via a free radical chain reactions. Furthermore, the results indicate that the electrochemical growth of the polymeric films is dictated by pre-polymerization adsorption on the electrode surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008799724511
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