Kinetics and adsorption

Jin X, Talbot J and Wang N FI L 1994 Analysis of steric hindrance effects on adsorption kinetics and equilibria AlChE J. 40 1685-96... 

Surface SHG [4.307] produces frequency-doubled radiation from a single pulsed laser beam. Intensity, polarization dependence, and rotational anisotropy of the SHG provide information about the surface concentration and orientation of adsorbed molecules and on the symmetry of surface structures. SHG has been successfully used for analysis of adsorption kinetics and ordering effects at surfaces and interfaces, reconstruction of solid surfaces and other surface phase transitions, and potential-induced phenomena at electrode surfaces. For example, orientation measurements were used to probe the intermolecular structure at air-methanol, air-water, and alkane-water interfaces and within mono- and multilayer molecular films. Time-resolved investigations have revealed the orientational dynamics at liquid-liquid, liquid-solid, liquid-air, and air-solid interfaces [4.307]. 

This flattened erythrocyte preparation has been used to study reversible nonspecific adsorption kinetics and surface diffusion of insulin on the external surface of erythrocytes.(123) The nonspecific adsorption of insulin to the polylysine-coated substrate is very large compared to the adsorption to the flattened membrane adhered to the substrate. Fortunately, this nonspecific background fluorescence can be very successfully quenched simply by preparing the polylysine coating on an aluminum-film-coated glass surface, rather than on bare glass. As discussed in Section 7.3, the aluminum abolishes the fluorescence of fluorophores adsorbed directly onto the polylysine substrate, but the fluorophores adsorbed to the erythrocyte surface are not substantially quenched, because they are spaced at least two membrane thicknesses away. 

Adsorption kinetic and adsorption isotherm of pesticide metobromuron at the high area ACC were investigated in relation to water treatment. The ACC used in this study seems to be quite effective in adsorption of metobromnron from aqueous solutions. Adsorption of that pesticide was found to follow second-order kinetic model and the adsorption isotherm is well represented by Frenndlich model. 

Fluoride in minor concentrations is beneficial for animals and humans, bnt it becomes toxic when ingested in excessive amounts. Bar-Yosef et al. (1989) investigated adsorption kinetics and isotherms of K -montmorillonite and a series of soils (clay, 4-61% organic matter, 2-7%), as affected by solution pH. The flnoride... 

It has been known that adsorption kinetics and/or thermodynamics of proteins depend on the electric or electrochemical properties of solid supports on which the proteins are adsorbed. This has led us to elucidate the effects of electrode potential on the adsorption behavior of avidin on the electrode surface. For this purpose, the electrode potential of a Pt electrode was varied systematically in the range of -0.5-+2.0 V in an avidin solution (pH 7.4). Although the data was somewhat scattered, a general trend was observed that the adsorption of avidin is suppressed by the application of a positive potential (+1.0-+2.0 V). This may be originating from the fact that avidin is a basic protein and has net positive charges in the solution of neutral pH. In the potential range tested, no significant acceleration in the adsorption was induced. 

Kotsmar, Cs., Pradines, V., Alahverdjieva, V.S., Aksenenko, E.V., Fainerman, V.B., Kovalchuk, V.E, Kragel, J., Leser, M.E., Noskov, B.A., Miller, R. (2009). Thermodynamics, adsorption kinetics and rheology of mixed protein-surfactant interfacial layers. Ach cmces in Colloid and Interface Science, 150, 41-54. 

Krisdhasima, V., Vinaraphong, R, and McGuire, J. 1993. Adsorption kinetics and elutability of a-lactalbumin, p-casein, p-lactoglobulin and bovine serum albumin at hydrophobic and hydrophilic interfaces. J. Colloid Interface Sci. 161 325-334. 

The possibility of making such MIP membrane disks has been well demonstrated yet we do not know of real-life analytical applications. This may be related to the low selective capacity of the MIPs, the slow adsorption kinetics, and the known bleeding of MIPs which may be disturbing in environmental ultratrace analysis. A further problem is that the matrix of the large sample volume (typically aqueous) may not be compatible with the MIP separation. 

Desorption is always an activated process and may conveniently be studied by temperature-programmed techniques. Information is obtained in this way on the adsorption kinetics and the energetics of the gas/solid interactions. 

A useful literature relating to polypeptide and protein adsorption kinetics and equilibrium behavior in finite bath systems for both affinity and ion-ex-change HPLC sorbents is now available160,169,171-174,228,234 319 323 402"405 and various mathematical models have been developed, incorporating data on the adsorption behavior of proteins in a finite bath.8,160 167-169 171-174 400 403-405 406 One such model, the so-called combined-batch adsorption model (BAMcomb), initially developed for nonporous particles, takes into account the dynamic adsorption behavior of polypeptides and proteins in a finite bath. Due to the absence of pore diffusion, analytical solutions for nonporous HPLC sorbents can be readily developed using this model and its two simplified cases, and the effects of both surface interaction and film mass transfer can be independently addressed. Based on this knowledge, extension of the BAMcomb approach to porous sorbents in bath systems, and subsequently to packed-, expanded-, and fluidized-bed systems, can then be achieved. 

Adsorption investigations (determination of equilibrium data, uptake rates, adsorption kinetics, and intracrystalline diffusion). 

This paper presents some results of the studies of the influence of ion exchange cations on adsorption, kinetics, and chromatographic characteristics of zeolites of types A, X, and Y. 

It has been concluded that, for most cases, catalysis over zeolites occurs within the intracrystalline voids. Strong supporting evidence for this was provided by Weisz (71), who compared the rates of dehydration of 2-butanol over Linde lOX and 5A zeolites at relatively high temperatures and low conversion. The rate constant per unit volume of 5A was 1/lOO-l/lOOOth that for lOX, a magnitude consistent with the ratio of available surface areas for the external area of 1-5/x-sized 5A crystals and for lOX, where the internal surface area was available to the alcohol. The strong driving force for occlusion within the intracrystalline zeolite voids is exemplified by the rapid adsorption kinetics and rectangular adsorption isotherms observed for molecules whose dimensions are not close to those of the entry pores. 

One way in split-peak measurements can be performed is by injecting a small amount of analyte onto an affinity column at various flow rates. A plot of the inverse negative log of the measured free fraction is then made versus the flow rate. The slope of this graph is related to the adsorption kinetics and mass-transfer rates within the column. If the system is known to have adsorption-limited retention or if the mass-transfer rates are known, then the association rate constant for ana-... 

In studies of ethylene [41, 42], propylene, isobutylene [42], 1-butene and 2-butene [43], and cyclohexene [44], adsorption kinetics and TPD measurements showed little or no effect of alloyed Sn on either the initial sticking coefficient or the saturation coverage of these small alkenes on the two Sn/Pt(lll) alloys when compared with Pt(lll) at 100 K. The adsorption ensemble requirement for chemisorption of... 

Measurement of weight changes is a very direct method of obtaining adsorption kinetics, and is also used to follow the course of other heterogeneous reactions (see Section 3). It is particularly suitable for adsorption measurements with small surface areas at relatively high pressures, where the volumetric method is insensitive. Several comprehensive reviews are available " which discuss the theory,... 

The rapid adsorption kinetics and rectangular adsorption isotherms observed with faujasite-type zeolites, at least with molecules whose dimensions are not close to those of the pores, attest to the strong driving force for occlusion within the intracrystalline volume. Further,... 

Activated carbon fibers have attracted increasing attention in recent years as a better adsorbent than granular activated carbons, because they normally present much higher adsorption kinetics and adsorption capacity. Activated carbon fibers only have micropores, which are directly accessible from the external surface of the fiber. Thus, adsorptive molecules reach adsorption sites through micropores without the additional difiusion resistance of macropores, which is usually the rate-controlling step in granular adsorbents. 

Alkan, M. et al.. Surface properties of bovine serum albumin-adsorbed oxides Adsorption, adsorption kinetics and electrokinetic properties, Micropor. Mesopor. Mater., 96, 331, 2006. 

The most suitable technique for studying adsorption kinetics and dynamic surface tension is the maximum bubble pressure method, which allows measurements to be obtained in the millisecond range, particularly if correction for the so-called dead time, t. The dead time is simply the time required to detach the bubble after it has reached its hemispherical shape. A schematic representation of the principle of maximum bubble pressure is shown in Figure 18.14, which describes the evolution of a bubble at the tip of a capillary. The figure also shows the variation of pressure p in the bubble with time. 

SERS was discovered with pyridine. Other aromatic nitrogen- or oxygen-containing compounds, such as aromatic amines or phenols, also display strong enhancement due to SERS. The enhancement can also be seen with other electron-rich analytes such as carboxylic acids. Although SERS allows easy observation of Raman spectra from solutions with concentration in the micromolar (10 ) range, slow adsorption kinetics and competitive adsorption limit its application in analytical chemistry. 

Miller R, Fainerman VB, Aksenenko EV, Makievski AV, Kraegel J, Liggieri L, Ravera F, Wuestneck R, and Loglio G (2000) "Surfactant Adsorption Kinetics and Exchange of Matter for Surfactant Molecules with Changing Orientation within the Adsorption Layer" in Emulsion, Foams, and Thin Films, Mittal and Kumar Editors, Ch. 18, Marcel Dekker, pp. 313-327 Miller R, Fainerman VB, Makievski AV, Leser M, Michel M and Aksenenko EV (2004) Determination of Protein Adsorption by Comparative Drop and Bubble Profile Analysis Tensiometry. Colloids Surfaces B 36 123-126 Neumann AW and Spelt JK Eds., Applied Surface Thermodynamics, Surfactant Science Series, Vol. 63, Marcel Dekker Inc., New York, 1996 Noskov B and Logho G (1998) Dynamic surface elasticity of surfactant solutions. Colloids Surfaces A 143 167-183... 

The equation of state for a surface layer and the respective adsorption isotherm are the basis for calculations of adsorption kinetics and dynamic surface ten-... 

The role of adsorption kinetics and the diffusion of surfactants is especially important in controlling capillary impregnation. According to studies by N.N. Churaev, the solution impregnating the capillary quickly loses its dissolved surfactant due to adsorption of the latter on capillary walls, so the rate of impregnation may be limited by the diffusional transport of surfactant from the bulk of the solution to the menisci in the pores. 

Chq)ter 3 is devoted to processes strongly influenced by hydrodynamics, adsorption kinetics and surface rheology. There are at the moment several weak points in the description of... 

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