Adsorption-Desorption Models

Samples Surface area (m /g) Pore volume (cm /g) Pore diameter (nm) Type Isotherm Hysteresis 

Noteworthy is the high surface area of the flowerlike Ce02 (F) and of the mixed CeZr02. 

There are several proposed models, which explain the adsorptiOTi-desorption phenomena. The most important models were described through the isotherms introduced by Langmuir, Freundlich, and Temkin. 

The first model of adsorption of gases on solids was proposed by Irving Langmuir in 

Langmuir suggested the following hypotheses for this model [6, 12]  

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Jain, A.K., Hudgins, R.R. and Silveston, P.L., "Adsorption/ Desorption Models How Useful to Predict Catalyst Behavior under Transient Conditions", paper submitted to Seventh North American Meeting, The Catalysis Society, Boston, 1981. 

Selim, H, M., Davidson, J. M., and Mansell, R. S. (1976a). Evaluation of a two-site adsorption-desorption model for describing solute transport in soils. Proc. Summer Comput. Simul. Conf. pp. 444-448. 

Kinetic regime. The first mechanism corresponds to the so-called kinetic regime (Popel 1994, Grigorenko et al. 1998) which is similar to the adsorption/desorption model (Blake 1993). Contrary to macroscopic hydrodynamic models, the adsorption/desorption model is based on the hypothesis that the motion of the triple line is ultimately determined by the statistical kinetics of atomic or molecular events occurring within the three-phase zone (Samsonov and Muravyev 1998). Such processes may be limiting at the very early stages of spreading of low... 

The texture and morphology of the synthesized objects were studied by the set of the instrumental methods XRD, FT-IR, SEM, TEM, BET, N2 adsorption-desorption. Model reaction of thiophene hydrodesulfurization (HDS) was used to investigate the chemical mobility of Ni-containing particles obtained by different ways. 

The isothermal and non-isothermal effectiveness factors for the single unimolecular irreversible reaction. Equilibrium adsorption-desorption model with linear isotherm For simplicity of presentation and without any loss of generality we consider here the case where the bulk temperature and concentration are taken as the reference temperature and concentration. In this case the boundary conditions (5.127) become at fu= 1.0... 

From the above equations, models of different degrees of sophistication can be obtained. The simplest physically realistic one is that based on the assumption of equilibrium adsorption-desorption with linear Langmuir adsorption isotherm, which will be presented first, followed by the general non-equilibrium adsorption-desorption model. 

The equations can be put in a dimensionless form in a manner similar to the case of the equilibrium adsorption-desorption model, but using more parameters. 

In the following sections, we will first consider metal—silicon and metal/III—V compound systems, covering electronic and chemical interface effects. We will then present a general treatment of the adsorption-desorption models which have been proposed, including some discussion of the interpretation of thermal desorption spectra, and finally we will discuss to what extent the two sets of data can be reconciled. We will not be concerned with metal films in device fabrication, nor the formation of additional phases by heat treatment. We shall only deal with interactions and interface chemistry which is directly relevant to adsorption-desorption behaviour. 

In the framework of the Langmuir adsorption-desorption model, all O atoms approaching the fraction 1 - 0 of the caibon surface not covered by C 0 complexes immediately react, forming the complexes. The kinetic equation for the fraction 6 can be written as (Lieberman Lichtenberg, 1994)... 

A adsorption-desorption model was proposed to explain pulse duration behavior for protein molecules, and the statistical analysis of Ai and t for the preceding three protein molecules showed they were distinguished. Further, tiny vibrations around the average steady-state current value revealed that the protein molecules engage in repeated adsorption/desorption events to/from the nanotube wall as they translocate through the detection zone. Additionally, it is believed that the rate of physical adsorption/desorption events for the smaller protein molecules to the membrane was larger than for the larger protein molecules. 

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