Models multi-site adsorption

Koretsky C. M., Sveijensky D. A., and Sahai N. (1998) A model of surface site types on oxide and sihcate minerals based on crystal chemistry imphcations for site types and densities, multi-site adsorption, surface infrared spectroscopy, and dissolution kinetics. Am. J. Sci. 298(5), 349-438. 

Due to this were proposed models of multi-site adsorption or multireaction. Their substance is in the differentiation of adsorption sites on the mineral surface in correlation with the rate of their exchange. 

The last section deals with the multi-site adsorption model of Nitta and his coworkers. In such model each adsorbate molecule is adsorbed onto n active sites and the adsorption is localised. For surfaces where mobile adsorption is possible, the approach using the scaled particle theory can be used in the statistical thermodynamics to obtain the required adsorption isotherm equation. This has been addressed by Nitta and co-workers and what to follow is the brief account of then-theory (Nitta et al., 1991). 

Multi-site adsorption model.Upon the assumption that there are two sites with different natures, in the course of TPD, and they only take place adsorption and desorption, it can be imagined that following adsorption-desorption process can occur on the surface (Fig. 7.17). The adsorption rate equation for each adsorption site is ... 

Narkiewicz-Michalek, J. Electrostatic theory of ion-pair chromatography multi-site occupancy model for modifier and solute adsorption. Chmmatographia 1993, 35, 527-538. 

It may be noted that the potentials used in the simulations are approximations, and that the selected equation of state for N2 is only applicable over restricted ranges of pressure and temperature. Like many other authors we have used these simple approximations to reveal broad patterns of behaviour. However, we are currently exploring more realistic models (e.g., multi-site LJ potentials) to explore the detail of adsorption in nanotubes. 

Siegel, M. D., V. S. Tripathi, M. G. Rao, and D. B. Ward. 1992. Development and validation of a multi-site model for adsorption of metals by mixtures of minerals 1 Overview and preliminary results. Proc. 7th inti. symp. water rock interaction, ed Y. K. Kharaka and A. S. Maest, I, pp. 63-67. Rotterdam A. A. Balkema. 

Nitta, T., Kuro-oka, M., and Katayama, T. (1984). An adsorption isotherm of multi-site occupance model for heterogeneous surface./. Chem. Eng.Jpn., 17, 45. 

Weerasooriya. R., Aluthpatabendi, I), and Tobschall, H.J., Charge distribution multi-site complexation (CD-MUSIC) modeling of Pb(II) adsorption on gibbsite. Colloids Surf. A. 189, 131, 2001. 

A multi-component gas solubility model and a multi-component surface adsorption model are generally required to estimate the monomer concentration at active sites. If the latter equilibrium can be neglected then the gas-solubility in the suspending agent determines the monomer concentration near the active site, which changes significantly with temperature and pressure. 

Fundamentals of sorption and sorption kinetics by zeohtes are described and analyzed in the first Chapter which was written by D. M. Ruthven. It includes the treatment of the sorption equilibrium in microporous sohds as described by basic laws as well as the discussion of appropriate models such as the Ideal Langmuir Model for mono- and multi-component systems, the Dual-Site Langmuir Model, the Unilan and Toth Model, and the Simphfied Statistical Model. Similarly, the Gibbs Adsorption Isotherm, the Dubinin-Polanyi Theory, and the Ideal Adsorbed Solution Theory are discussed. With respect to sorption kinetics, the cases of self-diffusion and transport diffusion are discriminated, their relationship is analyzed and, in this context, the Maxwell-Stefan Model discussed. Finally, basic aspects of measurements of micropore diffusion both under equilibrium and non-equilibrium conditions are elucidated. The important role of micropore diffusion in separation and catalytic processes is illustrated. 

During the early researching stages of melting-iron catalyst, the concept of multi-component mixed catalyst proposed by Mittasch, the BET equation and the selective chemisorption method for determining active site on catalyst proposed by Emmett et al, proposed the iron catalyst as a prototypical model catalyst established on the basis of N2 adsorption on iron catalyst. Brill has proved that Fe (111) face first adsorbs N2, and found that the transformation of small distorted manifests... 

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