Revised physical adsorption

Attention was paid early on to solution pH, and in particular, to a surface — bulk proton balance. Various models of hydroxyl chemistry have been developed in colloid science literature [21], Perhaps the simplest and most common model assumes a single type of OH group and amphoteric behavior (i.e., one set of Kx and K2 from Figure 6.1). More complicated models invoke multiple OH groups and proton affinity distributions [22]. It will be demonstrated below that the simpler type has worked well for the revised physical adsorption (RPA) model. 

Hao X, Spieker WA, Regalbuto JR. A further simplification of the revised physical adsorption (RPA) model. J Colloid Interface Sci. 2003 267 259-64. 

Much more work on the experimental verification and quantification of this physical adsorption process has been conducted in our own laboratory for the chloroplatinic acid (HzPtCL, or CPA)/alumina system [3,4]. The Revised Physical Adsorption (RPA) model [4], with which all known sets of Pt/alumina adsorption data can be satisfactorily simulated with no adjustable parameters, is a result of these efforts. The basis of the RPA model is the a priori calculation of adsorption equilibrium constants, seen as the center regime of Fig. 1. 

It is assumed that the surface charges are balanced by an equal number of charged metal complexes in a region adjacent to the solid surface. In this mechanism, it is also assumed that only the metal ions can be adsorbed onto the solid support. An excellent model of this type is the revised physical adsorption (RPA) model developed by Regalbuto s group [20,22, 23]. It has been experimentally verified for several metal/support systems. 

Fully revised and expanded, this new edition deeply explores physical and chemical equilibrium, including a new appendix on the Bridgman Table and its uses, a new chapter on Equilibrium in Biochemical Reactions, and new sections on minimum work, eutectics and hydrates, adsorption, buffers and the charge-balance method of computing them. Its appendix on Calculation of Fugacities from Pressure-explicit EOSs shows clearly how modern computer equilibrium programs actually do their work using the SRK and related equations. 

Hammer, B., Hansen, L.B., and Norskov, J.K. Improved adsorption energetics within density-functional theory nsing revised Perdew-Burke-Eimzerhof functionals. Physical Review B Condensed Matter and Materials Physics, 59, 7413-7421,1999. www.fysik. dtu.dk/campos. 

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