Mechanism of solution

Consequences of the Snyder and Soczewinski model are manifold, and their praetieal importance is very signifieant. The most speetaeular conclusions of this model are (1) a possibility to quantify adsorbents ehromatographic activity and (2) a possibility to dehne and quantify chromatographic polarity of solvents (known as the solvents elution strength). These two conclusions could only be drawn on the assumption as to the displacement mechanism of solute retention. An obvious necessity was to quantify the effect of displacement, which resulted in the following relationship for the thermodynamic equilibrium constant of adsorption, K,, in the case of an active chromatographic adsorbent and of the monocomponent eluent ... 

SZ Song, JR Cardinal, SJ Wisniewski, SW Kim. Mechanisms of solute permeation through hydrogel films An irreversible thermodynamic approach. Abstracts of Papers Presented at the 126th National Meeting of the American Pharmaceutical Association, 1979. 

Bassolino-Klimas, D., Alper, H. E. and Stouch, T. R. (1995). Mechanism of solute diffusion through lipid bilayer membranes by molecular dynamics simulation, J. Am. Chem. Soc., 117, 4118 4129. 

Various criteria can be applied in order to arrive at a useful classification scheme for the different mechanisms of solute transport through biological membranes. 

Mass transfer. It is not yet possible to predict the mass transfer coefficient with a high degree of accuracy because the mechanisms of solute transfer are but imperfectly understood as discussed Light and Conway(14), Coulson and Skinner(15) and Garner and Hale 16 1. In addition, the flow in spray towers is not strictly countercurrent due to recirculation of the continuous phase, and consequently the effective overall driving force for mass transfer is not the same as that for true countercurrent flow. 

Dill, K.A., The mechanism of solute retention in reversed-phase liquid chromatography, J. Phys. Chem., 91, 1980, 1987. 

As in most membranes, the liquid membrane must have selective permeability to specific solutes. The overall mechanism of solute transfer consists of three steps (1) extraction of the solute into the liquid membrane ... 

The two main mechanisms of solute separation by liquid membranes involve chemical reactions. In the case illustrated in Fig. 15.2a, the solute first dissolves in the liquid membrane, then diffuses toward phase 3 due to the buildup of a concentration gradient, and finally transfers to phase 3 at the... 

The kinetics of back extraction are equally important to obtain a better understanding of the mechanism of solute transfer, and to determine the rate-limiting step for the process. Such information is crucial for the rational design of an extraction apparatus and, as discussed above, Jar-udilokkul et al. [33] showed that counterion extraction resulted in remarkable increases in the back-extraction of proteins. 

For the chemists, this variability of ILs presents a challenge. As concerns extraction, it is associated with the possibility of different mechanisms of solute transfer, differenf mufual solubilities in biphasic systems, different solvation abilities, and probably, even different bulk phase structures. We should develop a deeper understanding of IL-based extraction systems undoubtedly technological and analytical applications will benefit a great deal. 

Most of the mathematical theories and approaches have been developed originally for sorption rather than ion exchange. However, they are sufficiently general to be applicable with minor, if any, modifications to a number of similar phenomena such as ion exclusion and ligand exchange. According to Helfferich (1995), the applicability of a simplified theory depends more on the mode of operation than on the particular mechanism of solute uptake. 

In the past decade, many new techniques have been developed and applied to the study of interfaces. While earlier measurements involved only macroscopic characteristics of the interface (e.g., surface charge, surface tension, and overall potential drop), new spectroscopic techniques have opened a window to the microstructure of the interface, and insight at the atomic level in this important region is now possible. Parallel to these discoveries and supported by them, more realistic theoretical models of the interface have been developed that combine quantum mechanical theories of metal surfaces and the statistical mechanics of solutions. 

Kinetics and Mechanism of Solution of High Volatile Coal... 

The statistical mechanics of solutions at nonvamshing concentration is best-formulated within the grand canonical ensemble, where the number of solute molecules contained in volume Si is allowed to fluctuate. We only control the average concentration cp via the chemical potential fi.p This has great technical advantages, allowing for a very simple, analysis of the thermodynamic limit. In contrast, in the canonical ensemble, where the particle number M = Qc.p is taken as basic variable, an analysis of the thermodynamic limit is more tricky. A short discussion is given in the appendix. 

Korsmeyer, R., Gurny, R., Doelker, E., et al. Mechanism of solute release from porous hydrophilic polymers. Int. J. Pharm. 15 25-35, 1983. 

Two models have been developed to describe the adsorption process. The first model, known as the competition model, assumes that the entire surface of the stationary phase is covered by mobile phase molecules and that adsorption occurs as a result of competition for the adsorption sites between the solute molecule and the mobile-phase molecules.1 The solvent interaction model, on the other hand, suggests that a bilayer of solvent molecules is formed around the stationary phase particles, which depends on the concentration of polar solvent in the mobile phase. In the latter model, retention results from interaction of the solute molecule with the secondary layer of adsorbed mobile phase molecules.2 Mechanisms of solute retention are illustrated in Figure 2.1.3... 

Toluene and xylenes were removed with similar efficiency at low concentration. At high concentration, toluene was removed at a rate twice that of the xylenes, perhaps due to increased participation by the H atom. For high concentrations of toluene and xylenes, OH scavenging may have been compensated for by H atom attack. This may then have become the dominant mechanism of solute decomposition. Information such as this may be important in predicting by-product distributions when treating water of varying quality. 

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