Flory-Huggins type isotherm

Flory-Huggins-type isotherms and the Bockris-Swinkels isotherm in particular. If n is assumed equal to 3 in the latter case, the value of 01 becomes 0.582." ... 

The Flory-Huggins-Type Isotherm A Substitutional Isotherm... 

With this in mind, some important adsorption isotherms were introduced, and we found that each of them describes important characteristics of the adsorption process (Table 6.10). Thus, the Langmuir isotherm considers the basic step in the adsorption process the Frumkin isotherm was one of the first isotherms involving lateral interactions the Temkin is a surface heterogeneity isotherm and the Flory-Huggins-type isotherms include the substitution step of replacing adsorbed water molecules by the adsorbed entities (Fig. 6.98). 

Irreversible reaction, 1251, 1419 Isoconic, definition, 933, 978, 982 Isotherm, 932, 964, 1197 applicability, 941 and charge transfer, 954, 955 Conway and Angersein-Kozlowska, 943 definition, 933 in electrode kinetics, 1197 Flory—Huggins type, 941,942, 944, 965 Frumkin, 938, 942, 965 Frumkin-Temkin, 1197, 1198 Habib-Bockris, 943... 

Type III is the sorption isotherm of Flory-Huggins. Here the solubility coefficient increases continuously with pressure. It represents a preference for formation of penetrant pairs and clusters it is observed when the penetrant acts as a swelling agent for the polymer without being a real solvent. An example is water in relatively hydrophobic polymers containing also some polar groups. 

This type of sorption isotherm arises when the interactions between permeant molecules are strong relative to permeant/polymer interactions, and the solubility coefficient increases continuously with increasing pressure. This sorption can be described for non-polar systems by the Flory-Huggins relationship... 

Sorption and diffusion of water vapour in polymers have been studied mainly for development of water vapour barriers. Some of these studies date back to 1944 [41]. Many attempts have been made in order to describe the sorption behavior of water vapor onto solid surfaces of the membrane and its pores. As described by Vieth [41], a deviation from Henry s law was observed in 1944, in the sorption of water by hydrated cellulose membranes. It was postulated that two competing phenomena are responsible for this observation dissolution, which obeys Henry s law, and adsorption, which follows the Langmuir isotherm. With other polymer systems the ability of water molecules and/or polar groups in the polymer matrix to interact with each other has given rise to sorption isotherms which may follow Henry s law, Flory-Huggins or BET types [41]. 

The original treatment of this type of displacement isotherm was developed by Flory and Huggins separately, back in 1942. They developed the isotherm for adsorption of large molecules (polymers). However, applicability to small molecules (e.g., ions) displacing only few water molecules has been proved. 

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