Free energy of sorption

The proposed form of data presentation became highly popular and opportune in gas chromatography. Up to the present, some thousand references to the Kovat s work [1] have been known. The RI values are proportional to the free energies of sorption this is their thermodynamic interpretation. Further development of the RI concept was aimed at its application to nonisothermal conditions of gas chromatographic (GC) analysis. For linear temperature programming regimes (which are characterized by two variables initial temperature, Tq, and rate of its increase, r, deg X min ), the linear relationship (3) does not hold. In some partial cases, other linear dependence seems more precise for the retention time approximation ... 

The total partial molar Gibb s free energy of sorption (aG°t = aG°s) is directly related to Kp by... 

The variable sorptive tendencies of different classes of organic molecules can best be understood by evaluating all of the energy and entropy terms that contribute to the total free energy of sorption from aqueous solution. The important energy terms are ... 

From enthalpy AH, entropy AS and Kelvin temperature T, the free energy of sorption process AG has been obtained by adopting Gibbs s thermodynamics expression (Equation (27.19)). ... 

This paper deals with the principles, advantages and limitations of measurement of sorption equilibria under isosteric conditions. It further assesses the sorption-isosteric method (SIM) as an effective tool for providing complete sets of sorption-thermodynamic functions, viz., enthalpy, standard entropy and standard Gibbs free energy of sorption, for nanoporous solids, i.e., micro- and mesoporous ones, as functions of sorption-phase concentration, n, over its entire range, and to approach such data for mixtures. The usefulness of SIM is exemplified by sorption systems that comprise atmospheric gases on zeolites and carbon dioxide, CO2, on carbonaceous sorbents, as well as several of their mixtures. 

Gibbs free energies of water sorption, AG "(/l), can be extracted from isopiestic vapor sorption isotherms this analysis shows that AG (T) < AG", where AG" = -44.7 kj moH is the Gibbs free energy for vapor sorption at a free water surface at ambient condihons. Water absorbed by the membrane is therefore more strongly bound than water at a free bulk water surface this affirms the hydrophilic nature of water sorption in PEMs. 

Gibbs free energy of water sorption by Nation 117. Comparison of energies obtained from sorption isotherms (solid line), corresponding to Figure 6.10(a), and from capillary isotherms (dashed line), corresponding to Figure 6.10(b). 

The sorption of a nonpolar organic contaminant on a solid phase is derived by enthalpy and entropy related forces. Hasset and Banwart (1989) suggested that sorption occurs when the free energy of the reaction is negative due to enthalpy or entropy. The enthalpy is primarily a function of the changes in the bonding between the adsorbing surface and the sorbate (solute) and between the solvent (water) and the solute. The entropy is related to the increase or decrease in the order of the system on sorption. 

Relative sorption of the permeants in the membrane depends on the interactions between the solutes and the membrane polymer. Solubility or miscibility of a component with the membrane polymer depends on their relative solubility parameter values. For mutual solubility of two components their free energy of mixing, AGm should be negative. 

The solubility and diffusivity can each be treated separately as activated processes with relationships similar to Equation 15.3. The activation parameter for solution is called the Gibbs free energy for sorption (AGS), and consists of the enthalpy of sorption(AHs) and the entropy of... 

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