Sorption energy, free

Values of isosteric sorption enthalpy, -AH, standard sorption entropy, AS°, and standard Gibbs free sorption energy, AG°, are calculated as dependences on n, cf., [4-8]. To calculate AG°, the boiling-point temperature of N2O is chosen as reference state. This choice provides a check for thermodynamic consistency of experimental data since dG°... 

Figare 5. Standard Gibbs free sorption energies of N2O and CO2 on CaLSX and NaLSX, referred to the boiling temperatures as standard. 

Inverse gas chromatography, IGC, has been used to study water sorption of two poly (vinylidene chloride-vinyl chloride) and poly (vinylidene chloride-acrylonitrile) copolymers, at temperatures between 20 and 50°C and low water uptakes. It was found that the specific retention volume of water increases with decreasing amount of water injected, increases dramatically with decreasing temperature and strongly depends on the type of copolymer. Thermodynamic parameters of sorption namely free energy, entropy, enthalpy of sorption and activity coefficient were calculated. 

Q = heat of sorption G = free energy TS = entropy term M is the experimentally observed water sorption isotherm (after reference 32). ... 

Ke)rwords polarity, adhesion, wettability, solubility, diffusion, physical separation, chemical sorption, grafting, free surface energy. 

Thermodynamically [4-6], the retention of a solute, A, can be expressed as a function of its free sorption energy, (A), and the phase volume ratio, O ... 

If A is a member of a homologous or quasi-homologous series of compounds, the result is with AAG s corresponding to the change of free sorption energy with each incremental step of the homologous series. 

Investigations by Mockel et al. [6] revealed that the latter may be approximately estimated in reversed-phase chromatography. For that, the capacity fectors of individual members of a homologous series are determined using two different eluent compositions, and are then plotted versus n. Since the free sorption energy becomes zero for solutes with K = 1, the phase volume ratio may be direcdy taken via Eq. (3.23) from the intersection of the two straight lines ... 

Sorption-thermodynamic functions as dependences on concentration, n, e.g., the isosteric molar sorption enthalpy, Af/(n), the standard sorption entropy, AS°(n), and the standard Gibbs free sorption energy, AG°(n), can be calculated by basic formulas (21), (22) and (14), respectively,... 

Gibbs free energy characterizes the natural tendency of a system to its spontaneous change. Dependences of standard Gibbs free sorption energies, AG°, on sorption-phase concentration in Li,RE-LSX as referred to the boiling temperatures and 760 torr are shown in Figure 27. 

Figure 27. Concentration dependences of standard Gibbs free sorption energy for N2, O2 and binary mixtures at sorption-phase composition, 80 % N2 and 20 % O2, on Li,RE-LSX zeolite, referred to the boiling temperatures and 750 torr.

Figure 30. Initial Gibbs free sorption energy change vi. sorption-phase composition for N2 - O2 mixtures on Li,RE-LSX at 298 K.

Gibbs energy of water sorption at free water surface (kj mol ) Enthalpy change in the reaction (J mol )... 

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). 

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