New Physicochemical Methodology for the Determination of the Surface Thermodynamic Properties of Solid Particles

Abstract

The study of the surface thermodynamic properties of solid materials is primordial for the determination of the dispersive surface energy, polar enthalpy of adsorption and Lewis’s acid base properties of solid particles. The inverse gas chromatography technique (IGC) at infinite dilution is the best surface technique for the determination of the surface physicochemical properties of materials. (1) Background: This paper was devoted to studying the surface properties of solid materials, such as alumina, titania and silica particles, using the IGC technique. (2) Methods: Different methods and molecular models, such as the spherical, cylindrical, Van der Waals, Redlich–Kwong, Kiselev and geometric models, were used to determine the London dispersive surface energy of solid surfaces. The Hamieh model was also used and highlighted the thermal effect on the surface area of solvents. (3) Results: The variations of the dispersive surface energy and the free energy of adsorption were determined for solid particles as a function of the temperature, as well as their Lewis’s acid base constants. Alumina surfaces were proved to exhibit a strong Lewis amphoteric character three times more basic than acidic, titanium dioxide more strongly basic than acidic and silica surface exhibited the stronger acidity. (4) Conclusions: The new methodology, based on the Hamieh model, gave the more accurate results of the physicochemical properties of the particle surfaces.

Some Irregularities in the Evaluation of Surface Parameters of Solid Materials by Inverse Gas Chromatography

“…The error committed by the other models relative to the thermal model exceeds 25% with respect of Hamieh model. − From Table , by taking the examples of the Kiselev method (γ s d (343.15 K ) = 57.8 mJ/m 2 )) and Hamieh model (γ s d (343.15 K) = 79.3 mJ/m 2 ), one obtained an error equal to . These results clearly showed that the various models that did not consider the change in the surface areas of molecules when the temperature varied cannot give accurate values.…”

“…The dispersive components of the surface energy of Ni-MOF-74 surfaces were determined using the Dorris–Gray method, the molecular models, and the thermal model. − ,− …”

“…On the other hand, one proposed, in previous studies, − new entropic Lewis’s acid ω A and base ω D parameters (by analogy to the enthalpic Lewis’s acid K A and base K D parameters of a solid) determined by relations or : false( prefix− normalΔ S normala sp false) = ω A DN ′ + ω D AN ′ or true( − normalΔ S normala sp A N ′ true) = ω A true( DN ′ AN ′ true) + ω D In several studies, − one proved the inaccuracy of the methods of Dorris–Gray and Schultz et al, by showing the dependency of the surface area of molecules on the temperature. − Consequently, the values of γ s d obtained by several authors − ,− are not accurate and they have to be corrected.…”

“…For example, it was proved that the value of γ s d obtained by the spherical model is three times larger than that of the Kiselev method (see Figure 1 and Table 3). This gave an importance to Hamieh's works 27,28,30 based on the thermal model that allowed more accurate results.…”

“…The use of Schultz et al method to determine the specific variables of adsorption of polar molecules on the solid surfaces gave inaccurate results and consequently led to incorrect values of the Lewis acid–base parameters. Some new models and methods were recently proposed in literature − to correct some irregularities on the surface properties and give more accurate results.…”