Adsorption Equilibrium of Water on a Composite Adsorbent Employing Lithium Chloride in Silica Gel

Abstract

This paper presents a new method to develop a composite adsorbent hygroscopic salt inside silica gel which can eliminate corrosion effects. A salt solution would be formed when a conventional composite adsorbent adsorbed water and corroded the adsorbent bed quickly. The adsorption equilibrium of water on a composite adsorbent (lithium chloride confined to silica gel) was measured by the sorption isosteric method. The temperature T which ranged from (308 to 368) K was controlled by a thermostatic bath, and the absolute pressure was in the range (0 to 25 000) Pa using a membranometer. The results showed that though the isosteric enthalpy (the average isosteric enthalpy is 42.82 kJ·mol−1) is lower than the conventional composite adsorbent, the new composite adsorbent still had a larger water sorption capacity (x = 0.702 g·g−1) in comparison with that of pure silica gel. The Freundlich equation, the modified Freundlich equation, and the Dubinin−Astakhov (D-A) equation are used to fit the experimental data. In our case, they are best-fitted by the D-A equation, even though it has fewer parameters than the modified Freundlich equation.