Composites Based on CaCl2-CaBr2 Salt System for Adsorption Applications: Designing the Optimal Sorbent for Gas Drying and Air Conditioning

Abstract

The different adsorption applications require the development of sorbents with predetermined properties. One of the ways for fine tuning the adsorption properties of the material is using a binary salt system as an active sorbing component. The aim of this work is to conduct a precision investigation of thermodynamic data on the sorption equilibrium of composite sorbents “(CaCl2 + CaBr2) confined to the silica gel pores” with water vapour. The isotherms and isosteres (at an uptake of N = 1.5 and 3.6 mole/mole) of water sorption on the composites were measured. It was shown that at a fixed temperature, the composites based on solid solutions of CaCl2 in CaBr2 form complexes with water at a pressure that is dependent on the CaCl2/CaBr2 molar ratio. The isosteric enthalpy and entropy of water sorption (ΔH = −48 ± 3 kJ/mol ΔS = −108 ± 2 J/(mol·K)) at N = 3.6 mole/mole were midway between the same parameters for composites on the base of the pure salts CaCl2 and CaBr2. The novelty of this work is in the design of sorbents optimized for air conditioning in hot climates and air drying cycles. It was shown that the use of the binary CaCl2 + CaBr2 system confined to the silica pores can be an effective tool for designing innovative materials with predetermined properties.