Microstructure and sorption performance of consolidated composites impregnated with LiCl

Abstract

Desiccant materials play a crucial role in the whole performance of novel desiccant coated heat exchanger based systems which can handle sensible and latent loads simultaneously and separately within one single component. To improve sorption performance of widely utilized coated desiccant, i.e., silica gel, this paper introduces a new type of consolidated composite desiccant, by mixing silica gel with expanded natural graphite treated with sulfuric acid (ENG-TSA) and impregnating with LiCl. Consolidated samples with different densities of ENG-TSA were developed. Microstructure, sorption kinetics and sorption isotherms were investigated and compared with loose parent and composite silica gels. Results showed that both ENG-TSA and LiCl had negative influence on surface areas and pore volumes of consolidated composites. With proper choice of the density of ENG-TSA, both dynamic water uptake quantities and sorption rate coefficients of consolidated composites can be greatly enhanced than those of parent and composite silica gels. Calculated theoretical water uptakes for consolidated composites were approx. 20% less than those of composite silica gel, while measured water isotherms showed that consolidated composites possesses better adsorption capacity than composite silica gel. Fitting equations were developed based on the Polanyi theory for further system modeling.