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Investigation into adsorption equilibrium and thermodynamics for water vapor on montmorillonite clay |
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| Authors: | Xidong Du Na Wang |
| Affiliation: | 1. Faculty of Land Resources Engineering, Kunming University of Science and Technology, Kunming, Yunnan, China
Yunnan Key Laboratory of Sino-German Blue Mining and Utilization of Special Underground Space, Kunming, Yunnan, China Contribution: Data curation (equal), Formal analysis (equal), Funding acquisition (equal), Writing - original draft (equal), Writing - review & editing (equal);2. School of Public Health, Dali University, Dali, Yunnan, China |
| Abstract: | The isothermal adsorption curves for water vapor on montmorillonite were measured by a gravimetric adsorption system. Dent's model was employed to estimate the adsorption behaviors of water vapor on primary adsorption sites and secondary adsorption sites. The thermodynamics analysis of water vapor adsorption was performed. At low vapor pressure region, primary adsorption predominates, and with increasing vapor pressure, secondary adsorption becomes notable. Primary adsorption sites have an evidently stronger adsorption affinity than secondary adsorption sites. With increasing vapor pressure, Gibbs free energy variation rapidly increases and then reduces slowly. Although increasing vapor pressure raises adsorption spontaneity on primary adsorption sites, the enhancement in vapor pressure decreases the spontaneity of water vapor adsorption on secondary adsorption sites. As adsorbed loading increases, isosteric heat of adsorption and entropy loss decrease first and then increase quickly. The gradually growing water clusters are responsible for the increase of entropy loss at late stage. |
| Keywords: | adsorption Dent's model montmorillonite pore structure water vapor |