Application of the Thermodynamic Model to the Couple Water vapor-Raw Clayc

Jhider N

doi:10.4172/2157-7048.1000144

Abstract

This work is based on data from adsorption isotherms and isosteric enthalpies of El Hamma raw clay at different temperatures (30, 40, 50 and 60°C). These previously obtained data were used here to show the variation of the thermodynamic properties of water adsorbed on the surface of the clay: Gibbs energy, enthalpy and entropy. Then we present a model of solid solution based on a polynomial expression of degree 7. This model was applied to calculate the excess quantities: excess Gibbs energy of mixing, entropy term and Gibbs energy of mixing. The variations of free energy, enthalpy and entropy of adsorbed water show fluctuations that characterize three areas. For low water contents the entropy of the adsorbed water is greater than that of liquid water. As the amount of adsorbed water increases the entropy gradually approaches the normal value. Close to saturation, the model shows that the term of excess energy of mixing is always positive, although the water remains bound to the solid. Since the term of enthalpy of mixing is negative this means that the solution is stable.

Highlights

The study of water transfers in soil has interested scientists and engineers in different fields
The determination of the thermodynamic properties of the adsorbed water at the surface of raw clay is carried out using the experimental data of adsorption isotherms obtained at different temperatures
We conducted a comprehensive analysis of the adsorption isotherms of water vapor adsorbed on the surface of El Hamma raw clay in a range of temperature from 30°C to 60°C

Summary

Introduction

The study of water transfers in soil has interested scientists and engineers in different fields. The amount and condition of the water in the soil can significantly affect its agronomic, hydraulic and geological. If knowledge of the two extreme states of the soil, saturated or dry, seems well under way, an unsaturated state, at low water contents, merits further investigation. Systems using solid adsorbents such as activated carbons, activated aluminas and clays play an important role in the process of separation, purification, drying, dehumidification, air handling and water treatment. In the case of the solid adsorption, the mode of association between the molecules of water vapor and the adsorbent is purely physical. The adsorption does not change the volume of the solid, it means a variation of the adsorbed mass and physical and thermodynamic properties of couple’s adsorbent/adsorbate

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Results

Conclusion