Abstract:

In this work,mesoporous silica gel was separately modified with CaCl₂,or LiCl solution.and the kinetic expenments of water vapor adsorption on the mesoporous silica gels were carried out by means of batch adsorption.The temperature program desorption(TPD)curves of water on the modified mesoporous silica gels are measured bv means of the TPD technique,and then the corresponding activation energies of water desorption are also estimated.The effects of surface modification on the hygroscopic ability of the silica gels and the desorption activation energY of water on the modified silica gels were finally discussed.Experimental results show that.in comparison with the unmodified mesoporous silica gel,the average pore diameter of the silica gel modified with CaCl₂,or IACl becomes larger,and the pore volume of the modified silica gel becomes smaller. Its hygroscopic ability is improved.and the desorption activation energy of water on the modified mesoporous silica gels at a relative humiditv less than 80% in.creases.Moreover,the desorption activation energy of water on the mesoporous silica gel modified with CaCl₂.is much hi gher than that on the silica gel modified by LiCl, due to the higher polarizability of Ca²⁺.

Key words: mesoporous silica gel, modification, water vapour, adsorption, desorption activation energy