Evaporation of polar and nonpolar liquids from silica gels and fumed silica

Abstract

Abstract Thermogravimetry data on evaporation of polar water, acetone and 1-butanol and nonpolar benzene, n-hexane and carbon tetrachloride liquids from mesoporous silica gels Si-40 and Si-100 are analysed using theoretical computation of the evaporation/condensation coefficients and evaporation rate and time. The processes on silica gels Si-40, Si-60, and Si-100 are compared to the evaporation of nanodroplets in the gas phase and evaporation of water, 1-butanol, and n-hexane from fumed silica A-300 at room temperature. The evaporation rate k(T) depends strongly on the characteristics of adsorbates (molecular weight, intermolecular bond type and strength, surface tension, boiling, Tb and critical, Tc temperatures) and adsorbents (surface structure, porosity characteristics), and it is exponential function of temperature. Different sequence order of the values of Tb and Tc for water and butanol lead to intersection of curves of evaporation rate (or time) vs. temperature between Tb and Tc. For other liquids, the curve position over the used temperature range correlates to the value of Tb; however, the gap between curves is not constant vs. T. Described approach can be useful to analyse experimental data on evaporation of pore-confined adsorbates, as well as free droplets of various liquids.