Water vapor sorption on surfactant-templated porous silica xerogels

Abstract

Porous silica xerogels are prepared by sol–gel syntheses templated with Brij56 or F127 surfactants. The porous properties of the obtained silica xerogels are characterized by N 2 sorption measurements. The F127 surfactant-templated silica xerogel exhibits a pore size distribution peaking at 4.2 nm in the mesopore region, a pore surface are of 510 m 2 g −1, and a pore volume of 0.545 mL g −1, while the Brij56 surfactant-templated silica xerogel has a bimodal pore size distribution with maxima at 0.65 nm and near 2 nm in the micropore region, a pore surface area of 739 m 2 g −1, and a pore volume of 0.354 mL g −1. Their water vapor sorption properties are evaluated under various relative humidity at 25 and 35 °C using gravimetric technique. The results show that the F127 surfactant-templated xerogel with larger pore size and higher volume could absorb a large amount of water molecules at high humidity and efficiently release it at low humidity, such that it has a large water adsorption–desorption capacity, whilst the Brij56 surfactant-templated xerogel with smaller pore size and larger pore surface area could maintain a high water content even at low humidity levels.