Dynamics of water vapor adsorption on humidity-indicating silica gel

Abstract

Well-defined CoCl 2-containing silica gels were prepared by impregnation of the aqueous solution of the salt to silica hydrogel, drying and aging methods. Silica gels having 392–437 m 2 g −1 surface area and 0.21–0.37 cm 3 g −1 pore volume and having an average particle size of 3 mm were obtained. Aging in CoCl 2 solutions decreased the surface area of silica gels from 540 cm 2 g −1 to 392–430 m 2 g −1 and pore volume from 0.27 to 0.21–0.23 cm 3 g −1 for CoCl 2 concentration smaller than 0.28 mol dm −3 in silica gel. Adsorbed water desorbed from the gels absorbing 1917–2555 J g −1 energy as determined by differential scanning calorimetry. The CoCl 2-containing gels were successfully used in dynamic column experiments, with linear relation between velocities of inlet air and movement of blue to pink boundary. The colour change also makes the detection of the defects in column filling which causes air channelling.