Dynamics of water vapor adsorption on humidity-indicating silica gel

Well-defined CoCl2-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 m2 gy1 surface area and 0.21–0.37 cm3 gy1 pore volume and having an average particle size of 3 mm were obtained. Aging in CoCl2 solutions decreased the surface area of silica gels from 540 cm2 gy1 to 392–430 m2 gy1 and pore volume from 0.27 to 0.21–0.23 cm3 gy1 for CoCl2 concentration smaller than 0.28 mol dmy3 in silica gel. Adsorbed water desorbed from the gels absorbing 1917–2555 J gy1 energy as determined by differential scanning calorimetry. The CoCl2-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. q1998 Elsevier Science B.V. All rights reserved.