Humidity control ability of monolithic bimodal porous silica gel prepared from water glass in the presence of poly (acrylic acid) was investigated from the viewpoints of both equilibrium and kinetic aspects. The humidity, at which adsorption-release of water vapor occurred reversibly, was systematically controlled by changing the mesopore size. The equilibrium adsorption amount of water was as high as 0.7 g per gram of silica. In addition, the presence of macropores made it possible to quickly response for humidity change by the adsorption-release cycle because of rapid gas diffusion in monolithic gel body. These features are quite attractive as a material for humidity control in the airtight buildings.
