Sepiolite-based adsorbents as humidity controller

Abstract A series of sepiolite-activated carbon pellets has been prepared with the aim of increasing the range of relative humidity (RH) in the application of sepiolite as humidity controller. At high RHs, sepiolite exhibits large variation in water uptake for a given change in RH, whereas for activated carbons this occurs at medium RH. When sepiolite is mixed with activated carbon, a material with better controlling ability is obtained if the range of RH is wide (for instance, 89–39%). This behavior is the consequence of the mixture of the hydrophilic and fibrous nature of the sepiolite with the hydrophobic and porous structure of activated carbon. The humidity uptake of sepiolite can be substantially improved when it is impregnated with calcium chloride since the latter retains a large amount of water, which is transferred to the sepiolite by absorption. Impregnation of sepiolite with calcium chloride also enhances the ability for the control of humidity.