Experimental study on the kinetics of water vapor sorption on the inner surface of silica nano-porous materials

An experiment of kinetic water vapor adsorption of inner surface of silica nano-porous materials is performed by using the thermal gravimetrical method in a relative humidity range from 0.15 to 0.9 at different temperature levels of 25, 35, 45, 55, 65 °C, respectively. The temperature and humidity environment was supplied by a hygrothermostat. This experiment work shows that the water vapor adsorption equilibrium on silica nano-porous materials belongs to Type IV according to Brunauer's classification and could be well correlated by BET (Stephen Brunauer, Paul Hugh Emmett and Edward Teller) equation. The exponential-decay-2 model proposed in this work could fit the full kinetic adsorption process while the pseudo models failed. Under the same relative humidity, although the water vapor concentration increases significantly with temperature, the saturated water uptake decreases slightly with the increase of temperature for the adverse effect of temperature on adsorption.