Study On Preparation And Performance Of Iron Silicate Humidity Controlling Materials

Humidity controlling materials can automatically control environmental humidity on its own adsorption-desorption properties.The research and application of humidity controlling materials are meaningful for improving living environment,advancing quality of preservations and reducing energy consumption.Iron silicate humidity controlling materials in this research was prepared with sodium silicate and ferric chloride by chemical precipitation method.Impacts of preparative conditions,which include hydrothermal time,pH,and modules of water glass,on humidity controlling properties was investigated by orthogonal experiments,and the best preparing conditions of iron silicate materials were confirmed.Based on materials controlling humidity performance and materials characterization,tested by FI-IR,XRD,SEM and BET method,the author discussed humidity controlling theory and influencing factors on the materials humidity controlling properties.At last,calcium chloride modification was used to improve hygroscopic properties of iron silicate.The results show that the best preparing conditions of iron silicate used as automatic humidity controlling materials are: hydrothermal time 0 h,pH 5,modules of water glass 1.0,and the best preparing conditions of iron silicate used as desiccant are: hydrothermal time 18 h,pH 8,modules of water glass 2.5.Iron silicate materials in this paper are amorphous particles,whose specific surface areas are more than 107 m2/g,pore volumes are about 0.1cm~3/g,and pore diameters approximately are 3.5nm(intensively distributing between 2~10 nm).The maximum equilibrium moisture contents under 84% RH are more than 120%,and full dehumidification just need 5h in 50? thermostatic drier box.Hygroscopic property under medium relative humidity can be improved by 20%wt calcium chloride modification.The hygroscopic velocity equation of iron silicate under different humidity and model parameters of Langmuir and Samejima were obtained by liner fitting.Based on the principle of capillary condensation,the relevant equation between RH and critical radius was derived.The paper preliminarily discussed the humidity controlling theory of iron silicate,which consider that hygroscopic process of iron silicate is co-determined by multilayer adsorption,capillary condensation and mineral salt.