Preparation of Intelligent Water Vapor Control Material by Selective Leaching Method

利用造纸工业中大量使用的废弃高岭石作为涂料和填料，对高岭石进行热处理和化学处理，制备高功能多孔材料。将高岭石进行热处理，分别转化为偏高岭石和γ-氧化铝和无定形二氧化硅的复合物。用KOH和H_2SO_4溶液在不同温度和时间下对它们进行化学处理。结果表明，用KOH溶液选择性浸出无定形SiO2得到多孔γ-Al 2 O3，用H2SO 4溶液选择性浸出Al 2 O3得到多孔SiO2。γ-氧化铝的多孔性质如下：比表面积约为300 m^2/g，总孔体积约为0.7 ml/g，孔径约为5-6 nm。孔径分布非常尖锐。二氧化硅的多孔性质如下：比表面积约为400 m^2/g，总孔体积约为0.3 ml/g，孔径约为0.6 nm。由于γ-氧化铝的水蒸气吸附从相对湿度约70%开始急剧增加，最大吸附量约为600 ml/g，因此被认为是智能蒸汽控制材料的候选者。另一方面，由于二氧化硅的吸附量从非常低的相对湿度开始急剧增加，并且最大吸附量为γ-氧化铝的1/3，因此这种多孔二氧化硅不适合作为蒸气控制材料。从影响多孔材料性能的物理因素和表面改性后的化学性能两个方面探讨了进一步提高智能化蒸汽控制功能的重要因素。

Preparation of high functional porous materials was investigated by heat treatment and chemical treatment of kaolinite to utilize the wasted kaolinite used abundantly in paper as coating and filler materials. The kaolinite was heat treated to convert into metakaolinite and composite in gamma-alumina and amorphous silica, respectively. They were chemically treated by KOH and H_2SO_4 solutions at various temperatures and times. As a result, porous gamma-alumina was obtained by selective leaching of amorphous silica using KOH solution while porous silica was obtained by selective leaching of alumina using H_2SO_4 solution. The porous properties of the gamma-alumina was as follows ; specific surface area about 300 m^2/g, total pore volume about 0.7 ml/g and pore size about 5-6 nm. The pore size distribution was very sharp. The porous properties of the silica was as follows ; specific surface area about 400 m^2/g, total pore volume about 0.3 ml/g and pore size about 0.6 nm. Since the water vapor adsorption of the gamma-alumina showed steep increase from about 70% of relative humidity and the maximum adsorption was about 600 ml/g, it is considered as a candidate of intelligent vapor control material. On the other hand, since that of the silica showed steep increase from very low relative humidity and the maximum amount of adsorption was 1/3 of that of the gamma-alumina, this porous silica is not suitable as a vapor control material. The important factors to further improve intelligence of vapor control function were discussed on the basis of physical factors of porous properties and also chemical properties by surface modification.