Preparation of Intelligent Water Vapor Control Material by Selective Leaching Method

利用废纸中大量使用的高岭土作为涂料和填料，对高岭石进行热处理和化学处理，制备高性能多孔材料。对高岭石进行热处理，使其转变为偏高岭石，并分别在γ-Al_2O_3和无定形二氧化硅中复合。在不同的温度和时间下，用KOH和H_2SO_4溶液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SiO_2得到了多孔的γ-Al_2O_3，用H_2SO_4溶液选择性地浸出了氧化铝得到了多孔SiO_2。制得的γ-Al_2O_3的孔性能为：比表面积约300m~2/g，总孔容约0.7ml/g，孔径约5~6 nm。孔的大小分布非常尖锐。所得二氧化硅的孔性能为：比表面积约400m^2/g，总孔容约0.3ml/g，孔径约0.6 nm。由于γ-Al_2O_3对水蒸气的吸附从相对湿度的70%左右急剧增加，最大吸湿量约为600ml/g，因此被认为是一种智能蒸汽控制材料。另一方面，由于二氧化硅在很低的相对湿度下表现出急剧的增长，最大吸附量是伽马氧化铝的1/3，因此这种多孔二氧化硅不适合作为蒸汽控制材料。从孔道性质的物理因素和表面改性后的化学性质两方面讨论了进一步提高调汽功能智能性的重要因素。

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.