Synthesis of Kaolinitic Clay Mineral from Amorphous Alumino-Silicate by Hydrothermal Process

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J. Korean Ceram. Soc. > Volume 31(9); 1994 > Article

Journal of the Korean Ceramic Society 1994;31(9): 1076.

비정질 Alumino-Silicate로부터 수열반응에 의한 Kaolinite질 인공점토의 합성에 관한 연구

김남일, 박계혁, 정창주¹

주식회사 행남자기 기술연구소
¹전남대학교 공과대학 무기재료공학과

Synthesis of Kaolinitic Clay Mineral from Amorphous Alumino-Silicate by Hydrothermal Process

ABSTRACT

This study covers synthetic effect of the various hydrothermal treatments on formation of artificially made kaolinite mineral. The hydrothermal treatment includes the temperature treatment with time duration, addition of seeds, particle size of the starting material used, pH variation and the different types of organic acids. A colloidal silica and alumina sol which are commercially available are used for this study. A colloidal silica and alumina sol are mixed by the atomic ratio of Al/Si = 1, based on the theoretical kaolinite composition and calcined at $600^{circ}C$ for 8 hours duration. It was found that the kaolinitic clay mineral was well developed; thereby, the different patterns of crystalline mineral are appeared. Spherical type as a crystal form was distinctively formed at the temperature of 20$0^{circ}C$ to 25$0^{circ}C$ with short duration time, while platy type as a crystal was highly yielded at 300~35$0^{circ}C$. Moreover, by adding more than 20 wt% of seed as the natural kaolinitic clay to the starting material is widely distributed and developed when 2 ${mu}{textrm}{m}$ or less particle size of the starting material is used; also, when they are heat-treated at the temperature of 25$0^{circ}C$ with 5 hours duration. With respect of the effect of pH variation on formation of the synthetic kaolinite minerals, the crystalline minerals are highly yielded at less than pH 2 and gradually diminished at more than pH9. Regarding to the effect of different acids on development of the kaolinite mineral, the organic acids with high chelating capacity produces good formation of crystalline minerals; whereas, amine radical-(NH2) is not an effective agent to generate the crystalline minerals.