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Characterization of the Kaolinite Synthesized According to the pH.  

Ryu, Gyoung-Won (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Jang, Young-Nam (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Bae, In-Kook (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Suh, Yong-Jae (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Publication Information
Economic and Environmental Geology / v.41, no.2, 2008 , pp. 165-172 More about this Journal
Abstract
Kaolinite [$Al_2Si_2O_5(OH)_4$] used in these experiments was synthesized at 250$^{\circ}C$ for 36 hrs by a hydrothermal process from amorphous $Al(OH)_3$ and $SiO_2$. The change of the mineralogical properties of the phase synthesized were observed in the pH range 2 to 9. The synthetic kaolinite were characterized by the analytical methods of XRD, IR, DIA, and FE-SEM. Kaolinite was obtained in a wide range of pH. The phases with high- to midium- defect kaolinite with high thermal stability were obtained from the acidic conditions and high-defect kaolinite with low thermal stability from the basic conditions. These variations of kaolinite properties appears to be related to the pH dependence of kaolinite surface speciation. The peaks intensity and resolution of the kaolinite decrease according to the alkalinity of the solution by the results of the IR testing. And the peak intensity increases in the 60 to 70$^{\circ}C$ range due to dehydration reaction observed by TG-DTA. Such phenomena was the result of increase of unreacted amorphous materials in the high pH condition, which could be identified by FE-SEM.
Keywords
kaolinite; amorphous; hydrothermal synthesis; defect;
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