Synthesis and alteration of 3-octahedral clay minerals.

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Kaolinite and 3-octahedral smectites were synthesized under several hydrothermal conditions from diatomaceous earth, which occurs at Takanosu, Akita Prefecture, and from rice husk ash.1. Synthesis of kaolinite from diatomaceous earth. Kaolinite has been prepared from dispersions of diatomaceous earth in aqueous solution of AlCl_3 at 170-230ﾟC. Kaolinite began to produce at 170ﾟC for 3 hours. Its yield in synthetic products was estimated by DTA and X-ray methods. For 180 hours, kaolinite was produced about 10 % at 170ﾟC, about 30 % at 200ﾟC, and 60 % at 230ﾟC.2. Synthesis of smectite from diatomaceous earth. (1) Mg-smectite. Mg-smectite has been prepared from the HCl treated diatomaceous earth in aqueous solutions of MgCl_2 at 200ﾟC in various Si : Mg molar ratios ranging from 8 : 8-3. Smectites were produces from the starting materials with Si : Mg (molar ratio) = 8 : 6. Smectites and talcs were produced from the starting materials with Si : Mg (molar ratio) = 8 : 8. Smectites and serpentine minerals were produced from the starting materials with Si : Mg (molar ratio) = 8 : 4.5. The starting materials with Si : Mg (molar ratio) = 8 : 3 altered spectites having very broad basal reflection. (2) Ni-seectite. Diatomaceous earth was ground at 10 hours (10-h) and 30 hours (30-h). Ni-smectite has been prepared from dispersions [Si : Mg Li (solar ratio) = 8 : 5.33 : 0.66] of the ground diatomaceous earth in aqueous solutions of NiCl_2 (pH 13.50) at 200ﾟC. Smectite began to produce from 3 hours treatment. Smectites were produced easier the starting material ground 30 hours (30-h) than that of 10 hours ground (10-h).3. Synthesis of 3-octahedral smectite from rice husk ash. Rice husk ash can be used as a superior siliceous material for production of smectite. The best condition is as follows ; Temperature of calcination : 450ﾟC, Si : Mg : Li (solar ratio) = 8 : 5.34 : 0.66, pH of the dispersion before reaction : 13.2-13.5, Reaction time : 4 days.