| Summary: | 碩士 === 國立臺北科技大學 === 資源工程研究所 === 96 === Smectites are one of the most common groups of phyllosilicates. Due to Smectites negative charge on the surface of interlayers, which cause special properties, the substance is widely used in the following industries: oil drilling, casting , metallurgy , building materials , the chemical industry, food science, and textile engineering .
In this study, trioctahedral smectite was synthesized, using a hydrothermal method. Different Mg/Al ratio, starting materials, pH value and reaction times were discussed, based on the structural formula of smectite Na2x(Al2(1-x)Mg2x□)Si4O10(OH)2.
The results indicated that the trioctahedral stevensite was synthesized with Mg/Al ratio 0.8-0.9 in alkaline solution. Better crystallization was obtained at Mg/Al ratio 0.7-0.9 and pH value 5 and 8. Furthermore, crystal is a short- range order along axis b and axis c, thus silicon dioxide is better than sodium silicate as a silicon source. Sodium silicate must dissolve in water. Moreover, crystal growth under hydrothermal conditions, takes place after nucleation, resulting in slower stacking rates on axis c. Therefore, stacking on axis c is unobvious in the structure of stevensite. It can be improved by extending the reaction time. SEM-EDS and ICP-AES elements analysis have shown that silicon dioxide and magnesium oxide are the major components of trioctahedral stevensite. We know that magnesium ion mainly occupies the octahedral layer cationic site.
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