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Changes in the surface and microstructure of montmorillonites after thermal treatment

I. Novák and Ľ. Nováková

Institute of Inorganic Chemistry, Slovak Academy ofSciencesy 809 34 Bratislava

 

Abstract:  The changes in the microstructure and specific surface of three samples of the Ca forms of dioctahedral smectites due to thermal treatment have been investigated. The measurements of external surface area by the BET method, total surface area by the method of retention of the ethylene glycol monoethyl ether and the distribution of pore sizes obtained from the adsorption isotherms of argon have shown that the changes in external surface area in the heating region up to 400°C are significantly affected by the residual molecular water film as well as residual negative charge of the three-layer of smectite. From 500°C, the total as well as external surface of the investigated smectites starts to decrease considerably owing to dehydroxylation and this process is finished in the temperature region under 900°C. It appears that plenty of cavities and transport canals remain preserved up to 800°C. Through these canals, the gaseous aqueous phase may escape during dehydroxylation or conversely, a gaseous reagent can penetrate to accessible surface in adsorption or in catalytic processes.

Full paper in Portable Document Format: 343a348.pdf

 

Chemical Papers 34 (3) 348–356 (1980)

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