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Syntheses of Disordered and Al-Rich Hydrotalcite-Like Compounds

Published online by Cambridge University Press:  02 April 2024

I. Pausch ,
H.-H. Lohse ,
K. Schürmann  and
R. Allmann
I. Pausch
Affiliation:
Fachbereich Geowissenschaften, Lahnberge D-3550 Marburg, Federal Republic of Germany
H.-H. Lohse
Affiliation:
Fachbereich Geowissenschaften, Lahnberge D-3550 Marburg, Federal Republic of Germany
K. Schürmann
Affiliation:
Fachbereich Geowissenschaften, Lahnberge D-3550 Marburg, Federal Republic of Germany
R. Allmann
Affiliation:
Fachbereich Geowissenschaften, Lahnberge D-3550 Marburg, Federal Republic of Germany
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Abstract

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Hydrotalcite-like compounds, [Mg1-xAlx(OH)2]x+ [xX−·n H2O], where X− = ½CO32− or OH−, were prepared by hydrothermal syntheses at PH2O=100MPa and T = 100°–350°C. Starting materials were MgO, γ-Al2O3, H2O, and MgC2O4·2H2O. The synthesis depended on temperature, pressure, the Al/(Al + Mg) ratio x, and the CO2 content of the starting material. Previously an Al content of x = 0.33 was thought to be the upper limit in these double-layer compounds, but by using pressure the Al-content was increased to x = 0.44. Up to x = 0.33, a0 decreased linearly to about 3.04 Å, but for x ≥0.33, a0 remained nearly constant at this value. For the synthesized products the layer thickness c’ varied between 7.40 and 7.57 Å in contrast to the natural phases wherein c’ varies from 7.60 to 7.80 Å. At higher temperatures CO2-free syntheses, i.e., those without Mg-oxalate, resulted in a disordered hydrotalcite-like phase. The transition temperature between the ordered and the disordered hydrotalcite-like phase depended on the Al-content, x.

Type
Research Article
Information
Clays and Clay Minerals , Volume 34 , Issue 5 , October 1986 , pp. 507 - 510
Copyright
Copyright © 1986, The Clay Minerals Society

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