Hydrothermal transformation of mixed metal oxides and silicate anions to phyllosilicate under highly alkaline conditions

Hydrothermal transformation of mixed metal oxides and silicate anions to phyllosilicate under... Mixed metal oxides (MMO) were transformed to phyllosilicate in the presence of silicate anions under hydrothermal conditions. The product was shown to be saponite with a trioctahedral layer structure by characterization with XRD, FTIR, 27Al and 29Si MAS NMR, HRTEM and TG-DTG. The formation of saponite was through a rehydration-dissolution-precipitation pathway, involving the critical steps such as the reconstruction of MMO to hydrotalcite (Ht), exsolution of Al3+ from Ht, condensation of metasilicate anions with Ht, and finally crystallization of saponite. Isomorphous substitution of Al3+ for Si4+ in silicate oligomers is the key for the above conversion, which generated the negative charge necessary for the condensation between the silicate oligomers and Ht surface and the formation of 2:1 saponite TOT layers. High pH value (over 14.0) favored the condensation of silicate oligomers and led to crystallization of saponite. Thus, we report a novel method for the crystallization of saponite. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Applied Clay Science Elsevier

Hydrothermal transformation of mixed metal oxides and silicate anions to phyllosilicate under highly alkaline conditions

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Publisher
Elsevier
Copyright
Copyright © 2018 Elsevier B.V.
ISSN
0169-1317
eISSN
1872-9053
D.O.I.
10.1016/j.clay.2018.02.013
Publisher site
See Article on Publisher Site

Abstract

Mixed metal oxides (MMO) were transformed to phyllosilicate in the presence of silicate anions under hydrothermal conditions. The product was shown to be saponite with a trioctahedral layer structure by characterization with XRD, FTIR, 27Al and 29Si MAS NMR, HRTEM and TG-DTG. The formation of saponite was through a rehydration-dissolution-precipitation pathway, involving the critical steps such as the reconstruction of MMO to hydrotalcite (Ht), exsolution of Al3+ from Ht, condensation of metasilicate anions with Ht, and finally crystallization of saponite. Isomorphous substitution of Al3+ for Si4+ in silicate oligomers is the key for the above conversion, which generated the negative charge necessary for the condensation between the silicate oligomers and Ht surface and the formation of 2:1 saponite TOT layers. High pH value (over 14.0) favored the condensation of silicate oligomers and led to crystallization of saponite. Thus, we report a novel method for the crystallization of saponite.

Journal

Applied Clay ScienceElsevier

Published: May 1, 2018

References

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