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Instability of SiO2 Colloids and Sorption of Ca2+ Ions

Published online by Cambridge University Press:  28 February 2024

Sook Peng Chan ,
David S. Fraser ,
Stephen Y. S. Cheng ,
Yingnian Xu  and
Yoshikata Koga
Sook Peng Chan
Affiliation:
Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
David S. Fraser
Affiliation:
Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
Stephen Y. S. Cheng
Affiliation:
Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
Yingnian Xu
Affiliation:
Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
Yoshikata Koga
Affiliation:
Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1 Center for Ceramics Research, Research Laboratory of Engineering Materials, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, 227 Japan
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Abstract

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SiO2 sols were made unstable by addition of Ca2+ ions. The resulting states of instability were classified as gelation, flocculation, and precipitation by means of observation, by checking the Tyndall effects on the supernatant or suspending solution, as appropriate, and by measuring the apparent densities of flocculated mass. The concentrations of free Ca2+ ions left in solution were measured by means of a Ca2+ ion selective electrode. The amounts sorbed onto SiO2 particles were then calculated by material balance. It was found that while the amount sorbed dictates the limit of stability, the SiO2 concentration in the mixture is an important factor deciding the state of instability. Depending on the SiO2 concentration, there were two distinct flocs with the apparent floc density of 6 ± 1 and 12 ± 1 mg SiO2/ml.

Keywords

Ca2+ induced instabilityCa2+ sorptionFlocculationGelationPrecipitationSilica colloidsTwo distinct flocculates
Type
Research Article
Information
Clays and Clay Minerals , Volume 43 , Issue 4 , August 1995 , pp. 478 - 481
Copyright
Copyright © 1995, The Clay Minerals Society

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