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INSTABILITY OF SIO2 COLLOIDS AND SORPTION OF CA2+ IONS

TitleINSTABILITY OF SIO2 COLLOIDS AND SORPTION OF CA2+ IONS
Publication TypeJournal Article
Year of Publication1995
AuthorsChan, SP, Fraser, DS, Cheng, SYS, Xu, YN, Koga, Y
JournalClays and Clay Minerals
Volume43
Pagination478-481
Date PublishedAug
Type of ArticleArticle
ISBN Number0009-8604
Keywords2 DISTINCT FLOCCULATES, CA2+ INDUCED INSTABILITY, CA2+ SORPTION, flocculation, GELATION, MASS TITRATION, POINT, precipitation, SILICA COLLOIDS, ZERO CHARGE
Abstract

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.

URL<Go to ISI>://A1995TG44900012