Premium
STRUCTURE FORMATION UPON MIXING Na‐MONTMORILLONITE WITH BI‐ AND TRIVALENT ION‐CLAYS 1
Author(s) -
FRENKEL H.,
SHAINBERG I.
Publication year - 1981
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1981.tb01703.x
Subject(s) - montmorillonite , adsorption , ion , chemistry , ion exchange , inorganic chemistry , materials science , analytical chemistry (journal) , chromatography , organic chemistry
Summary The light transmittance of montmorillonite suspensions saturated with Na + , Mg ++ , Ca ++ , Al +++ , Fe +++ or La +++ and with known mixtures of these ions was investigated. Also, the kinetics of bi‐ and trivalent ion montmorillonite tactoid formation and breakdown was followed by recording changes in light transmission as a function of time when M‐montmorillonite suspensions (M = Mg ++ , Ca ++ , Al +++ , Pe +++ or La +++ ) were added to Na‐montmorillonite suspensions of the same concentration in a titrating vessel placed in the light path of a spectrophotometer. Introduction of a small fraction of Na + onto the exchange complex of M‐clay had no effect on the size of the M‐tactoids. The breakdown of Mg ++ and Ca ++ tactoids occurred as the equivalent fraction of adsorbed Na + increased from 0.2 to 0.5, with mixed Na‐M montmorillonite particles having an equivalent fraction of adsorbed Mg ++ and Ca ++ less than 0.3 remaining as single platelets. Conversely, introducing even a small fraction (<10%) of trivalent onto the exchange complex of Na‐montmorillonite caused the formation of tactoids. Instantaneous formation of an intermediate unstable structure occurred upon mixing Na‐montmorillonite with M‐montmorillonite. It is proposed that edge‐to‐face association stabilizes this intermediate structure, whereas face‐to‐face association stabilizes the eventual tactoids.