Flocculation of Selected Clays by Various Electrolytes

Abstract

The flocculation behavior of clay specimens from altered basalt, altered granodiorite, and a transported (?) deposit in Latah County, Idaho, was investigated in order to determine if flocculation behavior would be an aid in characterizing clay samples in a way that could be related to the origin and history of the clays. The clay minerals are of the kaolinite group.

As flocculants, various chlorides differ one hundred-fold and sodium salts twenty-fold in the concentrations necessary to flocculate a clay to a fixed settling rate. The concentrations of individual chlorides necessary to flocculate different clays vary three-fold and the concentrations of individual sodium salts vary ten-fold. In all cases the higher the valence of the cation the lower is the concentration required for flocculation; the relative effectiveness, however, varies with the clay. The relative effectiveness of the anions as flocculants varies greatly with the clay and no definite order of effectiveness is apparent.

Halloysite requires less electrolyte for flocculation and has a larger settling volume than kaolinite. Well crystallized kaolinite has a smaller settling volume than poorly crystallized kaolinite.

Wide differences of flocculation behavior may provide a valuable, rapid method of classifying the clays of a district.