F. Hetzel et He. Doner, SOME COLLOIDAL PROPERTIES OF BEIDELLITE - COMPARISON WITH LOW AND HIGH CHARGE MONTMORILLONITES, Clays and clay minerals, 41(4), 1993, pp. 453-460
Recent evidence of the occurrence of beidellite in many soils around t
he world necessitates a better understanding of the role of charge loc
ation on the colloidal behavior of this smectite as compared to the mo
re frequently studied montmorillonites. Clay suspension stability and
sorption of an organic polymer, two properties sensitive to surface ch
arge characteristics, were selected to examine the differences in coll
oidal behaviors of these smectites. The Otay montmorillonite was shown
to have a higher charge than either the beidellite or the SWy-1 montm
orillonite. Even though structural formulae resulted in a higher perma
nent charge for the beidellite as compared to the SWy-1, effective cha
rge of these two smectites is the same. The pH dependency of the criti
cal coagulation concentration of the smectites could not be explained
based only on edge charge considerations, and it is proposed that tetr
ahedral charge location enhances the pH effect on the CCC. Decreased p
oly(vinyl) alcohol sorption with either increasing surface charge or t
etrahedral charge location was observed. Both parameters affect the ea
se of replacement of water molecules by PVA on the surface of smectite
s.