O. Altin et al., USE OF GENERAL-PURPOSE ADSORPTION-ISOTHERMS FOR HEAVY-METAL CLAY MINERAL INTERACTIONS, Journal of colloid and interface science, 198(1), 1998, pp. 130-140
General purpose adsorption isotherm equations were fitted to the sorpt
ion data of lead and cadmium on both unmodified and Ca-saturated kaoli
nite and montmorillonite. Langmuir-Freundlich, Redlich-Petersen, Toth,
Dubinin-Radushkevich, competitive Langmuir, and some modified forms o
f these isotherms were fitted to experimental data, and their goodness
es of fit are compared. The adjustable parameters of the Langmuir-and
Freundlich-based isotherms were estimated by nonlinear least-squares a
nalysis. The application of these two isotherms which allow for the ef
fect of surface heterogeneity for both multiple and single desorbing i
ons during the sorption process was also studied. It was concluded tha
t Redlich-Petersen, Toth, and original and modified forms of Dubinin-R
adushkevich isotherms perform superior to the others both in high and
lour concentration regions for both unmodified and Ca-saturated clays.
Competitive Langmuir adsorption isotherm for Ca-saturated clays fitte
d web for Pb adsorption, while a change of slope was observed for Cd a
dsorption. (C) 1998 Academic Press.