ISOTHERMS OF CADMIUM SORPTION DENSITY

To study Cd sorption, 16 soil samples of different chemical soil react ions were taken and analyzed for their physical and chemical propertie s. Adsorption of ethylene glycol monoethyl ether (EGME) and N2 were de termined to establish the specific surface area of the soils. The sorp tion of Cd was modeled on a per-mass basis using the Langmuir and Freu ndlich equations as well as per-surface area basis. Traditional sorpti on isotherms reveal the relation between the amount of Cd sorbed and t he Cd concentration in the soil solution only for the soil under study and can therefore not be applied, or can be applied only with restric tions, to other soils. To meet the aim of modeling Cd sorption and mob ility for other soils or locations differing greatly in their properti es, we attempted to establish a generalizing sorption isotherm for soi ls of entirely different composition of the solid phase. On the basis of characteristic values the 16 soil samples taken were grouped into t hree different reaction types (aluminum-hydroxide, silicate, and carbo nate-buffer range). The generalizing Cd sorption density isotherms for these different soil groups introduced in the following provide a use ful mathematical model for the quantity-intensity relation of Cd in so ils that differ greatly in their specific surface area and their compo sition.