Exchange Adsorption of Trace Quantities of Cadmium in Soils Treated with Chlorides of Aluminum, Calcium and Sodium

Abstract

Abstract The exchange adsorption of Cd has been studied in Cecil sandy loam (clay fraction 45% kaolinite and 25% vermiculite), Winsum clay loam (clay fraction 80% illite), and Yolo silt loam (clay fraction 47% montmorillonite and 22% mica). Experimental variables were the major cations Al 3+ , Ca 2+ , and Na + , salt (chloride) levels (from 5 to 50 meq/liter), and the initial concentration of CdCl 2 (from 22 to 170 µeq/liter). The exchange of Cd 2+ in Al 3+ ‐ and Ca 2+ ‐treated soils was normal in that the adsorption was greater in the presence of Ca 2+ than of Al 3+ , and decreased with increasing concentration of AlCl 3 or CaCl 2 . In the Na + ‐treated, alkalized soils, Cd 2+ did not precipitate. The exchange was unusual because the adsorption of Cd 2+ decreased as NaCl concentrations decreased. The same behavior was shown by 109 Cd 2+ . At NaCl concentrations decreasing below 30 meq/liter, the adsorption of Ca 2+ by Na + ‐treated soils also decreased, as did the adsorption of Na + . The result was attributed to decreasing soil exchange capacity with decreasing NaCl concentration due to increased adsorption of products derived from alkaline corrosion of the soil matrix.