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Soil Science Society of America Journal Abstract -

Influence of Ionic Strength and Inorganic Complex Formation on the Sorption of Trace Amounts of Cd by Montmorillonite1


This article in SSSAJ

  1. Vol. 40 No. 5, p. 658-663
    Received: June 30, 1975
    Accepted: Apr 27, 1976

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  1. J. Garcia-Miragaya and
  2. A. L. Page2



Cadmium sorption by montmorillonite from solutions in the 15 to 120 ppb range was studied in the presence of increasing concentrations of NaClO4, NaCl, and Na2SO4 solutions. The ionic strengths ranged from 0.01 to 1.00. Increasing ionic strengths decreased the amount of Cd sorbed on the clay surfaces. The percentage sorbed decreased from around 90% for I = 0.01 to about 50% for I = 1.00 in the ClO4 systems. The sorption of Cd in the chloride system was in the range between 25 to 50% less than the ClO4 systems for the same ionic strength. This was attributed to the presence of uncharged and negatively charged complexes of Cd with Cl ligands. This fact has some implications, especially in arid zone soils where high Cl concentrations in soil solutions are not unusual; there, Cd will behave mainly as a neutral species (CdCl20) and as an anion (CaCl3- and CdCl42-), rather than as a cation (Cd2+).

The SO4 systems showed a moderate decrease in the amount of Cd sorbed with respect to the ClO4 systems for the same salt concentrations. This observation was interpreted as due to the presence of a fraction of Cd in solution as the CdSO40 species.

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