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Influence of Ionic Strength and Inorganic Complex Formation on the Sorption of Trace Amounts of Cd by Montmorillonite
Author(s) -
GarciaMiragaya J.,
Page A. L.
Publication year - 1976
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1976.03615995004000050019x
Subject(s) - sorption , chemistry , cadmium , montmorillonite , ionic strength , salt (chemistry) , ionic bonding , inorganic chemistry , chloride , divalent , soil water , environmental chemistry , ion , adsorption , aqueous solution , organic chemistry , geology , soil science
Cadmium sorption by montmorillonite from solutions in the 15 to 120 ppb range was studied in the presence of increasing concentrations of NaClO 4 , NaCl, and Na 2 SO 4 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 ClO 4 systems. The sorption of Cd in the chloride system was in the range between 25 to 50% less than the ClO 4 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 (CdCl 2 0 ) and as an anion (CaCl 3 ‐ and CdCl 4 2‐ ), rather than as a cation (Cd 2+ ). The SO 4 systems showed a moderate decrease in the amount of Cd sorbed with respect to the ClO 4 systems for the same salt concentrations. This observation was interpreted as due to the presence of a fraction of Cd in solution as the CdSO 4 0 species.