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The Effect of Cation Exchange Capacity on the Retention of Diquat 2+ and Paraquat 2+ by Three‐Layer Type Clay Minerals I. Adsorption and Release
Author(s) -
Weed S. B.,
Weber J. B.
Publication year - 1969
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/sssaj1969.03615995003300030014x
Subject(s) - vermiculite , chemistry , adsorption , montmorillonite , diquat , inorganic chemistry , sorption , clay minerals , cation exchange capacity , ion exchange , paraquat , divalent , nuclear chemistry , mineralogy , soil water , organic chemistry , geology , ion , paleontology , soil science
Diquat (1,1′‐ethylene‐2,2′‐dipyridinium dibromide) and paraquat (1,1′‐dimethyl‐4,4′‐dipyridinium dichloride) were equilibrated for thirty minutes with suspensions of three‐layer clay minerals varying in CEC from about 1–1.6 meq/g. Maximum adsorption of the divalent organic cations, expressed as percent of CEC, decreased from 100% for a montmorillonite (CEC = 1.03 meq/g) to 13% for a K + ‐depleted muscovite (CEC = 1.63 meq/g). The exchangeable inorganic cation initially present markedly affected adsorption of diquat 2+ and paraquat 2+ by vermiculite but had much less effect on adsorption by montmorillonite. The order of adsorption was Na + ‐vermiculite > Ca 2+ ‐vermiculite ≥ Mg 2+ ‐vermiculite. Less than 15% of the adsorbed diquat 2+ or paraquat 2+ was released from montmorillonite by a single equilibration with approximately five symmetry of 0.005 N chloride salt solutions of Al 3+ , Ca 2+ , Mg 2+ , or K + . Similar treatment of vermiculite released up to 70% of the adsorbed organic cation, the order of release being Al 3+ > Ca 2+ > Mg 2+ > K + for diquat 2+ and Ca 2+ > Al 3+ > Mg 2+ > K + for paraquat 2+ . Three successive treatments of vermiculite released up to 89% of the diquat 2+ or paraquat 2+ .