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The Effect of Saturating Cations on the Adsorption of Dasanit®, O,O‐diethyl O‐[p‐(methyl sulfinyl) phenyl] phosphorothioate, by Montmorillonite Suspensions
Author(s) -
Bowman Bruce T.
Publication year - 1973
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/sssaj1973.03615995003700020015x
Subject(s) - montmorillonite , adsorption , desorption , chemistry , monolayer , suspension (topology) , sulfoxide , inorganic chemistry , infrared spectroscopy , nuclear chemistry , organic chemistry , biochemistry , mathematics , homotopy , pure mathematics
A study was conducted to examine the adsorptive behavior of Dasanit in montmorillonite suspensions as affected by saturating cations and the clay suspension concentration. Adsorption isotherms, similar to Type III or Class “S” isotherms, were constructed for 10 cation‐saturated montmorillonites. Infrared spectroscopy was used to examine the relative polarities of the sulfoxide, sulfone, phosphoryl, and carbonyl groups as they occur in Dasanit, in some of its oxidation products, and in several other insecticides. Despite its polar nature, Dasanit did not appear to adsorb on the interlayer surfaces of montmorillonite. X‐ray diffraction data for dry Dasanit‐montmorillonite systems showed a maximum interlayer expansion of 2.7Å. Kinetic data showed that the adsorption process reached equilibrium in less than 15 min. The sequence of the upper linear segments of the 10 isotherms appeared to be related to valence, atomic weight, and co‐ordinating habits of the saturating cations. The Fe‐montmorillonite system adsorbed the most Dasanit. At a suspension concentration of 15 mg/ml, this system removed 99% of the Dasanit from solution. The maximum adsorption value obtained for Fe‐montmorillonite was 0.354 mg/mg clay at a suspension concentration of 0.25 mg/ml. This value corresponded to approximately 4.8 Dasanit monolayers on the exterior clay surface. Desorption studies indicated that those clays with the greatest adsorption capacity exhibited the least desorption tendency. The decreasing order of desorption was Na − > Ca − > Al − > Cu − montmorillonite.