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Effect of Fulvic Acid on Adsorption of Methyl Parathion and Parathion by Ca 2+ − and Fe 3+ ‐Montmorillonite Suspensions.
Author(s) -
Bowman Bruce T.
Publication year - 1978
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/sssaj1978.03615995004200030013x
Subject(s) - adsorption , montmorillonite , chemistry , parathion , parathion methyl , freundlich equation , nuclear chemistry , solubility , langmuir adsorption model , langmuir , chromatography , inorganic chemistry , organic chemistry , pesticide , agronomy , biology
A study was conducted to examine the effect of fulvic acid (FA) on the adsorption of methyl parathion and parathion by Ca 2+ − and Fe 3+ ‐montmorillonite suspensions, and to determine whether FA in solution could alter the water solubility of these insecticides. FA, in the 10‐ to 100‐mg/liter range, did not affect the water solubility of the two insecticides. In Ca 2+ ‐montmorillonite suspensions, increasing FA concentrations first enhanced methyl parathion adsorption, followed by adsorption decrease at higher FA levels. Methyl parathion adsorption in Fe 3+ ‐montmorillonite suspensions decreased, with increasing FA levels. Parathion adsorption was not significantly altered in either clay suspension. The order in which the FA, clay, and insecticide were mixed affected methyl parathion adsorption. The greatest effects were observed where FA was adsorbed by the clay before the insecticide solutions were added. FA adsorption by Ca 2+ ‐montmorillonite fitted the Freundlich isotherm, whereas the much greater adsorption by Fe 3+ ‐montmorillonite fitted the Langmuir isotherm. Although both CaCl 2 and FeCl 3 solutions greatly enhanced FA removal by their respective clay suspensions (even at low concentrations), parathion adsorption was not affected. The presence of FA in the FeCl 3 ‐Fe 3+ ‐montmorillonite suspensions appeared to prevent parathion degradation.