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A Kinetic and Equilibrium Study of the Adsorption of Carbaryl and Parathion upon Soil Organic Matter Surfaces
Author(s) -
Leenheer J. A.,
Ahlrichs J. L.
Publication year - 1971
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/sssaj1971.03615995003500050022x
Subject(s) - adsorption , loam , chemistry , carbaryl , diffusion , sorption , organic matter , freundlich equation , parathion , soil water , organic chemistry , pesticide , thermodynamics , soil science , geology , agronomy , physics , biology
Insight into the mechanisms of carbaryl (1‐Napthyl‐ N ‐methyl carbamate) and parathion ( O , O ‐Diethyl‐ o ‐ p ‐nitrophenylphosphorothioate) adsorption upon organic matter derived from the Romney silty clay loam, Zanesville silt loam, and Carlisle muck soils was obtained by twofold kinetic and equilibrium study of adsorption in nonflow aqueous systems. The differences in adsorptive characteristics of the various types of organic matter were small in both the kinetic and equilibrium studies, but changing the saturating cation from calcium to hydrogen greatly increased the adsorptive capacities for both insecticides. The magnitude of the adsorptive capacities was explained in terms of the magnitude of the hydrophobic natures of the insecticide adsorbates and the organic matter adsorbents. Kinetic adsorption studies conducted at 5, 25, and 40C showed the rate to increase as the temperature increased with the magnitude of the initial rate constant being 10 ‐4 sec ‐1 . The rate‐limiting step was interpreted to be diffusion of the insecticide solute molecules to the surface of the adsorbent for the first 10 min of adsorption. At longer times, intraparticle diffusion of the adsorbate into the interior of the adsorbent particles was rate limiting.