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Soil Science Society of America Journal Abstract -

The Surface Catalyzed Hydrolysis of Parathion on Kaolinite1


This article in SSSAJ

  1. Vol. 38 No. 2, p. 231-234
    Received: Aug 17, 1973
    Accepted: Nov 7, 1973

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  1. Sarina Saltzman,
  2. Bruno Yaron and
  3. Uri Mingelgrin2



The decomposition of parathion on various monoionic kaolinites was investigated. The degradation was found to proceed via the hydrolysis of the phosphate ester to p-nitrophenol and diethyl thiophosphate. The kaolinites were found to catalyze the hydrolysis. The nature of the exchangeable cation greatly affected the rate of hydrolysis. Ca-kaolinite was the most active in inducing the degradation of parathion, the hydrolysis being twice as fast as in a water solution at pH 8.5 at the same temperature. The presence of a large excess of water decreased the catalytic effect of the kaolinite. The mechanism of the hydrolysis is via adsorption of the parathion upon the exchangeable cation or its hydration shell. The temperature dependence of the process is consistent with this proposed mechanism. The significant catalytic activity of kaolinites and its dependence on the exchangeable cation is important to the understanding of the degradation of parathion in soil and may be utilized in the formulation of parathion for various purposes.

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