Hexazinone Adsorption‐Desorption Studies with Soil and Organic Adsorbents

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Abstract
Hexazinone [13‐cyclohexyl‐6‐(dimethylamino)‐1‐methyl‐1,3,5‐triazine‐ 2,4(1H,3H)‐dione] adsorption‐desorption was studied using soil from different horizons and using organic adsorbents. Hexazinone was adsorbed less than atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] by soil. The Oi horizon (leaf litter) of a forest soil showed the greatest adsorptivity for hexazinone (K = 15.09). Hexazinone was desorbable from all soil horizons with 0.01M CaCl2. Normalizing for the organic C content of the soil horizons with Koc removed differences in the adsorptivity between soils. The octanol‐water partition coefficient (Kow) estimated the Koc for the hexazinone‐soil horizon systems within a factor of 2 to 3.Hexazinone was not adsorbed from 0.01M CaCl2 by purified cellulose, or by anionic (pH = 5.8) or neutral (pH = 2.8) carboxymethyl cellulose. Nonpolar surfaces seem to be important in hexazinone adsorption as polystyrene adsorbed all of the hexazinone from 0.01M CaC2. The hexazinone adsorbed by polystyrene was not desorbable with 0.01M CaCl2, but was desorbable with a 3:2 methanol/water (vol/vol) solution. In the absence of competing water molecules, hexazinone was adsorbed from hexane solution on cellulose.