Hexazinone Adsorption‐Desorption Studies with Soil and Organic Adsorbents

Hexazinone [13‐cyclohexyl‐6‐(dimethylamino)‐1‐methyl‐1,3,5‐triazine‐ 2,4(1 H ,3 H )‐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 0.01 M CaCl 2 . Normalizing for the organic C content of the soil horizons with K oc removed differences in the adsorptivity between soils. The octanol‐water partition coefficient (K ow ) estimated the K oc for the hexazinone‐soil horizon systems within a factor of 2 to 3. Hexazinone was not adsorbed from 0.01 M CaCl 2 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 0.01 M CaC 2 . The hexazinone adsorbed by polystyrene was not desorbable with 0.01 M CaCl 2 , 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.