Exchange of Diquat2+ in Soil Clays, Vermiculite, and Sniectite
1970
Dixon, J. B. | Moore, D. E. | Agnihotri, N. P. | Lewis, D. E.
Clay samples were saturated with diquat²⁺ by a centrifuge washing procedure. Exchangeable diquat²⁺ was replaced by washing samples with 1N KCl solutions. Exchange of diquat²⁺ by K⁺ was 23 to 26% complete for three Wyoming montmorillonites and was 35 to 44% for three montmorillonite samples from Alabama and Mississippi. Diquat cations were 59% exchangeable in a nontronite. Diquat cations satisfied 57 and 82% of the cation exchange charge of Texas and Montana vermiculites and K⁺ replaced 98 and 88% of the diquat²⁺, respectively. There was a direct relationship between K⁺-diquat²⁺ exchange and layer charge density (CEC) of the montmorillonites and vermiculites. Hydroxy-Al interlayers had little influence on the exchange of diquat²⁺ in vermiculite and in montmorillonite except where double interlayers were deposited. Eleven soil clays had from 27 to 98% of their cation exchange charge countered by diquat²⁺. The exchangeability of diquat²⁺ in the diverse group of soil clays was directly related to vermiculite content. Montmorillonitic soil clays fixed more diquat²⁺ than vermiculitic soil clays. Diquat²⁺ was about 70% exchangeable in montmorillonitic soil clays which also contained vermiculite and kaolinite. The exchangeability of diquat²⁺ in montmorillonitic Houston and Iredell soil clays and their K⁺ fixing ability on oven drying indicate that vermiculite may have an important influence on their K⁺ exchange reactions.
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