Controlled Release of Diuron from an Alginate−Bentonite Formulation: Water Release Kinetics and Soil Mobility Study

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Abstract
The herbicide diuron was incorporated in alginate-based granules to obtain controlled release (CR) properties. The standard formulation (alginate−herbicide−water) was modified by the addition of different sorbents. The effect on diuron release rate caused by incorporation of natural and acid-treated bentonites in alginate formulation was studied by immersion of the granules in water under static conditions. The release of diuron was diffusion-controlled. The time taken for 50% release of active ingredient to be released into water, T50, was calculated for the comparison of formulations. The addition of bentonite to the alginate-based formulation produced the higher T50 values, indicating slower release of the diuron. The mobility of technical and formulated diuron was compared by using soil columns. The use of alginate-based CR formulations containing bentonite produced a less vertical distribution of the active ingredient as compared to the technical product and commercial formulation. Sorption capacities of the various soil constituents for diuron were also determined using batch experiments. Keywords: Diuron; controlled release; bentonite; soil; sorption−desorption; leaching