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Controlled release of isoproturon from an alginate-bentonite formulation: water release kinetics and soil mobility

Villafranca-Sanchez, M., Gonzalez-Pradas, E., Fernandez-Perez, M., Martinez-Lopez, F., Flores-Cespedes, F., Urena-Amate, M.D.
Pest management science 2000 v.56 no.9 pp. 749-756
isoproturon, granules, alginates, bentonite, sorption, leaching, kinetics, groundwater contamination, pollution control
The herbicide isoproturon [3-(4-isoprophylpenyl)-1,1-dimethylurea] was incorporated in alginate-based granules to obtain controlled-release (CR) properties. The basic formulation (sodium alginate (1.87%)-isoproturon (0.67%) in water) was modified by addition of different sorbents. The effect on isoproturon release rate, modified by the incorporation of natural and acid-treated bentonite in alginate formulation, was studied by immersion of the granules in water while shaking. The release of isoproturon was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, T50, was longer for those formulations containing added bentonite (5.98 and 7.43 days, for natural and acid-treated (1M H2SO4) bentonite, respectively) than for the preparation without bentonite (3.78 days). The mobilities of non-formulated technical grade (98%) and formulated isoproturon were compared using soil columns. The use of alginate-based CR formulations containing bentonite reduced isoproturon movement compared with the technical product. Sorption capacity of the soil for isoproturon was measured using batch experiments (0.29 litre kg(-1)) and the results obtained here in agreement with those obtained under dynamic conditions.