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

Abstract

The herbicide isoproturon [3-(4-isopropylphenyl)-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 (1 M 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. © 2000 Society of Chemical Industry