Controlled release of carbofuran from an alginate-bentonite formulation: water release kinetics and soil mobility.
The insecticide-nematicide carbofuran was incorporated in alginate-based granules to obtain controlled-release (CR) properties. The basic formulation [sodium alginate (1.61%)-carbofuran (0. 59%)-water] was modified by addition of sorbents. The effect on carbofuran release rate, caused by the incorporation of natural and acid-treated bentonite (0.5 and 1.0 M H(2)SO(4)) in alginate formulation, was studied by immersion of the granules in water under shaking. The time taken for 50% of the active ingredient to be released into water, t(50), was longer for those formulations containing natural bentonite (6.1 h) or acid-treated bentonite (9.0 and 11.7 h for 0.5 and 1.0 M H(2)SO(4) treatments, respectively) than for the preparation without bentonite (4.7 h). It appears from the results that the release of carbofuran from the various formulations is controlled by a diffusion mechanism according to the n values obtained, which were close to 0.5 in all cases. The mobility of carbofuran from alginate-based CR formulations was investigated by using soil columns packed with a clay soil (53% clay and 0.08% organic matter). Two alginate-based CR formulations containing natural bentonite or acid-treated bentonite (0.5 M H(2)SO(4)) were compared to technical grade carbofuran. The use of alginate-based CR formulations resulted in a reduction of the leached amount of carbofuran compared with the total amount of pesticide leached using the technical product (50 and 75% for CR granules containing natural and acid-treated bentonite, respectively). Alginate-bentonite CR formulations might be efficient systems for reducing carbofuran leaching in clay soils, which would reduce the risk of groundwater pollution.
Fernández-Pérez
M
M
Departamento de Química Inorgánica, Universidad de Almería, Almería 04120, Spain. mfernand@ualm.es
Villafranca-Sánchez
M
M
González-Pradas
E
E
Martinez-López
F
F
Flores-Céspedes
F
F
D000464:Alginates / Q000737:chemistry*; D000969:Antinematodal Agents / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D002235:Carbofuran / Q000737:chemistry*; D003692:Delayed-Action Preparations; D006801:Humans; D007306:Insecticides / Q000737:chemistry*; D007700:Kinetics; D012989:Soil Pollutants / Q000378:metabolism; D014876:Water Pollution / Q000517:prevention & control*
D000464:Alginates; D000969:Antinematodal Agents; D003692:Delayed-Action Preparations; D007306:Insecticides; D012989:Soil Pollutants; D001546:Bentonite; D002235:Carbofuran