Removal and detoxification of iprodione in water using didodecyldimethylammonium bromide-montmorillonite organoclay and manganese dioxide.

Abstract

Combination of organoclay sorption with manganese(IV) oxide (MnO₂) catalyzed catechol oxidation was studied for the removal of a dicarboximide fungicide, iprodione, from water. Iprodion in water was sorbed on didodecyldimethylammonium bromide (DDAB)-modified montmorillonite (MT) organoclay and converted into the degraded product, 3,5-dichloroaniline (DCA). The degree of sorption increased by the modification with DDAB, because of the formation of a hydrophobic region for the incorporation of iprodione and negligibly interfered by coexisting MnO₂. The half-life for the degradation of irodione in water at 25 °C was 7 days, whreas it reduced to 15 min in the organoclay. The activation energy, 65.4 ± 4.8 kJ mol^-1, for the first-order reaction in the aqueous solution (pH 7.0) decreased to 43.9 ± 1.8 kJ mol^-1 in the organoclay, indicating the catalytic activity of the organoclay that accelerates the hydrolysis reaction of iprodione. In the coexistence of appropriate amounts of MnO₂ and catechol, the degraded product, DCA, reacted with oxidized products of catechol to form a water-insoluble precipitate and was successfully eliminated from water. The results obtained in the present study strongly suggest the applicability of the combined method of organoclay sorption method and MnO₂-catalyzed oxidation for the diffusion control of toxic agrochemicals.