Bentonite and Humic Acid as Modifying Agents in Controlled Release Formulations of Diuron and Atrazine

Abstract

Abstract The herbicides diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea] and atrazine [6‐chloro‐N 2 ‐ethyl‐N 4 ‐isopropyl‐1,3,5‐triazine‐2,4‐diamine] were incorporated in alginate‐based granules to obtain controlled release (CR) properties. The basic formulation [sodium alginate (14.0 g kg −1 )‐herbicide(6.0 g kg −1 )‐water] was modified by addition of sorbents. The effect on (Huron and atrazine release rate, caused by incorporation of natural bentonite and humic acid in the alginate formulation, was studied by immersion of the granules in water under static conditions. The release of the active ingredient from alginate‐based CR granules in water was affected by the addition of natural bentonite, and to a greater extent, by the addition of the humic acid. The water uptake, permeability, and the time taken for 50% of active ingredient to be released into water, T 50 , were calculated for the comparison of the preparations. Addition of both bentonite and humic acid samples to the basic alginate‐based formulation produced the higher T 50 values (43.11 and 50.49 d for diuron and atrazine formulations, respectively), indicating a slower release of herbicide. Based on parameters of an empirical equation used to fit the herbicide release data, it appears that the release of diuron and atrazine from the various formulations into water is controlled by a diffusion mechanism. Sorption capacity of the sorbent and the permeability of the formulations (ranging from 3.77 to 20.83 mg d −1 mm −1 ) were the most influential factors affecting herbicide release.