Use of Activated Bentonites in Controlled-Release Formulations of Atrazine

Abstract

The herbicide atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) was incorporated in alginate-based granules to obtain controlled-release (CR) properties. The basic formulation [sodium alginate (1.40%)-atrazine (0.60%)-water] was modified by the addition of sorbents. The effect on atrazine release rate caused by the incorporation of acid-treated bentonite (0.5 and 2.5 M H2SO4) in alginate formulation was studied by immersion of the granules in water under static conditions. The water uptake, sorption capacity of the sorbent, permeability, and time taken for 50% of the active ingredient to be released into water, t50, were calculated for the comparison of the preparations. t50 values were longer for those formulations containing acid-treated bentonite (36.78 and 29.01 days for 0.5 and 2.5 M H2SO4 treatments, respectively) than for the preparation without bentonite (9.69 days). On the basis of a parameter of an empirical equation used to fit the herbicide release data, it appears that the release of atrazine from the various formulations into water is controlled by diffusion mechanism. The sorption capacity of the sorbents and the permeability of the formulations (ranging from 4.99 to 20.83 mg day(-1) mm(-1)) were the most important factors affecting herbicide release.

Adsorption-desorption behavior of thiram: effect of soil type, temperature and pH

“…The adsorption isotherms of the fungicide thiram on the two soil were classified as L-type as the sorption kinetics corresponded to that of the L-type in the classification by Giles et al (1960). The L-types isotherms represent a system where the solid surface has average affinity for the pesticide and the solvent is relatively inert, i.e., there is no strong competition from the solvent for adsorption sites (Fernandez-Perez et al, 2004;Sharma et al, 2011). This isotherm shape was also reported by ValverdeGarcia et al (1988) to fit the adsorption of thiram onto eight Mediterranean soil types typical of Almería (Spain).…”

Controlled release system for ametryn using polymer microspheres: Preparation, characterization and release kinetics in water

“…These include materials composed of silica [12], clays such as bentonites [13] and sepiolite [14], polymers such as alginate [15] and 0304-3894/$ -see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2010.12.044 lignin [16], and synthetic polymers such as polyhydroxyalkanoates (PHAs) [17], including polyhydroxybutyrate (PHB) and its copolymer hydroxyvalerate (PHBV), which are the most widely used PHA polymers [18].…”

Pulse polarographic determination of thiophanate methyl fungicide in relation to its soil adsorption study

“…These adsorption isotherms have been classified as L type of Gile's classification (Somasundaran and Wang 2006;Calvet 1989) which represents a system where the solid surface has average affinity for the pesticide and the solvent is relatively inert. In other words, there is no strong competition from solvent for adsorption sites (Fernandez-Perez et al 2004). The Freundlich's adsorption coefficients K f and n f were calculated from the plot of log C s vs log C e (Figure 3), and results are summarized in Table 3.…”