Organoclays for controlled release of the herbicide fenuron

Abstract

Organoclays were assayed as matrices in which to associate herbicides, with the aim of decreasing product losses that could give rise to water contamination from agricultural activities. Fenuron was selected as model of a very mobile and highly water-soluble herbicide. Two different organoclays of high (A-HDT) and low (H-C18) reversible fenuron sorption were selected. Herbicide-organoclay complexes were prepared from the two organoclays and with two different fenuron contents (20 and 40 g AI kg-1) and two different mixing times, so as to form a series of weak and strong complexes. The release of fenuron from those complexes into water and water/soil suspensions gave values of T50 (time to release 50% of the fenuron content) ranging from 0.3 min to 2400 h. The total fenuron released in these closed systems ranged from 48 to 80% of the fenuron in the complex. The organoclay type (high or low sorptivity) had the greatest influence on fenuron release, followed by the strong or weak complex, suggesting that herbicide-organoclay interactions are the main factors controlling release. Soil column leaching experiments showed fenuron-organoclay complexes to be effective in reducing the peak herbicide concentration in the leachate to a half (6 microns) or a quarter (3 microns) of that obtained from the free technical compound (12 microns). Herbicide lost through leaching was reduced from 78% for the free technical fenuron to 50-30%, depending on the organoclay used as carrier and the strength of the complex. Bioassay with ryegrass showed that the weak fenuron/H-C18 complex (40 g AI kg-1) gave the same herbicidal activity as technical fenuron. The potential suitability of low-sorptive organoclays for conferring slow-release properties on the fenuron complex has been demonstrated.

Mobility and efficacy of 2,4-D herbicide from slow-release delivery systems based on organo-zeolite and organo-bentonite complexes

“…[16] Various surfactant-mineral complexes have been tested for preparing SRFs of different herbicides such as norflurazon, [19,20] acetochlor, [21] fenuron, [22] metolachlor [23] and diuron. [24] Very few attempts have been made to synthesize and evaluate SRFs of 2,4-D using organo-minerals.…”

Organoclay‐Based Formulations to Reduce the Environmental Impact of the Herbicide Diuron in Olive Groves

“…Bene cial e ects related to the use of slow release formulations include reduced mobility of the active ingredient, reduction in the amount of chemical required for pest control, savings in manpower and energy by reducing the number of applications required in comparison with conventional formulations, increased safety for the pesticide applicator, and a general decrease in nontarget e ects (Gerstl et al, 1998). Organoclays, that is, natural clay minerals with their original inorganic exchange cations replaced with organic cations, have been proven to be very good adsorbents for di erent classes of pesticides and, accordingly, have been proposed as carriers for the design of slow release formulations of pesticides (El-Nahhal et al, 2001;Hermosín et al, 2001;Prost and Yaron, 2001;Lagaly, 2001;Carrizosa et al, 2003;Cornejo et al, 2008). e organic cations most commonly used for the preparation of organoclays are synthetic, quaternary ammonium ions of the general form [(CH 3 ) 3 NR] + or [(CH 3 ) 2 NR 2 ] + , where R is an aromatic or aliphatic hydrocarbon ( Jaynes and Boyd, 1991).…”

A comparative study of tubular halloysite and platy kaolinite as carriers for the loading and release of the herbicide amitrole

“…In addition, natural porous materials that can be used as pesticide carriers in controlled-release formulations, such as zeolite (Zhang et al, 2006) and some swelling clay minerals, e.g., montmorillonite (Celis et al, 1999(Celis et al, , 2002Carrizosa et al, 2000;Hermosin et al, 2001Hermosin et al, , 2006Undabeytia et al, 2013) and hydrotalcite (Celis et al, 1999;Bruna et al, 2008), have attracted considerable attention. Natural zeolites and clay minerals have several advantages for use as pesticide carriers: (i) in comparison with synthetic porous materials, these natural minerals are readily available at low cost because of their abundant deposits; (ii) they are environmentally friendly because they are common soil constituents; and (iii) the loading of pesticides on these carriers is readily achieved via simple adsorption and/or ion exchange because they normally possess high ion-exchange capacity.…”