Imazaquin Adsorbed on Pillared Clay and Crystal Violet–Montmorillonite Complexes for Reduced Leaching in Soil

Abstract

Ground water pollution due to herbicide leaching has become a serious environmental problem. Imazaquin [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)quinoline-3-carboxylic acid] is an herbicide used to control broadleaf weeds in legume crops. Imazaquin is negatively charged at the basic pH of calcareous soils and exhibits high leaching potential in soils. Our aim was to design formulation of imazaquin to reduce herbicide leaching. Imazaquin sorption on pillared clay (PC) and crystal violet (CV)-montmorillonite complexes was studied. The CV-montmorillonite complexes become positively charged with adsorption of CV above the cation exchange capacity (CEC) of montmorillonite, and thus can sorb imazaquin. The Langmuir equation provides a good fit to isotherms of imazaquin sorption on PC and CV-montmorillonite complexes, but for charged complexes an equation that combines electrostatics with specific binding was preferred. Maximal imazaquin sorption was 17.3 mmol kg-1 for PC and 22.2 mmol kg-1 for CV-montmorillonite complexes. The extents of imazaquin desorption into water were 21% for PC and 5% for CV-clay complexes. The presence of anions decreased imazaquin sorption on both sorbents in the sequence phosphate > acetate > sulfate. Reduction of imazaquin sorption by the anions and the extent of its desorption in electrolyte solutions were higher for PC than for CV-clay complexes. Leaching of imazaquin from CV-montmorillonite formulations through soil (Rhodoxeralf) columns was two times less than from PC formulations and four times less than that of technical imazaquin. The CV-montmorillonite complexes at a loading above the CEC appear to be suitable for preparation of organo-clay-imazaquin formulations that may reduce herbicide leaching significantly.

Surface modification of alumina nanofibres for the selective adsorption of alachlor and imazaquin herbicides

“…Herbicides are usually released into the environment through the industrial and agricultural operations resulting in them being detected in many surface and ground waters at extremely low concentrations. The removal of these compounds from water may be achieved with a variety of absorbents but the complete removal of these at low concentration is still somewhat difficult [1][2][3][4][5][6][7][8][9]. This study clearly illustrates that wide range of compounds with varied structures, sizes and functionality can be adsorbed effectively from aqueous systems only by the fine tuning of the adsorption sites [10][11][12][13][14][15][16].…”

Using the dual-mode model to describe adsorption of organic pollutants onto an organoclay

“…SWy-2 montmorillonite was obtained from the Source Clays Repository (Clay Minerals Society, Columbia, MO); the CEC of the clay is reported as 0.8 mol/kg [22]. 2,4,5-TCP (99%) and CV were purchased from Aldrich (Germany), whereas picric acid solution (1.2%) was obtained from Ridley (Reidelde Haan, Germany).…”

“…Interactions of the monovalent cationic dye crystal violet (CV) with montmorillonite were extensively studied and modeled [20], and the ability of the montmorillonite-CV complex to sorb anionic dyes and nonionic organic pollutants from water was investigated [15,21,22].…”

A clay‐based formulation of the herbicide imazaquin containing exclusively the biologically active enantiomer

“…For the specific case of imazaquin, several controlled release formulations based on clays and organoclays have been designed. Polubesova et al . showed that an organoclay‐imazaquin formulation prepared from a crystal violet‐montmorillonite complex reduced imazaquin leaching in soil.…”