Cationic and anionic clay nanoformulations of imazamox for minimizing environmental risk

摘要

A synthesized anionic clay (layered double hydroxide or LDH) and a commercial cationic organoclay (Cloisite 10A, Clo10A) were assayed as host nanocarriers for imazamox (Imz) herbicide. Imz-LDH complexes were obtained by direct synthesis (DS) and regeneration (RE), whereas Imz-Clo10A complexes were prepared by ground mixing (GM) and through methanol addition (weak [WC] and strong [SC] complexes). Characterization of the complexes showed that Imz was partially hosted in the interlayer structure of the resulting nanoherbicides, as anion or as neutral molecule, with some of the herbicide at the external surfaces, depending on the carrier and preparation. The nanoherbicides showed a total water release from 73 (Imz-LDH DS) to 98% (Imz-Clo10A GM) with an immediate release from 67 (Imz-LDH DS) to 93% (Imz-Clo10A GM). while technical Imz released instantaneously 98%. The herbicide maximum concentration in the leachates from Imz-treated soil columns decreased between 20 and 35% for nanoherbicides with respect to the technical Imz, and between 10 and 30% with respect to a commercial Imz formulation. Total herbicide soil leaching losses were reduced from 95 or 98%, for technical and commercial Imz, to 77-67% for nanoherbicides. Bioassays showed similar efficacy for nanoherbicides and commercial product. The diverse Imz-clay complexes are revealed as smart delivery systems for this systemic herbicide by decreasing Imz water pollution risk while maintaining efficacy, with the advantages of their soil compatible matrix and the possibility to be located at action point in the subsoil.