Organohydrotalcites as novel supports for the slow release of the herbicide terbuthylazine

Abstract

The design of slow release formulations of pesticides is the subject of increasing attention with the aim of prolonging the biological efficacy of pesticides and attenuating their adverse environmental effects. In this work, organohydrotalcites (OHTs) are proposed as novel supports for the slow release of terbuthylazine, a herbicide widely applied to agricultural land. Two different OHTs were prepared by intercalating dodecylsulfate (DDS) and sebacate (SEB) anions into Mg–Al hydrotalcite (HT). Adsorption experiments revealed that terbuthylazine was well adsorbed by both HT–DDS and HT–SEB, whereas terbuthylazine adsorption by unmodified (inorganic) Mg–Al HT was negligible. Different terbuthylazine–OHT complexes were prepared by mixing the herbicide with the OHTs, using different solvents to favor the adsorbent–herbicide interaction. The ability of the herbicide–OHT complexes to slow the release of the herbicide into water and to reduce the herbicide leaching losses in soil was evaluated through batch release and column leaching tests. Compared to a standard commercial formulation of the herbicide, the complexes prepared from both HT–DDS and HT–SEB retarded the release of terbuthylazine into aqueous solution and reduced the herbicide leaching through soil columns. These results indicated promising usefulness of OHTs as suitable supports for the design of pesticide slow release formulations with the aim of reducing the adverse effects derived from rapid transport losses of the chemical once applied to soils.