Controlled release of herbicides by 2,4-D-, MCPA-, and bromoxynil-intercalated hydrotalcite nanosheets

Abstract

Volatilization and leaching are two critical pathways for pesticide transportation from their applied areas to non-target regions. Nanocarrier-based formulations can improve the use efficiency and reduce the off-target effects of pesticides, however, the complicated preparation process seriously restricts the large-scale application of nanopesticides in the agricultural field. In this work, taking 2-(2,4-dichlorophenoxy) acetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), and 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) as model herbicides, herbicide-intercalated Zn–Al hydrotalcites (herbicide@HTlcs) were facilely fabricated by a modified co-precipitation method without heating, aging, organic solvents, and inert gas. The obtained herbicide@HTlcs showed high entrapment efficiencies (71.7%–86.7%), a sheet structure with an average size of 339.4 nm, and positive surface charges (+40.5). The volatilities of herbicide@HTlcs were reduced more than 3-fold compared with those of pure herbicides. The release rates of 2,4-D@HTlcs were in line with the selectivity sequence of HTlcs for the anions and controlled by non-Fickian diffusion. The leaching experiments performed in two agricultural topsoils collected from Beijing and Yunnan province and a grassland soil from Neimenggu province all demonstrated that the developed 2,4-D@HTlc nanosheets could evidently retard 2,4-D leaching through the soil. Additionally, 2,4-D@HTlcs exhibited no delay in the control efficacy against Amaranthus retroflexus compared with free 2,4-D sodium salt. This study provides a novel insight into the facile fabrication of controlled release formulations of pesticides that can reduce the volatilization and leaching risks simultaneously.