•The [C10mim][Br] was studied as an alternative to organic solvent of EC.•The addition of [C10mim] [Br] makes the solubility of clethodim great improved.•The new formulation is stable and environment friendly.•The new formulation can achieve the same bioactivity of clethodim(EC).1-decyl-3-methyl imidazolium bromide ([C10mim][Br]) aqueous solution was studied as an alternative to aromatic compounds of clethodim emulsifiable concentrate (EC). The solubility of clethodim in [C10mim][Br] aqueous solution (1253.19 g·L− 1) has been greatly improved compared with that in pure water (5.45 g·L− 1) when the mass fraction of [C10mim][Br] was 35%. The electrical conductivity, viscosity and average diameter of [C10mim][Br] aqueous solution were measured. The thermodynamic parameters of electrical conductivity indicate that [C10mim][Br] in aqueous solution can spontaneously occur micelle formation and micellization is an entropy-driven process. The result of the average diameter of [C10mim][Br] can proved the presence of the micelle. And a higher fluidity is more suitable for pesticide dissolution, but not too high. After storage stability test, clethodim formulation water-based with [C10mim][Br] aqueous solution was stable under three different temperatures. The result of bioassay of clethodim formulation water-based with [C10mim][Br] aqueous solution indicates that the new formulation has high herbicidal activity (df = 6, F = 5.871, P = 0.001).Download high-res image (278KB)Download full-size image

In this work, quaternary ammonium based ionic liquids (ILs) are proven to be good candidates to act as green solvents/solubilizers for pesticide formulations. The surface activity of six ionic liquids ([M3CnN]X; M = CH3; n = 10, 12, 14; X = Cl, Br) was tested, along with the corresponding critical aggregation concentration (CAC), lowest surface tension (γCAC), maximum surface excess concentration (Γmax), minimum area per molecule (Amin) and higher adsorption efficiency (pC20), which were measured using several methods, including surface tension measurements, electrical conductivity measurements, steady-state fluorescence measurements and 1H NMR. The thermodynamic parameters of micellization, the viscosities and the activation energies of the six ILs in 30% aqueous solutions, over the temperature range of 288–308 K, were determined and calculated. The results indicated that the solubilities of representative pesticides (metolachlor, acetochlor, clethodim, thiamethoxam, prochloraz, acetamiprid and fosthiazate) in different concentrations of these ILs were significantly higher than in pure water, especially for prochloraz (e.g., 137.2 g L−1 in 30% C10Br, 4035 times higher than in pure water). The microenvironment existing between the pesticide and micelle was investigated using 1H NMR techniques, revealing that micelle localization of pesticide molecules and a change in micelle conformation occurred in the dissolving process.

Mixed ionic liquids (ILs) of 1-butyl-3-methylimidazolium bromide ([C4mim][Br], A) and 1-decyl-3-methylimidazolium bromide ([C10mim][Br], B) were used as solubilizers for six water-insoluble pesticides (i.e., metolachlor, acetamiprid, acetochlor, clethodim, thiamethoxam, and prochloraz). The solubilities of six pesticides were improved by increasing the B content of the mixed ILs. The aggregation behavior of the mixed IL systems was investigated by means of surface tension, conductivity, and fluorescence measurements. Enhancements in solubility were related to the surface activities of the mixed ILs, as indicated by measurements of their surface active and thermodynamic parameters. This work can reduce the cost and toxicity of using ILs, and the data shown in this paper provide valuable information for choosing a proper mixing proportion of suitable ILs for application to agriculture.

Ionic liquids may be considered as “environment-friendly solvents” for sparingly soluble pesticides. In this study, a series of aqueous ionic liquids (ILs) with different cations and different anions was used as environment-friendly alternative to harmful organic solvents sparingly dissolved in soluble pesticides (metolachlor, acetochlor, clethodim, thiamethoxam, and prochloraz). The aggregation behavior of aqueous ILs was investigated through surface tension measurement. Minimum area per IL molecule (Amin) values from the surface tension measurement showed that alkyl chain length and the halide anions strongly affect the aggregation behavior of ILs and the solubilization of pesticides. The solubility of metolachlor, acetochlor, clethodim, thiamethoxam, nitenpyram, and prochloraz in aqueous ILs increased. More importantly, the solubility of prochloraz in [C10mim][I] became 5771-fold higher than that in pure water. The substantially enhanced solubility of the above pesticides proved that aqueous ILs are promising environment-friendly solvents for pesticides that are commercially processed in emulsifiable concentrate (EC) formulation.