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The solubility of 9 sparingly soluble pesticide active ingredients (PAIs) was predicted in 133 deep eutectic solvents (DESs) based on 7 hydrogen bond acceptors and 19 hydrogen bond donors, using a COSMO-RS model. 13 DESs with superior solubility of water-insoluble PAIs were screened out and verified with experiments. The actual measurement results agree well with the forecasting results. When compared with the solubility in pure water, some PAIs can even be mutually dissolvable with tetraethylammonium chloride: decanoic acid (1:2), tetrabutylammonium chloride: decanoic acid (1:3), and tetrabutylammonium chloride: phenol (1:5), such as butachlor, acetochlor, and metolachlor. IR and 1H NMR spectra suggested that hydrogen bonding between DESs and PAIs molecules played a crucial role in solvation. Crucially, the study indicated that it’s feasible to replace toxic organic solvents with DESs in emulsifiable concentrates formulations. The effects of different concentrations of tetraethylammonium chloride: decanoic acid (1:2) on the growth of wheat seedlings were also explored. The results showed that it did not affect the germination rate of wheat seeds, but with the increase of concentration, the growth indexes such as the lengths of shoots and roots grew shorter, the fresh weight of aboveground and underground decreased. This study not only provides COSMO-RS as a useful and reliable tool to screen DESs but also highlights that DESs can be an alternative to replace toxic and harmful organic solvents in emulsifiable concentrates (EC) formulations, which provide ideas and a basis for designing new green pesticide formulations.

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).

In line with the requirements of green chemistry, the preparation of eco-friendly pesticide formulations has become an inevitable development trend. In this work, we explored the feasibility of four new ionic liquids (ILs, [Octyl trimethyl ammonium] anions, anions = proline, valine, leucine, tartaric acid) as environmentally-friendly solvents for pesticide emulsifiable concentrates, and also as alternatives to traditional imidazole-based ILs since they do not contain the imidazole ring and the anions are natural substances. The results showed that the solubility of pesticides (clethodim, metolachlor, acetochlor, prochloraz, thiamethoxam, glyphosate, acetamiprid) in water with 25%w/v ILs was significantly improved, especially for acetamiprid, where the solubility was increased 19-fold, while it only increased about 4 to 5-fold after adding imidazole-based ILs in our previous work. In addition, the solubilization mechanism was explored by many methods and found that the solubilization effect does not completely depend on the critical micelle concentration (CMC) value but has a great relationship with the hydrophilicity of the ILs which may affect the size of micelles and release behavior to pesticides. Finally, 1H NMR was used to investigate the solubilization sites of ILs for glyphosate, and the interaction between pesticides and anions was explored by the quantum chemical method.