Herbicidal Ionic Liquids: A Promising Future for Old Herbicides? Review on Synthesis, Toxicity, Biodegradation, and Efficacy Studies

Abstract

The transformation of agrochemicals into herbicidal ionic liquids (HILs) has been suggested as a solution to problems associated with commercial forms of herbicides. The aim of this review was to summarize the latest progress in the field of HILs, including their synthesis as well as physicochemical and biological properties, and to address the areas that require further research in order to ensure their safe commercialization (e.g., data regarding biodegradability, toxicity, and environmental fate). The first part of the review provides an in-depth summary of the current state of knowledge regarding HILs, particularly the anions and cations used for their synthesis. The second part highlights the employed synthesis methods and elucidates their respective advantages and limitations. The third section is focused on the characterization of HILs with emphasis on the methods and factors that are significant in terms of their practical application. Subsequently, the issues associated with the biodegradation and toxic effects of HILs are discussed based on the relevant literature reports. All sections include comprehensively tabulated data in order to enable rapid comparison of utilized approaches. Finally, all the findings are critically analyzed in terms of crucial disadvantages (especially the lack of standardization), which allowed us to establish future recommendations and basic guidelines that are presented in the last section.

Transformation of Iodosulfuron-Methyl into Ionic Liquids Enables Elimination of Additional Surfactants in Commercial Formulations of Sulfonylureas

“…Herbicidal ionic liquids (HILs) have numerous advantages such as adjustable physicochemical properties e.g., phase transitions (i.e., melting point), viscosity, polarity, water solubility or mobility in soils and waters [ 7 , 20 , 26 ]. The presence of an ionic bond in their structure reduces the volatility which positively affects the safety associated with their application [ 27 ]. Additionally, HILs possessing at least one long alkyl chain can exhibit excellent surface active properties, eliminating the need for additional surfactants, and often allowing herbicide application at lower than normal concentrations [ 28 , 29 ].…”

The Challenge of Combining High Yields with Environmentally Friendly Bioproducts: A Review on the Compatibility of Pesticides with Microbial Inoculants

“…Examples of herbicides applied worldwide include glyphosate, paraquat, and diuron. Among these, the most well-known is glyphosate; since its introduction in the 1970s, its use spread quickly, facilitated cropping, but also implied in the growing appearance of resistant weeds, resulting from a natural process of plant adaptation, and decreasing its efficacy [111][112][113]. An important alternative to minimize this problem, in addition to integration with other control methods, would be diversification in the use of herbicides, including others with different mechanisms of action [114].…”

Naturally based ionic liquids with indole-3-acetate anions and cations derived from cinchona alkaloids

“…24,25 In practice, this effect can be easily achieved by converting the nonionic form of the active ingredient into an ionic liquid (IL). 5,25 In the course of research on third generation ILs (i.e., ILs designed for targeted biological activity), 26,27 compounds characterised by specic effects on plants, including herbicidal activity, 28 stimulated resistance against phytoviruses 29,30 or limited plant growth, 31 have been discovered. However, converting compounds from the auxin group into biologically active ILs constitutes a very recent approach.…”