Ionic Liquids Toxicity—Benefits and Threats

Abstract

Ionic liquids (ILs) are solvents with salt structures. Typically, they contain organic cations (ammonium, imidazolium, pyridinium, piperidinium or pyrrolidinium), and halogen, fluorinated or organic anions. While ILs are considered to be environmentally-friendly compounds, only a few reasons support this claim. This is because of high thermal stability, and negligible pressure at room temperature which makes them non-volatile, therefore preventing the release of ILs into the atmosphere. The expansion of the range of applications of ILs in many chemical industry fields has led to a growing threat of contamination of the aquatic and terrestrial environments by these compounds. As the possibility of the release of ILs into the environment s grow systematically, there is an increasing and urgent obligation to determine their toxic and antimicrobial influence on the environment. Many bioassays were carried out to evaluate the (eco)toxicity and biodegradability of ILs. Most of them have questioned their “green” features as ILs turned out to be toxic towards organisms from varied trophic levels. Therefore, there is a need for a new biodegradable, less toxic “greener” ILs. This review presents the potential risks to the environment linked to the application of ILs. These are the following: cytotoxicity evaluated by the use of human cells, toxicity manifesting in aqueous and terrestrial environments. The studies proving the relation between structures versus toxicity for ILs with special emphasis on directions suitable for designing safer ILs synthesized from renewable sources are also presented. The representants of a new generation of easily biodegradable ILs derivatives of amino acids, sugars, choline, and bicyclic monoterpene moiety are collected. Some benefits of using ILs in medicine, agriculture, and the bio-processing industry are also presented.

Enzymatic Activity and Its Relationship with Organic Matter Characterization and Ecotoxicity to Aliivibrio fischeri of Soil Samples Exposed to Tetrabutylphosphonium Bromide

“…Sorption plays an important role in the toxicity of ILs in the soil [ 73 ]. The results from available studies show that the cations present in ILs with long-chain hydrophobic substitutes can easily adsorb on different types of soil, and become persistent contaminants in the environment [ 74 , 75 , 76 ].…”

Multiproduct Microalgae Biorefineries Mediated by Ionic Liquids

“…For instance, the cost and environmental impact (e.g., biodegradability and toxicity) of using ILs as extractants or solvents (for biomass pretreatment) needs to be considered. Despite the overgeneralised idea that ILs are toxic [67][68][69][70][71][72][73], this is not necessarily correct. The toxicity of ILs mainly depends on the length of their alkyl chains, and generalisations that all ILs are toxic are neither straightforward nor supported by recent literature data.…”

Ionic Liquid-Based Surfactants: Recent Advances in Their Syntheses, Solution Properties, and Applications

“…Thus, several studies on the relationship between their molecular structures and toxicity showed that the most toxic (to aquatic life) are those carrying aromatic/heterocyclic cations and long alkyl chains; most anions play a minor role in toxicity. Therefore, the synthesis of a new generation of easily biodegradable ILs and ILBSs from renewable sources was studied [ 36 , 37 , 38 ]. It was shown that ester functionality enhances biodegradation of ILs; furthermore, adding a methyl group to the 2-position of the imidazolium cation and use of alkyl sulfate as a counter-ion also improves the biodegradability [ 36 ].…”