Toxic Effects Of Ionic Liquids Research Articles

Comparison of the toxic effects of non-task-specific and task-specific ionic liquids on zebrafish

Ionic liquids (ILs) are composed of only anions and cations and are liquid solvents at room temperature. Different functional groups were introduced into the ILs, conferring them with specific functions or purposes and thus forming special ILs, namely task-specific ILs (TSILs). Imidazolium-based ILs are the most widely used ILs in industrial production. To date, there have been some studies on the toxic effects of ILs on different organisms. However, the effect of functionalized groups on the toxicity of ILs is still unclear. In the present study, zebrafish were used as model organisms to study the toxic effects of 1-ethyl-3-methylimidazolium nitrate ([C2mim]NO3) and 1-hydroxyethyl-3-methylimidazolium nitrate ([HOC2mim]NO3). The results showed that both promoted an increase in reactive oxygen species (ROS) contents, leading to lipid peroxidation and DNA damage. Furthermore, integrated biological response analysis showed that [HOC2mim]NO3 was less toxic to zebrafish than [C2mim]NO3, which indicated that adding functional groups decreased the toxicity of ILs to organisms. The influence of chemical structure on IL toxicity was also reported. These results could provide a scientific basis for better synthesis and utilization of ILs in the future.

Effects of ionic liquid [N4444] AOT on rice seedling growth cytomembrane damage and rhizobacteria resistance.

Ionic liquids (ILs) are solvents composed of ions, containing a large asymmetric cation with an anion. With increasing and widespread applications, the toxic effects of ILs have been considerable in recent years. This study explained the effects of the new functional ionic liquids [N4444] bis(2-ethylhexyl) sulfonyl succinate (AOT) on rice seedling and the growth of rhizobacteria. The rice seeds pretreated by [N4444] AOT revealed that it exhibited a significant negative impact on rice seedlings. The inhibition of rice growth increased with increasing concentration. When the concentration of [N4444] AOT increased to 0.25 and 0.5 mL L-1, the germination potential decreased by 40.0% and 86.3%, respectively, compared with the control. The germination potential and germination rate of rice were reduced, and the stress effect of ionic liquid on the root parts was higher than the aerial parts. The biomass of rice seedlings was decreased by 34.8 to 91.2%. Iodinic propane staining showed that by increasing concentration, the root cell cytomembrane damage level was increased and also changed the cell shapes, especially under 0.25 mg L-1 concentration stress. However, rhizobacteria of rice showed strong [N4444] AOT-resistant characteristics when the concentration was reached to 120 mg L-1. The ILs even more promoted the growth of Enterobacter sp. NP1142 and Pantoea sp. BR23. It was indicated that IL [N4444] AOT can be degraded easily by rhizobacteria to eliminate the eco-risk of ILs.

The acute toxic effects of 1-alkyl-3-methylimidazolium nitrate ionic liquids on Chlorella vulgaris and Daphnia magna

Given their increasingly widespread application, the toxic effects of ionic liquids (ILs) have become the subject of significant attention in recent years. Therefore, the present study assessed the acute toxic effects of 1-alkyl-3-methylimidazolium nitrate ([Cnmim]NO3 (n = 2, 4, 6, 8, 10, 12)) on Chlorella vulgaris and Daphnia magna. The sensitivity of the tested organism Daphnia magna and the investigated IL concentrations in water using high-performance liquid chromatography (HPLC) were also evaluated to demonstrate the reliability of the present study. The results illustrated that Daphnia magna is indeed sensitive to the reference toxicant and the investigated ILs were stable in the aquatic environment. The 50% effect concentration (EC50) was used to represent the acute toxic effects on Chlorella vulgaris and Daphnia magna. With the increasing alkyl-chain lengths, the toxicity of the investigated ILs increased in both the test organisms. Accordingly, the alkyl-chain lengths can cause significantly toxic effects on aquatic organisms, and Daphnia magna are much more sensitive than Chlorella vulgaris to the imidazolium-based ILs used in the present study. Furthermore, the present study provides more information on the acute toxic effects of 1-alkyl-3-methylimidazolium nitrate.

Toxic effects of ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate on soil enzyme activity and soil microbial community diversity

Ionic liquids (ILs) were considered as “green” solvents and have been used widely because of their excellent properties. But ILs are not as “green” as has been suggested, and the toxic effects of ILs on organisms have been shown in recent years. In the present study, the toxic effects of the IL 1-octyl-3-methylimidazolium tetrafluoroborate ([Omim]BF4) on soil enzyme activity and soil microbial communities at three different concentrations (1.0, 5.0 and 10.0mg/kg) and a control treatment over 40 days of incubation time (sampled on days 10, 20, 30 and 40) were examined under laboratory conditions. The concentrations of [Omim]BF4 in soils were detected by high performance liquid chromatography (HPLC) and the results indicated that [Omim]BF4 were maintained stable in the soil during the exposure period. However, the enzyme activity results showed that urease activity was stimulated on day 20 and then decreased after 30 days of incubation. The activity of β-glucosidase was stimulated after 20 days of incubation in both treatment groups. Moreover, both dehydrogenase and acid phosphatase were inhibited at a high level (10.0mg/kg) only on day 20. The analysis of terminal restriction fragment length polymorphism (T-RFLP) revealed that the soil microbial community structures were altered by [Omim]BF4 and that the soil microbial diversity and evenness of high levels (5.0mg/kg and 10.0mg/kg) treatments were decreased. Moreover, the dominant structure of the microbial communities was not changed by [Omim]BF4. Furthermore, the abundance of the ammonia monooxygenase (amoA) genes of both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) was examined using real time polymerase chain reaction (RT-PCR). The results revealed that the copy numbers of the amoA-gene were decreased by [Omim]BF4 with the 5.0 and 10.0mg/kg treatments. Based on the experiment, we concluded that high levels (5.0 and 10.0mg/kg) of [Omim]BF4 could have significantly toxic effects on soil enzyme activities and the diversity of the microbial communities.

Phytotoxicity of imidazolium-based ILs with different anions in soil on Vicia faba seedlings and the influence of anions on toxicity.

To evaluate the toxic effects of ionic liquids (ILs) in soil on plants at the molecular and cellular levels and to assess the influence of anions on IL toxicity, the toxic effects of 1-decyl-3-methylimidazolium chloride ([Demim]Cl), 1-decyl-3-methylimidazolium bromide ([Demim]Br) and 1-decyl-3-methylimidazolium nitrate ([Demim]NO3) in soil on Vicia faba (V. faba) seedlings were studied for the first time. Our results show that these ILs had little impact on the growth of V. faba seedlings at 1, 5 and 25 mg kg(-1); however, the shoot length, root length, dry weight and pigment contents of the seedlings were significantly affected at 50 mg kg(-1). Furthermore, the EC50 values for effects of [Demim]Cl, [Demim]Br and [Demim]NO3 on the shoot length, root length and dry weight induced were consistent, indicating that the anion may have little influence on IL toxicity. ROS levels were also significantly enhanced at 50 mg kg(-1), resulting in cellular lipid peroxidation, DNA damage and oxidative damage.

Effects of the ionic liquid 1-hexyl-3-methylimidazolium bromide on root gravitropism in Arabidopsis seedlings

The toxic effects of ionic liquids (ILs) have attracted increasing attention in recent years. However, the knowledge about the toxic effects of ILs on tropism in organisms remains quite limited. In this study, the effects of 1-hexyl-3-methylimidazolium bromide [C6mim]Br on root gravitropism were evaluated using Arabidopsis seedlings. Our results showed that the root growth and gravity response were significantly inhibited with increasing IL concentration. [C6mim]Br treatment affected the amount and distribution pattern of amyloplasts in root cap compared with controls. The auxin distribution marked with DR5rev::VENUS was altered in IL-treated seedlings. The signal intensity and gene expression of auxin efflux carriers PIN2 and PIN3 were obviously decreased by IL stress. Moreover, as consequences in response to gravity stimulus, the asymmetric DR5 signals in control root apex were impaired by IL treatment. The predominant PIN2 signals along the lower flank of root and PIN3 polarization in columella cells were also significantly reduced in seedlings exposed to IL. Our results suggest that the ionic liquid [C6mim]Br affects the amount and distribution of amyloplasts and disturbs the deployment of PIN2 and PIN3, thus impairing auxin flows in response to gravity stimulus and causing deficient root gravitropism in Arabidopsis seedlings.

The genotoxic and cytotoxic effects of 1-butyl-3-methylimidazolium chloride in soil on Vicia faba seedlings

Although considered as “green” solvents, the toxic effects of ionic liquids (ILs) on organisms have been widely investigated in recent years. However, studies on the toxic effects of ILs on plants all focus on toxicity in nutrient solution. In the present paper, the toxic effects of 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) on Vicia faba seedlings in soil at 0, 500, 1500, and 2500mgkg−1 on day 10 were studied. The present results showed that the growth of V. faba seedlings may be seriously inhibited when the IL concentrations were higher than 500mgkg−1. The EC50 values for shoot length, root length, and dry weight were 3886, 2483, and 3359mgkg−1, respectively. In addition, [C4mim]Cl caused lipid peroxidation and DNA damage at 500mgkg−1 and oxidative stress at 1500mgkg−1, which indicated that [C4mim]Cl may have genotoxicity and cytotoxicity on V. faba seedlings. Moreover, oxidative damage may be the main toxic mechanism of ILs.

Use of ion-exchange resins for the adsorption of the cationic part of ionic liquid, 1-ethyl-3-methylimidazolium

Ionic liquids (ILs) are low melting organic salts with wide potential applications due to their fascinating properties and have emerged as promising “green” replacements for volatile organic solvents. Despite their non-measurable vapor pressure, some ILs inevitably occur in effluent discharges since they do have significant solubility in water. Recently, the toxic effects of ILs toward aquatic communities have been intensively investigated, but little is known about their removal from industrial wastewater. This study proposes adsorption by ion-exchange resins for the removal of the cationic part of the IL, 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc). Twelve ion-exchange resins with different functional groups like thiourea, iminodiacetic acid, aminophosphonic acid, carboxylic acid, and sulfonic acid were examined. The resins with sulfonic acid functional groups showed the highest sorption abilities ranging from 578.2 to 616.2mg/g. Large bead size led to lower kinetics of [EMIM] adsorption. But the bead size and the degree of cross-linking of the resins insignificantly affected the sorption performance of [EMIM] cations.

The toxic effects of ionic liquids on the activities of acetylcholinesterase and cellulase in earthworms

The earthworm Eisenia foetida was exposed to different concentrations of imidazolium ionic liquids with varying chain lengths according to the method of OECD [ OECD, 1984. (The Current Organization of Economic and Cooperative Development Acute Earthworm Toxicity Test) Guidelines for the Testing of Chemicals, No. 207. Earthworm Acute Toxicity Tests]. The acute and subchronic toxic effects of [C 8mim]Br on the activities of acetylcholinesterase (AChE) and cellulase in earthworms were determined under an artificial soil condition. Using filter paper contact tests, the 48 h-LC 50 values of [C 4mim]Br, [C 6mim]Br, [C 8mim]Br, [C 10mim]Br and [C 12mim]Br on the earthworm were 73.33, 28.25, 2.69, 0.37 and 0.02 μg cm −2, respectively. The 7 d-LC 50 of [C 8mim]Br was 206.8 mg kg −1 artificial soil (dry weight) and the 14 d-LC 50 was 159.4 mg kg −1 artificial soil (dry weight), under the condition of artificial soil. After 1 d and 3 d of acute exposure, the activity of AChE was markedly inhibited when compared to the control, while it was increased at 7 d. The cellulase activity was elevated significantly in the treatment groups of 20–160 mg kg −1 after 3 and 7 d of acute exposure. The activity of cellulase was also promoted under the subchronic exposure condition in the 10 and 20 mg kg −1 groups. The experimental results suggest that [C 8mim]Br may interfere with the nervous function of the earthworms and increase their cellulase activity. These results indicate that [C 8mim]Br-exposure can affect the metabolized enzyme activity of earthworms at low concentrations and can even cause worm death at high doses, both of which have potential impacts on the soil environment.

Acute toxic effects of ionic liquids on zebra mussel (Dreissena polymorpha) survival and feeding

Ionic liquids (ILs) are being designed as green alternatives to volatile organic solvents that are currently used in a wide range of industrial processes. While knowledge about the toxicity of various ILs to aquatic organisms has expanded in recent years, toxicity data remains limited to a few animal taxa. Furthermore, few studies have examined the non-lethal effects of ILs on aquatic organisms. We investigated how ILs affect mortality and feeding of the zebra mussel (Dreissena polymorpha), a sessile bivalve that is invasive in North America and much of Europe. Lethal effects of six ILs (butyl-, hexyl-, or octyl-chains on either a methylpyridinium or methylimidazolium cationic base) were studied with 96 h acute bioassays. Filtering behavior was examined in 2 h feeding trials of individual mussels fed Chlamydomonas reinhardtii and exposed to sublethal concentrations of the three imidazolium-based ILs. The ILs tested caused acute mortality over a wide range of concentrations (LC50 = 21.4 to 1290 mg L−1), ILs with longer alkyl chains were more toxic, and pyridinium- and imidazolium-based ILs had similar toxicities. When comparing toxicity to the same IL across organisms, zebra mussels exhibit some of the highest LC50 values and would be among the most resistant aquatic organisms in the event of an IL release. Short-term exposure to any IL reduced zebra mussel feeding. For butyl- and hexyl-chain ILs, feeding was significantly reduced at the acute LC50, whereas the octyl-chain IL reduced feeding at the acute LC5. Reduced survival and feeding by zebra mussels in the presence of ILs could have substantial effects on other trophic levels, which could lead to changes to affected ecosystems that would not have been predicted solely from standard mortality bioassays. Based on our mortality data, ILs are no worse than currently used industrial solvents; however, results from our feeding experiments demonstrate the potential for significant effects at sublethal concentrations. Consequently, we suggest that more ecologically relevant endpoints should be incorporated into a thorough hazard assessment of ILs.

Identification of Metabolites Involved in the Biodegradation of the Ionic Liquid 1-Butyl-3-methylpyridinium Bromide by Activated Sludge Microorganisms

Ionic liquids (ILs) are low melting organic salts that potentially comprise wide application due to their fascinating properties and have emerged as promising "green" replacements for volatile organic solvents. Despite their nonmeasurable vapor pressure, some quantities of ILs will soon be present in effluent discharges since they do have significant solubility in water. Recently, the toxic effects of ILs toward aquatic communities have been intensively investigated, but little information is available concerning the biodegradable properties of these compounds. The objective of this study was to identify the metabolites generated during the biotransformation of 1-butyl-3-methylpyridinium by microorganisms in aerobic activated sludge. The obtained results revealed that the alkylpyridinium salt was metabolized through the sequential oxidization in different positions of the alkyl side chains. High-performance liquid chromatography and mass-spectrometry analyses demonstrated that this biodegradation led to the formation of 1-hydroxybutyl-3-methylpyridinium, 1-(2-hydroxybutal)-3-methylpyridinium, 1-(2-hydroxyethyl)-3-methylpyridinium, and methylpyridine. On the basis of these intermediate products, biodegradation pathways were also suggested. These findings provide the basic information that might be useful for assessing the factors related to the environmental fate and behavior of this commonly used pyridinium IL.