Synthesis and toxicity evaluation of hydrophobic ionic liquids for volatile organic compounds biodegradation in a two-phase partitioning bioreactor

Abstract

Synthesis of several hydrophobic ionic liquids (ILs), which might be selected as good candidates for degradation of hydrophobic volatile organic compounds in a two-phase partitioning bioreactor (TPPB), were carried out. Several bioassays were also realized, such as toxicity evaluation on activated sludge and zebrafish, cytotoxicity, fluoride release in aqueous phase and biodegradability in order to verify their possible effects in case of discharge in the aquatic environment and/or human contact during industrial manipulation. The synthesized compounds consist of alkylimidazoliums, functionalized imidazoliums, isoqinoliniums, triazoliums, sulfoniums, pyrrolidiniums and morpholiniums and various counter-ions such as: PF6(-), NTf2(-) and NfO(-). Toxicity evaluation on activated sludge of each compound (5% v/v of IL) was assessed by using a glucose uptake inhibition test. Toxicity against zebrafish and cytotoxicity were evaluated by the ImPACCell platform of Rennes (France). Fluoride release in water was estimated by regular measurements using ion chromatography equipment. IL biodegradability was determined by measuring BOD28 of aqueous samples (compound concentration,1mM). All ILs tested were not biodegradable; while some of them were toxic toward activated sludge. Isoquinolinium ILs were toxic to human cancerous cell lines. Nevertheless no toxicity was found against zebrafish Danio rerio. Only one IL released fluoride after long-time agitation.

Physicochemical properties of some hydrophobic room‐temperature ionic liquids applied to volatile organic compounds biodegradation processes

“…The water influence is milder than the Cl ‐ influence. Assuming that most water was eliminated by means of the purification procedure previously described the slight differences found between the literature and our results can be explained by different Cl ‐ contents.…”

“…Table shows the 23 ILs synthesized and their density, viscosity and surface tensions measured in the range 288.15–318.15 K . The plots of the temperature variations of these variables are presented in the Supplementary data.…”

“…In previous work, cytotoxicity and toxicity against activated sludge and zebrafish Danio rerio were assessed . Fluoride release in water and biodegradability were also tested in order to verify possible toxic effects when discharging a hydrophobic IL into the environment or during handling . The principle of using ILs to treat VOCs is to absorb targeted compounds in a non‐aqueous phase liquid (NAPL), exhibiting high affinity for pollutants from a gaseous flow.…”

Assessment of VOC absorption in hydrophobic ionic liquids: Measurement of partition and diffusion coefficients and simulation of a packed column

“…Indeed, besides good absorption capacities for VOCs, these solvents are advantageously characterized by a low or a null vapor tension, a low miscibility in water and good thermal and chemical stabilities. Furthermore, being non-biodegradable and non-toxic, silicon oils and many ILs can be recycled by a biological process [3,[10][11][12][13][14].…”

“…Furthermore, since the ionic liquids cost is still high, no pilot-plant study has been performed to confirm their potential for VOCs absorption in real gas-liquid contactors such as packed columns. Thus, the aim of this article is to measure the partition and diffusion coefficients of two model hydrophobic VOCs, toluene and dichloromethane (DCM), in an extended panel of 23 ILs presented elsewhere [9,11]. Several cationic scaffolds were explored (imidazolium, isoquinolinium, pyrolidinium, morpholium, triazolium and sulfonium) including functionalized or non-functionalized alkyl side chains and associated with various anions (…”