Nicolas Papaiconomou

Correlating the structure and composition of ionic liquids with their toxicity on Vibrio fischeri: A systematic study

A systematic screening of the toxicity of ionic liquids (IL) towards Vibrio fischeri, a bioluminescent marine bacteria generally used in ecotoxicological bioassays, was carried out. The objectives of this work were to find hydrophilic or hydrophobic low toxicity IL and to investigate structure-toxicity relationship of IL. Toxicity of 54 IL to V. fischeri have been measured, some referring to new IL based on quinuclidinol or tropinol and some to generic IL (i.e., imidazolium, pyridinium, pyrrolidinium or piperidinium). For 47 of them, toxicity values have not been reported elsewhere. Water-soluble IL containing hydrophilic anions halide, thiocyanate, dicyanamide, trifluoromethansulfonate were studied. Some IL were found to exhibit very low toxicity towards V. fisheri. Hydrophobic IL based on bis(trifluoromethanesulfonyl)imide, tetrafluoroborate tetraphenylborate and tetracyanoborate were also studied. Toxicity was measured in a consistent way starting from aqueous solutions saturated with IL. The least toxic hydrophobic IL found in this study was [EMIM][B(CN)(4)]. A multifactorial analysis was found to be convenient for finding relevant structure parameters influencing the toxicity of IL. From this analysis, the planarity of the cation ring appeared to be a relevant parameter. Finally, good linear correlations were found when toxicity of IL was plotted either against the number of aliphatic carbons surrounding a pyridinium cation or the total number of carbons of a cation.

Efficient removal of gold complexes from water by precipitation or liquid–liquid extraction using ionic liquids

Extraction of tetrachloroaurate or tetrabromoaurate anions has been carried out at acidic pHs (1 and 4) with several ionic liquids bearing halide or bis(trifluoromethanesulfonyl)imide NTf2− anions and cations 1-octyl-3-methylimidazolium, 1-octylpyridinium or 1-methyl-1-octylpyrrolidinium. The removal of gold anionic moieties from water was first studied by mixing aqueous solutions containing gold complexes and water soluble halide (chloride or bromide) ionic liquids. This lead to the formation of either a solid precipitate or a liquid phase corresponding to a hydrophobic ionic liquid based on a tetrahalogenoaurate anion. Values below 10−6 for the solubility products of gold-bearing ionic liquids were obtained. Liquid–liquid extraction of anionic gold complexes with hydrophobic ionic liquids was also carried out. Gold was successfully extracted from water whatever the pH and the ionic liquid used. Distribution coefficients ranged from 3 × 102 to 3 × 104. Investigation on the extraction mechanism revealed an anion exchange between one anionic gold complex and one NTf2− anion.

Extraction of iridium(IV) from aqueous solutions using hydrophilic/hydrophobic ionic liquids

Anionic complexes of iridium(IV) were extracted from acidic solutions of HCl using ionic liquids (IL). The influence of the cationic structure of IL and of the aqueous phase pH on the distribution coefficients of IrCl62− was investigated. Liquid–-liquid extraction and precipitation of iridium(IV) were studied. Iridium(IV) was precipitated from aqueous solutions using water-soluble ionic liquids by forming a water-insoluble salt composed of two cations from the ionic liquid. Pyridinium cations appear to be the most efficient at precipitating iridium(IV). Iridium(IV) was found to be efficiently extracted using simple hydrophobic ionic liquids, exhibiting D values ranging up to 71. Investigations on the extraction mechanism tend to show that iridium(IV) is exchanged with two [NTf2]− anions from the IL phase. Finally, elution of iridium(IV) from ionic liquids towards aqueous solutions was carried out from [BMIM][NTf2], [OMIM][NTf2] or [OdMIM][NTf2] into solutions containing high amounts of hydrochloric acid or nitric acid.

Removal of platinum from water by precipitation or liquid–liquid extraction and separation from gold using ionic liquids

Precipitation and liquid–liquid extraction of PtX62− (X = Cl−, Br−, SCN−) in acidified aqueous solutions ranging from 0.1 M to 9 M HBr or 11 M of HCl have been studied using water-soluble or hydrophobic ionic liquids. Divalent hexachloroplatinate(IV) anions appear to be extracted much less efficiently than tetrachloroaurate(III) complexes. At a concentration of 11 M HCl, values of 15 and 800 for the distribution coefficients of PtCl62− and PtBr62− in [OMIM][NTf2] have been obtained accordingly. The presence of a labile hydrogen on the imidazolium ring has been found to play a specific role in the extraction of platinum(IV) complexes in concentrated HCl or HBr. Pt(SCN)62− appears to be very efficiently extracted at pH 1 using [OMIM][NTf2], exhibiting a distribution coefficient of 6150. Finally, two methods for quantitative separation of gold and platinum in water using in each method two extraction steps have been proposed. The back extraction of platinum(IV) during the second separation process was also discussed.

Experimental connections between aqueous–aqueous and aqueous–ionic liquid biphasic systems

Aqueous–ionic liquid (A–IL) biphasic systems containing deuterated water, deuterated nitric acid (10−2 M to 7 M) and either [C1C4im+][Tf2N−], [C1C10im+][Tf2N−] or [Me3BuN+][Tf2N−] have been examined in terms of water and acid solubilities in the IL-rich phase and in terms of IL cation and anion solubilities in the water-rich phase. Other experiments focused on the IL cation and anion solubility in the water-rich phase upon addition of either [C1C4im+][Cl−] or [Li+][Tf2N−]. The results evidence a complex interplay between all negatively and positively charged ions of the samples that could be described following the usual approach used for aqueous–aqueous (A–A) biphasic systems. Other examples from the literature are discussed and demonstrate that the frontier between A–A and A–IL systems is questionable. Predictions are made for the extraction of metallic ions by use of biphasic systems in this work that are successfully compared to literature data.

Ionic liquids for rechargeable lithium batteries

We have investigated possible anticipated advantages of ionic-liquid electrolytes for use in lithium-ion batteries. Thermal stabilities and phase behavior were studied by thermal gravimetric analysis and differential scanning calorimetry. The ionic liquids studied include various imidazoliumTFSI systems, pyrrolidiniumTFSI, BMIMPF{sub 6}, BMIMBF{sub 4}, and BMIMTf. Thermal stabilities were measured for neat ionic liquids and for BMIMBF{sub 4}-LiBF{sub 4}, BMIMTf-LiTf, BMIMTFSI-LiTFSI mixtures. Conductivities have been measured for various ionic-liquid lithium-salt systems. We show the development of interfacial impedance in a Li|BMIMBF{sub 4} + LiBF{sub 4}|Li cell and we report results from cycling experiments for a Li|BMIMBF{sub 4} + 1 mol/kg LIBF{sub 4}|C cell. The interfacial resistance increases with time and the ionic liquid reacts with the lithium electrode. As expected, imidazolium-based ionic liquids react with lithium electrodes. We seek new ionic liquids that have better chemical stabilities.

Quantitative extraction of Rh(III) using ionic liquids and its simple separation from Pd(II)

The extraction of Pd(ii) and Rh(iii) from acidic solutions containing between 1 and 8 M HCl towards three ionic liquids, namely [P66614][Cl], [P66614][Br] and [P66614][DCA], based on the trihexyltetradecylphosphonium cation ([P66614]) and chloride, bromide or dicyanamide (DCA) anions, respectively, is reported. Extraction of Pd(ii) is quantitative up to 6 M HCl (D > 3000). A value of 258 for the distribution coefficient of Rh(iii) extracted from 1 M HCl towards [P66614][Br] is also reported. [P66614][Cl] and [P66614][Br] were found to be very efficient at separating these two metals from aqueous solutions containing at least 6 mol L-1 HCl.

Ionic‐Liquid‐Based Acidic Aqueous Biphasic Systems for Simultaneous Leaching and Extraction of Metallic Ions

The first instance of an acidic aqueous biphasic system (AcABS) based on tributyltetradecyl phosphonium chloride ([P44414 ][Cl]) and an acid is here reported. This AcABS exhibits pronounced thermomorphic behavior and is shown to be applicable to the extraction of metal ions from concentrated acidic solutions. Metal ions such as cobalt(II), iron(III), platinum(IV) and nickel(II) are found to partition preferentially to one of the phases of the acidic aqueous biphasic system and it is here shown that it successfully allows the difficult separation of CoII from NiII , here studied at 24 and 50 °C.

Unusual electrochemical behaviour of AuBr4− in ionic liquids. Towards a simple recovery of gold(III) after extraction into an ionic liquid

The electrochemistry of AuBr4− complexes extracted into ionic liquids [C8PYR][NTf2] or [C8MIM][NTf2] saturated with water and gas has been studied by cyclic voltammetry on a glassy carbon macro electrode and by linear voltammetry on a platinum microelectrode. Unlike AuCl4−, the reduction of AuBr4− to Au(0) is achieved following a one reduction step involving three electrons. The deposition of Au(0) from AuBr4− is carried out at a potential above that of water, leading to the simple and easy deposition of gold and subsequently to the extraction of AuBr4− into an ionic liquid.

Toxicological consequences of extracting KNbO3 and BaTiO3 nanoparticles from water using ionic liquids

Hydrophobic room-temperature ionic liquids were used to remove KNbO3 and BaTiO3 nanoparticles from water at 25 °C. A very good extraction efficiency was obtained with distribution coefficients as high as 500. After extraction, toxicity of the aqueous phase containing residual amounts of nanoparticles and ionic liquids was assessed using Vibrio fischeri. A preliminary investigation of the toxicity mechanism was carried out with propidium iodide tests. A key result is that the simultaneous presence of a small amount of nanoparticles and ionic liquid in water can result in adverse toxicological effects compared to aqueous solutions containing solely nanoparticles or ionic liquids.