Extraction Mechanism of Metal Ion from Aqueous Solution to the Hydrophobic Ionic Liquid, 1-Butyl-3-methylimidazolium Nonafluorobutanesulfonate

We studied the extraction behavior of metal ionic species in aqueous solutions into the hydrophobic ionic liquid, 1-butyl-3-methylimidazolium nonafluorobutanesulfonate ([bmi][NfO]). The extraction ratios (E/%) of Li(I), Na(I), Cs(I), Ca(II), Sr(II), and La(III) species were found to be 39, 24, 5.0, 81, 79, and 98. This result is similar to the phenomena that the metal ions with larger charge are more easily adsorbed onto cation exchange resins. In order to examine the extraction mechanism, we studied the extraction behavior of La(III) species from the aqueous to the [bmi][NfO] phase. As a result, it was found that the E values of La(III) decrease remarkably with an increase in concentrations of HNO₃ (0–1 M) in the aqueous phase and that the amount of La(III) transferred into [bmi][NfO] phase increases linearly with an increase in the amount of [bmi] transferred into the aqueous phase. Furthermore, we investigated the extraction behavior of La(III) species using 1-pentyl- and 1-hexyl-3-methylimidazolium nonafluorobutansulfonate ([pmi][NfO], [hmi][NfO]), which are more hydrophobic than [bmi][NfO], and found out that the E values of La(III) decrease in order of [bmi][NfO] > [pmi][NfO] > [hmi][NfO]. From these results, it was proposed that the extraction of metal ionic species from the aqueous to the [bmi][NfO], [pmi][NfO], or [hmi][NfO] phase is mainly ascribed to the cation exchanges between two phases.     

Synthesis of task-specific ionic liquids with grafted diglycolamide moiety. Complexation and stripping of lanthanides

Task-specific ionic liquids (TSILs) of a novel class, with the diglycolamide moietity grafted in the alkyl chain of imidazolium cation, were synthesized and characterized. Lanthanide complexation capabilities of TSILs as active components of solid phase extractants were evaluated by studies on the adsorption of lanthanides from aqueous solutions. The TSIL-based solid adsorbents prepared by immobilization of long-alkyl-chain TSILs in siliceous mesostructured cellular foams adsorb trivalent lanthanides. No extraction of lanthanides from aqueous solution into 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₆mim][Nf₂T]) was observed at any acidity in the presence of these TSILs in the aqueous phase. This implies that TSILs suppress the extraction of lanthanides by formation of water-soluble complexes. The TSILs added to solvent extraction systems consisting of N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) in [C₆mim][Nf₂T] and aqueous HNO₃ solutions show very good stripping properties for lanthanides.     

Recovery of Metals from Electronic Waste-Printed Circuit Boards by Ionic Liquids,DESs and Organophosphorous-Based Acid Extraction

The extraction of metals from waste printed circuit boards (WPCBs) with ionic liquids (ILs), Deep Eutectic Solvents (DESs) and organophosphorous-based acid (Cyanex 272) has been presented. The study was undertaken to assess the effectiveness of the application of the new leaching liquids, and the new method of extraction of metals from the leachate and the solid phase with or without the leaching process. Solvent extraction from the liquid leachate phase has been studied in detail with popular ILs, such as tetraoctylphosphonium bromide, {[P_8,8,8,8][Br] and tributyltetradecylphosphonium chloride, [P_4,4,4,14][Cl] using Aqueous Biphasic Systems (ABS) method. Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate, [P_6,6,6,14][Cyanex272], ([P_6,6,6,14][BTMPP]), trihexyltetradecylphosphonium thiocyanate, [P_6,6,6,14][SCN], methyltrioctylammonium chloride (Aliquat 336), as well as bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) were also used in the extraction of metals from the leachate. Two DESs (1) {choline chloride + lactic acid, 1:2} and (2) {choline chloride + malonic acid, 1:1} were used in the extraction of metals from the solid phase. The extraction behavior of metals with DESs was compared with that performed with three new bi-functional ILs: didecyldimethylammonium salicylate, [N_10,10,1,1][Sal], didecyldimethylammonium bis(2-ethylhexyl) phosphate, [N_10,10,1,1][D2EHPA], and didecyldimethylammonium bis(2,4,4-trimethylpentyl) phosphinate, [N_10,10,1,1][Cyanex272]. The [P_6,6,6,14][Cyanex272]/toluene and (Cyanex 272 + diethyl phosphite ester) mixtures exhibited a high extraction efficiency of about 50–90% for different metal ions from the leachate. High extraction efficiency of about 90–100 wt% with the ABS method using the mixture {[P_8,8,8,8][Br], or [P_4,4,4,14][Cl] + NaCl + H₂O₂ + post-leaching liquid phase} was obtained. The DES 2 revealed the efficiency of copper extraction, E_Cu = 15.8 wt% and silver, E_Ag = 20.1 wt% at pH = 5 from the solid phase after the thermal pre-treatment and acid leaching. The solid phase extraction efficiency after thermal pre-treatment only was (E_Cu = 9.6 wt% and E_Ag = 14.2 wt%). The use of new bi-functional ILs did not improve the efficiency of the extraction of metal ions from the solid phase. Process factors such as solvent concentration, extraction additives, stripping and leaching methods, temperature, pH and liquid/solid as well as organic/water ratios were under control. For all the systems, the selectivity and distribution ratios were described. The proposed extraction processes can represent alternative paths in new technologies for recovering metals from electronic secondary waste.     

Extraction of rare earth elements with phosphoryl-containing lariat crown ether in the presence of ionic liquids

Interfacial distribution of rare earth elements (REE) La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous solutions of their nitrates and solutions of the lariat crown ether 1,4,10,13-tetraoxa-7,16-diaza(diphenylphosphinylmethyl)cyclooctadecane in dichloroethane was studied in the presence of the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide. The stoichiometry of extracted complexes was determined; the effect of HNO₃ concentration in the aqueous phase and the nature of extractant and ionic liquid on the extraction efficiency of REE(III) was considered.     

Separation of Am(III) from nitric acid medium by phosphonium ionic liquid–hydroxyacetamide mixture

A strongly hydrophobic phosphonium ionic liquid, trihexyltet radecylphosphonium bis(trifluoromethanesulfonyl)imide ([P₆₆₆₁₄][NTf₂]) was employed as the diluent for the extraction behavior of Am(III) using N,N-dihexyl-2-hydroxyacetamide(DHHy) as extractant. The extractibility of americium(III) in [P₆₆₆₁₄][NTf₂] phase was measured as a function of various parameters such as aqueous phase acidity (0.1–8 M), extractant concentration (0.01–0.15 M), equilibration time (5–120 min) and temperature (298–333 K). The extraction performance observed in DHHy/[P₆₆₆₁₄][NTf₂] was compared with those observed in N,N-dihexyloctamide (DHOA) in [P₆₆₆₁₄][NTf₂] and DHHy in other diluents such as [C₄mim][NTf₂] and n-dodecane. The effect of temperature on D _Am(III) in ionic liquid system and recovery of Am(III) from the loaded phase were ascertained in detail.     

Extraction of rare earths and scandium by 2-phosphorylphenoxyacetic acid amides in the presence of ionic liquids

The distribution of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc between aqueous solutions of their salts and solutions of 2-phosphorylphenoxy acid amides in dichloroethane containing an ionic liquid (1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide) have been studied. Metal ion extraction has been found to increase considerably in the presence of this ionic liquid in the organic phase. The stoichiometries of extractable complexes have been determined. The influence of aqueous HNO₃ concentration and of the nature of extractant and ionic liquid on the efficiency of REE(III) and scandium(III) recovery to the organic phase has been considered.     

Room temperature ionic liquid as a novel medium for liquid/liquid extraction of metal ions

Room temperature ionic liquids (RTILs) have been used as novel solvents to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. The hydrophobic character and water immiscibility of certain ionic liquids allow their use in solvent extraction of hydrophobic compounds. In this work, a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆], was used as an alternative solvent to study liquid/liquid extraction of heavy metal ions. Dithizone was employed as a metal chelator to form neutral metal-dithizone complexes with heavy metal ions to extract metal ions from aqueous solution into [C₄mim][PF₆]. This extraction is possible due to the high distribution ratios of the metal complexes between [C₄mim][PF₆] and aqueous phase. Since the distribution ratios of metal dithiozonates between [C₄mim][PF₆] and aqueous phase are strongly pH dependent, the extraction efficiencies of metal complexes can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation, and preconcentraction of heavy metal ions with the biphasic system of [C₄mim][PF₆] and aqueous phase can be achieved by controlling the pH value of the extraction system. Preliminary results indicate that the use of [C₄mim][PF₆] as an alternate solvent to replace traditional organic solvents in liquid/liquid extraction of heavy metal ions is very promising.     

[Omim][NO3], a Green and Base-Free Medium for One-Pot Synthesis of Benzothiazinones at Room Temperature

A general and efficient room-temperature procedure is developed for high-yield synthesis of 2H-benzo[b][1,4]thiazin-3(4H)-one derivatives in one pot from the reaction of 2-aminothiophenols with 2-bromoalkanoates in ionic liquid [bmim]NO₃ without the use of any catalyst, base, or additive. Products were obtained in good yields by simple extraction with Et₂O followed by evaporation of the volatile contents and recrystallization from Et₂O. The ionic liquid was recycled and reused in the next reaction without the loss of its activity.     

Intermolecular C—H...O and C—H...X interactions in substituted spiroacenaphthylene structures

In the three spiroacenaphthylene structures 5′′‐[(E)‐2,3‐dichlorobenzylidene]‐7′‐(2,3‐dichlorophenyl)‐1′′‐methyldispiro[acenaphthylene‐1,5′‐pyrrolo[1,2‐c][1,3]thiazole‐6′,3′′‐piperidine]‐2,4′′‐dione, C₃₅H₂₆Cl₄N₂O₂S, (I), 5′′‐[(E)‐4‐fluorobenzylidene]‐7′‐(4‐fluorophenyl)‐1′′‐methyldispiro[acenaphthylene‐1,5′‐pyrrolo[1,2‐c][1,3]thiazole‐6′,3′′‐piperidine]‐2,4′′‐dione, C₃₅H₂₈F₂N₂O₂S, (II), and 5′′‐[(E)‐4‐bromobenzylidene]‐7′‐(4‐bromophenyl)‐1′′‐methyldispiro[acenaphthylene‐1,5′‐pyrrolo[1,2‐c][1,3]thiazole‐6′,3′′‐piperidine]‐2,4′′‐dione, C₃₅H₂₈Br₂N₂O₂S, (III), the substituted aryl groups are 2,3‐dichloro‐, 4‐fluoro‐ and 4‐bromophenyl, respectively. The six‐membered piperidine ring in all three structures adopts a half‐chair conformation, the thiazolidine ring adopts a slightly twisted envelope and the pyrrolidine ring an envelope conformation; in each case, the C atom linking the rings is the flap atom. In all three structures, weak intramolecular C—H...O interactions are present. The crystal packing is stabilized through a number of intermolecular C—H...O and C—H...X interactions, where X = Cl in (I) and F or S in (II), and C—H...O interactions are observed predominantly in (III). In all three structures, molecules are linked through centrosymmetric ring motifs, further tailored through a relay of C—H...X [Cl in (I), Br in (II) and O in (III)] interactions.     

The interaction of 1-oxy-2,6-di[(N,N-biscarboxymethyl)aminomethyl]4-chlorobenzene with lanthanides

This paper reports on some complexes of lanthanum(III) and europium(III) with the title ligand (H₅L) which possesses two similar coordination sites: mononuclear and homo- and hetero-dinuclear species are described. The isolated compounds have the formulas [M(H₂L)·3H₂O], [M₂LNO₃·4H₂O], (M = La, Eu); [MM′LOH·nH₂O] (M = Fe, M′= La, n = 2; M = Eu, M′= La, n = 4). In addition [Li₂LaL·3H₂O] and [CuLaL·3H₂O] have also been obtained. Relevant IR and visible spectral data and magnetic moment values are given and discussed.     

On the importance of the nature of the ionic liquids in the selective simultaneous separation of the substrates and products of a transesterification reaction through supported ionic liquid membranes

Previously, we reported the selective simultaneous separation of the substrates and products of a transesterification reaction (vinyl butyrate, 1-butanol, butyl butyrate, and butyric acid) through supported liquid membranes (SLMs) based on two ionic liquids (ILs): 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim⁺][PF₆⁻], and 1-octyl-3-methylimidazolium hexafluorophosphate, [omim⁺][PF₆⁻]. The significant differences observed in the selectivity values, attributed to the different nature of the ionic liquid phase used, led us to further investigate this matter.     

Influence of alkyl chain on the thermodynamic properties of aqueous solutions of ionic liquids 1-alkyl-3-methylimidazolium bromide at different temperatures

Osmotic coefficients ?, mean activity coefficients γ_±, vapor pressure p data, and excess Gibbs free energies G^E of aqueous solutions of three ionic liquids 1-propyl-3-methylimidazolium bromide [PMIm]Br, 1-pentyl-3-methylimidazolium bromide [PnMIm]Br, and 1-hexyl-3-methylimidazolium bromide [HMIm]Br were determined by the vapor pressure osmometry method at four temperatures (298.15 K to 328.15 K) in intervals 10 K. From the comparison of osmotic coefficients it follows that aqueous solution of [PMIm]Br shows a more pronounced deviation from Debye–Hückel limiting law (DHLL) and vapor pressure depression more than the other studied ionic liquids which was interpreted in terms of hydrophobic interactions. The Pitzer-ion interaction and MNRTL electrolyte models satisfactorily correlate experimental osmotic coefficient data with good precision. The parameters of the Pitzer-ion interaction model are used to calculate the mean molal activity coefficients and excess Gibbs free energies.     

Selective extraction of light lanthanides(III) with 18-crown-6 and perfluorooctanoate

The extraction of La(III), Gd(III), and Lu(III) with 18-crown-6 (18C6) has been studied using pentadecafluorooctanoate (PDFO) as a counter anion. Very high extractability of La(III) was observed in various organic solvents such as benzene, chloroform, 1,2-dichloroethane, and nitrobenzene. The predominant species extracted into benzene was found to be Ln(PDFO)₃ (18C6), and the extraction constants (K _ex,s1 =[Ln(PDFO)₃ (18C6)]_org/[Ln³⁺][PDFO]³[18C6]_org) were 10^13.12 for La(III), 10^9.74 for Gd(III), and 10^9.67 for Lu(III). These values are 10¹⁰ times higher than those in the trichloroacetate-18C6 system reported previously. The present PDFO-18C6 system was superior to the picrate- and hexafluoroacetylacetonate-18C6 system for the separation efficiency of light lanthanides(III).     

The physicochemical properties of some imidazolium-based ionic liquids and their binary mixtures

The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl- 3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at dif- ferent temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temper- ature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich re- gion. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.     

Correlations between phase behaviors and ionic conductivities of (ionic liquid + alcohol) systems

To understand the basic properties of ionic liquids (ILs), we examined the phase behavior and ionic conductivity characteristics using various compositions of different ionic liquids (1-ethyl-3-methylimidazolium hexafluorophosphate [emim] [PF6] and 1-benzyl-3-methylimidazolium hexafluorophosphate [bzmim] [PF6]) in several different alcohols (ethanol, propanol, 1-butanol, 2-butanol, and hexanol). We conducted a systematic study of the impact of different factors on the phase behavior of imidazolium-based ionic liquids in alcohols. Using a new experimental method with a liquid electrolyte system, we observed that the ionic conductivity of the ionic liquid/alcohol was sensitive to the surrounding temperature. We employed Chang et al.’s thermodynamic model [Chang et al. (1997, 1998) [21], [22]] based on the lattice model. The obtained co-ordinated unit parameter from this model was used to describe the phase behavior and ionic conductivities of the given system. Good agreement with experimental data of various alcohol and ILs systems was obtained in the range of interest.     

Reaction of sulfenes with heterocyclic N,N-disubstituted α-aminomethyleneketones. XII. Synthesis of [1]benzothiepino[4,5-e][1,2]oxathiin derivatives

The 1,4-cycloaddition of sulfene to N,N-disubstituted (E)-4-aminomethylene-3,4-dihydro[1]benzothiepin-5(2H)-ones I occurred only in the case of aliphatic N,N-disubstitution to give in good yield 4-dialkylamino-3,4,5,6-tetrahydro[1]benzothiepino[4,5-e][1,2]oxathiin 2,2-dioxides, which are derivatives of the new heterocyclic system [1]benzothiepino[4,5-e][1,2]oxathiin. Also the reaction of I with chlorosulfene occurred only in the case of aliphatic N,N-disubstitution to afford chiefly trans-4-dialkylamino-3-chloro-3,4,5,6-tetrahydro-[1]benzothiepino[4,5-e][1,2]oxathiin 2,2-dioxides III in satisfactory yield. Adducts III were dehydrochlorinated with DBN to 4-dialkylamino-5,6-dihydro[1]benzothiepino[4,5-e][1,2]oxathiin 2,2-dioxides in good yield.     

3d-Metal Nitroprusside–Thiosemicarbazide Complexes: Synthesis and Properties

The following complexes were synthesized from 3d-metal nitroprussides and thiosemicarbazide: [CrL₃][Fe(CN)₅H₂O] · 6H₂O, [FeL₃]₂[Fe(CN)₅NO]₃ · 14H₂O, [CoL₃]₂[Fe(CN)₅NO]₃ · 4H₂O, [NiL₂][Fe(CN)₅NO], [CuL₂][Fe(CN)₅NO] · 5H₂O, and [[ZnL₂][Fe(CN)₅NO], where L is thiosemicarbazide. Their structures and properties were studied by IR and diffuse reflection spectroscopies and DTA.     

Extraction of scandium(III) by bis(diphenylphosphorylmethylcarbamoyl)alkanes

The extraction of trace amounts of scandium(III) from HCl,HNO₃, and HClO₄ solutions in the form of complexes with neutral polyfunctional organophosphorus compounds bis(diphenylphosphorylmethylcarbamoyl)alkanes [Ph₂P(O)CH₂C(O)NH]₂(CH₂) _n (n = 3, 5, 8) was studied. The effect of the structure of the extractant, the aqueous phase composition, and the nature of the organic solvent on the efficiency of transition of scandium(III) ions into the organic phase was considered, and the stoichiometry of the extracted complexes was determined. The studied ligands exhibit a higher extraction power toward scandium(III) ions than their analog Ph₂P(O)CH₂C(O)NHC₉H₁₉ containing only one bidentate carbamoylmethylphosphoryl moiety per molecule. Scandium(III) passes into the organic phase most efficiently in the presence of HClO4 in the aqueous phase. It was shown that scandium(III) can be selectively recovered and preconcentrated by a complexing adsorbent obtained by noncovalent immobilization of bis(diphenylphosphorylmethylcarbamoyl)pentane on a macroporous polymer matrix.     

Effect of additives on the surface active and morphological features of 1-octyl-3-methylimidazolium halide aggregates in aqueous media

The influence of two salts as additives namely sodium chloride and sodium sulphate and a nonelectrolyte, 2-butoxyethanol on surface chemical and aggregation characteristics of ionic liquids (IL) of 1-octyl-3-methylimidazolium chloride, [C₈mim][Cl], 1-octyl-3-methylimidazolium bromide, [C₈mim][Br], and 1-octyl-3-methylimidazolium iodide, [C₈mim][I] in aqueous media were monitored through surface tension and small angle neutron scattering measurements. The addition of salts drastically decreased the critical aggregation concentration (CAC) and increased the area per adsorbed IL molecule. The co-ions of salts modify the surface of IL molecules and aggregates through various interactions such as charge neutralization, specific interactions and dehydration The results obtained by analyzing the SANS curves in the whole Q range showed that the oblate ellipsoidal shape of the aggregates of ionic liquids is un-altered upon the addition of additives. However the additives facilitate the growth of the aggregates in to microstructures with cubic packing at high salt concentrations.     

室温离子液体对氨基苯磺酸的萃取性能

系统研究了[C₄mim][PF₆], [C₆mim][PF₆], [C₆mim][BF₄]和[C₈mim][BF₄]室温离子液体对间氨基苯磺酸、对氨基苯磺酸稀水溶液的萃取平衡. 实验结果表明: 萃取温度和相体积比的变化对分配比影响不大; 水相pH值对萃取平衡有较大的影响, 氨基苯磺酸在离子液体/水体系中的分配比在pH＝4.2时达到最大值; 水相中CaCl₂或Na₂SO₄的存在能较大幅度地提高氨基苯磺酸的分配比; 离子液体的阴离子的性质对分配比有显著的影响, 阴离子为[BF₄]^－的离子液体对氨基苯磺酸的萃取能力大于阴离子为[PF₆]^－的离子液体; 咪唑环上烷基链的长度也对萃取效果有一定的影响. 在所研究的离子液体中, [C₆mim][BF₄]和[C₈mim][BF₄]对氨基苯磺酸有较好的萃取性能, 且萃取相中的氨基苯磺酸可回收利用, 离子液体也可循环使用.