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Cu(II) extraction using quaternary ammonium and quaternary phosphonium based ionic liquid
... Non-volatility, thermal stability, high conductivity, and recyclability are some aspects of ILs [19][20][21][22]. ILs based on ammonium or phosphonium are reported in the literature as good extractants in metal SX systems [23][24][25]. These ILs have attracted the attention of metal recovery because of their low volatility, thermal stability, good extraction for metal, and chemical stability [26][27][28]. ...
... Finall the pH is lowered to 0.5, there is a significant decrease in copper, manganese, a extraction, with the first two species decreasing to zero and the third to 9.7%. Previous work [24,46] demonstrates the influence of pH on the Cu(II), Fe(III) and Mn(II) extractions using R4NCy. The above results showed that all the eleme an extraction efficiency close to 100% at pH 2 and 3. ...
... On the other hand, the current research indicate that, surprisingly, the extraction of Fe(III) and Zn(II) approaches 100% though the solution contains four elements simultaneously. Perhaps the most int Previous work [24,46] demonstrates the influence of pH on the Cu(II), Fe(III), Zn(II), and Mn(II) extractions using R 4 NCy. The above results showed that all the elements had an extraction efficiency close to 100% at pH 2 and 3. ...
Recent works suggest that the use of ionic liquids in the copper solvent extraction industry is feasible. However, the reports did not use real solutions (or synthetic solutions with various elements). This fact remains poorly established, and the interaction efficiencies are still under study. The objective of this research is to explore the extraction and stripping of the four major elements present in a copper industrial pregnant leach solution (Cu(II), Fe(III), Mn(II), and Zn(II)) using the methyltrioctyl/decylammonium bis(2,4,4-trimethylpentyl)phosphinate (R4NCy) ionic liquid as an extractant. The work conditions studied in extraction were ionic liquid concentration, initial pH, and O/A ratio, and in stripping were H2SO4 concentration and O/A ratio. The test was carried out at room temperature and ambient pressure. High efficiency and selectivity (99.82% and 113,755 over Cu(II), respectively) were observed for Fe(III) extraction over the other elements. Moreover, after the extraction test, significant difficulty in stripping Fe(III) loaded in the ionic liquid was observed (28.7% at 0.5 M of H2SO4). Finally, the present study demonstrates that the R4NCy ionic liquid is not suitable for copper extraction because it has a higher selectivity for Fe(III) and Zn(II).
... Ionic liquid methyltrioctyl/decylammonium bis 2,4,4-(trimethylpentyl)phosphinate denoted as R 4 NCy was synthesized according to procedures published in the literature [35,36], mixing equimolar ratio of Cyanex 272 (HCy) and Aliquat 336 (R 4 NCl), and dissolved the mixture in kerosene to obtain the desired IL concentration. The mixture of Cyanex 272 and Aliquat 336 was washed twice with sodium bicarbonate 0.5 M to remove the chloride anion and the proton from the organic phase. ...
... Ionic liquid methyltrioctyl/decylammonium bis 2,4,4-(trimethylpentyl)phosphinate denoted as R4NCy was synthesized according to procedures published in the literature [35,36], mixing equimolar ratio of Cyanex 272 (HCy) and Aliquat 336 (R4NCl), and dissolved the mixture in kerosene to obtain the desired IL concentration. The mixture of Cyanex 272 and Aliquat 336 was washed twice with sodium bicarbonate 0.5 M to remove the chloride anion and the proton from the organic phase. ...
... The mechanism of metal extraction with R 4 NCy involves both the metal and the medium in which the tests are carried out. Previous work [35] reported of Cu(II) extraction mechanism with R 4 NCy as shown below: ...
The leaching of copper ores produces a rich solution with metal interferences. In this context, Fe(III), Zn(II), and Mn(II) are three metals contained in industrial copper-rich solutions in high quantities and eventually can be co-extracted with the copper. The purpose of the current study was to determine the feasibly of solvent extraction with the use of ionic liquid methyltrioctyl/decylammonium bis (2,4,4-trimethylpentyl)phosphinate (R4NCy) as an extractant of Cu(II) in the presence of Fe(III), Zn(II), and Mn(II). In general terms, the results showed a high single extraction efficiency of all the metals under study. In the case of Fe(III) and Zn(II), the extraction was close to 100%. On the contrary, the stripping efficiency was poor to Fe(III) and discrete to Zn(II), but very high to Cu(II) and Mn(II). Finally, the findings of this study suggest that the ionic liquid R4NCy is feasible for the pre-treatment of the copper solvent extraction process to remove metal impurities such as Fe(III) and Zn(II).
... The percentage of IL lost varied between 10 to 25%, even after 456 h of operation. A study by Castillo et al. [124] investigated the use of quaternary ammonium-and phosphonium-based ionic liquids for Cu(II)-extraction from liquid mining waste containing sulfates or chlorides. Stability tests for different ILs indicated that a mixture of Aliquat 336 and Cyanex 272 had the best performance, with extraction efficiencies up to 95%. ...
... Stability tests for different ILs indicated that a mixture of Aliquat 336 and Cyanex 272 had the best performance, with extraction efficiencies up to 95%. Although Kim et al. [125] reported that membrane-based extraction systems typically do not experience fouling caused by an accumulation of particulate matter, Castillo et al. [124] observed a fouling problem after approximately 4 h of testing, which decreased permeability. The stability of the liquid membrane was G. Van Eygen et al. ...
... Ionic liquids are deemed to be excellent solvents, because of their tunable solubility behaviour and low volatility. Castillo et al. [124] tested the use of different quaternary ammonium-and phosphonium-based ionic liquids for copper extraction. They obtained extraction efficiencies of up to 95% for a carrier mixture of Aliquat 336 and Cyanex 272. ...
This review examines the recent trends and developments in membrane-based extraction technology, with a focus on supported liquid membrane (SLM) extraction. This paper attempts to review the studies on polymeric membrane extraction, relating to mass transfer, stability, fluxes and performance. Prospects for future research, on the use of membrane extraction for in-situ product removal of chiral amines, are presented as well. The main challenge of the current state-of-the-art membrane extraction technology is limited SLM-stability. Conventionally, polymeric membrane materials are used as an SLM-support. The use of ceramic membranes, either with or without surface modification, should be looked at as a possible means of stability enhancement. The use of ionic liquids as the solvent for membrane impregnation is already studied intensively in literature. However, the performance of a certain IL is strongly dependent on the system at hand. Techniques such as hollow fibre renewal liquid membranes and polymer inclusion membranes, can also increase membrane stability and are discussed further. Lastly, the industrial application potential of membrane extraction is hindered by the lack of scaled-up pilot plants, which is addressed as well.
... Ionic liquids, known as green chemicals, have been extensively employed in many fields and in many processes, including catalysis, electrochemistry, organic synthesis, and the separation and recovery of metals [14][15][16] [17][18][19]. However, very little research has investigated the use of ionic liquids to extract hydrogen ions. ...
... However, very little research has investigated the use of ionic liquids to extract hydrogen ions. It has been observed that during the extraction of metal ions by ionic liquids, the equilibrium pH of the aqueous phase can be higher than the initial pH in the range from 3 to 6 [17,18,20]. Since metal ions can be precipitated when the solution pH is higher than a certain threshold, control of solution pH is very important in the continuous operation of solvent extraction. ...
During the extraction of metal ions from a weak acidic chloride solution by ionic liquids consisting of an organophosphorus extractant and Aliquat 336, the equilibrium pH is sometimes observed to be higher than the initial pH. To compare the hydrogen ion extraction behavior of tertiary and quaternary amines, Alamine 336, Aliquat 336 and their mixture with Cyanex 272, and an ionic liquid (prepared by mixing Cyanex 272 and Aliquat 336, R 4 NA) were employed in solvent extraction experiments at a pH range from 0.05 to 5. R 4 NA showed the highest extraction percentage of hydrogen ions. The initial pH of the chloride solution had a great effect on the extraction of hydrogen ions and the equilibrium pH value produced by these extractants. The order of hydrogen ion extraction was R 4 NA>Alamine 336>mixture of Alamine 336 and Cyanex 272. The addition of sodium chloride improved phase separation. The solvent extraction reaction of hydrogen ions with R 4 NA in the chloride solution was verified by applying a slope analysis method to the extraction data. UV-Vis and FT-IR spectra indicated a strong interaction between the hydrogen ions and R 4 NA during the extraction. The obtained results provide some information on the change in solution pH during the extraction of metal ions from weak acidic solution by an ionic liquid (R 4 NA).
... Furthermore, a study reported insignificant extraction of Cu from its simulated sulfate solution when single Aliquat 336 (0%) and Cyanex 272 (1.4%) were employed as a carrier (Devi 2016). However, the synergist IL of Aliquat 336/Cyanex 272 provided 99.9% of Cu extraction with the same total concentration as the single carrier which is strongly in agreement with the results obtained by Castillo et al. (2014). This is because bifunctional ILs can extract Note that "-" denotes not reported while E, S, and R indicate extraction, stripping, and recovery performance, respectively metal ions via an ion-association mechanism (Sun et al. ...
Waste electrical and electronic equipment or e-waste has recently emerged as a significant global concern. This waste contains various valuable metals, and via recycling, it could become a sustainable resource of metals (viz. copper, silver, gold, and others) while reducing reliance on virgin mining. Copper and silver with their superior electrical and thermal conductivity have been reviewed due to their high demand. Recovering these metals will be beneficial to attain the current needs. Liquid membrane technology has appeared as a viable option for treating e-waste from various industries as a simultaneous extraction and stripping process. It also includes extensive research on biotechnology, chemical and pharmaceutical, environmental engineering, pulp and paper, textile, food processing, and wastewater treatment. The success of this process depends more on the selection of organic and stripping phases. In this review, the use of liquid membrane technology in treating/recovering copper and silver from industrial e-waste leached solutions was highlighted. It also assembles critical information on the organic phase (carrier and diluent) and stripping phase in liquid membrane formulation for selective copper and silver. In addition, the utilization of green diluent, ionic liquids, and synergist carrier was also included since it gained prominence attention latterly. The future prospects and challenges of this technology were also discussed to ensure the industrialization of technology. Herein, a potential process flowchart for the valorization of e-waste is also proposed.
... The most commonly encountered phosphonium compounds have four organic substituents attached to a phosphorus center, forming the quaternary phosphonium cation. Along with a multitude of available anions, salts of these quaternary compounds are extensively used as Wittig reagents [1], phase transfer catalysts in asymmetric synthesis [2][3][4][5][6], ionic liquids [7][8][9], corrosion inhibitors [10], and polymer-based anion exchange membranes [11,12], as well as tracers for tumor imaging [13]. The versatility of the phosphonium quaternary compounds is known to be contributed by the different molecular features and self-organization of the ions within the compound. ...
Quaternary phosphonium salts are popular candidates used in many chemical transformations and synthetic chemistry, notably in catalysis. We have examined the single crystals of two bulky phosphonium compounds, tetra([1,1′-biphenyl]-4-yl) phosphonium dicyanamide (C48H36P+·N(CN)2−, compound 1), and tetra([1,1′-biphenyl]-4-yl) phosphonium bromide hydrate (C48H36P+·Br−, CH3CN, H2O, compound 2), and herein report the structural properties for the compounds with an emphasis on the influence of the ion-ion interaction towards self-assembly; the overall self-assembly for both structures is very similar, with subtle differences in the cell parameters. The symmetrical tetra ([1,1′-biphenyl]-4-yl) phosphonium cations in both compounds self-assembled to form robust stacked columns in the solid-state, with voids occupied by anions or solvent molecules. Quantitative examination of intermolecular interactions using Hirshfeld surface analysis found that classical and non-classical hydrogen bonding appears to be the dominant contributor in stabilizing the self-assembly in both cases. The present work can not only benefit in understanding the mutual interaction between the sterically encumbered tetra ([1,1′-biphenyl]-4-yl) phosphonium cations and between counterions, but also provide insights for the self-assembled arrays in the solid-state.
... The ILs-based separation and extraction approach is a modern approach that takes the place of volatile organic compounds as an extract [23,24]. The properties of ILs make them predominantly suitable for solvent extraction, including their combustibility and low volatility, thermal stability, wide liquid range, adjustable functional groups, high conductivity, and a wide range of electrochemical applications [25][26][27][28]. The ILs have shown excellent performance in the extraction techniques used in sample preparation and preconcentration of targeted analytes [29][30][31][32][33][34]. ...
Sample preparation is the crucial and most challenging part of analytical chemistry for the speciation of environmental pollutants' traces. Along with the development of the sample preparation methods, the ionic liquid-based microextraction technique plays an important role. Due to the unequivocally unique "green" characteristic of ionic liquids (ILs), they owe their tunable properties, such as highly selective and high reaction efficiency, reusability, and good thermal stability, to present advancements in the sample preparation process. The ionic liquid-based microextraction techniques miniaturize the sample preparation process. Liquid phase microextraction intermediate solvents, desorption solvent extractants, and mediators have been used. They are quoting the benefits and limitations of each method. A few essential sample preparation methods covered the microextraction technique. In this context, miniaturized microextraction methods have been developed. They are generally used for their unlimited positive features, including easy, simple, and environmentally friendly; they also extract inorganic and organic species with low-cost instrumentation. This review advances the sample preparation process using ILs-based liquid phase microextraction as an intermediate solvent, extractant desorption, and mediator solvents.
... Using the bifunctional ionic liquid [A336][Cy272] diluted with kerosene, complete recovery of Cu(II) from a solution containing other divalent metals, such as iron(II), zinc(II), cadmium(II), cobalt(II), and nickel(II), was attained [43,44]. ...
This review addresses research and development on the use of ionic liquids as extractants and diluents in the solvent extraction of metals. Primary attention is given to the efficiency and selectivity of metal extraction from industrial wastewater with ionic liquids composed of various cations and anions. The review covers literature sources published in the period of 2010–2021. The bibliography includes 98 references dedicated to research on the extraction and separation of lanthanides (17 sources), actinides (5 sources), heavy metals (35 sources), noble metals, including the platinum group (16 sources), and some other metals.
... 4−14 Typical basic extractants are protonated amines ([R y NH] + X − ), quaternary ammonium salts ([R 4 N] + X − ), or quaternary phosphonium salts ([R 4 P] + X − ). 1,15,16 In textbooks, these extractants are often said to be anion exchangers, which extract metals as anionic metal complexes by exchanging them for extractant anions (X − ). This mechanism explains the typical observation that extraction by basic extractants is more efficient when anions coordinate more easily to the metal ion and when more anions are present in the aqueous phase. ...
Solvent extraction is often applied to separate and purify metals on an industrial scale. Nevertheless, solvent extraction processes are challenging to develop because of the complex chemistry involved. For basic extractants, much of the chemical behavior remains poorly understood due to the conditions far from thermodynamic ideality. To elucidate the extraction mechanism, we studied the speciation and extraction of zinc(II) and cadmium(II) from chloride, bromide, and iodide media by using a basic extractant consisting of a trioctylmethylammonium cation and, respectively, a chloride, bromide, or iodide anion. These systems were specifically selected to increase the understanding of the less-studied bromide and iodide media and to focus on the effect of hard–soft interactions on solvent extraction systems. It was observed that, in general, a metal is more efficiently extracted when its hydration in the aqueous phase is lower and its stabilization in the organic phase is higher. In the investigated systems, these conditions are obtained by forming metal complexes with a lower charge density by coordinating the right number of halide anions and by selecting a halide with a lower charge density. In the organic phase, the stability of the metal complex can be increased by forming strong metal–anion bonds and by decreasing the water content. These insights might be of interest in the development and optimization of separation schemes for metals.
... Instead of mixing some extractants, synthesis of some kinds of task specific ionic liquids (ILs) is regarded as a means to achieve synergistic extraction [11,12]. In particular, the synthesized ILs derivated from commercial extractants such as Aliquat 336 (N-Methyl-N,N,N-trioctylammonium chloride) or Cyphos IL (phosphonium ionic liquid) have been employed for the extraction and separation of metals [11][12][13][14][15][16][17][18]. Some advantages of the above-mentioned ILs are good extractability, efficient separation, high recovery, and environmental friendliness [14,18]. ...
The development of extraction systems to improve the extraction efficiency of metals using commercial extractants and ionic liquids is of importance. The extraction behavior of Co(II) between mixture of Alamine 336/Aliquat 336 and D2EHPA and synthesized ionic liquid ALi-D2 was compared in this work. Some factors, such as equilibrium pH, properties of the extractants, and concentration of components in the mixture had a remarkable effect on the extraction of Co(II). The interactions occurring in the mixtures as well as the change in solution pH were analyzed. Co(II) was completely extracted by ionic liquid when equilibrium pH was higher than 6.5, while it was difficult to extract Co(II) by employing the mixture of D2EHPA and Alamine 336/Aliquat 336. The formation of ionic liquid in the mixture of D2EHPA and Aliquat 336 was verified through FT-IR spectra. In addition, the competition extraction of hydrogen ion and Co(II) by ionic liquid ALi-D2 was explained. Among the three kinds of extractants, the ionic liquid showed the best extraction efficiency for Co(II) and pH control from weak acidic solutions. The present study provides valuable information on the extraction behavior of metal ion by the mixtures of commercial extractants, and thus can give some light on the development of metal extraction systems.
... The removal extraction of La(III) and Ce(III) from the aqueous solutions was carried out by means of the same procedure reported in our previous work [18] [19]. The solvent extraction experiments were conducted by contacting 1 mL of aqueous solution with 1 mL of organic phase, where the phases were mixed in magnetic stirrers (SBS ® model ANS-001) at 140 rpm for 40 minutes at room temperature. ...
In this work, an experimental study was carried out to find the best-operating conditions for the study of the extraction percentage (%E) and the separation factor (SF) of La(III) and Ce(III) complexes. To carry out this study, a variation of β-diketone concentrations was used, keeping the concentration of tri-octyl phosphine oxide (TOPO) continuous at 0.05 M. The ratio of organic phase to the aqueous phase (O/A) was also studied. The %E and SF were analyzed and compared in the 1,1,1-trifluoro-2, 4-pentanedione (TFA) with TOPO, and 1,1,1,5,5,5-Hexafluoro-2,4-pentanedione (HFAc) with TOPO in Ionic Liquid (IL) and Kerosene. The one-stage extraction efficiency in IL of La(III) and Ce(III) complexes was 42.13% and 77.48% for the TFA-TOPO system and La(III) and Ce(III) complexes were 94.33% and 97.67% for the HFAc-TOPO system. While the SF between Ce(III) and La(III) complexes was 4.91 for TFA-TOPO and 2.64 for HFAc-TOPO. On the other hand, the one-stage extraction efficiency in Kerosene of La(III) and Ce(III) complexes was 27.57% and 63.70% in the TFA-TOPO system. The one-stage extraction efficiency of La(III) and Ce(III) complexes were 99.87% and 99.73% for the HFAc-TOPO system in Kerosene while the SF between Ce(III) and La(III) complexes was 4.62 for TFA-TOPO and 0.49 for HFAc-TOPO. The main conclusion was that using two extractants (β-diketone and TOPO) produced a synergistic effect improving the extraction capacity and SF of La(III) and Ce(III) complexes for both systems in IL and Kerosene.
... The use of imidazolium, ammonium, or phosphonium ILs for the separation of metal ions has recently been reported [10][11][12][13]. However, the use of hydrophilic ILs often results in the loss of IL components during the extraction, which requires regeneration of the ILs [14]. ...
Ionic liquids have emerged in hydrometallurgy as potential extractants for metals. In this work, the interactions of ALiCY (R<sub>4</sub>N<sup>+</sup>A<sup>-</sup>) synthesized by Aliquat336 and Cyanex272, and a mixture of ALiCY and TBP, were analyzed using extraction data and FT-IR spectroscopy. Co(II) and Ni(II) were extracted from two HCl concentrations (1.0×10<sup>-4</sup> and 6.8 mol·L<sup>-1</sup>) using ALiCY and its mixture with TBP. The extraction results indicated that ALiCY has a dual function, as a cationic extractant at low HCl concentration and an anionic extractant at high HCl concentration depending on the types of metal complexes. The addition of TBP to ALiCY had a negative effect on the extraction of Co(II) from the 6.8 mol·L<sup>-1</sup> HCl, while the effect was negligible from the 1.010<sup>-4</sup> mol·L<sup>-1</sup> HCl. The solvation of R<sub>4</sub>N<sup>+</sup> by TBP significantly affected the extraction behavior of ALiCY for metal ions. The formation of hydrogen bonding between TBP and Cyanex272 was verified. These findings shed light on the behavior and interaction occurring between bif-ILs and solvating extractants for the extraction of metals in acidic media.
... Combining technologies to recover and remove metals and sulfates with high adaptability to changes in feed flow, low operating time, and ease of operation are important characteristics in AMD treatment. One of these technologies, which allows solving these demands, is the membrane separation process J o u r n a l P r e -p r o o f Journal Pre-proof (Andalaft et al., 2018;Castillo et al., 2014). In particular, nanofiltration can be an attractive alternative to concentrate metallic species present in AMD, such as copper, to be recovered by traditional hydrometallurgy processes. ...
The high levels of metals and sulfate ions in acid mine drainage (AMD) constitutes a severe risk to the environment. Our study evaluated at pilot-scale the operational conditions of actual AMD nanofiltration (NF) to recover water and subsequent recovery of copper from the concentrated retentate solution by a solvent extraction (SX) process. NF showed a high copper concentration capacity (0.6 to 2.4 g/L) and good total rejection of species (~82%). While NF treatment allowed a high water recovery of 80%, the polarization resistance could limit its performance. A 1.1 g/L copper retentate solution was selected for use in the SX study to prevent membrane fouling in a possible in-series process (NF-SX). Equilibrium isotherms and McCabe-Thiele diagrams obtained using LIX 84-IC as the extractant indicated that using two countercurrent extraction stages and one stripping stage, it could be recovered 97% of the copper. The use of antiscalants and CaSO4 precipitates formed during NF had a negligible effect on the copper extraction yield by SX. The combined NF-SX results showed that a high recovery of water and copper from AMD is possible. This technology can have an impact on the reduction of freshwater consumption and wastewater treatment costs of mining, and its development is the subject of further research work.
... Additionally, they are adaptable to specific chemical tasks [18][19][20][21]. Relating with hydrometallurgy, ILs are considered "green reactive agents", and they have been applied to remove contaminants, extracting metal ions and additives by electrodeposition [19,[22][23][24][25][26][27][28][29][30]. ...
The unique properties of ionic liquids (ILs) drive the growing number of novel applications in different industries. The main features of ILs are high thermal stability, recyclability, low flash point, and low vapor pressure. This study investigated pure chalcopyrite dissolution in the presence of the ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate, [BMIm]HSO4, and a bromide-like complexing agent. The proposed system was compared with acid leaching in sulfate media with the addition of chloride and bromide ions. The results demonstrated that the use of ionic liquid and bromide ions improved the chalcopyrite leaching performance. The best operational conditions were at a temperature of 90 °C, with an ionic liquid concentration of 20% and 100 g/L of bromide.
... Owing to their negligible vapor pressures and nonflammabilities, ILs are promising alternatives to VOCs [18][19][20]. Therefore, the extraction of metal ions using ILs has been extensively investigated in the field of sustainable separation processes [21][22][23][24], including the solvent extraction of rare earth ions based on functionalized ionic liquids [25,26], removal of lithium from aqueous solutions by two non-fluorinated ionic liquids [27], and partition of Co (II) and Ni (II) using pure phosphonium ionic liquids or ammonium-type ionic liquids [28,29]. Nonetheless, there are only few reports on the use of trin-octylmethylammonium chloride (TOMAC) for the extraction and separation of vanadium from acid leaching solutions. ...
An efficient separation and extraction method for the recovery of V (V) from a sulfuric acid leaching solution of vanadium shale was developed using the ionic liquid tri-n-octylmethylammonium chloride (TOMAC). In this study, the main factors affecting the extraction of vanadium using TOMAC were investigated. Under optimum conditions, including a TOMAC concentration of 20 vol%, initial aqueous phase pH of 1.8, phase ratio (O/A) of 1:10, and extraction time of 2 min, 98.1% of vanadium was separated by a three-stage extraction, while almost no other impurities were extracted. The V (V) present in the scrubbed organic phase could be quantitatively stripped using 1.0 mol/L NaOH. Moreover, the extraction mechanism using TOMAC was analyzed by Fourier transform infrared (FT-IR) spectroscopy as well as the slope method. The obtained results supported the existence of an anion exchange mechanism between the Cl⁻ atoms of TOMAC and H2V10O28⁴⁻ (HV10O28⁵⁻) within the extraction system.
... Scheme of FSSLM experimental set-up.38 ...
BACKGROUND
Recovering Nd(III) from waste magnets is an alternative method to satisfy the increasing demand for this metal. For this reason, the separation of Nd from a mixture containing Nd/Tb/Dy in chloride media using Cyanex 272 and Cyanex 572 has been evaluated.
RESULTS
Using Cyanex 272 and Cyanex 572, the metals are transported in the order Dy(III) > Tb(III) > > Nd(III) in all conditions studied. The optimum feed conditions to achieve Nd(III) separation are: Cyanex 272: pH 2 and Cyanex 572: pH 1.5 with 1.2 mol L ‐1 HCl as a receiving agent for both carriers.
CONCLUSION
The results obtained suggest that Cyanex 572 is a better carrier than Cyanex 272 for separating Nd(III) from a mixture containing Nd/Tb/Dy. © 2017 Society of Chemical Industry
... Furthermore, academic studies report the use of pyrridinium, ammonia and phosphonium-based ILs for copper recuperation. These ILs are proposed as extractants and as solvents, which show high extraction efficiencies and selectivities, achieving very high values of Cu(II) recovery and other metal species such as Zn, Co and Pb [34][35][36][37]. ...
This study deals with the improvement of the recovery performance in the solvent extraction of Cu(II) using the ionic liquid [bmim][Tf2N] and the β-diketone 1,1,1-trifluoro-2,4-pentanedione (TFA) as extractant and its stripping with supercritical carbon dioxide.
This work describes a modified procedure, which shows better L-L extraction percentages with a decreasing of the concentration of TFA, the contacting time and the volumetric O/A ratio respect to the previously reported tests. Thus, the extraction was implemented with a concentration of TFA in [bmim][Tf2N] equal to 60 mol m-3, a contacting time of 5 min and an O/A ratio equal to 1:7.
The stripping of the metal complex from the organic phase was achieved in semi-continuous mode with scCO2. This configuration allowed obtaining a stripping percentage higher than the obtained with a previously tested procedure in batch mode with a consumption of CO2 4.3 times lower than the observed one in previous work.
The liquid structure of three common ionic liquids (ILs) was investigated by neutron scattering for the first time. The ILs were based on the bis(trifluoromethanesulfonyl)imide anion, abbreviated in the literature as [NTf2]⁻ or [TFSI]⁻, and on the following cations: 1-ethyl-3-methylimidazolium, [C2mim]⁺; 1-decyl-3-methylimidazolium, [C10mim]⁺; and trihexyl(tetradecyl)phosphonium, [P666,14]⁺. Comparative analysis of the three ILs confirmed increased size of nonpolar nanodomains with increasing bulk of alkyl chains. It also sheds light on the cation–anion interactions, providing experimental insight into strength, directionality, and angle of hydrogen bonds between protons on the imidazolium ring, as well as H–C–P protons in [P666,14]⁺, to oxygen and nitrogen atoms in the [NTf2]⁻. The new Dissolve data analysis package enabled, for the first time, the analysis of neutron scattering data of ILs with long alkyl chains, in particular, of [P666,14][NTf2]. Results generated with Dissolve were validated by comparing outputs from three different models, starting from three different sets of cation charges, for each of the three ILs, which gave convergent outcomes. Finally, a modified method for the synthesis of perdeuterated [P666,14][NTf2] has been reported, with the aim of reporting a complete set of synthetic and data processing approaches, laying robust foundations that enable the study of the phosphonium ILs family by neutron scattering.
A short review of the literature data on extraction with hydrophobic bifunctionalized ionic liquids and binary extractants is given to show that these compounds are identical in their compositions and properties. It is noted that the papers on binary extractants were published earlier than the first papers on extraction with bifunctionalized ionic liquids. In contrast to the extraction systems with ionic liquids, extraction processes in the systems with binary extractants are studied in greater detail and grouped into a special class, i.e., binary extraction. It is shown that the main regularities of the distribution of the components in the extraction systems with binary extractants depend on the type of chemical reaction and the character of the interphase distribution.
Ionic Liquids: Eco-friendly Substitutes for Surface and Interface Applications explores the growing interest in utilizing ionic liquids as sustainable alternatives for various industrial and biological applications. With their unique properties and environmentally friendly nature, ionic liquids have emerged as promising substitutes for toxic and volatile solvents, offering significant advantages in surface and interface chemistry.
This book is divided into two parts: Part 1 covers the basics of ionic liquids, their surface/interface properties, and interactions with metallic surfaces. Part 2 focuses on the wide range of surface and interface applications of ionic liquids, including wastewater treatment, corrosion protection, catalysis, separation processes, medical devices, and sensing applications.
Key Features:
A complete book fully dedicated to the surface and interface chemistry of ionic liquids with seventeen chapters Covers fundamentals, recent progress, and applications in surface/interface chemistry Presents up-to-date research and interdisciplinary insights Includes relevant references and resources for further exploration
This is a valuable reference for scientists and engineers who want to learn about ionic liquids' chemistry and applications
The distribution of Ag(I) between acidic aqueous phase (HNO3) and organic phases, composed of trihexyl(tetradecyl)phosphonium bis-(2,4,4-trimethylpentyl)phosphinate (Cyphos® IL 104) diluted in kerosene or kerosene/1-decanol, has been studied. In order to elucidate the interactions in solution and the chemical equilibria responsible for Ag(I) extraction by Cyphos® IL 104, ionic conductivity, dynamic viscosity, and interfacial tension measurements, determination of water and nitric acid extraction were performed, and the organic phases were characterized by infrared spectroscopy (FT-IR). Ag(I) is extracted by Cyphos® IL 104 with high affinity, even under slightly acidic conditions (close to 100% at pH 5). The linear relationship between the logarithm of the distribution ratio of Ag(I) (D) and the logarithm of Cyphos® IL 104 concentration exhibits a slope greater than the stoichiometry expected (1:1), demonstrating an atypical extraction equilibrium. The change in the physicochemical properties as a function of Cyphos® IL 104 concentration permits to deduce the formation of reverse micelles or aggregates in organic phases at the critical micellar concentration CMC=0.001 mol L⁻¹. The FT-IR characterization showed that Ag(I) was extracted by the phosphinate group of Cyphos® IL 104 with the transfer of water and nitric acid. A thorough analysis of these data indicates a similar mechanism to solvation, and the reverse micelles (or agglomerates) are involved in Ag(I) extraction.
Separation and recovery of U(VI) and Th(IV) from rare earth minerals is a very challenging work in rare earth industrial production. In the present study, a homemade membrane emulsification circulation (MEC) extractor was used to separate U(VI) and Th(IV) from rare earth elements by using Cyphos IL 104 as an extractant. Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104 could reach the extraction equilibrium within 30 min for all the three elements, i.e., U(VI), Th(IV), and Eu(III). Besides, the MEC extractor possessed a strong phase separation ability. The extraction efficiencies of U(VI), Th(IV), La(III), Eu(III) and Yb (III) increased with the increase of pH. La(III), Eu(III) and Yb(III) were hardly extracted when pH ≤ 1.50, which was beneficial for effectively separating of U(VI) and Th(IV) from La(III), Eu(III) and Yb(III). In the multi-stages stripping experiments, when the stripping stage number was 3, the effective separation could be achieved by using HCl and H2SO4, since the stripping efficiency reached 80.0% and 100.0% for Th(IV) and U(VI), respectively. Slope method and FT-IR spectra showed that Cyphos IL104 reacted with U(VI) and Th(IV) by chelation mechanism. The extraction of multi-elements indicated that U(VI) and Th(IV) could be well separated from the solution which containing all rare earth elements, and the extraction efficiencies of U(VI) and Th(IV) both were close to 100.0%. Based on the above experimental results, a flowchart for efficient separation of U(VI) and Th(IV) from rare earth elements was proposed.
Progress a chemical reaction through catalysis is a privileged approach that includes almost 95% (in volume) of all of the usual chemical compounds. Therefore investigation about high efficient catalysts is an attractive and very prosperous research area. In this regard, quaternary phosphonium salts have gained considerable attention as catalysts in many chemical transformations and synthetic chemistry. In this review, recently important advances on the properties, synthesis, and applications of quaternary phosphonium salts in both homogeneous and heterogeneous catalysis forms are summarized. We also discussed the asymmetric phosphonium salts in a wide range of applications in phase-transfer catalysis into enantioselective organic reaction.
The utilization of renewable feedstock is paramount for the sustainable production of materials, and not merely for the chemical industry. Ionic liquid (IL) catalytic conversions of mono-, di-, and polysaccharides give 5-hydroxymethylfurfural (HMF) – a versatile intermediate. In this study, local bamboo was the source of biomass. Three different anions of ILs had a noticeable effect on the HMF yield. The chromium chloride catalyst was found to be the most effective in the 1-butyl-3-methylimidazolium chloride system among all tested ILs since it provided a HMF yield of 48%, with more than 95% of glucose
conversion after 3 h at 120°C.
During the past decade, the synthesis of sugar-based ionic liquids (SILs) from natural sugars has been described as a promising candidate. This is due to their natural abundance in large...
The objective of this work is to investigate the extraction behavior of samarium from chloride medium using trihexyl(tetradecyl)phosphonium bis-2,4,4-(trimethylpentyl)phosphinate (Cyphos IL 104), and separation efficiency of samarium in presence of other rare-earth and transition metals. It is then extended to Sm-Co separation from secondary magnetic waste. The extraction efficiency of Cyphos IL 104 is studied in detail by varying the key extraction parameters like shaking time, aqueous phase pH, ionic liquid, metal and chloride ion concentration, type of diluents, and temperature of aqueous phase. Quantitative extraction of 0.002 mol/dm3 Sm(III) has been found using 0.02 mol/dm3 Cyphos IL 104. Extraction equilibrium of samarium with Cyphos IL 104 is explained using the slope analysis method and FT-IR study. NaCl is used as a salting out agent that increases the samarium extraction. Toluene is found to be best diluents for dilution of Cyphos IL 104. The stripping efficiency is observed to be quantitative with 20% H2SO4 and 5% HNO3. The extraction process is endothermic in nature revealed from the temperature variation study. The investigation of samarium extraction in the presence of transition metals has been conducted and highest separation factors of 189.5 and 158.5 are obtained for Sm/Co and Sm/Ni, respectively, at initial pH 3.0.Graphic abstract
Pollution by toxic, non-degradable metals is a rising health concern in the context of increasing industrialization and metal demand. Diseases may include brain damage, cardiovascular problems, gastrointestinal disorders and cancer, calling for advanced methods to clean soil, water, wastewater and air. Here, we review the use of ionic liquids, which are considered as eco-friendly solvents, to remove metals. Ionic liquids have unique properties such as no vapor emission, good solvation ability, higher thermal stability and tunability. Ionic liquids separate efficiently metal ions from aqueous solutions by electrostatic, Van der Waals and ion–pair interactions. Ionic liquids can be recovered by stripping, then reused several times for liquid–liquid extraction, adsorption and membrane separation. Ionic liquids improve membrane stability in membrane separation, and they act as surfactant for adsorption.
The present review covers achievements in the development and application of phosphorous-containing extractants for varios metals. The extractants based on industrial organophosphorus compounds, chelating compounds, ionic liquids, as well as polymers and copolymers bearing phosphorus-containing groups capable of complexing metals have been considered. Especial attention was paid to the efficiency and selectivity of these classes of compounds in the recovery of used metals from industrial wastewater, soil, and ashes via liquid-liquid, supercritical fluid, solid-phase, and synergistic extractions.
The bibliography includes 184 references published within the last 10 years (2010−2020).
Pollution by toxic, non-degradable metals is a rising health concern in the context of increasing industrialization and metal demand. Diseases may include brain damage, cardiovascular problems, gastrointestinal disorders and cancer, calling for advanced methods to clean soil, water, wastewater and air. Here, we review the use of ionic liquids, which are considered as eco-friendly solvents, to remove metals. Ionic liquids have unique properties such as no vapor emission, good solvation ability, higher thermal stability and tunability. Ionic liquids separate efficiently metal ions from aqueous solutions by electrostatic, Van der Waals and ion–pair interactions. Ionic liquids can be recovered by stripping, then reused several times for liquid–liquid extraction, adsorption and membrane separation. Ionic liquids improve membrane stability in membrane separation, and they act as surfactant for adsorption.
The present work deals with the investigation of solvent extraction of Sm(III) from chloride medium using di-(2-ethylhexyl)phosphoric acid (D2EHPA) and trihexyl tetradecyl phosphonium bis(2-ethylhexyl)phosphate ([P66614][D2EHP]) as extractants. In the extraction stage, the effect of contact time, aqueous phase pH, extractant concentration, NaCl concentration, temperature effect, stripping and O:A ratio variation are investigated to compare the extraction abilities of D2EHPA and the ionic liquid made from that. The complex formation ability and extraction mechanism of samarium with two extractants are explained by FTIR spectra and slope analysis method. Solvent extraction of samarium is better noticeable with D2EHPA than that of [P66614][D2EHP]. It is evident that with rise in pH of the aqueous medium, the extraction percentage of samarium is increased for both the extractants. Optimum extraction (100%) of Sm3+ is obtained with 0.1 mol/L D2EHPA and 0.1 mol/L [P66614][D2EHP], respectively. HNO3 is the best stripping agent for back-extraction of samarium from the loaded extractants. Separation studies are carried out in the presence of transition metal ions (mostly present in magnets) to know the efficiency of D2EHPA and ionic liquid [P66614][D2EHP]. The extraction studies with mixture of other rare earth metal ions similar to monazite composition follow the order as Gd(III) > Sm(III) > Nd(III) > Ce(III) > La(III) for both the extractants. Using 0.03 mol/L D2EHPA, complete separation of Gd and Sm from the rare earth mixtures is found at two stages with O:A ratio of unity.
The dielectric constants and viscosities of binary mixtures of organophosphorus acids (D2EHPA, Cyanex 301, PC88A, and Cyanex 272) and quaternary amine (Aliquat 336) were measured by varying their chemical compositions. The strength of the interaction between the components in the binary mixture was analyzed through the deviation of dielectric constant, viscosity, and Grunberg-Nissan interaction parameters. The interaction of binary mixture was also verified through Fourier-transform infrared spectroscopy (FT-IR). The results indicated that the mixtures of D2EHPA/ Cyanex 301 + Aliquat 336 showed the stronger interaction among four acidic extractants in this work. FTIR data and analysis of the interaction on the basis of chemical structure indicate that ionic liquid can form in the mixture of D2EHPA and Aliquat 336 at specific composition. Adduct can be formed between Aliquat 336 and organophosphorus acids through hydrogen bond of methyl group. Our results can give some information on the selection of the composition of binary mixtures between organophosphorus acids and Aliquat 336 for the synergistic extraction of metal ions in hydrometallurgy.
Among ionic liquids, phosphonium-based ionic liquids (PILs) are quite elegant. These categories of ionic liquids represent
some merits over other types of ionic liquids such as imidazolium- and pyridinium-based ionic liquids. PILs have more
thermal and chemical stability than other reported ILs. These influential characteristics connected with PILs make them as
potential structures for varied applications in academic and industrial processes. In recent years, however, PILs become
popular because of relatively low cost of their synthesis (the rate of phosphonium salt formation is faster than those of
nitrogen-based salts, implying higher productivity and lower cost in industrial manufacturing of PILs) as well as their good
thermal stability, beneficial for high-temperature operation. Room temperature ionic liquids (RTILs) have numbers of
unique applications in electrochemical systems and among them, phosphonium room temperature ionic liquids (PRTILs)
have been increasing for their considerable advantages such as chemical and thermal stabilities, relatively low viscosities
and high conductivities when compared to the corresponding ammonium RTILs. PRTILs are yummy electrolysis solutions
because of their wide electrochemical window. Determination of the electrochemical stability of the PRTILs is important
for detection and application of these ionic salts as electrolytes in electrochemistry. In order to evaluate electrochemical
stability of the phosphonium RTILs, various voltammetric techniques such as cyclic voltammetry, linear sweep voltammetry
and square wave voltammetry have been used. PRTILs characterized by a wide electrochemical window have been
regarded as attractive candidates for lithium-battery electrolytes because of their stability and safety aspects. Contrary to
what is seen in conventional organic solvents, superoxide is stable in ionic liquids. PILs are an unprecedented class of
electrolytes that can support the electrochemical generation of a stable superoxide ion and can offer many advantages such
as low combustibility, ionic conductivity, low volatility and a wide electrochemical window. PILs have been intensively
developed as new electrolytic mediator for various electrochemical devices such as supercapacitors and lithium-ion
batteries. There is also a growing interest for their use in separation processes including metal ions extraction, extractive
desulfurization, gas adsorption and dissolution or extraction of biologically relevant compounds and materials. In mentioned
processes and other applications where PIL is the solvent, of particular interest are physicochemical properties (e.g.,
viscosity, density, surface tension, solubility, polarity and so on). Moreover, the quantum chemical method is invoked to
interpret superior properties of PILs. Experimental works have also satisfied that the PILs fulfill the necessary requirement
of being a good inhibitor of metal corrosion in different media because of surface active properties. Owning to special
physicochemical properties, the PILs are emerging as possible candidates to improve surfactant-enhanced oil recovery
methods. Because they have also shown great importance in a vast number of industrial and pharmaceutical applications,
such as lubricants, electrolytes, or solvents/catalysts for organic reactions, ecotoxicity of these ILs was studied for
environmental and human health risks assessments. PILs have been used as efficient solvents and/or catalysts for synthesis
of various kinds of organic compounds. This review article presents an excellent puzzle that each of its pieces lead to the
rational design, synthesis and applications of novel and task-specific PILs as multi-purpose materials.
Ionic liquids can be considered as green reagents for the removal of pollutants from water sources. Ionic liquids display wonderful chemical and physical properties such as high thermal stability, low vapor pressure, and good recyclability. The limit of use of traditional methods of separation of pollutants from water can be overcome by using ionic liquid-based membranes as ionic liquids display negligible vapor pressure and choice of anionic or the cationic part can dictate the solubility. This book chapter is aimed to highlight state-of-the-art ionic liquid-based membranes and proven strategies applied earlier for water purification.
This paper presents synthesis and structural characterization of new members of phosphorus-based organic bromides. 1,3-Propanediylbis(triphenylphosphonium) dibromide I and 1,3-propanediylbis(triphenylphosphonium) monotribromide II, as a new brominating agent for double bonds and phenolic rings, were synthesized. ¹H NMR, ¹³C NMR, ³¹P NMR, FT-IR, single crystal X-ray diffraction crystallography, differential scanning calorimetry, thermogravimetric analysis and differential thermal analysis were used to characterize these salts. Thermal and physicochemical stability, simple working up, non-toxicity in comparison to liquid bromine and high yield are some of the advantages of these salts. These salts have good solubility in organic solvents, such as methanol, ethanol, acetone, dichloromethane and THF. Crystallographic data showed that compound I crystallized in the monoclinic crystal system, in P21 space group and compound II crystallized in the monoclinic crystal system, in P21/c space group and one of the bromide ions was replaced by tribromide ion in II. The crystal packing structures of title compounds were stabilized by various intermolecular interactions, especially of the type C-H∙∙∙π contacts. The molecular Hirshfeld surface analysis and 2D fingerprint analysis revealed that the C∙∙∙H (30.4% for the compound I and 28.3% for compound II) contact, which was related to C-H∙∙∙π interactions, had the major contribution in the crystal architectures. To get more insight about molecular structures of titled compounds, DFT calculations were performed (energy, structural optimization and natural bond orbital analysis). Bromination of double bonds and phenolic rings was carried out to prove the ability of the tribromide salt to bromine such organic substrates.
The metal extraction mechanism of basic extractants is typically described as an anion exchange process, but this mechanism does not correctly explain all observations. This paper introduces a novel model for the extraction of metals by basic extractants from chloride media supported by experimental data on methyltrioctylammonium chloride and Aliquat 336 chloride systems. This model relies on the hypothesis that the metal species least stabilized in the aqueous phase by hydration (i.e., the metal species with the lowest charge density) is extracted more efficiently than the more water stabilized species (i.e., species with higher charge densities). Once it is transferred to the organic phase, the extracted species can undergo further Lewis acid-base adduct formation reactions with the chloride anions available in the organic phase to form negatively charged chloro complexes, which than associate with the organic cations. Salting-out agents influence the extraction, most likely by decreasing the concentration of free water molecules, which destabilizes the metal complex in the aqueous phase. The evidence provided includes (1) the link between extraction and transition-metal speciation, (2) the trend in extraction efficiency as a function of the concentration of different salting-out agents, and (3) the behavior of HCl in the extraction system. The proposed extraction model better explains the experimental observations in comparison to the anion exchange model and allows the prediction of optimal conditions for metal extractions and separations a priori, by selecting the most suitable salting-out agent and its concentration.
In this study, propane 3-bromo-1- (triphenyl phosphonium) bromide, I, and propane 3-bromo-1- (triphenyl phosphonium) tribromide, II, (II as a new brominating agent) were synthesized and characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, FT-IR, spectroscopy, Thermogravimetric Analysis, Differential thermal analysis, Differential scanning calorimetry and single crystal X-ray analysis. Density functional theory calculations (energy, structural optimization and frequencies, Natural Bond Orbital, absorption energy and binding energy) were performed by using B3LYP/6-311 G++ (d, p) level of theory. Hirshfeld surface analysis and fingerprint plots were utilized to investigate the role of bromide and tribromide anions on the crystal packing structures of title compounds. The results revealed that the change of accompanying anionic moiety can affect the directional interactions of C-H⋯Br hydrogen bonds between anionic and cationic units in which the H⋯Br with a proportion of 53.8% and 40.9% have the major contribution in the stabilization of crystal structures of I and II, respectively. Furthermore, the thermal stability of new brominating agent II with tribromide anion was compared with compound I with bromide anion. Nontoxicity, short reaction time, thermal stability, simple working up and high yield are some of the advantages of these salts.
Herein, we adopted a hydrophobic, lighter-than-water phosphonium-based ionic liquid (LTWP-IL)for preconcentration of trace Pb(II)-dithizone complexes prior to detection by graphite furnace atomic absorption spectrometry (GFAAS)in human fluids. Because the solvent injected into GFAAS contained LTWP-IL phase, the routine pyrolysis temperature such as 300–400 °C was not appropriate for LTWP-IL, and the optimized pyrolysis and atomization temperatures of Pb(II)were 800 °C and 1800 °C, respectively. The hydrophobic LTWP-IL floats on the surface of the aqueous phase after centrifugation, which allows for convenient and complete collection after solidification of the aqueous phase (HLILM-SAP), and thus overcomes the prominent disadvantage of conventional heavier-than-water ionic liquids-based microextraction. Ultrasound was used to disperse hydrophobic LTWP-IL in the absence of a dispersive solvent. Several operational parameters were optimized using a one-factor-at-a-time approach: LTWP-IL extractant, 30 μL; chelating agent, 0.3% dithizone; ultrasonic time, 5 min; solution pH = 6.0; solidification at −20 °C, 60 min and back extractant, 200 μL of 0.5 mol L ⁻¹ HNO 3 . Under optimized conditions, limits of detection were as low as 0.014–0.018 μg L ⁻¹ and enrichment factors reached >43-fold in urine and blood samples. Inter- and intra-day precisions had relative standard deviations of 3.77–6.79%. Trueness was evaluated by determining four certified reference materials of Pb(II)resulting in recovery values of 95–103%. Overall, the HLILM-SAP-GFAAS method is convenient, efficient and robust, making it suitable for rapid and accurate analysis of trace Pb(П)in complex biological fluids.
Synergistic strippants of palladium complex with Trialkylmethylammonium chloride (Aliquat 336) has been investigated. Results show that synergistic strippants of thiourea and HCl can enhance the palladium stripping efficiency from the loaded Aliquat 336. Extraction of Pd (II) ions is sensitive to the concentration of extractant and chloride medium. The partition coefficient ascertained from the model was fitted with an experimental value. Thermodynamics analysis showed that ΔH and ΔS values were obtained at 10.74 kJ/mol and 77.81 J/molK, respectively.
Polyethylene glycol (PEG) modified magnetic nanoparticles with low toxicity and good biocompatibility were fabricated as the adsorbent for removal of Cr(VI), Cu(II), and Pb(II) from aqueous solution. These nanocomposites were characterized by TEM, VSM, XRD, TGA, and FTIR. The adsorption capacity, kinetics, acid resistance, and the key factors affecting the adsorption process were evaluated for the adsorbent in a batch mode. The characterization results demonstrated that the magnetic nanocomposite with 3.6% PEG modification was successfully prepared. According to the Langmuir model, the maximal saturated adsorption capacity of Cr(VI), Pb(II), and Cu(II) on the adsorbent at pH 7.0 were 15.07 mg/g, 21.27 mg/g, and 41.0 mg/g, respectively. The adsorption followed pseudo-second-order kinetics with fast speed, and was highly dependent on pH. The acid resistance performance of magnetic nanoparticles was obviously improved by PEG modification on its surface, and this adsorbent showed good reusability for heavy metals. The obtained adsorbent with good performance has a potential application for removal of heavy metals from water.
In this paper, the comparative study between an ionic liquid (Cyphos IL 104) and an acidic extractant (D2EHPA) on europium (III) extraction from chloride medium has been reported. Effect of different extraction parameters such as equilibrium pH, extractant and metal ion concentration, salt, diluent and temperature effect has been investigated. Quantitative extraction of europium is achieved with 0.02 M Cyphos IL 104 and with 0.05 M D2EHPA and the loading capacity of 0.01 M Cyphos IL 104 is found to be 0.004 mol and that of 0.01 M D2EHPA is 0.0027 mol, respectively showing Cyphos IL 104 is a better extractant than D2EHPA. The extraction occurred via ion association mechanism for Cyphos IL 104 and cation exchange mechanism for D2EHPA. Stripping studies have been carried out using H2SO4 and HNO3. The effect of thermodynamic parameters, stability and reusability test of both the extractants studied in detail. The loss of extractants while stripping with nitric acid is negligible for both the extractants. The extraction behavior of europium is studied in presence of some transition elements. Separation studies of europium in presence of yttrium, cerium and lanthanum from a mixed solution indicate that D2EHPA is more suitable than Cyphos IL 104 for Y(III)/Eu(III) separation but the selectivity of Eu(III)/La(III) and Eu(III)/Ce(III) are better with Cyphos IL 104 than D2EHPA.
Ionic liquids (ILs), also termed “green” and “designer” solvents, have been proposed as promising solvents for diverse applications. This review focused on the improvements brought about by mixing ILs with molecular extractants (MEs) in solvent extraction processes for metal extraction and separation. Mixture systems consisting of IL with ME were collected and discussed on the basis of the functional cations of ILs, such as ammonium-type, phosphonium-type and imidazolium-type ILs. IL was found to play a role as an active component by generating a new acid/base coupling bi-functional ionic liquid (ABC-BIL) or as a diluent when combined with acidic or neutral ME in IL-ME mixture systems. The merits and drawbacks of IL-ME systems were reviewed and compared with conventional ME systems alone in terms of the preparation route, separation behavior and extraction mechanism. Further approaches to the improvement of IL-ME systems, such as extraction enhancement, stripping and regeneration, were discussed. The summaries and comparisons made in the present review may indicate future directions for the development and application of ILs in metal solvent extraction technology.
In this study, liquid–liquid extraction with Aliquat 336 in the presence of cyclohexane as a mobile carrier was investigated to purify Pd(II) from industrial wastewater. Kinetic and thermodynamics analysis showed that Pd(II) extraction was of first-order reaction: the reaction was endothermic reaction which was governed by the diffusion region. The influence of temperature on isotherm model was also investigated. With an increase in reaction temperature, all three isotherms Langmuir, Freundlich and Temkin isotherm become inaccurate. Results show that the Langmuir isotherm model was preferred for the study of the Pd(II) ion experimental isotherm. Response surface methodology was employed to study the five independent variables which have an effect on the percentage of extraction of palladium(II) ions as a dependent variable. Optimum extraction conditions for the five independent variables were as follows: Aliquat 336 concentration (0.6 M), pH of feed solution (2.0), stirring speed (600 rpm), reaction time (10 min.) and reaction temperature (318 K).
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Solvent extraction of yttrium(III) from chloride and nitrate solutions were carried out using two bifunctional ionic liquids Cyphos IL 104 and [A336/Cy272]. Comparative study with their constituent extractants showed higher extraction abilities of the ionic liquids for Y(III). The extraction behavior of yttrium using the above ionic liquids was studied as function of different parameters. Ion association neutral complexes were formed in the organic phase. 0.5 M HNO3 could strip 82% and 75.6 % yttrium from the loaded organic phases of 0.01M [A336/Cy272] and Cyphos IL 104, respectively. Separation studies involving binary systems were also investigated.
KEYWORDS: Yttrium, [A336/Cy272], Cyphos IL 104, extraction, separation
Ionic liquid ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of the aqueous phase was used for preconcentration of Ni2+, Co2+, Cd2+, Cu2+, Pb2+in natural water samples prior to liquid chromatography with UV detection. In the proposed method, the ammonium pyrrolidinedithiocarbamate was used as a complexing agent and the phosphonium ionic liquid trihexyl(tetradecyl)phosphonium bis[(2,4,4-trimethyl)pentyl]phosphinate (Cyphos IL 104) was used as an extractant. Ultrasound energy was used to disperse the extractant in the aqueous phase. After microextraction, the ionic liquid and aqueous phases were separated by centrifugation. Then the aqueous phase was frozen and the lighter than water ionic liquid phase containing metal ions complexes with pyrrolidinedithiocarbamate was separated and dissolved in a small volume of methanol prior to injection into the liquid chromatograph. Several parameters including the volume of extractant, the pH of the sample, the concentration of complexing agent, the time of ultrasound energy treatment, the time and speed of centrifugation and the effect of ionic strength were optimized. Under the optimized conditions (10 µL of Cyphos IL 104, pH = 5, 0.3% w/v ammonium pyrrolidinedithiocarbamate, 60 s of ultrasound use, 5 min/5000 rpm (2516×g) of centrifugation, 2.0 mg of NaCl), preconcentration factors were 211, 210, 209, 207 and 211 for Ni2+, Co2+, Cd2+, Cu2+and Pb2+respectively. Linearity was observed in the ranges 0.2-75.0 µg L-1for Pb2+, Cd2+, Co2+and 0.5-100.0 µg L-1for Cu2+, Ni2+. The limits of detection were 0.03 µg L-1for Ni2+, 0.03 µg L-1for Co2+, 0.03 µg L-1for Cd2+, 0.02 µg L-1for Cu2+, 0.02 µg L-1for Pb2+, respectively. The accuracy of this method was evaluated by preconcentration and determination of Ni2+, Co2+, Cd2+, Cu2+, Pb2+in certified reference materials (TMRAIN-04 and NIST 1643e) with the recovery values in the range of 97-102%. The presented method has been successfully applied for the determination of analytes in natural water samples (river and lake waters).
The present study describes the extraction behavior of gallium(III) using a novel ionic liquid trihexyl(tetradecyl) phosphonium chloride (Cyphos IL 101) diluted with kerosene from acidic chloride medium. The extraction of gallium was found to depend on the hydrochloric acid concentration and quantitative extraction of gallium took place at 2.0 mol/L HCl concentration. The nature of the extracted complex in the organic phase was determined using Job’s method and proposed to be [R 3 R ′ PGaCl 4 ]. The loading capacity of 5.0 × 10 ⁻³ mol/L Cyphos IL 101 was determined to be 320.0 mg/L. Two stages of stripping were required for complete removal of gallium from the loaded organic phase using 0.1 mol/L HCl. From the temperature variation study, the extraction process was found to be endothermic. The separation efficiency of gallium from its associated metal ions such as Al(III), Fe(III), Zn(II), Cu(II), and Ni(II) was investigated from binary mixtures and in the presence of all these metal ions, which revealed that the extraction of Zn(II) and Cu(II) were more preferred to Ga(III) while extractions of Al(III) and Ni(II) were nil. The potential of the extractant was assessed to recover gallium from photodiodes.
Novel processes based on SIMALE have been proposed as effective methods for the selective separation of different chemical species such as metal ions, organic/biologically important compounds and gas mixtures from different waste streams including nuclear waste. The industrial use of supported liquid membranes based on conventional liquids is limited by their relative instability and short lifetime. Under SIMALE techniques, the stability of the SLM is ensured by a modified SLM with pseudo emulsion based hollow fiber strip dispersion or non-dispersive solvent extraction techniques. In order to promote operational stability, SIMALE, using ionic liquids, as a liquid membrane phase could overcome these inconveniences due to their negligible vapour pressure and the possibility of minimizing their solubility in the surrounding phases. SIMALE studies on membrane-based dense gas extraction reported higher extraction efficiencies when the near critical or supercritical solvent is used. This review also discuss important applications including scale up, process intensification aspects, current status of the technology and future directions.
An environmentally friendly process for the separation of the transition metals copper, cobalt, iron, manganese and zinc from rare earths by solvent extraction with the ionic liquid trihexyl(tetradecyl)phosphonium chloride has been developed. The solvent extraction process is carried out without the use of organic diluents or extra extraction agents and it can be applied as a sustainable hydrometallurgical method for removing transition metals from neodymium–iron–boron or samarium–cobalt permanent magnets. The recycling of rare earths is of high importance because of the possible supply risk of these elements in the near future. The method was tested for the removal of cobalt and iron from samarium and neodymium, respectively. The highest distribution ratios for cobalt and iron were found with 8.5 and 9 M HCl. At the tested conditions, the concentrations of neodymium and samarium in the ionic liquid were below 0.5 mg L−1 (0.5 ppm), even for feed concentrations of 45 g L−1. The separation factors of Nd/Fe and Sm/Co are 5.0 × 106 and 8.0 × 105, respectively. The percentage extraction of iron is still higher than 99.98% at loadings of the ionic liquids with 70 g L−1 of iron. The viscosity of the ionic liquid containing the tetrachloroferrate(III) complex [FeCl4]− is lower, and less depending on the feed concentration, than in the case with a tetrachlorocobaltate(II) anion [CoCl4]2−. After extraction, cobalt can be stripped very easily from the ionic liquid phase with water. However, due to the very high distribution ratio, iron could only be stripped by forming a water-soluble iron complex with ethylenediaminetetraacetic acid (EDTA). Also the possibility to extract chromium, nickel, aluminium, calcium and magnesium with trihexyl(tetradecyl)phosphonium chloride has been investigated, but the distribution ratios of these elements are very low in the tested conditions.
While a great deal of attention has been given to imidazolium ionic liquids in recent years, very few investigations involving phosphonium ionic liquids have been reported in the journal literature. The same is not true in the patent literature, where, in addition to filings concerning phosphonium ionic liquids specifically, filings concerning imidazolium ionic liquids routinely claim the manufacture and/or use of phosphonium ionic liquids as well. Despite this activity, commercial applications, and hence commercial production, have not materialized for any ionic liquids to date. Here we present an account of our research into ionic liquids from the perspective of a future, large-scale producer of ionic liquids for industrial applications. Several phosphonium ionic liquids are discussed with respect to synthesis and physical characteristics, and broad comparisons are made to relevant imidazolium systems. Full synthetic and characterization data are reported for several representative compounds including trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate, trihexyl(tetradecyl)phosphonium tetrafluoroborate, triisobutyl(methyl)phosphonium tosylate, and triisobutyl(methyl)phosphonium dimethylphosphate.
Although there have been numerous studies on metal sulphide precipitation, the research field as a whole is not well integrated. This paper reviews the disparate areas of study into metal sulphide precipitation in an attempt to summarise the current work, as well as to suggest potential for future consolidation in the field. The review encompasses (1) fundamental studies into metal sulphide precipitation, which usually focus on mechanisms and are carried out at very low (micromolar) concentrations; (2) applied studies focussing on metal removal and reaction kinetics (mostly via the aqueous phase); (3) studies that focus on the solid phase and address the crystallization kinetics of the formed particles; (4) studies into precipitation of metal sulphide nanocrystals and lastly, (5) applications of metal sulphide precipitation to effluent treatment processes such as Acid Mine Drainage (AMD) treatment as well as industrial hydrometallurgical processes.
While a great deal of attention has been given to imidazolium ionic liquids in recent years, very few investigations involving phosphonium ionic liquids have been reported in the journal literature. The same is not true in the patent literature, where, in addition to filings concerning phosphonium ionic liquids specifically, filings concerning imidazolium ionic liquids routinely claim the manufacture and/or use of phosphonium ionic liquids as well. Despite this activity, commercial applications, and hence commercial production, have not materialized for any ionic liquids to date. Here we present an account of our research into ionic liquids from the perspective of a future, large-scale producer of ionic liquids for industrial applications. Several phosphonium ionic liquids are discussed with respect to synthesis and physical characteristics, and broad comparisons are made to relevant imidazolium systems. Full synthetic and characterization data are reported for several representative compounds including trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate, trihexyl(tetradecyl)phosphonium tetrafluoroborate, triisobutyl(methyl)phosphonium tosylate, and triisobutyl(methyl)phosphonium dimethylphosphate.
Ionic liquids (ILs) are no longer just a class of esoteric compounds, but are proving to be valuable and useful in a multitude of different applications. Herein, novel quaternary ammonium ionic liquids have been synthesized and characterised. These ionic liquids are Brønsted acidic, available from cheap raw materials and easy to prepare. They have been used both as a catalyst and environmentally benign solvent for the hydrolytic reaction of 1,1,1,3-tetrachloro-3- phenylpropane, eliminating the need for a volatile organic solvent and additional catalyst. The results clearly demonstrate that these ILs can be easily separated and reused without losing their activity and quality. Also, the yields obtained with this methodology are significantly increased in comparison with those reported in organic solvents to date.
This article represents a step towards how to choose an ionic liquid as the solvent to improve metal ion (Ag+ and Pb2+) extraction. The liquid-liquid solvent extraction is proposed with the following imidazolium ionic liquids (ILs): 1-ethyl-3-ethylimidazolium,
or 1-butyl-3-ethylimidazolium, or 1-hexyl-3-ethylimidazolium bis{(trifluoromethyl)sylfonyl}imide [EEIM][NTf2], or [BEIM][NTf2], or [HEIM][NTf2], or 1-butyl-3-ethylimidazolium hexafluorophosphate [BEIM][PF6], or 1-hexyl-3-ethylimidazolium hexafluorophosphate [HEIM][PF6] and the popular 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] for comparison. The effect of anion type (NTf2− versus PF6−) and the effect of structural components of an ionic liquid including alkyl chain length at the cation and the ethyl substituent
instead methyl at the cation, on the extraction and re-extraction processes by using dithizone as a metal chelator, were studied
at 296 K. Dithizone was employed to form neutral metal-dithizone complexes with heavy metal ions to extract them from aqueous
solution into the ILs.
This review will examine the most recent research and developments in hollow fibre contactor technology and membrane-based extraction processes, including the latest improvements with regard to stability and flux. The described classification attempts to cover all studies performed by means of non-dispersive contact using hydrophilic/hydrophobic microporous polymeric supports, either by impregnating the membrane or filling its pores with the bulk of the aqueous/organic solution. All membrane processes covered under these categories will be compared with improved versions in terms of performance, mass transfer modelling, stability issues, applications and the state of the art in membrane-based separation techniques. In general, an attempt will be made to review the literature published between 2005 and 2012 (August 2012) in order to focus on the real status of hollow fibre technology and membrane-based extraction processes. In a modern approach, the prospects for the use of ionic liquid (IL) as a membrane carrier for different applications with different membrane morphologies are also presented. In addition, new highly stabilised techniques developed by different researchers, such as hollow fibre renewal liquid membranes (HFRLMs) and pseudo-emulsion-based hollow fibre strip dispersion (PEHFSD), are also discussed.
In this Article, bifunctional ionic liquid extractants (Bif-ILEs) tricaprylmethylammonium sec-octylphenoxy acetic acid ([A366][CA-12]) and tricaprylmethylammonium sec-nonylphenoxy acetic acid ([A336][CA-100]) used for the rare earths (REs) extraction from the chloride medium have been investigated. The effects of extractants concentration, equilibrium pH of aqueous phase, salt concentration, temperature, etc., were discussed. The results show that the extraction ability of [A336][CA-12] and [A336][CA-100] is higher than that of the conventional extractants sec-octylphenoxy acetic acid (CA-12), sec-nonylphenoxy acetic acid (CA-100), tri-n-butyl phosphate (TBP), and di-(1-metylheptyl)methyl phosphate (P350) under the same conditions. Furthermore, in the [A336][CA-12] system, the separation factors (β) between La(III) and other REs(III) are higher than 6.0, which indicates that [A336][CA-12] would be suitable for the La(III) extraction and separation. The extraction mechanism is also proposed, and there is a similar extraction tendency in both the [A336][CA-12] and the [A336][CA-100] systems. The loaded organic phase is easy to strip; more than 95% La(III) could be stripped from the loaded organic phase when the stripping acidity is higher than 0.03 M. The recycling experiments also indicate that the two extraction systems could be recycled without loss of the extraction efficiency.
Room temperature ionic liquids are regarded as “Green solvents” for their nonvolatile and thermally stable properties. They are employed to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. In this work, a water immiscible room temperature ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate [C4mim][PF6], was used as an alternative solvent for liquid/liquid extraction of copper ions. Metal chelators, including dithizone, 8‐hydroxyquinoline, and 1‐(2‐pyridylazo)‐2‐naphthol, were employed to form neutral metal‐chelate complexes with copper ions so that copper ions were extracted from aqueous solution into [C4mim][PF6]. The parameters that affect the extraction of copper ions with this biphasic system were investigated. The extraction behavior in this novel biphasic system is shown to be consistent with that of traditional solvents. For example, the extraction with this biphasic system is strongly pH dependent. So, the extraction efficiency of coppers ion from an aqueous phase can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation and preconcentraction of copper ions can be accomplished by controlling the pH value of the extraction system. It appears that the use of ionic liquid as an alternate solvent system in liquid/liquid extraction of copper ions is very promising.
Recently phosphonium ionic liquids (ILs) are frequently used for separation of metal ions. This paper presents research on successful application of two quaternary phosphonium salts for removal of Zn(II) and iron ions from chloride solutions in classical liquid–liquid extraction and polymer inclusion membranes. Trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) and trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) are investigated as carriers to extract Zn(II), Fe(II) or Fe(III) from chloride media. Cyphos IL 101 and 104 extract Zn(II) and Fe(III) quickly and almost completely from low concentrated feed (extraction efficiency near 100%). They are effective and prospective extractants. Ion exchange and addition mechanism is proposed as description of extraction mechanism. Further, sulfuric acid is found to be an effective stripping phase. In addition, polymer inclusion membranes containing Cyphos IL 101 are applied for Zn(II) and Fe(III) transport. Although the process is slow, more efficient transport through the membrane (with Cyphos IL 101 as a carrier) is noted for Fe(III) than Zn(II). Fe(III) could be separated from Zn(II) with PIM containing Cyphos IL 101.
The ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF6, was synthesized and characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The optimum conditions for the extraction of Ni2+, Cu2+ and Pb2+ in water by liquid–liquid extraction method were investigated using the synthetic ionic liquid combined with 2-aminothiophenol ligand. The results showed that while the optimum pH for the extraction of Ni2+ and Pb2+ was 4–6 and 5, respectively; the extraction of Cu2+ was independent of the pH of solution. The extraction equilibria of Ni2+, Cu2+ and Pb2+ were reached within 120, 30 and 30 min, respectively. The existence of sodium, calcium, magnesium, sulfate and chloride ions did not significantly affect the extraction efficiency of all metal ions. The stoichiometries of complexes between Ni2+, Cu2+ and Pb2+ and the ligand are 1:3, 1:2 and 1:2, respectively. The extracted Ni2+ in ionic liquid phase could be back-transferred into 3% H2O2 in 0.5 M HNO3 at 20 min of contact time and the extracted Cu2+ and Pb2+ could be stripped with 1 M HNO3 at the contact time of 20 and 10 min, respectively, with the percentage stripping higher than 95%. The extraction efficiency of all metal ions with the ligand in the ionic liquid was higher than that obtained in chloroform using the same conditions. The association constants of complexes between Ni2+and Pb2+ and the ligand in ionic liquid are 2.26 × 107 and 2.97 × 102, respectively.
The partitioning of simple, substituted-benzene derivatives between water and the room temperature ionic liquid, butylmethylimidazolium hexafluorophosphate, is based on the solutes’ charged state or relative hydrophobicity; room temperature ionic liquids thus may be suitable candidates for replacement of volatile organic solvents in liquid–liquid extraction processes.
Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) and its sodium salt were used as extractants to treat copper(II) sulphate solutions. Solvent extraction of Cu(II) is more efficient with Na-Cyanex 272 than with its acidic form, and a significant change in pH of the raffinate is observed after extraction. Two mol/dm3 H2SO4 is an effective stripping solution of Cu(II) from the loaded Na-Cyanex 272, and gives 75% of the stripped metal ions in one step. Adsorption parameters show that molecules of Na-Cyanex 272 are populated more densely at the saturated water/toluene interface than Cyanex 272 molecules. Equilibrium and dynamic interfacial tension measurements confirm the interfacial mechanism of Cu(II) extraction and high surface activity of Na-Cyanex 272. Diffusion coefficients estimated for Na-Cyanex 272 are two orders greater than with its acidic form. The differences between both FT-IR and UV/VIS spectra of metal–ligand complexes point out the presence of two types of complex structures depending on the metal–ligand molar ratio (probably planar for 1:1 and tetrahedral for 1:2). Finally, photostability studies show that both extractants are chemically resistant even after contact with H2SO4. The results presented in this paper confirm that conditioning of Cyanex 272 greatly improves the efficiency of Cu(II) extraction in comparison to its acidic form.
Supported liquid membranes (SLM) are studied in various fields like analytical, inorganic and organic chemistry, chemical engineering, biotechnology and biomedical engineering. This technique offers the advantages of active transport, possible usage of expensive carriers, high selectivity, easy scale-up, low energy requirements, low capital and operating costs, etc. This paper gives a brief overview of mechanism and kinetic studies of SLM based separations. The problems with stability and possible applications of SLM are also reviewed.
Copper(II) can be extracted in supercritical CO2 from a room temperature ionic liquid using CO2-philic fluorinated β-diketonate ligands; thanks to the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIMTf2N) ionic liquid properties, there is no need to add modifiers to the neat supercritical CO2 to reach high extraction efficiencies.
Several quaternary ammonium or lithium bis(trifluoromethane sulfone) imide (TFSI) salts were dissolved into N,N,N,N-hexyltrimethyl ammonium TFSI ionic liquid, and the conductivities of the resulting solutions were measured. Some asymmetric quaternary ammonium salts contributed to increase the conductivity of the solution, while cyano-containing quaternary ammonium and lithium salts decreased the conductivity. Based on the results of differential scanning calorimetry (DSC) measurements, such conductivity behaviors appeared to be related to the intrinsic miscibility of the ionic liquid solutions.
Extraction of copper (II) from aqueous solutions using trifluoro-acetylacetone (TFA) diluted in 1-decanol, MIBK and tetradecane at 298 and 313K was investigated experimentally and theoretically. Experimental part of the study concerns with the partitioning of copper (II) in both phases at equilibrium. Distribution of copper (II) in aqueous and organic phases was studied to investigate the hypothesis of constant partition coefficient for solvent extraction mass transfer analysis in hollow fiber membrane contactors (HFMCs). Partition coefficient of copper complexant was measured from extraction equilibrium analysis. Hatta number was calculated to define the kinetic regime. In the second part of experimentation, copper (II) extraction with TFA diluted in 1-decanol using hollow fiber membrane contactor closed system was examined based on aforementioned batch extraction kinetics. Previously developed theoretical model [M. Younas, S. Druon-Bocquet, J. Sanchez, Kinetic and dynamic study of liquid–liquid extraction of copper in a HFMC: experimentation, modeling and simulation, AIChE J. 56 (2010) 1469–1480] was modified to a more robust single-fiber flow model for mass transfer in non-dispersive solvent extraction in HFMC-based integrated plant. The model was, then, validated with the experimental results for dynamic responses of the solute concentration in reservoir. Experimental results were analysed with various shell side mass transfer correlations. It has been shown, by model simulations that the extent and speed of the extraction depend upon the copper (II) and TFA initial concentration, temperature and physical characteristics of solute and solvents. Likewise flow configuration affects the speed of extraction depending upon the nature of solute and solvent.
The permeation of copper(II) through a supported liquid membrane impregnated with LIX 973N (oxime derivative) in Iberfluid has been studied. A model is proposed describing the transport mechanism, which consists of diffusion process through the source aqueous diffusion layer, fast interfacial chemical reaction and diffusion through the membrane. The experimental results are explained by equations describing the rate of transport. Various rate-controlling processes take place as the metal transport occurs.
Selective removal of metal ions was examined in the present paper integrating in the same tank/cell two effective removal processes. This was accomplished taking advantage of flotation, for membranes cleaning among others, combined with microfiltration by submerged membranes. The operation of the hybrid cell was investigated in depth applying initially a metal sorption process using suitable bonding agents and solid/liquid separation of the fine particles downstream. Dispersed-air flotation was capable for a preliminary solids recovery of the order of 90%, with the Cu content in the froth concentrate approaching 6%. The investigation of this innovative idea was focused ultimately to a pilot-scale study at a Bulgarian mine wastewater with promising experimental results, following the development of the separation technique at the laboratory. It was found that the residual heavy metal (Cu, Mn, Fe and Pb) concentrations in the membranes permeate were below 0.05mgL−1.
Acid-rock drainage (ARD) – also known as acid-mine drainage (AMD) – results from the exposure of sulfide minerals, particularly pyritic and pyrrhotitic minerals, to atmospheric oxygen and water. AMD directly impacts tens of thousands of kilometers of streams, lakes and estuaries throughout the world. The impacted water bodies tend to have elevated concentrations of metals in the water column or sediments, and are also stressed by significant inputs of hydrogen ions.There are several conventional treatment technologies available. The most common is chemical precipitation using lime or other basic substances. These systems produce large volumes of wet sludge that often require drying facilities to concentrate the metal hydroxide sludge. Wetland treatment systems have also been used for several decades to treat AMD. Recent developments and improvements have resulted in construction of bioreactors that have a smaller footprint, and treat the metals and acidity more effectively.Many studies have demonstrated that the primary removal mechanisms for the metals are sulphate-reducing bacteria (SRB). These microbes facilitate the conversion of sulphate to sulphide. The sulphides react with metals to precipitate them as metal sulfides, many of which are stable in the anaerobic conditions of the treatment system.Plants have been shown to remove metals by uptake or oxidative precipitation near the roots. Plants seem to account for only a small percentage of the metal removal capacity of the wetland treatment systems. Adsorption of metals to the organic substrates of the treatment systems can result in metal removal, but adsorption capacity is saturated in short periods of time.High oxygen, low pH waters often enter the treatment systems. The SRB are obligate anaerobes which prefer conditions between pH 5 and 8. Thus, the input water characteristics could impact the efficiency and life expectancy of the treatment systems. The most important characteristic of input waters seems to be pH. Low oxygen of the influent waters did not enhance treatment capabilities. Low pH waters do reduce the capacity of the treatment systems to treat metals effectively.Oxyanions such as chromate and arsenate can be removed using the wetland treatment system (passive bioreactor) technology. Arsenic is removed as an arsenic sulfide compound and chromate is reduced to Cr(III) and precipitated as a hydroxide.The passive bioreactor – wetland treatment system – offers a less expensive alternative to the conventional chemical precipitation technologies. There still are problems of system hydraulics and useful life to be addressed.
New functionalized ILs based on quaternary ammonium cations with three or four ether groups and TFSI− anion were synthesized and characterized. Physical and electrochemical properties, including melting point, thermal stability, viscosity, conductivity and electrochemical stability were investigated for these ILs. Five ILs with lower viscosity in these ILs were applied in lithium battery as new electrolytes. Behavior of lithium redox and charge–discharge characteristics of lithium battery were investigated for these IL electrolytes with 0.6 mol kg−1 LiTFSI. Lithium plating and striping on Ni electrode could be observed in these IL electrolytes. Li/LiFePO4 cells using these IL electrolytes without additives had good capacity and cycle property at the current rate of 0.1 C, and the N(2o1)3(2o2)TFSI and N2(2o1)3TFSI electrolytes owned better rate property.Research highlights► Some new functionalized ILs with three or four ether groups are reported. ► They have good electrochemical stability. ► Li/LiFePO4 cells using five IL electrolytes have good capacity and cycle property.
An important problem associated with the development of continuous process for the extraction and separation of Co(II) and Ni(II) is the decrease in the pH of the aqueous phase after its equilibration with organic solvent containing cationic extractants such as Cyanex 272, LIX 860, etc. An improvement in the solvent extraction and separation of Co(II) and Ni(II) from neutral chloride solutions is obtained using ionic liquid extractant tertiary alkyl (C16–C22) primary ammonium bis 2,4,4-(trimethylpentyl) phosphinate (HJMT–Cy272) generated by reacting primary amine, Primene®JMT (JMT) and bis(2,4,4-trimethylpentyl)phosphinic acid, Cyanex 272 (Cy272) in the organic phase. The presence of JMT allows to control the pH of the equilibrated aqueous phase during the extractions of Co(II) and Ni(II). This has facilitated the application of continuous counter current liquid–liquid extraction in the given metal extraction system without applying any in-between acid neutralization process. The liquid–liquid extractions were carried out under different experimental conditions such as concentration of JMT and Cy272 in the organic phase, and concentration of metal ions in the aqueous phase. The optimized composition of the organic phase to obtain better recovery and separation of Co(II) and Ni(II) is 10% Cy272 + 10% JMT in D100. The equal percentage of Cy272 and JMT in the organic phase gave minimum change in the pH of the aqueous phase before and after its equilibration. The McCabe-Thiele plot suggested three theoretical stages of counter current operation for obtaining greater than 99% extraction of Co(II) from its 1 g/L solution. For two metal system, four stage counter current extraction was carried out using bench scale mixer–settler equipment which gave > 99% extraction of Co(II) along with 11% of Ni in the organic phase whereas about 89% of Ni(II) with about 0.3% of Co(II) remained in the aqueous phase. The loaded organic phase was treated with 0.02 M EDTA to strip metal ions and the same was used successfully for the second run of the extraction and stripping process.
Recent restriction of boron concentration in drinking water has produced some problems in the seawater desalinization plants because the rejection of boron in most of the plants is inadequate. Three ionic liquids derived from Cyanex 272 as an anion with different cations (from Aliquat 336, Cyphos IL 101 and Cyphos IL 167) were prepared to be used as boron extractants. Liquid–liquid extraction experiments were carried out to evaluate the viability of boron separation from high chloride media. The effect of ILs and boron concentration and pH were determined. Successive extractions, maintaining the organic phase, provided satisfactory results in order to implement these ILs on supported liquid membrane technologies.
The use of the ionic liquid as a carrier can overcome the inconvenience associated with the membrane stability. In this sense, the ionic liquids ALiCY and the mixture of Cyphos IL 101 and Cyphos IL 167 with Cyanex 272 have been tested as liquid carrier for boron separation by using a flat sheet supported liquid membrane. The results obtained allow us to think about the application of this kind of ILs on the process intensification to remove boron from chloride solutions.
Carrier-mediated transport through supported liquid membranes is currently recognized as a potentially valuable technology for selective separation and concentration of toxic and valuable metal ions. In this paper, a review of the fundamental aspects concerning metal ion transport and the influencing factors are surveyed in terms of data modeling, membrane efficiency (permeability, selectivity, stability), and data acquisition and evaluation. An account of the information reviewed demonstrates the need for critical reflection on system performances in order to accomplish scaling up operations. On the same basis, an attempt to outline some future trends in the field is presented.
Extraction of dilute metal ions from water was performed near room temperature with a variety of ionic liquids. Distribution coefficients are reported for fourteen metal ions extracted with ionic liquids containing cations 1-octyl-4-methylpyridinium[4MOPYR]+, 1-methyl-1-octylpyrrolidinium[MOPYRRO]+, or 1-methyl-1-octylpiperidinium[MOPIP]+ and anions tetrafluoroborate[BF4]+, trifluoromethyl sulfonate[TfO]+, or nonafluorobutyl sulfonate[NfO]+. Ionic liquids containing octylpyridinium cations are good for extracting mercury ions. However, other metal ions were not significantly extracted by any of these ionic liquids. Extractions were also performed with four new task-specific ionic liquids. When these liquids contain a disulfide functional group, they are efficient and selective for mercury and copper, whereas those containing a nitrile functional group are efficient and selective for silver and palladium.
Novel processes based on supported liquid membranes have been proposed as effective methods for the selective separation of different chemical species in dilute streams, such as metal ions, organic compounds or biologically important compounds and gas mixtures. However, the industrial use of supported liquid membranes based on conventional liquids is limited by their relative instability and short lifetime. The use of ionic liquids as a liquid membrane phase could overcome these inconveniences due to their negligible vapour pressure and the possibility of minimizing their solubility in the surrounding phases by adequate selection of the cation and anion. The possibility of designing suitable ionic liquids for specific separation problems has also opened up new potential fields of industrial application of supported ionic liquid membranes. In this review an overview is given of recent advances in supported membranes based on ionic liquids, including issues such as methods of preparation, transport mechanisms, configurations, stability, fields of application and process intensification using supported ionic liquid membranes.
A novel bifunctional task-specific ionic liquid (TSIL), i.e. [trialkylmethylammonium][sec-nonylphenoxy acetate] ([A336] [CA-100]) was impregnated on intermediate polarized XAD-7 resin, and the prepared solvent impreganated resin (SIR) was studied for rare earth (RE) separation. Adsorption ability of the SIR was indicated to be obviously higher than that prepared by [A336][NO3] because of the functional anion of [A336][CA-100]. Adsorption kinetics, adsorption isotherm, separation and desorption of the SIR were also studied.
The partitioning of simple, substituted-benzene derivatives between water and the room temperature ionic liquid, butylmethylimidazolium hexafluorophosphate, is based on the solutes' charged state or relative hydrophobicity; room temperature ionic liquids thus may be suitable candidates for replacement of volatile organic solvents in liquid-liquid extraction processes.
New hydrophobic ionic liquids were synthesized from tricaprylmethylammonium chloride (Aliquat 336©) and selected Bronsted acids by a sustainable, simple and cost-saving deprotonation-metathesis route. Prepared ionic liquids were evaluated as potential extracting agents for cadmium from different aqueous solutions. High efficiency and selectivity were reached for the extraction of cadmium from a natural river matrix with tricaprylmethylammonium thiosalicylate, [A336][TS], a thiol-containing task specific ionic liquid.
The use of room-temperature chloroaluminate(III) ionic liquids, specifically 1-butylpyridinium chloride–aluminium(III) chloride and 1-ethyl-3-methylimidazolium chloride–aluminium(III) chloride, as solvents for clean synthesis and catalytic processes, particularly those applicable to clean technology, is becoming widely recognised and accepted. The design principles for room-temperature ionic liquids, some of their properties, and the rationale for using these neoteric solvents, are discussed here, and an indication of the scope of these solvents for future industrial processes is given. © 1997 SCI.
A novel extraction technique using an emulsion liquid membrane within a hollow-fiber contactor was developed and utilized to extract copper using LIX 84 extractant. Emulsion liquid membranes are capable of extracting metals from dilute waste streams to levels much below those possible by equilibrium-limited solvent extraction. Utilizing an emulsion liquid membrane within a hollow-fiber contactor retains the advantages of emulsion-liquid-membrane extraction, namely, simultaneous extraction and stripping, while eliminating problems encountered in dispersive contacting methods, such as swelling and leakage of the liquid membrane. Mathematical models for extraction in hollow-fiber contactors were developed. The models satisfactorily predict the outcome of both simple solvent extraction and emulsion-liquid-membrane extraction of copper by LIX 84 in a hollow-fiber contactor over a wide range of conditions. Emulsion-liquid-membrane extraction performs exceptionally well when the extraction is close to equilibrium limit. It is also capable of extracting a solute from very dilute solutions. Stability of the liquid membrane is not crucial when used in hollow-fiber contactors; the surfactant in liquid membrane can be reduced or even eliminated without severely impairing the performance.
One of the key steps in printed circuit board (PCB) production is etching of a thin copper layer. Ammoniacal etching solutions are widely used for this purpose. Earlier we have developed a supported liquid membrane based method to treat wastewater containing ammonia and copper (up to 1 g/L), where the membrane is stable for at least 1 month and can be easily regenerated if necessary [1]. Now we are describing an effective hollow fiber supported liquid membrane (HFSLM) based technology for copper recovery from spent ammoniacal etching solutions, where copper is present in much higher concentrations.A bench-scale HFSLM system with 1.4 m2 effective membrane surface area was firstly used to screen out the optimal hydrodynamic and other operation conditions for potentially practical spent ammoniacal etching solutions treatment. It was found that the excess of ammonia in spent etching solutions had negative effect on copper removal, especially when copper concentration became low in the feed solutions as the result of treatment. Different methods were employed to control the ammonia level and their efficiencies were compared.Finally, successful pilot-scale experiments were conducted on a hollow fiber membrane contactor with a surface area of 130 m2. The process results in copper removal by a factor of ∼3000 from spent etching solution through the membrane and formation of nearly saturated copper sulfate solution in the sulfuric acid, used as a striping phase. Compositions of the regenerated etching solution and purity of CuSO4·5H2O crystals formed in the striping phase were comparable or even better than their commercial analogues. The stability of the pilot-scale system is promising for further industrial scale-up.
Removal of arsenic, antimony and bismuth impurities from copper electrolytes is a primary target in copper electrorefineries. The present work investigates the possibilities of carbon adsorption technology in the removal of arsenic and antimony from a real Chilean electrolyte. Various variables which affect the metal adsorption/desorption operations are studied.
A series of silica-based organic–inorganic hybrid materials were prepared by the sol–gel process for Cr(III) and Cr(VI) adsorption. These silica materials generally had high surface areas, good physical–chemical stability and high thermal stability. Trialkylmethylammonium bis 2,4,4-trimethylpentylphosphinate ([A336][C272]) and trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104) were explored as porogens to prepare porous silica and as extractants to extract chromium ions. Cyphos IL 104 and [A336][C272] functionalized silica sorbents (SG-2, SG-5) can be effectively used for the removal of Cr(III) and Cr(VI) from aqueous solutions by adjusting pH values, whereas trialkylmethylammonium chloride (Aliquat 336) and bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) functionalized silica sorbents (SG-3, SG-4) can only be used for the removal of the single chromium species, Cr(VI) or Cr(III). The maximum adsorption amounts of Cr(III) and Cr(VI) were 2.14 and 19.31 mg g−1 for SG-2 and 2.32 and 15.29 mg g−1 for SG-5. Langmuir and Freundlich isotherm models were used to evaluate the adsorption of Cr(III) and Cr(VI) on sol–gel sorbents. The adsorption kinetics of Cr(III) and Cr(VI) on SG-2 and SG-5 could be well described by pseudo-second-order kinetic model. In terms of Cr(III) and Cr(VI) uptake capacities and kinetics, SG-2 and SG-5 appeared to be more suitable for Cr(III) and Cr(VI) removal than SG-3 and SG-4.
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.
Ionic liquids (ILs), considered to be a relatively recent magical chemical due their unique properties, have a large variety of applications in all areas of the chemical industries. The areas of application include electrolyte in batteries, lubricants, plasticizers, solvents and catalysis in synthesis, matrices for mass spectroscopy, solvents to manufacture nano-materials, extraction, gas absorption agents, etc. Non-volatility and non-flammability are their common characteristics giving them an advantageous edge in various applications. This common advantage, when considered with the possibility of tuning the chemical and physical properties of ILs by changing anion–cation combination is a great opportunity to obtain task-specific ILs for a multitude of specific applications. There are numerous studies in the related literature concerning the unique properties, preparation methods, and different applications of ILs in the literature. In this review, a general description of ILs and historical background are given; basic properties of ILs such as solvent properties, polarity, toxicology, air and moisture stability are discussed; structure of ILs, cation, anion types and synthesis methods in the related literature are briefly summarized. However, the main focus of this paper is how ILs may be used in the chemicals processing industries. Thus, the main application areas are searched and the basic applications such as solvent replacement, purification of gases, homogenous and heterogeneous catalysis, biological reactions media and removal of metal ions are discussed in detail. Not only the advantages of ILs but also the essential challenges and potentials for using ILs in the chemical industries are also addressed. ILs have become the partner of scCO2 in many applications and most of the reported studies in the literature focus on the interaction of these two green solvents, i.e. ILs and scCO2. The chemistry of the ILs has been reviewed in numerous papers earlier. Therefore, the major purpose of this review paper is to provide an overview for the specific chemical and physical properties of ILs and to investigate IL–scCO2 systems in some detail. Recovery of solutes from ILs with CO2, separation of ILs from organic solvents by CO2, high-pressure phase behavior of IL–scCO2 systems, solubility of ILs in CO2 phase, and the interaction of the IL–scCO2 system at molecular level are also included.
During the past 10 years, there have been incremental advances in the application of solvent extraction to process hydrometallurgy. The most cited areas in the literature include chemistry, chemical engineering, pilot plants, and plant operation. Within these areas, there were considerable interest in synergism, diluents, degradation, contactors, surfactants, hydrometallurgical applications, environmental and secondary applications, and health and safety. The summary to the present is followed by a prediction for the future in the above areas of interest. These include the use of speciation; improved understanding of the role of surfactants on the system; optimization through modelling, pilot plants, and contactor selection; improvements in plant operation; further new applications; and plant safety. The review has indicated that considerable knowledge is now available to optimize and improve on process design and plant applications.
One of the best available technologies for the removal of metals from water is in the form of metal sulphides. Metal removal by sulphide precipitation is a well-known process that is characterised by compact residues and very high removal efficiencies. Compared to neutralisation alone the sludge volume is 6 to 10 times lower and the toxic metals are removed to a 0.01–1 ppm level. Furthermore, selective metal precipitation is possible, allowing for separate recovery of valuable metals like copper, nickel, cobalt and zinc from nuisance metals like arsenic and antimony. However, the cost of reagent (NaHS or H2S gas) and safety aspects are often prohibitive.This paper describes a novel biological process for safe and cost effective production of sulphide from elemental sulphur, waste sulphuric acid or sulphate present in effluents. With this technology, gaseous or dissolved H2S is produced on-site and on-demand in an engineered, high rate bioreactor.Experience with industrial applications at metal processing plants will be presented. The technology can serve to selectively recover metals from e.g. bleed streams, leach liquor, effluent streams and acid mine drainage. Lower overall costs and increased safety (no transport or storage of sulphide, production on-demand and at ambient pressure) are the main advantages of this new process compared to its alternatives.
This is a communication on the removal of copper(II) ions from a residual mine water using an emulsified liquid membrane (ELM). The membrane was prepared by dissolving the extractant LIX-860 (a salicylaldoxime), used as a mobile carrier, and Span-80, a surfactant, in kerosene. The ELM allowed an efficient metal transport from the feed solution towards the strip liquor, in experiments carried out in a batch-type stirred tank at 30 °C. A screening factor-type experimental statistical design was developed, which established the variables and their interrelation affecting the studied process. The experimental results and the variance analysis indicated that the statistically significant variables on copper transport through the membrane were the extractant concentration, the stirring time and the stirring speed of the double emulsion. The surfactant concentration range employed in this study adequately stabilized the membrane. However, it did not produce any positive effect on metal extraction. It was observed that the use of an excessively high content of surfactant produced lower metal transport extraction since it gave rise to a higher interfacial resistance. The experimental results reported show the potential for removal of valuable or toxic metals from dilute mine solutions using an extractor based on emulsified liquid membranes.
The transport of copper(II) from an aqueous solution containing zinc, cadmium, nickel and cobalt through supported liquid membrane using LIX 984 dissolved in different diluents as a mobile carrier was studied. A transport rate model has been derived taking into account diffusion through an aqueous feed boundary layer, diffusion of carrier–copper complex through supported liquid membrane and diffusion through an aqueous strip boundary layer as simultaneous controlling factors. For different types of supported liquid membrane (kerosene/Teflon; n-heptane/Teflon; n-octane/Teflon; and kerosene/Durapore), the mass transfer coefficients, kf (m s−1), were calculated from the described transport rate equation to lie between 2.4 to 2.5·10−5, whilst the membrane diffusion coefficients of the carrier–copper complex, DR2Cu, m (m2 s−1), were 2.6·10−10, 5.7·10−10, 1.1·10−9, and 4·10−10, respectively. The results showed that Cd2+, Zn2+, Co2+, and Ni2+ ions were not transported in the pH range 1–5 studied.
The transport of copper through supported liquid membranes (SLM) using Celgard and Accurel membranes as supports and a novel commercial extractant LIX 984N as a carrier was investigated. LIX 984N provides good overall transport performance for copper from the acidic and dilute solution to the concentrated copper sulfuric acid. The instability of the supported liquid membranes using Celgard 2500 as the membrane support has been studied. It has been demonstrated that initially the surface shear forces due to stirring are a main cause for membrane liquid loss leading to SLM instability. However, during long term permeation no single instability mechanism dominants. The instability of long term operation involves a complex interaction of a number of factors, including surface shear forces, Marangoni effects, changes to membrane morphology, Bernard instabilities and membrane preparation protocal.
Phosphonium ionic liquid: trihexyl(tetradecyl)phosphonium chloride (Cyphos®IL 101) has been used as a novel reagent in the presence of toluene to extract palladium(II) from hydrochloric acid solutions of various concentrations. Extraction data indicate that Cyphos®IL 101 is a very efficient and fast extractant. The increase in HCl concentration has negative influence on the extraction and about 97 and 54% of palladium(II) can be effectively extracted with Cyphos®IL 101 from 0.1 and 3 M HCl, respectively. The equilibrium of palladium(II) extraction from aqueous 0.1 and 3 M HCl with this phosphonium ionic liquid is achieved after 5 min. Successful stripping of palladium(II) from the loaded organic phase is achieved with 0.5 M ammonia solution. Cyphos®IL 101 can be reused at least in 5 cycles of extraction-stripping process.
Three functionalized ionic liquids (ILs), tetrabutylammonium di(2-ethylhexyl)phosphate ([TBA][DEHP]), trioctylmethylammonium di(2-ethylhexyl)phosphate ([TOMA][DEHP]), and trihexyl(tetradecyl)phosphonium di(2-ethylhexyl)phosphate ([THTP][DEHP]), are synthesized and characterized. These ILs are used as DEHP-based ionic extractants and are investigated for rare earth elements (REEs) separation in 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(6)mim][NTf(2)]) and diisopropylbenzene (DIPB) along with di(2-ethylhexyl)phosphoric acid (HDEHP). Solubilities of the DEHP-based ionic extractants in [C(6)mim][NTf(2)] are much better than that of HDEHP in [C(6)mim][NTf(2)]. We herein report the achievement of enhanced extractabilities and selectivities for separation of REEs using DEHP-based ionic extractants in [C(6)mim][NTf(2)]. This work highlights the potential of developing a comprehensive ionic liquid-based extraction strategy for REEs using ionic liquids as both extractant and diluent.
The selection of separation process of organic compounds is a critical issue in the chemical industry. Different conventional methods, such as coagulation, precipitation, ion exchange, electrodialysis, adsorption, ultrafiltration and liquid-liquid extraction have been used for the separation processes since last so many years, but supported liquid membrane (SLM)-based separation processes have been predicted as a promising option. Ionic liquids (ILs) are considered a new miraculous chemical due their unique properties and large variety of applications in all areas of the chemical sciences. The use of ionic liquids as a liquid membrane phase results in the stabilization of the SLMs due to their negligible vapor pressure, possibility of minimizing their solubility in the surrounding phases and greater capillary force associated with their high viscosity, which can reduce the displacement of liquids from micron pores under pressure. This review article summarizes the role of ionic liquids in supported liquid membrane technology for extraction processes, stability of the membranes and show promise in the liquid/liquid extraction of organics from water, gases, amino acids, toxic metal ions from their aqueous solution and separating isomeric organic compounds.
Several hydrophobic long-chain quaternary ammonium and phosphonium ionic liquids (ILs) with functionalized aromatic anions were prepared following a metathesis route using tricaprylmethylammonium chloride (Aliquat 336) and trihexyl(tetradecyl)phosphonium chloride (Cyphos IL101) as precursors. The incorporation of aromatic anions bearing hydroxy-, methoxy-, thiol-, and thioether functionalities as well as tetraphenylborate anions resulted in an increased chemical stability of the ILs and an alteration of their physico-chemical properties. Furthermore, aromatic anions significantly decreased the water solubility and water uptake of both ammonium and phosphonium-based ILs. Thiol- and thioether ILs were applied for the extraction of platinum from aqueous phase using liquid phase micro-extraction. Time dependent studies showed a rapid elimination of up to 95% platinum after 30 min. With a leaching of the anion <0.01 wt-% into the aqueous media, the evaluated ILs were found to be suitable as extracting agents for platinum from aqueous solutions.
In a fundamental study the potential of ionic liquids based on quaternary ammonium- and phosphonium cations and thiol-, thioether-, hydroxyl-, carboxylate- and thiocyanate-functionalized anions has been assessed for future application in advanced sewage treatment. The elimination of the metal(oid)s Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Pt, Sn, Zn and the cancerostatic platinum compounds cisplatin and carboplatin was screened using a liquid phase micro-extraction set-up. The analytical tool-set consisted of ICP-SFMS and LC-ICP-MS for quantification of metal(oid)s and cancerostatic platinum compounds, respectively. The purity of the ILs was assessed for the investigated metal(oid)s on the base of present EU environmental quality standards and was found to be sufficient for the intended use. In model solutions at environmental relevant concentrations extraction efficiencies≥95% could be obtained for Ag, Cu, Hg and Pt with both phosphonium- and ammonium-based ILs bearing sulphur functionality in the form of thiosalicylate and 2-(methylthiobenzoate) anions, as well as with tricaprylmethylammonium thiocyanate within an extraction time of 120 min. All other metals were extracted to a lower extent (7-79%). In the case of cancerostatic platinum compounds a phosphonium-based IL bearing thiosalicylate functionality showed high extraction efficiency for monoaquacisplatin. For the first time, liquid phase micro extraction with ionic liquids was applied to industrial and communal waste water samples. The concentration of all investigated metal(oid)s could be significantly reduced. The degree of elimination varied with the initial concentration of metals, pH and the amount of suspended particulate matter.
The recently synthesized ionic liquid (IL) 2-butylthiolonium bis(trifluoromethanesulfonyl)amide, [mimSBu][NTf(2)], has been used for the extraction of copper(II) from aqueous solution. The pH of the aqueous phase decreases upon addition of [mimSBu](+), which is attributed to partial release of the hydrogen attached to the N(3) nitrogen atom of the imidazolium ring. The presence of sparingly soluble water in [mimSBu][NTf(2)] also is required in solvent extraction studies to promote the incorporation of Cu(II) into the [mimSBu][NTf(2)] ionic liquid phase. The labile copper(II) system formed by interacting with both the water and the IL cation component has been characterized by cyclic voltammetry as well as UV-vis, Raman, and (1)H, (13)C, and (15)N NMR spectroscopies. The extraction process does not require the addition of a complexing agent or pH control of the aqueous phase. [mimSBu][NTf(2)] can be recovered from the labile copper-water-IL interacting system by washing with a strong acid. High selectivity of copper(II) extraction is achieved relative to that of other divalent cobalt(II), iron(II), and nickel(II) transition-metal cations. The course of microextraction of Cu(2+) from aqueous media into the [mimSBu][NTf(2)] IL phase was monitored in situ by cyclic voltammetry using a well-defined process in which specific interaction with copper is believed to switch from the ionic liquid cation component, [mimSBu], to the [NTf(2)] anion during the course of electrochemical reduction from Cu(II) to Cu(I). The microextraction-voltammetry technique provides a fast and convenient method to determine whether an IL is able to extract electroactive metal ions from an aqueous solution.
The extraction equilibria of copper(II) with Cyanex 301, LIX 984N, and their mixtures have been investigated. Extraction was studied as a function of organic phase composition, sulfuric acid concentration, pH, temperature, initial copper concentration, mixing speed, and aqueous/organic volume ratio. Considerable synergistic enhancement has been observed in the extraction of Cu(2+) with mixtures of Cyanex 301 and LIX 984N. The results demonstrate that copper ion is extracted as CuRL(2)H with synergistic mixture. The thermodynamic parameter, enthalpy change (Delta H) of Cyanex 301, LIX 984N, and their mixtures have been determined and the endothermic process has been found. The synergistic enhancement factor of copper(II) with mixtures is higher at more acidic solutions, which suggests that it is a promising synergistic extraction system for the separation of copper(II) from more acidic medium. HCl was found to be more efficient for copper stripping from loaded synergistic mixtures.
Applications and prospects of two-phase, tuneable solvent systems composed of ionic liquids (ILs) and supercritical fluids with an emphasis on supercritical carbon dioxide (scCO(2)) are reviewed. The IL-scCO(2) biphasic systems have increasingly been used in diverse fields of chemistry and technology, and some examples of these applications are mentioned here. Rational design of such applications can obviously benefit from pertinent data on phase equilibria including the partition coefficients of the prospective products and reactants between the two phases. Therefore, a reliable technique to measure the limiting partition coefficients would be of value. Here, the pros and cons of supercritical fluid chromatography in this respect are discussed. An overview of methods for predictive thermodynamic modelling of binary (IL-scCO(2)) and ternary (solute-IL-scCO(2)) systems is also included.