Separation of tungsten and molybdenum with solvent extraction using functionalized ionic liquid tricaprylmethylammonium bis(2,4,4-trimethylpentyl)phosphinate

Functionalized ionic liquids(FILs)as extractants were employed for the separation of tungsten and molybdenum from a sulfate solution for the first time.The effects of initial pH,extractant concentration,metal concentrations in the feed were comprehensively investigated.The results showed that tricaprylmethylammonium bis(2,4,4-trimethylpentyl)phosphinate([A336][Cyanex272])could selectively extract W over Mo at an initial pH value of 5.5;the best separation factorβ_(W/Mo) of 25.61 was obtained for a solution with low metal concentrations(WO3:2.49 g/L,Mo:1.04 g/L).The[A336][Cyanex272]system performed effectively for solutions of different W/Mo molar ratios and different metal ion concentrations in the feed.The chemical reaction between[A336][Cyanex272]and W followed the ion association mechanism,which was further proved by the Fourier-transform infrared(FTIR)spectra of loaded[A336][Cyanex272]and the free extractant.The stripping experiments indicated that 95.48%W and 100.00%Mo were stripped using a 0.20 mol/L sodium hydroxide solution.Finally,the selective extractions of W and Mo from two synthetic solutions of different high metal concentrations were obtained;the separation factorβW/Mo reached 23.24 and 17.59 for the first and second solutions,respectively.The results suggest the feasibility of[A336][Cyanex272]as an extractant for the separation of tungsten and molybdenum.

Application of hydrophobic ionic liquid [Bmmim][PF6] in solvent extraction for oily sludge

In this study, an ionic liquid(IL), 1-butyl-2,3-dimmmethylimidazolium hexafluorophosphate([Bmmim][PF6]),was used in combination with a composite solvent of methyl acetate and n-heptane to enhance the oil extraction from oily sludge. The oil recovery increased by approximately 15% compared with that of solvent extraction without [Bmmim][PF6] at the optimal ratios of IL to sludge and solvents to sludge, which were at 2:5(M/M) and 4:1(V/M), respectively. The saturate, aromatic, resin and asphaltene(SARA) analysis revealed that the recovery of resins and asphaltenes was increased by 14% and 38%, respectively, in the solvent extraction with the addition of [Bmmim][PF6]. [Bmmim][PF6] maintained a good performance after its reuse four times. The addition of[Bmmim][PF6] changed the adhesion forces between oil and soil. The IL-assisted solvent extraction procedure followed the pseudo second-order kinetic model, while the unassisted solvent extraction procedure followed the pseudo first-order kinetic model. The results also demonstrated that [Bmmim][PF6] decreased the solvent consumption by approximately 60% each time. Additionally, [Bmmim][PF6] can be easily separated. The results suggested that enhancing the solvent extraction with this IL is a promising way to recover oil from oily sludge with a higher oil recovery rate and lower organic solvent consumption than those with the unassisted solvent extraction method.

Cu(II) Extraction in Ionic Liquids and Chlorinated Solvents: Temperature Effect

Room temperature ionic liquids have been currently used in liquid/liquid extraction processes in order to substitute conventional organic solvents. In this paper, a series of chlorinated solvents and 1-alkyl-3-me- thylimidazolium-based ionic liquids were selected to study the extraction efficiency of a lipophilic polya- mine 1,1,7,7-tetraethyl-4-tetradecyldiethylenetriamine (TE14DT) towards the model ion Cu(II) in such dif-ferent media. The effect of temperature on the extraction efficiency was also investigated. The metal ion par-tition was found to be strongly dependent on both the nature of the solvent and on the working temperature. The viscosity of ionic liquids and the water content in ionic liquid were found to affect the extraction effi-ciency of TE14DT. The chemical nature of the cation of ionic liquids, and in particular the alkyl chain length on imidazolium ring, also seemed to be important in determining the efficiency of the extraction process. Finally, preliminary experiments on back-extraction of Cu(II) ions from ionic liquid also revealed interesting hints to the development of a continuous transport process.

Application of bifunctional ionic liquids for extraction and separation of Eu^(3+) from chloride medium

The extraction of Eu^(3+)from chloride medium using bifunctional ionic liquid extractants(Bif-ILEs)tri-n-octylmethyl ammonium bis(2-ethyl hexyl)phosphate([A336][D2EHP])and trihexyltetradecyl phosphonium bis(2-ethylhexyl)phosphate([P_(66614)][D2EHP])in kerosene was studied to develop environmentally friendly extraction process.The extraction behavior of Eu^(3+)was examined by varying key process parameters.The extraction behavior indicates that ammonium-based ionic liquid[A336][D2EHP]shows better extraction efficiency of Eu^(3+)than that of phosphonium-based ionic liquid[P_(66614)][D2EHP].Quantitative extraction of Eu^(3+)is obtained with 0.05 mol/L[A336][D2EHP],whereas,0.1 mol/L of[P_(66614)][D2EHP]is required to achieve the same extraction rate of Eu^(3+).The extraction process is endothermic with respect to[A336][D2EHP].Stripping experiments indicate that 100%of Eu^(3+)can be back extracted from both the loaded ionic liquids using 20 vol.%HNO_(3).The highest separation factor(βY/Eu)of 653.59 is reported at pH of 3.2,and the separation factor of Eu^(3+)over La^(3+)is 30.6 at the same pH.From the leach liquors of waste tube light powder,99.98%of Eu and 99.99%Y are recovered using 0.2 mol/L[A336][D2EHP]in 2-stage cross current extraction with aqueous to organcic ratio(O/A)of 1:1 and 1:2.

Adsorption by Liquid-Liquid Extraction of Hg(II) from Aqueous Solutions Using the 2-Butyl-imidazolium Di-(2-ethylhexyl) Phosphate as Ionic Liquid

In this work, a novel room temperature ionic liquid (2-butyl-imidazolium di-(2-ethylhexyl) phosphate) ([C4mim] [D2EHPA]) was synthesized and tested as extractant in the mercury(II) liquid-liquid extraction. The effects of parameters such as aqueous to organic phase’s volume ratio, metal concentration IL concentration, pH levels, ionic strength, and temperature were reported. For the extraction of metal, [C4mim]3[R.HR]3[HgCl2]org and [C4mim]3[R.HR]3 [HgClOH]org species were formed where (H2R2) was D2EHPA. In the case of ionic strength, the results showed that the addition of sodium acetate at 0.302 mmol·L?1 to the aqueous phase strongly increased the mercury extraction yield (R = 100%). The extracted species were investigated by a calculation program using CHEAQS V. L20.1 inorder to determine the relation between the percentages of the extracted species and the extraction yield. The results showed that the extracted species in the best conditions were HgCl2 and HgClOH with respective percentages 80.66% and 18.29%.

Photocatalytic oxidative of Keggin-type polyoxometalate ionic liquid for enhanced extractive desulfurization in binary deep eutectic solvents

A series of novel binary deep eutectic solvents(DESs)composed of choline chloride(ChCl)and formic acid(HCOOH)with different molar ratios have been successfully synthesized and applied in extractive desulfurization(EDS).Keggin-type polyoxometallate ionic liquid[TTPh]_(3)PW_(12)O_(40) was prepared and used as catalyst to enhance the EDS capacity by means of photocatalytic oxidative process.Both of the DESs and[TTPh]_(3)PW_(12)O_(40) ionic liquid catalyst were characterized in detail by Fourier transform infrared spectroscopy spectra(FT-IR),elemental analysis,and X-ray photoelectron spectroscopy(XPS).It was found that the molar ratios of Ch Cl:HCOOH had a major impact on desulfurization performance,and the optimal desulfurization capacity 96.5%was obtained by ChCl/5 HCOOH.Besides dibenzothiophene(DBT),the desulfurization efficiencies of 4-methylbenzothiophene(4-MDBT)and 4,6-dimethyldibenzothiophene(4,6-DMDBT),two kinds of DBT derivatives,were also investigated under the same experimental conditions.Moreover,the free radical scavenging experiments manifested that superoxide radical(·O_(2)^(-)) and hole(h^(+)) played important roles in the desulfurization system.After further analysis of the oxidation products by gas chromatography-mass spectrometry(GC–MS),the possible reaction mechanism was proposed.Thus,photocatalytic oxidative has been proved to be one of the efficient approaches for enhancing the extractive desulfurization performance in DES.

Solvent extraction of U(VI) by trioctylphosphine oxide using a room-temperature ionic liquid

The unique physical and chemical properties of room-temperature ionic liquids(RTILs) have recently received increasing attention as solvent alternatives for possible application in the field of nuclear industry, particularly in liquid-liquid separations of radioactive nuclides. We investigated solvent extraction of U(VI) from aqueous solutions into a commonly used ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([C4mim][NTf2]) using trioctylphosphine oxide(TOPO) as an extractant. The effects of contact time, TOPO concentration, acidity, and nitrate ions on the U(VI) extraction are discussed in detail. The extraction mechanism was proposed based on slope analysis and UV-Vis measurement. The results clearly show that TOPO/[C4mim][NTf2] provides a highly efficient extraction of U(VI) from aqueous solution under near-neutral conditions. When the TOPO concentration was 10 mmol/L, the extraction of 1 mmol/L U(VI) was almost complete(> 97%). Both the extraction efficiency and distribution coefficient were much larger than in conventional organic solvents such as dichloromethane. Slope analysis confirmed that three TOPO molecules in [C4mim][NTf2] bound with one U(VI) ion and one nitrate ion was also involved in the complexation and formed the final extracted species of [UO2(NO3)(TOPO)3]+. Such a complex suggests that extraction occurs by a cation-exchange mode, which was subsequently evidenced by the fact that the concentration of C4mim+ in the aqueous phase increased linearly with the extraction percent of U(VI) recorded by UV-Vis measurement.

Ionic Liquids: Progress and Prospective

Ionic liquids （ILs） are green solvents that have attracted great attention in recent years due to their unique properties. In this paper the latest progresses in both the fundamental studies and applications of ILs have been summarized, with the emphasis on the topics of physical properties, catalytic reactions, and biochemical engineering. The critical problems in the applications of the ILs have been addresses, and the prospective of the ILs were finally predicted.

Separation of lithium and nickel using ionic liquids and tributyl phosphate

With the vigorous development of the electronics industry,the consumption of lithium continues to increase,and more lithium needs to be mined to meet the development of the industry.The content of lithium in the solution is much higher than that of minerals,but the interference of impurity ions increases the difficulty of extracting lithium ions.Therefore,we prepared an imidazole-based ionic liquid(1-butyl-3-methylImidazolium bis(trifluoromethyl sulfonyl)imide)(IL)for efficient lithium extraction from aqueous solutions by solvent extraction.Using an extraction consisting of 10%IL,85% tributyl phosphate(TBP),and 5% dichloroethane and an organic to aqueous phase ratio(O/A)of 2/1,over 64.23% of Li were extracted,and the extraction rate after five-stage extraction could reach more than 96%.The addition of ammonium ions to the solution inhibited the extraction of Ni,and the separation coefficient between lithium and nickel approached infinity,showing a very perfect separation effect.Fouriertransform infrared spectroscopy and slope methods were used to analyze the changes that occurred during extraction,revealing possible extraction mechanisms.In addition,the LiCl solution generated during the preparation of ionic liquids was mixed with the stripping solution,and the battery-grade lithium carbonate was prepared by Na_(2)CO_(3) precipitation,with a purity of 99.74%.This study provides an efficient and sustainable strategy for recovering lithium from the solution.

Equilibrium and mechanism studies of gold(Ⅰ)extraction from alkaline aurocyanide solution by using fluorine-free ionic liquids

Solvent extraction based on ionic liquids is generally considered to be an environmentally benign and effective technology for gold(Ⅰ)recovery.The aim of this work is to study gold(Ⅰ)extraction from aurocyanide solution using fluorine-free ionic liquids[A336][SCN],[A336][MTBA]and[A336][Mal].Various factors that affect gold(Ⅰ)extraction(including concentration of ionic liquids,equilibrium pH,concentration of the modifier tributyl phosphate(TBP),reaction time and initial concentration of gold in an aqueous solution)were studied and optimized.The results indicate that the three Aliquat336-based ionic liquids all exhibit excellent behaviors for gold(Ⅰ)extraction.More than 99.8%of gold(Ⅰ)can be extracted from the aqueous phase into the ionic liquid phase.The gold-loaded ionic liquids were characterized using infrared spectroscopy and mass spectrometry to study the extraction mechanism of gold(Ⅰ).The results revealed that extraction of gold(Ⅰ)into the ionic liquid phase was based on an exchange reaction between the anion Au(CN)2-in aqueous solution and the anion SCN-in ionic liquid[A336][SCN].The logarithmic relationship between distribution coefficient and TBP concentration indicates that two TBP molecules are involved in the formation of the extracted complex.The extracted complex was determined to be A336^(+)·Au(CN)_(2)^(-)·2 TBP.In addition,the gold(Ⅰ)-loaded ionic liquids can be efficiently stripped using NH4 SCN,2-methylthiobenzoic acid and methyl maltol.The results establish that Aliquat 336-based ionic liquids have potential application prospects in gold(Ⅰ)recovery from cyanide solutions.

Effect of the Structure of Cations and Anions of Ionic Liquids on Separation of Aromatics from Hydrocarbon Mixtures

The effects of the structure of typical cations and anions of ionic liquids on the separation of benzene and toluene from aromatic/paraffin mixtures were studied. The .results showed that the corresponding separation factors were considerably larger than those of the traditional solvents （Benzene＋Hexane＋sulfolane）, and that the ionic liquids could be used as novel solvents for the separation of aromatics from hydrocarbon mixtures. The key parameters governing the ability of ionic liquids for separating aromatics from hydrocarbon sources were investigated. It was found that the effectiveness of the ionic liquids, based on the same anion, changed in the cation order of [BIqu]^＋〈 [BPy]^＋〈 [BMIM]^＋. The selectivity of the ionic liquid toward aromatics decreased apparently with the increasing length of the substituted alkyl chain of its cationic head ring. The separation factors, based on the same cation, changed in the anion order of [Tf2N]^-〈[PF6]^-〈[BF4]^-〈[C2H5SO4]^-. The solubilities of the aromatics were greater in the ionic liquids based on the former three anions than that in the ionic liquids involving [C2H5SO4]^-.

New process development and process evaluation for capturing CO2 in flue gas from power plants using ionic liquid[emim][Tf2N]

Using the ionic liquid[emim][Tf2N]as a physical solvent,it was found by Aspen Plus simulation that it was possible to attempt to capture CO2 from the flue gas discharged from the coal-fired unit of the power plant.Using the combination of model calculation and experimental determination,the density,isostatic heat capacity,viscosity,vapor pressure,thermal conductivity,surface tension and solubility of[emim][Tf2N]were obtained.Based on the NRTL model,the Henry coefficient and NRTL binary interaction parameters of CO2 dissolved in[emim][Tf2N]were obtained by correlating[emim][Tf2N]with the gas–liquid equilibrium data of CO2.Firstly,the calculated relevant data is imported into Aspen Plus,and the whole process model of the ionic liquid absorption process is established.Then the absorption process is optimized according to the temperature distribution in the absorption tower to obtain a new absorption process.Finally,the density,constant pressure heat capacity,surface tension,thermal conductivity,and viscosity of[emim][Tf2N]were changed to investigate the effect of ionic liquid properties on process energy consumption,solvent circulation and heat exchanger design.The results showed that based on the composition of the inlet gas stream to the absorbers,CO2 with a capture rate of 90%and a mass purity higher than 99.5%was captured.These results indicate that the[emim][Tf2N]could be used as a physical solvent for CO2 capture from coal-fired units.In addition,the results will provide a theoretical basis for the design of new ionic liquids for CO2 capture.

Complexation between uranyl(Ⅵ)and CMPO in a hydroxyl-functionalized ionic liquid:An extraction,spectrophotography,and calorimetry study

The extraction complexes of uranyl(Ⅵ)in HNO_(3)to a hydroxyl-functionalized ionic liquid(IL)phase,HOEtmimNTf2bearing CMPO,were investigated.Three possibly successive extraction complexes,UO_(2)L^(2+)(L=CMPO),UO2L_(2)^(2+) and UO_(2)L_(3)^(2+),were detected based on variable U/L ratios.Uranyl(Ⅵ)prefers to be extracted as complex UO_(2)L_(3)^(2+),combining with the ions from HOEtmimNTf_(2) to construct a solid material through self-assembly.The thermodynamics of complexes,UO_(2)L_(j)^(2+)(j=1-3),were studied by spectrophotometry and microcalorimetry.All the formation reactions are principally driven by entropy,although a small part of the driving force of complexes UO_(2)L_(2)^(2+)and UO_(2)L_(3)^(2+) comes from enthalpy.Based on the thermodynamic properties for complex UO_(2)L_(3)^(2+),we provide a possible coordination mode in HOEtmim NTf_(2):the first CMPO molecule coordinates with UO_(2)^(2+) in a bidentate fashion while the others do in a monodentate fashion.The results offer a thermodynamic insight into the formation behaviors of the uranyl(Ⅵ)/CMPO complexes involving the special IL HOEtmimNTf_(2),which is of significance to advance the novel IL extraction strategy.

Revisiting greenness of ionic liquids and deep eutectic solvents

Green solvents are one of the hot topics of green chemistry.Ionic liquids(ILs)and deep eutectic solvents(DESs)are deemed as green solvents to a certain extent,and they have been applied in many areas,such as dissolution,separation,catalysis,electrochemistry and material synthesis.However,the greenness of ILs and DESs should be revisited because more and more evidences have shown that they are not always green.In this perspective,besides the reported merits,the disadvantages and problems of some ILs and DESs,such as instability,volatility,hygroscopicity,toxicity,flammability,regenerability,cost,energy consumption and impurities are discussed.Moreover,13 strategies to avoid the disadvantages of ILs and DESs and to increase the greenness are proposed.Comparison of the greenness of ILs and DESs is further conducted.This perspective provides some new viewpoints on the greenness of ILs and DESs.

Recovery of natural active molecules using aqueous two-phase systems comprising of ionic liquids/deep eutectic solvents

Due to environmental protection requirements,extraction of bioactive compounds from plant materials using environment-friendly green solvents has always been a research hotspot.And great efforts of scholars have been made in this direction,as well as environment-friendly solvents have been used to develop many innovative extraction techniques.Ionic liquids(ILs)and deep eutectic solvents(DESs)are two kinds of typical designable green solvents,which are potential replacements for traditional volatile organic solvents used for extracting.Under the substances action of inorganic salts or polymers,ILs/DESs can form an aqueous two-phase system(ATPS),which has obvious advantages for separating natural products.This paper discussed the phase separation principle of ILs/DESs-based ATPSs and reviewed the applications in the extraction of natural active molecules in recent years,as well as to promote the development of separation of the active constituents in Chinese materia medica.

Rational design of novel carboxylic acid functionalized phosphonium based ionic liquids as high-performance extractants for rare earths

Developing the novel ionic liquids as the potential substitutes for conventional organic solvents in extraction of the rare-earth metals is highly desirable but challenges still remain.In this study,the welldesigned carboxylic acid functionalized phosphonium based ionic liquids,(4-carboxyl)butyl-trioctylphosphonium chloride/nitrate,were synthesized and characterized.The as-prepared samples were tested as the undiluted hydrophobic acidic extractant for rare-earth metal ions,affording the maximal loading of 3 mol/mol towards Nd(Ⅲ)in aqueous solution and the remarkable stripping performance.The results also reveal their excellent extractability and selectivity for Sc(Ⅲ)in the mixtures of six rare-earth ions,as well as the outstanding separation properties between rare-earth and first row transition-metal ions(i.e.,La/Ni,Sm/Co).Moreover,the extraction mechanism indicates that the extracted rare-earth complex via a proton exchange in the ionic liquid phase is structurally similar to the complexes obtained with neutral extractants.This work presents a prototype for the fabrication of the hydrophobic cation-functionalized ionic liquids for highly efficient rare-earth extraction and provides the future application in recycling of rare-earth metals from the spent magnets.

Separations of Metal Ions Using Ionic Liquids: The Challenges of Multiple Mechanisms

Ionic liquids are a distinct sub-set of liquids, comprising only of cations and anions, often with negligible vapor pressure. As a result of the low or non-volatility of these fluids, ionic liquids are often considered in liquid/liquid separation schemes where the goal is to replace volatile organic solvents. Unfortunately, it is often not yet recognized that the ionic nature of these solvents can result in a variety of extraction mechanisms, including solvent ion-pair extraction, ion exchange, and simultaneous combinations of these. This paper discusses current ionic liquid-based separations research where the effects of the nature of the solvent ions, ligands, and metal ion species were studied in order to be able to understand the nature of the challenges in utilizing ionic liquids for practical applications.

Green solvent-based approaches for synthesis of nanomaterials

The use of green solvents (including supercritical fluids and ionic liquids) in the synthesis of nanomaterials is highlighted. The methods described can not only reduce or eliminate the use or generation of substances hazardous to health and the environment, but can also be used to efficiently prepare nanomaterials with high performances. The unique characteristics of green solvents are responsible for the green features and unusual advantages of these approaches.

An effective process for the separation of U(Ⅵ),Th(Ⅳ)from rare earth elements by using ionic liquid Cyphos IL 104

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 104could 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 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 H_(2)SO_(4),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 IL 104 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 contains 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.

Screening ionic liquids for efficiently extracting perfluoroalkyl chemicals (PFACs) from wastewater

Liquid-liquid extraction(LLE)using ionic liquids(ILs)-based methods to remove perfluoroalkyl chemicals(PFACs),such as perfluorooctanoic acid(PFOA)and perfluorooctane sulfonic acid(PFOS),from wastewater,is an important strategy.However,the lack of physicochemical and LLE data limits the selection of the most suitable ILs for the extraction of PFACs.In this work,1763 ILs for PFACs extraction from water were systematically screened using COSMOtherm to estimate the infinite dilution activity coefficient(lnγ^(∞))of PFOA and PFOS in water and ILs.To evaluate the accuracy of COSMOtherm,8 ILs with various lnγ^(∞)values were selected,and their extraction efficiency(E)and distribution coefficient(D_(exp))were measured experimentally.The results showed that the predicted lnγ^(∞)decreased as the increase of experimental extraction efficiency of PFOA or PFOS,while the tendency of predicted distribution coefficient(D_(pre))was consistent with the experimental(D_(exp))results.This work provides an efficient basis for selecting ILs for the extraction of PFACs from wastewater.