Extraction Behaviour of Cyanex‐923 and Cyanex‐471X Towards the Rhodium(III) from Bromide Media and Its Separation from other Platinum Metals

The extraction of Rh(III) from bromide media with Cyanex‐923 and Cyanex‐471X in toluene was studied. The quantitative extraction of Rh(III) with extractants was found by studying the different parameters like, hydrobromic acid concentration, extractant concentration, diluents and effect of temperature on extraction. The optimum condition was [HBr] = 1.0–1.5 moll^?1, [SnCl₂] = 0.2 moll^?1 with [Cyanex‐923] = 0.15 moll^?1, while it was [HBr] = 1.5–2.0 moll^?1, [SnCl₂] = 0.4 moll^?1 with [Cyanex‐471X] = 0.8 moll^?1 in toluene. The quantitative extraction was observed only in the presence of SnCl₂ for both extractants. The complete recovery of Rh(III) from the Cyanex‐923 extracted organic phase was observed with the 1:1 mixture of (4.0 moll^?1 HCl + 2.0 moll^?1 HNO₃), and that with the Cyanex‐471X extracted organic phase was found with 1:1 mixture of (2.0 moll^?1 H₂SO₄ + 1.0 moll^?1 KMnO₄). Stoichiometric ratio of Rh(III) with both extractants was 1:1. The proposed methods were employed for extraction and separation of Rh(III) from other platinum metal ions and also for recovery of Rh(III) from a synthetic solution of spent autocatalysts.     

Extraction of neodymium(III) using binary mixture of Cyanex 272 and Cyanex 921/Cyanex 923 in kerosene

The extraction of Nd(III) using binary mixtures of Cyanex 272 (HA), Cyanex 921/Cyanex 923 (B) in kerosene from nitric acid medium has been investigated. The effect of aqueous phase acidity, extractant concentration, nitrate ion concentration and diluents on the extraction of Nd(III) has been studied. On the basis of slope analysis results, extracted species are proposed as Nd(NO₃)A₂·3HA and Nd(NO₃)₂·A·3HA·B using Cyanex 272 and its mixture with Cyanex 921/Cyanex 923, respectively. With the mixture of 0.1 M Cyanex 272 and 0.1 M Cyanex 923 in kerosene, the extraction of 0.001 M Nd(III) from 0.001 M HNO₃ solution was found to be 83.3 % whereas it was 73.3 % when 0.1 M Cyanex 921 used as synergist under same experimental conditions. The stripping data of Nd(III) from the loaded organic phase containing 0.1 M Cyanex 272 and 0.1 M Cyanex 921/Cyanex 923 with different acids indicated sulphuric acid to be the best stripping agent.     

A green strategy for lithium isotopes separation by using mesoporous silica materials doped with ionic liquids and benzo-15-crown-5

Three new mesoporous silica materials IL15SGs (HF15SG, TF15SG and DF15SG) doped with benzo-15-crown-5 and imidazolium based ionic liquids (C₈mim⁺PF₆ ^?, C₈mim⁺BF₄ ^? or C₈mim⁺NTf ₂ ^? ) have been prepared by a simple approach to separating lithium isotopes. The formed mesoporous structures of silica gels have been confirmed by transmission electron microscopy image and N₂ gas adsorption–desorption isotherm. Imidazolium ionic liquids acted as templates to prepare mesoporous materials, additives to stabilize extractant within silica gel, and synergetic agents to separate the lithium isotopes. Factors such as lithium salt concentration, initial pH, counter anion of lithium salt, extraction time, and temperature on the lithium isotopes separation were examined. Under optimized conditions, the extraction efficiency of HF15SG, TF15SG and DF15SG were found to be 11.43, 10.59 and 13.07 %, respectively. The heavier isotope ⁷Li was concentrated in the solution phase while the lighter isotope ⁶Li was enriched in the gel phase. The solid–liquid extraction maximum single-stage isotopes separation factor of ⁶Li–⁷Li in the solid–liquid extraction was up to 1.046 ± 0.002. X-ray crystal structure analysis indicated that the lithium salt was extracted into the solid phase with crown ether forming [(Li_0.5)₂(B15)₂(H₂O)]⁺ complexes. IL15SGs were also easily regenerated by stripping with 20 mmol L^?1 HCl and reused in the consecutive removal of lithium ion in five cycles.     

Synergistic extraction of rare earths with bis(2,4,4-trimethyl pentyl) dithiophosphinic acid and trialkyl phosphine oxide

Synergistic extraction of trivalent rare earths from nitrate solutions using mixtures of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301=HX) and trialkyl phosphine oxide (Cyanex 923=TRPO) in xylene has been investigated. The results demonstrate that these trivalent metal ions are extracted into xylene as MX(3).3HX with Cyanex 301 alone. In the presence of Cyanex 923, La(III) and Nd(III) are found to be extracted as MX(2).NO(3).TRPO. On the other hand, Eu(III), Y(III) and heavier rare earths are found to be extracted as MX(3).HX.2TRPO. The addition of a trialkylphosphine oxide to the metal extraction system not only enhances the extraction efficiency of these metal ions but also improves the selectivities significantly, especially between yttrium and heavier lanthanides. The separation factors between these metal ions were calculated and compared with that of commercially important extraction systems like di-2-ethylhexyl phosphoric acid.     

Solvent-Impregnated Resins Based on the Mixture of (2-Diphenylphosphoryl)-4-ethylphenoxy)methyl) diphenylphosphine Oxide and Ionic Liquid for Nd(III) Recovery from Nitric Acid Media

Novel solvent-impregnated resins (SIRs) were prepared by treatment of styrene–divinylbenzene copolymer (LPS-500) with mixtures of the promising polydentante extractant (2-diphenylphosphoryl)-4-ethylphenoxy)methyl)diphenylphosphine oxide (L) and an ionic liquid [C₄mim]⁺[Tf₂N]⁻for the extraction chromatography recovery of Nd(III) from nitric acid solutions. It was shown that introduction of the ionic liquid into the SIR composition results in considerable enhancement of the Nd(III) recovery efficiency compared with resin impregnated only by L in slightly acidic media. The influence of the L: ionic liquid molar ratio in the SIRs composition, their percentages, concentration of metal and HNO₃ in the eluent, and acid type on the value of synergistic effect and adsorption efficiency of Nd(III) recovery was studied. The SIR containing 40% of mixture of L and [C₄mim]⁺[Tf₂N]⁻ with molar ratio 2:1 turned out to be the most efficient. The selectivity of Nd(III) separation from light and heavy rare-earth elements was studied and the optimal conditions of Nd(III) adsorption recovery and stripping by this SIR were chosen. It was found that in recovery efficiency of Nd(III) developed SIR exceeded the SIR containing Cyanex 923 (a mixture of monodentate trialkylphosphine oxides) and [C₄mim]⁺[Tf₂N]⁻.     

Liquid-liquid extraction and recovery of indium using Cyanex 923

The extraction of In(III) from HCl, H₂SO₄, and HNO₃ media using a 0.20 mol l⁻¹ Cyanex 923 solution in toluene is investigated. In(III) is quantitatively extracted over a fairly wide range of HCl molarity while from H₂SO₄ and HNO₃ media the extraction is quantitative at low acid concentration. The extracted metal ion has been recovered by stripping with 1.0 mol l⁻¹ H₂SO₄. The stoichiometry of the In(III): Cyanex 923 complex is observed to be 1:2. The extraction of In(III) is insignificantly changed in diluents namely toluene, n-hexane, kerosene (160-200 °C), cyclohexane, and xylene having more or less the same dielectric constants, whereas, it decreases with increasing polarity of diluents such as cyclohexanone and chloroform. The extractant is stable towards prolonged acid contact and there is a negligible loss in its extraction efficiency even after recycling for 20 times. The extraction behavior of some commonly associated metal ions namely V(IV), Ti(IV), Al(III), Cr(III), Fe(III), Ga(III), Sb(III), Tl(III), Mn(II), Fe(II), Cu(II), Zn(II), Cd(II), Pb(II), and Tl(I) has also been investigated. Based on the partition data the conditions have been identified for attaining some binary separations of In(III). These conditions are extended for the recovery of pure indium from zinc blend, zinc plating mud, and galena. The recovery of the metal ions is around 95% with purity approximately 99%.     

New ionic liquid for inorganic cations analysis by capillary electrophoresis: 2-hydroxy- N , N , N -trimethyl-1-phenylethanaminium bis(trifluoromethylsulfonyl)imide (phenylcholine NTf2)

The potentialities of new ionic liquids (ILs) based on choline were evaluated as an electrophoretic medium in capillary electrophoresis for the analysis of alkaline and alkaline earth cations (Li⁺, K⁺, Na⁺, Cs⁺, Mg²⁺, Ba²⁺, Ca²⁺, and Sr²⁺) with indirect UV detection. Two types of capillaries were tested: an untreated fused silica and fused silica coated with a film of polyvinylalcohol. The coated capillary proved to be the best adapted for the metal ions studied. Moreover, it appeared that the nature of the ionic liquid anion influenced the baseline stability, and the bis(trifluoromethylsulfonyl) imide (NTf₂ ⁻) anion seemed to be the most efficient. These preliminary studies led us to synthesize a new ionic liquid, 2-hydroxy-N,N,N-trimethyl-1-phenylethanaminium NTf₂ (phenylcholine NTf₂). This liquid was able to act as the running electrolyte and probe, generating the background signal in indirect UV light and consequently simplifying the electrophoretic medium. Excellent baseline stability, good reproducibility, as well as good sensitivity of detection were obtained with this new ionic liquid. Thus, 510,000 plates/meter for Li⁺ with 40 mM IL were successfully obtained. The optimal concentration of IL was 20 mM with a detection limit ranging from 28 μg L⁻¹ for Li⁺ to 1,000 μg L⁻¹ for Cs⁺. This method (phenylcholine NTf₂ with polyvinylalcohol capillary) was applied to analyze different commercial source and mineral waters. Finally, the potentiality of this ionic liquid in nonaqueous capillary electrophoresis was explored. The use of phenylcholine NTf₂ with a fused silica capillary, in pure methanol medium and in the presence of acetic acid, made it possible to obtain separation selectivity different from that obtained in aqueous medium.     

The preparation of supported ionic liquids (SILs) and their application in rare metals separation

This review summarizes the preparation methods of support ionic liquids (SILs) and their applications in rare metals separation. The rare metals separation includes the recovery of high value metal ions and the removal of heavy metal ions from wastewater. SILs can be used as a kind of highly efficient multifunctional separation materials. The preparation methods of SILs include chemical immobilization technique in which ILs moieties are supported on solid supports via covalent bonds and physical immobilization techniques in which ILs are immobilized on solid supports via physical method such as simple im- pregnation, sol-gel method. According to the difference of solid supports, this review summarizes the application of polymer supported ionic liquids (P-SILs), silica based material supported ionic liquids (SM-SILs) and membrane supported ionic liq- uids (M-SILs) in rare metals separation. P-SILs and SM-SILs prepared by chemical method with N-methylimidazolium group can be used as highly efficient anion exchangers with high thermal stability and good chemical stability for adsorption of Cr(VI), Re(VII), Ce(IV). P-SILs prepared via simple impregnation afforded IL functionalized solvent impregnated resins (SIRs) which showed high separation efficiency and selectivity in the separation of rare earths(III) (REs(III)). SM-SILs prepared via sol-gel method with IL doped in the support as porogens or extractant show high removal efficiencies and excellent stability for the separation of RE(III), Cr(III) and Cr(VI). M-SILs with IL as plasticizer or carrier show improved stability, high perme- ability coefficient and good selectivity for Cr(VI) transport. Different supports and different supporting methods were suffi- ciently compared. Based on the different practical application, different forms of SILs can be prepared for separation of rare metals with high separation efficiency and selectivity.     

On-line solid phase extraction coupled to ICP-OES for simultaneous preconcentration and determination of some transition elements

An on-line solid phase extraction method coupled to ICP-OES was developed for the simultaneous determination of Ce(III), La(III), Sm(III), Y(III), Yb(III), Dy(III), Hf(IV), Zr(IV) and Th(IV) ions in aqueous samples. The ions forming hydrophobic complexes with 3,5,7,2?,4?-pentahydroxy flavone (morin) and were retained on an octadecyl silica (C₁₈) minicolumn. The adsorbed chelates were subsequently eluted from the column and directly transferred into the plasma with 80% (v/v) propanol:H₂O solution for the simultaneous determination of the metal ions. Different parameters affecting the ICP-OES signal intensities and extraction efficiency including pH of the solution, concentration of the chelating agent, flow rate and type of the eluent, loading rate and ionic strength were evaluated and optimized. The calibration graphs were linear in the range of 0.2–100 μg L^?1 and limit of detections for the extraction and determination of the ions in the aqueous sample (25 mL) were in the range 0.10–0.46 μg L^?1. The enhancement factors of the method for the metal ions obtained were in the range of 23 to 242 (V _Sample?=?25 mL) and the precision expressed as relative standard deviations (RSD %) was below 6.9%. Finally, the method was successfully applied to determine the target analytes in natural water samples.     

Continuous Transport of Zn(II) by Ammonium Chloride Media via Supported Liquid Membrane System

With the gradual depletion of traditional zinc resources, the full use of various non-traditional zinc-containing resources has received intensive attention. However, the efficient recovery of zinc ions with low concentrations remains challenging. Here efficient and continuous recovery of zinc ions in ammoniacal chloride media by a flat supported liquid membrane system is achieved, using Cyanex923 and TBP mixed extractant as the membrane phase. This article discusses the synergistic effect between Aliquat336, Cyanex923 and TBP, the effects of feed pH, total ammonia concentration, Cl⁻ concentration and temperature on Zn(II) transport.     

Lithium,rubidium and cesium ion removal using potassium iron(III) hexacyanoferrate(II) supported on polymethylmethacrylate

Potassium iron(III) hexacyanoferrate(II) supported on poly methyl methacrylate, has been developed and investigated for the removal of lithium, rubidium and cesium ions. The material is capable of sorbing maximum quantities of these ions from 5.0, 2.5 and 4.5 M HNO₃ solutions respectively. Sorption studies, conducted individually for each metal ion, under optimized conditions, demonstrated that it was predominantly physisorption in the case of lithium ion while shifting to chemisorption with increasing ionic size. Distribution coefficient (K _d) values followed the order Cs⁺ > Rb⁺ > Li⁺ at low concentrations of metal ions. Following these findings Cs⁺ can preferably be removed from 1.5 to 5 M HNO₃ nuclear waste solutions.     

Study of adsorption and preconcentration by using a new silica organomodified with [3‐(2,2′‐dipyridylamine)propyl] groups

In this work, a silica surface chemically modified with [3‐(2,2′‐dipyridylamine)propyl] groups, named [3‐(2,2′‐dipyridylamine)propyl]silica (Si‐Pr‐DPA) was prepared, characterized, and evaluated for its heavy metal adsorption characteristics from aqueous solution. To our knowledge, we are the first authors who have reported the present modification. The material was characterized using infrared spectroscopy, SEM, and NMR ²⁹Si and ¹³C solid state. Batch and column experiments were conducted to investigate for heavy metal removal from dilute aqueous solution by sorption onto Si‐Pr‐DPA. From a number of studies the affinity of various metal ions for the Si‐Pr‐DPA sorbent was determined to follow the order Fe(III) > Cr(III) >> Cu(II) > Cd(II) > Pb(II) > Ni(II). Two standard reference materials were used for checking the accuracy and precision of the method. The proposed method was successfully applied to the analysis of environmental samples. This ligand material has great advantage for adsorption of transition‐metal ions from aqueous medium due to its high degree of organofunctionalization associated with the large adsorption capacity, reutilization possibility, and rapidity in reaching the equilibrium.     

Preparation of Cyanex 272-containing silica composite by sol–gel method for neodymium adsorption

A kind of silica composite containing bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) was prepared via a in situ sol–gel approach. ³¹P solid-state NMR and FT–IR spectra were employed to analyze the structure of the composite. The thermal stability and surface properties were characterized, and the adsorption ability towards trivalent neodymium (Nd(III)) was evaluated by batch experiments. The Cyanex 272 loaded silica composite showed the advantage of an effective adsorption of Nd(III) from low acidic or neutral solutions with a capacity of ~50 mg/g. The influence of contact time, acidity and initial metal concentration of the stock solutions on the adsorption were comprehensively investigated.     

Adsorption of Cd(II) by Sol-Gel Silica Doped with N-(dipropylcarbamothioyl)thiophene-2-carboxamide

Sol-gel silica was doped with N,N-(dipropylcarbamothioyl) thiophene-2-carboxamide to investigate the sorption of cadmium (Cd) ions from aqueous media. In doped sol-gel silica, the large reagent molecules entrap into pores, whereas, small metal ions diffuse into pores where they make complex with doped reagent. This complexation can be accomplished by either ion exchange or chelation. Doped sol-gel sorbent was applied for removal of Cd(II) from aqueous solution in our study. Adsorption kinetics, adsorption isotherm, equilibration time, effect of initial concentration of adsorbate, and pH effect on the metal removal were studied to optimize the conditions. The prepared adsorbent shows rapid equilibrium and high stability toward high temperature and applied medium. In addition, desorption of metal ions was carried out by 1 M HCl and, thereafter, sol-gel silica adsorbent was regenerated and reused periodically.     

Removal of 63Ni and 57Co from aqueous solution using antimony doped tin dioxide–polyacrylonitrile (Sb doped SnO2–PAN) composite ion-exchangers

Tin dioxide and its antimony doped counterpart were synthesized using traditional sol–gel procedure. The metal oxides were then turned into composites by mixing them with polyacrylonitrile (PAN) and composite spheres ready for use in traditional column applications were obtained. The characterization of materials was investigated by X-ray diffraction, scanning electron microscopy–energy dispersive X-ray, surface area, point of zero charge and thermal analyses. Static batch experiments showed that the antimony doped tin dioxide–PAN (Sb doped SnO₂–PAN) is an effective material for nickel removal and the composite maintains its good metal uptake properties in dynamic column conditions. The composite showed a high nickel uptake capacity of 9 mmol/g in 0.1 M NaNO₃ solution. It was observed that the ion exchange kinetics of antimony doped tin dioxide (Sb doped SnO₂) was remarkably fast for ⁵⁷Co and ⁶³Ni ions but turning the material into PAN composite significantly decreased the materials kinetic properties.     

氧化铝对稀土有机配合物掺杂溶胶凝胶玻璃结构及发光性能的影响

Both silica glass materials singly doped with rare earth organic complex and co-doped with Al^3 were prepared by in situ sol-gel method respectively. XRD and SEM measurements were performed to verify the non-crystalline structure of the glass. The excitation spectra, emission spectra and IR spectra were measured to analyze the influence of the glass contents on the structure of the glass and the energy level of the doped Eu(IH) ions. The effect of Al^3 on the photoluminescence properties of rare earth organic complex in silica glass was investigated. The IR spectra indicated that the in situ synthesized europium complex molecule was confined to the micropores of the host and the vibration of the ligands was frozen. When Al2O3 was doped into the silica host gel, the rare earth ions in the silica network were wrapped up and dispersed by Al2O3, so the distribution of Eu(Ⅲ) complex in the host was morehomogeneous, and the luminescence intensity of ^5D0-^7F2 transition emission of the Eu^3 ions was improved. The results showed that an appropriate amount of Al^3 added to the gel glass improved the emission intensity of the complex in the silica glass, and when the content of Al2O3 reached 4 mol%, the maximum emission intensity could be obtained compared with that of other samples containing different Al2O3 contents.     

Phase‐ and Size‐Controllable Synthesis of Hexagonal Upconversion Rare‐Earth Fluoride Nanocrystals through an Oleic Acid/Ionic Liquid Two‐Phase System

Herein, we introduce a facile, user‐ and environmentally friendly (n‐octanol‐induced) oleic acid (OA)/ionic liquid (IL) two‐phase system for the phase‐ and size‐controllable synthesis of water‐soluble hexagonal rare earth (RE=La, Gd, and Y) fluoride nanocrystals with uniform morphologies (mainly spheres and elongated particles) and small sizes (<50 nm). The unique role of the IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BmimPF₆) and n‐octanol in modulating the phase structure and particle size are discussed in detail. More importantly, the mechanism of the (n‐octanol‐induced) OA/IL two‐phase system, the formation of the RE fluoride nanocrystals, and the distinctive size‐ and morphology‐controlling capacity of the system are presented. BmimPF₆ is versatile in term of crystal‐phase manipulation, size and shape maintenance, and providing water solubility in a one‐step reaction. The luminescent properties of Er³⁺‐, Ho³⁺‐, and Tm³⁺‐doped LaF₃, NaGdF₄, and NaYF₄ nanocrystals were also studied. It is worth noting that the as‐prepared products can be directly dispersed in water due to the hydrophilic property of Bmim⁺ (cationic part of the IL) as a capping agent. This advantageous feature has made the IL‐capped products favorable in facile surface modifications, such as the classic Stober method. Finally, the cytotoxicity evaluation of NaYF₄:Yb,Er nanocrystals before and after silica coating was conducted for further biological applications.     

A new photoluminescent silica aerogel based on N-hydroxysuccinimide–Tb(III) complex

The paper describes the preparation of a new photoluminescent silica aerogel by embedding a new Tb(III) complex in a silica matrix by using N-hydroxysuccinimide as ligand. The Tb(III) complex prepared at a metal to ligand ratio of 1:3 (mol%) exhibits strong photoluminescence as a result of specific radiative transitions within the Tb(III) cation with the most intense peak located at 543 nm due to ⁵D₄ → ⁷F₅ transition. The synthesized complex was doped in the silica matrix through a catalyzed sol–gel process. After ageing in ethanol, the alcogel was dried under supercritical regime by exchanging the ethanol with liquid carbon dioxide followed by supercritical evaporation. The leaching of the free complex from the alcogel during ageing and solvent exchange phases was found to be minimal most likely due to the interactions between chemical groups of complex with those specific to silica matrix. The obtained regular shaped monolithic aerogel preserved the remarkable photoluminescent properties and also improved the thermal stability of the free complex. Both, the free complex and doped aerogel were characterized through thermal analysis, FT-IR, powder X-ray diffraction, Scanning electron microscopy and fluorescence spectroscopy. For comparison purposes, an undoped silica aerogel was also prepared and investigated through FT-IR, BET analysis and powder X-ray diffraction. The excellent photoluminescent properties might recommend the prepared aerogel for applications in optoelectronic devices where photonic conversion materials are required.     

Task-specific ionic liquid tetraalkylammonium hydrogen phthalate as an extractant for U(VI) extraction from aqueous media

In this paper a quaternary ammonium based room temperature ionic liquid (IL) trioctylmethylammonium hydrogen phthalate has been reported as promising extractant for separation of U(VI) from other metal ions from aqueous media. The IL was synthesized via metathesis route and characterized using various techniques such as hydrogen nuclear magnetic resonance, electron spray ionization mass spectrometry and infra red etc. The newly synthesized IL was evaluated for extraction of U(VI), Th(IV), La(III), Y(III), Nd(III) and Fe(III) from aqueous solutions and follow the order: U(VI) > Th(IV) > Fe(III) > Y(III) >> Nd(III) ~ La(III).     

Separation of no-carrier-added 109Cd from natural silver target using RTIL 1-butyl-3-methylimidazolium hexafluorophosphate

The room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] has various applications in the separation of a range of metal ions replacing volatile and toxic traditional organic solvents in liquid–liquid extraction systems. In this study, the RTIL [C₄mim][PF₆] was used to separate no-carrier-added (NCA) ¹⁰⁹Cd from α-particle irradiated Ag target. A natural Ag foil was bombarded by 30 MeV α-particles to produce ¹⁰⁹Cd. After the decay of all co-produced short-lived products, NCA ¹⁰⁹Cd was separated from the bulk Ag using [C₄mim][PF₆] as extractant from HNO₃ medium. Ammoniumpyrrolidine dithiocarbamate (APDC) was used as a complexing agent. At the optimum condition, 3 M HNO₃, 0.01 M APDC in presence of [C₄mim][PF₆], ~99 % bulk Ag was extracted to the IL phase, leaving NCA ¹⁰⁹Cd in the aqueous phase. The amount of Ag became negligibly small after re-extraction in the same condition. The ionic liquid was recovered by washing it with 1 M HCl.