Chromatographic separation of rare earths from aqueous and ethanolic leachates of NdFeB and SmCo magnets by a supported ionic liquid phase

The separation of rare-earth elements (REEs) from other components of end-of-life NdFeB and SmCo magnets was investigated by column chromatography. A carboxylic-acid functionalized supported ionic liquid phase (SILP) was studied as a stationary phase. The magnets were firstly leached with a dilute aqueous or ethanolic hydrochloric acid solution at room temperature. Leaching of REEs from a NdFeB magnet was similarly efficient with both lixiviants, but the REEs were more efficiently leached from a SmCo magnet with the ethanolic lixiviant. The SILP exhibited a high affinity towards trivalent cations of REEs, which were successfully recovered from the aqueous and ethanolic leachates of magnets. Divalent cations of iron and cobalt, which were the major components of the acidic aqueous leachates of magnets, were rejected by the SILP. Iron and cobalt were present as negatively charged chloro complexes in the ethanolic leachates of magnets, and were not recovered by the cation-exchanging SILP. A versatile column chromatography method is developed, suitable for the separation of REEs from iron and cobalt, either from aqueous or ethanolic leachates of permanent magnets.

Chromatographic separation of rare earths, iron and cobalt from the aqueous and ethanolic leachates of NdFeB and SmCo magnets.     

Solvent extraction of rare earths elements from nitrate media in DMDOHEMA/ionic liquid systems: performance and mechanism studies

Extraction of La(iii), Eu(iii) and Fe(iii) was compared in n-dodecane and two ionic liquids (ILs) (1-ethyl-1-butylpiperidinium bis (trifluoromethylsulfonyl)imide [EBPip⁺] [NTf₂⁻] and 1-ethyl-1-octylpiperidinium bis (trifluoromethylsulfonyl)imide [EOPip⁺] [NTf₂⁻]). Using the extractant N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide (DMDOHEMA), the effect of pH was investigated in detail to recover extraction mechanisms. The use of ILs as the organic solvent instead of n-dodecane, greatly enhances extraction efficiency, and an ionic liquid with a shorter alkyl chain [EBPip⁺] [NTf₂⁻] provides higher extraction than [EOPip⁺] [NTf₂⁻]. The mechanistic study points out that for low nitric acid concentrations ([HNO₃] ≤ 0.01 M), metal is extracted via a cation of the ionic liquids, while for higher nitric acid concentrations ([HNO₃] ≥ 1.0 M), extraction occurs through pure solvation mechanism of DMDOHEMA as in conventional diluents. This latter case is of high interest for applications, as higher extraction can be obtained without any loss of ILs by ion exchange mechanisms.

Extraction of La(iii), Eu(iii) and Fe(iii) was compared in n-dodecane and in two ionic liquids (ILs) [EBPip⁺] [NTf₂⁻] and [EOPip⁺] [NTf₂⁻]. Extraction mechanisms have been investigated as a function of pH.     

Split-anion solvent extraction of light rare earths from concentrated chloride aqueous solutions to nitrate organic ionic liquids

Despite its benefits, the extraction of rare earths (REEs) from chloride solutions with neutral or basic extractants is not efficient, so that separation is currently carried out by using acidic extractants. This work aims to improve this process by replacing the conventional molecular diluents in the organic phase by ionic liquids (ILs) which contain coordinating anions. The extraction of La(iii), Ce(iii) and Pr(iii) from concentrated chloride solutions was tested with a quaternary ammonium and a phosphonium nitrate IL extractant. Dissolution of a trialkylphosphine oxide neutral extractant (Cyanex 923) in the nitrate ILs changed the preference of the organic phase from lighter to heavier REE and increased the overall extraction efficiency and the loading capacity of the organic phase. An increase of the CaCl₂ concentration in the feed solution resulted in higher extraction efficiencies, due to a lower activity of water and hence to a poorer hydration of the REE ions. In that respect, chloride ions were not coordinating to the REE ion after extraction from concentrated chloride solutions. To achieve selectivity, one should fine-tune the loading by varying the CaCl₂ and/or Cyanex 923 concentrations. Adjustment of the CaCl₂ concentration in the feed and stripping solutions is essential for the separation of mixtures of REE. However, and unlike in the case of acidic extractants, no control of equilibrium pH is required. The split-anion extraction offers the possibility to separate mixtures of REEs in different groups without having to change the chloride feed solution. It leads to safer and environmentally friendlier extraction processes by (1) using solvents that are not volatile, not flammable and do no accumulate static electricity, (2) consuming no acids or alkali, (3) easy stripping with water and (4) avoidance to create nitrate-containing effluents.

Rare earths are extracted efficiently by nitrate ionic liquids from a chloride feed solution.     

Performance of butanol separation from ABE mixtures by pervaporation using silicone-coated ionic liquid gel membranes

This work aims at the separation of n-butanol from aqueous solutions by means of pervaporation using membranes based on gelled ionic liquids (IL). These membranes were mechanically stabilized with a double silicone coating using two polydimethylsiloxane (PDMS) films. The first step of the membrane preparation considered the formation of a gelled ionic liquid layer, which was formed using two different imidazolium-based ionic liquids: [omim][Tf₂N] and [bmim][Tf₂N], and two different phosphonium-based ionic liquids: [P_6,6,6,14][Tf₂N] and [P_6,6,6,14][DCA]. The gelation procedure was carried out on a porous paper support using a low molecular weight gelator. The membranes obtained from this method were tested in pervaporation assays to separate butanol from model ABE (Acetone–Butanol–Ethanol) fermentation solutions. These assays were done in an experimental setup especially built for this purpose. The pervaporation performance of these ionic liquid-based membranes was compared to that obtained with a single PDMS layer membrane. From these experimental results, butanol/water selectivity for [P_6,6,6,14][Tf₂N]-based membranes reached a value equal to 892, which is 150 times higher than the value obtained for a single PDMS layer membrane. Simultaneously, for the same IL, the transmembrane fluxes (kg h⁻¹ m⁻²) of butanol and water were 37% and 99.6% lower than the values obtained using a single PDMS layer membrane, respectively. The hydrophobic character of the selected ionic liquid and its relatively high values for the transport parameters can explain this experimental response.

This work aims at the separation of n-butanol from aqueous solutions by means of pervaporation using membranes based on gelled ionic liquids (IL).     

Correction: Split-anion solvent extraction of light rare earths from concentrated chloride aqueous solutions to nitrate organic ionic liquids

Correction for ‘Split-anion solvent extraction of light rare earths from concentrated chloride aqueous solutions to nitrate organic ionic liquids’ by Mercedes Regadío et al., RSC Adv., 2018, 8, 34754–34763, DOI: 10.1039/c8ra06055j.

The authors regret that an incorrect figure caption was given for Fig. 5. The correct version is presented below.Open in a separate windowFig. 5Viscosity as a function of the temperature and the organic phase composition: (1) after loading 39 g L⁻¹ of REE in 20 v% Cy923 in [C101][NO₃], (2) pure [C101][NO₃], (3) 20 v% Cy923 in [C101][NO₃] and (4) pure Cy923.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Palladium nanoparticles on a pyridinium supported ionic liquid phase: a recyclable and low-leaching palladium catalyst for aminocarbonylation reactions

A new SILP (Supported Ionic Liquid Phase) palladium catalyst was prepared and characterized by ¹³C and ²⁹Si CP MAS NMR, DTG, FTIR and TEM. The presence of the grafted pyridinium cations on the surface of the support was found to result in the formation of highly dispersed Pd nanoparticles with their diameter in the range of 1–2 nm. The catalyst was proved to be active not only in the aminocarbonylation of some model compounds but also in the synthesis of active pharmaceutical ingredients. Catalyst recycling and palladium leaching studies were carried out for the first time in aminocarbonylations leading to CX-546(1-(1,4-benzodioxan-6-ylcarbonyl)piperidine), Moclobemide, Nikethamide and a precursor of Finasteride. The latter reaction proves that not only aryl iodides but also an iodoalkene can be converted into the products with the help of the heterogeneous catalyst. The results show that the conditions should be always fine-tuned in the reactions of different substrates to achieve optimal results. Palladium loss was also observed to depend considerably on the nature of the reaction partners.

SILP catalyst with grafted pyridinium ions was used for either mono- or double carbonylation depending on the reaction conditions. Good recyclability and low palladium loss were observed during the synthesis of pharmaceutically active compounds.     

Efficient and controllable ultrasound-assisted depolymerization of organosolv lignin catalyzed to liquid fuels by MCM-41 supported phosphotungstic acid

In this study, effects of catalyst types, reaction temperatures, reaction times, reaction solvents and ultrasound frequencies were carefully investigated to improve the yields and characteristics of various depolymerization products of organosolv lignin. Generally, both catalyst types and ultrasound frequencies played important roles in promoting lignin depolymerization and reducing char yield. In particular, the yield and distribution of phenolic monomer (PM) products were greatly influenced by pore structure and acidity of the catalyst. The optimal reaction condition was got in isopropanol at 310 °C for 6 h with 30% ultrasound frequency and 50% phosphotungstic acid (PTA)/MCM-41 catalyst. The highest yields of PM, bio-oil, liquid fuels and lignin conversion were reached as 8.63 wt%, 86.89 wt%, 95.52 wt% and 98.54 wt%, respectively. The results showed that ultrasound acoustic cavitation could enhance the depolymerization of lignin, thus greatly enhancing production of liquid fuels. Simultaneously, the hydrogen composition and high heating value of various lignin depolymerization products improved, and the oxygen content decreased, indicating that hydrogenation and/or hydrodeoxygenation happened during the depolymerization process. Finally, we also found that the 50% PTA/MCM-41 catalyst had high stability; it could be reused for up to five cycles without loss of catalytic activity.

Lignin was subjected to different contents of PTA/MCM-41-catalyzed ultrasound-assisted depolymerization for efficient β-O-4 aryl ether bond cleavage to achieve efficient liquid fuel yields.     

Efficient immobilization of ionic corrosion products by a silica-hydroxyapatite composite via a cold sintering route

We have successfully demonstrated a new method of radioactive waste immobilization by hosting a waste-bearing form in another waste matrix. A cold sintering route was used to consolidate a silica-incorporated hydroxyapatite (Si-HAp) composite at 200 °C by applying a uniaxial pressure of 500 MPa for a short holding time of 10 min. The higher relative sintered density of up to 98.0 ± 1.3% was achieved by 25 wt% Si loaded HAp. Results from high resolution X-ray diffraction, micro-hardness, and high resolution scanning electron microscopy confirmed the densification with good mechanical strength (micro-hardness = 2.9 ± 0.3 GPa). For practical applications, two kinds of wastes (25 wt% ionic corrosion product-sorbed EDTA functionalized mesoporous silica and 75 wt% ionic corrosion product-sorbed HAp) were mixed, consolidated and tested. The chemical stability of the solidified composite matrix was positively assessed for low leaching rates of 5.9 × 10⁻⁹ to 1.2 × 10⁻⁵ g per m² per day using a standard product consistency test. The consolidated composite can bear compressive stress up to 358 MPa, which is orders of magnitude higher than the waste acceptance criteria of 3.5 MPa. The low process temperature can make this sintering process very powerful for the immobilization of radionuclides with volatility and low boiling point. Such a low temperature solidified matrix hosting various wastes may be a promising path for waste management because of its simplicity, reliability, scalability, cost effectiveness and environmental friendliness.

We have successfully demonstrated a new method of radioactive waste immobilization by hosting a waste-bearing form in another waste matrix.     

Tuning the Biginelli reaction mechanism by the ionic liquid effect: the combined role of supported heteropolyacid derivatives and acidic strength

Herein, a combination of heteropolyacids and ionic liquids as a catalytic system was studied for the Biginelli multicomponent reaction; the positive ionic liquid effect associated with the acidic strength of zeolite-supported heteropolyacids made this combination an efficient catalytic system for the multicomponent synthesis of 3,4-dihydropyrimidin-2(1H)-one/thione derivatives. The acidic strength effect was evaluated, and a range was determined in which the reaction provided better results. The mechanism of the reaction was also investigated in the presence and absence of ionic liquids, and two features of paramount importance were revealed: the mechanism could be tuned to proceed through only one reaction path among three possibilities and the kinetics of the reaction was significantly faster in the presence of an ionic liquid.

Heteropolyacids and ionic liquid effect allowed tuning of the Biginelli reaction mechanism and synthesis of 3,4-dihydropyrimidin-2(1H)-one/thione derivatives in an efficient, recyclable fashion. The role of acidic strength and supported heteropolyacid is disclosed.     

Controlling the oxidation state of molybdenum oxide nanoparticles prepared by ionic liquid/metal sputtering to enhance plasmon-induced charge separation

Nanoparticles composed of molybdenum oxide, MoO_x, were successfully prepared by room-temperature ionic liquid (RTIL)/metal sputtering followed by heat treatment. Hydroxyl groups in RTIL molecules retarded the coalescence between MoO_x NPs during heat treatment at 473 K in air, while the oxidation state of Mo species in MoO_x nanoparticles (NPs) could be modified by changing the heat treatment time. An LSPR peak was observed at 840 nm in the near-IR region for MoO_x NPs of 55 nm or larger in size that were annealed in a hydroxyl-functionalized RTIL. Photoexcitation of the LSPR peak of MoO_x NPs induced electron transfer from NPs to ITO electrodes.

MoO_x NPs, prepared by sputtering Mo metal on a room-temperature ionic liquid (RTIL) followed by heating in air, produced anodic photocurrents with the excitation of their LSPR peak.     

Correction: Gold nanoparticles supported on supramolecular ionic liquid grafted graphene: a bifunctional catalyst for the selective aerobic oxidation of alcohols

Correction for ‘Gold nanoparticles supported on supramolecular ionic liquid grafted graphene: a bifunctional catalyst for the selective aerobic oxidation of alcohols’ by Mojtaba Mahyari et al., RSC Adv., 2013, 3, 22509–22517, DOI: 10.1039/C3RA44696D.

The authors regret that Fig. 6A was re-used from an article published in the Journal of Power Sources¹ without being cited and without permission from the publisher to reproduce the image.The authors have now received the permission to reuse the image and the corrected caption is shown below:Fig. 6 HR-TEM images of graphene oxide (A), and Au NP@SIL-g-G (B). (a). Reproduced from Hadi Hosseini et al., with permission from Elsevier, 2014.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Clinical impact of molecular identification of rare yeasts and nonsporulating molds recovered in culture from clinical specimens

Uncommon fungi can cause opportunistic infections and are often unidentifiable using phenotypic methods. Molecular techniques, like DNA sequencing, may permit species-level identification but results may be challenging to interpret. To determine the clinical impact of molecular identification in this setting, we performed a retrospective review of fungal isolates referred for molecular identification. Seventy-five distinct fungal species were identified from 93 referred isolates, 31 (41%) of which are not known to be human pathogens. DNA sequencing prompted change in anti-infective therapy in only 3 (3.5%) cases but significantly delayed culture turnaround time (40 ± 31 vs. 30 ± 13 days, P < 0.001). Patient immune status and concurrent histologic or serologic testing significantly correlated with the proportion of pathogenic isolates recovered and patients treated (χ², P < 0.05). Molecular identification of uncommon fungal isolates should be limited to specialized clinical settings such as patients with immunosuppression and/or concurrent positive histology or fungal serology.     

Self-assembly of a short-chain ionic liquid within deep eutectic solvents

Ionic liquids (ILs) and deep eutectic solvents (DESs) are receiving increased attention from both academic and industrial research due to their immense application potential. These designer solvents are environmentally friendly in nature with tunable physicochemical properties. In the present investigation, we have studied the aggregation behavior of a short-chain IL 1-butyl-3-methylimidazolium octylsulphate [Bmim][OS] within aqueous DESs using fluorescence, UV-vis, dynamic light scattering (DLS) and FT-IR spectroscopic techniques. We have prepared two DESs, ChCl–urea and ChCl–Gly, which are obtained by heating a mixture of an ammonium salt choline chloride with hydrogen bond donor urea or glycerol, respectively, in 1 : 2 molar ratios. The local microenvironment and size of the aggregates are obtained from steady state fluorescence (using pyrene and pyrene-1-carboxaldehyde as polarity probes) and DLS measurements, respectively. DLS results shows that IL [Bmim][OS] forms relatively larger micelles within the aqueous solution of DES ChCl–urea (avg. hydrodynamic radii = 209 nm) than compared to ChCl–Gly (avg. hydrodynamic radii = 135 nm). A significant decrease in the critical micelle concentration and increase in the aggregation number (N_agg) are observed within DES solutions as compared to that in water, thus indicating that the micellization process of the IL [Bmim][OS] is much favored in the DES solutions. Molecular interactions of [Bmim][OS] in DESs are revealed from FT-IR spectroscopic investigation. Furthermore, these systems were applied to study the IL-drug binding of the antidepressant drug promazine hydrochloride (PH).

Self-assembly of short-chain imidazolium-based ILs within DESs have been investigated by fluorescence, UV-Vis, DLS and FT-IR spectroscopy. Further, these micellar systems [Bmim][OS]-DESs are utilized to study the IL-drug binding of an antidepressant drug (PH).     

Isocratic separation of ATP and its degradation products from biological fluids by automated liquid chromatography

Two groups of metabolites (a) IMP, AMP, ADP, ATP, and cAMP in extracts of fibroblasts and erythrocytes and (b) hypoxanthine, xanthine, adenosine, and inosine in plasma and urine have been separated by ion-pairing reversed-phase chromatography on a microBondapak C18 column, with use of the following reagents: 60 mmol/L KH2PO4, 0.45 mmol/L tetrabutylammonium phosphate, and 1.26 mol/L acetonitrile, pH 3.2 (at 23 degrees C) (group a) and 20 mmol/L KH2PO4, 0.45 mmol/L tetrabutylammonium phosphate, and 0.35 mol/L acetonitrile, pH 2.70 (at 24 degrees C) (group b). Under both sets of conditions, the compounds are completely separated in less than 15 min. The separation is isocratic, so the method is easily adaptable to automation.     

Adsorption of arsenic from aqueous solution using a zero-valent iron material modified by the ionic liquid [Hmim]SbF6

The environmental and health impacts caused by arsenic (As) in wastewater make it necessary to carefully manage As wastes. In the present work, a composite of the ionic liquid [Hmim]SbF₆ and nano-iron (H/Fe) was used as an adsorbent to remove As(v) from aqueous solution. To better understand the removal effect of H/Fe on As(v) in aqueous solution, the reaction parameters of pH, reaction temperature, time and H/Fe dosage were systematically analyzed in detail. The results show that H/Fe has significant removal efficiency toward As(v), and that the adsorption of As(v) by 0.5 g H/Fe reaches its maximum adsorption capacity within 2 h. The adsorption of As(v) on H/Fe is a non-linear, time-varying process. The initial adsorption reaction is fast; however, unlike at the beginning, the later reaction involves sustained slow absorption, resulting in a distinct two-phase adsorption characteristic. Redox reaction may be one of the mechanisms responsible for the slow adsorption of As(v) on H/Fe. At the same time, the As(v) removal effect of H/Fe is greatly restricted by the pH. Electrostatic adsorption, adsorption co-precipitation and redox reactions act together on H/Fe in the As(v) removal process. This study provides a basis for further clarifying the adsorption, adsorption rules and mechanism of As(v) on H/Fe and a feasible method for the improvement of As(v) removal efficiency of zero-valent iron materials.

The environmental and health impacts caused by arsenic (As) in wastewater make it necessary to carefully manage As wastes.     

Fractionation of plasma recovered from blood collected by metered anticoagulation

This study investigated some possible explanations for the observations that, compared with plasma conventionally recovered from whole blood, plasma collected by automated apheresis gives a higher yield of factor VIII but also a higher incidence of activated factor IX concentrate. Platelet-poor plasma (PPP) was obtained from the same three panels of donors by three different procedures: conventional whole blood donation, whole blood donation with metered anticoagulation and centrifugal plasmapheresis by Haemonetics PCS. The yields of factor VIII and factor IX concentrates and the potential thrombogenicity of factor IX were similar when all other parameters were constant.     

Evaluating the potential of a novel hardwood biomass using a superbase ionic liquid

Lignocellulosic biomass, being ubiquitous and easily accessible, bears a huge potential for sustainable energy and other products. Fractionation, delignification, and subsequent utilization of hardwood biomass has been ever challenging for a bio-based refinery. Acacia nilotica (kikar in local language) is a hardwood tree commonly found in Pakistan, where its abundance owes to favorable and benign environmental conditions. Ionic liquids based on superbase “tetramethylguanidine (TMG)” are green solvents that are found to be good cellulose processing agents. Previously, TMG-based protic ionic liquids (PILs) have been used for cellulose processing and transformation into value-added products. In this study, an ionic liquid comprising a tetramethylguanidinium cation and a hydrogen sulfate anion was employed for the evaluation of the potential of acacia for fermentable sugars and lignin. Pretreatment was carried out at 100, 120, and 140 °C for 0.5, 1, 2 and 4 hours. The results indicate that [TMG][HSO₄] is an efficient delignifying agent affording 81% lignin removal and 76% sugar yield by subsequent enzymatic hydrolysis. The evaluation of the efficiency of IL and the biomass was verified by compositional analysis, FT-IR, HSQC, and SEM analyses.

Lignocellulosic biomass, being ubiquitous and easily accessible, bears a huge potential for sustainable energy and other products.     

The conversion of α-pinene to cis-pinane using a nickel catalyst supported on a discarded fluid catalytic cracking catalyst with an ionic liquid layer

The concept of a solid catalyst coated with a thin ionic liquid layer (SCILL) was applied to the stereoselective hydrogenation of α-pinene. Nickel, a non-noble metal, was supported on a discarded fluid catalytic cracking catalyst (DF3C) and then modified with different loadings of the ionic liquid 1-ethanol-3-methylimidazolium tetrafluoroborate ([C₂OHmim][BF₄]). The resulting catalysts showed a range of conversions and selectivities for the hydrogenation of α-pinene. The SCILL catalysts afforded cis-pinane with high selectivity and their activity depended on the ionic liquid loading. For an ionic liquid loading of 10 wt%, although the catalytic activity was suppressed, the selectivity and conversion could reach above 98% and 99%, respectively. In addition, the catalyst remained stable after 13 runs and the activity was almost unchanged with the conversion maintained at approximately 99%. Thus, the ionic liquid layer not only improved the selectivity for cis-pinane but also protected the active site of the catalyst and prolonged the service lifetime of the catalyst. The SCILL catalytic system provides an example of an ionic liquid catalytic system which eliminates organic solvents from the catalytic process.

The Ni/DF3C coated with ionic liquid layer exhibits excellent selectivity toward cis-pinane and stability in the hydrogenation of α-pinene.     

Preparation of mesoporous ZnAl2O4 nanoflakes by ion exchange from a Na-dawsonite parent material in the presence of an ionic liquid

Herein, mesoporous ZnAl₂O₄ spinel nanoflakes were prepared by an ion-exchange method from a Na-dawsonite parent material in the presence of an ionic liquid, 1-butyl-2,3-dimethylimidazolium chloride ([bdmim][Cl]), followed by calcination at 700 °C for 2 h. The as-obtained products were characterized by several techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The ZnAl₂O₄ nanoflakes with the thickness of ∼20 nm were composed of numerous nanoparticles, which resulted in a high specific surface area of 245 m² g⁻¹. The formation mechanism of the ZnAl₂O₄ nanoflakes was comprehensively investigated, and the results showed that a 2D growth process of the Zn₆Al₂(OH)₁₆(CO₃)·4H₂O crystallites with the assistance of [bdmim][Cl] was the key for the induction of ZnAl₂O₄ nanoflakes. Moreover, mesopores were formed between adjacent nanoparticles due to the release of CO₂ and H₂O molecules from Zn₆Al₂(OH)₁₆(CO₃)·4H₂O during the calcination process.

Herein, mesoporous ZnAl₂O₄ spinel nanoflakes were prepared by an ion-exchange method from a Na-dawsonite parent material in the presence of an ionic liquid, 1-butyl-2,3-dimethylimidazolium chloride ([bdmim][Cl]), followed by calcination at 700 °C for 2 h.