Task-specific Ionic Liquids Research Articles

Novel resource-efficient recovery of high purity indium products: Unlocking value from end-of-life mobile phone liquid crystal display screens

Liquid crystal display (LCD) screens found in most electrical and electronic equipment consume approximately 75% of the total indium produced globally. Due to indium’s unique properties and applications, the escalation in demand for the metal and the threat to supply of the metal, mined primarily as a by-product of zinc production, are critical. To mitigate these challenges the need to recover indium from end-of-life (EoL) products is becoming an imperative. In this work, EoL mobile phones (EoL-MPs), which represent a resource-rich stream for critical metals in general, and, specifically indium from LCDs, are used as a feedstock. Using a simulated Model Test System, with the task-specific ionic liquid, Cyphos 101, the optimal conditions for recovery of indium are determined before application to real samples. A complete hydrometallurgical process was developed for the recovery of indium from as-received EoL-MP LCDs as a four-step process involving pre-treatment, liquid-liquid extraction, elution and reduction, using the task-specific IL, Cyphos 101, as extractant. This novel hydrometallurgical process developed can achieve overall efficiencies of ≥ 90% for indium recovery in the form of two high-purity (≥ 99%) indium products of commercial value and offers a promising approach for recovery from any e-waste stream rich in indium. Moreover, this low energy process permits the reuse of the IL up to five consecutive times and has the potential to unlock value as polymeric films, glass substrate and liquid crystal for recycle and reuse within the circular economy.

Highly efficient one-pot aerobic oxidation of cyclohexane to adipic acid using task-specific metal-based ionic liquid

Adipic acid is a significant building block of polymers and is manufactured on a massive scale, primarily to produce nylon. However, the current route depends heavily on using corrosive HNO3 while releasing N2O as a potent greenhouse gas. Herein, we developed an efficient strategy for the highly selective aerobic oxidation of cyclohexane into adipic acid using metal-based ionic liquid as a catalyst. Particularly, the optimised catalyst 1-carboxymethyl-3-methylimidazolium chloride cobalt exhibited a high selectivity towards adipic acid (73.9%). It was discovered that the electron-donating ability of anions and the electrostatic between cations and anions could influence the charge density of Co(II) by anion coordination and then influence the oxidation performance. Meanwhile, the hydrogen bond interaction between the hydrogen-bond donor groups of the IL and cyclohexanone, as well as between the hydrogen-bond donor groups of the IL and the carboxylic radicals could promote the formation of adipic acid. This simple, efficient and green protocol has great potential for industrial applications in adipic acid production.

Expeditious Discovery of Small-Molecule Thermoresponsive Ionic Liquid Materials: A Review.

Ionic liquids (ILs) are a class of low-melting molten salts (<100 °C) constituted entirely of ions, and their research has gained tremendous attention in line with their remarkably growing applications (>124,000 publications dated 30 August 2023 from the Web of ScienceTM). In this review, we first briefly discussed the recent developments and unique characteristics of ILs and zwitterionic liquids (ZILs). Compared to molecular solvents and other conventional organic compounds, (zwitter) ionic liquids carry negligible volatility and are potentially recyclable and reusable. For structures, both ILs and ZILs can be systematically tailor-designed and engineered and are synthetically fine-tunable. As such, ionic liquids, including chiral, supported, task-specific ILs, have been widely used as powerful ionic solvents as well as valuable additives and catalysts for many chemical reactions. Moreover, ILs have demonstrated their value for use as polymerase chain reaction (PCR) enhancers for DNA amplification, chemoselective artificial olfaction for targeted VOC analysis, and recognition-based affinity extraction. As the major focus of this review, we extensively discussed that small-molecule thermoresponsive ILs (TILs) and ZILs (zwitterionic TILs) are new types of smart materials and can be expeditiously discovered through the structure and phase separation (SPS) relationship study by the combinatorial approach. Using this SPS platform developed in our laboratory, we first depicted the rapid discovery of N,N-dialkylcycloammonium and 1,3,4-trialkyl-1,2,3-triazolium TILs that concomitantly exhibited LCST (lower critical solution temperature) phase transition in water and displayed biochemically attractive Tc values. Both smart IL materials were suited for applications to proteins and other biomolecules. Zwitterionic TILs are ZILs whose cations and anions are tethered together covalently and are thermoresponsive to temperature changes. These zwitterionic TIL materials can serve as excellent extraction solvents, through temperature change, for biomolecules such as proteins since they differ from the common TIL problems often associated with unwanted ion exchanges during extractions. These unique structural characteristics of zwitterionic TIL materials greatly reduce and may avoid the denaturation of proteins under physiological conditions. Lastly, we argued that both rational structural design and combinatorial library synthesis of small-molecule TIL materials should take into consideration the important issues of their cytotoxicity and biosafety to the ecosystem, potentially causing harm to the environment and directly endangering human health. Finally, we would concur that before precise prediction and quantitative simulation of TIL structures can be realized, combinatorial chemistry may be the most convenient and effective technology platform to discover TIL expeditiously. Through our rational TIL design and combinatorial library synthesis and screening, we have demonstrated its power to discover novel chemical structures of both TILs and zwitterionic TILs. Undoubtedly, we will continue developing new small-molecule TIL structures and studying their applications related to other thermoresponsive materials.

From Biological Source to Energy Harvesting Device: Surface Protective Ionic Liquid Coatings for Electrical Performance Enhancement of Wood-Based Electronics.

This study explores task-specific ionic liquids (TSILs) in smart floor systems, highlighting their strong electrical rectification abilities and previously established wood preservative properties. Two types of TSILs, featuring a "sweet" anion and a terpene-based cation, were used to treat selected wood samples, allowing for a comparison of their physical and electrical performance with untreated and commercially treated counterparts. Drop shape analysis and scanning electron microscopy were employed to evaluate the surface treatment before and after coating. Near-IR was used to confirm the presence of a surface modifier, and thermogravimetric analysis (TGA) was utilized to assess the thermal features of the treated samples. The different surface treatments resulted in varied triboelectric nanogenerator (TENG) parameters, with the molecular structure and size of the side chains being the key determining factors. The best results were achieved with TSILs, with the instantaneous voltage increasing by approximately five times and the highest voltage reaching 300 V under enhanced loading. This work provides fresh insights into the potential application spectrum of TSILs and opens up new avenues for directly utilizing tested ionic compounds in construction systems.

Rapid extraction of BTEX in water and milk samples based on functionalized multi-walled carbon nanotubes by dispersive homogenized-micro-solid phase extraction.

An advanced synthesis based on the phenylalanine (Phe) and task-specific ionic liquid (TSIL) functionalized on multi-walled carbon nanotubes (Phe/TSIL@MWCNTs), was used to extract benzene, ethylbenzene, toluene, and xylene (BTEX) from cow's milk, powdered milk, and farm water samples. The BTEX was efficiently extracted by ultrasound-assisted dispersive homogenized-micro-solid phase extraction (USA-DH-µ-SPE) between 95.1% and 103.4%. By procedure, 50mg of Phe/TSIL@MWCNTs was added to 0.2mL of acetone and injected into 10mL of the samples. The upper aqueous solution was vacuumed, the vial heated to 80°C, and the BTEX desorbed in the vial. Then, using a Hamilton syringe, 1-20µL of gas in the headspace vial was determined by injecting it into the gas chromatography with flame ionization detection (GC-FID). The linear range, LOD, and LOQ for BTEX in milk and water samples were obtained at 0.05-500µg L-1, 15ng L-1, and 50ng L-1, respectively (r=0.9997, RSD%=2.27).

Nanoconfinement of functionalized ionic liquid for enhanced adsorption and rapid sensitive detection of phenylurea herbicides in food and environmental samples

The novel ILs@CNTs was synthesized by encapsulating task-specific ionic liquids (ILs) within carbon nanotubes (CNTs) derived from ZIF-67. These hybrid materials served as multifunctional adsorbents enabling simultaneous sorptive removal, sensitive detection, molecular sieve selection, and magnetic separation. In contrast to pristine CNTs, ILs@CNTs demonstrate significantly enhanced adsorption of phenylurea herbicides (PUHs). The complex interactions between ILs@CNTs and PUHs were comprehensively analyzed using a combination of experimental results and theoretical calculations. Furthermore, a magnetic solid phase extraction-high performance liquid chromatography (MSPE-HPLC) method was developed for the determination of multiple trace PUHs in real samples. The method exhibited lower detection limits (0.02–0.03 μg L−1) and higher enrichment factors (131 < EFs < 185). Interestingly, a portable lab-in-a-syringe device was developed to facilitate rapid on-site extraction and enrichment of PUHs. Additionally, the developed methods successfully applied in river water, tea drinks, and cucumber samples, highlighting its substantial potential for rapid PUH detection.

Novel electrolytes based on mixtures of dimethyl sulfoxide task specific zwitterionic ionic liquid and lithium salts: Synthesis and conductivity studies

Novel methyl sulfoxide imidazolium-based zwitterionic low melting salts was synthesized and characterized. The combination of this functionalized zwitterion and lithium bis(trifluoromethylsulfonyl)amide (LiNTf2) salts at different molar ratios of render to low melting mixtures, which can exhibit an ionic conductivity as high as 3.4 × 10−5 S cm−1 at 30 °C or 2.9 × 10−3 S cm−1 at 120 °C and a high thermal decomposition temperature higher than 250 °C. The thermal activation energy shown two clearly different Arrhenius trend. For all the mixtures the temperature where the slope of the Arrhenius plot changes is on the range of the melting temperature experimentally observed for the mixture. Below the melting temperature, the values of activation energy are around of two times higher than the values observed for all the mixtures above the melting temperature. On the other hand, in all the mixtures, we have observed that conductivity increases monotonically on the composition of the mixture. These non-volatile and highly polar novel materials can be used for the development of devices targeting high ionic Li-ion conductivity.

Novel hydrometallurgical process for the recovery of copper from end-of-life mobile phone printed circuit boards using ionic liquids

Printed circuit boards, which are embedded in mobile phones, are complex composite materials containing valuable components of strategic and critical importance. With the number of mobile phone devices operating worldwide expected to reach 18bn by 2025, their low recycling rate leads to high tonnages of waste printed circuit boards (WPCBs) at their end of life. Copper, representing 58% of the total metal content in an end-of-life mobile phone (EoL-MP) and the main metal present in the printed circuit board, with an average of 27.8 wt %, offers a resource-rich source of this strategic metal for recovery. To overcome the limitations associated with conventional technologies for recycling WPCBs, use of greener technologies (ionic liquids (ILs) as leaching agents), offers greater potential for the recovery of copper from this waste stream. Presented here for the first time is an optimised hydrometallurgical process for recovery of copper involving pre-treatment, leaching, and electrowinning and the use of two task-specific ionic liquids. The pre-treatment step, using the IL [Bmim]BF4 proved to be a clean, efficient, and non-polluting system for the separation of solder and electronic components (ECs) from WPCBs, at 210 °C, 150 rpm for 15 min, favouring the enrichment of copper for a subsequent recovery process. The IL, [Bmim]HSO4, successfully leaches >99% of copper from pretreated WPCBs under the optimal conditions of 30 %v/v [Bmim]HSO4, 10 %v/v H2O2, and 60 %v/v H2O at 60 °C, 1:15 solid to liquid ratio for 2 h. Recovery of copper is achieved through direct electrowinning from the [Bmim]HSO4-leach solution, as electrolyte. Under controlled deposition conditions of 100 mA (4.2 V) during 2 h, 100% of copper (>99% purity) is recovered with an average current efficiency of 78% and an energy consumption of 4.5 kWh/kg Cu. This work combines a dual leaching and electrowinning system that is clean, environmentally friendly, minimises reagent use and spent wastes, permits multiple reuses of both the ILs, and maximises resource conservation through recovery of copper metal and return of secondary streams (electronic components and solder) for reuse in new or refurbished components or products.

New task-specific ionic liquids as bifunctional organocatalysts; Synthesis, characterization, and computational insights

A new class of functionalized imidazolium-based Task-Specific Ionic Liquids (TSILs) is designed as low-cost bifunctional organocatalyst. New alkoxymethylimidazolium ILs are efficiently synthesized under solvent free conditions and extensively characterized by physical and spectral studies. The newly synthesized ILs demonstrate excellent catalytic potential in condensation reactions of high importance, such as the Biginelli reaction for the synthesis of medicinally important dihydropyrimidiones. The effect of the alkoxy group and counter-ions in the imidazolium salts were evaluated in detail. Moreover, computational studies were employed to explore the structural dynamics and physicochemical properties of the prepared ionic liquids. 3-(iso-butoxymethyl)-1-methyl-1H-imidazol-3-ium tetrafluoroborate (iBOMMIMBF47) exhibited the highest catalytic ability due to the combined influence of the alkoxy group structure, counterion nature, high electrophilicity index, and availability of the reactive C2-H. Some notable advantages of the new TSILs include efficient catalyst preparation, simple work-up procedure, recyclability, short reaction times, and excellent yields.

Highly stable Lewis acidic trifloaluminate ionic liquid supported on silica and metallosilicates as an efficient catalyst for continuous flow aminolysis of epoxides

In this work heterogeneous catalysts based on hybrid materials consisted of calcium and/or magnesium silicates and modern task-specific ionic liquids (supported ionic liquid phase material) dedicated particularly for continuous flow synthesis of fine chemicals with liquid reagents were designed. Pure SiO2 (as a reference sample), as well as magnesium (MgO-SiO2) or calcium (CaO-SiO2) silicates were used as supports for Lewis acidic trifloaluminate ionic liquids immobilized via chemical bound. The lowest ionic liquid loading was determined for SiO2 (15.58 wt%) and the highest for CaO-SiO2 (23.70 wt%). Resulted catalysts were used for the optimization of process parameters of the synthesis of β-amino alcohols in batch reactor (molar ratio aniline: styrene oxide 1.1:1; 1 mol% of catalyst, 60 °C). Not only the most active (conversion of styrene oxide 100.0% and selectivity to main product 98.7%) but also stable in 3 cycles of the process was the catalyst based on MgO-SiO2. The activity of poorly recyclable precursor of ionic liquid used as an active phase Al(OTf)3 was also lower (conversion 87.3% and selectivity 94.6%). Substrate scope confirmed the versatility of this method. The key achievement of the research was the confirmation of activity and stability of the most active catalyst in batch process for the aminolysis of epoxide in the presence of heterogeneous catalyst based on MgO-SiO2 in flow system through 72 h (conversion 81.1%, selectivity 95.9%). The proof of concept for the design of this catalytic system for production of selected fine chemicals is shown in this study.

Task-Specific Ionic Liquids Catalysts Efficiently Catalyze Atmospheric CO2 Gas Mixture to Cyclic Carbonates Under Mild Conditions

Task-Specific Ionic Liquids Catalysts Efficiently Catalyze Atmospheric CO2 Gas Mixture to Cyclic Carbonates Under Mild Conditions

Imidazolium-based task-specific ionic liquid for selective Ag, Cu, Pd and Pt determination by means of dispersive liquid-liquid microextraction and inductively coupled plasma optical emission spectrometry

This work explores chelating capabilities of 1-butyl-2-diphenylphosphino-3-methylimidazolium hexafluorophosphate (BDPPIMPF6) as a task-specific ionic liquid (TSIL) for metal extraction/preconcentration procedures. To this end, metal extraction by BDPPIMPF6 for 21 elements (Ag, Al, As, Au, Co, Cr, Cu, Fe, Ir, Mn, Ni, Pb, Pd, Pt, Re, Rh, Ru, Sc, Ti, V, and Zn) were evaluated. This TSIL specifically forms chelating complexes with several elements of Group 10 (Pd and Pt) and Group 11 (Ag and Cu) of the Periodic Table. Chelating capabilities of BDPPIMPF6 has been exploited for developing a novel methodology for the simultaneous determination of Ag, Cu, Pd, and Pt by means of dispersive liquid-liquid microextraction and inductively coupled plasma optical emission spectrometry detection (DLLME-ICP-OES). This methodology afforded enrichment factors of 14 to 70 and limits of detection (LoD) of 0.2–2 μg L−1 for Ag, Cu, Pd and Pt. These LoD values were between 110 and 35-fold lower than those obtained by direct analyses with ICP-OES (i.e., no DLLME treatment). Finally, the proposed method has been applied to the analysis of Ag, Cu, Pd, and Pt in water and pharmaceutical products. Irrespective of matrix characteristics, quantitative recoveries were found for all the elements investigated thus highlighting methodology robustness.

Synthesis and Characterization of New Lutidinium Ionic Liquid-Supported Vanadylsalicylaldoxime Complex for Catalytic Application in Epoxidation Reaction.

A new chelating task-specific ionic liquid (TSIL), lutidinium-based salicylaldoxime (LSOH), and its square pyramidal vanadyl(II) complex (VO(LSO)2 ) have been successfully synthesized and structurally characterized using elemental (CHN), spectral, and thermal analyses. The catalytic activity of the lutidinium-salicylaldoxime complex (VO(LSO)2 ) in the alkene epoxidation reactions was studied under various reaction conditions, such as solvent effect, alkene/oxidant molar ratio, pH, reaction temperature, reaction time, and the catalyst dose. The results demonstrated that the CHCl3 solvent, 1 : 3 of the cyclohexene/H2 O2 ratio, pH 8, temperature of 340 K, and catalyst dose of 0.012 mmol are assigned as the optimum conditions for achieving maximum catalytic activity for VO(LSO)2 . Moreover, the VO(LSO)2 complex has the potential for application in the effective and selective epoxidation of alkenes. Notably, under optimal VO(LSO)2 conditions, cyclic alkenes convert more efficiently to their corresponding epoxides than linear alkenes.

Self-separation ionic liquid catalyst for the highly effective conversion of H2S by α,β-unsaturated carboxylate esters under mild conditions

The deep-processing utility of pure hydrogen sulfide (H2S) is a significant direction in natural gas chemical industry. Herein, a brand-new strategy of H2S conversion by α,β-unsaturated carboxylate esters into thiols or thioethers using task-specific carboxylate ionic liquids (ILs) as catalyst has been developed, firstly accomplishing the phase separation of product and catalyst without introducing the third component. It can be considered as a cascade reaction in which the product selectivity can be controlled by adjusting the molar ratio of H2S to α,β-unsaturated carboxylate esters. Also, the effects of ILs with different anions and cations, intermittent feeding operations, as well as pressure−time kinetic behaviors on cascade reaction were investigated. Furthermore, the proposed interaction mechanism of H2S conversion using butyl acrylate catalyzed by [Emim][Ac] was revealed by DFT-based theoretical calculation. The approach enables the self−phase separation promotion of catalyst and product and achieves 99% quantitative conversion under mild conditions in the absence of solvent, making the entire process ecologically benign. High-efficiency reaction activity can still be maintained after ten cycles of the catalyst. Therefore, the good results, combined with its simplicity of operation and the high recyclability of the catalyst, make this green method environmentally friendly and cost−effective. It is anticipated that this self-separation method mediated by task-specific ILs will provide a feasible strategy for H2S utilization, which will guide its application on an industrial scale.

Evaluation of task-specific ionic liquids applied in pervaporation membranes: Experimental and COSMO-RS studies

The production of dimethyl carbonate (DMC) from CO2 and methanol (MeOH) is an attractive route for CO2 capture and utilization. In this process, the separation of DMC from the reaction medium is critical to maximize the conversion of CO2. However, DMC and MeOH form an azeotropic mixture that is difficult to separate. This work investigates the possibility of using task-specific ionic liquids (TSILs) in the form of supported ionic liquid membranes (SILMs) to separate and purify DMC by using pervaporation. Two tertiary amine ILs, i.e., 1-octyl-3-methylimidazolium bromide ([Omim][Br]) and 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Omim][NTf2]), and one cyclic quaternary ionic liquid, i.e., 1-octyl-1,4-diazabicyclo[2.2.2]octanium bromide ([ODABCO][Br]), were prepared. The structure and purity of the synthesized ILs were confirmed by NMR and FTIR, and the as-synthesized ILs along with one commercial quaternary ammonium IL, tetrabutylammonium bromide ([TBA][Br]), were further characterized using TGA/DSC. SEM-EDX, tensile tests and stability tests were also performed to characterize the SILMs. During the pervaporation experiments, the SILMs showed an initial decrease in DMC and MeOH permeance over time, followed by a gradual stabilization, with a relatively stable DMC/MeOH selectivity as pure liquids. In addition, an increase in temperature is shown to have negative effect on DMC and MeOH permeance because sorption, which is an exothermic process, governed the transport of molecules across the membrane. The studied SILMs exhibited higher selectivity at low temperatures, especially at 30 °C. Furthermore, the COSMO-RS model provided insights of the effect of IL structures on the separation of DMC from MeOH at molecular level.

New approach for efficient separation of U and Mo using a task-specific ionic liquid from hydrochloric acid medium: extraction and electrochemical investigation

This investigation reports the extraction of UO2Cl42− and MoO22+via neutral (R4N)2UO2Cl4 and cationic MoO2(Ph)+ complexes (following ‘solvation’ and ‘cation exchange’ mechanisms), using a task-specific ionic liquid (TSIL).

Selective isomerization of α-pinene oxide totrans-carveol by task-specific ionic liquids: mechanistic insightsviaphysicochemical studies

A waste-free chemical process involving comparatively greener solvents with recyclability is one of the desired goals of sustainable development.

Newly synthesized imidazolium precursors for CO2utilization and sequestration: aproticversusprotic salts

This work describes the one-pot synthesis for 1,3-bis(3-(1,3-dioxoisoindolin-2-yl)propyl)-1H-imidazol-3-ium bromide, and other protic and aprotic derivatives.

Extraction of rare earth elements from aqueous solutions using the ionic liquid trihexyltetradecylphosphonium 3-hydroxy-2-naphthoate.

The task-specific ionic liquid trihexyltetradecylphosphonium 3-hydroxy-2-naphthoate has been described as a suitable extraction agent for numerous metals from aqueous phases, while additionally providing reduced leaching into the used matrices. Here, we investigate the extraction properties of this extractant towards rare earth elements. Of these, La, Ce, Nd, Ho und Lu were chosen as a representative mix of light and heavy elements. Single- as well as double-element extractions were carried out under varying conditions regarding pH, temperature and extraction time. The highest extraction efficacies and minimalized precipitation of the respective metals were recorded at a pH of 2.5. Satisfactory extraction efficacies (>80%) were achieved already after 6 hours for the elements Ce, Nd and Lu in single-element extraction experiments at room temperature. Increased temperatures improved the extraction efficacy for Nd from 36% at 20 °C to 80% at 30 °C after only 2 hours. Surprisingly, this effect was not observed for Ce in single-element experiments. In double-element feed solutions containing both Ce and Nd, however, the time-dependant extraction efficacy of Ce mirrored that of Nd. The pH in the aqueous extraction matrix changed during the extraction, showing a positive correlation with the extraction efficacy and revealing the extraction mechanism to be via anion exchange. The leaching was in good agreement with literature values, showed a positive correlation with extraction efficacies, and ranged for all extractions between 0.8 and 1.2%. Remarkably, increasing the temperature from 20 °C to 30 °C had no significant influence on leaching.

A perspective on task-specific ionic liquids for the separation of rare earth elements

Herein, we review recent advances in liquid–liquid extraction systems using task-specific ionic liquids as extractants for the separation of rare earth elements.