Chelating Solvent Research Articles

A comprehensive study on the extraction of transition metals from waste random access memory using acetic acid as a chelating solvent

The reduced lifespan of electrical and electronic equipment results in the generation of electronic waste (e-waste), one of the fastest-growing solid waste streams. A systematic and practical approach is needed for the sound management of e-waste and metal recovery. We report an effective and comprehensive study for metal extraction from waste random access memory using acetic acid as a chelating solvent. Under the optimized conditions, Cu, Pb, Zn, and Ni extraction was 97.5%, 88.2%, 79.3%, and 83.7%, respectively. Subsequently, the kinetic study revealed that the diffusion-controlled mechanism governs the metal extraction. The calculated activation energy for Cu, Pb, Zn, and Ni are 11.3, 12.6, 17.6, and 13.3 kJ/mol, respectively, which indicates Cu-extraction could be more favourable than the rest of the metals. Furthermore, the metal leached salt was recovered from the leached solution and was thoroughly characterized to understand the nature of the compound formed and the corresponding leaching mechanism. It was observed that the leached salt could be comparable with standard copper acetate, revealing the acetic acid's ligation property. Finally, the Cu-content in the cathode was recovered as 92.7 wt% from the leached solution using the electrowinning process. We believe, our contribution can be a paradigm for promoting the effective extraction of transition metals from waste random access memory.

Germanium: A review of its US demand, uses, resources, chemistry, and separation technologies

• Efficient and economic production process can mitigate criticality of germanium. • US germanium resources remain unused due to inefficiency in production. • Production processes including leaching, precipitation, and separation are reviewed. • Separation includes precipitation, solvent-extraction, ion-exchange, and adsorption. • Ge chemistry differs from other cations as it remains as neutral species in acidic pH. Germanium (Ge) is one of the critical elements of modern technologies, with supply risk, inefficient production, and increased demand. It is used in high technology applications such as infrared systems, fiber optics, polymer catalysis, electronics, and solar cells. Its demand is expected to increase due to lack of suitable substitutes, increasing demand for solar cells and 5G networks, and the continuous increasing trend of Ge demand for the past 20 years. Globally, 130 tonnes (t) of Ge are being produced (2020) primarily in China. Germanium is recovered as a byproduct from Zn-refineries and coal fly ash. Yet very low amount (<3%) of Ge contained in Zn-ores and fly ash is recovered worldwide, which suggests that the criticality of Ge is due to lack of economical and efficient extraction and recovery process rather than lack of resources. Worldwide, it is estimated that Zn-ores contain 7–13 kt Ge, and coal and coal fly ash, 25–112 kt. The production of Ge involves leaching followed by recovery of Ge by chlorination-distillation, precipitation, solvent extraction, ion flotation, supported liquid membranes, ion exchange, or solid-phase extraction. Leaching from Zn-refinery residues is primarily done with mineral acids, whereas from coal fly ash is achieved with organic ligands. Ge is different from common metal cations, as it exists as neutral species in acidic pH (1–7). Thus, organic ligands are used to form anionic germanium-ligand complexes in solvent extraction and ion-exchange processes so that the species can be separated through anion-exchange. Alternatively, chelating solvent extractants, chelating ion-exchange resins, and ligand functionalized adsorbents in solid-phase extraction (SPE) are used to recover Ge. The primary challenges in Ge hydrometallurgical production are high energy and chemical requirements in precipitation/chlorination-distillation, high chemical consumption, impurities co-extraction, and waste stream generation in solvent extraction, and lack of selective and high-capacity adsorbents in SPE. An improved, efficient, and economical production method, utilizing unconventional resources, can reduce Ge supply risk. SPE has various advantages over other processes, which makes it an attractive option to recover Ge efficiently and economically.

Particle-free compositions for printing dense 3D ceramic structures by digital light processing

ABSTRACT UV-curable particle-free ceramic compositions for stereolithography-based 3D printing technologies present a promising alternative to the commonly used particle-based compositions. So far, such compositions were mainly based on solutions of pre-ceramic polymers which limit their applications to silicon-containing materials. However, the application of particle-free inks for the fabrication of other ceramic materials, in particular dense polycrystalline ones, is very little explored. We present a new and general fabrication approach based on all-solution compositions, by combining sol–gel chemistry and photopolymerization, for obtaining dense 3D ceramic structures by DLP printing. The process is demonstrated here for the fabrication of barium titanate (BaTiO3). By using chelating solvent and monomer, a stable UV-curable solution is obtained. An aging period of 8–14 days was crucial for obtaining dense ceramic objects without any secondary phases. The heat treatment was found to affect the microstructure, density and hardness of the resulting ceramics. The presented process enables obtaining objects free of carbon materials, having a density as high as 98% of the theoretical value, and a hardness of 4.3 GPa.

Chelating Ligands as Electrolyte Solvent for Rechargeable Zinc-Ion Batteries

Rechargeable zinc-ion batteries (RZIBs) are mostly powered by aqueous electrolytes. However, uncontrolled water interactions often confer a small voltage window and poor battery capacity retention. Here, we explore replacing water with ethylene glycol as the primary solvent in zinc electrolyte formulations. The assembled batteries reveal suppressed electrolyte-induced parasitic reactions, leading to (1) expanded voltage stability windows up to 2.2 V, (2) prolonged zinc stripping/plating stability up to 2.4 times longer compared to the water-based counterparts, and (3) doubled cathode capacity retentions as observed in full-cell Zn-FeVO4 RZIBs. Using a combination of synchrotron EXAFS and FTIR, we investigate the molecular level salt-solvent interactions and explain how the chelation ability of EG ligands reduces parasitic reactions to enable the enhanced electrochemical performances. The structural insights should provide guidelines on the selection of salt, concentration, and chelating solvents for robust multivalent-ion battery systems.

TFSI and TDI Anions: Probes for Solvate Ionic Liquid and Disproportionation-Based Lithium Battery Electrolytes.

Highly concentrated electrolytes based on Li-salts and chelating solvents, such as glymes, are promising as electrolytes for lithium batteries. This is due to their unique properties, such as higher electrochemical stabilities, compliance with high-voltage electrodes, low volatility and flammability, and inertness toward aluminum current collector corrosion. The nature of these properties originates from the molecular-level structure created in either solvate ionic liquids (SILs) or the less common ionic aggregates by disproportionation reactions. The nature of the anion plays a crucial role, and here, we present a computational study using TFSI and TDI anions as probes, revealing increasing differences upon increased salt concentration. TFSI-based electrolytes preferably form SILs, while TDI-based electrolytes form ionic aggregates. The latter lead to an unexpected creation of "free" cationic species even at (very) high salt concentrations and thus promise of ample lithium ion transport.

Chiral Memory in Silylium Ions.

The configurational stability of the chiral silicon center in Lewis base-stabilized silyliums has been studied. Complete retention of configuration at silicon is observed at low temperature in silylium ions stabilized by lone-pair interactions. In contrast, loss of chiral memory is observed with systems involving π-interactions. Epimerization of the silicon center was observed by simply allowing equilibration of the diastereomeric silyliums at RT or by adding a catalytic amount of a chelating solvent. Conditions for the transfer of axial chirality to Si-centered chirality were shown to rely on the strength of the Lewis base-silylium ion interaction.

Direct transfer of magnetic sensor devices to elastomeric supports for stretchable electronics.

A novel fabrication method for stretchable magnetoresistive sensors is introduced, which allows the transfer of a complex microsensor systems prepared on common rigid donor substrates to prestretched elastomeric membranes in a single step. This direct transfer printing method boosts the fabrication potential of stretchable magnetoelectronics in terms of miniaturization and level of complexity, and provides strain-invariant sensors up to 30% tensile deformation.

Novel solution process for synthesis of CIGS nanoparticles using polyetheramine as solvent

Chalcopyrite, CuInxGa1−xSe (CIGS), is widely applied in the fabrication of thin-film solar cells, due to its high efficiency and stability. The high costs and complexity of vacuum processes have driven the development of non-vacuum methods, such as solvothermal approaches using organic solvents and metal salts. To overcome the problems of energy waste and carbon residue, this study synthesized ink of CIGS nanoparticles using the solvent-thermal refluxing method at 250°C with polyetheramine as the chelating solvent. The resulting CIGS particles were characterized by XRD, Raman, TEM and UV–vis to investigate the crystal structure, composition, morphology, and band gap. This paper demonstrates the considerable potential for the synthesis of nanoscale CIGS particle ink using a low-cost, simple process, applicable for mass production.

Nanocrystalline copper sulfide of varying morphologies and stoichiometries in a low temperature solvothermal process using a new single-source molecular precursor

Surfactantless synthesis of copper sulfide nanoparticles (NPs) with varied morphologies such as hexagonal rods, rhombohedral, and spherical, has been carried out via low-temperature thermolysis of a new single-source precursor, [Cu(SMDTC)Cl2], (where SMDTC is S-methyl dithiocarbazate). The reaction parameters e.g., temperature and nature of solvent can be used to control the size and morphology of the nanoparticles. It is observed that the solvents played an important role to control the morphology and stoichiometry of copper sulfide. The anisotropic absorption by the chelating solvent (diamine or ethyleneglycol) at the different facets of the newborn microcrystals results the growth of one-dimensional (1D) copper sulfide NPs. The possible formation mechanism of copper sulfide NPs has also been discussed.

Effect of pyridine as a ligand in precursor on morphology of CdS nanoparticles

[Cd(thqdtc)2], [Cd(thqdtc)2(py)] and [Cd(thqdtc)2(2,2′-bipy)] (where thqdtc=1,2,3,4-tetrahydroquinolinecarbodithioate; py=pyridine; 2,2′-bipy=2,2′-bipyridine) have been found to be effective single source precursors for the preparation of diethylenetriamine capped CdS nanoparticles via solvothermal method. Flower-like and rod-like CdS nanoparticles were prepared at a relatively low temperature by thermolysis of the precursors using chelating solvent diethylenetriamine. Use of [Cd(thqdtc)2] and [Cd(thqdtc)2(2,2′-bipy)] afforded rod-shaped nanoparticles and flower-like nanoparticles obtained from [Cd(thqdtc)2(py)]. UV–Visible spectroscopy established pronounced quantum confinement effect. X-ray diffraction (XRD) analysis revealed hexagonal crystal phase for so obtained CdS nanoparticles. The nanoparticles were also characterized by transmission electron microscopy (TEM) and fluorescence spectroscopy.

Efficient Trifluoromethylation of Activated and Non‐Activated Alkenyl Halides by Using (Trifluoromethyl)trimethylsilane

AbstractAn efficient method for the trifluoromethylation of halogenated double bonds by using in situ generated “trifluoromethyl copper” is described. Herein, the most common trifluoromethyl source, (trifluoromethyl)trimethylsilane, was converted selectively into “trifluoromethyl copper” by using copper iodide as copper source and potassium fluoride as promoter. In 1,3‐dimethyl‐3,4,5,6‐tetrahydro‐2(1H)‐pyrimidinone (DMPU) as chelating solvent the trifluoromethylation of activated and non‐activated alkenyl halides occurred mostly in good to excellent yields in up to a gram scale.

Synthesis of nanocrystalline CdS from cadmium(II) complex of S-benzyl dithiocarbazate as a precursor

The single X-ray crystal structure of the cadmium(II)–S-benzyl dithiocarbazate (SBDTC) complex, [Cd(SBDTC)Cl 2] 2, is reported. The compound has been found to be an effective single-source precursor for the preparation of CdS nanocrystals (NCs) via solvothermal method. CdS NCs including spheres and rods were prepared at a relatively low temperature by thermolysis of the precursor using chelating solvent like ethylene glycol (EG), ethylenediamine (EN), hydrazine hydrate (HH) or in a mixture of EG and EN. The influence of solvent, temperature and reaction time was investigated on the size and morphology of the NCs. Use of EG afforded spherical CdS NCs while EN uniquely yielded rod-shaped NCs, and mixture of spheres and rods are obtained from the mixture of EN and EG with a ratio 0.2 (v/v: EN/EG). UV–visible spectroscopy established pronounced quantum confinement with enhanced band gap and XRD analyses revealed hexagonal crystal phase for so obtained CdS NCs. The NCs were also characterized by transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), energy-dispersive X-ray spectroscopy (EDS) and FTIR. The possible formation mechanism for the anisotropic growth of NCs was also discussed.

Pressurized liquid extraction followed by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry for arsenic and selenium speciation in atmospheric particulate matter

This paper describes the development of a chelating solvent-based pressurized liquid extraction (PLE) method for the simultaneous extraction of As and Se species (As(III), As(V), Se(IV) and Se(VI)) in atmospheric particulate matter (PM 10). The extracted As and Se species were evaluated by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). The feasibility of several pressurized chelating solvents was recently investigated to leach As and Se species from atmospheric particulate matter. The best results (high recoveries) were obtained when using EDTA. Experimental design approaches were used to achieve the best compromise conditions for the simultaneous extraction of As and Se species by EDTA-PLE. Analytical performances, such as limits of detection (in the range of 0.01–0.02 ng m −3), quantification (in the range of 0.02–0.07 ng m −3), and repeatability of the over-all procedure (∼10%) were established. Finally, As and Se species were determined in several atmospheric particulate matter (PM 10) samples collected in an urban area of A Coruña city (northwest coast of Spain) in 2006. In all the atmospheric particulate matter samples that were analysed, As(V) and Se(IV) (in the range of 0.17–0.60 ng m −3) were the major species found.

The Structure of Potassium and Tetramethylammonium Salts of the Cyclic Organohydroborate Anion [H2BC8H14]– with Different Solvent Ligands

AbstractSolvated potassium salts of the 9‐BBN hydroborate anion have been prepared and their structures have been determined by single‐crystal X‐ray diffraction analyses. A tetrameric complex {LK[(μ‐H)2BC8H14]}4 is formed when L is toluene, MeTHF, toluene/THF, THF/Et2O mixtures. The basic framework consists of a distorted K4B4 cube in which potassium and boron are at alternate corners of the cube linked by bridging hydrogen atoms and α‐C–H hydrogen atoms from the 9‐BBN hydroborate that appear to form agostic interactions with potassium. There are two types of bridging hydrogen atoms: one is connected to three potassium atoms and one boron atom in a μ4‐coordination arrangement, and the other one is connected to two potassium atoms and one boron atom in a μ3‐coordination arrangement. There are four μ4‐hydrogen arrangements in the structure. They are located inside of the K4B4 cube. The four μ3‐hydrogen arrangements are located outside of the distorted K4B4 cube. The coordination number of potassium is 8 with the three μ4‐, two μ3‐bridging hydrogen atoms, two α‐C–H hydrogen atoms, and one oxygen atom of the solvent, L (there is a weak π‐η6 interaction when the solvent is toluene). On the other hand, in the chelating solvent DME, a dimeric structure is formed in which the inner part is planar with potassium and boron located at alternate corners. The potassium is connected to four μ3‐bridging hydrogen atoms, two apparent agostic α‐C–H bonding hydrogen atoms, and four oxygen atoms of two DME molecules. Its coordination number is 10 including the agostic interactions. The structure of the uncoordinated [H2BC8H14]– anion is observed in the tetramethylammonium salt. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

Persistent π-arene interactions in bulky formamidinate complexes of potassium

The reaction of potassium hexamethyldisilazide (K-HMDS) with 1 equiv. of the bulky formamidine N(Diep) C(H)NH(Diep) (DiepFormH, Diep = 2,6-Et 2C 6H 3) in THF yields the half deprotonated compound [K(DiepForm)(DiepFormH)] ( 1), which exhibits suppressed reactivity with the hexamethyldisilazide anion. Reaction of 1 with n-BuLi gives the polymer [{Li(THF) 2K(DiepForm) 2} n ] ( 2). Preparation of 1 in the presence of the chelating solvents 1,2-dimethoxyethane (DME) or N, N, N′, N″, N″-pentamethyldiethylenetriamine (PMDETA) gives the fully deprotonated species [{K 3(DiepForm) 3(DME) 3} n ] ( 3) and [{K(PMDETA)K(DiepForm) 2} n ] ( 6). The syntheses of compounds 1– 3, 6 and related compounds, e.g. [{K 3{N(Dimp)C(H)N(Dimp)} 3(DME) 3} n ] ( 4) (Dimp = 2,6-Me 2C 6H 3), are described.

Use of chelating solvent-based pressurized liquid extraction combined with inductively coupled plasma-optical emission spectrometry for trace element determination in atmospheric particulate matter

The feasibility of pressurized chelating solvents [ethylenediaminotetracetic acid (EDTA) dipotassium salt, 1,10-ortho-phenanthroline (PHEN), 8-hydroxyquinoline (8HQ), chloramine-T (CT), 1,1,1-trifluoro-2,4-pentanedione (H(fta)), 2,2′-azobis-(2-methylpropionamidine) dihydrochloride (AMPAHC) and 1,5-diphenylcarbazone (DFC)] has been investigated from a novel aspect to speed up metals leaching from atmospheric particulate matter (PM10). The target elements (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, V and Zn) have been evaluated by inductively coupled plasma-optical emission spectrometry (ICP-OES). The highest metal recoveries (within the 85–100% range) were found when using EDTA. Variables inherent to pressurized liquid extraction (temperature, chelating solvent concentration, static time, pressure, number of cycles, dispersing agent mass, flush volume and purge time) were simultaneously studied by applying a Plackett–Burman design (PBD) as the screening method. Results showed statistical significance for some factors such as extraction temperature and EDTA concentration. The static time and the number of cycles were statistically non-significant for most of the elements, meaning that the pressurized leaching procedure can be finished after 12 min (5 min for pre-heating the extraction cell at 100 °C plus 5 min of static time plus 1 min of purge time plus 1 min of end relief time). In addition, the presence of dispersing agent was not necessary, which reduces the time for filling of the cells. Quantitative recoveries for all metals were reached under the following extraction conditions: 40 mM EDTA, extraction temperature of 100 °C, pressure of 1000 psi, static time of 5 min and one extraction cycle. Analytical performances, such as limits of detection and quantification and repeatability of the over-all procedure, have been established. Finally, results obtained by EDTA-based pressurized liquid extraction have been found to be statistically comparable with those obtained after conventional acid digestion with nitric, hydrofluoric and perchloric acids.

Continuous flow chemical processing on a microchip using microunit operations and a multiphase flow network

The new methodology for integration of chemical processing on a microchip was proposed. This methodology, continuous flow chemical processing (CFCP), is based on a combination of microunit operations (MUOs) and a multiphase flow network. Chemical operations in microchannels, such as mixing, reaction, and extraction, were classified into several MUOs. The complete procedure for Co(II) wet analysis, including a chelating reaction, solvent extraction, and purification was decomposed into MUOs and reconstructed as CFCP on a microchip. Chemical reaction and molecular transport were realized in and between continuous liquid flows in a multiphase flow network, such as aqueous/aqueous, aqueous/organic, and aqueous/organic/aqueous flows.

Studies on the Regioselectivity of Horner-Wadsworth-Emmons (Hwe) Reactions on 3,4-Enuloses. Further Evidence of Phosphonate-Phosphate Rearrangements Through Five Membered Cyclic Intermediates.

ABSTRACT The Horner-Wadsworth-Emmons (HWE) reaction was performed on methyl 3,6-di-O-benzoyl-2-deoxy-α-D-glycero-hex-2-enopyranosid-4-ulose (1) with the potassium enolates of dimethyl [(methoxycarbonyl)methyl]phosphonate (2) or diethyl [(ethoxycarbonyl) methyl]phosphonate (3) under different conditions (metallic cation and solvent) in order to study regio- and stereochemical aspects of the reaction. In the presence of lithium ions, no reaction took place. When sodium enolates were employed, 1,2-addition was the main reaction in chelating solvents, whereas the 1,4-adduct is favoured in the less polar, non chelating toluene. Only 1,2-addition was observed with potassium enolates. Evidence of phosphonate-phosphate rearrangements through five membered cyclic intermediates is described.

A pyridine-based chelating solvent extraction system for selective extraction of nickel and cobalt

A novel pyridine-based chelating extractant, 2,6-bis-[5-n-nonylpyrazol-3-yl] pyridine (BNPP), has been developed and characterized. The solvent extraction of Ni and Co by a mixed system of BNPP and dinonyl naphthalene sulfonic acid (DNNSA) was studied as a function of pH, diluent, temperature, and DNNSA concentration. Stripping of Ni and Co was examined as a function of HCl and H 2SO 4 concentration. The novel system can extract Ni and/or Co selectively against Fe, Mn, Ca, Mg, and A1 from acidic sulfate solutions at a pH as low as 0.5. Separation of Ni and Co can be achieved either during loading, or during stripping stages of solvent extraction. The extractant system is stable and can be regenerated with acid. The synergistic extraction distribution diagrams and the slope analyses methods {log D vs. log[BNPP]} showed that both BNPP and DNNSA are present in the extracted Co and Ni complexes, and that two molecules of BNPP are coordinated with one metal cation.

One and two-stage synthesis of ethanol by hydrocarbonylation of methanol in chelating solvents

Two methods for the production of ethanol by hydrocarbonylation of methanol are described. Both methods combine cobalt and ruthenium catalysts and use the chelating properties of glymes and cyclic ethers. In the one-step method, all the procedure is carried out under one set of conditions, while in the two-step method the reaction is carried out for a period of time at 140/sup 0/C in order to produce the maximum amount of acetaldehyde and then at 200/sup 0/C for the same period of time to complete the conversion of acetyladehyde to ethanol. No difinitive advantage of one method over the other was noted, and the actual mechanism for the conversion of acetaldehyde to ethanol is not yet known.