Metal Impurities Research Articles

The temperature dependence investigation of the frequency dispersion of the electrical properties of lithium-iron spinel doped with La, Y

The temperature-frequency dependences of the electrical characteristics of Li2 Fe2,5-x Mex O4 (Ме=La;Y, x=0.01; 0.03; 0.05) spinels synthesized by the «sol-gel» autocombustion technology were obtained by the method of impedance spectroscopy in the temperature range of 298-473 K.
 Based on their analysis, the main mechanisms of conductivity of these materials in the studied temperature range were identified: hopping and activation, which are competing. The effect of doping lithium-iron spinels with rare-earth metal impurities on these conductivity mechanisms has been investigated. It has been established that the presence of impurities in small concentrations in the synthesized samples significantly decreases their conductivity, mainly due to destruction of the hopping mechanism of electronic conductivity.

Manufacture of Eco-cleaner Based on Eco-enzyme Reinforced Catalyst as Reduction of Metals and Impurities on Roller and Blanked to Improve Offset Quality

Offset printing machines play an important role in the printing process in the printing industry, so many industrial players make various efforts to maintain the quality of offset machine printouts. One of the efforts made is to keep the rollers and blankets on the offset machine clean from metal impurities that come from printing inks. To keep rollers and blankets clean, industry players usually use chemical fluids that can clean rollers and blankets on offset machines. However, the continuous use of chemical fluids can damage the rollers and blankets due to oxidation of these chemicals over time. This affects the printing results, such as the paper getting easily damaged, the blanket becoming sticky, the print being uneven, and the density becoming low. In addition, the cleaning chemicals used can cause environmental damage such as water pollution and soil pollution. This research synthesizes an eco-cleaner from an organic waste fermentation process reinforced with a catalyst that can be used as a substitute for the chemicals used today. This research aims to produce an eco-cleaner product that can reduce metal impurities on rollers and blankets to improve the printing quality of offset machines. The resulting product works effectively to remove metal impurities without damaging the rollers and blankets because the eco-cleaner is non-corrosive. The resulting products can be used by the public and the printing industry. The method used in this research is an experiment with the fermentation synthesis method. Furthermore, the eco-cleaner is tested for characterization for feasibility according to SNI standards. The tests carried out are the organic plating test, physical properties test, test and then analysis of the test results to see the feasibility of the eco-cleaner.
 Keywords: eco-cleaner, roller-blanket, printing quality, offset printing

Unraveling the Prominent Existence of Trace Metals in Photocatalysis: Exploring Iron Impurity Effects.

Metal impurities can complicate the identification of active catalyst species in transition metal catalysis and electrocatalysis, potentially leading to misleading findings. This study investigates the influence of metal impurities on photocatalysis. Specifically, the photocatalytic reaction of inert alkanes using chlorides without the use of an external photocatalyst was studied, achieving successful C(sp3)-H functionalization. The observations reveal that Fe and Cu impurities are challenging to avoid in a typical laboratory environment and are prominently present in normal reaction systems, and iron impurities play a dominant role in the aforementioned apparent 'metal-free' reaction. Additionally, iron exhibits significantly higher catalytic activity compared to Cu, Ce, and Ni at low metal concentrations in the photocatalytic C(sp3)-H functionalization using chlorides. Considering the widespread presence of Fe and Cu impurities in typical laboratory environments, this study serves as a reminder of their involvement in reaction processes.

LITEC: An experimental facility for the validation of the IFMIF-DONES Impurity Control System

The Impurity Control System (ICS) of IFMIF-DONES is devoted to assuring lithium purity. After its circulation through the target, some undesired products will contaminate the lithium: deuterium, hydrogen, tritium, and beryllium. In addition, due to the high velocity of the flowing lithium, the target assembly, piping system, and other auxiliaries are subjected to a significant corrosion rate, thus leading also to the presence of metallic impurities in the liquid lithium (iron, nickel, molybdenum…). Finally, nitrogen, oxygen, and carbon will also be present.These impurities may compromise the operation of the facility: they may enhance the erosion/corrosion effect, shortening the operational life of equipment; they may be activated having an important impact on safety strategy, maintenance, and operational procedures; finally, the erosion caused to the target nozzle may produce fluid perturbations affecting to different aspects: fluid-dynamics, cavitation, and thermo-mechanics.The ICS extracts a fraction of the liquid from the DONES main lithium loop to be purified in dedicated traps, to maintain impurities below permissible levels to achieve the required safety and operational conditions.The validation of the ICS at a relevant circuit size will be performed in a new experimental facility called LITEC (The LIthium TEchnologies CIEMAT loop). It consists of a forced circulation lithium circuit. An electromagnetic pump provides a wide operational range for testing all the purification systems envisioned in the ICS. It has four test sections, where trap prototypes will be installed. An injection system also foresees the possibility of introducing impurities to simulate realistic IFMIF-DONES conditions. Finally, a specific branch will monitor online and offline the impurities.LITEC will contribute significantly to clarifying key aspects of the design and operation of IFMIF-DONES lithium systems and will be a reference facility for research activities in lithium technologies. In this work, its engineering design, operational parameters, and characteristics are presented.

Transition Metal Impurities as Shallow Donors in β‐Ga2O3

An in‐depth investigation of transition metal impurities (Hf, Zr, Nb, and W) is presented as shallow donors in monoclinic Ga2O3 using first‐principles calculations within the framework of density functional theory. A combination of semilocal and hybrid functionals is used to predict their binding energies and hyperfine parameters. The generalized gradient approximation (GGA) allows performing calculations for supercells of up to 2500 atoms, enabling an extrapolation to the dilute limit. The shortcoming of GGA in correctly describing the electron localization is then overcome by the use of the hybrid functional. Results are presented and discussed in light of the application of these transition‐metal elements as shallow donors in Ga2O3 and their identification in the experiment. The methodology applied here can be used in calculations for shallow donors in other systems.

Detection of Metal Impurities in Fluids through Microwave Near-Field Imaging

Detection of Metal Impurities in Fluids through Microwave Near-Field Imaging

A general indicator for the tolerance to impurities of metals and alloys

The tolerances of alloys to impurities can vary significantly across impurity-alloy combinations and are largely unknown beyond the most common alloys and impurities. Further, a more general framework to quantify, compare, and practically utilize the tolerance of elements and alloys to impurities is missing. Here, we propose such a framework based on the parameter CIM, the maximum content of an impurity that can be added to a pure element before it no longer crystallizes and instead vitrifies, as measured under sputtering conditions. Using high throughput combinatorial methods, CIM can be readily determined for practically important impurity-element combinations. We argue that CIM generally indicates impurity tolerance because it ubiquitously measures solid solution stability and provide arguments on how conclusions may be drawn from impurity-element to impurity-alloy tolerance. This practical metric for evaluating impurity tolerances for alloys may help metallurgy by enabling greater recycled feedstock compatibility during manufacturing and, in the future, the design of more impurity tolerant alloys.

Effect of metal impurities on the adsorption energy of cesium and work function of the cesiated Mo (0 0 1) surface

Based on the DFT method, the effects of copper and tungsten impurities present in the negative ion source of neutral beams on the cesiated surface were studied, including their effects on the adsorption energy of cesium on the surface and the surface work function. The results indicate that copper impurities significantly increase the average adsorption energy of cesium, whereas tungsten has limited enhancement on the average adsorption energy of cesium and may even reduce it. The work function calculations show that, at cesium coverages below 4/16 θ, copper impurities cause a significant increase in the work function. However, at cesium coverages above 6/16 θ, high-coverage copper impurities lead to a further decrease in the work function, causing the cesium coverage corresponding to the lowest work function to shift towards higher cesium coverage. Under any tungsten impurity and cesium coverage, tungsten impurities can significantly increase the surface work function, with the maximum increase reaching 0.50 eV. The dipole moment density analysis shows that in most cases, impurities significantly reduce the dipole moment density of the cesiated surface, except when the coverage of cesium and copper impurities is above 6/16 θ. The charge transfer results show that the copper impurity layer has more positive charge compared to the tungsten impurity layer, which significantly affects the dipole moment density of the surface system. In addition, adsorbed atoms cause electrons in the molybdenum atomic layer to migrate to the surface, resulting in the molybdenum substrate having a pronounced negative dipole moment.

Powders of Diamond Nanoparticles as a Promising Material for Reflectors of Very Cold and Cold Neutrons.

More than 15 years ago, the study of nanodiamond (ND) powders as a material for designing reflectors of very cold neutrons (VCNs) and cold neutrons (CNs) began. Such reflectors can significantly increase the efficiency of using such neutrons and expand the scope of their application for solving applied and fundamental problems. This review considers the principle of operation of VCN and CN reflectors based on ND powders and their advantages. Information is presented on the performed experimental and theoretical studies of the effect of the size, structure, and composition of NDs on the efficiency of reflectors. Methods of chemical and mechanical treatments of powders in order to modify their chemical composition and structure are discussed. The aim is to avoid, or at least to decrease, the neutron inelastic scatterers and absorbers (mainly hydrogen atoms but also metallic impurities and nitrogen) as well as to enhance coherent elastic scattering (to destroy ND clusters and sp2 carbon shells on the ND surface that result from the preparation of NDs). Issues requiring further study are identified. They include deeper purification of NDs from impurities that can be activated in high radiation fluxes, the stability of NDs in high radiation fluxes, and upscaling methods for producing larger quantities of ND powders. Possible ways of solving these problems are proposed.

Transformation mechanism and selective leaching of nickel and cobalt from limonitic laterite ore using sulfation-roasting-leaching process

The sulfation-roasting-leaching process holds promise as an environmentally friendly method of production but has low recovery efficiency and poor selectivity for Ni and Co in ores containing impurity metals, including Fe, Al, and Cr. In this study, the transformation mechanism and leaching behavior of metals in a limonitic laterite ore during the sulfation-roasting-leaching process were investigated. Results suggest that the transformation of ferrous ion can reduce leaching efficiency for impurity metals in air atmosphere. The leaching efficiencies for Ni, Co, and Al were 91.1%, 91.5%, and 3.3%, respectively, during roasting at 725 °C for 1.5 h. The leaching solution equilibrium pH value was 3, the concentration of the added H2O2 was 0.5 wt%, and Fe and Cr were not detected in the leaching solution. Simulation and characterization results indicated that the conversion of Fe(II) into Fe(III) reduced the amount of FeSO4 in the roasting product and inhibited iron dissolution, demonstrating that the sulfation-roasting-leaching process is a feasible and environmentally friendly method that selectively leaches Ni and Co in ores containing trivalent metals.

Production of vanadyl sulfate electrolyte from stone coal acidic leaching solution using mediation solvent extraction-complex reductive stripping method

In this study, a new method for vanadium extraction and separation from acidic stone coal leaching solution was proposed. With the addition of H2O2 in the solution, the positive vanadium VO2+ ion in the solution was converted into anionic di-peroxo vanadium VO(O2)2- ion. Using methyl tri-octyl ammonium chloride (N263) + n-octanol + sulfonated kerosene as extractant, vanadium was fully separated from Fe (III) and other metal impurities during the extraction process. Under the conditions of 10 % N263, 10 % n-octanol, reaction time 10 min, and O/A ratio 1:1, 99 % of vanadium was extracted into the organic phase. After extraction, an organic phase containing V and Mo was obtained. Due to low solubility of V (V) in acidic solution, oxalic acid was mixed with sulfuric acid solution and employed as complex-stripping solution. It was found that oxalate ion formed a complex with V (V), which could break the solubility barrier of V (V) in acidic solution, realizing the direct stripping of V (V). The effect of oxalic acid amount and temperature on the stripping process were investigated, the results showed that increase in oxalic acid amount and reaction temperature favored vanadium stripping. Under conditions of 25 % H2SO4, oxalic acid concentration of 1 g/L, 80 °C temperature, reaction time 50 min, and O/A ratio of 6:1, 99.7 % of vanadium was stripped into the aqueous solution. The vanadyl sulfate product obtained was compared with standard vanadium electrolyte, and it was found that vanadyl sulfate obtained by this method meets the requirements of vanadium electrolyte relevant standards. This paper proposed a new process for high purity vanadyl sulfate production from acidic stone coal leaching solution, which could provide a reference for Vanadium Redox Flow Batteries (VRFB) industry.

Gettering of iron by aluminum oxide thin films on silicon wafers: Kinetics and mechanisms

Metallic impurities in the silicon wafer bulk are one of the major efficiency-limiting factors in silicon solar cells. Gettering can be used to significantly lower the bulk metal concentrations. Aluminum oxide thin films from plasma-enhanced atomic layer deposition (PE-ALD) have been reported to getter iron from silicon wafers. However, its gettering mechanism and kinetics remain unclear. In this study, by experimentally monitoring the kinetics of iron reduction in the silicon wafer bulk, aluminum oxide gettering of iron is shown to be caused by a segregation mechanism. Fitting the experimental iron reduction kinetics by the simulation of a segregation gettering process based on various diffusion scenarios suggests that the gettering kinetics is limited by both the diffusivities of iron in the silicon wafer bulk and in the aluminum oxide film. The activation energy of the segregation gettering process (negative meaning exothermic reaction) is estimated to be −0.47 ± 0.16 eV for the investigated as-deposited PE-ALD aluminum oxide film at 550–900 °C, and −0.35 ± 0.06 eV at 400–900 °C for the same film after a 400 °C forming gas anneal (FGA), i.e., after activating the passivation effect of the film. Capacitance–voltage measurements of the films indicate a higher surface defect density in the as-deposited films as compared to the FGA-activated films, which suggests a possible correlation between the surface defect density and gettering.

Effect of nanoclusters formed by metal impurity on magnesium vapor condensation in silicothermic process: a molecular dynamics study

In the silicothermic process, some metal oxide impurities that coexist with dolomite are inevitably reduced to metal vapors, which condense to metal impurities in the magnesium crystallizer. In this paper, the molecular dynamics simulation method was adopted to investigate the effect of impurity clusters on the crystallization transition of undercooled magnesium vapor. The results showed that saturated vapor atoms tend to nucleate on the pre-existing impurity cluster, promoting the crystallization rate of magnesium vapor. The promoting effects of impurity clusters on the crystallization of magnesium vapor depend on their sizes and species. The cluster with a larger size demonstrated a more substantial promoting impact. Moreover, in the three impurities studied in this paper, magnesium vapor condenses on the Fe cluster at the fastest rate due to the bcc structure of the Fe cluster and the strong interaction between Fe and Mg atoms. For Ni and Cu clusters with the same fcc structure, the promoting effect of the Ni cluster on the crystallization of Mg vapor is more evident because the interaction between Ni-Mg atoms is stronger than between Cu-Mg atoms.

Development of the Purification Process of Gallium-68 Eluted from Germanium-68/Gallium-68 Generator

Objective: 68Ga has a half-life of 68 minutes, with 89% of its decay is through positron emission. It is available from generator systems and possesses suitable property for labeling radioligands. These aspects make 68Ga a promising tracer for positron emission tomography (PET) imaging. This study aims to develop the purification process of the 68Ga eluates from 68Ge/68Ga generator after its recommended shelf-life and ensuring the quality through the radiolabeling process. Materials and Methods: In this study, we explored the development of a purification method for 68Ga eluted from a68Ge/68Ga generator before radiolabeling was investigated. Cation and anion exchange chromatography techniques were combined to remove trace amounts of competing metal ion impurities. Post-purification, the eluate’s metal contents were analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Breakthrough of 68Ge was measured using a multi-channel analyzer (MCA) spectrometer with high-purity germanium (HPGe) radiation detectors. Additionally, the radiochemical purity of 68Ga-NOTA-RGD was analyzed by high-performance liquid chromatography (HPLC). Results: Metal impurities including Fe(II), Zn(II) and Al(III) were reduced by 61%, 38% and 44% respectively. The 68Ge breakthrough was approximately ~10–3%. The labeling efficiency with NOTA-RGD, a tracer for angiogenesis imaging, resulted in an average yield of 68Ga-NOTA-RGD (not corrected for decay) of around 50%, with aradiochemical purity by HPLC of approximately 98%–99%. Conclusion: Cation exchange in combination with anion exchange chromatography was thus proven to be an efficient method for purification of the 68Ga eluate from a 68Ge/68Ga generator prior to labeling the 68Ga PET radiotracer.

Combination Effect of Transition Metal Impurities on Oxygen Vacancy Formation Energetics in TiO2

Combination Effect of Transition Metal Impurities on Oxygen Vacancy Formation Energetics in TiO2

Exploring Synergistic Effect on the Stability of Ni-, Pd-, Ir-Doped TiN (N = 1–15) Nanoparticles

Bimetallic nanoclusters have attracted great interest due to their ability to enhance the catalytic properties of nanoclusters through synergetic effects that emerge from the combination of the metal nanocluster with different transition metal (TM) species. However, their indefinite composition and broad distribution hinder the insightful understanding of the interaction between these invasive metals in bimetallic doped nanoalloys. In this study, we report a density functional theory calculation with the PBEsol exchange-correlation functional for 16-atom TiN−1TM (TM = Ni, Ir, Pd) nanoalloys, which provides new insights into the synergetic effect of these invasive metals. The probe into the effect of these metal impurities revealed that the replacement of a Ti atom with Ni, Ir and Pd enhances the relative stability of the nanoalloys, and the maximum stability for a lower bimetallic composition is reached for Ti4Ir, Ti5Pd and Ti7Ni. The most stable nanoalloy is reached for the Ti12Ir cluster in comparison with the Ti12Pd and Ti12Ni clusters and pure Ti13 monoatomic nanocluster. This stability trend is as revealed well by both the binding energy and the dissociation energy. The average HOMO-LUMO gap for the bigger clusters revealed that the valence electrons in the HOMO can absorb lower energy, which is indicatory of a higher reactivity and lower stability. The quantum confinement is higher for the smaller clusters, which illustrates a higher stability and lower reactivity for those systems.

Extraction of Palladium from Spent Nuclear Fuel Reprocessing Solutions

New solvent systems for selective separation of palladium from nuclear wastes represent a prospective way to reduce the total waste volume and induce this metal’s extraction. For this purpose, the potential of modern green solvent room-temperature ionic liquid was assessed with diamide-type extractants based on N-heterocycles and S-donating thiodiglicolic acid. The N-donating heterocyclic extractants demonstrate structure-dependent high selectivity toward palladium in the presence of various impurity metals (such as Zr, Cs, Sr, Mo, Ce, Fe, and Cr) from spent nuclear fuel. Palladium is extracted into the organic phase quite selectively with a separation factor greater than a thousand for all extractants. Ionic liquid media are capable of selective palladium separation from platinum group metals and synergetically increase the selectivity of the extractants.

Regeneration of graphite from spent lithium‐ion batteries as anode materials through stepwise purification and mild temperature restoration

AbstractGraphite is one of the most widely used anode materials in lithium‐ion batteries (LIBs). The recycling of spent graphite (SG) from spent LIBs has attracted less attention due to its limited value, complicated contaminations, and unrestored structure. In this study, a remediation and regeneration process with combined hydrothermal calcination was proposed to remove different impurities as value‐added resources from SG. This study focuses on the application of different removal methods for different impurity metals by hydrothermal and acid leaching under different conditions for the removal of Cu, Li, Co, Mn, and Ni from SG. Then, mild‐tempreture calcination of SG was performed to remove residual organic compounds. The regenerated graphite (RG) was found to have a better morphology structure and increased pore volume, which is more favorable for the embedding and desorption of lithium (Li) in graphite. In terms of electrochemical performance, the first discharge‐specific capacity of RG at 0.5 C is 359.40 mAh/g, with a retention of 353.49 mAh/g after 100 cycles (retention rate of 98.36%). This study can be a green and efficient candidate for the regeneration of graphite from spent lithium‐ion batteries as anode material by reduced restoration temperature, with different metal resources as by‐products.

Spectroscopic Analysis of Lipsticks for the Traces of Heavy Metals: A Comprehensive Review

Abstract: Heavy metal impurities are typically discovered in cosmetic products since they are abundant naturally. Lipstick's metal concentration has raised health concerns across the globe. This is so because applying cosmetics to the face always starts with lipstick. Since they are a potential source of daily, widespread, and frequently longterm exposure to a range of chemicals, the safety of cosmetic and personal care products has come under increased scrutiny in recent years. Hazardous heavy metals are included in cosmetics and other products in general, which can cause a multitude of health issues. Therefore, they ought to be kept to a minimum use wherever it is technically feasible. Analysing the levels of harmful heavy metals present in commercially available cosmetic products is important for reducing exposure to those substances. In this study, we investigated the levels of a few harmful heavy metals in lipsticks, such as lead, cadmium, nickel, arsenic, and chromium. For this purpose, we have studied around 50 research articles that explain the spectroscopic analysis of lipsticks for the traces of heavy metals. This article includes the determination of levels of these toxic heavy metals by Atomic Absorption Spectroscopy. Due to its hyphenated nature, low cost, quick analysis time, and reliable results, the atomic absorption spectroscopic (AAS) methodology is currently the one that is most frequently employed for metal ion detection despite the availability of a number of other methods.

A "Two-Step" Electrochemical Approach for Recovery of Plutonium and Uranium from Aqueous Acidic Waste Solutions.

Chemical quality control of nuclear fuel, particularly the determination of Pu and U contents by chemical methods, results in analytical acidic aqueous waste solutions from which Pu and U must be recovered efficiently for the remediation of radioactive wastes. Reported methods involve several complicated steps requiring addition of chemical oxidants/reductants for valence adjustments and generation of secondary wastes, thereby making the recovery process cumbersome. Herein, we report a novel two-step electrochemical approach for Pu and U recovery from acidic aqueous waste solutions containing different metallic impurities (Fe, Cr, Mn, Cd, Al, Ni, Co, Zn, and Mg) by bulk electrolysis using a Pt gauze electrode. Pu and U are recovered from these waste solutions in a two-step process: (i) bulk electrolysis of the mixed solution at a constant potential of 0.1 V vs Ag/AgCl/3 M KCl that results in the reduction of PuO22+ to Pu3+ followed by the precipitation of Pu3+ as K2(K0.5Pu0.5)(SO4)2, which is then filtered and separated and (ii) the filtrate solution is again subjected to bulk electrolysis at a constant potential of -0.35 V vs Ag/AgCl/3 M KCl resulting in the reduction of UO22+ to U4+. The U4+ is then precipitated as K2(K0.67U0.33)(SO4)2, which is filtered and separated, leading to a Pu- and U-free aqueous acidic waste solutions. Biamperometry shows that 97.8% and 99.1% recovery of Pu and U, respectively, is possible, and emission spectrometry confirms the purity of K2(K0.5Pu0.5)(SO4)2 and K2(K0.67U0.33)(SO4)2. Because of its operational simplicity, potential for remote handling, and excellent extraction efficiency, the present methodology can easily replace traditional methods for the recovery of Pu and U from acidic aqueous waste solutions.