Abundant Impurity Research Articles

Detachment and flow behaviour of anode slimes in high nickel copper electrorefining

Most of the world’s copper is produced via copper electrorefining, where nickel is the most abundant impurity in the process. Previously it has been suggested that nickel affects the adhesion of anode slimes on the anode as well as the porosity of the slime layer that forms. This paper investigates the effects of nickel, oxygen, sulphuric acid and temperature on the detachment of anode slimes from the anode surface. The detachment of particles as a function of both anode and electrolyte composition was studied on laboratory scale using a camera connected to a Raspberry Pi, and particle detection and movement analysed using TrackPy. The results revealed four different slime detachment mechanisms: cloud formation, individual particle detachment, cluster detachment and avalanche. These were found to be dependent on the electrolyte (0, 10, 20, 30 g/dm3 Ni2+ & 100, 200 g/dm3 H2SO4), with increasing nickel concentration promoting cluster detachment and increasing sulphuric acid concentration favouring detachment of individual particles. Anode composition (0.05-0.44 wt% O and 0.07-0.64 wt% Ni) was shown to affect the flow direction of anode slimes, with increasing nickel leading to more upward-flowing slimes. Typical particle movement velocities were from -0.5 to 1.0 mm/s regardless of the electrolyte and anode composition, and regardless of the operating temperature (25 °C & 60 °C) for small particles (<0.5 mm). The results also support previous findings that increasing the nickel concentration of the electrolyte leads to a more porous anode slime layer on the anode.

Trace element impurities in anode copper from Olympic Dam, South Australia

Anode copper is the intermediate product between copper smelting and electrorefining. Anodes are typically 98.5 to 99.8 % pure and require electrorefining to high-purity copper cathode that can be sold to customers. Impurity elements, including Ag, Au, As, Sb, Bi, Se, Te, Sn, Pb, Co, and Ni (alongside minor Fe, Al, and Si), are either dissolved within anode copper, or contained within micron-scale inclusions. To better understand the distribution of these impurities, a study of anode copper was undertaken on representative samples from the Olympic Dam anode plant, South Australia. Bulk assay for 61 elements of 269 sub-samples collected on a grid across a single anode, including the ‘ears’, shows homogeneity irrespective of location. The five most abundant impurity elements are As (mean 1279 ± 41 ppm), Se (218 ± 11 ppm), Sb (211 ± 8 ppm), Bi (202 ± 9 ppm), and Ni (195 ± 6 ppm). The assay data demonstrate that reliable, representative compositional data on the anode can be obtained from sampling and assay of only a limited part of the whole, including the ‘ears’.Trace element analysis of copper metal by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) allows quantification of dissolved minor components. Some metals, notably Ni, occur almost completely dissolved in copper. Other elements occur only partially in dissolved form, but the proportions measured in copper metal relative to bulk assay vary significantly from only ∼ 9 % for Pb, 13 % for Bi and Te, 25 % for Se, 29 % for Sn, 34 % for Sb, 55 % for As, and 60–70 % for Au, Ag, and Co. These results are consistent with the observation of a diverse suite of 1–10 µm-sized, rounded impurity inclusions containing Pb, Bi, As, Sb, Te, Se etc. that are associated with cuprite, Cu2O, and largely follow copper grain boundaries. The inclusions, each containing one or more crystalline (e.g., Cu-selenides, some Cu-Bi-arsenates, Sn-oxides and cuprite) and/or glassy phases (e.g., Cu-Pb-As-Sb-Bi-oxides), represents a trapped melt droplet, leading to the observed broad range of compositions.

Combination of ERDA, FTIR spectroscopy and NanoSIMS for the characterization of hydrogen incorporation in natural diamonds

Hydrogen is a volatile element involved in several geological processes ranging from rock weakening to the initiation of tectonic plates. Because it is present in diamond, the investigation of hydrogen content in natural diamonds could provide valuable information. Such studies are scarce despite hydrogen being among the main impurities in their structure. Using Elastic Recoil Detection Analysis, Fourier Transform Infrared spectroscopy and Nanoscale Secondary Ions Mass Spectrometry, we analyzed the incorporation of hydrogen in three diamonds growth habits: octahedral, cuboid and fibrous. Up to 25 wt. ppm of hydrogen was measured in some samples, placing hydrogen as the second most abundant impurity in natural diamonds after nitrogen and before boron. Comparison between the three methods indicates a difference in the main mode of hydrogen incorporation depending on the growth habit. Hydrogen is more readily incorporated in the fibrous and cuboid habits compared to the octahedral one. We also show that the incorporation of hydrogen is not correlated with the incorporation of nitrogen. Results suggest no chemical equilibration of hydrogen by diffusion through geological times and also confirm that not all hydrogen may be infrared active.

Biogas upgrading via CO2 removal onto tailor-made highly ultramicroporous adsorbent materials

Biogas is a renewable energy source that can be an alternative to meet growing energy demand and reduce greenhouse gas emissions. The calorific value of biogas is diminished by the presence of CO2, the most abundant impurity presents in the production of this biofuel. In this study, ultramicroporous activated carbons (ACs) were developed from Prosopis ruscifolia sawdust (Vinal) by activation with KOH solution. The influence of temperature (873, 973, and 1073 K) and the KOH/biochar impregnation mass ratio (IR = 1, 2 or 3) on ACs main chemical, textural, and morphological characteristics were examined and related to its ability to capture CO2. The impregnation mass ratio was the most influential variable for the capture of this polluting species. The developed ACs were highly ultramicroporous and presented BET surface areas between 500 and 2430 m2 g−1. The AC developed at 973 K and IR = 2 showed the best performance in CO2 adsorption, under equilibrium conditions, at 273 K (6.2 mmol g−1). This result was attributed to its higher content of pores with diameters between 0.4 and 0.9 nm. Dynamic studies carried out in a fixed-bed column with this AC showed that it was able to capture 1.5 mmolg−1 of CO2 and ∼0.3–0.4 mmol g−1 of CH4 from single component streams, whereas when the conditions were similar to those of a biogas upgrade process (CH4 80% and CO2 20%), CO2 uptakes slightly decreased. Competition studies carried out using a CO2/CH4 mixture of equimolar concentrations pointed out a greater selectivity towards CO2. Regeneration studies showed that this AC retained between 97 and 98% of its maximum initial CO2 adsorption capacity after five adsorption-desorption cycles.

Embedment of Multiple Transition Metal Impurities into WS2 Monolayer for Bandstructure Modulation

AbstractBand structure by design in 2D layered semiconductors is highly desirable, with the goal to acquire the electronic properties of interest through the engineering of chemical composition, structure, defect, stacking, or doping. For atomically thin transition metal dichalcogenides, substitutional doping with more than one single type of transition metals is the task for which no feasible approach is proposed. Here, the growth of WS2 monolayer is shown codoped with multiple kinds of transition metal impurities via chemical vapor deposition controlled in a diffusion‐limited mode. Multielement embedment of Cr, Fe, Nb, and Mo into the host lattice is exemplified. Abundant impurity states thus generate in the bandgap of the resultant WS2 and provide a robust switch of charging/discharging states upon sweep of an electric filed. A profound memory window exists in the transfer curves of doped WS2 field‐effect transistors, forming the basis of binary states for robust nonvolatile memory. The doping technique presented in this work brings one step closer to the rational design of 2D semiconductors with desired electronic properties.

Intentional carbon doping reveals CH as an abundant charged impurity in nominally undoped synthetic WS2 and WSe2

Understanding the physical properties and controlling the generation of intrinsic and extrinsic defects is central to the technological adoption of 2D materials in devices. Here we identify a charged carbon-hydrogen complex at a chalcogen site (CHX) as a common, charged impurity in synthetically grown transition metal dichalcogenides (TMDs). This conclusion is drawn by comparing high resolution scanning probe microscopy measurements of nominally undoped and intentionally carbon doped TMD samples. While CH impurity densities in undoped CVD-grown WS2 and MOCVD-grown WSe2 can range anywhere from parts per million to parts per thousand, CH densities in the percentage levels were selectively generated by a post-synthetic methane plasma treatment. Our study indicates that methane plasma treatment is a selective and clean method for the controlled introduction of a charged carbon-hydrogen complex at a surface chalcogen site, a defect that is commonly present in synthetic TMDs.

On the electrical properties of meridianiite and implications for radar sounding of icy satellites

Salts are important secondary components of the icy shells of outer-planet satellites. Salt hydrates formed from freezing brines may influence reflectivity and absorption of surface-penetrating radars. We compare new measurements of frozen mixtures of water and magnesium sulfate with those made by Pettinelli et al. (2016) and Grimm et al. (2008). We find a high-frequency real dielectric constant of the hydrate endmember (meridianiite) of 4.9 ± 0.3 at −85°C, within the error bounds derived by Pettinelli and colleagues. We confirm the existence of a dielectric relaxation in meridianiite, similar to the well-known response of ice but at higher frequency and with lower amplitude. However, the meridianiite relaxation is evident only at supereutectic concentrations and for a freezing history that maximizes annealing and partitioning of soluble impurities into the lattice. Dielectric relaxation is nonetheless important for radar sounding of Europa because it controls absorptive loss. Chloride is the most abundant ice-soluble impurity on Europa and will have the greatest impact on radar absorption, whether in ice or hydrates. Salt hydrates may generate reflectivity contrasts in surface-penetrating radar but are unlikely to be uniquely identified.

A Novel Impurity-Profiling Workflow with the Combination of Flash-Chromatography, UHPLC-MS, and Multivariate Data Analysis for Highly Pure Drugs: A Study on the Synthetic Cannabinoid MDMB-CHMICA.

In this paper we present a new, versatile workflow for a synthesis impurity profiling concept, using the combination of flash chromatography (F-LC), liquid chromatography coupled to mass spectrometry (LC-MS), and multivariate data analysis. For three highly pure, structurally different synthetic cannabinoids, we demonstrate that via F-LC more than 99% of the main component (API) can be removed from a sample to enrich present impurities and yield combined fractions of targeted synthesis impurities with reproducible chromatographic signatures via LC-MS. The maximum overall relative standard deviation (RSD) of the complete experimental procedure for isolation and measurement of the impurity profiles (FL-C + LC-MS) was found to be 13.8% on average. The impurity signatures of 40 1 kg samples of MDMB-CHMICA (methyl ( S)-2-(1-(cyclohexylmethyl)-1 H-indole-3-carboxamido)-3,3-dimethylbutanoate) from one large seizure by Luxembourg customs were assessed via UHPLC-MS and compared via principle component analysis (PCA) to possibly discriminate between individual synthesis pathways or production batches and to deduce batch sizes. Three of these 40 samples could be identified as outliers, i. a., as a result of a highly abundant impurity with m/ z 498, isolated via F-LC and identified as methyl 2-(2-(1-(cyclohexylmethyl)-1 H-indole-3-carboxamido)-3,3-dimethylbutanamido)-3,3-dimethylbutanoate, most probably manufactured with a varying synthesis pathway. The remaining 37 samples were subdivided via PCA and hierarchical cluster analysis into five clusters between five and ten samples, representing a maximum possible batch size of 10 kg of pure MDMB-CHMICA. Furthermore, the profiling concept was successfully applied to self-produced and seized "spice-products" to extract impurity profiles of MDMB-CHMICA without any ion suppression or chemical interference.

Balancing Sodium Impurities in Alumina for Improved Properties

As there are direct and indirect impacts of feed material purity on the aluminum production process and metal grade, there is a high demand on the so-called pure smelter grade alumina (SGA)—the main feedstock for aluminum production. In this work, impurities within the precursor gibbsite used for SGA production and SGA are studied using NanoSIMS and XPS with a focus on sodium—the most abundant impurity. Although the industry trend is towards minimizing sodium due to the well-known negative impacts on the process, high sodium is also correlated with relatively attrition-resistant calcined products. Here, we show that this relationship is indirect and arises from sodium’s role in inhibiting α-alumina formation. Alpha alumina formation in SGA has previously been demonstrated to induce a macro-porous and therefore attrition-prone microstructure. Sodium distribution within the precursor gibbsite and its migration during the calcination process are proposed to be most likely responsible for the spatial distribution of α-alumina within the calcined product grain. This in turn determines the behavior of the product during its transportation and handling (i.e., attrition). Therefore, tolerance of a certain amount of sodium within the precursor material does demonstrate a net benefit while balancing its negative impacts on the process.

Characterization of low-abundance species in the active pharmaceutical ingredient of CIGB-300: A clinical-grade anticancer synthetic peptide.

CIGB-300 is a first-in-class synthetic peptide-based drug of 25 amino acids currently undergoing clinical trials in cancer patients. It contains an amidated disulfide cyclic undecapeptide fused to the TAT cell-penetrating peptide through a beta-alanine spacer. CIGB-300 inhibits the CK2-mediated phosphorylation leading to apoptosis of tumor cells in vitro, and in vivo in cancer patients. Despite the clinical development of CIGB-300, the characterization of peptide-related impurities present in the active pharmaceutical ingredient has not been reported earlier. In the decision tree of ICHQ3A(R2) guidelines, the daily doses intake, the abundance, and the identity of the peptide-related species are pivotal nodes that define actions to be taken (reporting, identification, and qualification). For this, purity was first assessed by reverse-phase chromatography (>97%) and low-abundance impurities (≤0.27%) were collected and identified by mass spectrometry. Most of the impurities were generated during peptide synthesis, the spontaneous air oxidation of the reduced peptide, and the lyophilization step. The most abundant impurity, with no biological activity, was the full-length peptide containing Met17 transformed into a sulfoxide residue. Interestingly, parallel and antiparallel dimers of CIGB-300 linked by 2 intermolecular disulfide bonds exhibited a higher antiproliferative activity than the CIGB-300 monomer. Likewise, very low abundance trimers and tetramers of CIGB-300 linked by disulfide bonds (≤0.01%) were also detected. Here we describe for the first time the presence of active dimeric species whose feasibility as novel CIGB-300 derived entities merits further investigation.

Major impurity elements in native gold and their association with gold mineralization settings in deposits of Asian folded areas

Contents of major impurities (Ag, Cu, and Hg) have been studied in gold from ore deposits of various types: (1) associated with skarns and black shales (Altai-Sayan folded area (ASFA) and North Vietnam), (2) pluton-related porphyry Cu-Mo (ASFA), and (3) volcanic pyritic (Rudny Altai, the Urals, and North Vietnam). Analysis of gold ore mineralization in deposits of these types reveals diverse gold compositions along with diverse compositions of productive mineral assemblages. Silver is the most abundant impurity in gold from all fields studied, but its contents vary broadly even within a field type. The content of silver in gold depends not only on its abundance in hydrothermal solutions but also on other independent solution parameters: sulfur fugacity, temperature, salt composition, and pH. The regular decrease in native gold fineness from early to late generations in sulfide ore deposits is related to temperature decrease and large-scale sulfide formation. These processes reduce sulfur fugacity in the solutions and favor silver deposition in native gold rather than in sulfides. Gold of later generations is enriched in mercury in many deposits studied, whereas copper gravitates to earlier, high-temperature ones. In addition to deposition temperature, the contents of copper in gold are determined by its content in hydrothermal solutions, as evidenced by the association of copper-rich gold with basic-ultrabasic, skarn, and porphyry copper deposits. The processes causing the deposition of gold of various chemical compositions are complex. They correlate, to an extent, with gold mineralization temperature, whereas the spectrum of impurities often depends on the belonging of a gold deposit to a certain igneous complex.

Evolution of impurity incorporation during ammonothermal growth of GaN

Ammonothermally grown GaN is a promising substrate for high-power optoelectronics and electronics thanks to its scalability and high structural perfection. Despite extensive research, ammonothermal GaN still suffers from significant concentrations of impurities. This article discusses the evolution of impurity incorporation during growth of basic ammonothermal GaN, in specific whether the impurity concentration changes temporally along the growth direction and how the autoclave influences the impurity concentration. The effect of the impurities on the structural, electrical and optical properties of the grown crystal is also discussed. The chemical analysis is carried out by time of flight secondary ion mass spectroscopy (ToF-SIMS) and laser-ablation inductively-coupled plasma mass spectroscopy (LA-ICP-MS). Strain and dislocation generation caused by impurity concentration gradients and steps are studied by synchrotron radiation x-ray topography (SR-XRT). Fourier transform infrared (FTIR) reflectivity is used to determine the effect of the impurities on the free carrier concentration, and the luminescent properties are studied by low temperature photoluminescence (PL). The influence of the autoclave is studied by growing a single boule in multiple steps in several autoclaves. LA-ICP-MS and ToF-SIMS ion intensities indicate that the impurity concentrations of several species vary between different autoclaves by over an order of magnitude. SR-XRT measurements reveal strain at the growth interfaces due to impurity concentration gradients and steps. Oxygen is determined to be the most abundant impurity species, resulting in a high free carrier concentration, as determined by FTIR. The large variation in Mn concentration dramatically affects PL intensity.

Comparative profiling of highly enriched 22L and Chandler mouse scrapie prion protein preparations

Transmissible spongiform encephalopathies (TSEs) or prion diseases are characterized by the accumulation of an aggregated isoform of the prion protein (PrP). This pathological isoform, termed PrP(Sc), appears to be the primary component of the TSE infectious agent or prion. However, it is not clear to what extent other protein cofactors may be involved in TSE pathogenesis or whether there are PrP(Sc)-associated proteins which help to determine TSE strain-specific disease phenotypes. We enriched PrP(Sc) from the brains of mice infected with either 22L or Chandler TSE strains and examined the protein content of these samples using nanospray LC-MS/MS. These samples were compared with "mock" PrP(Sc) preparations from uninfected brains. PrP was the major component of the infected samples and ferritin was the most abundant impurity. Mock enrichments contained no detectable PrP but did contain a significant amount of ferritin. Of the total proteins identified, 32% were found in both mock and infected samples. The similarities between PrP(Sc) samples from 22L and Chandler TSE strains suggest that the non-PrP(Sc) protein components found in standard enrichment protocols are not strain specific.

Impurity elements study of carbon nanotubes fabricated by chemical vapor deposition

It is widely known that materials properties are very sensitive to the presence of impurity elements. In this study we performed Rutherford backscattering spectroscopy (RBS) and particle induced X-ray emission (PIXE) analysis of impurity elements in carbon nanotubes (CNTs) fabricated by chemical vapor deposition. Impurities such as O, Si, P, S, Cl, Ar, Ti, Cr and Fe were found. The O was uniformly distributed and the most abundant impurity in CNTs. Sources of contamination were investigated and it was suggested that the presence of Si, S, Cl, Ti and Cr can be eliminated.

Hydrogen in the Wide Bandgap Semiconductor Silicon Carbide

In this paper we give a review of our recent results related to the incorporation of hydrogen (H) in silicon carbide (SiC) and its interaction with acceptor doping atoms and implantation induced defects. Hydrogen is an abundant impurity in the growth of epitaxial SiC since it is present in the precursor gases and since H2 is used as the carrier gas. High concentrations of hydrogen are indeed incorporated into highly doped p-type epi-layers and it is shown that the main source is the carrier gas. Furthermore, it is revealed that the entire substrate becomes homogeneously filled with hydrogen during growth and that this hydrogen is more thermally stable than that in the epi-layer. Incorporation of hydrogen from an H2 ambient, at temperatures considerably lower than those used for epitaxy, is also demonstrated in p-type samples coated with a catalytic metal film. This effect is most likely the cause for the increased series resistance observed in p-type SiC Schottky sensor devices using a catalytic metal gate after annealing at 600 °C in a H2 containing ambient. Hydrogen is found to passivate the acceptors Al and B by forming electrically neutral H-acceptor complexes. Unlike in Si and GaAs, the two H-acceptor complexes in SiC exhibit very different dissociation energies, suggesting that the atomic configurations of the complexes are significantly different. The migration of mobile hydrogen in the presence of externally applied, or internal built-in, electric fields further reveals that hydrogen is present as H+ in p-type SiC. Finally, the redistribution and subsequent out-diffusion of low energy implanted 1H and 2H is investigated. Two annealing phases for the redistribution are observed, and the activation energies for the processes are extracted.

Report on the influence of HPHT annealing on the 3107 cm−1 hydrogen related absorption peak in natural type Ia diamonds

After nitrogen, hydrogen is the most abundant impurity in natural diamond with concentrations varying between 0.1 and 1%. It has been shown that the 3107 cm−1 absorption line in diamond is related to the hydrogen–carbon stretch vibration. The influence of HPHT conditions on the 3107 cm−1 absorption line in natural diamond is reported. A type Ia sample with mixed IR active A and B defects and samples with a majority of B defects were subjected to conditions of T∼1900 °C, P∼7 GPa, t∼12 h. It is observed that in some diamonds of type IaA/B the 3107 cm−1 absorption related defect was stable while it is not in the type IaB diamonds.

Reduced models of the dynamics of light impurity stripping

“Closed” and “open” reduced models of two or three most abundant light impurity ions in an optically thin hydrogen plasma are considered. The models are shown to satisfactorily describe the average ion charge and radiative losses within a wide range of parameters typical of laboratory and astrophysical plasmas, including the case when the relaxation time of the impurity distribution over ionization states is comparable to or longer than the characteristic times of the most important dynamic processes. The potentialities of the models are demonstrated using the carbon impurity as an example. The models proposed make it possible to analytically study the dynamics of a radiating plasma, obtain qualitatively new results, and significantly reduce the computation time when solving complicated self-consistent dynamical problems.

Lower Incorporation of Impurities in Ferritin Crystals by Suppression of Convection: Modeling Results

We have developed an axi-symmetric time-dependent numerical model of the diffusive-convective transport of a crystallizing protein and an impurity, in an isothermal crystal growth system at standard and zero gravity. We model crystallization of ferritin, a protein with Mw = 440 000, and its most abundant impurity, the protein's native dimer. The diffusivities of the protein and the dimer and the kinetic coefficients for crystallization and impurity incorporation are available. The model assumes the geometry of a cylindrical vessel used in protein crystallization trials on earth and in space, the DCAM. At terrestrial gravity, buoyancy-driven convection with a maximum velocity of 12 μm/s enhances the supply of both protein and impurity. In the absence of convection, e.g., at 0g, the diffusion depletion zone is wider and the interfacial concentrations drop significantly. The lower diffusivity of the larger dimer results in its incorporation at 0g lower by factors of 2−3 than on earth. The three-dimensional c...

Hydrogen in Cvd Diamond Films

AbstractUnderstanding of the incorporation of hydrogen and its role in determining the properties of CVD diamond is critical to the successful commercial production of these films. Hydrogen is usually the most abundant impurity in solid‐state CVD diamond and has been studied extensively by a variety of techniques, including nuclear magnetic resonance, infrared spectroscopy, and several others. This article reviews the application of a number of characterization methods to the study of hydrogen in CVD diamond, with particular attention toward understanding the incorporation of this impurity and its effect on properties of commercial significance.

Wet Chemical Cleaning and Surface Analysis of ZnSe

In this paper we report on oxidation/oxide strip sequences for the cleaning of . Bromine in methanol solutions are shown to give surface layers which are reasonably stoichiometric with the most abundant impurity begin identified as carbon with traces of oxygen, sulfur, and chlorine. While the solutions are effective in removing the oxide, the carbon contamination remains fairly stable. Ultraviolet oxygen ambient oxidations are found to result in the removal of carbon below Auger electron spectroscopy (AES) detection limits. However, subsequent acid oxide strips lead to recontamination. In addition, the acid strips typically result in an increase in the surface oxygen, chlorine, and nitrogen content over the process alone. Electron beam induced oxidation during ultrahigh vacuum (UHV) AES is identified, and the important parameters for its elimination are investigated.