Source Of Impurities Research Articles

A new sustainable concept for silicon recovery from diamond wire saw silicon powder waste: Source control and comprehensive conservation

Metal impurities and SiO2 shell are two key components that must be eliminated for 6 N silicon remanufacturing from diamond wire saw silicon powder waste. Previous research on 6 N silicon recovery has focused more on metal impurity removal without paying sufficient attention to the relationship between metal impurities and the SiO2 shell, even though the surface oxidation of silicon particles is an important factor restricting metal removal. In this study, a novel investigation into the source of metal impurities and the SiO2 shell growth was conducted, combined with acid leaching and linear regression analysis to determine the relationship between the metal impurities and the SiO2 shell. The results indicated that both raw materials displayed strong negative correlations of -0.952 and -0.996 between the removal efficiency and the thickness of the SiO2 shell. And the Al, Fe, Ni, and Mg are more likely to be enriched in the SiO2 shell due to the improper management of metal contaminants and an increase in the O content in the waste stream. Furthermore, source control and comprehensive conservation are recommended for the efficient remanufacture of 6 N silicon. This study provides a new sustainable concept for silicon recovery from diamond wire saw silicon powder waste.

Raw Sheep Wool Management for Thermal Insulation Materials: The Case of Lithuania

ABSTRACT Raw sheep wool preparation processes are closely related to the use of environmentally harmful raw materials. To solve this problem, alternative ways of cleaning wool, often called environmentally friendly, are being sought. In this research, the possibilities of using Lithuanian wool for the production of thermal insulation materials were investigated. For this purpose, 4 tons of raw wool of different breeds of sheep was selected from various Lithuanian sheep breeders’ farms. Sources of impurities in wool were identified and the amount of fat in wool was assessed. After the initial re-selection, the wool was washed in different modes and with different detergents. The recycled and washed wool was supplied to the factory for the production of thermal insulation material.The aim of this work is to identify the main sources of wool impurities, analyze the quality of wool of different sheep breeds from different farms and evaluate the washing efficiency of different detergents and methods for different sheep breeds wool, and evaluate the quality of prepared wool raw material during different actual production processes. The results of the research provide preconditions for the improvement of thermal insulation materials of the sheep wool production and its quality management.

Anthropogenic influence on surface changes at the Olivares glaciers; Central Chile

We have investigated the source and role of light-absorbing impurities (LAIs) deposited on the glaciers of the Olivares catchment, in Central Chile. LAIs can considerably darken (lowered albedo) the glacier surface, enhancing their melt. We combined chemical and mineralogical laboratory analyses of surface and ice core samples with field-based spectral reflectance measurements to investigate the nature and properties of such LAIs. Using remote sensing-based albedo maps, we upscaled local information to glacier-wide coverage. We then used a model to evaluate the sensitivity of surface mass balance to a change in ice and snow albedo. The across-scale surface observations in combination with ice core analysis revealed a history of over half a century of LAIs deposition. We found traces of mining residuals in glacier surface samples. The glaciers with highest mass loss in the catchment present enhanced concentrations of surface dust particles with low reflectance properties. Our results indicate that dust particles with strong light-absorbing capacity have been mobilized from mine tailings and deposited on the nearby glacier surfaces. Large-scale assessment from satellite-based observations revealed darkening (ice albedo lowering) at most investigated glacier tongues from 1989 to 2018. Glacier melt is sensitive to ice albedo. We believe that an accelerated winter and spring snow albedo decrease, partially triggered by surface impurities, might be responsible for the above-average mass loss encountered in this catchment.

Structural and geochemical features of coal-bearing sediments and sources of rare element impurities in coals of the Rakovka depression, Primorsky Krai, Russia

There are known brown coal deposits in Primorsky Krai (Russian Federation), where coals contain rare elements (Ge, U, REE, etc.) up to industrial concentrations. One of the known metalliferous coals is the Rakovka coal-bearing depression, located on the southern edge of the Khanka (Prikhankaiskaya) Lowland, with an area of about 70 km2. Rare-metal granites with a developed weathering crust are spread in its basement and flanks. The structural conditions forming the depression were studied using measurements of orientations of structural elements (layering, contacts, veins, and dikes) with regard to kinematic conditions of faulting. The coal and host rocks were sampled in sections in the cross strike of the coal seam. Granites and dikes cutting them were sampled by separate rock chip samples. The chemical composition and element content were determined for all samples. It was found that the adjacent rocks played a major role in the formation of the Rakovka rare-metal-coal deposit. The rare-elements enrichment is not associated with active tectonics, faults, and hydrothermal sources, as was previously assumed. Rather, it was caused by the hydrogenic and clastogenic removal of these metals from the weathering crust of granites of the depression's flanks and argillated basite dikes cutting the granites. The hydrogenic nature of the anomalous accumulation of U in sorbed form on organic matter of coals is confirmed by the predominant enrichment of low-ash beds. Rare earth elements entered coal seams both in mineral and dissolved forms. A model of REE and uranium input into the coal-bearing sediments of the Rakovka depression was proposed.

Advanced Ni tar reforming catalysts resistant to syngas impurities: Current knowledge, research gaps and future prospects

Catalytic reforming is a promising technology for the removal of tar from syngas. However, due to the presence of other impurities such as H2S, HCl, HBr, siloxanes, alkali metals, and NH3, the lifetime, activity, and stability of commonly used Ni-based catalysts is limited. This review investigates the recent findings related to poisoning effects of both common and under-researched syngas impurities on nickel catalysts and achievements in the synthesis of poison tolerant catalysts. The source and content of impurities produced from the gasification of different feedstock are examined. As current catalysts used for tar reforming require further improvement to ensure tolerance to poisoning, two approaches for catalytic tar reforming gas products from gasification of biomass/solid waste with and without prior syngas pre-treatment are evaluated to emphasize the importance of developing poison-tolerant catalysts. The deactivation mechanisms of Ni catalysts by syngas impurities, regeneration techniques, and strategies for developing poison-tolerant catalysts are reviewed. Finally, limitations of current catalytic tar reforming processes and promising approaches for future works are further discussed.

Development and validation of a simple and sensitive HPLC method for the determination of related substances in regorafenib tablets.

Regorafenib as an oral multi-kinase inhibitor has displayed a promising future in the anticancer drug market. However, there are no articles reporting the method for the determination of related substances in regorafenib tablets. A quality standard was first included in the Ph. Eur. 10.4 until April 2021 but could not detect seven known impurities A, C, D, E, FP-A, FP-B, and FP-C simultaneously. In this paper, a simple and sensitive HPLC method was established for the determination of related substances in regorafenib tablets. The determination was performed on a Polar-RP column with dual wavelength detection set at 230nm and 260nm. This method was validated according to the ICH guidelines. Furthermore, the possible sources of impurities were analyzed and forced degradation tests were performed, which provided guidance for formulation development and storage conditions. The established method is simple, sensitive and accurate for the determination of related substances in regorafenib tablets. A specified and sensitive HPLC method for the determination of related substances in regorafenib tablets.

Understanding the Water-in-Salt to Salt-in-Water Characteristics across the Zinc Chloride : Water Phase Diagram.

Using a series of time- and temperature-resolved synchrotron diffraction experiments, the relationship between multiple polymorphs of ZnCl2 and its respective hydrates is established. The δ-phase is found to be the pure anhydrous phase, while the α, β, and γ phases result from partial hydration. Diffraction, gravimetric, and calorimetric measurements across the entire ZnCl2·R H2O, 0 > R > ∞ composition range using ultrapure, doubly sublimed ZnCl2 establish the ZnCl2 : H2O phase diagram. The results are consistent with the existence of crystalline hydrates at R = 1.33, 3, and 4.5 and identify a mechanistic pathway for hydration. All water is not removed from hydrated ZnCl2 until the system is heated above its melting point. While hydration/dehydration is reversible in concentrated solutions, dehydration from dilute aqueous solutions can result in loss of HCl, the source of hydroxide impurities commonly found in commercial ZnCl2 preparations. The strong interaction between ZnCl2 and water exerts a significant impact on the solvent water such that the system exhibits a deep eutectic at a composition of about R = 7 (87.5 mol %) and a eutectic temperature below -60 °C.

Oxidation of Drugs during Drug Product Development: Problems and Solutions.

Oxidation is the second most common degradation pathway for pharmaceuticals, after hydrolysis. However, in contrast to hydrolysis, oxidation is mechanistically more complex and produces a wider range of degradation products; oxidation is thus harder to control. The propensity of a drug towards oxidation is established during forced degradation studies. However, a more realistic insight into degradation in the solid state can be achieved with accelerated studies of mixtures of drugs and excipients, as the excipients are the most common sources of impurities that have the potential to initiate oxidation of a solid drug product. Based on the results of these studies, critical parameters can be identified and appropriate measures can be taken to avoid the problems that oxidation poses to the quality of a drug product. This article reviews the most common types of oxidation mechanisms, possible sources of reactive oxygen species, and how to minimize the oxidation of a solid drug product based on a well-planned accelerated study.

TOF-SIMS analysis of decoherence sources in superconducting qubits

Superconducting qubits have emerged as a potentially foundational platform technology for addressing complex computational problems deemed intractable with classical computing. Despite recent advances enabling multiqubit designs that exhibit coherence lifetimes on the order of hundreds of μs, material quality and interfacial structures continue to curb device performance. Two-level system defects in the thin superconducting film and adjacent dielectric regions introduce stochastic noise and dissipate electromagnetic energy at the cryogenic operating temperatures. In this study, we utilize time-of-flight secondary ion mass spectrometry to understand the role specific fabrication procedures play in introducing such dissipation mechanisms in these complex systems. We interrogated Nb thin films and transmon qubit structures fabricated through slight modifications in the processing and vacuum conditions. We find that when the Nb film is sputtered onto the Si substrate, oxide and silicide regions are generated at various interfaces. We also observe that impurity species, such as niobium hydrides and carbides, are incorporated within the niobium layer during the subsequent lithographic patterning steps. The formation of these resistive compounds likely impacts the superconducting properties of the Nb thin film. Additionally, we observe the presence of halogen species distributed throughout the patterned thin films. We conclude by hypothesizing the source of such impurities in these structures in an effort to intelligently fabricate superconducting qubits and extend coherence times moving forward.

Design and physics basis for the upcoming DIII-D SAS-VW campaign to quantify tungsten leakage and transport in a new slot divertor geometry

A set of experiments are planned to exploit the high SOL collisionality enabled by a tightly baffled slot divertor geometry to suppress tungsten leakage in DIII-D. A toroidal row of graphite tiles from the Small Angle Slot (SAS) divertor is being coated with 10–15 μm of tungsten. New spectroscopic viewing chords with in-vacuo optics will measure the W gross erosion source from the divertor surface with high spatial and temporal resolution. In parallel, the bottom of the SAS divertor is changed from a flat to a ‘V’ shape. New SOLPS-ITER/DIVIMP simulations conducted with drifts using the planned ‘V’ shape predict a substantial reduction in W sourcing and SOL accumulation in either B × ∇B direction relative to either the old SAS divertor shape or the open, lower divertor. Dedicated studies are planned to carefully characterize the level of W sourcing, leakage, and scrape-off-layer (SOL) accumulation in DIII-D over a wide range of plasma scenarios. Various actuators will be assessed for their efficacy in further reducing high-Z impurity sources and leakage from the slot divertor geometry. This coupled code-experiment validation effort will be used to stress-test physics models and build confidence in extrapolations to advanced, high-Z divertor geometries for next-step devices.

Plasma-wall interaction studies in W7-X: main results from the recent divertor operations

Wendelstein 7-X (W7-X) is an optimized stellarator with a 3-dimensional five-fold modular geometry. The plasma-wall-interaction (PWI) investigations in the complex 3D geometry of W7-X were carried out by in situ spectroscopic observations, exhaust gas analysis and post-mortem measurements on a large number of plasma-facing components extracted after campaigns. The investigations showed that the divertor strike line areas on the divertor targets appeared to be the major source of carbon impurities. After multistep erosion and deposition events, carbon was found to be deposited largely at the first wall components, with thick deposits of >1 μm on some baffle tiles, moderate deposits on toroidal closure tiles and thin deposits at the heat shield tiles and the outer wall panels. Some amount of the eroded carbon was pumped out via the vacuum pumps as volatile hydrocarbons and carbon oxides (CO, CO2) formed due to the chemical processes. Boron was introduced by three boronizations and one boron powder injection experiment. Thin boron-dominated layers were found on the inner heat shield and the outer wall panels, some boron was also found at the test divertor unit and in redeposited layers together with carbon. Local erosion/deposition and global migration processes were studied using field-line transport simulations, analytical estimations, 3D-WallDYN and ERO2.0 modeling in standard magnetic field configuration.

Investigation of the double peak in the visible-light range of radiative divertor emission profiles on the EAST tokamak

The double-peaked emission profile has been identified by tomographic reconstruction from the signals of the tangentially viewing visible-light imaging system on EAST. In the upper-single-null discharge with neon seeding, two light emission peaks are located near the X-point and in the high-field-side (HFS) scrape-off layer (SOL) on the poloidal cross-section while the outer divertor target is still attached. The double-peaked emission phenomenon has not been reported for other tokamaks. In particular, the existence of the emission peak near the X-point under the attached condition is unexpected because it is usually an indication of X-point multifaceted asymmetric radiation from the edge under the detached condition. Therefore, it is of fundamental importance for the divertor physics to make clear the mechanism of the double-peaked emission phenomenon. The computational simulations with SOLPS-ITER and DIVIMP are performed in this work. The simulated results show the contribution of W impurity to the double-peaked emission profile is negligible with the upper tungsten divertor. Considering the existence of a lower carbon divertor in EAST, the influence of the possible deposition of the carbon on the upper divertor is further investigated. The simulating CIII (465 nm) and CII (514 nm) emissions, which make a significant contribution to the visible-light emission in channel B (blue) and G (green), respectively, are found to be similar tothe experimental results. The emission peak near the X-point is related to the carbon deposited on the dome, while that in the HFS SOL is contributed by the carbon on the inner baffle. The ionization source of the carbon impurity and the net force pointing to the X-point are analyzed to understand the concentration of the carbon impurity near the X-point, which in turn causes the emission peak.

Reduction of impurity sources in Si crystal growth system with electron gun beam heating

A new series of experiments was conducted to determine the source of impurities in the process of silicon crystal growth with electron beam heating. A gas-dynamic window was placed between the electron gun and growth chamber. Also positively-charged traps were placed along the crucible to reduce the number of electrons hitting the chamber and the crucible. Five experiments were conducted: two with the window, two with charge traps, and one with both the window and charge traps. The analysis of obtained samples showed that the gas-dynamic window decreases the content of Al, Cu, Fe, Cr and O2, and the trap, used in the experiments, decreases the content of Fe, Cr and Cu in residues of the melt. The content of all impurities, except Al, is close to the goal level. Al impurities come only from the gun, but the gas-dynamic window cannot eliminate them completely. It seems that Al impurities come either as neutral atoms carried by the gas or as positively charged ions. To reduce these impurities, a separation of the Al flow from the beam by the magnetic field is proposed.

A Review on Metal Impurities in Pharmaceuticals

Sources of metal impurities can from anywhere in drug product as raw material which may produce using metal catalyst, excipients, process materials, Water or any solvent used, manufacturing equipment, environment, packaging materials. So, it leads to metal impurity in high amount present in final drug product that is why it is important to check the impurity level in final drug product or as well as in process also that it should be present in low or acceptable amount. Any Drug product is not completely pure, some amount of metal impurities are always present in pharmaceutical product may cause various toxicity when it will be administered. Thus it is necessary to check impurity level is present at acceptable amount. The present review gives an account of updated information about metal impurities and reviews the regulatory aspects for such metal impurities in drug substance/drug product. In addition the aim of this article is to discuss the currently used different analytical techniques for detection of metals from drug product like spectrophotometry, X – Ray florescence spectrometry, AAS, INAA, ICP – AES, ICP – MS, MP – AES, Laser Ablation – ICP – MS etc which is used for quality control of metal impurities in pharmaceuticals.

Statistical analysis of the distribution of impurities during copper electrorefining

Electrolytic copper refining makes it possible to obtain high purity metal, so the analysis of the main ways of impurity transition into electrolysis products is an actual problem. If it is solved, the process can be controlled when changing the composition of raw materials and, as a result, the content of impurities in the anodes. This paper uses the comprehensive analysis and synchronization of a large array of data on impurities concentrations in various process media (anodes, electrolyte, slime, and cathode metal) obtained on the series of commercial cells to identify the directions of impurity flows and relationship between their content in these media. It is shown that the transition of impurities from one process medium (source) to another (receiver) is implemented according to four main patterns: linear increase, no visible dependence, the presence of a limit concentration in the receiver and the presence of a threshold concentration in the source. The paper provides the results obtained in the statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel and silver) belonging to different groups in four main pairs of the impurity source – receiver: anode – solution, anode – slime, slime – cathode, solution – cathode. The coefficients of linear regression equations are determined and their significance is estimated for all dependencies of the impurity concentration in the source on the content in the receiver. The coefficients obtained make it possible to explain the impurity transition paths observed in the commercial cells and predict the quality of cathode copper and the composition of slimes when the anode composition changes. The calculations showed that impurities are accumulated in cathodes due to the occlusion of slime particles and incomplete solution removal from the surface of commercial cathodes rather than due to electrochemical reactions. The copper electrorefining technology should be improved and developed so as to find surface-active additives that would prevent the adsorption of suspended slime particles on the cathode surface, as well as better wash them from the electrolyte.

Characterization of Nonmetallic Inclusions in Different Ferroalloys used in the Steelmaking Processes

Ferroalloys are one of the most important raw materials widely used in the steelmaking processes. Depending on the cleanliness of used ferroalloys, they can be an inevitable source of impurities and nonmetallic inclusions (NMIs) in steelmaking products. Herein, the inclusions in five different industrial ferroalloys (FeTi, FeMo, FeW, MnN, and FeCrN) are investigated. This is done using 2D investigations on polished cross sections of ferroalloy samples and using 3D investigations of NMIs on film filters and metal surfaces after electrolytic extraction (EE) using scanning electron microscopy in combination with energy‐dispersive spectroscopy (SEM‐EDS). Moreover, the characteristics of the main types of inclusions presented on film filters and metal surfaces after EE are compared and their possible transformations in Al‐killed steel are evaluated. The results show that the main inclusions are more likely the oxidization products of the reductant and some unreduced ore during the ferroalloy production process. The 3D investigations of inclusions on metal surfaces after extraction are found to be very useful in detection and evaluation of larger‐sized inclusions. Overall, this study helps to better understand the impurities in different ferroalloys and their possible effect on the steel cleanliness.

Characterization of eight unknown impurities and analysis of their source in xinfujunsu and injection by liquid chromatography coupled with ion trap/time-of-flight mass spectrometry

Eight unknown impurities in xinfujunsu and its injection were characterized by liquid chromatography coupled with ion trap/time-of-flight mass spectrometry (LC-IT-TOF MS). In order to determine the m/z values of the molecular ions and predict the formulas of all detected impurities, full scan LC–MS in positive ion mode was firstly executed to obtain the m/z value of the molecules. Then LC–MS2, LC–MS3 and LC–MS4 were carried out on target compounds to obtain as much structural information as possible. Based on MSn spectral data and exact mass measurements, the chemical structures of eight unknown impurities were characterized, among which three impurities were degradation impurities and five impurities were process impurities. In addition, the source of impurities and the correlation between process and impurities were also studied. The production of degraded impurities was caused in the high pressure sterilization process of xinfujunsu injection. Based on characterization of impurities, this study revealed the cause of impurity production and provided guidance for enterprises to improve the process to reduce impurity content. Furthermore, this study also provided scientific basis for the further improvement of official monographs in pharmacopoeias.

RF wave coupling, plasma heating and characterization of induced plasma-material interactions in WEST L-mode discharges

Plasma heating in the full tungsten (W) environment in a steady-state tokamak (WEST) relies on electromagnetic waves in both the lower hybrid (LH) and ion cyclotron range of frequencies (ICRF). The present study focuses mostly on the optimization of discharges heated with ICRF, by reporting different methods to first optimize wave coupling, optimize their absorption and reduce the impurity production. It is shown that ICRF coupling can be optimized by moving the plasma closer to antennas, increasing the plasma density, wave frequency and LH power. We show that the absorption efficiency correlates with the hydrogen concentration with the existence of an optimum between 7% and 10% as expected for a minority heating scenario. Absolutely calibrated visible spectroscopy sightlines were used to monitor ion fluxes in different locations as part of an effort to quantitatively estimate the contribution of different impurity sources to the core contamination by tungsten. It is typically found that in discharges with high total RF-power (above 5 MW of LH and 3 MW of ICRF), divertor and antenna limiter sources can reach a similar order of magnitude during the ICRF phase.

Hydrogen and Deuterium Incorporation in ZnO Films Grown by Atomic Layer Deposition

Zinc oxide (ZnO) thin films were grown by atomic layer deposition using diethylzinc (DEZ) and water. In addition to depositions with normal water, heavy water (2H2O) was used in order to study the reaction mechanisms and the hydrogen incorporation at different deposition temperatures from 30 to 200 ∘C. The total hydrogen concentration in the films was found to increase as the deposition temperature decreased. When the deposition temperature decreased close to room temperature, the main source of impurity in hydrogen changed from 1H to 2H. A sufficiently long purging time changed the main hydrogen isotope incorporated in the film back to 1H. A multiple short pulse scheme was used to study the transient steric hindrance. In addition, the effect of the storage of the samples in ambient conditions was studied. During the storage, the deuterium concentration decreased while the hydrogen concentration increased an equal amount, indicating that there was an isotope exchange reaction with ambient H2 and/or H2O.

On problem of controlling the process of cleaning a pond from impurity

The problem of controlling the process of cleaning a pond from impurity using the river flowing from it is considered. A controlled variable is the concentration of impurity entering the river from the pond. The spread of impurity in the river is described by the convection-diffusion equation. This equation includes a term that is determined by other sources of impurity entering the river. The exact value of this term is unknown. Only the boundaries of its change are set. An indicator of the control quality is the value of the linear combination of the concentration of the impurity in the river at a given moment of time and the remaining amount of the mass of the impurity at that moment in the pond. The goal of the control is to bring the value of this indicator within the specified interval.