Cadmium Impurities Research Articles

A new targetry system for cyclotron production of pharmaceutical grade indium-111 radioisotope

Abstract The aim of this research is to present a new, fast, simple, low-cost and innovative method for the production and purification of pharmaceutical grade indium-111 chloride for use in nuclear medicine.In the previous methods for cyclotron production of indium-111 radioisotope, besides the need for high amount of enriched cadmium, in electrodeposition of enriched cadmium on copper backings for target preparation and its chemical dissolution step, impurities of isotopes of copper and zinc enter the final product. So, radiolabeling of such products was hard or impossible with some molecules. In this research, due to the proper selection of the target isotope, enriched cadmium-112, and the optimal proton bombardment energy, only very low amount radioisotopic impurities were produced and observed in the sample solution. After the separation process, the amounts of zinc-65 and indium-114 were less than the standard permissible amounts in indium-111 radiopharmaceuticals. The concentration of cadmium impurities in the final product was less than 0.1 ppm. The radionuclidic purity of the sample was confirmed by gamma ray spectroscopy, and it was found to be suitable for use in preclinical studies.

Removing Cadmium Impurities from Cation‐Exchange‐Derived CuInSe2/CuInS2 Nanorods for Enhanced Infrared Emission and Photodetection

AbstractMetal chalcogenide nanocrystals with variable composition and shape can conveniently be produced using cation exchange synthesis; however, the presence of cation‐containing ligands inherited from the starting material often results in contamination of the final product. To address this issue, a two‐step ligand replacement strategy is developed to fabricate CuInSe2/CuInS2 nanorods from CdSe/CdS nanorods via removal of Cd‐phosphonates from an intermediate Cu2‐xSe/Cu2‐xS phase used in the cation exchange conversion. This synthetic approach furnishes CuInSe2/CuInS2 nanorods with cadmium content below 1 at.%, and high photoluminescence quantum yields reaching 40% in the near‐infrared spectral range. Transient absorption studies reveal that the band alignment in the CuInSe2/CuInS2 heterostructure features a quasi‐type II character, with an electron localized in the core and a hole wavefunction spread over the entire nanorod. The efficient passivation of the core and the reduced Cd content leads to excitonic emission with full width at half maximum down to 110 meV, superimposed with a broad emission band from copper‐induced defects. Field‐effect transistors based on cadmium‐free CuInSe2/CuInS2 nanorods show two orders of magnitude lower noise current density compared with the cadmium‐rich devices. The responsivity and specific detectivity of these devices reach 230 mA W−1 and 108 Jones, respectively, under near‐infrared excitation at room temperature.

The Toxicological Risk Assessment of Lead and Cadmium in Valeriana officinalis L., radix (Valerian root) as Herbal Medicinal Product for the Relief of Mild Nervous Tension and Sleep Disorders Available in Polish Pharmacies

Studies related to the toxicological risk assessment (TRA) of heavy metal impurities (HMIs) in pharmaceuticals are an important issue but there is a lack of refereed literature around the safety of Valeriana officinalis L., radix (Valerian root) as herbal medicinal product (HMP) for the relief of mild nervous tension and sleep disorders according to lead and cadmium impurities. The aim of the study was to estimate the TRA of lead and cadmium in Valeriana officinalis L., radix (Valerian root) as HMP (n = 5) available in Polish pharmacies. In the case of herbal pharmaceuticals, it is particularly important to control the level of HMIs accumulated during the plant’s growth. Perhaps, the exposure for a single dose is not relevant; however, justification of our studies is a fact that herbal therapies are usually long term. Therefore, even small HMI doses as present in particular plant may accumulate in patient body over a long period of time. Levels of lead and cadmium were measured by electrothermal atomization atomic absorption spectrometry. The levels of lead and cadmium as HMIs (independently of the producer and declared composition) are quite similar. Our results are satisfactory, confirming the safety of Valeriana officinalis L., radix (Valerian root) as herbal medicinal product for the relief of mild nervous tension and sleep disorders available in Polish pharmacies according to ICH guideline Q3D. To the best of our knowledge, this paper is the first study about lead and cadmium content as HMIs in HMP containing Valeriana officinalis L., radix (Valerian root).

Providing Practical Instruction for Solving Environmental Problems from Residue (cake) of Cold Purification Process in Zinc Production Process

Background and Objective: In the waste from the cold treatment process in zinc production plants, there is about 40 to 50% of zinc and other harmful heavy metals such as cadmium and nickel. Cadmium and nickel are among the heavy metals that are harmful to human health in high concentrations. Removal of bio-pollutants from these wastes is one of the concerns of the zinc industry. The purpose of this study is to remove nickel and cadmium as impurities in the zinc production process by cementation method. Methodology:The procedure consists of three steps: cold purification cake leaching, impurity purification and electrolysis. The cake is first liquefied with sulfuric acid and the resulting solution contains zinc ions along with nickel and cadmium impurities. Optimal conditions for the removal of impurities were obtained by the surface response method (RSM), then the filtration process was performed by the cementation method and the impurities were removed and finally the solution was electrolyzed to produce zinc. Using Design Expert (DOE) test design software, the parameters affecting the filtration process such as temperature, zinc powder concentration, retention time and additive concentration were investigated. Findings: It was found that most influences related to contact time, temperature, zinc powder amount and additive concentration, respectively. So, optimum conditions for removal of nickel and cadmium containing temperature of 85 centigrade, concentration of 6.63 mg L-1 of zinc powder, contact time of 100 min and concentration of 10.29 mg L-1 for additive were obtained. At these conditions, impurities amounts were reached to the allowed limit for electrolysis and zinc in the cake was recovery. Conclusions: Using cementation method by removing impurities and then recovering zinc, in addition to solving some of the environmental problems caused by the cake, the recovery of these metals is of great economic importance.

Formation of 107Cd radionuclide impurities during 18F production

Cd isotopes (107Cd and 109Cd) are generated from the silver target body during the bombardment of [18O]water in the routine production of 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) for PET (Positron Emission Tomography) diagnosis. Cadmium isotopes contribute significantly to the total activity of generated impurities and, due to being potentially radiotoxic to living organisms, they should be effectively reduced from FDG to prevent accidental injection of even small concentrations into patients. Purification of the final [18F]FDG can be based on a set of columns, fulfilling various functions in the cleaning process. To assess cadmium impurities and the efficiency of the purification process, a low background gamma spectrometry system with high resolution has been applied.Even activity of 3.5 kBq and 290 kBq has been measured on QMA (Sep-Pak Light Accell Plus QMA) columns for 109Cd and 107Cd isotopes, respectively. 107Cd activity in the five column set was higher than that of 109Cd. The rate of 18F production process was about 1 GBq/min, while that of 107Cd and 109Cd radionuclides was about 4.2 kBq/min and 50 Bq/min respectively.The same purification efficiency of both isotopes has been obtained at each step of the process. The production rate of 107Cd and 109Cd radionuclides was insignificant compared to the 18F production rate. Therefore [18F]FDG final product for use in injections before PET diagnostics was efficiently purified from cadmium radionuclide impurities.

Sequential coprecipitation and matrix removal for determination of cadmium impurities from multivitamin supplements by inductively coupled plasma mass spectrometry and method validation by isotope dilution analysis of SRM 3280 multivitamin/multielement tablets

In this paper, we examined three different sequential coprecipitation schemes based on Mg(OH)2 and CaF2 precipitation using triethylamine (TEA) and hydrofluoric acid (HF), respectively, for determination of cadmium (Cd) impurities from multivitamin/mineral (MVM) supplements by isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS). The schemes involved three-step coprecipitation with either TEA alone or in combination with HF and are designated as Scheme 1 (TEA-TEA-TEA), Scheme 2 (TEA-HF-TEA) and Scheme 3 (HF-TEA-TEA) according to the addition sequence of each reagent. Experiments were carried out with MVM solutions spiked with 60μgL−1 Cd from a multielement standard solution. All schemes provided quantitative separation of Cd from MVM matrix. Scheme 1 was the least effective in removal of interfering concomitant elements, molybdenum (Mo) and tin (Sn). Scheme 2 performed better for Sn, but failed in eliminating Mo. Scheme 3 was the most effective in eliminating both Mo and Sn. Mo levels in test MVM solutions reduced from 4.3μgmL−1 to as low as 0.014μgmL−1 while that for Sn decreased from 0.5μgmL−1 to 0.018μgmL−1 allowing interference-free determination of Cd to be achieved. Salt-matrix due to Mg, Ca, P and K along with the essential elements (Mn, Fe, Cu and Zn) levels was also reduced significantly. Reagent blanks from HF and TEA were insignificant (0.008μgL−1) allowing a limit of detection of 0.004μgL−1 or 0.26ngg−1 Cd to be achieved (3σ, n=6). The performance of the coprecipitation method (Scheme 3) was validated by determination of Cd in multivitamin/multielement tablets certified reference material (SRM 3280) by ID-ICP-MS. Experimental results (ngg−1) and recoveries were 78.8±4.7 (98.5%), 77.9±5.2 (97.4%) and 76.5±4.8 (95.6%) for 110Cd, 111Cd and 114Cd isotopes, respectively. Several commercial MVM supplements were analyzed using the method. Mean Cd concentration ranged from 21.4ngg−1 to 93.3ngg−1. These values are much lower than those reported to date for various MVM supplements by ICP-MS determinations without chemical separation.

Impact of cadmium and phosphate ions on the hematite nanorings formation

It has been suggested that the addition of divalent metal cations during the hydrothermal synthesis of hematite (α-Fe2O3) in the presence of phosphate ions has a strong impact on the hematite morphology, crystal growth and dissolution (Gotić et al., J. Mol. Struct. 993 (2011) 167). In this work, the same system was modified with divalent cadmium ions and the impacts of cadmium and phosphate ions on the hematite nanorings formation have been studied. It has been found that formed hematite and akaganeite (β-FeOOH) precipitates did not contain any trace of cadmium impurities. On the contrary, the modification with divalent cadmium cations changes the PO43−/Fe3+ molar ratio in the system. Upon the addition of cadmium ions the PO43−/Fe3+ molar ratio changes from 0.036 in a pure system to 0.051 in the cadmium modified system. The relative increase of phosphate concentration at early stage of precipitation induced the change of spindle to spherical morphology and formation of the poorly crystallised akaganeite-like phase. The appearance of akaganeite-like phase directly correlated with the delay in the crystallisation of hematite. Besides, the relative increase of phosphate concentration has the prevailing effect for the change of spindle to pseudosphere and nanotube to nanoring particle morphologies.

Local distortions revealed by neutron holography inSnCd0.0026alloy

Local distortions of the ideal periodic structure in crystals around impurity atoms play an important role in various physical properties of materials. The aim of this study was to investigate the static distortions around cadmium impurity atoms in a ${\text{SnCd}}_{0.0026}$ single crystal using atomic resolution neutron holography technique. The cadmium nucleus was used as an inside detector to measure the holographic interference pattern from which the three-dimensional (3D) atomic arrangement of tin nuclei around the cadmium impurities was reconstructed. Detailed analysis of the reconstructed image revealed the 3D static displacements of Sn atoms around the impurity. It was found that the crystal structure contracts around the cadmium impurity atom and the displacements tend to transform the crystal to the $\ensuremath{\alpha}$ phase. The local contraction of the lattice was used to explain the slower phase transformation to $\ensuremath{\alpha}$-Sn phase when Cd impurity atoms are present. The study shows the ability of neutron holography to measure 3D displacements around impurities which can be used, e.g., to understand the mechanisms that block the phase transformations in the presence of impurities.

A new approach to the optimisation of zinc electrolyte cold purification process by Taguchi’s method

The neutralised zinc sulfate solution obtained from hydrometallurgical process of Angouran zinc concentrate has cadmium, nickel and cobalt impurities that must be purified before electrowinning. Therefore, cadmium and nickel are usually cemented out by addition of zinc dust under cold purification conditions. The present research aims to introduce a new technique for determination of effective parameters and optimisation of zinc electrolyte cold purification process using statistical design of experiments. The Taguchi’s method, based on orthogonal array design (OAD), was used to arrange the experiments. The experimental conditions addressed in the study were: the temperature range of 45–65°C for reaction temperature (T), one to five series for zinc dust particle size distributions (S), 15–75 min for reaction time (t), 1–2⋅5 g L−1 for zinc powder concentration (M), and 200–600 rev min−1 (R) for stirring speed. Optimum conditions for cold purification obtained in this study were T4 (60°C), S1 (series 1), t3 (45 min), M5 (2⋅5 g L−1), and R1 (200 rev min−1).La solution neutralisée de sulfate de zinc, obtenue à partir du procédé d’hydrométallurgie du concentré de zinc provenant d’Angouran, contient des impuretés de cadmium, de nickel et de cobalt que l’on doit purifier avant l’extraction électrolytique. Habituellement, on extrait le cadmium et le nickel par cémentation par addition de poudre de zinc sous des conditions de purification à froid. La recherche actuelle a pour but d’introduire une nouvelle technique pour la détermination des paramètres efficaces et pour l’optimisation du procédé de purification à froid de l’électrolyte de zinc en utilisant un plan d’expérience statistique. On a utilisé la méthode de Taguchi, basée sur un concept d’arrangement orthogonal (OAD), pour planifier les expériences. Les conditions expérimentales examinées dans l’étude incluaient la gamme de température de 45 à 65°C pour la température de réaction (T), une série d’une à cinq distributions de taille de particule de la poudre de zinc (S), de 15 à 75 min pour le temps de réaction (t), de 1 à 2⋅5 g L−1 pour la concentration de la poudre de zinc (M) et de 200 à 600 rpm (R) pour la vitesse d’agitation. Les conditions optimales obtenues dans cette étude pour la purification à froid étaient de T4 (60°C), S1 (série 1), t3 (45 min), M5 (2⋅5 g L−1) et R1 (200 rpm).

On the nature of a lattice vibrational mode at a frequency of 135 cm−1 in Hg1 − x Cd x Te alloys

The vibrational spectrum of a cadmium impurity atom in the HgTe crystal has been calculated using the microscopic theory of lattice dynamics in the approximation of a low impurity concentration. Within this theory, the behavior of the local and quasi-local modes induced upon substitution of the lighter Cd atom for the Hg atom in the region of the zero or very low one-phonon density of states in the HgTe crystal has been considered. It has been found that, apart from the local mode at a frequency of 155 cm−1, the calculated vibrational spectra exhibit a weak (but clearly pronounced) feature at a frequency of 134 cm−1, which coincides with the experimentally observed vibrational mode (the “minicluster” mode) at a frequency of 135 cm−1 in the Hg1 − xCdxTe (x = 0.2–0.3) alloys at 80 K.

Paramagnetic center Cd+(2 S 1/2) in natural carbonate apatites Ca5(PO4)3 − n (CO3) n (F,OH)

The stable paramagnetic center Cd+(2S1/2) in natural sedimentary calcium phosphates containing a cadmium impurity has been studied using electron paramagnetic resonance. The parameters of the spectrum have been determined, and the influence of different radiation types on the paramagnetic center has been investigated.

Levels of Mercury, Cadmium, and Zinc in the Topsoil of Some Selected Towns in the Wassa West District of the Western Region of Ghana

The Wassa West District of the western region of Ghana is noted for a large deposit of gold ores. As a result, there is a lot of mining activity in the district, which include both legal and illegal miners. A large number of illegal (“galamsey”) miners employ mercury in the amalgamation of gold, whereas some of the mining companies use zinc dust (with associated cadmium impurities) in the extraction of gold. Due to the potentially toxic and adverse effect of mercury and cadmium on humans, livestock, and aquatic organisms, this research seeks to determine the concentration of mercury, cadmium, and zinc in the topsoil (up to 30cm), which constitutes the absorption zone of most food crops grown in the district, and compares these levels with literature values as well as control samples taken from other non-mining districts, thus assess the pollution due to these metals. The results for mercury gave a peak average concentration of 2.8 mg/kg around Aboso and decreased to 0.41 mg/kg at Dompem to the south and 0.33 mg/kg at Huni Valley to the north. All these concentrations were higher than those found in the control samples as well as the standard (0.3 mg/kg) found in literature. The contamination of control samples with mercury suggests aerial distribution of the metal. Zinc concentrations, however, did not show any trend that could be due to anthropogenic sources or natural deposition of the metal. However, high concentrations of 387 mg/kg at Aboso, 170 mg/kg at Tarkwa, and 221 mg/kg at Dompem give an indication of the use of zinc dust in the extraction of gold. The research, however, did not detect cadmium above the detection limit of the instrument used.

Raman scattering and optical normal vibrations of the Zn1−x CdxSe crystal lattice

The nonresonant spectra of the Raman scattering in Zn1−x CdxSe crystals (0≤ x≤1) are investigated. The mode doublet was found to gradually shift with increasing x from the longitudinal-transverse frequencies of ZnSe to the longitudinal-transverse frequencies of CdSe. Furthermore, an additional branch of weak modes was observed between the doublet components. The frequencies of this branch are shown to correspond to the frequencies of the cadmium impurity vibrations in the ZnSe lattice at x=0 and the zinc impurity vibrations in the CdSe lattice at x=1. The concentration dependences of the modes and atomic displacements are analyzed by using the isodisplacement model that includes the interaction between ZnSe-and CdSe-like vibrations. It is concluded that a one-mode behavior with the formation of an additional weak branch in the longitudinal-transverse splitting region is characteristic of this system.

Microtopography and field emission properties of carbon films grown in a microwave gas discharge plasma

Graphite-like carbon films are grown in an ethanol vapor plasma in a microwave gas discharge. The electrical parameters controlling the microtopography and electronic properties of carbon films are determined. It is shown that electron bombardment affects the fine structure of graphite-like nanocrystallites and their emissive power with characteristics close to those of carbon nanotubes. The emission properties of layered graphite-like films can be improved by metal (cadmium) impurity doping. For nanocrystalline graphite-like films, emission currents with a density of 0.3 A/cm2 are induced at an electric field strength of less than 7 V/µ m in the gap.

The removal of cadmium impurities from cobalt–nickel solutions by precipitation with sodium diisobutyldithiophosphinate

Cadmium sometimes occurs as a minor impurity in cobalt–nickel solutions which are to be processed by solvent extraction for the recovery of cobalt. However, the organophosphorus reagents used for this purpose extract cadmium in preference to cobalt. Consequently, the feed solutions must be pretreated for the removal of cadmium in order to avoid contamination of the final product. This note describes a selective method of removing cadmium by precipitation as its diisobutyldithiophosphinate complex.

Hafnium, cadmium and indium impurities in 4H-SiC observed by perturbed angular correlation spectroscopy

Abstract The annealing behaviour of hafnium impurities in silicon carbide after ion implantation and the formation and stability of complexes of hafnium in 4H-SiC were studied by perturbed angular correlation spectroscopy (PAC) for the first time. Samples of 4H-silicon carbide single crystals were doped with radioactive 181Hf ( t 1 2 = 42.5 d ) and annealed at temperatures of between 600 and 1850 K. After an annealing step at 900 K two axially symmetric electric field gradients (EFGs) were observed oriented along the c-axis of the crystal. Depending on the implantation dose, the fraction of probe atoms exposed to these EFGs increases with the annealing temperature.

Perturbed -Angular -Correlation Spectroscopy on Indium- and Cadmium- Complexes in Silicon Carbide

ABSTRACTComplex formation at indium and cadmium impurities implanted into samples of 3C-, 4H-and 6H- SiC was investigated by means of Perturbed Angular Correlation (PAC)-Spectroscopy. After annealing at 1600 K up to five different configurations characterized by their specific electric field gradients (EFG(i)) were observed in 6H- SiC, only four complexes in 4H- SiC; in the 3C- modification no complex was observed. All EFG's are axially symmetric and are oriented along the c- axis of the crystal. In a highly nitrogen doped 6H- SiC epi- layer an new EFG was observed. It is tentatively assigned to a close indium- nitrogen pair.

Drilling Fluids: Making Peace With the Environment

Summary Environmental problems, although nettlesome and often costly, have stimulated new developments in drilling-fluid technologies. Minimizing environmental impact involves reducing levels of toxic components in drilling fluids, waste minimization, and recycling. Significant progress is being made. This paper assesses the current state of technology and likely future directions. The constructive role of regulatory agencies in recognizing, fostering, and encouraging the use of emerging technologies, as opposed to blanket prohibitions, also is discussed. Introduction Mud companies have identified replacements for diesel and mineral oils in lubricants and spotting fluids that combine performance and environmental acceptability. Non-chloride potassium sources have replaced KCl in many water-based muds. New cationic polymer muds often are touted as replacements for oil-based muds, and preliminary field results are encouraging. The trend to polymer muds, in general, has reduced consumption of traditional linosulfonate additives and other organometallic complexes. Weighting agents also have been affected. Barite ore sources are scrutinized carefully for their trace heavy metal content, particularly cadmium and mercury impurities. Muds based on synthetic, low-toxicity, biodegradable, organic liquids are now available. These synthetic muds offer "designed-in" performance and environmental characteristics. Processing of drilling-fluid waste is a rapidly growing industry. Commercially available technologies include dewatering, land farming, cuttings injection, fixation, and distillation. Bioremediation and solvent extraction have promise for the future. All of these affect the economics and the environmental acceptability of drilling operations. Tradeoffs between environmentally desired features (e.g., lower toxicity but larger waste volumes) also are addressed. Background Drilling-fluids companies supply and engineer the properties of fluids required in drilling of oil and gas wells. Although "mud" still describes the appearance of drilling fluids and is used freely in this paper, the term understates their complexity. Historically, as the performance demands on drilling fluids increased, chemicals were found that enhanced performance at relatively low concentrations. Oil-based muds were developed for situations where water-based muds were inadequate. By the mid-1970's, the technology had matured almost to self-satisfied complacency. Drilling-fluids companies received an unmistakable environmental wake-up call in 1978. Oil companies wishing to drill exploratory wells off the U.S. mid-Atlantic coast had agreed, as a permit condition, to support a drilling-mud bioassay program.1 A testing protocol using the shrimp species Mysidopsis bahia (Mysid shrimp), worked out with the U.S. Environmental Protection Agency (EPA), became the basis for assessing toxicity of drilling fluids and additives. Also in 1978, the state of Alabama moved aggressively to enforce discharge regulations on oil companies drilling in Mobile Bay, signaling that local governments also would look more closely at drilling fluids. While environmental considerations had always been present, they surged to the foreground. Environmental acceptability now ranked with traditional cost and performance considerations in decisions on drilling fluids and additives. This paper provides a snapshot of the current status of drilling fluids vis-à-vis the environment in the U.S. It describes progress made in improving environmental acceptability and suggests future directions. A deliberate attempt is made to present technical matters in a straightforward manner with enough background that environmentally concerned persons outside the industry can use it as a reference. At the same time, this paper touches on the most advanced fluids and technologies available today and those undergoing significant development. The interplay among environmental concerns, new technology, and the regulatory framework is an underlying theme. Issues addressed in this paper include toxicity of water-based muds, heavy-metal impurities in barite, limitations of water-based muds, oil-based muds and alternatives, drilling-waste volumes, disposal options, and regulatory impact. Biodegradability and bioaccumulation issues are in early stages of definition in terms of test protocols and interpretations2 and are more properly the subject of a separate paper.

Microscopical studies at cadmium impurities in compound semiconductors

Molecule-like defect complexes have been studied at Cd acceptors in the III–V semiconductors GaAs, GaP, InP, InAs, and InSb by PAC spectroscopy. After hydrogen plasma treatment, the formation of Cd-H complexes was observed in all these compounds. Additionally, the formation and stability of Cd-S and Cd-Se pairs in GaAs have been analyzed.

Electrolytic Separation and Recovery in Caustic of Steel and Zinc from Galvanized Steel Scrap

Abstract Experiments were conducted to examine the technical and economic feasibility of a single-step process for electrochemically separating and recovering in hot caustic the components of galvanized steel. Electrochemical separation is practical because: 1. maximum anodic zinc dissolution currents yield commercially acceptable throughputs and are 1000 times greater than those for steel, 2. steel is not seriously corroded by caustic under conditions proposed and 3. the process is robust in the presence of expected aluminum, lead, cadmium and iron impurities. Stripping experiments in 5 M NaOH at 90°C indicate that a G-90 grade (275 g Zn/m2) of galvanized steel can be stripped in about five minutes at a current density of 200 mA/cm2 in a cell with parallel electrodes separated 15 to 59 mm. Tests with scrap at densities of 30 and 150 lbs/ft2 were successful at estimated current densities of about 20 mA/cm2. Residual zinc levels on the steel are less than 0.1 wt%. A technical and economic analysis of alter...