Pure Cobalt Metal Research Articles

Electrolytic Recovery of Metal Cobalt from Waste Catalyst Pickling Solution.

Terephthalic acid production plant uses liquid cobalt–manganese bromide as a catalyst. The waste catalyst is burned with exhaust gas and accumulated in fly ash, which is further pickled and impregnated with a sulfuric acid solution. The resultant solution is rich in cobalt and manganese metal ions with few metal impurities from other petroleum raw materials. An electrochemical reduction method is used to recover cobalt metal from the waste catalyst fly ash pickling solution of terephthalic acid. Various steps have been taken to remove impurities and extract and separate the required pure cobalt metal solution. Afterward, the process of electrolytic reduction smelting is conducted. Variables investigated include current density, electrolyte pH, electrode materials, and electrolytic cell diaphragms, among several others. Results show that the product purity can reach up to 99.84% for the electrolyte feed composition of 21.4 g L−1 Co, 38.2 g L−1 Na, and 2.02 g L−1 Mg.

Carcinogenic assessment of cobalt-containing alloys in medical devices or cobalt in occupational settings: A systematic review and meta-analysis of overall cancer risk from published epidemiologic studies

In 2020, the European Commission up-classified pure cobalt metal to a Category 1B hazard, based primarily on data from rodent inhalation carcinogenicity studies of metallic cobalt. The European Commission review did not evaluate cobalt-containing alloys in medical devices, which have very different properties vs. pure cobalt metal and did not include a systematic epidemiologic review. We performed a systematic review and meta-analysis of published, peer-reviewed epidemiologic studies evaluating the association between overall cancer risk and exposure to orthopedic implants containing cobalt alloys or cobalt particulates in occupational settings. Study-specific estimates were pooled using random-effects models. Analyses included 20 papers on orthopedic implants and 10 occupational cohort papers (~1 million individuals). The meta-analysis summary estimates (95% confidence intervals) for overall cancer risk were 1.00 (0.96–1.04) overall and 0.97 (0.94–1.00) among high-quality studies. Results were also similar in analyses stratified by type of exposure/data sources (occupational cohort, implant registry or database), comparators (general or implant population), cancer incidence or mortality, follow-up duration (latency period), and study precision. In conclusion, meta-analysis found no association between exposure to orthopedic implants containing cobalt alloys or cobalt particulates in occupational settings and overall cancer risk, including an analysis of studies directly comparing metal-on-metal vs. non-metal-on-metal implants.

59Co Internal field NMR analysis of Co35Fe35Ni30 alloy synthesized via novel low cost chemical reduction technique

We have synthesized ternary cobalt alloy using a chemical reduction process using hydrazine as a reducing agent . X-Ray Diffraction (XRD) measurements shows that the synthesized cobalt ternary alloy exists in the pure face centred cubic (fcc) phase with lattice parameter of 3.5562 ± 5 Å. The SEM micrograph shows that the particles exist in the spherical shape which suggests that the particles are crystallized in fcc phase. The magnetic properties are determined using Vibrating Sample Magnetometry (VSM) and 59Co IFNMR technique. The saturation magnetization (MS) of the synthesized sample is ~80 emu/g, a slightly lower value compared to the pure cobalt metal. 59Co IFNMR technique shows that there is a broad distribution of hyperfine field (~6 T) compared to the pure fcc cobalt metal. Further, from the deconvoluted NMR peaks suggests that the variation in the nearest neighbours to the central cobalt atom leads to the different hyperfine field.

Elucidating the K‐Edge X‐Ray Absorption Near‐Edge Structure of Cobalt Carbide

AbstractThe cobalt K‐edge X‐ray absorption near‐edge structure of a cobalt carbide compound, synthetized under in‐situ conditions, has been determined by using laboratory‐based and synchrotron‐based X‐ray absorption spectroscopy. We have carburized pure cobalt metal in‐situ, avoiding all adverse effects of metal‐support interactions as well as any degradation of the cobalt carbide formed. A non‐negative matrix factorization was applied to determine the features of the spectrum of cobalt carbide, highly needed to identify this phase in an unambiguous manner in cobalt‐based Fischer‐Tropsch catalysts.

Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel.

Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially 'clean' strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2(•-) radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO(-)) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems, especially once the influence of both the atomic-scale structure and the presence of oxide are mechanistically better understood.

A density functional theory study on influence of 3d alloying elements on electrochemical properties of cobalt-base alloys

The paper systematically studies the impact of the 3d transition metals Ti, V, Cr, Mn, Fe, Ni and Cu on electrochemical stability of non-passivated cobalt-base alloys {0001} surface by evaluating the chemical potential and the electrode potential shift relative to pure cobalt metal using density functional theory calculations. Cr, Fe, Mn, and V are found to make the Co atoms more stable on the {0001} surfaces of the corresponding alloys compared to pure Co {0001} surfaces, whereas Ti, Ni, and Cu make Co atoms much less stable. Among all the considered alloying elements, chrome is the most beneficial to the stability enhancement of alloys. Furthermore, the effects of water and hydroxyl adsorption on the electrochemical stability are considered. It is found that the surface adsorption properties may be considerably modified by introducing the Cr atoms. Our results indicate that water or hydroxyl adsorption destabilizes both the Co–Cr alloy and pure Co surface. However, the Co–Cr alloy surface is still more stable than the pure Co surface in the presence of adsorbed water, while the pure Co surface is more stable than the Co–Cr alloy surface in the presence of adsorbed hydroxyl. Our calculation reveals that the electrochemical corrosion property of the Co–Cr alloy is insensitive to water adsorption and sensitive to hydroxyl adsorption in comparison with the pure Co metal.

First-principles study on influence of alloying elements on electrochemical stability of cobalt-base alloys

The paper studies the impact of the metal elements Nb, Ta, Zr, Mo, W, Al, Si, and Y on electrochemical stability of non-passivated cobalt-base alloys by evaluating the chemical potential and the electrode potential shift relative to pure cobalt metal using first-principles calculations. Nb, Ta, and Si are found to make the surface Co atoms more stable on the {0001} surfaces of the corresponding alloys compared to pure Co {0001} surfaces, whereas Al, W, Mo, Y, and Zr make Co atoms less stable. Among all the considered alloying elements, niobium is the most beneficial to the stability enhancement of alloys. Furthermore, the effects of water adsorption on the electrochemical stability are considered. It is found that the surface adsorption properties may be considerably modified by introducing the Nb atoms. Our results indicate that water adsorption destabilizes both the alloy and pure metal surface. However, the CoNb alloy surface is still more stable than the pure Co surface in the presence of absorbed water. Our calculation reveals that the electrochemical stability of the CoNb alloy is sensitive to water molecular adsorption in comparison with that of the pure Co metal.

Investigations on cobalt doped GaN for spintronic applications

(Ga1−xCox)N was synthesized at 1223K using pure gallium and cobalt metal as precursors in a reactor specially designed for this purpose with ammonia as the nitrogen source. The structural confirmation of wurtzite phase of GaN is done using powder X-ray diffractometer. Photoluminescence shows red shift in band edge emission as the cobalt concentration increases from 1 to 5 atomic percentage together with nitrogen related vacancy emission at 3.24eV and cobalt related emission at 3.13eV. The magnetic properties were studied at 10K using superconducting quantum interface device (SQUID). The obtained maximum magnetic moments for 1%, 3% and 5% cobalt doped GaN are 1.63, 0.21 and 0.14μB, respectively. The decrease in magnetic moment with increase in dopant concentration may be due to the formation of secondary phases or cobalt cluster, which contributes to anti-ferromagnetism. From temperature dependent magnetization measurements it is observed that there is no drastic change in the magnetic moment upto room temperature for 1% cobalt doped GaN. Theoretical calculations based on the density functional theory within Tight Binding Linear Muffin-tin Orbital (TBLMTO) method has been carried out to study the magnetic properties of cobalt doped GaN. The obtained magnetic moment values per Co atom are 2.56μB for 1.56% and 2.77% and 1.50μB for 4.20%. This is found to be higher when compared with experimental values and this difference is explained based on structural defects and percentage of dopant used during synthesis. The half metallic behavior is observed for 1.56% and 2.77% Co dopants, but for higher percentage of dopant the system becomes metallic. Hence, it is concluded that only lower percentage of cobalt doped GaN is suitable for spintronic applications.

Synthesis and crystal structure of [Co(NH3)6][AuX4]X2 (X = Cl−, Br−)

[Co(NH3)6][AuX4]X2 binary complex salts, where X = Cl− (I) and Br− (II), have been obtained and defined by element, X-ray diffraction, and thermal analyses and by IR, Raman, and electron spectroscopy. The compounds are isostructural. Their structural units are the [Co(NH3)6]3+ complex cations, the [AuX4]− complex anions, and the X− anions. The plane square environment of the gold atom is completed to an elongated bipyramid by two halide ions lying at distances Au...Cl 3.245 A for I and Au...Br 3.362 A for II. The thermolysis products of I and II are pure gold and cobalt metal powders when thermolysis is performed under hydrogen and a mixture of metallic gold with cobalt halide in a reaction under an inert atmosphere.

Allotropic phase transformations in HCP, FCC and BCC metastable structures in Co-nanoparticles

The effect of particle size on stability of crystal structure of pure cobalt metal is studied. The common HCP allotrope of it is stable in bulk. It assumes an FCC or a BCC structure on reducing its size below a critical value R c at a nanometer scale. Separated Co-particles coreduced (using a reducing agent) from highly dispersed Co 2+-cations in a liquid or a solid medium have a strict control of size at D=2–5 nm for the BCC structure and D=10–20 nm for the FCC structure. Both of them are substantially stable at least within the temperature range of 700°C and do not transform to the HCP structure as long as their size is controlled within these regions. The present crystal structure modification in a particle occurs in a manner that it has a minimal value of its total surface energy Ω=Aσ, with A its total surface area and σ the surface-energy density. It yields a stable equilibrium configuration of atoms with its minimal internal energy.

Germanium segregation in the Co/SiGe/Si(001) thin film system

Cobalt disilicide contacts to silicon–germanium alloys were formed by direct deposition of pure cobalt metal onto silicon–germanium films on Si(001) substrates. Segregation of germanium was observed during the reaction of the cobalt with the silicon–germanium alloy. The nature of the Ge segregation was studied by transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. In the case of cobalt films deposited onto strained silicon–germanium films, the Ge segregation was discovered to be in the form of Ge-enriched Si1−xGex regions found at the surface of the film surrounding CoSi and CoSi2 grains. In the case of cobalt films deposited onto relaxed silicon–germanium films, the Ge segregation was dependent on formation of CoSi2. In samples annealed below 800 °C, where CoSi was the dominant silicide phase, the Ge segregation was similar in form to the strained Si1−xGex case. In samples annealed above 800 °C, where CoSi2 was the dominant silicide phase, the Ge segregation was also in the form of tetrahedron-shaped, Ge-enriched, silicon–germanium precipitates, which formed at the substrate/silicon– germanium film interface and grew into the Si substrate. A possible mechanism for the formation of these precipitates is presented based on vacancy generation during the silicidation reaction coupled with an increased driving force for Ge diffusion due to silicon depletion in the alloy layer.

The oxidation of a co-15 wt% ce alloy under low oxygen pressures at 600–800°c

The scaling of pure cerium and of a cobalt-base alloy containing approximately 15 wt% cerium was studied at 600–800°C in H 2-CO 2 mixtures providing at equilibrium an oxygen pressure of 10 −24 atm at 600°C and of 10 −20 atm at 700 and 800°C. Scaling of Co-15Ce formed internal oxidation region where the Ce-rich phase produced a mixture of cobalt metal and cerium oxide. The kinetics of internal oxidation were very much faster than calculated from the known values of the diffusivity\\solubility of oxygen in pure cobalt. The microstructure of the internal oxidation region followed closely that of the original alloy, while cerium was not depleted in the alloy. At 700 and 800°C a thin outermost layer of pure cobalt metal was also produced.

The oxidation of a Co-15wt%y alloy under low oxygen pressures at 600–800 °C

The corrosion of pure yttrium and of a cobalt alloy containing approximately 15 wt% yttrium was studied at 600–800 °C in H 2CO 2 mixtures providing an equilibrium oxygen pressure of 10 −24 atm at 600 °C and 10 −20 atm at 700 and 800 °C. The corrosion of yttrium under these low oxygen pressures resulted in the growth of Y 2O 3 scales which was rather protective at 800 °C, presenting two approximately parabolic stages with a smaller rate constant at longer times, but non-protective and faster at lower temperature. The oxidation of Co15Y was rather irregular under all conditions, but generally slow: in particular, at 800 °C the rate decreased almost to zero after about 17 h oxidation. The oxidation of this alloy produced a thin external layer of pure cobalt metal overlying a region of internal oxidation, where the Y-rich phase was transformed into a mixture of cobalt metal and yttrium oxide. The microstructure of the internal oxidation region followed closely that of the original alloy, while no yttrium depletion was observed beneath the front of internal oxidation. These results are examined by taking into account the low solubility of Y in Co and the existence of an intermetallic compound in the alloy.

Effects of neocortical implants of cobalt and other seizure-inducing metals on brain C-14 2-deoxyglucose uptake.

Nine days after insertion of a pure cobalt metal rod into the visual cortex, regions of increased 2-DG uptake are observed both in relatively normal Nissl-staining tissue lying around the implant site and in the connecting dorsal lateral geniculate nucleus of the thalamus. These hypermetabolic regions have been claimed to be the metabolic 'signatures' of tissue made epileptogenic by the cobalt. The present study showed, however, that while the 'dark patches' develop following posterior cortex implants, they do not appear after anterior cortex cobalt implants. Moreover, the dark patches were not detectable after cortical implants of other seizure-inducing metals such as antimony and nickel. These new findings indicate that the dark patches occur too idiosyncratically to make them the metabolic 'signatures' of tissue made epileptic by cobalt.

Human toxicity of cobalt-containing dust and experimental studies on the mechanism of interstitial lung disease (hard metal disease).

In the industry, the potential for exposure to cobalt metal dust is particularly important during the production of cobalt powder and the processing and use of hard metals and other cobalt-containing alloys. The different adverse health effects reported in these workers are reviewed. One of the main target organs is the respiratory tract, and this article concentrates on the lung parenchymal reactions induced by cobalt-containing dust. Clinical and epidemiological data indicate that this manifestation is rarely, if ever, induced by pure cobalt metal dust alone, but requires the concomitant inhalation of other compounds such as tungsten carbide in the hard metal industry (hard metal disease). Experimental studies demonstrate that cobalt metal and metallic carbides interact to produce an elective lung toxicity. Recent work on the mechanism of this interaction, which is based on the production of activated oxygen species, is reviewed. A practical implication in industrial hygiene should be that permissible exposure levels to Co dust might have to be different when exposure is to pure Co particles or an association with carbides.

The Delayed Lung Responses to Single and Repeated Intratracheal Administration of Pure Cobalt and Hard Metal Powder in the Rat

Epidemiological and clinical studies suggest that inhalation of cobalt metal dust (Go) mixed with tungsten carbide particles (WC), but not of cobalt dust alone, may cause interstitial pulmonary lesions (hard metal disease). In previous experimental studies in the rat, we have demonstrated the greater acute pulmonary toxicity of a WC-Co mixture compared to Co or WC alone. The present study was undertaken to compare in the same animal model the delayed lung response after intratracheal administration of Co or WC-Co particles (cobalt particle 6.3 wt%). The responses were also compared with those obtained after treatment with arsenic trioxide and crystalline silica used as reference materials producing an acute toxic insult and a progressive fibrogenic response, respectively. Cellular (total and differential counts) and biochemical parameters (LDH, N-acetyl-β-D-glucosaminidase, total protein, albumin, fibronectin, and hyaluronic acid) were measured in bronchoalveolar lavage fluid following single and repeated intratracheal instillations. The results indicate that the delayed lung response observed after WC-Co is different from that after cobalt metal alone. A single intratracheal dose of WC-Co (1, 5, or 10 mg/100 g body wt) induced an acute alveolitis which persisted for at least 1 month. Four months after a single instillation of WC-Co, no clear histological lung fibrosis could however be evidenced, indicating a reversibility of the lesions. The effects of cobalt (0.06, 0.3, or 0.6 mg/100 g body wt) or tungsten carbide alone (1, 5, or 10 mg/100 g body wt) were very modest, if any. Following repeated intratracheal instillations (four administrations at 1-month interval), increased lung hydroxyproline content and histopathological evidence of interstitial fibrosis were observed after WC-Co (4 × 1 mg/100 g body wt), but not after administration of each component separately, i.e., Co (4 × 0.06 mg/100 g body wt) or WC (4 × 1 mg/100 g body wt). The mechanism of the fibrotic reaction induced by WC-Co seems different from the progressive inflammatory reaction induced by crystalline silica. We suggest that it might result from a scarring reaction elicited by repeated acute insults as observed after repeated administration of arsenic trioxide.

Study of the mechanism responsible for the elective toxicity of tungsten carbide-cobalt powder toward macrophages

We have previously demonstrated that tungsten carbide-cobalt powder (WC-Co) is more toxic toward murine macrophages in vitro than pure cobalt metal particles and that the cellular uptake of cobalt is enhanced when the metal is present in the form of WC-Co mixture. The present study was undertaken to assess the possible mechanism(s) of this interaction. We found that solubilization of cobalt in the extracellular milieu was increased in the presence of WC. This phenomenon, however, is not the critical factor explaining the greater toxicity of the WC-Co mixture since increasing the amount of solubilized cobalt in the extracellular medium in the absence of WC did not result in increased toxicity. Moreover, the amount of cobalt solubilized from a toxic dose of WC-Co was insufficient to affect by itself macrophage viability. A toxic effect was only observed when the WC-Co mixture came directly in contact with the cells. The elective toxicity of WC-Co can also not be explained by stimulation of phagocytosis of cobalt metal particles due to the simultaneous presence of other particles (WC) in the extracellular fluid since stimulation of phagocytosis by latex beads or zymosan particles did not amplify the toxicity of cobalt metal particles. These results indicate that the toxicity of the WC-Co mixture does not simply result from an enhanced bioavailability of its cobalt component. This suggests that hard metal dust behaves as a specific toxic entity.

Comparative study of the acute lung toxicity of pure cobalt powder and cobalt-tungsten carbide mixture in rat

Alveolitis progressing to lung fibrosis has been reported in workers exposed to cobalt containing dust (e.g., tungsten carbide-cobalt mixture as produced by the hard metal industry) but rarely following exposure to pure cobalt dust (e.g., in cobalt-producing factories). We have previously demonstrated that tungsten carbide-cobalt mixture is more toxic toward rat alveolar macrophages in vitro than pure cobalt metal powder. The present study was undertaken to compare in female rats the acute pulmonary response (lung weight, lung histology, cellular and biochemical analyses of bronchoalveolar lavage fluid, and mortality) following the intratracheal instillation of pure cobalt (Co) particles (median particle size, d50:4 μm), pure tungsten carbide (WC) particles (d50:2 μm), tungsten carbide-cobalt (WC-Co) powder (d50:2 μm; cobalt 6.3%, tungsten 84%, carbon 5.4%) and crystalline silica (d50 < 5 μm) used as pneumotoxic reference material. WC alone (15.67 mg/100 g body wt) behaves as an inert dust producing only a mild accumulation of macrophages in the alveolar duct walls. Co alone (1.0 mg/100 g) only causes a moderate inflammatory response. An identical amount of Co given as WC-Co mixture (16.67 mg/100 g; corresponding to 1.0 mg Co/100 g) produces a severe alveolitis and fatal pulmonary edema. Cellular and biochemical characteristics of bronchoalveolar lavage fluid collected 24 hr after the intratracheal instillation of WC (1.0 mg/100 g) or Co 10.06 mg/100 g) are not significantly different from those of control animals instilled with sterile saline. On the contrary, bronchoalveolar lavage fluid changes following administration of the WC-Co mixture (1.0 mg/100 g; corresponding to 0.06 mg Co/100 g) are very similar to those induced by crystalline silica (1.0 mg/100 g). The amount of cobalt excreted in urine is significantly higher when the animals are exposed to WC-Co powder as compared to an equivalent amount of pure cobalt particles, suggesting an increased bioavailability of cobalt metal when combined with tungsten carbide. This study demonstrates that the acute lung toxicity of tungsten carbide-cobalt mixture is much higher than that of each individual component and may explain why lung fibrosis is rarely if ever induced by exposure to pure cobalt dust.

In Vitro cytotoxic effects of cobalt-containing dusts on mouse peritoneal and rat alveolar macrophages

"Hard metal disease" is a chronic lung disease characterized by the presence of interstitial fibrosis; the role of cobalt in the development of this entity is still debated. Indeed, most cases have been observed in some workplaces (grinding) of the hard metal industry and in the diamond polishing industry whereas no similar cases have been reported from workers exposed to pure cobalt powders in cobalt refineries. This study was designed to assess the in vitro toxicity (LDH release, morphology) of different cobalt-containing dusts toward murine peritoneal and alveolar macrophages. The results clearly demonstrate that, both in terms of dust particle and cobalt concentrations, the reactivity of the tungsten carbide-cobalt mixture is quite different from that of cobalt metal powder. The ground tungsten carbide-cobalt mixture prepared by the hard metal industry is almost as toxic as crystalline silica whereas, when tested separately, tungsten carbide has no effect and pure cobalt metal powder slightly impairs cell viability. The uptake of cobalt by macrophages in the presence of tungsten carbide was found to be increased. These observations may have some practical implications in industrial hygiene; they suggest that the acceptable exposure level to cobalt metal should be different when handled alone or in association with other powders such as tungsten carbide.

Derivatographic thermoanalysis of [Co(NH 3) 5Cl]Cl 2

Simultaneous TG, DTG, DTA and TGT (thermogravimetnc titration) measurements using a MOM-derivatograph and a thermo-gas-titnmeter show that the complex [Co(NH 3) 5Cl]Cl 2 ( I) decomposes in a static air atmosphere. In the first step three NH 3 molecules are lost. This step overlaps with a second step where the fourth NH 3 molecule is lost; the fifth NH 3 molecule is lost in the third step. A part of the fourth NH 3 molecule reduces Co( III) to Co( II) forming NH 4Cl and N 2. Pure CoCl 2 with almost theoretical yield is obtained at 510 ° C. A melting endotherm of CoCl 2 appears at 730 ° C and has a Δ H f ⊖ value of −310.8±0.7 kJ mol −1. The final decomposition product is pure cobalt metal. A kinetic study of the first decomposition step of complex I gives value of kinetic constants (apparent or procedural) of n = 0.5 and E a = 124.64 and 129.42 kJ mol −1 (depending on the method of calculation); values of log Z are 10.9 and 20.9 ( Z in s −1). The root mean square deviation (for ten E a masurements within the first step) is 1.8%.