Excess Of Cobalt Research Articles

Synthesis of Sr2(Co1.1;Mo0.9)O6-δ double perovskite and its electrochemical performance in the oxygen reduction reaction

Mixed ionic-electronic conductors composed of Sr2(Co;Mo)O6-δ double perovskites have been identified as potential candidates for symmetric Solid Oxide Fuel Cells, but their performance and stability under cathodic conditions remain unclear. Typically, a Co:Mo ratio of 1:1 leads to the formation of SrMoO4 as a by-product when the material is treated in air. In this study, we show that employing a glycine-nitrate combustion process with a high fuel ratio, along with an excess of cobalt, leads to a single-phase material with a double perovskite crystal structure (I4/m space group) after air calcination at high temperatures. Detailed Co and Mo speciation studies conducted using XPS and XANES spectroscopies are also presented to support these findings. Our electrochemical impedance spectroscopy study shows that this material exhibits excellent electrocatalytic response for the oxygen reduction reaction, with oxygen ion diffusion through the cathode being the rate-limiting process. Furthermore, the material shows strong chemical compatibility with (La;Sr)(Ga;Mg)O3-δ electrolytes at temperatures up to 1000 °C. For comparison purposes, we also present the properties of single perovskite cathodes with the composition Sr(Co0.95;Mo0.05)O3-δ.

Hydrometallurgical Technology for Producing Rhenium(VII) and Cobalt(II) from Waste

This paper presents a method for obtaining cobalt(II) perrhenate from waste derived from two types of materials, i.e., Li-ion battery scrap, or more precisely, battery mass, and superalloy scrap. Both of the above-mentioned materials are a source of Co. However, a source of rhenium is perrhenic acid produced from ammonium perrhenate (recycled) by the ion exchange method using resins. Co(OH)2 can be precipitated from solutions resulting from the leaching of Li-ion battery mass, sludge from the Zn-Pb industry and superalloy scrap. The compound, after proper purification, can be used in a reaction with perrhenic acid to form Co(ReO4)2. The reaction should be conducted under the following conditions: time 1 h, room temperature, 30% excess of cobalt(II) hydroxide, and rhenium concentration in HReO4 from about 20 g/dm3 to 300 g/dm3. This work shows that with the use of Co(OH)2, obtained from waste, an anhydrous form of cobalt(II) perrhenate can be obtained, containing < 1000 ppm of the cumulative metal impurities.

Family of Well-Defined Chiral-at-Cobalt(III) Complexes as Metal-Templated Hydrogen-Bond-Donor Catalysts: Effect of Chirality at the Metal Center on the Stereochemical Outcome of the Reaction.

A family of well-defined Λ- and Δ-diastereomeric octahedral cationic chiral-at-cobalt complexes were obtained by a simple two-step reaction of (R,R)-1,2-diaminocyclohexane, (R,R)-1,2-diphenylethylenediamine, or (S)-2-(aminomethyl)pyrrolidine and substituted salicylaldehydes with a cobalt(III) salt. It was observed for the first time that the use of an excess of cobalt(III) salt provides both the enantiopure Λ and Δ forms of the corresponding cobalt(III) complexes 1 and 2 in a ratio of diastereomers ranging from 1:1.6 to >20:1 (Λ/Δ) and in 31-95% combined yields. The obtained complexes were robust, air- and bench-stable, soluble in most of organic solvents, and insoluble in water. Through variation of the substituents in the phenyl ring of the salicylaldehyde moiety, it was shown that both steric and electronic effects of substituents have a significant impact on the formation of Λ and Δ isomers. Next, the efficacies of the enantiopure metal-templated complexes 1-3 were investigated in three benchmark asymmetric reactions in order to compare their catalytic activity. The chiral cobalt(III) complexes 1-3 were tested as enantioselective hydrogen-bond-donor catalysts in such important reactions as the Michael addition of the O'Donnell substrate to methyl acrylate, epoxidation of chalcone, and trimethylsilylcyanation of benzaldehyde. It was clearly demonstrated that the chirality at the cobalt center has an impact on the stereochemical outcome of the reactions. In particular, the Λ(R,R)-1 and Δ(R,R)-1 complexes acted as "pseudoenantiomeric" catalysts in the epoxidation and trimethylsilylcyanoation reactions, providing both enantiomers of the products with up to 57% enantiomeric excess.

Use of a Zeolite and Molecular Sieve to Restore Homeostasis of Soil Contaminated with Cobalt

Since contamination of soil with cobalt disturbs the soil’s biological balance, various types of compounds are being sought that could be used to restore the homeostasis of contaminated soil. The aim of the study was to determine the use of a Bio.Zeo.S.01 zeolite and molecular sieve in restoring the microbiological and biochemical balance of soil contaminated with cobalt. Soil samples were contaminated with cobalt (CoCl2·6H2O) at 0, 20, 80 mg·kg−1, and a Bio.Zeo.S.01 zeolite and molecular sieve were introduced at 0 and 15 g·kg−1. The soils on which the experiment was conducted were loamy sand and sandy clay loam. The experiment was carried out in two series on soil with and without a crop sown in it. The multiplication of microorganisms and the soil enzymes’ activity were determined on days 25 and 50 (harvest) of the experiment, and the yield of the underground and above-ground parts of maize and chemical and physical properties of soil were determined on the day of harvest. It was found that the microorganisms’ multiplication, enzyme activity, and maize yield were significantly disturbed by the excess of cobalt in the soil regardless of the soil type. The zeolite Bio.Zeo.S.01 used in the study had a smaller impact on microorganisms and soil enzyme activity than the molecular sieve. Cobalt accumulated more in the roots than in the above-ground parts of maize. An addition of sorbents decreased the accumulation of cobalt in maize grown only on sandy clay loam.

EXTRACTION OF Pd(II), Ni(II), Co(II), Cu(II), Fe(III) AND Zn(II) IONS WITH 1,2,3-BENZOTRIAZOLE IN SYSTEMS BASED ON ANIONIC SURFACTANTS

The phase state and extraction capacities of aqueous systems based on sulfonol, sodium dodecylsulfate or alkylbenzenesulfonic acid as anionic surfactants and hydrochloric (or sulfuric) acid against the influence of 1,2,3-benzotriazole as an organic complexing reagent were studied. Introduc-tion of 1,2,3-benzotriazole into the systems resulted in its exfoliation in two liquid phases. Optimal concentration parameters of the extraction process in the systems under investigation were found: the total volume of the system (10 ml) contained sulfonol or sodium dodecyl sulfate (0.6 g), alkylbenzenesulphonic acid (0.5 g), and 1,2,3-benzotriazole (0.35 g). The aliquation state was maintained in the following concentration interval of HCl (H2SO4), mol L-1, for the systems with: (a) sodium dodecylsulfate: 0.5-6 (0.5-4), (b) sulfonol: 0.1-4 (0.05-3), (c) alkylbenzenesulfonic acid: 0-4 (0-3). Distribution of 0.01 mol L-1 of Pd(II), Ni(II), Cu(II), Co(II), Zn(II) and Fe(III) ions in the above systems was studied at the optimal components ratios. In the systems containing sodium dodecylsulfate, no quantitative extraction of metal ions was observed. In the systems with sulfonol and alkylbenzenesulfonic acid, practically complete (99.9%) extraction of palladium appeared to be possible in the entire range of acid concentrations; with minimal acid content, over 95% of copper and nickel were extracted. The extraction of palladium ions in the presence of interfering ions was studied. Quantitative recovery of palladium ions was found to not be obstructed by 500-fold molar excess of copper, 300-fold excess of cobalt and 70-fold excess of nickel.

Over– and low–exchanged Co/BEA catalysts: General characterization and catalytic behaviour in ethane ammoxidation

Ethane ammoxidation into acetonitrile was successfully catalyzed between 380 and 450°C over Co/BEA solids issued from solid–state ion exchange with different metal loads. During the preparation, in the presence of NH4+–Beta zeolite (Si/Al=12.5), CoCl2 precursor decomposes under helium stream without evaporation, leading to the stabilization of bare Co2+ at the exchange cationic sites as revealed by spectroscopic tools. However, at 4.13 and 5.63wt.% of Co (Co/Al molar ratio equal to 0.75 and 1, respectively), the corresponding solids stabilized, besides bare β–type Co2+ ions, Co oxo [Co(III)O]+ species, revealed by H2–TPR. These species exhibit highest catalytic activity on the basis of TOF calculation and play a key role in ethane ammoxidation into acetonitrile at low temperature (380°C). Nevertheless, the excess of cobalt is transformed into Co3O4 oxide (as revealed by XRD and TPR experiments) which catalyzes the hydrocarbons combustion into CO2.

Thermal behavior of CoxFe3−xO4/SiO2 nanocomposites obtained by a modified sol–gel method

The thermal behavior of CoxFe3−xO4/SiO2 nanocomposites obtained by direct synthesis starting from nonahydrate ferric nitrate and hexahydrate cobalt nitrate in different ratios with and without the addition of 1,4-butanediol was studied. For the synthesis of CoxFe3−xO4 (x = 0.5–2.5) dispersed in the silica matrix a wide Co/Fe molar ratio was used. The decomposition processes, formation of crystalline phases, gases evolvement and mass changes during gels annealing at different temperatures were assessed by thermal analysis. The absence of succinate precursor and a low mass loss were observed in the case of the gel obtained in the absence of 1,4-butanediol. In case of gels obtained using a stoichiometric ratio of Co/Fe, no clear delimitation between Co and Fe succinates was observed, while for samples with a Fe or Co excess, the formation of the two succinates was observed. The evolution of the crystalline phase after annealing (673, 973 and 1273 K) investigated by X-ray diffraction analysis and Fourier transformed infrared spectrometry revealed that in samples with Fe excess, stoichiometric Fe/Co ratio or low Co excess, the cobalt ferrite (CoFe2O4) was obtained as a single phase, while in samples with higher cobalt excess, olivine (Co2SiO4) as a main phase, cobalt oxide and CoFe2O4 as secondary phases were obtained after annealing at 1273 K. The SEM images confirmed the nanoparticles embedding in the silica matrix, while the TEM and X-ray diffraction data showed that the obtained nanoparticles’ size was below 10 nm in most samples.

Metabolic effects of iodine in poultry for its deficiency or excess in the diet

The article is a generalization of the literature on the impact fn the iodine om a birds, depending on the amount in the diet. In particular, we show that lack of iodine in the body of animals with food and water leads to metabolic disorders, the development of organs and body systems, weakening the function of the reproductive organs and the body's resistance to infection, resulting disruption of the thyroid gland. Iodine deficiency is characterized by the development of secondary immunodeficiency, which manifests a high propensity to disease. This weak immune response correlated with impaired thyroid function. The absorption of bioelements may affect the availability of natural feed goitrogenes. However, it is shown that an excess of cobalt, iron, boron, manganese poultry diets may correlate with the biosynthesis of thyroid and promote the development of endemic goiter. Noted features integrated application of iodine with other trace elements, as well as the need for admission with food vitamin A. From the standpoint of modern scientific research proved that the metabolism of iodine and selenium are closely related and can affect each other manifestations of deficiency of essential bioelements. Shown that excess of iodine in laying hens, reduced their egg production and average egg weight in breeding poultry hatching degrade the quality of the eggs. Permanent, but reduced vitellogenesis that continues for a period of excess consumption of iodine and inhibiting ovulation is associated with the formation of progesterone violation largest follicle, resulting in blocked signal for preovulatory allocation of luteinizing hormone, which leads to the cessation of egg. Excess iodine in the diet inhibits puberty young male and female birds. Thus, there is a reverse chronological relationship between feeding forages with high iodine content and the expected time of puberty. According to a toxic level of iodine in the diet, the liver bird aminotransferase increased activity and blood – alkaline phosphatase, decreased phagocytic activity of neutrophils. Thus, the deficit and surplus iodine leads to metabolic disorders, reproductive functions of animals and birds and lost productivity.

Tetranuclear Eu(III)-Co(II) complex of an N4O4 macrocycle

The reaction of an Eu(III) complex of the protonated form of the macrocyclic Schiff base derived from 1,3-diamino-2-hydroxypropane and 2,6-diformylphenol, [Eu(H4L)Cl3], with three equivalents of base results in a mononuclear complex of the triply deprotonated form of the ligand, [Eu(HL)]. The photophysical properties of the [Eu(HL)] complex are discussed on the basis of emission and excitation spectra, as well as of the emission decay times. The [Eu(HL)] complex in a reaction with cobalt(II) chloride gives a heterometallic Eu(III)-Co(II) macrocyclic complex, [EuCo(HL)(CH3OH)2Cl]2Cl2·4CH3OH. In the presence of base and an excess of cobalt(II) chloride the starting [Eu(H4L)Cl3] complex is converted to a dinuclear Co(II) complex, [Co2(H2L)Cl2(CH3OH)2]·1.5CH3OH.

Disturbances in Growth, Yield, Sucrose Concentration and Antioxidative Defense System by Excess Cobalt in Sugarcane

The aim of the study was to implicate induction of oxidative stress and antioxidative responses with the effects of cobalt excess on sugarcane plants. Sugarcane (Saccharum officinarium L.) cv. ‘CoS 99225’ grown in refined sand at excess cobalt i.e. 100, 200, 300, 400, and 500 μM. The effect of excess cobalt (>300 μM) was observed on sugarcane as interveinal chlorosis and necrotic spots in middle leaves. Later, affected leaves turned necrotic, dry, and withered. The toxicity of cobalt was also discernible on root weight, cane yield, reduced concentration of sucrose in cane juice, carotenoides, Hill reaction activity, chlorophylls, iron (Fe), relative water content, decreased activity of catalase in leaves, and increase in concentration of lipid peroxidation, phenols, sugars, starch, proline and higher activity of peroxidase, ascorbate peroxidase and superoxide didmutase and accumulation of cobalt in sugarcane leaves.

Electrocatalytic oxidation of methanol on CoNi electrodeposited materials

Cobalt–nickel bimetallic materials electrodeposited on Si/Ti/Ni substrates were evaluated for the oxidation of methanol in alkaline media. CoNi samples were prepared potentiostatically selecting conditions adequate to achieve the desired Co/Ni ratio. All samples were characterized by X-ray fluorescence and cyclic voltammetry to determine their composition and electrochemical behaviour. The electrocatalytical performance of prepared samples was evaluated also by cyclic voltammetry using methanol solutions in alkaline media. Material composition, methanol and NaOH concentration, and temperature were the variables studied. The results indicate that a cobalt excess inhibits the methanol oxidation. In the same way, a significant enhancement of the oxidation current was observed on increasing the NaOH concentration up to 0.5 M, but for higher concentrations the electrocatalytic performance of these materials decreases. With regard to the increase of MeOH concentration or temperature, both variables are related to an improvement of the electrocatalytic performance. Finally, the effect of platinum skin on the CoNi deposits was evaluated, concluding that it favours MeOH oxidation but does not protect the substrate surface from the damage exerted by excessive NaOH concentration.

Living Radical Polymerization of Acrylates Mediated by 1,3‐Bis(2‐pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

A new type of mediator for cobalt(II)-mediated radical polymerization is reported which is based on 1,3-bis(2-pyridylimino)isoindolate (bpi) as ancillary ligand. The modular synthesis of the bis(pyridylimino)isoindoles (bpiH) employed in this work is based on the condensation of 2-aminopyridines with phthalodinitriles. Reaction of the bpiH protio-ligands with a twofold excess of cobalt(II) acetate or cobalt(II) acetylacetonate in methanol gave [Co(bpi)(OAc)], which crystallize as coordination polymers, and a series of [Co(acac)(bpi)(MeOH)], which are mononuclear octahedral complexes. Upon heating the [Co(acac)(bpi)(MeOH)] compounds to 100 degrees C under high vacuum, the coordinated methanol was removed to give the five-coordinate complexes [Co(acac)(bpi)]. The polymerization of methyl acrylate at 60 degrees C was investigated by using one molar equivalent of the relatively short-lived radical source 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as initiator (monomer/catalyst/V-70: 600:1:1). The low solubility of the acetato complexes inhibits their significant activity as mediators in this reaction, whereas the acetylacetonate complexes control the radical polymerization of methyl acrylate more effectively. The radical polymerizations of the hexacoordinate complexes did not show a linear increase in number-average molecular weight (M(n)) with conversion; however, the polydispersities were relatively low (PDI=1.12-1.40). By using the pentacoordinate complexes [Co(acac)(bpi)] as mediators, a linear increase in M(n) values with conversion, which were very close to the theoretical values for living systems, and very low polydispersities (PDI<1.13) were obtained. This was also achieved in the block copolymerization of methyl acrylate and n-butyl acrylate. The intermediates with the growing acrylate polymer radical ((.)PA) were identified by liquid injection field desorption/ionization mass spectrometry as following the general formula [Co(acac)(4-methoxy-bpi)-(MA)(n)-R] (MA: methyl acrylate; R: C(CH(3))(CH(2)C(CH(3))(2)OCH(3))CN), a notion also confirmed by NMR end-group analysis.

Mutations and environmental factors affecting regulation of riboflavin synthesis and iron assimilation also cause oxidative stress in the yeast Pichia guilliermondii

Iron deficiency causes oversynthesis of riboflavin in several yeast species, known as flavinogenic yeasts. However, the mechanisms of such regulation are not known. We found that mutations causing riboflavin overproduction and iron hyperaccumulation (rib80, rib81 and hit1), as well as cobalt excess or iron deficiency all provoke oxidative stress in the Pichia guilliermondii yeast. Iron content in the cells, production both of riboflavin and malondialdehyde by P. guilliermondii wild type and hit1 mutant strains depend on a type of carbon source used in cultivation media. The data suggest that the regulation of riboflavin biosynthesis and iron assimilation in P. guilliermondii are linked with cellular oxidative state.

Microstructure of cobalt oxide doped sintered ceria solid solutions

The sintering of ceria solid solutions, such as Ce0.9Gd0.1O1.95 (CGO10), is strongly promoted by the addition of 1 cat% of cobalt oxide, lowering the maximum sintering temperature by 200∘C and triplicating the maximum densification rate. This change in sintering behavior results from cobalt ion segregated at the grain boundaries. An average cobalt ion boundary coverage is at maximum 3.0 ± 1.9 at/nm2 and is shown to depend on the cooling rate. Coverage by segregated gadolinium is also found and amounts to 13.2 ± 11.4 at/nm2 for a slowly cooled sample. From cobalt excess measured at the boundary, an estimated concentration of only 0.06 cat% of cobalt oxide is necessary to promote the sintering effect. The remaining amount of cobalt oxide is found in triple points and as particles in clusters. It is expected that the amount of cobalt oxide necessary for fast densification can be reduced with a doping process that distributes the additives more homogeneously.

Mechanistic Study on the Oxidation of Promazine and Chlorpromazine by Hexaimidazolcobalt(III) in Acidic Aqueous Media

The kinetics of the oxidation of promazine and chlorpromazine by hexaimidazolcobalt(III) were studied in the presence of a large excess of cobalt(III) and H+ ions using u.v.–vis. spectroscopy ([CoIII] = (1–6) × 10−3 m, [ptz] = (2.5–10) × 10−5 m, [H+] = 0.05–0.8 m, I = 1.0 m (H+, Na+, Cl−), T = 333–353 K, l = 1 cm). In each case, the reversible reaction leads to formation of cobalt(II) species and a stable cationic radical. A linear dependence of the pseudo-first-order rate constant (kobs) on [CoIII] with a non-zero intercept was established for both phenothiazine derivatives. A marked difference in the observed reaction rate for promazine and chlorpromazine is associated with the difference in its ability to undergo oxidation and is consistent with a trend in the redox potential changes for these reductants. The activation parameters for reactions studied were determined. Mechanistic consequences of all the results are discussed.

Polymorphism of response to cobalt excess in individual Vicia faba plants

A high and unique expression of individual plant polymorphism for metal stress has been observed after exposure of seeds of Vicia faba to cobalt excess. The reproducibility of the phenomenon, the stability of variations in de-etiolation assay, the coincidence of differences in Co uptake and plant injury extent, a simultaneous increase of the uptake of several elements depending on plant injury extent allow to use this phenomenon for studying the evolution of the initial stages of tolerance and hyperaccumulation, multiple metal uptake and the ‘break-through’ effect. The high individual DNA polymorphism revealed by RAPD analysis and different response of individual plants to Co excess are separate, unrelated phenomena.

The X-ray crystallographic structures, spectral and magnetic properties of nickel(II), copper(II) and cobalt(II) complexes with tetra(3- iso-propylpyrazol-1-yl)borate

Tetra(3- iso-propylpyrazol-1-yl)borate ligand (L) forms mono-ligand LMX and bis-ligand L 2M complexes (where M=Ni(II), and Cu(II), and X=Cl − or NO 3 − ) depending on the stoichiometry of the synthesis, while a polynuclear (NCS) 2Co(L)Co(L)Co(NCS) 2 complex is obtained when excess of cobalt(II) thiocyanate is used. The L coordinates to metal ions in a κ 3 fashion in LNiCl, LNi(NO 3)(5- i PrpzH) and LCuCl(5- i PrpzH), whereas a κ 2 binding mode was found in L 2Ni and in unique (NCS) 2Co(L)Co(L)Co(NCS) 2, in which L bridges two metal ions.

STEPWISE DETERMINATION OF ALUMINUM AND CHROMIUM IN WATER AND BIOMEDICAL SAMPLES BY HPLC-UV, BASED ON THEIR DIFFERENT KINETICS WITH 8-HYDROXYQUINOLINE

ABSTRACT A reversed-phase high performance liquid chromatographic (RP-HPLC) method, with spectrophotometric detection for determination of trace amounts of aluminum (Al) and chromium (Cr) in water and biomedical samples, has been developed using 8-hydroxylquinoline (8-HQ) as a precolumn reagent based on the differential chelation kinetics of these two ions. The analysis is achieved with a Spherisorb ODS 2 column, with an eluent consisting of 4.0 mmol L−1 acetate buffer (pH 6.0) and 3.2 mmol L−1 8-HQ in 57% (v/v) methanol–water, at a flow rate of 1.0 mL min−1. On the basis of the fact that the peaks of Al and Cr chelates appear at the same retention time, the procedure is divided into two stages: 1. (1) determining Al concentration by peak area after precolumn chelation at ambient temperature; 2. (2) measuring total peak area of Al and Cr after reaction at 90°C for 30 min, and the concentration of Cr being determined by the difference between Al peak area and the total area. The response of both Al and Cr is linear from 0.002 to 0.6 µg mL−1 with a detection limit of 0.001 µg mL−1. The analysis is free from interference from common ions except 10-fold excess of cobalt. The values obtained by this method are in good agreement with those of ICP-AES or GF-AAS. The proposed method has been successfully applied to the direct determination of Al and indirect determination of Cr in natural water, serum, synthetic renal dialysate, parenteral solution, and pharmaceutical-grade organic acid with the recoveries of over 90%.

Ligand‐catalyzed metal ion reduction: Kinetics and analytical applications of nickel reduction catalyzed by nicotinamide

AbstractThe catalytic reduction of Ni (II) in the presence of nicotihamide (NA) at pH &lt; 7 was studied by direct‐current and differential‐pulse polarography (DPP). The prewave (with E1/2 around –0.78 V (versus saturated calomel electrode (SCE)) shows the typical behavior of an electrode process with regeneration of the reactant by a second‐order, rate‐determining chemical reaction. This reaction consists in the formation of the reducible nickel complex. The kinetics of the electrode process was studied by means of an adapted form of the equation derived by Koutecký for electrochemical reactions with a parallel chemical step. The rate constant for the formation of nickel‐nicotinamide complex is slightly dependent en pH and buffer composition and ranges between 4.5 and 6.7 × 103 mole−1 L s−1. This electrode process enables the selective determination of Ni (II) in presence of a large excess of cobalt. For example, nickel impurity in cobalt salts can be determined by DPP, in acetate buffer (pH 4.6) containing 0.01 M nicotinamide and about 0.1 M cobalt salt sample.

Magnetic ordering in the ternary germanides U 2Co 3Ge 5 and UCo 2Ge 2

We have investigated the UCo 2 xGe 2+x, system for −0.2x0.5. The new ternary germanide U 2Co 3Ge 5 orders ferromagnetically below T c = 21 K. UCo 2Ge 2 shows a narrow range of homogeneity on the cobalt-rich side. The stoichiometric germanide orders antiferromagnetically near T N = 160 K. The lattice parameters and the magnetic ordering of the compounds containing an excess of cobalt depend on their thermal treatment. This fact is proposed as an explanation for the ambivalence in the literature concerning the structural and physical properties of this last germanide.