Cobalt In Solution Research Articles

A novel pyridine based polymer for highly efficient separation of nickel from high-acidity and high-concentration cobalt solutions

A novel pyridine based polymer (PAPY) bearing typical bis(2-pyridylmethyl)amine and additional amino groups was newly prepared with much lower cost (46.5 USD/kg) than commercial resins with bis(2-pyridylmethyl)amine functional groups such as M4195 and TP220 (134.6 USD/kg). PAPY is a weakly basic resin with polymethacrylate–divinylbenzene matrix. Due to the relatively more hydrophilic matrix and more modified functional groups, PAPY owned the highest selectivity for nickel from high-concentration cobalt solutions even under highly acidic condition (pH ∼ 2). The highest separation factor of 129.2 (C0, Ni/C0, Co = 1:5000) could be achieved for Ni(II) versus Co(II) with PAPY, which is 100.1%, 53.6% more than those with M4195 and TP220, respectively. Because of the stronger deprotonation ability and the higher chelation binding energy, Ni(II) could form the more stable structure of two five-member rings in solid phase than Co(II). This may be the predominant mechanisms for the highly efficient separation between Ni(II) and Co(II). More attractively, Co(II) could speed up the initial adsorption rate of Ni(II) by 16.30% due to the affinity of functional groups and the electrostatic repulsion of Co(II). Far more high-purity cobalt (>99.99%) could be obtained by PAPY in the dynamic tests. With good regeneration and reusability, PAPY possesses great potential in the green and economical preparation of high-purity cobalt.

Study of the Structure and Hardness of Alloys of the Sn – Cu – Co System Used as Diamond Abrasive Tool Binders

The effect of the chemical composition of alloys of the Sn – Cu – Co system used as a binder for diamond abrasive tools on their structure and hardness is studied. It is shown that in the range of concentrations of the elements studied alloy structure is represented by three phases, i.e., β-Co, a solid solution of tin and cobalt in copper (Cu), and an e (Cu3Sn) intermetallic phase. The lowest microhardness of the three phases is exhibited by β-Co, as a result of which with an increase in cobalt content alloy macrohardness decreases.

Corrosion Resistance and Microstructure of Recasting Cobalt Alloys Used in Dental Prosthetics

AbstractThe work presents the results of the studies of Co-Cr-Mo casting alloys used in the production of frame casts of removable dentures, crowns and bridges in dental prosthetics. The studies were performed on four Co-Cr-Mo alloys of different contents of Mo, W and other additives. Electrochemical tests were performed, which aimed at examining the corrosion resistance of the alloys and observing the alloy structure after chronoamperometric tests with the potential in the area of the occurrence of the passive layer breakpoint. The alloy microstructure images after chronoamperometric tests show the presence of non-uniformly distributed general corrosion. Moreover, a project of cobalt alloy casting was elaborated using a ceramic mold casting. Additionally, analysis of the obtained microstructure was performed. The microstructure of the examined alloys was of the dendrite type. This microstructure was chemically inhomogeneous and consisted of an austenitic matrix formed by a solid cobalt solution and chromium in the core dendritic structure.

Thioglycolate-based task-specific ionic liquids: Metal extraction abilities vs acute algal toxicity

We studied the extraction behavior of two thioglycolate-based ionic liquids (ILs), for heavy metals from aqueous solutions; substances of interest were methyltrioctylammonium S-hexyl thioglycolate [N1888][C6SAc] and methyltrioctylphosphonium S-hexyl thioglycolate [P1888][C6SAc]. Theses ILs previously have shown very good extraction abilities towards cadmium and copper, therefore we investigated time-dependent metal removal experiments with aqueous solutions of cobalt(II), nickel(II) and zinc(II). The highest distribution ratio (RIL/Water) was determined for zinc (RIL/Water=2000). Recovery studies for zinc after extraction were performed with different stripping agents showing a successful recycling. Additionally, the two ILs were immobilized on active charcoal, displaying great potential for solid-liquid extraction. Regarding the extraction mechanism, quantum-mechanical calculations were included, which indicate that the metal extraction depends on the stability of the metal-water cluster. Ligands (water as well as ILs) are planar coordinated in nickel complexes but showed a tetrahedral configuration for zinc. As a first estimate of the ecotoxicity of the ILs, in vivo tests toward three freshwater green algae species Tetradesmus obliquus, Desmodesmus armatus and Raphidocelis subcapitata were carried out. The EC50 values (effective concentration after 72 h) confirm high toxicity of all tested ILs to all species, displaying only small differences between the species and EC50ies.

Hydrogen generation by oxidation of “mechanical alloys” of magnesium with iron and copper in aqueous salt solutions

Oxidation processes of magnesium and magnesium “mechanical alloys” with iron and copper (1–15 wt%) in presence of aqueous solutions of sodium, cobalt, nickel and copper chlorides have been investigated. The rate of hydrogen generation increases with the increase of the transition metal content in the “alloys” and levels out for the Mg–Cu system. The overall hydrogen yield does not exceed 92% of theoretical one at the initial solution concentrations of 0.032 M and chloride/Mg molar ratios of 0.0075 (0.85 M and 0.20 for NaCl), but becomes close to 100% at double concentration of the transition metal salt solutions. The electrochemical corrosion mechanism of the magnesium oxidation process has been suggested.

Synthesis, Crystal Structures, and Properties of Zeolite‐Like T3(H3O)2[M(CN)6]2·uH2O (T = Co, Zn; M = Ru, Os)

We report the synthesis, crystal structures, and related properties of six new zeolite‐like hexacyanometallates of formula unit T3(H3O)2[M(CN)6]2·uH2O (T = Co2+, Zn2+; M = RuII, OsII). Their crystal structures were solved and refined from their X‐ray powder diffraction patterns in combination with the IR and UV/Vis/NIR spectroscopic data. The Co and Zn ions are coordinated tetrahedrally to the N atoms of four CN groups. The deconvolution of the overlapped UV/Vis/NIR spectral bands provided conclusive evidence of the tetrahedral coordination of the Co atoms. These materials have porous frameworks, which are characterized by a 3D array of TN4tetrahedral units linked to the MC6octahedral blocks in a 3:2 ratio. From the IR spectroscopy results, we found that all of the compounds reported here contain hydronium countercations. Two different structures in the same space group (R3c) were identified for the Co‐based materials. However, only a single phase was found for the Zn‐containing compounds. Density functional theory (DFT) modeling predicts hydrogen bonds between the hydronium ions and the CN groups at the surfaces of the pores. These materials were prepared through the hydrothermal recrystallization of the solids obtained from mixing ethanol solutions of H4[M(CN)6] with aqueous solutions of cobalt(II) nitrate and zinc nitrate. Our results illustrate the potential of the hydrothermal recrystallization technique for the preparation of metal hexacyanometallates with new structures and pore topologies that are not obtainable by the traditional precipitation method.

Improvement of corrosion properties of porous alloy supports for solid oxide fuel cells

The development of protective coatings for porous metal supports is critical for sufficient life time for the fuel cells by enabling improved oxidation resistance, reduced chromium evaporation, and increased conductivity of the protective oxide scale. The oxidation of coated and non-coated substrates has been compared, and shows that it is possible to increase the oxidation resistance at 600 °C in air by a factor of 10 and in wet hydrogen by a factor of 1000, after vacuum coating of the porous metal supports by infiltration of a lanthanum–manganese–cobalt solution and fast curing in air at 900 °C. Chromium evaporation is also lowered by a factor of 10 in air at 600 °C. The experiments on pre-coated porous metal supports verify that the coating is well suited to use for metal supported fuel cells prepared by a low temperature fabrication route (below 1100 °C). An alternative coating procedure for coating of the metal supports after co-sintering of the anode and electrolyte has also been investigated and is well suited for the high-temperature fabrication route. For the high temperature fabrication route, the oxidation tests at 600 °C for 500 h in air and 100 h in wet hydrogen showed that post-coating is better than the pre-coating approach since the cell sintering steps has a detrimental effect on the pre-coated samples.

Structural Transitions and Thermochromism of Linear Polynuclear Cobalt(II)-4-Octadecyl-1,2,4-triazole Complexes

Combination of methanolic solutions of cobalt(II) chloride hexahydrate and 4-octadecyl-1,2,4-triazole (C18trz) leads to precipitation of a linear polynuclear complex (“coordination polymer”) established by Co2+ centers bridged by two C18trz molecules. The compound exists in a blue and a pink form in the solid, gel and dissolved state. The blue form represents tetrahedrally coordinated [Co(C18trz)2]2+ repeat units and the pink form octahedrally coordinated [Co(C18trz)2(H2O)2]2+ repeat units, therewith reflecting the affinity of Co2+ for both tetrahedral and octahedral coordination geometry. The blue and the pink form can be reversibly transformed into each other by humidification or, respectively, drying of the material. Thermochromism is observed in the dissolved state, where the pink form is reversibly transformed to the blue form upon increase in temperature. The results differ in some aspects from assumptions in previous reports on this subject.

Solvent extraction process for the recovery of nickel and cobalt from Caldag laterite leach solution: The first bench scale study

A solvent extraction application consisting of two-sequential solvent extraction circuits to separate the nickel and cobalt from a synthetic sulphate leach solution which simulates a typical Caldag lateritic leach solution was conceived and experimentally explored. The first circuit allowed the simultaneous extraction of most of the nickel (98%), cobalt (98%) and manganese (94%) with 20% neodecanoic acid (Versatic 10) and 5% tri-n-butyl phosphate (TBP) in ShellSol 2046 at pH7.2 together with substantial amounts of calcium (65%) and magnesium (12%). Three stages of scrubbing at pH5.6 using diluted sulphuric acid solution allowed the removal of most of the magnesium (90%) and substantial amount of calcium (16%). Complete stripping of nickel, cobalt, manganese, magnesium and calcium was achieved at pH0.75. This loaded strip solution was the feed for the second circuit. The use 15% bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) and 5% TBP in ShellSol 2046 allowed the extraction of most of the cobalt (94%) and manganese (98%) at pH5.0 but with substantial co-extraction of magnesium (41%) and calcium (40%) and a minor amount of nickel (3%). A two-stage scrubbing of this loaded organic with cobalt (20g L−1) solution was performed. Magnesium, calcium and nickel were completely displaced with cobalt. Most of the manganese (93%) was removed from the organic. Complete stripping of the cobalt and manganese in the scrubbed organic phase was achieved at pH1.0. Therefore, nickel (94%) and cobalt (91%) were totally separated from the feed solution. In addition, slope analyses were carried out to determine the nature of the extracted complexes of the nickel and cobalt with each extractant. Based on the experimental results, a flowsheet for the separation process is presented.

Effect of Cobalt Application and Mycorrhizal Fungi Inoculation on Growth and Some Nutrients Content of Barley and Egyptian Clover Plants Grown in Calcareous Soil

Two pot experiments were carried out at the green-house of Faculty of agriculture (Saba Bash), Alexandria University to study the effect of cobalt applied with seeds through soaking in relation to mycorrhiza inoculation on growth and quality of barely and clover as forage crops under calcareous soil conditions during 2012-2013 and 2013-2014 growing seasons, respectively. The seeds of barley and clover were soaked in continuously aerated solution of different cobalt concentrations (0.0, 0.3, 0.6, 0.9, 1.2, and 1.5 mg/l) using cobalt sulphate salt and inoculated with two mycorrhizal spices (G. intraradiaces and G. macrocarpium) separately before sowing.The obtained results showed that soaking seeds of barley and clover (forage crops) in cobalt solutions and mycorrhizal inoculation had significant effects on all growth parameters and the tested nutrients content in the plants of the two crops.The Co significantly increased the contents of N, P, K, and Co in shoot and root of the tested plants. It was found that G. intraradiaces was more effective than G. macrocarpium for the studied traits. Also, the recommended cobalt concentration for barley crops was lower (0.6 mg/l) than that for E.Clover (1.2mg/l). However, Co concentration above 0.6 and 1.2 mg/l for barley and E. Clove, respectively, reduced growth of plants.

Synthesis, Characterization and Permofarmance Activity of Metal Soap of Calcium, Cobalt, Iron and Copper from Palm Kernel Oil as a Drier in Paint

The behavior of Palm Kernel Oil was saponified by potassium hydroxide to form soluble soap which was later reacted with solutions of copper, cobalt, Iron and calcium to produce the metal soaps which were used as drier in coating mixture (Paint). The performance of these metal soaps has been studied. The effect of environmental and corrosive factors on paints was also studied. From the study, the formulated paint samples using metal soap had low specific gravity (1.45-1.47). This is an indication that more metal soap can be incorporated into the paint. Full hardness of paint samples was within the range (0.38-0.41mm) which implies that the samples will have high tolerance to anti-corrosive coating. The paints showed strong adhesion properties that are capable to withstand abrasive and corrosive agents. Also when exposed to surfaces like paper and glass, the exhibited strong adaptability without rust. Considering the drying time of coating mixture (paints) containing metal soaps showed increased oxidizing activity of drier and shortened drying time. The progress of the formulated metal soap paint reaction on storage was monitored and confirmed using physical methods. The high performance of the paints prepared from metal soap is good evidence to justify their utilization as driers in the surface coat industry.

Synthesis, Characterization and Permofarmance Activity of Metal Soap of Calcium, Cobalt, Iron and Copper from Palm Kernel Oil as a Drier in Paint

The behavior of Palm Kernel Oil was saponified by potassium hydroxide to form soluble soap which was later reacted with solutions of copper, cobalt, Iron and calcium to produce the metal soaps which were used as drier in coating mixture (Paint). The performance of these metal soaps has been studied. The effect of environmental and corrosive factors on paints was also studied. From the study, the formulated paint samples using metal soap had low specific gravity (1.45-1.47). This is an indication that more metal soap can be incorporated into the paint. Full hardness of paint samples was within the range (0.38-0.41mm) which implies that the samples will have high tolerance to anti-corrosive coating. The paints showed strong adhesion properties that are capable to withstand abrasive and corrosive agents. Also when exposed to surfaces like paper and glass, the exhibited strong adaptability without rust. Considering the drying time of coating mixture (paints) containing metal soaps showed increased oxidizing activity of drier and shortened drying time. The progress of the formulated metal soap paint reaction on storage was monitored and confirmed using physical methods. The high performance of the paints prepared from metal soap is good evidence to justify their utilization as driers in the surface coat industry.

Taguchi analysis on erosive wear behavior of cobalt based microwave cladding on stainless steel AISI-420

Abstract The strength, hardness, wear and corrosion resistance are the most important mechanical properties of the tribological components. Martensitic stainless steel plays very important role to represent these characteristics. The AISI-420 stainless steel widely used to manufacture the hydraulic and gas turbine components. The present work deals with microstructure and slurry erosive wear studies of cobalt based clad developed through microwave energy at a frequency of 2.45 GHz. The scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis result reveals the presence of cobalt and chromium rich solid solution in the intercellular substances. The Taguchi orthogonal array was used to gauge the factors affecting the wear significantly. The influence of various factors such as speed, particle size and impingement angle on wear behavior was evaluated by Means and ANOVA (analysis of variance). It was observed that the slurry speed significantly influenced the more mass loss on unclad substrate. The wear mechanism of the worn surface was studied through a scanning electronic microscope. It shows the mixed mode of erosion in the form of microcutting, ploughing, and fractures appeared are major wear mechanisms.

Hydrometallurgical recycling of cobalt from zinc plants residue

A large amount of hot filter cake (HFC) is annually generated in Iranian zinc plants. It contains 1% zinc, 16–30% manganese, 5–25% calcium and 1–4.5% cobalt. Usually, zinc is selectively leached by an alkaline medium and its residue is known as alkaline leached HFC (ALHFC). In the present study, the possibility of cobalt extraction from ALHFC was investigated using a creative hydrometallurgical process. At the first stage, zinc and cadmium were selectively removed with sulfuric acid. At the second stage, it was deeply focused on the possibility of selective reductive leaching of cobalt by H2O2 as a reductant in the presence of manganese. As results, several differences were found between the mechanism of cobalt and manganese leaching. Accordingly, cobalt leaching was more affected by acid concentration and manganese leaching was more affected by reductant concentration. Consequently, with manipulating these important parameters, it was made possible to selectively separate cobalt from manganese. Based on the obtained results, 90.9% of cobalt and only 10.04% of manganese were leached with 1% of H2O2. At the third stage, pregnant cobalt solution was successfully purified through a solvent extraction process with D2EHPA. Finally, cobalt hydroxide as our final product with a purity of more than 99% was precipitated from the pure pregnant solution at 70 °C.

Cobalt carbonate and cobalt oxide nanoparticles synthesis, characterization and supercapacitive evaluation

Taguchi robust design methodology was used to optimize direct precipitation reaction conditions for simple and fast synthesis of cobalt carbonate nanoparticles. The effects of several parameters that influence on particle size of prepared cobalt carbonate were investigated. The significance of these parameters on the size of cobalt carbonate particles were quantitatively evaluated by using of analysis of variance (ANOVA). The results showed that flow rate and the concentrations of cobalt and carbonate solutions have significant effect on the size of cobalt carbonate nanoparticles. Also, optimum conditions for synthesis of cobalt carbonate nanoparticles via precipitation reaction were achieved. The ANOVA demonstrated that under optimum condition, cobalt carbonate nanoparticles will have of 39.6 ± 2.2 nm sizes. In addition, the solid state thermal decomposition reaction of precursor was used for preparation of Co3O4 nanoparticles. The results showed that the Co3O4 nanoparticles synthesized by thermal decomposition of cobalt carbonate nanoparticles have 53 nm sizes. Cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy were used to investigate the supercapacitive property of the Co3O4 electrode. The Co3O4 electrode shows high specific capacitance of 396 F g−1 at scan rate of 2 mV s−1 in 2.0 M H2SO4 electrolyte. Thus, the prepared electrode could be used for supercapacitor.

Cobalt(II) complexes with hydroxypyridines and halogenides

We have synthesized and characterized two new cobalt(II) complexes: difluoridotetrakis(3-hydroxypyridine-κN)cobalt(II), [CoF2(C5H5NO)4] (1) and hexa(2-pyridone-κO)cobalt(II) tetrachloridocobaltate(II), [Co(C5H5NO)6][CoCl4] (2). The complexes were prepared by solvothermal synthesis. A methanol solution of hydroxypyridine was added to water solution of cobalt(II) acetate dihydrate followed by a few drops of concentrated hydrofluoric or hydrochloric acid into the mixture. The crystals of the compounds 1 and 2 are stable on air. The compounds were characterized structurally by single-crystal X-ray diffraction analysis, spectrally by FT-IR spectroscopy and thermally. Thermal analysis showed that the final product of both complexes after heating to 900 °C is elemental cobalt. The interactions between building units in the crystal structures include intra- and intermolecular hydrogen bonds in both compounds and π–π interactions in compound 2.

Preparation of cobalt polyporphine and its catalytic properties in oxygen electroreduction

A new member of the polyporphine series—cobalt polyporphine of type I (pCoP-I)—was prepared from the starting magnesium polyporphine of type I (pMgP-I) by ion exchange, i.e. by sequential processing of the pMgP-I polymer film on the electrode surface with solutions of trifluoroacetic acid (forming metalfree polyporphine of type I, pH2P-I) and cobalt(II) acetate in organic solvents. The completeness of each stage of ion exchange can be judged from the change in the electrochemical and spectral characteristics of the obtained polymer films of unsubstituted porphine (?H2P-I) and cobalt porphine (pCoP-I) of type I. Oxidative transformation of this polyporphine pCoP-I was performed, which led to the formation of additional bonds between the neighboring porphine units in the polymer film (transition of polymer of type I into polymer of type II, pCoP-II). The behavior of the polymer films of cobalt polyporphine of types I and II in oxygen electroreduction was studied. The films showed catalytic activity in this process.

Cobalt Chloride Treatment Used to Ablate the Lateral Line System Also Impairs the Olfactory System in Three Freshwater Fishes.

Fishes use multimodal signals during both inter- and intra-sexual displays to convey information about their sex, reproductive state, and social status. These complex behavioral displays can include visual, auditory, olfactory, tactile, and hydrodynamic signals, and the relative role of each sensory channel in these complex multi-sensory interactions is a common focus of neuroethology. The mechanosensory lateral line system of fishes detects near-body water movements and is implicated in a variety of behaviors including schooling, rheotaxis, social communication, and prey detection. Cobalt chloride is commonly used to chemically ablate lateral line neuromasts, thereby eliminating water-movement cues to test for mechanosensory-mediated behavioral functions. However, cobalt acts as a nonspecific calcium channel antagonist and could potentially disrupt function of all superficially located sensory receptor cells, including those for chemosensing. Here, we examined whether CoCl2 treatment used to ablate the lateral line system also impairs olfaction in three freshwater fishes, the African cichlid fish Astatotilapia burtoni, goldfish Carassius auratus, and the Mexican blind cavefish Astyanax mexicanus. To examine the impact of CoCl2 on the activity of peripheral receptors, we quantified DASPEI fluorescence intensity of the olfactory epithelium from fish exposed to control and CoCl2 solutions. In addition, we examined brain activation in olfactory processing regions of A. burtoni immersed in either control or cobalt solutions. All three species exposed to CoCl2 had decreased DASPEI staining of the olfactory epithelium, and in A. burtoni, cobalt treatment caused reduced neural activation in olfactory processing regions of the brain. To our knowledge this is the first empirical evidence demonstrating that the same CoCl2 treatment used to ablate the lateral line system also impairs olfactory function. These data have important implications for the use of CoCl2 in future research and suggest that previous studies using CoCl2 should be reinterpreted in the context of both impaired mechanoreception and olfaction.

Crystal structure of two homochiral metal-organic polymers based on S-3,3-dimethyllactic acid

By heating of an aqueous solution of zinc(II) or cobalt(II) acetates, 4,4-bipyridyl (bpy), and S-3,3-dimethyl hydroxypropionic acid (H2dml) two homochiral coordination polymers [Zn(H2O)(bpy)(Hdml)](CH3COO)∙ ∙2H2O (1) and [Co(H2O)(bpy)(Hdml)2] (2) are obtained. The crystal structure is determined by single crystal X-ray diffraction. Compound 1 has a layered structure and compound 2 has a chain structure.

Flotation-assisted dispersive liquid–liquid microextraction method for preconcentration and determination of trace amounts of cobalt: Orthogonal array design

A simple, rapid, and efficient flotation-assisted dispersive liquid–liquid microextraction method was developed for preconcentration of trace amount of cobalt(II) ions. In this technique, a mixture of toluene and methanol (20: 80, v/v) was injected through the septum in the bottom of a narrow-bore tube containing cobalt solution. Afterwards, the fine droplets of extraction solvent were formed and cobalt (as 1-nitroso-2- naphtol complex) was collected on the surface of solution by aeration. The effect of different variables on the extraction efficiency of cobalt such as pH of solution, ligand concentration and injection volume was investigated using orthogonal array design. At optimum conditions, the calibration curve was linear over the range of 10–1000 μg/L. The detection limit, relative standard deviation and enrichment factor were 3 μg/L, 3.9% (n = 10) and 120, respectively. The developed method was successfully applied to the determination of cobalt in water and drug samples.