Cobalt Speciation Research Articles

Liquid-Phase Cyclic Chemiluminescence for the Identification of Cobalt Speciation.

Accurate discrimination of metal species is a significant analytical challenge. Herein, we propose a novel methodology based on liquid-phase cyclic chemiluminescence (CCL) for the identification of cobalt speciation. The CCL multistage signals (In) of the luminol-H2O2 reaction catalyzed by different cobalt species have different decay coefficients k. Thereby, we can facilely identify various cobalt species according to the distinguishable k values, including the complicated and structurally similar cobalt complexes, such as analogues of [Co(NH3)5X]n+ (X = Cl-, H2O, and NH3), Co(II) porphyrins, and bis(2,4-pentanedione) cobalt(II) derivatives. Especially, the number of substituent atoms also influences the k value greatly, which allows excellent discrimination between complexes that only have a subtle difference in the substituent group. In addition, linear discriminant analysis based on In provides a complementary solution to improve the differentiating ability. We performed density functional theory calculations to investigate the interaction mode of H2O2 over cobalt species. A close negative correlation between the adsorption energy and the k value is observed. Moreover, the calculation of energy evolutions of H2O2 decomposition into a double hydroxide radical shows that a high level of consistency exists between the activation energy barrier and the k value. The results further demonstrate that the decay coefficient of the CCL multistage signal is associated with the catalytic reactivity of the cobalt species. Our work not only broadens the application of chemiluminescence but also provides a complementary technology for speciation analysis.

Analyses of Observed Speciation of Cobalt in NMC cathodes Using Laboratory X-ray Absorption Spectroscopy (XAS)

Analyses of Observed Speciation of Cobalt in NMC cathodes Using Laboratory X-ray Absorption Spectroscopy (XAS)

Cobalt speciation and cycling in Linsley Pond, Connecticut, USA

Cobalt speciation and cycling in Linsley Pond, Connecticut, USA

Impact of aquatic humic substances on speciation and toxicity of arsenic and cobalt to Ceriodaphnia dubia.

Humic substances (HS) interact with trace metals such as As and Co, affecting their mobility and availability in aquatic systems. However, their combined effects on toxicity to aquatic organisms are not totally understood. The objective of this study was to evaluate the toxicity of Co(II) and As(III) to the water flea Ceriodaphnia dubia in the presence of HS, considering element speciation. Toxicity assays were performed in the presence and absence of HS at two different concentrations of As(III) (10 and 20 μg/L) and Co(II) (50 and 100 μg/L). The free As(III) and Co(II) (< 1 kDa, fraction most potentially bioavailable) in the test solutions were determined via ultrafiltration. While free Co(II) decreased by approximately 80% in the presence of HS, free As(III) decreased just by 1%. Despite the higher percentage of As(III) potentially bioavailable, the presence of HS reduced significantly the toxicity of As at 20 μg/L (no toxicity was observed at 10 μg/L). This was attributed to direct effects of HS such as hormesis, hormone-like effects of HS and/or formation of protective coating. These effects also stimulated the reproduction, including in the assays in the absence of As and Co. HS reduced the toxicity of Co(II) at both test concentrations. The results of this investigation support that HS should be considered when safe limits for As and Co are defined.

Ligand field parameters, optical, thermal, magnetic, and structural features of ZnO containing cobalt-borate glasses

This article presents a study of cobalt speciation in borate glass samples, with up to 20 mol. % of zinc oxide. The samples were prepared by the melt-quenching method. The glass properties were presented utilizing a set of complementary investigations of all samples to evaluate structural, optical, thermal, and magnetic properties. XRD technique was exploited to scrutinize the structural nature of samples. Macrostructural modifications were demonstrated using Archimedes’ principle. FT-IR was utilized to probe the internal components of the glass network. Thermograms analysis was used to determine the thermal stability of the samples, which is required for applications. Optical band gap energy was decreased while the Urbach energy was enhanced. Using ligand field theory of cobalt ions, the optical absorption transitions were studied of Co2+ ions. Astonishingly, the usability of ligand field theory to evaluate the optical parameters was presented, in addition to their relation to the structural changes was demonstrated. Non-linearity aspects were enhanced with ZnO addition. Finally, ESR signals confirmed the existence of Co2+ ions in octahedral and tetrahedral symmetry, with a possibility of tetrahedral ions converting to octahedral symmetry. Based on the evaluation of ligand field parameters, besides the structural, optical, thermal, and magnetic features due to ZnO addition, our study reveals a significant potential for utilizing Zn-BNC glass for different optoelectronic purposes.

Further to quantification of content, can reflectance spectroscopy determine the speciation of cobalt and nickel on a mine waste dump surface?

Toxic elements released due to mining activities are of the most important environmental concerns, characterised not only by their concentration, but also by their distribution among different chemical species, known as speciation. These are conventionally determined using chemical analysis and sequential extraction, which are expensive and time-demanding. In this study, the possibility of using visible–near-infrared–shortwave infrared (VNIR–SWIR) reflectance spectroscopy was investigated as an alternative technique to quantify the contents of cobalt (Co) and nickel (Ni) in soil samples collected from Sarcheshmeh copper mine waste dump surface, in Iran. As a novel approach, the capability of VNIR–SWIR spectroscopy was also investigated in speciation of those elements. Three machine learning (ML) techniques (i.e., extreme gradient boosting (EGB), random forest (RF) and support vector regression (SVR)) were used to make relationships between soil spectral responses and Co and Ni contents of the samples. For all ML algorithms, the best prediction accuracies were obtained by the models developed on the first derivative (FD) spectra (for Co: RMSEp values of 7.82, 8.03 and 9.22 mg·kg−1, and for Ni: RMSEp values of 9.88, 10.32 and 11.02 mg·kg−1, using EGB, RF and SVR, respectively). Spatial variability maps of elements showed relatively similar patterns between observed and predicted values. Correlation and ML (EGB, RF, SVR)-based methods revealed that the most important wavelengths for Co and Ni prediction were those related to iron oxides/hydroxides and clay minerals, as two main soil properties responsible for controlling their speciation. This study demonstrated that the EGB technique was successful at indirect quantification and spatial variability mapping of Co and Ni on the mine waste dump surface. In addition, it provided an inspiration for implementation of the VNIR–SWIR reflectance spectroscopy as a potentially fast and cost-effective method for speciation studies of toxic elements, especially in heterogeneous soil environments.

Enrichment and Chemical Speciation of Vanadium and Cobalt in Stone Coal Combustion Products in Ankang, Shanxi Province, China

Stone coal enriches more elements compared to other coals, especially Vanadium (V). The content of Co is relatively low, while its environmental risk is relatively high. This study collected the stone-coal samples to investigate the enrichment characteristics and the chemical speciation in the combustion products of V and Co in stone coal at an open-pit coal mine in Ankang City, Shanxi Province, China. A simulation combustion experiment and sequential chemical extraction were conducted. Mineral composition was analyzed for raw-stone coal and its combustion products. The results showed that most of V and Co are mainly enriched in combustion products during the combustion process, the enrichment capacity of Co is higher than V. With the increase in the combustion temperature, the bioavailable chemical speciation of V in stone coal combustion products increased, while Co decreased. If the combustion products are stored without effective treatment, the surrounding environment will be polluted, and then human health might be endangered.

Constraints on the Genesis of Cobalt Deposits: Part I. Theoretical Considerations

Abstract Cobalt is in high demand because of the key role that cobalt-lithium-ion batteries are playing in addressing the issue of global warming, particularly in facilitating the transition from the internal combustion engine to electrically driven vehicles. Here, we review the properties of cobalt and the history of its discovery, briefly describe its mineralogy, and explore the processes that concentrate it to potentially exploitable levels. Economic cobalt deposits owe their origin to the compatible nature of Co2+, its concentration in the mantle in olivine, and its release, after high degrees of partial melting, to komatiitic and (to a lesser extent) basaltic magmas. Primary magmatic deposits, in which Co is subordinate to Ni, develop through the separation of immiscible sulfide liquids from mafic and ultramafic magmas and the very strong partitioning of these metals into the sulfide liquid. We evaluate the factors that concentrate cobalt to economic levels by these processes. Cobalt is also concentrated by aqueous fluids, either at ambient temperature in laterites developed over ultramafic rocks or hydrothermally in sediment-hosted copper deposits and in cobalt-rich vein deposits, where it crystallizes mainly as sulfide and arsenic-bearing minerals, respectively. Using the available thermodynamic data for aqueous Co species, we evaluate cobalt speciation as a function of temperature and show that, whereas it is transported at ambient temperature in most environments as the simple ion (Co2+), it is most mobile in hydrothermal systems as chloride species. Based on thermodynamic data compiled from a variety of sources, we evaluate stability relationships among some of the principal cobalt sulfide and oxide minerals as a function of temperature, pH, fO2, and αH2S and, in conjunction with the aqueous speciation data, determine their solubility. This information is used, in turn, to predict the physicochemical conditions most favorable for cobalt transport and ore formation by hydrothermal fluids. As thermodynamic data are not available for the cobalt arsenide and sulfarsenide minerals that form the vein-type ore deposits, we use chemographic analysis to qualitatively evaluate their stability relationships and predict the physicochemical controls of ore formation. The data and interpretations of processes presented in this paper provide the theoretical basis for a companion paper in this issue in which we develop plausible models for the genesis of the principal cobalt deposit types.

Accumulation and Speciation of Cobalt in Paracentrotus lividus.

Since the first human release of radionuclides on Earth at the end of the Second World War, impact assessments have been implemented. Radionuclides are now ubiquitous, and the impact of local accidental release on human activities, although of low probability, is of tremendous social and economic consequences. Although radionuclide inventories (at various scales) are essential as input data for impact assessment, crucial information on physicochemical speciation is lacking. Among the metallic radionuclides of interest, cobalt-60 is one of the most important activation products generated in the nuclear industry. In this work, a marine model ecosystem has been defined because seawater and more generally marine ecosystems are final receptacles of metal pollution. A multistep approach from quantitative uptake to understanding of the accumulation mechanism has been implemented with the sea urchin Paracentrotus lividus. In a well-controlled aquarium, the day-by-day uptake of cobalt and its quantification in different compartments of the sea urchin were monitored with various conditions of exposure by combining ICP-OES analysis and γ spectrometry. Cobalt is mainly distributed following the rating intestinal tract ≫ gonads > shell spines. Cobalt speciation in seawater and inside the gonads and the intestinal tract was determined using extended X-ray absorption fine structure (EXAFS). The cobalt inside the gonads and the intestinal tract is mainly complexed by the toposome, the main protein in the sea urchin P. lividus. Complexation with purified toposome was characterized and a complexation site combining EXAFS and AIMD (ab initio molecular dynamics) was proposed implying monodentate carboxylates.

Co-Co3O4 encapsulated in nitrogen-doped carbon nanotubes for capacitive desalination: Effects of nano-confinement and cobalt speciation

Capacitive deionization (CDI) has gained increasing attention as an environmentally friendly and energy-efficient technology for brackish water desalination. However, traditional CDI electrodes still suffer from low salt adsorption capacity and unsatisfactory reusability, which inhibit its application for long-term operations. Herein, we present a facile and effective approach to prepare Co and Co3O4 nanoparticles co-incorporating nitrogen-doped (N-doped) carbon nanotubes (Co-Co3O4/N-CNTs) via a pyrolysis route. The Co-Co3O4 nanoparticles were homogeneously in-situ encapsulated in the inner channels of the conductive CNTs to form a novel and efficient CDI electrode for the first time. The encapsulation of Co-Co3O4 nanoparticles in CNTs not only inhibits the Co leaching but also significantly enhances the desalination capacity. The morphology, structure, and capacitive desalination properties of the Co-Co3O4/N-CNTs were thoroughly characterized to illuminate the nano-confinement effects and the key roles of the interaction between cobalt species in the CDI performance. The co-existing metallic cobalt and cobalt oxides act as the roles of effective active sites in the CDI performance. As a consequence, the optimum Co-Co3O4/N-CNTs electrode displays an outstanding desalination capacity of 66.91 mg NaCl g−1 at 1.4 V. This work provides insights for understanding the nano-confinement effects and the key roles of the interaction between cobalt species on the CDI performance.

High efficient activation of peroxymonosulfate by Co9S8 anchored in N, S, O co-doped carbon composite for degradation of sulfamethoxazole: Effect of sulfur precursor and sulfur doping content

Cobalt sulfides as persulfate activator have received increasing interest in the field of persulfate-based advanced oxidation process. In this study, Co9S8 anchored in N, S, O heteroatoms co-doped carbon (CoSx@N-S-O-C) composite was prepared with different sulfur precursors (sulfur, thiourea, thiophene and benzyl disulfide), and used to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation. The effect of temperature, pH, inorganic ions, humic acids and water components on SMX degradation was investigated. The results showed that sulfur precursor could regulate the catalytic activity of the composite through changing the cobalt speciation and carbon structure. The catalytic activity was highest when the molar ratio of sulfur to cobalt was 5:1 (CoSx@N-S-O-C-5). Sulfate radicals (dominant) and hydroxyl radicals contributed to SMX degradation. The intermediate products during SMX degradation were identified, and the possible pathway of SMX degradation was proposed. Pyridinic N, Co-N, cobalt, S2−, S22−, C-S-C and C-SOx were active sites for PMS activation.

Cobalt Speciation and Cycling in Linsley Pond, Connecticut, USA

Cobalt Speciation and Cycling in Linsley Pond, Connecticut, USA

Effect of Cobalt Speciation and the Graphitization of the Carbon Matrix on the CO2 Electroreduction Activity of Co/N-Doped Carbon Materials.

The electroreduction of carbon dioxide is considered a key reaction for the valorization of CO2 emitted in industrial processes or even present in the environment. Cobalt-nitrogen co-doped carbon materials featuring atomically dispersed Co-N sites have been shown to display superior activities and selectivities for the reduction of carbon dioxide to CO, which, in combination with H2 (i.e., as syngas), is regarded as an added-value CO2-reduction product. Such catalysts can be synthesized using heat treatment steps that imply the carbonization of Co-N-containing precursors, but the detailed effects of the synthesis conditions and corresponding materials' composition on their catalytic activities have not been rigorously studied. To this end, in the present work, we synthesized cobalt-nitrogen co-doped carbon materials with different heat treatment temperatures and studied the relation among their surface- and Co-speciation and their CO2-to-CO electroreduction activity. Our results reveal that atomically dispersed cobalt-nitrogen sites are responsible for CO generation while suggesting that this CO-selectivity improves when these atomic Co-N centers are hosted in the carbon layers that cover the Co nanoparticles featured in the catalysts synthesized at higher heat treatment temperatures.

Evaluation and speciation of cobalt, copper, and zinc in saline soil bymicrowave‐assistedsingle extraction

AbstractThe present research assessed the chemical fractionation of Cobalt (Co), Copper (Cu), and Zinc (Zn), detected in saline soil samples of Hyderabad Pakistan. The partitioning of Co, Cu, and Zn in soil samples was carried by single‐step extraction using microwave irradiation energy. The validity of the methods was confirmed using the same operating conditions applied and checked as in BCR sequential extraction fractionation using certified reference material BCR‐701 and the standard method of addition (recoveries 96%–102%). Atomic absorption spectrometry was used to test extractable Co, Cu, and Zn contents obtained by the comparative method. Using compromised microwave conditions steps 1–3 of the sequential extraction (excluding hydrogen peroxide digestion in step 3) could be accomplished with an ultrasonic bath between 15 and 30 min, whereas 60–120 s were needed for microwave single‐extraction (MSE). The total concentrations of Co, Cu, and Zn extractable metals produced by three separate extractions ranged from 1.02–3.30, 5.02–9.95, and 3.97–8.01 μg/g respectively. Consequently, the use of single‐step extraction with the aid of microwave and ultrasound energy to reduce the time required for single‐step extraction based on the BCR sequential extraction method. However, with the aid of developed single‐step extraction methods, the obtained results were comparable to those values obtained from BCR sequential extraction method. For further study, the MSE can be frequently used to know the metal‐bound intensity with a different chemical fraction on environmental solid samples.

Study of bioaccessibility of cobalt species in berries and seeds by mass spectrometry techniques

In recent years, açai berries (Euterpe Oleracea M.), goji berries (Lycium barbarum L.), bilberries (Vaccinium myrtillus L.), and chia seeds (Salvia hispanica L.) have increased interest worldwide due to their nutritional value and health benefits. In the present study, SEC-ICP-MS and μ-HPLC-ESI-MS/MS were used for the investigation of cobalt speciation and evaluation of its bioaccessibility in these products. Total cobalt content was determined, and açai berries (0.348 ± 0.042 μg g−1) and chia seeds (0.352 ± 0.036 μg g−1) were found as the best sources of this element. Different elution profiles of the extracts of examined berries and seeds obtained with the use of ammonium acetate, Tris-HCl, and SDS suggested that cobalt is bound by different bioligands in each biomatrix.The bioaccessibility of cobalt species was evaluated by SEC-ICP-MS. On the chromatograms of extracts obtained after simulation of gastrointestinal digestion, peaks corresponding to low molecular mass (17.00–1.35 kDa) cobalt complexes were observed. In the case of goji berries, their intensities were significantly higher on chromatograms of gastrointestinal than gastric extract. In enzymatic extracts, different forms of vitamin B12 were identified by μ-HPLC-ESI-MS, including its natural forms—methylcobalamin (Me-Cbl) and adenosylcobalamin (Ado-Cbl).

Speciation of iron, nickel and cobalt in the anaerobic biodegradation of rice straw

The bioavailability of Fe, Ni and Co and its impact on the mono-digestion of rice straw with addition of a natural nutrient source were assessed. The chemical forms and the degree of bioavailability of Fe, Ni and Co were investigated in two reactors during 311 days of experimentation at 37°C. The reactor (R2) was supplemented with 1 g/L of mineral once a week. The control reactor R1 was limited in mineral during the study. The greatest methane yield of 238 mL/g VS was obtained with mineral supply with an increment of 45% respect to reactor without metals (164 mL/g VS). The sequential extraction confirmed that 70, 88 and 75% of Fe, Ni and Co were mainly in bioavailable forms (interchangeable and carbonate), respectively, with mineral supply in R2. Fe and Co were mainly associated to the carbonate and oxidizable fractions (43% and 41% respectively), while the Ni concentrations were not detected during the experimentation. As a result, the methane yield in R2 increased by 45%, with a potential bioavailability (Ni ˃ Co ˃ Fe) higher compared to control reactor (Co ˃ Fe). Trace elements deficit in R1 result in the reduction of metal-binding forms until the end of experiment, with a negative impact on methanogenic community.

Elemental distribution and chemical speciation of copper and cobalt in three metallophytes from the copper-cobalt belt in Northern Zambia.

Three metallophyte species, Persicaria capitata, P. puncata (Polygonaceae), Conyza cordata (Asteraceae) from mineral wastes in the Zambian copper-cobalt belt were studied. This study focused on the elemental distribution in the roots, stems and leaves, using a range of techniques: micro-PIXE, SEM-EDS synchrotron XFM and XAS. The species differed in their responses to growing on Co-Cu-enriched soils: Persicaria puncata is a Co hyperaccumulator (up to 1060 μg g-1 in leaves), while Persicaria capitata and Conyza cordata are Co-excluders. All three species are Cu-accumulators. The highest concentrations of Cu-Co are in the epidermal cells, whereas in Persicaria puncata Co was also enriched in the phloem. The Co coordination chemistry shows that an aqueous Co(ii)-tartrate complex was the predominant component identified in all plants and tissues, along with a minor component of a Co(iii) compound with oxygen donor ligands. For Cu, there was considerable variation in the Cu speciation in the various tissues and across the three species. In contrast to hyperaccumulator plants, excluder and accumulator type plants have received far less attention. This study highlights the different biopathways of transition elements (Cu, Co) in hyper-tolerant plant species showing different responses to metalliferous environments.

Solvation and speciation of cobalt(II). A theoretical X-ray absorption and RIXS study

The X-ray spectroscopic signatures of solvated Co2+ ions mimicking the aqueous solution of CoCl2 are investigated accounting for multiconfigurational as well as spin–orbit coupling effects. To this end the RASSCF/RASSI methodology with second order corrections due to dynamical correlation (RASPT2) is employed. Emphasis is put on the identification of spectral signatures of different species in octahedral, [Co(H2O)6−xClx](2−x)+, and tetrahedral, [Co(H2O)4−xClx](2−x)+, coordination. X-ray absorption spectra show distinct differences in the L3 band only. Here, the best agreement between theory and experiment is obtained for the hexaaqua complex [Co(H2O)6]2+. For better identification of particular species it is proposed to use RIXS spectroscopy, which shows pronounced species-dependent inelastic features.

Analysis of Solvent Effect on Formation Constants and Speciation of Cobalt(II), Copper(II) and Lead(II) Complexes of L-Methionine and Uracil

The analysis of coordination of chelating agents to metal ions in the formation of complexes under different experimental conditions provide information on the effects of the conditions on the extent of the coordination of the ligands to the metal ions for potential applications in bioinorganic and environmental Inorganic Chemistry. The effect of solvent on the coordination of L-methionine (primary ligand) and uracil (secondary ligand) to Co(II), Cu(II) and Pb(II) ions in the formation of binary and ternary complexes have been potentiometrically investigated in water and 40% (v/v) ethanol- water media at 27 °C and ionic strength of 0.02 mol dm–3was maintained by using NaNO3. The proton-ligand stability constants and formation constants of the binary and ternary systems were established under the experimental conditions. The formation constants of the ternary complexes were numerically compared with the corresponding binary complexes in terms of Δ log K and percentage relative stabilization (%RS). Speciation of the metal ions, binary and ternary complexes as a function of pH in the solutions was investigated by using HYSS program. The ligands were observed to form more stable ternary complexes than binary complexes. The proton-ligand stability constants the ligands and the formation constants of the metal complexes were found to be higher in 40% (v/v) ethanol-water than water. The distribution of the species revealed a decrease in the metal ion concentrations with increase in the concentrations of the binary and ternary as pH increased. The chelating agents interacted strongly with the metal ions and showed different selectivity towards the metals ions. These properties can be exploited in combating metal poisoning, separating the metals and expounding the bioinorganic chemistry of the metal ions and the ligands.

Speciation and Ecological Risks of Cobalt and Antimony in Black-Necked Crane (&lt;i&gt;Grus nigricollis&lt;/i&gt;) Habitat Sediments in China’s Caohai Lake

Speciation and Ecological Risks of Cobalt and Antimony in Black-Necked Crane (&lt;i&gt;Grus nigricollis&lt;/i&gt;) Habitat Sediments in China’s Caohai Lake