Ni Amounts Research Articles

A stable ZnMn2O4 cathode for aqueous Zn-ion batteries via Ni doping to suppress Mn dissolution

ZnMn2O4 (ZMO) emerges as a promising cathode for aqueous Zn-ion batteries due to its high theoretical capacity of 224 mAh g−1 and operating voltage of ∼1.9 V (vs. Zn2+/Zn). However, it suffers from capacity degradation over cycling, attributed to the dissolution of redox-active Mn through Mn3+ disproportionation. In this study, we propose a strategy to stabilize ZMO cathodes by transforming Mn3+ into Mn4+ via Ni doping, aiming for charge balance. The ZnMn2−xNixO4 (x = 0, 0.5, 1.0, and 1.5) with different Ni amounts was prepared by straightforward precipitation and calcination. The mitigation of redox-active Mn dissolution enhanced the specific capacity of all Ni-doped ZMO compared to 201 mAh g−1 of ZMO. ZnMn1.5Ni0.5O4 and ZnMnNiO4 exhibit 277 and 278 mAh g−1, respectively, surpassing ZMO’s theoretical capacity (224 mAh g−1) of ZMO. This additional capacity was attributed to MnOx deposition on the cathode and the charge storage reaction with Zn-ion within the MnOx deposit. Furthermore, Ni doping induces a structural transition of the tetragonal into a cubic spinel, expanding the unit cell volume. This structural modification combined with suppressed Mn dissolution contributes to improved cycling stability. ZnMnNiO4 exhibits 80 % retention of initial capacity after 1000 cycles, outperforming ZMO (57 % retention). The expanded unit cell reduces repulsion between inserted Zn ions, enabling a higher rate performance than pure ZMO. The change in Mn valence states induced by Ni doping enhanced the lifespan and rate capability of ZMO cathodes, underscoring their potential as cathodes for Zn-ion batteries.

Heavy metal contamination assessment and potential human health risk of water quality of lakes situated in the protected area of Tisa, Romania

Protected areas are significant due to the high value of natural resources they shelter. This study's primary objective is to assess the quality status of the water resources (13 lakes and Tisa River) localized in the protected area of Tisa River on the territory of Romania. A number of 13 lakes and surface water (Tisa River) situated in the protected area through the Natura 2000 ecological network are studied. The chemistry and potential pollution status were analyzed by measuring and analyzing a set of twenty elements and sixteen physico-chemical parameters. The potential impact of anthropogenic activities was settled through the applied analysis and obtained results. A potential human health risk was noticed. Results indicated that waters are rich in Ni and Fe probably due to interaction with groundwater rich in Fe and Ni. Waters are characterized by potential contamination, which if directly or through the food chain consumed could negatively influence the human health. Piper and Gibbs plots indicated that the studied waters are divided into three categories based on water-rock interactions: mixed Ca2+-Na+-HCO3-, CaCO3−, and Na+-HCO3-. Likewise, the applied pollution indices (Heavy metal Pollution Index, HPI and Heavy metal Evaluation Index, HEI) indicated three pollution categories correlated to the As, Ni and Fe amounts. The findings of this research imply that the chemistry of the studied lakes and surface waters is influenced by the geogenic origin and emergence of anthropogenic activities. The significance of this research is related to understanding of mechanisms that influence the water quality, improving and conserving the natural water resources, and correspondingly understanding if any potential human health risks could be identified.

Catalytic conversion of guaiacol to phenol and alkylphenols over Mo-promoted Ni/CeO2 catalyst in supercritical ethanol

The study explored the catalytic hydrodeoxygenation (HDO) of guaiacol using nickel-loaded cerium oxide (Ni/Ce) and molybdenum-promoted Ni/Ce (Mo-Ni/Ce) catalysts in supercritical ethanol. The use of Mo-Ni/Ce at 300 °C maximized H2 production, guaiacol conversion (84.1%), and deoxygenation compared to Ni/Ce. Mo-Ni/Ce also achieved the highest efficiency for producing desired products, resulting in 7.8% phenol and 29.0% alkylphenols selectivities. Mo-Ni/Ce's better efficiency stemmed from enhanced ethanol dehydrogenation, H2 dissociation and spillover, and accelerated HDO reactions owing to improved Ni dispersion and catalyst oxygen vacancies. Testing different Ni and Mo loading amounts revealed the optimum catalyst efficiency when using 20% Ni and 5% Mo (5Mo-20Ni/Ce). Temperature optimization with 5Mo-20Ni/Ce increased guaiacol conversion (up to 95.6% at 340 °C) and yielded more phenol (27.4%) and alkylphenols (66.1%). DFT calculations revealed that adding molybdena clusters notably reduced the energy required for creating oxygen vacancies, indicating enhanced catalytic properties for oxygen vacancy generation in 5Mo-20Ni/Ce.

Structural and morphological characterizations of glass based composites in thin films form

By using a low-cost sol gel method, neat and loaded phosphate glass containing Cr, Co, Ni, and Zn was synthesized and then placed on a silica glass substrate. Cr, Ni, Co, and Zn loading amounts were diluted inside the matrix using rates varying from 0 wt% to 16 wt% in order to study the impact of loading elements on glass characteristics. By using XRD and SEM, it was determined how loading factors affected the structural and morphological characteristics of glass thin layers. When the annealing temperature was maintained at 250 °C, X-ray diffractograms revealed that the deposited glass films had an amorphous nature, whilst also X-ray pattern results revealed that the loaded films had a low crystalline nature. Morphology studies indicated the homogeneity and the edge of crystallinity of the obtained thin films. All results were described in detail and they indicated that the films prepared in this study can be used in many nanotechnology applications.

Nickel Supported on Multilayer Vanadium Carbide for Dry Reforming of Methane

AbstractA multilayer vanadium carbide MXene (m‐V2C) was used as a robust oxy‐carbide support to prepare a series of Ni/m‐V2O3‐V2C catalysts with various Ni amounts by an impregnation method and used for dry reforming of methane (DRM). The results show that the Ni addition increases the catalyst alkalinity, and the interaction between the Ni metal and m‐V2C increases with increasing Ni amount. Ni/m‐V2O3‐V2C with a Ni amount of 13 wt% showed optimal CH4 and CO2 conversions of 94 % and 89 %, respectively. In addition, 13Ni/m‐V2O3‐V2C exhibits excellent catalytic stability and anti‐coking ability in a 90‐hour stability test, which is attributed to the strong metal‐support interaction. In situ DRIFTS analysis showed that methane activated on the Ni particles generates CHx and H, while CO2 interacts with m‐V2O3‐V2C to form carbonates on Ni/m‐V2O3‐V2C; carbonate species come into contact with methane pyrolysis products and quickly form formate species, which are further decomposed into CO.

Effect of salt solution treatment on impurity removal: A case study on phosphogypsum

AbstractThis study gives a brief demonstration of impurity removal efficiency upon salt solution treatment of phosphogypsum (PG). The experimental set up has been designed according to a multi‐variable Box–Behnken Design (BBD) with stirring time, solid: liquid (PG:salt solution) ratio and temperature as the conducted in various salt solutions. PG sample has been treated with sea water, 5% NaCl and 10% NaCl solutions according to the BBD matrix. Fluoride (F), copper (Cu), manganese (Mn), and nickel (Ni) amounts in the PG sample have been measured upon pre‐ and post‐treatment with salt solutions. Among other operating conditions, temperature has been the dominant factor on fluoride removal efficiency, and responses for the factors determined in the experiment runs indicated that a significant correlation could be established between temperature and fluoride removal, sea water being the most efficient salt solution. Higher copper, manganese, and nickel removal efficiencies have been observed in single salt NaCl solution systems however no significant correlation could be established between factors. Results indicate that pre‐treatment of PG located near coastal regions with sea water can be a cost‐effective approach and applicable on industrial scale when fluoride removal is of importance.

Controlling the D-band for improved oxygen evolution performance in Ni modulated ultrafine Co nanoparticles embedded in Nitrogen-doped carbon microspheres

Despite the challenges on tuning the d-band structure of transition metals, the d-band is of great importance for promoting the interaction between catalytic and intermediates during the oxygen evolution reaction (OER) process. Herein, ultrafine Co nanoparticles embedded in the surface layer of nitrogen-doped carbon microspheres are prepared through an in-situ co-coordination strategy, and its d-band is modulated by introducing different Ni amounts. The introduction of Ni in the Co crystal lattice can tune the d-band center and unpaired electrons, which collectively result in an enhancement of OER activity and kinetics. By investigating the catalysts with Ni content from 0% to 75%, it is concluded that the catalyst with 25% Ni shows optimal OER activity, lower overpotential (285 mV at 10 mA cm−2) and higher current densities (73.75 mA cm−2 at 1.63 V). Moreover, the good stability is also demonstrated with the negligible decrease on current densities after 3000 CV cycles or 100 h of continuous test in alkaline media. This concept of modulating the d-band structure by introducing a transition metal with different contents in another transition metal crystal lattice could present an alternative pathway to the development of highly active catalytic materials for OER and beyond.

Trace-element composition of pyrite and its implications for hydrothermal process within the Mesoproterozoic metasedimentary sequences of the São Francisco Craton, northeastern Brazil

The distribution of trace elements in pyrite has been documented for the first time in quartz veins hosted in the Mesoproterozoic metasedimentary sequence of the Tombador Formation, São Francisco Craton, northeast Brazil. In this study, Electron Microprobe Analyses (EPMA) were used to determine the trace-element compositions of pyrite in these hydrothermal quartz veins. Three pyrite types have been distinguished and interpreted from petrographical relationships and trace-element patterns. Pre-existing pyrite (Py1), derived from the host-rock quartzite, is Ni-poor with concentrations varying from 600 – 6,100 ppm. Elongated syn-tectonic pyrite (Py2) has similar trace-element composition to the Py1, with Ni amounts ranging between 830 and 7,870 ppm. In contrast, possibly post-tectonic, euhedral to subhedral hydrothermal pyrite (Py3), contains higher contents of Ni (7,970 – 26,120 ppm). Mafic and/or metasedimentary rocks from the Espinhaço Supergroup were probably the source of Ni for this fluid-flow event. Fluid generation is related to the devolatilization of the base of the thickened crust, with migration of fluids by preexisting structures. Several shear zones and large-scale NNW-trending folds were developed during the inversion of the Espinhaço basin, as a result of the ca. 0.6 Ga Brasiliano orogenic event. Regional fluid movement through the crust at this time is supported by several mineralized veins and hydrothermal deposits in the São Francisco Craton and adjacent Neoproterozoic belts.

Ni-based electrocatalysts for unconventional CO2 reduction reaction to formic acid

Electrochemical reduction stands as an alternative to revalorize CO2. Among the different alternatives, Ni single atoms supported on carbonaceous materials are an appealing catalytic solution due to the low cost and versatility of the support and the optimal usage of Ni and its predicted selectivity and efficiency (ca. 100% towards CO). Herein, we have used noble carbonaceous support derived from cytosine to load Ni subnanometric sites. The large heteroatom content of the support allows the stabilization of up to 11 wt% of Ni without the formation of nanoparticles through a simple impregnation plus calcination approach, where nickel promotes the stabilization of C3NOx frameworks and the oxidative support promotes a high oxidation state of nickel. EXAFS analysis points at nickel single atoms or subnanometric clusters coordinated by oxygen in the material surface. Unlike the well-known N-coordinated Ni single sites selectivity towards CO2 reduction, O-coordinated-Ni single sites (ca. 7 wt% of Ni) reduced CO2 to CO, but subnanometric clusters (11 wt% of Ni) foster the unprecedented formation of HCOOH with 27% Faradaic efficiency at − 1.4 V. Larger Ni amounts ended up on the formation of NiO nanoparticles and almost 100% selectivity towards hydrogen evolution.

Accumulation of heavy metal pollution caused by traffic in forest trees in the park of Kerey and Janibek Khans of the city of Nur-Sultan, Kazakhstan

Air quality in Nur-Sultan, the fast-growing new capital city of Kazakhstan, has been poorly investigated. This research was carried in Kerey and Janibek Khans Park in Nur-Sultan, the capital city of Kazakhstan, which is affected by “different traffic density” on the roads. Three different categories of contamination (i) high pollution (distance from the main road 10–15 m), (ii) moderate pollution (distance from the side road 15–30 m), and (iii) low pollution (distance from the source of contamination 30–80 m) at different levels resulting from urban transportation were examined. The aim of the study is to determine the pollution accumulation amounts of Ni, Cd, Pb, Cr, Li, Co, Fe, and Zn in five different tree species: Norway spruce (Picea abies /L./ H. Karst.), blue spruce (Picea pungens Engelm.), Scots pine (Pinus sylvestris L.,), Siberian larch (Larix sibirica Ledeb.), and silver birch (Betula pendula Roth). Significant differences in Ni, Cd, Pb, Cr, Li, Co, Fe, and Zn accumulation amounts were determined between three different parts of the park exposed to different levels of contamination. Approximately twice higher Ni, 2.3 times Cd, 3.3 times Pb, 2.7 times Co, 1.6 times Zn accumulation were determined in the area exposed to high pollution than in the parts of the park exposed to low pollution. Cd deposition in the area exposed to high contamination was higher in silver birch than in Scots pine and Norway spruce, while Cr and Co deposition values were higher in Norway spruce than in birch and Scots pine.

Morphological modulation of cobalt selenide on carbon cloth by Ni doping for high-performance electrodes in supercapacitors

Transition metal selenides are desirable electrode materials in supercapacitors due to the good electron conductivity and high theoretical specific capacity. In this work, the relationship between the elemental composition and electrochemical performance of cobalt nickel selenide is studied. Cobalt nickel selenide samples with different morphologies are prepared on the carbon cloth by a solvothermal technique and selenation process using different Ni amounts. Ni doping is observed to modulate the morphology of CoSe 2 and enhance the electrochemical properties. The Co 0.8 Ni 0.2 Se 2 electrode shows a high specific capacitance of 1472 mF cm −2 at a current density of 1 mA cm −2 as well as good cycling stability. As a verification of the practicality, the asymmetrical supercapacitor assembled shows a capacity of 120 mF cm −2 after 8000 cycles at 1 mA cm −2 while delivering a superior power density 3.75 mW cm −2 with an energy density of 0.052 mWh cm −2 . These results demonstrate the high potential of Co 0.8 Ni 0.2 Se 2 as electrode materials in supercapacitors.

Fabrication and characterization of in-situ Al3Ni intermetallic and CeO2 particulate-reinforced aluminum matrix composites

Al-xNi-yCeO2 (x = 6, 10, 15, 20 and y = 0, 5, 10 wt%) composites were produced by a powder metallurgical production route. Powder mixtures of Al, Ni and CeO2 were fabricated via mechanical alloying (MA) for 4 h in a Spex-type high-energy ball mill. Both the mechanically alloyed (MAed) and non-MAed (as-blended mixtures) powders were pre-compacted in a hydraulic press under 650 MPa and then pressurelessly consolidated at 630 °C for 2 h under an inert atmosphere. The effects of MA process and the amounts of Ni and CeO2 on the microstructural, mechanical and tribological properties of the sintered composites were determined. Based on the SEM and XRD investigations, the MAed powders illustrated a homogenous structure, comprising flaky particles with smaller crystallite sizes and greater lattice strain. According to the XRD analysis, Ni formed Al–Ni intermetallic compounds in the matrix of sintered composites that act as secondary reinforcement phases. The SEM observations conducted on the MAed samples demonstrated more uniformly and finely distributed Al3Ni and CeO2 phases in the microstructure of the MAed samples, unlike the non-MAed ones. The hardness values of sintered composites increased due to the MA process and increasing Ni and CeO2 amounts, and the hardness value of the MAed Al20Ni–10CeO2 sample reached 179 HV. The ultimate compressive strength and failure strain of the MAed Al6Ni–10CeO2 sample were 441 MPa and 11.3%. In the Al20Ni–10CeO2 sample, the compressive strength and failure strain were 391 MPa and 5.5%, respectively. Additionally, the reciprocating wear test results illustrated that both wear resistance and hardness values of the composites increased as the amounts of Ni and CeO2 increased, and the Al20Ni–10CeO2 sample exhibited the highest wear resistance as 0.175 × 10-3 mm3/Nm.

Diversity of Ni growth response and accumulation in Central-Eastern Mediterranean Odontarrhena (Brassicaceae) populations on and off serpentine sites

Nickel response and accumulation were analyzed in 12 populations from seven Central-Eastern Mediterranean Odontarrhena taxa on and off serpentine sites to test the presence of metal-induced growth stimulation and its relationship with tolerance and plant Ni concentration. Seedlings were cultivated in hydroponics with increasing NiSO4 concentrations to obtain dose-response curves and to evaluate Ni levels in roots and shoots. In all the accessions, a metal stimulatory effect on growth was present in the low-dose zone and significantly fitted the Brain-Cousens hormetic model. Accessions showed broad variation in tolerance, with the most tolerant plants requiring the highest Ni concentrations in the culture medium for optimal growth. Significant differences were also detected in plant Ni concentrations and a positive relationship was found between tolerance and accumulation. The serpentine and non-serpentine populations of O. chalcidica were similarly capable of hyperaccumulation, suggesting this ability to a be a species-wide trait. In the case of O. muralis, a species that preferentially avoids serpentine soils, the two populations from non-serpentine sites showed the same Ni-enhanced growth of the serpentine accessions of the other species investigated here, but only at the lowest concentration, and reached shoot Ni amounts approaching the Ni hyperaccumulation threshold. Therefore, in Odontarrhena the capacity to tolerate and accumulate Ni could be considered a specieswide trait in all the serpentine taxa, both endemic and facultative. Regarding the metal concentration showed by the accessions in nature, neither Ni levels in the field-collected plants nor those in their natural soils of origin were related to Ni tolerance. On the other hand, Ni accumulation capacity appeared as the main driving factor for the metal concentration in the plants in their native habitats.

Solubilities of Nickel, Iron, and Chromium in Liquid Magnesium in the Presence of Austenitic Stainless Steel

Steel containers and instruments are used to hold and transport Mg melts. Thus, quantitative analysis of the dissolution of metallic elements from the steel materials into the liquid Mg is important for controlling the impurities in processes such as Mg alloy production and Ti smelting. When austenitic stainless steels containing Cr and Ni come in contact with a Mg or Mg alloy melt, a large amount of Ni and limited amounts of Fe and Cr dissolve into the melt. In this study, the composition of a Mg-Ni-based melt in equilibrium with SUS316 was investigated to determine the maximum amounts of impurities dissolved from SUS316 into the liquid Mg. Mg-Ni melts of different compositions were held in a closed crucible of SUS316 at 1073 K (800 °C) to 1273 K (1000 °C), and the compositions of the inner wall of the crucible and the Mg-Ni alloy were evaluated after quenching. Subsequently, the relationships between the solubility limit of element i (i: Ni, Fe, and Cr) in liquid Mg with the coexistence of SUS316, $$ C_{{{\text{sol}},{i}}}^{*} $$ (mass pct), and the temperature, T (K), were determined: $$ \log \,(C_{{{\text{sol}},{\text{Ni}}}}^{*} ) = {{ - 1.40 \times 10^{3} }}/{T} + 2.57 \, ( \pm \,0.12), $$ $$ \log \,(C_{{{\text{sol}},{\text{Fe}}}}^{*} ) = - {{5.20 \times 10^{3} }}/{T} + 3.93 \, ( \pm \,0.16),\;{\text{and}} $$ $$ \log \,(C_{{{\text{sol}},{\text{Cr}}}}^{*} ) = - {{5.96 \times 10^{3} }}/{T} + 3.80 \, ( \pm \,0.05). $$ These solubility limits were compared with those estimated based on the available thermodynamic data for the SUS316 and Mg-i binary systems. The validity of the obtained data and the reliability of the previously reported thermodynamic data were also discussed.

Nickel doping induced amorphization of brookite TiO2: Photoluminescence enhancement

In this work, we have elaborated nickel doped TiO2 thin films by low temperature spray pyrolysis technique from ethanol based precursor. For the sample free of nickel, The FTIR spectrum reveals a large amount of organic species bonded to TiO2, resulting in a carbon-doped brookite. Ni doping causes extinction of the organic related peak that fade away for highly (> 10 %) Ni doped films. XRD spectra reveal the presence of brookite phase for low Ni amounts. While increasing Ni rate, the crystalline phase undergoes a transition to amorphous state and brookite XRD peaks vanishes. Optical and electronic (SEM) micrographs show a smooth surface with small brookite nanoparticles, for low Ni rate. Increasing Ni rate results in a fractured morphology composed of micrometric smooth ships. Optical absorption obtained by transmittance-reflectance spectra is enhanced in the transparency region of TiO2, by Ni doping due to the increase of defect density and the brookite to amorphous phase transformation. Visible and UV emission spectra are obtained from PL measurements at room temperature. A spectacular PL magnification is obtained for high Ni doping levels due to increase of oxygen vacancies in the amorphous film. However, thermal annealing at 500 °C causes recrystallization to anatase phase, leading to a dramatic PL quenching.

Effect of cage culture environment on farmed fish in terms of metal accumulation

Metal pressure under farm conditions was examined on the gill and muscle tissues of farmed Sparus aurata and compared with their wild counterparts (Sparus aurata, Trachurus trachurus, Mullus barbatus). Al, Mn, Cd, Co, Cr, Cu, Ni, Pb and Zn accumulation amounts in gill tissue of farmed fish were 28.821, 37.620, 0.136, 0.300, 3.730, 2.441, 3.222, 2.474 and 127.494 mg/kg respectively. Among them, Cd, Cr, Cu and Pb concentrations in gill tissue of farmed fish were higher than that in wild fishes. Metal depositions in muscle tissue of farmed fish were far below that in the gill tissue. The accumulated Al (6.700 mg/kg) in the muscle tissue of farmed fish was higher than in wild ones. The results showed that metal accumulation levels (especially Cd, Cr, Cu and Pb) in the gill tissue of farmed fish indicate metal pressure under captive conditions. Furthermore, the calculated hazard index (HI) and total hazard index (THI) of the considered elements in the edible part of farmed fish were below the level considered safe, which elucidates that farmed fish do not pose any threat to the human consumer in terms of metal toxicity.

Base alteration of some heavy metal concentrations on local and seasonal in Bartin River.

Fresh water resources have always been an extremely invaluable economic and strategic resource in the world. There are about 1.4 billion people who have no access to pure water resources mainly due to the discharge of 95% of unpurified wastewater and 70% of industrial wastes into water resources in underdeveloped and developing countries. More than half of the world's rivers are contaminated. Eighty percent of diseases are caused by contaminated waters in developing countries. Among the pollutants in these streams, heavy metals are of particular significance, as heavy metals do not dissolve and degenerate easily in nature. They also tend to bio-accumulate. This is why determining heavy metal concentrations is of great importance because it can help detect risk zones and risk levels. This study aims to determine the alteration of some heavy metal concentrations during a year in Bartin River on a point and seasonal base. Within the scope of the study, samples were collected from 5 chosen locations on Bartin River during a year and the alteration of Cu, Fe, Zn, Mn, Ni, and Pb concentration amounts were determined monthly. As a result of the study, it was determined that there were various rates of contamination with heavy metals at all stations, and that the amount of all studied heavy metal concentrations decreased depending on seasonal alteration when precipitation and hence the flow rates were high, and the highest concentrations were calculated in samples that were collected from L3 and L5 stations. Results shows that some of the toxic metals' accumulations are higher than the suggestion of value, which recommended that the Bartin River is to some extent a toxic metal polluted river and that animals are not totally safe. Since this study constitutes a sample, all international samples should be controlled especially in the Organized Industrial Zone and foundation areas and the wastewater entering the river should be controlled and the pollution source should be determined and precautions should be taken. According to the results of the study, it also shows the water quality of the rivers in general. Pollution levels of rivers should be taken into account in the use of river water and care should be taken to use river water directly or indirectly in agricultural activities that may cause harm to human health. The results of this study can be a guide for identifying suitable areas to use the water of rivers. In future river planning, these studies will have an important guide value.

The R-Process Alliance: Discovery of a Low-α, r-process-enhanced Metal-poor Star in the Galactic Halo

Abstract A new moderately r-process-enhanced metal-poor star, RAVE J093730.5−062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937−0626 is likely a horizontal branch star. At [Fe/H] = −1.86, J0937−0626 is found to have subsolar [X/Fe] ratios for nearly every light, α, and Fe-peak element. The low [α/Fe] ratios can be explained by an ∼0.6 dex excess of Fe; J0937−0626 is therefore similar to the subclass of “iron-enhanced” metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = −2.5 suggests that J0937−0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937−0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937−0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937−0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment.

Functionalized multi-walled carbon nanotubes supported Ni-based catalysts for adiponitrile selective hydrogenation to 6-aminohexanenitrile and 1,6-hexanediamine: Switching selectivity with [Bmim]OH

Functionalized multi-walled carbon nanotubes supported nickel-based catalysts were prepared and applied in adiponitrile (ADN) hydrogenation. The characterization results show that different functional groups such as NH2, COOH, OH on MWCNTs surface can effectively act on metal ions by electrostatic attractions and chemical interactions so as to provide nucleation sites, and N species in MWCNTs can act as active sites for Ni deposition due to the strong electronic interactions between N species and Ni so as to promote ultra-small Ni nanoparticles formation, decrease NiO reduction activation energy, increase zero-valent Ni amounts as well as Ni nanoparticles dispersion. Furthermore, the doped N increases the lewis basicity, which favors the formation of primary amine of 6-aminohexanenitrile (ACN) and 1,6-hexanediamine (HDA). Moreover, the basic ionic liquid [Bmim]OH may switch the selectivity by inhibiting nucleophilic addition of the primary amine to the α-carbon of aldimine via the stabilization of NH2 groups in the amino-imine intermediates so as to impede by-products formation. In addition, the mechanism for ADN hydrogenation in [Bmim]OH was studied by density functional theory calculations. Under optimized conditions, it gives 97.80% total selectivity to ACN and HDA at 95.34% ADN conversion over Ni/N-MWCNTs-800 in the presence of [Bmim]OH.

Heavy metal pollution assessment in agricultural soils of Kermanshah province, Iran

Heavy metals in agricultural soils are of major environmental concern because of the longstanding toxicity and bioaccumulation of metals. We collected 53 soil samples from agricultural fields in Kermanshah province, Iran. Our results showed average concentrations of Zn, Cu, Ni, Cr, Mn and Fe were 74.6, 41.2, 131.5, 79.2, 559.1, and 25,935 mg kg−1, respectively. The concentrations of Zn (81%), Cu (98%), Ni (100%), Cr (98%) and Mn (79%) were greater than their background values in the world soils. Except for Ni (68%) and Cr (4%), the concentrations of Zn and Cu were lower than the maximum permissible levels suggested by the Iranian Environmental Quality Standard for agricultural soils. Multivariate statistical analyses successfully grouped the metals according to their anthropogenic or natural origins. The anthropogenic activities have resulted in Zn, Cu, and Fe accumulation in the agricultural fields, whereas Ni and Cr amounts are mainly derived from natural, combined with anthropogenic origins. On the other hand, Mn shows evidences of a geogenic source in the soils. The calculated results of enrichment factor (EF) and geo-accumulation index (Igeo) of the heavy metals reveal a similar order of Ni > Cu > Cr > Mn > Zn > Fe. The high EF and Igeo for Ni and Cu in agricultural soils indicate that there is a considerable Ni and Cu pollution probably. The EF and Igeo of Zn and Fe are low and the assessment results indicate an absence of distinct Zn and Fe pollution in agricultural soils. The assessment results of pollution indexes also support serious pollution of agricultural soils by Ni and Cu. In general, the integrated pollution index analysis indicates the agricultural soils in the region as seriously polluted.