Simple, Selective, and Sensitive Spectrophotometric Method for Determination of Trace Amounts of Nickel(Ⅱ), Copper (Ⅱ), Cobalt (Ⅱ), and Iron (Ⅲ) with a Novel Reagent 2-Pyridine Carboxaldehyde Isonicotinyl Hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone（2-PYAINH） was synthesized and studied for the spectrophotometric determination of nickel, copper, cobalt, and iron in detail. At a pH value of 7.0, 9,0, 9.0, and 8.0, respectively, which greatly increased the selectivity; nickel, copper, cobalt, and iron reacted with 2-PYAINH to form a 1：2 yellow-orange, 1：2 yellow-green, 1：2 yellow and 1：1 yellow complexes, with absorption peaks at 363, 352, 346, and 359 nm, respectively. Under the optimal conditions, Beer＇s law was obeyed over the ranges of 0.01-1.4, 0.01-1.5, 0.01-2.7, and 0.01-5.4 mg/L respectively. The apparent molar absorptivity and Sandell＇s sensitivities were 8.4×10^4, 5.2×10^4, 7.1×10^4, and 3.9×10^4 L·mol^-l·cm^-1, respectively, and 0.00069, 0.0012, 0.00078, and 0.0014 μg·cm2, respectively. The detection limits were found to be 0.001, 0.002, 0.003, and 0.01 mg/L, respectively. The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.

Recent advances in cobalt-, nickel-, and iron-based chalcogen compounds as counter electrodes in dye-sensitized solar cells

The electroactive materials used in the counter electrode(CE)are of great concern as they influence the photovoltaic performances of dye-sensitized solar cells.The main functions of CE materials are collecting electrons from the external circuit and transferring them to the electrolyte and realizing the catalytic reduction of the redox species(I3^– or Co^3+)present in the electrolyte.The research hotspot of CE materials is seeking functional materials that display high efficiency,low cost,and good electrochemical stability and can substitute the benchmark platinum electrode.Chalcogen compounds of cobalt,nickel,and iron have been widely applied as CE materials and exhibit excellent electrocatalytic performances owing to their unique electrical properties,similar energies of adsorption of I atoms as platinum,excellent catalytic activities,and good chemical stabilities.In this review,we trace the developments and performances of chalcogen compounds of iron,cobalt,and nickel as CE materials and present the latest research directions for improving the electrocatalytic performances.We then highlight the optimization strategies for further improving their performances,such as fabrication of architectures,regulation of the components,synthesis of composites containing carbon materials,and elemental doping.

Solubility of iron(Ⅲ) and nickel(Ⅱ) acetylacetonates in supercritical carbon dioxide

As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic materials.In this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility data.Solubility was measured using a static weight loss method.The semi-empirical models proposed by Chrastil and Sung et al.were used to correlate the solubility data of Fe(acac)3 and Ni(acac)2.The equations obtained can be used to predict the solubility of the same system in the experimental range.

Extraction of arsenic from arsenic-containing cobalt and nickel slag and preparation of arsenic-bearing compounds

The arsenic extraction from the arsenic-containing cobalt and nickel slag,which came from the purification process of zinc sulfate solution in a zinc smelting factory,was investigated.The alkaline leaching method was proposed according to the mode of occurrence of arsenic in the slag and its amphoteric characteristic.The leaching experiments were conducted in the alkaline aqueous medium,with bubbling of oxygen into the solution,and the optimal conditions for leaching arsenic were determined.The results showed that the extraction rate of arsenic was maximized at 99.10%under the optimal conditions of temperature 140 ℃,NaOH concentration 150 g/L,oxygen partial pressure 0.5 MPa,and a liquid-to-solid ratio 5：1.Based on the solubilities of As2O5,ZnO and PbO in NaOH solution at 25 ℃,a method for the separation of As in the form of sodium arsenate salt from the arsenic-rich leachate via cooling crystallization was established,and the reaction medium could be fully recycled.The crystallization rate was confirmed to reach 88.9%（calculated on the basis of Na3AsO4） upon a direct cooling of the hot leachate down to room temperature.On the basis of redox potentials,the sodium arsenate solution could be further reduced by sulfur dioxide（SO2） gas to arsenite,at a reduction yield of 92%under the suitable conditions.Arsenic trioxide with regular octahedron shape could be prepared successfully from the reduced solution,and further recycled to the purification process to purify the zinc sulfate solution.Also,sodium arsenite solution obtained after the reduction of arsenate could be directly used to purify the zinc sulfate solution.Therefore,the technical scheme of alkaline leaching with pressured oxygen,cooling crystallization,arsenate reduction by SO2 gas,and arsenic trioxide preparation,provides an attractive approach to realize the resource utilization of arsenic-containing cobalt and nickel slag.

Generation process of FeS and its inhibition mechanism on iron mineral reduction in selective direct reduction of laterite nickel ore

Numerous studies have demonstrated that Na2SO4 can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na2SO4 is added in the roasting, the FeO content in the roasted ore increases accompanied by the emergence of FeS phase. Further analysis indicates that NaeS formed by the reaction of Na2SO4 with CO reacts with SiO2 at the FeO surface to generate FeS and Na2Si2Os. As a result, a thin film forms on the surface of FeO, hindering the contact between reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.

Effects of preparation and operation conditions on precipitated iron nickel catalysts for Fischer-Tropsch synthesis

Iron nickel oxide catalysts were prepared using co-precipitation procedure and studied for the conversion of synthesis gas to light olefins.In particular,the effects of a range of preparation variables such as Fe/Ni molar ratios of the precipitation solution,precipitate aging times,calcination conditions,different supports and loading of optimum support on the structure of catalysts and their catalytic performance for the tested reaction were investigated.It was found that the catalyst containing 40%Fe/60%Ni/40wt%Al 2O3 ,which was aged for 180 min and calcined at 600 ℃ for 6 h was the optimum modified catalyst.The catalytic performance of optimal catalyst has been studied in different operation conditions such as reaction temperatures,H2 /CO molar feed ratios and reaction total pressure.Characterization of both precursors and calcined catalysts was carried out by powder X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Brunauer-Emmett-Teller（BET） surface area measurements,thermal analysis methods such as thermal gravimetric analysis（TGA） and differential scanning calorimetry（DSC）.

Research on nodular iron joint welded with nickel-iron electrode by the moire fringe method

Nickel-iron type cast iron electrodes are widely used for welding QT600-3 nodular iron.Nevertheless,the research work has demonstrated that the strength of these heterogeneous welded joints is low.In this paper,the uni- axial tension of the joints is studied by the Moire fringe method,and the dis- placement,strain and stress in the total fields are obtaind.Based on the uneven distribution of strain and stress,the reason of crack initiation and propagation is discussed.Through examining the appearance of the fracture by scanning elec- tron microscope,a lot of spherical substances distributed on the fracture surface are found,which may be another reason leading to cracking of the welded joint under the lower tensile stress.These new findings will help to improve the properties of nickel-iron type cast iron electrodes and the strength of the welded joint.

Rapid treatment of atrazine-contaminated water by nickel/iron bimetallic system

The utility of nickel/iron in the remediation of atrazine-contaminated water was investigated. The experimental results showed that nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic conditions. The dechlorination reaction approximately followed the first-order kinetics under the experimental conditions(nickel/iron:1.0 g/250 ml;C atrazine=20.0 mg/L), the reaction rate increased with decreasing pH value of the reaction solution and increasing the proportion of Ni:Fe within 2.95%. For condition with 2.95% nickel/iron, the reaction rate constants were 0.07518(R=0.9927), 0.06212(R=0.9846) and 0.00131 min -1(R=0.9565) at pH=2.0, 3.0 and 4.0, respectively. HPLC analysis was used to monitor the decline of atrazine concentration.

Graphitic Carbon Quantum Dots Modified Nickel Cobalt Sulfide as Cathode Materials for Alkaline Aqueous Batteries

Carbon quantum dots(CQDs)as a new class of emerging materials have gradually drawn researchers’concern in recent years.In this work,the graphitic CQDs are prepared through a scalable approach,achieving a high yield with more than 50%.The obtained CQDs are further used as structure-directing and conductive agents to synthesize novel N,S-CQDs/NiCo2S4 composite cathode materials,manifesting the enhanced electrochemical properties resulted from the synergistic effect of highly conductive N,S-codoped CQDs offering fast electronic transport and unique micro-/nanostructured NiCo2S4 microspheres with Faradaic redox characteristic contributing large capacity.Moreover,the nitrogen-doped reduced graphene oxide(N-rGO)/Fe2O3 composite anode materials exhibit ultrahigh specific capacity as well as significantly improved rate property and cycle performance originating from the high-capacity prism-like Fe2O3 hexahedrons tightly wrapped by highly conductive N-rGO.A novel alkaline aqueous battery assembled by these materials displays a specific energy(50.2 Wh kg^−1),ultrahigh specific power(9.7 kW kg^−1)and excellent cycling performance with 91.5%of capacity retention at 3 A g^−1 for 5000 cycles.The present research offers a valuable guidance for the exploitation of advanced energy storage devices by the rational design and selection of battery/capacitive composite materials.

Rapid dechlorination of chlorinated organic compounds by nickel/iron bimetallic system in water

Detoxification of chlorinated organic compounds via reaction with nickel/iron powder was implemented in aqueous solution. Compared to iron, nickel/iron bimetallic powder had higher hydrodechlorination activities for both atrazine (ATR) and p-chlorophenol (pCP); nickel/iron (2.96%, w/w) was shown to have the largest specific surface area and the optimum proportion for the dechlorination of both ATR and pCP. Electrochemical measurements showed that the adsorbed hydrogen atom on the nickel must have been the dominant reductive agent for the dechlorination of both ATR andpCP in this system.

Efficient electrocatalytic overall water splitting and structural evolution of cobalt iron selenide by one-step electrodeposition

Developing bifunctional electrocatalysts with both high catalytic activity and high stability is crucial for efficient water splitting in alkaline media.Herein,a Fe-incorporated dual-metal selenide on nickel foam(Co_(0.9)Fe_(0.1)-Se/NF) is synthesized via a facile one-step electrodeposition method.As-synthesized materials could serve as self-supported bifunctional electrocatalysts with excellent catalytic activity towards oxygen evolution reaction(OER) and hydrogen evolution reaction(HER) in alkaline media.Experimental results show that delivering a 10 mA cm^(-2) water splitting current density only requires a cell voltage of 1.55 V.In addition,a very stable performance could be kept for about 36 hours,indicating their excellent working stability.Moreover,by means of phase analysis,we have identified that the evolution of the synthesized Co_(0.9)Fe_(0.1)-Se/NF experiences two entirely different processes in HER and OER,which hydroxide and oxyhydroxide are regarded as the real active sites,respectively.This work may pave the way to further understanding the relationships between the reactivity and stability of chalcogenide-based electrocatalysts and facilitating the rational design of efficient electrocatalysts for future renewable energy system applications.

Highly-dispersed iron element decorated nickel foam synthesized by an acid-free and one-pot method for enzyme-free glucose sensor

The highly-dispersed iron element decorated Ni foam was prepared by simple immersion in a ferric nitrate solution at room temperature without using acid etching, and characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), EDAX spectrum(EDAX mapping) and Raman spectroscopy. The EDAX spectrum illustrated that iron element was highly-dispersed over the entire surface of nickel foam, and the Raman spectroscopy revealed that both Ni-O and Fe-O bonds were formed on the surface of the as-prepared electrode. Moreover, the iron element decorated Ni foam electrode can be used as non-enzymatic glucose sensor and it exhibits not only an ultra-wide linear concentration range of 1-18 mmol/L with an outstanding sensitivity of 1.0388 m A·mmol/(L·cm2), but also an excellent ability of stability and selectivity. Therefore, this work presents a simple yet effective approach to successfully modify Ni foam as non-enzymatic glucose sensor.

Chemical forms of cobalt and nickel extracted by M1,M3 and CaCl_(2)-DTPA

Mehlich 1(M1), mehlich 3(M3) and CaCl 2 DTPA have been used to predict the available micronutrient in soil. However, the forms of micronutrient extractable by these extractants are not known. In the present study, ten soils, collected from five provinces and the capital of China, representing a wide range of chemical and physical properties, were analyzed by sequential extraction to isolate five forms of cobalt and nickel, they are exchangeable, carbonate bound, Fe Mn oxide bound, organically bound and residual forms. The chemical forms extracted by M1, M3 and CaCl 2 DTPA were also investigated. The results show strong correlation between the carbonate bound or organically bound forms of Co or Ni and the amounts of extractable by any of the above three extractants. The main forms extracted by these extractants are carbonate and organically bound forms. The ranking of these three extractants for extraction of Co and Ni are M1>M3=CaCl 2 DTPA and M1=M3>CaCl 2 DTPA, respectively.

Model of In Situ Composite of Cobalt(Ⅱ)-Phthalocyanine and Carbonyl Iron for Organic/Inorganic Nanocomposites

Cobalt-phthalocyanine/iron nanocomposite particles have been obtained using method of composite in situ, with the mixture of carbonyl iron and solution of cobalt ( Ⅱ ) - phthalocyanine (Co-Pc) ultrasonic dispersing in N,N-dimethyl-formamide (DMF). Structure characterization of their inner and surface have relation with method of carbonyl iron joined in the mixture, contents of carbonyl iron and Co-Pc in the mixture of Co-Pc ultrasonic dispersing in DMF. With a method of composite in situ controlling reasonable experiment condition, it can be obtained that cobalt-phthalocyanine/iron nanocomposite particles has completely been covered with Co-Pc, they had structure of Chinese gooseberry in inner and mere made up of almost regular spherical shape and the average diameter is 1. 4 μm.

PROSPECTS AND CRUCIAL PROBLEMS IN OLIGOMERIZATION AND POLYMERIZATION WITH IRON AND COBALT COMPLEX CATALYSTS

The discovery of highly active 2,6-bis（imino）pyridyl iron and cobalt complexes provided a milestone of latetransition metal catalysts for ethylene oligomerization and polymerization with being currently investigated for the scale-up process. The crucial problems are remaining in the catalytic systems： the catalytic systems targeting ethylene polymerization produce more oligomers at elevated reaction temperatures, however, there is a recognizable amount of high-molecularweight polyethylene remained in the modified catalytic system for the oligomerization process. Beyond the modification of bis（imino）pyridyl metal complexes, several alternative proeatalysts＇ models have been developed in our group. This review highlighted the achievements in exploring new iron and cobalt complexes with tridentate NNN ligands as procatalysts for ethylene oligomerization and polymerization.

CHARACTERIZATION OF COBALT(Ⅱ)-PHTHALOCYANINE-METAL IRON COMPOSITES FOR MAGNETORHEOLOGICAL FLUIDS

Magnetorheological suspension based on 20 (v/V) % CoPc-iron composite particles dispersed in sili-cone oil have been obtained, which exhibited dynamic shear stress up to 2000Pa upon application of external magnetic field at 1300 Oe. The response is faster than 0. 15 -with superior reversibility of changes in viscosity induced by external magnetic field at above 12. 5℃. Further, it was found that the MR fluid is in possession of long-term stability a-gainst sedimentation.

Electrodeposited Cobalt-Iron Alloy Thin-Film for Potentiometric Hydrogen Phosphate-Ion Sensor

A cobalt-iron alloy thin-film electrode-based electrochemical hydrogen-phosphate-ion sensor was prepared by electrodepositing on an Au-coated Al2O3 substrate from an aqueous solution of metal-salts. The use of a cobalt-iron alloy electrode greatly improved the hydrogen-ion sensor response performance, i.e., the sensor worked stably for more than 7 weeks and showed a quick response time of several seconds. Among the cobalt and iron alloy systems tested, the electrodeposited Co58Fe42 thin-film electrode showed the best EMF response characteristics, i.e., the sensor exhibited a linear potentiometric response to hydrogen-phosphate ion at the concentration range between 1.0 × 10–5 and 1.0 × 10–2 M with the slope of –43 mV/decade at pH 5.0 and at 30℃. A sensing mechanism of the Co-based potentiometric hydrogen-phosphate ion sensor was proposed on the basis of results of instrumental analysis.

Catalytic Effect of Cobalt and Iron Complexes Incorporating Bis(2-aldiminoethyl)amine Ligands on Ethylene Oligomerization

Complexes [MCl 2{CH 3N(CH 2CH 2N[CDS1]CR 1R 2) 2}]((3, M=Co, R 1=H, R 2=Ph ; 4, M=Fe, R 1=H, \{R 2=Ph\}; 5, M=Co, R 1=R 2=Ph) were prepared and characterized by IR spectra and elemental analysis. The combination of each of complexes 3-5 with ethylaluminoxane(EAO), respectively, was found to be moderately active for ethylene oligomerization to low carbon olefins. The activity of 113 kg oligomers·mol -1 Co·h -1 for complex 3(100 mol of EAO, 180 ℃ and 1 8 MPa ethylene) was observed with a selectivity of 93% to C 4-10 olefins, of which 96% were linear C4 10 olefins. The catalytic properties of complexes 3-5 were compared with those of analogous P,P coordinated complexes [MCl 2{CH 3N(CH 2CH 2PPh 2) 2}](1, M=Co; 2, \{M=\}Fe).

Dimerization of Propylene by Nickel (Ⅱ) and Cobalt (Ⅱ) Catalysts Based on Bidentate Nitrogen-phosphino Chelating Ligands

The catalytic property of propylene dimerization by several nickel (Ⅱ), cobalt (Ⅱ) complexes containing N-P bidentate ligands was studied in combination with organoaluminum co-catalysts. The effects of the type of aluminum co-catalysts and its relative amount, the nature of precursors in terms of ligand backbone and metal center were investigated. The results indicated that precursor I (N,N-dimethyl-2-(diphenylphosphino)aniline nickel (Ⅱ) dichloride) exhibited high activity in propylene dimerization in the presence of the strong Lewis acid Et3Al2Cl3, whereas low productivity by its cobalt analogues was observed under identical reaction conditions.

Metallic Iron and Nickel in Cretaceous and Cenozoic Sediments: The Results of Thermomagnetic Analysis

With the aid of thermomagnetic analysis (TMA) up to 800ºС the composition and distribution of particles of native iron and Fe-Ni alloy was studied in 15 sections, Gams (Austria), Verhorechie and Selbuhra (Crimea), Kvirinaki and Tetritskaro (Georgia), Aimaki, Bass, Dzhengutaj, Madzhalis and Gergebil (North Caucasus, Russia), Klyuchi and Tep-lovka (Volga Region, Russia), Koshak (Kazakhstan), Kara-Kala and Khalats (Turkmenistan). The age of sediments varies from Miocene to Early Cretaceous. Iron particles are present at 521samples out of 921studied. Their percentage varies from 10-5% to 0.05%. The distribution consists of two groups: 1) “zero” group (iron is not found by TMA);2) group of logarithmic normal distribution with a differing modes. The global enrichment by iron particles in synchronous deposits of Miocene, Maastrichtian-Danian, Santonian and Cenomanian was discovered. With respect to nickel content, the iron particles fall into two groups: 1) nearly pure iron without nickel;and 2) iron with nickel content up to 20%, with modal value of 5%. The source of iron particles is the cosmic dust. Particles of pure nickel and the alloy containing more of 20% of nickel are very rare. Possibly, such particles are related mainly with impact events. A peak of elevated iron content with nearly constant nickel of 5-6% was found in almost all studied sections. It is a global effect which is not dependent of place and time of deposition of iron particles.