Separation and recovery of Ni from copper electrolyte by crystallization of nickel ammonium sulfate double salt

The separation and recovery of Ni from the copper electrolyte by crystallization of nickel ammonium sulfate double salt were studied. It is found that the solubility of copper sulfate at the same temperature is less than that of nickel sulfate, while the solubility of copper ammonium sulfate is greater than that of nickel ammonium sulfate. So, by adding (NH₄)₂SO₄, the Ni can be selectively crystallized from the copper electrolyte. By adding (NH₄)₂SO₄ at the molar ratio of (NH₄)₂SO₄/NiSO₄ ≤0.8, and crystallizing at —15 °C for 10 h, the Ni in the copper electrolyte can be crystallized in the form of Ni(NH₄)₂(SO₄)₂·6H₂O. The qualified product of NiSO₄·6H₂O can be obtained by pyrolyzing the crystals, dissolving the pyrolysis product in water, and then concentrating the dissolved solution for crystallization. The method of double salt crystallization is a clean, environmentally-friendly, cost-effective and efficient method for separating and recovering nickel from copper electrolyte.     

Enhanced selectivity of hydrolytic precipitation of Zn from Zn-Ni sulfate solution via chelation of Ni

The selective precipitation of zinc from zinc–nickel sulfate solution with the Zn/Ni molar ratio of 20:1 was studied. Dropwise addition of 0.5 mol/L NaOH solution into the zinc–nickel sulfate solution containing 0, 0.01, 0.02, 0.03 and 0.04 mol/L ethylene diamine tetraacetate (EDTA) as a chelating agent was done. The equilibrium analysis of precipitation pathway was performed using Visual MINTEQ program. The equilibrium analysis showed that the presence of small amounts of EDTA can prevent nickel precipitation in alkaline conditions without any negative effect on zinc precipitation. On this basis, more than 90% of zinc could be precipitated as a product with about 50% Zn and only 0.11% Ni at pH=9.0 merely as a result of the presence of 0.03 mol/L EDTA in the solution. The stirring time of 120 min after precipitation was found to be essential for more complete separation. The X-ray diffraction studies on the precipitate revealed that the precipitated phase was Zn₄(OH)₆SO₄.4H₂O.     

Characteristics of nickel sulphide reduction in Ni2+ free background and Watts nickel plating electrolytes

Abstract

The electrochemical behaviour and composition of nickel sulphide coatings deposited on glassy carbon (GC) electrode by the successive ionic layer adsorption and reaction (SILAR) method using a nickel(II) ammonia complex and Na₂S solutions have been studied in Ni²⁺ free background, Watts nickel plating and 0·05 M H₂SO₄ electrolytes by the cyclic voltammetry and X-ray photoelectron spectroscopy (XPS) methods. Analysis of XPS data suggests that the coating is a mixture of two sulphides where NiS dominates. In the Ni²⁺ free background solution at first the electrochemical reduction of the sulphur rich nickel sulphide to NiS occurs. After that the NiS to metallic Ni is reduced in the potential range of H₂ evolution. During the cathodic reduction of the coating in Watts nickel plating electrolyte the sulphur is reduced in the potential range from 0·0 to ?0·4 V, while at the potential values <?0·5 V the sulphur rich nickel sulphide and NiS reduction in the H₂ evolution range and Ni plating occur.     

Synthesis,structure and luminescent properties of 3D lanthanide (La(III), Ce(III)) coordination polymers possessing 1D nanosized cavities based on pyridine-2,6-dicarboxylic acid

Two novel coordination polymers, namely, {[Ln₂(PDA)(HPDA) (H₂O)₄ClSO₄]·2H₂O}_n (Ln = La(III) and Ce(III) for complexes I and II, respectively) were synthesized through the reaction between pyridine-2,6-dicarboxylic acid (H₂PDA) and La(NO₃)₃·6H₂O and Ce₂(SO₄)₃·8H₂O under hydrothermal conditions. Both of these polymers possess 1D infinite nanosized cavities embedding guest water molecules. The complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. Two compounds crystallize in orthorhombic system, space group Pna2(1). Both of the complexes exhibit 3D metal–organic framework structure, where SO₄^2? anions play as the bridge between 1D wavelike chains and the adjacent parallel pyridine rings were arranged through π–π interactions. The bi-bidentate coordination mode of SO₄^2? anion was observed. Luminescent emissions of complex I were measured in the solution of DMF at room temperature. In addition, the luminescent emissions of complex I showed certain selectivity among some metal ions.     

Nickel electrodeposition from novel lactate bath

Abstract

A new electroplating bath for nickel deposition has been developed. Lactic acid was used as a complexing agent in the bath replacing boric acid. The effect of bath composition, current density, pH and temperature on the cathodic polarisation, cathodic current efficiency, morphology and structure of the deposit was carried out. Optimum conditions for producing sound and satisfactory nickel deposits were: 0·30M NiSO₄.7H₂O, 0·50–1·0M lactic acid and 0·3M Na₂SO₄ at pH=10, c.d.=0·98 to 9·80 mA cm^?2 and 25°C. The surface morphology of the deposited nickel was investigated using SEM. The crystal structure was examined by X-ray diffraction analysis. The results showed that the nickel deposits have a face centred cubic structure.     

Corrosion Products Formed on Copper exposed to humid SO2-containing atmospheres

X-ray diffraction analyses have been performed on samples of electrolytic copper (min. 99,9% Cu) exposed to humid atmoshperes at SO₂-supplies of 10 and 100μg SO₂ per cm² surface area per hour (10 and 100 ppm SO₂. respectively). During the SO₂ -exposures copper (II) sulphate (CuSO₄ · 5 H₂O) were the only crystalline phases formed in detectable amounts. Interruption of the SO₂- supply resulted in the formation of copper (I) oxide and antlerite (CuSO₄) · 2Cu (OH)₂. During prolonged exposure brochanite (CuSO₄ · 3Cu(OH)₂) and langite (CuSO₄· 3Cu(OH)₂) and langite (CuSO₄ · Cu(OH)₂ · 2H₂O) were also formed i. E. the Cu:S ratio of the basic copper sulphates increased with time. The formation of antlerite was preceeded by formation of an unidentified intermediate compound, probably a basic copper sulphate with a Cu:S ratio of less than three, and a simultaneous transformation of the copper (II) sulphate and copper (I, II) sulphite formed during the SO₂-exposure.     

Aluminum extraction from aluminum industrial wastes

Aluminum dross tailings, an industrial waste from the Egyptian Aluminum Company (Egyptalum), was used to produce two types of alums: aluminum sulfate alum (Al₂(SO₄)₃·12H₂O) and ammonium aluminum alum {(NH₄)₂SO₄AL₂ (SO₄)₃·24H₂O}. This was carried out in two processes. The first involves leaching the impurities using diluted H₂SO₄ with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of aluminum sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purified aluminum dross tailings thus produced. This was carried out in an autoclave. The effects of temperature, time of reaction, and acid concentration on pressure leaching and extraction processes were studied in order to specify the optimum conditions to be applied in the bench scale production as well as the kinetics of leaching process.     

A new mixed-valent iron arsenate black crystal

Scorodite (FeAsO₄·2H₂O) is the most popular phase for arsenic (As) immobilization while the reductive dissolution of Fe(III) to Fe(II) will promote As release. In the present study, an equilibrium between Fe(III) and Fe(II) was achieved in scorodite preparation system by introducing certain alcohol (methanol, ethanol, isopropanol or tert-butanol), and thus a new mixed-valent iron arsenate black crystal formulated as Fe(II)_5.2Fe(III)_8.8(HAsO₄)₄(AsO₄)₈·H₂O was prepared. In comparison with scorodite, the black crystal has higher As content (36.4%, mass fraction) and lower crystal water content (0.73%, mass fraction). Additionally, the leaching concentration of As can be lower than the threshold value (5 mg/L) regulated by identification standards for hazardous wastes of China (GB 5080.3–2007). Therefore, this new mixed-valent iron arsenate crystal could be classified as a non-hazardous and promising As-bearing phase in environmental applications.     

Electrochemical characteristics of 316l stainless steel processed with a thermally treated Ni- and Cr-rich surface coating

The influence of a thermally treated Ni-Cr rich protective coating on the corrosion behavior and contact resistance of stainless steel in a 0.1NH₂SO₄+ 2 ppmHF electrolyte at 80 °C was evaluated using electrochemicals, interfacial contact resistance (ICR) measurements and X-ray photoelectron spectroscopy. Through a low-cost, continuous production line, the Ni-rich coating film for stainless steels was developed by dipping steel samples in acrylic resin and CrO₃ solutions with different levels of NiSO₄·6H₂O added as a nickel source. Each sample was then heated at 800 for 10 min in a hydrogen-reducing environment. It was shown that an increase in residual Ni content in the surface coating noticeably lowered the interfacial contact resistance and raised the corrosion resistance, depending on the remaining nickel content and the thickness of the surface coatings. In support of the XPS depth profile, this was ascribed to the relative enrichment of the Ni element and the detectable reduction of oxygen content in the coating, which could be associated with the significant evaporation of acrylic resin that occurred during thermal treatment. The optimum Ni composition in the resultant coating film, achieved through the addition of 15 wt.% NiSO₄·6H₂O to the acrylic resin and CrO₃ solution, was estimated to be about 10 wt.%.     

Corrosion behavior of AZ91D magnesium alloy in sodium sulfate solution

The corrosion behavior of as‐cast AZ91D magnesium alloy in 0.1M sodium sulfate solution at the corrosion potential (E_corr) was investigated by using electrochemical impedance spectroscopy (EIS), environmental scanning electron microscopy (ESEM), energy dispersive X‐ray spectroscopy (EDS) and X‐ray diffraction (XRD). The results showed that the corrosion of AZ91D started at both the primary α‐Mg and the eutectic α‐Mg. The surface first was covered by a film (MgO, Mg(OH)₂) which became thicker with time. Due to the dissolution of the eutectic α‐Mg, the concentration of aluminum increased, MgAl₂(SO₄)₄ · 2H₂O precipitated at the primary α‐Mg and progressively spread to the eutectic α‐Mg areas. The surface film changed from two‐layer to three‐layer structure with the increase of immersion time.     

An XPS study of passive films on Nickel and alloy 600 in acids

Compositions of surface films formed on nickel and Alloy 600 in I M HCI, 0.5 M H₂SO₄ and I/3 M H₃PO₁ solutions were investigated as a function of polarization potential. The main constituent of surface films formed on Ni in 0.5 M H₂SO₄ or 1/3 M H₃PO₄ solution was hydrated nickel oxyhydroxide, in which the ratio of O₂ to OH⁻ increased when passivation occurred. The surface films formed on Ni and Alloy 600 at lower potentials in 0.5 M H₂SO₄ solution contain S² ions other than SOP_4²⁻ ions, whereas S²⁻ ions were not incorporated in the passive film. Passivation of Alloy 600 took place by the formation of hydrated chromium oxyhydroxide. Pitting led to no substantial change in the average composition of the film.     

PS 微球的制备及表面镀镍工艺研究

以聚乙烯吡咯烷酮为分散剂,偶氮二异丁腈为引发剂,无水乙醇为分散介质,通过分散聚合,制备出表面光滑、分散均匀的聚苯乙烯(PS)微球。在PS微球表面化学镀Ni,制得具有较好导电性能的PS/Ni复合粒子。研究了PS微球表面镀Ni前后的表观形貌及晶相变化,并分析了制备工艺对复合粒子导电性能的影响。分析表明,PS微球表面镀Ni的优化工艺为:PS/NiCl2·6H2O质量比4∶7,络合剂用量2 g,NH3·H2O用量30mL。     

Nickel(II), palladium(ii), platinum(ii), and magnesium(ii) fluorene-substituted porphyrinates: Synthesis,structure, and comparative analysis of fluorescence spectra

Using free meso-tetra(2-fluorenyl)porphine (H₂TFP) and nickel(II), palladium(II), and platinum(II) chlorides and an MgBr₂ · Et₂O complex, corresponding metal porphyrinates were synthesized with a high yield. The structures of these new compounds were studied by means of ¹H NMR spectroscopy and electron absorption spectroscopy. The fluorescence spectra of the synthesized compounds in toluene solution were comparatively analyzed. Coordination of Mg²⁺ ion with porphyrinic cycle H₂TFP significantly increases the fluorescence intensity of porphyrinic luminophore; however, the coordination of platinum metal ions (Pt²⁺, Pd²⁺) with tetrapyrrole fragment H₂TPP decreases the fluorescence intensity of porphyrinic cycle and, in the case of nickel ions, fluorescence transitions disappear     

Long-range magnetic order displayed by a bimetallic pentanuclear cluster complex [(Ni(2,2′-bipy)2)3(Fe(CN)6)2]·13H2O and by a Cu(II) analog

A bimetallic pentanuclear cluster complex contains three bis(2,2′-bipyridine)nickel(II) moieties bridged, through two vacant cis-positions around each nickel, to two separate hexacyanoferrate(III) groups via NiNCFe linkages. Freshly prepared crystals of this compound contain 17 water and two dimethylformamide molecules of solvation per cluster. Loss of some solvent molecules is rapid in air, the resulting ‘partly desolvated’ material showing intracluster ferromagnetic coupling and a S=4 ground state, but without long-range magnetic order. In contrast, a rapidly precipitated powder sample, containing 13 waters of hydration [(Ni(2,2′-bipy)₂)₃(Fe(CN)₆)₂]·13H₂O, displays long-range order at a T_C of 11 K. Inter-cluster interactions occur via the H-bonded water pathways which join neighbouring Fe(CN)₆³⁻ groups in separate clusters. Thus, a new example of inter-cluster magnetic ordering has been achieved. A copper(II)-bipy analog also shows long-range order, with T_C of 13 K. In the absence of a crystal structure, the magnetic and spectral properties of this Cu derivative point to a different structural topology being present.     

Oxidation Mechanisms of Copper and Nickel Coated Carbon Fibers

Differential-Thermal Analysis (DTA) and X-ray diffraction analysis were applied to determine the mechanisms of high-temperature oxidation of copper- and nickel-coated carbon fibers. Both kinds of coatings were deposited by electroless plating onto the fiber surface. The as-deposited copper film was crystalline, whereas the nickel coating consisted of an amorphous Ni–P alloy. Coated fibers were heated from room temperature to 900 °C in air at 10 °C min^?1. For the copper coating, the main oxidation product formed at low temperatures was Cu₂O, while at higher temperatures was CuO. The crystallization of Ni–P took place at 280–360 °C with the formation of Ni and Ni₃P. The final compounds were NiO, Ni₂P and Ni₃(PO₄)₂. After complete oxidation of the carbon fibers, copper and nickel-oxidized microtubes were obtained. Besides, while copper reduced the temperature of the fiber oxidation, nickel coatings increased the minimum temperature needed for this reaction.     

A Refined Scheme of the Mechanism of Iron Anodic Dissolution in Acidic Sulfate Solutions

A refined scheme of iron anodic dissolution in acidic sulfate solution, in which Fe₀ is oxidized to Fe⁺ in stages, is proposed. The first stage consists in chemisorption of H₂O molecules with participation of SO₄ ^2– anions; the degree of the participation x 0.5 per a water molecule. This stage produces adsorbed OH groups (Fe(OH)_ads), which, as a result of their interaction with sulfate anions, form an adsorption complex Fe((OH)SO₄ ^2– _ads. The schemes of oxidation of Fe⁺ to Fe²⁺ do not differ from conventional ones. The scheme put forward agrees with the literature data on the kinetics of iron dissolution under steady-state conditions.     

Influence of tensile stress on corrosion behaviour of high‐strength galvanized steel bridge wires in simulated acid rain

Corrosion behaviour of the high‐strength galvanized steel wires under tensile stress was researched by electrochemical polarization and salt spray test (SST) using simulated acid rain as electrolyte. Electrochemical polarization and SST results showed corrosion rate rose significantly with increasing tensile stress; white grains were observed by SEM after polarization, while cellular and dendritic crystals appeared on the rust layer after SST. XRD and TG‐DTA results revealed (Zn(OH)₂)₃ · ZnSO₄ · 5H₂O was the main corrosion product, and traces of Fe₂(SO₄)₂O · 7H₂O, Fe₂(SO₄)₃, Fe₂O₃ · H₂O were also detected. A three‐stage corrosion process for the galvanized steel wires during SST was proposed.     

Microstructural characterisation and corrosion behaviour of electroless Ni–W–P deposits of mixed nanocrystalline/amorphous structures

Abstract

An investigation has been undertaken of the influence of the mixed nanocrystalline and amorphous microstructure on the corrosion behaviour of electroless Ni–5·5W–6·5P (wt-%) deposits on steel substrates. The effects of annealing temperature on microstructure evolution were investigated. The corrosion behaviour of the deposits was evaluated by potentiodynamic polarisation in 0·5M H₂SO₄ solution and EIS measurements in 3·5%NaCl solution. Relationships between the microstructure and corrosion mechanisms of the as plated and the annealed deposits were considered by reference to microstructural information, including degree of crystallisation, grain sizes of both nickel and Ni₃P phases, porosity development, microstrains and residual stresses.     

Das anodische und kathodische Verhalten des Eisens in sulfathaltigen Elektrolyten. Chaire d'Electrochimie,Faculté des Sciences,Strasbourg, France

The anodic and cathodic behaviour of iron in sulphate containing electrolytes The formation of Fe₂(SO₄)₃ on passive iron at p_H = 1 appears probable from a thermodynamical point of view. At high SO₄^2? concentrations the equilibrium system contains but low concentrations of Fe³⁺, and no Fe²⁺ ions, a fact showing the relatively elevated stability of the Fe₂(SO₄)₃ layer on passive iron. In slightly acid solution (p_H = 4) the passivity of the iron is determined by iron oxide layers. The formation of FeSO₄ from metallic iron and sulphate ions is restricted to the transpassive zone (p_H 4 to 7), in alkaline solutions even to the active zone. In the p_H region 2 to 14 the passive layer on iron has about the same composition in the systems Fe|H₂O + SO₄^2? and Fe|H₂O.     

Application of NMR relaxometry for determining the concentration of nanopowder magnetite in aqueous media

The use of the effect of a decrease in the transverse relaxation time T ₂ of the NMR signal of water protons in the presence of magnetic particles has been suggested for the quantitative estimation of the concentration of magnetite (Fe₃O₄) nanopowder in water. A calibration dependence of the relaxivity T ₂ ^?1 on the iron concentration has been obtained for model suspensions of magnetite nanoparticles with sizes of approximately 20 nm in the concentration range of 0.15–70 mg/L. For comparison, the concentration dependences of T ₂ ^?1 for aqueous solutions of Fe(NO₃)₃ · 9H₂O and FeSO₄ · 7H₂O and paramagnetic salts Ni(NO₃)₂ · 9H₂O, Cr(NO₃)₃ · 9H₂O, and CuSO₄ · 5H₂O have been studied to show that they correlate with their paramagnetic susceptibilities.