Preparation and properties of raney nickel electrodes on Ni-Zn base for H2 and O2 evolution from alkaline solutions Part I: electrodeposition of Ni-Zn alloys from chloride solutions

Experimental results for the electrodeposition of Ni-Zn alloys from chloride solutions, with addition of H₃BO₃ and without other additives, in a laboratory cell with a perforated nickel sheet cathode and with recirculating electrolyte are presented. The dependence of the zinc content in the alloy on the following operating conditions was investigated: cathodic current density, 1.0–20.0 A dm^–2; temperature, 35–65°C; pH 1.5–5.5; total molarity,M _tot=M _Ni ²⁺ +M _Zn ²⁺ =1.1–2.8 M; and, molar ratio,P=M _Ni ²⁺ /M _Zn ²⁺ =1.0–15. Depending on the operating conditions the Zn content in the alloy varied over the range 22–88 mol%. In separate experiments galvanostatic polarization curves were measured in the direction of increasing and then decreasing cathodic current density in the range 0.1–20.0 A dm^–2 with all other operating conditions as used for electroplating experiments. In all cases significant hysteresis effects were observed. It was found that the current efficiency for the electrodeposition of Ni-Zn alloys from chloride solutions as a function of the zinc content in the alloy showed a sharp minimum of about 55% atX _Zn=55 mol % irrespective of other operating conditions.     

Electrochemical Behaviour of Al, Al—In and Al–Ga–In Alloys in Chloride Solutions Containing Zinc Ions

The electrochemical behaviour of Al, Al—In and Al–Ga–In alloys in 0.6 m NaCl solutions with and without Zn²⁺ was investigated. The study was performed by means of open circuit potential, potentiodynamic polarization, potentiostatic current-time and electrochemical impedance spectroscopy measurements as well as by SEM-EDAX examination. It was found that the Al—In alloy exhibits the highest negative open circuit potential in 0.6 m NaCl and the corrosion resistance of the tested electrodes decreases in the following order: Al > Al–Ga–In > Al—In. The greater activity of the Al—In alloy was interpreted on the basis of the autocatalytic attack by indium. The potentiostatic current–time measurements in Zn²⁺ containing electrolyte at potentials above the pitting potential revealed that Zn²⁺ has an insignificant influence on the Al electrode, while it enhances the corrosion of the Al–Ga–In alloy and improves the attack morphology of the Al—In alloy. Furthermore, the impedance spectra recorded under open circuit conditions showed a decrease in the polarization resistance of Al—In and Al–Ga–In alloys in presence of Zn²⁺ indicating the activating effect of Zn²⁺ ions.     

Catalytic Activity of ZSM-11 Zeolites Modified with Metal Cations for the Ethane Conversion

ZSM-11 zeolite samples differing by their active sites (H⁺ and different metal cations) have been studied in the transformation of ethane into aromatic hydrocarbons. A relationship between Lewis sites increasing–aromatization capacity and possible reaction steps have been suggested.     

HIF-1α Dependent Upregulation of ZIP8, ZIP14, and TRPA1 Modify Intracellular Zn2+ Accumulation in Inflammatory Synoviocytes

Intracellular free zinc ([Zn²⁺]_i) is mobilized in neuronal and non-neuronal cells under physiological and/or pathophysiological conditions; therefore, [Zn²⁺]_i is a component of cellular signal transduction in biological systems. Although several transporters and ion channels that carry Zn²⁺ have been identified, proteins that are involved in Zn²⁺ supply into cells and their expression are poorly understood, particularly under inflammatory conditions. Here, we show that the expression of Zn²⁺ transporters ZIP8 and ZIP14 is increased via the activation of hypoxia-induced factor 1α (HIF-1α) in inflammation, leading to [Zn²⁺]_i accumulation, which intrinsically activates transient receptor potential ankyrin 1 (TRPA1) channel and elevates basal [Zn²⁺]_i. In human fibroblast-like synoviocytes (FLSs), treatment with inflammatory mediators, such as tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α), evoked TRPA1-dependent intrinsic Ca²⁺ oscillations. Assays with fluorescent Zn²⁺ indicators revealed that the basal [Zn²⁺]_i concentration was significantly higher in TRPA1-expressing HEK cells and inflammatory FLSs. Moreover, TRPA1 activation induced an elevation of [Zn²⁺]_i level in the presence of 1 μM Zn²⁺ in inflammatory FLSs. Among the 17 out of 24 known Zn²⁺ transporters, FLSs that were treated with TNF-α and IL-1α exhibited a higher expression of ZIP8 and ZIP14. Their expression levels were augmented by transfection with an active component of nuclear factor-κB P65 and HIF-1α expression vectors, and they could be abolished by pretreatment with the HIF-1α inhibitor echinomycin (Echi). The functional expression of ZIP8 and ZIP14 in HEK cells significantly increased the basal [Zn²⁺]_i level. Taken together, Zn²⁺ carrier proteins, TRPA1, ZIP8, and ZIP14, induced under HIF-1α mediated inflammation can synergistically change [Zn²⁺]_i in inflammatory FLSs.     

Electrochemical and reflectance study of the conversion of zinc oxide by hexacyanoferrate (II) in offset lithography

Zinc taken from –1.4 to –0.7 V/SCE in the presence of hexacyanoferrate(II) solution generates first a tough glassy material from –1.25 to –1.0 V, breaches through which then produce a gel. The two types of zinc hexacyanoferrate(II) product are probably related to their Zn^II oxide and Zn²⁺ (aquo) progenitors. The electrochemistry depends on the zinc pretreatment which governs the amount (from zero, to appreciable) of nucleating Zn^II oxide initially present. H₂PO₄ ^– is shown to play a crucially modifying part, while Na₂EDTA, malic acid, disodium 1-ethoxy-sulphosuccinate surfactant and isopropanol have minor roles in product modification. Possibly procrustean compositions for glass, gel and conversion product are suggested. Diffuse reflectance, AAS, SEM, XRD and i.r. spectroscopy were used in characterisations. The mechanism of electrophotographic conversion is discussed.     

Aluminium alloys in sulphuric acid Part I: Electrochemical behaviour of rotating and stationary disc electrodes

Anodic oxidation of various aluminium alloys was investigated by means of rotating disc electrodes in 3 M H₂SO₄ as a function of Cl^–, F^–, Zn²⁺ and In³⁺ concentration. Al-In, Al-Zn/In and Al-Zn/Sn alloys yielded current-potential curves at the lowest overpotentials and faradaic efficiencies for anodic oxidation of up to 98% at currents 50 mA cm^–2. While these alloys were electrochemically active in the presence of chloride as the only additive in sulphuric acid, binary aluminium alloys with Ce, Ga, La, Nd, Sn, Ta, Te, Ti or Tl were only active when Cl^–, Zn²⁺ and In³⁺ species were added to the electrolyte. With the exception of Al-Ga, binary alloys displayed high faradaic efficiencies of up to 95%. Fluoride additives resulted in current-potential curves at even more negative potentials than those with chlorides. In contrast to Cl^–, fluoride ions are consumed during the aluminium oxidation process due to complexation with Al(III).     

Reversible collapse and Mg release of de- and rehydroxylated homoionic cis-vacant montmorillonites

Homoionic Na⁺, Ca²⁺, Sr²⁺, Li⁺, Cu²⁺ and Zn²⁺ samples of the <2 μm fraction of a cis-vacant montmorillonite from Linden (Bavaria) were steam treated at 200°C (≈1.5 MPa), 240°C (≈3.3 MPa) and 300°C (≈8.0 MPa) after dehydroxylation at temperatures up to 630°C. Cation exchange capacity (CEC) measurements, determination of exchangeable cations and X-ray diffraction (XRD), supplemented by thermoanalytical investigations of the evolved water in a thermobalance linked to a mass spectrometer, infrared (IR) and electron spin resonance (ESR) spectroscopy were employed to obtain information about the state of expandability and structural changes of swellable montmorillonite and the sites of interlayer and octahedral cations after heating and rehydroxylation.The XRD pattern of the initial samples showed a well-defined (001) reflection according to the interlayer cation and its hydration state under laboratory atmosphere. After dehydroxylation the pattern exhibited (001) reflections between 9.6 and 9.8 Å, corresponding to a collapsed structure for all samples. The Na⁺-, Ca²⁺- and Sr²⁺-rich montmorillonites regained partial expandability after rehydroxylation at 200°C and full expandability after rehydroxylation at 300°C if the dehydroxylation temperature was less than 630°C. Rehydroxylation at 300°C of the Cu²⁺- and Zn²⁺-rich montmorillonites did not cause reexpansion, whereas the Li⁺-rich samples recovered a partial swellability after rehydroxylation at 240°C and nearly the full swellability after rehydroxylation at 300°C.The Li⁺-, Cu²⁺- and Zn²⁺-rich samples underwent a strong CEC reduction due to migration of the interlayer cations into the 2:1 layer before dehydroxylation started. After rehydroxylation under water steam Cu²⁺- and Zn²⁺-rich samples released 16–30 meq/100 g of Mg²⁺ from the structure, increasing with the steam temperature. Mg²⁺ release was not observed for the Li⁺-rich montmorillonite.     

Enhancement of the Water Affinity of Histidine by Zinc and Copper Ions

Histidine (His) is widely involved in the structure and function of biomolecules. Transition-metal ions, such as Zn²⁺ and Cu²⁺, widely exist in biological environments, and they are crucial to many life-sustaining physiological processes. Herein, by employing density function calculations, we theoretically show that the water affinity of His can be enhanced by the strong cation–π interaction between His and Zn²⁺ and Cu²⁺. Further, the solubility of His is experimentally demonstrated to be greatly enhanced in ZnCl₂ and CuCl₂ solutions. The existence of cation–π interaction is demonstrated by fluorescence, ultraviolet (UV) spectroscopy and nuclear magnetic resonance (NMR) experiments. These findings are of great importance for the bioavailability of aromatic drugs and provide new insight for understanding the physiological functions of transition metal ions.     

Electrochemical hydrodynamics in magnetic fields with laser interferometry: Influence of paramagnetic ions

The electrochemical reduction of Zn²⁺ was studied galvanostatically at current densities ranging from 0.10 to 7.0 mA cm^–2 by using the system Zn/ZnSO₄/Zn, and operating it at its natural pH, under the influence of imposed non-variant magnetic field strengths ranging from 0.09 to 0.50 T in the V-position, C/A-position and A/C-position. The convective contours were visibly defined in the V- and A/C positions. The extent of convection in the C/A-position was negligible in the presence of the applied magnetic field. The presence of a paramagnetic ion (Mn²⁺ or Cr³⁺) in the medium produced noticeable deviations in the concentration gradients. The mass transport coefficient for Zn²⁺ was evaluated in the presence of the applied magnetic field. The fluid flow velocities in the reduction of Zn²⁺ under the imposed magnetic field were estimated at 1–7 cm s^–1. The diffusion layer relaxation was followed by the fringe shift, after the electrolysis had terminated. The relaxation mechanism appears to be a slow rotational and translational movement of the paramagnetic fluid in the C/A-position. The exact mode of interaction between the magnetohydrodynamic effect, studied previously, and the paramagnetic effect studied in this work is not yet obvious. It is proposed that the mechanism by which energy dispersion is limited and momentum conserved is by suppression of microturbulence in the non-variant magnetic field.     

Effect of magnesium carbonate on the uptake of aqueous zinc and lead ions by natural kaolinite and clinoptilolite

Adsorption behavior of Zn²⁺ and Pb²⁺ ions on kaolinite and clinoptilolite, originating from natural resources, was studied as a function of contact time and concentration. Zn²⁺ and Pb²⁺ ions are quickly adsorbed on both minerals and the uptake of the latter is more favored. The uptake of both ions was then examined on kaolinite–MgCO₃ and clinoptilolite–MgCO₃ mixtures over a metal ions range from 1 to 10 000 mg/L. The sorption behavior of Zn²⁺ and Pb²⁺ on pure MgCO₃ was also studied. MgCO₃ is much more effective in the retention of Zn²⁺ and Pb²⁺ ions, in particular at higher concentrations. The large increase in the retarded amounts of both ions was associated with formation of the hydroxy-carbonate phases; namely hydrozincite for Zn²⁺, and cerussite and hydrocerussite in the case of Pb²⁺.     

Carbon Monoxide Hydrogenation over Zirconia Supported Ni and Co-Ni Bimetallic Catalysts

Zirconia supported nickel and cobalt-nickel bimetallic catalysts were prepared and characterized for various physico-chemical properties. The hydrogenation of carbon monoxide was studied over these catalysts in the pressure range of 101.3–1654kPa, temperature range of 513–533K, weight hourly space velocity range of 8–14h^–1 and H2/CO mole ratio of 2. Catalysts containing both Co and Ni were found to give higher C₅₊ hydrocarbons selectivity compared to that containing only Ni. A maximum C₅₊ hydrocarbons selectivity of 55wt% was obtained at 655kPa pressure, 523K and 9.6h^–1 of WHSV with catalyst containing 4.03wt% Co and 2.64wt% Ni. The C₂ and C₃ olefin contents of the products decreased with increase in pressure. Improved deactivation behavior of the catalysts was observed when operated at high pressure.     

The role of surface vanadia species in butane dehydrogenation over VOx/Al2O3

A series of θ-Al₂O₃ supported VO_x catalysts, of different vanadium loadings, have been characterised and employed for the selective dehydrogenation of n-butane. Characterisation of the unreacted catalysts has been carried out by solid-state NMR (⁵¹V MAS NMR, ²⁷Al MAS NMR and ²⁷Al 3Q-MAS NMR), and FT-IR spectroscopies, with reference to previously acquired Raman and UV–vis spectroscopy data. As vanadium loading increases, so does the domain size of the supported vanadate units with significant quantities of V₂O₅ observed at the highest loadings. The influence of calcination, pre-reduction, reaction and regeneration on the structure of the catalysts has been studied by NMR, FT-IR, EPR, microanalysis and TEOM. Calcination disperses crystalline vanadate units, and at high loadings AlVO₄ formation is observed. Pre-reduction reduces the vanadium oxidation state from 5+ to 3+, while regeneration results in the formation of highly crystalline V⁵⁺ species. From these data it is possible to determine structure–activity relationships, with polymeric vanadia clusters favouring the formation of butenes and butadienes, while more isolated species are highly active towards the formation of polynuclear aromatic hydrocarbons retained on the catalyst surface post-reaction. These large polynuclear aromatic hydrocarbons are however not the principle cause of catalyst deactivation in this reaction.     

DFT study of oxygen-bridged Zn2+ ion pairs in Zn/ZSM-5 zeolites

A cluster model for Zn/ZSM-5 zeolite is proposed, which consists of an oxygen-bridged [Zn–O–Zn]²⁺ moiety attached to two framework aluminum ions of two adjacent ZSM-5 5-rings. Its stability and catalytic activity in ethane dehydrogenation were considered using the DFT method and compared with those for single Zn²⁺ ions in the same rings. It is shown that the oxygen-bridged Zn²⁺ pair is rather reactive towards ethane dissociation and that the rate-limiting step is release of hydrogen.     

Biosorption of Zn(II) from Seawater Solution by the Microalgal Biomass of Tetraselmis marina AC16-MESO

Biosorption refers to a physicochemical process where substances are removed from the solution by a biological material (live or dead) via adsorption processes governed by mechanisms such as surface complexation, ion exchange, and precipitation. This study aimed to evaluate the adsorption of Zn²⁺ in seawater using the microalgal biomass of Tetraselmis marina AC16-MESO “in vivo” and “not alive” at different concentrations of Zn²⁺ (0, 5, 10, and 20 mg L⁻¹) at 72 h. Analysis was carried out by using the Langmuir isotherms and by evaluating the autofluorescence from microalgae. The maximum adsorption of Zn²⁺ by the Langmuir model using the Q_max parameter in the living microalgal biomass (Q_max = 0.03051 mg g⁻¹) was more significant than the non-living microalgal biomass of T. marine AC16-MESO (Q_max = 0.02297 mg g⁻¹). Furthermore, a decrease in fluorescence was detected in cells from T. marina AC16-MESO, in the following order: Zn²⁺ (0 < 20 < 5 < 10) mg L⁻¹. Zn²⁺ was adsorbed quickly by living cells from T. marine AC16-MESO compared to the non-living microalgal biomass, with a decrease in photosystem II activities from 0 to 20 mg L⁻¹ Zn²⁺ in living cells.     

Autointoxication mechanism ofOryza sativa

Ammonium sulfate and potassium nitrate added as a top dressing and rice straw were incorporated into soil to understand their effect on the chemical nature of the paddy soil and on the growth and yield of rice plants during two successive crop seasons. Redox potential (Eh) determination indicated that the paddy soil appeared to be the reduced form in mixture with rice residues. The amounts of ammonium nitrogen (NH₄ ⁺—N) and nitrate nitrogen (NO₃ ^–—N) were significantly higher in the second crop than in the first crop, and the quantity of NH₄ ⁺—N was about 10 times greater than that of NO₃ ^–—N. The incorporation of rice straw decreased both the available nitrogen and the soil cations, Zn²⁺, Cu²⁺, Ca²⁺, Mn²⁺, and Na⁺. The quantity of Zn²⁺, Cu²⁺, Mg²⁺, and Na⁺ was significantly lower in the second crop that that in the first. The growth and yield of rice plants were significantly affected by cultural treatment; thus the ammonium sulfate dressing treatment resulted in higher yields than the potassium nitrate treatment. The NH₄ ⁺—N treatment had an antagonistic effect on the phytotoxic nature of rice straw decomposed in soil. The phytotoxicity (primarily phenolic type compounds) of aqueous extracts of soil varied between treatments and was significantly higher in the soil which had been mixed with rice straw. This finding correlated well with the higher amounts of phytotoxic plant phenolics produced by the decomposing rice residues in the soil.This study was supported by the National Science Council of the Republic of China.Paper No. 215 of the Scientific Journal Series, Institute of Botany, Academia Sinica.     

Interaction of metal ions with montmorillonite and vermiculite

The behaviour of montmorillonite and vermiculite toward adsorption of Cd²⁺, Pb²⁺, Zn²⁺, Mn²⁺, Cu²⁺ and Zn²⁺ was compared. In general, the uptake of metal ions on both clay minerals decreased with decreasing of pH and in the presence of ligands forming stable complexes. Metal ion retention on montmorillonite was less affected by the competition of sodium ions at high ionic strengths with respect to vermiculite. On the other hand, the total capacity of vermiculite with respect to the investigated metal ions was found to be much higher than that of montmorillonite, whereas the order of affinity of the metal ions for the two clay minerals was similar, i.e.: Pb²⁺ = Cd²⁺ < Cu²⁺ < Zn²⁺ < Mn²⁺ < Ni²⁺ for montmorillonite and Pb²⁺ < Cu²⁺ < Cd²⁺ < Zn²⁺ < Ni²⁺ < Mn²⁺ for vermiculite.The similarities and differences between the two clay minerals were also investigated by principal component analysis and hierarchical cluster analysis.The results of this study may be used to predict the uptake efficiency of these adsorbents in view of their application for the removal of metal ions from contaminated effluents. The choice of vermiculite or montmorillonite for the uptake of metal ions or other elements will depend on the composition of the effluent to be treated.     

Numerical models for reactions catalysed by homogeneous mediators: the case of Fenton's reagent

A numerical model has been developed to describe the behaviour of a batch reactor in which Fenton's reagent is used for hydroxylating aromatic hydrocarbons under conditions of electrochemical regeneration. The test reaction considered is the conversion of benzene into phenol. Comparison is made with previously published experimental results.Nomenclature A electrode area, m² - a ₁ parameter defined by Equation 21 - C _i concentration of species, i, in the bulk solution, mol m^–3 - c _i local concentration of species, i, in the diffusion layer, mol m^–3 - K _i effective mass-transfer coefficient, m s^–1 - k _j rate constant of reaction j - R _j rate of reaction j, mol m^–3 s^–1 - r _i rate of change of concentration of species i due to chemical reaction, mol m^–3 s^–1 - t time, s - V reactor volume, m³ - x distance from the cathode surface, m - x ^* maximum thickness of the diffusion layer, m - period of diffusion layer renewal, s Subscrpts 1 oxygen - 2 Fe³⁺ - 3 hydrogen peroxide - 4 Fe²⁺ - 5 benzene - 6 phenol - 7 biphenyl This paper was presented at the meeting on Electroorganic Process Engineering held in Perpignan, France, 19–20 September 1985.     

Cation composition during recrystallization of layered double hydroxides from mixed (Mg, Al) oxides

Changes in cation composition and M²⁺/M³⁺ ratio during hydrotalcite regeneration were studied. Regenerated hydrotalcites were obtained by recrystallization of mixed (Mg, Al) oxides in solutions of divalent (Mg, Zn, Co, Ni, Cu) or trivalent (Al, Fe) cations.Heating Mg–Al–CO₃ hydrotalcites with Mg/Al=2, 3 and 3.7, at 600 °C for 2 h yielded periclase-like mixed (Mg, Al) oxides (HT-P). The hydrotalcite structure was restored by dispersing oxides 48 h in water or aqueous solutions of different cations.The presence of Mg²⁺, Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ salts or of low soluble hydromagnesite increased the M²⁺/Al ratio, reaching a maximum value of 3.8. An incorporation of Zn²⁺, Ni²⁺, Co²⁺ and Cu²⁺ cations in the newly formed hydrotalcite was detected, while Mg²⁺ remained in solution. In the presence of soluble Al salts or freshly precipitated Al(OH)₃, the M²⁺/Al ratio approximated the minimal possible value of 2.The Mg/Al ratio of a hydrotalcite crystallized from a mixture of two HT-P samples with different Mg/Al ratios is equal to the weighted average value.The results obtained support the conception of the dissolution–crystallization mechanism of hydrotalcite regeneration from mixed (Mg, Al) oxides contrary to the widely accepted concept of topotactic processes.     

Effect of metal salts on the dyeing of freshly spun polyacrylonitrile fibre with acid dyes

Conclusions The effect of the metal cations Al³⁺, Zn²⁺, and Cr³⁺ on the process of dyeing freshly spun PAN fibres with acid dyes has been studied. It has been found that the greatest amount of dye is fixed on the fibre when Al³⁺ ions are introduced into the dye bath.On the basis of analysis of the IR spectra of the dyed fibres, a mechanism has been proposed for the interaction of both the metal cations and also of the dye with PAN fibre. It has been found that the metal cation is bonded with the fibre both by an ionic bond with the—COOH groups and also by a coordination bond with >C=0 groups of the polymer substrate.Translated from Khimicheskie Volokna, No. 6, pp. 13–14, November–December, 1986.     

Conceptual process design for aromatic/aliphatic separation with ionic liquids

Presently, there are no processes available to separate low concentration (<20%) aromatic hydrocarbons from mixed aromatic aliphatic hydrocarbon streams, such as a feed stream to naphtha crackers, which may contain 10–25% of aromatic components, depending on the source of the feed (naphtha or gas condensate). Present practice is removal of the aromatic hydrocarbons from the C₅⁺-stream in the naphtha cracker by extractive or azeotropic distillation. If a major part of the aromatic compounds present in the feed to the crackers could be separated upstream of the furnaces, it would offer several advantages: higher capacity, higher thermal efficiency and less fouling. The improved margin will be around €20/t of feed or €48 million per year for a naphtha cracker with a feed capacity of 300 t/h, due to lower operational costs.Extraction with sulfolane will result in a negative margin of €10 million per year. Therefore, a conceptual process for the extraction of aromatic hydrocarbons with the ionic liquid 4-methyl-N-butylpyridinium tetrafluoroborate was developed using ASPEN. The investment costs are estimated to be €56 million and the annual costs about €28 million per year, resulting in a positive margin of about €20 million per year.