Voltammetric Determination of Cobalt(II) in Zinc Sulfate Solution

A method for automated polarographic analysis for Co(II) ions in technological solutions of zinc production was developed. The influence exerted by the components of a supporting electrolyte on the sensitivity and selectivity of measurements was studied. The method is intended for determining the content of cobalt(II) in purification of a zinc sulfate solution to remove impurities and for ecological monitoring of wastewater produced at nonferrous metallurgy plants.     

Competitive adsorption of Ca2+ and Zn(II) ions at monodispersed SiO2/electrolyte solution interface

A study of competitive adsorption of Ca(2+) and Zn(II) ions at the monodispersed SiO(2)/electrolyte solution interface is presented. Influence of ionic strength, pH, and presence of other ions on adsorption of Ca(2+) and Zn(II) in the mentioned system are investigated. zeta potential, surface charge density, adsorption density, pH(50%), and DeltapH(10-90%) parameters for different concentrations of carrying electrolyte and adsorbed ions are also presented. A high concentration of zinc ions shifts the adsorption edge of Ca(2+) ions adsorbed from solutions with a low initial concentration at the SiO(2)/NaClO(4) solution interface to the higher pH values. This effect disappears with a concentration increase of calcium ions. The presence of Ca(2+) ions in the system slightly affects the adsorption of zinc ions on SiO(2), shifting the adsorption edge toward lower pH values and thereby increasing the adsorption slope.     

A Self-Healing Metal–Organic Hydrogel for an All-Solid Flexible Supercapacitor

A zinc containing metal–organic gel (Zn-MOG) with embedded free ions, which exhibits self-healing properties, has been synthesized for application in supercapacitors. The activated carbon-based flexible supercapacitor device with the MOG electrolyte has a broad potential window of 2.1 V, with high retention of specific capacitance compared to the traditional polyvinyl alcohol (PVA)-based gel. The Zn-MOG does not require an additional electrolyte. The sodium and sulphate ions embedded in the MOG are sufficient enough for the charge storage.     

The Effect of Supporting Electrolyte Concentration on Zinc Electrodeposition Kinetics from Methimazole Solutions

The kinetic parameters of Zn²⁺ ion electroreduction in sodium perchlorate used as the supporting electrolyte on the mercury electrode in the presence of methimazole were determined using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and DC polarography. The two‐stage nature of this process was demonstrated. Both steps are catalysed by a methimazole. The size of the acceleration effect depends on the concentrations of methimazole and the supporting electrolyte. The acceleration of the electrode process involves the formation of active complexes between the depolarizer ions and methimazole on the electrode surface. These complexes facilitate the exchange of charge between the electrode and zinc ions during electroreduction process. The change of the hydrating sphere of the zinc ion is also important here. This in turn depends on its oxidation state and the concentration of the supporting electrolyte.     

Surface and capillary forces encountered by zinc sulfide microspheres in aqueous electrolyte

The colloid probe technique was used to investigate the interactions between individual zinc sulfide (ZnS) microspheres and an air bubble in electrolyte solution. Incorporation of zinc ions into the electrolyte solution overcomes the disproportionate zinc ion dissolution and mimics high-volume-fraction conditions common in flotation. Determined interaction forces revealed a distinct lack of long-ranged hydrophobic forces, indicated by the presence of a DLVO repulsion prior to particle engulfment. Single microsphere contact angles were determined from particle-bubble interactions. Contact angles increased with decreasing radii and with surface oxidation. Surface modification by the absorption of copper and subsequently potassium O-ethyldithiocarbonate (KED) reduced repulsive forces and strongly increased contact angles.     

Séparation chromatographique du plomb contenue dans des solutions concentrées de sulfate de zinc

Spectrographic analysis of lead traces in concentrated zinc sulphate solutions is only possible after elimination of zinc and sulphate ions. Two methods of separation on ion exchangers are proposed : the first method consists in a separation of Pb from Zn on an anion exchanger after elimination of sulphate on a cation exchanger; in the second method, the two steps of the separation are realized on the same cation-exchanger column. Both methods are satisfactory, but the second is faster and simpler.The blank of the method is about 1.5 μg Pb (i.e. 0.15 mg Pb/l) for a separation made with 10 ml of electrolyte. The method is therefore suitable for accurate determinations of Pb contents as low as 1 mg/l of concentrated zinc sulpliate electrolyte.     

Visualisation of chemical processes during corrosion of zinc using magnetic resonance imaging

Compositional and structural changes within an electrolyte solution above an electrochemically active metal surface have been visualised using magnetic resonance imaging (MRI) for the first time. In these proof-of-concept experiments, zinc metal was galvanically corroded in a saturated lithium chloride solution. Magnetic resonance relaxation maps were taken during the corrosion process and spatial variations in both T₁ and T₂ relaxation times were observed to change with time. These changes were attributed to changes in the speciation of zinc ions in the electrolyte.     

Adsorptive Stripping Voltammetric Determination of Ultra Trace of Zinc and Lead with Carbidopa as Complexing Agent in Food and Water Samples

In the present work, the cathodic stripping voltammetric methodology using a hanging mercury drop electrode was described for simultaneous determination of lead and zinc in different real samples. The method is based on adsorption of metal ions on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. Optimal conditions were found to be: accumulation time; 70 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s^?1, supporting electrolyte; 0.01 M ammonia buffer at pH 8.5, and concentration of carbidopa; 8.0 μM. The relationship between the peak current versus concentration was linear over the range of 0.1–210 and 0.2–170 nM for lead and zinc, respectively. The detection limits are 0.09 and 0.15 nM for lead and zinc ions respectively. The relative standard deviations at a concentration level of 70 nM of both metal ions are found 1.08 and 1.24% for lead and zinc ions respectively.     

几种稀土盐对NH4Cl溶液中锌电极腐蚀的影响

几种稀土盐对ＮＨ４Ｃｌ溶液中锌电极腐蚀的影响＊张校刚王田芳夏熙＊＊（新疆大学化学系电化学研究室乌鲁木齐８３００４６）关键词无汞Ｚｎ／ＭｎＯ２干电池锌阳极稀土缓蚀剂中图分类号Ｏ６４６．５４锌广泛地用作一次和二次电池的阳极材料。但是锌锰电池在搁置期间存在...     

Electrolytic co-deposition of silicate and mica particles with zinc

Particles of silicate and mica were co-deposited with zinc from a weakly acid zinc electrolyte.The co-deposition became possible after 3 h of milling of the particles. A pH of 4.5, a rotation speed of 600 rpm and a particle concentration of 50 g/l were the optimal conditions. A change of the zeta potential to positive values was observed, caused by adsorption of zinc ions on the particle surface. Under these conditions the particle concentration in the zinc matrix was up to 20 mass per cent. The compound layers showed increased hardness and considerably improved corrosion resistance.     

The thermodynamic characteristics of formation of Zn<Superscript>2+</Superscript> complexes with D,L-tryptophan in aqueous solution

The heat effects of formation of D,L-tryptophan complexes with doubly charged zinc ions were determined calorimetrically. The heat effects of interaction of amino acid solutions with a solution of Zn(II) were measured at 288.15, 298.15, and 308.15 K and ionic strengths of 0.25, 0.50, and 0.75 against the background of KNO₃. The heats of dilution of solutions of zinc nitrate with solutions of the background electrolyte were determined under the same conditions. The corresponding corrections were introduced. The thermochemical data were processed taking into account step equilibria. Along with complex formation, “side” protolytic processes were included. The standard thermodynamic characteristics of complex formation were calculated. The influence of temperature on the heat effects of complex formation in the β-alanine-zinc(II) ions system was considered.     

The thermochemical characteristics of complex formation reactions between 3<Emphasis Type="Italic">d</Emphasis> transition metal ions and L-serine in aqueous solution

The heat effects of complex formation between nickel(II), cobalt(II), cadmium (II), and zinc(II) ions and L-serine in aqueous solution over the ionic strength range 0.25–0.75 (background electrolyte KNO₃) were determined calorimetrically at 298.15 K. The heats of dilution of solutions of metal nitrates with solutions of the background electrolyte were measured under identical conditions for the introduction of the corresponding corrections. The thermodynamic characteristics of complex formation between 3d transition metals and L-serine were calculated. The results were analyzed using the Herny theory. The complex-forming ability of transition metals in reactions with the ligand was characterized with the use of the Irving-Williams series.     

Intercalation and Electrochemical Studies of Nitroprusside Anion into Zn-Al Layered Double Hydroxide

The aim of the present work was to investigate the synthesis,characterization and electrochemical properties of the nitroprusside anions (NP)into zinc and aluminium layered double hydroxides (LDHs). The materials were prepared by thecoprecipitation method under constant pH, followed by a hydrothermal treatment. Theprepared materials were characterised by a set of analysis methods, such as powderX-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry(TG), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The resultsshowed that the electrochemical response of NP ions into LDH structure is similar to thatfound for complex ions free in solution. In addition, our results reveal the dependence ofthe electrochemical response on the nature of the supporting electrolyte, for either cationic oranionic species.     

Photoelectrochemical kinetics of eosin y-sensitized zinc oxide films investigated by scanning electrochemical microscopy

Eosin Y is used as a sensitizer for nanoporous zinc oxide films for prospective applications in photoelectrochemical solar cells. The kinetics of the reduction of the intermittently formed photo-oxidized dye molecules by iodide ions in the electrolyte phase was investigated by using the feedback mode of scanning electrochemical microscopy (SECM). The bulk solution phase contained triiodide as electron transfer mediator, from which the ultramicroelectrode-generated iodide ions acted as electron donors for photo-oxidized Eosin Y molecules (D(+) (ads)) at the zinc oxide sample. Effective rate constants for the dye regeneration could be extracted from the SECM approach curves. The effective rate constants at different triiodide concentrations could be related to the rate constant for the reaction of the dissolved donor with photo-oxidized Eosin Y bound to ZnO, as well as to the overall rate of the photosensitization process. For the reaction D(+) (ads) + 1.5 I(-)-->D(ads) + 0.5 I(3) (-) a rate constant of k(ox) = (1.4+/-0.8)x10(8) cm(9/2) mol(-3/2) s(-1) was determined.     

Application of gallium film electrode for elimination of copper interference in anodic stripping voltammetry of zinc

For elimination of copper interference in anodic stripping determinations of zinc at mercury and bismuth film electrodes gallium ions are usually added to the supporting electrolyte. In the presented studies novel ex situ formed gallium film electrode was applied for this purpose. The proposed electrode is less toxic than mercury one while the detection limit for zinc was lower than for bismuth film electrode following the same deposition time. The calibration graph for deposition time of 60 s was linear from 5 × 10⁻⁸ to 2 × 10⁻⁶ mol L⁻¹. The determinations of zinc were carried out from undeaerated solutions. The proposed procedure was applied to zinc determination in certified reference material and tap water sample.     

Separation and sweeping of metal ions with EDTA in CZE-ESI-MS

Ethylenediaminetetraacetic acid (EDTA) in the background electrolyte (BGE) of capillary zone electrophoresis coupled to an electrospray ionization mass spectrometer is presented as an approach for the determination of metal ions. Significant signals for the metal-ligand complexes were observed even when EDTA was continually eluted from the capillary during the entire electrophoretic run. The signal-to-noise ratio was improved by the addition of ammonia to the sheath liquid and by using an acquisition m/z range above the m/z of EDTA. The LODs for the test metal ions (i.e. calcium(II), manganese(II), and zinc(II)) with conventional injection were around 1-2 mg/L with corrected peak areas that are linear from 8 to 100 mg/L. The presence of EDTA in the BGE was critical not only for the separation but also for sweeping via complexation as an on-line sample concentration technique. The peak height of the test metal ions was improved at least tenfold with sweeping via EDTA complexation and yielded LODs in the μg/L range.     

Kinetics of the Zn(II)/Zn(Hg) electrode reactions in DMSO solutions of halide ions

The electrode reaction Zn(II)/Zn(Hg) in complex chloride, bromide, and iodide solutions with DMSO as solvent and ammonium perchlorate as supporting electrolyte has been studied at the equilibrium potential by the faradaic impedance method and a square-wave method. Furthermore, double-layer data have been determined by electrocapillary measurements. The results indicate that the zinc chloride and bromide complexes do not contribute noticeably to the exchange current density, while in the iodide system both the solvated zinc ion and the first complex take part in the charge transfer. From the dissimilar results valid for water and DMSO solutions the conclusion is made that probably ligand bridging at the amalgam by the halide ions is operative in water solutions, whereas in DMSO the larger solvent molecules adsorbed can form a steric hindrance to ligand bridging by chloride or bromide ions.     

Intradiffusion coefficients for perchlorate ions in zinc perchlorate and zinc chloride solutions at 25°C: Comparing transport properties of zinc chloride and zinc perchlorate systems

Intradiffusion coefficients for³⁶ClO ₄ ^– have been measured in solutions of zinc perchlorate of concentration 0.1 to 3 mol dm^–3 at 25°C by the diaphragm cell technique. In addition, intradiffusion coefficients for perchlorate ions in zinc chloride solutions have been measured over a concentration range at 25°C. The results confirm previous work on the effect of complexation on diffusion in zinc chloride solutions above a salt concentration of 0.1M. The present data, together with literature data for diffusion coefficients of the other species present in the zinc perchlorate electrolyte system, have enabled a simple analysis of the hydration around the zinc ions to be carried out. This indicates that the water diffusion data are consistent with the zinc ions having an effective hydration sphere of 11 (±2) water molecules. This is in keeping with values obtained for other simple divalent electrolytes using the same model. The model is extended here to allow analysis of water diffusion in zinc chloride solutions taking into account the presence of complexed chloro-zinc species. The experimental data are consistent with the effective hydration of the chloro-zinc complexes being independent of the number of chloride ligands and equal to 18±3 over a concentration range of 0 tol mol-dm^–3. This postulate is discussed in terms of its consequences on the water ligand dynamics for the complex equilibria.     

Colloido-chemical characteristics of zinc oxide in electrolyte solutions

The electrosurface characteristics (total surface charge, electrokinetic potential, and positions of the point of zero charge and isoelectric point) of zinc oxide have been comprehensively studied as depending on pH and background electrolyte (NaCl) concentration. The constants of surface reactions and the adsorption potentials of potential determining of background electrolyte ions have been obtained in terms of the 2pK-model. The aggregation stability of aqueous zinc oxide suspensions has been studied in a wide range of concentrations of 1: 1 and 1: 2 electrolytes, and the threshold of sol coagulation has been found. Within the framework of the DLVO theory, the interaction energy between ZnO particles has been calculated as a function of the interparticle distance. It has been demonstrated that the experimental data can be qualitatively described in terms of the classical DLVO theory, which takes into account only ion-electrostatic and molecular (dispersion) forces of interparticle interaction.     

A Batch Injection Analysis System with Square-wave Voltammetric Detection for Fast and Simultaneous Determination of Zinc and Ascorbic Acid

The determination of organic and inorganic compounds in a single run is still a great challenge. In this paper, we developed a method for fast simultaneous determination of ascorbic acid (AA) and zinc ions (Zn) using batch injection analysis with detection by square-wave anodic stripping voltammetry (BIA-SWASV). Britton-Robinson (BR) buffer solution (pH=6.0) as the supporting electrolyte and boron doped diamond (BDD) as the working electrode. The method presented favorable analytical characteristics such as fast response (67 injections h⁻¹), low detection limits (0.2 and 5.4 μmol L⁻¹ for Zn ions and AA, respectively) and recovery values of 99±3%.