On the induced reduction of chlorate ions

The induced reduction of chlorate ions can be carried out only by 1-equivalent oxidising agents. As^IV is formed by these, and this reduces chlorate very rapidly. The properties and mechanism of the induced reduction are discussed in detail.

For the determination of chlorate ions a reliable method is given, based on this induced reduction.     

Electrochemical reduction of actinide ions in aqueous solution

Electrochemical reduction of heavy elements from aqueous solution to amalgams was studied by radiopolarography and radiocoulometry. Mechanism of actinide reduction on a mercury pool is discussed through simulation techniques. Special emphasis is placed on redox reactions and potentials, kinetics of the process and effect of acetate and citrate ions as complexing agents. Three groups of actinides have been found. The first group represents actinium and from uranium to berkelium. Reduction occurs in the experimental conditions via an irreversible 3–0 process. The second group consists of the elements from fermium to nobelium, which are reduced in non-complexing solutions, or with acetate ions, similarly as barium and radium, via a reversible 2–0 reaction. Finally, californium and einsteinium behave as intermediate elements. It is noticeable that such groups are also observed in the actinide series by studying the structure of the trivalent aqua ions. On the basis of the above mentioned investigations of actinides and lanthanides several examples of electrochemical application are presented. Californium has been separated from preceding transuranium and lanthanide elements (except europium) by electrochemical reduction to amalgams in acetic solution. Separation factors from 25–90 are achieved with appropriate cathodic potentials. Similarly, this element could be separated from several heavier actinides with citric media. The electrochemical preparation of mixed uranium-nickel and uranium-tin amalgams from aqueous acetate solutions is investigated. The dependence of redox potentials of mixed amalgams on different atomic ratio UNi and USn in amalgams is measured. The large shift of redox potentials of mixed amalgams to the positive direction is detected when the atomic ratio UNi or USn in amalgams reaches 15. The thermal distillation of mercury from mixed amalgams with different UNi and USn atomic ratios was carried out and the products were identified by chemical analysis and X-ray diffraction. The intermetallics UNi₅ and USn₃ were prepared from mixed amalgams with the atomic ratios UNi=15 and USn=13. The uranium and neptunium amalgams are prepared by electrolysis of aqueous acetate solutions and are processes into metals or nitrides U₂N₃, NpN by thermal distillation of mercury in vacuum or in nitrogen atmosphere.     

Mechanism of reduction of thiosulfate ions on the cathode

The effect exerted by current density, cathode material (platinum, palladium, nickel, silver, copper, and cadmium), and temperature on the rate of the reduction of sodium thiosulfate was studied.     

Electrochemical generation of N-nitramine ions upon the reduction of N-nitramines

N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Trnaslated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, p. 2653–2654, November, 1989. Original article submitted June 30, 1989.     

Radiation-chemical reduction of CO2+ ions in aqueous solution. Metal sols and their properties

The radiation-chemical reduction of Co²⁺ ions in an aqueous solution of Co(ClO₄)₂ containing sodium formate was studied. Stable metal sols containing spherical particles with a diameter of 2–4 nm are formed under γ-irradiation in the presence of polyacrylate as the stabilizing additive. An aqueous solution of colloidal cobalt has an optical absorption that increrases smoothly in the UV region without a maximum to 200 nm (ɛ₂₀₀=1.3·10⁴ mol^-1 L cm^-1). It is established that the radiation-chemical reduction of the Co²⁺ ions occursvia an autocatalytic mechanism. The metal sols catalyze the reduction of the Co²⁺ ions by Co₂ ⁻ radical ions formed under irradiation. The properties of the sols were studied, and it is shown that they are readily oxidized by hydrogen peroxide and other oxidants. The mechanism of chemical reactions involving the sols is discussed. Tranalated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1959–1964, October, 1998.     

Spontaneous reduction of metal ions on the sidewalls of carbon nanotubes

Nanotube/nanoparticle hybrid structures are prepared by forming Au and Pt nanoparticles on the sidewalls of single-walled carbon nanotubes. Reducing agent or catalyst-free electroless deposition, which purely utilizes the redox potential difference between Au3+, Pt2+, and the carbon nanotube, is the main driving force for this reaction. It is also shown that carbon nanotubes act as a template for wire-like metal structures. The successful formation of the hybrid structures is monitored by atomic force microscopy (AFM) and electrical measurements.     

Kinetic aspects of the reduction of mercury ions by humic substances

A combination of a computer controlled titration device with a cold vapour atomic absorption spectrometer was set up to examine the kinetics of the reaction between humic substances and Hg(II). Subsequent injections of Hg(II) into an excess of humic acid produce data about short and long term changes in the reaction velocity of humic substances. This experimental design is suitable for the examination of the effects of pH, reaction time, light and interfering substances like chloride on the formation of elemental mercury. The obtained data agree with data from the literature. With the accumulation of the produced elemental mercury on a gold net it is possible to enhance the sensitivity of the method. This enables examinations at environmental concentrations.     

Autoinhibition of photocatalytic reduction of safranin and dichromate ions at anatase

The photocatalytic transformations of safranin and dichromate ion at titanium dioxide involve the formation of reduction products at the first stage. With increase in the concentration of catalyst the rate constant increases at [E] 1 g/L and subsequently reaches a plateau in accordance with the Michaelis-Menten equation. With increase in the concentration of the substrate, however, the rate of the process increases, passes through a maximum, and then decreases. The retardation of the process is due to inhibition by the substrate or by the product of the photocatalytic transformation. The proposed equation predicts a hyperbolic dependence of the rate and the rate constant on [E] and an extremal dependence of these kinetic parameters on the concentration of the substrate.     

Kinetic aspects of the reduction of mercury ions by humic substances

A combination of a computer controlled titration device with a cold vapour atomic absorption spectrometer was set up to examine the kinetics of the reaction between humic substances and Hg(II). Subsequent injections of Hg(II) into an excess of humic acid produce data about short and long term changes in the reaction velocity of humic substances. This experimental design is suitable for the examination of the effects of pH, reaction time, light and interfering substances like chloride on the formation of elemental mercury. The obtained data agree with data from the literature. With the accumulation of the produced elemental mercury on a gold net it is possible to enhance the sensitivity of the method. This enables examinations at environmental concentrations.     

Effect of lithium ions on oxygen reduction in ionic liquid-based electrolytes

The effect of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on the oxygen redox reaction (ORR) in several pyrrolidinium-based ionic liquids (ILs) is investigated by cyclic voltammetry. The results are compared to those found with LiTFSI-tetraglyme and LiTFSI-1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidone solutions. The effect of the addition of tris(pentafluorophenyl) borane (TPFPB) to IL-LiTFSI solutions is also investigated. The results demonstrate that the presence of 0.1 M Li⁺ renders the ORR similar in the investigated ILs, lowers the reduction voltammetric currents and makes ORR electrochemically irreversible. The addition of TPFPB to IL-TFSI solutions favours the solubility of oxygen-based products of Li⁺ and should positively affect the performance of IL-based lithium-air batteries.     

Exchange and reduction of Cu(2+) ions in clinoptilolite

The ion-exchange and reduction processes for Cu(2+) ions in clinoptilolite from the Caimanes deposit (Moa, Cuba) were studied at different temperatures. The ion-exchange studies were done to determine the kinetic parameters of Cu(2+) removal from solution by this clinoptilolite modified previously to NH(+)(4) form, and thermodynamic parameters of Cu(2+) elution from zeolite using NH(4)Cl solution. The results show that temperature increase favors the exchange and that it is a reversible process. The external diffusion rate appreciably increases with temperature, while, the internal diffusion coefficient rises relatively little. This means that besides ion exchange other processes (such as precipitation of the low-solubility phase and/or salt adsorption) occur, which cause copper removal from solution and affect the intracrystalline diffusion of the ions. For steric reasons the exchange of [Cu(H(2)O)(6)](2+) ions from a solution must occur with a number of water molecules n smaller than 6 (6 > n > or = 0). Cu(2+) reduction by hydrogen and the formation of Cu-particles in the clinoptilolite were verified. The Cu(2+) reduction mechanism is complex, indirect, and sensitive to reduction temperature; consequently, Cu(+)(n) states intermediate between Cu(2+) and Cu(0) should be present in the reduced samples.     

Comparative study of various methods of the heterogeneous reduction of nitrate ions

Working pH ranges of heterogeneous reductors of nitrate ions based on metallic cadmium, zinc, and brass as well as on cadmium-copper, cadmium-mercury, zinc-copper, and zinc-mercury galvanic couples were examined. Metallic cadmium and the cadmium-copper couple were selected as reductants; freshly prepared, these reductants provided the 100% reduction of nitrate ions to nitrite ions in the pH range from 3.4 to 9.5. A method was developed for prolonging the reducing properties of reductants based on metallic cadmium by permanently copper-plating these reductants. The relationship between the degree of reduction of nitrate ions in a cadmium reductor and the concentration of Cd²⁺ ions in the solution at the outlet of the reductor was determined.     

Electrochemical reduction of the lanthanide ions: Part I. First reduction step of ytterbium(III) in acidic 1 M NaClO4 solution

The reduction of Yb(III) to Yb(II) in 1 M NaClO₄ in the pH range 1.9–6.6 was studied by d c. polarography, cyclic voltammetry and electrode impedance measurements as a function of frequency and electrode potential. It results that the d.c. reversible reduction is followed by a homogeneous chemical reaction and is accompanied, by an irreversible process which is attributed to a lowering of the overpotential of the reduction of the hydrogen ions. Values of the rate constant and transfer coefficient pertaining to the charge transfer step were deter mined.     

Separation radiochimique rapide des ions argent par reduction sur le mercure

A rapid separation .of silver on mercury is proposed in order to utilize shortlived isotopes for the determination of silver by activation. The conditions allowing quantitative reduction of silver were studied; a. kinetic study showed that after 90 sec, 97% of silver could be transferred to the mercury. The spectrometric analysis of ¹¹⁰Ag was also examined. Only metals with a redox potential greater than that of mercury form amalgams, and under the irradiation conditions these metals produce virtually no activity.     

The effect of specific adsorption of halide ions on electrochemical CO2 reduction

In the electrochemical CO₂ reduction reaction (CO₂RR), halide ions could impose a significant effect on multi-carbon (C₂₊) product production for Cu-based catalysts by a combined contribution from various mechanisms. However, the nature of specific adsorption of halide ions remains elusive due to the difficulty in decoupling different effects. This paper describes a facile method to actively immobilize the morphology of Cu-based catalysts during the CO₂RR, which makes it possible to reveal the fundamental mechanism of specific adsorption of halide ions. A stable morphology is obtained by pre-reduction in aqueous KX (X = Cl, Br, I) electrolytes followed by conducting the CO₂RR using non-buffered and non-specifically adsorbed K₂SO₄ as the supporting electrolyte, by which the change of local pH and cation concentration is also maintained during the CO₂RR. In situ spectroscopy revealed that the specific adsorption of halide ions enhances the adsorption of *CO intermediates, which enables a high selectivity of 84.5% for C₂₊ products in 1.0 M KI.

Reconstruction of catalyst morphology induced by halide ions over of Cu-based catalysts during CO₂ electroreduction is suppressed using K₂SO₄ as supporting electrolyte. Adsorption of halide ions is an enabling factor to enhance CO₂ electroreduction.     

The effect of UV irradiation on the reduction of Au(III) ions adsorbed on manganese dioxide.

The effect of UV (ultraviolet) irradiation on the adsorption of Au(III) ions on manganese dioxide and their reduction to Au(0) (gold with 0 valence state) was investigated using XPS (X-ray photoelectron spectroscopy) and 197Au M?ssbauer spectroscopy. The UV irradiation accelerated the adsorption and the reduction. From the fact that the proportion of Au(0) estimated from Au 4f XPS spectra for surface analysis was significantly smaller than that from 197Au M?ssbauer spectra for bulk analysis, we deduced that Au(0) was interpenetrated to the inside of manganese dioxide (into deeper places than about 30 A) where XPS is impossible to detect. The content of surface hydroxyl groups on manganese dioxide also increased due to the UV irradiation. The relationship between the charge in the content of hydroxyl groups and the interpenetration of Au(0) is discussed.