Electrochemical oxidation of binary copper-nickel alloys in cryolite melts

Anodic oxidation of copper, nickel and two copper-nickel alloys was studied in cryolite melts at 1000°C. In an oxide-free melt, anodic dissolution of each material was observed, and the dissolution potential increases with the content of copper. SEM characterization of a Cu55-Ni45 alloy showed that nickel is selectively dissolved according to a de-alloying process. In an alumina-containing melt, a partial passivation occurs at the copper-containing electrodes, at potentials below the oxygen evolution potential. A passive film forms on the copper electrode, while on the nickel electrode no dense oxide layer develops. Copper-nickel alloys were found to form a mixed oxide layer. At higher potentials, the formation of oxygen bubbles on the electrodes results in a degradation of the passive films and a strong corrosion

Anodic dissolution of metals in oxide-free cryolite melts

The anodic behavior of metals in molten cryolite-alumina melts has been investigated mostly for use as inert anodes for the Hall-Héroult process. In the present work, gold, platinum, palladium, copper, tungsten, nickel, cobalt and iron metal electrodes were anodically polarized in an oxide-free cryolite melt (11%wt. excess AlF3 ; 5%wt. CaF2) at 1273 K. The aim of the experiments was to characterize the oxidation reactions of the metals occurring without the effect of oxygen-containing dissolved species. The anodic dissolution of each metal was demonstrated, and electrochemical reactions were assigned using reversible potential calculation. The relative stability of metals as well as the possibility of generating pure fluorine is discussed

Neodymium and gadolinium extraction from molten fluorides by reduction on a reactive electrode

This work describes the electrochemical extraction on a reactive cathode (Cu, Ni) of two lanthanides Ln (Ln = Nd and Gd) from molten LiF-CaF2 medium at 840 and 920°C for Nd and 940°C for Gd. Extraction runs have been performed and the operating conditions (cathodic material and temperature) optimised. The titration of the Nd and Gd concentrations in the melt during extraction used square wave voltammetry. At the end of each run, the residual Ln content was checked by ICP-AES; the extraction efficiencies of the two lanthanides were found to be more than 99.8% on both reactive substrates

Kinetic study of the dissolution of vanadyl sulfate and vanadium pentoxide in sulfuric acid aqueous solution

The study deals with the ‘vanadium (IV) sulfate’ and ‘vanadium (V) pentoxide’ dissolution processes in 3 M H2SO4 aqueous media. Several measurements of the concentration of dissolved VO2+ and VO2+ were achieved in the range of 0–40 °C, and allowed to understand the limitations of the dissolution process (‘endothermic’ – mass transport for VOSO4 and ‘exothermic’ – reaction with the proton for V2O5). In addition, simple models were proposed (diffusion/accumulation for VOSO4 and kinetic rate for V2O5) and their resolution leads to theoretical kinetic equations describing the temporal evolution of these concentrations with satisfactory agreement with the experimental curves. Solubility’s data and their temperature dependence were determined for both vanadium compounds involved

Ivermectin, ‘Wonder drug’ from Japan: the human use perspective

Discovered in the late-1970s, the pioneering drug ivermectin, a dihydro derivative of avermectin—originating solely from a single microorganism isolated at the Kitasato Intitute, Tokyo, Japan from Japanese soil—has had an immeasurably beneficial impact in improving the lives and welfare of billions of people throughout the world. Originally introduced as a veterinary drug, it kills a wide range of internal and external parasites in commercial livestock and companion animals. It was quickly discovered to be ideal in combating two of the world’s most devastating and disfiguring diseases which have plagued the world’s poor throughout the tropics for centuries. It is now being used free-of-charge as the sole tool in campaigns to eliminate both diseases globally. It has also been used to successfully overcome several other human diseases and new uses for it are continually being found. This paper looks in depth at the events surrounding ivermectin’s passage from being a huge success in Animal Health into its widespread use in humans, a development which has led many to describe it as a “wonder” drug

electroreduction of oxides in molten fluoride salts

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@inp-toulouse. b s t r a c t A new kind of electrolyte composed of molten fluorides has been evaluated in order to perform a feasibility study of the direct electroreduction reaction. The direct reduction of SnO 2 and Fe 3 O 4 was realised in LiF-NaF at 750 • C and in LiF-CaF 2 at 850 • C for TiO 2 and TiO. The electrochemical behaviour of these oxides was studied by linear sweep voltammetry: a current corresponding to the oxide reduction was evidenced for TiO 2 , SnO 2 and Fe 3 O 4 . After galvanostatic electrolyses, a complete conversion was obtained for all oxides, except TiO, and the structure of reduced Ti and Fe samples had a typical coral-like structure while dense drops of Sn were recovered (Sn is liquid at operating temperature). After TiO electrolysis, a thin external metallic titanium layer was detected, acting as a barrier for the oxide ion diffusion and no complete reduction can be achieved. This could be explained by a Pilling-Bedworth ratio around 1 for Ti/TiO

Pyrolysis of Epoxy resin in a pilot furnace mass balance and parametric study on operating conditions

International audienceIn order to optimize a thermal treatment for the elimination of epoxy resin from nuclear fuel samples by pyrolysis, experimental investigations are carried out with virgin epoxy resin on a pilot scale furnace and a thermogravimetric device. The main target of the treatment is an optimized reduction of the final hydrogen content in the residual solid, the so-called char. The condensable products of the pyrolysis (tar-water mixture) and the char are carefully quantified and characterized by elemental analysis, while the permanent exhaust gases are quantified by gas chromatography. In order to complete the mass balances on each element C-H-O-N and pyrolysis products, a data reconciliation procedure is applied to adjust the values of raw measurements. The reconciled mass distributions after pyrolysis at 450 DC are 78.74 wtpercent tar, 2.60 wtpercent gas, 12.84 wtpercent char and 5.82 wtpercent of water. Pilot experiments, as well as the TGA from 380 DC to 750 DC, help to quantify the significant impact of the temperature on the pyrolysis balance. Organized with a two-level fractional factorial design, 11 pilot experiments have been then conducted to achieve a parametric study on heating rate, argon gas flow rate, resin mass and plateau time for a pyrolysis temperature of 450DC. Heating rate and plateau time have been found as the two predominant factors for reducing char ratio. For residual hydrogen, the plateau time is the only significant parameter. The heating rate has been confirmed to be a factor of second order in the range of 1 to 15 DC/min with two complementary experiments