Electrochemical leaching

The most efficient electrokinetic removal of radioactive nuclides from polluted ground can be achieved in combination with electrochemical leaching, that is, with... 

Electrochemical leaching of Pt alloy catalysts has been deliberately applied to form core-shell materials with enhanced activities, either in half-cell tests [24, 25] or even... 

It should be noted that the MogSg material is thermodynamically unstable and can be obtained only indirectly by chemical or electrochemical leaching of the more stable, metal-containing Chevrel phases, e.g. Cu2Mo6Sg. which can be synthesized from the Cu, Mo and S elements (or the metal sulfides) at high temperatures in quartz tubes. In contrast, Mo6Seg can be synthesized directly from the elements. 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

Electrodes that are prepared from acid-leached LT-LiCo, xNix02 compounds (0< x<0.2) show significantly enhanced electrochemical behavior over the parent LT-LiCo1 xNix02 structure. The improved performance has been attributed to the formation of compounds with a composition and cation arrangement close to the ideal Li[B2]04 spinel structure (B = Co, Ni) [62]. These spinel-type structures have cubic symmetry, which is maintained on lithiation the unit cells expand and contract by only 0.2 percent during lithium insertion and extraction. 

A minor source of metallic Ca is the recovery of the Ca that crystallizes from the liq Na produced in the electrochemical cell. This can be effected either by filtration of the liquid metal or by aleohol leaching of the residual Na-Ca sludge. 

The metallic or semi-metallic character of many common sulfides implies the significance of electrochemical factors in the study of their oxidation, which is relevant to environmental, energy, and metallurgical issues, e.g., in connection with the direct electrochemical conversion of sulfide ores to metals, the pressure leaching of ore materials, or flotation processes. 

Separation and detection methods The common methods used to separate the Cr(III)/(VI) species are solvent extraction, chromatography and coprecipitation. In case of Cr(VI) from welding fumes trapped on a filter, a suitable leaching of the Cr(VI) from the sample matrix is needed, without reducing the Cr(VI) species. The most used detection methods for chromium are graphite furnace AAS, chemiluminescence, electrochemical methods, ICP-MS, thermal ionization isotope dilution mass spectrometry and spectrophotometry (Vercoutere and Cornelis 1995)- The separation of the two species is the most delicate part of the procedure. 

Jeffrey, M. I. Ritchie, I. M. The leaching and electro chemistry of gold in high-purity cyanide solutions. J. Electrochem. Soc. 2001, 148, D29-D36. 

Hybinette A process for extracting nickel from sulfide ores. The nickel ore that occurs in Canada is a mixture of the sulfides of nickel, copper, and iron. Several methods have been used to separate these metals. In the Hybinette process, the ore is first smelted in a blast furnace, yielding a nickel-copper matte (i.e., a mixture of their lower sulfides). This is roasted to remove sulfur and leached with dilute sulfuric acid to remove copper. The resulting crude nickel oxide is used as the anode of an electrochemical cell. The nickel deposits on the cathode, which is contained in a cloth bag. Precious metals collect in the anode slime. The process was invented by N. V Hybinette in 1904 and operated at the Kristiansand refinery, Norway, from 1910. 

Hamilton, S.M. 1998. Electrochemical mass transport in overburen a new model to account for the formation of selective leach geochemical anoamalies in Glacial Terren. Journal of Geochemical Exploration, 63, 155-172. 

Chemical separation may be considered (acid treatment, leaching) when the parts to be removed are more reactive than the compound to be isolated and can be dissolved and washed away. A special case may be the electrolytic extraction when, in a solidified sample, there is sufficient electrochemical difference between the various phases an example is the extraction from Al-rich ingots of compounds such as CrAl7 and MnAl6 (Raynor and Wakeman 1947). 

Although the titanium oxide layer at the surface of the nitinol is highly biocompatible and protects the underlying substrate from electrochemical corrosion, the titanium oxide layer itself is mechanically very brittle. Under mechanical stress, such as the shear of blood flow in the aorta or under the bending moments of aortic pulsations, the titanium oxide surface layer can fracture, exposing the underlying metal to corrosion. Not only is corrosion undesirable in terms of biocompatibility (i.e., leaching of nickel and its... 

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