Copper extractants functionality

Chakraborty et al. [76] also found that degree of chromiuin(VI) extraction is a function of time in acidic pH with the extractants Aliquat 336, tri- -octyl amine and their mixtures (see Fig. 4.9). Furthermore, a slight synergistic effect was observed when the two extractants were mixed. Valenzuela et al. [77] studied that the initial copper extraction rate was proportional to the concentration of oximic carrier in the organic phase and to the metal content in the acid mine drainage. 

The first commercial reagents were aU based on ketoxime functionality and were used exclusively for copper extraction for over a decade after the first full-scale application at Bluebird Ranchers Mine, Arizona, in 1968 (Arbiter and Fletcher 1994). Today, ketoximes are still successfully used in niche applications for the recovery of copper from dilute leach liquors and also find applications in nickel SX from ammoniacal solutions and in precious metal refining (see Sections S.3.3.3 and 5.3.6.2). Particular applications of ketoximes in copper production are at El Tesoro and Lomas Bayas in the Atacama Desert of Chile, where the leach liquors of circuits often contain high... 

In 1997 and 1998, the authors306 307 also examined acid leached Raney copper catalysts, whereby the alloy was leached with either nitric or perchloric acid of 5, 14, or 27.5 wt% strength. The acid solution was added dropwise over 15 min to an equal volume of deionized water containing the alloy particles. After leaching at 50 °C, the particles were removed and washed to a pH of 7. Air drying at 120 °C was then carried out for one hour. The dissolution rates of catalyst components were observed to be functions of the extraction time (Table 56). 

Table 56 time307 Compositions of Raney copper catalysts as function of acid type and extraction ... 

The presence of residual unbound transition-metal ions on a dyed substrate is a potential health hazard. Various eco standards quote maximum permissible residual metal levels. These values are a measure of the amount of free metal ions extracted by a perspiration solution [53]. Histidine (5.67) is an essential amino acid that is naturally present as a component of perspiration. It is recognised to play a part in the desorption of metal-complex dyes in perspiration fastness problems and in the fading of such chromogens by the combined effects of perspiration and sunlight. The absorption of histidine by cellophane film from aqueous solution was measured as a function of time of immersion at various pH values. On addition of histidine to an aqueous solution of a copper-complex azo reactive dye, copper-histidine coordination bonds were formed and the stability constants of the species present were determined [54]. Variations of absorption spectra with pH that accompanied coordination of histidine with copper-complex azo dyes in solution were attributable to replacement of the dihydroxyazo dye molecule by the histidine ligand [55]. 

Carboxylic acids represent a group of readily available and relatively inexpensive extractants. They have found rather limited application in commercial processes, however, probably on account of their generally low selectivity and poor pH functionality. Nevertheless, they have been used for the separation of copper from nickel,37 the removal of iron from the rare-earth metals,38 separations among yttrium and the rare earths,39 the recovery of indium40 and gallium,41 the removal of... 

The importance of zinc for a normal functioning of the Cu-Zn-SOD was shown in Lemna gibba. In zinc-deficient culture media the activity of Cu-Zn-SOD was strongly inhibited whereas in copper-deficient media little change was found in the enzyme activity (Vaughan et al., 1982). In extracts of zinc-deficient plants, restoration of enzyme activity was possible by supplying zinc to the enzyme assay medium. 

Displacement of the bromide by cyanide ion, using the copper (I) salt as the nucleophile, gives a mixture of nitriles in which the more stable primary nitrile predominates even more. These can be separated by a clever device. Hydrolysis in concentrated HCl is successful with the predominant primary nitrile but the more hindered secondary nitrile does not hydrolyse. Separation of compounds having two different functional groups is easy in this case the acid can be extracted into aqueous base, leaving the neutral nitrile in the organic layer. 

A method for extracting cadmium, copper, europium, and nickel metal ions from aqueous solution using modified polyethyleneimine is described. The polymer modification consists of grafting an imide, diol, triol, carboxylic acid, or thiocar-boxylic acid function to poly(ethyleneimine), which then forms stable metal complexes that are readily removed from solution. 

Although the study of materials chemistry is a relatively new entry in both undergraduate and graduate curricula, it has always been an important part of chemistry. An interesting timeline of materials developments from Prehistoric times to the present may be found in Appendix A. By most accounts. Neolithic man (10,000-300 B.C.) was the first to realize that certain materials such as limestone, wood, shells, and clay were most easily shaped into materials used as utensils, tools, and weaponry. Applications for metallic materials date back to the Chalcolithic Age (4,000-1,500 B.C.), where copper was used for a variety of ornamental, functional, and protective applications. This civilization was the first to realize fundamental properties of metals, such as malleability and thermal conductivity. More importantly, Chalcolithic man was the first to practice top-down materials synthesis (see later), as they developed techniques to extract copper from oxide ores such as malachite, for subsequent use in various applications. 

Profilometry was performed on a wafer which was polished in 40 second time increments under baseline conditions using an experimental grade copper slurry at 4 psi on a perforated IClOOO/Suba rv pad on an IPEC 372MU. Figure 3 displays the extracted step-height-reduction as a function of trench width. Several important conclusions are immediately evident. 

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