Copper concentrations

Copper compounds Copper concentrates Copper-constantan Copper-constantan Copper-Count-N Copper cyanide... 

Some of the earlier BWR units had feedwater heaters having copper alloy tubes. The environment of high oxygen and neutral pH water led to high copper concentrations in the feedwater and to undesirable deposits on the fuel and inlet fuel nozzles (20). In some instances, the copper deposits resulted in an increase in core pressure drop and necessitated plant power reduction. The copper alloys were eliniinated from the feedwater system in subsequent plants and most existing plants. 

One, the CLEAR process, was investigated by Duval Corporation near Tucson, Arizona (29). It involves leaching copper concentrated with a metal chloride solution, separation of the copper by electrolysis, and regeneration of the leach solution in a continuous process carried out in a closed system. Elemental sulfur is recovered. Not far from the Duval plant, Cypms Mines Corporation operated a process known as Cymet. Sulfide concentrates undergo a two-step chloride solution leaching and are crystallized to obtain cuprous chloride crystals. Elemental sulfur is removed during this stage of the process. 

Thus, roasting is avoided. The process, especially amenable to high iron and copper concentrates, has been installed by Cominco, Ltd. (44) at Trad, B.C., Canada, and will be installed at the Kidd Creek Mines, Ltd., plant at Timmins, Ontario. 

The Phalaborwa complex ia the northeastern Transvaal is a complex volcanic orebody. Different sections are mined to recover magnetite, apatite, a copper concentrate, vermicuhte, and baddeleyite, Hsted in order of aimual quantities mined. The baddeleyite is contained in the foskorite ore zone at a zirconium oxide concentration of 0.2%, and at a lesser concentration in the carbonatite orebody. Although baddeleyite is recovered from the process tailings to meet market demand, the maximum output could be limited by the requirements for the magnetite and apatite. The baddeleyite concentrate contains ca 96% zirconium oxide with a hafnium content of 2% Hf/Zr + Hf. A comminuted, chemically beneficiated concentrate containing ca 99% zirconium oxide is produced also. 

Coal pipelines have been built in countries such as France (8.8 km), and Russia (61 km), and pipelines are also used for transporting limestone, copper concentrates, magnetite, and gHsonite in other parts of the world. The first coal pipeline, built in Ohio, led to freight rate reductions. The pipeline stopped operation after introduction of the unit train, used exclusively to transport coal from the mine to an electric power generation station. 

Sulfide Ores ores. In the Zairian ores, cobalt sulfide as carroUite is mixed with chalcopyrite and chalcocite [21112-20-9]. For processing, the ore is finely ground and the sulfides are separated by flotation (qv) using frothers. The resulting products are leached with dilute sulfuric acid to give a copper—cobalt concentrate that is then used as a charge in an electrolytic cell to remove the copper. Because the electrolyte becomes enriched with cobalt, solution from the copper circuit is added to maintain a desirable copper concentration level. After several more steps to remove copper, iron, and aluminum, the solution is treated with milk of lime to precipitate the cobalt as the hydroxide. 

Eigure 2 shows a simplified flow diagram for a typical copper concentrator. The term mill is used interchangeably with the term concentrator to describe the faciUty, although milling more correctly refers to just the grinding step. 

Molybdenite [1309-56 ] M0S2, normally floats with the copper sulfides. Therefore, the copper concentrate from the cleaner cells frequently has to be separated from molybdenite in a separate flotation circuit before the copper concentrate goes to the smelter. Gold, silver, selenium, and tellurium are collected with the copper concentrate. 

Smelting. The term copper smelting designates the operations of melting the concentrate and extracting the copper by heat, flux, and the addition of oxygen. Copper concentrate is a mixture of the sulfides of copper, copper—iron, and iron with smaller amounts of gangue minerals. It normally contains 25—35% copper. 

Current densities and cell voltages have been increased in some refineries, but the majority of refineries are still operating at 175—230 A/m, copper concentrations of 30—50 g/L, electrolyte temperatures of 55—65°C, and circulation rates of 10—20 L/min to obtain good-quafity cathodes. 

Electrowinning. Vat leaching often yields copper solutions having concentrations sufficiently high for direct electrowinning. However, high concentrations of cations other than copper and low copper concentrations make it more difficult to obtain high purity electrolytic copper by direct electrolysis of leach solutions than by electrolysis of purified solutions obtained from solvent extraction. 

Copper has been employed as a bactericide, moUuscicide, and fungicide for a long time and is of importance in the control of schistosomiasis (see also Antiparasitic AGENTS, ANTHELMINTICS FUNGICIDES, AGRICULTURAL). Addition of copper to lake water acts as an efficient deterrent to transmittal of the disease by eliminating snails that act as hosts for the responsible parasite. Copper is commonly utilized at ca 0.1 mg/L as an algicide. In fresh water, acute toxicosis in fish is unusual if the copper concentration is below 0.025 mg/L (70) (see Poisons, economic). 

To measure a residence-time distribution, a pulse of tagged feed is inserted into a continuous mill and the effluent is sampled on a schedule. If it is a dry miU, a soluble tracer such as salt or dye may be used and the samples analyzed conductimetricaUy or colorimetricaUy. If it is a wet mill, the tracer must be a solid of similar density to the ore. Materials hke copper concentrate, chrome brick, or barites have been used as tracers and analyzed by X-ray fluorescence. To plot results in log-normal coordinates, the concentration data must first be normalized from the form of Fig. 20-15 to the form of cumulative percent discharged, as in Fig. 20-16. For this, one must either know the total amount of pulse fed or determine it by a simple numerical integration... 

In these particular experiments it proved impossible to investigate the effect of copper concentration on the catalytic activity of alloys free of the hydride phase. Figure 10 69, 64a, 65) illustrates the changing values of the recombination coefficient on nickel-copper alloys related to the composition of the alloy at room temperature. The small amount of copper introduced into the nickel already distinctly decreased the catalytic ac-... 

Kojic acid (5-hydroxy-4 pyran 4-1-2 methyl) is a fungal derivative which inactivates tyrosinase via chelation of copper. Concentrations range from 2 to 4%. It can be used for monotherapy or in combination with retinoids or other cosme-ceutical products such as glycolic acid. Compared with hydroquinone, these kojic acid formulations usually show less efficacy. However, they may be effective in patients who do not... 

The ruthenium-copper and osmium-copper systems represent extreme cases in view of the very limited miscibility of either ruthenium or osmium with copper. It may also be noted that the crystal structure of ruthenium or osmium is different from that of copper, the former metals possessing the hep structure and the latter the fee structure. A system which is less extreme in these respects is the rhodium-copper system, since the components both possess the face centered cubic structure and also exhibit at least some miscibility at conditions of interest in catalysis. Recent EXAFS results from our group on rhodium-copper clusters (14) are similar to the earlier results on ruthenium-copper ( ) and osmium-copper (12) clusters, in that the rhodium atoms are coordinated predominantly to other rhodium atoms while the copper atoms are coordinated extensively to both copper and rhodium atoms. Also, we conclude that the copper concentrates in the surface of rhodium-copper clusters, as in the case of the ruthenium-copper and osmium-copper clusters. 

Figure 2. Transmission electron micrographs of the copper nanocube from the spherical seed particles. Conditions total copper concentration 2xl0 M and [M ]/[M ] = 1 99. (Reprinted from Ref [30], 1998, with permission from Current Science Association.)...

Blake, 1989 Winyard et al., 1989). We suggest that within the inflamed rheumatoid joint (or the artery wall in atherogenesis), the production of ROM and proteases by endothelial cells and/or macrophages may cause the release of copper ions from Cp (see Section 2.2.3.2). It has been reported that Cp is cleaved faster in serum from patients with inflammatory diseases when compared to normal serum (Laurell, 1985). The oxidative modification of LDL by Cp-derived copper ions may explain the observation that increased serum cholesterol values are associated with accelerated atherosclerotic progression in men with high serum copper concentrations (Salonen et al., 1991). 

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