Process hydrometallurgical

From such a concentrated aqueous solution of the metal, the recovery of the metal is achieved in a variety of the ways. The metal may be precipitated as a hydroxide, an oxide, or calcined as an oxide or recovered as a metal via electrowinning (e.g., Cu, Co, Ni), etc. Illustrations of process flowsheets for the recovery of a variety of metals, e.g. copper, zinc, nickel, uranium, chromium, beryllium, etc., are available in Ritcey and Ashbrook (1984b). Benedict et al. (1981) also provide process flowsheets and descriptions of metals relevant to the nuclear power industry. 

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Hydrometallurgical Processes. Recovery of sulfur in the processing of nonferrous metal sulfides has been in the form of SO2 and/or H2SO4 when smelter (pyrometallurgical) operations are employed. However, there have been accounts of processes, mainly hydrometallurgical, in which sulfur is recovered in the elemental form (see Metallurgy, extractive). 

In the most common hydrometallurgical process for zinc manufacturing, the ore is leached with sulfuric acid to extract the lead/zinc. These processes can operate at atmospheric pressure or as pressure leach circuits. Lead/zinc is recovered from solution by electrowinning, a process similar to electrolytic refining. The process most commonly used for low-grade deposits is heap leaching. Imperial smelting is also used for zinc ores. 

Alcohols with a C8 - Cn chain length, characterized by low solubility in aqueous media, may have a particular commercial potential as perspective extractants for tantalum and niobium hydrometallurgical processing. Particular emphasis has been placed recently on the investigation of tantalum and niobium extraction using octanol (C8Hi80) in the forms of 1-octanol and 2-octanol [462,466-473]. 

The copper product is known as blister copper because of the appearance of air bubbles in the solidified metal. In the hydrometallurgical process, soluble Cu2+ ions are formed by the action of sulfuric acid on the ores. Then the metal is obtained by reducing these ions in aqueous solution either electrolytically or chemically, by using an inexpensive reducing agent that has a more negative standard potential than that of copper, such as hydrogen or iron (see Section 14.3) ... 

By way of an example, one may consider the case of hydrometallurgical reactors. Leaching is the most important of the different unit operations, and is prominently placed and assigned due emphasis in a typical hydrometallurgical process flowsheet. A representative list of the various types of reactors used for agitation leaching is given in Table 1.21. 

At present, leaching is one of the most essential front-end operations in hydrometallurgy, but in future hydrometallurgical processes for secondary metal recovery, treatment of low grade and complex ores, and research and development into high-temperature and high-pressure processes will become increasingly important. 

The employment of charcoal adsorption in hydrometallurgical processes offers several advantages (i) the process flowsheet is simplified, since thickening, washing, and filtration steps are avoided this implies a reduction in the capital as well as the operating costs, and... 

Although precipitation constitutes the concluding part of the hydrometallurgical process flowsheet, the process is also put to use as a purification step in order to separate impurities. The different methods of precipitation are shown in Figure 5.25. The crystallization process is probably the simplest method to remove metals from solutions as compounds. No reagents are added, and the process simply involves the complete dissolution of the metal salt at a suitable temperature and pressure to obtain as high a metal content as possible. As the temperature is raised or lowered, depending on the particular system, the solubility of the metal salt in solution is exceeded and the salt precipitates or crystallizes... 

H. Y. Sohn and M. E. Wadsworth, Rate Processes of Extractive Metallurgy, Section 3, Hydrometallurgical Processes, Plenum Press, 1979. 

R. G. Bautista, ed., Hydrometallurgical Process Fundamentals, Plenum Press, New York, 1984. 

In future, the developments in hydrometallurgy will need to be concerned more with environmental problems associated with pertinent processes. Hydrometallurgical processes produce a variety of waste liquors and unwanted solid products which must be treated before their final disposal. There are two main objectives in such waste treatments the first is to recover valuable impurities and unused reagents from the solutions and the second is to ensure that the release of associated materials does not pollute the environment to an unacceptable extent. 

Torma, A. E. The role of Thiobacillus ferrooxidans in hydrometallurgical processes. Advances in Biochemical Engineering 1977, 6, 1-37. 

Mihaylov, I. Krause, E. Colton, D. F. Okita, Y. Duterque, J. P. Perraud, J. L. The development of a novel hydrometallurgical process for nickel and cobalt recovery from Goro laterite ore. CIM Bull. 2000, 93, 124-130. 

The almost quantitative oxidation/complexation of palladium(O) in powder or foils by Me2dazdt 2I2 in THF, acetone, acetonitrile, and methylethylketone (MEK) to afford [Pd(Me2dazdt)2](I3)2 makes this synthetic route appealing for practical industrial applications. A selective process for Pd-recovery from model three-way car converters was simulated obtaining a Pd-extraction yield > 90%, and was proposed as an alternative to hydrometallurgical processes.62... 

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