Hydrometallurgy

Chemical Metallurgy Principles and Practice. Chiranjib Kumar Gupta 

Copyright 2003 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-30376-6 

The separation of solids from liquids forms an important part of almost all front-end and back-end operations in hydrometallurgy. This is due to several reasons, including removal of the gangue or unleached fraction from the leached liquor the need for clarified liquors for ion exchange, solvent extraction, precipitation or other appropriate processing and the post-precipitation or post-crystallization recovery of valuable solids. Solid-liquid separation is influenced by many factors such as the concentration of the suspended solids the particle size distribution the composition the strength and clarity of the leach liquor and the methods of precipitation used. Some important points of the common methods of solid-liquid separation have been dealt with in Chapter 2. 

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. 

Thermodynamic considerations are important in leaching in that they provide basic guidance in choosing the combination of reagents and their concentrations so as to obtain favorable free energy changes associated with any proposed reaction. Kinetic considera- 

Typical scrap materials for hydrometallurgical treatment are grinding sludges, floor sweepings, contaminated powder qualities, tungsten-copper, and solid pieces, which can be dissolved by electrolysis. 

Hydrometallurgical scrap conversion has already been discussed in detail (Chapter 5) and will not be further treated here. 

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J. N. Butler, Studies in the Hydrometallurgy ofMercuy Sulfide, Nevada Bureau of Mines, Rept. No. 5. 

Hydrometallurgy. The treatment of ores, concentrates, and other metal-bearing materials by wet processes, usually involving the solution of some component, and its subsequent recovery from solution. 

In some respects, hydrometallurgy can be described as wet analytical chemistry carried out on a large scale. Many different dow sheets can be designed with various types of unit operations and most metals can be extracted from a complex ore and recovered at the desired level of purity. A viable hydrometaHurgical process, however, must achieve that goal at an economically acceptable cost. 

Hydrometallurgical Flow Sheets. The various hydrometallurgy operations can be combined in many ways to design processes appropriate for specific metals. 

S. Eugelberg, Principles of Cadmium Production and Their Application at Outokumpu, International Symposium on Hydrometallurgy, AIME, Chicago, 1973, p. 1144. 

V. Ramachandran and co-workers, MLMRCOV Corpus Christi Electrolytic Zinc Plant, Hydrometallurgy Symposium, AIME, Adanta, Ga., 1983, p. 982. R. Capps and co-workers. Zinc Eead Kesidue Treatment and Solution Purification at the National Zinc Company, AIME, BardesviUe, OHa., 1984, paper A84-30. 

A. H. Leigh, "Precious Metal Refining Practice," in D. J. I. Evan and R. S. Shoemaker, eds.. International Symposium on Hydrometallurgy, AIME, New York, 1973. 

Hydrometallurgy Department, R D Division, vSarcheshmeh Copper Complex, Rafsanjan,Kerman, Iran sagedeh2 yahoo.com... 

White, D.A., Fathurrachman, Extraction of uranium (VI) and uranium (IV) from hydrochloric acid using tri-n-octylamine in a benzene diluent, Hydrometallurgy, v.36, pp. 161-168, 1994. 

Such reactions are discussed at appropriate points throughout the book as each individual compound is being considered. A particularly important set of reactions in this category is the synthesis of element hydrides by hydrolysis of certain sulfides (to give H2S), nitrides (to give NH3), phosphides (PH3), carbides (C Hm), borides (B Hm), etc. Useful reviews are available on hydrometallurgy (the recovery of metals by use of aqueous solutions at relatively low temperatures), hydrothermal syntheses and the use of supercritical water as a reaction medium for chemistry. 

Nassmahlen, n. wet grinding, wet milling, nassmechanisch, a. wet mechanical, wet-mill. Nass-metallurgie,/. hydrometallurgy. -mUhle,. f. wet mill, -probe, /. wet test. 

The liquid-liquid extraction (solvent extraction) process was developed about 50 years ago and has found wide application in the hydrometallurgy of rare refractory and rare earth metals. Liquid-liquid extraction is used successfully for the separation of problematic pairs of metals such as niobium and tantalum, zirconium and hafnium, cobalt and nickel etc. Moreover, liquid-liquid extraction is the only method available for the separation of rare earth group elements to obtain individual metals. 

E.A. Brocchi, P.K. Jena, F.J. Moura, O. Barbosa-Filho, R.J. de Carvalho, Chloride metallurgy 2002 Practice and theory of chlorine/metal interaction, Annual Hydrometallurgy Meeting, Oct. 19-23,2002,1 (2002) 229. 

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