Metals extractive industries

The above covers most conventional mixers there is another class of mixers, called pump-mix impellers, where the impeller serves not only to mix the fluids, but also to move the fluids through the extraction stages. These are speciahzed designs, often used in the metals extraction industries. For these types of impellers, a knowledge of the power characteristics for pumping is required in addition to that for mixing. For a more detailed treatment of these special cases, the reader is referred to Lo et al. 

Raked hearth reactors were once extensively used in the metals extraction industries but are now being superseded. 

Caro s acid, an equilibrium mixture of sulfuric acid, water, and peroxymono-sulfuric acid, is used in the metal-extraction industry. It is manufactured by reacting concentrated sulfuric acid with hydrogen peroxide. Caro s acid is a powerful oxidizing agent and decomposes readily. A process was developed to manufacture 1000 kg/day of Caro s acid in a tubular reactor with a volume of 20 ml and a residence time of less than one second, with the product immediately mixed with the solution to be treated (16). 

Assessing the quality of a product . Geochemical analyses are a vital tool in the metal extraction industry where a few micrograms per gram may represent an ore for some elements. Ores may also contain significant concentrations of toxic or polluting trace elements. Phosphate ore, for instance, may... 

Extraction, a unit operation, is a complex and rapidly developing subject area (1,2). The chemistry of extraction and extractants has been comprehensively described (3,4). The main advantage of solvent extraction as an industrial process Hes in its versatiHty because of the enormous potential choice of solvents and extractants. The industrial appHcation of solvent extraction, including equipment design and operation, is a subject in itself (5). The fundamentals and technology of metal extraction processes have been described (6,7), as has the role of solvent extraction in relation to the overall development and feasibiHty of processes (8). The control of extraction columns has also been discussed (9). 

In order to maintain a definite contact area, soHd supports for the solvent membrane can be introduced (85). Those typically consist of hydrophobic polymeric films having pore sizes between 0.02 and 1 p.m. Figure 9c illustrates a hoUow fiber membrane where the feed solution flows around the fiber, the solvent—extractant phase is supported on the fiber wall, and the strip solution flows within the fiber. Supported membranes can also be used in conventional extraction where the supported phase is continuously fed and removed. This technique is known as dispersion-free solvent extraction (86,87). The level of research interest in membrane extraction is reflected by the fact that the 1990 International Solvent Extraction Conference (20) featured over 50 papers on this area, mainly as appHed to metals extraction. Pilot-scale studies of treatment of metal waste streams by Hquid membrane extraction have been reported (88). The developments in membrane technology have been reviewed (89). Despite the research interest and potential, membranes have yet to be appHed at an industrial production scale (90). 

Ketones are an important class of industrial chemicals that have found widespread use as solvents and chemical intermediates. Acetone (qv) is the simplest and most important ketone and finds ubiquitous use as a solvent. Higher members of the aUphatic methyl ketone series (eg, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone) are also industrially significant solvents. Cyclohexanone is the most important cycHc ketone and is primarily used in the manufacture of y-caprolactam for nylon-6 (see Cyclohexanoland cyclohexanone). Other ketones find appHcation in fields as diverse as fragrance formulation and metals extraction. Although the industrially important ketones are reviewed herein, the laboratory preparation of ketones is covered elsewhere (1). 

Wisniewski, M. Szymanowski, J. Industrial applications of noble metals extraction. Pol. J. Appl. Chem. 1996, 40, 17-26. 

Used industrially for electroplating, precious metal extraction and in the synthesis of dyes, pigments, pharmaceuticals, and pesticides. 

METEX [Metal extraction] A process for extracting heavy metals from industrial waste waters by adsorption on activated sludge under anaerobic conditions. It is operated in an up-flow, cylindrical reactor with a conical separation zone at the top. Developed by Linde, originally for removing dissolved copper from winemaking wastes. First commercialized in 1987. 

Davidson CM, Duncan AL, Littlejohn D, Garden LM. A critical evaluation of the three-stage BCR sequential extraction procedure to assess the potential mobility and toxicity of heavy metals in industrially-contaminated land. Anal. Chim. Acta 1998 363 45-55. 

Some metals are extracted in electrolytic cells. In section 11.3, you saw the extraction of sodium from molten sodium chloride in a Downs cell. Other reactive metals, including lithium, beryllium, magnesium, calcium, and radium, are also extracted industrially by the electrolysis of their molten chlorides. 

The second part deals with applications of solvent extraction in industry, and begins with a general chapter (Chapter 7) that involves both equipment, flowsheet development, economic factors, and environmental aspects. Chapter 8 is concerned with fundamental engineering concepts for multistage extraction. Chapter 9 describes contactor design. It is followed by the industrial extraction of organic and biochemical compounds for purification and pharmaceutical uses (Chapter 10), recovery of metals for industrial production (Chapter 11), applications in the nuclear fuel cycle (Chapter 12), and recycling or waste treatment (Chapter 14). Analytical applications are briefly summarized in Chapter 13. The last chapters, Chapters 15 and 16, describe some newer developments in which the principle of solvent extraction has or may come into use, and theoretical developments. 

Elemental mercury is used industrially in electric lamps and switches, gauges and controls (e.g. thermometers, barometers, thermostats), battery production, nuclear weapons production, and the specialty chemical industry, including the production of caustic soda. Because elemental mercury has a high affinity for gold and silver, it has been, and continues to be, used in precious metal extraction from ore. Elemental mercury has been used for over one hundred years in mercury-silver amalgam preparations to repair dental caries. Mercury continues to be used in folk remedies and in certain cultural practices, with unknown public health implications. 

Mercapto-l,5-diphenylformazan (dithizone, dzH) (42) was first prepared by Emil Fischer over a century ago.146 In 1925 Hellmut Fischer147 introduced dithizone as a versatile analytical reagent and subsequently explored its use for the solvent extraction and quantitative determination of a number of metals of industrial and toxicological interest. The conditions for the isolation and... 

Metal and metalloid pollutant analysis of environmental matrices may be conducted with several elemental analysis techniques. For analysis to be possible, all matrices, including unfiltered groundwater, leaching procedure extracts, industrial and organic wastes, soils, sludges, and sediments must be digested with acid. Exceptions are... 

Of all the many and varied aspects of the chemistry of metals, the industrial importance of iron and the various products derived from it are traditionally singled out for special emphasis. It is certainly true that the many rich deposits of high-grade iron ores, the relative ease and low cost with which the metal may be extracted, and its many useful properties have made iron the cornerstone of industrial development. Although modern trends in the metallurgical industries indicate rather clearly that certain of the light metals may eventually come to rival the dominant position of iron, many years will elapse before it is relegated to a position of secondary importance. 

Koopman, C. and Witkamp, G.J. (2002) Extraction of heavy metals from industrial phosphoric add in a transverse flow hollow-fiher membrane contactor. Separation Science and Technology, 37,1273. 

Reverse osmosis also serves some of the waste management and resource recovery needs in the metals and metal finishing industry. Effluent streams from mining and plating operations containing heavy metals, acids, and other chemicals can be treated with reverse osmosis to recover both the metal as its salt, and purified water for reuse. For metal ion recovery from dilute solutions, however, reverse osmosis faces competition from conventional solvent extraction, membrane-based solvent extraction, and its variant, coupled transport (see Section V.F.3). 

The use of electrochemistry in industry is affected by the price of electricity and its ease of supply, principally in cases where there is an alternative production method. For this reason large-scale energy-intensive electrolysis processes such as metal extraction have developed where electricity can be generated at low cost. This criterion is more... 

---