Precipitation hydrometallurgy

ViRClKOVA E., Molnar L., Lech P. and Reitznerova E. (1995) Solubilities of amorphous Fe-As precipitates. Hydrometallurgy 38, 111-123. 

Louis P., Cobalt Solution Purification By Solvent Extraction or by Selective Precipitation , Hydrometallurgy of Nickel and Cobalt 2009, 39 Annual Hydrometallurgical Meeting, Sudbury, Canada, 2009, 255-270... 

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. 

In the broadest sense, coordination chemistry is involved in the majority of steps prior to the isolation of a pure metal because the physical properties and relative stabilities of metal compounds relate to the nature and disposition of ligands in the metal coordination spheres. This applies both to pyrometallurgy, which produces metals or intermediate products directly from the ore by use of high-temperature oxidative or reductive processes and to hydrometallurgy, which involves the processing of an ore by the dissolution, separation, purification, and precipitation of the dissolved metal by the use of aqueous solutions. 4... 

Approximately 80% of Zn production involves hydrometallurgy, in which roasted sulfide concentrates are dissolved in sulfuric acid.181 Currently, the major separation steps involve the precipitation of other metals from the sulfate stream (Figure 7) 181>182 The precipitation of iron is achieved by raising the pH with calcine, the mixture of zinc/iron oxides from roasting, producing large volumes of iron oxy-hydroxide materials, the disposal of which presents major challenges.183-185... 

Y. Bal, K. E. Bal, G. Cote, and A. Lallam. Characterization of the solid third phases that precipitate from the organic solutions of aliquat (r) 336 after extraction of molybdenum)VI) and vanadium(V). Hydrometallurgy, 75(1-4) 123-134, 2004. 

Another unique feature of the interfacial reaction for metal complexes is the formation of the aggregate of the complex. As observed in many cases, the liquid/liquid interface can be saturated by any active surface molecules at the interfacial concentration of the order of 10 mol cm, which can be attained even at adiluted bulk concentration as in the case of highly hydrophobic solutes. Thus, the interface is prepared to become a two-dimensionally concentrated state for the solute. This situation very often results in the formation of the metal complex aggregates at the liquid/liquid interface. During the solvent extraction procedure for metal ions, the precipitate at the interface was observed, which was called crud or scum in the field of hydrometallurgy. This crud or scum must... 

One of the most important developments in the field of hydrometallurgy has been the application of elevated pressures and temperatures to complex sulfide and oxide ores (B21, F8, G8, M5, M6). The pressure-leaching of bauxite ores by the Bayer process (E3) is probably the first successful commercial application of this technique. The bauxite ore is leached with sodium hydroxide solution with a specific gravity of 1.36-1.4 at 160-170°C for 1 2 hr under a working pressure of 100 psig. The alumina is produced by calcining the aluminum hydrate precipitated from the leach liquor. 

Stage 8 column (c) on stand-by to become column (b) in next cycle PL = pregnant liquor W = water 1 = 1st eluant 2 = 2nd eluant P = to precipitation BD = barren discharge (Reproduced by permission from Ion Exchange In Uranium Extraction , in Ion Exchange Sorption Processes In Hydrometallurgy , Critical Reports on Applied Chemistry, Vol. 19, ed. M. Streat and D. Naden, Wiley, Chichester, 1987, Ch. 1)... 

Riveros, P. A. and Dutrizac, J. E. (1997) The precipitation of hematite from ferric chloride media. Hydrometallurgy 46 85-104. 

Hydrometallurgy, where the ore is crushed and concentrated by flotation, then roasted and leached with acid. Finally, selectively precipitation is followed and then refining by electrolysis. 

Panias, D.. Role of boehmite/solution interface in boehmite precipitation from supersaturated sodium aluminate solutions. Hydrometallurgy, 74, 203, 2004. 

Today, hydrometaUurgy is well established as the principal method for extraction of many important industrml metals. Hydrometallurgy for the direct treatment of base metal sulfide concentrates, as a widely used technology, must yet prove itself. The roast-leach electrowinning of zinc is a noteworthy exception and is evolving as standard practice hi the zinc industiy worldwide. Relatively recent developments by way of jarosite and iron oxide hydrolysis and precipitation processes have improved recovery and helped secure zinc hydromemllurgy as standard in the industiy.w... 

The "qual scheme" served as the basis for the development of radiochemical analysis by the chemists of the Manhattan Project in the 1940s. There are a number of industrial processes including those utilized in hydrometallurgy that are based on precipitation steps to produce the desired intermediate or product. In nature, production of various minerals from natural waters and brines can be understood in terms of precipitation equilibria (and kinetics). 

S. Agatzini, A. Kontopoulos, P. Marboutis, A. Xenidis, Removal of iron from iron-nickel-cobalt solutions by precipitation and solvent extraction techniques. Iron Control in Hydrometallurgy, ed. J.E. Dutrizac, A.J. Monhemius, Ellis Norwood Ltd, 1986 (CIM, Montreal, Quebec, 1996), 353-373. 

R. Das, S. Anand, Precipitation of iron oxides from ammonia-ammonium sulphate solutions . Hydrometallurgy, 38 (1995), pp. 161-173. 

R.J. de Klerk et al., Continuous circuit coprecipitation of arsenic(V) with ferric iron by lime neutralization Process parameter effects on arsenic removal and precipitate quality, Hydrometallurgy, 111-112 (2012), 65-72. 

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