Solvent extraction and leaching

Solvent extraction and leaching Solvent extraction (liquid-liquid extraction) 

Solvent extraction, also called liquid-liquid extraction, can be used to separate a substance from a solution by extraction into another solvent. It can be used ether to recover a valuable substance from the original solution, or to purify the original solvent by removing an unwanted component. Examples of solvent extraction are the extraction of uranium and plutonium salts from solution in nitric acid, in the nuclear industry and the purification of water. 

The process depends on the substance being extracted, the solute, having a greater solubility in the solvent used for the extraction than in the original feed solvent. The two solvents must be essentially immiscible. 

The solvents are mixed in a contactor, to effect the transfer of solute, and then the phases separated. The depleted feed solvent leaving the extractor is called the raffinate, and the solute rich extraction solvent, the extract. The solute is normally recovered from the extraction solvent, by distillation, and the extraction solvent recycled. 

The simplest form of extractor is a mixer-settler, which consist of an agitated tank and a decanter. 

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Recovery of Uranium from Leach Solutions. The uranium can be recovered from leach solutions using a variety of approaches including ion exchange (qv), solvent extraction, and chemical precipitation. The most common methods in practice are ion exchange and solvent extraction to purify and concentrate the uranium prior to final product precipitation. 

Vanadium Sulfates. Sulfate solutions derived from sulfuric acid leaching of vanadium ores are industrially important in the recovery of vanadium from its raw materials. Vanadium in quadrivalent form may be solvent-extracted from leach solutions as the oxycation complex (VO) ". Alternatively, the vanadium can be oxidized to the pentavalent form and solvent-extracted as an oxyanion, eg, (V O ) . Pentavalent vanadium does not form simple sulfate salts. 

Sediments Sample leached with HNO3/HF, filtered, purified by KL-HDEHP resin columns, solvent extracted, and electrodeposition a -Spectroscopy No data 95-99% Guogang et al. 1998... 

Distillation is probably the most widely used separation technique in the chemical process industries, and is covered in Chapter 11 of this volume, and Chapter 11 of Volume 2. Solvent extraction and the associated technique, leaching (solid-liquid extraction) are covered in Volume 2, Chapters 13 and 10. Adsorption, which can be used for the separation of liquid and gases mixtures, is covered in Chapter 17 of Volume 2. Adsorption is also covered in the books by Suziki (1990) and Crittenden and Thomas (1998). 

The application of solvent extraction to copper recovery has been a major growth area since the last review of this series.11,13 Almost 30% of world production in 2000 involved the use of sulfuric acid heap leaching, solvent extraction, and electrowinning, far exceeding earlier predictions.136... 

Figure 5 A simplified flowsheet and materials balance for the recovery of copper from oxidic and transition ores by heap leaching, solvent extraction and electrowinning.

Arbiter Previously known as the Sherritt-Gordon ammonia process. A process for leaching copper from sulfide concentrates, using ammoniacal ammonium sulfate solution at 85°C and relying on air oxidation. Copper is produced from the leachate by solvent extraction and electrowinning. Sulfur is recovered as ammonium sulfate. Operated on a large scale by the Anaconda Copper Company in Montana from 1974 to 1979. See Sherritt-Gordan. 

Cymet (1) [Cyprus Metallurgical] A process for extracting copper from sulfide ores. It involves leaching, solvent extraction, and electrowinning. Developed by the Cyprus Metallurgical Processes Corporation, Golden, CO. Superseded by Cymet (2). 

It will be instructive to consider briefly the methodology employed in the development of solvent extraction processes that have become operational. The development of the Bluebird Mine operation for the extraction of copper from dump leaching liquors by solvent extraction and the subsequent recovery of copper as either copper sulfate or cathode copper is used as an example. The initial investigations [11] included the following ... 

Non-electrostatic assembly is particularly well suited for the direct synthesis of derivatized mesostructures because the framework-forming surfactants can be removed by ambient-temperature solvent extraction and does not necessitate the potentially destructive acid leaching necessary in electrostatic direct assembly.17 Also, HMS and MSU-X materials typically have ultrafine (<1 pm) particle sizes, while electrostatically assembled MCM-type compounds usually have blocky and monolithic morphologies with comparatively large particle sizes (>10 pm). On this basis, non-electrostatically assembled mesostructures are expected to have improved diffusion properties compared to their electrostatic MCM analogs, as will be demonstrated in section 3.3 below. 

BioNIC [Biological NICkel] A biological process for leaching nickel from its ores. It comprises bacterial leaching, solvent extraction, and electrowinning. Developed by BHP Billiton at Yabulu from 1999, but not commercialized by 2004 because no ore body of a suitable concentration and size had been identified. 

Soil Soil leached with HCI-HNO3-HF purification by ion-exchange, and solvent extraction, and electrodeposition a-Spectrometry (isotope quantification) No data No data Golchert et al. 1980... 

Resistance to Leaching. If the chemical that caused the cell wall to swell is bonded to the cell wall polymers, then solvent extraction cannot leach it out. Nonbonded chemicals will leach out resulting in weight loss. Table VII shows that methyl isocyanate-, butylene oxide-, and acetic anhydride-modified wood are very resis-... 

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