Applications solvent extraction

The actual stage can be a mixing vessel, as in a mixer-settler used for solvent extraction applications, or a plate of a distillation or gas absorption column. In order to allow for non-ideal conditions in which the compositions of the two exit streams do not achieve full equilibrium, an actual number of stages can be related to the number of theoretical stages, via the use of a stage-efficiency factor. 

A wide variety of extraction column forms are used in solvent extraction applications and many of these, such as rotary-disc contactors (RDC), Oldshue-Rushton columns, and sieve-plate column extractors, have rather distinct compartments and a geometry, which lends itself to an analysis of column performance in terms of a stagewise model. As the compositions of the phases do not come to equilibrium at any stage, however, the behaviour of the column is therefore basically differential in nature. 

Still, in most liquid—liquid distribution systems one of the liquid phases is more aqueous while the other is mainly non-aqueous. Therefore, a major consideration of the choice of the solvent for solvent extraction is its immiscibility with water and the expected losses of the solvent to the aqueous phase. In many solvent extraction applications the solvent is used as a diluent for an active extractant, which may be either a solid or a liquid when neat. In these cases, where a separate active extractant is used, the chemical processes taking place in the selective extraction of the desired solute or solutes and their recovery in the stripping stage are of prime importance, but a discussion of which is outside the... 

In the absence of a solvent-recovery method, entrainment is expected to be the major solvent-loss factor in all solvent-extraction applications [94], including CSSX [89], potentially amounting to several hundred ppm of the aqueous effluent. Solvent loss is known to be the economic determinant in most commercial solvent-extraction systems... 

Organic extractants can be used to complex metal ions and to increase lipophilic-ity. The traditional metal extractants l-(2-pyridylazo)naphthol (PAN) and l-(2-thia-zolyl)-2-naphthol (TAN) have been used in polymer-based aqueous biphasic systems [43] and traditional solvent extraction systems [44], These are conventional metal extractants widely used in solvent extraction applications. When the aqueous phase is basic, both molecules are ionized, yet they quantitatively partition into [HMIM][PF6] over the pH range 1-13. The distribution ratios for Fe3+, Co2+, and Cd2+ (Figure 3.3-4) show that the coordinating and complexing abilities of the extractants are dependent on pH and that metal ions can be extracted from the... 

About the same time a novel liquid-liquid or solid-liquid counter-current contacting system was being developed by W. H. Morris (30, 31) at ROF Pembrey who proposed its use for the manufacture of TNT as one of a number of applications (including the manufacture of antibodies and other solvent-extraction applications and ion exchange).cThe equipment... 

D. Martin, M.A. Garcia, G. Diaz and J. Falgueras, A New Zinc Solvent Extraction Application Spent Domestic Batteries Treatment Plant , Paper presented at the Intemational Solvent Extraction Conference fISECL Barcelona, Spain, 1999. 

R. Kautzmann, C. H. Sampaio, V. Korovin, Y. Shestak, M. Aguilar, and J.L. Cortina in Solvent Extraction Applications, International Solvent Extraction Conference, Cape Town, South Africa, Ed. P. A. South African Institute of Mininig and Metallurgy, Marshalltown, 506-511, 2002. 

An important goal in many solvent extraction applications is the purification of the desired solute i vis-k-vis another solute j present in the feed. One could employ various separation indices to determine the extent of purification achieved. If we employ the definition of separation factor ay between the extract phase (/ = E) and the feed phase (/ = j), then... 

Increasing interest in volatile chelating agents and derived complexes for use in the separation of metals by distillation or gas chromatography, oltratrace analysis of metals, vapour deposition work, solvent extraction applications, etc., has assured a steady flow of publications centred around fluorinated / -diketones. The new polyfluorinated chelating agents (29),... 

G. M. Ritcey and A. W. Ashbtook, Solvent Extraction—Principles and Applications to Process Metallurgy, Part I and II, Elsevier, Amsterdam, the... 

U.S. EPA, Resources Conservation Company B.E.S.T Solvent Extraction Technology Applications Analysis Report, EPA/540/AR-92/079 (1993). 

Suitable organic solvents, such as ether, benzene, naphtha and the like, are more soluble than in water. This makes it possible to separate them from other substances which may accompany them in the water solution but which are not soluble in the solvents employed. Hence, one application of solvent extraction is the analytical determination of unsaponifiable oils and waxes in admixture with fatty material by submitting the mixture to vigorous saponification with alcoholic potash or, if necessary, sodium ethylate, and to dilute the product with water and extract with petroleum ether. The soaps remain in the aqueous solution while the unsaponifiable oils and waxes dissolved in the ether. The addition of a salt to an aqueous solution prior to extraction is sometimes practiced in some processes. In older processes, SOj is employed in the separation of aromatic and highly saturated hydrocarbons, taking advantage of the much greater solubility of the solubility of the aromatics and... 

Section A The following references are recommended for more in-depth readings on absorption and solvent extraction theory, design principles, and practical applications. 

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. 

Cupferron (ammonium salt of N-nitroso-A -phenylhydroxylamine). The reagent is used in cold aqueous solution (about 6 per cent). Metal cupferrates are soluble in diethyl ether and in chloroform, and so the reagent finds wide application in solvent-extraction separation schemes. Thus Fe(III), Ti, and Cu may be extracted from 1.2 M HC1 solution by chloroform numerous other elements may be extracted largely in acidic solution. 

The number of reported applications to analytical determinations at the trace level appear to be few, probably the best known being the determination of beryllium in various samples. The method generally involves the formation of the volatile beryllium trifluoroacetylacetonate chelate, its solvent extraction into benzene with subsequent separation and analysis by gas chromatography..61... 

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