Solvent extraction reagents

Although phosphine [7803-51-2] was discovered over 200 years ago ia 1783 by the French chemist Gingembre, derivatives of this toxic and pyrophoric gas were not manufactured on an industrial scale until the mid- to late 1970s. Commercial production was only possible after the development of practical, economic processes for phosphine manufacture which were patented in 1961 (1) and 1962 (2). This article describes both of these processes briefly but more focus is given to the preparation of a number of novel phosphine derivatives used in a wide variety of important commercial appHcations, for example, as flame retardants (qv), flotation collectors, biocides, solvent extraction reagents, phase-transfer catalysts, and uv photoinitiators. 

Solvent Extraction Reagents. Solvent extraction is a solution purification process that is used extensively in the metallurgical and chemical industries. Both inorganic (34,35) and organic (36) solutes are recovered. The large commercial uses of phosphine derivatives in this area involve the separation of cobalt [7440-48-4] from nickel [7440-02-0] and the recovery of acetic acid [61-19-7] and uranium [7440-61-1]. 

In this section, we describe three simple cases of rates and mechanisms that have been found suitable for the interpretation of extraction kinetic processes in kinetic regimes. These simple cases deal with the exuaction reaction of a monovalent metal cation (solvation water molecules are omitted in the notation) with a weakly acidic solvent extraction reagent, BH. The overall extraction reaction is... 

Perhaps the area of environmental pollution most pertinent to solvent extraction processing is that of water pollution and, consequently, the toxicity of solvent extraction reagents to aquatic life then become important. Thus, the primary consideration in the development of water quality criteria for these reagents is to determine their toxicity toward fish and their biodegradability [70]. 

Ashbrook, A. W. Commercial chelating solvent extraction reagents. 1. o-Hy-droxyoximes Purification and isomer separation/extraction. Metallurgy Division, Mines Branch, Dept. Energy, Mines and Resources, Canada, Report EMA 73-10, 1973. 

McDowell, W. J., Shoun, R. R., An evaluation of crown compounds as solvent extraction reagents. Proc. ISEC 77,1,95-97,1977. 

McDowell, W. J., Crown ethers as solvent extraction reagents Where do we stand, Sep. Sci. Technol, 23,1251-1268,1988. 

Among ion exchange separation methods for transuranics, strong base anion exchange in hydrochloric and nitric acids is important (Keder, 1962 Keder et al., 1960 Horowitz et al., 1990 Chu, 1971 Wong, 1971 Diamond et al., 1954 Korkisch, 1989). Among solvent extraction reagents for transuranics, thenoyltrifluoroacetone (TTA) and trioctylamine (TOA) are important (Keder, 1962 Chieco et al., 1990). 

Precipitation of cobalt as sulfide is done in ammoniacal nickel matte leaching. From sulfate or sulfate/chloride solutions, cobalt is nowadays normally removed by using solvent extraction [46]. Phosphine-based solvent extraction reagents such as di-2-ethylhexylphosphoric acid (D2EHPA) are used to extract cobalt from nickel sulfate solutions. From pure chloride electrolytes, solvent extraction is done with a tertiary amine such as tri-isooctylamine. 

Source C. F, Coleman et al., Amine Salts as Solvent Extraction Reagents for Uranium and Other Metals, PICG(2) 28 278 (1958). 

Van der Zeuw,A.J. and R.Kok. "Ideas and practice in the design of solvent extractant reagents". (Proceedings of the Inter.Solvent Extraction Conf., 1SEC 77, Canada, 1977). 

Neutral extractants constitute the third important class of solvent extraction reagents for the rare-earth elements. Since they have no charge, neutral extractants only extract neutral complexes or charge-balanced ion pairs. They also tend to extract ion-paired acid molecules such as HNO3. Solvating extractants may be dissolved in an organic diluent, or they may be the organic diluent itself (e.g., diethylether, methylisobutylketone, tributyl-phosphate). Phase transfer is accomplished by solvation of the complex by the extractant, and a typical equilibrium can be written as... 

Coleman, C. F. Amine salts as solvent extraction reagents for uranium and other metals. Proc. 2nd Int. Conf. on the Peaceful Uses of Atomic Energy, 1958, Paper 510. 

In spite of the change in demands on selectivity there does not seem to be a need currently to produce new solvent extraction reagents, with the existing range producing sufficient versatility to remove the metals singly or in combination. 

Kordosky, G. A. 2003. Copper SX circuit design and operation current advances and future possibilities. In Proceedings ALTA copper 2003. Melbourne ALTA Metallurgical Services. Kordosky, G. and Vimig, M. 2003. Equilibrium modifiers in copper solvent extraction reagents friend or foe In Hydrometallurgy 2003, vol. 1, Leaching and solution purification, eds. 

Kordosky, G. A., Olafson, S. M., Lewis, R. G., and Defner, V. L. 1987. A state-of-the-art discussion on the solvent extraction reagents used for the recovery of copper from dilute sulfuric acid solutions. Sep. Sci. Tech. 22 215-232. 

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