Extraction diluents

The development of a suitable solvent system is important for successful operation. Solvent systems generally consist of at least the following components extractant, diluent, inorganic salts or acids, and water. The relative optimization of these components yields the best conditions with which to achieve separation. A key factor to success is the choice of the appropriate extractant. Many extractants may be used for REE separation. These may be divided into three groups on the basis of the mechanisms involved. These extractants are tisted in Table 7. 

In the development of solvent extraetion systems, the initial eon-siderations of the chemistry of the system will limit the choiee of extractant, diluent, and modifier. Shake-out tests and a study of extraetion and stripping characteristics will further limit the choiee. Simple graphie eonstruetion of extraction and stripping isotherms will permit the design of a small-seale continuous operation in terms of the number of stages and flow rates. 

The solvent system extractant, diluent, and, if necessary, modifier Equilibrium data extraction and stripping isotherms Kinetic data, as these will govern, to a large extent, the type of contactor required... 

Fig. 12.20 Extractants, diluents, and aqueous feeds for the trivalent 5f-4f ion group separations used in the SANEX processes.

Build a core extraction system choose components such as extractant, diluent, modifier, scrubbing/stripping agents, aqueous-phase conditions, etc. 

Figure 7.23 summarizes the four possible different organizations found in some extractant/diluent solutions. The presence in a given system of any of the four microstructures described here could have profound consequences on its dynamic and kinetic properties. 

Examination of such degraded solvents is difficult from the analytical point of view. In multicomponent extractant-diluent/aqueous phase systems, free radicals are produced by radiolysis of major compounds water, acid, extractant, and diluent. These radicals, after dimerization or coupling with other compounds, are responsible for the formation of several families of compounds. For instance, in the PUREX process, the exposure of the solvent to radiolysis gives rise to a mixture of over 200 secondary products, most of them in trace quantities. 

Blake, C.A., Davis, W., Schmitt, J.M. 1963. Properties of degraded TBP-Amsco solutions and alternative extractant-diluent systems. Nucl. Sci. Eng. 17 626-637. 

Nowak, Z. 1977. Radiolytic degradation of extractant-diluent systems used in the PUREX process. Nukleonika 22 155-171. 

Solute Process" Solvent" (extractant/diluent) Contactor type" Literature... 

A detailed information regarding the distribution of each of the extractants between a given aqueous medium and an organic diluent is essential, not only for knowing the changes from initial to equilibrium values of extractant concentration, but also for understanding the extractant-diluent interaction. 

Sr Sr-87 and Sr-90 C12 BOPPA (2-butyloctyl phenylphosphonic acid), C16 HDPPA (2-hexyldecyl phenylphosphonic acid), C18 ODPPA/HDPPA (2-octyldecyl phenylphosphonic acid), C20 ODPPA (2-octyldecyl phenylphosphonic acid), 2wt% dodecanol (modifier for the extractant), diluent n-dodecane 1 M HCl and extractant at ratio of 1 3 [33,38]... 

A wide variety of the flat-sheet SLM systems have been described in Section 4.2.1. The advantages of the flat-sheet SLM arrangement in the removal of organic compounds from wastewater can be achieved, if lowcost extractants/diluents, such as vegetable oils, are used. However, the energy considerations will probably lead to the preferential application of hollow-fiber SLM system in the industry. On the basis of the laboratory study results, the SLM technology provides an ideal tool for the removal of trace amount of the antibiotics, and potentially even other pharmaceutical products, from wastewaters. This will prevent the exposure of the MOs in the environment to antibiotics, thus eliminating the potential for the selection of microbial strains resistant to the respective antibiotic(s). 

It must also be recognized thet one is seldom working with pare chemicals in these extraction systems. Not only are the aqueous feed streams usually complex mixtures, but the commarcial extractants, diluents, and modifiers are themselves mixtures and contain unknown impurities. Therefore, ench system of interest must be characterized hy experimental investigation. 

Uses Solvent solvent extraction diluent Trade Name Synonyms Orfom SX-1 [Chevron Ph i 11 i ps http //www. cpchem. com] Naphtha, heavy alkylate CAS 64741-65-7 EINECS/ELINCS 265-067-2 UN 1268... 

Extractant Diluent Extractant Concentration Vol. %(M) Nitric Acid Concentration (M) (a) Pu Cone. (M) D Given in Paper D at 1 M Extractant (b) Relative Extract ibility (TBP = 1.0)(c) Reference... 

Basic work is required to study interactions among extractants, diluents, and modifiers. 

Flett, D. S. and West, D. W. 1986. The cobalt-catalysed oxidation of solvent extraction diluents. In Proceedings international solvent extraction conference, vol. II, 3-10. Frankfurt Dechema. 

Ionic liquids have become widely used as solvents for organic reactions, however their use as solvents in extraction systems seems much promising. Separation with imidazolium ILs is best described and broadly investigated. In most cases ILs replace typical solvent extraction diluents. The most frequently applied are l-alkyl-3-methylimidazolium hexafluorophosphate [CnmimJpFe], tetrafluoroborate [Cnmim][BF4] and bis(trifluoromethyl-sulphonyl)imide [Cnmim][N(S02CF3)2] (anion also abbreviated as [Tf2N]) (Table 2). 

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