Separation chemistry

E. P. Horwitz and W. Schulz, ia L. CeciUe, M. Casarci, and L. PietrieUi, eds.. New Separation Chemistry Techniquesfor Radioactive Waste and Other... 

S. Ahuja, Chromatography and Separation Chemistry Advances and Developments, ACS, Washington DC, 1986. ISBN 0841209537. 

Although, MediChem is a biosecurity products manufacturer, its biotechnology-based R D capabilities are worth mentioning here. The attended markets include Medical, Laboratory, Veterinary, and Environmental sectors. Medicinal chemistry services and drug discovery form the basis of the company, though their capabilities might be applied in a broader range of sectors. These capabilities comprise the areas of Proteomics, Combinatorial and Computational Chemistry, Medicinal Chemistry, Enzymes, Process Development, Analytical and Separations Chemistry, Chemical Synthesis and Scale Up. 

Process chemists have long sought to couple reaction and separation chemistry when possible because it is often the separation steps that account for much of the cost of a chemical synthesis (material, labor, time, energy).121 The chromatographic techniques that are so powerful for separation of small quantities of mixtures of organic molecules become less and less attractive as scales of reactions increase. 

For elemental interferences, mass difference between overlapping species is normally too small to be resolvable. An efficient separation chemistry is most commonly the solution, but the utmost care must be exercised to maintain quantitative yields because ion exchange chromatography can produce mass-dependent fractionations as shown for the elution of Ca (Russell and Papanastassiou 1978), Cu and Zn (Marechal et al. 1999 Marechal and Albarede 2002), and Fe (Anbar et al. 2000 Roe et al. 2003). 

As documented in Chapter 5, zeolites are very powerful adsorbents used to separate many products from industrial process steams. In many cases, adsorption is the only separation tool when other conventional separation techniques such as distillation, extraction, membranes, crystallization and absorption are not applicable. For example, adsorption is the only process that can separate a mixture of C10-C14 olefins from a mixture of C10-C14 hydrocarbons. It has also been found that in certain processes, adsorption has many technological and economical advantages over conventional processes. This was seen, for example, when the separation of m-xylene from other Cg-aromatics by the HF-BF3 extraction process was replaced by adsorption using the UOP MX Sorbex process. Although zeolite separations have many advantages, there are some disadvantages such as complexity in the separation chemistry and the need to recover and recycle desorbents. 

Wakui, Y. Matsunaga, H. Suzuki, T. M. Anal. Sci, 1988, 4, 325. Muscatello, A. C. Yarbro, S. L. Marsh, S. F. New Separation Chemistry Techniques for Radioactive Waste and other Specific Applications, Cecille, L. Casarci, M. Pietrelli, L. Eds. Elsevier Science Publishing Amsterdam, 1991 ... 

One primary goal is to conserve selectivity throughout scale-up. This means attempting to use the same separation chemistry in development that will eventually be used in production. This avoids the need to re-optimize in each stage of the scale-up process. It is desirable to use the same support matrix to avoid unforeseen matrix effects causing uimecessary modification of developed procedures. 

Albert K. Online use of NMR detection in separation chemistry. Journal of Chromatography A 703, 123-147, 1995. 

Education to stimulate young researchers, good materials (textbooks, books), good practices (exciting experiences), opportunities of in situ exercises and schools should be offered to them. The Institute of Separation Chemistry of Marcoule (ICSM) is a good example. 

Apostilidos, C., Meester, R., de Koch, L. et al. 1990. The extraction of actinides and other constituents from highly-active waste (HAW) by trialkyl phosphine oxide (TRPO). Technical seminar on new separation chemistry techniques for radioactive waste and other specific applications, Rome (Italy), May 16-18. EUR-13390-EN. 

Rais, J., Griiner, B. 2004. Extraction with metal bis(dicarbollide) anions Metal bis(dicarbollide) extractants and their applications in separation chemistry. In Ion Exchange and Solvent Extraction, A Series of Advances Vol. 17. Marcus, Y., SenGupta, A.K., Marinsky, J.A. Eds. Marcel Dekker, New York, pp. 243-334. 

Actinides, particularly the lighter ones, display multiple oxidation states and complex chemical behavior, which makes their chemistry quite fascinating. Some isotopes of these elements, such as 232Th, 233,235,238 and 239Pu, are important for the nuclear industry due to their utility as fissile/fertile materials. Therefore, the separation chemistry of different oxidation states of Th, U, and Pu need to be reviewed with respect to both basic as well as applied aspects. Some fundamental chemical properties of the lighter actinides, including oxidation states, hydrolysis, and complexation characteristics form the basis of their separation. 

Nash, K. 1994. Separation chemistry for lanthanides and trivalent actinides. In Handbook on the Physics and Chemistry of Rare Earths (Vol. 18, Lanthanides/Actinides Chemistry), eds. K.A. Gschneider, J.L. Eyring, G.R. Choppin, G.H. Lander, pp. 198-238. Elsevier Science B.V., Amsterdam. 

Nash, K., Choppin, G. 1997. Separation chemistry for actinide elements Recent developments and historical perspective. Separation Science and Technology 32(1—4) 255-274. 

Horwitz, E.P., Schulz, W.W. 1990. The TRUEX process A vital tool for disposal of US defense nuclear wastes. Conference on New Separation Chemistry for Radioactive Waste and Other Specific Applications, May, Rome, Italy. 

A large number of such studies have been reported, and these are summarized in Tables 9.3 through 9.5. In this section, we will highlight selected examples to illustrate the separation chemistries and automation approaches used. 

Opportunities remain to develop new or improved separation chemistries, and the engineered solid-phase materials that utilize them, in order to support radioanalyti-cal needs. Selectivity remains a key issue in order to support isolation of particular elements or groups of elements from complex sample matrixes. Selectivity to support determination of TRU actinides in the presence of large excesses of uranium is often required. The engineered form is also significant, as it must enable the separation chemistry to work while providing a robust material that can be used over and over again. 

EXTRACTION WITH METAL BIS(DICARBOLLIDE) ANIONS METAL BIS(DICARBOLLIDE) EXTRACTANTS AND THEIR APPLICATIONS IN SEPARATION CHEMISTRY ]iH Rais and Bohumir Griiner... 

Wai, C. M. (1997) Separation of lanthanides and actinides with ionizable crown ethers, Recent Progress in Actinides Separation Chemistry, Proceedings of the Workshop on Actinides Solution Chemistry, WASC 94, Tokai, Japan, Sept. 1-2, 1994, 81-94. 

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