Industrial extractants crown ether

Tetraphenylborate (TPB) was used at Savannah River to recover cesium from alkaline solutions, but attempts to treat HLW tanks with TPB resulted in the production of benzene (a TPB decomposition product) at levels that did not permit the safe operation of the process.8 Crown ethers and dicarbollides were proposed as extractants to remove cesium from acidic HAW, but these compounds are not selective enough to allow cesium to be removed from solutions containing large amounts of nitric acid or sodium nitrate.9 Dicarbollides were used in Russia at industrial scale to recover cesium from HAW, but the removal of cesium was only possible after partial denitration of the liquid waste.10... 

Dual-host approaches have also been used to good effect for CsN03 extraction. Nitrate is a common anion found upon nitric acid extraction of 137Cs+ in the nuclear industry. Cs+ is conveniently com plexed by a large crown ether such as tetrabenzo[24] crown-8 while simple tripodal amide hosts of type 5.31 (where R is a long alkyl group to impart lipophilicity) are effective at binding N03 . Extraction efficiency of Cs+ from water into 1,2-dichloroethane was found to be enhanced by a factor of up to 4.4 in the presence of the anion host.28... 

Baitsch RA, Chun S, Dzyuba SV (2002) Ionic liquids as novel dUuenfs for solvenf extraction of metal salts by crown ethers. In Rogers RD, Seddon KR (eds) Ionic liquids industrial applications for green chemistry. American Chemical Society, Washington, DC... 

Figure 25 shows a specific example of extraction of furfural using a hydrocarbon solvent. Sharma (1988) has considered several other examples of reactions which would profit from introduction of an additional phase. Sharma (1988) has also provided several examples of liquid-liquid reactions of industrial interest which could benefit from the addition of substances such as quaternary ammonium and phosphonium salts, crown ethers and trialkyl amines, which function as phase transfer catalysts, significantly enhancing the reaction rates and in some cases improving the reaction selectivity. 

Extractants from liquid-liquid systems such as HDEHP [di(2-ethylhexyl) or-thophosphoric acid] and CMPO/TBP (carbamoylmethylphosphine oxide derivative and tri-n-butyl phosphate) are supported on the solid material, as are newer ion-selective crown ethers (such as 4,4 (50-di-f-butylcyclohexano 18-crown-6 for Sr). Various SPE columns available commercially from Eichrom Industries have proven useful to separate radionuclides such as Sr, Tc, Ra, Ni, Pb, Am, Pu, Th, U, Np, Cm, and lanthanides. These columns usually are small (approximately 2 ml resin bed). Their effectiveness depends on their specificity for the ion that includes the radionuclide of interest, but the small volume limits the amount (i.e., less than 10 mg) of carrier that can be retained. The specificity of each product shows promise for development of procedures for sequential radionuclide analyses from a single sample aliquot. (Burnett et al. 1997, Horowitz et al. 1998)... 

In the case of separation of Ni ions, 8-hydroxyquinoline and the industrial extractant Kelex 100 were used in water/SDS/butanol or pentanol/dodecane microemulsions. The kinetic and mechanistic formalisms in the extraction process were worked out by Tondre and coworkers [144,147]. To understand the coupled transport, crown ether or Kelex 100 were used by Derouiche and Tondre [143]. In several instances of metal ion transport, synergistic effects were observed the results were explained on the basis of carrier diffusion in the stagnant layers. 

In the case of clathrates and adducts described earlier, the so-called compounds formed are separated by crystallization. Although handling of slurry/soUd in an industrial context is sometimes not desired, the solid phase conclusively demonstrates the nature of the non-stoichiometric dissociable host-guest compound formed. That macrocyclic ethers form reasonably stable complexes has also been demonstrated by the isolation of the complexes as crystals (Pedersen, 1988). That a particular crown ether having a certain cavity diameter will prefer a certain alkali metal cation having a certain diameter is illustrated in Table 4.1.12 for the extraction of a particular alkali metal picrate salt from water into methylene chloride containing the crown ether. From the table it appears that potassium picrate is most effl-ciently extracted by 18-crown-6 compared to other crown ethers, since the cavity size of 18-crown-6 is quite close to that of (see Table 4.1.11). 

Zr. Used in explosives, textile and leather industries. Ion-pairing agent in extraction-photometric detn. of Cu, Ag, Li, K, Na using crown ethers. Yellow leaflets (H2O), colourless cryst. (ligroin or cone. HCl). Mod. sol. H2C). Mp 122.5°. 0.33 (25°). Metastable forms, Mp 101°... 

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