Extractants ion exchange

However, the quantity of Pa produced in this manner is much less than the amount (more than 100 g) that has been isolated from the natural source. The methods for the recovery of protactinium include coprecipitation, solvent extraction, ion exchange, and volatility procedures. AH of these, however, are rendered difficult by the extreme tendency of protactinium(V) to form polymeric coUoidal particles composed of ionic species. These caimot be removed from aqueous media by solvent extraction losses may occur by adsorption to containers and protactinium may be adsorbed by any precipitate present. 

The wastes from uranium and plutonium processing of the reactor fuel usually contain the neptunium. Precipitation, solvent extraction, ion exchange, and volatihty procedures (see Diffusion separation methods) can be used to isolate and purify the neptunium. 

Because of the technical importance of solvent extraction, ion-exchange and precipitation processes for the actinides, a major part of their coordination chemistry has been concerned with aqueous solutions, particularly that involving uranium. It is, however, evident that the actinides as a whole have a much stronger tendency to form complexes than the lanthanides and, as a result of the wider range of available oxidation states, their coordination chemistry is more varied. 

A knowledge of stability constant values is of considerable importance in analytical chemistry, since they provide information about the concentrations of the various complexes formed by a metal in specified equilibrium mixtures this is invaluable in the study of complexometry, and of various analytical separation procedures such as solvent extraction, ion exchange, and chromatography.2,3... 

Figure 2.5 Possible technological solutions to bioprocess problems a) Fed-batch culture b) Continuous product removal (eg dialysis, vacuum fermentation, solvent extraction, ion exchange etc) c) Two-phase system combined with extractive fermentation (liquid-impelled loop reactor) d) Continuous culture, internal multi-stage reactor e) Continuous culture, dual-stream multi-stage reactor f) Continuous culture with biomass feedback (cell recycling). (See text for further details).

The caprolactam obtained must meet die specifications of permanganate number, volatile bases, hazen color, UV transmittance, solidification point, and turbidity in order to be used for repolymerization alone or in combination witii virgin CL.5 Reported CL purification methods include recrystallization, solvent extraction, and fractional distillation. One solvent extraction technique involves membrane solvent extraction. Ion exchange resins have been shown to be effective in the purification of aqueous caprolactam solutions. In one such process,... 

Chromatography including extraction, ion exchange, adsorption Distillation, volatilization Electrolysis, electrodeposition... 

Extraction of a selected metal by applying solvent extraction, ion exchange, electrolysis, or gaseous reduction. 

Several methods have been used to separate the lanthanides chemically solvent extraction, ion exchange chromatography, HPLC using Q-hydroxyisobutyric acid and, in limited cases, selective reduction of a particular metal cation.40-43 The use of di(2-ethylhexyl)orthophosphoric acid (HDEHP) for the separation of various rare-earth elements via solvent extraction has also been reported.44 16 This separation method is based on the strong tendency of Ln3+ ions to form complexes with various anions (i.e., Cl- or N03 ) and their wide range of affinities for com-plexation to dialkyl orthophosphoric acid. When the HDEHP is attached to a solid phase resin, the lanthanides can be selected with various concentrations of acid in order of size, with the smallest ion being the most highly retained. 

Element Direct Chelation- extraction Ion exchange Ion exchange... 

Tanimizu M, Asada Y, Hirata T (2002) Absolute isotopic composition and atomic weight of commercial zinc using inductively coupled plasma mass spectrometry. Anal Chem 74 5814-5819 Van der Walt TN, Strelow FWE, Verheij R (1985) The influence of crosslinkage on the distribution coefficients and anion exchange behavior of some elements in hydrochloric acid. Solvent Extract Ion Exchange 3 723-740... 

Purification and separation—solvent extraction, ion exchange, cementation, adsorption, liquid membranes, reverse osmosis, etc. 

Finally, when ultratrace determinations are being performed it is often necessary to preconcentrate the sample or separate the analyte of interest from the matrix. The most commonly employed methods for preconcentration and separation of water samples include evaporation, chelation, coprecipitation, extraction, ion-exchange, chromatography, and electrochemistry. The procedure adopted will depend on the analyte, the form in which it exists, and the sample matrix. 

Separation of niobium from tantalum and impurity metals is the most important step in its extraction from the ore. It may be achieved by several methods that include solvent extraction, ion exchange, fractional crystallization, fractional sublimation, and other techniques. Solvent extraction is apphed mostly in several large-scale commercial processes. Although the classical fractional crystalhzation method forms effective separation, it is a tedious... 

At trace levels, polonium can be separated effectively by solvent extraction, ion exchange, paper chromatography, and other techniques. Diisopropyl ketone, di-n-octylamine, and tri-n-butylphosphate are suitable solvents for extraction. Trace amounts of polonium in solutions or sohd mixtures containing no other emitters can be determined by measuring its alpha activity. 

Praesodymium may be recovered from its minerals monazite and bastana-site. The didymia extract of rare earth minerals is a mixture of praesodymia and neodymia, primarily oxides of praesodymium and neodymium. Several methods are known for isolation of rare earths. These are applicable to all rare earths including praesodymium. They include solvent extractions, ion-exchange, and fractional crystallization. While the first two methods form easy and rapid separation of rare earth metals, fractional crystaUization is more tedious. Extractions and separations of rare earths have been discussed in detail earlier (see Neodymium and Cerium). 

Tc-99, which has a half life of 2.12 x 10 years, can be recovered from nuclear fission waste in kilogram quantities. Solvent extraction, ion exchange, and volatilization processes are employed to separate it from the numerous other fission products. Because of its long half life and its emission of a soft (low energy) beta particle, it can be safely handled in milligram quantities. Almost all chemical studies of the element have been carried out with this isotope. 

Molecular modelling of transition metal complexes (TMC), reproducing characteristic features of their stereochemistry and electronic structure, is in high demand in relation with studies and development of various processes of complex formation with an accent on ion extraction, ion exchange, isotope separation, neutralization of nuclear waste, and also when studying structure and reactivity of metal-containing enzymes. Solving these techno-... 

Thermal water ICP-QMS + USN (PlasmaQuad PQ2) extraction, ion exchange 226 Ra 2 fgml 1 Joannon and Pin49... 

After the coal or coal ash sample has been brought into solution, radiochemical separations may be made by any of several techniques, such as distillation, precipitation, solvent-extraction, ion exchange, etc. 

The long story of the methods for the separation of the individual rare earths may broadly be divided into two main parts a) classical methods b) modern methods. Old-fashioned classical techniques like fractional crystallization, fractional precipitation and fractional thermal decomposition were not only used by the early workers in the past, but still remain as very important methods for economical production of rare earths on commercial scales. Modem methods like solvent (liquid-liquid) extraction, ion exchange or chromatographic (paper, thin layer and gas) techniques have both advantages and limitations. 

Fig. 2 The model of ion extraction/ion exchange for an optode based on a neutral ionophore and a lipophilic cationic dye in relation to the ion-optode response mechanism i+ cation to be extracted, H+ proton, S neutral ionophore, R lipophilic cationic additive, D color-changeable dye. The subscripts o and w represent the organic phase and the water phase, respectively)...

Carboxylic -acids, nitriles, aldehydes, ketones Steam - distillation, solvent extraction, ion exchange chromatography, GC [677]... 

Prior to experiments with SHE, systematic studies with homologues at the tracer scale have to be carried out to select the experimental conditions (solvent extraction, ion exchanger, aqueous media,. ..). On line experiments with short lived isotopes of homologues are also necessary to improve the setup, e.g. to evaluate the eventual impact of edge effects (sorption,. ..). Furthermore, on line experiments involving SHE may preferably be performed with homologues since it is the only way to ensure strictly identical experimental conditions for all present elements. 

The heart of TRU is a battery of nine heavily shielded hot cells housed in a two-story building. Of the nine cells, four contain chemical processing equipment for dissolution, solvent extraction, ion exchange, and precipitation operations. Three... 

If a high-purity acid is desired, further purification steps such as solvent extraction, ion exchange, and carbon decolorization are used. 

Cf244 25 m Cn folta) Cm 44(95 ) containing small amounts of Heavier Cm Isotopes Recoil Extraction Ion exchange... 

There are four widely used methods for preconcentrating trace metals from water, namely evaporation, chelation—solvent extraction, ion-exchange and coprecipitation. 

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