Fractional extraction, process

He, P.J., Jiao, R.Z., Zhu, Y.J. 1996. HEHEHP fractional extraction process with three outlets for separation of Am from rare earths. Nuclear Science and Techniques 7(3) 161-165. 

A dual-solvent fractional extraction process can provide a powerful separation scheme, as indicated by the examples given above, and some authors suggest that fractional extraction is not utilized as much as it could be. In many cases, instead of using full fractional extraction, standard extraction is used to recover solute from a crude feed and if the solvent-to-feed ratio is less than 1.0, concentrate the solute in a smaller solutebearing stream. Another operation such as crystallization, adsorption, or process chromatography is then used downstream for solute purification. Perhaps fractional extraction schemes should be evaluated more often as an alternative processing scheme that may have advantages. 

Edeleanu process An extraction process utilizing liquid sulphur dioxide for the removal of aromatic hydrocarbons and polar molecules from petroleum fractions. 

The physical process of Hquid—Hquid extraction separates a dissolved component from its solvent by transfer to a second solvent, immiscible with the first but having a higher affinity for the transferred component. The latter is sometimes called the consolute component. Liquid—Hquid extraction can purify a consolute component with respect to dissolved components which are not soluble in the second solvent, and often the extract solution contains a higher concentration of the consolute component than the initial solution. In the process of fractional extraction, two or more consolute components can be extracted and also separated if these have different distribution ratios between the two solvents. 

Fractional extraction has been used in many processes for the purification and isolation of antibiotics from antibiotic complexes or isomers. A 2-propanol—chloroform mixture and an aqueous disodium phosphate buffet solution are the solvents (243). A reciprocating-plate column is employed for the extraction process (154). 

The early developments of solvent processing were concerned with the lubricating oil end of the cmde. Solvent extraction processes are appHed to many usefiil separations in the purification of gasoline, kerosene, diesel fuel, and other oils. In addition, solvent extraction can replace fractionation in many separation processes in the refinery. For example, propane deasphalting (Fig. 7) has replaced, to some extent, vacuum distillation as a means of removing asphalt from reduced cmde oils. 

The feed to a liquid-liquid extraction process is the solution that contains the components to be separated. The major liquid component in the feed can be referred to as the feed solvent. Minor components in solution are often referred to as solutes. The extraction solvent, or just plain solvent, is the immiscible liquid added to a process for the purpose of extracting a solute or solutes from the feed. The extraction-solvent phase leaving a liquid-liquid contactor is called the extract. The raffinate is the liquid phase left from the feed after being contacted by the second phase. A wash solvent is a hquid added to a liquid-liquid fractionation process to wash or enrich the purity of a solute in the extract phase. 

Fractionation. The process by which components are extracted firm bacterial eells or from the medium in whieh the baeteria are grown and obtained in a purified form. The polysaccharide antigens of Neisseria meningitidis are separated from the bacterial cells by treatment with hexadecyltrimethylammonium bromide and those of Streptococcus pneumoniae with ethanol. The purity of an extracted material may be improved by resolubilization in a suitable solvent and precipitation. After purification, a component may be dried to a powder, stored indefinitely and, as required, incorporated into a vaccine in precisely weighed amounts at the blending stage. 

These opposing tendencies may defeat the purpose of the fractional precipitation process. The fractional precipitation of crystalline polymers such as nitrocellulose, cellulose acetate, high-melting polyamides, and polyvinylidene chloride consequently is notoriously inefficient, unless conditions are so chosen as to avoid the separation of the polymer in semicrystalline form. Intermediate fractions removed in the course of fractional precipitation may even exceed in molecular weight those removed earlier. Separation by fractional extraction should be more appropriate for crystalline polymers inasmuch as both equilibrium solubility and rate of solution favor dissolution of the components of lowest molecular weight remaining in the sample. 

Several models relating the isotopic effects of U-series disequilibria to the timescales of the melting process have now been proposed (e.g., McKenzie 1985 Williams and Gill 1989 Spiegelman and Elliott 1993 Qin 1992 Iwamori 1994 Richardson and McKenzie 1994). While these models differ mainly in their treatment of the melt extraction process (i.e., reactive porous flow vs near fractional melting), because they incorporate the effect... 

Many analytical techniques are in use for the qualitative and quantitative evaluation of monomers and oligomers extracted from PA6 (GC, differential refrac-tometry, IR, PC, SEC, HPLC, RPLC, etc.). FTIR has been used for quantitative analysis of caprolactam oligomer content (extract %) in polyamide-6 [113], The method, which involves a 3h extraction in boiling methanol, is suitable for process control and plant environment. Kolnaar [114] has used FTIR characterisation of fractional extracts with pentane, hexane, and heptane of HDPE for blow moulding applications. Vinyl acetate in packaging film has similarly been determined by quantitative FUR. 

Inhibition of ferrochelatase in the heme pathway causes accumulation of protoporphyrin in erythrocytes (CDC 1985). Most protoporphyrin in erythrocytes (about 90%) exists as zinc protoporphyrin (ZnPP). This fraction is preferentially measured by hematofluorometers. Extraction methods measure all the protoporphyrin present, but strip the zinc from the ZnPP during the extraction process. For this reason,... 

CAA [Cuprous ammonium acetate] A general process for separating alkenes, di-alkenes, and alkynes from each other by extraction of their cuprous complexes from aqueous cuprous ammonium acetate into an organic solvent. Exxon used it for separating C4 fractions containing low concentrations of butadiene. The liquid-liquid extraction processes for butadiene have all been replaced by extractive distillation processes. 

Hojilla-Evangelista, M.P., Johnson, L.A., and Myers, D.J. 1992. Sequential extraction processing of flaked whole com Alternative com fractionation technology for ethanol production. Cereal... 

Dual nickel, 9 820—821 Dual-pressure processes, in nitric acid production, 17 175, 177, 179 Dual-solvent fractional extraction, 10 760 Dual Ziegler catalysts, for LLDPE production, 20 191 Dubinin-Radushkevich adsorption isotherm, 1 626, 627 Dubnium (Db), l 492t Ductile (nodular) iron, 14 522 Ductile brittle transition temperature (DBTT), 13 487 Ductile cast iron, 22 518—519 Ductile fracture, as failure mechanism, 26 983 Ductile iron... 

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