Solvent solution purification

Solvent Extraction Reagents. Solvent extraction is a solution purification process that is used extensively in the metallurgical and chemical industries. Both inorganic (34,35) and organic (36) solutes are recovered. The large commercial uses of phosphine derivatives in this area involve the separation of cobalt [7440-48-4] from nickel [7440-02-0] and the recovery of acetic acid [61-19-7] and uranium [7440-61-1]. 

A compound whose solubility increases with temperature can be purified by recrystallization. The impure solid is dissolved in a minimum volume of hot water. The hot solution is filtered to remove insoluble impurities, and then the solution is cooled in an ice bath. The solubility of the compound decreases as the temperature drops, causing the substance to precipitate from solution. Soluble impurities usually remain in solution. Purification by recrystallization is not restricted to aqueous solutions. An organic solid can be purified by recrystallization from an appropriate organic solvent. 

The parent hexathiaadamantane (185) is obtained preparatively when a solution of formic acid and hydrochloric acid in nitrobenzene is allowed to stand for several weeks in a hydrogen sulfide atmosphere the product which separated is almost insoluble in all common solvents and purification presents a problem. Only large volumes of dimethyl sulfoxide at reflux serve for recrystallization.224 The reaction of thioacetic acid with formic acid in the presence of zinc chloride gives tetramethyl-(186), monomethyl-, dimethyl-and trimethylhexathiaadamantane derivatives (187).225 Other variations include the reaction of thioacetic acid with a /i-diketone,226 and the use of boron trifluoride227 or aluminum chloride as a catalyst.228... 

General Procedure for the Hydroformylation/Carbonyl ene Reaction/O,O-acetal Forma-tion/Dehydration. Synthesis of Chromane Derivatives. A solution of the substrate (1 eq) RhCl(PPh3)3 (1 mol %) and PPh3 (3 mol %) in dry dioxane was heated for 70 h to 120 °C und an atmosphere of CO/H2 (1 1, 100 bar). The crude product was filtered through basic alumina (eluated with MTBE). After evaporation of the solvent further purification by column chromatography (silica, PE/MTBE) furnished the title compounds. 

In the solvent extraction purification of the uranium ore concentrate, TBP is the extractant of choice although, in the past, Butex, diethyl ether and MIBK have also been used for this purpose. The uranium ore concentrate is first dissolved in nitric acid to produce a solution of uranyl nitrate from which insoluble impurities are separated. The consumption of nitric acid in this step will depend upon the nature of the concentrate, as shown in equations (104)-( 109). Many impurities... 

Chiarizia, R., Thiyagarajan, P., Jensen, M.P. et al. 2003. Third phase formation in TBP solvent extraction systems as a result of interaction between reverse micelles. In Leaching and Solution Purification, Vol. 1. Proc. Hydrometallurgy 2003 5th Int. Conf. in Honor of Prof. I. Ritchie. Young, C. A. et al. Eds. The Minerals, Metals and Materials Society, Warrendale, PA, pp. 917-928. 

Titration of electro- Stoichiometric product yield lyte solution to other regardless of mixing ratio no electrolyte solution purification of starting materials required no waste of solvent Dilute solution (< 0.1%) requires excessive water filtration may be difficult 436... 

Equimolar amounts of pyrryl fulgide (62e) and malonitrile were dissolved in dry tetrahydrofuran (THF) 2 equivalent molars of diisopropylamine dissolved in dry THF were added dropwise to this solution. After addition, the mixture was maintained at ambient temperature for 2.5 h and the white precipitate appeared (disalt 30%). The disalt was filtered off and thoroughly dried under vacuum pressure, then dissolved in 1,2-dichloroethane and treated with acetyl chloride for 2 h without exposure to UV light. Removal of the solvent and purification by silica-gel column... 

The process required four steps the loading of the cell, with the CO2 entering from the bottom of the precipitator and bubbling through the liquid solution the washing out of the solvent the purification of the product the depressurization of the vessel. 

Phthalocyanines are tetraaza tetrabenzo analogues of porphyrins. Lanthanide complexes with phthalocyanines are prepared by the condensation of phthalonitrile (4 moles) with a lanthanide salt. The monocomplexes were prepared by heating a 1 4 mixture of lanthanide saltiphthalonitrile at 275°C. The molten solution solidified after an hour and purification of the complex is done by removal of excess phthalonitrile and impurities with organic solvents. Final purification is done by chromatography [85]. The bis complexes are prepared in a similar fashion but with a large excess of phthalonitrile [86]. Mixed ligand... 

Rainwater Coprecipitation with iron hydroxide, radiochemical, ion-exchange and solvent extractive purification, and electrodeposition on steel a-Spectrometry (isotope quantification) 0.02 dpm/Lfor in solution 68% Jiang et al. 1986... 

Solute selectivity. In certain applications, it is important not only to recover a desired solute from the feed, but also to separate it from other solutes present in the feed and thereby achieve a degree of solute purification. The selectivity of a given solvent for solute i compared to solute j is characterized by the separation factor = K,/Kj. Values must be greater than Ofjj = 1.0 to achieve an increase in solute purity (on a solvent-free basis). When solvent blends are used in a commercial process, often it is because the blend provides higher selectivity, and often at the expense of a somewhat lower partition ratio. The degree of purification that can be achieved also depends on the extraction scheme chosen for the process, the amount of extraction solvent, and the number of stages employed. 

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. 

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