Solvent extraction purification

Solvent extraction—purification of wet-process phosphoric acid is based on preferential extraction of H PO by an organic solvent vs the cationic impurities present in the acid. Because selectivity of acid over anionic impurities is usually not sufficient, precipitation or evaporation steps are included in the purification process for removal. Cmde wet-process acid is typically concentrated and clarified prior to extraction to remove post-precipitated sludge and improve partition of the acid into the solvent. Concentration also partially eliminates fluoride by evaporation of HF and/or SiF. Chemical precipitation of sulfate (as Ba or Ca salts), fluorosiUcates (as Na salt), and arsenic (as sulfides) may also be used as a prepurification step preceding solvent extraction. 

Fig. 4. Schematic diagram of the solvent extraction purification of wet-process phosphoric acid.

Analytical methods for determining disulfoton in environmental samples are reported in Table 6-2. The steps included in the methods are solvent extraction, purification and fractionation, and gas chromatographic analysis. Other analytical techniques, including capillary gas chromatography with mass selective detection (Stan 1989), high-performance liquid chromatography with either mass spectrometric (MS) or MS-MS detection (Betowski and Jones 1988), have been used to determine disulfoton in environmental samples. 

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... 

Nording, M., M. Nichkova, E. Spinnel, et al. 2006. Rapid screening of dioxin-contaminated soil by accelerated solvent extraction/purification followed by immunochemical detection. Anal. Bioanal. Chem. 385 357-366. 

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... 

The principal steps in producing refined thorium compounds from thorium-bearing ores are concentration of thorium minerals, extraction of thorium from concentrates, purification or refining of thorium, and conversion to metal or the thorium compound finally wanted. This section describes the concentration of monazite, the principal source of thorium in the past the extraction of thorium from monazite and the recovery of thorium from leach liquors by solvent extraction. Purification of thorium is described in Sec. 9 and conversion in Sec. 10. 

In summary, a heavy-water-moderated nuclear fission reactor fueled with UO3 or U3O8 can be operated with natural uranium that is produced by means of a standard uranium wet chemistry solvent extraction purification process. Additionally, given the neutronic properties of other elements, it is expected that similar reactors can be operated with uranium carbide, uranium tetrafluoride, and uranium-beryllium alloys. 

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