Rhenium extraction

L. Rhenus, Rhine) Discovery of rhenium is generally attributed to Noddack, Tacke, and Berg, who announced in 1925 they had detected the element in platinum ore and columbite. They also found the element in gadolinite and molybdenite. By working up 660 kg of molybdenite in 1928 they were able to extract 1 g of rhenium. 

Polymers containing 8-hydroxyquinoline appear to be selective adsorbents for tungsten in alkaline brines (95). In the presence of tartrate and citrate, quinaldic acid [93-10-7] allows the separation of zinc from gallium and indium (96). Either of these compounds can selectively separate lead and zinc from oxide ores as complexes (97). It is also possible to separate by extraction micro quantities of rhenium(VII), using quinoline in basic solution (98). The... 

The discovery of the elements 43 and 75 was reported by Noddack et al. in 1925, just seventy years ago. Although the presence of the element 75, rhenium, was confirmed later, the element 43, masurium, as they named it, could not be extracted from naturally occurring minerals. However, in the cyclotron-irradiated molybdenum deflector, Perrier and Segre found radioactivity ascribed to the element 43. This discovery in 1937 was established firmly on the basis of its chemical properties which were expected from the position between manganese and rhenium in the periodic table. However, ten years later in 1937, the new element was named technetium as the first artificially made element. 

The El source is formed by a tungsten or rhenium filament, an anode, an ion repeller, a magnet, and a series of lenses for extracting, focusing and accelerating the ions formed (Figure 2.2). 

Koide et al. [537] have described a graphite furnace atomic absorption method for the determination of rhenium at picomolar levels in seawater and parts-per-billion levels in marine sediments, based upon the isolation of heptavalent rhenium species upon anion exchange resins. All steps are followed with 186-rhenium as a yield tracer. A crucial part of the procedure is the separation of rhenium from molybdenum, which significantly interferes with the graphite furnace detection when the Mo Re ratio is 2 or greater. The separation is accomplished through an extraction of tetraphenylarsonium perrhenate into chloroform, in which the molybdenum remains in the aqueous phase. 

These include the simplest ion-association systems in which bulky cations and anions are extracted as pairs or aggregates without further coordination by solvent molecules. An example of this type of system is the extraction of manganese or rhenium as permanganate or perrhenate into chloroform by association with the tetraphenylarsonium cation derived from a halide salt... 

Preparation. Rhenium is extracted commonly as a by-product from molybdenum smelter flue dust. The volatile Re207 is collected, converted to NH4Re07 which is reduced in a stream of hydrogen. 

An efficient method has been developed by Pozdnyakov and Spivakov . In alkaline solution pertechnetate, in contrast to perrhenate, is reduced by hydrazine sulfate. After reduction technetiiun is no more extracted by methyl ethyl ketone. The distribution coefficient of technetium is by a factor up to 2500 smaller than that of rhenium. 

Procedure Hydrazin sulfate is added to a mixture of pertechnetate and perrhenate in 3-6 N NaON or KOH until its concentration is about 3 x 10 M. The solution is stirred and, after 10 min, rhenium is extracted by an equal voliune of methyl ethyl ketone. For complete separation of rhenium from technetium the extraction must be repeated 2-3 times. After a twofold extraction 99% of technetium and only 0.8 % of rhenium remain in the aqueous phase. 

The different behavior of technetium and rhenium may arise because Re (VII) is not reduced by xanthic acid to the same oxidation state as Tc (VII). Other suitable extracting solvents are chloroform, 1.1.1-trichloroethane and isopropyl ether. 

Introduction.—The identification of technetium in stars has been confirmed, thus establishing that stellar synthesis of this element is occurring. Recent developments in the analytical chemistries of technetium and rhenium have been reviewed, as has the extraction of rhenium from hydrochloric acid solutions a text describing the analytical chemistry of technetium and other man-made elements has been published. ... 

Rhenium can be analyzed by various instrumental techniques that include flame-AA, ICP-AES, ICP-MS, as well as x-ray and neutron activation methods. For flame-AA analysis the metal, its oxide, or other insoluble salts are dissolved in nitric acid or nitric-sulfuric acids, diluted, and aspirated directly into nitrous oxide-acetylene flame. Alternatively, rhenium is chelated with 8-hydroxy quinoline, extracted with methylisobutyl ketone and measured by flame-AA using nitrous oxide-acetylene flame. 

The uranium is separated, after dissolving the sample as described for lead, by extraction with tributyl phosphate (TBP) from 4M nitric acid. After the organic phase is scrubbed with 4M nitric acid, the uranium is back-extracted into distilled water and evaporated to dryness. The uranium is loaded on a rhenium filament for analysis by dissolving the purified sample in a small volume of 0.05M nitric acid. 

X-ray absorption spectroscopy has proved the presence of rhenium dioxide within this nanostructure [12]. Extraction of the surfactant with various solvents remained inefficient since either the surfactant persists within the composite or the nanostructure is lost. Calcination at mild temperatures as low as 300-350°C in nitrogen atmosphere leads to a mass loss under these pyrolytic conditions of about 50% with only little loss of the nanostructure. Similar results are obtained when the composite is oxidatively treated in an oxygen plasma for not more than ten minutes. Physisorption measurements on the calcined or plasma treated samples show only very small surface areas, which cannot be assigned to a mesoporous structure. Right now we believe that residual carbon may introduce some pore blocking effects within the nanostructure preventing good access of the inner pore surfaces. 

The origin of the majority of rhenium—rhenium quadruple bonds can be traced directly to the parent Re2Clg anion. Several routes to the octachloro-dirhenate(III) ionic complex have been compared (42). The method of choice is the reaction of trirhenium nonachloride with molten diethylammonium chloride (12). Yields of up to 65% are attainable when the reaction mixture is extracted with hydrochloric acid and the anion is precipitated as the salt of a large cation (i.e., tetrabutylammonium cation). 

Pyrolysis of Et4N[ReH2(CO)4] at 250°C in n-tetradecane yields a mixture of polynuclear products from which two carbidocarbonyl clusters of rhenium have been isolated. Extraction of the pyrolysis product mixture with tetrahydrofuran results in a residue of (E N ReyCfCO iJ, 34 (76), and a solution from which may be isolated (Et4N)2[Re8C(CO)24], 35, (77), the structures of which are shown in Figs. 42 and 43. Both are based on an... 

Yatsenko, N. A. Pal ant, A. A. Micelle formation in liquid-liquid extraction of tungsten(VI), molybdenum(VI), and rhenium(VII) by diisododecylamine, dioctylamine, and trioc-tylamine from sulfuric acid solutions, Russ. J. Inorg. Chem. 45 (2000) 1460-1464. 

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