Rhenium extraction with

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. 

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). 

A suspension of 3.83 g (5.4 mmol) of mer-trichlorotris(dimethylphenyl-phosphine)rhenium(HI) (or its benzene solvate)1 and 2.48 g (65 mmol) of sodium tetrahydroborate(l —) in 100 mL of absolute ethanol is heated under nitrogen on a steam bath until the orange complex dissolves to give a colorless suspension. The solvent is evaporated under reduced pressure, and the residue is extracted with three 75-mL portions of benzene. The benzene extract is evaporated, and the residue is crystallized from 60 mL of absolute ethanol to give prisms of tris(dimethylphenylphosphine)pentahydrido-rhenium(V) the yield is 2.2 g (67%). Anal. Calcd. for C24H38P3Re C, 47.59 H, 6.32 P, 15.34. Found (checkers values) C, 47.60 H, 6.24 P, 15.51. 

A 1-L two-necked flask, equipped with magnetic stirrer, addition funnel, and condenser surmounted by a nitrogen-flushed tee tube, is charged with 7.30 g (15 mmol) of rhenium(VII) oxide (or 8.68 g of potassium perrhenate), 50 mL of concentrated hydrochloric acid, and 250 mL of absolute ethanol. The solution is stirred and heated to boiling, and a solution of 45 g (170 mmol) of triphenylphosphine in 250 mL of hot ethanol is added. The mixture becomes green immediately, and a precipitate forms even before the addition is complete. The mixture is boiled for 30 min. It is allowed to cool to 55° and is filtered. The lime-green solid product is extracted with 100 mL... 

Many catalysts used in chemical synthesis can be treated in the same way, often the nitrous oxide/acetylene flame is used because of the refractory nature of the elements to be determined. Harrington and Bramstedt [56] have determined rhenium in electro-chemical surface catalysts by stripping the coating with molten potassium hydroxide/ potassium nitrate. This melt was extracted with hydrochloric acid, the residue was fused with sodium peroxide for further rhenium determination. Titanium, being the substrate on which the catalyst was coated, was added to the standards, an air/acetylene flame and 343.3 nm were used for the finish. 

These metals can be extracted from sea water by Chelex-100 and Permutit S 1005 the rare earths and tungsten are completely retained, rhenium only with an efficiency of 90 %. The rare earths are removed from the resins by means of 2 N mineral acids, tungsten and rhenium by 4 N ammonia S6). 

Re(VII) has been separated by extraction with cyclohexanone from various inorganic acids [8]. Rhenium can be extracted from bromide media into CHCI3 as ReOBt4 with dithiol [9]. Nitrotetrazolium chloride has been used for extraction (dichloroethane) of Re from mixed chloride and iodide media [10]. 

H. Koshima, H. Onishi, Separation of rhenium by extraction with crown ethers and flow-injection extraction spectrophotometric determination with Brilliant Green, Anal. Chim. Acta 232 (1990) 287. 

Lead extraction by volatilization through melting. Mass spectrometric analysis uses the surface emission mode of ionization of PbS-NH4N03 from a rhenium filament with Faraday cup collection of ions. Data are not corrected for fractionation effects in the ionization process. 

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... 

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. 

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... 

---