Fluorine extraction

Although the existence of fluorine had been known since early in the nineteenth century, no one was able to devise a chemical reaction to extract the free element from its compounds. Finally, in 1886, Henri Moissan succeeded in preparing p2(g) by an electrolysis reaction. Moissan s method, which is still the only important commercial method for fluorine extraction, involves the... 

Production Technology. Processes for extraction of P2O3 from phosphate rock by sulfuric acid vary widely, but all produce a phosphoric acid—calcium sulfate slurry that requires soHds-Hquid separation (usually by filtration (qv)), countercurrent washing of the soHds to improve P2O3 recovery, and concentration of the acid. Volatilized fluorine compounds are scmbbed and calcium sulfate is disposed of in a variety of ways. 

Significant amounts of cryoHte are also recovered from waste material ia the manufacture of aluminum. The carbon lining of the electrolysis ceUs, which may contain 10—30% by weight of cryoHte, is extracted with sodium hydroxide or sodium carbonate solution and the cryoHte precipitated with carbon dioxide (28). Gases from operating ceUs containing HF, CO2, and fluorine-containing dusts may be used for the carbonation (29). 

Chemical precipitation and solvent extraction are the main methods of purifying wet-process acid, although other techniques such as crystallisa tion (8) and ion exchange (qv) have also been used. In the production of sodium phosphates, almost all wet-process acid impurities can be induced to precipitate as the acid is neutralized with sodium carbonate or sodium hydroxide. The main exception, sulfate, can be precipitated as calcium or barium sulfate. Most fluorine and siUca can be removed with the sulfate filter cake as sodium fluorosiUcate, Na2SiFg, by the addition of sodium ion and control of the Si/F ratio in the process. 

The optimal temperature range for the fluorination process was found to be about 230-290°C. The resulting cake was leached with water. The prepared solution was separated from the precipitate by regular filtration and the separated insoluble precipitate was identified as lithium fluoride, LiF. The solution contained up to 90 g/1 Ta205. Solution acidity was relatively low, with a typical pH = 3-4, and was suitable for the precipitation of potassium heptafluorotantalate, K2TaF7, tantalum hydroxide or further purification by liquid-liquid extraction after appropriate adjustment of the solution acidity [113]. 

Another way of applying the selective extraction method directly on the initial solution is to produce a solution of low acidity. This can be achieved by using the hydrofluoride method for fluorination and decomposition of raw material. As was discussed in Paragraph 8.2.2, the raw material is fluorinated by molten ammonium hydrofluoride yielding soluble complex fluorides of ammonium and tantalum or niobium. The cake obtained following fluorination is dissolved in water, leading to a solution of low initial acidity that is related for the most part to the partial hydrolysis of complex fluoride compounds. The acidity of the solution is first adjusted to ensure selective tantalum extraction. In the second step, the acidity of the raffinate is increased to provide the necessary conditions for niobium extraction. 

Modem refining technology uses tantalum and niobium fluoride compounds, and includes fluorination of raw material, separation and purification of tantalum and niobium by liquid-liquid extraction from such fluoride solutions. Preparation of additional products and by-products is also related to the treatment of fluoride solutions oxide production is based on the hydrolysis of tantalum and niobium fluorides into hydroxides production of potassium fluorotantalate (K - salt) requires the precipitation of fine crystals and finishing avoiding hydrolysis. Tantalum metal production is related to the chemistry of fluoride melts and is performed by sodium reduction of fluoride melts. Thus, the refining technology of tantalum and niobium involves work with tantalum and niobium fluoride compounds in solid, dissolved and molten states. 

Other fluorinated derivatives of acetylacetone are trifluoroacetylacetone (CF3COCH2COCH3) and hexafluoroacetylacetone (CF3COCH2COCF3), which form stable volatile chelates with aluminium, beryllium, chromium(III) and a number of other metal ions. These reagents have consequently been used for the solvent extraction of such metal ions, with subsequent separation and analysis by gas chromatography [see Section 9.2(2)]. 

An overview is presented of plutonium process chemistry at Rocky Flats and of research in progress to improve plutonium processing operations or to develop new processes. Both pyrochemical and aqueous methods are used to process plutonium metal scrap, oxide, and other residues. The pyrochemical processes currently in production include electrorefining, fluorination, hydriding, molten salt extraction, calcination, and reduction operations. Aqueous processing and waste treatment methods involve nitric acid dissolution, ion exchange, solvent extraction, and precipitation techniques. 

We have already described the refining of copper and the electrolytic extraction of aluminum, magnesium, and fluorine. Another important industrial application of electrolysis is the production of sodium metal by the Downs process, the electrolysis of molten rock salt (Fig. 12.15) ... 

The metabolism of pentafluoro-, pentachloro-, and pentabromophenol by Mycobacterium fortuitum strain CG-2 is initiated by a monooxygenase that carries out hydroxylation at the para position (Uotila et al. 1992). Cell extracts of Rhodococcus chiorophenoiicus Mycobacterium chlorophenolicunt) strain PCP-1 in the presence of a reductant transformed tetrafluoro-, tetrachloro-, and tetrabromohydroquinone to 1,2,4-trihydroxybenzene by reactions that clearly involve both hydrolytic and reductive loss of fluorine (Uotila et al. 1995). 

Freshly extracted degassing crude oil can be defoamed with fluorinated nor-bomylsiloxanes [171]. The compounds are highly effective and show a broad area of application for defoaming degassing crude oils of different origins. The compounds can be used in concentrations as small as 20 ppm. 

R. Berger, H. F. Fink, G. Koemer, J. Langner, and C. Weitemeyer. Use of fluorinated norbomylsiloxanes for defoaming freshly extracted degassing crude oil. Patent US 4626378, 1986. 

Chlorination and fluorination, as processes of metal extraction, are important not only because they are effective in liberating metal values from refractory ores but also because the chlorides and the fluorides are excellent interprocess intermediates for metal reduction. The chlorides have the additional advantage of being compounds which may be made very pure by certain additional processes. 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

The use of plant extracts for insect control dates into antiquity the use of Paris green as an insecticide for control of the Colorado potato beetle in 1867 probably marks the beginning of the modern era of chemical control of injurious insects. The development of lead arsenate followed later in the nineteenth century for gypsy moth control. The commercial production of nicotine insecticides, the production of calcium arsenate at the time of the first world war, and the use of fluorine, arsenical, and cyanide compounds, as well as other inorganic chemicals for insect control, were important steps in pest control. These chemicals were applied largely by dilute high pressure sprays or dusts. 

Schroder, H.E (2003). Determination of fluorinated surfactants and their metabolites in sewage sludge samples by liquid chromatography with mass spectrometry and tandem mass spectrometry after pressurized liquid extraction and separation on fluorine-modified reversed-phase sorbents. J. Chromatogr. A 1020(1), 131-151. 

Some of the disadvantages of the Stille reaction, e. g. the low reactivity of some substrates, separation difficulties in chromatography, and the toxicity of tin compounds, have been ameliorated by recent efforts to improve the procedure. Curran has, in a series of papers, reported the development of the concept of fluorous chemistry, in which the special solubility properties of perfluorinated or partly fluorinated reagents and solvents are put to good use [45]. In short, fluorinated solvents are well known for their insolubility in standard organic solvents or water. If a compound contains a sufficient number of fluorine atoms it will partition to the fluorous phase, if such a phase is present. An extraction procedure would thus give rise to a three-phase solution enabling ready separation of fluorinated from nonfluorinated compounds. 

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