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Molten salts salt purification

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. [Pg.172]

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. [Pg.175]

Other catalyst systems such as iron V2O5-P2O5 over silica alumina are used for the oxidation. In the Monsanto process (Figure 6-4), n-butane and air are fed to a multitube fixed-bed reactor, which is cooled with molten salt. The catalyst used is a proprietary modified vanadium oxide. The exit gas stream is cooled, and crude maleic anhydride is absorbed then recovered from the solvent in the stripper. Maleic anhydride is further purified using a proprietary solvent purification system. ... [Pg.176]

The following pages will describe several examples of pyrochemical processing as applied to the recycle of plutonium, and will briefly review the fundamental chemistry of these processes. We shall review the conversion of plutonium oxide to plutonium metal by the direct oxide reduction process (DOR),the removal of americium from metallic plutonium by molten salt extraction (MSE), and the purification of metallic... [Pg.378]

Figure 10 shows in graphic form the utility of molten salt extractions for americium removal in one, two, and three stage extractions for various salt-to-metal extraction feeds. This graph demonstrates the impressive power of molten salt extraction systems for purification of plutonium from americium and related rare earth elements. [Pg.389]

Electrorefining has been used for the purification of many common as well as reactive metals. It has been seen that the emf or the potential required for such a process is usually small because the energy needed for the reduction of the ionic species at the cathode is almost equal to that released by the oxidation of the crude metal at the anode. Some metals, such as copper, nickel, lead, silver, gold, etc., are refined by using aqueous electrolytes whereas molten salt electrolytes are necessary for the refining of reactive metals such as aluminum,... [Pg.716]

Molten salt pyrolysis, 21 466-467 Molten salts, 26 836-837 electrolysis of, 16 161-163 Molten selenium fluxing, selenium and tellurium purification via, 22 85... [Pg.597]

Dunbobbin, B. R. and W. R. Brown. 1987. Air separation by a high temperature molten salt process. Gas separation and purification 1 23-29. [Pg.59]

If an actinide metal is available in sufficient quantity to form a rod or an electrode, very efficient methods of purification are applicable electrorefining, zone melting, and electrotransport. Thorium, uranium, neptunium, and plutonium metals have been refined by electrolysis in molten salts (84). An electrode of impure metal is dissolved anodically in a molten salt bath (e.g., in LiCl/KCl eutectic) the metal is deposited electrochemically on the cathode as a solid or a liquid (19, 24). To date, the purest Np and Pu metals have been produced by this technique. [Pg.13]

White [7] gives a general review that includes information about the preparation and purification of a variety of alkali and alkaline earth halide melts. Information about fluorides can also be found in an earlier review article by Bamberger [8]. Many different halide melts have been used as solvents for electrochemistry, and a complete discussion of all of these melts is outside the scope of this chapter. However, two systems that have generated continuous interest over the years are the LiCl-KC1 eutectic (58.8-41.2 mol%, mp = 352°C) [9] and the LiF-NaF-KF (46.5-11.5-42.0 mol%, mp = 454°C) also known as FLINAK [10]. The former is an electrolyte commonly used in thermal batteries, whereas the latter molten salt is of interest for refractory metal plating. [Pg.514]

Comprehensive reviews describing the preparation, purification, and physical and electrochemical properties of these melts have been published [17-20]. The most popular systems are mixtures of A1C13 with either l-(l-butyl)pyridinium chloride (BupyCl) or 1 -methyl-3-ethylimidazolium chloride (MeEtimCl). These systems are very versatile solvents for electrochemistry because they are stable over a wide temperature range. In many ways they can be considered to be a link between conventional nonaqueous solvent/supporting electrolyte systems and conventional high-temperature molten salts. [Pg.516]

Pu metal has recently been produced in kilogram batches in a coordinated reduction-purification sequence (pyrochemical processing) with Ca reductant, CaCL flux, and subsequent molten salt Am extraction (9.2.2.6.1), yielding single ingots of Pu metal. ... [Pg.36]

Good descriptions of the production of aluminum can be found in the literature (Grjotheim etal. [7], Grjotheim and Welch [8], Grjotheim and Kvande [9], Burkin [10], and Peterson and Miller [11]). Referring to Fig. 2 [12], the first step in the production of aluminum from its ore ( bauxite ) is the selective leaching of the aluminum content (present as oxides/hy dr oxides of aluminum) into hot concentrated NaOH solution to form sodium aluminate in solution. After solution purification, very pure aluminum hydroxide is precipitated from the cooled, diluted solution by addition of seed particles to nucleate the precipitation. After solid-liquid separation the alumina is dried and calcined. These operations are the heart of the Bayer process and the alumina produced is shipped to a smelter where the alumina, dissolved in a molten salt electrolyte, is electrolyt-ically reduced to liquid aluminum in Hall- Heroult cells. This liquid aluminum,... [Pg.225]

The latest technologies (especially Toyo Soda) do not include the separation and intermediate purification of acrolein. They employ two trains of reactors in series, operating in different conditions, with catalysts of distinct compositions based on molybdenum oxide, and through which the reaction medium flows. These are multitube systems with molten salt circulation (sodium and potassium nitrites and nitrates) on the shell side, to remove heat generated by the transformation, ensure effective temperature control, and the production of low-pressure steam. The catalyst is placed in a fixed bed in the tubes. [Pg.191]

Preparation Methods. Actinide metal preparation is based on methods known or developed to yield high purity material by metallothermic reduction or thermal dissociation of prepurified compounds. Electrolytic reduction is possible from molten salts, but not from aqueous solutions. Further purification of the metals can be achieved by electrorefining, selective evaporation or chemical vapour transport. [Pg.182]

Assuming a pK value of 2 to be the threshold for the carbonate-ion stability in molten salts in a C02-free atmosphere, it may be concluded that in halide melts consisting, even partially, of lithium salts and more acidic multivalent cations (Ca2+, Mg2+, Ln3+, etc.) carbonate ion is unstable and undergoes complete decomposition with the formation of the equivalent quantity of oxide ions in the melt. As for the other alkali metal halides studied, similar behaviour of CO2-ions can be expected only for CsCl, CsBr, and KBr melts at temperatures exceeding 800 °C. Of course, instability of carbonate ion in the melts does not mean an automatic disappearance of the oxygen admixture from the melt, since oxide ions arise instead of CO2- owing to their complete breakdown. This means that only for the melts characterized by a low pK value of the equilibrium (1.2.3), the carbohalogenation method of purification is the most suitable. [Pg.217]


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See also in sourсe #XX -- [ Pg.161 , Pg.162 ]




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Metal molten-salt electrolysis purification

Salts , purification

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