Salts electrolysis of molten

An electrolytic cell, you may recall, is an electrochemical cell in which an electric current drives an otherwise nonspontaneous reaction. The process of producing a chemical change in an electrolytic cell is called electrolysis. Many important substances, including aluminum and chlorine, are produced commercially by electrolysis. We will begin by looking at the electrolysis of molten salts. 

Sodium metal forms at the cathode from the reduction of Na ion chlorine gas forms at the anode from the oxidation of Cl ion.Sodium metal is produced commercially this way, although the commercial cell must be designed to collect the products and to keep them away from one another. 

In this commercial cell,sodium is produced by the electrolysis of molten sodium chloride.The salt contains calcium chloride, which is added to lower the melting point of the mixture. Liquid sodium forms at the cathode, where it rises to the top of the molten salt and collects in a tank. Chlorine gas is a by-product. 

A number of other reactive metals ate obtained by the electrolysis of a molten salt or ionic compound. Lithium, magnesium, and calciiun metals are all obtained by the electrolysis of the chlorides. The first commercial preparation of sodiinn metal adapted the method used by Humphry Davy when he discovered the element in 1807. Davy electrolyzed molten sodium hydroxide, NaOH, whose melting point (318°C) is relatively low for an ionic compound. The half-reactions ate 

Many of the commercial uses of electrolysis involve aqueous solutions. We will look at electrolysis in aqueous solution in the next section. 

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Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Yu.V. Baimakov, M.M. Vetukov, Electrolysis of molten salts, Metallurgiya, Moscow 1966 (in Russian). 

Although the electrolysis of molten salts does not in principle differ from that of aqueous solutions, additional complications are encountered here owing to the problems related to the higher temperatures of operation, the resultant high reactivities of the components, the thermoelectric forces, and the stability of the deposited metals in the molten electrolyte. As a result of this, processes taking place in the melts and at the electrodes cannot be controlled to the same extent as in aqueous or other types of solutions. Considerations pertaining to Faraday s laws have indicated that it would be difficult to prove their applicability to the electrolysis of molten salts, since the current efficiencies obtained are generally too small in such cases. 

D. Inman and S. H. White, The Production of Refractory Metals by Electrolysis of Molten Salts Design Factors and Umitations, J. Appl. Electrochemistry, Vol. 8, p. 385,1978. 

Predict the products of the electrolysis of molten salts and aqueous solutions. 

Metallic State. The actinide metals, like the lanthanide metals, are highly electropositive. They can be prepared by the electrolysis of molten salts or by the reduction of a halide with an electropositive metal, such as calcium or barium. Their physical properties are summarized in Table 3. 

The principle possibility of carbon nanotubes generation by the electrolysis of molten salts saturated by carbon dioxide was shown. The method advantage is the apparatus simplicity, ecological cleanness, economy, possibility of control of product structure and morphology by choice of the optimum electrolysis conditions. 

Two principal methods of producing magnesium metal [264] are being used metallothermic reaction and electrolysis of molten salts. Two-thirds of the magnesium production is obtained by the electrolytic process. On the market there are few producers of magnesium. Therefore, process research and development work have been conducted by these producers, and the results have often been kept secret. Hence, there are few publications in this field, except for patents. 

All the Group 1A and 2A metals are produced by electrolysis of molten salts. Why ... 

But the electrode reactions for dilute salt solutions are entirely difiEerent from those for molten salts. Electrolysis of dilute salt solution produces hydrogen at the cathode and oxygen at the anode, whereas electrolysis of molten salt produces sodium and chlorine. 

Production and Refining. The production of tungsten or its refining via electrolysis of molten salts, although technically possible, has never gained greater importance. 

Fluorine is produced by electrolysis of molten salts on carbon anodes including KF-21TF at about 100°C, potassium bifluoride at about 250°C, and fluoride salts at about 1000°C. The decomposition potential of molten potassium bifluoride is 1.75 V at 250°C, a value close to that estimated thermodynamically [80]. The kinetics of the anodic process is characterized by a Tafel slope of 0.56 V per decade, j), = 1 x 10 A/cm [81], and by a complex reaction mechanism involving the formation of fluorine atoms on carbon. During the electrolysis, C-F surface compounds on the carbon anode are formed via side reactions. Intercalation compounds such as (CF) contribute to the anodic effect in the electrochemical cell, which can be made less harmful by addition of LiF. 

Electrolysis of Molten Salts and the Industrial Production of Sodium Many electrolytic applications involve isolating a metal or nonmetal from a molten binary ionic compound (salt). Predicting the product at each electrode is simple if the salt is pure because the cation will be reduced and the anion oxidized. The electrolyte is the molten salt itself, and the ions move through the cell because they are attracted by the oppositely charged electrodes. 

Electrolysis of molten salts is widely applicable to the synthesis of transition-metal compounds including those with tunnel structures. 

Why is the electrolysis of molten salts much easier to predict in terms of what occurs at the anode and cathode than the electrolysis of aqueous dissolved salts ... 

Because of the high melting points of ionic substances, the electrolysis of molten salts requires very high temperatures. Do we obtain the same products if we electrolyze the aqueous solution of a salt instead of the molten salt Frequently the answer is no because water itself might be oxidized to form O2 or reduced to form H2 rather than the ions of the salt. 

Electrochemistry of molten salts. Electrolysis of molten salts. 

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