Use of sodium beta alumina in novel processes for the production of metals
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Sodium metal is an excellent reductant and can be used to reduce most metallic chlorides and many oxides. However, sodium is relatively expensive and is hazardous to store so that it is only used to reduce titanium tetrachloride to titanium. In-situ electrolytic preparation of sodium from sodium chloride in a reactor is difficult due to the evolution of chlorine, another hazardous substance.
A novel cell is described where the sodium salt is separated from the salt to be reduced by a sodium beta alumina membrane. The anode is in the sodium salt and the cathode is in the metallic salt and, on the application of current, it has been found that the metal ions are reduced to the metal and the anion in the sodium salt is oxidised. By using sodium hydroxide or sodium carbonate as the sodium salt, the anodic products are oxygen and water vapour or oxygen and carbon dioxide.
Examples are given of electrolytic cells incorporating beta alumina membranes for the production of magnesium and zirconium from the chlorides where the metal is produced and the anodic gases are not toxic. Overall these cells are very efficient as the anodic and cathodic products are separated by the beta alumina membrane and compared with existing cells some of the electrical energy requirement is replaced by chemical energy. The environmental benefits of these cells are very attractive for the production of reactive metals on a small scale.
KeywordsSodium Hydroxide Sodium Salt Sodium Carbonate Electrolytic Cell Titanium Tetrachloride
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