Process for the production of chlorine dioxide

A process for the production of chlorine dioxide, and the production of sulfuric acid from by-product alkali metal sulfate, comprising the steps of:

• (a) reacting in a reaction vessel an alkali metal chlorate, mineral acid and a reducing agent in such proportions that chlorine dioxide is produced in a reaction medium, maintained at a temperature of from about 50.degree. C. to about 100.degree. C. and at an acidity of from about 2 to about 12 N and which is subjected to subatmospheric pressure sufficient for evaporating water;
• (b) withdrawing a mixture of chlorine dioxide and water vapor from an evaporation zone in the reaction vessel;
• (c) precipitating crude alkali metal sulfate in a crystallization zone in the reaction vessel;
• (d) contacting the precipitated alkali metal sulfate with a saturated aqueous solution of neutral alkali metal sulfate, thereby converting the precipitated crude alkali metal sulfate to a purified, neutral alkali metal sulphate precipitate;
• (e) dissolving the purified, neutral sulphate in water;
• and
• (f) electrolyzing the resulting neutral sulphate solution in an electrochemical membrane cell, thereby forming sulfuric acid in an anode compartment of the cell and alkali metal hydroxide in the cathode compartment of the cell.