Combined process for production of chlorine dioxide and sodium hydroxide

A method for the production of chlorine dioxide and sodium hydroxide, which comprises:

• reacting sodium chlorate with hydrochloric acid in a reaction zone to form chlorine dioxide and an aqueous effluent containing sodium chloride,
• recovering chlorine dioxide from said reaction zone,
• passing said aqueous effluent to the central compartment of a three-compartment electrolytic cell divided into an anode compartment, said central compartment and a cathode compartment by two cation-exchange membranes located between the anode and cathode of said cell,
• electrolytically forming hydrogen ions from an electrolyte in said anode compartment of said three-compartment electrolytic cell and transferring said electrolytically-formed hydrogen ions from said anode compartment to said central compartment of said three-compartment electrolytic cell across one of said cation-exchange membranes to form hydrochloric acid therein,
• electrolytically forming hydroxyl ions from an electrolyte in said cathode compartment of said three-compartment electrolytic cell and transferring sodium ions from said central compartment to said cathode compartment across the other of said cation-exchange membranes to form sodium hydroxide therein,
• forwarding effluent from said central compartment to said reaction zone to provide part of the hydrogen chloride required for said reaction with sodium chlorate, and
• recovering sodium hydroxide solution from said cathode compartment.