Process for regeneration of spent reaction solutions

Claim 1

A process for manufacture of chlorine dioxide by contacting and mixing in a reaction zone an alkali or alkali earth metal chlorate with sulfuric acid and/or hydrochloric acid in the presence of water and a reducing cathode or a reducing agent for the chlorate such as sulfur dioxide, chloride ion and/or methanol whereby chlorine dioxide is liberated and withdrawn and a residual aqueous solution is produced containing alkali or alkali earth metal ions, comprising the steps of: (a) withdrawing the residual solution from the reaction zone and feeding it to a compartment of an electrolytic cell containing at least one membrane between an anode and a cathode, whereby the membrane closest to the anode is permeable to cations when the residual solution is fed to the anode compartment and permeable to anions when the residual solution is fed to a compartment opposite the anode, (b) electrolytically producing hydrogen ions in the anode compartment, (c) withdrawing the solution from the anode compartment with, in relation to the residual solution, decreased concentration of the alkali or alkali earth metal ions, (d) feeding at least a part of the so withdrawn anode compartment solution to the reaction zone, and (e) withdrawing a product containing alkali or alkaline earth metal ions from a compartment of the cell other than the anode compartment.