METHODS FOR ELECTROCHEMICAL DECHLORINATION OF ANOLYTE BRINE FROM NaCl ELECTROLYSIS

Abstract

Methods for the reductive post-treatment of NaCl-containing solutions, wherein such methods comprise: providing a NaCl-containing solution obtained from an anode side of an NaCl electrolysis cell, the solution comprising reducible components; and subjecting the solution to cathodic electrochemical reduction.

1 . A method comprising: providing a NaCl-containing solution obtained from an anode side of an NaCI electrolysis cell, the solution comprising reducible components; and subjecting the solution to cathodic electrochemical reduction. 
     
     
         2 . The method according to  claim 1 , further comprising treating the NaCl-containing solution with hydrogen peroxide. 
     
     
         3 . The method according to  claim 2 , wherein the NaCl-containing solution is treated with hydrogen peroxide before the cathodic electrochemical reduction. 
     
     
         4 . The method according to  claim 2 , wherein the NaCl-containing solution is treated with hydrogen peroxide after the cathodic electrochemical reduction. 
     
     
         5 . The method according to  claim 1 , further comprising treating the NaCl-containing solution with an aqueous hydrogen peroxide solution. 
     
     
         6 . The method according to  claim 5 , wherein the NaCl-containing solution is treated with the aqueous hydrogen peroxide solution before the cathodic electrochemical reduction. 
     
     
         7 . The method according to  claim 5 , wherein the NaCl-containing solution is treated with the aqueous hydrogen peroxide solution after the cathodic electrochemical reduction. 
     
     
         8 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out in a cell having an anode compartment and a cathode department separated by an ion-exchange membrane or diaphragm. 
     
     
         9 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out galvanostatically. 
     
     
         10 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out potentiostatically. 
     
     
         11 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out with an anode and a cathode each independently comprising a material selected from the group consisting of carbon, graphitized carbon, graphite, and titanium coated with a noble metal or a noble metal oxide. 
     
     
         12 . The method according to  claim 1 , wherein during the cathodic electrochemical reduction of the reducible components, which is carried out in an electrolysis cell having an anode compartment and a cathode compartment, an anodic reaction occurs in the anode compartment, the anodic reaction selected from the group consisting of chlorine production, oxygen production, oxidation of iron(II) chloride to iron(III) chloride, and combinations thereof. 
     
     
         13 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out using a cathode having an internal surface area and an external, geometric surface area, wherein the internal surface area is greater than the external, geometric surface area. 
     
     
         14 . The method according to  claim 13 , wherein the internal surface area is at least twice the external, geometric surface area. 
     
     
         15 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out in an electrolysis cell having a cathode compartment, and wherein the NaCl-containing solution has a residence time in the cathode compartment of 1 to 30 minutes. 
     
     
         16 . The method according to  claim 15 , wherein the NaCl-containing solution has a residence time in the cathode compartment of 1 to 10 minutes. 
     
     
         17 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out at a current density of 5 to 100 A/m 2 . 
     
     
         18 . The method according to  claim 1 , wherein the cathodic electrochemical reduction is carried out at a charge introduction amount of 0.05 to 0.5 Ah/l where the NaCl-containing solution has a chlorine content of about 100 mg/l. 
     
     
         19 . The method according to  claim 1 , wherein at least 80% of the reducible components are reduced by the cathodic electrochemical reduction. 
     
     
         20 . The method according to  claim 19 , wherein remaining residues of compounds to be reduced are treated by addition of one or more sulfur-containing reducing agents.