Method for producing peroxodisulfates in aqueous solution

Abstract

A process for preparing or regenerating peroxodisulfuric acid and its salts by electrolysis of an aqueous solution containing sulfuric acid and/or metal sulfates at diamond-coated electrodes without addition of promoters is described, with bipolar silicon electrodes which are coated with diamond on one side and whose uncoated silicon rear side serves as cathode being used.

1 - 7 . (canceled)  
   
   
       8 . A process for preparing peroxodisulfuric acid or a salt thereof by performing electrolysis of an aqueous solutions of at least one of sulfuric acid or a metal sulfate at diamond-coated electrodes without addition of a promoter, wherein bipolar silicon electrodes which are coated on one side with doped diamond and whose uncoated silicon rear side serves as a cathode.  
   
   
       9 . The process of  claim 8 , wherein the electrolysis is carried out in undivided electrolysis cells.  
   
   
       10 . The process of  claim 8 , wherein the electrolysis is carried out in electrolysis cells which are divided by at least one of an ion-exchange membrane or a porous diaphragm.  
   
   
       11 . The process of  claim 8 , wherein a diamond-coated anode composed of a valve metal and provided with a power supply lead is used as a boundary anode.  
   
   
       12 . The process of  claim 9 , wherein a diamond-coated anode composed of a valve metal, e.g. niobium, and provided with a power supply lead is used as a boundary anode.  
   
   
       13 . The process of  claim 10 , wherein a diamond-coated anode composed of a valve metal, e.g. niobium, and provided with a power supply lead is used as a boundary anode.  
   
   
       14 . The process of  claim 8 , wherein stainless steel, Hastelloy, platinum, impregnated graphite or silicon which has been metallized on one side is used for the boundary cathode provided with a power supply lead.  
   
   
       15 . The process of  claim 9 , wherein stainless steel, Hastelloy, platinum, impregnated graphite or silicon which has been metallized on one side is used for the boundary cathode provided with a power supply lead.  
   
   
       16 . The process of  claim 10 , wherein stainless steel, Hastelloy, platinum, impregnated graphite or silicon which has been metallized on one side is used for the boundary cathode provided with a power supply lead.  
   
   
       17 . The process of  claim 8 , wherein a plurality of electrode stacks comprising bipolar electrodes and boundary electrodes with power supply lead are connected electrically in parallel within an electrolysis cell.  
   
   
       18 . A bipolar undivided or divided electrolysis cell comprising bipolar electrodes coated with diamond on one side.  
   
   
       19 . The process of  claim 11 , wherein the valve metal is niobium.