Acid separation by acid retardation on an ion exchange resin in an electrochemical system

Abstract

A method and system of separating an acid from an acid-salt solution produced in an electrochemical system using an ion exchange resin bed, by processing the acid-salt solution through the ion exchange resin bed such that the acid is retarded at the bottom of the bed and a de-acidified salt solution is recovered from the top of the bed. After removing the salt solution from the bed, the acid is recovered by back-flushing the resin bed with water.

1 . A method comprising:
 producing an acid in an anode electrolyte in contact with an anode in an anode compartment of an electrochemical system; and   separating the acid from the anode electrolyte by retarding the acid on an ion exchange resin to produce a de-acidified anode electrolyte.   
     
     
         2 . The method of  claim 1 , further comprising returning the de-acidified anode electrolyte to the anode compartment. 
     
     
         3 - 4 . (canceled) 
     
     
         5 . The method of  claim 1 , comprising producing the acid in the anode electrolyte by reducing hydrogen gas to protons at the anode and migrating the protons into the anode electrolyte by applying a voltage across the anode and a cathode in contact with a cathode electrolyte in the electrochemical system. 
     
     
         6 . The method of  claim 5 , comprising preventing formation of a gas at the anode. 
     
     
         7 . (canceled) 
     
     
         8 . The method of  claim 1 , further comprising reducing water to hydroxide ions and hydrogen gas at the cathode and producing a hydroxide in the cathode electrolyte by migrating the hydroxide ions into the cathode electrolyte. 
     
     
         9 . The method of  claim 8 , wherein the anode electrolyte, the cathode electrolyte, or both comprise salt solution and the salt solution comprises sodium chloride or sodium sulfate and wherein the anode electrolyte comprises hydrochloric acid or sulfuric acid and the cathode electrolyte comprises sodium hydroxide. 
     
     
         10 . (canceled) 
     
     
         11 . The method of  claim 9 , further comprising contacting the cathode electrolyte with carbon dioxide and producing carbonic acid and/or bicarbonate ions and/or carbonate ions in the cathode electrolyte. 
     
     
         12 - 13 . (canceled) 
     
     
         14 . The method of  claim 1 , comprising separating the acid from the anode electrolyte by: feeding the anode electrolyte comprising the acid into a lower portion of an ion exchange resin bed comprising a resin selected to retard the acid on the resin without retarding the salt; and removing the anode electrolyte comprising the salt from the upper portion of the ion exchange resin bed. 
     
     
         15 . The method of  claim 14 , further comprising eluting the acid from the ion exchange resin bed by back-flushing the ion exchange resin to produce an eluted acid. 
     
     
         16 . The method of  claim 15 , wherein the ion exchange resin comprises a strong base anion exchange resin comprising particle sizes in the range of 525-625 microns. 
     
     
         17 - 18 . (canceled) 
     
     
         19 . The method of  claim 16 , further comprising dissolving a mineral with the eluted acid in a mineral dissolution system to produce a mineral solution comprising divalent cations and un-reacted acid and processing the mineral solution through a nano-filtration system to produce an acid-salt solution comprising the un-reacted acid and the salt solution in a first solution stream, and a divalent cation solution comprising calcium and/or magnesium ions in a second solution stream. 
     
     
         20 . (canceled) 
     
     
         21 . The method of  claim 19 , further comprising processing the first solution stream through a reverse osmosis system to separate the salt solution from the un-reacted acid and produce a concentrated salt solution and a dilute acid. 
     
     
         22 . (canceled) 
     
     
         23 . A system comprising:
 an electrochemical system comprising an anode electrolyte in contact with an anode in an anode compartment and configured to produce an acid in the anode electrolyte; and   an acid retardation system comprising an ion exchange resin bed operatively connected to the anode compartment and configured to receive the anode electrolyte and retard the acid on an ion exchange resin and produce a de-acidified anode electrolyte.   
     
     
         24 . The system of  claim 23 , wherein the acid retardation system is configured to retard the acid in a lower portion of the ion resin bed and produce the de-acidified anolyte in an upper portion of the ion exchange resin bed. 
     
     
         25 . The system of  claim 24 , wherein the ion exchange resin bed comprises a short bed comprising a fine mesh resin. 
     
     
         26 . (canceled) 
     
     
         27 . The system of  claim 24 , wherein the acid retardation system is configured to extract and return the de-acidified anode electrolyte to the anode electrolyte compartment. 
     
     
         28 - 29 . (canceled) 
     
     
         30 . The system of  claim 23 , further comprising a mineral dissolution system operatively connected to the acid retardation system, wherein the mineral dissolution system is configured to dissolve a mineral with the eluted acid to produce a mineral solution comprising divalent cations. 
     
     
         31 . (canceled) 
     
     
         32 . The system of  claim 30 , wherein the electrochemical system comprises a cathode in electrical communication with the anode and in contact with a cathode electrolyte, wherein the electrochemical system is configured to produce the acid in the anode electrolyte by reducing hydrogen gas at the anode to protons and migrating the protons into the anode electrolyte, on application of a voltage across the anode and cathode. 
     
     
         33 . The system of  claim 32 , wherein the electrochemical system comprises a salt solution in the anode electrolyte and wherein the cathode is configured to produce a hydroxide in the cathode electrolyte by reducing water at the cathode to hydroxide ions and hydrogen gas, migrate cations from the anode electrolyte to the cathode electrolyte across a cation exchange membrane separating anode electrolyte and the cathode electrolyte, and migrate the hydroxide ions into the cathode electrolyte. 
     
     
         34 . (canceled) 
     
     
         35 . The system of  claim 23 , further comprising a carbonate precipitation system operatively connected to the cathode compartment, and wherein the carbonate precipitation system is configured to mix the divalent cation solution with cathode electrolyte and carbon dioxide, and sequester the carbon dioxide as a divalent cation carbonate and/or bicarbonate comprising calcium and/or magnesium. 
     
     
         36 - 37 . (canceled)