High-efficiency electrolysis of iron ore for iron production

Abstract

A method of producing iron metal by electrolysis of iron ore can include introducing iron ore into an anode chamber. The anode chamber can include a first electrolyte and an anode. The anode can oxidize water to form O2 gas and H+ ions in the anode chamber. The iron ore can be dissolved to form Fe3+ and/or Fe2+ ions in the anode chamber. The Fe3+ and/or Fe2+ ions can be transferred from the anode chamber to a cathode chamber through a cation exchange membrane that separates the anode chamber from the cathode chamber. The cathode chamber can include a second electrolyte and a cathode. The Fe3+ and/or Fe2+ ions can be reduced to form iron metal at the cathode.

What is claimed is: 
     
         1 . A method of producing iron metal by electrolysis of iron ore, comprising:
 introducing iron ore into an anode chamber, wherein the anode chamber includes a first electrolyte and an anode;   oxidizing water at the anode to form O 2  gas and H +  ions in the anode chamber;   dissolving the iron ore to form Fe 3+  and/or Fe 2+  ions in the anode chamber;   transferring the Fe 3+  and/or Fe 2+  ions from the anode chamber to a cathode chamber through a cation exchange membrane that separates the anode chamber from the cathode chamber, wherein the cathode chamber includes a second electrolyte and a cathode; and   reducing the Fe 3+  and/or Fe 2+  ions to form iron metal at the cathode.   
     
     
         2 . The method of  claim 1 , wherein the first electrolyte has a pH less than 1, and wherein the second electrolyte has a pH from about 4 to about 5. 
     
     
         3 . The method of  claim 1 , wherein the first electrolyte and the second electrolyte are both aqueous. 
     
     
         4 . The method of  claim 3 , wherein the first aqueous electrolyte comprises a perchlorate and wherein the second aqueous electrolyte comprises a chloride. 
     
     
         5 . The method of  claim 3 , wherein the second aqueous electrolyte includes a dissolved iron salt and a dissolved co-salt, wherein the co-salt comprises magnesium, calcium, or a combination thereof. 
     
     
         6 . The method of  claim 5 , wherein the dissolved co-salt is present in the second aqueous electrolyte at a concentration from about 4 mol/L to about 5 mol/L. 
     
     
         7 . The method of  claim 1 , wherein the first electrolyte and the second electrolyte include a deep eutectic solvent (DES). 
     
     
         8 . The method of  claim 7 , wherein the DES includes an iron salt mixed with an organic molecule, wherein the iron salt includes an anion and the organic molecule is capable of donating protons to form hydrogen bonds with the anion. 
     
     
         9 . The method of  claim 8 , wherein the iron salt is at least one of an iron chloride, bromide, iodide, sulfate, phosphate, perchloride, tetraboron fluoride, nitrate, bis(trifluoromethanesulfonyl)imide, and trifluoromethanesulfonate. 
     
     
         10 . The method of  claim 8 , wherein the organic molecule is at least one of acetamide, urea, propionamide, methyl carbamate, thiourea, ethylene glycol, methanol, ethanol, sucrose, citric acid, glacial acetic acid (AcOH), propanoic acid, glycine, diethylamine HCl, and triethylamine HCl (TEHCl). 
     
     
         11 . The method of  claim 8 , wherein the first electrolyte and the second electrolyte are non-aqueous. 
     
     
         12 . The method of  claim 8 , wherein the first electrolyte and the second electrolyte are aqueous to form a hybrid aqueous DES electrolyte. 
     
     
         13 . The method of  claim 1 , wherein the cation exchange membrane is a first cation exchange membrane, wherein the anode chamber includes a second cation exchange membrane dividing the anode chamber into a water oxidation compartment and an iron ore feed compartment, wherein the anode is in the water oxidation compartment and the iron ore is introduced into the iron ore feed compartment, the method further comprising transferring H +  ions from the water oxidation compartment to the iron ore feed compartment across the second cation exchange membrane. 
     
     
         14 . The method of  claim 13 , wherein the iron ore is introduced through an iron ore inlet formed in the iron ore feed compartment, and wherein the O 2  gas exits the water oxidation compartment through an O 2  gas outlet formed in the water oxidation compartment. 
     
     
         15 . The method of  claim 1 , wherein the Fe 3+  and/or Fe 2+  ions are reduced to iron metal at the cathode with a faradaic efficiency of 90% or greater. 
     
     
         16 . The method of  claim 1 , wherein the second electrolyte has a temperature from about 25° C. to about 150° C. 
     
     
         17 . The method of  claim 1 , wherein the iron ore comprises hematite, magnetite, goethite, limonite, siderite, wustite, or a combination thereof. 
     
     
         18 . The method of  claim 17 , wherein the iron ore is introduced as particles having a particle size from 1 micrometer to 1000 micrometers. 
     
     
         19 . The method of  claim 1 , wherein the iron metal forms iron particles and the method further comprises collecting the iron particles in a non-aqueous liquid that is substantially immiscible with the second electrolyte, wherein the iron particles flow by gravity from the cathode to the non-aqueous liquid. 
     
     
         20 . The method of  claim 1 , further comprising flowing the second electrolyte through a recycle flow line connected to the cathode chamber. 
     
     
         21 . The method of  claim 1 , wherein the cation exchange membrane is positioned at least partially above the anode chamber and in contact with the first electrolyte, and wherein the cathode chamber is positioned at least partially above the cation exchange membrane. 
     
     
         22 . The method of  claim 21 , wherein the anode chamber comprises an O 2  gas outlet at an upper portion of the anode chamber, and wherein the cation exchange membrane is inclined upward toward the O 2  gas outlet to direct rising O 2  gas bubbles toward the O 2  gas outlet. 
     
     
         23 . The method of  claim 22 , wherein the cathode chamber comprises an iron metal collector comprising a non-aqueous liquid that is substantially immiscible with the second electrolyte, wherein the inclined cation exchange membrane directs falling iron metal particles toward the iron metal collector. 
     
     
         24 . An iron ore electrolysis reactor, comprising:
 an anode chamber to receive a feed of iron ore, the anode chamber including a first aqueous electrolyte and an anode;   a cathode chamber including a cathode and a second aqueous electrolyte, wherein the second aqueous electrolyte includes a dissolved iron salt and a dissolved co-salt, wherein the dissolved co-salt comprises magnesium, calcium, or a combination thereof; and   a cation exchange membrane separating the anode chamber from the cathode chamber, wherein the cation exchange membrane is configured to transfer Fe 3+  ions from the anode chamber to the cathode chamber.   
     
     
         25 . The iron ore electrolysis reactor of  claim 24 , wherein the anode and cathode are separated by a distance from about 0.1 cm to about 10 cm. 
     
     
         26 . The iron ore electrolysis reactor of  claim 24 , wherein the cathode comprises glassy carbon, graphite, carbon felt, carbon cloth, carbon paper, porous carbon, activated carbon, titanium, copper or a combination thereof. 
     
     
         27 . The iron ore electrolysis reactor of  claim 24 , wherein the cation exchange membrane is a first cation exchange membrane, wherein the anode chamber includes a second cation exchange membrane dividing the anode chamber into a water oxidation compartment and an iron ore feed compartment, wherein the anode is in the water oxidation compartment and wherein the iron ore feed compartment includes an iron ore feed inlet. 
     
     
         28 . An iron ore electrolysis flow reactor, comprising:
 an anode chamber comprising a first electrolyte, an anode, and an iron ore inlet;   a cation exchange membrane positioned at least partially above the anode chamber and in contact with the first electrolyte;   a cathode chamber positioned at least partially above the cation exchange membrane, wherein the cathode chamber comprises a second electrolyte and a cathode, wherein the cation exchange membrane is configured to transfer iron ions from the anode chamber to the cathode chamber;   a recycle flow line connected to the cathode chamber to cycle the second electrolyte through the cathode chamber; and   an iron metal collector connected to the recycle flow line to collect iron metal particles from the second electrolyte.   
     
     
         29 . The iron ore electrolysis flow reactor of  claim 28 , wherein the cation exchange membrane is inclined downward at an incline with respect to a direction of flow such that the iron metal particles are directed down the incline by gravity and flow of the second electrolyte.