Recovery of Rare Earth Metals and Other Metals from Natural Liquid Sources by Electrodialysis Metathesis

Abstract

Provided herein is an electrodialysis metathesis (EDM) system that has at least one stack or quad of compartments arranged so each compartment is in fluid communication with its adjacent compartment via alternating cation- and anion-exchange membranes. The compartments in a stack are a feed compartment, a substitution salt solution compartment, a first concentrated compartment and a second concentrated compartment. Also provided are processes and methods for separating or recovering a metal, for example, a rare earth element, or a salt or a combination thereof from a salt-containing water. Simultaneous metathesis reactions and electrodialysis across the stack recovers one or more metal or salts from the salt-containing water which desalinates the salt-containing water.

What is claimed is: 
     
         1 . An electrodialysis metathesis (EDM) system comprising at least one electrodialysis stack of four compartments, each in fluid communication with its adjacent compartment via alternating cation- and anion-exchange membranes, said compartments comprising:
 a feed compartment to receive a salt-containing water;   a substitution solution compartment containing a substitution salt solution;   a first concentrated compartment; and   a second concentrated compartment.   
     
     
         2 . The electrodialysis metathesis system of  claim 1 , wherein the substitution salt solution comprises a salt or a hydroxide or other solution combination of elements from the Periodic Table of the Elements compatible with a metathesis reaction with a rare earth element or other metal or metalloid. 
     
     
         3 . The electrodialysis metathesis system of  claim 2 , wherein the substitution salt solution is a sodium chloride solution, a sodium carbonate solution, a sodium sulfate solution, a sodium hydroxide solution, or a sodium phosphate solution. 
     
     
         4 . A process for separating a metal of interest from a salt-containing water, comprising:
 applying an electric field across the EDM system of  claim 1  thereby producing in the first concentrated compartment a first concentrate of a salt composed of cations from the substitution salt solution and anions from the salt-containing water and producing in the second concentrated compartment a second concentrate of a salt composed of metal cations and other cations from the salt-containing water and anions from the substitute salt solution;   removing the first concentrate and the second concentrate from the EDM system and combining the same to produce a combined concentrate; and   adjusting pH of the combined concentrate to precipitate the metal of interest.   
     
     
         5 . The process of  claim 4 , further comprising sequentially readjusting the pH of the combined concentrate to selectively precipitate other metals or salts. 
     
     
         6 . The process of  claim 5 , further comprising recovering the metals or salts. 
     
     
         7 . The process of  claim 4 , wherein producing the first concentrate and the second concentrate simultaneously desalinates the salt-containing water in the feed cell. 
     
     
         8 . The process of  claim 7 , further comprising recovering the desalinated water from the feed cell. 
     
     
         9 . The process of  claim 4 , wherein the metal of interest is a rare earth element or a metalloid present in the Periodic Table of the Elements. 
     
     
         10 . The process of  claim 9 , wherein the rare-earth element is lanthanum, cerium or europium, or a combination thereof. 
     
     
         11 . The process of  claim 4 , wherein the salt-containing water is from a geothermal source, is a seawater, a brackish water, a produced water, a hyper-saline water, is a solution generated from rare earth element-rich ores, or a processed natural liquid from naturally occurring rare earth elements and metal sources or a combination thereof. 
     
     
         12 . A process for recovering a rare-earth element of interest from a salt-containing water, comprising:
 feeding the salt-containing water into the feed compartment of the electrodialysis metathesis system of  claim 1 ;   applying an electric field across the EDM system to initiate an exchange of cations and anions in the salt-containing water with cations and anions in the substitution salt solution via a metathesis reaction;   concentrating the substitution salt solution cations and the salt-containing water anions in the first concentrated compartment and the salt-containing water REE cations and other cations and the substitution salt solution anions in the second concentrated compartment via electrodialysis metathesis;   combining the cations and anions in the first concentrated compartment with the cations and anions in the second concentrated compartment as a combined concentrate;   adjusting pH of the combined concentrate to precipitate the rare-earth element of interest; and   recovering the rare earth element from the combined concentrate.   
     
     
         13 . The process of  claim 12 , further comprising:
 selectively readjusting the pH of the combined concentrate to sequentially precipitate other rare earth elements contained therein; and   recovering the other rare earth elements from the combined concentrate.   
     
     
         14 . The process of  claim 12 , wherein the concentrating step simultaneously desalinates the salt-containing water to produce a desalinated water in the feed cell. 
     
     
         15 . The process of  claim 14 , further comprising recovering the desalinated water from the feed cell. 
     
     
         16 . The method of  claim 12 , wherein the rare-earth element is lanthanum, cerium or europium, or other rare-earth element present in the Periodic Table of the Elements or a combination thereof. 
     
     
         17 . The process of  claim 12 , wherein the salt-containing water is from a geothermal source, is a seawater, a brackish water, a produced water, a hyper-saline water, is a solution generated from rare earth element-rich ores, or a processed natural liquid from naturally occurring rare earth elements and metal sources or a combination thereof. 
     
     
         18 . A method for a simultaneous recovery of at least one rare earth element from and desalinization of a geothermal water, comprising:
 feeding the geothermal water into the feed compartment of the electrodialysis metathesis system of  claim 1 ;   applying an electric field across the EDM system to move all cations in the substitution salt solution and all anions in the geothermal water to the first concentrated compartment and the rare earth element cations and all other cations in the geothermal water and all anions in the substitution salt solution to the second concentrated compartment, said geothermal water desalinated thereby;   removing the cations and anions from the first concentrated compartment and from the second concentrated compartment and combining the same as a combined concentrate; and   adjusting pH to selectively precipitate at least one of the rare earth elements in the combined concentrate, thereby recovering the rare earth element.   
     
     
         19 . The method of  claim 18 , further comprising selectively readjusting the pH of the combined concentrate to sequentially precipitate other rare earth elements. 
     
     
         20 . The method of  claim 18 , further comprising recovering the desalinated geothermal water from the feed cell. 
     
     
         21 . The method of  claim 18 , wherein the rare-earth element is lanthanum, cerium or europium, or other rare-earth element present in the Periodic Table of the Elements or a combination thereof.