Processing for the extraction of rare earth elements

Abstract

Processing schemes for the extraction and/or separation of rare earth elements (REEs) from rare earth containing products such as rare earth mineral ore bodies and intermediate products derived from rare earth mineral ore bodies. The processing schemes may be applied independently or in various combinations to produce end-products that have a very high purity with respect to REEs, including high value critical REEs. The processes may include acid digestion, formation of rare earth oxalate compounds, metathesizing of rare earth oxalate compounds, selective precipitation and/or solvent extraction to form the high purity REE end products.

1 . A method for leaching a mineral ore body comprising rare earth elements, comprising the steps of:
 contacting the mineral ore body with a hydrochloric acid solution for a period of time that is sufficient to solubilize at least a portion of the rare earth elements and form a pregnant liquor solution and a solid residue, wherein during the contacting the leach temperature does not exceed about 60° C.; and   separating the pregnant liquor solution from the solid residue.   
     
     
         2 - 10 . (canceled) 
     
     
         11 . A method for the selective separation of rare earth elements, comprising the steps of:
 digesting a rare earth oxide powder in nitric acid to form a first rare earth solution comprising solubilized rare earth elements;   contacting the first rare earth solution with ammonium hydroxide to precipitate a first precipitation product and form a second rare earth solution;   separating the first precipitation product from the second rare earth solution;   increasing the pH of the second rare earth solution to precipitate additional rare earth elements from the second rare earth solution as a first intermediate particulate feed;   digesting the first intermediate particulate feed in nitric acid to form a third rare earth solution; and   contacting the third rare earth solution with ammonium hydroxide to precipitate a second precipitation product and form a fourth rare earth solution.   
     
     
         12 - 20 . (canceled) 
     
     
         21 . A method for the removal of thorium from an REE-containing acidic solution, the REE-containing acidic solution comprising thorium and at least one rare earth element, the method comprising the steps of:
 contacting the REE-containing acidic solution with a thorium selective extractant to extract at least a portion of the thorium from the REE-containing acidic solution, whereby a thorium-depleted raffinate and a thorium-loaded phase are formed; and   removing the extracted thorium from the thorium-loaded extractant phase to form a thorium-depleted extractant.   
     
     
         22 - 30 . (canceled)