Continuous ion exchange process integrated with membrane separation for recovering uranium

Abstract

A continuous ion exchange system and method for recovering uranium from a pregnant liquor solution wherein the method includes the steps of: (a) treating the pregnant liquor solution ( 16 ) with a membrane ( 28 ) to produce: i) a leach permeate solution ( 30 ) at least partially depleted of uranium and carbonate and ii) a leach concentrate solution ( 30′ ) having a relatively higher concentration of uranium and carbonate and which is at least partially depleted of chloride; (b) passing the leach concentrate stream ( 30′ ) through an ion exchange bed to load uranium onto a strong base anion exchange resin and produce an untreated barren ( 18 ) solution depleted of uranium, (c) passing an eluant solution ( 20 ) comprising bicarbonate through the loaded ion exchange bed to strip uranium from the strong base anion exchange resin and produce an eluate ( 22 ) comprising uranium and bicarbonate, (d) precipitating uranium ( 24 ) from the eluate ( 22 ) to produce a residual eluant solution ( 26 ) depleted of uranium, and (e) repeating steps (a)-(d).

1 . A method for recovering uranium from an alkaline pregnant liquor solution comprising uranium, carbonate and chloride, by passing the pregnant liquor solution through a plurality of ion exchange beds ( 12 ,  14 ) containing strong base anion exchange resin that cycle through process zones as part of a repeating uranium recovery circuit, wherein the method comprises the steps of:
 (a) treating the pregnant liquor solution ( 16 ) with a membrane ( 28 ) to produce: i) a leach permeate solution ( 30 ) at least partially depleted of uranium and carbonate and ii) a leach concentrate solution ( 30 ′) having a relatively higher concentration of uranium and carbonate and which is at least partially depleted of chloride;   (b) passing the leach concentrate stream ( 30 ′) through an ion exchange bed to load uranium onto the ion exchange resin and produce an untreated barren ( 18 ) solution depleted of uranium,   (c) passing an eluant solution ( 20 ) comprising bicarbonate through the loaded ion exchange bed to strip uranium from the ion exchange resin and produce an eluate ( 22 ) comprising uranium and bicarbonate,   (d) precipitating uranium ( 24 ) from the eluate ( 22 ) to produce a residual eluant solution ( 26 ) depleted of uranium, and   (e) repeating steps (a)-(d).   
     
     
         2 . The method of  claim 1  including the steps of:
 (f) treating a portion of the untreated barren solution ( 18 ) of step (b) with a membrane ( 31 ) to produce:
 i) a barren permeate solution ( 32 ) at least partially depleted of carbonate and 
 ii) a barren concentrate solution ( 32 ′) having a relatively higher concentration of carbonate, and 
 
 (g) combining the barren permeate solution ( 32 ) with at least one of the pregnant liquor solution ( 16 ) or the leach leach concentrate solution ( 30 ′) of step (a). 
 
     
     
         3 . The method of  claim 1  including the steps of:
 (h) treating a portion of the residual eluant solution ( 26 ) of step (d) with a membrane ( 38 ) to produce:
 i) a residual eluate permeate solution ( 40 ) at least partially depleted of bicarbonate and 
 ii) a residual eluate concentrate solution ( 40 ′) having a relatively higher concentration of bicarbonate than the residual eluate solution ( 26 ), and 
 
 (i) combining the residual eluate concentrate solution ( 40 ′) with at least one of the pregnant liquor solution ( 16 ) or the leach concentrate solution ( 30 ′) of step (a).