Process for producing lithium carbonate from concentrated lithium brine

Abstract

Disclosed are methods for a simplified process for preparing lithium carbonate from concentrated lithium brine which can be used for battery grade, pharmaceutical and other high purity grade applications. Impure lithium carbonate is precipitated from lithium concentrated brine, preferably lowered in magnesium, subsequently suspended in aqueous solution and reacted with carbon dioxide to form dissolved lithium bicarbonate. The insoluble impurities are filtered and the dissolved boron and metal impurities such calcium, magnesium and iron are physically separated from the lithium bicarbonate solution using ion selective mediums or other selective processes. Lithium carbonate is then subsequently precipitated.

1 . A method of producing lithium carbonate, comprising the steps of:
 a) precipitating impure lithium carbonate from an impure lithium containing brine by addition of soda ash;   b) reacting the precipitate of impure lithium carbonate in a first aqueous solution with CO 2  to form a second aqueous solution containing dissolved LiHCO 3  and dissolved impurities and insoluble impurities from said impure lithium carbonate;   c) separating said insoluble impurities from said second aqueous solution;   d) separating said dissolved impurities from said second aqueous solution by contacting said dissolved impurities with one or more ion selective mediums to remove said dissolved impurities wherein at least one of the ion selective mediums removes boric acid and/or borates; and   e) precipitating Li 2 CO 3  from said second aqueous solution.   
     
     
         2 . The method according to  claim 1 , wherein said lithium containing brine is concentrated to approximately between 0.4% and 6.5% wt Li/wt brine. 
     
     
         3 . The method according to  claim 1 , wherein said reacting step (a) to form impure lithium carbonate from the lithium containing brine is carried out at a temperature of approximately between 20 and 100° C. 
     
     
         4 . The method according to  claim 1 , wherein said impure lithium carbonate is separated using a solid-liquid device. 
     
     
         5 . The method according to  claim 1 , wherein said impure lithium carbonate is reacted with CO 2  at a temperature of between approximately −15° C. to 40° C. 
     
     
         6 - 7 . (canceled) 
     
     
         8 . The method according to  claim 1 , wherein said impure lithium carbonate is reacted with CO 2  at a pressure between approximately 0.7 atm and 20 atm. 
     
     
         9 . The method according to  claim 1 , wherein said impure lithium carbonate is reacted with CO 2  at a pressure between approximately 1 and 8 atm at a temperature between approximately 0 and 10° C. 
     
     
         10 . The method according to  claim 1 , wherein said impure lithium carbonate is reacted with CO 2  at a pressure between approximately 8 and 15 atm at a temperature between approximately 10 and 40° C. 
     
     
         11 . The method according to  claim 1 , wherein said impure lithium carbonate is reacted with an excess of the stoichiometric amount of CO 2  with respect to LiHCO 3 . 
     
     
         12 - 14 . (canceled) 
     
     
         15 . The method according to  claim 1 , wherein said dissolved impurities include ions selected from the group consisting of Ca, Mg, Fe, Cr, Pb, Cd, As, Al, Ni, Cu, Zn, Mn, Si and a combination thereof. 
     
     
         16 . The method according to  claim 1 , wherein said one or more ion selective medium is an ion exchange resin or fiber. 
     
     
         17 . The method according to  claim 16 , wherein said resin or fiber has an aminophosphonic acid functional group. 
     
     
         18 . The method according to  claims 16 , wherein said resin or fiber has an iminodiacetic acid functional group. 
     
     
         19 . The method according to  claim 16 , wherein a resin or fiber having an aminophosphonic acid functional group and a resin or fiber having an iminodiacetic acid functional group can be used in series, 
     
     
         20 . The method according to  claim 1  wherein said boric acid and/or borates is removed by an ion exchange resin or fiber having a N-methyl-glucamine functional group. 
     
     
         21 . The method according to  claim 1  , wherein said precipitation step (e) of lithium carbonate is carried out at a temperature between approximately 20° C. and 100° C. 
     
     
         22 - 24 . (canceled) 
     
     
         25 . The method according to  claim 1 , wherein said precipitation step (e) of lithium carbonate is carried out at a pressure between vacuum and 20 atm. 
     
     
         26 . The method according to  claim 25 , wherein said pressure is between vacuum and 1 atm. 
     
     
         27 . The method according to  claim 1 , wherein said steps are carried out continuously or in batch mode. 
     
     
         28 . (canceled)