Processes for preparing lithium hydroxide

Abstract

There are provided processes for preparing lithium hydroxide that comprise submitting an aqueous composition comprising a lithium compound to an electrolysis or an electrodialysis under conditions suitable for converting at least a portion of the lithium compound into lithium hydroxide. For example, the lithium compound can be lithium sulphate and the aqueous composition can be at least substantially maintained at a pH having a value of about 1 to about 4.

1 - 85 . (canceled) 
     
     
         86 . A process for preparing lithium hydroxide, said process comprising:
 submitting an aqueous composition comprising lithium sulphate to an electrolysis or an electrodialysis under conditions suitable for converting at least a portion of said lithium sulphate into lithium hydroxide, wherein during said electrolysis or said electrodialysis, said aqueous composition comprising lithium sulphate is at least substantially maintained at a pH having a value of about 1 to about 4.   
     
     
         87 . The process of  claim 86 , wherein said aqueous composition comprising lithium sulphate is submitted to an electrolysis. 
     
     
         88 . The process of  claim 86 , wherein said aqueous composition comprising lithium sulphate is submitted to a monopolar membrane electrolysis process. 
     
     
         89 . The process of  claim 86 , wherein during said electrolysis, said pH is at least substantially maintained at a value of about 2 to about 4 
     
     
         90 . The process of  claim 86 , wherein said aqueous composition comprising lithium sulphate is submitted to an electrodialysis. 
     
     
         91 . The process of  claim 90 , wherein during said electrodialysis, said pH is at least substantially maintained at a value of about 1 to about 2. 
     
     
         92 . The process of  claim 86 , wherein said process is carried out by introducing said lithium sulphate into a central compartment, an aqueous composition comprising lithium hydroxide into a cathodic compartment, and an aqueous composition comprising sulphuric acid into an anodic compartment. 
     
     
         93 . The process of  claim 92 , wherein during said process said aqueous composition comprising lithium hydroxide is at least substantially maintained at a concentration of lithium hydroxide of about 35 to about 70 g/L. 
     
     
         94 . The process of  claim 93 , wherein during said process said aqueous composition comprising sulphuric acid is at least substantially maintained at a concentration of sulphuric acid of about 20 to about 50 g/L. 
     
     
         95 . The process of  claim 94 , wherein during said process said aqueous composition comprising lithium sulphate is at least substantially maintained at a concentration of lithium sulphate of about 10 to about 20 g/L. 
     
     
         96 . The process of  claim 95 , wherein during said process, temperature of said aqueous composition comprising lithium sulphate is at least substantially maintained at a value of about 20 to about 80° C. 
     
     
         97 . The process of  claim 92 , wherein during said process said aqueous composition comprising lithium hydroxide is at least substantially maintained at a concentration of lithium hydroxide of about 45 to about 65 g/L. 
     
     
         98 . The process of  claim 86 , wherein during said process electrical current is at least substantially maintained at a density of about 400 to about 3000 A/m 2 . 
     
     
         99 . The process of  claim 86 , wherein during said process electrical current is at least substantially maintained at a density of about 400 to about 1000 A/m 2 . 
     
     
         100 . The process of  claim 86 , wherein during said process electrical current is at least substantially maintained at a density of about 400 to about 600 A/m 2 . 
     
     
         101 . The process of  claim 86 , wherein during said process electrical current is at least substantially maintained at a constant value. 
     
     
         102 . The process of  claim 86 , wherein during said process voltage is at least substantially maintained at a constant value. 
     
     
         103 . The process of  claim 86 , wherein an anolyte used during said process comprises ammonia. 
     
     
         104 . The process of  claim 86 , further comprising adding ammonia in an anolyte used for said process, thereby generating an ammonium salt. 
     
     
         105 . The process of  claim 86 , wherein said ammonium salt is (NH 4 ) 2 SO 4 .