Method to purify aluminum and use of purified aluminum to purify silicon

Abstract

The present invention provides a method of purifying aluminum, and/or use of the purified aluminum as a solvent metal to purify silicon.

1 . A method for purifying aluminum, the method comprising:
 (a) forming a molten liquid from aluminum and a metal additive selected from at least one of titanium, vanadium, zirconium, and chromium;   (b) allowing impurities to form in the molten liquid, wherein the impurities comprise a reaction product of the metal additive and boron;   (b) optionally removing at least a portion of the impurities from the molten liquid;   (d) cooling the molten liquid to form solidified aluminum; and   (e) optionally removing a portion of the solidified aluminum comprising at least a portion of the impurities;   wherein at least one of the optional steps is carried out, to provide purified aluminum.   
     
     
         2 . The method of  claim 1 , wherein at least some boron is removed, such that the purified aluminum contains less boron than the aluminum in step (a). 
     
     
         3 . The method of  claim 1 , wherein the purified aluminum comprises less than about 0.55 ppmw boron. 
     
     
         4 - 6 . (canceled) 
     
     
         7 . The method of  claim 1 , wherein at least about 200 ppmw metal additive is employed, relative to the aluminum. 
     
     
         8 - 9 . (canceled) 
     
     
         10 . The method of  claim 1 , wherein metal additive comprises titanium. 
     
     
         11 . The method of  claim 1 , wherein the aluminum in step (a) comprises at least about 0.40 ppmw boron. 
     
     
         12 . (canceled) 
     
     
         13 . The method of  claim 1 , wherein the impurities that comprise a reaction product of metal additive and boron comprise titanium diboride (TiB 2 ). 
     
     
         14 - 16 . (canceled) 
     
     
         17 . The method of  claim 1 , wherein the metal additive is added to the aluminum in step (a), is added to the molten liquid, or a combination thereof 
     
     
         18 - 19 . (canceled) 
     
     
         20 . The method of  claim 1 , wherein the optional step of removing the at least a portion of the impurities from the molten liquid is not carried out. 
     
     
         21 . (canceled) 
     
     
         22 . The method of  claim 1 , wherein the optional step of removing a portion of the solidified aluminum comprising at least a portion of the impurities is not carried out. 
     
     
         23 . The method of  claim 1 , wherein the optional step of removing the at least a portion of the impurities from the molten liquid is carried out, and the optional step of removing a portion of the solidified aluminum comprising at least a portion of the impurities is carried out. 
     
     
         24 . The method of  claim 1 , which is carried out two or more times. 
     
     
         25 . A method for purifying silicon, the method comprising:
 (a) forming a molten liquid from silicon and aluminum, wherein the aluminum comprises less than about 0.55 ppmw boron;   (b) cooling the molten liquid, to form silicon crystals and a mother liquor; and   (c) separating the silicon crystals and the mother liquor.   
     
     
         26 - 27 . (canceled) 
     
     
         28 . The method of  claim 25 , wherein the aluminum comprises less than about 0.10 ppmw boron. 
     
     
         29 . The method of  claim 25 , wherein the silicon crystals comprise less than about 0.40 ppmw boron. 
     
     
         30 . (canceled) 
     
     
         31 . The method of  claim 25 , wherein the silicon crystals comprise about 0.20 ppmw boron. 
     
     
         32 . The method of  claim 25 , wherein in step (a), the silicon is metallurgical grade (MG) silicon. 
     
     
         33 . The method of  claim 25 , wherein in step (a), the silicon is employed in about 20 wt. % to about 50 wt. %. 
     
     
         34 - 37 . (canceled) 
     
     
         38 . The method of  claim 25 , wherein the silicon crystals comprise silicon in at least about 65 wt. %. 
     
     
         39 . The method of  claim 25 , which is carried out two or more times.