Methods for preparing hematite

Abstract

There are provided methods for preparing hematite. For example, the method can comprise reacting a basic aqueous composition comprising the iron and the aluminum with hematite under conditions suitable for at least partially converting the iron into hematite under the form of a precipitate, thereby obtaining a liquid phase and a solid phase; and separating the liquid phase from the solid phase.

What is claimed is: 
     
         1 . A method for preparing hematite, said method comprising obtaining said hematite from a basic aqueous composition comprising at least one precipitated iron ion, having a pH of about 10.5 to about 13 and being at temperature of about 50° C. to about 150° C., by reacting said composition with a predetermined quantity of hematite in the absence of a growth regulating agent, thereby promoting, catalyzing and/or enhancing formation of said hematite, wherein said basic aqueous composition is obtained by:
 leaching an iron-containing material comprising said at least one iron ion with an acid so as to obtain a leachate and a solid residue; 
 separating said leachate from said solid residue; and 
 reacting said leachate with a base 
 or by: 
 leaching said iron-containing material comprising said at least one iron ion with an acid so as to obtain a leachate and a solid residue; 
 optionally removing at least a portion of said at least one iron ion from said leachate; 
 separating said leachate from said solid residue; and 
 reacting said leachate with a base. 
 
     
     
         2 . The method of  claim 1 , wherein said at least one precipitated iron ion is chosen from Fe 3+ , Fe 2+ , and a mixture thereof. 
     
     
         3 . The method of  claim 1 , wherein said at least one precipitated iron ion is under the form of Fe(OH) 3 . 
     
     
         4 . The method of  claim 1 , wherein said at least one precipitated iron ion is under the form of Fe(OH) 2 , Fe(OH) 3 , or a mixture thereof. 
     
     
         5 . The method of  claim 1 , wherein said predetermined quantity of hematite is added to said composition, over a predetermined period of time, under agitation. 
     
     
         6 . The method of  claim 1 , wherein said basic aqueous composition has a temperature of about 50° C. to about 70° C. 
     
     
         7 . The method of  claim 1 , wherein said basic aqueous composition has a temperature of about 80° C. to about 100° C. 
     
     
         8 . The method of  claim 1 , wherein said basic aqueous composition has a temperature of about 70° C. to about 120° C. 
     
     
         9 . The method of  claim 1 , wherein said basic aqueous composition has a pH of about 10.8 to about 11.8. 
     
     
         10 . The method of  claim 1 , wherein said basic aqueous composition has a pH of about 11.0 to about 11.6. 
     
     
         11 . The method of  claim 1 , wherein said basic aqueous composition has a pH of about 11.2 to about 11.5. 
     
     
         12 . The method of  claim 1 , wherein said basic aqueous composition has a pH of about 10.5 to about 12. 
     
     
         13 . The method of  claim 1 , wherein said basic aqueous composition has a pH of about 11.5 to about 12.5. 
     
     
         14 . The method of  claim 1 , wherein said basic aqueous composition has a pH of about 11.8 to about 12.2. 
     
     
         15 . The method of  claim 1 , wherein said basic aqueous composition is maintained at said pH when being reacted with said hematite. 
     
     
         16 . The method of  claim 1 , wherein said basic aqueous composition is maintained at said temperature when being reacted with said hematite. 
     
     
         17 . The method of  claim 1 , wherein said predetermined quantity of hematite is added at a molar ratio hematite/said at least one iron ion of about 0.01 to about 0.1. 
     
     
         18 . The method of  claim 1 , wherein said iron-containing material is chosen from argillite, red mud, fly ashes and mixtures thereof. 
     
     
         19 . The method of  claim 1 , wherein said base has a concentration of about 3 to about 4 M. 
     
     
         20 . The method of  claim 1 , wherein said base has a concentration of about 30 to about 60 weight %. 
     
     
         21 . The method of  claim 1 , wherein said leachate and a first portion of said base are added simultaneously into a reactor comprising a second portion of said base. 
     
     
         22 . The method of  claim 1 , wherein said basic aqueous composition is obtained by:
 leaching said iron-containing material comprising said at least one iron ion with an acid so as to obtain a leachate and a solid residue;   separating said leachate from said solid residue; and   reacting said leachate with said base.   
     
     
         23 . The method of  claim 1 , wherein said basic aqueous composition is obtained by:
 leaching said iron-containing material comprising said at least one iron ion with said acid so as to obtain a leachate and a solid residue;   optionally removing at least a portion of said at least one iron ion from said leachate;   separating said leachate from said solid residue; and   reacting said leachate with a base.