Mixed chloride process for the extraction of alumina

Abstract

A process for the extraction of alumina from an aluminum-bearing ore or concentrate, comprising the steps of leaching the aluminum-bearing ore or concentrate with a lixiviant of hydrochloric acid and magnesium chloride at atmospheric pressure at a temperature of from 90° C. to the boiling point of the solution and at an Eh of at least 200 mV. After a liquid/solids separation step, the solution obtained is subjected to steps for removal of iron and for recovery of alumina.

What we claim is: 
     
         1 . A process for the extraction of alumina from an aluminum-bearing ore or concentrate, comprising the steps of:
 a) leaching the aluminum-bearing ore or concentrate with a lixiviant of hydrochloric acid and magnesium chloride at atmospheric pressure at a temperature of from 80° C. to the boiling point of the solution; and   b) subjecting the leach solution so obtained to a liquid/solids separation step.   
     
     
         2 . The process of  claim 1  in which, prior to step a), the aluminum-bearing ore or concentrate has been subjected to a calcination step. 
     
     
         3 . The process of  claim 2  in which liquid from step b) is subjected to steps for recovery of alumina. 
     
     
         4 . The process of  claim 3  in which the temperature is in the range of 80-90° C. 
     
     
         5 . A process for the extraction of an aluminum-bearing ore or concentrate, comprising the steps of:
 a) leaching the aluminum-bearing ore or concentrate with a lixiviant of hydrochloric acid and magnesium chloride at atmospheric pressure at a temperature of from 90° C. to the boiling point of the solution and an Eh of at least 200 mV;   b) subjecting the leach solution so obtained to a liquid/solids separation step;   c) subjecting the liquid from the liquid/solids separation of step b) to a solvent extraction step for removal of iron;   d) subjecting the raffinate obtained from step c) to an organic solvent extraction step to remove aluminum from the raffinate; and   e) recovering aluminum in the form of alumina.   
     
     
         6 . The process of  claim 5  in which, prior to step a), the aluminum-bearing ore or concentrate has been subjected to a calcination step. 
     
     
         7 . The process of  claim 6  in which, in step e), the pregnant aluminum-bearing organic solution is subjected to stripping followed by recovery of alumina. 
     
     
         8 . The process of  claim 7  in which alumina is recovered by precipitation or crystallization. 
     
     
         9 . The process of  claim 8  in which the temperature in step a) is in the range of 80-90° C.