Method for nickel and cobalt recovery from laterite ores by reaction with concentrated acid and water leaching

Abstract

A process for leaching laterite ores containing limonite and saprolite in a two stage process. The first stage consisting of mixing and reacting the ore with concentrated mineral acid, and the second stage consisting of preparing a slurry of the acid/ore mixture in water and leaching the mixture to dissolve nickel and cobalt. Iron is efficiently separated from nickel and cobalt in the solid leach residue primarily as an oxide or hydroxide of ferric iron other than jarosite.

1 . A process for leaching laterite ores containing limonite and saprolite, comprising the following steps: 
 (a) mixing the limonite and saprolite with sufficient concentrated mineral acid to form salts with soluble non-ferrous components of the ore;    (b) water leaching the mixture of step (a) at a temperature and for a time sufficient to cause hydrolysis of dissolved ferric iron whereby an iron containing precipitate is formed, while substantially dissolving at least one of either nickel or cobalt into the leach solution; and    (c) recovering at least one of either nickel or cobalt compounds from the leach solution.    
   
   
       2 . A process as recited in  claim 1 , in which step (a) is carried out by first mixing the acid with the limonite, and subsequently adding the saprolite.  
   
   
       3 . A process as recited in claims  1  or  2 , in which at least a portion of the ore is crushed to promote intimate mixing of the acid with the ore.  
   
   
       4 . A process as recited in  claim 2 , in which the saprolite is crushed separately and then added to the mixture of limonite and acid.  
   
   
       5 . A process as recited in  claim 1 , in which combined limonite and saprolite is crushed and ground prior to mixing with the acid.  
   
   
       6 . A process as recited in claims  1 ,  2 ,  4  or  5 , in which the water leaching of step (b) is carried out in an autoclave at a temperature up to approximately 150° C.  
   
   
       7 . A process as recited in  claim 6 , in which the water leaching of step (b) is carried out at a temperature range of approximately 95-105° C.  
   
   
       8 . A process as recited in claims  1 ,  2 ,  4  or  5 , in which the water leaching of step (b) is carried out at a temperature range of approximately 95-105° C. and at a pressure range of approximately 15-70 psia.  
   
   
       9 . A process as recited in claims  4  or  5 , in which the water leaching of step (b) is conducted in two stages, the first stage being carried out at atmospheric pressure and at a temperature up to the boiling point of the leach solution, and the second stage being carried out in an autoclave at a temperature up to approximately 150° C.  
   
   
       10 . A process as recited in claims  4  or  5 , in which the acid is selected from the group of sulfuric, hydrochloric, and nitric acid, or mixtures thereof.  
   
   
       11 . A process as recited in  claim 8 , in which the acid is sulfuric acid and the salts formed in step (a) include sulfates.  
   
   
       12 . A process as recited in claims  1 ,  2 ,  4  or  5 , in which the recovering of at least one of either nickel or cobalt compounds from the leach solution in step (c) includes adding an ion exchange resin to the leach solution without prior solid/liquid separation.  
   
   
       13 . A process as recited in claims  1 ,  2 ,  4  or  5 , in which the leach solution is first separated from the precipitate prior to the recovering of at least one of either nickel or cobalt compounds from the leach solution in step (c).  
   
   
       14 . A process as recited in claims  1 ,  2 ,  4  or  5 , in which a reductant is added during the water leaching of step (b) to enhance the dissolution of cobalt from the ore.  
   
   
       15 . A process as recited in  claim 14 , in which the reductant is selected from the group of sulfur dioxide, hydrogen sulfide, soluble bisulfite and sulfite compounds, or soluble ferrous iron compounds.  
   
   
       16 . A process as recited in  claim 1  or  2 , further comprising the step of curing the mixture of step (a) prior to the water leaching of step (b).