Sequential lixivation and precipitation of metals from refractory ores by utilising variable oxidation reduction potentials and a variable PH system

Abstract

This invention relates to an improved electrochemical process for winning platinum group and incidental precious metals from ore. The process utilizes a peroxide leach in combination with electricity to produce higher valency metals and comprises the following steps: combining ground ore with a solution comprising water with a selected amount of H 2 O 2 and an anion source to form a slurry; applying a direct current while allowing the metal in the ore to leach into the solution for a selected period of time; filtering and clarifying the leached slurry to obtain a pregnant solution; and treating the pregnant solution to yield metal, metal salts or both.

1 . A method for extracting certain valuable metals from ore comprising:
 a) immersing ore in a solution comprising water with a selected amount of hydrogen peroxide and an anion source;   b) applying a direct current to the solution while allowing a valuable metal in the ore to leach into the solution for a selected period of time;   c) filtering the leached solution from the ore to obtain a pregnant solution; and   d) treating the pregnant solution to yield metal, metal salts or both.   
   
   
       2 . The method as claimed in  claim 1  wherein the valuable metal extracted is one or more metals from the group consisting of platinum group metals, gold and silver. 
   
   
       3 . The method claimed in  claim 1  wherein the ore is ground into fine particles prior to immersion in the solution. 
   
   
       4 . The method as claimed in  claim 1  wherein anion source is selected from the group consisting of inorganic acids, soluble inorganic salts, and alkaline solutions. 
   
   
       5 . The method as claimed in  claim 1  wherein the process is utilized for assay and analysis. 
   
   
       6 . The method as claimed in  claim 1  wherein the anion source is selected from the group consisting of HCl, NaCl, HBr, HNO 3 , HSO 4 , H 3 PO 4 , KBr, KNO 3 , FeC 3 , NaOH, KOH, and organic acids. 
   
   
       7 . The method as claimed in  claim 1  wherein the length of the leaching period is selected based on the grade of ore being leached. 
   
   
       8 . The method as claimed in  claim 6  wherein the ore is low grade ore and the leaching period is between 1 and 6 hours. 
   
   
       9 . The method as claimed in  claim 1  wherein the length of the leaching period is selected based on the specific metal that is selected to be extracted. 
   
   
       10 . The method as claimed in  claim 8  wherein a shorter leaching period is selected for extracting only metals in the ore that are more reactive to the anions in the solution, and the longer leaching period is selected for extracting more metals in the ore. 
   
   
       11 . The method as claimed in  claim 1  wherein the direct current is set as high as possible without heating the solution to such an extent that the hydrogen peroxide is boiled away. 
   
   
       12 . The method as claimed in  claim 1  wherein the method is directed at recovering platinum group metals, the anion source is HCl and the pregnant solution is treated to recover platinum from the solution. 
   
   
       13 . The method as claimed in  claim 11 , further comprising after step (d), repeating the method as claimed in  claim 1  using HSO 4  as the anion source and treating the pregnant solution to recover palladium from the solution 
   
   
       14 . A method for extracting certain valuable metals from another material comprising:
 a) immersing a material containing valuable metal in a solution comprising water with a selected amount of hydrogen peroxide and anion source;   b) applying a direct current to the solution while allowing a valuable metal in the material to leach into the solution for a selected period of time;   c) filtering the leached solution form the material to obtain a pregnant solution;   d) treating the pregnant solution to yield metal, metal salts, or both.   
   
   
       15 . The method as claimed in  claim 13  wherein the material is ore. 
   
   
       16 . The method as claimed in  claim 14  wherein the valuable metal is one or more metals selected from the group consisting of platinum group metals, gold and silver, rare earths, neuclides, and transition metals.