Cobalt extraction and recycling from permanent magnets

Abstract

Systems and methods for recovering cobalt and other valuable metals from cobalt permanent magnets of various compositions, such as samarium cobalt magnets, are presented herein. In one embodiment, a method includes converting the permanent magnet material to a higher surface area form, such as a powder. The method also includes treating the converted permanent magnet material with an aqueous solution of ammonium carbonate to form a mixture (e.g., a slurry) that includes dissolved cobalt. In some embodiments, the method includes exposing the mixture to an oxidant to oxidize metallic constituents and form soluble species. The method also includes filtering the mixture to yield a filtrate and electroplating the cobalt onto a cathode from the filtrate.

What is claimed is: 
     
         1 . A method of recovering cobalt from a permanent magnet material having variable composition, the method comprising:
 converting the permanent magnet material to a higher surface area form;   treating the converted permanent magnet material with an aqueous solution of ammonium carbonate to form a mixture that includes dissolved cobalt;   filtering the mixture to yield a filtrate; and   electroplating the cobalt onto a cathode from the filtrate.   
     
     
         2 . The method of  claim 1 , wherein:
 the permanent magnet material comprises samarium cobalt magnets.   
     
     
         3 . The method of  claim 1 , wherein converting the permanent magnet material to a higher surface area form comprises:
 at least one of grinding or milling the permanent magnet material.   
     
     
         4 . The method of  claim 1 , further comprising:
 heating the mixture in at least one of air, oxygen, an inert atmosphere, or hydrogen to temperatures up to 1500° C.   
     
     
         5 . The method of  claim 1 , further comprising:
 demagnetizing the mixture using an externally applied magnetic field or a mechanical shock treatment.   
     
     
         6 . The method of  claim 1 , further comprising:
 adjusting an oxidation state of the mixture prior to extraction with a chemical oxidant, a reductant, or an electrochemical method that employs an electric current to transfer electrons between materials.   
     
     
         7 . The method of  claim 1 , wherein:
 the aqueous solution of ammonium carbonate comprises ammonium carbonate and ammonia.   
     
     
         8 . The method of  claim 1 , further comprising:
 recycling the aqueous solution of ammonium carbonate after use.   
     
     
         9 . The method of  claim 8 , wherein recycling the aqueous solution of ammonium carbonate after use comprises:
 thermally treating the aqueous solution of ammonium carbonate after use to convert the used ammonium carbonate solution into ammonia and carbon dioxide.   
     
     
         10 . The method of  claim 1 , wherein treating the converted permanent magnet material with an aqueous solution of ammonium carbonate comprises:
 adding at least one of oxygen gas, air, hydrogen peroxide, a chemical oxidant, hydrogen gas, or a chemical reductant.   
     
     
         11 . The method of  claim 1 , further comprising:
 applying an electrical potential to a slurry containing alkaline carbonates and the permanent magnet material to increase a dissolution rate.   
     
     
         12 . The method of  claim 1 , further comprising:
 heating the aqueous solution of ammonium carbonate to a temperature between 0° C. and 100° C. at a pressure above 1 bar.   
     
     
         13 . The method of  claim 1 , wherein:
 one or more of said converting, treating the converted permanent magnet material, filtering, and treating the filtrate are performed in a container constructed of at least one of stainless steel, glass, polytetrafluoroethylene, fiberglass-reinforced plastic, corrosion resistant alloy, or a corrosion barrier.   
     
     
         14 . The method of  claim 1 , further comprising:
 electroplating at least one of copper or nickel onto the cathode.   
     
     
         15 . The method of  claim 1 , further comprising:
 adding reagents to the mixture to slow hydrogen evolution at the cathode or to increase a rate of oxygen evolution at an anode.