Efficient process for previous metal recovery from cell membrane electrode assemblies
A method is provided for recovering a catalytic element from a fuel cell membrane electrode assembly. The method includes grinding the membrane electrode assembly into a powder, extracting the catalytic element by forming a slurry comprising the powder and an acid leachate adapted to dissolve the catalytic element into a soluble salt, and separating the slurry into a depleted powder and a supernatant containing the catalytic element salt. The depleted powder is washed to remove any catalytic element salt retained within pores in the depleted powder and the catalytic element is purified from the salt.
1. A method for recovering a catalytic element from a fuel cell membrane electrode assembly, comprising:
grinding the membrane electrode assembly into a powder;
adding an agglomerant to the powder to facilitate forming a slurry with an acid leachate;
extracting the catalytic element by forming a slurry comprising the powder and an acid leachate adapted to dissolve the catalytic element into a soluble salt;
separating the slurry into a depleted powder and a supernatant containing the catalytic element salt;
washing the depleted powder to remove any catalytic element salt retained within pores in the depleted powder; and
purifying the catalytic element from the salt.
2. The method of claim 1 , wherein the acid leachate comprises HCl and HNO 3 .
3. The method of claim 2 , wherein the concentration ratio of HCl to HNO 3 is about 3:1.
4. The method of claim 2 , wherein the concentration ratio of HCl to HNO 3 is about 30:1.
5. The method of claim 1 , wherein the acid leachate comprises HCl and H 2 O 2 .
6. The method of claim 1 , wherein the acid leachate comprises HCl and chlorine gas.
7. The method of claim 1 , wherein the acid leachate comprises HCl and NaClO 3 .
8. The method of claim 1 , further comprising recycling the supernatant to be used as an acid leachate.
9. The method of claim 8 , wherein recycling the supernatant comprises distilling the supernatant and concentrating acid in the distillate using an azeotrope breaker.
10. The method of claim 1 , further comprising adding a surfactant solution to the powder to facilitate forming the slurry with the acid leachate.
11. The method of claim 1 , wherein the depleted powder comprises residual catalytic element, the method further comprising:
extracting the residual catalytic element by forming a second slurry comprising the depleted powder and an acid leachate adapted to dissolve the catalytic element into a soluble salt;
separating the second slurry into a second depleted powder and a second supernatant containing the catalytic element salt;
washing the second depleted powder to remove any catalytic element salt retained within pores in the second depleted powder; and
purifying the catalytic element from the salt.
12. The method of claim 1 , wherein the fuel cell membrane assembly comprises phosphoric acid, the method further comprising leaching the phosphoric acid by washing the powder with hot water prior to extracting the catalytic element.
13. The method of claim 1 , wherein the catalytic element is platinum.
14. The method of claim 1 , wherein the catalytic element is ruthenium.
15. A method for recovering platinum from a fuel cell membrane electrode assembly, comprising:
shredding and cryogrinding the membrane electrode assembly into a powder;
adding an agglomerant to the powder to facilitate forming a slurry with an acid leachate;
mixing the powder with a surfactant and a leachate to form a slurry;
separating the slurry into solids and a liquid, the liquid including a platinum salt;
concentrating the platinum salt in the liquid; and
refining the platinum from the platinum salt.
16. The method of claim 15 , wherein the leachate comprises hydrochloric acid and an oxidant.
17. The method of claim 16 , wherein the oxidant comprises at least one of nitric acid, hydrogen peroxide, chlorine gas, and sodium chlorate, alone or in combination.
18. The method of claim 15 , wherein the platinum concentration in the powder is in the range of about 0.5% to about 4% by weight.
19. The method of claim 15 , further comprising:
mixing the solids with a second leachate to form a second slurry;
separating the second slurry into residual solids and a second liquid, the second liquid including a platinum salt; and
refining the platinum from the platinum salt.
20. The method of claim 19 , further comprising recycling the second liquid to be used as a leachate.
21. A method for recovering platinum from a fuel cell membrane electrode assembly which contains phosphoric acid, comprising:
shredding and grinding the membrane electrode assembly into a powder;
leaching the shredded and ground powder with water to remove the phosphoric acid;
adding a surfactant solution to the powder using a high shear mixer;
mixing hydrochloric acid and an oxidant with the powder to form a slurry having supernatant and solids;
separating the supernatant from the solids;
distilling the supernatant to separate a hydrochloric acid distillate and a heel, whereby platinum salts are concentrated in the heel; and
recovering platinum from the platinum salts.
22. The method of claim 21 , further comprising:
washing the solids with a wash liquid;
treating the wash liquid with a resin to capture platinum from the wash liquid; and
recovering the platinum from the resin.
23. The method of claim 21 , further comprising:
recycling the distillate for use in forming a slurry with another powder.
24. The method of claim 21 , further comprising:
concentrating hydrochloric acid in the distillate by using an azeotrope breaker; and
recycling the concentrated acid distillate for use in forming a slurry with another powder.