Process for the Recovery of AB5 Alloy from Used Nickel/Metal Hydride Batteries
View Patent ↗There is provided a process for recovering AB 5 alloy from spent nickel hydride storage batteries and/or their cells without thermal melting or dissolving the AB 5 alloy. The process comprises a step of dissolving the Ni(OH) 2 and separating AB 5 alloy and still containing the lanthanum metal.
1. A process for the recovery of AB 5 intermetallic alloy from spent nickel metal hydride batteries and cells which comprises the steps of:
A) wet crushing nickel metal hydride batteries and cells to form a slurry containing nickel hydroxide and metal particles;
B) screening the product of step A) to separate metal particles from the slurry;
C) treating the slurry from step B) with a non-oxidizing non-halogenated acid to selectively dissolve the nickel hydroxide in the slurry without dissolving the AB 5 alloy; and then
D) recovering the AB 5 alloy.
2. The process of claim 1 wherein the process is conducted in an inert atmosphere.
3. The process of claim 1 wherein step B) comprises screening through a 25 mesh screen and then through a −200 mesh screen.
4. The process of claim 1 wherein the AB 5 alloy recovered contains lanthanum.
5. The process of claim 1 wherein the non-oxidizing non-halogenated acid of step C) is selected from the group consisting of acetic acid, glycolic acid, formic acid and sulfuric acid.
6. The process of claim 1 which comprises dissolving the nickel hydroxide in step C) at a pH of 2-5.
7. The process of claim 6 wherein the slurry from step B) is neutralized at pH 5.
8. The process of claim 1 wherein in step D) AB 5 alloy is recovered by allowing the AB 5 alloy to settle and decanting off a solution from the settled AB 5 alloy, and comprising the additional steps of filtering the solution to form a filtrate and treating the filtrate with a sodium hydroxide solution to pH 10-11 to precipitate nickel hydroxide.
9. The process of claim 1 wherein the electrodes of nickel metal hydroxide batteries are crushed.
10. The process of claim 1 , wherein step C) comprises adding a non-oxidizing non-halogenated acid in estimated 50-95% by mole of a theoretical amount to dissolve a molar amount of nickel hydroxide present.
11. The process of claim 1 wherein in step D) AB 5 alloy is recovered by allowing the AB 5 alloy to settle and decanting off a solution from the settled AB 5 alloy.
12. The process of claim 11 , comprising an additional step after decanting of washing the settled AB 5 alloy.
13. The process of claim 11 , comprising additional steps after decanting of washing, filtering and drying the settled AB 5 alloy.
14. The process of claim 1 , wherein said recovering of the AB 5 alloy comprises employing a circulating system, and including a continuous controlled cyclic wash with filtration of the circulating system.