Process for the recovery of metals from used nickel/metal hydride batteries

1. A method for the purification of hydrogen storage intermetallic alloy AB 5 together with any lanthanum present in a mixture obtained from spent nickel metal hydride batteries and the selective removal of Ni(OH) 2 present which comprises the steps of;

A) Selectively dissolving the Ni(OH) 2 from the mixture containing AB 5 with a carboxylic acid having 1-8 carbon atoms and maintaining a pH of about 2.7 to 3.4 without dissolving the AB 5 and lanthanum;

B) filtering the product of step A) to remove the solution containing any dissolved Ni(OH) 2 ;

C) washing the solids from step B), and then

D) drying the solids under an inert atmosphere.

2. The method of claim 1 wherein said carboxylic acid is selected from the group consisting of acetic propionic, lactic, formic, citric, glycolic and glyoxylic.

3. The method of claim 1 wherein the product of step D) is treated with hydrogen at an elevated temperature and pressure to remove any metal oxide.

4. The method of claim 1 including treating the product of step D) with 10-30% sodium metal in an inert atmosphere.

5. The method of claim 1 wherein the mixture of step A) is obtained from a froth flotation step of an AB 5 recovery process.

6. The method of claim 1 including the step of screening the product of step D) through −325 mesh.

7. A method for the purification of hydrogen storage intermetallic alloy AB 5 and lanthanum containing mixture having Ni(OH) 2 impurity which comprises the step of;

a) forming a slurry of the mixture with a carboxylic acid having 1 to 8 carbon atoms and maintaining a pH of about 2.7 to 3.4 without dissolving AB 5 and lanthanum;

b) filtering the product of step a);

c) washing the solids from step b);

d) drying the solids from step d) with hydrogen at a temperature of 300° C.

8. The method of claim 7 wherein the carboxylic acid is selected from the group consisting of acetic, lactic and glycolic.