Process for the recovery of metals from used nickel/metal hydride batteries
View Patent ↗The present invention provides a process of recovering AB 5 and/or AB 2 as well as other metals from spent nickel metal hydride batteries from a slury by a series of separation steps utilizing the screening off of larger metal particles, removal of magnetizable small metal particles from a filter and then separating AB 5 and/or AB 2 by passing the filtrate through a froth flotation step to separate AB 5 and/or AB 2 from lighter small particles.
1. A process for the recovery of metals from spent NiMH batteries selected from the group thereof consisting of hydrogen-storage alloy AB 5 type, AB 2 intermetallic compound and mixtures thereof which comprises the steps of:
A) reducing spent battery pieces to small particles under an aqueous spray to produce a slurry;
B) screening the slurry from step A) through a coarse mesh to remove any large particles and plastic material;
C) screening the filtrate from step B) through at least one screen to remove any nickel, nickel plated steel particles or nickel alloys;
D) passing the filtrate from step C) through a magnetic stripping device to remove metals selected from the group consisting of nickel and iron;
E) passing the filtrate from step D) into a froth or foam flotation device whereby the froth or foam retains residual light matter and the denser metals selected from the group consisting of AB 5 , AB 2 and a mixture thereof sink to the bottom of the filtrate, and then;
F) recovering the metals from the filtrate of step E) whereby the AB 5 and AB 2 particles are not dissolved in the process and recovered in step F).
2. The process of claim 1 wherein metals selected from the group consisting of nickel, and nickel plated steel are recovered from step C).
3. The process of claim 1 wherein rare earth metals are recovered.
4. The process of claim 1 wherein the froth or foam from step D) is separated from the filtrate, washed and nickel hydroxide and cobalt hydroxide are recovered.
5. The process of claim 1 wherein the spent batteries comprise battery electrode without AB 2 .
6. The process of claim 1 wherein the spent NiMH batteries have been previously crushed and treated with dilute sulfuric acid wherein AB 2 and AB 5 are not dissolved.
7. A process for the recovery of hydrogen-storage alloy AB 5 type intermetallic compound from spent NiMH batteries comprising the steps of;
a) hammer-milling spent batteries under a water spray to form a slurry with small particles;
b) passing the resulting slurry from a) through a series of mesh screens to remove any large particles;
c) passing the resulting filtrate from step b) through a magnetic stripping apparatus to remove any small magnetizable particle metals;
d) passing the resulting filtrate from step c) into a froth flotation device whereby AB 5 sinks to the bottom of the filtrate and the froth contains light non-magnetizable particles, and then
e) recovering AB 5 from the filtrate from step d)
whereby AB 5 particles are not dissolved in the process and recovered in step e).
8. The process of claim 7 wherein a non-ionic surfactant is used in the froth flotation device.
9. The process of claim 7 wherein an anionic surfactant is used in the froth flotation device.
10. The process of claim 7 wherein AB 5 particles are recovered from the filtrate of step d) by centrifuging.
11. The process of claim 10 wherein the recovered AB 5 particles are washed with dilute acid and dried.
12. The process of claim 7 wherein nickel hydroxide and cobalt hydroxide are recovered from the froth of step d).
13. The process of claim 7 wherein nickel and iron metal particles are recovered from step b).
14. The process of claim 7 wherein rare earth metals are recovered.