Process for obtaining highly pure litharge from lead acid battery paste
View Patent ↗The present invention relates to the recovery of high purity litharge from spent lead acid battery paste at a low temperature which does not produce sulfur dioxide. In the process lead acetate or other lead salt is produced which is converted to high purity litharge by precipitation with a base.
1. A process for obtaining high purity litharge (PbO) from spent lead acid battery paste which comprises the steps of:
treating lead acid battery paste with a reducing agent in an acid medium to form an aqueous slurry;
combining a first base with the aqueous slurry;
filtering the aqueous slurry to form a cake and washing the cake to form a washed cake;
combining the washed cake with an acid to form a concentrated solution of a lead salt;
filtering the solution to remove any insoluble material and to form a filtered solution; and
combining a second base with the filtered solution at an elevated temperature to form litharge.
2. The process of claim 1 wherein adding the second base to the solution is performed at a temperature of about 50° C. to 100° C.
3. The process of claim 1 which comprises treating the lead acid battery paste at a pH of <5 with said reducing agent.
4. The process of claim 3 wherein sulfuric acid is used to maintain the pH at <5.
5. The process of claim 1 wherein the reducing agent is selected from the group consisting of sodium meta bisulfite and SO 2 .
6. The process of claim 1 wherein the lead salt comprises at least one of an acetate, a nitrate, a formate, a lactate, a citrate, a perchlorate, or a glycolate.
7. The process of claim 1 wherein the first base is selected from the group consisting of sodium carbonate and an alkali hydroxide.
8. The process of claim 1 wherein the second base is selected from the group consisting of sodium hydroxide and potassium hydroxide.
9. The process of claim 1 wherein the acid medium is formed with an acid selected from the group consisting of acetic acid and sulfuric acid.
10. The process of claim 1 wherein the litharge is further heated in air at about 450° C. to about 500° C. to form red lead.
11. The process of claim 1 further comprising at least one of drying the litharge in an oven at a temperature of between about 120° C. and 180° C. or milling the litharge to form a mesh powder.
12. The process of claim 1 wherein combining the second base with the solution results in the solution having a pH of at least about 10.
13. The process of claim 1 wherein combining the second base with the solution results in the solution having a pH of at least about 11.
14. The process of claim 1 wherein the lead acid battery paste is screened to remove plastic and metal from the paste.
15. The process of claim 7 wherein the alkali hydroxide is selected from the group consisting of sodium hydroxide and potassium hydroxide.
16. The process of claim 1 wherein at least part of the process is carried out in a stainless steel container or an acid-resistant metal alloy container.
17. The process of claim 1 wherein combining the second base with the solution is performed at a temperature of about 70° C. about 90° C.
18. The process of claim 1 wherein the acid comprises at least one of acetic acid, nitric acid, perchloric acid, glycolic acid, formic acid, citric acid, or lactic acid.