Recovery of high purity PbO
View Patent ↗A process for producing high purity lead oxide from impure lead compounds particularly from waste lead battery paste which includes an oxidation-reduction step. The process results in a reduction of impure lead compounds to the +2 valence state and metal particle contaminants are oxidized to the +2 state.
1. A process for producing high purity lead oxide (PbO) from a composition consisting of waste lead battery paste which comprises the steps of:
A. slurrying the lead battery paste in an aqueous acidic medium;
B. adding sufficient alkali metal halide salt to reduce all lead to a valence of +2;
C. filtering the composition from Step B;
D. washing a filter cake from Step C to remove soluble salts;
E. treating the filter cake from Step D with an alkali hydroxide solution and then
F. washing the product from Step E and recovering high purity lead oxide.
2. The process of claim 1 wherein Step 1 is slurried at a pH less than 1.
3. The process of claim 2 wherein the composition is slurried in an aqueous sulfuric acid.
4. The process of claim 1 wherein the alkali metal halide in Step B is an alkali chloride.
5. The process of claim 1 wherein the composition from Step A was screened to remove coarse material and the screened slurry is further treated with sulfuric acid prior to Step B.
6. The process of claim 5 wherein the resulting slurry after Step B is heated to remove any gas formed.
7. The process of claim 1 wherein the filter cake is washed with dilute sulfuric acid and water.
8. The process of claim 7 wherein the sulfuric acid is greater than 15%.
9. The process of claim 1 wherein the alkali metal hydroxide of Step E is potassium hydroxide.
10. The process of claim 9 wherein the pH is at 12-13.
11. The process of claim 10 including washing with water after the potassium hydroxide is added to have a pH of 7-8.
12. The process of claim 1 wherein in Step E the alkali hydroxide solution comprises 45% potassium hydroxide.