Process for recycling alkaline batteries
View Patent ↗The invention relates to the recovery of manganese dioxide, zinc hydroxide/oxide and steel from metal cased alkaline dry cell batteries which have been wet crushed. There is also a process for recovery of the steel and high purity manganese dioxide which can be directly utilized in the electrode for alkaline dry cell batteries.
1. A process for recovering high purity manganese dioxide from a slurry wherein alkaline batteries have been wet crushed and the casing particles have been removed which comprises the steps of;
1) filtering said slurry to obtain a filter cake;
2) treating the filter cake from step 1) with a solution of sulfuric acid to obtain a first product;
3) filtering the first product from step 2) to obtain a cake of insoluble manganese oxides and a filtrate and adjusting the pH of the filtrate to pH 3-5;
4) oxidizing the filtrate from step 3) to obtain a second product;
5) filtering the second product from step 4) to obtain a filtrate and treating the filtrate with a solution of sodium persulfate to precipitate manganese dioxide; and then
6) recovering the manganese dioxide.
2. The process of claim 1 which comprises adjusting the pH of the filtrate from step 3) with sodium hydroxide.
3. The process of claim 1 which comprises using air oxidation in step 4) at a pH of about 4 and at an elevated temperature.
4. The process of claim 1 which comprises treating the filter cake in step 2) with a 15 to 25% by weight solution of sulfuric acid.
5. The process of claim 1 comprising treating the filtrate of step 5) with an alkali hydroxide.
6. The process of claim 1 which comprises adjusting the pH of the filtrate of step 3) to pH 4-5 with sodium hydroxide and then adding sodium persulfate to form MnO 2 .
7. The process of claim 1 which comprises dewatering the filter cake from step 1) prior to treatment with a sulfuric acid solution.
8. The process of claim 1 wherein step 2) includes heating the slurry after the treatment with said sulfuric acid solution at an elevated temperature.
9. The process of claim 8 wherein said elevated temperature is 80° C.