Recovery of high purity lead oxide from lead acid battery paste

1. In a low temperature process for recovering high purity litharge PbO from lead acid battery paste, the improvement which comprises the steps of;

A) treating spent battery paste containing Pb 3 O 4 , PbSO 4 and Pb(SO 4 ) 4 with an alkali chloride and sulfuric acid;

B) treating the product from step A) with soda ash or alkali hydroxide solution to a pH of about 12 to form PbO or PbCO 3 ;

C) treating the PbO or PbCO 3 from step B) with a carboxylic acid having 1-3 carbon atoms to form a solution of lead carboxylate; and then

D) treating the solution of lead carboxylate with an alkali hydroxide to obtain highly pure litharge PbO or Pb(OH) 2 .

2. The process of claim 1 wherein the alkali hydroxide is sodium hydroxide or potassium hydroxide.

3. The process of claim 1 wherein the carboxylic acid is acetic acid and in step C) a pH of about 3 to 4 is obtained.

4. The process of claim 1 wherein the temperature in step D) is about 80-90° C. and there is an inert atmosphere.

5. The process of claim 1 wherein chlorine gas is formed and collected in a sodium hydroxide solution and sodium hypochlorite is collected.

6. The process of claim 1 wherein PbO is recovered from step D) and mixed under an oxygen-free atmosphere with molten lead metal to form leady lead oxide.

7. The process of claim 1 wherein PbO is recovered from step D) and heated at an elevated temperature to form Pb 3 O 4 .

8. The process of claim 1 wherein the lead carboxylate solution of step C) is added to a solution of sodium hydroxide under an inert atmosphere at a pH of about 10.5 to form Pb(OH) 2 .

9. The process of claim 8 wherein 50% sodium hydroxide is used and the temperature is below 25° C.

10. A process for recovering highly pure litharge PbO from spent lead acid battery paste which comprises the steps of;

1) treating an aqueous mixture of spent lead acid battery paste with dilute sulfuric acid and then with sodium chloride to reduce any Pb 3 O 4 present to PbO;

2) filtering the product of step 1) and washing the filter cake with dilute sodium hydroxide until the pH of the filtrate formed was about 12;

3) washing the filter cake of step 2) until a pH of about 8 is obtained and then treating an aqueous mixture of the filter cake with acetic acid and maintaining a temperature at 60-80° C. to form a solution of lead acetate;

4) adding the filtrate containing lead acetate from step 3) to a sodium hydroxide solution at elevated temperatures to obtain pure litharge PbO, and then

5) recovering the litharge PbO.

11. The process of claim 10 wherein the PbO recovered in step 4) is heated at an elevated temperature to form Pb 3 O 4 .

12. The process of claim 10 wherein a solution of sodium hydroxide is added to the lead acetate solution of step 3) under an inert atmosphere at a pH of about 10.5 to form Pb(OH) 2 .