Lead recycling
The present invention describes a method of recycling lead from lead containing waste, the method comprising the steps of mixing the battery paste with aqueous citric acid solution so as to generate lead citrate; isolating lead citrate from the aqueous solution; and converting the lead citrate to lead and/or lead oxide.
1. A method for the recovery of lead from lead waste comprising one or more of Pb, PbO, PbO 2 , and PbSO 4 , the method comprising the steps of:
(a) treating the lead waste with aqueous citric acid solution so as to generate lead citrate;
(b) isolating lead citrate from the aqueous solution; and
(c) converting the isolated lead citrate to Pb and/or PbO.
2. The method according to claim 1 , wherein the lead citrate is Pb(C 6 H 6 O 7 ) and hydrates thereof, as well as the product of PbSO 4 treated with aqueous citric acid solution and aqueous trisodium citrate.
3. The method according to claim 1 wherein the lead waste is lead battery paste.
4. The method according to claim 1 wherein the pH of the aqueous citric acid solution is in the range pH 1.4 to 6 .
5. The method according to claim 1 wherein the aqueous citric acid solution additionally comprises a metal citrate.
6. The method according to claim 5 wherein the metal citrate is sodium citrate.
7. The method according to claim 1 wherein the aqueous citric acid solution additionally comprises hydrogen peroxide.
8. The method according to claim 7 wherein the lead waste comprises PbO and the mole ratio of PbO to hydrogen peroxide is in the range 1:0.1 to 1:4 and/or the mole ratio of PbO to citric acid is in the range 1:1 to 1:7 .
9. The method according to claim 1 wherein the temperature of the aqueous citric acid solution is maintained in the range 0 to 45° C.
10. The method according to claim 1 wherein the solid to liquid ratio of the lead waste to aqueous solution is in the range 1:1 to 1:50 w/w.
11. The method according to claim 1 wherein the isolated lead citrate is converted to Pb and/or PbO by calcination.
12. The method according to claim 11 wherein the calcination temperature is in the range 250 to 1,100° C.
13. The method according to claim 11 wherein the partial pressure of oxygen in the calcination is in the range to 0.01 to 5 atm.
14. A method of recycling a lead battery, the method comprising the steps of:
(a) obtaining lead battery paste from a lead battery;
(b) treating the lead battery paste with aqueous citric acid solution so as to generate lead citrate;
(c) isolating lead citrate from the aqueous solution;
(d) converting the isolated lead citrate to Pb and/or PbO; and
(e) incorporating the Pb and/or PbO into a battery plate.
15. The method according to claim 14 , wherein the lead citrate is Pb(C 6 H 6 0 7 ) and hydrates thereof, as well as the product of PbSO 4 treated with aqueous citric acid solution and aqueous trisodium citrate.
16. The method according to claim 14 wherein the lead citrate is isolated together with PbSO 4 .
17. The method according to claim 16 wherein the Pb and/or PbO includes PbSO 4 .