Desulfurisation of lead-containing waste

Patent metadata

Field	Value
Publication number	US-2023235427-A1
Application number	US-202318190899-A
Country	US
Kind code	A1
Filing date	Mar 27, 2023
Priority date	Aug 12, 2019
Publication date	Jul 27, 2023
Grant date	—

Abstract

The present invention relates to the desulfurisation of lead-containing waste. In particular, the present invention relates to a method in which lead-containing waste is desulfurised to form a desulfurised lead-containing waste material which is suitable for recycling into lead or leady oxide. The method is particularly suitable for desulfurising lead-acid battery paste.

First claim

1 . A method for desulfurising lead-containing waste, the lead containing waste comprising PbSO 4 , said method comprising:
(a) treating an aqueous slurry of the lead-containing waste with a hydroxide base thereby forming desulfurised lead-containing waste in which PbSO 4 has been converted to PbO and an aqueous solution comprising sulfate anions; and (b) separating the desulfurised lead-containing waste from the aqueous solution comprising sulfate anions, wherein a pH in the range of from 11 to 15 is maintained during step (a).

2 . The method of claim 1 , wherein the lead-containing waste comprises Pb, PbO, PbO 2 , or a combination thereof.

3 . The method of claim 1 , wherein the lead-containing waste is derived from lead-acid battery paste or from electric arc furnace dusts.

4 . The method of claim 1 , wherein the lead-containing waste used in step (a) is in a particulate form where at least 100% by weight of the granules pass through a mesh having openings with a diameter of 1 cm.

5 . The method of claim 1 , wherein a pH in the range of from 11.5 to 14.5 is maintained in step (a).

6 . The method of claim 1 , wherein the pH is maintained during step (a) by further addition of the hydroxide base to the aqueous slurry.

7 . The method of claim 1 , wherein the base is a metal hydroxide base.

8 . The method of claim 1 , wherein the hydroxide base is consumed in step (a) in an amount of from 1.9 to 2.1 moles per mole of lead sulfate in the lead-containing waste.

9 . The method of claim 1 , wherein the aqueous slurry in step (a) has a solids content of from 30 to 80 by weight.

10 . The method of claim 1 , wherein step (a) is carried out at a temperature of from 0 to 70° C.

11 . The method of claim 1 , wherein the lead-containing waste is comminuted during step (a).

12 . The method of claim 11 , wherein step (a) is carried out in a mill.

13 . The method of claim 12 , wherein the mill is operated at a speed of from 5 to 60 rpm.

14 . The method of claim 12 , wherein the mill is operated:
in a continuous mode; and/or as a closed circuit mill.

15 . The method of claim 11 , wherein the desulfurised lead-containing waste that is produced in step (a) is in a particulate form, where at least 80% by weight of the particles pass through a mesh having openings with a diameter of 150 μm or less.

16 . The method of claim 1 , wherein a conditioning step is carried out between steps (a) and (b), the conditioning step comprising:
leaving the desulfurised lead-containing waste and the aqueous solution comprising sulfate ions that are formed in step (a) in a tank for a period of time; and/or then adding water to the desulfurised lead-containing waste and the aqueous solution comprising sulfate ions that is formed in step (a).

17 . The method of claim 1 , wherein the desulfurised lead-containing waste is separated from the aqueous solution comprising sulfate anions using filtration.

18 . The method of claim 1 , wherein step (b) comprises washing the desulfurised lead-containing waste with water and monitoring the sulfate content of the used wash water to determine when a target level of sulfate has been achieved.

19 . The method of claim 18 , wherein monitoring comprises measuring the conductivity of the used wash water.

20 . The method of claim 1 , wherein:
at least 95% of the sulfur is removed from the lead-containing waste; and/or at least 95 of the lead that was present in the lead-containing waste used in step (a) is retained.

21 . The method of claim 1 , wherein the desulfurised lead-containing waste which is obtained at the end of step (b) comprises:
PbSO 4 in an amount of less than 1% by weight; lead hydroxide forms in an amount of less than 1% by weight; PbCO 3 in an amount of less than 2% by weight; and/or PbO in an amount of at least 40 by weight.

22 . A desulfurised lead-containing waste which is obtainable using a method as defined in claim 1 .

23 . A desulfurised lead-containing waste, which comprises:
PbO in an amount of at least 40%; PbO 2 in an amount of at least 10%; Pb in an amount of at least 1%; and lead hydroxide forms in an amount of less than 5%, by weight.

24 . A method of recycling lead-containing waste, said method comprising processing a desulfurised lead-containing waste into a lead-containing material, wherein the desulfurised lead-containing waste is as defined in claim 22 .

25 . The method of claim 24 , wherein the desulfurised lead-containing waste is further processed:
in furnace into a lead ingot;
or by:
(a) treating 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;

or by:
(a) dissolving the lead-containing waste in an aqueous solution of a first acid to form a solution of a first lead salt;
(b) adding a second acid to the solution of the first lead salt to form a lead-depleted solution and a precipitate of a second lead salt; and
(c) converting the precipitate of the second lead salt into leady oxide, wherein the first lead salt has a higher solubility in water than the second lead salt.

Assignees

• Ever Resource Ltd
• Cambridge Entpr Ltd

Inventors

• Selvaraj Vimalnath
• Andrew Stephen Charles
• Fox Athan
• Kumar Ramachandran Vasant
• Lowe Spencer David
• Yiao Marcel

Classifications

• C22B13/045 Primary

  Recovery from waste materials · CPC title

• C01G21/06

  Lead monoxide [PbO] · CPC title

• C22B1/005

  Preliminary treatment of scrap (C22B1/02 - C22B1/26 take precedence) · CPC title

• C22B7/006

  Wet processes · CPC title

• C22B7/02

  Working-up flue dust · CPC title