Complete non-cyanogens wet process for green recycling of waste printed circuit board

• US 9,689,055 B2
• Filed: 08/29/2012
• Issued: 06/27/2017
• Est. Priority Date: 05/28/2010
• Status: Expired due to Fees

• Current Assignee: Beijing University of Science and Technology
• Original Assignee: Beijing University of Science and Technology
• Inventors: Liu, Bo, Zhang, Shengen, Pan, Dean, Tian, Jianjun, Li, Bin
• Primary Examiner(s): THOMAS, CIEL P
• Application Number:
  US13/598,177
• Publication Number:
  US 20120318681A1
• Time in Patent Office: 1,763 Days
• Field of Search: 205574-586
• CPC Class Codes: C22B 11/046 from manufactured products, e.g. from printed circuit boards, from photographic films, paper or baths
• CPC Class Codes: C22B 15/0056 Scrap treating
• CPC Class Codes: C22B 7/00 Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals briquetting of scrap C22B1/248; preliminary treatment of scrap C22B1/005
• CPC Class Codes: C25C 1/12 of copper
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

The invention related to the recycling field of waste printed circuit boards (WPCB), and especially involved a complete non-cyanogens wet process for green recycling of WPCB, which belonged to the field of recycle economy. In the invention, the process included that WPCB were broken by the jaw crusher, and then mixed copper powders and nonmetallic powders were separated by the method of air classification, the mixed copper powders were smelted and casted to get copper anode plates, the copper was purified by electrolytion, the valuable metals (such as copper, gold, silver, platinum and palladium, lead and tin) were recycled from the copper anode slime, and the waste water was recycled. The recovery ratio of all-metal was above 98%. The purity of the cathode copper was up to 4N level. The ratio of de-coppering was above 96%. The recovery ratio of gold was above 98.

Claims

1. A method of recycling a waste printed circuit board (WPCB) comprising:

1) breaking the WPCB to obtain a powder mixture, separating a copper powder from the powder mixture by a gravity separation, and casting copper anode plates by smelting the copper powder;

2) electrolyzing the copper anode plates in an electrolytic bath comprising CuSO₄ and H₂SO₄ to obtain a cathode copper and a copper anode slime;

3) performing a de-coppering process that comprises mixing the copper anode slime with a de-coppering solution containing H₂SO₄ and NaCl;

adding MnO₂ into the de-coppering solution;

separating a first slag from the de-coppering solution by filtration; and

returning a first filtrate after separating the first slag to the electrolytic bath;

4) performing a de-golding process that comprises putting the first slag in a de-golding solution comprising NaCl, H₂SO₄ and NaClO₃;

separating a second slag from the de-golding solution by filtration;

reducing a second filtrate after separating the second slag by Na₂SO₃ to obtain rough gold powders, wherein a residual solution of the second filtrate after removing rough gold powders is a first remanent reduction liquid;

5) performing a process of obtaining a platinum and palladium concentrate that comprises adjusting a pH value of the first remanent reduction liquid to 0-2;

adding a metathesis metal into the first remanent reduction liquid until the pH value thereof reaches 2.5-3, wherein the metathesis metal is zinc, iron, or a mixture thereof;

6) performing a de-silvering process that comprises;

putting the second slag in a de-silvering solution comprising Na₂SO₃;

separating a third slag from the de-silvering solution by filtration, and reducing a third filtrate after separating the third slag to obtain rough silver powders;

7) performing a de-leading process that comprises heating the third slag in a de-leading solution comprising HCl, NaCl and CaCl₂;

separating a fourth slag from the de-leading solution by filtration;

cooling a fourth filtrate to precipitate out PbCl₂;

separating the PbCl₂ solids from the fourth filtrate to obtain a second remanent reduction liquid and returning the second remanent reduction liquid to the de-leading solution; and

8) performing a de-tinning process that comprises mixing the fourth slag and NaOH to obtain a mixture;

roasting the mixture;

quenching the roasted mixture by water to obtain a de-tinning solution;

separating a fifth slag from the de-tinning solution by filtration; and

evaporating a fifth filtrate after separating the fifth slag to obtain Na₂SnO₃.

2. The method of claim 1, wherein the electrolytic bath has a H₂SO₄ concentration of 0.5-2 mol/L, a CuSO₄ concentration of 0.2-1.5 mol/L, a gelatin concentration of 50-300 mg/L, a thiourea concentration of 50-300 mg/L, a current density of 100-500 A/m², and an electrolytic temperature of 30-80°

C.

3. The method of claim 2, wherein the electrolytic bath has the H₂SO₄ concentration of 1-2 mol/L, the CuSO₄ concentration of 0.5-1 mol/L, the gelatin concentration of 50-100 mg/L, and the thiourea concentration of 100-150 mg/L.

4. The method of claim 1, wherein the de-coppering solution has a H₂SO₄ concentration of 0.5-5 mol/L, a NaCl concentration of 0.1-5 mol/L, an amount of MnO₂ at 2-40% of a weight of the anode slime, a solid-to-liquid ratio of 1:

4-1;

20, wherein the de-coppering process has a reaction temperature of 30-90°

C., and a reaction time of 0.5-5 h.

5. The method of claim 4, wherein the de-coppering solution has the H₂SO₄ concentration of 1-2 mol/L, the NaCl concentration of 0.5-2 mol/L, the amount of MnO₂ at 10-20% of the weight of the anode slime, and the solid-to-liquid ratio of 1:

5-1;

10.

6. The method of claim 1, wherein the de-golding solution has a NaCl concentration of 20-100 g/L, a H₂SO₄ concentration of 50-300 g/L, a molar ratio of NaClO₃ and NaCl of 1:

5-3;

5, a solid-to-liquid ratio of 1;

4-1;

20, wherein the de-golding process has a reaction temperature of 50-95°

C., a reaction time of 0.5-5 h, a Na₂SO₃ concentration of 70-280 g/L, a reduction temperature of 10-50°

C., and a reduction time of 5-60 min.

7. The method of claim 6, wherein the de-golding solution has a NaCl concentration of 20-100 g/L, the H₂SO₄ concentration of 100-200 g/L, the solid-to-liquid ratio of 1:

5-1;

10, and wherein the concentration of Na₂SO₃ used for reducing the second filtrate is 150-250 g/L.

8. The method of claim 1, wherein the de-silvering solution has a Na₂SO₃ concentration of 70-280 g/L, a solid-to-liquid ratio of 1:

4-1;

20, a pH value of 11-14, a reducing agent that is formaldehyde or oxalic acid at a mass ratio of the reducing agent to silver of 1;

5-5;

5, wherein the de-silvering process has a reaction temperature of 20-50°

C. and a reaction time of 0.5-5 h.

9. The method of claim 8, wherein the de-silvering solution has the Na₂SO₃ concentration of 100-230 g/L and the solid-to-liquid ratio of 1:

5-1;

10.

10. The method of claim 1, wherein in the de-leading solution has a HCl concentration of 10-200 g/L, a NaCl concentration of 50-350 g/L, a CaCl₂ concentration of 10-300 g/L, a total concentration of chloride ion of 3-6.5 mol/L, a solid-to-liquid ratio of 1:

5-1;

30, wherein the de-leading process has a reaction temperature is 70-110°

C., and a reaction time is 0.5-5 h.

11. The method of claim 10, wherein in the de-leading solution has a HCl concentration of 50-150 g/L, the NaCl concentration of 200-300 g/L, the CaCl₂ concentration of 10-100 g/L, and the solid-to-liquid ratio of 1:

10-1;

20.

12. The method of claim 1, further comprising adding CaCl₂ to the second remanent reduction liquid of the de-leading process so that the CaCl₂ concentration in the second remanent reduction liquid reaches 10-300 g/L.

13. The method of claim 12, wherein the CaCl₂ concentration in the second remanent reduction liquid reaches 10-100 g/L.

14. The method of claim 1, employing no aqua regia or cyanide.

15. The method of claim 1, wherein the copper anode slime comprises PbSO₄, SnO₂, Ag₂SO₄, copper, and a noble metal that is gold, platinum, or palladium.

16. The method of claim 1, wherein in step 8), a mass ratio of the fourth slag and NaOH is 1:

1-10;

1, a roasting temperature is 300-600°

C., and a roasting time is 0.5-5 h.

17. The method of claim 1, wherein the metathesis metal is zinc.

18. The method of claim 1, wherein the third filtrate is reduced using formaldehyde.