METHOD FOR EXTRACTING PALLADIUM

Abstract

A method for extracting palladium includes: (1) mixing a palladium-containing material with nitric acid and an alkali metal ion-containing catalyst to obtain a mixed solution, heating the mixed solution, and removing a resulting residue to obtain a palladium-containing leaching liquor; and (2) subjecting the palladium-containing leaching liquor obtained in step (1) to separative extraction to obtain metallic palladium or at least one palladium-containing product, and reusing a residual solution for step (1) in a subsequent extraction. The alkali metal ion-containing catalyst of the present disclosure can leach palladium at a higher rate than that when pure nitric acid of the same concentration is used and does not volatilize, such that the recycling of a mother liquor can be realized. The method involves simple operations, has low production costs, greatly shortens the palladium extraction time, does not lead to secondary pollution, and meets the requirements of environmental protection.

Claims

1. A method for extracting a palladium, comprising the following steps: (1) mixing a palladium-containing material with nitric acid and an alkali metal ion-containing catalyst to obtain a mixed solution, heating the mixed solution to allow a reaction, and removing a resulting residue to obtain a palladium-containing leaching liquor; and (2) subjecting the palladium-containing leaching liquor obtained in the step (1) to a separative extraction to obtain a metallic palladium or at least one palladium-containing product, and reusing a residual solution for the step (1).

2. The method according to claim 1, wherein in the step (1), an alkali metal ion comprises any one selected from the group consisting of Li.sup.+, Na.sup.+, and K.sup.+.

3. The method according to claim 1, wherein in the step (1), a concentration of the alkali metal ion in the mixed solution is higher than or equal to 1 mol/L.

4. The method according to claim 1, wherein in the step (1), the palladium-containing material has a palladium content of higher than or equal to 100 ppm.

5. The method according to claim 1, wherein in the step (1), the mixed solution has a hydrogen ion concentration of higher than or equal to 1 mol/L.

6. The method according to claim 1, wherein in the step (1), the reaction is conducted at a temperature higher than or equal to 40° C. and preferably higher than or equal to 60° C.

7. The method according to claim 1, wherein in the step (2), a method for the separative extraction comprises an electrolysis, an extractive separation, an ion exchange, an adsorption, or an evaporative crystallization.

8. The method according claim 7, wherein in the step (2), the method for the separative extraction comprises: subjecting the palladium-containing leaching liquor obtained in the step (1) to the electrolysis, so the metallic palladium is obtained at a cathode; and reusing the residual solution obtained after the electrolysis for the step (1).

9. The method according to claim 1, comprising the following steps: (1) mixing the palladium-containing material having a palladium content of higher than or equal to 100 ppm with a catalyst having a higher concentration than or equal to 1 mol/L and comprising Li.sup.+, Na.sup.+, or K.sup.+ and the nitric acid having a hydrogen ion concentration of higher than or equal to 1 mol/L, heating to allow the reaction at a temperature of higher than or equal to 40° C., and removing the resulting residue to obtain the palladium-containing leaching liquor; and (2) subjecting the palladium-containing leaching liquor obtained in the step (1) to the separative extraction to obtain the metallic palladium or the at least one palladium-containing product, and reusing the residual solution for the step (1) to realize a recycling of a mother liquor.

10. The method according to claim 2, wherein in the step (1), the alkali metal ion is Li.sup.+.

11. The method according to claim 3, wherein in the step (1), the concentration of the alkali metal ion in the mixed solution is higher than or equal to 5 mol/L.

12. The method according to claim 6, wherein the temperature is higher than or equal to 60° C.

13. The method according to claim 2, wherein in the step (1), a concentration of the alkali metal ion in the mixed solution is higher than or equal to 1 mol/L.

14. The method according to claim 13, wherein in the step (1), the concentration of the alkali metal ion in the mixed solution is higher than or equal to 5 mol/L.

15. The method according to claim 2, wherein in the step (1), the palladium-containing material has a palladium content of higher than or equal to 100 ppm.

16. The method according to claim 3, wherein in the step (1), the palladium-containing material has a palladium content of higher than or equal to 100 ppm.

17. The method according to claim 2, wherein in the step (1), the mixed solution has a hydrogen ion concentration of higher than or equal to 1 mol/L.

18. The method according to claim 3, wherein in the step (1), the mixed solution has a hydrogen ion concentration of higher than or equal to 1 mol/L.

19. The method according to claim 4, wherein in the step (1), the mixed solution has a hydrogen ion concentration of higher than or equal to 1 mol/L.

20. The method according to claim 2, wherein in the step (1), the reaction is conducted at a temperature higher than or equal to 40° C.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To facilitate the understanding of the present disclosure, some examples of the present disclosure are listed below. Those skilled in the art should understand that these examples help to explain the present disclosure and should not be regarded as specific limitations to the present disclosure.

Example 1

[0037] In this example, a method for extracting palladium is provided, including the following steps:

[0038] (1) 79 g of a palladium powder (palladium content: 95%) was mixed with a solution including 1.5 mol/L lithium nitrate and 6 mol/L nitric acid. The resulting mixture was heated to allow leaching at 80° C. The resulting residue was removed to obtain a palladium-containing leaching liquor.

[0039] (2) The palladium-containing leaching liquor obtained in step (1) was subjected to evaporative concentration for crystallization. The resulting crystal was separated to obtain a palladium nitrate product. The residual mother liquor was reused for step (1).

Example 2

[0040] In this example, a method for extracting palladium is provided, including the following steps:

[0041] (1) 3.5 g of a palladium powder (palladium content: 87%) and 0.16 mol of a lithium carbonate solid were mixed to obtain a resulting solution. Nitric acid was added to adjust the H.sup.+ concentration of the resulting solution to 1 mol/L and a Li.sup.+ concentration to 1 mol/L. The resulting mixture was heated to allow leaching at 80° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0042] (2) The palladium-containing leaching liquor obtained in step (1) was subjected to electrolysis with a current density of 100 A/m.sup.2 to obtain pure metallic palladium, and the residual solution obtained after the electrolysis was reused for step (1).

Example 3

[0043] In this example, a method for extracting palladium was provided, including the following steps:

[0044] (1) 100 g of anode sludge with a palladium content of 100 ppm was mixed with a solution including 7 mol/L sodium nitrate and 1.3 mol/L nitric acid. The resulting mixture was heated to allow leaching at 60° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0045] (2) The palladium-containing leaching liquor obtained in step (1) was subjected to adsorption replacement with a copper powder to obtain a metallic palladium precipitate, and the residual solution was reused for step (1).

Example 4

[0046] In this example, a method for extracting palladium was provided, including the following steps:

[0047] (1) 3.8 g of a palladium powder (palladium content: 99.95%) was mixed with a solution including 5 mol/L potassium nitrate, 1 mol/L lithium nitrate, and 1.0 mol/L nitric acid. The resulting mixture was heated to allow leaching at 40° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0048] (2) The palladium-containing leaching liquor obtained in step (1) was subjected to electrolysis with a current density of 500 A/m.sup.2 to obtain a palladium sponge. Nitric acid was added to the residual solution obtained after the electrolysis, and the resulting solution was reused for step (1).

Example 5

[0049] In this example, a method for extracting palladium was provided, including the following steps:

[0050] (1) 150 g of an aluminum oxide-palladium catalyst with 0.3% of palladium was mixed with a solution including 6 mol/L lithium nitrate and 1.5 mol/L nitric acid. The resulting mixture was heated to allow leaching at 50° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0051] (2) Diisoamyl sulfide (S201) was added to the palladium-containing leaching liquor obtained in step (1) for extraction. The raffinate was reused for step (1), and the resulting organic phase was subjected to reverse extraction to obtain a palladium nitrate product.

Example 6

[0052] In this example, a method for extracting palladium was provided, including the following steps:

[0053] (1) 100 g of an aluminum oxide-palladium catalyst with 0.5% of palladium was mixed with a solution including 6 mol/L sodium nitrate and 1.8 mol/L nitric acid. The resulting mixture was heated to allow leaching at 60° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0054] (2) The palladium-containing leaching liquor obtained in step (1) was allowed to pass through a chelating piperidine resin (R410) adsorption column. The adsorption column was then washed with dilute hydrochloric acid and subjected to elution with thiourea to obtain a highly-pure palladium salt product, and the residual solution was reused for step (1).

Example 7

[0055] This example was different from Example 6 only in that, in step (2), activated carbon was used to adsorb palladium in the leaching liquor, and the resulting product was washed and dried to obtain a palladium-carbon composite.

Example 8

[0056] In this example, a method for extracting palladium was provided, including the following steps:

[0057] (1) 1.04 g of a palladium powder (palladium content: 99.95%) was mixed with a solution including 6 mol/L lithium nitrate and 1 mol/L nitric acid, the resulting mixture was heated to allow leaching at 80° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0058] (2) The palladium-containing leaching liquor obtained in step (1) was subjected to electrolysis with a current density of 400 A/m.sup.2 to obtain pure metallic palladium, and the residual solution obtained after the electrolysis was reused for step (1).

Example 9

[0059] This example was different from Example 8 only in that, in step (1), a concentration of lithium nitrate in the solution was 0.5 mol/L.

Example 10

[0060] This example was different from Example 8 only in that, in step (1), the leaching was conducted at 30° C.

Example 11

[0061] This example was different from Example 8 only in that, in step (1), a concentration of nitric acid in the solution was 0.5 mol/L.

Comparative Example 1

[0062] In this comparative example, a method for extracting palladium was provided, which was different from Example 8 only in that: in step (1), 1.04 g of a palladium powder (palladium content: 99.95%) was mixed with 7 mol/L nitric acid, the resulting mixture was heated to allow leaching at 80° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

Comparative Example 2

[0063] In this comparative example, a method for extracting palladium was provided, which was different from Example 8 only in that: in step (1), 1.04 g of a palladium powder (palladium content: 99.95%) was mixed with a 7 mol/L lithium nitrate solution, the resulting mixture was heated to allow leaching at 80° C., and the resulting residue was removed to obtain a palladium-containing leaching liquor.

[0064] A concentration of palladium in the palladium-containing leaching liquor was determined by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). A leaching time of 5 h was adopted in each of Examples 1 to 11 and Comparative Examples 1 and 2. Palladium leaching rates in Examples 1 to 11 and Comparative Examples 1 and 2 are shown in Table 1.

TABLE-US-00001 TABLE 1 Palladium leaching rate Example 1 91.3% Example 2 92.7% Example 3 93.4% Example 4 92.3% Example 5 95.6% Example 6 94.3% Example 7 93.4% Example 8 99.6% Example 9 22.17% Example 10 5.83% Example 11 7.71% Comparative Example 1 0.6% Comparative Example 2 Not leached

[0065] It can be seen from Table 1 that, the method of the present disclosure can efficiently achieve the extraction of palladium. The palladium nitrate leaching rate in each of Examples 1 to 8 is higher than 91%. In the method for extracting palladium in Example 9, due to the low alkali metal ion concentration in the solution in step (1), the catalytic effect is poor, and thus a palladium nitrate leaching rate is decreased, which reduces the palladium recovery rate. In the method for extracting palladium in Example 10, due to a low leaching temperature in step (1), the leaching reaction is incomplete, which reduces the palladium nitrate leaching rate and palladium recovery rate. In the method for extracting palladium in Example 11, due to insufficient acidity in the solution in step (1), the oxidizing ability is weak, which reduces the palladium nitrate leaching rate and palladium recovery rate.

[0066] In Comparative Example 1, a system with 7 mol/L HNO.sub.3 is used to leach palladium. After the heated leaching is conducted for 5 h, a palladium leaching rate is only 0.6%; the palladium leaching rate is very low and a large amount of a waste acid solution is produced.

[0067] In Example 8, the same amount of a solution including 6 mol/L lithium nitrate and 1 mol/L nitric acid and the same temperature are adopted, and after the heated leaching is conducted for 5 h, a palladium leaching rate is 99.6%, indicating that the addition of lithium ions plays a prominent catalytic role.

[0068] In Comparative Example 2, a system including 7 mol/L lithium nitrate is used to leach palladium. After the leaching is conducted for 5 h, the palladium still cannot be leached out, indicating that the acidic condition is a necessary condition for palladium leaching.

[0069] The above are merely specific implementations of the present disclosure, and the protection scope of the present disclosure is not limited thereto. Those skilled in the art should understand that any modification or replacement easily conceived by those skilled in the art within the technical scope of the present disclosure should fall within the protection scope and disclosure scope of the present disclosure.