Method for leaching platinum group metals from spent catalyst by UV-vis

Abstract

The present invention belongs to the field of recovery of secondary resources of noble metals, and discloses a method for leaching platinum group metals from spent catalyst by UV-vis, which uses ferric oxalate complex/hydrogen peroxide-chloride salt solution as a solvent for extracting platinum group metals under the condition of UV-vis, converts the platinum group metals from metallic state to platinum group metal complex, and obtains platinum group metal lixivium to realize the leaching of the platinum group metals. The platinum leaching rate of the method of the present invention can reach more than 97%. The present invention has mild reaction conditions, realizes the green recovery of platinum group metals from spent catalyst, avoids the use of strong acids and bases and toxic substances and avoids the production of toxic gases in the leaching process, so as to reduce the environmental hazards of the spent catalyst.

Claims

1. A method for leaching platinum group metals from spent catalyst by UV-vis, which uses a platinum group metal lixiviant for extracting platinum group metals from spent catalyst under the condition of UV-vis to obtain platinum group metal lixivium, so as to recover platinum group metals from spent catalyst, comprising the following steps: (1) shearing spent catalyst, crushing to 80-200 meshes, and sieving; (2) preparing the platinum group metal lixiviant: uniformly mixing ferric oxalate complex with chloride salt solution at a liquid-to-solid ratio of 40:1 to 10:1, adding 30 wt % aqueous hydrogen peroxide solution with a volume fraction of 0.1-4 vol. % of the system, and mixing uniformly; wherein the chloride salt is at least one of sodium chloride, potassium chloride and ammonium chloride; (3) leaching platinum group metals: adding the spent catalyst sieved in step (1) to the platinum group metal lixiviant obtained in step (2) at a liquid-to-solid ratio of 20:1 to 5:1, and stirring under the condition of UV-vis for 10-120 min at a speed of 200-600 r/min to obtain a mixture, wherein the wavelength range of the UV-vis is 200-760 nm; (4) carrying out solid-liquid separation: carrying out solid-liquid separation of the mixture obtained in step (3), the liquid phase obtained is a mixture of platinum group metal lixivium and ferric oxalate complex, and the solid phase is solid catalyst; (5) separating the platinum group metals: placing the liquid phase obtained in step (4) under UV-vis for 2-24 h to obtain a solid-liquid mixture, the solid phase is ferrous oxalate solid, and the liquid phase is platinum group metal lixivium; (6) stirring the platinum group metal lixivium obtained in step (5) at 40-80? C. for 2-8 h at a speed of 200-600 r/min to obtain a solid substance enriched with platinum group metals; (7) recycling iron: collecting the ferrous oxalate solid obtained in step (5), washing with deionized water, drying at 40-80? C. for 12-24 h, and roasting at 300-700? C. for 4-8 h to obtain ferric oxide; (8) the ferric oxide obtained in step (7) can be recycled as a reactant for preparing ferric oxalate complex.

2. The method according to claim 1, wherein the spent catalyst is derived from spent catalyst for industrial treatment of VOCs with platinum group metals as the active component, and the platinum group metals include at least one of platinum (Pt), palladium (Pd) and rhodium (Rh).

3. The method according to claim 1, wherein the ferric oxalate complex is obtained from oxalic acid and ferric oxide under the condition of oil bath, wherein water is used as a solvent, a mass ratio of the oxalic acid to the ferric oxide is 5:1 to 1:1, a liquid-to-solid ratio is 10:1 to 2:1, stirring is carried out at 60-98? C. for 0.5-10 h at a speed of 400-800 r/min, and a concentration of the ferric oxalate complex obtained is 50-370 g/L.

Description

DESCRIPTION OF DRAWINGS

(1) The sole figure is a process flow chart of a method for recovering platinum group metals from spent VOC catalyst by UV-vis in specific embodiments of the present invention.

DETAILED DESCRIPTION

(2) The present invention is further described below in detail in combination with some specific embodiments, but the protection scope of the present invention is not limited to the following content.

(3) The process flow chart of the method for recovering platinum group metals from spent catalyst by UV-vis of the present invention is shown in the sole figure, comprising the following specific steps: (1) Grinding, milling and sieving spent catalyst; (2) Thoroughly mixing the powder sample obtained in step (1) with lixiviant, stirring under a UV lamp (200-400 nm, 90-400 mW/cm 2) to obtain a solid-liquid mixture, the solid is catalyst carrier, and the liquid is a mixture of lixivium enriched with platinum group metals and ferric oxalate.

(4) (3) Placing the liquid mixture obtained in step (2) under the UV lamp to obtain a solid-liquid mixture, the solid is ferrous oxalate precipitation and is recycled as a raw material after roasting, and the liquid is lixivium enriched with platinum group metals.

(5) The following embodiments 1-11 and reference examples 1, 2 and 3 adopt the process flow as shown above.

(6) The components of platinum group metals in the spent catalyst used in the following embodiments 1-11 and reference examples 1, 2 and 3 comprise 185-640 g/t Pt, 105-865 g/t Pd and 120-735 g/t Rh.

Embodiment 1

(7) (1) Spent catalyst (637 g/t Pt) is ground, milled and crushed to 200 meshes, and sieved for later use; 40 mL of ferric oxalate complex with the oxalate concentration of 200-220 g/L is uniformly mixed with sodium chloride at a liquid-to-solid ratio of 20:1, and 30% aqueous hydrogen peroxide solution with a volume fraction of 2.2-2.6 vol. % is added and uniformly mixed for later use; and the ground and milled sample is added to lixiviant at a liquid-to-solid ratio of 10:1, and stirred under the condition of UV-vis with a wavelength of 320-400 nm for 10-30 min at a speed of 200-400 r/min to obtain a mixture;

(8) (2) The mixture obtained in step (1) is subjected to solid-liquid separation, the liquid phase obtained is a mixture of platinum group metal lixivium and ferric oxalate complex, and the solid phase is solid catalyst; and the liquid-phase mixture is placed under UV-vis for 24-48 h to obtain a solid-liquid mixture, the solid phase is ferrous oxalate solid, and the liquid phase is platinum group metal lixivium;

(9) (3) The ferrous oxalate solid obtained in step (2) is collected, washed with deionized water, dried at 60-80? C. for 24-48 h, and roasted at 500-700? C. for 4-8 h to obtain ferric oxide which is recycled as a reactant for preparing ferric oxalate complex.

Embodiment 2

(10) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 60-80 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 3

(11) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 4

(12) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 340-360 g/L, the volume of the ferric oxalate complex is 20 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 5

(13) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume fraction of hydrogen peroxide is changed from 2.2-2.6vol.% to 1.8-2.2vol.%, and the other conditions are exactly the same as in embodiment 1.

Embodiment 6

(14) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume fraction of hydrogen peroxide is changed from 2.2-2.6vol.% to 1.4-1.8vol.%, and the other conditions are exactly the same as in embodiment 1.

Embodiment 7

(15) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume fraction of hydrogen peroxide is changed from 2.2-2.6vol.% to 0.6-1.0vol.%, and the other conditions are exactly the same as in embodiment 1.

Embodiment 8

(16) In the present embodiment, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume fraction of hydrogen peroxide is changed from 2.2-2.6vol.% to 0.2-0.6vol.%, and the other conditions are exactly the same as in embodiment 1.

Embodiment 9

(17) In the present embodiment, the spent catalyst (637 g/t Pt) in embodiment 1 is replaced with spent catalyst (185 g/t Pt), the concentration of oxalate in the ferric oxalate complex is changed from 200-220 g/L to 340-360 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 10

(18) In the present embodiment, the spent catalyst (637 g/t Pt) in embodiment 1 is replaced with spent catalyst (106 g/t Pd), the concentration of oxalate in the ferric oxalate complex is changed from 200-220 g/L to 340-360 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 11

(19) In the present embodiment, the spent catalyst (637 g/t Pt) in embodiment 1 is replaced with spent catalyst (863 g/t Pd), the concentration of oxalate in the ferric oxalate complex is changed from 200-220 g/L to 340-360 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 12

(20) In the present embodiment, the spent catalyst (637 g/t Pt) in embodiment 1 is replaced with spent catalyst (328 g/t Rh), the concentration of oxalate in the ferric oxalate complex is changed from 200-220 g/L to 340-360 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 13

(21) In the present embodiment, the sodium chloride in embodiment 1 is replaced with potassium chloride of the same mass, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 14

(22) In the present embodiment, the wavelength of the UV lamp in embodiment 1 is changed from 320-400 nm to 200-320 nm, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Embodiment 15

(23) In the present embodiment, the wavelength of the UV lamp in embodiment 1 is changed from 320-400 nm to 400-760 nm, the concentration of oxalate in the ferric oxalate complex in embodiment 1 is changed from 200-220 g/L to 270-290 g/L, the volume of the ferric oxalate complex is 80 mL, and the other conditions are exactly the same as in embodiment 1.

Reference Example 1

(24) Compared with embodiment 1, no ferric oxalate complex is added in the present reference example, and the other conditions are exactly the same as in embodiment 1.

Reference Example 2

(25) Compared with embodiment 1, no hydrogen peroxide is added in the present reference example, and the other conditions are exactly the same as in embodiment 1.

Reference Example 3

(26) Compared with embodiment 1, the volume fraction of hydrogen peroxide is changed from 2.2-2.6vol.% to 0.1-0.4vol.% in the present reference example, and the other conditions are exactly the same as in embodiment 1.

(27) The platinum group metal lixivium obtained in embodiments 1-15 and reference examples 1-3 is detected by an inductively coupled plasma optical emission spectrometry (ICP-OES), and the leaching rate of platinum group metals is calculated.

(28) The leaching rate of platinum group metals is calculated as follows:

(29) $\mathrm{Leaching}\mathrm{rate}\left(\%\right)\mathrm{of}\mathrm{platinum}\mathrm{group}\mathrm{metals}=\frac{\mathrm{Mass}\mathrm{of}\mathrm{platinum}\mathrm{group}\mathrm{metals}\mathrm{in}\mathrm{lixivium}}{\mathrm{Mass}\mathrm{of}\mathrm{platiunum}\mathrm{group}\mathrm{metals}\mathrm{in}\mathrm{spent}\mathrm{catalyst}}?100\%$

(30) The leaching conditions of the methods in embodiments 1-15 and reference examples 1-3 are shown in Table 1:

(31) TABLE-US-00001 TABLE 1 Platinum Group Metals Leaching Conditions Embodi- Pt Pt = 637 g/t, C.sub.oxalate = 200-220 g/L, V.sub.oxalate = ment 1 40 mL, ?.sub.hydrogen peroxide = 2.2-2.6 vol. %, and chloride is sodium chloride Embodi- Pt C.sub.oxalate = 60-80 g/L, V.sub.oxalate = 80 mL, and the other ment 2 conditions are the same as in embodiment 1 Embodi- Pt C.sub.oxalate = 270-290 g/L, V.sub.oxalate = 80 mL, and the ment 3 other conditions are the same as in embodiment 1 Embodi- Pt C.sub.oxalate = 340-360 g/L, V.sub.oxalate = 20 mL, and the ment 4 other conditions are the same as in embodiment 1 Embodi- Pt C.sub.oxalate = 270-290 g/L, ?.sub.hydrogen peroxide = 1.8-2.2 ment 5 vol. %, and the other conditions are the same as in embodiment 1 Embodi- Pt C.sub.oxalate = 270-290 g/L, ?.sub.hydrogen peroxide = 1.4-1.8 ment 6 vol. %, and the other conditions are the same as in embodiment 1 Embodi- Pt C.sub.oxalate = 270-290 g/L, ?.sub.hydrogen peroxide = 0.6-1.0 ment 7 vol. %, and the other conditions are the same as in embodiment 1 Embodi- Pt C.sub.oxalate = 270-290 g/L, ?.sub.hydrogen peroxide = 0.2-0.6 ment 8 vol. %, and the other conditions are the same as in embodiment 1 Embodi- Pt Pt = 185 g/t, C.sub.oxalate = 340-360 g/L, V.sub.oxalate = ment 9 80 mL, and the other conditions are the same as in embodiment 1 Embodi- Pd Pd = 106 g/t, C.sub.oxalate = 340-360 g/L, V.sub.oxalate = ment 10 80 mL, and the other conditions are the same as in embodiment 1 Embodi- Pd Pd = 863 g/t, C.sub.oxalate = 340-360 g/L, V.sub.oxalate = ment 11 80 mL, and the other conditions are the same as in embodiment 1 Embodi- Rh Rh = 328 g/t, C.sub.oxalate = 340-360 g/L, V.sub.oxalate = ment 12 80 mL, and the other conditions are the same as in embodiment 1 Embodi- Pt Chloride is potassium chloride, C.sub.oxalate = 270- ment 13 290 g/L, V.sub.oxalate = 80 mL, and the other conditions are the same as in embodiment 1 Embodi- Pt ? = 200-320 nm, C.sub.oxalate = 270-290 g/L, V.sub.oxalate = ment 14 80 mL, and the other conditions are the same as in embodiment 1 Embodi- Pt ? = 400-760 nm, C.sub.oxalate = 270-290 g/L, V.sub.oxalate = ment 15 80 mL, and the other conditions are the same as in embodiment 1 Reference Pt No ferric oxalate complex is added, and the other example 1 conditions are the same as in embodiment 1 Reference Pt No hydrogen peroxide is added, and the other example 2 conditions are the same as in embodiment 1 Reference Pt ?.sub.hydrogen peroxide = 0.1-0.4 vol. %, and the other example 3 conditions are the same as in embodiment 1

(32) The leaching rates of platinum group metals in the methods in embodiments 1-15 and reference examples 1-3 are shown in Table 2:

(33) TABLE-US-00002 TABLE 2 Platinum Leaching Group Metals Rate (%) Embodiment 1 Pt 98.91 Embodiment 2 Pt 90.20 Embodiment 3 Pt 99.02 Embodiment 4 Pt 98.75 Embodiment 5 Pt 97.64 Embodiment 6 Pt 99.83 Embodiment 7 Pt 97.92 Embodiment 8 Pt 98.65 Embodiment 9 Pt 99.71 Embodiment 10 Pd 95.42 Embodiment 11 Pd 90.06 Embodiment 12 Rh 91.43 Embodiment 13 Pt 98.77 Embodiment 14 Pt 97.64 Embodiment 15 Pt 97.23 Reference example 1 Pt 11.48 Reference example 2 Pt 85.62 Reference example 3 Pt 97.22

(34) It can be seen from comparison of embodiments 1-4 that when the concentration of oxalate in the ferric oxalate complex used in the present invention is 50-370 g/L, the leaching effect of platinum group metals is good. It can be seen from comparison of embodiments 1 and 5-8 that when the volume fraction of hydrogen peroxide used in the present invention is 0.2-2.6vol.%, the leaching rate of platinum group metals is above 97%, and the leaching effect is the best. It can be seen from comparison of embodiments 1 and 9-12 that the present invention is suitable for the leaching of platinum group metals from spent catalyst, and the leaching rate is above 90%. It can be seen from comparison of embodiments 1 and 14-15 that the present invention can effectively leach platinum group metals from spent catalyst in the wave band of UV-vis, and the leaching rate is above 97%. It can be seen from comparison of embodiment 1 and reference examples 1-3 that the ferric oxalate complex can leach most of platinum group metals, and the addition of hydrogen peroxide further enhances the leaching of platinum group metals.

(35) It can be seen from the test results of the above embodiments and reference examples that the method for recovering platinum group metals from spent catalyst of the present invention has a leaching rate of platinum group metals above 90%, wherein the leaching rate of Pt can reach more than 97%, and the method of the present invention has mild operating conditions without secondary pollution and is easy to realize industrial application.

(36) The applicant declares that the above only describes specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any change or replacement contemplated easily by those skilled in the art within the technical scope disclosed by the present invention shall be included in the protection scope and disclosure scope of the present invention.