Method for selectively recovering platinum from platinum-containing aluminum oxide waste

Abstract

The invention provides a method for selectively recovering platinum from platinum-containing aluminum oxide waste, and belongs to the technical field of platinum group metal secondary resource recycling. The method comprises the following steps: removing impurities from the platinum-containing aluminum oxide waste, crushing and grinding into powder; calcining the platinum-containing waste powder to obtain a calcined material; mixing the calcined material with an extraction agent, and digesting under microwaves to obtain a digestion solution; and filtering the digestion solution to obtain a platinum-containing filtrate. According to the method, Pt is selectively recycled by adopting the platinum-containing aluminum oxide waste, gamma-Al2O3 is directionally converted into alpha-Al2O3 with stable chemical properties through calcination, meanwhile, Pt is dissolved and leached by adopting low-concentration aqua regia with the concentration of 20%-40%, dissolution of an aluminum oxide carrier is reduced, selective recycling and efficient leaching of platinum are achieved, meanwhile, a leaching agent can be repeatedly used, and the cost is low. The treatment cost and the reagent cost are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary resource recycling of platinum group metals, and specifically relates to a method for selectively recovering platinum from platinum-containing aluminum oxide waste. Background Art

[0002] Precious metal catalysts, such as platinum, palladium, silver and gold, have been shown to have high catalytic activity for the catalytic degradation of volatile organic compounds, but their poor thermal stability and coke deposition can lead to catalyst deactivation. Therefore, the recovery of spent precious metal catalysts not only realizes the recycling of secondary resources, but also obtains huge economic benefits. In addition, transition metal oxide catalysts have good thermal stability and high-temperature catalytic activity, but their catalytic activity will fail at low temperatures.

[0003] Platinum alumina (Pt / γ-Al2O3) catalysts have been widely used in the removal of industrial volatile organic compounds due to their excellent catalytic activity. Among them, platinum has the characteristics of high cost and scarcity. Efficient recovery of platinum from waste catalysts helps to achieve resource recycling. Currently, platinum recovery strategies mainly include photocatalysis, pyrometallurgy and hydrometallurgy. The literature studied a photocatalytic oxidation method in which the holes generated by the TiO2 photocatalyst can effectively convert Pt 0 Oxidation to Pt x+ . For spent Pt / γ-Al2O3 catalysts, most of the platinum nanoparticles are dispersed on the pore walls of the γ-Al2O3 molecular sieve. Since it is difficult for TiO2 particles to enter the pores, platinum oxidation cannot be carried out through heterogeneous photocatalysis, so the efficiency of photocatalytic technology becomes very low. Pyrometallurgy needs to be carried out at a high temperature of 1500-1700℃, which not only increases energy consumption, but also produces harmful gases and slag.

[0004] Chinese patent CN 117947277 A discloses a method for recovering platinum from a platinum reforming catalyst, which first roasts the catalyst to remove carbon deposits and organic matter; after crushing and grinding, add elemental iron powder, quartz sand powder, and calcium oxide, smelt enrichment water quenching and grinding to obtain platinum-containing iron alloy powder; dissolve the platinum-iron alloy powder, remove iron to obtain an enrichment with a higher platinum content; dissolve the enrichment, repeatedly precipitate, purify and reduce to obtain sponge platinum. This method requires the addition of a slag-making agent for smelting, and the amount of aqua regia used is 2 to 5 times the weight of the platinum enrichment, so it also faces the problems of high energy consumption, high cost, large amount of aqua regia, and high impurity content of aqua regia that is difficult to recycle.

[0005] Chinese patent CN 117089713 A discloses a method for recovering platinum from platinum / alumina waste catalyst and a platinum leaching system. The method performs a first stage roasting and a second stage roasting on the waste catalyst to transform γ-Al2O3 into α-Al2O3; a solution composed of NaCl, NaHSO4, H2O2 and water is used as a leaching system to leach platinum from the calcined waste catalyst, and the leaching solution is filtered to obtain a platinum-containing solution. Although the method uses a special leaching solution that is environmentally friendly and has mild reaction conditions, its use concentration is high and the H2O2 in the leaching solution will decompose quickly and is difficult to recycle.

[0006] Moreover, in the hydrometallurgical process, aqua regia and organic solvents are used as etchants to dissolve Pt0 into Ptx+. Toxic aqua regia and organic solvents can cause environmental pollution and harm human health. How to reduce the amount of aqua regia used to recover platinum from waste catalysts and selectively recover platinum to reduce the amount of platinum residue in the leached slag is still a huge challenge. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a method for selectively recovering platinum from platinum-containing alumina waste. The method of the present invention utilizes platinum-containing alumina waste to selectively recover Pt, converts γ-Al2O3 into chemically stable α-Al2O3 through calcination, and simultaneously uses an extractant with a low aqua regia content of 20% to 40% to dissolve Pt and reduce the dissolution of Al2O3, and then microwave-assisted digestion can improve the digestion speed and effect, so that the platinum leaching rate reaches 99.31%.

[0008] In order to achieve the above object, the present invention provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalyst, comprising the following steps:

[0009] 1) removing impurities, crushing and grinding the waste Pt / γ-Al2O3 catalyst into catalyst powder;

[0010] 2) calcining the catalyst powder to obtain a calcined material;

[0011] 3) mixing the calcined material and the extractant and digesting them under microwave to obtain a digestion solution;

[0012] 4) filtering and recovering the digestion solution in sequence to obtain platinum;

[0013] 5) The filtrate is extracted and separated to obtain aqua regia and platinum ion solution.

[0014] Preferably, the platinum-containing alumina waste in step 1) is discarded Pt / γ-Al2O3 catalyst.

[0015] Preferably, the mesh size of the catalyst powder in step 1) is 50-200 meshes.

[0016] Preferably, the calcination temperature in step 2) is 1000-1300°C and the calcination time is 4-8h. By calcining the catalyst powder at high temperature through the above technical solution, the γ-Al2O3 in the waste catalyst can be converted into α-Al2O3 with stable chemical properties.

[0017] Because in hydrometallurgy, both platinum and γ-Al2O3 particles in Pt / γ-Al2O3 will undergo dissolution reaction, the specific process is as follows:

[0018] 6H + +Al2O3→2Al 3+ +3H2O

[0019]

[0020] Since the weight percentage of γ-Al2O3 particles in the waste Pt / γ-Al2O3 catalyst is much greater than that of platinum particles, there are problems of high consumption of chemicals and dissolution of γ-Al2O3, making it impossible to selectively recover Pt. Converting γ-Al2O3 into chemically stable α-Al2O3 can reduce the dissolution of Al2O3 and achieve the purpose of selectively recovering Pt.

[0021] Preferably, the extractant in step 3) is a mixture of aqua regia and water; the volume proportion of aqua regia in the extractant is 20-40%. The inventors found that after the conversion of γ-Al2O3 to α-Al2O3, compared with undiluted aqua regia, a low aqua regia content of 20% to 40% can selectively leach platinum from the waste catalyst; moreover, since the low concentration of aqua regia can simultaneously reduce the dissolution of Al2O3 and the amount of reagents used without affecting the dissolution of platinum, the impurity content in the extractant can be extremely low, which is conducive to later recovery and reuse.

[0022] More preferably, the volume proportion of aqua regia in the extractant is 40%.

[0023] More preferably, the aqua regia is a mixture of 35.0-37.0 wt % HCl solution and 65.0-68.0 wt % HNO 3 solution in a volume ratio of 3:1.

[0024] Preferably, in step 3), the ratio of the calcined material to the extractant is 1 g / 3-8 ml.

[0025] Preferably, the digestion temperature in step 3) is 100-120° C. and the digestion time is 0.5-3 h.

[0026] More preferably, the digestion temperature in step 3) is 110°C.

[0027] Further preferably, the aqua regia obtained by extraction in step 5) can be reused after adjusting the concentration; and the platinum ion solution is recycled.

[0028] The beneficial effects of the present invention include at least:

[0029] The present invention removes impurities, crushes and grinds platinum-containing alumina waste into catalyst powder; calcines the catalyst powder to obtain calcined material; mixes the calcined material with an extractant and digests it under microwave to obtain a digestion solution; and sequentially filters and recovers the digestion solution to obtain platinum. The method utilizes platinum-containing alumina waste to selectively recover Pt, converts γ-Al2O3 into chemically stable α-Al2O3 through calcination, and simultaneously uses an extractant with a low aqua regia content of 20% to 40% to dissolve Pt and reduce the dissolution of Al2O3, and then microwave-assisted digestion can improve the digestion speed and effect, so that the platinum leaching rate reaches 99.31%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below by specific examples. These examples are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. The test methods in the following examples, unless otherwise specified, are conventional methods. Unless otherwise specified, the reagents and materials used can all be obtained through commercial channels.

[0032] The platinum-containing alumina waste material used in the embodiment of the present invention is discarded Pt / γ-Al2O3 catalyst.

[0033] Example 1

[0034] Experimental study on Pt leaching from waste Pt / γ-Al2O3 catalyst

[0035] Calcination catalyst:

[0036] The waste Pt / γ-Al2O3 catalyst is removed from impurities, crushed, and ground into a catalyst powder of 100 mesh; the catalyst powder is placed in a muffle furnace and calcined at 1200°C for 6 hours.

[0037] Preparation of extract:

[0038] 35.0-37.0 wt % HCl solution and 65.0-68.0 wt % HNO3 solution are mixed in a volume ratio of 3:1 to form aqua regia, and then mixed with deionized water to form an extractant with a 20%-100% aqua regia content.

[0039] Leaching experiment:

[0040] 1. The calcined catalyst was subjected to microwave at 110°C to determine the Pt and Al2O3 leaching rates of extractants with different concentrations (the ratio of calcined catalyst to extractant was 1 g / 5 mL, and the digestion time was 1.5 h). Figure 1 a and b. The volume percentage of aqua regia is controlled between 20% and 100%. Figures a and b show the changing trends of Pt and Al2O3 with the volume percentage of aqua regia. As the aqua regia content increases, the leaching of platinum from the waste catalyst first increases and then decreases (Figure a). When the volume percentage of aqua regia is 40%, the corresponding platinum leaching efficiency reaches a maximum value of 99.31%. On the contrary, as the aqua regia content increases from 20% to 100%, the leaching efficiency of Al2O3 gradually increases from 0% to 53.04% (Figure b). The above results show that a low aqua regia content of 20% to 40% helps to selectively leach platinum from the waste catalyst, and α-Al2O3 particles show sufficient chemical stability to avoid dissolution. At the same time, the extractant with a high aqua regia content of 60% to 100% significantly promotes the dissolution of α-Al2O3 particles from the waste Pt / Al2O3 catalyst.

[0041] 2. Using an extractant containing 40% aqua regia, the leaching rates of Pt and Al2O3 at different microwave temperatures were determined (the ratio of calcined catalyst to extractant was 1 g / 5 mL, and the digestion time was 1.5 h). Figure 1 c and d. As the leaching temperature increases from 90°C to 130°C, the leaching efficiency of platinum first increases and then decreases (Figure c). At a temperature of 110°C, the leaching efficiency of platinum reaches 99.31%. If the temperature exceeds 110°C, the leaching efficiency of platinum begins to decline. It is worth noting that high temperature promotes the dissolution of α-Al2O3 particles (Figure d). Under low temperature conditions of 90 to 100°C, α-Al2O3 is not dissolved in the extract, but if the temperature exceeds 110°C, the leaching rate of α-Al2O3 will gradually increase (Figure d). Therefore, an aqua regia content of 20-40% and a leaching temperature of 100-120°C are the optimal leaching conditions for selectively recovering platinum from waste Pt / Al2O3 catalysts; an aqua regia content of 40% and a leaching temperature of 110°C are the best leaching conditions for selectively recovering platinum from waste Pt / Al2O3 catalysts. Under such conditions, the leaching efficiency of platinum is as high as 99.31%, and there is no obvious dissolution of α-Al2O3.

[0042] Example 2

[0043] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalyst:

[0044] 1) removing impurities, crushing and grinding the waste Pt / γ-Al2O3 catalyst into 50 mesh catalyst powder;

[0045] 2) placing the catalyst powder in a muffle furnace and calcining at 1000° C. for 6 hours to obtain a calcined material;

[0046] 3) 37.0 wt % HCl solution and 68.0 wt % HNO3 solution were mixed in a volume ratio of 3:1 to prepare aqua regia and mixed with deionized water to prepare an extractant having a 40% aqua regia content;

[0047] 4) mixing 1 g of the calcined material with 5 mL of an extractant, and performing digestion at a microwave temperature of 100° C. for 1 h in a microwave digestion / extraction workstation to obtain a digestion solution;

[0048] 5) The digestion solution is filtered in sequence and the filtrate is extracted to obtain aqua regia and platinum ion solution.

[0049] After testing, the leaching rates of Pt and Al2O3 were 98.57% and 0.92% respectively.

[0050] Example 3

[0051] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalyst, which is different from Example 2 only in that the digestion time is 3 hours.

[0052] After testing, the leaching rates of Pt and Al2O3 were 99.54% and 0.98% respectively.

[0053] Comparative Example 1

[0054] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalysts, which is different from Embodiment 3 only in that heating digestion is used instead of microwave-assisted digestion.

[0055] After testing, the leaching rates of Pt and Al2O3 were 82.38% and 0.94% respectively.

[0056] Comparative Example 2

[0057] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalysts, which is different from Example 3 only in that heating digestion is used instead of microwave-assisted digestion, and the digestion time is increased to 5 hours.

[0058] After testing, the leaching rates of Pt and Al2O3 were 88.12% and 0.95% respectively.

[0059] Comparative Example 3

[0060] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalysts, which is different from Example 3 only in that heating digestion is used instead of microwave-assisted digestion, and the digestion time is increased to 10 hours.

[0061] After testing, the leaching rates of Pt and Al2O3 were 98.12% and 1.96% respectively.

[0062] It can be seen from Comparative Examples 1 to 3 that microwave-assisted aqua regia digestion plays an important role in accelerating the recovery of platinum from spent Pt / γ-Al2O3 catalysts. Microwave-assisted digestion can greatly shorten the leaching time, thereby reducing energy consumption and is suitable for industrial applications.

[0063] Comparative Example 4

[0064] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalysts, which is different from Example 3 only in that in step 2), the catalyst powder is first calcined at 500°C for 2 hours and then at 1100°C for 4 hours.

[0065] After testing, the leaching rates of Pt and Al2O3 were 97.12% and 2.96% respectively.

[0066] Comparative Example 5

[0067] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalysts, which is different from Embodiment 3 only in that in step 2), the catalyst powder is calcined at 500°C for 6 hours.

[0068] After testing, the leaching rates of Pt and Al2O3 were 76.12% and 27.97% respectively.

[0069] Comparative Example 6

[0070] This embodiment provides a method for selectively recovering platinum from waste Pt / γ-Al2O3 catalysts, which is different from Embodiment 3 only in that in step 2), the catalyst powder is calcined at 800°C for 6 hours.

[0071] After testing, the leaching rates of Pt and Al2O3 were 85.36% and 20.88% respectively.

[0072] Experimental Example 1

[0073] The filtrate after filtering the residue from the leachate of Example 3 is separated by extraction to obtain aqua regia and platinum ion solution; the aqua regia contains very few impurities, and part of the aqua regia is consumed, and part of the aqua regia and water are added according to the concentration to reach the required concentration; it is reused according to the method of Example 3.

[0074] After testing, the leaching rates of Pt and Al2O3 were 99.52% and 0.99% respectively;

[0075] According to the method of Experimental Example 1, the extractant was used repeatedly 10 times and the leaching rates of Pt and Al2O3 were 99.27% ​​and 1.24% respectively after the 10th extraction.

[0076] Therefore, it is shown that the calcination method of the present invention and low-concentration aqua regia can improve the extraction effect of Pt and reduce the leaching rate of Al2O3; at the same time, the extractant can be reused, which greatly reduces the processing cost and reagent cost.

[0077] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for selectively recovering platinum from discarded platinum-containing alumina waste catalyst, characterized in that: The following steps are involved: 1) removing impurities, crushing and grinding the discarded platinum-containing alumina waste into powder; 2) calcining the platinum-containing waste powder to obtain a calcined material; 3) mixing the calcined material and the extractant and digesting them under microwave to obtain a digestion solution; 4) filtering the digestion solution in sequence to obtain a filtrate and an aluminum oxide solid; 5) The filtrate is extracted and separated to obtain aqua regia and platinum ion solution.

2. The method according to claim 1, characterized in that The platinum-containing alumina waste in step 1) is discarded Pt / γ-Al2O3 catalyst.

3. The method according to claim 1, characterized in that The mesh size of the catalyst powder in step 1) is 50-200 meshes.

4. The method according to claim 1, characterized in that: In the step 2), the calcination temperature is 1000-1300° C. and the calcination time is 4-8 hours.

5. The method according to any one of claims 1 to 4, characterized in that: In the step 3), the extractant is a mixture of aqua regia and water; the volume proportion of aqua regia in the extractant is 20-40%.

6. The method according to claim 5, characterized in that In the step 3), the ratio of the calcined material to the extractant is 1 g / 3-8 ml.

7. The method according to claim 5, characterized in that The digestion temperature in step 3) is 100-120° C. and the digestion time is 0.5-3 h.

8. The method according to claim 5, characterized in that The aqua regia obtained by extraction in step 5) can be reused after adjusting the concentration; and the platinum ion solution can be recycled.

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