Method for recovering platinum group metal in waste automobile catalyst

Abstract

The invention belongs to the technical field of platinum group metal recovery, and discloses a method for recovering platinum group metal in a waste automobile catalyst, which comprises the following steps: mixing the waste automobile catalyst, a reducing agent, a slag former and a trapping agent, and smelting to obtain molten Fe-Cu-PGMs alloy and smelting slag; the molten Fe-Cu-PGMs alloy is subjected to injection, and iron-rich slag and alloy are obtained; the obtained alloy is electrolyzed, and electrolyte, cathode precipitates and anode mud are obtained; and mixing the electrolyte with sodium hydroxide to obtain Fe (OH) 3 precipitates and Cu (OH) 2 precipitates, and calcining the obtained precipitates to obtain Fe2O3 and CuO. According to the technology, bimetal is adopted as a trapping agent, the trapping advantages of Fe and Cu on Pt, Pd and Rh are integrated, the smelting temperature is lowered, energy consumption is reduced, generation of ferrosilicon alloy is avoided, and the dissolving efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of platinum group metal recovery, and in particular to a method for recovering platinum group metals from waste automobile catalysts. Background Art

[0002] Platinum group metals (PGMs) include palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir). Platinum group metals are a scarce strategic resource. Their scarcity stems from their unique geological formation process and extremely low natural abundance. There are currently three main methods for recycling waste car catalysts: metal capture, chlorination volatilization and synergistic capture. Among them, the metal capture method is a method of using base metals such as iron, copper or bismuth as a single capture agent to capture PGMs in slag at high temperature, that is, after smelting is completed, a metal alloy is first obtained, and then high-purity precious metals are obtained through refining; the chlorination volatilization method utilizes the principle of selective chlorination of platinum group metals. After chlorine gas is introduced into the pretreated catalyst for heating and insulation, the volatile chloride formed is cooled by a condenser, resulting in the separation of metal chlorides from the carrier, thereby achieving the purpose of separation and enrichment of platinum group metals; the synergistic capture method refers to the use of two or more metal capture agents to enrich PGMs in automotive catalysts. The synergistic effect between the main capture agent and the secondary capture agent can more effectively combine with PGMs, thereby improving the capture efficiency.

[0003] However, traditional iron capture has the disadvantages of high melting temperature and easy production of ferrosilicon alloy; copper capture has a lower melting temperature, but the poor thermodynamic affinity between Cu and Rh leads to a low recovery rate of Rh during the recovery process. The chlorination volatilization method is prone to chlorine leakage and equipment corrosion during the introduction of chlorine, which increases the maintenance cost of the equipment, so this method is not suitable for large-scale industrial application. The use of iron-copper synergistic capture can not only reduce the melting temperature and optimize the slag system, but also improve the comprehensive recovery rate of PGMs.

[0004] The patent with application number 201911199155.1 proposes a method of using iron and (tin + antimony) as collectors to synergistically capture PGMs in catalysts. Although this method avoids the problem of traditional iron capture that easily produces ferrosilicon alloys and reduces the smelting temperature, it does not propose a specific refining method after enrichment, and the collectors are difficult to recover after the three collectors are used to complete the recovery of the multi-metal PGMs alloy. The patent with application number 202311808267.9 proposes a method of using multi-element alloys to smelt PGMs in automotive catalysts. This method performs secondary capture on high-grade catalysts, obtains PGMs alloys, and uses oxygen volatilization to recycle base metals. However, the PGMs content in the precious metal enriched body obtained by this method is less than 6%, and a large amount of collectors still exist in the alloy and cannot be recovered. Patent application number 201911178983.7 proposes a method for iron-based alloy capture-crushing and recycling platinum group metals. This method uses iron capture and aluminum, zinc or aluminum-zinc alloy as crushing agents. The purpose is to generate Fe-Al-Zn-PGMs alloy with low melting point, low hardness and easy solubility. However, the aluminum and zinc elements introduced by this method not only increase the production cost, but also the Fe, Al and Zn solution after the alloy acid hydrolysis and filtration is not recovered. Patent application number 202210730823.4 discloses a method for enriching PGMs in waste catalysts using nickel and antimony as collectors. Although the method is designed to optimize the low melting point antimony nickel alloy phase, nickel and antimony are not recovered.

[0005] Therefore, it is of great significance to develop a method for recovering platinum group metals from waste automobile catalysts that can achieve full-process metal recovery, enrich metal content in one go, and have low cost. Summary of the invention

[0006] In view of this, the present invention provides a method for recovering platinum group metals from waste automobile catalysts, the purpose of which is to solve the technical problems existing in the prior art of pyrometallurgical co-enrichment of platinum group metals from waste catalysts, such as difficulty in subsequent refining, difficulty in handling solid waste and high process cost.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a method for recovering platinum group metals from waste automobile catalysts, comprising the following steps:

[0009] (1) mixing a waste automobile catalyst, a reducing agent, a slag-forming agent and a collector and then smelting the mixture to obtain a molten Fe-Cu-PGMs alloy and smelting slag;

[0010] (2) spraying the molten Fe-Cu-PGMs alloy to obtain iron-rich slag and alloy;

[0011] (3) electrolyzing the alloy obtained in step (2) to obtain an electrolyte, a cathode precipitate and an anode mud;

[0012] (4) The electrolyte is mixed with sodium hydroxide to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate, and the obtained precipitate is calcined to obtain Fe2O3 and CuO.

[0013] Preferably, in step (1), the particle size of the waste automobile catalyst is 75 to 300 μm, and the reducing agent is coke.

[0014] Preferably, in step (1), the slag-forming agent includes two or three of Na2B4O7, CaO and Na2CO3;

[0015] The collector is a Fe-Cu collector, and the molar ratio of the iron element to the copper element in the collector is 1-2:0.2-2.

[0016] Preferably, in step (1), the mass ratio of the waste automobile catalyst, the reducing agent, the slag-forming agent and the collecting agent is 100:3-6:32-106:2-15.

[0017] Preferably, in step (1), the smelting is arc melting, the arc melting temperature is 1450-1550° C., and the arc melting time is 1-3 hours.

[0018] Preferably, in step (2), the gas sprayed is an O2-CO2 mixed gas, the volume ratio of O2 to CO2 is 75-90:10-25; the spraying speed is 0.1-0.5 Nm 3 / min; the blowing is completed when the Fe content in the molten Fe-Cu-PGMs alloy is less than 20%.

[0019] Preferably, in step (3), the electrolytic electrolyte solution is a copper sulfate solution, the concentration of the copper sulfate solution is 2.8-3.2 mol / L, the cathode precipitate is refined copper, the anode mud is a mixture of platinum group metals, and the electrolyte contains Fe.

[0020] Preferably, in the step (4), the ratio of the electrolyte to the sodium hydroxide is 1L:120-130g; the calcination temperature is 480-540°C, and the calcination time is 150-200min.

[0021] Preferably, the iron-rich slag obtained in step (2), the cathode precipitate obtained in step (3) and the Fe2O3 and CuO obtained in step (4) are returned to step (1) as collectors to participate in the reaction.

[0022] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0023] The method of the present invention adopts bimetallic as a collector, and combines the advantages of Fe and Cu in capturing Pt, Pd and Rh, which not only reduces the smelting temperature and energy consumption, but also avoids the formation of ferrosilicon alloy and improves the dissolution efficiency. In addition, the method realizes the cyclic recycling of platinum group metals and collectors, and the recovery rate of platinum group metals is greater than 99%. It is a green, economical and environmentally friendly recycling method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 The present invention is a process flow chart of the method for recovering platinum group metals from waste automobile catalysts. DETAILED DESCRIPTION

[0026] The present invention provides a method for recovering platinum group metals from waste automobile catalysts, comprising the following steps:

[0027] (1) mixing a waste automobile catalyst, a reducing agent, a slag-forming agent and a collector and then smelting the mixture to obtain a molten Fe-Cu-PGMs alloy and smelting slag;

[0028] (2) spraying the molten Fe-Cu-PGMs alloy to obtain iron-rich slag and alloy;

[0029] (3) electrolyzing the alloy obtained in step (2) to obtain an electrolyte, a cathode precipitate and an anode mud;

[0030] (4) The electrolyte is mixed with sodium hydroxide to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate, and the obtained precipitate is calcined to obtain Fe2O3 and CuO.

[0031] In the present invention, in step (1), the waste automobile catalyst is obtained by crushing and grinding, and the particle size of the waste automobile catalyst is preferably 75 to 300 μm, more preferably 100 to 250 μm, and more preferably 150 to 200 μm. The reducing agent is preferably coke.

[0032] In the present invention, in the step (1), the slag-forming agent includes two or three of Na2B4O7, CaO and Na2CO3. When the slag-forming agent is Na2B4O7 and CaO, the mass ratio of Na2B4O7 and CaO is preferably 2-6:25-60, more preferably 3-5:30-55, and more preferably 3-5:40-50. When the slag-forming agent is Na2B4O7, CaO and Na2CO3, the mass ratio of Na2B4O7, CaO and Na2CO3 is preferably 2-6:25-60:5-40, more preferably 2-6:30-55:10-30, and more preferably 3-5:35-40:15-25.

[0033] The collector is preferably a Fe-Cu collector, and the molar ratio of the iron element to the copper element in the collector is preferably 1-2:0.2-2, more preferably 1.2-1.8:0.4-1.8, and more preferably 1.4-1.6:0.6-1.2.

[0034] In the present invention, in the step (1), the mass ratio of the waste automobile catalyst, the reducing agent, the slag-forming agent and the collector is preferably 100:3-6:32-106:2-15, more preferably 100:4-5:45-90:4-12, and more preferably 100:4-5:50-60:7-10.

[0035] In the present invention, in the step (1), the smelting is preferably arc melting, the arc melting temperature is preferably 1450-1550°C, more preferably 1480-1530°C, more preferably 1500-1510°C, and the arc melting time is preferably 1-3h, more preferably 1.5-2.5h, more preferably 2h.

[0036] In the present invention, in the step (1), the PGMs content in the smelting slag is less than 20 g / t.

[0037] In the present invention, in step (2), the gas sprayed is preferably an O2-CO2 mixed gas, and the volume ratio of O2 to CO2 is preferably 75-90:10-25, more preferably 78-88:15-20, and more preferably 80-85:16-18; the spraying speed is preferably 0.1-0.5 Nm 3 / min, more preferably 0.2 to 0.4 Nm 3 / min, more preferably 0.3Nm 3 / min; when the Fe content in the molten Fe-Cu-PGMs alloy is less than 20%, the injection is completed, and no heat supplement is required during the injection process; the molten alloy is oxidized by using an O2-CO2 mixed gas to make the Fe content in the alloy less than 20%, thereby achieving preliminary separation of Fe, and the iron-rich slag is returned to the capture stage for use.

[0038] In the present invention, in the step (3), the electrolytic electrolyte solution is preferably a copper sulfate solution, the concentration of the copper sulfate solution is preferably 2.8-3.2 mol / L, more preferably 2.9-3.1 mol / L, and more preferably 3 mol / L, the cathode precipitate is refined copper, the anode mud is a mixture of platinum group metals, and the anode mud also includes less than 1% Fe and less than 2% Cu; the electrolyte contains Fe; Fe, Cu and precious metals are separated by electrolysis, refined copper is obtained at the cathode and returned to the capture stage for use, and the dissolved Fe is precipitated and returned to the capture stage for use.

[0039] In the present invention, in the platinum group metal mixture, the recovered Pt accounts for more than 99.2% of the mass of Pt in the waste automobile catalyst, the recovered Pd accounts for more than 99.% of the mass of Pt in the waste automobile catalyst, and the recovered Rh accounts for more than 99% of the mass of Rh in the waste automobile catalyst.

[0040] In the present invention, in the step (4), the ratio of the amount of electrolyte to sodium hydroxide is preferably 1L:120-130g, more preferably 1L:122-128g, more preferably 1L:124-125g; the calcination temperature is preferably 480-540°C, more preferably 490-530°C, more preferably 500-520°C, and the calcination time is preferably 150-200min, more preferably 160-190min, more preferably 170-180min.

[0041] In the present invention, the iron-rich slag obtained in step (2), the cathode precipitate obtained in step (3) and the Fe2O3 and CuO obtained in step (4) are returned to step (1) as collectors to participate in the reaction.

[0042] In the present invention, the recycling of Fe-Cu collector significantly reduces the recovery cost of platinum group metals, which is a green recovery method.

[0043] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0044] In the embodiments of the present invention, the waste automobile catalyst used includes the components shown in Table 1.

[0045] Table 1 Main components and contents of waste automobile catalysts

[0046] Element <![CDATA[Al2O3]]> <![CDATA[SiO2]]> MgO <![CDATA[ZrO2]]> <![CDATA[CeO2]]> Pt Pd R content 39wt% 34wt% 13wt% 4wt% 3wt% 78g / t 1596g / t 207g / t

[0047] Example 1

[0048] The bulk waste automobile catalyst was crushed and ground to a particle size of 250 μm, 100 kg of the waste automobile catalyst, 5 kg of coke, 60 kg of slag-making agent (5 kg of Na2B4O7 and 55 kg of CaO), and 8 kg of Fe-Cu collector (the molar ratio of iron to copper was 1:1) were mixed and arc-melted at 1500 ° C for 2.5 h to obtain molten Fe-Cu-PGMs alloy and smelting slag. The PGMs content in the obtained smelting slag was 16 g / t;

[0049] The O2-CO2 mixed gas (the volume ratio of O2 to CO2 is 80:20) was used at 0.2Nm 3 The obtained molten Fe-Cu-PGMs alloy was sprayed by top blowing at a flow rate of / min, and the spraying was completed when the Fe content in the molten Fe-Cu-PGMs alloy reached 9.3%, thereby obtaining iron-rich slag and 4.56kg of alloy, and the iron-rich slag was returned to the process as a collector to participate in the reaction;

[0050] The obtained alloy is used as an anode and a copper rod is used as a cathode, and the mixture is placed in a copper sulfate solution with a concentration of 3 mol / L for electrolysis to obtain an electrolyte, a cathode precipitate and anode mud. The cathode precipitate is refined copper and is returned to the process as a collector to participate in the reaction.

[0051] The obtained electrolyte was mixed with sodium hydroxide in a dosage ratio of 1L:125g to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate. The obtained precipitate was calcined at 500°C for 180min to obtain Fe2O3 and CuO. The obtained Fe2O3 and CuO were returned to the process as collectors to participate in the reaction.

[0052] In this embodiment, 0.19 kg of anode mud is obtained, and the obtained anode mud includes 0.69% of iron, 1.33% of copper, and the rest is PGMs; the PGMs in the obtained anode mud account for 99.1% of the PGMs in the waste automobile catalyst.

[0053] Example 2

[0054] The bulk waste automobile catalyst was crushed and ground to a particle size of 250 μm. 100 kg of the waste automobile catalyst, 5 kg of coke, 50 kg of slag-making agent (5 kg of Na2B4O7 and 45 kg of CaO), and 6 kg of Fe-Cu collector (the molar ratio of iron to copper was 1:2) were mixed and arc-melted at 1550 ° C for 2 h to obtain molten Fe-Cu-PGMs alloy and smelting slag. The PGMs content in the obtained smelting slag was 16 g / t.

[0055] The O2-CO2 mixed gas (the volume ratio of O2 to CO2 is 75:25) was used at 0.2Nm 3The obtained molten Fe-Cu-PGMs alloy was sprayed by top blowing at a flow rate of / min, and the spraying was completed when the Fe content in the molten Fe-Cu-PGMs alloy reached 12%, thereby obtaining iron-rich slag and 3.68kg of alloy, and the iron-rich slag was returned to the process as a collector to participate in the reaction;

[0056] The obtained alloy is used as an anode and a copper rod is used as a cathode, and the mixture is placed in a copper sulfate solution with a concentration of 3 mol / L for electrolysis to obtain an electrolyte, a cathode precipitate and anode mud. The cathode precipitate is refined copper and is returned to the process as a collector to participate in the reaction.

[0057] The obtained electrolyte was mixed with sodium hydroxide in a dosage ratio of 1L:125g to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate. The obtained precipitate was calcined at 500°C for 200min to obtain Fe2O3 and CuO. The obtained Fe2O3 and CuO were returned to the process as collectors to participate in the reaction.

[0058] In this embodiment, 0.189 kg of anode mud is obtained, and the obtained anode mud includes 0.85% of iron, 1.09% of copper, and the rest is PGMs; the PGMs in the obtained anode mud account for 99% of the PGMs in the waste automobile catalyst.

[0059] Example 3

[0060] The bulk waste automobile catalyst was crushed and ground to a particle size of 250 μm, 100 kg of the waste automobile catalyst, 5 kg of coke, 56 kg of slag-making agent (6 kg of Na2B4O7 and 50 kg of CaO), and 7 kg of Fe-Cu collector (the molar ratio of iron to copper was 1.1:1) were mixed and arc-melted at 1500 ° C for 2.5 h to obtain a molten Fe-Cu-PGMs alloy and smelting slag. The PGMs content in the obtained smelting slag was 16 g / t;

[0061] The O2-CO2 mixed gas (the volume ratio of O2 to CO2 is 79:21) is used at 0.4Nm 3 The obtained molten Fe-Cu-PGMs alloy is sprayed by top blowing at a flow rate of / min, and the spraying is completed when the Fe content in the molten Fe-Cu-PGMs alloy is 8.6%, thereby obtaining iron-rich slag and 4.05kg of alloy, and the iron-rich slag is returned to the process as a collector to participate in the reaction;

[0062] The obtained alloy is used as an anode and a copper rod is used as a cathode, and is placed in a copper sulfate solution with a concentration of 3 mol / L for electrolysis to obtain an electrolyte, a cathode precipitate and anode mud. The cathode precipitate obtained is refined copper, which is returned to the process as a collector to participate in the reaction;

[0063] The obtained electrolyte was mixed with sodium hydroxide in a dosage ratio of 1L:125g to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate. The obtained precipitate was calcined at 500°C for 170min to obtain Fe2O3 and CuO. The obtained Fe2O3 and CuO were returned to the process as collectors to participate in the reaction.

[0064] In this embodiment, 0.195 kg of anode mud was obtained, and the obtained anode mud included 0.87% of iron, 1.12% of copper, and the remainder was PGMs; the PGMs in the obtained anode mud accounted for 99.2% of the PGMs in the waste automobile catalyst.

[0065] Example 4

[0066] The bulk waste automobile catalyst was crushed and ground to a particle size of 250 μm, 100 kg of the waste automobile catalyst, 5 kg of coke, 50 kg of slag-making agent (5 kg of Na2B4O7 and 45 kg of CaO), and 8 kg of Fe-Cu collector (the molar ratio of iron to copper was 1:2) were mixed and arc-melted at 1550 ° C for 2 h to obtain molten Fe-Cu-PGMs alloy and smelting slag. The PGMs content in the obtained smelting slag was 16 g / t.

[0067] The O2-CO2 mixed gas (the volume ratio of O2 to CO2 is 77:23) was used at 0.2Nm 3 The obtained molten Fe-Cu-PGMs alloy was sprayed by top blowing at a flow rate of / min, and the spraying was completed when the Fe content in the molten Fe-Cu-PGMs alloy reached 9.5%, thereby obtaining iron-rich slag and 4.42kg of alloy, and the iron-rich slag was returned to the process as a collector to participate in the reaction;

[0068] The obtained alloy is used as an anode and a copper rod is used as a cathode, and is placed in a copper sulfate solution with a concentration of 3 mol / L for electrolysis to obtain an electrolyte, a cathode precipitate and anode mud. The cathode precipitate obtained is refined copper, which is returned to the process as a collector to participate in the reaction;

[0069] The obtained electrolyte was mixed with sodium hydroxide in a dosage ratio of 1L:125g to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate. The obtained precipitate was calcined at 500°C for 180min to obtain Fe2O3 and CuO. The obtained Fe2O3 and CuO were returned to the process as collectors to participate in the reaction.

[0070] In this embodiment, 0.19 kg of anode mud is obtained, and the obtained anode mud includes 0.64% of iron, 1.08% of copper, and the rest is PGMs; the PGMs in the obtained anode mud account for 99.5% of the PGMs in the waste automobile catalyst.

[0071] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering platinum group metals from waste automobile catalysts, characterized in that: The steps include: (1) mixing a waste automobile catalyst, a reducing agent, a slag-forming agent and a collector and then smelting the mixture to obtain a molten Fe-Cu-PGMs alloy and smelting slag; (2) spraying the molten Fe-Cu-PGMs alloy to obtain iron-rich slag and alloy; (3) electrolyzing the alloy obtained in step (2) to obtain an electrolyte, a cathode precipitate and an anode mud; (4) The electrolyte is mixed with sodium hydroxide to obtain Fe(OH)3 precipitate and Cu(OH)2 precipitate, and the obtained precipitate is calcined to obtain Fe2O3 and CuO.

2. The method for recovering platinum group metals from waste automobile catalysts according to claim 1, characterized in that: In the step (1), the particle size of the waste automobile catalyst is 75 to 300 μm, and the reducing agent is coke.

3. The method for recovering platinum group metals from waste automobile catalysts according to claim 2, characterized in that: In the step (1), the slag-forming agent includes two or three of Na2B4O7, CaO and Na2CO3; The collector is a Fe-Cu collector, and the molar ratio of the iron element to the copper element in the collector is 1-2:0.2-2.

4. The method for recovering platinum group metals from waste automobile catalysts according to claim 3, characterized in that: In the step (1), the mass ratio of the waste automobile catalyst, the reducing agent, the slag-forming agent and the collecting agent is 100:3-6:32-106:2-15.

5. The method for recovering platinum group metals from waste automobile catalysts according to claim 2, 3 or 4, characterized in that: In the step (1), the smelting is arc smelting, the arc smelting temperature is 1450-1550° C., and the arc smelting time is 1-3 hours.

6. The method for recovering platinum group metals from waste automobile catalysts according to claim 1, characterized in that: In step (2), the gas sprayed is an O2-CO2 mixed gas, the volume ratio of O2 to CO2 is 75-90:10-25; the spraying speed is 0.1-0.5Nm 3 / min; the blowing is completed when the Fe content in the molten Fe-Cu-PGMs alloy is less than 20%.

7. The method for recovering platinum group metals from waste automobile catalysts according to claim 6, characterized in that: In the step (3), the electrolytic electrolyte solution is a copper sulfate solution, the concentration of the copper sulfate solution is 2.8-3.2 mol / L, the cathode precipitate is refined copper, the anode mud is a mixture of platinum group metals, and the electrolyte contains Fe.

8. The method for recovering platinum group metals from waste automobile catalysts according to claim 7, characterized in that: In the step (4), the ratio of the electrolyte to the sodium hydroxide is 1L:120-130g; the calcination temperature is 480-540°C, and the calcination time is 150-200min.

9. The method for recovering platinum group metals from waste automobile catalysts according to claim 5, characterized in that: The iron-rich slag obtained in step (2), the cathode precipitate obtained in step (3) and the Fe2O3 and CuO obtained in step (4) are returned to step (1) as collectors to participate in the reaction.

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