Method for recovering iridium from low-content platinum group material

Abstract

The invention belongs to the field of resource recovery, and discloses a method for recovering iridium from a low-content platinum group material, which comprises the following steps: mixing iridium-containing zirconium oxide crucible powder, a trapping agent, a reducing agent and an additive to obtain a mixed material A, and then laying a layer of covering agent on the mixed material to obtain a mixed material B; and heating the mixed material B in a protective atmosphere, cooling, and separating a slag phase from an alloy phase to obtain the iridium-containing alloy. Wherein the trapping agent is any one or two of mixed powder of iron powder and copper powder and iron-copper alloy. Compared with the high-temperature requirement of a pure iron or pure copper trapping agent in the prior art, the iron-copper alloy achieves balance of performance advantages through the synergistic effect, the production cost can be remarkably reduced, the trapping temperature can be effectively reduced, the trapping efficiency is improved, and industrialization and marketization are facilitated.

Description

Technical Field

[0001] The invention belongs to the field of resource recovery and relates to a method for recovering platinum group metals, in particular to a method for recovering iridium from low-content platinum group materials. Background Art

[0002] Iridium, a rare and precious metal, has important applications and is widely used in electronics, catalysis, aviation, and other fields. However, the extraction and enrichment of iridium has always faced certain challenges, especially the low extraction efficiency of low-grade iridium. Traditional metallurgical methods are difficult to meet the requirements of efficient extraction in some cases.

[0003] In traditional fire assaying, iron or copper is often used as a collector to extract the precious metal iridium, but this method has certain limitations. Iron has a high capture temperature, generally exceeding 1400°C, requiring high temperatures to effectively capture iridium. This not only increases energy consumption but can also result in partial loss of iridium, thus affecting the final iridium recovery efficiency. Furthermore, iron has a low capture rate, typically only reaching 60% to 70%. Using iron as a collector to extract iridium from low-grade iridium materials results in poor recovery, high raw material waste, and high energy consumption during the recovery process. Summary of the Invention

[0004] In view of the defects and shortcomings of the prior art, the present invention provides a method for recovering iridium from low-content platinum group materials.

[0005] A method for recovering iridium from a low-content platinum group material comprises the following steps: Step 1: mixing iridium-containing zirconia crucible powder, a collector, a reducing agent, and an additive to obtain a mixed material A, and then laying a layer of a covering agent on the mixed material to obtain a mixed material B; Step 2: heating the mixed material B under a protective atmosphere, cooling it, and separating the slag phase and the alloy phase to obtain the iridium-containing alloy; The collector is any one or both of a mixed powder of iron powder and copper powder, and an iron-copper alloy.

[0006] Preferably, the mass ratio of the iron element to the copper element in the collector is 1:1.5-4.

[0007] Preferably, the particle size of the iridium-containing zirconia crucible powder is 70-250 μm.

[0008] Preferably, the reducing agent is any one or more of coal powder, coke powder, activated carbon, and graphite.

[0009] Preferably, the additive comprises calcium oxide, waste glass and calcium fluoride, and the mass ratio of calcium oxide, waste glass and calcium fluoride is 1:1-3.75:0.2-0.88.

[0010] Preferably, the covering agent includes component one and component two, component one is any one or more of sodium carbonate and potassium carbonate; component two is any one or more of borax, boric acid, and lithium tetraborate.

[0011] Preferably, the mass ratio of component one to component two is 1:0.1-0.2.

[0012] Preferably, the mass ratio of the iridium-containing zirconia crucible powder, the collector, the reducing agent, the additive, and the covering agent is 1:0.20-0.35:0.10-0.38:0.41-0.88:0.65-2.82.

[0013] Preferably, the basicity of the mixture B is 0.8-1.2.

[0014] Preferably, in step 2, the heating includes a pre-activation stage and a smelting and capturing stage, wherein: The pre-activation stage includes the first stage and the second stage: the heating temperature of the first stage is 250~300℃, and the heating time is 30~60min; the heating temperature of the second stage is 350~800℃, and the heating time is 15~30min; Smelting and capturing stage: heating temperature is 1000~1100℃, and heating time is 15~30min.

[0015] Preferably, the gas providing the protective atmosphere is any one or both of nitrogen and argon.

[0016] Compared with the prior art, the present invention has the following obvious beneficial effects: In this invention, optimizing the collector composition and adjusting its reducing power and reactivity enable a gentler and more uniform reduction reaction, avoiding the overly violent reaction and resulting iridium volatilization loss caused by a single strong reducing agent (such as pure iron), while also ensuring that the iridium is fully reduced and captured. Compared to the high temperature requirements of pure iron or pure copper collectors in the prior art, the iron-copper alloy achieves a balanced performance advantage through a synergistic effect, significantly reducing production costs, effectively lowering the capture temperature, and improving capture efficiency, facilitating industrialization and marketization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a simplified flow chart of the method for recovering iridium from low-content platinum group materials. DETAILED DESCRIPTION

[0018] The present invention provides the following specific technical solutions.

[0019] A method for recovering iridium from a low-content platinum group material comprises the following steps: Step 1: mixing iridium-containing zirconia crucible powder, a collector, a reducing agent, and an additive to obtain a mixed material A, and then laying a layer of a covering agent on the mixed material to obtain a mixed material B; Step 2: heating the mixed material B under a protective atmosphere, cooling it, and separating the slag phase and the alloy phase to obtain the iridium-containing alloy; The collector is any one or both of a mixed powder of iron powder and copper powder, and an iron-copper alloy.

[0020] Research has revealed that both iron and copper possess a certain degree of reducing power at high temperatures, but their reducing activities differ. Iron has a stronger reducing ability, capable of reducing some iridium compounds to elemental iridium at high temperatures; copper has a relatively weaker reducing ability. The technical solution provided by the present invention optimizes the composition of the collector and adjusts its reducing power and reactivity, enabling a gentler and more uniform reduction reaction. This avoids the excessively violent reaction that can occur with a single strong reducing agent (such as pure iron), which can lead to iridium volatilization and loss, while also ensuring that the iridium is fully reduced and captured. The collector is a mixed powder of iron and copper powders or an iron-copper alloy. The iron and copper powders alloy during heating to form an iron-copper alloy. Compared to the high-temperature requirements of pure iron or pure copper collectors in the prior art, the iron-copper alloy achieves a balanced performance advantage through synergistic effects, significantly reducing production costs, effectively lowering the capture temperature, and improving capture efficiency, facilitating industrialization and marketization.

[0021] In actual production, the slag and alloy phases are separated by first crushing the product obtained after cooling in step 2 (a mixture of slag and alloy phases). The alloy and slag phases are then separated by utilizing their density differences. Generally speaking, iridium-containing alloys have a higher density, while slag has a lower density. After cooling, the alloy phase sinks to the bottom, while the slag phase floats to the top.

[0022] Preferably, the mass ratio of the iron element to the copper element in the collector is 1:1.5-4.

[0023] The inventors have discovered that iridium has good solubility and affinity in a molten iron and copper powder mixture / iron-copper alloy. When the iron-to-copper ratio in the collector is appropriate, the resulting alloy phase can more effectively dissolve and capture the reduced iridium, increasing the iridium enrichment in the alloy phase and thus improving the iridium recovery rate. If the iron ratio is too high, the alloy phase may have properties that favor iron, and the iridium capture efficiency may not be as good as when the iron-copper ratio is appropriate. If the copper ratio is too high, the relatively weak reducing ability of copper may lead to insufficient iridium reduction, thus affecting the capture efficiency.

[0024] Preferably, the particle size of the iridium-containing zirconia crucible powder is 70-250 μm.

[0025] In the actual production process, the iridium-containing zirconia crucible is first placed in a crocodile crusher for coarse crushing to a particle size of 10~50mm, and then the coarsely crushed iridium-containing zirconia particles are placed in a grinder for further crushing. The particle size of the obtained iridium-containing zirconia crucible powder is 70~250μm.

[0026] After research, the inventors found that during the heating activation process, the smaller the particle size, the larger the reaction area, which is conducive to activation; however, if the particle size is too small, it is easy to cause material agglomeration, reducing the reaction area, and the agglomerated particles coat the capture agent and other materials, affecting the sedimentation of the iridium element, thereby affecting the capture efficiency.

[0027] Preferably, the reducing agent is any one or more of coal powder, coke powder, activated carbon, and graphite.

[0028] Preferably, the additive comprises calcium oxide, waste glass and calcium fluoride, and the mass ratio of calcium oxide, waste glass and calcium fluoride is 1:1-3.75:0.2-0.88.

[0029] The inventors have discovered that the combination of the additive and collector provided by the present invention can lower the melting point of the reaction system and reduce energy consumption. Furthermore, the melt formed by the components at high temperature exhibits good fluidity, promoting mixing of reactants and separation of reaction products, and facilitating the sedimentation of the iridium element. Components such as calcium fluoride and calcium oxide can reduce iridium volatilization losses and improve iridium recovery. The oxides generated by the decomposition of carbonates and borates stabilize the reaction environment, improving reaction stability and efficiency. The use of inexpensive materials such as waste glass significantly reduces the cost of the additives.

[0030] By adding an appropriate amount of waste glass, the optimization effect of SiO2, Na2O and other components in the waste glass on the slag system greatly reduces the need for adding traditional flux materials while ensuring the stability of the metallurgical process. At the same time, it provides an innovative solution for the efficient recycling of waste glass, which is in line with the development trend of green metallurgy.

[0031] Preferably, the covering agent includes component one and component two, component one is any one or more of sodium carbonate and potassium carbonate; component two is any one or more of borax, boric acid, and lithium tetraborate.

[0032] Preferably, the mass ratio of component one to component two is 6-18:1-4.

[0033] Preferably, the mass ratio of the iridium-containing zirconia crucible powder, the collector, the reducing agent, the additive, and the covering agent is 1:0.20-0.35:0.10-0.38:0.41-0.88:0.65-2.82.

[0034] Preferably, the basicity of the mixture B is 0.8-1.2.

[0035] In actual application, the basicity of the mixture is calculated as the ratio of oxides to the total material × relative molecular mass / the ratio of acidic oxides to the total material × relative molecular mass. The basic oxide in the mixture is sodium oxide, formed by the high-temperature decomposition of calcium oxide and sodium carbonate, while the acidic oxide is boron trioxide, formed by the high-temperature decomposition of silica and borax in waste glass. By further optimizing the basicity range, the fluidity of the mixture during heating is ensured, thereby improving the iridium recovery rate. By adjusting the basicity and the slag-to-auxiliary ratio (including iridium-containing zirconium oxide crucible powder and other materials), the physicochemical properties of the slag are optimized, the capture efficiency of precious metals is significantly improved, and the internal environment of the slag is precisely controlled. Through the synergistic effect of various components, the residual precious metals in the slag phase are effectively reduced.

[0036] Preferably, in step 2, the heating includes a pre-activation stage and a smelting and capturing stage, wherein: The pre-activation stage includes the first stage and the second stage: the heating temperature of the first stage is 250~300℃, and the heating time is 30~60min; the heating temperature of the second stage is 350~800℃, and the heating time is 15~30min; Smelting and capturing stage: heating temperature is 1000~1100℃, and heating time is 15~30min.

[0037] The inventors discovered that during the pre-activation stage, when part of the charge melts and initially forms a paste, a portion of the collector dissociates and evenly permeates the molten charge paste. At this point, the charge has a high viscosity, making it nearly impossible for the metal particles to settle, resulting in a more uniform distribution of the collector. During this stage, the collector dissociates and disperses into smaller particles, reaching a nanoscale state with high surface activity and reactivity, making it more susceptible to iridium adsorption.

[0038] During the smelting and capturing stage, the collector is more easily transformed into liquid and exhibits excellent activity.

[0039] In actual application, the heating temperature of the first stage can be 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, and the heating time of the first stage can be 30min, 40min, 50min, or 60min. The heating temperature of the second stage can be 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃, and the heating time of the second stage can be 15min, 20min, 25min, or 30min. In the smelting and capturing stage, the heating temperature can be 1000℃, 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, or 1100℃, and the heating time can be 15min, 20min, 25min, or 30min.

[0040] The inventors further discovered that the pre-activation temperature is closely related to the selection of auxiliary materials. When the content of basic oxides is high, the pre-activation temperature is low, and when the content of acidic oxides is high, the pre-activation temperature is low.

[0041] More preferably, during heating, the heating rate is 8-10°C / min.

[0042] Preferably, the gas providing the protective atmosphere is any one of nitrogen and argon, or two or more thereof.

[0043] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention clearer, they will be described in detail below with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0044] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0045] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0046] Figure 1 The present invention provides a simplified flow chart of the method for recovering iridium from low-content platinum group materials.

[0047] In the specific embodiments and comparative examples of the present invention, the low-content platinum group metal materials used are all iridium-containing zirconia crucible powders, and the Ir content in the iridium-containing zirconia crucible powders is 2300 ppm.

[0048] Example 1: A method for recovering iridium from a low-content platinum group material comprises the following steps: Step 1: Weigh 85g of iridium-containing zirconia crucible powder with a particle size of 70-250μm, 20g of copper powder, 10g of iron powder, 15g of calcium oxide, 25g of waste glass, 5g of calcium fluoride, and 15g of carbon powder, stir them thoroughly, and pour them into a graphite crucible. Mix 90g of sodium carbonate and 14g of borax to obtain a covering agent, and then evenly cover the surface of the mixed material in the graphite crucible with the covering agent.

[0049] Step 2: Place the graphite crucible in a nitrogen atmosphere and heat it to 280° C. at 9° C. / min and keep it warm for 35 minutes; then continue to heat it to 600° C. at 9° C. / min and keep it warm for 20 minutes; then enter the capture stage, continue to heat it to 1085° C. at 9° C. / min and keep it warm for 30 minutes. After the end, transfer the melt in the graphite crucible to a preheated mold, wait for the slag to cool, and separate the slag phase to obtain the iridium-containing alloy.

[0050] Example 2: A method for recovering iridium from a low-content platinum group material comprises the following steps: Step 1: Weigh 85g of iridium-containing zirconia crucible powder with a particle size of 70-250μm, 18g of copper powder, 12g of iron powder, 15g of calcium oxide, 15g of waste glass, 5g of calcium fluoride, and 9g of carbon powder, stir them thoroughly, and pour them into a graphite crucible. Mix 50g of sodium carbonate and 5g of borax, and then evenly cover the surface of the mixed material in the graphite crucible with a covering agent.

[0051] Step 2: Place the graphite crucible in a nitrogen atmosphere and heat it to 250° C. at 8° C. / min and keep it warm for 30 minutes; then continue to heat it to 355° C. at 8° C. / min and keep it warm for 20 minutes; then enter the capture stage, continue to heat it to 1008° C. at 9° C. / min and keep it warm for 30 minutes. After the end, transfer the melt in the graphite crucible to a preheated mold, wait for the slag to cool, and separate the slag phase to obtain the iridium-containing alloy.

[0052] Example 3: A method for recovering iridium from a low-content platinum group material comprises the following steps: Step 1: Weigh 85g of iridium-containing zirconia crucible powder with a particle size of 70-250μm, 24g of copper powder, 6g of iron powder, 25g of calcium oxide, 30g of waste glass, 5g of calcium fluoride, and 18g of carbon powder, stir them thoroughly, and pour them into a graphite crucible. Mix 100g of sodium carbonate and 20g of borax to obtain a covering agent, and then evenly cover the surface of the mixed material in the graphite crucible with the covering agent.

[0053] Step 2: Place the graphite crucible in a nitrogen atmosphere and heat it to 300° C. at a rate of 10° C. / min, and keep it warm for 30 minutes; then continue to heat it to 800° C. at a rate of 10° C. / min, and keep it warm for 20 minutes; then enter the capture stage, continue to heat it to 1100° C. at a rate of 9° C. / min, and keep it warm for 30 minutes. After the end, transfer the melt in the graphite crucible to a preheated mold, and separate the slag phase after the slag is cooled to obtain the iridium-containing alloy.

[0054] Example 4: A method for recovering iridium from a low-content platinum group material comprises the following steps: Step 1: Weigh 85g of iridium-containing zirconia crucible powder with a particle size of 70-250μm, 30g of copper-iron alloy (copper: iron = 2:1), 8g of calcium oxide, 30g of waste glass, 7g of calcium fluoride, and 12g of carbon powder, stir them thoroughly, and pour them into a graphite crucible. Mix 65g of sodium carbonate and 10g to obtain a covering agent, and then evenly cover the surface of the mixed material in the graphite crucible with the covering agent.

[0055] Step 2: Place the graphite crucible in a nitrogen atmosphere and heat it to 275° C. at 9° C. / min and keep it warm for 30 minutes; then continue to heat it to 650° C. at 9° C. / min and keep it warm for 20 minutes; then enter the capture stage, continue to heat it to 1060° C. at 9° C. / min and keep it warm for 30 minutes. After the end, transfer the melt in the graphite crucible to a preheated mold, wait for the slag to cool, and separate the slag phase to obtain the iridium-containing alloy.

[0056] Comparative Example 1: A method for recovering iridium from a low-content platinum group material, which differs from Example 1 in that the collector used is 30 g of copper powder.

[0057] Comparative Example 2: A method for recovering iridium from a low-content platinum group material, which differs from Example 1 in that the collector used is 30.00 g of iron powder.

[0058] The amount of iridium in the iridium-containing alloy was measured and the Ir capture rate was calculated. The Ir capture rates of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1.

[0059] Table 1 Ir capture rates of Examples 1-4 and Comparative Examples 1-2 As shown in Table 1, the technical solution provided by the present invention, using a mixed powder of copper and iron or a copper-iron alloy as the collector significantly increases the capture rate of iridium in iridium-containing zirconia crucible powder. The inventors also found that the capture effect is best when the mass ratio of copper to iron is 1:0.5. The inventors speculate that this may be due to the fact that excessive iron content may lead to poor melt fluidity at the same temperature, thus affecting the capture rate. As the iron content decreases, the fluidity of the slag increases, leading to an increase in the capture rate. If the collector is pure iron or pure copper, the capture rate of Ir is low.

[0060] The embodiments described above are only preferred specific implementation methods of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and concepts of the present invention within the technical scope of the present invention, and they should be covered by the scope of protection of the present invention.

Claims

1. A method for recovering iridium from low-content platinum group materials, characterized in that: The steps include: Step 1: mixing iridium-containing zirconia crucible powder, a collector, a reducing agent, and an additive to obtain a mixed material A, and then laying a layer of a covering agent on the mixed material to obtain a mixed material B; Step 2: heating the mixed material B under a protective atmosphere, cooling it, and separating the slag phase and the alloy phase to obtain the iridium-containing alloy; The collector is any one or both of a mixed powder of iron powder and copper powder, and an iron-copper alloy.

2. The method for recovering iridium from a low-content platinum group material as claimed in claim 1, wherein: The mass ratio of iron element to copper element in the collector is 1:1.5~4.

3. The method for recovering iridium from a low-content platinum group material as claimed in claim 1, wherein: The reducing agent is any one or more of coal powder, coke powder, activated carbon and graphite.

4. The method for recovering iridium from a low-content platinum group material according to claim 1 or 3, wherein: The additives include calcium oxide, waste glass and calcium fluoride, and the mass ratio of calcium oxide, waste glass and calcium fluoride is 1:1~3.75:0.2~0.

88.

5. The method for recovering iridium from a low-content platinum group material as claimed in claim 1, wherein: The covering agent comprises component one and component two, wherein component one is any one or more than two of sodium carbonate and potassium carbonate; and component two is any one or more than two of borax, boric acid and lithium tetraborate.

6. The method for recovering iridium from a low-content platinum group material as claimed in claim 5, wherein: The mass ratio of component one to component two is 1:0.1~0.

2.

7. The method for recovering iridium from a low-content platinum group material as claimed in claim 1, wherein: The mass ratio of the iridium-containing zirconia crucible powder, the collector, the reducing agent, the additive and the covering agent is 1:0.20-0.35:0.10-0.38:0.41-0.88:0.65-2.

82.

8. The method for recovering iridium from a low-content platinum group material according to claim 1 or 7, wherein: The alkalinity of mixed material B is 0.8~1.

2.

9. The method for recovering iridium from a low-content platinum group material as claimed in claim 1, wherein: In step 2, the heating includes a pre-activation stage and a smelting and capturing stage, wherein: The pre-activation stage includes the first stage and the second stage: the heating temperature of the first stage is 250~300℃, and the heating time is 30~60min; the heating temperature of the second stage is 350~800℃, and the heating time is 15~30min; Smelting and capturing stage: heating temperature is 1000~1100℃, and heating time is 15~30min.

10. The method for recovering iridium from a low-content platinum group material according to claim 1 or 9, wherein: The protective atmosphere gas is any one of nitrogen and argon, or two or more thereof.

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