Method for recovering ruthenium and iridium

Abstract

The invention discloses a method for recovering ruthenium and iridium in a noble metal material based on a low-temperature plasma technology, and particularly relates to the field of noble metal recovery. The method comprises the following specific steps: putting a ruthenium and iridium-containing noble metal material into a low-temperature plasma reduction device, and carrying out low-temperature plasma treatment on the noble metal material by using a certain power in a chlorine atmosphere under a fixed low-pressure condition, converting a noble metal simple substance or a noble metal oxide which is difficult to dissolve in the aqua regia into a chloride which is easy to dissolve in the aqua regia, and finally carrying out various tests on the content of the noble metal in the filtrate. A novel precious metal material recovery technology is adopted, so that the precious metal can be dissolved in aqua regia more easily, and the purpose of improving the precious metal recovery efficiency is achieved. In the whole pretreatment process, the pollution to the environment is relatively small, and the energy consumption is relatively small; and the content of noble metals ruthenium and iridium which can be finally dissolved in aqua regia is relatively high, so that the method has more excellent economic benefits.

Description

[0001] This invention is a divisional application. The original application is titled "Method for Recovering Ruthenium and Iridium from Precious Metal Materials Based on Low-Temperature Plasma Technology." The application number is 202210347552.4, and the filing date is April 3, 2022. Technical field:

[0002] The present invention relates to the technical field of precious metal recovery and processing, and in particular to a method for recovering ruthenium and iridium from precious metal materials based on low-temperature plasma technology. Background technology:

[0003] Precious metals primarily consist of eight metallic elements, including iridium and ruthenium group metals. Precious metals often possess strong chemical stability, making them less susceptible to chemical reactions with other substances. Their rarity and difficulty in mining lead to relatively high application costs. Therefore, secondary recovery of precious metals effectively recirculates them, reducing costs and conserving resources. Secondary recovery is an essential component of industrial processes. Currently, the main technologies for secondary precious metal recovery include pyrometallurgical and hydrometallurgical processes.

[0004] The basic principle of pyrometallurgical processing is to use high-temperature heating in a metallurgical furnace to strip away non-metallic materials, melt precious metals into other metal smelting materials or molten salts, and then separate them. The greatest advantages of pyrometallurgical processing are its simplicity of operation and high recovery rates. However, pyrometallurgical processing technology is relatively energy-intensive and causes greater environmental pollution. It also easily produces harmful gases and solid waste. The control of harmful gases and the disposal of solid waste are also relatively complex aspects of pyrometallurgical processing. Especially in today's environmental protection development concept, pyrometallurgical processing technology has gradually become obsolete.

[0005] Wet processing involves using chemicals such as strong acids to dissolve a mixture of metals, producing a solution of metals and non-metals, which is then chemically reduced to precious metals. Wet processing involves separating the metals from the liquid phase through processes such as precipitation, displacement, and ion exchange. Compared to pyrometallurgical processing, wet processing offers more diverse production processes, and different processing techniques offer varying advantages. Today, wet processing is the primary method for recovering precious metals.

[0006] The traditional wet process is widely used due to its advantages of low cost, environmental protection and high efficiency. However, the recovery rate of precious metals is low because precious metal elements or oxides are difficult to dissolve in aqua regia.

[0007] Currently, there are various dissolution methods for dissolving insoluble precious metals. The main methods are: (1) Alkali Oxidation Melting-Chlorination Leaching Method: Precious metal materials are mixed with sodium peroxide in proportion, melted at a certain temperature, soaked in water, filtered, and the residue is leached with HCl / Cl2 to obtain a precious metal solution. The disadvantages of this method are that the operation is cumbersome and filtering is difficult. For sulfur-containing materials, it also causes gold, palladium, platinum, etc. to be dispersed in the alkali solution. (2) Sulfate Melting Method: Precious metal materials are heated and melted with potassium hydrogen sulfate or potassium pyrosulfate in a porcelain crucible, and then transferred into the solution through leaching. The leaching rate of this method is not high. It must be repeated many times, the process is lengthy, and it cannot handle large amounts of materials. (3) Electrochemical Dissolution Method: This method is to dissolve insoluble platinum group metal materials by passing alternating current in a certain acidic medium. Electrochemical dissolution can only be used for the dissolution of metals or alloys. Its most significant advantage is that it is not easy to introduce new impurities and can directly process flake and powder materials such as iridium and its alloys. However, this method has a small processing capacity and equipment difficulties, so its practical application is limited. (4) Hot-pressure dissolution method: The precious metal material and the solvent are placed in a closed container and heated to generate high pressure, causing the precious metal material to decompose and dissolve at a temperature higher than the boiling point of the solvent. The characteristics of this method are a wide range of solvents to choose from, a wide range of materials to dissolve, and the avoidance of pollution. However, the dissolution cycle is long and the energy consumption is high. Summary of the invention:

[0008] The present invention aims to overcome the shortcomings and deficiencies of existing technologies by providing a method for recovering ruthenium and iridium from precious metal materials using low-temperature plasma technology. This method utilizes novel precious metal material recovery technology to make the precious metals more soluble in aqua regia, thereby improving precious metal recovery efficiency. The entire pretreatment process is minimally polluting the environment and requires less energy. Furthermore, the content of precious metals ruthenium and iridium that can ultimately be dissolved in aqua regia is high, resulting in superior economic benefits. This method is a highly efficient precious metal material recovery method.

[0009] The technical solution adopted by the present invention is as follows: a method for recovering ruthenium and iridium from precious metal materials based on low-temperature plasma technology. The recovery equipment includes a low-temperature plasma device consisting of a reaction vessel, a vacuum pump, a magnetic stirrer, an inductive coupling coil, and a radio frequency power supply. The reaction vessel is connected to the magnetic stirrer, and the inductive coupling coil is connected to the radio frequency power supply. The method is characterized by:

[0010] (1) Low-temperature and low-pressure plasma treatment: Take a small amount of precious metal material and place it in a reaction vessel of a 25°C low-temperature plasma device. Use a vacuum pump to evacuate the reaction vessel and then replace it with chlorine gas to make the reaction vessel a low-pressure environment of 10-20Pa. After the gas replacement is completed, turn on the magnetic stirrer and the radio frequency power supply, and perform low-temperature and low-pressure plasma treatment on the stirred precious metal material to convert the precious metal element or oxide that is difficult to dissolve in aqua regia into precious metal chloride that is easily soluble in aqua regia; thus obtaining the pretreated precious metal material A;

[0011] (2) Dissolution of precious metal materials: The pretreated precious metal material A obtained in step (1) is placed in a beaker, and the corresponding aqua regia is added in a ratio of 1:6 between the precious metal material and aqua regia, and then heated on an electronic multi-purpose furnace, boiled, cooled at room temperature for 2 hours, and filtered with filter paper to obtain a precious metal filtrate B for separation and refining;

[0012] (3) The undissolved precious metal material obtained in step (2) is then weighed and compared with the precious metal material before dissolution. The dissolution rate of the precious metal is calculated based on the amount of precious metal dissolved before and after dissolution.

[0013] In step (1), the noble metal material is reduced for 0.5 to 5 hours under low pressure in the reaction vessel and a chlorine atmosphere at a power of 100-200W, and low-temperature and low-pressure plasma treatment is performed.

[0014] The precious metal material contains ruthenium and iridium in solid form. The precious metals in the precious metal material include simple substances of ruthenium and iridium and their oxides.

[0015] In step (1), the reaction vessel is wrapped with an inductive coupling coil to cool the reaction vessel; the inductive coupling coil is a water pipe connected to circulating water, and a water inlet and a water outlet are set at both ends.

[0016] During the chlorine replacement process in step (1), the harmful gas Cl2 discharged from the vacuum pump exhaust port is collected and washed away with excess KOH solution.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention adopts the above technical solution, converting the precious metal element or oxide that is difficult to dissolve in aqua regia into a precious metal chloride that is easily soluble in aqua regia after being treated with chlorine plasma, thereby improving the solubility rate of the precious metal material in aqua regia, thereby improving the recovery efficiency of the precious metal. The present invention can fully recycle the precious metal in the precious metal material, reduce resource waste, and maximize the recovery of valuable precious metal resources. The entire experimental process of the present invention is environmentally friendly and efficient, and the operation is simple; the present invention ultimately improves the recovery efficiency of the precious metal by increasing the solubility rate of the precious metal in aqua regia, and has better economic benefits. Description of the drawings:

[0019] Figure 1 This is a schematic diagram of the structural principle of the low-temperature plasma device used in the present invention.

[0020] Figure 2 for Figure 1 Schematic diagram of the structural principle of the reaction device part. Specific implementation method:

[0021] The present invention is further described in detail below with reference to examples. The following examples are intended to illustrate the present invention only and should not be construed as limiting the scope of the invention. Where specific techniques or conditions are not specified in the present specification, the techniques or conditions described in the literature in the art or in the product specifications were used. Materials or equipment used, where the manufacturer is not specified, are all commercially available conventional products.

[0022] The present invention provides a method for recovering ruthenium and iridium from precious metal materials based on low-temperature plasma technology. The precious metal materials contain ruthenium and iridium in solid form.

[0023] It includes the following steps:

[0024] Step 1: Pretreatment (low-temperature, low-pressure plasma treatment): A small amount of precious metal material is placed in a low-temperature plasma device. After evacuation, the container is replaced with chlorine gas to create a low-pressure environment. After the gas replacement is complete, the stirred precious metal material is subjected to low-temperature plasma reduction for 0.5 hours, 1 hour, or 2 hours. After the treatment is complete, the precious metal material is removed.

[0025] Step 2: Dissolving the precious metal material: Place the precious metal material after low-temperature and low-pressure plasma treatment in a beaker, add the corresponding aqua regia according to the mass ratio of precious metal material to aqua regia of 1:6, then heat it on an electronic multi-purpose furnace, boil it, and finally cool it at room temperature for 2 hours, and then filter it with filter paper.

[0026] Step 3: Analyze the dissolution rate of precious metal materials.

[0027] The contained noble metal material is a raw material containing noble metal elements of ruthenium and iridium or noble metal oxides.

[0028] In step one, the chlorine replacement time is at least 20 min,

[0029] In step two, after adding aqua regia, the boiling duration on the electronic universal furnace is 15-20 min,

[0030] In step three, the mass of the noble metal material before and after dissolution is weighed.

[0031] Example 1:

[0032] 1. Take a small amount of noble metal material and weigh 1 g.

[0033] 2. Place it in the reaction container of the low-temperature plasma device, and after vacuum pumping with a vacuum pump, perform chlorine replacement to make the vacuum gauge show a low-pressure environment of about 10 Pa in the reaction container.

[0034] 3. After the gas replacement is completed, turn on the magnetic stirrer and open the radio frequency power source to perform low-temperature plasma treatment of 100 W on the stirred noble metal material for 0.5 h. The induction coupling coil is wrapped around the reaction container, and the inlet and outlet are set for circulating water to cool the reaction container. KOH solution is used to wash away harmful gases generated during the reaction. After the treatment is completed, take out the noble metal material.

[0035] 4. Place the noble metal material treated by low-temperature plasma in a beaker, and add the corresponding aqua regia according to the mass ratio of noble metal material:aqua regia of 1:6.

[0036] 5. Place it on the electronic universal furnace for heating and boiling.

[0037] 6. Cool at room temperature for 2 h, and then filter with filter paper.

[0038] 7. Then weigh the undissolved noble metal material and compare it with the noble metal material before dissolution.

[0039] Example 2:

[0040] 1. Take a small amount of noble metal material and weigh 1 g.

[0041] 2. Place it in the reaction container of the low-temperature plasma device, and after vacuum pumping with a vacuum pump, perform chlorine replacement to make the vacuum gauge show a low-pressure environment of about 20 Pa in the reaction container.

[0042] 3. After the gas replacement is completed, the magnetic stirrer is turned on, and the radio frequency power is turned on to treat the stirred noble metal material with low-temperature plasma at 100 W for 0.5 h. The inductive coupling coil is wrapped around the reaction container, and the inlet and outlet of the circulating water are set to cool the reaction container. The KOH solution is used to wash away the harmful gas generated in the reaction process. After the treatment is completed, the noble metal material is taken out.

[0043] 4. The noble metal material treated with low-temperature plasma is placed in a beaker, and the corresponding aqua regia is added according to the mass ratio of noble metal material to aqua regia of 1:6.

[0044] 5. It is placed on an electronic universal furnace for heating and boiling.

[0045] 6. It is cooled at room temperature for 2 h, and then filtered with filter paper.

[0046] 7. Then, the undissolved noble metal material is weighed again and compared with the noble metal material before dissolution.

[0047] Example 3:

[0048] 1. A small amount of noble metal material is taken and weighed 1 g.

[0049] 2. It is placed in the reaction container of the low-temperature plasma device, and after vacuum pumping, chlorine replacement is performed to make the vacuum gauge show a low-pressure environment of about 10 Pa in the reaction container.

[0050] 3. After the gas replacement is completed, the magnetic stirrer is turned on, and the radio frequency power is turned on to treat the stirred noble metal material with low-temperature plasma at 200 W for 0.5 h. The inductive coupling coil is wrapped around the reaction container, and the inlet and outlet of the circulating water are set to cool the reaction container. The KOH solution is used to wash away the harmful gas generated in the reaction process. After the treatment is completed, the noble metal material is taken out.

[0051] 4. The noble metal material treated with low-temperature plasma is placed in a beaker, and the corresponding aqua regia is added according to the mass ratio of noble metal material to aqua regia of 1:6.

[0052] 5. It is placed on an electronic universal furnace for heating and boiling.

[0053] 6. It is cooled at room temperature for 2 h, and then filtered with filter paper.

[0054] 7. Then, the undissolved noble metal material is weighed again and compared with the noble metal material before dissolution.

[0055] Example 4:

[0056] 1. A small amount of noble metal material is taken and weighed 5 g.

[0057] 2. Place the reaction vessel in a low-temperature plasma device, use a vacuum pump to evacuate the air, and then replace the chlorine gas until the vacuum gauge shows a low pressure environment of about 10 Pa in the reaction vessel.

[0058] 3. After gas replacement is complete, turn on the magnetic stirrer and RF power supply, and subject the stirred precious metal material to a low-temperature plasma treatment at 200W for 0.5 hours. An inductively coupled coil is wrapped around the reaction vessel, and circulating water is provided with an inlet and outlet to cool the reaction vessel. KOH solution is used to wash away harmful gases generated during the reaction. After treatment is complete, remove the precious metal material.

[0059] 4. Place the precious metal material after low-temperature plasma treatment in a beaker, and add the corresponding aqua regia according to the mass ratio of precious metal material to aqua regia of 1:6.

[0060] 5. Heat on an electronic multi-purpose stove and bring to a boil.

[0061] 6. Cool at room temperature for 2 hours, then filter with filter paper.

[0062] 7. Then weigh the undissolved precious metal material and compare it with the precious metal material before dissolution.

[0063] Example 5:

[0064] 1. Take a small amount of precious metal material and weigh 5g.

[0065] 2. Place the container in a low-temperature plasma device, evacuate with a vacuum pump, and then replace the chlorine gas until the vacuum gauge shows a low pressure environment of about 10 Pa in the container.

[0066] 3. After gas replacement is complete, turn on the magnetic stirrer and RF power supply, and subject the stirred precious metal material to a low-temperature plasma treatment at 200W for 1 hour. An inductively coupled coil is wrapped around the reaction vessel, and circulating water is provided with an inlet and outlet to cool the reaction vessel. KOH solution is used to wash away harmful gases generated during the reaction. After treatment is complete, remove the precious metal material.

[0067] 4. Place the precious metal material after low-temperature plasma treatment in a beaker, and add the corresponding aqua regia according to the mass ratio of precious metal material to aqua regia of 1:6.

[0068] 5. Heat on an electronic multi-purpose stove and bring to a boil.

[0069] 6. Cool at room temperature for 2 hours, then filter with filter paper.

[0070] 7. Then weigh the undissolved precious metal material and compare it with the precious metal material before dissolution.

[0071] Example 6:

[0072] 1. Take a small amount of precious metal material and weigh 5g.

[0073] 2. Place the container in a low-temperature plasma device, evacuate with a vacuum pump, and then replace the chlorine gas until the vacuum gauge shows a low pressure environment of about 10 Pa in the container.

[0074] 3. After gas replacement is complete, turn on the magnetic stirrer and RF power supply, and subject the stirred precious metal material to a low-temperature plasma treatment at 200W for 2 hours. An inductively coupled coil is wrapped around the reaction vessel, and circulating water is provided with an inlet and outlet to cool the reaction vessel. KOH solution is used to wash away harmful gases generated during the reaction. After treatment is complete, remove the precious metal material.

[0075] 4. Place the precious metal material after low-temperature plasma treatment in a beaker, and add the corresponding aqua regia according to the mass ratio of precious metal material to aqua regia of 1:6.

[0076] 5. Heat on an electronic multi-purpose stove and bring to a boil.

[0077] 6. Cool at room temperature for 2 hours, then filter with filter paper.

[0078] 7. Then weigh the undissolved precious metal material and compare it with the precious metal material before dissolution.

[0079] The following data can be obtained from Examples 1-6:

[0080] Mass before experiment (g) Mass after test (g) Dissolved mass (g) Dissolution rate Blank experiment 1.0000 0.9970 0.0030 0.30％ Experiment 1 1.0000 0.8563 0.1437 14.37％ Experiment 2 1.0000 0.8965 0.1035 10.35％ Experiment 3 1.0000 0.8172 0.1828 18.28％ Experiment 4 5.0000 3.8951 1.1049 22.10％ Experiment 5 5.0000 3.7540 1.2460 24.92％ Experiment 6 5.0000 3.7484 1.2516 25.03％

[0081] As can be seen from the table above, the methods of plasma pretreatment of precious metal materials to improve precious metal recovery rates in Examples 1-6 all improve the solubility of precious metals in aqua regia. Chlorine plasma treatment of precious metal materials effectively converts the elemental elements or oxides of ruthenium and iridium in the precious metal materials into chlorides, thereby increasing the solubility of the precious metals in aqua regia and ultimately improving the recovery rate of the precious metal materials. The present invention is simple to operate, has a good leaching effect, a high recovery rate, and is environmentally friendly.

[0082] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering ruthenium and iridium, characterized in that: The following steps are involved: (1) Low-temperature and low-pressure plasma treatment: Take a small amount of precious metal material and place it in a reaction vessel of a low-temperature plasma device at 25°C. Use a vacuum pump to evacuate the reaction vessel and then replace it with chlorine gas to make the reaction vessel a low-pressure environment of 10-20Pa. After the gas replacement is completed, turn on the magnetic stirrer and the radio frequency power supply, and perform low-temperature and low-pressure plasma treatment on the stirred precious metal material to convert the precious metal element or oxide that is difficult to dissolve in aqua regia into precious metal chloride that is easily soluble in aqua regia; Obtaining the pretreated precious metal material A; (2) Dissolution of precious metal materials: The pretreated precious metal material A obtained in step (1) is placed in a beaker, and the corresponding aqua regia is added in a ratio of 1:6 between the precious metal material and aqua regia, and then heated on an electronic multi-purpose furnace, boiled, cooled at room temperature for 2 hours, and filtered with filter paper to obtain a precious metal filtrate B for separation and refining; (3) Then weigh the undissolved precious metal material obtained in step (2) and compare it with the precious metal material before dissolution. The dissolution rate of the precious metal is calculated based on the amount of the precious metal dissolved before and after dissolution. The method for recovering ruthenium and iridium is implemented using the following apparatus: The recovery equipment includes a low-temperature plasma device consisting of a reaction container, a vacuum pump, a magnetic stirrer, an inductive coupling coil and a radio frequency power supply. The reaction container is connected to the magnetic stirrer, and the inductive coupling coil is connected to the radio frequency power supply.

2. The method according to claim 1, wherein: The reaction container is wrapped with an inductive coupling coil to cool the reaction container; the inductive coupling coil is a water pipe connected to circulating water, and a water inlet and a water outlet are arranged at both ends of the inductive coupling coil.

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