Method and system for recovering valuable metals contained in waste liquid

Abstract

To provide a method and a system for safely and efficiently recovering palladium used as a catalyst in organic synthesis and polymerization, from a waste liquid.SOLUTION: By bringing a waste liquid containing a new chemical substance to be treated into contact little by little with a granular or flake heat medium that has a heat at or above a boiling point and below an ignition point of a volatile component contained in the waste liquid, and that is flowing, to evaporate and separate a volatile component. Thereby, a valuable metal contained in the waste liquid is efficiently and safely concentrated. Thereafter, the concentrated valuable metal is taken out and exposed to another combustion atmosphere of 1,000°C or higher for 2 seconds or longer to detoxify and remove the waste liquid containing new chemical substances accompanying the valuable metal. The copper can be recycled by using copper grain derived from a negative electrode current collector of a lithium ion secondary battery as a heat medium. A volatile gas evaporated during the concentration is rendered harmless by combustion in a combustion tower 13. Thereafter, a temperature can be lowered by diluting with air, and further, the volatile gas can be discharged into the atmosphere through a cooling tower 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering valuable metals such as palladium (Pd) contained in waste liquid, and a recovery system that utilizes the recovery method. [Background technology]

[0002] Palladium complexes have excellent catalytic properties and are therefore widely used as catalysts for the synthesis of organic compounds such as pharmaceutical intermediates and for the polymerization of polymer compounds such as organic thin films contained in solar cells, as described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-132553 Summary of the Invention [Problem to be solved by the invention]

[0004] However, technology has not yet been established to safely and efficiently recover palladium, which has been used as a catalyst in organic synthesis and polymerization, from waste liquids. Given the need for recycling to promote a resource-circulating society, establishing recovery technology has become an urgent task. This is not limited to palladium, but is a common issue for valuable metals in general. Furthermore, in order to put the recovery system into practical use, it is necessary to safely treat the large amount of waste liquid that is produced, but this waste liquid may contain new chemical substances that are not designated by government ordinance.

[0005] Therefore, an object of the present invention is to provide a method for safely and efficiently recovering valuable metals from waste liquids. Another object of the present invention is to provide a practical recovery system that utilizes the recovery method to recover valuable metals and detoxify wastewater that also contains new chemical substances. [Means for solving the problem]

[0006] The present invention has been made to solve the above-mentioned problems, and the invention [1] is a method for recovering valuable metals contained in organic waste liquid, characterized by comprising a concentration step in which the waste liquid is brought into contact in small amounts with a granular or flake-like heat transfer medium that has a heat level above the boiling point but below the ignition point of the volatile components contained in the waste liquid to be treated and is in a flowing state, thereby concentrating the valuable metals contained in the waste liquid by evaporating and separating the volatile components.

[0007] The invention [2] is a method for recovering valuable metals contained in waste liquid described in [1], characterized by including a recovery step in which the concentrated valuable metals are extracted and melted in a melting furnace at a temperature of 1,000°C or higher (exposed to a combustion atmosphere for 2 seconds or more) to neutralize and remove the waste liquid containing new chemical substances, etc. that were accompanying the valuable metals.

[0008] The invention [3] is a method for recovering valuable metals contained in waste liquid described in [2], characterized in that a metal is used as a heat transfer medium to dissolve and alloy metal particles in the recovery process.

[0009] The invention [4] is a method for recovering valuable metals contained in waste liquid described in [3], characterized in that copper particles derived from the negative electrode current collector of a lithium-ion secondary battery are used as a heat transfer medium, and copper alloys containing the valuable metals as additive components are formed during the recovery process.

[0010] The invention [5] is a system for recovering valuable metals contained in waste liquid, characterized by comprising equipment for carrying out a concentration step of the method for recovering valuable metals contained in waste liquid described in any one of [2] to [4], a recovery step, and a detoxification step in which the volatile gases of the waste liquid containing new chemical substances, etc. separated from the concentration step are exposed to a combustion atmosphere of 1,000°C or higher for at least 2 seconds. [Effects of the Invention]

[0011] According to the recovery method of the present invention, valuable metals can be recovered safely and efficiently from waste liquid containing new chemical substances, etc. Furthermore, the recovery system of the present invention utilizes the above recovery method to safely and efficiently recover valuable metals and detoxify waste liquid containing new chemical substances, etc., making it practical. Furthermore, if copper particles derived from the negative electrode current collector of a lithium-ion secondary battery are used as the heat transfer medium in the recovery method, these copper particles can be recovered as high-value-added scrap, and the lithium-ion secondary battery can be recycled at the same time. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flow diagram of a system for recovering valuable metals from organic waste liquid according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the Pd enrichment section of the recovery system of FIG. 1. [Figure 3] FIG. 2 is an enlarged view of the detoxification section of the recovery system of FIG. 1. [Figure 4] FIG. 2 is an enlarged view of the cooling section of the recovery system of FIG. 1. [Figure 5] 1 is a photograph of copper particles used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Material to be processed) The material to be treated is wastewater containing new chemical substances containing valuable metals, such as palladium (Pd). Palladium complexes have excellent catalytic properties and are used as catalysts for the synthesis of organic compounds such as pharmaceutical intermediates and for the polymerization of polymer compounds such as organic thin films contained in solar cells. Significant amounts of palladium are discharged into the organic wastewater. Below is an example of an organic solvent waste liquid containing palladium, i.e., Pd waste liquid, which is actually discharged. This Pd waste liquid is made by concentrating an original solution with a Pd concentration of about 100 ppm to a Pd concentration of about 500 ppm. The concentration is done by evaporation separation, and since residual solid matter adheres to the bottom and sides of the evaporation furnace and becomes impossible to remove, taking into account work safety and residue removal, the limit is set at 5 times concentration. The waste liquid may be not only an organic solvent but also an aqueous solvent, that is, a water-soluble liquid, and both are included in the present invention.

[0014] [Table 1]

[0015] <Collection system configuration> Figure 1 shows a flow diagram of a system 1 for recovering palladium contained in organic wastewater, which is composed of a Pd concentration section, a detoxification section, a cooling section, and a melting alloying section, and these sections are arranged in a continuous treatment line. In addition, the melting alloying section is arranged in a treatment line branching off from the Pd concentration section. The equipment that makes up each section and the interconnectedness between the equipment are described in detail below.

[0016] In this recovery system 1, the Pd waste liquid shown in Table 1 is treated. The heat transfer medium may be any material that is granular or flake-shaped, has a large surface area, and has heat storage and thermal conductivity. In this embodiment, copper particles derived from the negative electrode current collector of a lithium-ion secondary battery are used as the heat transfer medium. Copper foil discarded as waste from the production process or as scrap from dismantled used batteries is crushed to approximately 3 to 5 mm in size to produce copper particles with a large surface area. Melting the copper waste to produce a copper alloy increases the scrap value and simultaneously enables recycling of the lithium-ion secondary battery.

[0017] [Pd enrichment section] The Pd enrichment section performs the enrichment step, and is configured using a cylindrical furnace 3, as shown in the enlarged view of FIG. This furnace body 3a is a horizontal type, and inside it, multiple stirring blades 3b are installed so that they protrude outward from an axially extending mounting shaft. This mounting shaft is connected to a motor, and the stirring blades 3b rotate inside when driven by the motor. A copper particle inlet 3c is installed at the top of one axial side of the furnace body 3a, and a volatile gas outlet 3d is installed at the top of the other axial side. After the copper particle inlet 3c is installed, it is closed, and the inside of the furnace body 3a is sealed. The furnace body 3a is tiltably supported by a support base 3e, and an outlet 3g is provided at a position that is underneath the furnace body 3a when it is raised by a swing cylinder 3f. When removing the copper particles after treatment, the furnace body 3a is raised and the copper particles are removed from the outlet 3g.

[0018] In addition, a pipe 7 for a spray device is connected to the drum 5 storing the Pd waste liquid. This pipe 7 enters the interior from one axial end of the furnace body 3a and extends parallel to the axial direction through the upper space inside toward the other end. Inside, multiple spray nozzles (not shown) are attached to the pipe 7 and arranged at regular intervals, with the nozzle holes of each spray nozzle facing downward. A pump is installed in the conduit between the drum 5 and the pipe 7, and the pressurized Pd waste liquid is sprayed from the spray nozzles. The inside of the furnace body 5a is heated by a duct heater 9. The outlet 3d for the volatile gas is connected to the detoxification section via a pipe 11.

[0019] The Pd concentration section is configured as described above, and during operation of the recovery system 1, the furnace body 3a is closed with a large amount of copper particles inside. The inside of the furnace body 3a is heated by the duct heater 9 within a range of 200 to 250°C, and the copper particles are heated to a temperature above the boiling point of the volatile components contained in the Pd waste liquid, but well below their ignition point. Furthermore, the agitator blade 3b rotates inside the furnace body 3a, and the large amount of copper particles are repeatedly lifted and dropped by the agitator blade 3b, causing them to become fluidized.

[0020] In this state, the Pd waste liquid is sprayed. The Pd waste liquid is supplied as a spray, and it comes into continuous contact with the large amount of flowing copper particles in small amounts. As the copper particles are lifted and fall, gaps are created around them, and they rotate, constantly changing the surface that the Pd waste liquid comes into contact with, so the entire surface is efficiently used for contact with the Pd waste liquid. The volatile components contained in the Pd waste liquid evaporate when they come into contact with the copper particles, turning into volatile gases. The inlet 3c and outlet 3g of the furnace body 3a are closed, creating an enclosed space inside, and air is not actively introduced later. Even so, if the volatile components were to combine with the oxygen in the air that was already inside the furnace body 3a and burn, there is a risk of explosion, but this risk is avoided because the temperature is well below the ignition point. Therefore, the volatile components are safely separated as volatile gases without burning. The generated volatile gas is sent to the detoxification section through a pipe 11 in sequence.

[0021] [Detoxification Department] The detoxification section carries out a detoxification process to detoxify the volatile gases that have been evaporated and separated and sent to it, and is configured using a combustion tower 13, as shown in the enlarged view of Figure 3. This tower body 13a is erected, and an inlet 13b for receiving the volatile gases is provided on the lower side, and is connected to a pipeline 11. An outlet 13c for discharging the detoxified gases is provided on the ceiling side, and is connected to a pipeline 15. Burners 17a, 17a of the combustion device 17 are attached in two rows, one above the other, to the lower side of the tower body 13a, and fuel is supplied from a fuel tank 17b, mixed with an appropriate amount of air, and a combustion flame is ejected into the interior of the tower body 13a. In addition, air inlets 19a, 19a of an air supply device 19 are provided between the burners 17a and above the upper burner 17a, and combustion air is blown into the inside of the tower body 13a by driving an air blowing fan 19b.

[0022] Burners 17a and 17a and air inlets 19a are provided on the side of the lower half of tower body 13a, and another air inlet 19c is provided on the side of the upper part of tower body 13a. Dilution air is blown into tower body 13a from air inlet 19c by driving air blowing fan 19b.

[0023] The detoxification section is configured as described above, and when the recovery system 1 is in operation, the volatile gases sent thereto are exposed to a combustion flame in the presence of a quantity of air (oxygen) that allows for complete combustion, causing them to be oxidized and decomposed into detoxified gases. By exposing them to temperatures of 1000°C or higher for 2 seconds or more, 99.9% of solvents containing the new chemical substances listed in Table 1 can be rendered harmless. Inside the tower body 13a, this oxidative decomposition is carried out at the bottom, and the generated harmless gas is at a very high temperature, but as it rises inside the tower 13a, it is diluted and its temperature is lowered by dilution air blown in from the air inlet 19c, and then it is sent to the cooling section. Inside tower body 13a, the area near burners 17a, 17a is a high-temperature combustion zone of 1500 to 1600°C, but by introducing dilution air, the temperature is lowered to 1000 to 1100°C in the middle section and further to 600 to 800°C in the upper section. Therefore, the harmless gas cooled to 600 to 800°C is sent to the cooling section.

[0024] [Cooling section] The cooling section performs a cooling process to further lower the temperature of the detoxified gas that has been diluted and lowered to a certain temperature, and is configured using a cooling tower 21, as shown in the enlarged view of Fig. 4. This tower body 21a is erected, and an inlet 21b for receiving the detoxified gas is provided on the ceiling side and connected to the pipeline 15. An outlet 21c is provided on the bottom and is connected to an exhaust pipe 21d. An exhaust fan 21e is connected to this exhaust pipe 21d, and the sufficiently cooled detoxified gas is released into the atmosphere. Heat exchangers 23a, 23a, 23a of a gas cooler device 23 are attached to the outside of the side of the tower body 21a, and when a gas cooler fan 23b is driven, cooling air flows inside the heat exchanger 23a, cooling the inside of the tower body 21a. If the detoxified gas can be cooled sufficiently by, for example, extending the furnace length of the combustion tower 13 in the detoxification section, it is also possible to directly release the detoxified gas from the detoxification section into the atmosphere.

[0025] [Melting alloying section] The melting and alloying section carries out the melting and alloying process of melting and alloying copper particles using palladium contained in the concentrated Pd waste liquid as an additive component, and is configured using a high-frequency induction furnace 25 (see Figure 1). In the Pd concentration section, the amount of organic solvent decreases relatively due to the generation of volatile gases, and the Pd waste liquid becomes concentrated, and palladium complexes precipitate on the surface of the copper particles. It is like an automobile catalyst, with palladium complexes attached to the copper particles. When a certain amount of Pd waste liquid has been treated and a certain amount has accumulated, this concentrated liquid containing copper particles is removed from the cylindrical furnace 3 and charged into the high-frequency induction furnace 25. In the high frequency induction furnace 25, copper and palladium are melted, and after they are completely melted, they are poured into a suitable mold and solidified, allowing them to be recovered as ingots. These ingots have high scrap value and can be bought and sold.

[0026] The furnace is heated to a high temperature of over 1000°C in order to melt the metals mentioned above. Although the concentrated liquid still contains a small amount of organic waste liquid, by exposing it to this high-temperature atmosphere for 2 seconds or more, the organic waste liquid is evaporated and separated in the same way as in the detoxification process. Therefore, it is safe to open the high frequency induction furnace 25 when removing the molten metal from the furnace. The melting and alloying step is a step of alloying and recovering a copper alloy containing palladium as an additive component, and is one aspect of the recovery step.

[0027] Although the embodiments of the present invention have been described in detail above, the specific configuration is not limited to these embodiments, and the invention also includes design changes within the scope of the present invention without departing from the gist of the present invention. For example, the Pd waste liquid to be treated is not limited to the composition shown in Table 1 above, and the valuable metal to be recovered is not limited to palladium, so the type of solvent will vary depending on the type of valuable metal. Not only organic solvents but also aqueous solvents, i.e., water-soluble liquids, can be used. However, any solvent containing valuable metals can be treated by the recovery method and recovery system of the present invention. Furthermore, valuable metals such as palladium can be recovered by melting and alloying as described above, or by recovering the valuable metals alone. Heat transfer media are not limited to metals such as copper, so in the latter case, an insoluble material such as ceramic can be used as the heat transfer media. In either case, the recovery process involves evaporation and separation of the solvent, just as in the detoxification process. [Example]

[0028] The Pd concentration section was reproduced at a laboratory level using a container heated by a heater. Copper particles (approximately 300 g) heated to 200-250°C were placed in this container, and the Pd waste liquid was continuously added in small amounts while stirring. A total of 1800 mL of Pd waste liquid was added to the copper particles. The copper particles were derived from the negative electrode current collector of a lithium-ion secondary battery, and the Pd waste liquid used was that listed in Table 1. However, because this was a test sample, the Pd concentration was 416 ppm instead of 600 ppm. The test conditions are shown in Table 2. A portion of it was then removed and reheated to over 500°C to remove tar-like components. The copper particles that were reheated to 500°C or higher and the remaining copper particles that were not reheated were then analyzed using an ICP optical emission spectrometer (n=2). The results are shown in Table 3. Photographs of copper particles before the addition of Pd waste liquid, copper particles without reheating after the addition, and copper particles with reheating after the addition are shown in FIG.

[0029] [Table 2]

[0030] [Table 3]

[0031] When the Pd waste liquid was dropped little by little onto copper particles heated to 200-250°C, white smoke was generated, but it was confirmed that the volatile components of the organic solvent could be safely evaporated. In addition, there was a slight difference between the calculated value (2,260 ppm) and the analytical value (2,510 ppm) of palladium content, and it was confirmed that palladium could be recovered with a good yield. Furthermore, it was confirmed that the very small amount of organic solvent that had been accompanying the copper particles was evaporated and separated by reheating to 500°C. Looking at the photograph in Figure 5, the color is different with and without reheating at 500°C, suggesting that the complex was decomposed by reheating. [Explanation of symbols]

[0032] 1. Palladium recovery system for organic wastewater 3... Cylindrical furnace 3a... Furnace body 3b... Stirring blade 3c...Inlet 3d...Outlet 3e...Support base 3f...Swing cylinder 3g...Removal port 5...Drum 7...Piping 9...Duct heater 11...Pipe 13... Combustion tower 13a... Tower body 13b... Receiving port 13c...Discharge port 15...Pipeline 17...Combustion device 17a...Burner 17b...Fuel tank 19...Air supply device 19a, 19c...Air inlet 19b...Air blowing fan 21...Cooling tower 21a...Tower body 21b...Inlet 21c...Exhaust port 21d...Exhaust pipe 21e...Exhaust fan 23...Gas cooler device 23a...Heat exchanger 23b...Gas cooler fan 25...High frequency induction furnace

Claims

1. A method for recovering valuable metals contained in organic waste liquid, comprising a concentration step in which the waste liquid is sprayed into contact with a flowing granular or flake-like heat transfer medium having a heat level equal to or higher than the boiling point but lower than the ignition point of the volatile components contained in the waste liquid to be treated, thereby concentrating the valuable metals contained in the waste liquid by evaporating and separating the volatile components.

2. 2. The method for recovering valuable metals contained in wastewater according to claim 1, This recovery method is characterized by comprising a recovery step in which the concentrated valuable metals are extracted and exposed to a combustion atmosphere of 1,000°C or higher for at least 2 seconds to neutralize and remove waste liquid containing new chemical substances that were associated with the valuable metals.

3. 3. The method for recovering valuable metals contained in wastewater according to claim 2, A recovery method characterized in that metal particles are melted and alloyed in the recovery step using a metal as a heat medium.

4. 4. The method for recovering valuable metals contained in wastewater according to claim 3, A recovery method characterized by using copper particles derived from the negative electrode current collector of a lithium-ion secondary battery as a heat transfer medium, and attempting to form a copper alloy with valuable metals as added components in the recovery process.

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