Metal recovery method

Abstract

Metal deposited by electrolysis is integrated with a negative electrode so as to be able to be solidified from wastewater. However, for actual recovery, it is necessary to extract the negative electrode and, for example, scrape off the surface thereof so as to recover the metal.　A metal recovery method according to the present invention comprises: a treatment target solution injection step for injecting, into a container in which electrode plates are disposed, a solution containing metal which exists in an ionic state; a resting step for leaving the solution stationary with respect to the electrode plates; a sponge-like metal porous body formation step for supplying an electric current between the electrode plates and causing a sponge-like metal porous body to be formed on the electrode plate which has become a negative electrode; and a separation step for separating the sponge-like metal porous body from the electrode. The metal which has been deposited on the electrode is not fixed to the electrode plate, and can therefore be easily recovered.

Description

[Technical field]

[0001] The present invention relates to a method for recovering a metal present in an ionic state in a waste liquid, in particular, copper, from a waste liquid containing a large amount of hydrogen peroxide in the solution. [Background technology]

[0002] In recent years, highly conductive copper has been used for the fine wiring used in ICs, etc. When forming very fine wiring, the subtractive method is used, in which a copper film is formed over the entire surface and unnecessary parts are removed by etching to form a circuit. This method generates waste liquid that contains a lot of copper.

[0003] Electrolysis is often used to recover metals from waste liquids containing metal ions. Patent Document 1 discloses a method of electrolytic extraction of powder metal from a solution in which a cylindrical cathode is formed on the inside of a cylindrical electrolytic cell, the inner surface of the electrolytic cell is used as the anode, and a treatment liquid is passed through the solution to deposit the metal. In Patent Document 1, a flushing solution is passed in the opposite direction to the treatment liquid when depositing the metal, and the metal powder deposited on the cathode is removed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2003-505598 Summary of the Invention [Problem to be solved by the invention]

[0005] When recovering metals from waste liquid, electrolysis is used, which is advantageous because it increases the recovery rate. However, the metals precipitated by electrolysis become one with the cathode, and although it is possible to solidify them from the waste liquid, in order to actually recover them, it is necessary to remove the cathode and scrape its surface to recover the metals. In Patent Document 1, it has been discovered that by lowering the speed of the fluid passing through the electrolytic cell and the current density, it is easier to generate powdered metal, rather than plate-like metal, on the cathode, and this is an attempt to increase the ease of recovery.

[0006] However, even with this method, if wastewater is flowing during treatment, metal will adhere to the cathode. If the adhered metal grows, the precipitated metal cannot be collected as a powder even if a flushing solution is flowed. As a result, there was a problem that the device had to be disassembled, the electrodes removed, and the precipitated metal scraped off. [Means for solving the problem]

[0007] The present invention was conceived in consideration of the above-mentioned problems, and was completed based on the discovery that when the waste liquid to be treated (hereinafter referred to as the "liquid to be treated") is left stationary rather than flowing relative to the electrodes, and a high current density is applied to the cathode, the precipitated metal fine particles form a structure that embraces hydrogen generated by electrolysis.

[0008] More specifically, the metal recovery method of the present invention comprises the steps of: a process of injecting a solution containing a metal present in an ionic state into a container in which an electrode plate is disposed; After the injection process of the liquid to be treated, the process waits for a certain period of time. A stilling step; a step of forming a sponge-like porous metal body on the electrode plate serving as a cathode by passing an electric current between the electrode plates; The sponge-like porous metal body is Become a cathode electrode board A peeling step of peeling the The peeling step is characterized in that it is a step of bringing air bubbles into contact with the electrode plate or the sponge-like metal porous body. Effect of the Invention

[0009] In the metal recovery method of the present invention, when the liquid to be treated is electrolyzed, the liquid is not allowed to flow, and only a slight upward flow of hydrogen bubbles generated from the electrodes occurs. When a relatively large current is applied to the cathode in this state, the deposited metal becomes fine particles that reach a certain size. Then, before metallic bonding is formed with the electrode, the metal is pushed out of the electrode by the hydrogen bubbles generated at the cathode.

[0010] Meanwhile, the hydrogen bubbles that push out the metal particles are also surrounded by the metal particles that have precipitated around them. As a result, an unstable precipitate is formed in which metal particles embrace the hydrogen bubbles (hereinafter, this will be referred to as a "sponge-like porous metal body" or "spongy-like porous metal body"). This precipitate is not attached to the cathode, and has the effect of being easily peeled off and collected from the cathode by slight physical or electrical stimulation. Therefore, the effort of scraping off the metal that has adhered to the electrode plate and collecting it is no longer necessary.

[0011] In addition, since the fine particles are usually difficult to settle and difficult to filter, they tend to remain on the inner walls of the storage tank, the surfaces of the electrode plates, or the connection terminals. However, this sponge-like metal porous body maintains a certain shape in the liquid unless it is subjected to strong stimulation, and can be handled as a mass, so it has the effect of being able to be recovered without leaving anything behind.

[0012] In addition, since almost no metal remains attached to the electrodes, the electrodes can be used for a long period of time without polishing the surface, resulting in a dramatic increase in the life of the device implementing the metal recovery method according to the present invention. [Brief description of the drawings]

[0013] [Figure 1] 1 is a configuration diagram of a metal recovery device for carrying out a metal recovery method according to the present invention. [Diagram 2] FIG. 2 is a partially enlarged view of FIG. [Diagram 3]FIG. 4 is a flow chart showing the process (main flow) of a controller. [Figure 4] FIG. 11 is a flow diagram showing a process of adding hydrogen peroxide during step S108. [Diagram 5] FIG. 2 is a conceptual diagram showing the process of forming a sponge-like metal porous body. [Figure 6] FIG. 2 is a conceptual diagram of a sponge-like metal porous body grown on a cathode plate. [Figure 7] FIG. 1 is a conceptual diagram showing how a sponge-like metal porous body on a cathode is peeled off by air bubbles. [Figure 8] FIG. 13 is a diagram showing a configuration in which an electrode vibrator that vibrates an electrode plate is provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The metal recovery method according to the present invention will be described below with reference to the drawings. Note that the following description is an example of one embodiment of the present invention and an example, and the present invention is not limited to the following description. The following description can be modified without departing from the spirit of the present invention.

[0015] [Explanation of components] FIG. 1 illustrates an example of a configuration diagram of an apparatus (hereinafter, also referred to as "metal recovery apparatus 1") for carrying out the metal recovery method according to the present invention. FIG. 2 illustrates a partially enlarged view. With reference to FIGS. 1 and 2, the metal recovery apparatus 1 includes a storage tank 10 for storing the liquid to be treated, an electrode plate 12 serving as an electrode, a power source 14 for providing power to the electrode plate 12, a bubble generator 16, and a controller 18. It is more preferable that a concentration meter 20 and a water level meter 22 are also provided. Note that a filter 26 for separating the metal recovered after treatment from the liquid to be treated in which the metal has been recovered may be provided below the storage tank 10.

[0016] Furthermore, an injection pipe 40 for injecting the liquid to be treated into the storage tank 10 and an injection pipe opening / closing valve 40a for opening and closing the injection pipe 40 may be provided. Also, an addition tank 28 for adding hydrogen peroxide solution to the storage tank 10 and an addition opening / closing valve 28a for opening and closing the tank may be provided.

[0017] <Storage tank 10> The storage tank 10 is a container that stores the liquid to be treated and electrolyzes the treated liquid. It may be sealed, but since hydrogen is generated by electrolysis, an outlet (not shown in the drawing) is necessary for discharging the hydrogen. In addition, an injection port for injecting the liquid to be treated is also provided at the top of the storage tank 10. In the drawing, the top of the storage tank 10 is shown as open, so the injection port is the top opening of the storage tank 10. Note that the injection port may be provided at a location other than the top of the storage tank 10.

[0018] At the bottom of the storage tank 10, a discharge port 10a is provided for recovering the liquid to be treated after electrolysis and the metals precipitated by electrolysis. If the periphery of the discharge port 10a is funnel-shaped, this is a more suitable shape because it pushes out the sponge-like porous metal body in which the liquid to be treated has settled. The sponge-like porous metal body will be described in detail later.

[0019] The opening and closing of the exhaust port 10a is controlled by an instruction signal C from the controller 18, which will be described later. EV The opening and closing may be made by

[0020] A through hole 10b is provided on the side surface of the storage tank 10 for guiding a power line 14c from the power source 14 into the storage tank 10. The power line 14c passes through the through hole 10b in a liquid-tight manner. Therefore, even if the liquid to be treated enters the storage tank 10, there is no leakage from the through hole 10b.

[0021] <Electrode plate 12> The electrode plate 12 is a conductive material that becomes a cathode or an anode. It may be in a plate shape, but may be in a shape other than a plate shape. Titanium or stainless steel is suitable for use as the electrode plate 12, as the deposited metal is less likely to adhere to the material. It is also preferable that the surface of the electrode plate 12 is smooth, because the sponge-like metal porous body is less likely to bond to the smooth surface. It is more preferable that the surface of the electrode plate 12 is mirror-finished.

[0022] The electrode plates 12 are connected so that the opposing electrode plates 12 have opposite polarities. In other words, except for the electrode plates 12 at both ends, electrode plates 12 of the same polarity are arranged with electrode plates 12 of different polarities sandwiched between them. Figure 2 shows a state in which five electrode plates 12 are arranged. These are referred to as electrode plates 12a, 12b, 12c, 12d, and 12e. Among these electrode plates 12, the opposing electrode plates 12 have opposite polarities.

[0023] More specifically, the set of electrode plates 12a, 12c, and 12e and the set of electrode plates 12b and 12d are the same-polarity electrode plates 12. These are electrode plates that always have the same polarity. These sets may be called the same electrode plate 12A and the same electrode plate 12B. In other words, the same electrode plate 12A on one side is the electrode plates 12a, 12c, and 12e, and the same electrode plate 12B on the other side is the electrode plates 12b and 12d. Of course, "one side" and "the other side" may be reversed.

[0024] <Power supply 14> The power supply 14 may be either a constant voltage power supply or a constant current power supply, but a constant current power supply is preferable. A bipolar power supply is more preferable. Here, a bipolar power supply is a power supply that can reverse the positive and negative polarities of the electrode terminals. The power supply 14 has at least two terminals 14a and 14b. A power line 14c is connected to each terminal. The power supply 14 also receives an instruction signal C from a controller 18, which will be described later. VI is controlled by.

[0025] One pole (terminal) of the power source 14 is connected to one of the identical electrode plates 12, and the other pole (terminal) is connected to the other identical electrode plate of the electrode plate 12. Fig. 2 shows a state in which the terminal 14a of the power source 14 is connected to one identical electrode plate 12A, and the other terminal 14b is connected to the other identical electrode plate 12B. The power line 14c is electrically connected to the electrode plate 12 via a connection terminal 14d.

[0026] <Bubble Generator 16> The air bubble generator 16 is composed of an air blower pump 16a, an air blower pipe 16b, and an air diffusion nozzle 16c. When the air blower pump 16a is operated and sends air through the air blower pipe 16b to the air diffusion nozzle 16c, air is ejected from the nozzle 16d of the air diffusion nozzle 16c (see FIG. 2). In the liquid, the ejected air becomes air bubbles and rises.

[0027] The air diffusion nozzle 16c is disposed below the electrode plate 12. The air bubble generator 16 serves to blow the generated air bubbles against the electrode plate 12 and vibrate the electrode plate 12. Therefore, when the air bubbles generated from the air diffusion nozzle 16c hit the electrode plate 12, it is preferable that the air bubbles have a diameter large enough to vibrate the electrode plate 12.

[0028] The diameter and speed of the air bubbles that are sufficient to shake the electrode plate 12 cannot be determined in general terms depending on the position of the storage tank 10 and the aeration nozzle 16c. However, if the air bubbles have a diameter of less than 100 μm at the time they come into contact with the electrode plate 12, it is difficult to shake the electrode plate 12. On the other hand, air bubbles that are too large will crush the sponge-like metal porous body and return it to fine particles, making it more difficult to recover the precipitated metal. The operation of the air bubble generator 16 is controlled by an instruction signal C from the controller 18, which will be described later. B is controlled by.

[0029] <Controller 18> The controller 18 is composed of a CPU (Central Processor Unit), a memory, and an input / output device. The controller 18 controls the operation of at least the power supply 14 and the bubble generator 16. More specifically, the controller 18 receives an instruction signal C VIThe ON / OFF of the power supply 14, the applied power (voltage or current), the polarity, etc. can be controlled by the signal S VI It is possible to know the current operating status of the power source 14. The operating status includes information such as the currently applied voltage and current as well as polarity.

[0030] The controller 18 also outputs an instruction signal C B This allows control of ON / OFF of the air bubble generator 16 and the amount of air bubbles to be generated (directly, the amount of air blown by the air blower pump 16a).

[0031] The controller 18 also outputs an instruction signal C to open or close the outlet 10a of the storage tank 10. EV The injection pipe opening / closing valve 40a of the injection pipe 40 for injecting the liquid to be treated into the storage tank 10 is controlled by an instruction signal C MV Furthermore, the additional supply opening / closing valve 28a for supplying the hydrogen peroxide solution stored in the additional supply tank 28 to the storage tank 10 may be controlled by an instruction signal C. PV It may be controlled by.

[0032] In addition, when the concentration meter 20, the water level meter 22, and the hydrogen peroxide concentration meter 30 are provided, the received signals S Q , S L , S H2O2 By receiving this signal, the metal ion concentration of the liquid to be treated in the storage tank 10, the liquid level position of the liquid to be treated in the storage tank 10, and the hydrogen peroxide concentration in the storage tank 10 can be known.

[0033] Furthermore, when the metal ion concentration in the liquid to be treated becomes equal to or lower than a predetermined value, the controller 18 can output a notification signal SF indicating that the recovery of the metals has been completed. The notification signal SF may be used by the controller 18 itself.

[0034] <Concentration meter 20> The concentration meter 20 measures the metal ion concentration of the liquid to be treated in the storage tank 10. The measurement result is expressed as a received signal S QThe concentration meter 20 may be of any type as long as it can measure the metal ion concentration. FIG. 1 shows the concentration meter 20 composed of a concentration meter main body 20a, a first pipe 20b, a pump 20c, and a second pipe 20d. In addition, a concentration meter using a method in which a part of the storage tank 10 main body is composed of a transparent material and information on the light absorption of the liquid from the transparent material is obtained by image processing or the like to measure the metal ion concentration can also be used. This is because, even if the metal ion concentration is not measured directly in this way, if an index that is an alternative to the metal ion concentration can be measured and converted to the metal ion concentration, it can be said that the metal ion concentration is being measured.

[0035] The first pipe 20b collects the liquid to be treated from the bottom of the storage tank 10 and sends it to the concentration meter main body 20a by the pump 20c. After measurement, the liquid to be treated is returned to the top of the storage tank 10 by the second pipe 20d. Since the amount of liquid used in the concentration meter 20 is extremely small, the circulation of the liquid to be treated in the storage tank 10 brought about by the pump 20c does not affect the generation of the sponge-like metal porous body.

[0036] <Water level gauge 22> The water level gauge 22 detects the level of the liquid to be treated in the storage tank 10 and transmits a received signal S to the controller 18. L The water level gauge 22 can be suitably used when disposing of the treated liquid from the storage tank 10 after treatment, and when filling the empty storage tank 10 with new treated liquid.

[0037] <Hydrogen peroxide concentration meter 30> The hydrogen peroxide concentration meter 30 measures the concentration of hydrogen peroxide in the liquid to be treated and outputs the measurement result as a reception signal S H2O2 The controller 18 is notified by a signal from the liquid to be treated. The liquid to be treated contains a relatively high concentration of hydrogen peroxide, which contributes to the dissolution of copper. If copper remains as a solid on the inner wall of the storage tank 10 or on the surface of the electrode plate 12, the copper in the storage tank 10 can be removed by being re-dissolved by the liquid to be treated. Therefore, the hydrogen peroxide concentration meter 30 is provided to measure the hydrogen peroxide concentration in the liquid to be treated so that hydrogen peroxide can be added to the storage tank 10 when necessary.

[0038] <Rectification Guide 24> The flow straightening guide 24 is provided between the electrode plate 12 and the inner wall of the storage tank 10. The lower end 24d has an opening that can take in all the air bubbles from the aeration nozzle 16c. Therefore, it has a size that can completely surround the outlet 16d of the aeration nozzle 16c at least when viewed in a plan view. The upper end 24u is arranged so as to be below the liquid surface of the liquid to be treated. With this configuration, the air bubbles generated from the aeration nozzle 16c rise from the bottom to the top of the storage tank 10. The upward flow generated at that time flows to the inner wall surface of the storage tank 10 at the liquid surface, and circulates between the flow straightening guide 24 and the inner wall surface of the storage tank 10 as a flow from the top to the bottom.

[0039] The flow straightening guide 24 is a component intended to suppress the generation of an in-plane swirling flow, which will be described later. Therefore, as long as the in-plane swirling flow can be suppressed, the shape does not have to completely surround the electrode plate 12. For example, in the example of FIG. 2, the flow straightening guide 24 may be provided as a flat plate-shaped component parallel to the electrode plate 12a and the electrode plate 12e between the electrode plate 12a and the storage tank 10, and between the electrode plate 12e and the storage tank 10. It is also preferable to arrange the electrode plate 12 parallel to the inner wall of the storage tank 10, and to arrange the flow straightening guide 24 between the inner wall and the electrode plate 12.

[0040] <Filter 26> The filter 26 is attached below the discharge port 10a of the storage tank 10. It filters the fine powder precipitated by electrolysis. Since the precipitated metal from the discharge port 10a is discharged as a sponge-like metal porous body, the filter 26 does not need to be fine enough to filter fine particles of several microns or less. It is sufficient to capture fine particles of 10 μm or more, for example.

[0041] [Description of operating status] Fig. 3 shows the process flow (main flow) of the controller 18. See also Figs. 1 and 2. The metal recovery method according to the present invention is carried out according to this process flow. When the operation of the metal recovery device 1 starts (step S100), an end determination is made (step S102). If the process is to be continued (N branch of step S102), control proceeds to the next process. Note that, in the end determination, the device may enter a standby state due to a signal from another device.

[0042] If it is to be ended (Y branch of step S102), the process is stopped (step S104). The end conditions include the user stopping the device itself, an emergency stop, the end of the liquid to be treated, etc. Of course, other conditions may also be used.

[0043] When the treatment is continued (N branch in step S102), first, the liquid to be treated is poured into the storage tank 10 (step S106). The liquid to be treated is poured until at least the electrode plate 12 and the connection terminal 14d portion between the electrode plate 12 and the power source 14 are entirely immersed in the liquid. This is because, if the connection terminal 14d is immersed in the liquid to be treated, even if a spark is generated at the connection terminal 14d, there is no risk of the hydrogen present on the surface of the liquid to be treated igniting.

[0044] The injection of the liquid to be treated is controlled by a command signal C from the controller 18. MV The process starts by opening the injection pipe opening / closing valve 40a at , and the received signal S L The controller 18 determines that the injection is complete and issues an indication signal C MV The process may be stopped by closing the injection pipe opening / closing valve 40a at this point. This process is a process of injecting a liquid to be treated, in which a solution containing metals present in an ionized state is injected into a container in which an electrode plate is disposed.

[0045] Next, the process waits for a certain period of time (step S108). The liquid to be treated here is assumed to be a copper etching solution. Copper etching solutions contain a relatively large amount of hydrogen peroxide and are often strong acids with a pH of approximately 1. The liquid to be treated is held in the storage tank 10 for a while in order to dissolve copper components remaining on the electrode plate 12, the inner wall surface of the storage tank 10, the electrode terminals, etc. Therefore, this step is not a main step in metal recovery and may be skipped. Of course, this step may be a static step in which the solution is allowed to stand still against the electrode plate.

[0046] FIG. 4 shows the flow of the process of adding hydrogen peroxide during step S108. Step S108 can be considered a waiting process for dissolving the remaining copper components. However, if the concentration of hydrogen peroxide in the liquid to be treated is low, the expected effect cannot be obtained. Therefore, when step S108 is entered, the hydrogen peroxide concentration M HO In this step, the hydrogen peroxide concentration is measured by the hydrogen peroxide concentration meter 30, and the result is transmitted as a received signal S H2O2 This is implemented by notifying the controller 18 via

[0047] Next, the measured hydrogen peroxide concentration M HO and the threshold M THO (Step S132) is compared with the threshold value M THO The hydrogen peroxide concentration M can be suitably set to 1 to 20 mass%. HO is the threshold M THO If it is less than or equal to the threshold value M (Y branch of step S132), hydrogen peroxide is added at least THO The hydrogen peroxide is further added up to the amount above (step S134). This is because there is a risk that the copper remaining in the storage tank 10 may not be dissolved properly due to a shortage of hydrogen peroxide.

[0048] On the other hand, hydrogen peroxide concentration M HO is the threshold M THO If it is higher (N branch in step S132), nothing is done and the process returns to the main routine (step S136).

[0049] Referring again to FIG. 3, after step S108, a current is applied between the electrode plates 12 (step S110). In FIG. 3, this is represented as "power application". This is performed when the controller 18 sends an instruction signal C VI This is carried out by transmitting a current between the opposing identical electrode plate 12A and the other identical electrode plate 12B of the electrode plate 12, and as a result, copper is precipitated while hydrogen is generated from the identical electrode plate that serves as the cathode. In FIG. 2, for example, when the identical electrode plate 12A is the anode and the identical electrode plate 12B is the cathode, hydrogen is generated from the electrode plates 12b and 12d that are the identical electrode plate 12B, and copper is precipitated.

[0050] At this time, if there is a flow of the liquid to be treated between the electrode plates 12, the precipitated copper will adhere to the electrode plates 12 as if plated. However, if the liquid to be treated between the electrode plates 12 is stationary, the precipitated copper will take in tiny hydrogen bubbles and the electrolytic reaction will proceed.

[0051] Figure 5 shows a conceptual diagram of the progression of this state. Figure 5 shows the cross section of a cathode plate. For the sake of explanation, copper and hydrogen are generated only on one side. Copper is represented by black circles and hydrogen by white circles. Referring to Figure 5(a), copper fine powder Cu1 is precipitated on the surface of the first cathode plate. After copper is precipitated by electrolysis for a while, the liquid remains stationary as mentioned above, so that when viewed microscopically, the cathode surface becomes deficient in copper ions, making it easier for hydrogen to be generated. Hydrogen H1 generated from the surface of the cathode plate becomes microscopic bubbles, which prevents the precipitated copper Cu1 from adhering to the electrode (Figure 5(b)). It can be said that the copper Cu1 is pushed away from the electrode. Therefore, the precipitated copper Cu1 cannot become large agglomerates, and is pushed away from the cathode plate surface as fine powder. At this time, a force is acting to attract the copper Cu1 fine powder to the cathode side.

[0052] Meanwhile, the hydrogen microbubbles H1 are pushed away from the cathode plate together with the copper Cu1 micropowder by the copper micropowder Cu2 that is generated next (Fig. 5(c)). The hydrogen microbubbles H1 maintain their shape without breaking due to surface tension, and capture the copper Cu1 micropowder on their surface. The copper Cu2 is also pushed away from the cathode plate surface by the hydrogen microbubbles H2 that are generated next (Fig. 5(d)).

[0053] In this way, the hydrogen microbubbles that are generated one after another push back the metal micropowder that is attracted to the cathode plate, and the hydrogen microbubbles are further pushed away from the cathode plate by the metal micropowder. As this reaction continues, a mass of hydrogen microbubbles that look as if they are embraced by copper micropowder is formed on the cathode plate. This formed object is called a "sponge-like metal porous body." In this case, the metal is copper, so it may be called a "sponge-like copper porous body" or a "sponge-like copper porous body."

[0054] 6 shows a conceptual diagram of a sponge-like porous metal body (reference numeral 60) grown on a cathode plate. The sponge-like porous metal body 60 is made up of fine metal powder that is simply captured and connected by the surface tension of minute hydrogen bubbles, so it maintains an integrated shape in the liquid, but the bond itself is very weak and will shake even with slight vibration. In addition, since it is not fixed to the electrode plate 12, it will easily peel off and fall off when the electrode plate 12 is subjected to slight physical vibration.

[0055] Furthermore, the sponge-like porous metal (copper) body 60 grows on the cathode plate because the precipitated copper fine powder is attracted to the cathode plate, but when the polarity of the electrode plate 12 is reversed, the force attracting it toward the cathode plate disappears and it falls. If the sponge-like porous metal body 60 that has fallen into the liquid is poked with a stick or the like, tiny hydrogen bubbles separate and foam. Therefore, if bubbles appear when the sponge-like porous metal body 60 is held in the liquid, it can be determined that the sponge-like porous metal body 60 has been generated.

[0056] It is believed that the sponge-like metal porous body 60 is formed by the above mechanism, so when the current flowing between the electrode plates 12 increases, the amount of hydrogen microbubbles generated increases, and a more unstable sponge-like metal porous body 60 can be formed. This allows the metal to be precipitated in a state that makes it easy to peel off from the electrode plate 12, that is, easy to recover. In experiments to date, 2 ~200A / dm 2 It has been confirmed that within this range, a sponge-like metal porous body 60 suitable for recovery can be obtained. If the current density is too low, the sponge-like metal porous body 60 is not formed, and the metal precipitates and adheres to the cathode. If the current density is too high, the efficiency of copper generation (precipitation) may decrease.

[0057] This reaction is a phenomenon that occurs according to the current density of the cathode electrode plate 12. Therefore, if the area of ​​the cathode electrode plate 12 is smaller than the area of ​​the anode electrode plate 12, the generation of the sponge-like metal porous body 60 on the cathode plate can be promoted even if the same current is passed through them.

[0058] In the configuration shown in FIG. 2, the identical electrode plate 12A is composed of three electrode plates 12, and the identical electrode plate 12B is composed of two electrode plates 12. If the identical electrode plate 12B is used as the cathode, the number of electrode plates 12 serving as the cathode is less than the number of electrode plates 12 serving as the anode. This makes it possible to increase the current density of the identical electrode plate 12B compared to the identical electrode plate 12A, and to form the sponge-like porous metal body 60 more efficiently. Of course, the area of ​​the electrode plate 12 serving as the cathode may be reduced with the same number of plates. As described above, this step (step S110 in FIG. 3) can be said to be a sponge-like porous metal body forming step in which a current is passed between the electrode plates to form the sponge-like porous metal body 60 on the electrode plate serving as the cathode.

[0059] 2, if the same electrode plate 12B is used as the cathode, then there will be an anode plate on both sides of every cathode plate. This is more preferable because it can reduce the flow of the solution on the surface of the cathode plate.

[0060] Referring again to FIG. 3, after a current is passed between the electrode plates 12 for a certain period of time (step S110), the current is then stopped and the bubble generator 16 is operated (step S112). This is performed when the controller 18 outputs an instruction signal C B This is carried out by sending the air to the air bubble generator 16 (more specifically, the air blower pump 16a).

[0061] A conceptual diagram of this process is shown in Figure 7. The air bubble generator 16 generates air bubbles from below the electrode plate 12. The generated air bubbles collide with the electrode plate 12 or the sponge-like porous metal body 60, shaking the electrode plate 12. They also rise upward on the surface of the electrode plate 12. The vibration of the electrode plate 12 at this time and the stimulation caused by the air bubbles sweeping the surface of the electrode plate 12 cause the sponge-like porous metal body 60 to peel off from the electrode plate 12 and drop.

[0062] Therefore, this step (step S112 in FIG. 3) can be said to be a peeling step in which the spongy porous metal body 60 is peeled off from the electrode. In addition, since the spongy porous metal body 60 is peeled off from the electrode plate by air bubbles, this is a peeling step in which the spongy porous metal body 60 is peeled off from the electrode, and is a step in which the air bubbles are brought into contact with the electrode plate.

[0063] At this time, a flow from below to above occurs within the storage tank 10. Here, if a flow straightening guide 24 is provided between the electrode plate 12 and the inner wall of the storage tank 10, the flow from below to above passes between the electrode plate 12 and the inner wall of the storage tank 10 and flows from above to below. In this way, it is possible to suppress the occurrence of a swirling flow (called an "in-plane swirling flow") in which a flow from below to above and a flow from above to below occur simultaneously between the electrode plates 12.

[0064] The in-plane swirling flow breaks the sponge-like metal porous body 60 into pieces, breaking it down into minute hydrogen bubbles and fine metal powder. The fine metal powder may float in the liquid being treated, making it difficult to recover, which is undesirable.

[0065] The process of generating the air bubbles (step S112) is a process of peeling off the sponge-like metal porous body 60 from the electrode plate 12. In the metal recovery device 1 according to the present invention, a sponge-like metal porous body 60 in which fine metal powder is loosely bound is generated, and the bond to the electrode plate 12 is also loose, so that it can be peeled off from the electrode plate 12 by means other than air bubbles.

[0066] For example, by providing an electrode plate vibrator for directly vibrating the electrode plate 12, the sponge-like porous metal body 60 can be peeled off from the electrode plate 12. Fig. 8 shows a state in which an electrode plate vibrator 50A and an electrode plate vibrator 50B capable of vibrating the identical electrode plate 12A and the identical electrode plate 12B, respectively, are provided. These electrode plate vibrators 50 can be controlled by instruction signals from the controller 18. The process using the electrode plate vibrator is a peeling process in which the sponge-like porous metal body 60 is pulled off from the electrode, and is a process of applying vibration to the electrode plate.

[0067] Also, the sponge-like porous metal body 60 can be peeled off from the electrode plate 12 by reversing the polarity of the same electrode plate 12A and the same electrode plate 12B. As already described, the sponge-like porous metal body 60 is attracted to the cathode plate. Then, by reversing the polarity of the opposing electrode plate 12, the cathode to which the sponge-like porous metal body 60 was attracted turns into an anode, and a repulsive force acts on the sponge-like porous metal body 60. On the other hand, by changing the opposing electrode plate 12 to a cathode, an attractive force acts toward the opposing electrode plate 12. Therefore, the sponge-like porous metal body 60 can be peeled off from the electrode plate 12. Therefore, the process of reversing the polarity is a peeling process of pulling the sponge-like porous metal body 60 away from the electrode, and is a process of reversing the polarity of the electrode plate.

[0068] In addition, if the power supply 14 is of a bipolar type, the polarity of the electrode plate 12 is inverted by an instruction signal C from the controller 18. VI This can be done by:

[0069] As described above, step S110 is a peeling process for separating the sponge-like metal porous body 60 from the electrode, and the peeling means may be replaced with a process of applying air bubbles to the electrode plate 12, a process of vibrating the electrode plate 12, or a process of reversing the polarity of the electrode plate 12.

[0070] 3 again, after the air bubble generator 16 is operated for a certain period of time, the air bubble generator 16 is stopped and the system waits for a certain period of time (step S114). The purpose of this waiting period is to settle the flow of the liquid to be treated that has been generated between the electrode plates 12 by the air bubble generator 16.

[0071] Next, the metal ion concentration Mq in the liquid to be treated is measured and compared with the threshold value Mth (step S116). Q If the metal ion concentration Mq is equal to or lower than the threshold value Mth (Y branch in step S116), the process proceeds to the draining step (step S118) assuming that the recovery of metals from the liquid to be treated is completed. Note that the measurement of the metal ion concentration may be performed continuously.

[0072] At this time, the controller 18 may internally generate and transmit a notification signal SF of the end of treatment (see FIG. 1). If the metal ion concentration Mq is not equal to or lower than the threshold value Mth (N branch in step S116), control is returned to the process of passing a current between the electrode plates 12 again (step S110). In other words, the leaving step, the sponge-like metal porous body forming step, and the peeling step are repeated until the metal ion concentration in the liquid to be treated falls to a predetermined value or lower.

[0073] When the process proceeds to step S118, it can be determined that the process for the liquid to be treated has been completed, and the liquid to be treated is discarded. This is because the controller 18 outputs an instruction signal C V This can be done by opening the outlet 10a of the storage tank 10.

[0074] The metal recovered as a sponge-like porous metal body 60 and the liquid to be treated are discharged from the outlet 10a. The precipitated metal can be recovered by filtering the liquid with an appropriate filter 26. This process is a process for filtering the liquid to be treated and recovering the sponge-like porous metal body 60.

[0075] As described above, according to the metal recovery method of the present invention, metal ions in the liquid to be treated can be recovered as loosely bound lumps. [Industrial Applicability]

[0076] The present invention can be used not only for recovering copper from waste etching liquid, but also for recovering dissolved metals from waste liquid containing other metals. [Explanation of symbols]

[0077] 1 Metal recovery equipment 10 Reservoir 10a outlet 10b Through hole 12 Electrode plate 12a, 12b, 12c, 12d, 12e electrode plate 12A same electrode plate 12B Same electrode plate 14 Power supply 14a, 14b terminals 14c power line 14d Connection terminal 16 Bubble Generator 16a Air Pump 16b Air pipe 16c Aeration nozzle 16d spout 18 Controller 20 Densitometer 20a Concentration meter body 20b 1st piping 20c Pump 20d Second piping 22 Water level gauge 24 Rectification Guide 24u (upper end of straightening guide) 24d (Lower end of flow guide) 26 Filters 28 Addition Tank 28a Additional opening and closing valve 30 Hydrogen peroxide concentration meter 40 Injection tube 40 Injection pipe opening and closing valve a 50 Electrode plate exciter 60 Spongy metal porous body C EV instruction signal C VI instruction signal C B indication signal C MV instruction signal C PV instruction signal S Q , S L , S H2O2 Received signal S VI Received signal SF notification signal M HO Hydrogen peroxide concentration M THO Threshold Mq metal ion concentration Mth threshold

Claims

1. a process of injecting a solution containing a metal present in an ionic state into a container in which an electrode plate is disposed; a stilling step of waiting for a certain period of time after the injection step of the liquid to be treated; a step of forming a sponge-like porous metal body on the electrode plate serving as a cathode by passing an electric current between the electrode plates; A peeling step is provided in which the sponge-like metal porous body is separated from the electrode plate serving as the cathode, A metal recovery method, wherein the peeling step is a step of bringing air bubbles into contact with the electrode plate or the sponge-like metal porous body.

2. a process of injecting a solution containing a metal present in an ionic state into a container in which an electrode plate is disposed; a stilling step of waiting for a certain period of time after the injection step of the liquid to be treated; a step of forming a sponge-like porous metal body on the electrode plate serving as a cathode by passing an electric current between the electrode plates; A peeling step is provided in which the sponge-like metal porous body is separated from the electrode plate serving as the cathode, The metal recovery method, wherein the peeling step is a step of applying vibration to the electrode plate.

3. a process of injecting a solution containing a metal present in an ionic state into a container in which an electrode plate is disposed; a stilling step of waiting for a certain period of time after the injection step of the liquid to be treated; a step of forming a sponge-like porous metal body on the electrode plate serving as a cathode by passing an electric current between the electrode plates; A peeling step is provided in which the sponge-like metal porous body is separated from the electrode plate serving as the cathode, A metal recovery method, wherein the peeling step is a step of reversing the polarity of the electrode plate.

4. 2. The metal recovery method according to claim 1, wherein the leaving step, the sponge-like metal porous body forming step, and the peeling step are repeated until the metal ion concentration in the solution falls to a predetermined value or less.

5. 3. The metal recovery method according to claim 2, wherein the leaving step, the sponge-like metal porous body forming step, and the peeling step are repeated until the metal ion concentration in the solution falls to a predetermined value or less.

6. 4. The metal recovery method according to claim 3, wherein the leaving step, the sponge-like metal porous body forming step, and the peeling step are repeated until the metal ion concentration in the solution falls to a predetermined value or less.

7. A metal recovery method described in any one of claims 1 to 6, wherein in the standing process, the hydrogen peroxide concentration of the treated liquid is measured, and if the hydrogen peroxide concentration is lower than a predetermined threshold value, a waiting process is performed in which additional hydrogen peroxide is added up to at least the threshold value.

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