JP5125278B2 - Method of electrolytic oxidation of etching waste liquid - Google Patents

Description

  The present invention relates to a method for electrolytic oxidation of an etching waste liquid, and more specifically, an etching waste liquid containing iron chloride or copper chloride is passed through an electrolytic bath as an electrolytic solution, and low-valent ions in the etching waste liquid are converted to high-valence ions. The present invention relates to a method for electrolytically oxidizing an etching waste liquid while suppressing excessive oxidation of the etching waste liquid on the anode surface and preventing generation of chlorine gas from the electrolytic cell.

  In a method of recovering valuable metals from scraps containing various metals or alloys, or in a processing step involving a metal melting step, the metal is dissolved using an etching solution, and then the metal is separated from the solution. ing. For example, in the manufacture of a lead frame serving as a base for a semiconductor integrated circuit, an acidic aqueous solution containing generally a high number of ions of copper chloride and / or iron chloride as a main component is generally used as an etching solution. An etching process that melts and processes a metal plate into a predetermined shape is widely adopted. At this time, an acidic aqueous solution having a reduced metal dissolving power after etching treatment, so-called etching waste liquid, is used to separate the dissolved metal and recycle and reuse the metal dissolving power in order to improve the metal dissolving power. Is done.

By the way, in the etching process, a reaction in which expensive ions of copper chloride or iron chloride are leached out of the metal and reduced to low valence ions is performed. The etching waste liquid is rich in low-valent ions. Therefore, in order to regenerate the metal dissolving power of the etching waste liquid, low-valent ions contained in the liquid, that is, divalent iron ions or monovalent copper ions are respectively converted into expensive valence ions, that is, trivalent iron ions, What is necessary is just to oxidize to a bivalent copper ion.
For this reason, conventionally, oxidation and regeneration have been performed by blowing chlorine gas into the etching waste liquid. However, chlorine gas is toxic and requires great care in its management such as transportation, storage and installation from the factory. In addition, since chlorine gas is extremely corrosive, safety and environmental considerations and investments such as selection of piping materials and atmosphere management to prevent leakage cannot be ignored.

In addition, a method using electrolytic oxidation is known as a method for regenerating an etching waste liquid that does not directly use chlorine gas. In this method, an electrolytic cell is used to energize between an anode and a cathode installed inside the electrolytic cell to electrolytically oxidize the etching waste liquid. However, if oxidation is performed on the anode side, a reduction reaction naturally occurs on the cathode side, so that the oxidation and reduction cancel each other, and the oxidation efficiency is lowered, so that the liquid cannot be regenerated.
For this reason, a diaphragm electrolysis method that can prevent the gas or ions generated on the anode side from diffusing near the cathode side is adopted, and the anode chamber is separated from the anode and the cathode by an ion exchange membrane. There has been proposed a method (for example, refer to Patent Documents 1 and 2) in which an etching waste liquid is electrolytically oxidized in an electrolytic cell divided into a cathode chamber.

  However, in this method, there are major problems to be solved in the problem relating to the diaphragm and the problem relating to the generation of chlorine gas. That is, as a problem related to the diaphragm, the ion exchange membrane is expensive, and when the oxide is likely to be precipitated like an etching waste liquid, the membrane is clogged or the exchange permeation ability of the membrane is lowered, resulting in a lifetime. There is a problem in that it is disadvantageous in terms of management and costs, such as shortening the length, increasing the resistance and increasing the cell voltage. Moreover, in general, the electrolytic cell used in the method of electrolytic oxidation of the etching waste liquid has a structure in which the anode is inserted into a box partitioned by a diaphragm, but this structure is extremely complicated, and investment and Administratively, it was a problem.

Next, as a problem relating to the generation of chlorine gas, there is a problem relating to a control method for preventing the generation of chlorine gas in electrolytic oxidation. That is, when electrolytically oxidizing the etching waste liquid, chlorine is generated as a gas from the electrode surface when the low valence ions are excessively oxidized on the anode surface beyond the high-value ions. In order to avoid the influence of the generated chlorine gas on the environment, it is indispensable to collect it using a collector, neutralize it and eliminate it, and the cost of such investment and chemical costs increases.
By the way, such generation of chlorine gas can be prevented by suppressing the excessive oxidation state on the anode surface by controlling the amount of electric current or the amount of liquid flow through electrolysis. However, it is difficult to maintain the uniformity of the electrolytic solution in the electrolytic cell by controlling the amount of current or the amount of liquid flow. For example, it is too much to suppress the generation of chlorine gas due to excessive oxidation on the anode surface. In such a case, there is a risk that the insufficiently oxidized electrolyte may be discharged. For example, in order to homogenize the electrolyte in the electrolytic cell, a method of stirring the vicinity of the anode with an overflow type liquid flow (for example, see Patent Document 3) has been proposed. It is not always practical because of the installation cost.

  Furthermore, there are many problems to be solved regarding the structure of the electrolytic cell. For example, in the electrolytic oxidation of etching waste liquid, in order to process a large amount of liquid, a large number of anodes and cathodes, which have been conventionally used in metal electrolytic smelting and the like, are alternately and densely installed in the electrolytic cell at narrow intervals. However, in this method, the structure for supplying and discharging the electrolytic solution to both the anode side and the cathode side becomes complicated. Investment costs will also increase. In addition, it is not easy from the viewpoint of operation and management to supply the liquid flow to a large number of electrode boxes in a uniform manner.

  From the above situation, in the method of regenerating etching waste liquid by electrolytic oxidation, the above problems related to equipment or control are solved, and the etching waste liquid is efficiently electrolytically oxidized while preventing generation of chlorine gas from the electrolytic cell. There was a need for a way to do it.

JP-A-6-207281 (first page, second page) JP-A-10-18062 (first page, second page) JP 2000-303192 A (first page, second page) Japanese Unexamined Patent Publication No. 7-70784 (first page, second page, FIG. 1)

  The object of the present invention is to solve the above-mentioned problems of the prior art, by passing an etching waste liquid containing iron chloride or copper chloride as an electrolytic solution through an electrolytic bath, and converting low-valent ions in the etching waste liquid to high-valence ions. In the method of electrolytic oxidation, the method of efficiently oxidizing the etching waste liquid in terms of capital investment and operation cost while suppressing the excessive oxidation of the etching waste liquid on the anode surface and preventing the generation of chlorine gas from the electrolytic cell. It is to provide.

  In order to achieve the above-mentioned object, the inventors have passed an etching waste liquid containing iron chloride, copper chloride, etc. through an electrolytic cell comprising an anode chamber and a cathode chamber partitioned by a diaphragm as an electrolytic solution. As a result of intensive research on the method of electrolytic oxidation of low valence ions in etching waste liquid to expensive ions, specific diaphragm materials, means for adjusting supply / drainage, means for controlling oxidation-reduction potential, and energization Using an electrolytic cell equipped with a power supply means for adjusting the current, the etching waste liquid is supplied to the electrolytic cell, and a specific amount of the drainage liquid from the anode chamber is circulated as a supply liquid while the drainage liquid from the anode chamber is discharged. When the oxidation-reduction potential of was controlled to a specific value, it was found that the etching waste liquid can be efficiently electrolytically oxidized while suppressing excessive oxidation of the etching waste liquid on the anode surface and preventing the generation of chlorine gas. And it completed the present invention.

That is, according to the first aspect of the present invention, an etching waste solution containing iron chloride is passed through an electrolytic cell composed of an anode chamber and a cathode chamber partitioned by a diaphragm as an electrolytic solution, and the low concentration of the etching waste solution is reduced. In the method of electrolytic oxidation of valence ions to expensive ions,
Using the following electrolytic cell (B), the etching waste liquid is supplied to the electrolytic cell, and 15 to 50% of the amount discharged from the anode chamber is circulated as the supplied liquid, while oxidizing the discharged liquid from the anode chamber. There is provided an electrolytic oxidation method of an etching waste liquid, wherein a control value of a reduction potential (silver / silver chloride electrode reference) is controlled to 550 to 800 mV.
Electrolyzer (B): An anode array in which 2 to 6 mesh-shaped anodes are arranged in series in the electrode width direction in a horizontally long box, and in the anode chamber, on the electrode surface A cathode having a baffle plate that changes the flow of the electrolyte along the meshed anode so that the same number of cathodes as the anodes are arranged in series so that only one side of both electrode faces faces on one side of the anode row 2 to 6 electrode pairs composed of rows are composed of an anode chamber and a cathode chamber separated by a filter cloth diaphragm, and each of the anode chamber and the cathode chamber independently has an electrolyte solution. Means for adjusting the supply / drainage of liquid supplied from one side orthogonal to the row and drained from the opposite side and repeating the drainage of the anode chamber to the supply fluid; Detect and control on the side Comprising stages, means for setting the distance between electrodes of the anode columns and the cathode row, and power supply means for regulating the current supplied to each individual electrode pair.

  Further, according to the second invention of the present invention, in the first invention, the means for adjusting the supply / drainage liquid of the electrolytic cell (B) is characterized in that the circulation of the drainage liquid of the anode chamber to the supply liquid is Through the storage tank that accepts the drainage liquid and can circulate the liquid to the electrolytic cell and perform self-circulation, it is continuously performed until the oxidation-reduction potential of the liquid in the anode chamber and the storage tank becomes constant, and then In order to continue the electrolytic oxidation, the electrolytic oxidation of the etching waste liquid is characterized in that it is discharged from the storage tank as an electrolytic oxidation completion liquid and is controlled to receive a new etching waste liquid corresponding to the discharged electrolytic oxidation completion liquid. A method is provided.

According to the third invention of the present invention, in the first or second invention, the means for detecting and controlling the oxidation-reduction potential of the electrolytic cell (B) is the oxidation-reduction potential of the effluent from the anode chamber. There is provided an electrolytic oxidation method for an etching waste liquid, characterized in that a control value is controlled by increasing or decreasing an energization current to an electrolytic cell.

According to the fourth invention of the present invention, in the first or second invention, the power feeding means for adjusting the energization current of the electrolytic cell (B) regulates the energization current for each electrode pair. An electrolytic oxidation method of an etching waste liquid is provided.

According to a fifth aspect of the present invention, in the fourth aspect , the energization current is set to be high at the liquid supply side electrode and low at the drainage side electrode. A method for electrolytic oxidation of an etching waste liquid is provided.

According to the sixth invention of the present invention, in the first or second invention, the means for setting the interelectrode distance of the electrolytic cell (B) sets the set value of the interelectrode distance to the electrical conductivity of the etching waste liquid. The method of electrolytic oxidation of an etching waste liquid, which is selected according to the above, is provided.

According to the seventh invention of the present invention, in the first or second invention, the electrolytic cell is one in which at least two electrolytic cells (B) are arranged in parallel or in series. An electrolytic oxidation method for the etching waste liquid is provided.

According to the eighth invention of the present invention, in the seventh invention, in the parallel arrangement, power is supplied to each electrolytic cell (B) by using an individual power supply device, or at least 2 of all the electrolytic cells or each electrolytic cell. The feeding device is electrically connected in series to the tank or more. On the other hand, the liquid supply to each electrolytic cell (B) is divided into the etching waste liquid containing iron chloride to each of the anode chamber and the cathode chamber of each electrolytic cell. A method for electrolytic oxidation of an etching waste liquid is provided.

Further, according to the ninth invention of the present invention, in the first or second invention, according to the indication value of the oxidation-reduction potential of the electrolytic cell (B) or the alarm value of the installed chlorine gas concentration meter, There is provided an electrolytic oxidation method of an etching waste liquid, characterized by comprising emergency means for inserting drainage liquid from the cathode chamber into the anode chamber and adjusting the oxidation-reduction potential of the anode chamber to the control value.

According to the tenth invention of the present invention, in the electrolytic oxidation method of the etching waste liquid according to any one of the first to ninth inventions, the etching waste liquid contains copper chloride instead of iron chloride, and the oxidation-reduction potential. (A silver / silver chloride electrode standard) is 400 to 800 mV, and an electrolytic oxidation method of an etching waste liquid is provided.

Electrolytic oxidation method of the etching waste liquid of the present invention, the etching waste liquid containing iron or copper chloride, was passed through the electrolytic cell to electrolytically oxidized to high valence ions of low valence ions in the etching waste liquid as an electrolyte In the method, excessive oxidation of the etching waste liquid on the anode surface is suppressed, and the etching waste liquid can be efficiently electrolytically oxidized in terms of capital investment and operation cost while preventing generation of chlorine gas from the electrolytic cell. Industrial value is extremely high.

  Further, if a horizontally long electrolytic cell (B) composed of two or more electrode pairs is used, in particular, the circulation of the drainage liquid in the anode chamber to the liquid supply receives the drainage liquid and This is continued until the oxidation-reduction potential of the liquid in the anode chamber and the liquid storage tank is made constant through the liquid storage tank capable of self-circulation, and then discharged from the liquid storage system as a regeneration completion liquid. By using a means for adjusting the supply / drainage liquid of the electrolytic cell by the control of receiving the new etching waste liquid corresponding to the discharged regeneration completion liquid, it is more advantageous because the electrolytic oxidation can be performed more efficiently.

Hereinafter, the electrolytic acid method for etching waste liquid according to the present invention will be described in detail.
The method for electrolytic oxidation of an etching waste liquid according to the present invention comprises passing an etching waste liquid containing iron chloride as an electrolytic solution through an electrolytic cell composed of an anode chamber and a cathode chamber separated by a diaphragm, and reducing the low valence in the etching waste liquid. In the method of electrolytically oxidizing ions into an expensive number of ions, using the following electrolytic cell (A) or electrolytic cell (B), the etching waste liquid is supplied to the electrolytic cell, and the amount of liquid discharged from the anode chamber is 15 to 15%. The control value of the oxidation-reduction potential (silver / silver chloride electrode standard) of the drainage from the anode chamber is controlled to 550 to 800 mV while circulating 50% as the supply liquid.
Electrolysis cell (A): an electrode pair comprising an anode and a cathode installed in a box is composed of an anode chamber and a cathode chamber separated by a filter cloth diaphragm, each of the anode chamber and the cathode chamber being Independently, means for adjusting the supply and discharge liquid for supplying and discharging the electrolyte and repeating the discharge of the anode chamber to the supply liquid, detecting the redox potential on the drain side of the anode chamber and detecting the redox potential Means for controlling the control value of (silver / silver chloride electrode standard) by increasing or decreasing the supply flow rate of the electrolytic cell or the energization current, and the power supply means for adjusting the energization current.
Electrolyzer (B): An anode array in which at least two or more anodes are arranged in series in the electrode width direction in a horizontally long box, and the same number of cathodes on both sides of the anode array At least two electrode pairs consisting of a cathode array arranged in series so that only one side of each of them faces each other is composed of an anode chamber and a cathode chamber separated by a filter cloth diaphragm, and the anode chamber Each of the cathode chambers independently controls the supply and discharge of the electrolyte solution from one side orthogonal to each row, drains from the opposite side, and repeats the discharge from the anode chamber to the supply solution. Means for detecting and controlling the oxidation-reduction potential on the drain side of the anode chamber, means for setting the distance between the anode row and the cathode row, and adjustment of the energization current for each individual electrode pair Power supply means to perform Provided.

  In the present invention, using the electrolytic cell (A) or the electrolytic cell (B), the etching waste liquid is supplied to the electrolytic tank, and 15 to 50% of the drainage amount from the anode chamber is circulated as the supply liquid. This is important for controlling the control value of the oxidation-reduction potential (silver / silver chloride electrode standard) of the effluent from the anode chamber to 550 to 800 mV.

  That is, first, the respective electrolytes are circulated in the anode chamber and the cathode chamber, and in particular, 15 to 50%, preferably 25 to 50%, of the drainage amount from the anode chamber is circulated as the supply liquid. is important. That is, by repeating a part of the drainage to the liquid supply side, the relative liquid flow rate in the electrolytic cell is increased, and the uneven liquid flow in the electrolytic cell is forcibly eliminated. As a result, even if an inexpensive general filter cloth is used as a diaphragm, mixing of liquids in both chambers can be minimized, and oxidation efficiency without any practical problems can be achieved. No membrane is needed. If it is a general filter cloth, there is an advantage that the material cost required for replacement is greatly reduced, and even if the blockage occurs, the influence on the flow rate control can be reduced.

  Here, when the circulation rate of the drainage from the anode chamber is less than 15% of the drainage, the situation where chlorine gas is generated due to excessive oxidation is prevented when the flow rate is reduced due to the fluctuation error of the pump or the control range in the actual operation. Can not do it. On the other hand, when the circulation amount of the drainage from the anode chamber exceeds 50% of the drainage, the effect on the homogenization is not improved any more, and the power cost is rather increased.

  Second, it is important to control the control value of the oxidation-reduction potential (silver / silver chloride electrode standard) of the effluent from the anode chamber to 550 to 800 mV, preferably 580 to 700 mV. Therefore, using the electrolytic cell (A) or the electrolytic cell (B), an electrode for measuring the oxidation-reduction potential (hereinafter sometimes referred to as ORP) is provided in the drainage portion from the anode chamber, and the anode chamber The oxidation-reduction potential is detected on the drain side, and the energization current is controlled so that the value becomes the control value. Thereby, generation | occurrence | production of chlorine gas can be prevented effectively.

  Etching waste liquid containing iron chloride used in the above-mentioned oxidation electrolysis method etches a metal such as copper by using a so-called iron-based etching liquid mainly composed of an acidic aqueous solution containing trivalent iron chloride as an oxidative leaching agent. It is produced upon treatment, and usually contains divalent and trivalent iron chlorides and etched and dissolved metal. Further, in this recycling process of the etching waste liquid, since the metal dissolved before being saturated in the liquid is separated and recovered, the liquid after the metal is separated and recovered is also used. As a method for separating and recovering this metal, methods such as solvent extraction, electrowinning, and substitution are used, although it varies depending on the metal species. For example, when the metal is copper, a substitution method with metallic iron or a method of electrolytic deposition by a cathode reaction simultaneously with electrolytic oxidation can be mentioned.

  That is, in the electrolytic oxidation of the iron-based etching waste liquid, even if the iron ions in the liquid become 100% more expensive, the chlorine gas is not generated as long as the chlorine gas can be dissolved in the liquid. There is almost no impact on the environment. This dissolved chlorine is consumed to easily and effectively oxidize unreacted low-valent ions while the liquid is circulated. By the way, it was found that the range in which chlorine gas can be dissolved in the liquid is approximately 700 to 1000 mV in terms of the ORP value (silver / silver chloride electrode standard). However, normally, the ORP value (silver / silver chloride electrode standard) during energization rapidly increases from 700 mV to over 1000 mV, and it is practically difficult to strictly control this. Therefore, the control value of the redox potential (silver / silver chloride electrode standard) of the drainage from the anode chamber is 800 mV, preferably 700 mV. is there.

  On the other hand, the lower limit is 550 mV, preferably 580 mV. That is, from the measurement of the dissolution rate of the copper plate, when used as an etching solution, the dissolution rate decreases rapidly at less than 550 mV. Moreover, when it is 580 mV or more, it is desirable because there is almost no difference in the dissolution rate of the copper plate even when compared with the case where a new solution made of 100% ferric chloride is used.

Here, the dissolution rate of the copper plate was measured as follows.
Ferric chloride and ferrous chloride are mixed at a predetermined ratio to mix an iron chloride aqueous solution with an iron concentration of 180 g / L, and cupric chloride and cuprous chloride are mixed at a predetermined ratio to obtain a copper concentration of 80 g. A solution of different ORPs was prepared using an aqueous copper chloride solution adjusted to / L, and 100 mL of each was put into a beaker, and a 0.3 mm thick copper plate was cut into a weight of 10 g. The mixture was put in, stirred at 60 ° C. for 15 minutes, and after a predetermined time passed, it was lifted, washed and dried, and the amount dissolved was determined by taking an amount, and the dissolution rate per liter of liquid per hour was calculated. The results are shown in FIG.
FIG. 1 shows the relationship between the redox potential and the dissolution rate. From FIG. 1, the dissolution rate rapidly decreases at ORP (silver / silver chloride electrode standard) 550 to 580 mV, and the ORP (silver / silver chloride electrode standard) is below 400 mV. You can see that there is no power.

  The electrolytic cell (A) used in the above method is composed of an anode chamber and a cathode chamber in which an electrode pair consisting of an anode and a cathode installed in a box is partitioned by a filter cloth diaphragm. Each cathode chamber independently supplies and discharges electrolyte, and means to adjust the supply and discharge of the anode chamber, and the redox potential is detected on the drain side of the anode chamber. And a means for controlling the control value of the oxidation-reduction potential (silver / silver chloride electrode reference) by increasing / decreasing the supply flow rate of the electrolytic cell or the energization current, and a power supply means for adjusting the energization current.

As means for controlling the ORP, the energizing current or the liquid supply flow rate may be increased or decreased. That is, when the ORP increases too much, in order to prevent excessive oxidation, the current applied per unit liquid is reduced by decreasing the current or increasing the liquid supply flow rate. On the other hand, when the ORP is too low, the supply flow rate is decreased or the current is increased in order to prevent insufficient oxidation.
The relationship between the energization current and the minimum required liquid supply flow rate can be expressed by the following equation (1).
V = (2.08 × A) / (60 × C _Fe ) (1)
(In the formula, V represents the liquid supply flow rate (L / min), A represents the energization current (A), and C _Fe represents the Fe (II) concentration (g / L) of the liquid supply.)
For example, if A: 4.73 A and C _Fe : 20 g / L, V = 8.2 mL / min.

  However, in the electrolytic cell (A), in order to increase or decrease the flow rate of the liquid supplied to the electrolytic cell, a device such as finely controlling the pump with an inverter is required, and the cost is increased accordingly. In addition, it is desirable to regenerate the etching waste liquid continuously in the etching line as much as possible from the viewpoint of reducing the amount of liquid retained and keeping the temperature of the liquid, and increasing or decreasing the liquid supply flow rate is the liquid necessary for the etching operation. From the point of securing, there may be an operational bottleneck. As this solution, a horizontally long electrolytic cell (B) composed of the following two or more electrode pairs is preferable.

  As the electrolytic cell (B) used in the above method, an anode row in which at least two or more anodes are arranged in series in the electrode width direction in a horizontally long box-shaped box, and the same number of cathodes are arranged. From an anode chamber and a cathode chamber in which at least two electrode pairs consisting of a cathode row arranged in series so that only one side of both electrode surfaces face each other on one side of the anode row are partitioned by a filter cloth diaphragm Each of the anode chamber and the cathode chamber independently supplies the electrolyte from one side orthogonal to each row, drains from the opposite side, and drains the anode chamber. Means for adjusting the supply and discharge liquid repeatedly for the supply liquid, means for detecting and controlling the oxidation-reduction potential on the drain side of the anode chamber, means for setting the distance between the anode row and the cathode row, and individual For each electrode pair Comprising a feed means for regulating the electric current.

  It does not specifically limit as an electrode pair of the said electrolytic cell (B), It is at least 2 or more, It is preferable that it is 2-6 especially, and it is more preferable that it is 2-4. That is, if there is one electrode pair, there is a problem in that the number of electrolytic cell facilities increases. On the other hand, if the number of electrode pairs exceeds 6, the influence in the length direction of the electrolytic cell becomes so great that liquid drift occurs in the cell. There is a concern that chlorine gas is partially generated.

  In the electrolytic cell (B), the electrolytic solution is supplied from one side orthogonal to the respective rows and discharged from the opposite side. Therefore, the flow of the electrolytic solution along a plurality of anode surfaces is formed. Thus, the liquid supply with less bias by each anode is held. Therefore, the means for controlling the oxidation-reduction potential of the electrolytic cell (B) can be performed by controlling the control value of the oxidation-reduction potential of the effluent from the anode chamber by increasing / decreasing the energization current to the electrolytic cell. Here, increase / decrease of the energization current can be performed by finely adjusting the energization current for each pair of electrodes as a power supply means. For example, if it is set so that it is high on the electrode on the liquid supply side and low on the electrode on the one side of drainage, it can be energized with a high current because there are many unoxidized ions in the anode on the side close to the liquid supply, At the drain side anode, the amount of unoxidized ions is reduced, so that the energization current can be reduced to prevent excessive oxidation.

Here, control of the oxidation-reduction potential in the horizontally long electrolytic cell characteristic of the electrolytic cell (B) will be described. Here, in order to clarify the effect of the horizontally long electrolytic cell, without using a means for repeating the drainage of the anode chamber for supplying the liquid, the following conditions (1) to (3) are used. One electrode was supplied at a constant flow rate of 8.2 mL / min, and the drainage was a one-pass solution that was passed through a drainage tank. Moreover, electricity supply was 4.725A with respect to one electrode. The current density is 500 A / m ² .

(1) Electrolyzer: The size of the electrolyzer corresponding to one electrode pair is 90 mm in the length in the electrode width direction and 70 mm in the length in the direction of the facing anode and cathode. The number of boxes was changed from 2 to 6, and a box extended in the electrode width direction by that number was used. Here, the depth of the electrolytic cell was 160 mm. Further, at the position where the anode side is 30 mm and the cathode side is 40 mm, the longitudinal direction of the electrolytic cell is partitioned using a Tetoron filter cloth as a diaphragm, and an anode chamber and a cathode chamber are provided. Further, the drainage port from the electrolytic cell was attached to a position 15 mm downward from the upper end of the electrolytic cell in the anode chamber and 10 mm downward from the upper end of the electrolytic cell in the cathode chamber. An example of the electrolytic cell is shown in FIG. FIG. 2 is a longitudinal sectional view showing a schematic structure of the electrolytic cell (B) 10 in the case of four electrode pairs. Here, the electrolytic solution was supplied from the starter tank 2 by the metering pump 1 and discharged to the drainage tank 3. Moreover, the change of the oxidation-reduction potential was recorded by the ORP meter 4 installed at the discharge port of the anode chamber.

(2) Anode and cathode: As the anode, a chlorine-generating insoluble anode (mesh shape) manufactured by Permerek Electrode Co., Ltd., masked with tape so that the electrode area becomes 70 × 135 mm, and the cathode A 1 mm thick titanium plate masked so that the electrode area was the same as that of the anode was used. Here, the anode and cathode were fixed such that the distance from the diaphragm to the anode was 20 mm, and the distance from the diaphragm to the cathode was 40 mm. The back surface of the anode was left as it was, and the entire back surface of the cathode was masked.

(3) Electrolyte: In accordance with the approximate composition of the etching waste liquid in actual operation, the reagent ferric chloride is 107 g / L in iron concentration, the ferrous chloride in iron concentration is 53 g / L, and the reagent chloride 2 copper was melt | dissolved so that it might become 60 g / L in copper concentration, and it adjusted so that pH might be set to about -0.3 with hydrochloric acid. The liquid supply temperature of the electrolyte was 60 ° C.

  As a result, it was found that the ORP of the drainage was stably controlled to 1000 mV or less and the generation of chlorine gas could be suppressed in any case of the electrolytic cell composed of 2 to 6 electrode pairs. An example is shown in FIG. FIG. 3 shows the ORP change of drainage when energized for 60 hours using an electrolytic cell composed of four electrode pairs. As shown in FIG. 3, the oxidation-reduction potential is stable after the initial time. Thus, it can be seen that if the horizontally long electrolytic cell (B) is used, the oxidation-reduction potential can be controlled by adjusting the energization current.

  The anode used in the electrolytic cell (B) is not particularly limited, and various insoluble anodes are used. Commercially available graphite, platinum-coated titanium, ruthenium oxide-coated titanium, iridium oxide-based coated titanium, etc. However, a chlorine-generating type coated with ruthenium oxide is preferably used. Further, as the shape, a plate shape, a perforated plate shape, a rod shape, a bowl shape, a mesh shape, or the like is used, but a mesh shape is preferable. In other words, when the anode is opposed to only one side, the back side does not contribute to the reaction, so there is a concern that a short pass will occur and the use of the electrode becomes inefficient, but the mesh type electrode is used. In this case, the oxidation is sufficiently performed on the back surface, and other problems are not problematic.

Further, at this time, it is preferable to provide a baffle plate in the anode chamber for changing the flow of the electrolytic solution along the electrode surface formed by supplying the electrolytic solution to a flow crossing the mesh of the anode. Thereby, higher oxidation efficiency can be obtained. This point will be described in detail below using specific examples.
The electrolytic cell (B) is a horizontally long electrolytic cell consisting of two electrode pairs. When the baffle plate is installed in the anode chamber and when there is no baffle plate, electrolysis is performed with the same liquid supply amount and the same energization current. As a starting liquid, a liquid having a composition of 125 g / L of trivalent iron and 55 g / L of divalent iron was supplied and energized. FIG. 4 is a vertical cross-sectional view of an electrolytic cell showing an example of how to install baffle plates in the anode chamber. Here, the cathode chamber 7 is not provided with a baffle plate. FIG. 4 shows that the baffle plate 6 in the anode chamber 5 causes the electrolyte flow 8 indicated by the dotted line to flow across the mesh of the anode 9. The change in the ORP of the anode drainage accompanying the energization at this time was measured. FIG. 5 shows a change in the ORP of the anode drainage due to energization depending on the presence or absence of the baffle plate in the anode chamber. From FIG. 5, it was found that the ORP increases faster and the oxidation efficiency is higher when the baffle plate is installed for the same liquid supply amount and the same energization current.

  The means for setting the inter-electrode distance of the electrolytic cell (B) is not particularly limited, but the set value of the inter-electrode distance can be selected according to the electrical conductivity of the etching waste liquid. That is, in the electrolytic cell (B), since the interval between the anode row and the cathode row can be set at an arbitrary position, it can be set to the optimum inter-electrode distance according to the electrical conductivity of the etching waste liquid. Inadvertent troubles such as shorting of the anode and cathode can be avoided, and there are also advantages such as improved handling of the electrode.

  The means for adjusting the supply / drainage liquid of the electrolytic cell (B) is not particularly limited, but the circulation of the drainage liquid in the anode chamber to the supply liquid accepts the drainage and is an electrolytic cell for the liquid. This is continued until the oxidation-reduction potential of the liquid in the anode chamber and the liquid storage tank becomes constant through a liquid storage tank that can circulate and self-circulate, and then the electrolytic oxidation is continued. It is preferable to perform control to discharge out of the system as an electrolytic oxidation completion liquid from the tank and to receive a new etching waste liquid corresponding to the discharged electrolytic oxidation completion liquid. By performing this control, electrolytic oxidation is continuously performed, so that it can be incorporated into an etching operation line.

  FIG. 6 shows a cross-sectional view of a schematic structure showing an example of an electrolytic apparatus using the control. In FIG. 6, the electrolyzer comprises an electrolytic cell (B) 10 composed of four electrode pairs and a liquid storage tank 11 that receives the drainage of the electrolytic cell and can circulate the liquid to the electrolytic cell and perform self-circulation. The electrolytic bath (B) 10 is provided with an ORP meter 4, and the liquid storage tank 11 is provided with a level meter 12, an etching waste liquid receiving port 13, and a post-treatment liquid discharge port 14.

  That is, by repeating a part of the drainage to the liquid supply side, the relative liquid flow rate in the electrolytic cell is increased and the uneven liquid flow in the electrolytic cell is forcibly eliminated. Since it is difficult to increase the size due to various factors such as space, it is actually effective to circulate between separately provided reservoirs. In the energization in the electrolytic tank integrated with the liquid storage tank as described above, the ORP of the liquid in the electrolytic tank and the liquid storage tank can stably shift to a substantially constant value. Unlike the case of passing the liquid, there is an advantage that strict control of the liquid supply flow rate is not required. Furthermore, since the residence time in the main part of the electrolytic cell is shortened, and the temperature control such as heating and cooling of the electrolytic solution may be performed in the liquid storage tank if necessary, simplify the structure of the equipment. There is an advantage that can be.

  In the electrolytic cell used in the above method, if necessary, from the cathode chamber according to the control value of the oxidation-reduction potentiometer of the electrolytic cell (A) or the electrolytic cell (B) or the alarm value of the installed chlorine gas concentration meter. An emergency means for inserting the drainage liquid into the anode chamber and adjusting the redox potential of the anode chamber to the control value can be provided. That is, in the electrolytic oxidation method according to the present invention, the generation of chlorine gas can be almost prevented, but it cannot be assumed that the chlorine gas itself abnormally occurs due to a plurality of causes. In preparation for this situation, equipment that can drop the drainage from the cathode chamber onto the liquid level in the anode chamber is provided, and this is linked to the redox potentiometer or chlorine gas alarm in the electrolytic cell (A) or electrolytic cell (B). It is preferable to keep it.

  In the cathode chamber of the electrolytic cell used in the above method, liquid passage at a certain flow rate is required. That is, when the oxidation proceeds on the anode side, the reduction of the catholyte corresponding to the same amount of electricity proceeds. Therefore, when etching waste solution containing copper is passed through the cathode chamber, it is excessively reduced and copper is electrodeposited. A flow rate is required. For example, in an etching waste liquid in actual operation, the supply flow rate to the cathode chamber may be about 1/9 of the supply flow rate to the anode chamber due to the composition of iron ions in the etching waste solution.

  The anode of the electrolytic cell used in the above method is not particularly limited, and various insoluble anodes are used, and commercially available graphite, platinum-coated titanium, ruthenium oxide-coated titanium, iridium oxide-based coated titanium, etc. Although it can be mentioned, a chlorine-generating type coated with ruthenium oxide is preferably used. Further, as the shape, a plate shape, a perforated plate shape, a rod shape, a bowl shape, a mesh shape, or the like is used, but a mesh shape is preferable.

  As the cathode of the electrolytic cell used in the above method, titanium having corrosion resistance in a corrosive iron chloride aqueous solution is preferable. As the shape, a plate shape, a perforated plate shape, a rod shape, a bowl shape, an expanded metal shape, or the like is used.

The filter cloth of the electrolytic cell used in the above method is not particularly limited, and for example, a material made of a material such as polypropylene, polyester, acrylic resin, modacrylic resin, polytetrafluoroethylene, or polyvinylidene fluoride is used. Of these, a filter cloth woven so as to have a fine mesh and a low water permeability is preferable. The water permeability is not particularly limited, but when handling iron ions, 0.04 to 0.15 L / m ² . The range of s is preferable.

As an electrolytic cell used in the above method, an electrolytic cell (B) having at least two electrolytic cells (B) arranged in parallel or in series can be used as necessary. That is, when the ORP difference between the ORP before electrolytic oxidation and the target value of electrolytic oxidation is small, the amount of the processing liquid is increased by installing in parallel, and when the ORP difference is sufficiently large, the ORP difference is elongated vertically and uniform. It is preferable to carry out at a low flow rate.
FIG. 7 shows an example of the parallel arrangement of the electrolytic cells (B), and FIG. 8 shows an example of the series arrangement of the electrolytic cells (B). In the parallel arrangement, if necessary, power feeding to each electrolytic cell (B) is performed by an individual power feeding device or a power feeding device electrically connected in series to at least two tanks or all of the electrolytic cells, The liquid supply to each electrolytic cell (B) can be divided into an etching waste liquid containing iron chloride to form a liquid supply 15 to each of the anode chamber and the cathode chamber of each electrolytic cell. Thereby, there is an advantage that the number of power supply devices is reduced and control becomes easy. Furthermore, by stopping the power supply to a specific battery case, it is possible to take measures such as sequentially preparing and adjusting a specific battery case while operating the entire apparatus.

  Further, in the parallel arrangement, by securing a gap of about 1 to 5 cm between the electrolytic cell and the electrolytic cell, it is possible to prevent heat sag in the electrolytic cell and suppress an increase in liquid temperature. That is, the etching waste liquid has a low electric conductivity, so that the electrolytic cell voltage is increased and the power cost is increased. In addition, there is a concern that the amount of heat generation increases and the liquid temperature is excessively increased. However, this can be suppressed.

The method for electrolytic oxidation of the etching waste liquid described above relates to an iron-based etching waste liquid, but can also be used for a copper-based etching waste liquid containing copper chloride as a main component. The copper-based etching waste liquid contains divalent and monovalent copper chloride and a dissolved metal.
In this case, the control value of the oxidation-reduction potential (silver / silver chloride electrode standard) is 400 to 800 mV, preferably 450 to 700 mV. That is, the upper limit of the control value of the oxidation-reduction potential (silver / silver chloride electrode standard) of the effluent from the anode chamber is 800 mV, preferably 700 mV, for the same reason as in the case of the iron-based etching waste liquid. On the other hand, when the oxidation-reduction potential (silver / silver chloride electrode reference) is less than 400 mV, there is almost no dissolving power from the measurement of the dissolution rate of the copper plate, and 450 mV or more is particularly desirable.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, as an analysis of the metal used by the Example and the comparative example, it performed by the ICP emission analysis method.

(Example 1 (Reference Example) , Comparative Example 1)
When the following electrolytic cell, anode and cathode, and etching waste liquid were used, (a) when the ORP was not controlled by adjusting the energization current (Comparative Example 1) and (b) the ORP was controlled by adjusting the energization current The case where it was carried out (Example 1) was compared. The drainage of the anode chamber is circulated.
[Electrolysis tank]
A box type electrolytic cell (A) made of vinyl chloride was produced. The length in the electrode width direction was 90 mm, the length in the direction of the facing anode and cathode was 70 mm, and the depth of the electrolytic cell was 160 mm. Further, at the position where the anode side is 30 mm and the cathode side is 40 mm, the longitudinal direction of the electrolytic cell is partitioned using a Tetoron filter cloth as a diaphragm, and an anode chamber and a cathode chamber are provided. Further, the drainage port from the electrolytic cell was attached to a position 15 mm downward from the upper end of the electrolytic cell in the anode chamber and 10 mm downward from the upper end of the electrolytic cell in the cathode chamber. In addition, the change in oxidation-reduction potential was recorded with an ORP meter installed at the discharge port of the anode chamber.

[Anode and cathode]
The anode is a chlorine-generating insoluble anode (mesh) manufactured by Permerek Electrode Co., Ltd., masked with tape so that the electrode area is 70 × 135 mm, and the cathode is a 1 mm thick titanium plate Was masked so that the electrode area was the same as that of the anode. Here, one each of the anode and the cathode was used, and the installation position was fixed so that the distance from the diaphragm to the anode was 20 mm, and the distance from the diaphragm to the cathode was 40 mm. The back surface of the anode was left as it was, and the entire back surface of the cathode was masked.
[Etching waste liquid]
In accordance with the approximate composition of the etching waste liquid in actual operation, the reagent ferric chloride is 107 g / L in iron concentration, the ferrous chloride in iron concentration is 53 g / L, and the reagent cupric chloride is in copper concentration. It melt | dissolved so that it might become 60 g / L, and it adjusted so that pH might be set to about -0.3 with hydrochloric acid. The liquid supply temperature of the electrolytic solution was 60 ° C.

  As the liquid passing condition, based on the above formula (1), the anode chamber is supplied at a constant flow rate of 3.1 mL / min and supplied at a rate of 1.6 mL / min from the drained liquid. It circulated to. At this time, the circulation amount of the drained liquid to the supply liquid was 50%, and the liquid flowed at a rate of 4.7 mL / min in the anode chamber. Further, the cathode chamber was supplied at a constant flow rate of 3.1 mL / min, and the drainage did not circulate.

First, in the case of (a), the current was energized to be constant at a current of 4.73 A corresponding to a current density of 500 A / m ² without controlling the ORP by adjusting the energization current. The ORP (silver / silver chloride electrode standard) of the electrolysis starting solution was 560 mV.
Here, the cell voltage accompanying energization and the ORP of the anode chamber were measured. Further, the chlorine gas concentration in the upper gas phase portion of the anode chamber was measured with a detector tube. The results are shown in FIG. FIG. 9 shows the relationship between the amount of energization current, the cell voltage, and the ORP (silver / silver chloride electrode standard) of the anode chamber. From FIG. 9, it can be seen that the battery cell voltage gradually increases as the energization current increases, and the ORP increases rapidly from the time when the ORP exceeds 750 mV. At this time, chlorine gas was detected from 1000 mV or later. When the ORP (silver / silver chloride electrode standard) was up to 700 mV, chlorine gas was not detected and it was confirmed that no chlorine gas was generated from the anode. When the ORP (silver / silver chloride electrode standard) of the anode chamber exceeded 1000 mV, when a liquid having the same composition as the starting liquid was added to the anode chamber, the release of chlorine gas to the atmosphere stopped. It was confirmed that it was effective as an emergency measure.

Next, in the case of (b), the control value of ORP (silver / silver chloride electrode standard) for drainage from the anode chamber is set to 580 to 700 mV, and a current corresponding to a current density of 500 A / m ² is obtained. Based on 73A, the energization current was increased or decreased to control the ORP. As a result, the divalent iron in the drained liquid after treatment is oxidized to trivalent, and an etching solution in which the metal dissolving power is regenerated is obtained, and stable electrolytic oxidation without generation of chlorine gas is continued. It was done.

(Example 2)
The electrolytic apparatus shown in FIG. 6 and the same anode, cathode, and etching waste solution as in Example 1 were used. The electrolysis apparatus is improved by providing a baffle plate in the anode chamber so that the liquid flow passes through the mesh of the anode.

As the liquid flow conditions, the anode chamber was newly fed at a constant flow rate of 3.1 mL / min, and the drainage of the anode chamber passed through the liquid storage tank, and the drainage amount was 50%. % Was circulated in the feed liquid, and the liquid flowed at a rate of 4.7 mL / min in the anode chamber. Further, the cathode chamber was supplied at a constant flow rate of 3.1 mL / min, and the drainage did not circulate.
As energization conditions, the control value of ORP (silver / silver chloride electrode standard) for drainage from the anode chamber is set to 580 to 700 mV, and energization is performed based on a current of 4.73 A corresponding to a current density of 500 A / m ^2. The ORP was controlled by increasing or decreasing the current. The ORP (silver / silver chloride electrode standard) of the electrolysis starting solution was 560 mV.
As a result, after passing the initial energization, the instruction of the ORP meter stably maintained the control value, and the electrolytic oxidation process was continued while accepting a considerable amount of new liquid dispensed as the treated liquid. Thereby, the divalent iron in the obtained post-treatment liquid was oxidized to trivalent, and an etching solution in which the metal dissolving power was regenerated was obtained, and stable electrolytic oxidation without generation of chlorine gas was continued. .

(Example 3)
As a power supply means for adjusting the energization current of the electrolytic cell (B), the energization current is adjusted for each individual electrode pair. The same procedure as in Example 2 was performed except that the liquid electrode pair was set to be low.
As a result, after passing the initial energization, the instruction of the ORP meter stably maintained the control value, and the electrolytic oxidation process was continued while accepting a considerable amount of new liquid dispensed as the treated liquid. Thereby, the divalent iron in the obtained post-treatment liquid was oxidized to trivalent, and an etching solution in which the metal dissolving power was regenerated was obtained, and stable electrolytic oxidation without generation of chlorine gas was continued. .

Example 4
As the etching waste liquid, in accordance with the approximate composition of the etching waste liquid in actual operation, the reagent cupric chloride is dissolved at a copper concentration of 60 g / L and the reagent cuprous chloride is dissolved at a copper concentration of 20 g / L, The same procedure as in Example 2 was performed except that hydrochloric acid adjusted to a pH of about -0.3 was used, and the control value of ORP (silver / silver chloride electrode standard) was set to 450 to 700 mV. It was.
As a result, after passing the initial energization, the instruction of the ORP meter stably maintained the control value, and the electrolytic oxidation process was continued while accepting a considerable amount of new liquid dispensed as the treated liquid. As a result, monovalent copper in the obtained post-treatment liquid was divalently oxidized to obtain an etching solution in which the metal dissolving power was regenerated, and stable electrolytic oxidation without generation of chlorine gas was continued. .

  From the above, in Examples 1 to 4, the electrolytic cell specifications, the method of supplying the electrolytic cell, the circulation condition of the drainage of the anode chamber, and the control condition of the oxidation-reduction potential were performed according to the method of the present invention. In the method of electrolytic oxidation of low valence ions in the etching waste liquid to expensive ions, the etching waste liquid is made efficient while suppressing excessive oxidation of the etching waste liquid on the anode surface and preventing generation of chlorine gas from the electrolytic cell. It can be seen that it can be electrolytically oxidized. On the other hand, in Comparative Example 1, since the control conditions for the redox potential do not meet these conditions, it can be seen that satisfactory results cannot be obtained in preventing the generation of chlorine gas.

  As is apparent from the above, the electrolytic oxidation method of the etching waste liquid according to the present invention is copper chloride and / or as a main component used for the production of a lead frame which is a base of a semiconductor integrated circuit, etc. This is suitable as a method for regenerating an etching solution comprising an acidic aqueous solution containing an expensive number of iron chloride ions.

It is a figure showing the relationship between the oxidation reduction potential of an aqueous solution containing iron chloride and copper chloride, and a dissolution rate. It is a figure which shows the cross section of the longitudinal direction showing schematic structure in the case of four electrode pairs. It is a figure showing ORP change of the drainage at the time of energizing for 60 hours using the electrolytic cell which consists of four electrode pairs. It is sectional drawing of the vertical direction of the electrolytic cell showing an example of the installation method of a baffle plate in an anode chamber. It is a figure showing the change of ORP of the anode drainage accompanying the electricity supply by the presence or absence of the baffle plate in the anode chamber. It is a figure showing the cross section of the electrolyzer provided with the electrolytic cell (B) and the liquid storage tank which accepts the drainage liquid of an electrolytic cell, and can perform the circulation to the electrolytic cell and a self-circulation. It is a figure showing an example of parallel arrangement | positioning of an electrolytic vessel (B). It is a figure showing an example of series arrangement of an electrolytic cell (B). It is a figure showing the relationship between the energizing current amount of the comparative example 1, a battery case voltage, and ORP of an anode chamber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metering pump 2 Initial liquid tank 3 Drainage tank 4 ORP meter 5 Anode chamber 6 Baffle plate 7 Cathode chamber 8 Flow of electrolyte 9 Anode 10 Electrolyzer (B)
DESCRIPTION OF SYMBOLS 11 Liquid storage tank 12 Level meter 13 Etching waste liquid inlet 14 Discharge liquid outlet 15 Liquid supply to each of anode chamber and cathode chamber

Claims (10)

In a method in which an etching waste solution containing iron chloride is passed through an electrolytic cell composed of an anode chamber and a cathode chamber partitioned by a diaphragm as an electrolytic solution, and low-valent ions in the etching waste solution are electrolytically oxidized to expensive ions. ,
Using the following electrolytic cell (B), the etching waste liquid is supplied to the electrolytic cell, and 15 to 50% of the amount discharged from the anode chamber is circulated as the supplied liquid, while oxidizing the discharged liquid from the anode chamber. A method for electrolytic oxidation of an etching waste liquid, wherein a control value of a reduction potential (a silver / silver chloride electrode standard) is controlled to 550 to 800 mV.
Electrolyzer (B): An anode array in which 2 to 6 mesh-shaped anodes are arranged in series in the electrode width direction in a horizontally long box, and in the anode chamber, on the electrode surface A cathode having a baffle plate that changes the flow of the electrolyte along the meshed anode so that the same number of cathodes as the anodes are arranged in series so that only one side of both electrode faces faces on one side of the anode row 2 to 6 electrode pairs composed of rows are composed of an anode chamber and a cathode chamber separated by a filter cloth diaphragm, and each of the anode chamber and the cathode chamber independently has an electrolyte solution. Means for adjusting the supply / drainage of liquid supplied from one side orthogonal to the row and drained from the opposite side and repeating the drainage of the anode chamber to the supply fluid; Detect and control on the side Comprising stages, means for setting the distance between electrodes of the anode columns and the cathode row, and power supply means for regulating the current supplied to each individual electrode pair.   The means for adjusting the supply / drainage liquid of the electrolytic cell (B) is a storage device that allows the circulation of the drainage liquid in the anode chamber to the supply liquid, accepts the drainage liquid, and allows the circulation and self-circulation of the liquid to the electrolytic cell. This is continued until the oxidation-reduction potentials of the liquid in the anode chamber and the storage tank are made constant through the liquid tank, and then the electrolytic oxidation is continued. 2. The method of electrolytic oxidation of etching waste liquid according to claim 1, wherein control is performed to receive a new etching waste liquid corresponding to the discharged and discharged electrolytic oxidation end liquid. The means for detecting and controlling the oxidation-reduction potential of the electrolytic cell (B) controls the control value of the oxidation-reduction potential of the effluent from the anode chamber by increasing or decreasing the energization current to the electrolytic cell. 3. The method for electrolytic oxidation of etching waste liquid according to 1 or 2 . The method for electrolytic oxidation of an etching waste liquid according to claim 1 or 2 , wherein the power supply means for adjusting the energization current of the electrolytic cell (B) adjusts the energization current for each electrode pair. 5. The method for electrolytic oxidation of an etching waste liquid according to claim 4 , wherein the energization current is set so as to be high at an electrode on a liquid supply side and low at an electrode on a drain side. Setting the distance between the electrodes of the electrolytic cell (B) means of etching waste liquid according to claim 1 or 2, characterized in that selected according to the set value of the distance between the electrodes in the electrical conductivity of the waste etching solution Electrolytic oxidation method. 3. The method for electrolytic oxidation of an etching waste liquid according to claim 1, wherein the electrolytic cell is one in which at least two electrolytic cells (B) are arranged in parallel or in series. In the parallel arrangement, power feeding to each electrolytic cell (B) is performed by an individual power feeding device, or a power feeding device electrically connected in series to at least two or more of all the electrolytic cells, or each electrolytic cell, 8. The electrolytic oxidation of the etching waste liquid according to claim 7 , wherein the supply liquid to (B) is divided into an etching waste liquid containing iron chloride and supplied to each of the anode chamber and the cathode chamber of each electrolytic cell. 9. Method. Further, according to the indication value of the oxidation-reduction potential of the electrolytic cell (B) or the alarm value of the installed chlorine gas concentration meter, the drainage from the cathode chamber is inserted into the anode chamber, and the oxidation-reduction potential of the anode chamber is set. The method for electrolytic oxidation of an etching waste liquid according to claim 1 or 2 , further comprising emergency means for adjusting to the control value. In the electrolytic oxidation process of the etching waste liquid according to any one of claims 1 to 9 that the etching waste liquid are those containing copper chloride instead of ferric chloride, and redox potential (silver / silver electrode reference chloride) is 400 An electrolytic oxidation method of an etching waste liquid, characterized by being 800 mV.

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