JP7478163B2 - Adsorption filter for refining plating solution, and plating solution refining device and plating solution refining method using the same - Google Patents

Description

The present invention relates to an adsorption filter, as well as a filter for purifying a plating solution using the same, a plating solution purification apparatus, and a plating solution purification method.

Activated carbon has excellent adsorption capacity for various pollutants and has been used as an adsorbent in various fields, both for household and industrial use. Filters containing activated carbon are also widely used for purifying liquids, not just for water purification. For example, Patent Document 1 discloses an activated carbon-containing filter used for purifying alkali-resistant plating solutions.

On the other hand, various additives are added to plating solutions, and it is known that the additives gradually decompose during electrolytic plating and become impurities. If the decomposition products of these impurities increase in the plating solution, they will cause problems in the plating finish and must be removed. For example, Patent Document 2 discloses a method of using an activated carbon-containing filter to remove the decomposition products from the plating solution and reuse the plating solution.

As for the means for removing the decomposition products in the plating solution, as described in the above-mentioned Patent Document 2, there are two ways to do it: the decomposition products are removed using activated carbon or the like and the plating solution is reused, and the decomposition products and additives are removed, the plating solution is transferred, and then the plating solution is reused.

The former method has the problem that repeated treatment reduces the concentration of additives in the reused plating solution. On the other hand, the latter method requires transferring the plating solution to a different bath, so recently, a method of generating and reusing plating solution without transferring is becoming mainstream. However, with this method, when removing the decomposition products and additives and reusing the plating solution, if an adsorbent that selectively removes only the decomposition products is used, the decomposition products can be removed, but the additives will remain, resulting in the addition of excess additives, which causes problems with the plating surface.

In addition, decomposition products are relatively small molecules, and additives are often polymers, so it is necessary to remove substances with a wide range of molecular weights at the same time. Therefore, if an adsorbent that is good at adsorbing polymers but not suitable for adsorbing low molecules is used, the additives can be removed, but the decomposition products will remain, causing problems with the plating surface.

Therefore, the objective of the present invention is to provide an adsorption filter that can efficiently remove both decomposition products and additives in the plating solution.

JP 2012-61390 A JP 2005-240108 A

An adsorption filter according to one aspect of the present invention is an adsorption filter comprising a molded body containing activated carbon, characterized in that the molded body is heat-treated in an inert gas at 500°C for 1 hour to obtain a carbonized material having a specific surface area of 1500 to 2500 ^m2 /g, and that the carbonized material has pores with a BJH method mesopore volume of 0.1 ^cm3 /g or more and an MP method micropore volume of 0.6 ^cm3 /g or more.

FIG. 1 is a perspective view of a mold for preparing a molded body of the adsorption filter of this embodiment. FIG. 2 is a perspective view showing an example of a molded body of this embodiment obtained using the mold frame of FIG. FIG. 3 is a diagram for explaining how to cut out a sample when measuring the specific surface area, etc., of the activated carbon in the molded body.

Below, the embodiments of the present invention are described in detail with reference to specific examples, but the present invention is not limited to these.

<Adsorption filter>
The adsorption filter of this embodiment includes a molded body containing activated carbon as described above, and is characterized in that the molded body is heat-treated in an inert gas at 500°C for 1 hour to obtain a carbonized material having a specific surface area of 1500 to 2500 ^m2 /g, and that the carbonized material has pores with a BJH method mesopore volume of 0.1 ^cm3 /g or more and an MP method micropore volume of 0.6 ^cm3 /g or more.

By purifying the plating solution with an adsorption filter having such a configuration, both the additives and decomposition products in the plating solution can be efficiently removed, and the plating solution can be restored to a clean state. Therefore, according to the present invention, it is possible to provide an adsorption filter that can efficiently remove both the decomposition products and additives in the plating solution.

The adsorption filter of this embodiment is defined by the properties of the carbonized material obtained by subjecting the molded body to a specific heat treatment. The heat treatment is a heat treatment of the molded body containing activated carbon in an inert gas at 500°C for 1 hour. The inert gas used for the heat treatment is not particularly limited, and inert gases such as nitrogen gas, helium gas, and argon gas can be used. The heating means used for the heat treatment is also not particularly limited as long as it is capable of heating at 500°C for 1 hour. By undergoing the heat treatment, the binder and the like are decomposed and removed from the molded body, and the carbonized material obtained is mostly the activated carbon contained in the molded body.

It is important that the specific surface area of the carbonized material and the pores possessed by the carbonized material in the adsorption filter of this embodiment are within a specified range.

In this embodiment, the specific surface area of the carbonized material is determined by the BET method from the nitrogen adsorption isotherm. By making the specific surface area 1500 m ² /g or more, the ability to remove polymeric additives can be ensured, and more preferably 1600 m ² /g or more. On the other hand, by making the specific surface area 2500 m ² /g or less, the packing density of the activated carbon can be increased, and therefore the adsorption capacity per filter can be ensured, and is preferably 2100 m ² /g or less, more preferably 2000 m ² /g or less. The specific surface area when made into a carbonized material reflects the composition of the activated carbon in the adsorption filter, and is an index indicating the removal ability and packing state of the adsorption filter.

In this embodiment, the pores of the carbonized material are defined by a BJH mesopore volume and an MP micropore volume, and the BJH mesopore volume is 0.1 ^cm3 /g or more and the MP micropore volume is 0.6 ^cm3 /g or more. The BJH mesopore volume and the MP micropore volume of the pores can be measured by the method described in the examples below.

By making the BJH method mesopore volume of the pores of the carbonized material 0.1 cm ³ /g or more, the ability to remove polymeric additives can be ensured, and it is more preferable that it is 0.11 cm ³ /g or more. The upper limit of the BJH method mesopore volume is not particularly limited, but it is preferably 1.2 cm ³ /g or less, and more preferably 1.0 cm ³ /g or less, for reasons such as the ability to increase the molded body density. By making the MP method micropore volume 0.6 cm ³ /g or more, the ability to remove decomposition products can be ensured, and it is more preferable that it is 0.66 cm ³ /g or more. The upper limit of the MP method micropore volume is not particularly limited, but it is preferably 1.50 cm ³ /g or less, and more preferably 1.20 cm ³ /g or less, for reasons such as the ability to increase the molded body density. The mesopore volume when made into a carbonized material reflects the composition of the activated carbon in the adsorption filter, and is an index showing the ability to remove polymeric additives in the adsorption filter and the packed state of the activated carbon. Similarly, the micropore volume reflects the composition of the activated carbon in the adsorption filter, and serves as an index showing the ability of the adsorption filter to remove decomposition products and the packing state of the activated carbon in the adsorption filter.

Furthermore, in the adsorption filter of this embodiment, it is preferable that the standard deviation when the volume particle size distribution of the carbonized material is measured is 70 μm or more. By having the standard deviation of 70 μm or more, there is an advantage that the packing density of the molded body can be increased and the adsorption capacity of the filter can be maintained high. Furthermore, it is preferable that the standard deviation is 80 μm or more. There is no particular limit to the upper limit, but from the viewpoint of preventing the activated carbon from falling off and maintaining the shape, it is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less. The standard deviation reflects the composition of the activated carbon in the adsorption filter and can be an indicator of the adsorption capacity and moldability of the adsorption filter.

In addition, in the adsorption filter of this embodiment, it is preferable that the 50% particle size (D50) in the cumulative particle size distribution based on volume of the carbonized material is 120 to 450 μm. Having D50 in such a range has the advantage of being able to reduce the resistance to liquid passage. Furthermore, it is more preferable that the D50 is 130 to 420 μm. The D50 reflects the composition of the activated carbon in the adsorption filter, and can be an index of the performance of the adsorption filter, such as the resistance to liquid passage.

Furthermore, in the adsorption filter of this embodiment, the ratio of the 90% particle size (D90) to the 10% particle size (D10) in the cumulative particle size distribution based on the volume of the carbonized material, i.e., D90/D10, is preferably 5.0 or more. By having D90/D10 in such a range, there is an advantage that the packing density of the molded body can be increased and the adsorption capacity of the filter can be maintained high. For this reason, it is more preferable that the D90/D10 is 7.0 or more, and even more preferable that it is 10.0 or more. There is no particular limit to the upper limit value, but from the viewpoint of not dropping off the activated carbon and maintaining the shape, D90/D10 is preferably 20.0 or less, and even more preferable that it is 17.0 or less. D90/D10 when made into a carbonized material reflects the composition of the activated carbon in the adsorption filter, and is an index that directly indicates the performance when made into an adsorption filter.

The above-mentioned D50, D90 and D10 values are values measured by particle size distribution measurement using laser diffraction/scattering method, and can be measured, for example, using a wet particle size distribution measuring device (Microtrac MT3300EX II) manufactured by Microtrac Bell, which will be described later.

(Activated carbon)
The activated carbon contained in the molded body of the adsorption filter of this embodiment is not particularly limited as long as the carbonized material of the molded body containing the activated carbon has the above-mentioned characteristics, and any activated carbon can be used.

Specifically, for example, activated carbon obtained by subjecting a carbonaceous material to at least one of carbonization and activation can be used.

When carbonizing a carbonaceous material, oxygen or air is usually blocked and the process can be carried out at, for example, 400 to 800°C, preferably 500 to 800°C, and more preferably 550 to 750°C. As the activation method, either the gas activation method or the chemical activation method can be used, or both may be combined. In particular, the gas activation method, which leaves less impurities behind, is preferred. The gas activation method can be carried out by reacting the carbonized carbonaceous material with an activation gas (e.g., water vapor, carbon dioxide gas, etc.) at, for example, 750 to 1100°C, preferably 800 to 980°C, and more preferably 850 to 950°C. In consideration of the safety of the work and the reactivity of the carbonaceous material, the activation gas is preferably a water vapor-containing gas containing 10 to 40% by volume of water vapor. There are no particular limitations on the activation time and the heating rate, and they can be selected appropriately depending on the type, shape, and size of the carbonaceous material selected.

The carbonaceous material is not particularly limited, but examples thereof include plant-based carbonaceous materials (e.g., plant-derived materials such as wood, sawdust, charcoal, fruit shells such as coconut shells and walnut shells, fruit seeds, pulp manufacturing by-products, lignin, and blackstrap molasses), mineral-based carbonaceous materials (e.g., mineral-derived materials such as peat, lignite, brown coal, bituminous coal, anthracite, coke, coal tar, coal pitch, petroleum distillation residue, and petroleum pitch), synthetic resin-based carbonaceous materials (e.g., synthetic resin-derived materials such as phenolic resins, polyvinylidene chloride, and acrylic resins), and natural fiber-based carbonaceous materials (e.g., natural fibers such as cellulose, and natural fiber-derived materials such as regenerated fibers such as rayon). These carbonaceous materials can be used alone or in combination of two or more types. Among these carbonaceous materials, coconut shells and phenolic resins are preferred from the viewpoint of obtaining a molded body having the above-mentioned characteristics, and coconut shells are more preferred from the viewpoint of easily controlling both the mesopore volume and the micropore volume.

After activation, the activated carbon may be washed to remove ash and chemicals, especially when using plant-based carbonaceous materials such as coconut shells or mineral-based carbonaceous materials. An acid is used for washing, and hydrochloric acid is preferred as the acid because of its high cleaning efficiency. After pickling, the acid is thoroughly washed away with water.

The shape of the activated carbon in this embodiment may be any of powder, particulate, fibrous (thread, woven cloth, felt), etc., and may be selected appropriately depending on the application, but a particulate shape with high adsorption performance per volume is preferred.

The particle size of the activated carbon used in this embodiment is not particularly limited, but the 50% particle size (D50) in the cumulative particle size distribution based on volume is preferably about 10 to 500 μm, more preferably about 12 to 450 μm, and even more preferably about 13 to 400 μm. If the activated carbon has a particle size in this range, there are advantages in that the activated carbon does not fall off, the shape can be maintained, and the plating solution can be regenerated with low resistance to liquid flow. In this embodiment, the above D50 value is a value measured by a laser diffraction/scattering method, as with the above-mentioned carbide, and can be measured, for example, by a wet particle size distribution measuring device (Microtrac MT3300EX II) manufactured by Nikkiso Co., Ltd.

The molded adsorption filter of this embodiment can use one or a combination of two or more types of activated carbon as described above.

Some examples of means for making the adsorption filter of this embodiment have the above-mentioned characteristics (specific surface area as a carbonized material, mesopore volume, micropore volume, and, as optional characteristics that may be satisfied, standard deviation when measuring the volumetric particle size distribution, D50, D90/D10) are given below. For example, in order to satisfy the above-mentioned characteristics, a method of mixing activated carbon before crushing with a powder obtained by crushing activated carbon having a relatively large average particle size (D50) (e.g., mixing granular activated carbon with powdered activated carbon), a method of mixing activated carbon having various D50, specific surface area, mesopore volume, and micropore volume, a method of using activated carbon with a relatively large volumetric particle size distribution (D90/D10 is, for example, 5.0 or more), and the like can be mentioned. However, as long as the obtained adsorption filter satisfies the above-mentioned characteristics, it is not limited to these methods.

In particular, it is preferable that the activated carbon contained in the molded body contains 5 to 20 parts by mass of fibrous activated carbon having a specific surface area of 1700 m ² /g or more. This has the advantage of being able to increase the adsorption rate. The specific surface area of the fibrous activated carbon is determined by the BET method from the nitrogen adsorption isotherm, similar to the specific surface area of the carbonized material. If the content of the fibrous activated carbon in the activated carbon is 5 parts by mass or more and 20 parts by mass or less, the adsorption rate can be improved without decreasing the adsorption capacity of the filter. A more preferable range of the specific surface area of the fibrous activated carbon is 1750 m ² /g or more, and although there is no particular upper limit, it is desirable that it is 2500 m ² /g or less from the viewpoint of removal capacity.

(binder)
The molded body of this embodiment preferably contains a binder in addition to activated carbon. As the binder, a powder binder such as polyethylene or a fibrous binder described later can be used, but it is preferable to contain a fibrous binder from the viewpoint of ensuring the adhesiveness of the molded body. The fibrous binder is not particularly limited as long as it can be shaped by entangling the activated carbon as described above, can be mixed with the activated carbon after pickling, and has acid resistance so that the filter can be used in an acidic plating solution, and can be widely used regardless of whether it is a synthetic product or a natural product. Examples of such fibrous binders include acrylic fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, cellulose fibers, nylon fibers, aramid fibers, and pulp. The fiber length of the fibrous binder is preferably 4 mm or less.

These fibrous binders may be used in combination of two or more. It is particularly preferable to use polyacrylonitrile fiber or cellulose pulp as the binder. This can further increase the density and strength of the molded body and suppress performance degradation.

In this embodiment, the water permeability of the fibrous polymer binder is about 10 to 150 mL in terms of CSF value. In this embodiment, the CSF value is a value measured in accordance with JIS P 8121-2:2012 (Pulp - Freeness test method - Part 2: Canadian standard freeness method). The CSF value can be adjusted, for example, by fibrillating the binder.

If the CSF value of the fibrous polymer binder is less than 10 mL, liquid permeability may not be achieved and pressure loss may increase. On the other hand, if the CSF value exceeds 150 mL, the powdered activated carbon may not be sufficiently retained, resulting in a molded body with low strength and poor adsorption performance.

The mixing ratio of activated carbon and fibrous binder in the molded body of this embodiment is preferably about 4.0 to 6.0 parts by mass of fibrous binder per 100 parts by mass of activated carbon, from the viewpoints of the adsorption effect of decomposition products in the plating solution, moldability, etc. If the amount of fibrous binder is less than 4.0 parts by mass, there is a risk that sufficient strength cannot be obtained and the molded body cannot be molded. Furthermore, if the amount of fibrous binder exceeds 6.0 parts by mass, there is a risk that the adsorption performance will decrease. More preferably, it is desirable to mix 4.5 to 5.5 parts by mass of fibrous binder.

The adsorption filter of this embodiment comprises a molded body containing the activated carbon and, preferably, the fibrous binder. The shape, form, etc. of the adsorption filter can be designed appropriately depending on the application. Since the shape is suitable for passing liquid, the adsorption filter of this embodiment may be a cylindrical filter containing a core in addition to the activated carbon and the fibrous binder. The cylindrical shape has the advantage of reducing water resistance and allowing liquid to pass through evenly.

The core that can be used in this embodiment is not particularly limited as long as it can be inserted into the hollow part of the cylindrical filter and reinforce the cylindrical filter, but for example, a trical pipe, a netron pipe, or a ceramic filter is preferable. Furthermore, a nonwoven fabric or the like can be wrapped around the outer periphery of the core.

The adsorption filter of this embodiment is preferably used for purification, and in particular, is preferably used for plating solution purification, since it can efficiently remove both decomposition products and additives in the plating solution.

Therefore, this embodiment also includes a filter for purifying plating solution that uses the above-mentioned adsorption filter. The plating solution can be purified by immersing the filter for purifying plating solution of this embodiment in a plating solution tank that contains the plating solution. By circulating the plating solution through the filter, both the decomposition products and additives in the plating solution can be adsorbed and removed, making it extremely useful for industrial use.

<Method of manufacturing the adsorption filter>
The molded body of the adsorption filter of this embodiment can be produced by any method, and is not particularly limited. The slurry suction method is preferred in terms of efficient production.

As an example, the manufacturing method of the cylindrical molded body of this embodiment will be described in detail below, but the present invention is not limited thereto. The following description will be given with reference to the drawings, in which the reference numerals indicate 1 mold frame, 2 core body, 3 suction hole, 4, 4' flanges, 5 filtrate outlet, and 6 molded body.

Specifically, for example, a cylindrical molded body can be obtained by a manufacturing method including a slurry preparation process in which powdered activated carbon and a fibrous binder are dispersed in water to prepare a slurry, a suction filtration process in which the slurry is filtered while being suctioned to obtain a preformed body, a drying process in which the preformed body is dried to obtain a dried molded body, and, if necessary, a grinding process in which the outer surface of the molded body is ground.

(Slurry preparation process)
In this embodiment, in the slurry preparation step, a slurry is prepared by dispersing the powdered activated carbon and the fibrous binder in a solvent so that, for example, the fibrous binder is 4.5 to 5.5 parts by mass per 100 parts by mass of activated carbon, and the solid content concentration is 4.0 to 6.0% by mass (particularly preferably 4.5 to 5.5% by mass). The solvent is not particularly limited, but it is preferable to use water or the like. If the solid content concentration of the slurry is too high, there is a problem that the dispersion is likely to become non-uniform and the molded body is likely to become spotty. On the other hand, if the solid content concentration is too low, not only does the molding time increase and productivity decrease, but the density of the molded body increases and clogging due to the capture of particulate matter is likely to occur.

(Suction filtration process)
Next, in the suction filtration step, for example, as shown in Fig. 1, a core as described above is attached to a cylindrical molding frame 1 having a large number of small suction holes 3 on the surface of a core body 2 and flanges 4, 4' attached to both ends, and the core is immersed in the slurry contained in a container, and the slurry is filtered while being sucked from the inside of the frame 1 through a filtrate discharge port 5, thereby attaching the slurry to the frame 1. As a suction method, a conventional method such as a method of sucking using a suction pump or the like can be used. The preform 7 is compressed to a predetermined diameter while attached to the frame 1.

(Drying process)
After the preform 7 is produced by the suction filtration step, the flanges 4, 4' at both ends of the mold 1 are removed, and the core 2 is pulled out to obtain the preform 7 having a hollow cylindrical shape. In the drying step, the preform 7 removed from the mold 1 is dried in a dryer or the like to obtain the molded body 6 (the molded body of this embodiment) shown in Fig. 2.

The drying temperature is, for example, about 100 to 150°C (particularly 110 to 130°C), and the drying time is, for example, about 4 to 24 hours (particularly 8 to 16 hours). If the drying temperature is too high, the fibrous binder may be altered or melted, which may lead to a decrease in filtration performance and a decrease in the strength of the molded body 6. If the drying temperature is too low, the drying time may be long or the drying may be insufficient.

(Grinding process)
If necessary, after the drying step, a grinding step can be performed to further adjust the outer diameter of the filter or to reduce unevenness on the outer peripheral surface. The grinding means used in this embodiment is not particularly limited as long as it can grind (or polish) the outer surface of the dried molded body 6, and a conventional grinding method can be used, but from the viewpoint of grinding uniformity, a method using a grinding machine that rotates and grinds the molded body 6 itself is preferred.

The grinding process is not limited to the method using a grinding machine, and may be performed, for example, by grinding the molded body 6 fixed to a rotating shaft with a fixed flat grinding wheel. In this method, the generated grinding swarf tends to accumulate on the grinding surface, so it is effective to grind while blowing air.

The molded body thus obtained can be used as the adsorption filter of this embodiment. For example, after producing the molded body by the above-mentioned production method, it can be shaped and dried depending on the application, and then cut into the desired size and shape to obtain an adsorption filter. Furthermore, if necessary, a cap can be attached to the tip portion, or a nonwoven fabric can be attached to the surface.

As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

That is, an adsorption filter according to one aspect of the present invention is an adsorption filter comprising a molded body containing activated carbon, characterized in that the molded body is heat-treated in an inert gas at 500°C for 1 hour to obtain a carbonized material having a specific surface area of 1500 to 2500 ^m2 /g, and that the carbonized material has pores with a BJH method mesopore volume of 0.1 ^cm3 /g or more and an MP method micropore volume of 0.6 ^cm3 /g or more.

With this configuration, it is possible to provide an adsorption filter that can efficiently remove both decomposition products and additives in the plating solution.

It is more preferable that the specific surface area of the carbonized material is 1500 to 2100 m ² /g, which is believed to enable the above-mentioned effects to be obtained more reliably.

In the adsorption filter, it is preferable that the standard deviation of the volume particle size distribution of the carbonized material is 70 μm or more. This has the advantage that the packing density of the molded body can be increased and the adsorption capacity of the filter can be maintained high.

It is also preferable that the D50 of the carbonized material is 120 to 450 μm. Furthermore, it is preferable that the ratio of D90 to D10 (D90/D10) of the carbonized material is 5.0 or more. This has the advantage that the packing density of the molded body can be increased and the adsorption capacity of the filter can be maintained high.

In the adsorption filter, it is preferable that the activated carbon contained in the molded body contains 5 to 20 parts by mass of fibrous activated carbon having a specific surface area of 1700 m ² /g or more, which has the advantage of enabling the adsorption rate to be increased.

It is preferable that the adsorption filter further contains a fibrous binder in the molded body. This has the advantage that the shape can be maintained with a minimum amount of binder, thereby maximizing the adsorption performance of the activated carbon.

Furthermore, the present invention also includes an adsorption filter for purifying plating solution, which comprises the above-mentioned adsorption filter.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited in any way by the following examples.

First, we will explain the manufacturing methods and evaluation methods for the activated carbon and adsorption filters prepared in each example and comparative example.

[Activated carbon A to H ]
"Kuraray Coal GW-H32/60" manufactured by Kuraray Co., Ltd. was activated with steam at 850 to 950°C in a fluidized bed furnace, and the activation time was adjusted so that the specific surface area was about 1700 ^m2 /g. The activated sample was sieved with a JIS standard sieve to obtain 30 to 60 Mesh granular activated carbon A.

"Kuraray Coal GW-H32/60" manufactured by Kuraray Co., Ltd. was activated with steam at 850 to 950°C in a fluidized bed furnace, and the time was adjusted so that the specific surface area would be about 2200 m ² /g. The activated sample was sieved with an IS standard sieve to obtain 30 to 60 Mesh granular activated carbon B.

100 g of coconut shell activated carbon with an alkaline earth metal content of 4 g/kg was activated at a temperature of 920° C. The activation time was adjusted so that the specific surface area was approximately 2100 m ² /g. The activation gas had a CO ₂ partial pressure of 10%, an H ₂ O partial pressure of 30%, and other gases of N 2 . The activated carbon obtained was washed with a 1 mol/L aqueous hydrochloric acid solution, washed with water, and then dried to obtain granular activated carbon C.

Phenolic resin fiber (KT-2800 manufactured by Gun-ei Chemical Industry Co., Ltd.) was treated in LPG combustion gas at 980°C to obtain fibrous activated carbons D and E.

Coconut shell char carbonized at 400°C to 600°C was activated with steam at 900°C to 950°C. The activation time was adjusted so that the specific surface area was about 1000 ^m2 /g. The obtained activated carbon was washed with 1 mol/L hydrochloric acid solution, washed with water, dried, and then sieved with a JIS standard sieve to 30 to 60 Mesh to obtain granular activated carbons F and G.

Bituminous coal was used as the carbonaceous raw material, and a carbonized product was obtained by carbonization at 650° C. The obtained carbonized product was supplied to a furnace with a mixed gas of 15% water vapor partial pressure, 11% carbon dioxide partial pressure, and 74% nitrogen partial pressure at a total gas pressure of 1 atmosphere, and activated at 880° C. to adjust the specific surface area to about 1450 m ² /g. The obtained activated carbon was washed with a 1 mol/L hydrochloric acid aqueous solution, washed with water, dried, and then sieved with a JIS standard sieve to 10 to 30 Mesh to obtain granular activated carbon H.

The activated carbons A to H obtained above are summarized in Table 1.

[Activated carbon I to O]
The granular activated carbons A, B, and C obtained above were pulverized in a ball mill to obtain powdered activated carbons I, J, and L shown in Table 2. The activated carbon C obtained above was pulverized in a ball mill and then sieved using a JIS standard sieve with an upper mesh of 80 Mesh and a lower mesh of 325 Mesh to obtain powdered activated carbon K. The activated carbons F and G obtained above were pulverized in a ball mill and then air-classified to obtain powdered activated carbons M and N, respectively. The activated carbon H obtained above was pulverized in a ball mill and then sieved using a JIS standard sieve with an upper mesh of 80 Mesh and a lower mesh of 325 Mesh to obtain powdered activated carbon O.

The powdered activated carbons I to O obtained by the above secondary processing are summarized in Table 2.

(fibrous binder)
As the fibrous binder, "Fibrillated acrylic pulp Bi-PUL/F" manufactured by Nippon Exlan Kogyo Co., Ltd. (Examples 1 to 7 and Comparative Examples 1 to 4) and high-density polyethylene powder "Mipelon MX-220" manufactured by Mitsui Chemicals, Inc. (Example 8) were used.

[Production of Molded Body]
(Examples 1 to 7 and Comparative Examples 1 to 4)
Each of the granular activated carbons and powdered activated carbons obtained above was dispersed in tap water by stirring in an amount of 2.0 kg of activated carbon in total and 0.1 kg of a fibrous binder ("Fibrillated acrylic pulp Bi-PUL/F" (CSF = 55 ml) manufactured by Nippon Exlan Kogyo Co., Ltd.) in terms of solid content to obtain 30 L of a slurry.

For the fibrous activated carbon, 1 kg of fibrous activated carbon and 0.05 kg of the fibrous binder in solids were added to 100 L of tap water in a small beater, and the mixture was beaten until the molded body density was 0.22 g/ml. The density of the molded body for measuring the beaten density, which was made from the beaten slurry, was measured as follows. First, a cylindrical molded body was produced by sucking the slurry from the center using a double-tube mold with many small suction holes as shown in Figure 1, with a 300-mesh wire net wrapped around the center axis with a suction hole diameter of 3 mmφ and a pitch of 5 mm, and a mold with a center axis diameter of 18 mmφ, an outer diameter of 40 mmφ, and an outer diameter flange spacing of 50 mm. The molded body density was measured from the weight and dimensions after drying (beaten density measurement).

For each activated carbon, the granular activated carbon, powdered activated carbon, and fibrous activated carbon were mixed and used in the ratio (weight ratio) shown in Table 3 below to prepare a filter. The amount of the fibrous binder was about 5 parts by mass per 100 parts by mass of solids in the molded body slurry. More specifically, for example, in Example 4, 1600 g of activated carbon A and 200 g of activated carbon I were weighed out. Then, first, 90 g of the fibrous binder was dispersed in water in a container in advance, 20 L of beaten fibrous activated carbon slurry (equivalent to 200 g of fibrous activated carbon) was added and stirred, activated carbon A and I were further added, stirred well, and water was further added to make the slurry amount 30 L, and the slurry was used to obtain a filter.

Using this mixed slurry, a molding die (a tubular die with many small suction holes) as shown in Fig. 1 was used, and an "MF filter" (mesh size 30 μm, inner diameter 30 mmφ, outer diameter 33 mmφ, length 245 mm) manufactured by Asahi Textile Industries Co., Ltd. was attached to the die having an outer diameter of 63 mmφ, a center shaft diameter of 30 mmφ, and an outer diameter flange interval of 245 mm, and the slurry was sucked up to about 65 mmφ, which is about 2 mm larger than the outer diameter of the die. After that, the slurry was compressed and molded (rolling molding) by pressing it with a plate while rotating until it had the same outer diameter as the die (63 mmφ), and then it was removed from the die and dried to complete a cylindrical molded body.

After drying, a single layer of nonwoven fabric (Spunbond nonwoven fabric "ELVES T0703WDO" manufactured by Unitika Ltd.) was wrapped around the outer circumference of the molded body, and then packings punched out of a 2 mm thick foamed polyethylene sheet into a doughnut shape with an outer diameter of 63 mmφ and an inner diameter of 30 mmφ were attached to both ends of the molded body with hot melt adhesive and the length was adjusted to 250 mm, thereby obtaining the adsorption filters of Examples 1 to 7 and Comparative Examples 1 to 3.

(Example 8)
0.3 kg of powder binder (high density polyethylene powder "Mipelon MX-220" manufactured by Mitsui Chemicals, Inc.) was added to 1.7 kg of activated carbon in total, which was a mixture of the granular activated carbon A and powdered activated carbon I obtained above in the ratio (76:9) shown in Table 3, and the mixture was charged into a micro speed mixer "MS-25 type" manufactured by Takara Koki Co., Ltd. and stirred for 2 minutes. The blending amount of the powder binder was 15 parts by mass with respect to 85 parts by mass of the solid content in the mixture.

Next, the mixture obtained was gradually filled into a cylindrical stainless steel mold with an inner diameter of 63 mmφ, a center diameter of 33 mmφ, and a height of 300 mm, covered on one side, while vibrating it with a wooden mallet, and the open side was covered to fix the contents. The mixture filled into the mold was placed in a dryer at 160°C together with the mold, heated for 120 minutes, and then allowed to cool to 50°C or less. The lid was removed, and the molded product was removed from the mold without breaking it, and the obtained molded product was cut to produce a dry molded product with an outer diameter of 63 mmφ, an inner diameter of 33 mmφ, and a height of 280 mm. Both ends of the obtained molded product were cut with a saw to a height of 245 mm. An "MF filter" manufactured by Asahi Textile Industry Co., Ltd. (mesh size 30 μm, inner diameter 30 mmφ, outer diameter 33 mmφ, length 245 mm) was inserted into the inner diameter side, and a single layer of nonwoven fabric (spunbond nonwoven fabric "Elves T0703WDO" manufactured by Unitika Ltd.) was wrapped around the outer circumference of the molded body. Furthermore, packings punched out of a 2 mm thick foamed polyethylene sheet into a doughnut shape with an outer diameter of 63 mmφ and an inner diameter of 30 mmφ were bonded to both ends of the molded body with a hot melt adhesive and the length was adjusted to 250 mm, thereby obtaining the adsorption filter of Example 8.

[Preparation of carbide of molded body]
The obtained molded bodies in each of the Examples and Comparative Examples before the attachment of the peripheral nonwoven fabric and the packing were arbitrarily cut out by about 6 mm lengthwise from a position 115 mm from the end face with a cutter knife as shown in Fig. 3. The cut sample was placed in a crucible and heated at 500°C in a nitrogen atmosphere for 1 hour, and then cooled to room temperature in a nitrogen atmosphere to prepare a sample for measuring the specific surface area, pore distribution, and particle size distribution.

[Measurement of specific surface area, pore diameter, and pore volume of carbonized material]
(Specific surface area)
First, a carbonaceous material was heated at 300° C. for 3 hours under a nitrogen flow (nitrogen flow rate: 50 mL/min) using a high-precision fully automatic gas adsorption apparatus "BELSORP-mini" manufactured by Microtrac-Bell Corporation, and then the nitrogen adsorption/desorption isotherm of the carbonaceous material was measured at 77 K. Analysis was performed by the multipoint method using the BET equation from the adsorption isotherm obtained by the above method, and the specific surface area was calculated from the straight line in the region of the relative pressure P/P0 = 0.01 to 0.1 of the obtained curve.

(Total pore volume/average pore diameter)
The total pore volume was calculated by the Gurvish method from the nitrogen adsorption amount at a relative pressure P/P0=0.99 in the adsorption isotherm obtained by the above method. The average pore diameter was calculated based on the total pore volume and the specific surface area obtained by the BET method described above, according to the following formula: Average pore diameter (nm)=total pore volume ( ^cm3 /g)/specific surface area ( ^m2 /g)×4000

(Micropore volume measurement by MP method)
The MP method was applied to the adsorption isotherm obtained by the above method to calculate the pore volume of the micropores. For the analysis by the MP method, the standard isotherm for t method analysis "NGCB-BEL.t" provided by Microtrack-Bel Co., Ltd. was used.

(Mesopore volume measurement by BJH method)
The pore volume of mesopores was calculated by applying the BJH method to the adsorption isotherm obtained by the above method. Note that, for the analysis by the BJH method, the standard curve "NGCB-BEL.t" provided by Microtrac-BEL Co., Ltd. was used.

(Measurement of particle size)
The particle sizes (D10, D50, D90) of the charcoal were measured by the laser diffraction measurement method described below. That is, the activated carbon to be measured was placed in ion-exchanged water together with a surfactant, and ultrasonic vibration was applied to prepare a uniform dispersion, which was then measured using a particle size distribution measuring device (Microtrac MT3300EX-II manufactured by Microtrac-Bell). As the surfactant, "Polyoxyethylene (10) octylphenyl ether " manufactured by Wako Pure Chemical Industries, Ltd. was used. The analysis conditions are shown below.

(Analysis conditions)
Number of measurements: Average value of 3 measurements Measurement time: 30 seconds Distribution display: Volume particle size classification: Standard Calculation mode: MT3000II
Solvent name: WATER
Upper limit of measurement: 2000 μm, lower limit of measurement: 0.021 μm
Residual ratio: 0.00
Passing ratio: 0.00
Residual ratio setting: Ineffective particle transmittance: Absorbing particle Refractive index: N/A
Particle shape: N/A
Solvent refractive index: 1.333
DV value: 0.0882
Transmittance (TR): 0.800 to 0.930
Extended filter: Invalid Flow rate: 70%
Ultrasonic output: 40W
Ultrasonic time: 180 seconds

(Measurement of standard deviation)
The standard deviation of the particle size distribution obtained above is an SD value calculated as summary data when measured using a Microtrack particle size distribution measuring device.

SD = (d84% - d16%) / 2
(In the formula, d84% is the particle diameter (μm) at the point where the cumulative curve is 84%, and d16% is the particle diameter (μm) at the point where the cumulative curve is 16%.)

The above results are summarized in Table 3.

Next, the performance of the adsorption filters of the examples and comparative examples was evaluated by the following tests.

[Polyethylene glycol (PEG) removal performance evaluation]
The PEG removal performance evaluation was carried out for the purpose of evaluating the filter's ability to remove decomposition products from the plating solution. In the PEG removal performance evaluation test, the plating solution was replaced with ion-exchanged water, the additives (high molecular weight organic compounds) added to the plating solution were replaced with polyethylene glycol 20,000 (PEG 20000) and polyethylene glycol 10,000 (PEG 10,000), and the decomposition products (low molecular weight organic compounds) generated from the additives in the plating solution were replaced with polyethylene glycol 4,000 (PEG 4,000) and polyethylene glycol 400 (PEG 400).

The PEG aqueous solutions were prepared by adding each of the above PEGs to ion-exchanged water so that the TOC concentration in the ion-exchanged water was approximately 1,650 mg/L, and 5 L of each of the four types of raw water was produced.

The adsorption filters obtained in each of the Examples and Comparative Examples were wrapped in the same nonwoven fabric as that used in producing the above filters, and cut to a thickness of 16.3 mm into cylindrical molded bodies. Gaskets made by punching out a 2 mm thick foamed polyethylene sheet into a doughnut shape with an outer diameter of 63 mmφ and an inner diameter of 30 mmφ were attached to both ends with hot melt to prepare evaluation test samples.

The above evaluation test sample was placed in a homemade column with an inner diameter of 70 mmφ and a structure that allows both ends of the molded body to be sealed with ribs, and the four types of stock solutions (PEG aqueous solutions) obtained above were circulated through the sample at 20°C and a flow rate of 0.5 L/min. The TOC concentration after 3 hours was measured and the removal rate from the stock solution was calculated. Since it is preferable to remove all decomposition products and additives, for PEG400 to PEG20,000, which correspond to decomposition products and additives, a removal rate of 23% or more was evaluated as pass (○), and if any of them was less than 23%, it was evaluated as fail (×).

A digital pump "07522-20" manufactured by Yamato Scientific Co., Ltd. was used as the liquid delivery pump, and a total organic carbon meter "TOC-Lcsh ASI-L" manufactured by Shimadzu Corporation was used for the TOC concentration measurement.

[Plating finish judgment]
The above evaluation samples were distributed to users, and the users were asked to judge the finish of plating performed using the copper sulfate plating solution refined from the samples. The evaluation criteria were as follows: ◯ if there were no problems, △ if it was judged usable, and × if it was unusable.

The above evaluation results are shown in Table 4.

(Discussion)
As is clear from Table 4, the adsorption filters of the Examples were shown to be capable of removing both additives (high molecular weight organic compounds) and decomposition products (low molecular weight organic compounds) in terms of PEG removal performance. In addition, good results were obtained in the plating finish evaluation regardless of which filter of the Examples was used.

On the other hand, in the comparative example in which the carbonized material of the molded body of the filter did not satisfy the requirements of the present invention, it was confirmed that although the decomposition products (low molecular weight organic compounds) could be removed, the additives (high molecular weight organic compounds) could not be sufficiently removed. Furthermore, the plating finish was also inferior to that of the examples.

This application is based on Japanese Patent Application No. 2019-199678 filed on November 1, 2019, the contents of which are incorporated herein by reference.

In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to specific examples, etc., but it should be recognized that a person skilled in the art can easily change and/or improve the above-mentioned embodiments. Therefore, as long as the changes or improvements made by a person skilled in the art are not at a level that deviates from the scope of the claims described in the claims, the changes or improvements are interpreted as being included in the scope of the claims.

The present invention has wide industrial applicability in technical fields such as adsorbents, adsorption filters, and plating solution purification.

Claims (9)

An adsorption filter for purifying a plating solution , comprising a molded body containing activated carbon,
The molded body is heat-treated in an inert gas at 500° C. for 1 hour to obtain a carbonized product having a specific surface area of 1500 to 2500 m ² /g; and
The adsorption filter for purifying a plating solution , wherein the carbonized material has pores having a BJH method mesopore volume of 0.1 cm ³ /g or more and an MP method micropore volume of 0.6 cm ³ /g or more. 2. The adsorptive filter for purifying a plating solution according to claim 1, wherein the specific surface area of the carbonized material is 1500 to 2100 m ² /g. 3. The adsorptive filter for purifying a plating solution according to claim 1, wherein the standard deviation of the volumetric particle size distribution of the charcoal is 70 μm or more. The adsorptive filter for purifying a plating solution according to any one of claims 1 to 3, wherein the carbonized material has a D50 of 120 to 450 µm. The adsorptive filter for purifying a plating solution according to any one of claims 1 to 4, wherein the ratio of D90 to D10 (D90/D10) of the carbonized material is 5.0 or more. 6. The adsorptive filter for refining a plating solution according to claim 1, wherein the activated carbon contained in the molded body contains 5 to 20 parts by mass of fibrous activated carbon having a specific surface area of 1700 m ² /g or more. The adsorption filter for refining a plating solution according to any one of claims 1 to 6, wherein the molded body further comprises a fibrous binder. A plating solution purification apparatus comprising the adsorption filter for purifying a plating solution according to any one of claims 1 to 7. A method for purifying a plating solution, comprising a step of passing a solution to be treated through the adsorption filter for purifying a plating solution according to any one of claims 1 to 7.

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