JP7305090B2 - Valuable metal powder recovery method from resist waste liquid and valuable metal powder recovery apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for recovering valuable metal powder contained in resist waste liquid, and an apparatus suitable for the recovery method.

2. Description of the Related Art In the manufacturing process of semiconductor devices such as ICs and LSIs, lithography technology is used for fine pattern processing. In lithography, after forming a resist pattern using a polymer resist material such as a photosensitive resin, gold, silver, palladium, platinum, rhodium, ruthenium, iridium, copper, nickel, cobalt, and a desired metal thin film (hereinafter referred to as a valuable metal thin film) such as chromium is formed, and then the resist is removed (lifted off) with a solvent such as stripping solution. Therefore, since the resist waste liquid contains a valuable metal thin film, it has been desired to recover the valuable metal. The recovery of valuable metals from resist waste liquid is also desired in the manufacturing processes of printed wiring boards, semiconductors and other products.

As a method for removing the solid content in the resist waste liquid, for example, it is known to separate and remove the solid content in a treatment tank provided with a plurality of filters (Patent Document 1). However, the valuable metal thin film in the resist waste liquid is partly micronized by contact in pipes, pumps, or storage tanks during the period from the resist waste liquid generation source to the supply to the processing tank. Therefore, a filter with a small opening is required in order to recover finely divided valuable metals (hereinafter referred to as valuable metal fine particles). However, there is also a valuable metal that exists in the form of a relatively large thin film (hereinafter referred to as a thin film of valuable metal), and the thin film of valuable metal has a large surface area, so there is a problem that it easily causes clogging of the filter. In addition, since the resist waste liquid has high viscosity, clogging is likely to occur if the opening of the filter is made small. Therefore, the filter requires frequent maintenance, which increases the cost of recovering valuable metals.

Japanese Patent Publication No. 2001-502847

The present invention has been made in view of the above circumstances, and its object is to establish a technique capable of separating and recovering valuable metal powder from resist waste liquid. Another object is to prolong the life of filtration membranes used for treatment of resist waste liquid.

The present invention, which has solved the above problems, has the following configuration.
[1] A method for recovering valuable metal powder from a resist waste liquid containing valuable metal powder, comprising a step of separating the resist waste liquid into a supernatant liquid containing floating valuable metal powder and a sediment containing sedimentary valuable metal powder. A method for recovering a valuable metal powder, comprising the steps of: adding insoluble particles to a supernatant liquid overflowing from the sedimentation separation step; and filtering the supernatant liquid containing the insoluble particles.

[2] The valuable metal powder recovery method according to [1], wherein the step of filtering comprises filtering the supernatant after forming the precoat layer.

[3] The method for recovering valuable metal powder according to [1] or [2], wherein the valuable metal powder contained in the resist waste liquid has a particle size of 0.1 μm or more.

[4] The valuable metal powder is at least one selected from the group consisting of gold, silver, palladium, platinum, rhodium, ruthenium, iridium, copper, nickel, cobalt, and chromium [1]-[3] The method for recovering valuable metal powder according to any one of the above.

[5] A precipitation mixer used in the sedimentation separation step and the insoluble particle addition step of the method for recovering valuable metal powder according to any one of [1] to [4], wherein the precipitation mixer comprises a valuable metal powder a sedimentation separation tank for separating the resist waste liquid containing the and an addition mixing vessel for adding the precipitation mixing apparatus.

[6] A filtration device used in the filtration step of the valuable metal powder recovery method according to any one of [1] to [4], wherein the filtration device has a precoat layer and a filtration membrane. .

[7] Valuable metal powder recovery equipment comprising the precipitation mixer described in [5] and the filtering device described in [6].

According to the present invention, valuable metal powder can be separated and recovered from resist waste liquid. Further, according to the present invention, it is possible to extend the life of the filtration membrane used for treating the resist waste liquid.

FIG. 1 is a schematic illustration of the flow of the valuable metal powder recovery method of the present invention. FIG. 2 is an exploded view of the precipitation mixer of the present invention, where (A) is a side view, (B) is a view from the sedimentation tank side, and (C) is a view from the mixing tank side. FIG. 3 is an exploded view of the precipitation mixer of FIG. 2, (D) is a view from the ceiling side, and (E) is a view from the bottom side. 4A and 4B are schematic explanatory diagrams of the filtering device, in which (A) is a side view, (B) is a front view, and (C) is a schematic explanatory diagram of the liquid mixture supply means as seen from the ceiling side. FIG. 5 is a graph showing changes in filtration rate in Examples. FIG. 6 is a graph showing changes in filtration rate in Examples.

The present inventors have studied a method for recovering valuable metal powder contained in resist waste liquid. Resist waste liquid contains valuable metal fine particles and valuable metal thin films of various sizes, and these must be treated simultaneously (hereinafter, valuable metal fine particles and valuable metal thin films are collectively referred to as valuable metal powder). Moreover, since the resist waste liquid is highly viscous due to the resist, there is a problem that the filter is easily clogged. The present inventors attempted to collect valuable metal powder step by step by providing multiple filters with different openings, but clogging occurred in the filters in a short period of time and the filters had to be replaced frequently. . As another method for recovering valuable metal powder, for example, we considered collecting the valuable metal powder from the resist waste liquid by sedimenting it, but in order to process the resist waste liquid discharged from the factory in a short time, a large sedimentation tank is required. As a result, it was difficult to secure the installation space. As described above, the conventional method for recovering valuable metal powder requires frequent maintenance, and in order to secure a sufficient throughput, the apparatus must be large, which requires a large installation space.

The inventors of the present invention have extensively studied a method for recovering valuable metal powder. In this case, it was found that if insoluble particles were added to the supernatant prior to filtration, the valuable metal powder could be recovered in a high yield while saving space. In particular, according to the present invention, it was found that the frequency of maintenance can be greatly reduced because the service life of the filtration membrane can be extended.

Hereinafter, the valuable metal powder recovery method of the present invention and an apparatus suitable for the valuable metal powder recovery method will be described.

The method of recovering valuable metal powder from the resist waste liquid of the present invention has the following steps.
(1) A step of separating a valuable metal powder-containing resist waste liquid into a floating valuable metal powder-containing supernatant liquid and a sedimentary valuable metal powder-containing sediment (hereinafter referred to as sedimentation separation step).
(2) A step of adding insoluble particles to the supernatant liquid overflowed from the sedimentation separation step (hereinafter referred to as an addition step)
(3) A step of filtering the insoluble particle-containing supernatant (hereinafter referred to as a filtering step)
Valuable metal powder can be recovered in a high yield from the resist waste liquid as a precipitate or filtration residue by the recovery method described above. Moreover, the maintenance period of the filtration membrane can be greatly extended.

(Resist waste liquid)
The resist waste liquid targeted by the present invention includes various known polymeric resist components such as phenolic resins, various known resist removers such as developer, etchant, and cleaning liquid used for removing the resist, and valuable metal powder. It is a waste liquid containing Moreover, the resist waste liquid may contain various additives such as a photosensitizer and a solvent. Although the composition of the resist waste liquid varies depending on the source of discharge, all of them can be treated by the present invention. The resist waste liquid has viscosity due to the resist material, but the viscosity of the resist waste liquid targeted by the present invention varies depending on the discharge source and is not particularly limited. The viscosity of the resist waste liquid is, for example, 1.0 cP or more at room temperature.

Valuable metal powder contained in the resist waste liquid in the present invention is exemplified by gold, silver, palladium, platinum, rhodium, ruthenium, iridium, copper, nickel, cobalt, and chromium. Valuable metal powder to be recovered is preferably at least one selected from the group consisting of gold, silver, palladium, platinum, rhodium, ruthenium, iridium, copper, nickel, cobalt, and chromium, more preferably gold. . Therefore, if the sediment or filtration residue contains metals other than those to be recovered, they may be separated by various known methods. Valuable metals to be recovered in the present invention are metals deposited in the resist waste liquid in the form of fine particles or thin films, and do not include undeposited metals.

The concentration of the valuable metal powder in the resist waste liquid is not particularly limited because it varies depending on the amount of the valuable metal used, the amount of the resist, the amount of the resist remover, etc. in various manufacturing processes such as the semiconductor manufacturing process. In the present invention, valuable metal powder can be recovered at a high yield without causing problems such as clogging even if the resist waste liquid has a high concentration of valuable metal powder. Therefore, the concentration of the valuable metal powder contained in the resist waste liquid may be preferably 0.001 g/L or more, more preferably 0.01 g/L or more. Moreover, an upper limit is not specifically limited. The valuable metal powder concentration is measured by filtering the resist waste liquid, drying the residue together with the filter paper, measuring the weight, and subtracting the dry weight of the filter paper to calculate the solid weight.

The maximum particle size of the valuable metal powder contained in the resist waste liquid is preferably 0.1 μm or more. Valuable metal powder in the resist waste liquid is made finer by collision or the like during the transfer process. high yields can be achieved. The upper limit of the maximum particle diameter of the valuable metal powder and the film thickness of the thin-film valuable metal powder are not limited because they depend on the manufacturing conditions in the semiconductor manufacturing process. The maximum particle size of the valuable metal powder in the present invention is measured with a laser diffraction/scattering particle size distribution analyzer.

Hereinafter, the valuable metal powder recovery method of the present invention will be described based on FIG.
A resist waste liquid is supplied to a sedimentation separation process 3 of the present invention from a resist waste liquid generation source 1 such as a semiconductor manufacturing process. The resist waste liquid may be supplied to the sedimentation separation process 3 directly from the resist liquid waste generation source 1 or once stored in the resist liquid waste storage tank 2 . By providing the resist waste liquid storage tank 2, it is not necessary to stop the production line for semiconductors or the like even during maintenance of the valuable metal powder recovery process of the present invention. Further, by providing the resist waste liquid storage tank 2, the component composition of the resist waste liquid supplied to the valuable metal powder recovery process of the present invention can be made uniform. Furthermore, the supply amount of the resist waste liquid can be adjusted according to the processing amount of the valuable metal powder recovery step of the present invention. The resist waste liquid may be supplied continuously to the sedimentation separation step 3, or may be supplied in fixed amounts at a time and subjected to batch treatment. Batch processing is preferable in consideration of the sedimentation efficiency of the valuable metal powder in the sedimentation separation step 3 .

(1) Sedimentation Separation Step The sedimentation separation step 3 of the present invention is a step of separating the resist waste liquid into a supernatant liquid containing floating valuable metal powder and a sediment containing sedimentary valuable metal powder. By precipitating part of the valuable metal powder in the resist waste liquid, the concentration of the valuable metal powder in the supernatant can be reduced. Therefore, clogging of the filtration membrane due to the valuable metal powder can be suppressed when the supernatant liquid is filtered in the filtration process. In the present invention, both the floating valuable metal powder and the precipitating valuable metal powder are valuable metal powder in the resist waste liquid. Precipitable valuable metal powder is defined as valuable metal powder and precipitated valuable metal powder with high specific gravity. The supernatant means the resist waste liquid supplied from the sedimentation separation process 3 to the addition process 4 .

In order to suppress clogging of the filter membrane in the filtration step 7, it is desirable to precipitate valuable metal powder in the resist waste liquid in the sedimentation separation step 3 as much as possible. The amount of the valuable metal powder to be precipitated may be appropriately determined according to the concentration of the valuable metal powder in the resist waste liquid, the throughput of the filtration step 7, and the like. For example, the amount of valuable metal powder in the supernatant liquid supplied from the sedimentation separation process 3 to the addition process 4 with respect to the amount of valuable metal powder in the resist waste liquid introduced into the sedimentation separation process 3 (= the amount of valuable metal powder in the supernatant liquid ( g)/amount of valuable metal powder in resist waste liquid (g)×100%) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less. is.

The separation treatment conditions in the sedimentation separation step 3, particularly the residence time of the resist waste liquid, may be appropriately determined so that the valuable metal powder in the supernatant liquid has a predetermined concentration. Also, the precipitated valuable metal powder may be recovered by various known methods. In the present invention, sedimentation separation of the valuable metal powder is carried out by natural sedimentation, and various additives such as flocculants are not added.

In the present invention, it is also preferable to remove the valuable metal powder floating in the vicinity of the water surface of the resist waste liquid among the valuable metal powder floating in the resist waste liquid in the sedimentation separation step 3 . By removing the valuable metal powder floating near the water surface of the resist waste liquid, the concentration of the valuable metal powder in the supernatant supplied to the next step can be further reduced. Valuable metal powder in the vicinity of the water surface of the resist waste liquid is removed by any means, such as contacting a non-woven fabric with the resist liquid waste to attach the valuable metal powder to the non-woven fabric, or by using a solid-liquid separation means such as a filter. may be removed. Alternatively, as will be described later, a plate member such as a blocking plate 16 may be provided to prevent the resist waste liquid from overflowing.

When the resist waste liquid is supplied to the sedimentation separation step 3 in a batch manner, the water level of the resist waste liquid rises as new resist liquid waste is supplied. Further, when the resist waste liquid is continuously supplied to the sedimentation separation process 3, the surface of the resist waste liquid rises continuously. When the resist waste liquid in the sedimentation separation process 3 exceeds a certain water level, the excess amount is supplied to the addition process 4 as a supernatant liquid. In the present invention, the resist waste liquid is supplied from the sedimentation separation process 3 to the addition process 4 by overflow. Therefore, compared with the case where the resist waste liquid is transferred by connecting the processes with pipes, pumps, etc., it is possible to suppress the reduction of the valuable metal powder into fine particles, which is effective in suppressing the clogging of the filtration membrane.

(2) Addition step The addition step 4 of the present invention is a step of adding insoluble particles to the supernatant liquid overflowed from the sedimentation separation step 3 . Since the insoluble particles also function as a body feed in the subsequent filtration step 7, adhesion of valuable metal powder and resist components to the filtration membrane can be suppressed.

(Insoluble particles)
The insoluble particles used in the present invention are solids that are insoluble in the resist waste liquid. Organic particles or inorganic particles that are insoluble in the resist removing liquid contained in the resist waste liquid are preferred, and inorganic particles are more preferred. Also, the insoluble particles are preferably porous. The porous insoluble particles adsorb fine valuable metal powder among the valuable metal powder in the supernatant liquid, and retain the valuable metal powder in the pores during filtration, further reducing the adhesion of valuable metal powder to the filtration membrane. can. Moreover, the insoluble particles preferably have a specific gravity to the extent that they precipitate during filtration.

Examples of insoluble particles include organic adsorbents such as cellulose and carbon, and inorganic adsorbents such as diatomaceous earth, perlite, and glass beads. Among these, porous inorganic adsorbents are preferred, and diatomaceous earth is more preferred. The insoluble particles may be used singly or in combination of two or more.

The average particle size of the insoluble particles is preferably 1 µm or more, more preferably 5 µm or more, still more preferably 20 µm or more, and preferably 100 µm or less, more preferably 80 µm or less, and still more preferably 40 µm or less. From the viewpoint of improving the body-feeding effect, the average particle diameter of the insoluble particles is preferably as large as possible. Also, if the average particle diameter of the insoluble particles having porosity is too large, the adsorption amount of the fine valuable metal powder may decrease due to the decrease in the surface area.

The amount of the insoluble particles added varies depending on the concentration of the valuable metal powder in the resist waste liquid and the specific gravity of the insoluble particles to be added. It is preferably 0.01 g/L or more, preferably 10 g/L or less, more preferably 5 g/L or less, and still more preferably 1 g/L or less. As the amount of the insoluble particles added increases, the above effects are enhanced, but if the amount is too large, the amount of treatment increases.

The added insoluble particles are preferably mixed with the supernatant and dispersed uniformly. The insoluble particles may be added to the supernatant as they are in powder form, or after being added to a solvent such as water to form a liquid (hereinafter referred to as "insoluble particle-containing liquid"). A liquid containing insoluble particles is preferable in an environment such as a clean room where scattering of powder is undesirable.

Since the insoluble particles added to the supernatant tend to settle, it is desirable to stir the supernatant to maintain a uniformly dispersed state. A means for stirring the supernatant is not particularly limited. For example, it is preferable to agitate the supernatant with non-mechanical agitation means. Examples of non-mechanical stirring means include injection means such as nozzles. For example, a gas such as air; a liquid such as a liquid containing insoluble particles or a supernatant liquid in a mixing vessel is preferably supplied from a jet means to the supernatant liquid, and agitated by jet flow (hereinafter referred to as non-mechanical means). In the present invention, the insoluble particle-containing liquid prepared in advance may be stored in the insoluble particle storage tank 5, and may be supplied from the tank 5 to the supernatant liquid through an injection means such as a nozzle, or The supernatant liquid may be extracted and supplied from the injection means, and the supernatant liquid may be circulated.

(3) Filtration Step Filtration step 7 is a step of solid-liquid separation of the supernatant liquid to which insoluble particles have been added (hereinafter referred to as mixed liquid) into valuable metal powder-containing residue and valuable metal powder-free waste liquid. After filtration, the valuable metal powder can be recovered from the residue containing the valuable metal powder by known means. Filtration is superior to other solid-liquid separation means such as sedimentation separation, centrifugation, filter separation, etc., because it is excellent in recoverability of valuable metal powder, maintainability, space saving, processing speed, and the like.

The filtration membrane used for filtration may be appropriately determined in consideration of the yield of the valuable metal powder, processing efficiency, and the like. The smaller the pore size of the filtration membrane, the higher the yield of the valuable metal powder. On the other hand, if the pore size of the filtration membrane is too small, clogging due to resist components is likely to occur. In the present invention, the transfer of the supernatant liquid from the sedimentation separation step 3 to the addition step 4 and the mixing of the supernatant liquid and the insoluble particles suppress the refinement of the valuable metal powder. If the metal powder can be collected, a sufficiently high yield, for example, preferably 99% or more, more preferably 99.9% or more, of the valuable metal powder contained in the mixed liquid can be recovered. Therefore, according to the present invention, it is possible to secure a high yield while suppressing clogging for a long period of time.

Specifically, microfiltration (MF) is preferred. Valuable metal powder can be collected by ultrafiltration (UF) and nanofiltration (NF), but clogging may occur easily due to resist components and valuable metal powder. preferable. Considering that the object to be recovered in the present invention is valuable metal powder having a maximum particle size of 0.1 μm or more, the pore size of the filtration membrane is preferably 0.01 μm or more, more preferably 0.05 μm or more, and preferably 10 μm or less. 5 μm or less is more preferable. Filtration may be natural filtration, vacuum filtration, or pressure filtration, but from the viewpoint of improving the filtration rate, vacuum filtration or pressure filtration is preferable.

Filtration membrane materials include organic membranes such as polyethylene, tetrafluoroethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, and pulp, and inorganic membranes such as aluminum oxide, zirconium oxide, titanium oxide, stainless steel, and glass. are exemplified. It is desirable that the material of the filtration membrane be appropriately selected in consideration of the durability and the like according to the liquid properties of the resist waste liquid (for example, pH, liquid temperature, composition of organic substances, components to be removed from the resist, etc.). In the present invention, paper filter paper and glass filter paper are preferred.

Filtration conditions may be appropriately determined in consideration of the performance of the filtration device. For example, the filtration flow rate is 20 L/min and the filtration pressure is -0.07 MPa.

In the present invention, it is preferable to form the precoat layer 6 before filtering. By providing the precoat layer 6, clogging of the filter medium with valuable metal powder and resist components can be further suppressed. As the material for forming the precoat layer 6, the materials exemplified as the insoluble particles can be preferably used. Also, the materials used for the precoat layer 6 may be used alone or in combination of two or more. The difference between the material used for the precoat layer 6 and the material used for the insoluble particles does not matter.

Insoluble particles contained in the liquid mixture supplied from the addition step 4 to the filtration step 7 are sequentially deposited on the filtration membrane or the precoat layer 6 to form a filter cake. Therefore, the outermost surface of the filter cake is sequentially renewed, and an increase in cake resistance accompanying the progress of filtration can be suppressed, and clogging of the filtration membrane can be suppressed for a long time.

As described above, according to the present invention, the valuable metal powder can be separated and recovered from the resist waste liquid. Further, according to the present invention, it is possible to extend the life of the filtration membrane used for treating the resist waste liquid.

Valuable metal powder recovery equipment suitable for the method for recovering valuable metal powder of the present invention will be described below with reference to FIGS.

Valuable Metal Powder Recovery Equipment Valuable metal powder recovery equipment suitable for the valuable metal powder recovery method of the present invention has at least a precipitation mixing device 10 (FIGS. 2 and 3) and a filtering device 11 (FIG. 4). The valuable metal powder recovery equipment of the present invention may further have a resist waste liquid storage tank (2 in FIG. 1) and/or an insoluble particle-containing liquid storage tank (5 in FIG. 1). These devices and tanks are interconnected by pipes (8a to 8e in FIG. 1). In addition, the pipes are provided with pumps and valves (not shown) as necessary to adjust the amount of supply.

Sedimentation and Mixing Apparatus The precipitation and mixing apparatus 10 of the present invention is configured to have a sedimentation tank 12 for performing the sedimentation separation step 3 and a mixing tank 13 for performing the addition step 4 . The precipitation mixer 10 is preferably rectangular parallelepiped or cubic. The partition 17 is installed so that a gap is formed between the ceiling surface 22 and the upper end of the partition 17 . By providing the gap, when the liquid surface of the resist waste liquid in the sedimentation tank 12 exceeds the upper end of the partition wall 17 , it overflows and is supplied to the mixing tank 13 . Note that, unlike the illustrated example, when the partition 17 is installed so as to be in contact with the ceiling surface 22, an opening is provided in the partition 17 and the supernatant liquid is supplied to the mixing tank 13 from the opening. good too.

Sedimentation Tank The sedimentation tank 12 is a means for allowing the resist waste liquid to stay for a predetermined period of time to precipitate at least part of the valuable metal powder. The sedimentation tank 12 has a resist waste liquid supply port 19 and a channel plate 14 . Below, the space between the channel plate 14 and the wall surface 20c of the sedimentation tank 12 (that is, the side where the resist waste liquid supply port 19 is provided) is defined as the first sedimentation part 30, and the space between the channel plate 14 and the partition wall 17 is sometimes referred to as a second sedimentation section 31.

The resist waste liquid supply port 19 is means for supplying the resist waste liquid supplied from the resist waste liquid generation source to the sedimentation tank 12 . The resist waste liquid supply port 19 is connected to a resist waste liquid generation source, a resist waste liquid storage tank, and the like in a semiconductor manufacturing process (not shown). The resist waste liquid supply port 19 is provided on the ceiling surface 22 on the first sedimentation section 30 side. The position of the lower end of the resist waste liquid supply port 19 is not particularly limited. In the illustrated example, it extends to the vicinity of the resist waste liquid receiving portion 15 .

The channel plate 14 is means for controlling the flow of the supplied resist waste liquid. The channel plate 14 is provided between the wall surface 20 c of the sedimentation tank 12 and the partition wall 17 . The side surfaces of the channel plate 14 are fixed to the opposed wall surfaces 20a and 20b of the sedimentation tank 12 as shown in FIG. The upper end portion of the channel plate 14 may be higher than the upper end portion of the partition wall 17 and may or may not come into contact with the ceiling surface 22 of the sedimentation tank 12 . Further, the lower end of the channel plate 14 is installed so as to form a gap with the bottom surface 21 of the sedimentation tank 12 . The resist waste liquid supplied from the first sedimentation section 30 side passes through the gap between the lower end of the channel plate 14 and the bottom surface 21 of the sedimentation tank 12 and is supplied to the second sedimentation section 31 side. The lower end of the channel plate 14 is preferably lower than the upper end of the partition wall 17 or, if an opening is provided in the partition wall 17, the opening (hereinafter the same). If the gap between the lower end of the channel plate 14 and the bottom surface 21 of the sedimentation tank 12 is too narrow, the flow velocity of the resist waste liquid passing through the gap becomes faster, and sediments may be swirled up. From the viewpoint of suppressing such curling up, the height of the gap between the lower end of the channel plate 14 and the bottom surface is preferably about 20% of the height of the sedimentation tank, more preferably 10% or more. be. By providing the channel plate 14 , the flow velocity of the supplied resist waste liquid can be attenuated, and as a result, sedimentation inhibition of the valuable metal powder in the resist waste liquid staying in the second sedimentation section 31 can be suppressed.

An inclined plate 18 may be provided on the bottom surface 21 of the sedimentation tank 12 as required. The inclined plate 18 is means for moving the sediment from the first sedimentation section 30 side to the second sedimentation section 31 side. It is preferable to install the inclined plate 18 so that it becomes lower toward the partition wall 17 from the wall surface 20c side of the first sedimentation section 30 side. Since the resist waste liquid supplied from the resist waste liquid supply port 19 passes through the gap at the lower end of the channel plate 14, sediments are likely to accumulate in the vicinity of the gap. Therefore, if the inclined plate 18 is provided, it is possible to suppress the accumulation of sediment in the gap. In addition, since the sediment accumulates on the second sedimentation section 31 side, the sediment can be easily recovered.

A blocking plate 16 may be provided in the sedimentation tank 12 if necessary. The blocking plate 16 is a means for suppressing the valuable metal powder floating on the surface of the resist waste liquid from being supplied to the mixing tank 13 together with the supernatant liquid. The side surfaces of the blocking plate 16 are fixed to the opposing wall surfaces 20a and 20b of the sedimentation tank 12 shown in FIG. The lower end of the blocking plate 16 is installed so as to be lower than the upper end of the partition wall 17 . Also, the lower end surface of the blocking plate 16 is preferably horizontal to the wall surfaces 20a and 20b. The lower end of the blocking plate 16 may be installed so as to form a space between it and the bottom surface 21 of the sedimentation tank 12 . The lower end of the shielding plate 16 may be positioned preferably 1 cm to 5 cm, more preferably 5 cm to 10 cm, lower than the upper end of the partition wall 17 . The upper end of the blocking plate 16 may be higher than the upper end of the partition wall 17 so that the resist waste liquid does not overflow, and it does not matter whether or not the plate is in contact with the ceiling surface 22 of the sedimentation tank 12 . The blocking plate 16 may be installed at an angle with respect to the wall surface 20c of the sedimentation tank 12. In this case, the blocking plate 16 is placed so that the partition wall 17 side of the blocking plate 16 is on the upper side and the channel plate 14 side is on the lower side. A tilt is preferred. When the blocking plate 16 is inclined, the valuable metal powder accumulated on the blocking plate 16 is pushed out toward the partition wall 17 (in the direction opposite to the liquid surface), so that the accumulated valuable metal powder returns to the resist waste liquid. Valuable metal powder can be efficiently recovered without

The sedimentation tank 12 may be provided with a resist waste liquid receiver 15 as required. The resist waste liquid receiver 15 is means for attenuating the flow velocity of the resist waste liquid supplied from the resist waste liquid supply port 19 . In the illustrated example, the resist waste liquid receiving portion 15 has a bottom surface and four wall surfaces, and the ceiling surface has an open shape. As shown in the figure, the side surfaces of the resist waste liquid receiver 15 are fixed to the walls 20a and 20b of the sedimentation tank 12. As shown in FIG. A gap 32 is provided between the wall surface 20c and the resist waste liquid receiver 15. As shown in FIG. The supplied resist waste liquid is supplied to the first sedimentation section 30 from the opening 15a of the resist waste liquid receiving section 15 along the wall surface 20c.

A discharge port 38 is preferably provided on the bottom surface 21 of the sedimentation tank 12 . The discharge port 38 is means for discharging the sediment in the sedimentation tank 12 . The resist waste liquid in the sedimentation tank 12 may be discharged together with the sediment from the discharge port 38, or an extraction port 36 may be provided separately from the discharge port 38 to extract the resist waste liquid. An extraction port 36 may be provided at an arbitrary position in the sedimentation tank 12, preferably in the vicinity of the bottom surface 21, and the sediment may be recovered from the sedimentation tank 12 after the resist waste liquid is discharged. The discharged resist waste liquid may be returned to the resist waste liquid storage tank and supplied to the sedimentation tank 12 again. Alternatively, the discharged resist waste liquid may be supplied to the filtering device 11 for solid-liquid separation.

Mixing Tank The mixing tank 13 is means for adding insoluble particles to the supernatant liquid supplied from the sedimentation tank 12 and stirring and mixing them. The mixing tank 13 has an insoluble particle supply means 34 , a stirring/mixing means 35 and a discharge port 33 .

The insoluble particle supplying means 34 is means for supplying insoluble particles to the supernatant liquid supplied to the mixing tank 13 . The tip portion of the insoluble particle supplying means 34 is not particularly limited, and known supplying means such as a nozzle can be employed. The insoluble particle supply means 34 is connected to an insoluble particle supply source such as an insoluble particle storage tank (not shown), and is configured to supply the insoluble particles to the mixing tank 13 via a supply means such as a pump. The powdery insoluble particles may be supplied by a feeder or the like, or the insoluble particles may be mixed with a liquid or the like and supplied by compressed air or the like. Considering the treatment with a filtering device, it is also preferable to supply the insoluble particles in the form of powder rather than mixing them with the liquid. It is desirable to adjust the installation position of the tip of the insoluble particle supply means 34 so that the supplied insoluble particles do not scatter. For example, when diatomaceous earth is supplied as insoluble particles by compressed air, when the tip of the insoluble particle supply means 34 is in contact with the supernatant liquid in the mixing tank, the supernatant liquid is bubbled by the compressed air, causing the diatomaceous earth to scatter, and the sedimentation tank. 12 may be mixed. Therefore, it is desirable to install the tip portion so as not to contact the liquid surface.

The stirring/mixing means 35 is means for stirring and mixing the supernatant liquid and the insoluble particles. The stirring/mixing means 35 has injection means such as nozzles 37a and 37b at the tip thereof, and the liquid or gas ejected from the nozzles 37a and 37b causes the supernatant liquid to flow. From the viewpoint of suppressing the fineness of the valuable metal powder at the time of mixing, it is desirable that the injection means be installed so that the supernatant liquid flows in a spiral shape by the injection material at the tip of the stirring/mixing means 35 . From the viewpoint of efficiently flowing the supernatant liquid, the vicinity of the bottom surface 21 is more preferable. The number of stirring/mixing means 35 installed is one or two or more, preferably two. In the illustrated example, nozzles 37a and 37b, which are injection means, are installed on diagonal lines in the horizontal plane. The stirring/mixing means 35 is connected to the bottom of the mixing tank 13 , that is, to the discharge port 33 . During operation, the supernatant liquid extracted from the mixing tank 13 via a pump (not shown) is supplied from the supply port 35a of the stirring/mixing means 35 and injected into the supernatant liquid from the nozzles 37a and 37b.

The discharge port 33 is means for extracting the supernatant liquid mixed with the insoluble particles (hereinafter referred to as mixed liquid). The pipe connected to the discharge port 33 is branched and connected to the supply port 35 and the filter device 11 . It is preferable that each of the branched pipes is provided with an adjusting means such as a valve. The discharge port 33 is provided on the bottom surface of the mixing tank 13, and the mixed liquid is appropriately extracted from the discharge port 33 and supplied to the filtration membrane 39 from the mixed liquid supply means 40 of the filtering device 11 through a pipe (not shown). For example, adjusting means such as a valve or a temporary storage tank may be provided to adjust the amount of supernatant liquid supplied to the filtering device 11 .

Filtration Device As the filtration device used in the present invention, an industrially used filtration device can be used. Therefore, it is not limited to the illustrated example, and can be changed as appropriate. The filtering device 11 is means for separating the supernatant liquid into a valuable metal powder-containing residue and a waste liquid from which the valuable metal powder has been removed (hereinafter referred to as a treated liquid). The filtering device 11 has a filtering membrane 39 and a liquid mixture supplying means 40 . A filtration membrane having desired filtration performance is used for the filtration membrane 39 . It is preferable that the peripheral portion of the filtration membrane 39 is fixed by a fixing means such as a protective plate 44 . In the illustrated example, the filter membrane 39 is shown through.

The mixed liquid supply means 40 is means for supplying the mixed liquid supplied from the mixing tank 13 to the filtration membrane 39 . The mixed liquid supply means 40 has a supply port 42 for supplying the mixed liquid to the filtration membrane 39 . In the illustrated example, the liquid mixture is supplied to the filtration membrane 39 from the supply port 42 via the supply path 43a installed so that the mixed liquid flows down in the vertical direction and the supply path 43b installed so that the mixed liquid flows in the horizontal direction. configured to be supplied. Specifically, the supply path 43b is formed in a ring shape as shown in FIG. 4(C). Further, the supply port 42 is arranged obliquely downward on the outer side of the ring-shaped supply path 43 b , preferably so that the mixed liquid hits the protective plate 44 . With such a configuration, the mixed liquid supplied from the supply port 42 is supplied to the filtration membrane 39 after the drop impact is attenuated by the protective plate 44 . Moreover, if the distance from the supply port 42 to the protective plate 44 is long, the droplets dropped from the supply port 42 may rebound and damage the filtration membrane 39 . Therefore, it is preferable that the distance between the supply port 42 and the protection plate 44 is as short as possible. A specific distance can be appropriately set in consideration of the droplet size, the strength of the filtration membrane, and the like. Note that the precoat layer 41 is omitted in FIG. 4(C). The filtrate is temporarily stored in filtrate tank 46 and then treated as appropriate.

A precoat layer 41 may be provided on the filtration membrane as necessary. For the precoat layer 41, various known precoat materials already exemplified can be used. It is also possible to use insoluble particles of the invention.

Hereinafter, a method for recovering valuable metal powder from a resist waste liquid using the apparatus of the present invention will be described.

The resist waste liquid is supplied batchwise or continuously from the resist waste liquid supply port 19 to the sedimentation tank 12 . The resist waste liquid is supplied to the first sedimentation section 30 through the wall surface 20c from the opening 15a provided in the resist waste liquid receiving section 15, and further through the gap between the lower end of the channel plate 14 and the bottom surface 21 to the second sedimentation section. 31 side. When the liquid surface of the resist waste liquid becomes higher than the upper end of the partition wall 17 in the second sedimentation section 31 , it overflows and is supplied to the mixing tank 13 . A sediment containing valuable metal powder accumulates in the lower part of the sedimentation tank 12 . Also, part of the valuable metal powder floating on the liquid surface of the resist waste liquid accumulates on the blocking plate 16 . Insoluble particles are supplied from the insoluble particle supplying means 34 to the supernatant introduced into the mixing tank 13 . Also, the supernatant liquid extracted from the discharge port 33 is injected into the supernatant liquid from the nozzles 37a and 37b. The supernatant liquid is swirled by the injection, and the supernatant liquid and the insoluble particles are mixed. After being mixed for a predetermined time, the mixed liquid extracted from the discharge port 33 is supplied to the mixed liquid supply means of the filtering device 11 . The mixed liquid is supplied to the filtration membrane 39 from the supply port 42 via the supply paths 43a and 43b. The mixed liquid is separated by the filtration membrane 39 into a solid containing valuable metal powder and a treated liquid from which the valuable metal powder has been removed. Valuable metal powder is recovered from the sedimentation tank 12 as a sediment, as an accumulation on the blocking plate 16, and from the filter 11 as a filtration residue.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be modified appropriately within the scope that can conform to the gist of the above and later descriptions. It is of course possible to implement them, and all of them are included in the technical scope of the present invention.

Experiment 1
Gold powder was recovered from the resist waste liquid under the following conditions, and the service life of the used filtration membrane was examined. The life of the filtration membrane was judged to have reached its end when the resist waste liquid supply rate to the filtration membrane exceeded the filtration rate. Specifically, the filtration life was determined when the filtration rate became less than 0.043 mL/sec·4.9 cm ² . The results of each experiment are shown in Table 1, and the relationship between the throughput of the filtration membrane and the filtration rate is shown in FIG.

Filtration membrane lifetime was obtained by filtering 200 ml of 4 L of supernatant liquid at a time and creating a filtration time transition data graph. From the function of the graph, the amount of liquid passing when the filtration rate becomes the lower limit (0.043 ml/sec 4.9 cm ² ) that can be tolerated is obtained, and the average amount of resist waste liquid discharged from the factory where the installation is assumed ( L/day) was used to calculate the number of days.

Comparative example 1
Resist components discharged from semiconductor manufacturing plants, resist stripping solution, and resist waste liquid (52 L) containing gold powder (0.04 g / L) are supplied to a sedimentation tank (width 320 mm x depth 460 mm x height 500 mm) Sedimentation separation of metal powder was performed. After 50 minutes, the supernatant liquid (10 L) was extracted and subjected to suction filtration (filtration pressure: -0.07 MPa). A 1 μm glass filter paper (filtration area: 4.9 cm ² ) was used as the filter paper, and neither body feeding nor precoating was performed.

Comparative example 2
Filtration was performed in the same manner as in Comparative Example 1, except that a precoat layer of diatomaceous earth (0.2 g: Radiolite (registered trademark) #800 manufactured by Showa Kagaku Kogyo Co., Ltd.) was formed during the filtration. Filtration area: precoated with 0.2 g of diatomaceous earth per 4.9 cm ² .

Example 1
In the same manner as in Comparative Example 1, the resist waste liquid was supplied to the sedimentation tank to separate the gold powder by sedimentation. After sedimentation and separation, the supernatant (10 L) was transferred to another beaker, 0.5 g of diatomaceous earth powder was added as insoluble particles, and the mixture was stirred with a glass rod for about 10 seconds to mix the supernatant and diatomaceous earth. The resulting mixed solution was subjected to suction filtration (filtration pressure: -0.07 MPa). A 1 μm glass filter paper (filtering area: 4.9 cm ² ) was used as the filter paper.

Example 2
Filtration was performed in the same manner as in Example 1, except that a precoat layer of diatomaceous earth (0.2 g) was formed on the filtration membrane to a thickness of about 2 mm.

Table 1 and FIG. 5 show the following.
It can be seen that in Examples 1 and 2, the life of the filtration membrane was remarkably extended by adding insoluble particles to the supernatant. Furthermore, it can be seen that the life of the filtration membrane was further extended by providing the precoat layer.

On the other hand, in Comparative Examples 1 and 2, in which no insoluble particles were added, the lifetime of the filtration membrane was remarkably short regardless of the presence or absence of the precoat layer. Compared with Comparative Example 1, Example 1 was three times or more, and Example 2 was four times or more.

In addition, when the concentration of gold powder in the treated liquid after filtration in Examples 1 and 2 and Comparative Examples 1 and 2 was examined, gold powder was not contained in any of them. This result was achieved by the filtration performance of the filtration membrane, but the life of the filtration membrane differs depending on the treatment method as described above. Therefore, Examples 1 and 2 have superior effects as compared with Comparative Examples 1 and 2 in consideration of filtration life.

Experiment 2
The amount of the insoluble particles added in Example 1 was changed as shown in Table 2, and the service life of the filtration membrane was similarly examined. Although the gold powder content of the resist waste liquid used was the same (0.04 g/L), the resist waste liquid contained the stripping solution before the renewal, so the concentration of the resist component was higher than in Experiment 1, and the viscosity was high. there were. The results of each experiment are shown in Table 2, and the relationship between the throughput of the filtration membrane and the filtration rate is shown in FIG.

As shown in Table 2, the higher the concentration of the insoluble particles added to the supernatant, the longer the filtration life.

Experiment 3
No. 3-1
An experiment was conducted in the same manner as in Example 1 except that the resist waste liquid used in Experiment 2 was used.
No. 3-2
An experiment was conducted in the same manner as in Example 2, except that the resist waste liquid used in Experiment 2 was used.
Table 3 shows the results.

Forming a precoat layer as shown in Table 3 extended the life of the filtration membrane. Considering the results of Examples 1 and 2, the formation of the precoat layer extends the life of the filtration membrane regardless of the properties of the resist waste liquid, and can reduce the frequency of maintenance.

Experiment 4
The gold powder concentration before and after sedimentation was investigated. Specifically, the resist waste liquid (5 L) used in Experiment 1 was supplied to a sedimentation tank (width 320 mm × depth 57.5 mm × height 500 mm) at the amount shown in Table 4, and The concentration of gold powder contained in the treated resist waste liquid and the concentration of gold powder contained in the resist waste liquid after treatment were measured, respectively, and the removal rate of gold powder in the sedimentation separation was investigated. The conditions were the same except for the liquid flow rate. The concentration of gold powder contained in the resist waste liquid before sedimentation and separation was 0.3045 g/L each time. Table 4 shows the results of examining the concentration of gold powder contained in the resist waste liquid after sedimentation and separation. Experiments were performed four times using the same resist effluent. Table 4 shows the results.

From the results in Table 4, the concentration of gold powder in the resist waste liquid after sedimentation separation was high in the fourth experiment in which the liquid flow rate was high. Therefore, it can be seen that the concentration of gold powder contained in the resist waste liquid after sedimentation and separation can be reduced by appropriately controlling the liquid flow rate. Since the particle size distribution of the gold powder was not constant for each test, the passage rate and the like fluctuated, but generally good results were obtained.

1 Resist waste liquid generation source 2 Resist waste liquid storage tank 3 Sedimentation separation process 4 Addition process 5 Insoluble particle storage tank 6 Precoat layer 7 Filtration processes 8a to 8e Pipe 10 Precipitation mixing device 11 Filtering device 12 Sedimentation tank 13 Mixing tank 14 Channel plate 15 Resist waste liquid receiving portion 15a Opening 16 Blocking plate 17 Partition wall 18 Inclined plate 19 Resist waste liquid supply ports 20a, 20b, 20c Wall surface 21 Bottom surface 22 Ceiling surface 30 First sedimentation section 31 Second sedimentation section 32 Gap 33 Discharge port 34 Insoluble particle supply Means 35 Stirring/Mixing Means 35a Supply Port 36 Extraction Ports 37a, 37b Nozzle 38 Discharge Port 39 Filtration Membrane 40 Mixed Liquid Supply Means 41 Precoat Layer 42 Supply Port 43a 43b Supply Path 44 Protective Plate 46 Filtrate Tank

Claims (8)

A method for recovering valuable metal powder from resist waste liquid containing valuable metal powder,
a step of sedimentation separation of the resist waste liquid into a supernatant liquid containing floating valuable metal powder and a sediment containing sedimentary valuable metal powder;
A step of supplying new resist waste liquid to the sedimentation and separation step to raise the liquid level to cause the supernatant to overflow, and adding insoluble particles to the supernatant that overflowed from the sedimentation and separation step; A method for recovering a valuable metal powder, comprising a step of filtering a supernatant liquid containing the insoluble particles. 2. The method for recovering valuable metal powder according to claim 1, wherein the step of filtering comprises filtering the supernatant after forming the precoat layer. 3. The method for recovering valuable metal powder according to claim 1, wherein the valuable metal powder contained in the resist waste liquid has a particle size of 0.1 [mu]m or more. The valuable metal powder is at least one selected from the group consisting of gold, silver, palladium, platinum, rhodium, ruthenium, iridium, copper, nickel, cobalt, and chromium, according to any one of claims 1 to 3. Valuable metal powder recovery method. 2. A method for recovering a valuable metal powder according to claim 1, wherein said resist waste liquid is sedimented and separated without adding a coagulant to said resist waste liquid in said sedimentation separation step. A precipitation mixing apparatus used in the precipitation separation step and the insoluble particle addition step of the valuable metal powder recovery method according to any one of claims 1 to 5 ,
The precipitation mixer is
a sedimentation separation tank for separating a resist waste liquid containing valuable metal powder into a supernatant liquid containing floating valuable metal powder and a sediment containing sedimentary valuable metal powder by sedimentation;
and an addition/mixing tank for adding insoluble particles to the supernatant liquid overflowed from the sedimentation/separation tank. A filtering device used in the filtering step of the valuable metal powder recovery method according to any one of claims 1 to 5 ,
The filtering device is
A filtration device comprising a precoat layer and a filtration membrane. Valuable metal powder recovery equipment comprising the precipitation mixing device according to claim 6 and the filtering device according to claim 7 .

Images