Hydrofluoric acid-containing water processing device, and hydrofluoric acid-containing water processing method

Abstract

To provide a hydrofluoric acid-containing water processing device that suppresses decrease of a filter material due to dissolution of the filter material when processing hydrofluoric acid-containing water, and can be stably operated.SOLUTION: A processing device 1 for hydrofluoric acid-containing water with a pH less than 4 has a filtration device 12 charged with a filter material, and a deionization unit 16 which is located on a subsequent stage of the filtration device 12 and is charged with an ion exchanger. The filter material contains filter sand with silicon component ratio of 90% by mass or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a treatment apparatus for hydrofluoric acid-containing water and a treatment method for hydrofluoric acid-containing water.

Background Art

[0002] In recent years, in order to reduce the amount of water intake and drainage at production sites in various industries, the case of recovering water from drainage and reusing the water has been increasing. Although the water treatment systems for performing such water recovery vary depending on the raw water quality, for example, after turbidity removal processes such as coagulation sedimentation, turbidity removal membranes, and sand filtration, it is common to perform a deionization process such as RO membranes or ion exchange.

[0003] For example, in a semiconductor factory, hydrofluoric acid-containing drainage (for example, drainage from a decontamination system facility: decontamination system drainage) obtained by treating HF gas components with a scrubber is discharged. When recovering water from such water containing hydrofluoric acid, the problem is that each material is dissolved by hydrofluoric acid. In a semiconductor factory, since a high water recovery rate is often required, the deionization process is often performed using an ion exchanger instead of RO membranes.

[0004] For example, Patent Document 1 discloses a flow for recovering water from fluorine-containing drainage by crystallization + sand filtration + ion exchange resin. Note that crystallization is performed in a neutral range where the pH in the crystallization tank is adjusted to the range of 4 to 10 and hydrofluoric acid is converted into fluoride ions.

[0005] When recovering water, two-layer filtration using filtration sand mainly composed of SiO 2 and carbon-based anthracite as filter media is often applied. However, when water is passed through with hydrofluoric acid as it is, there is a problem that the part of the filtration sand is dissolved and disappears as fluoride ions due to HF.

[0006] In addition, there is also a problem that components such as SiO 2 and Al eluted from the filtration sand affect the subsequent treatment. Specifically, there is a problem that the load on the ion exchange resin increases.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, an object of the present invention is to provide a treatment apparatus and a treatment method for hydrofluoric acid-containing water that can suppress a decrease in a filter medium due to dissolution of the filter medium and stably operate the apparatus when treating hydrofluoric acid-containing water.

Means for Solving the Problems

[0009] This embodiment is a treatment apparatus for hydrofluoric acid-containing water having a pH of less than 4, comprising a filtration device filled with a filter medium and a deionization device filled with an ion exchanger, disposed downstream of the filtration device, wherein the filter medium includes filtration sand having a silicon component ratio of 90% by mass or more.

[0010] Further, in the treatment apparatus for hydrofluoric acid-containing water, the aluminum component ratio of the filtration sand is preferably 2% by mass or less.

[0011] Further, in the treatment apparatus for hydrofluoric acid-containing water, the filtration device is provided with a support for supporting the filter medium, and the support preferably has a silicon component ratio of 90% by mass or more, an aluminum component ratio of 2% by mass or less, and is gravel having an effective diameter of 2 to 6 mm.

[0012] Further, in the treatment apparatus for hydrofluoric acid-containing water, the filter medium is preferably composed of a combination of the filtration sand and a carbon-based filter medium.

[0013] Further, in the treatment apparatus for hydrofluoric acid-containing water, it is preferable that the filter medium is composed of a combination of the filtration sand and a synthetic resin filter medium.

[0014] Further, in the treatment apparatus for hydrofluoric acid-containing water, the hydrofluoric acid-containing water is the drainage of the decontamination facility of a semiconductor factory, and it is preferable that the fluorine concentration of the drainage is 100 mg / L or less.

[0015] Further, the present embodiment is a method for treating hydrofluoric acid-containing water having a pH of less than 4, including a filtration step of passing the hydrofluoric acid-containing water through a filtration device filled with a filter medium to obtain filtered water, and a deionization step of passing the filtered water through a deionization device filled with an ion exchanger to obtain ion-exchanged treated water. The filter medium includes filtration sand having a silicon component ratio of 90% by mass or more.

[0016] Further, in the method for treating hydrofluoric acid-containing water, it is preferable that the aluminum component ratio of the filtration sand is 2% by mass or less.

[0017] Further, in the method for treating hydrofluoric acid-containing water, the filtration device is provided with a support for supporting the filter medium. The support is preferably gravel having a silicon component ratio of 90% by mass or more, an aluminum component ratio of 2% by mass or less, and an effective diameter of 2 to 6 mm.

[0018] Further, in the method for treating hydrofluoric acid-containing water, it is preferable that the filter medium is composed of a combination of the filtration sand and a carbon-based filter medium.

[0019] Further, in the method for treating hydrofluoric acid-containing water, it is preferable that the filter medium is composed of a combination of the filtration sand and a synthetic resin filter medium.

[0020] Further, in the method for treating hydrofluoric acid-containing water, the hydrofluoric acid-containing water is the drainage of the decontamination facility of a semiconductor factory, and it is preferable that the fluorine concentration of the drainage is 100 mg / L or less.

Advantages of the Invention

[0021] According to the present invention, when treating hydrofluoric acid-containing water, a decrease in the filter medium due to dissolution of the filter medium can be suppressed, and the apparatus can be stably operated.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0023] Embodiments of the present invention will be described below. This embodiment is an example of carrying out the present invention, and the present invention is not limited to this embodiment.

[0024] FIG. 1 is a schematic diagram showing an example of an apparatus for treating hydrofluoric acid-containing water according to the present embodiment. The apparatus 1 for treating hydrofluoric acid-containing water shown in FIG. 1 includes a raw water tank 10, a filtration apparatus 12, a treatment water tank 14, a deionization apparatus 16, pipes 18a, 18b, 18c, 18d, supply pumps 20a, 20b, backwash pipes 22a, 22b, a backwash pump 24, regenerant pipes 26a, 26b, a regenerant pump 28, and a regenerant storage tank 30.

[0025] One end of the pipe 18a is connected to the raw water tank 10, and the other end is connected to the filtration device 12 via the supply pump 20a. One end of the pipe 18b is connected to the filtration device 12, and the other end is connected to the treatment water tank 14. One end of the pipe 18c is connected to the treatment water tank 14, and the other end is connected to the deionization device 16 via the supply pump 20b. The pipe 18d is connected to the deionization device 16.

[0026] One end of the backwash pipe 22a is connected to the treatment water tank 14, and the other end is connected to the filtration device 12 via the backwash pump 24. The backwash pipe 22b is connected to the filtration device 12. Also, one end of the regenerant pipe 26a is connected to the regenerant storage tank 30, and the other end is connected to the deionization device 16 via the regenerant pump 28. The regenerant pipe 26b is connected to the deionization device 16.

[0027] The filtration device 12 is filled with filter media. In order to suppress the outflow of the filter media during backwashing, for example, the filter media may be packed, a perforated plate may be installed to press the filter media from above, or a filter may be installed at an appropriate location of the pipe 22b from the outlet side of the filtration device 12.

[0028] The filter media includes filter sand in which the component ratio of silicon is 90% by mass or more. Hereinafter, the filter sand of the present embodiment refers to filter sand in which silicon satisfies the above component ratio. The filter sand of the present embodiment is hardly dissolved even when it comes into contact with hydrofluoric acid-containing water. Therefore, by including the filter sand of the present embodiment in the filter media, a decrease in the filter media due to dissolution of the filter media can be suppressed, and the device can be stably operated.

[0029] In terms of the acid resistance of the filter sand of the present embodiment to hydrofluoric acid-containing water, the component ratio of silicon is preferably 95% by mass or more, the component ratio of aluminum is preferably 2% by mass or less, and more preferably 1.5% by mass or less. Further, the filter sand of the present embodiment may contain iron, but the component ratio of iron may be, for example, 5% by mass or less, and 3% by mass or less. The component ratio of the filter sand can be analyzed by a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Corporation).

[0030] The filter medium may contain filter media other than the filter sand of the present embodiment. As filter media other than the filter sand of the present embodiment, for example, carbon-based filter media, synthetic resin filter media, etc. are preferable in that they are hardly soluble in hydrofluoric acid-containing water. In addition, the filter sand filled in the filtration device may contain filter sand other than the filter sand of the present embodiment. The content of the filter sand other than the filter sand of the present embodiment is preferably, for example, 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0% by mass with respect to the total amount of the filter sand filled in the filtration device 12.

[0031] The filter medium is preferably composed of the filter sand of the present embodiment, preferably composed of a combination of the filter sand of the present embodiment and a carbon-based filter medium, or preferably composed of a combination of the filter sand of the present embodiment and a synthetic resin filter medium. Here, when the filter medium is composed of the filter sand of the present embodiment, it only needs to contain substantially no filter medium other than the filter sand of the present embodiment, and the content of the filter medium other than the filter sand of the present embodiment in the filter medium is, for example, 5% by mass or less, preferably 1% by mass or less, and more preferably 0% by mass. In addition, when it is composed of a combination of the filter sand of the present embodiment and a carbon-based filter medium, it only needs to contain substantially no filter medium other than the filter sand and the carbon-based filter medium of the present embodiment, and the content of the filter medium other than the filter sand and the carbon-based filter medium of the present embodiment in the filter medium is, for example, 5% by mass or less, preferably 1% by mass or less, and more preferably 0% by mass or less. In addition, when it is composed of a combination of the filter sand of the present embodiment and a synthetic resin filter medium, it only needs to contain substantially no filter medium other than the filter sand and the synthetic resin filter medium of the present embodiment, and the content of the filter medium other than the filter sand and the synthetic resin filter medium of the present embodiment in the filter medium is, for example, 5% by mass or less, preferably 1% by mass or less, and more preferably 0% by mass or less.

[0032] The filtration device 12 is filled with a single layer or multiple layers of filter media. A single layer means that only one type of filter media is filled, and a multiple layer means that multiple (for example, two or three types) of filter media with different effective diameters and specific gravities are filled. For example, when the filter media is composed of the filtration sand of the present embodiment, it is preferable to fill the filtration sand of the present embodiment in a single layer. Also, for example, when it is composed of a combination of the filtration sand of the present embodiment and a carbon-based filter media (or a synthetic resin filter media), it is preferable to prepare the filtration sand of the present embodiment and the carbon-based filter media (or the synthetic resin filter media) with different effective diameters and specific gravities and fill them in multiple layers.

[0033] The filtration sand of the present embodiment is preferably filtration sand with an effective diameter of 0.4 mm to 1.0 mm, and more preferably filtration sand with an effective diameter of 0.45 mm to 0.70 mm. When the effective diameter is less than 0.4 mm, the backwashing frequency due to clogging may be higher than that in the case of 0.4 mm or more. Also, when the effective diameter exceeds 1.0 mm, the turbidity treatment performance may decrease compared to the case of 1.0 mm or less. The effective diameter in the present embodiment refers to the size of the particles in mm when the cumulative passing mass percentage from fine particles becomes 10% on the normal distribution probability line of the sieve analysis calculation diagram (logarithmic graph) of the filter media.

[0034] The carbon-based filter media is, for example, a filter media containing 90 mass% or more of carbon. Specifically, anthracite, activated carbon, etc. are mentioned, and anthracite is preferably used. Note that since the activated carbon is not intended for adsorbing organic substances, used activated carbon for other purposes may be applied. The shape of the carbon-based filter media is not particularly limited, and examples include granular, cylindrical, etc. The carbon-based filter media is preferably a carbon-based filter media with an effective diameter of 0.5 mm to 2.5 mm, and more preferably 0.7 mm to 1.5 mm. When the effective diameter is less than 0.5 mm, the backwashing frequency due to clogging may be higher than that in the case of 0.5 mm or more. Also, when the effective diameter exceeds 2.5 mm, the turbidity treatment performance may decrease compared to the case of 2.5 mm or less.

[0035] Examples of the synthetic resin filter medium include filter media mainly composed of any one of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyester, polyamide (PA), polycarbonate (PC), polyvinyl alcohol (PVA), or polytetrafluoroethylene (PTFE). The shape of the synthetic resin filter medium is not particularly limited, and examples include granular, cylindrical, and the like. The effective diameter of the synthetic resin filter medium may be in the same range as that of the carbon-based filter medium, for example.

[0036] Further, the synthetic resin filter medium may be fibrous. The fibrous filter medium is preferably a filter medium having a fiber diameter (major axis) of 500 mm or more and less than 3000 mm, and more preferably 1000 mm or more and less than 1500 mm. For example, a fibrous filter medium is used which is made by bundling fibers having a fiber thickness of 10 to 80 μm and a fiber length of about 500 to 3000 mm.

[0037] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the filtration device. Inside the filtration device 12 shown in FIG. 2, a filtration layer 40 and a support 42 are arranged in the order of the water flow direction of the hydrofluoric acid-containing water. The filtration layer 40 is filled with a filter medium such as the filtration sand of the present embodiment described above. The support 42 may be any one that supports the filter medium so that the filter medium of the filtration layer 40 does not escape outside the filtration device 12. However, in terms of water permeability, solubility resistance to hydrofluoric acid-containing water, etc., it is preferably gravel having a silicon component ratio of 90% by mass or more and an aluminum component ratio of 2% by mass or less. The gravel used for the support 42 in the present embodiment preferably has a silicon component ratio of 95% by mass or more and an aluminum component ratio of 1.5% by mass or less in terms of solubility resistance to hydrofluoric acid-containing water. Further, the gravel used for the support 42 in the present embodiment may contain iron, but the iron component ratio may be, for example, 5% by mass or less, and 4% by mass or less.

[0038] The gravel constituting the support 42 preferably has an effective diameter larger than that of the filter medium of the filtration layer 40. For example, gravel with an effective diameter of 2 mm to 6 mm is preferable, and gravel with an effective diameter of 3 mm to 5 mm is more preferable. If the effective diameter of the gravel constituting the support 42 is too small, the differential pressure is likely to increase. If the effective diameter of the gravel constituting the support 42 is too large, there is a risk that the filter medium such as filter sand will mix into the support 42. Note that in this embodiment, the support 42 is not an essential component and may be appropriately installed as needed.

[0039] As the deionization device 16, for example, an ion exchange tower filled with an ion exchanger can be used. The deionization device 16 only needs to be able to remove at least fluorine (fluoride ions) in the hydrofluoric acid-containing water, but preferably, the specifications necessary to meet the required recovered water quality are selected. The deionization device 16 only needs to be an ion exchange tower filled with at least an anion exchanger in terms of removing fluorine (fluoride ions). From the perspective of obtaining better water quality, the deionization device 16 includes a cation exchange tower filled with a cation exchanger such as a strongly acidic resin or a weakly acidic resin, and an anion exchange tower filled with an anion exchanger such as a strongly basic resin or a weakly basic resin. Devices that pass water in the order of the cation exchange tower and the anion exchange tower, or devices equipped with a resin tower of a mixed bed of a cation exchanger and an anion exchanger are preferable. When the hydrofluoric acid-containing water is decontamination system drainage, from the perspective of reducing the amount of regenerant used, a so-called 2B3T type device using a cation exchange tower filled with a mixed bed type cation exchanger of a strongly acidic resin + a weakly acidic resin, a decarbonation tower, and an anion exchange tower filled with a mixed bed type anion exchanger of a strongly basic resin + a weakly basic resin is preferable.

[0040] The pH of the hydrofluoric acid-containing water is less than 4, may be less than 3.5, or may be 1 or more and less than 3. By passing water while keeping the pH acidic, neutralizing chemicals can be reduced, and the load on the subsequent ion exchanger can be reduced. The fluorine concentration in the hydrofluoric acid-containing water is preferably, for example, 100 mg / L or less in that the dissolution of the filter sand of the present embodiment hardly occurs. When the fluorine concentration in the hydrofluoric acid-containing water is less than 10 mg / L, dissolution can be suppressed even with filter sand other than the filter sand of the present embodiment. Therefore, it is preferable to apply the apparatus and method of the present embodiment to the treatment of hydrofluoric acid-containing water having a fluorine concentration of 10 mg / L or more. Examples of the hydrofluoric acid-containing water include wastewater from decontamination facilities in semiconductor factories.

[0041] An example of the operation of the hydrofluoric acid-containing water treatment apparatus 1 shown in FIG. 1 will be described.

[0042] The supply pump 20a is operated to supply the hydrofluoric acid-containing water having a pH of less than 4 in the raw water tank 10 from the pipe 18a to the filtration device 12. The hydrofluoric acid-containing water is passed through the filtration device 12 to obtain filtered water (filtration step). In the filtration step, turbidity in the hydrofluoric acid-containing water can be removed. The linear velocity (LV) of the hydrofluoric acid-containing water in the filtration device 12 is not particularly limited, but may be, for example, in the range of 2 to 20 m / h.

[0043] The hydrofluoric acid-containing water (filtered water) from which turbidity has been removed is supplied from the pipe 18b to the treatment tank 14. The supply pump 20b is operated to supply the filtered water in the treatment tank 14 from the pipe 18c to the deionization device 16. The filtered water is passed through the deionization device 16 to obtain ion-exchanged treated water (deionization step). In the deionization step, fluorine (fluoride ions) in the filtered water can be removed. Further, when the hydrofluoric acid-containing water contains cations such as sodium, calcium, and ammonium, anions such as chloride ions, sulfate ions, nitrate ions, phosphate ions, and bicarbonate ions, or silica, etc., it is preferable to remove them. The filtered water (deionized water) from which fluorine has been removed is recovered from the pipe 18d.

[0044] When backwashing the filter medium in the filtration device 12, the supply pumps 20a and 20b are stopped, the backwash pump 24 is operated, and the filtered water in the treatment water tank 14 is supplied from the backwash pipe 22a to the filtration device 12. The filtered water is passed through the filtration device 12 to wash the filter medium. Then, the backwash wastewater discharged from the filtration device 12 is discharged out of the system from the backwash pipe 22b. Incidentally, air may be supplied into the filtration device 12 together with or separately from the above backwashing to perform air scrubbing to wash the filter medium. The timing of backwashing and air scrubbing is not particularly limited. For example, it is preferable to perform backwashing and air scrubbing after passing water for a certain period (after 24 hours, etc.) or after the differential pressure of the filtration device 12 reaches 0.1 MPa, etc. The backwash wastewater containing turbidity may be discharged after treatment such as coagulation sedimentation, or may be filtered again by the filtration device 12 and recovered as filtered water. At the time of backwashing, sodium hypochlorite or the like may be added to the filtered water for sterilization of the filter medium. In this case, in order to prevent the generation of chlorine gas, it is carried out while maintaining the system neutral during backwashing. Incidentally, in this embodiment, filtered water is used for backwashing, but pure water, service water, etc. may be distributed from another water treatment line (not shown) and used for backwashing.

[0045] When regenerating the ion exchanger in the deionization device 16, the supply pumps 20a and 20b are stopped, the regenerant pump 28 is operated, and the regenerant in the regenerant storage tank 30 is supplied from the regenerant pipe 26a to the deionization device 16. The regenerant is passed through the deionization device 16 to regenerate the ion exchanger. Then, the regenerated wastewater discharged from the deionization device 16 is discharged out of the system from the regenerant pipe 26b. The regenerant may be a conventionally known one used for regenerating the ion exchanger. For example, ion-exchanged water, hydrochloric acid, sulfuric acid, sodium hydroxide, etc. are used. The ion exchanger of the deionization device 16 may be regenerated at any timing.

[0046] (Effects of this Embodiment) (1) The conventional filter sand used for removing turbidity has a low silicon purity. When it comes into contact with hydrofluoric acid-containing water with a pH of less than 4, the filter sand dissolves due to HF in the water and decreases or disappears. Also, filter media such as garnet and ceramic commonly used in water treatment have the same main components as sand, so although there are differences in degree, they dissolve due to HF and the same problem occurs. Therefore, conventionally, it is common to adjust the pH of hydrofluoric acid-containing water to the neutral range of 4 - 10 for treatment. On the other hand, the filter sand used in this embodiment is a filter sand with a silicon component ratio of 90% by mass or more, and has a higher silicon purity than the conventional filter sand. When using the filter sand with high silicon purity of this embodiment, even when it comes into contact with hydrofluoric acid-containing water with a pH of less than 4, the dissolution by HF in the water is suppressed. As a result, it is possible to suppress the reduction of the filter media due to the dissolution of the filter media, and the device can be stably operated. (2) In the method of neutralizing and treating hydrofluoric acid-containing water with a pH of less than 4, the amount of the neutralizing agent for neutralizing the hydrofluoric acid-containing water becomes extremely large, and the salt load in the hydrofluoric acid-containing water increases. On the other hand, in this embodiment, since the treatment is carried out while remaining acidic with a pH of less than 4, it is possible to reduce chemicals such as neutralizing agents and equipment for neutralization, and it is possible to achieve cost reduction. Although a deionization device filled with an ion exchanger can obtain good treated water quality even when passing acidic hydrofluoric acid-containing water, in a deionization device using an RO membrane, when passing acidic hydrofluoric acid-containing water, poor treated water quality may occur, and neutralization treatment is required in the previous stage. (3) Filter media that are difficult to dissolve even when in contact with hydrofluoric acid-containing water with a pH of less than 4 include synthetic resin filter media and carbon-based filter media, but the filter sand of this embodiment is cheaper than these filter media. For example, by combining a synthetic resin filter media or a carbon-based filter media with the filter sand of this embodiment to form a multi-layer, it is possible to remove turbidity while suppressing an increase in the filter media cost compared to a single layer of a synthetic resin filter media or a carbon-based filter media. (4) In order to prevent the dissolution of the filter material, when filtration is performed using only a single layer of anthracite, which is a carbon-based filter material, the differential pressure tends to increase with respect to the supplementary amount of turbidity, and the backwash frequency increases, which may cause a decrease in the water recovery rate of the system. Since a high water recovery rate is required in semiconductor factories and the like, the decrease in the water recovery rate due to the increase in the backwash frequency becomes a major problem. Further, when filtration is performed using a multi-layer combination of a carbon-based filter material and a synthetic resin filter material, the amount of turbidity removed is improved, but since the specific gravity difference between these two filter materials is small, the filter materials may mix with each other during backwashing, and the effect of multi-layer filtration may not be obtained. On the other hand, when filtration is performed using a multi-layer combination of the filtration sand of the present embodiment and a carbon-based filter material or a synthetic resin filter material, the amount of turbidity removed is improved and a high water recovery rate can be obtained. Further, since the specific gravity difference between the filtration sand of the present embodiment and the carbon-based filter material or the synthetic resin filter material is relatively large, mixing of the filter materials with each other during backwashing is suppressed, and the effect of multi-layer filtration can be maintained. Note that filtration by fiber filtration can pass water at a higher speed than filtration by filtration sand, but the turbidity supplementing ability is not high. (5) Conventionally, as a method for removing turbidity, there is also a method using membrane treatment such as an MF membrane or a UF membrane, but this method has a higher equipment cost than filtration using a filter material. That is, by adopting turbidity removal using a filter material as in the present embodiment, the equipment cost can be suppressed as compared with membrane treatment using an MF membrane, a UF membrane, or the like.

Example

[0047] Hereinafter, examples will be given to more specifically explain the present invention, but the present invention is not limited to the following examples.

[0048] In Examples 1-4 and Comparative Examples 1-4, hydrofluoric acid-containing water was passed downward through a column (filtration device) filled with filtration sand at a linear velocity of water flow (LV) of 10 m / h to perform a filtration step. As the hydrofluoric acid-containing water, the decontamination wastewater shown in Table 1 was used. As the column filled with filtration sand, a column having a size of φ20 mm × 1000 mm was used. The filling height of the filtration sand filled in the column was 100 mm.

[0049]

Table 1

[0050] Table 2 shows the component ratios, effective diameters, and uniformity coefficients of the filter sands A to D used in Comparative Examples 1 to 4, and Table 3 shows the component ratios, effective diameters, and consideration coefficients of the filter sands E to H used in Examples 1 to 4.

[0051]

Table 2

Table 3

[0052] Fig. 3 shows the silicon dioxide concentration (elution amount) in the filtered water obtained in Examples 1 to 2 and Comparative Examples 1 to 2, and Fig. 4 shows the silicon dioxide concentration (elution amount) in the filtered water obtained in Examples 3 to 4 and Comparative Examples 3 to 4. Further, Fig. 5 shows the aluminum concentration (elution amount) in the filtered water obtained in Examples 1 to 2 and Comparative Examples 1 to 2, and Fig. 6 shows the aluminum concentration (elution amount) in the filtered water obtained in Examples 3 to 4 and Comparative Examples 3 to 4.

[0053] As shown in Figs. 3 to 6, in Examples 1 to 4, the elution amounts of silicon dioxide and aluminum into the filtered water were suppressed as compared with Comparative Examples 1 to 4. From these results, it can be said that by using a filter sand in which the component ratio of silicon is 90% by mass or more (preferably the component ratio of aluminum is 2% by mass or less), dissolution of the filter medium in the treatment of hydrofluoric acid-containing water can be suppressed.

[0054] [Appendix] (1) A treatment apparatus for hydrofluoric acid-containing water having a pH of less than 4, comprising a filtration apparatus filled with a filter medium, and a deionization apparatus filled with an ion exchanger and disposed downstream of the filtration apparatus. The filter medium contains a filter sand in which the component ratio of silicon is 90% by mass or more. A treatment apparatus for hydrofluoric acid-containing water, characterized in that. (2) The treatment apparatus for hydrogen fluoride-containing water according to (1) above, wherein the aluminum component ratio of the filter sand is 2% by mass or less. (3) A support for supporting the filter medium is provided in the filtration device, The support is gravel having a silicon component ratio of 90% by mass or more, an aluminum component ratio of 2% by mass or less, and an effective diameter of 2 to 6 mm, and is the treatment apparatus for hydrofluoric acid-containing water according to (1) or (2) above. (4) The filter medium is composed of a combination of the filter sand and a carbon-based filter medium, and is the treatment apparatus for hydrofluoric acid-containing water according to any one of (1) to (3) above. (5) The filter medium is composed of a combination of the filter sand and a synthetic resin filter medium, and is the treatment apparatus for hydrofluoric acid-containing water according to any one of (1) to (3) above. (6) The hydrofluoric acid-containing water is the drainage of the decontamination equipment in a semiconductor factory, and the fluorine concentration of the drainage is 100 mg / L or less, and is the treatment apparatus for hydrofluoric acid-containing water according to any one of (1) to (5) above. (7) A method for treating hydrofluoric acid-containing water with a pH of less than 4, A filtration step of passing the hydrofluoric acid-containing water through a filtration device filled with a filter medium to obtain filtered water, A deionization step of passing the filtered water through a deionization device filled with an ion exchanger to obtain deionized treated water, and has The filter medium includes filter sand having a silicon component ratio of 90% by mass or more, and is a method for treating hydrofluoric acid-containing water. (8) The method for treating hydrofluoric acid-containing water according to (7) above, wherein the aluminum component ratio of the filter sand is 2% by mass or less. (9) A support for supporting the filter medium is provided in the filtration device, The support is gravel with a silicon component ratio of 90% by mass or more, an aluminum component ratio of 2% by mass or less, and an effective diameter of 2 to 6 mm, and is characterized by the method for treating hydrogen fluoride acid-containing water according to the above (7) or (8). (10) The filter medium is composed of a combination of the filter sand and a carbon-based filter medium, and is characterized by the method for treating hydrogen fluoride acid-containing water according to any one of the above (7) to (9). (11) The filter medium is composed of a combination of the filter sand and a synthetic resin filter medium, and is characterized by the method for treating hydrogen fluoride acid-containing water according to any one of the above (7) to (9). (12) The hydrogen fluoride acid-containing water is the drainage of the decontamination equipment in a semiconductor factory, and the fluorine concentration of the drainage is 100 mg / L or less, and is characterized by the method for treating hydrogen fluoride acid-containing water according to any one of the above (7) to (11).

Explanation of symbols

[0055] 1 Hydrogen fluoride acid-containing water treatment device, 10 Raw water tank, 12 Filter device, 14 Treatment water tank, 16 Deionization device, 18a, 18b, 18c, 18d Pipes, 20a, 20b Supply pumps, 22a, 22b Backwash pipes, 24 Backwash pump, 26a, 26b Regenerant pipes, 28 Regenerant pump, 30 Regenerant storage tank, 40 Filter layer, 42 Support.

Claims

1. A treatment device for hydrofluoric acid-containing water with a pH of less than 4, comprising: a filtration device filled with a filter medium, and a deionization device filled with an ion exchanger, which is arranged downstream of the filtration device; The treatment device for hydrofluoric acid-containing water is characterized in that the filter medium contains filter sand with a silicon component ratio of 90% by mass or more.

2. The treatment device for hydrofluoric acid-containing water according to claim 1, wherein the aluminum component ratio of the filter sand is 2% by mass or less.

3. The filtration device is provided with a support for supporting the filter medium, The treatment device for hydrofluoric acid-containing water according to claim 1 or 2, wherein the support is gravel with a silicon component ratio of 90% by mass or more, an aluminum component ratio of 2% by mass or less, and an effective diameter of 2 to 6 mm.

4. The treatment device for hydrofluoric acid-containing water according to claim 1 or 2, wherein the filter medium is composed of a combination of the filter sand and a carbon-based filter medium.

5. The treatment device for hydrofluoric acid-containing water according to claim 1 or 2, wherein the filter medium is composed of a combination of the filter sand and a synthetic resin filter medium.

6. The treatment device for hydrofluoric acid-containing water according to claim 1 or 2, wherein the hydrofluoric acid-containing water is the drainage of the decontamination equipment in a semiconductor factory, and the fluorine concentration of the drainage is 100 mg / L or less.

7. A treatment method for hydrofluoric acid-containing water with a pH of less than 4, comprising: a filtration step of passing the hydrofluoric acid-containing water through a filtration device filled with a filter medium to obtain filtered water; and a deionization step of passing the filtered water through a deionization device filled with an ion exchanger to obtain ion-exchanged treated water. The treatment method for hydrofluoric acid-containing water is characterized in that the filter medium contains filter sand with a silicon component ratio of 90% by mass or more.

8. The treatment method for hydrofluoric acid-containing water according to claim 7, wherein the aluminum component ratio of the filter sand is 2% by mass or less.

9. The filtration device is provided with a support for supporting the filter medium, The treatment method for hydrofluoric acid-containing water according to claim 7 or 8, wherein the support is gravel with a silicon component ratio of 90% by mass or more, an aluminum component ratio of 2% by mass or less, and an effective diameter of 2 to 6 mm.

10. The filter medium is composed of a combination of the filtration sand and a carbon-based filter medium, and the method for treating hydrofluoric acid-containing water according to claim 7 or 8.

11. The filter medium is composed of a combination of the filtration sand and a synthetic resin filter medium, and the method for treating hydrofluoric acid-containing water according to claim 7 or 8.

12. The hydrofluoric acid-containing water is the drainage of the decontamination equipment in a semiconductor factory, and the fluorine concentration of the drainage is 100 mg / L or less, and the method for treating hydrofluoric acid-containing water according to claim 7 or 8.

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