Treatment device for hydrofluoric acid-containing water and treatment method for hydrofluoric acid-containing water

Abstract

The invention provides a treatment device for hydrofluoric acid-containing water, which can inhibit the reduction of a filter material caused by the dissolution of the filter material when the hydrofluoric acid-containing water is treated, and enables the device to stably operate. The device for treating hydrofluoric acid-containing water is a device (1) for treating hydrofluoric acid-containing water having a pH of less than 4, and is provided with: a filter device (12) filled with a filter material; and a deionizing device (16) which is disposed in the subsequent stage of the filter device (12) and is filled with an ion exchanger, the filter material containing filter sand having a silicon component ratio of 90% by mass or more.

Description

Technical Field

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

[0002] In recent years, in various industries, in order to reduce the water intake and drainage volume at production sites, the situation of water recovery from drainage and reuse of water has increased. The water treatment systems for this water recovery vary depending on the raw water quality, but for example, they generally perform deionization processes such as RO membranes and ion exchange after turbidity removal processes such as coagulation sedimentation, turbidity removal membranes, and sand filtration.

[0003] For example, in a semiconductor factory, hydrofluoric acid-containing drainage (for example, drainage from a decontamination system equipment: decontamination system drainage) after treating HF gas components with a scrubber is discharged. However, when recovering water from such hydrofluoric acid-containing water, there is a problem that various materials are dissolved by hydrofluoric acid. It should be noted that in semiconductor factories, the water recovery rate is often required to be high, so the deionization process is mostly carried out using ion exchangers instead of RO membranes.

[0004] For example, in Patent Document 1, a process for water recovery from fluorine-containing drainage using crystallization + sand filtration + ion exchange resin is disclosed. It should be noted that crystallization is carried out in a range where the pH in the crystallization tank is adjusted to 4 to 10 and in a neutral region where hydrofluoric acid is used as fluoride ions.

[0005] When recovering water, double-layer filtration is mostly applied. In this double-layer filtration, filtration sand mainly composed of SiO 2 and carbon-based anthracite are used as filter media. However, if hydrofluoric acid is directly introduced, there is a technical problem that part of the filtration sand becomes silicon fluoride ions and dissolves and disappears due to HF.

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

[0007] Patent Documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-96281 Summary of the Invention Technical Problem 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, which can suppress the reduction of filter media due to the dissolution of the filter media and enable the apparatus to operate stably when treating hydrofluoric acid-containing water.

[0009] Technical solution for solving technical problems This embodiment is a treatment device for hydrofluoric acid-containing water, where the pH of the hydrofluoric acid-containing water is less than 4. The treatment device for hydrofluoric acid-containing water has: a filtration device filled with filter media; and a deionization device arranged at the subsequent stage of the filtration device and filled with ion exchangers. The filter media includes filter sand with a silicon component ratio of 90% by mass or more.

[0010] In addition, in the treatment device for hydrofluoric acid-containing water, preferably, the aluminum component ratio of the filter sand is 2% by mass or less.

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

[0012] In addition, in the treatment device for hydrofluoric acid-containing water, preferably, the filter media is composed of a combination of the filter sand and a carbon-based filter media.

[0013] In addition, in the treatment device for hydrofluoric acid-containing water, preferably, the filter media is composed of a combination of the filter sand and a synthetic resin filter media.

[0014] In addition, in the treatment device for hydrofluoric acid-containing water, preferably, 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.

[0015] In addition, this embodiment is a treatment method for hydrofluoric acid-containing water, where the pH of the hydrofluoric acid-containing water is less than 4. The treatment method for hydrofluoric acid-containing water has: a filtration step of passing the hydrofluoric acid-containing water through a filtration device filled with filter media to obtain filtered water; and a deionization step of passing the filtered water through a deionization device filled with ion exchangers to obtain ion-exchange treated water. The filter media includes filter sand with a silicon component ratio of 90% by mass or more.

[0016] In addition, in the treatment method for hydrofluoric acid-containing water, preferably, the aluminum component ratio of the filter sand is 2% by mass or less.

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

[0018] In addition, in the method for treating hydrofluoric acid-containing water, preferably, the filter medium is composed of a combination of the filter sand and a carbon-based filter medium.

[0019] In addition, in the method for treating hydrofluoric acid-containing water, preferably, the filter medium is composed of a combination of the filter sand and a filter medium made of synthetic resin.

[0020] In addition, in the method for treating hydrofluoric acid-containing water, preferably, the hydrofluoric acid-containing water is the drainage of a decontamination device in a semiconductor factory, and 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, it is possible to suppress the reduction of the filter medium caused by the dissolution of the filter medium, and enable the device to operate stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram showing an example of a device for treating hydrofluoric acid-containing water according to the present embodiment.

[0023] Figure 2 It is a schematic cross-sectional view showing an example of the structure of a filtration device.

[0024] Figure 3 It is a graph showing the change in the concentration (dissolution amount) of silicon dioxide in the filtered water obtained in Examples 1 to 2 and Comparative Examples 1 to 2.

[0025] Figure 4 It is a graph showing the change in the concentration (dissolution amount) of silicon dioxide in the filtered water obtained in Examples 3 to 4 and Comparative Examples 3 to 4.

[0026] Figure 5 It is a graph showing the change in the concentration (dissolution amount) of aluminum in the filtered water obtained in Examples 1 to 2 and Comparative Examples 1 to 2.

[0027] Figure 6 It is a graph showing the change in the concentration (dissolution amount) of aluminum in the filtered water obtained in Examples 3 to 4 and Comparative Examples 3 to 4. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present invention will be described. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

[0029] Figure 1 It is a schematic diagram showing an example of a device for treating hydrofluoric acid-containing water according to the present embodiment. Figure 1The treatment device 1 for hydrofluoric acid-containing water shown is equipped with a raw water tank 10, a filtration device 12, a treatment tank 14, a deionization device 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.

[0030] One end of 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 pipe 18b is connected to the filtration device 12, and the other end is connected to the treatment tank 14. One end of pipe 18c is connected to the treatment tank 14, and the other end is connected to the deionization device 16 via the supply pump 20b. Pipe 18d is connected to the deionization device 16.

[0031] One end of the backwash pipe 22a is connected to the treatment 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. In addition, 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.

[0032] 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 can be packaged, or a perforated plate can be provided to press the filter media from above, or a filter can be provided at an appropriate location on the pipe 22b from the outlet side of the filtration device 12.

[0033] The filter media contains filter sand with a silicon component ratio of 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 soluble even when in contact with hydrofluoric acid-containing water. Therefore, by including the filter sand of the present embodiment in the filter media, it is possible to suppress the reduction of the filter media caused by the dissolution of the filter media and enable the device to operate stably.

[0034] From the viewpoint of the acid resistance of hydrofluoric acid-containing water, the silicon component ratio of the filter sand of the present embodiment is preferably 95% by mass or more, and the aluminum component ratio is preferably 2% by mass or less, more preferably 1.5% by mass or less. In addition, the filter sand of the present embodiment may contain iron, but the iron component ratio can be, for example, 5% by mass or less, and can be 3% by mass or less. The component ratio of the filter sand is analyzed by a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Corporation).

[0035] The filter medium may also include filter media other than the filtration sand of the present embodiment. As filter media other than the filtration sand of the present embodiment, from the viewpoint of being hardly soluble in hydrofluoric acid-containing water, for example, carbon-based filter media, synthetic resin filter media, etc. are preferred. It should be noted that the filtration sand filled in the filtration device may also include filtration sand other than the filtration sand of the present embodiment. The content of the filtration sand other than the filtration sand of the present embodiment is preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0% by mass, relative to the total amount of the filtration sand filled in the filtration device 12.

[0036] The filter medium is preferably composed of the filtration sand of the present embodiment, preferably composed of a combination of the filtration sand of the present embodiment and a carbon-based filter medium, or preferably composed of a combination of the filtration sand of the present embodiment and a synthetic resin filter medium. Here, that the filter medium is composed of the filtration sand of the present embodiment means that as long as it does not substantially contain filter media other than the filtration sand of the present embodiment, the content of the filter media other than the filtration 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, that it is composed of a combination of the filtration sand of the present embodiment and a carbon-based filter medium means that as long as it does not substantially contain filter media other than the filtration sand of the present embodiment and the carbon-based filter medium, the content of the filter media other than the filtration sand of the present embodiment and the carbon-based filter medium 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, that it is composed of a combination of the filtration sand of the present embodiment and a synthetic resin filter medium means that as long as it does not substantially contain filter media other than the filtration sand of the present embodiment and the synthetic resin filter medium, the content of the filter media other than the filtration sand of the present embodiment and the synthetic resin filter medium 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.

[0037] In the filtration device 12, the filter medium is filled in a single layer or multiple layers. A single layer means that only one type of filter medium is filled, and multiple layers mean that multiple (for example, two or three types) filter media with different effective diameters and specific gravities are filled. For example, when the filter medium is composed of the filtration sand of the present embodiment, it is preferred to fill the filtration sand of the present embodiment in a single layer. In addition, for example, when it is composed of a combination of the filtration sand of the present embodiment and a carbon-based filter medium (or a synthetic resin filter medium), it is preferred to prepare the filtration sand of the present embodiment and a carbon-based filter medium (or a synthetic resin filter medium) with different effective diameters and specific gravities and fill them in multiple layers.

[0038] The filter sand of the present embodiment is preferably, for example, filter sand having an effective diameter of 0.4 mm to 1.0 mm, and more preferably filter sand having an effective diameter of 0.45 mm to 0.70 mm. If the effective diameter is less than 0.4 mm, the backwashing frequency due to clogging becomes higher than in the case of 0.4 mm or more. In addition, if the effective diameter exceeds 1.0 mm, the turbidity treatment performance deteriorates compared to the case of 1.0 mm or less. The effective diameter in the present embodiment means the size of the particles at which the cumulative passing mass percentage from the fine particles is 10% on the normal distribution probability line in the sieve analysis chart (logarithmic chart) of the filter medium, expressed in mm.

[0039] The carbon-based filter medium refers to, for example, a filter medium containing 90% by mass or more of carbon. Specifically, anthracite, activated carbon, etc. are cited, but anthracite is preferred. It should be noted that since the activated carbon is not for the purpose of adsorbing organic substances, activated carbon that has been used in other applications can also be used. The shape of the carbon-based filter medium is not particularly limited, and examples include granular, cylindrical, etc. The carbon-based filter medium is preferably, for example, a carbon-based filter medium having an effective diameter of 0.5 mm to 2.5 mm, and more preferably 0.7 mm to 1.5 mm. If the effective diameter is less than 0.5 mm, the backwashing frequency due to clogging becomes higher than in the case of 0.5 mm or more. In addition, if the effective diameter exceeds 2.5 mm, the turbidity treatment performance deteriorates compared to the case of 2.5 mm or less.

[0040] 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, etc. The effective diameter of the synthetic resin filter medium can be, for example, in the same range as that of the carbon-based filter medium.

[0041] In addition, the synthetic resin filter medium can also be fibrous. The fibrous filter medium is preferably, for example, 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. The fibrous filter medium is, for example, a filter medium formed by bundling fibers having a fiber fineness of 10 μm to 80 μm and a fiber length of about 500 mm to 3000 mm.

[0042] Figure 2 It is a schematic cross-sectional view showing an example of the structure of the filtration device. In Figure 2Inside the shown filtration device 12, a filtration layer 40 and a support 42 are arranged in the order of the water flow direction of the hydrofluoric acid-containing water. Filter materials such as the filtration sand of the present embodiment are filled in the filtration layer 40. The support 42 only needs to support the filter materials so that the filter materials of the filtration layer 40 do not escape outside the filtration device 12. However, from the viewpoints of water permeability, solubility resistance to hydrofluoric acid-containing water, etc., gravel with a silicon component ratio of 90% by mass or more and an aluminum component ratio of 2% by mass or less is preferred. From the viewpoint of solubility resistance in hydrofluoric acid-containing water, in the gravel used in the support 42 of the present embodiment, the silicon component ratio is preferably 95% by mass or more, and the aluminum component ratio is preferably 1.5% by mass or less. In addition, the gravel used in the support 42 of the present embodiment may contain iron, but the iron component ratio can be, for example, 5% by mass or less, and can be 4% by mass or less.

[0043] The gravel constituting the support 42 preferably has an effective diameter larger than that of the filter materials of the filtration layer 40. For example, gravel with an effective diameter of 2 mm to 6 mm is preferred, and gravel with an effective diameter of 3 mm to 5 mm is more preferred. If the effective diameter of the gravel constituting the support 42 is too small, the pressure difference is likely to increase. If the effective diameter of the gravel constituting the support 42 is too large, filter materials such as filtration sand may be mixed into the support 42. It should be noted that in the present embodiment, the support 42 is not an essential structure and can be provided as needed.

[0044] 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 it is preferably selected according to the required specifications to meet the required recovered water quality. From the viewpoint of removing fluorine (fluoride ions), the deionization device 16 only needs to be an ion exchange tower filled with at least an anion exchanger. From the viewpoint of obtaining better water quality, the deionization device 16 preferably includes a cation exchange tower filled with cation exchangers such as strongly acidic resins and weakly acidic resins, and an anion exchange tower filled with anion exchangers such as strongly basic resins and weakly basic resins, and a device for sequentially passing water through the cation exchange tower and the anion exchange tower; a resin tower device of a mixed bed of cation exchangers and anion exchangers, etc. When the hydrofluoric acid-containing water is the drainage of the decontamination system, from the viewpoint of reducing the amount of regenerant used, a so-called 2B3T type device is preferred, that is, the device uses a cation exchange tower filled with a mixed bed type cation exchanger of strongly acidic resin + weakly acidic resin, a decarbonation tower, and an anion exchange tower filled with a mixed bed type anion exchanger of strongly basic resin + weakly basic resin.

[0045] The pH of the hydrofluoric acid-containing water is less than 4, can be less than 3.5, or can be 1 or more and less than 3. By passing water in a state where the pH is acidic, neutralizing chemicals can be reduced, and the load on the ion exchanger in the subsequent stage can be decreased. From the viewpoint of hardly causing dissolution of the filter sand of the present embodiment, the fluorine concentration in the hydrofluoric acid-containing water is preferably 100 mg / L or less, for example. It should be noted that when the fluorine concentration in the hydrofluoric acid-containing water is less than 10 mg / L, the dissolution of filter sand other than the filter sand of the present embodiment is also inhibited. Therefore, it is preferable to apply the apparatus and method of the present embodiment to the treatment of hydrofluoric acid-containing water with a fluorine concentration of 10 mg / L or more. Examples of the hydrofluoric acid-containing water include the drainage of the decontamination equipment in a semiconductor factory.

[0046] For Figure 1 An example of the operation of the hydrofluoric acid-containing water treatment apparatus 1 shown will be described.

[0047] Operate the supply pump 20a to supply the hydrofluoric acid-containing water with a pH less than 4 in the raw water tank 10 to the filtration device 12 through the pipe 18a. Pass the hydrofluoric acid-containing water 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 and can be in the range of 2 m / h to 20 m / h, for example.

[0048] Supply the hydrofluoric acid-containing water (filtered water) from which turbidity has been removed to the treatment tank 14 through the pipe 18b. Operate the supply pump 20b to supply the filtered water in the treatment tank 14 to the deionization device 16 through the pipe 18c. Pass the filtered water 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. In addition, 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. Recover the filtered water (deionized water) from which fluorine has been removed from the pipe 18d.

[0049] 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 clean the filter medium. Then, the backwash drainage discharged from the filtration device 12 is discharged from the backwash pipe 22b to the outside of the system. It should be noted that air can also be supplied into the filtration device 12 together with or separately from the above-mentioned backwash for air washing to clean the filter medium. The timing of backwashing and air washing is not particularly limited. For example, it is preferably carried out after a certain period of water passage (such as after 24 hours) or after the pressure difference of the filtration device 12 reaches 0.1 MPa, etc. The backwash drainage containing turbidity can be discharged after treatments such as coagulation precipitation, or can be filtered again using the filtration device 12 and recovered as filtered water. During backwashing, in order to sterilize the filter medium, sodium hypochlorite or the like can be added to the filtered water. In this case, in order to prevent the generation of chlorine gas, the system is maintained at neutral during backwashing. It should be noted that in this embodiment, filtered water is used for backwashing, but pure water, water, etc. discharged from other water treatment series (not shown) can also be used for backwashing.

[0050] 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 regenerant drainage discharged from the deionization device 16 is discharged from the regenerant pipe 26b to the outside of the system. The regenerant can be a conventionally known regenerant 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 can be regenerated at any time.

[0051] (Effects of this Embodiment) (1) The purity of silicon in the conventional filter sand used for removing turbidity is low. If it comes into contact with hydrofluoric acid-containing water with a pH less than 4, the filter sand dissolves, decreases, and disappears due to HF in the water. In addition, the main components of filter media such as garnet and ceramics commonly used in water treatment are the same as those of sand. Therefore, although there are differences in degree, they dissolve due to HF and cause the same problems. Therefore, conventionally, the pH of hydrofluoric acid-containing water is usually adjusted to the neutral range of 4 - 10 for treatment. On the other hand, the filter sand used in this embodiment has a silicon component ratio of 90% by mass or more, and the purity of silicon is higher than that of the conventional filter sand. Moreover, if the filter sand with high silicon purity of this embodiment is used, even when it comes into contact with hydrofluoric acid-containing water with a pH less than 4, the dissolution caused by HF in the water is suppressed. As a result, the reduction of the filter medium caused by the dissolution of the filter medium can be suppressed, and the device can be stably operated.

[0052] (2) In the method of neutralizing hydrofluoric acid-containing water with a pH less than 4, the amount of the neutralizing agent used to neutralize the hydrofluoric acid-containing water becomes large, and the salt load in the hydrofluoric acid-containing water increases. On the other hand, in the present embodiment, the treatment is carried out while maintaining an acidic pH less than 4, so that it is possible to reduce chemicals such as neutralizing agents and equipment for neutralization, and cost reduction can be achieved. It should be noted that the deionization device filled with the ion exchange body can obtain good treated water quality even when passing acidic hydrofluoric acid-containing water, but in the deionization device using the RO membrane, if acidic hydrofluoric acid-containing water is passed, there is a case where the treated water quality deteriorates, and neutralization treatment needs to be carried out at the pre-stage.

[0053] (3) As filter materials that are difficult to dissolve even when in contact with hydrofluoric acid-containing water with a pH less than 4, there are synthetic resin filter materials and carbon-based filter materials, but the filter sand of the present embodiment is cheaper than these filter materials. For example, by forming a multi-layer by combining a synthetic resin filter material, a carbon-based filter material and the filter sand of the present embodiment, compared with a single layer of a synthetic resin filter material and a carbon-based filter material, it is possible to remove turbidity while suppressing an increase in the cost of the filter material.

[0054] (4) In order to prevent the dissolution of the filter material, if only a single layer of anthracite, which is a carbon-based filter material, is used for filtration, there is a case where the pressure difference easily rises, the backwashing frequency increases, and the water recovery rate of the system decreases with respect to the amount of turbidity captured. A high water recovery rate is required in semiconductor factories and the like, so the decrease in the water recovery rate caused by the increase in the backwashing frequency becomes a major problem. In addition, if filtration is carried out with a multi-layer combining a carbon-based filter material and a synthetic resin filter material, although the amount of turbidity removed increases, since the specific gravity difference between these two filter materials is small, the filter materials are mixed with each other during backwashing, and the effect of multi-layer filtration cannot be obtained. On the other hand, if filtration is carried out with a multi-layer combining the filter sand of the present embodiment and a carbon-based filter material or a synthetic resin filter material, the amount of turbidity removed increases, and a high water recovery rate is obtained. In addition, the specific gravity difference between the filter sand of the present embodiment and a carbon-based filter material or a synthetic resin filter material is relatively large, so it is possible to suppress the mixing of the filter materials with each other during backwashing and maintain the effect of multi-layer filtration. It should be noted that filtration using fiber filtration can pass water at a high speed compared with filtration using filter sand, but the turbidity capture ability is not high.

[0055] (5) Conventionally, as a method for removing turbidity, there is also a method of membrane treatment using an MF membrane, a UF membrane, etc., but this method has a higher device cost compared with filtration using filter materials. That is, as in the present embodiment, by adopting filtration using filter materials to remove turbidity, the device cost can be suppressed compared with membrane treatment using an MF membrane, a UF membrane, etc.

[0056] Examples Hereinafter, examples are given to more specifically illustrate the present invention, but the present invention is not limited to the following examples.

[0057] In Examples 1 to 4 and Comparative Examples 1 to 4, hydrofluoric acid-containing water was passed through a column (filtering device) filled with filtering sand at a water flow rate (LV) of 10 m / h in a downward flow manner, and a filtering step was carried out. As the hydrofluoric acid-containing water, the drainage water of the decontamination system shown in Table 1 was used. Regarding the column filled with filtering sand, a column with a size of φ20 mm × 1000 mm was used. The filling height of the filtering sand filled in the column was 100 mm.

[0058] [Table 1]

[0059] The component ratios, effective diameters, and uniformity coefficients of the filtering sands A to D used in Comparative Examples 1 to 4 are shown in Table 2, and the component ratios, effective diameters, and uniformity coefficients of the filtering sands E to H used in Examples 1 to 4 are shown in Table 3.

[0060] [Table 2]

[0061] [Table 3]

[0062] Figure 3 Indicates the silica concentration (dissolution amount) in the filtered water obtained from Examples 1 to 2 and Comparative Examples 1 to 2, Figure 4 Indicates the silica concentration (dissolution amount) in the filtered water obtained from Examples 3 to 4 and Comparative Examples 3 to 4. In addition, Figure 5 Indicates the aluminum concentration (dissolution amount) in the filtered water obtained from Examples 1 to 2 and Comparative Examples 1 to 2, Figure 6 Indicates the aluminum concentration (dissolution amount) in the filtered water obtained from Examples 3 to 4 and Comparative Examples 3 to 4.

[0063] As Figures 3 to 6 shown, compared with Comparative Examples 1 to 4, Examples 1 to 4 suppressed the dissolution amounts of silica and aluminum in the filtered water. From these results, it can be said that by using filtering sand with a silicon component ratio of 90% by mass or more (preferably an aluminum component ratio of 2% by mass or less), the dissolution of the filter material in the treatment of hydrofluoric acid-containing water can be suppressed.

[0064] [Supplementary Note] (1) A treatment device for hydrofluoric acid-containing water, which is a treatment device for hydrofluoric acid-containing water with a pH less than 4, having: A filtering device filled with a filter material; and a deionization device disposed at the subsequent stage of the filtering device and filled with an ion exchanger, The filter material includes filtering sand with a silicon component ratio of 90% by mass or more.

[0065] (2) Regarding the treatment device for hydrogen fluoride-containing water described in (1) above, the aluminum component ratio of the filter sand is 2% by mass or less.

[0066] (3) Regarding the treatment device for hydrofluoric acid-containing water described in (1) or (2) above, a support for supporting the filter medium is provided in the filtration device. The support is gravel with an effective diameter of 2 to 6 mm. In this gravel, the silicon component ratio is 90% by mass or more, and the aluminum component ratio is 2% by mass or less.

[0067] (4) Regarding the treatment device for hydrofluoric acid-containing water described in any one of (1) to (3) above, the filter medium is composed of a combination of the filter sand and a carbon-based filter medium.

[0068] (5) Regarding the treatment device for hydrofluoric acid-containing water described in any one of (1) to (3) above, the filter medium is composed of a combination of the filter sand and a synthetic resin filter medium.

[0069] (6) Regarding the treatment device for hydrofluoric acid-containing water described in any one of (1) to (5) above, 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.

[0070] (7) A method for treating hydrofluoric acid-containing water, which is a method for treating hydrofluoric acid-containing water with a pH 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 filter medium contains filter sand with a silicon component ratio of 90% by mass or more.

[0071] (8) Regarding the method for treating hydrofluoric acid-containing water described in (7) above, the aluminum component ratio of the filter sand is 2% by mass or less.

[0072] (9) Regarding the method for treating hydrofluoric acid-containing water described in (7) or (8) above, a support for supporting the filter medium is provided in the filtration device. The support is gravel with an effective diameter of 2 to 6 mm. In this gravel, the silicon component ratio is 90% by mass or more, and the aluminum component ratio is 2% by mass or less.

[0073] (10) Regarding the method for treating hydrofluoric acid-containing water described in any one of (7) to (9) above, the filter medium is composed of a combination of the filter sand and a carbon-based filter medium.

[0074] Regarding the method for treating hydrofluoric acid-containing water described in any one of (7) to (9) above, the filter medium is composed of a combination of the filter sand and a filter medium made of synthetic resin.

[0075] Regarding the method for treating hydrofluoric acid-containing water described in any one of (7) to (11) above, the hydrofluoric acid-containing water is the drainage of a decontamination device in a semiconductor factory, and the fluorine concentration of the drainage is 100 mg / L or less.

[0076] Reference numeral description 1 Hydrofluoric 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 body.

Claims

1. A device for treating water containing hydrofluoric acid, wherein the pH of the water containing hydrofluoric acid is less than 4, characterized in that: The hydrofluoric acid-containing water treatment device comprises: a filter device filled with filter material; and a deionization device, which is arranged at the rear stage of the filtering device and is filled with an ion exchanger, The filter medium includes filter sand having a silicon content of 90% by mass or more.

2. The device for treating hydrofluoric acid-containing water according to claim 1, characterized in that: The aluminum component ratio of the filter sand is 2 mass % or less.

3. The device for treating hydrofluoric acid-containing water according to claim 1 or 2, characterized in that: The filter device is provided with a support body for supporting the filter material. The support body is gravel having an effective diameter of 2 to 6 mm, wherein the gravel has a silicon component ratio of 90 mass % or more and an aluminum component ratio of 2 mass % or less.

4. The device for treating hydrofluoric acid-containing water according to claim 1 or 2, characterized in that: The filter material is composed of a combination of the filter sand and a carbon-based filter material.

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

6. The device for treating hydrofluoric acid-containing water according to claim 1 or 2, characterized in that: The hydrofluoric acid-containing water is wastewater from a decontamination device in a semiconductor factory, and the fluorine concentration of the wastewater is below 100 mg / L.

7. A method for treating water containing hydrofluoric acid, wherein the pH of the water containing hydrofluoric acid is less than 4, characterized in that: The method for treating hydrofluoric acid-containing water comprises: a filtering step of passing the hydrofluoric acid-containing water into a filtering device filled with a filter material to obtain filtered water; and In the deionization process, the filtered water is passed through a deionization device filled with an ion exchanger to obtain ion exchange treated water. The filter medium includes filter sand having a silicon content of 90% by mass or more.

8. The method for treating hydrofluoric acid-containing water according to claim 7, characterized in that: The aluminum component ratio of the filter sand is 2 mass % or less.

9. The method for treating hydrofluoric acid-containing water according to claim 7 or 8, characterized in that: The filter device is provided with a support body for supporting the filter material. The support body is gravel having an effective diameter of 2 to 6 mm, wherein the gravel has a silicon component ratio of 90 mass % or more and an aluminum component ratio of 2 mass % or less.

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

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

12. The method for treating hydrofluoric acid-containing water according to claim 7 or 8, characterized in that: The hydrofluoric acid-containing water is wastewater from a decontamination device in a semiconductor factory, and the fluorine concentration of the wastewater is below 100 mg / L.

Images