Method for treating water containing fluorine and aluminum

Abstract

A method for treating water containing fluorine and aluminum, in which a chelating agent having a concentration of at least 100 times the concentration of aluminum in the water containing fluorine and aluminum is added to the water containing fluorine and aluminum, and then water is passed through a reverse osmosis membrane device. The pH value of the water containing fluorine and aluminum is preferably 4-6. The chelating agent is preferably EDTA. The F ion concentration in the water to be treated is preferably 50 mg / L to 700 mg / L, and the Al ion concentration is preferably 0.01 mg / L to 1 mg / L.

Description

Technical Field

[0001] The present invention relates to a method for treating water containing fluorine and aluminum, and in particular to a method for treating water containing fluorine and aluminum by performing reverse osmosis (RO) membrane treatment on the water containing fluorine and aluminum. Background Art

[0002] In the manufacturing plants of the electronic industry such as electronic displays and semiconductors, a variety of chemicals are used. Fluorides such as hydrogen fluoride / hydrofluoric acid (HF), fluoroboric acid (HBF4), and ammonium fluoride (NH4F) are used in large quantities in the production processes such as etching and cleaning. Therefore, a large amount of drainage containing such fluorides is generated from these processes. In particular, drainage containing fluorides and silicon dioxide is discharged from the etching process of silicon wafers. In addition, drainage containing ammonium components is discharged from the process using ammonium fluoride.

[0003] Previously, as a method for treating fluoride-containing water, a method of subjecting the fluoride-containing water to RO (Reverse Osmosis) membrane treatment to recover desalted water was widely known. For example, Patent Document 1 describes a case where after pH adjustment of wastewater containing heavy metals with a fluoride concentration of 4 mg / L to 43 mg / L, a coagulation treatment is performed, followed by an RO treatment. Patent Document 1 does not describe a case where the wastewater containing heavy metals contains aluminum.

[0004] Patent Document 2 describes that after the pH value of mixed water of industrial water containing Ca ions and wastewater from electronic component manufacturing containing F ions is adjusted to 3 to 6, EDTA (ethylenediaminetetraacetic acid) is added as a chelating agent, followed by RO treatment. Patent Document 2 does not describe that the mixed water contains aluminum.

[0005] Patent Document 3 describes the following: after calcium salt is added to the wastewater of the electronic component manufacturing process, a coagulation treatment is performed, followed by a solid-liquid separation treatment, a chelating agent is added, and then an RO treatment is performed. Although the examples of Patent Document 3 describe that the raw water, i.e., raw water containing Ca, Mg, Al, P, NH4, F, and Si with a F concentration of 565 mg / L and an Al concentration of 0.2 mg / L, is subjected to a coagulation treatment, followed by solid-liquid separation, followed by the addition of 0.0025 mmol / L of EDTA, the RO treatment is performed, there is no description of the Al concentration in the RO feed water.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2003-340450

[0009] Patent Document 2: Japanese Patent Application Publication No. 2001-104955

[0010] Patent Document 3: Japanese Patent Application Publication No. 2014-213264 Summary of the invention

[0011] Problems to be solved by the invention

[0012] When water containing fluorine and aluminum is subjected to RO treatment, it is found that cryolite or the like is precipitated on the RO membrane surface, depending on the concentration of fluorine and aluminum and the pH conditions, thereby reducing the flux (permeable water flow rate).

[0013] An object of the present invention is to provide a method for treating water containing fluorine and aluminum, which can suppress a decrease in RO flux caused by aluminum.

[0014] Technical means of solving problems

[0015] The method for treating water containing fluorine and aluminum of the present invention comprises adding a chelating agent having a concentration of 100 times or more by weight of the aluminum concentration in the water containing fluorine and aluminum to the water containing fluorine and aluminum and then passing the water through a reverse osmosis membrane device.

[0016] In one embodiment of the present invention, the pH value of the water containing fluorine and aluminum is 4-6.

[0017] In one embodiment of the present invention, the chelating agent is EDTA.

[0018] Effects of the Invention

[0019] According to the method for treating water containing fluorine and aluminum of the present invention, it is possible to suppress a decrease in RO flux when fluorine and aluminum are subjected to RO treatment, thereby efficiently performing the treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [ Figure 1 ] Figure 1 (a) and (b) are structural diagrams of test devices used in Examples and Comparative Examples.

[0021] [ Figure 2 ] Figure 2 It is a graph which shows the results of Examples and Comparative Examples.

[0022] [ Figure 3 ] Figure 3 It is a graph which shows the results of Examples and Comparative Examples. DETAILED DESCRIPTION

[0023] The present invention is described in more detail below.

[0024] [Water to be treated]

[0025] As the water to be treated in the method of the present invention, wastewater from the process of using F is exemplified, and wastewater from the process of manufacturing electronic components is preferred.

[0026] The F ion concentration in the water to be treated is preferably 50 mg / L to 700 mg / L, particularly preferably 50 mg / L to 150 mg / L, and the Al ion concentration is preferably 0.01 mg / L to 1 mg / L, particularly preferably 0.01 mg / L to 0.1 mg / L.

[0027] Other main ion concentrations include the following.

[0028] Na: 20mg / L~200mg / L, especially 100mg / L~150mg / L

[0029] Ca: 0mg / L~50mg / L, especially 0.01mg / L~1mg / L

[0030] Fe: 0mg / L~50mg / L, especially 0.01mg / L~1mg / L

[0031] Mg: 0mg / L~50mg / L, especially 0.01mg / L~1mg / L

[0032] Mn: 0mg / L~50mg / L, especially 0.01mg / L~1mg / L

[0033] Si: 0mg / L~100mg / L, especially 0mg / L~50mg / L

[0034] NH 4 + (NH 4 -N): 20mg / L~200mg / L, especially 20mg / L~100mg / L

[0035] The total organic carbon (TOC) concentration in the water to be treated is preferably 0 mg / L to 10 mg / L, and particularly preferably about 0 mg / L to 3 mg / L.

[0036] The pH of the water to be treated is not particularly limited, but it is preferably adjusted with NaOH, hydrochloric acid, sulfuric acid, etc. as necessary so that the pH of the RO feed water is about 4 to 6, particularly about 5.0 to 5.5.

[0037] The water to be treated is preferably subjected to a turbidity removal treatment as necessary. Examples of the turbidity removal treatment include sand filtration and ultrafiltration (UF) membrane filtration.

[0038] [Chelating agent]

[0039] In the present invention, a chelating agent is added to RO feed water in an amount of 100 times or more, preferably 100 to 1500 times, more preferably 200 to 1500 times, and particularly preferably 300 to 1500 times the Al concentration in the RO feed water.

[0040] The chelating agent is preferably EDTA (ethylenediaminetetraacetic acid), and may also be citric acid, etc. The chelating agent is preferably added as an aqueous solution.

[0041] Example

[0042] [Example 1]

[0043] use Figure 1 In the flat membrane test apparatus shown in (a) and (b), 100 mg / L of EDTA was added to the wastewater of the following water quality and RO treatment was performed: EDTA / Al=100 / 0.07=1429.

[0044] The wastewater is wastewater obtained by concentrating wastewater from an electronic component manufacturing process using a UF membrane.

[0045] [Water quality of drainage]

[0046] Al: 0.07mg / L

[0047] Na: 113mg / L

[0048] F: 138mg / L

[0049] Si: 7.5mg / L

[0050] pH: 5.0

[0051] Silica antiscalant: 20mg / L

[0052] Figure 1 The RO membrane used in the flat-plate membrane test apparatus shown in (a) and (b) was "ES20" manufactured by Nitto Denko Corporation, and the recovery rate was set to 80%.

[0053] In the flat-plate membrane test apparatus, RO membrane feed water is supplied from a pipe 11 to a raw water chamber 1A located below a flat-plate membrane pool 2 provided with an RO membrane in a closed container 1 by a high-pressure pump 4. Figure 1As shown in (b), the closed container 1 includes a lower shell 1a on the raw water chamber 1A side and an upper shell 1b on the permeate water chamber 1B side, and the flat membrane pool 2 is fixed between the lower shell 1a and the upper shell 1b via an O-ring 8. The flat membrane pool 2 is constructed such that the permeate water side of the RO membrane 2A is supported by a porous support plate 2B. In the raw water chamber 1A on the lower side of the flat membrane pool 2, the stirring bar 5 is rotated by the stirrer 3 to stir. The permeate water of the RO membrane is taken out from the pipe 12 through the permeate water chamber 1B on the upper side of the flat membrane pool 2. The concentrated water is taken out from the pipe 13. The pressure in the closed container 1 is adjusted by the pressure gauge 6 provided on the water supply pipe 11 and the pressure regulating valve 7 provided on the concentrated water taking-out pipe 13.

[0054] The change in flux ratio over time when the wastewater is passed through the flat membrane test device is shown in FIG. Figure 2 In addition, the flux ratio indicates the ratio relative to the initial pure water flux.

[0055] [Example 2, Example 3, Comparative Example 1]

[0056] The test was conducted under the same conditions as in Example 1 except that the amount of EDTA added was set as follows. The change in flux ratio over time is shown in Figure 2 .

[0057] Example 2: 80 mg / L (EDTA / Al=1143)

[0058] Example 3: 60 mg / L (EDTA / Al=857)

[0059] Comparative Example 1: 0 mg / L (EDTA / Al=0)

[0060] <Investigation>

[0061] like Figure 2 As described above, Examples 1 to 3 in which EDTA was added in an amount of about 800 to 1500 times that of Al, could suppress the decrease in flux compared to Comparative Example 1 in which EDTA was not added.

[0062] [Example 4, Comparative Example 2]

[0063] In Example 2 and Comparative Example 1, aluminum chloride reagent was added to the wastewater to adjust the Al concentration to 0.2 mg / L, and the wastewater was treated.

[0064] The addition amount of EDTA is the same as that of Example 2 and Comparative Example 1, which is

[0065] Example 4: 80 mg / L (EDTA / Al=80 / 0.2=400)

[0066] Comparative Example 2: 0 mg / L (EDTA / Al=0).

[0067] The time-dependent change of the flux ratio is shown in Figure 3 .

[0068] like Figure 3 As described above, it was confirmed that the decrease in flux can be suppressed by adding EDTA in an amount 400 times that of Al.

[0069] While the present invention has been described in detail using specific embodiments, it will be apparent to one skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention.

[0070] This application is based on Japanese Patent Application No. 2022-090349 filed on June 2, 2022, the entire contents of which are incorporated herein by reference.

[0071] Explanation of symbols

[0072] 1: Container

[0073] 2: Flat membrane pool

[0074] 2A: RO membrane

[0075] 2B: Porous support plate

[0076] 3. Blender

[0077] 4: High pressure pump

[0078] 5. Stirring bar

[0079] 6: Pressure gauge

[0080] 7: Pressure regulating valve

[0081] 8: O-ring

Claims

1. A method for treating water containing fluorine and aluminum, comprising adding a chelating agent having a concentration of 100 times or more by weight of the aluminum concentration in the water containing fluorine and aluminum to the water containing fluorine and aluminum, and then passing the water through a reverse osmosis membrane device.

2. The method for treating water containing fluorine and aluminum according to claim 1, wherein: The pH value of the water containing fluorine and aluminum is 4-6.

3. The method for treating water containing fluorine and aluminum according to claim 1 or 2, wherein: The chelating agent is ethylenediaminetetraacetic acid.

4. The method for treating water containing fluorine and aluminum according to claim 1 or 2, wherein: The chelating agent is added to the water containing fluorine and aluminum at a concentration of 100 to 1500 times by weight of the aluminum concentration in the water containing fluorine and aluminum.

5. The method for treating water containing fluorine and aluminum according to claim 1 or 2, wherein: The chelating agent is added to the water containing fluorine and aluminum at a concentration of 800 to 1500 times by weight of the aluminum concentration in the water containing fluorine and aluminum.

6. The method for treating water containing fluorine and aluminum according to claim 1 or 2, wherein: The water containing fluorine and aluminum has a F ion concentration of 50 mg / L to 700 mg / L, and an Al ion concentration of 0.01 mg / L to 1 mg / L.

7. The method for treating water containing fluorine and aluminum according to claim 1 or 2, wherein: The total organic carbon concentration of the water containing fluorine and aluminum is less than 10 mg / L.

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