JPH05253575A - Treatment of fluorine-containing water - Google Patents

Abstract

PURPOSE:To obtain high purity treated water and to efficiently recover fluorine by bringing a separated solution being low concn. fluorinecontaining water separated from fluorine-containing water into contact with a fluorine adsorbing resin and adding a waste regenerating solution of the fluorine adsorbing resin to separated high concn. fluorine-containing water to pass said water through a calcium carbonate crystal seed packed tank. CONSTITUTION:Fluorine-containing water is separated into low concn. fluorine- containing water and high concn. fluorine-containing water and a calcium compd. such as Ca(OH)2 is added to the low concn. fluorine-containing water in a mixing tank 2 to subject said water to solid-liquid separation and the separated solution is brought into contact with a fluorine adsorbing resin in a fluorine adsorbing resin tower 7. The fluorine adsorbing resin is subjected to regeneration treatment and, after the waste regenerating solution of the fluorine adsorbing resin is added to the high concn. fluorine-containing water, said water is passed through a colcium carbonate crystal seed packed tank 13. By this constitution, the high concn. fluorine-containing water is reacted with CaCo3 along with the waste regenerating solution of the fluorine adsorbing resin and contained fluorine can be efficiently recovered as CaF2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating fluorine-containing water, and particularly, in a system in which low-concentration fluorine-containing water and high-concentration fluorine-containing water are discharged, each fluorine-containing water can be efficiently produced at low cost. And a method for efficiently recovering fluorine.

[0002]

2. Description of the Related Art A large amount of etching agents are used in the field of semiconductor manufacturing and related fields, and in the field of surface treatment of various metal materials, single crystal materials, optical materials and the like. As the etching agent, hydrogen fluoride or an etching agent containing hydrogen fluoride and ammonium fluoride as main components is mainly used.

An etching agent containing hydrogen fluoride as a main component is an etching agent containing about 0.9% of fluorine as HF, and is used in a large amount. On the other hand, although the etching agent containing hydrogen fluoride and ammonium fluoride (buffered hydrofluoric acid) is used in a small amount, it contains about 7% of fluorine as HF, which becomes a problem when it is transferred to a wastewater system. .. That is, these etching agents flow out to the wastewater system as they are, and become a high concentration fluorine-containing waste liquid.

On the other hand, during or after the etching, since the materials treated with these etching agents are washed with a large amount of washing water, a large amount of low concentration fluorine-containing waste liquid is discharged from the washing step.

Conventionally, these high-concentration fluorine-containing waste liquids and low-concentration fluorine-containing waste liquids have been mixed and collectively processed. For the treatment of this fluorine-containing wastewater, a method of adding a calcium salt such as calcium hydroxide (Ca (OH) ₂ ) and precipitating and removing it as calcium fluoride (CaF ₂ ) is generally used.

Alternatively, the high-concentration fluorine-containing waste liquid is separated from the low-concentration fluorine-containing waste liquid, the high-concentration fluorine-containing waste liquid is subjected to precipitation treatment with calcium salt, and the obtained treated water (fluorine concentration of about 200 mg-HF / liter) is obtained. Is mixed with a low-concentration fluorine-containing waste liquid, and a calcium salt or an aluminum salt together with a calcium salt is added to the waste water treatment facility for coagulation-precipitation treatment. In this case, the final discharged water has a fluorine concentration of 8 mg-HF / liter or less, and the precipitate is treated as waste sludge.

[0007]

Among the above-mentioned conventional methods, in order to treat fluorine below the drainage standard value by a method of mixing a high concentration fluorine-containing waste liquid and a low concentration fluorine-containing waste liquid and treating them collectively, A large excess of calcium salt needs to be added. Moreover, it has been extremely difficult to treat efficiently in a short time only by adding this calcium salt.

Further, in the method of separately treating the waste liquid containing high-concentration fluorine and the waste liquid containing low-concentration fluorine, the amount of waste sludge generated in the final coagulation-sedimentation treatment is large and there is a problem in sludge treatment.

By applying a fluorine-adsorbing resin to the coagulation-sedimentation treatment system, the treated water quality can be stably maintained and the amount of sludge generated can be reduced, and further, the installation area of the device can be expected to be reduced. In this case, the fluorine concentrated by the fluorine-adsorbing resin is usually returned to the waste liquid raw water tank, treated again, and finally discharged as waste sludge out of the system.

By the way, at present, there is a system for producing hydrofluoric acid (HF) again by recovering the fluorine contained in the high concentration fluorine-containing waste liquid and the low concentration fluorine-containing waste liquid as CaF ₂ by calcium carbonate (CaCO ₃ ). It has been studied and it is desired to efficiently collect the fluorine removed from the waste liquid containing high-concentration fluorine and the waste liquid containing low-concentration fluorine as waste sludge.

The present invention solves the above-mentioned conventional problems, and in a system in which low-concentration fluorine-containing wastewater and high-concentration fluorine-containing wastewater are discharged, these fluorine-containing wastewater are treated efficiently in a short time at low cost, An object of the present invention is to provide a method for efficiently collecting fluorine while obtaining highly purified treated water.

[0012]

The method for treating fluorine-containing water according to the present invention is a method for treating fluorine-containing water, which comprises treating a fluorine-containing water with a calcium compound and a fluorine-adsorbing resin. A step of separating into fluorine-containing water and high-concentration fluorine-containing water, solid-liquid separation after adding a calcium compound to low-concentration fluorine-containing water, a step of contacting the separated liquid with a fluorine-adsorbing resin, a step of regenerating the fluorine-adsorbing resin, And a step of adding the recycled waste liquid of the fluorine-adsorbing resin to the high-concentration fluorine-containing water, and then passing the solution through a calcium carbonate crystal seed filling tank.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a system diagram showing an implementation method of the fluorine-containing water treatment method of the present invention.

In FIG. 1, 1, 5, 9, and 12 are storage tanks, 2 are mixing tanks, 3 are coagulation tanks, 4 are sedimentation tanks, 6 is a sand filtration tank, 7 is a fluorine adsorption resin tower, and 8 is pH adjustment. Tank 10, 10 is a concentrating tank, 11 is a dehydrator, and 13 is a CaCO ₃ filling tank.

Reference numeral 20 is a pipe for introducing a low-concentration fluorine-containing waste liquid into the storage tank 1, 21 is a pipe for feeding the stored water of the storage tank 1 to the mixing tank 2, 22 is a sand filter tank for storing the stored water in the storage tank 5. 6, pipe 23 for feeding the filtrate of the sand filtration tank 6 to the fluorine adsorption resin tower 7, 24 for piping the treated water of the fluorine adsorption resin tower 7 to the pH adjusting tank 8, and 25 for It is a discharge pipe for treated water in this treatment process. 26 is a pipe for sending the precipitate in the settling tank 4 to the concentrating tank 10, 27 is a pipe for sending the concentrate in the concentrating tank 10 to the dehydrator 11, 28 is a draining pipe for the dehydrated cake, and 29 is for the dehydrator 11. It is a pipe for returning the separated water to the storage tank 1. 30 is a storage tank 1 for waste liquid containing high-concentration fluorine
2 is a pipe for feeding to 2, and 31 is Ca for storing water in the storage tank 12.
A pipe for feeding the CO ₃ filling tank 13, a pipe 32 for extracting CaF _2, a pipe 33 for feeding the treated water of the CaCO ₃ filling tank 13 to the storage tank 1, and a pipe 34 for recycling waste liquid of the fluorine adsorption resin tower 7. It is a discharge pipe, and is branched into a pipe 34A for feeding the concentrated regeneration waste liquid to the storage tank 12 and a pipe 34B for feeding the non-concentration regeneration waste liquid to the storage tank 1. 35 is a calcium compound supply pipe, 36 is a coagulant supply pipe, and 37 is HC
1 is a supply pipe, and 38 is a NaOH supply pipe.

In the present invention, the separation treatment is carried out without mixing the high-concentration fluorine-containing water and the low-concentration fluorine-containing water.

Examples of the high-concentration fluorine-containing water and the low-concentration fluorine-containing water include treatment process wastewater using the above-mentioned etching agent and cleaning wastewater thereof. In addition, the standard of high concentration fluorine-containing water is 500mg-HF /
The standard for waste water of liter or more and water containing low concentration of fluorine is 5
Waste water less than 00 mg-HF / liter.

In the illustrated embodiment, the low-concentration fluorine-containing wastewater is mixed with the separated water from the dehydrator 11, which will be described later, and the non-concentrated reclaimed wastewater of the fluorine-adsorbing resin tower 7 through the pipe 20, the storage tank 1 and the pipe 21. It is fed to the tank 2 and a calcium compound such as Ca (OH) ₂ is added. Incidentally, the etching agent-containing wastewater which is one of the preferred water to be treated of the present invention,
Often contains hydrogen peroxide. Since hydrogen peroxide inhibits precipitation separation and deteriorates the resin in the subsequent stage, it is preferable to decompose hydrogen peroxide by using a reducing agent such as NaHSO ₃ and a hydrogen peroxide decomposing enzyme together. In addition, an inorganic acid such as H ₂ SO ₄ or HCl is added as a pH adjuster and mixed.

The mixed liquid in the mixing tank 2 is subjected to coagulation treatment by adding a coagulant such as polyacrylamide partial hydrolyzate in the coagulation tank 3 and then precipitated and separated in the settling tank 4, and the precipitate (sludge) is piped. From the 26, it is sent to the concentration tank 10, while the supernatant water is transferred to the storage tank 1.

Here, as the calcium compound added to the mixing tank 2, calcium chloride (CaCl ₂ ) is used in addition to basic calcium compounds such as calcium oxide (CaO) and calcium hydroxide (Ca (OH) ₂ ). It is possible to add it, and it is preferable that the addition amount thereof is about 0.5 to 3 times the equivalent of the fluorine ion in the water to be treated in terms of Ca. It is preferable to appropriately adjust the pH in the mixing tank 2 to be about 6 to 11. Further, the addition amount of the aggregating agent in the aggregating tank 3 is preferably about 0.01 to 10 ppm.

The reaction conditions in the mixing tank 2 and the aggregating tank 3 are not particularly limited, but in the usual case, the residence time is each 1 minute to 5 minutes.
It is treated under rapid stirring for about a time.

From the precipitation tank 4 through the pipe 26, the concentration tank 10
The sludge that has been sent to is then concentrated here and then sent to the dehydrator 11 via the pipe 27 for dehydration processing. The dehydrated cake is discharged to the outside of the system through the pipe 28, and the separated water is returned to the storage tank 1 through the pipe 29 and treated together with the low concentration fluorine-containing waste liquid.

On the other hand, the stored water in the storage tank 5 is sent to the sand filtration tank 6 through the pipe 22 and sand filtered. The pH of the filtrate is adjusted to pH 3 in the pipe 23 with an acid such as HCl from the pipe 37.
After being adjusted to about ˜7, it is fed to the fluorine adsorption resin tower 7 and is brought into contact with the fluorine adsorption resin for adsorption treatment. As a result, the coagulated separated water such as a low concentration fluorine-containing waste liquid has a low fluorine content, and thus can be easily treated to a discharge water standard value (15 mg-HF / liter) or less.
The treated water obtained by the adsorption treatment in the fluorine adsorption resin tower 7 is fed to the pH adjusting tank 8 through the pipe 24, and after adjusting the pH by adding an alkali such as NaOH as necessary through the pipe 38, the storage tank. 9. It is discharged to the outside of the system through the pipe 25. Since the treated water obtained is below the discharge water standard value,
It may be discharged as it is, or may be recovered and reused as raw water for producing ultrapure water or other industrial water.

As the fluorine adsorbing resin, for example,
Examples thereof include resins adsorbing metal ions forming complex compounds with fluorine ions such as cerium, hafnium, titanium, zirconium, iron, aluminum and lanthanide, activated carbon, activated alumina, hydrous titanium oxide, zeolite and magnesia adsorbents. Further, the adsorption treatment condition is not particularly limited, but for example, the treatment is carried out at SV of about 0.5 to 30 hr ⁻¹ .

In the fluorine adsorption resin tower 7, the adsorption treatment is stopped and a regeneration agent is supplied to perform a regeneration treatment, if necessary. As the regenerant, an aqueous solution of sodium hydroxide, potassium hydroxide, hydrochloric acid, sodium carbonate or the like is used. Since a part of the regenerated waste liquid obtained by this regenerating process contains a large amount of fluorine component, it is fed to the later-described high-concentration fluorine-containing waste liquid storage tank 12 through the pipes 34 and 34A for treatment.

By the way, the fluorine concentration of the recycled waste liquid obtained by this recycling treatment changes with time. That is, in the very early stage of regeneration, the waste liquid containing almost no fluorine flows out, in the early to middle stages of the regeneration, the concentrated waste liquid containing relatively high concentration of fluorine flows out, and in the latter stage of the regeneration, it gradually recovers. The fluorine concentration in the waste liquid will decrease.

In the present embodiment, among such regeneration waste liquids, only the concentrated regeneration waste liquid having a high fluorine-containing concentration, which flows out from the initial stage to the middle stage of the regeneration, is fed to the storage tank 12, and the very early and late stages of the regeneration. The non-concentrated regenerated waste liquid having a relatively low fluorine-containing concentration flowing out to is sent to the storage tank 1 through the pipes 34 and 34B and treated together with the low-concentration fluorine-containing waste liquid.

As described above, by separately treating the recycled waste liquid into the concentrated recycled waste liquid and the non-concentrated recycled waste liquid, the load can be reduced and the fluorine recovery efficiency can be improved.

As a method of separating the recycled waste liquid into a concentrated recycled waste liquid and a non-concentrated recycled waste liquid, for example, a predetermined timer is used based on pH detection or fluorine ion concentration detection of the recycled waste liquid flowing out from the fluorine adsorption resin tower 7. Only the recycled waste liquid having a value equal to or higher than the detection value of is taken out as a concentrated recycled waste liquid for a predetermined time. Specifically, (i) the regenerated waste liquid having a pH range of 4 to 13.6 is collected by setting a timer for a predetermined time. (ii) Fluorine ion concentration of 1 with fluorine ion selective electrode
Recycled waste liquid of 00 mg-HF / liter or more is collected by setting a timer for a predetermined time. Can be adopted.

On the other hand, the waste liquid containing high-concentration fluorine is supplied to the pipe 30.
It is further fed to the storage tank 12, and is introduced into the CaCO ₃ filling tank 13 through the pipe 31 together with the concentrated regeneration waste liquid from the pipe 34A and processed. In this CaCO ₃ filling tank 13, most (about 98%) of fluorine in the liquid is recovered from the pipe 32 as CaF ₂ . This CaCO ₃ filling tank 1
The liquid from which fluorine has been removed in 3 is stored in the storage tank 1 through the pipe 33.
And is treated together with a low concentration fluorine-containing waste liquid and the like.

Here, as the CaCO ₃ filling tank 13,
A CaCO ₃ crystal seed having a particle size of about 0.1 to 0.5 mm is used, and the liquid passing conditions are not particularly limited, but for example, SV is processed at about 0.1 to 5 hr ⁻¹ .

According to the method of this embodiment, the fluorine-containing water is separated into the low-concentration fluorine-containing waste liquid and the high-concentration fluorine-containing waste liquid, and the high-concentration fluorine-containing waste liquid and the concentrated regeneration waste liquid of the fluorine adsorption resin tower are mixed with CaCO ₃ crystals. Treated with seeds to remove fluorine from Ca
It can be efficiently recovered as F ₂ . After treating the fluorine-collected treated water with a low-concentration fluorine-containing waste liquid and a non-concentrated reclaimed waste liquid of a fluorine-adsorbing resin tower with a calcium compound, and then contacting the fluorine-adsorbing resin, highly-treated treated water is efficiently recovered. Is possible.

The example shown in FIG. 1 is an embodiment of the method for treating fluorine-containing water of the present invention, and the present invention is not limited to the method shown. For example, in the illustrated method, the settling tank 4 and the sand filtration tank 6 are used as the solid-liquid separation means, but the method is not limited to this. For example, membrane separation using a reverse osmosis membrane, an ultrafiltration membrane, or a microfiltration membrane. A device may be used.

[0034]

In the method for treating fluorine-containing water of the present invention,
The low concentration fluorine-containing water and the high concentration fluorine-containing water can be separately treated without mixing, and optimal treatment can be performed according to each fluorine concentration. That is, the low-concentration fluorine-containing water can be easily made into high-purity water having a discharge water reference value or less by adsorption treatment. On the other hand, the high-concentration fluorine-containing water can efficiently recover the contained fluorine as CaF ₂ by reacting with CaCO ₃ together with the waste liquid for regeneration of the fluorine-adsorbing resin. Since the recovered CaF ₂ is of extremely high purity,
It can be effectively reused as a raw material for producing hydrofluoric acid. Further, since the treated water obtained by the adsorption treatment has an extremely high purity, it can be effectively reused as raw water for producing ultrapure water or the like.

Moreover, the amount of sludge generated in the treatment of the low-concentration fluorine-containing waste liquid is very small. By the way, according to the method of the present invention, the sludge generation amount is 5% as compared with the conventional method.
It can be reduced by 0 to 60% and the operating cost is 50 to 5
It can be reduced by about 5%. In addition, the installation area can be reduced by about 30% by improving the processing efficiency. Furthermore, of the fluorine that has been conventionally treated by wastewater, 10-20
% Can be recovered as CaF ₂ and reused.

Particularly, the regeneration waste liquid is separated into a concentrated regeneration waste liquid containing a high concentration of fluorine and a non-concentrated regeneration waste liquid, and only the concentrated regeneration waste liquid is treated together with the high concentration fluorine-containing waste liquid to reduce the load on the apparatus and CaF. ₂ Recovery efficiency can be improved.

[0037]

EXAMPLES The present invention will be described in more detail with reference to the following examples. In the following, the fluorine concentration is shown in HF conversion value.

Example 1 The high-concentration fluorine-containing waste liquid and the low-concentration fluorine-containing waste liquid having the water quality shown in Table 1 were treated according to the method shown in FIG. The processing conditions were as follows.

Mixing tank Ca (OH) ₂ addition amount: 750 ppm H ₂ SO ₄ addition amount: Add until pH = 7 NaHSO ₃ addition amount: 650 ppm pH = 7 Residence time = 30 minutes Coagulation tank Flocculant (polyacrylamide part Hydrolyzate) Addition amount:
0.5 ppm retention time = 5 minutes Fluorine adsorption resin tower Fluorine adsorption resin: Resin mixed with hydrated cerium oxide SV = 20 hr ⁻¹ pH = 3 CaCO ₃ filling tank CaCO ₃ particle size: 0.1 to 0.5 mm CaCO ₃ Filling amount: 1 liter SV = 1 hr ⁻¹ Outflow liquid (Ca (OH) ₂ treated water) of the sand filtration tank 6 and outflow water (adsorption treated water) of the fluorine adsorption resin tower 7 in the treatment system of the low concentration fluorine-containing waste liquid. Table 1 shows the water quality.

[0040]

[Table 1]

The above-mentioned low-concentration fluorine-containing waste liquid is added to 500 to 60
0B. V. When treated, the fluorine adsorption resin tower was regenerated with 60 g-NaOH / liter-resin.
Fig. 2 shows the change over time in the quality of the recycled waste liquid during this recycling process.
It was as shown in. Therefore, the effluent having a high fluorine concentration (the effluent having a pH of 4 to 13.6) shown in FIG.
It is collected for 0 minutes, and CaCO is added together with the waste liquid containing high-concentration fluorine.
Processed in ₃ filling tanks.

As a result, 98% or more of the fluorine content was CaF
It could be converted to ₂ and recovered. This recovered CaF ₂
In the product CaF ₂ obtained from
Na ⁺ ions from H were uncontaminated. Note that C
The liquid obtained by the aF ₂ recovery treatment was treated again together with the low concentration fluorine-containing waste liquid.

[0043]

As described in detail above, according to the method for treating fluorine-containing water of the present invention, each fluorine-containing water is optimized in a system in which high-concentration fluorine-containing water and low-concentration fluorine-containing water are discharged. According to the method, it is possible to process efficiently and at low cost in a short time, and recover highly purified treated water and highly purified CaF ₂ . In addition, the regeneration waste liquid of the adsorption tower can be treated at the same time, and the amount of sludge generated can be significantly reduced, which is extremely industrially advantageous.

[Brief description of drawings]

FIG. 1 is a system diagram showing an implementation method of a method for treating fluorine-containing water according to the present invention.

FIG. 2 is a graph showing changes over time in the water quality of the recycled waste liquid obtained in Example 1.

[Explanation of symbols]

1, 5, 9, 12 Storage tank 2 Mixing tank 3 Coagulation tank 4 Precipitation tank 6 Sand filtration tank 7 Fluorine adsorption resin tower 8 pH adjusting tank 10 Concentrating tank 11 Dehydrator 13 CaCO ₃ filling tank

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masahiro Furukawa 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (72) Naoto Ichiyanagi 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (72) Inventor Masahiro Miki 1-chome 14-521, 1-23, Tezukayama, Abeno-ku, Osaka-shi, Osaka (72) Inventor Toshiro Fukudome 68-335, Kobuki, Chihaya-akasaka-mura, Minamikawachi-gun, Osaka (72) Invention Person Maeno Matagoro 2-42-6, Komeidai, Izumi City, Osaka Prefecture

Claims (1)

[Claims] 1. A method for treating fluorine-containing water, which comprises treating a fluorine-containing water with a calcium compound and a fluorine-adsorbing resin, the method comprising: separating the fluorine-containing water into low-concentration fluorine-containing water and high-concentration fluorine-containing water; A step of solid-liquid separation after adding a calcium compound to the concentration fluorine-containing water, a step of contacting the separated liquid with the fluorine adsorption resin, a step of regenerating the fluorine adsorption resin, and a high-concentration fluorine-containing water containing the regeneration waste liquid of the fluorine adsorption resin. After adding
And a step of passing the solution through a calcium carbonate crystal seed filling tank.