JPH07195071A - Treatment of waste water and device therefor - Google Patents

Abstract

PURPOSE:To lower the concn. of fluorine and to recover fluorine resources by forming treated water obtd. by removing the fluorine from waste water to form a treated water and subjecting the eluting liquid of the fluorine to an electrodialysis to separate concd. water and dilute water, then forming the treated water from which the fluorine is removed again from the dilute water. CONSTITUTION:This waste water treating device is composed of a first electrodialysis chamber 1 in a fore stage where the waste water contg. the fluorine is charged, an adsorption column 3 of a first stage and a second electrodialysis chamber 5 of a second stage. Meanwhile, the fluorine-contg. waste water is introduced from a piping P1 into the first electrodialysis chamber 1 and the fluorine-concd. water is led out of a piping P3. The dilute water is introduced from a piping P5 into the adsorption column 3 and a regenerating agent of an adsorbent is introduced therein from a piping P11. The treated water and the fluorine eluting liquid are led out of respective pipings P7, P8. Further, the fluorine concd. liquid is led out of a piping P13 of the second electrodialysis chamber 5 and the fluorine dilute water is led out of a piping P15. In addition, the alkali concd. water is led out of a piping P17.

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 waste water containing fluorine, and more particularly to a method and apparatus for treating waste water for recovering fluorine resources while keeping the fluorine concentration of treated water stable and low.

[0002]

2. Description of the Related Art An etching agent containing fluorine is used in semiconductor manufacturing, surface treatment of metal and glass, and the like. Wastewater containing the etching solution after use contains fluorine, neutralized with calcium compounds such as slaked lime and calcium chloride,
A common method is to perform coagulation-precipitation as calcium fluoride to remove the fluorine content, and then perform treatment such as pH adjustment and discharge.

[0003]

However, the drainage standard for fluorine is generally 15 mg / lit. It is set below, and is set to a stricter and lower value in some regions. However, in the conventional treatment with calcium compounds, a large excess of calcium compounds must be added in order to satisfy this standard, and therefore a large amount of sludge containing unreacted calcium compounds is inevitably generated. On the other hand, there is a limit to the landfill site for sludge, and there is a problem that valuable fluorine resources are simply discarded.

The present invention has been made in view of the above problems, and wastewater treatment that does not generate sludge, keeps the fluorine concentration of the treated water lower than the standard value of the wastewater, and can recover the fluorine resources in the wastewater. It is an object to provide a method and an apparatus thereof.

[0005]

To achieve the above object, the first aspect of the present invention is to produce a treated water in which fluorine is removed from a wastewater containing fluorine by a fluorine adsorbent, and to remove the fluorine from the fluorine adsorbent. A step of eluting and electrodialyzing a fluorine eluent containing the fluorine to separate fluorine-concentrated water and diluted fluorine water, and a step of generating treated water from which fluorine is removed again by the fluorine adsorbent from the diluted fluorine water. It is the gist to have.

The second aspect of the present invention is an adsorbing means for removing fluorine from waste water containing fluorine by a fluorine adsorbent, and a fluorine adsorbing agent after removing fluorine by the adsorbing means to elute the fluorine from the adsorbent. The gist of the present invention is to have electrodialysis means for electrodialyzing the eluent to separate it into fluorine-concentrated water and diluted fluorine water, and return means for returning the diluted fluorine water to the adsorption means again.

Preferably, the fluorine-containing waste water is recovered as treated water from which fluorine has been removed in the first step using a fluorine adsorbent, and the fluorine-containing eluent used for regeneration of the fluorine adsorbent is electrodialyzed. It is preferable that the fluorine-concentrated water and the fluorine-diluted water are separated by two steps, the fluorine-concentrated water is recovered, the fluorine-diluted water is returned to the first step, and fluorine is removed again.

Preferably, a bipolar membrane is used in the electrodialysis step by combining an anion exchange membrane and a cation exchange membrane. Further, it is preferable to use an electrodialysis method, more specifically, a three-chamber electrolytic dialysis method, in the electrodialysis step.
Further, it is preferable to use a fluorine selective adsorption resin as the fluorine adsorbent in the adsorption step. More preferably, the fluorine-concentrated water and the fluorine-diluted water are prepared in the preceding step by electrodialysis, the concentrated water is recovered, and the diluted water is treated with the fluorine adsorbent in the steps after the first step.

[0009]

In the wastewater treatment method of the first invention of the present application, after removing the fluorine from the wastewater containing fluorine by the fluorine adsorbent,
Fluorine is eluted from this fluorine adsorbent, and the fluorine eluent containing the fluorine is electrodialyzed to obtain fluorine-concentrated water.

In the wastewater treatment equipment of the second invention of the present application, fluorine is removed from the wastewater containing fluorine by the adsorbing means using the fluorine adsorbent, and the fluorine adsorbent after the fluorine is removed by the adsorbing means contains fluorine. Since it is adsorbed and contained, fluorine is eluted from the fluorine adsorbent by the fluorine eluent, and the fluorine eluent containing the fluorine is electrodialyzed to separate into fluorine-concentrated water and diluted fluorine water to obtain fluorine-concentrated water. Therefore, there is no generation of sludge.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a wastewater treatment method and an apparatus thereof according to the present invention.

Referring to FIG. 1, the waste water treatment apparatus of this embodiment comprises a first electrodialysis tank 1 in the preceding stage into which waste water containing fluorine is introduced, an adsorption tower 3 in the first step, and a second step in the second step. The electrodialysis tank 5 of FIG. Further, these are a pipe P1 for introducing the fluorine-containing wastewater into the electrodialysis tank 1 and a pipe P3 for withdrawing the fluorine-concentrated water from the first electrodialysis tank 1.
And a pipe P5 for extracting diluted water to the adsorption tower 3, and the adsorption tower 3
Pipe P7 for extracting the treated water of No. 3, pipe P9 for extracting the fluorine eluent of the adsorption tower 3 to the second electrodialysis tank 5, and the regenerant of the adsorbent in the adsorption tower 3 is introduced from the regenerant tank for adsorbent 7 Pipe P11, a pipe P13 for withdrawing the fluorine-concentrated water from the second electrodialysis tank 5, a pipe P15 for returning the diluted fluorine water in the second electrodialysis tank 5 to the adsorption tower 3, and a second electrodialysis tank. Pipe P1 for returning the alkaline concentrated water of No. 5 to the adsorption tower 3
7 and. Here, the pipe P15 functions as a return means for returning the diluted fluorine water in the second electrodialysis tank 5 to the adsorption tower 3, which is an adsorption means.

The wastewater treatment apparatus shown in FIG. 1 can be applied to wastewater having a wide range of fluorine concentration, but in this embodiment, the fluorine concentration is 10,000 mg / lit. This will be explained by taking the drainage of the above as an example. The fluorine-containing wastewater was treated with a fluorine concentration of 50000 mg / lit. Fluorine-concentrated water and fluorine concentration 200 mg / lit. It is divided into diluted fluorine water. The fluorine-concentrated water is extracted as a fluorine raw material through the pipe P3 and is reused.

For electrodialysis, in addition to the usual method using an anion exchange membrane and a cation exchange membrane suitable for acid concentration, a three-chamber electrolytic dialysis method capable of salt concentration, or a more efficient bipolar membrane Alternatively, an electrodialysis method in which an anion exchange membrane and a cation exchange membrane are combined may be used.

Fluorine concentration in raw wastewater is 1000 mg / li
t. In the case of the following low concentrations, the step using the first electrodialysis tank 1 can be omitted, and the raw waste water should be introduced into the first adsorption step directly or appropriately diluted via a pipe P19 shown by a dotted line in the figure. You can

The diluted fluorine water is adsorbed in the adsorption tower 3 through the pipe P5.
Was introduced into the reactor, the fluorine was removed by the fluorine adsorbent, and the fluorine concentration was 5 mg / lit. And the wastewater is treated below the standard value. This treated water is recovered in the treated water recovery tank 9 and reused or discharged as a water resource.

As the fluorine adsorbent, a chelate resin that adsorbs fluorine ions, a resin that adsorbs metal ions forming a complex compound with fluorine ions, or the like can be used.

After adsorbing a predetermined amount of fluorine, the fluorine adsorbent elutes fluorine ions using an alkaline aqueous solution such as caustic soda as an eluent, and then the fluorine adsorbing ability is regenerated with a regenerant containing an acid or specific ions.

At this time, the treated eluent contains 1000 m
g / lit. The above fluorine and alkali ions are included. The regenerant is separately stored in the regenerant tank for adsorbent 7 through the pipe P21 and repeatedly used.

The used eluent is sent to the second electrodialysis tank in the second step through the pipe P9. In the second step, a bipolar membrane and an anion exchange membrane, which is a method for separating and concentrating fluorine ions and alkali ions contained in the eluent,
Electroanalytical method combined with cation exchange membrane, or 3
Use the room electrolysis dialysis method.

Fluorine concentration of 50,000 m
g / lit. Fluorine-enriched water and alkali-enriched water,
Fluorine concentration 200 mg / lit. The following diluted fluorine water is obtained. The fluorine-concentrated water is extracted through the pipe P13 and reused as a fluorine raw material. At this time, by using an adsorbent having a high fluorine selectivity in the first step, it is possible to obtain fluorine-containing water having a higher purity than in the electrodialysis step of the first stage. The alkali-concentrated water is returned to the first step through the pipe P17 and repeatedly used as an eluent for the fluorine adsorbing resin. The diluted fluorine water is returned to the first adsorption step through the pipe P15, treated to a fluorine concentration below the regulation value, and discharged or reused.

FIG. 1 shows the concept of the treatment method of the present invention. As necessary, a filter or chemical treatment for removing solids or a specific substance in waste water, treatment of each step, and treatment of each step. Needless to say, pH adjustment to match the conditions and storage tanks for raw wastewater and treated water / chemical solution may be added.

In the fluorine-containing wastewater treatment method of the present invention, the fluorine concentration is 50000 mg / lit. As described above, it is possible to obtain concentrated water capable of recovering fluorine resources and highly purified treated water that satisfies the wastewater standards sufficiently. Moreover, sludge, which has been a problem in the past, does not occur.

Next, the first embodiment will be described. First, the fluorine concentration mainly containing hydrogen fluoride is 9000 mg / lit.
An etching waste liquid containing a small amount of impurities in a semiconductor factory was treated with the waste water treatment apparatus shown in FIG.

The first electrodialysis tank in the first step using the anion exchange membrane and the cation exchange membrane was used to obtain a fluorine concentration of 520.
00 mg / lit. Concentrated water and 200 mg / lit. I got dilute water. The concentrated water was recovered and reused, and the diluted water was sent to the adsorption tower 3 in the second step.

By the adsorption treatment in the second step, the fluorine concentration was 1 mg / lit. The following treated water was obtained. The treated water is
It could be used as raw water of pure water. A selective adsorption resin of fluorine and fluorine complex ions holding cerium oxide was used as an adsorbent. Although the process of the first step is stopped during the regeneration of the adsorption resin, continuous operation becomes possible by providing two or more adsorption towers.

After adsorbing a predetermined amount of fluorine, the adsorbent used in the first step was regenerated with hydrochloric acid after eluting fluorine ions with an aqueous potassium hydroxide solution. 2 for the processing liquid that eluted fluorine.
000 mg / lit. And the potassium ions used for the elution of fluorine were included. Here, potassium hydroxide is used as an eluent of fluorine for the purpose of increasing the efficiency of electrodialysis using the bipolar membrane in the second step, and it is also possible to use other alkali such as caustic soda. .

The used eluent is the second combined bipolar membrane of the second step and an anion exchange membrane / cation exchange membrane.
It was treated in the electrodialysis tank 5. Fluorine concentration 650 in this process
00 mg / lit. Fluorine-concentrated water with a fluorine concentration of 15
0 mg / lit. Dilute fluorine dilute water and potassium hydroxide aqueous solution were obtained. The concentrated water was recovered and reused through the pipe P13, and the dilute water was treated through the pipe P15 in the adsorbent step of the first step. The potassium hydroxide solution was returned to the adsorption tower 3 in the first step through the pipe P17 and used as a fluorine ion eluent for the adsorption resin. Although not shown, a storage tank for an aqueous solution of potassium hydroxide was provided and used as an eluent according to the time for regeneration of the adsorbent.

By the above treatment, the fluorine concentration was 52000 mg / lit. , Fluorine concentration 65 in the second step
000 mg / lit. Fluorine-enriched water was recovered. These have a high fluorine concentration and can be reused as fluorine resources. The fluorine concentration of the treated water is 1 mg / li.
t. The following and the drainage standards were sufficiently satisfied, and it was possible to use it as raw water for pure water.

Next, a second embodiment will be described. Example 1
In the second step, a chelate resin that selectively adsorbs only fluorine ions was used in the second step. Fluorine recovery water having the same fluorine concentration as in Example 1 and fluorine concentration 2 mg / lit. Treated water was obtained. As described above, according to the method for treating fluorine-containing wastewater of the present embodiment, it is possible to obtain and reuse treated water having a low fluorine concentration without generating sludge, and at the same time, it is possible to recover fluorine resources. It is extremely useful industrially and in terms of resource reuse.

[0031]

As described above, the present invention has the effect that the fluorine resources contained in the waste water can be efficiently recovered by adsorption with the fluorine adsorbent and electrodialysis of the fluorine eluent. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment to which a method for treating fluorine-containing wastewater according to the present invention is applied.

[Explanation of symbols]

 1 1st electrodialysis tank 3 adsorption tower 5 2nd electrodialysis tank 7 adsorbent regenerant tank 9 treated water recovery tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Terunobu Hayada 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock company Toshiba Yokohama office

Claims (2)

[Claims] 1. A step of producing treated water in which fluorine is removed from a waste water containing fluorine by a fluorine adsorbent, and fluorine is eluted from the fluorine adsorbent, and a fluorine eluent containing the fluorine is electrodialyzed to obtain concentrated fluorine water. And a diluted fluorine water, and a step of generating treated water in which fluorine is removed from the diluted fluorine water by the fluorine adsorbent again. 2. Adsorption means for removing fluorine from waste water containing fluorine with a fluorine adsorbent; and fluorine eluent from the fluorine adsorbent after the fluorine is removed by the adsorbing means to electrodialyze the fluorine eluent containing the fluorine. A wastewater treatment apparatus comprising: an electrodialysis unit for separating the fluorine-concentrated water and the diluted fluorine water; and a return unit for returning the diluted fluorine water to the adsorption unit again.