JP2911506B2 - Treatment method for fluorine-containing wastewater - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for treating fluorine-containing wastewater.

(Prior art) Conventionally, various metal surface treatment plants, aluminum electrolytic refining plants, phosphate fertilizer production plants, ceramic plants, waste incineration plants,
Semiconductor manufacturing plant, printed circuit board manufacturing plant, ceramics manufacturing plant, industrial waste treatment plant, waste landfill site, etc.
As a method of treating fluorine-containing wastewater discharged from a fluorine-related plant, one or more calcium compounds, aluminum compounds, phosphorus compounds, etc. are added to the fluorine-containing wastewater to insolubilize fluorine ions in the wastewater. After that, a method of removing by solid-liquid separation has been proposed.

For example, Japanese Patent Publication No. Sho 60-117 discloses a method using a combination of an aluminum compound such as a sulfuric acid band and a calcium compound such as calcium hydroxide, and JP-A No. 62-125894 discloses a method using a calcium compound such as calcium chloride and phosphorus. Acid second
A method using a combination of phosphorus compounds such as potassium is described.

(Problems to be solved by the invention) However, in the above conventional methods, the amount of chemicals used and the amount of sludge generated are large, fluorine is eluted after landfilling sludge, there are many alkaline chemicals required for neutralization, and calcium scale There were problems such as the occurrence of phosphorus, exceeding the phosphorus regulation value, the complicated equipment and operation, and the inability to completely remove fluorine to low concentrations.

An object of the present invention is to provide a method for treating fluorine-containing wastewater, which can solve the above problems.

(Means for Solving the Problems) The present inventors have conducted intensive studies in order to solve the above problems, and as a result, have found that a water-soluble composition centering on a rare earth compound can be used for treating fluorine-containing wastewater. The present invention has been reached.

That is, the present invention relates to a method of adding a water-soluble composition comprising a rare earth compound, an alkaline earth metal compound and an alkali metal compound to a fluorine-containing wastewater to insolubilize the fluorine ions in the wastewater, followed by solid-liquid separation. The gist of the present invention is a method for treating fluorine-containing wastewater.

The water-soluble composition used in the present invention comprises a rare earth compound,
It is composed of an alkaline earth metal compound and an alkali metal compound. The composition range of the water-soluble composition is, for example, 100 to 250 g / l as a rare earth compound and 1 to 10 g / l as an alkaline earth metal compound. The range is suitably from 1 to 10 g / l as the alkali metal compound, and the pH of the water-soluble composition is suitably from 0 to 5.

Examples of the rare earth compound used in the present invention include cerium, lanthanum, neodymium, praseodymium, samarium, europium, gadolinium, terbium, disprosium, holmium, erbium, thulium, ytterbium, lutesium, yttrium chloride, sulfate, and nitrate. , Acetates, and these may be used alone or in combination of two or more.

Examples of the alkaline earth metal compound used in the present invention include calcium, magnesium, and barium chlorides, sulfates, nitrates, and acetates, and one or more of these may be used.

Examples of the alkali metal compound used in the present invention include chlorides, sulfates, nitrates and acetates of lithium, sodium and potassium, and one or more of these may be used.

To treat the fluorine-containing wastewater in the present invention, first, a water-soluble composition comprising a rare earth compound, an alkaline earth metal compound and an alkali metal compound is added to the fluorine-containing wastewater to insolubilize the fluorine ions in the wastewater. It is necessary.
For this purpose, 300 to 3000 mg of the above water-soluble composition may be usually injected into the fluorine-containing wastewater 1 although it varies depending on the properties of the fluorine wastewater, such as the fluorine concentration and coexisting substances. The reaction time at that time is suitably about 5 to 20 minutes, and the pH during the reaction is preferably in the range of 5 to 9, particularly preferably in the range of 6 to 8. If the pH of the fluorine-containing wastewater or the pH when an inorganic coagulant is added is outside the above range, adjust the pH to the above range by adding a normal acidic chemical such as hydrochloric acid or a normal alkaline chemical such as caustic soda. Good to do. Further, as the temperature, for example, 5 to 40 ° C. is appropriate.

Next, it is necessary to carry out solid-liquid separation of the insolubilized substance produced above. For that purpose, for example, precipitation, floating, dehydration, filtration and the like may be performed. At this time, the insolubilized product formed by adding the water-soluble composition is agglomerated and flocculent, and is easily separated into solid and liquid. If necessary, a conventional inorganic flocculant such as a sulfate band or ferric chloride may be used. Alternatively, a coagulant may be further enhanced by using a polymer coagulant such as an acrylic polymer in combination.

In the present invention, solid-liquid separation may be performed in combination with other methods such as lime agglomeration, sulfate band agglomeration, fluorapatite agglomeration, ion exchange resin adsorption, and chelate resin adsorption.

(Action) According to the present invention, when a water-soluble composition is added, fluorine and insolubilized matter in the wastewater are formed by a rare-earth compound and an alkaline-earth metal compound in the water-soluble composition. It is considered that the insolubilizing effect of the rare earth compound other than the alkaline earth metal compound is large, and the other alkaline earth metal compound and the alkali metal compound have an action of further increasing the insolubilizing effect of the rare earth compound.

(Examples) Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1, Comparative Example 1 Suspended substance 120 mg / l, fluorine 92.1 mg / l, aluminum 48 mg / l
l, wastewater 1 discharged from an aluminum metal surface treatment plant with a pH of 2.1 contains 143 g / l of cerium chloride, 47 g / l of neodymium chloride, 14 g / l of praseodymium chloride, and 1 g of samarium chloride.
2000 mg of a water-soluble composition containing 3.2 g of calcium chloride, 5 g / l of calcium chloride and 5 g / l of sodium chloride and having a pH of 3.2 was injected, stirred for 5 minutes, and the pH was measured to be 2.4.

While stirring the solution, 4100 mg / l of a caustic soda solution of 24% (expressed by weight, hereinafter the same) was injected to adjust the pH to 7.0, and the mixture was floated and separated with about 200 ml of pressurized water.

The concentration of fluorine in the separated treated water was analyzed by lanthanum-alizarin complexone spectrophotometry according to JIS K0102.

For comparison, the same treatment as above was carried out except that a component not containing calcium salt and sodium chloride was used in the components of the water-soluble composition (Comparative Example 1).

As a result, the fluorine concentration in the treated water was 6.90 in Example 1.
Comparative Example 1 was 16.3 mg / l at mg / l, and it was found that Example 1 was clearly superior.

Example 2, Comparative Examples 2 and 3, containing 5 mg / l of a suspended substance, 16.3 mg / l of fluorine, 0.64 mg / l of copper, 61 mg / l of sodium, etc., and is discharged from a printed circuit board manufacturing plant of pH 7.5. In wastewater 1, lanthanum acetate 121 g / l, europium sulfate 32 g / l, cadmium nitrate 13 g / l, terbium chloride
1000 mg of a water-soluble composition containing 2 g / l, disprosium sulfate 1 g / l, calcium nitrate 5 g / l, magnesium nitrate 3 g / l, potassium sulfate 3 g / l, and lithium acetate 2 g / l and having a pH of 4.3 was injected. For 10 minutes, then inject 300 mg of ferric chloride and add 1
After stirring for 0 min, the pH was measured to be 3.5. While stirring the mixture, 250 mg of a 24% sodium hydroxide solution was injected to adjust the pH to 7.0, and then 2 mg of a polyacrylamide anionic polymer flocculant (manufactured by Unitika) was injected.

Next, the mixture was allowed to stand for 30 minutes to precipitate, and then subjected to solid-liquid separation using a centrifugal dehydrator (manufactured by Tokyo Rikakikai Co., Ltd.) at 2,000 rpm. The fluorine concentration in the separated treated water was analyzed in the same manner as in Example 1.

For comparison, the same treatment was performed except that the water-soluble composition was not injected (Comparative Example 2).

Further, the same treatment was performed except that calcium hydroxide was used instead of the above water-soluble composition (Comparative Example 3).

As a result, the fluorine concentration in the treated water was 0.40 in Example 2.
mg / l, Comparative Example 2 was 14.8 mg / l, Comparative Example 3 was 12.8 mg / l, Comparative Example 2 had little effect compared to Example 2, and Comparative Example 3 had very little effect. The sludge production amount was 340 mg in Example 2, 710 mg in Comparative Example 3, more than twice as much in Comparative Example 3 as in Example 2, and the residual calcium concentration in the treated water was as high as in Example 2. Was 65 mg / l, Comparative Example 3 was 520 mg / l, and Comparative Example 3 had a much higher concentration than Example 2, indicating that the possibility of calcium scale adhesion to each device was large.

After leaving the sludge for 30 days, the Environment Agency Notification 13
As a result of conducting a detection test using the test sample, the elution value of fluorine was not detected in Example 2 and was 3.9 mg / l in Comparative Example 3, indicating that fluorine was eluted in Comparative Example 3 compared to Example 2. There was found.

Example 3, Comparative Example 4 Suspended substance 290 mg / l, fluorine 34.1 mg / l, sodium 6100 mg / l
l, calcium 22 mg / l, aluminum 35 mg / l, etc.
Sewage from the 8.9 waste incineration plant
110 g / l yttrium nitrate, 6 g / l holmium sulfate, 5 g / l erbium chloride, 5 g / l thulium acetate, 5 g / ytterbium nitrate
l, lutetium chloride 5 g / l, barium chloride 5 g / l and lithium chloride 5 g / l, 2000 mg of a water-soluble composition with a pH of 3.1 was injected and stirred for 15 minutes.

Next, after injecting 100 mg of ferric chloride and stirring for 15 minutes,
When measured, the pH was 7.0. While stirring this, 2 mg of polyacrylamide anionic polymer flocculant (manufactured by Unitika) was injected, allowed to stand for 30 minutes to precipitate, and then a centrifugal filter using a filter cloth (manufactured by Tokyo Rikakiki Co., Ltd.) To perform solid-liquid separation under the condition of 2000 rpm. The fluorine concentration in the separated treated water was analyzed in the same manner as in Example 1.

For comparison, exactly the same as above except that a sulfuric acid band was injected instead of the water-soluble composition, and 2200 mg of a 24% aqueous sodium hydroxide solution was injected without adjusting the ferric chloride to adjust the pH to 7.0. (Comparative Example 4).

As a result, the fluorine concentration in the treated water was 5.76 in Example 3.
mg / l, Comparative Example 4 was 16.2 mg / l, Comparative Example 4 had no effect compared to Example 3, and sludge production was 490 mg in Example 3 and 760 mg in Comparative Example 4, which was smaller than Example 3. The amount of 24% sodium hydroxide solution used in Example 3 was 0 mg, whereas that of Comparative Example 6 was 2200 mg, and that of Comparative Example 4 was much larger than that of Example 3. Each turned out.

In addition, as a result of testing the fluorine elution value from the sludge as in Example 2, Example 3 was not detected, and Comparative Example 6 was 5.
At 7 mg / l, it was found that fluorine was eluted in Comparative Example 6 as compared with Example 3.

Example 4 21 mg / l suspended material, 1960 mg / l fluorine, 820 mg / l calcium,
First, 40 g of calcium hydroxide was injected into 10 liters of wastewater discharged from a ceramics manufacturing plant containing 52 mg / l of sodium and having a pH of 1.1, and the mixture was stirred for 20 minutes.
The pH was adjusted to 1.4 by injecting 103 g of a 24% sodium hydroxide solution with stirring. While stirring, 30 mg of a polyacrylamide anionic polymer flocculant (manufactured by Unitika) was injected, and allowed to stand for 1 hour to precipitate.
The supernatant water (this supernatant water is referred to as first coagulation supernatant water) was separated by decantation. The fluorine concentration in the first coagulated supernatant water was analyzed in the same manner as in Example 1.

Next, 13.5 g of the same water-soluble composition as in Example 1 was poured into 9 l of the first coagulation supernatant water, and the mixture was stirred for 20 minutes. The pH was measured to be 5.8. While stirring, 1260 mg of a 24% sodium hydroxide solution was injected to adjust the pH to 7.0. Further, 27 mg of an anionic polyacrylamide polymer flocculant (manufactured by Unitika) was injected with stirring, allowed to stand for 1 hour to precipitate, and then filtered through filter paper to obtain solid-liquid separation (filtrated water). This filtered water is referred to as second aggregated filtered water). The fluorine concentration in the second flocculated filtered water was analyzed in the same manner as in Example 1.

Further, after injecting 140 mg of a 20% hydrochloric acid solution into 8 liters of the second flocculated filtered water to adjust the pH to 4.0, the solution was quantified into a 7 mmφ column filled with 30 ml of a fluorine-adsorbing resin Uniselect UR-3700 (manufactured by Unitika). Water was passed through the pump at a flow rate of 2.5 ml / min in a downward flow, and fluorine was adsorbed and removed to obtain treated water (this treated water was called adsorption treated water). The fluorine concentration in the water subjected to the adsorption treatment was analyzed in the same manner as in Example 1 for each water flow rate of 1.

 Table 1 shows the results.

As is evident from the results in Table 1, by performing in combination with other processing methods, the characteristics of each processing method were utilized.
Fluorine-containing wastewater can be treated efficiently and completely.

That is, the first treatment with calcium hydroxide is suitable for removing fluorine from waste water from a high concentration to a medium concentration, and the method using the second water-soluble composition removes fluorine from waste water. Suitable for removing medium to low concentrations. Further, the third method using a fluorine-adsorbing resin is suitable for completely removing fluorine from wastewater from a low concentration.
By skillfully combining these methods, high-concentration fluorine can not only be completely removed,
The sludge amount and running cost can be reduced.

(Effects of the Invention) According to the present invention, fluorine-containing wastewater can be removed to a lower concentration than conventional coagulation treatment methods, the amount of chemicals and types are reduced, and the generation of sludge is reduced. At the same time, it is possible to make it difficult for fluorine to elute from the sludge. Further, according to the present invention, since no phosphorus compound or calcium compound is used, there is no problem of phosphorus regulation and calcium scale, and furthermore, fluorine can be efficiently and completely removed in combination with another treatment method.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-132993 (JP, A) JP-A-51-107662 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 1/58

Claims (1)

(57) [Claims] (1) A water-soluble composition comprising a rare earth compound, an alkaline earth metal compound and an alkali metal compound is added to a fluorine-containing wastewater to insolubilize the fluorine ions in the wastewater, followed by solid-liquid separation. A method for treating fluorine-containing wastewater.