TW201500297A - Method and apparatus for treating borofluoride-containing water - Google Patents

Abstract

Borofluoride-containing water is treated without carrying out warming so as to highly remove boron as well as fluorine therefrom. A method for treating borofluoride-containing water, which comprises: a first step of adding an aluminum compound to the borofluoride-containing water to decompose a borofluoride at pH 1 to 4; a second step of adding a calcium compound to treated water obtained in the first step to react the treated water with the calcium compound at pH 7 to 13, thereby producing an insoluble substance; and a third step of separating the insoluble substance into a solid material and a liquid material. The aluminum compound is added in such a manner that the Al/F ratio becomes 1.2 to 2.5 (by mole). The calcium compound is added in such a manner that the Ca/Al ratio becomes 2.5 to 4.0 (by mole). Each of the treatment temperature employed in the first step and the treatment temperature employed in the second step is 10 to 35 not C.

Description

Treatment method and treatment device for water containing borofluoride

The present invention relates to a method and apparatus for treating water containing borofluoride, and more particularly to a method and apparatus for treating water containing borofluoride to obtain treated water having significantly reduced borofluoride, fluorine and boron.

Conventionally, as a method of treating fluorine-containing water, a method of adding a calcium compound to precipitate fluorine as calcium fluoride and performing solid-liquid separation has been known. When boron is contained in the fluorine-containing water, a part of boron exists in the form of a boron fluoride. The borofluoride does not react with the calcium compound. Therefore, the treatment with the above-described fluorine-containing water cannot be carried out (Non-Patent Document 1).

There has been proposed a method of treating fluorine and boron by adding an aluminum compound to water containing a borofluoride, and reacting under acidic conditions and heating conditions to decompose borofluoride and further adding a calcium compound (Patent Documents 1 and 2).

Patent Document 1 discloses that an aluminum compound is added in a water containing borofluoride so that an Al/F molar ratio is 0.3 to 1.05, and a borofluoride is decomposed at pH 2 to 3, and then a calcium compound is added thereto at pH 9 to 10. Health After insolubilization, solid-liquid separation is carried out, and an aluminum compound is added in the separated water so that the Al/F molar ratio is 5 or more, and an insoluble compound is formed at pH 6 to 7, and solid-liquid separation is performed. According to the method of Patent Document 1, in order to improve the reactivity and the precipitation property, the series of steps are carried out at 50 to 80 °C.

Patent Document 2 describes that in water containing borofluoride, When a polyvalent metal compound such as an aluminum compound is added at a pH of 3 or less, the mixture is heated to 35° C. or higher, preferably 40° C. or higher, and after the borofluoride is decomposed, calcium hydroxide is added to form an insoluble compound at pH 10 or higher, and after cooling to 35° C. or lower. , agglutination, solid-liquid separation.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent No. 4954131

Patent Document 2: Japanese Patent No. 4338705

[Non-patent literature]

Non-Patent Document 1: "Environmental Technology" Vol. 29, No. 4 (2000)

In the past, the treatment method of water containing boron fluoride was not sufficient. The removal of fluorine is carried out, and since it is reacted at a high temperature, there is a problem that the running cost is also high.

The present invention provides a solution to the above conventional problems. A treatment method and a treatment apparatus for water containing borofluoride are problems in that water containing borofluoride is treated at a low temperature (normal temperature), and not only the fluorine can be removed highly, but also the boron can be removed.

As a result of repeating the positive review, the inventors of the present invention have found that the above problem can be solved by optimizing the amount of the aluminum compound added and the amount of the calcium compound added and treating it at room temperature.

The present invention has been achieved based on the above findings, and the main contents are as follows.

[1] A method for treating water containing borofluoride, which comprises the steps of: adding an aluminum compound to water containing borofluoride, and decomposing borofluoride at pH 1-4, and a second step of reacting a calcium compound in the treated water of the first step, reacting at pH 7-13 to form an insoluble compound, and a third step of solid-liquid separating the insoluble material, the aluminum compound of the first step The addition amount is Al/F=1.2 to 2.5 (mole ratio) based on the fluorine concentration of the borofluoride-containing water in the Al conversion value, and the calcium compound addition amount in the second step is relative to the Ca conversion value. The Al conversion value of the aluminum compound is Ca/Al = 2.5 to 4.0 (mole ratio), and the processing temperatures of the first and second steps are 10 to 35 °C.

[2] A method for treating water containing borofluoride as in [1], A fourth step of treating the separated water obtained in the third step at pH 6 to 7 to form an insoluble material, and a fifth step of subjecting the insoluble material to solid-liquid separation.

[3] The method for treating water containing borofluoride according to [1] or [2], wherein the amount of the aluminum compound added in the first step is a fluorine concentration in terms of Al relative to the water containing the borofluoride. The ratio of Al/F = 1.2 to 2.5 (mole ratio) is defined as Al/B = 2.0 to 4.5 (mole ratio) with respect to the boron concentration of the boron fluoride-containing water in terms of Al.

[4] The method for treating water containing borofluoride according to any one of [1] to [3], wherein the aluminum concentration of the separated water obtained in the third step is 30 to 70 mg/L.

[5] A treatment apparatus for water containing borofluoride, characterized by having a first reaction tank in which an aluminum compound is added to water containing borofluoride and decomposing borofluoride at pH 1 to 4, and a calcium compound is added. a second reaction tank which reacts in the treated water of the first reaction tank at pH 7 to 13 to form an insoluble compound, and a borofluoride-containing water of the first solid-liquid separation mechanism which separates the insoluble solid-liquid separation a processing apparatus, wherein an amount of the aluminum compound added to the first reaction tank is Al/F=1.2 to 2.5 (mole ratio) based on a fluorine concentration of the borofluoride-containing water in terms of Al, and the second reaction The addition amount of the calcium compound in the tank is Ca/Al=2.5 to 4.0 (mole ratio) in terms of Ca conversion value with respect to the Al value of the aluminum compound, and the treatment temperature of the first and second reaction tanks is 10 to 35 °C.

[6] A treatment device for water containing borofluoride as in [5], A third reaction tank for treating the separated water obtained by the solid-liquid separation mechanism at pH 6 to 7 to form an insoluble product, and a second solid-liquid separation mechanism for separating the insoluble solid-liquid.

[7] Treatment equipment containing borofluoride-containing water as in [5] or [6] The amount of the aluminum compound added to the first reaction tank is Al/F=1.2 to 2.5 (molar ratio) relative to the fluorine concentration of the borofluoride-containing water, and the Al conversion value is relatively The boron concentration of the borofluoride-containing water is Al/B = 2.0 to 4.5 (mole ratio).

[8] The borofluoride-containing water according to any one of [5] to [7] The processing device, wherein the separated water obtained by the first solid-liquid separation mechanism has an aluminum concentration of 30 to 70 mg/L.

According to the present invention, by controlling the addition amount of the aluminum compound and the addition amount of the calcium compound, and treating at a normal temperature of 10 to 35 ° C, not only the fluorine can be highly removed but also the boron can be highly removed.

The reason for the present invention does not require basic heating, so that the running cost can be reduced. Since the present invention performs the reaction at normal temperature, it may be heated in the winter depending on the situation. However, in this case, since it is kept at normal temperature, the running cost can be reduced more than the prior art.

It is also possible to treat residual aluminum in water and remove the fluorine to a very low concentration by a higher degree of treatment.

1‧‧‧First reaction tank

2‧‧‧Second reaction tank

3‧‧‧Aggregation tank

4‧‧‧ solid-liquid separation tank

5‧‧‧ Third reaction tank

6‧‧‧Aggregation tank

7‧‧‧ solid-liquid separation tank

Fig. 1 is a system diagram showing an embodiment of a treatment apparatus for borofluoride-containing water of the present invention.

Fig. 2 is a graph showing the relationship between the BF ₄ concentration of treated water and Ca/Al (Mo ratio) in Experimental Examples 1 to 4.

Fig. 3 is a graph showing the relationship between the F concentration of the treated water and Ca/Al (Mo ratio) in Experimental Examples 1 to 4.

Fig. 4 is a graph showing the relationship between the B concentration of the treated water and Ca/Al (Morby ratio) in Experimental Examples 1 to 4.

Fig. 5 is a graph showing the relationship between the Al concentration of the treated water and Ca/Al (Morby ratio) in Experimental Examples 1 to 4.

Fig. 6 is a graph showing the relationship between the SO ₄ concentration of treated water and Ca/Al (Mo ratio) in Experimental Examples 1 to 4.

Fig. 7 is a graph showing the relationship between the Ca concentration of the treated water and Ca/Al (Mo ratio) in Experimental Examples 1 to 4.

Fig. 8 is a graph showing the relationship between the B concentration of the treated water and Al/B (Morby ratio) in Experimental Examples 5 and 6.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Fig. 1 is a system diagram showing an embodiment of a treatment apparatus for borofluoride-containing water of the present invention.

In Fig. 1, 1 indicates the first reaction tank (the first reaction tank) 2 is a second reaction tank (second reaction tank), 3 is a condensation tank, 4 is a solid-liquid separation tank (first solid-liquid separation mechanism), and 5 is a third reaction tank (third reaction tank). 6 denotes a coagulation tank, and 7 denotes a solid-liquid separation tank (second solid-liquid separation mechanism). The raw water is added to the first reaction tank 1, and an aluminum compound (Al compound) and an acid are added, and the borofluoride in the raw water is subjected to decomposition treatment at a pH of 1-4 (first step).

Secondly, the treated water of the first reaction tank 1 is supplied to the second reverse In the tank 2, a calcium compound (Ca compound) and, if necessary, a base are added, and the treatment is carried out at pH 7 to 13, thereby producing an insoluble material such as calcium fluoride (second step).

Then, the treated water of the second reaction tank 2 is in the agglutination tank 3 After the addition of the polymer flocculant to the agglutination treatment, solid-liquid separation is carried out in the solid-liquid separation tank 4 (third step).

The separated sludge of the solid-liquid separation tank 4 is discharged out of the system, and The separated water is supplied to the third reaction tank (third reaction tank) 5, and an aluminum compound and an acid are added as needed, and insolubilization treatment is carried out at pH 6 to 7 (fourth step).

Then, the treated water of the third reaction tank 5 is in the agglutination tank 6 After the addition of the polymer aggregating agent to the agglutination treatment, solid-liquid separation is carried out in the solid-liquid separation tank 7 (fifth step).

The separated sludge of the solid-liquid separation tank 7 is discharged out of the system, and The separated water is taken out as treated water.

Hereinafter, the raw water and the processing of each step will be described.

<原水>

The borofluoride-containing water (raw water) treated by the present invention is exemplified by glass products, pharmaceuticals, cosmetics, resin products, electroplating products, water discharge, coal-fired power plants, flue gas desulfurization water, and garbage incineration plants. The water is discharged from the smoke, and the water is discharged from the nickel plating factory. Typically, such emissions contain water of boron fluoride, are also not be BF ₄ ^- and to F ^-, the presence of fluorine, and boron ^_33- morphology of BO.

Water these raw water treated of the present invention is generally based BF ₄ concentration (dissolved in BF water of ₄ ^- ion concentrations, the present invention is described as "BF ₄ concentration") L, F concentration of 5 ~ 2000mg / (dissolved in the water The fluorine concentration is described in the present invention as "F concentration") of 5 to 10000 mg/L, and the B concentration (boron concentration dissolved in water, referred to as "B concentration" in the present invention) is 1 to 500 mg/L, and the pH is 0.5. 11.5.

F concentration can be used in JIS K0102 34.1 (镧-茜素 coordination The ketone (lanthanum Alizarin Complexone) spectrophotometric method is determined by the method specified, and the B concentration can be analyzed by the method specified in JIS K0102, 47.3 (ICP emission spectrometry).

<first step>

In the first step, an aluminum compound is added to the raw water, and the boron fluoride is decomposed by the following reaction.

3BF ₄ ^- +2Al ³⁺ +9H ₂ O→2AlF ₆ ^3- +3H ₃ BO ₃ +9H ⁺

As the aluminum compound to be added to the raw water, as long as the aluminum ion is dissolved under the pH condition at the time of the reaction, for example, sulfuric acid can be used. One or more of aluminum, aluminum chloride, polyaluminum chloride (PAC), and aluminum sulfate.

The amount of aluminum compound added to raw water is converted into Al The amount of addition to the F concentration in the raw water is 1.2 to 2.5, preferably 1.5 to 2.5, in terms of Al/F (molar ratio), and the amount of addition of Al to the B concentration in the raw water is Al/B (Mo The ear ratio is preferably added in the range of 2.0 to 4.5. When the amount of the aluminum compound added is less than the above lower limit, the borofluoride cannot be sufficiently decomposed, and if it is more than the above upper limit, the effect corresponding to the added amount cannot be obtained, and as a result, the amount of the aluminum compound used is increased, which is degraded.

Decomposition of boron fluoride in aluminum compounds due to The reaction proceeds rapidly under acidic conditions, so the pH of the first step is set to 1 to 4, preferably 1.5 to 2.5. Therefore, an acid (for example, sulfuric acid, hydrochloric acid, more preferably sulfuric acid) is added to the raw water in the raw water as needed, and the pH is adjusted to pH 1 to 4, preferably 1.5 to 2.5.

In the present invention, by using the above-mentioned aluminum compound addition amount and The pH condition can be treated at a liquid temperature of 10 to 35 ° C, preferably 15 to 30 ° C, so that no heating is necessary in the first step.

The reaction time of the first step is based on ensuring boron in the raw water The decomposition time of the fluoride is preferably set to about 0.5 to 10 hours.

<Second step>

In the second step, a calcium compound is added to the treated water in the first step, and calcium fluoride is precipitated by the following formula and further adsorbed by boron as described later. Remove.

AlF ₆ ^3- +3Ca ²⁺ +3OH ^- →3CaF ₂ +Al(OH) ₃

As the calcium compound, for example, one type or two or more types of calcium hydroxide, calcium chloride, and calcium carbonate can be used.

The amount of the calcium compound added is from 2.5 to 4.0, preferably from 2.7 to 3.8, in terms of Ca/Al (molar ratio), based on the amount of Al converted to the aluminum compound added in the first step. range.

By setting the amount of the calcium compound added in the above range, the adsorption removal efficiency of boron can be improved. In addition, by setting the amount of the calcium compound to be in the above range, the concentration of Al remaining in the treated water in the second step (the concentration of aluminum dissolved in water, which is described as "Al concentration" in the present invention) can be improved. The fluorine is removed by the fourth step described later.

The Al concentration can be analyzed by the method specified in JIS K0102, 58.4 (ICP emission spectrometry).

In the present invention, in order to carry out the second step under the conditions of pH 7 to 13, pH adjustment is carried out by adding an alkali such as sodium hydroxide or an acid such as sulfuric acid to the calcium compound in the treated water in the first step as needed. Further, when calcium hydroxide is used as the calcium compound and calcium hydroxide is added, the pH adjustment is not required when the desired pH is obtained.

Generally, the precipitation of calcium fluoride is preferably set to a pH of 4 to 10, but it is more preferably pH 9 to 11 in the case of preferentially removing fluorine. This is because the bond between aluminum and fluorine is easily cut under alkaline conditions, thereby promoting the precipitation of calcium fluoride.

In the case of preferential removal of boron, it is preferably pH 10 to 12.5. This is because, under high alkaline conditions of pH 10 or higher, calcium aluminate (CaO‧Al ₂ O ₃ ) is precipitated by the following reaction, and at the same time, boron is adsorbed/removed at the same time. Therefore, in terms of simultaneous removal of fluorine and boron, a better pH condition is 10-12.

6Ca(OH) ₂ +Al ₂ (SO ₄ ) ₃ →3CaO. Al ₂ O ₃ . 3CaSO ₄ . 6H ₂ O

The removal of boron in the second step is an adsorption reaction. Since the adsorption amount becomes high when the liquid temperature is low, in the present invention, the second step is carried out at a normal temperature of 10 to 35 ° C, preferably 15 to 30 ° C. Therefore, there is no need to warm up in this step.

The reaction time in the second step is preferably about 0.5 to 4 hours in terms of ensuring the reaction time of the fluorine and the calcium compound in the raw water.

<third step>

In the third step, the insoluble matter (the sludge containing calcium fluoride and calcium aluminate) precipitated in the second step is subjected to solid-liquid separation to obtain separated water. In order to improve the solid-liquid separation performance, a step of adding a polymer flocculating agent for agglutination may be performed between the second step and the third step.

As a polymer aggregating agent, it can be used as a user in the discharge water treatment, and an anionic polymer aggregating agent such as a polyacrylamide partial hydrolyzate, a sodium polyacrylate, a copolymer of acrylamide and acrylic acid (salt), or the like can be used. Or one or two or more kinds of nonionic polymer flocculants such as polyacrylamide. The amount of the polymer aggregating agent varies depending on the water quality of the raw water to be treated or the polymer aggregating agent to be used, but it is usually 0.1 to 20 mg/L. about.

The solid-liquid separation in the third step is performed by using a sedimentation tank or the like. A membrane separation device, a filtration device, a dehydrator or the like may be used in addition to the solid-liquid separation tank.

In the third step, although the amount of the raw water of the treatment target, the amount of the aluminum compound and the calcium compound added varies, generally, the F concentration is about 3 to 15 mg/L, the B concentration is about 1 to 10 mg/L, and BF is obtained. ₄ Treatment water having a concentration of 0.1 mg/L or less. As will be described later, the Al concentration of the treated water is usually about 30 to 70 mg/L.

<Fourth step>

In the present invention, the solid-liquid separation water in the third step may be used as the treated water, but the fourth step of treating the solid-liquid separation water to remove the fluorine may be further carried out. That is, in the second step, fluorine is insolubilized as calcium fluoride, but only a small amount of fluorine remains in the solid-liquid separation water in the third step from the solubility relationship of calcium fluoride. Therefore, the fourth step can be carried out to further remove residual fluorine.

In the fourth step, according to the needs of the aluminum compound and the acid, The amount of the calcium compound added is adjusted by adding a base to pH 6 to 7, thereby precipitating aluminum hydroxide. The fluorine in the water is insolubilized and removed by coprecipitation when the aluminum hydroxide is precipitated.

In the present invention, the aluminum compound is added by the first step Thereafter, in the second step, the calcium compound is added by the Ca/Al (mole ratio), and the aluminum in the solid-liquid separation water obtained in the third step can be left at about 30 to 70 mg/L. Therefore, the amount of aluminum necessary in the fourth step can be supplied by the amount of residual aluminum. In the fourth step, the fluorine can be removed only by adding an acid for 5 to 30 minutes and stirring at a normal temperature (10 to 35 ° C). Aluminum compounds may also be added in the fourth step as needed. The aluminum compound can be exemplified using the aluminum compound used in the first step.

<Fifth step>

In the fifth step, the insoluble matter (coprecipitated sludge containing fluorine of aluminum hydroxide) precipitated in the fourth step is subjected to solid-liquid separation to obtain treated water. Here, in order to improve the solid-liquid separation performance, a step of adding a polymer flocculating agent to agglomerate may be performed between the fourth step and the fifth step.

In this case, as a polymer flocculating agent, polypropylene can be used. One or two or more kinds of the anionic polymer aggregating agents such as the ketamine partial hydrolyzate, the sodium polyacrylate, and the polyvinyl hydrazine. The amount of the polymer flocculating agent varies depending on the quality of the raw water to be treated or the polymer aggregating agent to be used, but is usually about 0.1 to 5 mg/L.

The solid-liquid separation in the fifth step is not limited to the use of a sedimentation tank or the like. A membrane separation device, a filtration device, or the like may be used in addition to the solid-liquid separation tank.

In the fifth step, the amount of the raw water of the raw material to be treated, the amount of the aluminum compound and the calcium compound to be added varies, but an F concentration of 1.1 mg/L or less, a B concentration of 3.5 mg/L or less, and a BF ₄ concentration are generally obtained. High-quality treated water of 0.1 mg/L or less and Al concentration of 1 mg/L or less.

<other steps>

The following steps may be further added in the present invention.

Raw water can also be added before being processed in the first step. The insoluble matter precipitated by the reaction of the calcium compound at pH 4 to 10 is subjected to solid-liquid separation, and a part of fluorine in the raw water is removed in advance. By additionally removing the fluorine in the raw water in advance by adding the above-mentioned previous treatment steps, the F concentration of the water flowing into the first step can be reduced, and the amount of the aluminum compound added in the first step can be reduced.

Separating sludge obtained by solid-liquid separation in the third step Some can also be sent back and added to the second step. In this case, the calcium compound added in the second step is added to the returned sludge to reform the sludge, so that the modified sludge can be added in the second step. Calcium fluoride is newly precipitated on the surface of the sludge by performing the above-mentioned sludge return. Thereby, the dehydration property of the solid-liquid separation sludge obtained in the third step is improved, and the moisture content of the dehydrated cake obtained by dehydrating the sludge can be reduced.

Example

The present invention will be more specifically described below by showing experimental examples of the examples of the invention and comparative examples.

In addition, in the following, the following water quality is used as the raw water system.

<Original water quality>

F concentration: 600 mg / L (31.6 mmol / L)

B concentration: 200 mg-B/L (18.5 mmol/L)

BF ₄ concentration: 250mg/L

Aluminum sulfate (8 wt%, Al ₂ O ₃ ) was used as the aluminum compound, and calcium hydroxide (Ca(OH) ₂ ) was used as the calcium compound. An anionic polymer aggregating agent "KURIFARM (registered trademark) PA823" manufactured by Kurita Industrial Co., Ltd. was used as a polymer aggregating agent, and the amount of addition was 10 mg/L.

[Experimental Examples 1~4]

Aluminum sulfate was added to the raw water in an amount shown in the following Table 1, and the mixture was adjusted to pH 2 with sulfuric acid, and then reacted for 4 hours. Subsequently, calcium hydroxide was added and reacted at pH 10 for 1 hour. The calcium hydroxide is added in various amounts in the range of 1 to 6 in terms of the amount of aluminum sulfate added and the amount of calcium hydroxide added, and is added in various ways.

When the pH is not 10 due to the addition of calcium hydroxide, a suitable acid (sulfuric acid) or a base (sodium hydroxide) is added to adjust to pH 10.

Next, a polymer flocculant was added and agglutination treatment was performed for 5 minutes, and the agglomerated water was subjected to solid-liquid separation.

The above series of treatments were carried out at a liquid temperature of 20 °C.

Analyze the water quality of the treated water (solid-liquid separation water) Check the relationship between Ca/Al Mobi ratio and the results are shown in Figures 2-7.

As is apparent from Fig. 2, when Al/F (mole ratio) is 1.5 or more, the borofluoride (BF ₄ ) in the raw water can be completely decomposed.

3 and 4, if Al/F (Morby ratio) is 1.5 or more and Ca/Al (Morby ratio) is in the range of 2.5 to 4.0, the removal rate of fluorine and boron is high, and the removal efficiency of boron is particularly improved. .

As can be seen from Fig. 5, when the Ca/Al ratio is in the range of 2.5 to 4.0, the amount of residual Al in the treated water is increased, and the fluorine treatment can be effectively utilized.

As shown in Fig. 6, if the Ca/Al ratio is in the range of 2.5 to 4.0, the SO ₄ concentration (SO ₄ ^2- ion concentration) in the treated water is low, and the CaSO in the latter stage (treated water piping) can be reduced. ₄ fouling troubles.

As shown in Fig. 7, if the Ca/Al ratio is in the range of 2.5 to 4.0, the Ca concentration (Ca ²⁺ ion concentration) in the treated water is low, and the CaSO ₄ junction in the latter stage of the apparatus (treatment water piping) can be alleviated. Distressed.

[Experimental Examples 5 and 6]

A specific amount of aluminum sulfate was added to the raw water, and after adjusting to pH 2 with sulfuric acid, the reaction was carried out for 4 hours. Subsequently, calcium hydroxide was added and reacted at pH 10 for 1 hour. Calcium hydroxide is added so that Ca/Al (Mohr ratio) calculated from the amount of addition of aluminum sulfate and the amount of calcium hydroxide added is 2.5.

When the pH is not 10 due to the addition of calcium hydroxide, a suitable acid (sulfuric acid) or a base (sodium hydroxide) is added to adjust to pH 10.

Next, add a polymer flocculant for 5 minutes of agglutination The solid-liquid separation of the agglomerated water is carried out.

Aluminum sulfate is added in the amount of Al in terms of raw water. Boron is added in various changes in terms of Al/B (Morby ratio). Since the fluorine concentration in the raw water is about 1.7 times the boron concentration, if Al/B (mole ratio) is in the range of about 2.0 to 4.0, the Al/F (mol ratio) is 1.2 to 2.5.

In the above series of treatments, the experimental example 5 was carried out at a liquid temperature of 20 ° C. The experimental example 6 was carried out at a liquid temperature of 60 °C.

Analysis of the B concentration of the treated water (solid-liquid separation water), The relationship between Al/B molar ratio is shown in Fig. 8.

As can be seen from Figure 8, compared to the processing temperature of 60 ° C In the case where the treatment temperature is 20 ° C, the boron removal rate is exceptionally high. When Al/B (mole ratio) is in the range of 2.0 to 4.5, the boron removal effect is excellent.

[Experimental Example 7]

Solid-liquid separation water obtained by adding aluminum sulfate in the manner of Al/F (Mohr ratio) = 1.5, Al/B (Mohr ratio) = 2.5, and Ca / Al (Mole ratio) = 3.3 in Experimental Example 3. (F concentration = 9 mg/L, B concentration = 3.5 mg/L, BF ₄ concentration < 0.1 mg/L, Al concentration = 61 mg/L), sulfuric acid was added to pH 6.5, and the mixture was stirred for 15 minutes to precipitate insolubles.

Next, add a polymer flocculant for 5 minutes of agglutination The solid-liquid separation of the agglomerated water is carried out.

The obtained treated water (solid-liquid separation water) was treated water having a F concentration = 1.1 mg/L, a B concentration = 3.5 mg/L, a BF ₄ concentration of <0.1 mg/L, and an Al concentration of <1 mg/L.

The present invention has been described in detail with reference to the preferred embodiments of the invention.

The present application is based on Japanese Patent Application No. 2013/039193, filed on Feb. 28, 2013, which is incorporated herein by reference.

1‧‧‧First reaction tank

2‧‧‧Second reaction tank

3‧‧‧Aggregation tank

4‧‧‧ solid-liquid separation tank

5‧‧‧ Third reaction tank

6‧‧‧Aggregation tank

7‧‧‧ solid-liquid separation tank

Claims (8)

A method for treating water containing borofluoride, characterized by the steps of: adding an aluminum compound to water containing borofluoride, decomposing borofluoride at pH 1 to 4, and adding a calcium compound a second step of reacting at pH 7 to 13 to form an insoluble compound, and a third step of subjecting the insoluble compound to solid-liquid separation in the treated water of the first step, wherein the amount of the aluminum compound added in the first step is The Al conversion value is Al/F=1.2 to 2.5 (mole ratio) with respect to the fluorine concentration of the borofluoride-containing water, and the calcium compound addition amount in the second step is relative to the aluminum in terms of Ca conversion value. The Al conversion value of the compound is calculated as Ca/Al = 2.5 to 4.0 (mole ratio), and the treatment temperatures in the first and second steps are 10 to 35 °C. A method for treating borofluoride-containing water according to claim 1, which has a fourth step of treating the separated water obtained in the third step at pH 6 to 7 to form an insoluble compound, and subjecting the insoluble material to solid-liquid separation. The fifth step. The method for treating borofluoride-containing water according to claim 1 or 2, wherein the amount of the aluminum compound added in the first step is Al/F based on the fluorine concentration of the borofluoride-containing water in terms of Al. = 1.2 to 2.5 (mole ratio), and the Al conversion value is Al/B = 2.0 to 4.5 (mole ratio) with respect to the boron concentration of the borofluoride-containing water. Where the water containing borofluoride is contained in any one of claims 1 to 3 The method comprises the method wherein the concentration of aluminum in the separated water obtained in the third step is 30-70 mg/L. A treatment device for water containing borofluoride, characterized by comprising a first reaction tank in which an aluminum compound is added to water containing borofluoride and decomposing borofluoride at pH 1-4, and a calcium compound is added to the first a treatment tank for treating the water in a reaction tank at a pH of 7 to 13 to form an insoluble compound, and a treatment device for the boron-containing fluoride-containing water of the first solid-liquid separation mechanism for separating the insoluble solid. The amount of the aluminum compound added to the first reaction tank is Al/F=1.2 to 2.5 (molar ratio) relative to the fluorine concentration of the borofluoride-containing water in terms of Al, and the calcium of the second reaction tank The amount of the compound to be added is Ca/Al = 2.5 to 4.0 (mole ratio) based on the Al conversion value of the aluminum compound, and the treatment temperature of the first and second reaction tanks is 10 to 35 °C. A treatment apparatus for borofluoride-containing water according to claim 5, which has a third reaction tank which processes the separated water obtained by the solid-liquid separation mechanism at pH 6 to 7 to form an insoluble product, and separates the insoluble solid-liquid. The second solid-liquid separation mechanism. A processing apparatus for borofluoride-containing water according to claim 5, wherein the amount of the aluminum compound added to the first reaction tank is Al/F based on the fluorine concentration of the borofluoride-containing water. = 1.2 to 2.5 (mole ratio), and the Al conversion value is Al/B = 2.0 to 4.5 (mole ratio) with respect to the boron concentration of the boron fluoride-containing water. The apparatus for treating borofluoride-containing water according to any one of claims 5 to 7, wherein the separated water obtained by the first solid-liquid separation means has an aluminum concentration of 30 to 70 mg/L.