JP2011025158A - Removing agent and treatment method for borofluoride in water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent removing agent of borofluorides in water which can easily and efficiently remove borofluorides from a borofluoride-containing water by one step treatment and has a high removal ratio of borofluorides in water, and also to provide a treatment method for borofluorides in water which can easily and efficiently recover borofluorides from a treated liquid after removing borofluorides. <P>SOLUTION: The removing agent for borofluorides in water includes at least one of a burned product of magnesium aluminate hydrate, a burned product of hydrotalcite, and magnesium aluminate, and removes borofluorides from a borofluoride-containing water. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an underwater borofluoride removing agent for removing borofluoride from borofluoride-containing water and a method for treating borofluoride in water.

  The borofluoride is used for metal surface treatment, an electrolytic bath for plating, an organic synthesis catalyst, and the like, and waste water generated from these processes contains borofluoride. Boron and fluorine are used in various industrial applications such as glass industry, raw materials for pharmaceuticals, cosmetics, dyes, soap industry, components of alloys and semiconductor materials, electroplating, etc. The waste water contains boron and fluorine. In addition, wastewater generated from power plants, smoke washing wastewater at garbage incineration sites, landfill disposal site leachate wastewater, etc. often contain boron and fluorine. Boron and fluorine may also be contained in the wastewater of the inn business that operates hot springs. Thus, boron and fluorine are contained in various wastewaters.

  Boron and fluorine are essential trace elements for animals and plants. However, excessive intake may cause plant growth inhibition, animal reproduction inhibition toxicity, nerve and digestive system disorders, and the like. Therefore, a part of the Enforcement Ordinance for Water Pollution Control Law was revised in 2001, and the drainage standard for boron and its compounds in public waters such as rivers and lakes is 10 mg / L or less, and the drainage standard for fluorine is 8 mg / L. It was determined as follows. For this reason, it is necessary to reduce the boron concentration and fluorine concentration in the wastewater below the wastewater standard.

  When boron and fluorine are mixed in the same wastewater, if it is acidified, a hardly decomposable borofluoride is generated. In general, as methods for removing boron and fluorine from wastewater, coagulation precipitation method, ion adsorption method, solvent extraction method, evaporation concentration method, reverse osmosis membrane method, etc. are known. Boron fluoride is boron and fluorine. Is a very stable substance that is strongly bonded to each other. Therefore, the conventional boron or fluorine treatment method has a low removal performance, which is problematic in that borofluoride remains.

As a method of removing borofluoride that is difficult to remove from wastewater, calcium or aluminum salt is added to wastewater containing borofluoride, and calcium fluoride or aluminum fluoride and boron are added under acidic conditions. There is known a method of removing the generated fluorine as a calcium salt or an aluminum salt after decomposition into an acid (see Patent Documents 1 to 3).
However, this method has a problem in that the reaction rate is slow and the treatment time becomes long because it cannot be removed without two steps of the decomposition step and the removal step.

  Further, as another method for removing borofluoride from wastewater, a method of exchanging and removing fluoroborate ions with a basic anion exchange resin is known (see Patent Document 4), but this method has low removal performance. This is a problem in that it is difficult to recover fluoroborate ions from the chelate resin after removal due to high point and processing cost.

  Therefore, an excellent underwater borofluoride removal agent that can easily and efficiently remove borofluoride from borofluoride-containing water in a single step and has a high borofluoride removal rate, and a treatment liquid after removal of borofluoride Therefore, the development of a method for treating borofluoride in water that can easily and efficiently recover borofluoride is still desired.

JP-A-7-16577 Japanese Patent No. 2912934 Japanese Patent No. 3229277 Japanese Patent No. 3976219

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention can easily and efficiently remove borofluoride from borofluoride-containing water by one-step treatment, and has an excellent borofluoride removal agent and borofluoride removal with a high borofluoride removal rate. It is an object of the present invention to provide a method for treating borofluoride in water capable of easily and efficiently recovering borofluoride from the treatment liquid.

  In order to solve the above problems, the present inventors have intensively studied, and as a result, a borofluoride remover in water containing at least one of a calcined product of magnesium aluminate hydrate, a calcined product of hydrotalcite, and magnesium aluminate. Has a very high removal rate of borofluoride in water, and by using the above-mentioned borofluoride remover, borofluoride in borofluoride-containing water can be easily and efficiently removed in one step without any decomposition process. As a result, it was found that borofluoride can be easily and efficiently recovered from the treatment liquid by adding an anionic polymer flocculant to the treatment liquid after removal of the borofluoride, and the present invention has been completed.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as follows. That is,
<1> A borofluoride in water containing at least one of a fired product of magnesium aluminate hydrate, a fired product of hydrotalcite, and magnesium aluminate, and removing borofluoride from borofluoride-containing water Remover.
<2> A removal step of removing the borofluoride remover according to <1> above to the borofluoride-containing water to remove the borofluoride, and an anionic polymer flocculant to the treatment liquid of the removal step A method for treating borofluoride in water, comprising a coagulation step for coagulation treatment and a separation step for performing solid-liquid separation of the treatment liquid in the coagulation step.

  According to the present invention, the conventional problems can be solved, the object can be achieved, borofluoride can be easily and efficiently removed from borofluoride-containing water in one step, and It is possible to provide an excellent underwater borofluoride removing agent having a high borofluoride removal rate and a method for treating borofluoride in water that can easily and efficiently recover borofluoride from a treatment solution after borofluoride removal.

(Underwater borofluoride remover)
The borofluoride removing agent of the present invention contains at least one of a calcined product of magnesium aluminate hydrate, a calcined product of hydrotalcite, and magnesium aluminate, and further contains other components as necessary. .

<Magnesium aluminate>
There is no restriction | limiting in particular as said magnesium aluminate, Although it can select suitably according to the objective, At least any of the compound represented by following General formula (1) and the following General formula (2) It is preferable that
_{Mg 1-x Al x O 1} + 0.5x ··· general formula (1)
(1-x) MgO.0.5xAl ₂ O ₃ ... General formula (2)
In the general formula (1) and the general formula (2), “x” is a number satisfying a range of 0 <x <1. “X” is preferably a number that satisfies 0.1 ≦ x <0.5, more preferably a number that satisfies 0.1 ≦ x <0.4, and satisfies 0.1 ≦ x <0.3. More preferred is the number to be.

As the magnesium aluminate satisfying at least one of the general formulas (1) and the general formula (2) is not particularly limited and may be appropriately selected depending on the purpose, for example, Mg 0.7 _{Al 0. 3} O _1.15 , Mg _0.333 Al _0.667 O _{1.333, and the} like.

<< How to obtain >>
There is no restriction | limiting in particular as an acquisition method of the said magnesium aluminate, According to the objective, it can select suitably, For example, the method obtained from a commercial item, the method obtained by synthesis, etc. are mentioned.

<Magnesium aluminate hydrate>
There is no restriction | limiting in particular as said magnesium aluminate hydrate, Although it can select suitably according to the objective, The compound represented by following General formula (3) and the following general formula (4) It is preferable that it is at least one of these.
_{Mg 1-x Al x O 1} + 0.5x · mH 2 O ··· formula (3)
(1-x) MgO · 0.5xAl 2 O 3 · mH 2 O ··· formula (4)
In the general formula (3) and the general formula (4), “x” is a number satisfying a range of 0 <x <1. “X” is preferably a number that satisfies 0.1 ≦ x <0.5, more preferably a number that satisfies 0.1 ≦ x <0.4, and a number that satisfies 0.1 ≦ x <0.3. Is more preferable. “M” is a positive number.

The magnesium aluminate hydrate satisfying at least one of the general formula (3) and the general formula (4) is not particularly limited and may be appropriately selected depending on the intended purpose. For example, Mg _{0.556 Examples} include Al _0.444 O _1.222 · mH ₂ O (manufactured by Kyowa Chemical Industry Co., Ltd.).

<< How to obtain >>
There is no restriction | limiting in particular as the acquisition method of the said magnesium aluminate hydrate, According to the objective, it can select suitably, For example, the method of obtaining from a commercial item, the method of obtaining by synthesis, etc. are mentioned. By firing the magnesium aluminate hydrate, a fired product of the magnesium aluminate hydrate can be obtained.

<< Baking temperature >>
There is no restriction | limiting in particular as temperature which bakes the said magnesium aluminate hydrate, Although it can select suitably according to the objective, 400 to 900 degreeC is preferable and 400 to 700 degreeC is more preferable. When the firing temperature is less than 400 ° C., the borofluoride removal rate decreases. This is considered because dehydration of hydration water becomes insufficient. Even if the firing temperature exceeds 900 ° C., the borofluoride removal rate may decrease. This is presumably because not only the decomposition of the product occurs, but also the particles fuse together when approaching the melting point of the product.

<< Baking time >>
The time for firing the magnesium aluminate hydrate is not particularly limited and may be appropriately selected depending on the intended purpose. However, the retention time of the firing temperature is preferably 10 minutes or more, more preferably 15 minutes or more. Preferably, 30 minutes or more is more preferable.

<Hydrotalcite fired product>
There is no restriction | limiting in particular as said hydrotalcite, Although it can select suitably according to the objective, It is preferable that it is a compound represented by following General formula (5).
_{Mg 1-x Al x (OH} ) 2 α n- x / n · mH 2 O ··· formula (5)
In the general formula (5), “α ⁿ⁻ ” represents an n-valent anion such as OH ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , Cl ⁻ , NO ₃ ⁻ , and CH ₃ COO ⁻ . “X” is a number satisfying a range of 0 <x <1. “X” is preferably a number that satisfies 0.1 ≦ x <0.5, more preferably a number that satisfies 0.1 ≦ x <0.4, and a number that satisfies 0.1 ≦ x <0.3. Is more preferable. “M” is a positive number.

The hydrotalcite satisfying the general formula (5) is not particularly limited and may be appropriately selected depending on the purpose, for _{example, Mg 0.692 Al 0.308 (OH)} 2 (CO 3) 0. ₁₅₄ · 0.538H ₂ O, Mg _0.75 Al _0.25 (OH) ₂ (CO ₃ ) _0.125 · 0.5H ₂ O, Mg _0.667 Al _0.333 (OH) ₂ (CO ₃ ) such as _0.167 · 0.5H ₂ O, and the like.

<< How to obtain >>
There is no restriction | limiting in particular as an acquisition method of the said hydrotalcite, According to the objective, it can select suitably, For example, the method obtained from a commercial item, the method obtained by synthesis, etc. are mentioned. By baking the hydrotalcite, a fired product of the hydrotalcite can be obtained.

<< Baking temperature >>
There is no restriction | limiting in particular as temperature which bakes the said hydrotalcite, Although it can select suitably according to the objective, 400 to 900 degreeC is preferable and 400 to 700 degreeC is more preferable. When the firing temperature is less than 400 ° C., the borofluoride removal rate decreases. This is thought to be due to insufficient dehydration of hydrated water and elimination of interlayer water, carbonate radicals, hydroxyl groups, and the like. Even if the firing temperature exceeds 900 ° C., the borofluoride removal rate may decrease. This is presumably because not only the decomposition of the product occurs, but also the particles fuse together when approaching the melting point of the product.

<< Baking time >>
The time for firing the hydrotalcite is not particularly limited and may be appropriately selected depending on the intended purpose. However, the retention time of the firing temperature is preferably 10 minutes or more, more preferably 15 minutes or more, 30 More preferred is minutes or more.

<Content and blending ratio>
As the content of at least one of the calcined product of the magnesium aluminate hydrate, the calcined product of the hydrotalcite, and the magnesium aluminate in the borofluoride removing agent, as long as the effect of the present invention is not impaired. There is no particular limitation, and it can be appropriately selected according to the purpose. Further, the borofluoride removing agent in water may be at least one of the calcined product of magnesium aluminate hydrate, the calcined product of hydrotalcite, and the magnesium aluminate itself.
There is no particular limitation on the blending ratio of the fired product of the magnesium aluminate hydrate, the fired product of the hydrotalcite, and the magnesium aluminate in the borofluoride remover, and it is appropriately selected according to the purpose. be able to.

<Other ingredients>
The other components in the borofluoride remover are not particularly limited and can be appropriately selected depending on the purpose within a range not impairing the effects of the present invention. For example, pH adjustment of borofluoride-containing water Examples include acids and alkalis for the purpose.
There is no restriction | limiting in particular as said acid, According to the objective, it can select suitably, For example, hydrochloric acid, a sulfuric acid, nitric acid etc. are mentioned.
There is no restriction | limiting in particular as said alkali, According to the objective, it can select suitably, For example, sodium hydroxide, sodium carbonate, calcium hydroxide etc. are mentioned.
There is no restriction | limiting in particular as content of the said other component, According to the objective, it can select suitably.

<Dosage form>
There is no restriction | limiting in particular as a dosage form of the said borofluoride removal agent, According to the objective, it can select suitably, For example, a lump shape, a granular form, a powder form etc. are mentioned.
The method for producing the granular and powdery borofluoride remover is not particularly limited and may be appropriately selected according to the purpose. For example, the magnesium aluminate hydrate calcined product, the hydro It can be produced by pulverizing at least one of the calcined talcite and the magnesium aluminate, and if necessary, the other components.
The pulverization method is not particularly limited and can be performed using a known apparatus. At least any of the calcined product of the magnesium aluminate hydrate, the calcined product of the hydrotalcite, and the magnesium aluminate. If necessary, the other components may be pulverized before mixing or may be pulverized after mixing.

<Addition method>
The method for adding the borofluoride-removing agent to the borofluoride-containing water is not particularly limited and can be appropriately selected according to the dosage form of the borofluoride-removing agent, and the magnesium aluminate hydrate. Or a calcined product of the hydrotalcite, and at least one of the magnesium aluminate, and if necessary, the other component may be added to the borofluoride-containing water at a time, At least one of magnesium aluminate hydrate calcined product, hydrotalcite calcined product, and magnesium aluminate, and, if necessary, the other components are separately added to the borofluoride-containing water. It may be a method.

<Manufacturing method>
The method for producing the underwater borofluoride removing agent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the magnesium aluminate hydrate calcined product, the hydrotalcite calcined product, and At least one of the magnesium aluminate and, if necessary, the other components may be mixed and produced by a conventional method according to the desired dosage form.

<Removal rate of borofluoride in water>
The method for measuring whether the borofluoride-removing agent has removed borofluoride in borofluoride-containing water is not particularly limited and can be appropriately selected according to the purpose. For example, the borofluoride-containing solution After adding the borofluoride remover to water and stirring for a certain period of time, the treatment solution is filtered, neutralized with an aqueous sulfuric acid solution and then added with an aqueous methylene blue solution, and the resulting ion aggregate is extracted with chloroform. For example, a method of measuring the borofluoride concentration by measuring the absorbance.
The removal rate of borofluoride in water can be calculated by the following calculation formula (1).
Removal rate of borofluoride in water (%) = (1−C ₁ / C ₀ ) × 100 (1)
In the calculation formula (1), “C ₁ ” indicates the borofluoride concentration (mg / L) after the treatment, and “C ₀ ” indicates the initial borofluoride concentration (mg / L) before the treatment.

  The removal rate of borofluoride in water is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose, but is preferably 60% or more, more preferably 70% or more, and 85%. The above is more preferable.

<Use>
The said borofluoride remover may be used individually by 1 type, may use 2 or more types together, and may use together with the chemical | medical agent which uses another component as an active ingredient. Moreover, the said borofluoride removal agent may be the state mix | blended in the chemical | medical agent which uses another component as an active ingredient.

<Application>
The borofluoride remover can remove borofluoride from borofluoride-containing water in a single stage simply and efficiently, and has a high borofluoride removal rate. It can be used suitably.

(Treatment method of borofluoride in water)
The method for treating borofluoride in the present invention includes a removal step of removing the borofluoride by adding the borofluoride remover to the borofluoride-containing water, and an anionic polymer flocculant added to the treatment liquid of the removal step At least a coagulation step for coagulation treatment and a separation step for performing solid-liquid separation of the treatment liquid of the coagulation step, and further include other treatments as necessary.

<Removal process>
The removal step is a step of removing the borofluoride by adding the borofluoride remover to the borofluoride-containing water.
The method for removing borofluoride from borofluoride-containing water is not particularly limited and may be appropriately selected depending on the intended purpose. The above-described borofluoride remover is added to the borofluoride-containing water and stirred. The removal method is preferable in that the operation is simple.
The amount of the borofluoride remover added is not particularly limited as long as the borofluoride can be removed, and can be appropriately selected according to the dosage form of the borofluoride remover. 1 to 500 times is preferable, and 10 to 300 times is more preferable.
There is no restriction | limiting in particular as temperature and time of the said stirring, According to the objective, it can select suitably.
There is no restriction | limiting in particular as pH of the said borofluoride containing water at the time of removing borofluoride from borofluoride containing water, Although it can select suitably according to the objective, pH2 or more is preferable and pH4 or more is more preferable. . When the pH is less than 2, at least one of the calcined product of magnesium aluminate hydrate, the calcined product of hydrotalcite, and magnesium aluminate in the borofluoride remover is decomposed, and the removal rate is May decrease.

<Aggregation process>
The aggregation step is a step of adding an anionic polymer flocculant to the treatment liquid of the removal step and performing an aggregation treatment.
There is no restriction | limiting in particular as the method of performing the said aggregation process, According to the objective, it can select suitably, For example, the method etc. which add anionic polymer flocculant to the process liquid of the said removal process, and stir are mentioned. .
There is no restriction | limiting in particular as said anionic polymer flocculant, According to the objective, it can select suitably, For example, Diafloc AP350M (acrylic acid type | system | group, molecular weight about 5 million, the product made from a Dia Nitrix Co., Ltd.), Aronbis MS ( Acrylic acid type, molecular weight of about 3 million, manufactured by Nippon Pure Chemicals Co., Ltd.), Diaflock AP825B (acrylic amide / acrylic acid type, molecular weight of about 16 million, manufactured by Dianitrix Co., Ltd.) and the like.
There is no restriction | limiting in particular as temperature and time of the said stirring, According to the objective, it can select suitably.

<Separation process>
The separation step is a step of performing solid-liquid separation of the treatment liquid in the aggregation step.
There is no restriction | limiting in particular as a method of performing the said solid-liquid separation, According to the objective, it can select suitably, For example, the method etc. which leave the process liquid obtained at the said aggregation process are mentioned.
There is no restriction | limiting in particular as the temperature and time to leave, and it can select suitably according to the objective.

<Evaluation of cohesiveness>
The method for evaluating the cohesiveness of the borofluoride-removing agent bonded with borofluoride present in the treatment liquid obtained by the separation step is not particularly limited and may be appropriately selected depending on the purpose. For example, the method of evaluating by the turbidity of the supernatant of the treatment liquid may be mentioned.
The method for measuring the turbidity is not particularly limited and may be appropriately selected depending on the intended purpose. For example, using Water Analyzer 2000N (manufactured by Nippon Denshoku Industries Co., Ltd.), by integrating sphere photoelectric photometry The method of measuring is mentioned.

  The turbidity is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose, but is preferably 20 degrees or less, and more preferably 10 degrees or less.

<Application>
The borofluoride treatment method can efficiently remove borofluoride in a single step with simple equipment and operation, and can easily and efficiently recover borofluoride from the treatment solution after borofluoride removal. Therefore, it can be suitably used for removing borofluoride from wastewater.
Conventional removal of borofluoride has been performed in two stages, in which borofluoride is decomposed into boric acid and fluorine, and then the generated fluorine is removed. Is advantageous in that it can be removed in one step.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples.

(Examination of borofluoride remover in water)
<Examples 1-4, Comparative Examples 1-3>
About 8 g of the components shown in Table 1 below (component B-1, component B-2, and component B-3) are each taken in a magnetic crucible (capacity 100 mL), and an electric furnace (FP41, manufactured by Yamato Scientific Co., Ltd.) is used. Thus, the underwater borofluoride removers of Examples 2 to 4 were produced by firing according to the firing temperature and firing time shown in “Method for preparing underwater borofluoride remover” in Tables 2-3 below. After treating the borofluoride-containing water according to the “underwater borofluoride removal treatment conditions” in Tables 2-3 below using the underwater borofluoride removers of Examples 1-4 and Comparative Examples 1-3, The borofluoride removal rate was measured.
The “weight reduction rate after firing (%)” shown in Tables 2 to 3 below was calculated from the following formula (2) by comparing the weight before firing and the weight after firing.
Mass reduction rate after firing (%) = (mass before firing−mass after firing) / mass before firing × 100 (2)

<< Measurement of removal rate of borofluoride in water >>
-Measurement method-
500 mL of borofluoride-containing water having a borofluoride concentration of 100 mg / L is placed in a 1 L beaker, and the borofluoride removing agents in Examples 1 to 4 and Comparative Examples 1 to 3 are added at a concentration of 1% by mass, Using a 4 cm stir bar, the magnetic stirrer was stirred for about 300 minutes at about 300 rpm at room temperature. The treatment solution was filtered through a 0.45 μm filter and neutralized with 0.2 mol / L sulfuric acid. To 15 mL of the treatment solution, 3 mL of 0.4 g / L methylene blue solution and 10 mL of chloroform were added and vigorously shaken for 1 minute in a polyethylene separatory funnel. The chloroform layer was transferred to another separatory funnel, 5 mL of 0.3 g / L silver sulfate solution was added, and the mixture was shaken for about 1 minute and allowed to stand. A portion of the chloroform layer was placed in an absorption cell, the absorbance at a wavelength of 660 nm was confirmed, and the borofluoride concentration in the treatment liquid was measured using a borofluoride calibration curve prepared in advance. A spectrophotometer (Shimadzu MultiSpec-1500, manufactured by Shimadzu Corporation) was used for the absorbance measurement. The removal rate of borofluoride in water was calculated by the following calculation formula (3).
Removal rate of borofluoride in water (%) = (1−C ₁ / C ₀ ) × 100 Formula (3)
In the calculation formula (3), “C ₁ ” represents the borofluoride concentration (mg / L) after the treatment, and “C ₀ ” represents the initial borofluoride concentration (mg / L) before the treatment.

-Evaluation criteria-
The borofluoride removal rate in water indicates that the borofluoride removal rate is higher when it is closer to 100%. An underwater borofluoride removal rate of 60% or more was effective as an underwater borofluoride remover. The results of the borofluoride removal rate in water are shown in Tables 2-3 below.

  From the results of Table 3, when magnesium aluminate hydrate (Comparative Example 1) and hydrotalcite (Comparative Examples 2 to 3) were used as borofluoride removal agents in water without firing, the borofluoride removal rate was very high. The borofluoride in water was not able to be removed. On the other hand, from the results of Table 2, magnesium aluminate (Example 1), a fired product of magnesium aluminate hydrate (Example 2), and a fired hydrotalcite (Example 3) as a borofluoride remover in water. When 4) was used, the removal rate of borofluoride in water was high, and it was confirmed that borofluoride can be removed efficiently.

<Examples 5-9>
<< Examination of firing temperature >>
Example 5 By calcining using magnesium aluminate hydrate (component B-1) or hydrotalcite (component B-3) according to “Preparation method of borofluoride remover” in Tables 4 to 5 below. To 9 borofluoride removers (component A-2 and component A-4) were produced. The underwater borofluoride removal rate was calculated by the same method as described above, except that the borofluoride removers of Example 2 and Examples 4 to 9 were used as the borofluoride remover. The results of the removal rate of borofluoride in water at each firing temperature are shown in Tables 4 to 5 below.

  From the results of Tables 4 to 5, it was possible to obtain a good borofluoride removal rate by firing magnesium aluminate hydrate or hydrotalcite at a temperature of 400 ° C. or higher.

<Examples 10 to 17>
<< Examination of firing time >>
Example 10 By calcining using magnesium aluminate hydrate (component B-1) or hydrotalcite (component B-3) according to “Method for preparing borofluoride remover” in Tables 6 to 7 below. ~ 17 borofluoride removers (component A-2 and component A-4) were produced. The underwater borofluoride removal rate was calculated by the same method as described above except that the borofluoride removers of Examples 2 and 4 and Examples 10 to 17 were used as the borofluoride remover. The results of the borofluoride removal rate in each firing time are shown in Tables 6 to 7 below.

  From the results of Tables 6 to 7, a good removal rate of borofluoride in water could be obtained by baking hydrotalcite for 10 minutes or more. It was also found that a better borofluoride removal rate can be obtained by increasing the hydrotalcite firing time.

<Examples 18 to 20>
<< Examination of pH of borofluoride-containing water >>
500 mL of borofluoride-containing water having a borofluoride concentration of 100 mg / L is placed in a 1 L beaker, and 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide aqueous solution is added according to the “treatment conditions for borofluoride remover” in Table 8 below. Was used to adjust the pH of borofluoride-containing water. A hydrotalcite fired product (component A-4) was used as a borofluoride remover, and the borofluoride removal rate in water was calculated in the same manner as described above. The results of the removal rate of borofluoride in water at each pH are shown in Table 8.

表８の結果より、ホウフッ化物含有水のｐＨを２以上に調整することにより、良好な水中ホウフッ化物除去率を得ることができた。また、ホウフッ化物含有水のｐＨを４以上にした場合、更に良好な水中ホウフッ化物除去率を得ることができた。

From the results shown in Table 8, by adjusting the pH of the borofluoride-containing water to 2 or more, a good removal rate of borofluoride in water could be obtained. In addition, when the pH of the borofluoride-containing water was set to 4 or more, an even better borofluoride removal rate could be obtained.

<Examples 21 to 22>
<< Consideration of combined use of borofluoride remover in water >>
Boron fluoride remover in Example 1 using magnesium aluminate (Component A-1), Boron fluoride remover in Example 2 using a calcined hydrate of magnesium aluminate (Component A-2) , And the same method as in Examples 1 to 4, except that at least one of the underwater borofluoride removers in Example 4 using the calcined product of hydrotalcite (Component A-4) was used in combination according to Table 9 below. The borofluoride removal rate in water was calculated. The results are shown in Table 9 below.

表９の結果より、マグネシウムアルミネート（成分Ａ−１）及びハイドロタルサイトの焼成物（成分Ａ−４）を併用した場合（実施例２１）、並びにマグネシウムアルミネートの水和物の焼成物（成分Ａ−２）及びハイドロタルサイトの焼成物（成分Ａ−４）を併用した場合（実施例２２）ともに、良好な水中ホウフッ化物除去率を得ることができた。

From the results in Table 9, when magnesium aluminate (component A-1) and a calcined product of hydrotalcite (component A-4) were used in combination (Example 21), a calcined product of magnesium aluminate hydrate ( In both cases where the component A-2) and the calcined hydrotalcite (component A-4) were used in combination (Example 22), a good removal rate of borofluoride in water could be obtained.

(Examination of treatment method for borofluoride in water)
<Examples 23 to 25 and Comparative Examples 4 to 8>
Using the fired hydrotalcite (component A-4), a method for treating borofluoride in water was examined.

<< Removal process >>
500 mL of borofluoride-containing water with a borofluoride concentration of 20 mg / L is placed in a 1 L beaker, and the fired hydrotalcite (component A-4) is added at a concentration of 0.25% by mass, and a 4 cm stirrer is used. Then, the mixture was stirred with a magnetic stirrer at about 300 rpm at room temperature for 300 minutes.

<< Aggregating process >>
The treatment liquid obtained in the removal step was set in a jar tester (manufactured by Miyamoto Seisakusho Co., Ltd.) with the 1 L beaker subjected to the borofluoride removal treatment. The polymer aqueous solution was added according to the conditions shown in the following Tables 11-12, stirring at 120 rpm with a magnetic stirrer using a 4 cm stir bar at room temperature. Next, the mixture was stirred at 120 rpm for 5 minutes with a magnetic stirrer at room temperature using a 4 cm stirring bar, and then stirred at 30 rpm for 2 minutes. Details of the flocculant used in the flocculation step are shown in Table 10 below.

<< Separation process >>
The treatment solution obtained in the aggregation step was allowed to stand at room temperature for 3 minutes, and then the supernatant solution was sampled.

<< Measurement of removal rate of borofluoride in water >>
The removal rate of borofluoride in water was performed by the same method as described above. The evaluation criteria were the same as those described above.

<< Measurement of cohesiveness >>
-Measurement method-
Evaluation of the cohesiveness was performed based on the turbidity of the supernatant solution. Turbidity was measured by an integrating sphere photoelectric photometry method using Water Analyzer 2000N (manufactured by Nippon Denshoku Industries Co., Ltd.).

-Evaluation criteria-
The agglomeration property indicates that the smaller the turbidity value of the supernatant solution is, the better the agglomeration property is.

  From the results of Tables 11 to 12, the nonionic polymer flocculant, the amphoteric polymer flocculant, and the cationic polymer flocculant were obtained in the treatment method (Examples 23 to 25) to which the anionic polymer flocculant was added. When compared with the treatment method (Comparative Examples 4 to 8) to which was added, it was confirmed that the turbidity value was small and the cohesiveness was good.

  The underwater borofluoride removing agent of the present invention can easily and efficiently remove borofluoride from borofluoride-containing water in a single step and has a high borofluoride removal rate. For example, in various industrial wastewater It can be suitably used for removing borofluoride. Further, the borofluoride treatment method of the present invention is advantageous compared to conventional borofluoride treatment methods because borofluoride can be easily and efficiently recovered from the treatment solution after borofluoride removal.

Claims (2)

  An underwater borofluoride remover that contains at least one of a calcined product of magnesium aluminate hydrate, a calcined product of hydrotalcite, and magnesium aluminate, and removes borofluoride from borofluoride-containing water. A removing step of removing the borofluoride by adding the underwater borofluoride remover according to claim 1 to the borofluoride-containing water;
An agglomeration step in which an anionic polymer flocculant is added to the treatment liquid in the removal step to perform an agglomeration treatment;
A separation step for performing solid-liquid separation of the treatment liquid in the aggregation step;
A method for treating borofluoride in water, comprising: