JP2002210475A - Treating method of waste water containing boron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method of waste water containing boron. SOLUTION: A solution containing boric acid, solid boric acid or a solid boron compound and reduced in sulfate ions can be obtained by adding a barium compound and/or a strontium compound to the waste water containing sulfate acidic boron to precipitate the sulfate ions as barium sulfate and/or strontium sulfate. The solution containing boric acid, solid boric acid and the solid boron containing compound can be obtained in such a simple manner that the optimum adding volume can be determined by using easily measured parameters such as pH and conductivity as an index without directly measuring the sulfate ions in the waste by using a specified compound such as barium hydroxide or strontium hydroxide as the barium compound or the strontium compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a boron-containing solution in which sulfate ions are reduced from a sulfate-acid-boron-containing wastewater,
The present invention relates to a wastewater treatment method capable of recovering solid boric acid or a solid boron compound, and more particularly, to the treatment method for regenerated wastewater of a boron adsorbent.

[0002]

2. Description of the Related Art Boron compounds are widely used in the fields of dyes, pigments, pharmaceuticals, raw materials for cosmetics, preservatives, photography, glass, plating, and the like. It is included. In addition, radioactive wastewater generated from nuclear power plants, geothermal wastewater, flue gas desulfurization wastewater from thermal power plants, ash dumped wastewater, garbage incineration smoke and other wastewater also contain boron compounds. Although boron is an essential element for plants, it is known that excessive administration inhibits its growth, and its toxicity to the human body has been regarded as a problem. For this reason, in Japan, there are some regulations that set extremely strict standards of 1 to 2 mg / L or less as the wastewater standard for boron. A standard of 0.0 mg / L was added.

Conventionally, as a method of treating boron-containing wastewater, a method of removing boron as an insoluble precipitate with slaked lime and aluminum sulfate, for example, Japanese Patent Publication No. 3-103
No. 78, a method of adsorbing and removing boron with a boron-adsorbing resin such as an N-methylglucamine-type boron-selective anion-exchange resin, and a method of extracting and removing boron by solvent extraction (JP-B-1) -50476), a method of removing boron as an insoluble precipitate by using a sulfide agent and a magnesium agent (Japanese Patent Publication No. 2-55558).
Is known. Among these, the treatment method using a boron-selective adsorption resin is used as a method for removing only boron from boron-containing water, but requires a resin regenerating operation, and requires a high concentration of a high concentration discharged by the regenerating operation. In order to treat the recycled wastewater containing boron, a coagulation sedimentation method, a solvent extraction method and the like are combined.

However, the method of coagulating and sedimenting the reclaimed wastewater is
A large amount of chemicals is required, which increases the cost and generates a large amount of boron-containing sludge. The sludge itself is not suitable for use in any application, and it is difficult to recover useful substances from the sludge. Has a problem that since it contains a large amount of boron, there is a limit to the disposal. In addition, in the method of recovering boron by solvent extraction, operations such as extraction into a solvent and back extraction from a solvent into an aqueous alkali solution are required, which complicates the treatment process as a whole. The effect on workers is also a problem. Furthermore, in the solvent extraction method, since the COD (chemical oxygen demand) of the treated water increases due to the incorporation of the solvent into the treated water, the necessity of performing the COD treatment in the latter stage of the solvent extraction arises. Requires more complicated processing steps. Further, in order to prevent the above-mentioned adverse effects, it is conceivable that the regenerated wastewater containing high-concentration boron is evaporated and concentrated by a heating operation or the like as it is to recover boron in the form of boric acid. However, in order to elute boron from the boron adsorbent, an acid is used.
% Sulfuric acid is often used, and in this case, it is difficult to directly heat and concentrate due to the corrosiveness of sulfuric acid. Further, in the heat concentration, there is a problem that the boiling point is increased in the concentration process due to the sulfuric acid contained, and the concentration efficiency is reduced.

[0005]

For this reason, the boron-containing wastewater can be treated by a simple treatment method without polluting the environment with boron, and the boron can be recovered from the boron-containing wastewater simply for disposal. Instead, a wastewater treatment method capable of recovering a boron compound in a reusable form is desired. In particular, in the treatment method using a boron-selective adsorbent, which has recently been used as an excellent method for removing only boron from the boron-containing water, a high-concentration boron-containing reclaimed wastewater generated by an adsorbent regeneration operation is treated. There is a need for a method for doing so.

[0006] The present invention has been made in view of such circumstances, and the present invention is to add a barium compound and / or a strontium compound to waste water containing acidic boron sulfate to convert the sulfate ions in the waste water into barium sulfate. And / or by precipitation as strontium sulfate,
It is an object of the present invention to provide a method for treating a boron-containing wastewater, in which a subsequent treatment is easy and a boric acid or boron compound having a small amount of impurities can be recovered, and a boric acid-containing solution with reduced sulfate ions can be obtained. Aim. Further, the present invention provides a boric acid-containing solution in which sulfate ions are reduced by adjusting the amount of a barium compound and / or a strontium compound to be added to sulfated acidic boron-containing wastewater without coexisting ions derived from the compound. It is an object of the present invention to provide a processing method capable of obtaining a solution. Further, the present invention can obtain a boric acid-containing solution in which coexisting substances such as sulfate ions are reduced by a simple method such as monitoring pH by using barium hydroxide, strontium hydroxide, or the like. It is an object of the present invention to provide a processing method that can be used. Another object of the present invention is to provide the wastewater treatment method, wherein an alkaline compound is further added to recover a boron compound such as a borate, which has a small amount of impurities.

[0007]

According to the present invention, as a first aspect, a barium compound and / or a sulfuric acid-acid-boron-containing wastewater is contained.
Alternatively, a method for treating a sulfate-acid-boron-containing wastewater, comprising adding a strontium compound to precipitate sulfate ions, subjecting the resulting precipitate to solid-liquid separation to obtain a boric acid-containing solution with reduced sulfate ions. I will provide a. According to a second aspect of the present invention, there is provided the method according to the first aspect, wherein the barium compound and / or the strontium compound is added to the sulfated boron-containing wastewater so as to be substantially equivalent to sulfate ions. I do. The present invention provides a method according to claim 1 or 2, wherein an alkaline compound other than a barium compound and / or a strontium compound is further added to wastewater containing acidic boron sulfate. The present invention provides the method according to any one of claims 1 to 3, wherein the barium compound is barium hydroxide and the strontium compound is strontium hydroxide. According to a fifth aspect of the present invention, there is provided a method for treating a sulfated acidic boron-containing wastewater, further comprising a step of recovering a solid boric acid or a solid boron compound from a boric acid-containing solution produced by the method of the first to fourth aspects. . According to the present invention, the recovery treatment of the solid boric acid or the solid boron compound is performed by evaporating and concentrating the boric acid-containing solution, or separating and separating the boric acid or the boron compound from the boric acid-containing solution. The method according to claim 5, which is performed by a crystallization method. The present invention as claim 7, wherein the sulfuric acid acidic boron-containing wastewater is a regenerated wastewater of a cellulosic boron adsorbent or an N-methylglucamine-type boron-selective anion exchange resin. To provide a way.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The sulfuric acid-acid-boron-containing wastewater to be treated in the method of the present invention may be any wastewater containing sulfuric acid and boron.
For example, regenerated wastewater such as a cellulose-based boron adsorbent and an N-methylglucamine-type boron-selective anion exchange resin;
Wastewater discharged from industries such as dyes, pigments, pharmaceuticals, cosmetic raw materials, preservatives, photographs, glass, and plating; flue gas desulfurization wastewater from thermal power plants, radioactive wastewater from nuclear power plants, geothermal power generation wastewater, ash disposal Examples include, but are not limited to, drainage such as local drainage and garbage incineration and smoke drainage. In the present invention, the sulfated acidic boron-containing wastewater may contain impurities other than sulfuric acid and boron, but when the wastewater contains impurities, the impurities are contained in the finally recovered boric acid-containing solution. It will be. For this reason,
The amount and type of impurities allowed in the sulfated acidic boron-containing wastewater treated in the present invention are determined according to the purity desired as the boric acid-containing solution, solid boric acid, or solid boron compound finally recovered. The Rukoto. From the viewpoint of recovering a boric acid-containing solution containing a small amount of impurities, the sulfuric acid-acid-boron-containing wastewater preferably has little impurities other than sulfuric acid and boron, and more preferably contains no impurities. Cellulosic boron adsorbent, N
-Boron adsorbents such as methyl-glucamine-type boron-selective anion exchange resin do not adsorb anything other than boron, so only boron is eluted in the regeneration treatment, and as long as a sulfuric acid solution with less impurities is used in the regeneration treatment. Can reduce the amount of impurities other than boron and sulfuric acid. Therefore, when the regenerated wastewater of the boron adsorbent is used as the sulfuric acid-acidic boron-containing wastewater, a boron-containing solution finally recovered, solid boric acid, or a solid boron compound is obtained with high purity. It will be.

[0009] The sulfuric acid concentration of the sulfuric acid acidic boron-containing wastewater treated in the present invention is generally 0.5 to 8% by weight.
And preferably 1 to 5% by weight. Further, the boron concentration is 800 to 5000 mg / L, and preferably 1000 to 3500 mg / L. When barium chloride or strontium chloride is dropped into the boric acid solution, no precipitate of barium borate or strontium borate is formed even at a boron concentration of 5000 mg / L.
Therefore, if the boron concentration is within the above range, even if the barium compound or the strontium compound is added to the wastewater, the boron is not mixed into the precipitated fraction as barium borate or strontium borate. In addition, the sulfuric acid concentration in the regeneration wastewater of a general boron adsorbent is 1 to 5% by weight, and the boron concentration is 800 to 5000 mg / L. In the present invention, in order to obtain a boric acid solution with a small amount of impurities, the boron concentration in the sulfated acidic boron-containing wastewater to be treated is higher than the sulfate ion concentration in the general concentration range in the reclaimed wastewater. It is desirable. When the boron adsorbent regeneration wastewater is used as a method for adjusting the ratio of boron and sulfate ions to an appropriate ratio, a method of separating a lean part and a rich part of the wastewater and reusing a part (particularly, However, the present invention is not limited to this, and can be adjusted by any method.

The barium compound usable in the present invention is soluble in wastewater containing acidic sulfuric acid, and barium ions generated from the barium compound combine with sulfate ions in the wastewater to form hardly soluble barium sulfate precipitates. Any compound can be used as long as it can be used. For example, barium hydroxide, barium oxide, barium hydride,
Examples include, but are not limited to, soluble compounds such as barium chloride, barium bromide, barium fluoride, barium iodide, and barium nitrate. Barium chloride,
When barium bromide, barium fluoride, barium iodide, barium nitrate, or the like is used, hydrochloric acid, hydrobromic acid, hydrofluoric acid, hydroiodic acid, and nitric acid are generated as by-products, respectively. . Thus, in these cases, the sulfate ions are removed, but the resulting boric acid-containing solution contains the by-products, from which the solution is not pure boric acid,
As a result, a boron compound containing no sulfate ion is obtained. In contrast, when barium hydroxide, barium oxide, or barium hydride is used, the boric acid-containing solution to be recovered contains no coexisting ions derived from the compound, and a substantially pure boric acid-containing solution is used. Obtainable. When barium hydroxide, barium oxide, or barium hydride is used, the amount of the barium compound added can be easily adjusted by monitoring the pH of the wastewater, and the neutralization of the solution can be performed simultaneously. Since the barium compound can be used, barium hydroxide, barium oxide, and barium hydride are preferable. From the viewpoint of easy handling, barium hydroxide is more preferable.

The strontium compounds usable in the present invention are soluble in wastewater containing acidic boron sulfate, and strontium ions generated from the strontium compound combine with the sulfate ions in the wastewater to form hardly soluble strontium sulfate precipitates. Any compound can be used as long as it can be used. For example, strontium hydroxide, strontium oxide, strontium hydride,
Examples include, but are not limited to, soluble compounds such as strontium chloride, strontium bromide, strontium fluoride, strontium iodide, and strontium nitrate. Strontium chloride, strontium bromide, strontium fluoride, strontium iodide,
When strontium nitrate or the like is used, hydrochloric acid, hydrobromic acid, hydrofluoric acid,
Generates hydroiodic acid and nitric acid. Thus, in these cases, the sulfate ions are removed, but the resulting boric acid-containing solution contains the by-products, from which the pure boronic acid, rather than the pure boric acid, a boron compound that does not contain sulfate ions. Will be obtained. In contrast, strontium hydroxide,
When strontium oxide or strontium hydride is used, the boric acid-containing solution to be recovered does not contain coexisting ions derived from the compound, and a substantially pure boric acid-containing solution can be obtained. In addition, when strontium hydroxide, strontium oxide, or strontium hydride is used, the amount of the strontium compound to be added can be easily adjusted by monitoring the pH of the wastewater, and simultaneously neutralizing the solution. Since strontium compounds can be used, strontium hydroxide, strontium oxide, and strontium hydride are preferable.
From the viewpoint of easy handling, strontium hydroxide is more preferable.

The barium compound and the strontium compound that can be used in the present invention may be hydrates or anhydrides. Further, as the barium compound and / or strontium compound, one kind of compound may be used, or a plurality of compounds may be used in combination. When a plurality of compounds are used, a mixture of a plurality of barium compounds, a mixture of a plurality of strontium compounds, or a mixture of a barium compound and a strontium compound may be used. In the present invention, the barium compound and / or the strontium compound may be added as they are to the wastewater containing sulfuric acid-acidic boron as they are, or may be added in an aqueous solution in advance. When any of barium oxide, barium hydride, strontium oxide and strontium hydride is used, it is preferable to add it after preparing an aqueous solution in consideration of its reactivity. When it is added as an aqueous solution, it can be appropriately added as an aqueous solution of any concentration depending on the wastewater treatment system used.

In the present invention, by adding a barium compound and / or a strontium compound to wastewater containing acidic boron sulfate, sulfate ions in the wastewater react with barium ions and / or strontium ions, and barium sulfate and / or strontium ions are reacted. Strontium sulfate is produced. The solubility of barium sulfate is 2.30 mg / water 10
0 g (18 ° C.), and the solubility of strontium sulfate is very small at 11.4 mg / 100 g of water (18 ° C.).
These will form a precipitate in water. Thereby, the sulfate ions present in the wastewater are removed as precipitates according to the total amount of the added barium compound and strontium compound.

The amounts of the barium compound and the strontium compound to be added are appropriately set according to the amount of sulfate ions contained in the sulfated boron-containing wastewater and the purity of boron required in the finally recovered boric acid-containing solution. . Preferably, the added amount of the barium compound and / or the strontium compound is approximately equivalent to sulfate ions contained in the wastewater. In this case, sulfate ions corresponding to the amount exceeding the solubility of barium sulfate and / or strontium sulfate precipitate as barium sulfate or strontium sulfate, are removed from the wastewater, and the amount of sulfate ions in the solution is determined by the solubility of the compound. Less than that. On the other hand, when the barium compound and / or the strontium compound is added in an amount exceeding approximately the equivalent of the sulfate ion in the wastewater, the barium ion and the strontium ion remain as coexisting substances in the recovered boron-containing solution. This results in increased impurities in the resulting boric acid-containing solution, solid boric acid, or solid boron compound. Further, when the barium compound and / or strontium compound is added in an amount smaller than substantially equivalent to the sulfate ion in the wastewater, the sulfate ion remains in the recovered boron-containing solution.

In the present specification, the "approximately equivalent" as the addition amount of the barium compound and the strontium compound refers to the case where impurities other than sulfate ions and boron are contained in the sulfated acidic boron-containing wastewater. It is. For example, when the impurity is a substance which forms a hardly soluble salt with barium and / or strontium, a part of the added barium ion and strontium ion is consumed to form a precipitate with the impurity, and the sulfate ion is sufficiently removed. become unable. Therefore, in such a case, in order to reduce the sulfate ion in the solution most, a barium compound and / or a strontium compound more than the equivalent of the sulfate ion contained in the wastewater are added according to the amount of the impurity. It will be. Not limited to this example, the addition amounts of the barium compound and the strontium compound are appropriately adjusted according to the amounts of the impurities.

In the present invention, the sulfate ion precipitation treatment comprises:
Any known treatment apparatus, as long as sulfate ions in the wastewater react with barium ions and / or strontium ions derived from the added barium compound and / or strontium compound to form precipitates;
Processing methods can be used. For example, while continuously supplying the wastewater and the compound to the reaction tank, a continuous method such as a solid-liquid separation treatment of the liquid after the reaction may be performed, or the reaction may be performed by a batch method. Alternatively, a method of performing a solid-liquid separation treatment may be used. Since it is convenient to adjust the addition amount of barium compound and / or strontium compound,
Batch methods are preferred. Further, a device provided with a stirring device or the like may be used.

The addition amount of the barium compound and / or the strontium compound can be controlled by using any known method and apparatus. For example, using a pH meter and an electric conductivity meter, a method of controlling the pH and the electric conductivity as indices, respectively, and an ion chromatography method,
Examples include, but are not limited to, a method in which the content of sulfate ions is quantified by barium chromate absorption spectrophotometry, gravimetric method, or the like, and this is used as an index for control. Also,
It is also possible to control by using a plurality of the above methods and apparatuses. From the viewpoint of simple measurement, a method using pH and electric conductivity as indexes is preferable. Since the pH and electric conductivity change depending on the amount and type of impurities contained in the wastewater, when these are used as indices, when the concentration of sulfate ions in the wastewater containing the acidic boron sulfate is minimum. It is preferable to previously measure the pH and the electric conductivity.

The pH of the wastewater is adjusted when a compound which becomes alkaline when dissolved in water is used, such as barium hydroxide, barium oxide, barium hydride, strontium hydroxide, strontium oxide, and strontium hydride. It can be used as an indicator of the amount of addition. In this case, the pH of the wastewater is increased by the addition of the barium compound and / or the strontium compound.
It is almost equivalent to sulfate ion in wastewater. For example, when regenerated wastewater of a boron adsorbent is used, the pH is 6-7.
The addition amount is adjusted so as to be in the range of 5.
When the electric conductivity is used as an index, the electric conductivity is generally 100 μS / cm or less, preferably 50 μS / c.
The amount of the barium compound and / or the strontium compound is controlled so as to be equal to or less than m. The above value is a condition using pure water as a diluent for the regenerating chemical. Is used, and the value changes according to the amount and type of impurities. When electric conductivity is used as an index, since no by-product is generated when added to wastewater, barium hydroxide, barium oxide, barium hydride,
Strontium hydroxide, strontium oxide and strontium hydride are preferred.

In the present invention, after the precipitation treatment, the precipitate and the solution are subjected to a solid-liquid separation treatment. As the solid-liquid separation treatment, any known method can be used as long as it can separate a precipitate and a solution component, and examples thereof include, but are not limited to, coagulation sedimentation filtration, centrifugation, and membrane filtration. However, it is also possible to perform processing by combining the above-described methods. Further, it is also possible to simultaneously perform a method and means for assisting the solid-liquid separation treatment. For example, when coagulation sedimentation filtration is performed as solid-liquid separation treatment, when solid-liquid separation is difficult, an inorganic coagulant such as ferric chloride or polyaluminum chloride or an organic polymer coagulant such as polyacrylamide is used. It can be added to improve the solid-liquid separation characteristics.

In the method of the present invention, boron contained in the wastewater does not react with barium or strontium to form a precipitate. Therefore, by a solid-liquid separation treatment, boron-free high-purity barium sulfate or strontium sulfate, Or a mixture thereof can be obtained. By subjecting the precipitate after the solid-liquid separation treatment to an appropriate treatment such as washing with water, the purity of the precipitate can be further improved. Barium sulfate recovered by the method of the present invention, for example,
In a coal-fired power plant having a flue gas desulfurization unit of the wet lime-gypsum method, it can be used by mixing with gypsum produced as a by-product when desulfurizing flue gas. Although gypsum produced from coal-fired power plants is used as a gypsum board material for building materials, barium sulfate obtained by the method of the present invention is a white alkaline earth metal sulfate having many similar parts to gypsum. By mixing with gypsum, it can be used as a gypsum board raw material. Therefore, if this gypsum and the present invention are used, the amount of sludge can be reduced, and the processing cost can be reduced. The strontium sulfate recovered by the method of the present invention can be used, for example, as a raw material for strontium carbonate.

In the method of the present invention, the precipitate is removed by the solid-liquid separation treatment to obtain a boric acid-containing solution with reduced sulfate ions. The sulfate ion concentration in the solution is
A boric acid-containing solution having a purity of several mg / L is obtained. From this boric acid-containing solution, high-purity solid boric acid can be recovered. As a method for recovering solid boric acid, any known method capable of generating solid boric acid from a boric acid-containing solution can be used. For example, a method of evaporating the water content of a boric acid-containing solution using various concentrators, a drum dryer, or the like to obtain solid boric acid, or a crystallization method of precipitating and separating solid boric acid from a boric acid-containing solution, and the like. Examples include, but are not limited to:

In the method of the present invention, an alkaline compound other than a barium compound and / or a strontium compound (hereinafter, referred to as “alkaline compound”) may be added to waste water containing acidic boron sulfate to adjust the pH of the waste water. It is possible. As the alkaline compound that can be added to the wastewater, any compound that is soluble in water and shows alkalinity can be added, and examples thereof include alkali metal salts such as sodium hydroxide and potassium hydroxide, and ammonia. It is not something to be done. The alkaline compound may be used alone, or a plurality of compounds may be used as a mixture. The alkaline compound may be added as it is or as an aqueous solution.

Preferably, the alkaline compound is an alkali metal salt, more preferably sodium hydroxide or potassium hydroxide. For example, when sodium hydroxide or potassium hydroxide is used, sodium ions or potassium ions coexist in the solution recovered after the precipitation treatment, and when the boron-containing solid material is subjected to the recovery treatment for the solution. , A solid boron compound such as sodium borate or potassium borate is obtained. Therefore, when the purpose is to obtain boric acid in the waste water as a solid boron compound such as a solid borate instead of solid boric acid, it is preferable to add an alkaline compound. In order to obtain a solid boron compound from a boric acid solution, the same method as described above for obtaining solid boric acid can be used, and the method is not particularly limited. Also,
As an alkaline compound, for example, when ammonia is added, the pH of a boric acid solution containing ammonia
Is adjusted to the alkali side, aeration, heating and the like are performed, and stripping or the like is removed to obtain solid boric acid. If ammonia is not removed, solid ammonium borate can be obtained.

In the method of the present invention, the alkaline compound may be added at any stage of the method of the present invention, for example, before, simultaneously with, or simultaneously with the precipitation of barium sulfate and / or strontium sulfate. It can be added later or in these multiple stages. In addition, when the alkaline compound is added before or simultaneously with the precipitation treatment, the barium compound and the strontium compound cannot be used as an index for adjusting the addition amount of the strontium compound, and the sulfate ion is directly quantified. Need arises. Therefore, when pH or electric conductivity is used as an indicator of the amount of the barium compound and / or strontium compound to be added, the alkaline compound is added after the precipitation treatment.

As one embodiment of the processing method of the present invention, FIG.
Fig. 2 shows a flow sheet in the case where the regenerated wastewater of the boron adsorbent is treated by the method of the present invention, but the present invention is not limited to this embodiment. In FIG. 1, the boron adsorbent 1 subjected to boron adsorption is treated with a sulfuric acid-acidic regenerant, and the regenerated wastewater containing sulfuric acid-acidic boron is stored in a reclaimed drainage tank 2. The reclaimed wastewater is transferred from the reclaimed drainage tank 2 to the reaction tank 3. Next, while measuring pH, electric conductivity, and the like, barium hydroxide is supplied to the reaction tank 3 so as to be substantially equivalent to sulfate ions existing in the reaction tank 3, thereby causing precipitation of barium sulfate. After the precipitating treatment, the waste water is transferred to the coagulating sedimentation tank 4, where it is separated into a sediment slurry and a boric acid solution, and the sediment slurry is dehydrated by the dehydrator 5 to obtain solid barium sulfate. Further, the boron solution is concentrated by the evaporation and concentration device 6, and solid boric acid is obtained.

[0026]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. Example 1 (Recovery of boric acid-containing solution) Boron-containing wastewater having a boron concentration of 20 mg / L was subjected to boron-selective adsorption resin (Amberlite (registered trademark) IRA74).
3: Organo Co., Ltd.) and treated to obtain treated water having a boron concentration of less than 0.5 mg / L. When the water flow was continued and the flow-through capacity of the boron-selective adsorption resin was reached and the treated water quality was increased to 2 mg / L, the boron-selective adsorption resin was regenerated with 5% sulfuric acid.
Regenerated wastewater of 200 mg / L was obtained. Subsequently, barium hydroxide anhydride (special grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the regenerated wastewater while stirring, whereby a white precipitate was formed. The addition of barium hydroxide results in a pH of the wastewater of 6.
I went to 2 The generated white precipitate is filtered using a quantitative filter paper (No. 5C filter paper), and sulfate ions in the filtrate are subjected to ion chromatography (JIS K0102).
And azomethine H absorption spectrophotometry (JI
SK0102). Table 1 shows the results.

[0027]

[Table 1]

By the treatment according to the method of the present invention, the sulfate ion concentration of 24,000 mg / L in the reclaimed wastewater becomes:
Reduced to less than 20 mg / L. The boron concentration is
Little changed. From this, it was clarified that the method of the present invention can accurately separate sulfate ions and boron in the sulfate-acid-boron-containing wastewater.

Example 2 (Recovery of solid boric acid) The filtrate obtained in Example 1 was heated in an evaporating dish to evaporate water, whereby a white powder was obtained. This powder was weighed in the same manner as a standard boric acid (special grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.), dissolved in pure water, and the concentration was measured. From the measurement results, boric acid purity was determined using the following formula: boric acid purity (%) = (boric acid concentration of white powder solution / boric acid concentration of standard product) × 100.

As a result of the measurement, the boron concentration of the white powder solution obtained in Example 2 was 95% of the standard boric acid. Therefore, it was confirmed that the boric acid content of the white powder obtained in Example 2 was 95%.

[0031]

As described above, according to the present invention, a barium compound and / or a strontium compound is added to waste water containing acidic boron sulfate to precipitate sulfate ions in the waste water as barium sulfate and / or strontium sulfate. In addition, a boric acid-containing solution, a solid boric acid, or a solid boron compound in which sulfate ions are reduced can be obtained by optionally adding an alkaline compound. Further, by making the amount of the barium compound and / or strontium compound substantially equivalent to that of the sulfate ion, not only the sulfate ion can be reduced but also the coexisting substance derived from the barium compound and the strontium compound can be reduced. In addition, the present invention uses an alkaline barium compound such as barium hydroxide and strontium hydroxide, and a strontium compound, which eliminates the need to directly measure sulfate ions in wastewater, and facilitates measurement of pH, electric conductivity, and the like. This makes it possible to obtain a high-purity boric acid-containing solution, a solid boric acid, and a solid boron-containing compound by a simple method in which an optimum addition amount can be determined using a parameter as an index.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flow sheet in the case where the regenerated wastewater of a boron adsorbent is treated by the method of the present invention.

[Explanation of symbols]

 1 Boron adsorbent 2 Regeneration drain tank 3 Reaction tank 4 Coagulation sedimentation tank 5 Dehydrator 6 Evaporation concentrator

Claims (7)

[Claims] 1. A barium compound and / or a strontium compound is added to waste water containing acidic boron sulfate to precipitate sulfate ions, and the resulting precipitate is subjected to solid-liquid separation treatment to obtain a boric acid-containing solution having reduced sulfate ions. A method for treating sulfuric acid-acid-boron-containing wastewater, comprising: 2. The method according to claim 1, wherein the barium compound and / or the strontium compound are added to the sulfated boron-containing wastewater in such a manner as to be substantially equivalent to sulfate ions. 3. The method according to claim 1, wherein an alkaline compound other than a barium compound and / or a strontium compound is further added to the waste water containing acidic boron sulfate. 4. The method according to claim 1, wherein the barium compound is barium hydroxide and the strontium compound is strontium hydroxide. 5. A method for treating a sulfuric acid-acidic boron-containing wastewater, further comprising a step of recovering a solid boric acid or a solid boron compound from the boric acid-containing solution produced by the method according to claim 1. 6. A crystallization method for recovering a solid boric acid or solid boron compound by evaporating and concentrating a boric acid-containing solution, or separating and separating a boric acid or boron compound from a boric acid-containing solution. The method according to claim 5, which is performed by: 7. The wastewater containing sulfuric acid-acidic boron is a regenerated wastewater of a cellulosic boron adsorbent or an N-methylglucamine-type boron-selective anion exchange resin.
The method according to claim 1.