JP2011104459A - Waste water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment method which can easily and inexpensively treat hardly decomposable borofluoride ions contained in waste water. <P>SOLUTION: The treatment method of waste water containing fluorine and boron and containing at least hardly decomposable borofluorides has a decomposition process where a polyvalent metal or its salt is added to the waste water and the pH of the waste water is maintained at 4 or less, and ultraviolet rays are irradiated to the waste water to decompose the hardly decomposable borofluorides. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for treating wastewater containing a hardly decomposable compound, and particularly relates to a method for treating wastewater containing fluorine and boron and containing a hardly decomposable borofluoride formed by a reaction between fluorine and boron. .

Conventionally, as a method for treating waste water containing fluorine, a method of precipitating and separating hardly soluble calcium fluoride (CaF ₂ ) by adding a calcium salt such as calcium hydroxide or calcium chloride has been most frequently used. However, it is difficult to decompose by the reaction of fluorine and boron in the wastewater, such as plating factory wastewater, glass manufacturing factory wastewater, flue gas desulfurization wastewater from coal-fired power plants, nonferrous metal refining factory wastewater and semiconductor manufacturing wastewater. When a soluble borofluoride is formed, soluble Ca (BF ₄ ) ₂ is only produced as shown in the following reaction formula (1) even if a calcium salt is added. The concentration is hardly reduced.

  In addition, since fluorine is the element with the highest electronegativity among all the elements, polyfluoride is a defluorination treatment method that uses the property that fluoride ions have a high affinity for polyvalent metal elements. There is a metal coagulation precipitation separation method.

  In this polyvalent metal coagulation precipitation separation method, a polyvalent metal salt compound such as sulfate band, polyaluminum chloride (PAC), ferric sulfate or ferric chloride is added as an inorganic coagulant to the waste water to be treated. To do. Then, the pH is adjusted using an alkali agent, and fluorine is adsorbed and co-precipitated on the produced aluminum hydroxide or iron hydroxide colloid for solid-liquid separation.

  However, also in this polyvalent metal aggregation precipitation separation method. Since borofluoride ions hardly adsorb to gelled aluminum hydroxide or iron hydroxide, they can hardly be treated even if a polyvalent metal salt is added.

In other words, borofluoride in aqueous solution forms a stable complex ion, so it is not easy to remove fluorine from aqueous solution, and it is important to break the bond between fluorine and boron when removing fluorine. It becomes. However, borofluoride ion (BF ₄ ⁻ ) has a very strong binding energy between boron (B) and fluorine (F), and as shown in the following general formulas (2) to (5), HBF ₄ ⁻ When subjected to hydrolysis, decomposition proceeds gradually while F coordinated to B is substituted with hydroxyl groups one by one. This decomposition reaction is usually slow, and it is thought that these series of reactions are determined by factors such as temperature, pH, and removal of free HF. The general formulas (2) to (5) are equilibrium reactions in an acidic solution.

  Therefore, in order to promptly advance the reactions to the above general formulas (2) to (5), for example, a treatment for applying thermal energy for decomposing borofluoride from the outside of the reaction system is required. In addition, it is necessary to efficiently remove the free HF generated on the right side in each of the general formulas (2) to (5) to the outside of the reaction system. Does not progress.

  Therefore, under acidic conditions, heat treatment is performed at a high temperature to decompose borofluoride ions, and an aluminum compound is added, and the generated free hydrogen fluoride is converted to hexafluoroaluminum acid as shown in the following general formula (6). The method of stabilizing and removing substantially outside the reaction system is employed.

  For example, Patent Document 1 (Japanese Patent Publication No. 54-18064) discloses hexafluoroaluminum by temporarily stabilizing the fluorine component contained in borofluoride as hexafluoroaluminum acid and then adding calcium ions or the like. A method for separating and removing a fluorine component in an acid as hardly soluble calcium fluoride is disclosed.

  Further, in Patent Document 2 (Japanese Patent Laid-Open No. 9-131593), for example, an iron salt is added, heat treatment is performed under acidic conditions to decompose borofluoride, and the resulting iron fluorocomplex is converted to calcium or aluminum salt. A method for precipitation treatment is disclosed.

  However, in such a general treatment method, the decomposition reaction rate shown in the above general formulas (2) to (5) is slow at low temperatures, and it is practically necessary to heat to a high temperature of about 60 ° C. or higher. As a result, the energy cost is increased, the economic efficiency is deteriorated, and a special material needs to be used for the processing equipment.

  In response to these problems, for example, Patent Document 3 (Japanese Patent Application Laid-Open No. 2000-189980) adds aluminum hydroxide to waste water containing borofluoride, and adds air by blowing air into the waste water. A method for increasing the solubility of aluminum hydroxide is disclosed. Moreover, in patent document 4 (Unexamined-Japanese-Patent No. 2002-143841), an aluminum compound is added to the waste_water | drain containing borofluoride, a firing phenomenon is produced by the powerful sound pressure obtained by ultrasonic irradiation, and reaction A method for promoting speed is disclosed.

  However, all of these prior art methods are techniques for accelerating dissolution of the aluminum compound, and the generated hydrogen fluoride is stabilized as hexafluoroaluminum acid and substantially removed from the reaction system. For the purpose of promoting the reaction to the right side of the general formula (6), and does not improve the decomposition efficiency of the hardly decomposable borofluoride. For this reason, the problem of an increase in energy cost due to heating has not been solved.

  As described above, in the conventional methods for treating wastewater containing fluorine and boron and containing hardly-decomposable borofluoride formed by the reaction of fluorine and boron, the hardly-decomposable borofluoride is used. In order to decompose at room temperature, the reaction time becomes very long and the decomposability is low. Therefore, in practice, it is necessary to heat to a temperature as high as 60 ° C. or more at a minimum. However, heating requires a large amount of energy, and there is a serious problem that the cost is increased as the cost increases. As described above, there is a big problem in the conventional wastewater treatment method containing refractory borofluoride, etc., and the borofluoride is efficiently decomposed to easily and inexpensively reduce the fluorine concentration in the wastewater. A processing method is desired.

Japanese Patent Publication No.54-18064 JP-A-9-131593 JP 2000-189980 A JP 2002-143841 A

  This invention is proposed in view of such a situation, and provides the processing method of the wastewater which can process the hardly decomposable borofluoride ion contained in wastewater easily and cheaply. Objective.

  As a result of extensive studies, the present inventors have found that the decomposition efficiency of borofluoride can be improved by irradiating the wastewater containing the hardly-decomposable borofluoride with ultraviolet rays.

  That is, the wastewater treatment method according to the present invention is a wastewater treatment method containing fluorine and boron and containing at least hardly decomposable borofluoride, wherein a polyvalent metal or a metal salt thereof is added to the wastewater. And a decomposition step of decomposing the hardly decomposable borofluoride by irradiating with ultraviolet rays while maintaining the pH of the wastewater at 4 or less.

  The metal element constituting the polyvalent metal or metal salt thereof is preferably at least one selected from aluminum, iron and titanium, and is contained in the waste water when the metal element is aluminum or iron. The polyvalent metal or the metal salt thereof is added so that the aluminum ion or iron ion is 0.8 to 5 times mol per mol of the borofluoride ion. In addition, when the metal element is titanium, the polyvalent metal or the metal salt compound thereof is used so that the titanium ion is 0.4 to 3 times the mol of 1 mol of the borofluoride ion contained in the wastewater. Add.

  In the decomposition step, the waste water is preferably stirred.

  According to the wastewater treatment method of the present invention, the decomposition efficiency of the hardly decomposable borofluoride contained in the wastewater can be improved, and the wastewater treatment can be performed easily, quickly and inexpensively.

It is process explanatory drawing of the processing method of the wastewater which concerns on this Embodiment.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

FIG. 1 is a treatment process diagram of a method for treating wastewater 1 containing fluorine and boron and containing at least hardly decomposable borofluoride according to the present embodiment. As shown in FIG. 1, waste water 1 containing borofluoride is first introduced into a BF ₄ decomposition reaction tank 2.

In the BF ₄ decomposition reaction tank 2, the polyvalent metal salt 4 and the pH adjuster 5 are added to the wastewater 1 and ultraviolet rays are irradiated by the ultraviolet irradiation device 3 provided in the BF ₄ decomposition reaction tank 2. . This ultraviolet irradiation accelerates the decomposition of the hardly decomposable borofluoride contained in the wastewater 1 and accelerates the reaction of the following general formulas (2) to (5) in the BF ₄ decomposition reaction tank 2. As a result, borofluoride is efficiently decomposed.

  Specifically, in the present embodiment, by irradiating the wastewater 1 with ultraviolet rays, the decomposition efficiency of the borofluoride is increased based on the strong energy of the ultraviolet rays, and is expressed by the following general formulas (2) to (5). The reaction can proceed efficiently. That is, by irradiating with ultraviolet rays, the bond between fluorine and boron in the borofluoride can be efficiently cut, and the decomposition reaction efficiency of the borofluoride itself can be improved.

In the BF ₄ decomposition reaction tank 2, the polyvalent metal salt 4 is used to remove free hydrogen fluoride, which is the final decomposition product of borofluoride ions, out of the system and promote the decomposition reaction of borofluoride ions by ultraviolet irradiation. Added.

  The polyvalent metal element constituting the polyvalent metal salt 4 is at least one selected from aluminum, iron, titanium and the like, and the polyvalent metal salt 4 may be a substance that reacts with free hydrogen fluoride. Examples thereof include, but are not limited to, aluminum salts such as aluminum sulfate, ferric salts such as ferric chloride and ferric sulfate, and ferric salts such as titanium chloride.

  When the metal element constituting the polyvalent metal salt 4 is aluminum or iron, the addition amount of the polyvalent metal salt 4 is aluminum ion or 1 mol per 1 mol of borofluoride ion contained in the waste water 1. Iron ions are added so as to be 0.8 to 5 mol. Moreover, when the metal element which comprises the polyvalent metal salt 4 is titanium, it adds so that a titanium ion may be 0.4-3 mol with respect to 1 mol of borofluoride ions contained in the wastewater 1. FIG.

Thus, by adding the polyvalent metal salt 4 to the waste water 1 in the BF ₄ decomposition reaction tank 2, the polyvalent metal ion decomposes the borofluoride as shown in the following general formula (6). It reacts with the generated free hydrogen fluoride to produce stable AlF _n ^3-n , FeF _n ^3-n , TiF _n ^4-n . Thereby, the decomposition reaction of borofluoride ions shown in the general formulas (2) to (5) can be efficiently promoted. The following general formula (6) is a reaction formula when aluminum is added as a polyvalent metal element.

In addition, what is added to the waste water 1 in the BF ₄ decomposition reaction tank 2 to promote the borofluoride ion decomposition reaction is not limited to a polyvalent metal salt, but a polyvalent metal composed of the same type of polyvalent metal element should be added. Similarly, the decomposition reaction of borofluoride ions can be promoted. Even when a polyvalent metal such as aluminum, iron, or titanium is added to the wastewater 1, the above-described addition amount is added.

The pH adjuster 5 added in the BF ₄ decomposition reaction tank 2 adjusts the pH condition of the waste water 1 in the BF ₄ decomposition reaction tank 2 to acidic conditions, preferably pH 4 or less, more preferably pH 2 or less. Hold. Thus, the borofluoride ion can be efficiently decomposed by adjusting the pH of the wastewater 1 to acidic conditions, particularly pH 4 or lower.

  Further, by adjusting the pH to 2 or less, dirt is attached to the ultraviolet light source by the hydrolysis product produced by hydrolysis of the added polyvalent metal salt 4 and the elements contained in the wastewater 1, and ultraviolet irradiation. It is possible to prevent the efficiency from decreasing. Furthermore, by adjusting the pH to 2 or less, it is possible to improve the ultraviolet irradiation efficiency, and it is possible to decompose the borofluoride in a shorter time, and between the fluorine generated by the decomposition of the borofluoride and the polyvalent metal ion. Reaction efficiency can also be improved.

  As the pH adjuster 5, for example, acid agents such as sulfuric acid, hydrochloric acid, and nitric acid, and alkali agents such as sodium hydroxide, potassium hydroxide, and calcium hydroxide can be used.

In the present embodiment, as described above, the wastewater 1 is irradiated with ultraviolet rays in the BF ₄ decomposition reaction tank 2. By irradiating the wastewater 1 with ultraviolet rays in this way, the bond between fluorine and boron in the borofluoride is efficiently cut by the strong energy of the ultraviolet rays, thereby improving the decomposition reaction efficiency. The ultraviolet irradiation of the waste water 1 containing the hardly decomposable borofluoride is performed using an ultraviolet irradiation device 3 provided in the BF ₄ decomposition reaction tank 2.

The ultraviolet irradiation device 3 provided in the BF ₄ decomposition reaction tank 2 is preferably capable of irradiating ultraviolet rays having a wavelength region of 180 to 400 nm, and the light source generates electromagnetic waves from the ultraviolet part to the visible part. A light source is used. Specifically, a metal vapor lamp in which another metal is sealed in a mercury lamp, such as a rare gas discharge lamp such as a mercury lamp or a xenon lamp, or an alkali vapor lamp, can be used. In particular, when a mercury lamp is used as an ultraviolet light source, either a low-pressure mercury lamp (0.01 to 0.1 mmHg) or a high-pressure mercury lamp (0.1 to 10 atm) can be used. It is more preferable at the point which is excellent in energy efficiency.

Moreover, the ultraviolet irradiation device 3 provided in the BF ₄ decomposition reaction tank 2 is provided with the above-described light source housed in a jacket made of quartz or the like. The jacket for housing the light source is made of an organic polymer material in addition to quartz glass, Pyrex (registered trademark) glass, as long as it efficiently transmits the radiation emitted from the light source and supplies light energy. It is desirable to select appropriately according to the purpose. Furthermore, the jacket for accommodating the light source, throughout the waste water 1 is introduced into BF ₄ decomposition reactor 2, it may be positioned to form a uniform illumination distribution, top of BF ₄ decomposition reactor 2, a lower Alternatively, one or a plurality of them can be arranged such as charging in the liquid. Moreover, you may arrange | position in the outer periphery and piping of a circulation type reaction tube. When the jacket containing the light source is inserted into the liquid, it is preferable to provide a cleaning mechanism for preventing a decrease in BF ₄ decomposition efficiency due to dirt on the jacket.

  Moreover, it is preferable that the ultraviolet irradiation time by this ultraviolet irradiation device 3 shall be 30 minutes or more. By irradiating the wastewater 1 containing borofluoride with ultraviolet rays for 30 minutes or more, the borofluoride can be efficiently decomposed in a short time. The upper limit of the ultraviolet irradiation time is not particularly limited, but even if the irradiation is continued for a long time, if the predetermined time is exceeded, the decomposition efficiency cannot be improved by irradiation after that, and the efficiency is reduced in a short time. If the effect of decomposing borofluoride is taken into account, it is preferable that the time be up to about 120 minutes.

In this manner, the wastewater 1 is irradiated with ultraviolet rays by the ultraviolet irradiation device 3 provided in the BF ₄ decomposition reaction tank 2, and at that time, the waste water 1 in the BF ₄ decomposition reaction tank 2 is stirred. It is preferable. By irradiating the wastewater 1 with ultraviolet rays while stirring, the ultraviolet irradiation area of the wastewater 1 can be increased and the irradiation distribution can be made uniform, and the borofluoride can be efficiently decomposed in a shorter time. The agitation mechanism of the waste water 1 is not particularly limited. For example, in addition to a mechanical type such as a vertical agitator, a turbine agitator, and a propeller agitator, a jet agitator using a pump or the like, and a gas injection agitation Etc. can be adopted.

  In the wastewater treatment method according to the present embodiment, as described above, the wastewater containing the hardly-decomposable borofluoride formed by the reaction of fluorine and boron in the wastewater is subjected to acidic conditions. In addition to adding a polyvalent metal element (aluminum, iron, titanium, etc.), it has a decomposition step in which ultraviolet irradiation is used in combination. Thereby, decomposition | disassembly of a hardly decomposable borofluoride can be accelerated | stimulated and reaction of the fluorine ion liberated by the decomposition | disassembly and a polyvalent metal element can be accelerated | stimulated. Specifically, by irradiating the wastewater 1 with ultraviolet light having a stronger energy than visible light, the strong light energy efficiently binds fluorine and boron in the borofluoride. Can be cut. As a result, the decomposition efficiency of borofluoride can be improved, the reaction between halogen ions such as fluorine and polyvalent metal elements can be promoted, and the decomposition rate can be dramatically accelerated.

  From the above, according to the wastewater treatment method according to the present embodiment, the wastewater 1 containing the hardly decomposable borofluoride formed by the reaction of fluorine and boron can be easily, quickly and inexpensively. Can be processed.

As described above, the waste water 1 introduced into the BF ₄ decomposition reaction tank 2 and decomposed with the borofluoride by ultraviolet irradiation is then introduced into the defluorination (F) reaction tank 6.

In the de-F reaction tank 6, a calcium salt 7 such as slaked lime and a pH adjuster 8 are added to the wastewater 1 to insolubilize fluorine contained in the wastewater 1 (fluorine insolubilization step). That is, fluorine ions generated by the decomposition of borofluoride by ultraviolet irradiation in the BF ₄ decomposition reaction tank 2 are insolubilized.

Here, the calcium salt 7 is added in order to convert the fluorine ions contained in the waste water 1 into insoluble substances. Specifically, for example, when an aluminum salt, a ferric salt or a second titanium salt is used as the polyvalent metal salt 4 in the BF ₄ decomposition reaction tank 2 in the previous stage, after the borofluoride is decomposed by ultraviolet irradiation, Soluble AlF _n ^3-n , FeF _n ^3-n , and TiF _n ^4-n complexes are generated in the waste water 1. Fluorine ions are converted into CaF ₂ and insolubilized by adding a calcium salt in the de-F reaction tank 6 to the wastewater 1 in which these complexes are formed. Alternatively, fluorine ions are converted into CaF ₂ and insolubilized by an adsorption reaction of fluorine ions to calcium hydroxide, which is a hydrolysis product of solid calcium hydroxide or calcium salt. By converting the fluorine component into insoluble CaF ₂ and insolubilizing in this manner, the fluorine component can be easily flocated and removed in the aggregation tank 12 described later.

  As the calcium salt to be added, inorganic calcium salts such as calcium chloride, calcium hydroxide, calcium carbonate, and calcium phosphate can be suitably used.

The pH adjuster 8 adjusts the pH condition of the waste water 1 in the de-F reaction tank 6. The pH condition in the de-F reaction tank 6 is preferably set to a pH at which a reaction product reacted by adding a calcium salt is precipitated. For example, when an aluminum salt is used as the polyvalent metal salt 4 in the BF ₄ decomposition reaction tank 2, the pH is preferably adjusted to 4 to 8, and a ferric salt and a second titanium salt are preferably used as the polyvalent metal salt 4. When used, it is preferably adjusted to pH 4 or higher. Thereby, the fluorine component in the wastewater 1 can be efficiently insolubilized and removed.

  The pH adjuster 8 to be added is not particularly limited, and for example, acid agents such as sulfuric acid, hydrochloric acid and nitric acid, and alkali agents such as sodium hydroxide, potassium hydroxide and calcium hydroxide can be used. .

  As described above, the waste water 1 introduced into the de-F reaction tank 6 and having the fluorine component precipitated as an insoluble substance is then introduced into the deboronation (B) reaction tank 9.

In the de-B treatment tank 9, a calcium salt 10 such as slaked lime and a pH adjuster 11 are further added to the waste water 1 to insolubilize boron contained in the waste water 1 (boron insolubilization step). That is, boron ions generated by the decomposition of borofluoride by ultraviolet irradiation in the BF ₄ decomposition reaction tank 2 are insolubilized.

Here, the calcium salt 10 is obtained by adding boron ions (borate ions) contained in the waste water 1 in the reaction product of calcium salt in the above-mentioned de-F reaction tank 6 or the BF ₄ decomposition reaction tank 2. Wrapped with hydroxide of valent metal ions, added to insolubilize and remove. In this way, the boron component can be easily flocked and removed in the agglomeration tank 12 to be described later by wrapping the boron component with a calcium salt reaction product or a hydroxide of a polyvalent metal ion to insolubilize the boron component. become able to.

  The calcium salt and pH adjuster added in the de-B treatment tank 9 can be the same as those added in the de-F reaction tank 6.

  As described above, the waste water 1 introduced into the de-B treatment tank 9 and having the boron component precipitated as an insoluble substance is then introduced into the coagulation tank 12.

In the coagulation tank 12, a polymer coagulant 13 such as an anionic polymer coagulant is added to the waste water 1 to coarsen, that is, flock the particles of the reaction product (aggregation step). That is, the fluorine ions and boron ions that are decomposed and generated in the BF ₄ decomposition reaction tank 2 and insolubilized in the de-F reaction tank 6 and the de-B treatment tank 9 are flocked.

  Here, the polymer flocculant 13 is added in order to flock the particles of insoluble substances generated in the above-described de-F reaction tank 6 and de-B treatment tank 9.

  As the polymer flocculant 13, a nonionic polymer flocculant is used in the acidic region, a weak anionic polymer flocculant is used in the acidic to weakly acidic region, and neutral in the weakly acidic to weakly alkaline region. It is preferable to use an anionic polymer flocculant, but it is desirable to select appropriately according to the sedimentation, clarity, etc. of the obtained floc. Further, these polymer flocculants 13 may be used alone or in combination. More than one species may be used in combination. The addition amount of the polymer flocculant 13 is, for example, a concentration range of 0.5 mg / L to 15 mg / L with respect to the wastewater 1 to be treated.

  In this flocculation tank 12, after adding the polymer flocculant 13, it is preferable to stir the waste water 1 by stirring means, such as a turbine type stirrer and a propeller type stirrer. As described above, by stirring the waste water 1 to which the polymer flocculant 13 is added, the polymer flocculant 13 can promote flocking of an insoluble substance containing a fluorine component or a boron component.

  In this embodiment, an example of using a polymer flocculant as a flocculant has been described. However, if an insoluble substance can be flocked in the flocculant tank 12 by addition, a flocculant to be used is particularly preferable. For example, an inorganic flocculant may be used.

  As described above, when insoluble particles are flocculated in the agglomeration tank 12, the flocs having the sedimentation property are settled in the sedimentation tank 14, and as a result, the waste water 1 is separated into solid and liquid, and clear supernatant water That is, the treated water 16 is obtained.

Specifically, in the sedimentation tank 14, the fluorine and boron contained in the waste water 1 are treated as CaF ₂ and boron is precipitated and separated as boric acid, whereby the fluorine and boron in the supernatant water are treated to a low concentration. Thus, treated water 16 is obtained. In addition, the solid component separated by solid-liquid separation, that is, floc containing fluorine or boron, is discharged as a precipitate (damage discharge 15).

  As described above in detail, the method for treating wastewater according to the present embodiment is a method for treating wastewater 1 containing fluorine and boron and containing at least hardly decomposable borofluoride. In addition to adding a polyvalent metal salt, the pH of the wastewater is maintained under an acidic condition, and a decomposition step of decomposing the hardly decomposable borofluoride by irradiating with ultraviolet rays is included. The metal element constituting the polyvalent metal salt is at least one selected from aluminum, iron, titanium and the like.

  According to the present invention, the decomposition reaction of the hardly-decomposable borofluoride can be promoted by adding a polyvalent metal element to the wastewater 1 and using ultraviolet irradiation together under the acidic condition. The reaction between the fluorine ions liberated by the decomposition reaction and the polyvalent metal element can be promoted. Thereby, the waste water containing the hardly decomposable borofluoride formed by the reaction of fluorine and boron can be easily and inexpensively treated. In addition, since the decomposition reaction efficiency of the hardly-decomposable borofluoride is improved, the treatment time of waste water can be dramatically accelerated.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. In particular, the present invention is characterized by a decomposition process in which borofluoride is decomposed by irradiating wastewater with ultraviolet rays. The operation of removing fluorine or boron before or after the decomposition process has been described above. The present embodiment is not limited at all.

  Therefore, in the latter stage of the borofluoride decomposition step, for example, a general coagulation precipitation treatment using, for example, calcium salts such as slaked lime, calcium carbonate, calcium chloride, aluminum salts such as aluminum sulfate, magnesium salts such as magnesium sulfate, etc. You may make it perform a process.

  Further, in the present embodiment, a case has been described in which the de-F reaction tank 6 and the de-B treatment tank 7 are provided separately, and there is a step of insolubilizing fluorine ions and boron ions separately in each tank. The treatment for insolubilizing ions and boron ions may be performed simultaneously in a single reaction tank.

  Hereinafter, specific examples of the present invention will be described. Note that the scope of the present invention is not limited to any of the following examples.

<Examples 1-9>
The JIS special grade reagent NaBF ₄ was dissolved in city water, BF ₄ ^- concentration 2000 mg / L (fluoroborate hydride ion containing simulated wastewater concentration of fluorine components contained in the calculation value 1750mg (F / L), boron content is 249 mg ( B / L)) and so that, BF ₄ ^- to adjust the content simulated wastewater 10L.

Then, adjusted BF ₄ ^- ion containing simulated wastewater 1L water samples in a polyethylene beaker, commercial aluminum sulfate as a polyvalent metal salt (8 wt% Al ₂ O ₃ in terms of products; aluminum sulfate solution) using the following The aluminum ion concentration shown in Table 1 was added. Then, the pH is adjusted to 2.0 with H ₂ SO ₄ and NaOH, and UV irradiation is performed for a predetermined time shown in Table 1 using a UV lamp (10 W low-pressure mercury lamp; manufactured by UL1-1DQ experimental T-USHIO) while stirring. Went.

After irradiation with ultraviolet rays, BF ₄ in the waste water ^- it was measured residual amount. In the measurement, Ca (OH) ₂ was added to simulated wastewater and stirred at pH 4.0 for 20 minutes, and then a part of the obtained slurry solution (about 20 ml) was collected and subjected to solid-liquid separation, and BF ₄ ^- by measuring rapidly at a concentration of ion chromatographic analyzer (DIONEX manufactured DX-500 Model Dionex), BF ₄ ^- was determined residual amount.

Subsequently, the remaining slurry solution ^- in (BF ₄ decomposing residual solution), Ca (OH) was added to ₂ or _H 2 SO ₄ or the like was adjusted to pH 11, an organic polymer flocculant (anionic polymer coagulant Sumifloc FA-40 or nonionic polymer flocculant Acofloc ND-102) was added, and a general coagulation sedimentation treatment was carried out for flocking with stirring for 20 minutes. Thereafter, solid-liquid separation is performed, and the fluorine (F) concentration in the obtained treated water is measured with an ion chromatograph analyzer (DIONEX DX-500, manufactured by Dionex), and the boron (B) concentration is measured with an ICP emission spectroscopic analyzer ( Iris AP type manufactured by Thermo-scientific).

Incidentally, BF ₄ ^- in each processing step of containing the simulated wastewater was conducted by adjusting the liquid temperature to 18 ° C. to 25 ° C..

<Comparative Examples 1-9>
In Comparative Examples 1 to 9, using a commercially available sulfuric acid band as a polyvalent metal salt, the aluminum ion concentration shown in Table 1 below was added, adjusted to pH 2.0 with H ₂ SO ₄ and NaOH, and then irradiated with ultraviolet light. It stirred for the predetermined time shown in Table 1 without irradiating. Other conditions were the same as in Examples 1 to 9.

Table 1, in each of Examples 1-9 and Comparative Examples 1-9, BF ₄ residual amount measurement results, as well as together F concentration and the B concentration in the treated water. In addition, “-” in the column of the ultraviolet (UV) irradiation time (min) of the comparative example in Table 1 indicates that the corresponding example (comparative example) of the same conditions except for the presence or absence of ultraviolet irradiation without irradiating the ultraviolet ray. It is shown that it was left as it was for the time of ultraviolet irradiation in the example of the same number as (No. 3 in the following Table 3). In addition, “DL” in the result of the residual amount of BF ₄ indicates that it is the analytical quantification limit of the ion chromatograph analyzer used, and the parentheses in the pH value indicate actually measured values (Table 2 and below). The same applies to 3).

As shown in Table 1, in the example in which the wastewater was irradiated with ultraviolet rays, the borofluoride was efficiently decomposed in a short time as compared with the comparative example in which ultraviolet rays were not irradiated. It can be seen that the residual amount of the compound (BF ₄ ) has drastically decreased. This is because, in the comparative example, although the decomposition of borofluoride gradually progressed, the decomposition rate was slow, so that the fluorine and boron whose bonds were broken were recombined to form borofluoride again. It is done. On the other hand, in the examples to which the present invention was applied, the reaction rate of borofluoride could be accelerated by ultraviolet irradiation. As a result, fluorine and boron were not recombined but combined with the added aluminum ions. It is thought that the regeneration of borofluoride was suppressed and the residual amount of borofluoride was drastically reduced.

  Moreover, it turns out that the residual amount of borofluoride decreases, so that there is much addition amount of the aluminum sulfate which is a polyvalent metal salt. This is because, in addition to the accelerated decomposition of the hard-to-decompose borofluoride by ultraviolet irradiation, the fluorine ions liberated by the decomposition of the borofluoride reacted efficiently with the aluminum ions, and the decomposition reaction was accelerated. I can say that.

In Comparative Example 6 and Comparative Example 9 in Table 1, the residual amount of BF ₄ was 5 mg / L or less as in the corresponding Examples 6 and 9. However, BF ₄ in these Comparative Examples ^- Determination of residual amount, BF ₄ in the corresponding example ^- since after measurement several more hours the remaining amount was measured after a lapse, the results shown in Table 1 It is thought that it became. That is, in Comparative Example 6 and Comparative Example 9, the residual amount of BF ₄ was 5 mg / L or less, but the corresponding Examples were 5 mg / L or less in a short time of about 60 minutes and about 120 minutes, respectively. On the other hand, in a comparative example, it turns out that it became 5 mg / L or less after the long time beyond it passed. Therefore, it can be seen from these Examples and Comparative Examples that by applying the present invention and irradiating with ultraviolet rays, the decomposition rate of borofluoride can be accelerated and the treatment can be performed in a shorter time.

<Examples 10 to 18>
The JIS special grade reagent NaBF ₄ was dissolved in city water, BF ₄ ^- concentration 2000 mg / L (fluoroborate hydride ion containing simulated wastewater concentration of fluorine components contained in the calculation value 1750mg (F / L), boron content is 249 mg ( B / L)) and so that, BF ₄ ^- to adjust the content simulated wastewater 10L.

Then, adjusted BF ₄ ^- and water sampling for containing simulated wastewater 1L in a polyethylene beaker, using a commercially available ferric sulfate (41% aqueous product) as a polyvalent metal salt, an iron ion concentrations as shown in Table 2 below It added so that it might become. Then, a predetermined time shown in Table 2 using an ultraviolet lamp (100 W high-pressure mercury lamp; manufactured by LM-102 T-USHIO) adjusted to pH 2.0 with H ₂ SO ₄ and NaOH and increasing visible light while stirring. UV irradiation.

After irradiation with ultraviolet rays, BF ₄ in the waste water ^- it was measured residual amount. In the measurement, Ca (OH) ₂ was added to the simulated wastewater and stirred at pH 4 for 20 minutes, followed by solid-liquid separation. A part (20 ml) of the obtained treated water was collected, and BF ₄ ⁻ by measuring rapidly the concentration by ion chromatography analyzer (DIONEX manufactured DX-500 Model Dionex), BF ₄ ^- was determined residual amount.

Then, BF ₄ ^- in decomposing residual solution was adjusted to pH11 by addition of Ca (OH) ₂ and _H 2 SO ₄ or the like, while adding an organic polymer flocculant (anionic polymer flocculant) floc A general agglomeration and precipitation treatment was performed. After that, solid-liquid separation is performed, and F concentration in the treated water obtained is ion chromatograph analyzer (DIONEX DX-500, manufactured by Dionex), and B concentration is measured using ICP emission spectrophotometer (Iris AP type Thermo-scientific). Analysis).

Incidentally, BF ₄ ^- in each processing step of containing the simulated wastewater was conducted by adjusting the liquid temperature to 18 ° C. to 25 ° C..

Table 2, in each example 10 to 18, BF ₄ residual amount measurement results, as well as the F concentration and the B concentration in the treated water.

  As shown in Table 2, even when ferric sulfate was added as a polyvalent metal salt, borofluoride could be efficiently decomposed in a short time by irradiating with ultraviolet rays. It can be seen that the remaining amount of can be effectively reduced. In addition, as the amount of ferric sulfate, which is a polyvalent metal salt, increases, the residual amount of borofluoride tends to decrease. Particularly when 3000 mg / L is added as the iron ion concentration, the amount of borofluoride is dramatically increased. It can be seen that the compound could be decomposed. This is because, in addition to the accelerated decomposition of the hard-to-decompose borofluoride by ultraviolet irradiation, the fluorine ions liberated by the decomposition of the borofluoride efficiently reacted with iron ions, and the decomposition reaction was accelerated. I can say that.

<Examples 19 to 27>
The JIS special grade reagent NaBF ₄ was dissolved in city water, BF ₄ ^- concentration 2000 mg / L (fluoroborate hydride ion containing simulated wastewater concentration of fluorine components contained in the calculation value 1750mg (F / L), boron content is 249 mg ( and adjust the content simulated wastewater 10L ^- BF ₄ in B / L) and so as.

It was then adjusted BF ₄ ^- the content simulated wastewater 1L water samples in a polyethylene beaker, using a titanium tetrachloride solution as a polyvalent metal salt was added to a titanium ion concentration shown in Table 3 below. Then, it was adjusted to about pH 1 with H ₂ SO ₄ and NaOH, and irradiated with ultraviolet rays for a predetermined time shown in Table 3 below using an ultraviolet lamp (10 W low pressure mercury lamp; manufactured by UL1-1DQ T-USHIO Co., Ltd.) while stirring. .

After irradiation with ultraviolet rays, BF ₄ in the waste water ^- it was measured residual amount. In the measurement, Ca (OH) ₂ was added to the simulated wastewater and stirred at pH 4 for 20 minutes, followed by solid-liquid separation. A part (20 ml) of the obtained treated water was collected, and BF ₄ ⁻ by measuring rapidly the concentration by ion chromatography analyzer, BF ₄ ^- was determined residual amount.

Then, BF ₄ ^- in decomposing residual solution was adjusted to pH11 by addition of Ca (OH) ₂ and _H 2 SO ₄ or the like, while adding an organic polymer flocculant (anionic polymer flocculant) floc A general agglomeration and precipitation treatment was performed. Thereafter, solid-liquid separation was performed, and the F concentration in the obtained treated water was analyzed with an ion chromatograph analyzer and the B concentration was analyzed with an ICP emission spectroscopic analyzer.

Incidentally, BF ₄ ^- in each processing step of containing the simulated wastewater was conducted by adjusting the liquid temperature to 18 ° C. to 25 ° C..

<Comparative Examples 10-18>
In Comparative Examples 10 to 18, using a commercially available titanium tetrachloride solution as a polyvalent metal salt, the titanium ion concentration shown in Table 3 was added, and the pH was adjusted to about pH 1 with H ₂ SO ₄ and NaOH, followed by ultraviolet rays. The mixture was stirred for a predetermined time as shown in Table 3 below. The other conditions were the same as in Examples 19 to 27.

Table 3, each, BF ₄ residual amount of the measurement results of Examples 19 to 27 and Comparative Examples 10 to 18, and also shows the F concentration and the B concentration in the treated water.

  As shown in Table 3, in the example in which the wastewater was irradiated with ultraviolet rays, borofluoride was efficiently decomposed in a short time as compared with the comparative example in which ultraviolet rays were not irradiated. It can be seen that the residual amount of the chemical compound has decreased dramatically. Moreover, it turns out that the residual amount of borofluoride decreases, so that there is much addition amount of the titanium tetrachloride which is a polyvalent metal salt. This is because, in addition to the accelerated decomposition of the hardly decomposable borofluoride by ultraviolet irradiation, the fluorine ions liberated by the decomposition of the borofluoride reacted efficiently with the titanium ions, and the decomposition reaction was promoted. I can say that.

DESCRIPTION OF SYMBOLS 1 Waste water, 2BF ₄ decomposition reaction tank, 3 Ultraviolet (UV) irradiation apparatus, 4 Polyvalent metal salt, 5 pH adjuster, 6 Defluorination (F) reaction tank, 7 Calcium salt, 8 pH adjuster, 9 Deboronization (B) Reaction tank, 10 Calcium salt, 11 pH adjuster, 12 Coagulation tank, 13 Polymer flocculant, 14 Sedimentation tank, 15 Dispensing material, 16 Treated water

Claims (6)

In a method for treating wastewater containing fluorine and boron and containing at least a hardly decomposable borofluoride,
And a decomposition step of adding a polyvalent metal or a metal salt thereof to the waste water, maintaining the pH of the waste water at 4 or less, and irradiating ultraviolet rays to decompose the hardly decomposable borofluoride. Wastewater treatment method.   2. The method for treating wastewater according to claim 1, wherein the metal element constituting the polyvalent metal or the metal salt thereof is at least one selected from aluminum, iron and titanium.   The metal element is aluminum or iron, and the polyvalent metal or the metal thereof is used so that the aluminum ion or iron ion is 0.8 to 5 mol with respect to 1 mol of borofluoride ion contained in the waste water. The method for treating wastewater according to claim 2, wherein salt is added.   The metal element is titanium, and the polyvalent metal or the metal salt thereof is added so that the titanium ion is 0.4 to 3 mol with respect to 1 mol of the borofluoride ion contained in the waste water. The method for treating wastewater according to claim 2, wherein:   The wastewater treatment method according to any one of claims 1 to 4, wherein the irradiation time of the ultraviolet rays is 30 minutes or more.   The wastewater treatment method according to any one of claims 1 to 5, wherein in the decomposition step, the ultraviolet light is irradiated while stirring the wastewater.

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