WO2016157452A1

WO2016157452A1 - Method for treating wastewater, and system for treating wastewater

Info

Publication number: WO2016157452A1
Application number: PCT/JP2015/060249
Authority: WO
Inventors: 治雄柴山; 務村木
Original assignee: 住友金属鉱山エンジニアリング株式会社
Priority date: 2015-03-31
Filing date: 2015-03-31
Publication date: 2016-10-06
Also published as: JPWO2016157452A1; KR20170132206A; JP6728546B2; KR102434086B1

Abstract

A method for treating wastewater that contains sparingly decomposable BF₄ ^- is provided in which the BF₄ ^- can be more efficiently decomposed on the basis of the BF₄ ^- concentration in the wastewater. The method for treating wastewater according to the present invention is a method for treating wastewater that contains fluorine and sparingly decomposable BF₄ ^-, the method comprising: a fluorine removal step S1 in which free fluorine ions contained in the wastewater are removed; a BF₄ ^- measurement step S2 in which the concentration of BF₄ ^- in the wastewater from which the free fluorine ions have been removed is measured; and a decomposition step S3 in which the BF₄ ^- is decomposed on the basis of the BF₄ ^- concentration measured in the BF₄ ^- measurement step S2. The method is characterized in that in the BF₄ ^- measurement step S2, the pH of the wastewater is regulated to 4 or less and the BF₄ ^- concentration is measured and that in the decomposition step S3, a polyvalent metal or a salt of the metal is added to the wastewater in an amount determined on the basis of the BF₄ ^- concentration.

Description

Wastewater treatment method, wastewater treatment system

The present invention relates to a processing system processing method and wastewater wastewater containing a hardly decomposable compound, more particularly, with fluorine, BF ₄ of persistent ^- implementing the method and method for processing waste water containing It relates to a processing system.

Conventionally, as a method for treating fluorine-containing wastewater, a method of precipitating and separating poorly soluble calcium fluoride (CaF ₂ ) by adding calcium salts such as calcium hydroxide and calcium chloride has been widely used. However, it is difficult to react with 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 decomposable borofluoride is formed, soluble Ca (BF ₄ ) ₂ is only produced even if calcium salt is added, and the fluorine concentration in the wastewater is hardly reduced.

Since borofluoride in wastewater forms stable complex ions, it is important to break the bond between fluorine (F) and boron (B) when removing fluorine from the aqueous solution. However, borofluoride ion (BF ₄ ⁻ ) has a very strong binding energy between fluorine and boron, and as shown in the following reaction formulas (i) to (iv), HBF ₄ ⁻ undergoes hydrolysis. The decomposition proceeds gradually while F coordinated to B is substituted with a hydroxyl group 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. Reaction formulas (i) to (iv) are equilibrium reactions in an acidic solution.

HBF ₄ + H ₂ O⇔HBF ₃ (OH) + HF (i)
HBF ₃ (OH) + H ₂ O⇔HBF ₂ (OH) ₂ + HF (ii)
HBF ₂ (OH) ₂ + H ₂ O⇔HBF (OH) ₃ + HF (iii)
HBF (OH) + H ₂ O⇔H ₃ BO ₃ + HF (.iv)

Therefore, BF ₄ ^- in the treatment of waste water containing, the BF ₄ ^- decomposing performed efficiently in, F ^- the it becomes necessary to separate and remove from the waste water as fluoride salts, for which the BF ₄ ^- the amount of degradation conditions and optimum drug, BF ₄ contained in the waste water ^- or F ^- concentration becomes important to determine by measuring the.

Patent Document 1, hardly degradable BF ₄ ^- processing method of waste water containing is proposed. According to the method disclosed in Patent Document 1, BF ₄ ⁻ contained in waste water can be treated easily, quickly and inexpensively with high decomposition efficiency. However, the concentration of BF ₄ ^{− in} the wastewater changes with time. For this reason, it is preferable to continuously change the amount of the medicine to be used in accordance with this, and this makes it possible to control the amount of the medicine to be used and to perform the decomposition process more efficiently. .

For this reason, there is a need for a method for treating wastewater with an optimal amount of drug based on the result of concentration measurement while accurately measuring the concentration of BF ₄ ^{− in} the wastewater.

JP 2011-104559 A JP 2011-27722 A

The present invention has been proposed in view of such circumstances, BF ₄ of persistent ^- in the process of wastewater containing, BF ₄ included in the waste water ^- based on the concentration of more efficient and to provide a method of processing waste water that can degrade ^- BF ₄ in.

The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, the free fluorine ions contained in the wastewater are removed, the concentration of BF ₄ ⁻ contained in the wastewater from which the free fluorine ions have been removed is measured, and the amount of drug used determined based on the obtained concentration measurement results ( BF ₄ was added to the polyvalent metal or polyvalent metal salts) ^- by performing the decomposition process of, found that it is possible to perform efficient processing, thereby completing the present invention. That is, the present invention is as follows.

(1) A first invention of the present invention is a method for treating wastewater containing BF ₄ ^- which is hardly decomposable together with fluorine, and a fluorine removing step for removing free fluorine ions contained in the wastewater; BF in the removal of the free fluorine ion wastewater ₄ ^- measuring the concentration BF ₄ ^- decomposition decompose ^- a measuring step, the BF ₄ ^- the BF ₄ based on the concentration of ^- BF ₄ measured by the measuring step has a step, the BF ₄ ^- in the measurement step, by adjusting the pH of the wastewater to 4 below BF ₄ ^- to determine the concentration, in the decomposition step, the waste water, the BF ₄ ^- to a concentration of This is a wastewater treatment method in which a polyvalent metal or a metal salt thereof whose addition amount is determined based on the addition amount is added.

(2) the second invention of the present invention, in the first aspect, the BF ₄ ^- In the measurement step, the wastewater BF ₄ ^- is the waste water to determine the concentration processing method ^- into contact with the electrode BF ₄ .

(3) According to a third aspect of the present invention, in the first or second aspect of the invention, in the fluorine removal step, the waste water is set so that the concentration of free fluorine ions in the waste water is less than 0.1 mol / L. It is a processing method.

(4) According to a fourth aspect of the present invention, in any one of the first to third aspects of the invention, in the fluorine removal step, waste water is generated and removed by generating a precipitate of free fluorine ions using a calcium salt. It is a processing method.

(5) Fifth aspect of the present invention, together with fluorine, hardly degradable BF ₄ ^- and a waste water treatment system containing, fluorine removal device to remove free fluorine ions contained in the waste water, the measuring the concentration BF ₄ ^- ^- BF ₄ in the removal of the free fluorine ion wastewater and concentration measuring device, the BF ₄ ^- BF was measured by the concentration measuring apparatus ₄ ^- BF of the waste water based on the concentration _{of 4} ^- and a decomposition treatment unit degrades, the BF ₄ ^- in a concentration measuring apparatus, BF ₄ by adjusting the pH of the wastewater to 4 below ^- using electrodes BF ₄ ^- to determine the concentration, the decomposition treating apparatus is, BF ₄ with a polyvalent metal or a metal salt to the wastewater ^- and decomposing decomposition reaction unit, and a drug loading unit for adding the polyvalent metal or a metal salt to the decomposition reaction unit, the multi Addition of valent metal or metal salt And a control unit to determine the amount, and the control unit, the BF ₄ ^- determine the amount of the polyvalent metal or a metal salt thereof based on the information on the concentration ^- BF ₄ was measured at the concentration measuring apparatus And a wastewater treatment system for sending information on the amount of addition to the chemical addition unit.

According to the present invention, BF ₄ of persistent ^- in the process of wastewater containing, BF ₄ included in the waste water ^- based on the concentration of efficiently BF ₄ ^- capable of degrading.

It is a figure which shows an example of a structure of the wastewater treatment system.

Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail in the following order. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention.

<< 1. About wastewater treatment method≫
The waste water treatment method according to the present embodiment is a method for treating waste water containing BF ₄ ⁻ which is hardly decomposable together with fluorine. Specifically, the processing method of the wastewater, the fluorine removal process S1 to remove free fluorine ions contained in waste water, BF ₄ included in the waste water to remove fluoride ions ^- BF ₄ for measuring the concentration ^- concentration measurement process S2 And a decomposition step S3 for decomposing BF ₄ ⁻ based on the measured BF ₄ ⁻ concentration.

Then, in the processing method of this waste water, BF ₄ ^- in concentration measurement step S2, by adjusting the pH of the wastewater to 4 below to determine the concentration, also in the decomposition step S3, the measured BF ₄ ^- on the basis of the concentration added A feature is that BF ₄ ^- is decomposed by adding a polyvalent metal or a metal salt thereof (polyvalent metal salt) whose amount is determined to waste water.

According to such a wastewater treatment method, based on the measurement result of the concentration of BF ₄ ^{− in} the waste water, the addition amount of the polyvalent metal or the metal salt as a chemical for decomposing the BF ₄ ⁻ is determined. and for which, BF ₄ varies with decomposition treatment ^- the amount of continuous drug based on the concentration can be controlled, it is possible to perform a more efficient treatment of wastewater as compared with the conventional.

In the processing method of this waste water, BF ₄ contained in the waste water ^- prior to measuring the concentration, also with the addition of agents such as polyvalent metal salts in the waste water BF ₄ ^- Prior to decompose, in advance, the By removing the free fluorine ions (free F ⁻ ) contained in the wastewater, the free F ⁻ contained in the wastewater can be prevented from becoming strong hydrofluoric acid, and the concentration of BF ₄ ⁻ can be measured more accurately. Can do. Further, by removing free F 2 ⁻ from wastewater, waste of chemicals such as polyvalent metal salts added for the decomposition of BF ₄ ⁻ can be suppressed, and an efficient decomposition process can be performed.

Hereinafter, an example of the configuration of a wastewater treatment system for carrying out this wastewater treatment method will be shown and described more specifically.

≪2. About wastewater treatment system≫
FIG. 1 is a diagram illustrating an example of a configuration of a wastewater treatment system for carrying out a wastewater treatment method according to the present embodiment. As shown in FIG. 1, a wastewater treatment system 1 is larger, free fluorine ions contained in the waste water to be processed BF contained in waste water to remove ^- ^- fluorine removal apparatus 10 for removing the free F (F) ₄ ^- BF ₄ for measuring the concentration of ^- the concentration measuring device 20, BF ₄ of the waste water ^- and a decomposition treatment unit 30 for processing the degradation to the wastewater.

<2-1. Fluorine removal device for removing fluorine>
The fluorine removal apparatus 10 is an apparatus for performing the fluorine removal step S1 in the above-described wastewater treatment method, and is a place where wastewater to be treated is first introduced, and measures the concentration of BF ₄ ⁻ and BF _4. ^- prior to decomposition treatment of the free F contained in the waste water ^- the removal.

Waste water to be processed is adapted to contain fluorine, BF ₄ of hardly decomposable ^- it contains a. BF ₄ ⁻ contained in this waste water is decomposed over time as shown in the following reaction formula (v). If F ⁻ is present in the waste water as shown in this reaction formula, BF ₄ ⁻ is stable. Will come to do. From this point of view, it is considered that the presence of F ^{− in} the wastewater is preferable from the viewpoint of measuring the concentration of BF ₄ ⁻ over time and measuring the concentration accurately.
BF ₄ ⁻ + 3H ₂ O⇔H ₃ BO ₃ + 4F ⁻ + 3H ⁺ .. (v)

However, as will be described later, BF ₄ ^- in a concentration measuring device 20 BF ₄ by adjusting the pH of the wastewater to 4 below ^- performs the density measurement while suppressing the degradation of, F in its pH4 following waste ^- Is present, the F ⁻ becomes hydrogen fluoride and the wastewater becomes a strong hydrofluoric acid solution. Then, BF ₄ ^- provided in the concentration measuring device 20, pH electrode (pH meter) made of glass electrode or the like for measuring the pH of the wastewater to measure the concentration becomes difficult to correct pH measurements are corroded , BF ₄ as a result ^- is impossible to accurately measure the concentration.

Further, the decomposition of BF ₄ ⁻ in the wastewater in the decomposition treatment apparatus 30 described later is performed by adding a chemical whose use amount is determined based on the measurement result of the BF ₄ ⁻ concentration, specifically, a polyvalent metal salt or the like. However, if F ⁻ is present in the wastewater, the polyvalent metal element constituting the added polyvalent metal salt reacts with F ⁻ in the wastewater, and the polyvalent metal salt is consumed. It will be. As a result, the amount of the polyvalent metal salt to be used for decomposing BF ₄ ⁻ is reduced, and BF ₄ ⁻ cannot be effectively decomposed, and by-produced by the reaction between the polyvalent metal salt and F ⁻ . Precipitates (AlF ₃ ) and hydroxide precipitates of polyvalent metal salts added excessively for the decomposition of BF ₄ ⁻ become flocs, resulting in enormous waste.

Therefore, in the present embodiment, prior to measuring the BF ₄ ⁻ concentration in the wastewater, and prior to decomposing BF ₄ ⁻ by adding a chemical such as a polyvalent metal salt to the wastewater, the fluorine removing device 10 Then, a treatment for removing free F 2 ^{− in} waste water is performed. In this way, by removing free F 2 ⁻ from waste water, corrosion of the pH electrode, such as a glass electrode, used when measuring the BF ₄ ⁻ concentration is suppressed, and appropriate pH adjustment and accurate BF ₄ ⁻ concentration measurement are performed. In addition, the waste of the polyvalent metal salt added to the decomposition of BF ₄ ⁻ can be prevented, and the BF ₄ ⁻ in the waste water can be decomposed effectively and efficiently.

Specifically, in the fluorine removing apparatus 10, it is preferable to remove free F ⁻ in the waste water so that the free F ⁻ concentration in the waste water is less than 0.1 mol / L. Further, it is more preferable to remove free F ⁻ from the waste water so that the free F ⁻ concentration is less than 0.01 mol / L.

As shown in FIG. 1, the fluorine removal apparatus 10, for example, waste water is introduced free F ^- those with the fluorine removal reaction tank 11 to remove, and a sedimentation tank 12 for settling the precipitate containing fluorine It can be. As described above, as a method for removing free F 2 ⁻ from wastewater, there is a method in which a chemical is added to wastewater to fix free F ⁻ as an insoluble substance (precipitate), and the precipitate is separated and removed from wastewater. Can do.

More specifically, in the fluorine removal reaction tank 11, calcium salt can be added to waste water to make free F ⁻ into a CaF ₂ precipitate, which can be separated and removed to remove free F ⁻ . As the calcium salt, for example, inorganic calcium salts such as calcium hydroxide, calcium carbonate, calcium chloride, calcium oxide, and calcium sulfate are preferably used. Further, the free F using calcium salt ^- when removing, it is preferable to add an excess amount as the amount added.

Further, when removing the free F 2 ⁻ in the wastewater in the fluorine removal reaction tank 11, it is preferable to adjust the pH of the wastewater to 4 to 11. By adjusting the pH to 4 to 11, for example, a CaF ₂ precipitate can be efficiently generated by adding a calcium salt.

In the fluorine removing device 10, for example, a slurry containing a precipitate generated by adding calcium salt is transferred to a settling tank 12 or the like, and the generated precipitate such as CaF ₂ is settled and separated from waste water from which F ⁻ is removed. (Solid-liquid separation). The precipitate obtained was separated off waste water, i.e. free F ^- waste water was removed is then BF ₄ ^- is transferred to the concentration measuring apparatus 20. On the other hand, sediments such as sedimented CaF ₂ are dispensed.

<2-2. BF ₄ ^- BF ₄ for measuring the concentration ^- concentration measuring device>
BF ₄ ^- concentration measuring device 20 has been transferred from the fluorine removal apparatus 10, the free F ^- is introduced waste water was removed, BF ₄ contained in the waste water ^- measuring the concentration of.

BF ₄ ^- BF ₄ in the concentration measuring device 20 ^- As a method for measuring the concentration is not particularly limited, and a method for example using an ion-selective electrode. BF ₄ indicated by a dotted line enclosing unit in the diagram of Figure 1 ^- concentration measuring device 20 is cited as an example a device for performing the density measurement by ion electrode. Incidentally, BF ₄ using an ion electrode ^- with respect to the concentration measurement, it is possible to refer to the patent document 2.

BF ₄ shows a part of Figure 1 ^- concentration measuring device 20, BF ₄ ^- and the container 21 for accommodating the waste water is the concentration of the measurement target, BF ₄ ^- ion electrode device portion having a reference electrode 22b and the electrode 22a and a concentration measuring unit 24 for measuring the concentration ^- 22, a liquid feed portion 23 for feeding the waste water from the container 21 to the ion electrode device unit 22, BF ₄ ^- BF ₄ contained in the waste water in contact with the electrode 22a. The BF ₄ ^- concentration measuring device 20, BF ₄ wastewater contained in the container 21 ^- while measuring the concentration continuously feeding the decomposition treating apparatus 30 described below the measurement result, using at decomposition treating apparatus 30 it is made possible to properly control the drug amount for decomposing ^- BF ₄ to be.

(container)
Container 21, BF ₄ ^- is intended to accommodate the waste water is the concentration of the measuring object, the liquid supply unit 23 to be described later, the liquid feed portion of the waste water contained within the chamber 21 to the ion electrode device 22 Is done. The container 21 is, BF ₄ ^- is also possible to decomposition reactor 31, thereby, BF ₄ in the wastewater in real time ^- ^- BF ₄ of decomposition treating apparatus 30 for performing decomposition treatment while measuring the concentration, the Based on the concentration measurement result, the amount of the drug (polyvalent metal or a salt of the polyvalent metal) used for the decomposition of BF ₄ ⁻ can be controlled.

(Ion electrode unit)
Ion electrode device 22, BF ₄ ^- and the electrode 22a, provided with a reference electrode 22b, the BF ₄ ^- BF to the electrode 22a ₄ ^- contacting the wastewater the concentration of the measurement target. For example, BF ₄ ^- as the electrode 22a, it is possible to use an ion electrode of DKK-TOA Corporation. Thus, BF ₄ ^- By contacting the waste water with the electrode 22a, BF ₄ in the wastewater in the concentration measuring unit 24 to be described later ^- the concentration is measured.

The ion electrode device unit 22 is provided with a pH electrode (pH meter) 22A made of a glass electrode or the like. By providing this pH electrode 22A, the pH of the wastewater can be monitored as appropriate. This makes it possible to stably adjust the pH of the wastewater for measuring the BF ₄ ⁻ concentration to 4 or less, and to accurately measure the BF ₄ ⁻ concentration in the waste water. Incidentally, BF ₄ ^- will be described in detail later pH adjustment during concentration measurement.

Incidentally, the ion electrode device 22 the vessel 21 ^- may be a device incidental to (BF ₄ decomposition reactor 31), this case may not be provided liquid feed section 23 to be described later.

(Liquid feeding part)
The liquid feeding part 23 is for sending waste water accommodated in the container 21 to the ion electrode device part 22. As the liquid feeding part 23, for example, a liquid feeding pump capable of feeding waste water at a desired liquid feeding speed is configured. In addition, after measuring the BF ₄ ⁻ concentration in the ion electrode device section 22, the waste water may be returned to the container 21 through the liquid feeding section 23.

(Concentration measurement unit)
The concentration measuring unit 24 measures the BF ₄ ⁻ concentration contained in the waste water in contact with the BF ₄ ⁻ electrode 22a in the ion electrode device unit 22. The concentration measuring unit 24, for example, BF ₄ ^- can be made to measure by the AC electrical conductivity of the waste water in contact with the electrode 22a electrode method.

Here, BF ₄ ^- the density measuring device 20, BF ₄ by adjusting the pH of the wastewater to 4 below ^- to measure the concentration. Preferably, BF ₄ was adjusted to pH 2 ~ 3 ^- measuring the concentration. If the pH of the wastewater exceeds 4, the BF ₄ ⁻ decomposition over time in the wastewater cannot be sufficiently suppressed, and accurate concentration measurement cannot be performed. As a result, the amount of the chemical used for decomposing BF ₄ ⁻ added in the decomposition processing apparatus 30 cannot be appropriately controlled.

The pH adjustment of the wastewater is not particularly limited as long as the pH can be adjusted to 4 or less. For example, various inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, or various organic acids can be used. These acids for adjusting the pH can be added to the container 21. The pH of the waste water can be measured by a pH electrode 22A provided in the ion electrode device unit 22. Further, a pH electrode may be further provided in the container 21 so that the pH can be measured.

Density measurement part 24, BF ₄ in is connected to the control unit 32 constituting the decomposition treating apparatus 30 to be described later were measured wastewater ^- it is possible to transmit the information on the concentration. Thereby, the amount of the agent (polyvalent metal salt or the like) for decomposing BF ₄ ⁻ used in the decomposition processing apparatus 30 can be controlled based on the measurement result of the BF ₄ ⁻ concentration. In particular, in the present embodiment, prior to the measurement of the BF ₄ ⁻ concentration, the fluorine removing apparatus 10 removes free F ⁻ from the wastewater. Thus, the free F ^- According to, BF ₄ ^- effective in determining the concentration ^- to prevent corrosion of the pH electrode 22A made of glass electrodes or the like to be used for the measurement of concentration, BF ₄ it is possible to appropriately adjust the pH It is possible to control the amount of medicine used in the decomposition processing apparatus 30 appropriately.

<2-3. BF ₄ ^- decomposing decomposition treating apparatus>
In the decomposition treatment apparatus 30, BF ₄ ⁻ contained in the waste water is decomposed. Specifically, in the decomposition processing apparatus 30, the addition amount of the chemical for decomposing BF ₄ ⁻ is determined based on the measurement result of BF ₄ ⁻ concentration measured by the BF ₄ ⁻ concentration measuring apparatus 20, and BF ₄ ⁻ concentration is measured. ₄ ^- the decomposition process is performed of. As described above, in the present embodiment, the amount of drug is controlled based on the measurement result of the BF ₄ ⁻ concentration, and the BF ₄ ⁻ decomposition process is continuously performed. Therefore, efficient processing can be performed using an appropriate amount of medicine.

Decomposition treating apparatus 30 shown in part in FIG. 1, BF ₄ containing wastewater ^- and BF ₄ decomposition reactor 31 for decomposition treatment of, BF ₄ in the waste water ^- based on the concentration agent (polyvalent metal salt) It includes the control unit 32 which determines the amount, and a medicated portion 33 of adding a polyvalent metal salt based on the amount determined by the control unit 32 to the BF ₄ decomposition reactor 31. Further, decomposition processor 30, BF ₄ ^- and defluorination (F) treatment vessel 34 for immobilizing the resulting fluorine by decomposing and removing boron (B) treating tank 35 for fixing the boron, the insoluble material It can be set as the structure provided with the aggregation tank 36 to aggregate and the sedimentation tank 37 which makes an insoluble substance settle and obtains water after a process.

Here, as shown in FIG. 1, BF ₄ constituting the decomposition treating apparatus 30 ^- decomposition reaction vessel, BF ₄ ^- is identical to the container 21 in the concentration measuring device 20. Therefore, the decomposition treating apparatus 30, BF ₄ ^- BF in the wastewater that has been measured by the concentration measuring device 20 ₄ ^- concentration is sent periodically, BF ₄ was measured by the real-time ^- continuously based on the density to determine the drug loading amounts, BF ₄ ^- decomposition process can be performed in.

(1) BF ₄ ^- configuration for the degradation process of the [BF ₄ ^- decomposition reactor]
BF ₄ ^- decomposition reactor 31 is housed wastewater to be processed is, BF ₄ included in the waste water ^- the decomposing reaction field. The BF ₄ ^- in the decomposition reactor, BF of the contained waste water ₄ ^- is added drug amount determined based on the concentration, BF ₄ ^- performing the decomposition process.

More specifically, in the BF ₄ decomposition reaction tank 31, a polyvalent metal salt is added to the wastewater to cause a decomposition reaction of BF ₄ ⁻ . In BF ₄ decomposition reactor 31, BF ₄ the following reaction formula (i) ~ (iv) progresses ^- are decomposed.

HBF ₄ + H ₂ O → HBF ₃ (OH) + HF (i)
HBF ₃ (OH) + H ₂ O → HBF ₂ (OH) ₂ + HF (ii)
HBF ₂ (OH) ₂ + H ₂ O → HBF (OH) ₃ + HF (iii)
HBF (OH) + H ₂ O → H ₃ BO ₃ + HF (.)

The polyvalent metal salt is an agent for decomposing BF ₄ ⁻ , and more specifically, free hydrogen fluoride, which is a final decomposition product of BF ₄ ⁻ , is removed from the system to decompose BF ₄ ⁻ . It is a drug for promoting (the above reaction formulas (i) to (iv)).

The polyvalent metal element constituting the polyvalent metal salt is at least one selected from aluminum, iron, titanium and the like. Specifically, the polyvalent metal salt is not particularly limited as long as it reacts with free hydrogen fluoride. For example, aluminum salts such as aluminum sulfate, ferric salts such as ferric chloride and ferric sulfate. Or a second titanium salt such as titanium chloride.

Polyvalent metal salt, when the polyvalent metal element is aluminum or iron which constitutes it, BF 4 contained in wastewater _- relative to ¹ mole of aluminum ions or iron ions of 0.8 to 5 moles Are added as follows. Further, when the polyvalent metal elements constituting the polyvalent metal salt is Titanium, BF 4 contained in wastewater _- relative to ¹ mol of titanium ions are added so that 0.4 to 3 moles.

Here, in the present embodiment, the amount of the polyvalent metal salt, BF ₄ ^- BF was measured by the concentration measuring device 20 ₄ ^- is characterized by determining based on the concentration of the measurement results. Specifically, BF ₄ ^- in a concentration measuring device 20, BF ₄ ^- decomposition reactor 31 BF ₄ contained in the contained wastewater (vessel 21) ^- BF ₄ concentration is provided in the ion electrode device 22 of the ^- as measured by contact with the electrodes 22a, the density measurement part 24 BF ₄ ^- the transmitted information related to the measurement result of the concentration of the control unit 32, the BF ₄ in the control unit 32 ^- polyvalent metal salts based on concentration Is added. Details will be described later.

The addition of a polyvalent metal salt with respect to the waste water, as shown in the following reaction formula (v), the polyvalent metal ion BF ₄ ^- reacts with generated by decomposing the free hydrogen fluoride, for example, AlF _n ^{3 -N} , FeF _n ^3-n and TiF _n ^4-n are generated. Thereby, the decomposition reaction of BF ₄ ⁻ shown in the above reaction formulas (i) to (iv) is promoted. The following general formula (v) is a reaction formula in which aluminum is added as a polyvalent metal element.

6HF + Al ₃ ⁺ + 3OH ⁻ → H ₃ AlF ₆ + 3H ₂ O (v)

The agent for promoting the decomposition reaction of BF ₄ ⁻ is not limited to the polyvalent metal salt, and a polyvalent metal composed of the same kind of polyvalent metal element can also be added. That is, for example, aluminum, iron, can be added a polyvalent metal such as titanium, in this case, BF ₄ ^- may be added in amount based on the concentration.

Further, BF ₄ ^- for the waste water containing, by adding a pH adjusting agent with the addition of a polyvalent metal salt, it is preferable to adjust the pH conditions of the waste water under acidic conditions. Specifically, the pH is preferably 4 or less, more preferably 3 or less, and particularly preferably adjusted to 2 or less. Thus, by adding a pH adjuster to adjust the pH of the wastewater to 4 or less, BF ₄ ⁻ can be decomposed more efficiently. As the pH adjuster, 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.

Further, BF ₄ contained in the waste water ^- the decomposition process is preferably performed by ultraviolet irradiation of the waste water. By irradiating the wastewater with ultraviolet rays, the bond between fluorine (F) and boron (B) in BF ₄ ⁻ is easily broken by the strong energy of the ultraviolet rays, and the decomposition reaction efficiency can be improved.

Further, in the BF ₄ decomposition reaction tank 31, it is preferable to perform the decomposition treatment of BF ₄ ⁻ while stirring the waste water 1. By stirring the wastewater, the decomposition reaction efficiency is improved, and even when the ultraviolet rays are irradiated, the irradiation area can be increased to make the irradiation distribution uniform, and the treatment can be performed in a shorter time. In the stirring treatment, for example, a mechanical stirrer such as a vertical stirrer, a turbine stirrer, a propeller stirrer, a jet stirrer using a pump or the like, a gas blowing stirrer, or the like can be used.

[Control unit]
The control unit 32, BF ₄ ^- BF in the wastewater that has been measured by the density measurement part 24 in the concentration measuring device 20 ₄ ^- receives the information on the concentration, the BF ₄ ^- on the basis of the concentration, BF ₄ decomposition reactor 31 The amount of the polyvalent metal salt added to. Thus, in the present embodiment, the decomposition processing unit 30 definitive BF ₄ ^- the amount of the polyvalent metal salt used in the decomposition treatment, BF ₄ ^- BF ₄ was measured by the concentration measuring device 20 ^- the concentration of It is characterized by being determined based on the measurement result.

Thus, the decomposition treating apparatus 30, BF ₄ contained in the waste water ^- recognizes the concentration in real time, the time-varying BF ₄ ^- to determine continuously the drug amount based on the concentration, BF ₄ ^- allow disassembly process. Therefore, changing BF ₄ ^- in accordance with the concentration can control the drug amount, it can be performed more appropriately and efficient processing.

Specifically, in the control unit 32, BF ₄ ^- on the basis of the density measurement results, determined as follows the amount of the polyvalent metal salt. For example, the control unit 32, BF ₄ ^- receives the information on the concentration, the BF ₄ ^- ^- from the density measuring unit 24 in the concentration measuring device 20 BF ₄ measurements and concentrations, also was controlled to less than 0.1 mol / L The value obtained by multiplying the free F ⁻ concentration and the like by a predetermined coefficient is taken as the addition amount of the polyvalent metal salt.

As described above, when the addition amount of the polyvalent metal salt is determined by the control unit 32, information on the calculated addition amount is transmitted to the drug addition unit 33.

[Drug addition part]
The medicated portion 33 receives the information about the amount of the polyvalent metal salt from the control unit 32, the addition amount thereof, i.e. BF ₄ ^- a polyvalent metal salt of the addition amount based on the concentration of the measurement results, BF ₄ ^- It adds to the wastewater accommodated in the decomposition reaction tank 31.

The drug addition unit 33 is connected to, for example, a polyvalent metal salt supply tank that supplies a polyvalent metal salt. A predetermined ratio of the polyvalent metal salt is supplied from the polyvalent metal salt supply tank, and the predetermined amount is supplied. Store. The medicated portion 33, on the basis of information about the amount of the control unit 32, a polyvalent metal salt which stores the partial multivalent metal salt of the amount added BF ₄ ^- is added to the decomposition reaction vessel 31.

In the present embodiment, as described above, BF ₄ ^- BF by adjusting the pH of the wastewater to 4 below in a concentration measuring device 20 ₄ ^- concentration were measured, and sends the measurement result to the decomposition treating apparatus 30 , BF ₄ in the decomposition processor 30 ^- so that to determine the amount of drug based on the concentration. According to such a wastewater treatment method, since the amount of the chemical used can be controlled continuously based on the BF ₄ ⁻ concentration in the wastewater that varies with time, the wastewater can be treated more efficiently. be able to.

In the present embodiment, prior to measuring the BF ₄ ⁻ concentration contained in the wastewater, and before decomposing BF ₄ ⁻ by adding a chemical such as a polyvalent metal salt to the wastewater, the wastewater By removing the free F ⁻ contained in the water, it is possible to suppress the free F ⁻ contained in the wastewater from becoming strong hydrofluoric acid, and to measure the concentration of BF ₄ ⁻ more accurately. Further, by removing free F 2 ⁻ from wastewater, waste of chemicals such as polyvalent metal salts added for the decomposition of BF ₄ ⁻ can be suppressed, and an efficient decomposition process can be performed.

(2) About F removal treatment (defluorination treatment tank)
Next, the decomposition treatment apparatus 30 can perform a defluorination treatment that removes fluorine obtained by decomposing BF ₄ ⁻ contained in wastewater. As shown in the block diagram of FIG. 1, this defluorination treatment can be performed in a defluorination (F) treatment tank.

Specifically, in the defluorination treatment in the defluorination treatment tank 34, a calcium salt such as slaked lime and a pH adjuster are added to wastewater obtained by decomposing BF ₄ ⁻ to insolubilize fluorine contained in the wastewater ( Fluorine insolubilization treatment). That is, fluorine ions generated by the decomposition of BF ₄ ⁻ are insolubilized.

Here, the calcium salt is added to convert fluorine ions into an insoluble substance. Specifically, the preceding stage of BF ₄ ^- aluminum salts in the decomposition reaction vessel 31 as polyvalent metal salts, ferric salts, BF ₄ with a second titanium salt such as ^- when degrade, AlF n _^3-n soluble , FeF _n ^3-n and TiF _n ^4-n complexes are formed. By adding calcium salts to the waste water in which these complexes are formed, fluorine ions are converted into CaF ₂ and insolubilized. be able to. Alternatively, fluorine ions can be converted to CaF ₂ and insolubilized by an adsorption reaction of fluorine ions to calcium hydroxide of a hydrolysis product of solid calcium hydroxide or calcium salt. By converting the fluorine component into insoluble CaF ₂ and insolubilizing in this way, the fluorine component can be easily flocated and removed in the agglomeration tank 36 described later.

As the calcium salt, it is preferable to use inorganic calcium salts such as calcium chloride, calcium hydroxide, calcium carbonate, calcium oxide, and calcium sulfate.

Further, the pH adjuster is added to adjust the pH condition of the wastewater in the defluorination treatment tank 34, but it is adjusted to a pH condition that can precipitate the reaction product generated by the addition of the calcium salt described above. Is preferred. For example, when an aluminum salt is used as the polyvalent metal salt, the pH is preferably adjusted to 4 to 8, and when a ferric salt and a second titanium salt are used, the pH is preferably adjusted to 4 or more. Thereby, the fluorine component in wastewater can be efficiently insolubilized and removed.

As the pH adjuster, 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.

(3) About the removal process of B (deboronation processing tank)
When fluorine in the wastewater is insolubilized, next, a boron removal treatment for insolubilizing boron contained in the wastewater can be performed. As shown in the configuration diagram of FIG. 1, this deboronation treatment can be performed in a deboronation (B) treatment tank 35.

Specifically, in the deboronation treatment in the deboronation treatment tank 35, a calcium salt such as slaked lime and a pH adjuster are further added to the wastewater to insolubilize boron contained in the wastewater (boron insolubilization treatment). That is, boron ions generated by the decomposition of BF ₄ ⁻ are insolubilized.

Here, the calcium salt, a boron ion (borate ion), a reaction product of a calcium salt in defluorination treatment tank 34 described above and BF ₄ ^- is added in decomposition reactor 31 the hydroxides of polyvalent metal ions Acts to encapsulate the boron ions, thereby insolubilizing the boron ions. In this way, the boron component is encapsulated by the calcium salt reaction product or polyvalent metal ion hydroxide and insolubilized, whereby the boron component can be easily flocked and removed in the agglomeration tank 36 described later. It becomes like this.

In addition, the thing similar to what was added in the defluorination processing tank 34 can be used for a calcium salt and a pH adjuster. Further, the defluorination treatment tank 34 and the deboronation treatment tank 35 described above may be integrated, and the defluorination treatment and the deboronation treatment may be performed together.

(4) About aggregation treatment (aggregation tank)
Next, in the defluorination treatment tank 34 and the deboronation treatment tank 35, the reaction product of fluorine and boron in the wastewater precipitated as an insoluble substance is aggregated to form a floc (coagulation treatment). As shown in the configuration diagram of FIG. 1, this aggregation treatment can be performed in the aggregation tank 36.

Specifically, in the flocculation treatment in the flocculation tank 36, a flocculant such as an anionic polymer flocculant is added to the wastewater to coarsen (flocculate) the particles of the reaction product in the wastewater. That, BF ₄ ^- decomposition produced in the decomposition reaction vessel 31, to flock the fluorine ions or boron ions insolubilized by defluorination treatment tank 34 and the deboronation treatment tank 35.

Here, the flocculant is added to flock the particles of the insoluble material generated in the defluorination treatment tank 34 and the deboronation treatment tank 35. Specifically, as the flocculant, 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 a neutral anionic high concentration agent is used in the weakly acidic to weakly alkaline region. It is preferable to use a molecular flocculant, but it is desirable to select it appropriately according to the sedimentation and clarity of the resulting floc. Moreover, a flocculant may be used individually by 1 type, or may use 2 or more types together. Further, the flocculant is not limited to a polymer flocculant, and an inorganic flocculant may be used as long as it can flock insoluble substances. The addition amount of the flocculant is, for example, a concentration range of 0.5 mg / L to 15 mg / L with respect to the wastewater to be treated.

In the flocculation tank 36, after adding the flocculant, it is preferable to treat the waste water with stirring with, for example, a turbine stirrer or a propeller stirrer. By stirring in this way, flocking by the flocculant can be promoted.

(5) About sedimentation treatment (sedimentation tank)
In this way, when the insoluble substance is floculated in the coagulation tank 36, the floc having the sedimentation property is settled in the sedimentation tank 37, and a clear supernatant water, that is, water after treatment is obtained ( Sedimentation treatment).

Specifically, in the sedimentation tank 37, the fluorine contained in the wastewater is separated as CaF ₂ and boron is precipitated and separated as boric acid, and the fluorine and boron in the supernatant water are treated to a low concentration, and after the treatment Water can be obtained. The solid component separated by solid-liquid separation, that is, floc containing fluorine or boron is discharged from the settling tank 37 as a precipitate.

1 wastewater treatment system 10 fluorine removal apparatus 11 for removing fluorine reaction vessel 12 sedimentation tank 20 BF ₄ ^- concentration measuring apparatus 21 vessel 22 liquid supply unit 23 ion electrode device 30 decomposition treating apparatus 31 BF ₄ ^- decomposition reactor 32 controller 33 drugs Addition part 34 Defluorination treatment tank 35 Deboronation treatment tank 36 Coagulation tank 37 Sedimentation tank

Claims

With fluorine, BF 4 of persistent - a processing method for wastewater containing,
A fluorine removal step for removing free fluorine ions contained in the waste water;
A measuring step, - BF 4 for measuring the concentration - BF 4 in the wastewater obtained by removing the free fluorine ion
The BF 4 - measuring step BF 4 was measured at - based on the concentration of the BF 4 - anda decomposition step of decomposing the,
In the measurement step, by adjusting the pH of the wastewater to 4 below BF 4 - - the BF 4 was measured density,
In the decomposing step, the wastewater treatment method is characterized in that a polyvalent metal or a metal salt thereof whose addition amount is determined based on the concentration of BF 4 − is added to the wastewater.
The BF 4 - in the measuring step, the wastewater BF 4 - processing method of waste water according to claim 1, characterized in that measuring the concentration - in contact with the electrode BF 4.
The wastewater treatment method according to claim 1 or 2, wherein in the fluorine removal step, the concentration of free fluorine ions in the wastewater is less than 0.1 mol / L.
The wastewater treatment method according to claim 1 or 2, wherein in the fluorine removal step, a precipitate of the free fluorine ions is generated and removed using a calcium salt.
With fluorine, BF 4 of persistent - a processing system wastewater containing,
A fluorine removing device for removing free fluorine ions contained in the waste water;
A concentration measuring device, - BF 4 for measuring the concentration - BF 4 in the wastewater obtained by removing the free fluorine ion
The BF 4 - BF 4 was measured by the concentration measuring device - and a decomposition treatment unit degrades, - BF 4 of the waste water on the basis of the density
The BF 4 - in a concentration measuring apparatus, BF 4 by adjusting the pH of the wastewater to 4 below - using electrodes BF 4 - to determine the concentration,
The decomposition processing apparatus includes:
And decomposing the decomposition reaction unit, - BF 4 with a polyvalent metal or metal salt thereof to said waste water
A drug addition part for adding the polyvalent metal or a metal salt thereof to the decomposition reaction part;
A controller for determining the amount of the polyvalent metal or metal salt thereof added,
Wherein the control unit, the BF 4 - concentration measuring device BF 4 was measured at - determining the amount of the polyvalent metal or a metal salt thereof based on the information on the concentration, the addition to the drug addition unit Wastewater treatment system characterized by sending information on volume.