JP2004097860A - Removing agent of fluorine or phosphorus and removing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently remove fluorine and/or phosphorus from fluorine and/or phosphorus-containing water. <P>SOLUTION: In a titanium reaction tank 10, a titanyl salt or a titanium salt is added to fluorine-containing water to insolubilize fluorine. Next, a polymeric flocculant is added to the treated water from the reaction tank 10 in a flocculation tank 12 to form flocs. Then, the treated water from the flocculation tank 12 is subjected to sedimentation treatment in a sedimentation tank 14 to remove a solid to obtain treated water from which fluorine is removed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fluorine or phosphorus removing agent and a removing method.
[0002]
[Prior art]
In the electronics industry that manufactures semiconductors, liquid crystals, and the like, fluorine is used in the manufacturing process, and thus the wastewater in the electronics industry often contains fluorine. As a method for removing the fluorine discharged from the fluorine-containing water, a calcium salt is added to raw water to precipitate fine particles of calcium fluoride, and these fine particles are made of an Al, Fe-based inorganic coagulant or A method of coagulating with a molecular coagulant and separating by precipitation is employed. According to this method, the amount of treated water fluorine can be reduced to 10 to 20 mg / l. However, in Japan in July 2001, the emission standard for fluorine was increased from 15 mg / l to 8 mg / l, and it became necessary to further treat fluorine.
[0003]
As a method of treating fluorine to a high degree, a method of increasing the amount of an aggregating agent added in the above-mentioned coagulation precipitation, or performing another coagulation precipitation again in the latter stage of the above coagulation precipitation treatment is employed. The use amount of the flocculant in such a treatment is 2000 to 5000 mg / l, and fluorine is adsorbed on the hydroxide of Al or Fe to increase the fluorine removal rate. By this method, the concentration of fluorine in the treated water can be reduced to 2 to 8 mg / l.
[0004]
As another method, it has been proposed to increase the fluorine removal rate by supporting a hydrated oxide of Zr or Ce on a resin or using a fluorine adsorbent granulated with a polymer substance (Patent Document 1). (Japanese Patent Publication No. 6-79665) and Patent Document 2 (Japanese Patent Publication No. 61-47134). It is stated that these methods can reduce the treated water fluorine to 0 to 1 mg / l.
[0005]
Here, the adsorbent is a hydrated oxide MO _n · XH ₂ O (≒ M (OH) _m ) generated by adding an alkali to a rare earth element or a salt of Ti or Zr or heating and hydrolyzing the salt. Utilizing such a property that a substance as shown exchanges anions with anions such as PO ₄ ³⁻ , F ⁻ , and SO ₄ ²⁻ on the acidic side and exchanges cations on the alkali side (Patent Document 3 (Patent Document 3)). Japanese Patent Publication No. 2-17220) and Patent Document 4 (JP-A-60-172353). M is a metal, and X, m, and n are arbitrary numbers.
[0006]
In addition, phosphorus is often contained in wastewater from the electronics industry, and phosphorus is also contained in wastewater from households. Phosphorus must be removed from the viewpoint of preventing eutrophication in closed water areas, and is subject to additional regulations in many areas. In order to remove phosphorus, similarly to the case of fluorine, a calcium salt is added and coagulated and precipitated as calcium phosphate, and an aluminum or iron-based inorganic coagulant is used to coagulate as aluminum phosphate or iron phosphate. Settling has been performed. Further, the above adsorbent can treat not only fluorine ions (F ⁻ ) but also phosphoric acid (PO ₄ ³⁻ ). Therefore, these adsorbents can also be used for phosphorus removal.
[0007]
[Patent Document 1]
Japanese Patent Publication No. 6-79665 [Patent Document 2]
Japanese Patent Publication No. 61-47134 [Patent Document 3]
Japanese Patent Publication No. 2-17220 [Patent Document 4]
JP-A-60-172353
[Problems to be solved by the invention]
In the above-mentioned coagulation sedimentation method, several thousand mg / l of an Al or Fe-based coagulant is added to reduce fluorine. Such flocculated sludge incorporates water molecules into its floc, so that the sludge dewatering property is poor, and the amount of added flocculant increases the amount of generated sludge. Therefore, there is a problem that the sludge disposal cost increases. In addition, the process of generating such a large amount of waste is a technology that goes against the social demand for reducing the amount of waste.
[0009]
On the other hand, the fluorine adsorbent does not increase sludge, but has a low adsorption speed and a large amount of adsorbent used. For this reason, there is a problem that the processing cost is very high. There is also a problem that the adsorbent is degraded by the oxidizing agent such as hydrogen peroxide contained in the wastewater of the electronics industry and the hydrofluoric acid of the raw water, and the base material collapses and flows out.
[0010]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a fluorine or phosphorus removing agent or a removing method capable of efficiently removing fluorine and / or phosphorus from water containing fluorine and / or phosphorus.
[0011]
[Means for Solving the Problems]
The fluorine or phosphorus removing agent according to the present invention includes an aqueous solution of a titanyl salt or an aqueous solution of a titanium salt, and is used for a treatment for insolubilizing and removing fluorine or phosphorus by adding to water containing fluorine or phosphorus.
[0012]
Further, the method for removing fluorine or phosphorus according to the present invention is characterized in that an aqueous solution of titanyl salt or an aqueous solution of titanium salt is added to water containing fluorine or phosphorus to make the solution insoluble, and then solid-liquid separation is performed.
[0013]
Titanyl salts and titanium salts react with fluorine ions in water to insolubilize and remove fluorine. In particular, this reaction is effectively performed even when the fluorine concentration is low. Therefore, advanced treatment of fluorine-containing water can be efficiently performed using the fluorine or phosphorus removing agent according to the present invention.
[0014]
For example, when fluorine and phosphorus are removed using titanyl sulfate and titanium tetrachloride, the following reaction occurs.
Embedded image
TiOSO ₄ + 2F ⁻ → TiOF ₂ + SO ₄ ^2-
TiCl ₄ + 4F ⁻ → TiF ₄ + 4Cl ⁻
TiOSO ₄ + 2H ₂ PO ₄ ⁻ → TiO (H ₂ PO ₄ ) ₂ + SO ₄ ^2-
TiOSO ₄ + HPO ₄ ²⁻ → TiOOHPO ₄ + SO ₄ ²⁻
TiCl ₄ + 4H ₂ PO ₄ ⁻ → Ti (H ₂ PO ₄ ) ₄ + 4Cl ⁻
TiCl ₄ + 2HPO ₄ ²⁻ → Ti (HPO ₄ ) ₂ + 4Cl ⁻
[0015]
By such treatment, it is possible to surely treat the treated water fluorine concentration to several mg / L or less. Then, the amount of the drug used at this time can be reduced. Therefore, compared with the case where the fluorine concentration is lowered by adding a calcium salt, the sludge disposal cost is lower, and the equipment can be made smaller and the equipment cost can be reduced.
[0016]
Further, when an aqueous solution of titanyl salt or aqueous solution of titanium salt is added to water containing fluorine or phosphorus for insolubilization, it is preferable to maintain the pH at 3 to 6. With such a pH, fluorine or phosphorus can be efficiently removed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a removing method using a fluorine or phosphorus removing material according to the present invention. In this example, a description will be given using fluorine-containing wastewater as raw water.
[0018]
Raw water containing fluorine such as hydrofluoric acid is introduced into the titanium reaction tank 10. The titanium reaction tank 10 is supplied with an aqueous solution of a titanyl salt or a titanium salt, and is also supplied with a pH adjuster such as sodium hydroxide (acid when the pH of raw water is lowered, and alkali when it is raised).
[0019]
When titanyl sulfate or titanium tetrachloride is added, a reaction as shown in the following formula occurs,
Embedded image
TiOSO ₄ + 2F ⁻ → TiOF ₂ + SO ₄ ^2-
TiCl ₄ + 4F ⁻ → TiF ₄ + 4Cl ⁻
Fluorine is insolubilized. The pH in the titanium reaction tank 10 is adjusted to a range of 3 to 6 with sodium hydroxide or the like. Thereby, the above-mentioned reaction proceeds rapidly.
[0020]
The treated water in the titanium reaction tank 10 is supplied to the coagulation tank 12. The coagulation tank 12 is supplied with a polymer coagulant, and the insolubilized fluorine generated in the titanium reaction tank 10 is coagulated and coarsened. The polymer coagulant may be any of a cation, an anion, and a nonion, and a material having a good coagulation effect is appropriately employed. Further, an aluminum-based or iron-based inorganic coagulant may be used instead of the polymer coagulant, and these may be used in combination.
[0021]
The coagulation water from the coagulation tank 12 is introduced into the sedimentation tank 14, where solids are separated by sedimentation. That is, the above-mentioned aggregates of TiOF ₂ and TiF ₄ are precipitated and separated, and treated water having a low fluorine concentration is obtained as a supernatant. The solid-liquid separation means is not limited to the sedimentation tank 14, and various devices such as a membrane separation device can be used. In particular, when a membrane separation device is employed, the coagulation treatment using a polymer coagulant can be omitted.
[0022]
Here, titanyl sulfate is preferably used as the titanate added in the titanium reaction tank 10, and titanium tetrachloride is preferably used as the titanium salt. However, other titanyl salts and titanium salts may be used. Further, as can be seen from the above-mentioned reaction formula, it is preferable to add the titanate and the titanium salt in an amount equal to or more than Ti as an amount relative to fluorine (F) in the raw water. That is, in the case of titanic acid, the molar ratio of Ti: F = 1: 2, and in the case of a titanium salt, the molar ratio of Ti: F = 1: 4 or more may be added. The pH needs to be in the range of 3 to 6, but is preferably in the range of 4.0 to 5.0.
[0023]
FIG. 2 shows the results obtained by adding an acid or an alkali to a 200 mg-Ti / L TiOSO ₄ solution to generate a solid. Here, the solid matter generation rate is calculated by the ratio of Ti amount / Ti addition in the generated solid matter. In this experiment, since no fluorine was present, the produced solid was considered to be titanium hydroxide. However, the production was large at pH = 6 or more. From this, it is inferred that when the pH is 6 or more, solids of titanium hydroxide are generated, which is not suitable for removing fluorine. In particular, by setting the pH to 5 or less, the insolubilization of titanium hydroxide can be reliably prevented.
[0024]
"Experimental example"
Next, a treatment experiment of fluorine-containing water was performed using a titanic acid aqueous solution. As a fluorinating agent, titanyl sulfate was dissolved to prepare a 20% titanyl sulfate solution. Sodium fluoride was diluted and adjusted, and 50 mg-Ti / l of a 20% titanyl sulfate solution as Ti was added to 1 L of 20 mg-F / l simulated fluorine water to adjust the pH to 2 to 10. The generated solid was filtered with a 0.45 μ filter, and the fluorine concentration of the filtrate was measured. The results are shown in FIG.
[0025]
Thus, in the pH range of 3 to 6, the treated water fluorine concentration is 7 mg / L or less. Then, in the pH range of 4.0 to 5.0, the concentration is extremely low at 1.5 mg / L or less of fluorine.
[0026]
It is considered that when the pH is high, titanium hydroxide is generated and fluorine cannot be insolubilized, and when the pH is low, fluorine is not insolubilized by the above-described reaction.
[0027]
On the other hand, sodium fluoride was diluted and adjusted to a pH of 4.5 by adding 10 to 200 mg / L of a titanyl sulfate solution as Ti to 1 L of 20 mg-F / L of simulated fluorine water, and the pH of the filtrate was similarly adjusted. Was measured. FIG. 4 shows the results.
[0028]
As described above, up to a treated water fluorine concentration of 5 mg / L, the addition of the titanyl sulfate solution removes fluorine according to the theoretical amount. That is, fluorine decreases in the straight line of F (19 × 2 = 38) / Ti (48) according to the amount of titanium added. Therefore, it is understood that it is sufficient to add an equivalent or more titanyl salt to the fluorine to be removed.
[0029]
"Other Configurations"
In addition, from an economic viewpoint, it is preferable that the treatment of the present embodiment is applied to raw water having a fluorine concentration of 20 mg / L or less. On the other hand, in the case of industrial industrial wastewater, the fluorine concentration is often about 100 to 2000 mg / L. In such a case, it is preferable to remove the remaining fluorine by the treatment of the present embodiment after performing the conventional fluorine treatment with a calcium salt.
[0030]
FIG. 5 shows this type of processing. Raw water containing a high concentration of fluorine is first introduced into the calcium reaction tank 20. A calcium salt such as slaked lime or calcium chloride is supplied to the calcium reaction tank 20. If necessary, a pH adjuster such as sodium hydroxide is also added to adjust the pH to a suitable pH (about 4 to 11) for the precipitation of calcium fluoride.
[0031]
The treated water in the calcium reaction tank 20 is introduced into the inorganic coagulant reaction tank 22. An aluminum-based or iron-based inorganic coagulant (for example, polyiron sulfate or PAC (polyaluminum chloride)) is supplied to the inorganic coagulant reaction tank 22, and the fine particles of calcium fluoride are coagulated and flocculated. Note that some of the fluorine remaining in the treated water is also taken into the flocculated flocs.
[0032]
The treated water in the inorganic coagulant reaction tank 22 is supplied to the coagulation tank 24. A polymer flocculant is added to the flocculation tank 24 to further coarsen the inorganic floc. Then, the treated water in the flocculation tank 24 is introduced into the sedimentation tank 26, where solids are precipitated and separated, and a supernatant liquid is obtained. In this case, it is only necessary to obtain a treated water having a fluorine concentration of 20 mg / L or less, and the calcium salt, the inorganic coagulant, and the polymer coagulant may be added in the same amount as or slightly smaller than the conventional fluorine treatment. Good.
[0033]
Then, the thus obtained fluorine-containing water having a fluorine concentration of 20 mg / L or less is treated in the titanium reaction tank 10, the coagulation tank 12, and the precipitation tank 14 as described above. By such a treatment, the fluorine concentration can be reduced to a low concentration, and the addition amount of the calcium salt or the inorganic / organic coagulant can be relatively reduced. Further, the addition amount of the titanyl salt or the titanium salt may be relatively small.
[0034]
In addition, as shown in FIG. 6, in a calcium reaction tank 20, a calcium salt is added to generate calcium fluoride, which is then introduced into a titanium reaction tank 10 as it is, and a titanyl salt or a titanium salt is added to insolubilize residual fluorine. May be. This makes it possible to collectively perform the aggregation with the polymer flocculant and the solid-liquid separation. In this process, an inorganic coagulant may be further added.
[0035]
Here, in the above-described experimental example, only the treatment of the fluorine-containing water with titanyl sulfate was described, but it has been confirmed that the treatment can be similarly performed with titanium tetrachloride or the like. The amount of titanium tetrachloride to be added may be equal to or more than that of Ti as fluorine (molar ratio: Ti: F = 1: 4) according to the above-mentioned reaction formula.
[0036]
Furthermore, in the above description, only the treatment of the fluorine-containing water was targeted. However, titanyl salts and titanium salts cause the same insolubilization reaction with phosphorus as fluorine. Therefore, the above treatment can be directly applied to the phosphorus-containing wastewater. In addition, since phosphorus can be removed as calcium phosphate, the treatment of FIG. 5 can be applied to phosphorus-containing water as it is. In the treatment with phosphorus, phosphorus is insolubilized by the following reaction. Note that the form of phosphorus changes depending on the pH and the like.
Embedded image
TiOSO ₄ + 2H ₂ PO ₄ ⁻ → TiO (H ₂ PO ₄ ) ₂ + SO ₄ ^2-
TiOSO ₄ + HPO ₄ ²⁻ → TiOOHPO ₄ + SO ₄ ²⁻
TiCl ₄ + 4H ₂ PO ₄ ⁻ → Ti (H ₂ PO ₄ ) ₄ + 4Cl ⁻
TiCl ₄ + 2HPO ₄ ²⁻ → Ti (HPO ₄ ) ₂ + 4Cl ⁻
[0037]
Further, the present invention can be suitably applied to wastewater containing both fluorine and phosphorus. In this case, a titanyl salt or a titanium salt may be added in an amount equivalent to or more than the total amount of fluorine and phosphorus.
[0038]
【The invention's effect】
As described above, according to the present invention, titanyl salts and titanium salts can react with fluorine ions in water to insolubilize and remove fluorine. In particular, this reaction is effectively performed even when the fluorine concentration is low. Therefore, advanced treatment of fluorine-containing water can be efficiently performed using the fluorine or phosphorus removing agent according to the present invention. In addition, the amount of chemicals used in the treatment can be reduced, the sludge disposal cost can be reduced, and the equipment can be made smaller and the equipment cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a process according to an embodiment.
FIG. 2 is a graph showing the solid matter production rate with respect to the pH of titanyl sulfate.
FIG. 3 is a diagram showing the concentration of treated water fluorine with respect to pH.
FIG. 4 is a diagram showing the concentration of fluorine in treated water with respect to the amount of Ti added.
FIG. 5 is a diagram showing another configuration example.
FIG. 6 is a diagram showing still another configuration example.
[Explanation of symbols]
10 titanium reaction tank, 12 coagulation tank, 14 sedimentation tank.

Claims (3)

A fluorine or phosphorus removing agent which contains a titanyl salt aqueous solution or a titanium salt aqueous solution, and is used for a treatment for insolubilizing and removing fluorine or phosphorus by adding to water containing fluorine or phosphorus. A method for removing fluorine or phosphorus, which comprises adding an aqueous solution of titanyl salt or aqueous solution of titanium salt to water containing fluorine or phosphorus to make it insoluble, and then performing solid-liquid separation. 3. The method according to claim 2, wherein
A method for removing fluorine or phosphorus by maintaining a pH of 3 to 6 when an aqueous solution of titanyl salt or an aqueous solution of titanium salt is added to water containing fluorine or phosphorus for insolubilization.

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