JP2004000827A - Removing agent of fluorine and phosphorus and processing method for removing fluorine and phosphorus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removing agent for efficiently removing fluorine and/or phosphorus from fluorine and/or phosphorus-containing wastewater or the like to easily treat fluorine and/or phosphorus so as to bring it to a target low concentration, and a processing method for removing fluorine and/or phosphorus. <P>SOLUTION: The fluorine and/or phosphorus removing agent comprises a zirconium salt aqueous solution. In the processing method for treating fluorine and/or phosphorus-containing water, the zirconium salt aqueous solution is added to fluorine and/or phosphorus-comtaining water to insolubilize fluoride ions and/or phosphate ions as a fluorine compound and/or a phosphate compound and this compound is subjected to solid-liquid separation treatment. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fluorine and phosphorus removing agent and a removing method, and in particular, to efficiently remove fluorine and / or phosphorus from waste water or the like containing fluorine and / or phosphorus to easily remove the fluorine and / or phosphorus to a target low concentration. It relates to possible removal agents and removal treatment methods.
[0002]
[Prior art]
The following methods are known as a method for removing fluorine and / or phosphorus contained in wastewater or process water in various industrial fields. For example, as a method for removing fluorine discharged from the electronics industry wastewater, slaked lime is added to raw water to generate fine particles of calcium fluoride, and the generated fine particles are subjected to Al, Fe-based coagulant or polymer coagulation. After coagulation with an agent, a method of separating by precipitation is employed. According to this method, fluorine in the treated water can be reduced to about 10 to 20 mg / l. Therefore, it was possible to clear the conventional discharge standard value of 15 mg / l.
[0003]
However, in July 2001, the emission standard value of fluorine was increased from 15 mg / l to 8 mg / l, and it became necessary to further treat fluorine.
[0004]
As a method for treating fluorine to a high degree, a method in which coagulation and precipitation are further performed in a subsequent stage in addition to the coagulation and precipitation method described above can be employed. The amount of the flocculant used here is 2000 to 5000 mg / l, and fluorine is adsorbed and removed on hydroxides of Al and Fe. According to this method, the fluorine concentration of the treated water can be reduced to about 2 to 8 mg / l.
[0005]
As another treatment method, a method in which a hydrated oxide of Zr or Ce is supported on a resin or a method of using a fluorine adsorbent granulated with a polymer substance is known (for example, Japanese Patent Publication No. 61-47134). ). According to this method, the fluorine concentration of the treated water can be reduced to 0 to 1 mg / l. The adsorbent used here is represented by a hydrated oxide MOn.XH ₂ O (≒ M (OH) _m ) formed by adding an alkali to a rare earth element or a salt of Ti or Zr or by heating and hydrolyzing. Such substances have been devised by utilizing the property of anion exchange with anions such as PO ₄ , F, and SO _{4 on the} acidic side and cation exchange on the alkali side (for example, Japanese Patent Publication No. 172220, JP-A-60-172353). This adsorbent can be regenerated with a regenerant.
[0006]
On the other hand, as a method of removing phosphorus, a method of removing calcium phosphate by the above-described coagulation precipitation, and a method of reacting with a coagulant to precipitate and separate as aluminum phosphate and iron phosphate are known. Moreover, it is also possible to remove using the above adsorbent.
[0007]
[Problems to be solved by the invention]
However, in the coagulation sedimentation method as described above, since several thousand mg / l of an Al or Fe-based coagulant is added in order to reduce fluorine, the dewatering property of the sludge is reduced or the amount of generated sludge is extremely large. There is a problem that the sludge disposal cost increases. It is also a technology that goes against the waste reduction in society.
[0008]
On the other hand, in the method using the fluorine adsorbent, although the sludge does not increase, there is a problem that the adsorption cost is slow and the amount of the adsorbent is large, so that the treatment cost is extremely high. In addition, there is also a problem that the matrix may be deteriorated by an oxidizing agent such as hydrogen peroxide contained in the wastewater of the electronics industry or hydrofluoric acid of the raw water, and the base may be collapsed.
[0009]
In addition, when an adsorbent is used to remove phosphorus, there is a problem that a large amount of the regenerant is consumed during regeneration because of strong binding force with the adsorbent. Further, when an Al or Fe-based coagulant is used, there is a problem that sludge having a high moisture content is generated and dewatering is difficult.
[0010]
Therefore, an object of the present invention is to focus on the problems in the prior art as described above, and to efficiently remove fluorine and / or phosphorus from a wastewater containing fluorine and / or phosphorus to a target low concentration. An object of the present invention is to provide a removing agent and a removing method which can be easily treated.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a fluorine and / or phosphorus removing agent according to the present invention is characterized by comprising a zirconyl salt aqueous solution in which a zirconyl salt is dissolved in water.
[0012]
This removing agent is preferably used for removing fluorine and / or phosphorus in a pH range of 3.5 to 7, preferably in a pH range of 4 to 5.5.
[0013]
As the zirconyl salt, for example, any of zirconyl chloride, zirconyl sulfate and zirconyl nitrate can be used.
[0014]
In the method for treating fluorine- and / or phosphorus-containing water according to the present invention, a zirconyl salt aqueous solution is added to fluorine- and / or phosphorus-containing water to convert fluorine-type ions and / or phosphate-type ions into a fluorine compound and / or phosphate. After insolubilizing as a compound, solid-liquid separation is performed. Examples of the fluorine- and / or phosphorus-containing water to be treated include wastewater and process water in various industrial fields, and for example, treatment of electronics industry wastewater is particularly effective.
[0015]
As a solid-liquid separation method, an inorganic coagulant or a polymer coagulant may be added to wastewater containing an insolubilized substance to perform precipitation separation, or separation may be performed by a membrane separation device.
[0016]
In this treatment method, it is preferable that the water containing fluorine and / or phosphorus is adjusted to pH 3.5 to 7, preferably pH 4 to 5.5, and reacted with the aqueous zirconyl salt solution.
[0017]
As the addition amount, it is preferable to add an aqueous solution in which one or more zirconyl salts are dissolved at an equivalent ratio in the insolubilization reaction with respect to the target amount of fluorine or phosphorus contained in the water to be treated. It is preferable that the concentration of the target substance to be removed from the water to be treated is low to some extent from an economic viewpoint, and it is possible to apply the method of the present invention to the water to be treated whose concentration has been reduced to some extent by a known inexpensive method. It is advantageous in terms of processing cost and removal effect. For example, it is preferable to apply the raw water to a raw water having a fluorine concentration of 20 mg / l or less from an economic viewpoint, and the Zr concentration is preferably 200 mg / l or less from an economic viewpoint.
[0018]
In the fluorine and phosphorus removing agent and the removing method according to the present invention, the removing agent is in the form of an aqueous solution in which a zirconyl salt is dissolved, and is not in the form of solid powder or granules. Then, in the removal treatment, fluorine-based ions and / or phosphate-based ions contained in the water to be treated are not chemically or physically adsorbed by the hydrated oxide of Zr, but by the chemical reaction. It is insolubilized as a fluorine compound (especially, zirconyl fluoride is generated) and / or a phosphate compound (especially, zirconyl phosphate is thought to be generated). Provided. That is, an insolubilized substance suitable for solid-liquid separation is generated by a chemical reaction instead of adsorption, and the contained fluorine and / or phosphorus are efficiently removed by the solid-liquid separation.
[0019]
In the case of zirconyl chloride, for example, this chemical reaction is considered as the following reaction, and it is considered that zirconyl fluoride and zirconyl phosphate are generated.
ZrOCl ₂ + 2F ⁻ → ZrOF ₂ + 2Cl ⁻
ZrOCl ₂ + 2H ₂ PO ₄ ⁻ → ZrO (H ₂ PO ₄ ) ₂ + 2Cl ⁻
ZrOCl ₂ + HPO ₄ ²⁻ → ZrOHPO ₄ + 2Cl ⁻
[0020]
In this way, since the insolubilized matter is generated by a chemical reaction instead of adsorption, etc., it is not necessary to add a large amount of the removing agent, and it is necessary for the chemical reaction according to the content concentration of the object to be removed and the target removal amount. It is sufficient to add only a small amount, and it is possible to reduce the amount to be added and to reduce the processing cost as compared with the conventional case where a large amount of coagulant is added.
[0021]
In addition, since the removal is based on a chemical reaction, by adding an appropriate amount of a removing agent and causing a sufficient chemical reaction, the removal treatment can be performed down to an extremely low concentration, and the new emission standard value can be sufficiently satisfied. Will be able to respond to
[0022]
Further, since the removing agent is in the form of an aqueous solution of a zirconyl salt, and the treatment is performed based on the above-mentioned expected chemical reaction, there is no problem of disintegration of the matrix of the removing agent, and It is not substantially affected by the oxidizing agent contained in the water to be treated. Therefore, the removal process is performed stably.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, with respect to the embodiment of the present invention, a test conducted to confirm the mechanism of removal agent generation according to the present invention, and an experiment conducted to confirm preferable conditions in the present invention will be mainly described with reference to the drawings. It will be described with reference to FIG.
[0024]
First, the following test was conducted to confirm the mechanism of the removal agent generation according to the present invention. That is, the fluorine and / or phosphorus removing agent according to the present invention is an aqueous solution in which a zirconyl salt is dissolved, and is not a solid. As shown in FIG. 1, the pH was varied by adding an acid or an alkali to a ZrOCl ₂ solution containing 200 mg-Zr / l, and the rate of formation of solids was observed. The generated solid was considered to be zirconium hydroxide, but as shown in FIG. 1, the amount of the generated solid was large at pH 7 or more. That is, since the removing agent according to the present invention is not such a solid substance, it is considered that the removing agent is in the form of an aqueous solution of a zirconyl salt in a pH range of 7 or less. In addition, the solid matter production rate in FIG. 1 is the ratio of the amount of Zr / the amount of added Zr in the produced solid matter.
[0025]
Next, for each of fluorine and phosphorus, the following experiments (Experiment 1 and Experiment 2 were carried out) in order to confirm the optimal treatment pH range for the removal treatment and the amount of the necessary remover to be added. However, in these experiments, in the wastewater of the electronics industry, etc., fluorine and phosphorus to be removed are often contained in a relatively large amount (for example, the concentration of fluorine or phosphorus is about 100 to 2000 mg / l. Many), if the removal treatment according to the present invention is performed suddenly, a large amount of the removal agent is required, and the efficiency may be low and the cost may be high. From the viewpoint that the removal treatment according to the present invention is performed more efficiently as a secondary treatment after the concentration is reduced to the level or less, and the treatment can be carried out to a target low concentration at a low cost, the treatment in the experiment is performed. As elephant raw water, fluorine, were used those prepared in a relatively low concentration of phosphorus both.
[0026]
Experiment 1
Zirconyl chloride was dissolved as a fluorinating agent (removing agent) to prepare a 20% zirconyl chloride solution. Sodium fluoride was diluted and adjusted, and 50 mg-Zr / l of zirconyl chloride solution as Zr was added to 1 liter of 20 mg-F / l simulated fluorine water to adjust the pH to 3-10. The generated solid was filtered with a 0.45 μ filter, and the fluorine concentration of the filtrate was measured. That is, the amount of residual fluorine (fluorine concentration) in the treated water was measured depending on the pH at a constant addition amount. FIG. 2 shows the results. On the other hand, sodium fluoride was diluted and adjusted, and the pH was adjusted to 5 by adding 10 to 200 mg / l of zirconyl chloride solution as Zr to 1 liter of 20 mg-F / l simulated fluorine water. That is, the amount of residual fluorine (fluorine concentration) in the treated water was measured depending on the amount of the remover added at a constant pH. The results are shown in FIG.
[0027]
From FIG. 2, it can be seen that the range of pH 3.5 to 7 is suitable for the removal treatment of the contained fluorine, and the range of pH 4 to 5.5 or pH 4 to 6 is more suitable. Also, from FIG. 3, if a target fluorine removal amount is set for the fluorine-containing raw water of 20 mg-F / l, how much removal agent should be added to clear the target value? I understand. In particular, it can be seen that in the region where the characteristics are linear in FIG. 3, the necessary minimum addition amount can be set efficiently.
[0028]
Experiment 2
As a phosphorus treating agent (removing agent), zirconyl chloride was dissolved to prepare a 20% zirconyl chloride solution. The potassium hydrogen phosphate was diluted and adjusted, and 25 mg-Zr / l of zirconyl chloride solution as Zr was added to 1 liter of 10 mg-P / l simulated phosphoric acid water to adjust the pH to 3-10. The generated solid was filtered with a 0.45 μ filter, and the fluorine concentration of the filtrate was measured. That is, the amount of residual phosphorus (phosphorus concentration) in the treated water was measured depending on the pH at a constant addition amount. FIG. 4 shows the results. On the other hand, potassium hydrogen phosphate was diluted and adjusted, and the pH was adjusted to 5 by adding 5 to 100 mg / l of zirconyl chloride solution as Zr to 1 liter of 10 mg-P / l simulated fluorine water. That is, the amount of residual phosphorus (phosphorus concentration) in the treated water was measured depending on the amount of the remover added at a constant pH. FIG. 5 shows the results.
[0029]
From FIG. 3, it is understood that the range of pH 3.5 to 7 is suitable for the removal treatment of the contained phosphorus, and the range of pH 4 to 6 is more suitable. Also, from FIG. 4, if a target phosphorus removal amount is set for the 10 mg-P / l phosphorus-containing raw water, how much removal agent should be added to clear the target value? I understand. In particular, it can be seen that in the region where the characteristics are linear in FIG. 4, the necessary minimum addition amount can be set efficiently.
[0030]
【The invention's effect】
As described above, according to the fluorine and phosphorus removing agent and the removing method according to the present invention, the zirconyl salt aqueous solution and the fluorine ion and / or the phosphate ion contained in the water to be treated are chemically reacted to form a fluorine compound. And / or a phosphate compound is generated and insolubilized, and the generated insolubilized substance can be efficiently separated by solid-liquid separation and removed without being caused by adsorption or the like. Since the treatment can be performed to a low concentration with the minimum necessary amount of the removing agent added, the cost of the removal treatment can be reduced. In addition, since the treatment is based on the premise of a chemical reaction, the fluorine and / or phosphorus contained can be removed very efficiently as long as an appropriate amount of the removing agent is added, and the concentration of the residual fluorine in the treated water is reduced to an extremely low concentration. It becomes possible.
[0031]
Moreover, since it is only necessary to add an aqueous solution of a zirconyl salt as a removing agent, the equipment cost for the treatment is extremely low. Furthermore, since it only causes a chemical reaction expected in advance, it is substantially unaffected by the oxidizing agent in the raw water. Further, since the removing agent is in the form of an aqueous solution, there are also problems such as collapse of the mother body. Does not occur. Therefore, the removal process can be performed stably and easily.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing a solid substance generation characteristic in a test in which an acid or an alkali is added to a ZrOCl ₂ solution to change the pH.
FIG. 2 is a graph showing the effect of removing fluorine by pH in Experiment 1.
FIG. 3 is a characteristic diagram of fluorine removal effect depending on the amount of a remover added in Experiment 1.
FIG. 4 is a characteristic diagram of phosphorus removal effect by pH in Experiment 2.
FIG. 5 is a graph showing phosphorus removal effect characteristics depending on the amount of a remover added in Experiment 2.

Claims (6)

A fluorine and / or phosphorus remover comprising an aqueous zirconyl salt solution. The removing agent according to claim 1, which is used for removing fluorine and / or phosphorus within a pH range of 3.5 to 7. The removal agent according to claim 1 or 2, wherein the zirconyl salt comprises any of zirconyl chloride, zirconyl sulfate, and zirconyl nitrate. It is characterized in that a zirconyl salt aqueous solution is added to water containing fluorine and / or phosphorus to insolubilize fluorine-based ions and / or phosphate-based ions as a fluorine compound and / or a phosphate compound, followed by solid-liquid separation. Of water containing fluorine, fluorine and / or phosphorus. The treatment method according to claim 4, wherein the water containing fluorine and / or phosphorus is adjusted to have a pH of 3.5 to 7 and reacted with an aqueous solution of a zirconyl salt. The treatment method according to claim 4 or 5, wherein an aqueous solution in which one or more zirconyl salts are dissolved in an equivalent ratio in the insolubilization reaction with respect to the target amount of the contained fluorine or phosphorus is added.

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