JP2002066570A - Method of removing fluorine ion, and removing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently removing dissolved fluorine ions from water, particularly the water in which a large amount of calcium ions exist with a lowered amount of sludge generation. SOLUTION: In the method of removing the dissolved fluorine ions included in the water to be treated, the pH of the water is regulated to 6 to 9 in the presence of aluminum ions, phosphoric acid ions and, if necessary, a carboxyl group-containing hydrophilic polymer material and/or hydrolysis product, by which the dissolved fluorine ions are precipitated as hardly soluble materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for removing dissolved fluoride ions contained in water to be treated and a fluoride ion remover.

[0002]

2. Description of the Related Art Conventionally, the most common method of removing fluoride ions contained in water to be treated is a calcium coagulation precipitation method in which lime or slaked lime is added to the water to precipitate fluoride ions as calcium fluoride. Has been done. In this method, a high concentration (100 m
g / L or more) of fluorine ions at a medium concentration (10 to 20 mg).
/ L), but it is almost impossible to remove to a low concentration (10 mg / l or less) even by using a large amount of calcium salt. In the calcium coagulation sedimentation method, as described above, 10
Since it cannot be removed at mg / L or less, several methods have been studied as a method for removing fluorine ions at a low concentration. As such a method, an adsorption method using an adsorbent has been proposed, but in this method, the adsorbent cost is considerably high, and the processing conditions are severely restricted, and there are problems such as regeneration of the adsorbent, It is hardly practical.
There is also an aluminum method in which an aluminum hydroxide-forming agent is added to generate a hardly water-soluble gelled aluminum hydroxide, and fluorine ions in water are adsorbed and removed by the aluminum hydroxide gel. Since a large amount of an aluminum compound must be added, and flocs having good sedimentation and dehydration properties cannot be obtained, there is a problem that dehydration is difficult and a large amount of sludge is generated. In particular, when fluorine ions are present at a high concentration, a method in which calcium hydroxide is subjected to one-step treatment to 20 to 30 ppm and then treated in the above-described two-step treatment has been studied. At present, the treatment is more difficult and sludge is increased.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a method for efficiently removing dissolved fluorine ions from water, particularly water having a large amount of calcium ions, with a reduced amount of sludge, and a method for removing fluorine ions used in the method. It is an object to provide a remover.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, in the method for removing dissolved fluorine ions contained in the water to be treated, the pH is adjusted to 6 to 9 in the presence of aluminum ions and phosphate ions.
Thus, a method for removing fluorine ions is provided, wherein the dissolved fluorine ions are precipitated as a hardly soluble substance. Further, according to the present invention, in the method for removing dissolved fluorine ions contained in the water to be treated, in the presence of an aluminum ion, a phosphate ion and a carboxyl group-containing hydrophilic polymer substance and / or a hydrolysis product thereof, By adjusting the pH to 6-9,
There is provided a method for removing fluorine ions, comprising precipitating the dissolved fluorine ions as a hardly soluble substance. Further, according to the present invention, there is provided an agent for removing dissolved fluoride ions contained in water to be treated, which comprises (i) a phosphate compound, (ii) an aluminum compound, and (iii) a carboxyl group-containing hydrophilic polymer substance, And / or a hydrolysis product thereof.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A fluoride ion remover (hereinafter simply referred to as a remover) of the present invention comprises a phosphoric acid compound, an aluminum compound, a carboxyl group-containing hydrophilic polymer and / or a hydrolysis product thereof. It consists of a mixture. Phosphoric acid compounds include, in addition to phosphoric acid (H ₃ PO ₄ ), compounds that hydrolyze in water to generate phosphoric acid, for example, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, phosphoric acid Potassium, dipotassium hydrogen phosphate,
Potassium dihydrogen phosphate, sodium hexane metaphosphate, sodium tripolyphosphate and the like can be mentioned. Examples of the aluminum compound include aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, aluminum hydroxide, and sodium aluminate. The removing agent of the present invention is used in the form of a powder or an aqueous solution.

The carboxyl group-containing hydrophilic polymer substance includes various water-soluble polymer substances. Such high-molecular substances include polysaccharides such as alginic acid, dielan gum, xanthan gum, pectin, pectic acid, pectinic acid, anionized starch, propylene glycol alginate, carboxymethylcellulose, starch glycolic acid, cellulose glycolic acid, and the like. Metal salts and the like.

In the present invention, it is particularly preferable to use sodium alginate or calcium alginate. In the case of using these, the content ratio (molar ratio) of mannumaric acid (M) and guluronic acid (G) constituting alginic acid is preferably used. ratio)
[M] / [G] is 0.1 to 4.0, preferably 0.1
It is preferable to use those in the range of ~ 3. The higher the content of guluronic acid, the better the floc-forming property.

In the present invention, the carboxyl group-containing hydrophilic high-molecular substance used as the main remover can be used alone or in the form of a mixture. As the mixture, it is preferable to use a mixture containing alginic acid or a salt thereof.

In the present invention, the carboxyl group-containing hydrophilic polymer substance used mainly as a removing agent can be used alone or in the form of a mixture. In this case, as a preferred mixture containing alginic acid or a salt thereof,
(I) alginic acid or a salt thereof, (ii) dielan gum,
Examples thereof include a mixture with at least one hydrophilic polymer substance selected from xanthan gum, pectin, pectic acid, pectinic acid and salts thereof. When the mixture ratio is shown, for example, when a mixture of sodium alginate and another anion group-containing hydrophilic polymer is used, the mixture of sodium alginate (A) and another anion group-containing hydrophilic polymer (B) is used. The weight ratio [A] / [B] is
It is 1-100, preferably 2-50.

In order to preferably produce the removing agent of the present invention,
First, a hydrophilic polymer substance containing a carboxyl group is
It is heated in water containing an alkaline substance, hydrolyzed and dissolved in water. For example, sodium alginate is present in water containing sodium hydroxide as an alkaline substance, and heated to dissolve the sodium alginate. The heating temperature at this time is 70
C. or higher and lower than 100 ° C., more preferably,
75 ° C to 90 ° C, more preferably 80 ° C to 85 ° C
It is. The heating time is not particularly limited as long as the carboxyl group-containing hydrophilic substance is dissolved, but about 0.5 to 2 hours is sufficient. Next, the removing agent of the present invention can be produced by mixing a phosphoric acid compound and an aluminum compound with the obtained alkaline aqueous solution containing a carboxyl group-containing hydrophilic polymer substance and / or a hydrolysis product thereof. .

The ratio of the anionic group-containing hydrophilic polymer substance and / or the hydrolysis product thereof to the phosphoric acid compound is not particularly limited, but generally, the anion group-containing hydrophilic polymer substance and / or the hydrolyzate thereof. 10 to 10000 parts by weight of the phosphoric acid compound, preferably 50 to 5000 parts by weight, more preferably 100 to 10 parts by weight, based on 1 part by weight of the decomposition product.
The ratio is 00 parts by weight.

In order to remove fluorine ions in the water to be treated according to the present invention, the pH is reduced in the presence of a mixture of a phosphate compound and an anionic group-containing hydrophilic polymer and / or a hydrolysis product thereof and aluminum ions. It may be adjusted to 6 to 9. In this case, the addition order of the mixture of the aluminum compound, the phosphoric acid compound, the anionic group-containing hydrophilic polymer substance and / or the hydrolysis product thereof may be any order. The ratio of the phosphoric acid compound and the mixture of the anionic group-containing hydrophilic polymer substance and / or the hydrolysis product thereof to aluminum is 0.01 to 500 parts by weight of aluminum, preferably 1 part by weight of phosphorus in the remover. Is 0.05 to 200 parts by weight, more preferably 0.1 to 10 parts by weight.
0 parts by weight. Aluminum concentration in water is 5
-1000 mg / L, preferably 10-200 mg / L
It is. The amount of the aluminum compound added to the fluorine ions in the water to be treated is 0.2 to 20 mol, preferably 0.5 to 10 mol, as aluminum atoms per 1 mol of fluorine atoms.

When fluorine ions dissolved in the water to be treated are removed using the removing agent of the present invention, if the water to be treated is acidic or alkaline, the pH is adjusted so that precipitation occurs after the addition of the removing agent. Is preferred. Its pH is generally in the range 6-9.

When the pH of the water to be treated is adjusted to an alkaline range or an acidic range, a pH adjuster is used. Examples of such a pH adjuster include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like. An alkaline substance such as calcium hydroxide or an acidic substance such as hydrochloric acid, sulfuric acid or nitric acid is used.

In the removing agent of the present invention, it is preferable to use a coagulant in combination. The flocculant in this case is used for floc flocculation.
Cationically modified polyacrylamide, dimethylaminoethyl polyacrylate, dimethylaminoethyl polymethacrylate, cationic organic coagulants such as polyethyleneimine and chitosan, nonionic organic coagulants such as polyacrylamide, polyacryl Anionic organic coagulants such as acids, copolymers of acrylamide and acrylic acid, and salts thereof are included. The amount of the coagulant used is 1 to 20 mg / L, preferably 3 to 10 mg / L, in water.

The water to be treated containing flocs after the completion of the pH adjusting step is subjected to a solid-liquid separation treatment. The solid-liquid separation method in this case includes a conventional method, for example, filtration separation, centrifugation, sedimentation separation and the like.

The water to be treated used in the present invention contains dissolved fluorine ions (F ⁻ ), and various types of industrial wastewater are used. The concentration of fluorine ions in the water to be treated is 10 mg / L or more, particularly 15 mg / L or more, as fluorine atoms (F). Its upper limit is about 50 mg / L. Further, the water to be treated used in the present invention includes a large amount, for example, 50 tons.
About 0 to 50,000 ppm of calcium ions may be contained. The water to be used in the present invention may be 200 to 50,000 ppm in terms of calcium (Ca),
In particular, water to be treated containing 500 to 10000 ppm of calcium ions can be advantageously used. Calcium ions have the effect of promoting the insolubilization of dissolved fluorine ions. Therefore, when calcium ions are not present in the water to be treated, a calcium compound such as calcium chloride or calcium sulfate is added to the water to be treated,
The amount of the calcium ions is 1000 to 5000 pp
It is advantageous to adjust to about m, whereby the insolubilization of fluorine ions can be promoted, and the removal of fluorine ions can be performed efficiently.

[0018]

According to the method of the present invention, dissolved fluorine ions contained in the water to be treated can be removed efficiently and with a reduced amount of sludge. According to the present invention, the fluorine ions in the water to be treated can be almost completely removed, and the dissolved fluorine ions contained in the treated water after removing the fluoride ions are 10 ppm or less, preferably 8 ppm or less, more preferably 5 ppm or less. It is as follows.

[0019]

Next, the present invention will be described in more detail with reference to examples.

Reference Example 1 A 2% amount of sodium alginate was added to a 1N aqueous solution of sodium hydroxide, heated to 75 to 85 ° C., and stirred for 30 minutes to 1 hour. This solution is kept at room temperature (25-3
After cooling to 5 ° C.), an 85% phosphoric acid aqueous solution was mixed with the solution at a volume ratio of 1:19.

REFERENCE EXAMPLE 2 An aqueous solution of polyaluminum chloride (A
l ₂ O ₃ 10%) or aluminum sulfate aqueous solution (Al ₂
(SO ₄ ) ₃ · 18H ₂ O 60%) were mixed and stirred at a volume ratio of 1: 8. These are referred to as a removing agent (I) and a removing agent (II), respectively.

Example 1 A model wastewater (pH 3, 1) containing 15 ppm of fluorine and 1000 ppm of calcium was prepared. This solution does not precipitate on standing. Reference Example 2
500 mg / l or 1000 mg / l of the removing agent (I)
After the addition, the pH was adjusted to 8 with a sodium hydroxide solution, and the mixture was stirred for 20 minutes.
m and stirred, good flocs were formed. Solid-liquid separation was performed, and the fluorine concentration in the treated water was measured by ion chromatography.
pm and 3.0 ppm.

Example 2 The removal agent (II) of Reference Example 2 was added to the model waste water of Example 1
The same treatment as in Example 1 was carried out except that 000 mg / l was added, and the fluorine concentration of the treated water was 2.5 ppm.

Example 3 An aluminum sulfate aqueous solution (A
l ₂ (SO ₄ ) ₃ · 18H ₂ O 60%) at 1000 mg /
Then, 200 mg / l of the mixed solution of Reference Example 1 was added, and an aqueous solution of sodium hydroxide was added to adjust the pH to 7.7.
Was adjusted. After stirring for 20 minutes, 5 ppm of an anionic polymer flocculant was added, and after stirring, solid-liquid separation was performed. The fluorine concentration in the treated water was 2.7 ppm.

Example 4 Sodium aluminate (Al ₂ O ₃₎ was added to the model waste water of Example 1.
20%) 200 mg / l, the mixture of Reference Example 1 was added at 200 mg / l, the pH was adjusted to 7 with an aqueous sodium hydroxide solution, the mixture was stirred for 20 minutes, and then 5 ppm of an anionic polymer flocculant was added. After that, solid-liquid separation was performed. The fluorine concentration in the treated water was 2 ppm.

Example 5 The mixed solution of Reference Example 1 was added to the model wastewater of Example 1 for 100 times.
mg of polyaluminum chloride solution (Al ₂ O ₃
(10%) 500 mg / l and adjusted to pH 8 with aqueous sodium hydroxide solution. After stirring for 20 minutes, 5 ppm of an anionic polymer flocculant was added, followed by stirring and solid-liquid separation. The fluorine concentration in the treated water was 2.4 ppm.

Comparative Example 1 An aqueous solution of calcium chloride (Ca
(Cl ₂ 30%) was added, and the pH was raised with an aqueous solution of sodium hydroxide. When the pH was raised to 12.7, a small amount of precipitate was formed, but the fluorine concentration in the treated water subjected to solid-liquid separation was 13.5 p.
pm.

Comparative Example 2 A calcium hydroxide suspension (C
a (OH) ₂ 30%) was added to 1000 mg / l, and the pH became 12.9. Solid-liquid separation was performed, and the fluorine concentration in the treated water was measured to be 13.7 ppm.

Comparative Example 3 The waste water of Example 1 was replaced with a polyaluminum chloride aqueous solution (Al
_{2 O 3 10%) 500mg /} l was added, and adjusted to pH8 with aqueous sodium hydroxide, was stirred for 20 minutes to produce a gel-like floc, an anionic polymer coagulant 5ppm the added but solid-liquid separation is difficult Met.

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 000005979 Mitsubishi Corporation 2-6-3 Marunouchi, Chiyoda-ku, Tokyo (74) The above three agents 100074505 Patent Attorney Toshiaki Ikeura (72) Inventor Kenji Tatsumi Ibaraki 16-3 Onogawa, Tsukuba, Japan Prefectural Institute of Advanced Industrial Science and Technology (72) Inventor Shinji Wada 16-3 Onogawa, Tsukuba, Ibaraki Pref.Research Institute of Natural Resources and Environmental Science (72) Inventor Yasuhiro Yukawa Ibaraki 2-1-6 Tsugen, Sengen Tsukuba Mitsubishi Corporation Project Development Department Environmental Resources Research Laboratory F-term (Reference) 4D015 BA11 BA19 BA21 BB12 BB14 CA20 DB07 DB12 DB15 DB32 DB33 DC08 EA15 EA32 EA33 EA39 4D038 AA08 AB40 BB13 BB18 4D062 BA11 BB12 CA20 DB07 DB12 DB15 DB32 DB33 DC08 EA15 EA32 EA35 EA39 FA01

Claims (7)

[Claims] 1. A method for removing dissolved fluorine ions contained in water to be treated, wherein the pH is adjusted to 6 to 9 in the presence of aluminum ions and phosphate ions so that the dissolved fluorine ions are hardly soluble substances. A method for removing fluorine ions, comprising: 2. A method for removing dissolved fluorine ions contained in water to be treated, the method comprising the steps of:
Alternatively, a method for removing fluorine ions, comprising adjusting the pH to 6 to 9 in the presence of a hydrolysis product thereof to precipitate the dissolved fluorine ions as a poorly soluble substance. 3. The hydrophilic high molecular substance having a carboxyl group comprises (i) alginic acid or a salt thereof or (ii) a mixture of alginic acid or a salt thereof and another hydrophilic high molecular substance having an anion group. Removal method. 4. The method according to claim 1, wherein a coagulant is added. 5. An agent for removing dissolved fluoride ions contained in water to be treated, comprising (i) a phosphate compound and (ii)
A fluorine ion remover comprising an aluminum compound and (iii) a carboxyl group-containing hydrophilic polymer substance and / or a hydrolysis product thereof. 6. The carboxyl group-containing hydrophilic polymer substance comprises (i) alginic acid or a salt thereof or (ii) a mixture of alginic acid or a salt thereof and another hydrophilic polymer containing an anion group. Remover. 7. The removing agent according to claim 5, wherein the phosphoric acid compound is phosphoric acid.