JP3364833B2 - How to remove fluorine ions - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing dissolved fluorine ions contained in water to be treated.

[0002]

2. Description of the Related Art Conventionally, the most common method for removing the fluorine ions contained in the water to be treated is the calcium coagulation precipitation method in which lime or slaked lime is added to the water to precipitate the fluorine ions as calcium fluoride. Has been done to. In this method, high concentration (100 mg /
l or more) Medium concentration of fluoride ion (10 to 20 mg / l)
However, even if a large amount of calcium salt is used, it is almost impossible to remove to a low concentration (10 mg / l or less). In the calcium coagulation sedimentation method, 10 mg of fluoride ion was added as described above.
Since it cannot be removed below 1 / l, 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 the case of this method, the adsorbent cost is considerably high, and the treatment conditions are severely restricted, and there are problems such as regeneration of the adsorbent, It has hardly been put to practical use. In addition, there is an aluminum method in which an aluminum hydroxide forming agent is added to generate a sparingly water-soluble gel-like aluminum hydroxide and fluorine ions in water are adsorbed and removed to the aluminum hydroxide gel. Since a large amount of aluminum compound must be added, and flocs having good sedimentation and dehydration properties cannot be obtained, dehydration is difficult and a large amount of sludge is generated. Several treatment methods other than these have been investigated, but all have many problems, and fluoride ion is 10 mg /
At present, it cannot be removed below 1.

[0003]

An object of the present invention is to provide a method for efficiently and almost completely removing dissolved fluorine ions contained in water to be treated.

[0004]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a method of removing dissolved fluorine ions contained in the for-treatment water after the solution exist fluorine ions are insolubilized by reaction with the calcium compound with the addition of calcium compound in the water, the non Dissolution
An anionic group-containing hydrophilic polymer substance and an iron salt additive are added, the anion group-containing hydrophilic polymer substance is dispersed in water in an insoluble state, and the iron salt is dissolved in water. A method for removing fluorine ions is provided. Further, according to the present invention, in the method for removing the dissolved fluorine ions contained in the water to be treated, the aluminum hydroxide forming agent, the non-dissolved anionic group-containing hydrophilic polymer and the iron salt are contained in the water. An additive is added to form aluminum hydroxide from the aluminum hydroxide forming agent in the water, and the anionic group-containing hydrophilic polymer substance is dispersed in water in a non-dissolved state, and the iron salt is There is provided a method for removing fluoride ions, which is characterized by being dissolved in water.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the first method of the present invention, in order to remove fluorine ions dissolved in water to be treated, a calcium compound is added to the water and the fluorine ions are reacted with the calcium compound. After the conversion to insoluble calcium fluoride, a step of adding an additive composed of a non-dissolved anionic group-containing hydrophilic polymer and an iron salt is included. The calcium compound may be any compound that reacts with fluorine ions in water to generate calcium fluoride, and various water-soluble compounds can be used. Examples of such substances include calcium chloride, calcium sulfate, calcium oxide, calcium hydroxide, and calcium nitrate. The second method of the present invention is to
It includes a step of adding an aluminum hydroxide forming agent, an anionic group-containing hydrophilic polymer substance in a non-dissolved state, and an additive composed of an iron salt. As a result, gelled aluminum hydroxide is formed in the water by the aluminum hydroxide forming agent , the anionic group-containing hydrophilic polymer in the undissolved state is dispersed in the undissolved state , and the iron salt is dissolved. To be done. Dissolved fluorine ions contained in water are adsorbed (captured) by gel-like aluminum hydroxide and removed from water. The aluminum hydroxide-forming agent may be any one that can be hydrolyzed in water to form gel aluminum hydroxide, and various conventionally known materials can be used.
Examples of such a material include aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, sodium aluminate, and the like. The timing for adding the aluminum hydroxide forming agent is before, after, or simultaneously with the addition of the additive, and is not particularly limited.

When the dissolved fluorine ion is removed from the water to be treated containing the dissolved fluorine ion, when the dissolved fluorine ion is in a relatively large amount, for example, 30 mg / l or more, particularly 50 mg / l or more, calcium is used. It is preferred to add the compound. In this case, the amount of the calcium compound added is 0.5 to 10 per mol of the fluorine atom.
The molar ratio is preferably 1 to 5 mol. The upper limit of dissolved fluorine ions in the water to be treated is not particularly limited, but is usually about 1000 mg / l.

When the dissolved fluorine ion is removed from the water to be treated containing the dissolved fluorine ion, when the dissolved fluorine ion is in a small amount, for example, 10 to 30 mg / l, particularly 1
In the case of 0 to 25 mg / l, it is preferable to add an aluminum hydroxide forming agent. In this case, the addition amount is as aluminum atom per mol of fluorine atom,
The ratio is 0.5 to 10 mol, preferably 1 to 5 mol.

The method of the present invention, as described above, uses a non-dissolved form.
The method includes a step of adding an additive consisting of anionic group-containing hydrophilic polymer (hereinafter, also simply referred to as polymer) and iron salt, in which case the pH of the water to be treated before the additive is added. Is usually 1 to 8, preferably 2 to 7.

The anion group-containing hydrophilic polymer substance used as an additive component in the present invention includes various water-soluble polymer substances containing anion groups such as a carboxyl group, a sulfonic acid group and a phosphoric acid group, Although both natural products and synthetic products can be used, those having biodegradability are preferred from the viewpoint of environmental protection. As such a high molecular substance,
Alginic acid, dielan gum, xanthan gum, tragacanth gum, pectin, pectic acid, pectinic acid, carrageenan, gelatin, agar, anionized starch, alginic acid propylene glycol ester, carboxymethyl cellulose, starch glycolic acid, fibrin glycolic acid, starch phosphoric acid, galactomannan, etc. Polysaccharides and metal salts thereof; polyacrylic acid, copolymers of acrylamide and acrylic acid and metal salts thereof; superabsorbent polymers (eg, Sumitomo Chemical Co., Ltd., “Sumika Gel”, Sanyo Chemical Co., Ltd., Sunwet ", Showa Denko KK," Pre-Apple ", Nitto Kagaku KK," WAS ", etc.) and the like.

In the present invention, it is particularly preferable to use alginic acid and its salt, but when this is used, the content ratio (molar ratio) of mannuronic acid (M) and guluronic acid (G) constituting the alginic acid. ) [M] / [G] is 0.1
It is preferable to use those in the range of -4.0, preferably 0.1-3. The higher the content ratio of guluronic acid, the better the floc forming property due to the reaction with the polyvalent cation. As the alginate, Na salt, Ca salt, Mg salt,
Al salt etc. are mentioned. These anionic group-containing hydrophilic polymer substances are in powder form (including short fiber form) or undissolved state
Used in the liquid form. When used in powder form, the average particle size is 10 to 500 μm, preferably 20 to 20 μm.
It is 0 μm, more preferably 50 to 150 μm. On the other hand, when used in the form of undissolved state liquid, the liquid may be an aqueous liquid containing dispersed anionic group-containing hydrophilic substance in a non-dissolved form. The liquid in this case includes
Water, water / organic solvent mixtures and organic solvents are included,
Usually, it is water or an aqueous solution of an organic solvent. The anionic group-containing hydrophilic polymer substance used in the present invention 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 this case, the mixture containing alginic acid or a salt thereof includes (i) alginic acid or a salt thereof and (ii) at least one hydrophilic selected from dielan gum, xanthan gum, pectin, pectic acid, pectinic acid and salts thereof. It is a mixture with a polymeric substance. For example, when a mixture of sodium alginate and another anionic group-containing hydrophilic polymer substance is used, the weight ratio of sodium alginate (A) to another anion group-containing hydrophilic polymer substance (B) [A] / [ B] is 1 to 100, preferably 2
~ 50.

The iron salt used as an additive component in the present invention is
It is a water-soluble iron salt. Examples of the iron salt include iron salts such as ferrous sulfate, ferric sulfate, ferrous chloride and ferric chloride.
These iron salts form an ionic bond or a chelate bond with respect to the anionic group-containing hydrophilic polymer substance, and exhibit the action of controlling the solubility of the polymer substance.

The additive used in the present invention can be a powdery mixture of a non-dissolved polymer substance and an iron salt, an aqueous liquid mixture, or the like. In the case of an aqueous liquid mixture, the polymer substance does not dissolve in the aqueous liquid but exists in a dispersed state. The addition ratio of the polymer substance is 0.01 to 50 parts by weight per 100 parts by weight of the calcium compound added in water,
It is preferably 0.1 to 10 parts by weight. The ratio is 0.1 to 50 parts by weight, preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the aluminum hydroxide forming agent added to water. On the other hand, the addition amount of iron salt is not particularly limited,
It is appropriately selected depending on the pH of the water to be treated, etc.
1 to 10000 parts by weight, preferably 20 to 5000, relative to 100 parts by weight of the anionic group-containing hydrophilic polymer substance.
The ratio is parts by weight.

It is preferable to use a cationic group-containing hydrophilic polymer substance in combination with the additive used in the present invention. In this case, the cationic group-containing hydrophilic polymer substance contributes to the enlargement of flocs. Examples of such substances include chitosan, polyacrylamide cationized modified products, polyacrylic acid dimethylaminoethyl ester, and polyacrylic acid dimethylaminoethyl ester. Methacrylic acid dimethylaminoethyl ester, polyethyleneimine and the like are included. In the present invention, it is preferable to use a polymer substance having an amino group or a cation group (such as a quaternary ammonium group), particularly chitosan. In this case, chitosan is preferably used as a mixture with another cationic group-containing hydrophilic polymer substance such as polyacrylic acid dimethylaminoethyl ester.

The cationic group-containing hydrophilic polymer substance is used in the form of powder or aqueous solution. The use ratio of this substance is 0.1 to 500 parts by weight, preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the anionic group-containing hydrophilic polymer substance.
The ratio is 0 part by weight. When chitosan is used as an aqueous solution, it is preferably prepared with an organic acid solution including an acetic acid solution, but it is also prepared with an inorganic acid solution such as hydrochloric acid. The cationic group-containing hydrophilic polymer substance may be added after addition of the additive.

In the polymer substance used in the present invention, it is preferable to use a coagulant together. In this case, the flocculant is used for floc flocculation, and examples of such flocculants include chitosan, calcium chloride, bis (phosphoric acid 2
Hydrogen) calcium, cationized modified polyacrylamide, polyacrylic acid dimethylaminoethyl ester,
Cationic organic flocculants such as polymethacrylic acid dimethylaminoethyl ester, polyethyleneimine and chitosan, nonionic organic flocculants such as polyacrylamide,
Anionic organic flocculants such as polyacrylic acid, copolymers of acrylamide and acrylic acid, and salts thereof are included. The coagulant may be added after the additive is added.

It is preferable to use a floc sedimentation accelerator together with the polymer substance used in the present invention. Any insoluble fine particles having a large specific gravity can be used as this. Its specific gravity is 3 or more, preferably 4.5 or more, and its average particle size is 1 to 100 μm.
m, preferably 30 to 70 μm. Examples of such a material include barium sulfate, fine metal particles (for example, Fe, Ti, etc.), barite, and the like. The usage rate is
1 per 100 parts by weight of anionic group-containing hydrophilic polymer
-60 parts by weight, preferably 5-30 parts by weight. The floc sedimentation accelerator may be added after the additive is added.

In the present invention, a calcium compound or an aluminum hydroxide forming agent is added to water to be treated, and then the water is not dissolved.
After adding an additive consisting of a high molecular weight substance and iron salt,
When the water to be treated is acidic, alkali is added to adjust the pH of the water to be treated to a range of 7 to 10, preferably 7 to 8. By this pH adjustment, coagulation and precipitation of insolubilized fluorine is promoted. The addition amount may be an amount that maintains the pH of the water to be treated within the above range. Examples of the alkali include sodium hydroxide, sodium carbonate, calcium hydroxide, magnesium hydroxide and the like.

The water to be treated after the pH adjustment step is subjected to solid-liquid separation treatment. As a solid-liquid separation method in this case,
Conventional methods such as filtration separation, centrifugation, sedimentation separation and the like can be mentioned.

[0019]

According to the method of the present invention, dissolved fluorine ions contained in water as water to be treated can be efficiently removed with a reduced sludge generation amount. In this case, the pH of the water to be treated is usually 0-9, especially 1
~ 8. The content of fluorine ion is usually 1
It is 0 to 10,000 ppm. In the method of the present invention, the amount of generated sludge is small, and the amount of generated sludge is usually 10 parts by weight or less per 100 parts by weight of the water to be treated.
According to the present invention, the fluorine ion in the water to be treated can be almost completely removed, and the dissolved fluorine ion contained in the treated water after removing the fluorine ion is 10 ppm or less, preferably 8 ppm or less, more preferably 5 ppm. It is the following.

[0020]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 A 37.5 wt% aqueous solution of ferric chloride (for industrial use) was adjusted to pH 1 with sodium hydroxide, stirred at 80 ° C. or higher for 3 hours, added with sodium alginate (4.8 wt%) and stirred for 3 hours. When it did, it became a brown suspension. This was used as an additive [I]. In this additive [I], algin
Sodium acid exists in a non-dissolved state. Sodium fluoride was dissolved in pure water at a concentration of 221 mg / L to adjust the fluorine ion concentration to 100 ppm to obtain model drainage.
After adding 1000 ppm of calcium chloride, 100 ppm of additive [I] was added to this liquid. This solution was stirred for 5 minutes, adjusted to pH 7 with sodium hydroxide, and then solid-liquid separated. When the residual fluorine concentration of the treated water was measured, 4.
It was 1 ppm. The fluoride ion concentration when treated with calcium chloride alone without adding the additive [I] was 44.5 ppm. Moreover, the flocs at that time were very small and in a colloidal form, and even if a polymer flocculant was added, grown flocs could not be obtained. On the other hand, when the additive [I] was added, grown flocs could be obtained without adding the polymer flocculant. Furthermore, by adding 3 ppm of a polymer flocculant, it was possible to grow stronger and more stable flocs. in this way,
The remarkable effect of the additive [I] was observed on the floc formation state and the effect of removing the fluorine ion concentration.

Example 2 In Example 1, ferrous chloride (for industrial use) 37.5 wt
% Aqueous solution was adjusted to pH 1 with sodium hydroxide, 4.8% by weight of sodium alginate was added, and the mixture was stirred for 3 hours. Then, the additive [Ia] obtained was used in place of the additive [I] to conduct an experiment. As a result, the same treatment effect was recognized.

Example 3 Additive obtained in Example 1 by stirring 20 wt% aqueous solution of ferric chloride (reagent) at 80 ° C. or higher for 3 hours, then adding 2.4 wt% of sodium alginate and stirring for 3 hours. [I
As a result of conducting an experiment using I] instead of the additive [I], the same treatment effect was observed.

Example 4 In Example 1, the additive [IIa] obtained by adding 2.4% by weight of sodium alginate to a 20 wt% aqueous solution of ferric chloride (reagent) and stirring for 3 hours was added to the additive [I ], The same treatment effect was recognized as a result of experiment.

Example 5 12% by weight of anionic group-containing hydrophilic polymer (sodium alginate (Pronova Biopolymer)
Manufactured by the company, the molar ratio of mannuronic acid (M) and guluronic acid (G) [M] / [G]: 1/1) and ferrous sulfate heptahydrate 8
50 ppm of the additive [III] consisting of 8% by weight was added to the above fluorine model wastewater after adding 1000 ppm of calcium chloride and stirring for 30 minutes. The fluorine concentration measured after solid-liquid separation was 4.2 ppm.

Example 6 Wastewater from an actual plant containing 433 pm of fluorine and ammonia (pH
Calcium hydroxide was added to 4.1) until the pH reached 10.0, and the mixture was stirred for 30 minutes. Next, add 100 p of additive [I]
After the addition of pm, 4 ppm of an anionic coagulant was added, and the mixture was stirred for 5 minutes, followed by solid-liquid separation. The fluorine concentration at that time was measured and found to be 5.21 ppm.

Example 7 Instead of the additive [I] in Example 6, the additive [Ia],
Similar fluorine removal rates were obtained using any of [II], [IIa], and [III].

Example 8 Polyaluminum chloride (PAC) was added to the model waste water having a fluorine ion concentration of 20 ppm as Al in an amount of 50 ppm to obtain 5
After stirring for minutes, 100 ppm of the additive [I] was added. The solution was stirred for 5 minutes, adjusted to pH 7 with sodium hydroxide, added with 2 ppm of an anionic flocculant, and subjected to solid-liquid separation. When the residual fluorine concentration of the treated water was measured, it was 3.5
It was ppm.

Example 9 50 ppm of sodium aluminate as Al was added to the above fluorine model waste water and stirred for 5 minutes, and then 100 parts of the additive [I] was added.
ppm was added. After stirring this solution for 5 minutes, adjust the pH to 7 with sodium hydroxide, and then add 5 pp of anionic coagulant.
After the addition of m, solid-liquid separation was performed. When the residual fluorine concentration in the treated water was measured, it was 3.3 ppm.

Example 10 50 ppm of aluminum sulfate as Al was added to the above fluorine model waste water and stirred for 5 minutes, and then 100 parts of the additive [I] was added.
ppm was added. After stirring this solution for 5 minutes, the pH was adjusted to 7 with sodium hydroxide, and then the anionic flocculant 3 pp was added.
After the addition of m, solid-liquid separation was performed. When the residual fluorine concentration in the treated water was measured, it was 4.6 ppm.

Example 11 Instead of the additive [I] of Examples 6 to 8, the additive [I] was used.
Similar fluorine removal rates were obtained using any of a], [II], [IIa], and [III].

Example 12 100 ppm of the additive [I] was added to model wastewater having a fluorine ion concentration of 20 ppm, and the mixture was stirred for 5 minutes.
Was added as 50 ppm. After stirring this solution for 5 minutes,
After adjusting the pH to 7 with sodium hydroxide, solid-liquid separation was performed after adding 2 ppm of an anionic coagulant. When the residual fluorine concentration of the treated water was measured, it was 3.7 ppm.

Example 13 100 pp of the additive [I] was added to the above fluorine model wastewater.
After adding m and stirring for 5 minutes, use sodium aluminate as Al
0 ppm was added. After stirring this solution for 5 minutes, the pH was adjusted to 7 with sodium hydroxide, and then the anionic flocculant 5 p
After adding pm, solid-liquid separation was performed. The residual fluorine concentration of the treated water was measured and found to be 3.2 ppm.

Example 14 100 pp of the additive [I] was added to the above fluorine model wastewater.
After adding m and stirring for 5 minutes, aluminum sulfate was changed to Al to 5
0 ppm was added. After stirring this solution for 5 minutes, the pH was adjusted to 7 with sodium hydroxide, and then the anionic flocculant 3 p
After adding pm, solid-liquid separation was performed. When the residual fluorine concentration in the treated water was measured, it was 3.8 ppm.

Example 15 Similar fluorine removal rates were obtained by using any of the additives [Ia], [II], [IIa] and [III] instead of the additive [I] in Examples 12 to 14. Was obtained.

Example 16 100 ppm of additive [I] and 50 ppm of PCA as Al were added to model wastewater having a fluorine ion concentration of 20 ppm.
Is added at the same time and stirred for 5 minutes, then pH is adjusted with sodium hydroxide
After adjusting to 7, the solid-liquid separation was performed after adding 2 ppm of the anionic coagulant. When the residual fluorine concentration of the treated water was measured,
It was 4.1 ppm.

Example 17 100 pp of the additive [I] was added to the above fluorine model wastewater.
m and sodium aluminate were added at 50 ppm at the same time as Al, stirred for 5 minutes, adjusted to pH 7 with sodium hydroxide, added with 5 ppm of an anionic flocculant, and subjected to solid-liquid separation. When the residual fluorine concentration of the treated water was measured, it was 3.8.
It was ppm.

Example 18 100 pp of the additive [I] was added to the above fluorine model wastewater.
m and aluminum sulfate as Al at 50 ppm were added at the same time, stirred for 5 minutes, adjusted to pH 7 with sodium hydroxide, added with 3 ppm of anionic coagulant, and subjected to solid-liquid separation. When the residual fluorine concentration of the treated water was measured, it was 3.6.
It was ppm.

Example 19 The same fluorine removal rate was obtained by using any of the additives [Ia], [II], [IIa] and [III] in place of the additive [I] in Examples 16 to 18. Was obtained.

Continuation of front page (73) Patent holder 000005979 Mitsubishi Corporation 2-3-6 Marunouchi, Chiyoda-ku, Tokyo (74) Attorney of the above 3 persons 100074505 Attorney Toshiaki Ikeura (72) Inventor Kenji Tatsumi Tsukuba, Ibaraki Prefecture 16-3 Onogawa City, Institute of Industrial Science and Technology (72) Inventor, Shinji Wada, Tsukuba City, Ibaraki Prefecture 16-3 Onogawa Institute, Institute of Natural Resources and Environment (72) Inventor, Yasuhiro Yukawa, Tsukuba, Ibaraki Prefecture Ninomiya 2-chome Century Clock Tower No. 1 205 (56) Reference JP-A-50-15356 (JP, A) JP-A-50-105578 (JP, A) JP-A-3-109993 (JP, A ) JP-A-56-70893 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/58 C02F 1/56

Claims (6)

(57) [Claims] 1. A method for removing dissolved fluorine ions contained in water to be treated, wherein a calcium compound is added to the water to cause the dissolved fluorine ions to react with the calcium compound to insolubilize it, and then a non-dissolved state is obtained. An additive comprising an anion group-containing hydrophilic polymer substance and an iron salt is added, the anion group-containing hydrophilic polymer substance is dispersed in water in a non-dissolved state, and the iron salt is dissolved in water. And a method for removing fluorine ions. 2. A method for removing dissolved fluorine ions contained in water to be treated, comprising: an aluminum hydroxide forming agent in the water; an additive consisting of a non-dissolved anionic group-containing hydrophilic polymer and an iron salt. Is added to form aluminum hydroxide from the aluminum hydroxide forming agent in the water, the anionic group-containing hydrophilic polymer is dispersed in water in an insoluble state, and the iron salt is dissolved in water. A method for removing fluorine ions, which comprises: 3. The concentration of dissolved fluorine ions contained in the water to be treated is 30 mg / l or more, and the pH of the treated water after removing the dissolved fluorine ions from the water is 7 to 8.
The concentration of dissolved fluorine ions contained in the treated water is 8 mg /
The method of claim 1, which is 1 or less. 4. The concentration of dissolved fluorine ions contained in the water is 10 to 30 mg / l, the pH of the treated water after removing the dissolved fluorine ions from the water is 7 to 8, and the dissolved water contained in the treated water. The method according to claim 2, wherein the dissolved fluorine ion concentration is 8 mg / l or less. 5. The addition amount of the anionic group-containing hydrophilic polymer substance is 0.1 to 10 parts by weight per 100 parts by weight of the calcium compound or aluminum hydroxide forming agent added in water. Either way. 6. The method according to claim 1, wherein the amount of the iron salt added is 1 to 10000 parts by weight based on 100 parts by weight of the anionic group-containing hydrophilic polymer.