JP3491022B2 - Fluorine ion removal method and remover - 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 and a fluorine ion removing agent.

[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 sedimentation method in which lime or slaked lime is added to the water to precipitate the fluorine ions as calcium fluoride. Has been done. In this method, high concentration (100m
g / L or more) fluoride ion at a medium concentration (10 to 20 mg)
/ L), it is almost impossible to remove to a low concentration (10 mg / l or less) even if a large amount of calcium salt is used. In the calcium coagulation precipitation method, 10
Since it cannot be removed below mg / L, several methods have been studied as methods for removing fluoride ions at low concentrations. 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. In particular, when the fluorine ion is present at a high concentration, a method of performing one-step treatment with calcium hydroxide to 20 to 30 ppm and then the two-step treatment described above is being investigated. In this case, dissolved calcium generated by the one-step treatment is being investigated. Therefore, it is the current situation that makes the treatment more difficult and increases sludge.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a method for efficiently removing dissolved fluorine ions from water, particularly water containing a large amount of calcium ions, with a reduced sludge generation amount, and a fluorine ion used therefor. It is an object to provide a removing agent.

[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, in a method for removing dissolved fluorine ions contained in water to be treated, in the water, calcium ion, phosphate ion and carboxyl group-containing hydrophilic polymer substance and / or its hydrolysis product. Alkaline substance is added in the presence of
Adjustment to adjust the dissolved fluorine ion as a sparingly soluble substance .
The ratio is such that the carboxyl group-containing hydrophilic polymer substance and /
Or 10 to 1000 per 1 part by weight of its hydrolysis product
There is provided a method for removing fluorine ions, which is characterized in that the ratio is 0 part by weight . Further, according to the present invention, there is provided a chemical agent for removing dissolved fluorine ions contained in water to be treated, which comprises (i) a phosphate compound and (ii) a carboxyl group-containing hydrophilic polymer substance and / or its hydrolysis product. Thing and body
The ratio of the phosphate compound is
1 part by weight of aqueous polymeric substance and / or hydrolysis product thereof
There is provided a fluoride ion removing agent characterized in that the ratio is 10 to 10,000 parts by weight .

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine ion removing agent of the present invention (hereinafter also simply referred to as a removing agent) comprises a mixture of a phosphoric acid compound and a carboxyl group-containing hydrophilic polymer substance and / or a hydrolysis product thereof. It is a thing. Examples of the phosphoric acid compound include phosphoric acid (H ₃ PO ₄ ) and compounds that hydrolyze in water to generate phosphoric acid, such as sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and phosphoric acid. Examples thereof include potassium, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium hexane metaphosphate, and sodium tripolyphosphate. The removing agent of the present invention is used in the form of powder or aqueous solution.

[0006] The carboxyl group-containing hydrophilic polymer substance includes various water-soluble polymer substances. Such polymeric substances include alginic acid, dielan gum, xanthan gum, pectin, pectic acid, pectinic acid, anionized starch, propylene glycol alginate, carboxymethyl cellulose, starch glycolic acid, polysaccharides such as fibrin glycolic acid and the like. Examples thereof include metal salts.

In the present invention, it is particularly preferable to use sodium alginate or calcium alginate, but when this is used, the content ratio of mannumamaronic acid (M) and guluronic acid (G) constituting the alginic acid (mol ratio)
[M] / [G] is 0.1 to 4.0, preferably 0.1.
It is preferable to use those in the range of 3 to 3. The higher the content ratio of guluronic acid, the better the floc forming property.

The above-mentioned carboxyl group-containing hydrophilic polymer substance used mainly as a removing agent 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.

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

In order to preferably produce the removing agent of the present invention,
First, a hydrophilic polymer substance containing a carboxyl group,
It is heated in water containing an alkaline substance to be 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 not boiling 70
C. or higher and lower than 100.degree. C. is preferable, more preferably
75 ° C to 90 ° C, more preferably 80 ° C to 85 ° C
Is. The heating time is not particularly limited as long as the carboxyl group-containing hydrophilic substance is dissolved, but is not limited to 0.5 hours to 2 hours. Next, the removing agent of the present invention can be produced by mixing the phosphoric acid compound with the alkaline aqueous solution containing the obtained carboxyl group-containing hydrophilic polymer substance and / or its hydrolysis product.

The ratio of the carboxyl group-containing hydrophilic polymer substance and / or its hydrolysis product to the phosphoric acid compound is not particularly limited, but in general, the carboxyl group-containing hydrophilic polymer substance and / or its hydrolyzate is generally used. 10 to 10,000 parts by weight of the phosphoric acid compound, preferably 50 to 5,000 parts by weight, and more preferably 100 parts by weight, relative to 1 part by weight of the decomposition product.
˜1000 parts by weight.

In order to remove the fluorine ions in the water to be treated according to the present invention, an alkaline substance may be added in the presence of a removing agent and calcium ions to adjust the pH to 10-13. If sufficient calcium ions are present in the water, it is not necessary to add the calcium compound. On the other hand, when there is no calcium ion in the water or the amount thereof is not sufficient, a calcium compound that gives calcium ion, such as calcium chloride or calcium hydroxide, may be added. In this case, the calcium compound and the removing agent may be added in any order. Further, it is preferable to use sodium hydroxide as the alkaline substance. The ratio of the remover to calcium is 1 to 1000 parts by weight of calcium to 1 part by weight of phosphorus in the remover,
Preferably 5 to 500 parts by weight, more preferably 10 to 1
The proportion is 00 parts by weight. The calcium concentration in water is
1000-50000 mg / L, preferably 5000-
It is 10000 mg / L.

When the fluorine ion dissolved in the water to be treated is removed by using the removing agent of the present invention, if the water to be treated is acidic or neutral, after the addition of the removing agent, precipitation may occur.
It is preferable to adjust H. Its pH is generally
It is in the range of 7 to 14, preferably in the range of 10 to 13.

When the fluorine ion dissolved in the water to be treated is removed using the removing agent of the present invention, an acidic substance is added to the water to be treated containing the precipitate generated by making the water to be treated alkaline. Flock can be further grown by making it sex.

When the pH of the water to be treated is adjusted to an alkaline range or an acidic range, a pH adjusting agent is used. Examples of such a pH adjusting agent include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, 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 together. The aggregating agent in this case is used for floc aggregating, and in such a thing,
Cationic modified polyacrylamide, polyacrylic acid dimethylaminoethyl ester, polymethacrylic acid dimethylaminoethyl ester, polyethyleneimine, cationic organic flocculant such as chitosan, nonionic organic flocculant such as polyacrylamide, polyacrylic Anionic organic flocculants such as acids, copolymers of acrylamide and acrylic acid and salts thereof are included. The amount of the flocculant used is, in terms of concentration in water, 1 to 20 mg / L, preferably 3 to 10 mg / L.

The water to be treated containing flocs after the pH adjusting step is subjected to solid-liquid separation treatment. Examples of the solid-liquid separation method in this case include conventional methods such as filtration separation, centrifugation and sedimentation separation.

The treatment water to be used in the present invention, the dissolved fluoride ions (F ^-) is intended to include various industrial wastewater are used. The fluorine ion concentration in the water to be treated is 10 mg / L or more, particularly 15 mg / L or more, as a fluorine atom (F). The upper limit is about 50 mg / L.

[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. 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.

Reference Example 1 In a 500 ml beaker, 2% sodium alginate was added to 300 ml of 1N NaOH, and then 75 ° C. to 8 ° C.
Heat to 5 ° C. and stir for 30 minutes to 1 hour. The stirred solution was allowed to cool to room temperature (25 to 35 ° C.), and then 300 ml of the sodium alginate solution at room temperature and 5700 ml of 85% phosphoric acid solution were mixed in a 10 L beaker. Thus, the removing agent of the present invention was obtained.

Example 1 Fluorine concentration in raw water was 424.29 ppm and pH was 2.3.
With the wastewater of No. 3, 66% calcium hydroxide was used as the primary treatment.
After adjusting the pH to 13 by adding 00 ppm, the pH was adjusted to 7 to 8 with sulfuric acid. Then, 5 ppm of an anionic polymer flocculant is added. The clear water obtained by this treatment had a fluorine ion concentration of 24.49 ppm and a calcium concentration of 1384 ppm. The clear water obtained by this primary treatment was subjected to the following treatments. (1) Existing treatment A To the clear water obtained by the primary treatment, polyaluminum chloride (P
After addition of AC), the pH was adjusted to 13 with calcium hydroxide and then to 7 to 8 with sulfuric acid. After that, the fluorine ion concentration of the clear water obtained by adding 5 ppm of the anionic polymer flocculant was analyzed. The results are shown in the table below.

[Table 1] (2) Existing treatment B Phosphoric acid solution was added to the clear water obtained by the primary treatment as phosphorus 1
After adding 00 ppm, the pH was adjusted to 13 with calcium hydroxide. Then, the fluorine ion concentration of the clear water obtained by adding 5 ppm of the anionic polymer flocculant was analyzed, and as a result, it was 20.19 ppm. (3) Treatment of the present invention 100 pp of the removing agent of the present invention is added to the clear water obtained by the primary treatment.
After adding m, the pH was adjusted to 11 with sodium hydroxide. After that, as a result of analyzing the fluorine ion concentration of the clear water obtained by adding 5 ppm of the polymer flocculant, the fluorine ion concentration was removed up to 3.82 ppm.

Example 2 Fluorine concentration in raw water was 712.26 ppm and pH was 9.5.
Effluent of 700, calcium hydroxide as a primary treatment
After adjusting the pH to 12.5 by adding 0 ppm,
The pH was adjusted to 7-8 with sulfuric acid. After that, as a result of analyzing the fluorine ion concentration of the clear water obtained by adding 5 ppm of the polymer flocculant, the fluorine ion concentration was 1
It was removed up to 4.19 ppm. (1) Existing treatment After adding 3,000 ppm of PAC to the clear water obtained by the primary treatment, the pH was adjusted to 13 by adding 3000 ppm of calcium hydroxide, and then adjusted to 7 to 8 with sulfuric acid. Then, the fluorine ion concentration of the clear water obtained by adding 5 ppm of the anionic polymer flocculant was analyzed, and as a result, it was 11.75 ppm. (2) Treatment of the present invention In the clear water obtained by the primary treatment, 100 ppm of the removing agent of the present invention
After the addition, the pH was adjusted to 10 with sodium hydroxide.
After that, as a result of analyzing the fluorine ion concentration of the clear water obtained by adding the polymer flocculant at 5 ppm,
The fluorine ion concentration was removed up to 3.73 ppm.

Example 3 100 ppm of the removing agent of the present invention was added to waste water having a fluorine concentration of 25.86 ppm and a pH of 8.67, and the pH was adjusted to 13 with sodium hydroxide. After that, add 5 p of polymer flocculant
As a result of analyzing the fluorine ion concentration of the clear water obtained by adding pm, the fluorine ion concentration was 4.55.
It was removed up to ppm.

─────────────────────────────────────────────────── ─── Continuation of the front page (73) Patent holder 000005979 Mitsubishi Corporation 2-3-6 Marunouchi, Chiyoda-ku, Tokyo (74) The above three agents 100074505 Patent Attorney Toshiaki Ikeura (72) Inventor Kenji Tatsumi 16-3 Onogawa, Tsukuba, Ibaraki, Institute of Natural Resources and Environmental Technology, Institute of Industrial Technology (72) Inventor, Shinji Wada, 16-3, Onogawa, Tsukuba, Ibaraki, Institute of Resources, Environmental Technology (72) Inventor, Yasuhiro Yukawa, Ibaraki 2-3-10 Ninomiya, Tsukuba, Japan Century Clock Tower 1205 (56) References JP-A 1-236202 (JP, A) JP-A 5-293474 (JP, A) JP-A 6-23371 ( JP, A) JP 6-182349 (JP, A) JP 8-1197 (JP, A) JP 1-310791 (JP, A) JP 49-90273 (JP, A) JP 50-105578 (JP, A) JP 51-79957 (JP, A) JP 56-70893 (JP, A) JP 60-202788 (JP, A) JP 61-4515 (JP , A) Japanese Patent Publication No. 53-42743 (JP, B2) International Publication 99/031017 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/58 C02F 1/52

Claims (7)

(57) [Claims] 1. A method for removing dissolved fluorine ions contained in water to be treated, wherein the hydrophilic ion containing calcium ion, phosphate ion and carboxyl group and / or its hydrolysis product is present in the water. By adding an alkaline substance to adjust the pH to 10 to 13 to precipitate the dissolved fluorine ion as a hardly soluble substance , and the proportion of the phosphate compound is
Sil group-containing hydrophilic polymer substance and / or its hydrolyzed product
10 to 10000 parts by weight per 1 part by weight of the product
A method for removing fluorine ions, which is characterized in that Wherein said alkaline material The method of claim 1 which is sodium hydroxide. Wherein said carboxyl group-containing hydrophilic polymeric substance, according to claim 1 comprising a mixture of (i) alginic acid or a salt thereof, or (ii) alginic acid or a salt thereof with other anionic group-containing hydrophilic polymeric substance 2 ) The removal method according to any one of 2 ). Wherein any of the method for removing of claim 1-3 for adding a coagulant. 5. An agent for removing dissolved fluorine ions contained in water to be treated, which comprises (i) a phosphate compound and (ii)
A hydrophilic polymer containing a carboxyl group and / or a hydrolysis product thereof, and the proportion of the phosphoric acid compound is
Hydrophilic polymer containing carboxyl group and / or addition thereof
10 to 10000 parts by weight per 1 part by weight of water decomposition product
A fluorine ion remover characterized by a ratio . 6. The hydrophilic polymer substance containing 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 polymer substance containing an anion group. Remover. 7. The removing agent according to claim 5, wherein the phosphoric acid compound is phosphoric acid.