JPH0194948A - Fluorine ion removal method - Google Patents

Abstract

PURPOSE:To absorb and remove fluorine ions efficiently by treating aqueous solution containing fluorine ions with a bonded compound of chelate polymer with aminomethyl phosphonate multidentate ligand and metallic ions having an affinity to fluorine ions. CONSTITUTION:An aqueous solution containing fluorine ions is treated with a bonded compound of chelate polymer with an aminomethyl phosphonate multidentate ligand and metallic ions having an affinity to fluorine ions as shown in a formula I(n is 1 or 2). In this way, the fluorine ions are removed from the water. Chelate polymer which is a main component of the bonded compound (absorbent) can be manufactured by introducing the aminomethyl phosphonate multidentate ligand shown in the formula I into the base resin such as styrene, phenol or acrylate. When the above-mentioned adsorbent is used, the fluorine ions contained in industrial waste water can be efficiently removed at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for easily removing fluorine ions contained in aqueous solutions, such as industrial wastewater. To be more specific, one aspect of the present invention is IP! The present invention relates to a method for efficiently adsorbing and removing fluorine ions contained in water using a chelate resin having a constant f.

BACKGROUND OF THE INVENTION In recent years, the removal of fluorine ions from industrial wastewater has become an important issue due to problems such as environmental pollution.

Industrial wastewater containing fluorine ions is used in various processes, such as semiconductor manufacturing processes in the electronics industry, etching of germanium using hydrofluoric acid or ammonium heptadide, cleaning the inner surface of glass pulp for cathode ray tubes, etching in the glass industry, and etching of steel. Hydrofluoric acid is emitted from processes such as pickling of stainless steel, or pickling of stainless steel using a mixed acid of hydrofluoric acid and nitric acid, as well as hydrofluoric acid in waste gas generated during phosphate rock roasting furnaces and crystal stone electrolysis. Examples include gas cleaning wastewater containing fluorosilicic acid and fluorosilicic acid.

Conventionally, various methods have been used to treat fluoride ions in aqueous solutions such as wastewater, such as adding lime or slaked lime to the aqueous solution to precipitate and remove fluoride ions as CaF2, and using anion exchange resin. There are known methods for removing fluorine ions.

However, in the former method, the solubility of CaF2 is about 16 μ/l, and if lime or slaked lime is added in excess, the fluoride ion concentration should theoretically be able to be reduced considerably. However, in reality, it is difficult to remove fluorine ions to a desired low concentration due to the influence of coexisting substances.

On the other hand, in the latter method of removing fluoride ions using an anion exchange resin, the exchange order of anions in the anion exchange resin is OH) S04 > OH, and the selectivity for fluoride ions is extremely low. Since the influence of coexisting anions is large, this anion exchange resin is unsuitable for practical use.

In addition, a method of adsorbing and removing fluorine ions using iminodiacetic acid type chelate resin bound with metal ions such as iron ions and aluminum ions (Japanese Unexamined Patent Application Publication No. 1983-1995)
115058), a method of adsorbing and removing fluorine ions using an aminophosphoric acid type chelate resin bound with metal ions such as lanthanum ions (Japanese Unexamined Patent Publication No. 115058),
107287), but although these methods can selectively adsorb fluorine ions, during the regeneration treatment of the resin after adsorbing fluoride ions, metal ions are also removed along with fluoride ions. In order to be desorbed, a treatment must be performed to bond the metal ions again, which has the disadvantage that the regeneration treatment becomes complicated. This is because the stability of the complex formed between the ligand moiety of the chelate resin and the metal ion is insufficient, so when attempting to elute the adsorbed fluorine ions and regenerate the resin,
This seems to be because the metal ions are also desorbed from the resin.

Therefore, a fluoride ion adsorbent that can selectively and efficiently adsorb fluoride ions in an aqueous solution and can be regenerated through simple treatment has not been known so far.

Problems to be Solved by the Invention The present invention provides a method suitable for industrial implementation for selectively adsorbing fluorine ions in an aqueous solution onto a specific adsorbent and removing them efficiently. It was made for the purpose of

Means for Solving the Problems In order to develop a method that can efficiently remove fluorine ions contained in water, the present inventors have conducted various studies and have developed an aminomethylphosphonic acid type polydentate ligand. By using a combination of a chelate resin and a metal with ion affinity as an adsorbent, fluorine ions in water can be selectively and efficiently adsorbed and removed.
They discovered that scales can be regenerated into a reusable state simply by washing them with alkali, and that this adsorbent can be used to remove fluoride ions from aqueous solutions containing fluoride ions on an industrial scale. Based on these findings, the present invention has been completed.

In other words, the present invention provides a composite of a chelate resin having an aminomethylphosphonic acid type polydentate ligand represented by the general formula (n is 1 or 2) and a metal ion having an affinity for fluorine ions. , provides a method for removing fluorine ions in water, which is characterized by treating an aqueous solution containing fluorine ions.

The chelate α-fat that is a component of the adsorbent used in the method of the present invention can be produced by introducing an aminomethylphosphonic acid type polydentate ligand represented by the general formula (1) into a suitable base resin. .

As this base resin, for example, styrene resin, phenol resin, acrylate resin, etc. are used.

The introduction of the aminomethylphosphonic acid type polydentate ligand into the base resin involves introducing into the base resin a compound having a group capable of reacting with a reactive group present in the base resin and a group represented by the general formula (1). This can be done by reacting. For example, in order to introduce an aminomethylphosphonic acid type polydentate ligand into a styrene resin as a base resin, first, a styrene homopolymer, a copolymer of styrene and other vinyl compounds, or a crosslinked product of these or the like is used. A styrenic polymer, preferably a styrene-divinylbenzene copolymer, can be prepared by a known method [
“Journal of Chemical Society (J,C
hem, Soc, ) J No. 4097 page (195
3)] to produce chloromethylated polystyrene by introducing dichloromethyl groups.

Next, this chloromethylated polystyrene is reacted with diethylenetriamine in which the primary amino group has been protected, and this is introduced into a pendant form via the secondary amino group. Methylphosphonic acid is introduced into the amino group. The above-mentioned diethylenetriamine with a protected primary amino group can be obtained by, for example, reacting the primary amino group of diethylenetriamine with aldehydes or ketones such as salicylaldehyde, benzaldehyde, acetylacetone, etc. by a known method. A thick base type condensate can be used. Among these thick base type condensates, particularly preferred is diethylenetriamine-N,N'-disalicylideneiminate, which is obtained by condensation of diethylenetriamine and salicylaldehyde and is represented by the formula.

The reaction of the Schiff base type condensate with respect to the base resin is carried out by heating and refluxing the chloromethylated polystyrene and the Schiff base type condensate in a solvent such as dioxane, benzene, or ethanol while stirring. . Through this reaction, the secondary amino group of the thick base type condensate selectively reacts with the chloromethyl group of the chloromethylated polystyrene, and the thick base type condensate is introduced into the base resin via the secondary amino group. Introduced in pendant type.

The chelate resin obtained in this way does not have a crosslinked structure in the ligand part, and the Schiff base type condensate is introduced in a pendant form. The moieties are readily hydrolyzed and quantitatively converted to chelated m-fats containing pendant diethylenetriamine of the formula:

Next, this product is reacted with a methylphosphonate oxidizing agent to methylphosphonate the primary amino group of the diethylenetriamine residue in the chelate resin.
) is introduced into the resin matrix in a pendant form. As the methylphosphonic oxidizing agent, a combination of formalin and phosphorous acid is used.

The thus obtained chelate resin has a particle size of 30~
A range of 200 meshes is preferred.

In the present invention, the fluorine ionic affinity metal ion of the component to be bound to the chelate a-fat has an adsorption ability for fluoride ions and is capable of forming a complex with the polydentate ligand of the chelate a-fat. There is no particular limitation, but in order to prevent the metal ion from being desorbed from the chelate a fat during regeneration of the chelate resin, it is necessary to use a metal ion whose complex with the ligand is highly stable. is desirable. As such metal ions, metal ions in a high oxidation state with a valence of 1 or 2 are suitable, such as At, Fθ, and Zr.

Hf4+ or lanthanide ions such as La are suitable. These metal ions may be used alone or in combination of two or more.

Next, there are no particular restrictions on the method of bonding the metal ions to the chelate resin, and conventionally used methods such as immersing the chelate resin in an aqueous solution containing metal ions or filling the column with A method such as passing an aqueous solution containing metal ions through a chelate resin can be used. At this time, the pH of the aqueous solution containing metal ions is important; for example, when 8+ La is supported on an aminomethylphosphonic acid-type chelate resin based on polystyrene, the pH of the aqueous solution containing the metal ion is 2. It is preferable that the ridges are in the range of 5 to 6.5. If this pH is less than 2.5, the lower the pH, the more La'
” binding amount decreases, which is undesirable because it leads to a decrease in the adsorption amount of fluorine ions.
In the range of , the amount of La bound is constant at 1.1 mmol per 12 equivalents of the chelate resin; on the other hand, if it exceeds 6.5, La in the aqueous solution will precipitate as La(OH)3, making it difficult to remove. Difficult to handle.

As a method for adsorbing and removing fluorine ions using the chelate resin that binds metal ions to form a complex, for example, a column method or a batch method can be used, but they are easy to operate, and Column methods with excellent throughput are advantageous.

The pH of the aqueous solution containing fluorine ions that binds the metal ions and passes through the chelating resin is usually 2.5 to 2.5.
Selected within the range of 5.0. If the pH is less than 2.5, bound metal ions are likely to be desorbed, and if it exceeds 5.0, the rate of adsorption of fluorine ions is extremely slow and the ability to adsorb fluorine ions tends to decrease rapidly. The speed at which the liquid is passed depends on the concentration of fluorine ions in the liquid to be treated, but is usually selected within a volumetric rate of 5 to 10 hours.

After the fluoride ions in the liquid to be treated are adsorbed and removed in this way, according to the present invention, an alkaline aqueous solution is passed through the chelate resin that has adsorbed the fluoride ions, thereby removing the fluoride ions from the chelate resin. Elute quantitatively. This elution is.

This occurs through ligand exchange between the fluorine ion on the bound metal ion and OH- in the alkaline aqueous solution. Therefore, the type of alkaline aqueous solution to be passed may be one that contains OH"". Although there is no particular limitation, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, ammonia water, etc. are usually suitably used. Further, the concentration of the alkaline aqueous solution is preferably 0.1 to 2M as a range in which the elution of fluorine ions occurs quantitatively.

If this concentration is less than 0.1M, the concentration of OH- is too low and it is difficult to elute all the fluorine ions;
Exceeding this is not preferable since problems may arise in terms of alkali solubility and handling of alkaline aqueous solutions.

Even when such an alkaline aqueous solution with a concentration of 0.1 to 2M is passed through, no desorption of the bound metal ions is observed.
Therefore, in regenerating a resin that has adsorbed fluorine ions, by passing an alkaline aqueous solution through the chelate resin, it is possible to elute only fluorine ions without desorbing metal ions from the chelate resin. Further, the flow rate of the alkaline aqueous solution is usually selected within the range of 5 to 15 hours per volume.

In order to use the clean resin after passing through an alkaline aqueous solution for adsorption and removal of fluoride ions, the resin should be adjusted to pH 2.5 in order to return the hydroxide ions exchanged with fluoride ions to acidic water. Requires conditioning with an aqueous solution of ~5.0. If you omit this step and adsorb and remove fluoride ions immediately after passing the alkaline aqueous solution,
Since the pH of the liquid to be treated increases during passage through the column, the adsorption rate may decrease, and fluorine ions may leak out due to insufficient adsorption.

The pH used for this conditioning is 2.0-5.
As the aqueous solution having a pH of 0.0, a buffer solution commonly used within this pH range is suitable. Conditioning is possible using an acidic aqueous solution such as hydrochloric acid or nitric acid, but the ability to return the alkaline chelate resin to the acidic form is weaker than a buffer solution, so a large amount of aqueous solution is required, and treatment is difficult. Problems arise such as it takes a long time. Note that the liquid passing rate at this time is usually selected within the range of a volumetric rate of 5 to 15 h"-".

The chelate resin that has been conditioned in this way is no different from a new resin, and there is no discernible difference in its ability to adsorb fluorine ions.

In addition, in the adsorption and removal of fluorine ions, the aminomethylphosphonic acid type chelate resin bonded with metal ions has other anions such as Ct-1Nob, S
Even under conditions where O42-'' and the like coexist in an amount 100 times or more of fluorine ions, it is hardly affected by the coexistence of fluorine ions, and has extremely excellent adsorption selectivity for fluorine ions.

Effects of the Invention According to the method of the present invention, by using an aminomethylphosphonic acid type chelate resin bonded with a specific metal ion, fluoride ions contained in industrial wastewater etc. together with other anions can be selectively adsorbed and removed. can be done, and
It is possible to elute the adsorbed fluorine ions without desorbing the bound metal ions and regenerate the chelate resin so that it can be used repeatedly.

Therefore, the method of the present invention can efficiently adsorb and remove fluorine ions contained in industrial wastewater and the like with extremely simple operations and low processing costs, and can be said to be a method of extremely high industrial value.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Production Example Production of aminomethylphosphonic acid type chelate resin A gel-type styrene-divinylbenzene copolymer (content of divinylbenzene units: 2 mol%) was chloromethylated to produce chloromethylated polystyrene with a chlorine content of 20.8% by weight. Obtained.

In 400 pieces of dioxane, 34.6f of the chloromethylated polystyrene and diethylenetriamine-N,N'-
124 f of disalicylidene imina) was added thereto, and the mixture was refluxed for 48 hours with stirring. Next, the obtained yellow resin was filtered, 6N hydrochloric acid 600- was added to this resin, and the mixture was heated at 60°C.
By stirring for 24 hours, chelate resin 67.5f into which diethylenetriamine was introduced was obtained.

Next, 459 of the chelate resin obtained above and 822 of sonic acid were added to 200 g of 6N hydrochloric acid, heated to 100°C, and 2 g of formalin 160 was added to the mixture while stirring.
After dropping over a period of time, the mixture was refluxed for another 2 hours with stirring. This reaction product was filtered, washed with water, further washed with acetone, and then vacuum-dried at 50°C.
．． Obtained 3t. Since the nitrogen content of this resin is 6.5%, the capacity of the ligand contained in this resin is 1.
It was 54 mmol/9. The particle size of this chelate m-fat was 60-100 mesh.

Example 1 Aminomethylphosphonic acid type chelate resin obtained in Production Example (
La was bound to MR type) 52 from an aqueous solution at pH 2.5.

This resin has an inner diameter of 1c! The resin was packed into a column of 100 ml of resin and washed with water until no more La 2 leaked out from the resin. At this time, the resin volume was 10 crIl. Next, this resin has a pH of
After passing an aqueous solution of 3.5 (0.1 M phthalate buffer) until the pH of the leaked liquid reached 3.5, a pH 3 solution containing 50 ppm of fluorine ions (dissolved as NaF) was added.
, 5 aqueous solution (0.1M phthalate buffer) was mixed with 5v-6 (
Fl! + 6 times the volume of fat/Hr), and the fluorine ion concentration after passing through the resin tower was measured.

As a result, the fluorine ion concentration was 1 p at the point where the resin volume was 10 times, 20 times, 30 times, 40 times, 50 times, and 60 times.
If it is below pm, it is 5 at the liquid passing point of 70 times, 80 times, and 90 times.
It was less than ppm. Furthermore, the amount of La that leaked out up to the point where 120 times the resin volume was passed was less than 1 part of the total amount of adsorption.

Example 2 A 1M aqueous sodium hydroxide solution 200- was passed through the column that had adsorbed fluoride ions in Example 1 at 5V-6 to elute fluoride ions. In the aqueous sodium hydroxide solution after passing through the column, 97% of the total amount of fluorine ions adsorbed in Example 1 was contained, and no La was detected at all. Therefore, only fluorine ions could be eluted without desorption of J and La from the chelate resin by passing a 1M aqueous solution of IJ hydroxide.

Next, an aqueous solution with a pH of 3.5 (0.1 M phthalate buffer) was passed through the leakage solution until the pH reached 3.5, and then
A liquid to be treated having the same composition as in Example 1 was passed in the same manner as in Example 1, and the fluorine ion concentration after passing through the resin tower was measured.

As a result, as in Example 1, 10 times the resin volume and 20 times the resin volume.
The fluorine ion concentration was 1 ppm or less at the point where the liquid was passed through 1x, 30x, 40x, 50x, and 60x, and was 5 ppm or less at the point where the liquid was passed 70x, 80x, and 90x. In addition, the La leaked up to the point where the resin volume is 120 times that of the resin is
It was less than 0.2% of the total adsorption amount.

Example 3 An aqueous solution of pH 3.5 was passed through the same La adsorbed chelate as in Example 1 in the same manner as in Example 1 until the pH of the leaked liquid reached 3.5, and then F- : 50
ppm (dissolved as NaF), C1-: 5000
ppm (dissolved as NaCL), 804:500
0 ppm (dissolved as Na2804), NO3:
Aqueous solution at pH 3.5 containing 5000 ppm (dissolved as NaNO3) (1 ffl 0.1M phthalate buffer)
) was passed through the resin column at 5V=6, and the fluorine ion concentration after passing through the resin column was measured.

As a result, as in Example 1, 10 times the resin volume and 20 times the resin volume.
The fluorine ion concentration should be 1 ppm or less at the point where the liquid is passed through 1x, 30x, 40x, 50x, and 60x.

It was 5 ppm or less at the 70x, 80x, and 90x liquid passage points. Furthermore, the amount of La that leaked out up to the point where 120 times the resin volume was passed was less than 1 inch of the total adsorption amount.

Claims (1)

[Claims] 1 A chelate resin having an aminomethylphosphonic acid type polydentate ligand represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (n in the formula is 1 or 2) and a fluorine ion A method for removing fluorine ions in water, which comprises treating a fluorine ion-containing aqueous solution with a conjugate with an affinity metal ion.