JPS61287443A - Fluorine adsorbent - Google Patents

Abstract

PURPOSE:To obtain the titled adsorbent which adsorbs and removes F2 efficiently and selectively and is easily capable of desorption and regeneration and has high operability and economicity by making phosphoric acid or pyrophosphoric acid compd. of Ce the component. CONSTITUTION:F2 is selectively adsorbed and removed in high efficiency by bringing water dissolved with F2 having <=7pH into contact with cerous phosphate and ceric pyrophosphate as a compd. consisting of trivalent or tetravalent Ce and phosphoric acid or pyrophosphoric acid. The adsorbent F2 can be easily desorbed and regenerated by bringing it into contact with an alkali aq. soln. having 10-14pH. Still more since the aimed adsorbent has the excellent adsorption performance even in the copresence of F<-> and fluorine complex ion, it is avialable in the adsorption and the removal of F2 dissolved in the raw water of potable water or in an industrial drainage and has high operability and economicity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an adsorbent that can selectively remove fluorine dissolved in water at low concentrations with high efficiency. moreover,
The present invention adsorbs and removes fluorine dissolved in raw drinking water or industrial wastewater, and the adsorbent desorbs and regenerates adsorbed ions with a simple operation, and is operable and economical, allowing repeated use. Concerning high adsorbents.

(Prior art) Fluorine is originally present in extremely small amounts in nature, for example, 1.2 to 4 ppm in seawater, and usually 0.1 to 0.6 in river water.
Although it is dissolved at a level of approximately p%, this amount poses no problem in the ecological environment. However, it is known that the concentration of fluorine ions in groundwater exceeds 10 p- due to the release of hydrogen fluoride from volcanic activity, and it is also known that the concentration of fluorine ions in groundwater exceeds 10p.
Fluorine wastewater discharged from metal surface treatment, glass, ceramic, electronic, chemical, etc. industries has a high concentration, and due to recent advances in fluorine chemistry, fluorine emissions from these industries are increasing day by day. .

Such highly concentrated fluorine-containing water, as environmental water, has various negative effects on the human body, animals and plants, and therefore must be maintained and managed at a level as low as possible. 0.8p in case of
% or less, and in the case of industrial wastewater, it must be 15 pva or less.

As a method for removing fluorine dissolved in water, 0.8p of fluorine
For raw drinking water containing water of 1 m or more, the activated alumina adsorption method or the combined treatment of ion exchange resin and activated alumina have been conventionally carried out. However, the activated alumina adsorption method has the disadvantage that the amount of fluorine ions adsorbed by activated alumina is low and is affected by coexisting ions such as carbonate ions, making it difficult to obtain the expected removal effect. Regarding this point, there has been an attempt to remove fluorine ions by treating the liquid with activated alumina after adsorbing and removing other coexisting ions with an ion exchange resin, but in this case, more harmless ions than necessary are also removed. Therefore, there are problems such as the water quality not being desirable as drinking water and requiring a large amount of cost for treatment.

On the other hand, a commonly used method for removing fluorine ions and fluorine complex ions from industrial wastewater is to use calcium salts such as slaked lime or calcium chloride, and separate them by precipitation as calcium fluoride, which has low solubility. Ru. However, calcium fluoride is soluble in water, and even in ideal treatment, the fluorine concentration cannot be reduced to 8p% or less.Furthermore, fluoride ions complex with silicon, iron, aluminum, etc. in wastewater. The great tendency to form ions and the high solubility of their calcium salts make treatment by precipitation separation very difficult.

In addition, a method of adsorbing fluorine ions using activated alumina or a metal-supported chelate adsorbent (Japanese Unexamined Patent Publication No. 58-56632) has been proposed, but the adsorption performance for fluorine complex ions is unclear and is a practical problem. A point remains. Furthermore, fluorine ions are reacted with silicon (% open/closed 58-8582), iron, aluminum, and zirconium (Japanese Patent Application Laid-Open No. 58-64181) to form fluorine complex ions to increase selective adsorption, and then adsorbed using an anion exchange resin. A treatment method has been proposed, but this method requires adsorption pretreatment, which complicates the process, and since fluorine complex ions have a dissociation constant, fluorine ions remain in the wastewater. It is considered that it is difficult to set the conditions for advanced treatment to reduce the fluorine ion concentration to 'I ppm or less.

(Problem to be solved by the invention) Currently, from the perspective of environmental conservation and pollution prevention, the concentration of fluorine in wastewater discharged into public water bodies is regulated to 15 pIIa or less, and on the other hand, wastewater standards are regulated even more strictly. Some local governments are attempting to do so, and there is a desire to establish even more efficient advanced treatment.

(Means for Solving the Problems) In order to solve these problems, the present inventors have intensively studied a method for selectively and efficiently separating and removing fluorine dissolved in water, and as a result, the present invention has been developed. Reached.

Therefore, an object of the present invention is to provide an adsorbent that efficiently removes dissolved fluorine at a low concentration, and a further object of the present invention is to provide an adsorbent that efficiently removes dissolved fluorine at a low concentration. In addition to efficiently removing fluorine from wastewater and treating it to drinking water or wastewater with a fluorine concentration below the regulatory value, it also economically desorbs and regenerates the fluorine adsorbed by the adsorbent, making it possible to recycle it. The objective is to provide an adsorbent that

That is, the adsorbent of the present invention has 1-
fc is characterized by consisting of a pyrophosphate compound.

The adsorbent of the present invention efficiently adsorbs fluorine by contacting it with fluorine-dissolved water with a pH of 7 or less, and the adsorbed fluorine can be easily desorbed and regenerated by contacting with an alkaline aqueous solution with a pH of 10 to 14. , reuse becomes possible.

Hereinafter, the adsorbent of the present invention will be explained in detail.

The reason why the adsorbent of the present invention is trivalent is tetravalent cerium □
It is a compound consisting of aluminum and phosphoric acid or pyrophosphoric acid,
Typical examples include ceric phosphate, acidic ceric pyrophosphate, ceric pyrophosphate, ceric phosphate, acidic ceric phosphate, ceric pyrophosphate, and ceric phosphate. There are cerium sodium and ceric sodium pyrophosphate.

These phosphoric acid compounds and pyrophosphoric acid compounds may be used alone (or as a mixture of two or more types).In addition, other adsorbents such as activated carbon, activated alumina,
It may also be used together with hydrous titanium oxide or the like.

The compound of cerium and phosphoric acid of the present invention can be prepared, for example, by adding a solution of distrium hydrogen phosphate in an acidic hydrochloric acid solution to a solution of cerous chloride in an acidic sulfuric acid solution. Ceric acid phosphate can be prepared by adding a solution of a soluble ceric salt to a sodium hydrogen phosphate solution, and ceric acid phosphate can be prepared by adding a solution of a soluble ceric salt to a nitric acid solution of disodium hydrogen phosphate. It can be obtained as a precipitate by adding .

Compounds of cerium and pyrophosphate can be prepared, for example, by adding a solution of sodium pyrophosphate to a solution of a soluble cerous salt; It can be obtained as a precipitate by adding a solution of diserium ammonium.

Further, when the adsorbent of the present invention is prepared by the above-mentioned preparation method, it may be a composite metal phosphate compound or a composite metal pyrophosphate compound produced by coexisting various metal ions. Examples of metal elements that can coexist include La
% Pr b Nd b Purl b 81714
Eu bGd, Tb, Dy, Ho%Er
, Tm, Yb, Lu, Y, Sc
, Th.

AZhCr, Co, Ga, Fe, Mn, Ni
, Ti, V, Sn, Ge.

Examples include Nb, Ta, etc., and two or more types of these may coexist. The amount of these metal elements that can coexist is
The amount is not more than 40 mat %, preferably not more than 20 mol, relative to the metal element of the present invention.

Furthermore, the cations and anions used in the above preparation may be present as part of the structure of the phosphoric acid compound or pyrophosphoric acid compound of the present invention.

These coexisting cations and anions are, for example, NH4, Na, K, Ca, Mg, and Ct, Br.

so, , po4. It is CO8 etc.

The structural characteristics of the phosphoric acid compound and pyrophosphoric acid compound prepared by the above production method will be explained in detail.

An example of a phosphoric acid compound is cerium phosphate (CeP).
O4.nH,O) exhibits a hexagonal diffraction pattern of cerium phosphate in X-ray diffraction, but the crystallinity is poor and the diffraction line width is wide. 3500 cr in infrared absorption spectrum
Absorption bands due to hydroxyl groups are shown near n-1 and 1620 crrl-1, and absorption bands due to phosphoric acid groups are shown at 1050 crn-1.

Examples of pyrophosphate compounds (-, cerium pyrophosphate CCe4(PtO2)s-nH,Ol do not show specific diffraction lines in X-ray diffraction, and only slowly scattered lines are detected. Infrared absorption The spectrum has absorption bands due to hydroxyl groups near 34ooCrn-1 and 1650crr1-1, and 1
It shows a broad absorption band around 100, -1 which is considered to be due to the pyrophosphate group.

As an example of an acidic phosphoric acid compound, acidic ceric phosphate CCe4H1 (PO4)6 .nH2O) does not show specific diffraction lines in X-ray diffraction, and only slowly scattered lines are detected. The infrared absorption spectrum has absorption bands due to hydroxyl groups at around 340010M-', 1650 tM-'% 1400 Cm-' and 1500Cn1-1, and 10
00 to 1100 crIt-'' shows a wide absorption band that is thought to be due to phosphoric acid groups.

The cerium phosphate or pyrophosphate compound of the present invention is
The weight decreases by heating, and the main component that causes the weight loss is water molecules, and the heat loss is 5 to 40% by weight.

Incidentally, the term "thermal loss" as used in the present invention refers to the percentage decrease with respect to the initial weight when a sample is heated at 500C for 5 hours.

The adsorbent of the present invention is a cake obtained by filtering a cerium phosphoric acid or pyrophosphoric acid compound by the above-mentioned preparation method, or a dried powder, and a method such as supporting the same on a suitable porous carrier. It is a molded body formed into any shape such as granules, strings, strips, plates, etc. The molded body is extremely effective in increasing the practicality of adsorption operations.

Various inorganic and organic materials that can produce the effects of the present invention can be used as the material for the carrier, but various organic polymeric materials are preferred from the viewpoints of supporting processability, carrier strength, chemical durability, and the like.

Organic polymer materials include phenol resin, urea resin, melamine resin, polyester resin, diallyl phthalate resin, xylene resin, alkylbenzene resin, epoxy resin, epoxy acrylate resin, silicon resin, urethane resin, fluororesin, vinyl chloride resin, and chloride resin. Vinylidene resin, polyethylene, chlorinated polyolefin, polypropylene, polystyrene, ABS resin, polyamide, methacrylic resin, polyacetal, polycarbonate, cellulose, vinyl alcohol, polyimide, polysulfone, polyacrylonitrile, etc., and the above copolymers However, it is preferable to use materials that have appropriate water resistance, chemical resistance, high hydrophilicity, and can form a porous structure, such as polyamide, cellulose resin, polysulfone, polyacrylonitrile, vinyl chloride, and vinyl. Alcohol copolymers and the like are particularly preferred.

Various known methods can be applied to the method of supporting the above-mentioned organic polymer material. For example, a method in which particles of the cerium phosphoric acid or pyrophosphate compound are suspended and dispersed in a solution containing a suitable polymer and formed into particles, threads, strings, or strips, or a suitable polymer monomer a method of polymerizing the cerium phosphoric acid or pyrophosphoric acid compound particles by emulsion or suspension polymerization to form particles;
Alternatively, a method can be adopted in which a suitable high molecular weight polymer, the cerium phosphoric acid or pyrophosphoric acid compound, and various extractants are kneaded and molded, and then the extractant is extracted with a suitable solvent to make the material porous. In the case of deviation b, it is necessary to have a porous structure, a sufficient amount of the cerium phosphoric acid or pyrophosphoric acid compound is supported on the molded body, and the structure must be difficult to leak. Any method may be used.

Among these, particularly preferred methods include the above-mentioned polyamide,
A hydrophilic polymer such as cellulose resin, polystyrene, poly7+)ronitrile% vinyl chloride, vinyl alcohol copolymer, etc. is dissolved in a suitable solvent, and the cerium phosphoric acid or pyrophosphoric acid compound is suspended in this. This is a method of forming particles into particles using water as a coagulation bath.

The granules obtained by this method have a porous structure, sufficient adsorption rate and physical strength, and are suitable for adsorption and desorption regeneration operations by engineering methods such as fixed bed or fluidized bed. ing.

In particular, the amount of polymer used is from 5 to 50, particularly preferably from 10 to 30, by weight of the cerium phosphate or pyrophosphate compound. If it is less than 5% by weight, sufficient supporting effect will not be exhibited and the strength of 5% will be insufficient.
If it exceeds 0% by weight, the adsorption rate will drop significantly.

Furthermore, the particle size and volumetric porosity of the granules affect the adsorption action of the present invention, particularly the speed. The particle size is an average particle size of 0.1 to 511111. Or the volume porosity is 0.5~
0.85 is preferred.

The volumetric porosity as used in the present invention refers to the compressed volume (Vl) at the time of pressure compression relative to the apparent volume (Vl) of the granular material in a dry state.
The value of the volume change (■□−■.) to vo), that is,
It is expressed as (V-V)/V□.

O Here, the apparent volume (■□) is the volume measured by the mercury pycnometer method of a granular material of a constant weight, while the compressed volume (vo) is the volume of a sample of the same weight measured between press plates at 100C. This is the volume of the product molded under pressure at a pressure of 50 kg/d.

If the volume porosity is less than 0.5, the adsorption rate is too slow, and
If it is 0.85 or more, the strength is insufficient.

In addition, the properties and surface condition of the particles of the cerium phosphoric acid or pyrophosphate compound are extremely important for achieving the effects of the present invention, and the structural water or adhering water amount of the particles, the particle size, and the degree of aggregation are important. It is preferable to adjust the particle size, and it is preferable that the particle size is as fine as possible, and the primary particle size as an average particle size is 0.01 μ to 1 μ.
Particularly preferably, the particle size is 0.01 to 0.5μ, and fine particles of about 0.05 to 5μ are preferable as agglomerated particles with a low degree of aggregation.The method for adsorbing fluorine to the adsorbent is to use phosphoric acid of cerium. Alternatively, any method may be used as long as the pyrophosphate compound is brought into contact with water in which fluorine is dissolved. For example, a method in which a cake, powder, or the above-mentioned molded product of cerium phosphoric acid or pyrophosphate compound is added to the water and then dispersed and brought into contact; An effective method is to

The fluorine adsorbents of the present invention, metal hydrated oxides and metal hydrated fluorides of Group I of the periodic table B1Zr and Hf, contain fluorine in water not only as fluorine ions but also in the form of fluorine complex ions. It is a completely new adsorbent that has excellent adsorption performance even when used in the past. Examples of fluorine complex ions present in water include hexafluorosilicate ion, borofluoride ion, hexafluoroaluminum ion, hexafluoroiron ion, hexafluorotitanium ion, and hexafluorozirconium ion, and these may be used singly or in combination. The above may be dissolved in water. Among them, fluorine is often present as hexafluorosilicate ions, but if the acidic ceric phosphate of the present invention is used, for example, it exhibits excellent adsorption performance at pH 6 or lower.

However, hexafluoroaluminum ions and hexafluorotitanium ions dissociate due to changes in pH, and in some cases, precipitate occurs.
It is difficult to determine the exact adsorption amount of each complex ion.

Since the adsorbent of the present invention has excellent adsorption performance even when fluorine ions and fluorine complex ions coexist, it also exhibits excellent effectiveness in the adsorption treatment of fluorine complex ions as described above. I can do it.

The mechanism by which the phosphoric acid or pyrophosphate compound of cerium, which is the fluorine adsorbent of the present invention, adsorbs fluorine ions and fluorine complex ions is that the fluorine adsorbent containing dissolved hydroxyl groups, phosphoric acid groups, or pyrophosphate groups present on the surface of the fluorine adsorbent is It is considered to be an anion exchange reaction in which ions or fluorine complex ions are exchanged. When the pH of the aqueous solution is lower than 7, preferably 6 or lower, the adsorption performance for fluorine is high (and when the pH is higher than 7, the adsorption performance is significantly reduced. Therefore, the adsorbent that has adsorbed fluorine should be brought into contact with an aqueous solution with a pH of 8 or higher. This allows for easy reproduction.

The saturated adsorption amount per unit weight of the fluorine adsorbent of the present invention has a correlation with the fluorine concentration in the solution. For example, in the case of acidic ceric phosphate, the pH of the aqueous solution at adsorption equilibrium is 3.
5, the fluorine ion concentration in the aqueous solution is 0.04 m
mot/l, 0.1 mmot/l.

1, Ommot/t, the saturated adsorption amount of fluorine ions of the adsorbent is 0.52 mmot/t, respectively.
? -Adsorbent, 0.75 dishes Ot/1 -Adsorbent, 1,9
0 mmol/t-adsorbent. Therefore, when adsorbing fluorine using the fluorine adsorbent, a suitable mixing ratio of the fluorine adsorbent and fluorine-containing water can be set depending on the initial concentration of fluorine and the target concentration.

The temperature of the adsorption operation described above affects the adsorption rate, and heating is effective. . However, it has a practically sufficient speed even at room temperature, and 5-90C1 is practically 2
A range of 0 to 60C is preferred.

In addition, the contact time varies depending on the contact method and the type of adsorbent, but it usually takes about 1 minute to 3 days for the amount of K to reach saturation, but 1 minute to 60 minutes is practical. .

These temperature and time conditions can also be applied to the desorption and regeneration operations described below.

The adsorbent of the present invention desorbs fluorine by contacting it with an alkaline solution after adsorbing fluorine, and can be subjected to repeated adsorption operations. In the above desorption operation, the amount of fluorine adsorbed on the adsorbent, the concentration of the desorption liquid, the mixing ratio of the adsorbent and the desorption liquid, and the temperature affect the desorption rate and the fluorine concentration in the desorption liquid.

For example, when using the acidic ceric phosphate of the present invention, the relationship between the equilibrium pH of the desorption solution and the desorption rate is as shown in Table 2.
The desorption rate increases rapidly with the equilibrium pH of the desorption solution. Therefore, the equilibrium pH of the desorption solution in the desorption operation is preferably 8 or higher, more preferably 12 or higher.

In the above desorption operation, an inorganic alkali such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. can be used as the alkaline aqueous solution.

Sodium hydroxide and potassium hydroxide are particularly preferred because of their high desorption efficiency. The concentration of alkaline solution is 0.01
mot/1 or more, preferably o, o s mol/
That's all.

The method for desorbing fluorine fixed on the adsorbent of the present invention is as follows:
Any method may be used as long as the adsorbent is brought into contact with an alkaline aqueous solution, and the same method as the above-mentioned adsorption method can be employed.

(Effects of the Invention) Next, the characteristics of the fluorine adsorbent of the present invention are summarized as follows.

(1) Shows excellent fluorine adsorption performance at pH 7 or lower.

(2) The equilibrium adsorption amount is large even in the range of low concentration of fluorine ions in the liquid phase, for example, when the concentration of fluorine ions in the liquid phase is 0.1
When mmot/t, the adsorption amount is 0.75mmot/t.
1- It also acts as an adsorbent and can lower the fluorine concentration in treated water.

(3) Adsorbed fluorine can be desorbed by an alkaline aqueous solution, and it can be used repeatedly.

(Example) Hereinafter, this will be explained in detail using examples.

In addition, the adsorption amount and removal rate in 5 main text were calculated|required by the following formula.

Example 1 Ceric acid phosphate [Ce4H, (PO,
).

・nH, O, thermal loss 22 inches, average particle size of -order particles 0.
12μ, X-ray diffraction figure 3a, infrared absorption spectrum figure 6b
An example of the pH dependence of adsorption performance for fluorine ions in Figure] is shown below.

Fluoride ions are converted to 1009 using fluorinated hydroacid (special grade reagent).
Prepare an aqueous solution of 11m, and add the adsorbent to the aqueous solution.
The mixture was mixed at a ratio of adsorbent/110 and stirred.

0.0% to the mixed solution. Add IN aqueous sodium hydroxide solution,
A predetermined pH was set. After 2 hours, the concentration of fluorine ions dissolved in the mixture was measured using ion chromatography (Dio
nex aQ 2 o 2 o 1 type).

The results are shown in FIG. 1 as the relationship between the pH of the solution and the amount of fluorine ions adsorbed.

Adsorbent manufacturing method 1 Add ceric nitrate solution to a nitric acid acidic solution of IJium (special grade reagent). The resulting gel-like precipitate is washed by decantation several times, air-dried, and then dried at 100C.

Example 2 Using acidic ceric phosphate (the same substance as in Example 1), the relationship between the fluorine concentration in the liquid phase and the equilibrium adsorption amount at that time was determined. The experimental method was the same as in Example 1, and the results are shown in FIG. 2, including the case where activated alumina was used as a comparative example.

Examples 5 to 5 Examples will be shown regarding the adsorption performance of the adsorbent of the present invention for fluorine ions.

An aqueous solution containing 100% of fluorine ions is prepared, and the aqueous solution is added to cerium phosphate (preparation method described later, heat loss: 11%,
Average particle diameter of -order particles 0.1μ, X-ray diffraction figure 4a, infrared absorption spectrum figure 4b), cerium pyrophosphate (preparation method described later, heat loss 19 cm, average particle size of -order particles 0
．． 15μ, X-ray diffraction Figure 5a, Infrared absorption spectrum Figure 5
Figure b), or 1 ton of ceric phosphate (preparation method described later, heat loss 29 cm, average particle size 0.12μ)
/1 was mixed at a ratio of one part adsorbent and stirred. 0.1N hydrochloric acid or 0.1N aqueous sodium hydroxide solution was added to the mixture to adjust the pH of the mixture to 3.5. 2 hours later,
The fluorine ion concentration in the mixed liquid was measured by the same method as in Example 1, and the amount of fluorine adsorption was calculated. The results are shown in Table 1.

As a comparative example, the same experiment as in Example 3 was conducted using activated alumina (commercial product, Neobead I) 5).
The results are shown in Table 1.

Table 1 Adsorbent manufacturing method 2 = Add a hydrochloric acid acidic solution of disodium hydrogen phosphate (reagent special grade) to a sulfuric acid acidic aqueous solution of cerous chloride (reagent special grade), heat at 60C for 1 hour, and then heat-form overnight. . Repeat the decantation several times, wash the precipitate with water, and after air drying,
Dry at 00C.

Adsorbent manufacturing method 6 Add an aqueous solution of ceric ammonium nitrate (reagent grade) to an aqueous solution of disodium phosphate (reagent grade). The resulting gel-like precipitate is decanted and washed several times using hot water, air-dried, and then dried at 100C.

Adsorbent manufacturing method 4 Add an aqueous solution of sodium pyrophosphate (special grade reagent) to an aqueous solution of cerous chloride (special grade reagent) and age overnight. After filtration, the precipitate is washed with water until no chlorine ions are observed, and dried at 100C.

Example 5 An example will be shown regarding the adsorption performance of acidic ceric phosphate (same substance as in Example 1) for silicofluoride ions.

An aqueous solution was prepared using sodium silicofluoride (reagent special grade) so that the concentration of silicofluoride ions was 100 p%. The adsorbent was mixed into the aqueous solution at a ratio of 11-adsorbent/1 t, adjusted to pH 3.5, and stirred for 24 hours.

The residual silicofluoride ion concentration in the aqueous solution was measured by ion chromatography to determine the adsorption amount of the adsorbent, and it was found that the adsorbent exhibited excellent adsorption performance of 55η/V-adsorbent.

Example 6 An example will be shown regarding the pH dependence of the desorption rate in a desorption regeneration operation using an aqueous alkaline solution of the adsorbent of the present invention.

2.8 mmot / fluorine ion in advance - 0.01 to 0.1 N of acidic ceric phosphate adsorbed with adsorbent
was mixed with an aqueous sodium hydroxide solution at a ratio of 107-adsorbent/1 t, and stirred, and after 2 hours, the pH and fluorine ion concentration of the mixed solution were measured. The results are shown in Table 2.

Table 2 Examples 7 to 9 Examples of desorption/regeneration operations using various alkali species in the desorption/regeneration operations of the adsorbent of the present invention are shown.

Acidic ceric phosphate f, 0.5N aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, or aqueous ammonia with 2.8 mmot/adsorbent of fluorine ions adsorbed in advance at a ratio of 10 g/adsorbent/1 t. Mix and stir with
After a period of time, the pH and fluorine ion concentration of the mixture were measured. The results are shown in Table 5.

Table 3 Example 10 An example of adsorption/desorption operations performed using acidic ceric phosphate granulated with ethylene-vinyl alcohol copolymer is shown.

Dilute sodium fluoride (special grade reagent) with distilled water to prepare a pH 3 solution with a fluorine ion concentration of 100 p-.
This was used as raw water.

The granules (average particle diameter 0°6BUImφ, volumetric porosity 0.
A column was filled with 15- of No. 61), and the above-mentioned raw water was passed through the column at a superficial velocity SV = 20 hr""', and the fluorine concentration in the treated water at the outlet of the two-force ram was measured. The treatment magnification of one adsorbent until the fluorine concentration in the treated water reached 1 ppl was 90 times, demonstrating excellent performance.

Next, after washing with water, a 0.1N aqueous solution of sodium hydroxide was passed under the condition of superficial velocity SV = 5 hr-'', and the fluorine ion concentration in the desorption solution was 1.!
68.4 mmot/L) was obtained at a high concentration of shiri. By using an equivalent amount of alkali 1.3 times the fluorine ion concentration, a desorption rate of 100% could be achieved.

[Brief explanation of the drawing]

FIG. 1 is a chart showing the relationship between the adsorption amount of acidic ceric phosphate of the present invention and the fluorine ion concentration in the liquid phase, and FIG. Diagram showing pH dependence, Figure 6a is an X-ray diffraction diagram of Cu' of acidic ceric phosphate using alpha rays, Figure 3b is
The figure shows its infrared absorption spectrum, Figure 4a shows the X-ray diffraction diagram of cerium phosphate using the CuKa line, Figure 4b shows its infrared absorption spectrum, and Figure 5a shows the X-ray diffraction diagram of cerium pyrophosphate using the CuKa line. The line diffraction diagram, Figure 5b, is a diagram showing its infrared absorption spectrum. 1st residence 脣に” / 101-LIL + - 1st residence bonito is trace 6 /
1ouuu nourishment elimination''! i Kakumachi Hijimi no Mikoto i ■ V Masu Kano (%) net award

Claims (1)

[Claims] Fluoride adsorbent consisting of cerium phosphoric acid or pyrophosphoric acid compound.