JPH06154750A - Method for separating chloride ion - Google Patents

Abstract

PURPOSE:To selectively separate chloride ions forming the cause of corrosion of stainless piping or the like by bringing a fluid containing sulfate ions and chloride ions into contact with phophate of lead hydroxide in a manner that pH after contact represents a specified value in a factory drainage or the like. CONSTITUTION:When chloride ions are separated from liquid such as factory drainage containing sulfate ions and chloride ions, the liquid is brought into contact with phosphate of lead hydroxide in a manner that pH after contact is in the range of more than four (4) and less twelve (12). As for phosphate of lead hydroxide, for example, a substance which belongs to Pb10(PO4)6 (O family P63/m and provided with apatite crystal structure) is used. The ratio of the phophate of lead hydroxide is, for example, 10g or more per one (1) mol of chloride ion, and the contact time of liquid with phosphate of lead hydroxide is set for several minutes to several hours. Chloride ions forming the cause of corrosion of the stainless piping, concentrate and the like are separated selectively to protect the piping and a concentrater from getting corrosion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention removes chloride ions, which cause corrosion of stainless steel pipes, concentrators, etc., from a liquid containing sulfate ions and chloride ions in factory wastewater, etc.
The present invention relates to a method for separation using lead hydroxyphosphate.

[0002]

2. Description of the Related Art Chloride ions contained in factory wastewater are
It is a cause of corrosion of stainless steel water pipes and drainage storage tanks. For example, in nuclear facilities such as nuclear power plants and nuclear fuel reprocessing plants, washing wastewater is subjected to pretreatment and concentration by evaporation in order to reuse it, but this wash wastewater contains chloride ions due to salt such as sweat. Exists,
If the concentration exceeds 1500ppm, there is a risk of corroding the stainless steel concentrator. Therefore, as an anticorrosion measure,
The concentration rate of wastewater is limited and the chloride ion concentration is kept below 1500ppm. However, in order to reduce the waste liquid, even higher concentration is required, but at present, the chloride ion concentration is limited, and it is necessary to separate the chloride ion in the laundry drainage. In addition, the laundry wastewater contains a large amount of sulfate ions, which are the components of the coagulant, because it is subjected to coagulation-precipitation treatment before being concentrated. Further, since it is an alkaline aqueous solution having a pH of 11 to 12, Coexist and
It is required to selectively separate chloride ions under conditions that are in the alkaline region.

As a method for separating chloride ions, it is possible to use an ion exchange resin, but the affinity between the ion exchange resin and the anion is generally different although it depends on the skeleton structure of the resin and the kind of the exchange group. _{^{SO 4 2-> I -> NO}} 3 -> CrO 4 2 -> Cl -> F - is said to order of. Therefore, when an ion exchange resin is used for a liquid in which sulfate ions coexist, sulfate ions are preferentially separated, and it is almost impossible to preferentially separate chloride ions.

In addition, it is possible to use an inorganic ion exchanger as a method for separating chloride ions.
As an inorganic ion exchanger having an adsorption ability for chloride ions, lead hydroxide phosphate, hydrous oxide bismuth nitrate, hydrous bismuth oxide, hydrotalcite, hydrous zirconium oxide and the like are known. However, a method for selectively separating chloride ions under the condition that sulfate ions coexist has not been found.

[0005]

SUMMARY OF THE INVENTION According to the present invention, when removing chloride ions, which cause corrosion of stainless steel pipes, concentrators, etc., from a liquid containing sulfate ions and chloride ions, such as factory wastewater, sulfuric acid is used. It is intended to provide a method for selectively separating chloride ions from an aqueous solution in which ions coexist.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, a liquid containing a sulfate ion and a chloride ion was used as an inorganic ion exchanger having excellent adsorption properties for a chloride ion, phosphoric acid hydroxide. The inventors have found that chloride ions can be preferentially separated by contacting with lead so that the pH after contacting is 4 or more and 12 or less, and has completed the present invention. That is, according to the present invention, a liquid containing a sulfate ion and a chloride ion is mixed with lead hydroxyphosphate to obtain a p
The method for separating chloride ions is characterized in that H is brought to 4 or more and 12 or less. Hereinafter, the present invention will be described in detail.

Lead Hydroxyl Phosphate The lead hydroxyphosphate used in the present invention is represented by the following composition formula, and has an apatite crystal structure belonging to the hexagonal system P6 ₃ / m. Pb ₁₀ (PO ₄ ) ₆ (OH) ₂ The method for producing lead hydroxide phosphate used in the present invention is not particularly limited, and the preferred examples are as follows. That is, an aqueous solution of lead nitrate and an aqueous solution of sodium phosphate are mixed so that the Pb / P molar ratio is preferably 1.0 to 2.5, more preferably 1.5 to 1.9, and preferably 20 to 80 ° C. It is obtained by aging at. The aging time is not particularly limited, but is preferably several minutes or more and more preferably 1 hour or more in order to promote crystallization of lead hydroxyphosphate. As another example, there is a method of treating hydroxyapatite [Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ] with a mixed solution of lead nitrate and nitric acid.

The lead hydroxyphosphate used in the present invention has the following shape.
It is not particularly limited and may be in the form of powder, but for facilitating separation of chloride ion in the liquid containing sulfate ion and chloride ion of the present invention, that is, containing sulfate ion and chloride ion In order to facilitate separation after contact with a liquid and passage through the column, the powder may be formed into a granular or pellet form using a binder or the like, or the powder may be supported on a carrier. In this case, especially, Japanese Patent Laid-Open No. 3-1
The one described in No. 31349, in which a clay mineral and a metal alkoxide hydrolyzate are used together as a binder, and the powder is formed into particles is excellent in the effect of removing chloride ions and is stable in strength, which is preferable. In this case, the clay mineral used is preferably sepiolite, and the metal alkoxide hydrolyzate is preferably ethyl silicate hydrolyzate.

Method for separating chloride ion In order to separate chloride ion in a liquid containing a sulfate ion and a chloride ion, the lead hydroxide phosphate in the present invention is separated from the liquid containing a sulfate ion and a chloride ion. Must be in contact with.

In the present invention, the preferable time for contacting the lead hydroxide phosphate with the liquid containing the sulfate ion and the chloride ion is not unconditionally determined depending on the object to be treated, but may be from several minutes to several hours, depending on the case. Is a few days.
The temperature at which they are brought into contact with each other is not particularly limited, and may be any temperature that does not affect the ion exchange characteristics of lead hydroxide phosphate.

In the present invention, the pH of the liquid containing sulfate ion and chloride ion to be brought into contact with lead hydroxide phosphate is
After contacting with lead hydroxyphosphate, it may be 4 or more and 12 or less. In addition, when the liquid has a pH of less than 4 or more than 12 after contact with lead hydroxyphosphate, the phosphoric acid hydroxide can be prepared by pretreatment such as using an alkali or an acid that can coexist in advance. P after contact with lead
It may be appropriately adjusted so that H becomes 4 or more and 12 or less. If the liquid has a pH of less than 4 after contact with lead hydroxide phosphate, lead which is a component of lead hydroxide phosphate may be eluted, and if the liquid has a pH of more than 12, lead hydroxide phosphate may be dissolved. There is a risk that lead, which is a component, may elute, and that the chloride ion separation effect of lead hydroxide phosphate may be significantly reduced.

The ratio of the liquid containing the sulfate ion and the chloride ion to the lead hydroxide phosphate to be brought into contact with the liquid varies depending on the shape of the lead hydroxide phosphate and the like. It is preferable that the amount of lead is 10 g or more, and it may be appropriately selected depending on the conditions for separating chloride ions, such as the contact time between lead hydroxide phosphate and liquid, the contact method or contact temperature, the pH of the liquid, and the type and amount of coexisting ions Just adjust it.

Further, as a component other than lead hydroxide phosphate, it is known as an inorganic cation exchanger, and when a water-containing antimony pentoxide represented by the following general formula or tin phosphate is used together, excellent chlorination is achieved. It is preferable because the effect of separating product ions is produced. Hydrous antimony pentoxide Sb ₂ O ₅ .nH ₂ O (where n is a positive number of 4 or less) Tin phosphate H ₂ Sn (PO ₄ ) ₂ .mH ₂ O (where m is a positive number). )

Three types of hydrous antimony pentoxide are known, crystalline, amorphous and glassy. When used together with lead hydroxide phosphate in the present invention, a chemically stable crystalline ( It is preferable to use cubic crystals. In this case, the ratio of hydrous antimony pentoxide is 1
1 to 60 parts are preferable, and 2 to 30 parts are more preferable, relative to 00 parts by weight (hereinafter abbreviated as parts). If it is less than 1 part, there is almost no effect of contributing to the coexistence of hydrous antimony pentoxide.
If it exceeds 0 parts, the pH of the liquid may be less than 4 due to the effect of hydrogen ions released from hydrous antimony pentoxide, and lead, which is a component of lead hydroxide phosphate, may be eluted. The separation effect of chloride ions may be significantly reduced.

When tin phosphate is used together, the proportion of tin phosphate is 1-80 with respect to 100 parts of lead hydroxide phosphate.
Parts are preferable, and 2 to 40 parts are more preferable. If it is less than 1 part, there is almost no effect of contributing to the coexistence of tin phosphate, and if it exceeds 80 parts, the pH of the liquid becomes less than 4 due to the effect of hydrogen ions released from tin phosphate, and it is a component of lead hydroxide phosphate. May be eluted.

As a specific example of the method for separating chloride ions from a liquid containing sulfate ions and chloride ions using lead hydroxide phosphate, the lead hydroxide phosphate in the present invention is
A method of separating lead hydroxide phosphate after contacting with a liquid containing sulfate ions and chloride ions by adding to a liquid containing sulfate ions and chloride ions and stirring, and a method of separating phosphoric acid hydroxide into a column, etc. There is a method of filling lead and passing a liquid containing sulfate ions and chloride ions.

Further, as a field to which the method for separating chloride ion of the present invention can be applied, there is separation of chloride ion from a liquid containing sulfate ion and chloride ion such as industrial wastewater. There is an example. For example, in nuclear facilities such as nuclear power plants and nuclear fuel reprocessing plants, pre-treatment and concentration by evaporation are performed to reuse laundry wastewater, but chloride ions that cause corrosion of stainless steel concentrators are used. The method for separating chloride ions according to the present invention can be applied to the removal of the wastewater from the laundry drainage. It is also possible to separate chloride ions from general wastewater treated with various water treatment agents containing a compound having a sulfonic acid group, such as detergents, dispersants, flocculants or scale inhibitors. it can. General wastewater is wastewater discharged from general factories, households, various test facilities, etc., excluding nuclear facilities such as nuclear power plants.

[0018]

EXAMPLES AND COMPARATIVE EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing sulfate ions with a concentration of 20000 mg / l and chloride ions with a concentration of 100 mg / l,
The mixture was contacted with 2.0 g of lead hydroxyphosphate (hereinafter abbreviated as PBP) at a temperature of 25 ° C. After 24 hours, PBP was filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was adjusted to pH.
The concentration of Pb eluted in the filtrate was measured with an atomic absorption spectrophotometer. The results are shown in Table 1 below.

Example 2 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing sulfate ions with a concentration of 20000 mg / l and chloride ions with a concentration of 100 mg / l,
2.0 g of PBP and 0.2 g of hydrous antimony pentoxide (hereinafter abbreviated as SBO) having the following composition formula, and a temperature of 25
Contacted at 0 ° C. After 24 hours of hydrous antimony pentoxide Sb ₂ O ₅ .2H ₂ O, PBP and SBO were filtered off, the concentration of chloride ion in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was further measured. The pH was measured with a pH meter, and the concentration of Pb eluted in the filtrate was measured with an atomic absorption spectrophotometer.
The results are shown in Table 1 below.

Example 3 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing sulfate ions with a concentration of 20000 mg / l and chloride ions with a concentration of 100 mg / l,
The mixture was contacted with 2.0 g of PBP and 0.2 g of tin phosphate (hereinafter abbreviated as SNP) having the following composition formula at a temperature of 25 ° C. After 24 hours of tin phosphate H ₂ Sn (PO ₄ ) ₂ · H ₂ O, PBP and SNP were separated by filtration, and the concentration of chloride ion in the filtrate was measured by ion chromatography (manufactured by DIONEX). The pH was measured with a pH meter, and the concentration of Pb eluted in the filtrate was measured with an atomic absorption photometer.
The results are shown in Table 1 below.

Comparative Example 1 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing a sulfate ion having a concentration of 20000 mg / l and a chloride ion having a concentration of 100 mg / l,
Amberlite IRA-40, a strongly basic anion exchange resin
It was contacted with 2.0 g of 0T (trade name, manufactured by Rohm and Haas Company) at a temperature of 25 ° C. After 24 hours, IRA-400T was filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was adjusted to p.
It was measured with an H meter and the results are shown in Table 1 below.

Comparative Example 2 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing sulfate ions with a concentration of 20000 mg / l and chloride ions with a concentration of 100 mg / l,
2.0 g of bismuth hydrous oxide nitrate (hereinafter, abbreviated as BIN) having the following composition was contacted at a temperature of 25 ° C. Hydroxylated Bismuth nitrate (〓) Bi ₆ O ₆ (O
H) _4.2 (NO ₃ ) _1.8 · H ₂ O 24 hours later, BIN was filtered off, the concentration of chloride ion in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was measured by a pH meter. The measurement was performed and the results are shown in Table 1 below.

Comparative Example 3 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing a sulfate ion having a concentration of 20000 mg / l and a chloride ion having a concentration of 100 mg / l,
It was contacted with 2.0 g of BIN and 2.0 g of SBO at a temperature of 25 ° C. After 24 hours, BIN and SBO were filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was adjusted to pH.
The results were shown in Table 1 below.

Comparative Example 4 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing sulfate ions with a concentration of 20000 mg / l and chloride ions with a concentration of 100 mg / l,
Aluminum-magnesium composite oxide having the following composition (hereinafter abbreviated as ALMG) 2.0 g and temperature 25 ° C.
Contacted under. Aluminum-magnesium composite oxide Mg _0.7 Al _0.3 O _1.15
-After 24 hours of 0.13 H ₂ O, ALMG was filtered off, the concentration of chloride ion in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was measured by a pH meter. The results are shown in Table 1 below.

Comparative Example 5 50 ml of a Na ₂ SO ₄ / NaCl aqueous solution containing a sulfate ion having a concentration of 20000 mg / l and a chloride ion having a concentration of 100 mg / l,
Hydrous zirconium oxide having the following composition (hereinafter, ZR
(Abbreviated as O) 2.0 g was contacted at a temperature of 25 ° C. After 24 hours of hydrous zirconium oxide ZrO ₂ · 2H ₂ O, ZRO was filtered off, the concentration of chloride ions in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was measured by a pH meter. The results are shown in Table 1 below.

Comparative Example 6 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing a sulfate ion having a concentration of 20000 mg / l and a chloride ion having a concentration of 100 mg / l,
It was contacted with 2.0 g of PBP and 1.4 g of SBO at a temperature of 25 ° C. After 24 hours, PBP and SBO were filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was adjusted to pH.
The concentration of Pb eluted in the filtrate was measured with an atomic absorption spectrophotometer. The results are shown in Table 1 below.

Comparative Example 7 50 ml of an aqueous Na ₂ SO ₄ / NaCl solution containing a sulfate ion having a concentration of 20000 mg / l and a chloride ion having a concentration of 100 mg / l,
It was contacted with 2.0 g of PBP and 1.8 g of SNP at a temperature of 25 ° C. After 24 hours, PBP and SNP were filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was adjusted to pH.
The concentration of Pb eluted in the filtrate was measured with an atomic absorption spectrophotometer. The results are shown in Table 1 below.

Comparative Example 8 50 ml of an aqueous Na ₂ SO ₄ /NaCl/0.01M-HNO ₃ solution containing sulfate ions with a concentration of 20000 mg / l and chloride ions with a concentration of 100 mg / l was added to 2.0 g of PBP at a temperature of 25 ° C. The original contact was made. After 24 hours, PBP was filtered off, the concentration of chloride ions in the filtrate was measured by ion chromatography (manufactured by DIONEX), and the pH of the filtrate was measured by a pH meter to determine the concentration of Pb eluted in the filtrate. Was measured with an atomic absorption spectrophotometer.
The results are shown in Table 1 below.

Comparative Example 9 50 ml of an aqueous Na ₂ SO ₄ /NaCl/0.1M-HNO ₃ solution containing a sulfate ion having a concentration of 20,000 mg / l and a chloride ion having a concentration of 100 mg / l was added to 2.0 g of PBP at a temperature of 25 ° C. The original contact was made. After 24 hours, PBP was filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), the pH of the filtrate was further measured by a pH meter, and the concentration of Pb eluted in the filtrate was measured. Was measured with an atomic absorption spectrophotometer.
The results are shown in Table 1 below.

Example 4 To 50 ml of a Na ₂ SO ₄ /NaCl/0.1M-HNO ₃ aqueous solution containing a sulfate ion of a concentration of 20000 mg / l and a chloride ion of a concentration of 100 mg / l, 5.6 ml of a 1M-NaOH aqueous solution was added. And then P
It was contacted with 2.0 g of BP at a temperature of 25 ° C. 24
After a lapse of time, PBP was filtered off, and the concentration of chloride ion in the filtrate was measured by ion chromatography (manufactured by DIONEX),
Further, the pH of the filtrate was measured with a pH meter, and P eluted in the filtrate
The concentration of b was measured with an atomic absorption photometer. The results are shown in Table 1 below.

Comparative Example 10 50 ml of an aqueous Na ₂ SO ₄ /NaCl/0.1M-NaOH solution containing a sulfate ion having a concentration of 20000 mg / l and a chloride ion having a concentration of 100 mg / l was added to 2.0 g of PBP at a temperature of 25 ° C. Contacted with. After 24 hours, PBP was filtered off, the chloride ion concentration in the filtrate was measured by ion chromatography (manufactured by DIONEX), the pH of the filtrate was further measured by a pH meter, and the concentration of Pb eluted in the filtrate was measured. Was measured with an atomic absorption spectrophotometer.
The results are shown in Table 1 below.

Example 5 2.7 ml of 1M-H ₂ SO ₄ aqueous solution was added to 50 ml of Na ₂ SO ₄ /NaCl/0.1M-NaOH aqueous solution containing sulfate ions of 20000 mg / l concentration and chloride ions of 100 mg / l concentration. Is added, and P
It was contacted with 2.0 g of BP at a temperature of 25 ° C. 24
After a lapse of time, PBP was filtered off, and the concentration of chloride ion in the filtrate was measured by ion chromatography (manufactured by DIONEX),
Further, the pH of the filtrate was measured with a pH meter, and P eluted in the filtrate
The concentration of b was measured with an atomic absorption photometer. The results are shown in Table 1 below.

[0034]

[Table 1]

From Table 1 above, after the liquid containing the sulfate ion and the chloride ion was contacted with the ion exchanger, the concentration of the chloride ion in the liquid was compared with that in Comparative Examples 1 to 6 and It can be seen that the numbers in Examples 1, 2, and 3 are decreased. In addition, since the chloride ion concentration in the liquid is significantly lower than the coexisting sulfate ion concentration, it is clear that chloride ions are preferentially separated. . Further, it can be seen that the Pb concentration of the component of lead hydroxyphosphate eluted in the liquid is significantly smaller in the cases of Examples 1, 2 and 3 than in Comparative Examples 6 and 7. In addition, from Table 1 above, Example 4 in which the pH of the liquid after contact with lead hydroxyphosphate was adjusted to 4 or more and 12 or less
5, P of the component of lead hydroxyphosphate eluted in the liquid
It can be seen that the concentration of b is significantly smaller than that of Comparative Examples 8 to 10 in which the pH is not adjusted to 4 or more and 12 or less. Furthermore, in Examples 1, 4, and 5, it is found that chloride ions are almost completely separated even in the alkaline region where the anion exchange reaction is difficult to occur.

Example 6 PBP formed into granules having a particle diameter of about 0.5 to 1.0 liter by using sepiolite as a binder and hydrolyzed ethyl silicate as a binder, as described in JP-A-3-131349.
100 g was packed in a glass column with a diameter of 20 ㎓, and Na ₂ SO ₄ / NaCl aqueous solution containing sulfate ion with a concentration of 20000 mg / l and chloride ion with a concentration of 10 mg / l was added to SV = 5.
The solution was passed at H ^-1 and a temperature of 30 ° C. When the chloride ion concentration of the column outlet liquid was measured, it was 1 mg until the liquid passage magnification of 700 times.
It was less than / l.

[0037]

The chloride ion separation method of the present invention is a method capable of selectively separating chloride ions from a liquid such as factory wastewater in which sulfate ions coexist. Furthermore, stainless steel pipes, which may be corroded by chloride ions,
It is useful as an anticorrosion method for concentrators.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Shindo 72-1 Nakayama, Aoba-ku, Sendai City, Miyagi Prefecture (72) Nobuhiko Aiba 1 No. 1 Funami-cho, Minato-ku, Nagoya City, Aichi Toagosei Synthetic Chemistry Industrial Research Institute Nagoya Research Institute

Claims (1)

[Claims] 1. A method for separating chloride ions, which is characterized in that a liquid containing sulfate ions and chloride ions is contacted with lead hydroxide phosphate so that the pH after contacting is 4 or more and 12 or less.