JP2909336B2 - Decomposer for free chlorine in water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agent for decomposing free chlorine in water. More specifically, the present invention relates to an agent for decomposing free chlorine in water, comprising a hydrotalcite-based solid solution containing a reducing anion as an active ingredient. The agent for decomposing free chlorine according to the present invention is extremely useful for decomposing residual chlorine dissolved in tap water.

[0002]

2. Description of the Related Art In tap water, chlorine added for the purpose of sterilization or decomposition of ammonia is generally 0.5% as free chlorine.
~ 1 ppm remains. The free chlorine causes off-flavor and generation of carcinogenic trichloromethane due to reaction with organic matter in water. In addition, since free chlorine in water has an oxidizing effect, it may have an adverse effect depending on an object to be used.

[0003] For example, tap water loaded on an aircraft needs to effectively reduce or remove chlorine remaining in the tap water. Aircraft structural materials are vulnerable to oxidizing chlorine and are corroded by residual chlorine in tap water. For this reason, a method of reducing or removing residual chlorine by contacting tap water used for aircraft with calcium sulfite or the like has been adopted.

[0004] However, calcium sulfite dissolves in an aqueous system, and the reducing action continues until calcium sulfite disappears. Therefore, when drinking tap water in which calcium sulfite is dissolved, there is a risk that calcium sulfite may act harmfully in a living body.

Therefore, it has been desired to treat residual chlorine in tap water with a chlorine-decomposing agent that is safe for living organisms.

An object of the present invention is to provide a decomposer which eliminates the above-mentioned disadvantages of a conventional decomposer for free chlorine in water. A further object of the present invention is to provide a decomposing agent of safety Do, water free chlorine in vivo.

[0007]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, formula (1)

[0008]

_{Embedded image} [(M ₁ ²⁺ ) _{y 1} (M ₂ ²⁺ ) _{y 2} ] _{1-x
^{M x 3+ (OH) 2 A}} p 1- A q 2- · mH 2 O ···
... (1) _wherein, ^{M 1 2+} represents a least one divalent metal selected from the group consisting of Mg and _{Ca, M} ^{2 2} + is Zn,
2 selected from the group consisting of Mn, Ni, Cu and Fe
M ³⁺ represents a trivalent metal; A ^1- represents at least one monovalent anion;
^2- represents at least one divalent anion, x,
y ₁ , y ₂ and m represent the following numbers, and 0.1 ≦ x ≦
0.7, preferably 0.25 ≦ x ≦ 0.330.5 <y
₁ ≦ 1 , preferably 0.6 <y ₁ ≦ 10 ≦ y ₂ <0.
5, preferably 0 ≦ y ₂ <0.40 ≦ m ≦ 1, preferably 0 ≦ m ≦ 0.7 p and q are numbers satisfying the following formula, but p can be 0, = XA ^1-
And ^A total per 10 to 95 mol% of ^2-anion, preferably 35 to 95 mol%, and most preferably 50
９５95 mol% is a reducing anion], as an active ingredient, there is provided a decomposer for decomposing free chlorine in water.

[0009] In the above formula (1), examples of the monovalent anion represented by A ^{1-is, F -, Cl -, Br} -, N
O ₃ ⁻ , NO ₂ ⁻ , OH ⁻ , ClO ₄ ⁻ , OH ⁻ , HCO ₃ ⁻ , C
^{_{6 H 4 (OH) COO -}} ,

[0010]

Embedded image

And the like. F ⁻ , Cl ⁻ ,
Br ⁻ , NO ₃ ⁻ , NO ₂ ⁻ , CH ₃ COO ⁻ and H
CO ₃ ^- are preferred, especially ^{F -, Cl -, Br -} , NO
₃ ^-, NO ₂ ^- and OH ^- are preferred.

Examples of the divalent anion represented by A ²⁻ include CO ₃ ⁻ , SO ₄ ⁻ , SO ₃ ⁻ , S ₂ O ₃ ⁻ ,

[0013]

Embedded image

[0014] _{^{SiO 3 -, HPO 4 -,}} HBO 3 -,

[0015]

Embedded image

And the like. Above all, CO _{3
^{-, SO 4 -, SO 3}} -, S 2 O 3 - and

[0017]

Embedded image

[0018] Preferably, in particular _{^{CO 3 -, SO 4 -,}} SO
₃ ^- and S ₂ O ₃ ^- are preferred.

On the other hand, in the above formula (1), examples of the reducing anion include SO ₃ ⁻ , S ₂ O ₃ ⁻ , NO ₂ ⁻ , and PHO _3.
^- (Phosphite ion) and the like. SO ₃
^- , S ₂ O ₃ ^- and NO ₂ ^- are preferred, and in particular, SO 2
₃ ^- and S ₂ O ₃ ^- are preferred.

Examples of the trivalent metal represented by M ³⁺ include Al, Fe, Cr, Co, In and the like. Of these, Al is particularly preferred.

Examples of preferred compounds of the formula (1) include:
The following equation (1 ′)

[0022]

Embedded image ^{_{(M 1 2+) 1-x}} Al x (OH) 2 A p 1- A q 2- · mH 2 O ···· (1 ') [ wherein, M ₁ ^2+, x, p, q and m have the meanings according to claim 1, wherein A ^1- is F ⁻ , Cl ⁻ , Br ⁻ , NO ₃ ⁻ , N
O ₂ ^- and OH ^- become more indicates at least one monovalent anion selected from the group, A ^{2-is _{SO 4 -, CO 3 -,}} S
O ₃ ^- and S ₂ O ₃ ^- at least divalent anion selected from the group consisting indicates a kind, total per 35-95 mole percent of A ^1-and A ^2-anion is a reducing anion , and the said reducing anion is SO ₃ ^- and / or S ₂ O ₃ ^-
- it can be mentioned hydrotalcite solid solution represented by a is.

The hydrotalcite-based solid solution represented by the above formula (1) used in the present invention and represented by the above formula (1 ′) included in the above formula (1) is represented by the following formula:

[0024]

Embedded image It has the same crystal structure as natural hydrotalcite represented by Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, and thus has a powder X-ray diffraction pattern similar to natural hydrotalcite It is a compound which shows. However, lattice
The number varies according to the general rules of anion size and solid solution.

The natural hydrotalcite has a positive charge by partially replacing Mg ²⁺ with Al ³⁺ [Mg ₆ Al ₂
CO ₃ , which is exchangeable with water molecules, between (OH) ₁₆ ] ²⁺ layers
^- it has a crystal structure including a.

The reason that the hydrotalcite-based solid solution of the above formula (1) according to the present invention is effective in decomposing free chlorine in water is that when it comes into contact with water containing free chlorine, the free solution in water that has penetrated between the layers of the crystal structure is free. chlorine SO ₃ ^- harmless is reduced by the reducing anions such as Cl ^- next, SO ₃ ^- reducing anions such is oxidized, SO ₄ ^- presumably because changes in non-reducing anions such as .

The hydrotalcite-based solid solution of the formula (1) used in the present invention can be produced, for example, by the following ion exchange method or hydration reaction method.

(I) In the ion exchange method, first, a hydrotalcite-based compound containing a monovalent anion is synthesized by a reaction, and then the synthesized product is subjected to an ion exchange treatment with an aqueous solution containing a reducing anion. The hydrotalcite-based solid solution of the formula (1) of the invention is produced. The hydrotalcite-based compound as an intermediate material is prepared by adding a sodium hydroxide solution at a temperature of 20 to 60 ° C. with stirring to a mixed aqueous solution of monovalent anion compounds of divalent and trivalent metals adjusted to a predetermined concentration and composition ratio. PH to 9.0 to 10.5, preferably 9.0 to
A precipitate is formed at 9.5, separated by filtration and dehydrated from the reaction mother liquor, and then washed with water. The ion exchange treatment is completed by dispersing and suspending the obtained hydrotalcite-based compound in an aqueous solution containing a reducing anion and stirring or standing at 80 ° C. or lower for 6 hours. This ion exchange treatment is preferably performed under an inert gas atmosphere. The optimal amount of the reducing anion used in the ion exchange treatment is in the range of 0.5 to 2.0 in terms of the molar ratio (reducing anion / trivalent metal) to the amount of trivalent metal in the synthesized product.

The divalent and trivalent metal compounds used in the above synthesis reaction include magnesium chloride, magnesium nitrate, magnesium acetate, calcium chloride, calcium nitrate, calcium acetate, calcium hydroxide, zinc chloride, zinc nitrate and acetic acid. Examples include chlorides, nitrates, acetates, and hydroxides of zinc, aluminum chloride, aluminum nitrate, sodium aluminate, aluminum hydroxide, and the like.

(Ii) In the hydration reaction method, a hydration reaction of a solid solution of an oxide of a divalent metal and a trivalent metal in an aqueous solution containing a reducing anion is carried out, whereby the hydrotalcite-based compound of the formula (1) of the present invention is obtained. Obtain a solid solution. As the oxide solid solution of a divalent metal and a trivalent metal used, for example, a carbonate ion type hydrotalcite compound [(M ₁ ²⁺ ) y
^{_{1 (M 2 2+) y 2}} ] 1-x M x 3+ (OH) 2 · CO
^{_{3 2- x / 2 · mH 2}} O, ( wherein _M ^{1 2+} is Mg or C
a, M ₂ ²⁺ represents one kind of divalent metal selected from Zn, Ni, Cu and Fe, M ³⁺ represents a trivalent metal, x, y ₁ ,
y ₂ and m are respectively 0.10 ≦ x ≦ 0.66, 0.5 <y
₁ ≦ 1 , 0 ≦ y ₂ <0.5, 0 ≦ m ≦ 1.0) at about 500 to 700 ° C. The hydration reaction of the oxide solid solution is carried out at a temperature of 20 to 170 ° C., preferably 20 to 100 ° C., while stirring the oxide solid solution in an aqueous solution containing a reducing anion under air or preferably under an inert gas atmosphere. By maintaining the temperature for 2 to 15 hours.

As the decomposing agent for free chlorine in water of the present invention, the powder of the hydrotalcite-based solid solution of the above formula (1) may be used as it is, but in order to increase the processing speed of water, it is appropriately formed into granules or the like. It is preferable to have it.

The molding of the powder of the hydrotalcite-based solid solution of the formula (1) is carried out by usual methods such as rolling granulation, extrusion granulation, compression granulation, fluidized bed granulation, and stirring granulation. As crystalline cellulose, polyvinyl alcohol, boehmite gel, hydroxyapatite, alumina sol, silica sol, bentonite, diatomaceous earth, sepiolite, etc., 0.5
It is preferred to mold to a particle size of ~ 3.0 mm.

Hereinafter, the present invention will be described specifically with reference to examples. In these examples, the free chlorine was measured by the ortho-toluidine colorimetric method, and when no coloring was found, the amount of free chlorine was less than 0.01 ppm to 0.00 pp.
m. The sulfite ion was measured by the potassium iodate starch paper method.
pm. The measurement of thiosulfate ion was carried out by the iodine azide reaction method, and its detection limit was 3 ppm.

[0034]

EXAMPLE 1 In a reaction vessel under a nitrogen atmosphere, sodium sulfite (Na ₂ SO 4) was added to demineralized water (ion-exchanged water) which had been boiled in advance.
₃ ) Dissolve 60 g and then add Mg _4.5 Al
50 g of a magnesium-aluminum oxide solid solution obtained by calcining a hydrotalcite compound of ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O at 600 ° C. for 2 hours was added, and the mixture was stirred and dispersed and suspended. For 6 hours. The obtained dispersion suspension was filtered and washed, the attached water was replaced with ethyl alcohol, and then dried at 110 ° C. for 3 hours.
After drying, it was ground to 100 mesh. The pulverized product is Mg-Al from X-ray diffraction, infrared absorption spectrum measurement, and chemical analysis.
It was confirmed that the composition was a hydrotalcite-based solid solution having the following formula and containing -SO ₃ as a main component.

[0035]

_{Embedded image} [Mg _0.70 Al _0.30 (OH) ₂ ]
(SO ₃ ) _0.107 (SO ₄ ) _0.005 (CO ₃ )
_{0.015 (OH)} in 0.03 · 0.51H ₂ O above formula, reducing anion _SO ^{3 -} wherein A,
The ratio of the ^1- and A2 ^- anions to the total is 0.1.
107 ° (0.107 + 0.015 + 0.015 + 0.
03), that is, 64.1 mol%. It is presumed that SO ₄ ⁻⁻ was generated in the solid solution due to oxidation of SO ₃ ^{− −} , and CO ^{3 −−} was generated in the solid solution due to mixing of trace CO ₂ remaining in the air and in the oxide solid solution. .

The pulverized hydrotalcite-based solid solution obtained was molded by adding water to the pulverized product with a kneader, kneading the extruded product to a particle size of 1 mm by extrusion granulation, and then drying at 110 ° C. for 6 hours. 5.0 g of the molded product was placed in a glass column having a diameter of 3 cm, and tap water containing 0.5 ppm of free residual chlorine was added to 0.06 g of tap water.
It was passed at a flow rate of 1 / min · cm ² .

For the obtained water, free chlorine was measured by an ortho-toluidine colorimetric method.
Did not cause any coloring with the ortho-tolidine hydrochloride solution. Also,
Sulfite ions were measured on potassium iodate starch paper but were not detected at all. Example 2 1 liter of demineralized water and 118 g of sodium thiosulfate (Na ₂ S ₂ O ₃ .5H ₂ O), which had been boiled in advance, were put into a reaction vessel and dissolved in a nitrogen atmosphere. 50 g of the magnesium / aluminum oxide solid solution obtained in the same manner as in Example 1 was added to the obtained solution, dispersed and stirred, and reacted at a temperature of 80 ° C. for 6 hours. The resulting dispersion suspension was washed by filtration, and the attached water was replaced with ethyl alcohol.
Let dry for hours. After drying, it was ground to 100 mesh.

The pulverized product was obtained from Mg-Al-S _{2 by} X-ray diffraction or the like.
It was confirmed that the composition was a hydrotalcite-based solid solution having the following formula containing O ₃ as a main component.

[0039]

[Mg _0.70 Al _0.30 (oH) ₂ ] (S ₂ O ₃ ) _0.11 (S
O ₄ ) _0.01 (CO ₃ ) _0.015 (oH) _0.03 · 0.64 H ₂ O In the above formula, the proportions of the reducing anions are A ⁻¹ and A
^Of the obtained hydrotalcite-based solid solution pulverized product in an amount of 66.7 mol% based on the total weight of ^-2 , by adding 4% of the total weight of the pulverized product and crystalline cellulose as a binder by a kneader, and adding After forming into a particle size of 1 mm by extrusion granulation method,
Dry at 110 ° C. for 6 hours.

5.0 g of the molded product was placed in a glass column having a diameter of 3 cm, and tap water containing 0.5 ppm of free chlorine was added to 0.1 g of tap water.
It passed at a flow rate of 06 l / min · cm ² .

The amount of free chlorine in the obtained water was measured by the ortho-toluidine colorimetric method in the same manner as in Example 1, but no coloring was observed with 90 l of the ortho-toluidine hydrochloride solution per g of the molded product. The thiosulfate ion was examined by the iodine azide reaction method, but was not detected at all.

Example 3 A mixed solution A solution of 1.35 mol / l magnesium chloride and 0.6 mol / l aluminum chloride and a B solution of 3.5 mol / l sodium hydroxide aqueous solution are prepared. 1 liter of water is put into a reaction tank with overflow, and the mixture is stirred, and solution A and solution B are added via a metering pump. The reaction was carried out by maintaining the reaction pH at 9.5 ± 0.2 and the reaction temperature at 40 ± 1. The resulting reaction suspension was filtered and washed to obtain a cake-like solid.

From the result of X-ray diffraction and chemical analysis, it was confirmed that the obtained cake-like solid was a hydrotalcite-based solid solution of the following formula mainly composed of Mg-Al-Cl.

[0044]

_{Embedded image} [Mg _0.69 Al _0.31 (OH) ₂ ] Cl _0.279 (C
O ₃ ) _0.023 · 0.67H ₂ O 167 g cake-like solid (equivalent to 50 g in terms of dry matter)
With 1 liter of a 0.2 mol / l aqueous solution of sodium sulfite
And maintained at a temperature of 30 ° C. for 1 hour. After washing by filtration and replacing attached water with ethyl alcohol, the resultant was dried at a temperature of 110 ° C. for 3 hours. After drying, it was ground to 100 mesh.

The pulverized product is made of Mg-Al-SO by X-ray diffraction or the like.
It was confirmed that the composition was a hydrotalcite-based solid solution having the following formula and composed mainly of _three systems.

[0046]

[Mg _0.69 Al _0.31 (OH) ₂ ] (SO ₃ ) _0.093 (S
_{O 4) 0.023 (CO 3)} 0.031 Cl 0.015 · 0.56H 2 O the reducing formula As is clear from the anion SO ₃ ^- of A
The ratio of the ^-1 and A ^-2 anions to the total was 57.4 mol%.

To form the pulverized hydrotalcite-based solid solution obtained, 10% by weight of the pulverized product and boehmite gel as a binder are added to the pulverized product by a kneader, and the mixture is kneaded with water and extruded by a granulation method. After molding to a particle size of 1 mm, it was dried at 110 ° C. for 6 hours.

5.0 g of the molded product was put into a glass column having a diameter of 3 cm, and water containing 0.5 ppm of free chlorine was added to 0.06 g of water.
It was passed at a flow rate of 1 / min · cm ² .

The amount of free chlorine in the obtained water was measured by the ortho-toluidine colorimetric method, but no coloring was observed with 23 liters of ortho-toluidine hydrochloride solution per g of the molded product. Also, no sulfite ion was detected at all by potassium iodate starch paper.

Example 4 In a reactor, 24 g of Ca (NO ₃ ) ₂ .4H ₂ O was added to demineralized water 7
Dissolve in 00 ml. Among this, stirring quality single Ca (O
20 g of H) ₂ and 10.5 g of Al (OH) ₃ were added, mixed, heated to 90 ° C., and reacted for 4 hours. The reaction suspension was filtered and washed, and the attached water was replaced with ethyl alcohol.
Dry at a temperature of 0 ° C. for 3 hours. After drying, it was ground to 100 mesh.

The obtained pulverized product has a layered structure in which a cation layer and an anion and a layer of water of crystallization are alternately repeated by X-ray diffraction or the like, and has basically the same crystal structure as the hydrotalcite compound. Having the following formula Ca-Al-N
It was an O ₃ -based solid solution.

[0052]

[Ca _0.69 Al _0.31 (OH) ₂ ] [(NO ₃ ) _0.29 (C
_{O 3) 0.01 · 0.4H 2 O} ] a ground product 20g was dispersed in 0.077 mol / l sodium thiosulfate aqueous solution with a concentration 700 ml, 3 at a temperature of 30 ° C.
It was maintained for 0 minutes. After filtration and washing, the attached water was replaced with ethyl alcohol, and dried at 110 ° C. for 3 hours.
After drying, it was ground to 100 mesh.

The pulverized product was obtained from Ca-Al-S by X-ray diffraction or the like.
It was a hydrotalcite-based solid solution of the following formula containing ₂ O ₃ as a main component.

[0054]

_{Embedded image} [Ca _0.69 Al _0.31 (OH) ₂ ] (S ₂ O ₃ )
_0.122 (NO ₃ ) _0.017 (SO ₄ ) _0.005・ (CO ₃ ) _0.02・ 0.36
H ₂ O As is apparent from the above formula, the ratio of the reducing anion to the total of A ⁻¹ and A ⁻² was 74.4 mol%.

To form the pulverized hydrotalcite-based solid solution, the kneader was used to add 10% of the total weight of the pulverized product and alumina sol as a binder. Dry at 6 ° C. for 6 hours.

5.0 g of the molded product was put into a glass column having a diameter of 3 cm, and tap water containing 0.5 ppm of free residual chlorine was passed at a flow rate of 0.06 l / min · cm ² .

The amount of free chlorine in the obtained water was measured by an ortho-toluidine colorimetric method.
No coloration was observed with 00 l orthotoluidine hydrochloride solution.
In addition, the test method for thiosulfate ion was not detected at all by the iodine azide reaction method.

Example 5 A mixed aqueous solution (solution A) of 0.95 mol / l magnesium magnesium nitrate, 0.5 mol / l aluminum nitrate and 0.05 mol / l zinc nitrate and a 3.5 mol / l aqueous sodium hydroxide solution (B
Liquid). 1 liter of water is put into a reaction tank with overflow, and the mixture is stirred, and solution A and solution B are added via a metering pump. The reaction was performed at a reaction pH of 9.5 ± 0.1 and a reaction temperature of 30 ° C. ±.
Performed by maintaining at 1. The reaction suspension was filtered and washed to obtain a cake-like solid.

[0059] cake solids have been found to be X-ray diffraction, the hydrotalcite solid solution of formula mainly composed of Mg-Zn-Al-NO ₃ system from chemical analysis.

[0060]

_{Embedded image} [Mg _0.63 Zn _0.033 Al _0.33 (OH) ₂ ] (N
O ₃ ) _0.27 (CO ₃ ) _0.03 · 0.5 H ₂ O About 143 g of the obtained cake-like solid (50 in terms of dry matter)
g) is dispersed in 1 liter of a 0.2 mol / l aqueous solution of sodium sulfite and maintained at a temperature of 30 ° C. for 30 minutes.
Then, the mixture was filtered and washed, and the attached water was replaced with ethyl alcohol, and then dried at 110 ° C. for 3 hours. 100 after drying
Crushed to a mesh.

The pulverized product was Mg-Zn-Al from chemical analysis and the like.
It was confirmed that the composition was a hydrotalcite-based solid solution having the following formula and containing -SO ₃ as a main component.

[0062]

[Mg _0.63 Zn _0.033 Al _0.33 (OH) ₂ ] (S
(O ₃ ) _0.107 (SO ₄ ) _0.014 (CO ₃ ) _0.04 · (NO ₃ ) _0.01 · 0.6
H ₂ O above equation As is apparent, reducing anion SO ₃ ^- of A
The ratio of ^-1 and A- ^{2 to} the total was 62.6 mol%.

In shaping the obtained hydrotalcite-based solid solution pulverized product, a kneader is used to add 15% by weight of hydroxyapatite as a binder and a binder as a binder, and the mixture is kneaded with water and extruded to obtain a particle size by a granulation method. After forming to 1 mm, it was dried at 110 ° C. for 6 hours.

5.0 g of the molded product was placed in a glass column having a diameter of 3 cm, and tap water containing 0.5 ppm of free residual chlorine was passed at a flow rate of 0.06 l / min · cm ² .

The amount of free chlorine in the obtained water was measured by an ortho-toluidine colorimetric method.
No coloring occurred with 6 l of orthotoluidine hydrochloride solution.
Also, sulfite ions were not detected at all by potassium iodate starch paper.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C01G 49/00 C01G 49/00 C C02F 1/58 C02F 1/58 L 1/70 1/70 Z (58) Fields surveyed ( Int.Cl. ⁶ , DB name) C01G 53/00 C01F 7/00 C01G 45/00 C01G 19/00 C02F 1/58 C02F 1/70

Claims (6)

(57) [Claims] 1. Formula (1): [(M ₁₂ ⁺ ) _y1 (M _{2 2} ⁺ ) _y2 ] _{1 -x
^{M x 3+ (OH) 2 A}} p 1- A q 2- · mH 2 O ···
... (1) _wherein, ^{M 1 2+} represents a least one divalent metal selected from the group consisting of Mg and Ca, _M ^{2 2+} is Zn, Mn, Ni, group consisting of CU and Fe M ³⁺ represents a trivalent metal; A ^1- represents at least one monovalent anion; and A ^2- represents at least one divalent anion. X, y ₁ , y ₂ and m represent the following numbers: 0.1 ≦ x ≦ 0.7 0.5 <y ₁ ≦ 10 ≦ y ₂ <0.50 ≦ m ≦ 1 p and q indicate a number satisfying the following formula, but p can be 0: p + 2q = x 10−95 per total of anions of A ¹⁻ and A ²⁻
Mol% is a reducing anion]. A decomposer for free chlorine in water, comprising a hydrotalcite-based solid solution represented by the following formula: Wherein A ^-1 is ^{F -, Cl -, Br -} , NO 3 -, N
^{_{O 2 -, OH -, CH}} 3 COO - and HCO ₃ ^- represents a monovalent least one anion selected from the group consisting of, A ^-2
There ^{_{CO 3 -, SO 4 -,}} SO 3 -, S 2 O 3 - and ## STR2 ## The decomposer according to claim 1, which shows at least one divalent anion selected from the group consisting of: 3. The method according to claim 1, wherein the reducing anions are SO ₃ ^2- and S ₂ O _3.
3. The decomposer according to claim 1, which is at least one divalent anion selected from the group consisting of ^2- . 4. The decomposer according to claim 1, wherein M ³⁺ is Al. 5. A hydrotalcite solid solution has the formula (1 ') embedded image ^{_{(M 1 2+) 1-x}} Al x (OH) 2 A p 1- A q 2- · mH 2 O ··· (1 ') ^{_{wherein, M 1 2+, x, p}} , q and m have the meanings given in claim 1, a ^{1-is F -, Cl -, Br -} , NO 3 -, N
O ₂ ^- and OH ^- become more indicates at least one monovalent anion selected from the group, A ^{2-is _{SO 4 -, CO 3 -,}} S
O ₃ ^- and S ₂ O ₃ ^- at least divalent anion selected from the group consisting indicates a kind, total per 35-95 mole percent of A ^1-and A ^2-anion is a reducing anion , and the said reducing anion is SO ₃ ^- and / or S ₂ O ₃ ^-
Degradation agent according to claim 4, wherein represented by a is ^-. 6. The decomposer according to claim 1, which is used for decomposing free chlorine in tap water.