CN113660996A - Acidic exhaust gas treatment agent, acidic exhaust gas treatment method, and acidic exhaust gas treatment device - Google Patents

Abstract

To provide: Acid waste gas treatment agent, acid waste gas treatment method, which can improve the removal efficiency of nitric oxide when using layered double hydroxide to treat acid waste gas generated by combustion facilities such as thermal power plants and incineration facilities. And acid waste gas treatment equipment. The acid waste gas treatment method of the present invention includes the following steps: Step (1), treatment of acid waste gas using a complex compound based on at least one of manganese oxide and a permanganic acid compound containing a Mg-Al-based layered double hydroxide The above-mentioned acid waste gas is contacted with the above-mentioned acid waste gas treatment agent, and the acid substance in the acid waste gas is adsorbed; step (2), the acid substance adsorbed on the acid waste gas treatment agent in the above-mentioned step (1) is desorbed , regenerating the acidic waste gas treating agent; and step (3), recovering the acidic substances desorbed from the acidic exhaust gas treating agent in the aforementioned step (2).

Description

Acid waste gas treatment agent, acid waste gas treatment method, and acid waste gas treatment equipment

technical field

The present invention relates to an acid waste gas treatment agent, acid waste gas treatment method, and acid waste gas treatment equipment suitable for the treatment of acid waste gas produced by combustion facilities such as thermal power plants and incineration facilities.

Background technique

The combustion exhaust gas generated by thermal power generation, waste incineration, etc. contains harmful acidic substances such as hydrogen chloride, sulfur oxides, and nitrogen oxides. Therefore, with respect to the acidic waste gas containing the said acidic substance, the process for removing the said acidic substance is performed based on various methods.

Hydrogen chloride and sulfur oxides among the above-mentioned acidic substances are generally treated by neutralization using an alkaline agent such as slaked lime, a dry method in which the product is collected with a dust collector, and a wet method in which the neutralization treatment is performed with a scrubber. processing.

In addition, for nitrogen oxides, treatments by selective catalytic reduction (SCR) and non-catalytic reduction (SNCR) in which a reducing agent such as ammonia and urea is mixed with combustion exhaust gas have become popular. A catalyst in which vanadium, platinum, etc. are supported on a carrier such as ceramics is decomposed into nitrogen and water, and the non-catalytic reduction method is a treatment in which a reducing agent such as ammonia or urea is directly sprayed into an incinerator to decompose nitrogen oxides.

However, the above-mentioned treatment based on the neutralization treatment requires a treatment process of the neutralized product, and further treatment of nitrogen oxides is required.

In addition, the treatment of nitrogen oxides by SCR and SNCR has problems such as the need to use a reducing agent, a catalyst, and the like, and the cost of equipment, energy, and the like for this.

In response to such a problem, the present inventors have proposed a method for efficiently treating the acidic waste gas at a lower cost by using a carbonic acid-type Mg—Al-based layered double hydroxide (see Patent Document 1).

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2016-190199

SUMMARY OF THE INVENTION

Invention to solve problem

However, even if the treatment method described in the above-mentioned Patent Document 1 is used, the removal treatment of nitric oxide may not always be sufficient.

Therefore, in the treatment of the acidic waste gas using the layered double hydroxide, it is required to improve the removal efficiency of nitric oxide.

The present invention has been accomplished under such circumstances, and an object of the present invention is to provide a method capable of increasing the level of nitrogen monoxide in the treatment of acidic waste gas generated by combustion facilities such as thermal power plants and incineration facilities using layered double hydroxides. Acid waste gas treatment agent with high removal efficiency, acid waste gas treatment method, and acid waste gas treatment equipment.

solution to the problem

The present invention is based on the discovery that a complex based on manganese oxide or the like of a Mg-Al-based layered double hydroxide (hereinafter also referred to as Mg-Al LDH (Layered Double Hydroxide)) has excellent nitric oxide removal performance.

That is, the present invention provides the following [1] to [7].

[1] An acidic exhaust gas treating agent comprising a composite of at least one of manganese oxide and a permanganic acid compound of a Mg—Al-based layered double hydroxide.

[2] The acidic exhaust gas treatment agent according to the above [1], wherein the composite is a manganese dioxide composite Mg-Al-based layered double hydroxide and a permanganate-type Mg-Al-based layered double hydroxide at least any of the oxides.

[3] The acidic exhaust gas treating agent according to the above [1] or [2], comprising a carbonic acid-type Mg—Al-based layered double hydroxide.

[4] A method for treating acidic waste gas using the acidic waste gas treating agent according to any one of the above [1] to [3], the processing method comprising the steps of: step ( 1), the acid waste gas is brought into contact with the acid waste gas treatment agent, and the acid substance in the acid waste gas is adsorbed; step (2), the acid substance adsorbed on the acid waste gas treatment agent in the step (1) is removed. Attached, regenerating the acidic waste gas treating agent; and step (3), recovering the acidic substance desorbed from the acidic exhaust gas treating agent in the aforementioned step (2).

[5] The acid waste gas treatment method according to the above [4], wherein the treatment cycle including the above-mentioned steps (1) to (3) is repeatedly performed, and at least any one of the second and subsequent treatment cycles of the treatment cycle is performed repeatedly. In the step (1) of the above, the acidic waste gas treating agent regenerated in the step (2) of at least one of the treatment cycles preceding the treatment cycle is used as at least a part of the acidic exhaust gas treating agent.

[6] An acid waste gas treatment facility for treating acid waste gas using the acid waste gas treatment agent according to any one of the above [1] to [3], the treatment facility including a device ( 1), the above-mentioned acidic waste gas is brought into contact with the above-mentioned acidic waste gas treatment agent, and the acidic substances in the above-mentioned acidic waste gas are adsorbed; device (2), in the above-mentioned device (1), the acidic substances adsorbed on the above-mentioned acidic waste gas treatment agent are removed Attached, regenerating the above-mentioned acidic waste gas treatment agent; and a device (3), recovering the acidic substance desorbed from the above-mentioned acidic waste gas treatment agent in the above-mentioned device (2).

[7] The acid waste gas treatment method according to the above [4], wherein the manganese dioxide composite Mg-Al-based layered double hydroxide is produced by a production method that does not require a reduction step, and the manganese dioxide The composite Mg-Al-based layered double hydroxide is produced by adding Mg-Al oxide to an aqueous potassium permanganate solution, filtering and drying the precipitate.

effect of invention

By using the acid waste gas treatment agent of the present invention, it is possible to simultaneously remove acid waste gas such as hydrogen chloride, sulfur oxides, and nitrogen oxides generated by combustion facilities such as thermal power plants and incineration facilities. The removal efficiency of nitric oxide is improved compared to the case of the double hydroxide.

Moreover, according to the acidic waste gas processing method of this invention using the said acidic waste gas processing agent, acidic waste gas can be removed efficiently with a smaller treatment amount than the prior art, and the said acidic waste gas processing agent can be regenerated.

Moreover, according to the acidic waste gas processing apparatus of this invention, the said acidic waste gas processing method can be suitably performed, and it becomes possible to process an acidic waste gas more efficiently and at low cost than before.

Description of drawings

FIG. 1 is a graph showing the change with time of the _NOx concentration in the outlet gas of the reaction tube in the acid exhaust gas treatment performance evaluation test of the Example.

FIG. 2 is a powder X-ray diffraction pattern of the product of Synthesis Example 1. FIG.

3 is a powder X-ray diffraction pattern of the product of Synthesis Example 2. FIG.

Figure 4 is a powder X-ray diffraction pattern of _CO3 -type Mg-Al LDH.

FIG. 5 is the XPS spectrum of the product of Synthesis Example 1. FIG.

FIG. 6 is the XPS spectrum of the product of Synthesis Example 2. FIG.

Detailed ways

Hereinafter, the acidic waste gas processing agent of this invention, the acidic waste gas processing method and the acidic waste gas processing equipment using the same are demonstrated in detail.

[Acid waste gas treatment agent]

The acidic exhaust gas treating agent of the present invention contains a complex of Mg-Al LDH based on at least one of manganese oxide and permanganic acid compound (hereinafter also referred to as Mn-O compound.).

In this way, by using Mg-Al LDH as a complex compound based on a compound of manganese and oxygen (Mn-O compound) as an acidic exhaust gas treatment agent, it is possible to use Mg-Al LDH as a conventional layered double hydroxide, etc. Compared with the case of nitric oxide, the removal efficiency of nitric oxide can be improved.

It is presumed that this is because Mg-Al LDH itself is not easy to adsorb nitric oxide, but under the catalytic action of the composite Mn-O compound, nitric oxide is oxidized to nitrogen dioxide, and then becomes easily oxidized to nitric acid The root ion becomes easily adsorbed to the complex of Mg-Al LDH.

Manganese may have an oxidation number of +2 to +7, but from the viewpoint of its function as an oxidation catalyst, a larger oxidation number is preferred. As the composite compound, from the viewpoint of ease of synthesis and the like, for example, a manganese dioxide composite Mg-Al layered double hydroxide based on manganese having an oxidation number of +4 (hereinafter also referred to as MnO ₂ composite Mg-Al LDH) is preferable. .), or a permanganate-type Mg-Al-based layered double hydroxide based on manganese with an oxidation number of +7 (hereinafter also referred to as MnO ₄ -type Mg-Al LDH.), etc. The above-mentioned complexes may be contained alone or two or more types may be contained.

The structural formula of the MnO ₂ complex Mg-Al LDH is represented by the following formula (1), and the structural formula of the MnO ₄ type Mg-Al LDH is represented by the following formula (2).

Mg _1-x Al _x (OH) ₂ (MnO ₂ ) _2.5x (Cl) _x mH ₂ O (1)

Mg _1-x Al _x (OH) ₂ (MnO ₄ ) _x mH ₂ O (2)

In the aforementioned formulas (1) and (2), usually x=0.20 to 0.40 and m=1 to 12.

The acidic exhaust gas treating agent preferably contains a carbonic acid-type Mg-Al-based layered double hydroxide (hereinafter also referred to as _CO3 -type Mg-Al LDH.).

As described in the above-mentioned Patent Document 1, CO ₃ type Mg—Al LDH is a compound that can be suitably used for the treatment of acidic exhaust gas, and can effectively remove, for example, hydrogen chloride, sulfur dioxide, nitrogen dioxide, etc. contained in the acidic exhaust gas except for nitrogen monoxide. of acidic compounds. Therefore, it is preferably used in combination with the aforementioned complex.

In this case, the content ratio of the composite compound and CO ₃ -type Mg-Al LDH in the acid waste gas treating agent is not particularly limited, and may be determined according to the components of the acid waste gas such as the amount of nitric oxide contained in the acid waste gas to be treated. The composition is appropriately set.

CO ₃ -type Mg—Al LDH also exists as hydrotalcite in naturally occurring clay minerals, but when synthesizing, the method for synthesizing is not particularly limited, and a known method (for example, the method described in Patent Document 1 above) can be used.

For example, dropping an aqueous solution in which magnesium nitrate (Mg(NO ₃ ) ₂ ) and aluminum nitrate (Al(NO ₃ ) ₃ ) are mixed at Mg/Al=2/1 (molar ratio) at pH 10.5 can be added. It can be obtained by adding it to an aqueous solution of sodium carbonate (Na ₂ CO ₃ ). Specifically, it can be synthesized by the method shown in the following examples.

In addition, the method for synthesizing MnO ₂ composite Mg-Al LDH and MnO ₄ type Mg-Al LDH is also not particularly limited, and can be synthesized by using CO ₃ type Mg-Al LDH as a raw material compound and utilizing the anion exchange function based on its intercalation. .

For example, CO ₃ -type Mg-Al LDH is pre-calcined at 500° C. to obtain Mg-Al oxide, which is then added to and mixed with an aqueous potassium permanganate (KMnO ₄ ) solution to synthesize and capture permanganate ions ( MnO ₄ ^- ) of the MnO ₄ type Mg-AlLDH.

Furthermore, MnO ₄ type Mg-Al LDH becomes MnO ₂ complex Mg-Al LDH in potassium permanganate (KMnO ₄ ) aqueous solution.

In addition, the MnO ₄ -type Mg-Al LDH can be synthesized by adding and mixing the aforementioned MnO ₄ -type Mg-Al LDH to a manganese chloride (MnCl ₂ ) aqueous solution.

The aforementioned acidic waste gas treatment agent may contain, for example, calcium hydroxide (slaked lime), calcium oxide, sodium bicarbonate (sodium bicarbonate), sodium carbonate, hydroxide dolomite, and light-burned dolomite within a range that does not impair the effects of the present invention. , Chemicals other than layered double hydroxides such as aluminum hydroxide, aluminum oxide, magnesium hydroxide, and magnesium oxide. However, in the acidic waste gas treatment method described later, when the above-mentioned acidic waste gas treatment agent is regenerated and reused, it is preferable not to contain these chemicals from the viewpoints of the purity of the regenerated product, the recovery operation, and the like.

[Acid waste gas treatment method]

The method for treating acidic exhaust gas using the above-mentioned acidic exhaust gas treating agent is not particularly limited, but the aforementioned acidic exhaust gas treating agent (hereinafter also simply referred to as a treating agent) is preferably suitable for the acidic exhaust gas treating method of the present invention.

The acid waste gas treatment method of the present invention includes the following steps: step (1), contacting the acid waste gas with the treatment agent, and adsorbing the acid substances in the acid waste gas; The acidic substances on the treatment agent are desorbed to regenerate the treatment agent; and in step (3), the acidic substances desorbed from the treatment agent in the step (2) are recovered.

According to the above-mentioned treatment method, the regenerated treatment agent can be reused. In addition, an acidic substance is dissolved in water, for example, and is recovered as an acid (aqueous solution), and this acid can also be used for industrial use or the like.

In the above-mentioned step (1), the nitric oxide is oxidized by the above-mentioned complex compound in the above-mentioned treatment agent, and the above-mentioned nitric oxide is oxidized by anion exchange of the acidic substance in the acid waste gas incorporated between the layers of the layered double hydroxide, and the like. The acidic substance is adsorbed on the aforementioned treating agent.

Next, in the said step (2), the said acidic substance adsorbed on the said processing agent is desorbed from the said processing agent by reversible anion exchange etc. The anion exchange at this time can be performed, for example, by using various aqueous solutions and mixing and stirring in the same manner as in the synthesis method of CO ₃ type Mg-Al LDH, MnO ₂ composite Mg-Al LDH, and MnO ₄ type Mg-Al LDH. , the treatment agent can be easily regenerated.

The treatment agent thus regenerated can be reused, so that the treatment cost of the acid waste gas can be reduced.

In the aforementioned step (3), the acidic substance desorbed from the aforementioned treatment agent in the aforementioned step (2) is recovered. For example, it can be dissolved in water and recovered as an acid (aqueous solution), and the above-mentioned acid can also be used for industrial use or the like.

In this way, the treatment method of the present invention is a method that is excellent in recyclability not only with respect to the aforementioned treatment agent but also with respect to the acidic exhaust gas to be treated.

In the aforementioned treatment method, it is preferable to repeat the treatment cycle including the aforementioned steps (1) to (3), and to use the treatment agent as the aforementioned treatment agent in the second and subsequent step (1) of at least one treatment cycle. At least a part of it uses the treatment agent regenerated in step (2) of at least any one treatment cycle preceding this treatment cycle.

In this way, when the above-described treatment method is repeated, by reusing the treatment agent regenerated in the previous step, the total amount of the treatment agent required for the treatment of the acid waste gas can be reduced, and the treatment cost of the acid waste gas can be reduced.

The above-described method for treating an acidic waste gas of the present invention can simultaneously remove various acidic substances in an acidic waste gas with a single treatment agent, and thus is excellent in work efficiency. In particular, the removal efficiency of nitric oxide can be improved compared with the prior art by using the above-mentioned complex as a treatment agent.

In addition, neutralization products are not generated during the treatment, and the treatment load of the waste generated accompanying the treatment can be reduced.

[Acid waste gas treatment equipment]

The equipment for treating acidic exhaust gas using the aforementioned acidic exhaust gas treating agent is not particularly limited, and the aforementioned treating agent is preferably applied to the acidic exhaust gas treating equipment of the present invention.

The acid waste gas treatment equipment of the present invention is provided with the following means: a device (1) for contacting the acid waste gas with the treatment agent to adsorb the acid substances in the acid waste gas; and a device (2) for adsorbing the acid in the device (1) on The acid substance of the treatment agent is desorbed to regenerate the treatment agent; and a device (3) is used to recover the acid substance desorbed from the treatment agent in the device (2).

The said apparatus (1) can be comprised by providing the flow path of an acidic waste gas in the container which accommodated the said processing agent, for example.

The apparatus (2) can be configured as, for example, a dipping tank that can use the above-mentioned CO ₃ type Mg-Al LDH and MnO ₂ to compound the treatment agent taken out from the container through which the acidic waste gas flows. Mg-Al LDH and MnO ₄ -type Mg-Al LDH were immersed in various aqueous solutions and mixed and stirred according to the chemical type to be complexed with Mg-Al LDH in the same method.

The said apparatus (3) can be comprised so that it may be comprised so that the aqueous solution storage tank which melt|dissolved in water, and was collect|recovered as an acid (aqueous solution), for example.

The aforementioned acid waste gas treatment equipment may be attached to combustion equipment in thermal power generation, waste incineration, and the like. For example, when treating the acid waste gas generated by the waste incinerator, it may be configured as follows: the above-mentioned acid waste gas treatment is provided after the boiler, the waste gas cooling device, and the dust collector, which are sequentially installed in the combustion waste gas system of the main body of the incinerator. A device from which the treated exhaust gas from the acid exhaust gas treatment plant is introduced into a chimney by means of a suction fan or the like, from which it is released into the atmosphere.

Example

The present invention will be described in more detail below, but the present invention is not limited to the following examples.

[Synthesis Example 1] Synthesis of _MnO2 -composite Mg-Al LDH

Using magnesium nitrate hexahydrate and aluminum nitrate nonahydrate, a mixed aqueous solution having a magnesium concentration of 0.33 mol/L and an aluminum concentration of 0.17 mol/L (magnesium/aluminum=2/1 (molar ratio)) was prepared.

The mixed solution was added dropwise to an aqueous sodium carbonate solution having a concentration of 0.1 mol/L at 30°C with stirring. At this time, the pH was kept at 10.5 by dropwise addition of an aqueous sodium hydroxide solution having a concentration of 1.25 mol/L.

After completion of the dropwise addition, the mixture was stirred at 30°C for 1 hour. Then, the precipitate was filtered and repeatedly washed, and then dried under reduced pressure at 40° C. for 40 hours to obtain CO ₃ type Mg—Al LDH.

The obtained CO ₃ type Mg-Al LDH was pre-calcined at 500°C for 2 hours, then put into a potassium permanganate aqueous solution with a concentration of 0.2 mol/L under nitrogen flow, and stirred at 30°C for 6 hours. Then, after filtering the precipitate and repeating the washing, the product obtained by drying under reduced pressure at 40°C for 40 hours was put into an aqueous solution of manganese chloride with a concentration of 0.1 mol/L under nitrogen flow, and stirred at 30°C for 3 hours. . Then, the precipitate was filtered and repeatedly washed, and then dried under reduced pressure at 40° C. to obtain MnO ₂ composite Mg-Al LDH (Mg _0.62 Al _0.38 (OH) ₂ (MnO ₂ ) _0.95 (Cl) _0.38 1.13H ₂ ) O).

[Synthesis example 2] Synthesis of MnO ₂ composite Mg-Al LDH

Using magnesium nitrate hexahydrate and aluminum nitrate nonahydrate, a mixed aqueous solution having a magnesium concentration of 0.33 mol/L and an aluminum concentration of 0.17 mol/L (magnesium/aluminum=2/1 (molar ratio)) was prepared.

The mixed solution was added dropwise to an aqueous sodium carbonate solution having a concentration of 0.1 mol/L at 30°C with stirring. At this time, the pH was kept at 10.5 by dropwise addition of an aqueous sodium hydroxide solution having a concentration of 1.25 mol/L.

After completion of the dropwise addition, the mixture was stirred at 30°C for 1 hour. Then, the precipitate was filtered and repeatedly washed, and then dried under reduced pressure at 40° C. for 40 hours to obtain CO ₃ type Mg—Al LDH.

The obtained CO ₃ type Mg-Al LDH was pre-calcined at 500°C for 2 hours, then put into a potassium permanganate aqueous solution with a concentration of 0.2 mol/L under nitrogen flow, and stirred at 30°C for 6 hours. Then, the precipitate was filtered and repeatedly washed, and then dried under reduced pressure at 40° C. for 40 hours.

It should be noted that CO ₃ type Mg-Al LDH, MnO ₄ type Mg-Al LDH, and MnO ₂ composite Mg-Al in Synthesis Example 1 and Synthesis Example 2 were identified by powder X-ray diffraction measurement (powder XRD). LDH. For the _CO3 -type Mg-Al LDH, Figure 4 shows the powder X-ray diffraction pattern. In addition, the X-ray diffraction measurement apparatus used was "RINT-2200VHF" by Rigaku Corporation, and CuKα rays (1.5418A) were used for measurement as characteristic X-rays. In addition, the elemental analysis value by inductively coupled plasma emission spectrometry (ICP-AES) is also shown for the complex compound based on the Mn-O compound. In addition, the MnO ₄ type Mg-Al LDH and the MnO ₂ complex Mg-Al LDH in Synthesis Example 1 and Synthesis Example 2 were identified by determining the oxidation number of Mn using X-ray photoelectron spectroscopy (XPS).

[Acid waste gas treatment performance evaluation test]

(Example 1)

1.0 g of MnO ₂ composite Mg-Al LDH obtained in Synthesis Example 1 was filled on glass wool in a reaction tube (inner diameter: 16 mm) of a tubular electric furnace. The set temperature of the tubular electric furnace was set at 170°C, and the flow rate of the test gas (carrier gas: nitrogen, 150 volppm of nitric oxide gas concentration, 10 vol% of oxygen concentration) was adjusted by a mass flow controller, and flowed at a linear velocity of 1.0 m/min. in the reaction tube. The time-dependent change (90 minutes) of the _NOx concentration in the outlet gas of the reaction tube was measured with a combustion exhaust gas analyzer (manufactured by Testo SE & Co. KGaA) based on the potentiostatic electrolysis method.

(Comparative Example 1)

In Example 1, the evaluation test was carried out in the same manner as in Example 1, except that the MnO ₂ complex Mg-Al LDH was changed to the CO ₃ type Mg-Al LDH obtained in the synthesis process of Synthesis Example 1.

In FIG. 1 , the change with time of the _NOx concentration in the outlet gas of the reaction tubes in Example 1 and Comparative Example 1 is shown.

In addition, the reaction rate of the nitric oxide gas in the test gas was obtained from the cumulative concentration of _NOx concentration, and as a result, Example 1 was 91.5 vol%, and Comparative Example 1 was 2.2 vol%.

From these results, it became clear that the complex of manganese dioxide and Mg-Al-based layered double hydroxide is superior in removal performance of nitric oxide than CO ₃ type Mg-Al LDH.

[Analysis of Existence Ratio of _MnO Composite Mg-Al LDH Based on Synthesis Example 1 and Synthesis Example 2]

The powder X-ray diffraction patterns of the products based on Synthesis Example 1 and Synthesis Example 2 are shown in FIGS. 2 and 3 . 5 and 6 show the XPS patterns of the products based on Synthesis Example 1 and Synthesis Example 2.

From the elemental analysis value, the Mg/Al molar ratios of the products of Synthesis Example 1 and Synthesis Example 2 are 1.9 and 1.6, respectively, which are basically consistent with the initial Mg/Al molar ratio of 2.0.

任意产物均具有LDH结构。From the powder X-ray diffraction patterns of FIGS. 2 and 3 , X-ray peaks all attributed to LDH were shown, and it was confirmed that the interplanar spacing (d 003 ) was

Any product has the LDH structure.

From the XPS spectra of FIGS. 5 and 6 , the peak of Mn(IV) derived from MnO ₂ was confirmed, and it was confirmed from the peak area that 95% or more of Mn(IV) was present with respect to the total amount of Mn.

From these results, it was confirmed that MnO ₂ composite Mg—Al LDH can be synthesized even without the reduction step of adding the manganese chloride aqueous solution shown in Synthesis Example 1 as in Synthesis Example 2.

In addition, the MnO ₂ composite Mg-Al LDH in Synthesis Example 2 is considered to be produced as follows.

First, after pre-calcining CO ₃ type Mg-Al LDH at 500°C for 2 hours, the resulting Mg-Al oxide (Mg _{1- x} Al _x O _1+x/2 ) was charged in a nitrogen gas stream at a concentration of 0.2 mol MnO ₄ type Mg-Al LDH (Mg _1-x Al _x (OH) ₂ (MnO ₄ ) is produced as shown in formula (3) when stirred in a potassium permanganate aqueous solution of /L for 6 hours at 30° C. _x ).

Mg _1-x Al _x O _1+x/2 +xMnO ₄ ^- +(1+x/2)H ₂ O

→Mg _1-x Al _x (OH) ₂ (MnO ₄ ) _x +xOH- (3)

Furthermore, in the potassium permanganate aqueous solution, the reaction represented by the formula (4) occurs to generate MnO ₂ type Mg—Al LDH (Mg _{1- x} Al _x (OH) ₂ (MnO ₂ ) _x ).

Mg _1-x Al _x (OH) ₂ (MnO ₄ ) _x +x/2H ₂ O

→Mg _1-x Al _x (OH) ₂ (MnO ₂ ) _x +3/4xO ₂ +xOH- (4).

Claims (7)

1 . An acidic exhaust gas treatment agent comprising at least one of a manganese oxide and a permanganic acid compound of a Mg—Al-based layered double hydroxide-based complex. 2 . The acid waste gas treatment agent according to claim 1 , wherein the composite is a manganese dioxide composite Mg-Al-based layered double hydroxide and a permanganate-type Mg-Al-based layered double hydroxide. 3 . at least any of them. 3. The acidic waste gas treating agent according to claim 1 or 2, comprising a carbonic acid-type Mg-Al-based layered double hydroxide. 4. A method for treating acid waste gas, which is a method for processing acid waste gas using the acid waste gas treatment agent according to any one of claims 1 to 3, the treatment method comprising the following steps: Step (1), contacting the acid waste gas with the acid waste gas treatment agent, and adsorbing the acid substances in the acid waste gas; step (2), desorbing the acidic substance adsorbed on the acidic waste gas treating agent in the step (1), and regenerating the acidic exhaust gas treating agent; and In step (3), the acidic substance desorbed from the acidic waste gas treating agent in the step (2) is recovered. 5 . The acid waste gas treatment method according to claim 4 , wherein the treatment cycle including the steps (1) to (3) is repeated, and at least any one of the second and subsequent treatment cycles of the treatment cycle is performed. 6 . In the step (1) of the above, the acidic waste gas treating agent regenerated in the step (2) of at least one of the treatment cycles preceding the treatment cycle is used as at least a part of the acidic exhaust gas treating agent. 6 . An acid waste gas treatment equipment, which is an equipment for processing acid waste gas using the acid waste gas treatment agent according to any one of claims 1 to 3, wherein the treatment equipment includes the following devices: A device (1) for contacting the acid waste gas with the acid waste gas treatment agent, and adsorbing the acid substances in the acid waste gas; A device (2) for desorbing the acidic substance adsorbed on the acidic waste gas treatment agent in the device (1) to regenerate the acidic waste gas treatment agent; and A device (3) for recovering the acidic substances desorbed from the acidic waste gas treatment agent in the device (2). 7 . The acid waste gas treatment method according to claim 4 , wherein the manganese dioxide composite Mg-Al-based layered double hydroxide is produced by a production method that does not require a reduction step, and the manganese dioxide composite Mg -Al-based layered double hydroxide is produced by adding Mg-Al oxide to an aqueous potassium permanganate solution, filtering and drying the precipitate.

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