JP2002045687A - Adsorbent for dioxins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dioxin adsorbent capable of adsorbing, collecting or removing any fume, tarry material, or the like, each containing environmental pollutants such as dioxins. SOLUTION: This adsorbent consists of alumina containing a silica component and in particular comprises, as its effective ingredient, alumina containing an alkali-treated silica component, wherein, after the alkali treatment of the alumina containing the silica component, the resulting alumina is further immersed in a metal salt solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dioxins ("dioxins" prescribed in Article 2 of the Law for Special Measures against Dioxins of 1999, Law No. 105 of 1999; Polychlorinated dibenzo-para-dioxin, coplanar-polychlorinated biphenyl "
Is used as a generic expression. The same shall apply hereinafter).

[0002]

2. Description of the Related Art Dust and fumes are present in the ambient air due to exhaust gas generated when incinerating waste such as industrial waste and general household waste, and exhaust gas from automobiles. Contains environmental pollutants such as dioxins. Here, dust can be collected by a bag filter or the like, but fumes or the like cannot be collected or removed by conventional collecting or removing means.

[0003] By the way, tar-like substances derived from unburned hydrocarbons and carbon compounds such as carbon monoxide often dissolve the environmental pollutants and take them into the interior. It is more likely that they cannot be collected or removed. Therefore, in order to completely collect or remove environmental pollutants, it is also necessary to collect or remove environmental pollutants contained in tar-like substances.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an adsorbent capable of adsorbing or removing fumes and tar-like substances containing environmental pollutants.

[0005]

Means for Solving the Problems The present invention has been made to solve the above problems, and the invention according to claim 1 is an alumina containing a silica component, wherein the silica component is an alkali. It is characterized in that the treated alumina is used as an active ingredient.

Further, the invention according to claim 2 is characterized in that the alumina is further immersed in a metal salt.

[0007]

Next, an embodiment of the present invention will be described. The present invention relates to dioxins contained in exhaust gas from incinerators and automobiles, or in ambient air, etc.
In particular, it is suitably used for collecting or removing fumes and tar-like substances containing dioxins. According to the present invention, fumes and tar-like substances containing environmental pollutants can be collected or removed by using alumina obtained by treating a silica component in an alkaline solution.

First, alumina containing a silica component will be described. If the silica component content of this alumina is low, the silica component does not dissolve, so that cavities cannot be formed, and the specific surface area does not increase, so that the adsorption capacity is small, and it is not suitable for adsorbing or collecting fumes and tar-like substances. Conversely, when the silica content is high, the silica component dissolves to form cavities, but the dissolved silica re-adheres, so the adsorption capacity does not increase so much, and it is suitable for adsorption sampling or removal of fumes and tar-like substances. Absent. Therefore, the silica content of alumina is 5 to 60% by weight, preferably 10 to 5% by weight.
A range of 0% by weight is desirable. By keeping the silica content within this range, the silica component is dissolved to form a cavity, and the dissolved silica does not adhere again. As a result, the specific surface area is increased and the adsorption capacity is increased, which is suitable for adsorbing or removing fumes and tar-like substances.

The shape of the alumina is not particularly limited. However, when the alumina is used in a fibrous form, it is more convenient to handle in the next alkali treatment (treatment of immersion in an alkaline solution) than a powder. It is easy to process into molded products such as filters. Furthermore, even if it blows into a bag filter, pressure loss is low and clogging can be made difficult. In the case of this fibrous alumina, the fiber diameter is 0.5 μm
In the following cases, the fiber shape cannot be maintained due to the durability problem due to the alkali treatment. On the other hand, if it is 30 μm or more, the specific surface area cannot be obtained, and the adsorption capacity is reduced. for that reason,
The fiber diameter of the fibrous alumina is desirably 0.5 to 30 μm, preferably 1 to 20 μm. By keeping the content within this range, the adsorption capacity can be increased, and this is suitable for the adsorption and collection or removal of fumes and tar-like substances.

Next, immersion in an alkaline solution,
That is, the alkali treatment will be described. The alkali used here has a high solubility when converted to an aqueous solution,
Alkali such that the reaction rate is further increased is preferable,
For example, an alkali metal hydroxide is preferred. Conversely, the alkaline earth metal hydroxide binds to silicon dissolved from alumina containing silica and produces scale on the surface of alumina, which is not preferred because alkali treatment is inhibited. When the alkali has a low concentration, the alkali treatment takes a long time (20 hours or more).
It is preferable to use an alkali of 5 mol / l or more, more preferably 1 mol / l or more. Furthermore, when the temperature during the alkali treatment is high, the amount of silica eluted is large, and the eluted silica is easily concentrated around the gas-liquid interface, and scale is easily generated on the alumina surface. More preferably, it is 80 ° C. or lower.

Further, by immersing the alumina containing silica, which has been subjected to the alkali treatment, in a metal salt, alumina having a large adsorption capacity can be obtained. The metal salt used here is preferably one that does not destroy the product formed by the alkali treatment, and an alkaline or neutral salt is preferable as the property of the aqueous solution. For example, silver nitrate, calcium chloride and the like.

The alumina-containing silica that has been subjected to the alkali treatment and granulated with a binder can be used to collect fumes and tar-like substances containing dioxins in exhaust gas from incinerators, automobiles, and the like. .
In addition, those formed into a flat film or a cylindrical shape can be used as a filter for collecting fumes and tar-like substances containing dioxins, so that a large flow rate and high concentration of dioxins can be collected. Furthermore, the powdered material can be used as a dioxin-removing material for blowing into a bag filter, and the dioxin-removing material has a small amount of blowing, and as a result, generated fly The amount of ash can be reduced.

[0013]

Next, specific embodiments of the present invention will be described. Here, FIG. 1 is an electron micrograph of fibrous alumina (6 μm) having a silica content of 28% by weight before alkali treatment. FIGS. 2 and 3 are electron micrographs of the fibrous alumina having a silica content of 28% by weight after the alkali treatment.

First, fibrous alumina having a silica content of 28% by weight (FIG. 1) was subjected to alkali treatment at 90 ° C. using 3 mol / l of sodium hydroxide. FIG.
Fig. 3 is an electron micrograph when alkali treatment was performed for 1 hour. FIG. 3 is an electron micrograph when the alkali treatment was performed for 15 hours.

Here, the alkaline treatment at 90 ° C. shown in FIG. 2 for 1 hour and the 90 ° C. shown in FIG.
When the alkali treatment was performed for 15 hours, the tar adsorption capacity increased by 6 times and 2 times, respectively, as compared with before the alkali treatment.

Next, with respect to fibrous alumina having a silica content of 28% by weight, the treatment temperature of the alkali treatment is set at 20.
The tar adsorption capacity was measured at temperatures of 80 ° C, 80 ° C, 90 ° C and 95 ° C. The result is shown in FIG. Here, alkali treatment was performed using 3 mol / liter of sodium hydroxide. Further, the tar adsorption capacity is represented by a relative value when 0 hour is set to 1.

As shown in FIG. 4, when the heating is performed at 90 ° C. or more,
The point at which the tar adsorption capacity reaches a peak is earlier, and the silica component is immediately recrystallized to reduce the tar adsorption capacity. Therefore, the processing temperature is preferably 90 ° C. or less. further,
The treatment temperature is preferably 80 ° C. or lower where a point where the tar adsorption capacity reaches a peak exists for a long time.

Next, with respect to fibrous alumina having a silica content of 28% by weight, the alkali treatment temperature was set to 20 ° C.
And an alkali treatment concentration of 0.5 mol / liter, 1 mol /
The tar adsorption capacity at liter and 3 mol / liter was measured. The result is shown in FIG.

As shown in FIG. 5, when the concentration of sodium hydroxide is 0.5 mol / liter or less, it takes a considerable time (20 hours or more) to reach a point where the tar adsorption capacity reaches a peak. Is not preferred. Therefore, the concentration of sodium hydroxide is 0.5 mol /
If it is more than liter, it is relatively short (within 20 hours)
Therefore, it is preferable as an alkali treatment. Further, the concentration of sodium hydroxide is preferably 1 mol / liter or more where the point where the tar adsorption capacity reaches a peak exists within 15 hours.

As described above, alumina containing silica was treated at a processing temperature of 90 ° C. or less and an alkali concentration of 0.5 mol.
By carrying out the alkali treatment at / l or more, the adsorption capacity of tar and the like increases.

Next, the fibrous alumina having a silica content of 28% by weight was alkali-treated, and the tar adsorption capacity when immersed in a calcium chloride solution was measured. FIG. 6 shows the result. Here, an alkali treatment temperature was set to 20 ° C., 3 mol / liter of sodium hydroxide was used as an alkali, and alumina treated with an alkali for 10 hours was used.

As shown in FIG. 6, the tar adsorption capacity is increased by immersing the alkali-treated alumina in the calcium chloride solution. That is, by further immersing the alkali-treated alumina in the metal salt, the tar adsorption capacity can be increased.

[0023]

As described above, according to the present invention, it is possible to increase the capacity of adsorbing or collecting fumes and tar-like substances containing environmental pollutants.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of a fibrous alumina containing 28% by weight of silica before alkali treatment.

FIG. 2 is an electron micrograph of a fibrous alumina containing 28% by weight of silica after alkali treatment at 90 ° C. for 1 hour.

FIG. 3 is an electron micrograph of fibrous alumina containing 28% by weight of silica after alkali treatment at 90 ° C. for 15 hours.

FIG. 4 is a graph showing the relationship between the treatment time and the tar adsorption capacity with respect to the alkali treatment temperature when alkali treatment is performed using 3 mol / liter sodium hydroxide.

FIG. 5 is a graph showing the relationship between the treatment time and the tar adsorption capacity with respect to the alkali treatment concentration when the alkali treatment is performed at 20 ° C.

FIG. 6 is a graph showing a tar adsorption capacity when immersed in a metal salt.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/70 G01N 30/88 C G01N 30/00 B01D 53/34 B 134E // G01N 30/88 (72 ) Inventor Satoshi Takahashi 7F Horie-cho, Matsuyama-shi, Ehime F-term (reference) 2E191 BA12 BC01 4D002 AA21 AA40 AC04 BA04 CA07 CA11 CA20 DA46 4D012 BA01 4G066 AA13D AA20B AA22B AA36D BA16 BA36 CA01 DA02 DA03 FA

Claims (2)

[Claims] 1. An adsorbent for dioxins, comprising an alumina containing a silica component, wherein the silica component is an alkali-treated alumina as an active ingredient. 2. The adsorbent for dioxins according to claim 1, wherein the alumina is further immersed in a metal salt.