JPS59154126A - Removing method of arsenic in gas - Google Patents

Abstract

PURPOSE:To adsorb and remove efficiently an arsenic component by bringing gas contg. the arsenic component into contact with a soln. of an oxidizing agent and granulated titanic acid having excellent heat resistance and chemical resistance to be used repeatedly. CONSTITUTION:Granulated titanic acid obtained by granulating powdered titanic acid packed in a packed tower as an adsorbent. The gas contg. an arsenic component such as an arsenic element or AsH3 is introduced into a tank contg. a soln. of an oxidizing agent such as KMnO4. Then the gas is passed through the packed tower packed with granulated titanic acid, and the arsenic component is removed. The granulated titanic acid after adsorbing gaseous arsenic is taken out from the packed tower, and thrown into an aq. alkaline soln. to form a slurry state. The titanic acid is transferred into the aq. alkaline soln. by dissolution, and the slurry is stirred and filtered to recover titanic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for adsorption and removal of arsenic compounds in exhaust gas, which has excellent heat resistance and chemical resistance, is easy to handle, and can be used repeatedly.

Conventional methods for treating mixed gases containing arsenic include passing the mixed gas into a solution of copper sulfate to precipitate the arsenic as copper arsenide, or passing the mixed gas through a heated quartz tube and then cooling it to release metallic arsenic. A method in which a mixed gas is introduced onto heated copper, iron, nickel, or cobalt, arsenic is reacted with these metals, and a reaction product is diffused into the metal is known. However, these methods are incomplete as methods for removing arsenic even at a temperature difference of several hundred degrees Celsius. The reaction is carried out under extremely high heat, and the process is dangerous and consumes a large amount of energy. Furthermore, since it is difficult to re-separate arsenic from the reaction product with arsenic, the reaction product must be removed from the treatment system and disposed of, making it impossible to reuse it.

The present inventors have conducted intensive studies on a method for adsorbing and removing arsenic compounds in exhaust gas that has excellent heat resistance and chemical resistance, is easy to handle, and can be used repeatedly, which was impossible with conventional methods. completed.

The present invention is a method for removing arsenic components in a gas, which is characterized by bringing a gas containing an arsenic component into contact with an oxidizing agent solution and titanic acid particles.

The titanic acid used in the present invention has the chemical formula 'I'i0□・
Any titanium dioxide hydrate represented by nH,,O (n=0.5-2.0) may be used, but titanyl sulfate (Ti0
8O,), titanium tetraisogropoxide (Ti[○C
H(CH3)2I14), titanium tetrachloride (TiC14)
Those produced by hydrolysis are convenient for the purpose of obtaining an adsorbent with a large specific surface area and a large retention capacity.

To granulate powdered titanic acid, any of the general methods such as single-screw extrusion granulation, compression granulation, basket extrusion granulation, rolling granulation, and spray granulation may be applied. Can be done. - For example, water and sulfuric acid are added to powdered titanic acid, and the mixture is kneaded, extruded, granulated, and fired by the method disclosed in JP-A-55-8844. This method provides sufficient strength and specific surface area (approximately 200 nz2) as an adsorbent.
/g) are obtained. By further pulverizing and sieving this, granules of arbitrary size with a particle size of ten-odd mm or less can be obtained.

Further, by forming the mixed wire into a sphere by compression granulation, which is commonly used as a method for forming the mixed wire, a granular material having an arbitrary particle size up to several α can be obtained without causing a decrease in specific surface area.

If you want a high degree of arsenic adsorption treatment effect, you can use particles with a small particle size by sieving, but the particle size is usually 0.1 mm.
1 cm, particularly 0.5 to 5 M. In order to avoid an increase in ventilation resistance due to adsorbent filling, an adsorbent with a large particle size may be used.

The titanic acid granules of the present invention are titanic acid alone and have sufficient granulation strength as a packed adsorbent, but they are also granulated from a mixture containing alumina or silica, or a total of 30% by weight of both. Even when molded and fired, it still maintains its strength. Further increasing the content decreases the strength. If priority is given to strength, the content of these inorganic substances can be reduced, but if priority is given to changes in the properties of the filler due to their inclusion, molding that mixes these two or other inorganic or organic substances is recommended. The body can be used as an adsorbent. It is also possible to mix separately granulated, molded and sieved titanic acid with alumina and/or silica and use it as a mixed-packing type adsorbent. Granulation,
The inorganic substance to be mixed during molding and firing or separately granulated, molded and mixed is preferably zirconium, hafnium, tin, lead, etc. in order to maintain adsorption ability.

Examples of the oxidizing agent used in the present invention include permanganic acid or its salts, (bi)chromic acid or its salts, nitric acid or its salts, peroxide 2, sulfuric acid, and the like. The concentration of the oxidizing agent in the solution is about 0.1% or more, preferably 6%. As the solvent for the oxidizing agent, any organic solvent may be used as long as it does not react with the oxidizing agent, but water is particularly preferred from the viewpoint of solubility, boiling point, and non-polluting nature.

As a method of bringing the oxidizing agent solution and the titanic acid granules into contact with the arsenic component-containing gas, for example, there is a method in which an oxidizing agent solution tank is provided at the bottom of the column packed with the titanic acid granules. When a gas containing a gaseous arsenic compound is passed through this tank, the gas rises in the packed column together with a portion of the oxidizing agent solution, is oxidized on the surface of the titanic acid particles, and the arsenic component is efficiently adsorbed and removed. . Although the oxidizing agent is consumed depending on the amount of processing gas, it can be used repeatedly if replaced or replenished as appropriate. For long-term use, a larger amount of oxidizing agent solution may be used. At this time, in order to avoid an increase in ventilation resistance, the tank may be designed so that the water level of the oxidizing agent solution is low.

The contact between the titanic acid particles and the gas can be carried out in a packed column of any shape, either vertically or horizontally. The contact temperature may remain the same as the gas temperature, and no special cooling or heating is required, but the gas may be pretreated if necessary.

When carrying out the method of the present invention, it is preferable to pass the arsenic-containing gas through the oxidizing agent solution and then passing it through a column packed with titanic acid granules. In addition, a gas containing an arsenic component is passed through a multi-stage packed column roughly packed with titanic acid particles, and an oxidizing agent solution is sprayed onto this, and the titanic acid particles are circulated inside and outside the tower for repeated use. You can also. This is a little complicated, but
This is an efficient engineering method.

The arsenic component to be removed is arsenic alone (As4
, As2), arsine (ASH3), arsenic trifluoride (AsF5), or organic compound derivatives thereof. In the method of the present invention, in addition to arsenic components, substances that are oxidized by an oxidizing agent to produce oxygen acid anions are also adsorbed and removed. When applied to arsenic components, these are also removed at the same time, which is extremely convenient.

To recover arsenic from titanate granules that have adsorbed arsenic gas, the titanate granules are taken out of the packed tower, put into an alkaline aqueous solution, stirred as a slurry, and then filtered. It can be transferred and recovered in an aqueous solution. The liquid should be alkaline, but if the speed of dissolution is important, it should be strongly alkaline (pH 1).
0 or more), in which case more than 90% of the adsorbed arsenic can be recovered within 1 hour. As the alkali, sodium hydroxide, potassium hydroxide, etc. are used, and it is advantageous to use sodium hydroxide from the viewpoint of effectiveness and economy. Since the required amount of alkaline aqueous solution is sufficient to maintain a slurry state with titanic acid, arsenic can be recovered as a small amount of extremely concentrated arsenic solution.

This dearsenized titanium.

Acid granules can also be used repeatedly.

Furthermore, this titanic acid granule has excellent heat resistance, so
Although it can be used for high-temperature mixed gases up to 300°C without any damage to its shape, it is preferable to use it at 100°C or lower in an oxidizing agent solution bath.

Example 1 Titanic acid granules (0.5 mmφ x 7 mmL) granulated and molded by the method described in JP-A-55-8844
) was filled into a glass tube with a diameter of 0.7 cm to a length of 10 Crn, and both ends were fixed with wire mesh. One end of this glass tube was brought into contact with 5.0 ml of an oxidizing agent solution.

The oxidizing agent solution is 6 g of concentrated nitric acid in 0.6 g of potassium permanganate.
．． , Oml was added and the total volume was adjusted to 100ml with water. JIS KOlol-197 is applied to this connection system.
Connect the conduit in the As analysis method shown in Figure 9, connect the flow meter (6) between the arsine generation amount (1) and the oxidizing agent solution (4) as shown in the drawing, and The connection was sealed with glass wool (2), and this glass wool was impregnated with lead acetate. In the amount of arsine generated (1), arsenic acid, potassium iodide, tin chloride (
■) and zinc were added to generate arsine, and this gas was passed through the oxidizing agent solution (4) and through the titanic acid granule packed tower (5) while monitoring the flow rate with a flow meter (6). Thereafter, it was absorbed into an arsine absorption solution (6) consisting of a silver diethyldithiocarbamate solution, and the absorbance of the reddish-purple color produced was measured to determine the amount of arsenic that was not adsorbed and removed.

When the amount of unadsorbed arsenic was measured by varying the amount of arsine generated, it was found that up to 100 μg of generated arsenic was completely adsorbed and removed in terms of arsenic atoms (AS).

Further, when adsorption and removal were repeated under the same conditions, the adsorption and removal was completed up to 15 times with a generation amount of 100 μJ.

It has been found that arsine can be effectively removed by a combination of a smaller amount of oxidizing agent solution bath and titanic acid particles.

Comparative Example 1 Using the same equipment as in Example 1, 100 μg of arsine in terms of arsenic atoms was generated without filling the packed tower (5) with titanic acid particles, and only 5.0 ml of the oxidizing agent solution was added. It was known that when the oxidizing agent solution (4) alone had almost no removal ability, the -arsine absorption solution (6) immediately turned deep reddish-purple when it was conducted.

Comparative Example 2 Using the same equipment as in Example 1, without using the oxidizing agent solution (4), 100 μg of arsine was generated in terms of arsenic atoms, and conduction was conducted only through the titanic acid particles, resulting in an arsine-absorbing liquid. (6) immediately became a deep reddish-purple color, and it was known that granules alone had almost no removal ability.

Example 2 Arsine of any concentration was prepared by collecting the arsine generated by the method of Example 1 in a 60 ffl Teflon bag and diluting it with mononitrogen gas.

In addition, by connecting a flow meter to the outlet of the Teflon bag via an air pump, an arbitrary constant flow rate was obtained.

Other than that, when arsine was conducted under the same conditions as in Example 1, at a flow rate of 260 ml for 7 minutes, 6 in terms of arsenic atoms.
For the arsenic generated in 30 ml of bag at 0, only 2
．． 5 μg of arsenic was not adsorbed. At the same flow rate, the arsenic generated at 15ff19% in the 60 type bag was completely adsorbed and removed. In addition, 151n9 in 60J3 bug
When the oxidizing agent solution was replaced with a new solution every time arsenic was conducted, it was completely adsorbed and removed even after repeating this 15 times. The total amount of arsenic generated at this time was 225 m9, titanic acid granules i,
Adsorption amount per o g is AS 64.8 m';//g
It was observed that the effect of the combination of oxidizing agent solution and titanic acid granules was significant.

[Brief explanation of the drawing]

The drawing shows an apparatus for explaining one embodiment of the present invention, in which 1 is an arsine generating bottle, 2 is glass wool, 6 is a flow meter, 4 is an oxidizing agent solution, 5 is a column packed with titanic acid granules, and 6 is an apparatus for explaining an embodiment of the present invention. Shows arsine absorption liquid. Applicant Mitsubishi Rayon Co., Ltd.

Claims (1)

[Claims] A method for removing arsenic components in a gas, the method comprising bringing a gas containing an arsenic component into contact with an oxidizing agent solution and titanic acid particles.