JPS58122026A - Removal of arsenic component in gas - Google Patents

Abstract

PURPOSE:To make heat resistance and chemical resistance high, handling easy and reiterative use possible by using titanic acid granules impregnated and held with an aq. oxidizing agent soln. for adsorption and removal of arsenic compds. in waste gases. CONSTITUTION:Aq. solns. of oxidizing agents such as permanganic acid and salts thereof, chromic acid salt and thereof, nitric acid, sulfuric acid, etc. are adsorbed and held on titanic acid granules obtd. by adding water and sulfuric acid to titanium dioxide hydrate and granulating the mixture after kneading in such a way that the surfaces thereof are wetted. The titanic acid granules adsorbed with the oxidizing agent obtd. in the above-mentioned manner are packed in a packed column, and waste gases contg. arsenic compds. such as As4, As2, AsH3, AsF5 or the like are introduced into the packed column, whereby the arsenic compds. are adsorbed away. The titanic acid granules adsorbing arsenic are removed from the packed column, and are charged into an aq. alkali soln. and are made into a slurry state. The slurry is agitated to recover the arsenic solns., and the titanic acid granules made free from arsenic are filtered out and are used reiteratively.

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 method for treating mixed gas containing arsenic; 1. A method of passing a mixed gas into a solution of sulfuric acid steel to precipitate it as copper arsenide, or a method of applying high heat, passing the mixed gas through a quartz tube, and then cooling it to solidify it as metallic arsenic.
Additionally, a method is known in which a mixed gas of heated copper, iron, and nickel is introduced onto cobalt to cause arsenic to react with these metals and to diffuse the reaction product into the interior of the metal. All of these methods are incomplete as methods for removing arsenic, and the arsenic concentration in the process gas is
In order to sufficiently lower L, not only is a complex and large-scale device required, but also the reaction under high heat of several hundred degrees
This is a method that is dangerous and consumes a large amount of energy. Furthermore, since it is difficult to re-separate the arsenic from the reaction products with arsenic, the reaction products must be removed from the treatment system and disposed of, and needless to say, they cannot be reused and must be carefully .

The present inventors have conducted extensive studies to develop a new method for adsorption and removal of arsenic compounds in exhaust gas that has excellent heat resistance and chemical resistance, is easy to handle, and can be used repeatedly, which was not possible using conventional methods. Results: Powdered titanium @ (titanium dioxide hydrate) A mixture obtained by adding K water and sulfur # The granules obtained by granulating, molding and firing the whole microparticles are impregnated with an oxidizing agent aqueous solution, It has been discovered that when adsorbed and retained, it has properties suitable for adsorbing and removing gaseous arsenic compounds. The present invention is a method for removing arsenic components in a gas, which comprises adsorbing and retaining an oxidizing agent aqueous solution and bringing subtitanic acid particles into contact with an arsenic component/containing gas for 1 hour.

The gland removal method of the present invention will be explained in detail below.

The titanic acid used in the present invention has the chemical formula Ti0w・nH.
to (n = 0.5 to 2.0), titanium sulfate (Tio80
i17 Titanium tetraisogloboxide fT i (
If it can be produced by hydrolysis of OOH (OHM) titanium tetrachloride (TiOL), it is convenient for the purpose of obtaining an adsorbent with a large specific surface area and a large retention capacity.

Powdered titanic acid can be granulated and molded by adding water and sulfuric acid, and then mixed, extruded, granulated, and fired according to the method shown in JP-A-55-8844, which has sufficient strength and specific surface area as an adsorbent. (approximately 200-7 g), but if this is further crushed and sieved, any particle size of ten-odd millimeters or less can be obtained. Furthermore, if the kneaded product is molded into a spherical shape by compression granulation, which is commonly used as a molding method, it is possible to adsorb arsenic up to a particle size of several centimeters/temeter without causing a decrease in the specific surface area. t
If you want the treatment effect of IJ degree, you can get it by sieving the small particle size, but usually the particle size is 0.1W to 1K, more preferably 7 or 0.5 to 5K. suitable. 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 of the present invention is titanic acid alone and has sufficient granulation strength as a packed adsorbent, but it also has alumina.
Even when silica or a mixture containing silica or both in a total amount of 6% by weight is granulated and calcined, a sufficient degree of hardness is maintained. When the content is further increased, the strength decreases. If strength is given priority, 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, these two or even other inorganic substances should be mixed with organic substances. It can be used as an adsorbent in the form of a molded article having the following properties. It is also possible to mix titanic acid, alumina, or silica filler that has been granulated, molded, and sieved separately and use it as a mixed-packing type adsorbent.

In the present invention, the oxidizing agent used for adsorption and retention on the titanic acid granules is permanganic acid or its salts, chromic acid and its salts, nitric acid and its salts, peroxide, sulfur It! Any common oxidizing agent that is water-soluble may be used. It is effective if the concentration of the oxidizing agent in the aqueous solution is about 0.1 or more, but preferably 6 moss is sufficient. The required amount of the oxidizing agent aqueous solution is the amount required for the purpose of moistening the surface of the adsorbent, and is 0.1 to 2 per 1 g of the adsorbent.
．． It may be 0-, but preferably 0.5 to 1°0-. When adsorbing and retaining an oxidizing agent aqueous solution of 2.04 or more, the minute spaces between the adsorbent particles are filled with the water, making it difficult for gaseous substances to enter and causing an increase in ventilation resistance, so low ventilation resistance is required. This is inconvenient if you want it. When the thus obtained titanic acid granules carrying the oxidizing agent water bath liquid are brought into contact with a gas containing a gaseous arsenic compound, the arsenic compound is efficiently adsorbed onto the granules and removed. The single arsenic component targeted for removal is arsenic itself (A
84.

Alternatively, arsenic compounds such as organic compound derivatives thereof may be mentioned. Furthermore, in the present invention, in addition to the arsenic component, substances that are oxidized by an oxidizing agent to produce oxygen acid anions are also adsorbed and removed, so phosphine fPHsl and stibine (S
When applied to a mixed gas containing coexisting arsenic components such as bHi), these are removed at the same time as the arsenic component, which is extremely convenient. The contact between the particulate matter and the gas can be carried out using either a packed column type, vertical type, or horizontal type of any shape. The contact temperature can be adsorbed and removed at the gas temperature, and there is no need for special cooling or heating, but the gas may be pretreated if necessary.

To recover arsenic from granular titanic acid that has adsorbed arsenic gas, it is taken out from the granular titanium Ilt packed column.

The titanic acid can be transferred into an aqueous solution and recovered by pouring it into an aqueous alkaline solution to form a slurry, stirring, and passing the titanic acid through the mouth. The liquid should be alkaline, but
Strong alkalinity (pH 10 or higher) is advantageous if the bath rotation speed is important; in this case, 90% of the adsorbed arsenic can be removed within 1 hour.
% or more can be recovered. The type of alkali is sodium hydroxide.

If a normal alkali such as potassium hydroxide is used, there is no time difference at all, so 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 the entire slurry state with titanic acid, arsenic can be recovered as a small amount of extremely concentrated arsenic lacquer solution.

Further, the dearsenicated tomo titanate granules can be used repeatedly.

In general, this titanic acid granule has excellent heat resistance, so it can be used up to 600°C in high-temperature mixed gases without any problems, but the oxidizing agent water solution is As it evaporates, performance deteriorates slightly.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to the following Examples unless the scope thereof is exceeded.

The titanic acid granules IQ, 5 war[F]× are granulated and molded by the method shown in Japanese Patent Application Laid-Open No. 55-8844.
7,, L12. 1.6 d of oxidizing agent water solution on the surface of Og.
'ft suction and hold. The oxidizing agent solution was prepared by adding 1.3 g of potassium permanganate [3.0 g of K concentrated nitric acid and adding 1.0 g of potassium permanganate to a total of 1 with water.
ljl to be 00d! lI! ! did. This oxidant-adsorbed titanic acid 1JIs KOl 01-1979 was used to fill a conduit in the As analysis method described in 1JIs KOl 01-1979, and both ends were sealed with glass wool as shown in FIG. The glass cooler on the gas introduction side was impregnated with lead acetate. Potassium iodide, tin chloride (ll) according to JI8 analytical method
Then, zinc is added to generate arsine, the togas is filled with oxidizing agent-absorbing titanium granules, passed through a good conduit, and then absorbed into a silver diethyldithiocarbamate solution, and the absorbance of the red-purple color produced is measured. The amount of arsenic that was not adsorbed and removed was measured.

When the amount of arsine generated was varied and the amount of unadsorbed arsenic t' was measured, the amount generated was 100 μg'' in terms of arsenic atoms (A8).
! In this case, Hi-X was completely removed by adsorption.

It is found that arsine is effectively removed by the combination of a minimal amount of oxidizing agent and particulate titanic acid.

Comparative Example As shown in Figure 2, one end of a glass conduit in which granular titanic acid was not sealed was connected to the same arsine generating solution as in the example, and the other end was led into the same oxidizing agent 100d as in the example. The arsine was further introduced into the arsine absorption tube through a glass tube.

Arsine was generated under the same conditions as in the example, and the amount of unadsorbed arsenic was measured under the same analytical conditions. Already generated is 0.
45 μg was not adsorbed, and for the generated amount of 100 μg, 4.55 μg was unadsorbed.

The adsorption effect showed almost no improvement even when the amount of the oxidizing agent was increased or the concentration of the oxidizing agent. It is found that the effect is far from that of retained titanic acid.

[Brief explanation of drawings]

FIG. 1 shows an example of a gaseous arsenic removal device used to carry out the method of the present invention, and FIG.
This is an example of a removal device for comparison. 1 Arsine generating liquid 2 Glass wool 3 Oxidizing agent adsorbing titanic acid particles 4 Glass conduit 5 Arsine absorbing liquid 6 Oxidizing agent aqueous solution

Claims (1)

[Claims] A method for removing arsenic components in a gas, which is characterized by bringing a gas containing an arsenic component into contact with titanium particles adsorbed and held by an oxidizing agent aqueous solution.