JP3412455B2 - Activated alumina for arsenate ion adsorption and method for adsorbing arsenate ions from aqueous solution using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to activated alumina for adsorbing arsenate ions, and more particularly to activated alumina for adsorbing arsenate ions suitable for removing arsenate ions from an arsenate ion-containing liquid.

[0002]

2. Description of the Related Art In recent years, coagulation-sedimentation method, lime softening method, adsorption method, bio-concentration method, reverse osmosis method, in order to highly reduce the arsenic concentration from purified water or waste water containing arsenate ions of various chemical forms. Various methods such as a method have been studied. Of these, the adsorption method does not require a large treatment plant area, does not generate waste mud, etc., and does not require a troublesome filtration operation.

As the adsorbent used in the adsorption method, activated carbon, activated alumina, magnesia, magnesia modified slag, titania modified activated carbon, manganese dioxide, cerium oxide, anion exchange resin, red mud particles and the like are known. Above all, activated alumina is applied as an inexpensive and safe adsorbent.

An example of using activated alumina for adsorbing arsenic acid is "Environmental Progress"
S., Vol. 6, No. 3, p. 150, M.S. M. Gho
sh. R. There is a paper by Yuan. In this paper, a column was packed with crushed activated alumina agglomerates having a Na ₂ O content of 0.9% by weight, a BET surface area of 218 m ² / g, and a particle size of 28 to 48 mesh. Water containing 0.08 to 10 mg / l of arsenate ion in terms of conversion is passed through to adsorb and remove arsenic acid.

[0005] As another example, a paper by Mr. Tsukamoto, Inoue, Matsumoto, Kimura and Kobayashi of the Fukuoka Prefecture Wide Area Water Supply Company, described in the 45th Waterworks Research Presentation Lecture, page 244 (May 1994). There is. In this paper, powdered activated alumina of 325 mesh or more is brought into contact with water containing 0.047 mg / l of arsenate ion in terms of arsenic by shaking to adsorb and remove arsenate ion in a batch method, and a granular material having an average particle diameter of 2 mm. A method has been disclosed in which activated alumina is packed in a column, and water containing arsenate ions is passed through the column to adsorb and remove arsenate ions.

[0006] As another example of using activated alumina for adsorbing arsenic acid, "Waterworks Association Magazine" Vol. 65, No. 4, p. 18-2
Fukuoka Prefecture Wide Area Water Supply Company Tsukamoto, described on page 4 (1996)
There are papers by Inoue, Matsumoto, Kimura and Kobayashi. In this paper, in order to elucidate which of the outer surface and the inner micropore surface of the activated alumina particles controls the arsenic adsorption amount when the activated alumina particles adsorb arsenic, two types of spherical particles having different particle diameters are used. Using activated alumina particles, the influence of the particle size on the arsenic removal rate and the arsenic distribution inside the activated alumina particles after arsenic adsorption are measured. As a result, it has been concluded that activated alumina adsorbs arsenic almost uniformly up to the center of the particle, and that the arsenic removal rate does not differ even if the particle size is different (arsenic adsorption is not limited to the outer surface area of the particle). That is,
Arsenic concentrations of 20 mg / l, 100 mg / l and 500 using spherical activated alumina with an average particle size of 0.8 mm and 2 mm.
Table 1 shows the measurement results of changes over time in the arsenic removal rate (%) for three levels of mg / l of raw water, but there is a substantial difference in the arsenic removal rate between the two due to the difference in average particle size. There is no. The distribution of arsenic from the central part of the activated alumina to the outer surface after the adsorption treatment was measured by an energy dispersive X-ray spectroscope, and the results are shown in Fig. 4. Arsenic is spherical activated alumina. It is described that they are almost evenly distributed from the outer surface to the center of the.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have found that in a water supply reservoir or the like, the arsenic concentration is usually 0.2 mg / l.
A low-cost, easy-to-handle adsorbent and aqueous solution capable of adsorbing / removing a large amount of an aqueous solution, which is extremely low at ~ 0.01 mg / l, to an arsenic concentration of less than 0.01 mg / l that passes the water supply standard. As a result of diligent studies to find out a treatment method, they have found that all of the above objects can be satisfied when using activated alumina having specific physical properties, and have completed the present invention.

[0008]

Means for Solving the Problems That is, the present invention is based on Na
₂ O content is 0.3% by weight or less, wear rate is 5% or less, and sphere-converted outer specific surface area calculated from sieved particle size is 4 to ²⁰ m ² /
1, a BET specific surface area of 100 m ² / g or more, and a pore volume of 0.2 to 10 μm measured by mercury porosimetry is 0.
Another object of the present invention is to provide activated alumina for adsorbing arsenate ions, which has a pore volume of 04 cc / g or more and a pore volume of 0.2 to 1 μm of 0.02 cc / g or more.

Further, according to the present invention, the arsenic concentration is 0.2 mg / l.
˜0.01 mg / l aqueous solution with a Na ₂ O content of 0.
3% by weight or less, abrasion rate 5% or less, sphere-equivalent specific surface area calculated from sieved particle size of 4 to ²⁰ cm ² / g, BET specific surface area of 100 m ² / g or more, pore radius measured by mercury porosimetry The pore volume of 0.2 to 10 μm is 0.04 cc / g or more and the pore volume of 0.2 to 1 μm is 0.02 cc / g.
In the activated alumina was continuously fed to a column packed or more, certain砒acid ion in aqueous solution to provide an adsorption treatment method of arsenate ions from an aqueous solution, characterized in that the adsorption treatment.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The activated alumina for adsorbing arsenate ions of the present invention is Na₂Including O
Content is 0.3% by weight or less, wear rate is 5% or less, particle size by sieving
Sphere converted outer specific surface area calculated from ²/ G,
BET specific surface area is 100m²/ G or more, measured by mercury porosimetry
The pore volume with a determined pore radius of 0.2 to 10 μm is 0.04
cc / g or more and a pore volume of 0.2 to 1 μm is 0.0
It is 2 cc / g or more.

The Na ₂ O content of the activated alumina is about 0.
It is 3% by weight or less, preferably about 0.2% by weight or less.
Activated alumina made from aluminum hydroxide obtained by the Bayer method is usually 0.2 to 0.6% by weight of Na ₂ O.
Contains. For the adsorption of arsenic by activated alumina, the removal efficiency is excellent when the pH of the treatment liquid (raw water) is about 5 to 6.
However, when activated alumina having a Na ₂ O concentration of more than 0.3% by weight is packed in a column and used, for example, pH
Even if the raw water adjusted to 5 to 6 is passed through the column, the pH of the effluent becomes 9 to 11 at the initial stage of passing water and the arsenic removal rate decreases, which is not preferable.

The activated alumina applied to the present invention has a sphere-equivalent specific surface area of about 4 to ²⁰ m ² / l, preferably about 6 to 1
4 m ² / l. According to the conventional knowledge, the size of the activated alumina particles (the size of the external specific surface area) does not affect the arsenic removal efficiency. However, when the activated alumina is packed in a column and the column contains a trace amount of impurities, When the raw water for tap water (well water, river water) is continuously supplied and arsenic is removed from this raw water, the smaller the activated alumina particle size (the larger the external specific surface area), the better the arsenic removal efficiency. The present inventors have discovered.

That is, the sphere-equivalent external specific surface area calculated from the sieved particle size is about 4 to ²⁰ m ² / l, preferably about 6 to 14 m ² /
In case of 1, the column has relatively low liquid resistance, so that high-speed water can be passed, and when the pore conditions satisfy the above range, the breakthrough time of the column filled with the activated alumina is long. Meet Sphere-converted specific surface area is approx. 4m ² /
If it is less than 1, the breakthrough time of the column packed with activated alumina becomes short and the arsenic removal cost becomes high. When the sphere-converted specific surface area is about 20 m ² / l or more, liquid permeation resistance during column operation becomes large and high-speed water permeation becomes difficult, which is not preferable.

The BET specific surface area of the activated alumina applied to the present invention is about 100 m ² / g or more, preferably about 200 m.
² / g or more. The larger the BET specific surface area, the greater the column breakthrough time extension effect with respect to the increase in the outer surface area of the activated alumina particles. If the BET specific surface area is less than about 100 m ² / g, the effect of extending the column breakthrough time for increasing the external specific surface area of the activated alumina particles is reduced.

Furthermore, the activated alumina of the present invention has a pore volume of 0.2 to 10 μm, measured by mercury porosimetry, of about 0.04 cc / g or more, preferably about 0.08 cc / g.
Above, and the pore volume of 0.2-1 μm is about 0.02c
c / g or more, preferably about 0.04 cc / g or more. Here, the pore volume with a pore radius of 0.2 to 1 μm represents the macropore volume inside the activated alumina particles, but the pore volume with a pore radius of 0.2 to 10 μm refers to the macropore volume inside the particles and the particles between particles. It represents the total value of the void volume.

The presence of macropores having a pore radius of 0.2 to 10 μm facilitates the diffusion of arsenic into the particles and prolongs the breakthrough time of a column packed with activated alumina. Macropores and mesopores with a pore radius of less than 0.2 μm (having a pore radius of 2 nm to 100 nm) also help the diffusion of arsenic, but they do not have the effect of extending the breakthrough time as much as the macropores with a pore diameter of 0.2 to 10 μm.

When the pore volume with a pore radius of 0.2 to 10 μm is 0.04 cc / g or more and the pore volume with 0.2 to 1 μm is 0.02 cc / g or more, activated alumina is filled. The breakthrough time of the column is longer than that without macropores having a pore radius of 0.2 to 10 μm. On the other hand, when the pore volume of the pore radius of 0.2 to 10 μm is less than 0.04 cc / g and the pore volume of 0.2 to 1 μm is less than 0.02 cc / g, the column packed with activated alumina is The breakthrough time is about the same as when there is no macropore having a pore radius of 0.2 to 10 μm.

The wear rate of the activated alumina particles used in the present invention is about 5% or less, preferably 1% or less. If the wear rate of the activated alumina molded body exceeds 5%, or if the activated alumina particles are in the form of powder or a lump obtained by crushing, when packed and used in a column, the water after passing through the column is used. Becomes cloudy or the filter is clogged,
Not only the activated alumina particles have to be suspended and washed to remove dust before filling, but also an operation of treating white turbid water is required, which makes the operation complicated, which is not preferable. The particle shape of the activated alumina molded body is not particularly limited, but spherical particles are preferable because the wear rate is small and the molding is easy.

[0019]砒ion adsorption activated alumina of the present invention as described above, Na ₂ O content of 0.3 wt% or less, the wear rate of 5% or less, in terms of sphere out specific surface area calculated from the sieved particle size 4-20 m ² / l, BET specific surface area of 100 m ² / g
As described above, the pore radius measured by the mercury penetration method is 0.2 to 10 μm.
Has a pore volume of 0.04 cc / g or more and 0.2 to 1 μm
The pore volume of m is 0.02 cc / g or more, and when the activated alumina is immersed in water at 80 ° C., an acid component having a water pH of 3 to 6 is deposited. Preferably. In this case, the arsenic adsorption performance is improved,
The adsorption operation becomes easy. When the pH of the water when immersed in water having an inorganic acid deposition of 80 ° C. is less than 3, the pH of the raw water passing through the column will be low and the adsorption efficiency of arsenic acid will be reduced, as well as the treated raw water (outflow). Water) needs to be neutralized. On the other hand, when the pH of the water when immersed in water having an inorganic acid deposition amount of 80 ° C. does not reach 6, the effect of improving the adsorption of arsenic acid is small.

[0020] Preparation of砒ion adsorption activated alumina having the above-described physical properties of the present invention is not particularly limited, active alumina having a BET specific surface area and particle strength greater method via rehydratable alumina easily obtained Recommended from that. More specifically, the total Na2 O content is about 0.3% by weight, preferably about 0.2% by weight, more preferably about 0.
1% by weight or less of aluminum hydroxide such as gibbsite is instantaneously calcined in a hot air stream of about 500 to 1200 ° C. for about 0.1 seconds to several minutes, and then separated and cooled to first improve rehydration property. The activated alumina powder (hereinafter sometimes referred to as rehydratable alumina) is obtained.

The rehydrated activated alumina powder is shaped as it is or after being further crushed into a desired shape. The shape of the molded body is not particularly limited as long as the wear rate falls within the range of the present invention, such as a spherical shape, a cylindrical shape, a ring shape, and a honeycomb shape, but a spherical shape is preferable. Examples of the method for forming a spherical shape include known methods such as rolling granulation, spray drying, submerged granulation method, oil drop method and oil flotation method. The molded product has a wear rate of activated alumina of about 5% after rehydration and firing.
Hereafter, the molding conditions should be selected so that they are preferably about 1% or less. A rolling granulation method is preferable as an inexpensive molding method with a wear rate of about 5% or less.

During rolling granulation, a combustible organic substance is added to the raw material alumina powder, or a rehydratable alumina powder having a narrow particle size distribution (quarter deviation value of 1.3 or less, preferably 1.2 or less) is used as a raw material. By selecting molding conditions such as (1), a molded product having the physical properties applied in the present invention can be obtained. When using a transition alumina powder having a wide particle size distribution with a quartile deviation value of more than 1.4, the pore radius is 0.2 to 1 μm.
The pore volume (measured by mercury porosimetry) is about 0.01 cc / g, and the pore volume with a pore radius of 0.2 to 10 μm is 0.02 c.
Only those having a small pore volume of about c / g can be obtained. Although the addition of an organic substance increases the pore volume, the wear resistance is markedly reduced, so it is recommended to use it while appropriately adjusting it.

The molded body after molding is usually separated by a sieving method or the like.
Outer specific surface area equivalent to sphere is 4 to 20m ²Adjust to / l.
The molded body has sufficient time for rehydration to increase its mechanical strength,
Water steam at room temperature to 120 ° C, preferably 50 to 90 ° C
Retained by aging and aging in gas containing steam or steam
It Rehydration is generally performed for 1 minute to 1 week. Rehydrated
The spherical molded body is then fired to remove moisture and moisture attached to the molded body.
Remove water of crystallization. The firing temperature is about 300-900 ° C, preferably
The temperature is about 300 to 500 ° C., and the firing time is about 10 minutes.
100 hours.

The calcined activated alumina is optionally treated with an acid. The adhesion of the acid component to the activated alumina is carried out by keeping 10 g of the adsorbent in 100 ml of water at 80 ° C. for 30 minutes, and then filtering the adsorbent from the water.
The water after separation may be applied in an amount such that the pH of the water exhibits a value of 3 to 6, and the application method is not particularly limited. For example, the spherical activated alumina obtained by the above method contains an acid component. And a method of obtaining it by contacting with an aqueous solution.

As a method of contacting the activated alumina with the aqueous solution containing the acid component, a method of impregnating the activated alumina into the aqueous solution,
There is a method of supplying and absorbing an aqueous solution having a water absorption rate of activated alumina. The molded product impregnated with the acid component or absorbed is
You may perform operations, such as washing with water, filtration, drying, or baking. Washing with water and filtration are preferable because the amount of Na ₂ O in the activated alumina decreases. Drying or baking may be omitted.

Acid components to be applied include hydrochloric acid, hydrofluoric acid,
At least one of nitric acid, sulfuric acid, aluminum sulfate and acetic acid can be mentioned, but hydrochloric acid or sulfuric acid or a mixture of sulfuric acid and aluminum sulfate is preferable. The concentration of the acid component of the aqueous solution is usually used in the range of 0.001 to 0.5N,
Strictly speaking, it varies depending on the type of acid, the weight ratio of the acid component and activated alumina, etc., so that "10 g of activated alumina compact after acid treatment is kept in 100 ml of water at 80 ° C. for 30 minutes, and thereafter the activated alumina compact is molded from the water. If the body is filtered and separated,
The amount at which the pH of the water exhibits a value of 3 to 6 "may be determined by preliminary experiments. The temperature of the aqueous solution in this case is about 0 to 100.
C., the contact time is about 10 minutes to 24 hours.

The equilibrium adsorption amount of arsenate ions at 25 ° C. of the activated alumina for adsorbing arsenate ions of the present invention is 0.
It is about 2 mg / l or more, preferably about 5 mg / l or more at 1 mg / l and pH 5.5. Packing density 0.4-0.8
kg / l, the compressive strength is usually 0.1 kg or more. An adsorbent or a filtering agent having another function can be added to the activated alumina for adsorbing arsenate ions of the present invention within a range where the arsenic acid removal performance is not reduced.

The activated alumina for adsorbing arsenate ions obtained in the present invention can be applied to purification of raw water for river water, lake, well water or raw water for industrial use and purification of various industrial wastewater. It is particularly suitable for purification. In use,
Although adsorption purification of the water to be treated can be carried out in the form of a column type fixed bed, moving bed, fluidized bed, batch type or the like, a column type fixed bed is preferable. An appropriate SV value is about ¹ to 100 h ^−1, but preferably, an SV value is about 2 to 15 h ⁻¹ .

When the water to be treated contains arsenite ions, it is advisable to oxidize the treated water in advance to form it in the form of arsenate ions and then carry out the adsorption treatment.

When the pH of the treated water is out of the range of 4 to 6, a pH adjusting agent is added to adjust the pH of the treated water to 4
It is preferable to adjust to ˜6 and to provide for arsenate ion removal treatment. Since ordinary raw water is often neutral to weakly alkaline, it may be adjusted by adding hydrochloric acid, sulfuric acid or van sulphate.

[0031]

As described in detail above, according to the present invention, when activated alumina having specific physical properties is selected as an arsenate ion adsorbent and the activated alumina is packed in a column and applied, arsenic like raw water for water supply is used. Concentration is 0.2mg / l ~ 0.01mg
Even if an extremely thin aqueous solution of 1 / l is continuously treated for a long time,
It makes it possible to remove arsenate ions in the aqueous solution after treatment specified as the water quality standard of the Waterworks Law to less than 0.01 mg / l in terms of arsenic. The industrial value is great because the treatment method is easy and the treatment material is inexpensive.

[0032]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the scope of the present invention is not limited by the examples. In the present invention, the measurement of the outer surface area based on the sieving method, the pore volume by the nitrogen adsorption method and the BE
Measurement of T specific surface area, measurement of pore volume by mercury porosimetry,
The following methods were used to measure the pH value, analyze As, measure the wear rate, and measure the quartile deviation value.

External surface area based on sieving method: A fixed amount of a sample dried at 200 ° C. for 3 hours was weighed out, and the openings defined by JIS Z8801 were 4.00 mm, 3.35 mm, 2.80 mm,
2.36 mm, 2.00 mm, 1.40 mm, 1.18
mm, 0.71 mm, 0.36 mm sieving group, select 3 or more sieves with appropriate openings corresponding to the particle size distribution of the sample, and perform sieving analysis [of the average particle diameter of each fraction of the obtained sieving analysis. When it is set to di (cm), Then, the specific surface area based on sphere was calculated.

Pore Volume and BET Specific Surface Area by Nitrogen Adsorption Method: A sample was dried at 200 ° C. for 3 hours and then weighed in a fixed amount to make a gas adsorption / desorption analyzer Omnisorb 3 manufactured by Coulter Co.
Vacuum degassing (150 ° C, 8h, 2
× 10 ^-5 Torr or less), and then to measure the adsorption and desorption by continuous volume method using nitrogen gas.

Pore volume measured by mercury porosimetry: 200 ° C. ・ 3
h A fixed amount of the dried measurement sample was weighed and vacuum-suctioned for 30 minutes by the Autoscan 33 mercury porosimetry pore volume measuring device manufactured by Kantachrome Co., Ltd., and then the measurement was performed.

PH value: 10 g of a measurement sample was added to water 10 at 80 ° C.
Hold in 0 ml for 30 minutes, filter, pH of filtrate after cooling
Was measured with a Horiba Mfg. Model F8, pH meter.

As analysis: Measured according to JIS-K0102.

Abrasion rate: Measured according to JIS-K1464.

Quaternion deviation value: (D75 / D25) × 1/2 (D75: particle size at a cumulative weight of 75% by weight from the particle size distribution table, D25: particle size at a cumulative weight of 75% by weight from the particle size distribution table).

Example 1 [Manufacturing Method of Activated Alumina for Removing Arsenate Ion] It has a particle size distribution of 0.15% by weight of Na ₂ O obtained from the Bayer process, an average particle size of 8 μm and a quartile deviation of 1.2. Gibbsite (alumina trihydrate) is put into a hot gas of about 700 ° C. and instantaneously calcined. The burning raw material has a particle size distribution of 4.5%, an average particle size of 7 μ, and a quartile deviation value of 1.2. A rehydratable alumina having crystal forms of χ and ρ was obtained. About 0.5 kg of water was added to 1 kg of the rehydratable alumina thus obtained.
After adding kg, the mixture was molded into a spherical shape having a diameter of about 0.9 mm with a plate-shaped granulator and then sieved with a sieve having openings of 1.18 mm and 0.36 mm to form a spherical shape having a particle diameter of 1.18 to 0.36 mm. Got the body Next, the spherical molded body was placed in a container with a lid, sealed, and kept at a temperature of 80 ° C. for 16 hours for rehydration. This molded body was placed in an electric furnace, heated to 380 ° C. for 1 hour and held for 3 hours to obtain spherical activated alumina A. The characteristics of the spherical activated alumina A are shown in Table 1.

[Arsenate Ion Removal Test] The spherical activated alumina A obtained by the above method was added to the glass column shown in FIG.
ml (19.8 g) was filled, and then raw water having a composition shown in Table 3 containing sodium arsenate as arsenic of 0.05 mg / l was supplied from the upper part of the column to treat treated water at a flow rate of 250 ml / h or 125 ml (SV = 10 h ⁻¹ or Equivalent to 5h ^-1 )
The flow rate was adjusted so that the arsenic in the raw water was adsorbed and removed. The test results are shown in Tables 4 and 5. With an adsorbent of pH 5.5, the flow rate is 60000 BV (3000 hours)
Up to 7,000 BV (1400 hours), the column did not break through with the adsorbent having a pH of 7.5 and treated water having an arsenic concentration of 0.01 mg / l or less was obtained.

Example 2 [Manufacturing Method of Activated Alumina for Removing Arsenate Ions] 1.2 kg of the spherical activated alumina A obtained in Example 1 was impregnated in 4.3 liters of 0.3% hydrochloric acid solution for 16 hours, washed with water and filtered. Then, it was placed in an electric furnace and kept at 250 ° C. for 4 hours to obtain spherical activated alumina B having a characteristic that the pH of the eluate at 80 ° C. was 4. The characteristics of the spherical activated alumina B are shown in Table 1.

[Arsenate Ion Removal Test] Arsenate ion removal from raw water was carried out in the same manner except that 25 ml (19.8 g) of spherical activated alumina B was used instead of 25 ml of spherical activated alumina A in the arsenate ion removal test of Example 1. I did a test. The test results are shown in Tables 4 and 5. Volume of adsorbed liquid at pH 5.5 is 61,000 BV (6100 hours)
Up to 8200 BV (1640
The column does not break through until the time passes and the arsenic concentration is 0.01 mg.
Treated water of less than 1 / l was obtained. In addition, it was possible to prevent the pH of the treated water at the beginning of the passage from rising to 8 or more.

Comparative Example 1 Instead of the activated alumina A used in Example 1, a commercially available activated alumina (manufactured by Mizusawa Chemical Co., Ltd., trade name: Mizusawa R) was used.
N) was used. This is called spherical activated alumina C,
The characteristics are shown in Table 2.

[Arsenate Ion Removal Test] Arsenate ion removal from raw water was performed by the same operation except that 25 ml (17.8 g) of spherical activated alumina C was used instead of 25 ml of spherical activated alumina A in the arsenate ion removal test of Example 1. Tested The test results are shown in Table 6. This product broke through the adsorbent having a pH of 5.5 at a flow rate of 10500 BV (1050 hours).

[0046] with a particle size distribution of Comparative Example 2 [arsenate ion method of removing activated alumina] Bayer Na obtained from step ₂ O content 0.16% by weight, average particle diameter 18μm in quartile deviation 2.0 Gibbsite (alumina trihydrate) was put into a hot gas at about 700 ° C and instantaneously calcined, the burning raw material was 5.0%, and the average particle size was 17
A rehydratable alumina consisting mainly of χ and ρ crystal forms with a particle size distribution of μ, quartile deviation 2.0 was obtained. About 0.5 kg of water was added to 1 kg of the rehydratable alumina thus obtained, and the mixture was molded into a spherical shape having a diameter of about 3.3 mm by using a plate-shaped granulator, and then the openings were 4.0 mm and 2.36 mm. Sieving was performed to obtain a spherical molded body having a particle diameter of 4.00 to 2.36 mm. Next, the spherical molded body was placed in a container with a lid, sealed, and kept at a temperature of 80 ° C. for 16 hours for rehydration. This molded body was placed in an electric furnace, heated to 380 ° C. for 1 hour and held for 3 hours to obtain spherical activated alumina D. The characteristics of the spherical activated alumina D are shown in Table 2.

[Arsenate ion removal test] Arsenate ion removal from raw water was carried out by the same operation except that 25 ml (21.3 g) of spherical activated alumina D in the arsenate ion removal test of Example 1 was replaced with 25 ml of spherical activated alumina D. I did a test. The test results are shown in Table 6. This one has a pH of 5.5
6500BV of liquid flow for the adsorbed liquid (650 hours of liquid flow)
I passed through.

Example 3 [Manufacturing Method of Activated Alumina for Removing Arsenate Ion] The diameter of the spherical molded body molded by the plate type granulator in Example 1 is 0.9 mm.
Was replaced with 0.7 mm, and a sieve with a mesh opening of 0.36 mm was used.
Screen instead of 25 mm sieve, 1.18-0.36 m
A spherical activated alumina F was obtained by the same operation except that a spherical molded body having a particle diameter of m was obtained. The characteristics of the spherical activated alumina are shown in Table 1. [Arsenate ion removal test] An arsenate ion removal test from raw water was conducted in the same manner except that the spherical activated alumina A 25 ml in the arsenate ion removal test of Example 1 was replaced with spherical activated alumina F 25 ml (16.3 g). The test results are shown in Table 4. The flow rate is 820 for the pH 5.5 adsorbent.
The column did not break through even with 00BV (passage for 8200 hours), and treated water having an arsenic concentration of 0.01 mg / l or less was obtained.

Comparative Example 3 [Manufacturing Method of Activated Alumina for Removing Arsenate Ion] The diameter of the spherical molded body molded by the dish granulator in Comparative Example 2 is 3.3 mm.
In place of 1.8 mm and openings 4.0 mm and 2.3
Spherical activated alumina E was obtained by the same operation except that a 6 mm sieve was replaced with sieves having openings of 2.0 mm and 1.18 mm and sieved to obtain a spherical molded body having a particle diameter of 2.0 to 1.18 mm. Obtained. The characteristics of the spherical activated alumina are shown in Table 2. [Arsenate ion removal test] Arsenate ions from raw water were subjected to the same operation except that 25 ml (16.3 g) of spherical activated alumina A in the arsenate ion removal test of Example 1 was replaced with 25 ml (21.3 g) of spherical activated alumina E. A removal test was done. The test results are shown in Tables 6 and 7. The amount of adsorbed liquid at pH 5.5 is 16300 BV (1630 hours).
Up to 1200 BV (240 hours) with an adsorbent of PH 7.5, the column did not break through and the arsenic concentration was 0.01 mg /
Less than 1 liter of treated water was obtained.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

[Table 7] Space velocity 10h for column test of adsorbent pH 5.5
^-1 , column test with adsorbent pH 7.5 is space velocity 5h
Conducted at ^-1 . The unit of arsenic concentration is mg / l. BV: 2 means the volume of activated alumina packed in the column
It is 5 ml. Breakthrough: Arsenic concentration of treated water at the column outlet is 0.01 mg / l
The time when it exceeds is defined as breakthrough.

[Brief description of drawings]

FIG. 1 shows a schematic view of an apparatus used for an arsenate ion removal test in Examples and Comparative Examples.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-75717 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 20/00-20/34

Claims (7)

(57) [Claims] 1. A Na ₂ O content of 0.3% by weight or less, an abrasion rate of 5% or less, a sphere-equivalent external specific surface area calculated from a sieving particle size of 4 to ²⁰ m ² / l, and a BET specific surface area of 100 m ^2. / G
As described above, the pore radius measured by the mercury penetration method is 0.2 to 10 μm.
Has a pore volume of 0.04 cc / g or more and 0.2 to 1 μm
An activated alumina for adsorbing arsenate ions, characterized in that the pore volume of m is 0.02 cc / g or more. 2. A Na ₂ O content of 0.3% by weight or less, an abrasion rate of 5% or less, a sphere-equivalent external specific surface area calculated from a sieved particle size of 6 to 14 m ² / l, and a BET specific surface area of 100 m ^2. / G
As described above, the pore radius measured by the mercury penetration method is 0.2 to 10 μm.
Pore volume of 0.08 cc / g or more and 0.2 to 1 μ
An activated alumina for adsorbing arsenate ions, characterized in that the pore volume of m is 0.04 cc / g or more and the particle shape is spherical. 3. The method according to claim 1, wherein an acidic component is deposited.
Is an activated alumina for adsorbing arsenate ions according to 2. 4. Arsenic concentration 0.2 mg / l to 0.01 mg
/ L aqueous solution, Na ₂ O content is 0.3 wt% or less,
Abrasion rate is 5% or less, sphere-equivalent specific surface area calculated from particle size by sieving is 4 to ²⁰ m ² / l, BET specific surface area is 100 m ² /
g or more, pore radius measured by mercury porosimetry 0.2-10μ
The pore volume of m is 0.04 cc / g or more and 0.2 to 1
pore volume of μm are continuously fed to a column packed with activated alumina at 0.02 cc / g or more, arsenate of砒acid Lee <br/>-one in an aqueous solution from the aqueous solution, characterized in that the adsorption treatment Ion adsorption treatment method. 5. Activated alumina coated with an acid component
The method according to claim 4, wherein 6. The method according to claim 4, wherein the activated alumina is coated with an acid component having a water pH of 3 to 6 when immersed in water at 80 ° C. 7. The method according to claim 5, wherein the acid component is at least one selected from hydrochloric acid, hydrofluoric acid, nitric acid, sulfuric acid, aluminum sulfate and acetic acid .