JP2003160338A - Arsenic-adsorptive manganese compound, arsenic adsorbent, and method for adsorbing and removing arsenic in aqueous solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new technical means by which not only a pentavalent arsenic but also a trivalent one, removal of which has been difficult in the prior art can be removed efficiently. <P>SOLUTION: This means comprises treating an arsenic-containing aqueous solution by using an arsenic-adsorptive manganese compound which is an oxygen compound of manganese containing bismuth and includes manganese as a main component, and then adsorbing and removing arsenic. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an arsenic-adsorptive manganese compound, an arsenic adsorbent, and a method for adsorbing and removing arsenic in an aqueous solution.

[0002]

BACKGROUND OF THE INVENTION There are many cases of arsenic pollution problems in rivers and lakes both in Japan and abroad, especially in Bangladesh. The soil in this area is rich in arsenic, and local residents who use well water contaminated with arsenic as drinking water have many skin disorders and diseases caused by arsenic. Nawabganj district is said to be the most severely damaged in Bangladesh
Then, the arsenic concentration in drinking water is 0.01 to 1 mg / l (W
Although it has been reported that the water quality standard for HO will reach 0.01 mg / l), the current situation is that no substantial measures have been taken. On the other hand, the arsenic pollution problem in Japan is mainly due to wastewater from abandoned mines. At the Sasagaya mine in Shimane prefecture, the arsenic concentration in the river water around the mine exceeds the environmental standard value due to the wastewater from the tunnel after the closing of the mine 0.08-1.3 mg / l
It was reported that it was. In addition, around the former Horibetsu sulfur mine in Hokkaido, the concentration of arsenic in river water was large until 1975 due to the outflow of strongly acidic water containing a large amount of arsenic to the Benkei River, which exceeded the environmental standard value. On the other hand, due to mine pollution countermeasures such as the blockage of the mine mouth by Sobetsu Town and the installation of a neutralization treatment facility for the mine water, the initial arsenic concentration of 0.2 m after 1981.
It is reported to be reduced to about 0.02 mg / l, which is 1/10 of g / l. However, the total amount of lime cake, slaked lime and calcium carbonate used for neutralization and coprecipitation removal of arsenic at this treatment facility is 4
It is a big problem that the amount of ~ 50,000 tons is reached, and a large amount of precipitate generated by this is required to secure a treatment site and an annual cost of about 300 million yen. In addition to the above, there are many water pollution problems caused by arsenic, such as wastewater from geothermal power plants and industrial waste. However, the coprecipitation method that is mainly performed at present has problems such as waste disposal after processing and cost, and an alternative method for treating arsenic is expected to be an arsenic adsorbent. In particular, it is an economical arsenic to realize a novel adsorbent capable of directly adsorbing trivalent arsenic by omitting the process of oxidizing trivalent arsenic to pentavalent arsenic which is relatively easy to adsorb by adding an oxidizing agent. It is considered to be valuable in establishing removal technology.

Therefore, the invention of this application solves the problems of the prior art as described above, and efficiently removes not only pentavalent arsenic but also trivalent arsenic, which has been conventionally difficult. It is an object to provide a new technical means capable of doing so.

[0004]

Means for Solving the Problems The invention of the present application is to solve the above-mentioned problems. Firstly, it is an oxygen compound of manganese containing bismuth, which contains manganese as a main component. An arsenic adsorbing manganese compound is provided.

The invention of this application is, with respect to the above invention, secondly, bismuth is distributed in a part of the surface of the oxygen compound of manganese, and is disposed. Thirdly, a manganese compound, and thirdly, an arsenic-adsorptive manganese compound characterized in that manganese or a compound thereof to which bismuth or a compound thereof is added, is fired in the air or an oxygen-containing atmosphere, Fourthly, an arsenic-adsorptive manganese compound characterized in that the bismuth compound is bismuth carbonate oxide and the manganese compound is manganese carbonate,
The arsenic-adsorptive manganese compound is characterized in that bismuth is added to a solution containing an oxygen compound of manganese and dried and dehydrated, and sixthly, the manganese compound is crushed. An arsenic-adsorptive manganese compound, which is characterized by the above, and a arsenic-adsorptive manganese compound, which is characterized in that the manganese compound is acid-treated.

Eighthly, the invention of this application is more specifically characterized in that a mixture of bismuth carbonate oxide powder and manganese carbonate powder is fired at a temperature of 100 ° C to 450 ° C. The ninth is the arsenic-adsorptive manganese compound described above, and the ninth is the arsenic-adsorptive manganese compound characterized by being calcined at a temperature near 200 ° C. The tenth is bismuth and manganese. An arsenic-adsorptive manganese compound characterized by having a mixed molar ratio of 0.001: 1 to 1: 1.
Has a mixed molar ratio of bismuth and manganese of 0.01: 1.
An arsenic-adsorptive manganese compound is provided in the range from 1 to 1: 1.

Twelfth, the invention of this application provides an arsenic adsorbent characterized by comprising any of the above manganese compounds or those containing the same, and thirteenth, the manganese compound is a carrier material. The present invention provides an arsenic adsorbent characterized by being supported or filled with a carrier material.

The fourteenth aspect of the invention of the present application is:
A method for adsorbing and removing arsenic in an aqueous solution, which comprises contacting the arsenic adsorbent with an aqueous solution containing arsenic to adsorb and remove arsenic in the aqueous solution. There is also provided a method for regenerating an arsenic adsorbent, which comprises subjecting the adsorbent described above to acid treatment to desorb arsenic in an acid solution so that the adsorbent having desorbed arsenic can be reused.

As described above, the oxygen compound containing manganese as a main component according to the invention of the present application solves the problem of low economic efficiency of the conventional methods other than the adsorbent method, and the conventional adsorbent method is more efficient. The characteristic feature is that trivalent arsenic, which was technically difficult to remove, can be adsorbed and removed efficiently in an extremely short time. For example, in the case of the adsorbent according to the present invention, the amount of trivalent arsenic adsorbed per gram of the adsorbent reaches as high as 50 mg. Further, it is also possible to easily collect the adsorbed arsenic in the acid solution by bringing the adsorbent having adsorbed arsenic into contact with an acid solution such as dilute sulfuric acid, and the adsorbent can be reused.

It is an important feature that the invention of this application is effective not only for trivalent arsenic arsenous acid but also for pentavalent arsenic arsenic acid. In general, arsenic in industrial wastewater is often dissolved in the form of pentavalent arsenic acid. Therefore, it is effective not only for trivalent arsenous acid but also for pentavalent arsenic acid. Means that the invention of (1) has wide applicability in the treatment of arsenic-containing wastewater.

Further, as described above, the adsorbent of the present invention exhibits excellent performance, and is also an advantage of the water purification method using the adsorbent, that is, it is not necessary to increase the electrolyte concentration of the aqueous solution to be treated. Hold. That is, the main feature of the adsorbent is that manganese and bismuth hardly elute into the arsenic aqueous solution to be treated.

Further, as a method for holding the powdery adsorbent, a method in which granules are granulated using PVC or the like and then packed in a column or the like is generally used. However, in this conventional method, a contact surface between the adsorbent particles and the liquid to be treated becomes small because an adhesion surface with PVC is generated,
As a result, the throughput of the column was reduced. Therefore, in the present invention, for example, by using a carrier material such as ashless pulp or glass wool and the like, which holds the powdery adsorbent, a new method is developed to improve the above-mentioned disadvantages of the conventional method. There is.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the characteristics as described above, and the embodiments thereof will be described below.

First, the manganese compound provided by the invention of this application has arsenic adsorption as its function. This is an oxygen compound of manganese (Mn) containing bismuth (Bi) and has manganese as a main component. In the manganese compound of the invention of this application, it is illustrated that bismuth is partially distributed and disposed on the surface of the oxygen compound of manganese as a more preferable form. Note that the definition of "oxygen compound" means an oxide as an oxide or a complex oxide, or a compound mainly containing this and having an oxygen-containing group such as a carbonate group. As the oxygen compound of manganese, those obtained as a fired product can be considered, but the oxygen compound is not limited thereto.

For example, for firing, usually 10
At a temperature of about 0 ° C. to 500 ° C., bismuth or a compound thereof and manganese or a compound thereof constitute the oxygen compound of manganese as described above. In this firing, metal bismuth or various compounds thereof or metal manganese or various compounds thereof can be used as a raw material capable of producing the above-mentioned oxygen compound in the air or oxygen atmosphere.
More specifically, as this compound, for example, sulfides, bromides, carbonates, nitrates, sulfates, organic acid salts, halides and the like, which are present as solid powders, are preferably used. . It may be one produced by precipitation by a sol-gel method.

More typically, the manganese compound of the invention of this application is prepared by mixing a powder of bismuth carbonate oxide and a powder of manganese carbonate, and mixing the powder as a mixed powder or a molded body at 100 to 450 ° C., preferably 170. ℃ ~ 250
For example, those fired in a temperature range of about 200 ° C., more specifically about 200 ° C., are exemplified. Here, near 200 ° C. means 200
It can be understood as indicating a temperature range of about ± 20 ° C. The mixing ratio of the raw material substances such as bismuth carbonate oxide and manganese carbonate in this representative example is a molar ratio of bismuth: manganese of 0.1 in terms of arsenic adsorption performance.
It is preferably in the range of 001: 1 to 1: 1. And, under the normal environment of arsenic adsorption, 0.0
1: 1 to 1: 1 range, more specifically 0.01: 1 to
It can be shown as a preferable example that the range is 0.5: 1.

On the other hand, the manganese compound of the invention of the present application is not limited to be obtained as a calcined product, for example, one obtained by adding bismuth to a solution containing an oxygen compound of manganese and drying and dehydrating it. Is also realized. More specifically, for example, potassium permanganate and manganese sulfate are mixed and stirred in a sulfuric acid bath to prepare a solution containing manganese dioxide, and bismuth nitrate, for example, is added to the solution to dry and dehydrate at 200 ° C. with stirring. Examples thereof are those obtained. The ratio of bismuth and manganese in this case can be the same as above.

The arsenic-adsorptive manganese compound of the invention of this application is also effective as an arsenic adsorbent by activating the manganese compound by acid treatment. For example, this acid treatment can be carried out using dilute nitric acid, dilute sulfuric acid, dilute hydrochloric acid or the like, and the arsenic adsorption performance of the manganese compound of the invention of this application will be significantly improved by this acid treatment.

Further, this manganese compound as an arsenic adsorbent can be obtained as a fired product having a desired specific surface area by firing the raw material as a mixed powder or a molded body. ing.

The manganese compound can be crushed to a desired size at an arbitrary timing to adjust the specific surface area before use. Therefore, the adsorption performance of the manganese compound can be improved by crushing the calcined product and adjusting the specific surface area in addition to the activation by the above acid treatment.

The arsenic adsorbent of the invention of this application is used for adsorbing and removing arsenic in an aqueous solution by supporting or filling a carrier material such as ashless pulp or glass wool on the carrier material. You can also

In the prior art, after oxidizing trivalent arsenic in water into pentavalent arsenic which is easy to process by administering an oxidizing agent,
Was processing. In this conventional method, deterioration of water quality due to an increase in electrolyte concentration in water poses a problem, and further, since the economical efficiency is low, it is desired to develop an adsorbent capable of directly adsorbing trivalent arsenic in water. It was In the invention of this application, for example, a metal oxide containing bismuth and containing manganese as a main component, which is obtained by adding a small amount of a bismuth compound to a manganese compound and then firing, is more preferably acid-treated, and then arsenic wastewater is used. In addition to the case of pentavalent arsenic, it is possible to realize a highly efficient and economical adsorption treatment for trivalent arsenic. Regarding the adsorption of trivalent arsenic, in the demonstration experiment of the present invention, the arsenous acid (HAs
It is confirmed as the case of arsenic in the state of O ₂ ).

Further, by using glass wool or the like as the adsorbent holding material, it is possible to obtain a powdery adsorbent holding layer having excellent chemical resistance when the column is repeatedly used. Further, by using the ashless pulp as the adsorbent holding material, after the column is repeatedly used, it becomes possible to incinerate it in an incinerator or the like when discarding. At this time, the ashless pulp, which occupies most of the volume of the holding layer enclosing the powder adsorbent, is almost completely burned, and only the adsorbent component remains as a residue after incineration.

As described above, according to the invention of this application,
A novel adsorbent capable of efficiently adsorbing trivalent arsenic, which has been difficult to remove from water by the conventional technique as well as pentavalent arsenic, is provided. This adsorbent exhibits high performance in which the maximum arsenic adsorption amount per 1 g of the adsorbent reaches 50 mg or more.

In applying the adsorbent according to the present invention to an aqueous arsenic solution, for example, the following procedure is most effective. This is apparent from the examples described below.

(A) Manganese carbonate powder MnCO ₃ (special grade reagent) and bismuth carbonate oxide powder Bi ₂ (CO ₃ ) O ₂ (special grade reagent) were mixed in a weight ratio of 1: 0.1 to 0.2. A metal oxide containing bismuth and containing manganese as a main component is synthesized by firing at 200 ° C. for 4 hours and 30 minutes using an electric furnace.

(B) The metal oxide containing bismuth obtained in (a) and containing manganese as a main component has a concentration of 0.5 mol /
It is suspended in about 1 of dilute nitric acid and the residual carbonic acid component is vaporized and removed. Then, it is washed with pure water to remove the attached dilute nitric acid.

The samples obtained in (c) and (b) are dried for 1 hour at about 100 ° C. using a dryer. An adsorbent is manufactured by the above operation.

(D) When using the adsorbent, the adsorbent of (c) is brought into contact with the aqueous arsenic solution. If necessary, a concentration of 0.5m
It can be suspended in dilute nitric acid of about ol / l, stirred for about 30 minutes to 1 hour, collected by filtration, washed with pure water, and then suspended in an arsenic aqueous solution.

(E) After the arsenic concentration in the aqueous arsenic solution has dropped to 0.1 mg / l which is the standard value for wastewater, the adsorbent is recovered from the aqueous arsenic solution by a technique such as filtration. The purified wastewater can be released to public water bodies.

(F) A small amount of diluted sulfuric acid having a concentration of about 0.5 mol / l is added to the recovered adsorbent after adsorbing arsenic, and the mixture is stirred for about 30 minutes to desorb and concentrate the adsorbed arsenic in the diluted sulfuric acid.

(G) After the desorption of arsenic, the adsorbent of the present invention is again brought into contact with an aqueous arsenic solution for reuse in order to restore the adsorption capability for arsenic again.

Further, in the above examples, the adsorbent is suspended as a powder in an arsenic aqueous solution, but in the industrialization, it is granulated if necessary, or if necessary, it is adjusted to an appropriate size. It is crushed, or loaded on a column by supporting it on a porous body,
It is also possible to apply arsenic by passing an aqueous arsenic solution through the column.

Therefore, an embodiment will be shown below and further detailed description will be given. Of course, the invention is not limited to the following examples.

[0035]

Examples Example 1: Synthesis of adsorbent and adsorption of arsenic [Synthesis of adsorbent] Manganese carbonate MnCO ₃ powder (special grade reagent) and bismuth carbonate oxide Bi ₂ (CO ₃ ) O ₂ powder (special grade reagent) were mixed. The ratio was changed in several stages and mixed well. Approximately 20 g of each mixed powder mixture was transferred to a porcelain crucible and baked in an electric furnace at 400 ° C. for 4.5 hours, and then allowed to cool to room temperature. An arsenic adsorption experiment was carried out using a metal oxide containing bismuth and containing manganese as a main component, which was obtained as a result of calcination, as an adsorbent, and the optimum manganese carbonate MnCO ₃ powder and bismuth carbonate Bi were obtained. ₂
The mixing weight ratio with the (CO ₃ ) O ₂ powder was determined. Further, the effect of adding bismuth by comparing adsorption performance with manganese oxide obtained by firing only manganese carbonate MnCO ₃ powder without mixing bismuth carbonate Bi ₂ (CO ₃ ) O ₂ powder under the same conditions. It was confirmed.

Next, the firing temperature is 150 ° C., 200 ° C., 2
Arsenic adsorption experiments using bismuth-containing metal oxides containing manganese as the main component as an adsorbent after cooling to room temperature after changing the temperature to 50 ° C and 300 ° C for several hours and baking for 4.5h. The optimal firing temperature was investigated by carrying out.

The adsorbent containing bismuth and containing manganese as a main component and the fired product of manganese carbonate powder all had a particle size of 1 to 10 μm and a specific surface area of 50 m ² / g.
It was about. [Method of arsenic adsorption experiment] Arsenic standard solution (made by Wako Pure Chemical Industries, Ltd.) having a total concentration of 1000 mg / l and containing trivalent arsenic prepared from reagent As ₂ O ₃ was diluted with ion-exchanged water to obtain a concentration of 1000 ml of 10 mg / l, 20 mg / l, and 40 mg / l arsenic solutions were prepared and subjected to each experiment. An aqueous sodium hydroxide solution was used to adjust the pH of the arsenic aqueous solution. Next, 1.0 g of the adsorbent obtained by the above-mentioned synthesis was weighed by an electronic balance, suspended in 1000 ml of 0.5 mol / l dilute nitric acid (dilute sulfuric acid or dilute hydrochloric acid), and stirred for 1 hour. After stirring, glass fiber filter paper with a pore size of 0.6 mm (GS25 Advantech Toyo Corp.)
Was filtered with suction, and washed with 1000 ml of ion-exchanged water (hereinafter, this operation is referred to as acid treatment). The activated adsorbent obtained as a result of the acid treatment was suspended in an aqueous arsenic solution and stirred for 1 hour. 5 minutes while stirring
After 10 minutes, 20 minutes, 30 minutes and 60 minutes, 20 ml of each sample was collected from the aqueous arsenic solution by filtration. A disposable membrane filter (DISMIC-25 Advantech Toyo Corp.) having a pore diameter of 0.2 μm was used for the filtration. The arsenic concentration in each sample collected by filtration was measured with an ICP emission spectrometer (ICPS-1000III Shimadzu Corporation), and the time course of the arsenic concentration in the arsenic aqueous solution was examined. [Arsenic Adsorption Amount and Raw Material Mixing Ratio] In synthesizing the arsenic adsorbent, as described above, manganese carbonate MnCO ₃ powder (special grade reagent) and bismuth carbonate oxide Bi ₂ (CO ₃ ) O ₂ powder (special grade reagent) were mixed. The optimum mixing ratio was examined by changing the ratio. The firing temperature was 400 ° C. The results are shown in Fig. 1. From FIG. 1, the optimum mixing ratio for obtaining the highest adsorption amount is that the mixing weight ratio is MnCO ₃ : Bi ₂ (CO ₃ ) O ₂ = 1:
It was found to be about 0.1 to 0.2. On the other hand, the adsorbed amount of manganese oxide having a mixing ratio of 1: 0, which is the case without adding bismuth, is significantly lower than that of the case where bismuth is added, and it was found that the mixing of bismuth improves the arsenic adsorption performance. did.

When confirmed by an X-ray diffraction pattern,
In the case of a burned product having a weight ratio of 1: 0.1 to 0.2 as described above, peaks of bismuth oxide and bismuth carbonate oxide,
A broad peak, which is considered to be due to amorphous manganese oxide, was observed when the value of 2θ was around 37 deg. [Arsenic adsorption amount and firing temperature] In synthesizing an arsenic adsorbent, changes in the arsenic adsorption amount due to the difference in firing temperature were examined when firing a mixed powder of manganese carbonate and bismuth carbonate using an electric furnace. . The results are shown in Fig. 2. From FIG. 2, it can be seen that a high adsorption amount can be obtained when the firing temperature is about 300 ° C. However, when the adsorbent suspended in the aqueous arsenic solution was collected by filtration after the adsorption operation and weighed, it was found that the weight decreased from the initial weight of 1 g to nearly half. This decrease in adsorbent weight is considered to be due to the fact that manganese carbonate, which is the raw material reagent, remains in the adsorbent obtained after firing, and the carbonic acid component vaporizes and escapes during the acid treatment of the adsorbent. To be
When FIG. 2 was corrected in consideration of this weight reduction amount, it became clear that the adsorbent obtained by firing at 200 ° C. showed the highest adsorption amount as shown in FIG. [Arsenic Adsorption Amount and pH] It was investigated how the arsenic adsorption amount was affected by the pH of the aqueous solution to be removed. As a result, it was revealed that good arsenic adsorption was exhibited when the pH of the aqueous arsenic solution was weakly acidic as shown in FIG. Therefore,
It is considered that the arsenic can be efficiently removed by adjusting the pH of the arsenic aqueous solution to be removed to weak acidity in advance. [Method of desorbing arsenic from adsorbent] Arsenic adsorbed on the adsorbent exhibits good desorbability when brought into contact with an acid such as dilute sulfuric acid. The relationship between the type of acid solution used for desorption and the desorption rate is shown in FIG. From FIG. 5, it can be seen that high desorption is possible when dilute hydrochloric acid or dilute sulfuric acid is used. [Arsenic Concentration in Aqueous Solution and Adsorption Amount] FIG. 6 shows the influence of the arsenic concentration in the aqueous solution on the adsorption amount. As is clear from FIG. 6, the adsorbed amount increases as the arsenic concentration increases. [Example of application to actual arsenic wastewater] It was confirmed whether the synthesized adsorbent is effective against actual arsenic wastewater containing trivalent arsenic. The target of treatment is the wastewater generated at the geothermal power plant currently in operation. Arsenic is present in this wastewater at a concentration of 3.5 mg / l. The components and pH of this wastewater are shown in Table 1. As can be seen from Table 1, this wastewater contains many components in addition to arsenic. Actually, the mixing weight ratio of 1: 0.2 is 20 with respect to 1 liter of this wastewater.
1 g of the adsorbent calcined at 0 ° C. was acid-treated with dilute nitric acid having a concentration of 0.5 mol / l, suspended in waste water, and stirred for 1 hour.
The obtained results are shown in FIG. 7. From Fig. 7, the arsenic concentration in the wastewater has decreased from the initial value of 3.5 mg / l to less than the wastewater standard value of 0.1 mg / l within just 5 minutes. However, it proved to be extremely effective.

[0039]

[Table 1]

Example 2 [Holding and adsorption of powdery adsorbent using ashless pulp or glass wool] In industrialization, granulation or supporting on a porous body was carried out and packed in a column when necessary. Arsenic can be removed by passing an aqueous arsenic solution through the column. (1) Method for holding powdery adsorbent An appropriate amount of ashless pulp or glass wool having a thickness of about 1 μm is added to pure water and sufficiently stirred. The thickness of the ashless pulp or glass wool used depends on the size of the adsorbent particles retained. For example, an adsorbent particle having a diameter of about 1 to several tens of μm is set as a holding target. Next, an adsorbent is added and further stirred. Here, if necessary depending on the nature of the adsorbent, a mineral acid such as hydrochloric acid or nitric acid is added and stirred for a predetermined time.
The surface of the adsorbent particles is activated by the treatment of adding the mineral acid and stirring.

When glass wool is used, the above-mentioned suspension is added little by little from the upper part of the cylinder forming the adsorption column, and each time, the liquid is discharged by completely sucking it from the lower part with a pump or the like. This is repeated until the desired thickness is reached, and the holding layer in which the glass wool fiber encloses the powdery adsorbent is formed.

On the other hand, when ashless pulp is used, the above suspension is poured from the upper part of the cylinder forming the adsorption column,
While the liquid is gradually discharged from the lower part, the ashless pulp fiber forms a holding layer in which the powdery adsorbent is contained while stirring with a rod or the like so that the pulp and the adsorbent are uniformly settled in the column cylinder. (2) Example of holding method The following is an example of arsenic-containing water treatment in which this holding method is applied to the adsorption method described in the previous section.

A) Adsorption column method This method is an example in which arsenic wastewater containing trivalent arsenic discharged from a semiconductor factory is targeted.
As shown in FIG. 8, this is a method in which waste water is pressed into the adsorption column from the waste water tank by using a pump to remove arsenic, and it is possible to treat the waste water continuously and in large quantities. A valve is provided between the pump and the adsorption column to control the amount of liquid sent to the adsorption column. Further, the adsorption column is hermetically sealed to prevent contact between the arsenic adsorbent and the atmosphere and prevent performance deterioration of the adsorption column due to drying of the adsorbent. Figure 9
Shows the results of arsenic wastewater treatment by this method. The results of this experiment were obtained from the results of experiments in which a 1 ppm arsenic aqueous solution was passed through the column at a rate of 300 ml / h using a cylindrical column having a diameter of 2 cm and a column length of 10 cm.

B) Adsorption mat method This method is an example devised as a water purification technique against severe arsenic contamination of drinking water which occurs in Bangladesh and the like. It is expected as a simple water purification method that does not require any power source. The processing device shown in FIG.
It is composed of an outer frame with a water tap, an arsenic adsorption mat, and charcoal, sand, and pebbles that have been used in household filtration tanks. The features of this device are that the structure is simple and it is not easily broken, and it is possible to purify arsenic by supplying only the outer frame and adsorption mat to the site. Safe drinking water can be easily obtained by removing suspended fine particles in water in the pebbles layer and sand layer, removing organic matter and the like in the charcoal layer, and further removing arsenic by the arsenic adsorption mat. Another structural feature is that the position of the water intake plug is raised depending on the installation position of the arsenic adsorption mat so that the adsorption mat is always in water. This prevents the adsorbent from drying due to contact between the adsorption mat and the atmosphere, resulting in deterioration of the performance of the adsorption mat.

The adsorption mat holds an arsenic adsorbent that has been activated by a mineral acid in advance.
In order to prevent the performance of the adsorbent from deteriorating due to contact between the adsorbent mat and the atmosphere, the adsorbent mat needs to be evacuated and sealed in a state where the adsorbent mat is sufficiently moistened in addition to the outer frame part. To the site where this device is used, send the adsorption mat in a sealed state with a film etc., peel off the film at the beginning of use and open it, spread it in the outer frame, and sand from above, as shown in the figure.
Used by filling with pebbles and charcoal.

C) Adsorption pack method This method is an embodiment devised as a portable arsenic water purification method for the purpose of improving the simplicity and convenience of the method of b). An example of this technique is shown in FIG. A small amount of glass wool or ashless pulp fiber chamber and arsenic adsorbent are enclosed in the adsorption pack to improve water permeability, and the arsenic adsorbent is thrown into the water to be treated and the water to be treated is agitated. Are adsorbed and removed.

The arsenic adsorbent in the adsorption pack is previously activated with mineral acid and sealed in a wet state with a vinyl bag or the like. Due to this sealing, the adsorption capacity of the arsenic adsorbent is maintained for a long time. When using the adsorption pack, it can be used immediately by breaking the sealed bag and removing the adsorption pack. FIG. 12 shows the result of implementation of this method. In FIG. 12, it can be seen that the concentration of arsenic decreases when one adsorption pack is added to 1 liter of trivalent arsenic-containing water and stirred.

Example 3: [Removal of arsenic acid (pentavalent arsenic) from industrial wastewater] (Experimental wastewater) Removal of arsenic (V) from actual industrial wastewater having the components shown in Table 2 was carried out as described above. The mixing weight ratio of is 1:
Tried with an adsorbent calcined at 0.2 and 200 ° C. The arsenic concentration is 0.028 mg / l, which is 0.0 of the environmental standard.
Greater than 1 mg / l. By measuring the redox potential, it was confirmed that the arsenic in this wastewater was arsenic acid.

[0049]

[Table 2]

(Experimental conditions) For 1 liter of experimental wastewater,
Adsorbent acid-treated with nitric acid having a concentration of 0.5 N
44 g was suspended and stirred. 5 minutes after suspending the adsorbent,
After 15 min, 30 min, 60 min, 120 min, a sample of the experimental wastewater was collected by filtration, and the arsenic concentration in the experimental wastewater was changed by an ICP emission spectrometer equipped with a hydride generator, which has a higher analytical sensitivity than ordinary ICP emission analysis. I checked. (Experimental Results) As shown in FIG. 13, the arsenic concentration decreased with the passage of stirring time on the horizontal axis, and the environmental standard value of 0.01 mg / l was cleared 30 minutes after suspension of the adsorbent. Therefore,
As shown in Table 2, it was confirmed that the adsorbent of the present invention is effective for removing arsenic (V) from actual industrial wastewater in which various other components coexist.

Example 4 [Removal of Arsenic from Artificial Arsenic (V) Wastewater] (Experimental Wastewater) Reagent Na ₂ HAsO ₄ was dissolved in pure water,
3 liters of artificial arsenic (V) wastewater was prepared. The arsenic concentration was 10 mg / l and the pH was adjusted to pH 7 by adding aqueous sodium hydroxide solution. (Experimental conditions) 1 g of the adsorbent of Example 3, which had been acid-treated with 0.5 N nitric acid for 30 minutes, was washed with pure water, suspended in experimental waste water, and stirred for 1 hour. (Experimental result) The arsenic concentration in the experimental wastewater after 1 hour was calculated as I
The arsenic concentration was found to be 7.2 m when examined with a CP emission spectrometer.
It had fallen to g / l. Filter the adsorbent from the experimental wastewater,
The result of measuring the weight was 0.5 g. From these results, when the adsorption amount of arsenic (V) per unit weight of the adsorbent was calculated, a value of 16.8 mg / g was obtained. This value is almost the same as the result of the experiment conducted using the artificial arsenous acid wastewater containing arsenic (III) prepared by using the reagent As ₂ O ₃ , and the adsorbent of the present invention is a trivalent arsenic. Not only that, it is an adsorbent that is also effective for pentavalent arsenic.

Example 5: [Observation of Arsenic Adsorption State on Adsorbent Surface] In order to observe the adsorption state of arsenic on the adsorbent of the invention of this application,
An adsorbent that adsorbed a large amount of arsenic was prepared.

As the adsorbent, a bismuth carbonate powder and a manganese carbonate powder are used in a molar ratio of Mn: Bi = 0.1: 1.
The resulting mixture was mixed for 4 hours and half at 200 ° C., the mixture was stirred with 0.5 mol / l dilute nitric acid for 30 minutes, and a 25 μm glass filter paper was filtered and washed with water. 0.7 g of this adsorbent was precisely weighed, suspended in 1 L of 40 mg / l high-concentration artificial arsenic-containing water prepared from an arsenic standard solution for atomic absorption analysis, and adsorbed arsenic for 200 hours with stirring.

The arsenic concentration 200 hours after the start of the removal treatment was about 7.2 mg / l as shown in FIG.
By simple calculation, about 46.8 g of arsenic is adsorbed per 1 g of the adsorbent.

The surface of the adsorbent having adsorbed arsenic was observed with a scanning electron microscope (SEM), and the results are shown in FIG. The portion corresponding to this SEM image was examined by energy dispersive X-ray spectroscopy (EDS) analysis, and the distribution state of Mn, As, and Bi on the surface of the adsorbent was observed. The results are shown in FIGS. 16 (a) to 16 (c), respectively. From these figures, it was confirmed that Bi was unevenly distributed on the surface of the adsorbent, and As was almost uniformly present on the surface of the adsorbent except for the locations where Bi was unevenly distributed.

Further, X-ray photoelectron spectroscopy (XPS) analysis is performed on the adsorbent before adsorbing arsenic, the adsorbent after adsorbing arsenic, and the adsorbent whose surface has been scraped by several tens of nm by argon ion etching after adsorbing arsenic. The results are shown in FIGS. 17 (a) to (c), respectively. Compared to (a),
As for the adsorbent after (b) arsenic adsorption, the binding energy of As _3d orbital electrons was found to be 44.9 eV, and it was confirmed that arsenic in a trivalent state was adsorbed. Also,
Since this spectrum is not observed for the adsorbent whose surface is cleaved in (c), it is expected that this adsorbent adsorbs arsenic on the very surface rather than inside pores.

From the above, it was found that the adsorbent of the invention of this application adsorbs arsenic in a trivalent state mainly at the position where manganese exists.

Example 6 [Removal of Arsenic from Water of Bangladesh Well] Bismuth carbonate oxide powder and manganese carbonate powder were mixed in a molar ratio of Mn:
The mixture was mixed so that Bi = 0.1: 1, and the calcined product was calcined at 200 ° C. for 4 hours and a half, and diluted with dilute nitric acid at 0.5 mol / l to 3 times.
After stirring for 0 minutes, a 25 μm glass filter paper was filtered and washed with water to obtain an arsenic adsorbent of the invention of this application.

First, in order to confirm the basic arsenic adsorption capacity of this adsorbent, an adsorption test was conducted by using an artificial arsenic aqueous solution prepared from an arsenic standard solution for atomic absorption spectrometry, and an adsorption isotherm was prepared. The result is shown in FIG. The adsorption characteristics of this adsorbent were classified into Langmuir type, and it was confirmed that saturated adsorption was reached at an equilibrium concentration of 25 mg / l.

Further, the pH of the artificial arsenic aqueous solution was changed, and the relationship between the pH at equilibrium and the partition coefficient K _d is shown in FIG.
The distribution coefficient K _d is calculated according to the following equation.

K _d = (arsenic adsorption amount per 1 g of adsorbent / m
ol) / (amount of arsenic remaining in 1 cm3 of the artificial arsenic aqueous solution / mol) From FIG. 19, this adsorbent exhibits an adsorbing ability in a wide pH range from acidic to alkaline, and particularly the artificial arsenic aqueous solution has a pH of 4.5. It was found that the K _d value was maximized in the vicinity and the arsenic adsorption capacity was highest.

Next, as shown in FIG. 20, 1.5 g of ashless pulp was loaded with 2 g of the above-mentioned acid-treated adsorbent to give an inner diameter of 2
It was filled in a chromatographic tube of cm and used as a column type arsenic adsorbent.

A breakthrough test was conducted in which an artificial arsenic aqueous solution of 1 mg / l, pH 5.0 was passed through this column at a water flow rate of 100 ml / 1.0 hour, and the results are shown in FIG.
The arsenic treatment capacity for this column was found to be 35 l for a 1 mg / l artificial arsenic solution.

Then, using the same column as above,
Attempted to remove arsenic from well water in Bangladesh. This water was taken from a well in Chapai Nawabganji near the border with India, west of Dhaka. The well water flow rate to the column is 10
It was 0 ml / 10 min. Changes in the concentration of each component of well water before and after column water flow were measured and are shown in Table 3. Here, regarding the concentrations of As, Mn, and Bi, an ICP emission spectrometer with a hydride generator (manufactured by Shimadzu Corporation: I)
CPS-1000III) and the concentrations of other components were measured using an ion chromatograph (manufactured by Shimadzu Corporation: Ion Chromatograph PIA-1000,).

[0065]

[Table 3]

It was confirmed that the concentration of arsenic contained in the well water decreased from the initial concentration of 0.01 mg / l to the concentration below the detection limit value. Thus, it has been shown that the adsorbent of the invention of this application can almost completely remove arsenic from well water in Bangladesh or water containing arsenic at a higher concentration.

Example 7: [Removal of Arsenic by Adsorbent without Acid Treatment] Bismuth carbonate powder and manganese carbonate powder were mixed in a molar ratio of Mn: Bi.
= 0.1: 1, and calcined at 200 ° C for 4 hours and a half, and lightly crushed without acid treatment in an agate mortar to an average particle size of about 1/2. The arsenic adsorbent of the invention of this application was used.

0.5 g of this adsorbent was placed in a 10 mg / l arsenic aqueous solution prepared from an arsenic standard solution for atomic absorption spectrometry, and the mixture was stirred for 120 minutes with a magnetic stirrer,
The arsenic concentration in the arsenic aqueous solution was measured by an ICP emission spectrometer. As a result, the concentration of the arsenic aqueous solution was 4.1 mg / l.
It was confirmed that it was lowered to. After the adsorption test was completed, the adsorbent was collected and dried to weigh 0.39 g. From these results, the amount of arsenic adsorbed per 1 g of the adsorbent is about 30 mg, which is comparable to the result of the same adsorption test of the adsorbent treated with acid, which is 35 mg / g. I knew it wasn't.

From the above, it was confirmed that the adsorbent of the invention of this application can also improve the arsenic adsorption capacity by increasing its specific surface area. It was also shown that it is effective to appropriately adjust the specific surface area of the adsorbent in order to solve the problems such as the cost for the acid treatment and the decrease in the weight of the adsorbent due to the acid treatment.

Example 8: [Removal of Arsenic by Adsorbents Produced from Different Raw Materials] Manganese sulfate and bismuth sulfate in a molar ratio of Mn: Bi =
The mixture was mixed at a ratio of 0.1: 1 and calcined at 400 ° C. for 4 hours and half to obtain the arsenic adsorbent of the invention of this application. The particle size of the obtained adsorbent was 1 to 10 μm, and the specific surface area was about 50 m ² / g.

It is recognized that this substance is almost the same substance as the adsorbent obtained by firing bismuth carbonate oxide and manganese carbonate as shown in the above examples, and although it can be produced at a lower cost, arsenic The adsorption capacity was about 70%. On the other hand, it was confirmed that the arsenic adsorption capacity was about twice as high as that of the calcined product of manganese oxide containing no bismuth. Therefore, it was found that an arsenic adsorbent having higher adsorption performance can be obtained by using bismuth carbonate and manganese carbonate as the raw materials. Further, it has been found that it is also effective to use manganese sulfate, bismuth sulfate or the like as a raw material in order to manufacture the adsorbent of the invention of this application at a lower cost.

[0072]

As described in detail above, according to the invention of this application, it is possible to efficiently remove pentavalent arsenic as well as trivalent arsenic, which has hitherto been difficult, from wastewater and the like. Technical means can be provided.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of the relationship between the mixed weight ratio of manganese carbonate and bismuth carbonate oxide and the amount of arsenic adsorption.

FIG. 2 is a diagram illustrating a relationship between a firing temperature and an arsenic adsorption amount.

FIG. 3 is a diagram exemplifying a relationship after correction in FIG.

FIG. 4 is a diagram illustrating a relationship between an initial pH and an arsenic adsorption amount.

FIG. 5 is a diagram exemplifying a relationship between a desorption rate and an adsorption time.

FIG. 6 is a diagram exemplifying a relationship between an aqueous solution arsenic concentration and an arsenic adsorption amount.

FIG. 7 is a diagram showing an example of the relationship between stirring time and arsenic concentration.

FIG. 8 is a schematic diagram illustrating wastewater treatment by an adsorption column.

FIG. 9 is a view showing an example of the result of arsenic wastewater treatment by the adsorption column method.

FIG. 10 is a schematic view illustrating a simple water purification method using an adsorption mat.

FIG. 11 is a schematic diagram illustrating a portable water purification method using an adsorption pack.

FIG. 12 is a diagram showing an example of the result of wastewater treatment by the adsorption pack method.

FIG. 13 is a diagram exemplifying a treatment result of pentavalent arsenic-containing wastewater.

FIG. 14 is a view exemplifying a time-dependent change in arsenic concentration when an adsorbent is added to 40 mg / l artificial arsenic-containing water.

FIG. 15 is a view exemplifying the result of SEM observation of the surface of the adsorbent on which arsenic is adsorbed.

16 is an EDS analysis showing (a) Mn, (b) As, (c) Bi in a portion corresponding to the SEM image of FIG.
It is the figure which illustrated the distribution state of.

FIG. 17 shows X-ray photoelectrons of (a) an adsorbent before adsorbing arsenic, (b) an adsorbent after adsorbing arsenic, and (c) an adsorbent whose surface has been scraped by several tens of nm by argon ion etching after adsorbing arsenic. It is the figure which illustrated the result of having performed a spectrum (XPS) analysis.

FIG. 18 is a diagram illustrating an arsenic adsorption isotherm of an adsorbent.

FIG. 19 is a diagram exemplifying a relationship between pH and a distribution coefficient K _d at the adsorption equilibrium of an adsorbent.

FIG. 20 is a diagram exemplifying a configuration of a column type arsenic adsorbent.

FIG. 21 is a diagram illustrating a breakthrough curve in a column water flow test.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 1/28 C02F 1/28 EF term (reference) 4D024 AA01 AA04 AB17 BA05 BA14 BB01 BB02 BB03 BB08 CA01 DA07 DB03 DB20 4G048 AA03 AB05 AC08 AD04 AE05 4G066 AA02A AA02B AA26A AA26B AA43A AA47A AA71C AC07C BA20 BA26 CA46 DA07 DA08 EA20 FA02 FA22 FA34 FA37 GA11

Claims (15)

[Claims] 1. An arsenic-adsorptive manganese compound, which is an oxygen compound of manganese containing bismuth and contains manganese as a main component. 2. The arsenic-adsorptive manganese compound according to claim 1, wherein bismuth is distributed and disposed on a part of the surface of the oxygen compound of manganese. 3. The arsenic-adsorptive manganese according to claim 1, wherein the manganese to which bismuth or a compound thereof is added or the compound thereof is baked in the air or an oxygen-containing atmosphere. Compound. 4. The arsenic-adsorptive manganese compound according to claim 3, wherein the bismuth compound is bismuth carbonate oxide and the manganese compound is manganese carbonate. 5. The arsenic-adsorptive manganese compound according to claim 1 or 2, wherein bismuth is added to a solution containing an oxygen compound of manganese and dried and dehydrated. 6. An arsenic-adsorptive manganese compound, characterized in that the manganese compound according to any one of claims 1 to 5 is pulverized. 7. An arsenic-adsorptive manganese compound, wherein the manganese compound according to claim 1 is acid-treated. 8. The arsenic adsorbent according to claim 1, wherein the mixture of the bismuth carbonate oxide powder and the manganese carbonate powder is calcined at a temperature of 100 ° C. to 450 ° C. Manganese compound. 9. The arsenic-adsorptive manganese compound according to claim 8, which has been baked at a temperature near 200 ° C. 10. The arsenic-adsorptive manganese compound according to claim 1, wherein the mixing molar ratio of bismuth and manganese is in the range of 0.001: 1 to 1: 1. 11. The arsenic-adsorptive manganese compound according to claim 10, wherein the mixing molar ratio of bismuth and manganese is in the range of 0.01: 1 to 1: 1. 12. An arsenic adsorbent comprising the manganese compound according to claim 1 or one containing the manganese compound. 13. The arsenic adsorbent according to claim 12, wherein the manganese compound is supported on the carrier material or is packed in the carrier material. 14. A method for adsorbing and removing arsenic in an aqueous solution, which comprises contacting the arsenic adsorbent according to claim 12 or 13 with an aqueous solution containing arsenic to adsorb and remove arsenic in the aqueous solution. 15. The method according to claim 14, wherein the adsorbent having adsorbed arsenic is treated with an acid to desorb the arsenic in an acid solution, and the adsorbent having desorbed arsenic can be reused. Regeneration method of arsenic adsorbent.