JPWO2019172164A1 - Arsenic-adsorbing cellulose material - Google Patents

Abstract

An object of the present invention is to provide an adsorbent for efficiently and inexpensively removing arsenic from arsenic-containing water, targeting all arsenic-containing water such as drinking groundwater, industrial wastewater, mine wastewater, and hot spring water. The present invention relates to an arsenic-adsorptive cellulose material in which a metal component having arsenic-adsorbing property is supported on cellulosic fine fibers.

Description

The present invention relates to a material for adsorbing arsenic. More specifically, the present invention relates to an adsorbent material for efficiently removing arsenic from arsenic-contaminated water such as drinking groundwater, industrial wastewater, mine wastewater, and hot spring water.

Arsenic compounds are known to be highly toxic. The tap water quality standard value and environmental standard value of arsenic are 0.01 mg / L or less, and the standard value of arsenic in business wastewater is 0.1 mg / L or less.

Arsenic is also widely distributed in soil, and elution into environmental water such as groundwater becomes a problem. It is known that groundwater such as mine wastewater, hot spring water, and geothermal hot water contains arsenic at a relatively high concentration. In particular, arsenic pollution in drinking well water in areas around China, India and Bangladesh is serious and causes health hazards. In addition, there are areas where water-soluble arsenic compounds are contained in the soil, and there are many cases where arsenic compounds flow out into the environmental water due to civil engineering work such as tunnel excavation.

A large amount of arsenic is contained in the wastewater of business establishments such as phosphorus and phosphorus compound manufacturing factories using arsenic-containing luteinizing stone and phosphate ore as raw materials, and sulfuric acid manufacturing factories. In addition, since arsenic is also used as a raw material for semiconductors, arsenic may be contained in wastewater from semiconductor manufacturing and processing factories. In recent years, wastewater treatment standards for harmful substances have become stricter due to social demands, and as mentioned above, strict regulations have been laid down that the standard value of arsenic in business wastewater is 0.1 mg / L or less. There is a need for an arsenic removal method that can comply with this regulation.

As a method for removing arsenic contained in waste water and the like, a coagulation precipitation method (see Patent Documents 1 to 3) in which arsenic is precipitated together with a hydroxide of a metal such as iron, aluminum, calcium or magnesium has been used. However, in order to reduce arsenic to below the wastewater standard value by the coagulation sedimentation method, a large amount of metal hydroxide must be added, and the post-treatment of a large amount of sludge generated becomes a problem. In addition, since the ions contained in the metal hydroxide used as the coagulation-precipitant are mixed in the water to be treated, the water treated by the coagulation-precipitation method is not suitable as drinking water.

There is also a method of removing arsenic by a membrane treatment using a semipermeable membrane. However, the treatment speed is slow and it is not suitable for treating a large amount of water. In addition, the treatment of wastewater with concentrated arsenic becomes a problem. Furthermore, since ions other than arsenic are also removed, it is difficult to say that the water obtained by the membrane treatment is suitable as drinking water.

Further, a method for removing arsenic using an adsorbent made of a hydrous oxide of a rare earth element or a hydrous oxide of a rare earth element supported on an organic polymer porous carrier (see Patent Document 4), a phenol resin and a metal hydroxide. An arsenic removing method using an adsorbent (see Patent Document 5), an arsenic removing method using a chelate adsorbent obtained by graft-polymerizing N-methyl-D-glucamine on a resin, and an arsenic removing method using an anion exchange resin are available. Are known. However, the materials used in these methods are expensive.

On the other hand, as a relatively inexpensive material, an arsenic adsorbent carrying iron ions is also known. For example, an adsorbent in which iron ions are supported on a carboxy group introduced by chemical modification of a fiber or a non-woven fabric (see Patent Documents 6 to 7), and an arsenic adsorption property of iron ions or the like on a carboxy group introduced by chemical modification of resin particles. An adsorbent carrying a metal ion having the above (see Patent Document 8) is known. However, in order to produce such an adsorbent, it is indispensable to introduce a chelating group such as a carboxy group by a radical polymerization reaction using a redox oxidation catalyst or radiation. Since these reactions need to be carried out in an atmosphere of an inert gas such as nitrogen gas, the production of the above-mentioned adsorbent is not easy. In addition, it is difficult to manufacture these adsorbents at low cost.

Further, an adsorbent in which iron ions are supported on a carboxy group derived from polyacrylic acid of a fiber kneaded with polyacrylic acid (see Patent Document 9) is also known. However, since polyacrylic acid is water-soluble, polyacrylic acid may flow out into untreated water during use, resulting in deterioration of performance.

Further, it is known that the support of a metal ion having arsenic adsorption property using the metal chelate bond by the above-mentioned carboxy group strongly depends on the pH of the aqueous metal ion solution to be reacted. For example, the pH of the equivalence point of acrylic acid (pKa = 4.35) is 4.35, and the pH of the equivalence point of the carboxy group serving as a functional group is around 4. From this, it is considered that efficient chelate formation is usually performed only in the weakly acidic range to the alkaline range of about pH 4. On the other hand, the ferric chloride aqueous solution, the diammonium cerium nitrate aqueous solution, and the zirconium chloride aqueous solution, which are used as the metal ion aqueous solution having arsenic adsorption property, all have high acidity and have a concentration of about 0.2% by mass. Sometimes it shows a pH of around 2. Therefore, it cannot be said that these metal ion aqueous solutions are suitable for metal chelate bonds. Further, the pH can be increased by lowering the concentration, but the efficiency is reduced. This is because it is necessary to contact with a large amount of aqueous solution for metal chelate formation. That is, it can be said that, despite the introduction of the carboxy group by a complicated operation, many of the above-mentioned adsorbents cannot support metal ions having sufficient arsenic adsorption property.

Thus, despite the strict regulations on arsenic in wastewater, no sufficient treatment method has yet been found to comply with these regulations.

Japanese Unexamined Patent Publication No. 7-289805 Japanese Unexamined Patent Publication No. 10-128396 Japanese Unexamined Patent Publication No. 11-333468 Japanese Unexamined Patent Publication No. 61-187931 JP-A-59-69151 Japanese Unexamined Patent Publication No. 2004-68182 Japanese Unexamined Patent Publication No. 2007-752 Japanese Unexamined Patent Publication No. 2012-16667 Japanese Unexamined Patent Publication No. 2014-171996

In view of the above circumstances, an object of the present invention is to provide an adsorbent that efficiently and inexpensively removes arsenic from arbitrary arsenic-containing water such as drinking groundwater, industrial wastewater, mine wastewater, and hot spring water.

The present inventors have diligently studied the above-mentioned problems, found a method of supporting a metal component having arsenic-binding property on the surface of a relatively inexpensive cellulose material by a simple operation, and adsorbed arsenic having excellent arsenic adsorption characteristics. We have developed a sex cellulose material. More specifically, by efficiently dispersing the cellulosic fine fibers in an aqueous solution containing metal ions having arsenic-binding properties using a homogenizer or the like, the metal components in the aqueous solution are supported on the surface of the cellulosic fine fibers. I succeeded in doing so.

That is, the present invention is an arsenic-adsorptive cellulose material in which a metal component having arsenic-adsorbing property is supported on cellulosic fine fibers. Here, the cellulosic fine fibers may be unmodified cellulose nanofibers or chemically modified cellulose nanofibers. Alternatively, the cellulosic fine fibers may be unmodified pulp, chemically modified pulp or bacterial cellulose. Chemical modification of cellulose nanofibers and pulp can be carried out by oxidation of hydroxy groups in cellulose, carboxymethylation of hydroxy groups in cellulose, or phosphoric acid esterification or phosphite esterification of hydroxy groups in cellulose. it can. In cellulose nanofibers or pulp that have undergone chemical modification by oxidation, the amount of carboxy groups may be in the range of 0.10 mmol / g to 3.00 mmol / g. In cellulose nanofibers or pulp that have undergone chemical modification by carboxymethylation, the degree of carboxymethyl substitution may be in the range of 0.02 to 0.5. Further, the metal component may be iron, cerium or zirconium. Further, the arsenic-adsorbing cellulose material of the present invention preferably supports 1.0% by mass or more of a metal component.

According to the present invention, in the treatment of arsenic-containing solutions such as drinking groundwater, industrial wastewater and environmental water, arsenic can be efficiently treated with an inexpensive material. Further, by using nanomaterials such as cellulose nanofibers and bacterial cellulose, the surface area of molecules and fibers is increased, so that a significant increase in arsenic adsorption performance can be expected. In particular, the cellulosic fine fibers preferable in the present invention include cellulose nanofibers (unmodified CNF) obtained by mechanical defibration, chemically modified cellulose nanofibers, and the like. The chemically modified cellulose nanofibers of the present invention are most preferably anion-modified cellulose nanofibers. An example of anion-modified cellulose nanofibers is an oxidized cellulose nanofiber (TEMPO-CNF) that has been defibrated by introducing a carboxy group using an oxidation reaction with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO). )including. Includes carboxymethylated cellulose nanofibers (CM-CNF), phosphate esterified cellulose nanofibers, and phosphite esterified cellulose nanofibers. Further, since the effect of the metal chelate bond can be expected when supporting the metal component having a binding property to arsenic, the anion-modified cellulose material can support the metal component more firmly. The arsenic-adsorbing cellulose material made from these cellulose nanofibers can be easily molded into a film shape. The arsenic-adsorbing cellulose material molded into a film shape can remove arsenic in untreated water simply by immersing it in arsenic-contaminated water, and can be easily separated from water. Further, by molding into a shape such as a fiber or a non-woven fabric, the arsenic-adsorbing cellulose material of the present invention can also be used for a water-permeable water treatment application such as a water treatment cartridge.

As the oxidation reaction other than 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), an oxidation reaction with an N-oxyl compound is used. The N-oxyl compound is a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it is a compound that promotes the desired oxidation reaction. For example, 2,2,6,6-tetramethylpiperidin-1-oxyrad radical (TEMPO) and its derivative (for example, 4-hydroxyTEMPO), azaadamantane type nitroxyl radical, azanoruadamantane type nitroxyl radical and the like can be mentioned. ..

Alternatively, unmodified pulp having a larger fiber diameter than various cellulose nanofibers, chemically modified pulp such as pulp having a carboxy group introduced (TEMPO-pulp) using an oxidation reaction by TEMPO, or a cellulose material such as paper is used. In some cases, a greater effect can be obtained by finely defibrating and using these cellulose materials. For the chemical modification of pulp, the same method as for cellulose nanofibers can be used. The surface treatment reaction used in the present invention is simple and inexpensive. This is because the surface treatment can be carried out only by stirring in a metal ion aqueous solution, and does not require a special environment such as a nitrogen atmosphere as proposed in Patent Documents 6 and 7 described above. Further, unlike the proposal of Patent Document 9, in the arsenic-adsorbing cellulose material of the present invention, there is no risk of outflow of components contributing to arsenic adsorption.

In the present invention, the cellulosic fine fiber is a fine fiber containing cellulose obtained by polymerizing β-glucose. Cellulose-based fine fibers are generally available in various shapes processed from natural materials such as cotton and wood. Specific examples of cellulosic fine fibers include cellulose nanofibers, pulp Japanese paper, Western paper, recycled paper and the like. In addition, cellulosic materials produced by microorganisms such as bacterial cellulose can also be used as the cellulosic fine fibers of the present invention.

The fiber diameter of the cellulosic fine fibers used in the present invention is preferably 50 μm or less, particularly preferably 30 μm or less. Representative examples of the cellulosic fine fibers of the present invention include cellulose nanofibers having a general fiber diameter of 100 nm or less, and pulp having a general fiber diameter of about 30 μm. There are no particular restrictions on other characteristics of cellol-based fine fibers such as fiber length and chemical modification of cellulose.

In particular, preferred examples of the cellulosic fine fibers of the present invention include unmodified cellulose nanofibers, bacterial cellulose, and chemically modified cellulose such as carboxymethylated cellulose. The chemical modification in the present invention may be oxidation of a hydroxy group in cellulose, carboxymethylation, phosphate esterification, or phosphite esterification. Oxidation of hydroxy groups in cellulose is preferably the formation of carboxy groups by selective oxidation of primary alcohols. On the other hand, recycled fibers such as rayon cannot be preferably used as they are. However, those in which a carboxy group is introduced into a regenerated fiber by using an oxidation reaction by TEMPO can be used in the present invention.

In the present invention, when nanofibers or pulp-shaped carboxymethylated cellulose is used as the chemically modified cellulosic fine fibers, the degree of carboxymethyl substitution per glucose unit of the carboxymethylated cellulose is not particularly limited. However, the degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose is preferably 0.02 to 0.50. By introducing a carboxymethyl substituent into cellulose, the celluloses electrically repel each other. Therefore, cellulose into which a carboxymethyl substituent has been introduced can be easily nano-defibrated. If the carboxymethyl substituent per glucose unit is less than 0.02, carboxymethylated cellulose cannot be sufficiently nano-defibrated. On the other hand, if the carboxymethyl substituent per glucose unit is larger than 0.50, the carboxymethylated cellulose swells or dissolves, so that a nanofiber-shaped carboxymethylated cellulose may not be obtained. Carboxymethylation of cellulosic fine fibers can be carried out using a compound such as sodium monochloroacetate.

In the present invention, when TEMPO-CNF or TEMPO-pulp is used as the chemically modified cellulosic fine fiber, the amount of carboxy group introduced in the cellulose obtained by TEMPO oxidation is not particularly limited. However, the amount of the carboxy group and its salt (hereinafter collectively referred to as "carboxy group or the like") is preferably 0.10 mmol / g or more, more preferably 1.20 mmol / g or more, based on the dry mass of the cellulosic fine fiber. It is preferable, and more preferably 1.40 mmol / g or more. However, the condition for obtaining a larger amount of carboxy groups or the like is uneconomical because the yield decreases due to the cleavage of cellulose, which is a side reaction during the oxidation reaction. Therefore, the upper limit of the amount of the carboxy group or the like is preferably 3.00 mmol / g or less, and more preferably 2.00 mmol / g or less.

In the present invention, iron, cerium, and zirconium are preferable as the metal that binds to arsenic supported on the cellulose material. For support on cellulose-based fine fibers, for example, an aqueous solution of ferric chloride, iron sulfate, iron nitrate, diammonium cerium nitrate, cerium sulfate, cerium nitrate, cerium chloride, zirconium chloride, zirconium sulfate, zirconyl nitrate, etc. is used. Can be used. The concentration of the aqueous solution is preferably about 0.1 to 1% by mass, but is not limited to that range. Higher concentrations are uneconomical because the amount of metal ions in the metal solution becomes excessive. At a concentration lower than that, the amount of metal ions in the metal solution decreases, and it is necessary to bring the cellulosic fine fibers into contact with a large amount of aqueous solution.

In the present invention, the support form of the metal component on the cellulosic fine fiber includes not only the physical adsorption of the metal hydroxide nanoparticles generated in the system but also the metal chelate bond by a carboxy group or the like in the case of modified cellulose. .. Further, the supported metal component preferably exists in an amount of 1% by mass or more in order to obtain a sufficient arsenic adsorption effect.

In the present invention, the method of contacting the cellulosic fine fibers with the aqueous solution containing metal ions having arsenic-binding properties is not particularly limited. However, especially when using unmodified cellulose nanofibers or chemically modified cellulose nanofibers with fine fibers, nanofibers are dispersed using an ultra-high-speed homogenizer, ultrasonic homogenizer, high-pressure homogenizer, etc., and metal ions and cellulose materials are efficiently used. It is preferable to bring them into contact with each other. This is because it is difficult to uniformly disperse the fine nanofibers by stirring with a magnetic stirrer or the like.

A film-shaped arsenic-adsorbing cellulose material can be easily molded by filtering the arsenic-adsorbing cellulose material with a membrane filter to form a thin film, and then drying the material. At this time, the transparency is increased by press-drying the film-shaped material with a heat roll or the like. The arsenic-adsorbing cellulose material molded into a film shape does not dissolve even when immersed in water again.

There is no particular limitation on the method of contacting the adsorbent with the arsenic-containing solution. Examples of batch processing include (1) a method of adding an arsenic-containing solution and the arsenic-adsorbing cellulose material of the present invention to a tank, stirring the mixture, and then filtering the mixture with a membrane filter, and (2) an arsenic-containing solution and a film in the tank. It includes a method of adding an arsenic-adsorbing cellulose material in a shape and recovering an arsenic-adsorbing cellulose material film after arsenic adsorption. An arsenic-adsorbing cellulose material can be filled in a water treatment cartridge, a water purification adsorption tower, or the like and used for continuous water treatment by a water flow method.

The arsenic removing method using the arsenic-adsorbing cellulose material of the present invention uses, for example, a coagulation precipitation method in which a metal hydroxide such as iron, aluminum, calcium, or magnesium is precipitated, or an ion exchange resin, a chelate resin, or a semipermeable membrane. It can also be used in combination with known treatment methods such as precipitated membrane treatment.

(Example 1)
By defibrating pulp oxidized with TEMPO, sodium bromide, and sodium hypochlorite with a high-pressure homogenizer, TEMPO- having an average fiber diameter of 3 nm, an aspect ratio of 250, and a carboxy group amount of 1.6 mmol / g. A 1% by mass aqueous dispersion of CNF was obtained. 10 parts by mass of 1% by mass aqueous dispersion TEMPO-CNF and 100 parts by mass (pH 2.4) of a 0.2% by mass ferric chloride aqueous solution were mixed in advance, and a homogenizer (ULTRA-TURRAX T50basic manufactured by IKA-AERKE) was used for 10 minutes. It was dispersed at 6000 rpm to uniformly disperse the cellulose nanofibers and to carry iron. At this time, the temperature of the reaction mixture was raised to about 55 ° C. by stirring the homogenizer. The film was cooled at room temperature for 1 hour, filtered through a membrane filter to form a thin film, and then dried in a dryer at 100 ° C. to obtain an iron-supported arsenic-adsorbing TEMPO-CNF film. The obtained sample was liquefied by wet decomposition using concentrated nitrate, and the iron content in the sample was measured using an inductively coupled plasma mass spectrometer (ICP-MS). The iron content of the obtained iron-supported arsenic-adsorbing TEMPO-CNF film was 14.4%.

(Example 2)
Cerium-supported arium-adsorbing TEMPO-CNF was carried out in the same manner as in Example 1 except that a 0.2 mass% diammonium cerium nitrate aqueous solution (pH 2.0) was used instead of the 0.2 mass% ferric chloride aqueous solution. The film was synthesized. The cerium content in the sample measured by ICP-MS as in Example 1 was 23.1%.

(Example 3)
Zirconium-supported arsenic adsorption by the same operation as in Example 1 except that a 0.2 mass% zirconium chloride octahydrate aqueous solution (pH 2.5) was used instead of the 0.2 mass% ferric chloride aqueous solution. A TEMPO-CNF film was synthesized. The zirconium content in the sample measured by ICP-MS as in Example 1 was 17.3%.

(Example 4)
The papermaking pulp was treated 10 times with an ultra-high pressure homogenizer having a treatment pressure of 150 MPa to obtain a 1% by mass aqueous dispersion of unmodified CNF. An iron-supported arsenic-adsorbing unmodified CNF film was synthesized by the same procedure as in Example 1 except that 1 mass% water-dispersed unmodified CNF was used instead of 1 mass% water-dispersed TEMPO-CNF. The iron content in the sample measured by ICP-MS as in Example 1 was 14.9%.

(Example 5)
A cerium-supported arsenic-adsorbing unmodified CNF film was synthesized by the same procedure as in Example 4 except that a 0.2 mass% diammonium cerium nitrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. The cerium content in the sample measured by ICP-MS as in Example 1 was 19.8%.

(Example 6)
A zirconium-supported arsenic-adsorbing unmodified CNF film was prepared by the same operation as in Example 4 except that a 0.2 mass% zirconium chloride octahydrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. Synthesized. The zirconium content in the sample measured by ICP-MS as in Example 1 was 2.16%.

(Example 7)
By defibrating pulp carboxymethylated with sodium monochloroacetate with a high-pressure homogenizer, a 1% by mass aqueous dispersion of CM-CNF having an average fiber diameter of 15 nm, an aspect ratio of 50, and a carboxymethyl substitution degree of 0.25 was obtained. Obtained. Except that 1% by mass water-dispersed CM-CNF was used instead of 1% by mass aqueous dispersion TEMPO-CNF, and 0.2% by mass diammonium cerium nitrate aqueous solution was used instead of 0.2% by mass ferric chloride aqueous solution. A cerium-supported arsenic-adsorbing CM-CNF film was synthesized by the same operation as in Example 1. The cerium content in the sample measured by ICP-MS as in Example 1 was 35.3%.

(Example 8)
A zirconium-supported arsenic-adsorbing CM-CNF film was prepared in the same manner as in Example 7 except that a 0.2 mass% zirconium chloride octahydrate aqueous solution was used instead of the 0.2 mass% diammonium cerium nitrate aqueous solution. Synthesized. The zirconium content in the sample measured by ICP-MS as in Example 1 was 11.7%.

(Example 9)
Pulp was oxidized with TEMPO, sodium bromide, and sodium hypochlorite to produce an average fiber diameter of 30 μm, a length of 1-2 mm, a carboxy group content of about 1.6 mmol / g, and a water content of 76.7%. TEMPO-pulp having the above was obtained. 0.43 parts by mass of the above-mentioned TEMPO-pulp was stirred in 1 part by mass of pure water to obtain a defibrated product. The same operation as in Example 1 was carried out using the above-mentioned defibrated product and 100 parts by mass of a 0.2 mass% ferric chloride aqueous solution to synthesize iron-supported arsenic-adsorbing TEMPO-pulp. The iron content in the sample measured by ICP-MS as in Example 1 was 13.1%.

(Example 10)
A cerium-supported arsenic-adsorbing TEMPO-pulp was synthesized by the same procedure as in Example 9 except that a 0.2 mass% diammonium cerium nitrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. The cerium content in the sample measured by ICP-MS as in Example 1 was 12.5%.

(Example 11)
Zirconium-supported arsenic-adsorbing TEMPO-pulp was synthesized by the same operation as in Example 9 except that a 0.2 mass% zirconium chloride octahydrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. did. The zirconium content in the sample measured by ICP-MS as in Example 1 was 12.5%.

(Example 12)
0.22 parts by mass of unmodified pulp having an average fiber diameter of 30 μm, a length of about 1 to 2 mm, and a water content of 54.3% was stirred in 1 part by mass of pure water to obtain a defibrated product. The defibrated product was immersed in 100 parts by mass of a 0.2 mass% ferric chloride aqueous solution and heated at 55 ° C. for 1 hour using an oil bath while stirring with a magnetic stirrer. After heating, the naturally cooled sample was filtered and washed. The washed sample was dried in a dryer at 100 ° C. to obtain iron-supported arsenic-adsorbing unmodified pulp. The iron content in the sample measured by ICP-MS as in Example 1 was 11.8%.

(Example 13)
A cerium-supported arsenic-adsorbing unmodified pulp was synthesized by the same operation as in Example 12 except that a 0.2 mass% diammonium cerium nitrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. The cerium content in the sample measured by ICP-MS as in Example 1 was 3.5%.

(Example 14)
Iron-supported arsenic-adsorbing TEMPO-CNF was carried out in the same manner as in Example 1 except that a 0.1 mass% ferric chloride aqueous solution (pH 2.6) was used instead of the 0.2 mass% ferric chloride aqueous solution. The film was synthesized. The iron content in the sample measured by ICP-MS as in Example 1 was 8.3%.

(Example 15)
An iron-supported TEMPO-CNF film was obtained by the same operation as in Example 1 except that a 0.4 mass% ferric chloride aqueous solution (pH 2.2) was used instead of the 0.2 mass% ferric chloride aqueous solution. It was. The iron content in the sample measured by ICP-MS as in Example 1 was 14.1%.

(Example 16)
An iron-supported TEMPO-CNF film was synthesized by the same operation as in Example 1 except that a 0.6 mass% ferric chloride aqueous solution (pH 2.1) was used instead of the 0.2 mass% ferric chloride aqueous solution. did. The iron content in the sample measured by ICP-MS as in Example 1 was 11.2%.

(Example 17)
An iron-supported TEMPO-CNF film was synthesized by the same operation as in Example 1 except that a 0.8 mass% ferric chloride aqueous solution (pH 2.0) was used instead of the 0.2 mass% ferric chloride aqueous solution. did. The iron content in the sample measured by ICP-MS as in Example 1 was 4.8%.

(Comparative Example 1)
0.1 part by mass of rayon fiber having a fineness of 3.3 dtex and a length of 76 mm was immersed in 100 parts by mass of a 0.2 mass% ferric chloride aqueous solution, and heated at 55 ° C. for 1 hour using an oil bath. After heating, the naturally cooled sample was filtered and washed. The washed sample was dried in a dryer at 100 ° C. to obtain iron-supported rayon fibers. The iron content in the sample measured by ICP-MS as in Example 1 was 0.6%.

(Comparative Example 2)
A cerium-supported rayon fiber was synthesized by the same operation as in Comparative Example 1 except that a 0.2 mass% diammonium cerium nitrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. The cerium content in the sample measured by ICP-MS as in Example 1 was 0.9%.

(Comparative Example 3)
Zirconium-supported rayon fibers were synthesized by the same procedure as in Comparative Example 1 except that a 0.2 mass% zirconium chloride octahydrate aqueous solution was used instead of the 0.2 mass% ferric chloride aqueous solution. The zirconium content in the sample measured by ICP-MS as in Example 1 was 0.8%.

(Comparative Example 4)
10 parts by mass of 1% by mass aqueous dispersion TEMPO-CNF obtained in Example 1 and 100 parts by mass of pure water were dispersed with a homogenizer at 6000 rpm for 10 minutes to obtain a uniform dispersion solution. The obtained dispersion solution was cooled at room temperature for 1 hour and filtered through a membrane filter to obtain a thin film. The obtained thin film was dried in a dryer at 100 ° C. to obtain a TEMPO-CNF film.

(Comparative Example 5)
An unmodified CNF film was obtained by the same operation as in Comparative Example 4 except that the 1% by mass water-dispersed unmodified CNF obtained in Example 4 was used instead of the 1% by mass water-dispersed TEMPO-CNF.

(Comparative Example 6)
A CM-CNF film was obtained by the same operation as in Comparative Example 4 except that the 1 mass% aqueous dispersion CM-CNF obtained in Example 7 was used instead of the 1 mass% aqueous dispersion TEMPO-CNF.

(Comparative Example 7)
A TEMPO-pulp defibrated product was obtained by the same procedure as in Example 9. The TEMPO-pulp defibrated product and 100 parts by mass of pure water were dispersed with a homogenizer at 6000 rpm for 10 minutes to obtain a uniform dispersion solution. The obtained dispersion solution was cooled at room temperature for 1 hour and filtered through a membrane filter to obtain a thin film. The obtained thin film was dried in a dryer at 100 ° C. to obtain a paper made of TEMPO-pulp.

(Comparative Example 8)
The unmodified pulp defibrated product obtained in Example 12 was heated at 55 ° C. for 1 hour using an oil bath while stirring with a magnetic stirrer. After heating, the naturally cooled sample was filtered, washed, and then dried in a dryer at 100 ° C. to obtain a paper made of unmodified pulp.

(Comparative Example 9)
0.1 part by mass of rayon fiber having a fineness of 3.3 dtex and a length of 76 mm was immersed in 100 parts by mass of pure water and heated at 55 ° C. for 1 hour using an oil bath. After heating, the naturally cooled sample was filtered and washed. The washed sample was dried in a dryer at 100 ° C. to obtain rayon fibers for comparison.

(Arsenic adsorption test 1)
The arsenic adsorption performance of the materials synthesized in Examples 1 to 13 and Comparative Examples 1 to 9 was evaluated using an arsenic standard solution (1,000 mg / L) manufactured by Wako Pure Chemical Industries. Arsenic concentration was measured using ICP-MS. The arsenic concentration of the arsenic solution diluted to 3 mg / L in advance and adjusted to neutral was measured and used as the initial arsenic concentration. A 10 mg sample was added to 10 ml of this arsenic solution, shaken at room temperature for 15 hours, and then the sample was removed. Next, the arsenic concentration in the solution was measured and used as the final arsenic concentration. The arsenic removal rate was calculated by the following formula.
Arsenic removal rate (%) = {(initial arsenic concentration-final arsenic concentration) / initial arsenic concentration x 100}
The test results are summarized in Table 1.

(Arsenic adsorption test 2)
The arsenic adsorption performance of the materials synthesized in Examples 1 and 14 to 17 was evaluated using an arsenic solution having an initial arsenic concentration of 2 mg / L in the same manner as in the arsenic adsorption test 1.
The test results are summarized in Table 2.

Claims (7)

An arsenic-adsorbing cellulose material in which a metal component having arsenic-adsorbing property is supported on cellulosic fine fibers. The arsenic-adsorbing cellulose material according to claim 1, wherein the cellulosic fine fibers are at least one selected from the group consisting of unmodified cellulose nanofibers and chemically modified cellulose nanofibers. The arsenic-adsorbing cellulose material according to claim 1, wherein the cellulosic fine fibers are at least one selected from the group consisting of unmodified pulp, chemically modified pulp, and bacterial cellulose. The second or third claim, wherein the chemical modification is at least one selected from the group consisting of oxidation, carboxymethylation, phosphate esterification, and phosphite esterification of hydroxy groups in cellulose. Phosphite adsorptive cellulose material. The cellulosic fine fibers are oxidized cellulose nanofibers or oxidized pulp obtained by oxidizing hydroxy groups in cellulose, and the amount of carboxy groups is 0.10 mmol / g to the dry mass of the cellulosic fine fibers. The arsenic-adsorbing cellulose material according to claim 1, which is 3.00 mmol / g. The cellulosic fine fibers are carboxymethylated cellulose nanofibers or carboxymethylated pulp obtained by carboxymethylation of hydroxy groups in cellulose, and the degree of carboxymethyl substitution per glucose unit is 0.02 to 0.5. The arsenic-adsorbing cellulose material according to claim 1. Claims 1 to 6 wherein the metal component is at least one selected from the group consisting of iron, cerium, and zirconium, and the metal component is further supported in an amount of 1.0% by mass or more. The arsenic-adsorbing cellulose material according to any one item.