WO2023210025A1

WO2023210025A1 - Complex and manufacturing method therefor

Info

Publication number: WO2023210025A1
Application number: PCT/JP2022/019877
Authority: WO
Inventors: 浩長谷川; 優斗阪井; 航季湯之下; 圭佑中窪; 麻彩実眞塩; クオホンウォン; 克遠藤; 隆新井; 陽子三橋
Original assignee: 国立大学法人金沢大学; 株式会社ダイセル
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2023-11-02
Also published as: WO2023210831A1

Abstract

Provided are a novel complex having the effect of efficiently adsorbing and collecting arsenic(V) dissolved in water, and a novel arsenic adsorbent. The complex has a structure in which metal particles including zero-valent and/or trivalent iron are supported on a microfibrous cellulose surface. The metal particles of the complex contain at least one type of metal oxide, hydroxide or oxyhydroxide selected from zirconium and titanium, together with zero-valent and/or trivalent iron. The molar ratio [iron/(zirconium + titanium)] of iron (elementary iron equivalent) and the metal oxide, hydroxide and oxyhydroxide (elementary metal equivalent; total amount when containing two or more compounds) is preferably 1 to 100. The arsenic adsorbent contains the complex.

Description

Composite and its manufacturing method

The present disclosure relates to a novel composite, a method for producing the composite, an arsenic adsorbent containing the composite, a method for producing water using the arsenic adsorbent, and a water purification device equipped with the arsenic adsorbent.

Although arsenic is widely distributed in the environment, it is highly toxic and is known to cause various diseases and harm health when ingested even in minute amounts over a long period of time.

Inorganic arsenic contamination of well water, which is occurring in Southeast Asia and other parts of the world, has become a major environmental problem. Therefore, there is a need for a method to remove arsenic contained in water.

For example, Patent Document 1 describes that an adsorbent obtained by mixing ferric hydroxide with a styrene-acrylic copolymer binder and pelletizing the mixture is capable of adsorbing and removing arsenic (III) from strongly acidic water. It is stated that it is useful.

JP2008-207110A

Arsenic (V) is adsorbed on the surface of iron, but because the ferric hydroxide supported on the binder dissolves in water, it is difficult to secure a wide adsorption surface for arsenic (V). there were. In addition, since ferric hydroxide is supported by bonding to the carboxyl group of the styrene-acrylic acid copolymer binder, it is difficult to increase the amount of iron supported per unit weight, and arsenic (V) is efficiently It was not possible to adsorb it well.

Therefore, an object of the present disclosure is to provide a novel composite that has the effect of efficiently adsorbing and recovering arsenic (V) dissolved in water.
Another object of the present disclosure is to provide a method for producing the composite.
Another object of the present disclosure is to provide a novel arsenic adsorbent that can efficiently adsorb and recover arsenic (V) dissolved in water.
Another object of the present disclosure is to provide a method for producing purified water using the arsenic adsorbent.
Another object of the present disclosure is to provide a water purification device equipped with the arsenic adsorbent.

The present inventors have made extensive studies to solve the above problems, and as a result, have discovered the following matters.
1. 2. Microfibrous cellulose has an extremely large surface area and also has three hydroxyl groups per constituent unit to which iron can be bonded, so it is possible to increase the amount of iron supported per unit weight. 3. When metal particles are supported on the surface of microfibrous cellulose, agglomeration of metal particles can be suppressed, and a wide surface area of metal particles, which is effective in adsorbing arsenic, can be secured.3. Microfibrous cellulose has excellent hydrophilicity, and when immersed in water, water easily penetrates into the microfibrous cellulose. Therefore, arsenic dissolved in water is efficiently transferred to the metal particles supported on the microfibrous cellulose. Being Adsorbed The present disclosure has been completed based on these findings.

That is, the present disclosure provides a composite having a structure in which metal particles containing zero-valent and/or trivalent iron are supported on the surface of microfibrous cellulose.

The present disclosure also provides the composite, in which the total supported amount of zero-valent and trivalent iron (in terms of iron element) is 1 to 100 mmol per gram of microfibrous cellulose.

The present disclosure also provides the composite, wherein the microfibrous cellulose is microfibrillated cellulose.

The present disclosure also provides that the metal particles contain an oxide, hydroxide, or oxyhydroxide of at least one metal selected from zirconium and titanium, as well as zero-valent and/or trivalent iron. ,
The molar ratio of the iron (in terms of iron element) and the oxide, hydroxide, or oxyhydroxide of the metal (in terms of metal element; if two or more are contained, the total amount) [iron/(zirconium + titanium)] )] is 1 to 100.

The present disclosure also provides the composite, wherein the trivalent iron is at least one iron compound selected from iron oxide, iron hydroxide, and iron oxyhydroxide.

The present disclosure also provides the composite, wherein the metal particles have a volume-equivalent spherical particle diameter of 1 μm or more.

The present disclosure also provides a method for producing a composite, which comprises producing the composite through Reaction 1 or Reaction 2 below.
[Reaction 1] Mixing microfibrous cellulose and an iron compound in water, allowing the iron compound to be adsorbed onto the microfibrous cellulose, and reducing the adsorbed iron compound [Reaction 2] Mixing microfibrous cellulose and an iron compound in water and a basic compound to adsorb trivalent iron colloid to microfibrous cellulose and grow it into particles.

The present disclosure also provides an arsenic adsorbent comprising the composite.

The present disclosure also provides a method for producing purified water, in which purified water is obtained by treating arsenic-contaminated water with the arsenic adsorbent.

The present disclosure also provides a water purification device including the arsenic adsorbent.

The composite of the present disclosure has a structure in which metal particles having an arsenic-adsorbing surface are dispersed and supported on microfibrous cellulose having excellent hydrophilicity and an extremely large surface area. Therefore, when the composite is immersed in water, arsenic dissolved in water can be efficiently adsorbed and recovered.
Furthermore, the complex can selectively adsorb and recover arsenic even if phosphorus (P), which has chemical properties similar to arsenic, coexists.
Furthermore, the above-mentioned composite does not cause any emission problems even when burned, and by burning it to reduce its volume after adsorbing arsenic, it is possible to significantly reduce the cost of disposal such as landfilling. .
Therefore, the composite is extremely useful as an arsenic adsorbent.

FIG. 3 is a diagram showing the relationship between the As(V) adsorption rate and pH of the composite (1) obtained in the example. FIG. 2 is a diagram showing the As(V) adsorption rate of the complex (1) obtained in Examples in the presence of anions. FIG. 3 is a diagram showing a SEM image of composite (2) obtained in Example.

[Complex]
The composite of the present disclosure has a structure in which metal particles containing zero-valent iron or trivalent iron are supported on the surface of microfibrous cellulose. The composite includes at least one metal particle selected from metal particles containing zero-valent iron, metal particles containing trivalent iron, and metal particles containing zero-valent iron and trivalent iron. .

The trivalent iron compounds include, for example, water-insoluble compounds such as iron oxide (Fe ₂ O ₃ ), iron hydroxide (Fe(OH) ₃ ), and iron oxyhydroxide (FeOOH).

Furthermore, the metal particles contain at least zero-valent iron (i.e., metallic iron) or trivalent iron as an iron component, and may contain other iron components, but the iron component contained in the metal particles (In other words, the total amount of iron-containing compounds), the total content of zero-valent iron and trivalent iron is, for example, 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more. , particularly preferably 80% by weight or more, most preferably 90% by weight or more, particularly preferably 95% by weight or more. Note that the upper limit is 100% by weight.

The metal particles may contain other metal components in addition to the iron component, such as zirconium oxide, zirconium hydroxide, zirconium oxyhydroxide, titanium oxide, titanium hydroxide, titanium oxyhydroxide, etc. It may contain an oxide, hydroxide, or oxyhydroxide of at least one metal selected from zirconium and titanium. Further, it may contain a combination of two or more selected from oxides, hydroxides, and oxyhydroxides of the metals. The metal oxide, hydroxide, or oxyhydroxide has excellent affinity for arsenic (eg, pentavalent arsenic). Therefore, if the oxide, hydroxide, or oxyhydroxide of the metal is supported on the surface of the microfibrous cellulose together with the iron component, the arsenic adsorption power can be further improved.

When the metal particles contain zero-valent and/or trivalent iron and an oxide, hydroxide, or oxyhydroxide of the metal, the iron (iron element equivalent value), the oxide of the metal, and water The molar ratio [iron/(zirconium+titanium)] of the oxide or oxyhydroxide (metal element equivalent value; if two or more types are contained, the total amount thereof) is, for example, 1 to 100. The upper limit of the molar ratio is preferably 50, more preferably 30, even more preferably 20, particularly preferably 15. The lower limit of the molar ratio is preferably 2, particularly preferably 3, and most preferably 5.

The shape of the metal particles is not particularly limited, and examples thereof include spherical shapes (true spheres, substantially true spheres, elliptical spheres, etc.), polyhedral shapes, needle shapes, plate shapes, scale shapes, irregular shapes, and the like.

The particle diameter of the volume equivalent sphere of the metal particles (hereinafter sometimes referred to as "volume equivalent diameter") is, for example, 100 μm or less, preferably 50 μm or less, particularly preferably 20 μm or less, and most preferably 10 μm or less. . The lower limit of the particle diameter is, for example, 1 μm. The particle diameter can be determined by SEM observation or image analysis.

The total supported amount of zero-valent and trivalent iron (in terms of iron element) in 1 g of the composite (or the total of the microfibrous cellulose and the metal particles contained in the composite) is, for example, 1 to 100 mmol. It is. The upper limit of the supported amount is preferably 80 mmol, more preferably 70 mmol, still more preferably 60 mmol, even more preferably 40 mmol, particularly preferably 30 mmol, most preferably 10 mmol, particularly preferably 5 mmol. The lower limit of the supported amount is preferably 1.5 mmol, particularly preferably 2 mmol, and most preferably 3 mmol.

The total amount of zero-valent and trivalent iron supported per gram of microfibrous cellulose (in terms of iron element) is, for example, 1 to 10 mmol, preferably 1 to 5 mmol, particularly preferably 1.5 to 4 mmol.

Microfibrous cellulose is, for example, cellulose fibers torn longitudinally and made into fine particles, and is preferably microfibrillated cellulose.

The average fiber length of the microfibrous cellulose is, for example, 0.5 to 1.5 mm, preferably 0.5 to 1.2 mm, particularly preferably 0.6 to 0.8 mm. The average fiber diameter of the microfibrous cellulose is, for example, 0.5 to 50 μm.

The composite may further contain other components, but the proportion of the microfibrous cellulose and metal particles is, for example, 50% by weight or more, preferably 60% by weight or more, particularly preferably 60% by weight or more of the total amount of the composite. is 70% by weight or more, most preferably 80% by weight or more, particularly preferably 90% by weight or more. If the proportion of microfibrous cellulose and metal particles is below the above range, it tends to be difficult to efficiently and selectively adsorb arsenic.

Arsenic (V) exists as arsenate ions in an aqueous solution. The above-mentioned complex is produced by complexing the zero-valent and/or trivalent iron contained in the metal particles through the hydroxyl group of arsenic (especially arsenate ion) in water. Adsorb and fix (see below).

The arsenic adsorption capacity of the complex is, for example, 300 μmol/g or more, preferably 350 μmol/g or more, more preferably 400 μmol/g or more, still more preferably 450 μmol/g or more, particularly preferably 500 μmol/g or more, and most preferably It is 520 μmol/g or more. The upper limit of the arsenic adsorption capacity is, for example, 5000 μmol/g, particularly 1000 μmol/g.

The adsorption capacity of arsenic per 1 mol of the total amount of zero-valent and trivalent iron (converted value as iron element) contained in the composite is, for example, 0.05 mol or more, preferably 0.08 mol or more, particularly preferably 0.1 mol. The above amount is particularly preferably 0.15 mol or more. The upper limit of the arsenic adsorption capacity is, for example, 10 mol, further 5 mol, particularly 3 mol.

Zero-valent and/or trivalent iron has a high affinity for arsenic ions, but other ions such as dihydrogen phosphate ions containing phosphorus, which have chemical properties similar to arsenic, halide ions, and sulfate ions, have a high affinity for arsenic ions. It has low affinity with anions. Since the above-mentioned complex contains zero- and/or trivalent iron having the above-mentioned characteristics, it can adsorb arsenic even in the coexistence of other anions (e.g., halide ions, sulfate ions, dihydrogen phosphate ions, etc.). Power is maintained without decreasing.

The adsorption capacity of arsenic by the above composite is determined by immersing 0.01 g of the above complex in 10 mL of a 1000 mg/L arsenic (V) aqueous solution at 25°C and shaking it for 30 minutes with a shaker. It is the capacity and is calculated from the formula described in the examples.

Since the above-mentioned composite has the above characteristics, it is suitable as an arsenic adsorbent (especially an arsenic (V) adsorbent) for efficiently adsorbing and recovering arsenic (in particular, arsenic (V)) dissolved in water. can be used.

[Method for manufacturing composite]
The complex can be produced, for example, through the following reaction [1] or [2].
[Reaction 1] Mixing microfibrous cellulose and an iron compound in water, allowing the iron compound to be adsorbed onto the microfibrous cellulose, and reducing the adsorbed iron compound [Reaction 2] Mixing microfibrous cellulose and an iron compound in water and a basic compound to adsorb trivalent iron colloid to microfibrous cellulose and grow it into particles.

(Reaction 1)
Reaction 1 includes an adsorption step in which microfibrous cellulose and an iron compound are mixed in water and the iron compound is adsorbed onto the microfibrous cellulose, and a reduction step in which the adsorbed iron compound is reduced.

Reaction 1 may include a drying step after the reduction step.

The adsorption step is a step in which microfibrous cellulose and an iron compound are mixed in water and the iron compound is adsorbed onto the microfibrous cellulose.

Microfibrous cellulose is, for example, cellulose fibers that are longitudinally torn and made into fine particles, that is, microfibrillated cellulose. Microfibrous cellulose can be produced, for example, by subjecting cellulose fibers having a specific fiber length to, for example, beating treatment and/or mechanical shearing treatment (for example, homogenization treatment).

As the cellulose fibers, for example, cellulose fibers derived from wood pulp (softwood pulp, hardwood pulp) or cotton linter pulp can be suitably used. These can be used alone or in combination of two or more. Note that the pulp may contain different components such as hemicellulose.

Furthermore, the cellulose fiber may have a hydrophilic group added to its surface.

As the microfibrous cellulose, for example, commercially available products such as the product names "Selish", "Filtration Meijin", "PC110S", and "PC110T" (manufactured by Daicel Millize Co., Ltd.) can be used.

As the iron compound, it is preferable to use, for example, a trivalent iron compound such as FeCl ₃ . When a trivalent iron compound is used, the iron compound adsorbed on the microfibrous cellulose is, for example, a trivalent iron ion.

The amount of iron compound used is, for example, 1 to 100 mmol, preferably 1 to 50 mmol, per 1 g of microfibrous cellulose.

Additionally, at least one metal compound selected from zirconium compounds, titanium compounds, etc. may be added to the adsorption reaction system (or in water) together with the iron compound. By adding the metal compound together with the iron compound, the iron compound and the metal compound can be adsorbed onto the microfibrous cellulose.

When using an iron compound and the metal compound, the molar ratio of the iron compound (in terms of iron element) and the metal compound (in terms of metal element; if two or more are contained, the total amount) [iron/(zirconium + titanium)] )] is, for example, 1 to 100 (preferably 1 to 50, particularly preferably 1 to 10, most preferably 2 to 10, particularly preferably 3 to 10) to improve the arsenic adsorption power. It is preferable because it has a particularly excellent effect.

Examples of the zirconium compound include zirconium oxide (ZrO ₄ ), zirconium hydroxide, zirconium oxyhydroxide, and zirconium chloride oxide (ZrCl ₂ O). These can be used alone or in combination of two or more.

Examples of the titanium compound include titanium chloride, titanium oxide, titanium hydroxide, titanium oxyhydroxide, and the like. These can be used alone or in combination of two or more.

As the metal compound, a zirconium compound such as zirconium chloride oxide (ZrCl ₂ O) is preferable because it has excellent affinity with arsenic and is particularly effective in improving the amount of arsenic adsorbed.

In the adsorption step, it is preferable to mix the microfibrous cellulose and the iron compound in water and stir them. The stirring conditions are not particularly limited, but are, for example, 100 rpm for about 30 to 120 minutes. Further, the temperature of the mixed liquid during the stirring is, for example, 25 to 60°C.

The reaction atmosphere during the stirring is not particularly limited as long as it does not inhibit the reaction, and may be, for example, any of air atmosphere, nitrogen atmosphere, argon atmosphere, etc.

The reduction step is a step in which microfibrous cellulose adsorbed with iron compounds is subjected to a reduction reaction to obtain microfibrous cellulose supporting metal particles containing zero-valent iron.

The reduction reaction can be performed using a reducing agent. Examples of the reducing agent include C _1-5 alkyllithium such as methyllithium, ethyllithium, and t-butyllithium; lithium borohydride, sodium borohydride, sodium cyanoborohydride, lithium triethylborohydride, and hydrogen. Borate salts such as sodium triethylborohydride, lithium tri(sec-butyl)borohydride, potassium tri(sec-butyl)borohydride; lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride Examples include aluminum hydride compounds such as. These can be used alone or in combination of two or more.

The amount of the reducing agent used is, for example, 0.1 to 10 mol, preferably 0.1 to 5 mol, particularly preferably 0.3 to 2 mol, per 1 mol of the iron compound.

The reduction reaction can be carried out, for example, by adding a reducing agent to a mixture of microfibrous cellulose and an iron compound, and stirring the mixture. There are no particular restrictions on stirring conditions, but for example, stirring is performed using a stirrer for about 1 hour. The temperature of the mixed liquid during stirring is, for example, 25 to 60°C.

The atmosphere for the reaction is not particularly limited as long as it does not inhibit the reaction, and may be, for example, an air atmosphere, a nitrogen atmosphere, an argon atmosphere, or the like.

Through the reduction reaction, the iron compound adsorbed on the microfibrous cellulose is reduced, and zero-valent iron can be precipitated on the surface of the microfibrous cellulose.

After the reduction reaction is completed, the obtained reaction product can be separated and purified by conventional precipitation, washing, and filtration.

Drying process This is a process of drying the microfibrous cellulose supporting metal particles containing zero-valent iron obtained through the reduction process. As a drying method, a well-known and commonly used method can be adopted. The drying temperature is, for example, about room temperature to 50°C. Through the drying process, a powdered composite is obtained, which has metal particles containing zero-valent iron supported on the surface of microfibrous cellulose.

(Reaction 2)
Reaction 2 includes at least an adsorption step in which microfibrous cellulose, an iron compound, and a basic compound are mixed in water, and a trivalent iron colloid is adsorbed onto the microfibrous cellulose, and a growth step in which the trivalent iron colloid is grown into particles.

Reaction 2 may include a drying step after the adsorption/growth step.

As the iron compound and the microfibrous cellulose, the same ones as the iron compound and the microfibrous cellulose in Reaction 1 can be used.

The amount of microfibrous cellulose used is, for example, 10 to 1000 mg per 1 mmol of the iron compound.

In the adsorption/growth process, for example, microfibrous cellulose, an iron compound, and a basic compound are mixed in water and stirred to adsorb the trivalent iron colloid onto the microfibrous cellulose. Trivalent iron colloid can be grown to precipitate metal particles containing trivalent iron (iron hydroxide and/or iron oxyhydroxide).

The stirring conditions are not particularly limited, but are, for example, 100 rpm for about 30 to 120 minutes. Further, the temperature of the mixed liquid during the stirring is, for example, 25 to 60°C.

The concentration of iron compounds (in terms of iron element) in the adsorption/growth reaction system (or in water) is, for example, 10 to 0.1% by weight.

Examples of the basic compound include organic bases such as ammonia and inorganic bases such as hydroxides of alkali metals (eg, sodium, potassium, etc.). These can be used alone or in combination of two or more.

In the adsorption/growth reaction, the pH is set to, for example, 4 to 13 (the lower limit of pH is preferably 5, particularly preferably 6; the upper limit of pH is preferably 12, particularly preferably 10, and most preferably 9). It is preferable to adjust the temperature to 100% because the effect of promoting the precipitation of metal particles containing trivalent iron can be obtained. To adjust the pH, a well-known and commonly used pH adjuster or a buffer solution can be used.

The adsorption/growth reaction temperature is, for example, room temperature to 100°C. The adsorption/growth reaction time is, for example, 0.5 to 10 hours.

The adsorption/growth reaction produces metal particles containing trivalent iron (for example, iron hydroxide and/or iron oxyhydroxide).

Furthermore, by adding at least one metal compound selected from zirconium compounds, titanium compounds, etc. together with the iron compound into the adsorption/growth reaction system, metal particles containing trivalent iron and the metal compound can be formed. can get.

Examples of the zirconium compound include ZrCl ₂ O, ZrO ₄ and the like. These can be used alone or in combination of two or more.

Examples of the titanium compound include titanium chloride, titanium oxide, and the like. These can be used alone or in combination of two or more.

Among the zirconium compounds and titanium compounds, zirconium compounds are preferred because they have excellent affinity with arsenic and are particularly effective in improving the amount of arsenic adsorbed.

Drying process The microfibrous cellulose carrying trivalent iron-containing metal particles (for example, iron hydroxide and/or iron oxyhydroxide-containing metal particles) obtained through the adsorption/growth process is dried in the drying process. be. The drying temperature is, for example, from room temperature to about 50°C. A structure in which metal particles containing trivalent iron (for example, metal particles containing at least one selected from iron hydroxide, iron oxyhydroxide, and iron oxide) are supported on the surface of microfibrous cellulose through a drying process. A powdered composite is obtained.

[Arsenic adsorbent]
The arsenic adsorbent of the present disclosure includes the composite. The arsenic adsorbent may contain other components in addition to the complex, but the proportion of the complex in the total amount of the arsenic adsorbent (or the total amount of nonvolatile content contained in the arsenic adsorbent) is For example, it is 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, particularly preferably 80% by weight or more, most preferably 90% by weight or more, particularly preferably 95% by weight or more. Note that the arsenic adsorbent may be composed only of the composite.

In the present disclosure, "nonvolatile content" refers to the total weight of components other than the solvent (including water and organic solvents), and for example, the amount remaining after heating 1 g of arsenic adsorbent at 100 ° C. for 1 hour under normal pressure. It is an ingredient.

The shape of the arsenic adsorbent is not particularly limited as long as it does not impair the effects of the present disclosure, but it may be gel-like or powdery in that it can be easily recovered from the aqueous solution after adsorbing arsenic therein. or pellet form is preferable.

Since the arsenic adsorbent of the present disclosure contains the above-mentioned complex, it can be suitably used for adsorbing and removing arsenic (V) dissolved in water.

The arsenic adsorbent can be prepared by manufacturing a composite by the method for manufacturing the composite, adding other components as necessary, and molding as necessary.

[Production method of purified water]
The method for producing purified water of the present disclosure includes treating arsenic-contaminated water (water contaminated with arsenic, where the arsenic concentration is, for example, 5 mM or more) with the arsenic adsorbent (or the complex), This is a method for obtaining purified water (for example, purified water in which 99% by weight or more (more preferably 99.9% by weight or more) of arsenic contained in the contaminated water has been removed).

Arsenic (V) exists as arsenate ions in an aqueous solution. The arsenic adsorbent (or the composite) adsorbs arsenic ions by complexing the zero-valent and/or trivalent iron contained in the metal particles with the hydroxyl groups of arsenate ions. ,to recover.

The method of treating contaminated water with the arsenic adsorbent is a method in which arsenic contained in contaminated water is adsorbed onto the arsenic adsorbent. The method is not particularly limited, and examples include a method in which the arsenic adsorbent is packed in a column or the like and contaminated water is poured therein, a method in which the arsenic adsorbent is added to contaminated water, and the mixture is stirred. Can be mentioned.

When treating with the arsenic adsorbent, adjusting the pH of contaminated water to, for example, 10 or less (for example, 1 to 10, preferably 2 to 10), preferably 8 or less, recovers arsenic more efficiently. This is preferable because it can be done. In addition, the said pH adjustment can be performed using a well-known and commonly used pH adjuster.

Furthermore, after arsenic is adsorbed onto the arsenic adsorbent, by burning the arsenic adsorbent that has adsorbed arsenic, the volume can be significantly reduced and the cost of disposal can be reduced.

According to the method for producing purified water of the present disclosure, arsenic can be efficiently removed from water contaminated with arsenic, and purified water without arsenic contamination can be efficiently produced.

[Water purification device]
The water purification device of the present disclosure includes the arsenic adsorbent (or the composite).

There are no particular restrictions on the method of installing the arsenic adsorbent. For example, there is a method in which a column or the like is filled with an arsenic adsorbent.

Therefore, the water purification device may include a column filled with the arsenic adsorbent.

In addition to the arsenic adsorbent, the water purification device may include necessary configurations such as a device for supplying unpurified water to the arsenic adsorbent and a device for discharging water after being purified by the arsenic adsorbent. I can do it.

Since the water purification device includes the arsenic adsorbent, it can efficiently remove arsenic from arsenic-contaminated water, and can efficiently produce purified water free of arsenic contamination.

The above configurations and combinations thereof of the present disclosure are merely examples, and additions, omissions, substitutions, and changes to the configurations can be made as appropriate without departing from the gist of the present disclosure. Furthermore, the present disclosure is not limited by the embodiments, but only by the claims.

Hereinafter, the present disclosure will be explained more specifically using Examples, but the present disclosure is not limited to these Examples.

Example 1
In a 100 mL flask, add cellulose nanofiber (hereinafter sometimes referred to as "CNF") (average fiber length: 0.6 to 0.8 mm, reference fiber diameter: 0.5 to 50 μm, product name "Filtration Meijin", Daicel 0.10 g (manufactured by Millize Co., Ltd.) and 10 mL of 10% FeCl ₃ .6H ₂ O were added thereto, and the mixture was stirred with a stirrer at room temperature for 1 hour.
Thereafter, 7.0 mL of 1 mM NaBH ₄ was added into the flask while stirring the solution, and the mixture was stirred with a stirrer at room temperature for 1 hour.
Thereafter, a solid content was obtained by suction filtration using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the obtained solid content was dried at 40°C. As a result, a composite (1) (Fe ⁰ -CNF) in which zero-valent iron particles were supported on cellulose nanofibers (volume equivalent diameter: 1 μm or more) was obtained.

(Rating 1)
0.010 g of composite (1) or zero-valent iron powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as Comparative Example 1 was dispersed in 10 mL of water, stirred with a stirrer for 10 minutes, and visually checked for dispersibility. confirmed.
As a result, aggregation of the complex (1) was suppressed and the dispersion was maintained. This shows that the composite (1) can maintain a wide surface area of zero-valent iron particles that contribute to arsenic adsorption in water.
On the other hand, zero-valent iron powder coagulated and precipitated in water.

(Evaluation 2)
Regarding the complex (1), the pH dependence of the As(V) aqueous solution was determined by changing the pH of the As(V) aqueous solution from 2 to 12 to determine the arsenic adsorption rate. The results are shown in Figure 1.

From FIG. 1, it can be seen that the composite (1) exhibits an arsenic adsorption rate of over 90% at pH 10 or lower. It can be seen that at pH 8 or lower, the arsenic adsorption rate is close to 100%.

(Rating 3)
0.02 g of complex (1) was added to a 10 μM As(V) aqueous solution (pH 3) and stirred.
In addition, 0.1 mM, 1 mM, or 100 mM of an anion solution (Cl ⁻ , SO ₄ ²⁻ , or H ₂ PO ₄ ⁻ ) was added to a 10 μM As(V) aqueous solution (pH 3), and the complex ( 1) 0.02g was added and stirred.
The arsenic ion concentration in the solution after stirring was measured, the adsorption rate of arsenic (V) was calculated, and the change in the arsenic adsorption rate of the complex (1) obtained in the example in the presence of anions was calculated. confirmed. The results are shown in Figure 2.

From Figure 2, it can be seen that even when anions coexist (in particular, phosphorus, which has similar chemical properties to arsenic), complex (1) remains the same as when no anions coexist, including arsenic (V ) can be efficiently adsorbed.

Example 2
NaOH was added to a mixed solution of 10% by weight FeCl ₃ .6H ₂ O and a buffer solution to adjust the pH to 6 to obtain an iron compound solution (1).
Pour 10 mL of the above iron compound solution (1) into a 100 mL flask, and add cellulose nanofibers (average fiber length: 0.6 to 0.8 mm, reference fiber diameter: 0.5 to 50 μm, product name "Filtration Meijin", Daicel 0.10 g of Millize Co., Ltd.) was added thereto, and the mixture was stirred for 1.0 hour using a stirrer at room temperature. Thereafter, a solid content was obtained by suction filtration, and the obtained solid content was dried.
Thereby, a composite (2) (Fe ^III -CNF) in which iron oxide (Fe ₂ O ₃ ) particles were supported on cellulose nanofibers (volume equivalent diameter: 1 μm or more) was obtained. A SEM image of the obtained composite (2) is shown in FIG.

Example 3
NaOH was added to a solution containing 10% by weight FeCl ₃ .6H ₂ O and NH ₄ buffer to adjust the pH to 9 to obtain an iron compound solution (2).
A composite (3) in which iron oxide (Fe ₂ O ₃ ) particles are supported on cellulose nanofibers was prepared in the same manner as in Example 2 except that the iron compound solution (2) was used instead of the iron compound solution (1). ) (Fe ^III -CNF) (volume equivalent diameter: 1 μm or more) was obtained.

Example 4
10 mL of 10 wt% FeCl ₃ .6H ₂ O, 10 mL of 1.0 wt % ZrCl ₂ O, and Good's buffer were added to a 100 mL flask, and the mixture was stirred using a stirrer for 30 minutes. Next, while heating the solution to 60° C., NaOH was added dropwise to adjust the pH to 6.0. Thereafter, the mixture was further stirred for 30 minutes to obtain a dispersion of iron oxide/zirconia oxide containing particles (Fe/Zr (molar ratio) = 7/1).
In a 100 mL flask, 0.10 g of cellulose nanofiber (average fiber length: 0.6 to 0.8 mm, reference fiber diameter: 0.5 to 50 μm, product name "Furoku Meijin", manufactured by Daicel Millize Co., Ltd.), and the above. 10 mL of a dispersion of particles containing iron oxide/zirconia oxide was added and stirred for 1 hour using a stirrer to support the particles on the cellulose nanofibers. Thereafter, a solid content was obtained by suction filtration, and the obtained solid content was dried. As a result, a composite (4) in which particles containing iron oxide and zirconia oxide are supported on cellulose nanofibers (Fe ^III /Zr-CNF; Fe/Zr (molar ratio) = 7/1) (volume equivalent diameter : 1 μm or more).

Example 5
Iron oxide/titanium oxide containing particles were supported on cellulose nanofibers in the same manner as in Example 4 except that 0.10 mL of 10 wt% TiCl ₂ was used instead of 10 mL of 1.0 wt % ZrCl ₂ O. A composite (5) (Fe ^III /Ti-CNF; (Fe/Ti (molar ratio) = 7/1) (volume equivalent diameter: 1 μm or more) was obtained.

Comparative example 2
10 mL of 10 wt% FeCl ₃ , 10 mL of 1 wt % ZrCl ₂ O, and a buffer solution were added to the flask, and the mixture was stirred at room temperature using a stirrer for 0.5 hour. NaOH was added thereto to adjust the pH to 6.0, and the mixture was stirred at 60° C. for 0.5 hour using a stirrer. Thereby, particles containing iron oxide and zirconium oxide (Fe ^III /Zr particles; Fe/Zr (molar ratio) = 7/1) were obtained.

(Rating 4)
The volume reduction rate of the composites obtained in Examples was measured by the following method.
0.102 g (w1) of the composite was burned at 800° C. for 1 hour, the weight (w2) of the ash remaining after combustion was measured, and the volume reduction rate was calculated from the following formula.
Volume reduction rate (%) = (w1-w2)/w1×100

(Rating 5-1)
Using the composites obtained in Examples 1 to 5 or the particles of Comparative Examples 1 and 2, the adsorption capacity of arsenic (V) was determined by the following method.
10 mL of a 1000 mg/L As(V) aqueous solution and 0.010 g of arsenic adsorbent were added to a 100 mL centrifuge tube, and the mixture was stirred for 20 minutes with a shaker at 25°C.
It was filtered using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the arsenic ion concentration (Ce: μmol/L) in the filtrate was determined using an ICP emission spectrometer (iCAP6300 manufactured by Thermo Fischer Scientific). Let the initial concentration of arsenic ions in the solution be C ₀ (μmol/L), the amount of liquid added Vo (L), the weight of the composite or particle used m (g), and calculate the adsorption capacity (μmol/L) from the following formula. g) was calculated.
Adsorption capacity = (C ₀ - Ce) x V ₀ /m

(Rating 5-2)
A column was filled with the complex obtained in the example, and an aqueous solution having an arsenic concentration of 5 μM was continuously flowed through the column. As a result, 99.9% by weight of arsenic in the aqueous solution could be removed.

The results of

evaluations

4 and 5 are summarized in Table 1 below.

From Table 1 above, it can be seen that when metal particles containing iron are supported on the surface of microfibrous cellulose, the amount of arsenic adsorption is significantly improved. It is also found that when metal particles containing iron as well as zirconium and titanium are supported on the surface of microfibrous cellulose, the arsenic adsorption power is further improved.
The complex of the present disclosure can efficiently adsorb and recover arsenic in a solution, and can significantly reduce the arsenic concentration in the solution, and after adsorbing arsenic to the complex, It can be seen that by firing, the volume can be significantly reduced, and the cost of disposal such as landfilling can be significantly reduced.

As a summary of the above, the configuration of the present disclosure and its variations are additionally described below.
[1] A composite having a structure in which metal particles containing zero-valent and/or trivalent iron are supported on the surface of microfibrous cellulose.
[2] The total supported amount of zero-valent and trivalent iron (in terms of iron element) per 1 g of the metal particles containing microfibrous cellulose and zero-valent and/or trivalent iron is 1 to 100 mmol, The complex according to [1].
[3] The composite according to [1] or [2], wherein the microfibrous cellulose is microfibrillated cellulose.
[4] The composite according to any one of [1] to [3], wherein the volume-equivalent sphere of the metal particles has a particle diameter of 1 μm or more.
[5] The metal particles contain zero-valent and/or trivalent iron as well as an oxide, hydroxide, or oxyhydroxide of at least one metal selected from zirconium and titanium,
The molar ratio of the iron (in terms of iron element) and the oxide, hydroxide, or oxyhydroxide of the metal (in terms of metal element; if two or more are contained, the total amount) [iron/(zirconium + titanium)] )] is 1 to 100, the complex according to any one of [1] to [4].
[6] The trivalent iron according to any one of [1] to [5], wherein the trivalent iron is at least one iron compound selected from iron oxide, iron hydroxide, and iron oxyhydroxide. complex.
[7] A method for producing a composite, which comprises producing the composite according to any one of [1] to [6] through Reaction 1 or Reaction 2 below.
[Reaction 1] Mixing microfibrous cellulose and an iron compound in water, allowing the iron compound to be adsorbed onto the microfibrous cellulose, and reducing the adsorbed iron compound [Reaction 2] Mixing microfibrous cellulose and an iron compound in water and a basic compound to adsorb trivalent iron colloid to microfibrous cellulose and grow it into particles [8] Contains the composite described in any one of [1] to [6] Arsenic adsorbent.
[9] Use of the composite according to any one of [1] to [6] as an arsenic adsorbent.
[10] A method for producing purified water, comprising treating arsenic-contaminated water with the arsenic adsorbent according to [8] to obtain purified water.
[11] A method for producing purified water, comprising treating arsenic-contaminated water with the complex according to any one of [1] to [6] to obtain purified water.
[12] A water purification device comprising the arsenic adsorbent according to [8].
[13] A water purification device comprising the composite according to any one of [1] to [6].

The composite and arsenic adsorbent of the present disclosure can efficiently adsorb and recover arsenic dissolved in water. After arsenic has been adsorbed, it is burned to reduce its volume, thereby significantly reducing the cost of disposal such as landfilling. Therefore, it can be suitably used for purifying water contaminated with arsenic.

Claims

A composite having a structure in which metal particles containing zero-valent and/or trivalent iron are supported on the surface of microfibrous cellulose.
The composite according to claim 1, wherein the total amount of zero-valent and trivalent iron supported per gram of microfibrous cellulose (in terms of iron element) is 1 to 100 mmol.
The composite according to claim 1 or 2, wherein the microfibrous cellulose is microfibrillated cellulose.
The metal particles contain an oxide, hydroxide, or oxyhydroxide of at least one metal selected from zirconium and titanium, along with zero-valent and/or trivalent iron,
The molar ratio of the iron (in terms of iron element) and the oxide, hydroxide, or oxyhydroxide of the metal (in terms of metal element; if two or more are contained, the total amount) [iron/(zirconium + titanium)] )] is 1 to 100, the composite according to claim 1 or 2.
The composite according to claim 1 or 2, wherein the trivalent iron is at least one iron compound selected from iron oxide, iron hydroxide, and iron oxyhydroxide.
The composite according to claim 1 or 2, wherein the particle diameter of the volume-equivalent sphere of the metal particles is 1 μm or more.
A method for producing a composite, which comprises producing the composite according to claim 1 or 2 through reaction 1 or reaction 2 below.
[Reaction 1] Mixing microfibrous cellulose and an iron compound in water, allowing the iron compound to be adsorbed onto the microfibrous cellulose, and reducing the adsorbed iron compound [Reaction 2] Mixing microfibrous cellulose and an iron compound in water and a basic compound to adsorb trivalent iron colloid to microfibrous cellulose and grow it into particles.
An arsenic adsorbent comprising the composite according to claim 1 or 2.
A method for producing purified water, comprising treating arsenic-contaminated water with the arsenic adsorbent according to claim 8 to obtain purified water.
A water purification device comprising the arsenic adsorbent according to claim 8.