JP7084602B2 - Adsorbent and its manufacturing method - Google Patents

Description

The present invention relates to an adsorbent made of modified cellulose fibers. The present invention also relates to a method for producing the adsorbent.

There are various odors in the living environment, and the unpleasant one is called a bad odor. Examples of substances that cause malodor include nitrogen-containing compounds such as ammonia and trimethylamine, sulfur-containing compounds such as methyl mercaptan and hydrogen sulfide, aldehydes such as acetaldehyde, and fatty acids such as isovaleric acid.

So far, the present inventor has produced a modified cellulose fiber in which a cellulose molecule constituting a cellulose fiber and a metal phthalocyanine derivative are bonded to each other and the average fiber diameter is 2 to 300 nm. Then, it was reported that this cellulose fiber can be used as a deodorant for methyl mercaptan and hydrogen sulfide (Patent Document 1).

The deodorant material in Patent Document 1 is excellent in deodorizing performance of methyl mercaptan and hydrogen sulfide. However, among the substances that cause bad odors, aldehydes in particular could not be sufficiently deodorized, and improvement was required.

Japanese Unexamined Patent Publication No. 2017-88697

The present invention has been made to solve the above problems, and an object of the present invention is to provide an adsorbent having excellent adsorption performance of a substance that causes a bad odor. Another object of the present invention is to provide a method for producing such an adsorbent.

The above-mentioned problem is an adsorbent made of a modified cellulose fiber; the cellulose molecule constituting the modified cellulose fiber has a hydrazide group or a hydrazine group, and the average fiber diameter of the modified cellulose fiber is 2 to 1000 nm. It is solved by providing an adsorbent, which is characterized by the above.

At this time, it is preferable that the cellulose molecule has a carboxylate group, and a hydrazide group or a hydrazine group is bonded via the carboxylate group. It is also preferable that the carboxylate group is formed by oxidizing the primary hydroxyl group at the C6 position of the glucose unit, which is a constituent unit of the cellulose molecule.

Further, it is preferable that the carboxylate group is a hydrazinium carboxylate group or an ammonium carboxylate group.

Further, it is preferable that the cellulose molecule further has a free carboxyl group.

An aldehyde adsorbent is a preferred embodiment of the present invention. Further, an adsorbent capable of adsorbing ammonia or amine is also a preferred embodiment of the present invention.

Further, a method for preserving fruits in the presence of the adsorbent of the present invention is a preferred embodiment of the present invention.

Another object of the present invention is to provide a method for producing an adsorbent, which comprises mixing and reacting a cellulose fiber having an average fiber diameter of 2 to 1000 nm with a nitrogen-containing compound having a hydrazide group or a hydrazine group. It is also solved by.

At this time, it is preferable that the cellulose fiber has a carboxyl group and the nitrogen-containing compound has a hydrazide group or a hydrazine group and also has a group capable of reacting with the carboxyl group. It is also preferable that the group capable of reacting with the carboxyl group is a hydrazinium group or an ammonium group.

The adsorbent of the present invention has excellent adsorption performance for substances that cause bad odors. In particular, it is suitable as an aldehyde adsorbent because it has excellent aldehyde adsorption performance.

It is a figure which showed the infrared spectroscopic measurement result of the TEMPO oxide CNF obtained in Example 1. FIG. It is a figure which showed the infrared spectroscopic measurement result of adipic acid dihydrazide used as a raw material in Example 1. FIG. It is a figure which showed the infrared spectroscopic measurement result of the modified CNF-1 obtained in Example 1. FIG. FIG. 3 is a photograph showing grapes left at room temperature for 15 days in Example 1. In Comparative Example 1, it is a photograph which shows the grape which was left at room temperature for 15 days.

The present invention relates to an adsorbent made of modified cellulose fiber (modified CNF). In the present invention, it is important that the cellulose molecule constituting the modified cellulose fiber has a hydrazide group or a hydrazine group. As a result of diligent studies, the present inventors have found that a modified cellulose fiber having a hydrazide group or a hydrazine group has excellent adsorption performance for a substance that causes a bad odor, and have completed the present invention. Here, the hydrazide group means a nitrogen-containing functional group represented by -CO-NH-NH ₂ , and the hydrazine group means a nitrogen-containing functional group represented by -NH-NH ₂ .

Hereinafter, the method for producing the adsorbent of the present invention will be described. The adsorbent of the present invention can be obtained by mixing and reacting a cellulose fiber and a nitrogen-containing compound to bond a cellulose molecule and a nitrogen-containing compound. A suitable production method is a method in which a cellulose fiber having an average fiber diameter of 2 to 1000 nm and a nitrogen-containing compound having a hydrazide group or a hydrazine group are mixed and reacted.

The cellulose fiber used in the present invention has an average fiber diameter of 2 to 1000 nm, and has a smaller fiber diameter than a normal cellulose fiber such as pulp. Such fine cellulose fibers are called "cellulose nanofibers (CNFs)" and are produced by highly fibrillating ordinary cellulose fibers. The average fiber diameter is preferably 800 nm or less, more preferably 500 nm or less. On the other hand, cellulose fibers having an average fiber diameter of less than 2 nm are difficult to obtain by a usual method, and it is not realistic to use them industrially. The average fiber diameter is preferably 5 nm or more. The average fiber diameter is a value obtained by observing the cellulose fibers using a scanning electron microscope.

The CNF used in the present invention is not particularly limited as long as it has the above-mentioned average fiber diameter, and general fibrillated cellulose fibers can be used. Examples of raw materials for fibrillated cellulose fibers include wood, straw, bamboo, bagasse, bamboo grass, reeds, and rice husks. Fibrilization can be performed by applying a mechanical shearing force to a cellulose fiber having a normal diameter such as pulp using a disc mill, a beating machine, a homogenizer, or the like. In addition, the cellulose fibers can be fibrillated by chemical treatment.

It is preferable that the cellulose molecule of CNF used in the present invention has a free carboxyl group. At this time, it is preferable that the carboxyl group is formed by oxidizing the primary hydroxyl group at the C6 position of the glucose unit, which is a constituent unit of the cellulose molecule. Cellulose fibers in which the primary hydroxyl group at the C6 position of the glucose unit is oxidized can be easily synthesized by using 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO). By reacting the cellulose molecule with TEMPO, the primary hydroxyl group at the C6 position of the glucose unit can be selectively oxidized to form a carboxyl group.

At this time, the content of the free carboxyl group in the cellulose molecule is preferably 0.1 mmol or more per 1 g of the modified CNF. If the content is less than 0.1 mmol, a predetermined amount of hydrazide group or hydrazine group may not be introduced into the cellulose molecule. In addition, excellent adsorption performance for ammonia or amine may not be obtained. The content is more preferably 0.5 mmol or more. On the other hand, the content of the carboxyl group is usually 5 mmol or less. The above content is obtained by the titration method.

The nitrogen-containing compound to be mixed and reacted with CNF is not particularly limited as long as it has a hydrazide group or a hydrazine group. Examples of the nitrogen-containing compound having a hydrazide group include a monohydrazide compound having one hydrazide group in the molecule, a polyhydrazide compound having two or more hydrazide groups in the molecule, and the like. Among them, a polyhydrazide compound having two or more hydrazide groups in the molecule is preferable, and a dihydrazide compound having two hydrazide groups in the molecule is more preferable.

Examples of the dihydrazide compound include adipic acid dihydrazide, succinic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, and terephthalic acid dihydrazide. Of these, adipic acid dihydrazide is preferable.

Examples of the nitrogen-containing compound having a hydrazine group include a monohydrazine compound having one hydrazine group in the molecule, a polyhydrazine compound having two or more hydrazine groups in the molecule, and the like. Of these, a monohydrazine compound having one hydrazine group in the molecule is preferable.

In the present invention, the CNF has a carboxyl group, and the nitrogen-containing compound that reacts with the CNF has a hydrazide group or a hydrazine group and has a group capable of reacting with the carboxyl group (hereinafter referred to as a reactive group). Is preferable. Examples of the reactive group include a group capable of ionic bonding with a carboxyl group and a group capable of covalently bonding with a carboxyl group. Above all, it is preferable that the reactive group is a group capable of ionic bonding with the carboxyl group.

From the viewpoint of reactivity with the carboxylate group, the reactive group is preferably a hydrazinium group or an ammonium group. Above all, it is more preferable that the reactive group is a hydrazinium group.

The nitrogen-containing compound to be reacted with CNF may have a functional group other than the hydrazide group and the hydrazine group as long as the effect of the present invention is not impaired. Examples of the functional group include a hydroxyl group, a halogen group, an ester group, an amide group, a nitrile group, a nitro group and the like.

In this way, a modified CNF can be obtained by mixing and reacting CNF and a nitrogen-containing compound. In the modified CNF of the present invention, the content of nitrogen element obtained from elemental analysis (combustion method) is preferably 0.05% by mass or more. If it is less than 0.05% by mass, excellent adsorption performance may not be obtained for substances that cause bad odors. The content is more preferably 0.1% by mass or more, further preferably 0.5% by mass or more, and particularly preferably 1% by mass or more.

On the other hand, the content of the nitrogen element is usually 20% by mass or less, preferably 15% by mass or less. Since CNF does not contain a nitrogen element, the nitrogen element detected by the above elemental analysis is derived from the nitrogen element contained in the nitrogen-containing compound used for producing the modified CNF.

In the present invention, the cellulose molecule constituting the modified CNF has a hydrazide group or a hydrazine group. At this time, it is preferable that the cellulose molecule has a carboxylate group, and a hydrazide group or a hydrazine group is bonded via the carboxylate group, and it is more preferable that the cellulose molecule is bonded via the hydrazide group.

Further, the carboxylate group is preferably a hydrazinium carboxylate group or an ammonium carboxylate group, and more preferably a hydrazinium carboxylate group.

The adsorbent of the present invention comprises a modified CNF, and the cellulose molecule constituting the modified CNF has a hydrazide group or a hydrazine group. Since the hydrazide group or the hydrazine group easily binds to an aldehyde, the adsorbent of the present invention is suitable as an adsorbent for an aldehyde. Above all, from the viewpoint of aldehyde adsorption performance, it is preferable that the cellulose molecule has a hydrazide group.

Further, it is preferable that the cellulose molecule in the present invention further has a free carboxyl group. Carboxyl groups easily bind to ammonia or amines. Therefore, since the cellulose molecule has a free carboxyl group, the adsorbent of the present invention can also be used as an adsorbent capable of adsorbing ammonia or amine in addition to aldehyde.

Since the adsorbent of the present invention has excellent adsorption performance for substances that can cause malodor, one of the suitable uses is a deodorant. At this time, the form of the deodorant is not particularly limited, and it may be in the form of powder or in the form of solid. Further, it may be a dispersion liquid in which the adsorbent is dispersed in a dispersion medium such as water.

The method of use is not particularly limited, and the solid or dispersion can be used as it is as a deodorant, or an adsorbent can be applied to a base material and the base material can be used as a deodorant. The type of the base material is not particularly limited, and examples thereof include woven fabrics, knitted fabrics, non-woven fabrics and the like, paper, wood, wood flour, plastics, rubber, activated charcoal, cement and plaster. Examples of places where deodorants are used include chemical factories, cleaning factories, sewage treatment plants, hospitals, nursing care facilities, houses (particularly toilets), agricultural product processing plants, and livestock processing plants.

Further, by using the cloth coated with the adsorbent of the present invention, it is possible to obtain clothing having deodorizing performance. Furthermore, prevention of sick house syndrome can be expected by using the building material containing the adsorbent of the present invention.

Another preferred embodiment of the present invention is a method for preserving fruits in the presence of the adsorbent. As demonstrated in the examples described below, storage of the fruit in the presence of the adsorbent suppressed fruit spoilage. The reason for this is not necessarily clear at this time, but it is speculated that the adsorbent of the present invention was able to effectively adsorb the gas generated from the fruit.

The fruits to be stored in the presence of the adsorbent are not particularly limited. The present inventors have confirmed that the decay of grapes can be suppressed. However, not only grapes but also various fruits are expected to have an anti-rot effect.

Example 1
[Sample synthesis]
(Synthesis of TEMPO Oxidized CNF)
Cellulose fibers were reacted with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) to synthesize cellulose fibers oxidized with TEMPO (TEMPO oxide CNF). The synthesis scheme is shown in the following formula (1).

The specific synthesis method is as follows.
After adding 688 g of an aqueous dispersion of cellulose fibers (content of dry cellulose fibers 36 g), 672 mg (2.08 mmol) of tetrabutylammonium bromide, and 1.02 g (9.9 mmol) of sodium bromide to a flask having a capacity of 10 L. , 2.5 L of water, and 300 mL of saturated aqueous sodium hydrogen carbonate solution were added to obtain a mixed solution. The water dispersion of cellulose fibers used here is a cellulose nanofiber water dispersion manufactured by Mori Machinery Co., Ltd. (average fiber diameter: 20 to 200 nm, average fiber length: 500 μm, cellulose fiber content of the water dispersion: 5. 26% by mass).

Next, while maintaining the temperature of the above mixture at 22 to 25 ° C. and stirring, 508 mg (3.25 mmol) of TEMPO and 140 mL of an aqueous solution of sodium hypochlorite (commercially available: Cl content 8.5 to 13.5%) were added. . Dropped over 5 hours. After the dropping, the mixture was further stirred for 2.5 hours while maintaining the temperature of the mixed solution at 22 to 25 ° C., and left overnight.

After completion of the reaction, 13 mL of a 1.0 M aqueous sodium thiosulfate solution was added to the flask to decompose unreacted sodium hypochlorite, and then 153 mL of 6N hydrochloric acid was added. The pH of the mixed solution at this time was 1.58. Then, the mixed solution was filtered under reduced pressure to obtain a solid substance, and the solid substance was washed with water to obtain TEMPO-oxidized CNF.

The carboxyl group content in the obtained TEMPO oxidized CNF was measured. The measurement method is as follows.
190.7 mg of freeze-dried TEMPO-oxidized CNF was placed in a beaker, and 70 mL of ion-exchanged water was added. A dispersion of TEMPO oxide CNF was prepared by adding 1.0 mL of a 1 M aqueous sodium chloride solution to the mixture and stirring the mixture. The pH was adjusted to 2.98 by adding 1.0 mL of 0.1N hydrochloric acid to this dispersion. Then, using a burette, a 0.01 N sodium hydroxide aqueous solution was added dropwise to the dispersion, and the conductivity and pH were measured until the pH reached 10.9 to obtain an conductivity curve. From the obtained conductivity curve, the carboxyl group content in TEMPO oxide CNF was determined. As a result, the carboxyl group content in TEMPO-oxidized CNF was 1.6 mmol per 1 g of TEMPO-oxidized CNF.

Infrared spectroscopy (total reflection method (ATR)) was performed on the obtained TEMPO oxide CNF. The results are shown in FIG. As shown in FIG. 1, a peak due to expansion and contraction of C = O of the carboxyl group of the TEMPO-oxidized CNF was confirmed at 1726 cm ^-1 .

(Synthesis of modified CNF-1)
Modified CNF-1 was synthesized by reacting TEMPO oxidized CNF with adipic acid dihydrazide. The synthesis scheme is shown in the following formula (2).

Here, infrared spectroscopic measurement (ATR) was performed on the adipic acid dihydrazide used as a raw material. The results are shown in FIG. As shown in FIG. 2, peaks due to amide C = O were confirmed at 1531 cm ^-1 and 1626 cm ^-1 .

The method for synthesizing the modified CNF-1 is as follows.
A dispersion was prepared by dispersing 54 g of TEMPO-oxidized CNF (weight in terms of solid content) (carboxyl group content: 1.6 mmol per 1 g of TEMPO-oxidized CNF) in 4 L of water. 810 mL of a 0.1 M aqueous solution of dihydrazide adipic acid was added to this dispersion and stirred. The pH of the dispersion changed from 3.73 to 4.91 by adding an aqueous solution of adipic acid dihydrazide. After stirring the dispersion for 5 hours, water was added to bring the total volume to 5.4 L to obtain a modified CNF-1.

Infrared spectroscopy (ATR) was performed on the obtained modified CNF-1. The results are shown in FIG. As shown in FIG. 3, peaks derived from C = O were observed at 1598 cm ^-1 and 1630 cm ^-1 . Of these, the peak of 1630 cm ^-1 is derived from the amide C = O. In addition, the peak of 1598 cm ^-1 indicates that carboxylate was generated from TEMPO-oxidized CNF carboxylic acid (see FIG. 1). From this, it was found that adipic acid dihydrazide was bound to TEMPO-oxidized CNF.

In addition, as shown by the arrow in FIG. 3, a shoulder peak was observed near 1700 cm ^-1 . This shoulder peak was a shoulder peak due to C = O of the carboxyl group in TEMPO oxidized CNF, and it was also found that the obtained modified CNF-1 contained an unreacted carboxyl group.

(Preparation of cloth coated with modified CNF-1)
An aqueous dispersion was prepared by dispersing 1 g (dry weight equivalent) of modified CNF-1 in 100 mL of water. This dispersion was sprayed uniformly on both sides of a polyester / rayon mixed non-woven fabric (manufactured by Nippon Paper Crecia Co., Ltd .: 9 cm × 18 cm), and then the non-woven fabric was dried. Next, the amount of modified CNF-1 adhering to the nonwoven fabric was determined from the difference between the weight of the nonwoven fabric after spraying the dispersion and the weight of the nonwoven fabric before spraying the dispersion. The amount of denatured CNF-1 attached was 110 mg.

[Gas adsorption test]
(Ammonia gas adsorption test)
A cloth coated with modified CNF-1 and a beaker containing 28% aqueous ammonia were placed in a closed bottle having a capacity of 2.8 L. Next, an aqueous potassium hydroxide solution was added dropwise to a beaker containing ammonia water to generate ammonia gas, and then the lid of the closed bottle was closed. When the concentration of ammonia gas in the closed bottle was measured using a detector tube, the concentration at the start of the experiment was 80 ppm (“Experiment start (0 minutes)” in Table 1). Then, the concentration of ammonia gas in the closed bottle was measured after 15 minutes, 30 minutes, and 60 minutes. The results are shown in Table 1.

(Acetaldehyde gas adsorption test)
A cloth coated with modified CNF-1 and a beaker containing 1 mL of an acetaldehyde aqueous solution (diluted stock solution to 1.5 / 10000) were placed in a closed bottle having a capacity of 2.8 L. At this time, a magnet stirrer was also put in the beaker. Then, after closing the lid of the closed bottle, the closed bottle was placed on a magnetic stirrer and the magnetic stirrer in the beaker was rotated to generate acetaldehyde gas in the closed bottle. After stopping the rotation of the stirrer, the concentration of acetaldehyde gas in the closed bottle was measured using a detector tube, and the concentration was 18 ppm at the start of the experiment (“Experiment start (0 minutes)” in Table 1). .. Then, the concentration of acetaldehyde gas in the closed bottle was measured after 15 minutes, 30 minutes, and 60 minutes. The results are shown in Table 1.

[Evaluation of grape preservation]
(Evaluation of ball drop)
I got a commercially available grape (Delaware, a variety from Okayama prefecture). Along with this grape, a cloth coated with modified CNF-1 was placed in a polypropylene container and sealed with a lid (made of polyethylene). Then, after leaving this container at room temperature for 30 days, the grapes were taken out from the container with the spikes. At this time, the ball drop evaluation was performed by counting the grape grains that came off the bunch and remained in the container. The results are shown in Table 2.

(Freshness evaluation)
I got a commercially available grape (Muscat, a variety from Okayama prefecture). Along with this grape, a cloth coated with modified CNF-1 was placed in a polypropylene container and sealed with a lid (made of polyethylene). Then, after leaving this container at room temperature for 15 days, the grapes were taken out from the container with the spikes, and the freshness of the grapes was visually evaluated. The results are shown in Table 2 and FIG.

Example 2
(Synthesis of modified CNF-2)
Modified CNF-2 was synthesized by reacting TEMPO-oxidized CNF with the cationized hydrazine shown below. First, a method for synthesizing cationized hydrazine will be described. The synthesis scheme is as shown in the following formula (3).

The specific synthesis method is as follows.
A mixture was obtained by adding 5 mL of methanol to 1.01 mg (5.35 mmol) of an 80% aqueous solution of 2,3-epoxypropyltrimethylammonium chloride. The temperature of this mixed solution was cooled to 0 to 4 ° C., and 702 mg (14 mmol) of hydrazine monohydrate (NH ₂ NH ₂ · H ₂ O) was added dropwise. Then, the mixture was stirred for 1 hour while maintaining the liquid temperature at 0 to 4 ° C., the liquid temperature was raised to room temperature, and then the mixture was further stirred for 1 hour.

The obtained mixed solution was concentrated by a rotary evaporator, and then 5 mL of tetrahydrofuran was added to the concentrated solution and co-evaporated to remove water. The operation of co-evaporation was repeated several times. The concentrate obtained by co-evaporation was dried under high vacuum to obtain 930 mg of cationized hydrazine chloride ((3-hydrazine-2-hydroxypropyl) trimethylammonium chloride) as a paste-like oil.

The obtained cationized hydrazine was dissolved in DMSO _- d6 and NMR measurement was performed. The results are shown below.
¹ H NMR (DMSO-d ₆ ) δ 2.54 (m, 1H), 3.14 (s, 9H), 3.15-3.32 (m, 2H), 3.41 (m, 1H), 4.22 (m, 1H)
¹³ C NMR (DMSO-d ₆ ) δ 53.5 (3C), 58.6, 63.2, 69.9

Infrared spectroscopy (ATR) was performed on the obtained cationized hydrazine chloride. As a result, a peak derived from a hydroxyl group was observed at 3272 cm ^-1 (not shown).

Then, the modified CNF-2 was synthesized by reacting the TEMPO oxidized CNF with the above-mentioned cationized hydrazine hydroxide. The synthesis scheme is shown in the following formula (4). The TEMPO-oxidized CNF used here was obtained by the synthetic method described in Example 1.

The specific synthesis method is as follows.
A mixture in which the above-mentioned cationized hydrazine chloride was dissolved in 10 mL of methanol was obtained. The temperature of this mixed solution was cooled to 0 to 4 ° C., and 4.8 mL (1N, 4.8 mmol) of a cold potassium hydroxide methanol solution was added dropwise. The mixture is then filtered using a membrane filter (PTFE, 0.45 μm), the membrane filter washed with a small amount of cold methanol, and cationized hydrazine hydroxide ((3-hydrazino-2-hydroxypropyl) trimethylammonium chloride). A methanol solution of hydroxydone) was obtained. Since this cationized hydrazine hydroxide is unstable, it was immediately used for the next reaction with TEMPO-oxidized CNF.

A dispersion was prepared by dispersing 3 g of TEMPO oxide CNF (carboxyl group content: 1.6 mmol per 1 g of TEMPO oxide CNF) in 300 mL of water. A methanol solution of the above-mentioned cationized hydrazine hydroxide was added to this dispersion, and the mixture was stirred. Stirring for 1 hour gave modified CNF-2. In the obtained modified CNF-2, the nitrogen-containing functional group contained in the cellulose molecule is a hydrazine group.

The obtained modified CNF-2 was subjected to elemental analysis by the combustion method. The results are shown below (values are mass%).
C (carbon): 41.10, H (hydrogen): 5.76, N (nitrogen): 2.03

Then, in the same manner as in Example 1, a cloth coated with the modified CNF-2 was prepared, and a deodorization test was conducted using the cloth. The results are shown in Table 1.

Comparative Example 1
In the "deodorant test", the deodorant test was carried out in the same manner as in Example 1 except that a cloth to which the modified CNF-1 was not applied was put. The results are shown in Table 1. Further, in the "evaluation of the preservation of grapes", the preservation of grapes was evaluated in the same manner as in Example 1 except that the cloth to which the modified CNF-1 was not applied was placed in a polypropylene container. The results are shown in Table 2 and FIG.

Claims (10)

An adsorbent made of modified cellulose fibers;
The cellulose molecule constituting the modified cellulose fiber has a hydrazide group or a hydrazine group, and has a hydrazide group or a hydrazine group.
The cellulose molecule has a carboxylate group, a hydrazide group or a hydrazine group is bonded via the carboxylate group, and the average fiber diameter of the modified cellulose fiber is 2 to 1000 nm. Adsorbent. The adsorbent according to claim 1 , wherein the carboxylate group is formed by oxidizing a primary hydroxyl group at the C6 position of a glucose unit, which is a constituent unit of the cellulose molecule. The adsorbent according to claim 1 or 2 , wherein the carboxylate group is a hydrazinium carboxylate group or an ammonium carboxylate group. An adsorbent made of modified cellulose fibers;
The cellulose molecule constituting the modified cellulose fiber has a hydrazide group or a hydrazine group, and has a hydrazide group or a hydrazine group.
An adsorbent , wherein the cellulose molecule further has a free carboxyl group, and the average fiber diameter of the modified cellulose fiber is 2 to 1000 nm. The adsorbent according to any one of claims 1 to 4 , which is an aldehyde adsorbent. The adsorbent according to claim 5 , which can further adsorb ammonia or amine. A method for preserving fruits in the presence of an adsorbent consisting of modified cellulose fibers;
A method for preserving fruits, wherein the cellulose molecules constituting the modified cellulose fiber have a hydrazide group or a hydrazine group, and the average fiber diameter of the modified cellulose fiber is 2 to 1000 nm. The production of the adsorbent according to any one of claims 1 to 6 , wherein the cellulose fiber having an average fiber diameter of 2 to 1000 nm is mixed and reacted with a nitrogen-containing compound having a hydrazide group or a hydrazine group. Method. The method for producing an adsorbent according to claim 8 , wherein the cellulose fiber has a carboxyl group, and the nitrogen-containing compound has a hydrazide group or a hydrazine group and has a group capable of reacting with the carboxyl group. The production method according to claim 9 , wherein the group capable of reacting with the carboxyl group is a hydrazinium group or an ammonium group.

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