JP6737453B2 - Cellulose derivative, metal removing material containing the same, and metal removing method using the same - Google Patents

Description

The present invention relates to a novel cellulose derivative, a method for producing the same, a metal removing material containing the cellulose derivative, and a metal removing method using the cellulose derivative.

Heavy metals such as arsenic, cadmium and lead are used in various fields. For example, arsenic is used as medicines, insecticides, rodenticides, preservatives, high-tech industrial materials and the like. Therefore, the heavy metal may be dissolved in the stratum, ocean, river, well water, etc., but it is known that even a trace amount thereof causes environmental pollution. Therefore, a method for efficiently recovering and removing the heavy metal from soil, seawater, industrial waste liquid, mine drainage, etc. contaminated with the heavy metal is desired.

In Patent Document 1, a cellulosic adsorbent obtained by introducing a graft chain into the surface of a cellulosic base material and binding a chelate forming group or an ion exchange group to the introduced graft chain is easily compatible with water, and boron and germanium are used. It is described that it is excellent in the adsorptive power of semi-metals such as arsenic and heavy metals. The rate of introduction of the graft chain influences the binding amount of the chelate-forming group or ion-exchange group that exerts a metal adsorbing power, and when the rate of introduction of the graft chain is low, chelate formation that effectively acts on the adsorption of the metal. It is described that it is not possible to secure a sufficient amount of bonding of the group or the ion exchange group. However, since the cellulose-based substrate has low solubility in an organic solvent, it is very difficult to introduce the graft chain efficiently, and the introduction of the graft chain can be achieved only by a method using an expensive device such as a radiation graft method. The problem is that the cost cannot be increased because the rate cannot be improved.

JP, 2009-13204, A

Therefore, an object of the present invention is to provide a novel cellulose derivative which can be produced at low cost and which can selectively adsorb and recover a metal, and a production method thereof.
Another object of the present invention is to provide a metal removing material that can be manufactured at low cost and that can selectively adsorb and recover metals.
Another object of the present invention is to provide a method for inexpensively and selectively adsorbing and recovering a metal.

The present inventors have conducted extensive studies to solve the above-mentioned problems, and as a result, acylated cellulose has excellent solubility in an organic solvent, can efficiently and inexpensively introduce a dithiocarbamate group, and has a dithiocarbamate group and an acyl group. It has been found that the cellulose derivative provided with is excellent in metal adsorption power and is useful as a metal removing material. The present invention has been completed based on these findings.

［式中、Ｒは、同一又は異なって、水素原子、下記式（ａ）で表される基、又は下記式（ｂ）で表される基である。セルロース誘導体に含まれる全てのＲのうち、少なくとも１つは下記式（ａ）で表される基であり、少なくとも１つは下記式（ｂ）で表される基である］

（式中、Ｒ¹は単結合又は炭素数１〜１０のアルキレン基を示し、Ｒ²は水素原子又は炭素数１〜１０のアルキル基を示す。Ｒ³、Ｒ⁴は、同一又は異なって、炭素数１〜１０のアルキル基を示す） That is, the present invention provides a cellulose derivative having a repeating unit represented by the following formula (1).

[In the formula, R is the same or different and is a hydrogen atom, a group represented by the following formula (a), or a group represented by the following formula (b). Among all Rs contained in the cellulose derivative, at least one is a group represented by the following formula (a), and at least one is a group represented by the following formula (b)]

(In the formula, R ¹ represents a single bond or an alkylene group having 1 to 10 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ³ and R ⁴ are the same or different, (Indicates an alkyl group having 1 to 10 carbon atoms)

The present invention also provides the above cellulose derivative, wherein the molar ratio (former/latter) of the group represented by formula (a) and the group represented by formula (b) is 1/99 to 99/1. To do.

（式中、Ｒ³は、同一又は異なって、炭素数１〜１０のアルキル基を示し、Ｒ⁵は同一又は異なって、水素原子又は炭素数１〜３のアルキル基を示す。ｎは１〜３の整数を示す） The present invention also provides the above cellulose derivative, wherein the group represented by the formula (a) is a group represented by the following formula (a-1).

(In formula, R< ³ > is the same or different and shows a C1-C10 alkyl group, R< ⁵ > is the same or different and shows a hydrogen atom or a C1-C3 alkyl group. Indicates an integer of 3)

The present invention also provides the above cellulose derivative, wherein the group represented by formula (b) is an acetyl group.

In the present invention, the total average substitution degree of the group represented by the formula (a) is 0.2 to 2.1, and the total average substitution degree of the group represented by the formula (b) is 0.9 to. The above cellulose derivative is provided which is 2.8.

The present invention also provides a method for producing a cellulose derivative, which obtains the above cellulose derivative through the following steps.
[1] An amino acid having an amino group protected is reacted with a hydroxyl group of acylated cellulose (total average degree of substitution of acyl groups: 0.9 to 2.8), and then the amino group protecting group is removed [2 ] In the presence of a sulfur compound, a deprotected amino group has a quaternary ammonium salt (N ⁺ (R ³ ) ₄ X ⁻ ; R ³ is the same or different and represents an alkyl group having 1 to 10 carbon atoms, and X ⁻ Represents a counter anion)

The present invention also provides a metal adsorbent containing the above cellulose derivative.

The present invention also provides a metal removal method using the above cellulose derivative.

The cellulose derivative of the present invention can be produced at low cost, and can selectively adsorb and recover metals (for example, heavy metals such as arsenic, cadmium and lead). Moreover, the cellulose derivative of the present invention is excellent in chemical resistance, heat resistance, and water resistance. Therefore, the cellulose derivative of the present invention is extremely useful as a metal removing material, and is preferably used for purification of metal-contaminated soil or seawater, industrial wastewater containing the metal, mine wastewater, hot spring water, etc. can do.

FIG. 3 is a diagram showing an IR spectrum of a cellulose derivative (MI96) obtained in Example 1. FIG. 3 is a diagram showing an IR spectrum of a cellulose derivative (MI98) obtained in Example 2. FIG. 3 is a diagram showing an IR spectrum of a cellulose derivative (MI77) obtained in Example 4. 5 is a diagram showing an IR spectrum of a cellulose derivative (MI64) obtained in Example 5. FIG. It is a figure which shows the pH dependence of the metal adsorption force of a cellulose derivative. It is a figure which shows the arsenic adsorption force of the cellulose derivative obtained in the Example. It is a figure which shows the adsorption power with respect to arsenic, cadmium, and lead of a cellulose derivative and acetyl cellulose.

［式中、Ｒは、同一又は異なって、水素原子、下記式（ａ）で表される基、又は下記式（ｂ）で表される基である。前記式（１）で表される繰り返し単位を有するセルロース誘導体に含まれる全てのＲのうち、少なくとも１つは下記式（ａ）で表される基であり、少なくとも１つは下記式（ｂ）で表される基である］

（式中、Ｒ¹は単結合又は炭素数１〜１０のアルキレン基を示し、Ｒ²は水素原子又は炭素数１〜１０のアルキル基を示す。Ｒ³、Ｒ⁴は、同一又は異なって、炭素数１〜１０のアルキル基を示す） [Cellulose derivative]
The cellulose derivative of the present invention has a repeating unit (glucose unit) represented by the following formula (1).

[In the formula, R is the same or different and is a hydrogen atom, a group represented by the following formula (a), or a group represented by the following formula (b). Among all Rs contained in the cellulose derivative having the repeating unit represented by the above formula (1), at least one is a group represented by the following formula (a), and at least one is the following formula (b): Is a group represented by]

(In the formula, R ¹ represents a single bond or an alkylene group having 1 to 10 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ³ and R ⁴ are the same or different, (Indicates an alkyl group having 1 to 10 carbon atoms)

Examples of the alkylene group having 1 to 10 carbon atoms in R ¹ include methylene group, methylmethylene group, dimethylmethylene group, ethylene group, 2-methylethylene group, 1,2-dimethylethylene group, propylene group, trimethylene group, A linear or branched alkylene group such as a 2-methyl-trimethylene group may be mentioned.

Among them, as R ¹ , the longer the carbon chain between the cellulose main chain skeleton and the dithiocarbamate group, the more the metal adsorbing power tends to be improved.

Examples of the alkyl group having 1 to 10 carbon atoms in R ² , R ³ and R ⁴ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a t-butyl group, A straight chain or branched chain alkyl group such as a pentyl group may be mentioned.

Among them, R ² is preferably a hydrogen atom. Further, as R ³ and R ⁴ , an alkyl group having 1 to 3 carbon atoms is preferable.

As the group represented by the formula (a), among others, a group represented by the following formula (a-1) (in the formula, n represents an integer of 1 to 3, R ^{5 s} are the same or different, and are hydrogen; An atom or an alkyl group having 1 to 3 carbon atoms, R ³ is preferably the same as defined above, and particularly preferably a group represented by the following formula (a-1) in which n is 2 is there.

As the group represented by the formula (a), more preferably a group represented by the following formula (a-1′) (in the formula, n represents an integer of 1 to 3, R ^{5 s} are the same or different, A hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and among the groups represented by the following formula (a-1′), n in the formula is a group of 2.

The group represented by the formula (a) is particularly preferably a group represented by the following formula (a-1-1) or (a-1-2), and particularly preferably a group represented by the following formula (a-1- It is a group represented by 2). R ³ in the following formula is the same as above.

The group represented by the formula (a) is most preferably a group represented by the following formula (a-1'-1) or (a-1'-2), and particularly preferably the following formula (a- It is a group represented by 1'-2).

Among them, the acetyl group is preferable as the group represented by the formula (b).

The group represented by the formula (a) (preferably the group represented by the formula (a-1), more preferably the group represented by the formula (a-1′), and further preferably the group represented by the formula (a-1-1) ) And a group represented by (a-1-2), most preferably a group represented by the formula (a-1'-1) and a group represented by (a-1'-2) The total average degree of substitution of (group) (the total average degree of substitution of the groups substituting the 2, 3 and 6-positions of glucose units constituting cellulose) is, for example, 0.2 to 2.1, preferably 0.2 to 1.8, particularly preferably 0.5 to 1.5. When the cellulose derivative contains the group represented by the formula (a) in the above range, it is preferable because it can exhibit an excellent metal adsorption force.

Examples of the total average degree of substitution of the group represented by formula (b) (particularly preferably acetyl group) (the total average degree of substitution of the groups substituting the 2, 3 and 6-positions of glucose units constituting cellulose) include It is 0.9 to 2.8, preferably 1.2 to 2.8, particularly preferably 1.5 to 2.5, and most preferably 1.8 to 2.5.

The cellulose derivative of the present invention has an excellent metal adsorption force (the metal adsorption amount is, for example, 0.1 μmol/g or more, preferably 0.3 μmol/g or more, and particularly preferably 0.5 μmol/g or more). In particular, it has an excellent adsorption ability for heavy metals such as As(III), Cd(II) and Pb(II). The As(III) adsorption amount is, for example, 0.1 μmol/g or more, the Cd(II) adsorption amount is, for example, 0.5 μmol/g or more, and the Pb(II) adsorption amount is, for example, 0.6 μmol/g or more. Is.

The shape of the cellulose derivative of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and examples thereof include a sheet shape, a spherical shape (a true spherical shape, a substantially true spherical shape, an elliptic spherical shape, etc.), a polyhedral shape, and a rod shape ( (Cylindrical shape, prismatic shape, etc.), scaly shape, irregular shape and the like.

Since the cellulose derivative of the present invention has an excellent metal adsorbing power as described above, it can be suitably used, for example, as a metal adsorbent.

The metal adsorbent containing the cellulose derivative of the present invention (or the metal adsorbent composed of the cellulose derivative of the present invention) is, for example, a metal (especially a heavy metal such as As(III), Cd(II), Pb(II)). It can be suitably used for the purpose of purifying soil and seawater contaminated with, industrial wastewater containing the metals, mining wastewater, hot spring water, and the like.

The metal removal method of the present invention, that is, the soil or seawater contaminated with metals (in particular, heavy metals such as As(III), Cd(II), Pb(II)) using the cellulose derivative of the present invention as a metal adsorbent. Other than the above, the method for adsorbing and removing the metal from the industrial wastewater containing the metal, the mine wastewater, the hot spring water, etc. is not particularly limited, and for example, the cellulose derivative of the present invention is packed in a column or the like, and Examples thereof include a method of flowing industrial wastewater and the like, and a method of adding the cellulose derivative of the present invention to industrial wastewater and the like and stirring. In particular, when the cellulose derivative of the present invention exhibits solubility in an organic solvent, it can be used as a homogeneous metal adsorbent (that is, one that exhibits an action of adsorbing/removing metal in a state of being dissolved in industrial wastewater etc.). ..

In the metal removal method of the present invention, adjusting the pH of the cellulose derivative to, for example, 1 to 9 (among others, 1 to 7) can further improve the metal adsorption force and efficiently remove the metal. It is preferable because it can be obtained. The pH of the cellulose derivative can be adjusted using a well-known and commonly used pH adjusting agent (an acid such as nitric acid or an alkali such as sodium hydroxide).

Moreover, the metal can be easily recovered by baking the cellulose derivative having adsorbed the metal, and the recovered metal can be reused as a useful resource.

[Method for producing cellulose derivative]
The cellulose derivative of the present invention can be produced, for example, through the following steps.
[1] Acylated cellulose (a part of the hydroxyl groups of cellulose is substituted with an acyl group [—COR ⁴ ] (R ⁴ is the same as above), the total average degree of substitution of the acyl groups: 0.9 to 2. An amino group-protected amino acid is reacted with the hydroxyl group of 8), and then the amino-group-protecting group is removed [2] In the presence of a sulfur compound, the deprotected amino group is quaternary ammonium salt (N ⁺ (R ³ ) ₄ X ⁻ ; R ³ are the same or different and each represents an alkyl group having 1 to 10 carbon atoms, and X ⁻ represents a counter anion).

The acylated cellulose used in the step [1] and having a total average degree of substitution of acyl groups of 0.9 to 2.8 is, for example, a hydroxyl group of cellulose obtained by reacting an acylating agent with a hydroxyl group of cellulose. Can be produced by obtaining a acylated triacylated cellulose and deacylating a part of the acyl groups in the obtained triacylated cellulose (see, for example, JP-A-56-59801).

As the cellulose, for example, wood pulp (softwood pulp, hardwood pulp) or cellulose derived from cotton linter pulp can be preferably used. These can be used individually by 1 type or in combination of 2 or more types. The pulp may contain a different component such as hemicellulose. Cellulose is preferably used in a state of being finely pulverized by, for example, performing a crushing treatment.

The total average degree of substitution of acyl groups in the acylated cellulose is 0.9 to 2.8, preferably 1.2 to 2.8, particularly preferably 1.5 to 2.5, and most preferably 1.8 to. It is 2.5. When an acylated cellulose having a total average degree of substitution of an acyl group in the above range is used as a reaction substrate, an acylated cellulose having a total average degree of substitution of the acyl group in the above range has a total average degree of substitution of the acyl group outside the above range. It has better solubility in solvents than acylated cellulose and can react with amino acids whose amino groups are protected in the state of being dissolved in organic solvents, thus improving the introduction rate of the group represented by formula (a). It is possible to produce a cellulose derivative that exhibits excellent metal adsorption power.

As the acylated cellulose, for example, commercially available products such as trade names “L-20”, “L-30”, “L-50”, “L-70” (above, acetyl cellulose, manufactured by Daicel Corp.) It can be used preferably.

The amino acid whose amino group is protected is represented by, for example, the following formula (3).
HOOC-R ¹ -NHY (3)
R ¹ in the formula (3) corresponds to R ¹ in the formula (a). Y is a protecting group for protecting an amino group, and examples thereof include a t-butoxycarbonyl group (Boc) and a 9-fluorenylmethyloxycarbonyl group (Fmoc). Among them, Fmoc is preferable as the amino-protecting group because it can be deprotected under mild conditions.

The amino acid before protecting the amino group is represented by the following formula (3′).
HOOC-R ¹ -NH ₂ (3')
R ¹ in the formula (3 ') in correspond to R ¹ in the formula (a). Examples of the amino acid (=the compound represented by the formula (3′)) before protecting the amino group include L-alanine, β-alanine, 4-aminobutyric acid, 5-aminopentanoic acid, and 7-aminoheptanoic acid. Etc. can be mentioned.

The reaction of the acylated cellulose with the amino group-protected amino acid is preferably carried out in the presence of a catalyst. Examples of the catalyst include triethylamine, pyridine, N,N-dimethyl-4-aminopyridine (DMAP) and the like. These can be used individually by 1 type or in combination of 2 or more types.

The amount of the catalyst used is, for example, about 0.01 to 1.0 mol with respect to 1 mol of the amino group-protected amino acid.

Further, the reaction is preferably performed in the presence of a condensing agent. Examples of the condensing agent include 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC-HCl), N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide and the like. it can. These can be used individually by 1 type or in combination of 2 or more types.

The amount of the condensing agent used is, for example, about 0.01 to 1.0 mol with respect to 1 mol of the amino group-protected amino acid.

The reaction is preferably carried out in the presence of a solvent. Examples of the solvent include aliphatic hydrocarbons such as hexane, heptane, and octane; alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; chloroform, dichloromethane, 1,2- Halogenated hydrocarbons such as dichloroethane; ethers such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate; N, N Examples include amides such as dimethylformamide and N,N-dimethylacetamide; nitriles such as acetonitrile, propionitrile and benzonitrile; alcohols such as methanol, ethanol, isopropyl alcohol, butanol; and dimethyl sulfoxide. These may be used alone or in combination of two or more.

The amount of the solvent used is, for example, about 0.5 to 30 times the total amount of the reaction substrate. If the amount of the solvent used exceeds the above range, the concentration of the reaction components tends to be low and the reaction rate tends to be low.

After the reaction, from the acylated cellulose (1-1), at least a part of the hydroxyl group (OH group) in the acylated cellulose is —OOC—R ¹ —NHY group (Y is an amino group-protecting group, A compound (1-2) substituted with Y in formula (3) is obtained.

The reaction for removing the amino-protecting group is carried out by removing the amino-protecting group (Y) in the compound (1-2) obtained through the above reaction, and at least a part of the hydroxyl group (OH group) in the acylated cellulose is is the reaction to obtain compound substituted by -OOC-R ¹ -NH ₂ group of (1-3). The reaction for removing the protecting group is preferably selected appropriately according to the type of the protecting group. For example, when Y is Fmoc, the protective group can be rapidly removed by reacting with a secondary amine such as pyridine. When Y is Boc, the protecting group can be removed rapidly by reacting with a strong acid such as trifluoroacetic acid.

In the step [2], the deprotected amino group, that is, the —OOC—R ¹ —NH ₂ group in the compound (1-3) obtained through the step [1] is added to the fourth compound in the presence of a sulfur compound. Cellulose of the present invention by reacting a primary ammonium salt (N ⁺ (R ³ ) ₄ X ⁻ ; R ³ are the same or different and each represents an alkyl group having 1 to 10 carbon atoms, and X ⁻ represents a counter anion). This is a step of obtaining a derivative.

Examples of the counter anion (X ⁻ ) in the quaternary ammonium salt include OH ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , F ⁻ , SO ₄ ²⁻ , BH ₄ ⁻ , BF ₄ ⁻ , PF ₆ ^{− and the} like. Are listed.

Examples of the quaternary ammonium salt include tetramethylammonium hydroxide and tetraethylammonium hydroxide.

The amount of the quaternary ammonium salt used is, for example, about 20 to 500 parts by weight with respect to 100 parts by weight of the compound (1-3).

Examples of the sulfur compound include carbon disulfide. The amount of the sulfur compound used is, for example, 100 parts by weight or more based on 100 parts by weight of the compound (1-3).

The reaction in step [2] is preferably performed in the presence of a solvent. Examples of the solvent include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; alcohols such as methanol, ethanol, 2-propanol, isopropyl alcohol and butanol; N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide and the like. Is mentioned. These can be used individually by 1 type or in combination of 2 or more types. The amount of the solvent used is, for example, about 0.5 to 30 times the total amount of the reaction substrate.

The reaction temperature in step [2] is, for example, about 10 to 100°C. The reaction time is, for example, about 1 to 24 hours. After completion of the reaction, the obtained reaction product can be separated and purified by a separation means such as filtration, concentration, distillation, extraction, crystallization, adsorption, recrystallization, column chromatography, or a combination of these.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 (Preparation of cellulose derivative (MI96))
In a nitrogen atmosphere, put acetyl cellulose (total average degree of substitution of acetyl group: 2.4, 6% viscosity: 53 mPa·s) (4.02 g, 15.3 mmol) in a two-necked eggplant flask and vacuum at 80° C. for 2 hours. Dried. After adding Fmoc-β-alanine (3.13 g, 10.1 mmol), dichloromethane (76 mL) and DMAP (1.23 g, 10.1 mmol) to this reaction vessel, the reaction system was cooled to 0°C.
After further adding EDC-HCl (1.93 g, 10.1 mmol), the reaction system was returned to room temperature and stirred overnight.
After the solvent was distilled off under reduced pressure, a DMSO/piperidine mixed solvent (DMSO/piperidine=80/20 (v/v), 76 mL) was added under nitrogen, and the mixture was stirred at room temperature for 2 hours. Methanol was added to the precipitated solid to wash it, and the solid was collected by centrifugation. Vacuum drying was performed to obtain a compound represented by the following formula (I) as a white solid (3.30 g, 71%). ^From the result of ¹ H-NMR measurement, the total average substitution degree of Fmoc-β-alanine was calculated to be 0.47.
¹ H-NMR (500MHz, DMSO-d6): δ5.61-3.26 (glucose ring, CH ₂ ), 2.92-2.70 (CH ₂ ), 2.21-1.69 (Acetyl)

In a mixed solution of toluene (320 mL), 2-propanol (32 mL), CS ₂ (64 mL) and 10% tetramethylammonium hydroxide (8 mL), the compound represented by the above formula (I) (2.04 g, 6. A solution of 67 mmol) dissolved in DMSO (32 mL) was slowly added dropwise, and the mixture was stirred at room temperature for 2 hours in the dark. The progress of the reaction was confirmed by the appearance of C═S absorption at 1489 cm ⁻¹ by IR measurement (see FIG. 1). Methanol was added to the precipitated solid to wash it, and the solid was collected by centrifugation. Vacuum drying gave MI96 (2.15 g, 82%) as a white solid. From the results of elemental analysis (S), the total average substitution degree of the dithiocarbamate group (-CS ₂ ^- ) of MI96 was calculated to be 0.13.

Example 2 (Preparation of cellulose derivative (MI98))
Under a nitrogen atmosphere, acetylcellulose (total average degree of substitution of acetyl groups: 1.7) (2.02 g, 8.63 mmol) was placed in a two-necked eggplant flask, and vacuum dried at 80° C. for 2 hours. Fmoc-β-alanine (3.80 g, 12.2 mmol), dichloromethane (42 mL) and DMAP (1.50 g, 12.3 mmol) were added to this reaction vessel, and then the reaction system was cooled to 0°C. After further adding EDC-HCl (2.34 g, 12.2 mmol), the reaction system was returned to room temperature and stirred overnight. After the solvent was distilled off under reduced pressure, a DMSO/piperidine mixed solvent (DMSO/piperidine=80/20 (v/v), 42 mL) was added under nitrogen, and the mixture was stirred at room temperature for 2 hours. Methanol was added to the precipitated solid to wash it, and the solid was collected by centrifugation. Vacuum drying was performed to obtain a compound represented by the following formula (II) as a white solid (2.16 g, 77%). ^From the result of ¹ H-NMR measurement, the total average substitution degree of Fmoc-β-alanine was calculated to be 1.01.
¹ H-NMR (500MHz, DMSO-d6): δ5.45-3.18 (glucose ring, CH ₂ ), 2.86-2.59 (CH ₂ ), 2.10-1.79 (Acetyl)

In a mixed solution of toluene (160 mL), 2-propanol (16 mL), CS ₂ (32 mL) and 10% tetramethylammonium hydroxide (4 mL), the compound represented by the above formula (II) (1.0 g, 3. A solution of 08 mmol) in DMSO (15.4 mL) was slowly added dropwise, and the mixture was stirred at room temperature for 2 hours under light shielding. The progress of the reaction was confirmed by the appearance of C=S absorption at 1489 cm ^-1 by IR measurement (see Fig. 2). Methanol was added to the precipitated solid to wash it, and the solid was collected by centrifugation. Vacuum drying gave MI98 (0.89 g, 56%) as a white solid. From the result of elemental analysis (S), the total average degree of substitution of the dithiocarbamate group (-CS ₂ ^- ) of MI98 was calculated to be 0.33.

Example 3 (Preparation of cellulose derivative (MI101))
Instead of acetyl cellulose (total average degree of substitution of acetyl groups: 2.4, 6% viscosity: 53 mPa·s), acetyl cellulose (total average degree of substitution of acetyl groups: 2.4, 6% viscosity: 132 mPa·s) MI101 was obtained as a white solid in the same manner as in Example 1 except that was used. From the result of elemental analysis (S), the total average degree of substitution of the dithiocarbamate group (—CS ₂ ^— ) of MI101 was calculated to be 0.13.

Example 4 (Preparation of cellulose derivative (MI77))
Under a nitrogen atmosphere, acetyl cellulose (total average degree of substitution of acetyl groups: 2.4) (5.02 g, 19.1 mmol) was placed in a two-necked eggplant flask, and vacuum dried at 80° C. for 2 hours. After adding Boc-L-alanine (3.24 g, 17.1 mmol), DMSO (95 mL), and DMAP (2.10 g, 17.1 mmol) to this reaction container, the reaction system was cooled to 0°C. After further adding EDC-HCl (3.32 g, 17.3 mmol), the reaction system was returned to room temperature and stirred overnight. The solid precipitated by reprecipitation in a MeOH/H ₂ O (80/20, v/v) mixed solvent was recovered by centrifugation. After vacuum drying at 60° C., a compound represented by the following formula (III) was obtained as a white solid (5.60 g, 80%). ^From the result of ¹ H-NMR measurement, the total average substitution degree of Boc-L-alanine was calculated to be 0.30.
¹ H-NMR(500MHz,DMSO-d6)δ7.23-6.59 (NH), 5.56-3.35 (glucose ring, CH), 2.14-1.75 (Acetyl), 1.47-1.35 (Boc), 1.35-1.04 (CH ₃ )

Under a nitrogen atmosphere, the compound (2.26 g, 6.18 mmol) represented by the above formula (III), dichloromethane (64 mL) and trifluoroacetic acid (1.48 mL, 19.3 mmol) were placed in a two-necked eggplant flask, and the mixture was kept at room temperature. Stir overnight. After removing the supernatant of the gelled reaction system, the gel was dissolved in MeOH and reprecipitated in a saturated aqueous sodium hydrogen carbonate solution. The precipitated solid was collected by centrifugation and vacuum dried to obtain a compound represented by the following formula (IV) as a white solid (1.95 g, 103%).
¹ H-NMR (500 MHz, DMSO-d6) δ7.22-6.53 (NH ₂ ), 5.73-3.28 (glucose ring, CH), 2.28-1.64 (Acetyl), 1.35-1.01 (CH ₃ ).

To a mixed solution of toluene (160 mL), 2-propanol (16 mL), CS ₂ (32 mL), and 10% tetramethylammonium hydroxide (4 mL), a compound (1) represented by the above formula (IV) crushed finely in a mortar. (0.000 g, 3.27 mmol) was added, and the mixture was stirred at room temperature for 2 hours in the dark. The progress of the reaction was confirmed by the appearance of C=S absorption at 1489 cm ^-1 by IR measurement (see Fig. 3). Methanol was added to wash the solid in the reaction system, and the solid was collected by centrifugation. It was dried under vacuum to give MI77 (1.00 g, 87%) as a white solid.

Example 5 (Preparation of cellulose derivative (MI64))
Under a nitrogen atmosphere, acetyl cellulose (total average degree of substitution of acetyl groups: 1.7) (3.01 g, 12.9 mmol) was placed in a two-necked eggplant flask, and vacuum dried at 80° C. for 2 hours. Boc-L-alanine (4.71 g, 24.9 mmol), DMSO (64 mL) and DMAP (3.07 g, 25.1 mmol) were added to this reaction vessel, and the reaction system was cooled to 0°C. Furthermore, after adding EDC-HCl (4.77 g, 24.9 mmol), the reaction system was returned to room temperature and stirred overnight. The solid precipitated by reprecipitation in a MeOH/H ₂ O (70/30, v/v) mixed solvent was recovered by centrifugation. After vacuum drying at a temperature of 60° C., a compound represented by the following formula (V) was obtained as a white solid (4.13 g, 71%). ^From the result of ¹ H-NMR, the substitution degree of Boc-L-alanine was calculated to be 0.91.
¹ H-NMR(500MHz,DMSO-d6)δ7.31-6.16 (NH), 5.39-3.38 (glucose ring, CH), 2.24-1.66 (Acetyl), 1.48-1.35 (Boc), 1.34-1.07 (CH ₃ )

Under a nitrogen atmosphere, the compound (2.00 g, 4.40 mmol) represented by the above formula (V), dichloromethane (44 mL) and trifluoroacetic acid (2.17 mL, 28.4 mmol) were added to a two-necked eggplant flask, and the mixture was cooled to room temperature. Stir overnight. After removing the supernatant of the gelled reaction system, the gel was dissolved in MeOH and reprecipitated in a saturated aqueous sodium hydrogen carbonate solution. The precipitated solid was collected by centrifugation and vacuum dried to obtain a compound represented by the following formula (VI) as a white solid (0.593 g, 41%).
¹ H-NMR(500MHz,DMSO-d6)δ7.96-7.66 (NH), 5.26-3.33 (glucose ring, CH), 2.26-1.70 (Acetyl), 1.33-1.01 (CH ₃ )

Toluene (64 mL), 2-propanol (6.4 mL), CS ₂ (12.8 mL), 10% tetramethylammonium hydroxide (1.60 mL) in a mixed solution was crushed finely in a mortar with the above formula (VI). The compound shown (0.378 g, 1.16 mmol) was added, and the mixture was stirred at room temperature for 2 hours under light shielding. The progress of the reaction was confirmed by the appearance of C═S absorption at 1489 cm ⁻¹ by IR measurement (see FIG. 4). Methanol was added to wash the solid in the reaction system, and the solid was collected by centrifugation. Vacuum drying gave MI64 (0.350 g, 72%) as a white solid.

Evaluation [1] The pH dependency of the metal adsorption force of the cellulose derivative was evaluated by the following method.
1. Preparation of sample solution and buffer solution Diarsenic trioxide (As(III)) (special grade; manufactured by Wako Pure Chemical Industries, Ltd.), disodium hydrogen arsenate heptahydrate (As(V)) (special grade; A sample solution was prepared by dissolving Kako Pure Chemical Industries, Ltd.) and sodium cacodylate (DMA(V)) (for electron microscope; Nacalai Tesque, Inc.) in 0.01M NaOH solution. Regarding the buffer solution, the following reagents were dissolved in purified water to prepare a 0.1 M buffer solution, and a small amount of 1 M nitric acid or 1 M NaOH solution was added to adjust the pH.

2. Preparation of solid phase column and solid phase extraction About 1 g of the cellulose derivative (MI96) obtained in Example 1 was transferred to a mortar and ground with a pestle until the particle size became about 2 mm or less. The place that was hard and could not be ground with a pestle was cut with scissors.
0.050 g of the crushed cellulose derivative (MI96) was weighed and filled in a Teflon (registered trademark) tube having an inner diameter of 2 mm and a length of 3 cm, and Teflon (registered trademark) wool was packed at both ends to prepare a solid phase column. ..
A silicon tube having an inner diameter of 2 mm was connected to the obtained solid phase column, and each solution was sent by a tube pump (Perista Pump, manufactured by As One Co., Ltd.). First, 10 mL of 0.1 M buffer solution was sent to the solid phase column to adjust the pH in the column, and then 5 mL of 10-5 M sample solution was passed at a flow rate of 5 mL/min to perform solid phase extraction of arsenic. 1 mL of 1M HCl was added to 5 mL of the eluate and the mixture was stored. The metal concentration in each eluate was quantified by ICP-OES (iCAP6300DUO manufactured by Thermo Fisher Scientific Co., Ltd.) to determine the amount of adsorption by the solid phase. Results are shown in FIG. From FIG. 5, it was found that the cellulose derivative of the present invention can exhibit particularly excellent metal adsorption force in the pH range of 1 to 7.

[2] The arsenic adsorption power of each cellulose derivative was evaluated by the following method.
Diarsenic trioxide (As(III)) (special grade; manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in a 0.01 M NaOH solution to prepare a sample solution.
Using the cellulose derivative obtained in the example, a solid phase column was prepared by the same method as above, and 5 mL of the sample solution was passed through the solid phase column at 5 mL/min to adsorb arsenic by the solid phase. The amount was determined (however, the pH in the column was 2.5 or 3). Results are shown in FIG. From FIG. 6, it was found that the longer the carbon chain between the cellulose main chain skeleton and the dithiocarbamate group, the better the arsenic adsorption power.

[3] The adsorption power of each metal of the cellulose derivative was evaluated by the following method.
As a sample solution, 10 ⁻⁵ M As(III), Pb(II), Cd(II)/0.1 M MES buffer solution (pH 3) was prepared.
1. The cellulose derivative (MI64) obtained in Example 5, acetyl cellulose (total average degree of substitution of acetyl groups 1.7) (=AC(1.7)), and acetyl cellulose (total average degree of substitution of acetyl groups 2. 4) (=AC(2.4)) was used to prepare a solid-phase column in the same manner as above, and 5 mL of the sample solution was passed through the solid-phase column at 5 mL/min to obtain arsenic by solid phase. The adsorbed amounts of cadmium, cadmium and lead were obtained. The results are shown in Fig. 7. From FIG. 7, it was found that the cellulose derivative of the present invention has a remarkably excellent adsorption power for arsenic, cadmium, and lead as compared with acetyl cellulose.

Claims (8)

A cellulose derivative having a repeating unit represented by the following formula (1).

[In the formula, R is the same or different and is a hydrogen atom, a group represented by the following formula (a), or a group represented by the following formula (b). Among all Rs contained in the cellulose derivative, at least one is a group represented by the following formula (a), and at least one is a group represented by the following formula (b)]

(In the formula, R ¹ represents a single bond or an alkylene group having 1 to 10 carbon atoms, R ² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ³ and R ⁴ are the same or different, (Indicates an alkyl group having 1 to 10 carbon atoms) The cellulose derivative according to claim 1, wherein the molar ratio (former/latter) of the group represented by formula (a) and the group represented by formula (b) is 1/99 to 99/1. The cellulose derivative according to claim 1, wherein the group represented by the formula (a) is a group represented by the following formula (a-1).

(In formula, R< ³ > is the same or different and shows a C1-C10 alkyl group, R< ⁵ > is the same or different and shows a hydrogen atom or a C1-C3 alkyl group. Indicates an integer of 3) The cellulose derivative according to any one of claims 1 to 3, wherein the group represented by the formula (b) is an acetyl group. The total average substitution degree of the group represented by the formula (a) is 0.2 to 2.1, and the total average substitution degree of the group represented by the formula (b) is 0.9 to 2.8. The cellulose derivative according to any one of claims 1 to 4. The manufacturing method of a cellulose derivative which obtains the cellulose derivative according to any one of claims 1 to 5 through the following steps.
[1] An amino acid having an amino group protected is reacted with a hydroxyl group of acylated cellulose (total average degree of substitution of acyl groups: 0.9 to 2.8), and then the amino group protecting group is removed [2 ] In the presence of a sulfur compound, a deprotected amino group has a quaternary ammonium salt (N ⁺ (R ³ ) ₄ X ⁻ ; R ³ is the same or different and represents an alkyl group having 1 to 10 carbon atoms, and X ⁻ Represents a counter anion) A metal adsorbent, comprising the cellulose derivative according to claim 1. A metal removing method using the cellulose derivative according to claim 1.

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