JP2020019845A - Cellulose derivative, heavy metal removal material containing the same, and heavy metal removing method using the same - Google Patents

Abstract

To provide a cellulose derivative that has excellent adsorption of heavy metals and can selectively adsorb and recover heavy metals.SOLUTION: The present invention provides a cellulose derivative illustrated by the formula (MI198).SELECTED DRAWING: None

Description

  The present invention relates to a novel cellulose derivative, a method for producing the same, a heavy metal removing material containing the cellulose derivative, and a heavy 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 pharmaceuticals, insecticides, rodenticides, preservatives, high-tech industrial materials, and the like. For this reason, the heavy metals may be dissolved in the stratum, the ocean, rivers, well water, and the like, but it is known that even a trace amount of them may cause environmental pollution. Therefore, a method of efficiently collecting and removing the heavy metal from soil, seawater, industrial wastewater, mine drainage, and the like contaminated with the heavy metal is desired.

  Patent Literature 1 discloses that a cellulose-based adsorbent obtained by introducing a graft chain on the surface of a cellulose-based substrate and binding a chelate-forming group or an ion-exchange group to the introduced graft chain is easily compatible with water, and contains boron and germanium. It is described that it has excellent adsorption power for semimetals or heavy metals such as arsenic. The amount of the chelate-forming group or the ion-exchange group that exerts the metal adsorbing power depends on the rate of graft chain introduction, and the lower the rate of graft chain introduction, the lower the rate of chelate formation that effectively acts on the metal adsorption. It is described that it is not possible to secure a sufficient amount of a group or an ion exchange group. However, since the cellulosic base material has low solubility in an organic solvent, it is very difficult to efficiently introduce the graft chain, and the introduction of the graft chain can be performed only by a method using an expensive apparatus such as a radiation graft method. However, there has been a problem that the rate cannot be improved and the cost increases.

  Patent Document 2 discloses that acylated cellulose has excellent solubility in an organic solvent, a dithiocarbamate group can be efficiently and inexpensively introduced, and a cellulose derivative having a dithiocarbamate group and an acyl group obtained is a metal derivative. It is described as being useful as a metal removing material having excellent adsorption power.

JP 2009-13204 A JP, 2018-83882, A

  Although acylated cellulose has excellent solubility in organic solvents, it can efficiently introduce a dithiocarbamate group.However, since the degree of substitution of the group containing the dithiocarbamate group is limited, it is necessary to further improve the adsorption amount of heavy metals. There were challenges. In addition, metal ions other than heavy metals, such as calcium, often coexist in soil, seawater, industrial effluent, mine drainage, etc., which are contaminated with heavy metals. Is likely to decrease.

  Thus, the development of a metal removing material that is excellent in the amount of heavy metal adsorbed and that can selectively adsorb heavy metal is desired.

Accordingly, an object of the present invention is to provide a novel cellulose derivative which has excellent heavy metal adsorption power and can selectively adsorb heavy metals, and a method for producing the same.
Another object of the present invention is to provide a heavy metal removing material which has an excellent ability to adsorb heavy metals and can selectively adsorb heavy metals.
It is another object of the present invention to provide a method for selectively adsorbing and recovering heavy metals.

  The present inventors have conducted intensive studies in order to solve the above problems, and as a result, have found a method capable of efficiently and inexpensively introducing a dithiocarbamate group into cellulose. In addition, they have found that a cellulose derivative having a dithiocarbamate group bonded via a specific linker structure has excellent heavy metal adsorption power and is useful as a heavy metal removing material capable of selectively adsorbing heavy metals. 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、又は下記式（ａ）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）で表される基である］

（式中、Ｒ¹は炭素数１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).

Wherein R is the same or different and is a hydrogen atom or a group represented by the following formula (a). At least one of all Rs contained in the cellulose derivative is a group represented by the following formula (a)]

(Wherein, R ¹ represents an alkylene group having 1 carbon atom, R ² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. R ³ is the same or different and has an alkyl group having 1 to 10 carbon atoms) Is shown.)

（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 the formula, R ³ is the same or different and represents an alkyl group having 1 to 10 carbon atoms.)

  The present invention also provides the above cellulose derivative, wherein the total average degree of substitution of the group represented by the formula (a) is from 0.1 to 2.95.

The present invention also provides a method for producing a cellulose derivative, wherein the cellulose derivative is obtained through the following steps.
[1] Cellulose hydroxyl group is reacted with an amino group-protected amino acid, and then the amino-protecting group is removed. [2] A quaternary ammonium salt is added to the deprotected amino group in the presence of a sulfur compound. 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 present invention also provides a heavy metal adsorbent containing the above-mentioned cellulose derivative.

  The present invention also provides a method for removing heavy metals using the above-mentioned cellulose derivative.

  The cellulose derivative of the present invention has a high adsorption amount of heavy metals (for example, heavy metals such as arsenic, cadmium, and lead), and can selectively adsorb and recover heavy metals. Further, 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 heavy metal removing material, and is suitably used for purifying soil and seawater contaminated with heavy metals, industrial wastewater containing the above metals, mine wastewater, hot spring water, and the like. can do.

FIG. 2 is a graph showing the pH dependence of heavy metal adsorption power of the cellulose derivative (MI203) obtained in Example 1. FIG. 2 is a view showing the metal adsorption amount of the cellulose derivative (MI203) obtained in Example 1. "None" indicates the adsorption amount of only arsenic without calcium. “Ca ²⁺ ” indicates the amount of metal adsorbed in the presence of arsenic and calcium. The left column indicates the amount of arsenic adsorbed, and the right column indicates the amount of calcium adsorbed. FIG. 4 is a view showing the metal adsorption amount of the cellulose derivative (MI198) obtained in Comparative Example 1. "None" indicates the adsorption amount of only arsenic without calcium. “Ca ²⁺ ” indicates the amount of metal adsorbed in the presence of arsenic and calcium. The left column indicates the amount of arsenic adsorbed, and the right column indicates the amount of calcium adsorbed.

［式中、Ｒは、同一又は異なって、水素原子、又は下記式（ａ）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）で表される基である］

（式中、Ｒ¹は炭素数１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).

Wherein R is the same or different and is a hydrogen atom or a group represented by the following formula (a). At least one of all Rs contained in the cellulose derivative having the repeating unit represented by the formula (1) is a group represented by the following formula (a)]

(Wherein, R ¹ represents an alkylene group having 1 carbon atom, R ² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. R ³ is the same or different and has an alkyl group having 1 to 10 carbon atoms) Indicates)

Examples of the alkylene group having 1 carbon atom in R ¹ include a methylene group. Since R ¹ is an alkylene group having 1 carbon atom, particularly a methylene group, the amount of heavy metal adsorbed is surprisingly improved, and in the presence of a metal ion other than heavy metal (eg, calcium ion). The adsorption selectivity of heavy metal ions (for example, arsenic (III) ions) also tends to be improved.
Although the cause is not clear, when the carbon number of R ¹ is larger than 2, the S atom and a divalent metal ion such as Ca form a coordination bond, and further form a coordination bond with a hydroxyl group remaining in cellulose. It is thought that a stable structure is formed and the heavy metal adsorption function of the S atom is hindered. At this time, if the carbon number of R ¹ is 1, it is considered that a stable structure is not formed by coordination bond with the cation and the hydroxyl group remaining in cellulose. However, this is only an estimation, and the present invention is not limited to such a mechanism.

Examples of the alkyl group having 1 to 10 carbon atoms in R ² and R ³ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, and the like. And a straight-chain or branched-chain alkyl group.

R ² is preferably a hydrogen atom. R ³ is preferably an alkyl group having 1 to 3 carbon atoms.

As the group represented by the formula (a), a group represented by the following formula (a-1) (in the formula, R ³ is the same as above) is preferable.

The group represented by the formula (a) is more preferably a group represented by the following formula (a-1 ′).

  The total average degree of substitution of the group represented by the formula (a) (preferably a group represented by the formula (a-1), more preferably a group represented by the formula (a-1 ′)) (constituting cellulose) (The total average degree of substitution of the groups substituted at positions 2, 3 and 6 of the glucose unit) is, for example, 0.1 to 2.95, preferably 0.2 to 2.9, and particularly preferably 0.3 to 2 .9. It is preferable that the cellulose derivative contains the group represented by the formula (a) in the above range in that excellent heavy metal adsorption power can be exhibited.

  The cellulose derivative of the present invention has an excellent heavy metal adsorption power (the adsorption amount of heavy metal is, for example, 1 μmol / g or more, preferably 3 μmol / g or more, particularly preferably 4 μmol / g or more). In particular, it has excellent adsorption capacity for heavy metals such as As (III), Cd (II), and Pb (II). The adsorption amount of As (III) is, for example, 1 μmol / g or more, the adsorption amount of Cd (II) is, for example, 1 μmol / g or more, and the adsorption amount of Pb (II) is, for example, 1 μmol / g or more.

  The cellulose derivative of the present invention has excellent adsorption selectivity for heavy metals. Adsorption selectivity of heavy metal ion (for example, arsenic (III) ion) in the coexistence of metal ion other than heavy metal (for example, calcium ion) of the cellulose derivative of the present invention (adsorption amount of heavy metal ion / adsorption amount of metal ion other than heavy metal; mole) The ratio) is not particularly limited, but is preferably 3.5 times or more, more preferably 4.0 times or more, and particularly preferably 4.5 times or more.

  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 oval spherical shape, etc.), a polyhedral shape, a rod shape ( Columnar, prismatic, etc.), scaly, irregular, and the like.

  Since the cellulose derivative of the present invention has excellent adsorption power and adsorption selectivity for heavy metals as described above, it can be suitably used, for example, as a heavy metal adsorbent.

  The heavy metal adsorbent containing the cellulose derivative of the present invention (or the heavy metal adsorbent composed of the cellulose derivative of the present invention) includes, for example, heavy metals (particularly, heavy metals such as As (III), Cd (II), and Pb (II)). It can be suitably used for purifying soil, seawater, industrial wastewater containing the heavy metals, mine wastewater, hot spring water, etc.

  The method for removing heavy metals of the present invention, that is, soil or seawater contaminated with heavy metals (particularly heavy metals such as As (III), Cd (II) and Pb (II)) using the cellulose derivative of the present invention as a heavy metal adsorbent. The method of adsorbing and removing heavy metals from industrial wastewater containing the heavy metals, mine wastewater, hot spring water and the like is not particularly limited.For example, a cellulose derivative of the present invention is filled in a column or the like, and the column is filled therein. Examples of the method 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 stirring the mixture. In particular, when the cellulose derivative of the present invention shows solubility in an organic solvent, it can be used as a homogeneous heavy metal adsorbent (that is, a substance exhibiting an action of adsorbing and removing heavy metals in a state of being dissolved in industrial wastewater or the like). .

  In the heavy metal removal method of the present invention, adjusting the pH of the cellulose derivative to, for example, 1 to 9 (especially 1 to 7) can further improve the adsorption power of heavy metals and efficiently remove heavy metals. It is preferable in that it can be performed. The pH of the cellulose derivative can be adjusted using a commonly used pH adjuster (acid such as nitric acid or alkali such as sodium hydroxide).

  Further, the heavy metal can be easily recovered by firing the cellulose derivative having the heavy metal adsorbed thereon, and the recovered heavy 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] Cellulose hydroxyl group is reacted with an amino group-protected amino acid, and then the amino-protecting group is removed. [2] A quaternary ammonium salt is added to the deprotected amino group in the presence of a sulfur compound. 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.

  As the cellulose used in the step [1], for example, wood pulp (softwood pulp, hardwood pulp), cellulose derived from cotton linter pulp, or the like can be suitably used. These can be used alone or in combination of two or more. The pulp may contain a different component such as hemicellulose. The cellulose is preferably used in a finely pulverized state, for example, by subjecting it to a crushing treatment.

The amino acid whose amino group is protected is represented, for example, by 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). As the amino-protecting group, Fmoc is particularly preferred 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 before protecting the amino group (= the compound represented by the formula (3 ′)) include glycine and the like.

  The reaction between the cellulose and the amino acid whose amino group is protected is preferably performed 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 alone or in combination of two or more.

  The amount of the catalyst to be used is, for example, about 0.01 to 1.0 mol per 1 mol of the amino acid in which the amino group is protected.

  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 alone or in combination of two or more.

  The amount of the condensing agent to be used is, for example, about 0.01 to 1.0 mol per 1 mol of the amino acid in which the amino group is protected.

  The reaction is preferably performed 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 and dioxane; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters such as methyl acetate, ethyl acetate, isopropyl acetate and butyl acetate; Amides such as dimethylformamide and N, N-dimethylacetamide; nitriles such as acetonitrile, propionitrile and benzonitrile; alcohols such as methanol, ethanol, isopropyl alcohol and butanol; Sulfoxide, and the like. These can be used alone or in combination of two or more.

  In particular, it is preferable to use a mixture of dimethylacetamide and lithium chloride as a solvent. However, this reaction does not require the raw material cellulose to be dissolved to form a uniform solution, but can be allowed to proceed as a slurry in which the solvent and the cellulose are suspended. Therefore, it is not necessary to use a large amount of expensive lithium chloride necessary for dissolving ordinary cellulose. The concentration of lithium chloride in the organic solvent is not particularly limited as long as cellulose is dissolved, but is, for example, about 0.5 to 30% by weight.

  The amount of the solvent used is, for example, about 0.5 to 30 times the total amount of the reaction substrates. When the amount of the solvent used exceeds the above range, the concentration of the reaction component tends to decrease, and the reaction rate tends to decrease.

Through the above reaction, at least a part of the hydroxyl group (OH group) in the cellulose is converted from the cellulose (1-1) into a —OOC—R ¹ —NHY group (Y is a protecting group for an amino group, and a compound represented by the formula (3) (Same as Y in the formula (1)).

In the reaction for removing the amino-protecting group, the amino-protecting group (Y) in the compound (1-2) obtained through the above-mentioned reaction is removed, and at least a part of the hydroxyl group (OH group) in the cellulose is- This is a reaction for obtaining a compound (1-3) substituted with an OOC-R ¹ -NH ₂ group. The reaction for removing the protecting group is preferably appropriately selected according to the type of the protecting group. For example, when Y is Fmoc, the protecting group can be quickly removed by reacting a secondary amine such as pyridine. When Y is Boc, the protecting group can be promptly removed 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 group in the presence of a sulfur compound. grade ammonium _{^{(N + (R 3) 4}} X -; R 3 are the same or different and each represents an alkyl group having 1 to 10 carbon atoms, X ^- represents a counter anion) were reacted to cellulose of the present invention 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. Is mentioned.

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

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

  Examples of the sulfur compound include carbon disulfide. The amount of the sulfur compound to be 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 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 substrates.

  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 thereof.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 (Preparation of cellulose derivative (MI203))
Under a nitrogen atmosphere, cellulose (Wako Pure Chemical Industries, Ltd.) (3.00 g, 18.62 mmol) and a solution of lithium chloride in N, N-dimethylacetamide (62.0 mL) were placed in a two-necked eggplant flask. After adding Boc-glycine (6.52 g, 37.24 mmol) and DMAP (4.55 g, 37.24 mmol) to the reaction vessel, the reaction system was cooled to 0 ° C. After addition of EDC-HCl (7.14 g, 37.24 mmol), the reaction system was returned to room temperature and stirred overnight. The solid precipitated by reprecipitation in a mixed solvent of MeOH / H ₂ O (70/30, v / v) was collected by centrifugation. The mixture was heated at 60 ° C. and dried under vacuum to obtain a compound represented by the following formula (I) as a white solid (7.22 g, 69.0%). ^From the result of ¹ H-NMR, the degree of substitution of Boc-glycine was calculated to be 2.55.
¹ H-NMR (500MHz, DMSO-d ₆ ) δ 7.23-6.59 (NH), 5.56-3.35 (glucose ring, CH), 1.47-1.35 (Boc), 1.35-1.04 (CH ₂ )

Under a nitrogen atmosphere, a compound represented by the above formula (I) (2.00 g, 3.56 mmol), dichloromethane (45.0 mL), and trifluoroacetic acid (1.76 mL, 22.97 mmol) were added to a two-necked eggplant flask. And stirred at room temperature 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 dried under vacuum to obtain a compound represented by the following formula (II) as a white solid (1.08 g, 51.0%).
¹ H-NMR (500MHz, DMSO-d ₆ ) δ 7.22-6.53 (NH ₂ ), 5.73-3.28 (glucose ring, CH), 1.35-1.01 (CH ₂ )

In a mixed solution of dimethyl sulfoxide (93.0 mL), CS ₂ (16.93 mL), and 10% tetramethylammonium hydroxide (2.12 mL), the compound represented by the formula (II), .50 g, 0.84 mmol) and 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. The solid in the reaction system was washed by adding methanol, and collected by centrifugation. Vacuum drying provided MI203 (0.39 g, 68.0%) as a white solid. From the results of the elemental analysis (S), the total average degree of substitution of the dithiocarbamate group (—CS ₂ ⁻ ) of MI203 was calculated to be 2.55.

Comparative Example 1 (Preparation of cellulose derivative (MI198))
Under a nitrogen atmosphere, cellulose (Wako Pure Chemical Industries, Ltd.) (3.00 g, 18.61 mmol) and an N, N-dimethylacetamide solution of lithium chloride (64.0 mL) were placed in a two-necked eggplant flask. After adding Boc-β-alanine (7.05 g, 37.24 mmol) and DMAP (4.55 g, 37.24 mmol) to the reaction vessel, the reaction system was cooled to 0 ° C. After addition of EDC-HCl (7.14 g, 37.24 mmol), the reaction system was returned to room temperature and stirred overnight. The solid precipitated by reprecipitation in a mixed solvent of MeOH / H ₂ O (70/30, v / v) was collected by centrifugation. The mixture was heated at 60 ° C. and dried under vacuum to obtain a compound represented by the following formula (III) as a white solid (8.94 g, 79.0%). ^From the result of ¹ H-NMR, the degree of substitution for Boc-β-alanine was calculated to be 2.61.
¹ H-NMR (500MHz, DMSO-d ₆ ) δ 7.23-6.59 (NH), 5.56-3.35 (glucose ring, CH), 1.47-1.35 (Boc), 1.35-1.04 (CH ₃ )

Under a nitrogen atmosphere, the compound represented by the above formula (III) (2.00 g, 3.29 mmol), dichloromethane (45.0 mL), and trifluoroacetic acid (1.62 mL, 21.23 mmol) were added to a two-necked eggplant flask. And stirred at room temperature 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 dried under vacuum to obtain a compound represented by the following formula (IV) as a white solid (1.25 g, 59.0%).
¹ H-NMR (500MHz, DMSO-d ₆ ) δ 7.22-6.53 (NH ₂ ), 5.73-3.28 (glucose ring, CH), 1.35-1.01 (CH ₃ )

Compound (0.50 g) represented by the above formula (IV) which was finely crushed with a mortar in a mixed solution of dimethyl sulfoxide (92 mL), CS ₂ (16.93 mL), and 10% tetramethylammonium hydroxide (2.12 mL). , 0.78 mmol) and 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. The solid in the reaction system was washed by adding methanol, and collected by centrifugation. Drying in vacuo gave MI198 (0.42 g, 73.0%) as a white solid. From the result of the elemental analysis (S), the total average degree of substitution of the dithiocarbamate group (—CS ₂ ⁻ ) of MI198 was calculated to be 2.61.

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

2. Preparation of Solid Phase Column and Solid Phase Extraction Approximately 1 g of the cellulose derivative (MI203) obtained in Example 1 was transferred to a mortar and ground with a pestle so that the particle size became 212 to 600 μm. Hard and pestle-free parts were cut with scissors.
0.010 g of the crushed cellulose derivative (MI203) was weighed out, filled in a Teflon (registered trademark) tube having an inner diameter of 2 mm and a length of 3 cm, and filled with Teflon (registered trademark) wool 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 fed by a tube pump (Peristalpump, manufactured by AS ONE Corporation). First, 20 mL of a 0.1 M buffer solution was sent to a solid phase column to adjust the pH in the column, and then 5 mL of a 10 μM sample solution was passed at a flow rate of 5 mL / min to perform solid phase extraction of arsenic. 1 mL of 1 M HCl was added to 5 mL of the eluate and stored. The metal concentration in each eluate was quantified using ICP-AES (manufactured by Thermo Fisher Scientific Co., Ltd., iCAP6300DUO), and the amount of adsorption by the solid phase was determined. The results are shown in FIG. From FIG. 1, it was found that the cellulose derivative (MI203) of the present invention can exhibit particularly excellent heavy metal adsorption power, particularly high adsorption power for As (III) ions in the pH range of 1 to 7.

[2] The arsenic adsorption power of the cellulose derivative and the adsorption selectivity in the presence of arsenic and calcium were evaluated by the following methods.
Arsenic trioxide (As (III)) (special grade; manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in a 0.01 M NaOH solution, and the pH was adjusted with a 0.1 M MES buffer (pH 3.0). A sample solution (pH 3.0) containing 10 μM As (III) was prepared. Also, arsenic trioxide (As (III)) (special grade; manufactured by Wako Pure Chemical Industries, Ltd.) and calcium hydroxide (special grade; manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved in a 0.01 M NaOH solution. The pH was adjusted with 0.1 M MES buffer (pH 3.0) to prepare a sample solution (pH 3.0) containing 10 μM As (III) and 10 μM Ca ²⁺ .
Using the cellulose derivative obtained in Example 1 (MI203), a solid phase column was prepared in the same manner as described above. Further, a solid phase column was prepared in the same manner as described above, except that 0.020 g of the cellulose derivative obtained in Comparative Example 1 (MI198) was used. After adjusting the pH in the column by sending 20 mL of a 0.1 M MES buffer solution to each solid phase column, 5 mL of the sample solution was passed at 5 mL / min to perform solid phase extraction of arsenic and calcium. . 1 mL of 1 M HCl was added to 5 mL of the eluate and stored. The metal concentration in each eluate was quantified by ICP-AES (manufactured by Thermo Fisher Scientific KK, iCAP6300DUO), and the arsenic adsorption amount and calcium adsorption amount by the solid phase were determined. The results are shown in FIG. 2 (Example 1) and FIG. 3 (Comparative Example 1). 2 and 3, the cellulose derivative (R ¹ = methylene group) obtained in Example 1 (MI203) is different from the cellulose derivative (R ¹ = ethylene group) obtained in Comparative Example 1 (MI198) The amount of adsorption to arsenic has improved dramatically. Further, in the cellulose derivative (R ¹ = ethylene group) obtained in Comparative Example 1 (MI198), the amount of arsenic adsorbed decreases when calcium coexists, but the cellulose derivative (R1) obtained in Example 1 (MI203) is reduced. ¹ = methylene group) showed high adsorption selectivity for arsenic without decreasing the arsenic adsorption amount even in the presence of calcium.

Claims (6)

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

Wherein R is the same or different and is a hydrogen atom or a group represented by the following formula (a). At least one of all Rs contained in the cellulose derivative is a group represented by the following formula (a)]

(Wherein, R ¹ represents an alkylene group having 1 carbon atom, R ² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. R ³ is the same or different and has an alkyl group having 1 to 10 carbon atoms) Indicates) 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 the formula, R ³ is the same or different and represents an alkyl group having 1 to 10 carbon atoms.)   The cellulose derivative according to claim 1 or 2, wherein the total degree of substitution of the group represented by the formula (a) is from 0.1 to 2.95. A method for producing a cellulose derivative, wherein the cellulose derivative according to any one of claims 1 to 3 is obtained through the following steps.
[1] Cellulose hydroxyl group is reacted with an amino group-protected amino acid, and then the amino-protecting group is removed. [2] A quaternary ammonium salt is added to the deprotected amino group in the presence of a sulfur compound. 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.   A heavy metal adsorbent comprising the cellulose derivative according to claim 1.   A method for removing heavy metals using the cellulose derivative according to claim 1.

Images