Cellulose derivative and boron adsorbent including said cellulose derivative

Abstract

Provided is a cellulose derivative in which an amount of a chelating adsorption group introduced is large and which has wettability and is capable of quickly and efficiently recovering boron.　The cellulose derivative of the present disclosure has a repeating unit represented by formula (I-1).　In formula (I-1), each Ra is a hydroxy group or a group represented by formula (a). Provided that at least one of all Ra's included in the cellulose derivative is a group represented by formula (a). In formula (a), x1 to X3 are the same or different and are each a group forming a complex with a hard acid according to the HSAB theory.

Description

Cellulose derivative and boron adsorbent containing said cellulose derivative

[0001] The present disclosure relates to a novel cellulose derivative, a method for producing the cellulose derivative, a boron adsorbent containing the cellulose derivative, and a method for recovering boron using the cellulose derivative.

[0002] Boron is used as a raw material for insulation and glass fiber, as well as in the manufacture of specialty glass for liquid crystal displays, etc. Therefore, boron is widely present in rivers and seawater via industrial wastewater.

[0003] Boron is an essential trace nutrient for plants, but it is known that large amounts of boron in agricultural water inhibit plant growth, so there is a need to remove boron from the water.

[0004] Patent Document 1 describes that by introducing chloromethyl groups into a polystyrene-divinylbenzene crosslinked copolymer to produce a chloromethylated polymer, reacting the produced polymer with N-methylglucamine to introduce boron chelating adsorption groups, and further reacting the polymer with a low molecular weight alkylamine to introduce hydrophilic groups, the resulting aromatic crosslinked polymer can be packed into a column or the like and used as a solid-phase adsorbent, whereby boron dissolved in water can be recovered by chelating adsorption.

[0005] Japanese Patent Application Laid-Open No. 2005-239961

[0006] However, the aromatic crosslinked polymer has low wettability and is poorly compatible with the boron aqueous solution, making it take too long to recover the boron. In the examples of Patent Document 1, the aromatic crosslinked polymer is immersed in the boron solution for 72 hours to recover the boron in the solution. Furthermore, increasing the introduction rate of hydrophilic groups improves wettability, but the introduction amount of chelating adsorption groups decreases accordingly, making it difficult to increase wettability while maintaining a high introduction amount of chelating adsorption groups.

[0007] Therefore, an object of the present disclosure is to provide a cellulose derivative having a high amount of chelating adsorption groups introduced, wettability, and capable of recovering boron quickly and efficiently. Another object of the present disclosure is to provide a cellulose derivative having a high amount of chelating adsorption groups introduced, wettability, and capable of recovering boron quickly and efficiently, and which is resistant to dissolution in water and can be used as a solid-phase adsorbent. Another object of the present disclosure is to provide a method for producing the cellulose derivative. Another object of the present disclosure is to provide a boron adsorbent that can recover boron efficiently. Another object of the present disclosure is to provide a method for recovering boron using the cellulose derivative.

[0008] As a result of intensive research to solve the above problems, the present inventors have found the following: 1. Because cellulose is a polymer compound with high wettability, introducing chelating adsorption groups into cellulose makes it possible to introduce a high amount of chelating adsorption groups without impairing wettability; 2. Although cellulose is soluble in water, introducing chelating adsorption groups into cellulose via a linking group containing an aromatic ring confers resistance to dissolution in water, making it possible to use the cellulose as a solid-phase adsorbent without the need for insolubilization treatment such as crosslinking; and 3. Because a cellulose derivative into which a high percentage of chelating adsorption groups have been introduced via a linking group containing an aromatic ring has high wettability in aqueous solutions, when the cellulose derivative is applied to an aqueous boron solution, the aqueous boron solution quickly penetrates the cellulose, and boron in the boron solution is efficiently adsorbed and captured. The present disclosure has been completed based on the above findings.

[0009] That is, the present disclosure provides a cellulose derivative having a repeating unit represented by the following formula (I-1): [In the formula, R a are the same or different and are hydroxyl groups or groups represented by the following formula (a): a at least one of which is a group represented by the following formula (a): (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2are the same or different and each is a single bond or a linking group. 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form complexes with hard acids in the HSAB rule.

[0010] The present disclosure also provides the cellulose derivative, wherein the total average degree of substitution of the group represented by formula (a) is 0.1 to 3.0.

[0011] The present disclosure also provides the cellulose derivative, wherein the amount of the group represented by formula (a) introduced is 1.0 mmol / g or more.

[0012] The present disclosure also provides a boron adsorbent comprising the cellulose derivative.

[0013] The present disclosure also provides a method for recovering boron, in which boron dissolved in an aqueous solution is adsorbed onto the cellulose derivative and recovered.

[0014] The present disclosure also provides a method for producing the cellulose derivative through the following steps: [1] adding a compound represented by the following formula (2) to cellulose; (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to form a compound represented by the following formula (II): [wherein R b are the same or different and are hydroxyl groups or are represented by the following formula (b): (In the formula, Ar, L 1 , L 2 , Y 2 is the same as above). All R bwherein at least one of the repeating units is a group represented by the formula (b). [2] A cellulose derivative having a repeating unit represented by the formula (II) is treated with a compound represented by the following formula (3): (In the formula, R 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form complexes with hard acids according to the HSAB rule)

[0015] In this specification, "mol / kg" can be read as "mmol / g".

[0016] The cellulose derivative of the present disclosure has a side chain represented by formula (a). The side chain has the property of easily forming a chelate with a hard acid according to the HSAB rule. Therefore, by using the cellulose derivative, boron, which corresponds to a hard acid according to the HSAB rule, can be selectively and efficiently adsorbed and recovered. Furthermore, because the cellulose derivative has high wettability, when an aqueous solution containing boron is contacted with the cellulose derivative, the aqueous solution containing boron easily and quickly penetrates the interior of the cellulose derivative, and the boron in the aqueous solution is adsorbed and fixed by the side chain represented by formula (a). Therefore, by using the cellulose derivative, boron dissolved in the aqueous solution can be adsorbed and recovered in a short period of time. Therefore, the cellulose derivative can be suitably used for applications such as selectively and quickly adsorbing and recovering boron contained in wastewater, etc. Furthermore, because the cellulose derivative is insoluble in water, it can be used as a solid-phase adsorbent. For example, by passing an aqueous solution containing boron through the cellulose derivative packed in a column, an aqueous solution with a significantly reduced boron content can be obtained. Furthermore, the cellulose derivative does not cause any exhaust problems when burned, and by burning the cellulose derivative to which boron is adsorbed to reduce its volume, disposal costs such as landfilling can be significantly reduced.

[0017] Fig. 1 shows the IR spectrum of the cellulose derivative (1) obtained in Example 1. Fig. 2 shows the IR spectrum of the cellulose derivative (2) obtained in Example 2. Fig. 3 shows the IR spectrum of the cellulose derivative (3) obtained in Example 3. Fig. 4 shows the relationship between the immersion time in an aqueous boron solution and the boron adsorption amount of the adsorbents of the Examples and Comparative Examples.

[0018] [Cellulose Derivative] The cellulose derivative of the present disclosure (hereinafter, may be referred to as "cellulose derivative (I)") has a repeating unit represented by the following formula (I-1). [In the formula, R a are the same or different and are hydroxyl groups or groups represented by the following formula (a): a at least one of which is a group represented by the following formula (a): (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form complexes with hard acids in the HSAB rule.

[0019] The group represented by the formula (a) is a group containing a group that has the property of easily forming a chelate with a hard acid (hereinafter, sometimes referred to as a "chelate adsorption group").

[0020] The aromatic hydrocarbon group in Ar is preferably C 6-14 Aromatic hydrocarbon groups are preferred, and C 6-10 Aromatic hydrocarbon groups are particularly preferred. That is, examples of the aromatic hydrocarbon group in Ar include phenyl, naphthyl, and anthracenyl groups, with phenyl and naphthyl groups being particularly preferred.

[0021] The aromatic hydrocarbon group in Ar may have one or more substituents. The number of substituents that the hydrocarbon group in Ar may have is, for example, 1 to 3, and preferably 1 to 2.

[0022] Examples of the substituent include a halogen atom, a hydrocarbon group (e.g., C 1-3 alkyl groups), halogenated hydrocarbon groups (e.g., haloC 1-3 alkyl group).

[0023] R 1 The hydrocarbon group in the formula (I) includes an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group formed by combining these groups.

[0024] The aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 1 to 20 carbon atoms. Examples include alkyl groups having 1 to 20 carbon atoms (preferably 1 to 10, particularly preferably 1 to 3), such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, decyl, and dodecyl; alkenyl groups having 2 to 20 carbon atoms (preferably 2 to 10, particularly preferably 2 to 3), such as vinyl, allyl, and 1-butenyl; and alkynyl groups having 2 to 20 carbon atoms (preferably 2 to 10, particularly preferably 2 to 3), such as ethynyl and propynyl.

[0025] The alicyclic hydrocarbon group includes C 3-20 Alicyclic hydrocarbon groups are preferred, and examples thereof include 3- to 20-membered (preferably 3- to 15-membered, particularly preferably 5- to 8-membered) cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclooctyl groups.

[0026] The aromatic hydrocarbon group may be C 6-14 (Especially C 6-10 ) Aromatic hydrocarbon groups are preferred, such as phenyl and naphthyl groups.

[0027] R 1 The hydrocarbon group in is preferably an aliphatic hydrocarbon group, particularly preferably an alkyl group, and particularly preferably an alkyl group having 1 to 5 carbon atoms.

[0028] R 2 The hydrocarbon group in R 1 Among these, aliphatic hydrocarbon groups are preferred, alkyl groups are particularly preferred, and alkyl groups having 1 to 5 carbon atoms are particularly preferred.

[0029] R 2 As the alkyl group, a hydrocarbon group having a hydroxyl group is preferred, an aliphatic hydrocarbon group having a hydroxyl group is more preferred, an alkyl group having a hydroxyl group is particularly preferred, and an alkyl group having 1 to 5 carbon atoms and having a hydroxyl group is most preferred.

[0030] L 1 , L 2 The linking group in is a divalent group having one or more atoms, and examples thereof include a divalent hydrocarbon group, an ether bond (-O-), a thioether bond (-S-), an -NR- bond (where R represents a hydrogen atom, an alkyl group, or an acyl group), and groups in which multiple of these are linked together. The linking group may have a substituent such as a hydroxyl group or a carboxyl group. 1 and L 2、 may be the same or different.

[0031] Examples of the divalent hydrocarbon group include linear or branched alkylene groups having 1 to 18 carbon atoms, such as methylene, methylmethylene, dimethylmethylene, ethylene, and propylene; cycloalkylene groups having 3 to 18 carbon atoms, such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylidene; C alkylene groups such as phenylene groups (e.g., o-phenylene, m-phenylene, and p-phenylene), phenylenebis(methylene) groups (e.g., 1,2-phenylenebis(methylene), 1,3-phenylenebis(methylene), and 1,4-phenylenebis(methylene)), biphenylene groups, naphthylene groups, binaphthylene groups, anthracenylene groups, and phenanthrylene groups. 6-14 Examples include an arylene group.

[0032] L 1The linking group in is preferably a divalent hydrocarbon group.

[0033] L 1 Among these, a single bond is preferable.

[0034] L 2 As the linking group in the formula (I), a divalent hydrocarbon group is particularly preferred. Furthermore, as the divalent hydrocarbon group, a divalent aliphatic hydrocarbon group is particularly preferred, and an alkylene group (for example, a linear or branched alkylene group) is particularly preferred.

[0035] L 2 As the linking group in the formula (I), a divalent hydrocarbon group having 1 to 18 carbon atoms is preferred, a divalent hydrocarbon group having 1 to 10 carbon atoms is particularly preferred, a divalent hydrocarbon group having 1 to 5 carbon atoms is most preferred, and a divalent hydrocarbon group having 1 to 3 carbon atoms is particularly preferred.

[0036] L 2 As the linking group in the formula (I), a linear or branched alkylene group having 1 to 18 carbon atoms, such as a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, or a propylene group, is preferred, a linear or branched alkylene group having 1 to 5 carbon atoms is more preferred, a linear or branched alkylene group having 1 to 3 carbon atoms is particularly preferred, and a methylene group is particularly preferred.

[0037] X 1 ~X 3 The cellulose derivative (I) having the formula: is a hard base according to the HSAB rule. 1 ~X 3 In this case, it forms a complex with a hard acid according to the HSAB rule (hereinafter, sometimes simply referred to as a "hard acid").

[0038] The X 1 ~X 3 is a group that forms a complex with a hard acid, and examples thereof include groups containing an oxygen atom such as -OR and -OH, and groups containing a nitrogen atom such as -NH2, -NHR and -NR2. The R is an alkyl group having 1 to 5 carbon atoms. The X 1 ~X 3 As the alkyl group, a hydroxyl group or an amino group is preferred, and a hydroxyl group is particularly preferred.

[0039] Therefore, the group represented by the formula (a) is preferably a group represented by the following formula (a-1): 1 , R 2 , L 1 , L 2 is the same as above.

[0040] As the group represented by the formula (a), a group represented by the following formula (a-2) (i.e., a group containing an aromatic hydrocarbon group and a glucamine group as a chelate-adsorbing group) is particularly preferred. 1 , L 1 , L 2 is the same as above.

[0041] The total average degree of substitution (DS; the average value of the degree of substitution of hydrogen atoms of hydroxyl groups at the 2-, 3-, and 6-positions of glucose units constituting cellulose with said groups) of the group represented by formula (a) [preferably a group represented by formula (a-1), more preferably a group represented by formula (a-2)] is, for example, 0.1 to 3.0. In terms of obtaining the effect of increasing the amount of hard acid adsorbed, the lower limit of the total degree of substitution is preferably 0.5, particularly preferably 0.8, most preferably 1.2, and especially preferably 1.5. In terms of obtaining the effect of further reducing solubility in water, the upper limit of the total degree of substitution is preferably 2.7, particularly preferably 2.5, most preferably 2.4, and especially preferably 2.3.

[0042] The amount of the group represented by formula (a) [preferably a group represented by formula (a-1), more preferably a group represented by formula (a-2)] introduced into the cellulose derivative (I) is, for example, 1.0 mol / kg or more and 2.75 mol / kg or less. From the viewpoint of obtaining the effect of increasing the amount of hard acid adsorption and obtaining the effect of further reducing solubility in water, the lower limit of the amount of the group introduced is preferably 1.1 mol / kg, more preferably particularly preferably 1.2 mol / kg, even more preferably 1.3 mol / kg, particularly preferably 1.4 mol / kg, most preferably 1.5 mol / kg, and particularly preferably 1.7 mol / kg. The upper limit of the amount of the group introduced is preferably 2.75 mol / kg, more preferably 2.70 mol / kg, even more preferably 2.65 mol / kg, particularly preferably 2.5 mol / kg, most preferably 2.4 mol / kg, and particularly preferably 2.3 mol / kg.

[0043] The cellulose derivative (I) has a group represented by the formula (a), and the group forms a complex with a hard acid. Therefore, by using the cellulose derivative (I), it is possible to capture a metalloid (e.g., boron) that corresponds to a hard acid.

[0044] Furthermore, the cellulose derivative (I) is insoluble in water because it has an aromatic hydrocarbon group in its side chain, and therefore does not require insolubilization treatment such as crosslinking. Furthermore, since the cellulose derivative (I) is insoluble in water, by using it as a solid-phase adsorbent, hard acids present in an aqueous solution can be efficiently recovered by solid-phase extraction.

[0045] The cellulose derivative (I) is insoluble in water, and the amount of solubility in water is, for example, less than 15% by weight, preferably less than 10%, and particularly preferably less than 5%. The amount of solubility can be measured by the method described in the Examples.

[0046] Furthermore, as described below, the cellulose derivative (I) is produced using a cellulose derivative having a repeating unit represented by the following formula (2) as an intermediate, but the side chain represented by formula (b) of the intermediate has low reactivity with the hydroxyl groups of cellulose, so the intermediate does not form a crosslinked structure or forms one with difficulty.

[0047] From the above, the intermediate has many reaction sites with the compound (3) described below, and by reacting it with the compound (3), it is possible to produce a cellulose derivative (I) having a high introduction amount of the group represented by formula (a).

[0048] The shape of the cellulose derivative (I) is not particularly limited as long as the effects of the present disclosure are not impaired. However, a gel, powder, particles, pellets, flakes, needles, threads, or nonwoven fabric is preferred in terms of ease of recovery from the aqueous solution after adsorbing boron in the aqueous solution.

[0049] The cellulose derivative (I) has an adsorption capacity (or adsorption amount) of a metalloid (e.g., boron) corresponding to a hard acid of, for example, 0.1 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.6 mmol / g or more, and even more preferably 0.8 mmol / g or more. The upper limit of the adsorption capacity is, for example, 2 mmol / g.

[0050] The cellulose derivative (I) has an adsorption capacity (or adsorption amount) of a metalloid (e.g., boron) corresponding to a hard acid of, for example, 0.5 mg / g or more, preferably 1 mg / g or more, more preferably 2 mg / g or more, even more preferably 4 mg / g or more, particularly preferably 6 mg / g or more, and most preferably 8 mg / g or more. The upper limit of the adsorption capacity is, for example, 15 mg / g.

[0051] The adsorption capacity of the metalloids and the like by the cellulose derivative (I) is the amount of adsorption when 10 mg of the cellulose derivative (I) is immersed in an aqueous solution (pH 8) containing the metalloids and the like at a concentration of 1 mM at 25°C and stirred at 200 rpm for 1 hour, and is calculated from the formula described in the Examples.

[0052] Because the cellulose derivative (I) has the above properties, it can be suitably used as an adsorbent (particularly, a solid-phase adsorbent) for semimetals (for example, boron) that are hard acids.

[0053] [Method for Producing Cellulose Derivative (I)] The cellulose derivative (I) can be produced, for example, through the following steps [1] and [2]. [1] Adding a compound represented by the following formula (2) to cellulose. (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to form a compound represented by the following formula (II): [wherein R b are the same or different and are hydroxyl groups or are represented by the following formula (b): (In the formula, Ar, L 1 , L 2 , Y 2 is the same as above). All R b wherein at least one of the repeating units is a group represented by the formula (b). [2] A cellulose derivative having a repeating unit represented by the formula (II) is treated with a compound represented by the following formula (3): (In the formula, R 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form complexes with hard acids according to the HSAB rule)

[0054] Ar and L in the above formula 1 , L 2 , R 1 , R 2 , X 1 ~X 3 is the same as above.

[0055] Step [1] is a step of reacting a compound represented by formula (2) (hereinafter, sometimes referred to as "compound (2)") with the hydroxyl groups of cellulose to produce a cellulose derivative having a repeating unit represented by formula (II) (hereinafter, sometimes referred to as "cellulose derivative (II)").

[0056] Suitable examples of the cellulose include cellulose derived from wood pulp (softwood pulp, hardwood pulp) and cotton linter pulp, and crystalline cellulose. These can be used alone or in combination of two or more. The pulp may contain other components such as hemicellulose. It is preferable to use cellulose that has been finely pulverized, for example, by crushing treatment (for example, powdered cellulose).

[0057] Examples of the aromatic hydrocarbon group for Ar in the compound (2) include the same examples as those for Ar in the group represented by the formula (a).

[0058] The aromatic hydrocarbon group includes L in formula (2). 2 -Y 2 In addition to the group represented by the formula (I), one or more other substituents may be present. Examples of the other substituents include a halogen atom, a hydrocarbon group (e.g., C 1-3 alkyl groups), halogenated hydrocarbon groups (e.g., haloC 1-3 alkyl group).

[0059] When the aromatic carboxylic acid has other substituents, the number of the substituents is, for example, 1 to 3, and preferably 1 to 2.

[0060] The amount of compound (2) used is, for example, 1 part by weight or more, preferably 3.5 to 10.5 parts by weight, per part by weight of the cellulose.

[0061] The reaction in step [1] is preferably carried out in the presence of a base, which includes organic and inorganic bases.

[0062] Examples of the organic base include aliphatic amines (e.g., secondary aliphatic amines such as diisopropylamine, and tertiary aliphatic amines such as triethylamine, tri-n-propylamine, tri-n-butylamine, tri-s-butylamine, tri-t-butylamine, ethyldiisopropylamine, dimethylcyclohexylamine, dicyclohexylethylamine, tribenzylamine, and benzyldimethylamine), aromatic amines (e.g., N,N-dimethylaniline, N,N-diethylaniline, diaminodiphenylmethane, methylaniline, diphenylamine ... cyclohexane, cyclohexanediamine ...

[0063] Examples of the inorganic base include alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium t-butoxide, and potassium t-butoxide; alkali metal carbonates such as sodium hydrogencarbonate, sodium carbonate, potassium hydrogencarbonate, potassium carbonate, rubidium carbonate, and cesium carbonate; alkali metal phosphates such as sodium phosphate, disodium hydrogenphosphate, sodium dihydrogenphosphate, potassium phosphate, dipotassium hydrogenphosphate, dipotassium hydrogenphosphate, and potassium dihydrogenphosphate; and alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0064] As the base, an organic base is preferred, and a tertiary amine is particularly preferred, from the viewpoint of excellent effect of promoting the reaction between cellulose and compound (2). Ethyldiisopropylamine is particularly preferred, from the viewpoint of suppressing a side reaction with compound (2).

[0065] The amount of the base used is, for example, 0.01 to 2.0 moles per mole of compound (2).

[0066] The reaction in step [1] may be carried out in the presence of a condensing agent. Examples of the condensing agent include 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC-HCl), N,N'-dicyclohexylcarbodiimide, and N,N'-diisopropylcarbodiimide. These can be used alone or in combination of two or more.

[0067] The amount of the condensing agent used is, for example, 1 to 10 moles per mole of compound (2).

[0068] The reaction in step [1] 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; halogenated hydrocarbons such as chloroform, dichloromethane, and 1,2-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 N,N-dimethylformamide, N,N-dimethylacetamide (DMA), and N-methylpyrrolidone; nitriles such as acetonitrile, propionitrile, and benzonitrile; alcohols such as methanol, ethanol, isopropyl alcohol, and butanol; and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more.

[0069] The solvent is preferably an amide such as N,N-dimethylacetamide (DMA), and it is particularly preferable to use a solvent containing a lithium salt such as lithium chloride, as this provides excellent cellulose solubility. The concentration of the lithium salt in the solvent can be adjusted as appropriate within a range that does not impair the effect of dissolving cellulose, and is, for example, 1 to 30 wt %.

[0070] The amount of the solvent used is, for example, 10 to 500 mL, preferably 20 to 100 mL, per gram of cellulose. If the amount of the solvent used exceeds this range, the concentration of the reaction components will be low, and the reaction rate will tend to decrease.

[0071] The reaction temperature in step [1] is, for example, 20 to 120°C. By adjusting the reaction temperature within this range, it is possible to control the total average degree of substitution of the groups represented by formula (b) in the resulting cellulose derivative (II). For example, if the reaction temperature is set lower within the above range, the total average degree of substitution of the groups represented by formula (b) in the resulting cellulose derivative (II) tends to be lower.

[0072] The cellulose derivative (II) obtained via step [1] has a total average degree of substitution of the group represented by formula (b) (the average value of the degree of substitution of the hydrogen atoms of the hydroxyl groups at positions 2, 3, and 6 of the glucose units constituting the cellulose with the group) of, for example, 0.1 to 3.0. In terms of obtaining the effect of increasing the amount of hard acid adsorbed, the lower limit of the total degree of substitution is preferably 0.5, particularly preferably 0.8, most preferably 1.2, and especially preferably 1.5. In terms of obtaining the effect of further reducing the solubility in water, the upper limit of the total degree of substitution is preferably 2.7, particularly preferably 2.5, most preferably 2.4, and especially preferably 2.3.

[0073] In step [2], the cellulose derivative (II) produced in step [1] is reacted with a compound represented by formula (3) (hereinafter, sometimes referred to as "compound (3)"). Through step [2], the cellulose derivative (I) is obtained.

[0074] As the compound (3), for example, D-glucamine, N-methyl-D-glucamine, N-ethyl-D-glucamine, etc. are preferred.

[0075] The amount of the compound (3) used is, for example, 1.0 part by weight or more, preferably 1.0 to 6.0 parts by weight, and particularly preferably 2.0 to 5.0 parts by weight, per part by weight of the cellulose derivative (II).

[0076] The reaction in step [2] is preferably carried out in the presence of a base. Examples of the base include the same as those mentioned above.

[0077] As the base, an organic base is preferred from the viewpoint of excellent effect of promoting the reaction between the cellulose derivative (II) and the compound (3), a tertiary amine is particularly preferred, and ethyldiisopropylamine is most preferred from the viewpoint of suppressing a side reaction with the compound (2).

[0078] The amount of the base used is, for example, 0.01 to 1.5 moles per mole of compound (3).

[0079] The reaction in step [2] is preferably carried out 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 (DMSO), and N,N-dimethylformamide. These solvents can be used alone or in combination of two or more.

[0080] The amount of the solvent used is, for example, 10 to 500 mL, preferably 20 to 100 mL, per gram of cellulose derivative (II). If the amount of the solvent used exceeds the above range, the concentration of the reaction components decreases, and the reaction rate tends to decrease.

[0081] The reaction temperature in step [2] is, for example, 20 to 120° C. The reaction time is, for example, 1 to 72 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 separation means.

[0082] [Boron Adsorbent] The boron adsorbent of the present disclosure contains the cellulose derivative (I).

[0083] The boron adsorbent may contain other components in addition to the cellulose derivative (I), but the proportion of the cellulose derivative (I) in the total amount of the boron adsorbent is, for example, 50% by weight or more, preferably 60% by weight or more, particularly preferably 70% by weight or more, most preferably 80% by weight or more, and particularly preferably 90% by weight or more. If the proportion of the cellulose derivative (I) is below the above range, it tends to be difficult to efficiently and selectively adsorb boron.

[0084] The boron adsorbent may contain other cellulose derivatives in addition to the cellulose derivative (I), but the proportion of the cellulose derivative (I) is, for example, 60% by weight or more, preferably 70% by weight or more, particularly preferably 80% by weight or more, most preferably 90% by weight or more, and particularly preferably 95% by weight or more of the total amount of cellulose derivatives contained in the boron adsorbent. If the proportion of the cellulose derivative (I) is below the above range, it tends to be difficult to efficiently and selectively adsorb boron.

[0085] The dosage form of the boron adsorbent is not particularly limited as long as it is effective, and examples thereof include powder, particles, pellets, flakes, needles, threads, and nonwoven fabric.

[0086] The boron adsorbent has the properties of the cellulose derivative (I), i.e., it has a high adsorption power for boron, which corresponds to a hard acid according to the HSAB rule.

[0087] The boron adsorbent has an adsorption capacity (or adsorption amount) of a metalloid (e.g., boron) corresponding to a hard acid of, for example, 0.1 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.6 mmol / g or more, and even more preferably 0.8 mmol / g or more. The upper limit of the adsorption capacity is, for example, 2 mmol / g.

[0088] The boron adsorbent has an adsorption capacity (or adsorption amount) of a metalloid (e.g., boron) corresponding to a hard acid of, for example, 3 mg / g or more, preferably 4 mg / g or more, more preferably 5 mg / g or more, even more preferably 6 mg / g or more, particularly preferably 7 mg / g or more, and most preferably 8 mg / g or more. The upper limit of the adsorption capacity is, for example, 15 mg / g.

[0089] Because the boron adsorbent has the above-mentioned properties, it is suitable for use in selectively recovering boron from industrial wastewater, mine wastewater, hot spring water, seawater, and the like.

[0090] The boron adsorbent is insoluble in water, and the amount of dissolution in water is, for example, less than 15% by weight, preferably less than 10%, and particularly preferably less than 5%. The amount of dissolution can be measured by the method described in the Examples.

[0091] As described above, the boron adsorbent has resistance to dissolution, and therefore, by using it as a solid-phase adsorbent, boron present in industrial wastewater, mine wastewater, hot spring water, seawater, etc. can be efficiently recovered by solid-phase extraction.

[0092] [Method for Recovering Boron] The method for recovering boron according to the present disclosure involves recovering boron dissolved in an aqueous solution (or boron present in an aqueous solution) by adsorbing it onto the cellulose derivative (I).

[0093] The aqueous solution contains at least boron in a dissolved state. The aqueous solution may contain other components in addition to the dissolved boron. Examples of the aqueous solution include aqueous solutions containing dissolved boron from which boron removal or reduction in boron concentration is required (e.g., industrial wastewater containing dissolved boron, boron aqueous solution, and brackish water containing boron replicated during seawater desalination).

[0094] The boron concentration (specifically, weight concentration) in the aqueous solution is not particularly limited, but is, for example, 1 ppm or more, 10 ppm or more, or 100 ppm or more. The upper limit of the boron concentration is, for example, 10,000 ppm, 1,000 ppm, or 500 ppm.

[0095] In an aqueous solution, boron strongly interacts with hydroxyl groups, which are hard bases, and exists as boric acid or tetrahydroxyborate ions. The cellulose derivative (I) adsorbs and recovers boron ions by forming a chelate complex in which the group represented by formula (a) substitutes for the hydroxyl groups of the boric acid or tetrahydroxyborate ions contained in the aqueous solution.

[0096] The method for adsorbing boron dissolved in an aqueous solution onto the cellulose derivative (I) is not particularly limited, and examples thereof include a method in which the cellulose derivative (I) is packed into a column or the like and an aqueous solution in which boron is dissolved is passed through the column, and a method in which the cellulose derivative (I) is added to an aqueous solution in which boron is dissolved and the mixture is stirred.

[0097] In the method for recovering boron, it is preferable to adjust the pH of the cellulose derivative (I) to, for example, 6 to 12 (preferably 7 to 10, and particularly 7 to 9), since this further improves the adsorption power of boron and allows for more efficient recovery of boron. The pH of the cellulose derivative can be adjusted using a well-known, commonly used pH adjuster (an acid such as nitric acid or an alkali such as sodium hydroxide).

[0098] After the cellulose derivative (I) has adsorbed boron, the boron-adsorbed cellulose derivative (I) can be separated from water by a simple and energy-saving method such as centrifugation, filtration, etc. The separated boron-adsorbed cellulose derivative (I) can then be burned to significantly reduce its volume, thereby reducing disposal costs.

[0099] The above-described configurations and combinations thereof of the present disclosure are merely examples, and additions, omissions, substitutions, and modifications of the configurations are possible as appropriate within the scope of the present disclosure. Furthermore, the present disclosure is not limited to the embodiments, but is limited only by the claims.

[0100] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0101] Example 1 (Preparation of Cellulose Derivative (1) and Adsorbent) (Step I) Cellulose (a polymer having a repeating unit represented by the following formula (1-1), 2.10 g, 13.0 mmol) was placed in a two-necked eggplant flask and vacuum dried at 90 ° C. for 2 hours. Then, under a nitrogen atmosphere, N,N-dimethylacetamide (70 mL) was added and stirred for 21 hours. The reaction vessel was cooled to 0 ° C. in an ice bath, and lithium chloride (4.32 g) was added to the cellulose-containing solution, and the cellulose was dissolved by stirring while warming to room temperature (25 ° C.). The reaction vessel was again cooled to 0 ° C. in an ice bath, and ethyldiisopropylamine (20 mL, 117 mmol) and 4-(chloromethyl)benzoic acid chloride (11 mL, 78 mmol) were added to the cellulose-containing solution, and the mixture was stirred for 20 hours while warming to room temperature (25 ° C.) to obtain reaction solution A. The obtained reaction solution A was poured into methanol and re-precipitated to obtain solid A. The resulting solid A was collected by suction filtration and washed with methanol and diethyl ether. The washed solid A was dried in vacuo to obtain cellulose (4-chloromethyl)benzoate (1) (a polymer having a repeating unit represented by the following formula (II-1), 4.56 g, yield: approximately 91%) as a colorless solid. 1 From the results of H-NMR measurement, the total average degree of substitution of 4-(chloromethyl)benzoyloxy groups was calculated to be about 1.5.

[0102] (Cellulose (4-chloromethyl) benzoate) 1 H-NMR (500MHz, DMSO-d6, rt.): δ7.0-8.1 (br, Ar-H), 2.6-5.8 (br, cellulose-H, overlapped with Ar-CH2 and residual H2O), 4.5-4.9 (br, Ar-CH2, overlapped with Cellulose-H)

[0103] (Step II) Under a nitrogen atmosphere, cellulose (4-chloromethyl) benzoate (1) (0.200 g, 1.01 mmol) obtained in step (I) was added to a two-necked recovery flask, and dimethyl sulfoxide (3.2 mL) was added to dissolve the cellulose (4-chloromethyl) benzoate (1). Subsequently, N-methylglucamine (0.562 g, 4.32 mmol) and triethylamine (0.60 mL, 4.3 mmol) were added to the solution of cellulose (4-chloromethyl) benzoate (1), and the mixture was stirred at 80°C for 3 hours to obtain reaction solution B. Reaction solution B was poured into ethanol for reprecipitation to obtain solid B. The obtained solid B was recovered by centrifugation and washed with ethanol and diethyl ether. The obtained solid B was dried in vacuo to obtain cellulose derivative (1) (a polymer having a repeating unit represented by the following formula (I-1), 290 mg, yield approximately 90%) as a colorless powder. 1 From the results of H-NMR measurement, the total average substitution degree of N-methylglucamine groups was calculated to be about 1.5, and the amount introduced was calculated to be 2.4 mmol / g. The IR spectrum of cellulose derivative (1) is shown in Figure 1.

[0104] Cellulose derivatives (1) 1 H-NMR (500MHz, DMSO-d6, rt.): δ6.7-8.2 (br, Ar-H), 2.7-5.8 (br, Cellulose-H, overlapped with Ar-CH2, O-CH, O-CH2, and residual H2O), 4.2-4.7 (br, Ar-CH, overlapped with Cellulose-H), 2.8-3.9 (br, O-CH, O-CH 2、 and residual H2O, overlapped with Cellulose-H), 2.3-2.7 (br, N-CH3, N-CH 2、 overlapped with residual DMSO) 1.6-2.3 (br, C-OH)

[0105] The resulting cellulose derivative (1) was classified into particles of 212 to 600 μm. The classified cellulose derivative (1) was used as an adsorbent (CE(1)).

[0106] Example 2 (Preparation of cellulose derivative (2) and adsorbent) (Step I) Cellulose (4-chloromethyl)benzoate (2) (a polymer having a repeating unit represented by the above formula (II-1)) was obtained as a colorless solid in the same manner as in Example 1, except that the reaction temperature was changed from room temperature (25°C) to 60°C. 1 From the results of H-NMR measurement, the total average degree of substitution of 4-(chloromethyl)benzoyloxy groups was calculated to be about 2.0.

[0107] (Step II) A cellulose derivative (2) (hereinafter sometimes referred to as “CE (2)”) was obtained in the same manner as in Example 1, except that cellulose (4-chloromethyl) benzoate (2) was used instead of cellulose (4-chloromethyl) benzoate (1). 1 From the results of H-NMR measurement, the total average substitution degree of N-methylglucamine groups was calculated to be about 2.0, and the amount introduced was 2.6 mmol / g. The IR spectrum of cellulose derivative (2) is shown in Figure 2.

[0108] The resulting cellulose derivative (2) was classified into particles of 212 to 600 μm. The classified cellulose derivative (2) was used as an adsorbent (CE(2)).

[0109] Example 3 (Preparation of cellulose derivative (3) and adsorbent) (Step I) Cellulose (4-chloromethyl)benzoate (3) (a polymer having a repeating unit represented by the above formula (II-1)) was obtained as a colorless solid in the same manner as in Example 1, except that the reaction temperature was changed from room temperature (25°C) to 80°C. 1 From the results of H-NMR measurement, the total average degree of substitution of 4-(chloromethyl)benzoyloxy groups was calculated to be about 2.5.

[0110] (Step II) A cellulose derivative (3) was obtained in the same manner as in Example 1, except that cellulose (4-chloromethyl)benzoate (3) was used instead of cellulose (4-chloromethyl)benzoate (1). 1 From the results of H-NMR measurement, the total average substitution degree of N-methylglucamine groups was calculated to be about 2.5, and the amount introduced was 2.7 mmol / g. The IR spectrum of cellulose derivative (3) is shown in Figure 3.

[0111] The resulting cellulose derivative (3) was classified into particles of 212 to 600 μm, and the classified cellulose derivative (3) was used as an adsorbent (CE(3)).

[0112] The adsorbents obtained in Examples 1 to 3 and the adsorbents shown in the table below as Comparative Examples 1 to 3 were evaluated for boron adsorption and resistance to dissolution in water by the following methods. The results are summarized in the table below. The evaluation results for boron adsorption are also shown in Figure 4.

[0113] [Evaluation of boron adsorption amount] The boron adsorption amount was evaluated by the following method (batch method). First, an adsorption treatment was performed. That is, 10 mg of the adsorbent of each of the examples and comparative examples and 10 mL of a 1 mM boron aqueous solution (pH 8) were added to a 100 mL centrifuge tube to obtain an adsorbent-containing solution. Then, an adsorption treatment was performed in which the obtained adsorbent-containing solution was stirred at 25°C and 200 rpm for 1 hour, 6 hours, 10 hours, or 12 hours. Next, the adsorbent-containing solution after the adsorption treatment was filtered using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the boron ion concentration (Ce: mmol / mL) in the filtrate was quantified using an ICP atomic emission spectrometer (iCAP6300, manufactured by Thermo Fischer Scientific).

[0114] The boron ion concentration of the adsorbent-containing solution before the adsorption treatment was C (mmol / mL), the volume of the boron aqueous solution was Vo (mL), and the weight of the added adsorbent was m (g), and the molar amount of boron adsorption (mmol / g) was calculated from the following formula: mol (mmol / g)=(C0-Ce)×V0 / m

[0115] The boron adsorption weight is the boron adsorption molar amount B calculated by the above formula. mol The boron adsorption weight B was calculated using the following formula: w (mg / g) = boron atomic weight 10.811 (mg / mmol) × B mol (mmol / g)

[0116] [Evaluation of Dissolution Resistance of Adsorbents] The dissolution resistance of the adsorbents of the Examples and Comparative Examples was evaluated by the following method. Specifically, 10 mg of the adsorbent of each Example or Comparative Example and 10 mL of a 1 mM boron aqueous solution (pH 8) were added to a 100 mL centrifuge tube to obtain an adsorbent-containing solution. The resulting adsorbent-containing solution was then subjected to an adsorption treatment by stirring at 25°C and 200 rpm for 10 hours. Next, the adsorbent-containing solution after the adsorption treatment was filtered using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the adsorbent obtained as filter cake was placed in a desiccator filled with a drying material (silica gel) and dried in a thermostatic chamber at 40°C for 24 hours, after which its weight (We: mg) was measured. Then, assuming the initial weight of the adsorbent as W0 (mg), the amount of solubility (%) of the adsorbent in water was calculated using the following formula, and the dissolution resistance in water was evaluated according to the following criteria. Dissolution amount (%) = (W0 - We) / W0 <Evaluation criteria for dissolution resistance> Excellent: Dissolution amount in water is less than 5% Good: Dissolution amount in water is 5% or more but less than 10% Fair: Dissolution amount in water is 10% or more but less than 15% Poor: Dissolution amount in water is 15% or more

[0117]

[0118] CRB03: Chelate resin "Diaion CRB03", a styrene-DVB copolymer with an N-methylglucamine group introduced as a chelating adsorption group, manufactured by Mitsubishi Chemical Corporation. CRB05: Chelate resin "Diaion CRB05", a styrene-DVB copolymer with an N-methylglucamine group introduced as a chelating adsorption group, manufactured by Mitsubishi Chemical Corporation. GRY-HW: Aminopolyol-type cellulose chelating fiber "Chilest Fiber GRY-HW", a cellulose fiber with an N-methylglucamine group introduced, manufactured by Chubu Chelest Co., Ltd.

[0119] The cellulose derivatives of the Examples can rapidly adsorb large amounts of boron and, in addition, have excellent resistance to dissolution in water. Therefore, it can be seen that they can be suitably used as solid-phase adsorbents for boron. On the other hand, the adsorbents of Comparative Examples 1 and 2 have resistance to dissolution in water and can be used as solid-phase adsorbents, but they have low wettability and are not easily compatible with aqueous boron solutions, so it takes a long time to adsorb boron. Furthermore, the boron adsorption capacity is also low. The adsorbent of Comparative Example 3 is a cellulose-based fiber, which has high wettability and is easily compatible with aqueous boron solutions, but has a low content of chelating adsorption groups, resulting in a low boron adsorption capacity.

[0120] In summary, the configuration of the present disclosure and its variations are noted below: [Note 1] A cellulose derivative having a repeating unit represented by formula (I-1). [In the formula, R a are the same or different and are hydroxyl groups or groups represented by the following formula (a): a at least one of which is a group represented by the following formula (a): (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3are the same or different and are groups that form a complex with a hard acid according to the HSAB rule.) [Appendix 2] The cellulose derivative according to [Appendix 1], in which the total average degree of substitution of the group represented by formula (a) is 0.1 to 3.0. [Appendix 3] The cellulose derivative according to [Appendix 1] or [Appendix 2], in which the amount of the group represented by formula (a) introduced is 1.0 mmol / g or more. [Appendix 4] A boron adsorbent comprising the cellulose derivative according to any one of [Appendix 1] to [Appendix 3]. [Appendix 5] A method for recovering boron, in which boron dissolved in an aqueous solution is adsorbed onto the cellulose derivative according to any one of [Appendix 1] to [Appendix 3] and recovered. [Appendix 6] A method for producing a cellulose derivative according to any one of [Appendix 1] to [Appendix 3], through the following steps: [1] Adding a cellulose derivative represented by the following formula (2) to cellulose (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to form a compound represented by the following formula (II): [wherein R b are the same or different and are hydroxyl groups or are represented by the following formula (b): (In the formula, Ar, L 1 , L 2 , Y 2 is the same as above). All R b wherein at least one of the repeating units is a group represented by the formula (b). [2] A cellulose derivative having a repeating unit represented by the formula (II) is treated with a compound represented by the following formula (3): (In the formula, R 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form complexes with hard acids according to the HSAB rule)

[0121] The cellulose derivatives of the present disclosure can be suitably used as boron adsorbents (particularly solid-phase adsorbents for boron). Furthermore, because the cellulose derivatives have high wettability with aqueous boron solutions, when applied to the aqueous boron solution, they can rapidly adsorb and recover boron from the solution. Furthermore, the boron adsorbents do not cause exhaust problems when burned, and by burning them after adsorbing boron to reduce their volume, disposal costs, such as landfill disposal, can be significantly reduced.

Claims

1. A cellulose derivative having a repeating unit represented by the following formula (I-1): [In the formula, R a are the same or different and each is a hydroxyl group or a group represented by the following formula (a). a At least one of these is a group represented by the following formula (a): (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form complexes with hard acids according to the HSAB rule.

2. The cellulose derivative according to claim 1, wherein the total average degree of substitution of the group represented by formula (a) is 0.1 to 3.

0.

3. The cellulose derivative according to claim 1, wherein the amount of the group represented by formula (a) introduced is 1.0 mmol / g or more.

4. A boron adsorbent comprising the cellulose derivative according to any one of claims 1 to 3.

5. A method for recovering boron, comprising adsorbing boron dissolved in an aqueous solution onto the cellulose derivative according to any one of claims 1 to 3 and recovering the boron.

6. A method for producing a cellulose derivative, comprising the steps of: producing the cellulose derivative according to any one of claims 1 to 3, wherein: [1] a cellulose derivative represented by the following formula (2) is added to the cellulose derivative; (Wherein, Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each is a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to obtain a compound represented by the following formula (II): [wherein R b are the same or different and each is a hydroxyl group or a group represented by the following formula (b): (In the formula, Ar, L 1 , L 2 , Y 2 is the same as above). All R b at least one of which is a group represented by the formula (b) above; [2] A cellulose derivative having a repeating unit represented by the formula (II) is treated with a compound represented by the following formula (3): (In the formula, R 1 is a hydrogen atom or a hydrocarbon group. 2 is a hydrogen atom or a hydrocarbon group which may have a hydroxyl group. 1 ~X 3 are the same or different and are groups that form a complex with a hard acid according to the HSAB rule)

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