Cellulose derivatives, transition metal adsorbents, method for recovering transition metal

Abstract

To provide a cellulose derivative capable of rapidly and efficiently capturing transition metals when the derivatives immersed in water containing transition metals.SOLUTION: A cellulose derivative disclosed herein is a cellulose derivative in which one or more OH groups are esterified with a group represented by the following formula (a). In formula (a), Ar is an aromatic hydrocarbon group. n denotes an integer of 0 or greater. L1 to L5 are the same or different and represent a single bond or a connecting group. R1 and R2 are the same or different and represent hydrogen atom or a carboxyl group. The carboxyl group may form a salt.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a novel cellulose derivative, a method for producing the cellulose derivative, a transition metal adsorbent containing the cellulose derivative, and a method for recovering transition metals using the cellulose derivative. [Background technology]

[0002] Lead is used in batteries, electrical wire coatings, alloys, paints, printing inks, etc., and when it is released into the environment through industrial wastewater, it is known to contaminate groundwater and soil and cause various diseases due to lead poisoning. In addition, with the improvement in productivity in plating processes and printed circuit board manufacturing, copper and nickel are increasingly being found in wastewater.

[0003] On the other hand, with increasing environmental awareness, environmental standards and water quality standards for the transition metals have become stricter.

[0004] Patent Document 1 discloses that a styrene-based chelate resin obtained by introducing an iminodiacetic acid type chelate functional group into a chloromethylated styrene-based crosslinked copolymer selectively adsorbs copper.

[0005] However, since the styrene-based chelate resin has low wettability with water, it takes a long time to adsorb transition metals in water, resulting in poor recovery efficiency of the transition metals. In Patent Document 1, the styrene-based chelate resin is made porous to increase its specific surface area, thereby compensating for the low wettability and improving the recovery efficiency of transition metals in water, but this is still insufficient. Furthermore, when the styrene-based chelate resin is burned, exhaust problems occur.

[0006] Patent Document 2 discloses an adsorbent obtained by directly reacting iminodiacetic acid with the hydroxyl groups of cellulose. Although this adsorbent does not cause exhaust problems when burned, the reaction method does not efficiently introduce iminodiacetic acid-type chelating functional groups into cellulose, and therefore, no adsorption effect was obtained for transition metals such as Cu and Ni. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-8313 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-247981 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present disclosure is to provide a cellulose derivative that can quickly and efficiently capture transition metals when immersed in water containing the transition metals. 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 transition metal adsorbent that can efficiently recover transition metals. Another object of the present disclosure is to provide a method for recovering transition metals using the cellulose derivatives. [Means for solving the problem]

[0009] As a result of extensive research into solving the above problems, the present inventors have discovered the following. 1. A cellulose derivative obtained by introducing a functional group that forms a chelate with a transition metal ion (sometimes referred to as a "chelating functional group" in this specification) into cellulose, which has high wettability with water, easily blends with water containing dissolved transition metals and captures the transition metal ions in the water by forming a chelate. 2. When cellulose is reacted with a compound represented by formula (2) described below and then with a compound represented by formula (3) described below, many chelating functional groups can be introduced into the cellulose, improving its ability to adsorb transition metals. 3. When the hydroxyl groups of cellulose are replaced with hydrophilic chelating functional groups, the cellulose becomes more soluble in water. However, when the chelating functional groups are introduced into cellulose via a linking group containing an aromatic ring, the cellulose becomes resistant to dissolution in water, making it possible to use the cellulose as a solid-phase adsorbent without undergoing insolubilization treatment such as crosslinking. The present disclosure has been completed based on the above findings.

[0010] That is, the present disclosure provides a cellulose derivative having a repeating unit represented by the following formula (I): [ka] [In formula (I), three R a are the same or different and are a hydrogen atom or a group represented by the following formula (a): a at least one of which is a group represented by the following formula (a): [ka] (In formula (a), Ar is an aromatic hydrocarbon group. n is an integer of 0 or more. L 1 , L 2 , 2 L 3 , 2n L 4 , and 2n L 5 are the same or different and are a single bond or a linking group. 1 , and 2n R 2 are the same or different and are a hydrogen atom or a carboxy group. 1 , and 2n R 2 at least two selected from the above are carboxy groups, and the carboxy groups may form salts)

[0011] The present disclosure also provides the cellulose derivative, wherein the total average degree of substitution of the group represented by formula (a) is from 0.1 to 3.0.

[0012] The present disclosure also provides the cellulose derivative, wherein the amount of the group represented by formula (a) introduced is 1.6 mmol / g or more.

[0013] The present disclosure also provides a transition metal adsorbent comprising the cellulose derivative.

[0014] The present disclosure also provides the transition metal adsorbent, which is an adsorbent for at least one metal selected from mercury, copper, lead, nickel, zinc, cadmium, cobalt, iron, and manganese.

[0015] The present disclosure also provides a method for recovering a transition metal, which comprises adsorbing the transition metal dissolved in an aqueous solution onto the cellulose derivative and recovering the transition metal.

[0016] The present disclosure also provides a method for producing the cellulose derivative, which comprises the steps of Step 1 and Step 2 below: [Step 1] Cellulose is treated with a compound represented by the following formula (2): [ka] (In formula (2), Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each represents a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to react a compound represented by the following formula (II): [ka] [The three R in formula (II) b are the same or different and are a hydrogen atom or a group represented by the following formula (b). b at least one of which is a group represented by the following formula (b): [ka] (In the formula, Ar, L 1 , L 2 , Y 2 (same as above) A cellulose derivative having a repeating unit represented by [Step 2] A cellulose derivative having a repeating unit represented by formula (II) is treated with a compound represented by formula (3) below: [ka] (In formula (3), n represents an integer of 0 or more. 3 , 2n L 4 , and 2n L 5 are the same or different and are a single bond or a linking group. 1 , and 2n R 2 are the same or different and are a hydrogen atom or a carboxy group. 1 , and 2n R 2 At least two selected from R are carboxy groups, and the carboxy groups may form salts or may be protected with protecting groups. 3 is a hydrogen atom or a hydrocarbon group) React the compound represented by [Effects of the Invention]

[0017] The cellulose derivative of the present disclosure has high wettability with water. Therefore, there is no need for treatment to increase the specific surface area, such as by making it porous. When the cellulose derivative is brought into contact with an aqueous solution containing a transition metal, the aqueous solution containing the transition metal easily and quickly penetrates into the interior of the cellulose derivative. Furthermore, the group represented by formula (a) on the side chain of the cellulose derivative can form a chelate with the transition metal in the aqueous solution and capture it. Therefore, the cellulose derivative can be suitably used for selectively and quickly adsorbing and recovering transition metals contained in wastewater and the like. Furthermore, the cellulose derivative is insoluble in water. Therefore, the cellulose derivative can be used as a solid-phase adsorbent. For example, when the cellulose derivative is packed in a column and an aqueous solution containing transition metals is injected into the column, an aqueous solution with a significantly reduced transition metal concentration can be obtained as the column effluent. Furthermore, the cellulose derivative does not cause any exhaust problems when burned, and by burning the cellulose derivative to which the transition metal is adsorbed to reduce its volume, disposal costs such as landfilling can be significantly reduced. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing the IR spectrum of the cellulose derivative (1) obtained in Example 1. [Figure 2] FIG. 1 is a diagram showing the IR spectrum of the cellulose derivative (2) obtained in Example 2. [Figure 3] FIG. 1 is a diagram showing the IR spectrum of the cellulose derivative (3) obtained in Example 3. [Figure 4] FIG. 1 is a graph showing the equilibrium adsorption amounts of Pb(II) ions and Cu(II) ions for the cellulose derivative (3) obtained in Example 3 and the adsorbents of Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0019] [Cellulose derivatives] The cellulose derivative of the present disclosure (hereinafter sometimes referred to as "cellulose derivative (I)") has a repeating unit represented by the following formula (I). [ka] [In formula (I), three R a are the same or different and are a hydrogen atom or a group represented by the following formula (a): a at least one of which is a group represented by the following formula (a): [ka] (In formula (a), Ar is an aromatic hydrocarbon group. n is an integer of 0 or more. L 1 , L 2 , 2 L 3 , 2n L 4 , and 2n L 5are the same or different and are a single bond or a linking group. 1 , and 2n R 2 are the same or different and are a hydrogen atom or a carboxy group. 1 , and 2n R 2 at least two selected from the above are carboxy groups, and the carboxy groups may form salts)

[0020] The group represented by the formula (a) contains a chelating functional group that has a property of easily forming a chelate with a transition metal ion. a It bonds to the oxygen atom that makes up the group.

[0021] The aromatic hydrocarbon group (particularly, a divalent aromatic hydrocarbon group) in Ar is, for example, 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 preferred phenylene, naphthylene and anthracenylene groups, with phenylene and naphthylene groups being particularly preferred and phenylene being particularly preferred.

[0022] The aromatic hydrocarbon group may have one or more kinds of substituents. The number of substituents that the aromatic hydrocarbon group may have is, for example, 1 to 3, and preferably 1 to 2.

[0023] 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).

[0024] The n represents an integer of 0 or more, for example, 0, 1, or 2, and preferably 0 or 1.

[0025] The linking group is a divalent group having one or more atoms, such as a divalent hydrocarbon group, or a group in which two or more divalent hydrocarbon groups are linked via an ether bond (-O-) or a thioether bond (-S-), etc. The linking group may have a substituent such as a hydroxyl group or a carboxyl group.

[0026] Examples of the divalent hydrocarbon group include linear or branched alkylene groups having 1 to 18 carbon atoms (preferably 1 to 10 carbon atoms, particularly preferably 1 to 5 carbon atoms, most preferably 1 to 3 carbon atoms, and particularly preferably 1 or 2 carbon atoms), such as methylene, methylmethylene, dimethylmethylene, ethylene, and propylene; 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylene. cycloalkylene groups having 3 to 18 carbon atoms (preferably 3 to 6 carbon atoms, particularly preferably 4 to 6 carbon atoms, most preferably 5 or 6 carbon atoms), such as a cyclohexylidene group; C groups such as a phenylene group (e.g., o-phenylene, m-phenylene, p-phenylene), a phenylenebis(methylene) group (e.g., 1,2-phenylenebis(methylene), 1,3-phenylenebis(methylene), 1,4-phenylenebis(methylene)), a biphenylene group, a naphthylene group, a binaphthylene group, an anthracenylene group, and a phenanthrylene group; 6-14 Examples include an arylene group.

[0027] The linking group is preferably a divalent hydrocarbon group, and particularly preferably an alkylene group.

[0028] L 1 is preferably a single bond or a divalent hydrocarbon group, more preferably a single bond or an alkylene group, and particularly preferably a single bond.

[0029] L 2 is preferably a linking group, more preferably a divalent hydrocarbon group, particularly preferably an alkylene group, most preferably a methylene group or an ethylene group, and particularly preferably a methylene group.

[0030] L3 is preferably a single bond or a divalent hydrocarbon group. As the divalent hydrocarbon group, an alkylene group is particularly preferred, and an ethylene group or a propylene group is most preferred.

[0031] L 4 , L 5 is preferably a single bond or a divalent hydrocarbon group. As the divalent hydrocarbon group, an alkylene group is particularly preferred, a methylene group or an ethylene group is most preferred, and a methylene group is particularly preferred.

[0032] 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 5 and n is the same as defined above. The phenylene group in the following formula may have a substituent. Examples of the substituent include the same examples as the substituents that the aromatic hydrocarbon group in Ar in formula (a) may have. [ka]

[0033] As the group represented by the formula (a), a group represented by the following formula (a-2) or a group represented by the following formula (a-2') is also preferred. 1 , L 2 , n is the same as above. Two L 3 ', 2n L 4 ', and 2n L 5 In the following formula (a-2'), Ar, L 1 ~L 3 , n is the same as above. 3 ', n L 4 ', and n L 5 ' may be the same or different and each represents a linking group. Examples of the linking group include the same as those mentioned above. [ka]

[0034] The group represented by the formula (a-2) is preferably a group represented by the following formula (a-2-1) or a group represented by the following formula (a-2-2). 1 , L 2 is the same as above. Two L 3 In the following formula (a-2-2), Ar, L 1 , L 2 is the same as above. Two L 3 ', two L's 4 ', and two L's 5 ' may be the same or different and each represents a linking group. Examples of the linking group include the same as those mentioned above. [ka]

[0035] The group represented by the formula (a-2') is preferably a group represented by the following formula (a-2'-1) or a group represented by the following formula (a-2'-2). 1 , L 2 is the same as above. 3 In the following formula (a-2'-2), Ar, L 1 , L 2 , L 3 is the same as above. 3 'L 4 ', and L 5 ' may be the same or different and each represents a linking group. Examples of the linking group include the same as those mentioned above. [ka]

[0036] As the group represented by the formula (a), groups represented by the following formulae (a-3-1) to (a-3-4) are particularly preferred. 1 ~L 3 , L 3 '~L 5 ' is the same as above. [ka]

[0037] The carboxy group in the formula may form a salt, such as a monovalent metal salt such as an alkali metal salt (e.g., lithium salt, sodium salt, potassium salt), a divalent metal salt such as an alkaline earth metal salt (e.g., calcium salt, magnesium salt), or an ammonium salt (e.g., ammonium salt, primary to quaternary alkyl ammonium salt).

[0038] The total average degree of substitution of the group represented by formula (a) (the average value of the degree of substitution of the hydrogen atoms of the hydroxyl groups at the 2-, 3-, and 6-positions of the glucose units constituting the cellulose with the group represented by formula (a)) is, for example, 0.1 to 3.0. In terms of obtaining the effect of increasing the amount of transition metal adsorbed, the lower limit of the total degree of substitution is preferably 0.5, particularly preferably 0.8, most preferably 1.2, and particularly preferably 1.5. The upper limit of the total degree of substitution may be 2.8, 2.5, or 2.3.

[0039] The amount of the group represented by formula (a) introduced into the cellulose derivative (I) is, for example, 1.6 mmol / g or more. From the viewpoint of obtaining the effect of increasing the amount of transition metal adsorption, the lower limit of the amount of the group introduced is preferably 1.8 mmol / g, particularly preferably 2.0 mmol / g, and most preferably 3.0 mmol / g. Furthermore, from the viewpoint of obtaining the effect of increasing the amount of transition metal adsorption, the upper limit of the amount of the group introduced is, for example, 3.3 mmol / g, and may be 3.2 mmol / g.

[0040] The group represented by formula (a) possessed by the cellulose derivative (I) forms a chelate with the transition metal when the transition metal is present, and captures the metal. The mode in which the cellulose derivative (I) forms a chelate with the transition metal is schematically explained below, taking as an example the case of a cellulose derivative having a group represented by formula (a-3-1). In the following formula, M t+ represents a t-valent transition metal cation, where t is, for example, an integer of 1 to 6, preferably 2 to 4, and particularly preferably 2 or 3.1 , L 2 , L 3 ' is the same as above. [ka]

[0041] Examples of transition metals include mercury, copper, lead, nickel, zinc, cadmium, cobalt, iron, manganese, etc. Among these, at least one selected from copper, lead, and nickel is preferred, and copper and / or lead are particularly preferred.

[0042] When a 1.0 mM aqueous solution of transition metals is used, the equilibrium adsorption amount of the cellulose derivative (I) is, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption amount is, for example, 4.4 mmol / g.

[0043] The cellulose derivative (I) has an equilibrium copper adsorption capacity of, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more, when a 1.0 mM copper aqueous solution is used. The upper limit of the equilibrium adsorption capacity is, for example, 4.4 mmol / g.

[0044] The cellulose derivative (I) exhibits an equilibrium adsorption of lead in a 1.0 mM aqueous lead solution of, for example, 0.1 mmol / g or more, preferably 0.2 mmol / g or more, more preferably 0.4 mmol / g or more, more preferably 0.5 mmol / g or more, more preferably 1 mmol / g or more, and more preferably 1.5 mmol / g or more. The upper limit of the equilibrium adsorption is, for example, 3.0 mmol / g.

[0045] When a 2.0 mM aqueous solution of transition metals is used, the equilibrium adsorption amount of the cellulose derivative (I) is, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption amount is, for example, 4.4 mmol / g.

[0046] When a 2.0 mM copper aqueous solution is used, the copper equilibrium adsorption amount of the cellulose derivative (I) is, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption amount is, for example, 4.4 mmol / g.

[0047] The cellulose derivative (I) exhibits an equilibrium adsorption capacity of lead in a 2.0 mM aqueous lead solution of, for example, 0.1 mmol / g or more, preferably 0.2 mmol / g or more, more preferably 0.4 mmol / g or more, more preferably 0.5 mmol / g or more, more preferably 1 mmol / g or more, and more preferably 1.5 mmol / g or more. The upper limit of the equilibrium adsorption capacity is, for example, 3.0 mmol / g.

[0048] The equilibrium adsorption amount of the transition metal by the cellulose derivative (I) is the adsorption amount when 2.5 mg of the cellulose derivative (I) is immersed in 5 mL of an aqueous transition metal solution having a pH of 5 and a transition metal concentration of 1.0 mM or 2.0 mM at 25°C and stirred at 200 rpm for 1 hour, and is calculated using the formula described in the Examples.

[0049] Furthermore, the cellulose derivative (I) is insoluble in water because it has an aromatic hydrocarbon group represented by Ar in its side chain, and therefore does not require insolubilization treatment such as crosslinking. Furthermore, since the cellulose derivative (I) is insoluble in water, if it is used as a solid-phase adsorbent, transition metals present in an aqueous solution can be efficiently recovered by solid-phase extraction.

[0050] 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% by weight, and particularly preferably less than 5% by weight.

[0051] The amount (%) of the cellulose derivative (I) dissolved in water can be determined by the following method. 1. 10 mg of the cellulose derivative (I) and 10 mL of a 2.0 mM copper aqueous solution (pH 5) are added to a 100 mL centrifuge tube to obtain an adsorbent-containing solution. 2. The resulting adsorbent-containing liquid is subjected to adsorption treatment by stirring at 200 rpm at 25°C for 1 hour. 3. After the adsorption treatment, the adsorbent-containing liquid is filtered using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the adsorbent obtained as filter cake is placed in a desiccator filled with a drying agent (silica gel). After drying for 24 hours in a constant temperature bath at 40°C, the weight (We: mg) is measured. 4. The amount of cellulose derivative (I) dissolved in water (%) is calculated using the following formula, assuming the initial weight of the cellulose derivative (I) to be W0 (mg). Dissolution amount (%)=(W0-We) / W0

[0052] Furthermore, as described below, the cellulose derivative (I) is produced using a cellulose derivative having a repeating unit represented by the following formula (II) 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 a crosslinked structure with difficulty.

[0053] 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 many groups represented by formula (a) introduced therein.

[0054] The shape of the cellulose derivative (I) is not particularly limited as long as it does not impair the effects of the present disclosure, and examples thereof include gel, powder, particles, pellets, flakes, needles, threads, nonwoven fabric, etc. Among these, powder, particles, pellets, flakes, needles, threads, and nonwoven fabric are preferred because they can be easily recovered from the aqueous solution after adsorbing a transition metal in the aqueous solution.

[0055] The cellulose derivative (I) has the above properties and can therefore be suitably used as an adsorbent (particularly, a solid-phase adsorbent) for transition metals.

[0056] [Method for producing cellulose derivative (I)] The cellulose derivative (I) can be produced, for example, through the following steps 1 and 2. [Step 1] Cellulose is treated with a compound represented by the following formula (2): [ka] (In formula (2), Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each represents a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to react a compound represented by the following formula (II): [ka] [The three R in formula (II) b are the same or different and are a hydrogen atom or a group represented by the following formula (b). b at least one of which is a group represented by the formula (b). [ka] (In the formula, Ar, L 1 , L 2 , Y 2 (same as above) A cellulose derivative having a repeating unit represented by [Step 2] A cellulose derivative having a repeating unit represented by formula (II) is treated with a compound represented by formula (3) below: [ka] (In formula (3), n represents an integer of 0 or more. 3 , 2n L 4 , and 2n L 5 are the same or different and are a single bond or a linking group. 1 , and 2n R 2 are the same or different and are a hydrogen atom or a carboxy group. 1 , and 2n R 2 At least two selected from R are carboxy groups, and the carboxy groups may form salts or may be protected with protecting groups. 3 is a hydrogen atom or a hydrocarbon group) React the compound represented by

[0057] Ar and L in the above formula 1 ~L 5 , R 1 , R 2 , n is the same as above.

[0058] R in the formula (3) 3 is a hydrogen atom or a hydrocarbon group. The hydrocarbon group is, for example, a hydrocarbon group having 1 to 10 carbon atoms, preferably a hydrocarbon group having 1 to 5 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 3 carbon atoms. The hydrocarbon group is preferably an aliphatic hydrocarbon group, and particularly preferably an alkyl group having 1 to 10 carbon atoms (preferably 1 to 5, particularly preferably 1 to 3, and most preferably 1 to 2), such as a methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, decyl group, or dodecyl group.

[0059] R 3 Among these, a hydrogen atom is preferred.

[0060] [Process 1] Step 1 is a step in which a compound represented by the formula (2) (hereinafter, sometimes referred to as "compound (2)") is reacted with the hydroxyl groups of cellulose to produce a cellulose derivative having a repeating unit represented by the formula (II) (hereinafter, sometimes referred to as "cellulose derivative (II)").

[0061] 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).

[0062] Examples of the aromatic hydrocarbon group for Ar in the compound (2) include the same as those for Ar in the group represented by the formula (a).

[0063] The aromatic hydrocarbon group may be -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).

[0064] When the aromatic hydrocarbon group has other substituents, the number of the other substituents is, for example, 1 to 3, and preferably 1 to 2.

[0065] The amount of compound (2) used is, for example, 1 part by weight or more, preferably 3.5 to 10.5 parts by weight, relative to 1 part by weight of the cellulose.

[0066] Also, Y in compound (2) 1 When is a halogen atom, the reaction in step 1 is preferably carried out in the presence of a base. The base includes organic bases and inorganic bases.

[0067] Examples of the organic base include aliphatic amines (e.g., secondary aliphatic amines such as diisopropylamine, and tertiary aliphatic amines such as triethylamine, tripropylamine, tributylamine, ethyldiisopropylamine, dimethylcyclohexylamine, dicyclohexylethylamine, tribenzylamine, and benzyldimethylamine), aromatic amines (e.g., N,N-dimethylaniline, N,N-diethylaniline, methyldiphenylamine, and triphenylamine), cyclic amines (e.g., Examples include 1,5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene, 1,4-diazabicyclo[2.2.2]octane, N-methylpiperidine, 1,4-dimethylpiperazine, N-methylpyrrolidine, N-methylmorpholine, 1-methyl-2,2,6,6-tetramethylpiperidine, pyridine, 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine (DMAP), 2,6-di-t-butylpyridine, etc. These may be used alone or in combination of two or more.

[0068] Examples of the inorganic base include alkali metal carbonates such as sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate; and alkali metal phosphates such as sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate. These may be used alone or in combination of two or more.

[0069] As the base, an organic base is preferred because it has an excellent effect of promoting the reaction between cellulose and compound (2), a tertiary amine is particularly preferred, and ethyldiisopropylamine is particularly preferred because it suppresses side reactions with compound (2).

[0070] The amount of the base used is, for example, 0.5 to 2.0 moles per mole of compound (2).

[0071] Y in compound (2) 1 When is a hydroxyl group, 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.

[0072] The amount of the condensing agent used is, for example, 1 to 10 moles per mole of compound (2).

[0073] 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, and N-methylpyrrolidone; nitriles such as acetonitrile, propionitrile, and benzonitrile; and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more.

[0074] As the solvent, an amide such as N,N-dimethylacetamide is preferred because of its excellent cellulose solubility, and it is particularly preferred to use a solvent mixed with a lithium salt such as lithium chloride. The concentration of the lithium salt in the solvent is, for example, 1 to 30% by weight. When a solvent with excellent cellulose solubility is used, not only the hydroxyl groups present on the outer surface of the cellulose but also those present inside the cellulose can be substituted with the group represented by formula (a), and the total degree of substitution of the resulting cellulose derivative (I) is significantly increased.

[0075] The amount of the solvent used is, for example, 10 to 500 mL, preferably 20 to 100 mL, per 1 g 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.

[0076] The reaction temperature in step 1 is, for example, 20 to 120°C. By adjusting the reaction temperature within the above range, it is possible to control the total average substitution degree 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 substitution degree of the groups represented by formula (b) in the resulting cellulose derivative (II) tends to be lower.

[0077] The cellulose derivative (II) obtained via step 1 has a total average degree of substitution of the group represented by formula (b) of, for example, 0.1 to 3.0. In terms of obtaining the effect of increasing the amount of transition metal adsorbed, the lower limit of the total degree of substitution is preferably 0.5, particularly preferably 0.8, most preferably 1.2, and particularly preferably 1.5. The upper limit of the total degree of substitution may be 2.7, 2.5, 2.4, or 2.3.

[0078] [Process 2] Step 2 is a step of reacting the compound represented by the formula (3) (hereinafter, sometimes referred to as "compound (3)") with the cellulose derivative (II) produced through step 1. Through step 2, the cellulose derivative (I) is obtained.

[0079] As the compound (3), for example, a compound represented by the following formula (3-1), a compound represented by the following formula (3-1′), and a compound represented by the following formula (3-1″) are preferred. In the following formula (3-1), R 3 , n is the same as above. Two L 3 ', 2n L 4 ', and 2n L 5 In the following formula (3-1'), R 3 , L 3 , n is the same as above. 4 ', and two L's 5 ' are the same or different and are linking groups. In the following formula (3-1"), R 3 , L 3 , n is the same as above. Two L 3 ', n+1 L 4 ', and n L 5 ' may be the same or different and is a linking group. [ka]

[0080] As the compound represented by formula (3-1), compounds represented by the following formulae (3-1-1), (3-1-2), and (3-1-3) are particularly preferred. In the following formula (3-1-1), R 3 is the same as above. Two L 3 ' may be the same or different and is a linking group. In the following formula (3-1-2), R 3 is the same as above. Two L 3 ', L 4 ' and L 5 ' may be the same or different and is a linking group. In the following formula (3-1-3), R 3 is the same as above. Two L 3 ', two L's 4 ' and two L's 5 ' may be the same or different and is a linking group. [ka]

[0081] As the compound represented by formula (3-1'), a compound represented by the following formula (3-1'-1) is particularly preferred. 3 , L 3 is the same as above. 3 ', L 4 ' and L 5 ' may be the same or different and is a linking group. As the compound represented by formula (3-1"), a compound represented by the following formula (3-1"-1) is particularly preferred. In the following formula (3-1"-1), R 3 , L 3 is the same as above. Two L 3 ', two L's 4 ', and L 5 ' may be the same or different and is a linking group. [ka]

[0082] Examples of compound (3) include iminodiacetic acid, ethylenediaminetriacetic acid, propylenediaminetriacetic acid, butylenediaminetriacetic acid, diethylenetriaminetetraacetic acid, dipropylenetriaminetetraacetic acid, and salts thereof, which can be used alone or in combination of two or more.

[0083] The carboxyl group contained in compound (3) may form a salt, such as an alkaline earth metal salt of calcium or magnesium.

[0084] The carboxy group contained in compound (3) may be protected with a protecting group, such as a benzyl group, an allyl group, or a t-butyl group.

[0085] The amount of 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, relative to 1 part by weight of the cellulose derivative (II).

[0086] 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. As the base, an organic base is preferred, in that it can suppress side reactions between the cellulose derivative (II) and the base, and a tertiary amine is particularly preferred, with triethylamine and ethyldiisopropylamine being most preferred.

[0087] The amount of the base used is, for example, 0.5 to 1.5 moles per mole of compound (3).

[0088] 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, propanol, and butyl alcohol; N-methylpyrrolidone, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide. These solvents can be used alone or in combination of two or more.

[0089] 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.

[0090] The reaction temperature in step 2 is, for example, 20 to 120° C. The reaction time is, for example, 1 to 72 hours.

[0091] When a compound in which the carboxy group is protected with a protecting group is used as compound (3), it is preferable to provide a step of removing the protecting group introduced into the carboxy group of the produced cellulose derivative after completion of the reaction in step 2. Through this step, cellulose derivative (I) is produced.

[0092] The method for removing the protecting group can be appropriately selected depending on the type of the protecting group.

[0093] When a t-butyl ester group is present as a protecting group, the protecting group can be removed by reacting with an acid such as trifluoroacetic acid.

[0094] When a benzyl group or an allyl group is present as a protecting group, the protecting group can be removed by reacting with a catalyst (Pd—C, etc.).

[0095] After the reaction is completed, the resulting 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.

[0096] [Transition metal adsorbent] The transition metal adsorbent of the present disclosure contains the cellulose derivative (I).

[0097] The transition metal 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 transition metal 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 transition metals.

[0098] The transition metal adsorbent may contain other cellulose-based components 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-based components contained in the transition metal adsorbent. If the proportion of the cellulose derivative (I) is below the above range, it tends to be difficult to efficiently and selectively adsorb transition metals. The cellulose-based components are cellulose and cellulose derivatives.

[0099] The dosage form of the transition metal adsorbent is not particularly limited as long as it is effective, and examples thereof include powder, particles, pellets, flakes, needles, threads, and nonwoven fabric.

[0100] The transition metal adsorbent has the properties of the cellulose derivative (I). That is, it has a high adsorption power for transition metals. Examples of transition metals include mercury, copper, lead, nickel, zinc, cadmium, cobalt, iron, and manganese. Among them, at least one selected from copper, lead, and nickel is preferred, and copper and / or lead are particularly preferred.

[0101] The transition metal adsorbent has an equilibrium adsorption capacity of transition metals when a 1.0 mM aqueous transition metal solution is used, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption capacity is, for example, 4.4 mmol / g.

[0102] When a 1.0 mM copper aqueous solution is used, the equilibrium adsorption amount of the transition metal adsorbent is, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption amount is, for example, 4.4 mmol / g.

[0103] The equilibrium adsorption amount of lead of the transition metal adsorbent when a lead aqueous solution having a concentration of 1.0 mM is used is, for example, 0.1 mmol / g or more, preferably 0.2 mmol / g or more, more preferably 0.4 mmol / g or more, more preferably 0.5 mmol / g or more, more preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more. The upper limit of the equilibrium adsorption amount is, for example, 3.0 mmol / g.

[0104] The transition metal adsorbent has an equilibrium adsorption capacity of transition metals when a 2.0 mM aqueous transition metal solution is used, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption capacity is, for example, 4.4 mmol / g.

[0105] When a 2.0 mM copper aqueous solution is used, the equilibrium copper adsorption capacity of the transition metal adsorbent is, for example, 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, more preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more, more preferably 2 mmol / g or more, and more preferably 3 mmol / g or more. The upper limit of the equilibrium adsorption capacity is, for example, 4.4 mmol / g.

[0106] The equilibrium adsorption amount of lead of the transition metal adsorbent when a lead aqueous solution having a concentration of 2.0 mM is used is, for example, 0.1 mmol / g or more, preferably 0.2 mmol / g or more, more preferably 0.4 mmol / g or more, more preferably 0.5 mmol / g or more, more preferably 1 mmol / g or more, more preferably 1.5 mmol / g or more. The upper limit of the equilibrium adsorption amount is, for example, 3.0 mmol / g.

[0107] The equilibrium adsorption amount of a transition metal by a transition metal adsorbent is the adsorption amount when 2.5 mg of the transition metal adsorbent is immersed in 5 mL of an aqueous transition metal solution having a pH of 5 and a transition metal concentration of 1.0 mM or 2.0 mM at 25°C and stirred at 200 rpm for 1 hour, and is calculated using the formula described in the Examples.

[0108] Because the transition metal adsorbent has the above-mentioned properties, it is suitable for use in selectively recovering transition metals from industrial wastewater, mine wastewater, hot spring water, seawater, groundwater, and the like.

[0109] The transition metal adsorbent is insoluble in water, and the amount of the adsorbent dissolved in water is, for example, less than 15% by weight, preferably less than 10% by weight, and particularly preferably less than 5% by weight. The amount of the adsorbent dissolved in water can be determined in the same manner as the amount of the cellulose derivative (I).

[0110] The transition metal adsorbent has resistance to dissolution as described above and can therefore be used as a solid-phase adsorbent. The use of the transition metal adsorbent makes it possible to efficiently recover transition metals present in industrial wastewater, mine wastewater, hot spring water, seawater, groundwater, etc. by solid-phase extraction.

[0111] [Transition metal recovery method] The method for recovering a transition metal according to the present disclosure involves recovering a transition metal dissolved in an aqueous solution (or a transition metal dissolved in an aqueous solution) by adsorbing it onto the cellulose derivative (I).

[0112] The aqueous solution contains at least a transition metal in a dissolved state. The aqueous solution may contain other components in addition to the transition metal. Examples of the aqueous solution include aqueous solutions containing dissolved transition metals from which removal of the transition metal or reduction of the transition metal concentration is desired (e.g., industrial wastewater, mine wastewater, hot spring water, seawater, groundwater, etc. containing dissolved transition metals).

[0113] The transition metal 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 transition metal concentration is, for example, 10,000 ppm, 1,000 ppm, or 500 ppm.

[0114] The method for adsorbing a transition metal 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 a transition metal is dissolved is passed through the column, and a method in which the cellulose derivative (I) is added to an aqueous solution in which a transition metal is dissolved and the mixture is stirred.

[0115] In the method for recovering transition metals, it is preferable to adjust the pH of the cellulose derivative (I) to, for example, 1 to 9 (preferably 3 to 7), since this can further improve the adsorption power of transition metals and allow more efficient recovery of transition metals. 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).

[0116] Furthermore, cellulose derivative (I) does not cause any exhaust emissions when burned. Therefore, after adsorbing transition metals, if necessary, water can be separated and removed by centrifugation or filtration, and then burned, allowing the volume to be reduced without causing exhaust emissions and reducing disposal costs.

[0117] 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 without departing from the spirit of the present disclosure. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, the present disclosure is not limited by the embodiments. [Example]

[0118] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0119] Example 1 (Preparation of cellulose derivative (1)) (Process I) Cellulose (a polymer having a repeating unit represented by the following formula (V), 2.10 g, 13.0 mmol) was placed in a reaction vessel and dried in vacuum at 90° C. for 2 hours. Then, N,N-dimethylacetamide (70 mL) was added under a nitrogen atmosphere, and the mixture was stirred for 21 hours. Thereafter, the reaction vessel was cooled to 0° C. in an ice bath, lithium chloride (4.32 g) was added, and the mixture was stirred while being heated to room temperature (25° C.) to dissolve the cellulose. The reaction vessel was cooled again 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, followed by stirring for 20 hours while warming to room temperature (25°C), thereby obtaining reaction solution A. The resulting reaction liquid A was poured into methanol and reprecipitated 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 the 4-(chloromethyl)benzoyloxy group in cellulose (4-chloromethyl)benzoate (1) was calculated to be approximately 1.5.

[0120] [ka] 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-CH2and residual H2O),4.5-4.9(br,Ar-CH2,overlapped with Cellulose-H)

[0121] (Process II) Under a nitrogen atmosphere, the cellulose (4-chloromethyl)benzoate (1) (0.200 g, 0.510 mmol) obtained in step (I) was placed in a two-necked recovery flask, and dimethyl sulfoxide (3.2 mL) was added to dissolve it. Thereafter, iminodiacetic acid (0.326 g, 2.88 mmol) and triethylamine (0.89 mL, 6.4 mmol) were added to the solution of cellulose (4-chloromethyl)benzoate (1), and the mixture was stirred at 80° C. for 5 hours to obtain reaction solution B. While cooling the reaction solution B in an ice bath, concentrated hydrochloric acid (0.6 mL) was added, and the mixture was poured into ethanol to reprecipitate, yielding solid B. The resulting solid B was collected by centrifugation and washed with ethanol, water, and diethyl ether. The resulting solid B was dried in vacuo to obtain cellulose derivative (1) (a polymer having a repeating unit represented by the following formula (I-1), 163 mg, yield approximately 60%) as a colorless powder. The total average degree of substitution of chelating functional groups in cellulose derivative (1) and the amount of chelating functional groups introduced are 1 The total average degree of substitution of chelate functional groups in cellulose derivative (1) was 1.2 to 1.5. The amount of chelate functional groups introduced into cellulose derivative (1) is shown in the table below. The IR spectrum of the cellulose derivative (1) is shown in FIG.

[0122] [ka] Cellulose 4-(N,N'-biscarboxymethylamino)methylbenzoate 1 H-NMR(500MHz,DMSO-d6,rt):δ6.7-8.3(br,Ar-H),2.6-5.8(br,cellulose-H,overlapped with Ar-CH2and residual H2O),2.6-4.0(br,Ar-CH2,overlapped with Cellulose-H,and residual H2O)

[0123] Example 2 (Preparation of cellulose derivative (2)) (Process 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 the 4-(chloromethyl)benzoyloxy group in cellulose (4-chloromethyl)benzoate (2) was calculated to be approximately 2.0.

[0124] (Process II) A cellulose derivative (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). The total average degree of substitution of chelating functional groups in cellulose derivative (2) and the amount of chelating functional groups introduced are 1 The total average degree of substitution of chelate functional groups in cellulose derivative (2) was 1.6 to 2.0, as calculated from the results of H-NMR measurement. The amount of chelate functional groups introduced into cellulose derivative (2) is shown in the table below. The IR spectrum of the cellulose derivative (2) is shown in FIG.

[0125] Example 3 (Preparation of cellulose derivative (3)) (Process 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 substitution degree of the 4-(chloromethyl)benzoyloxy group in cellulose (4-chloromethyl)benzoate (3) was calculated to be approximately 2.5.

[0126] (Process 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). The total average substitution degree of the chelating functional group of the cellulose derivative (3) and the amount of the chelating functional group introduced are 1 The total average degree of substitution of the chelate functional groups in the cellulose derivative (3) was 2 to 2.5. The amount of the chelate functional groups introduced into the cellulose derivative (3) is shown in the table below. The IR spectrum of the cellulose derivative (3) is shown in FIG.

[0127] [Evaluation of transition metal adsorption amount 1] The cellulose derivatives of the examples and the adsorbents of the comparative examples were used as test specimens, and the adsorption ability of the test specimens for transition metals was evaluated by the following method (batch method). That is, 2.5 mg of the test sample and 5 mL of an aqueous transition metal solution (pH and transition metal concentration as shown in the table) were added to a 50 mL centrifuge tube to obtain an adsorbent-containing solution. The resulting adsorbent-containing liquid was subjected to adsorption treatment by stirring at 25°C and 200 rpm for the time shown in the table. Next, the test specimen-containing liquid after the adsorption treatment was filtered using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the transition metal ion concentration (Ce: mmol / L) in the filtrate was quantified using an ICP emission spectrometer (iCAP6300, manufactured by Thermo Fischer Scientific).

[0128] The transition metal ion concentration in the adsorbent-containing solution before adsorption treatment was defined as C0 (mmol / L), the volume of the transition metal aqueous solution was defined as V0 (L), and the weight of the added test specimen was defined as m (g), and the equilibrium adsorption amount of the transition metal (mmol / g) was calculated using the following formula. Equilibrium adsorption amount of transition metal (mmol / g) = (C0-C e )×V0 / m

[0129] [Evaluation of transition metal adsorption amount 2] The cellulose derivative (3) obtained in Example 3 and the adsorbent of the comparative example were used as test specimens, and the equilibrium adsorption amount was calculated in the same manner as in Transition Metal Adsorption Amount Evaluation 1, except that an aqueous solution (pH 5) with a Cu(II) ion or Pb(II) ion concentration of 2.0 mM was used as the transition metal aqueous solution and the adsorption treatment was carried out at 25°C and 200 rpm for 1 hour. The results are shown in Figure 4.

[0130] [Dissolution resistance evaluation] The cellulose derivatives of the examples and the adsorbents of the comparative examples were used as test specimens, and the dissolution resistance of the test specimens was evaluated by the following method. That is, 10 mg of the test sample and 10 mL of a 2 mM copper aqueous solution (pH 5) were added to a 50 mL centrifuge tube to obtain a test sample-containing solution. The obtained liquid containing the test specimen was subjected to an adsorption treatment by stirring at 200 rpm at 25°C for 10 hours. Next, the adsorbent-containing liquid after the adsorption treatment was filtered using a membrane filter (nitrocellulose, pore size: 0.45 μm), and the test specimen obtained as filter cake was placed in a desiccator filled with a drying agent (silica gel) and dried in a thermostatic bath at 40°C for 24 hours, after which its weight (We: mg) was measured. The initial weight of the test specimen was taken as W0 (mg), and the amount of the test specimen that dissolved in water (%) was calculated using the following formula, and the resistance to dissolution in water was evaluated according to the following criteria. Dissolution amount (%)=(W0-We) / W0 <Evaluation criteria for dissolution resistance> Excellent: Less than 5% solubility in water Good: Dissolution in water is 5% or more, but less than 10% Acceptable: Dissolving amount in water is 10% or more, but less than 15% Unacceptable: Dissolving in water is 15% or more

[0131] [Table 1]

[0132] The adsorbents of Comparative Examples 1 to 3 are explained below. Adsorbent of Comparative Example 1: Adsorbent based on styrene-divinylbenzene copolymer and having chelating functional groups derived from iminodiacetic acid and EDTA, product name "Chelex 100", manufactured by Bio-Rad Laboratories, Inc. Adsorbent of Comparative Example 2: Adsorbent having a chelating functional group derived from iminodiacetic acid and based on hydrophilic methacrylate, product name "InertStep ME-2", manufactured by GL Sciences, Inc. Adsorbent of Comparative Example 3: Adsorbent based on hydrophilic methacrylate and having chelating functional groups derived from iminodiacetic acid and EDTA, product name "NOBIAS CHELATE PA-1", manufactured by Hitachi High-Technologies Corporation

[0133] As can be seen from Table 1, the cellulose derivatives of the Examples can adsorb large amounts of transition metals more quickly than the adsorbents of the Comparative Examples. Furthermore, the cellulose derivatives of the Examples have excellent resistance to dissolution in water. Therefore, it can be seen that they can be suitably used as solid-phase adsorbents for transition metals.

Claims

1. A cellulose derivative having a repeating unit represented by the following formula (I): 【Chemistry 1】 [In formula (I), three R a are the same or different and are a hydrogen atom or a group represented by the following formula (a): a at least one of which is a group represented by the following formula (a): 【Chemistry 2】 (In formula (a), Ar represents an aromatic hydrocarbon group. n represents an integer of 0 or more. L 1 , L 2 , two L 3 , 2n L 4 , and 2n L 5 are the same or different and each represent a single bond or a linking group. 1 , and 2n R 2 are the same or different and each represent a hydrogen atom or a carboxy group. 1 , and 2n R 2 At least two selected from the above are carboxy groups, and the carboxy groups may form salts.

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. 2. The cellulose derivative according to claim 1, wherein the amount of the group represented by formula (a) introduced is 1.6 mmol / g or more.

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

5. The transition metal adsorbent according to claim 4, which is an adsorbent for at least one metal selected from mercury, copper, lead, nickel, zinc, cadmium, cobalt, iron, and manganese.

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

7. A method for producing a cellulose derivative, comprising the steps of: producing the cellulose derivative according to any one of claims 1 to 3 through the following steps 1 and 2: [Step 1] Cellulose is treated with a compound represented by the following formula (2): 【Transformation 3】 (In formula (2), Ar is an aromatic hydrocarbon group. L 1 , L 2 are the same or different and each represents a single bond or a linking group. 1 is a hydroxyl group or a halogen atom. 2 is a halogen atom) to react a compound represented by the following formula (II): 【Chemistry 4】 [wherein the three R b are the same or different and are a hydrogen atom or a group represented by the following formula (b). b at least one of which is a group represented by formula (b). 【Transformation 5】 (In the formula, Ar, L 1 , L 2 , Y 2 is the same as above) A cellulose derivative having a repeating unit represented by [Step 2] A cellulose derivative having a repeating unit represented by formula (II) is treated with a compound represented by formula (3) below: 【Transformation 6】 (In formula (3), n represents an integer of 0 or more. Two L 3 , 2n L 4 , and 2n L 5 are the same or different and each represent a single bond or a linking group. 1 , and 2n R 2 are the same or different and each represent a hydrogen atom or a carboxy group. 1 , and 2n R 2 At least two selected from R are carboxy groups, and the carboxy groups may form salts or may be protected with protecting groups. 3 is a hydrogen atom or a hydrocarbon group) React the compound represented by

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