JPH0673635B2 - Method for producing chitosan-based chelate molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention introduces branched polyethyleneimine into a porous chitosan molded article to improve the ion exchange capacity, and then introduces iminodiacetic acid as a metal coordinating group. The present invention relates to a method for producing a chitosan-based chelate molded product obtained by the method. The chitosan-based chelate molded product obtained in the present invention is suitable for use as a versatile chelate resin for adsorption and recovery of various metals, and has a large adsorption affinity for various metals even in an acidic region where the pH is low, It is a chelate molded product with excellent ability.

[Conventional technology]

The applicant of the present invention has disclosed that, in Japanese Patent Application No. 63-198613 (Japanese Patent Laid-Open No. 2-48044), a porous chitosan molded product is reacted with a glycidyl ether of an aliphatic polyalcohol, and then polyethyleneimine is introduced to obtain an extremely high ion content. A method for producing anion exchange chitosan moldings with exchange capacity was proposed. The molded product is excellent not only in anion exchange capacity but also in metal collection capacity, and is capable of adsorbing and recovering metal with extremely high efficiency. Furthermore, since it has a large number of primary, secondary, and tertiary amines that form a complex with a metal, the once adsorbed metal easily elutes in an acidic aqueous solution, and therefore a molded article for separation and purification of the metal by adjusting the pH. Is suitable as

In addition, the present applicant has filed Japanese Patent Application No. 1-51089 (Japanese Patent Laid-Open No. 2-229830).
No. 1) and Japanese Patent Application No. 1-51090 (JP-A No. 2-229831), the chitosan molded product obtained as described above is reacted with an acid anhydride of an aromatic polycarboxylic acid in a polar solvent, or By reacting this with acetic anhydride, yttrium,
A method for producing a chitosan-based chelate resin that adsorbs a rare metal such as indium has been disclosed.

However, the chitosan-based molded product obtained by any of the above methods easily elutes a metal with a weak acidic aqueous solution and is suitable for separation and purification, but adsorbs and recovers metal ions in a stronger acidic aqueous solution. It was unsuitable for use for that purpose.

[Problems to be Solved by the Invention]

The present invention, after introducing a branched polyethyleneimine into the porous chitosan molded article to improve the exchange capacity, by introducing iminodiacetic acid that forms a strong complex with a metal ion as a metal coordination group, the use pH is low. Even in the range, it has a large adsorption affinity for various metals, and exhibits excellent ability to adsorb and recover various metal ions even under strong acidic conditions.

[Means for Solving the Problems]

The present invention, a porous chitosan molded article is reacted with a glycidyl ether of an aliphatic polyalcohol, with or without reaction with epichlorohydrin, then with polyethyleneimine, then with epichlorohydrin,
Further, it is a method for producing a chitosan-based chelate molded product by reacting with iminodiacetic acid and then with acetic anhydride.

After reacting the glycidyl ether of the aliphatic polyalcohol with the porous chitosan molded product in the present invention, when reacting with polyethyleneimine, it is not always necessary to react with epichlorohydrin before the reaction with polyethyleneimine. The ion exchange capacity can be further increased by adding this step.

The low molecular weight chitosan having an average molecular weight of 10,000 to 230,000 is used for producing the porous chitosan molded product used in the present invention. The low molecular weight chitosan is dissolved in an aqueous solution of acetic acid, dichloroacetic acid, formic acid alone or in a mixture to obtain a chitosan acidic aqueous solution. The concentration of chitosan in the chitosan acidic aqueous solution is 2 to 20% (wt%), and can be freely selected within a range that is easy to handle. In order to regenerate chitosan to obtain a porous chitosan molded article, for example, porous granular chitosan is prepared by dropping the chitosan acidic aqueous solution into the basic coagulation bath under pressure from a nozzle having a pore size of 0.1 to 0.25 mmφ. Is obtained,
Also, chitosan acidic aqueous solution is extruded from a nozzle with a pore size of 0.1 to 0.25 mmφ into a basic coagulation bath with a metering pump, spun and regenerated to produce chitosan fibers, and also extruded into a film in the basic coagulation bath for regeneration. Then, a chitosan molded product of a chitosan film is obtained. As the basic substance added to the basic coagulation bath, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonia, ethylenediamine or the like is used, and water, methinol, ethanol or the like is used as a basic solution. The polar alcohols or the mixture of water and alcohol are used in addition to the above-mentioned basic substance. The chitosan molded product obtained as described above is a porous chitosan molded product having a large number of pores.

In the method of the present invention, polyethyleneimine is first introduced into the porous chitosan molded product obtained as described above. As the introduction method, a glycidyl ether of an aliphatic polyalcohol is reacted with an amino group of a porous chitosan molded product to carry out a cross-linking reaction between chitosan molecules and at the same time introduce an epoxy group into the amino group of chitosan for activation. . Polyethyleneimine is then reacted, but in order to increase the ion-exchange capacity as described above, after reaction with the glycidyl ether of the aliphatic polyalcohol, it may be reacted with epichlorohydrin and then with polyethyleneimine. .

As the glycidyl ether of aliphatic polyalcohol,
Polyethylene glycol diglycidyl ether and alkylene glycol glycidyl ether are used. Examples of the polyethylene glycol diglycidyl ether include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, and the alkylene glycol diglycidyl ether includes trimethylene glycol diglycidyl ether and tetramethylene glycol diglycidyl ether. Examples thereof include glycidyl ether and hexamethylene glycol diglycidyl ether.

The reaction between the porous chitosan molded product and the glycidyl ether of the aliphatic polyalcohol is carried out in an aqueous solution at 20 to 100 ° C., preferably 25 to 90 ° C. for 1 to 24 hours under mild stirring to obtain the aliphatic polyalcohol. When glycidyl ether has low solubility in water, methanol, ethanol, n-
A polar solvent such as propanol or isopropyl alcohol may be added.

The polyethyleneimine to be subsequently reacted is not particularly limited, but in order to efficiently introduce epichlorohydrin in the next step, one having as much primary amine content as possible is preferable. Further, the molecular weight is used in the range of 300 to 100,000, but in the case of low molecular weight, the ion exchange capacity does not improve so much because the molecular chain of polyethyleneimine is short, so it is appropriate depending on the required ion exchange capacity. The molecular weight may be selected. The reaction with polyethyleneimine is to wash the porous chitosan molded product obtained by reacting the glycidyl ether of an aliphatic polyalcohol thoroughly with water, and then gently stir in an aqueous solution at 5 to 90 ° C, preferably 10 to 80 ° C for 1 to 48 hours. It is done by doing. In the case of high molecular weight polyethyleneimine, it is difficult to react unless it is sufficiently diffused inside the porous chitosan molded product, so it is important to select the addition amount, temperature and time of polyethyleneimine according to the desired ion exchange capacity. is there. After the completion of the reaction, the product is thoroughly washed with water to obtain a porous chitosan molded product having an excellent ion exchange capacity.

On the other hand, in the case where epichlorohydrin is reacted with the porous chitosan molded product obtained by reacting the glycidyl ether of the aliphatic polyalcohol as described above prior to the reaction with polyethyleneimine, methanol, ethanol, n-propanol, 20 ~ in polar solvent such as isopropyl alcohol
The epichlorohydrin is reacted with gentle stirring at 100 ° C, preferably 25-90 ° C for 1-24 hours. Then
The reaction with polyethyleneimine may be performed by the method described above.

Next, epichlorohydrin is reacted with the porous chitosan molded product obtained by reacting polyethyleneimine as described above,
Activates polyethyleneimine. This reaction is carried out in a polar solvent such as methanol, ethanol, n-propanol or isopropyl alcohol at 20 to 100 ° C, preferably 25
Gently stir at ~ 90 ° C for 1-24 hours with gentle stirring. Further, with respect to the activated porous chitosan molded product obtained as described above, 0.1 to 10 equivalents of iminodiacetic acid, which is the ion exchange capacity after introduction of polyethyleneimine, is added in an aqueous solution to 10 to 90%.
The reaction is carried out at ℃ for 1 to 24 hours with gentle stirring. At this time, the pH of the aqueous solution is preferably maintained in the neutral to alkaline range. After completion of the reaction, the unreacted iminodiacetic acid is removed by washing thoroughly with water.

Next, 1 to 5 parts of the obtained porous chitosan molded product was mixed with 1 to 5 parts of the polar solvent used during the reaction of polyethyleneimine.
In addition, add a large excess amount of acetic anhydride to the remaining ion exchange capacity, react at 10 to 50 ° C for 1 to 48 hours, remove unreacted acetic anhydride with the polar solvent used, and then wash thoroughly with water. Thus, the chitosan-based chelate molded product of the present invention is obtained.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the scope described in the Examples. The ion exchange capacity, compressive modulus, and metal ion adsorption amount were measured by the following methods.

Anion exchange capacity Approximately 50 ml of sample is packed in a column and 1N-NaOH 1 is passed through with SV50, and then washed with deionized water until it becomes neutral. Accurately weigh 30 ml with a graduated cylinder by the tapping method, after dehydrating while being careful not to absorb carbon dioxide in the air,
Add to 1 / 5N-HCl 500ml and gently stir 24
Leave for hours. This supernatant was used as a test solution and 10 ml was sampled. Neutralization titration was performed with 1 / 10-NaOH using a phenolphthalein solution as an indicator, and the anion exchange capacity (CTV) was determined by the following formula.

a; 1/10 N-NaOH amount required to neutralize 10 ml of test solution b; Necessary to neutralize 10 ml of 1/5 N-HCl before adding sample
1 / 10N-NaOH amount f ₁ ; 1 / 10N-NaOH titer Cation exchange capacity Approximately 50 ml of sample is packed in a column, 1N-HNO ₃ 1 is passed through SV50, and then deionized water is sufficient to neutralize. Wash with water. Accurately weigh 30 ml with a graduated cylinder by the tapping method and after dehydration
Add to 500 ml of 1 / 5N-NaOH and gently stir.
Leave for 24 hours. 10 ml of this supernatant was used as a test solution,
Methyl red was performed to neutralization titration with 1 / 10N-H ₂ SO ₄ and bromocresol green mixture as an indicator calculated cation exchange capacity (CTV) by the following equation.

c; required to neutralize the previous 1 / 5N-NaOH10ml placing _{samples; 1 / 10N-H 2 SO} 4 amount d required for neutralizing the test solution 10ml
1 / 10N-H ₂ SO ₄ amount _{f 2; 1 / 10N-H} 2 SO 4 titers compressive modulus test Rheometer NRM-2010J-CW diameter using (immobility Industry Co., Ltd.) 3.5Mmfai, depth The sample was packed in a 2 mm sample adapter, and a compressive strength when a rod having a diameter of 3.0 mm was pushed 0.2 mm at a speed of 2 cm / min was measured as an elastic modulus.

Specific surface area It was measured by the BET method using a specific surface area measuring device.

Pore size The molded product was freeze-dried and then measured with a scanning electron microscope.

Dilute the metal standard for atomic absorption with a metal ion concentration of 1,000 ppm with pure water,
A test solution having a concentration of 100 ppm was prepared by appropriately adding a 0.1 M aqueous solution of bis (2-hydroxyethyl) and iminotris (hydroxymethyl) methane to adjust the pH to a predetermined value. A resin (1 m) was added to 80 ml of the test solution, and the mixture was gently stirred at 25 ° C. for 3 days, and then the metal ion concentration in the adsorption residual liquid was measured by a plasma emission spectrophotometer (Seiko Denshi Kogyo SPS-7000).

Example 1. 78 g of chitosan having a deacetylation degree of 80% and an average molecular weight of 48,000
Was dissolved in 922 g of a 3.9% acetic acid aqueous solution. The aqueous solution was discharged together with compressed air, 6.5% NaOH, 20% ethanol, 73.5%
The mixture was dropped into a mixed aqueous solution of water, coagulated and regenerated, and sufficiently washed with water until it became neutral to obtain 700 ml (wet) of porous granular chitosan having an average particle diameter of 0.3 mmφ. 700 ml of water and 70 g of ethylene glycol diglycidyl ether were added to 700 ml (wet) of the obtained porous granular chitosan, and the mixture was reacted at 60 ° C for 1 hour. After completion of the reaction, it is washed thoroughly with water. Polyethyleneimine (SP-200, average molecular weight 10,000, Nippon Shokubai Chemical Industry Co., Ltd.)
180 g of water was dissolved in 420 g of water, and 600 ml of porous granular chitosan obtained by reacting the above ethylene glycol diglycidyl ether was added, and after gently stirring at 25 ° C for 24 hours, 70 ° C.
After the temperature was raised to 3, the reaction was stirred for 3 hours. After completion of the reaction, unreacted polyethyleneimine was removed by sufficiently washing with water. When the anion exchange capacity was measured, a porous chitosan granular molded product into which polyethyleneimine was introduced having a high exchange capacity of 1.4 meq / ml was obtained.

The water contained in the molded product was sufficiently replaced with isopropyl alcohol, and 194 g of epichlorohydrin and water were added to 500 ml of the molded product.
The mixture was placed in an aqueous solution containing 250 g and 250 g of isopropyl alcohol and reacted at 50 ° C. for 2 hours. After sufficiently removing unreacted epichlorohydrin with isopropyl alcohol, washing with water,
Isopropyl alcohol was removed.

400 ml of the molded product was placed in 149 g of iminodiacetic acid and 400 ml of water,
While adjusting the pH to 7.0 to 8.0 with 0% NaOH, the mixture was reacted with stirring at 70 ° C for 2 hours.

After sufficiently washing unreacted iminodiacetic acid by washing with water, after replacing the water contained in the molded product with ethanol, acetic anhydride 57.2
g (large excess amount) was added, and the mixture was reacted at room temperature for 24 hours with light stirring. After unreacted acetic anhydride was sufficiently removed with ethane, the product was washed with water to obtain a chitosan-based chelate molded product (Sample A). Table 1 shows the measurement results of cation exchange capacity, compressive elastic modulus, specific surface area, and pore size.

Example 2. 78 g of chitosan having a deacetylation degree of 75% and an average molecular weight of 48,000
Was dissolved in 922 g of a 3.9% acetic acid aqueous solution. The aqueous solution was discharged together with compressed air, dropped into a mixed aqueous solution of 6.5% NaOH, 20% ethanol, and 73.5% water to coagulate and regenerate, and washed sufficiently with water until neutral and then porous particles having an average particle diameter of 0.3 mmφ. Obtained 700 ml (wet) of chitosan. To 700 ml (wet) of the obtained porous granular chitosan, 700 ml of water and 3.8 g of ethalene glycol diglycidyl ether were added, reacted at 80 ° C. for 2 hours, and then thoroughly washed with water. Next, 124 g of epichlorohydrin was reacted in 50% isopropyl alcohol aqueous solution at 50 ° C. for 2 hours, washed thoroughly with water, and then 180 g of polyethyleneimine (SP-200, average molecular weight 10,000, manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) in 420 g of water.
600 ml of porous granular chitosan reacted with epichlorohydrin was added, gently stirred at 25 ° C. for 24 hours, heated to 70 ° C., and reacted with stirring for 3 hours. After completion of the reaction, unreacted polyethyleneimine was removed by sufficiently washing with water. When the anion exchange capacity was measured, it was 1.7 meq / ml
A porous chitosan granular molded product into which polyethyleneimine was introduced having a high exchange capacity was obtained.

The water contained in the molded product was sufficiently replaced with isopropyl alcohol, and 500 ml of the molded product had 236 g of epichlorohydrin and water.
The mixture was placed in an aqueous solution containing 250 g and 250 g of isopropyl alcohol and reacted at 50 ° C. for 2 hours. After sufficiently removing unreacted epichlorohydrin with isopropyl alcohol, washing with water,
Isopropyl alcohol was removed.

400 ml of the molded product was placed in 179 g of iminodiacetic acid and 400 ml of water,
While adjusting the pH to 7.0 to 8.0 with 0% NaOH, the mixture was reacted with stirring at 70 ° C for 2 hours.

After washing with water to sufficiently remove unreacted iminodiacetic acid, the water contained in the molded product was replaced with ethanol, and then acetic anhydride 69.4
g (large excess amount) was added, and the mixture was reacted at room temperature for 24 hours with light stirring. Unreacted acetic anhydride was sufficiently removed with ethanol and then washed with water to obtain a chitosan-based chelate molded product (Sample B). Table 2 shows the measurement results of cation exchange capacity, compressive elastic modulus, specific surface area and pore system.

Comparative Example 1. 78 g of chitosan having a deacetylation degree of 80% and an average molecular weight of 48,000.
Was dissolved in 922 g of a 3.9% acetic acid aqueous solution. The aqueous solution was discharged together with compressed air, dropped into a mixed solution of 6.5% NaOH, 20% ethanol, and 73.5%, coagulated and regenerated, washed sufficiently with water until neutral, and then porous granular chitosan having an average particle diameter of 0.3 mmφ. 700 ml (wet) were obtained. 700 ml of the obtained granular chitosan
700 ml of water and 70 g of ethylene glycol diglycidyl ether were added to (wet) and reacted at 60 ° C for 1 hour. After completion of the reaction, it is washed thoroughly with water. 180 g of polyethyleneimine (SP-200, average molecular weight 10,000, Nippon Shokubai Chemical Co., Ltd.) was added to water 4
600 ml of porous granular chitosan which was dissolved in 20 g and reacted with the above ethylene glycol diglycidyl ether was added, gently stirred at 25 ° C. for 24 hours, heated to 70 ° C. and then reacted for 3 hours with stirring. After completion of the reaction, unreacted polyethyleneimine was removed by sufficiently washing with water. When the anion exchange capacity was measured, a polyethyleneimine-introduced porous granular molding having a high exchange capacity of 1.4 meq / ml was obtained (Sample C).

Further, the water contained in the molded product was sufficiently replaced with dimethylformamide, 161 g of trimellitic anhydride was added to 300 ml of the molded product, and the mixture was reacted by gently stirring at room temperature for 32 hours. After sufficiently removing unreacted trimellitic anhydride with dimethylformamide, 200 ml of the molded product was sampled, 200 ml of dimethylformamide was added, and acetic anhydride 29 g (large excess amount)
Was added, and the mixture was reacted at room temperature for 24 hours with light stirring. Unreacted acetic anhydride was sufficiently removed with dimethylformamide and then washed with water to obtain a porous granular chitosan molded product (Sample D).

Example 3. Samples A, B, C and D obtained in Examples 1 and 2 and Comparative Example 1 respectively 1
80 ml of Ni ^{+ +} , Hg ^{+ +} , Cd ^{+ +} ion aqueous solution whose pH has been adjusted in advance
The metal ion concentration and the pH value in the adsorption residual liquid were measured by putting the solution inside and the results are shown in Tables 3, 4, and 5. Furthermore, the relationship between the metal ion concentration and the pH value shown in Tables 3, 4, and 5 is shown in FIGS. 1, 2, and 3, respectively. Fig. 1 shows the relationship between the Ni ⁺⁺ ion concentration and pH value when using the Ni ⁺⁺ ion aqueous solution, and Fig. 2 shows the Hg ⁺⁺ ion concentration and pH value when using the Hg ⁺⁺ ion aqueous solution. Figure 3 shows Cd ⁺⁺
Figure 1 shows the relationship with Cd ⁺⁺ pH value when using an ionic aqueous solution. In Figures 1 to 3, □ indicates sample A, * indicates sample B, ○ indicates sample C, and ● indicates sample. Each value of D is shown. Since the initial concentration is 100 ppm and the lower the ion concentration in the residual liquid is, the better the adsorption is, the samples A and B introduced with iminodiacetic acid according to the present invention have a lower pH range than the samples C and D of the comparative examples. However, it is clear that the metal ion adsorption capacity is excellent.

[Effect of the invention] After reacting the porous chitosan molded product obtained by the present invention with a glycidyl ether of an aliphatic polyalcohol,
Chitosan-based chelate moldings obtained by reacting epichlorohydrin with or without reaction, then reacting with polyethyleneimine, then reacting with epichlorohydrin, further reacting with iminodiacetic acid, and then reacting with acetic anhydride are Since the coordinating group iminodiacetic acid forms a strong complex with the metal ion, it exhibits an excellent function for adsorbing and recovering the metal ion from the acidic aqueous solution, as is clear from the results of the above examples. is there.

Further, the molded product of the chitosan-based chelate of the present invention is a molded product which is a base material thereof is a porous chitosan molded product and has a porous structure having a large specific surface area and an extremely large pore size, so that diffusion and adsorption of ions Since it has a high speed and high strength, it has an effect of having excellent column efficiency when used for adsorption and recovery of various metal ions.

[Brief description of drawings]

1, 2 and 3 use an aqueous metal ion solution,
6 is a graph showing the relationship between the pH value and the metal ion concentration in the adsorption residual liquid after the metal ions in each liquid were adsorbed by Samples A and B according to the present invention and Samples C and D of Comparative Examples.

Claims (2)

[Claims] 1. A porous chitosan molded product is reacted with a glycidyl ether of an aliphatic polyalcohol, then with polyethyleneimine, then with epichlorohydrin, then with iminodiacetic acid, and further with acetic anhydride. A method for producing a chitosan-based chelate molded article, comprising: 2. A porous chitosan molded product is reacted with a glycidyl ether of an aliphatic polyalcohol, followed by reaction with epichlorohydrin, followed by reaction with polyethyleneimine, followed by reaction with epichlorohydrin, and further iminodiacetic acid. The method for producing a chitosan-based chelate molded article, which comprises reacting acetic anhydride after the reaction.