A crosslinked chitosan amine and its preparation and application

Abstract

The present invention relates to the field of water treatment, and particularly relates to a cross-linked chitosan and its preparation and application. The cross-linked chitosan is obtained by cross-linking N -ethyl chitosan with glutaraldehyde. The advantages of the present invention are that the reaction process is simple, the conditions are mild, the reaction materials are cheap and easily available, and it is easy to promote industrial application. The amino cross-linked chitosan has a fast adsorption rate and a large adsorption capacity for phenoxycarboxylic acid compounds in water. Moreover, the amino cross-linked chitosan can be recycled, enhancing the adsorption performance of chitosan and expanding the application scope of chitosan. It can be applied to the fields of water treatment and pollutant adsorption. Formula (1) N -ethyl chitosan and glutaraldehyde are cross-linked. The advantages of the present invention are that the reaction process is simple, the conditions are mild, the reaction materials are cheap and easily available, and it is easy to promote industrial application. The amino cross-linked chitosan has a fast adsorption rate and a large adsorption capacity for phenoxycarboxylic acid compounds in water. Moreover, the amino cross-linked chitosan can be recycled, enhancing the adsorption performance of chitosan and expanding the application scope of chitosan. It can be applied to the fields of water treatment and pollutant adsorption. Formula (1)

Description

Technical Field

[0001] The present invention belongs to the field of water treatment, and particularly relates to a cross-linked amino chitosan and its preparation and application. Background Art

[0002] Chitosan is a natural amino polysaccharide with rich sources, renewable, non-toxic side effects, good biocompatibility and degradability. Chitosan and its derivatives have many unique physiological and pharmacological functional properties and are widely used in various fields such as medicine, food, and pollutant adsorption. Chitosan itself has adsorption properties, is non-toxic and pollution-free, and can be used as a modification object to develop secondary lead compounds.

[0003] Phenoxycarboxylic acid compounds are commonly used as herbicides and plant growth regulators in agriculture, with a wide range of uses and large usage amounts. Phenoxycarboxylic acid compounds have a certain solubility in water, and the phenoxycarboxylic acid compounds remaining on the soil and plant surfaces are easily transported with water, causing surface water and groundwater pollution. Phenoxycarboxylic acid compounds are difficult to degrade, have a long residual time, and have potential "carcinogenic, teratogenic and mutagenic" effects, seriously affecting water quality safety and human health. Using cross-linked chitosan products to adsorb and remove residual phenoxycarboxylic acid compounds in water is of great significance for the treatment and restoration of water pollution. Summary of the Invention

[0004] The purpose of the present invention is to provide a cross-linked amino chitosan and its preparation and application.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A cross-linked amino chitosan, which is obtained by cross-linking -ethylamino chitosan and glutaraldehyde; N -ethylamino chitosan is cross-linked with glutaraldehyde; Formula (1); wherein, n represents the degree of polymerization, and the average value range of n is 10 - 12000.

[0007] A preparation method of the cross-linked amino chitosan as described above, reacting chitosan with phthalic anhydride to protect the amino group at the C-2 position of chitosan to obtain amino-protected chitosan; reacting the amino-protected chitosan with 4-methylbenzenesulfonyl chloride to prepare 6-p-toluenesulfonylamino-protected chitosan; and then reacting 6-p-toluenesulfonylamino-protected chitosan with ethylenediamine to prepare -ethylamino chitosan as shown in formula (1) N -ethylamino chitosan, N -ethylamino chitosan is prepared into cross-linked amino chitosan through a cross-linking reaction with glutaraldehyde.

[0008] The amino-protected chitosan is: chitosan and phthalic anhydride are dissolved in N,N- In N,N-dimethylformamide, under nitrogen protection, react at 80 - 120 °C for 6 - 12 h. After the reaction, precipitate with ethanol, wash the precipitate with ethanol, filter by suction to obtain a filter cake, and dry it to constant weight to obtain amino-protected chitosan; wherein, the addition amount of phthalic anhydride is 2 - 8 times the molar amount of the raw material chitosan, N, N - The addition amount of N,N-dimethylformamide is 50 - 100 times the molar amount of the raw material chitosan.

[0009] The 6-p-toluenesulfonylamino-protected chitosan is: dissolve amino-protected chitosan and 4-methylbenzenesulfonyl chloride in N,N - N,N-dimethylformamide, add triethylamine, react at 0 °C for 2 - 6 h. After the reaction, precipitate with ethanol, wash the precipitate with ethanol, filter by suction to obtain a filter cake, and dry it to constant weight to obtain 6-p-toluenesulfonylamino-protected chitosan; wherein, the addition amount of 4-methylbenzenesulfonyl chloride is 5 - 10 times the molar amount of amino-protected chitosan, the addition amount of triethylamine is 2 - 6 times the molar amount of amino-protected chitosan, N,N - The addition amount of N,N-dimethylformamide is 50 - 100 times the molar amount of amino-protected chitosan.

[0010] The N - ethylamino chitosan is: dissolve 6-p-toluenesulfonylamino-protected chitosan in dimethyl sulfoxide, add ethylenediamine, react at 60 - 100 °C for 6 - 12 h. After the reaction, precipitate with ethanol, wash the precipitate with ethanol, filter by suction to obtain a filter cake, and dry it to constant weight to obtain N - ethylamino chitosan; wherein, the addition amount of ethylenediamine is 5 - 10 times the molar amount of 6-p-toluenesulfonylamino-protected chitosan, and the addition amount of dimethyl sulfoxide is N - 50 - 100 times the molar amount of ethylamino chitosan.

[0011] The crosslinked amino chitosan is: N - Dissolve ethylamino chitosan in an acetic acid aqueous solution, react with glutaraldehyde at room temperature for 1 - 5 h, add sodium hydroxide solution to adjust to neutral, then precipitate with absolute ethanol, and then wash with distilled water and absolute ethanol, filter by suction to obtain a filter cake, and dry it to constant weight to obtain crosslinked amino chitosan; wherein, the addition amount of glutaraldehyde is 2 - 10 times the molar amount of amino chitosan, the concentration of the acetic acid aqueous solution is 1% - 10%, and the volume of the acetic acid aqueous solution used is N - 10 - 30 times the molar amount of ethylamino chitosan.

[0012] An application of the crosslinked amino chitosan, the application of the crosslinked amino chitosan as a pollutant adsorbent.

[0013] The application of the crosslinked amino chitosan as an adsorbent for phenoxycarboxylic acid compounds in the environment.

[0014] The application of the crosslinked chitosan in adsorbing phenoxycarboxylic acid compounds in the water environment.

[0015] The phenoxycarboxylic acid compounds are one or more of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy)propionic acid.

[0016] A method for adsorbing phenoxycarboxylic acid compounds in the environment, adding the crosslinked chitosan to the sample to be treated, adsorbing the phenoxycarboxylic acid compounds in the sample at 15-45 °C, and then removing the pollutants in the sample. The addition amount of the crosslinked chitosan is 500-1200 mg / L.

[0017] Furthermore, adding the crosslinked chitosan to the sample to be treated, adsorbing 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy)propionic acid in the sample at 15-45 °C, and then removing the pollutants in the sample. The concentration of the aqueous solution of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy)propionic acid is 50-250 mg / L, and the addition amount of the crosslinked chitosan is 500-1200 mg / L.

[0018] After the adsorption treatment, the crosslinked chitosan is separated and collected for reuse.

[0019] Advantages of the present invention:

[0020] (1) Chitosan is prepared by chemical modification N -ethylamino chitosan, and the crosslinked chitosan prepared by crosslinking has a porous structure, an increased specific surface area, further increased adsorption sites, and further improved adsorption performance for phenoxycarboxylic acid compounds in water.

[0021] (2) The crosslinked chitosan prepared in the present invention retains the original good biocompatibility and biodegradability of chitosan. At the same time, it has a fast adsorption rate and a large adsorption capacity for phenoxycarboxylic acid compounds in water, which is significantly higher than that of chitosan and crosslinked chitosan. Moreover, the crosslinked chitosan can be recycled, enhancing the adsorption performance of chitosan and expanding the application range of chitosan. It can be widely applied in the fields of water treatment and pollutant adsorption. Description of the drawings

[0022] Figure 1 It is a flow chart for synthesizing the chitosan shown in formula (1) provided by the embodiment of the present invention.

[0023] Figure 2 It is an infrared spectrogram of the raw material chitosan provided by the embodiment of the present invention.

[0024] Figure 3 The infrared spectrogram of the amino-protected chitosan provided by the embodiment of the present invention.

[0025] Figure 4 The infrared spectrogram of 6-p-toluenesulfonylamino-protected chitosan provided by the embodiment of the present invention.

[0026] Figure 5 Provided by the embodiment of the present invention N -ethylamino chitosan infrared spectrogram.

[0027] Figure 6 Provided by the embodiment of the present invention N -ethylamino chitosan carbon nuclear magnetic spectrum.

[0028] Figure 7 The infrared spectrogram of the crosslinked amino chitosan provided by the embodiment of the present invention.

[0029] Figure 8 The carbon nuclear magnetic spectrum of the crosslinked amino chitosan provided by the embodiment of the present invention.

[0030] Figure 9 The scanning electron micrograph of the chitosan provided by the present invention.

[0031] Figure 10 The scanning electron micrograph of the crosslinked amino chitosan provided by the present invention.

[0032] Figure 11 The result of the adsorption amount of 2,4-dichlorophenoxyacetic acid by the crosslinked amino chitosan provided by the present invention varying with time.

[0033] Figure 12 The infrared spectrogram of the crosslinked amino chitosan after adsorbing 2,4-dichlorophenoxyacetic acid provided by the present invention. Detailed implementation manners

[0034] The following further illustrates the present invention in conjunction with examples and application examples. It should be noted that the specific implementation manners described herein are only for explaining and interpreting the present invention and are not limited to the present invention. Example 1

[0035] As Figure 1 shown, prepare the amino chitosan as the derivative shown in formula (1):

[0036] (1) Preparation of amino-protected chitosan: Weigh 5.8 g (36 mmol) of chitosan (see Figure 2 ) and 10.6 g (72 mmol) of phthalic anhydride and dissolve them in 200 mL N,NIn dimethylformamide, stir at 80 °C for 12 h. After the reaction, pour the reaction solution into excessive anhydrous ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain amino-protected chitosan (see Figure 3 ).

[0037] (2) Dissolve 3.2 g (11 mmol) of the amino-protected chitosan obtained in step (1) in 60 mL of N,N dimethylformamide, and then add 3.1 mL (22 mmol) of triethylamine; add 10.4 g (55 mmol) of 4-methylbenzenesulfonyl chloride to the above amino-protected chitosan solution, and react at 0 °C for 6 h. After the reaction, pour the reaction solution into excessive anhydrous ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain 6-p-toluenesulfonylamino-protected chitosan (see Figure 4 ).

[0038] (3) Dissolve 0.88 g (2 mmol) of the 6-p-toluenesulfonylamino-protected chitosan obtained in step (2) in 10 mL of dimethyl sulfoxide, and then add 0.6 mL (10 mmol) of ethylenediamine, and react at 60 °C for 12 h. After the reaction, pour the reaction solution into excessive anhydrous ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain N N-ethylamino chitosan (see Figure 5 and Figure 6 ).

[0039] (4) Dissolve 1.0 g (5 mmol) of the N N-ethylamino chitosan obtained in step (3) in 80 ml of acetic acid solution (5%), add 2 mL of glutaraldehyde solution (50%) to the above solution, stir at room temperature for 5 h, adjust to neutral with sodium hydroxide solution after the reaction, precipitate with excessive anhydrous ethanol, filter the precipitate by suction, wash the precipitate with anhydrous ethanol, and dry it at 65 °C to obtain amino-crosslinked chitosan (see Figure 7 and Figure 8 ). The obtained product is a yellow solid.

[0040] Figure 2 is the infrared spectrum of raw material chitosan: 1600.6 cm -1 is the bending vibration absorption peak of NH2.

[0041] Figure 3 is the infrared spectrum of amino-protected chitosan: 1710.5 cm -1 and 1776.4 cm -1 are the characteristic absorption peaks of C=O on the anhydride, and 720.8 cm -1 is the characteristic absorption peak of the benzene ring. The above data analysis proves the successful synthesis of amino-protected chitosan.

[0042] Figure 4 Infrared spectrum of 6 - p - toluenesulfonylaminoprotected chitosan: 1711.1 cm -1 and 1775.8 cm -1 are the characteristic absorption peaks of C=O on the anhydride, and 722.1 cm -1 is the characteristic absorption peak of the benzene ring. Based on the above data analysis, it is proved that the synthesis of 6 - p - toluenesulfonylaminoprotected chitosan is successful.

[0043] Figure 5 For N -ethylaminochitosan infrared spectrum: The peaks at 1711.1 cm -1 , 1775.8 cm -1 and 722.1 cm -1 disappear, and 1602.8 cm -1 is the bending vibration absorption peak of NH2.

[0044] Figure 6 For N -ethylaminochitosan carbon nuclear magnetic spectrum: The characteristic peaks of carbon on chitosan are at 104.52 - 59.32 ppm, and 41.12 ppm is the characteristic absorption peak of carbon on N -ethylamino. Based on the above data analysis, it is proved that N -ethylaminochitosan synthesis is successful.

[0045] Figure 7 Infrared spectrum of cross - linked aminochitosan: The peak at 1602.8 cm -1 disappears, and 1647.0 cm -1 is the characteristic absorption peak of C=N.

[0046] Figure 8 Carbon nuclear magnetic spectrum of cross - linked aminochitosan: The characteristic peak of carbon in C=N is at 148.63 ppm; the characteristic peaks of carbon on chitosan are at 101.81 - 58.61 ppm, and 34.13 ppm is the characteristic absorption peak of carbon on N -ethylamino. Based on the above data analysis, it is proved that the synthesis of cross - linked aminochitosan is successful. Example 2

[0047] As Figure 1 shown, prepare the derivative of aminochitosan shown in formula (1):

[0048] (1) Preparation of amino - protected chitosan: Weigh 5.8 g (36 mmol) of chitosan and 31.8 g (216 mmol) of phthalic anhydride and dissolve them in 140 mL N,NIn N,N-dimethylformamide, stir at 12 °C for 6 h. After the reaction, pour the reaction solution into excess absolute ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain amino-protected chitosan.

[0049] (2) Dissolve 3.2 g (11 mmol) of the amino-protected chitosan obtained in step (1) in 42 mL N,N of N,N-dimethylformamide, and then add 9.3 mL (66 mmol) of triethylamine; add 20.8 g (110 mmol) of 4-methylbenzenesulfonyl chloride to the above amino-protected chitosan solution, and react at 0 °C for 2 h. After the reaction, pour the reaction solution into excess absolute ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain 6-p-toluenesulfonylamino-protected chitosan.

[0050] (3) Dissolve 0.88 g (2 mmol) of the 6-p-toluenesulfonylamino-protected chitosan obtained in step (2) in 10 mL of dimethyl sulfoxide, and then add 1.2 mL (20 mmol) of ethylenediamine, and react at 100 °C for 6 h. After the reaction, pour the reaction solution into excess absolute ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain N N-ethylamino chitosan.

[0051] (4) Dissolve 1.0 g (5 mmol) of the N N-ethylamino chitosan obtained in step (3) in 150 ml of acetic acid solution (1%), add 10 mL of glutaraldehyde solution (50%) to the above solution, stir at room temperature for 1 h, adjust to neutral with sodium hydroxide solution after the reaction, precipitate with excess absolute ethanol, filter the precipitate by suction, wash the precipitate with absolute ethanol, and dry it at 65 °C to obtain amino-crosslinked chitosan. The obtained product is a yellow solid. Example 3

[0052] As Figure 1 shown, prepare the derivative of chitosan shown in formula (1):

[0053] (1) Preparation of amino-protected chitosan: Weigh 5.8 g (36 mmol) of chitosan and 21.2 g (144 mmol) of phthalic anhydride and dissolve them in 200 mL N,N of N,N-dimethylformamide, and stir at 100 °C for 8 h. After the reaction, pour the reaction solution into excess absolute ethanol to precipitate. Filter the precipitate by suction, wash the precipitate with ethanol, and dry it at 65 °C to obtain amino-protected chitosan.

[0054] (2) Dissolve 3.2 g (11 mmol) of the amino-protected chitosan obtained in step (1) in 84 mL N,NIn N,N-dimethylformamide, 6.2 mL (44 mmol) of triethylamine was added; 16.6 g (88 mmol) of 4-methylbenzenesulfonyl chloride was added to the above-mentioned amino-protected chitosan solution, and the reaction was carried out at 0 °C for 4 h. After the reaction, the reaction solution was poured into excessive absolute ethanol, and a precipitate was formed. The precipitate was filtered by suction, washed with ethanol, and dried at 65 °C to obtain 6-p-toluenesulfonylamino-protected chitosan.

[0055] (3) 0.88 g (2 mmol) of the 6-p-toluenesulfonylamino-protected chitosan obtained in step (2) was dissolved in 10 mL of dimethyl sulfoxide, 1.0 mL (16 mmol) of ethylenediamine was added, and the reaction was carried out at 80 °C for 8 h. After the reaction, the reaction solution was poured into excessive absolute ethanol, and a precipitate was formed. The precipitate was filtered by suction, washed with ethanol, and dried at 65 °C to obtain N N-ethylamino chitosan.

[0056] (4) The N N-ethylamino chitosan 1.0 g (5 mmol) obtained in step (3) was dissolved in 50 ml of acetic acid solution (10%), 5 mL of glutaraldehyde solution (50%) was added to the above solution, and the mixture was stirred at room temperature for 3 h. After the reaction, the solution was adjusted to neutral with sodium hydroxide solution, precipitated with excessive absolute ethanol, the precipitate was filtered by suction, washed with absolute ethanol, and dried at 65 °C to obtain amino-crosslinked chitosan. The obtained product was a yellow solid.

[0057] Application Example 1

[0058] Specific surface area test

[0059] Using the BET specific surface area detection method, the pore specific surface areas of the raw material chitosan and the crosslinked amino chitosan obtained in Examples 1-3 were tested, and the test results are as follows:

[0060] Table 1 Specific surface areas of chitosan and crosslinked amino chitosan

[0061]

[0062] As can be seen from Table 1, the specific surface areas of the crosslinked amino chitosan obtained in Examples 1-3 were 23.49-21.69 m 2 / g, which were larger than that of chitosan. The larger specific surface area was beneficial to improving the adsorption capacity of the crosslinked amino chitosan.

[0063] Application Example 2

[0064] Surface morphology test

[0065] The surface morphologies of chitosan and the crosslinked amino chitosan obtained in Example 1 were recorded using a scanning electron microscope (see Figure 9 and Figure 10 ). Figure 9It is the SEM image of chitosan, and there are basically no pores on the surface of chitosan. Figure 10 It is the SEM image of the crosslinked amino chitosan obtained in Example 1. The surface of the crosslinked amino chitosan is a porous structure, and the porous structure is beneficial to improving the adsorption capacity of the crosslinked amino chitosan. At the same time, the crosslinked amino chitosan obtained in Example 2 and Example 3 also has corresponding characteristics.

[0066] Application Example 3

[0067] Determination of adsorption performance

[0068] (1) Determination of the adsorption performance of the crosslinked amino chitosan obtained in Example 1 for phenoxycarboxylic acid compounds:

[0069] Prepare aqueous solutions of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid or 2-(2,4-dichlorophenoxy)propionic acid with a concentration of 0.2 g / L respectively. Weigh 50 mg and 100 mg of the crosslinked amino chitosan obtained in Example 1 respectively, add 100 mL of the above-mentioned obtained aqueous solutions of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid or 2-(2,4-dichlorophenoxy)propionic acid to them respectively, stir at room temperature for 2 h, and measure the concentrations C of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy)propionic acid in the solution. t (Note: All the samples to be measured are measured three times and the average value is taken).

[0070] Adsorption capacity q t =(C0 - C t )×100 / m

[0071] Where C0 is the initial concentration of the 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid solution, and m is the added amount of the crosslinked amino chitosan.

[0072] Determination results of the adsorption amounts of the crosslinked amino chitosan for 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid:

[0073] Table 2 Adsorption performance of the crosslinked amino chitosan for phenoxycarboxylic acid compounds

[0074]

[0075] As can be seen from Table 2, in 100 mL of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, or 2-(2,4-dichlorophenoxy)propionic acid solution, when the input amount of the crosslinked chitosan obtained in Example 1 is 50 mg, the adsorption capacities can reach 309 mg / g, 256 mg / g, 255 mg / g, and 374 mg / g respectively. This shows that the crosslinked chitosan obtained in Example 1 has a high adsorption capacity for these four kinds of phenoxycarboxylic acid herbicides. At the same time, the crosslinked chitosans obtained in Example 2 and Example 3 also have corresponding characteristics.

[0076] (2) Determination of the change of the adsorption amount of crosslinked chitosan to 2,4-dichlorophenoxyacetic acid with time:

[0077] Prepare 2,4-dichlorophenoxyacetic acid aqueous solutions with a concentration of 0.2 g / L respectively. Weigh 100 mg of the crosslinked chitosan obtained in Example 1 and add it to 100 mL of 2,4-dichlorophenoxyacetic acid aqueous solution. Stir at room temperature and take samples at 1 min, 2 min, 5 min, 10 min, 20 min, 30 min, 40 min, 60 min, 2 h, 3 h, and 4 h respectively to measure the concentration C of 2,4-dichlorophenoxyacetic acid in the solution t (Note: Each measured sample is measured three times and the average value is taken) (See Figure 11 ).

[0078] Adsorption capacity q t =(C0 - C t )×100 / m

[0079] Where C0 is the initial concentration of the 2,4-dichlorophenoxyacetic acid aqueous solution, and m is the added amount of the crosslinked chitosan.

[0080] The results of the change of the adsorption amount of crosslinked chitosan to 2,4-dichlorophenoxyacetic acid with time are as Figure 11 shown. The adsorption amount of crosslinked chitosan to 2,4-dichlorophenoxyacetic acid is basically unchanged after 1 h, indicating that the crosslinked chitosan can complete the rapid adsorption of 2,4-dichlorophenoxyacetic acid within 1 h.

[0081] At the same time, take the crosslinked chitosan adsorbed for 1 h and detect it (See Figure 12 ), Figure 12 is the infrared spectrum of the crosslinked chitosan adsorbed with 2,4-dichlorophenoxyacetic acid for 1 h: 1477.3 cm -1 is the deformation vibration peak of OH in 2,4-dichlorophenoxyacetic acid, and 1040.7 cm -1 is the stretching vibration peak of CO in 2,4-dichlorophenoxyacetic acid. Based on the above data analysis, it is proved that 2,4-dichlorophenoxyacetic acid is adsorbed on the crosslinked chitosan.

[0082] (3) Determination of the effect of the dosage of cross-linked chitosan on the adsorption performance:

[0083] The adsorption capacities of cross-linked chitosan under different dosages were measured and compared (Table 3): Prepare an aqueous solution of 2,4-dichlorophenoxyacetic acid with a concentration of 0.2 g / L. Weigh 50, 80, 100, and 120 mg of the cross-linked chitosan obtained in Examples 1-3 respectively, add them to 100 mL of the 2,4-dichlorophenoxyacetic acid aqueous solution, stir at room temperature for 2 h, and measure the concentration C of 2,4-dichlorophenoxyacetic acid in the solution. t (Note: Each measured sample was measured three times and the average value was taken).

[0084] Adsorption capacity q t =(C0 - C t )×100 / m

[0085] Adsorption rate (%) = (C0 - C t )×100 / C0

[0086] where C0 is the initial concentration of the 2,4-dichlorophenoxyacetic acid aqueous solution, and m is the dosage of the cross-linked chitosan.

[0087] Determination results of the adsorption amount of 2,4-dichlorophenoxyacetic acid by cross-linked chitosan with different dosages:

[0088] Table 3 Determination of the effect of the dosage of cross-linked chitosan on the adsorption performance

[0089]

[0090] As can be seen from Table 3, in 100 mL of the 2,4-dichlorophenoxyacetic acid aqueous solution, when the dosages of the cross-linked chitosan obtained in Example 1 are 50, 80, 100, and 120 mg, the adsorption rates are 77%, 93%, 95%, and 97% respectively. When the dosage of the cross-linked chitosan is 100 mg, the adsorption rate is 95%, and when the dosage of the cross-linked chitosan is 120 mg, the adsorption rate is 96%. It can be seen that increasing the dosage of the cross-linked chitosan has little effect on the improvement of the adsorption rate. At the same time, the cross-linked chitosan obtained in Examples 2 and 3 also has corresponding characteristics. Therefore, a dosage of 100 mg is selected as the optimal condition.

[0091] (4) Determination of the effect of the concentration of 2,4-dichlorophenoxyacetic acid aqueous solution on the adsorption performance of cross-linked chitosan: Measure the adsorption capacity of cross-linked chitosan in 2,4-dichlorophenoxyacetic acid aqueous solutions with different concentrations and make comparisons (Table 4): Prepare 2,4-dichlorophenoxyacetic acid aqueous solutions with concentrations of 0.05 g / L, 0.1 g / L, 0.15 g / L, 0.2 g / L, and 0.25 g / L respectively. Weigh 100 mg of the cross-linked chitosan obtained in Examples 1-3 and add them to 100 mL of the prepared 2,4-dichlorophenoxyacetic acid aqueous solutions with different concentrations. Stir for 2 h at room temperature and measure the concentration C of 2,4-dichlorophenoxyacetic acid in the solution t (Note: Each measured sample is measured three times and the average value is taken).

[0092] Adsorption capacity q t = (C0 - C t ) × 100 / m

[0093] Adsorption rate (%) = (C0 - C t ) × 100 / C0

[0094] Where C0 is the initial concentration of the 2,4-dichlorophenoxyacetic acid aqueous solution and m is the added amount of cross-linked chitosan.

[0095] Determination results of the adsorption amount of cross-linked chitosan in 2,4-dichlorophenoxyacetic acid aqueous solutions with different concentrations:

[0096] Table 4 Determination of the effect of the concentration of 2,4-dichlorophenoxyacetic acid aqueous solution on the adsorption performance of cross-linked chitosan

[0097]

[0098] As can be seen from Table 4, in 100 mL of 2,4-dichlorophenoxyacetic acid aqueous solutions with concentrations of 0.05 g / L, 0.1 g / L, 0.15 g / L, 0.2 g / L, and 0.25 g / L, when the input amount of the cross-linked chitosan obtained in Example 1 is 100 mg, the adsorption rates are 99%, 98%, 97%, 95%, and 92% respectively. The adsorption rate of the cross-linked chitosan obtained in Example 1 gradually decreases with the increase in the concentration of the 2,4-dichlorophenoxyacetic acid aqueous solution. When the concentration of the 2,4-dichlorophenoxyacetic acid aqueous solution is 0.25 g / L, the adsorption rate of the cross-linked chitosan obtained in Example 1 is relatively low. The cross-linked chitosans obtained in Examples 2 and 3 also have corresponding characteristics. Therefore, select 0.2 g / L of the 2,4-dichlorophenoxyacetic acid aqueous solution concentration as the condition for testing the adsorption performance of cross-linked chitosan.

[0099] (5) Determination of the effect of adsorption temperature on the adsorption performance of crosslinked amino chitosan: Measure the adsorption capacity of crosslinked amino chitosan at different temperatures and make comparisons (Table 5): Prepare an aqueous solution of 2,4-dichlorophenoxyacetic acid with a concentration of 0.2 g / L. Weigh 100 mg of the crosslinked amino chitosan obtained in Examples 1-3 and add it to 100 mL of the prepared aqueous solution of 2,4-dichlorophenoxyacetic acid. Stir for 2 h at 15 °C, 25 °C, 35 °C, and 45 °C respectively, and measure the concentration C of 2,4-dichlorophenoxyacetic acid in the solution t (Note: Each measured sample is measured three times and the average value is taken).

[0100] Adsorption capacity q t =(C0 - C t )×100 / m

[0101] where C0 is the initial concentration of the aqueous solution of 2,4-dichlorophenoxyacetic acid, and m is the amount of crosslinked amino chitosan added.

[0102] Determination results of the adsorption amount of crosslinked amino chitosan for 2,4-dichlorophenoxyacetic acid at different temperatures:

[0103] Table 5 Determination of the effect of adsorption temperature on the adsorption performance of crosslinked amino chitosan

[0104]

[0105] As can be seen from Table 5, the crosslinked amino chitosan obtained in Examples 1-3 all has a relatively high adsorption amount for 2,4-dichlorophenoxyacetic acid.

[0106] (6) Determination of the repeated use performance of crosslinked amino chitosan: Measure the adsorption capacity of crosslinked amino chitosan as an adsorbent for 2,4-dichlorophenoxyacetic acid after recovery and make comparisons (Table 6): Prepare an aqueous solution of 2,4-dichlorophenoxyacetic acid with a concentration of 0.2 g / L. Weigh 100 mg of the crosslinked amino chitosan obtained in Examples 1-3 and add it to 100 mL of the prepared aqueous solution of 2,4-dichlorophenoxyacetic acid. Stir at room temperature for 2 h and measure the concentration C of 2,4-dichlorophenoxyacetic acid in the solution t . After adsorption treatment, filter and separate the solution to recover the crosslinked amino chitosan. After drying, add it to anhydrous ethanol and stir for 1 h. The crosslinked amino chitosan is filtered, separated, and dried, and then added as an adsorbent to 100 mL of the prepared aqueous solution of 2,4-dichlorophenoxyacetic acid. Stir at room temperature for 2 h and measure the concentration C of 2,4-dichlorophenoxyacetic acid in the solution t . Repeat the above process and measure the concentration of 2,4-dichlorophenoxyacetic acid in the solution after each adsorption (Note: Each measured sample is measured three times and the average value is taken).

[0107] Adsorption rate (%)=(C0 - C t)×100 / C0

[0108] where C0 is the initial concentration of the 2,4-dichlorophenoxyacetic acid aqueous solution.

[0109] Determination results of the reusability of crosslinked chitosan:

[0110] Table 6 Determination of the reusability of crosslinked chitosan

[0111]

[0112] As can be seen from Table 6, the crosslinked chitosan obtained in Examples 1-3 can be recycled five times as an adsorbent for 2,4-dichlorophenoxyacetic acid and still maintain a high adsorption performance.

[0113] The results show that the crosslinked chitosan has a high adsorption capacity for 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid or 2-(2,4-dichlorophenoxy)propionic acid. Its adsorption capacity for 2,4-dichlorophenoxyacetic acid is high in different input amounts, different concentrations of 2,4-dichlorophenoxyacetic acid solutions and different adsorption temperatures, and it can be recycled multiple times.

[0114] The above application examples are the preferred application modes of the present invention, but the present invention is not limited by the above application examples. Any changes, modifications, substitutions, and combinations made under the condition of being consistent with the essence and principle of the present invention are equivalent substitution methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of cross-linked chitosan amino, characterized in that: The amino group at the C-2 position of chitosan was protected by reacting chitosan with phthalic anhydride to obtain amino-protected chitosan; 6-(p-toluenesulfonyl)amino-protected chitosan was prepared by reacting amino-protected chitosan with 4-methylbenzenesulfonyl chloride; then 6-(p-toluenesulfonyl)amino-protected chitosan was reacted with ethylenediamine to prepare the N -ethylamino chitosan, N -ethylamino chitosan and glutaraldehyde were crosslinked to prepare crosslinked amino chitosan; The N preparation method of -ethyl chitosan is as follows: Dissolve 6-p-toluenesulfonylamino-protected chitosan in dimethyl sulfoxide, add ethylenediamine, react at 60-100 °C for 6-12 h, after the reaction, precipitate with ethanol, wash the precipitate with ethanol, filter by suction to obtain a filter cake, dry it to constant weight to obtain N -ethyl chitosan; wherein, the addition amount of ethylenediamine is 5-10 times the molar amount of 6-p-toluenesulfonylamino-protected chitosan, and the addition amount of dimethyl sulfoxide is N 50-100 times the molar amount of -ethyl chitosan; Formula (1); wherein, n represents the degree of polymerization, and the average value range of n is 10 - 12000.

2. The preparation method of crosslinked chitosan amino described in claim 1, characterized in that: The amino-protected chitosan is prepared as follows: chitosan and phthalic anhydride are dissolved in N,N -dimethylformamide, and the reaction is carried out at 80-120 °C for 6-12 h under nitrogen protection. After the reaction, ethanol precipitation is carried out, and the precipitate is washed with ethanol and filtered to obtain a filter cake, which is dried to a constant weight to obtain amino-protected chitosan; wherein, the addition amount of phthalic anhydride is 2-8 times the molar amount of the raw material chitosan, N,N -the addition amount of dimethylformamide is 50-100 times the molar amount of the raw material chitosan.

3. The preparation method of cross-linked chitosan amino described in claim 1, characterized in that: The 6-p-toluenesulfonylamino-protected chitosan is prepared by dissolving amino-protected chitosan and 4-methylbenzenesulfonyl chloride in N,N -dimethylformamide, adding triethylamine, reacting at 0 °C for 2-6 h, precipitating with ethanol after the reaction, washing the precipitate with ethanol, filtering by suction to obtain a filter cake, drying to constant weight to obtain 6-p-toluenesulfonylamino-protected chitosan; wherein, the addition amount of 4-methylbenzenesulfonyl chloride is 5-10 times the molar amount of amino-protected chitosan, the addition amount of triethylamine is 2-6 times the molar amount of amino-protected chitosan, N,N -the addition amount of dimethylformamide is 50-100 times the molar amount of amino-protected chitosan.

4. The preparation method of crosslinked chitosan amino described in claim 1, characterized in that: The crosslinked amino chitosan is as follows: N -Ethylamino chitosan is dissolved in an acetic acid aqueous solution and reacted with glutaraldehyde at room temperature for 1-5 h. Sodium hydroxide solution is added to adjust to neutrality, and then precipitated with absolute ethanol. Then it is washed with distilled water and absolute ethanol and filtered to obtain a filter cake, which is dried to constant weight to obtain crosslinked amino chitosan. Among them, the addition amount of glutaraldehyde is 2-10 times the molar amount of amino chitosan, the concentration of the acetic acid aqueous solution is 1%-10%, and the volume of the acetic acid aqueous solution used is N -10-30 times the molar amount of ethylamino chitosan.

5. Use of the crosslinked chitosan prepared by the preparation method according to claim 1, characterized in that: Use of the crosslinked amino chitosan as an adsorbent for phenoxycarboxylic acid compounds in the environment.

6. The application according to claim 5, characterized in that: The phenoxycarboxylic acid compound is one or more of 2,4-dichlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy)propionic acid.

7. The application according to claim 5, wherein: After adsorption treatment, the crosslinked amino chitosan is separated and collected for reuse.

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