1. A novel chitosan-based pyridine quaternary ammonium salt adsorption biomaterial is characterized by having a molecular structure shown in a formula (I):

formula (I).

2. The method for preparing the chitosan-based pyridine quaternary ammonium salt novel adsorption biomaterial according to claim 1, is characterized by comprising the following steps:

(1) dropwise adding a certain amount of 1, 3-dibromopropane into pyridine, stirring at 50-80 ℃ for reaction for 8-16h, standing after reaction until the product is solidified, removing liquid-phase unreacted substances, and washing the solid-phase product with diethyl ether to obtain pyridine quaternary ammonium salt;

(2) dissolving the obtained quaternary ammonium salt of pyridine in N, N-dimethylformamide, adding 10-20wt% NaOH aqueous solution, stirring at 50-80 deg.C for 10-40min, adding a certain amount of chitosan, stirring at 50-80 deg.C for 10-15h, washing the solid phase product with diethyl ether after the reaction is finished, and drying to obtain the final product.

3. The method of claim 2, wherein: the deacetylation degree of the chitosan is more than or equal to 90.0 percent, and the viscosity is less than 100 cps.

4. The method of claim 2, wherein: the mass ratio of the pyridine to the 1, 3-dibromopropane used in the step (1) is 1 (0.8-1.2).

5. The method of claim 2, wherein: in the step (2), the dosage of the NaOH aqueous solution is 1-2 times of the weight of the quaternary ammonium salt.

6. The method of claim 2, wherein: the mass ratio of the quaternary ammonium salt pyridine to the chitosan monomer in the step (2) is 1 (0.8-1.2).

7. The method for treating Cr-containing adsorbing biological material with chitosan-based pyridine quaternary ammonium salt as claimed in claim 1₂O₇ ^2-The industrial wastewater.

Background

In recent years, with the rapid development of industries such As chemical fertilizers, paints, metal manufacturing, leather, alloys, electroplating, mining and the like, the amount of industrial wastewater is increased dramatically, and heavy metal ions in the wastewater, such As chromium (Cr), lead (Pb), cadmium (Cd), arsenic (As), copper (Cu) and the like, pollute the environment. The common treatment method of industrial wastewater mainly comprises a chemical precipitation method, an electrochemical method, a physical adsorption method and the like, the physical adsorption method is used for adsorbing pollutants in the wastewater through a porous adsorbent and a membrane adsorbent, the treatment method can greatly reduce the pollutants in the wastewater, the method is the sewage treatment method with the widest application range at present, the common adsorbents comprise activated carbon, activated alumina, molecular sieves, silica gel, peat, clay adsorbent, biological adsorbent and the like, however, most of the adsorbents are organic matter adsorbing substances, and only the biological adsorbent has the performance of adsorbing heavy metal ions. However, the biological adsorbent has certain defects, the adsorption rate is low, the release possibility exists in the adsorption process, and secondary pollution is caused.

Chitosan is an important marine polymer resource and is prepared by deacetylation of chitin. The application field of chitosan is very wide, but reports in domestic and foreign documents mainly focus on the aspects of adsorption, antibiosis and the like. The chitosan has certain adsorbability to heavy metal ions because the molecular structure contains amino nitrogen and hydroxyl oxygen which can form a matching bond with transition metal ions. The chitosan molecule is easy to be chemically modified due to the active groups such as amino, hydroxyl, oxygen bridge and pyran ring rich in electrons, and can generate various substances with different physicochemical properties by chemical reactions such as hydrolysis, alkylation, acylation, oxidation, complexation and the like under specific conditions. And chitosan shows certain antibacterial performance because amino groups on the molecules of the chitosan are positively charged.

Disclosure of Invention

In order to further improve the defects of low adsorption efficiency, long adsorption balance time and the like of chitosan in practical application, the invention prepares the novel chitosan-based pyridinium quaternary ammonium salt adsorption biomaterial by introducing the pyridinium quaternary ammonium salt to blend and modify the chitosan.

In order to achieve the purpose, the invention synthesizes a novel chitosan-based pyridine quaternary ammonium salt adsorption biomaterial, which has a molecular structure shown in a formula (I):

formula (I).

The preparation method of the chitosan-based pyridine quaternary ammonium salt novel adsorption biomaterial comprises the following steps:

(1) dropwise adding a certain amount of 1, 3-dibromopropane into pyridine, stirring at 50-80 ℃ for reaction for 8-16h, standing after reaction until the product is solidified, removing liquid-phase unreacted substances, and washing the solid-phase product with diethyl ether to obtain pyridine quaternary ammonium salt; the mass ratio of the pyridine to the 1, 3-dibromopropane is 1 (0.8-1.2);

(2) dissolving the obtained quaternary pyridinium salt in N, N-dimethylformamide, adding 10-20wt% NaOH aqueous solution (the amount is 1-2 times of the weight of the quaternary pyridinium salt), stirring and reacting at 50-80 ℃ for 10-40min, adding a certain amount of chitosan, continuing stirring and reacting at 50-80 ℃ for 10-15h, washing a solid-phase product with diethyl ether after the reaction is finished, and drying to obtain the quaternary pyridinium salt; the mass ratio of the quaternary ammonium salt pyridine to the chitosan monomer is 1 (0.8-1.2).

Preferably, the deacetylation degree of the chitosan is more than or equal to 90.0%, and the viscosity is less than 100 cps.

The invention has the following positive and beneficial effects:

the chitosan-based quaternary pyridinium salt for adsorbing the biological material is prepared by introducing the quaternary pyridinium salt to blend and modify chitosan, has simple synthesis method, wide raw material source, low cost and better adsorption efficiency, is an ideal physical adsorbent, is not easy to cause secondary pollution, and is used for treating Cr-containing substances₂O₇ ^2-Lays a foundation for industrial application of the industrial wastewater.

Drawings

FIG. 1 is a photomicrograph of a chitosan-based quaternized pyridinium salt prepared in example 1;

FIG. 2 is a mass spectrum of a cationic electron spray of quaternary ammonium salt of pyridine obtained in example 1;

FIG. 3 is a mass spectrogram of chitosan-based pyridinium quaternary ammonium salt cation electron spray obtained in example 1;

FIG. 4 is an infrared spectrum of a quaternary ammonium salt of pyridine obtained in example 1;

FIG. 5 is an infrared spectrum of chitosan-based pyridinium quaternary ammonium salt obtained in example 1;

FIG. 6 shows Cr₂O₇ ^2-Standard concentration-absorbance curve;

FIG. 7 is a graph of adsorption efficiency of chitosan-based quaternary ammonium pyridinium salts at different pH values.

Detailed Description

In order to better understand the present invention, the following embodiments are provided to illustrate the technical solution of the present invention.

Example 1

The preparation method of the chitosan-based pyridine quaternary ammonium salt comprises the following steps:

(1) dropwise adding 50mL (about 0.25 mol) of 1, 3-dibromopropane into 20mL (about 0.25 mol) of pyridine, stirring at 60 ℃ for reaction for 12h, standing for 20min until the product is solidified, removing the excessive 1, 3-dibromopropane (sucking liquid-phase unreacted products by a suction pipe), washing the product three times by using diethyl ether, and collecting 43.9207 g of oily solid product, namely quaternary pyridinium salt for later use;

(2) 7.0428g (0.025 mol) of quaternary pyridinium salt is dissolved in N, N-Dimethylformamide (DMF), 10mL of 15.0% NaOH aqueous solution is added, the mixture is stirred and reacted for 20min at 60 ℃, 4.0156g (0.025 mol monomer) of chitosan is added, the mixture is continuously stirred and heated for 12h, after the reaction is finished, the product is washed by diethyl ether and is filtered by suction for three times, and the product is dried in a vacuum drying oven to obtain 2.8358 g of brown solid powder, thus obtaining the brown solid powder.

Example 2

The preparation method of the chitosan-based pyridine quaternary ammonium salt comprises the following steps:

(1) dripping 40mL of 1, 3-dibromopropane into 20mL of pyridine, stirring and reacting for 16h at 50 ℃, standing for 20min until the product is solidified, removing excessive 1, 3-dibromopropane (sucking liquid-phase unreacted substances by a suction tube), washing the product with diethyl ether for three times, and collecting an oily solid product, namely quaternary pyridinium salt for later use;

(2) 7.0428g of quaternary ammonium salt pyridine is dissolved in N, N-Dimethylformamide (DMF), 8mL of 15.0% NaOH aqueous solution is added, stirring reaction is carried out at 50 ℃ for 40min, 3.21g of chitosan is added, stirring and heating are carried out continuously for 15h, after the reaction is finished, the product is washed by ethyl ether and is filtered by suction for three times, and the product is dried in a vacuum drying oven to obtain brown solid powder, thus obtaining the brown solid powder.

Example 3

The preparation method of the chitosan-based pyridine quaternary ammonium salt comprises the following steps:

(1) dripping 60mL of 1, 3-dibromopropane into 20mL of pyridine, stirring and reacting for 8h at 80 ℃, standing for 20min until the product is solidified, removing excessive 1, 3-dibromopropane (sucking liquid-phase unreacted substances by a suction tube), washing the product with diethyl ether for three times, and collecting an oily solid product, namely quaternary pyridinium salt for later use;

(2) 7.0428g of quaternary pyridinium salt is dissolved in N, N-Dimethylformamide (DMF), 12mL of 15.0% NaOH aqueous solution is added, the mixture is stirred and reacted for 10min at 80 ℃, 4.8g of chitosan is added, the mixture is continuously stirred and heated for 10h, after the reaction is finished, the product is washed by diethyl ether and is filtered by suction for three times, and the product is dried in a vacuum drying oven to obtain brown solid powder, thus obtaining the brown solid powder.

The chitosan-based quaternary ammonium pyridine salt prepared in example 1 was subjected to the following test studies:

1. as can be seen from fig. 1, the prepared chitosan-based pyridinium quaternary ammonium salt is a brown powdery solid.

2. And (3) carrying out mass spectrometry on the quaternary ammonium pyridine salt and the chitosan-based quaternary ammonium pyridine salt sample in a positive ion mode. The cation electron spray mass spectrogram of the pyridinium quaternary ammonium salt is shown in figure 2, the theoretical cation molecular ion weight is 200.1m/z, and is close to the actual molecular ion weight of 200m/z, so that the product pyridinium quaternary ammonium salt in a sample can be preliminarily judged. The chitosan-based pyridine quaternary ammonium salt cation electron spray mass spectrogram is shown in figure 3, the highest peak of the cation molecular ion peak is 359.7m/z, the difference with the fragment peak 329.5m/z is 30.2u, and the reasonable explanation is that CH in chitosan molecules is lost₂OH is different from the fragment peak 282.1m/z by 77.6u, and is presumed to lose the pyridyl in the quaternary ammonium pyridinium, so that the sample can be preliminarily judged to contain the target product chitosan-based quaternary ammonium pyridinium.

3. Adopting infrared spectroscopy at 4000-500cm^-1And (3) testing the absorption peaks of the quaternary ammonium pyridinium salt and the chitosan-based quaternary ammonium pyridinium salt samples within the range. The results are shown in FIGS. 4 and 5. The infrared spectrum of the quaternary ammonium salt of pyridine is shown in FIG. 4, which is at 3490cm^-1And 3316cm^-1The nearby absorption peak is O-H, N-H stretching vibration; 3156cm^-1The nearby absorption peak is stretching vibration = C-H on the pyridine ring; 1645cm^-1And 1540cm^-1Nearby absorption peaks are stretching vibration on C = C and C = N skeletons on pyridine rings; 1540cm^-1Nearby absorption peaks are respectively C-H asymmetric and symmetric deformation vibration on methylene; 1185cm^-1Nearby stretching vibration with an absorption peak of C-N; 830cm^-1The nearby absorption peak is the C-H deformation vibration of ortho-position substitution on the pyridine ring. When the ammonium salt is formed, the amino group in the molecule is converted into ammonium ion, the stretching vibration of the N-H bond is greatly shifted to low frequency within 3200-2200cm^-1The strong, wide and scattered absorption bands appear at the position of the catalyst and accord with the characteristics of the product.

The infrared spectrogram of chitosan-based quaternary ammonium pyridine salt is shown in figure 5, 3156cm^-1The absorption peak is caused by the stretching vibration of C-H on the pyridine ring; 1590cm^-1Nearby absorption peaks ascribed to stretching vibration on the C = C and C = N skeletons on the pyridine ring; 1353cm^-1Nearby absorption peak is stretching vibration of the inner C-N; 768cm^-1The nearby absorption peak is pyriAnd C-H substituted on the ortho-position of the pyridine ring is deformed and vibrated. The quaternary ammonium salt of pyridine reacts with chitosan to generate secondary amine, and the N-H stretching vibration of the secondary amine is 3500 cm-^-1Has an absorption single peak between them, and is 1650-1590cm^-1An N-H bending vibration absorption peak is arranged between the two, and C-N telescopic vibration 1350-^-1I.e. the characteristic absorption of the secondary amine.

4. Static adsorption experiments. By K₂Cr₂O₇The solid particles and distilled water as a solvent were prepared into standard solutions having concentrations of 0.01mg/mL, 0.02mg/mL, 0.03mg/mL, 0.04mg/mL, 0.05mg/mL, 0.06mg/mL, 0.07mg/mL, 0.08mg/mL, 0.09mg/mL, and 0.1mg/mL, respectively. The absorbance of the solution at the maximum absorption wavelength of 351nm was measured by UV-3100 type UV spectrophotometer, three parallel experiments were performed, the average value was taken, and a standard concentration-absorbance curve was plotted, as shown in FIG. 6.

Adsorbing Cr in a 40mL sample bottle₂O₇ ^2-And (4) performing experiments to determine the capability of the heavy metal ion removal. 0.1mg/mL Cr is prepared in each experiment₂O₇ ^2-Solution of 0.15g of chitosan based quaternary ammonium pyridine salt adsorbing 30mL of Cr₂O₇ ^2-Adjusting pH of the solution according to the requirement<5.30 adjustment with dilute hydrochloric acid, pH>5.30 with NaOH solution. Collecting the supernatant after adsorption under different conditions, after a static adsorption experiment, evaluating the absorbance of the adsorbed solution to Cr by using the chitosan-based pyridine quaternary ammonium salt₂O₇ ^2-The adsorption capacity of (1).

The adsorption amount (q, mg/g) and the adsorption rate (R,%) were calculated respectively as follows:

the adsorption results of the polysaccharide pyridinium quaternary ammonium salt at different pH are shown in table 1 and fig. 7.

Table 1 shows the comparison of adsorption rates of chitosan and product at different pH

。

The optimal dosage and time for adsorption are explored. At optimum pH =4, 30mL of 0.1mg/mL of Cr was adsorbed by 0.05g, 0.1g, 0.15g, 0.2g, 0.25g, 0.3g of chitosan based pyridinium quaternary ammonium salt at room temperature₂O₇ ^2-The adsorption rates of the solutions at adsorption times of 15min, 30min and 45min were calculated, and the obtained data are shown in Table 2. The results show that the adsorption is balanced and the adsorption rate is highest when the adsorption time is about 30min, and the adsorption rate is unchanged when the time is prolonged to 45 min. 0.15g of chitosan based quaternary ammonium pyridine salt is used for adsorbing 30mL of 0.1mg/mL Cr₂O₇ ^2-The solution has an adsorption rate of 89%, and the adsorption rate of the medicine is increased without obvious increase.

TABLE 2 Chitosan based pyridinium Quaternary ammonium salt vs. Cr₂O₇ ^2-Adsorption rate at different time and different dosage

。