CN111118895B

CN111118895B - Polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber and synthetic method and application thereof

Info

Publication number: CN111118895B
Application number: CN201911290278.6A
Authority: CN
Inventors: 熊春华; 张维权; 王小青; 孙静; 赵胜泽; 厉炯慧; 沈忱; 姚彩萍
Original assignee: Zhejiang Gongshang University
Current assignee: Zhejiang Gongshang University
Priority date: 2019-12-16
Filing date: 2019-12-16
Publication date: 2022-06-10
Anticipated expiration: 2039-12-16
Also published as: CN111118895A

Abstract

The invention discloses polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber, which has the following structural formula:

the invention also discloses a synthetic method of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber. The polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber can selectively adsorb Cr (VI), so that the polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber can be used for treating Cr (VI) -containing wastewater.

Description

Polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber and synthetic method and application thereof

Technical Field

The invention belongs to the technical field of chemistry, and particularly relates to polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber and a synthesis method and application thereof.

Background

The common valence of the chromium element is +2, +3 and +6, and hexavalent chromium is mainly contained in chromium-containing wastewater, and the toxicity of the hexavalent chromium is far higher than that of trivalent chromium. After excessive Cr (VI) is absorbed by plants, the seed germination rate is reduced, photosynthesis is abnormal and mutagenesis is initiated. When people eat vegetables, grains and other foods with Cr (VI) exceeding the standard, the cancer can be caused after the Cr (VI) in the body exceeds the standard. Meanwhile, Cr (VI) is absorbed by human body through mucosa and skin, and is accumulated in lung, kidney and spleen, and is also present in skeleton. The content of Cr (VI) in drinking water must not exceed 0.05mg/L, as specified in the sanitary Standard for Drinking Water, 2006 edition.

Due to the wide application of chromium products, a large amount of chromium-containing waste water, waste gas and waste residues are discharged, 600 million tons of chromium-containing waste residues are accumulated in the country over the years, more than 80 percent of chromium-containing waste residues cannot be properly treated, more than 40 billion cubic meters of chromium-containing waste water is discharged in the industry over the year, one half of the chromium-containing waste water does not reach the national discharge standard, and the hazard of the chromium-containing waste water cannot be ignored. The adsorption material can adsorb heavy metals in water, and a good separation and enrichment material needs to meet the requirements of high adsorption speed, good selectivity and high elution rate.

The chelate fiber is a fiber having a coordinating function, and a ligand containing N, O, P, S or the like is grafted to the fiber, and these atoms can coordinate with heavy metal ions to adsorb the heavy metal ions. The common functional fiber matrix includes polyacrylonitrile fiber, polyurethane fiber, polyvinyl alcohol fiber, cellulose fiber, etc. The diameter and the specific surface area of the fiber are small; the special physical form of the adsorbent enables the adsorbent to have larger contact area and smaller fluid resistance with the adsorbent, so that the adsorbent is high in adsorption rate and capacity, easy to desorb and very effective in adsorbing trace heavy metal ions. Therefore, the chelate fiber material has strong applicability in the aspect of separating and enriching heavy metals.

The conventional preparation method of the chelate fiber comprises a traditional heating method and an irradiation grafting method, the traditional heating method is commonly used at present, a water bath, an oil bath or an electric heating jacket is used for heating and stirring the reactant and the solvent together, the synthesis time of the method is generally long, and relatively much water and electricity are consumed. The irradiation grafting method is to irradiate the fiber matrix with high energy radiation to form several active points on the matrix skeleton and then to combine the ligand with the fiber via grafting reaction, but the irradiation method has high requirement on the apparatus and high cost. The microwave-assisted method is a new method for preparing the chelate fiber, wherein the microwave refers to electromagnetic waves with the frequency of 0.3-300 GHz and the wavelength range of 1 mm-1 m. The microwave can not cause chemical bond damage, but can heat polar substances to rearrange polar molecules, and electric energy is converted into heat energy due to intermolecular friction and dielectric consumption, so that the internal and integral heating of a reaction system is realized, the temperature rise is quicker, and the reaction time is greatly shortened. At present, most chelate fibers have more preparation steps and lack simpler preparation schemes.

Disclosure of Invention

The invention aims to solve the technical problem of providing polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber and a synthesis method and application thereof.

In order to solve the technical problems, the invention provides polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber, which has the following structural formula:

the invention also provides a synthetic method of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber, which comprises the following steps:

1) taking polyacrylonitrile fiber as a matrix and 5-amino-2-methoxypyridine as a ligand;

adding polyacrylonitrile fiber, 5-amino-2-methoxypyridine and sodium carbonate into a solvent, heating to 110-140 ℃ under the microwave condition, and stirring for reaction for 5-20 min;

0.6-1.2 ml of 5-amino-2-methoxypyridine is added to every 50mg of polyacrylonitrile fiber;

functional group-C ≡ N of polyacrylonitrile fiber: sodium carbonate is in a molar ratio of 1: 1-4;

2) and washing the polymer obtained by the reaction in the step 1) with deionized water, and drying (for example, drying at 50 ℃) to obtain the polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber.

Description of the drawings: filtering the reaction product obtained in the step 1), wherein the obtained filter cake is a polymer.

The improvement of the synthesis method of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber of the invention is as follows:

in the step 1), the solvent is ethylene glycol, and the material-liquid ratio of the polyacrylonitrile fiber to the ethylene glycol is 50.0mg/(15 +/-5) ml.

The synthesis method of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber is further improved as follows: in the step 1), the microwave power is 400-1000W, and the stirring speed is (300 +/-50) rpm/min.

When every 50mg of polyacrylonitrile fiber is used as the raw material, the above process parameters can be followed.

As a further improvement of the synthesis method of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber, the step 1) is as follows:

1ml of 5-amino-2-methoxypyridine is added to every 50mg of polyacrylonitrile fiber;

functional group-C ≡ N of polyacrylonitrile fiber: sodium carbonate in a molar ratio of 1: 2;

the microwave power is 600W, the temperature is 140 ℃, and the time is 20 min.

The invention also provides the application of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber: selectively adsorbing Cr (VI).

As an improvement of the use of the present invention: used for treating wastewater containing Cr (VI).

As a further improvement of the use of the invention: the desorbent is 4mol/L hydrochloric acid.

The synthetic route of the invention is as follows:

the polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber is prepared by a one-step method, can effectively and selectively adsorb Cr (VI), has good adsorption effect and desorption effect, and can be applied to treatment of Cr (VI) in sewage.

The invention has the following technical advantages:

(1) the compound synthesized by the invention is a new compound;

(2) the invention adopts a microwave-assisted one-step method for preparation, and has the advantages of simple synthetic method, high speed and less byproducts;

(3) the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber synthesized by the method has the advantages of good adsorption selectivity on Cr (VI), high adsorption speed, large adsorption quantity, good desorption effect, good thermal stability and the like.

(4) The polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber synthesized by the method has a good technical effect on removing Cr (VI) in the wastewater containing Cr (VI).

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

FIG. 1 is an infrared spectrum of polyacrylonitrile-based 5-amino-2-methoxypyridine chelate fiber, as well as acrylonitrile fiber and 5-amino-2-methoxypyridine;

FIG. 2 is a thermogravimetric plot of polyacrylonitrile fibers and polyacrylonitrile-5-amino-2-methoxypyridine chelate fibers;

FIG. 3 is a graph showing the effect of reaction temperature on the adsorption amount of polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber;

FIG. 4 is a graph showing the effect of reaction time on the adsorption amount of polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber;

FIG. 5 shows the mass of polyacrylonitrile fiber: influence of ligand volume ratio (mg: mL) on adsorption quantity of polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber;

FIG. 6 is a graph showing the effect of microwave power on the adsorption capacity of polyacrylonitrile-5-amino-2-methoxypyridine chelate fibers;

FIG. 7 is a graph showing the effect of sodium carbonate dosage on the adsorption capacity of polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fibers;

FIG. 8 shows the selective adsorption effect of polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber;

FIG. 9 shows the adsorption effect of polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fibers at different contact times;

FIG. 10 is a graph showing the effect of initial concentration of metal ion Cr (VI) on the adsorption capacity of polyacrylonitrile-5-amino-2-methoxypyridine chelate fibers;

FIG. 11 shows the removal rate of polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fibers in Cr (VI) -containing solutions of different concentrations.

Fig. 12 is a graph of XPS analysis results.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:

embodiment 1, a method for synthesizing polyacrylonitrile-5-amino-2-methoxypyridine chelating fiber, comprising the following steps:

1) 50.0mg (containing 0.855 mmol-C.ident.N group) of polyacrylonitrile fiber (PAN) as a parent substance, 1mL of 5-amino-2-methoxypyridine (FAMP) as a ligand and 1.71mmol of sodium carbonate were weighed, sequentially added to a three-necked flask, and then 15mL of ethylene glycol was added, and transferred to a microwave synthesis workstation.

Namely, polyacrylonitrile fiber: 5-amino-2-methoxypyridine 50.0 mg: 1 mL;

setting the microwave power of 600W, the temperature of 140 ℃ and the time of 20min, and controlling the rotor to stir at the speed of 300 rpm/min.

2) And after the reaction is finished, cooling the three-neck flask to room temperature, taking out the fiber (namely, filtering, taking a filter cake as a polymer), putting the fiber on a sand core funnel, adding deionized water, repeatedly performing suction filtration until the liquid (namely, the obtained washing liquid) is clear, so as to wash out the residual ligand and sodium carbonate on the surface, and then putting the clear liquid in a vacuum drying oven at 50 ℃ to dry the clear liquid to constant weight, thereby obtaining the polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber (PAN-FAMP).

The structural formula of the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber (PAN-FAMP) is as follows:

the structure of the synthesized new compound PAN-FAMP is characterized by a Fourier infrared spectrometer,

FIG. 1 is an infrared spectrum of PAN and PAN-FAMP fibers and ligand FAMP. As shown in figure 1, compared with polyacrylonitrile fiber, the synthesized PAN-FAMP functional fiber has the modified fiber with the length of 2243cm^-1The absorption peak of-C [ identical to ] N bond is obviously weakened, 800cm^-1To 1700cm^-1Peaks belonging to the group on FAMP appear; compared with ligand FAMP, 1274cm appears in PAN-FAMP functional fiber^-1Stretching vibration peak of-C-O-of (4) (-) 1654cm^-1C ═ C stretching vibration peak, 1617cm^-1(ii) a-C ═ N stretch band at the pyridine ring, 741cm^-1The out-of-plane deformation vibration peaks of C-H indicate that the ligand FAMP is successfully combined with polyacrylonitrile, and the PAN-FAMP is also 3414cm^-1The fiber is proved to contain no free ligand by a large and wide peak. In conclusion, the ligand 5-amino-2-methoxypyridine can be successfully reacted with polyacrylonitrile fiber to synthesize PAN-FAMP.

FIG. 2 is a thermogravimetric plot of PAN, PAN-FAMP. As shown in the thermogravimetric graph of FIG. 2, the cracking weight loss of PAN mainly comprises 3 stages, wherein 260-340 ℃ is stage 1, 340-400 ℃ is stage 2, and 400-500 ℃ is stage 3. The weight loss in

stages

1 and 2 is mainly due to ammonia gas generated by cyano decomposition, and-C.ident.N and-CH₂The hydrogen cyanide removed by the reaction is lost, and the 3 rd stage is due to the carbonization reaction of the fiber and the continuous loss of hydrogen cyanide, and the release of a little methane and hydrogen. Stage 1 of PAN-FAMP almost disappeared, indicating that the remaining cyano groups were few; the weight loss in the 2 nd stage is 330-500 ℃, similar to PAN, and related to the carbonization reaction of molecular chains. Thermogravimetric analysis shows that PAN-FAMP has good thermal stability, can reach the working temperature of more than 100 ℃, and meets the requirements of adsorption application.

Experiment 1, static adsorption experiment

(1) Selective adsorption

10mg of PAN-FAMP fiber synthesized in example 1 is weighed and added into 20mL of solution containing 100mg/L of Cr (VI), Cu (II), Zn (II), Ni (II) and Cd (II), the pH of the solution is adjusted to 1-6 by 0.1mol/L of HCl solution and NaOH solution, adsorption experiments are carried out at 25 ℃, the adsorption capacity is measured after 24 hours of adsorption, and parallel experiments are carried out at the same time.

The adsorption amount was calculated in the manner shown in formula (1).

Wherein Q (mg/g) is the adsorption amount of the functional fiber, C₀(mg/L) is the metal ion concentration, C, of a control group (i.e., without PAN-FAMP fiber, the remainder being as above)_eIn terms of the concentration of metal ions in the solution after adsorption, V (mL) is the volume of the solution, and m (mg) is the mass of the fiber.

As shown in fig. 8, the PAN-FAMP fiber obtained a maximum adsorption amount of 148.13mg/g at pH 2, and then the adsorption amount rapidly decreased as the pH increased. Under low pH condition, N atoms on the surface of the fiber are replaced by H⁺Protonation, HCrO negatively charged due to electrostatic attraction₄ ^-And Cr₂O₇ ^2-Are readily adsorbed to positively charged fibers. At pH 2 of the solution, the adsorption amount of PAN-FAMP for Cr (vi) is higher than that at pH 1 because Cr (vi) ions are mainly H at pH 1 ₂CrO₄And Cr₂O₇ ^2-Is in a form requiring 2 units of active sites to adsorb 1 unit of Cr₂O₇ ^2-And at pH 2, the Cr (VI) ion is mainly HCrO₄ ^-Mainly, only 1 unit of active site is required, so that the adsorption capacity is higher at pH 2 than at pH 1. At higher pH values, the reduction in the amount of adsorption is due to deprotonation of the nitrogen atoms of the fibers and to the OH groups present in the reaction solution^-Ions with CrO₄ ^2-Competitive adsorption between ions causes the adsorption capacity to be reduced continuously. What is needed isThe pH value of 2 is selected as the optimum pH value of PAN-FAMP fiber to adsorb Cr (VI).

(2) Effect of contact time on adsorption quantity

3 parts of PAN-FAMP fiber synthesized in example 1, 20mg each, was weighed and added to 40mL of a solution of metal ion Cr (VI) at a concentration of 100mg/L and pH 2, adsorption experiments were performed at 15 ℃, 25 ℃ and 35 ℃ respectively, 1mL of the solution was sucked into a 5mL cuvette at regular intervals, and deionized water was added to dilute the solution to 2mL, and the amount of adsorption at each spot was measured.

As shown in FIG. 9, the adsorption amount of PAN-FAMP increases rapidly with time and then gradually becomes gentle, and the equilibrium time is about 30 min. In the initial stage of adsorption, the number of active sites on the fiber is the largest, metal ions rapidly diffuse in a thin liquid layer on the surface of the fiber and are combined with the active sites, and a higher concentration difference can promote the adsorption effect, so that the adsorption rate is the largest; with the increase of time, the concentration of the metal ions is reduced, a large number of active sites are occupied, the adsorbed metal ions generate electrostatic repulsion to the subsequent metal ions, the diffusion of the metal ions in the adsorbent is also blocked by a chelate formed by the coordination atoms and the metal ions, the adsorption rate is reduced, and finally the adsorption balance is achieved. Meanwhile, it can be found that the higher the temperature, the higher the adsorption capacity, because the temperature rise can thin the thin liquid layer on the surface of the fiber, reduce the adsorption mass transfer resistance, and the active sites are increased with the temperature, so that the metal ions are more easily adsorbed.

(3) Effect of initial concentration on adsorption amount

10 parts of the PAN-FAMP fiber synthesized in example 1 were weighed, 10mg of each part was added to 20mL of a solution of metal ion Cr (VI) at a concentration of 20, 30, 40, 60, 80, 100, 200, 300, 400, or 500mg/L and pH 2, and the adsorption was carried out at 25 ℃ for 24 hours to measure the adsorption amount. Experiments were also performed at 15 ℃ and 35 ℃.

As shown in fig. 10, the adsorption amount of the fiber increases with the initial concentration at the same temperature due to the driving force of the concentration difference of the solid-liquid surface to the metal ions, so that the metal ions are more easily diffused to the fiber surface, and the driving force is larger as the concentration is higher. And at high concentrations, the active sites are more occupied, and the adsorption capacity does not increase until the active sites are saturated.

Examples 2,

The reaction temperature in example 1 was changed from 140 ℃ to 110 ℃, 120 ℃ and 130 ℃, and the rest was the same as in example 1. The influence of the reaction temperature on the adsorption amount of the fibers, which was measured in the manner of the above experiment 1(1), is shown in FIG. 3.

As can be seen from fig. 3, the adsorption amount of the functional fiber increases with the temperature increase in the experimental temperature range, because at higher temperature, the swelling degree of the fiber is higher, and more ligand can diffuse into the PAN fiber to react with the cyano group, so that the conversion rate is higher.

Examples 3,

The reaction time in example 1 was changed to 5min, 10min and 15min, and the rest was the same as in example 1. The influence of the reaction time on the amount of adsorbed fibers, which was examined in the manner of the above experiment 1(1), is shown in FIG. 4.

As can be seen from fig. 4, the adsorption amount of the fiber increases with the increase of the reaction time, because the contact time between the reactants becomes longer, the reaction becomes more sufficient, but too long reaction time causes the fiber to absorb a large amount of heat, and the fiber is broken into a fine powder state after exceeding 20 min.

Examples 4,

Polyacrylonitrile fiber in example 1: the mass/volume ratio of the ligand was changed from 50mg:1mL to 50mg:0.6mL, 50mg:0.8mL, 50mg:1.2mL, and the remainder was the same as in example 1. The effect of the obtained reaction molar ratio on the fiber adsorption amount as measured in the manner of experiment 1(1) is shown in FIG. 5.

As can be seen from FIG. 5, the addition amount of the ligand affects the adsorption amount of the fiber, and the more the ligand is, the higher the chance of contact with the cyano group is, of course, the excessive ligand will cause the PAN fiber to be broken and agglomerated, and the adsorption amount is greatly reduced.

Examples 5,

The microwave power in the embodiment 1 is changed from 600W to 400W, 800W and 1000W, and the rest is equal to the embodiment 1. The effect of the obtained microwave power on the amount of fiber adsorption is shown in fig. 6, which is measured in the manner of experiment 1(1) above.

As can be seen from fig. 6, as the microwave power increases, the adsorption capacity also increases, and the selection of high-power microwaves can accelerate the vibration of polar molecules, so as to rapidly increase the temperature, and at the same time, the increase of the microwave power can also promote the destruction of the molecular chain crystallization region of the PAN fiber, which is beneficial for the ligand to enter the fiber interior to react with cyano groups. However, the power is too high, which in turn causes a decrease in the effect.

Examples 6,

The reaction molar ratio (sodium carbonate: functional group-C.ident.N of parent polyacrylonitrile fiber) in example 1 was changed from 2 to 1, 3, 4, and the rest was the same as example 1. The effect of the molar ratio of sodium carbonate obtained on the amount of adsorbed fibers, as measured in

experiments

1 and 1 above, is shown in fig. 7.

As is clear from fig. 7, sodium carbonate accelerates hydrolysis of polyacrylonitrile to improve reaction efficiency, but excessive sodium carbonate also denatures polyacrylonitrile fibers, so the amount of sodium carbonate added was selected as the optimum amount.

Comparative examples 1,

The ligand (5-amino-2-methoxypyridine) in example 1 was changed to sulfapyridine, sulfanilic acid, diphenylsemicarbazide, and thiamine hydrochloride, and the synthesis conditions were determined in the manner of the above experiment 1(1) with reference to example 1, and the adsorption amounts of Cr (vi) to the obtained fibers were as shown in table 1.

As shown in Table 1, the products synthesized by PAN fiber and sulfapyridine, sulfanilic acid, diphenylsemicarbazide and thiamine hydrochloride under microwave conditions have substantially no adsorption force on Cr (VI), which indicates that not any ligand containing amino groups can be successfully grafted on PAN fiber.

TABLE 1 adsorption of Cr (VI) by different ligands and PAN fiber synthesis products

Ligands	Q(mg/g)
		5-amino-2-methoxypyridine	148.13
Sulfazopyridines	5.37
		Sulfanilic acid	7.82
Diphenylsemicarbazide	4.78
		Thiamine hydrochloride	3.98

Experiment 2, static desorption experiment:

weighing a plurality of portions of PAN-FAMP fibers synthesized in example 1, adding 10mg of the PAN-FAMP fibers into 20mL of a solution with metal ion Cr (VI) concentration of 100mg/L and pH value of 2, adsorbing for 3h, measuring the concentration of the residual metal ions, washing the fibers with deionized water for a plurality of times, and drying; and then putting the dried fibers into different desorbents, oscillating for 1h at a constant temperature of 25 ℃, determining the concentration of metal ions in the desorbents, taking out the desorbed fibers, washing and drying, and repeating the adsorption and desorption experiment. The calculation formula of the desorption rate is as shown in formula (2):

wherein E (%) is the desorption rate, C₀(mg/L) is the metal ion concentration of the blank control group, C₁For the residual metal ion concentration after adsorption, C ₂Is gold in the desorbentThe concentration of the metal ions.

The results of the experiment are shown in Table 2

TABLE 2 influence of desorbent on desorption Rate

When the concentration of the hydrochloric acid is 4mol/L, the desorption rate reaches 76.21 percent.

Experiment 3, the application of PAN-FAMP in removing Cr (VI) in wastewater containing Cr (VI):

accurately weighing 300mg of chopped chelate fiber PAN-FAMP, filling the weighed chelate fiber PAN-FAMP into a dynamic adsorption column with the diameter of phi 3mm multiplied by 30cm, plugging cotton on the bottom end and the top end of the column respectively, enabling 20mL of Cr (VI) containing solution with different initial concentrations to pass through the column at the flow rate of 1.0mL/min, measuring the concentration of Cr (VI) in the effluent solution by ICP-AES, calculating the removal rate, wherein the calculation formula of the removal rate is as shown in formula (3):

wherein R (%) is the removal rate, C₀As initial concentration, C_tThe results are shown in FIG. 11 for effluent concentrations:

as shown in FIG. 11, PAN-FAMP has good performance of removing Cr (VI) in the wastewater containing Cr (VI), and the removal rate of 5mg/L of the wastewater containing Cr (VI) reaches 99.9%.

Experiment 4,

The PAN-FAMP fiber synthesized in example 1 and the PAN-FAMP fiber after Cr (vi) adsorption were subjected to XPS analysis, and the results of XPS analysis are shown in fig. 12.

From fig. 12, panel (a) is an XPS broad spectrum of PAN-FAMP fibers, and it can be seen that the adsorbed fibers have detected the presence of Cr element, indicating that the fibers have successfully adsorbed Cr (vi) in solution. Panel (b) is a C1s spectrum of PAN-FAMP fibers, with three peaks observed with binding energies of 284.82eV, 287.05eV and 289.58eV, corresponding to the groups C-C/C-H, C-N/C-O and C ═ O, respectively. C1s plot of the post-absorption fibers observed binding energies 284.78eV, 286.49eV, and 288.52eV, as compared to absorption The binding energy before the attachment was all reduced, indicating that the functional group is involved in the adsorption of Cr (VI). Panel (C) is the N1 s spectrum of PAN-FAMP fiber, 399.26eV and 402.07eV for the-N-H and C-N groups, respectively. the-N-H content of the adsorbed fiber is reduced to 26.37 percent, and-C-N⁺The peak ratio is obviously increased, and simultaneously-NH⁺The new peak of (2) appears at 401.35eV, -NH⁺Obtained by protonation of-C ═ NH, and-C-N⁺Probably due to protonation of pyridine N or C-N-C on the ligand, which chelate chromate ions in solution, while the protonated amino group also has some adsorption on the negatively charged chromate ions. Graph (d) is the O1s spectrum for PAN-FAMP fiber, with 532.83eV and 535.96eV corresponding to the peaks for C-O and C-O-C/C ═ O, respectively, and a decrease in C-O content and an increase in C-O-C/C ═ O content was observed in the O1s graph for the fiber after adsorption, indicating that O atoms were complexed with Cr (vi). In order to further explore the adsorption effect of the fiber on chromium ions, a Cr 2p diagram of the fiber after metal adsorption is observed. Panel (e) is a Cr 2p spectrum of PAN-FAMP fibers: the detected binding energies 577.16eV, 579.24eV, 586.72eV and 588.40eV correspond to the groups Cr (OH)₃、CrO₄ ^2-、Cr₂O₄ ^2-And Cr₂O₇ ^2-In addition to Cr (VI), Cr (III) was detected, whereas no Cr (III) was added during the entire reaction, indicating that a portion of Cr (VI) was reduced to Cr (III) upon metal adsorption. Part of Cr (III) is combined with OH-in the solution to generate Cr (OH) ₃Adsorbed on the surface of the fiber. As mentioned above, the adsorption of the modified fiber to chromium ions is mainly due to the chelation of N, O atoms and chromate ions, and the simultaneous ion exchange and fiber to Cr (OH)₃The adsorption of the fibers to chromium ions is also promoted.

Finally, it is also noted that the above-mentioned lists merely illustrate a few specific embodiments of the invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.

Claims

1. The polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber is characterized by having the following structural formula:

。

2. the method of synthesizing polyacrylonitrile-5-amino-2-methoxypyridine chelating fibers as set forth in claim 1, comprising the steps of:

adding polyacrylonitrile fiber, 5-amino-2-methoxypyridine and sodium carbonate into a solvent, heating to 110-140 ℃ under a microwave condition, stirring and reacting for 5-20 min, wherein the microwave power is 400-1000W, and the stirring speed is (300 +/-50) rpm/min;

functional group-C ≡ N of polyacrylonitrile fiber: sodium carbonate =1: 1-4 molar ratio;

the solvent is ethylene glycol, and the material-liquid ratio of the polyacrylonitrile fiber to the ethylene glycol is 50.0 mg/(15 +/-5) ml;

2) and washing the polymer obtained by the reaction in the step 1) with deionized water, and drying to obtain the polyacrylonitrile-based-5-amino-2-methoxypyridine chelate fiber.

3. The method for synthesizing polyacrylonitrile-5-amino-2-methoxypyridine chelate fiber according to claim 2, wherein in the step 1):

functional group-C ≡ N of polyacrylonitrile fiber: sodium carbonate =1:2 molar ratio;

microwave power is 600W, temperature is 140 ℃, and time is 20 min.

4. The use of polyacrylonitrile-based-5-amino-2-methoxypyridine chelating fibres as claimed in claim 1, characterized in that: selectively adsorbing Cr (VI).

5. Use of polyacrylonitrile-based-5-amino-2-methoxypyridine chelating fibres as in claim 4, characterized in that: used for treating wastewater containing Cr (VI).

6. Use of polyacrylonitrile-based-5-amino-2-methoxypyridine chelating fibres as in claim 4 or 5, characterized in that: the desorbent is 4 mol/L hydrochloric acid.