Chitosan bipyridyl group acid-resistant adsorbent, and preparation method and application thereof

Abstract

The application discloses a kind of chitosan double pyridyl group acid-resistant adsorbents and its preparation method and application, belong to electroplating sludge processing technical field.The application selects chitosan as matrix, and carries out amine group and pyridyl group grafting on its basis, and the adsorbent containing amine group and pyridyl group is prepared, the problem that the hydroxyl group and amine group on chitosan body are protonated in acidic solution and the ability of chelating metal cation is poor is solved, and heavy metal in acidic solution cannot be effectively separated.The substitution reaction of amine group and the reagent 2-chloromethyl pyridine hydrochloride (2-CPD) with lower price is used in the application, compared with existing M4195 commercial resin, production cost is reduced, and it is suitable for wide range of popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electroplating sludge treatment, and more particularly relates to an acid-resistant adsorbent with chitosan bipyridine groups and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of economy and industrialization, the electroplating industry has also developed rapidly. Electroplating sludge (ES) is a kind of metal-containing waste generated in the electroplating and surface treatment industry. Because the sludge contains various complex highly toxic components, it is listed as a hazardous waste worldwide. As a hazardous waste, ES is landfilled or solidified to stabilize the toxic and harmful substances. In the past, improper disposal of hazardous solid waste has caused serious problems. For example, potential toxic metals are released and seep into the soil and groundwater, affecting animals and plants through chemical cycles and food, especially human health. In addition, because the content of some precious metals in ES is higher than that of natural minerals and concentrates, resources will be wasted. In order to achieve the purpose of environmental protection and metal resource recovery, it is urgent to explore effective ways for sludge resource recovery and detoxification.

[0003] Compared with other methods for recovering metals from ES, hydrometallurgical processes are considered promising because they show effectiveness in extracting metals. Metal dissolution is the first step of hydrometallurgy, involving chemical leaching and biological leaching. Commonly used chemical leaching includes acid leaching and alkali leaching. Yi et al. used sulfuric acid leaching to treat copper-containing electroplating sludge. Under the conditions of 1M sulfuric acid concentration and 15:1 liquid-solid ratio, the copper leaching rate can reach 90%. In addition, copper in electroplating sludge is recovered by ammonia leaching and hydrogen reduction under high pressure, and the leaching efficiency of copper can reach more than 77.42% under the condition of 6.5M ammonia concentration. Both acid leaching and alkali leaching can well extract metals from electroplating sludge, but also have disadvantages such as lack of selective leaching, secondary pollution and equipment corrosion. Biological leaching can overcome the above-mentioned shortcomings, but has the disadvantages of slow dynamic speed and difficult subsequent recovery. Therefore, it is urgent to develop an efficient and environmentally friendly method for recovering valuable metals from electroplating sludge.

[0004] Therefore, the selective recovery of metals after hydrometallurgy has always been a research hotspot. In this regard, adsorption is considered the most promising method because of its great flexibility in designing functional groups, which helps to create a variety of adsorbents with different selective absorption properties. However, so far, the research on the recovery of heavy metal ions (HMCs) by adsorption method has mostly focused on neutral or weakly acidic wastewater, and there is little research on strongly acidic wastewater, mainly because the functional groups of most adsorbents are inhibited by high concentrations of protons in a strongly acidic environment, and cannot capture HMCs. Therefore, if an acid-resistant adsorbent is developed for one or more HMCs in strongly acidic leaching solution, not only can the recovery of HMCs become simpler and more environmentally friendly, but also the low-toxicity acidic wastewater after purification can be further utilized, such as neutralizing other alkaline wastewater. SUMMARY

[0005] The purpose of the present application is to provide a chitosan double pyridine group acid-resistant adsorbent and its preparation method and application, in order to solve the problems existing in the prior art and realize the preparation of an adsorbent that can efficiently and selectively adsorb heavy metals (copper and nickel) in strongly acidic wastewater.

[0006] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0007] One of the technical solutions of the present application: a preparation method of a chitosan double pyridine group acid-resistant adsorbent, comprising the following steps:

[0008] Take spherical chitosan as raw material, after amino protection, carry out the first reaction with epichlorohydrin to obtain the first product;

[0009] Mix the first product, ethylenediamine and solvent, then carry out the second reaction to obtain the second product;

[0010] Mix the second product, 2-chloromethylpyridine hydrochloride, acid binding agent and solvent, then carry out the third reaction to obtain the chitosan double pyridine group acid-resistant adsorbent.

[0011] Preferably, the preparation of the spherical chitosan comprises: adding a chitosan solution into a sodium hydroxide solution to form spherical chitosan; the solvent in the chitosan solution is a mixture of acetic acid and water, and the mass fraction of chitosan in the chitosan solution is 2-5wt%; the mass fraction of sodium hydroxide in the sodium hydroxide solution is 2wt%.

[0012] Further, the present application does not specially limit the way of adding the chitosan solution into the sodium hydroxide solution, and uniform addition is enough to ensure the formation of uniform spherical chitosan.

[0013] Preferably, the amino protection comprises: mixing the spheroid chitosan and benzaldehyde and then standing to obtain the spheroid chitosan with protected amino groups; the use amount ratio of the benzaldehyde to the chitosan in the chitosan solution is 50-100 mL:3-10 g; and the standing time is 12-24 h.

[0014] Preferably, the use amount ratio of the epichlorohydrin to the chitosan in the chitosan solution is 6-10 mL:3-10 g; and the reaction conditions of the first reaction are as follows: pH value is 9-14, temperature is 50-65 ℃, and time is 6-10 h.

[0015] Preferably, the solvent in the second reaction and the third reaction is ethanol and water with a volume ratio of 1:1.

[0016] Preferably, the volume ratio of the first product, ethylenediamine and the solvent is 3-10:8-12:150-200; the temperature of the second reaction is 50-70 ℃, and the time is 6-10 h.

[0017] Further, the second product needs to be placed in water for storage.

[0018] Preferably, the acid-binding agent comprises one or more of sodium carbonate, potassium carbonate and sodium hydroxide; the use amount ratio of the second product, 2-chloromethylpyridine hydrochloride, the acid-binding agent and the solvent is 3-10 mL:1-5 g:1-3 g:150-200 mL; and the temperature of the third reaction is 80-100 ℃, and the time is 12-36 h.

[0019] Preferably, the step of mixing the second product, 2-chloromethylpyridine hydrochloride, sodium carbonate and the solvent comprises: first adding 2-chloromethylpyridine hydrochloride and sodium carbonate into water, then adding ethanol into the water, and finally adding the second product into the water.

[0020] The second technical scheme of the present application provides a chitosan double pyridine group acid-resistant adsorbent prepared by the preparation method.

[0021] The third technical scheme of the present application provides an application of the chitosan double pyridine group acid-resistant adsorbent in treating electroplating sludge.

[0022] Further, the application of the chitosan double pyridine group acid-resistant adsorbent in treating a strong acid leaching solution of electroplating sludge is provided.

[0023] Further, the pH value of the strong acid leaching solution is 1-5.

[0024] The fourth technical scheme of the present application provides a method for selectively recovering copper and nickel in electroplating sludge by leaching-adsorbing, comprising the following steps:

[0025] The electroplating sludge and nitric acid are mixed to carry out leaching reaction, then the supernatant is taken, and the leaching of copper and nickel in the supernatant is realized by using the above-mentioned chitosan bipyridine group acid-resistant adsorbent;

[0026] The dosage ratio of the electroplating sludge and nitric acid is 1-10g:10-100mL;

[0027] The pH value of the supernatant is 1-5;

[0028] The dosage ratio of the chitosan bipyridine group acid-resistant adsorbent and the supernatant is 0.029g:30mL.

[0029] The technical principle of the present application is:

[0030] Chitosan has the advantages of low price, non-toxicity, good biocompatibility, etc., and is widely used as an adsorbent. Chitosan-based adsorbents have good hydrophilicity, flexible structure, rich functional groups, good reaction activity and chelating capacity. The present application selects chitosan as a substrate, and carries out grafting of amine groups and pyridine groups based on it, to prepare an adsorbent containing amine groups and pyridine groups, solving the problem that the hydroxyl groups and amine groups on the chitosan body are protonated in an acidic solution and have poor chelating capacity for metal cations, and cannot effectively separate heavy metals in the acidic solution. Moreover, the present application uses amine groups to carry out substitution reaction with 2-chloromethyl pyridine hydrochloride (2-CPD) which is cheaper, compared with the existing M4195 commercial resin, reducing the production cost, and being suitable for wide range of popularization and application.

[0031] The present application discloses the following technical effects:

[0032] The application utilizes leaching-adsorption synergistic recovery of nickel and copper in electroplating sludge, first uses nitric acid to leach the metals in electroplating sludge, and since the leaching solution is strongly acidic, and in a strongly acidic medium (pH < 2.5), there is obvious protonation, so it is challenging to effectively separate heavy metal cations (HMCs) by using conventional adsorption method. On this basis, the application provides an acid-resistant adsorbent (APCS-CPD) with chitosan bipyridyl groups, which can adsorb copper and nickel in a strongly acidic solution. The results show that the adsorbent has excellent adsorption effect, APCS-CPD has good adsorption performance for Cu(II) and Ni(II) under acidic (PH = 1.5) conditions, and the maximum adsorption capacities are 69.303 mg / g and 59.217 mg / g, respectively. The adsorbent has high adsorption selectivity and good resistance to coexisting inorganic salts under acidic conditions, and the adsorption of other coexisting metal ions (Zn(II), Fe(II), Cr(III)) on Cu(II) and Ni(II) can be ignored. In addition, the repeated experiments show that APCS-CPD has good recovery performance, and the dynamic column experiment further proves that APCS-CPD has great potential for recovering Cu(II) and Ni(II) in industrial acidic solutions, and can directly realize the recovery and secondary utilization of metals. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is an XPS graph of the electroplating sludge, wherein (a) is an XPS energy spectrum of Ni2p, and (b) is an XPS energy spectrum of Cu2p;

[0034] Figure 2 It is a physical picture of APCS-CPD, APCS-ED after freeze-drying and APCS-CPD after freeze-drying, wherein (a) and (b) are physical pictures of APCS-CPD, (c) is a physical picture of APCS-ED after freeze-drying, and (d) is a physical picture of APCS-CPD after freeze-drying;

[0035] Figure 3 It is a characterization result picture of APCS, APCS-ED and APCS-CPD, wherein (a) and (b) are SEM pictures of APCS-CPD at different magnifications, (c) is an XPS full spectrum picture of APCS-CPD, (d) is a high-resolution XPS N1s spectrum picture of APCS-CPD, (e) is an FTIR spectrum picture of APCS, APCS-ED and APCS-CPD, and (f) is a TGA result picture of APCS, APCS-ED and APCS-CPD;

[0036] Figure 4Adsorption effect of APCS, APCS-ED, APCS-CPD on Cu(II) and Ni(II) at different acidity, wherein (a) corresponds to Cu(II), (b) corresponds to Ni(II);

[0037] Figure 5 Adsorption selectivity test results of APCS-CPD on Cu(II) and Ni(II), wherein (a) is the adsorption selectivity test results in the two-component system composed of Mn and Cu and Ni respectively, (b) is the adsorption selectivity test results in the two-component system composed of Zn and Cu and Ni respectively, (c) is the adsorption selectivity test results in the two-component system composed of Cr and Cu and Ni respectively, (d) is the adsorption selectivity test results in the two-component system composed of Fe and Cu and Ni respectively;

[0038] Figure 6 Adsorption affinity test results of APCS-CPD on different heavy metal ions;

[0039] Figure 7 Adsorption kinetics process curves of APCS-ED and APCS-CPD on Cu(II) and Ni(II), wherein (a) is the adsorption kinetics process curve on Cu(II), (b) is the adsorption kinetics process curve on Ni(II);

[0040] Figure 8 Adsorption isotherm process curves of APCS-ED and APCS-CPD on Cu(II) and Ni(II), wherein (a) is the adsorption isotherm process curve on Cu(II), (b) is the adsorption isotherm process curve on Ni(II);

[0041] Figure 9 Influence results of different inorganic salts on the adsorption performance of APCS-CPD;

[0042] Figure 10 Adsorption stability test results of APCS-CPD;

[0043] Figure 11 Structure stability results chart of APCS-CPD after adsorption;

[0044] Figure 12 Device chart of dynamic column test;

[0045] Figure 13 Adsorption performance of APCS-CPD on Cu(II) and Ni(II) in the process of dynamic column test;

[0046] Figure 14 Adsorption effect chart of APCS-CPD on heavy metal ions when treating electroplating sludge;

[0047] Figure 15 FTIR spectra of APCS-CPD before and after adsorption of heavy metal ions;

[0048] Figure 16 Full spectra and high resolution XPS N 1s spectra of APCS-CPD before and after adsorption of heavy metal ions, wherein (a) is the full spectrum and (b) is the high resolution XPS N 1s spectrum;

[0049] Figure 17 Mechanism of APCS-CPD adsorbing Cu(II) and Ni(II) under strong acidic conditions (pH = 1.5). DETAILED DESCRIPTION

[0050] Various exemplary embodiments of the present application will now be described in detail, with reference to the figures. The detailed description is not to be regarded as limiting the present application, but rather as exemplifying some aspects, features and embodiments of the present application.

[0051] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of a parameter, unless otherwise stated, the inclusion of either a lower or an upper limit of a range of values is specifically asserted. The scope of the present application also includes any and all intermediate values and ranges of values of the recited parameter that are not expressly disclosed, but which are either incited or inherent to the specification, examples, or any other statement of the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also encompassed by the application, subject to any specifically excluded limit in the stated range. Where particular combinations are stated herein, other, complementary combinations are also expressly stated.

[0052] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the patents, patent applications, publications, and descriptions are cited.

[0053] Many modifications and variations of this application description will be apparent to those of ordinary skill in the art from the foregoing description. Other embodiments of the application will be apparent to those of ordinary skill in the art from consideration of the specification and practice of the application disclosed herein. Further embodiments of this application can involve other elements, steps, methods, and materials differently arranged and otherwise combined than those expressed in the particular embodiments described herein. The foregoing description of the specific embodiments will be understood to be illustrative only and not limiting of the present application as recited in the claims.

[0054] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0055] It should be noted that the invention is not detailed in the place, which is the conventional operation means of the art, and is not the focus of the invention.

[0056] The sources of the chemicals and reagents used in the following examples, characterization and performance test process of the invention are as follows:

[0057] The electroplating sludge was provided by a electroplating factory in Jiangxi Province. The electroplating sludge was first dried at 60℃ to constant weight, and then ground into fine particles of about 100 mesh with a mortar for use. After digestion with a mixed acid of HCl / HNO3, the content of the main metals (Ni, Cu, Fe, Zn, Cr, Ca) in the sludge was determined by inductively coupled plasma emission spectrometer (ICP-MS). The composition of the electroplating sludge is shown in Table 1, and the form of the metals in the electroplating sludge was further analyzed by XPS. As shown in Table 1, the iron in the electroplating sludge mainly exists in the form of FeO and Fe2O3, and the copper mainly exists in the form of Cu(OH)2 and CuO. Figure 1

[0058] Table 1 Composition of electroplating sludge

[0059] Element class Ni (mg / g) Cu (mg / g) Fe (mg / g) Zn (mg / g) Content 156.862 44.107 15.775 19.564

[0060] CS (degree of deacetylation: 90%), benzaldehyde (C7H6O, 99%), epichlorohydrin (C3H5ClO, 99.7%), acetic acid (C2H4O2, 99.5%) were purchased from Shanghai Aldrin Industrial Co., Ltd. Ethylenediamine (C2H8N2, 99%) was purchased from Tianjin Damao Chemical Reagent Factory. 2-Chloromethylpyridine hydrochloride (C6H7Cl2N, 98%) was purchased from Shanghai Mayre Chemical Technology Co., Ltd. Sulfuric acid (H2SO4, 98%), hydrochloric acid (HCl, 37%), methanol (MeOH), ethanol (EtOH), sodium carbonate (Na2CO3), sodium hydroxide (NaOH, 99%) were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd. All the chemicals were pure analytical reagents or purer reagents, and all the ultrapure water was 18.20 MΩ ultrapure water.

[0061] The room temperature involved in the following examples and performance test process of the invention is 25±5℃ unless otherwise specified.

[0062] Example 1

[0063] ​Preparation of APCS: 3 g of chitosan powder was dissolved in 80 mL of 3 vol% acetic acid solution, and stirred magnetically for 30 min to form a 3.75 wt% chitosan solution, which was then defoamed by ultrasonic for 10 min. The chitosan solution was taken up with a 10 mL syringe and dropped into 200 mL of 2 wt% NaOH solution at a constant rate using an electrospinning machine to form uniform spherical chitosan. After the balling was completed, it was left to stand for 1 h, and the spherical chitosan was collected and washed with ultrapure water three times. The prepared spherical chitosan was added to 80 mL of benzaldehyde solution, and after standing at room temperature for 12 h, it was washed with methanol and ultrapure water three times each to remove the excess benzaldehyde solution on the spherical chitosan, obtaining benzaldehyde-protected amino group spherical chitosan. Then the spherical chitosan was added to 200 mL of ultrapure water, and the pH value was adjusted to 13. 8 mL of epichlorohydrin was added and heated in a 55°C water bath. The resulting spherical chitosan was washed and soaked in 200 mL of 2.5 vol% hydrochloric acid solution for 12 h, and then washed with ultrapure water three times to obtain APCS.

[0064] Preparation of APCS-ED: The APCS prepared above was added to 150 mL of a solution of ethanol and ultrapure water in a volume ratio of 1:1, and then 10 mL of ethylenediamine was added. The reaction was carried out at 60°C in a water bath for 6 h, and the product was washed with ultrapure water three times to obtain APCS-ED, which was stored in ultrapure water for standby.

[0065] Preparation of APCS-CPD: 2.5 g of anhydrous sodium carbonate and 3.75 g of 2-chloromethylpyridine hydrochloride (2-CPD) were sequentially added to 75 mL of ultrapure water, and then 75 mL of ethanol was added and ultrasonicated for 10 min. The APCS-ED prepared above was added to the solution and transferred to a three-necked flask, and heated to reflux at 90°C for 24 h. The product was washed with ultrapure water to obtain a chitosan double pyridine group acid-resistant adsorbent, denoted as APCS-CPD.

[0066] The APCS, APCS-ED and APCS-CPD described in Example 1 were characterized and tested for performance:

[0067] All samples for characterization and testing (APCS, APCS-ED and APCS-CPD) were freeze-dried at -60℃ before characterization and testing. The micro-morphology of the samples was characterized by scanning electron microscope (SEM, Nova Nano SEM450). The surface elemental state of the samples was measured by X-ray photoelectron spectrometer (XPS, Axis Ultra DLD). The C, H, N content of the samples was measured by organic elemental analyzer (EA, Lementar Unicube). The thermal stability of the materials was determined by thermal gravimetric differential thermal analyzer (TGA, HT1600) under nitrogen atmosphere (30-800℃) at a heating rate of 10℃ / min. Fourier transform infrared spectroscopy (FTIR) was obtained by VERTEX70. The concentration of metal ions was determined by inductively coupled plasma optical emission spectrometer (ICP-MS, iCAP Q).

[0068] 1. Structure and morphology characterization of APCS, APCS-ED and APCS-CPD:

[0069] Characterization results: Figure 2 are photographs of APCS-CPD, (c) is a photograph of APCS-ED after freeze-drying, (d) is a photograph of APCS-CPD after freeze-drying, and (e) is the adsorption performance test results of the small balls of the color shown in (a) and the small balls of the color shown in (b). It can be seen from Figure 2 that APCS-ED and APCS-CPD present uniform micro-red small ball shape with a diameter of 0.8-1mm. Separating the small balls with relatively different colors in the obtained product APCS-CPD (such as shown in (a) and (b) of Figure 2 it can be seen that the prepared APCS-CPD contains most of the micro-red small balls and a very small part of yellow small balls. It is found that the color of APCS-CPD is affected by the grafting amount of 2-CPD and the washing process, and the color is mostly between yellow and micro-red, such as shown in (a) and (b) of Figure 2 (a) is a small ball with a small grafting amount showing yellow, and (b) is a small ball with a relatively large grafting amount showing red.

[0070] Due to the deviation of grafting amount in the reaction process, the grafting amount of each small ball in the product will be different, which cannot be completely consistent, and the difference in grafting amount will lead to the difference in the adsorption capacity of the small ball. Therefore, the difference in grafting amount of each small ball in the obtained product and the relative color are determined by comparing the performance of the adsorption capacity. The specific adsorption capacity test process is: preparing a single-component metal ion solution of Cu(II) and Ni(II) with an initial concentration of 200 mg / L and pH = 1.5, respectively adding 0.3 g of the adsorbent of the small ball with less grafting amount (APCS-CPD-a, Figure 2 , the small ball with relatively more grafting amount (APCS-CPD-b, Figure 2 ), and oscillating at 25°C for 24 h, and then measuring the adsorption performance of the two, and the results are shown in Figure 2 (e).

[0071] In addition, the content of APCS-CPD-a in the synthesized product is a very small amount, which will not affect the adsorption effect of APCS-CPD as a whole.

[0072] The structure and morphology characterization results of APCS, APCS-ED and APCS-CPD are shown in Figure 3 . Figure 3 The characterization results of APCS, APCS-ED and APCS-CPD are shown in the figure, wherein (a) and (b) are SEM images of APCS-CPD at different magnifications, (c) is the XPS full spectrum of APCS-CPD, (d) is the high-resolution XPS N1s spectrum of APCS-CPD, (e) is the FTIR spectrum of APCS, APCS-ED and APCS-CPD, and (f) is the TGA result of APCS, APCS-ED and APCS-CPD.

[0073] The SEM images of APCS-CPD are shown in Figure 3 (a) and (b). As shown in Figure 3 (a) and (b), APCS-CPD has a porous structure on the surface and a reticular structure inside, which increases the specific surface area of the material and is more conducive to the mass transfer between the adsorbent and metal ions. The results of EA (Table 2) show that the nitrogen content of APCS-CPD increases from 6.39% to 9.17% compared with APCS-ED, which indicates the successful introduction of pyridine groups. The XPS results (as shown in Figure 3 (c) and (d)) also confirm this inference, and the sub-peaks at 398.67 eV, 399.14 eV and 401.24 eV correspond to pyridine nitrogen, amine group and protonated amine group, respectively, indicating the successful preparation of APCS-CPD adsorbent. The FTIR results are shown in Figure 3 (e), and the peak at 3425 cm-1-1 The wide band appearing at 1380 cm -1 The primary amine from chitosan in APCS-ED, 1078 cm -1 C-O-C in chitosan backbone, 1026 cm -1 The stretching vibration of -CO, while the elemental analysis data and the functional group density in EA (Table 2) showed that the nitrogen content in APCS-ED was higher than that in APCS, which indicated that the introduction of ethylenediamine and the increase of amine groups were achieved by chemical modification. The characteristic absorption peak at 1590 cm -1 derived from the vibration of aromatic ring skeleton, 765 cm -1 The characteristic absorption peak at 765 cm Figure 3 The TGA curves of APCS, APCS-ED and APCS-CPD (as shown in (f) of Figure 2) were analyzed, and it was found that the mass loss of the three materials was roughly divided into three stages, the first stage occurred at 30-180°C, the reason for the mass loss was probably due to the evaporation of physically adsorbed water, the second stage occurred at 180-550°C, the reason was the loss of chitosan skeleton caused by heating, the third stage, the three materials went through the molecular carbonization stage, and then entered the final stage. By comparison, it was found that the mass loss trend of the three materials was similar, but the overall weight loss of APCS-CPD, the material after introducing pyridine group, was the least among the three, so APCS-CPD had better thermal stability.

[0074] Table 2 EA results of APCS, APCS-ED and APCS-CPD

[0075] Adsorbent type C(％) H(％) N(％) APCS 29.48 6.12 4.11 APCS-ED 31.67 7.06 6.39 APCS-CPD 46.03 6.06 9.17

[0076] 2. Performance test of APCS, APCS-ED and APCS-CPD:

[0077] In the performance test process, the pH value of the metal ion solution used was adjusted to 1.5 with hydrochloric acid or nitric acid in addition to the specified acidity, 30 mL of metal ion solution was placed in a 50 mL conical flask with 0.3 g of wet (dry weight was 0.029 g) adsorbent sample (APCS, APCS-ED and APCS-CPD), and then placed in a constant temperature oscillator, oscillated at room temperature and 180 r / min for 24 h to reach adsorption equilibrium. The equilibrium adsorption capacity Qe (mg / g) of the adsorbent sample for metal ions was calculated by formula (1):

[0078]

[0079] In the formula, C0 (mg / L) is the initial Cu(II) and Ni(II) concentration of the metal ion solution; C e (mg / L) represents the equilibrium concentrations of Cu(II) and Ni(II) in the solution after adsorption; V(L) represents the volume of the Cu(II) and Ni(II) solutions; m(g) represents the mass of the adsorbent sample; Q e (mg / g) represents the equilibrium adsorption capacity.

[0080] 2.1. Effect of solution acidity on the adsorption performance of APCS, APCS-ED, and APCS-CPD:

[0081] A solution containing Cu(II) and Ni(II) with a concentration of 200 mg / L and an initial pH of 1.0–5.0 was prepared as the metal ion solution, and an adsorption experiment was conducted for 24 h to reach adsorption equilibrium. The supernatant was then used to determine the metal ion concentration to investigate the effect of solution acidity on the adsorption performance of APCS, APCS-ED, and APCS-CPD. The experimental conditions were: room temperature. The equilibrium adsorption capacity Qe (mg / g) of the adsorbent sample for metal ions was calculated using equation (1).

[0082] Experimental Results: Under normal circumstances, common functional groups such as amine and hydroxyl groups exhibit poor adsorption performance under acidic conditions due to protonation. Therefore, to verify the acid resistance of the introduced pyridine group, the effect of the initial acidity of the metal ion solution on the adsorption performance of the three adsorbents was investigated. The results are as follows: Figure 4 As shown, Figure 4 The adsorption effects of APCS, APCS-ED, and APCS-CPD on Cu(II) and Ni(II) at different acidities (pH 1.0–5.0) are shown, where (a) corresponds to Cu(II) and (b) corresponds to Ni(II). Figure 4 It can be seen that with the increase of the pH value of the metal ion solution, the adsorption capacity of APCS-CPD for these two HMCs first increases and then remains basically unchanged. This is mainly due to the deprotonation effect of the protonated functional groups (especially pyridine nitrogen); in addition, from Figure 4 It can be seen that the adsorption capacity of APCS-CPD for both Cu(II) and Ni(II) far exceeds that of APCS and APCS-ED, indicating that APCS-CPD has better adsorption performance for Cu(II) and Ni(II) than the other two materials. This is due to the high content of bispyridineamine groups in APCS-CPD. At pH=1.5, the adsorption capacities of APCS-CPD for Cu(II) and Ni(II) are 68.74 mg / g and 59.45 mg / g, respectively, which are much higher than other common adsorbents (adsorbent types and performance are shown in Table 3). Therefore, APCS-CPD is a promising adsorbent for recovering HMCs from acidic leachates and acidic wastewater.

[0083] Table 3 Performance of adsorbents

[0084]

[0085] 2.2. Adsorption selectivity of APCS-CPD:

[0086] Generally, the components in the acid leaching solution of electroplating sludge and acid wastewater are complex and contain various HMCs, and the adsorbent with certain selectivity for the HMCs to be recovered is more popular. In order to evaluate the adsorption selectivity of APCS-CPD, the effects of APCS-CPD on the adsorption of Cu(II) and Ni(II) in two-component systems coexisting with Zn(II), Fe(II), Cr(III) and Mn(II) at the same concentration were studied. The test conditions were: room temperature, 24 h. The two-component systems were as follows: a solution containing Cu(II) and Zn(II) with a concentration of 200 mg / L; a solution containing Cu(II) and Fe(II) with a concentration of 200 mg / L; a solution containing Cu(II) and Cr(III) with a concentration of 200 mg / L; a solution containing Cu(II) and Mn(II) with a concentration of 200 mg / L; a solution containing Ni(II) and Zn(II) with a concentration of 200 mg / L; a solution containing Ni(II) and Fe(II) with a concentration of 200 mg / L; a solution containing Ni(II) and Cr(III) with a concentration of 200 mg / L; a solution containing Ni(II) and Mn(II) with a concentration of 200 mg / L. The normalized selectivity coefficient ε was used as an index of the adsorption selectivity of APCS-CPD in the above two-component systems (pH = 1.0), which was calculated by formula (2). The higher the ε value, the stronger the adsorption capacity of APCS-CPD for the heavy metal ion, and the greater the relative adsorption advantage.

[0087]

[0088] In the formula, M1 and M2 represent two coexisting heavy metal ions in the two-component system, i.e. Q1 represents the equilibrium adsorption capacity of APCS-CPD for one of the two heavy metal ions in the two-component system, Q2 represents the equilibrium adsorption capacity of APCS-CPD for the other heavy metal ion.

[0089] Test results: According to the ε values calculated in the test (such as Figure 5As shown in the figure, among the coexisting components, εNi and εCu are both between 0.846 and 0.954, which is much higher than εZn, εFe, εCr, and εMn. Furthermore, the interference from Zn(II) and Fe(II) is relatively small, while the interference from Cr(III) and Mn(II) is almost negligible. The results indicate that this adsorbent has good selectivity for Cu(II) and Ni(II) in acidic leachate. This is because the nitrogen atom in the pyridine ring can act as a ligand, donating electrons to the metal ions to form a complex. Copper and nickel can form stable complexes with nitrogen-containing ligands, while the complex oxidation states of iron, manganese, and chromium reduce their binding ability with pyridine. In addition, Figure 6 The affinity test results also confirmed the selectivity of the adsorbent, fully demonstrating that APCS-CPD is an acid-resistant adsorbent with great application potential.

[0090] 2.3. Adsorption affinity test of APCS-CPD for different heavy metal ions:

[0091] Experimental method: Solutions containing Cu(II), Ni(II), Zn(II), Fe(II), Cr(III), and Mn(II) with an initial metal ion concentration of 200 mg / L and pH = 1.5 were prepared as metal ion solutions and subjected to adsorption experiments for 24 h to reach adsorption equilibrium. The supernatant was then used to determine the metal ion concentration to investigate the isothermal adsorption law of the adsorbent. The experimental conditions were: room temperature. The equilibrium adsorption capacity Qe (mg / g) of the adsorbent sample for metal ions was calculated using equation (1).

[0092] The results are as follows Figure 6 As shown. Figure 6 The results show the adsorption affinity of APCS-CPD for different heavy metal ions.

[0093] Depend on Figure 6 It can be seen that the adsorption affinity of APCS-CPD for Cu(II) and Ni(II) is much higher than that for other heavy metal ions (Zn(II), Fe(II), Cr(III) and Mn(II)), indicating that APCS-CPD has high selectivity and can efficiently remove Cu(II) and Ni(II).

[0094] 2.4. Adsorption kinetics of APCS-ED and APCS-CPD:

[0095] Adsorption rate is an important criterion for the industrial application of adsorbents. Slow adsorption rate is of low economic benefit and difficult to be applied in industry. Therefore, it is of great significance to explore the influence of adsorption time on the performance of materials. At the same time, adsorption kinetics can also preliminarily judge the adsorption properties of adsorbents and provide ideas for subsequent mechanism exploration. Therefore, Cu(II) and Ni(II) solutions with initial concentrations of 250 mg / L were used as metal ion solutions to explore the adsorption kinetics of APCS-CPD and APCS-ED.

[0096] Test method: 0.3 g of wet (dry weight 0.029 g) adsorbent sample (APCS-ED and APCS-CPD) was added to 50 mL of acidic metal ion solution with pH = 1.5, and 0.1 mL of supernatant was taken at specified intervals (0.1 h, 0.5 h, 1 h, 2 h, 3 h, 5 h, 8 h, 18 h, 19 h, 20 h, 21 h, 22 h and 24 h) to determine the concentration of metal ions (denoted as C t ), and the adsorption capacity of the adsorbent sample for metal ions Q t (mg / g) was calculated by formula (3):

[0097]

[0098] In the formula, C0(mg / L) is the initial Cu(II), Ni(II) concentration of the metal ion solution; C t (mg / L) is the equilibrium Cu(II), Ni(II) concentration after adsorption; V(L) is the volume of Cu(II), Ni(II) solution; m(g) is the mass of the adsorbent sample; Q t (mg / g) is the adsorption capacity at different times.

[0099] The test conditions were room temperature. The results are shown in Figure 7 . Figure 7 (a) and (b) are the adsorption process curves of APCS-CPD and APCS-ED adsorbing Cu(II) and Ni(II) at pH = 1.5, respectively, using pseudo-first-order kinetic model and pseudo-second-order kinetic model. The two kinetic parameters were calculated by equation fitting, Figure 7 In the formula, the dotted line represents pseudo-first-order kinetics, and the solid line represents pseudo-second-order kinetics. Test conditions: room temperature.

[0100] Experimental Results: Firstly, both materials rapidly adsorbed Cu(II) and Ni(II) within the first 150 minutes, reaching adsorption equilibrium at 300 minutes. The rapid adsorption rate is attributed to the large specific surface area and pore volume of both materials, exposing more functional sites. Comparison of the two adsorption kinetic models and their fitting parameters reveals that the correlation coefficients (R²) of the pseudo-second-order kinetic models for Cu(II) and Ni(II) adsorption by the two adsorbents are relatively high. 2 =0.929, 0.925, 0.920, 0.905) are all comparable to the correlation coefficients (R²) of a first-order dynamic model. 2 =0.814, 0.826, 0.758, 0.692) are higher (as shown in Table 4), indicating that the adsorption process of Cu(II) and Ni(II) metal ions by the two adsorbents can be explained by a pseudo-second-order kinetic model, which belongs to the chemical adsorption process involving chemical bonds and electron transfer.

[0101] Table 4. Parameters of the quasi-first-order and quasi-second-order dynamic models

[0102]

[0103]

[0104] 2.5. Adsorption isotherms of APCS-ED and APCS-CPD:

[0105] Experimental method: A solution containing Cu(II) and Ni(II) with an initial metal ion concentration of 100–500 mg / L and pH = 1.5 was prepared as the metal ion solution, and an adsorption experiment was conducted for 24 h to reach adsorption equilibrium. The supernatant was then used to determine the metal ion concentration to investigate the isothermal adsorption law of the adsorbent. The experimental conditions were: room temperature. The equilibrium adsorption capacity Qe (mg / g) of the adsorbent sample for metal ions was calculated using equation (1).

[0106] The parameters obtained by fitting the Langmuir and Freundlich models (as shown in Table 5) are obtained as follows. Figure 8 The adsorption isotherm curves of Cu(II) and Ni(II) by APCS-ED and APCS-CPDAPCS-CPD are shown in (a) and (b). Figure 8 In the diagram, the dashed line represents the Freundlich model, and the solid line represents the Langmuir model.

[0107] Depend on Figure 8 It can be seen that the R-value obtained by fitting the Langmuir model is... 2The values were significantly higher than the Freundlich model, indicating that Cu(II) and Ni(II) were adsorbed on the APCS-CPD in a monolayer, and the maximum adsorption capacity of APCS-CPD for Cu(II) and Ni(II) was 69.303 mg / g and 59.217 mg / g, respectively, at pH = 1.5, which was higher than that of APCS-ED adsorbent. This indicates that APCS-CPD has excellent ability to capture Cu(II) and Ni(II) under acidic conditions (pH = 1.5) and has great potential for industrial applications.

[0108] Table 5 Parameters obtained by fitting the Langmuir model and the Freundlich model

[0109]

[0110]

[0111] 2.6. Influence of inorganic salts on the adsorption performance of APCS-CPD:

[0112] Since the electroplating sludge leachate and industrial acid wastewater often contain various inorganic salts, it is necessary to explore the influence of these inorganic salts on the adsorption of Cu(II) and Ni(II) by the material.

[0113] Test method: A solution containing Cu(II) and Ni(II) with a concentration of 200 mg / L and pH = 1.5 was prepared as a metal ion solution. NaCl, CaCl2, MgCl2, NaNO3, and Na2SO4 with concentrations of 10 mmol / L and 100 mmol / L were added to the Cu(II) and Ni(II)-containing solution, respectively, and a 24-hour adsorption experiment was conducted to achieve adsorption equilibrium. The supernatant was taken for metal ion concentration determination to explore the influence of inorganic salts on the adsorption performance of APCS-CPD. The test conditions were: room temperature. The equilibrium adsorption capacity Qe(mg / g) of the adsorbent sample for metal ions was calculated by formula (1).

[0114] The results are shown in Table 6. Figure 9 Figure 9 Table 6 Influence of different inorganic salts on the adsorption performance of APCS-CPD.

[0115] From the results shown in Table 6, it can be seen that the presence of inorganic salts had a significant impact on the adsorption of Cu(II) and Ni(II) by APCS-CPD. The presence of NaCl, CaCl2, MgCl2, NaNO3, and Na2SO4 significantly increased the adsorption capacity of APCS-CPD for Cu(II) and Ni(II) compared to the control group without inorganic salts. Among them, the presence of NaCl, CaCl2, and MgCl2 had the most significant impact on the adsorption of Cu(II) and Ni(II) by APCS-CPD, while the presence of NaNO3 and Na2SO4 had a relatively small impact on the adsorption of Cu(II) and Ni(II) by APCS-CPD. Figure 9 ​It can be seen that different concentrations and different types of inorganic salts promote the adsorption of two metal ions, and the higher the concentration, the more significant the promotion effect, because the large number of anions can reduce the positive charge on the surface of the adsorbent under acidic conditions, and the anions can act as non-coordinated outer ions of heavy metal cations, so that the apparent charge of part of the heavy metal cations is reduced. And the adsorption promotion effect of Ca(II) and Mg(II) on the two ions is obviously lower than that of Na(I), because divalent alkaline earth metals have stronger competition with Cu(II) and Ni(II) at the binding sites of the adsorbent during the adsorption process than monovalent alkaline earth metals.

[0116] 2.7. Adsorption stability test of APCS-CPD:

[0117] The reuse performance and stability of APCS-CPD were evaluated by adsorption-desorption experiments.

[0118] Test method: A solution containing Cu(II) and Ni(II) with a concentration of 200 mg / L and pH = 1.5 was prepared as a metal ion solution, and a 24 h adsorption experiment was carried out to achieve adsorption equilibrium. The supernatant was taken for metal ion concentration determination, and the equilibrium adsorption amount measured at this time was recorded as Q1(mg / g). After adsorption, the adsorbent was recovered, and the recovered adsorbent was desorbed in 10 mL of 20wt% hydrochloric acid, and the adsorption-desorption test was repeated four times. The equilibrium adsorption amount measured each time during the repeated test was recorded as Qn(mg / g), and the value of Qn / Q1was calculated. Test conditions: room temperature. The equilibrium adsorption amount Qe(mg / g) of the adsorbent sample for metal ions was calculated by formula (1). n n

[0119] The results are shown in Figure 10 . Figure 10 The adsorption stability test results of APCS-CPD.

[0120] From Figure 10 it can be seen that the adsorption amount of the adsorbent for the two ions in the second adsorption is more than 90% of the first adsorption amount, in the third adsorption, the adsorption amount of the adsorbent for Ni(II) is 80.88% of the first adsorption amount, and the adsorption amount for Cu(II) reaches 82.32% of the first adsorption amount, and the adsorption amount of the fourth adsorption for the two ions can still reach more than 72% of the first adsorption amount, indicating that the adsorbent has a certain regeneration capacity; and after four adsorptions, the adsorbent can still maintain the complete spherical structure (as shown in Figure 11 ), which also indicates that the adsorbent has good stability. In Figure 11 , the left side is the real object picture of APCS-CPD after the fourth adsorption of Cu, and the right side is the real object picture of APCS-CPD after the fourth adsorption of Ni. ​​

[0121] 2.8. Test the adsorption performance of APCS-CPD in practical application:

[0122] Fixed bed column is widely used in large-scale industrial wastewater treatment due to its simple operation and continuous control. The device for dynamic column test is shown in Fig. 1, and APCS-CPD wet adsorbent is filled into a glass column to form an adsorption column (Φ16x100mm). A solution with initial pH=1.5 containing Cu(II) and Ni(II) is configured as the metal ion solution, in which the initial concentrations (C0) of Cu(II) and Ni(II) are 482.47mg / L and 506.76mg / L, respectively. The metal ion solution is flowed through the adsorption column at a flow rate of 0.34mL / min by a peristaltic pump, and the effluent is collected every certain time to determine the concentrations (C) of metal ions in the effluent. The test conditions are: room temperature. Figure 12

[0123] The results are shown in Fig. 2. Figure 13 Figure 13 The adsorption performance of APCS-CPD for Cu(II) and Ni(II) in the process of dynamic column test.

[0124] As can be seen from Fig. 2, in the continuous adsorption process, the effective operation time of the fixed bed for Cu(II) is 8.5h before reaching the breakthrough point (concentration <1mg / L), and the effective operation time for Ni(II) is 6.5h. APCS-CPD adsorption column adsorbs 60.208mg Cu(II) and 51.300mg Ni(II) in total, and the calculated adsorption capacities are 72.25mg / g and 61.56mg / g, respectively. The values are close to the maximum adsorption capacities of 61.301-69.303mg / g and 50.23-59.217mg / g in the static adsorption test, and are also higher than the maximum adsorption capacities in the static adsorption test. It is further confirmed that APCS-CPD material has great potential in actual industrial recovery. Figure 13 2.9. Test the adsorption of heavy metal ions by APCS-CPD when treating electroplating sludge:

[0125] 10g of electroplating sludge is added into 100mL of 1mol / L nitric acid, and stirred at room temperature for 2h by a magnetic stirrer. After the leaching is completed, the supernatant is collected by centrifugal separation, and the leaching rates of metal ions in the leaching solution are measured by atomic absorption spectrophotometry. The test conditions are: room temperature. The equilibrium adsorption capacity Qe(mg / g) of the adsorbent sample for metal ions is calculated by formula (1).

[0126] The results are shown in Fig. 3.

[0127] Figure 14 Figure 14 ​​​​The adsorption effect of APCS-CPD on heavy metal ions when treating electroplating sludge.

[0128] Depend on Figure 14 It can be seen that the APCS-CPD obtained in this invention can achieve efficient adsorption of heavy metal ions (Ni, Cu) when treating electroplating sludge. Note: Because the metal content in electroplating sludge is high, the concentration of metal ions in the leachate is also high. Therefore, the equilibrium adsorption capacity is used here to express the practicality of the adsorbent sample rather than the removal rate.

[0129] 2.10. Solid-phase characterization and mechanism analysis of APCS-CPD before and after adsorption of heavy metal ions:

[0130] A 200 mg / L solution containing Cu(II) and Ni(II) at an initial pH of 1.5 was prepared as the metal ion solution, and an adsorption experiment was conducted for 24 hours to reach adsorption equilibrium. The adsorbent was then recovered. Fourier transform infrared (FTIR) spectra of the adsorbent before and after adsorption were obtained using a VERTEX 70 microscope. Furthermore, the energy dispersive spectroscopy (EDS) spectra of the adsorbent before and after adsorption were obtained using an X-ray photoelectron spectroscopy (XPS, Axis Ultra DLD). The experimental conditions were: room temperature.

[0131] The results are as follows Figure 15 and Figure 16 As shown.

[0132] Figure 15 The image shows the FTIR spectra of APCS-CPD before and after adsorption of heavy metal ions.

[0133] Experimental results: Firstly, by Figure 4 It was found that the adsorption capacities of APCS and APCS-ED for both metal ions at pH 1.5 were below 25 mg / g, significantly lower than that of APCS-CPD. Therefore, it can be determined that the grafted pyridine groups are the primary active components. Furthermore, since no metal ions were present during the synthesis of APCS-CPD, this material cannot rely on cation exchange for adsorption; instead, it captures metal ions through chelation. To verify this conclusion, the above experiments were conducted and the results were obtained. Figure 15 ,Depend on Figure 15 It can be seen that after adsorbing metal ions, the bending vibration of -NH2 changes from 1611.4 cm⁻¹. -1 Offset to 1615.5cm -1 and 1619.8cm -1 The tensile vibration peak of C-OH is from 1062 cm⁻¹ -1 They decreased to 1058.6cm respectively. -1 and 1054.5cm -1 , indicating the 765.8 cm of the pyridine ring. -1 Offset to 763.1cm-1 and 763.8 cm -1 , which indicates that the pyridine ring reacts with the heavy metal ions, i.e. the pyridine nitrogen is coordinated.

[0134] Figure 16 are full spectrum and high-resolution XPS N1s spectrum of APCS-CPD before and after adsorbing heavy metal ions, wherein (a) is full spectrum, and (b) is high-resolution XPS N1s spectrum. Figure 16 In (a), APCS-CPD-Ni represents the adsorbent after adsorbing nickel ions, and APCS-CPD-Cu represents the adsorbent after adsorbing copper ions.

[0135] It can be seen from Figure 16 that in the full spectrum, the peaks of Cu 2p and Ni 2p are obviously observed, and in the fine spectrum of N1s, after adsorbing metal ions, the peak representing pyridine nitrogen on the adsorbent shifts from 398.4 eV to 399.51-399.53 eV, and the peak representing amine nitrogen also shifts from 401.53 eV to 401.65-401.66 eV, which indicates that the adsorbent realizes the adsorption of metal ions by the coordination of amine nitrogen and pyridine nitrogen with metal ions.

[0136] In addition, since the adsorption experiment is carried out under strong acidic conditions (pH = 1.5), the amine nitrogen and pyridine nitrogen on the adsorbent APCS-CPD will be protonated first, and then capture heavy metal ions through the deprotonation-chelation process, as shown in Figure 17 .

[0137] 2.11. Cost comparison:

[0138] The comparison results of the cost of reagents used in the actual production process of the technical solution of the present application and the cost of reagents used in the actual production process of the existing M4195 commercial resin are shown in Table 6.

[0139] Table 6 Cost comparison

[0140]

[0141] As can be seen from Table 6, the cost required for preparing the material of the present application is significantly lower than the cost of preparing conventional M4195.

[0142] In the specification, each embodiment is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between each embodiment can be referred to each other.

[0143] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synergistically selective recovery of copper and nickel from electroplating sludge under strong acidic conditions by leaching-adsorption, characterized in that, The method comprises the following steps: The electroplating sludge and nitric acid are mixed to carry out leaching reaction, then the supernatant is taken, and the leaching of copper and nickel in the supernatant is realized by using the chitosan double pyridine group acid-resistant adsorbent; The dosage ratio of the electroplating sludge to the nitric acid is 1-10 g:10-100 mL; The pH value of the supernatant is 1.5; The dosage ratio of the chitosan double pyridine group acid-resistant adsorbent to the supernatant is 0.029 g:30 mL; The preparation steps of the chitosan double pyridine group acid-resistant adsorbent are as follows: The spherical chitosan is used as raw material, after amino protection, the first product is obtained by carrying out the first reaction with epichlorohydrin; The second product is obtained by carrying out the second reaction after mixing the first product, ethylenediamine and a solvent; The third reaction is carried out after mixing the second product, 2-chloromethyl pyridine hydrochloride, an acid-binding agent and a solvent, to obtain the chitosan double pyridine group acid-resistant adsorbent; The preparation of the spherical chitosan comprises: adding a chitosan solution into a sodium hydroxide solution to form the spherical chitosan; the solvent in the chitosan solution is a mixed solution of acetic acid and water, the mass fraction of chitosan in the chitosan solution is 2-5 wt%, and the mass fraction of sodium hydroxide in the sodium hydroxide solution is 2 wt%; The amino protection comprises: mixing the spherical chitosan and benzaldehyde and then standing to obtain the spherical chitosan with protected amino groups; the dosage ratio of benzaldehyde to chitosan in the chitosan solution is 50-100 mL:3-10 g; and the standing time is 12-24 h.

2. The method of claim 1, wherein, The dosage ratio of epichlorohydrin to chitosan in the chitosan solution is 6-10 mL:3-10 g; and / or, the reaction conditions of the first reaction are as follows: the pH value is 9-14, the temperature is 50-65 DEG C, and the time is 6-10 h.

3. The method of claim 1, wherein, The solvent in the second reaction and the third reaction is ethanol and water in a volume ratio of 1:

1.

4. The method of claim 1, wherein, The volume ratio of the first product, ethylenediamine and a solvent is 3-10:8-12:150-200; and / or, the temperature of the second reaction is 50-70 DEG C, and the time is 6-10 h.

5. The method of claim 1, wherein, The acid-binding agent comprises one or more of sodium carbonate, potassium carbonate and sodium hydroxide; and / or, the dosage ratio of the second product, 2-chloromethyl pyridine hydrochloride, an acid-binding agent and a solvent is 3-10 mL:1-5 g:1-3 g:150-200 mL; and / or, the temperature of the third reaction is 80-100 DEG C, and the time is 12-36 h.

6. The method of claim 5, wherein, The step of mixing the second product, 2-chloromethyl pyridine hydrochloride, sodium carbonate and a solvent comprises: first adding 2-chloromethyl pyridine hydrochloride and sodium carbonate into water, then adding ethanol into the water, and finally adding the second product into the water.

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