Dicyandiamide-modified hypercrosslinked resin, method for preparing the same, and use thereof

Abstract

The application discloses a dicyandiamide modified hypercrosslinked resin and a preparation method and application thereof, and relates to the technical field of hypercrosslinked resin. The preparation method of the dicyandiamide modified hypercrosslinked resin comprises the following steps: adopting a Soxhlet extraction method to elute chloromethyl polystyrene resin until the eluent is clear and colorless, drying to obtain purified resin; mixing the purified resin and a first solvent, uniformly mixing, adding a Lewis acid catalyst, performing a Friedel-Crafts alkylation reaction, washing, drying to obtain hypercrosslinked resin; mixing the hypercrosslinked resin and a second solvent, adding dicyandiamide, performing an amination modification reaction, washing, drying to obtain the dicyandiamide modified hypercrosslinked resin. The dicyandiamide modified hypercrosslinked resin has the advantages of large specific surface area, good thermal stability, strong corrosion resistance, and stronger adsorption to CL-20 in an acidic liquid compared to other commercial resins on the market.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthetic resin preparation technology, specifically relating to a dicyandiamide-modified ultra-high crosslinked resin, its preparation method, and its uses. Background Technology

[0002] CL-20 (hexanitrohexaazaisowurtzitane) is a high-performance explosive with wide applications in the synthesis of high-energy materials for military and aerospace applications. It is a high-energy material with great development potential (P. Karakaya, C. Christodoulatos, A. Koutsospyros, W. Balas, S. Nicolich, M. Sidhoum, Biodegradation of the HighExplosive Hexanitrohexaazaisowurtzitane (CL-20)[J]. International Journal of Environmental Research and Public Health, 6 (2009) 1371-1392.). However, the synthesis of CL-20 involves high-concentration nitric acid (HNO3) and sulfuric acid (H2SO4) as the main reactants, generating a large amount of nitro compound byproducts. In subsequent separation steps, when filtering to retain solid CL-20 product, the reaction mother liquor containing excess strong acid is simultaneously filtered out (as waste liquid). This mother liquor not only carries away the nitro compound byproducts but also a small amount of dissolved CL-20 product due to its partial solubility, resulting in product yield loss. Currently, the main method for recovering CL-20 from waste liquid is adsorption, but this still suffers from problems such as low CL-20 recovery rate, significant resource waste, and high cost.

[0003] To address the shortcomings in CL-20 recovery, the development of high-performance adsorbent materials has become a research direction. Among them, ultra-high crosslinked resin is one of the candidate materials. Ultra-high crosslinked resin was invented by Russian scientist Davankov in 1969. It is prepared by Friedel-Crafts alkylation reaction of low-crosslinked polystyrene (L. Tan, B. Tan, Hypercrosslinked porous polymer materials: design, synthesis, and applications[J]. Chemical Society Reviews, 46 (2017) 3322-3356.). Its high specific surface area gives it excellent adsorption performance, and therefore it is widely used in wastewater treatment, resource recovery and other fields. However, the high adsorption capacity of traditional ultra-high crosslinked resin mainly depends on its huge specific surface area. This adsorption is essentially a physical adsorption process, which limits its application in adsorbing some highly polar adsorbates such as phenols, anilines, benzenesulfonic acids and so on, and the adsorption selectivity is weak. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a dicyandiamide-modified ultra-high crosslinked resin. This method involves introducing functional groups onto the surface of the ultra-high crosslinked resin and performing functionalization chemical modification to give it a specific adsorption capacity for CL-20. Furthermore, the adsorption process combines physical adsorption and chemical adsorption.

[0005] Another object of the present invention is to provide a dicyandiamide-modified ultra-high crosslinked resin obtained by the above preparation method.

[0006] Another object of the present invention is to provide the use of the above-mentioned dicyandiamide-modified ultra-high crosslinked resin in the adsorption of CL-20.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A method for preparing a dicyandiamide-modified ultra-high crosslinked resin includes the following steps: Step 1, eluting chloromethyl polystyrene resin by Soxhlet extraction until the eluent is clear and colorless, drying it, and obtaining purified resin.

[0009] In step 1, the eluent for Soxhlet extraction is an aqueous ethanol solution, wherein the ratio of ethanol to water in the eluent is (9~19):1 by volume.

[0010] In step 1, the drying temperature is 50~60℃ and the drying time is 6~12h.

[0011] Step 2: Mix the purified resin obtained in Step 1 with the first solvent until homogeneous, then add the Lewis acid catalyst and reflux at 65-75°C for 2-8 hours to carry out the Friedel-Crafts alkylation reaction. After the Friedel-Crafts alkylation reaction is completed, cool to room temperature, filter, wash until neutral, and dry to constant weight to obtain the ultra-high crosslinked resin. The ratio of purified resin to Lewis acid catalyst by mass is (1-5):1; the first solvent is 1,2-dichloroethane.

[0012] In step 2, the process of mixing evenly includes stirring at a speed of 150-300 rpm for 6-12 hours.

[0013] In step 2, the Lewis acid catalyst is one or a mixture of FeCl3, AlCl3 and ZnCl2.

[0014] In step 2, the ratio of the mass fraction of the purified resin to the volume fraction of the first solvent is 1:(10~15), where the mass fraction is in g and the volume fraction is in mL.

[0015] In step 2, the washing process uses a detergent, which is an aqueous ethanol solution, wherein the ratio of ethanol to water in the detergent is 1:(1~1.2) by volume.

[0016] In step 2, the drying temperature is 50~60℃.

[0017] Step 3: Mix the ultra-high crosslinked resin obtained in Step 2 with the second solvent, stir for 6-12 hours, add dicyandiamide, and carry out an amination modification reaction at 20-80°C for 4-12 hours. Cool to room temperature, filter, wash until neutral, and dry to obtain dicyandiamide-modified ultra-high crosslinked resin. The mass ratio of the ultra-high crosslinked resin to the molar ratio of dicyandiamide is 1:(0.002-0.020), where mass is in g and molar is in mol. The second solvent is 1,2-dichloroethane.

[0018] In step 3, the ratio of the mass fraction of the ultra-high crosslinked resin to the volume fraction of the second solvent is 1:(10~15), where the mass fraction is in g and the volume fraction is in mL.

[0019] In step 3, the stirring speed is 150~300 rpm.

[0020] In step 3, the washing process uses an aqueous ethanol solution, wherein the ratio of ethanol to water in the aqueous ethanol solution of step 3 is 1:(1~1.2) by volume.

[0021] In step 3, the drying temperature is 50~60℃ and the drying time is 6~12h.

[0022] The dicyandiamide-modified ultra-high crosslinked resin obtained by the above preparation method.

[0023] The use of the above-mentioned dicyandiamide-modified ultra-high crosslinked resin in the adsorption of CL-20.

[0024] In the above technical solution, a dicyandiamide-modified ultra-high cross-linked resin is used as an adsorbent, and the adsorbent is placed in an acidic liquid containing CL-20 to adsorb the CL-20 therein.

[0025] In the above technical solution, the dosage of adsorbent is 0.1~20g / L.

[0026] In the above technical solution, the pH of the acidic liquid is less than 2.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. The dicyandiamide-modified ultra-high cross-linked resin of the present invention has a large specific surface area, good thermal stability, and strong corrosion resistance. Compared with other commercial resins on the market, it has a stronger adsorption effect on CL-20 in acidic liquids and can be recycled. It has broad application prospects for treating acidic liquids containing CL-20.

[0028] 2. The preparation method of the present invention selects low-crosslinking degree chloromethyl polystyrene resin (chlorospheres) as raw material. This raw material is inexpensive and readily available. The high crosslinking of the purified resin is achieved through the mature Friedel-Crafts alkylation reaction. The whole process is simple to operate and uses simple equipment, which has direct value for the commercialization of the product.

[0029] 3. The preparation method of the present invention uses dicyandiamide as a functionalized chemical modification agent, which is different from the amination modifiers such as polyethylene polyamine, ethylene polyamine, and methylamine currently on the market. Dicyandiamide has a lower price and lower toxicity, is safe to use, and is environmentally friendly. At the same time, as a strong nitrogen source, dicyandiamide has high reactivity and can undergo cross-linking reaction with ultra-high cross-linked resin at a lower temperature and in a shorter time, so that a highly cross-linked network structure is formed between dicyandiamide and ultra-high cross-linked resin, thereby enhancing its physical properties.

[0030] 4. After the dicyandiamide-modified ultra-high cross-linked resin is saturated as an adsorbent, it can be reused to adsorb CL-20 after desorption with ethyl acetate. The removal rate of CL-20 can still reach 60% during the fourth cycle of adsorption. Attached Figure Description

[0031] Figure 1 a~d are scanning electron microscope images of the purified resin of Example 1 at different magnifications.

[0032] Figure 2 a~d are scanning electron microscope images of the ultra-high crosslinked resin of Example 1 at different magnifications.

[0033] Figure 3 a~d are scanning electron microscope images of the dicyandiamide-modified ultra-high crosslinked resin of Example 1 at different magnifications.

[0034] Figure 4 The images show the infrared spectra of the ultra-high crosslinked resin and the dicyandiamide-modified ultra-high crosslinked resin in Example 1.

[0035] Figure 5 This is a UV absorption spectrum, in which, Figure 5 Figure a shows the UV absorption spectrum of the waste liquid to be adsorbed in the range of 200-500 nm after adsorption of CL-20 using the purification resin (CMPS) of Example 1 and the dicyandiamide-modified ultra-high cross-linked resins of Examples 1-4 as adsorbents. Figure 5 b is the UV absorption spectrum of the waste liquid to be adsorbed in the range of 200-500 nm after adsorbing CL-20 using the purification resin (CMPS) of Example 1 and the dicyandiamide-modified ultra-high cross-linked resins of Examples 5-8 as adsorbents.

[0036] Figure 6 The adsorption isotherm is shown, where, Figure 6 'a' represents the adsorption isotherm fitted using the Langmuir model. Figure 6 b is the adsorption isotherm fitted using the Freundlich model.

[0037] Figure 7 The image shows the adsorption kinetics fitting curve of CL-20 in the waste liquid to be adsorbed by the dicyandiamide-modified ultra-high cross-linked resin of Example 1.

[0038] Figure 8 The graph shows the effect of the dosage of dicyandiamide-modified ultra-high crosslinked resin on the adsorption capacity and removal rate in Example 1.

[0039] Figure 9 The adsorption capacity and removal rate of the dicyandiamide-modified ultra-high crosslinked resin in Example 1 were measured in a cycle regeneration capacity test. Figure 9 'a' represents the adsorption amount. Figure 9 b represents the removal rate. Detailed Implementation

[0040] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0041] In the following examples, the water is RO-type deionized water.

[0042] The purity and source of the reagents involved in the following examples are as follows: Chloromethyl polystyrene resin (CMPS, abbreviated as chloropolymer) was purchased from Zhengzhou Aino Chemical Technology Co., Ltd., China (crosslinking degree <10%).

[0043] 1,2-Dichloroethane (AR), dicyandiamine (AR), anhydrous aluminum chloride (AR), anhydrous ethanol (AR), and acetonitrile (HPLC) were all purchased from Macklin Biochemical Co., Ltd., Shanghai, China.

[0044] CL-20 (99%) comes from the CL-20 R&D Laboratory of Beijing Institute of Technology.

[0045] The instrument model and manufacturer used in the following examples and tests are as follows: 3H-2000PS2 specific surface area and pore size analyzer, Beijing Best Instrument Technology Co., Ltd.

[0046] Thermo Scientific - Alpha Spectrometer, Thermo Fisher Scientific, USA.

[0047] SU8020 field emission scanning electron microscope, Hitachi, Japan.

[0048] Nexus 670 Fourier Transform Infrared Spectrometer, Nicolet Corporation, USA.

[0049] Dionex U3000 UPLC dual ternary liquid chromatograph, Thermo Fisher Scientific, USA.

[0050] In the following examples, the waste acid solution is the acidic waste liquid generated during the preparation of CL-20 according to the method in the literature "Wang Cai, Ou Yuxiang, Chen Boren. One-pot synthesis of hexanitrohexaazaisowulzane [J]. Journal of Beijing Institute of Technology, 2000, (04): 521-523."

[0051] In the following examples, the steps of the adsorption experiment were as follows: 0.2 g of adsorbent was added to 100 mL of the waste liquid to be adsorbed, placed in a constant temperature shaker, and shaken at 25 °C and 200 rpm for Y h. After adsorption was completed, the supernatant was filtered using a 0.45 μm organic filter membrane (polytetrafluoroethylene filter membrane) to obtain the sample to be tested. The concentration of CL-20 in the sample to be tested was detected using a Dionex U3000 UPLC dual ternary liquid chromatography. The waste liquid to be adsorbed was a mixture of waste acid solution and water. The concentration of CL-20 in the waste liquid to be adsorbed was 509.076 mg / L, and the pH of the waste liquid to be adsorbed was 1.38.

[0052] The formula for calculating the adsorption capacity of the adsorbent for CL-20 in the waste liquid to be adsorbed is as follows: .

[0053] in, C represents the adsorption capacity (mg / g) of the adsorbent in the waste liquid to be adsorbed, and C0 represents the initial concentration (mg / mL) of CL-20 in the waste liquid to be adsorbed. t V represents the concentration of CL-20 in the sample to be tested (mg / mL), V is the volume of the waste liquid to be adsorbed (mL), and M is the mass of the adsorbent added (g).

[0054] Examples 1-4

[0055] A method for preparing a dicyandiamide-modified ultra-high crosslinked resin includes the following steps: Step 1, chloromethyl polystyrene resin (chlorosphere) is eluted at 90°C using Soxhlet extraction until the eluent is clear and colorless, cooled to room temperature, and dried at 60°C for 12 hours to obtain purified resin. The eluent used in the Soxhlet extraction is an aqueous ethanol solution (the ratio of ethanol to water in the eluent is 19:1 by volume). The purified resin has a chlorine content of 17% and a crosslinking degree of ≤10%.

[0056] Step 2: The purified resin obtained in Step 1 is mixed with the first solvent (1,2-dichloroethane) and stirred at 150 rpm for 12 h. Then, a Lewis acid catalyst is added, and the mixture is refluxed at 70 °C for 8 h to carry out a Friedel-Crafts alkylation reaction. After the Friedel-Crafts alkylation reaction is completed, the mixture is cooled to room temperature, filtered, and washed with an ethanol-water solution (ethanol to water ratio of 1:1 by volume) until neutral. The mixture is then dried at 50 °C to constant weight to obtain a highly crosslinked resin. The ratio of purified resin to Lewis acid catalyst by mass is 5:1, and the ratio of purified resin mass to first solvent volume is 1:10. The units of mass parts are g, and the units of volume parts are mL. The Lewis acid catalyst is AlCl3.

[0057] Step 3: The ultra-high crosslinked resin obtained in Step 2 is mixed with the second solvent (1,2-dichloroethane) and stirred at 150 rpm for 12 h. Dicyandiamide is added, and the amination modification reaction is carried out at T℃ for 4 h. After cooling to room temperature, the mixture is filtered and washed with an ethanol-water solution (ethanol to water ratio of 1:1 by volume) until neutral. The mixture is then dried at 60℃ for 12 h to obtain the dicyandiamide-modified ultra-high crosslinked resin. The mass ratio of the ultra-high crosslinked resin to the volume ratio of the second solvent is 1:10, and the molar ratio of the ultra-high crosslinked resin to the dicyandiamide is 1:0.005. The units of mass parts are g, volume parts are mL, and molar parts are mol. The values ​​of T are shown in Table 1.

[0058] Table 1

[0059]

[0060] Examples 5-8

[0061] A method for preparing a dicyandiamide-modified ultra-high crosslinked resin is basically the same as that in Example 1, except that: the amination modification reaction is carried out at T℃ for 6h, the mass fraction of the ultra-high crosslinked resin and the molar fraction of dicyandiamide are X, the mass fraction is in g and the molar fraction is in mol, and the values ​​of T and X are shown in Table 2.

[0062] Table 2

[0063]

[0064] Examples 9-11

[0065] A method for preparing a dicyandiamide-modified ultra-high crosslinked resin is basically the same as that in Example 1, except that: the amination modification reaction is carried out at T℃ for 12h, the mass fraction of the ultra-high crosslinked resin and the molar fraction of dicyandiamide are X, the mass fraction is in g and the molar fraction is in mol, and the values ​​of T and X are shown in Table 3.

[0066] Table 3

[0067]

[0068] The microstructures of the purified resin (CMPS), ultra-high cross-linked resin, and dicyandiamide-modified ultra-high cross-linked resin from Example 1 were observed using a SU8020 field emission scanning electron microscope. The resulting scanning electron microscope images are shown below. Figures 1-3 As shown. By Figure 1 It can be seen that the surface of CMPS is smooth and dense, with no obvious porous structure. Figure 2 The surface of the ultra-highly crosslinked resin obtained after Friedel-Crafts alkylation changed from smooth to rough, and obvious cracks appeared. Figure 3 The dicyandiamide-modified ultra-high crosslinked resin also exhibits a distinct porous structure.

[0069] The infrared absorption spectra of the ultra-high crosslinked resin of Example 1 and the dicyandiamide-modified ultra-high crosslinked resin were measured using Fourier transform infrared spectroscopy. The results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the infrared spectral peak shapes of the ultra-highly crosslinked resin and the dicyandiamide-modified ultra-highly crosslinked resin are basically the same, indicating that the skeleton of the ultra-highly crosslinked resin did not change significantly during the dicyandiamide modification process. Compared with the ultra-highly crosslinked resin, the dicyandiamide-modified ultra-highly crosslinked resin shows a higher peak shape at 3400 cm⁻¹. -1 and 1600cm -1 The presence of a distinct NH stretching vibration peak indicates that the dicyandiamide-modified ultra-high crosslinked resin has introduced NH functional groups.

[0070] The dicyandiamide-modified ultra-high crosslinked resins of Examples 1-4, 6-7, and 11, the purified resin of Example 1, and the ultra-high crosslinked resin of Example 1 were used as samples. The N2- adsorption-desorption isotherms of each sample were detected using a 3H-2000PS2 specific surface area and pore size analyzer. The specific surface area of ​​the samples was calculated using the Brunauer-Emmett-Teller (BET) model, and the average pore size and pore volume of each sample were calculated using the Barrett-Joyner-Halenda (BJH) model. The results are shown in Table 4.

[0071] Table 4

[0072]

[0073] As shown in Table 4, the specific surface area of ​​the purification resin is 20.4653 m². 2 / g, after Friedel-Crafts alkylation, the specific surface area of ​​the resulting ultra-high crosslinked resin was increased from the original 20.4653m². 2 / g increased to 124.8182m 2 / g, the specific surface area of ​​the sample after further amination modification increased to 850.2928m². 2 Meanwhile, the average pore size of the sample decreased from 35.2010 nm to 3.0023 nm, and the pore volume increased from 0.1801 mL / g to 0.6382 mL / g. This means that the dicyandiamide-modified ultra-high crosslinked resin exhibits significantly increased specific surface area and pore volume, and a significantly decreased average pore size. This indicates that the addition of dicyandiamide functional groups leads to a refinement and higher density of the pore structure within the ultra-high crosslinked resin, resulting in the formation of more small or micropores.

[0074] Example 12

[0075] The purification resin (CMPS) of Example 1 and the dicyandiamide-modified ultra-high cross-linked resins of Examples 1-11 were used as adsorbents in the aforementioned "adsorption experiment" (Y=12 hours) to allow the adsorbents to fully adsorb CL-20 from the waste liquid to be adsorbed and reach adsorption equilibrium. The adsorption amounts of the purification resin (CMPS) of Example 1 and the dicyandiamide-modified ultra-high cross-linked resins of Examples 1-11 in the waste liquid to be adsorbed are shown in Table 5.

[0076] Table 5

[0077]

[0078] Example 13

[0079] The purified resin (CMPS) of Example 1 and the dicyandiamide-modified ultra-high cross-linked resins of Examples 1-8 were used as adsorbents, and the adsorption experiment (Y=12 hours) was carried out as described above. The difference was that the concentration of CL-20 in the waste liquid to be adsorbed was 254.538 mg / L and the pH of the waste liquid to be adsorbed was 1.56.

[0080] The supernatant after adsorption equilibrium with the adsorbent was taken and used as the test solution. The UV absorption spectra of the test solutions in the 200–500 nm range were measured using a UV-Vis spectrophotometer. Simultaneously, the UV absorption spectra of the unadsorbed waste liquid in the 200–500 nm range were also measured. The results are as follows: Figure 5 As shown, by Figure 5 It can be seen that after adsorption by the adsorbent, the waste liquid to be adsorbed has a strong absorption peak at 350~400nm, while the test solution does not have a strong absorption peak at 350~400nm. This indicates that the adsorbent has good adsorption performance and has a good adsorption effect on nitro compounds in the waste liquid to be adsorbed.

[0081] Example 14

[0082] The dicyandiamide-modified ultra-high cross-linked resin from Example 1 was used as an adsorbent to adsorb CL-20 from the waste liquid to be adsorbed, and the adsorption isotherm was analyzed: 0.5 g of adsorbent was added to 100 mL of the waste liquid to be adsorbed and placed in a constant temperature shaker at 200 rpm for 12 h to allow the adsorbent to fully adsorb CL-20 from the waste liquid to reach adsorption equilibrium. The waste liquid to be adsorbed was a mixture of waste acid solution and water, and the concentrations of CL-20 in the waste liquid to be adsorbed were 75.63 mg / L (pH=1.47), 114.34 mg / L (pH=1.64), 166.83 mg / L (pH=1.68), 282.00 mg / L (pH=1.71), or 576.78 mg / L (pH=1.78). After adsorption was complete, the supernatant was filtered using a 0.45 μm organic filter membrane (polytetrafluoroethylene filter membrane) to obtain the test sample. The concentration of CL-20 in the test sample was detected and the amount of CL-20 adsorbed by the adsorbent was calculated.

[0083] With Z℃ = 25℃, 30℃, or 35℃, the adsorption data were fitted using the Langmuir and Freundlich isotherm models, respectively. The fitting results are as follows: Figure 6 As shown. Among them, Figure 6 'a' represents the result of fitting the model using the Langmuir model. Figure 6 b is the result of fitting the model using the Freundlich model. Figure 6It can be seen that the Langmuir isotherm model fits well, indicating that the adsorption process of CL-20 in the waste liquid to be adsorbed is mainly monolayer adsorption, the adsorbent surface is a uniform adsorption site, and the interaction between CL-20 in the waste liquid to be adsorbed and the adsorbent is relatively strong. When the concentration of CL-20 in the waste liquid to be adsorbed is low, the isotherm is approximately a straight line, indicating that the adsorption process at this time is close to the ideal assumptions of the Langmuir isotherm adsorption model (monolayer, uniform surface, no interaction between adsorbate molecules), and the maximum adsorption capacity of the adsorbent reaches saturation.

[0084] Example 15

[0085] The dicyandiamide-modified ultra-high cross-linked resin of Example 1 was used as an adsorbent to adsorb CL-20 in the waste liquid to be adsorbed, and the adsorption kinetics were analyzed: 0.6 g of adsorbent was added to 200 mL of the waste liquid to be adsorbed and placed in a constant temperature shaker at 25 °C and 200 rpm. 2 mL of supernatant was collected at 0, 2, 5, 10, 15, 20, 30, 40, 60, 120, 240, 360, 480, 600 and 720 min respectively. The supernatant was filtered through a 0.45 μm organic filter membrane (polytetrafluoroethylene filter membrane) to obtain the sample to be tested. The concentration of CL-20 in the sample to be tested was detected and the adsorption capacity of the adsorbent for CL-20 was calculated. The waste liquid to be adsorbed was a mixture of waste acid solution and water. The concentration of CL-20 in the waste liquid to be adsorbed was 509.076 mg / L, and the pH of the waste liquid to be adsorbed was 1.38.

[0086] Adsorption kinetics aims to investigate the quantitative relationship between adsorption time and adsorption amount under certain temperature and concentration conditions. The adsorption kinetics of CL-20 in the waste liquid adsorbed by the adsorbent were fitted using pseudo-first-order and pseudo-second-order kinetic models. The results are as follows: Figure 7 As shown. By Figure 7 It can be seen that with increasing adsorption time, the adsorption capacity of the adsorbent for CL-20 in the waste liquid gradually increases until adsorption equilibrium is reached. The first 60 minutes of CL-20 adsorption on the adsorbent is a rapid adsorption process; as adsorption time increases, the adsorption rate gradually decreases, reaching adsorption equilibrium at 240 minutes. The pseudo-second-order kinetic model provides a better fit to the adsorption process of CL-20 in the waste liquid on the adsorbent, indicating that the adsorption rate is mainly controlled by chemisorption, involving processes such as electron sharing or electron exchange.

[0087] Example 16

[0088] The dicyandiamide-modified ultra-high cross-linked resin from Example 1 was used as the adsorbent, and the above-described "Adsorption Experiment" was performed (the mass of adsorbent added was 0.01 g, 0.1 g, 0.3 g, 0.5 g, 1 g, and 2 g, respectively, Y = 12 hours). The effect of the amount of adsorbent added on "the adsorption amount and removal rate of CL-20 in the waste liquid to be adsorbed" was analyzed. The formula for calculating the removal rate is as follows: .

[0089] Where D is the removal rate (%) of CL-20 in the waste liquid to be adsorbed by the adsorbent, and C e C0 represents the concentration of CL-20 in the sample to be tested (mg / L) when adsorption is complete, and C0 represents the initial concentration of CL-20 in the waste liquid to be adsorbed (mg / L).

[0090] The results are as follows Figure 8 As shown, by Figure 8 It can be seen that as the amount of adsorbent added increases, the removal rate of CL-20 in the waste liquid to be adsorbed gradually increases, while the adsorption amount gradually decreases. When the amount of adsorbent added is 5g / L (that is, when the mass of the adsorbent added is 0.5g), the removal rate can reach 90%, and the adsorption effect is much higher than that of the macroporous resins commonly used on the market. Furthermore, compared to the medium-polar polystyrene-divinylbenzene macroporous adsorption resin (NKA-2) mentioned in the literature "S. Ma, Y. Tan, N. Liu, C. Li, Z. Ye, Removal of CL-20 from waste acid using macroporous resin: Stabilization of waste acid and recovery of CL-20, Journal of Hazardous Materials, (2025)", which achieved a CL-20 removal rate of 90% at a dosage of 10 g / L (with an initial CL-20 concentration of 70~90 mg / L), the dicyandiamide-modified ultra-high crosslinked resin of this invention achieves the same removal rate with a lower dosage, indicating that the dicyandiamide-modified ultra-high crosslinked resin of this invention has a superior adsorption effect on CL-20.

[0091] Example 17

[0092] Conduct a recycling capacity test: Repeat the following steps n times, each time as follows: Perform the "Adsorption Experiment" once, and then perform the "Desorption Experiment" once.

[0093] The adsorption experiment included: adding 0.5g of adsorbent to 200mL of the waste liquid to be adsorbed, placing it in a constant temperature shaker, and shaking at 25℃ and 200rpm for 8h to allow the adsorbent to fully adsorb CL-20 in the waste liquid. The waste liquid was a mixture of waste acid solution and water, with a CL-20 concentration of 509.076mg / L and a pH of 1.38. After adsorption, 2mL of the supernatant was filtered through a 0.45μm organic filter membrane (polytetrafluoroethylene filter membrane) to obtain the test sample. The concentration of CL-20 in the test sample was detected, the adsorption capacity of the adsorbent in the waste liquid was calculated, and the removal rate of CL-20 in the waste liquid was calculated.

[0094] The desorption experiment included: filtering off the remaining reaction solution after removing the supernatant to obtain a solid adsorbent; mixing the solid adsorbent with 10 mL of desorption solvent; shaking the mixture in a constant temperature shaker at 25 °C and 200 rpm for 12 h to desorb; filtering to obtain the desorbed adsorbent; and washing the desorbed adsorbent three times with water before using it as the adsorbent for the next "operation".

[0095] The desorption solvent was one of methanol, ethanol, acetone, and ethyl acetate. In the first "adsorption experiment" of the cycle regeneration capacity test, the adsorbent used was the dicyandiamide-modified ultra-high crosslinked resin of Example 1.

[0096] The adsorption capacity and removal rate of CL-20 by the adsorbent in each "adsorption experiment" are as follows: Figure 9 As shown. By Figure 9It can be seen that after the recycling capacity test, the adsorption of CL-20 in the waste liquid to be adsorbed by the adsorbent decreased to varying degrees. In the first "adsorption experiment", the adsorption capacity of the adsorbent for CL-20 was 29.6~30.0 mg / g. In the fourth "adsorption experiment" of the recycling capacity test, the adsorption capacity of the adsorbent for CL-20 decreased to 5.47~19.7 mg / g. This may be because the adsorption of CL-20 by the adsorbent is chemical adsorption. During desorption, some adsorbate molecules were not eluted by the desorbent. Some organic macromolecules and inorganic particles still agglomerated and deposited, blocking the pores, resulting in a decrease in the specific surface area of ​​the adsorbent and a reduction in the active sites on the outer surface of the adsorbent. A comparison of different desorption solvents revealed that the adsorbent desorbed with ethyl acetate showed the best recovery of its adsorption capacity for CL-20 in the waste liquid. After two cycles of regeneration, the removal rate of CL-20 in the waste liquid showed no significant difference, and the change in adsorption capacity was also small, indicating that the adsorption capacity of the adsorbent did not change significantly after two cycles of regeneration. In the fourth "adsorption experiment" of the regeneration capacity test, although the adsorption capacity of the adsorbent for CL-20 decreased significantly, the removal rate of CL-20 in the waste liquid could still reach 60%, proving that the dicyandiamide-modified ultra-high crosslinked resin of this invention is recyclable and has high economic benefits.

[0097] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. Use of a dicyandiamide-modified hypercrosslinked resin in the adsorption of CL-20, characterized in that, Using a dicyandiamide-modified ultra-high crosslinked resin as an adsorbent, the adsorbent is placed in an acidic liquid containing CL-20 to adsorb the CL-20. The pH of the acidic liquid containing CL-20 is <2. The preparation method of the dicyandiamide-modified ultra-high crosslinked resin includes the following steps: Step 1: Elute the chloromethyl polystyrene resin using Soxhlet extraction until the eluent is clear and colorless, then dry to obtain purified resin; Step 2: Mix the purified resin obtained in Step 1 with the first solvent until homogeneous, then add the Lewis acid catalyst and reflux at 65-75°C for 2-8 hours to carry out the Friedel-Crafts alkylation reaction. After the Friedel-Crafts alkylation reaction is completed, cool to room temperature, filter, wash until neutral, and dry to constant weight to obtain the ultra-high crosslinked resin. The ratio of purified resin to Lewis acid catalyst by mass is (1-5):

1. The first solvent is 1,2-dichloroethane, and the Lewis acid catalyst is one or a mixture of FeCl3, AlCl3, and ZnCl2. Step 3: Mix the ultra-high crosslinked resin obtained in Step 2 with the second solvent, stir for 6-12 hours, add dicyandiamide, and carry out an amination modification reaction at 20-80°C for 4-12 hours. Cool to room temperature, filter, wash until neutral, and dry to obtain dicyandiamide-modified ultra-high crosslinked resin. The mass ratio of the ultra-high crosslinked resin to the molar ratio of dicyandiamide is 1:(0.002-0.020), where mass is in g and molar is in mol. The second solvent is 1,2-dichloroethane.

2. Use according to claim 1, characterized in that, In step 1, the eluent for Soxhlet extraction is an aqueous ethanol solution, wherein the ratio of ethanol to water in the eluent is (9~19):1 by volume.

3. Use according to claim 1, characterized in that, In step 1, the drying temperature is 50~60℃ and the drying time is 6~12h.

4. Use according to claim 1, characterized in that, In step 2, the process of mixing evenly includes stirring at a speed of 150-300 rpm for 6-12 hours.

5. The use according to claim 1, characterized in that, In step 2, the ratio of the mass fraction of the purified resin to the volume fraction of the first solvent is 1:(10~15), where the mass fraction is in g and the volume fraction is in mL.

6. Use according to claim 1, characterized in that, In step 3, the ratio of the mass fraction of the ultra-high crosslinked resin to the volume fraction of the second solvent is 1:(10~15), where the mass fraction is in g and the volume fraction is in mL.

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