Preparation and application of novel zero-valent iron-cyclodextrin polymer composite material with nano-crack structure

Abstract

The invention belongs to the technical field of environmental remediation materials, and discloses preparation and application of a novel zero-valent iron-cyclodextrin polymer composite material with a nano-crack structure. The preparation method comprises the following steps: firstly preparing a novel cyclodextrin polymer material with enhanced confinement effect, and then regulating and controlling the liquid-phase reduction process of iron ions to prepare the novel zero-valent iron-cyclodextrin polymer composite material with a nano-crack structure. According to the cyclodextrin polymer preparation method based on the citric acid double-stage shearing effect, a confinement effect enhanced cyclodextrin polymer material is prepared, citric acid cooperates with cyclodextrin to enhance the binding and confinement regulation effect on Fe < 2 + > / Fe < 3 + >, and the occurrence form of Fe < 2 + > / Fe < 3 + > in a liquid phase system and the potassium borohydride reduction reaction process are regulated; the nano zero-valent iron material with a nano crack structure and better dispersity is prepared, and the reaction activity and the long-term effect of activating persulfate to degrade organic pollutants in water are improved. The preparation method of the material is easy to regulate and control and simple in step, and has practical application significance.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental restoration materials and relates to the preparation and application of a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure. Background Art

[0002] Industrial and urban activities have led to the ubiquitous detection of highly toxic organic pollutants in water, including emerging pollutants such as polycyclic aromatic hydrocarbons, pesticides, benzene derivatives, antibiotics, and phenolic compounds. These key pollutants are highly toxic and difficult to degrade, posing a serious threat to water quality safety and human health. Among them, persulfate-based advanced oxidation processes have attracted much attention due to the good stability and high oxidation performance of the oxidants. Persulfate (PS) is easily activated by heat, alkali, carbonaceous materials, and transition metals to produce highly active free radicals (such as SO 4 ·- and ·OH) and non-radical active species (such as Fe(IV) and 1 O 2 ).

[0003] Nano-zero-valent iron (nZVI) has a high specific surface area and strong reducing ability, and has been widely used as an activator for persulfate and applied in the field of organic pollution remediation in water bodies. However, nano-zero-valent iron has high surface energy and magnetism, and is prone to agglomeration, resulting in a reduction in reactive sites. In addition, nano-zero-valent iron is easily oxidized and usually has a typical core-shell structure with a dense iron oxide shell, which hinders electron transfer and mass transfer, resulting in a low efficiency of nano-zero-valent iron in activating persulfate. In order to overcome these two problems, nano-zero-valent iron needs to be modified, usually by sulfidation modification, bimetallic modification, surface coating modification, and porous material loading modification.

[0004] Sulfidation and bimetallic modification of nano zero-valent iron can improve the electron transfer efficiency on its surface, thereby improving the reaction performance of the material. Patent CN116078383 A dissolves the sulfur modifier in a sodium borohydride solution to form a reducing solution, pumps the reducing solution into a solution containing ferrous ions at a constant rate under inert gas conditions and stirs it thoroughly to finally obtain spherical nano zero-valent iron particles. The oxidation system formed by this material and persulfate can exert a good degradation effect on polycyclic aromatic hydrocarbons in a wide pH range. The literature (Fang et al, "New insights into stoichiometric efficiency and synergistic mechanism of persulfate activation by zero-valent bimetal (Iron / Copper) for organic pollutant degradation" Journal of Hazardous Materials, 403 (2021), 123669) reported the degradation of 2,4-dichlorophenol by zero-valent bimetal (iron / copper) activated persulfate. Add an appropriate amount of FeSO 4 7H 2 O and CuSO 4 ·5H 2 O is dissolved in a methanol / water mixed solution, and sodium borohydride solution is added to the above mixture under vigorous stirring and nitrogen protection to obtain spherical nano-iron-copper bimetallic particles. However, these two modifications are often not enough to reduce the agglomeration of nano-zero-valent iron, so porous materials are usually used as mechanical supports to stabilize nanoparticles.

[0005] Coating a surfactant or polyelectrolyte on the surface of nano zero-valent iron can alleviate the agglomeration of nano zero-valent iron particles. Patent CN106000335 B adds pre-prepared nano zero-valent iron to a sodium alginate solution to obtain coated nano zero-valent iron under ultrasonic conditions, thereby improving the dispersibility and stability of nano zero-valent iron. Patent CN107010708 B adds FeSO 4 7H 2 O is dissolved in a mixed solution of ethanol and water, and a seaweed polysaccharide sulfate solution is poured into the mixed solution, mixed and stirred evenly, and then a sodium borohydride solution is added dropwise, and finally a spherical seaweed polysaccharide sulfate-coated nano zero-valent iron is obtained, which has uniform particles, good dispersion, and is not easy to agglomerate. The removal rates of trihalomethanes and nitrosodimethylamine, which are disinfection by-products, reach 98.6% and 99.1%, respectively. However, such methods usually inhibit the reactivity of nano zero-valent iron due to the presence of the coating layer, which occupies the reaction sites, reduces the diffusion channels of iron, and / or removes active free radicals.

[0006] Load modification is to fix nano zero-valent iron on porous carbon materials such as activated carbon and biochar to inhibit the agglomeration of nano zero-valent iron particles. Patent CN115025759 A adds modified biochar obtained by biomass carbonization (400-800°C) to an ethanol-water solution containing ferrous salt and polyethylene glycol, and then drips sodium borohydride solution under a nitrogen atmosphere to finally obtain a modified biochar-loaded nano zero-valent iron material with better dispersibility, which can activate persulfate to remove 96.3% of naphthalene in water. Patent CN113877579 B stirs lignin and dicyandiamide in water at 60-75°C and evaporates to dryness, and the resulting solid is calcined, ground, washed and dried in a protective atmosphere at 600-800°C to obtain nitrogen-doped biochar; then the nitrogen-doped biochar is added to FeSO 4 In the mixed solution of solution and anhydrous ethanol, stir evenly and add KBH 4 The solution was then converted into a multi-active site nitrogen-doped biochar-loaded nano zero-valent iron composite material, which can efficiently activate persulfate to remove bisphenol A in water. Patent CN115475955B discloses a preparation method and application of double-phosphorylated nano zero-valent iron with nanocracks. Phosphoric acid-modified corn straw powder was calcined at a temperature of 500-700°C to obtain phosphoric acid-modified biochar; then the phosphoric acid-modified biochar was added to the ferrous salt solution, and NaBH was added to the mixed solution in sequence under continuous mechanical stirring and nitrogen environment. 4 Solution and KH 2 PO 4 The solution was used to obtain double phosphated nano zero-valent iron with nanocracks. However, the preparation process of such materials usually requires high temperature conditions and relatively high energy consumption.

[0007] Cyclodextrin (CD) has a confinement effect, can regulate the physical and chemical properties and reactions of bound or encapsulated guest molecules, and is a multifunctional molecular reactor that catalyzes many important chemical reactions. Cyclodextrin polymer (CDP) obtained by cross-linking polymerization of cyclodextrin and a cross-linking agent can be used as a carrier of nano-metal particles to improve their dispersibility. Patent CN104475749 B uses β-cyclodextrin as the main raw material and epichlorohydrin as a cross-linking agent. During the cross-linking polymerization process, pre-prepared nano-zero-valent iron particles are added to cross-link and embed them, thereby improving the reactivity and stability of nano-zero-valent iron. Patent CN113019344 A adds cyclodextrin polymer to an iron salt solution, and after sufficient immersion, a reducing agent is added to obtain uniformly distributed and regular-shaped black spherical particles.

[0008] The present invention provides a preparation and application of a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure. First, a novel cyclodextrin polymer material with enhanced confinement effect is prepared, and then the liquid phase reduction process of iron ions is regulated to prepare a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure. A confinement effect-enhanced cyclodextrin polymer material is prepared by a cyclodextrin polymer preparation method based on the dual-stage shear effect of citric acid, and citric acid cooperates with cyclodextrin to enhance the Fe 2+ / Fe 3+ The combination and confinement regulation of Fe 2+ / Fe 3+ The occurrence form and potassium borohydride reduction reaction process of the nano-zero-valent iron material are studied to prepare nano-crack structure and better dispersibility, and to improve the reaction activity and long-term effect of activated persulfate in degrading organic pollutants in water, which has broad application prospects and practical application significance. Summary of the invention

[0009] The present invention provides a preparation and application method of a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure. First, a novel cyclodextrin polymer material with enhanced confinement effect is prepared, and then the liquid phase reduction process of iron ions is regulated to prepare a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure. A confinement effect-enhanced cyclodextrin polymer material is prepared by a cyclodextrin polymer preparation method based on the dual-stage shear effect of citric acid, and citric acid cooperates with cyclodextrin to enhance the Fe 2+ / Fe 3+ The combination and confinement regulation of Fe 2+ / Fe 3+ The occurrence form of and potassium borohydride reduction reaction process of the material were studied to prepare nano-zero-valent iron materials with nano-crack structure and better dispersibility, and to improve the reactivity and long-term effect of activated persulfate in degrading organic pollutants in water. The preparation method of the material is easy to control, does not require high temperature and high pressure, has simple steps, and has practical application significance.

[0010] The technical solution of the present invention:

[0011] A method for preparing a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure, comprising the following steps:

[0012] (1) Preparation of cyclodextrin polymer based on the dual-stage shear effect of citric acid

[0013] (1.1) The first stage: dissolving cyclodextrin in NaOH solution, and ultrasonicating for more than half an hour to ensure that cyclodextrin is completely dissolved; wherein, the mass ratio of cyclodextrin to NaOH is controlled to be 2:1-4:1, and the mass concentration of NaOH solution is 10-20%; at 30°C, epichlorohydrin solution and citric acid solution are successively added dropwise to the above mixed solution, wherein the mass ratio of cyclodextrin to epichlorohydrin is controlled to be 1.5:1-2.5:1, the mass ratio of cyclodextrin to citric acid is controlled to be 10:1-50:1, and the mass concentration of citric acid solution is 40-50%, the dropping speed of the two solutions is 1-2 mL / min, mechanical stirring is used, the stirring speed is 200-300 rpm, and the reaction is carried out for more than 1 hour;

[0014] (1.2) The second stage: adding a saturated sodium hydroxide solution to the reaction solution obtained in step (1.1), heating to 50°C, and quickly adding a dispersant-containing n-decane solution; increasing the speed of the mechanical stirrer to 500-600 rpm to fully emulsify the reaction solution; after stirring for 30 minutes, quickly pouring in the epichlorohydrin solution and the citric acid solution, adjusting the speed to 300-600 rpm, heating to 60-80°C, and reacting for more than 3 hours; wherein the mass ratio of cyclodextrin to NaOH is controlled to be 5:1, the mass ratio of cyclodextrin to epichlorohydrin is controlled to be 0.5:1-1.25:1, the mass ratio of cyclodextrin to citric acid is controlled to be 10:1-50:1, and the mass concentration of the citric acid solution is 40-50%; the dispersants are Span 80 and Tween 20, the mass ratio is 3:1 to 5:1, and the dispersant is dissolved in n-decane, accounting for 0.5 to 1% of the total mass of n-decane, and the amount of n-decane added is 2 to 3 times the total reaction volume of the reaction system;

[0015] (1.3) The reaction supernatant of step (1.2) was discarded, and the precipitate was collected and washed with deionized water 10 times the total reaction volume for 3 to 5 times until the washing liquid was neutral, and then placed in a freeze dryer for more than 48 hours to obtain a cyclodextrin polymer;

[0016] The cyclodextrin is one of α-CD, β-CD, γ-CD and HPCD.

[0017] (2) Preparation of novel zero-valent iron-cyclodextrin polymer composites with nanocrack structure

[0018] (2.1) Liquid-phase reduction based on the confinement effect of cyclodextrin polymer: Dissolve the iron salt in deionized water, add the cyclodextrin polymer prepared in step (1) to regulate the presence form of iron ions in the reaction system, stir mechanically at 350-450 rpm for 1 hour, then dropwise add potassium borohydride solution to start the liquid-phase reduction process based on the confinement effect of cyclodextrin polymer, and regulate the borohydride reduction reaction process of iron ions in the reaction system; the entire reaction process is carried out under a nitrogen atmosphere, and the iron salt is FeCl 2 or FeCl 3 , the mass ratio of cyclodextrin polymer to iron salt is controlled to be 10:1 to 1:10, the dropping speed of potassium borohydride solution is 2 mL / min, and the mass ratio of potassium borohydride to iron salt is controlled to be 1:1;

[0019] Wherein, the FeCl 3 With FeCl 3 6H 2 O replaces the FeCl 2 With FeCl 2 ·4H 2 O or FeSO 4 7H 2 O alternative.

[0020] The potassium borohydride is replaced by sodium borohydride.

[0021] (2.2) Drying of composite materials: The suspension after the reaction in step (2.1) is magnetically separated using a strong magnet, washed three times with deionized water, and then vacuum freeze-dried to obtain a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

[0022] The novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure obtained by the above preparation method is used to activate persulfate to degrade organic pollutants in water.

[0023] Beneficial effects of the present invention:

[0024] (1) The present invention provides a method for preparing a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure, wherein a confinement effect-enhanced cyclodextrin polymer material is prepared by a two-stage shearing effect of citric acid, and citric acid cooperates with cyclodextrin to enhance the Fe 2+ / Fe 3+ The combination and confinement regulation of Fe 2+ / Fe 3+The occurrence form of the activated persulfate and its potassium borohydride reduction reaction process induce the iron atoms to undergo non-uniform stacking and nucleation processes to form nano-zero-valent iron particles with a nanocrack structure, thereby improving the reaction activity and stability of activated persulfate in degrading organic pollutants in water; (2) The preparation process is simple and does not require high temperature and high pressure, making it easy to achieve large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a TEM image of a new zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

[0026] Figure 2 This is the TEM image of the control material of Comparative Example 1.

[0027] Figure 3 This is the TEM image of the control material of Comparative Example 2.

[0028] Figure 4 This is a diagram showing the degradation effect of naphthalene in water by persulfate activated by a new zero-valent iron-cyclodextrin polymer composite material with nanocrack structure.

[0029] Figure 5 This is a test result diagram of the long-term effectiveness of persulfate activated by a new zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

[0030] Figure 6 This is a diagram showing the degradation effect of persulfate activated by a new zero-valent iron-cyclodextrin polymer composite material with nanocrack structure on typical organic pollutants in natural water. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0032] Example 1 Preparation process of a novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure

[0033] (1) Add 100 g of β-CD to 250 g of 18% NaOH solution, ultrasonicate for 30 minutes, then transfer to a 500 mL round-bottom flask and stir at 300 rpm at 30°C. Subsequently, add 50 g of epichlorohydrin dropwise to the round-bottom flask and immediately add 10 mL of 3.0 mol / L citric acid solution. After reacting for 1 hour, add 50 g of saturated sodium hydroxide solution and raise the temperature to 50°C. Dissolve Span80 (3.0 g) and Tween20 (1.0 g) as dispersants in 300 mL of n-decane (emulsifier), pour into the round-bottom flask, and stir vigorously at 500 rpm for 30 minutes. Immediately add epichlorohydrin (75 g) and citric acid solution (3.0 mol / L, 10 mL), adjust the temperature to 75°C, and adjust the speed to 550 rpm. After reacting for 4 h, the precipitate was collected, washed with deionized water and freeze-dried to obtain a cyclodextrin polymer material.

[0034] (2) 5.808 g FeCl 3 Add to a 500 mL round bottom flask filled with 250 mL of deionized water. Under nitrogen atmosphere, mechanically stir the solution at 450 rpm and 25°C. After 30 minutes, add 10 g of the above cyclodextrin polymer to the flask and stir the mixed solution for 1 hour (450 rpm). To start the reduction reaction, add 100 mL of 3% KBH 4 After the reaction was terminated, the black precipitate was separated by magnetic force, washed with deionized water for 5 times, and then freeze-dried to obtain a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

[0035] Comparative Example 1: A zero-valent iron-cyclodextrin polymer composite material, the preparation method of which is to first prepare a cyclodextrin polymer according to step (1) of Example 1, but without adding a citric acid solution; and then prepare a zero-valent iron-cyclodextrin polymer composite material according to step (2) of Example 1.

[0036] Comparative Example 2: Nano-zero-valent iron, which was prepared according to step (2) in Example 1, but without adding cyclodextrin polymer.

[0037] Figure 1 This is a TEM image of the novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure. The nano zero-valent iron in the composite material exhibits an obvious radial nanocrack structure.

[0038] Figure 2 This is the TEM image of the material of Comparative Example 1. No obvious radial nanocracks are observed inside the nano zero-valent iron in Comparative Example 1.

[0039] Figure 3This is the TEM image of the material of Comparative Example 2. The nano zero-valent iron in Comparative Example 2 has a typical dense spherical core-shell structure.

[0040] The confinement effect enhanced cyclodextrin polymer material was prepared by the dual-stage shear effect of citric acid, and citric acid synergized cyclodextrin to enhance the Fe 3+ The combination and confinement regulation of Fe 3+ The occurrence form and potassium borohydride reduction reaction process of the nano-zero-valent iron material with radial nanocrack structure were finally prepared.

[0041] Example 2 Preparation process of a novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure

[0042] (1) Add 100 g of α-CD to 200 g of 15% NaOH solution, ultrasonicate for 30 minutes, then transfer to a 500 mL round-bottom flask and stir at 200 rpm at 30°C. Subsequently, add 50 g of epichlorohydrin dropwise to the round-bottom flask and immediately add 10 mL of 2.0 mol / L citric acid solution. After reacting for 1 hour, add 50 g of saturated sodium hydroxide solution and raise the temperature to 50°C. Dissolve Span80 (3.0 g) and Tween20 (1.0 g) as dispersants in 300 mL of n-decane (emulsifier), pour into the round-bottom flask, and stir vigorously at 500 rpm for 30 minutes. Immediately add epichlorohydrin (75 g) and citric acid solution (2.0 mol / L, 10 mL), adjust the temperature to 60°C, and adjust the speed to 600 rpm. After reacting for 4 h, the precipitate was collected, washed with deionized water and freeze-dried to obtain a cyclodextrin polymer material.

[0043] (2) 5.808 g FeCl 3 Add to a 500 mL round bottom flask filled with 250 mL of deionized water. Under nitrogen atmosphere, mechanically stir the solution at 350 rpm and 25°C. After 30 minutes, add 10 g of the above cyclodextrin polymer to the flask and stir the mixed solution for 1 hour (350 rpm). To start the reduction reaction, add 100 mL of 3% KBH 4 After the reaction was terminated, the black precipitate was separated by magnetic force, washed with deionized water for 5 times, and then freeze-dried to obtain a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

[0044] Example 3 Preparation process of a novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure

[0045] (1) Add 100 g of HPCD to 250 g of 20% NaOH solution, ultrasonicate for 30 minutes, then transfer to a 500 mL round-bottom flask and stir at 250 rpm at 30°C. Subsequently, add 60 g of epichlorohydrin dropwise to the round-bottom flask and immediately add 10 mL of 3.0 mol / L citric acid solution. After reacting for 1 hour, add 50 g of saturated sodium hydroxide solution and raise the temperature to 50°C. Dissolve Span80 (4.0 g) and Tween20 (1.0 g) as dispersants in 300 mL of n-decane (emulsifier), pour into the round-bottom flask, and stir vigorously at 500 rpm for 30 minutes. Immediately add epichlorohydrin (90 g) and citric acid solution (3.0 mol / L, 10 mL), adjust the temperature to 80°C, and adjust the speed to 450 rpm. After reacting for 4 h, the precipitate was collected, washed with deionized water and freeze-dried to obtain a cyclodextrin polymer material.

[0046] (2) 5.808 g FeCl 3 Add to a 500 mL round bottom flask filled with 250 mL of deionized water. Under nitrogen atmosphere, mechanically stir the solution at 400 rpm and 25°C. After 30 minutes, add 10 g of the above cyclodextrin polymer to the flask and stir the mixed solution for 1 hour (400 rpm). To start the reduction reaction, add 100 mL of 3% KBH 4 After the reaction was terminated, the black precipitate was separated by magnetic force, washed with deionized water for 5 times, and then freeze-dried to obtain a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

[0047] Example 4 Degradation of naphthalene in water by activation of persulfate using a novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure

[0048] The degradation reaction was carried out in a 40 mL glass bottle to ensure that the total volume of the reaction solution was 30 mL. First, 0.009 g of the composite material and nano zero-valent iron with the same iron content as that in the 0.009 g composite material were weighed into a glass centrifuge tube, and then 30 mL of naphthalene with a concentration of 10 mg / L was poured in. Finally, 1 mL of sodium persulfate stock solution (0.06 mol / L) was added to start the activation and degradation reactions. The glass bottle was placed on an oscillator at 180 rpm and 25 ° C to react. At pretreatment intervals (5, 15, 30, 60, 90 and 120 minutes), samples were drawn with a 1 mL syringe and filtered with a PTFE membrane filter (0.22 μm), and then transferred to an automatic sampler vial (2 mL) for HPLC analysis. To prevent further degradation of naphthalene, excess methanol (200 μL) was added to the vial to quench the active species produced. The results are shown in Figure 2. Figure 4As shown in Figure 2, the nZVI / PS system removed 25% of naphthalene within 30 minutes and 31% of Nap within 120 minutes. In contrast, the composite / PS system was able to rapidly remove 99% of naphthalene from water within 30 minutes.

[0049] Example 5 Long-term effect of persulfate activation on naphthalene degradation by novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure

[0050] The degradation reaction is carried out in a 40mL glass bottle to ensure that the total volume of the reaction solution is 30mL. First, weigh 0.015g of the composite material into a glass centrifuge tube, then pour in 30mL of naphthalene with a concentration of 10mg / L, and finally add 1mL of sodium persulfate stock solution (0.06mol / L) to start the activation and degradation reaction. Place the glass bottle on an oscillator and react at 180rpm and 25°C. After reacting for 24 hours, take a sample to test the concentration of naphthalene. If it has been completely degraded, add naphthalene stock solution again to make the concentration of naphthalene in the reaction system 10mg / L. If the degradation rate of naphthalene is less than 90%, add PS stock solution to continue the reaction. This cycle is carried out 17 times to evaluate the long-term effectiveness of the composite material. Figure 5 As shown, the removal rate of naphthalene in water by the composite material / PS system exceeded 90% in the first 14 cycles of the 17 naphthalene / PS supplementation cycles, indicating the good stability and long-term performance of the composite material / PS. Example 6 Degradation of typical organic pollutants in natural water by a novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure

[0051] The degradation reaction was carried out in a 40 mL glass bottle to ensure that the total volume of the reaction solution was 30 mL. First, 0.018 g of the composite material was weighed into a glass centrifuge tube, and then 30 mL of 10 mg / L naphthalene, imidacloprid, toluene, sulfamethoxazole or 4-chlorophenol was poured in, and finally 1 mL of sodium persulfate stock solution (0.06 mol / L) was added to start the activation and degradation reaction. The reaction system was the collected natural water body, and the main chemical composition included Cl - 、SO 4 2- , CO 3 2- 、Na + , Ca 2+ and COD Mn, with concentrations of 137 mg / L, 68 mg / L, 327 mg / L, 96 mg / L, 218 mg / L and 1.1 mg / L, respectively. The glass bottle was placed on an oscillator at 180 rpm and 25°C for reaction. At pretreatment intervals (5, 15, 30, 60, 90 and 120 minutes), samples were drawn with a 1 mL syringe and filtered with a PTFE membrane filter (0.22 μm), and then transferred to an autosampler vial (2 mL) for HPLC analysis. To prevent further degradation of naphthalene, excess methanol (200 μL) was added to the vial to quench the active species produced. The results are shown in Figure 6 As shown in the figure, in natural water, the removal rates of naphthalene, imidacloprid, toluene, sulfamethoxazole, and 4-bromophenol by the composite / PS system within 120 minutes were 96%, 87%, 94%, 90%, and 84%, respectively. This result shows the selectivity and adaptability of the composite / PS oxidation process in actual water matrices.

Claims

1. A method for preparing a novel zero-valent iron-cyclodextrin polymer composite material having a nanocrack structure, characterized in that: Here are the steps: (1) Preparation of cyclodextrin polymer based on the dual-stage shear effect of citric acid (1.1) The first stage: dissolving cyclodextrin in NaOH solution, and ultrasonicating for more than half an hour to ensure that cyclodextrin is completely dissolved; wherein, the mass ratio of cyclodextrin to NaOH is controlled to be 2:1-4:1, and the mass concentration of NaOH solution is 10-20%; at 30°C, epichlorohydrin solution and citric acid solution are successively added dropwise to the above mixed solution, wherein the mass ratio of cyclodextrin to epichlorohydrin is controlled to be 1.5:1-2.5:1, the mass ratio of cyclodextrin to citric acid is controlled to be 10:1-50:1, and the mass concentration of citric acid solution is 40-50%, the dropping speed of the two solutions is 1-2 mL / min, mechanical stirring is used, the stirring speed is 200-300 rpm, and the reaction is carried out for more than 1 hour; (1.2) The second stage: adding a saturated sodium hydroxide solution to the reaction solution obtained in step (1.1), heating to 50°C, and quickly adding a dispersant-containing n-decane solution; increasing the speed of the mechanical stirrer to 500-600 rpm to fully emulsify the reaction solution; after stirring for 30 minutes, quickly pouring in the epichlorohydrin solution and the citric acid solution, adjusting the speed to 300-600 rpm, heating to 60-80°C, and reacting for more than 3 hours; wherein the mass ratio of cyclodextrin to NaOH is controlled to be 5:1, the mass ratio of cyclodextrin to epichlorohydrin is controlled to be 0.5:1-1.25:1, the mass ratio of cyclodextrin to citric acid is controlled to be 10:1-50:1, and the mass concentration of the citric acid solution is 40-50%; the dispersants are Span 80 and Tween 20, the mass ratio is 3:1 to 5:1, and the dispersant is dissolved in n-decane, accounting for 0.5 to 1% of the total mass of n-decane, and the amount of n-decane added is 2 to 3 times the total reaction volume of the reaction system; (1.3) The reaction supernatant of step (1.2) was discarded, and the precipitate was collected and washed with deionized water 10 times the total reaction volume for 3 to 5 times until the washing liquid was neutral, and then placed in a freeze dryer for more than 48 hours to obtain a cyclodextrin polymer; (2) Preparation of novel zero-valent iron-cyclodextrin polymer composites with nanocrack structure (2.1) Liquid-phase reduction based on the confinement effect of cyclodextrin polymer: dissolve an iron salt in deionized water, add the cyclodextrin polymer prepared in step (1) to regulate the presence form of iron ions in the reaction system, mechanically stir at a speed of 350-450 rpm for 1 hour, then dropwise add a potassium borohydride solution to start a liquid-phase reduction process based on the confinement effect of the cyclodextrin polymer, and regulate the borohydride reduction reaction process of the iron ions in the reaction system; the entire reaction process is carried out under a nitrogen atmosphere, the iron salt is FeCl2 or FeCl3, the mass ratio of the cyclodextrin polymer to the iron salt is controlled to be 10:1-1:10, the dropping speed of the potassium borohydride solution is 2 mL / min, and the mass ratio of the potassium borohydride to the iron salt is controlled to be 1:1; (2.2) Drying of composite materials: The suspension after the reaction in step (2.1) is magnetically separated using a strong magnet, washed three times with deionized water, and then vacuum freeze-dried to obtain a novel zero-valent iron-cyclodextrin polymer composite material with a nanocrack structure.

2. The preparation method according to claim 1, characterized in that: The cyclodextrin is one of α-CD, β-CD, γ-CD and HPCD.

3. The preparation method according to claim 1, characterized in that: The FeCl3 is replaced by FeCl3·6H2O; the FeCl2 is replaced by FeCl2·4H2O or FeSO4·7H2O.

4. The preparation method according to claim 1, characterized in that: The potassium borohydride is replaced by sodium borohydride.

5. The novel zero-valent iron-cyclodextrin polymer composite material with nanocrack structure as claimed in claim 1 is used to activate persulfate to degrade organic pollutants in water.

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