Preparation method and application of graphene oxide cross-linked polyacrylic acid hydrogel loaded vulcanized nano zero-valent iron composite material

Abstract

The invention discloses a preparation method and application of a graphene oxide cross-linked polyacrylic acid hydrogel loaded vulcanized nano zero-valent iron composite material, and relates to the technical field of environmental functional materials. Graphene oxide, acrylic acid and a cross-linking agent are adopted as raw materials, three-dimensional graphene oxide cross-linked polyacrylic acid hydrogel is constructed through polymerization initiated by free radicals in a system, iron ions are introduced through a coprecipitation method by utilizing the heavy metal adsorption performance of the hydrogel, and the composite material is prepared by vulcanizing and reducing the iron ions. The nanoparticles are directly introduced into a polyacrylic acid hydrogel network through an in-situ synthesis method to ensure that the nanoparticles are uniformly dispersed in a hydrogel matrix, so that the morphology characteristics of the in-situ synthesized nanoparticles can be effectively controlled, and meanwhile, stacking of GO sheet layers is avoided. The graphene oxide cross-linked polyacrylic acid hydrogel loaded vulcanized nano zero-valent iron composite material prepared by the preparation method disclosed by the invention can be used for efficiently removing ciprofloxacin-copper ion combined pollution in a water body in a short time.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of environmental functional materials, in particular to a preparation method and application of a graphene oxide cross-linked polyacrylic acid hydrogel loaded sulfurized nano zero-valent iron composite material. BACKGROUND

[0002] With the continuous development of urbanization, the types of pollutants in actual water bodies have increased significantly. Antibiotics and heavy metals, as typical pollutants, can enter the aquatic environment through various pathways, leading to combined pollution of antibiotics and heavy metals in water bodies. There are interactions or reactions between pollutants causing combined pollution. Compared with single pollution, combined pollution is closer to the actual situation and is worthy of in-depth study. Among them, Ciprofloxacin (CIP) and Cu are typical organic and inorganic pollutants, respectively. The accumulation of the two in the environment and their potential ecological and health risks are increasingly serious.

[0003] Nano zero-valent iron (nZVI) has high specific surface area, high reactivity, high catalytic activity, and electron supply capacity and can continuously release divalent iron ions, which can better activate persulfate and be used for degrading Ciprofloxacin by advanced oxidation process. In addition, nZVI has a certain adsorption property and good performance in the enrichment and recovery of heavy metals. However, nZVI has the defects of serious surface passivation and narrow pH range. Studies have shown that the sulfurized nano zero-valent iron (S-nZVI) prepared by sulfurization modification has better reducibility, electron transfer performance, reactivity, and oxidation resistance than nZVI. In addition, the surface passivation of S-nZVI is weakened, and the pH application range is significantly widened, which greatly improves the catalytic activity of S-nZVI. However, S-nZVI is prone to agglomeration and cannot be effectively dispersed during the reaction process, resulting in a decrease in specific surface area, a reduction in active sites, and low stability.

[0004] In the prior art, the paper "Removal of arsenic and antimony pollution in soil leachate by graphene oxide supported sulfurized nanoscale zero-valent iron" (Zhu Yu, Jilin University, June 2022) discloses the use of graphene oxide as a carrier to load sulfurized nanoscale zero-valent iron to prepare a composite material for adsorbing heavy metals. However, the large-scale preparation of high-quality graphene oxide is costly, and the graphene sheets have strong van der Waals forces and π-π interactions between the layers, which easily leads to irreversible agglomeration, reduces the specific surface area and active site exposure, and affects the dispersion and stability of S-nZVI, thereby affecting the adsorption effect of the composite material on heavy metals. The paper "Study on the degradation of ciprofloxacin in water by carbon-supported sulfurized nanoscale zero-valent iron activated persulfate" (Chen Xinyu, Yangzhou University, June 2024) discloses the use of activated carbon or enteromorpha biochar to load S-nZVI, which provides a large number of active sites for the activation of persulfate, and can improve the degradation of ciprofloxacin. However, the structure and properties of enteromorpha biochar are not uniform, and its physical and chemical properties are highly dependent on the raw materials and pyrolysis conditions, resulting in large batch-to-batch differences, making it difficult to accurately control the stability and activity of S-nZVI. Moreover, the metal oxides / minerals (ash) in the biochar may occupy the loading sites or compete with S-nZVI / pollutants, interfering with the removal of target pollutants. In addition, the poor electrical conductivity of activated carbon / enteromorpha biochar hinders the efficient transfer of electrons from S-nZVI to pollutants, limiting the reaction rate.

[0005] Therefore, it is particularly important to construct a composite material based on sulfurized nanoscale zero-valent iron that can quickly and efficiently remove the combined pollution of ciprofloxacin and heavy metal Cu(II) in water. SUMMARY

[0006] In view of the above prior art, the purpose of the present application is to provide a preparation method and application of graphene oxide cross-linked polyacrylic hydrogel supported sulfurized nanoscale zero-valent iron composite material. The present application uses graphene oxide, acrylic acid and cross-linking agent as raw materials, initiates polymerization through free radicals in the system, constructs three-dimensional graphene oxide cross-linked polyacrylic hydrogel, utilizes the excellent heavy metal adsorption performance of graphene oxide cross-linked polyacrylic hydrogel, introduces iron ions by coprecipitation method, and prepares graphene oxide cross-linked polyacrylic hydrogel supported sulfurized nanoscale zero-valent iron composite material through sulfurization and reduction of iron ions. The graphene oxide cross-linked polyacrylic hydrogel supported sulfurized nanoscale zero-valent iron composite material prepared by the present application can efficiently remove ciprofloxacin and heavy metal Cu(II) in water in a short time.

[0007] To achieve the above purpose, the present application adopts the following technical solutions: The first aspect of the present application provides a preparation method of graphene oxide cross-linked polyacrylic hydrogel supported sulfurized nanoscale zero-valent iron composite material, comprising the following steps: (1) adding K2S2O8 solution and (NH4)2Ce(NO3)6 solution into the aqueous solution of graphene oxide, heating and mixing to obtain a mixed solution; adding acrylic acid and NaOH solution into the mixed solution in sequence, then adding Na2SO3 solution and stirring, adding a crosslinking agent after the stirring is completed, and reacting until the reaction is completed, collecting the reaction product, drying and crushing to obtain the graphene oxide crosslinked polyacrylic acid hydrogel; (2) mixing NaBH4 and Na2S2O4, dissolving them in water, and stirring to obtain a NaBH4 / Na2S2O4 mixed solution; placing the graphene oxide crosslinked polyacrylic acid hydrogel in a FeSO4·7H2O solution to adsorb iron ions, adding the NaBH4 / Na2S2O4 mixed solution dropwise after taking out to react, collecting the solid precipitate after the reaction is completed, and washing and drying to obtain the graphene oxide crosslinked polyacrylic acid hydrogel loaded with sulfurized nano zero-valent iron composite material.

[0008] Preferably, in step (1), the concentration of the aqueous solution of graphene oxide is 1-2 g / L, the concentration of the K2S2O8 solution is 15-25 g / L, the concentration of the (NH4)2Ce(NO3)6 solution is 8-12 g / L, the concentration of the NaOH solution is 5-7 mol / L, and the concentration of the Na2SO3 solution is 15-25 g / L.

[0009] Further, the concentration of the aqueous solution of graphene oxide is 1.5 g / L.

[0010] Preferably, in step (1), the crosslinking agent is methylene bisacrylamide.

[0011] Preferably, in step (1), the volume ratio of the aqueous solution of graphene oxide, the K2S2O8 solution, the (NH4)2Ce(NO3)6 solution, the acrylic acid, the NaOH solution, the Na2SO3 solution and the crosslinking agent is (8-12):(8-12):(3-5):10:(11.5-16):(3-5):(4-24).

[0012] Preferably, in step (1), the heating temperature is 60-80℃, and the mixing time is 10-20 min.

[0013] Preferably, in step (1), the stirring time is 10-20 min.

[0014] Preferably, in step (1), the reaction temperature is 45-55℃, and the reaction time is 4-6 h.

[0015] Preferably, in step (2), the ratio of the amount of NaBH4, Na2S2O4 and water added is 1.5 g:(0.005-0.05) g:200 mL.

[0016] As preferred, in step (2), the stirring mode is nitrogen blowing, and the stirring time is 25-35 min.

[0017] As preferred, in step (2), the FeSO4·7H2O solution is prepared by mixing FeSO4·7H2O and water at (0.6-5.0) g: 250 mL.

[0018] As preferred, in step (2), the mass ratio of NaBH4, Na2S2O4, FeSO4·7H2O in the FeSO4·7H2O solution and the graphene oxide cross-linked polyacrylic acid hydrogel is 1.5 g:(0.005-0.11) g:(0.6-5.0) g:0.5 g.

[0019] As preferred, in step (2), the adsorption time is 0.5-1.5 h.

[0020] As preferred, in step (2), the reaction time is 25-35 min.

[0021] As preferred, in step (2), the washing operation is that the solid precipitate is sequentially washed with deionized water and ethanol.

[0022] As preferred, in step (2), the drying mode is freeze-drying, the freeze-drying temperature is -40℃ to -60℃, and the freeze-drying time is 12-24 h.

[0023] In the second aspect of the present application, the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material prepared by the above method is provided.

[0024] In the third aspect of the present application, the application of the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material in simultaneously removing the combined pollution of ciprofloxacin and heavy metal copper ions in water is provided.

[0025] As preferred, the specific steps of using the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material to remove the combined pollution of ciprofloxacin and heavy metal copper ions are as follows: The graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material is added into the water body containing the combined pollution of ciprofloxacin and heavy metal copper ions for 1 h-2 h.

[0026] As preferred, the solid-liquid ratio of the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material and the water body containing the combined pollution of ciprofloxacin and heavy metal copper ions is (0.05-0.15) g: 100 mL; in the water body containing the combined pollution of ciprofloxacin and heavy metal copper ions, the concentration of ciprofloxacin is 15-25 mg / L, and the concentration of Cu 2+The concentration ratio is (0.01-10):1.

[0027] The beneficial effects of the present application are: 1. The present application uses graphene oxide, acrylic acid and crosslinking agent as raw materials, initiates polymerization through free radicals in the system, constructs three-dimensional graphene oxide crosslinked polyacrylic acid hydrogel, then directly introduces iron ions into the graphene oxide crosslinked polyacrylic acid hydrogel network through in-situ synthesis, introduces iron ions through coprecipitation, and through vulcanization and reduction of iron ions, obtains graphene oxide crosslinked polyacrylic acid hydrogel loaded vulcanized nano zero-valent iron composite material. The composite material can be used for removing ciprofloxacin and heavy metal Cu (II) composite pollution.

[0028] The present application carries out sulfurization modification on nano zero-valent iron and loads it with graphene oxide polyacrylic acid hydrogel, increases the specific surface area of the material, and improves the adsorption capacity; and contains rich functional groups, significantly improves the enrichment of organic pollutants, is beneficial to the enrichment-degradation of antibiotics in the microenvironment on the surface of the material, and finally improves the degradation rate.

[0029] 2. The present application directly introduces iron ions into the graphene oxide crosslinked polyacrylic acid hydrogel network through in-situ synthesis, generates vulcanized nano zero-valent iron inside the gel through chemical reaction. This method can ensure that the vulcanized nano zero-valent iron is uniformly dispersed in the graphene oxide crosslinked polyacrylic acid hydrogel matrix, can effectively control the morphology characteristics of the in-situ synthesized nanoparticles, avoid the stacking of GO sheets, and increase the active sites to improve the removal effect of ciprofloxacin and heavy metal Cu (II).

[0030] 3. The present application uses environmentally friendly materials as raw materials, which are non-toxic and harmless, and the raw materials are easy to obtain and low in price, which meets the principles of "resource" and "reduction". BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 : Scanning electron microscope images of the composite materials prepared in Example 1, Examples 10-11 and Comparative Example 1; Figure 2 : XRD spectra of the composite materials prepared in Example 1, Examples 12-13 and Comparative Example 3; Figure 3 : FT-IR spectra of the composite materials prepared in Example 1 and Comparative Examples 1-2; Figure 4 : XPS spectra of the composite materials prepared in Example 1, Comparative Example 1 and Comparative Example 3; Figure 5 : In test example 2, the adsorption effect of the composite materials prepared in Examples 1-9 and Comparative Example 2 on heavy metal copper ions; Figure 6Fig. 2 shows the degradation effect of the composite material prepared in Experimental Example 3 on ciprofloxacin, wherein the composite material is prepared from Example 1, Examples 10-11 and Comparative Example 1; Figure 7 Fig. 3 shows the degradation effect of the composite material prepared in Experimental Example 3 on ciprofloxacin, wherein the composite material is prepared from Example 1, Examples 12-14 and Comparative Example 3; Figure 8 Fig. 4 shows the adsorption effect of the composite material prepared in Experimental Example 4 on copper ions in a water body containing ciprofloxacin and heavy metal copper ions, wherein the composite material is prepared from Example 1; Figure 9 Fig. 5 shows the degradation effect of the composite material prepared in Experimental Example 4 on ciprofloxacin in a water body containing ciprofloxacin and heavy metal copper ions, wherein the composite material is prepared from Example 1. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, 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.

[0033] In the prior art, although sulfidized nano zero-valent iron (S-nZVI) has good reducibility, electron transfer performance, reactivity, etc., it is prone to agglomeration and cannot be effectively dispersed in the reaction process, resulting in a decrease in specific surface area and a decrease in active sites. Studies have shown that porous carbon materials can be used to load and modify S-nZVI to achieve effective dispersion of sulfidized nano zero-valent iron. Therefore, a suitable carrier is selected to load S-nZVI to prepare a composite material to improve its rapid and efficient removal for removing ciprofloxacin and heavy metal Cu(II) composite pollution.

[0034] Based on this, the application provides a graphene oxide cross-linked polyacrylic acid hydrogel loaded sulfidized nano zero-valent iron composite material. Graphene oxide, acrylic acid and methylene bisacrylamide are used as raw materials, free radicals in the solution initiate polymerization to form a three-dimensional porous structure, and the composite hydrogel has excellent heavy metal adsorption performance. Iron ions are introduced by a coprecipitation method, and the composite material is finally prepared by sulfidizing and reducing the iron ions. The composite material can be used to remove ciprofloxacin and heavy metal Cu(II) composite pollution.

[0035] The hydrogel is a polymer material composed of a cross-linked network structure, has good biocompatibility, controllable pore structure and high water absorption performance, and the polyacrylic acid hydrogel (PAA) can be used as a dispersion matrix of metal nanoparticles and a construction framework of three-dimensional graphene oxide, the adsorption process of the PAA to heavy metal ions accords with chemical adsorption, that is, single-layer adsorption is mainly adopted, so that the uniform distribution of metal ions in the gel network structure can be ensured, and the morphology characteristics of the in-situ synthesized nanoparticles can be effectively controlled. Moreover, the acrylic acid monomer can be used as a polymerization starting point of the graphene oxide, so that the construction of a novel organic-inorganic composite three-dimensional network structure is realized, and the stacking of GO sheets is effectively avoided. Meanwhile, the PAA / GO hydrogel network provides sufficient adsorption sites for the adsorption of pollutants, and has better adsorption performance.

[0036] The graphene oxide cross-linked polyacrylic acid hydrogel prepared from the graphene oxide and the acrylic acid has the following advantages when used as a carrier: (1) structure-function synergistic reinforcement: the GO sheets can improve the mechanical strength of the gel and inhibit the swelling deformation, the sp2, sp3 and sp hybridization of the GO sheets can improve the electron transfer efficiency, and the GO sheets can improve the mechanical strength of the gel and inhibit the swelling deformation. 3 The carbon network constructs an efficient electron channel, and greatly improves the electron transfer efficiency. (2) Stronger stability: the GO can buffer the pH fluctuation, the directional arrangement forms a through hole to guarantee the mass transfer stability, and the oxidation passivation of the S-nZVI particles is reduced to a certain extent. (3) Multifunctional integration: the π-π bond effect and the oxygen-containing groups of the GO can improve the adsorption capacity of pollutants, and the GO can cooperate with the PAA to better fix heavy metals.

[0037] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific embodiments.

[0038] The experimental materials used in the embodiments of the present application are all conventional experimental materials in the art, and can be purchased through commercial channels.

[0039] Embodiment 1: Preparation of graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfurized nano zero-valent iron composite material (1) 0.15g of graphene oxide powder and deionized water were mixed, and stirring was performed at room temperature until the graphene oxide was dissolved, so as to obtain 100mL of a translucent solution; the translucent solution was subjected to ultrasonic treatment under 250W for 0.5h, so as to obtain a graphene oxide aqueous solution with a concentration of 1.5g / L; Take 10 mL of graphene oxide aqueous solution, add 10 mL of 20 g / L K2S2O8 solution and 4 mL of 10 g / L (NH4)2Ce(NO3)6 solution, mix under water bath heating for 15 min to obtain a mixed solution; add 10 mL of acrylic acid and 15 mL of 6 mol / L NaOH solution to the mixed solution in turn, then add 4 mL of 20 g / L Na2SO3 solution and stir for 15 min, after stirring, add 8 mL of crosslinking agent methylene bisacrylamide, react under 50°C water bath for 4 h, collect the reaction product, dry and crush to obtain graphene oxide crosslinked polyacrylic acid hydrogel; (2) Mix 1.5 g of NaBH4 and 0.0273 g of Na2S2O4, dissolve in 200 mL of deionized water, and purify with nitrogen for 30 min to obtain a NaBH4 / Na2S2O4 mixed solution; Add 1.2445 g of FeSO4·7H2O to 250 mL of deionized water and mix uniformly to obtain a FeSO4·7H2O solution; add 0.5 g of graphene oxide crosslinked polyacrylic acid hydrogel to the FeSO4·7H2O solution for 1 h to enable the graphene oxide crosslinked polyacrylic acid hydrogel to adsorb iron ions, thereby obtaining graphene oxide crosslinked polyacrylic acid hydrogel loaded with iron ions; Then, the NaBH4 / Na2S2O4 mixed solution is added dropwise to the graphene oxide crosslinked polyacrylic acid hydrogel loaded with iron ions, stirred and reacted under nitrogen blowing for 30 min to ensure complete reaction, after the reaction is completed, the reaction product is separated by a magnet, washed with deionized water and ethanol, and freeze-dried at -45°C for 24 h to obtain graphene oxide crosslinked polyacrylic acid hydrogel loaded with sulfurized nano zero-valent iron composite material, denoted as GO-g-PAA / S-nZVI.

[0040] Example 2: The difference between this embodiment and Example 1 is that in step (1), the concentration of the graphene oxide aqueous solution is 1 g / L.

[0041] Example 3: The difference between this embodiment and Example 1 is that in step (1), the concentration of the graphene oxide aqueous solution is 2 g / L.

[0042] Example 4: The difference between this embodiment and Example 1 is that in step (1), the volume of the added NaOH solution is 11.5 mL.

[0043] Example 5: The difference between this embodiment and Example 1 is that in step (1), the volume of the added NaOH solution is 14 mL.

[0044] Example 6: The difference between this example and Example 1 is that in step (1), the volume of NaOH solution added is 16 mL.

[0045] Example 7: The difference between this example and Example 1 is that in step (1), the volume of crosslinking agent methylene bisacrylamide added is 4 mL.

[0046] Example 8: The difference between this example and Example 1 is that in step (1), the volume of crosslinking agent methylene bisacrylamide added is 16 mL.

[0047] Example 9: The difference between this example and Example 1 is that in step (1), the volume of crosslinking agent methylene bisacrylamide added is 24 mL.

[0048] Example 10: The difference between this example and Example 1 is that in step (2), the FeSO4·7H2O solution is prepared by mixing 0.6222 g of FeSO4·7H2O and 250 mL of deionized water.

[0049] Example 11: The difference between this example and Example 1 is that in step (2), the FeSO4·7H2O solution is prepared by mixing 4.9782 g of FeSO4·7H2O and 250 mL of deionized water.

[0050] Example 12: The difference between this example and Example 1 is that in step (2), the amount of Na2S2O4 used is 0.0055 g.

[0051] Example 13: The difference between this example and Example 1 is that in step (2), the amount of Na2S2O4 used is 0.0545 g.

[0052] Example 14: The difference between this example and Example 1 is that in step (2), the amount of Na2S2O4 used is 0.1091 g.

[0053] Comparative Example 1: Graphene oxide crosslinked polyacrylic acid hydrogel After mixing 0.15 g of graphene oxide powder with deionized water, stirring at room temperature until the graphene oxide is dissolved, a 100 mL semi-transparent solution is obtained; the semi-transparent solution is treated with ultrasonic waves at 250 W for 0.5 h to obtain a graphene oxide aqueous solution with a concentration of 1.5 g / L; Take 10 mL of graphene oxide aqueous solution, add 10 mL of 20 g / L K2S2O8 solution and 4 mL of 10 g / L (NH4)2Ce(NO3)6 solution, mix under water bath heating for 15 min to obtain a mixed solution; add 10 mL of acrylic acid and 15 mL of 6 mol / L NaOH solution to the mixed solution in turn, then add 4 mL of 20 g / L Na2SO3 solution and stir for 15 min, after stirring, add 8 mL of crosslinking agent methylene bisacrylamide, react under 50℃ water bath for 4 h, collect the reaction product, dry and crush it after drying, then sieve to obtain graphene oxide crosslinked polyacrylic acid hydrogel, recorded as GO-g-PAA.

[0054] Preparation of polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron The difference between this comparative example and example 1 is that in step (1), no graphene oxide solution is added. The specific steps are as follows: Mix 10 mL of 20 g / L K2S2O8 solution and 4 mL of 10 g / L (NH4)2Ce(NO3)6 solution under water bath heating for 15 min to obtain a mixed solution; add 10 mL of acrylic acid and 15 mL of 6 mol / L NaOH solution to the mixed solution in turn, then add 4 mL of 20 g / L Na2SO3 solution and stir for 15 min, after stirring, add 8 mL of crosslinking agent methylene bisacrylamide, react under 50℃ water bath for 4 h, collect the reaction product, dry and crush it after drying, then sieve to obtain polyacrylic acid hydrogel; then polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron is prepared according to the method of step (2) in example 1, recorded as PAA / S-nZVI.

[0055] Preparation of graphene oxide crosslinked polyacrylic acid hydrogel loaded with nano zero-valent iron composite The difference between this comparative example and example 1 is that in step (2), no Na2S2O4 is added. The specific steps are as follows: According to the method of example 1, graphene oxide crosslinked polyacrylic acid hydrogel and FeSO4·7H2O solution are prepared; 1.5 g of NaBH is dissolved in 200 mL of deionized water, and nitrogen is blown for 30 min to obtain NaBH4 solution; 0.5 g of graphene oxide crosslinked polyacrylic acid hydrogel is added to the FeSO4·7H2O solution to adsorb iron ions, and graphene oxide crosslinked polyacrylic acid hydrogel adsorbed with iron ions is obtained; drop 4 mL of 20 g / L Na2SO3 solution and stir under nitrogen blowing for 30 min to ensure complete reaction, after the reaction is completed, the reaction product is separated by magnet, and then washed with deionized water and ethanol, and then freeze-dried at-45℃ for 24 h to obtain graphene oxide crosslinked polyacrylic acid hydrogel loaded with nano zero-valent iron composite, recorded as GO-g-PAA / nZVI.

[0056] Comparative Example 4: Preparation of Sulfated Zero-Variant Iron Nanoparticles Supported in Graphene Oxide Hydrogel Aqueous solution of graphene oxide was prepared according to the method in Example 1. 10 mL of aqueous solution of graphene oxide was taken, and 10 mL of 20 g / L K2S2O8 solution and 4 mL of 10 g / L (NH4)2Ce(NO3)6 solution were added. The mixture was heated in a water bath for 15 min to obtain a mixed solution. 4 mL of 20 g / L Na2SO3 solution was added to the mixed solution and stirred for 15 min. After stirring, 8 mL of crosslinking agent methylenebisacrylamide was added, and the mixture was reacted in a water bath at 50 °C for 4 h. The reaction product was collected, dried, pulverized, and sieved to obtain graphene oxide hydrogel. Then, graphene oxide hydrogel loaded with sulfide nano-zero valent iron was prepared according to step (2) of Example 1, denoted as GO / S-nZVI.

[0057] Experimental Example 1: Structural Characterization 1. SEM analysis was performed on the composite materials prepared in Examples 1, 10, and 11, as well as the graphene oxide crosslinked polyacrylic acid hydrogel prepared in Comparative Example 1. The results are as follows: Figure 1 As shown.

[0058] Depend on Figure 1 It can be seen that the graphene oxide crosslinked polyacrylic acid hydrogel prepared in Comparative Example 1 only contains the porous structure of graphene. However, in the graphene oxide crosslinked polyacrylic acid hydrogel-supported sulfurized nano-zero valent iron composite material prepared in this invention, the sulfurized nano-zero valent iron is loaded in the graphene pores, and compared with the composite materials prepared in Examples 10 and 11, the hydrogel surface of the composite material prepared in Example 1 is loaded with more sulfurized nano-zero valent iron particles.

[0059] From a theoretical perspective: when the amount of FeSO4·7H2O is too small, Fe... 2+ It generates Fe 0 When the concentration of the precursor is too low, Fe formed during the reduction reaction of sodium borohydride... 0 Insufficient number of crystal nuclei leads to a reduction in the total number of S-nZVI particles generated. Excessive use of FeSO4·7H2O results in excess Fe... 2+ A large amount of Fe is generated after reduction. 0 Particles densely accumulate on the carrier surface, clogging the hydrogel pores and hindering subsequent Fe... 2+ Diffusion into the carrier interior renders deep loading sites unusable. Furthermore, when Fe... 2+ When the concentration is too high, Fe in the bulk solution 2+ Reduced to Fe 0 The adsorption rate exceeds the adsorption rate on the carrier surface, and these free particles agglomerate and precipitate because they are not fixed by the carrier, thus failing to be effectively loaded.

[0060] 2. The composite materials prepared in Example 1, Example 12, Example 13 and Comparative Example 3 were subjected to XRD analysis, and the results are shown in Figure 2

[0061] By Figure 2 It can be seen that by PDF library 89-7194, the three kinds of composite materials obviously appeared Fe 0 characteristic diffraction peak at 2 theta value of 44.9 (110), indicating that Fe 0 can be well loaded on GO-PAA, and the composite material is successfully synthesized.

[0062] Compared with GO-g-PAA / nZVI prepared in Comparative Example 3, GO-g-PAA / S-nZVI prepared in Example 1 and Example 12-13 also appeared Fe 0 characteristic peak at 2 theta value of 82.3 (210), and the Fe 0 characteristic peak intensity at 2 theta value of 44.9 (110) was obviously enhanced, indicating that the sulfurization process increased the content of Fe 0 of the material. In addition, it can be seen from the XRD patterns of the composite materials prepared in Example 1 and Example 13 that the material with high sulfur-iron ratio has higher Fe 0 characteristic peak at 2 theta value of 44.9 (110), and a new Fe 0 peak at 2 theta value of 65.1 (200), indicating that within a certain range, increasing the content of sulfur in the sulfurization process can increase the content of Fe 0 .

[0063] 3. The composite materials prepared in Example 1, Comparative Example 1, Comparative Example 2 and GO powder were subjected to FT-IR analysis, and the results are shown in Figure 3

[0064] In the spectrum of graphene oxide cross-linked polyacrylic acid hydrogel prepared in Comparative Example 1, there are both GO related characteristic peaks and PAA related characteristic peaks, and the relatively strong characteristic peak at 1650 cm - ¹ is shifted to 1620 cm - ¹, indicating that the successful grafting polymerization between GO-PAA. Although the introduction of iron may not directly reflect the characteristic absorption of iron on FTIR, the different states of iron can affect the electron cloud distribution of the surrounding functional groups, etc., thereby causing slight changes in the intensity or position of some absorption peaks. Compared with GO-PAA, GO-PAA / S-nZVI only has slight changes in the intensity of the peaks, also indicating the successful in-situ synthesis of S-nZVI nanoparticles.

[0065] 4. Example 1, Comparative Example 1 and Comparative Example 3 were subjected to XPS analysis, and the results are shown in Figure 4 ​​shown.

[0066] Figure 4 In the three C1s spectra of D-F, the whole can be divided into three peaks 284.5, 286.2, 288.1 eV, respectively corresponding to C-C / C=C, C-O, C=O on the PAA polymer chain and GO nanosheet layer skeleton. Fe 0 The introduction of Fe and the change of peaks after the sulfidation process are not obvious, indicating that the functional groups on GO-PAA are almost not affected during the loading process. In the GO-PAA O1s spectrum I, three different characteristic peaks are detected, and the characteristic peaks of 531.0, 531.8, and 533.0 eV correspond to C=O, O-H, and C-O-C bonds, respectively. In the GO-PAA / nZVI and GO-PAA / S-nZVI O1s spectra G and H, the above oxygen-containing functional groups are shifted to 530.8 (C=O), 532.0 (O-H), and 535.6 (C-O-O) eV, respectively. It can be seen that after the introduction of Fe 0 , the binding energies of the corresponding peaks all produce certain differences, among which the binding energy difference of the C-O-C corresponding peak is greater than 0.5 eV, confirming the important role of the C-O-C oxygen-containing group in the combination with Fe 0 through chemical bonds, and in addition, the sulfidation process has no obvious effect on the peak change, indicating that sulfidation has no effect on the oxygen-containing functional groups. The fitting results of the Fe 2p spectrum can be divided into four parts, which correspond to Fe 0 , Fe2p 3 / 2 , Fe2p 1 / 2 , and satellite peaks. The Fe 2p of GO-PAA / nZVI is shown in Figure K, and the peak value of Fe 0 appears at 707.8 eV, and the four satellite peaks are located at 715.1, 719.5, 728.5, and 732.4 eV. Fe2p 3 / 2 and Fe2p 1 / 2 are further decomposed into four peaks, and the peak values at 709.7 eV and 723.1 eV correspond to Fe 2+ , while the peaks at 711.8 eV and 725.1 eV correspond to Fe 3+ , as shown in Figure J for GO-PAA / S-nZVI. Compared with GO-PAA / nZVI, there is only a slight shift in most of the peaks, but the Fe 3+ peak at 725.1 eV shifts to 725.9 eV, and the binding energy difference is greater than 0.5 eV, proving that the sulfidation process will affect the Fe 3+ in the material, and according to Figure L, the results show that Fe 0 is successfully introduced into the GO-PAA polymer matrix, and the content of Fe 0 on the surface increases, while the content of Fe(III) decreases.

[0067] Experimental Example 2: Adsorption Capacity of Heavy Metal Copper Ions A copper ion adsorption test was conducted on the graphene oxide crosslinked polyacrylic acid hydrogel-supported sulfurized nano-zero-valent iron composite material prepared in Example 1. The results are as follows: Figure 5 As shown. The specific steps are as follows: (1) Weigh out 0.17g, 0.34g, 0.51g, 0.68g, 0.85g, and 1.02g of CuCl2·2H2O solid respectively, dissolve them in water, transfer them to a 1L volumetric flask and make up to volume to prepare solutions containing copper ions with concentrations of 64, 128, 192, 256, 320, and 384 mg / L respectively; (2) Weigh 0.10 g of the graphene oxide crosslinked polyacrylic acid hydrogel-supported sulfurized nano-zero valent iron composite material prepared in Example 1, add it to 100 mL of solutions containing copper ions of different concentrations, and stir continuously at room temperature. Every certain period of time, take 4 mL of the filtrate, filter it through a 0.45 μm microporous membrane, and use ICP-OES (inductively coupled plasma optical emission spectrometry) to test Cu². + The concentration is adjusted until adsorption equilibrium is reached.

[0068] Depend on Figure 5 As can be seen, the graphene oxide crosslinked polyacrylic acid hydrogel-supported sulfurized nano-zero-valent iron composite material prepared in Example 1 reached adsorption equilibrium for copper ion solutions of different concentrations (64, 128, 192, 256, 320, 384 mg / L) within 60 min, with maximum adsorption capacities of 59.337 mg / L, 125.89 mg / L, 180.65 mg / L, 228.86 mg / L, 242.7 mg / L, and 268.62 mg / L, respectively. Therefore, the graphene oxide crosslinked polyacrylic acid hydrogel-supported sulfurized nano-zero-valent iron composite material prepared in this invention exhibits excellent adsorption capacity for heavy metal copper ions.

[0069] Experimental Example 3: Degradation Effect of Ciprofloxacin 1. The composite materials prepared in Examples 1, 10, 11 and Comparative Example 1 were subjected to ciprofloxacin degradation tests, and the results are as follows: Figure 6 As shown. The specific steps are as follows: Accurately weigh 0.10 g of the composite material with a particle size of 20-40 mesh, add the weighed composite material to 100 mL of 20 mg / L CIP solution, and add 0.066 g of potassium persulfate. Stir continuously at room temperature (25°C). At regular intervals, take 1.5 mL of the filtrate and test the CIP concentration using HPLC (high-performance liquid chromatography).

[0070] Depend on Figure 6It can be seen that the composite materials of Examples 1, 10, and 11 reached adsorption equilibrium in 90 min. At adsorption equilibrium, the C / C0 ratios for Examples 1, 10-11, and Comparative Example 1 were 22.9, 24.1, 28.7, and 92.3, respectively.

[0071] 2. The composite materials prepared in Examples 1, 12-14, and Comparative Example 3 were subjected to ciprofloxacin degradation tests, and the results are as follows: Figure 7 As shown.

[0072] Depend on Figure 7 It can be seen that each composite material reached adsorption equilibrium at 60 min. The C / C0 values ​​corresponding to the equilibrium of Examples 1, Examples 12-14 and Comparative Example 3 were 7.3, 30.2, 36.7, 30.3 and 33.8, respectively.

[0073] When the sulfur-to-iron ratio is too low, the sulfur content is very low, resulting in an insignificant sulfidation process and the formation of only a small amount of iron sulfide. When the sulfur-to-iron ratio is moderate, appropriate sulfidation forms conductive FeS, replacing the passivation oxide layer on the S-nZVI surface. This FeS exhibits higher electronegativity, significantly improving electron transport efficiency, promoting PMS activation to generate more free radicals, and regulating Fe²⁺. + Continuous release maintains homogeneous activation. When the sulfur-to-iron ratio is too high, as sulfur increases, Fe... 0 The content of sulfur is significantly reduced. The surface of S-nZVI is mainly composed of polysulfides, which have lower activity compared to FeS. Furthermore, excessive sulfur forms an excessively thick sulfur layer, covering active sites and hindering electron transfer, thereby reducing the removal effect of CIP.

[0074] Experimental Example 4: Adsorption and Degradation Test of Ciprofloxacin-Copper Ion Composite Pollutants 1. Investigating the effect of the composite material prepared in Example 1 on CIP and Cu 2+ The removal efficiency of combined pollution was assessed. In water containing ciprofloxacin and copper ions, the concentration of ciprofloxacin was 20 mg / L. The concentrations of ciprofloxacin and copper ions were controlled. 2+ The molar ratios were 10:1, 2:1, 1:1, 1:10, 1:20, 1:40, 10:1, 1:60, and 1:100, respectively. The results are as follows: Figures 8-9 As shown.

[0075] Depend on Figure 8 and Figure 9 It can be seen that Cu 2+ The introduction of [a specific ingredient] significantly improved the degradation rate of CIP. When CIP / Cu [a specific ingredient]... 2+ When the molar ratio of Cu is 1:20, the reaction rate reaches its maximum value, approximately that of a single system (without Cu). 2+ The degradation rate is 3 times that of CIP / Cu. It can also be observed that... 2+The mass ratio control exhibits a dual effect: when the ratio is greater than 1:10, Cu 2+ The concentration is too low, which may be due to Cu²⁺. + Cu generated by reduction + Free radicals were consumed, and Cu 2+ with Fe 2+ The reaction consumes the activator Fe. 2+ This inhibited the degradation of CIP. When the ratio was less than 1:20, Cu... 2+ Too high concentration, excessive Cu 2+ The reduced deposition covers the material surface, and a high concentration of Cu is generated. + The continuous consumption of free radicals, with the free radical scavenging reaction rate exceeding the free radical formation rate, inhibits CIP degradation. When the ratio is 1:10–1:20, an appropriate amount of Cu... 0 A Cu-Fe bimetallic interface is formed on the nZVI surface, enhancing electron transfer efficiency, and an appropriate amount of Cu... + It can quickly reduce Fe 3+ To avoid Fe 3+ The accumulation of Fe maintained 2+ Continuous activation of PMS. Simultaneously, the material affects Cu. 2+ Adsorption rate at CIP:Cu 2+ It reaches 95% at a ratio of ≥1:20, and then decreases with Cu 2+ With increasing adsorption capacity, the increase in adsorption amount is not significant, while the adsorption rate decreases significantly. For example, at a CIP ratio of 1:100, the adsorption rate drops sharply to 30% due to adsorption site saturation. In summary, the CIP:Cu ratio is determined to be... 2+ =1:20 is the optimal mass ratio, achieving synergistic optimization of degradation efficiency and adsorption capacity.

[0076] The composite material of the present invention has a significantly higher removal capacity for CIP-Cu than that of Comparative Example 2, which also demonstrates that the present invention constructs a three-dimensional graphene oxide-polyacrylic acid composite hydrogel network. This network has a larger specific surface area and excellent mechanical properties, and it contains abundant functional groups, which are beneficial for adsorption, catalysis and loading, thereby improving the heavy metal adsorption performance and ultimately increasing the degradation rate.

[0077] 2. The composite materials prepared in Example 1, Comparative Example 2, and Comparative Example 4, along with sulfide nano-zero-valent iron, were used to conduct adsorption and degradation experiments on ciprofloxacin-copper ion composite pollution. The specific steps are as follows: 0.1 g of the composite materials prepared in Example 1, Comparative Example 2, and Comparative Example 4, along with sulfide nano-zero-valent iron, were weighed and added to 100 mL of water containing ciprofloxacin and copper ions for 120 min. Simultaneously, 0.066 g of potassium persulfate was added. The concentration of ciprofloxacin in the water containing ciprofloxacin and copper ions was 20 mg / L, and the concentration of Cu... 2+ The concentration is 64 mg / L.

[0078] Each group reached adsorption equilibrium at 60 min, and the concentration C of ciprofloxacin at adsorption equilibrium was calculated, and the ratio of C to the initial ciprofloxacin concentration C0 (20 mg / L) was obtained, which was used to characterize the degradation effect of different composite materials on ciprofloxacin, and the adsorption amount Qe of copper ions was calculated, which was used to characterize the adsorption effect of different composite materials on copper ions, and the results are shown in Tables 1 and 2.

[0079] Table 1 Degradation effect of different composite materials on ciprofloxacin in composite pollution at adsorption equilibrium Table 2 Adsorption effect of different composite materials on copper ions in composite pollution at adsorption equilibrium As can be seen from Tables 1 and 2, after the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron prepared by the method of the present application was treated, the C / C0 value of ciprofloxacin was 0.026, and the adsorption amount of copper ions was 60.34 mg / g; after the sulfidized nano zero-valent iron (control group) was treated, the C / C0 value of ciprofloxacin was 0.093, and the adsorption amount of copper ions was 42.75 mg / g; after the polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron prepared by using a single carrier (Comparative Example 2) and the graphene oxide hydrogel loaded with sulfidized nano zero-valent iron (Comparative Example 4) were treated, the C / C0 values of ciprofloxacin were 0.051 and 0.078, and the adsorption amounts of copper ions were 52.53 mg / g and 48.53 mg / g. Therefore, the composite hydrogel prepared by cross-linking graphene oxide and polyacrylic acid as a carrier to load sulfidized nano zero-valent iron has a synergistic effect in improving the degradation of ciprofloxacin and the adsorption of copper ions by the composite material.

[0080] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material, characterized in that, The method comprises the following steps: (1) adding K2S2O8 solution and (NH4)2Ce(NO3)6 solution into the aqueous solution of graphene oxide, heating and mixing to obtain a mixed solution; adding acrylic acid and NaOH solution into the mixed solution in sequence, then adding Na2SO3 solution and stirring, adding a crosslinking agent after the stirring is completed, and reacting until the reaction is completed; collecting the reaction product, drying and crushing to obtain the graphene oxide crosslinked polyacrylic acid hydrogel; (2) mixing NaBH4 and Na2S2O4, dissolving them in water, and stirring to obtain a NaBH4 / Na2S2O4 mixed solution; placing the graphene oxide crosslinked polyacrylic acid hydrogel in a FeSO4·7H2O solution to adsorb iron ions, then taking out the graphene oxide crosslinked polyacrylic acid hydrogel, adding the NaBH4 / Na2S2O4 mixed solution dropwise and reacting until the reaction is completed; collecting the solid precipitate after washing and drying to obtain the graphene oxide crosslinked polyacrylic acid hydrogel loaded with sulfurized nano zero-valent iron composite material.

2. The method of preparing graphene oxide cross-linked polyacrylic acid hydrogel supported sulfidized nano zero-valent iron composite material as claimed in claim 1, wherein, In step (1), the concentration of the aqueous solution of graphene oxide is 1-2 g / L, the concentration of the K2S2O8 solution is 15-25 g / L, the concentration of the (NH4)2Ce(NO3)6 solution is 8-12 g / L, the concentration of the NaOH solution is 5-7 mol / L, and the concentration of the Na2SO3 solution is 15-25 g / L.

3. The method of preparing graphene oxide cross-linked polyacrylic acid hydrogel supported sulfidized nano zero-valent iron composite material as claimed in claim 1, wherein, In step (1), the volume ratio of the aqueous solution of graphene oxide, the K2S2O8 solution, the (NH4)2Ce(NO3)6 solution, the acrylic acid, the NaOH solution, the Na2SO3 solution and the crosslinking agent is (8-12):(8-12):(3-5):10:(11.5-16):(3-5):(4-24).

4. The method for preparing graphene oxide cross-linked polyacrylic acid hydrogel supported sulfidized nano zero-valent iron composite material according to claim 1, characterized in that, In step (1), the mixing time is 10-20 min, the reaction temperature is 45-55℃, and the reaction time is 4-6 h.

5. The method for preparing graphene oxide cross-linked polyacrylic acid hydrogel supported sulfidized nano zero-valent iron composite material according to claim 1, characterized in that, In step (2), the adding amount ratio of NaBH4, Na2S2O4 and water is 1.5 g:(0.005-0.05) g:200 mL; the FeSO4·7H2O solution is prepared by mixing FeSO4·7H2O and water in a ratio of (0.6-5.0) g:250 mL.

6. The method for preparing graphene oxide cross-linked polyacrylic acid hydrogel supported sulfidized nano zero-valent iron composite material according to claim 1, characterized in that, In step (2), the mass ratio of NaBH4, Na2S2O4, FeSO4·7H2O in the FeSO4·7H2O solution and the graphene oxide crosslinked polyacrylic acid hydrogel is 1.5 g:(0.005-0.11) g:(0.6-5.0) g:0.5 g; the stirring time is 25-35 min, and the reaction time is 25-35 min.

7. The graphene oxide crosslinked polyacrylic acid hydrogel loaded with sulfurized nano zero-valent iron composite material prepared by the preparation method of any one of claims 1-6.

8. The application of the graphene oxide crosslinked polyacrylic acid hydrogel loaded with sulfurized nano zero-valent iron composite material of claim 7 in simultaneously removing the composite pollution of the copper ions and the heavy metal copper ions in water.

9. Use according to claim 8, wherein the compound is ###0002### The specific steps are: the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material in claim 7 is added to the water body containing ciprofloxacin-heavy metal copper ion composite pollution to process 1h-2h; Wherein, the material-liquid ratio of the graphene oxide cross-linked polyacrylic acid hydrogel loaded with sulfidized nano zero-valent iron composite material and the water body containing ciprofloxacin-heavy metal copper ion composite pollution is (0.05-0.15) g:100 mL.

10. Use according to claim 9, wherein In the water body containing ciprofloxacin-heavy metal copper ion complex pollution, the concentration of ciprofloxacin is 15-25 mg / L, the concentration ratio of ciprofloxacin and Cu 2+ is (0.01-10):1.

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