Adsorptive photocatalytic hydrogel material and preparation method and application thereof

Abstract

The present application is suitable for the technical field of water pollution treatment, and provides an adsorption type photocatalytic hydrogel material, a preparation method and application thereof. The present application successfully realizes the synergistic degradation of antibiotics in high-salinity wastewater through loading Ag2CO3 on a defect type SnZnAl-LDH, cross-linking with sodium alginate through calcium chloride to form a hydrogel material. The heterojunction design significantly improves the photocatalytic activity, and the tetracycline degradation efficiency is more than 90% within 30 min, and the high-salt stability of Ag2CO3 is also improved. The material maintains structural stability and mechanical strength in a high-salt environment, can be reused for 5 times, and the degradation efficiency is maintained above 85%. In addition, the material integrates double functions to simplify the treatment process, and can be recycled, and the salt after treatment can be recovered through evaporation crystallization to realize resource utilization, and the goal of developing a material with high adsorption capacity and stable photocatalytic activity and improving the degree of resource utilization is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water pollution treatment, and particularly relates to an adsorption type photocatalytic hydrogel material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of medicine, chemical industry and animal husbandry, antibiotic pollutants (such as tetracyclines, sulfonamides and quinolones) continuously enter the water environment through medical waste, pharmaceutical wastewater, domestic sewage and breeding wastewater, leading to the increasingly serious problem of antibiotic pollution in high-salinity wastewater. At present, high-salinity wastewater treatment technologies mainly include physical-chemical methods, advanced oxidation methods and biological methods. Among them, although membrane separation technology (such as reverse osmosis and nanofiltration) in the physical-chemical method can effectively desalt, it is easily polluted by salt and produces high-salt concentrated water which needs further treatment; although evaporation crystallization technology (such as MVR) can realize salt recovery, it has the shortcomings of high energy consumption, complex process and high cost. The advanced oxidation method (such as Fenton and ozone oxidation) can decompose organic matter, but it has poor adaptability to high-salinity environment, and the additional reagent may introduce secondary pollution. Although the biological treatment technology (such as salt-tolerant bacteria method) is environmentally friendly, the microbial activity is severely inhibited in the high-salinity environment, resulting in low treatment efficiency.

[0003] In the field of antibiotic degradation, photocatalytic technology (such as TiO2 and ZnO) and adsorption technology (activated carbon and ion exchange resin) are commonly used methods, but they are usually used independently and difficult to achieve synergistic effect. Photocatalytic technology is easily inhibited in high-salinity environment (such as ion competitive adsorption and intensified electron-hole recombination), and the catalyst is difficult to recover; adsorption technology can enrich pollutants, but lacks degradation ability and needs subsequent treatment. In recent years, researchers have tried to combine adsorption with photocatalysis, such as loading photocatalysts on porous adsorption materials, but there are still the following shortcomings: 1) the catalyst is easily inactivated in high-salinity environment; 2) it is difficult to simultaneously optimize the adsorption and photocatalytic efficiency; 3) the material is difficult to recycle, increasing the treatment cost; 4) the preparation process of the composite material is complex, and it is difficult to realize large-scale application.

[0004] Hydrogel as a carrier material shows application potential in wastewater treatment. For example, sodium alginate-based hydrogel has good biocompatibility and crosslinking ability, and can form a stable structure through ionic crosslinking. Sodium alginate hydrogel can still maintain a water absorption rate of 85 times in high-salinity environment, and the salt tolerance can be further improved by compounding with other materials. However, the existing hydrogel loaded with photocatalysts generally has the problems of low catalytic efficiency, poor material stability and difficulty in effective operation in high-salinity environment.

[0005] In recent years, layered hydrogen hydroxides (LDHs) have attracted widespread attention in the environmental field due to their unique layered structure and excellent adsorption and catalytic properties. LDHs can be loaded with photocatalytically active components through methods such as interlayer anion exchange and surface modification to construct adsorption-photocatalytic synergistic systems. Ag₂CO₃, as a visible light-responsive photocatalyst, possesses high photocatalytic activity but suffers from poor stability and susceptibility to photocorrosion. Loading Ag₂CO₃ onto LDHs can improve their stability and photocatalytic efficiency.

[0006] However, research on combining LDH-based composites with hydrogels to construct hydrogel materials with synergistic adsorption and photocatalysis effects for the degradation of antibiotics in high-salinity wastewater is still relatively lacking. Therefore, developing a material that achieves highly efficient synergy between adsorption and photocatalysis is of great significance for the removal of antibiotics from high-salinity wastewater.

[0007] Therefore, this invention proposes an adsorption-type photocatalytic hydrogel material, its preparation method, and its application. Summary of the Invention

[0008] The purpose of this invention is to provide an adsorption-type photocatalytic hydrogel material, its preparation method, and its application, in order to solve the problems mentioned in the background art.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] An adsorption-type photocatalytic hydrogel material is composed of defective SnZnAl-LDH, Ag2CO3, and a sodium alginate hydrogel network. The defective SnZnAl-LDH is synthesized by a hydrothermal method and oxygen vacancies are introduced by alkaline etching. The Ag2CO3 is loaded onto the surface of the defective SnZnAl-LDH by in-situ precipitation to form a heterojunction structure. The sodium alginate hydrogel network forms a stable three-dimensional network through crosslinking of sodium alginate and calcium chloride.

[0011] Furthermore, in the sodium alginate hydrogel network, the concentration of sodium alginate is 1-5 wt%, and the concentration of calcium chloride is 2-10 wt%.

[0012] A method for preparing the above-described adsorption-type photocatalytic hydrogel material includes the following steps:

[0013] Step 1: Synthesize defective SnZnAl-LDH;

[0014] Preparation containing Sn 2+ Zn 2+ Al 3+ A mixed solution of Sn and urea, wherein Sn 2+ Derived from stannous chloride dihydrate, Zn 2+Derived from zinc sulfate heptahydrate, Al 3+ Derived from aluminum sulfate octadechydrate; the mixed solution was subjected to a hydrothermal reaction to obtain SnZnAl-LDH; SnZnAl-LDH was subjected to alkaline etching treatment, stirred and reacted, centrifuged, washed and dried to obtain defective SnZnAl-LDH;

[0015] Step 2: Load Ag2CO3 onto the defective SnZnAl-LDH surface using an in-situ precipitation method;

[0016] Defective SnZnAl-LDH was dispersed in deionized water, silver nitrate was added, and the mixture was stirred. Sodium carbonate solution was added, and the reaction was continued with stirring to allow Ag2CO3 to precipitate in situ on the surface of the defective SnZnAl-LDH. After the reaction was completed, the Ov@LDH / Ag2CO3 composite material was obtained by sedimentation, centrifugation, washing, and drying.

[0017] Step 3: Prepare the hydrogel;

[0018] The Ov@LDH / Ag2CO3 composite material was dispersed in deionized water, sodium alginate was added, and the mixture was stirred until a homogeneous colloidal solution was formed. The colloidal solution was then dropped into a calcium chloride solution to crosslink and form stable hydrogel particles.

[0019] Furthermore, in step 1, the hydrothermal reaction conditions are: reaction temperature 200℃, reaction time 24 h; the alkaline solution used for alkaline etching is sodium hydroxide solution; washing is performed by alternating washing with anhydrous ethanol and deionized water, and the supernatant is removed by centrifugation at 3000 rpm for 5 min after each washing; the drying conditions are: drying temperature 70℃, drying time 12 h.

[0020] Furthermore, in step 2, the mass ratio of defective SnZnAl-LDH to silver nitrate is 2:1; the sodium carbonate solution is obtained by dissolving anhydrous sodium carbonate in deionized water, and the mass ratio of anhydrous sodium carbonate to silver nitrate is 1:1; washing is performed by alternating washing with anhydrous ethanol and deionized water, and the supernatant is removed by centrifugation at 3000 rpm for 5 min after each washing; the drying conditions are: drying temperature 70℃, drying time 12 h.

[0021] Furthermore, in step 3, the colloid is dripped into the calcium chloride solution at a constant rate using a 1 mL syringe with the needle removed, and the cross-linking standing time is 12 h.

[0022] An application of the above-described adsorption-type photocatalytic hydrogel material in the degradation of antibiotics in high-salt wastewater, wherein the salt concentration of the high-salt wastewater is 10-500 mM NaCl, and the antibiotic is tetracycline.

[0023] Furthermore, the specific implementation of the application is as follows:

[0024] Adsorption-type photocatalytic hydrogel materials were added to high-salt wastewater containing antibiotics;

[0025] Under illumination, the hydrogel material can simultaneously perform adsorption and photocatalytic degradation; the illumination conditions are natural light or simulated sunlight.

[0026] After processing, the hydrogel material is recycled, washed, and reused.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] This invention successfully achieves the adsorption and photocatalytic synergistic degradation of antibiotics in high-salt wastewater by loading Ag2CO3 onto defective SnZnAl-LDH and cross-linking it with sodium alginate via calcium chloride to form a hydrogel material. This solves the problems of low efficiency, complex process, and poor resource utilization of single technologies. Specifically, the results are as follows: The heterojunction design of defective SnZnAl-LDH and Ag2CO3 significantly enhances photocatalytic activity, achieving a tetracycline degradation efficiency exceeding 90% within 30 minutes. This heterojunction also solves the stability problem of Ag2CO3 in high-salt environments, inhibiting electron-hole recombination to improve catalytic efficiency. By optimizing the crosslinking conditions of the sodium alginate hydrogel, it maintains structural stability and mechanical strength even in high-salt environments. It possesses both adsorption capabilities to enrich antibiotics and shorten the contact distance with the catalyst, forming an adsorption-photocatalytic synergistic effect. Furthermore, the hydrogel material can be reused more than 5 times while maintaining a degradation efficiency of over 85%, solving the catalyst recovery problem. In addition, this material integrates adsorption and photocatalytic functions, avoiding the complexity and high cost of traditional multi-step processing. The hydrogel is recyclable, and the treated salt can be recovered through evaporation and crystallization, achieving resource utilization. This achieves the goal of developing materials with both high adsorption capacity and stable photocatalytic activity, while improving resource utilization. Attached Figure Description

[0029] Figure 1 High-resolution transmission electron microscopy (HRTEM) image of Ov@LDH / Ag2CO3.

[0030] Figure 2 X-ray diffraction (XRD) spectra of Ov@LDH / Ag2CO3, Ag2CO3, and Ov@LDH.

[0031] Figure 3 The BET spectra are for Ov@LDH / Ag2CO3, Ag2CO3, and Ov@LDH.

[0032] Figure 4X-ray photoelectron spectroscopy (XPS) analysis of Ov@LDH / Ag2CO3, Ag2CO3, and Ov@LDH; where: a is the XPS full scan spectrum; b is the O 1s spectrum.

[0033] Figure 5 The electron paramagnetic resonance (EPR) oxygen defect spectra of Ov@LDH / Ag2CO3 and Ov@LDH are shown.

[0034] Figure 6 The results are from a free radical capture experiment.

[0035] Figure 7 The efficiency of photocatalytic degradation of tetracycline by Ov@LDH / Ag2CO3 material.

[0036] Figure 8 The efficiency of Ov@LDH / Ag2CO3 material in photocatalytic degradation of tetracycline under different sodium chloride concentrations was measured.

[0037] Figure 9 The cycling stability of the Ov@LDH / Ag2CO3 material. Detailed Implementation

[0038] To provide a clearer understanding of the technical features, objectives, and beneficial effects of this invention, the technical solution of this invention is described in detail below, but this should not be construed as limiting the scope of implementation of this invention. In this invention, materials, reagents, or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] The required chemical reagents, stannous chloride dihydrate (SnCl2·2H2O), aluminum sulfate octadechydrate (Al2(SO4)3·18H2O), zinc sulfate heptahydrate (ZnSO4·7H2O), urea (CH4N2O), ethylene glycol, sodium chloride (NaCl), and sodium hydroxide (NaOH), were all purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Tetracycline (TCH) was purchased from Sangon Biotech (Shanghai) Co., Ltd.

[0040] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0041] Example 1: Preparation of adsorption-type photocatalytic hydrogel materials;

[0042] This hydrogel material is composed of the following components:

[0043] Defective SnZnAl-LDH: Synthesized via hydrothermal method, introducing Sn 2+ / Sn 4+ By regulating the interlayer structure and combining alkaline etching technology to form oxygen vacancies (Ov), the density of active sites can be increased, thus exhibiting both adsorption and photocatalytic properties.

[0044] Ag2CO3: It is loaded onto the surface of defective SnZnAl-LDH by in-situ precipitation to form a heterojunction structure, which can both inhibit photocorrosion and further enhance photocatalytic activity.

[0045] Sodium alginate hydrogel network: As a carrier material, it forms a stable three-dimensional network by cross-linking with calcium chloride, and has both physical adsorption function and catalyst immobilization function.

[0046] The specific preparation steps are as follows:

[0047] (1) Synthesis of defective SnZnAl-LDH:

[0048] First, dissolve 0.17 g of stannous chloride dihydrate in 1 mL of ethylene glycol and sonicate for 1 min, denoted as solution A. Dissolve 3.7 g of aluminum sulfate octahydrate in 15 mL of deionized water, sonicate for 5 min, and magnetically stir for 5 min. Repeat the sonication-magnetic stirring process 3-5 times to form a homogeneous solution, denoted as solution B. Dissolve 7.8 g of zinc sulfate heptahydrate in 15 mL of deionized water, sonicate for 5 min, and magnetically stir for 10 min to form a homogeneous solution, denoted as solution C. Dissolve 9 g of urea in 39 mL of deionized water, sonicate for 10 min, and stir clockwise at a uniform speed using a glass stirring rod to form a homogeneous solution, denoted as solution D. Then, pour solutions A-D sequentially into 100 mL beakers, sonicate for 10 min, and stir for 10 min, denoted as solution E. Transfer solution E to a 100 mL polytetrafluoroethylene-lined reactor and place it in a muffle furnace, reacting at 200℃ for 24 h. After the reaction is complete and cooled to room temperature, the reaction vessel is opened, the supernatant is removed, and the precipitate is transferred to a 50 mL centrifuge tube. The precipitate is centrifuged at 3000 rpm for 5 min, and the supernatant is removed. Next, 30 mL of anhydrous ethanol is added and the mixture is thoroughly shaken and washed for 5 min, then centrifuged at 3000 rpm for 5 min. The supernatant is removed, and then 30 mL of deionized water is added and thoroughly shaken and washed for 5 min, then centrifuged at 3000 rpm for 5 min. This washing process of "anhydrous ethanol—centrifugation—deionized water—centrifugation" is repeated 3-5 times. The supernatant is removed, and the washed precipitate is placed in a 60℃ electric heating oven and dried for 12 h. The dried precipitate is SnZnAl-LDH (labeled as LDH), which is stored at room temperature for later use.

[0049] Furthermore, defective SnZnAl-LDH was prepared by alkaline etching: 0.2 g of the prepared LDH was dispersed in 45 mL of deionized water, sonicated for 5 min, and then continuously stirred magnetically for 10 min. 5 mL of sodium hydroxide (1 M) was then added, and the mixture was continuously stirred magnetically for 3 h. After the reaction, the solution was transferred to a 50 mL centrifuge tube and centrifuged at 3000 rpm for 5 min. This process was repeated 3-5 times: washing thoroughly with anhydrous ethanol for 5 min – centrifuging at 3000 rpm for 5 min – washing thoroughly with deionized water for 5 min – centrifuging at 3000 rpm for 5 min. The precipitate was then dried in a 70℃ electric heating oven for 12 h. The dried precipitate was the defective SnZnAl-LDH (labeled Ov@LDH), which was stored at room temperature for later use.

[0050] (2) Loading of Ag2CO3:

[0051] First, 100 mg of the prepared Ov@LDH was dispersed in 50 mL of deionized water, sonicated for 5 min, and then magnetically stirred for 5 min. Next, 50 mg of silver nitrate was added, sonicated for 5 min, and then magnetically stirred for 10 min to ensure complete adsorption and mixing of Ov@LDH and silver nitrate. This solution is denoted as solution F. Then, 50 mg of anhydrous sodium carbonate was dissolved in 50 mL of deionized water, sonicated for 5 min, and magnetically stirred for 5 min. This solution is denoted as solution G. Finally, solution G was slowly added dropwise to solution F under continuous magnetic stirring, and the stirring was continued for 1 h. After the reaction was completed, the mixture was allowed to settle naturally for 30 min. The supernatant was removed, and the precipitate was transferred to a 50 mL centrifuge tube and centrifuged at 3000 rpm for 5 min. Then, it was washed with anhydrous ethanol and deionized water for 5 min each (centrifuged at 3000 rpm for 5 min after each wash). The precipitate was then transferred to a 70℃ electric heating drying oven and dried for 12 h. The dried precipitate is the defective SnZnAl-LDH supported Ag2CO3 material (labeled as Ov@LDH / Ag2CO3) and stored at room temperature for later use.

[0052] (3) Preparation of hydrogels:

[0053] First, 0.3 g of the prepared Ov@LDH / Ag2CO3 was dispersed in 10 mL of deionized water and sonicated for 5 min with continuous magnetic stirring. Then, 0.15 g of sodium alginate (1.5 wt%) was added, and stirring was continued for 10–12 h until a homogeneous colloidal solution was formed, denoted as solution H. Using a 1 mL syringe (without the needle), the well-mixed solution H was slowly and uniformly added dropwise to 100 mL of calcium chloride solution (2 wt%), ensuring that the gel particles were of uniform size. The solution was allowed to stand for 12 h to stabilize. The material after the reaction was completed was the prepared hydrogel, which was stored in a 2 wt% calcium chloride solution for later use. Before each use, the hydrogel was rinsed 3–5 times with deionized water to remove the calcium chloride solution from the surface.

[0054] Example 2: Characterization of adsorption-type photocatalytic hydrogel materials;

[0055] High-resolution transmission electron microscopy (HRTEM) analysis of the Ov@LDH / Ag2CO3 heterojunction showed that ( Figure 1 The Ov@LDH and Ag2CO3 components exhibit different morphological characteristics. Specifically, Ag2CO3 exists as a granular structure, while Ov@LDH exhibits a rod-like structure. The two are tightly bonded together, forming a unique heterojunction structure. The coupling of Ag2CO3 on the Ov@LDH surface does not affect the morphology of the Ov@LDH substrate, thus preserving the inherent properties of Ov@LDH.

[0056] XRD analysis was performed on the crystal structures of Ov@LDH, Ag2CO3, and Ov@LDH / Ag2CO3, as follows: Figure 2 As shown, the Ov@LDH / Ag2CO3 composite material exhibits characteristic diffraction peaks associated with Ov@LDH and Ag2CO3, corresponding to the 11.6° (003) crystal plane, 14.4° (020) crystal plane, 28.2° (021) crystal plane, 32.6° (104) crystal plane, and 34.5° (012) crystal plane of Ov@LDH (JCPDS No. 48-1021, JCPDS No. 74-1895 and JCPDS No. 83-1765) and the 18.6° (020) crystal plane, 20.5° (110) crystal plane, 39.6° (031) crystal plane and 32.6° (-101) crystal plane of Ag2CO3 (JCPDS No. 70-2184). Furthermore, the diffraction peaks of Ov@LDH / Ag2CO3 showed a slight shift relative to Ov@LDH and Ag2CO3, further supporting the formation of the Ov@LDH / Ag2CO3 heterojunction. This is because the introduction of Ag2CO3 into the structure of Ov@LDH leads to a change in lattice parameters, which in turn causes a characteristic shift in the diffraction peak positions.

[0057] also, Figure 3The N2 adsorption-desorption isotherms of Ov@LDH, Ag2CO3, and Ov@LDH / Ag2CO3, along with the resulting pore size distribution, are shown. It can be seen that all three samples exhibit type IV isotherms and typical H3 periodic closed loops, indicating that the material is a layered or layered polymer capable of forming slits. This is consistent with the layered structure characteristic of Ov@LDH, which has adjustable interlayer spacing. Specifically, the BET (specific surface area) of Ov@LDH, Ag2CO3, and Ov@LDH / Ag2CO3 are 126.59, 4.03, and 95.54 m², respectively. 2 The decrease in specific surface area of ​​Ov@LDH / Ag2CO3 is likely due to some Ag2CO3 entering the pore structure of Ov@LDH during Ag2CO3 loading. This phenomenon is consistent with the HRTEM characterization results, which show a close relationship between the two. Based on the average pore size, these three materials have similar pore structures; all samples exhibit micropores, mesopores, and macropores, with pore sizes concentrated in the 0–30 nm range. These hierarchical pores contribute to optimized impedance matching. Furthermore, the large surface area, mesopores, and multilayer hollow cavities of Ov@LDH / Ag2CO3 provide numerous heterointerfaces, which can improve dielectric properties and facilitate photocurrent transfer, thereby enhancing photocatalytic performance.

[0058] XPS analysis was used to analyze Ov@LDH, Ag2CO3 and Ov@LDH / Ag2CO3 ( Figure 4 The elemental composition, molecular structure, and chemical bonding of Ov@LDH / Ag2CO3 were comprehensively analyzed. The results showed that elements from both Ov@LDH and Ag2CO3 were present in the Ov@LDH / Ag2CO3 material. Compared to pure Ov@LDH, the peak intensities of C, O, and Ag in Ov@LDH / Ag2CO3 increased, indicating successful coupling of Ag2CO3, as the Ag2CO3 molecule contributed additional C, O elements, and the new element Ag to the composite structure. The high-resolution O 1s spectrum of Ov@LDH (…) was also analyzed. Figure 4 In (b), peaks appear at 533.3, 532.1, 531.1, and 529.9 eV, corresponding to Os (0.96%), Ov (11.91%), M-OH (30.36%), and MO (56.77%), respectively. The Ov (11.91%) and M-OH (30.36%) peaks are particularly significant, reflecting the abundance of oxygen vacancies and hydroxyl groups in Ov@LDH. The high-resolution O 1s spectrum of Ag2CO3 shows only one peak at 531.1 eV. Notably, in Ov@LDH / Ag2CO3, the intensity of the 531.1 eV peak corresponding to M-OH is significantly higher than that of Ov@LDH, indicating an increase in O content due to Ag2CO3 coupling. Furthermore, the Ov proportion significantly increases from 11.91% to 25.11%.

[0059] Further EPR was used to detect Ov in Ov@LDH / Ag2CO3 and Ov@LDH. Figure 5 The results showed that the Ov concentration in Ov@LDH / Ag2CO3 was significantly higher than that in Ov@LDH. This may be due to the lattice strain generated during the loading of Ag2CO3, which in turn increased the Ov concentration.

[0060] Mechanistic data of adsorption-photocatalysis synergistic effect: free radical capture experiment ( Figure 6 The results showed that the addition of TEA (hole scavenger), 4-BQ (superoxide radical scavenger), and IPA (hydroxyl radical scavenger) significantly inhibited the degradation rate, with the TEA and 4-BQ groups exhibiting particularly significant inhibition. This indicates that the main active species in the system are holes and superoxide radicals, followed by hydroxyl radicals, demonstrating that Ov@LDH / Ag2CO3 possesses excellent photogenerated electron-hole separation capabilities.

[0061] Example 3: Performance test of photocatalytic degradation of tetracycline;

[0062] The photocatalytic degradation of TCH in aqueous solution was evaluated by irradiating a photocatalyst suspension with a 300 W xenon lamp source (PLS-SXE300+ / UV from Beijing Pofila Technology Co., Ltd.) equipped with a <420 nm filter. This filter can transmit wavelengths from 420 to 780 nm. In the specific experiment, 20 mg of photocatalyst was added to a beaker containing 100 mL of TCH solution (10 mg / L), and the mixture was stirred in the dark for 30 min to reach adsorption-desorption equilibrium. At each irradiation interval, 1 mL of the suspension was taken and filtered through a 0.22 μm filter membrane. All experiments were performed in triplicate.

[0063] The Ov@LDH / Ag2CO3 material was applied to treat TCH wastewater with different initial concentrations (5, 10, 15, 20 mg / L). The experimental results showed that ( Figure 7 When the TCH concentration increased from 5 mg / L to 20 mg / L, the adsorption efficiency of the material showed a slight decreasing trend. This may be because, under the same temperature and time conditions, the total amount of pollutants that a fixed amount of material can adsorb tends to be consistent, and the relative adsorption rate naturally decreases with the increase of TCH concentration. However, after the light source was turned on, the degradation efficiency of TCH at all concentrations reached over 90% after 30 minutes of reaction. Therefore, the prepared Ov@LDH / Ag2CO3 material can not only achieve rapid adsorption-photocatalytic degradation of low-concentration TCH, but also effectively meet the degradation requirements of high-concentration TCH, demonstrating its wide applicability.

[0064] Furthermore, the Ov@LDH / Ag2CO3 material was applied to wastewater with different salinities (NaCl concentrations) to conduct TCH degradation experiments. Figure 8 Experimental results show that as the NaCl concentration increases from 10 mM to 500 mM, the overall trend of adsorption-photocatalysis first increases and then decreases. However, under both 10 mM and 500 mM high-salt conditions, the degradation efficiency of Ov@LDH / Ag2CO3 for TCH can reach over 94%. This is not only higher than the degradation efficiency under NaCl-free conditions, but also slightly improved in systems containing NaCl. This demonstrates that Ov@LDH / Ag2CO3 still possesses excellent pollutant degradation capabilities under high-salt environments.

[0065] To evaluate the cycling stability of the Ov@LDH / Ag2CO3 material, a cycling experiment was conducted. Under the same conditions, multiple sets of experimental materials were recovered, washed, dried, and then accurately weighed again (20 mg each time). Each sample was then added to 100 mL of a 10 mg / L TCH solution for photocatalytic degradation. The results showed (…). Figure 9 Even after five cycles, the degradation efficiency of TCH remained above 85% in the fifth experiment. The slight decrease in degradation efficiency may be due to the fact that incompletely mineralized intermediates were not completely removed after simple water washing in the earlier cycles. These residues adhered to the material surface or blocked pores, thus affecting the degradation effect of free radicals on TCH.

[0066] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. An adsorption-type photocatalytic hydrogel material, characterized in that, It is composed of defective SnZnAl-LDH, Ag2CO3, and a sodium alginate hydrogel network. The defective SnZnAl-LDH is synthesized by hydrothermal method and oxygen vacancies are introduced by alkaline etching treatment. The Ag2CO3 is loaded onto the surface of the defective SnZnAl-LDH by in-situ precipitation to form a heterojunction structure. The sodium alginate hydrogel network forms a stable three-dimensional network through cross-linking of sodium alginate and calcium chloride. The preparation method of the adsorption-type photocatalytic hydrogel material includes the following steps: Step 1: Synthesize defective SnZnAl-LDH; Preparation containing Sn 2+ Zn 2+ Al 3+ A mixed solution of Sn and urea, wherein Sn 2+ Derived from stannous chloride dihydrate, Zn 2+ Derived from zinc sulfate heptahydrate, Al 3+ Derived from aluminum sulfate octadechydrate; the mixed solution was subjected to a hydrothermal reaction to obtain SnZnAl-LDH. The hydrothermal reaction conditions were: reaction temperature 200℃, reaction time 24 h; SnZnAl-LDH was subjected to alkaline etching treatment, stirred and reacted, centrifuged, washed and dried to obtain defective SnZnAl-LDH. Step 2: Load Ag2CO3 onto the defective SnZnAl-LDH surface using an in-situ precipitation method; Defective SnZnAl-LDH was dispersed in deionized water, silver nitrate was added, and the mixture was stirred. Sodium carbonate solution was added, and the reaction was continued with stirring to allow Ag2CO3 to precipitate in situ on the surface of the defective SnZnAl-LDH. After the reaction was completed, the Ov@LDH / Ag2CO3 composite material was obtained by sedimentation, centrifugation, washing, and drying. Step 3: Prepare the hydrogel; The Ov@LDH / Ag2CO3 composite material was dispersed in deionized water, sodium alginate was added, and the mixture was stirred until a homogeneous colloidal solution was formed. The colloidal solution was then dropped into a calcium chloride solution to crosslink and form stable hydrogel particles.

2. The adsorption-type photocatalytic hydrogel material according to claim 1, characterized in that, In the sodium alginate hydrogel network, the concentration of sodium alginate is 1-5 wt%, and the concentration of calcium chloride is 2-10 wt%.

3. A method for preparing an adsorption-type photocatalytic hydrogel material according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Synthesize defective SnZnAl-LDH; Preparation containing Sn 2+ Zn 2+ Al 3+ A mixed solution of Sn and urea, wherein Sn 2+ Derived from stannous chloride dihydrate, Zn 2+ Derived from zinc sulfate heptahydrate, Al 3+ Derived from aluminum sulfate octadechydrate; the mixed solution was subjected to a hydrothermal reaction to obtain SnZnAl-LDH. The hydrothermal reaction conditions were: reaction temperature 200℃, reaction time 24 h; SnZnAl-LDH was subjected to alkaline etching treatment, stirred and reacted, centrifuged, washed and dried to obtain defective SnZnAl-LDH. Step 2: Load Ag2CO3 onto the defective SnZnAl-LDH surface using an in-situ precipitation method; Defective SnZnAl-LDH was dispersed in deionized water, silver nitrate was added, and the mixture was stirred. Sodium carbonate solution was added, and the reaction was continued with stirring to allow Ag2CO3 to precipitate in situ on the surface of the defective SnZnAl-LDH. After the reaction was completed, the Ov@LDH / Ag2CO3 composite material was obtained by sedimentation, centrifugation, washing, and drying. Step 3: Prepare the hydrogel; The Ov@LDH / Ag2CO3 composite material was dispersed in deionized water, sodium alginate was added, and the mixture was stirred until a homogeneous colloidal solution was formed. When the colloidal solution is dropped into a calcium chloride solution, it crosslinks to form stable hydrogel particles.

4. The preparation method according to claim 3, characterized in that, In step 1, the alkaline solution used for alkaline etching is sodium hydroxide solution; washing is performed by alternating washing with anhydrous ethanol and deionized water, and the supernatant is removed after each washing by centrifugation at 3000 rpm for 5 min; the drying conditions are: drying temperature 70℃, drying time 12 h.

5. The preparation method according to claim 3, characterized in that, In step 2, the mass ratio of defective SnZnAl-LDH to silver nitrate is 2:1; the sodium carbonate solution is obtained by dissolving anhydrous sodium carbonate in deionized water, and the mass ratio of anhydrous sodium carbonate to silver nitrate is 1:1; washing is performed by alternating washing with anhydrous ethanol and deionized water, and the supernatant is removed by centrifugation at 3000 rpm for 5 min after each washing; the drying conditions are: drying temperature 70℃, drying time 12 h.

6. The preparation method according to claim 3, characterized in that, In step 3, the colloid is dripped into the calcium chloride solution at a constant rate using a 1mL syringe with the needle removed, and the cross-linking and standing time is 12 hours.

7. An application of the adsorption-type photocatalytic hydrogel material according to claim 1 or 2 in the degradation of antibiotics in high-salt wastewater, characterized in that, The salt concentration of the high-salt wastewater is 10-500 mM NaCl, and the antibiotic is tetracycline.

8. The application according to claim 7, characterized in that, The specific implementation of the application is as follows: Adsorption-type photocatalytic hydrogel materials were added to high-salt wastewater containing antibiotics; Under illumination, the hydrogel material can simultaneously perform adsorption and photocatalytic degradation; the illumination conditions are natural light or simulated sunlight. After processing, the hydrogel material is recycled, washed, and reused.

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