Preparation method and application of HLDT hydrogel capable of being continuously used for adsorption and desorption of Fe < 3 + >, Cd < 2 + > and Pb < 2 + >

Abstract

The invention relates to the technical field of hydrogel materials and environmental remediation, and discloses a preparation method and application of HLDT hydrogel capable of continuously adsorbing and desorbing heavy metals, levodopa and tannic acid are co-grafted to hyaluronic acid through a condensation reaction for the first time, Na-AMPS is grafted to a hyaluronic acid derivative through a free radical polymerization reaction, and the HLDT hydrogel capable of continuously adsorbing and desorbing the heavy metals is obtained. More functional groups with heavy metal ion absorption capability are introduced, and the HLDT hydrogel is developed. The HLDT hydrogel has stable swelling property and antibacterial activity, shows remarkable absorption capacity to Fe < 3 + >, Cd < 2 + > and Pb < 2 + > ions, the absorption rates are 76.1%, 46.4% and 59.5% respectively, the HLDT hydrogel becomes an ideal selection for recovery due to the excellent absorption, desorption and regeneration capacity and the tolerance to 1M HCl, and when the HLDT hydrogel is used for treating sorghum in different heavy metal solutions, the recovery rate is greatly improved. Germination and growth of sorghum are remarkably improved, the HLDT hydrogel can effectively remove heavy metal ions in polluted soil, the growth characteristics of different sorghum varieties are enhanced, and the content of heavy metal is reduced.

Description

Technical Field

[0001] The present invention relates to the technical fields of polymer hydrogel materials and environmental soil remediation, and particularly to a preparation method and use of an HLDT hydrogel that can be sustainably used for Fe3+ , Cd2+ and Pb2+ adsorption and desorption. Background Art

[0002] The persistent stability, inability to naturally degrade, and potential to accumulate in biological systems of heavy metals in soil pose a serious threat to the ecological balance and human well-being. These pollutants can have adverse effects on living organisms through various exposure pathways and may endanger the aquatic environment and human physiological processes.

[0003] In recent years, sorption has emerged as a prominent method for heavy metal removal, characterized by simplicity, high performance, economic feasibility, and environmental friendliness. The development of effective sorbent materials is crucial for the successful elimination of heavy metal ions. Researchers have explored various materials such as activated carbon, clay minerals, agricultural by-products, polymers, and nanomaterials. Among them, polymeric substances with carboxyl, hydroxyl, amino, and sulfonic acid groups have shown excellent capabilities in heavy metal ion extraction.

[0004] Hydrogels have extensive applications in fields such as tissue engineering, drug delivery, water treatment, and environmental solutions. Hydrogels based on natural polymers have attracted significant research interest due to their environmental friendliness and biocompatibility characteristics. Hyaluronic acid (HA), as a particularly promising material, is renowned for its excellent biocompatibility and rich functional group composition. Although natural HA contains carboxyl and hydroxyl groups that can interact with heavy metal ions, its inherent metal-binding ability is still limited, and thus requires strategic modification to improve its performance.

[0005] Tannic acid (TA), as a polyphenolic compound, exhibits excellent potential in heavy metal removal due to its unique molecular structure, which has multiple phenolic hydroxyl groups and strong metal-binding ability. Its complex molecular configuration has numerous galloyl and hydroxyl groups, which can form stable metal ion complexes through coordination and hydrogen bonding. Scientific research has consistently confirmed the effectiveness of TA in eliminating heavy metal pollutants in environmental matrices. The remarkable metal ion-binding characteristics of TA make it a promising solution in environmental remediation strategies.

[0006] L-DOPA contains numerous carboxyl and phenolic hydroxyl functional groups, which can form strong metal ion coordination complexes. Its structural features have attracted interest in potential environmental remediation, particularly in the extraction of metal ions from contaminated water sources. Despite extensive research on the metal binding mechanism, the investigation of the ability of levodopa to adsorb metal ions in the soil environment remains limited.

[0007] Similarly, polymeric substances containing sulfonic acid groups have shown significant potential for eliminating heavy metal ions. The sulfonic acid groups ( -SO3H exhibit strong metal binding capabilities through mechanisms such as ion exchange, electrostatic interaction, and chelation. 2-Acrylamide-2-methylpropanesulfonic acid (AMPS) is a promising monomer for developing such materials due to its acidity and metal ion binding potential. The sulfonic acid groups provide stable binding sites for metal ions, while the amide groups contribute to metal coordination. AMPS-based materials have excellent water solubility and stability under different pH conditions. Studies have shown that cross-linked AMPS copolymers can effectively remove various metal ions, such as Cu(II), Pb(II), and Cd(II). By integrating AMPS into different polymer structures, researchers have created functional materials, including hydrogels, membranes, and nanocomposites. When neutralized with sodium hydroxide, Na-AMPS generates a large number of sulfonate groups that can capture heavy metal ions through ion exchange and coordination mechanisms.

[0008] The combination of biotechnology and chemical methods has the potential to be effective in soil remediation and expanding downstream applications. Notably, sorghum, as a versatile C4 crop, plays a crucial role in the food, feed, beverage, biofuel, and industrial sectors. With its excellent adaptability and high biomass, sorghum has shown potential in the phytoremediation of heavy metal-contaminated soils. Its C4 photosynthesis pathway enables it to efficiently convert light energy and produce a large amount of biomass, making sorghum a key resource for addressing environmental challenges and energy transition. The rich genetic diversity and sustainable characteristics of this crop highlight its importance in the agricultural and energy sectors. Such a comprehensive remediation strategy not only reduces treatment costs but also minimizes secondary pollution to the ecosystem, providing an innovative and sustainable solution for soil environmental management.

[0009] The HLDT hydrogel of the present invention promotes the inclusion of Fe3+ , Cd2+ and Pb2+Absorption of various heavy metal ions, aiming to promote the development of multifunctional polysaccharide-based absorbent materials. The present invention investigated the characteristics of the HLDT hydrogel, its ion absorption capacity, the effects on sorghum seed germination and growth, and its antibacterial properties. In addition, the potential of the HLDT hydrogel in soil remediation and its impact on the growth conditions of sorghum in heavy metal-polluted environments were also evaluated. This study provides a potential sustainable solution for remediating heavy metal-polluted farmland, improving soil environment, optimizing agricultural production conditions, and maximizing the utilization of polluted land. Summary of the Invention

[0010] Aiming at the deficiencies of the prior art, the present invention provides a preparation method and use of an HLDT hydrogel that can be sustainably used for Fe3+ , Cd2+ and Pb2+ adsorption and desorption.

[0011] To achieve the above object, the present invention provides the following technical solution: A preparation method and use of an HLDT hydrogel that can be sustainably used for Fe3+ , Cd2+ and Pb2+ adsorption and desorption, wherein the HLDT hydrogel is obtained by a free radical condensation reaction of hyaluronic acid grafted with L-dopamine and tannic acid with Na-AMPS; The weight ratio of hyaluronic acid: L-dopamine: tannic acid: Na-AMPS is: 3:1:1:1, 2:2:1:1, 3:3:1:1, 3:2:1:1, 2:3:2:1, 1:1:3:1, 1:2:3:1, 1:2:1:1, 1:2:2:1, 2:1:3:1.

[0012] Preferably, the amino group of L-dopamine is grafted onto the carboxyl group of hyaluronic acid through an amide condensation reaction. Subsequently, the phenolic hydroxyl group of tannic acid is grafted onto hyaluronic acid through an ester condensation reaction to obtain the HA-L-DOPA-TA macromolecule. Finally, Na-AMPS is grafted onto the HA-L-DOPA-TA macromolecule through a free radical polymerization reaction to prepare the HLDT hydrogel.

[0013] Preferably, the preparation method of the polymer HA-L-DOPA-TA is: dissolving hyaluronic acid in deionized water, adding EDCI / NHS to activate its carboxyl group, then adding solid L-dopamine, reacting at room temperature overnight, dialyzing in a cut-off dialysis bag with a cut-off molecular weight of 8000-14000 Da for 2 days, adding EDCI / NHS to activate the carboxyl group again, adding tannic acid to the reaction solution, reacting overnight at room temperature, dialyzing for three more days, and freeze-drying to obtain the HA-L-DOPA-TA macromolecule.

[0014] Preferably, the preparation method of the HLDT hydrogel is as follows: The hydrogel is prepared by dissolving HA-L-DOPA-TA, acrylamide, N,N-methylenebisacrylamide and Na-AMPS in 10 mL of pure water; ammonium persulfate is added and stirred for another 20 minutes, and then the mixture is allowed to stand at room temperature for 8 hours to prepare the HLDT hydrogel.

[0015] Preferably, after the HLDT hydrogel absorbs water and swells, the HLDT still has toughness and can efficiently adsorb three heavy metal ions. The heavy metal ions can be rapidly desorbed using 1 M hydrochloric acid. After washing with deionized water and ultrasonic treatment, the HLDT can adsorb heavy metals again. At the same time, the HLDT hydrogel can stably exist in an aqueous solution for a long time and can stably exist in a 1 M acid solution for 4 days.

[0016] Preferably, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy are used for the characterization of HA-L-DOPA-TA and the HLDT hydrogel; Weigh the HLDT hydrogel and place it in a petri dish. Add deionized water and weigh it at different time intervals to analyze the swelling kinetics of the hydrogel and determine the time required for them to reach the maximum swelling capacity. The swelling capacity is calculated using the following formula: Swelling capacity = W2 - W1, where W1 represents the weight of the hydrogel before water absorption, and W2 represents the weight of the swollen hydrogel. The swelling results are determined by the average value of three separate experiments conducted at room temperature.

[0017] Preferably, immerse the HLDT hydrogel in high-concentration CdCl2 (50 mM) , FeCl3 (50 mM) and PbCl2 (10 mM) solutions. At different time points, collect 10 μL solution samples respectively. After dilution, use ICP-MS to measure Fe3+ , Cd2+ and Pb2+ levels; The HLDT hydrogel can rapidly absorb Fe3+ , Cd2+ and Pb2+ within half an hour, and then the absorption rate gradually decreases. Eventually, the equilibrium absorption capacities of 76.1%, 46.4% and 59.5% are reached within 16 hours respectively; Use 1 M hydrochloric acid solution for desorption. The color of the hydrogel gradually fades within 20 minutes, indicating that H+ rapidly displaces Fe3+ , Cd2+ and Pb2+ , and then wash it three times with deionized water and ultrasonicate it, and it will be completely restored within 2 hours.

[0018] Preferably, the HLDT hydrogel has antibacterial activity. By measuring the size of the inhibition zone, the in vitro antibacterial activity of the HLDT hydrogel against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was tested, and the bacterial growth was significantly reduced, with the average radii of the inhibition zones being 3.06 mm, 1.87 mm, and 1.57 mm, respectively.

[0019] A preparation method and use of an HLDT hydrogel that can be sustainably used for Fe3+ 、 Cd2+ and Pb2+ adsorption and desorption, characterized in that: when treating sorghum seeds with the HLDT hydrogel in different heavy metal solutions, the germination and growth of sorghum were significantly improved. The HLDT hydrogel can effectively remove heavy metal ions from contaminated soil and enhance the growth characteristics of different sorghum varieties, reducing the heavy metal content. This study provides a potential solution for the sustainable restoration of heavy metal-contaminated farmland.

[0020] Compared with the prior art, the present invention provides a preparation method and use of an HLDT hydrogel that can be sustainably used for Fe3+ 、 Cd2+ and Pb2+ adsorption and desorption, having the following beneficial effects: 1. The cycle for Fe3+ 、 Cd2+ and Pb2+ the preparation method and use of the HLDT hydrogel for adsorption and desorption has the characteristics of being renewable, stable, and having the ability to efficiently adsorb different heavy metal ions. When treating sorghum with the HLDT hydrogel in different heavy metal solutions, the germination and growth of sorghum were significantly improved. Further, the HLDT hydrogel can effectively remove heavy metal ions from contaminated soil (from Zhuzhou, Hunan) and enhance the growth characteristics of different sorghum varieties, reducing the heavy metal content. This system is expected to protect crops from the accumulation of heavy metal ions in slightly contaminated soil, improve the phytoremediation efficiency in severely contaminated soil, and promote sustainable agricultural practices in affected areas. Generally speaking, our research results provide a potential solution for the sustainable restoration of heavy metal-contaminated farmland.

[0021] 2. The cycle for Fe3+ 、 Cd2+ and Pb2+ the preparation method and use of the HLDT hydrogel for adsorption and desorption, this hydrogel has excellent stability, sustainable regenerability, 1 M hydrochloric acid desorption stability, and antibacterial properties, and at the same time has effective absorption rates of 76.1%, 46.4%, and 59.5% for Fe3+ 、 Cd2+ and Pb2+The ability. The HLDT hydrogel can effectively remove heavy metal ions from contaminated soil, improve the growth environment of crops, and continuously repair contaminated soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 For the synthesis of HA-L-DOPA-TA macromolecule and HLDT hydrogel.

[0023] Figure 2 For the characterization of HLDT hydrogel, including NMR, FT-IR, XRD and SEM images.

[0024] Figure 3 For the properties of HLDT hydrogel, including the state change of HLDT hydrogel before and after swelling in water, the weight change curve of HLDT hydrogel with time, and the mechanical properties of HLDT hydrogel after swelling.

[0025] Figure 4 For the absorption efficiency of HLDT hydrogel for Fe3+ , Cd2+ and Pb2+ respectively.

[0026] Figure 5 For the absorption-desorption-regeneration process of whole and fragmented HLDT hydrogel for Fe3+ respectively.

[0027] Figure 6 For the antibacterial effects of HLDT hydrogel against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa.

[0028] Figure 7 For the effects of HLDT hydrogel on the germination and growth of sorghum seeds.

[0029] Figure 8 For the adsorption capacity of HLDT hydrogel for heavy metals in contaminated soil.

[0030] Figure 9 For the effects of contaminated soil treated with HLDT hydrogel on the growth of sorghum seedlings. DETAILED DESCRIPTION OF THE INVENTION

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Please refer to Figures 1-9 , a sustainable method for Fe3+ , Cd2+ andPb2+ Preparation method and use of an adsorptive and desorptive HLDT hydrogel, wherein the HLDT hydrogel is obtained by free radical condensation reaction of hyaluronic acid grafted with poly-L-dopamine and tannic acid simultaneously and Na-AMPS; The weight ratio of hyaluronic acid : L-dopamine : tannic acid : Na-AMPS is: 3:1:1:1, 2:2:1:1, 3:3:1:1, 3:2:1:1, 2:3:2:1, 1:1:3:1, 1:2:3:1, 1:2:1:1, 1:2:2:1, 2:1:3:1.

[0033] L-Dopamine is grafted onto hyaluronic acid through amide condensation reaction, and then tannic acid is grafted onto hyaluronic acid through ester condensation reaction to obtain HA-L-DOPA-TA macromolecule, and then HLDT hydrogel is prepared through free radical polymerization reaction.

[0034] Example 1: Preparation of HLDT hydrogel 1. Preparation of polymer HA-L-DOPA-TA Dissolve 2.0 g of hyaluronic acid (HA) in 150 mL of deionized water and dissolve it thoroughly overnight. Then, add 256.3 mg of N-hydroxysuccinimide (NHS) and 542.2 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI) to the HA solution. Then add 500 mg of solid L-dopamine hydrochloride (DA). Stir at room temperature for 12 hours, and then add 256.3 mg of NHS, 542.2 mg of EDCI and 500 mg of tannic acid (TA) to the solution again. React at room temperature for 12 hours, and then dialyze using a dialysis bag with a molecular weight cut-off of 8000 - 14000 Da. After 3 days, freeze-dry the solution under reduced pressure to obtain the polymer HA-L-DOPA-TA.

[0035] 2. Preparation of HLDT hydrogel Prepare the hydrogel by dissolving 800 mg of HA-L-DOPA-TA, 400 mg of acrylamide (AM), 400 mg of Na-AMPS and 150 mg of N,N'-methylenebisacrylamide (MBA) in 8 mL of deionized water. Add 50 mg of ammonium persulfate (APS) and stir for another 10 minutes. Then let the mixture stand at room temperature for 8 hours to prepare the HLDT hydrogel.

[0036] As Figure 1 shown in a, L-dopamine (DA) undergoes a condensation reaction with hyaluronic acid (HA), the carboxyl group combines with the amino group, and then the carboxyl group of hyaluronic acid condenses with the hydroxyl group of tannic acid again to form the polymer HA-L-DOPA-TA. In Figure 1In b, the dried HA-L-DOPA-TA was mixed with acrylamide (AM), Na-AMPS, and N,N'-methylenebisacrylamide (MBA) and deionized water and stirred well. Then, ammonium persulfate (APS) as the initiator was added. After standing overnight, the HLDT hydrogel was formed and the sites for heavy metal ion absorption in the HLDT hydrogel were indicated.

[0037] Example 2. Structural Characterization of the HLDT Hydrogel As Figure 2 shown, nuclear magnetic resonance spectroscopy ( 1 H-NMR), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffractometer (XRD) were used for the characterization of HA-L-DOPA-TA and the HLDT hydrogel.

[0038] As Figure 3 shown, the HLDT hydrogel swelled in deionized water and withstood a certain pressure. These findings highlight the stability of the HLDT hydrogel.

[0039] Example 3. Adsorption Performance, Regeneration, and Reusability of the HLDT Hydrogel The HLDT hydrogel was immersed in high-concentration CdCl2 (50 mM) , FeCl3 (50 mM) and PbCl2 (10 mM) solutions, respectively. At different time points, 10 μL solution samples were collected. After dilution, ICP-MS was used to detect the levels of Fe3+ , Cd2+ and Pb2+ , respectively. The results showed that the HLDT hydrogel could rapidly absorb Fe3+ , Cd2+ and Pb2+ ions within half an hour, and then the absorption rate gradually decreased, and finally reached the equilibrium absorption capacity of 76.1%, 46.4%, and 59.5% within 16 hours ( Figure 4 ). And after the HLDT hydrogel absorbed different heavy metal ions, the color changes of its colloid were different.

[0040] As Figure 5 shown, the absorption of Fe3+ , desorption of Fe3+ , and regeneration of the hydrogel with 1M hydrochloric acid of the whole HLDT hydrogel and hydrogel fragments were demonstrated. Multiple adsorption-desorption-regeneration experiments proved that the hydrogel remained basically intact and its weight was basically not lost, showing persistent stability in deionized water.

[0041] Example 4. Determination of the Antibacterial Activity of the HLDT Hydrogel As Figure 6As shown, by measuring the size of the inhibition zone, the in vitro antibacterial activities of the HLDT hydrogel against Escherichia coli (E. coli, ATCC25922), Staphylococcus aureus (S. aureus, ATCC43300), and Pseudomonas aeruginosa (P. aeruginosa, ATCC10145) were tested. The results showed that the bacterial growth was significantly reduced, and the average radii of the inhibition zones produced by all bacteria were 3.06 mm, 1.87 mm, and 1.57 mm, indicating that the HLDT hydrogel has strong antibacterial properties.

[0042] Example 5. Effect of HLDT Hydrogel on Sorghum Seed Germination This experiment used 1μM FeCl3 , CdCl2 and PbCl2 for experimental simulation. As shown in Figure 7 a - c, compared with the control group, heavy metal ions Fe3+ , Cd2+ and Pb2+ had a significant effect on sorghum seed germination, resulting in growth inhibition and bud bending. However, treatment with the HLDT hydrogel significantly improved the germination and growth of sorghum under different heavy metal stresses, showing performance similar to that under non - polluted conditions. In addition, according to Figure 7 d - f, the implementation of the HLDT hydrogel significantly improved the sorghum bud length, increasing it by 1.5 to 5 times compared with the untreated group. The effectiveness of the HLDT hydrogel in improving seed germination under heavy metal stress conditions indicates its potential application in polluted agricultural environments. This study shows that the HLDT hydrogel effectively alleviates heavy metal stress and improves seed germination performance, indicating its potential as a viable solution for increasing seed survival rates in polluted environments.

[0043] Example 6. Remediation Effect of HLDT Hydrogel on Polluted Soil As shown in Figure 8 a, when using HLDT to treat contaminated soil, its color changed from light yellow to black, reflecting that it can be absorbed by the HLDT hydrogel when exposed to heavy metal solutions. Elemental analysis of the contaminated soil showed that the concentrations of Fe, Cd, and Pb decreased significantly after treatment ( Figure 8 b), demonstrating the metal absorption efficacy of the HLDT hydrogel. It was confirmed that the HLDT hydrogel can effectively reduce the negative impacts of Fe, Cd, and Pb on sorghum and improve the stress resistance of plants, providing a basis for using hydrogels to remediate heavy metal pollution.

[0044] Example 7. HLDT Hydrogel for Crop Cultivation in Polluted Soil Compared with the untreated control, all sorghum varieties treated with the HLDT hydrogel showed enhanced growth parameters, including increased plant height, fresh weight, and dry weight ( Figure 9a-d). In the samples treated with the HLDT hydrogel, heavy metal accumulation in aboveground plant tissues was significantly lower ( Figure 9 e-g), indicating the potential for improved feed safety. This result suggests that integrating HLDT hydrogel treatment can not only mitigate soil pollution but also promote healthier plant development, leading to more sustainable agricultural practices. The findings emphasize the importance of exploring innovative materials such as hydrogels to enhance crop resilience and productivity while addressing environmental challenges. Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sustainable Fe3+ , Cd2+ and Pb2 The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: The HLDT hydrogel is obtained by free radical condensation reaction between hyaluronic acid grafted with L-dopamine and tannic acid and Na-AMPS; The weight ratios of hyaluronic acid: L-dopamine: tannic acid: sodium 2-acrylamido-2-methylpropane sulfonate (Na-AMPS) are: 3:1:1:1, 2:2:1:1, 3:3:1:1, 3:2:1:1, 2:3:2:1, 1:1:3:1, 1:2:3:1, 1:2:1:1, 1:2:2:1, 2:1:3:

1.

2. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: L-dopamine was grafted onto hyaluronic acid through an amide condensation reaction, and tannic acid was grafted onto hyaluronic acid through an ester condensation reaction to obtain HA-L-DOPA-TA macromolecules, which were then polymerized with Na-AMPS to prepare HLDT hydrogel.

3. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: The preparation method of the polymer HA-L-DOPA-TA is as follows: dissolving hyaluronic acid in deionized water, adding EDCI / NHS to activate carboxyl groups, then adding L-dopamine, reacting at room temperature overnight, dialyzing in a dialysis bag with a molecular weight cutoff of 8000-14000Da for 1 day, then adding EDCI / NHS to activate carboxyl groups, adding tannic acid to the reaction solution, reacting at room temperature overnight, dialyzing for three days, and freeze-drying to obtain HA-L-DOPA-TA macromolecules.

4. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: The preparation method of the HLDT hydrogel is as follows: HA-L-DOPA-TA, acrylamide, N,N-methylenebisacrylamide and NA-AMPS are dissolved in 10 mL of deionized water to prepare the hydrogel; ammonium persulfate is added to initiate a free radical reaction and stirred for another 10 minutes, and then the mixture is allowed to stand at room temperature for 8 hours to prepare the HLDT hydrogel.

5. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: After the HLDT hydrogel absorbs water and swells, the HLDT still has toughness and can efficiently absorb Fe3+ , Cd2+ and Pb2+ 1M hydrochloric acid can be used to quickly desorb cadmium ions, and then washed with deionized water to adsorb them again. Fe3+ , Cd2+ and Pb2+ At the same time, the HLDT hydrogel is stable in aqueous solution for a long time and in 1 M acid solution for 4 days.

6. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: Nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and heavy mechanical pressure were used for the characterization of HA-L-DOPA-TA and HLDT hydrogels; The HLDT hydrogels were placed in a culture dish, deionized water was added, and the hydrogels were weighed at different time intervals to analyze the swelling kinetics of the hydrogels and determine the time required for them to reach the maximum swelling capacity. The swelling capacity was calculated using the following formula: swelling capacity = W2-W1, where W1 represents the weight of the hydrogel before water absorption and W2 represents the weight of the swollen hydrogel. The swelling performance was determined by the average of three separate experiments performed at room temperature.

7. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: The same HLDT hydrogel was immersed in high concentration CdCl2 (50 mM) , FeCl3 (50 mM) and PbCl2 (10 mM) In the solution, 10 μL of solution samples were collected at different time points, diluted, and measured using ICP-MS Fe3+ , Cd2+ and Pb2+ level; HLDT hydrogels were rapidly absorbed within half an hour. Fe3+ , Cd2+ and Pb2+ ions, and then the absorption rate gradually decreased, eventually reaching a balanced absorption capacity of 76.1%, 46.4%, and 59.5% within 16 hours; The desorption was performed using 1 M hydrochloric acid solution, and the color of the hydrogel gradually became lighter within 20 minutes, indicating that H+ Quick Replacement Fe3+ , Cd2+ and Pb2+ , followed by three washes with deionized water and ultrasonication for 10 min, which resulted in complete recovery within 2 h.

8. A method for sustainable use according to claim 1 Fe3+ , Cd2+ and Pb2+ The preparation method of the adsorption-desorption HLDT hydrogel is characterized by: HLDT hydrogel has antibacterial activity. By measuring the size of the inhibition zone, the in vitro antibacterial activity of HLDT hydrogel against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was tested. The bacterial growth was significantly reduced, and the average radius of the inhibition zone produced by bacteria was 3.06 mm, 1.87 mm, and 1.57 mm.

9. A sustainable Fe3+ , Cd2+ and Pb2+ The use of HLDT hydrogel for adsorption and desorption is characterized by: HLDT hydrogel treatment significantly improved the growth of sorghum seeds in Fe3+ , Cd2+ and Pb2+ germination and growth under stress; Treatment with HLDT hydrogel significantly improved sorghum sprout length, increasing by 1.5 to 5 times compared with the untreated group; The effectiveness of HLDT hydrogel in improving seed germination under heavy metal stress conditions suggests its potential application in polluted agricultural environments; HLDT hydrogel effectively alleviated heavy metal stress and improved seed germination performance, thereby increasing seed survival rate in polluted environments.

10. A method for sustainable use according to claim 9 Fe3+ , Cd2+ and Pb2+ The use of HLDT hydrogel for adsorption and desorption is characterized by: The HLDT hydrogel demonstrated remarkable ability in removing multiple heavy metals from contaminated soils. The hydrogel showed particular effectiveness in reducing the levels of iron, cadmium, and lead in the soil. All sorghum varieties treated with HLDT hydrogels showed enhanced growth parameters, including increased plant height, fresh weight, and dry weight; Heavy metal accumulation in aboveground plant tissues was significantly lower in HLDT hydrogel-treated samples; HLDT hydrogel treatment may not only mitigate soil contamination but also promote healthier plant development, leading to more sustainable agricultural practices.

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