Gradient oxygen release material with multi-layer core-shell structure as well as preparation method and application of gradient oxygen release material

Abstract

The invention provides a multi-layer core-shell structure gradient oxygen release material as well as a preparation method and application thereof. The gradient oxygen release material comprises an inner core, an oxygen release functional shell layer and a permeation regulation and control layer from inside to outside, wherein the inner core is quartz sand; the oxygen release functional shell layer is powder wrapping the inner core, and the powder comprises calcium peroxide and sodium percarbonate; the permeation regulation and control layer is a paraffin film oxygen release material through the design of a multi-layer core-shell structure, the material shows the obvious gradient oxygen release characteristic of early-stage rapid oxygen release-middle-stage stable oxygen supply-later-stage slow attenuation in water, gradient and continuous release of oxygen is achieved, the stability of the oxygen release material is improved, the oxygen utilization rate is increased, and the service life of the oxygen release material is prolonged. The dissolved oxygen level of the water body can be effectively maintained, and the restoration requirements of different scenes of the underground water source are met.

Description

Technical Field

[0001] This invention belongs to the technical field of groundwater treatment, specifically relating to a multi-layered core-shell structure gradient oxygen-releasing material, its preparation method, and its application. Background Technology

[0002] In recent years, slow-release technology has attracted widespread attention in the field of groundwater remediation. The application of slow-release materials can overcome the tailing and rebound phenomena caused by the short-acting time and low utilization rate of oxidants in traditional ISCO technology, demonstrating its enormous application potential in in-situ groundwater remediation. Slow-release materials can carry various active components, including microbial communities, matrix, oxidants, and oxygen-releasing materials, allowing for the selection of appropriate active components for different contaminated sites. Slow-release material technology offers low cost, long-lasting action, and good treatment effects on stubborn organic pollutants, thus showing broad application prospects in groundwater remediation projects. However, currently, groundwater slow-release technology is mostly used for the remediation of organic pollution. For slow-release materials used to treat groundwater with excessive iron and manganese levels, current methods suffer from complex manufacturing processes, high costs, and the potential for secondary pollution.

[0003] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a multilayer core-shell structured gradient oxygen-releasing material, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A multi-layered core-shell structured gradient oxygen-releasing material, comprising, from the inside out, a core, an oxygen-releasing functional shell, and a permeation-regulating layer;

[0007] The core is made of quartz sand; the oxygen-releasing functional shell is a powder wrapped around the core, which includes calcium peroxide and sodium percarbonate; and the permeation control layer is a paraffin film.

[0008] Preferably, the oxygen-releasing functional shell also includes bentonite and calcium carbonate, and the weight ratio of calcium peroxide, sodium percarbonate, bentonite and calcium carbonate is 8-12:3-5:3-5:1-3.

[0009] Preferably, the weight ratio of calcium peroxide, sodium percarbonate, bentonite, and calcium carbonate is 10:4:4:2.

[0010] Preferably, the particle size of the quartz sand is 0.5-1 mm; the particle size after coating with the oxygen-releasing functional shell is 1.5-3 mm; and the particle size after coating with the permeation control layer is 2-3.5 mm.

[0011] A method for preparing a multilayer core-shell structured gradient oxygen-releasing material, comprising the following steps:

[0012] Step S1: Screen the quartz sand, rinse it multiple times with deionized water after screening, and dry it for later use.

[0013] Step S2: The quartz sand is spread on an inclined rotating disc for roller coating. Polyvinyl alcohol solution is sprayed evenly onto the quartz sand using a spraying device. The mixed oxygen-releasing functional shell powder is evenly sprinkled on the surface of the quartz sand. The rotating disc rotates to roll the quartz sand to form particles.

[0014] Step S3: Repeat step S2 4-6 times until the oxygen-releasing functional shell powder is completely coated.

[0015] Step S4: Dry the coated particles. During the drying process, turn the particles over at least once and break them up.

[0016] Step S5: After the particles are cooled to room temperature, they are sieved using 1.5mm and 3mm sieves to collect particles of 1.5-3.0mm.

[0017] Step S6: Melt the paraffin wax, load the particles collected in step S5 onto a metal mesh spoon, immerse the metal mesh spoon in the molten paraffin wax, lift the metal mesh spoon and cool it to form a paraffin wax film on the outside of the particles.

[0018] Preferably, in step S5, particles with a diameter <1.5mm are added to a rotating disk for secondary roll coating.

[0019] Preferably, the particle loading thickness inside the metal mesh spoon is ≤1cm, the particle immersion time in the paraffin is 2-3 seconds, and the metal mesh spoon is held above the molten paraffin for 10-15 seconds after being lifted.

[0020] Preferably, the particles are cooled by a cooling plate, and the cooling process is stirred by a glass stirring device to allow the paraffin to cool naturally to solidify at room temperature. After sieving out the agglomerated particles, a gradient oxygen-releasing material is obtained.

[0021] The application of a core-shell structured gradient oxygen-releasing material for the remediation of groundwater sources using any gradient oxygen-releasing material is characterized by the use of an in-situ injection method for the prevention and remediation of pollution sources.

[0022] The application of a core-shell structured gradient oxygen-releasing material for the remediation of groundwater sources using any gradient oxygen-releasing material is characterized by the use of an in-situ oxidant injection method to remediate and treat contaminants.

[0023] Beneficial effects: Through its multi-layered core-shell structure design, the oxygen-releasing material exhibits a distinct gradient oxygen release characteristic in water, characterized by "rapid oxygen release in the early stage, stable oxygen supply in the middle stage, and slow decay in the later stage." This achieves a gradient and continuous release of oxygen, enhances the stability of the oxygen-releasing material and its oxygen utilization rate, and can effectively maintain the dissolved oxygen level in the water, making it suitable for the remediation needs of different scenarios in groundwater sources.

[0024] Oxygen-releasing materials can not only efficiently increase the dissolved oxygen concentration in groundwater, but also have good environmental compatibility and will not disrupt the pH stability of the water body. At the same time, they can effectively control iron and manganese pollution by enhancing oxidation and precipitation, which fully demonstrates their effectiveness and feasibility in the remediation of iron and manganese pollution in groundwater. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0026] Figure 1 This is a cross-sectional electron microscope scan of the gradient oxygen-releasing material in a specific embodiment of the present invention;

[0027] Figure 2 This is a pore size distribution curve of the gradient oxygen release material in a specific embodiment of the present invention;

[0028] Figure 3 The graph shows the change in dissolved oxygen (DO) in water for the gradient oxygen release material in a specific embodiment of the present invention.

[0029] Figure 4 This is a graph showing the dissolved oxygen concentration variation of the gradient oxygen release material in a simulation experiment, as provided in a specific embodiment of the present invention.

[0030] Figure 5 This is a pH value change curve of the gradient oxygen release material in a simulation experiment provided in a specific embodiment of the present invention;

[0031] Figure 6 This is a graph showing the iron concentration variation of the gradient oxygen-releasing material in a simulation experiment, as provided in a specific embodiment of the present invention.

[0032] Figure 7 The graph shows the change in manganese concentration in a simulation experiment of the gradient oxygen-releasing material in a specific embodiment of the present invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0035] This invention provides a multi-layered core-shell structured gradient oxygen-releasing material, which is mainly used for pollution prevention and remediation of groundwater sources, providing a continuous and stable oxygen supply for the remediation of anaerobic groundwater environments.

[0036] The specific gradient oxygen release material consists of a core, an oxygen release functional shell, and a permeability regulation layer arranged sequentially from the inside out. The core is made of quartz sand, which has the advantages of strong chemical stability, high mechanical strength, and low cost. It can provide a stable support framework for the entire oxygen release material and avoid the problem of the material being easily broken in the groundwater environment.

[0037] The oxygen-releasing functional shell is a powder material wrapped around the core, which includes calcium peroxide (CaO2) and sodium percarbonate (SPC). The two work together as the main oxygen-releasing agent to achieve a gradient oxygen release characteristic of "rapid oxygen release in the early stage - stable oxygen supply in the middle stage - slow decay in the later stage". Preferably, the oxygen-releasing functional shell also includes bentonite and calcium carbonate (CaCO3). Bentonite can enhance the binding force between the oxygen-releasing functional shell and the core, and at the same time adsorb some oxygen-releasing agent to further regulate the oxygen release rate. Calcium carbonate can adjust the pH value during the oxygen release process, and at the same time improve the strength and stability of the oxygen-releasing functional shell.

[0038] The permeability control layer is a paraffin film, which wraps around the oxygen-releasing functional shell. It has good hydrophobicity and barrier properties, which can effectively control the contact rate between groundwater and the oxygen-releasing functional shell, thereby precisely controlling the oxygen release rate and preventing the material from being washed away and dissolved by groundwater, thus improving the overall stability and service life of the oxygen-releasing material.

[0039] Furthermore, the weight ratio of calcium peroxide, sodium percarbonate, bentonite, and calcium carbonate can be adjusted within the range of 8-12:3-5:3-5:1-3, for example, the ratio of the four is 8:3:3:1 or 12:5:5:3. The specific ratio can be flexibly adapted according to the degree of groundwater pollution and the severity of the anaerobic environment to improve the applicability of the material.

[0040] In one optional embodiment, to ensure that the particle size of the material is suitable for the injection requirements of the groundwater source and to ensure the rationality of the structure of each layer, the particle size of the quartz sand is 0.5-1mm; the particle size of the particles after coating the oxygen-releasing functional shell is 1.5-3mm; and the final particle size after coating the permeability control layer is 2-3.5mm. This particle size range can prevent the material from clogging the pipeline during the injection process, while ensuring the dispersion of the material in the groundwater and improving the oxygen-releasing coverage.

[0041] In this embodiment, the paraffin film is a discontinuous thin layer, with the thickest part not exceeding 0.5 mm. This application does not limit the thinnest area, and some areas may be coated with paraffin. This situation does not affect the normal use of this product.

[0042] In the optimal oxygen-releasing functional shell layer, the weight ratio of calcium peroxide, sodium percarbonate, bentonite, and calcium carbonate is 10:4:4:2. This ratio achieves an optimal balance between oxygen release rate, oxygen release duration, and pH adjustment effect, meeting the remediation needs of most groundwater sources. This material not only provides a high-performance oxygen-releasing filter medium for in-situ remediation of iron and manganese pollution in groundwater, but also offers an innovative solution that is both economical and practical, with a low cost advantage, possessing significant engineering application value and promotion potential. Cost estimates are shown in the table below:

[0043]

[0044] like Figure 1 The cross-sectional scanning electron microscope (SEM) image of the gradient oxygen-releasing material in region A shows that the paraffin wax exhibits a discontinuous thin-layer coating effect, which can improve the material's moisture resistance and slow-release stability without completely isolating the material from the water, thus facilitating subsequent staged oxygen release. The SEM images of different regions (regions B, C, and D) show that bentonite, sodium percarbonate (SPC), calcium peroxide, and calcium carbonate are uniformly mixed. The calcium peroxide is tightly bound to the composite powder and has good dispersion, with no obvious local agglomeration or clustering. All functional components are uniformly composited.

[0045] like Figure 2 The pore size distribution curve of the gradient oxygen release material shows a significant peak in the 0-10 nm range, with the pore volume contributing the most, indicating that the material has the largest number of small-diameter pores. In the 10-90 nm range, the curve has a gentle, broad peak, indicating the presence of a small number of mesopores or macropores. This "bimodal" pore size distribution indicates that the material has a hierarchical pore structure. Small-diameter pores provide a high specific surface area, while large-diameter pores facilitate mass transport, potentially offering both high activity and mass transfer efficiency in catalysis, adsorption, and other applications. In groundwater remediation projects, this structure can provide a large number of active sites while ensuring the rapid diffusion of pollutants and remediation agents.

[0046] Add 10g of oxygen-releasing material (approximately 2%) to 500mL of pure water and allow it to react under constant temperature conditions.

[0047] like Figure 3 The dissolved oxygen (DO) variation curve of the gradient oxygen release material in water is shown in the figure. The dissolved oxygen release process of this material exhibits a typical three-stage slow-release characteristic. The initial rapid oxygen release stage lasts approximately 0-20 days. During this rapid oxygen release stage, the dissolved oxygen rises slowly in the first few days, which is related to the paraffin film on the material surface preventing large-area contact between the material and the water. Subsequently, the dissolved oxygen concentration rapidly increases from approximately 4.6 mg / L to a peak of 8.8 mg / L. In this stage, the SPC and CaO2 in the material have sufficient contact with the water, and the desorption and diffusion rates of oxygen molecules reach their maximum, exhibiting a significant "burst oxygen release" effect, which can rapidly increase the dissolved oxygen level of the water in a short period of time. The intermediate stable oxygen release stage lasts approximately 15-30 days. After entering the intermediate stage, the dissolved oxygen concentration remains at a relatively high level of 8.7-8.8 mg / L, with relatively small overall fluctuations. During this stage, the oxygen-releasing components within the CaO2+CaCO3 material continuously and stably release oxygen into the water. The oxygen release rate reaches a dynamic equilibrium with the oxygen consumption / dissipation rate in the water, fully demonstrating the material's stable oxygen supply capacity. In water remediation, it can provide continuous oxygen support for aquatic organisms or the remediation process. After 30 days, the dissolved oxygen concentration began to slowly decrease, gradually dropping from 8.5 mg / L to approximately 5.9 mg / L, but still significantly higher than the initial value. During this stage, a large amount of the reactive oxygen-releasing components within the material were consumed, and the diffusion path of the remaining components became longer, leading to a gradual decrease in the oxygen release rate. However, it still maintained a slow oxygen release until the end of the experiment without a sudden drop. This curve shows that this material, through a "rapid start-up-stable maintenance-slow decay" oxygen release mode, achieved its long-term slow-release design goal. It can rapidly improve the anoxic environment in the initial stage and provide continuous oxygen supply in the medium to long term, demonstrating good potential for groundwater remediation applications.

[0048] Based on the previous preparation of oxygen-releasing materials, a column reactor was constructed using a clay-fine sand-clay mixture as the main filling medium. The oxygen-releasing material was then placed inside the column. By simulating the flow of groundwater in rock strata, dissolved oxygen, iron, manganese, and other elements in the water were measured to simulate the removal rate of iron, manganese, and other elements from polluted groundwater by the oxygen-releasing material. The experimental setup mainly consists of sample delivery bottles, a peristaltic pump, a reaction column, sample outlet bottles, and sampling bottles.

[0049] The collected raw water was placed in a sample bottle and connected to a peristaltic pump. The raw water sample was pumped into the reaction column at a flow rate of 0.25 mL / min. The water sample entered the sample bottle through the column outlet and was then sampled using a sampling needle. The experiment lasted for 20 days, with sampling conducted in a pattern of intensive sampling in the early stage and sparse sampling in the later stage to obtain iron and manganese removal curves, thereby exploring the effectiveness of the material.

[0050] like Figure 4 The dissolved oxygen concentration change curve of the gradient oxygen release material in the simulation experiment is shown in the figure. The dissolved oxygen concentration shows a change curve of first rising rapidly and then stabilizing. The initial DO concentration is 4.66 mg / L, which reaches 8.95 mg / L after 16 days, with a cumulative increase of 4.29 mg / L. The final DO concentration is about 8.72 mg / L, indicating that the oxygen release column has good oxygen release and transfer efficiency.

[0051] like Figure 5 The pH change curve of the gradient oxygen release material in the simulation experiment shows a continuous and gradual increase in pH value. The initial pH value was 7.235, which rose to 8.309 after 20 days, with a cumulative increase of 1.074 pH units. The entire process showed no significant fluctuations, demonstrating good pH stability and indicating that the slow-release material did not affect the acidity or alkalinity of the groundwater.

[0052] like Figure 6 The iron concentration variation curve of the gradient oxygen release material in the simulation experiment shows a three-stage variation characteristic: "stable in the early stage, slow decrease in the middle stage, and sharp drop in the later stage," exhibiting a significant overall downward trend. The initial iron concentration was 2.30 mg / L, decreasing to 0.41 mg / L at the end of the experiment (20 days), with a total change of -1.89 mg / L and a total change rate of -82.2%, indicating a stable decrease in iron concentration over time. This suggests that iron underwent an oxidation and precipitation reaction as dissolved oxygen in the water increased.

[0053] like Figure 7 The manganese concentration change curve of the gradient oxygen release material in the simulation experiment is shown in the graph. The overall decreasing trend of manganese is relatively gentler than that of iron. The initial concentration was 0.70 mg / L, and it dropped to 0.58 mg / L at the end of the experiment (20 days), with a total change of -0.12 mg / L and a total change rate of -17.0%, indicating that the manganese concentration decreased steadily over time. This suggests that manganese underwent an oxidation and precipitation reaction as dissolved oxygen in the water increased.

[0054] By monitoring the temporal dynamic changes of key groundwater quality indicators in the above-mentioned column experiments, the evolution pattern of water quality was clarified, and the effectiveness of the oxygen-releasing material was verified. The experiment showed that the dissolved oxygen concentration rapidly increased from its initial state and then stabilized at a high level, indicating that the oxygen-releasing material has excellent oxygen release and water transfer effects, continuously and efficiently replenishing dissolved oxygen to groundwater and meeting the needs of water oxidation reactions. The pH value maintained a gradual upward trend throughout the experimental period without significant fluctuations, demonstrating good stability. This characteristic fully demonstrates that the oxygen-releasing material will not damage the acid-base environment of groundwater, avoid secondary water pollution, ensure the benign stability of the water environment, and reflect the safety of the material's application. Simultaneously, no significant increase in turbidity or abnormal precipitation was observed during the experiment, indicating that the material's structure is stable during operation and will not produce significant particle shedding or release of solid pollutants.

[0055] On the other hand, the iron concentration showed a phased decrease over time, indicating a significant overall removal effect; the manganese concentration also showed a stable decreasing trend. The reduction in the concentration of these two elements is essentially due to the oxygen-releasing material increasing the dissolved oxygen concentration in the water, which promotes the oxidation and precipitation reaction of iron and manganese ions, proving that the oxygen-releasing material can effectively trigger the removal mechanism of the target pollutants.

[0056] In another embodiment, this application also provides a method for preparing a multilayer core-shell structured gradient oxygen-releasing material. This method, used to prepare the multilayer core-shell structured gradient oxygen-releasing material in any of the above embodiments, specifically includes the following steps:

[0057] Step S1: The quartz sand is screened to select quartz sand particles with a diameter of 0.5-1mm. The screened quartz sand is then rinsed multiple times with deionized water until the rinsing liquid is clear and removes soil, fine impurities and soluble contaminants. After rinsing, the sand is dried at a temperature of 105℃ for 2-3 hours. After drying, the sand is cooled to room temperature in a drying room.

[0058] Step S2: Spread the pretreated quartz sand evenly on an inclined rotating disc, with a thickness of approximately 2-3 cm. Start the rotating disc to rotate back and forth at a frequency of 1-2 times per second, with a rotation amplitude of 5-10 cm. Use a spraying device to evenly spray a 5% wt polyvinyl alcohol solution onto the surface of the quartz sand, continuously agitating the sand during spraying to ensure the sand particles are slightly damp (they should not clump together when squeezed but crumble easily when released). The polyvinyl alcohol acts as a binder. An agent is used to firmly adsorb the oxygen-releasing functional shell powder onto the surface of quartz sand. In this embodiment, the weight ratio of quartz sand to oxygen-releasing functional shell powder is 80:20. One-quarter to one-sixth of the total amount of the uniformly mixed oxygen-releasing functional shell powder (calcium peroxide, sodium percarbonate, or a mixture of calcium peroxide, sodium percarbonate, bentonite, and calcium carbonate) is evenly sprinkled on the surface of the quartz sand. The rotating disk is driven to rotate continuously, so that the quartz sand is evenly coated with a layer of powder during the rolling process, forming preliminary core-shell particles.

[0059] Step S3: Repeat the roller coating, spraying, and powdering process of step S2, keeping the amount of liquid sprayed consistent each time. Distribute the remaining oxygen-releasing functional shell powder evenly in 4-6 applications until the oxygen-releasing functional shell powder completely covers the outer side of the quartz sand core. Observe the particle state in real time. If slight clumping occurs, break it up to ensure that the coating thickness is uniform and that the thickness of the oxygen-releasing functional shell can meet the continuous oxygen release requirements. At the same time, avoid the coating layer being too thick, which would cause the oxygen release rate to be too slow.

[0060] Step S4: Place the coated granules into a drying oven for drying. The spreading thickness should be ≤1cm. The drying temperature should be controlled at 50-60℃ and the drying time should be 4-6 hours. During the drying process, the granules should be turned over at least once to break up any clumps and ensure that the granules are dried evenly. Generally, the granules should be turned over once after 2-3 hours of drying.

[0061] In step S5, the dried particles are cooled to room temperature and sieved using 1.5mm and 3mm sieves to collect particles with a diameter of 1.5-3.0mm. Particles in this size range can meet the requirements of subsequent permeability control layer coating and groundwater injection. Particles with a diameter <1.5mm after sieving are added back into the rotating disk and subjected to secondary roller coating according to the procedures in steps S2-S4.

[0062] Step S6: Place the paraffin wax in a heating container and heat it to 658℃ to completely melt the paraffin wax. Load the particles collected in step S5 into a metal mesh spoon, controlling the particle loading thickness to ≤1cm. Slowly immerse the metal mesh spoon containing the particles into the molten paraffin wax for 2-3 seconds to reduce the amount of paraffin wax adhering and ensure that a layer of paraffin wax adheres to the surface of the particles. Then lift the metal mesh spoon and hold it above the molten paraffin wax for 10-15 seconds to drain the excess paraffin wax, ensuring that only a thin layer of paraffin wax adheres to the surface of the particles.

[0063] Finally, the particles are cooled to allow the paraffin to solidify naturally at room temperature, forming a uniform paraffin film, thus obtaining a multi-layered core-shell structured gradient oxygen-releasing material.

[0064] Furthermore, the particles are cooled by a cooling plate. During the cooling process, the particles are gently stirred by a glass stirring device to create a discontinuous thin-layer coating effect of paraffin. After cooling, the agglomerated particles are screened out, which not only improves moisture resistance and slow-release stability, but also does not prevent the material from contacting water.

[0065] In another embodiment, the gradient oxygen-releasing material of the present invention is mainly used for groundwater source remediation. Based on the pollution scenario of the groundwater source (pollution source control, pollution receptor treatment), two targeted application methods are provided, as follows:

[0066] Method 1: Source Control and Remediation of Pollution through In-situ Injection: This method involves directly injecting gradient oxygen-releasing materials into the pollution source without disturbing or with minimal formation disturbance, thereby achieving the degradation, stabilization, or removal of pollutants. This embodiment targets the primary iron-manganese precipitates and minerals in the formation as the source of iron-manganese pollution. Based on the hydrogeological characteristics of the target aquifer, a low-cost slow-release oxygen material is developed and in-situ injection technology is employed to enable long-term oxygen release, continuously optimizing the redox environment of the aquifer. This drives the conversion of Fe²⁺ and Mn²⁺ into insoluble oxides / hydroxides, which are then precipitated and fixed, thus blocking the migration and release pathways of iron and manganese at the source. Method 2: In-situ oxidant injection for remediation of contaminants. Targeting wells with excessive pollution levels as the final stage directly affecting drinking water safety, in-situ oxidant injection technology is used to directly act on the well water. Gradient oxygen-releasing materials are injected directionally through an injection rod to achieve targeted regulation of the redox environment of the target aquifer, rapidly removing dissolved iron and manganese from the water. Simultaneously, the diffusion effect of the oxidant in the aquifer is utilized to construct a long-term stable oxidation domain around the well, inhibiting the secondary release of iron and manganese from the surrounding strata and ensuring that the effluent water quality continuously meets standards.

[0067] The two application methods described above are designed with low-cost treatment schemes for pollution sources and pollution receptors respectively, and are adapted to different pollution levels and actual construction conditions of water sources. The two technical means can be applied independently or in combination, and both can effectively control iron and manganese pollution, providing scientific and feasible technical experience for the remediation of iron and manganese pollution in similar porous water sources.

[0068] When the two application methods mentioned above are combined, the remediation technology route focuses on redox environmental regulation, achieving efficient removal by promoting the oxidation and precipitation of iron and manganese ions. The overall approach is structured around a dual dimension of "pollution source control - pollution receptor treatment," combining targeted and flexible measures while ensuring economic efficiency. The gradient oxygen-releasing material consists of quartz sand, calcium peroxide (CaO2), sodium percarbonate (SPC), calcium carbonate (CaCO3), bentonite, and small amounts of polyvinyl alcohol and paraffin. Quartz sand, calcium carbonate, and bentonite are all natural mineral materials with good environmental stability, and will not release toxic or harmful substances in groundwater environments. The reaction products of calcium peroxide and sodium percarbonate in water are mainly oxygen, calcium hydroxide, and carbonates, which are common water treatment chemical products and will not produce persistent organic pollutants or heavy metal pollution.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A multilayer core-shell structured gradient oxygen-releasing material, characterized in that, The gradient oxygen-releasing material comprises, from the inside out, a core, an oxygen-releasing functional shell, and a permeation control layer; The core is made of quartz sand; the oxygen-releasing functional shell is a powder wrapped around the core, which includes calcium peroxide and sodium percarbonate; and the permeation control layer is a paraffin film.

2. The multi-layered core-shell structured gradient oxygen-releasing material according to claim 1, characterized in that, The oxygen-releasing functional shell also includes bentonite and calcium carbonate, with the weight ratio of calcium peroxide, sodium percarbonate, bentonite and calcium carbonate being 8-12:3-5:3-5:1-3.

3. The multi-layered core-shell structured gradient oxygen-releasing material according to claim 2, characterized in that, The weight ratio of calcium peroxide, sodium percarbonate, bentonite, and calcium carbonate is 10:4:4:

2.

4. The multi-layered core-shell structured gradient oxygen-releasing material according to claim 1, characterized in that, The particle size of the quartz sand is 0.5-1mm; the particle size after being coated with an oxygen-releasing functional shell is 1.5-3mm; and the particle size after being coated with a permeability control layer is 2-3.5mm.

5. A method for preparing a multilayer core-shell structured gradient oxygen-releasing material, comprising preparing the gradient oxygen-releasing material according to any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Screen the quartz sand, rinse it multiple times with deionized water after screening, and dry it for later use. Step S2: The quartz sand is spread on an inclined rotating disc for roller coating. Polyvinyl alcohol solution is sprayed evenly onto the quartz sand using a spraying device. The mixed oxygen-releasing functional shell powder is evenly sprinkled on the surface of the quartz sand. The rotating disc rotates to roll the quartz sand to form particles. Step S3: Repeat the process of step S2 4-6 times until the oxygen-releasing functional shell powder is completely coated. Step S4: Dry the coated particles. During the drying process, turn the particles over at least once and break them up. Step S5: After the particles are cooled to room temperature, they are sieved using 1.5mm and 3mm sieves to collect particles of 1.5-3.0mm. Step S6: Melt the paraffin wax, load the particles collected in step S5 onto a metal mesh spoon, immerse the metal mesh spoon in the molten paraffin wax, lift the metal mesh spoon and cool it to form a paraffin wax film on the outside of the particles.

6. The method for preparing the multilayer core-shell structured gradient oxygen-releasing material according to claim 5, characterized in that, In step S5, particles with a diameter <1.5mm are added to a rotating disk for secondary roll coating.

7. The method for preparing the multilayer core-shell structured gradient oxygen-releasing material according to claim 5, characterized in that, The particle loading thickness inside the metal mesh spoon is ≤1cm. The particles are immersed in the paraffin for 2-3 seconds. After lifting the metal mesh spoon, it stays above the molten paraffin for 10-15 seconds.

8. The method for preparing the multilayer core-shell structured gradient oxygen-releasing material according to claim 5, characterized in that, The particles are cooled by a cooling pan, and the cooling process is stirred by a glass stirring device to allow the paraffin to cool naturally to solidify at room temperature. After sieving out the agglomerated particles, a gradient oxygen-releasing material is obtained.

9. An application of a multi-layered core-shell structured gradient oxygen-releasing material, wherein the gradient oxygen-releasing material described in any one of claims 1-4 is used for the remediation of groundwater sources, characterized in that, In-situ injection method is used to control and remediate pollution sources.

10. An application of a multi-layered core-shell structured gradient oxygen-releasing material, wherein the gradient oxygen-releasing material described in any one of claims 1-4 is used for the remediation of groundwater sources, characterized in that... The in-situ oxidant injection method was used to remediate and treat the contaminated receptors.

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