A high specific surface area polymer-based magnesium artificial wetland filter material and preparation method thereof

Abstract

The present invention discloses a method for preparing a high-specific-surface-area polymer-based magnesium artificial wetland filter material. The method comprises the following steps: first, separately preparing an aqueous phase containing a magnesium salt and an emulsifier, and an organic phase; then slowly dripping the aqueous phase into the organic phase by drip filtration, so that the aqueous phase forms tiny droplets in the organic phase, thereby causing a polymerization reaction at the interface to form a polymer matrix embedded with magnesium ions; then, foaming the polymer matrix embedded with magnesium ions and rapidly cooling it; finally, separating the embryos by suction filtration, washing, drying, and sieving to obtain the filter material. The filter material obtained by the method of the present invention can regulate the pH value of water bodies and slowly release magnesium ions, enhance plant nutrient supply, and improve wetland functions in low-temperature environments, and has a high specific-surface-area.

Description

Technical Field

[0001] The present invention relates to the fields of environmental engineering and water treatment, and in particular to a high-specific-surface-area polymer-based magnesium artificial wetland filter material and a preparation method thereof. Background Art

[0002] As a highly effective water purification system, constructed wetlands have been widely used in wastewater treatment and ecological restoration in recent years. However, they are somewhat vulnerable when it comes to phosphorus removal. Unlike nitrogen denitrification, phosphorus removal lacks an effective biodegradation mechanism, making wetland systems face numerous challenges in phosphorus removal. Although some microorganisms may participate in phosphorus transformation, existing research indicates that phosphorus removal in wetlands primarily relies on physical and chemical processes, rather than microbial action.

[0003] However, current research generally believes that wetland plants can absorb a certain amount of phosphorus, but their absorption capacity is limited, and the phosphorus in the plants needs to be harvested regularly to prevent re-release. The phosphorus absorbed by plants usually only accounts for a small part of the total phosphorus removal in the wetland. Therefore, phosphorus removal in wetland systems mainly depends on the physical and chemical processes of the matrix, especially the adsorption and precipitation of phosphorus. Traditional wetland matrices, such as gravel and soil, have a certain phosphorus adsorption capacity, but they will gradually become saturated during long-term use, resulting in a decrease in phosphorus removal efficiency. To address this problem, researchers have introduced modified matrix materials. For example, new matrices such as iron-aluminum-based composites and calcium-based materials have high phosphorus adsorption capacity. These materials react with phosphate to form insoluble phosphides, thereby improving phosphorus removal efficiency.

[0004] Magnesium ions, a key trace element in water, react with phosphate ions to form magnesium phosphate precipitates, demonstrating excellent phosphorus removal potential. However, existing constructed wetland filter media generally suffer from low surface area, limited adsorption capacity, and uneven magnesium ion release. These limitations limit the long-term effectiveness and stability of these filter media. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention proposes a high-specific surface area polymer-based magnesium artificial wetland filter material and a preparation method thereof. The filter material can not only improve the phosphorus removal efficiency of the wetland system, but also extend the service life of the filter material, meeting the long-term and stable water quality treatment needs.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material, the method comprising the following steps:

[0008] Step 1: Preparation of aqueous and organic phases:

[0009] The magnesium salt is dissolved in deionized water and stirred until the magnesium salt is completely dispersed to form a uniform magnesium salt solution; polyethylene glycol is added to the magnesium salt solution as an emulsifier and stirred thoroughly to form a stable aqueous phase to ensure sufficient emulsification and stability.

[0010] Polyethylene glycol diacrylate is dissolved in dichloromethane, and ammonium persulfate is added as an initiator to dissolve and uniformly disperse the polyethylene glycol diacrylate to form a stable organic phase; the mass ratio of the polyethylene glycol diacrylate to the dichloromethane is 1:5 to 1:10.

[0011] Step 2: The aqueous phase is slowly added to the organic phase by dripping, stirring while adding to ensure that the aqueous phase forms tiny droplets in the organic phase, thereby causing a polymerization reaction at the interface. During the stirring process, the magnesium ions at the interface undergo a cross-linking reaction with the monomers in the organic phase, gradually forming a polymer matrix in which the magnesium ions are embedded.

[0012] Step 3: Before the magnesium ion embedded polymer matrix is ​​formed and dried, the magnesium ion embedded polymer matrix is ​​subjected to a gas foaming treatment to generate a porous structure to increase the specific surface area; after the foaming is completed, the embryo is quickly cooled to room temperature to fix the bubble structure inside the material;

[0013] Step 4: Separate the embryos obtained in step 3 by suction filtration, and then repeatedly rinse with deionized water to remove unreacted monomers and residual solvents; dry and sieve to obtain filter material.

[0014] Furthermore, the magnesium salt in step 1 is magnesium chloride, magnesium hydroxide or magnesium carbonate. The mass volume ratio of the magnesium salt to deionized water is (0.15-0.25):1. In step 1, the magnesium salt required for filter material preparation can be selected according to the application scenario of the filter material. The selection of the magnesium salt is mainly based on the following reasons:

[0015] 1. Magnesium chloride (MgCl2)

[0016] High solubility: Magnesium chloride has a high solubility in water, which enables it to dissolve quickly and completely, thereby providing sufficient magnesium ions to support subsequent polymerization reactions and form a polymer matrix in which magnesium ions are embedded.

[0017] Cost-effectiveness: Magnesium chloride is generally affordable, readily available, and suitable for large-scale applications.

[0018] Ion source: The chloride ions it releases also have a certain disinfecting effect during the water treatment process, which helps to improve the sewage treatment effect.

[0019] 2. Magnesium hydroxide (Mg(OH)2)

[0020] Slow-release properties: Magnesium hydroxide releases magnesium ions slowly in water, making it suitable for applications that require long-term magnesium release, thereby enhancing the durability of the filter media.

[0021] Environmentally friendly: As an alkaline magnesium salt, magnesium hydroxide is relatively harmless in the environment, can increase the alkalinity of water, and is beneficial to regulating water quality.

[0022] Compatibility: It has good compatibility with other commonly used water treatment materials and is suitable for a variety of sewage treatment systems.

[0023] 3. Magnesium carbonate (MgCO3)

[0024] Buffering capacity: Magnesium carbonate has good buffering properties, which can stabilize the pH value of water and help control the acid-base balance during water treatment.

[0025] Mineralization effect: The magnesium ions generated by the reaction of magnesium carbonate in water help promote precipitation reactions and remove heavy metal ions or other pollutants in the water.

[0026] Low dissolution rate: Due to its relatively low dissolution rate, magnesium carbonate can provide a continuous source of magnesium in long-term operating wetland systems.

[0027] Taking all of the above factors into consideration, magnesium chloride, magnesium hydroxide, and magnesium carbonate all offer varying cost-effectiveness and environmental compatibility, making them the preferred magnesium salts for preparing high-surface-area polymer-based magnesium constructed wetland filter media. The appropriate magnesium salt can be selected to optimize filter media performance based on specific application requirements.

[0028] Furthermore, in step 1, the volume ratio of the added polyethylene glycol to the magnesium salt solution is 1:10 to 1:20. The mass ratio of the initiator to the sum of the polyethylene glycol diacrylate and the dichloromethane is 0.5% to 1%. After the magnesium salt is dissolved in deionized water, the volume of the magnesium salt solution is substantially equivalent to the volume of the deionized water. This is due to the following reasons:

[0029] 1. Emulsion stability

[0030] Appropriate emulsifier concentration: Polyethylene glycol, as an emulsifier, can form a stable aqueous phase and prevent the separation of the aqueous phase and the organic phase. If the dosage is too small (less than 1:20), it may not be effectively emulsified, resulting in uneven dispersion of magnesium salt in the aqueous phase, which in turn affects the uniformity and efficiency of the subsequent polymerization reaction.

[0031] Avoid phase separation: If the amount of polyethylene glycol used is too high (higher than 1:10), it may form over-emulsification, resulting in unstable interface between the aqueous phase and the organic phase, increasing the risk of phase separation and affecting product performance.

[0032] 2. Reaction efficiency

[0033] Reaction Rate: Within an appropriate concentration range, polyethylene glycol can effectively reduce interfacial tension, accelerate the formation of tiny droplets from the aqueous phase in the organic phase, and promote the cross-linking reaction between magnesium ions and polymer monomers. If the dosage is too low, the reaction rate may be slow, resulting in insufficient bonding of magnesium ions with the polymer matrix, thus affecting the ultimate performance of the filter media.

[0034] Reduce the concentration of unreacted monomers: The appropriate amount of polyethylene glycol can ensure that the concentration of unreacted monomers is moderate to avoid negative effects on filter media performance.

[0035] 3. Filter material performance

[0036] Physical properties: The dosage of polyethylene glycol directly affects the physical properties of the final filter media, such as specific surface area and pore size distribution. Too low a dosage may result in insufficient specific surface area, thereby reducing its adsorption and removal efficiency in wastewater treatment; while too high a dosage may cause the pore structure of the filter media to become too tight, affecting water flow and filtration effectiveness.

[0037] Comprehensive performance: The appropriate use of polyethylene glycol can enable the final filter material to achieve the best balance in filtration, adsorption and biocompatibility.

[0038] Therefore, a volume ratio of PEG to magnesium salt solution of 1:10 to 1:20 not only ensures the emulsification stability and reaction efficiency of the aqueous phase, but also optimizes the performance of the final filter media. If the amount of PEG is too low, it will lead to incomplete reaction and poor performance; if the amount is too high, it may cause phase separation and poor physical properties, ultimately affecting the application effect of the filter media.

[0039] Furthermore, in step 2, the reaction temperature is controlled between 40°C and 50°C for 2-6 hours, and the stirring speed is controlled between 150 and 400 rpm. By controlling the reaction time, temperature, stirring speed, and emulsifier dosage, the particle size and specific surface area of ​​the filter material can be adjusted. Faster stirring speeds and lower emulsifier concentrations generally produce smaller particle sizes, thereby increasing the specific surface area.

[0040] Furthermore, in step 3, the foaming agent is compressed air, the injection pressure is 0.5-1.5 MPa, the foaming temperature is 60°C to 80°C, and the foaming time is 2-3 hours. The reasons for the preference of these conditions are as follows:

[0041] 1. Injection pressure

[0042] Controlling Foam Size: Within a pressure range of 0.5-1.5 MPa, the formation and size of bubbles during the foaming process can be effectively controlled. Appropriate pressure helps to generate a uniform and stable bubble structure, avoiding overly large or uneven bubbles that will lead to uneven pore distribution in the final material.

[0043] Improve foaming efficiency: Lower pressure (such as 0.5MPa) can form larger bubbles in the embryo, while higher pressure (such as 1.5MPa) can produce smaller bubbles. By adjusting the pressure, bubbles of different pore sizes can be achieved to meet the specific surface area requirements of specific applications.

[0044] 2. Foaming temperature

[0045] Increased foaming reaction rate: In the temperature range of 60°C to 80°C, the fluidity of the polymer increases, which facilitates the formation and expansion of bubbles. At the same time, the increase in temperature can also accelerate the curing of the polymer matrix, thereby fixing the bubble structure more quickly.

[0046] Ensuring Material Stability: Too low a foaming temperature may cause bubbles to become unstable, while too high a temperature may break the polymer chains, affecting the material's strength and stability. This temperature range ensures that the polymer maintains appropriate mechanical strength and elasticity during the foaming process.

[0047] 3. Foaming time

[0048] Ensure sufficient foaming: Setting the foaming time to 2-3 hours ensures that bubbles are fully formed and stabilized, and the resulting porous structure is well fixed. A time that is too short may result in insufficient bubble formation, which may affect the specific surface area and physical properties of the final material.

[0049] Balanced performance and efficiency: The appropriate foaming time allows the foaming and curing processes of the material to be balanced, ensuring the number and distribution of bubbles while avoiding excessive expansion or polymer degradation caused by long foaming times.

[0050] In summary, an injection pressure of 0.5-1.5 MPa, a foaming temperature of 60°C to 80°C, and a foaming time of 2-3 hours can effectively optimize the foaming process of polymer-based magnesium filter media, ensuring the final material has an ideal porous structure, a high specific surface area, and good physical properties. These conditions were selected to balance efficiency and material quality during the foaming process to meet the application requirements of constructed wetlands.

[0051] Furthermore, in step 3, the diameter of the pores in the embryo obtained after foaming is 0.05 mm to 0.5 mm. The reasons for this preferred range are as follows:

[0052] 1. Increase in specific surface area

[0053] Increased specific surface area: Pore diameters between 0.05mm and 0.5mm can significantly increase the specific surface area of ​​the material. Smaller pores can increase the contact area between the material and the water, thereby enhancing its adsorption capacity and water treatment efficiency.

[0054] Optimize fluid dynamics: moderate pore size can provide better fluid channels, making water flow more smoothly in the filter material, avoiding blockage, and at the same time increasing the residence time of water flow, which is conducive to the removal of pollutants.

[0055] 2. Mechanical properties of materials

[0056] Improve material strength: Materials with too large a pore size may result in a decrease in strength, while a pore size range of 0.05mm to 0.5mm can effectively maintain the structural integrity and mechanical properties of the material. The appropriate pore size allows the material to remain stable even when subjected to external pressure.

[0057] Uniform pore structure: Pore diameters within this range help to form a uniform pore distribution, enhance the material's compressive strength, and avoid uneven loading caused by locally oversized or undersized pores.

[0058] 3. Optimization of processing performance

[0059] Adapt to different water qualities: The pore diameter range of 0.05mm to 0.5mm enables the filter material to adapt to a variety of water quality conditions. It can effectively remove smaller particles without affecting the passage of larger particles, thereby improving the overall treatment effect.

[0060] Improve biocompatibility: Smaller pores help provide a good habitat for the growth of microorganisms, promote the formation of biofilms, and help improve the biodegradability of constructed wetlands.

[0061] 4. Flexibility of process control

[0062] Easy to adjust and control: Within this pore diameter range, the manufacturing process is relatively easy to control, and the desired pore characteristics can be achieved by adjusting the injection pressure, temperature and foaming time of the foaming agent, thereby improving production flexibility and efficiency.

[0063] Furthermore, in step 4, the particle size of the filter material finally obtained is 8 mm to 10 mm. The reasons for the preference for this particle size range are as follows:

[0064] 1. Optimization of hydraulic characteristics

[0065] Fluidity and permeability: Particle sizes between 8mm and 10mm provide good hydraulic permeability, ensuring smooth flow of water through the filter media and preventing clogging. Larger particle sizes can reduce resistance to water flow and improve water flow efficiency.

[0066] Increase the flow rate of the filter media: This particle size range can effectively reduce the pressure drop of the filter media, allowing higher flow rates, thereby improving the overall treatment efficiency and system operation capacity.

[0067] 2. Pollutant removal capability

[0068] Optimized filtration: A particle size of 8mm to 10mm allows the filter media to effectively remove larger particulate matter in water. This particle size captures suspended solids without excessively obstructing water flow, ensuring effective treatment.

[0069] Compatible with different water qualities: The particle size in this range enables the filter media to adapt to a variety of water quality conditions, effectively deal with pollutants of different types and concentrations, and enhance the overall decontamination ability.

[0070] 3. Mechanical strength and stability

[0071] Improve structural stability: Larger particle size helps to enhance the mechanical strength of the filter media, avoid crushing or compression under high water flow rates, and ensure the stability of the filter media in long-term use.

[0072] Prevent sedimentation and stratification: The particle size ranges from 8mm to 10mm, which can reduce the sedimentation and stratification of the filter media, ensure the uniform distribution of the filter media during use, and improve the overall performance.

[0073] 4. Easy to operate and maintain

[0074] Reduced maintenance costs: Larger particle size filter media is relatively easy to clean and maintain, reducing wear and tear on equipment during maintenance. The use of large particle size filter media can reduce the frequent cleaning and replacement caused by blockage, reducing operating costs.

[0075] Improve biocompatibility: Moderate particle size can provide appropriate habitat space for the growth of microorganisms, promote the formation of biofilm, and improve the biodegradability of filter materials.

[0076] A high-specific-surface-area polymer-based magnesium artificial wetland filter material obtained by the above-mentioned preparation method. Ethylene glycol diacrylate and magnesium salt undergo a cross-linking reaction and foaming to produce a cross-linked polymer water treatment filter material containing magnesium ions. The structure of this product comprises a cross-linked network formed by magnesium ion bridging between acrylate monomers. The specific structure and properties of the reaction product will be affected by the reaction conditions (such as temperature, type and concentration of magnesium salt), and a solid porous structure is formed. In artificial wetland applications, it can be used as a slow-release magnesium source and as a filter material to enhance purification effects.

[0077] A filter bed used in an artificial wetland system. The filter bed is made of a high-specific-surface-area polymer-based magnesium artificial wetland filter material.

[0078] Furthermore, the high specific surface area polymer-based magnesium artificial wetland filter material is pressed and formed or added into a porous matrix to form a filter bed for artificial wetland system.

[0079] The beneficial effects of the present invention are as follows:

[0080] (1) Regulating the pH value of water and slow-release magnesium ions: The polymer-based magnesium slow-release material prepared by the present invention can regulate the pH value of water by slowly releasing magnesium ions. By regulating the cross-linking degree and structure of the polymer matrix, the release rate of magnesium ions can be effectively controlled to meet the demand for long-term slow-release. The release of magnesium ions can not only increase the alkalinity of water and inhibit the acidification process, but also provide necessary nutrients for microorganisms, optimizing the microbial treatment environment.

[0081] (2) Enhance plant nutrition supply: Magnesium is an important component of plant chlorophyll. Through the polymer filter material that slowly releases magnesium ions, the nutrients required by plants can be gradually released, promoting the growth of wetland plants, thereby improving the ecological function and purification capacity of the system.

[0082] (3) Improving wetland functions in low-temperature environments: Constructed wetlands generally have low treatment efficiency under low-temperature conditions. By using polymer-based magnesium slow-release materials, the cold tolerance of microorganisms and plants can be enhanced. The continuous release of magnesium ions at low temperatures helps maintain microbial activity and metabolism, promotes organic matter degradation, and removes nitrogen and phosphorus.

[0083] (4) High specific surface area: The microsphere structure formed by the interfacial polymerization method of the present invention has a large specific surface area, which effectively improves the adsorption capacity of the filter material.

[0084] (6) Environmental protection and stability: The filter material of the present invention is made of environmentally friendly materials, has good mechanical strength and chemical stability, and is suitable for long-term application in wetland environments. DETAILED DESCRIPTION

[0085] The present invention will be described in detail below based on preferred embodiments, and the purpose and effects of the present invention will become more apparent. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0086] The materials and equipment used in the following examples are:

[0087] Main materials: magnesium salt, deionized water, polyethylene glycol (PEG, emulsifier), polyethylene glycol diacrylate (monomer), dichloromethane (organic solvent), ammonium persulfate (initiator)

[0088] Main equipment: agitator, trickling filter, compressed air foaming device, suction filtration device, drying oven, screening device, wherein the screening device is an upper sieve with a pore size of 10 mm and a lower sieve with a pore size of 8 mm.

[0089] Example 1

[0090] In this embodiment, magnesium salt is selected as magnesium chloride (MgCl2). When magnesium chloride (MgCl2) is used as a magnesium source, it has high water solubility and good ion release characteristics. Its high solubility can provide an adequate source of magnesium ions during the filter material preparation process, thereby promoting the formation of magnesium-based filter material and its phosphorus removal effect in water treatment. It is suitable for scenarios where faster results are required in wetland systems.

[0091] Calculate magnesium chloride as 500g. The following are the detailed steps for preparing high specific surface area polymer-based magnesium filter material using magnesium chloride:

[0092] Step 1: Preparation of aqueous and organic phases

[0093] (1) Preparation of aqueous phase

[0094] Preparation method: Mix 500g magnesium chloride with 2500g deionized water (mass volume ratio is 0.2:1) and stir until completely dissolved, then add 125ml PEG (the volume ratio of PEG to magnesium salt solution is 1:20) and continue stirring for 15 minutes to ensure the stability of the aqueous phase and good dispersion.

[0095] (2) Preparation of organic phase

[0096] Preparation: Dissolve 2500g of PEGDA in 12500g of dichloromethane (PEGDA:dichloromethane mass ratio of 1:5) and add 75g of ammonium persulfate as an initiator (0.5% of the total mass of the organic phase). Stir and mix until the initiator is completely dispersed and the organic phase is uniform and stable.

[0097] Step 2: Add water phase and carry out interfacial polymerization reaction

[0098] The aqueous phase is slowly added dropwise to the organic phase while stirring at 400 rpm to ensure uniform, fine droplets of the aqueous phase are formed within the organic phase. The magnesium ions at the droplet interface undergo cross-linking polymerization with the monomers in the organic phase, forming a polymer matrix in which the magnesium ions are embedded. The reaction temperature is maintained at 40°C, and the addition and stirring rates are controlled to prevent agglomeration.

[0099] Step 3: Gas foaming and formation of porous structure

[0100] The resulting magnesium-based polymer matrix is ​​foamed to create a porous structure and increase the specific surface area. The foaming temperature is 70°C and the compressed air pressure is 1.5 MPa. After the foaming process lasts for 2 hours, it is rapidly cooled to room temperature to solidify the porous structure. The resulting embryonic body has a pore diameter of 0.05mm-0.5mm, creating a filter material with a large specific surface area.

[0101] Step 4: Filtration, rinsing and drying

[0102] The polymer matrix obtained after foaming is filtered to remove unreacted organic phase and impurities. It is then washed repeatedly with deionized water to ensure that residual monomers and solvents are removed. The washed filter material is dried in a drying oven at 50°C to constant weight. The dried filter material is sieved on a 10mm pore size sieve, and then the material that passes through the 10mm sieve is further sieved on an 8mm pore size sieve. The particles remaining between the 8mm and 10mm sieves are the filter material of the target particle size (8mm-10mm). Particles smaller than 8mm pass through the lower sieve and can be collected and processed again. Particles larger than 10mm can be further crushed to meet the particle size requirements.

[0103] The target filter material obtained in this embodiment is subjected to performance testing below.

[0104] (1) Phosphorus removal performance

[0105] The prepared filter material was placed in a water body with an initial phosphorus concentration of 5 mg / L. After 30 days of continuous treatment, the daily effluent phosphorus concentration dropped to <1.5 mg / L, showing a good phosphorus removal effect.

[0106] (2) Rapid response performance

[0107] The high solubility of magnesium chloride allows magnesium ions to be released quickly, which increases the activity and reaction rate of the filter material in a short period of time, helping to quickly reduce the concentration of pollutants in the water body in the initial stage.

[0108] (3) Excellent specific surface area and porosity

[0109] The polymer-based magnesium filter material obtained in Example 1 was tested for apparent density, specific surface area, porosity and phosphorus adsorption capacity, and compared with artificial ceramsite filter material for water treatment. The results are shown in Table 1:

[0110] Table 1 Comparison of physical properties of polymer-based magnesium filter media and artificial ceramsite filter media for water treatment

[0111]

[0112] As can be seen from Table 1, the specific surface area of ​​the polymer-based magnesium filter material obtained in this embodiment is 92 times the standard of "Artificial Ceramsite Filter Material for Water Treatment" (CJ / T299-2008), and the porosity is 1.3 times the above standard, and the phosphorus adsorption effect is significant.

[0113] Example 2

[0114] This example describes a method for preparing a high-surface-area, polymer-based magnesium constructed wetland filter material using magnesium hydroxide (Mg(OH)2) as the magnesium salt raw material. This filter material exhibits high surface area and long-term sustained release, effectively improving phosphorus removal efficiency in constructed wetland systems. It also maintains stable performance at low temperatures, making it suitable for long-term water treatment in constructed wetland systems. Based on 1000g of magnesium hydroxide, the following dosage is required for actual experiments:

[0115] Step 1: Preparation of aqueous and organic phases

[0116] (1) Preparation of aqueous phase

[0117] Preparation method: 1000g of magnesium hydroxide is added to 6667g of deionized water (the mass ratio of magnesium salt to deionized water is 0.15:1) and stirred at 300rpm until the magnesium hydroxide is completely dissolved. 666.7ml of polyethylene glycol (PEG) is added (the volume ratio of polyethylene glycol to magnesium salt solution is 1:10) and stirring is continued for 20 minutes to form a stable aqueous phase. Polyethylene glycol, as a surfactant, helps to enhance the interfacial stability of the aqueous phase and the organic phase.

[0118] (2) Preparation of organic phase

[0119] To prepare the organic phase, 1000g of polyethylene glycol diacrylate was dissolved in 7000g of dichloromethane (1:7 volume ratio). 80g of ammonium persulfate (1% of the total organic phase mass) was then added as an initiator and stirred until homogeneous, forming a stable organic phase. The ammonium persulfate initiator generates free radicals in the subsequent polymerization reaction, effectively initiating the polymerization reaction.

[0120] Step 2: Phase mixing and interfacial polymerization

[0121] The prepared aqueous phase is added dropwise to the stirred organic phase in a slow dripping manner, with the stirring speed controlled at 250rpm and the reaction temperature controlled at 50°C to ensure that the aqueous phase forms tiny droplets in the organic phase. During the stirring process, the magnesium hydroxide in the aqueous phase exists in the form of ions and gradually diffuses into the monomer in the organic phase at the interface, undergoes a cross-linking reaction with it, and forms a polymer matrix containing magnesium ions. The key to this step is to maintain the slow dripping of the aqueous phase and an appropriate stirring speed to ensure the formation of tiny droplets, thereby forming a stable interfacial polymerization reaction. This reaction effectively embeds magnesium ions into the polymer structure, thereby improving the mechanical strength and chemical stability of the filter material. In addition, by controlling the interfacial reaction rate, the pore size and distribution of the final filter material can be adjusted.

[0122] Step 3: Gas foaming and formation of porous structure

[0123] After the magnesium ion-embedded polymer matrix is ​​initially formed, a gas foaming process is performed to generate a porous structure. To this end, the polymer matrix is ​​placed in a compressed air atmosphere. By adjusting the compressed air pressure and temperature, the diffusion rate of the gas in the polymer matrix and the size of the bubbles are controlled to generate a porous structure. The foaming temperature is controlled at 80°C.

[0124] During the foaming process, the appropriate temperature must be maintained to prevent excessive expansion and unstable bubble structures. After foaming, the polymer matrix is ​​quickly cooled to room temperature to secure the resulting bubble structure within the material. The formation of this porous structure significantly increases the material's specific surface area, significantly enhancing its adsorption capacity for phosphate ions and providing higher phosphorus removal efficiency for constructed wetland systems.

[0125] Step 4: Filtration, rinsing and drying

[0126] The foamed embryo is separated using a suction filtration device to remove excess organic solvent and unreacted materials. The embryo is then placed in deionized water and repeatedly rinsed to remove any residual monomer, initiator, and solvent components, ensuring the purity of the filter media. After multiple rinses, the filter media is placed in a drying oven at 50°C to a constant weight and then sieved to obtain a filter media with uniform particle size and stable performance.

[0127] 3. Filter material performance test and application effect

[0128] The specific surface area of ​​the prepared filter material is about 24×10 4 m 2 / g. In order to verify the phosphorus removal efficiency and low temperature tolerance of the filter material in the constructed wetland system, the following tests were conducted:

[0129] (1) Phosphorus removal effect

[0130] When the filter media was applied to a constructed wetland, with an influent phosphorus concentration set at 5 mg / L, after 30 days of continuous operation, the influent phosphorus concentration stabilized at around 1 mg / L, achieving an 80% removal rate. Compared to traditional wetland filter media, it demonstrated higher adsorption capacity and removal efficiency. This is because the porous structure provides a larger specific surface area, allowing phosphate ions to more fully contact and be adsorbed.

[0131] (2) Low temperature tolerance

[0132] At 10°C, the filter media's phosphorus removal rate dropped to only 75%, demonstrating its excellent low-temperature adaptability and stability. This low-temperature tolerance is attributed to the embedded magnesium ions in the filter media, which enhance its mechanical strength and chemical stability, effectively reducing the impact of low temperatures on phosphorus removal.

[0133] (3) Service life

[0134] Simulated long-term operation tests revealed that the filter media maintained a high adsorption capacity after 120 consecutive days of phosphorus removal, suggesting that its service life will meet the long-term operational requirements of wetland systems. Its excellent durability is attributed to the cross-linking effect of magnesium ions, which strengthens the polymer structure and reduces wear.

[0135] 4. Technical advantages

[0136] Compared with traditional wetland filter materials, the high specific surface area polymer-based magnesium filter material of this embodiment has the following significant advantages:

[0137] High phosphorus removal efficiency: The porous structure provides a larger specific surface area, enabling more efficient removal of phosphate ions.

[0138] Strong low temperature tolerance: It maintains high phosphorus removal efficiency in low temperature environments and is suitable for artificial wetland applications in cold climates.

[0139] Long service life: The embedded cross-linked structure of magnesium hydroxide improves the durability of the filter media and reduces the cost of frequent filter media replacement.

[0140] In summary, the polymer-based magnesium filter material prepared in this embodiment has excellent water treatment effect, especially showing good phosphorus removal effect and low-temperature stability in artificial wetland systems, and can meet the long-term stable water quality treatment requirements.

[0141] Example 3

[0142] Step 1: Preparation of aqueous and organic phases

[0143] (1) Preparation of aqueous phase

[0144] 1000g of magnesium carbonate was added to 4000g of deionized water (the mass volume ratio of magnesium salt to deionized water was 0.25:1) and stirred thoroughly until the magnesium carbonate was completely dispersed. Stir thoroughly until the magnesium carbonate was completely dispersed into a uniform solution. To improve the emulsification effect of the aqueous phase and the organic phase, 266.7ml of polyethylene glycol was added to the magnesium carbonate solution (the volume ratio of magnesium carbonate to magnesium carbonate solution was 1:15) and stirring was continued for 15 minutes to ensure that the emulsification was stable.

[0145] (2) Preparation of organic phase

[0146] 1000 g of polyethylene glycol diacrylate (PEGDA) was dissolved in 10,000 g of dichloromethane (the volume ratio of polyethylene glycol diacrylate to dichloromethane was 1:10), 88 g of ammonium persulfate (ammonium persulfate accounted for 0.8% of the total mass of the organic phase) was added as an initiator, and stirred until uniformly dispersed, thereby forming a stable organic phase.

[0147] Step 2: Add water phase and interfacial polymerization reaction

[0148] Slowly add the aqueous phase dropwise to the stirring organic phase at a constant stirring speed of 150 rpm and a controlled reaction temperature of 45°C to form tiny droplets within the organic phase. The magnesium ions in the aqueous phase cross-link with the organic monomers at the interface, forming a magnesium-containing polymer matrix. Maintaining an appropriate droplet addition rate and stirring speed ensures uniform dispersion of the droplets and prevents agglomeration.

[0149] Step 3: Foaming and formation of porous structure

[0150] The resulting magnesium-based polymer matrix is ​​foamed in a compressed air atmosphere to create a porous structure. During the foaming process, the compressed air pressure is maintained at 1.5 MPa, the temperature is controlled at 60°C, and the foaming time is controlled for 3 hours to ensure uniform gas diffusion within the matrix and form small, uniform pores. After foaming, the matrix is ​​cooled to room temperature to solidify the bubble structure, resulting in a porous structure with a high specific surface area, which enhances the removal of phosphorus and other pollutants.

[0151] Step 4: Filtration, rinsing and drying

[0152] The foamed polymer matrix is ​​filtered to remove residual organic solvent and unreacted monomers. The resulting mixture is then repeatedly rinsed with deionized water to remove residual monomers and impurities. Finally, the filter material is dried in a drying oven at 50°C to a constant weight and sieved to obtain filter particles of uniform size.

[0153] 3. Filter material performance test and application effect

[0154] (1) Buffering performance test

[0155] After adding the filter media to water bodies with pH 6.5 and 8.5, the pH of the system water was maintained between 7.0 and 7.5, proving that the buffering capacity of magnesium carbonate helps stabilize the pH in the wetland system and provide a suitable living environment for microorganisms.

[0156] (2) Mineralization effect

[0157] Heavy metal ions (such as copper and lead) were added to polluted water and the prepared filter media was applied to the wetland system. After 20 days of operation, the heavy metal concentration in the water decreased significantly. Analysis showed that the magnesium ions in the magnesium carbonate formed insoluble complex precipitation with the heavy metal ions, effectively removing heavy metal ions from the water and further improving the overall treatment effect of the wetland system.

[0158] (3) Phosphorus removal effect

[0159] In water with an initial phosphorus concentration of 5 mg / L, the effluent phosphorus concentration dropped below 1 mg / L after 60 days of operation, achieving a phosphorus removal efficiency of approximately 78%. The large specific surface area and slow-release properties of magnesium carbonate significantly enhance the filter media's phosphorus removal capacity.

[0160] (4) Service life and low temperature adaptability

[0161] Even when tested at a low temperature of 8°C, the filter media still demonstrated a phosphorus removal rate exceeding 70%, demonstrating the excellent low-temperature tolerance of the magnesium carbonate embedded structure. Furthermore, the filter media maintained stable removal efficiency after 180 days of continuous operation, extending the filter media's service life and reducing replacement frequency.

[0162] 4. Filter material application effect

[0163] Magnesium carbonate is used as the magnesium source in this embodiment, which provides the following advantages:

[0164] Buffering stability: The buffering effect of magnesium carbonate can effectively maintain the pH balance of the wetland system, promote microbial activity, and improve the removal effect of pollutants.

[0165] Pollutant mineralization: The slowly released magnesium ions from magnesium carbonate promote the precipitation of low-concentration heavy metals and improve the filter media's ability to remove heavy metals and phosphorus.

[0166] Low dissolution rate: The slow release of magnesium ions by magnesium carbonate prolongs the service life of the filter media and reduces maintenance costs.

[0167] Therefore, polymer-based magnesium filter materials based on magnesium carbonate have obvious application advantages in phosphorus removal, treatment of water containing low concentrations of heavy metals, and pH buffering, and are suitable for long-term and stable use.

[0168] Those skilled in the art will understand that the foregoing descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art will still be able to modify the technical solutions described in the foregoing examples or substitute equivalents for some of the technical features therein. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the invention shall be included within the scope of protection of the invention.

Claims

1. A method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material, characterized in that: The method comprises the following steps: Step 1: Preparation of aqueous and organic phases: Dissolve the magnesium salt in deionized water and stir until the magnesium salt is completely dispersed to form a uniform magnesium salt solution; add polyethylene glycol as an emulsifier to the magnesium salt solution and stir thoroughly to form a stable aqueous phase to ensure sufficient emulsification and stability; Dissolving polyethylene glycol diacrylate in dichloromethane, adding ammonium persulfate as an initiator, dissolving and uniformly dispersing the polyethylene glycol diacrylate to form a stable organic phase; the mass ratio of the polyethylene glycol diacrylate to the dichloromethane is 1:5 to 1:10; Step 2: The aqueous phase is slowly added to the organic phase by dripping, stirring while adding to ensure that the aqueous phase forms tiny droplets in the organic phase, thereby causing a polymerization reaction at the interface. During the stirring process, the magnesium ions at the interface undergo a cross-linking reaction with the monomers in the organic phase, gradually forming a polymer matrix in which the magnesium ions are embedded. Step 3: Before the magnesium ion embedded polymer matrix is ​​formed and dried, the magnesium ion embedded polymer matrix is ​​subjected to a gas foaming treatment to generate a porous structure to increase the specific surface area; after the foaming is completed, the embryo is quickly cooled to room temperature to fix the bubble structure inside the material; Step 4: Separate the embryos obtained in step 3 by suction filtration, and then repeatedly rinse with deionized water to remove unreacted monomers and residual solvents; dry and sieve to obtain filter material.

2. The method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material according to claim 1, characterized in that: The magnesium salt in step 1 is magnesium chloride, magnesium hydroxide or magnesium carbonate; the mass volume ratio of the magnesium salt to deionized water is (0.15-0.25):

1.

3. The method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material according to claim 1, characterized in that: In the step 1, the volume ratio of the added polyethylene glycol to the magnesium salt solution is 1:10 to 1:20; the mass ratio of the initiator to the sum of the polyethylene glycol diacrylate and the dichloromethane is 0.5% to 1%.

4. The method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material according to claim 1, wherein: In the step 2, the reaction temperature is controlled between 40°C and 50°C, and the reaction time is 2-6 hours; the stirring speed is controlled between 150 and 400 rpm.

5. The method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material according to claim 1, wherein: In the step 3, the foaming agent is compressed air, the injection pressure is 0.5-1.5 MPa, the foaming temperature is 60°C to 80°C, and the foaming time is 2-3 hours.

6. The method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material according to claim 5, characterized in that: In the step 3, the diameter of the pores in the embryo obtained after foaming is 0.05 mm to 0.5 mm.

7. The method for preparing a high specific surface area polymer-based magnesium artificial wetland filter material according to claim 1, characterized in that: In the step 4, the particle size of the filter material finally obtained is 8mm-10mm.

8. A high specific surface area polymer-based magnesium artificial wetland filter material obtained by the preparation method according to any one of claims 1 to 7.

9. A filter bed used in an artificial wetland system, characterized in that: The filter bed matrix is ​​made of the high specific surface area polymer-based magnesium artificial wetland filter material according to claim 8.

10. The filter bed used in an artificial wetland system according to claim 9, characterized in that: The high specific surface area polymer-based magnesium artificial wetland filter material is pressed and formed or added into a porous filter material matrix to form a filter material bed used in an artificial wetland system.

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