Acid-resistant chelating polymer for household garbage treatment and preparation method thereof

Abstract

The present application relates to the field of environmental functional materials, and discloses an acid-resistant chelating polymer for household garbage treatment and a preparation method thereof, the acid-resistant chelating polymer for household garbage treatment comprises the following components in percentage by mass: 30-45% of phosphorylated acrylamide, 20-35% of vinyl imidazoline, 10-25% of sulfobetaine type zwitterionic monomer, 5-10% of RAFT functionalized crosslinking agent, and 3-8% of nano titanium dioxide-graphene quantum dot composite carrier. The present application breaks through the bottleneck of acid etching failure, pore blockage and insufficient mechanical strength of traditional adsorption materials in the treatment of household garbage leachate, and is suitable for heavy metal pollution treatment under complex working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental functional materials, and particularly relates to an acid-resistant chelating polymer for household garbage treatment and a preparation method thereof. BACKGROUND

[0002] The leachate of household garbage contains high-concentration heavy metal ions and strong acidic components, and traditional chelating materials are prone to problems such as protonation inactivation of functional groups, collapse of pore structure and deterioration of mechanical properties in such an extreme environment.

[0003] Conventional polymer adsorbents rely on static crosslinking networks and single pore size structures, and microcracks are expanded due to stress accumulation in multiple adsorption-desorption cycles, and the regeneration efficiency is exponentially attenuated with the number of cycles. In the prior art, the stability is improved by introducing rigid inorganic carriers or increasing the crosslinking density, but this aggravates the risk of brittle fracture of the material, and at the same time, the mass transfer rate and effective adsorption site density are sacrificed.

[0004] In addition, the presence of high-concentration calcium, sodium and other competitive ions significantly reduces the selectivity of traditional materials, and the modification strategy of simply increasing the content of chelating groups often causes excessive entanglement of molecular chains, resulting in deterioration of processing performance and decrease of batch stability.

[0005] In view of the technical bottleneck that the durability, adsorption selectivity and process adaptability of the material in the acidic medium are difficult to be simultaneously improved, it is urgent to develop a new functional polymer system with dynamic structure self-repairing, acid-erosion-resistant buffering and multi-stage mass transfer channels. SUMMARY

[0006] The purpose of the present application is to provide an acid-resistant chelating polymer for household garbage treatment and a preparation method thereof, which solves the problems of rapid attenuation of adsorption capacity, poor selectivity and insufficient regeneration performance of traditional chelating materials in the environment coupled with strong acid, high salt and mechanical stress.

[0007] To achieve the above purpose, the present application is implemented by the following technical scheme:

[0008] The present application provides an acid-resistant chelating polymer for household garbage treatment in the first aspect, which comprises the following components in mass percentage: 30-45% of phosphated acrylamide, 20-35% of vinyl imidazoline, 10-25% of sulfobetaine type zwitterionic monomer, 5-10% of RAFT functional crosslinking agent and 3-8% of nano titanium dioxide-graphene quantum dot composite carrier.

[0009] Preferably, the phosphated acrylamide is prepared by the following method: acrylamide monomer and phosphating reagent are reacted at a mass ratio of (100-120):(45-60) at 80-90 DEG C for 2.5-4 hours.

[0010] Preferably, the vinyl imidazoline is synthesized from ethylenediamine and acrylonitrile with a molar ratio of 1:(2.2-2.5) under the catalysis of zinc chloride.

[0011] Preferably, the sulfobetaine type zwitterionic monomer is methacryloyloxyethyl sulfobetaine.

[0012] Preferably, the RAFT functional crosslinker is the reaction product of pentaerythritol tetraacrylate and a dithioester chain transfer agent with a mass ratio of (50-70):(10-15).

[0013] The second aspect of the present application provides a preparation method of the acid-resistant chelating polymer for household waste treatment, comprising the following steps:

[0014] (1) pre-assembly treatment: directional arrangement of components in a supercritical CO2 environment;

[0015] (2) gradient polymerization reaction: stepwise initiation of polymerization reaction by microwave energy;

[0016] (3) mineralization treatment: introduction of calcium source and phosphorus source for mineralization modification in the polymerization system;

[0017] (4) post-treatment step: drying and crushing treatment of the product.

[0018] Preferably, the pre-assembly treatment step comprises:

[0019] Dissolve the phosphorylated acrylamide, vinyl imidazoline and sulfobetaine monomer in deoxygenated deionized water to form a mixed solution with a mass concentration of 8-12%;

[0020] Transfer the mixed solution to a high-pressure reaction kettle, introduce CO2 gas and pressurize to 30-35 MPa;

[0021] Stir at 40-45℃ with a stirring speed of 800-1200 rpm for 2.5-4 hours.

[0022] Preferably, the gradient polymerization reaction step comprises:

[0023] First stage polymerization: reaction at 43-47℃ with a microwave power of 280-320 W for 40-60 minutes;

[0024] Second stage crosslinking: increase the temperature to 58-62℃, increase the microwave power to 480-520 W, maintain the pressure at 0.5-0.8 MPa and react for 1.5-2.5 hours;

[0025] Third stage stabilization: decrease the temperature to 73-77℃, adjust the microwave power back to 300-350 W and continue the reaction for 50-70 minutes.

[0026] Preferably, the step of mineralization treatment comprises:

[0027] The 0.8-1.2 mol / L calcium chloride solution is premixed with the 0.5-0.7 mol / L sodium phosphate solution at a calcium-phosphorus molar ratio of 1.65-1.70;

[0028] The mixed solution is injected into the reaction system at a rate of 2-4 mL / min by a metering pump;

[0029] The reaction is carried out at 65-70°C under stirring at 400-600 rpm for 3-5 hours.

[0030] Preferably, the step of post-treatment comprises:

[0031] Supercritical drying: the product is flushed with 15-20 L / min of CO2 at a pressure of 8-10 MPa for 6-8 hours;

[0032] Jet milling: the dried product is broken using 0.6-0.8 MPa compressed air;

[0033] Screening treatment: the particle size D50 of the finished product is controlled to be 25-45 μm by passing through a 200-300 mesh screen.

[0034] The chelate of the application realizes the simultaneous capture of heavy metals and organic pollutants through a phosphonic acid-imidazoline synergistic coordination system, wherein the phosphonic acid group (-PO3H2) forms a five-membered ring chelate structure with heavy metals, and the imidazoline ring rigid skeleton provides a planar coordination site; the zwitterionic monomer of sulfobetaine dynamically buffers H + through intramolecular salt bonds; the RAFT functional crosslinking agent constructs a dynamic topological crosslinking network, giving the material self-repairing ability and high fracture toughness; the nanometer titanium dioxide-graphene quantum dot composite carrier relies on the Z-type heterojunction to enhance the electron transfer efficiency, and cooperates with the supercritical CO2 gradient pore forming to form a multi-level mass transfer channel, finally realizing the synergistic optimization of stability and high efficiency of adsorption-regeneration performance in a strong acid environment.

[0035] In summary, the application includes at least one of the following beneficial technical effects:

[0036] 1. The three-dimensional crosslinked network constructed based on the dynamic thioester bond of the application can spontaneously break and recombine in an acidic desorption environment, repairing the microscopic damage caused by repeated adsorption-desorption of heavy metal ions in real time, significantly prolonging the service life of the material. This feature breaks through the rapid failure bottleneck of traditional static crosslinked materials caused by irreversible structural damage, and is especially suitable for high corrosive scenarios such as domestic waste leachate.

[0037] 2.The application forms a through multi-level pore structure through the synergistic effect of the titanium dioxide-graphene quantum dot composite carrier and the supercritical CO2 gradient pore forming process, greatly improves the diffusion rate of heavy metal ions and the effective chelating site density. The design overcomes the capacity attenuation problem of conventional adsorption materials due to pore blockage or mass transfer limitation, and realizes efficient targeted treatment of complex component landfill leachate.

[0038] 3.The intramolecular salt bond network of the sulfobetaine type zwitterionic monomer in the application can form a protective barrier through dynamic protonation balance in a strong acid environment, effectively blocking H + from eroding the chelating sites. This mechanism enables the material to maintain more than 80% of the adsorption capacity at pH<1.0, solving the technical problem of easy deactivation of functional groups of traditional polymers in acidic leachate.

[0039] 4.The application combines microwave-assisted RAFT polymerization with supercritical pressure regulation to realize precise design of molecular chain topology and nanoscale ordered assembly. Compared with traditional free radical polymerization, this method avoids uneven crosslinking density or phase separation defects, ensuring that the material still has highly consistent physicochemical properties in batch production.

[0040] 5.The synergistic design of phosphorylated monomers, dynamic crosslinking agents, and mineral modification enables the material to have high selective chelation, ion interference resistance, and mechanical fatigue resistance. This multi-dimensional performance balance feature can adapt to the multiple harsh working conditions of pH fluctuation, high salt interference, and mechanical extrusion in domestic waste treatment, reducing system maintenance frequency and comprehensive treatment cost. DETAILED DESCRIPTION

[0041] In order to better understand the application, the above method is described in detail below in combination with specific examples.

[0042] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0043] Example 1:

[0044] The application provides an acid-resistant chelating polymer for domestic waste treatment, and the component ratio (wt%) is as follows:

[0045] Phosphorylated acrylamide 40%, vinyl imidazoline 28%, sulfobetaine type zwitterionic monomer 18%, RAFT functionalized crosslinking agent 8%, and nanometer titanium dioxide-graphene quantum dot composite carrier 6%;

[0046] The preparation method of the acid-resistant chelating polymer for domestic waste treatment comprises:

[0047] 1.Pre-assembly treatment:

[0048] Phosphated acrylamide (preparation condition: acrylamide 110 g, phosphating reagent 52 g, 85℃ for 3h) was mixed with the rest of the monomers and dissolved in 900 mL deoxygenated water to form a 10% solution;

[0049] The supercritical reactor was injected, CO2 was injected to 32 MPa, and stirred at 42℃ for 3 hours at 1000 rpm.

[0050] 2. Gradient polymerization reaction:

[0051] Stage I: 45℃ / 300W microwave treatment for 50 minutes;

[0052] Stage II: 60℃ / 500W, maintain 0.6 MPa pressure for 2 hours;

[0053] Stage III: 75℃ / 320W treatment for 60 minutes.

[0054] 3. Mineralization treatment:

[0055] The premixed solution (1.0 mol / L CaCl2+0.6 mol / L Na3PO4, calcium-phosphorus ratio 1.68) was injected;

[0056] The injection rate was controlled at 3 mL / min, and stirred at 500 rpm for 4 hours at 68℃.

[0057] 4. Post-processing:

[0058] Supercritical drying: 9 MPa pressure, CO2 flow rate 18 L / min for 7 hours;

[0059] Airflow crushing pressure 0.7 MPa, pass through a 250 mesh sieve, and obtain a D50=35μm product.

[0060] Example 2:

[0061] The acid-resistant chelating polymer for household garbage treatment provided by the embodiment of the application has the following component ratio (wt%):

[0062] Phosphated acrylamide 45%, vinyl imidazoline 20%, sulfobetaine type zwitterionic monomer 22%, RAFT functional crosslinking agent 5%, nano titanium dioxide-graphene quantum dot composite carrier 8%;

[0063] The preparation method of the acid-resistant chelating polymer for household garbage treatment comprises:

[0064] 1. Pre-assembly treatment:

[0065] Phosphated acrylamide (preparation condition: acrylamide 120 g, phosphating reagent 60 g, 90℃ for 2.5 h) was mixed with monomers; supercritical CO2 pressure 35 MPa, 45℃, 1200 rpm stirring for 2.5 h.

[0066] 2. Gradient polymerization reaction:

[0067] Stage I: 47℃ / 320W for 40 min;

[0068] Stage II: 62℃ / 520W, 0.8 MPa for 1.5 h;

[0069] Stage III: 77℃ / 350W for 50 min.

[0070] 3. Mineralization treatment:

[0071] Injection of 1.2 mol / L CaCl2 and 0.7 mol / L Na3PO4 (calcium-phosphorus ratio 1.70);

[0072] Injection rate 4 mL / min, 70℃, 600 rpm stirring for 5 h.

[0073] 4. Post-treatment:

[0074] Supercritical drying: 10 MPa pressure, CO2 flow rate 20 L / min for 6 h;

[0075] Jet milling pressure 0.8 MPa, 300 mesh screen, D50=25 μm product.

[0076] Example 3:

[0077] The acid-resistant chelating polymer for household garbage treatment provided by the embodiment of the application has the following component ratio (wt%):

[0078] Phosphated acrylamide 30%, vinyl imidazoline 35%, sulfobetaine type zwitterionic monomer 25%, RAFT functionalized crosslinking agent 5%, nano titanium dioxide-graphene quantum dot composite carrier 5%;

[0079] The preparation method of the acid-resistant chelating polymer for household garbage treatment comprises:

[0080] 1. Pre-assembly treatment:

[0081] Phosphated acrylamide (preparation condition: acrylamide 100 g, phosphating reagent 45 g, 80℃ for 4 h) was mixed with monomers; supercritical CO2 pressure 30 MPa, 40℃, 800 rpm stirring for 4 h.

[0082] 2. Gradient polymerization reaction:

[0083] Stage I: 43°C / 280W for 60 minutes;

[0084] Stage II: 58°C / 480W, 0.5 MPa for 2.5 hours;

[0085] Stage III: 73°C / 300W for 70 minutes.

[0086] 3. Mineralization:

[0087] Injection of 0.8 mol / L CaCl2and 0.5 mol / L Na3PO4(calcium to phosphorus ratio 1.65);

[0088] Injection rate 2 mL / min, 65°C with 400 rpm stirring for 3 hours.

[0089] 4. Post-treatment:

[0090] Supercritical drying: 8 MPa pressure, CO2flow rate 15 L / min for 8 hours;

[0091] Jet milling pressure 0.6 MPa, passed through a 200 mesh sieve, D50=45 μm product.

[0092] Comparative Example 1:

[0093] The difference compared to Example 1 is that the phosphorylated acrylamide is replaced by an equivalent amount of regular acrylamide (not phosphorylated), the remaining components and preparation steps are the same.

[0094] Comparative Example 2:

[0095] The difference compared to Example 1 is that the zwitterionic monomer of the sulfobetaine type is omitted, its weight percentage is equally distributed between the phosphorylated acrylamide and the vinyl imidazoline, the remaining components and preparation steps are the same.

[0096] Comparative Example 3:

[0097] The difference compared to Example 1 is that the RAFT functionalized crosslinker is replaced by an equivalent amount of N,N-methylene bisacrylamide (conventional crosslinker), the remaining components and preparation steps are the same.

[0098] Comparative Example 4:

[0099] The difference compared to Example 1 is that no nanoscale titanium dioxide-graphene quantum dot composite carrier is added, its weight percentage is distributed between the phosphorylated acrylamide and the vinyl imidazoline in the original proportions, the remaining preparation steps are the same.

[0100] Comparative Example 5:

[0101] The difference compared with Example 1 is that the supercritical CO2 pre-assembly step is omitted, and the monomers are mixed by mechanical stirring at room temperature and normal pressure, and the other components and subsequent steps are the same.

[0102] Comparative Example 6:

[0103] The difference compared with Example 1 is that the microwave gradient RAFT polymerization is replaced by conventional heating polymerization (oil bath heating at 80°C constant temperature), and the other components and steps are the same.

[0104] Comparative Example 7:

[0105] The difference compared with Example 1 is that the in-situ mineralization treatment step is omitted, and no CaCl2 / Na3PO4 mixed solution is injected, and the other components and preparation steps are the same.

[0106] Comparative Example 8:

[0107] The difference compared with Example 1 is that the amount of phosphorylated acrylamide is adjusted to 25%, and the amount of vinyl imidazoline is increased to 41% accordingly, and the other components and steps are the same.

[0108] Comparative Example 9:

[0109] The difference compared with Example 1 is that the amount of sulfobetaine type zwitterionic monomer is adjusted to 8%, and the reduced amount is supplemented by vinyl imidazoline, and the other components and steps are the same.

[0110] Comparative Example 10:

[0111] The difference compared with Example 1 is that the supercritical CO2 pressure is increased to 40 MPa, and the other components and preparation steps are the same.

[0112] Test Example 1: Verification of Chelating Ability

[0113] Test objects: Example 1, Comparative Example 1, Comparative Example 7, Comparative Example 8.

[0114] The experimental steps are as follows:

[0115] 1. Material pretreatment:

[0116] Take 1.0 g of each of the example and comparative example samples, soak in 0.1 M HCl for 30 minutes, wash with deionized water until neutral, and dry at 105°C for standby.

[0117] 2. Preparation of simulated landfill leachate:

[0118] Basic solution: containing Cd 2+ 100 mg / L, Pb 2+ 100 mg / L nitrate solution (pH = 2.0, adjusted with HNO3).

[0119] Interference system: Add Ca 2+ 2000 mg / L (Ca(NO3)2·4H2O) was used as a competing ion.

[0120] 3. Adsorption experiment:

[0121] Take 0.2g of the pretreated material, add 50mL of the above solution, and place it in a constant temperature shaker (25℃±1℃, 150rpm) for 24h.

[0122] 4. Centrifugal separation:

[0123] The reaction solution was centrifuged at 8000 rpm for 10 minutes, and the supernatant was filtered through a 0.45 μm filter membrane.

[0124] 5. Determination of heavy metal concentration:

[0125] Cd was determined using an atomic absorption spectrometer (AAS, PerkinElmer PinAAcle 900T). 2+ Pb 2+ Residual concentration.

[0126] The formula for calculating the selectivity coefficient (K) is as follows:

[0127]

[0128] Where D is the allocation coefficient: D = C 吸附 / C 溶液 .

[0129] The test results are shown in Table 1:

[0130] Table 1. Test results of heavy metal adsorption capacity and selectivity coefficient

[0131] Sample Cd 2+ Adsorption capacity (mg / g) Pb 2+ Adsorption capacity (mg / g) selectivity coefficient (K Hg / Ca)]]> Example 1 83.7 91.2 1.15 x 10 4 ]] Comparative Example 1 22.4 29.8 3.2 x 10 2 ]]> Comparative Example 7 65.3 58.9 8.7 x 10 3 ]]> Comparative Example 8 41.6 76.4 2.4 x 10 3 ]]>

[0132] Analysis of the data in Table 1 shows that:

[0133] This experiment, through heavy metal adsorption tests under high-concentration calcium ion interference conditions, revealed the mechanism by which the synergistic effect of phosphorylation monomers and mineralization enhances the selective adsorption capacity of materials. In Example 1, the phosphorylated acrylamide contained phosphate groups (-PO4). 3- ) through bidental coordination mode with Cd 2+ Pb 2+ To form a stable chelate, its Pb 2+ The adsorption capacity reached 91.2 mg / g, significantly higher than that of the unphosphorylated comparative example 1 (29.8 mg / g). Simultaneously, the in-situ generated hydroxyapatite nanocrystals created an ion-sieve effect on the material surface, preferentially adsorbing Pb with smaller radii. 2+ Instead of Ca2+ This resulted in a selectivity coefficient of 1.15 × 10⁻⁶. 4 Compared with control group 7 (without mineralization treatment), the improvement was 32 times, which confirms the synergistic effect of mineral phase and organic ligand.

[0134] Precise control of the component ratios has a decisive influence on the spatial distribution of adsorption sites. In Example 1, the specific ratio of phosphorylated acrylamide (35%) to vinyl imidazoline (28%) results in a gradient distribution structure within the material, with phosphate group main chelating sites and imidazoline auxiliary sites. 2+ Even at concentrations as high as 2000 mg / L, it still maintains its resistance to Cd. 2+ The adsorption capacity was 83.7 mg / g. In contrast, Comparative Example 8, due to an excess of phosphorylated monomer (25%), exhibited increased molecular chain rigidity and a decreased effective adsorption site density, resulting in a lower Cdd. 2+ The adsorption capacity plummeted to 41.6 mg / g, and the selectivity was only 21% of that in Example 1 (2.4 × 10⁻⁶). 3 This demonstrates the necessity of precise control over the monomer ratio threshold.

[0135] The dynamic mineralization process endows the material with the anti-interference advantage of a hierarchical porous structure. In Example 1, the supercritical CO2-assisted mineralization formed a continuous mesoporous and macroporous composite structure, providing a rapid transport channel for heavy metal ions, enabling Pb... 2+ Adsorption equilibrium was reached within 24 hours. However, Comparative Example 7, lacking a mineralization step and relying solely on the polymer matrix micropores (<2 nm), exhibited a pore blockage effect at high calcium ion concentrations, resulting in lower Pb content. 2+ The adsorption capacity (58.9 mg / g) decreased by 35% compared to Example 1, and the time to reach equilibrium was extended to 36 hours, highlighting the improved adaptability of the hierarchical porous structure to the treatment of complex wastewater in practice.

[0136] Test Example 2: Verification of Acid Resistance Stability

[0137] Test subjects: Example 1, Comparative Example 2, and Comparative Example 9.

[0138] The experimental steps are as follows:

[0139] 1. Acid pretreatment:

[0140] Take 0.5g of each sample and immerse them in 1.0M HNO3 solution. Treat them at 25℃ with constant shaking (120rpm) for 24 hours.

[0141] After removal, wash with deionized water until neutral, and vacuum dry at 60°C for 12 hours.

[0142] 2. Gradient pH adsorption experiment:

[0143] Cd was prepared at pH = 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 2+ solution (100 mg / L, adjusted with HNO3 / NaOH).

[0144] 0.1 g of the acid-treated material was added to 20 mL of each of the above pH solutions, and shaken for 12 hours.

[0145] 3. Centrifugal detection:

[0146] The reaction solution was centrifuged at 10,000 rpm for 15 minutes, and the supernatant was passed through a 0.22 μm filter membrane.

[0147] Cd was determined by ICP-OES (PerkinElmer Avio 500) 2+ residual concentration.

[0148] 4. Volume retention rate calculation:

[0149]

[0150] The test results are shown in Table 2:

[0151] Table 2: Adsorption capacity retention rate and pH tolerance range in acidic environment

[0152]

[0153] From the data analysis in Table 2, we can get:

[0154] This experiment reveals the core role of the proton buffer mechanism of the sulfobetaine zwitterionic group in the acid stability of the material through gradient acid treatment. In Example 1, the intramolecular salt bond formed by the sulfonic acid group (-SO3 - ) and the quaternary ammonium group (N + ) effectively neutralizes the attack of H+ + on the chelating sites through dynamic protonation-deprotonation balance, so that the Cd 2+ adsorption capacity remains 84.3% at pH = 0.5, and the critical failure pH is as low as 0.8. In Comparative Example 2, due to the complete absence of the zwitterionic structure, the amino functional group is protonated and deactivated at pH = 1.0, and the retention rate drops to 18.9%, which confirms the protective effect of the dynamic acid-base buffer system on the functional groups.

[0155] The precise control of component ratio directly affects the performance of acid resistance. In Example 1, the design of 18% sulfobetaine monomer ensures the formation of a continuous surface layer (thickness of about 2 pm) by intramolecular salt bond network. Experimental data show that the decay gradient of retention rate is only 13.2% (84.3% to 97.5%) from pH = 0.5 to pH = 2.0. In Comparative Example 9, due to insufficient monomer ratio (8%), the coverage of the buffer layer decreases, leading to H + Permeation is intensified, and the retention rate at pH = 0.5 is only 37.4%, and the critical failure pH rises to 1.6, proving the necessity of specific component ratio for building a complete buffer network.

[0156] The synergistic effect of mineralization modification and zwitterionic structure significantly enhances the anti-swelling ability of the material. In Example 1, the hydroxyapatite nanocrystals are combined with the polymer chains through Ca-O-P bonds, and the mesoporous structure remains intact after 24 hours of treatment in 1.0 M HNO3, resulting in an adsorption retention rate of 99.1% at pH = 3.0 after acid treatment. In Comparative Example 7 (without mineralization), due to the lack of inorganic phase support, acid treatment causes the swelling and rupture of the polymer chains, and the retention rate is only 34.6% at pH = 2.0, highlighting the contribution of mineralization treatment to the stabilization of the microstructure.

[0157] Test Example 3: Mechanical Strength Verification

[0158] Test object: Example 1, Comparative Example 3.

[0159] The experimental steps are as follows:

[0160] 1. Sample preparation:

[0161] Take the finished particles of Example 1 and Comparative Example 3, and use a tablet press (pressure 15 MPa) to prepare cylindrical test samples with a diameter of 10 mm and a height of 5 mm, and perform surface polishing treatment.

[0162] The test samples are equilibrated in a 25°C, 50% humidity environment for 48 hours.

[0163] 2. Compression strength test:

[0164] Use a universal material testing machine (Instron 5967) with a loading rate of 1 mm / min, and record the maximum stress value when the test sample is compressed to 50% deformation.

[0165] Test 5 parallel samples for each group of samples, and exclude data with a deviation of ±20%.

[0166] 3. Elongation at break test:

[0167] Blend the material with a plasticizer and injection mold into dumbbell-shaped films (thickness 0.5 mm), and perform tensile testing according to ASTM D638 standard, with a clamping distance of 50 mm and a tensile rate of 50 mm / min.

[0168] The percentage of the increment of the length at break to the original length was calculated.

[0169] 4. Data record:

[0170] The compressive strength was taken as the average of three effective tests, and the elongation at break was taken as the instantaneous value at the breaking point.

[0171] The test results are shown in Table 3:

[0172] Table 3 Mechanical property test results

[0173]

[0174] From the data analysis in Table 3, it can be concluded that:

[0175] In this experiment, the effects of different crosslinking systems on the mechanical properties of the material were compared, revealing the key role of the RAFT functional crosslinking agent in constructing a high-strength and tough network. In Example 1, the active polymerization characteristics of the thioester group precisely control the crosslinking density, forming a three-dimensional topological structure with narrow molecular weight distribution, and the compressive strength reaches 27.5 MPa, which is significantly higher than that of Comparative Example 3 (14.6 MPa). The breaking-recombination mechanism of dynamic covalent bonds uniformly disperses stress during compression, avoiding the local stress concentration defect of traditional static crosslinking networks, and the fluctuation of three test values in the experimental data is only ±3% (26.5-28.3 MPa), which confirms the self-adaptive advantage of the network structure.

[0176] The energy dissipation characteristics of the dynamic crosslinking network endow the material with excellent ductility. In Example 1, the thioester bond reversibly breaks at 50% deformation, and the mechanical energy is absorbed by molecular chain slipping and reconstruction, and the elongation at break is increased by 215% compared with Comparative Example 3. The rigid C-N crosslinking bond in Comparative Example 3 cannot be recombined, and the molecular chain breaks prematurely, resulting in a sharp drop in stress value (14.7→13.8 MPa) in the compression test, highlighting the decisive role of dynamic covalent bonds in improving toughness.

[0177] The synergistic effect of components further strengthens the mechanical properties through the order of microstructure. In Example 1, the hydrogen bond interaction between the RAFT crosslinking agent and the phosphorylated monomer forms a gradient structure with alternating arrangement of hard and soft segments, and the synergistic effect of the dense surface layer and the high-elasticity inner layer makes the material maintain structural integrity under extreme deformation. In Comparative Example 3, due to the random crosslinking characteristics of the conventional crosslinking agent, the interfacial bonding strength decreases to less than 5 MPa, and irreversible crack propagation occurs after cyclic compression, which confirms the necessity of specific crosslinking agents for the stabilization of multi-scale structures.

[0178] Test Example 4: Regeneration performance verification

[0179] Test object: Example 1, Comparative Example 4, Comparative Example 5.

[0180] The experimental procedure is as follows:

[0181] 1. Pretreatment of adsorption saturation:

[0182] 0.5 g of each sample was immersed in a solution containing Pb 2+ (500 mg / L, pH = 2.0), shaken to adsorption equilibrium (24 h), and then centrifuged to determine the saturated adsorption capacity.

[0183] 2. Desorption treatment:

[0184] The saturated adsorption material was immersed in 50 mL of desorption solution (0.1 M sodium citrate-0.05 M EDTA mixture, pH = 5.0) in a 50°C water bath and shaken for 6 hours.

[0185] After centrifugation, the material was washed with deionized water three times and dried at 60°C for standby use.

[0186] 3. Cycle performance test:

[0187] The "adsorption-desorption" process was repeated 5 times, with the same adsorption conditions each time (Pb 2+ initial concentration 500 mg / L, pH = 2.0, 25°C).

[0188] After the 5th cycle, the adsorption capacity retention rate of the material for Pb 2+ was determined.

[0189] 4. Data determination:

[0190] The ICP-OES was used to determine the Pb 2+ concentration in each desorption solution, and the desorption efficiency was calculated:

[0191]

[0192] The test results are shown in Table 4:

[0193] Sample Desorption efficiency (%) Cycle 1 retention (%) Cycle 3 retention (%) Cycle 5 retention (%) Example 1 94.2 98.5 96.7 92.3 Comparative Example 4 63.8 85.2 71.4 58.9 Comparative Example 5 77.5 89.7 76.3 63.8

[0194] From the data analysis in Table 4, it can be concluded that:

[0195] This experiment reveals the synergistic strengthening mechanism of the nanocomposite carrier and the supercritical pre-assembly process on the structural stability of the material through multiple cycle regeneration tests. The three-dimensional ion channel constructed by the titanium dioxide-graphene quantum dot composite carrier in Example 1 significantly accelerates the adsorption and desorption of Pb 2+The desorption efficiency reached 94.2%, which was 47.6% higher than that of Comparative Example 4 (without carrier). The gradient pore structure induced by supercritical CO2 effectively buffered the volume stress change during the desorption process, so that Example 1 still maintained 92.3% of the initial adsorption capacity after 5 cycles, while Comparative Example 5, which had disordered pores formed by conventional mixing, experienced structural collapse after 3 cycles, with a retention rate of only 63.8%.

[0196] The self-repairing property of the dynamic cross-linked network played a key role in the regeneration process. The reversible cleavage and recombination of the thioester bond in Example 1 were triggered by the weak acid desorption solution (pH = 5.0), which repaired the micro-cracks generated by ion desorption in real time, with a retention rate fluctuation of only ± 2% (96.7-92.3%) among three cycles. The static cross-linked network of Comparative Example 4 experienced irreversible cleavage of the C-N bond, with a retention rate of only 71.4% after 3 cycles and a mass loss of 0.5% in the desorption solution, which confirmed the core support of dynamic covalent bonds on the durability of regeneration.

[0197] The synergistic design of components improved the regeneration stability through interface reinforcement. In Example 1, the hydrogen bond network was formed between the hydroxyl groups on the surface of the nano-carrier and the thioester groups of the RAFT cross-linking agent, and there was no delamination phenomenon after cycling. However, in Comparative Example 5, the absence of supercritical processing led to carrier agglomeration, and the interface bonding strength was insufficient at 5 MPa, resulting in a carrier shedding rate of 12% during the desorption process, which directly caused irreversible attenuation of the adsorption capacity, highlighting the decisive influence of process-component matching on the regeneration performance.

[0198] Test Example 5: Process adaptability verification

[0199] Test object: Example 1, Comparative Example 6, Comparative Example 10.

[0200] The experimental steps are as follows:

[0201] 1. Polymerization yield test:

[0202] Take 10.00 g of the dried finished material (accurate to 0.1 mg, Sartorius CPA225D analytical balance), record the actual mass (m 实际 ).

[0203] Calculate the theoretical total mass of raw materials (m 理论 = total mass of monomers + cross-linking agent + initiator).

[0204] Yield calculation formula:

[0205]

[0206] 2. Particle size distribution test:

[0207] Take 0.5g of the material powder, disperse it in 50mL of anhydrous ethanol, and sonicate for 30 minutes (KQ-500DE ultrasonic cleaner, 40kHz).

[0208] Particle size distribution was determined using a laser particle size analyzer (Malvern Mastersizer 3000), and the median of the D10 / D90 ratio was obtained by repeating the test three times.

[0209] 3. Data standardization:

[0210] Test environment: 25℃±1℃, relative humidity 40%±5%.

[0211] Outlier removal: If the D10 / D90 deviation from the median by more than 15% in a single particle size test, the measurement should be repeated.

[0212] The test results are shown in Table 5:

[0213] Table 5 Results of polymerization process stability test

[0214] Sample Polymerization yield (%) D10 / D90 ratio Example 1 92.3 1.15 Comparative Example 6 78.5 1.87 Comparative Example 10 68.9 2.34

[0215] Analysis of the data in Table 5 shows that:

[0216] This experiment, through polymerization yield and particle size distribution tests, revealed the crucial role of the synergistic control of microwave gradient RAFT polymerization and supercritical CO2 pressure in achieving uniform material structure. In Example 1, microwave radiation precisely controlled the free radical concentration through non-thermal effects, achieving synchronous growth of molecular chains. The polymerization yield reached 92.3% with a D10 / D90 ratio of 1.15. In contrast, Comparative Example 6 (conventional heating polymerization) exhibited a wide molecular weight distribution due to uneven decomposition of the thermal initiator, resulting in a yield of only 78.5% and a sharp increase in particle size dispersion (D10 / D90 = 1.87). The swelling effect of supercritical CO2 at 25 MPa enabled uniform diffusion of monomers within the polymer network, forming a pore size gradient distribution. Compared to the pore collapse structure of Comparative Example 10 (40 MPa high pressure), this improved pore utilization by 40%, directly translating to a 32% increase in yield.

[0217] Dynamic pressure control and spatiotemporal matching with living polymerization are key to process stability. In Example 1, the supercritical pressure was adjusted in stages (10→25→15MPa). During the initiation phase, the system viscosity was reduced to promote monomer penetration, while during the growth phase, the pressure was maintained to ensure orderly chain segment arrangement, ultimately forming monodisperse particles (D10 / D90 = 1.15). In contrast, the constant high pressure (40MPa) in Comparative Example 10 suppressed the chain transfer activity of the RAFT reagent, resulting in locally excessive crosslinking density and inducing microphase separation. The particle size distribution dispersion reached 2.34, confirming the necessity of pressure gradient design.

[0218] The component-process synergy enhances the material processability through interface reinforcement. The microwave-induced dynamic reorganization of the thioester linkage in Example 1 synergizes with the supercritical CO2 plasticization to reduce the glass transition temperature. While the thermal hysteresis effect of conventional heating in Comparative Example 6 leads to premature gelation due to the shortened half-life of the initiator, which directly causes the yield reduction and abnormal particle size distribution, highlighting the maximum support of specific polymerization process to the component performance.

[0219] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary and that certain changes and modifications can be made thereto without departing from the principles and spirit of the application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An acid-resistant chelating polymer for municipal solid waste treatment, characterized in that, The raw materials for preparation comprise the following components by mass percentage: Phosphorylated acrylamide 30-45%, vinyl imidazoline 20-35%, sulfonated betaine-type zwitterionic monomer 10-25%, RAFT functionalized crosslinking agent 5-10%, nano-titanium dioxide-graphene quantum dot composite carrier 3-8%; The method for preparing the polymer includes the following steps: (1) Pre-assembly process: The components are oriented and arranged in a supercritical CO2 environment; (2) Gradient polymerization reaction: The polymerization reaction is initiated in stages by microwave energy; (3) Mineralization treatment: Introduce calcium and phosphorus sources into the polymerization system for mineralization modification; (4) Post-processing steps: The product is dried and pulverized.

2. The acid-resistant chelating polymer for municipal solid waste treatment according to claim 1, characterized in that, The phosphorylated acrylamide is prepared by reacting acrylamide monomer and phosphorylation reagent at a mass ratio of (100-120):(45-60) at 80-90°C for 2.5-4 hours.

3. The acid-resistant chelating polymer for municipal solid waste treatment according to claim 1, characterized in that, The vinylimidazoline was synthesized from ethylenediamine and acrylonitrile in a molar ratio of 1:(2.2-2.5) under zinc chloride catalysis.

4. The acid-resistant chelating polymer for municipal solid waste treatment according to claim 1, characterized in that, The zwitterionic monomer of the sulfonate betaine type is methacryloyloxyethyl sulfonate betaine.

5. The acid-resistant chelating polymer for municipal solid waste treatment according to claim 1, characterized in that, The RAFT functionalized crosslinking agent is the reaction product of pentaerythritol tetraacrylate and dithioester chain transfer agent, with a mass ratio of (50-70):(10-15).

6. A method for preparing an acid-resistant chelating polymer for municipal solid waste treatment according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Pre-assembly process: The components are oriented and arranged in a supercritical CO2 environment; (2) Gradient polymerization reaction: The polymerization reaction is initiated in stages by microwave energy; (3) Mineralization treatment: Introduce calcium and phosphorus sources into the polymerization system for mineralization modification; (4) Post-processing steps: The product is dried and pulverized.

7. The preparation method according to claim 6, characterized in that, The steps of the gradient polymerization reaction include: First-stage polymerization: Reaction at 43–47°C and 280–320W microwave power for 40–60 minutes; Second stage crosslinking: heat to 58-62℃, increase microwave power to 480-520W, maintain pressure at 0.5-0.8 MPa for 1.5-2.5 hours; The third stage is stabilization: the temperature is reduced to 73-77℃, the microwave power is adjusted back to 300-350W, and the reaction continues for 50-70 minutes.

8. The preparation method according to claim 6, characterized in that, The mineralization process includes the following steps: Premix a 0.8–1.2 mol / L calcium chloride solution with a 0.5–0.7 mol / L sodium phosphate solution at a calcium-to-phosphorus molar ratio of 1.65–1.

70. The mixture was injected into the reaction system at a rate of 2–4 mL / min using a metering pump; React at 65–70°C and 400–600 rpm for 3–5 hours.

9. The preparation method according to claim 6, characterized in that, The post-processing steps include: Supercritical drying: The product was washed for 6–8 hours at a CO2 flow rate of 15–20 L / min under a pressure of 8–10 MPa. Airflow milling: The dried product is broken down using compressed air at 0.6–0.8 MPa; Screening process: The finished particle size D50 is controlled to be 25-45 μm by using a 200-300 mesh sieve.

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