Doped hydroxyapatite-based heavy metal mineralization material, and preparation method and application thereof

Abstract

This invention discloses a doped hydroxyapatite-based heavy metal mineralization material, its preparation method, and its application, belonging to the field of heavy metal contaminated soil remediation technology. In an alkaline environment with a pH of 8-11, this invention involves in-situ polymerization and simultaneous mineralization reactions of a mixed mineralization precursor with hydrophilic monomers and phosphates under the action of a crosslinking agent and initiator. This induces the formation of Fe-Mn co-doped hydroxyapatite and iron-manganese oxide / hydroxide nanoclusters, constructing a flexible interpenetrating network. After granulation, aging, washing, and drying, the doped hydroxyapatite-based heavy metal mineralization material is obtained. Through a redox system and isomorphic substitution mechanism, it simultaneously and deeply locks in anionic and cationic heavy metals. Utilizing highly absorbent components, it self-heals soil cracks and slowly releases active groups, significantly improving the material's long-term remediation performance under acidic erosion and physical structural damage conditions.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal contaminated soil remediation technology. Specifically, it relates to a doped hydroxyapatite-based heavy metal mineralization material, its preparation method, and its application. Background Technology

[0002] With the acceleration of industrialization and urbanization, soil heavy metal pollution has become a focal environmental issue. In particular, due to the complex pollution sources in urban green spaces, industrial remnants, and surrounding areas, these areas often exhibit characteristics of complex pollution from multiple anionic and cationic heavy (or similar) metals. These pollutants are characterized by their high concealment, persistent toxicity, and ease of migration and diffusion through soil erosion, seriously threatening ecological security and the human living environment. Therefore, developing remediation materials capable of simultaneously and efficiently immobilizing multiple complex forms of heavy metals is a crucial technical challenge that urgently needs to be overcome in the field of soil remediation.

[0003] In-situ chemical stabilization technology is widely used due to its cost-effectiveness and efficiency. Currently, lime, fly ash, phosphates, metal oxides, and biochar materials are widely used in in-situ chemical stabilization and remediation of soil. However, when dealing with complex heavy metal pollution (i.e., coexistence of cations and anions), existing technologies face significant bottlenecks due to chemical antagonism: traditional remediation materials usually rely on adding alkaline matrices to raise the soil pH, inducing Cd and Pb cations to form hydroxides or carbonates for solidification. However, the increase in pH leads to a significant increase in the negative charge density on the soil colloid surface, which in turn significantly enhances the electrostatic repulsion between the colloids and As and Cr oxyanions, causing the activation and migration of anionic pollutants and leading to a sharp increase in the risk of leaching. Although iron / manganese (hydrogen) oxides have a specific adsorption affinity for anions, in a simple physical mixing mode, their active sites are easily occupied by a large number of coexisting ions in the soil, and they mainly rely on reversible surface adsorption, resulting in insufficient long-term stability and a high risk of secondary release.

[0004] Furthermore, existing stabilization materials have significant shortcomings in addressing complex environmental erosion and physical structural damage when applied to remediate heavy metal pollution in soil. In areas with acidic rainfall or severe soil acidification, the passivating agents in existing materials (such as calcium carbonate and amorphous iron oxide) are highly susceptible to acid dissolution, leading to the re-release of fixed heavy metals. Under natural conditions, alternating wet and dry periods and freeze-thaw cycles cause macroscopic cracking of the soil structure and breakage of micro-aggregates. Existing phosphate and clay mineral composite materials lack ductility and cannot adapt to changes in soil volume expansion and contraction, causing the encapsulated pollutants to be re-exposed to the environmental medium, thus failing to achieve long-term remediation. More critically, most existing phosphate and clay mineral composite remediation materials are limited to simple physical mixing or surface loading. This composite approach suffers from the following technical bottlenecks: phosphate crystals are only adsorbed on the clay surface, making them prone to detachment and exhibiting poor stability; the limited interlayer space of the clay layer cannot accommodate large molecular pollutants, resulting in poor remediation effects. Summary of the Invention

[0005] To address the technical problems of existing remediation materials, such as poor stability, electrostatic repulsion between anions and cations, weak resistance to acid rain erosion, susceptibility to failure due to soil fissures, and lack of long-term remediation mechanisms, this invention provides a doped hydroxyapatite-based ultra-stable mineralization material for heavy metals that is designed for combined anion and cation pollution and has anti-fissure and slow-release functions, thus achieving long-term and green remediation of heavy metal contaminated soils.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] The first objective of this invention is to provide a doped hydroxyapatite-based heavy metal mineralization material, which is obtained by in-situ polymerization and simultaneous mineralization reaction of a mixed mineralization precursor, hydrophilic monomer, and phosphate under the action of a crosslinking agent and an initiator in an alkaline environment with a pH of 8 to 11, inducing the generation of Fe-Mn co-doped hydroxyapatite and iron-manganese oxide / hydroxide nanoclusters, and constructing a flexible interpenetrating network.

[0008] The mixed mineralization precursor is a modified matrix slurry formed by mixing dispersed framework materials, biomass matrix, and humic acid source, with Ca... 2+ Source, Fe 2+ Source and Mn 2+ The source is intercalated into the interlayer domain of the dispersed skeleton material in the modified matrix slurry, and simultaneously loaded onto the surface of the biomass matrix.

[0009] The dispersion framework material is sodium-based montmorillonite, calcium-based montmorillonite, illite, or vermiculite.

[0010] In the process of in-situ polymerization and simultaneous mineralization reaction, this invention utilizes the slow-release of Ca from the mixed mineral precursor. 2+It undergoes an in-situ precipitation-crystallization reaction with phosphate to form hydroxyapatite; simultaneously, due to Fe... 2+ Mn 2+ With Ca 2+ The similarity of ionic radii induces Fe 2+ With Mn 2+ Entering the lattice and Ca 2+ Isomorphic substitution occurs, and Fe-Mn co-doped hydroxyapatite (Fe-Mn-HAP) is constructed in situ for deep lattice-targeted capture of Cd and Pb cations.

[0011] The undoped iron and manganese ions in the reaction system are transformed into iron and manganese oxide / hydroxide nanoclusters, which not only provide redox active sites for As and Cr anions and eliminate the electrostatic repulsion of anions through redox dual systems (such as Mn(IV) / Fe(II)), but also form stable mineral inclusions with phosphates, effectively solving the problem of electrostatic repulsion in anion-cation complex pollution.

[0012] As a preferred embodiment, the Ca 2+ Source, Fe 2+ Source and Mn 2+ The molar ratio of the sources is 3 to 8:1:1.

[0013] In a preferred embodiment, the mass ratio of the biomass matrix to the dispersed framework material is 0.5–2:1; the Ca 2+ Source, Fe 2+ Source and Mn 2+ The total molar amount of the source to the mass ratio of the dispersed framework material is 10 mmol to 30 mmol: 1 g.

[0014] As a preferred embodiment, the Ca 2+ Source, Fe 2+ Source and Mn 2+ The sum of the molar amounts of the sources and the PO4 in the phosphate 3- The molar ratio is 1.5 to 8:1. The Ca... 2+ The source is Ca(NO3)2·4H2O, CaCl2, or Ca(OH)2; Fe 2+ The source is FeSO4·7H2O, FeCl2·4H2O, or (NH4)2Fe(SO4)2·6H2O; Mn 2+ The source is MnSO4·H2O or MnCl2·4H2O.

[0015] In a preferred embodiment, the biomass matrix is ​​soluble starch, sodium carboxymethyl cellulose, or sodium alginate; and the humic acid source is sodium humate, fulvic acid, or peat extract.

[0016] In a preferred embodiment, the hydrophilic monomer is acrylic acid, acrylamide, or 2-acrylamide-2-methylpropanesulfonic acid; the mass of the hydrophilic monomer is 30% to 60% of the total mass of the solid phase in the mixed mineralization precursor solution.

[0017] The doped hydroxyapatite-based heavy metal mineralization material has a saturated water absorption ratio of 80 g / g to 300 g / g and a specific surface area of ​​120 m². 2 / g~250m 2 It has a density of 1 g / g and exhibits excellent lattice stability and pH buffering capacity in acidic environments with a pH of 3–5.

[0018] The second objective of this invention is to provide a method for preparing a doped hydroxyapatite-based heavy metal mineralization material, comprising the following steps: A modified matrix slurry is formed by mixing a dispersion framework material, a biomass matrix, and a humic acid source, with Ca... 2+ Source, Fe 2+ Source and Mn 2+ The source is intercalated into the interlayer domain of the dispersed framework material in the modified matrix slurry, and simultaneously loaded onto the surface of the biomass matrix to obtain a mixed mineralized precursor.

[0019] Under an alkaline environment with an inert gas protection and a pH of 8-11, the mixed mineralization precursor solution is subjected to in-situ polymerization and simultaneous mineralization reaction with hydrophilic monomers and phosphates in the presence of crosslinking agents and initiators to construct a flexible interpenetrating network, forming Fe-Mn co-doped hydroxyapatite and iron-manganese oxide / hydroxide nanoclusters, and obtaining an interpenetrating network gel product. The interpenetrating network gel product was sequentially granulated, aged, washed, and dried at low temperature to obtain a doped hydroxyapatite-based heavy metal mineralization material.

[0020] It should be noted that after granulation, washing, and low-temperature drying, the material transforms from a swollen hydrogel state into a dry organic-inorganic hybrid interpenetrating network xerogel. This process does not destroy the physical network formed by the chemical cross-linking network constructed by the cross-linking agent and the inorganic crystals; therefore, its microscopic topology remains an interpenetrating network structure. The "aging and curing" process promotes the perfection of the inorganic crystals, the "washing" process removes unreacted monomers, and the "low-temperature drying" process, while preserving the porous structure, endows the material with excellent swelling activity during subsequent rehydration. These are essential technical steps in the preparation of this mineralized material.

[0021] In a preferred embodiment, the in-situ polymerization and simultaneous mineralization reaction is carried out at 300 r / min to 600 r / min and 50°C to 80°C for 2 h to 5 h.

[0022] The induced doped hydroxyapatite crystals and iron-manganese oxides are uniformly dispersed between the polymer network and the dispersion framework material layers.

[0023] In a preferred embodiment, the low-temperature drying temperature is 50℃~80℃, and the material is dried to a moisture content of 5%~12% to maintain its rehydration and swelling activity.

[0024] The third objective of this invention is to provide the application of doped hydroxyapatite-based heavy metal mineralization materials in the remediation of heavy metal and / or heavy metal-like contaminated soils. Specifically, the application involves adding the doped hydroxyapatite-based heavy metal mineralization materials to heavy metal and / or heavy metal-like contaminated soils for remediation.

[0025] The heavy metals and heavy metal-like substances include Cd, Pb, Cu, Zn, As, Cr, or Ni.

[0026] Remediation of heavy metal and / or heavy metal-like contaminated soil is achieved by mixing it with doped hydroxyapatite-based heavy metal mineralization materials. The remediation process utilizes the slowly released Mn(IV) / Fe(II) system within the material to perform redox transformation on As(III) and Cr(VI) in the soil, and leverages the released active PO42- 3- and in-situ hydroxyapatite (HAP) lattice-induced isomorphic substitution of Cd and Pb to form (Ca) 10-x M x (PO4)6(OH)2) solid solution, utilizing the superabsorbent resin component of the material to absorb water and swell during alternating wet and dry conditions to heal soil micro-cracks, and utilizing the humic acid component to promote the growth of indigenous microorganisms to maintain long-term stability.

[0027] In a preferred embodiment, the dosage of the doped hydroxyapatite-based heavy metal mineralization material is 0.5% to 3% of the soil mass, the moisture content of the heavy metal and / or heavy metal-like contaminated soil is 25% to 60%, and the remediation time is 15 days to 60 days.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes the slow-release Ca from mixed mineral precursors. 2+ It undergoes an in-situ precipitation-crystallization reaction with the added phosphate to form hydroxyapatite, while utilizing Fe 2+ Mn 2+ With Ca 2+The similarity of ionic radii induces isomorphic substitution within the crystal lattice, leading to the in-situ construction of Fe-Mn co-doped hydroxyapatite (Fe-Mn-HAP). This structure utilizes its abundant lattice defects and excellent ionic radius matching to achieve deep lattice-targeted capture of Cd and Pb cations. Simultaneously, undoped iron and manganese ions in the reaction system are transformed into iron and manganese oxide / hydroxide nanoclusters, which not only provide redox active sites for As and Cr anions and eliminate electrostatic repulsion of anions through redox dual systems (such as Mn(IV) / Fe(II)), but also form stable mineral inclusions with phosphates, effectively solving the problem of electrostatic repulsion in anion-cation complex pollution.

[0029] 2. This invention utilizes the high cation exchange capacity and interlayer buffering capacity of the dispersed framework material to significantly improve the stability of the material in acidic environments; the introduction of a flexible polymer network with high water absorption and self-healing capabilities endows the material with excellent ductility and water absorption and retention capacity, which can effectively resist physical cracks caused by soil freeze-thaw and alternating wet and dry conditions, and maintain the integrity of the repair.

[0030] 3. This invention encapsulates humic acid sources and mineralization precursors within a polymer network, allowing for slow release as the environment changes. This not only replenishes the active groups lost due to aging but also provides a continuous carbon source and electron donor for soil microorganisms, thus constructing a long-term remediation system that integrates physicochemical and microbial processes.

[0031] 4. The raw materials (biomass matrix, starch, dispersion framework material, humic acid) selected in this invention are widely available and environmentally friendly. The preparation process is mild and has no secondary pollution. The materials obtained are not only suitable for farmland and urban green space restoration, but also for emergency treatment of heavy metal wastewater, and have broad prospects for large-scale application.

[0032] In summary, this invention constructs an ultrastable mineralization system integrating "lattice-targeted capture, acid rain erosion resistance, physical crack resistance, and long-term sustained release." It simultaneously and deeply locks in anionic and cationic heavy metals through a Mn(IV) / Fe(II) redox system and a lattice isomorphic substitution mechanism, and introduces a dispersed framework material as a pH buffer framework. Combined with an interpenetrating polymer network (superabsorbent polymer) formed by the polymerization of hydrophilic monomers, a flexible interpenetrating network is constructed. The superabsorbent component self-heals soil cracks and slowly releases active groups, significantly improving the material's stability under acidic erosion and its long-term repair performance under physically destructive environments, demonstrating broad application prospects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation process of Embodiment 1 of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0035] Currently, lime, fly ash, phosphates, metal oxides, and biochar materials are widely used in in-situ chemical stabilization and remediation of soil. However, when dealing with complex heavy metal pollution (i.e., coexistence of cations and anions), existing technologies face significant bottlenecks due to chemical antagonism. Traditional remediation materials typically rely on adding alkaline matrices to raise the soil pH, inducing Cd and Pb cations to form hydroxides or carbonates for solidification. However, the increase in pH leads to a significant increase in the negative charge density on the soil colloid surface, which in turn significantly enhances the electrostatic repulsion between these colloids and As and Cr oxyanions, causing the activation and migration of anionic pollutants and resulting in a sharp increase in the risk of leaching. Although iron / manganese (hydrogen) oxides have a specific adsorption affinity for anions, in a purely physical mixing mode, their active sites are easily occupied by a large number of coexisting ions in the soil, and they mainly rely on reversible surface adsorption, resulting in insufficient long-term stability and a high risk of secondary release.

[0036] Furthermore, existing stabilization materials have significant shortcomings in addressing complex environmental erosion and physical structural damage when applied to remediate heavy metal pollution in soil. In areas with acidic rainfall or severe soil acidification, the passivating agents in existing materials (such as calcium carbonate and amorphous iron oxide) are highly susceptible to acid dissolution, leading to the re-release of fixed heavy metals. Under natural conditions, alternating wet and dry periods and freeze-thaw cycles cause macroscopic cracking of the soil structure and breakage of micro-aggregates. Existing phosphate and clay mineral composite materials lack ductility and cannot adapt to changes in soil volume expansion and contraction, causing the encapsulated pollutants to be re-exposed to the environmental medium, thus failing to achieve long-term remediation. More critically, most existing phosphate and clay mineral composite remediation materials are limited to simple physical mixing or surface loading. This composite approach suffers from the following technical bottlenecks: phosphate crystals are only adsorbed on the clay surface, making them prone to detachment and exhibiting poor stability; the limited interlayer space of the clay layer cannot accommodate large molecular pollutants, resulting in poor remediation effects. To address the aforementioned issues, this invention provides a doped hydroxyapatite-based ultra-stable mineralization material for heavy metals that is designed to address both anion and cation contamination and possesses anti-crack and slow-release properties, thereby enabling long-term, green remediation of heavy metal-contaminated soils.

[0037] The technical solution of the present invention will be analyzed in detail below.

[0038] This invention provides a doped hydroxyapatite-based heavy metal mineralization material. Under an alkaline environment with a pH of 8-11, a mixed mineralization precursor, hydrophilic monomer, and phosphate are subjected to in-situ polymerization and simultaneous mineralization reaction in the presence of a crosslinking agent and an initiator. This induces the formation of Fe-Mn co-doped hydroxyapatite and iron-manganese oxide / hydroxide nanoclusters, constructing a flexible interpenetrating network to obtain the doped hydroxyapatite-based heavy metal mineralization material.

[0039] The mixed mineralization precursor is a modified matrix slurry formed by mixing dispersed framework materials, biomass matrix, and humic acid source, with Ca... 2+ Source, Fe 2+ Source and Mn 2+ The source is intercalated into the interlayer domain of the dispersed framework material in the modified matrix slurry, and simultaneously loaded onto the surface of the biomass matrix to obtain a mixed mineralized precursor.

[0040] The dispersion framework material is sodium-based montmorillonite, calcium-based montmorillonite, illite, or vermiculite.

[0041] In the above technical solution, an interpenetrating network composite material of doped hydroxyapatite and superabsorbent resin / modified clay was prepared by in-situ polymerization. First, in response to anion and cation combined pollution, the material generates iron-manganese oxide / hydroxide nanoclusters in situ, constructing a coupling barrier between the Mn(IV) / Fe(II) redox system and the isomorphic substitution mechanism of the HAP lattice: Mn(IV) is used to oxidize and fix highly toxic As(III), and Fe(II) is used to reduce and precipitate highly mobile Cr(VI), eliminating the electrostatic repulsion between anions and soil colloids; at the same time, the Fe-Mn co-doped HAP lattice induces Cd and Pb to undergo isomorphic substitution to form a stable solid solution, "locking" the heavy metals inside the lattice. Secondly, to address acid erosion and physical cracks, this invention introduces a dispersed framework material as a pH buffer framework, combined with an interpenetrating polymer network (superabsorbent polymer) formed by the polymerization of hydrophilic monomers to construct a flexible interpenetrating network. This network polymer component absorbs water and swells during soil wetting and drying cycles, enabling it to self-heal soil micro-cracks and prevent pollutant exposure caused by aggregate destruction. Finally, through the slow-release effect of the interpenetrating network structure, the material can continuously release active phosphate, redox agents, and humic acid, promoting the growth of indigenous microorganisms and achieving long-term ecological restoration.

[0042] The technical solution of the present invention will be further illustrated below through the following embodiments and comparative examples.

[0043] Example 1 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0044] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0045] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0046] Example 2 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 60:20:20, and the mixture was stirred for 30 minutes to allow the metal cations to enter the interlayer domain of the dispersed framework material.

[0047] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0048] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0049] Example 3 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 80:10:10, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0050] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0051] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0052] Example 4 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0053] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio of 1.5:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0054] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0055] Example 5 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0056] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 55% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0057] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0058] Example 6 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0059] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 30% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0060] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0061] Example 7 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: Under nitrogen protection, soluble starch (35% by weight of the total solid phase) was dissolved in 60°C warm water and gelatinized. Sodium humate (5% by weight of the total solid phase) and sodium montmorillonite (30% by weight of the total solid phase) were added. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0062] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0063] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0064] Example 8 A method for preparing a doped hydroxyapatite-based heavy metal mineralization material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0065] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio of 1.67:1); add ammonium persulfate initiator, heat to 80℃, maintain pH at 8.5 with NaOH solution, and react for 2.5 h to obtain interpenetrating network gel product.

[0066] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0067] To further illustrate the effects of the present invention, comparative examples are also provided, as follows: Comparative Example 1 A method for preparing a composite material without Mn / Fe doping includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O was added to the modified matrix slurry, wherein Ca... 2+ The molar ratio is 70% of the total molars, and stirring for 30 minutes allows the metal cations to enter the interlayer domain of the dispersed framework material.

[0068] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0069] S3, Post-processing: The interpenetrating network gel product is granulated, aged for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain a composite material without Mn / Fe doping.

[0070] Comparative Example 2 A method for preparing a mineralized material without an intracellular superabsorbent polymer network (IPN) includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and sodium montmorillonite was added at 20% of the total solid mass. The mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0071] S2, In-situ polymerization and simultaneous mineralization: Add (NH4)2HPO4 solution to the above system (to adjust Ca). 2+ +Fe 2+ +Mn 2+ With PO4 3- The molar ratio was 1.67:1. The temperature was raised to 60℃, and the pH was maintained at 9.5 with NaOH solution. The reaction was carried out for 4 hours to obtain the mineralized product.

[0072] S3, Post-processing: The mineralized product described in S2 is washed with deionized water and dried at 60°C to a water content of 8% to obtain a mineralized material that does not contain a superabsorbent polymer network (IPN).

[0073] Comparative Example 3 A method for preparing a composite material without a dispersed framework material includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water at 35% of the total solid mass and gelatinized. Sodium humate was added at 5% of the total solid mass, and the mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca... 2+ Fe 2 + Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0074] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0075] S3, Post-processing: The interpenetrating network gel product is granulated, aged and cured for 24 hours, washed with deionized water, and dried at 60°C to a moisture content of 8% to obtain a composite material without dispersed skeleton material.

[0076] Comparative Example 4 A method for preparing a physically mixed hydroxyapatite-based heavy metal material includes the following steps: S1, Preparation of Ca-Fe-Mn phosphate powder: Ca(NO3)2·4H2O, FeSO4·7H2O and MnSO4·H2O are dissolved in water, wherein Ca 2+ Fe 2+ Mn 2+ The molar ratio of the two compounds was 70:15:15. When (NH4)2HPO4 solution was added, a precipitate was formed. The precipitate was filtered, washed, dried, and ground into powder to obtain Ca-Fe-Mn phosphate powder.

[0077] S2, weigh out 5% of the total solid mass of sodium humate, 20% of the total solid mass of sodium montmorillonite, 40% of the total solid mass of commercially available sodium polyacrylate superabsorbent polymer (SAP) granules, and 35% of the total solid mass of soluble starch.

[0078] S3, the Ca-Fe-Mn phosphate powder obtained in S1 and the components in S2 are placed in a mechanical mixer and stirred and mixed evenly at room temperature to obtain a physically mixed hydroxyapatite-based heavy metal material.

[0079] Comparative Example 5 A method for preparing a material free of humic acid sources includes the following steps: S1, Precursor Intercalation and Loading: This was carried out under nitrogen protection. Soluble starch was dissolved in 60°C warm water and gelatinized. Sodium montmorillonite was added at 20% of the total solid mass, and the mixture was ultrasonically dispersed for 30 min to obtain a modified matrix slurry. Ca(NO3)2·4H2O, FeSO4·7H2O, and MnSO4·H2O were added to the modified matrix slurry, wherein Ca...2+ Fe 2+ Mn 2+ The molar ratio was 70:15:15, and stirring for 30 minutes allowed the metal cations to enter the interlayer domain of the dispersed framework material.

[0080] S2, In-situ polymerization and simultaneous mineralization: Hydrophilic monomer acrylic acid (70% neutralization, 40% of the total solid mass), crosslinking agent N,N'-methylenebisacrylamide (0.1% of the monomer mass), and (NH4)2HPO4 solution (to adjust Ca) were added to the above system. 2+ +Fe 2+ +Mn 2+ With PO4 3- (Molar ratio 1.67:1); add ammonium persulfate initiator, heat to 60℃, maintain pH at 9.5 with NaOH solution, and react for 4 hours to obtain interpenetrating network gel product.

[0081] S3, Post-processing: The interpenetrating network gel product is granulated, aged for 24 hours, washed with deionized water, and dried at 60°C to a water content of 8% to obtain doped hydroxyapatite-based heavy metal mineralization material.

[0082] Performance testing Soil samples were tested: Soil sample 1 was collected from anion-cation contaminated soil (containing As, Cr, Cd, and Pb) near an abandoned chemical plant; Soil sample 2 was collected from heavy metal contaminated farmland in a southern region prone to acid rain (pH=4.2, main pollutants were Cd and Pb, and the soil had poor physical structure and was prone to compaction and cracking). The samples were air-dried and sieved for later use.

[0083] Experimental method: The remediation materials obtained from Examples 1 to 8 and Comparative Examples 1 to 5 were added to the two types of contaminated soils at a ratio of 1.5%.

[0084] For soil 1 (complex pollution): maintain a moisture content of 60% and a constant temperature of 25℃ for 28 days.

[0085] For Soil 2 (crack resistance and acid resistance): "alternating dry and wet treatment + simulated acid rain leaching" was carried out. First, three dry and wet cycles were performed (drying at 40℃ to constant weight and then adding water to saturate). Then, leaching was carried out with simulated acid rain at pH 3.5, and the leaching solution was collected.

[0086] Detection indicators: Determine the available content of heavy metals in soil 1 ("Technical Specification for Solidification / Stabilization of Polluted Soil Remediation Engineering" (HJ1282-2023)), determine the average weight diameter (MWD, characterizing crack resistance) of aggregates in soil 2 after wet-dry cycles, and the cumulative release of heavy metals in the leachate.

[0087] Table 1. Remediation results of soil contaminated with both anion and cation exchange around the chemical plant (Soil 1) Table 2. Physical structure and leaching results of acidic heavy metal contaminated farmland (soil 2) after wet-dry cycles. As shown in Table 1, Examples 1 through 8 all demonstrated excellent performance in treating combined anion and cation contamination (As, Cr, Cd, Pb). In particular, Example 2 (high iron-manganese ratio) showed the best removal effect on As and Cr anions, verifying the importance of the Mn(IV) / Fe(II) redox system; while Example 3 (high calcium ratio) showed the best immobilization effect on Cd and Pb cations, confirming the mechanism of isomorphic substitution in the HAP lattice. In contrast, Comparative Example 1 (no Fe / Mn) showed almost no removal ability for As and Cr, indicating that HAP alone cannot solve anion contamination; Comparative Example 4 (physical mixing) showed the worst effect, proving that the interpenetrating network structure constructed by in-situ polymerization and simultaneous mineralization is crucial for improving reactivity.

[0088] As shown in Table 2, under acid rain erosion and alternating wet and dry conditions, Examples 1 to 8 significantly improved the stability of soil aggregates (significantly increased MWD values) and effectively resisted crack formation. Example 5 (high resin content) had the highest MWD and the strongest crack resistance. Comparative Example 2 (without a superabsorbent resin network) had an extremely low MWD, indicating that it could not improve the soil physical structure and had a high release of heavy metals under acid rain leaching. Comparative Example 3 (a composite material without a dispersed framework material) lacked a pH buffer "barrier," resulting in a low pH in the leachate and the re-dissolution and release of some heavy metals. The example systems maintained a neutral pH after leaching and had extremely low heavy metal release, fully demonstrating the triple synergistic protection mechanism of "lattice fixation - clay buffering - resin crack resistance."

[0089] Obviously, the above description is only a preferred embodiment of the present invention, and those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalents, the present invention also intends to include these modifications and variations.

Claims

1. Doped hydroxyapatite-based heavy metal mineralization material, characterized in that, The doped hydroxyapatite-based heavy metal mineralization material is obtained by in-situ polymerization and simultaneous mineralization reaction of mixed mineralization precursors, hydrophilic monomers, and phosphates under the action of crosslinking agents and initiators in an alkaline environment with pH 8-11, inducing the generation of Fe-Mn co-doped hydroxyapatite and iron-manganese oxide / hydroxide nanoclusters, constructing a flexible interpenetrating network, and then granulating and aging. The mixed mineralization precursor is a modified matrix slurry formed by mixing dispersed framework materials, biomass matrix, and humic acid source, with Ca... 2+ Source, Fe 2+ Source and Mn 2+ The source is intercalated into the interlayer domain of the dispersed skeleton material in the modified matrix slurry, and simultaneously loaded onto the surface of the biomass matrix; The dispersion framework material is sodium-based montmorillonite, calcium-based montmorillonite, illite, or vermiculite; The Ca 2+ Source, Fe 2+ Source and Mn 2+ The molar ratio of the sources is 3–8:1:1; The mass ratio of the biomass matrix to the dispersed framework material is 0.5–2:1; the Ca 2+ Source, Fe 2+ Source and Mn 2+ The total molar amount of the source to the mass ratio of the dispersed framework material is 10 mmol to 30 mmol: 1 g; The Ca 2+ Source, Fe 2+ Source and Mn 2+ The sum of the molar amounts of the sources and the PO4 in the phosphate 3- The molar ratio is 1.5 to 8:

1.

2. The doped hydroxyapatite-based heavy metal mineralization material of claim 1, characterized in that, The biomass matrix is ​​soluble starch, sodium carboxymethyl cellulose, or sodium alginate; the humic acid source is sodium humate, fulvic acid, or peat extract.

3. The doped hydroxyapatite-based heavy metal mineralization material of claim 1, wherein, The hydrophilic monomer is acrylic acid, acrylamide, or 2-acrylamide-2-methylpropanesulfonic acid; the mass of the hydrophilic monomer is 30% to 60% of the total solid mass in the mixed mineralization precursor.

4. Process for the preparation of doped hydroxyapatite-based heavy metal mineralization material according to any one of claims 1 to 3, characterized in that, Includes the following steps: A modified matrix slurry is formed by mixing a dispersion framework material, a biomass matrix, and a humic acid source, with Ca... 2+ Source, Fe 2+ Source and Mn 2+ The source is intercalated into the interlayer domain of the dispersed framework material in the modified matrix slurry, and simultaneously loaded onto the surface of the biomass matrix to obtain a mixed mineralized precursor; Under an alkaline environment with an inert gas protection and a pH of 8-11, the mixed mineralization precursor is subjected to in-situ polymerization and simultaneous mineralization reaction with hydrophilic monomers and phosphates in the presence of crosslinking agents and initiators to form Fe-Mn co-doped hydroxyapatite and iron-manganese oxide / hydroxide nanoclusters, resulting in an interpenetrating network gel product. The interpenetrating network gel product was granulated, aged, washed, and dried at low temperature to obtain a doped hydroxyapatite-based heavy metal mineralization material.

5. The method of producing a doped hydroxyapatite-based heavy metal mineralization material according to claim 4, characterized in that The in-situ polymerization and simultaneous mineralization reaction is carried out at 300 r / min to 600 r / min and 50℃ to 80℃ for 2h to 5h; the granulation is carried out by mechanical cutting or extrusion granulation; the aging and curing conditions are 20℃ to 40℃ under sealed conditions for 12h to 36h; the low temperature drying conditions are 50℃ to 80℃.

6. The application of the doped hydroxyapatite-based heavy metal mineralization material according to any one of claims 1 to 3 in the remediation of heavy metal and / or heavy metal-like contaminated soil, characterized in that, The specific application involves adding doped hydroxyapatite-based heavy metal mineralization materials to soil contaminated with heavy metals and / or heavy metal-like substances for remediation; the heavy metals and heavy metal-like substances include Cd, Pb, Cu, Zn, As, Cr, or Ni.

7. Use of a doped hydroxyapatite-based heavy metal mineralization material according to claim 6 for remediating heavy metal and / or metalloid contaminated soil, characterized in that, The dosage of the doped hydroxyapatite-based heavy metal mineralization material is 0.5% to 3% of the soil mass; the moisture content of the heavy metal and / or heavy metal-like contaminated soil is 25% to 60%; and the remediation time is 15 to 60 days.

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