Hollow microsphere heavy metal contaminated soil leaching material and preparation method and application thereof

Abstract

The application discloses a hollow microsphere heavy metal contaminated soil leaching material and a preparation method and application thereof, and the heavy metal contaminated soil leaching material is composed of surface mercapto-modified titanium dioxide and silicon dioxide composite oxides. The heavy metal contaminated soil leaching material is environment-friendly, simple in preparation process, and can effectively reduce the heavy metal content in soil, and the product can be widely applied to the field of soil heavy metal leaching.

Description

Technical Field

[0001] This invention relates to a hollow microsphere leaching material for heavy metal contaminated soil, its preparation method and application, belonging to the field of heavy metal contaminated soil remediation. Background Technology

[0002] Hollow microspheres, with their unique cavity structure, low density, high specific surface area, and good permeability, exhibit significant advantages in adsorption and separation. Hollow microspheres, in particular, constructed from self-assembled nanoparticles, not only retain the size effect of nanounits but also achieve easy separation through their micron-scale spherical structure, making them a hot research topic in heavy metal pollution remediation materials. Current technologies primarily employ hard template methods (such as polystyrene microspheres and silica spheres) or soft template methods (such as emulsion droplets and micelles) to construct hollow structures. Inorganic precursors are coated onto the template surface through a sol-gel process or hydrothermal reaction, followed by calcination or solvent dissolution to remove the template and obtain hollow microspheres. However, hard template methods are often cumbersome, and the template removal process may damage the shell structure; while soft template methods offer milder conditions, they are sensitive to synthesis conditions and struggle to precisely control the nanoparticle packing morphology and pore structure of the shell. Summary of the Invention

[0003] The purpose of this invention is to address the current status and existing problems of heavy metal contaminated soil leaching, and to propose a hollow microsphere heavy metal contaminated soil leaching material, its preparation method, and its application.

[0004] A hollow microsphere leaching material for heavy metal contaminated soil is prepared using a combined method of block copolymer micelle template self-assembly, spray freeze-drying-induced spherical shell stacking, hydrothermal-induced inorganic layer self-assembly reinforcement, and steam etching coupled in-situ functional modification, with the molar ratio of titanium to silicon being 1:(0.5~2).

[0005] A method for preparing the above-mentioned heavy metal contaminated soil leaching material, the method of which is as follows:

[0006] (1) Preparation of core-shell precursors by self-assembly of block copolymer micelle templates

[0007] S1: The dried Shrek tube was evacuated and purged with nitrogen 1-3 times. Then, under nitrogen protection, cuprous bromide, pentamethyldiethylenetriamine, anisole, styrene, and ethyl 2-bromoisobutyrate were added and mixed. The mixture was then circulated through liquid nitrogen freezing-evacuation-thawing 1-3 times and then placed in a water bath for reaction. After the reaction was completed, the mixture was diluted with tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to methanol to precipitate the product. After filtration, the product was dried under vacuum to obtain PS-Br powder.

[0008] S2: The dried Shrek tube was evacuated and purged with nitrogen 1-3 times. Then, under nitrogen protection, PS-Br powder, cuprous bromide, pentamethyldiethylenetriamine, toluene, and tert-butyl acrylate were added and mixed. The mixture was then circulated through liquid nitrogen freezing-evacuation-thawing 1-3 times and then placed in a water bath for water bath reaction. After the reaction was completed, it was diluted with tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to a mixture of methanol and deionized water to precipitate. After filtration, it was vacuum dried to obtain PS-b-PtBA powder.

[0009] S3: PS-b-PtBA powder and dichloromethane are mixed to form a mixture, then trifluoroacetic acid is added and stirred at room temperature. After the reaction is completed, the mixture is evaporated by rotary evaporation to obtain a block copolymer template.

[0010] S4: Weigh out the block copolymer template, ethylene glycol, and deionized water, mix them, and then stir them in a water bath at a constant temperature to form a micelle core solution.

[0011] S5: Weigh out silicon source, titanium source and anhydrous ethanol and mix them to form a precursor solution. Under constant temperature water bath stirring conditions, drop the precursor solution into the micelle core solution and adjust the alkalinity with dilute ammonia to carry out hydrolysis and condensation reaction. After the reaction is completed, a core-shell structured composite micelle sol is obtained.

[0012] (2) Preparation of hollow microsphere skeleton by spray freeze-drying-induced spherical shell stacking

[0013] The core-shell structured composite micelle sol obtained in step (1) was sprayed into an iron beaker containing liquid nitrogen under gas pressure through an atomizing nozzle. After being frozen by liquid nitrogen, the frozen droplets were placed in a freeze dryer for freeze drying to obtain hollow micron-sized spherical skeleton powder.

[0014] (3) Hydrothermal-induced self-assembly of inorganic layers to enhance the construction of nanopores

[0015] Weigh hexadecyltrimethylammonium bromide, ethanol, deionized water, and the hollow microsphere skeleton powder obtained in step (2) and mix them to form a dispersion. Then place it in a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, centrifuge and wash with deionized water and ethanol to obtain pretreated hollow microsphere powder.

[0016] (4) Preparation of rinsing materials by steam etching coupled with in-situ functional modification

[0017] The pretreated hollow microsphere powder obtained in step (3) was placed on a porous support of a hydrothermal reactor. An aqueous solution of ethylenediamine was added to the bottom of the hydrothermal reactor. The hydrothermal reactor was then placed in an oven for steam etching. After the steam etching was completed, the pretreated hollow microsphere powder was taken out and mixed with (3-mercaptopropyl)trimethoxysilane and toluene. The mixture was subjected to constant temperature reflux reaction under nitrogen protection. After the reaction was completed, the mixture was washed with toluene, acetone and deionized water in sequence. Finally, the mixture was vacuum dried to obtain the rinsing material.

[0018] In the above preparation method: in step (1) S1, the mass ratio of cuprous bromide, pentamethyldiethylenetriamine, anisole, styrene, ethyl 2-bromoisobutyrate, tetrahydrofuran, and methanol is 1:(0.8~1.6):(40~60):(80~160):(1~1.5):(400~600):(100~200), the water bath reaction temperature is 85~95℃, and the water bath reaction time is 5~10h; the vacuum drying temperature is 30~60℃, and the drying time is 6~8h.

[0019] In the above preparation method: the mass ratio of PS-Br powder, cuprous bromide, pentamethyldiethylenetriamine, toluene, tert-butyl acrylate, tetrahydrofuran, methanol, and deionized water in step (1) S2 is 1:(0.02~0.04):(0.02~0.04):(3~6):(4~8):(40~60):(20~40):(2~4); the vacuum drying temperature is 40~60℃, and the vacuum drying time is 6~8h;

[0020] In step (3), the mass ratio of PS-b-PtBA powder, dichloromethane, and trifluoroacetic acid in S3 is 1:(20~40):(10~15), the stirring rate is 100~200 rpm, and the stirring time is 24~36 h.

[0021] In the above preparation method: the silicon source mentioned in step (1) S5 is tetraethyl orthosilicate, the titanium source is tetrabutyl titanate or tetraethyl titanate, the mass fraction of dilute ammonia is 5~10%, the mass ratio of block copolymer template, ethylene glycol, deionized water, silicon source and anhydrous ethanol is 1:(30~60):(10~20):(2~4):(30~60), and the pH is adjusted to 8.5~9.0 with dilute ammonia;

[0022] In both S4 and S5, the stirring speed in the constant temperature water bath is 200~400 rpm, the stirring temperature in the constant temperature water bath is 50~70℃, and the stirring time in the constant temperature water bath is 4~8h.

[0023] In the above preparation method: the diameter of the atomizing nozzle in step (2) is 0.5~1mm, the gas pressure is 0.2~0.4MPa, the freeze-drying temperature is -40~-50℃, and the freeze-drying time is 36~72h.

[0024] In the above preparation method: the mass ratio of the hollow microsphere skeleton powder, hexadecyltrimethylammonium bromide, ethanol and deionized water in step (3) is 1:(0.1~0.2):(6~12):(6~12), the hydrothermal reaction temperature is 120~140℃, and the hydrothermal reaction time is 12~24h.

[0025] In the above preparation method: the mass fraction of the ethylenediamine aqueous solution in step (4) is 5~10%, the mass ratio of the pretreated hollow microsphere powder to the ethylenediamine aqueous solution is 1:(3~6), the temperature of the steam etching is 120~140℃, and the time of the steam etching is 3~6h.

[0026] In the above preparation method: the mass ratio of the pretreated hollow microsphere powder, (3-mercaptopropyl)trimethoxysilane and toluene in step (4) is 1:(0.2~0.4):(10~20), the temperature of the constant temperature reflux reaction is 110~120℃, the time of the constant temperature reflux reaction is 12~18h, the temperature of the vacuum drying is 40~60℃, and the time of the vacuum drying is 10~20h.

[0027] In the technical solution of the present invention, the application of the leaching material in the leaching of heavy metal contaminated soil is further preferably: the heavy metal is cadmium and / or arsenic.

[0028] Experimental conditions and results of this invention: 100 g of clay was mixed with 2000 mL of deionized water, dried, and passed through a 2 mm sieve for use as a pretreatment for cleaning soil. 10 mg of cadmium carbonate or arsenic sulfide was moistened with 3 mL of deionized water and sprayed onto 100 g of air-dried clean soil. The sample was then homogenized and aged at room temperature (25 °C) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed in a mass ratio of 1:10:10 and shaken for 1 h using a constant temperature shaker (200 r / min). The supernatant was then filtered. The content of heavy metals in the supernatant was determined by ICP, and the elution rate of heavy metals was calculated. The elution rates of cadmium carbonate and arsenic sulfide were both higher than 90%.

[0029] Beneficial effects:

[0030] (1) To avoid the problem that commercial block copolymers rely on hydrophilic and hydrophobic interactions in solution to form micelles, the size distribution and morphological stability of which are easily affected by external conditions such as temperature and concentration, and the lack of active sites on the micelle surface that specifically bind to inorganic precursors, this invention synthesizes polystyrene-polyacrylic acid (PS-b-PAA) block copolymer templates through atom transfer radical polymerization. The PAA blocks are rich in carboxyl groups, which can chemically bond with titanium and silicon sources through coordination or electrostatic interactions, thereby forming a strong organic-inorganic covalent interface on the micelle surface. The inorganic shell anchored by chemical bonds is not easy to peel off or collapse from the template surface during subsequent processing, ensuring the integrity and stability of the core-shell structure. In addition, the uniform combination of carboxyl groups and inorganic precursors enables the inorganic components to form a continuous and controllable coating layer on the micelle surface, avoiding the uneven coating or agglomeration caused by conventional physical adsorption, thereby providing a stable primary building block for obtaining hollow microspheres with regular morphology.

[0031] (2) To avoid the problem that direct hot air dehydration during spray drying can cause the capillary force generated by solvent evaporation to drive the nanoparticles to pack tightly, which can easily lead to particle densification or even spherical shrinkage and make it difficult to form a hollow cavity, this invention uses spray freeze-drying technology to construct a hollow structure through physical phase separation and sublimation mechanism. First, the core-shell structure micelle sol is atomized into micron-sized droplets and rapidly frozen under liquid nitrogen conditions, so that deionized water and ethylene glycol form solid ice crystals. Then, under vacuum freeze-drying conditions, the ice crystals directly sublimate and escape, leaving the space originally occupied by the ice crystals as macroporous channels, while the composite micelles are piled up at the ice crystal boundaries to form a loose micron-sized spherical skeleton. In addition, the particle size of the hollow microspheres can be controlled by controlling the diameter of the atomizing nozzle and the gas pressure. The freeze-drying process is carried out under low temperature vacuum, which can avoid the effect of liquid phase surface tension, so that the spherical shell structure formed by micelle stacking can be preserved in its original form.

[0032] (3) To avoid the problem that conventional hydrothermal crystallization often directly treats dense inorganic shells, with the reaction mainly occurring on the surface and making it difficult to form through-pores inside the shell, this invention performs hydrothermal treatment on the microsphere skeleton with the assistance of CTAB. In a high-temperature and high-pressure environment, an Oswald ripening process of dissolution-redeposition is initiated. Smaller, thermodynamically unstable inorganic nanoparticles gradually dissolve and recrystallize on the surface of larger particles. This process causes the micelle units that were originally physically stacked to be transformed into uniform nanoparticles connected by chemical bonds. The nanoparticles then aggregate and self-assemble. The CTAB is assembled into a robust shell framework. During this process, CTAB acts as a pore guiding agent and self-assembles into a micelle template during hydrothermal treatment. It is embedded in the inorganic framework and occupies the space at the nanoscale. After the reaction, CTAB is removed by centrifugation and washing, leaving mesopores in the gaps between the nanoparticles. The mesopores generated by CTAB and the macropores formed by freeze-drying in step (2) constitute a hierarchical pore structure. The mesopores provide adsorption sites with high specific surface area, while the macropores serve as fast channels for material transport. They have a significant synergistic effect on improving the adsorption rate and adsorption capacity of heavy metal ions.

[0033] (4) To avoid the problem that although conventional liquid phase etching can rapidly expand holes, the etching of nanoparticles by strong alkaline solutions is often anisotropic and difficult to control, which can easily cause local over-dissolution of the shell or even structural collapse, the present invention

[0034] Ethylenediamine vapor is used for gentle etching, followed by in-situ thiol functionalization, to achieve synergistic optimization of pore unblocking and active site introduction. Ethylenediamine vapor diffuses into the microsphere pores under high temperature and pressure to perform gentle chemical etching of SiO2-TiO2, unblocking potentially closed or narrow pores and exposing more active hydroxyl groups. After etching, the microspheres are transferred to a toluene solution containing MPTMS for reflux grafting. The highly reactive hydroxyl groups can undergo efficient condensation reactions with the methoxy groups of MPTMS to form stable Si-O-Si covalent bonds, ensuring that thiol functional groups are not only grafted on the outer surface of the microspheres but also uniformly distributed deep within the inner walls of the nanopores, improving the utilization rate of active sites and the accessibility to heavy metal ions.

[0035] Therefore, the heavy metal contaminated soil leaching material prepared by this invention has multiple advantages, such as high density of thiol complexation sites, rapid mass transfer characteristics of hierarchical channels, and chemical stability of composite oxide skeleton. In the application of heavy metal contaminated soil leaching, it exhibits large adsorption capacity, fast adsorption rate, and easy recycling and regeneration, and has strong application and promotion value. Attached Figure Description

[0036] Figure 1 This is a scanning electron microscope image of the elution material prepared in Example 1;

[0037] Figure 2 This is a scanning electron microscope image of the elution material prepared in Example 1;

[0038] Figure 3 The graph shows the performance of the elution materials prepared in Examples 1-3 in eluting cadmium carbonate.

[0039] Figure 4 The graph shows the performance of the rinsing materials prepared in Examples 1-3 in removing arsenic sulfide. Detailed Implementation

[0040] The present invention will be further described below with reference to the embodiments. The embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0041] Example 1

[0042] (1) Preparation of core-shell precursors by self-assembly of block copolymer micelle templates

[0043] The dried Shrek tube was evacuated and purged with nitrogen three times. Then, under nitrogen protection, 1.000 g cuprous bromide, 0.800 g pentamethyldiethylenetriamine, 40.000 g anisole, 80.000 g styrene, and 1.000 g ethyl 2-bromoisobutyrate were added and mixed. The mixture was then subjected to a cycle of liquid nitrogen freezing, evacuation, and thawing three times. Finally, it was placed in a water bath at 85°C and reacted for 10 hours. After the reaction, it was diluted with 400.000 g tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to 100.000 g methanol to precipitate the precipitate. After filtration, it was dried under vacuum at 40°C for 8 hours to obtain PS-Br powder.

[0044] The dried Shrek tube was evacuated and purged with nitrogen three times. Then, under nitrogen protection, 5.000g PS-Br powder, 0.100g cuprous bromide, 0.100g pentamethyldiethylenetriamine, 15.000g toluene, and 20.000g tert-butyl acrylate were added and mixed. The mixture was then subjected to a cycle of liquid nitrogen freezing, evacuation, and thawing three times. Finally, it was placed in a water bath at 85°C for 10 hours. After the reaction, it was diluted with 200.000g tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to a mixture of 100.000g methanol and 10.000g deionized water to precipitate the precipitate. After filtration, it was vacuum dried at 40°C for 8 hours to obtain PS-b-PtBA powder.

[0045] 10.000g of PS-b-PtBA powder and 200.000g of dichloromethane were mixed to form a mixture, and then 100.000g of trifluoroacetic acid was added and the mixture was stirred at 100rpm at room temperature for 36h. After the reaction was completed, the mixture was evaporated by rotary evaporation to obtain the block copolymer template.

[0046] Weigh 8.669g of block copolymer template, 260.070g of ethylene glycol and 86.690g of deionized water and mix them. Then stir the mixture in a water bath at 200rpm and 50℃ for 8h to form a micelle core solution.

[0047] 17.337 g of tetraethyl orthosilicate, 14.161 g of tetrabutyl titanate, and 260.070 g of anhydrous ethanol were weighed and mixed to form a precursor solution. The precursor solution was added dropwise to the micelle core solution under constant temperature water bath stirring at 50°C and 200 rpm. The pH was adjusted to 8.5 with 5% dilute ammonia water and the hydrolysis and condensation reaction was carried out for 8 hours. After the reaction was completed, a core-shell structured composite micelle sol was obtained.

[0048] (2) Preparation of hollow microsphere skeleton by spray freeze-drying-induced spherical shell stacking

[0049] The core-shell structured composite micelle sol obtained in step (1) was sprayed into an iron beaker containing liquid nitrogen through an atomizing nozzle with a diameter of 0.5 mm at a gas pressure of 0.2 MPa. After being frozen by liquid nitrogen, the frozen droplets were placed in a freeze dryer and freeze-dried at -40°C for 72 h to obtain hollow micron-sized spherical skeleton powder.

[0050] (3) Hydrothermal-induced self-assembly of inorganic layers to enhance the construction of nanopores

[0051] Weigh 0.800g cetyltrimethylammonium bromide, 48.000g ethanol, 48.000g deionized water, and 8.000g hollow microsphere skeleton powder obtained in step (2) and mix them to form a dispersion. Then place it in a hydrothermal reactor and react it at 120℃ for 24h. After the reaction is completed, centrifuge and wash with deionized water and ethanol to obtain pretreated hollow microsphere powder.

[0052] (4) Preparation of rinsing materials by steam etching coupled with in-situ functional modification

[0053] 6.000g of the pretreated hollow microsphere powder obtained in step (3) was placed on a porous support of a hydrothermal reactor. 18.000g of 5% ethylenediamine aqueous solution was added to the bottom of the hydrothermal reactor. The hydrothermal reactor was then placed in an oven and etched with steam at 120℃ for 6h. After the steam etching was completed, the pretreated hollow microsphere powder was taken out and mixed with 1.200g of (3-mercaptopropyl)trimethoxysilane and 60.000g of toluene. The mixture was subjected to constant temperature reflux reaction for 18h under nitrogen protection (the temperature of the constant temperature reflux reaction was 110℃). After the reaction was completed, the mixture was washed with toluene, acetone and deionized water in sequence. Finally, it was vacuum dried at 40℃ for 20h to obtain the elution material (the molar ratio of titanium to silicon was 1:2, and the scanning electron microscope image of the catalyst is shown in the figure). Figure 1 and Figure 2 (as shown)

[0054] (5) Rinsing performance test

[0055] Clay (100 g) was mixed with deionized water (2000 mL), dried, and passed through a 2 mm sieve for use in preparing clean soil. 10 mg of cadmium carbonate or arsenic sulfide was moistened with 3 mL of deionized water and sprayed onto 100 g of air-dried clean soil. The samples were then homogenized and aged at room temperature (25 °C) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed in a mass ratio of 1:10:10 and shaken for 1 h using a constant temperature shaker (200 r / min). The supernatant was then filtered, and the content of heavy metals in the supernatant was determined by ICP. The elution rate of heavy metals was calculated. The elution rates of cadmium carbonate and arsenic sulfide were both higher than 90%.

[0056] Example 2

[0057] (1) Preparation of core-shell precursors by self-assembly of block copolymer micelle templates

[0058] The dried Shrek tube was evacuated and purged with nitrogen three times. Then, under nitrogen protection, 1.000 g cuprous bromide, 1.600 g pentamethyldiethylenetriamine, 60.000 g anisole, 160.000 g styrene, and 1.500 g ethyl 2-bromoisobutyrate were added and mixed. The mixture was then subjected to a cycle of liquid nitrogen freezing, evacuation, and thawing three times. Finally, it was placed in a water bath at 95°C and reacted for 5 hours. After the reaction, it was diluted with 600.000 g tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to 200.000 g methanol to precipitate the precipitate. After filtration, it was dried under vacuum at 60°C for 6 hours to obtain PS-Br powder.

[0059] The dried Shrek tube was evacuated and purged with nitrogen three times. Then, under nitrogen protection, 5.000g PS-Br powder, 0.200g cuprous bromide, 0.200g pentamethyldiethylenetriamine, 30.000g toluene, and 40.000g tert-butyl acrylate were added and mixed. The mixture was then subjected to a cycle of liquid nitrogen freezing, evacuation, and thawing three times. Finally, it was placed in a water bath at 95°C for 5 hours. After the reaction, it was diluted with 300.000g tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to a mixture of 200.000g methanol and 20.000g deionized water to precipitate the precipitate. After filtration, it was vacuum dried at 60°C for 6 hours to obtain PS-b-PtBA powder.

[0060] 10.000g of PS-b-PtBA powder and 400.000g of dichloromethane were mixed to form a mixture, and then 150.000g of trifluoroacetic acid was added and the mixture was stirred at 200rpm at room temperature for 24h. After the reaction was completed, the mixture was evaporated by rotary evaporation to obtain the block copolymer template.

[0061] Weigh 1.734g of block copolymer template, 104.040g of ethylene glycol and 34.680g of deionized water and mix them. Then stir the mixture in a water bath at 400rpm and 70℃ for 4h to form a micelle core solution.

[0062] 6.935g of tetraethyl orthosilicate, 15.187g of tetraethyl titanate, and 104.040g of anhydrous ethanol were weighed and mixed to form a precursor solution. The precursor solution was added dropwise to the micelle core solution under constant temperature water bath stirring at 70℃ and 400 rpm. The pH was adjusted to 9.0 with 10% dilute ammonia water and the hydrolysis and condensation reaction was carried out for 4 hours. After the reaction was completed, a core-shell structured composite micelle sol was obtained.

[0063] (2) Preparation of hollow microsphere skeleton by spray freeze-drying-induced spherical shell stacking

[0064] The core-shell structured composite micelle sol obtained in step (1) was sprayed into an iron beaker containing liquid nitrogen through an atomizing nozzle with a diameter of 1 mm at a gas pressure of 0.4 MPa. After being frozen by liquid nitrogen, the frozen droplets were placed in a freeze dryer and freeze-dried at -50°C for 36 h to obtain hollow micron-sized spherical skeleton powder.

[0065] (3) Hydrothermal-induced self-assembly of inorganic layers to enhance the construction of nanopores

[0066] Weigh 1.600g cetyltrimethylammonium bromide, 96.000g ethanol, 96.000g deionized water, and 8.000g hollow microsphere skeleton powder obtained in step (2) and mix them to form a dispersion. Then place it in a hydrothermal reactor and hydrothermally react at 140℃ for 12h. After the reaction is completed, centrifuge and wash with deionized water and ethanol to obtain pretreated hollow microsphere powder.

[0067] (4) Preparation of rinsing materials by steam etching coupled with in-situ functional modification

[0068] 6.000g of the pretreated hollow microsphere powder obtained in step (3) was placed on a porous support of a hydrothermal reactor. 36.000g of 10% ethylenediamine aqueous solution was added to the bottom of the hydrothermal reactor. The hydrothermal reactor was then placed in an oven and etched with steam at 140°C for 3 hours. After the steam etching was completed, the pretreated hollow microsphere powder was taken out and mixed with 2.400g of (3-mercaptopropyl)trimethoxysilane and 120.000g of toluene. The mixture was subjected to constant temperature reflux reaction for 12 hours under nitrogen protection (the temperature of the constant temperature reflux reaction was 120°C). After the reaction was completed, the mixture was washed with toluene, acetone and deionized water in sequence. Finally, it was vacuum dried at 60°C for 10 hours to obtain the leaching material (the molar ratio of titanium to silicon was 1:0.5).

[0069] (5) Rinsing performance test

[0070] Clay (100 g) was mixed with deionized water (2000 mL), dried, and passed through a 2 mm sieve for use in preparing clean soil. 10 mg of cadmium carbonate or arsenic sulfide was moistened with 3 mL of deionized water and sprayed onto 100 g of air-dried clean soil. The samples were then homogenized and aged at room temperature (25 °C) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed in a mass ratio of 1:10:10 and shaken for 1 h using a constant temperature shaker (200 r / min). The supernatant was then filtered, and the content of heavy metals in the supernatant was determined by ICP. The elution rate of heavy metals was calculated. The elution rates of cadmium carbonate and arsenic sulfide were both higher than 90%.

[0071] Example 3

[0072] (1) Preparation of core-shell precursors by self-assembly of block copolymer micelle templates

[0073] The dried Shrek tube was evacuated and purged with nitrogen three times. Then, under nitrogen protection, 1.000 g cuprous bromide, 1.200 g pentamethyldiethylenetriamine, 50.000 g anisole, 120.000 g styrene, and 1.200 g ethyl 2-bromoisobutyrate were added and mixed. The mixture was then subjected to a cycle of liquid nitrogen freezing, evacuation, and thawing three times. Finally, it was placed in a water bath at 90°C for 7 hours. After the reaction, it was diluted with 500.000 g tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to 150.000 g methanol to precipitate the precipitate. After filtration, it was dried under vacuum at 50°C for 7 hours to obtain PS-Br powder.

[0074] The dried Shrek tube was evacuated and purged with nitrogen three times. Then, under nitrogen protection, 5.000g PS-Br powder, 0.150g cuprous bromide, 0.150g pentamethyldiethylenetriamine, 20.000g toluene, and 30.000g tert-butyl acrylate were added and mixed. The mixture was then subjected to a cycle of liquid nitrogen freezing, evacuation, and thawing three times. Finally, it was placed in a water bath at 90°C for 7 hours. After the reaction, it was diluted with 250.000g tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to a mixture of 150.000g methanol and 15.000g deionized water to precipitate the precipitate. After filtration, it was dried under vacuum at 50°C for 7 hours to obtain PS-b-PtBA powder.

[0075] 10.000g of PS-b-PtBA powder and 300.000g of dichloromethane were mixed to form a mixture, and then 120.000g of trifluoroacetic acid was added and the mixture was stirred at 150rpm at room temperature for 30h. After the reaction was completed, the mixture was evaporated by rotary evaporation to obtain the block copolymer template.

[0076] Weigh 5.779g of block copolymer template, 231.160g of ethylene glycol and 86.685g of deionized water and mix them. Then, stir the mixture in a water bath at 300rpm and 60℃ for 6h to form a micelle core solution.

[0077] 17.337 g of tetraethyl orthosilicate, 18.983 g of tetraethyl titanate, and 231.160 g of anhydrous ethanol were weighed and mixed to form a precursor solution. The precursor solution was added dropwise to the micelle core solution under constant temperature water bath stirring at 600 rpm and 300 rpm. The pH was adjusted to 9.0 with 7% dilute ammonia water and the hydrolysis and condensation reaction was carried out for 6 h. After the reaction was completed, a core-shell structured composite micelle sol was obtained.

[0078] (2) Preparation of hollow microsphere skeleton by spray freeze-drying-induced spherical shell stacking

[0079] The core-shell structured composite micelle sol obtained in step (1) was sprayed into an iron beaker containing liquid nitrogen through an atomizing nozzle with a diameter of 1 mm at a gas pressure of 0.3 MPa. After being frozen by liquid nitrogen, the frozen droplets were placed in a freeze dryer and freeze-dried at -50°C for 36 h to obtain hollow micron-sized spherical skeleton powder.

[0080] (3) Hydrothermal-induced self-assembly of inorganic layers to enhance the construction of nanopores

[0081] Weigh 1.200g cetyltrimethylammonium bromide, 80.000g ethanol, 80.000g deionized water, and 8.000g hollow microsphere skeleton powder obtained in step (2) and mix them to form a dispersion. Then place it in a hydrothermal reactor and hydrothermally react at 130℃ for 18h. After the reaction is completed, centrifuge and wash with deionized water and ethanol to obtain pretreated hollow microsphere powder.

[0082] (4) Preparation of rinsing materials by steam etching coupled with in-situ functional modification

[0083] 6.000g of the pretreated hollow microsphere powder obtained in step (3) was placed on a porous support of a hydrothermal reactor. 30.000g of 7% ethylenediamine aqueous solution was added to the bottom of the hydrothermal reactor. The hydrothermal reactor was then placed in an oven and etched with steam at 130°C for 4 hours. After the steam etching was completed, the pretreated hollow microsphere powder was taken out and mixed with 1.800g of (3-mercaptopropyl)trimethoxysilane and 90.000g of toluene. The mixture was subjected to constant temperature reflux reaction for 16 hours under nitrogen protection (the temperature of the constant temperature reflux reaction was 115°C). After the reaction was completed, the mixture was washed with toluene, acetone and deionized water in sequence. Finally, it was vacuum dried at 50°C for 15 hours to obtain the leaching material (the molar ratio of titanium to silicon was 1:1).

[0084] (5) Rinsing performance test

[0085] Clay (100 g) was mixed with deionized water (2000 mL), dried, and passed through a 2 mm sieve for use in preparing clean soil. 10 mg of cadmium carbonate or arsenic sulfide was moistened with 3 mL of deionized water and sprayed onto 100 g of air-dried clean soil. The samples were then homogenized and aged at room temperature (25 °C) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed in a mass ratio of 1:10:10 and shaken for 1 h using a constant temperature shaker (200 r / min). The supernatant was then filtered, and the content of heavy metals in the supernatant was determined by ICP. The elution rate of heavy metals was calculated. The elution rates of cadmium carbonate and arsenic sulfide were both higher than 90%.

Claims

1. A hollow microsphere soil leaching material for heavy metal contaminated soil, characterized in that: The heavy metal contaminated soil leaching material is composed of surface-thiolized modified titanium dioxide and silicon dioxide composite oxide. It is prepared by a combined method of block copolymer micelle template self-assembly-spray freeze-drying induced spherical shell stacking-hydrothermal induced inorganic layer self-assembly reinforcement-vapor etching coupled in-situ functional modification. The molar ratio of titanium to silicon is 1:(0.5~2).

2. A method for preparing the leaching material for heavy metal contaminated soil as described in claim 1, characterized in that: The preparation method of this heavy metal contaminated soil leaching material is as follows: (1) Preparation of core-shell precursors by self-assembly of block copolymer micelle templates S1: The dried Shrek tube was evacuated and purged with nitrogen 1-3 times. Then, under nitrogen protection, cuprous bromide, pentamethyldiethylenetriamine, anisole, styrene, and ethyl 2-bromoisobutyrate were added and mixed. The mixture was then circulated through liquid nitrogen freezing-evacuation-thawing 1-3 times and then placed in a water bath for reaction. After the reaction was completed, the mixture was diluted with tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to methanol to precipitate the product. After filtration, the product was dried under vacuum to obtain PS-Br powder. S2: The dried Shrek tube was evacuated and purged with nitrogen 1-3 times. Then, under nitrogen protection, PS-Br powder, cuprous bromide, pentamethyldiethylenetriamine, toluene, and tert-butyl acrylate were added and mixed. The mixture was then circulated through liquid nitrogen freezing-evacuation-thawing 1-3 times and then placed in a water bath for water bath reaction. After the reaction was completed, it was diluted with tetrahydrofuran and passed through a neutral alumina column. The filtrate was then added dropwise to a mixture of methanol and deionized water to precipitate. After filtration, it was vacuum dried to obtain PS-b-PtBA powder. S3: PS-b-PtBA powder and dichloromethane are mixed to form a mixture, then trifluoroacetic acid is added and stirred at room temperature. After the reaction is completed, the mixture is evaporated by rotary evaporation to obtain a block copolymer template. S4: Weigh out the block copolymer template, ethylene glycol, and deionized water, mix them, and then stir them in a water bath at a constant temperature to form a micelle core solution. S5: Weigh out silicon source, titanium source and anhydrous ethanol and mix them to form a precursor solution. Under constant temperature water bath stirring conditions, drop the precursor solution into the micelle core solution and adjust the alkalinity with dilute ammonia to carry out hydrolysis and condensation reaction. After the reaction is completed, a core-shell structured composite micelle sol is obtained. (2) Preparation of hollow microsphere skeleton by spray freeze-drying-induced spherical shell stacking The core-shell structured composite micelle sol obtained in step (1) was sprayed into an iron beaker containing liquid nitrogen under gas pressure through an atomizing nozzle. After being frozen by liquid nitrogen, the frozen droplets were placed in a freeze dryer for freeze drying to obtain hollow micron-sized spherical skeleton powder. (3) Hydrothermal-induced self-assembly of inorganic layers to enhance the construction of nanopores Weigh hexadecyltrimethylammonium bromide, ethanol, deionized water, and the hollow microsphere skeleton powder obtained in step (2) and mix them to form a dispersion. Then place it in a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, centrifuge and wash with deionized water and ethanol to obtain pretreated hollow microsphere powder. (4) Preparation of rinsing materials by steam etching coupled with in-situ functional modification The pretreated hollow microsphere powder obtained in step (3) was placed on a porous support of a hydrothermal reactor. An aqueous solution of ethylenediamine was added to the bottom of the hydrothermal reactor. The hydrothermal reactor was then placed in an oven for steam etching. After the steam etching was completed, the pretreated hollow microsphere powder was taken out and mixed with (3-mercaptopropyl)trimethoxysilane and toluene. The mixture was subjected to constant temperature reflux reaction under nitrogen protection. After the reaction was completed, the mixture was washed with toluene, acetone and deionized water in sequence. Finally, the mixture was vacuum dried to obtain the rinsing material.

3. The preparation method according to claim 2, characterized in that: In step (1), the mass ratio of cuprous bromide, pentamethyldiethylenetriamine, anisole, styrene, ethyl 2-bromoisobutyrate, tetrahydrofuran, and methanol in S1 is 1:(0.8~1.6):(40~60):(80~160):(1~1.5):(400~600):(100~200). The water bath reaction temperature is 85~95℃ and the water bath reaction time is 5~10h. The vacuum drying temperature is 30~60℃ and the drying time is 6~8h.

4. The preparation method according to claim 2, characterized in that: The mass ratio of PS-Br powder, cuprous bromide, pentamethyldiethylenetriamine, toluene, tert-butyl acrylate, tetrahydrofuran, methanol, and deionized water in step (1) S2 is 1:(0.02~0.04):(0.02~0.04):(3~6):(4~8):(40~60):(20~40):(2~4); the vacuum drying temperature is 40~60℃, and the vacuum drying time is 6~8h; In step (3), the mass ratio of PS-b-PtBA powder, dichloromethane, and trifluoroacetic acid in S3 is 1:(20~40):(10~15), the stirring rate is 100~200 rpm, and the stirring time is 24~36 h.

5. The preparation method according to claim 2, characterized in that: In step (1), S5, the silicon source is tetraethyl orthosilicate, the titanium source is tetrabutyl titanate or tetraethyl titanate, the mass fraction of dilute ammonia is 5-10%, and the mass ratio of block copolymer template, ethylene glycol, deionized water, silicon source, and anhydrous ethanol is 1:(30-60):(10-20):(2-4):(30-60). The pH is adjusted to 8.5-9.0 with dilute ammonia. In both S4 and S5, the stirring speed in the constant temperature water bath is 200~400 rpm, the stirring temperature in the constant temperature water bath is 50~70℃, and the stirring time in the constant temperature water bath is 4~8h.

6. The preparation method according to claim 2, characterized in that: The diameter of the atomizing nozzle in step (2) is 0.5~1mm, the gas pressure is 0.2~0.4MPa, the freeze-drying temperature is -40~-50℃, and the freeze-drying time is 36~72h.

7. The preparation method according to claim 2, characterized in that: The mass ratio of the hollow microsphere skeleton powder, hexadecyltrimethylammonium bromide, ethanol and deionized water in step (3) is 1:(0.1~0.2):(6~12):(6~12), the hydrothermal reaction temperature is 120~140℃, and the hydrothermal reaction time is 12~24h.

8. The preparation method according to claim 2, characterized in that: The mass fraction of the ethylenediamine aqueous solution in step (4) is 5~10%, the mass ratio of the pretreated hollow microsphere powder to the ethylenediamine aqueous solution is 1:(3~6), the temperature of the steam etching is 120~140℃, and the time of the steam etching is 3~6h.

9. The preparation method according to claim 2, characterized in that: The mass ratio of the pretreated hollow microsphere powder, (3-mercaptopropyl)trimethoxysilane, and toluene in step (4) is 1:(0.2~0.4):(10~20). The temperature of the constant temperature reflux reaction is 110~120℃, the time of the constant temperature reflux reaction is 12~18h, the temperature of the vacuum drying is 40~60℃, and the time of the vacuum drying is 10~20h.

10. The application of the leaching material according to claim 1 in the leaching of heavy metal contaminated soil, further preferably: the heavy metal is cadmium and / or arsenic.

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