Micron-spiked spherical soil leaching material, preparation method and application thereof

Abstract

The application discloses a micron thorn ball-shaped soil leaching material and a preparation method and application thereof, and belongs to the field of new materials. The heavy metal contaminated soil leaching material is composed of a composite inorganic nanocrystal core of iron oxide and trimanganese tetroxide, an organic cross-linking network framework of sodium alginate and polyaspartic acid, and an amino tris methylene phosphonic acid derivative phosphate. The heavy metal contaminated soil leaching material has the advantages of large specific surface area, environmental friendliness, simple preparation process, and effective reduction of the heavy metal content in soil, and can be widely applied to the field of soil heavy metal leaching.

Description

Technical Field

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

[0002] In recent years, researchers have begun to introduce nanomaterials into the field of soil heavy metal remediation, aiming to improve remediation efficiency by utilizing the ultra-large specific surface area and high surface activity of nanomaterials. Functional nanomaterials such as hydroxyapatite nanoparticles, nano-zero-valent iron, and nano-metal oxides have been widely used in the adsorption and passivation remediation of heavy metals. However, directly using nanoparticles as leaching agents has inherent drawbacks such as difficulty in solid-liquid separation, easy aggregation and blockage in soil pores, and inconvenience in recycling. Researchers have developed phosphate mineral-based biochar gel microspheres, which crosslink functional components such as hydroxyapatite and biochar through sodium alginate gel to form composite microsphere materials, achieving good results in the passivation remediation of lead pollution in soil. However, the microsphere materials prepared by existing methods mostly adopt simple random stacking or dense embedding of nanoparticles. The bonding strength between nanoparticles and between nanoparticles and the matrix is ​​weak. Under the mechanical disturbance and hydraulic scouring conditions of soil leaching, structural disintegration is very likely to occur, leading to the loss of functional nanoparticles and rapid blockage of leaching channels. In addition, the lack of controllability of the surface morphology of microspheres directly limits the contact area and mechanical action intensity between the material and the micro-area of ​​contaminated soil, resulting in a slow desorption kinetic rate of heavy metals and making it difficult to further improve the leaching efficiency. Summary of the Invention

[0003] The purpose of this invention is to address the current status and existing problems of soil leaching for heavy metal contaminated soil, and to propose a micron-sized spiky spherical soil leaching material, its preparation method, and its application.

[0004] A micron-sized spiky spherical soil leaching material is prepared using a combined method of oil-phase ultrasonic pulse electrochemical deposition, microfluidic coaxial emulsion isothermal crosslinking, breath map-assisted confined self-assembly, and selective etching coupled with fluorine and nitrogen co-doping, with the components being a composite inorganic nanocrystal nucleus of iron oxide and manganese tetroxide, an organic crosslinking network framework of sodium alginate and polyaspartic acid, and aminotrimethylene phosphonate-derived phosphate.

[0005] The preparation method of this heavy metal contaminated soil leaching material is as follows:

[0006] (1) Preparation of hybrid nanocrystal seeds by ultrasonic pulse electrochemical deposition in oil phase

[0007] Weigh out iron source, manganese source, propylene carbonate, ethylene glycol, 2,5-dimercapto-1,3,4-thiadiazole, and tetrabutylammonium hexafluorophosphate and mix them evenly to form an electrolyte. Use a titanium sheet as the working electrode and a platinum electrode as the counter electrode. Ag / Ag +The electrode is a reference electrode. Pulsed reduction potential is applied under ultrasonic assistance to perform pulsed reduction. After the reduction is completed, a hybrid nanocrystal seed suspension is obtained.

[0008] (2) Preparation of gel precursor by isothermal crosslinking of microfluidic coaxial emulsion

[0009] The hybrid nanocrystal seed suspension obtained in step (1) is used as the inner phase fluid. Sodium alginate modified with amino, sodium polyaspartate and deionized water are weighed and mixed to form the outer phase fluid. Span 80 and ethyl acetate are weighed and mixed to form the carrier liquid phase. The inner phase fluid, outer phase fluid and carrier liquid phase are respectively introduced into the syringe and placed in the micro-injection pump for injection. The syringe outlet is connected to the three inlets of the cross-shaped microfluidic chip. The emulsion flowing out of the cross-shaped microfluidic chip outlet is dropped into the mixed solution of genipin and phosphate buffer solution. After the cross-linking reaction is carried out in a water bath with constant temperature stirring, the gel precursor is obtained after centrifugation.

[0010] (3) Preparation of micron-sized spiked particles by confined self-assembly assisted by respiration diagram method

[0011] The gel precursor obtained in step (2) was evenly spread on a polytetrafluoroethylene mold, and a mixed solution of aminotrimethylene phosphonic acid and urea was added dropwise. Then it was transferred to a constant temperature and humidity chamber. Nitrogen gas was used to introduce dichloromethane vapor into the constant temperature and humidity chamber by bubbling. After standing at constant temperature and humidity, a seed solution was obtained. The seed solution, calcium nitrate tetrahydrate, diammonium hydrogen phosphate, aminotrimethylene phosphonic acid, urea and deionized water were mixed and placed in a microwave synthesizer. The reaction was carried out by microwave pulse irradiation. After the reaction was completed, the micron-sized spiked particle powder was obtained by centrifugation.

[0012] (4) Selective etching coupled with fluorine and nitrogen co-doping to prepare rinsing materials

[0013] Weigh out hydrogen peroxide solution, citric acid, hexadecyltrimethylammonium bromide and deionized water to form an etching solution. Then disperse the micron-sized spiked ball powder obtained in step (3) in the etching solution and treat it under constant temperature water bath magnetic stirring conditions. After the treatment is completed, vacuum dry to obtain micron-sized spiked ball etched powder. Place the micron-sized spiked ball etched powder in a plasma surface treatment instrument. First, evacuate the plasma surface treatment instrument, then introduce a mixture of ammonia and carbon tetrafluoride gas, and then perform surface treatment to obtain the rinsing material.

[0014] In the above method: the iron source in step (1) is iron acetylacetone, the manganese source is manganese acetate, the CAS number of 2,5-dimercapto-1,3,4-thiadiazole is 1072-71-5, the CAS number of tetrabutylammonium hexafluorophosphate is 3109-63-5, and the mass ratio of iron source, manganese source, propylene carbonate, ethylene glycol, 2,5-dimercapto-1,3,4-thiadiazole and tetrabutylammonium hexafluorophosphate is 1: (0.3~0.6): (30~50): (8~12): (0.1~0.2): (1.5~3.0).

[0015] In the above method: the area of ​​the titanium sheet mentioned in step (1) is 3~6 cm². 2 The platinum electrode is model 213 / 213-01, Ag / Ag + The electrode is a silver-silver ion electrode, purchased from Shanghai Chuxi Industrial Co., Ltd. The ultrasonic power is 100~150W, the reduction potential during the pulse reduction process is -1.8V, the pulse width is 5~10ms, the interval time is 25~50ms, and the pulse reduction time is 30~60min.

[0016] In the above method: the amino-modified sodium alginate mentioned in step (2) was purchased from Guangzhou Carbon Water Technology Co., Ltd., the CAS number of sodium polyaspartate was 181828-06-8, the CAS number of Span 80 was 1338-43-8, the CAS number of genipin was 6902-77-8, the pH of the phosphate buffer solution was 7.2~7.4, the mass ratio of amino-modified sodium alginate, sodium polyaspartate and deionized water in the external phase fluid was 1:(0.3~0.6):(40~60), the mass ratio of Span 80 and ethyl acetate in the carrier liquid phase was 1:(40~60), and the mass ratio of genipin and phosphate buffer solution was 1:(100~200).

[0017] In the above method: the injection rates of the internal phase fluid, external phase fluid, and carrier liquid phase in step (2) are 10~20μL / min, 40~80μL / min, and 80~120μL / min, respectively; the mass ratio of the internal phase fluid to the mixed solution of genipin and phosphate buffer is 1:(50~100); the temperature of the constant temperature stirring water bath is 35~45℃; the rotation speed of the constant temperature stirring water bath is 40~60rpm; and the time of the constant temperature stirring water bath is 4~6h.

[0018] In the above method: the CAS number of aminotrimethylenephosphonic acid mentioned in step (3) is 6419-19-8, the mass ratio of gel precursor, aminotrimethylenephosphonic acid and urea is 1:(0.1~0.2):(0.005~0.010), the flow rate of nitrogen is 200~400mL / min, the temperature of constant temperature and humidity is 15~20℃, the humidity of constant temperature and humidity is 80~90%, and the time of constant temperature and humidity is 1~2h.

[0019] In the above method: the mass ratio of the seed solution, calcium nitrate tetrahydrate, diammonium hydrogen phosphate, aminotrimethylene phosphonic acid, urea and deionized water in step (3) is 1:(0.05~0.10):(0.01~0.03):(0.04~0.06):(0.01~0.02):(3~6), the power of microwave pulse irradiation is 100~200W, the pulse width of microwave pulse irradiation is 10~15s, the interval time of microwave pulse irradiation is 30~40s, and the number of microwave pulse irradiations is 20~40 times.

[0020] In the above method: the mass fraction of hydrogen peroxide solution in step (4) is 20~30%, the mass ratio of micron-sized spiked particle powder, hydrogen peroxide solution, citric acid, hexadecyltrimethylammonium bromide and deionized water is 1: (0.2~0.4): (0.03~0.06): (0.01~0.02): (30~60), the temperature of the constant temperature water bath magnetic stirring is 35~45℃, the speed of the constant temperature water bath magnetic stirring is 150~200rpm, and the time of constant temperature water bath magnetic stirring is 30~60min.

[0021] In the above method: the plasma surface treatment instrument mentioned in step (4) is a Plasma clean-PL-5010 type, the flow rates of ammonia and carbon tetrafluoride are 20~40mL / min and 4~8mL / min respectively, the input voltage during surface treatment is 220V, the working distance is 5~12mm, the plasma flame scanning rate is 20~100 mm / s, and the treatment time is 5~10min.

[0022] A micron-sized spiky spherical soil leaching material, which is prepared by the above method.

[0023] In the technical solution of this invention, the leaching material prepared by the above method is used in the leaching of heavy metal contaminated soil.

[0024] 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 sulfide 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 sulfide and arsenic sulfide were both higher than 90%.

[0025] Beneficial effects:

[0026] (1) Although the traditional chemical coprecipitation method for preparing iron / manganese composite nanocrystals is simple to operate, the nucleation and growth processes are difficult to separate, resulting in a wide distribution of seed crystal size and poor crystal integrity. In addition, impurity ions introduced by the precipitant are easy to remain on the seed crystal surface, affecting the interfacial bonding strength of subsequent assembly. Although the traditional solvothermal method for preparing iron / manganese composite nanocrystals can improve crystallinity, it requires a long reaction under closed high pressure conditions. The functionalization of the seed crystal surface usually requires post-grafting treatment, which is cumbersome and the grafting rate is difficult to control precisely. This invention uses an oil-phase ultrasonic pulse electrochemical deposition method. First, a non-aqueous electrolysis system is constructed using a propylene carbonate / ethylene glycol mixed solvent to eliminate the interference of hydrogen evolution side reaction in aqueous electrolysis on the deposition process, thereby achieving simultaneous deep reduction and alloying of Fe and Mn. Then, the cavitation effect of ultrasound is used to continuously act on the process. As an electrode surface, the generated microjets and shock waves can effectively break through the diffusion layer boundary layer, compressing the thickness of the ion-depleted region on the electrode surface. At the same time, the periodic application of pulse potential enables the discontinuous growth of crystal nuclei on the electrode surface during the alternating conduction and relaxation process. The synergistic effect of ultrasound and pulsed electric field realizes the kinetic separation of nucleation and growth, ensuring the uniformity of crystal seed size. In addition, the 2,5-dithio-1,3,4-thiadiazole molecules pre-introduced in the electrolyte of this invention participate in the coordination chemical reaction on the electrode surface during the electrochemical reduction of metal ions. Its dithio-functional group forms a stable five-membered chelate ring with the newly formed Fe / Mn atoms, allowing the functional organic ligands to be grafted in situ onto the crystal seed surface in the form of covalent bonds, providing abundant anchoring sites for the interfacial chemical bonding between the nanocrystal seeds and the organic cross-linking network in subsequent steps.

[0027] (2) Although conventional spray drying method for preparing core-shell structured microspheres has high production efficiency, the droplet size is affected by the nozzle structure and airflow disturbance, and the high-temperature airflow is prone to partial thermal degradation of organic functional components. While electrostatic droplet method for preparing core-shell structured microspheres can improve particle size uniformity, the yield is low. In this invention, laminar co-focusing of inner phase fluid, outer phase fluid and carrier liquid phase occurs in the three-dimensional focusing area of ​​cross-shaped microfluidic chip. The symmetrical shear force generated by the carrier liquid phase accurately cuts the inner-outer phase fluid into water-oil-water double emulsion droplets with uniform size and height. In addition, the aminated sodium alginate and polyaspartic acid in the outer phase fluid Sodium alginate enters the genipin crosslinking bath immediately after droplet formation. The iridoid structure of the genipin molecule undergoes a Schiff base reaction with the amino group of sodium alginate, while its ester group undergoes transesterification crosslinking with the carboxyl group of polyaspartic acid, forming an organic gel shell with an interpenetrating network structure. Compared with the conventional ionic crosslinking of calcium alginate with calcium ions, the covalent crosslinking of genipin has irreversibility and pH stability, and will not cause the framework to disintegrate due to the chelation and dissolution of calcium ions in subsequent hydrothermal and etching steps. Finally, the high density of carboxyl groups on the side chains of polyaspartic acid forms a negatively charged microenvironment after crosslinking, which can provide a pre-concentration layer for the electrostatic enrichment of heavy metal ions.

[0028] (3) Traditional hydrothermal growth methods for constructing spiky structures on the surface of microspheres require long-term treatment in a high-pressure reactor. The length, density, and orientation of the spiky structures mainly depend on the growth habits of the crystals themselves, and the controllability is limited. Furthermore, the morphology consistency is poor between different batches due to fluctuations in the solution microenvironment. Although the template sacrifice method can accurately replicate the morphology, the template cost is high and the removal process is complex. This invention couples the breath diagram method from the field of polymer physics with microwave chemistry to achieve controllable construction of spiky structures on the surface of microspheres. By condensing dichloromethane vapor on the surface of low-temperature gel microspheres in a constant temperature and humidity chamber to form a discrete droplet array, water vapor in a high humidity environment preferentially undergoes heterogeneous nucleation and condensation between the droplets. The latent heat released during condensation causes the surface temperature of the dichloromethane droplets to be slightly higher than that of the interstitial region, creating temperature gradient-driven convection. This selectively enriches the pre-added ATMP-urea solution at the droplet edges. Meanwhile, Fe / Mn nanocrystals in the gel shell, in a confined and mobile state, migrate radially towards the droplet edges under the synergistic effect of capillary force and ATMP coordination, forming a ring-shaped seed enrichment zone regularly arranged along the periphery of the pits. Furthermore, this invention utilizes the selective dielectric heating effect of microwave pulses on the phosphonic acid groups of ATMP molecules, creating instantaneous high-temperature micro-regions on the seed surface enriched at the pit edges. This increases the ion deposition rate on the seed surface compared to the bulk solution, while urea slowly releases OH- during the intermittent period. -Maintaining a constant pH avoids the amorphous homogeneous nucleation caused by uncontrolled supersaturation of the solution under continuous heating conditions. Finally, the breath diagram method pre-confines the seed crystals to the micro-nano scale region at the edge of the pits. During microwave pulse growth, the crystals can only extend outward along the radial direction perpendicular to the surface of the microspheres, forming a spiky structure with a high aspect ratio. Furthermore, the spiky structures maintain an appropriate distance from each other due to the natural spacing of the pits, effectively avoiding the problem of fusion and adhesion between spiky structures due to excessive growth in the traditional hydrothermal method.

[0029] (4) In conventional preparation methods, the end treatment for surface functionalization of materials often adopts single-atmosphere plasma treatment. Oxygen plasma treatment can only introduce oxygen-containing functional groups and has limited selectivity for complexing heavy metals. Ammonia plasma treatment can introduce amino groups, but has no affinity for anionic heavy metals. This invention adopts a surface engineering strategy of selective chemical etching coupled with fluorine and nitrogen co-doped plasma. Hydrogen peroxide is used to preferentially oxidize and dissolve the small amount of amorphous hydroxyapatite connecting phase between the spikes during microwave pulse growth. Citric acid selectively etches the low crystallinity region of the nano-spiky sidewall through the strong coordination of carboxyl groups and calcium ions. CTAB quaternary ammonium salt cationic micelles are located at the tip of the nano-spiky. Preferential adsorption occurs due to the surface charge density difference induced by curvature, forming a dynamic protective layer. High-density amino radicals are generated on the material surface using ammonia plasma, and basic nitrogen-containing sites such as primary amines, secondary amines, and pyridine nitrogen are introduced into the nano-spiked surface through substitution reactions and radical addition reactions. Fluorine radicals generated by the decomposition of carbon tetrafluoride plasma form a semi-ionic fluorine-doped layer on the surface through CF and MF bonds. The lone pair electrons introduced by nitrogen doping can coordinate to the empty orbitals of metal ions, exhibiting a strong affinity for heavy metal ions. The strong electronegativity of fluorine doping forms a permanent dipole layer on the surface, generating a strong electrostatic attraction for anionic pollutants such as arsenate and chromate.

[0030] Therefore, the heavy metal contaminated soil leaching material prepared by this invention has a large specific surface area, is environmentally friendly, has a simple preparation process, and can effectively reduce the heavy metal content in the soil, thus having strong application and promotion value. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope image of the elution material prepared in Example 1;

[0032] Figure 2 The graph shows the performance of the rinsing materials prepared in Examples 1-3 in removing cadmium sulfide.

[0033] Figure 3 The graph shows the performance of the rinsing materials prepared in Examples 1-3 in removing arsenic sulfide. Detailed Implementation

[0034] 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.

[0035] The amino-modified sodium alginate was purchased from Tanshtech, a brand sold by Guangzhou Carbon Technology Co., Ltd., product number N / A.

[0036] Example 1

[0037] (1) Preparation of hybrid nanocrystal seeds by ultrasonic pulse electrochemical deposition in oil phase

[0038] Weigh out 5g of ferric acetylacetone, 1.5g of manganese acetate, 150g of propylene carbonate, 40g of ethylene glycol, 0.5g of 2,5-dimercapto-1,3,4-thiadiazole, and 7.5g of tetrabutylammonium hexafluorophosphate, mix them thoroughly to form an electrolyte, and use a titanium sheet (3cm²) as the electrolyte. 2 The working electrode is a platinum electrode (model 213 / 213-01), and the counter electrode is an Ag / Ag electrode. + The electrode (a silver-silver ion electrode, purchased from Shanghai Chuxi Industrial Co., Ltd.) was used as the reference electrode. Under the assistance of ultrasound (power of 100W), a pulse reduction potential was applied to perform pulse reduction (reduction potential of -1.8V, pulse width of 5ms, interval of 25ms, and pulse reduction time of 30min). After the reduction was completed, a hybrid nanocrystal seed suspension was obtained.

[0039] (2) Preparation of gel precursor by isothermal crosslinking of microfluidic coaxial emulsion

[0040] The hybrid nanocrystal seed suspension obtained in step (1) was used as the inner phase fluid. 24g of amino-modified sodium alginate (purchased from Guangzhou Carbon Water Technology Co., Ltd.), 7.2g of sodium polyaspartate (CAS No. 181828-06-8), and 960g of deionized water were weighed and mixed to form the outer phase fluid. 60g of Span 80 (CAS No. 1338-43-8) and 2400g of ethyl acetate were weighed and mixed to form the carrier phase. The inner phase fluid (injection rate of 10 μL / min), the outer phase fluid (injection rate of 40 μL / min), and the carrier phase (injection rate of...) were then combined. The emulsion was injected into a syringe at a rate of 80 μL / min and placed in a microinjection pump. The syringe outlet was connected to the three inlets of the cross-shaped microfluidic chip (the injection of the external phase fluid and the carrier liquid phase was stopped simultaneously after the internal phase fluid was injected). The emulsion flowing out of the cross-shaped microfluidic chip outlet was dropped into a mixed solution of 101.238 g genipin (CAS No. 6902-77-8) and 10123.8 g phosphate buffer solution (pH 7.2). After the cross-linking reaction was carried out at 35°C with stirring (40 rpm) in a water bath for 6 h, the gel precursor was obtained after centrifugation.

[0041] (3) Preparation of micron-sized spiked particles by confined self-assembly assisted by respiration diagram method

[0042] Weigh 10g of the gel precursor obtained in step (2) and spread it evenly on a polytetrafluoroethylene mold. Add a mixed solution of 1g aminotrimethylenephosphonic acid (CAS No. 6419-19-8) and 0.05g urea. Then transfer it to a constant temperature and humidity chamber at 15℃ and 80% humidity. Use nitrogen gas (flow rate of 200mL / min) to bubble dichloromethane vapor into the constant temperature and humidity chamber for 20min. After standing at constant temperature and humidity for 2h, obtain the seed crystal solution. Weigh again. Take 10g of seed solution, 0.5g of calcium nitrate tetrahydrate, 0.1g of diammonium hydrogen phosphate, 0.4g of aminotrimethylene phosphonic acid, 0.1g of urea, and 30g of deionized water and mix them in a microwave synthesizer. Grow the mixture by microwave pulse irradiation (the power of microwave pulse irradiation is 100W, the pulse width of microwave pulse irradiation is 10s, the interval time of microwave pulse irradiation is 30s, and the number of microwave pulse irradiations is 20). After the reaction is completed, centrifuge to obtain micron-sized spiked spherical particle powder.

[0043] (4) Selective etching coupled with fluorine and nitrogen co-doping to prepare rinsing materials

[0044] Weigh 1g of 20% hydrogen peroxide solution, 0.15g of citric acid, 0.05g of hexadecyltrimethylammonium bromide, and 150g of deionized water to form an etching solution. Then weigh 5g of the micron-sized spiked particle powder obtained in step (3) and disperse it in the etching solution. Treat it for 60min under magnetic stirring (150rpm) in a constant temperature water bath at 35℃. After treatment, vacuum dry it at 80℃ for 12h to obtain micron-sized spiked particle etched powder. Place the micron-sized spiked particle etched powder in a plasma surface treatment instrument. First, evacuate the plasma surface treatment instrument, then introduce a mixture of ammonia (flow rate 20mL / min) and carbon tetrafluoride (flow rate 4mL / min) and perform surface treatment (the input voltage during surface treatment is 220V, the working distance is 5mm, the plasma flame scanning rate is 20mm / s, and the treatment time is 10min) to obtain the rinsing material (the scanning electron microscope image of the rinsing material is shown in Figure 1). Figure 1 (as shown)

[0045] (5) Rinsing performance test

[0046] Clay (100 g) was mixed with deionized water (2000 mL), dried, and passed through a 2 mm sieve for use as a pretreatment for cleaning soil. 10 mg of cadmium sulfide 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 ℃) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed at a mass ratio of 1:10:10, shaken for 1 h using a constant-temperature shaker (200 r / min), and filtered to obtain the supernatant. The heavy metal content in the supernatant was determined using ICP, and the elution rate was calculated. The elution rates for both cadmium sulfide and arsenic sulfide were higher than 90%. Figures 2-3 .

[0047] Example 2

[0048] (1) Preparation of hybrid nanocrystal seeds by ultrasonic pulse electrochemical deposition in oil phase

[0049] Weigh out 2g of ferric acetylacetone, 1.2g of manganese acetate, 100g of propylene carbonate, 24g of ethylene glycol, 0.4g of 2,5-dimercapto-1,3,4-thiadiazole, and 6g of tetrabutylammonium hexafluorophosphate, mix them thoroughly to form an electrolyte, and use a titanium sheet (6cm²) as the electrolyte. 2 The working electrode is a platinum electrode (model 213 / 213-01), and the counter electrode is an Ag / Ag electrode. + The electrode (a silver-silver ion electrode, purchased from Shanghai Chuxi Industrial Co., Ltd.) was used as the reference electrode. Under the assistance of ultrasound (power of 150W), a pulsed reduction potential was applied to perform pulsed reduction (reduction potential of -1.8V, pulse width of 10ms, interval of 50ms, and pulsed reduction time of 60min). After the reduction was completed, a hybrid nanocrystal seed suspension was obtained.

[0050] (2) Preparation of gel precursor by isothermal crosslinking of microfluidic coaxial emulsion

[0051] The hybrid nanocrystal seed suspension obtained in step (1) was used as the inner phase fluid. 10g of amino-modified sodium alginate (purchased from Guangzhou Carbon Water Technology Co., Ltd.), 6g of sodium polyaspartate (CAS No. 181828-06-8), and 600g of deionized water were weighed and mixed to form the outer phase fluid. 20g of Span 80 (CAS No. 1338-43-8) and 1200g of ethyl acetate were weighed and mixed to form the carrier phase. The inner phase fluid (injection rate of 20μL / min), the outer phase fluid (injection rate of 80μL / min), and the carrier phase (injection rate of 80μL / min) were then mixed. The emulsion was injected into a syringe at a rate of 120 μL / min and placed in a microinjection pump. The syringe outlet was connected to the three inlets of the cross-shaped microfluidic chip (the injection of the external phase fluid and the carrier liquid phase was stopped simultaneously after the internal phase fluid was injected). The emulsion flowing out of the cross-shaped microfluidic chip outlet was dropped into a mixed solution of 66.468 g of genipin (CAS No. 6902-77-8) and 13293.6 g of phosphate buffer solution (pH 7.4). After the cross-linking reaction was carried out in a water bath at 45°C with stirring (60 rpm) for 4 h, the gel precursor was obtained after centrifugation.

[0052] (3) Preparation of micron-sized spiked particles by confined self-assembly assisted by respiration diagram method

[0053] Weigh 6g of the gel precursor obtained in step (2) and spread it evenly on a polytetrafluoroethylene mold. Add a mixed solution of 1.2g aminotrimethylenephosphonic acid (CAS No. 6419-19-8) and 0.06g urea. Then transfer it to a constant temperature and humidity chamber at 20℃ and 90% humidity. Use nitrogen gas (flow rate of 400mL / min) to bubble dichloromethane vapor into the constant temperature and humidity chamber for 20min. After standing at constant temperature and humidity for 1h, obtain the seed crystal solution. Weigh again. Take 5g of seed solution, 0.5g of calcium nitrate tetrahydrate, 0.15g of diammonium hydrogen phosphate, 0.3g of aminotrimethylene phosphonic acid, 0.1g of urea, and 30g of deionized water and mix them in a microwave synthesizer. Grow the mixture by microwave pulse irradiation (microwave pulse irradiation power is 200W, microwave pulse irradiation pulse width is 15s, microwave pulse irradiation interval is 40s, and microwave pulse irradiation is repeated 40 times). After the reaction is completed, centrifuge to obtain micron-sized spiked spherical particles powder.

[0054] (4) Selective etching coupled with fluorine and nitrogen co-doping to prepare rinsing materials

[0055] Weigh 2g of 30% hydrogen peroxide solution, 0.3g of citric acid, 0.1g of hexadecyltrimethylammonium bromide, and 300g of deionized water to form an etching solution. Weigh 5g of the micron-sized spiked particle powder obtained in step (3) and disperse it in the etching solution. Then, treat it for 30min under magnetic stirring (200rpm) in a constant temperature water bath at 45℃. After treatment, vacuum dry it at 80℃ for 12h to obtain micron-sized spiked particle etching powder. Place the micron-sized spiked particle etching powder in a plasma surface treatment instrument. First, evacuate the plasma surface treatment instrument, then introduce a mixture of ammonia (flow rate 40mL / min) and carbon tetrafluoride (flow rate 8mL / min) and perform surface treatment (the input voltage during surface treatment is 220V, the working distance is 12mm, the plasma flame scanning rate is 100mm / s, and the treatment time is 5min) to obtain the rinsing material.

[0056] (5) Rinsing performance test

[0057] Clay (100 g) was mixed with deionized water (2000 mL), dried, and passed through a 2 mm sieve for use as a pretreatment for cleaning soil. 10 mg of cadmium sulfide 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 ℃) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed at a mass ratio of 1:10:10, shaken for 1 h using a constant-temperature shaker (200 r / min), and filtered to obtain the supernatant. The heavy metal content in the supernatant was determined using ICP, and the elution rate was calculated. The elution rates for both cadmium sulfide and arsenic sulfide were higher than 90%. Figures 2-3 .

[0058] Example 3

[0059] (1) Preparation of hybrid nanocrystal seeds by ultrasonic pulse electrochemical deposition in oil phase

[0060] Weigh out 2g of ferric acetylacetone, 1g of manganese acetate, 80g of propylene carbonate, 20g of ethylene glycol, 0.3g of 2,5-dimercapto-1,3,4-thiadiazole, and 4g of tetrabutylammonium hexafluorophosphate, mix them thoroughly to form an electrolyte, and use a titanium sheet (4cm²) as the electrolyte. 2 The working electrode is a platinum electrode (model 213 / 213-01), and the counter electrode is an Ag / Ag electrode. + The electrode (a silver-silver ion electrode, purchased from Shanghai Chuxi Industrial Co., Ltd.) was used as the reference electrode. Under the assistance of ultrasound (power of 120W), a pulse reduction potential was applied to perform pulse reduction (reduction potential of -1.8V, pulse width of 10ms, interval of 50ms, and pulse reduction time of 40min). After the reduction was completed, a hybrid nanocrystal seed suspension was obtained.

[0061] (2) Preparation of gel precursor by isothermal crosslinking of microfluidic coaxial emulsion

[0062] The hybrid nanocrystal seed suspension obtained in step (1) was used as the inner phase fluid. 10g of amino-modified sodium alginate (purchased from Guangzhou Carbon Water Technology Co., Ltd.), 5g of sodium polyaspartate (CAS No. 181828-06-8), and 500g of deionized water were weighed and mixed to form the outer phase fluid. 16g of Span 80 (CAS No. 1338-43-8) and 800g of ethyl acetate were weighed and mixed to form the carrier phase. The inner phase fluid (injection rate of 15 μL / min), the outer phase fluid (injection rate of 60 μL / min), and the carrier phase (injection rate of...) were then combined. The emulsion was injected into a syringe at a rate of 90 μL / min and placed in a microinjection pump. The syringe outlet was connected to the three inlets of the cross-shaped microfluidic chip (the injection of the external phase fluid and the carrier liquid phase was stopped simultaneously after the internal phase fluid was injected). The emulsion flowing out of the cross-shaped microfluidic chip outlet was dropped into a mixed solution of 56.847 g genipin (CAS No. 6902-77-8) and 8527 g phosphate buffer solution (pH 7.4). After the cross-linking reaction was carried out in a water bath at 40 °C with stirring (50 rpm) for 5 h, the gel precursor was obtained after centrifugation.

[0063] (3) Preparation of micron-sized spiked particles by confined self-assembly assisted by respiration diagram method

[0064] Weigh 6g of the gel precursor obtained in step (2) and spread it evenly on a polytetrafluoroethylene mold. Add a mixed solution of 0.9g aminotrimethylenephosphonic acid (CAS No. 6419-19-8) and 0.05g urea. Then transfer it to a constant temperature and humidity chamber at 17℃ and 85% humidity. Use nitrogen gas (flow rate of 300mL / min) to bubble dichloromethane vapor into the constant temperature and humidity chamber for 20min. After standing at constant temperature and humidity for 1h, obtain the seed crystal solution. Weigh again. Take 5g of seed solution, 0.4g of calcium nitrate tetrahydrate, 0.1g of diammonium hydrogen phosphate, 0.25g of aminotrimethylene phosphonic acid, 0.08g of urea, and 25g of deionized water and mix them in a microwave synthesizer. Grow the mixture by microwave pulse irradiation (the power of microwave pulse irradiation is 150W, the pulse width of microwave pulse irradiation is 15s, the interval time of microwave pulse irradiation is 30s, and the number of microwave pulse irradiations is 30 times). After the reaction is completed, centrifuge to obtain micron-sized spiky particle powder.

[0065] (4) Selective etching coupled with fluorine and nitrogen co-doping to prepare rinsing materials

[0066] Weigh 1.5g of 25% hydrogen peroxide solution, 0.25g of citric acid, 0.08g of hexadecyltrimethylammonium bromide, and 200g of deionized water to form an etching solution. Weigh 5g of the micron-sized spiked ball powder obtained in step (3) and disperse it in the etching solution. Then, treat it for 40min under magnetic stirring (180rpm) in a constant temperature water bath at 40℃. After treatment, vacuum dry it at 80℃ for 12h to obtain micron-sized spiked ball etched powder. Place the micron-sized spiked ball etched powder in a plasma surface treatment instrument. First, evacuate the plasma surface treatment instrument, then introduce a mixture of ammonia (flow rate 30mL / min) and carbon tetrafluoride (flow rate 6mL / min) and perform surface treatment (the input voltage during surface treatment is 220V, the working distance is 12mm, the plasma flame scanning rate is 100mm / s, and the treatment time is 7min) to obtain the rinsing material.

[0067] (5) Rinsing performance test

[0068] Clay (100 g) was mixed with deionized water (2000 mL), dried, and passed through a 2 mm sieve for use as a pretreatment for cleaning soil. 10 mg of cadmium sulfide 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 ℃) for 2 months. The leaching material, deionized water, and simulated contaminated soil were mixed at a mass ratio of 1:10:10, shaken for 1 h using a constant-temperature shaker (200 r / min), and filtered to obtain the supernatant. The heavy metal content in the supernatant was determined using ICP, and the elution rate was calculated. The elution rates for both cadmium sulfide and arsenic sulfide were higher than 90%. Figures 2-3 .

Claims

1. A method for preparing a micron-sized spiky spherical soil leaching material, characterized in that: The method includes the following steps: (1) Preparation of hybrid nanocrystal seeds by ultrasonic pulse electrochemical deposition in oil phase An electrolyte was formed by uniformly mixing an iron source, a manganese source, propylene carbonate, ethylene glycol, 2,5-dimercapto-1,3,4-thiadiazole, and tetrabutylammonium hexafluorophosphate. A titanium sheet was used as the working electrode, and a platinum electrode as the counter electrode. The Ag / Ag ratio was [not specified in the original text]. + The electrode is a reference electrode. Pulsed reduction potential is applied under ultrasonic assistance to perform pulsed reduction. After the reduction is completed, a hybrid nanocrystal seed suspension is obtained. (2) Preparation of gel precursor by isothermal crosslinking of microfluidic coaxial emulsion The hybrid nanocrystal seed suspension obtained in step (1) is used as the inner phase fluid. Amino-modified sodium alginate, sodium polyaspartate and deionized water are mixed to form the outer phase fluid. Span 80 and ethyl acetate are mixed to form the carrier liquid phase. The inner phase fluid, outer phase fluid and carrier liquid phase are respectively introduced into a syringe and placed in a micro-injection pump for injection. The syringe outlet is connected to the three inlets of the cross-shaped microfluidic chip. The emulsion flowing out of the cross-shaped microfluidic chip outlet is dropped into a mixed solution of genipin and phosphate buffer solution. After the cross-linking reaction is carried out in a water bath with constant temperature stirring, the gel precursor is obtained after centrifugation. (3) Preparation of micron-sized spiked particles by confined self-assembly assisted by respiration diagram method The gel precursor obtained in step (2) was evenly spread on a polytetrafluoroethylene mold, and a mixed solution of aminotrimethylene phosphonic acid and urea was added dropwise. Then it was transferred to a constant temperature and humidity chamber. Nitrogen gas was used to introduce dichloromethane vapor into the constant temperature and humidity chamber by bubbling. After standing at constant temperature and humidity, a seed solution was obtained. The seed solution, calcium nitrate tetrahydrate, diammonium hydrogen phosphate, aminotrimethylene phosphonic acid, urea and deionized water were mixed and placed in a microwave synthesizer. The reaction was carried out by microwave pulse irradiation. After the reaction was completed, the micron-sized spiked particle powder was obtained by centrifugation. (4) Selective etching coupled with fluorine and nitrogen co-doping to prepare rinsing materials Hydrogen peroxide solution, citric acid, hexadecyltrimethylammonium bromide and deionized water are mixed to form an etching solution. The micron-sized spiked ball powder obtained in step (3) is then dispersed in the etching solution and treated under constant temperature water bath magnetic stirring conditions. After treatment, the micron-sized spiked ball etched powder is obtained by vacuum drying. The micron-sized spiked ball etched powder is placed in a plasma surface treatment instrument. The plasma surface treatment instrument is first evacuated, and then a mixture of ammonia and carbon tetrafluoride is introduced. The surface is then treated to obtain the rinsing material.

2. The preparation method according to claim 1, characterized in that: In step (1), the iron source is iron acetylacetone and the manganese source is manganese acetate. The mass ratio of iron source, manganese source, propylene carbonate, ethylene glycol, 2,5-dimercapto-1,3,4-thiadiazole and tetrabutylammonium hexafluorophosphate is 1: (0.3~0.6): (30~50): (8~12): (0.1~0.2): (1.5~3.0).

3. The preparation method according to claim 1, characterized in that: In step (1), the power of the ultrasonic assistance is 100~150W, the reduction potential during the pulse reduction process is -1.8V, the pulse width is 5~10ms, the interval time is 25~50ms, and the pulse reduction time is 30~60min.

4. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of amino-modified sodium alginate, sodium polyaspartate, and deionized water in the external phase fluid is 1:(0.3~0.6):(40~60); the mass ratio of Span 80 and ethyl acetate in the carrier liquid phase is 1:(40~60); the mass ratio of genipin and phosphate buffer solution is 1:(100~200); and the pH of the phosphate buffer solution is 7.2~7.

4.

5. The preparation method according to claim 1, characterized in that: In step (2), the injection rates of the internal phase fluid, external phase fluid, and carrier liquid phase are 10~20 μL / min, 40~80 μL / min, and 80~120 μL / min, respectively. The mass ratio of the internal phase fluid to the mixed solution of genipin and phosphate buffer is 1:(50~100). The temperature of the constant temperature stirring water bath is 35~45℃, the rotation speed of the constant temperature stirring water bath is 40~60 rpm, and the time of the constant temperature stirring water bath is 4~6h.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of gel precursor, aminotrimethylenephosphonic acid, and urea is 1:(0.1~0.2):(0.005~0.010); the flow rate of nitrogen is 200~400mL / min; the temperature for constant temperature and humidity is 15~20℃; the humidity for constant temperature and humidity is 80~90%; and the time for constant temperature and humidity is 1~2h.

7. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of seed solution, calcium nitrate tetrahydrate, diammonium hydrogen phosphate, aminotrimethylene phosphonic acid, urea, and deionized water is 1:(0.05~0.10):(0.01~0.03):(0.04~0.06):(0.01~0.02):(3~6); the power of microwave pulse irradiation is 100~200W, the pulse width of microwave pulse irradiation is 10~15s, the interval time of microwave pulse irradiation is 30~40s, and the number of microwave pulse irradiations is 20~40 times.

8. The preparation method according to claim 1, characterized in that: In step (4), the mass fraction of hydrogen peroxide solution is 20-30%, and the mass ratio of micron-sized spiked ball powder, hydrogen peroxide solution, citric acid, hexadecyltrimethylammonium bromide, and deionized water is 1:(0.2-0.4):(0.03-0.06):(0.01-0.02):(30-60); the temperature of the magnetic stirring in the constant temperature water bath is 35-45℃, the speed of the magnetic stirring in the constant temperature water bath is 150-200 rpm, and the time of magnetic stirring in the constant temperature water bath is 30-60 min; In step (4), the plasma surface treatment instrument is a Plasma Clean-PL-5010 model. The flow rates of ammonia and carbon tetrafluoride are 20~40 mL / min and 4~8 mL / min, respectively. The input voltage during surface treatment is 220V, the working distance is 5~12 mm, the plasma flame scanning rate is 20~100 mm / s, and the treatment time is 5~10 min.

9. A micron-sized, spherical soil leaching material, characterized in that, The material is prepared by the method described in any one of claims 1 to 8.

10. The application of the leaching material prepared by the method of claim 1 in the leaching of heavy metal contaminated soil.

Images