A heavy metal adsorption material in soil and preparation method thereof

Abstract

The present invention provides a heavy metal adsorption material in soil and a preparation method thereof. The method comprises the following steps: preparing a nanometer zero-valent iron dispersion; adding PVA to water for swelling; adding the nanometer zero-valent iron dispersion and stirring to obtain an electrospinning solution; performing electrospinning; drying to obtain a nanometer iron skeleton; preparing a NaOH-urea aqueous solution; pre-cooling, adding microcrystalline cellulose and stirring, and then adding a polyether-type gemini surfactant and stirring evenly; centrifuging to obtain a supernatant; taking the nanometer iron skeleton and placing it in a mold, slowly pouring the supernatant until the nanometer iron skeleton is submerged, and gelling reaction; aging, vacuum freeze drying; placing in a carbonization furnace and sintering. The present invention adopts a nanometer iron skeleton, which can form a fully flowing nanochannel in the aerogel after sintering, not only greatly increasing the specific surface area, but also enabling the flowable channels to quickly and more abundantly adsorb heavy metal ions; at the same time, the nanometer iron skeleton can also effectively enhance the frame structure of the aerogel and prevent the collapse of the aerogel.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a heavy metal adsorption material in soil and a preparation method thereof. Background Art

[0002] With the advancement of urbanization and industrialization, heavy metal pollution (such as Hg, Pb, Cu, Cd, As, Ni, and Cr) has become increasingly prominent. Heavy metal pollution not only poses a serious threat to the safety of the soil and water sources on which humans depend, but also poses a significant threat to human health. Heavy metals can be absorbed by the human body through various pathways, where they accumulate continuously and eventually bind to biological substances such as proteins, nucleic acids, and enzymes, rendering them inactive and severely impacting human growth and development. Therefore, the problem of heavy metal pollution urgently needs to be addressed. Remediation of heavy metal-contaminated soil involves the use of scientific techniques or methods to remove heavy metals from the soil or reduce their activity in the soil, thereby restoring normal ecosystem functions, reducing their uptake and utilization by plants, and disrupting their transfer through the food chain to humans. Based on the characteristics of heavy metal contamination, currently, the main methods include physical remediation, chemical remediation, and bioremediation. Among these, adsorption methods are widely used for physical remediation due to their high efficiency, flexibility, cost-effectiveness, and practicality. However, currently used materials for heavy metal ion adsorption have limitations, such as low adsorption capacity, difficulty in recycling, and high cost. Therefore, developing high-efficiency, easily recyclable and low-cost heavy metal adsorption materials is an urgent problem to be solved. Summary of the Invention

[0003] Technical problem to be solved: In response to the above technical problems, the purpose of the present invention is to provide a heavy metal adsorption material in soil and a preparation method thereof. By adopting a nano-iron skeleton, on the one hand, fully flowing nanochannels can be formed in the aerogel after sintering, which not only greatly increases the specific surface area, but also enables the flow-through channels to quickly and more abundantly adsorb heavy metal ions; on the other hand, the nano-iron skeleton can also effectively enhance the framework structure of the aerogel and prevent the collapse of the aerogel.

[0004] Technical solution: A heavy metal adsorption material in soil, wherein the heavy metal adsorption material in soil is an aerogel containing nano-iron with fully-flowing nano-channels.

[0005] The method for preparing the heavy metal adsorption material in soil comprises the following steps:

[0006] (1) Adding nano-zero-valent iron powder to water and performing ultrasonic dispersion to obtain nano-zero-valent iron dispersion;

[0007] (2) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h;

[0008] (3) Add nano-zero-valent iron dispersion, stir for 30 minutes, and cool to room temperature to obtain an electrospinning solution with a PVA concentration of 7-10%;

[0009] (4) electrospinning the spinning solution using an electrospinning device and receiving it on a receiving plate;

[0010] (5) drying in an oven to obtain a nano-iron skeleton;

[0011] (6) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0012] (7) Precool the NaOH-urea aqueous solution to -12°C, add microcrystalline cellulose and stir for 10 minutes, then add the polyether-type gemini surfactant and stir evenly;

[0013] (8) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0014] (9) Place the nano-iron skeleton in a mold, slowly pour the supernatant into it until the nano-iron skeleton is submerged, and keep it in a constant temperature water bath at 50°C for 4 hours to allow the gel reaction to proceed;

[0015] (10) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0016] (11) The composite aerogel is placed in a carbonization furnace protected by inert gas and sintered to obtain an aerogel containing nano-iron with fully flowing nanochannels.

[0017] Furthermore, the ultrasonic dispersion conditions in step (1) are: power of 150 W, temperature of 30° C., and time of 30 min.

[0018] Furthermore, the content of nano zero-valent iron in the electrospinning solution is 1-3 wt.%.

[0019] Furthermore, the electrospinning conditions in step (4) are as follows: the inner diameter of the needle is 0.16 mm, the spinning solution flow rate is 0.6-1.5 mL / h, the ambient temperature is 30-45°C, the humidity is 40%, the voltage is 25 kV, and the distance from the receiving plate is 13 cm.

[0020] Furthermore, the porosity of the nano-iron skeleton in step (5) is 70-80%, and the pore size is 40-50 μm.

[0021] Furthermore, the polyether-type gemini surfactant is a type of oligomer containing ether bonds and hydroxyl groups, in which an ethylene oxide chain segment is introduced into the designed molecule as a hydrophilic chain to form a double hydrophilic chain with a quaternary ammonium salt, an alkyl chain to form a double hydrophobic chain, and an alkyl group as a connecting group.

[0022] Furthermore, in step (7), the mass ratio of the NaOH-urea aqueous solution, microcrystalline cellulose and polyether-type gemini surfactant is 100:(5-7):(0.2-1.8).

[0023] Furthermore, the sintering method in step (11) is: heating to 250°C at a heating rate of 5°C / min, then heating to 600°C at a heating rate of 1°C / min, and finally heating to 900°C at a heating rate of 5°C / min and keeping the temperature for 2h.

[0024] Beneficial effects:

[0025] 1. The present invention adopts a nano-iron skeleton. On the one hand, after sintering, it can form fully flowing nano-channels in the aerogel, which not only greatly increases the specific surface area, but also enables the flowing channels to quickly and more abundantly adsorb heavy metal ions. On the other hand, the nano-iron skeleton can also effectively strengthen the framework structure of the aerogel and prevent the collapse of the aerogel.

[0026] 2. The nano-iron skeleton of the present invention contains nano-zero-valent iron, which is a good reducing agent. Due to its nano-scale particle size, it has a larger specific surface area and has a stronger passivation ability for heavy metal ions. At the same time, since nano-zero-valent iron has good magnetic responsiveness, it can be quickly magnetically separated by a magnetic field after treatment, which is convenient for recycling and reuse.

[0027] 3. The present invention adds a polyether-type gemini surfactant in the preparation of aerogel. Since the polyether-type gemini surfactant has an ethylene oxide chain segment, it has good permeability, good emulsification, and micelle assembly ability, making the aerogel easier to cross-link and form. DETAILED DESCRIPTION

[0028] The present invention provides a heavy metal adsorption material for soil and a method for preparing the same. To clarify the objectives, technical solutions, and effects of the present invention, the present invention will be further described in detail with reference to the following examples. It should be understood that the specific examples described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0029] Example 1

[0030] This example is a heavy metal adsorption material in soil with different PVA concentrations, specifically as follows:

[0031] A method for preparing a heavy metal adsorption material in soil comprises the following steps:

[0032] (1) Add nano-zero-valent iron powder to water and perform ultrasonic dispersion. The ultrasonic dispersion conditions are: power 150 W, temperature 30 °C, and time 30 min to obtain nano-zero-valent iron dispersion.

[0033] (2) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h;

[0034] (3) Add nano-zero-valent iron dispersion, stir for 30 min, and cool to room temperature to obtain electrospinning solutions with PVA concentrations of 7%, 8%, 9%, and 10%, respectively. The content of nano-zero-valent iron in the electrospinning solution is 2 wt.%;

[0035] (4) The spinning solution was electrospun using an electrospinning device. The electrospinning conditions were as follows: the inner diameter of the needle was 0.16 mm, the spinning solution flow rate was 1.1 mL / h, the ambient temperature was 40 °C, the humidity was 40%, the voltage was 25 kV, and the distance from the receiving plate was 13 cm, and the receiving plate was used for receiving.

[0036] (5) drying in an oven to obtain a nano-iron skeleton;

[0037] (6) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0038] (7) Precool the NaOH-urea aqueous solution to -12°C, add microcrystalline cellulose and stir for 10 minutes, then add isooctyl polyoxyethylene ether phosphate and stir evenly, wherein the mass ratio of NaOH-urea aqueous solution, microcrystalline cellulose and polyether type gemini surfactant is 100:6:1.0;

[0039] (8) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0040] (9) Place the nano-iron skeleton in a mold, slowly pour the supernatant into it until the nano-iron skeleton is submerged, and keep it in a constant temperature water bath at 50°C for 4 hours to allow the gel reaction to proceed;

[0041] (10) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0042] (11) The composite aerogel was placed in a carbonization furnace protected by inert gas, and the temperature was increased to 250°C at a heating rate of 5°C / min, then increased to 600°C at a rate of 1°C / min, and finally increased to 900°C at a rate of 5°C / min and kept at this temperature for 2 h, thereby obtaining heavy metal adsorption material No. 1, heavy metal adsorption material No. 2, heavy metal adsorption material No. 3, and heavy metal adsorption material No. 4, respectively.

[0043] The average porosity and pore size of the nano-iron skeleton in each heavy metal adsorption material were measured.

[0044] Average porosity (%) Pore ​​size (μm) Heavy metal adsorption material No. 1 78.6 49.3 Heavy metal adsorption material No. 2 77.3 47.1 Heavy metal adsorption material No. 3 75.9 45.6 Heavy metal adsorption material No. 4 75.2 43.3

[0045] Example 2

[0046] This embodiment is a heavy metal adsorption material in soil with different contents of nano zero-valent iron, specifically as follows:

[0047] A method for preparing a heavy metal adsorption material in soil comprises the following steps:

[0048] (1) Add nano-zero-valent iron powder to water and perform ultrasonic dispersion. The ultrasonic dispersion conditions are: power 150 W, temperature 30 °C, and time 30 min to obtain nano-zero-valent iron dispersion.

[0049] (2) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h;

[0050] (3) Add nano-zero-valent iron dispersion, stir for 30 minutes, and cool to room temperature to obtain an electrospinning solution with a PVA concentration of 9%, wherein the content of nano-zero-valent iron in the electrospinning solution is 1 wt.% and 3 wt.%, respectively;

[0051] (4) The spinning solution was electrospun using an electrospinning device. The electrospinning conditions were as follows: the inner diameter of the needle was 0.16 mm, the spinning solution flow rate was 1.1 mL / h, the ambient temperature was 40 °C, the humidity was 40%, the voltage was 25 kV, and the distance from the receiving plate was 13 cm, and the receiving plate was used for receiving.

[0052] (5) drying in an oven to obtain a nano-iron skeleton;

[0053] (6) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0054] (7) Precool the NaOH-urea aqueous solution to -12°C, add microcrystalline cellulose and stir for 10 minutes, then add isooctyl polyoxyethylene ether phosphate and stir evenly, wherein the mass ratio of NaOH-urea aqueous solution, microcrystalline cellulose and polyether type gemini surfactant is 100:6:1.0;

[0055] (8) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0056] (9) Place the nano-iron skeleton in a mold, slowly pour the supernatant into it until the nano-iron skeleton is submerged, and keep it in a constant temperature water bath at 50°C for 4 hours to allow the gel reaction to proceed;

[0057] (10) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0058] (11) The composite aerogel was placed in a carbonization furnace protected by inert gas, and the temperature was raised to 250°C at a heating rate of 5°C / min, then to 600°C at a heating rate of 1°C / min, and finally to 900°C at a heating rate of 5°C / min and kept at that temperature for 2 h, thereby obtaining heavy metal adsorption material No. 5 and heavy metal adsorption material No. 6, respectively.

[0059] The average porosity and pore size of the nano-iron skeleton in each heavy metal adsorption material were measured.

[0060] Average porosity (%) Pore ​​size (μm) Heavy metal adsorption material No. 5 75.9 45.7 Heavy metal adsorption material No. 6 75.8 45.6

[0061] Example 3

[0062] This embodiment is a heavy metal adsorption material in soil with different spinning solution flow rates, specifically as follows:

[0063] A method for preparing a heavy metal adsorption material in soil comprises the following steps:

[0064] (1) Add nano-zero-valent iron powder to water and perform ultrasonic dispersion. The ultrasonic dispersion conditions are: power 150 W, temperature 30 °C, and time 30 min to obtain nano-zero-valent iron dispersion.

[0065] (2) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h;

[0066] (3) Add nano-zero-valent iron dispersion, stir for 30 minutes, and cool to room temperature to obtain an electrospinning solution with a PVA concentration of 9%, wherein the content of nano-zero-valent iron in the electrospinning solution is 2 wt.%;

[0067] (4) The spinning solution was electrospun using an electrospinning device. The electrospinning conditions were as follows: the inner diameter of the needle was 0.16 mm, the spinning solution flow rates were 0.6 mL / h, 0.8 mL / h, 1.0 mL / h, 1.3 mL / h, and 1.5 mL / h, respectively; the ambient temperature was 40°C, the humidity was 40%, the voltage was 25 kV, and the distance from the receiving plate was 13 cm, and the receiving plate was used for receiving.

[0068] (5) drying in an oven to obtain a nano-iron skeleton;

[0069] (6) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0070] (7) Precool the NaOH-urea aqueous solution to -12°C, add microcrystalline cellulose and stir for 10 minutes, then add isooctyl polyoxyethylene ether phosphate and stir evenly, wherein the mass ratio of NaOH-urea aqueous solution, microcrystalline cellulose and polyether type gemini surfactant is 100:6:1.0;

[0071] (8) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0072] (9) Place the nano-iron skeleton in a mold, slowly pour the supernatant into it until the nano-iron skeleton is submerged, and keep it in a constant temperature water bath at 50°C for 4 hours to allow the gel reaction to proceed;

[0073] (10) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0074] (11) The composite aerogel was placed in a carbonization furnace protected by inert gas, and the temperature was increased to 250°C at a heating rate of 5°C / min, then increased to 600°C at a rate of 1°C / min, and finally increased to 900°C at a rate of 5°C / min and kept warm for 2 h, thereby obtaining heavy metal adsorption material No. 7, heavy metal adsorption material No. 8, heavy metal adsorption material No. 9, heavy metal adsorption material No. 10, and heavy metal adsorption material No. 11, respectively.

[0075] The average porosity and pore size of the nano-iron skeleton in each heavy metal adsorption material were measured.

[0076] Average porosity (%) Pore ​​size (μm) Heavy metal adsorption material No. 7 79.6 49.8 Heavy metal adsorption material No. 8 78.1 48.3 Heavy metal adsorption material No. 9 76.5 47.1 Heavy metal adsorption material No. 10 74.2 43.2 Heavy metal adsorption material No. 11 72.3 40.6

[0077] Example 4

[0078] This example is a heavy metal adsorption material in soil with different mass ratios of NaOH-urea aqueous solution, microcrystalline cellulose and polyether-type gemini surfactant, specifically as follows:

[0079] A method for preparing a heavy metal adsorption material in soil comprises the following steps:

[0080] (1) Add nano-zero-valent iron powder to water and perform ultrasonic dispersion. The ultrasonic dispersion conditions are: power 150 W, temperature 30 °C, and time 30 min to obtain nano-zero-valent iron dispersion.

[0081] (2) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h;

[0082] (3) Add nano-zero-valent iron dispersion, stir for 30 minutes, and cool to room temperature to obtain an electrospinning solution with a PVA concentration of 9%, wherein the content of nano-zero-valent iron in the electrospinning solution is 2 wt.%;

[0083] (4) The spinning solution was electrospun using an electrospinning device. The electrospinning conditions were as follows: the inner diameter of the needle was 0.16 mm, the spinning solution flow rate was 1.1 mL / h, the ambient temperature was 40 °C, the humidity was 40%, the voltage was 25 kV, and the distance from the receiving plate was 13 cm, and the receiving plate was used for receiving.

[0084] (5) drying in an oven to obtain a nano-iron skeleton;

[0085] (6) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0086] (7) The NaOH-urea aqueous solution was precooled to -12°C, microcrystalline cellulose was added and stirred for 10 min, and then isooctanol polyoxyethylene ether phosphate was added and stirred evenly. The mass ratios of the NaOH-urea aqueous solution, microcrystalline cellulose and polyether-type gemini surfactant were 100:5:0.2, 100:5:1.0, 100:5:1.8, 100:6:0.2 and 100:6:1.8, respectively;

[0087] (8) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0088] (9) Place the nano-iron skeleton in a mold, slowly pour the supernatant into it until the nano-iron skeleton is submerged, and keep it in a constant temperature water bath at 50°C for 4 hours to allow the gel reaction to proceed;

[0089] (10) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0090] (11) The composite aerogel was placed in a carbonization furnace protected by inert gas, and the temperature was increased to 250°C at a heating rate of 5°C / min, then increased to 600°C at a rate of 1°C / min, and finally increased to 900°C at a rate of 5°C / min and kept warm for 2 h, thereby obtaining heavy metal adsorption material No. 12, heavy metal adsorption material No. 13, heavy metal adsorption material No. 14, heavy metal adsorption material No. 15, and heavy metal adsorption material No. 16, respectively.

[0091] Comparative Example 1

[0092] The difference between this embodiment and heavy metal adsorption material No. 3 is that nano-iron is not added. Specifically:

[0093] A method for preparing a heavy metal adsorption material in soil comprises the following steps:

[0094] (1) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h;

[0095] (2) Cooling to room temperature to obtain an electrospinning solution with a PVA concentration of 9%;

[0096] (3) The spinning solution was electrospun using an electrospinning device. The electrospinning conditions were as follows: the inner diameter of the needle was 0.16 mm, the spinning solution flow rate was 1.1 mL / h, the ambient temperature was 40°C, the humidity was 40%, the voltage was 25 kV, and the distance from the receiving plate was 13 cm, and the receiving plate was used for receiving.

[0097] (4) Drying in an oven to obtain a skeleton;

[0098] (5) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0099] (6) Precool the NaOH-urea aqueous solution to -12°C, add microcrystalline cellulose and stir for 10 minutes, then add isooctyl polyoxyethylene ether phosphate and stir evenly, wherein the mass ratio of NaOH-urea aqueous solution, microcrystalline cellulose and polyether type gemini surfactant is 100:6:1.0;

[0100] (7) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0101] (8) Place the skeleton in a mold, slowly pour in the supernatant until the skeleton is submerged, and keep in a constant temperature water bath at 50°C for 4 h to allow the gel reaction to proceed;

[0102] (9) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0103] (10) The composite aerogel was placed in a carbonization furnace protected by inert gas, and the temperature was raised to 250°C at a heating rate of 5°C / min, then to 600°C at a heating rate of 1°C / min, and finally to 900°C at a heating rate of 5°C / min and kept at that temperature for 2 h, thereby obtaining heavy metal adsorption material No. 17.

[0104] The average porosity and pore size of the nano-iron skeleton in the heavy metal adsorption material were measured, and the results are shown in the following table:

[0105] Average porosity (%) Pore ​​size (μm) Heavy metal adsorption material No. 17 76.0 45.8

[0106] Comparative Example 2

[0107] The difference between this embodiment and heavy metal adsorption material No. 3 is that no nano-iron skeleton is added. Specifically:

[0108] A method for preparing a heavy metal adsorption material in soil comprises the following steps:

[0109] (1) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution;

[0110] (2) The NaOH-urea aqueous solution was precooled to -12°C, microcrystalline cellulose was added and stirred for 10 minutes, and then isooctanol polyoxyethylene ether phosphate was added and stirred evenly, wherein the mass ratio of the NaOH-urea aqueous solution, microcrystalline cellulose and polyether type gemini surfactant was 100:6:1.0;

[0111] (3) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant;

[0112] (4) Slowly pour the supernatant into the mold and keep it in a constant temperature water bath at 50°C for 4 h to allow the gel reaction to proceed;

[0113] (5) The composite aerogel was obtained by aging at room temperature (25°C) for 24 h and freeze-drying in vacuum;

[0114] (6) The composite aerogel was placed in a carbonization furnace protected by inert gas, and the temperature was raised to 250°C at a heating rate of 5°C / min, then to 600°C at a rate of 1°C / min, and finally to 900°C at a rate of 5°C / min and kept at that temperature for 2 h, thereby obtaining heavy metal adsorption material No. 18.

[0115] The specific surface area of ​​each heavy metal adsorption material was measured, and the results are shown in Table 1:

[0116] Table 1

[0117] <![CDATA[Specific surface area (m 2 / g)]]> Heavy metal adsorption material No. 1 452.3 Heavy metal adsorption material No. 2 461.1 Heavy metal adsorption material No. 3 470.4 Heavy metal adsorption material No. 4 473.3 Heavy metal adsorption material No. 5 470.7 Heavy metal adsorption material No. 6 470.2 Heavy metal adsorption material No. 7 449.3 Heavy metal adsorption material No. 8 456.4 Heavy metal adsorption material No. 9 467.1 Heavy metal adsorption material No. 10 472.9 Heavy metal adsorption material No. 11 474.1 Heavy metal adsorption material No. 12 468.2 Heavy metal adsorption material No. 13 471.7 Heavy metal adsorption material No. 14 473.9 Heavy metal adsorption material No. 15 466.8 Heavy metal adsorption material No. 16 472.3 Heavy metal adsorption material No. 17 470.7 Heavy metal adsorption material No. 18 198.6

[0118] Determination of the saturated adsorption capacity of heavy metal adsorption materials for heavy metal ions in soil: prepare Hg(NO3)2, Pb(NO3)2, Cu(NO3)2 and Cd(NO3)2 solutions with a concentration of 2000 mg / L respectively. At 25°C and pH=6, take 4 portions of 10 mg of heavy metal adsorption materials and mix them with 10 mL of Hg(NO3)2, Pb(NO3)2, Cu(NO3)2 and Cd(NO3)2 solutions respectively. Continuous adsorption at a frequency of 250 rpm / min until the adsorption capacity no longer changes.

[0119] The mass fraction of the preparation is 10×10-6 Hg 2+ , Pb 2+ 、Cu 2+ and Cd 2+ The adsorption rate of low concentration heavy metal contaminated soil was determined.

[0120] The mass fraction of the preparation is 10×10 -4 Hg 2+ , Pb 2+ 、Cu 2+ and Cd 2+ The adsorption rate in soil with high concentration of heavy metal pollution was determined.

[0121] Table 2

[0122]

[0123] It can be seen from Table 2 that with the increase of PVA concentration, the heavy metal adsorption material has a better effect on the heavy metal ion Hg 2+ , Pb 2+ 、Cu 2+ and Cd 2+ The saturated adsorption capacity and adsorption rate increased, which may be because the increase in PVA concentration leads to an increase in the final specific surface area, making it more suitable for heavy metal ions Hg 2+ , Pb 2+ 、Cu 2+ and Cd 2+ The saturated adsorption capacity and adsorption rate of the heavy metal ion Hg increased with the increase of the content of nano zero-valent iron. 2+ , Pb 2+ 、Cu 2+ and Cd 2+ The saturated adsorption capacity and adsorption rate of the heavy metal ions have also increased, mainly because the nano zero-valent iron is a good reducing agent. Due to the nano particle size, it has a larger specific surface area and has a stronger passivation ability for heavy metal ions. 2 + , Pb 2+ 、Cu 2+ and Cd 2+ The saturated adsorption capacity and adsorption rate are greatly reduced. This shows that the full flow channel formed by the nano-iron skeleton plays a very critical role in the adsorption of heavy metal ions. At the same time, we also observed that the aerogel of heavy metal adsorption material No. 18 collapsed.

Claims

1. A method for preparing a heavy metal adsorption material in soil, characterized in that: The heavy metal adsorption material in the soil is an aerogel containing nano-iron with full-flow nano-channels; The preparation method comprises the following steps: (1) Adding nano-zero-valent iron powder to water and performing ultrasonic dispersion to obtain nano-zero-valent iron dispersion; (2) PVA was added to water, swelled at room temperature for 30 min, and then magnetically stirred at 90 °C for 3 h; (3) Add nano-zero-valent iron dispersion, stir for 30 minutes, and cool to room temperature to obtain an electrospinning solution with a PVA concentration of 7-10%; (4) electrospinning the spinning solution using an electrospinning device and receiving it on a receiving plate; (5) drying in an oven to obtain a nano-iron skeleton; (6) NaOH, urea, and deionized water were mixed in a mass ratio of 7:12:81 to obtain a NaOH-urea aqueous solution; (7) Precool the NaOH-urea aqueous solution to -12°C, add microcrystalline cellulose and stir for 10 minutes, then add isooctyl polyoxyethylene ether phosphate and stir evenly; (8) Place the sample in a centrifuge and centrifuge at 5000 r / min for 10 min, and collect the supernatant; (9) Place the nano-iron skeleton in a mold, slowly pour the supernatant into it until the nano-iron skeleton is submerged, and keep it in a constant temperature water bath at 50°C for 4 h to allow the gel reaction to proceed; (10) The mixture was moved to room temperature at 25°C for aging for 24 h and then freeze-dried in vacuum to obtain the composite aerogel; (11) The composite aerogel is placed in a carbonization furnace protected by inert gas and sintered to obtain an aerogel containing nano-iron with fully flowing nanochannels.

2. The method for preparing a heavy metal adsorption material in soil according to claim 1, characterized in that: The ultrasonic dispersion conditions in step (1) are: power 150 W, temperature 30°C, and time 30 min.

3. The method for preparing a heavy metal adsorption material in soil according to claim 1, characterized in that: The content of nano zero-valent iron in the electrospinning solution is 1-3 wt.%.

4. The method for preparing a heavy metal adsorption material in soil according to claim 1, characterized in that: The electrospinning conditions in step (4) are as follows: the inner diameter of the needle is 0.16 mm, the spinning solution flow rate is 0.6-1.5 mL / h, the ambient temperature is 30-45 ° C, the humidity is 40%, the voltage is 25 kV, and the distance from the receiving plate is 13 cm.

5. The method for preparing a heavy metal adsorption material in soil according to claim 1, characterized in that: The porosity of the nano-iron skeleton in step (5) is 70-80%, and the pore size is 40-50 μm.

6. The method for preparing a heavy metal adsorption material in soil according to claim 1, characterized in that: In the step (7), the mass ratio of the NaOH-urea aqueous solution, microcrystalline cellulose and isooctyl polyoxyethylene ether phosphate is 100:(5-7):(0.2-1.8).

7. The method for preparing a heavy metal adsorption material in soil according to claim 1, characterized in that: The sintering method in step (11) is: heating to 250°C at a heating rate of 5°C / min, then heating to 600°C at a heating rate of 1°C / min, and finally heating to 900°C at a heating rate of 5°C / min and keeping the temperature for 2 hours.

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