A bamboo charcoal-based carboxylated magnetic soil remediation agent, a preparation method and application thereof

Abstract

The application provides a bamboo charcoal-based carboxylated magnetic soil remediation agent, a preparation method and application. The preparation method of the remediation agent comprises the following steps: (1) bamboo charcoal carrier preparation: 1) bamboo charcoal preparation; 2) bamboo charcoal modification; (2) magnetic soil remediation agent preparation: 1) preparation of Fe3O4@C / bamboo charcoal composite material; 2) carboxylation. The application takes bamboo charcoal as the carrier, the bamboo charcoal and Fe3O4@C both have a large specific surface area, and appropriate bamboo charcoal as an additive is beneficial to adjusting the soil PH, increasing the soil porosity and improving the accumulation of organic matter; through the modification of carboxylation, chemical reaction with heavy metals in the soil is generated, and the content of the available state of the heavy metals is reduced; the magnetic Fe3O4@C is used as the adsorbent, is recycled through the electromagnetic force equipment, and is reused, so that the use cost is reduced. The remediation agent has a good solidification effect on the soil heavy metals, has good stability of the remediation efficiency of the heavy metals, and is still efficient and stable after 30 days.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of bamboo charcoal base carboxylation magnetic soil remediation agent, preparation method and application, belong to soil treatment technical field. BACKGROUND

[0002] Environment is the basis for human and other living beings to survive, and is an important guarantee for social and economic development. However, with the development of science and technology industry, the damage to the environment by human beings is becoming more and more serious, and the treatment of environmental pollution has become a worldwide issue. There are many types of environmental pollution, among which, soil heavy metal pollution has become one of the serious environmental pollution problems due to its wide distribution, multiple types and difficult treatment. At present, the existing soil heavy metal remediation methods at home and abroad are mostly based on physics, chemistry, biology and agronomic control, and the main remediation technologies include solidification / stabilization technology, soil elution technology, oxidation / reduction technology, soil phytoremediation technology, etc.

[0003] Among these remediation technologies, solidification / stabilization remediation technology is a relatively effective and economical soil pollution remediation technology. The commonly used remediation agents include organic remediation agents and inorganic remediation agents. Among them, the organic remediation agents are organic fertilizer, organic clay, etc.; the inorganic remediation agents are lime, cement, modified cellulose, slag, etc. These remediation agents have large capacity, which leads to eutrophication of water body, unstable remediation effect, secondary pollution, deterioration of soil properties and high cost.

[0004] In recent years, magnetic nanomaterials have been widely used in the environment due to their large adsorption capacity, fast adsorption rate and recyclability, and have been widely used in wastewater treatment field. Although some studies have used them for remediation of soil heavy metal pollution, there are still many problems that need further study. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a bamboo charcoal base carboxylation magnetic soil remediation agent, a preparation method and application.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is

[0007] A preparation method of a bamboo charcoal base carboxylation magnetic soil remediation agent, comprising the following steps:

[0008] (1) Preparation of bamboo charcoal carrier

[0009] 1) Preparation of bamboo charcoal

[0010] Divide the bamboo material into long strips, crush and sieve to obtain powder; then dry the powder sample at 120 DEG C for 12h to obtain bamboo powder; after drying, calcine the bamboo powder at 600 DEG C for 1h to obtain bamboo charcoal;

[0011] 2) Bamboo charcoal modification

[0012] H2O2 solution, NaClO solution and deionized water were added to the obtained bamboo charcoal, stirred and heated to 50℃, and kept for 4h; then filtered, washed, and dried at 100℃ for 8h in vacuum to obtain modified bamboo charcoal;

[0013] (2) Preparation of magnetic soil remediation agent

[0014] 1) Preparation of Fe3O4@C / bamboo charcoal composite material: ferrocene was dissolved in acetone, and after ultrasonic treatment for 20min, the modified bamboo charcoal was added, and ultrasonic treatment was continued for 20min, then H2O2 solution was added, and stirred for 30min to fully mix, to obtain a mixed solution;

[0015] The mixed solution was transferred into a polytetrafluoroethylene reaction kettle, heated to 200℃, and reacted at this temperature for 48h; after the reaction was completed, it was cooled to room temperature, the supernatant was poured off, and the remaining residue was recovered; the remaining residue was washed with acetone by centrifugation for 3 times, and after washing, it was vacuum dried at 50℃ for 12h to obtain Fe3O4@C / bamboo charcoal composite material;

[0016] 2) Carboxylation: deionized water A was added to the Fe3O4@C / bamboo charcoal composite material, and after ultrasonic treatment for 30min, oleic acid was added, and stirred in a 70℃ water bath for 2h to fully react, to obtain black oily precipitate, the supernatant was poured off using a strong magnet, and the precipitate A was recovered; the precipitate A was washed with anhydrous ethanol for 3 times, and then washed with deionized water for 3 times; after washing, deionized water B and KMnO4 were added, ultrasonic treatment was carried out for 6h, and the precipitate B was separated and recovered using a strong magnet; the precipitate B was washed with deionized water for 3 times, and after washing, it was vacuum dried for 12h to obtain carboxylated Fe3O4@C / bamboo charcoal composite material.

[0017] The size of the long strip after the step (1) segmentation was 5cm×2cm, and after crushing, powder was obtained by passing through a 60 mesh sieve; calcination was from room temperature to 600℃ at a heating rate of 6℃ / min, and after reaching the target temperature, calcination was carried out for 1h; washing was with deionized water for 3-4 times.

[0018] The mass of the bamboo charcoal of the step (1), the volume of the H2O2 solution, the volume of the NaClO solution and the volume of the deionized water were 5g: 100mL: 40mL: 200mL; wherein the concentration of the H2O2 solution was 9.79mol / L; and the concentration of the NaClO solution was 0.7104mol / L.

[0019] The mass of the ferrocene, the volume of the acetone, the mass of the modified bamboo charcoal and the volume of the H2O2 solution of the step (2) were 1g: 150mL: 0.3g: 5mL; wherein the concentration of the H2O2 solution was 9.79mol / L.

[0020] The mass of the Fe3O4@C / bamboo charcoal composite material, the volume of deionized water A and the mass of oleic acid in step (2) are 0.5 g: 50 mL: 5 g.

[0021] The mass of the Fe3O4@C / bamboo charcoal composite material, the volume of deionized water B and the mass of KMnO4 in step (2) are 0.5 g: 150 mL: 1.8 g.

[0022] The bamboo charcoal-based carboxylated magnetic soil remediation agent prepared by the preparation method.

[0023] The bamboo charcoal-based carboxylated magnetic soil remediation agent prepared by the preparation method is applied to heavy metal contaminated soil remediation.

[0024] The heavy metal is Pb, Zn, Cr or Cu.

[0025] The dosage of the bamboo charcoal-based carboxylated magnetic soil remediation agent is 1.4 g of the remediation agent per 1 kg of soil.

[0026] The present application has the following beneficial effects:

[0027] The present application uses bamboo charcoal as a carrier, and bamboo charcoal and Fe3O4@C both have a large specific surface area. Appropriate bamboo charcoal as an additive is conducive to adjusting the soil PH, increasing the soil porosity and improving the accumulation of organic matter. Through the modification of carboxylation, chemical reactions can occur with heavy metals in the soil to reduce the content of available heavy metals. The magnetic Fe3O4@C is used as an adsorbent, which can be recycled and reused through electromagnetic force equipment, thereby reducing the use cost.

[0028] The bamboo charcoal-based carboxylated magnetic remediation agent has a good solidification effect on soil heavy metals. Experiments show that the recovery rate of heavy metals Pb, Zn, Cr and Cu after treatment is 97.3% to 102.2%, and the remediation effect gradually improves with the increase of the dosage of the remediation agent in the initial stage, and the optimal dosage is 1.4 g·kg -1 The bamboo charcoal-based carboxylated magnetic remediation agent has good stability in remediation efficiency of heavy metals, and the remediation efficiency is still efficient and stable after 30 days. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 X-ray diffraction pattern of the bamboo charcoal-based carboxylated magnetic remediation agent obtained in Example 1.

[0030] Figure 2 Infrared spectrum of the bamboo charcoal-based carboxylated magnetic remediation agent obtained in Example 1. DETAILED DESCRIPTION

[0031] The following further describes the specific embodiments of the present application in conjunction with examples. Unless otherwise specified, the instruments and equipment involved in the examples are conventional instruments and equipment; the reagents involved are commercially available conventional reagents; and the test methods involved are conventional methods.

[0032] Example 1

[0033] A preparation method of a bamboo charcoal-based carboxylated magnetic soil remediation agent, comprising the following steps:

[0034] (1) Preparation of a bamboo charcoal carrier

[0035] 1) Preparation of bamboo charcoal

[0036] The bamboo material was cut into 5 cm x 2 cm strips, crushed by a crusher and passed through a 60 mesh sieve to obtain a powder; the powder sample was then dried at 120°C for 12 h to obtain bamboo powder; after drying, the bamboo powder was calcined in a vacuum muffle furnace at 600°C for 1 h at a heating rate of 6°C / min to obtain bamboo charcoal for standby;

[0037] 2) Modification of bamboo charcoal

[0038] 5 g of bamboo charcoal was placed in a 500 mL flask, 100 mL of H2O2(9.79 mol / L, i.e., 30% hydrogen peroxide by mass fraction), 40 mL of NaClO(0.7104 mol / L) and 200 mL of deionized water were added, and a magnetic stirrer was used for stirring and heating to 50°C, and incubation for 4 h; after incubation, suction filtration was performed, and deionized water was used for rinsing 3-4 times, and the sample was placed in a vacuum drying oven at 100°C for drying for 8 h to obtain modified bamboo charcoal for standby;

[0039] (2) Preparation of a magnetic soil remediation agent

[0040] 1) Fe3O4@C was used as a magnetic material, and modified bamboo charcoal was used as a carrier to prepare Fe3O4@C / bamboo charcoal composite material: 1 g of ferrocene was dissolved in 150 mL of acetone, and ultrasonic treatment was performed for 20 min, then 0.3 g of modified bamboo charcoal obtained in step (1) was added, and ultrasonic treatment was continued for 20 min, then 5 mL of H2O2(9.79 mol / L) was added, and magnetic stirring was performed for 30 min to fully mix the solution to obtain a mixed solution;

[0041] The mixed solution was transferred into a polytetrafluoroethylene reaction kettle, heated to 200°C, and reacted for 48 h; after the reaction was completed, the solution was cooled to room temperature, the supernatant was poured off under the action of a strong magnet, and the black residue was recovered; the black residue was washed with acetone by centrifugation for 3 times, and after washing, vacuum drying was performed at 50°C for 12 h to obtain Fe3O4@C / bamboo charcoal composite material;

[0042] 2) Carboxylation: 0.5g of the above Fe3O4@C / bamboo charcoal composite material was added to a beaker, along with 50mL of deionized water. After ultrasonic treatment for 30min, 5g of oleic acid was added, and the mixture was stirred in a 70℃ water bath for 2h to allow for complete reaction, resulting in a black oily precipitate. The supernatant was poured off using a strong magnet, and precipitate A was recovered. Precipitate A was washed three times with anhydrous ethanol, and then three times with deionized water. After washing, 150mL of deionized water and 1.8g of KMnO4 were added, and the mixture was ultrasonically treated for 6h. Precipitate B was separated and recovered using a strong magnet. Precipitate B was washed three times with deionized water, and then freeze-dried under vacuum for 12h to obtain a stable carboxylated Fe3O4@C / bamboo charcoal composite material.

[0043] Characterization and analysis of the bamboo charcoal-based carboxylated magnetic soil remediation agent of the present invention

[0044] (1) XRD characterization analysis

[0045] The crystal structure of the bamboo charcoal-based carboxylated magnetic soil remediation agent obtained in Example 1 was characterized by XRD, as shown below. Figure 1 As shown, 2θ has strong and obvious characteristic peaks at 30.1°, 35.5°, 43.2°, 53.4°, 57.1° and 62.6°. The crystal shapes and corresponding structures of each diffraction peak are attributed to (220), (311), (400), (442), (511) and (440), respectively, which are basically consistent with the standard XRD pattern of Fe3O4.

[0046] (2) Infrared spectroscopy (FI-IR) characterization analysis

[0047] The changes in surface functional groups of the bamboo charcoal-based carboxylated magnetic soil remediation agent obtained in Example 1 were characterized using Fourier transform infrared spectroscopy (FI-IR). Figure 2 As shown, 578cm -1 The absorption peak at 2924 cm⁻¹ is a characteristic absorption peak of Fe₃O₄. -1 The corresponding stretching vibration peak of CH is 3455 cm⁻¹. -1 The absorption peak at 1702 cm⁻¹ is a characteristic absorption peak of -OH. -1 There is a strong peak at this point, which is the characteristic absorption peak of -COOH, thus proving that the material has been successfully carboxylated.

[0048] Application examples

[0049] Study on the solidification effect of bamboo charcoal-based carboxylated magnetic remediation agent on soil heavy metals in Example 1.

[0050] Soil samples were collected from the farmland around a lead-zinc smelting plant in a city. Five sampling points were set up in a range of 10 m x 10 m using the quincunx method. The surface soil at a depth of 0-20 cm was collected, mixed uniformly, and about 1 kg of soil was taken into a clean plastic self-sealing bag for use. The soil was naturally dried in the room, ground, and sieved through a 100-mesh sieve. The sieved soil was sealed in a bag and stored in a cool place for use.

[0051] The BCR sequential extraction method was used to extract four forms of heavy metals in the soil samples: weak acid extractable state, reducible state, oxidizable state, and residual state. The weak acid extractable state is greatly affected by water ions and pH. The reducible state is easily transformed in anoxic environments. The oxidizable state is released under the action of microorganisms. The residual state mainly exists in the crystal lattice of minerals and is relatively stable. Therefore, the bioavailable state (utilizable state) is the weak acid extractable state, the reducible state, and the oxidizable state. The content of heavy metals in the soil samples was determined using a flame-graphite furnace atomic absorption spectrometer.

[0052] Heavy metal determination: About 0.1000 g of sample was weighed into a polytetrafluoroethylene digestion tank, and concentrated nitric acid, concentrated hydrochloric acid, and hydrofluoric acid (molar ratio of HNO3: HCl: HF = 6:2:1) were added in sequence. The tank was left to cool overnight to prevent explosion. The next day, the tank was placed in a microwave digestion instrument for digestion. After digestion, the digestion solution was transferred to a 50 mL polytetrafluoroethylene beaker, 0.50 mL of HClO4 was added, and the acid was chased at 120°C until 1-2 mL of liquid remained. The solution was transferred to a 50 mL volumetric flask and diluted to the mark for measurement.

[0053] BCR sequential extraction method: 0.5000 g of sample was accurately taken into a 40 mL centrifuge tube, 20 mL of 0.1 mol / L CH3COOH was added, and the tube was shaken at 160 r / min for 16 h at room temperature. Then, the tube was centrifuged at 3000 r / min for 20 min, and the supernatant was collected to obtain the weak acid extractable state. The residue from the first step was added with 0.5 mol / L NH2OH·HCl, and the tube was shaken at 160±5 r / min for 16 h at room temperature. Then, the tube was centrifuged at 3000 r / min for 20 min, and the supernatant was collected to obtain the reducible state. 5 mL of 30% H2O2 was added to the residue from the second step, shaken, and placed for 1 h. Then, the tube was heated in a water bath (85±2°C) until H2O2 was nearly dry. After cooling, 5 mL of 30% H2O2 was added again, and the tube was heated in a water bath until nearly dry. After cooling, 25 mL of 1 mol / L NH4OAc was added, and the tube was shaken at 160±5 r / min for 16 h at room temperature. Then, the tube was centrifuged at 3000 r / min for 20 min, and the supernatant was collected to obtain the oxidizable state. The remaining residual state was digested according to the method for heavy metal determination. The results are shown in Table 1:

[0054] Table 1 Initial state of heavy metals in soil (unit: mg·kg -1 )

[0055] Statistical indicators Total amount Available content Available content ratio Pb 651.43 261.16 40.09％ Zn 132.46 58 43.79％ Cr 78.60 15.96 20.31％ Cu 66.58 24.47 36.76％

[0056] Take 1 kg of soil, adjust the soil moisture content to 30%, add 0.5 g, 0.8 g, 1.1 g, 1.4 g, 1.7 g, 2.0 g of remediation agent into the soil and stir well, stir every 2 h, for 12 h, and measure the available content of heavy metals in the soil. From Table 2, it can be seen that the total amount of heavy metals remains basically unchanged before and after treatment, the recovery rate is between 97.30% and 104.43%, and it is accurate and reliable.

[0057] From Table 3, it can be seen that with the increase of remediation agent dosage, the remediation efficiency (the percentage of the change of available heavy metal content after treatment relative to the available heavy metal content before treatment) gradually rises, and the rising rate is 1.4 g·kg -1 , so from the perspective of cost saving, the optimal dosage is 1.4 g·kg -1 .

[0058] Stability of remediation efficiency: according to the dosage of 1.4 g·kg -1 , the above experiment is continued for 30 d, the available content of heavy metals Pb, Zn, Cr and Cu is measured every 5 d, the remediation efficiency is calculated, and the results are shown in Table 4. The remediation efficiency slightly rises on the 5th day, and with the passage of time, the remediation efficiency is basically stable until the 30th day, which shows that the remediation agent is highly efficient and stable in remediation of heavy metals.

[0059] Table 2 Change of soil heavy metals before and after treatment and recovery rate under different remediation agent dosages

[0060]

[0061] Table 3 Remediation efficiency of soil heavy metals

[0062]

[0063] Table 4 Stability evaluation of remediation agent (remediation efficiency, %)

[0064] Statistical indicators 12h 5d 10d 10d 20d 25d 30d Pb 39.82 42.16 40.33 42.24 43 41.18 40 Zn 36.98 37.72 38.38 36 38.19 37.87 38.13 Cr 36.28 38.91 37.56 37.39 37.37 38.36 38.27 Cu 27.67 29.28 29.03 30.33 28.38 29.15 29.77

Claims

1. A method for preparing a bamboo charcoal-based carboxylated magnetic soil remediation agent, characterized in that, Includes the following steps: (1) Preparation of bamboo charcoal carrier 1) Bamboo charcoal preparation Bamboo raw materials are cut into long strips, crushed and sieved to obtain powder; then the powder sample is dried at 120℃ for 12 hours to obtain bamboo powder; after drying, the bamboo powder is calcined at 600℃ for 1 hour to obtain bamboo charcoal. 2) Bamboo charcoal modification H2O2 solution, NaClO solution and deionized water were added to the obtained bamboo charcoal, stirred and heated to 50℃, and kept at the temperature for 4 hours; then filtered, washed and dried under vacuum at 100℃ for 8 hours to obtain modified bamboo charcoal. (2) Preparation of magnetic soil remediation agent 1) Preparation of Fe3O4@C / bamboo charcoal composite material: Ferrocene was dissolved in acetone, sonicated for 20 min, and then the modified bamboo charcoal was added. The mixture was sonicated for another 20 min, and then H2O2 solution was added. The mixture was stirred for 30 min to ensure thorough mixing and obtain a mixed solution. The mixed solution was transferred into a polytetrafluoroethylene reactor and heated to 200°C. The reaction was carried out at this temperature for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, the supernatant was discarded, and the remaining residue was recovered. The remaining residue was washed three times with acetone by centrifugation and then dried under vacuum at 50°C for 12 hours to obtain the Fe3O4@C / bamboo charcoal composite material. 2) Carboxylation: Deionized water A was added to the Fe3O4@C / bamboo charcoal composite material, and after ultrasonic treatment for 30 min, oleic acid was added, and the mixture was stirred in a 70℃ water bath for 2 h to allow it to react fully, resulting in a black oily precipitate. The supernatant was poured off using a strong magnet, and precipitate A was recovered. Precipitate A was washed three times with anhydrous ethanol, and then three times with deionized water. After washing, deionized water B and KMnO4 were added, and the mixture was ultrasonically treated for 6 h. Precipitate B was separated and recovered using a strong magnet. Precipitate B was washed three times with deionized water, and then vacuum dried for 12 h to obtain the carboxylated Fe3O4@C / bamboo charcoal composite material.

2. The preparation method according to claim 1, characterized in that, The strips cut in step (1) are 5cm × 2cm in size. After being crushed, they are passed through a 60-mesh sieve to obtain powder. Calcination is carried out by heating from room temperature to 600℃ at a heating rate of 6℃ / min, and calcining for 1 hour after reaching the target temperature. Rinsing is done by rinsing with deionized water 3 to 4 times.

3. The preparation method according to claim 1, characterized in that, In step (1), the ratio of the mass of bamboo charcoal, the volume of H2O2 solution, the volume of NaClO solution, and the volume of deionized water is 5g:100mL:40mL:200mL; wherein, the concentration of H2O2 solution is 9.79mol / L; and the concentration of NaClO solution is 0.7104mol / L.

4. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the mass of ferrocene, the volume of acetone, the mass of modified bamboo charcoal, and the volume of H2O2 solution is 1g:150mL:0.3g:5mL; wherein the concentration of H2O2 solution is 9.79mol / L.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of Fe3O4@C / bamboo charcoal composite material, volume of deionized water A, and mass of oleic acid is 0.5g:50mL:5g.

6. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of Fe3O4@C / bamboo charcoal composite material, the volume of deionized water B, and the mass ratio of KMnO4 is 0.5g:150mL:1.8g.

7. A bamboo charcoal-based carboxylated magnetic soil remediation agent obtained by the preparation method described in claim 1.

8. The application of a bamboo charcoal-based carboxylated magnetic soil remediation agent obtained by the preparation method of claim 1 in the remediation of heavy metal contaminated soil.

9. The application according to claim 8, characterized in that, The heavy metal is Pb, Zn, Cr or Cu.

10. The application according to claim 8, characterized in that, The dosage of the bamboo charcoal-based carboxylated magnetic soil remediation agent is 1.4g of remediation agent per 1kg of soil.

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