CN111285574A - A kind of preparation method of sediment heavy metal pollution remediation agent and application thereof - Google Patents

Abstract

The invention discloses a preparation method of a bottom mud heavy metal pollution repairing agent, which mainly comprises the following steps: activating carbonized biomass by a hydrothermal method by using chenopodium quinoa as a raw material; under the anaerobic condition, preparing biochar by low-temperature pyrolysis and carbonization; stirring the biochar, clay, bentonite and kaolin uniformly; adding sodium dodecyl sulfate, and stirring at high speed; adding NaHCO₃、KHCO₃、Ca(HCO₃)₂、Mg(HCO₃)₂Stirring uniformly; carrying out heat treatment for 1h-2h under a vacuum condition; preparation of bottom mud heavy metal pollution remediation by high-temperature pyrolysis and carbonization under anaerobic conditionCompounding agent. The prepared biochar repairing agent overcomes the defects of large buoyancy and difficult sedimentation of biochar, and realizes the efficient adsorption of Cd in water and fixed bottom mud²⁺、Pb²⁺、Cu²⁺And Hg²⁺. The invention also discloses the application of the bottom sediment heavy metal pollution repairing agent in adsorbing water and fixing heavy metal pollutants in bottom sediment.

Description

A kind of preparation method of sediment heavy metal pollution remediation agent and application thereof

technical field

The invention relates to the field of water treatment, in particular to the preparation of a heavy metal pollution remediation agent in sediment by using biochar as a raw material, and the application in adsorbing water and fixing heavy metal pollutants in the sediment.

Background technique

The disorderly and illegal discharge of urban domestic sewage and industrial and agricultural wastewater has resulted in serious heavy metal pollution in urban rivers. After heavy metal pollutants enter the river water, most of them settle into the river sediment through physical, chemical and biological action. The content of heavy metals in the sediment is often several times or even ten times that in the overlying water, which brings adverse effects on the improvement of river water quality and pollution control. Once the heavy metals in the river sediment are released, it will lead to aggravation of river water pollution. Therefore, it is very meaningful to control the release of heavy metal pollutants in river sediments for improving the ecological environment of rivers.

At this stage, the control technology of heavy metal pollution in sediment mainly adopts sediment dredging technology, ex-situ restoration technology of polluted sediment, and in-situ control technology of polluted sediment. Among them, the in-situ control technology of polluted sediment refers to the technology of repairing sediment pollution in situ and controlling the migration and transformation of pollutants without dredging. In-situ pollutant control technologies mainly include in-situ sediment coverage, in-situ biological and chemical remediation, etc. Biochar is a carbonaceous material prepared by pyrolysis and chemical conversion of biomass under oxygen barrier conditions. Biochar possesses abundant surface functional groups, variable surface morphology and diverse pore structures and other physical and chemical properties. By virtue of its surface functional groups, morphological structure and other characteristics, biochar can adsorb and fix heavy metals in sediments and inhibit the migration and transformation of heavy metals in sediments. Compared with other sediment remediation agents, biochar has excellent heavy metal adsorption performance and can effectively restore the ecological environment of sediment. However, due to the large buoyancy of biochar itself, the use of biochar alone as a sediment restoration agent will prevent the biochar from sinking to the bottom of the river due to buoyancy, which affects the control effect of heavy metals in the sediment. Therefore, the existing technologies using biochar to control heavy metals in sediments only use biochar as a component of sediment remediation agents. The content of biochar in the remediation agent is not high, which will affect the remediation effect of heavy metals in the sediment.

Patent Publication No. CN109264944A discloses a method for remediating mercury-contaminated sediment with FeSO ₄ modified biochar. Obviously, the remediation agent cannot be used for in-situ remediation of heavy metal pollution in sediment due to the high buoyancy of biochar. The patent with publication number CN110104913A discloses a sediment restoration agent and a method for applying it to in-situ restoration of sediment. The method uses modified biochar as a component of the sediment restoration agent, and the mass of modified biochar accounts for 20%- 30%, the content is low, the sediment restoration agent is not suitable for the control of heavy metal pollutants in the sediment. The patent with publication number CN108892342A discloses a preparation method of a composite material for heavy metal immobilization in water body sediment. In the method, phosphoric acid modified biomass is used, and the preparation process is easy to produce pollution. At the same time, the method simply mixes biochar with inorganic salts, The obtained composite material is not tightly combined, which is not conducive to practical application.

SUMMARY OF THE INVENTION

The invention aims to increase the percentage content of biochar in the sediment repair agent, enhance the ability of the repair agent to absorb and fix heavy metals, and simultaneously overcome the shortcomings of biochar as a sediment repair agent, which has high buoyancy and is not easy to settle. The invention uses biochar as a raw material to prepare a heavy metal polluted sediment restoration agent, has high adsorption and solidification efficiency of heavy metals, and is environmentally friendly.

A preparation method of a sediment heavy metal pollution remediation agent, which mainly comprises the following steps:

(1) Using quinoa as raw material, 150℃-280℃ hydrothermally activated carbonized biomass, and collected samples;

(2) Biochar is prepared by pyrolysis and carbonization at 300℃-450℃ under anaerobic conditions;

(3) Mix the biochar with one or more of clay, bentonite and kaolin clay evenly;

(4) Add sodium dodecyl sulfate and stir at high speed evenly;

(5) Add one or more of NaHCO ₃ , KHCO ₃ , Ca(HCO ₃ ) ₂ , Mg(HCO ₃ ) ₂ , and stir evenly;

(6) Heat treatment at 120℃-200℃ under vacuum conditions;

(7) Under anaerobic conditions, pyrolysis and carbonization at 500℃-650℃ are used to prepare sediment restoration agent.

The efficiency of biochar used in the treatment of sediment pollutants is closely related to the structure and properties of biochar. In order to obtain biochar with good properties, the selection of biochar feedstock is very important.

As an annual herb, Chenopodium is a plant of the Chenopodiaceae family, belonging to the weed, easy to reproduce, with large biomass, high cellulose content and developed void structure. The present invention uses quinoa as the biochar raw material, and the biomass raw material yield is large, which is beneficial to the resource utilization of biomass waste.

Metal oxides on the surface of biochar have a significant effect on the adsorption capacity of heavy metals in biochar. Quinoa has strong environmental adaptability, grows well under high-concentration metal conditions, and has the ability to enrich a variety of metals. In order to ensure that the surface of the prepared biochar has enough multi-metal oxides, Fe ₂ (SO ₄ ) ₃ , Al ₂ (SO ₄ ) ₃ , NiSO ₄ were applied daily by spraying during the growth of quinoa, and Fe ₂ (SO ₄ ) was applied daily. ) ₃ concentration of 50mg/L-200mg/L, Al ₂ (SO ₄ ) ₃ concentration of 50mg/L-100mg/L, NiSO ₄ concentration of 100mg/L-200mg/L, continuous administration for 120 days-180 days. Mature quinoa plants were collected and dried at room temperature.

The application of Fe ₂ (SO ₄ ) ₃ , Al ₂ (SO ₄ ) ₃ , and NiSO ₄ concentrations in the present invention is beneficial to the growth of quinoa and ensures that the quinoa is enriched with Fe, Al and Ni.

Under vacuum conditions, the quinoa is immersed in one or more solutions of KCl, K ₂ CO ₃ , K ₂ SO ₄ or KNO ₃ , the concentrations of KCl, K ₂ CO ₃ , K ₂ SO ₄ , KNO ₃ are 0.1g respectively /L-0.5g/L.

Under vacuum conditions, potassium ions are embedded in quinoa cellulose, which is beneficial to increase the specific surface area of biochar and improve the yield of biochar. At the same time, KCl, K ₂ CO ₃ , K ₂ SO ₄ or KNO ₃ formed minerals on the surface of biochar, which improved the ability of biochar to adsorb and fix heavy metals. In addition, the high concentration of potassium ions on the surface of biochar is beneficial for the biochar to improve its heavy metal adsorption capacity through an ion exchange mechanism.

The concentration of KCl, K ₂ CO ₃ , K ₂ SO ₄ or KNO ₃ is 0.1 g/L-0.5 g/L.

Preferably, the concentration of KCl is 0.5g/L, or 0.1g/L.

Preferably, the K ₂ CO ₃ concentration is 0.2 g/L.

Preferably, the K ₂ SO ₄ concentration is 0.2 g/L.

Preferably, the concentration of KNO ₃ is 0.1 g/L.

In the technical scheme of the present invention, using quinoa as a raw material, a 150°C-280°C hydrothermal method is used to activate the carbonized biomass. In the technical scheme of the present invention, the hydrothermal method is firstly used, which is beneficial to the formation of Fe, Al, and Ni metal oxides in the quinoa plant, and is beneficial to the insertion of potassium ions into the quinoa cellulose. The hydrophilicity of biochar improves the binding efficiency of biochar to clay, bentonite and kaolin.

Preferably, the 150°C hydrothermal method activates the carbonized biomass to improve the generation efficiency of aluminum-containing oxides.

Preferably, the carbonized biomass is activated by hydrothermal method at 220°C or 280°C to improve the generation efficiency of iron-containing oxides.

In the technical solution of the present invention, after hydrothermal activation and carbonization of biomass, low-temperature pyrolysis carbonization is used to prepare biochar.

In the technical scheme of the present invention, under anaerobic conditions, the temperature is raised to 300°C-450°C at 1°C/min-5°C/min, and maintained for 0.5h-1h. The slower heating rate and lower carbonization temperature reduce the loss of oxygen-containing functional groups on the surface of biochar, which is conducive to maintaining the hydrophilicity of biochar, which in turn is conducive to the binding efficiency of biochar to clay, bentonite, and kaolin.

Preferably, the temperature is raised to 300°C at 1°C/min, or 450°C at 3°C/min, or raised to 450°C at 5°C/min.

In the technical scheme of the present invention, the biochar is evenly stirred with one or more of clay, bentonite and kaolin. Clay, bentonite or kaolin can effectively increase the quality of the remediation agent, accelerate the sedimentation rate of the biochar, and reduce the buoyancy of the biochar.

Since the subsequent high-temperature cracking process will further affect the carbonization rate, specific surface area, pore volume and other properties of the remediation agent, in order to ensure that the remediation agent has rapid sedimentation and high-efficiency heavy metal adsorption and curing capabilities, the composition of the remediation agent in the technical solution of the present invention, the quality of biochar The fraction is 90%-70%, and the mass fractions of clay, bentonite and kaolin are 5%-20% respectively. The proportion of biochar is much higher than that of clay, bentonite or kaolin, which not only ensures the repairing efficiency of heavy metals of the repairing agent, enhances its ability to solidify heavy metals, but also ensures the rapid settlement of the repairing agent. At the same time, during the pyrolysis process, a certain content of clay, bentonite or kaolin is beneficial to obtain biochar with higher pore volume.

Preferably, when the subsequent high-temperature pyrolysis temperature is 550 °C, the mass fraction of biochar is 90%, and the mass fraction of clay is 8%.

Preferably, when the subsequent high-temperature pyrolysis temperature is less than or equal to 550°C, the mass fraction of biochar is 85% and the mass fraction of clay is 5%; or the mass fraction of biochar is 85% and the mass fraction of kaolin is 5%; or the mass fraction of biochar is 80% %, and the mass fraction of bentonite is 10%.

Preferably, when the subsequent high-temperature pyrolysis temperature is >550°C, the mass fraction of biochar is 70%, and the mass fraction of kaolin is 20%; or the mass fraction of biochar is 75%, and the mass fraction of clay is 15%; or the mass fraction of biochar is 75% %, and the mass fraction of bentonite is 20%.

Preferably, when the subsequent pyrolysis temperature is 650°C, the mass fraction of biochar is 70%, the mass fraction of clay is 5%, the mass fraction of bentonite is 10%, and the mass fraction of kaolin is 5%.

In the technical scheme of the present invention, sodium lauryl sulfate is added, and the mixture is stirred at a high speed evenly. Sodium lauryl sulfate allows air to infiltrate during physical high-speed stirring, which is beneficial to the repair agent to form a porous structure and enhance its specific surface area and heavy metal curing ability. In the subsequent biochar preparation process, sodium lauryl sulfate is thermally decomposed to form sulfides, and the formation of sulfides on the surface of biochar is beneficial to the biochar to solidify heavy metals in the sediment.

Preferably, the mass fraction of sodium dodecyl sulfate is 2%.

In the technical scheme of the present invention, one or more of NaHCO ₃ , KHCO ₃ , Ca(HCO ₃ ) ₂ , and Mg(HCO ₃ ) ₂ are added, and stirred evenly; the mass fraction of bicarbonate is 5%-10% ; Under vacuum conditions, heat treatment at 120℃-200℃ for 1h-2h.

The technical scheme of the present invention adds bicarbonate to be decomposed by heat to generate CO ₂ , which is beneficial to the formation of pore sizes of different sizes in the repair agent and increases the specific surface area. In the technical solution of the present invention, the vacuum is used for slow heating, which is conducive to gas transmission and improves the generation efficiency of the pore size of the repair agent. At the same time, bicarbonate is decomposed by heat to form carbonate, which is loaded on the surface of biochar, increases the mineral content of biochar, accelerates the sedimentation rate of biochar, and improves the efficiency of biochar to solidify heavy metals in sediment.

Preferably, the heating rate is 1°C/min, the temperature is raised to 200°C, and the temperature is maintained for 2h.

Preferably, the mass fraction of NaHCO ₃ is 8%; or the mass fraction of KHCO ₃ is 5%; or the mass fraction of Ca(HCO ₃ ) ₂ is 10%; or the mass fraction of Mg(HCO ₃ ) ₂ is 10%.

In the technical solution of the present invention, after hydrothermal activation and carbonization of biomass, low temperature pyrolysis carbonization is performed to prepare biochar, and then high temperature pyrolysis carbonization is performed to prepare biochar. Under anaerobic conditions, the temperature was raised to 500°C-650°C at 30°C/min-50°C/min and maintained for 2h-3h.

In the technical scheme of the present invention, the preparation of biochar by high-temperature pyrolysis is beneficial to improve the hydrophobicity of the biochar, increase the specific surface area and pore volume of the biochar, increase the mineral content of the biochar, increase its sedimentation rate, and increase the solidified bottom of the repair agent. Mud heavy metal efficiency. At the same time, the high temperature is conducive to the thermal decomposition of sodium dodecyl sulfate to generate sulfide.

Preferably, under anaerobic conditions, the temperature is raised to 500°C at 50°C/min and maintained for 3h.

Description of drawings

Fig. 1 Flow chart of preparation of biochar remediation agent;

Fig. 2 SEM-Mapping image of biochar after immobilization of heavy metal Cd in sediment.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementation disclosed below.

Example 1

(1) Transplant the quinoa with a height of about 10cm;

(2) Configure Hoagland nutrient solution, and add Fe ₂ (SO ₄ ) ₃ , Al ₂ (SO4) ₃ or NiSO ₄ , wherein the concentration of Fe ₂ (SO ₄ ) ₃ is 50mg/L-200mg/L, Al ₂ (SO4 ) ₃ concentration is 50mg/L-100mg/L, NiSO ₄ concentration is 100mg/L-200mg/L,

(3) The above-mentioned culture solution was continuously applied for 180 days by spraying. Quinoa, grows well.

(4) Configure Hoagland nutrient solution, and add Fe ₂ (SO ₄ ) ₃ , Al ₂ (SO 4 ) ₃ and NiSO ₄ , which contains Fe ₂ (SO ₄ ) ₃ concentration of 200mg/L, Al ₂ (SO ₄ ) ₃ The concentration is 100mg/L, and the concentration of NiSO ₄ is 200mg/L;

(5) The above-mentioned culture solution is applied by spraying for 160 days;

(6) Collect quinoa plants and dry at room temperature.

(7) Determination of Fe, Al, Ni, and cellulose contents in quinoa, as shown in Table 1.

Table 1 Contents of Fe, Al, Ni and cellulose in quinoa

Analysis parameters Content, percentage Fe (mg/g) 4.298±0.258 Al (mg/g) 3.109±0.143 Ni (mg/g) 4.794±0.199 cellulose 29.5%

Example 2

(1) Take the biomass collected in Example 1;

(2) Under vacuum conditions, the biomass was immersed in one or several solutions of KCl, K ₂ CO ₃ , K ₂ SO ₄ or KNO ₃ for 24 hours, as shown in Table 2;

Table 2 Types of Impregnated Potassium Salts

Composition Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 KCl 0.5g/L 0.1g/L - - - 0.5g/L K₂CO₃ - - 0.2g/L - - - K₂SO₄ - - 0.2g/L 0.2g/L - - KNO₃ - 0.1g/L - - 0.2g/L 0.1g/L

(3) Activated carbonized biomass by hydrothermal method at 150℃-280℃, as shown in Table 3.

Table 3 Biomass hydrothermal activated carbonization temperature

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 temperature/℃ 150℃ 200℃ 200℃ 220℃ 250℃ 280℃

(4) Under anaerobic conditions, the temperature is raised to 300°C-450°C at 1°C/min-5°C/min, and maintained for 0.5h-1h, as shown in Table 4;

Table 4 Low temperature carbonization of biochar

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 temperature/℃ 300℃ 300℃ 350℃ 350℃ 450℃ 450℃ Heating rate 1℃/min 1℃/min 2℃/min 5℃/min 3℃/min 5℃/min time/h 0.5h 1h 0.5h 1h 1h 1h

(5) Collect biochar samples;

(6) Mix the biochar with clay, bentonite or kaolin, as shown in Table 5;

(7) Add sodium dodecyl sulfate, as shown in Table 5.

Table 5 Composition of restorative ingredients by mass percentage

Composition Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 bio-charcoal 90% 85% 85% 80% 75% 70% clay - 5% - 5% 3% 5% bentonite - - 10% - 5% 10% Kaolin 5% - - - 10% 5% Sodium dodecyl sulfate 1% 1% 3.5% 5% 2% 2%

(8) Stir at 1200rmp for 2-4h;

(9) As shown in Table 6, add NaHCO ₃ , KHCO ₃ , Ca(HCO ₃ ) ₂ or Mg(HCO ₃ ) ₂ ;

Table 6 Bicarbonate mass percentage

Composition Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 NaHCO₃ 8% 8% - 5% - - KHCO₃ - - 5% 5% - - Ca(HCO₃)₂ - - - - 10% - Mg(HCO₃)₂ 10% - - - - 10%

(10) Under vacuum conditions, the temperature is raised to 120°C-200°C at 1°C/min-5°C/min, and maintained for 1h-2h, as shown in Table 7.

Table 7 Sample heating and heating rate

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 temperature 120℃ 150℃ 150℃ 180℃ 200℃ 200℃ Heating rate 1℃/min 1℃/min 5℃/min 5℃/min 5℃/min 5℃/min time 1h 1h 2h 1h 2h 2h

(11) Under anaerobic conditions, the temperature is raised to 500°C-650°C at 30°C/min-50°C/min and maintained for 2h-3h, as shown in Table 8.

Table 8 High temperature carbonization of biomass

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 temperature 500℃ 500℃ 600℃ 600℃ 650℃ 650℃ Heating rate 30℃/min 30℃/min 35℃/min 45℃/min 50℃/min 50℃/min time 2h 3h 2h 3h 2h 3h

Example 3

(1) According to 100g-1000g/m ² , the sediment repair agent is put in as shown in Table 9 below.

Table 9 Restorative dosage

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Application amount 100g/m² 500g/m² 500g/m² 800g/m² 1000g/m² 1000g/m²

(2) The content of heavy metals in the overlying water and the percentage of heavy metal residues in the sediment were detected at 0 days, 30 days and 45 days respectively (Table 10-Table 17).

(3) Scanning electron microscope analysis was carried out on the biochar after adsorption and immobilization of Cd ²⁺ by the remediation agent in Example 3. SEM-Mapping confirmed that after the biochar immobilized Cd ²⁺ , Cd ²⁺ could exist in the form of CdCO ₃ on the surface of biochar ( figure 2).

Table 10 Cd content in overlying water before and after application (mg/L)

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 0.2 0.2 0.25 0.15 0.17 0.2 30 days 0.15 0.1 0.12 0.01 0.01 0.01 45 days - - - - - -

Table 11 The percentage of Cd residue in the sediment before and after application (%)

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 12.35 11.01 12.72 14.57 11.22 12.45 30 days 43.65 47.41 53.69 55.44 52.34 53.39 45 days 69.72 61.22 66.19 67.82 71.64 75.28

Table 12 Pb content in overlying water before and after application (mg/L)

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 0.24 0.31 0.53 0.51 0.51 0.47 30 days 0.18 0.13 0.21 0.01 0.01 0.01 45 days - - - - - -

Table 13 Percentage of sediment Pb residue (%) before and after application

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 12.4 13.57 11.27 18.45 12.34 10.98 30 days 23.42 23.89 30.18 34.75 43.23 49.09 45 days 79.27 68.18 67.93 65.5 74.19 74.64

Table 14 Cu content of overlying water before and after application (mg/L)

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 1.72 1.9 2.02 2.2 2.79 3.56 30 days 0.08 0.13 0.57 0.67 0.28 0.47 45 days - - 0.01 - - 0.02

Table 15 Percentage of Cu residue in sediment before and after application (%)

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 9.72 12.21 8.72 8.18 11.21 10.21 30 days 33.21 48.05 43.64 48.97 52.12 57.77 45 days 65.47 66.12 70.17 72.81 77.29 80.12

Table 16 Hg content of overlying water before and after application (ng/L)

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 12.3 17.5 13.75 32 34.53 27.36 30 days 5.35 10.21 9.72 10.76 12.32 11.43 45 days - - - - - -

Table 17 Sediment Hg residual state percentage (%) before and after application

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 0 days 9.45 10.13 11.98 15.78 9.23 3.56 30 days 25.76 35.12 39.05 38.04 38.75 40.21 45 days 50.51 53.63 43.39 52.21 59.94 50.32

Claims (10)

1. a preparation method of sediment heavy metal pollution repairing agent, is characterized in that, comprises the following steps: (1) Using quinoa as raw material, 150℃-280℃ hydrothermally activated carbonized biomass, and collected samples; (2) Biochar is prepared by pyrolysis and carbonization at 300℃-450℃ under anaerobic conditions; (3) Stir the biochar evenly with one or more of clay, bentonite and kaolin; (4) Add sodium dodecyl sulfate and stir at high speed evenly; (5) Add one or more of NaHCO ₃ , KHCO ₃ , Ca(HCO ₃ ) ₂ , Mg(HCO ₃ ) ₂ , and stir evenly; (6) Heat treatment at 120℃-200℃ under vacuum conditions; (7) Under anaerobic conditions, pyrolysis and carbonization at 500℃-650℃ are used to prepare sediment restoration agent. 2. The preparation method of a heavy metal pollution remediation agent for sediments according to claim 1, characterized in that, in step (1), under vacuum conditions, quinoa is immersed in KCl, K ₂ CO ₃ , K ₂ SO ₄ or In one or several solutions of KNO ₃ , the concentrations of KCl, K ₂ CO ₃ , K ₂ SO ₄ and KNO ₃ are respectively 0.1g/L-0.5g/L. 3 . The preparation method of a heavy metal pollution remediation agent for sediments according to claim 1 , wherein in step (2), under anaerobic conditions, the temperature is raised to 300°C-5°C/min at 1°C/min-5°C/min. 4 . 450°C for 0.5h-1h. 4. the preparation method of a kind of sediment heavy metal pollution remediation agent according to claim 1, is characterized in that, in step (3), biochar mass fraction is 90%-70%, clay, bentonite, kaolin mass fraction are respectively 5%-20%. 5 . The preparation method of a heavy metal pollution remediation agent in sediment according to claim 1 , wherein, in step (4), the mass fraction of sodium lauryl sulfate is 1%-5%. 6 . 6 . The preparation method of a heavy metal pollution remediation agent in sediment according to claim 1 , wherein, in step (5), the mass fraction of bicarbonate is 5%-10%. 7 . 7 . The preparation method of a heavy metal pollution remediation agent for sediments according to claim 1 , wherein in step (6), under vacuum conditions, the temperature is raised to 120°C-200°C at 1°C/min-5°C/min. 8 . ℃, maintained for 1h-2h. 8 . The preparation method of a heavy metal pollution remediation agent for sediments according to claim 1 , wherein in step (7), under anaerobic conditions, the temperature is increased to 500°C-50°C/min at 30°C/min-50°C/min. 9 . 650°C for 2h-3h. 9. the application of a kind of sediment heavy metal pollution remediation agent prepared by the method according to claim 1 in adsorbing water body and fixing heavy metal pollutants in sediment. 10. the application of a kind of heavy metal pollution remediation agent in sediment according to claim 9 in adsorbing heavy metal pollutants in water body and fixed sediment, it is characterized in that, remediation agent is applied to heavy metal polluted sediment according to 100g ^- 1000g/m , adsorbing one or more of Cd ²⁺ , Pb ²⁺ , Cu ²⁺ , Hg ²⁺ in water and fixed sediment.

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