CN112547024A - Magnetic carbon composite material for repairing heavy metal contaminated soil and preparation method thereof - Google Patents

Magnetic carbon composite material for repairing heavy metal contaminated soil and preparation method thereof Download PDF

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CN112547024A
CN112547024A CN202011525221.2A CN202011525221A CN112547024A CN 112547024 A CN112547024 A CN 112547024A CN 202011525221 A CN202011525221 A CN 202011525221A CN 112547024 A CN112547024 A CN 112547024A
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陈庆
陈巧和
司文彬
白涛
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Chengdu New Keli Chemical Science Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
    • B01J20/28009—Magnetic properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C1/00—Reclamation of contaminated soil
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    • C09K17/00—Soil-conditioning materials or soil-stabilising materials
    • C09K17/40—Soil-conditioning materials or soil-stabilising materials containing mixtures of inorganic and organic compounds

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Abstract

The invention relates to the technical field of soil remediation materials, and discloses a magnetic carbon composite material for remediating heavy metal contaminated soil and a preparation method thereof, wherein the preparation method comprises the following steps: mixing ferrous salt and ferric salt, adding biomass carbon and water, uniformly mixing, adsorbing ferrous salt and ferric salt by using charcoal, naturally filtering out liquid to obtain charcoal adsorbing ferrous salt and ferric salt, adding ammonia water, reacting to generate ferroferric oxide, and washing to obtain a magnetically modified charcoal material; and (3) uniformly stirring and mixing the magnetic modified biochar material and the beta-cyclodextrin modified starch, and granulating to form the magnetic soil remediation material. The invention solves the problems of complex preparation process and poor acid resistance of the existing magnetic material in soil remediation application. The composite magnetic modified charcoal material is prepared by compounding beta-cyclodextrin modified starch, so that the adsorption capacity of heavy metal ions in soil can be improved, the soil remediation efficiency is improved, and the magnetic soil remediation material has good acid resistance, so that the magnetic soil remediation material can be recycled after being washed to remove heavy metals by dilute acid.

Description

Magnetic carbon composite material for repairing heavy metal contaminated soil and preparation method thereof
Technical Field
The invention relates to the technical field of soil remediation materials, in particular to a magnetic carbon composite material for remediating heavy metal contaminated soil and a preparation method thereof.
Background
Soil is an important material foundation for production activities of human society, and is an indispensable natural resource difficult to regenerate. Causes of soil pollution, such as industrial sludge, garbage agriculture, sewage irrigation, pollutant sedimentation in the atmosphere, and the use of heavy metal-containing mineral fertilizers and pesticides in large quantities.
The polluted soil can cause the yield reduction of crops, and even can cause the pollutant in agricultural products to exceed the standard, thereby harming the human health. In addition, with the acceleration of economic development and urbanization, site pollution caused by industrial and mining enterprises is also very serious. Due to the change and adjustment of the industrial structure and the urban layout, some chemical, metallurgical and other polluted enterprises are moved in succession, and in addition, some enterprises are closed upside down, so that polluted sites are generated continuously.
The untreated contaminated site will be a chemical timed bomb, and once a large area of outbreak will cause immeasurable influence on national sustainable development, so great attention must be paid to soil pollution prevention and contaminated soil remediation.
Soil remediation is a technical measure to restore normal function to contaminated soil. Soil remediation refers to the physical, chemical and biological processes used to transfer, absorb, degrade and transform pollutants in soil to reduce their concentration to acceptable levels, or to transform toxic and harmful pollutants into harmless materials. Fundamentally, the technical principle of contaminated soil remediation may include: changing the existing form of pollutants in soil or the combination mode of the pollutants and the soil, and reducing the mobility and the bioavailability of the pollutants in the environment; ② the concentration of harmful substances in the soil is reduced.
The heavy metal pollution of soil is characterized by wide distribution, large pollution amount, high treatment cost, long restoration period and the like. Meanwhile, in the repairing process, if the repairing method is not applied or the repairing agent is not properly treated, secondary pollution is likely to be caused. The main repair methods at present comprise physical methods, chemical methods and biological methods, and the physical methods and the chemical methods are the most main repair methods at present. The physical remediation method usually depends on large-scale mechanical equipment, the defects of high energy consumption, high cost and the like exist in a vapor extraction technology, a thermal decomposition technology, an electric remediation technology and the like, the chemical remediation method usually uses a chemical remediation agent to convert heavy metal ions in soil into a stable state so as to reduce the biotoxicity of the soil, the method is low in cost and good in effect, but the heavy metal still exists in the soil, the heavy metal in the soil is not removed fundamentally, and secondary pollution possibly exists at the same time. The bioremediation method is green and environment-friendly, but the bioremediation method has long remediation period and low remediation efficiency and is greatly limited in practical application.
The magnetic material is widely applied to water treatment and other fields as a separable material, does not need to add external energy in the separation process by virtue of the characteristics of the magnetic material, can achieve the separation effect only in a permanent magnetic environment, and has outstanding advantages in energy conservation and environmental protection. Therefore, the introduction of magnetic materials into the soil remediation field is precedent.
Chinese patent application publication No. CN109913228A discloses a high-magnetism modified biochar, a preparation method thereof and application thereof in treating soil heavy metal pollution, wherein the preparation method comprises the following steps: grinding biochar, sieving, adding into NaOH solution, stirring, filtering, and washing with water; adding the filter residue into HCl solution, continuously stirring, filtering, washing with water to obtain basic biochar material, and drying for later use; adding a basic biochar material into a FeCl2.7H2O aqueous solution, adjusting the pH value, adding a sodium borohydride solution until no air bubbles are generated, adding a saturated sodium dimethyldithiocarbamate aqueous solution, continuously stirring, collecting residues in the solution through a magnetic field, washing and drying to obtain the high-magnetism modified biochar. The specific surface area of the biochar is increased, so that the passivation efficiency of heavy metals in the soil is improved; the magnetic modified biochar has stronger magnetism, so that the high-magnetism modified biochar can be removed from soil by using a magnet, and the total amount of heavy metals in the soil is reduced.
However, when the magnetic carbon is used for treating soil, adsorption of heavy metals is limited, and the magnetism is easily weakened or lost by an acid environment, and the obtained magnetically modified biochar material has weak acid resistance and is not easy to recycle.
Disclosure of Invention
In view of the above drawbacks of the prior art, the present invention provides a method for preparing a magnetic carbon composite material for repairing soil contaminated by heavy metals, which is used to solve the problems of complicated preparation process and poor acid resistance of the magnetic material in soil repairing applications, and also provides a magnetic carbon composite material for repairing soil contaminated by heavy metals. In the preparation method, the magnetic modified biochar material is prepared by a coprecipitation method, and then beta-cyclodextrin is used for modifying starch to form beta-cyclodextrin modified starch; the beta-cyclodextrin modified starch is compounded with the magnetic modified biochar material to obtain a magnetic carbon composite material, which not only has magnetism, but also can realize the separation of heavy metals from the polluted soil; in addition, the ferroferric oxide is coated by two layers of biochar and beta-cyclodextrin modified starch, so that the adsorption of heavy metals is more excellent, the acid resistance is higher, and the recycling performance is improved.
In order to achieve the above and other related objects, according to a first aspect of the present invention, there is provided a method for preparing a magnetic carbon composite for remediating heavy metal contaminated soil, comprising the steps of:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: the method comprises the following steps of (1-1.1) mixing a ferrous salt and a ferric salt according to a molar ratio: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing a ferrous salt and a ferric salt by using the charcoal, naturally filtering out liquid to obtain the charcoal adsorbing the ferrous salt and the ferric salt, then dropwise adding ammonia water, wherein the reaction temperature is 60-80 ℃, and the reaction time is 2-4 h; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and starch into water to prepare a suspension, heating, stirring and gelatinizing, adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step (S11) and the beta-cyclodextrin modified starch prepared in the step (S12), adding zeolite powder, and granulating by using a granulator to obtain the magnetic carbon composite material.
The biomass charcoal is a porous solid particulate matter which is highly aromatic and rich in carbon and is generated by pyrolysis of carbon-rich biomass under the condition of no oxygen or lack of oxygen. It contains a great deal of carbon and plant nutrient substances, has rich pore structures, larger specific surface area and more oxygen-containing active groups on the surface, and is a multifunctional material. It can improve soil, increase fertility, and adsorb heavy metals and organic pollutants in soil or sewage.
In the preparation method, the magnetic modified biochar material is prepared by a coprecipitation method, and then beta-cyclodextrin is used for modifying starch to form beta-cyclodextrin modified starch; the beta-cyclodextrin modified starch and the magnetic modified charcoal material are compounded to obtain the magnetic soil remediation material which has magnetism and can realize the separation of heavy metals from the polluted soil; in addition, the ferroferric oxide is coated by two layers of biochar and beta-cyclodextrin modified starch, so that the ferroferric oxide has good heavy metal adsorption, stronger acid resistance and improved recycling performance.
The composite magnetic modified charcoal material is prepared by compounding beta-cyclodextrin modified starch, so that the adsorption capacity of heavy metal ions in soil can be improved, the soil remediation efficiency is improved, and the magnetic soil remediation material has good acid resistance, so that the magnetic soil remediation material can be recycled after being washed to remove heavy metals by dilute acid.
On one hand, the biomass charcoal has rich pore structures and contains more oxygen-containing active groups on the surface, so that the biomass charcoal not only can improve soil, increase fertility, adsorb heavy metals and organic pollutants in soil or sewage, but also has a better fixing effect on carbon and nitrogen; on the other hand, the ferroferric oxide has larger specific surface area, so that the ferroferric oxide can be better deposited on the biochar by utilizing a coprecipitation method, and the acid resistance of the ferroferric oxide is improved.
On one hand, the beta-cyclodextrin modified starch has a plurality of adsorption sites on the surface and is easy to combine with metal ions (has good heavy metal adsorption performance, high adsorption efficiency and is environment-friendly), and in addition, the beta-cyclodextrin modified starch has a good protection effect on the coated magnetic modified charcoal material.
Further, the mole ratio of the ferrous salt to the ferric salt in the S11 is 1: 1; in the S11, the mass ratio of the iron salt mixture, water, biomass charcoal and ammonia water is (10-20): (200-300): (5-10): (10-20).
And S11, loading ferrous iron and ferric iron on the biochar by using a coprecipitation method under the protection of inert gas, then dropwise adding ammonia water to directly precipitate to generate magnetic nano ferroferric oxide particles, depositing the magnetic nano ferroferric oxide particles on the pore channel of the biochar, and separating to obtain the magnetic modified biochar material.
Further, in the S12, the mass ratio of beta-cyclodextrin, starch, water, phosphoric acid, humic acid and carboxymethyl cellulose is (10-20): (40-60): (200-300): (2-4): (4-6): (5-10).
And in the step S12, beta-cyclodextrin is used for modifying starch, and then phosphoric acid, humic acid and carboxymethyl cellulose are added. The carboxymethyl cellulose is used as an adhesive, so that the beta-cyclodextrin modified starch and the magnetic modified charcoal material can be conveniently compounded to form a core-shell structure. On one hand, the beta-cyclodextrin modified starch has a plurality of adsorption sites on the surface and is easy to combine with metal ions (has good heavy metal adsorption performance, high adsorption efficiency and is environment-friendly), and in addition, the beta-cyclodextrin modified starch has a good protection effect on the coated magnetic modified charcoal material.
Further, the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is (20-30): (10-20): (5-10).
Further, the ferrous salt is ferrous chloride, and the ferric salt is ferric chloride; the mass concentration of the ammonia water is 25-30%;
further, the starch in S12 is tapioca starch;
further, the particle size of the magnetic carbon composite material in the S2 is 3-5 mm.
Further, the gelatinization temperature in the S12 is 70-90 ℃, and the gelatinization time is 0.5-1 h; the reaction temperature in the S12 is 70-90 ℃, and the reaction time is 2-3 h.
In a second aspect of the invention, a magnetic carbon composite material for repairing heavy metal contaminated soil is provided, wherein the magnetic carbon composite material is prepared by the preparation method.
In the preparation process, ferrous iron and ferric iron are loaded on the biochar under the protection of inert gas by utilizing a coprecipitation method, ammonia water is dripped to directly precipitate and generate magnetic nano ferroferric oxide particles, the magnetic nano ferroferric oxide particles are deposited on the pore channel of the biochar, and the magnetic modified biochar material is obtained through separation. Modifying starch by using beta-cyclodextrin, and then adding phosphoric acid, humic acid and carboxymethyl cellulose. The carboxymethyl cellulose is used as an adhesive, so that the beta-cyclodextrin modified starch and the magnetic modified biochar material are conveniently compounded into granules by a granulator to form a magnetic core-shell structure, and the magnetic carbon composite material with the particle size of 3-5 mm is obtained. Ferroferric oxide can be better deposited on the biochar through a coprecipitation method, so that the biochar has better acid resistance; the beta-cyclodextrin modified starch has the characteristic that the outer edge of the cyclodextrin is hydrophilic and the inner cavity of the cyclodextrin is hydrophobic, has good protection effect on the coated magnetic modified charcoal material besides the heavy metal adsorption performance of the beta-cyclodextrin modified starch, enhances the acid resistance of the beta-cyclodextrin modified starch, and improves the recycling performance of the beta-cyclodextrin modified starch.
As described above, the magnetic carbon composite material for repairing heavy metal contaminated soil and the preparation method thereof provided by the invention have the following beneficial effects:
1. preparing a magnetic modified biochar material by a coprecipitation method, and then modifying starch by using beta-cyclodextrin to form beta-cyclodextrin modified starch; the beta-cyclodextrin modified starch is compounded with the magnetic modified charcoal material, so that heavy metal is separated from the polluted soil; and the ferroferric oxide is coated by a double layer of biochar and beta-cyclodextrin modified starch, so that the ferroferric oxide has stronger acid resistance and the recycling performance of the ferroferric oxide is improved.
2. The biomass carbon has rich pore structures and contains more oxygen-containing active groups on the surface, so that the biomass carbon can improve soil, increase fertility and adsorb heavy metals in the soil, and ferroferric oxide can be better deposited on the biomass carbon by a coprecipitation method so as to improve the acid resistance of the ferroferric oxide.
3. The beta-cyclodextrin modified starch has the characteristic that the outer edge of the cyclodextrin is hydrophilic and the inner cavity of the cyclodextrin is hydrophobic, has a plurality of surface adsorption sites, is easy to combine with metal ions, has good heavy metal adsorption performance, and also has a good protection effect on the coated magnetic modified biochar material.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
A preparation method of a magnetic carbon composite material for repairing heavy metal contaminated soil comprises the following steps:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: FeCl is added2•4H2O and FeCl3•6H2O is added into the mixture according to a molar ratio of 1: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing a ferrous salt and a ferric salt by the charcoal, naturally filtering out liquid to obtain the charcoal adsorbing the ferrous salt and the ferric salt, then dropwise adding ammonia water with the mass concentration of 25%, wherein the reaction temperature is 60 ℃, and the reaction time is 2 hours; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and cassava starch into water to prepare a suspension, heating, stirring and gelatinizing (the gelatinizing temperature is 70 ℃, the gelatinizing time is 1 h), adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting (the temperature is 70 ℃, the time is 3 h) to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step S11 and the beta-cyclodextrin modified starch prepared in the step S12, adding zeolite powder, and granulating through a granulator to obtain the magnetic carbon composite material with the particle size of 3-5 mm.
Specifically, the mass ratio of the iron salt mixture, the deionized water, the biomass charcoal and the ammonia water in the S11 is 10: 200: 5: 11;
the mass ratio of the beta-cyclodextrin, the cassava starch, the water, the phosphoric acid, the humic acid and the carboxymethyl cellulose in the S12 is 10: 40: 200: 2: 4: 5;
the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is 20: 10: 5.
example 2
A preparation method of a magnetic carbon composite material for repairing heavy metal contaminated soil comprises the following steps:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: FeCl is added2•4H2O and FeCl3•6H2O is added into the mixture according to a molar ratio of 1: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing a ferrous salt and a ferric salt by the charcoal, naturally filtering out liquid to obtain the charcoal adsorbing the ferrous salt and the ferric salt, then dropwise adding ammonia water with the mass concentration of 25%, wherein the reaction temperature is 70 ℃, and the reaction time is 3 hours; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and cassava starch into water to prepare a suspension, heating, stirring and gelatinizing (the gelatinizing temperature is 90 ℃ and the gelatinizing time is 0.6 h), adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting (the temperature is 90 ℃ and the time is 2.2 h) to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step S11 and the beta-cyclodextrin modified starch prepared in the step S12, adding zeolite powder, and granulating through a granulator to obtain the magnetic carbon composite material with the particle size of 3-5 mm.
Specifically, the mass ratio of the iron salt mixture, the deionized water, the biomass charcoal and the ammonia water in the S11 is 20: 300: 10: 19;
the mass ratio of the beta-cyclodextrin, the cassava starch, the water, the phosphoric acid, the humic acid and the carboxymethyl cellulose in the S12 is 20: 60: 300: 4: 6: 10;
the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is 30: 20: 9.
example 3
A preparation method of a magnetic carbon composite material for repairing heavy metal contaminated soil comprises the following steps:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: FeCl is added2•4H2O and FeCl3•6H2O is added into the mixture under the protection of nitrogen according to a molar ratio of 1.1: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing ferrous salts and ferric salts by the charcoal, naturally filtering liquid to obtain the charcoal adsorbing the ferrous salts and ferric salts, then dropwise adding ammonia water with the mass concentration of 25%, wherein the reaction temperature is 60 ℃, and the reaction time is 2 hours; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and cassava starch into water to prepare a suspension, heating, stirring and gelatinizing (the gelatinizing temperature is 80 ℃ and the gelatinizing time is 1 h), adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting (the temperature is 80 ℃ and the time is 3 h) to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step S11 and the beta-cyclodextrin modified starch prepared in the step S12, adding zeolite powder, and granulating through a granulator to obtain the magnetic carbon composite material with the particle size of 3-5 mm.
Specifically, the mass ratio of the iron salt mixture, the deionized water, the biomass charcoal and the ammonia water in the S11 is 15: 250: 6: 15;
the mass ratio of the beta-cyclodextrin, the cassava starch, the water, the phosphoric acid, the humic acid and the carboxymethyl cellulose in the S12 is 15: 45: 250: 3: 5: 7;
the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is 25: 13: 5.
example 4
A preparation method of a magnetic carbon composite material for repairing heavy metal contaminated soil comprises the following steps:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: FeCl is added2•4H2O and FeCl3•6H2O is added into the mixture according to a molar ratio of 1: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing ferrous salts and ferric salts by the charcoal, naturally filtering liquid to obtain the charcoal adsorbing the ferrous salts and ferric salts, then dropwise adding ammonia water with the mass concentration of 25%, wherein the reaction temperature is 60 ℃, and the reaction time is 2; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and cassava starch into water to prepare a suspension, heating, stirring and gelatinizing (the gelatinizing temperature is 85 ℃ and the gelatinizing time is 0.75 h), adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting (the temperature is 85 ℃ and the time is 2.5 h) to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step S11 and the beta-cyclodextrin modified starch prepared in the step S12, adding zeolite powder, and granulating through a granulator to obtain the magnetic carbon composite material with the particle size of 3-5 mm.
Specifically, the mass ratio of the iron salt mixture, the deionized water, the biomass charcoal and the ammonia water in the S11 is 18: 280: 8: 18;
the mass ratio of the beta-cyclodextrin, the cassava starch, the water, the phosphoric acid, the humic acid and the carboxymethyl cellulose in the S12 is 18: 55: 280: 4: 6: 9;
the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is 29: 17: 8.
example 5
A preparation method of a magnetic carbon composite material for repairing heavy metal contaminated soil comprises the following steps:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: FeCl is added2•4H2O and FeCl3•6H2O is added into the mixture according to a molar ratio of 1: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing ferrous salts and ferric salts by the charcoal, naturally filtering liquid to obtain the charcoal adsorbing the ferrous salts and ferric salts, then dropwise adding ammonia water with the mass concentration of 25%, wherein the reaction temperature is 80 ℃, and the reaction time is 2; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and cassava starch into water to prepare a suspension, heating, stirring and gelatinizing (the gelatinizing temperature is 85 ℃ and the gelatinizing time is 0.75 h), adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting (the temperature is 85 ℃ and the time is 2.5 h) to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step S11 and the beta-cyclodextrin modified starch prepared in the step S12, adding zeolite powder, and granulating through a granulator to obtain the magnetic carbon composite material with the particle size of 3-5 mm.
Specifically, the mass ratio of the iron salt mixture, the deionized water, the biomass charcoal and the ammonia water in the S11 is 17: 250: 8: 18;
the mass ratio of the beta-cyclodextrin, the cassava starch, the water, the phosphoric acid, the humic acid and the carboxymethyl cellulose in the S12 is 18: 50: 250: 3: 5: 8;
the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is 27: 15: 8.
comparative example 1
A preparation method of a magnetic carbon composite material for repairing heavy metal contaminated soil comprises the following steps:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: FeCl is added2•4H2O and FeCl3•6H2O is added into the mixture according to a molar ratio of 1: 1 mixing to form a mixture of iron salts, andadding biomass charcoal and water, uniformly mixing, adsorbing ferrous salt and ferric salt by the biomass charcoal, naturally filtering liquid to obtain the biochar adsorbing the ferrous salt and ferric salt, then dropwise adding ammonia water with the mass concentration of 25%, wherein the reaction temperature is 60 ℃, and the reaction time is 2 hours; washing to obtain a magnetic modified biochar material;
s12, adding cassava starch into water to prepare a suspension, heating, stirring and gelatinizing (the gelatinizing temperature is 70 ℃ and the gelatinizing time is 1 h), adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuing stirring and reacting (the temperature is 70 ℃ and the time is 3 h) to obtain modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step S11 and the modified starch prepared in the step S12, adding zeolite powder, and granulating through a granulator to obtain the magnetic carbon composite material with the particle size of 3-5 mm.
Specifically, the mass ratio of the iron salt mixture, the deionized water, the biomass charcoal and the ammonia water in the S11 is 10: 200: 5: 11;
the mass ratio of the cassava starch, the water, the phosphoric acid, the humic acid and the carboxymethyl cellulose in the S12 is 40: 200: 2: 4: 5;
the mass ratio of the magnetically modified biochar to the modified starch to the zeolite powder in the S2 is 20: 10: 5.
comparative example 1 compared to example 1, the tapioca starch of comparative example 1 was not modified with beta-cyclodextrin.
The core stems of the soil polluted by the magnetic carbon composite material for repairing the soil prepared in the examples 1 to 5 and the comparative example 1 are subjected to comparative test analysis:
the test soil is used for collecting soil in a cadmium heavy metal polluted area, the pH value of the soil is 6.8, and the heavy metal content in the surface layer of the soil in the area is higher than the third-level standard of soil environmental quality standard (GB 15618-1995).
The same amount of samples provided in the examples and the comparative examples are selected, 2% of the soil mass is used as the adding amount, the samples are added into the heavy metal contaminated soil, and mixed cultivation reaction is carried out for 30 days under the conditions that the temperature is 25 +/-1 ℃ and the field saturation water holding capacity is 60%.
The treatment effect is as follows: the soil before and after treatment was compared, a soil leaching test was performed by using an inverted oscillator according to "leaching toxicity leaching method, sulfuric acid-nitric acid method" (HJ/T299-2007) for solid waste, the concentration of heavy metal in the soil before remediation was detected, and the removal rate (%) of heavy metal Cd obtained as a result of the treatment was as shown in table 1 below.
Table 1
Figure DEST_PATH_IMAGE003
The acid resistance of the magnetic material was measured in a soaking test of the samples prepared in examples 1 to 5 and comparative example 1 in 0.1mol/L hydrochloric acid, and the results are shown in Table 2.
Table 2
Figure DEST_PATH_IMAGE005
As can be seen from tables 1 and 2, the soil remediation materials provided by the comparative example and the example have certain adsorption capacity on heavy metal ions Cd in the soil. However, the adsorption capacity of examples 1 to 5 is significantly better than that of comparative example 1.
The reason why the removal rate of Cd is high in the embodiments 1-5 is that the magnetic modified biochar material is compounded with beta-cyclodextrin modified starch, so that the adsorption capacity of the magnetic modified biochar material is enhanced.
In comparative example 1 no beta-cyclodextrin modified starch was added. Because the magnetic modified charcoal material is not modified, the adsorption capacity of the magnetic modified charcoal material to heavy metals is relatively poor, the acid resistance is also poor, and the magnetism basically disappears after 48 hours in an acid resistance test.
Therefore, the composite magnetic modified biochar material prepared by beta-cyclodextrin modified starch can improve the adsorption capacity of heavy metal ions in soil and improve the soil remediation efficiency, and has good acid resistance, so that the remediation material can be recycled after being washed to remove heavy metals by dilute acid.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (8)

1. The preparation method of the magnetic carbon composite material for repairing the heavy metal contaminated soil is characterized by comprising the following steps of:
s1, preparing a modified raw material:
s11, preparing a magnetic modified biochar material: the method comprises the following steps of (1-1.1) mixing a ferrous salt and a ferric salt according to a molar ratio: 1, mixing to form an iron salt mixture, adding biomass charcoal and water, uniformly mixing, adsorbing a ferrous salt and a ferric salt by using the charcoal, naturally filtering out liquid to obtain the charcoal adsorbing the ferrous salt and the ferric salt, then dropwise adding ammonia water, wherein the reaction temperature is 60-80 ℃, and the reaction time is 2-4 h; washing to obtain a magnetic modified biochar material;
s12, preparing beta-cyclodextrin modified starch: adding beta-cyclodextrin and starch into water to prepare a suspension, heating, stirring and gelatinizing, adding phosphoric acid, humic acid and carboxymethyl cellulose, and continuously stirring and reacting to obtain beta-cyclodextrin modified starch;
s2, preparing the magnetic soil remediation material: and (3) uniformly stirring and mixing the magnetic modified biochar material prepared in the step (S11) and the beta-cyclodextrin modified starch prepared in the step (S12), adding zeolite powder, and granulating by using a granulator to obtain the magnetic soil remediation material.
2. The preparation method of the magnetic carbon composite material for repairing heavy metal contaminated soil according to claim 1, wherein the preparation method comprises the following steps: the molar ratio of the ferrous salt to the ferric salt in S11 is 1: 1; the ferrous salt is ferrous chloride, and the ferric salt is ferric chloride.
3. The preparation method of the magnetic carbon composite material for repairing heavy metal contaminated soil according to claim 1, wherein the preparation method comprises the following steps: in S11, the mass ratio of the ferric salt mixture to the water to the biomass charcoal to the ammonia water is (10-20): (200-300): (5-10): (10-20); the mass concentration of the ammonia water is 25-30%.
4. The preparation method of the magnetic carbon composite material for repairing heavy metal contaminated soil according to claim 1, wherein the preparation method comprises the following steps: in the S12, the mass ratio of beta-cyclodextrin, starch, water, phosphoric acid, humic acid and carboxymethyl cellulose is (10-20): (40-60): (200-300): (2-4): (4-6): (5-10); the starch is tapioca starch.
5. The preparation method of the magnetic carbon composite material for repairing heavy metal contaminated soil according to claim 1, wherein the preparation method comprises the following steps: the mass ratio of the magnetically modified charcoal, the beta-cyclodextrin modified starch and the zeolite powder in the S2 is (20-30): (10-20): (5-10).
6. The preparation method of the magnetic carbon composite material for repairing heavy metal contaminated soil according to claim 1, wherein the preparation method comprises the following steps: in the S12, the gelatinization temperature is 70-90 ℃, and the gelatinization time is 0.5-1 h; the reaction temperature is 70-90 ℃, and the reaction time is 2-3 h.
7. The preparation method of the magnetic carbon composite material for repairing heavy metal contaminated soil according to claim 1, wherein the preparation method comprises the following steps: the particle size of the magnetic carbon composite material in S2 is 3-5 mm.
8. The magnetic carbon composite material for repairing heavy metal contaminated soil is characterized in that: the magnetic carbon composite material is prepared by the preparation method of any one of claims 1 to 7.
CN202011525221.2A 2020-12-22 2020-12-22 Magnetic carbon composite material for repairing heavy metal contaminated soil and preparation method thereof Withdrawn CN112547024A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113307535A (en) * 2021-06-18 2021-08-27 江苏建筑职业技术学院 Soil curing agent
CN113955855A (en) * 2021-10-28 2022-01-21 中国城市建设研究院有限公司 Ecological blanket for water body restoration and application thereof
CN114133931A (en) * 2021-10-28 2022-03-04 中冶南方都市环保工程技术股份有限公司 Repairing agent for heavy metal polluted clay and preparation method and application thereof
CN115430698A (en) * 2022-10-13 2022-12-06 蚌埠学院 Method for removing heavy metals in polluted soil by using magnetically modified biochar

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113307535A (en) * 2021-06-18 2021-08-27 江苏建筑职业技术学院 Soil curing agent
CN113955855A (en) * 2021-10-28 2022-01-21 中国城市建设研究院有限公司 Ecological blanket for water body restoration and application thereof
CN114133931A (en) * 2021-10-28 2022-03-04 中冶南方都市环保工程技术股份有限公司 Repairing agent for heavy metal polluted clay and preparation method and application thereof
CN113955855B (en) * 2021-10-28 2023-10-13 中国城市建设研究院有限公司 Ecological blanket for water body restoration and application thereof
CN115430698A (en) * 2022-10-13 2022-12-06 蚌埠学院 Method for removing heavy metals in polluted soil by using magnetically modified biochar
CN115430698B (en) * 2022-10-13 2023-06-30 蚌埠学院 Method for removing heavy metals in polluted soil by utilizing magnetic modified biochar

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