CN113072951B - Composite biochar, preparation method thereof and ecological restoration method for industrial solid waste - Google Patents
Composite biochar, preparation method thereof and ecological restoration method for industrial solid waste Download PDFInfo
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Abstract
The invention relates to composite biochar, a preparation method thereof and an ecological restoration method of industrial solid waste, belongs to the technical field of industrial solid waste disposal, and solves the technical problems that an acidic substance is still released after an acidic slag yard in the prior art is neutralized by alkali to cause acidification, and the pH is gradually reduced and is difficult to stabilize in the conventional reagent neutralization. The core structure of the composite biochar is hydrothermal carbon and red mud molding particles, and the shell structure is hydrothermal carbon and alkali molding particles. The preparation method of the composite biochar comprises the following steps: step 1, crushing waste biomass; step 2, preparing dehydrated hydrothermal carbon; step 3, preparing hydrothermal carbon and red mud molding particles; step 4, preparing composite molding particles which take hydrothermal carbon and red mud molding particles as cores and wrap the hydrothermal carbon and alkali molding particles outside; and 5, carbonizing the composite molding particles in inert gas to obtain the composite biochar. The composite biochar with the core-shell structure, which is prepared by the invention, has a good alkaline slow-release effect.
Description
Technical Field
The invention relates to the technical field of industrial solid waste disposal, in particular to composite biochar and a preparation method thereof, and an ecological restoration method of industrial solid waste.
Background
Industrial production processes generate a large amount of industrial waste, and a large amount of solid waste is mainly disposed in a stockpiling mode, so that serious environmental hazards are generated. The acid waste residue is one of industrial solid wastes, has strong acidity, and has huge pollution risk to underground water and soil. The sulfuric acid residue is an acidic waste residue generated in the process of producing sulfuric acid from pyrite, the emission of China is about 1200 ten thousand tons, the resource utilization rate is low, and the sulfuric acid residue is still treated in a stockpiling mode at present.
In order to reduce the environmental pollution of the acid slag storage yard, the problem of strong acidity of the acid slag storage yard needs to be solved, and ecological restoration can be performed through plant planting on the basis of acidity regulation. The key of harmless disposal of the acid slag yard is acidity regulation.
The common acidity regulation and control mainly comprises the step of adding an alkaline reagent for neutralization, the alkaline reagent adopted in the prior art can only realize one-time neutralization, the acid slag yard can continuously release acidic substances to gradually reduce the pH value, and how to realize the acidity neutralization and the long-term stability of the pH value is a problem to be solved urgently in the technical field at present, and a good foundation is provided for ecological restoration after the acid slag yard pH value is neutralized and stabilized.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a composite biochar, a preparation method thereof, and an ecological restoration method for industrial solid waste, so as to solve the technical problems that in the prior art, an acidic substance is still released after an acidic slag yard is neutralized by an alkali to cause acidification, and the pH is gradually reduced and is difficult to stabilize in the conventional reagent neutralization.
The invention is mainly realized by the following technical scheme:
on one hand, the invention provides composite biochar which is of a core-shell structure, and the core structure of the composite biochar is formed particles of hydrothermal carbon and red mud; the shell structure of the composite biochar is hydrothermal carbon and alkali molded particles.
On the other hand, the invention also provides a preparation method of the composite biochar, which is used for preparing the composite biochar and comprises the following steps:
step 3, uniformly mixing the partially dehydrated hydrothermal carbon and the red mud, adding the mixture into a granulator, spraying a binder for granulation and forming to obtain hydrothermal carbon and red mud formed particles;
step 4, continuously adding the uniformly mixed dehydrated hydrothermal carbon and alkali into the granulator, spraying a binder for granulation and forming to obtain composite formed particles taking the hydrothermal carbon and the red mud formed particles as cores and wrapping the hydrothermal carbon and alkali formed particles outside;
and 5, carbonizing the composite molding particles in inert gas to obtain the composite biochar.
Further, in step 1, the waste biomass is lignocellulosic biomass;
the mass content of lignin, cellulose and hemicellulose in the lignocellulose biomass is more than 50 percent;
the particle size of the crushed waste biomass is less than 0.2mm.
Further, in the step 2, in the hydrothermal carbonization process, the mass ratio of the waste biomass to water is 1-1;
the hydrothermal carbonization temperature is 150-280 ℃, and the hydrothermal carbonization time is 30-300min;
the water content of the dehydrated solid hydrothermal carbon is less than 10 percent.
Further, in the step 2, an activating agent with the dosage of 2-8% of the mass of the waste biomass is added during hydrothermal carbonization; the activator comprises one of citric acid, oxalic acid, tartaric acid or maleic acid.
Further, in the step 3, the particle size of the red mud is less than 0.074mm, and the mass ratio of the red mud to the dehydrated hydrothermal carbon is 1-1;
the binder is polyvinyl alcohol aqueous solution with the mass concentration of 2-8%; the dosage of the binder is 5-10% of the total mass of the dehydrated hydrothermal carbon and the red mud, and the diameter of the formed composite particle is 0.1-0.2mm.
Further, in the step 4, the alkali is sodium hydroxide or potassium hydroxide solid powder, and the mass ratio of the alkali to the dehydrated hydrothermal carbon is 1;
the adhesive is polyvinyl alcohol water solution with mass concentration of 2-8%, the dosage of the adhesive is 3-8% of the total mass of the dehydrated hydrothermal carbon and the alkali, and the diameter of the formed composite particle is 0.3-0.5mm.
Further, in step 5, the inert gas is nitrogen or argon;
the temperature rise rate during carbonization is 5-10 ℃/min, the carbonization temperature is 600-1200 ℃, and the carbonization time is 1-5h.
Further, in step 1, the lignocellulosic biomass comprises one or more of straw, wood chips, fallen leaves, bagasse, and coconut shells.
Furthermore, the invention also provides a harmless treatment method for industrial solid waste, which utilizes the composite biochar or the composite biochar prepared by the preparation method to carry out ecological restoration on the industrial solid waste and comprises the following steps:
and 3, carrying out plant field planting on the improved soil to realize ecological restoration.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
(1) The invention provides a composite biochar, wherein the core structure of the composite biochar is hydrothermal carbon and red mud molded particles, and the hydrothermal carbon and the red mud molded particles have good alkali slow-release capacity; the shell structure of the composite biochar is hydrothermal carbon and alkali forming particles, and the alkaline components of the hydrothermal carbon and the alkali forming particles can quickly neutralize acid in the acid slag yard, so that the long-term stability of the pH value of the environment around the acid slag yard can be realized after the acid neutralization of the acid slag.
(2) The preparation method of the composite biochar provided by the invention utilizes waste biomass which is rich in resources, low in cost and renewable as a raw material and alkaline industrial waste red mud to prepare the alkaline composite biochar for regulating and controlling acid slag, and has the advantages of low price, high efficiency and cooperative treatment.
(3) The hydrothermal treatment of the biomass is favorable for preparing the composite biochar with rich pore diameters, the alkaline phase (sodium hydroxide or potassium hydroxide) in the composite biochar is tightly combined with the carbon material, the composite biochar is favorable for adsorbing harmful metals in acid slag, and the solidification of the metals is realized, namely the porous structure of the composite biochar increases the specific surface area (200-800 m) 2 /g) and providing a channel for metal ions to enter the composite biochar, wherein polar groups on the surface of the composite biochar can combine with the metal ions through chemical action to realize metal ion solidification.
(4) The invention also provides a harmless treatment method of industrial solid wastes, the composite biochar is paved in the planting pit and uniformly mixed with soil, the plants are placed in the planting pit, ecological restoration is carried out through plant field planting, and the method is a cheap, efficient and synergistic method for realizing acidity regulation and control of acid residues.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic structural diagram of composite biochar;
FIG. 2 is a flow chart of the preparation of composite biochar;
FIG. 3 is a scanning electron microscope image of composite biochar powder.
Reference numerals:
1-hydrothermal carbon and red mud molding particles; 2-hydrothermal carbon and alkali forming granules.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention and not to limit its scope.
On one hand, the invention provides composite biochar, scanning electron microscopy of composite biochar powder is shown in figure 3, the composite biochar is of a core-shell structure, and the core structure of the composite biochar is hydrothermal carbon and red mud molding particles; the shell structure of the composite biochar is hydrothermal carbon and alkali molded particles.
Specifically, as shown in fig. 1, the composite biochar of the invention is of a core-shell structure, and the core structure of the composite biochar is formed by hydrothermal carbon and red mud; the shell structure of the composite biochar is formed particles of hydrothermal carbon and alkali. Compared with the prior art that the alkaline reagent is directly adopted for neutralization reaction, the hydrothermal carbon and red mud forming particles with the core structure in the composite biochar have good alkali slow-release capacity; the alkaline components of the hydrothermal carbon and alkali forming particles serving as the shell structure of the composite biochar can quickly neutralize acid in the acid slag yard, and long-term stability of pH of the environment around the acid slag yard can be realized after acid neutralization of acid slag.
On the other hand, the invention also provides a preparation method of the composite biochar, which comprises the following steps as shown in figure 2:
step 3, uniformly mixing part of the dehydrated hydrothermal carbon and the red mud, adding the mixture into a granulator, spraying a binder for granulation and forming to obtain hydrothermal carbon and red mud formed particles;
step 4, continuously adding the uniformly mixed dehydrated hydrothermal carbon and alkali into the granulator, spraying a binder for granulation and forming to obtain composite formed particles which take the hydrothermal carbon and red mud formed particles as inner cores and are coated with the hydrothermal carbon and alkali formed particles;
and 5, carbonizing the composite molding particles in inert gas to obtain the composite biochar.
Compared with the prior art, the method takes waste biomass as a raw material to prepare dehydrated hydrothermal carbon, prepares hydrothermal carbon and red mud molding particles by utilizing the dehydrated hydrothermal carbon and red mud, prepares hydrothermal carbon and alkali molding particles by utilizing dehydrated hydrothermal carbon and alkali (sodium hydroxide or potassium hydroxide solid powder), and finally prepares the composite biochar which takes the hydrothermal carbon and red mud molding particles as cores and is wrapped by the hydrothermal carbon and alkali molding particles through carbonization. The porous structure of the composite biochar increases the specific surface area (200-800 m) 2 And/g) providing a channel for metal ions to enter the interior of the composite biochar, wherein polar groups, mainly oxygen-containing functional groups such as hydroxyl, carboxyl and the like exist on the surface of the composite biochar, oxygen atoms in the oxygen-containing functional groups have empty electron orbitals, metal elements have free electrons, and the oxygen-containing functional groups can fix the metal ions through chelation, so that the metal ions can be solidified. In addition, the alkaline component in the composite biochar can quickly neutralize acid in the acid slag yard, and is beneficial to realizing long-term stability of the pH of the environment around the acid slag yard after the acid neutralization of the acid slag.
Specifically, in the step 1, the waste biomass is lignocellulose biomass, and specifically comprises one or more of straw, wood chips, fallen leaves, bagasse and coconut shells, the mass content of lignin, cellulose and hemicellulose in the waste biomass exceeds 50%, and the particle size of the crushed waste biomass is less than 0.2mm.
Compared with the prior art, the waste biomass raw material adopted by the invention is cheap, has wide source, is renewable and environment-friendly, and the waste biomass is subjected to hydrothermal carbonization treatment, so that wet waste biomass can be directly treated by the hydrothermal carbonization, and the drying process of the waste biomass is avoided.
In the step 2, the mass ratio of biomass to water in the hydrothermal carbonization process is 1-1 (e.g. 1, 2, 1).
In the step 2, an activating agent is added during hydrothermal carbonization, the dosage of the activating agent is 2-8% of the mass of the waste biomass, the activating agent comprises one of citric acid, oxalic acid, tartaric acid or maleic acid, and the purpose of adding the activating agent and controlling the dosage of the activating agent within the range is that the activating agent can regulate and control the specific surface area and the surface functional groups of the hydrothermal carbon, so that the obtained solid hydrothermal carbon has more functional groups and larger specific surface area, and the adsorption capacity of the hydrothermal carbon on heavy metals is increased.
It should be noted that, in the step 2, the solid hydrothermal charcoal is dehydrated because the water content of the solid hydrothermal charcoal is too high, which affects the subsequent forming process.
In the step 3, the particle size of the red mud is less than 0.074mm, the mass ratio of the red mud to the hydrothermal carbon is 1-1.
It is emphasized that the quality ratio of the red mud and the hydrothermal carbon is controlled within the above range, so that the final formation of the core structure of the composite biochar can be ensured, and the red mud can be better wrapped by the hydrothermal carbon, so as to achieve the effect of alkali slow release. The polyvinyl alcohol aqueous solution with the concentration of 2% -8% is used as the binder, and the dosage of the polyvinyl alcohol aqueous solution is controlled within the range of 5% -10% of the total mass of the dehydrated hydrothermal carbon and the red mud, so that the binding effect can be ensured, and a better forming effect can be achieved.
In the step 3, the particle size of the red mud is controlled to be less than 0.074mm, because the red mud and the dehydrated hydrothermal carbon are mixed unevenly due to the large particle size of the red mud; the smaller the particle size of the red mud is, the better the particle size of the red mud is, but the smaller the particle size of the red mud is, the high cost and the long time consumption of the red mud grinding are caused.
The red mud is solid waste residue generated in the production process of alumina, the total stock of the red mud in China exceeds 6 hundred million tons, the red mud is generated by about 1 hundred million tons every year, the stock of a large amount of the red mud not only occupies land resources, but also seriously harms the ecology near a stock dump, the grass on the stock dump cannot grow due to the strong basicity of the red mud, dust is easily generated to pollute air, harmful elements in the red mud are easily transferred to underground water and soil to pollute the underground water and the soil, and certain cost is required for maintaining the stock dump. According to the invention, the red mud component is added during the preparation of the composite biochar, so that on one hand, good utilization and disposal of the red mud solid waste are realized, and on the other hand, the hydrothermal carbon is activated by using the alkaline component of the red mud; in addition, the red mud contains a certain amount of chemically combined alkali, so that the release effect of the pH value of the soil around the stable acid residue yard of the biochar can be improved.
In the step 4, the alkali is sodium hydroxide and potassium hydroxide solid powder, the mass ratio of the alkali to the hydrothermal carbon is 1-5, the binder comprises a polyvinyl alcohol aqueous solution with the mass concentration of 2% -8%, the using amount of the binder is 3% -8% of the total mass of the dehydrated hydrothermal carbon and the alkali, and the particle diameter of the formed composite biochar is 0.3-0.5mm.
In the step 4, the binder further comprises one of soluble starch, sodium silicate and sodium humate.
And 5, carbonizing the formed particles in inert gas to obtain the composite biochar.
In the step 5, the inert gases are nitrogen and argon, the carbonization temperature is 600-1200 ℃, the heating rate is 5-10 ℃/min, and the carbonization time is 1-5h. The carbonization condition is controlled within the range, so that the biochar with better effect can be obtained, and the specific surface area of the biochar is 200-800m 2 /g) large and rich voids; wherein, the scanning electron micrograph of the powder of the composite biochar is shown in figure 3.
The embodiment provides an ecological restoration method for industrial solid waste, which utilizes the prepared composite biochar to carry out harmless treatment on the industrial solid waste and comprises the following steps:
and 3, carrying out plant field planting on the improved soil to realize ecological restoration.
Compared with the prior art, on one hand, the composite biochar is beneficial to adsorbing harmful metals in the environment, and the solidification of the metals is realized. On the other hand, the hydrothermal carbon and red mud formed particles are arranged in the composite biochar prepared by the invention, the hydrothermal carbon and alkali formed biochar are arranged outside the composite biochar, the alkaline component of the external biochar can quickly neutralize acid in an acid slag yard, and the internal biochar has good alkali slow release capacity, so that the effect of stabilizing the acidity and alkalinity in the acid slag yard for a long time is achieved.
The harmless treatment method for industrial solid wastes provided by the embodiment can establish large-scale vegetation around the acid slag storage yard to form a wood forest ecological system, so that the stability of the environment around the acid slag storage yard is improved, the release of acid, salt and heavy metals in the acid slag storage yard can be effectively controlled, the rain wash and the loss of acid slag are reduced, the ecological restoration purpose is achieved, and meanwhile, the environment ecological benefit, the social benefit and the economic benefit are good.
Example 1
The embodiment provides a preparation method of composite biochar, which comprises the following steps:
Step 3, uniformly mixing the partially dehydrated hydrothermal carbon and the red mud, adding the mixture into a granulator, spraying a binder for granulation and forming to obtain hydrothermal carbon and red mud formed particles; the particle size of the red mud is 0.070mm, and the mass ratio of the red mud to the dehydrated hydrothermal carbon is 1; the binder is polyvinyl alcohol aqueous solution with the mass concentration of 3%; the dosage of the binder is 6 percent of the total mass of the dehydrated hydrothermal carbon and the red mud, and the diameter of the formed composite particle is 0.1mm.
Step 4, continuously adding uniformly mixed dehydrated hydrothermal carbon and sodium hydroxide solid powder into the granulator, wherein the mass ratio of the sodium hydroxide solid powder to the dehydrated hydrothermal carbon is (1) - (1); spraying a binder to carry out granulation molding, wherein the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 3%, and the using amount of the binder is 4% of the total mass of the dehydrated hydrothermal carbon and alkali, so as to obtain composite molded particles which take the hydrothermal carbon and red mud molded particles as cores and wrap the hydrothermal carbon and alkali molded particles; the diameter of the formed composite particles is 0.35mm.
Step 5, carbonizing the composite molding particles in inert gas, wherein the inert gas is nitrogen or argon; the temperature rise rate during carbonization is 6 ℃/min, the carbonization temperature is 650 ℃, and the carbonization time is 1.2h, so that the composite biochar is obtained.
Example 2
The embodiment provides a preparation method of composite biochar, which comprises the following steps:
Step 3, uniformly mixing part of the dehydrated hydrothermal carbon and the red mud, adding the mixture into a granulator, spraying a binder for granulation and forming to obtain hydrothermal carbon and red mud formed particles; the particle size of the red mud is 0.06mm, and the mass ratio of the red mud to the dehydrated hydrothermal carbon is 1; the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 5%; the dosage of the binder is 7 percent of the total mass of the dehydrated hydrothermal carbon and the red mud, and the diameter of the formed composite particle is 0.15mm.
Step 4, continuously adding uniformly mixed dehydrated hydrothermal carbon and sodium hydroxide solid powder into the granulator, wherein the mass ratio of the sodium hydroxide solid powder to the dehydrated hydrothermal carbon is 1; spraying a binder to carry out granulation molding, wherein the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 6%, and the using amount of the binder is 4.5% of the total mass of the dehydrated hydrothermal carbon and alkali, so as to obtain composite molded particles which take hydrothermal carbon and red mud molded particles as cores and wrap the hydrothermal carbon and alkali molded particles; the diameter of the formed composite particles is 0.42mm.
Step 5, carbonizing the composite molding particles in inert gas, wherein the inert gas is nitrogen or argon; the temperature rise rate during carbonization is 5.5 ℃/min, the carbonization temperature is 800 ℃, and the carbonization time is 3h, so that the composite biochar is obtained.
Example 3
The embodiment provides a preparation method of composite biochar, which comprises the following steps:
Step 3, uniformly mixing part of the dehydrated hydrothermal carbon and the red mud, adding the mixture into a granulator, spraying a binder for granulation and forming to obtain hydrothermal carbon and red mud formed particles; the particle size of the red mud is 0.045mm, and the mass ratio of the red mud to the dehydrated hydrothermal carbon is 1; the binder is polyvinyl alcohol aqueous solution with the mass concentration of 7.9%; the dosage of the binder is 9.5 percent of the total mass of the dehydrated hydrothermal carbon and the red mud, and the diameter of the formed composite particle is 0.19mm.
Step 4, continuously adding uniformly mixed dehydrated hydrothermal carbon and alkali into the granulator, wherein the alkali is sodium hydroxide or potassium hydroxide solid powder, and the mass ratio of the alkali to the dehydrated hydrothermal carbon is 5; spraying a binder to carry out granulation molding, wherein the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 7.8%, and the using amount of the binder is 8% of the total mass of the dehydrated hydrothermal carbon and the alkali, so as to obtain composite molded particles which take hydrothermal carbon and red mud molded particles as cores and wrap the hydrothermal carbon and alkali molded particles; the diameter of the formed composite particles is 0.48mm.
Step 5, carbonizing the composite molding particles in inert gas, wherein the inert gas is nitrogen or argon; the temperature rise rate during carbonization is 10 ℃/min, the carbonization temperature is 1180 ℃, and the carbonization time is 4.5h, so that the composite biochar is obtained.
Example 4
Acid heavy metal wastewater generated after leaching, oxidation, leaching and hydrolysis of sulfur-containing waste slag yard piled between valley and lean ore zone of pyrite remained in the mined-out area of pyrite pollutes water resource and land. In abandoned pyrites, the soil is gradually acidified over time, making it difficult for plants to grow.
In the prior art, acid soil is generally neutralized by adding alkali, and plants are still difficult to grow when the alkali is excessive; when the amount of alkali is proper, the acid soil is well regulated, but as the time increases, acid wastewater is generated, and the soil quickly becomes acid.
In a waste pyrite area, the composite biochar prepared in example 1 is added into acid soil (the pH of the soil is about 3.5), the soil in the ore area is ploughed by 10cm for mixing, the mass addition amount of the composite biochar is 15% of that of the acid soil, the composite biochar is naturally placed for 5 days after watering, the pH of the soil is about 6.8, tall fescue, ryegrass and alfalfa are planted, the plants grow well in 6 months, and the pH of the soil is stabilized between 6 and 7.
Example 5
Sulfide oxidation leads to waste acidification of tailings, and sulfur-containing metal ores comprise pyrite, chalcopyrite, sphalerite, galena and the like. The sulfuric acid residue is waste residue discharged in the process of producing sulfuric acid by using pyrite, and the main chemical component of the sulfuric acid residue is SiO 2 45％、Fe 2 O 3 40％、Al 2 O 3 10 percent, 5 percent of MgO and the pH value of the pyrite cinder is about 2.5.
Firstly, adding a proper amount of sulfuric acid residue and composite biochar into water, stirring and regulating the pH value to be about 7.5, standing for 30 days, monitoring the change of the pH value, and displaying that the pH value is stabilized at 6.5-7.5.
In a comparative test 1, a proper amount of sulfuric acid residue and alkali are added into water, the pH value is regulated and controlled to be about 7.5 by stirring, the mixture is kept stand for 30 days, the pH value is gradually reduced, and the pH value is about 4.8 after 30 days.
The pH in the contrast test is gradually reduced mainly by continuously oxidizing the sulfate slag to generate acid, and the contrast test shows that the composite biochar has a good alkali slow release effect and can regulate and stabilize the pH of the sulfate slag.
And (II) uniformly mixing the soil containing the sulfate slag with the composite biochar according to a mass ratio of 5.
In comparative experiment 1, plants were grown directly on the pyrite cinder and were unable to grow.
In contrast experiment 2, the pH value was controlled to about 7 by mixing sodium hydroxide with the pyrite cinder, and the growth vigor was poor when tall fescue, ryegrass and alfalfa were planted.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. The preparation method of the composite biochar is characterized in that the composite biochar is of a core-shell structure; the core structure of the composite biochar is formed particles of hydrothermal carbon and red mud; the shell structure of the composite biochar is formed particles of hydrothermal carbon and alkali;
the specific surface area of the composite biochar is 200-800m 2 /g；
The method comprises the following steps:
step 1, crushing waste biomass;
step 2, performing hydrothermal carbonization on the crushed waste biomass, and performing solid-liquid separation on a hydrothermal carbonization product to obtain solid hydrothermal carbon; dehydrating the solid hydrothermal carbon to obtain dehydrated hydrothermal carbon;
step 3, uniformly mixing the partially dehydrated hydrothermal carbon and the red mud, adding the mixture into a granulator, spraying a binder for granulation and forming to obtain hydrothermal carbon and red mud formed particles;
in the step 3, the particle size of the red mud is less than 0.074mm, and the mass ratio of the red mud to the dehydrated hydrothermal carbon is 1-1;
the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 2% -8%; the dosage of the binder is 5-10% of the total mass of the dehydrated hydrothermal carbon and the red mud, and the diameter of the formed composite particle is 0.1-0.2mm;
step 4, continuously adding the uniformly mixed dehydrated hydrothermal carbon and alkali into the granulator, spraying a binder for granulation and forming to obtain composite formed particles which take the hydrothermal carbon and red mud formed particles as inner cores and are coated with the hydrothermal carbon and alkali formed particles;
in the step 4, the alkali is sodium hydroxide or potassium hydroxide solid powder; the mass ratio of the alkali to the dehydrated hydrothermal carbon is 1;
the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 2-8%, the usage amount of the binder is 3-8% of the total mass of the dehydrated hydrothermal carbon and the alkali, and the diameter of the formed composite particle is 0.3-0.5mm;
step 5, carbonizing the composite molding particles in inert gas to obtain composite biochar;
the composite biochar is used for ecological restoration of industrial solid waste, the industrial solid waste comprises sulfuric acid residues, and the components of the sulfuric acid residues comprise SiO 2 、Fe 2 O 3 、Al 2 O 3 MgO; the pH value of the sulfate slag is 2.5.
2. The method for producing composite biochar according to claim 1, wherein in the step 1, the waste biomass is lignocellulosic biomass;
the mass content of lignin, cellulose and hemicellulose in the lignocellulose biomass is more than 50%;
the particle size of the crushed waste biomass is less than 0.2mm.
3. The preparation method of composite biochar according to claim 1, wherein in the step 2, the mass ratio of the waste biomass to water is 1-1;
the hydrothermal carbonization temperature is 150-280 ℃, and the hydrothermal carbonization time is 30-300min;
the water content of the dehydrated solid hydrothermal carbon is less than 10 percent.
4. The method for preparing composite biochar according to claim 1, wherein in the step 2, an activating agent with the amount of 2-8% of the mass of the waste biomass is added during hydrothermal carbonization;
the activator comprises one of citric acid, oxalic acid, tartaric acid or maleic acid.
5. The method for preparing composite biochar according to claim 1, wherein in the step 3, the particle size of the red mud is less than 0.070mm, and the mass ratio of the red mud to the dehydrated hydrothermal carbon is 1;
the binder is a polyvinyl alcohol aqueous solution with the mass concentration of 3% -8%; the dosage of the binder is 6-10% of the total mass of the dehydrated hydrothermal carbon and the red mud, and the diameter of the formed composite particle is 0.1-0.19mm.
6. The method for preparing composite biochar according to claim 1, wherein in the step 4, alkali is sodium hydroxide or potassium hydroxide solid powder; the mass ratio of the alkali to the dehydrated hydrothermal carbon is 1;
the binder is polyvinyl alcohol aqueous solution with the mass concentration of 2-6%, the dosage of the binder is 4.5-8% of the total mass of the dehydrated hydrothermal carbon and the alkali, and the diameter of the formed composite particle is 0.3-0.42mm.
7. The method for preparing composite biochar according to claim 1, wherein in the step 5, the inert gas is nitrogen gas, argon gas;
the temperature rise rate during carbonization is 5-10 ℃/min, the carbonization temperature is 600-1200 ℃, and the carbonization time is 1-5h.
8. The method of preparing composite biochar as claimed in claim 1, wherein in step 1, the lignocellulosic biomass comprises one or more of straw, wood chips, fallen leaves, bagasse, coconut shells.
9. The composite biochar is characterized by being prepared by the preparation method of the composite biochar according to any one of claims 1 to 8, wherein the composite biochar is in a core-shell structure;
the core structure of the composite biochar is formed particles of hydrothermal carbon and red mud; the shell structure of the composite biochar is hydrothermal carbon and alkali molded particles.
10. An ecological restoration method for industrial solid waste, which is characterized in that the ecological restoration of the industrial solid waste is carried out by using the composite biochar prepared by the preparation method of the composite biochar as claimed in any one of claims 1 to 8, and comprises the following steps:
step 1, building a plant planting area around an acid slag storage yard;
step 2, uniformly mixing the composite biochar with soil in a planting area, and aging for a certain time;
step 3, carrying out plant field planting on the improved soil to realize ecological restoration, wherein the pH value of the soil is stabilized between 6 and 7;
in the step 2, the mining area soil is ploughed by 10cm for mixing, the mass addition amount of the composite biochar is 15% of that of the acid slag yard soil, and the mixture is watered and naturally placed for 5 days for aging.
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