CN107021714B - Curing agent for heavy metal contaminated soil and preparation and application methods thereof - Google Patents
Curing agent for heavy metal contaminated soil and preparation and application methods thereof Download PDFInfo
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- CN107021714B CN107021714B CN201710243109.1A CN201710243109A CN107021714B CN 107021714 B CN107021714 B CN 107021714B CN 201710243109 A CN201710243109 A CN 201710243109A CN 107021714 B CN107021714 B CN 107021714B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/08—Slag cements
- C04B28/082—Steelmaking slags; Converter slags
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00017—Aspects relating to the protection of the environment
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00767—Uses not provided for elsewhere in C04B2111/00 for waste stabilisation purposes
Abstract
The invention discloses a curing agent for heavy metal contaminated soil and a preparation and application method thereof, wherein the curing agent comprises the following materials in percentage by mass: 30-55% of steel slag powder; 20-50% of quicklime powder; 5-30% of phosphate-loaded biochar. The invention has the advantages that: firstly, the curing agent can obviously reduce the heavy metal migration and toxic leaching amount in heavy metal polluted soil, is particularly suitable for acid polluted sites with high heavy metal content and more pollutant types, can be used as an environment-friendly material for resource utilization after polluted soil is repaired, and obviously reduces the environmental risk in secondary development and utilization of the polluted sites; meanwhile, the curing agent has the advantages of easily available raw materials, low cost, simple preparation, convenient use and stable effect, and can be popularized and applied to curing stabilization repair of composite polluted sites on a large scale.
Description
Technical Field
The invention relates to the field of environmental geotechnical engineering, in particular to a curing agent for heavy metal polluted soil and preparation and application methods thereof.
Background
With the adjustment of urban functions and urban layout in China, enterprises in the central area and suburban areas of a city, such as chemical plants, metal smelting plants, electroplating plants and the like, are gradually shut down or move back to the city and enter the garden, but in the production process of the industry and the enterprises for many years, a large amount of pollutants are accumulated in the remaining land after the enterprises move, so that resistance is brought to the efficient utilization of the remaining land, and serious potential safety hazards are brought to the surrounding environment. In recent years, the action plan for preventing and treating soil pollution (ten items of soil) issued by the government also considers the remediation work of the polluted soil as one of the currently important civil engineering, and the development of the relevant remediation work of the pollution is urgent.
The heavy metal pollution of the soil in the industrial polluted site is characterized by multiple heavy metal species, high content, large acidity and the like. In the remediation of heavy metal contaminated sites, a solidification stabilization technique is widely adopted. The commonly used curing agent mainly comprises materials such as cement, lime, phosphate and the like, has good effect on curing and stabilizing heavy metals, but also has a great deal of defects, such as large energy consumption for producing cement, more greenhouse gas emission and the like; lime and phosphate are non-renewable natural minerals, and the cost is high; moreover, the application of a large amount of phosphate can seriously change the soil structure and further cause phosphorus pollution of underground water and surface water.
In summary, the conventional curing agent has many defects, and needs to reduce the use of cement and phosphate materials, and find a novel curing agent which can cure and stabilize heavy metals, and has the advantages of high curing stabilization efficiency, low cost, stable performance, wide material sources and environmental friendliness, which has become the focus of attention of environmental protection science and technology workers.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides a curing agent for heavy metal polluted soil, which can obviously reduce the migration and toxic leaching amount of heavy metals in the heavy metal polluted soil; the second purpose of the invention is to provide a preparation method of the heavy metal polluted soil curing agent; the third purpose of the invention is to provide an application method of the heavy metal contaminated soil curing agent.
The technical scheme is as follows: the curing agent for heavy metal polluted soil provided by the invention comprises the following materials in percentage by mass: 30-55% of steel slag powder; 20-50% of quicklime powder; 5-30% of phosphate-loaded biochar.
The curing agent preferably comprises the following components: 35-50% of steel slag powder; 25-45% of quicklime powder; 10-25% of phosphate-loaded biochar.
The steel slag powder is activated steel slag powder prepared by the following method:
(1) one or more of the high-activity steel slag such as the converter slag, the open-hearth slag, the electric furnace oxidizing slag and the like after magnetic separation are crushed and sieved;
(2) drying the material with the particle size of less than 2mm in the obtained product until the water content is less than 2%, preferably drying by adopting airflow at 100-105 ℃;
(3) grinding the obtained product, sieving the product with a sieve of 150-200 meshes (for example, ball milling can be adopted), and calcining the product at the temperature of 500-700 ℃ for 1-2h (for example, electric furnace calcination can be preferentially adopted, so that energy conservation and practicability are realized), thereby obtaining the activated steel slag powder.
The phosphate-loaded biochar is prepared by the following method:
(1) preparing phosphate solution with concentration of 0.01-0.05mol/L (the phosphate is preferably monopotassium phosphate, the water solution is acidic, and the activating effect on the steel slag is better), and grinding the biochar through a 0.1-0.3mm sieve to obtain biochar powder;
(2) mixing the charcoal powder and aluminum sulfate according to the mass ratio of 20-30:1 to obtain a charcoal powder mixture;
(3) soaking the obtained charcoal powder mixture in phosphate solution, stirring for 10-15min (until the mixture is uniform), stirring under oscillation at 20-30 deg.C for 10-15 hr, standing for 36-48 hr to obtain gel precipitate; wherein, the purpose of the two times of stirring is different, the first time of stirring is to ensure that solid and liquid are fully contacted, and the second time of stirring is to quickly generate gel precipitate;
(4) and drying the gel-like precipitate by adopting 100-250 ℃ airflow until the water content is less than 2%, grinding the obtained product and sieving the product by a 200-mesh sieve to obtain the phosphate-loaded biochar, wherein airflow drying is preferentially adopted quickly, the medicament is not easy to agglomerate, and the subsequent medicament production is facilitated.
One or more of coffee grounds, tea dust and traditional Chinese medicine residues are dried at the temperature of 100-105 ℃ until the mass of the coffee grounds, the tea dust and the traditional Chinese medicine residues is constant, and then the coffee grounds, the tea dust and the traditional Chinese medicine residues are cracked at the temperature of 400-700 ℃ under the anoxic condition to prepare the biochar.
The quicklime powder is prepared by the following method: and (3) drying the quick lime with CaO content of more than 96% by adopting airflow at the temperature of 100-250 ℃ until the water content is less than 2%, and grinding the quick lime through a 150-200-mesh sieve.
The preparation method of the curing agent for heavy metal contaminated soil comprises the following steps: mixing the activated steel slag powder, the quicklime powder and the phosphate-loaded biochar according to the weight percentage, stirring for 0.5-1h by a dry method until the mixture is uniform, and then sieving with a 150-mesh and 200-mesh sieve to obtain the curing agent.
The application method of the curing agent for heavy metal contaminated soil comprises the following steps: and mixing and stirring the curing agent and the heavy metal polluted soil, wherein the dosage of the curing agent is 5-15% of the dry weight of the heavy metal polluted soil, and the water content of the heavy metal polluted soil is 16-30%.
The content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 65-100%, wherein the content of heavy metal lead is more than 2000mg/kg, the content of heavy metal zinc is more than 2000mg/kg, the content of heavy metal copper is more than 2000mg/kg, and the content of heavy metal nickel is more than 2000 mg/kg.
Has the advantages that: compared with the prior art, the invention has the remarkable advantages that:
(1) the heavy metal curing effect is good. Firstly, the steel slag has an adsorption effect on heavy metal ions; secondly, the potential gelling property of the steel slag is shown under the excitation effect of the quicklime, the hydroxide sediment of the heavy metal is effectively wrapped, and the solidification effect of the heavy metal by using the quicklime alone is greatly enhanced; and thirdly, the phosphate-loaded charcoal generates partial hydroxyapatite crystals under the action of quick lime, the hydroxyapatite can efficiently adsorb and complex heavy metals such as Pb, Zn, Cu, Ni and the like, the solubility of the hydroxyapatite crystals and the heavy metal salts of the hydroxyapatite crystals generated by the heavy metals is lower than that of the heavy metal hydroxides by dozens of orders of magnitude, the hydroxyapatite crystals are lower in solubility under acidic and alkaline conditions, and the curing effect is better and more stable.
(2) The durability is good. The traditional curing agent is easily affected by carbon dioxide erosion and acid rain erosion, and the phenomena of degradation and attenuation of environmental safety and engineering characteristics of the cured polluted soil are generated. The curing agent can effectively overcome the defects, and because the generated heavy metal phosphate precipitates are agglomerated around the biochar, the solubility of the biochar is low in various pH environments, and the contact between the heavy metal precipitates and an acidic solution can be effectively reduced under the wrapping effect of a hydration product C-S-H gel of the steel slag; meanwhile, the steel slag has strong acid buffer capacity and carbon dioxide absorption capacity, and CaCO is generated under the action of carbon dioxide erosion3The crystal further fills the pores of the solidified body, so that the infiltration amount of an acid solution is effectively reduced, and the stability of the solidified body in a severe environment is further improved; in addition, the phosphate-loaded charcoal also has a good buffering effect on acid rain erosion, and the loaded phosphate can effectively inhibit the desorption effect of adsorbed heavy metals, so that the durability of the solidified body is further improved.
(3) Effectively utilizes waste raw materials and is an environment-friendly curing agent. Firstly, the steel slag is used as industrial waste slag and is piled in a large area, so that serious environmental pollution is caused, the utilization value of the steel slag is effectively improved through the activation of the steel slag, and waste materials are changed into valuable materials. Secondly, the steel slag is used as a high-alkalinity material and directly used for solidification and stabilization of heavy metal polluted soil, the pH value of the solidified soil is high, many problems can be brought to later development and utilization of land, through activation and modification, the pH value of the solidified soil is effectively reduced while the solidification effect of the steel slag on heavy metal is effectively improved, and the solidification and stabilization effect of the steel slag on the heavy metal is optimal through addition of quicklime. And thirdly, the coffee slag, the tea powder and the Chinese medicine slag are also domestic waste slag, and are further modified after being subjected to medium-high temperature cracking to prepare biochar, so that the curing effect on metal can be effectively improved after the biochar is loaded with phosphate, the excitation on the steel slag can be realized, the hydration activity of the steel slag is improved, and the curing and stabilizing effect on heavy metal is improved.
Detailed Description
Example 1
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 45 percent; quicklime powder: 35 percent; phosphate-loaded biochar: 20 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the converter slag, and then crushing and sieving; placing the material with the particle size of less than 2mm in an oven to dry the material by adopting airflow at the temperature of 105 ℃ until the water content of the material is 1%; grinding the obtained product, sieving the ground product by a 200-mesh sieve, and calcining the product for 2 hours in an electric furnace at 700 ℃. The basicity value of the steel slag powder is 2.07.
The main components and contents of the steel slag are shown in table 1, and it should be noted that the steel slag suitable for the present invention is not limited to the data in table 1, and is only the steel slag used in the present embodiment:
TABLE 1 Steel slag main component and content
| Main chemical composition | CaO | SiO2 | Al2O3 | Fe2O3 | MgO | P2O5 |
| Content (%) | 36.30 | 16.26 | 3.32 | 18.66 | 8.35 | 1.26 |
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.05mol/L, and grinding the biochar through a 0.2mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 30:1 to obtain a charcoal powder mixture; soaking the obtained mixture into the obtained potassium dihydrogen phosphate solution, stirring for 15min until the mixture is uniformly mixed, oscillating and stirring for 15h at 25 ℃, and standing for 48h to obtain a gelatinous precipitate; and drying the gelatinous precipitate by adopting airflow at 200 ℃ until the water content is 1%, grinding the obtained product and sieving the ground product by using a 200-mesh sieve to obtain the biological carbon loaded with the potassium dihydrogen phosphate. The biochar is prepared by drying coffee grounds at 105 ℃ until the mass of the coffee grounds is not changed, and then cracking the coffee grounds for 6 hours at 600 ℃ under a closed anoxic condition, and the physical and chemical characteristics and the main chemical components of the biochar are shown in table 2.
TABLE 2 basic chemical Properties and essential element contents of biochar
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 99% by using airflow at 200 ℃ until the water content is 1%, and grinding and sieving by using a 200-mesh sieve.
The curing agent for the heavy metal polluted soil is prepared by the following steps: and mixing the activated steel slag powder, the quicklime powder and the phosphate-loaded charcoal in parts by mass, stirring for 1h by a dry method until the mixture is uniform, and sieving by a 200-mesh sieve to obtain the curing agent.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: and (3) mixing and stirring the curing agent and the heavy metal polluted soil in situ, wherein the dosage of the curing agent is 5% of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil). There are two types of heavy metal contaminants: the polluted soil a is lead and zinc composite polluted soil taken from an industrial polluted site; and the polluted soil b is copper and nickel composite polluted soil taken from two industrial polluted sites. Other major physicochemical properties are shown in table 3.
TABLE 3 main physicochemical Properties of contaminated soil
Example 2
The same procedure as in example 1 was repeated except that the amount of the curing agent was 10% (dry weight of the heavy metal and organic compound contaminated soil).
Example 3
The same procedure as in example 1 was repeated except that 15% of the curing agent was added (based on the dry weight of the soil contaminated with heavy metals and organic compounds).
Comparative example 1
No curing agent is added, and only the soil sample polluted by the compound heavy metal in the example 1 is taken.
Comparative example 2
The steel slag in the example 1 is used for preparing the curing agent without activation, other preparation steps are not changed, and the mixing amount is 15 percent as in the example 3.
Example 4
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 50 percent; quicklime powder: 25 percent; phosphate-loaded biochar: 25 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the open hearth furnace slag, and then crushing and sieving; taking a material with the particle size of less than 2mm out of the obtained product, and drying the material by adopting airflow at the temperature of 100 ℃ until the water content of the material is 1.5%; grinding the obtained product, sieving the ground product by a sieve with 150 meshes, and calcining the product for 1h by an electric furnace at 500 ℃. The basicity value of the steel slag powder is 1.8.
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.01mol/L, and grinding the biochar through a 0.1mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 20:1 to obtain a charcoal powder mixture; soaking the obtained mixture into the obtained potassium dihydrogen phosphate solution, stirring for 10min until the mixture is uniformly mixed, oscillating and stirring for 10h at the temperature of 20 ℃, and standing for 36h to obtain a gelatinous precipitate; and drying the gelatinous precipitate by adopting airflow at 100 ℃ until the water content is 1.5%, grinding the obtained product and sieving the ground product by a 150-mesh sieve to obtain the biological carbon loaded with the potassium dihydrogen phosphate.
The biochar is prepared by drying coffee grounds at 100 ℃ until the quality of the coffee grounds is not changed, and cracking the coffee grounds at 400 ℃ under an anoxic condition.
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 98% by adopting airflow at 100 ℃ until the water content is 1.5%, and grinding and sieving by using a 150-mesh sieve to obtain quicklime powder.
The curing agent for the heavy metal polluted soil is prepared by the following steps: and mixing the steel slag powder, the quicklime powder and the phosphate-loaded charcoal in parts by mass, stirring for 0.5h by a dry method until the mixture is uniform, and sieving by a 150-mesh sieve to obtain the curing agent.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: and (2) mixing and stirring a curing agent and the heavy metal polluted soil in situ, wherein the dosage of the curing agent is 5% of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil), the water content of the heavy metal polluted soil is 16%, the heavy metal polluted soil is the same as the polluted soil selected in the embodiment 1, and the content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 65%.
Example 5
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 35 percent; quicklime powder: 45 percent; phosphate-loaded biochar: 20 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the open hearth furnace slag, and then crushing and sieving; drying the material with the particle size of less than 2mm in the obtained product by adopting airflow at the temperature of 150 ℃ until the material is completely dried; grinding the obtained product, sieving the ground product by a 180-mesh sieve, and calcining the product for 1.5 hours at 600 ℃ by an electric furnace. The basicity value of the steel slag powder is 2.2.
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.03mol/L by using phosphate, and grinding the biochar through a 0.3mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 25:1 to obtain a charcoal powder mixture; soaking the obtained mixture in the obtained potassium dihydrogen phosphate solution, stirring for 13min until the mixture is uniformly mixed, oscillating and stirring for 12.5h at 25 ℃, and standing for 42h to obtain a gelatinous precipitate; and drying the gelatinous precipitate to be completely dry by adopting airflow at 180 ℃, grinding the obtained product and sieving the ground product by a 160-mesh sieve to obtain the biochar loaded with the potassium dihydrogen phosphate.
The biochar is prepared by selecting tea leaves, drying the tea leaves at 102.5 ℃ until the quality of the tea leaves is not changed, and cracking the tea leaves at 550 ℃ under an anoxic condition.
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 97% by adopting airflow at 175 ℃ until the quicklime is completely dried, grinding and sieving by a 160-mesh sieve to obtain quicklime powder.
The curing agent for the heavy metal polluted soil is prepared by the following steps: mixing the steel slag powder, the quicklime powder and the phosphate-loaded biochar in parts by mass, stirring for 0.75h by a dry method until the mixture is uniform, and sieving by a 160-mesh sieve.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: and (2) mixing and stirring a curing agent and the heavy metal polluted soil in situ, wherein the dosage of the curing agent is 10% of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil), the water content of the heavy metal polluted soil is 23%, the heavy metal polluted soil is the same as the polluted soil selected in the embodiment 1, and the content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 82.5%.
Example 6
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 40 percent; quicklime powder: 50 percent; phosphate-loaded biochar: 10 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the open hearth furnace slag, and then crushing and sieving; taking a material with the particle size of less than 2mm from the obtained product, and drying the material by adopting airflow at the temperature of 125 ℃ until the water content of the material is 0.5%; grinding the obtained product, sieving the ground product by a 200-mesh sieve, and calcining the product for 2 hours in an electric furnace at 700 ℃. The basicity value of the steel slag powder is 2.6.
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.05mol/L, and grinding the biochar through a 0.2mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 30:1 to obtain a charcoal powder mixture; soaking the obtained mixture into the obtained phosphate solution, stirring for 15min until the mixture is uniformly mixed, oscillating and stirring for 15h at 30 ℃, and standing for 48h to obtain a gelatinous precipitate; and drying the gelatinous precipitate by adopting airflow at 250 ℃ until the water content is 0.5%, grinding the obtained product and sieving the ground product by using a 170-mesh sieve to obtain the biological carbon loaded with the potassium dihydrogen phosphate.
The biochar is prepared by drying the traditional Chinese medicine residues at 105 ℃ until the quality of the traditional Chinese medicine residues does not change any more, and then cracking the traditional Chinese medicine residues at 700 ℃ under an anoxic condition.
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 98% by adopting airflow at 250 ℃ until the water content is 0.5%, and grinding and sieving by using a 170-mesh sieve to obtain quicklime powder.
The curing agent for the heavy metal polluted soil is prepared by the following steps: and mixing the steel slag powder, the quicklime powder and the phosphate-loaded charcoal in parts by mass, stirring for 0.75h by a dry method until the mixture is uniform, and sieving by a 170-mesh sieve to obtain the curing agent.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: mixing and stirring the curing agent and the heavy metal polluted soil in situ. Wherein the dosage of the curing agent is 15 percent of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil), and the water content of the heavy metal polluted soil is 30 percent. The content of particles with the particle size of less than 0.075mm in the used heavy metal contaminated soil is 83%, the heavy metal contaminated soil is the same as the contaminated soil selected in the embodiment 1, and the content of the particles with the particle size of less than 0.075mm in the heavy metal contaminated soil is 100%.
Example 7
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 30 percent; quicklime powder: 40 percent; phosphate-loaded biochar: 30 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the electric furnace oxidation slag, and then crushing and sieving; drying the material with the particle size of less than 2mm in the obtained product by adopting airflow at the temperature of 150 ℃ until the material is completely dried; grinding the obtained product, sieving the ground product by a 180-mesh sieve, and calcining the product for 1.5 hours at 600 ℃ by an electric furnace. The basicity value of the steel slag powder is 2.2.
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.03mol/L by using phosphate, and grinding the biochar through a 0.3mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 25:1 to obtain a charcoal powder mixture; soaking the obtained mixture in the obtained potassium dihydrogen phosphate solution, stirring for 13min until the mixture is uniformly mixed, oscillating and stirring for 12.5h at 25 ℃, and standing for 42h to obtain a gelatinous precipitate; and drying the gelatinous precipitate to be completely dry by adopting airflow at 180 ℃, grinding the obtained product and sieving the ground product by using a 180-mesh sieve to obtain the biological carbon loaded with the potassium dihydrogen phosphate.
The biochar is prepared by drying a mixture of tea leaf foam and coffee grounds at 102.5 ℃ until the mass of the mixture is not changed, and cracking the mixture at 600 ℃ under an anoxic condition.
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 99% by adopting airflow at 175 ℃ until the quicklime is completely dried, grinding and sieving by using a 180-mesh sieve to obtain quicklime powder.
The curing agent for the heavy metal polluted soil is prepared by the following steps: mixing the steel slag powder, the quicklime powder and the phosphate-loaded charcoal in parts by mass, stirring for 0.75h by a dry method until the mixture is uniform, and sieving by a 180-mesh sieve.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: and (2) mixing and stirring a curing agent and the heavy metal polluted soil in situ, wherein the dosage of the curing agent is 5% of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil), the water content of the heavy metal polluted soil is 25%, the heavy metal polluted soil is the same as the polluted soil selected in the embodiment 1, and the content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 90%.
Example 8
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 55 percent; quicklime powder: 20 percent; phosphate-loaded biochar: 25 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the electric furnace oxidation slag, and then crushing and sieving; drying the material with the particle size of less than 2mm in the obtained product by adopting airflow at the temperature of 150 ℃ until the material is completely dried; grinding the obtained product, sieving the ground product by a 180-mesh sieve, and calcining the product for 1.5 hours at 600 ℃ by an electric furnace. The basicity value of the steel slag powder is 2.2.
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.03mol/L by using phosphate, and grinding the biochar through a 0.3mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 25:1 to obtain a charcoal powder mixture; soaking the obtained mixture in the obtained potassium dihydrogen phosphate solution, stirring for 13min until the mixture is uniformly mixed, oscillating and stirring for 12.5h at 25 ℃, and standing for 42h to obtain a gelatinous precipitate; and drying the gelatinous precipitate to be completely dry by adopting airflow at 180 ℃, grinding the obtained product and sieving the ground product by a 190-mesh sieve to obtain the biological carbon loaded with the potassium dihydrogen phosphate.
The biochar is prepared by drying a mixture of coffee grounds and Chinese medicine residues at 102.5 ℃ until the mass of the mixture is not changed, and cracking the mixture at 450 ℃ under an anoxic condition.
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 97% by adopting airflow at 175 ℃ until the quicklime is completely dried, grinding and sieving by using a 190-mesh sieve to obtain quicklime powder.
The curing agent for the heavy metal polluted soil is prepared by the following steps: mixing the steel slag powder, the quicklime powder and the phosphate-loaded charcoal in parts by mass, stirring for 0.75h by a dry method until the mixture is uniform, and sieving by a 190-mesh sieve.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: and (2) mixing and stirring a curing agent and the heavy metal polluted soil in situ, wherein the dosage of the curing agent is 10% of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil), the water content of the heavy metal polluted soil is 23%, the heavy metal polluted soil is the same as the polluted soil selected in the embodiment 1, and the content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 75%.
Example 9
The invention relates to a curing agent for heavy metal contaminated soil, which comprises the following materials in parts by mass: steel slag powder: 55 percent; quicklime powder: 40 percent; phosphate-loaded biochar: 5 percent.
The steel slag powder is activated steel slag powder prepared by the following method: carrying out magnetic separation on the electric furnace oxidation slag, and then crushing and sieving; drying the material with the particle size of less than 2mm in the obtained product by adopting airflow at the temperature of 150 ℃ until the material is completely dried; grinding the obtained product, sieving the ground product by a 180-mesh sieve, and calcining the product for 1.5 hours at 600 ℃ by an electric furnace. The basicity value of the steel slag powder is 2.2.
The phosphate-loaded biochar is prepared by the following method: preparing a potassium dihydrogen phosphate solution with the concentration of 0.03mol/L by using phosphate, and grinding the biochar through a 0.3mm sieve to obtain biochar powder; fully mixing the charcoal powder and aluminum sulfate according to the mass ratio of 25:1 to obtain a charcoal powder mixture; soaking the obtained mixture in the obtained potassium dihydrogen phosphate solution, stirring for 13min until the mixture is uniformly mixed, oscillating and stirring for 12.5h at 25 ℃, and standing for 42h to obtain a gelatinous precipitate; and drying the gelatinous precipitate to be completely dry by adopting airflow at 180 ℃, grinding the obtained product and sieving the ground product by using a 200-mesh sieve to obtain the biological carbon loaded with the potassium dihydrogen phosphate.
The biochar is prepared by selecting a mixture of tea leaf powder and Chinese medicine residues, drying the mixture at 102.5 ℃ until the mass of the mixture is not changed, and cracking the mixture at 550 ℃ under an anoxic condition.
The quicklime powder is prepared by the following method: and (3) drying quicklime with CaO content of 97% by adopting airflow at 175 ℃ until the quicklime is completely dried, grinding and sieving by using a 200-mesh sieve to obtain quicklime powder.
The curing agent for the heavy metal polluted soil is prepared by the following steps: mixing the steel slag powder, the quicklime powder and the phosphate-loaded charcoal in parts by mass, stirring for 0.75h by a dry method until the mixture is uniform, and sieving by a 200-mesh sieve.
The use method of the curing agent for heavy metal contaminated soil specifically comprises the following steps: mixing and stirring a curing agent and heavy metal polluted soil in situ, wherein the dosage of the curing agent is 15% of the dry weight of the heavy metal polluted soil (accounting for the dry weight of the composite metal polluted soil), the water content of the heavy metal polluted soil is 23%, the heavy metal polluted soil is the same as the polluted soil selected in the embodiment 1, and the content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 82.5%
Example 10
Toxicity leaching test: the sample soil after being implemented in example 1, example 2, example 3, comparative example 1, comparative example 2, example 4, example 5, example 6, example 7, example 8 and example 9 was tightly wrapped and sealed with a freshness protection package, and the toxicity leaching test was performed on the solidified contaminated soil after being cured for 28 days at 20 ℃ and a humidity of more than 95%:
test standards: the national environmental protection industry Standard sulfuric acid-nitric acid method for leaching toxicity of solid wastes (HJ/T299-2007).
The test process comprises the following steps: weighing 50g of the cured solidified polluted soil, drying at 105 ℃, and calculating to obtain the water content of the sample, wherein the error of the constant weight to the two weighing values is less than +/-1%. The dry weight of the remediation soil is calculated according to the water content, a remediation soil sample with the dry basis weight of 10g is weighed, and the test is carried out according to the method and the steps specified in the sulfuric acid-nitric method for leaching toxicity from solid waste (HJ/T299-2007). The test results are shown in table 4.
TABLE 4 toxicity Leaching test results (mg/L)
The sulfuric acid-nitric acid leaching method is used as a standard for evaluating whether solid waste is dangerous waste or not, and is a common method for analyzing the leaching toxicity characteristics of pollutants of the solid waste under the action of acid rainfall. From the toxicity leaching test results of Table 4, it can be seen by comparing examples 1-3, examples 4-6 and examples 7-9: according to the remediation soil doped with the curing agent, the leaching concentrations of Zn, Pb, Ni and Cu in the leaching solution are reduced along with the increase of the doping amount of the curing agent, the comparative example 1 shows that the heavy metal migration in untreated source polluted soil is extremely strong, the leaching amounts of the heavy metals of Zn, Pb, Ni and Cu are far higher than the limit value in hazardous waste identification standard leaching toxicity identification (GB 5085.3-2007), and the addition of the curing agent can be found to remarkably reduce the leaching amount of the heavy metals and increase the environmental safety by combining with the examples 1-9. As is clear from comparison between example 3 and comparative example 2, the stability of heavy metals was improved and the stabilizing effect in example 3 was more remarkable after curing for 28 days with the curing agent of the present invention added, the leaching amount is far lower than the limit value in the standard leaching toxicity identification of hazardous waste (GB 5085.3-2007), whereas the steel slag powder in the curing agent of comparative example 2 was formulated only from phosphate-loaded biochar without activation, which can reduce the migration characteristics of heavy metals Zn, Pb, Ni and Cu in soil to a certain extent, reduce the harm to the environmental safety and still meet the basic requirements of the invention, therefore, the steel slag is activated and modified, so that the solidification stabilizing effect of the solidifying agent on heavy metals can be effectively enhanced, if the steel slag is not subjected to activation treatment, the technical effect of the invention can be realized to a certain extent.
Example 11
The soil remediation ph test was performed on the solidified contaminated soil after the curing in examples 1, 2, 3, 1, 2, 4, 5, 6, 7, 8 and 9 by the method of example 10:
test standards: method 4972-01 for pH of soil.
The test process comprises the following steps: weighing 50g of the cured solidified polluted soil, drying at 105 ℃, and calculating to obtain the water content of the sample, wherein the error of the constant weight to the two weighing values is less than 1%. And calculating the dry weight of the remediation soil according to the water content, sieving the remediation soil by using a 1mm sieve, weighing a remediation soil sample with the dry basis weight of 10g, stirring and mixing the remediation soil sample with 10g of distilled water, standing the mixture for 1h, and then testing the pH value of the solution. The test results are shown in table 5.
TABLE 5 PH value test results
The pH value of the solidified soil body is an important index for evaluating the effect of the solidifying agent for solidifying the heavy metal, and has great influence on the development mode and the degree of secondary utilization of the repair field. From the test results of the pH value in the table 5, as can be seen from the comparison between the examples 1 to 3 and the comparative example 1, after the curing agent is added, the pH value of the cured soil is significantly increased, after 28 days of curing, the pH value of the contaminated soil is between 6 and 9 and is close to neutral, which is beneficial to the utilization of a repair site, meanwhile, the pH value of the cured soil in the examples 4 to 9 is also significantly increased, and after 28 days of curing, the pH value of the contaminated soil is also between 6 and 9 and is close to neutral; compared with the example 3, the comparative example 2 has slightly higher pH value because the steel slag is not subjected to the activation treatment, but can basically realize the technical scheme of the invention, and if the pH value is continuously increased, a plurality of problems are brought to the later development and utilization of the land.
Example 12
Phytotoxicity tests (seed germination percentage tests) were carried out on contaminated soils according to the method of example 10 of example 1, example 2, example 3, comparative example 1, comparative example 2, example 4, example 5, example 6, example 7, example 8 and example 9:
the test process comprises the following steps: the germination rate test of the seeds adopts soybeans which are sensitive to the content of heavy metal pollutants in soil, and the germination rate of the soybeans is used as an ecological index for carrying out toxicity analysis on the soil with heavy metal and organic compound pollution, so that the method is a commonly used important method for measuring the soil environment quality and the soil pollution from the ecological toxicology perspective. Firstly, the plain soil and the repair soil after 28 days of maintenance are naturally air-dried and sieved by a 2mm sieve for later use. Taking 4kg of soil (plain soil or each repair soil) for each sample, potting (the diameter of the upper opening is 25cm, the diameter of the bottom is 20cm, the height is 20cm), and the ridging height is 18 cm; the soil in the pot is thoroughly watered with distilled water until the water retention rate is 60 percent, and then the water retention rate is kept unchanged and the soil is soaked and placed indoors for 2 days; finally, soybean is sown, the soybean is sown at the depth of about 0.3cm, and 100 grains are sown in each pot; after sowing, the proper soil humidity is maintained by regularly spraying, so that the seeds germinate in the indoor sunny place at the room temperature of 18-22 ℃ under the condition of natural lighting. The germination rate (number of germinated seeds/number of test seeds) × 100%. The test results are shown in table 6.
Table 6 seed germination (%)
The seed germination rate test can reflect the toxic action of the soil to plants. As can be seen from table 6: the heavy metal content in the plain soil (comparative example 1, namely the polluted soil without the curing agent) is very high, the germination rate of the seeds is seriously influenced, and the germination rates of the soybean seeds in the polluted soil are only 8 percent and 11 percent. The curing agent in the comparative example 2 improves the germination rate to a certain extent, but the improvement range is limited, and the germination rate can only reach 58 percent and 60 percent, which shows that the curing agent prepared by using the unactivated steel slag powder has a certain stabilizing effect on heavy metals in the polluted soil and has limited effect at the moment; in contrast, the germination rates of seeds of the firming agent restoring soil of examples 1 to 9 of the present invention were more than 85% and even up to 100% in various blending amounts (example 3). The differences of the examples 1, 2 and 3 and the comparative example 1 show that the curing agent disclosed by the invention is ecological and friendly in repairing the composite heavy metal contaminated soil, and is beneficial to the development and growth of plants and microorganisms around the repaired site, and the comparison of the example 3 and the comparative example 2 shows that the activating treatment on the steel slag can also effectively reduce the toxic action of the soil on the plants, so that the curing stability of the curing agent on the heavy metals is reflected from the side surface.
Claims (8)
1. A curing agent for heavy metal contaminated soil is characterized in that: the material composition comprises the following materials in percentage by mass: 30-55% of steel slag powder; 20-50% of quicklime powder; 5-30% of phosphate-loaded charcoal;
the steel slag powder is activated steel slag powder and is prepared by the following method:
(1) one or more of the converter slag, the open hearth furnace slag and the electric furnace oxidation slag after magnetic separation are crushed and sieved;
(2) drying the material with the particle size of less than 2mm in the obtained product until the water content is less than 2%;
(3) grinding the obtained product, sieving the product by a sieve with 150-200 meshes, and calcining the product for 1-2h at the temperature of 500-700 ℃ to obtain the activated steel slag powder.
2. The curing agent for heavy metal contaminated soil according to claim 1, wherein: 35-50% of the steel slag powder; 25-45% of quicklime powder; 10-25% of phosphate-loaded biochar.
3. The curing agent for heavy metal contaminated soil according to claim 1, wherein: the phosphate-loaded biochar is prepared by the following method:
(1) preparing phosphate solution with concentration of 0.01-0.05mol/L, grinding the biochar through a sieve with 0.1-0.3mm to obtain charcoal powder;
(2) mixing the charcoal powder and aluminum sulfate according to the mass ratio of 20-30:1 to obtain a charcoal powder mixture;
(3) soaking the obtained charcoal powder mixture in phosphate solution, stirring for 10-15min, shaking and stirring at 20-30 deg.C for 10-15 hr, and standing for 36-48 hr to obtain gel precipitate;
(4) and drying the gelatinous precipitate by adopting 100-250 ℃ airflow until the water content is less than 2%, grinding the obtained product, and sieving the ground product by using a 150-200-mesh sieve to obtain the phosphate-loaded biochar.
4. The curing agent for heavy metal-contaminated soil according to claim 1 or 3, characterized in that: the biochar is prepared by drying one or more of coffee grounds, tea foams and traditional Chinese medicine residues at 105 ℃ of 100-.
5. The curing agent for heavy metal contaminated soil according to claim 1, wherein: the quicklime powder is prepared by the following method: and (3) drying the quick lime with CaO content of more than 96% by adopting airflow at the temperature of 100-250 ℃ until the water content is less than 2%, and grinding the quick lime through a 150-200-mesh sieve.
6. The method of preparing the curing agent for heavy metal contaminated soil according to claim 1, comprising the steps of: mixing the steel slag powder, the quicklime powder and the phosphate-loaded biochar according to the weight percentage, stirring for 0.5-1h by a dry method until the mixture is uniform, and then sieving by a sieve of 150 meshes and 200 meshes to obtain the curing agent.
7. The method of using the curing agent for heavy metal contaminated soil according to claim 1, wherein: and mixing and stirring the curing agent and the heavy metal polluted soil, wherein the dosage of the curing agent is 5-15% of the dry weight of the heavy metal polluted soil, and the water content of the heavy metal polluted soil is 16-30%.
8. The method for applying the curing agent for heavy metal contaminated soil according to claim 7, wherein: the content of particles with the particle diameter of less than 0.075mm in the heavy metal polluted soil is 65-100%, wherein the content of heavy metal lead is more than 2000mg/kg, the content of heavy metal zinc is more than 2000mg/kg, the content of heavy metal copper is more than 2000mg/kg, and the content of heavy metal nickel is more than 2000 mg/kg.
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| CN109133822B (en) * | 2018-10-08 | 2021-01-12 | 苏州市泽镁新材料科技有限公司 | Composite magnesium oxide-based curing agent, preparation method and application |
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