CN105950164A - Heavy metal polluted soil repairing agent and repairing method thereof - Google Patents

Abstract

The invention provides a remediation agent for heavy metal polluted soil, comprising porous carbon and iron-reducing bacteria agent, which is prepared according to the following steps: (1) pulverizing the porous carbon, and then performing sterilization treatment; (2) making the iron-reducing bacteria agent Mix with porous charcoal, vibrate and cultivate, then add carboxymethyl cellulose, and mix evenly to prepare the heavy metal polluted soil remediation agent. The invention utilizes the fine structure of the porous carbon and the various minerals it contains to provide a good place for the growth and reproduction of active microorganisms such as iron-reducing bacteria; the adsorption of the porous carbon can enrich the heavy metals in the soil, and then attach The iron-reducing bacteria on the carbon particles passivated heavy metals, and the synergistic effect of the two greatly accelerated the bioremediation process of heavy metal-contaminated soil.

Description

A kind of heavy metal polluted soil remediation agent and remediation method

technical field

The invention relates to the field of soil remediation, in particular to a heavy metal contaminated soil remediation agent and a remediation method.

Background technique

Heavy metal pollution in farmland not only leads to soil degradation, the reduction of crop yield and quality, but also may threaten human health through direct contact and food chain transmission. Therefore, the remediation of heavy metal-contaminated soil has become a hot spot at home and abroad in recent years. At present, the remediation of heavy metal-contaminated soil mainly includes physical, chemical, biological and other technical measures, but most of these measures are difficult to apply in general production due to cumbersome methods and high costs, and each method has its own advantages and disadvantages.

The microbial remediation technology of heavy metal-contaminated soil generally uses microbial adsorption and oxidation-reduction to achieve the remediation of heavy metal-contaminated soil; among them, in-situ microbial remediation is more commonly used, that is, without destroying the basic structure of the soil, relying on Indigenous or exogenous microorganisms transform heavy metals in soil into forms with low toxicity or interact with soil minerals to age and fix heavy metals. Compared with traditional physical and chemical remediation methods, microbial remediation engineering is simple, the treatment cost is lower, and the negative impact on soil fertility and metabolic activity is small, which can avoid the impact on human health and the environment due to the transfer of pollutants. However, due to the difficulty in finding suitable strains and the difficulty in colonizing free bacteria, most of the reported microbial remediation methods have no significant effect, slow effect, and unstable repair effect, which limits the popularization and application of this technology.

Contents of the invention

The technical problem to be solved by the present invention is to provide an effective, economical and applicable heavy metal polluted soil remediation agent.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme: a heavy metal polluted soil remediation agent, comprising porous carbon and iron-reducing bacteria agent.

Porous carbon is a porous substance made from plant raw materials by high-temperature carbonization. Common porous carbon materials include charcoal, bamboo charcoal, straw charcoal, rice husk charcoal, etc. The porous charcoal of the present invention can be selected from charcoal, bamboo charcoal, straw charcoal, rice husk charcoal, or a mixture of two or more in any proportion, and commercially available products can be selected, such as the charcoal products produced by Shanghai Hainuo Carbon Industry Co., Ltd. It can also be produced by itself according to the existing method of making biochar, such as solid products obtained after carbonization of wood and bamboo, crop straw, and rice husk in a carbonization furnace at 500-650°C. Porous carbon has rich pore structure and huge specific surface area, strong surface adsorption capacity, high affinity for organic and inorganic pollutants, and can be used as a passivator for pollutants in soil. Applying porous charcoal to soil can improve soil structure, loosen soil, retain water and fertilizer, and promote the reproduction of soil microorganisms.

Iron-reducing bacteria can oxidize organic matter and reduce ferric oxide to obtain energy. Iron-reducing bacteria have powerful metabolic functions, and they can utilize many other electron acceptors besides Fe(Ⅲ), including many toxic heavy metals and metalloids, such as Mn(Ⅳ), Cr(Ⅵ), Co(Ⅲ), As( Ⅴ), Se(Ⅴ), etc. and radioactive elements U(Ⅵ), Tc(Ⅶ), V(V), etc., so as to play the role of reduction detoxification or reduction fixation on these toxic heavy metals, or make them harmful to the environment due to reduction reduced toxicity.

Further, the heavy metal contaminated soil remediation agent is prepared according to the following steps:

(1) Porous carbon is pulverized, and then sterilized;

(2) Mix the iron-reducing bacteria agent with the porous carbon, and after vibrating culture, add carboxymethyl cellulose, and mix evenly to prepare the heavy metal-contaminated soil remediation agent.

The use of the carboxymethyl cellulose as a cross-linking agent can strengthen the adsorption and fixation of the porous carbon to the iron-reducing bacteria.

Further, the particle diameter of the porous carbon is 0.80-1.60 mm. The smaller the particle size and the larger the specific surface area of porous carbon, the stronger the adsorption capacity, but the particle size is too small, which is not conducive to the preparation and operation of repair particles. The above particle size range can combine the above two factors to achieve the best effect.

Further, the iron-reducing bacteria agent contains Bacillus cereus, Geobacter sulfur-reducing and Shewanella oneida. The above-mentioned mixed bacteria can adapt to different environmental conditions and ensure the reduction of ferric iron and passivation of heavy metals by microorganisms.

Further, the iron-reducing bacteria agent contains Bacillus cereus, Geobacter sulfur-reducing and Shewanella oneida, and the shaking culture temperature is 28-30° C., and the time is 24-48 hours. This culture condition is most suitable for the growth and reproduction of the above-mentioned iron-reducing bacteria.

Further, the effective number of viable bacteria of the iron-reducing bacteria agent is ≥1.0×10 ⁹ /ml, and the addition amount is 15-30 ml of the iron-reducing bacteria agent per 100 g of porous carbon. To ensure that the initial bacterial density in the soil can meet the requirements of bioremediation of contaminated soil.

The present invention also provides a method for remediating heavy metal-contaminated soil, comprising the following steps: taking heavy metal-contaminated soil, adding the above-mentioned heavy metal-contaminated soil remediation agent, the weight ratio of the above-mentioned heavy metal-contaminated soil remediation agent to heavy metal-contaminated soil is 1:5-10, After mixing evenly, stack and repair at room temperature.

Further, the heavy metal-contaminated soil was pulverized in advance to pass through a 1mm sieve. Fine soil particles are conducive to full contact with the restoration agent.

Further, during the stack restoration process, the humidity of the heavy metal-contaminated soil is maintained at 50-70% of the maximum field water holding capacity. The maximum water holding capacity in the field refers to the amount of water held when all the pores of the soil are filled with water, that is, the maximum holding (containing) water that the soil can hold. Keeping 50-70% of the maximum water holding capacity in the field is conducive to the full effect of the repair agent and soil particles, and will not affect the growth of microorganisms.

The beneficial effects of the present invention are:

1. The present invention uses porous carbon as the immobilization carrier. Porous carbon is a kind of highly aromatized refractory solid material produced by pyrolysis and carbonization of plant biomass under the condition of complete or partial anoxic, and has a porous microstructure. At the same time, its surface has rich functional groups such as carbonyl and carboxyl, endowing it with special functions such as adsorption of heavy metals and organic pollutants in the soil; at the same time, porous carbon can also improve the soil aggregate structure, activate the soil, and promote Soil water retention, fertilizer retention, aeration, improve soil fertility.

2. The present invention selects iron-reducing bacteria agent to process heavy metals. Iron-reducing bacteria can reduce heavy metals (Cr, As, Cu, etc.) The interaction of minerals ages heavy metals (Pb, Cd, Zn, etc.) to achieve the purpose of passivation and immobilization of heavy metals.

3. The present invention utilizes the fine structure of the porous carbon and the various minerals it contains to provide a good place for the growth and reproduction of active microorganisms such as iron-reducing bacteria; the adsorption of the porous carbon can enrich the heavy metals in the soil, Then the iron-reducing bacteria attached to the carbon particles passivated the heavy metals, and the synergistic effect of the two greatly accelerated the bioremediation process of heavy metal-contaminated soils. Tests showed that the present invention has a high remediation rate of Cd, Cr, Cu, Pb and Zn Respectively can reach 51.5%, 80.6%, 44.6%, 45.1%, 57.2% or more, the effect is remarkable and stable.

4. The porous carbon material used in the present invention is cheap, low in cost, and has a wide range of sources; the preparation method of the heavy metal-contaminated soil remediation agent is simple, and it is convenient to apply. It can be applied according to the method for remediating heavy metal-contaminated soil provided by the present invention, or it can be applied separately Farmland, or mixed with base fertilizer and applied, saves labor and effort when used. The invention has the advantages of microbial remediation technology, and has outstanding heavy metal immobilization, passivation and aging effects, and has good application prospects.

5. Applying according to the method for remediating heavy metal-contaminated soil provided by the present invention is not only simple and easy to implement, but also has low environmental requirements, low remediation cost and high remediation efficiency.

detailed description

The present invention will be further described below in conjunction with embodiment:

In the following examples:

The heavy metal-contaminated soil was taken from the polluted soil around a metal mining area. After removing impurities such as stones and tree roots, the soil is naturally air-dried for later use. The soil type is sandy clay loam, the specific physical and chemical properties are as follows: pH 5.90, organic matter content 1.68%, cation exchange capacity 19.52cmol/kg, clay, silt and sand content are 233g/kg, 352g/kg and 415g/kg/ kg. The total amount of heavy metals Cd, Cr, Cu, Pb and Zn in the soil is 1.22mg/kg, 267mg/kg, 113mg/kg, 295mg/kg and 452mg/kg respectively, of which the soil DTPA leaching state Cd, Cr, Cu, Pb The contents of Zn and Zn are 0.33mg/kg, 61.7mg/kg, 31.2mg/kg, 44.3mg/kg and 113.5mg/kg respectively;

The iron-reducing bacteria agent is made by mixing three strains of Bacillus cereus ATCC 10987, Geobacter sulfurreducens ATCC 51573 and Shewanella oneidenis MR-1ATCC 70050 , the strain culture method is as follows: LB medium, pH 7.0, 30°C aerobic culture for 48-72h; LB medium composition: peptone 10g/L, yeast extract 5g/L, sodium chloride 5g/L;

The composition of Fe(Ⅲ) reducing medium is: Na ₂ HPO ₄ 7H ₂ O 12.8g/L, KH ₂ PO ₄ 7H ₂ O 3.0g/L, NH ₄ Cl 1.0g/L, yeast extract 2.0g /L, NaAc 8.2g/L;

The porous charcoal used in Examples 1 to 4 is charcoal, bamboo charcoal, straw charcoal, and rice husk charcoal products purchased from Shanghai Hainuo Carbon Industry Co., Ltd. sequentially.

Example 1

A heavy metal contaminated soil remediation agent is prepared according to the following steps:

(1) Pulverize the porous carbon with a pulverizer or grind it with a ball mill, and sieve out particles with a diameter of 0.80 mm, then aerate the sieved porous carbon in distilled water for 4 hours to remove carbon powder and dust attached to its surface, Dry and reserve;

(2) Porous carbon is filled in the Erlenmeyer flask with stopper as the immobilized carrier, and the iron-reducing bacterial agent is inoculated at a ratio of 25ml/100g porous carbon, and the effective number of viable bacteria of the iron-reducing bacterial agent is 1.0× ¹⁰⁹ /ml, Among them, the effective number ratio of Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida is 0.5:0.5:1, then add Fe(Ⅲ) reducing medium, and then shake culture at 30°C After 24 hours, add carboxymethyl cellulose at a ratio of 3g/100g (porous carbon + iron-reducing bacterial agent), stir thoroughly, and mix evenly to obtain the heavy metal-contaminated soil remediation agent.

The method for remediating heavy metal-contaminated soil by using the above-mentioned heavy metal-contaminated soil remediation agent comprises the following steps: crushing the heavy metal-contaminated soil to pass through a 1mm sieve, adding the heavy metal-contaminated soil remediation agent, and the weight ratio of the heavy metal-contaminated soil remediation agent to the heavy metal-contaminated soil is 1 : 5. After mixing evenly, stack and repair at room temperature. During the process of stacking and repairing, maintain the humidity of the heavy metal-contaminated soil at 60% of the maximum water holding capacity in the field. Contents of Cd, Cr, Cu, Pb and Zn in DTPA-leached state of remediation soil.

The results showed that the pH value of the repaired soil rose to 7.4; the concentrations of Cd, Cr, Cu, Pb and Zn in the DTPA extraction state were 0.16mg/kg, 14.1mg/kg, 17.3mg/kg, 26.7mg/kg, respectively and 48.6mg/kg, decreased by 51.5%, 77.1%, 44.6%, 39.7% and 57.2%, respectively. The leaching state of DTPA represents the effective content of heavy metals in the soil; the leaching state of DTPA is greatly reduced, indicating that the heavy metals in the soil are fixed and passivated.

Example 2

A heavy metal contaminated soil remediation agent is prepared according to the following steps:

(1) Pulverize the porous carbon with a pulverizer or grind it with a ball mill, and sieve out particles with a diameter of 1.60 mm, then aerate the sieved porous carbon in distilled water for 4 hours to remove carbon powder and dust attached to its surface, Dry and reserve;

(2) Porous carbon is filled in the Erlenmeyer flask with stopper as the immobilized carrier, and the iron-reducing bacterial agent is inoculated at a ratio of 20ml/100g porous carbon, and the effective number of viable bacteria of the iron-reducing bacterial agent is 1.3×10 ⁹ pieces/ml, Among them, the effective number ratio of Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida is 1.2:0.8:1, then add Fe(Ⅲ) reducing medium, and then shake culture at 30°C After 36 hours, add carboxymethyl cellulose at a ratio of 4g/100g (porous carbon + iron-reducing bacteria agent), stir well, and mix evenly to obtain the heavy metal-contaminated soil remediation agent.

The method for remediating heavy metal-contaminated soil by using the above-mentioned heavy metal-contaminated soil remediation agent comprises the following steps: crushing the heavy metal-contaminated soil to pass through a 1mm sieve, adding the heavy metal-contaminated soil remediation agent, and the weight ratio of the heavy metal-contaminated soil remediation agent to the heavy metal-contaminated soil is 1 : 7.5, after mixing evenly, stack and repair at room temperature, during the process of stacking and repairing, maintain the humidity of the heavy metal-contaminated soil at 70% of the maximum water holding capacity in the field, after stacking and repairing for 30 days, get the repaired soil, and then measure Contents of Cd, Cr, Cu, Pb and Zn in DTPA-leached state of remediation soil.

The results showed that the pH value of the repaired soil rose to 7.7; the concentrations of Cd, Cr, Cu, Pb and Zn in the DTPA extraction state were 0.15mg/kg, 9.7mg/kg, 18.2mg/kg, 24.3mg/kg respectively and 44.7mg/kg, decreased by 54.5%, 84.3%, 41.7%, 45.1% and 60.6%, respectively.

Example 3

A heavy metal contaminated soil remediation agent is prepared according to the following steps:

(1) Pulverize the porous carbon with a pulverizer or grind it with a ball mill, and sieve out particles with a diameter of 1.20 mm, then aerate the sieved porous carbon in distilled water for 4 hours to remove carbon powder and dust attached to its surface, Dry and reserve;

(2) Porous carbon is filled in the Erlenmeyer flask with stopper as the immobilized carrier, and the iron-reducing bacteria agent is inoculated at a ratio of 30ml/100g porous carbon, and the effective number of viable bacteria of the iron-reducing bacteria agent is 1.1×10 ⁹ pieces/ml, Among them, the effective number ratio of Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida is 0.5:1:1, then add Fe(Ⅲ) reducing medium, and then shake culture at 28°C After 48 hours, add carboxymethyl cellulose at a ratio of 2g/100g (porous carbon + iron-reducing bacteria agent), stir well, and mix well to obtain the heavy metal-contaminated soil remediation agent.

The method for remediating heavy metal-contaminated soil by using the above-mentioned heavy metal-contaminated soil remediation agent comprises the following steps: crushing the heavy metal-contaminated soil to pass through a 1mm sieve, adding the heavy metal-contaminated soil remediation agent, and the weight ratio of the heavy metal-contaminated soil remediation agent to the heavy metal-contaminated soil is 1 : 6. After mixing evenly, stack and repair at room temperature. During the process of stacking and repairing, maintain the humidity of the heavy metal-contaminated soil at 50% of the maximum water holding capacity in the field. Contents of Cd, Cr, Cu, Pb and Zn in DTPA-leached state of remediation soil.

The results showed that the pH value of the repaired soil rose to 7.1; the concentrations of Cd, Cr, Cu, Pb and Zn in the DTPA extraction state were 0.18mg/kg, 21.5mg/kg, 15.7mg/kg, 32.0mg/kg respectively and 50.7mg/kg, decreased by 45.5%, 65.2%, 49.7%, 27.8% and 55.3%, respectively.

Example 4

A heavy metal contaminated soil remediation agent is prepared according to the following steps:

(1) Pulverize the porous carbon with a pulverizer or grind it with a ball mill, and sieve out particles with a diameter of 1.60 mm, then aerate the sieved porous carbon in distilled water for 4 hours to remove carbon powder and dust attached to its surface, Dry and reserve;

(2) Porous carbon is filled in the Erlenmeyer flask with stopper as the immobilized carrier, and the iron-reducing bacteria agent is inoculated at a ratio of 15ml/100g porous carbon, and the effective number of viable bacteria of the iron-reducing bacteria agent is 1.6×10 ⁹ pieces/ml, Among them, the effective number ratio of Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida is 1:0.5:1, then add Fe(Ⅲ) reducing medium, and then shake culture at 30℃ After 48 hours, add carboxymethyl cellulose at a ratio of 3g/100g (porous carbon + iron-reducing bacteria agent), stir well, and mix evenly to obtain the heavy metal-contaminated soil remediation agent.

The method for remediating heavy metal-contaminated soil by using the above-mentioned heavy metal-contaminated soil remediation agent comprises the following steps: crushing the heavy metal-contaminated soil to pass through a 1mm sieve, adding the heavy metal-contaminated soil remediation agent, and the weight ratio of the heavy metal-contaminated soil remediation agent to the heavy metal-contaminated soil is 1 : 10. After mixing evenly, stack and repair at room temperature. During the process of stacking and repairing, maintain the humidity of the heavy metal-contaminated soil at 70% of the maximum water holding capacity in the field. Contents of Cd, Cr, Cu, Pb and Zn in DTPA-leached state of remediation soil.

The results showed that the pH value of the repaired soil rose to 6.9; the concentrations of Cd, Cr, Cu, Pb and Zn in the DTPA leaching state were 0.19mg/kg, 12.0mg/kg, 19.5mg/kg, 19.5mg/kg respectively and 59.9mg/kg, decreased by 42.4%, 80.6%, 37.5%, 56.0% and 47.2%, respectively.

Example 5

Cabbage planting experiment

In order to verify the repairing effect of the present invention to heavy metals, after the stacking and repairing process of 30d in embodiment 2 ends, transplant pak choy seedlings in the unrepaired heavy metal contaminated soil and the soil after repairing respectively, and the growth period of pak choi seedlings is After 30 days, the concentration of heavy metals in the shoots and roots of pakchoi was detected.

The results showed that the upper and root Cd concentrations of pakchoi grown on unremediated heavy metal-contaminated soil were 0.72 mg/kg and 2.23 mg/kg, Cr were 57.3 mg/kg, 157.9 mg/kg, and Cu were 38.9 mg /kg, 112.4mg/kg, Pb were 12.4mg/kg, 53.1mg/kg, Zn were 87.1mg/kg, 177.4mg/kg respectively; 0.17mg/kg and 0.84mg/kg, Cr are 20.3mg/kg, 61.6mg/kg, Cu are 14.4mg/kg, 44.1mg/kg, Pb are 2.9mg/kg, 21.6mg/kg, Zn was 50.9 mg/kg and 83.9 mg/kg, respectively.

The above experimental results can further prove that the present invention has a very good remediation effect on heavy metal polluted soil.

Example 6

Experiment on Effect of Iron Reducing Bacteria Agent on Soil Remediation Effect

The test is divided into four groups, and all four groups are implemented according to the preparation method of the heavy metal-contaminated soil remediation agent provided in Example 1 and the method for remediating heavy metal-contaminated soil, wherein the iron-reducing bacteria agent of the first group is the same as that of Example 1, and the second The iron-reducing bacteria of the first group consisted of only the same amount of Geobacter sulfur-reducing, the iron-reducing bacteria of the third group only included the same amount of Bacillus cereus, and the iron-reducing bacteria of the fourth group only included the same amount of Oneida Shewanella, and finally the contents of Cd, Cr, Cu, Pb and Zn in the DTPA leaching state of the repaired soil were determined respectively. The results are shown in Table 1 below.

Table 1

From the above results, it can be seen that the restoration effect of the mixed bacterial agent of Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida is far better than that of a single bacteria, indicating that the above-mentioned mixed bacteria have better adaptability. powerful.

After the research of the inventor, the ratio of the effective number of viable bacteria of Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida is (0.5～1.2): (0.5～1): 1, heavy metal contaminated soil remediation agent The restoration effect is better, and the environmental adaptability is better.

It should be understood that the examples and implementations described herein are for illustration only, and those skilled in the art can make various modifications or changes based on them, all of which belong to the protection scope of the present invention without departing from the spirit of the present invention.

Claims (9)

1. A heavy metal contaminated soil remediation agent, characterized in that: it comprises porous charcoal and an iron-reducing bacterium agent. 2. The heavy metal contaminated soil remediation agent as claimed in claim 1, characterized in that: it is prepared according to the following steps: (1) Porous carbon is pulverized, and then sterilized; (2) Mix the iron-reducing bacteria agent with the porous carbon, and after vibrating culture, add carboxymethyl cellulose, and mix evenly to prepare the heavy metal-contaminated soil remediation agent. 3. The heavy metal contaminated soil remediation agent according to claim 1 or 2, characterized in that: the particle size of the porous carbon is 0.80-1.60 mm. 4. The heavy metal contaminated soil remediation agent according to claim 1 or 2, characterized in that: said iron-reducing bacteria agent contains Bacillus cereus, Geobacter sulfur-reducing and Shewanella oneida. 5. heavy metal contaminated soil remediation agent as claimed in claim 2, is characterized in that: contain Bacillus cereus, Geobacter sulfur reducing and Shewanella oneida in the described iron-reducing bacterial agent, the temperature of shaking culture is 28～30℃, the time is 24～48h. 6. The heavy metal-contaminated soil remediation agent according to claim 1 or 2, characterized in that: the effective number of viable bacteria of the iron-reducing bacteria agent is ≥1.0× ¹⁰⁹ /ml, and the addition amount is 15 per 100 g of porous carbon ~30ml iron-reducing bacteria agent. 7. A method for remediating heavy metal-contaminated soil, characterized in that: comprising the following steps: taking heavy metal-contaminated soil, adding the heavy metal-contaminated soil remediation agent according to any one of claims 1 to 6, and said heavy metal-contaminated soil remediation The weight ratio of agent to heavy metal polluted soil is 1:5-10. After mixing evenly, stack and repair at room temperature. 8. The method for remediating heavy metal-contaminated soil as claimed in claim 7, characterized in that: the heavy metal-contaminated soil is pulverized in advance to pass through a 1 mm sieve. 9. The method for remediating heavy metal-contaminated soil according to claim 8 or 9, characterized in that: during the stacking and remediation process, the humidity of the heavy metal-contaminated soil is maintained at 50-70% of the maximum water holding capacity in the field.