Method for repairing phenanthrene-cadmium co-polluted environment by using biochar-based immobilized microbial agent

Abstract

The invention discloses a method for repairing a phenanthrene-cadmium co-polluted environment by using a biochar-based immobilized microbial inoculum, the method is characterized in that the phenanthrene-cadmium co-polluted environment is treated by using the biochar-based immobilized microbial inoculum, and the biochar-based immobilized microbial inoculum is prepared by using modified peanut shell biochar as a carrier. The modified peanut shell biochar is loaded with a phenanthrene efficient degrading flora SMP, and the phenanthrene efficient degrading flora SMP is obtained by domesticating coking plant sludge as a raw material and polycyclic aromatic hydrocarbon as a carbon source. The method has the advantages of being high in treatment efficiency, good in remediation effect, simple in process, convenient to operate, low in treatment cost and the like, phenanthrene in the soil can be effectively removed, cadmium in the soil can be effectively fixed, the use value is high, the application prospect is good, and a green and environment-friendly biological way is provided for remediation of the phenanthrene-cadmium co-polluted environment.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental bioremediation, and in particular relates to a method for repairing a phenanthrene-cadmium co-polluted environment by utilizing a biochar-based immobilized bacterial agent. Background Art

[0002] Polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) often coexist in polluted environments. Their pollution sources include automobile exhaust emissions, fossil fuel combustion, metal smelting, waste incineration, wastewater discharge, and other pathways. Phenanthrene and cadmium are representative substances of PAHs and heavy metals, respectively. Because both have acute and chronic toxicity, they exist in the environment for a long time, especially in soil and sediments as the common confluence of phenanthrene and cadmium, which will threaten ecological security and human health. Therefore, how to repair phenanthrene-cadmium co-contaminated soil has received more and more attention.

[0003] At present, how to repair soil contaminated by single phenanthrene or cadmium has been widely studied. Physical methods include adsorption, leaching, electrodynamic remediation, etc., and chemical methods include electrochemistry, photocatalysis, microorganisms and advanced oxidation remediation. Although the above methods have achieved good results in the remediation of single pollutants, it is difficult to efficiently repair the environment of the two combined pollution at the same time. Due to the large differences in structure and characteristics between HMs and PAHs, some remediation methods are effective in remediating single pollution, but inefficient in remediating co-pollution; at the same time, phenanthrene and cadmium interact with each other, affecting their migration and transformation in the environment. For example, advanced oxidation can effectively remove phenanthrene from soil, but has limited effect on the remediation of cadmium pollution; physical methods such as adsorption cannot change the structure and morphology of pollutants and have the risk of secondary pollution. Among the existing treatment methods, microbial remediation has attracted widespread attention due to its safety, environmental friendliness and economy. Microorganisms can absorb and decompose phenanthrene during metabolism, and microorganisms also have a certain adsorption capacity for cadmium. However, the inventors of this application found in their previous studies that microbial remediation of phenanthrene and cadmium co-contaminated environments has the following deficiencies: First, in a complex environment such as natural soil, free degrading microorganisms have poor environmental adaptability, which greatly reduces the degradation efficiency of microorganisms; second, the adsorption and fixation effect of microorganisms on cadmium is very limited; third, a single type of degrading bacteria in a real soil environment is often difficult to become the dominant bacterial flora of the soil due to the influence of extreme environmental conditions and the competition of indigenous microorganisms, resulting in a decrease in degradation efficiency, and the remediation efficiency of phenanthrene, a persistent organic pollutant, is very limited. Therefore, finding a method for remediating phenanthrene-cadmium co-contaminated environments using biochar-based immobilized bacterial agents with high treatment efficiency and good remediation effect is of great significance for effectively remediating phenanthrene-cadmium co-contaminated soils. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent with high treatment efficiency, good repair effect, simple process, convenient operation and low treatment cost.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent, the method comprising treating a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent; the biochar-based immobilized bacterial agent uses modified peanut shell biochar as a carrier, and the modified peanut shell biochar is loaded with a phenanthrene-efficient degrading bacterial community SMP; the phenanthrene-efficient degrading bacterial community SMP uses coking plant sludge as a raw material and polycyclic aromatic hydrocarbons as a carbon source, and is obtained after domestication.

[0007] The above method is further improved, and the preparation method of the phenanthrene efficient degrading bacterial community SMP comprises the following steps: acclimating the coking plant sludge in a polycyclic aromatic hydrocarbons-containing culture medium with polycyclic aromatic hydrocarbons concentrations of 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, and 50 mg / L in sequence to obtain the phenanthrene efficient degrading bacterial community SMP.

[0008] The above method is further improved, wherein the duration of each cycle in the acclimation process is 7 days, the acclimation temperature is 30° C. to 35° C., the acclimation is carried out under oscillation conditions, and the oscillation speed is 160 r / min;

[0009] The volume ratio of the coking plant sludge to the PAH-containing culture medium is 1:20, and the PAH-containing culture medium further contains phenanthrene, pyrene, fluorene, fluoranthene and inorganic salt culture solution; the total mass of phenanthrene, pyrene, fluorene and fluoranthene in the PAH-containing culture medium is the same as the mass of the PAHs, and the mass ratio of phenanthrene, pyrene, fluorene and fluoranthene in the PAH-containing culture medium is 1:1:1:1; the inorganic salt culture solution is formed by mixing trace element solution, PBS buffer, magnesium ion solution, iron ion solution and water, and the volume ratio of the trace element solution, PBS buffer, magnesium ion solution, iron ion solution and water is 1:5:3:1:990; the trace element solution contains the following components: 44.7mg / L MnSO4·H2O, 68.6mg / L ZnSO4·7H2O, 34.7mg / L (NH4)MoO2·4H2O; the PBS buffer solution comprises the following components: 25.8g / L K2HPO4·3H2O, 33.4g / L Na2HPO4, 8.7g / L KH2PO4, 5g / L NH4Cl; the magnesium ion solution comprises the following components: 4.6g / L MgSO4·7H2O; the iron ion solution comprises the following components: 0.42g / L FeCl3·6H2O.

[0010] The above method is further improved, and the preparation method of the biochar-based immobilized bacterial agent comprises the following steps:

[0011] (1) adding the phenanthrene-efficient degrading bacterial community SMP to a phenanthrene-containing culture medium for activation culture to prepare a bacterial suspension;

[0012] (2) The bacterial suspension obtained in step (1) is mixed with the modified peanut shell biochar and cultured to obtain a biochar-based immobilized bacterial agent.

[0013] The above method is further improved, in step (1), the volume ratio of the phenanthrene efficient degrading bacterial community SMP to the phenanthrene-containing culture medium is 1:9, the concentration of phenanthrene in the phenanthrene-containing culture medium is 50 mg / L to 100 mg / L, and the OD of the bacterial suspension is 600 The phenanthrene-containing culture medium further comprises an inorganic salt culture solution, which is a mixture of a trace element solution, a PBS buffer solution, a magnesium ion solution, an iron ion solution and water, and the volume ratio of the trace element solution, the PBS buffer solution, the magnesium ion solution, the iron ion solution and water is 1:5:3:1:990; the trace element solution comprises the following components: 44.7mg / L MnSO4·H2O, 68.6mg / L ZnSO4·7H2O, 34.7mg / L (NH4)MoO2·4H2O; the PBS buffer solution comprises the following components: 25.8g / L K2HPO4·3H2O, 33.4g / L Na2HPO4, 8.7g / L KH2PO4, 5g / L NH4Cl; the magnesium ion solution comprises the following components: 4.6g / L MgSO4·7H2O; the iron ion solution comprises the following components: 0.42g / LFeCl3·6H2O; the activation culture temperature is 30°C to 35°C, and the activation culture time is 3d;

[0014] In step (2), the mass volume ratio of the modified peanut shell biochar to the bacterial suspension is 5g-10g:100mL, the temperature is controlled at 30°C-35°C during the culture process, the culture time is 18h-24h, and the modified peanut shell biochar also includes the following treatment before use: sterilizing the modified peanut shell biochar.

[0015] The above method is further improved, in step (2), the preparation method of modified peanut shell biochar comprises the following steps:

[0016] (a) pyrolyzing peanut shells to obtain peanut shell biochar; the pyrolysis temperature is 500° C., and the pyrolysis time is 2 h;

[0017] (b) Mixing peanut shell biochar and potassium hydroxide and performing pyrolysis to obtain modified peanut shell biochar; the pyrolysis temperature is 300° C., and the pyrolysis time is 1 hour.

[0018] The above method is further improved, in step (a), the pyrolysis is carried out under nitrogen or inert atmosphere, the heating rate during the pyrolysis is 10°C / min, and the peanut shells are further processed before use: washing, drying, crushing, and sieving the peanut shells; the mesh size of the sieving is 60 meshes;

[0019] In step (b), the mass ratio of the peanut shell biochar to potassium hydroxide is 1:2.5, the pyrolysis is carried out under nitrogen or an inert atmosphere, and the heating rate during the pyrolysis process is 10°C / min.

[0020] The above method is further improved, and the specific process of the treatment is: adding a biochar-based immobilized bacterial agent to a phenanthrene-cadmium co-contaminated environment for repair to achieve the removal of phenanthrene and the fixation of cadmium in the environment.

[0021] The above method is further improved, wherein the phenanthrene-cadmium co-contaminated environment is phenanthrene-cadmium co-contaminated soil or phenanthrene-cadmium co-contaminated water, and the volume mass ratio of the biochar-based immobilized bacterial agent to the phenanthrene-cadmium co-contaminated soil is 100mL:500g.

[0022] The above method is further improved, wherein the pH value of the phenanthrene-cadmium co-contaminated soil is 3.58, the soil in the phenanthrene-cadmium co-contaminated soil is acidic red soil, the initial concentration of phenanthrene in the phenanthrene-cadmium co-contaminated soil is 100 mg / kg, the initial concentration of cadmium in the phenanthrene-cadmium co-contaminated soil is 10 mg / kg, the remediation time is ≥50 days, and the remediation temperature is 20°C to 36°C.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] In view of the problem that the existing technology has poor effect and low efficiency in repairing phenanthrene-cadmium co-contaminated soil, the present invention creatively proposes a method for repairing phenanthrene-cadmium co-contaminated environment using biochar-based immobilized bacteria, and uses biochar-based immobilized bacteria to treat phenanthrene-cadmium co-contaminated environment, and the biochar-based immobilized bacteria include modified peanut shell biochar carrier and phenanthrene efficient degradation bacteria SMP loaded thereon. The biochar-based immobilized bacteria used in the present invention, on the one hand, the phenanthrene efficient degradation bacteria SMP has good biological activity and tolerance, and the interspecies synergy of the mixed bacteria is conducive to promoting the complete degradation of phenanthrene and shortening the degradation cycle of phenanthrene; on the other hand, the modified peanut shell biochar can not only provide a shelter for the phenanthrene efficient degradation bacteria SMP, reduce the impact of adverse environmental factors, and be conducive to the high-density enrichment of the phenanthrene efficient degradation bacteria SMP and maintain biological activity, but also promote the migration and fixation of cadmium to the biochar carrier, reduce the bioavailability of cadmium in the soil, and at the same time, as a soil conditioner, improve the physical and chemical properties of the soil, and finally achieve efficient and thorough removal of phenanthrene and effective fixation of cadmium in the phenanthrene-cadmium co-contaminated environment. The method of the present invention has the advantages of high treatment efficiency, good repair effect, simple process, convenient operation, low treatment cost, etc. It can effectively remove phenanthrene in the soil and fix cadmium in the soil, has high use value and good application prospects, and provides a green and environmentally friendly biological approach for the restoration of phenanthrene-cadmium co-polluted environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a heat map of the phenanthrene efficient degrading bacterial community SMP at the genus level in Example 1 of the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the biochar-based immobilized bacterial agent in Example 1 of the present invention.

[0027] Figure 3 This is a diagram showing the removal effect of the biochar-based immobilized bacterial agent on phenanthrene in phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention.

[0028] Figure 4 This is a diagram showing the effect of the biochar-based immobilized bacterial agent in Example 1 of the present invention on the remediation of cadmium in phenanthrene-cadmium co-contaminated soil.

[0029] Figure 5 This is a diagram of soil properties after the biochar-based immobilized bacterial agent was used to repair the phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention.

[0030] Figure 6 This is a graph of the soil Simpson index after the biochar-based immobilized bacterial agent was used to repair the phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention.

[0031] Figure 7 This is a comparison chart of seed germination rates after the biochar-based immobilized bacterial agent was used to repair the phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention.

[0032] Figure 8 This is a diagram showing the removal effect of phenanthrene in water by the phenanthrene efficient degrading bacteria SMP in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0034] Embodiment 1:

[0035] A method for repairing a phenanthrene-cadmium co-contaminated environment using a biochar-based immobilized bacterial agent of the present invention, specifically repairing phenanthrene-cadmium co-contaminated soil using a biochar-based immobilized bacterial agent, comprising the following steps:

[0036] According to the volume mass ratio of the biochar-based immobilized bacteria agent to the phenanthrene-cadmium co-contaminated soil of 100mL:500g, the biochar-based immobilized bacteria agent is added to the phenanthrene-cadmium co-contaminated soil (initial pH value is 3.58), the cadmium concentration in the phenanthrene-cadmium co-contaminated soil is 10mg / kg, the phenanthrene concentration is 100mg / kg, the phenanthrene-cadmium co-contaminated soil is southern acidic red soil, the soil moisture content is maintained at 20%, and the room temperature (20℃~36℃) is protected from light for 90 days to achieve the removal of phenanthrene and cadmium in the soil. The method of the present invention is named: soil repair by immobilized bacteria agent.

[0037] Unremediated soil: Phenanthrene-cadmium co-contaminated soil without any remediation materials added, other conditions being the same.

[0038] In this embodiment, the biochar-based immobilized bacterial agent used is a modified peanut shell biochar as a carrier, and the modified peanut shell biochar is loaded with a phenanthrene-efficient degrading bacterial community SMP; wherein, the phenanthrene-efficient degrading bacterial community SMP is obtained after domestication using coking plant sludge as raw material and polycyclic aromatic hydrocarbons as carbon source.

[0039] In this embodiment, the preparation method of the biochar-based immobilized bacterial agent used includes the following steps:

[0040] (1) Preparation of SMP, a highly efficient phenanthrene-degrading bacterial community

[0041] According to the volume ratio of coking plant sludge to PAH-containing inorganic salt culture medium of 1:20, the coking plant sludge was domesticated in PAH-containing inorganic salt culture medium with PAH concentrations of 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L and 50 mg / L, respectively, that is, it was domesticated in a constant temperature shaker at a temperature of 30°C and a rotation speed of 160 r / min. Each cycle in the domestication process was 7 days. After the domestication cycle, the mother liquor of the degradation bacteria was obtained, namely, the phenanthrene efficient degrading bacteria SMP.

[0042] The inorganic salt culture medium containing polycyclic aromatic hydrocarbons also includes phenanthrene, pyrene, fluorene, fluoranthene and inorganic salt culture solution, the total mass of phenanthrene, pyrene, fluorene and fluoranthene in the culture medium is the same as the mass of polycyclic aromatic hydrocarbons, and the mass ratio of phenanthrene, pyrene, fluorene and fluoranthene is 1:1:1:1. The specific preparation method of the inorganic salt culture solution is: take 1mL of trace element solution, 5mL of PBS buffer, 3mL of magnesium ion solution and 1mL of iron ion solution, mix them evenly, and add water to make the volume to 1L. The trace element solution contains the following components: 44.7mg / L McnSO4·H2O, 68.6mg / L ZnSO4·7H2O, 34.7mg / L (NH4)MoO2·4H2O; the PBS buffer solution contains the following components: 25.8g / L K2HPO4·3H2O, 33.4g / L Na2HPO4, 8.7g / L KH2PO4, 5g / L NH4Cl; the magnesium ion solution contains the following components: 4.6g / L MgSO4·7H2O; the iron ion solution contains the following components: 0.42g / L FeCl3·6H2O.

[0043] Through microbial diversity sequence analysis, the degradation bacterial mother liquor flora was mainly composed of Sphingobium, Methylophilu and Pseudomonas, so it was named SMP.

[0044] (2) Preparation of modified peanut shell biochar

[0045] (2.1) Wash the peanut shells with ultrapure water and dry them in a 60°C oven until they are constant weight. After drying, crush the peanut shells with a grinder and pass through a 60-mesh sieve to obtain peanut shell powder, which is stored in a sealed bag. Put the peanut shell powder into a tubular electric furnace, set the temperature to 500°C, and heat it to 500°C at a heating rate of 10°C / min in a nitrogen atmosphere for 2 hours. After cooling naturally to room temperature, open the tubular furnace, grind it with an agate mortar and pass through a 60-mesh sieve to obtain peanut shell biochar.

[0046] (2.2) The peanut shell biochar obtained in step (2.1) and potassium hydroxide are mixed according to a mass ratio of peanut shell biochar to potassium hydroxide (KOH) of 1:2.5, and placed in a tube furnace. The temperature is set to 300°C, and the temperature is increased to 300°C at a heating rate of 10°C / min under a nitrogen atmosphere for pyrolysis for 1 h. After naturally cooling to room temperature, the tube furnace is opened, and the pyrolysis product is washed with ultrapure water until neutral, and dried at 60°C to constant weight to obtain modified peanut shell biochar.

[0047] (3) Preparation of biochar-based immobilized bacterial agents

[0048] (3.1) According to the volume ratio of the phenanthrene-efficient degrading bacterial community SMP to the phenanthrene-containing inorganic salt culture medium of 1:9, the degrading bacterial community mother solution obtained in step (1) was added to the phenanthrene-containing inorganic salt culture medium, wherein the phenanthrene concentration in the phenanthrene-containing inorganic salt culture medium was 100 mg / L, and the culture was carried out in a constant temperature shaker at a temperature of 30° C. and a rotation speed of 160 r / min for 3 days to obtain a phenanthrene-efficient degrading bacterial community SMP bacterial suspension, and the OD of the bacterial suspension was 600 It is 0.4~0.5.

[0049] The phenanthrene-containing inorganic salt culture medium further comprises an inorganic salt culture solution, which is the same as the inorganic salt culture solution in step (1).

[0050] (3.2) The modified peanut shell biochar obtained in step (2.2) is placed in a conical flask and sterilized in a high-pressure sterilizer at 1.5 MPa and 121° C. for 30 minutes. After the conical flask is cooled, the pretreated modified peanut shell biochar is obtained; according to the mass volume ratio of the pretreated modified peanut shell biochar to the phenanthrene efficient degrading bacteria SMP bacterial suspension of 10 g: 100 mL, the pretreated modified peanut shell biochar is added to the phenanthrene efficient degrading bacteria SMP bacterial suspension obtained in step (3.1), and cultured in a constant temperature shaker at a temperature of 30° C. for 24 hours, and the phenanthrene efficient degrading bacteria SMP is fixed on the surface and inside of the modified peanut shell biochar by the adsorption effect of the modified peanut shell biochar to obtain a biochar-based immobilized bacterial agent.

[0051] Figure 1 This is a heat map of the phenanthrene efficient degrading bacterial community SMP at the genus level in Example 1 of the present invention. Figure 1 It can be seen that the phenanthrene efficient degrading bacterial community SMP is mainly composed of Pseudomonas, Sphingobium, Methylophilus, Hyphomicrobium, Chryseobacterium, Mesorhizobium, Ferrovibrio, Herbaspirillum, Cupriavidus and other genera. Among them, Sphingobium, Pseudomonas, Methylophilus and Sphingopyxis have been proved to be PAHs degrading bacteria, while Hyphomicrobium and other genera are mainly involved in downstream metabolic reactions related to PAHs.

[0052] Figure 2 This is a scanning electron microscope image of the biochar-based immobilized bacterial agent in Example 1 of the present invention. Figure 2 It can be seen that the phenanthrene efficient degrading bacteria SMP has been adsorbed on the modified peanut shell biochar and is in good condition.

[0053] After the remediation, the phenanthrene in the soil was extracted by shaking a mixture of acetone and dichloromethane (the volume ratio of acetone to dichloromethane was 1:3) at 150 r / min for 45 min, where the volume mass ratio of the mixture of acetone and dichloromethane to soil was 5 mL: 1 g. The phenanthrene content was determined by high performance liquid chromatography; the cadmium in the soil was extracted by shaking a DTPA shaker at 150 r / min for 45 min, where the volume ratio of DTPA to soil was 5 mL: 1 g. The cadmium content in the soil was determined by atomic absorption spectrometry. The results are as follows: Figure 3 and Figure 4 shown.

[0054] Figure 3 This is a diagram showing the removal effect of the biochar-based immobilized bacterial agent on phenanthrene in phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention. Figure 3 It can be seen that after 90 days, the concentration of phenanthrene in the unremediated soil was 80.4 mg / kg, and its removal rate was 19.6%; after adding the biochar-based immobilized bacteria, the content of phenanthrene in the soil dropped from 100 mg / kg to 10.4 mg / kg, and its removal rate reached 89.6%. The biochar-based immobilized bacteria removed phenanthrene from the soil more thoroughly. It can be seen that the addition of biochar-based immobilized bacteria significantly improved the degradation effect of phenanthrene in the soil.

[0055] Figure 4 This is a diagram showing the effect of the biochar-based immobilized bacterial agent on the remediation of cadmium in phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention. Figure 4 It can be seen that the soil itself has a weak adsorption and fixation effect on cadmium. On the 90th day, the extraction rate of DTPA on cadmium in unremediated soil was 80.5%; in the soil with biochar-based immobilized bacteria, the extraction rate of DTPA on cadmium in soil dropped to 44.0% on the 90th day. It can be seen that the addition of biochar-based immobilized bacteria effectively reduced the activity of cadmium in the soil and reduced the ecological risk of soil cadmium pollution.

[0056] Figure 5 This is a diagram of soil properties after the biochar-based immobilized bacterial agent repaired the phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention. Figure 5 It can be seen that compared with the unremediated soil, after the restoration of phenanthrene-cadmium co-contaminated soil using biochar-based immobilized bacteria, the total nitrogen and total phosphorus contents of the soil increased, and the total organic matter content increased significantly. This shows that biochar-based immobilized bacteria can improve the conditions of phenanthrene-cadmium co-contaminated soil, increase soil fertility, and make phenanthrene-cadmium co-contaminated soil more suitable for plant growth.

[0057] Figure 6This is the Simpson index graph of soil after the biochar-based immobilized bacteria agent was used to repair the phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention. The Simpson index reflects the probability that two individuals in a randomly selected sample belong to different species, that is, the diversity level. The higher the Simpson index, the greater the difference between species and the richer the diversity. Figure 6 It can be seen that compared with 0.019814 of the unremediated soil, the Simpson index of the soil was significantly increased to 0.024579 after the restoration of the phenanthrene-cadmium co-contaminated soil using biochar-based immobilized bacteria. It can be seen that the addition of biochar-based immobilized bacteria significantly increased the microbial diversity of the phenanthrene-cadmium co-contaminated soil and improved the stability of the soil microbial community structure.

[0058] The seeds were sown in unremediated soil and soil after the restoration of phenanthrene-cadmium co-contaminated soil using biochar-based immobilized bacteria in Example 1. The seed germination rates were as follows: Figure 7 shown.

[0059] Figure 7 This is a comparison chart of seed germination rates after the biochar-based immobilized bacterial agent was used to repair the phenanthrene-cadmium co-contaminated soil in Example 1 of the present invention. Figure 7 It can be seen that the seed germination rate in the soil repaired by biochar-based immobilized bacteria is 70%, while the seed germination rate in the unrepaired soil is 30%. In addition, the average lengths of the roots and buds of the germinated seeds in the soil repaired by biochar-based immobilized bacteria are 1.11cm and 0.81cm, respectively, while the average lengths of the roots and buds of the germinated seeds in the unrepaired soil are 0.45cm and 0.53cm, respectively. The average lengths of the roots and buds of the germinated seeds in the repaired soil are significantly greater than those in the unrepaired soil. It can be seen that the method of the present invention for repairing the phenanthrene-cadmium co-contaminated environment using biochar-based immobilized bacteria reduces the toxicity of the phenanthrene-cadmium co-contaminated soil to plants and is more suitable for plant growth.

[0060] In addition, this example also tests the degradation effect of the phenanthrene-efficient degrading bacteria SMP on phenanthrene-contaminated water. Specifically, the phenanthrene-efficient degrading bacteria SMP are inoculated into a phenanthrene-containing inorganic salt medium, wherein the phenanthrene concentration in the phenanthrene-containing inorganic salt medium is 50 mg / L, and the degradation effect on phenanthrene is observed. The results are as follows: Figure 8 shown.

[0061] Figure 8 This is a diagram showing the effect of the phenanthrene efficient degradation bacterial community SMP on the removal of phenanthrene in water in Example 1 of the present invention. Figure 8 It can be seen that after 58 hours of degradation, the removal rate of phenanthrene by the phenanthrene efficient degrading bacteria SMP reached 98.6%. It can be seen that the phenanthrene efficient degrading bacteria SMP of the present invention has a very good removal effect on phenanthrene, and the degradation cycle is shorter.

[0062] In summary, the present invention uses biochar-based immobilized bacteria to repair the phenanthrene-cadmium co-contaminated environment, which has the following advantages: (1) Due to the large specific surface area and strong adsorption capacity of the modified peanut shell biochar, it can promote the migration of phenanthrene and cadmium to the biochar carrier, increase the phenanthrene concentration in the biochar microenvironment, and the phenanthrene efficient degrading bacteria SMP loaded thereon can quickly use phenanthrene as a carbon source for proliferation, thereby achieving the adsorption and fixation of cadmium in the soil while degrading and removing phenanthrene; (2) Compared with free bacteria, the modified peanut shell biochar provides a habitat microenvironment for the phenanthrene efficient degrading bacteria SMP, reducing adverse environmental factors. (3) Compared with a single strain, the phenanthrene-efficient degradation bacterial community SMP has stronger environmental adaptability, and each strain can synergistically degrade phenanthrene, thereby obtaining a higher phenanthrene degradation rate; (4) Peanut shell modified biochar as an immobilized carrier can improve soil properties, especially increase the pH of southern acidic red soil, improve soil fertility, and make the soil more suitable for plant growth; (5) Peanut shell modified biochar is cheap and easy to obtain, which can effectively reduce the need for resources and energy, thereby significantly reducing the cost of restoration. The method of the present invention using biochar-based immobilized bacterial agent to repair phenanthrene-cadmium co-contamination has the advantages of simple process, convenient operation, low treatment cost, high treatment efficiency, good repair effect, etc., can effectively degrade and remove phenanthrene in the soil while adsorbing and fixing cadmium, has high use value, good application prospects, and provides a green and efficient way to repair phenanthrene-cadmium co-contaminated soil.

[0063] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent, characterized in that: The method uses a biochar-based immobilized bacterial agent to treat a phenanthrene-cadmium co-polluted environment; the biochar-based immobilized bacterial agent uses modified peanut shell biochar as a carrier, and the modified peanut shell biochar is loaded with a phenanthrene efficient degrading bacterial community SMP; the phenanthrene efficient degrading bacterial community SMP uses coking plant sludge as a raw material and polycyclic aromatic hydrocarbons as a carbon source, and is obtained after domestication.

2. The method for repairing phenanthrene-cadmium co-polluted environment using biochar-based immobilized bacterial agents according to claim 1, characterized in that: The method for preparing the phenanthrene efficient degrading bacterial community SMP comprises the following steps: acclimating the coking plant sludge in a PAH-containing culture medium with PAH concentrations of 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L and 50 mg / L in sequence to obtain the phenanthrene efficient degrading bacterial community SMP.

3. The method for repairing phenanthrene-cadmium co-polluted environment using biochar-based immobilized bacterial agents according to claim 2, characterized in that: The duration of each cycle in the acclimation process is 7 days, the acclimation temperature is 30°C to 35°C, and the acclimation is carried out under oscillation conditions, and the oscillation speed is 160r / min; The volume ratio of the coking plant sludge to the PAH-containing culture medium is 1:20, and the PAH-containing culture medium further contains phenanthrene, pyrene, fluorene, fluoranthene and inorganic salt culture solution; the total mass of phenanthrene, pyrene, fluorene and fluoranthene in the PAH-containing culture medium is the same as the mass of the PAHs, and the mass ratio of phenanthrene, pyrene, fluorene and fluoranthene in the PAH-containing culture medium is 1:1:1:1; the inorganic salt culture solution is formed by mixing trace element solution, PBS buffer, magnesium ion solution, iron ion solution and water, and the volume ratio of the trace element solution, PBS buffer, magnesium ion solution, iron ion solution and water is 1:5:3:1:990; the trace element solution contains the following components: 44.7mg / L MnSO4·H2O, 68.6mg / L ZnSO4·7H2O, 34.7mg / L (NH4)MoO2·4H2O; the PBS buffer solution comprises the following components: 25.8g / L K2HPO4·3H2O, 33.4g / L Na2HPO4, 8.7g / L KH2PO4, 5g / L NH4Cl; the magnesium ion solution comprises the following components: 4.6g / L MgSO4·7H2O; the iron ion solution comprises the following components: 0.42g / L FeCl3·6H2O.

4. The method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent according to claim 3, characterized in that: The preparation method of the biochar-based immobilized bacterial agent comprises the following steps: (1) adding the phenanthrene-efficient degrading bacterial community SMP to a phenanthrene-containing culture medium for activation culture to prepare a bacterial suspension; (2) The bacterial suspension obtained in step (1) is mixed with the modified peanut shell biochar and cultured to obtain a biochar-based immobilized bacterial agent.

5. The method for repairing phenanthrene-cadmium co-polluted environment using biochar-based immobilized bacterial agents according to claim 4, characterized in that: In step (1), the volume ratio of the phenanthrene efficient degrading bacterial community SMP to the phenanthrene-containing culture medium is 1:9, the concentration of phenanthrene in the phenanthrene-containing culture medium is 50 mg / L to 100 mg / L, and the OD of the bacterial suspension is 600 is 0.4-0.5; the phenanthrene-containing culture medium also comprises an inorganic salt culture solution, which is mixed with a trace element solution, a PBS buffer solution, a magnesium ion solution, an iron ion solution and water, and the volume ratio of the trace element solution, the PBS buffer solution, the magnesium ion solution, the iron ion solution and water is 1:5:3:1:990; the trace element solution comprises the following components: 44.7mg / L MnSO4·H2O, 68.6mg / L ZnSO4·7H2O, 34.7mg / L (NH4) MoO2·4H2O; the PBS buffer solution comprises the following components: 25.8g / L K2HPO4·3H2O, 33.4g / L Na2HPO4, 8.7g / L KH2PO4, 5g / L NH4Cl; the magnesium ion solution comprises the following components: 4.6g / L MgSO4·7H2O; the iron ion solution comprises the following components: 0.42g / L FeCl3·6H2O; the activation culture temperature is 30°C to 35°C, and the activation culture time is 3d; In step (2), the mass volume ratio of the modified peanut shell biochar to the bacterial suspension is 5g-10g:100mL, the temperature is controlled at 30°C-35°C during the culture process, the culture time is 18h-24h, and the modified peanut shell biochar also includes the following treatment before use: sterilizing the modified peanut shell biochar.

6. The method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent according to claim 5, characterized in that: In step (2), the method for preparing modified peanut shell biochar comprises the following steps: (a) pyrolyzing peanut shells to obtain peanut shell biochar; the pyrolysis temperature is 500° C., and the pyrolysis time is 2 h; (b) Mixing peanut shell biochar and potassium hydroxide and performing pyrolysis to obtain modified peanut shell biochar; the pyrolysis temperature is 300° C., and the pyrolysis time is 1 hour.

7. The method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent according to claim 6, characterized in that: In step (a), the pyrolysis is carried out under nitrogen or inert atmosphere, the heating rate during the pyrolysis is 10°C / min, and the peanut shells are further processed before use: washing, drying, crushing, and sieving the peanut shells; the mesh size of the sieving is 60 meshes; In step (b), the mass ratio of the peanut shell biochar to potassium hydroxide is 1:2.5, the pyrolysis is carried out under nitrogen or an inert atmosphere, and the heating rate during the pyrolysis process is 10°C / min.

8. The method for remediating a phenanthrene-cadmium co-contaminated environment using a biochar-based immobilized bacterial agent according to any one of claims 1 to 7, characterized in that: The specific process of the treatment is: adding a biochar-based immobilized bacterial agent into a phenanthrene-cadmium co-contaminated environment for repair, thereby achieving the removal of phenanthrene and the fixation of cadmium in the environment.

9. The method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent according to claim 8, characterized in that: The phenanthrene-cadmium co-contaminated environment is phenanthrene-cadmium co-contaminated soil or phenanthrene-cadmium co-contaminated water, and the volume mass ratio of the biochar-based immobilized bacterial agent to the phenanthrene-cadmium co-contaminated soil is 100 mL: 500 g.

10. The method for repairing a phenanthrene-cadmium co-polluted environment using a biochar-based immobilized bacterial agent according to claim 9, characterized in that: The pH value of the phenanthrene-cadmium co-contaminated soil is 3.58, the soil in the phenanthrene-cadmium co-contaminated soil is acidic red soil, the initial concentration of phenanthrene in the phenanthrene-cadmium co-contaminated soil is 100 mg / kg, the initial concentration of cadmium in the phenanthrene-cadmium co-contaminated soil is 10 mg / kg, the remediation time is ≥50 days, and the remediation temperature is 20°C to 36°C.

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