Method for reinforced remediation of contaminated soil based on microorganisms

Abstract

The invention relates to the technical field of soil remediation, in particular to a microorganism-based enhanced contaminated soil remediation method which comprises the following steps: S1, adding bacillus subtillis, rhodopseudomonas palustris, bacillus licheniformis and pseudomonas aeruginosa into a culture solution, and uniformly mixing to obtain a microbial agent; s2, soaking the carrier into a microbial agent, and culturing for 1-3 days at the temperature of 30-35 DEG C; and S3, scattering the carrier loaded with the microorganisms into the soil. The microbial agent can effectively adsorb and degrade heavy metal pollutants in soil, the content of heavy metal ions in the soil is reduced, the air permeability of the soil is improved, the microbial agent is fixed through the carrier, loss of the microbial agent can be reduced, and the remediation effect of the microbial agent is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a method for remediating contaminated soil based on microbial enhancement. Background Art

[0002] Due to the influence of human activities, such as industrial emissions, pesticide use, waste disposal, etc., heavy metals have accumulated excessively in the soil, causing the soil to contain a large amount of heavy metals such as lead, cadmium, arsenic, and mercury. Since these heavy metals are non-biodegradable in the soil, they are easily enriched in plants and eventually enter the human body, endangering human health.

[0003] At present, the methods used to repair soil heavy metals mainly include physical, chemical, and biological methods. Among them, physical and chemical methods are expensive, environmentally destructive, and easily cause secondary pollution, and often fail to achieve the purpose of truly removing heavy metals. Bioremediation technology has attracted people's attention due to its low secondary pollution, diverse treatment forms, relatively simple operation, and low disturbance to the environment. In the prior art, microbial remediation usually directly inoculates microorganisms into the soil. In this way, the strain is not easy to fix, and the microorganisms are often lost due to rainwater, resulting in poor results of microbial remediation and difficulty in improving the degree of soil pollution. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for remediating contaminated soil based on microbial enhancement.

[0005] The technical solution of the present invention is: a method for remediating contaminated soil based on microbial enhancement, comprising the following steps:

[0006] S1. Add Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, and Pseudomonas aeruginosa to the culture solution and mix them evenly to obtain a microbial agent, wherein the mass ratio of Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, Pseudomonas aeruginosa to the culture solution is 5-7:3-6:2-3:2-4:80-100;

[0007] S2, soaking the carrier in a microbial agent 3 to 5 times its own weight, placing it at 30 to 35°C for 1 to 3 days, and shaking the microbial agent in a shaker for 15 to 25 minutes every 5 to 8 hours during the culture process. The initial temperature of the shaker is 30 to 35°C, and the temperature of the shaker is gradually reduced to 5 to 10°C during the shaking process. After the culture is completed, the carrier is taken out to obtain a carrier loaded with microorganisms; the carrier is a chitosan / aluminum titanate composite gel;

[0008] S3. Dig 5 to 10 cm of soil in the area to be repaired, spread the carrier carrying microorganisms into the soil, then backfill the soil in the area to be repaired, and sprinkle water on the area to be repaired.

[0009] Description: The microbial agent of the above method can effectively adsorb and degrade heavy metal pollutants in the soil, reduce the content of heavy metal ions in the soil, increase the aeration of the soil, and the microbial agent is fixed by a carrier, which can reduce the loss of the microbial agent and ensure the restoration effect of the microbial agent.

[0010] Furthermore, the culture solution components include, by mass percentage: 0.5-3% glucose, 5-10% peptone, 1-3% sodium chloride, 0.2-0.6% vitamins, 5-10% arginine, 10-20% beef extract, 0.1-0.3% magnesium sulfate, 10-15% agar, and the rest is deionized water.

[0011] Note: The above culture medium can provide sufficient nutrition, necessary energy and raw materials for the proliferation of microorganisms, and ensure that the microbial agent can be fully loaded onto the carrier.

[0012] Furthermore, the amplitude of the shaking table is 20-30 mm, and the rotation speed is 100-150 rpm.

[0013] Note: Limiting the amplitude and speed of the shaker can ensure uniform distribution of nutrients and evenly load the microbial inoculant on the carrier.

[0014] Furthermore, the rate of decrease of the shaking table temperature during the shaking process is 2-3°C / min.

[0015] Note: Cooling can reduce the pores of the carrier and reduce the loss of microorganisms, and limiting the cooling rate can prevent the microorganisms from losing their activity too quickly.

[0016] Furthermore, the watering amount is 3 to 6 L per mu.

[0017] Note: Watering can ensure the water content of the land, improve soil moisture, and ensure that there is enough water for the growth and proliferation of microorganisms.

[0018] Furthermore, the spreading amount of the carrier loaded with microorganisms is 200-300g per mu.

[0019] Note: Limiting the amount of carriers carrying microorganisms can reduce waste and ensure the repair effect of microbial agents on the soil.

[0020] Furthermore, the carrier is a chitosan / aluminum titanate composite gel, and the preparation method of the chitosan / aluminum titanate composite gel comprises the following steps:

[0021] Step 1: dissolving aluminum nitrate in anhydrous ethanol, stirring until the aluminum nitrate is completely dissolved, to obtain a mixed solution A; adding chitosan to a glacial acetic acid solution, stirring until the chitosan is completely dissolved, to obtain a mixed solution B; the mass proportion of aluminum nitrate in the mixed solution A is 2-4%, the mass proportion of chitosan in the mixed solution B is 1-3%, and the mass ratio of the mixed solution A to the mixed solution B is 1:1-1.5;

[0022] Step 2: adding the mixed solution B into the mixed solution A in 3 to 5 equal portions, stirring the mixed solution A for 5 to 10 minutes after each addition of the mixed solution B, continuously adding tetrabutyl titanate to the mixed solution A during the stirring process, and adjusting the pH value of the mixed solution A to neutral with ammonia water after each stirring;

[0023] Step 3: After all the mixed solution B is added, the mixed solution A is stirred for 1 to 2 hours at 40 to 50° C., and the chitosan / aluminum titanate composite gel is obtained after filtering and drying.

[0024] Description: The above method generates aluminum titanate through the reaction of aluminum nitrate and tetrabutyl titanate. At the same time, tetrabutyl titanate can be used as a cross-linking agent to form a composite gel between chitosan and aluminum titanate. The chitosan / aluminum titanate composite gel has many pores, and microorganisms can be evenly distributed in the pores. The volume of chitosan / aluminum titanate can expand with temperature changes to control the slow release of microorganisms. Chitosan / aluminum titanate has an adsorption effect on heavy metal ions, so that microorganisms can fully degrade heavy metal ions in the soil.

[0025] Furthermore, the mass concentration of the glacial acetic acid solution is 2-4%.

[0026] Note: Limiting the concentration of glacial acetic acid solution can ensure the solubility of chitosan and avoid the inability of chitosan to fully dissolve.

[0027] Furthermore, the amount of tetrabutyl titanate added each time accounts for 30-40% of the mass of aluminum nitrate.

[0028] Note: Limiting the amount of tetrabutyl titanate added can ensure that tetrabutyl titanate and aluminum nitrate react fully and improve the conversion rate of aluminum titanate.

[0029] The beneficial effects of the present invention are:

[0030] (1) The microbial agent of the present invention can effectively adsorb and degrade heavy metal pollutants in the soil, reduce the content of heavy metal ions in the soil, and increase the aeration of the soil. In addition, the microbial agent is fixed by a carrier, which can reduce the loss of the microbial agent and ensure the restoration effect of the microbial agent.

[0031] (2) The present invention generates aluminum titanate by reacting aluminum nitrate with tetrabutyl titanate. Meanwhile, tetrabutyl titanate can be used as a cross-linking agent to form a composite gel between chitosan and aluminum titanate. The chitosan / aluminum titanate composite gel has a large number of pores, and microorganisms can be evenly distributed in the pores. The volume of chitosan / aluminum titanate can expand with temperature changes to control the slow release of microorganisms. Chitosan / aluminum titanate has an adsorption effect on heavy metal ions, so that the microorganisms can fully degrade the heavy metal ions in the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 1 of the present invention;

[0033] Figure 2 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 2 of the present invention;

[0034] Figure 3 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 3 of the present invention;

[0035] Figure 4 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 4 of the present invention;

[0036] Figure 5 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 5 of the present invention;

[0037] Figure 6 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 6 of the present invention;

[0038] Figure 7 is a line graph of the reduction rate of heavy metal ion content in Experimental Example 7 of the present invention;

[0039] Figure 8 It is a line graph of the reduction rate of heavy metal ion content in Experimental Example 8 of the present invention. DETAILED DESCRIPTION

[0040] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0041] Example 1: A method for remediating contaminated soil based on microbial enhancement, comprising the following steps:

[0042] S1. Add Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis and Pseudomonas aeruginosa to the culture solution and mix evenly to obtain a microbial agent, the mass ratio of Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, Pseudomonas aeruginosa and the culture solution is 6:4.5:2.5:3:90; Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis and Pseudomonas aeruginosa are all purchased from China Industrial Microbiological Culture Collection Center, and the collection numbers are CICC 24713, CICC 23812, CICC 10098 and CICC 24649, respectively.

[0043] S2, soaking the carrier in a microbial agent of 4 times its own weight, placing it at 32°C for 2 days, placing the microbial agent in a shaker for 20 minutes every 6.5 hours during the culture process, the initial temperature of the shaker is 32°C, and the temperature of the shaker is gradually reduced to 7°C during the shaking process, and the carrier is taken out after the culture is completed to obtain a carrier loaded with microorganisms; the carrier is chitosan / aluminum titanate composite gel; the amplitude of the shaker is 25mm, the rotation speed is 120rpm; the rate of decrease of the shaker temperature during the shaking process is 2.5°C / min;

[0044] S3. Dig 8 cm of soil in the area to be repaired, spread the carrier loaded with microorganisms into the soil, then backfill the soil in the area to be repaired, and sprinkle water on the area to be repaired; the amount of water sprinkled is 4 L per mu; the amount of microorganism-loaded carrier spread is 250 g per mu;

[0045] The culture solution comprises, by mass percentage, 1.5% glucose, 8% peptone, 2% sodium chloride, 0.4% vitamins, 8% arginine, 15% beef extract, 0.2% magnesium sulfate, 12% agar, and the remainder is deionized water;

[0046] The preparation method of chitosan / aluminum titanate composite gel comprises the following steps:

[0047] Step 1: dissolving aluminum nitrate in anhydrous ethanol, stirring until the aluminum nitrate is completely dissolved, to obtain a mixed solution A; adding chitosan to a glacial acetic acid solution with a mass concentration of 3%, stirring until the chitosan is completely dissolved, to obtain a mixed solution B; the mass proportion of aluminum nitrate in the mixed solution A is 3%, the mass proportion of chitosan in the mixed solution B is 2%, and the mass ratio of the mixed solution A to the mixed solution B is 1:1.25;

[0048] Step 2: adding the mixed solution B into the mixed solution A in 4 equal portions; stirring the mixed solution A for 8 minutes after each addition of the mixed solution B; continuously dropping tetrabutyl titanate into the mixed solution A during the stirring process; and adjusting the pH value of the mixed solution A to neutral with ammonia water after each stirring; the amount of tetrabutyl titanate added each time accounts for 35% of the mass of aluminum nitrate, and the mass concentration of ammonia water is 15%;

[0049] Step 3: After all the mixed solution B is added, the mixed solution A is stirred for 1.5 hours at 45°C, and the chitosan / aluminum titanate composite gel is obtained after filtration and drying.

[0050] Example 2: This example is basically the same as Example 1, except that the mass ratio of Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, Pseudomonas aeruginosa and culture solution is 5:3:2:2:80.

[0051] Example 3: This example is basically the same as Example 1, except that the mass ratio of Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, Pseudomonas aeruginosa and culture solution is 7:6:3:4:100.

[0052] Example 4: This example is basically the same as Example 1, except that the microbial inoculant is placed in a shaker and shaken for 15 minutes every 5 hours during the culture process.

[0053] Example 5: This example is basically the same as Example 1, except that the microbial inoculant is placed in a shaker and shaken for 25 minutes every 8 hours during the culture process.

[0054] Example 6: This example is basically the same as Example 1, except that the initial temperature of the shaker is 30°C, and the temperature of the shaker gradually decreases to 5°C during the shaking process.

[0055] Example 7: This example is basically the same as Example 1, except that the initial temperature of the shaker is 35°C, and the temperature of the shaker gradually decreases to 10°C during the shaking process.

[0056] Example 8: This example is basically the same as Example 1, except that the rate of decrease of the shaker temperature during the shaking process is 2°C / min.

[0057] Example 9: This example is basically the same as Example 1, except that the rate of decrease of the shaker temperature during the shaking process is 3°C / min.

[0058] Example 10: This example is basically the same as Example 1, except that the culture solution ingredients include, by mass percentage: 0.5% glucose, 5% peptone, 1% sodium chloride, 0.2% vitamins, 5% arginine, 10% beef extract, 0.1% magnesium sulfate, 10% agar, and the rest is deionized water.

[0059] Example 11: This example is basically the same as Example 1, except that the culture solution ingredients include, by mass percentage: 3% glucose, 10% peptone, 3% sodium chloride, 0.6% vitamins, 10% arginine, 20% beef extract, 0.3% magnesium sulfate, 15% agar, and the rest is deionized water.

[0060] Example 12: This example is basically the same as Example 1, except that the mass ratio of mixed solution A to mixed solution B is 1:1.

[0061] Example 13: This example is basically the same as Example 1, except that the mass ratio of mixed solution A to mixed solution B is 1:1.5.

[0062] Example 14: This example is basically the same as Example 1, except that the mixed solution B is added to the mixed solution A in three equal portions.

[0063] Example 15: This example is basically the same as Example 1, except that the mixed solution B is added to the mixed solution A in 5 equal portions.

[0064] Example 16: The amount of tetrabutyl titanate added each time accounts for 30% of the mass of aluminum nitrate.

[0065] Example 17: The amount of tetrabutyl titanate added each time accounts for 40% of the mass of aluminum nitrate.

[0066] Comparative Example 1: Using Example 1 as a reference, the microbial agent is a commercially available microbial remediation agent mixed with the culture solution.

[0067] Comparative Example 2: Using Example 1 as a reference, no shaking was used during the culture process.

[0068] Comparative Example 3: Using Example 1 as a reference, the shaking table temperature was kept constant at 32°C during the shaking process.

[0069] Comparative Example 4: Taking Example 1 as a reference, the rate of decrease of the shaking table temperature during the shaking process was 1°C / min.

[0070] Comparative Example 5: With reference to Example 1, the rate of decrease of the shaking table temperature during the shaking process was 4°C / min.

[0071] Comparative Example 6: Using Example 1 as a reference, the culture medium used was a commercially available microbial culture medium.

[0072] Comparative Example 7: With reference to Example 1, the mass ratio of mixed solution A to mixed solution B is 1:2.

[0073] Comparative Example 8: Using Example 1 as a reference, the mixed solution B was added to the mixed solution A all at once.

[0074] Comparative Example 9: Taking Example 1 as a reference, pure chitosan gel was used as the carrier.

[0075] Experimental example: In order to explore the soil restoration effect of each embodiment, the heavy metal contaminated soil in the same area was used as the test field of each embodiment. After 30 days of restoration, the copper, cadmium and lead ion contents of each experimental field before and after restoration were tested. After calculation, the reduction rate of copper, cadmium and lead ion contents before and after restoration of each embodiment was obtained. The specific exploration is as follows:

[0076] 1. Explore the influence of microbial agent components on the repair effect

[0077] like Figure 1 As shown, by comparing Examples 1, 2, and 3, it can be seen that the reduction rates of copper, cadmium, and lead ion contents in the test field of Example 1 are the highest. This may be because the microbial agent components of Example 1 are reasonable, and the microorganisms can effectively play a synergistic role, so the microbial agent components of Example 1 are optimal;

[0078] By comparing Example 1 with Comparative Example 1, it can be seen that after the microorganisms in the microbial agent are replaced with commercially available microbial remediation agents, the reduction rates of copper, cadmium and lead ion contents are all reduced. Therefore, the microbial agent of Example 1 has better repair ability for heavy metal pollution than the commercially available microbial remediation agents.

[0079] 2. Explore the effect of shaking time on the repair effect

[0080] like Figure 2 As shown, by comparing Examples 1, 4, and 5, it can be seen that the reduction rates of copper, cadmium, and lead ion contents in the test field of Example 1 are the highest. This may be because the shaking time of the shaking table in Example 1 allows the microbial agent to be evenly loaded on the carrier and avoids damage to the microorganisms caused by the shaking time of the shaking table. Therefore, the shaking time selected in Example 1 is optimal;

[0081] By comparing Example 1 with Comparative Example 2, it can be seen that when no shaking table is used for shaking during the culture process, the reduction rates of copper, cadmium and lead ion contents all decreased. This may be because the shaking table can make the nutrients and microorganisms evenly distributed on the carrier. Therefore, the culture method selected in Example 1 is better.

[0082] 3. Investigate the effect of shaker temperature on the repair effect

[0083] like Figure 3 As shown, by comparing Examples 1, 6, and 7, it can be seen that the reduction rates of copper, cadmium, and lead ion contents in the test field of Example 1 are the highest. This may be because the temperature of Example 1 can both shrink the pores of the carrier and reduce the loss of microorganisms, and avoid excessive reduction in microbial activity. Therefore, the shaking table temperature selected in Example 1 is optimal;

[0084] By comparing Example 1 with Comparative Example 3, it can be seen that when the shaking table temperature does not change during the culture process, the reduction rates of copper, cadmium and lead ion contents all decrease. This may be because lowering the temperature can reduce the pores of the carrier after microbial loading and reduce the loss of microorganisms. Therefore, the culture method selected in Example 1 is better.

[0085] 4. Investigate the effect of shaking table temperature change rate on the repair effect

[0086] like Figure 4 As shown, by comparing Examples 1, 8, 9 and Comparative Examples 4 and 5, it can be seen that the reduction rates of copper, cadmium and lead ion contents in Example 1 are the highest. This may be because the temperature reduction during the culture process can reduce the pores of the carrier and reduce the loss of microorganisms. However, too fast a temperature reduction rate will lead to a decrease in microbial activity. Therefore, the reduction rate of the shaking table temperature selected in Example 1 is optimal.

[0087] 5. Explore the influence of culture medium composition on the repair effect

[0088] like Figure 5 As shown, by comparing Examples 1, 10, and 11, it can be seen that the reduction rates of copper, cadmium, and lead ion contents in Example 1 are the highest. This may be because the culture solution components of Example 1 can provide the nutrients required for microbial growth and proliferation, so the culture solution components of Example 1 are optimal.

[0089] By comparing Example 1 with Comparative Example 6, it can be seen that after the culture solution of Example 1 was replaced with a commercially available microbial culture solution, the reduction rates of copper, cadmium and lead ion contents all decreased. This may be because the culture solution of Example 1 is more suitable for the microbial agent of the present application and can provide sufficient nutrients for the microorganisms of the present application. Therefore, the culture solution composition selected in Example 1 is better.

[0090] 6. Explore the effect of the ratio of mixed solution A to mixed solution B on the repair effect

[0091] like Figure 6 As shown, by comparing Examples 1, 12, 13 and Comparative Example 7, it can be seen that the reduction rates of copper, cadmium and lead ions in Example 1 are the highest. This may be because the chitosan / aluminum titanate composite gel prepared by the ratio of mixed solution A to mixed solution B in Example 1 has better stability, more pores, and can accommodate more microorganisms. Therefore, the ratio of mixed solution A to mixed solution B selected in Example 1 is better.

[0092] 7. Explore the effect of the number of times mixed solution B is added on the repair effect

[0093] like Figure 7As shown, by comparing Examples 1, 14, and 15, it can be seen that the reduction rate of the copper, cadmium, and lead ion contents in Example 1 is higher than that in Example 14. This may be because after the mixed solution B is added more times, the tetrabutyl titanate is hydrolyzed less, and the cross-linking effect can be better exerted, making the generated chitosan / aluminum titanate composite gel more stable; compared with Example 15, the reduction rates of the copper, cadmium, and lead ion contents in the two are not much different. Therefore, from a cost perspective, the number of additions of the mixed solution B selected in Example 1 is better.

[0094] By comparing Example 1 with Comparative Example 8, it can be seen that after the mixed solution B was added all at once, the reduction rate of the copper, cadmium and lead ion contents decreased. This may be because the tetrabutyl titanate added when the mixed solution B was added at one time underwent more hydrolysis, resulting in the chitosan / aluminum titanate composite gel being unstable and having fewer internal pores, making it impossible to stably load microorganisms. Therefore, considering the time cost, the mixed solution B addition method selected in Example 1 is better.

[0095] 8. Explore the effect of tetrabutyl titanate addition on the repair effect

[0096] like Figure 8 As shown, by comparing Examples 1, 16, and 17, it can be seen that the reduction rate of the copper, cadmium, and lead ion contents in Example 1 is higher than that in Example 16. This may be because the addition amount of tetrabutyl titanate in Example 1 can effectively play a cross-linking role to generate a stable chitosan / aluminum titanate composite gel. Compared with Comparative Example 17, the reduction rates of the copper, cadmium, and lead ion contents in Example 1 and Comparative Example 17 are not much different. Therefore, from a cost perspective, the addition amount of tetrabutyl titanate selected in Example 1 is better;

[0097] By comparing Example 1 with Comparative Example 9, it can be seen that after using pure chitosan gel as a carrier, the reduction rate of copper, cadmium and lead ion contents decreased. This may be because the chitosan / aluminum titanate composite gel has more internal pores and can carry more microorganisms, and the chitosan / aluminum titanate composite gel can adsorb heavy metal ions, making the heavy metal ions easier to be degraded by microorganisms.

Claims

1. A method for remediating contaminated soil based on microbial enhancement, characterized in that: The following steps are involved: S1. Add Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, and Pseudomonas aeruginosa to the culture solution and mix them evenly to obtain a microbial agent, wherein the mass ratio of Bacillus subtilis, Rhodopseudomonas palustris, Bacillus licheniformis, Pseudomonas aeruginosa to the culture solution is 5-7:3-6:2-3:2-4:80-100; S2, soaking the carrier in a microbial agent 3 to 5 times its own weight, placing it at 30 to 35°C for 1 to 3 days, and shaking the microbial agent in a shaker for 15 to 25 minutes every 5 to 8 hours during the culture process. The initial temperature of the shaker is 30 to 35°C, and the temperature of the shaker is gradually reduced to 5 to 10°C during the shaking process. After the culture is completed, the carrier is taken out to obtain a carrier loaded with microorganisms; the carrier is a chitosan / aluminum titanate composite gel; S3. Dig 5 to 10 cm of soil in the area to be repaired, spread the carrier carrying microorganisms into the soil, then backfill the soil in the area to be repaired, and sprinkle water on the area to be repaired.

2. The method for remediating contaminated soil based on microbial enhancement according to claim 1, characterized in that: The culture solution comprises, by mass percentage, 0.5-3% glucose, 5-10% peptone, 1-3% sodium chloride, 0.2-0.6% vitamins, 5-10% arginine, 10-20% beef extract, 0.1-0.3% magnesium sulfate, 10-15% agar, and the rest is deionized water.

3. The method for remediating contaminated soil based on microbial enhancement according to claim 1, characterized in that: The amplitude of the shaking table is 20-30 mm, and the rotation speed is 100-150 rpm.

4. The method for remediating contaminated soil based on microbial enhancement according to claim 1, characterized in that: The rate of decrease of the shaking table temperature during the shaking process is 2-3°C / min.

5. The method for remediating contaminated soil based on microbial enhancement according to claim 1, characterized in that: The watering amount is 3 to 6 L per mu.

6. The method for remediating contaminated soil based on microbial enhancement according to claim 1, characterized in that: The spreading amount of the carrier loaded with microorganisms is 200-300g per mu.

7. The method for remediating contaminated soil based on microbial enhancement according to claim 1, characterized in that: The preparation method of the chitosan / aluminum titanate composite gel comprises the following steps: Step 1: dissolving aluminum nitrate in anhydrous ethanol, stirring until the aluminum nitrate is completely dissolved, to obtain a mixed solution A; adding chitosan to a glacial acetic acid solution, stirring until the chitosan is completely dissolved, to obtain a mixed solution B; the mass proportion of aluminum nitrate in the mixed solution A is 2-4%, the mass proportion of chitosan in the mixed solution B is 1-3%, and the mass ratio of the mixed solution A to the mixed solution B is 1:1-1.5; Step 2: adding the mixed solution B into the mixed solution A in 3 to 5 equal portions, stirring the mixed solution A for 5 to 10 minutes after each addition of the mixed solution B, continuously adding tetrabutyl titanate to the mixed solution A during the stirring process, and adjusting the pH value of the mixed solution A to neutral with ammonia water after each stirring; Step 3: After all the mixed solution B is added, the mixed solution A is stirred for 1 to 2 hours at 40 to 50° C., and the chitosan / aluminum titanate composite gel is obtained after filtering and drying.

8. The method for remediating contaminated soil based on microbial enhancement according to claim 7, characterized in that: The mass concentration of the glacial acetic acid solution is 2-4%.

9. The method for remediating contaminated soil based on microbial enhancement according to claim 7, characterized in that: The amount of tetrabutyl titanate added each time accounts for 30-40% of the mass of aluminum nitrate.

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