Preparation and use methods of heavy metal soil solidification and remediation liquid
By forming a highly stable five-membered ring chelate and calcium carbonate encapsulated structure of Bacillus subtilis, the problems of uneven soil strength and poor stability of heavy metal ions caused by urease decomposition are solved, and the high stability and acid resistance repair effect is achieved. Avoid environmental pollution.
Patent Information
- Application Number
- CN202411230128.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2024-12-13
AI Technical Summary
In the existing microbial repair technology, the rate of decomposition of urease to generate calcium carbonate is too fast, the soil strength is uneven, the heavy metal ions are poor, the stability is easy to leaching and diffusion under acidic conditions, and the harmful gases ammonia and chloride ions residues lead to environmental pollution.
Bacillus subtilis forms a five-membered ring chelate with oxalate, and a highly stable calcium carbonate is generated through enzymatic reactions such as carbonic anhydrase, and binds calcium carbonate to cement the soil to avoid acidic environmental exposure and improve soil body Strength and uniformity.
It achieves high stability and anti-acid rain corrosion ability, significantly improves soil strength and uniformity, avoids harmful gas emissions and chloride ion residues, and ensures the safety of the repaired soil.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of heavy metal contaminated soil restoration and reinforcement, and in particular to a method for microbial restoration and reinforcement of heavy metal contaminated soil. Background Art
[0002] With the development of industrial society, due to the backward production technology and weak environmental awareness of some enterprises, the wastewater, waste gas and solid waste generated by industrial pollution sources are not discharged according to national standards, which eventually causes pollutants such as heavy metals to be deposited in the soil and groundwater, causing serious environmental problems. In order to develop and utilize contaminated land for industrial purposes, corresponding measures must be taken to repair and reinforce heavy metal contaminated land. Traditional remediation methods mostly use physical remediation, chemical remediation and biological remediation.
[0003] Although physical and chemical remediation can repair contaminated soil, they also have disadvantages such as changing soil composition and structure, large engineering workload, high cost, and easy to cause secondary pollution. Microbial remediation and solidification technology is gaining more and more attention due to its simple operation, relatively small environmental pollution, and its ability to strengthen the soil while repairing heavy metals.
[0004] Existing microbial remediation and solidification technologies for heavy metal contaminated soil:
[0005] Urea is hydrolyzed into carbonate ions by urease-producing bacteria and combined with calcium ions and heavy metal ions to form carbonate minerals with gelling properties, which absorb, transform and co-precipitate heavy metal ions into a non-toxic form. At the same time, the carbonates produced can cement soil particles.
[0006] Disadvantages of existing microbial remediation and solidification technologies for heavy metal contaminated soil:
[0007] The rate at which urease decomposes to generate calcium carbonate is too fast, resulting in uneven strength of the soil after repair; the stability of heavy metal ions after repair is poor, and they are easily leached and diffused under acidic conditions, causing secondary pollution; the use of the single principle of urease hydrolysis results in a small amount of calcium carbonate generated, poor strength of the soil after repair, and the material cannot be fully utilized; the process of urease decomposing urea will produce a large amount of harmful gas ammonia, which not only harms construction workers, but also causes secondary environmental pollution; the introduction of calcium chloride as a calcium source, and the excess chloride ions remaining in the soil will cause soil acidification, compaction, and aggravation of soil salt damage and other hazards. Summary of the invention
[0008] The purpose of the present invention is to solve the defects in the prior art and to propose a method for microbial restoration and solidification of heavy metal contaminated soil.
[0009] The principle of the present invention is as follows: 2CaO2+2H2O=2Ca(OH)2+O2 C2O4 2- +Heavy metal ions = Oxalate C2O4 2- +Ca=CaC2O4 2Na2C2O4+3O2=2CO2+2Na2CO3 NaCOOH+Ca(OH)2=Ca(COOH)2+NaOH Na2CO3+H2O=CO2+2NaOH CaC4H6O4+4O2=CaCO3+3CO2+3H2O Ca(COOH)2+Ca(OH)2+O2=2CaCO3+H2O CO3 2- +Ca==CaCO3 Ca(OH)2+CO2=CaCO3+2H2O First, heavy metal ions form extremely stable five-membered ring chelates through oxalate ionized by sodium oxalate, and the generated chelates are wrapped by calcium carbonate to form a highly stable wrapping structure, which prevents the leaching and diffusion of heavy metal ions after repair. Second, sodium oxalate is converted into carbon dioxide and sodium formate through the oxidation of sodium oxalate and the oxalate decarboxylase of Bacillus subtilis. Sodium formate reacts with calcium hydroxide to generate sodium hydroxide and calcium formate. Calcium acetate and calcium formate are converted into calcium carbonate and carbon dioxide through aerobic conversion of Bacillus subtilis. The generated carbon dioxide is converted into carbonate ions through the carbonic anhydrase of Bacillus subtilis, thereby generating calcium carbonate with calcium ions. At the same time, carbon dioxide also generates calcium carbonate with calcium hydroxide. The combination of multiple effects can generate a large amount of calcium carbonate to cement the soil, significantly improve the strength and uniformity of the soil, and make full use of the material. Third, the calcium hydroxide and sodium hydroxide generated during the reaction make the overall environment alkaline, avoiding the exposure of heavy metal ions after repair to the acidic environment.
[0010] Compared with the prior art, the present invention has the following beneficial effects:
[0011] First, dual control is achieved through the high-stability five-membered ring chelate and the unique calcium carbonate-encapsulated chelate structure, making the stability and acid rain resistance after repair stronger; second, the rate of calcium carbonate generation is lower than the method of generating calcium carbonate by urea hydrolysis, which avoids the destruction of calcium carbonate generated during stirring, and can generate a large amount of calcium carbonate at the same time, significantly improving the strength and uniformity of the soil after solidification; third, no urea and calcium chloride are used, which can effectively avoid the emission of harmful gas ammonia during the construction process, and no harmful ions and chloride ions remain after repair.
[0012] The technical solution steps of the present invention are as follows: S1: preparing a microbial culture solution: the microbial culture solution is composed of alkali-resistant domesticated Bacillus subtilis and a nutrient solution, wherein each liter of the nutrient solution is composed of 20 g of sodium acetate, 4 g of yeast extract powder and 1 L of deionized water; S2: preparing mineralization solution: each liter of mineralization solution is composed of 88-176 g of calcium acetate, 4-6 g of yeast extract powder and 1 L of deionized water; S3: Add 3% 72g / L calcium peroxide powder and 67-134g / L sodium oxalate to the microbial solution obtained in S1 and the mineralized solution obtained in S2, and stir rapidly to prepare a heavy metal soil solidification and repair solution; S4: After preparation, the contaminated soil is immediately stirred and repaired with heavy metal soil solidification and repair liquid. The volume of the soil repair liquid is 0.7-0.9 times the pore volume of the soil to be repaired. After stirring, the site is leveled and allowed to react for 5-9 days. DETAILED DESCRIPTION
[0013] Embodiment 1: In this example, a method for preparing and using a heavy metal soil solidification and repair liquid is used to repair and reinforce a heavy metal contaminated sandy soil site, where the leaching concentrations of cadmium, zinc, and lead ions are 13, 400, and 20 mg / L, respectively, and the bearing capacity is 70 kPa. The specific steps are as follows:
[0014] In step S1, the microbial liquid is composed of alkali-resistant domesticated Bacillus subtilis and nutrient solution, wherein each liter of nutrient solution is composed of 20g sodium acetate, 4g yeast extract powder and 1L deionized water.
[0015] As a preferred embodiment of the present application, the steps for preparing the microbial liquid are as follows: The alkali-resistant acclimated Bacillus subtilis was inoculated into the culture medium at an inoculation ratio of 10%, and cultured in the culture medium at 30° C. and 135 r / min for 48 hours, and the OD value reached 3.0.
[0016] As a preferred embodiment of the present application, in step S2, each liter of mineralization liquid is composed of 176 g of calcium acetate, 6 g of yeast extract powder and 1 L of deionized water.
[0017] As a preferred embodiment of the present application, in step S3, the specific process for preparing the heavy metal soil solidification and repair solution is as follows: The microbial liquid and the mineralized liquid were mixed, and 72 g / L of calcium peroxide powder and 134 g / L of sodium oxalate were quickly added and stirred continuously to obtain the heavy metal soil solidification and repair liquid.
[0018] As a preferred embodiment of the present application, the method for using the heavy metal soil solidification and repair liquid in step S4 is: After preparation, the contaminated soil is immediately stirred, repaired and reinforced with heavy metal soil solidification and remediation liquid. The volume of the soil remediation liquid is 0.9 times the pore volume of the soil to be repaired. After stirring, the site is leveled and allowed to react for 9 days.
[0019] Embodiment 2: In this example, a method for preparing and using a heavy metal soil solidification and repair liquid is used to repair and reinforce a heavy metal contaminated sandy soil site, where the leaching concentrations of cadmium, zinc, and lead ions are 7, 240, and 11 mg / L, respectively, and the bearing capacity is 94 kPa. The specific steps are as follows:
[0020] In step S1, the microbial liquid is composed of alkali-resistant domesticated Bacillus subtilis and nutrient solution, wherein each liter of nutrient solution is composed of 20g sodium acetate, 4g yeast extract powder and 1L deionized water.
[0021] In this embodiment, the preparation steps of the microbial culture liquid are as follows: The alkali-resistant acclimated Bacillus subtilis was inoculated into the culture medium at an inoculation ratio of 3%, and cultured in the culture medium at 30° C. and 135 r / min for 24 hours, and the OD value reached 1.8.
[0022] In step S2, each liter of mineralization solution is composed of 88 g of calcium acetate, 4 g of yeast extract powder and 1 L of deionized water.
[0023] In step S3, the specific process of preparing the heavy metal soil solidification and repair solution is as follows: The microbial liquid and the mineralized liquid were mixed, and 37 g / L of calcium peroxide powder and 67 g / L of sodium oxalate were quickly added and stirred continuously to obtain the heavy metal soil solidification and repair liquid.
[0024] In step S4, the method for using the heavy metal soil solidification and repair liquid is as follows: After preparation, the contaminated soil is immediately stirred and repaired with heavy metal soil solidification and repair liquid. The volume of the soil repair liquid is 0.7 times the pore volume of the soil to be repaired. After stirring, the site is leveled and allowed to react for 5 days.
[0025] Embodiment 3: In this example, a method for preparing and using a heavy metal soil solidification and repair liquid is used to repair and reinforce a heavy metal contaminated sandy soil site. The leaching concentrations of cadmium, zinc, and lead ions in the site are 12, 290, and 16 mg / L, respectively, and the bearing capacity is 81 kPa. The specific steps are as follows:
[0026] In step S1, the microbial liquid is composed of alkali-resistant domesticated Bacillus subtilis and a nutrient solution, wherein each liter of the nutrient solution is composed of 20 g of sodium acetate, 4 g of yeast extract powder and 1 L of deionized water.
[0027] In this embodiment, the preparation steps of the microbial culture liquid are as follows: The alkali-resistant acclimated Bacillus subtilis was inoculated into the culture medium at an inoculation ratio of 5%, and cultured in the culture medium at 30° C. and 135 r / min for 36 hours, and the OD value reached 2.4.
[0028] In step S2, each liter of mineralization solution is composed of 132 g of calcium acetate, 5 g of yeast extract powder and 1 L of deionized water.
[0029] In step S3, the specific process of preparing the heavy metal soil solidification and repair solution is as follows: The microbial solution and the mineral solution were mixed, and 54 g / L of calcium peroxide powder and 101 g / L of sodium oxalate were quickly added and stirred continuously to obtain the heavy metal soil remediation solution.
[0030] In step S4, the method for using the heavy metal soil solidification and repair liquid is as follows: After preparation, the contaminated soil is immediately stirred, repaired and reinforced with heavy metal soil solidification and remediation liquid. The volume of the soil remediation liquid is 0.8 times the pore volume of the soil to be repaired. After stirring, the site is leveled and allowed to react for 7 days.
Claims
1. A method for preparing and using a heavy metal soil solidification and repair solution, the steps of which are as follows: S1: preparing a microbial culture solution: the microbial culture solution is composed of alkali-resistant domesticated Bacillus subtilis and a nutrient solution, wherein each liter of the nutrient solution is composed of 20 g of sodium acetate, 4 g of yeast extract powder and 1 L of deionized water; S2: preparing mineralization solution: each liter of mineralization solution is composed of 88-176 g of calcium acetate, 4-6 g of yeast extract powder and 1 L of deionized water; S3: adding 37-72 g / L calcium peroxide powder and 67-134 g / L sodium oxalate to the microbial solution obtained in S1 and the mineralized solution obtained in S2, and rapidly stirring the mixture to prepare a heavy metal soil solidification and repair solution; S4: After preparation, the contaminated soil is immediately stirred and repaired with heavy metal soil solidification and repair liquid. The volume of the soil repair liquid is 0.7-0.9 times the pore volume of the soil to be repaired. After stirring, the site is leveled and allowed to react for 7-9 days.