Preparation method of oil shale residue and MICP synergistic heavy metal contaminated soil stabilizer

Abstract

The application discloses a preparation method of an oil shale residue and MICP (microbially induced carbonates precipitation) combined heavy metal contaminated soil stabilizer, and belongs to the technical field of heavy metal contaminated soil remediation. Firstly, lysine bacillus is separated from heavy metal contaminated soil; secondly, oil shale residue is pyrolyzed and modified; and then, the two are respectively applied to the heavy metal contaminated soil to form a modified oil shale residue and MICP system. The preparation method adopted by the application enables urease-producing bacteria and modified oil shale residue to respectively play a role in adsorbing heavy metals and further reduces the content of exchangeable Cu 2+ and Zn 2+ in the heavy metal contaminated soil through a synergistic mechanism. Moreover, the obtained composite mineral has good stability and strong resistance to external interference. The application realizes the unification of pollution treatment and solid waste resource utilization.

Description

Technical Field

[0001] This invention relates to the field of heavy metal contaminated soil remediation technology, and in particular to a method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergy with MIP. Background Technology

[0002] With the continued advancement of global industrialization, urbanization, and agricultural intensification, large amounts of heavy metal pollutants enter the soil environment through industrial emissions, mining, agricultural input application, and urban activities, leading to soil heavy metal pollution problems. Related studies indicate that approximately 14%-17% of global arable land is contaminated with toxic metals, with at least one heavy metal exceeding agricultural safety thresholds. Approximately 900-1.4 billion people live in polluted areas exceeding human health and ecological thresholds, demonstrating that soil heavy metal pollution has become a global environmental problem hindering food security and ecological health.

[0003] It is well known that heavy metal contaminated soil is characterized by its hidden nature, long-term duration, and complexity, possessing a strong biotransport capacity and easily entering the human body through bioaccumulation. Studies have shown that heavy metals (such as Cd, Pb, and As) in contaminated soil can be absorbed by plant roots and stored in the grains, stems, and leaves of crops such as rice and vegetables, leading to severely excessive levels of heavy metals in agricultural products and directly threatening human health. For example, high concentrations of toxic metals can induce diseases such as kidney failure, cardiovascular disease, immune system abnormalities, and nervous system damage. Children, as a particularly vulnerable target group, are at even greater risk. Due to the absorption mechanism of metal transport proteins, children's gastrointestinal absorption rate of Pb (40%-50%) is much higher than that of adults, which can seriously impair children's intellectual and nervous system development. In addition, heavy metals in contaminated soil may also spread to the surrounding environment through surface runoff, underground infiltration, and dust, further expanding their exposure range and exacerbating ecological risks. For agricultural land, heavy metal pollution reduces soil ecological function and arable land quality, limiting safe crop production. For construction land, abandoned mining areas, and industrial remnants, it may restrict land redevelopment and increase environmental remediation costs. Therefore, to reduce the bioavailability of heavy metals in soil, mitigate their migration and accumulation risks in the food chain, ensure agricultural product safety and ecological health, and simultaneously achieve sustainable land resource utilization, regional environmental risk prevention and control, and safe management of contaminated sites, it is necessary to develop scientific, systematic, and efficient heavy metal contaminated soil remediation technologies. These technologies will provide crucial theoretical basis and technical support for the safe utilization of agricultural land and risk management of construction land.

[0004] Current remediation technologies for heavy metal-contaminated soils mainly include physical, chemical, and biological methods. Physical remediation primarily includes soil removal, cover, and electric field-driven techniques, which are fast-acting but costly and cause significant soil disturbance. Chemical remediation uses solidification / stabilization or chemical leaching techniques to convert heavy metals into low-mobility forms, showing significant effects but potentially damaging the original physicochemical properties of the soil. Bioremediation includes phytoremediation and microbial remediation. Phytoremediation is low-cost and environmentally friendly but has a long cycle and mainly works on the topsoil. Microbial remediation reduces the toxicity and bioavailability of heavy metals in soil through adsorption, transformation, precipitation, or fixation, but its remediation effect is greatly affected by the environment. Combined remediation technologies are gradually becoming a trend, as they couple physical, chemical, and biological methods to balance remediation effectiveness and cost-effectiveness. In recent years, microbial-induced carbonate precipitation (MICP) has emerged as an environmentally friendly technology. It uses urease-producing microorganisms to catalyze the hydrolysis of urea to generate carbonate minerals, fixing heavy metals in mineral precipitates or crystal structures while improving soil structural stability. To improve the effectiveness of MIP, researchers screen heavy metal-tolerant strains, optimize temperature, pH, and substrate concentration, and introduce exogenous additives. Additives such as biochar, MgO, carboxymethyl chitosan, and phosphorus sources can provide microbial attachment sites, buffer toxicity, and promote the precipitation of CaCO3 or phosphates, enhancing the efficiency and long-term stability of heavy metal fixation. Oil shale residue (OSSC), as an industrial solid waste, has a porous structure, abundant surface active sites, and mineral components. It can passivate heavy metals through adsorption and complexation and provide carrier conditions for microbial growth and mineral nucleation. When OSSC and MICP work synergistically, the activity of heavy metals can be reduced first, and then further stabilized and solidified through carbonate mineralization, achieving efficient and long-term stable remediation of pollutants while realizing the resource utilization of waste, which aligns with the concept of green circular remediation. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergy with MIP.

[0006] A method for preparing a heavy metal contaminated soil stabilizer using oil shale residue and synergistic MIP (microbial polymerase chain reaction) includes the following steps:

[0007] Step 1: Screening and identification of functional bacteria;

[0008] Urease-producing strains with MICP function were isolated and screened from soils long-term contaminated with heavy metals. The strains with the most significant pH increase were selected as candidate strains for high-activity urease production. Genomic DNA was extracted from the candidate strains and 16S rDNA sequencing was performed for identification. The sequences were submitted to the NCBI database for BLAST comparison, and a phylogenetic tree was constructed to identify functional bacteria that can be used for the remediation of heavy metal contaminated soils.

[0009] Step 2: Preparation of modified oil shale residue (OSSC);

[0010] Oil shale residue is crushed and sieved, then pyrolyzed and modified to obtain modified OSSC material with good pore structure and abundant surface active sites.

[0011] Step 3: Modified OSSC synergistically with MIP remediation of heavy metal contaminated soil;

[0012] Modified OSSC and functional bacteria were applied to the soil to form a modified OSSC synergistic MIP system. The treatment conditions of the synergistic system were optimized according to the pyrolysis temperature, dosage and reaction time to determine the best stabilization effect and verify the advantages and feasibility of modified OSSC synergistic MIP in the long-term stabilization of heavy metal contaminated soil.

[0013] Preferably, the functional bacteria mentioned in step 1 is Bacillus lysine, which has a growth temperature of 17℃-37℃, a pH of 6.0-9.0, adsorption of heavy metals such as cadmium, chromium, copper, and zinc, and moderate salt tolerance.

[0014] Preferably, the test sieve in step 2 is 200 mesh, and the pyrolysis temperature is 300℃-800℃.

[0015] Preferably, the specific surface area of ​​the modified OSSC described in step 2 is 5.88 m². 2 / g-14.73m 2 / g, pore volume is 0.0232cm³ 3 / g-0.0449cm 3 / g, with an adsorption pore size of 13.15nm-25.42nm.

[0016] Preferably, the modified OSSC added in step 3 is 1%-7% (w / w) of the soil mass, the bacterial solution is 5% (v / w), and the bacterial solution concentration is 1×10⁻⁶. 8 CFU / mL, added either directly or by adsorption fixation.

[0017] This invention also provides the mechanism of action of the modified OSSC synergistic MIP system. In the initial stage of remediation, the modified OSSC preferentially adsorbs free metal ions in pore water, reducing the local heavy metal concentration. As the exchangeable Cu in the system... 2+ and Zn 2+ Initial reduction occurred, and synergistic remediation gradually entered a biological response-driven phase. After bacterial activity was established, the system entered the mineral transformation phase. The strain secreted urease to catalyze the hydrolysis of urea, continuously releasing NH4. + and CO3 2- Carbonate ions hydrolyze to form an alkaline solution, which raises the local pH level and increases the calcium content of the calcium ions. 2+ With CO32- Gradually becoming supersaturated, it eventually forms a carbonate precipitate dominated by calcite. During this process, exchanged Cu in the system... 2+ and Zn 2+ Through with Ca 2+ The methods of lattice transformation and co-encapsulation with carbonates have been further reduced.

[0018] The present invention can achieve the following beneficial effects:

[0019] (1) Compared with traditional soil microbial remediation methods, this invention modifies a bulk industrial solid waste, OSSC. After modification, its specific surface area and surface active sites can be significantly improved, which not only helps to enhance the adsorption and passivation of heavy metals, but also provides a carrier for microorganisms to attach, alleviate heavy metal toxicity, enhance urease activity and maintain high enzymatic efficiency, and promote the mineralization process of MIP.

[0020] (2) The combination of modified OSSC and MICP for the remediation of heavy metal contaminated soil can form a synergistic stabilizing mechanism of material adsorption and microbial mineralization. Furthermore, the resulting composite mineral has good stability and strong resistance to external interference, thus achieving the unity of pollution control and solid waste resource utilization. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0022] Figure 2 These are micrographs of the 10 strains in Example 1 of this invention.

[0023] Figure 3 This is a plate colony G1 diagram from Example 1 of the present invention.

[0024] Figure 4 This is a micrograph of G1 bacteria in Example 1 of the present invention.

[0025] Figure 5 This is the phylogenetic tree of the strain in Example 1 of the present invention.

[0026] Figure 6 This is a BLAST comparison diagram from Embodiment 1 of the present invention.

[0027] Figure 7 This is a sample image of the OSSC in Embodiment 2 of the present invention.

[0028] Figure 8 These are surface morphology analysis diagrams of OSSC samples modified at different pyrolysis temperatures in Example 2 of the present invention; the pyrolysis temperatures of (a)-(f) are 300℃, 400℃, 500℃, 600℃, 700℃ and 800℃, respectively.

[0029] Figure 9 This is a BET pore size distribution curve of OSSC samples modified at different pyrolysis temperatures in Example 2 of the present invention.

[0030] Figure 10 The images show the infrared spectra of OSSC samples modified at different pyrolysis temperatures in Example 2 of this invention; the pyrolysis temperatures of (a)-(f) are 300℃, 400℃, 500℃, 600℃, 700℃ and 800℃, respectively.

[0031] Figure 11 The following diagram illustrates the effect of modified OSSC on bacterial growth in Example 3 of this invention: (a) shows the effect of modified OSSC at different pyrolysis temperatures on bacterial growth at a dosage of 3% modified OSSC; (b) shows the effect of different dosages of modified OSSC at a pyrolysis temperature of 400℃ on bacterial growth.

[0032] Figure 12 The following graphs illustrate the effect of modified OSSC on urease activity in Example 3 of this invention: (a) shows the effect of modified OSSC at different pyrolysis temperatures on urease activity at a dosage of 3% modified OSSC; (b) shows the effect of different modified OSSC dosages on urease activity at a pyrolysis temperature of 400℃.

[0033] Figure 13 The following is a graph showing the effect of modified OSSC on the amount of calcium carbonate produced in Example 3 of the present invention: (a) shows the effect of modified OSSC at different pyrolysis temperatures on the amount of calcium carbonate produced under a dosage of 3% modified OSSC; (b) shows the effect of different dosages of modified OSSC at a pyrolysis temperature of 400℃ on the amount of calcium carbonate produced.

[0034] Figure 14 The image shows the XRD patterns of calcium carbonate induced by OSSC synergistic bacteria G1 modified at different pyrolysis temperatures in Example 3 of this invention.

[0035] Figure 15 This is a graph showing the effect of modified OSSC synergistically with MICP at different pyrolysis temperatures on the change of exchangeable heavy metal content in soil over time in Example 4 of the present invention; (a) shows the effect of modified OSSC synergistically with MICP at different pyrolysis temperatures on Cu at 3% modified OSSC dosage. 2+ (b) Effect of curing effect over time; (c) Synergistic effect of modified OSSC and MIP on Zn at different pyrolysis temperatures under 3% modified OSSC dosage. 2+ The effect of curing over time.

[0036] Figure 16 The effect of modified OSSC synergistically with MICP at different pyrolysis temperatures on the distribution of heavy metal copper speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days, respectively.

[0037] Figure 17 The effect of modified OSSC synergistically with MICP at different pyrolysis temperatures on the distribution of zinc speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days respectively.

[0038] Figure 18 This is a graph showing the effect of different dosages of modified OSSC synergistically with MICP on the change of exchangeable heavy metal content in soil over time in Example 4 of the present invention; (a) shows the effect of different dosages of modified OSSC synergistically with MICP on Cu at a pyrolysis temperature of 400℃. 2+ (b) Effect of curing effect over time; (c) Effect of modified OSSC synergistic with MIP on Zn at different dosages at a pyrolysis temperature of 400℃. 2+ The effect of curing over time.

[0039] Figure 19 The effect of different dosages of modified OSSC synergistic with MICP on the distribution of heavy metal copper speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days respectively.

[0040] Figure 20 The effect of different dosages of modified OSSC synergistic with MICP on the distribution of zinc speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days respectively.

[0041] Figure 21 This is a graph showing the effect of modified OSSC at different pyrolysis temperatures on the change of exchangeable heavy metal content in soil over time in Example 4 of the present invention; (a) shows the effect of modified OSSC at different pyrolysis temperatures on Cu at a dosage of 3% modified OSSC. 2+ (b) Effect of curing effect over time; (c) Effect of modified OSSC on Zn at different pyrolysis temperatures under a 3% modified OSSC dosage. 2+ The effect of curing over time.

[0042] Figure 22 The effect of modified OSSC at different pyrolysis temperatures on the distribution of heavy metal copper speciation in soil is shown in Example 4 of this invention; (a)-(d) are for 5 days, 10 days, 15 days and 20 days, respectively.

[0043] Figure 23 The effect of modified OSSC at different pyrolysis temperatures on the distribution of zinc speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days respectively.

[0044] Figure 24This is a graph showing the effect of different dosages of OSSC on the change of exchangeable heavy metal content in soil over time in Example 4 of the present invention; (a) shows the effect of different dosages of modified OSSC on Cu at a pyrolysis temperature of 400℃. 2+ (b) Effect of curing effect over time; (c) Effect of modified OSSC on Zn at different dosages at a pyrolysis temperature of 400℃. 2+ The effect of curing over time.

[0045] Figure 25 The effect of different dosages of modified OSSC on the distribution of copper speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days respectively.

[0046] Figure 26 The effect of different dosages of modified OSSC on the distribution of heavy metal zinc speciation in soil in Example 4 of this invention; (a)-(d) are 5 days, 10 days, 15 days and 20 days respectively.

[0047] Figure 27 The following figures illustrate the effects of modified OSSC synergistically with MIP at different pyrolysis temperatures and dosages on soil urease activity over time in Example 4 of this invention: (a) shows the effect of modified OSSC synergistically with MIP at different pyrolysis temperatures under a dosage of 3% modified OSSC on urease activity over time; (b) shows the effect of modified OSSC synergistically with MIP at different dosages under a pyrolysis temperature of 400℃ on urease activity over time.

[0048] Figure 28 This is a mechanism analysis diagram of the process of modified OSSC synergistically remediating heavy metal contaminated soil using MIP in Example 5 of the present invention. Detailed Implementation

[0049] To make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] A method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergistic with MIP (microbial polymerase). Figure 1 This is a schematic diagram of the overall process of the present invention, focusing on the repair of Cu by modified OSSC in conjunction with MICP. 2+ Zn 2+ The research on the goal of addressing soil pollution mainly focuses on the following three aspects.

[0051] (1) Screening, identification, growth characteristics and tolerance to heavy metals of urease-producing bacteria

[0052] Using heavy metal-contaminated soil as the inoculum source, strains capable of producing urease were isolated and purified. The target strains were identified using 16S rDNA sequence analysis, and a phylogenetic tree was constructed to clarify their classification. Simultaneously, the growth characteristics of the strains and their tolerance to pH and heavy metals were studied, providing a serotype basis for the subsequent construction of a MIP remediation system.

[0053] (2) Preparation, characterization, and influence of modified OSSC on the MIP process

[0054] OSSCs under different pyrolysis conditions were prepared and characterized. The effects of modified OSSCs on strain growth, urease activity, and carbonate precipitation were investigated, and their regulatory role in the MICP process was analyzed. The influence mechanism was revealed based on the characterization results.

[0055] (3) Modified OSSC synergistically with MICP to repair Cu 2+ Zn 2+ Research on contaminated soil

[0056] A modified OSSC-urease-producing bacteria synergistic remediation system was constructed, and the effects of different material conditions and dosage ratios on Cu in contaminated soil were studied. 2+ Zn 2+ Impact of Removal Efficiency. Through heavy metal speciation analysis and mineral characterization, the mechanism by which the synergistic system contributes to the immobilization and stabilization of heavy metals was explored.

[0057] The following provides a detailed description of each step of the present invention:

[0058] Example 1: Screening, identification, growth characteristics, and tolerance to heavy metals of functional bacteria

[0059] Urease-producing strains with MICP function were isolated and screened from soils that have been contaminated with heavy metals for a long time. The strains were identified by 16S rDNA sequencing, and their urease activity under alkaline conditions and tolerance to heavy metal ions were evaluated to determine the functional bacteria that can be used for the remediation of heavy metal contaminated soils.

[0060] After grinding and sieving the contaminated soil, 10g of soil was placed in an Erlenmeyer flask containing 90mL of sterile physiological saline. The flask was incubated at 30℃ and 150rpm / min for 30min with constant temperature shaking to prepare a soil suspension. After shaking, the soil suspension was removed and serially diluted with sterile physiological saline. Dilutes of 10-10 were then performed. -5 10 -6 10 -720 μL of a diluted soil solution was inoculated and spread onto the surface of autoclaved selection medium for enrichment culture and purification. Ten strains with good growth were ultimately obtained. Gram staining was used to stain the ten strains, and they were observed under a microscope. Figure 2 As shown in the figure. To further screen for highly active urease-producing strains, the 10 strains selected from the initial screening were inoculated at a 2% inoculum into LB liquid medium containing 20 g / L urea and cultured at 30℃ with shaking at 150 rpm for 48 h. The pH value of the culture medium for each strain was measured. Among them, strain G1 showed the most significant pH increase, with the pH of the medium rising from the initial 7.00 to 9.43, much higher than that of other strains (8.50-9.00), indicating that it had the strongest urea hydrolysis ability and was preliminarily selected as a highly active candidate strain. The screening plate colonies are shown in the figure. Figure 3 As shown. Malachite green was used to stain and observe the G1 strain; the results are as follows. Figure 4 As shown. Microscopic observation results showed that the G1 strain had rod-shaped cells and spores were observed. It was preliminarily identified as a Bacillus strain. Genomic DNA was extracted from strain G1, the 16S rDNA fragment was amplified and sequenced, and the sequence was submitted to the NCBI database for BLAST alignment. Its phylogenetic tree is shown below. Figure 5 As shown, strain G1 shares 99.31% homology with Lysinibacillus macroides, as... Figure 6 As shown; a phylogenetic tree constructed using MEGA software ( Figure 5 ), BLAST comparison image ( Figure 6 ) and Gram staining diagram of the strain ( Figure 2 The strain G1 was confirmed to belong to the genus Bacillus lysine.

[0061] The G1 strain was inoculated into LB liquid medium at a 2% inoculum and divided into two groups. One group was cultured under free air exchange, while the other group was cultured under N2 conditions. Both groups were shaken on a shaker at 200 rpm / min and cultured at 30°C for 48 hours. The optical density (OD) of the bacterial suspension at 600 nm was measured periodically. 600 Observe the turbidity of the bacterial culture. The strain can only grow normally under aerobic conditions, OD 600 A significant increase was observed, resulting in turbidity of the bacterial culture; however, under anaerobic conditions, OD... 600 There was essentially no change, and no visible colonies formed. Therefore, this bacterium is an aerobic bacterium.

[0062] The G1 strain was inoculated at a 2% inoculation rate into multiple aliquots of the same LB liquid medium and cultured in constant-temperature shakers at 7℃, 12℃, 17℃, 22℃, 37℃, 42℃, and 47℃ (200 rpm / min). OD values ​​were measured every 2 hours.600 Growth curves were plotted at different temperatures, and the maximum specific growth rate and final biomass were compared at each temperature. The results showed that the strain maintained a high growth rate and significant turbidity within the temperature range of 17℃-37℃, exhibiting the most vigorous growth; when the temperature was below 12℃ or above 42℃, growth was extremely slow or ceased. Therefore, the optimal growth temperature range was determined to be 17℃-37℃.

[0063] The initial pH of the liquid culture medium was precisely adjusted to 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, and 13.0 using HCl and NaOH, respectively. After sterilization, the pH was retested to confirm that the changes were within the allowable range. The G1 strain was inoculated at a 2% inoculum and cultured with shaking at 25°C for 48 hours. The OD values ​​before and after incubation were measured. 600 and viable cell count. The strains could all achieve normal proliferation in culture media with an initial pH of 6.0-9.0, OD... 600 Growth is significantly increased; when the pH is below 5.0 or above 10.0, growth is almost undetectable. Therefore, the optimal pH range for this bacterium's growth is 6.0-9.0.

[0064] Different masses of NaCl were added to LB liquid medium to prepare a series of media with NaCl concentrations (w / v) of 0%, 1%, 3%, 5%, 7%, and 10%. After inoculation with strain G1, the media were cultured with shaking (200 rpm / min), and OD was continuously monitored. 600 The changes in the bacterial cell morphology were observed. This strain grew well at 0%-5% NaCl concentrations, with a significantly slower growth rate at 7% NaCl concentration, although a certain level of turbidity could still be achieved after extended incubation. It showed almost no growth at a 10% NaCl concentration. Referring to the general classification standards for microbial salt tolerance (non-halophilic, mild, moderate, extreme halophilic), its salt tolerance characteristics meet the moderate salt tolerance level, therefore it is described as having moderate salt tolerance.

[0065] LB liquid medium with different heavy metal concentrations was prepared by adding CuCl2·2H2O and ZnCl2 to 100 mL of LB liquid medium with pH 7, respectively. 2+ The concentrations were 0 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, and 300 mg / L, respectively; Zn 2+ The concentrations were 0 mg / L, 30 mg / L, 60 mg / L, 90 mg / L, 120 mg / L, 150 mg / L, and 180 mg / L. The prepared 2% bacterial suspensions were inoculated into LB medium at each metal concentration and cultured at 30℃ with shaking at 150 rpm for 48 h. Odulescence (OD) was measured aseptically every 2 h. 600 To obtain Cu 2+ Zn2+ Bacterial OD under stress 600 The changes were observed. Three replicates were set up for each experiment. The G1 strain's response to Cu... 2+ and Zn 2+ Both exhibited strong tolerance, with maximum tolerance thresholds of 250 mg / L and 150 mg / L, respectively. However, under high concentrations of heavy metal stress, the process of establishing effective mineralization activity in the bacteria was significantly hindered, particularly in Zn. 2+ It exhibits stronger stress response. With Cu 2+ and Zn 2+ As Cu concentration increased, the lag phase of the strain was significantly prolonged; 2+ and Zn 2+ When the concentrations reached 250 mg / L and 150 mg / L, respectively, the cell activation time was extended to 24 h and 22 h, respectively, indicating that the initial metabolic activation process was significantly inhibited.

[0066] This bacterium grows aerobically, with an optimal temperature of 17℃-37℃ and a pH range of 6.0-9.5. It has moderate salt tolerance and adsorption capacity for heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), and zinc (Zn).

[0067] Example 2: Preparation and Characterization of Modified Oil Shale Residue (OSSC)

[0068] Pyrolysis modification of oil shale residue was carried out by adjusting the pyrolysis temperature and process parameters to obtain modified OSSC material with good pore structure and abundant surface active sites. The effects of modified OSSC on bacterial growth, urease activity and calcium carbonate production were evaluated in a liquid phase system to provide optimized conditions for the MIP process.

[0069] The OSSC used in this invention was obtained from an oil shale retorting plant in Liaoning Province. The OSSC sample is as follows: Figure 7As shown. The surface morphology and pore development characteristics of the material are important factors affecting its adsorption performance and microbial adhesion ability. The pyrolysis temperature is an important parameter for changing the surface morphology and pore development of the material. OSSC was washed with deionized water, dried to constant weight in a 105℃ forced-air drying oven, pulverized, and sieved through a 200-mesh sieve for later use. The dried OSSC was placed in a muffle furnace and heated to 300℃, 400℃, 500℃, 600℃, 700℃, and 800℃ at a heating rate of 10℃ / min, respectively, and calcined for 2 hours before cooling to room temperature for later use. The high-temperature pyrolysis activated modified OSSC was mixed with 32g / L NaOH solution at a solid-liquid ratio of 1:2, soaked for 8 hours, repeatedly rinsed with distilled water until neutral, and dried to constant weight in a 105℃ oven to obtain modified OSSC samples at different pyrolysis temperatures. The surface morphology, pore structure parameters, and functional group variations of modified OSSC samples at different pyrolysis temperatures were characterized using scanning electron microscopy (SEM), surface area analysis (BET), and Fourier transform infrared spectroscopy (FT-IR). This study aimed to reveal the regulatory effect of pyrolysis temperature on the material's structural properties and to provide a basis for screening optimal modification conditions and elucidating their subsequent mechanisms of action in adsorption and MIP systems. The SEM and BET pore size distribution curves and Fourier transform infrared spectra of the modified OSSC are shown below. Figure 8-10 As shown, OSSCs prepared at different pyrolysis temperatures (300℃, 400℃, 500℃, 600℃, 700℃, and 800℃) and then alkali-activated exhibit an irregular layered framework structure. The surface structure gradually evolves from dense to rough and porous with increasing temperature. After alkali modification, some silica-alumina phases undergo surface erosion, promoting pore structure development and forming channels conducive to solution diffusion and ion exchange. After thermal modification, residual volatiles are removed, the structure between the original mineral particles is weakened, and the number of surface cracks and pores increases. However, with increasing pyrolysis temperature, some micropores and small pores collapse or close due to framework shrinkage, local sintering, and mineral phase reconstruction, leading to local re-densification and potentially reducing the material's effective specific surface area and the number of available active sites. Therefore, a suitable pyrolysis temperature should promote the release of volatile components and alkali-induced pore formation while avoiding pore collapse caused by high temperatures, thus providing a more stable structural basis for the adsorption and fixation of heavy metals and MICP strengthening. The specific surface area, pore volume, and adsorption pore size of BET are shown in Table 1. Different pyrolysis temperatures significantly affect the pore structure parameters of the modified OSSC. The specific surface area of ​​BET for samples obtained at 300℃, 400℃, and 500℃ is 11.62 m². 2 / g, 14.73m 2 / g and 8.92m 2 / g, pore volume is 0.0426cm³ 3 / g, 0.0449cm 3 / g and 0.0377cm3 The average pore sizes were 14.09 nm, 13.15 nm, and 16.77 nm, respectively. Overall, the 400℃ sample had the largest specific surface area and pore volume among the three, while also having the smallest average pore size, indicating that this sample formed a more developed and uniform mesoporous structure. A larger specific surface area means that more adsorption sites can be exposed on the material surface, while a higher pore volume is conducive to the entry of ions from the solution into the pores and the diffusion and interfacial reactions. Therefore, the OSSC sample with a pyrolysis temperature of 400℃ is theoretically the most favorable for heavy metal adsorption.

[0070]

[0071] Example 3: Study on the effect of modified OCCS on the MIP process

[0072] Besides possessing certain heavy metal adsorption and buffering capabilities, modified OSSCs may also promote the MICP process by providing an attachment carrier, improving the local environment, and increasing nucleation sites. Based on this, this invention investigates the effects of modified OSSCs at different pyrolysis temperatures (300℃, 400℃, 500℃, 600℃, 700℃, and 800℃), dosages (1%, 3%, 5%, and 7%), and addition methods (direct addition and adsorption fixation) on bacterial growth and reproduction, urease activity, and carbonate precipitation formation, focusing on three aspects: bacterial growth, urease activity, and carbonate precipitation formation.

[0073] Direct addition method: 2% bacterial culture was inoculated into 100 mL of LB liquid medium containing 20 g / L urea. OSSC modified at pyrolysis temperatures of 300℃, 400℃, 500℃, 600℃, 700℃, and 800℃ was added at concentrations of 1%, 3%, 5%, and 7%, respectively. The cultures were then incubated at 30℃ and 150 rpm for 48 h with shaking. After incubation, the OD values ​​of the culture media in each treatment group were measured. 600 To characterize the growth of the strain, the sodium hypochlorite-phenol colorimetric method was used to determine urease activity, and the effect of direct addition of modified OSSC on bacterial growth and urease activity was analyzed.

[0074] Adsorption and fixation method: Modified OSSCs under different treatment conditions were sterilized and added to bacterial cultures in the logarithmic growth phase. The cultures were incubated at 30℃ and 150 r / min for 24 h with shaking to allow for complete adsorption of bacterial cells. The modified OSSCs with adsorbed bacterial cells were then added to 100 mL of LB liquid medium containing 20 g / L urea. After incubation, the OD values ​​of the culture media in each treatment group were measured. 600 The growth of the strain was characterized; at the same time, the urease activity was determined by the sodium hypochlorite-phenol colorimetric method.

[0075] The LB liquid medium containing urea was replaced with LB liquid medium containing urea and calcium chloride, with both urea and calcium chloride concentrations at 20 g / L, while other culture conditions remained unchanged. After culture, the culture medium was filtered, the solid precipitate was collected, washed with deionized water, dried at 105 °C to constant weight, and the amount of calcium carbonate precipitate formed was weighed. The effect of modified OSSC on the formation of MIP mineralization products under different conditions was analyzed.

[0076] The test results are as follows Figure 11-13 As shown, modified OSSC significantly affects bacterial growth and reproduction, urease activity, and carbonate precipitation in the MIP system. In the unfixed (direct addition) system, the pyrolysis sample at 400℃ exhibited the best mineralization-promoting ability. In the fixed (adsorption-fixation) system, the 500℃ sample showed a slight advantage in carbonate formation, indicating that pore structure morphology plays a crucial regulatory role in the immobilization and mineralization process. Overall, the OSSC sample with a pyrolysis temperature of 400℃ achieved a good comprehensive balance between bacterial growth, urease activity, and carbonate formation, thus remaining a preferred material for subsequent synergistic remediation systems. At a pyrolysis temperature of 400℃, the direct addition method resulted in better urease activity, bacterial growth and reproduction, and carbonate precipitation than the adsorption-fixation method. Therefore, the direct addition method was adopted. The 3% modified OSSC addition resulted in slightly higher urease activity, bacterial growth and reproduction, and carbonate precipitation than other addition methods, thus a 3% modified OSSC addition was selected.

[0077] To further clarify the influence of modified OSSC on the formation of MIP mineralization products, this invention performed XRD analysis on the precipitates induced by modified OSSC and strain G1 under different pyrolysis temperatures (300℃, 400℃, 500℃, 600℃, 700℃, and 800℃), direct addition, and 3% addition. By comparing the changes in the positions and intensities of mineral diffraction peaks in each treatment group, the influence of modified OSSC on the crystallization characteristics and mineral stability of calcium carbonate was analyzed. From a mineralogical perspective, its promoting effect and mechanism on the MIP process were further elucidated. The results are as follows: Figure 14 As shown in the figure, the precipitates obtained after MIP mineralization with modified OSSC prepared at different pyrolysis temperatures all exhibited obvious and sharp diffraction peaks near 2θ≈29.40°, indicating that highly crystalline calcium carbonate minerals were formed in each treatment group. According to existing research, the strong characteristic peak of CaCO3 at 2θ≈29.4° in XRD patterns usually corresponds to the main crystal plane diffraction peak of calcite, and the intensity of this peak is often used to reflect the degree of calcite formation and crystallization characteristics. Therefore, it can be determined that calcite is the main crystal form in the precipitates of each treatment group in this study, indicating that strain G1 can effectively induce the formation of stable calcium carbonate precipitates in the presence of modified OSSC.

[0078] Example 4: Modified OSSC synergistically with MIP repairs of Cu 2+ Zn 2+ Research on contaminated soil

[0079] Modified OSSC and functional bacteria were applied to the soil to form a synergistic MIP system. The experiment included four treatment groups: a blank control group, an OSSC group, a MIP group, and a modified OSSC+MICP synergistic group. The blank control group used only heavy metal-contaminated soil without any added remediation materials or bacterial solutions.

[0080] The OSSC component was divided into two experiments: a fixed dosage of 3% was used to screen the optimal preparation conditions by setting three pyrolysis temperatures of 300℃, 400℃, and 500℃; the temperature was fixed at 400℃ and dosages of 1%, 3%, 5%, and 7% were set, with the dosage ratio based on the dry weight of the soil.

[0081] 5 mL of MICP solution was added to the group at a concentration of 1×10⁻⁶. 8 Logarithmic growth phase bacterial culture (CFU / mL).

[0082] The modified OSSC+MICP synergistic group also set up two sets of experiments: under a fixed dosage of 3% modified OSSC, the modified OSSC and 5mL bacterial solution at different pyrolysis temperatures of 300℃, 400℃ and 500℃ were used for remediation experiments; under a fixed modified OSSC temperature of 400℃, the modified OSSC and 5mL bacterial solution at different dosages of 1%, 3%, 5% and 7% were used for synergistic remediation experiments.

[0083] 100g of pretreated heavy metal contaminated soil was weighed and placed in a culture container, with the soil moisture content adjusted to 25%–30%. 10mL of a 20g / L mixture of urea and anhydrous calcium chloride was added to each group to provide the substrate and calcium source for the MICP reaction.

[0084] The Tessier sequential extraction method was used to determine the occurrence speciation of heavy metals in soil or sediment. After drying, grinding, and passing through a 100-mesh sieve, 1.0 g of the sample was accurately weighed into a 50 mL centrifuge tube, and five consecutive extraction steps were performed. The first step was exchangeable extraction: 8 mL of 1.0 mol / L MgCl2 solution (pH=7.0) was added to the sample, shaken at room temperature for 1 h, and centrifuged at 4000 rpm for 20 min. The supernatant was collected for heavy metal concentration determination; this fraction represents the exchangeable heavy metal content. The second step was carbonate-bound extraction: 8 mL of 1.0 mol / L NaOAc buffer (adjusted to pH 5.0 with acetic acid) was added to the residue from the first step, shaken at room temperature for 5 h, and centrifuged at 4000 rpm for 20 min. The supernatant was collected for heavy metal concentration determination; this fraction represents the carbonate-bound heavy metal content. The third step was iron-manganese oxide extraction: 20 mL of 0.04 mol / L... The first step was extraction with NH2OH·HCl-25% acetic acid solution. The mixture was heated in a water bath at 96±3℃ for 6 hours with intermittent shaking during extraction. The sample was then centrifuged at 4000 r / min for 20 min, and the supernatant was collected for heavy metal concentration determination. This fraction represents the content of iron and manganese oxides. The second step was organic-bound extraction. 3 mL of 0.02 mol / L HNO3 and 5 mL of 30% H2O2 (pH=2) were added to the residue from the third step. The mixture was heated in a water bath at 85±2℃ for 2 hours with intermittent shaking. Then, another 3 mL of the same 30% H2O2 was added, and heating continued for another 3 hours. After cooling, 5 mL of 3.2 mol / L NH4OAc-20% HNO3 solution was added, and the mixture was shaken at room temperature for 30 min. The sample was then centrifuged at 4000 r / min for 20 min, and the supernatant was collected for heavy metal concentration determination. This fraction represents the content of organic-bound heavy metals. The third step was residual extraction. The residue from the fourth step was digested with strong acid, and the residual metal content was determined. The metal concentration in the extract at each step was determined using a flame atomic absorption spectrophotometer.

[0085] The treatment conditions of the synergistic system were optimized based on the pyrolysis temperature, dosage, and reaction time of the OSSC samples to determine the optimal stabilization effect and verify the effect of modified OSSC synergistic with MICP in the long-term stabilization of Cu. 2+ Zn 2+ Advantages and feasibility of using contaminated soil.

[0086] To investigate the effect of OSSC modified at different pyrolysis temperatures on Cu synergistically with MICP 2+ Zn 2+ The remediation effect of compound contaminated soil was investigated. Under the condition of 3% modified OSSC dosage, the Cu content in soil treated with modified OSSC and synergistic MIP at pyrolysis temperatures of 300℃, 400℃, and 500℃ was compared. 2+ Zn 2+The changes in the exchangeable state content were analyzed, and the results are as follows: Figure 15-17 As shown. To compare the effects of the synergistic system on the heavy metal Cu. 2+ Zn 2+ To investigate the effect of changes in exchangeable state content, separate experimental groups were set up for adding modified OSSC individually (pyrolysis temperatures of 300℃, 400℃, and 500℃ at a 3% dosage, and dosages of 1%, 3%, 5%, and 7% at a pyrolysis temperature of 400℃) as a control experiment. The results are as follows: Figure 21-26 As shown.

[0087] Depend on Figure 15-17 It can be seen that Cu in group CK 2+ and Zn 2+ The exchangeable state content remained relatively stable during the incubation period, indicating that the soil system itself had a weak fixation effect on the two heavy metals. After MICP treatment, Cu... 2+ and Zn 2+ The exchangeable Cu content gradually decreased with prolonged culture time, indicating that the MICP process itself can reduce heavy metal activity to some extent. Compared with MICP treatment alone, the addition of modified OSSC significantly reduced the exchangeable Cu content in each synergistic treatment group. 2+ and Zn 2+ The reduction effect was significantly enhanced, and the overall trend was a continuous decrease with the extension of culture time, indicating that modified OSSC can effectively enhance the stabilizing effect of MICP on heavy metals. For Cu... 2+ In the CK group, the exchangeable Cu content decreased only from 277 mg / kg to 274 mg / kg, while in the MIP group it decreased to 220 mg / kg at 20 days. After treatment with MIP+OSSC300, MIP+OSSC400, and MIP+OSSC500 in synergistic effect with MIP, the exchangeable Cu content decreased at 20 days. 2+ The concentrations of Cu were reduced to 165 mg / kg, 147 mg / kg, and 183 mg / kg, respectively, with OSSC400 showing the best synergistic effect with MIP treatment. Its concentration rapidly decreased from 277 mg / kg to 156 mg / kg within the first 10 days of cultivation, demonstrating strong initial stabilization ability. By day 20, the concentration had decreased by 46.93% from the initial value, significantly better than other experimental groups. This indicates that the modified OSSC obtained by pyrolysis at 400℃ is more conducive to the rapid reduction of Cu in the synergistic system. 2+ It maintains activity and provides good subsequent stabilization. (Zn) 2+ The variation pattern of Cu 2+ Basically the same, but the overall decrease is greater. CK group exchanged state Zn 2+ The concentration of Zn was maintained at approximately 159 mg / kg throughout the culture period, decreasing to 127 mg / kg in the MIP group at day 20. After synergistic treatment, the exchanged Zn concentration in the OSSC300+MICP, OSSC400+MICP, and OSSC500+MICP groups...2+ The concentrations were reduced to 100 mg / kg, 79 mg / kg, and 107 mg / kg, respectively, with the 3% OSSC400 treatment showing the best performance, reducing the concentration by 50.31% compared to the initial value. The results indicate that this synergistic system effectively reduces Cu... 2+ Zn 2+ Both exhibited strong stabilizing effects; OSSC modified by pyrolysis at 400℃ promoted Cu... 2+ Zn 2+ It has a more significant advantage in reducing activity. Compared with treatment that modifies OSSC materials alone, such as... Figure 21-23 As shown, the exchanged Cu after 20 days of 3% OSSC400 treatment 2+ The concentration of Zn decreased from 277 mg / kg to 240 mg / kg. 2+ The concentration decreased from 159 mg / kg to 132 mg / kg, indicating that the introduction of MICP significantly enhanced the stabilizing effect of modified OSSC on exchangeable heavy metals.

[0088] Depend on Figure 18-20 It can be seen that under the synergistic treatment of modified OSSC and MIP at different dosages, the 400℃ modified OSSC and MIP system exhibits a clear pattern of initial enhancement followed by stabilization. Regarding Zn... 2+ The exchangeable levels of MIP+1%OSSC400, MIP+3%OSSC400, MIP+5%OSSC400, and MIP+7%OSSC400 at 20 days were 109 mg / kg, 79 mg / kg, 77 mg / kg, and 71 mg / kg, respectively, all significantly lower than the control group and the MIP group. The rate of decrease slowed after 3%OSSC400. Although the levels continued to decrease in the 5%OSSC400 and 7%OSSC400 experimental groups, considering the aforementioned liquid phase experiments and changes in urease activity in the soil system, excessive dosage may cause soil pore compression, hindered mass transfer, and uneven local microenvironment, which may not be conducive to long-term stable mineralization. 2+ The changing trend of Zn 2+ Similarities but slight fluctuations were observed. At 20 days, the exchange states of the MICP+1%OSSC400, MIP+3%OSSC400, MIP+5%OSSC400, and MIP+7%OSSC400 synergistic groups were 181 mg / kg, 147 mg / kg, 145 mg / kg, and 146 mg / kg, respectively. This indicates that the MIP+3%OSSC400 group had achieved a relatively high level of fixation effect. Further increasing the dosage could slightly reduce the exchange state, but the improvement was limited. Therefore, considering both remediation efficiency and material economy, the dosage of modified OSSC obtained from 400℃ pyrolysis (3%) is more suitable as the optimized dosage for the synergistic system.

[0089] The effects of modified OSSC synergistically with MIP at different pyrolysis temperatures and dosages on soil urease activity, such as Figure 27 As shown in the figure, under different pyrolysis temperature synergistic systems, soil urease activity generally increased over time, but significant differences existed between treatments. In the MIP group, urease activities at 5d, 10d, 15d, and 20d were 24 μmol / min, 43 μmol / min, 51 μmol / min, and 52 μmol / min, respectively, indicating that the strain could survive in the soil and gradually establish mineralization capacity, but its activity growth was relatively slow under high heavy metal background. After adding modified OSSC, the 3% OSSC300 synergistic group reached 57 μmol / min at 20d, the 3% OSSC400 synergistic group reached 59 μmol / min, and the 3% OSSC500 synergistic group reached 55 μmol / min. Overall, the 400℃ synergistic group showed high and stable urease activity at all time points, especially significantly higher than the MIP group after 10d, indicating that the modified material at suitable pyrolysis temperature can provide a more ideal attachment and growth space for the bacteria, alleviate heavy metal toxicity, and maintain high enzymatic efficiency. The changes in urease activity under different dosage treatments further confirm the rationality of the 3% modified OSSC dosage. At 20 days, the urease activities of the 1% OSSC400, 3% OSSC400, 5% OSSC400, and 7% OSSC400 synergistic groups were 55 μmol / min, 59 μmol / min, 61 μmol / min, and 56 μmol / min, respectively. Although the value of the 5% OSSC400 group was slightly higher, the difference compared to the 3% OSSC400 group was not significant. Considering that higher dosages may lead to decreased soil porosity and increased mass transfer resistance, the 3% OSSC400 group showed a better balance between remediation efficiency, system uniformity, and material utilization. The trend in urease activity demonstrates that the stabilization of heavy metals in the synergistic system may not solely rely on material adsorption, but rather on the enhanced microbial mineralization process as the core driving force.

[0090] Example 5: Mechanism analysis of the synergistic repair process of modified OSSC and MIP

[0091] Based on the aforementioned evaluation of remediation effects, this study further elucidates the intrinsic reasons for the remediation of heavy metal pollution by modified OSSC in synergy with MICP from the perspective of mechanism of action, and confirms the promoting effect and synergistic mechanism of the synergistic system on the stabilization of heavy metals.

[0092] Based on the aforementioned strain screening, material characterization, liquid phase mineralization experiments, and soil remediation results, it can be concluded that modified OSSC synergistically utilizes MIP to remediate Cu. 2+ Zn 2+Contaminated soil remediation is not a simple superposition of single adsorption or single mineralization processes, but rather a continuous synergistic process that progresses in stages, including initial interfacial adsorption and buffering, intermediate microbial response and mineralization, and late-stage heavy metal stabilization and sequestration. The mechanism analysis of the modified OSSC synergistic MIP remediation process is as follows: Figure 28 As shown.

[0093] In the initial stages of remediation, modified OSSC primarily functions as an interfacial adsorption and toxicity buffer. Exchangeable Cu in the soil... 2+ and Zn 2+ Exhibiting high mobility and bioavailability, it is the main component causing direct toxicity to bacteria. Modified OSSC, after pyrolysis and alkali modification, exhibits increased surface roughness and a more developed mesoporous structure, exposing more oxygen-containing functional groups and mineral active sites. Therefore, it can preferentially adsorb free metal ions in pore water, reducing local heavy metal concentrations. With the free Cu in the system... 2+ and Zn 2+ Initial reduction occurred, and synergistic remediation gradually entered a biological response-dominated phase. After bacterial activity was established, the system entered the mineral transformation phase. The G1 strain secreted urease to catalyze the hydrolysis of urea, continuously releasing NH4. + and CO3 2- Carbonate ions hydrolyze to form an alkaline solution, which raises the local pH level and increases the calcium content of the calcium ions. 2+ With CO3 2- Gradually becoming supersaturated, it eventually forms a carbonate precipitate dominated by calcite. During this process, exchanged Cu... 2+ and Zn 2+ Further reduction can be achieved through two methods: embedding and lattice substitution. As mineralization continues, the system eventually enters the structural preservation stage. At this point, a composite structure gradually forms in the soil, with modified OSSC particles as the core, calcium carbonate minerals as the cementing phase, and microbial cells and their metabolites as the connecting interface. This result is particularly important for practical engineering applications because soil remediation is not just about reducing the content of extractable states in the short term; more importantly, it is about maintaining a low risk of re-release under subsequent fluctuations in rainfall, acidification, or redox conditions. Recent studies on the long-term stability of MICP have also gradually indicated that the composite mineral structure formed by the participation of carrier materials is often more resistant to external disturbances than single carbonate precipitation, thereby improving the durability of remediation.

[0094] In summary, modified OSSC synergistically with MICP can effectively improve Cu 2+ Zn 2+ The stabilization efficiency of heavy metals in complex contaminated soils and the realization of resource utilization of industrial solid waste provide a theoretical basis and technical support for the remediation of heavy metal contaminated soils by modified OSSC and synergistic MIP.

Claims

1. A method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergistic with MIP, characterized in that, Includes the following steps: Step 1: Screening and identification of functional bacteria; Urease-producing strains with MIP function were isolated and screened from soils that have been contaminated with heavy metals for a long time. The strains with the most significant pH increase were selected as high-activity urease-producing candidate strains. Genomic DNA was extracted from candidate strains and identified by 16S rDNA sequencing. The sequences were submitted to the NCBI database for BLAST comparison, and a phylogenetic tree was constructed to identify functional bacteria that can be used for the remediation of heavy metal contaminated soil. Step 2: Preparation of modified oil shale residue; The oil shale residue is crushed and sieved, and then pyrolyzed to obtain a modified oil shale residue material with good pore structure and abundant surface active sites. Step 3: Modified oil shale residue synergistically with MIP remediation of heavy metal contaminated soil; Modified oil shale residue and functional bacteria were applied to the soil to form a modified oil shale residue synergistic MIP system. The treatment conditions of the synergistic system were optimized according to the pyrolysis temperature, dosage and reaction time to determine the best stabilization effect and verify the advantages and feasibility of modified oil shale residue synergistic MIP in the long-term stabilization of heavy metal contaminated soil.

2. The preparation method of a heavy metal contaminated soil stabilizer based on oil shale residue and synergistic MIP according to claim 1, characterized in that, The functional bacteria in step 1 is Bacillus lysine. The growth temperature of this bacterium is 17℃-37℃, the pH is 6.0-9.0, it has an adsorption effect on heavy metals such as cadmium, chromium, copper and zinc, and has moderate salt tolerance.

3. The method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergistic with MIP according to claim 1, characterized in that, The test sieve in step 2 is 200 mesh, and the pyrolysis temperature is 300℃-800℃.

4. The preparation method of a heavy metal contaminated soil stabilizer based on oil shale residue and synergistic MIP according to claim 1, characterized in that, The specific surface area of ​​the modified oil shale residue material in step 2 is 5.88 m². 2 / g-14.73m 2 / g, pore volume is 0.0232cm³ 3 / g-0.0449cm 3 / g, with an adsorption pore size of 13.15nm-25.42nm.

5. The method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergistic with MIP according to claim 1, characterized in that, In step 3, the amount of modified oil shale residue added is 1%-7% (w / w) of the soil mass, the amount of bacterial solution added is 5% (v / w) of the soil mass, and the concentration of bacterial solution is 1×10⁻⁶. 8 CFU / mL, added either directly or by adsorption fixation.

6. The method for preparing a heavy metal contaminated soil stabilizer using oil shale residue in synergy with MIP according to claim 1, characterized in that, In the initial stage of remediation, the modified oil shale residue preferentially adsorbs free metal ions in the pore water, reducing the local heavy metal concentration. As the exchangeable Cu in the system... 2+ and Zn 2+ After initial reduction, the synergistic repair gradually enters the biological response-dominated stage. After the bacterial activity is established, the system enters the mineral transformation stage, where the strain secretes urease to catalyze the hydrolysis of urea, continuously releasing NH4. + and CO3 2- Carbonate ions hydrolyze to form an alkaline solution, which increases the local pH level and causes calcium levels to drop. 2+ With CO3 2- Gradually becoming supersaturated, it eventually forms a carbonate precipitate dominated by calcite. During this process, exchanged Cu in the system... 2+ and Zn 2+ Through with Ca 2+ The methods of lattice transformation and co-encapsulation with carbonates have been further reduced.

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