Stabilized repair method for associated lead element in mining area soil

Abstract

The invention discloses a stable remediation method for lead element in mining area soil, and relates to the technical field of heavy metal contaminated soil remediation, and the technical scheme is as follows: the method comprises the following steps: preparing heavy metal lead contaminated soil, adding a nonmetallic mineral material consisting of medical stone, montmorillonite and potassium phosphate into the heavy metal lead contaminated soil, and uniformly mixing; wherein the addition amount of the non-metallic mineral material is 0.5%-3% of the mass of the heavy metal lead polluted soil based on the heavy metal lead polluted soil, the ratio of the medical stone to the montmorillonite to the potassium phosphate is 1: 1: x, the value of x is 0.5 and 2, and the addition amount of the non-metallic mineral material accounts for 1%-8% of the total mass of the soil. According to the method, modified nonmetallic mineral materials, namely medical stone and montmorillonite, are applied, lead is precipitated by potassium phosphate, and then heavy metal lead in the soil is converted into a stable residue-state compound under the action of the medical stone and the montmorillonite, so that stable remediation of the lead element in the mining area soil is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal contaminated soil remediation, and more specifically, it relates to a method for stabilizing and remediating lead elements in mine soil. Background Art

[0002] Due to unreasonable mineral extraction and treatment methods, the soil around mining areas has been severely contaminated by heavy metals. In the past few decades, with the development of the national economy, the demand for mineral resources has increased, but the extraction technology at that time was relatively backward, resulting in serious environmental problems during the mining process. After mining, the slag was randomly piled up and not disposed of in a timely manner. With weathering and long-term rain leaching, it will inevitably lead to the pollution of the surrounding soil environment, and then cause heavy metal pollution.

[0003] In recent years, the area of land contaminated by heavy metals in China has been increasing continuously, causing serious economic losses. Most of them are agricultural lands. The heavy metal pollution of farmland soil is relatively hidden, and the pollution process is relatively long, which is not easily manifested in the short term. At the same time, it is difficult to effectively remove heavy metal pollutants in the soil. Research shows that during the pollution process of farmland soil, the most seriously polluted metal elements include lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), chromium (Cr), arsenic (As), etc. Especially in the land for vegetable planting, the heavy metal pollution far exceeds other types of land. These pollutants can harm humans through the transfer of the soil-plant system. Therefore, the treatment of heavy metal pollution in soil has become a research hotspot and difficulty in the international community in recent years. To solve this problem, it is necessary to strengthen the monitoring and assessment of farmland soil pollution, develop heavy metal treatment technologies suitable for local soil characteristics, and take preventive measures to avoid new pollution sources from entering the soil, promote the sustainable development of agriculture, rationally utilize agricultural resources, select heavy metal-tolerant plants, and pay attention to the supervision of the quality and safety of agricultural products, which are also important directions for treating soil heavy metal pollution.

[0004] To solve the above problems, the existing technology uses the method of soil heavy metal stabilization to stabilize the metals in the soil, including engineering technology fixation method, in-situ remediation method with amendments, and bioremediation method. The principles of these methods are mainly to remove heavy metals from the original soil or change their forms to fix them in the soil and reduce their migration ability and bioavailability. Among them, the in-situ remediation method with amendments is widely used. It has the characteristics of good economy, easy to achieve large-area treatment, and significant treatment effect on moderately and mildly heavy metal contaminated soil. This method was first used to treat heavy metal pollution in water bodies and then gradually applied to treat heavy metal contaminated soil. This method mainly fixes and remediates heavy metal pollutants in the soil by adding amendments (such as lime, inorganic fertilizers, organic fertilizers, clay minerals, etc.).

[0005] In addition to the in-situ remediation method using amendments, the engineering technology fixation method and the bioremediation method have also been applied to the treatment of heavy metal pollution in soil. The engineering technology fixation method mainly includes methods such as soil stripping, soil capping, and soil solidification / stabilization. By changing the physical structure of the soil and adding solidifying agents, etc., heavy metal pollutants are fixed. The bioremediation method utilizes the absorption and enrichment ability of plants. Through the biological absorption, transportation, and fixation of plants, heavy metals are stabilized in the plants or in the soil around the plant roots.

[0006] The above-mentioned solutions can effectively treat heavy metal pollution in soil to a certain extent; however, there are still some deficiencies in the above methods: First, although the in-situ remediation method using amendments has achieved remarkable results in treating moderately polluted heavy metal soil, the effect may not be ideal for severely polluted heavy metal soil. Moreover, some amendments have good adsorption effects on specific heavy metals, but may not work well for other heavy metals. At the same time, the substances applied during the heavy metal stabilization process also have a reducing effect on the fertility of the soil itself. Second, the bioremediation method requires suitable plants to absorb and enrich heavy metals, and there are limiting factors such as plant species selection, adaptability, and long growth cycles. In addition, the bioremediation method is relatively slow and takes a long time to achieve the desired remediation effect. Third, the engineering technology fixation method usually requires soil stripping, capping, or solidification treatment in the polluted area. These methods will damage the original soil structure and ecological environment, resulting in waste of land resources, and the cost of maintaining these projects in the long term is also relatively high.

[0007] Research shows that clay minerals are effective when applied to treat soil polluted by cadmium, lead, copper, and zinc. Combining with the pollution characteristics of the main associated pollution element lead in the mining area, this invention selects the farmland soil in the molybdenum mining area as the research object, provides a method for the adsorption performance of heavy metal lead in the farmland soil around the mining area using medical stone, montmorillonite combined with potassium phosphate, and for the blocking of lead pollution in the mining area soil, and provides a certain theoretical basis for finding suitable remediation methods, remediation materials, and increasing soil fertility. Summary of the Invention

[0008] The purpose of this invention is to provide a method for stabilizing and remediating lead elements in mining area soil to solve the problems of low adsorption efficiency and damage to the original ecology in the prior art.

[0009] The above technical object of the present invention is achieved by the following technical solutions: A method for stabilizing and repairing lead elements in mine soil, including preparing heavy metal lead-polluted soil, adding a mixed mineral repair material composed of zeolite, montmorillonite and potassium phosphate to the heavy metal lead-polluted soil and mixing evenly. Based on the heavy metal lead-polluted soil, the addition amount of the mixed mineral repair material is 0.5%-3% of the mass of the heavy metal lead-polluted soil. The ratio of zeolite, montmorillonite and potassium phosphate is 1:1:x, where the value of x is 0.5 or 2, and the added amount accounts for 1%-8% of the total soil mass.

[0010] Further, the organic bound state in the heavy metal lead-polluted soil accounts for about 18%-54% of the total amount, and the residual state content accounts for about 15%-41% of the total amount.

[0011] Further, the addition amount of the mixed mineral repair material is 2% of the mass of the heavy metal lead-polluted soil.

[0012] Further, the stabilization and repair method treats the heavy metal lead-polluted soil for 10-60 days.

[0013] Further, after adding the mixed mineral repair material, the soil humidity of the heavy metal lead-polluted soil is always maintained at 60% of the maximum water holding capacity in the field, and the temperature range is 20°C-30°C.

[0014] Further, the temperature maintained by the heavy metal lead-polluted soil after adding the mixed mineral repair material is 25°C.

[0015] Further, the soil humidity and temperature of the heavy metal lead-polluted soil after adding the mixed mineral repair material are mainly maintained by the weighing method and a constant temperature and humidity box.

[0016] By adopting the above technical solutions, the present invention adds a non-metallic mineral material composed of zeolite and montmorillonite to the heavy metal lead-polluted soil. This non-metallic mineral material has the effect of stabilizing the soil pH value. Applying zeolite can increase the pH value of the lead-polluted soil, mainly because zeolite itself is alkaline. Through adsorption, the content of free H + 、Al 3+ and other ions in the soil is reduced. After montmorillonite is applied, the pH value of the heavy metal lead-polluted soil is reduced in a short time because montmorillonite is acidic and its surface acidic ions are saturated. However, as it interacts with the soil, its physical and chemical properties change, and to achieve ion balance, the soil pH value increases. And the phosphate in potassium phosphate can quickly combine with heavy metals, increasing the reaction rate, so that various forms of heavy metals quickly transform into stable states under the action of the mixed mineral repair material;

[0017] In the present invention, both medical stone and montmorillonite have an adsorption effect on lead-contaminated soil, and most of the adsorbed lead exists in the form of organic bound state and residual state. The action speed of medical stone is fast, and the adsorption effect is very significant at 30 days. However, its adsorption effect on high-concentration lead treatment is relatively weak. While the adsorption effect of montmorillonite on lead-contaminated soil is slow, and there is still a significant adsorption effect from 30 days to 60 days, and it also has a good adsorption effect on high-concentration lead. This indicates that when medical stone and montmorillonite are mixed in a specific proportion, the adsorption, binding and precipitation effects can be optimized to form stable residual state lead compounds. The lead compounds after adsorption and binding are relatively stable. In this process, potassium phosphate reacts quickly with heavy metals to form stable heavy metal bound states, increasing the reaction speed, reducing the migration and release of lead, and making the repair effect have long-term stability.

[0018] Another object of the present invention is to provide the application of the above-mentioned method for stabilizing and repairing lead elements in mining area soil in the stabilization and repair of lead elements in mining area soil.

[0019] By adopting the above technical solutions, the present invention repairs the lead elements in mining area soil. By adding non-metallic mineral materials such as medical stone and montmorillonite under the action of potassium phosphate, the lead elements are converted into stable residual state lead compounds. This can reduce the dissolution risk of lead in the soil, reduce the potential harm to the environment and ecosystem, and at the same time improve the soil fertility level. The present invention can effectively remove lead elements from the soil and convert them into stabilized residual state lead compounds, thereby reducing the migration and release of lead, and protecting the health and safety of the soil, groundwater and organisms around the mining area. The medical stone and montmorillonite used in the present invention have high adsorption and binding capabilities, can stably fix lead elements persistently and reduce their bioavailability. At the same time, potassium phosphate increases the reaction speed, and the repair effect is relatively stable, capable of achieving long-term environmental protection and continuous repair effects.

[0020] Through the present invention, the lead elements in mining area soil can be effectively repaired, the environmental quality of the mining area can be restored and protected, and the potential impact of lead elements on the ecosystem and human health can be reduced. However, in order to ensure the reliability and long-term stability of the repair effect, specific implementation needs to be adjusted and optimized according to the actual situation and relevant standards on the spot, and monitoring and evaluation need to be carried out.

[0021] In summary, the present invention has the following beneficial effects:

[0022] 1. Through the stabilization and repair method of the present invention, using composite mineral repair materials such as medical stone, montmorillonite and potassium phosphate, it can effectively adsorb and bind lead elements in the soil, convert them into stable residual state lead compounds. This method has a stable repair effect, can stably fix lead elements persistently, reduce their bioavailability, and reduce the migration and release of lead;

[0023] 2. The remediation method of the present invention can reduce the leaching risk of lead in soil and mitigate the potential harm to the environment and ecosystem. By converting lead elements in the soil into stable residual lead compounds, the health and safety of the surrounding soil, groundwater, and organisms can be protected;

[0024] 3. The lead compounds after adsorption and combination in the present invention are relatively stable, and the remediation effect has long-term stability. Medical stone and montmorillonite can permanently stabilize lead elements and maintain the long-term persistence of the remediation effect. Description of the Drawings

[0025] Figure 1 It is the particle size distribution diagram of two non-metallic mineral materials after water dissolution in the embodiment of the present invention;

[0026] Figure 2 It is the adsorption rate linear diagram of different non-metallic mineral materials for different concentrations of lead in Example 2 of the present invention;

[0027] Figure 3 It is the adsorption of lead by non-metallic mineral materials with the initial pH value of the solution in Example 2 of the present invention;

[0028] Figure 4 It is the bar chart of the emergence rate of rape treated with lead by different composite mineral remediation materials in the embodiment of the present invention. Detailed Embodiments

[0029] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] 1. Test Materials

[0031] 1.1 Composite Mineral Remediation Materials

[0032] The selected composite mineral remediation materials of the present invention are provided by Xi'an Institute of Mineral Chemical Industry and mainly include medical stone, montmorillonite, and potassium phosphate. These materials need to be screened through a 20-mesh sieve before use.

[0033] In order to analyze the composite mineral remediation materials, the following detection methods are adopted in the present invention:

[0034] S1: The pH value is measured by the pH meter method;

[0035] S2: The organic matter is measured by the dichromate oxidation volumetric method;

[0036] S3: The total nitrogen is measured by the automatic Kjeldahl nitrogen analyzer method;

[0037] S4: The determination of phosphorus, potassium, calcium, sodium, and magnesium is carried out by digestion with aqua regia and then analyzed by inductively coupled plasma optical emission spectrometry;

[0038] S5: The determination of cation exchange capacity is carried out by the ammonium acetate exchange - volumetric method;

[0039] S6: The determination of the remaining heavy metal elements is analyzed by four - acid dissolution - inductively coupled plasma mass spectrometry.

[0040] Through the above - mentioned analysis methods, the properties and components of the composite mineral repair material can be accurately determined and evaluated.

[0041] Table 1 Basic chemical properties of the tested materials

[0042]

[0043]

[0044] Note: TOM is organic matter, TN is total nitrogen, and TP is total phosphorus.

[0045] By observing the data in Table 1, the following situations can be found: The pH value of zeolite is 9.49, showing alkalinity, while the pH value of montmorillonite is 5.02, showing acidity, which is determined by the properties of zeolite and montmorillonite themselves. However, montmorillonite can be modified to change its properties; in terms of element content, the total nitrogen, total phosphorus, potassium, sodium, calcium, magnesium, and cation exchange capacity (CEC) of zeolite are all higher than those of montmorillonite, while the content of organic matter, Pb, Cd, Cr, As, Hg and other elements in montmorillonite is relatively high, which is also determined by the properties of their raw materials. Although the content of As element in montmorillonite is relatively high, their contents can all meet the limit requirements of relevant standards for toxic and harmful elements.

[0046] The BET (N2) method is used in this invention to determine the specific surface area and average pore diameter of the tested and non - metallic mineral materials. As shown in Table 2, the results show that the surface area and average pore diameter of montmorillonite are larger.

[0047] Table 2 Basic physical properties of the tested materials

[0048]

[0049]

[0050] Through X-ray diffraction analysis (XRD), the present invention can obtain the mineral composition information of two non-metallic mineral materials, namely medical stone and montmorillonite. According to the data in Table 3, the following conclusions can be drawn: both medical stone and montmorillonite are mainly composed of SiO2 and other inorganic oxides, but the SiO2 in the two is not the same substance, but different variants of quartz; after analysis, the SiO2 in medical stone is SiO2 (01-070-3755, quartz); the SiO2 in montmorillonite is SiO2 (071-0261, tridymite), which means that there are differences in the crystal structure or morphology of SiO2 in the two materials.

[0051] Table 3 XRD Results of Two Non-Metallic Mineral Materials

[0052]

[0053] The present invention uses the laser particle size analyzer method (SALD-2300) to measure the particle size distribution of the two mineral materials after water dissolution. The results are as shown in the appendix Figure 1 and it can be concluded that after the two materials are dissolved in water, the particles below 100 μm account for 100%.

[0054] 1.2 Test Soils and Rape

[0055] The soil and rape samples used in this experiment were all prepared in advance in the laboratory and processed and analyzed according to the experimental requirements.

[0056] 1.3 Instrumentation

[0057] The instrumentation used in the present invention mainly includes an electronic balance (0.0001 g), a drying oven, a constant temperature oscillator, a centrifuge (greater than 3000 r / min - 5000 r / min), an electrothermal constant temperature water bath, a constant temperature and humidity incubator, a microwave digestion instrument, an inductively coupled plasma mass spectrometer (X Series 2, Thermo Fisher Scientific, USA), etc.

[0058] Example 1: A method for stabilizing and remediating lead in mine soil, including preparing heavy metal lead-contaminated soil samples, and adding Pb(NO3)2 to the test soils to make the lead contents 200 mg / kg, 500 mg / kg, and 1000 mg / kg respectively. These reagents were added to the soil samples in solution form, and after aging for 40 days, aged soils with lead contents of 225 mg / kg (Pb1), 537 mg / kg (Pb2), and 1041 mg / kg (Pb3) were obtained;

[0059] A mixed mineral remediation material consisting of medical stone (M), montmorillonite (P) and potassium phosphate is added to the heavy metal lead contaminated soil, and the mixed mineral remediation material is fully mixed with the soil. On the basis of using 1kg of heavy metal lead contaminated soil, the added amount of mixed mineral remediation material is 0.5%-3% of the mass of heavy metal lead contaminated soil. In this embodiment, 0.5% and 2% are selected, that is, 4.00g and 20.00g of mixed mineral remediation are added to about 1kg of soil. A total of 15 adding methods are set, and the specific details are shown in Table 4, among which M1 is regarded as low-content medical stone + low-content phosphate, M2 is regarded as medium-content medical stone + high-content phosphate, M3 is regarded as high-content medical stone + high-content phosphate, and similarly P1 is low-content montmorillonite + low-content phosphate, P2 is regarded as medium-content montmorillonite + high-content phosphate, and P3 is regarded as high-content montmorillonite + high-content phosphate. According to the above-mentioned treatment method, the samples are respectively placed in culture boxes and placed in a constant temperature and humidity chamber to maintain the temperature at 25±5℃. The soil moisture was maintained at 60% of the maximum water holding capacity in the field by weighing and constant temperature and humidity chamber. Soil samples were collected at 10, 30 and 60 days of cultivation. After each sampling, the remaining samples were fully stirred and continued to be cultivated for a total of 60 days. Three replicate samples were set for each treatment method.

[0060] Table 4 Constant temperature culture test on the effect of mixed mineral remediation materials on soil lead forms

[0061] Serial number Processing Serial number Processing Serial number Processing 1 Pb1 6 Pb2 11 Pb3 2 Pb1M1 7 Pb2M1 12 Pb3M1 3 Pb1M2 8 Pb2M2 13 Pb3M2 4 Pb1P1 9 Pb2P1 14 Pb3P1 5 Pb1P2 10 Pb2P2 15 Pb3P2

[0062] Example 2: Test on the adsorption performance of mixed mineral repair materials on lead

[0063] 2.1 Isothermal adsorption test of mixed mineral repair materials

[0064] The isothermal adsorption test of the mixed mineral repair material of the present invention comprises the following steps:

[0065] S1: preparing lead nitrate solutions into standby mother solutions with a lead concentration of 500 mg / L, respectively, by using deionized water to dissolve the lead nitrate, and using 0.05 mol / L potassium nitrate solution as a supporting electrolyte, preparing ten lead solutions with different concentration gradients (0.00 mg / L, 2.00 mg / L, 5.00 mg / L, 10.00 mg / L, 20.00 mg / L, 40.00 mg / L, 80.00 mg / L, 160.00 mg / L, 240.00 mg / L, 320.00 mg / L), and setting them aside;

[0066] S2: 0.5000 g of mixed mineral repair was weighed into 100 mL centrifuge tubes, and then 30 mL of the above lead solution was added. Each treatment method had 3 replicate samples;

[0067] S3: Cover the centrifuge tube and seal it with sealing film. Place the centrifuge tube with the sample in a constant temperature shaking incubator, set the temperature to 25 ± 3 °C, and shake at a speed of 250 r / min for 24 hours;

[0068] S4: Centrifuge and filter the sample using a centrifuge at 4000 r / min for 30 minutes;

[0069] S5: Dilute the filtered solution and use an inductively coupled plasma mass spectrometer to measure the concentration of lead in it;

[0070] According to the concentration data measured by the above method, calculate the adsorption amounts of lead by medical stone (M) and montmorillonite (P), as shown in the appendix Figure 2 as follows.

[0071] From the appendix Figure 2 it can be seen that as the concentration of lead in the original solution increases, the adsorption rates of both medical stone and montmorillonite for lead decrease, but the decreasing trends are different; for medical stone, when the lead concentration in the solution is less than 260 mg / L, its adsorption rate basically remains above 90%, but when the lead concentration in the solution exceeds 260 mg / L, the adsorption rate of medical stone begins to decrease significantly, from 98.7% to 76.7%;

[0072] For montmorillonite, when the lead concentration in the solution increases, its adsorption rate shows a trend of first decreasing, forming a plateau, and then decreasing again. This is because montmorillonite undergoes an activation process at a certain lead concentration. Before activation, as the lead concentration in the solution increases, the adsorption efficiency of montmorillonite gradually decreases, and after activation, the adsorption rate of montmorillonite remains stable within a certain lead concentration range, but when the lead concentration further increases, the adsorption efficiency of montmorillonite begins to decrease again, from the initial 87.0% to 48.0%.

[0073] In summary, the adsorption rate of medical stone + phosphate for lead elements is greater than that of montmorillonite + phosphate.

[0074] 2.2 Effect test of solution pH value on the lead adsorption capacity of the mixed mineral repair material

[0075] S1: Take a lead solution of 160.00 mg / L and use 0.05 mol / L potassium nitrate solution as the supporting electrolyte;

[0076] S2: Adjust the pH value of the solution to 2.00, 3.00, 4.00, 5.00, 6.00, 7.00, 8.00, 9.00, 10.00 and other 8 different gradients respectively using 0.1 mol / L potassium hydroxide (KOH) or 0.1 mol / L nitric acid solution;

[0077] S3: Take 30 mL of the above - adjusted solution and add it to a centrifuge tube containing 0.5000 g of the mixed mineral repair material;

[0078] S4: Cover the centrifuge tube and seal it with a sealing film. Oscillate, centrifuge, and filter according to the previous steps;

[0079] S5: Dilute the filtered solution and use an inductively coupled plasma mass spectrometer to measure the lead concentration in it

[0080] According to the measured concentration data, calculate the adsorption capacities of the two mixed mineral repair materials, as shown in the appendix Figure 3 As shown. From the appendix Figure 3 It can be seen that as the pH value of the solution increases, the adsorption amounts of the two mixed mineral repair materials for lead show a similar changing trend. When the pH value is less than 5, the adsorption amounts of the two materials for lead basically remain stable with little change; when the pH value is between 5 and 6, the adsorption amounts of the two materials slowly decrease; when the pH value of the solution exceeds 6, the adsorption amounts of the two non - metallic mineral materials for lead rapidly decrease; the adsorption amount of zeolite + phosphate for lead decreases from 10.9 mg / g to 2.1 mg / g, while the adsorption amount of montmorillonite + phosphate decreases from 6.9 mg / g to 0.8 mg / g. When the pH value of the solution increases, the formation of precipitates is also observed, indicating that the increase in the pH value of the solution significantly reduces the adsorption amounts of zeolite + phosphate and montmorillonite + phosphate for lead elements.

[0081] Test Example 1: Verify the influence of applying different mixed mineral repair materials on the forms of lead elements in simulated lead - contaminated soil;

[0082] The samples obtained in the present invention need to be air - dried first, and then the samples are ground, screened through 20 - mesh and 100 - mesh sieves, leached by the sequential extraction method, and the contents of various forms of lead in the soil are measured respectively by inductively coupled plasma mass spectrometry, obtaining the data of the contents of various forms of lead in the lead - contaminated soil with different mixed mineral repair materials, as shown in Table 5;

[0083] Table 5 Contents of various forms of lead in lead - contaminated soil with different composite mineral repair materials

[0084]

[0085]

[0086] Note: F1 (exchangeable state), F2 (carbonate - bound state), F3 (amorphous iron and manganese oxide - bound state), F4 (organic - bound state), F5 (residual state);

[0087] As can be seen from Table 5, in the simulated heavy metal lead-polluted soil, lead exists in the forms of organically bound state and residual state. The organically bound lead accounts for about 18% to 54% of the total lead content, while the content of residual lead accounts for about 15% to 41% of the total lead content. When applying a single lead treatment, with the extension of time, the content of exchangeable lead in the same concentration of lead treatment gradually decreases, indicating that there is a tendency for lead to transform from the active state to the fixed state in the soil;

[0088] Change trend of exchangeable lead (F1):

[0089] Group Pb1: decreased from 29.7±2.2 mg / kg at 10 days to 18.8±3.1 mg / kg at 60 days; Group Pb2: decreased from 42.7±4.8 mg / kg at 10 days to 30.1±5.5 mg / kg at 60 days; Group Pb3: decreased from 103±12 mg / kg at 10 days to 85.6±12.8 mg / kg at 60 days;

[0090] Change trend of carbonate-bound lead (F2): Pb1: increased from 44.8±3.6 mg / kg at 10 days to 54.8±2.7 mg / kg at 30 days, and then decreased to 46.8±4.5 mg / kg at 60 days; The change trend of Pb2 is similar to that of Pb1: changed from 85.4±6.5 mg / kg at 10 days to 89.4±7.0 mg / kg at 60 days; Pb3: continuously decreased from 117±11 mg / kg at 10 days to 82.4±11.5 mg / kg at 60 days;

[0091] Exchangeable and carbonate-bound lead: In the Pb1 treatment, from 10 days to 30 days, the exchangeable lead decreased from 17.7±1.5 mg / kg to 15.4±0.5 mg / kg, and the carbonate-bound lead decreased from 19.2±2.2 mg / kg to 12.7±1.2 mg / kg;

[0092] Amorphous iron and manganese oxide-bound and organically bound lead: In the Pb1 treatment, from 10 days to 30 days, the amorphous iron and manganese oxide-bound lead increased from 30.7±3.6 mg / kg to 23.4±2.7 mg / kg, and the organically bound lead increased from 53.9±5.5 mg / kg to 59.4±4.6 mg / kg; Residual lead: In the Pb1 treatment, from 10 days to 30 days, the residual lead changed from 58.6±6.1 mg / kg to 59.2±5.4 mg / kg, with no obvious change.

[0093] Exchangeable and organically bound lead: In the Pb1P1 treatment, from 10 days to 30 days, the exchangeable lead decreased from 32.7±3.5 mg / kg to 25.7±2.8 mg / kg, and the organically bound lead increased from 39.7±4.1 mg / kg to 46.5±3.5 mg / kg; Carbonate-bound and residual lead: In the Pb1P1 treatment, from 10 days to 30 days, the carbonate-bound lead decreased from 26.4±3.5 mg / kg to 19.5±2.9 mg / kg, and the residual lead increased from 96.5±9.2 mg / kg to 108±9 mg / kg;

[0094] Amorphous iron and manganese oxide-bound lead: In the Pb1P1 treatment, from 10 days to 30 days, the amorphous iron and manganese oxide-bound lead changed from 19.8±0.9 mg / kg to 23.1±1.1 mg / kg, with no significant change.

[0095] Low-content roxburghite + phosphate rock and montmorillonite + phosphate: In the Pb1M1 treatment, from 10 days to 30 days, the exchangeable lead decreased from 17.7±1.5 mg / kg to 15.4±0.5 mg / kg, indicating that the addition of phosphate helps to reduce the availability of lead.

[0096] As time goes by, lead transforms from an active state to an inactive state, which is particularly obvious in the decrease of exchangeable lead; Roxburghite + phosphate and montmorillonite + phosphate affect the forms of lead through different mechanisms, among which montmorillonite performs better under high potassium phosphate conditions. For example, in the Pb1P1 treatment, the contents of exchangeable and organically bound lead increase with time; The addition of phosphate significantly reduces the availability of lead and helps to immobilize lead. For example, in the Pb1M1 treatment, the content of exchangeable lead decreases with time.

[0097] Conclusion: The carbonate-bound lead first increases and then decreases with time under the same concentration treatment in the Pb1 and Pb2 treatments, but gradually decreases in the Pb3 treatment, indicating that the carbonate-binding capacity in the soil is relatively good in the Pb1 and Pb2 treatments and can increase with the prolongation of the treatment time, but finally decreases with the continuous action of the lead solution. In the Pb3 treatment, the carbonate in the soil cannot bind excessive lead, resulting in a continuous decrease in carbonate-bound lead; The amorphous iron and manganese oxide-bound lead gradually increases in the Pb1, Pb2, and Pb3 treatments with the prolongation of time, indicating that there are oxides such as iron and manganese in the soil. This may be due to the fact that the soil sampling site is a mining area, with a relatively high content of iron and manganese oxides, and the oxidizing property of the soil gradually increases during the placement process, etc.

[0098] Among the three different concentrations of lead treatment, the organically bound lead in the soil gradually decreased with the passage of time. This indicates that during the process of soil placement, the organically bound lead gradually decomposed because the oxidizing property of the soil increased, causing the decomposition of reducing substances, thereby leading to the degradation of organically bound lead. The residual lead increased gradually with the passage of time in the three different concentrations of lead treatment. This is because during the process of soil placement and aging, the transformation from the unstable state to the stable state led to the accumulation of residual lead.

[0099] After applying zeolite + phosphate, the contents of exchangeable lead and carbonate-bound lead in each treatment decreased compared with the case of treating lead element alone, while the contents of amorphous iron and manganese oxide-bound lead and organically bound lead increased, and the change of residual lead was not obvious. Specifically, in the Pb1 and Pb2 treatments, with the passage of time, the contents of exchangeable lead, carbonate-bound lead and amorphous iron and manganese oxide-bound lead gradually decreased, while the organically bound lead gradually increased. Especially during the period from the 10th day to the 30th day, these changes were very significant. In the Pb3 treatment, these changes were not obvious. This shows that in the simulated heavy metal lead-polluted soil, applying zeolite + phosphate can rapidly reduce the contents of exchangeable and carbonate-bound lead and increase the organically bound lead within the first 30 days, so it has a positive effect on fixing lead element. With the passage of time, the adsorption capacity of zeolite + phosphate will gradually become saturated, resulting in a weakened effect of fixing lead. For the polluted soil with a high lead content (Pb3, 1041 mg / kg), the fixing effect of zeolite + phosphate is weak because the lead content in the soil is too high, causing the adsorption of lead by zeolite to exceed the saturation point and become ineffective.

[0100] After applying montmorillonite + phosphate, the contents of exchangeable lead and organically bound lead in each treatment increased compared with the case of treating lead element alone, while the contents of carbonate-bound lead and residual lead decreased, and the content of amorphous iron and manganese oxide-bound lead did not change significantly. Specifically, with the passage of time for each treatment concentration of lead element, the contents of exchangeable and carbonate-bound lead gradually decreased, while the contents of amorphous iron and manganese oxide-bound and organically bound lead gradually increased. In terms of residual lead, it gradually increased in the Pb1 treatment, increased first and then decreased in the Pb2 treatment, and changed little in the Pb3 treatment. After applying montmorillonite, whether it is exchangeable, carbonate-bound, organically bound or iron and manganese oxide-bound lead, under different concentration treatments, there were obvious changes both from the 10th day to the 30th day and from the 30th day to the 60th day. This shows that the effect of montmorillonite + phosphate on lead-polluted soil is relatively slow, but it can continuously adsorb different concentrations of lead pollution.

[0101] In the groups of low-content medical stone + phosphate and montmorillonite + phosphate, as the content of potassium phosphate increased, the availability of lead decreased significantly. This may be because potassium phosphate can promote the formation of lead phosphate, thereby reducing the migration and bioavailability of lead. Montmorillonite + phosphate performed better than medical stone + phosphate, especially under high potassium phosphate conditions. This indicates that montmorillonite + phosphate can more effectively passivate lead when acting synergistically with potassium phosphate. During the entire 60-day incubation period, the passivation effect of the treatment group continued to increase, especially during the period from 30 days to 60 days. This may be related to the gradual action of the mineral materials in the soil. The extension of time allows the mineral materials to have more sufficient reaction time with lead in the soil, thereby forming more stable compounds.

[0102] Generally speaking, both medical stone + phosphate and montmorillonite + phosphate have precipitation and adsorption effects on lead-contaminated soil. The adsorption rate of medical stone + phosphate is relatively fast, and its adsorption effect is very significant at 30 days. However, the adsorption effect of medical stone + phosphate on high-concentration lead is relatively weak. In contrast, the adsorption of montmorillonite + phosphate on lead is relatively slow, and it still shows a significant adsorption effect during the period from 30 to 60 days, and it also has a good adsorption effect on high-concentration lead. Using these two mineral materials at a 2% concentration has a better effect than using them at a 0.5% concentration, and the adsorption effect on heavy metal lead is better.

[0103] Test Example 2: The effect of applying different composite mineral remediation materials on the pH value of lead-contaminated soil; the present invention also uses the electrode method to measure the soil pH value, and obtains the pH value of lead-contaminated soil with different composite mineral remediation materials, as shown in Table 6.

[0104] Table 6 The pH value of lead-contaminated soil with different composite mineral remediation materials

[0105]

[0106] It can be seen from Table 6 that after applying the composite mineral remediation materials, the pH value of the lead-contaminated soil changes between 7.13 and 7.78. For the simulated lead-contaminated soil, when lead is applied alone, as the lead concentration increases, the pH value of the soil will decrease. However, as the treatment time extends, the pH value of the soil will gradually increase. Under the treatment of medical stone + phosphate, the pH value of the lead-contaminated soil can be increased, but as time goes on, the pH value will slightly decrease. After the treatment of montmorillonite + phosphate, the pH value of the simulated lead-contaminated soil has a decreasing effect, but as the treatment time extends, the pH value will gradually increase;

[0107] The above situation shows that the composite mineral remediation materials have the effect of stabilizing the soil pH value. After applying medical stone + phosphate, the pH value of the lead-contaminated soil is increased. This may be because medical stone itself is alkaline and reduces the free H in the soil through adsorption.+ and the content of Al 3+ plasma. After the application of montmorillonite + phosphate, the pH value of lead - contaminated soil will be reduced in the short term. This may be because montmorillonite is acidic and the acidic ions on its surface are already saturated. However, with the interaction between montmorillonite and the soil, its physical and chemical properties change, and in order to achieve ionic balance, the pH value of the soil will increase.

[0108] Test Example 3: Verify the effect of the composite mineral remediation material on the bioavailability of lead;

[0109] When conducting the cultivation experiment, in addition to using the soil without adding any substances as the blank control group (CK), three composite mineral remediation materials were added for treatment, and six replicates were set for each treatment. Among them, three replicates were used for the emergence rate experiment, and the seedling rate was recorded within seven days after sowing the seeds. At the same time, a pot experiment was carried out, and rapeseed plants were cultivated for about 50 days, then the above - ground and underground rapeseed biomass was collected, and the lead content in the plants was measured. In addition, the available content of heavy metal lead and the pH value in the soil were also analyzed. According to the experimental results, the effects of different composite mineral remediation materials on the soil pH value, rapeseed biomass, and rapeseed's absorption of lead were sorted out and presented in Tables 7, 8, and 9.

[0110] Table 7 Soil pH values after different composite mineral remediation materials

[0111]

[0112]

[0113] It can be seen from Table 7 that compared with the control group, lead pollution significantly reduced the soil pH value (P < 0.05). In the Pb1 treatment, the soil pH value decreased by 0.26 compared with the control group. After adding zeolite + phosphate, the soil pH value increased significantly, and with the increase in the content of zeolite + phosphate, the soil pH value also increased significantly. In the M2 treatment, the soil pH value was significantly higher than that of the control group. However, after adding montmorillonite + phosphate, although the soil pH value increased compared with the single - lead treatment, the difference was not significant. In the Pb3 treatment, the soil pH value decreased compared with both Pb1 and the blank group, and decreased by 0.33 compared with the control group. Adding zeolite + phosphate can increase the soil pH value, but in the M1 treatment, the increase in pH value was not significant. After adding montmorillonite + phosphate, the soil pH value remained basically unchanged, probably because montmorillonite itself is acidic and has little effect on increasing the pH value of lead - contaminated potted soil.

[0114] Table 8 Effects of different composite mineral remediation materials on the biomass of rapeseed treated with lead

[0115]

[0116]

[0117] As can be seen from Table 8 above, the treatment of lead pollution alone will lead to a decrease in the length, fresh weight, dry weight, root fresh weight and dry weight of rape, but the root length increases. In the Pb1 treatment, the application of zeolite + phosphate can increase the length, fresh weight, dry weight of the above-ground part of rape, as well as the root fresh weight and dry weight compared with the single lead treatment, but it reduces the root length. The change in the M2 treatment is more significant compared with the M1 treatment, and in these two treatments, the biomass parameters of rape are higher than those of the control treatment. Similarly, similar changes also occur when montmorillonite + phosphate is applied. At the same concentration, the zeolite + phosphate treatment is superior to the montmorillonite + phosphate treatment in all aspects except for the fresh weight of the above-ground part. In the Pb3 treatment, the situation after the zeolite + phosphate and montmorillonite + phosphate treatments is similar to that in the Pb1 treatment, but the fresh weight of the above-ground part of rape after the zeolite + phosphate treatment is higher than that of the montmorillonite + phosphate treatment. In addition, although the zeolite + phosphate and montmorillonite + phosphate treatments increase the above-ground biomass, root fresh weight and dry weight compared with the single lead treatment, they are both lower than the control treatment.

[0118] Table 9 Lead uptake by rape treated with different composite mineral remediation materials

[0119]

[0120]

[0121] As can be seen from Table 9, at the two lead treatment concentrations, the content of available lead in the soil and lead in the plants increased significantly compared with the control.

[0122] Under different concentration treatments of Pb1, the final content of lead in the soil changed little, about 213 mg / kg - 217 mg / kg. However, when zeolite + phosphate was applied, the available lead in the soil and the lead uptake by rape decreased significantly. In addition, with the increase in the application amount of zeolite + phosphate, both the available lead in the soil and the lead uptake by rape decreased significantly, with a relatively large decrease amplitude. Under the M1 and M2 treatments, the decrease amplitude of available lead was 35.3% - 51.9%, the lead uptake by the rape roots decreased by 59.9% - 79.4%, and the lead uptake by the above-ground part of rape decreased by 58.9% - 77.9%. At the same time, the application of zeolite + phosphate also reduced the enrichment coefficient of rape for lead at the Pb1 concentration, but increased the translocation coefficient. This indicates that the application of zeolite + phosphate can effectively reduce the lead uptake and enrichment of rape under the Pb1 treatment, while increasing the lead translocation coefficient. This may be related to the decrease in the lead concentration in rape and the increase in the activity of related transport channels;

[0123] When montmorillonite + phosphate was applied, under the P1 and P2 treatments, the available lead in the soil decreased by 19.2% - 29.8% respectively, the lead uptake by rape roots decreased by 45.9% - 65.3%, and the lead uptake by the above-ground parts of rape decreased by 44.6% - 65.2%. In addition, the application of montmorillonite + phosphate also decreased the enrichment coefficient of lead in rape under the Pb1 concentration treatment and increased its translocation coefficient, although the increase was not significant. This indicates that when under the Pb1 concentration treatment, adding montmorillonite + phosphate can significantly reduce the absorption and enrichment of lead by rape and increase the translocation coefficient of lead. However, compared with the effect of zeolite + phosphate, montmorillonite + phosphate is less effective in inhibiting the absorption and enrichment of lead by rape.

[0124] Under different concentrations of Pb3 treatment, the final lead content in the soil changed little, about 1120 mg / kg - 1125 mg / kg. However, when zeolite + phosphate was applied, the available lead in the soil and the lead uptake by rape decreased. At the same time, with the increase in the application amount of zeolite + phosphate, the available lead in the soil and the lead uptake by rape also decreased, although the decrease was not significant. Under the M1 and M2 treatments, the decrease in available lead was 19.8% - 25.1%, the lead uptake by rape roots decreased by 5.88% - 22.5%, and the lead uptake by the above-ground parts of rape decreased by 10.7% - 27.7%. In addition, the application of zeolite + phosphate also decreased the enrichment coefficient of lead in rape under the Pb3 concentration treatment and relatively decreased the translocation coefficient. This shows that the application of zeolite + phosphate can reduce the absorption and enrichment of lead by rape to a certain extent under the Pb3 treatment, although the decrease is small. This may be because under the Pb3 concentration treatment, the adsorption amount of zeolite + phosphate in the soil has reached saturation, and although it still has precipitation and adsorption effects, it is less effective in reducing the absorption and enrichment of lead by rape.

[0125] When montmorillonite + phosphate was applied, under the P1 and P2 treatments, the available lead in the soil decreased by 25.1% - 27.9% respectively, the lead uptake by rape roots decreased by 8.19% - 24.4%, and the lead uptake by the above-ground parts of rape decreased by 10.2% - 29.7%. In addition, the application of montmorillonite + phosphate also decreased the enrichment coefficient and translocation coefficient of lead in rape under the Pb3 concentration treatment, although the decrease was not significant. This indicates that when under the Pb3 concentration treatment, adding montmorillonite + phosphate can reduce the absorption and enrichment of lead by rape, but the effect is not significant, which is similar to the effect of zeolite + phosphate. This shows that when under the Pb3 treatment, whether it is zeolite + phosphate or montmorillonite + phosphate under the actions of M1, M2, P1, and P2, the fixation effect on lead in the soil is limited and can no longer achieve the effect of reducing the lead uptake by rape.

[0126] Statistically analyze the emergence rates of rape treated with different composite mineral remediation materials for lead, as shown in the appendix Figure 4 As shown, when treated with lead alone, the emergence rate of rape decreased significantly. The emergence rate of the control group was 79.6%, while under the Pb1 treatment, the emergence rate of rape decreased by approximately 4.2% compared to the control. However, when adding zeolite and montmorillonite, both can promote the germination rate of rape, and the effect of zeolite is more significant. Except for the treatment with low content of montmorillonite (P1), the emergence rates of rape in the other treatments (M1, M2, P2) were higher than that of the control group;

[0127] Under the Pb3 treatment, the emergence rate of rape decreased by 21.1% compared to the control group. However, when adding zeolite + phosphate and montmorillonite + phosphate, the emergence rates of rape both increased, but did not reach the level of the control group. This indicates that lead can inhibit the emergence rate of rape, but when adding zeolite + phosphate and montmorillonite + phosphate, it can improve the emergence rate of rape in lead - polluted soil. Especially the effect of zeolite + phosphate is more significant.

[0128] In summary, the present invention finds that the composite mineral remediation materials zeolite + phosphate and montmorillonite + phosphate both have the function of stabilizing the soil pH value. At the same time, they can also adsorb lead pollutants in the soil. After adsorption, most of the lead exists in the soil in the form of organic - bound state and residual state under the rapid action of phosphate. The adsorption rate of zeolite + phosphate for lead is relatively fast, and the adsorption effect can be significantly improved within 30 days. However, when dealing with high - concentration lead, the adsorption effect of zeolite + phosphate is relatively weak. On the contrary, the adsorption of montmorillonite + phosphate for lead is slower, but still has a significant adsorption effect during the period from 30 days to 60 days. In addition, montmorillonite + phosphate also has a good adsorption effect on high - concentration lead.

[0129] Through pot experiments, the present invention obtains that when treated with low - concentration lead, adding zeolite + phosphate and montmorillonite + phosphate can both significantly reduce the absorption and enrichment of lead by rape. The effect of zeolite + phosphate is greater than that of montmorillonite + phosphate, which may be related to its higher cation exchange capacity. When treated with high - concentration lead, the fixation effect of zeolite + phosphate and montmorillonite + phosphate on heavy metals in the soil weakens, and the plants begin to absorb and enrich lead. Zeolite + phosphate and montmorillonite + phosphate both have the function of fixing heavy metal lead in the soil and reducing the pollution of rape, especially the effect is more obvious on low - and medium - concentration lead - polluted soil.

[0130] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A method for stabilizing and restoring lead in mining soil, characterized by: The method comprises preparing heavy metal lead contaminated soil, adding a mixed mineral repair material consisting of medical stone, montmorillonite and potassium phosphate into the heavy metal lead contaminated soil and mixing the mixed mineral repair material evenly, wherein the heavy metal lead contaminated soil is taken as a benchmark, the added amount of the mixed mineral repair material is 0.5%-3% of the mass of the heavy metal lead contaminated soil, the ratio of the medical stone, montmorillonite and potassium phosphate is 1:1:x, wherein the value of x is 0.5, 2, and the added amount accounts for 1%-8% of the total mass of the soil.

2. The method for stabilizing and restoring lead in mining soil according to claim 1, characterized in that: In the heavy metal lead polluted soil, the organic binding state accounts for 18%-54% of the total amount, and the residual state content accounts for 15%-41% of the total amount.

3. The method for stabilizing and restoring lead in mining soil according to claim 1, characterized in that: The added amount of the mixed mineral repair material is 2% of the mass of the heavy metal lead polluted soil.

4. The method for stabilizing and restoring lead in mining soil according to claim 1, characterized in that: The stabilization remediation method treats heavy metal lead contaminated soil for 10-60 days.

5. The method for stabilizing and restoring lead in mining soil according to claim 1, characterized in that: The heavy metal lead polluted soil after the mixed mineral repair material is added keeps the soil moisture at 60% of the maximum field water holding capacity and the temperature range is maintained at 20°C-30°C.

6. The method for stabilizing and restoring lead in mining soil according to claim 5, characterized in that: The temperature of the heavy metal lead contaminated soil after the mixed mineral repair material is added is maintained at 25°C.

7. The method for stabilizing and restoring lead in mining soil according to claim 5, characterized in that: The moisture and temperature of the heavy metal lead contaminated soil after the mixed mineral repair material is added are maintained mainly by weighing method and constant temperature and humidity chamber.

8. Use of the method for stabilizing and restoring lead in mining soil as claimed in claim 1 in stabilizing and restoring lead in mining soil.

9. Application of the method for stabilizing and restoring lead in mining soil as claimed in claim 1 to improving the survival rate of seedlings.

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