Preparation method and application of heavy metal cadmium contaminated soil remediation conditioner

Abstract

The invention discloses a preparation method and application of a heavy metal cadmium contaminated soil remediation conditioner, and relates to the technical field of environmental protection, the heavy metal cadmium contaminated soil remediation conditioner comprises the following components by weight: 30-40 parts of zinc modified charcoal, 10-20 parts of montmorillonite, 5-10 parts of nano iron powder, and 30-55 parts of high temperature activated sepiolite. The heavy metal cadmium contaminated soil remediation conditioner has high adsorptive selectivity, strong fixing stability and mild pH adjustment, can improve the soil fertility, is efficient in multi-component synergism, and is suitable for different types of cadmium contaminated soil.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, and in particular to a method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil and its application. Background Technology

[0002] Cadmium, a heavy metal, is a typical toxic pollutant in soil, characterized by high mobility, strong bioaccumulation, and non-degradability. With human activities such as industrial wastewater discharge, agricultural fertilizer and pesticide application, and solid waste disposal, soil cadmium pollution has become increasingly prominent, posing a significant challenge to sustainable agricultural development and threatening the quality and safety of agricultural products. Cadmium in soil is easily absorbed and accumulated by crops, entering the human body through the food chain and causing a series of health problems, including kidney damage, bone diseases, and weakened immune function. Therefore, the remediation of cadmium-contaminated soil is urgently needed.

[0003] Currently, remediation technologies for cadmium-contaminated soil mainly include physical remediation, chemical remediation, and bioremediation. Physical remediation techniques, such as topsoil replacement and soil replacement, while showing significant remediation effects, suffer from drawbacks such as large-scale engineering, high costs, and damage to soil structure, making large-scale application difficult. Bioremediation utilizes the absorption and transformation of cadmium by plants and microorganisms, offering advantages such as environmental friendliness and lower cost; however, it has a long remediation cycle, is greatly affected by environmental conditions, and has limited efficiency in remediating high-concentration cadmium-contaminated soil. Chemical remediation, due to its ease of operation and rapid remediation speed, has become one of the most widely used soil remediation methods, with the application of soil conditioners being the core approach. Existing soil conditioners mostly employ single or composite components such as biochar, clay minerals, and nanomaterials, fixing cadmium ions in the soil through adsorption, precipitation, and complexation, reducing their bioavailability. However, traditional biochar has limited adsorption capacity and insufficient adsorption stability for cadmium; nanomaterials such as nano-iron powder are prone to agglomeration, leading to reduced reactivity; and the fixation effect of single clay minerals is short-lasting, making long-term stable remediation difficult.

[0004] For example, patent document CN115385752A discloses a soil conditioner, its preparation method, and its application in phytoremediation of cadmium-contaminated calcareous soil. In this invention, sepiolite can achieve stable inner-layer adsorption or unstable outer-layer complexation physical adsorption of heavy metals, adsorbing free molecules or ions from fertilizers into its pores for slow release, improving soil fertility and alleviating symptoms of phosphorus, iron, and potassium deficiencies in calcareous soils. Chitosan can increase soil bulk density, improve soil fertility, and promote plant growth. Humic acid can improve soil, promote crop growth, and enhance crop resistance. Sulfur powder and ferrous sulfate can not only regulate soil pH and activate heavy metals in the soil but also serve as fertilizers for plant absorption. However, sepiolite has not undergone targeted modification for heavy metals, and its original pore structure and surface active sites are limited, resulting in insufficient adsorption selectivity for cadmium ions. It is easily competitively adsorbed by macro-cations such as calcium and magnesium in the soil, leading to a low actual cadmium fixation efficiency, especially with a significant decrease in remediation effect in high-concentration cadmium-contaminated soils. The pH-regulating effects of sulfur powder and ferrous sulfate are highly dependent and unstable. The high buffering capacity of calcareous soils can easily lead to uncontrolled pH regulation.

[0005] Therefore, developing a remediation conditioner with high adsorption selectivity, strong immobilization stability, mild pH adjustment, ability to improve soil fertility, synergistic high efficiency of multiple components, and applicability to different types of cadmium-contaminated soil, as well as its preparation method and application, has important practical significance and application value. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies and address the challenge of remediating cadmium-contaminated soil. Using readily available and readily accessible agricultural waste and clay minerals as raw materials, it proposes a preparation technology and application method for an in-situ passivation conditioner for remediating cadmium-contaminated soil. This technology offers abundant raw materials, low cost, and significant application effects, thereby reducing the mobility and bioavailability of cadmium in the soil, solving the problem of sustainable utilization of farmland due to cadmium pollution, and ensuring safe agricultural production and human health.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a soil remediation conditioner for heavy metal cadmium contaminated soil, comprising the following components by weight: 30-40 parts of zinc-modified biochar, 10-20 parts of montmorillonite, 5-10 parts of nano iron powder, and 30-55 parts of high-temperature activated sepiolite.

[0008] Preferably, the preparation method of the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 25-30℃ for continuous stirring for 10-15h. After the stirring is completed, drying is carried out at 80-90℃ for 22-26h. After pyrolysis of the dried material, zinc-modified biochar is obtained.

[0009] Preferably, the concentration of the NaOH solution is 1 mol / L.

[0010] Preferably, the Zn(NO3)2 solution has a mass percentage concentration of 10 wt%.

[0011] Preferably, the biochar is obtained by carbonizing agricultural waste by pyrolysis at 500-550℃ for 2-3 hours under nitrogen protection.

[0012] Preferably, the agricultural waste is one or more of corn stalks, durian shells, and locust tree branches.

[0013] Preferably, the ratio of Zn(NO3)2 solution to biochar is 10 mL: 1 g.

[0014] Preferably, the pyrolysis temperature is 490-520℃ and the time is 28-32 min.

[0015] Preferably, the average particle size of the nano-iron powder is 10-80 nm, and the average particle size of the montmorillonite is 800-1200 mesh.

[0016] Preferably, the high-temperature activated sepiolite is obtained by calcining sepiolite at 800°C for 2 hours in a muffle furnace, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve.

[0017] Preferably, the soil remediation conditioner for cadmium-contaminated soil further includes the following components in parts by weight: 1-5 parts of compound chelating agent and 0.5-2 parts of compound microbial agent.

[0018] Preferably, the composite chelating agent is a mixture of EDTA-disodium and citric acid in a mass ratio of 2:1.

[0019] Preferably, the compound microbial agent is a mixture of Bacillus subtilis and phosphate-solubilizing bacteria in a colony count ratio of 1:1.

[0020] Preferably, the viable count of the Bacillus subtilis is ≥10. 9 CFU / g; the viable count of the phosphate-solubilizing bacteria is ≥10. 9 CFU / g.

[0021] Another objective of this invention is to provide a method for preparing the soil remediation conditioner for heavy metal cadmium contaminated soil, comprising the following steps: mixing the components evenly according to their weight proportions, grinding them through a 100-mesh sieve to obtain the soil remediation conditioner for heavy metal cadmium contaminated soil.

[0022] Another object of the present invention is to provide an application of the aforementioned cadmium-contaminated soil remediation conditioner in the remediation of cadmium-contaminated soil.

[0023] (1) The soil remediation conditioner for heavy metal cadmium pollution disclosed in this invention has a wide range of raw material sources, low price, low production cost, simple usage method, and is easy to promote and apply; multiple compound in-situ passivation remediation of heavy metal cadmium pollution soil is labor-saving and easy to promote and apply to farmland contaminated with heavy metal cadmium; in addition, it can effectively improve the physical and chemical properties of soil and improve the soil's fertilizer and water retention capacity, and has great promotion and application value.

[0024] (2) The soil remediation conditioner for heavy metal cadmium pollution disclosed in this invention uses a zinc modification method to reasonably modify and optimize the surface of biochar. Based on fully utilizing the pore structure and surface functional characteristics of biochar, it significantly increases the amount of zinc on the surface of biochar. The mechanism of the zinc-modified biochar in regulating cadmium in the soil is mainly through the precipitation reaction of Cd(II) with carbonates in biochar, and the complexation reaction with oxygen-containing functional groups and metal-oxygen groups (Zn-O) (such as COO-Cd, Zn-O-Cd), ultimately reducing the bioavailability of Cd(II) in the soil in the form of Cd(OH)2, CdCO3 and CdO, without the risk of secondary pollution; Montmorillonite is a type of silicate sheet with a negatively charged surface and a thickness of nanometers, which is deposited on the surface by electrostatic interaction between layers. Montmorillonite, an earthy mineral, has a crystal structure consisting of two layers of silicon-oxygen tetrahedra sandwiching a layer of aluminum-oxygen octahedra. This unique one-dimensional layered nanostructure and cation exchange properties endow montmorillonite with a strong adsorption capacity for cadmium in the soil. Nano-iron powder acts like a "miniature magnet," adsorbing cadmium ions from the soil through its surface charge, forming a stable precipitate. Furthermore, nano-iron can induce plant roots to form an "iron membrane barrier," reducing the absorption and accumulation of cadmium ions in the plant. Sepiolite, a hydrous magnesium silicate clay mineral with a layered chain structure, has mostly large cations at the octahedral positions, with relatively few smaller Al ions. This not only provides good adsorption capacity for cadmium ions in the soil but also effectively precipitates them.

[0025] (3) The soil remediation conditioner for heavy metal cadmium pollution disclosed in this invention uses sepiolite that has been activated at high temperature (800℃, 2h) to significantly increase the number of surface active sites, thereby enhancing the specific adsorption of cadmium ions and avoiding competition with macro cations such as calcium and magnesium. The composite chelating agent synergistically uses EDTA-disodium to strongly chelate cadmium ions to form a stable complex, and citric acid adjusts the pH and enhances the chelation stability, avoiding the risk of soil acidification or alkalization caused by a single pH adjuster, and is suitable for different types of soil such as acidic, neutral, and calcareous soils; the extracellular polymer secreted by Bacillus subtilis in the composite microbial agent can enhance the adsorption and fixation of cadmium, and phosphate-solubilizing bacteria convert insoluble phosphorus in the soil into available phosphorus, improving soil fertility. At the same time, the microbial metabolites and inorganic components synergistically reduce the risk of cadmium leaching.

[0026] (4) The soil remediation conditioner for heavy metal cadmium contaminated by this invention uses zinc ions loaded on the surface of zinc-modified biochar to compete with cadmium ions for soil adsorption sites and plant root transport proteins. At the same time, the abundant functional groups after modification form a targeted adsorption network with the macroporous volume of high-temperature activated sepiolite, specifically capturing cadmium ions and reducing interference from cations such as calcium and magnesium; nano-iron powder can also be used to treat highly toxic cadmium ions. Reduced to low-toxicity Cd 0 The EDTA-disodium in the compound chelating agent rapidly chelates free... A stable complex is formed. Citric acid adjusts the pH to provide a suitable environment for the chelation reaction. The layered structure of montmorillonite physically encapsulates the reduction products and chelates, forming a closed loop of "reduction-chelation-fixation" to reduce the risk of cadmium leaching. The extracellular polymers secreted by the compound microbial agent enhance cadmium adsorption, phosphate-solubilizing bacteria increase the available phosphorus content in the soil, and the interaction between microbial metabolites and the functional groups of biochar and sepiolite improves soil aggregate structure and increases organic matter content, achieving simultaneous remediation and fertility enhancement. The synergistic effect of the various raw materials results in a product that combines high adsorption selectivity, strong fixation stability, mild pH adjustment, improved soil fertility, multi-component synergistic efficiency, and applicability to different types of cadmium-contaminated soils. Detailed Implementation

[0027] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0028] Example 1 A soil remediation conditioner for cadmium-contaminated soil comprises the following components by weight: 30 parts zinc-modified biochar, 10 parts montmorillonite, 5 parts nano iron powder, and 30 parts high-temperature activated sepiolite.

[0029] The preparation method of the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 25℃ for continuous stirring for 10 hours. After the stirring is completed, drying is carried out at 80℃ for 22 hours. The dried material is then pyrolyzed to obtain zinc-modified biochar. The concentration of the NaOH solution is 1 mol / L; the mass percentage concentration of the Zn(NO3)2 solution is 10 wt%; and the biochar is an agricultural product. The agricultural waste was obtained by pyrolysis and carbonization at 500℃ for 2 hours under nitrogen protection; the agricultural waste was corn stalks; the ratio of Zn(NO3)2 solution to biochar was 10mL:1g; the pyrolysis temperature was 490℃ and the time was 28min; the average particle size of the nano-iron powder was 10nm, and the average particle size of the montmorillonite was 800 mesh; the high-temperature activated sepiolite was obtained by calcining sepiolite at 800℃ for 2 hours in a muffle furnace, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve.

[0030] The cadmium-contaminated soil remediation conditioner also includes the following components in parts by weight: 1 part of a compound chelating agent and 0.5 parts of a compound microbial agent; the compound chelating agent is a mixture of EDTA-disodium and citric acid in a mass ratio of 2:1; the compound microbial agent is a mixture of Bacillus subtilis and phosphate-solubilizing bacteria in a colony count ratio of 1:1; the viable count of Bacillus subtilis is ≥10. 9 CFU / g; the viable count of the phosphate-solubilizing bacteria is ≥10. 9 CFU / g.

[0031] A method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil includes the following steps: mixing each component evenly according to the weight parts, grinding and passing through a 100-mesh sieve to obtain the soil remediation conditioner for heavy metal cadmium contaminated soil.

[0032] The application of the aforementioned cadmium-contaminated soil remediation conditioner in the remediation of cadmium-contaminated soil.

[0033] Example 2 A soil remediation conditioner for cadmium-contaminated soil comprises the following components by weight: 33 parts zinc-modified biochar, 13 parts montmorillonite, 6 parts nano iron powder, and 35 parts high-temperature activated sepiolite.

[0034] The preparation method of the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 27℃ for continuous stirring for 12 hours. After the stirring is completed, drying is carried out at 83℃ for 23 hours. The dried material is then pyrolyzed to obtain zinc-modified biochar. The concentration of the NaOH solution is 1 mol / L; the mass percentage concentration of the Zn(NO3)2 solution is 10 wt%; the biochar is obtained by carbonizing agricultural waste by pyrolysis at 510℃ for 2.3 hours under nitrogen protection; the agricultural waste is durian shell; the ratio of Zn(NO3)2 solution to biochar is 10 mL: 1 g; the pyrolysis temperature is 500℃ and the time is 29 min.

[0035] The average particle size of the nano-iron powder is 30 nm, and the average particle size of the montmorillonite is 900 mesh. The high-temperature activated sepiolite is obtained by calcining sepiolite at 800°C in a muffle furnace for 2 hours, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve.

[0036] A method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil includes the following steps: mixing each component evenly according to the weight parts, grinding and passing through a 100-mesh sieve to obtain the soil remediation conditioner for heavy metal cadmium contaminated soil.

[0037] The application of the aforementioned cadmium-contaminated soil remediation conditioner in the remediation of cadmium-contaminated soil.

[0038] Example 3 A soil remediation conditioner for cadmium-contaminated soil comprises the following components by weight: 35 parts zinc-modified biochar, 15 parts montmorillonite, 7.5 parts nano iron powder, and 43 parts high-temperature activated sepiolite.

[0039] The preparation method of the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 28℃ for continuous stirring for 13 hours. After the stirring is completed, drying is carried out at 85℃ for 24 hours. The dried material is then pyrolyzed to obtain zinc-modified biochar. The concentration of the NaOH solution is 1 mol / L; the mass percentage concentration of the Zn(NO3)2 solution is 10 wt%; the biochar is obtained by carbonizing agricultural waste by pyrolysis at 530℃ for 2.5 hours under nitrogen protection; the agricultural waste is locust tree branches; the ratio of Zn(NO3)2 solution to biochar is 10 mL: 1 g; the pyrolysis temperature is 505℃ and the time is 30 min.

[0040] The average particle size of the nano-iron powder is 50 nm, and the average particle size of the montmorillonite is 1000 mesh. The high-temperature activated sepiolite is obtained by calcining sepiolite at 800°C for 2 hours in a muffle furnace, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve. The heavy metal cadmium contaminated soil remediation conditioner also includes the following components in parts by weight: 3 parts of a compound chelating agent and 1.3 parts of a compound microbial agent. The compound chelating agent is a mixture of EDTA-disodium and citric acid in a mass ratio of 2:1. The compound microbial agent is a mixture of Bacillus subtilis and phosphate-solubilizing bacteria in a colony count ratio of 1:1. The viable count of Bacillus subtilis is ≥10. 9 CFU / g; the viable count of the phosphate-solubilizing bacteria is ≥10. 9 CFU / g.

[0041] A method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil includes the following steps: mixing each component evenly according to the weight parts, grinding and passing through a 100-mesh sieve to obtain the soil remediation conditioner for heavy metal cadmium contaminated soil.

[0042] The application of the aforementioned cadmium-contaminated soil remediation conditioner in the remediation of cadmium-contaminated soil.

[0043] Example 4 A soil remediation conditioner for cadmium-contaminated soil comprises the following components by weight: 38 parts zinc-modified biochar, 19 parts montmorillonite, 9 parts nano iron powder, and 53 parts high-temperature activated sepiolite.

[0044] The preparation method of the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 29℃ for continuous stirring for 14 hours. After the stirring is completed, drying is carried out at 89℃ for 25 hours. The dried material is then pyrolyzed to obtain zinc-modified biochar. The concentration of the NaOH solution is 1 mol / L; the mass percentage concentration of the Zn(NO3)2 solution is 10 wt%; the biochar is obtained by carbonizing agricultural waste at 540℃ for 2.9 hours under nitrogen protection; the agricultural waste is locust tree branches; the ratio of Zn(NO3)2 solution to biochar is 10 mL: 1 g; the pyrolysis temperature is 510℃ and the time is 3 minutes.

[0045] The average particle size of the nano-iron powder is 70 nm, and the average particle size of the montmorillonite is 1100 mesh. The high-temperature activated sepiolite is obtained by calcining sepiolite at 800°C for 2 hours in a muffle furnace, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve. The heavy metal cadmium contaminated soil remediation conditioner also includes the following components in parts by weight: 4 parts of a compound chelating agent and 1.8 parts of a compound microbial agent. The compound chelating agent is a mixture of EDTA-disodium and citric acid in a mass ratio of 2:1. The compound microbial agent is a mixture of Bacillus subtilis and phosphate-solubilizing bacteria in a colony count ratio of 1:1. The viable count of Bacillus subtilis is ≥10. 9 CFU / g; the viable count of the phosphate-solubilizing bacteria is ≥10. 9 CFU / g.

[0046] A method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil includes the following steps: mixing each component evenly according to the weight parts, grinding and passing through a 100-mesh sieve to obtain the soil remediation conditioner for heavy metal cadmium contaminated soil.

[0047] The application of the aforementioned cadmium-contaminated soil remediation conditioner in the remediation of cadmium-contaminated soil.

[0048] Example 5 A soil remediation conditioner for cadmium-contaminated soil comprises the following components in parts by weight: 40 parts zinc-modified biochar, 20 parts montmorillonite, 10 parts nano iron powder, and 55 parts high-temperature activated sepiolite.

[0049] The preparation method of the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 30℃ for continuous stirring for 15h. After the stirring is completed, drying is carried out at 90℃ for 26h. The dried material is then pyrolyzed to obtain zinc-modified biochar. The concentration of the NaOH solution is 1mol / L; the mass percentage concentration of the Zn(NO3)2 solution is 10wt%; the biochar is obtained by pyrolyzing agricultural waste at 550℃ for 3h under nitrogen protection; the agricultural waste is corn stalks; the ratio of Zn(NO3)2 solution to biochar is 10mL:1g; the pyrolysis temperature is 520℃ and the time is 32min.

[0050] The average particle size of the nano-iron powder is 80 nm, and the average particle size of the montmorillonite is 1200 mesh. The high-temperature activated sepiolite is obtained by calcining sepiolite at 800°C for 2 hours in a muffle furnace, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve. The heavy metal cadmium contaminated soil remediation conditioner also includes the following components by weight: 5 parts of a compound chelating agent and 2 parts of a compound microbial agent. The compound chelating agent is a mixture of EDTA-disodium and citric acid in a mass ratio of 2:1. The compound microbial agent is a mixture of Bacillus subtilis and phosphate-solubilizing bacteria in a colony count ratio of 1:1. The viable count of Bacillus subtilis is ≥10. 9 CFU / g; the viable count of the phosphate-solubilizing bacteria is ≥10. 9 CFU / g.

[0051] A method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil includes the following steps: mixing each component evenly according to the weight parts, grinding and passing through a 100-mesh sieve to obtain the soil remediation conditioner for heavy metal cadmium contaminated soil.

[0052] The application of the aforementioned cadmium-contaminated soil remediation conditioner in the remediation of cadmium-contaminated soil.

[0053] Comparative Example 1 This example provides a preparation and application of a soil remediation conditioner for heavy metal cadmium contaminated soil, which is basically the same as Example 1, except that an equal amount of sepiolite is used instead of high-temperature activated sepiolite.

[0054] Comparative Example 2 This example provides the preparation and application of a soil remediation conditioner for heavy metal cadmium contaminated soil, which is basically the same as Example 1, except that an equal amount of biochar is used instead of zinc-modified biochar.

[0055] Test Example 1 Montmorillonite, high-temperature activated sepiolite, zinc-modified biochar, nano-iron powder, and the cadmium-contaminated soil remediation conditioner prepared in Example 2 were selected as adsorbents and added respectively. Static adsorption experiments were conducted on the solution with a solid-liquid ratio of adsorbent: cadmium heavy metal solution = 0.1 g: 50 mL. The initial concentration of cadmium ions was 50 mg / L. The initial pH of the heavy metal solution was adjusted using 1% HNO3 and 1% NaOH solutions. The solution was shaken at 180 r / min for 6 h at room temperature, filtered, and the concentration of cadmium heavy metal in the filtrate was determined by ICP-MS. The removal efficiency of different adsorbents for cadmium heavy metal was investigated. The results are shown in Table 1 below: Table 1 Adsorbent Adsorption rate of heavy metal cadmium (%) Montmorillonite 62.7 High-temperature activated sepiolite 93.2 Nano iron powder 72.6 Zinc-modified biochar 88.2 Soil remediation conditioner 100 Note: Cadmium was not detected in the solution after adsorption treatment, so the adsorption rate is considered to have reached 100%.

[0056] As can be seen from the adsorption results in Table 1 above, the soil remediation conditioner has a significantly higher adsorption capacity for heavy metal cadmium than any individual component. In other words, there is a synergistic effect among the components of the heavy metal cadmium contaminated soil remediation conditioner of this invention.

[0057] Test Example 2 The heavy metal contaminated soil remediation conditioners prepared in Example 1 and Comparative Examples 1-2 were added at a mass fraction of 2% to cadmium-contaminated soil. This contaminated soil was taken from a cadmium-contaminated paddy field in Hunan Province, with a total cadmium content of 3.19 mg / kg. After thorough mixing, water was promptly added to bring the soil moisture to 60%-80% of field capacity. A blank control without any remediation agent was also included. After 30 days of stable curing, available cadmium was extracted using diethylenetriaminepentaacetic acid (DTPA) as the extraction solvent. The cadmium content was determined using inductively coupled plasma mass spectrometry (ICP-MS), and the reduction rate of available cadmium content in the soil was calculated. The test results are shown in Table 2.

[0058] Table 2 project Example 1 Comparative Example 1 Comparative Example 2 Reduction rate (%) of available cadmium content in soil 95.8 90.3 83.6 As can be seen from Table 2, the heavy metal contaminated soil remediation conditioner involved in the embodiments of the present invention has a better passivation effect on cadmium in soil than the comparative product; the high-temperature activation of sepiolite and zinc-modified biochar are beneficial to improving the above performance.

[0059] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A soil remediation conditioner for heavy metal cadmium contaminated soil, characterized in that, It includes the following components by weight: 30-40 parts zinc-modified biochar, 10-20 parts montmorillonite, 5-10 parts nano iron powder, and 30-55 parts high-temperature activated sepiolite.

2. The soil remediation conditioner for cadmium-contaminated soil according to claim 1, characterized in that, The method for preparing the zinc-modified biochar includes the following steps: adjusting the pH of the Zn(NO3)2 solution to 7.0 with NaOH solution, then adding biochar, stirring evenly, and placing it in a constant temperature shaker at 25-30℃ for continuous stirring for 10-15 hours. After the stirring is completed, drying is carried out at 80-90℃ for 22-26 hours. After pyrolysis of the dried material, zinc-modified biochar is obtained.

3. The soil remediation conditioner for cadmium-contaminated soil according to claim 2, characterized in that, The concentration of the NaOH solution is 1 mol / L; the mass percentage concentration of the Zn(NO3)2 solution is 10 wt%.

4. The soil remediation conditioner for cadmium-contaminated soil according to claim 2, characterized in that, The biochar is obtained by carbonizing agricultural waste by pyrolysis at 500-550℃ for 2-3 hours under nitrogen protection; the agricultural waste is one or more of corn stalks, durian shells, and locust tree branches.

5. The soil remediation conditioner for cadmium-contaminated soil according to claim 2, characterized in that, The ratio of Zn(NO3)2 solution to biochar is 10 mL: 1 g.

6. The soil remediation conditioner for cadmium-contaminated soil according to claim 2, characterized in that, The pyrolysis temperature is 490-520℃ and the time is 28-32 min.

7. The soil remediation conditioner for cadmium-contaminated soil according to claim 1, characterized in that, The average particle size of the nano-iron powder is 10-80 nm, and the average particle size of the montmorillonite is 800-1200 mesh. The high-temperature activated sepiolite is obtained by calcining sepiolite at 800°C for 2 hours in a muffle furnace, cooling it to room temperature, and then pulverizing it through a 100-mesh sieve.

8. The soil remediation conditioner for cadmium-contaminated soil according to claim 1, characterized in that, The soil remediation conditioner for cadmium-contaminated soil also includes the following components in parts by weight: 1-5 parts of a compound chelating agent and 0.5-2 parts of a compound microbial agent; the compound chelating agent is a mixture of EDTA-disodium and citric acid in a mass ratio of 2:1; the compound microbial agent is a mixture of Bacillus subtilis and phosphate-solubilizing bacteria in a colony count ratio of 1:1; the viable count of Bacillus subtilis is ≥10. 9 CFU / g; the viable count of the phosphate-solubilizing bacteria is ≥10. 9 CFU / g.

9. A method for preparing a soil remediation conditioner for heavy metal cadmium contaminated soil according to any one of claims 1-8, characterized in that, The process includes the following steps: after mixing the components evenly according to their weight proportions, grinding them through a 100-mesh sieve to obtain a soil remediation conditioner for cadmium-contaminated soil.

10. The application of a soil remediation conditioner for heavy metal cadmium contaminated soil according to any one of claims 1-8 in the remediation of heavy metal cadmium contaminated soil.