A heavy metal contaminated soil remediation conditioner and a preparation method thereof

Abstract

This invention discloses a soil remediation conditioner for heavy metal contaminated soil and its preparation method, belonging to the field of soil environmental remediation technology. The conditioner uses ultrafine kaolin / maifanite as a base material, combined with functional components such as slaked lime, lightly calcined magnesium oxide, sulfide-modified zeolite, humic acid powder, anionic PAM, and hydrophobic silica. Class II fly ash can be selectively added to reduce production costs. The components work synergistically to achieve multiple effects including slow-release alkali regulation, targeted fixation of mercury and cadmium heavy metals, resistance to rainwater leaching, and long-term anti-caking. The preparation process of this invention adopts a graded feeding and segmented mixing mode, involving eight major processes: material pretreatment, base material premixing, functional component fusion, explosion-proof pulverization, fine anti-caking mixing, closed sieving, index testing, and explosion-proof sealed packaging. The entire production process is equipped with a negative pressure dust removal system and a multi-dimensional explosion-proof protection system, effectively solving production problems such as powder dust and sulfur dust explosions. Tests have verified that the finished product of this invention has a 200-mesh pass rate of ≥95%, moisture content of ≤8%, and a pH value that is stable in the range of 7.5-8.5. It also has a Hg and Cd heavy metal fixation rate of ≥80% and a shelf life of up to 6 months under normal temperature and cool conditions. At the same time, the raw material cost is 15%-20% lower than that of similar products, the production safety factor is high, and it is green and environmentally friendly. It can be widely used in the remediation of farmland soil with light and moderate heavy metal pollution, and has broad prospects for industrialization.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation and agricultural environmental governance technology, specifically relating to a dry powder remediation conditioner suitable for farmland soil contaminated with heavy metals, and its industrialized safe production preparation process. Background Technology

[0002] With the rapid development of industrialization and intensive agriculture in China, the problem of heavy metal pollution in soil has become increasingly prominent. Excessive levels of heavy metal pollutants such as cadmium, mercury, lead, and arsenic not only damage the soil's ecological structure but also enter the food chain through crop accumulation, directly threatening the quality and safety of agricultural products and human health. The treatment of heavy metal pollution in farmland has become a key challenge in the field of agricultural environmental protection.

[0003] Currently available commercially available soil heavy metal remediation agents generally suffer from several technical shortcomings, including: 1) Rapid alkalinity release, causing drastic fluctuations in soil pH in a short period, scorching crop roots, and affecting normal crop growth; 2) Poor resistance to rainwater leaching, with effective remediation components easily lost with rainwater, resulting in short remediation cycles and insufficient sustained effects; 3) Dry powder agents are prone to moisture absorption and clumping during storage and transportation, reducing material flowability and directly impacting application effectiveness; 4) Insufficient formulation targeting, with weak ability to target and fix highly toxic heavy metals such as mercury and cadmium; 5) High raw material and production costs, making them unsuitable for large-scale farmland remediation operations; 6) Dust generation during powder material production, posing occupational health risks to operators and polluting the surrounding environment; 7) Imperfect production processes for sulfur-containing remediation agents, as sulfur dust is flammable and explosive, and existing production solutions lack systematic and targeted explosion-proof designs, posing significant production safety hazards. Summary of the Invention

[0004] Purpose of the invention.

[0005] To address the shortcomings of existing remediation conditioners, such as uncontrolled alkalinity, easy clumping, poor leaching resistance, weak targeted remediation, high cost, large production dust, and lack of explosion-proof system, this invention provides a heavy metal contaminated soil remediation conditioner and its industrial preparation method that features slow-release alkalinity adjustment, leaching resistance, long-term anti-caking effect, targeted heavy metal fixation, low production cost, and is equipped with a negative pressure dust removal and comprehensive explosion-proof system.

[0006] Technical solution

[0007] (a) Components of the Repair and Conditioning Agent Formula

[0008] Based on the preparation of 100kg of dry powder product, the functions and addition amounts of each component are shown in the table below, and the material specifications meet the standards defined in claim 2: 1 slaked lime 1.5 Rapidly adjusts soil alkalinity and passivates heavy metals 2 Lightly calcined magnesium oxide 0.7 Slow-release alkalinity to stabilize soil pH and prevent sudden changes in alkalinity. 3 superphosphate 1.8 Replenishing soil phosphorus and synergistically passivating heavy metals 4 Humic acid powder 2.0 Physical adsorption of heavy metals, improving soil aggregate structure 5 Zeolite + Bentonite (1:1) 2.5 Basic adsorption of heavy metals, improving soil porosity 6 Sulfide-modified zeolite 1.5 Targeted chelation and immobilization of highly toxic heavy metals such as mercury and cadmium 7 Ferrous sulfate monohydrate 0.3 Provides a stable iron source, assists in the passivation of heavy metals, and avoids problems of deliquescence and oxidation. 8 Sulfur powder 0.6 It helps to fine-tune soil pH and enhance the effect of heavy metal sulfidation and solidification. 9 Modified attapulgite 2.2 Promotes material aggregation and enhances the finished product's resistance to rain leaching. 10 Water-soluble silicon fertilizer 1.5 Optimizes powder flowability, replenishes soil silicon, and enhances crop stress resistance. 11 Anionic PAM 0.08 The agglomeration of auxiliary materials significantly improves the resistance of the repair layer to leaching and erosion. 12 Hydrophobic silica 0.5 It encapsulates powder particles, isolates moisture, and effectively prevents finished product from clumping (essential component). 13 Ultrafine kaolin / maifanite 66.72 Inert filler substrate, dilutes flammable powder, reduces explosion risk 14 Grade II fly ash (optional) 18.0 Replace some base materials to reduce raw material production costs

[0009] Additional notes: When the formula does not include Grade II fly ash, the amount of ultrafine kaolin / maifanite added is adjusted to 84.72 kg, while the amounts of other components remain unchanged.

[0010] (II) Overall preparation process

[0011] Material pretreatment and accurate weighing → Base material premixing → Intermediate material mixing → Functional material mixing → Explosion-proof pulverization → Fine mixing to prevent caking → Negative pressure closed sieving → Finished product index testing → Explosion-proof sealed packaging → Cool and dry storage Key points for process control: material weighing error ≤ ±0.1kg; mixing follows the principle of graded feeding; all crushed materials pass through a 200-mesh sieve; anionic PAM is pretreated separately and added slowly later; hydrophobic silica is fed last; the entire process is equipped with a negative pressure dust removal and graded explosion-proof system.

[0012] (III) Stepwise preparation process

[0013] 1. Material pretreatment and weighing: Control the ambient temperature of the production workshop to 15-30℃ and the relative humidity to ≤60%; start the negative pressure dust removal system and the complete set of explosion-proof protection system in advance; dry all solid materials uniformly to a moisture content of ≤8%; crush the anionic PAM separately and pass it through a 300-mesh sieve to avoid subsequent agglomeration problems; weigh each group of materials in the order of base material, medium material, and small material, and weigh the anionic PAM independently, with the single weighing error strictly controlled within ±0.1kg.

[0014] 2. Base material premixing: Use an explosion-proof double spiral mixer, add ultrafine kaolin / maifanite and optional Class II fly ash, set the speed to 150-200 r / min, and continue mixing for 10 min to complete the homogenization treatment of the base material.

[0015] 3. Mixing of intermediate materials: Quicklime, lightly calcined magnesium oxide, zeolite-bentonite mixture and sulfide-modified zeolite are added sequentially into the mixer. The initial mixing speed is maintained and the mixture is stirred continuously for 15 minutes to complete the fusion of the alkali-adjusting components and the basic adsorption components.

[0016] 4. Functional Material Mixing: Add superphosphate, humic acid powder, modified attapulgite, water-soluble silicon fertilizer, sulfur powder, and ferrous sulfate monohydrate to the mixing system. Stir for 20 minutes at 150-200 rpm to integrate all functional remediation components. During this stage, a large amount of inert substrate can dilute the sulfur powder concentration, reducing the risk of dust explosion from the source.

[0017] 5. Material crushing: The premixed homogenized material is conveyed to an explosion-proof universal crusher equipped with a 75μm (200 mesh) standard screen and a rotation speed set to 3000-4000 r / min; forced air cooling controls the discharge temperature to ≤50℃; the negative pressure of the crushing section system is maintained at -50~-150Pa, the static grounding resistance of all equipment is ≤4Ω, and a spark detection and extinguishing device is provided to eliminate safety hazards.

[0018] 6. Fine mixing and anti-caking treatment: Return the crushed material to the twin-screw mixer, slowly sprinkle anionic PAM at low speed, and finally add hydrophobic silica; adjust the speed to 250-300 r / min, and mix at high speed for 25-30 min under constant temperature ≤45℃; take samples every 10 min to check the material status, and if agglomeration occurs, crush and remix immediately.

[0019] 7. Material screening: A closed 200-mesh explosion-proof vibrating screen is used, with a vibration frequency of 1400 r / min and a screening angle of 5-8°. The negative pressure in the screening area is kept stable at -30 to -80 Pa to prevent dust leakage. The material under the screen is a qualified finished product, and the coarse material on the screen is returned to the crushing process for secondary processing.

[0020] 8. Testing and Sealing Packaging: The finished product shall be tested for appearance, particle size, moisture content, pH value, heavy metal fixation rate, and mixing uniformity in accordance with the standards specified in claim 5. After passing the tests, the finished product shall be sealed in a closed explosion-proof workshop with a relative humidity of ≤50% using moisture-proof composite packaging bags of two specifications: 25kg / bag and 50kg / bag. The product name, specifications, shelf life, and applicable scope shall be marked on the packaging surface. The finished product shall be stored in a cool, dry Class B explosion-proof warehouse with a shelf life of 6 months.

[0021] (iv) Systematic explosion-proof design

[0022] The formula of this invention contains 0.6% sulfur powder. The lower explosive limit of sulfur dust is 35 g / m³, and the minimum ignition energy is 15 mJ, classifying it as a highly hazardous combustible dust. Considering the dust-generating characteristics of powder production, a comprehensive explosion-proof system is established from four dimensions: process, equipment, building electrical systems, and operation management.

[0023] 1. Explosion-proof process: All materials are uniformly dried to a moisture content of ≤8% to increase material moisture and reduce dust generation; sulfur powder is added later in the functional material mixing stage, relying on a large amount of inert substrate to dilute the concentration, making it far below the lower explosive limit; the material temperature is strictly controlled throughout the process, with a mixing temperature of ≤45℃ and a discharge temperature of ≤50℃, which is far below the 190℃ auto-ignition temperature of sulfur dust.

[0024] 2. Equipment Explosion-proof: All production equipment that comes into contact with powder is equipped with ExtD A21 IP65 T130℃ level explosion-proof equipment; the air inlet pipes of crushers, screening machines, and dust collectors are equipped with spark detection and extinguishing devices with a response time of ≤0.1s as standard; the main body of dust-generating equipment is equipped with an explosion relief structure that conforms to GB / T 15605 standard; all equipment and conveying pipelines are uniformly treated with static electricity bridging and grounding, and the grounding resistance is ≤4Ω.

[0025] 3. Building and electrical explosion protection: The production workshop is constructed in accordance with the Class B explosion-proof building standard, and is equipped with explosion-proof walls and explosion-proof roofs; all electrical components such as workshop lighting, motors, and control cabinets are explosion-proof; a dual online monitoring system for combustible dust and oxygen concentration is installed, and when the dust concentration reaches 25% of the lower explosive limit and the oxygen concentration exceeds the range of 19.5%-23%, an automatic alarm is triggered and the machine is shut down.

[0026] 4. Explosion-proof operation management: Before each shift, verify the static grounding, dust removal system, and monitor the operating status of the equipment; clean the dust inside the equipment and on the workshop floor regularly to avoid the risk of secondary explosions; all operators should wear anti-static work clothes and anti-static shoes, and wear dust masks and protective gloves when in contact with corrosive materials such as quicklime.

[0027] Beneficial effects

[0028] 1. Excellent heavy metal targeted fixation effect: Relying on sulfide-modified zeolite to chelate and solidify mercury and cadmium heavy metals, combined with humic acid and attapulgite for multiple adsorption and passivation, the finished product has a fixation rate of ≥80% for Hg and Cd heavy metals, and is suitable for farmland remediation operations with light and moderate heavy metal pollution.

[0029] 2. Outstanding resistance to leaching: The synergistic effect of anionic PAM and modified attapulgite promotes the formation of a stable aggregate structure between the remediation agent and the soil, effectively preventing the effective components from being washed away by rainwater and extending the remediation time.

[0030] 3. Long-lasting anti-caking effect: The hydrophobic silica evenly coats the powder particles, forming a hydrophobic protective layer on the particle surface, which isolates moisture in the air. Under normal storage conditions, the finished product will not absorb moisture and clump within 6 months.

[0031] 4. Controllable production costs: Class II fly ash can be used to replace some of the expensive base materials. Without affecting the repair performance, the overall cost of raw materials is reduced by 15%-20% compared with similar products on the market, making it suitable for large-scale promotion.

[0032] 5. Stable product performance: Ferrous sulfate monohydrate is used instead of traditional ferrous sulfate heptahydrate, which completely solves the industry pain points of raw materials being prone to deliquescence and oxidation, and improves the batch stability of products.

[0033] 6. Green and safe production: The graded negative pressure dust removal system realizes dust collection in the entire process section, and the dust emission concentration in the exhaust gas is ≤10mg / m³, improving the working environment; the multi-dimensional explosion-proof system covers the entire process, diluting the risk of sulfur dust explosion, and ensuring production safety from the hardware, process and management levels.

[0034] Attached image description.

[0035] Figure 1 Process flow chart.

[0036]

[0037] Detailed implementation method.

[0038] Example 1 (Standard Example without Fly Ash)

[0039] This embodiment prepares 100 kg of heavy metal contaminated soil remediation conditioner that does not contain Class II fly ash. The production environment temperature is 25℃ and the relative humidity is 55%. A complete set of negative pressure dust removal and explosion-proof systems are provided. The specific steps are as follows:

[0040] 1. Material Preparation and System Verification: Beforehand, check the electrostatic grounding status of all equipment; the measured grounding resistance is 2.5Ω (qualified). Verify that the spark detection device, dust concentration monitor, and explosion relief device are functioning normally. Start the explosion-proof pulse-jet bag filter, setting the filtration velocity to 1.0 m / min. The negative pressures for each section are: feed inlet -80 Pa, crusher feed inlet -100 Pa, screening hood -60 Pa. Accurately weigh the raw materials: 84.72 kg of ultrafine kaolin and 1.5 kg of quicklime. kg, lightly calcined magnesium oxide 0.7 kg, zeolite-bentonite mixture 2.5 kg, sulfide-modified zeolite 1.5 kg, superphosphate 1.8 kg, humic acid powder 2.0 kg, modified attapulgite 2.2 kg, water-soluble silicon fertilizer 1.5 kg, sulfur powder 0.6 kg, ferrous sulfate monohydrate 0.3 kg, anionic PAM 0.08 kg, hydrophobic silica 0.5 kg; all materials are dried to a moisture content ≤8%, and the anionic PAM is separately pulverized and passed through a 300-mesh sieve for later use.

[0041] 2. Base material premixing: Put ultrafine kaolin into a 200L explosion-proof double spiral mixer and mix for 10 minutes at a speed of 180r / min.

[0042] 3. Mixing of intermediate materials: Add quicklime, lightly calcined magnesium oxide, zeolite-bentonite mixture and sulfide-modified zeolite in sequence, mix at the same speed for 15 minutes, and the operators should wear protective equipment throughout the process.

[0043] 4. Functional material mixing: Add the remaining functional materials and stir at 180 r / min for 20 min; at this time, the sulfur powder, after being diluted with an inert substrate, has a mass concentration of only 0.9%, which is far below the lower explosive limit and the production risk is extremely low.

[0044] 5. Material crushing: The mixed materials are fed into an explosion-proof crusher and crushed at 3500 r / min with a 200 mesh screen. The discharge temperature is 48℃. The crushing section is under negative pressure of -100 Pa, with no sparks generated. The recovered dust is mixed back into the next batch of materials at a ratio of 5%.

[0045] 6. Fine mixing: The crushed material is fed back into the mixer, PAM is added slowly, and finally hydrophobic silica is added; the mixture is mixed at 280 r / min for 28 min, and the material is kept at a constant temperature of 42℃; samples are taken every 10 min for testing, and the material shows no stratification or agglomeration.

[0046] 7. Material screening: A 200-mesh explosion-proof vibrating screen is used, with a vibration frequency of 1400 r / min, an inclination angle of 6°, and a negative pressure of -60 Pa; 0.2 kg of waste material on the screen is all reprocessed and crushed.

[0047] 8. Testing and Packaging: Finished product testing results: Appearance is grayish-white uniform powder; 200 mesh pass rate is 96.5%; moisture content is 6.2%; pH value is 8.1; Cd heavy metal fixation rate is 82%; workshop combustible dust concentration is ≤0.1g / m³; in an explosion-proof environment with a humidity of 48%, it is sealed in 25kg moisture-proof packaging bags and stored in a cool explosion-proof warehouse.

[0048] Example 2 (including optimized example with fly ash)

[0049] In this embodiment, 100 kg of a repair and conditioning agent containing Class II fly ash was prepared. The base material ratio was: 66.72 kg of ultrafine kaolin and 18.0 kg of Class II fly ash. The types and amounts of other materials were completely consistent with those in Example 1. In view of the dust-generating characteristics of fly ash, the negative pressure parameters were optimized: negative pressure at the feeding port was -120 Pa and negative pressure in the screening area was -80 Pa. The other process parameters and explosion-proof measures remained unchanged.

[0050] After preparation, the finished product was tested and found to have better material flowability than in Example 1, the heavy metal fixation performance was the same as in Example 1, and the raw material cost was reduced by 18%. The dust concentration and combustible dust concentration in the workshop throughout the production process met the safety standards and can be produced on a normal scale.

[0051] Example 3 (Process Parameter Boundary Verification)

[0052] Based on the fly ash-free formulation in Example 1, the feasibility of the upper and lower boundaries of the process parameters was verified:

[0053] 1. Low temperature and low speed boundary: ambient temperature 18℃, mixing speed 160r / min, pulverizing speed 3200r / min; initial mixing uniformity 89%, after extending the mixing time to 35min, the uniformity meets the standard, and all safety parameters are normal.

[0054] 2. High temperature and high speed boundary: ambient temperature 30℃, mixing speed 290r / min, crushing speed 3800r / min; discharge temperature 52℃, slightly exceeding the limit threshold, humic acid activity decreases by 3%; although there is no safety risk, the discharge temperature must be strictly controlled to ≤50℃.

[0055] 3. Negative pressure boundary: When the negative pressure of the crusher is lowered to below 40Pa, dust leakage occurs and the dust concentration in the workshop increases slightly; the minimum threshold of negative pressure in the crushing section is determined to be -50Pa, and the preferred range is -80 to -120Pa.

[0056] Example 4 (Specific Verification of Explosion-Proof System)

[0057] Based on the production conditions of Example 1, the effectiveness of each measure of the explosion-proof system was verified individually:

[0058] 1. Electrostatic grounding test: The grounding wire of the crusher was manually disconnected. After running continuously for 30 minutes, the electrostatic potential on the surface of the equipment reached 800V; the electrostatic discharge energy was 0.3mJ, which is lower than the minimum ignition energy of sulfur, but there is a cumulative risk, which proves that grounding measures are essential.

[0059] 2. Spark detection test: A test spark is manually introduced. The detection device responds and extinguishes the spark within 0.08 seconds, and the device's response performance meets the standard.

[0060] 3. Explosion relief device test: The explosion-proof chamber simulates a dust explosion. The explosion relief device opens within 5ms, the explosion relief pressure is controllable, and the main body of the equipment is undamaged, which meets the national standard design requirements.

[0061] Comparative Example 1 (lacking hydrophobic silica)

[0062] Based on the formulation of Example 1, 0.5 kg of hydrophobic silica was removed, and the amount of ultrafine kaolin was increased to 85.22 kg, while the rest of the process remained unchanged. After the finished product was stored at 25°C and 60% humidity for 15 days, the material agglomerated over a large area, and the hard lumps could not pass through a 200-mesh sieve, and the product became completely ineffective, proving that hydrophobic silica is the core essential component for achieving long-term anti-caking.

[0063] Comparative Example 2 (Improper PAM feeding method)

[0064] Based on the formulation of Example 1, anionic PAM and the substrate were fed simultaneously in one go, with other process parameters remaining unchanged. The finished product test revealed that PAM agglomerated in large quantities and could not be dispersed evenly, with a material mixing uniformity of only 78%. This proves that separate pretreatment of PAM and slow feeding in the later stage are the key processes to ensure product quality.

[0065] Comparative Example 3 (Negative pressure dust removal system turned off)

[0066] The entire formula and process of Example 1 were replicated, and the negative pressure dust removal system was shut down throughout the production process; severe dust occurred in each section, with the peak PM10 concentration in the workshop reaching 35mg / m³, far exceeding the occupational exposure limit, endangering the health of operators, and making production unsustainable; this confirms that the negative pressure dust removal system is an essential supporting facility for industrial production.

[0067] Comparative Example 4 (all explosion-proof measures removed)

[0068] The formula and process of Example 1 were replicated, but all protective measures such as electrostatic grounding, spark detection, explosion relief devices, and explosion-proof electrical equipment were eliminated. According to the engineering risk assessment, the high-speed operation of the crusher is prone to generating ignition sparks, and sulfur dust is prone to forming a high-risk dust cloud, posing an extremely high explosion hazard. For production operations containing sulfur powder, a complete set of explosion-proof measures is indispensable.

[0069] Industrial applicability

[0070] The raw materials used in this invention are readily available and inexpensive to purchase. The preparation process is simple and easy to understand, and can be completed and put into production using conventional powder mixing, crushing, and sieving equipment, without the need for special high-pressure or high-temperature conditions. The staged negative pressure dust removal and modular explosion-proof system are compatible with most powder processing workshops in China. This invention's product is specifically designed for farmland heavy metal pollution scenarios, with a recommended application rate of 50-200 kg per acre. It can effectively remediate lightly to moderately polluted soils with heavy metals such as cadmium and mercury, while also providing soil improvement and fertility enhancement effects, making it highly valuable for industrialization and promotion.

Claims

1. A soil remediation conditioner for heavy metal contaminated soil, characterized in that, Based on 100 kg of dry powder, the product consists of the following components in parts by weight: 1.5 parts slaked lime, 0.7 parts lightly calcined magnesium oxide, 1.8 parts superphosphate, 2.0 parts humic acid powder, 2.5 parts zeolite and bentonite mixture, 1.5 parts sulfide-modified zeolite, 0.3 parts ferrous sulfate monohydrate, 0.6 parts sulfur powder, 2.2 parts modified attapulgite, 1.5 parts water-soluble silicon fertilizer, 0.08 parts anionic polyacrylamide (PAM), 0.5 parts hydrophobic silica, and 66.72 parts ultrafine kaolin or maifanite; and optionally, 18.0 parts of grade II fly ash; wherein the mass ratio of the zeolite and bentonite mixture is 1:1; when grade II fly ash is not added, the amount of ultrafine kaolin or maifanite added is adjusted to 84.72 parts.

2. The soil remediation conditioner for heavy metal contaminated soil according to claim 1, characterized in that, The specifications of each component are as follows: The quicklime is an industrial-grade material with a purity of ≥90% and a powder fineness of ≥200 mesh; The lightly calcined magnesium oxide has an activity ≥85% and a powder fineness ≥200 mesh; The superphosphate has an effective phosphorus content of ≥12% and a powder fineness of ≥100 mesh; The humic acid powder has a humic acid content of ≥70%, a powder fineness of ≥100 mesh, and a material moisture content of ≤10%. The fineness of the zeolite and bentonite powders is ≥200 mesh; The sulfide-modified zeolite has a modification degree of ≥80% and a powder fineness of ≥200 mesh; The ferrous sulfate monohydrate has a purity of ≥98%, a powder fineness of ≥100 mesh, and a material moisture content of ≤5%. The sulfur powder has a purity of ≥99% and a fineness of ≥200 mesh; The modified attapulgite has a modification degree of ≥75% and a powder fineness of ≥200 mesh; The water-soluble silicon fertilizer has an effective silicon content of ≥20%, a water solubility of ≥95%, and a powder fineness of ≥100 mesh; The anionic PAM has a molecular weight of 8-12 million, a purity of ≥90%, and a powder fineness of ≥200 mesh. The hydrophobic silica has a specific surface area ≥150m² / g and a powder fineness ≥300 mesh; The fineness of the ultrafine kaolin or maifanite powder is ≥300 mesh, and the moisture content of the material is ≤8%. The grade II fly ash powder has a fineness of ≥100 mesh and a loss on ignition of ≤8%.

3. A method for preparing a soil remediation conditioner for heavy metal contaminated soil according to any one of claims 1-2, characterized in that, The operation includes the following steps: (1) Material pretreatment and weighing: Control the production environment temperature to 15-30℃ and relative humidity to ≤60%; keep the negative pressure dust removal system and explosion protection system running throughout the process, and dry all solid materials to a moisture content of ≤8%; pulverize the anionic PAM separately and pass it through a 300-mesh sieve for later use; weigh each group of materials according to the specified mass fractions, and the material weighing error is ≤±0.1kg; the weighing sequence follows the principle of "base material → medium material → small material", and the anionic PAM is weighed separately; (2) Base material premixing: Start the explosion-proof double spiral mixer, add ultrafine kaolin or maifanite, and selectively add Class II fly ash, and continue mixing for 10 minutes at a speed of 150-200 r / min; (3) Mixing of intermediate materials: Quicklime, lightly calcined magnesium oxide, zeolite and bentonite mixture, and sulfide-modified zeolite are added into the mixer in sequence, and the original speed is kept unchanged and the mixing continues for 15 minutes; (4) Mixing of functional materials: Add superphosphate, humic acid powder, modified attapulgite, water-soluble silicon fertilizer, sulfur powder, and ferrous sulfate monohydrate, and maintain a speed of 150-200 r / min for 20 min. (5) Material crushing: The premixed material is conveyed to an explosion-proof universal crusher, equipped with a 75μm (200 mesh) screen, and the crusher speed is set to 3000-4000r / min. The discharge temperature is strictly controlled to ≤50℃. The negative pressure dust removal and explosion-proof system is turned on throughout the crushing process. The negative pressure inside the system is maintained at -50 to -150Pa, and the static grounding resistance of all equipment is ≤4Ω. (6) Fine mixing and anti-caking treatment: The crushed material is put back into the double helix mixer, anionic PAM is added slowly, and finally hydrophobic silica is added; the speed of the mixer is adjusted to 250-300 r / min, and high-speed mixing is carried out for 25-30 min. The material temperature during the mixing process is ≤45℃; a negative pressure dust removal and explosion-proof system is provided throughout the process, and the material status is sampled and tested every 10 min. (7) Material screening: A 200-mesh explosion-proof vibrating screen is used to screen the mixture. The vibration frequency is set to 1400 r / min and the screening angle is 5-8°. The screening equipment is connected to the negative pressure dust removal system in a closed manner. The negative pressure in the screening area is stable at -30 to -80 Pa. Unqualified materials on the screen are returned to the crushing process for reprocessing. (8) Testing and sealing packaging: After screening, the finished product is tested for multiple indicators. After passing the test, it is sealed in an environment with relative humidity ≤50% and a negative pressure sealed explosion-proof packaging system. The packaging specifications are 25kg / bag and 50kg / bag. The product information is marked on the packaging surface.

4. The preparation method of the heavy metal contaminated soil remediation conditioner according to claim 3, characterized in that: In step (6), samples are taken every 10 minutes to observe the state of the material to ensure that the material does not agglomerate, separate into layers, or clump. If agglomeration is detected, the machine is stopped immediately, the agglomerated material is crushed and passed through a 200-mesh sieve, and then the material is re-added and mixed to avoid the problem of anionic PAM agglomeration failure.

5. The preparation method of the heavy metal contaminated soil remediation conditioner according to claim 3, characterized in that: The finished product testing indicators and qualification standards in step (8) are as follows: the appearance is uniform powder without lumps; the passing rate of 200 mesh sieve is ≥95%; the moisture content of the material is ≤8%; the pH value of 1:10 aqueous solution is 7.5-8.5; the fixation rate of mercury and cadmium heavy metals is ≥80%; and the overall mixing uniformity of the material is ≥90%.

6. The preparation method of the heavy metal contaminated soil remediation conditioner according to claim 3, characterized in that: The negative pressure dust removal system uses an explosion-proof pulse jet bag filter or an explosion-proof cartridge filter. The equipment filtration velocity is controlled at 0.8-1.2 m / min, and the dust emission concentration in the exhaust gas is ≤10 mg / m³. The dust collector body and connecting pipes are all electrostatically grounded to achieve dust collection throughout the entire production process.

7. The preparation method of the heavy metal contaminated soil remediation conditioner according to claim 3, characterized in that: The explosion-proof system includes any combination of the following protective measures: (a) All production equipment that generates dust (mixers, crushers, vibrating screens, packaging machines) are equipped with explosion vents or flameless explosion vents, and the explosion vent area is designed in strict accordance with the national standard GB / T 15605. (b) Spark detection and extinguishing devices shall be installed in the air inlet ducts of crushers, screening machines and dust collectors, with a response time of ≤0.1 seconds; (c) The production workshop is equipped with an online oxygen concentration monitoring device, which automatically triggers an audible and visual alarm when the oxygen concentration in the workshop is below 19.5% or above 23%. (d) All production equipment and conveying pipelines shall be electrostatically bonded and reliably grounded, with an overall grounding resistance ≤4Ω; (e) All electrical equipment in the workshop shall be explosion-proof, with an explosion-proof rating of not less than ExtD A21 IP65 T130℃; (f) The workshop is equipped with an online monitoring instrument for combustible dust concentration. When the dust concentration reaches 25% of the lower explosive limit of sulfur dust (35g / m³), the equipment will automatically alarm and link the production equipment to stop in an emergency. (g) When operating irritating materials such as quicklime, operators shall wear protective gloves, dust masks and other protective equipment.

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