Preparation method of repairing material for rapidly leaching and removing heavy metal cadmium in rice field

Abstract

The invention discloses a rice field heavy metal cadmium rapid leaching removal repair material preparation method, which comprises: S1, raw material screening: selecting rice straw and edible fungi residue as raw materials, the humic acid content of the rice straw is 18-22%, the cellulose / lignin ratio is 4: 1, the extracellular polysaccharide content of the edible fungi residue is more than or equal to 15%, the humic acid content is 22-25%, and the cellulose / lignin ratio is 4: 1; the ratio of cellulose to lignin is 2: 1; s2, pretreatment of the raw materials: adding the raw materials into a hammer crusher, crushing the raw materials to 0.5-2mm with the specific surface area of more than or equal to 2.5 m < 2 > / g, centrifugally dewatering the mushroom dreg raw materials until the water content is less than 60%, and adding the mushroom dregs into a high-pressure steam sterilization pot; the method is reasonable in design, coordination of efficient removal of cadmium pollution and improvement of soil fertility is achieved through treatment of pollution with waste, fertilizer efficiency coordination and intelligent regulation and control, circular economic benefits are created while the remediation cost is reduced, chemical residues are avoided, low-carbon emission is achieved, and a sustainable solution is provided for safe utilization of the rice field.

Description

Technical Field

[0001] The present invention relates to the technical field of paddy field cadmium pollution control, and particularly relates to a preparation method of a rapid leaching and removal repair material for heavy metal cadmium in paddy fields. Background Art

[0002] The half-life of cadmium in the human body is as long as 10 - 30 years, and long-term accumulation can lead to renal failure, osteoporosis ("itai-itai disease") and cancer. The heavy metal cadmium pollution in paddy fields will endanger food safety and human health. Therefore, we designed a preparation method of a rapid leaching and removal repair material for heavy metal cadmium in paddy fields to solve the above problems. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems existing in the prior art, and a preparation method of a rapid leaching and removal repair material for heavy metal cadmium in paddy fields is proposed. It realizes the synergy of efficient cadmium pollution removal and soil fertility improvement through "treating pollution with waste, synergistic fertilizer effect, and intelligent regulation", creates circular economic benefits while reducing the repair cost, and has no chemical residues and low carbon emissions, providing a sustainable solution for the safe utilization of paddy fields.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A preparation method of a rapid leaching and removal repair material for heavy metal cadmium in paddy fields, comprising the following steps:

[0006] S1. Raw material screening: Select rice straw and edible mushroom residue as raw materials. The humic acid content of the rice straw is 18 - 22%, and the cellulose / lignin ratio is 4:1. The edible mushroom residue contains extracellular polysaccharide ≥ 15%, the humic acid content is 22 - 25%, and the cellulose / lignin ratio is 2:1;

[0007] S2. Raw material pretreatment: Add the raw materials into a hammer crusher and crush them to 0.5 - 2 mm and specific surface area ≥ 2.5 m 2 / g. Centrifuge and dehydrate the mushroom residue raw material to a moisture content of less than 60%, and add the mushroom residue to a high-pressure steam sterilizer. Sterilize with steam at 120 - 122 °C for 20 min. Spray and humidify the rice straw raw material to a moisture content of 40 - 45% using a spray humidification system. Use a double-screw conical mixer to mix the straw raw material:mushroom residue = 7:3;

[0008] S3. Fermentation process: Inoculate the mixed raw materials with white rot fungi for aerobic fermentation. The inoculation amount is 5%. Ferment at a temperature of 53 - 57 °C and an aeration rate of 0.6 L / min·kg for 7 days, and turn the pile once every 24 h until the laccase activity in the target product lignin-degrading enzyme ≥ 50 U / g;

[0009] Inoculate acid-producing bacteria for anaerobic fermentation with an inoculation amount of 3%, and ferment for 14 days under the conditions of a closed environment temperature of 34 - 36°C and ORP < -200 mV until the volatile fatty acids in the target product short-chain fatty acids are ≥ 30 mg / g. After fermentation, the material is dried at 60°C until the moisture content is < 10%;

[0010] S4. Gradient chemical extraction: Alkaline extraction: Immerse the raw material in a 0.1 mol / L NaOH solution with a solid-liquid ratio of 1:10, shake at 60°C for 2 h, centrifuge to obtain the supernatant, and obtain macromolecular humic acid;

[0011] Acid activation: Immerse the raw material in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1:5, let it stand at room temperature for 1 h, centrifuge to obtain the supernatant, and obtain small molecular organic acids;

[0012] Separation and purification: Combine the two extraction solutions, filter through a 0.45 μm filter membrane, and concentrate to a solid content of 15% through a ceramic membrane ultrafiltration system;

[0013] Freeze-dry the concentrated extraction solution at -50°C and 0.1 mbar to obtain a humic acid-organic acid composite powder;

[0014] S5. Blending of eluent: The eluent includes 25% humic acid-organic acid composite powder, 0.8% nano-SiO2, 2% rhamnolipid, and 72.2% deionized water. First, mix the humic acid composite powder with nano-SiO2 dry powder, ball mill for 30 min, then add deionized water, perform ultrasonic treatment at 40 kHz for 30 min to form a uniform colloid, add rhamnolipid, stir until completely dissolved, and finally adjust the pH to 7.0 ± 0.5 with 0.1 mol / L NaOH to obtain the eluent.

[0015] Preferably, in S1, the screen aperture of the hammer crusher is 1 mm.

[0016] Preferably, in S3, measure the pH, volatile fatty acid concentration, and laccase activity every 24 h.

[0017] Preferably, in S2, manually remove impurities such as stones and plastics in rice straw and edible mushroom residues before crushing. During the crushing process of the hammer crusher, a cyclone separator is used for dust removal.

[0018] Preferably, in S2, the atomized water droplet diameter of the spray humidification system is < 50 μm, and it is evenly sprayed three times. If the edible mushroom residue is dried in a drum dryer at 70°C.

[0019] Preferably, in S2, after the raw materials are pretreated, the raw materials are stored in breathable woven bags, with the weight of each bag ≤ 20 kg, and stored under the conditions of temperature ≤ 25°C and humidity < 60%, and a ventilation system is used for ventilation during storage.

[0020] Preferably, in S5, random sampling is carried out for each batch to test the leaching efficiency.

[0021] Preferably, in S5, if the humic acid-organic acid composite powder agglomerates, it needs to be reground to a particle size < 50 μm, and the leaching agent can be stored sealed at 4°C for 6 months.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This rapid cadmium leaching and removal remediation material for paddy fields utilizes the principle of step-by-step utilization of "easy-stable", adopts biological fermentation and chemical extraction technologies to extract humic acid, dissolved organic carbon, etc. from waste, develops a new type of biomass leaching agent with high efficiency and environmental protection and good application prospects, reveals its mechanism of efficient cadmium leaching and removal from soil, and through "treating pollution with waste, synergistic fertilizer effect, and intelligent regulation", heavy metals are removed while soil fertility is improved, realizing the synergy of efficient cadmium removal and soil fertility improvement, creating circular economic benefits while reducing the remediation cost, and having no chemical residues and low carbon emissions, providing a sustainable solution for the safe utilization of paddy fields. Description of the Drawings

[0024] Figure 1 It is a schematic flow chart of a preparation method of a rapid cadmium leaching and removal remediation material for paddy fields proposed by the present invention. Detailed Embodiments

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0026] Refer to Figure 1 , a preparation method of a rapid cadmium leaching and removal remediation material for paddy fields, including the following steps:

[0027] S1. Raw material screening: Select rice straw and edible mushroom residues as raw materials. The humic acid content of rice straw is 18 - 22%, the cellulose / lignin ratio is 4:1, the edible mushroom residues contain extracellular polysaccharides ≥ 15%, the humic acid content is 22 - 25%, and the cellulose / lignin ratio is 2:1. A low cellulose / lignin ratio is beneficial for fermentation and degradation;

[0028] S2. Raw material pretreatment: Add the raw materials into a hammer crusher and crush them to 0.5 - 2 mm, with a specific surface area ≥ 2.5 m 2 / g. The screen aperture of the hammer crusher is 1 mm. Before crushing, stones, plastics and other impurities in rice straw and edible mushroom residues are manually removed. During the crushing process of the hammer crusher, a cyclone separator is used for dust removal;

[0029] If fresh edible mushroom residues with too high moisture content are used, a drum dryer is used to dry them at 70 °C. The mushroom residue raw materials are centrifugally dehydrated to a moisture content of less than 60%. Then the mushroom residues are added to a high-pressure steam sterilizer and sterilized with steam at 120 - 122 °C for 20 min to ensure thorough sterilization and avoid interference of miscellaneous bacteria in subsequent fermentation. Take 5 g of the sample and inoculate it on LB medium, and culture it at 37 °C for 48 h. If there is no microbial growth, it is qualified. The rice straw raw materials are sprayed and humidified to a moisture content of 40 - 45% by a spraying and humidifying system. The atomized water droplets of the spraying and humidifying system have a diameter < 50 μm and are evenly sprayed three times until it can be formed into a ball by hand and scattered when dropped to the ground to promote microbial colonization. A double-screw conical mixer is used to mix the straw raw materials and mushroom residues at a ratio of straw raw materials:mushroom residues = 7:3;

[0030] After the raw materials are pretreated, the raw materials are stored in breathable woven bags made of polyethylene to achieve the effect of mildew prevention. The weight of a single bag ≤ 20 kg, and they are stored under the conditions of temperature ≤ 25 °C (to avoid mildew caused by high temperature) and humidity < 60% (to prevent moisture from caking), and a forced exhaust system is used for ventilation (to prevent heat generation from anaerobic fermentation). The moisture content and microbial activity are randomly checked every 7 days for each batch of storage, and the longest storage time is 30 days. After the expiration date, the humic acid content needs to be detected. If the loss > 5%, it will be discarded;

[0031] S3. Fermentation process: Inoculate white rot fungi for aerobic fermentation, and the inoculation amount is 5%. Ferment at a temperature of 53 - 57 °C and an aeration rate of 0.6 L / min·kg for 7 days, and turn the pile once every 24 h until the laccase activity in the target product lignin-degrading enzyme ≥ 50 U / g;

[0032] Inoculate acid-producing bacteria for anaerobic fermentation, and the inoculation amount is 3%. Ferment in a closed environment at a temperature of 34 - 36 °C and ORP < -200 mV for 14 days until the volatile fatty acids in the target product short-chain fatty acids ≥ 30 mg / g. After fermentation, the materials are dried at 60 °C to a moisture content < 10%; Measure the pH, volatile fatty acid concentration, and laccase activity every 24 h;

[0033] During the fermentation process, the temperature, ORP, and VFA concentration are monitored online. When the deviation from the set value > 5%, an automatic alarm will be triggered;

[0034] S4. Gradient chemical extraction: Alkaline extraction: The raw materials are shaken in 0.1 mol / L NaOH solution with a solid-liquid ratio of 1:10 at 60 °C and a rotation speed of 150 rpm for 2 h, centrifuged at 4000 rpm × 10 min, and the supernatant is taken to obtain macromolecular humic acid with a molecular weight > 5 kDa and a yield ≥ 25%;

[0035] Acid activation: The raw materials are left standing at room temperature for 1 h in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1:5, centrifuged, and the supernatant is taken to obtain small molecule organic acids (such as citric acid, oxalic acid), and the yield is ≥12%;

[0036] Separation and purification: The two extraction liquids are combined, filtered through a 0.45 μm filter membrane, and concentrated to a solid content of 15% through a ceramic membrane ultrafiltration system (molecular weight cut-off 3 kDa);

[0037] The concentrated extraction liquid is freeze-dried at -50 °C and 0.1 mbar to obtain a humic acid-organic acid composite powder;

[0038] S5. Blending of eluent: The eluent includes 25% humic acid-organic acid composite powder, 0.8% nano-SiO₂, 2% rhamnolipid, and 72.2% deionized water. Among them, the humic acid-organic acid composite powder provides chelating groups (-COOH, -OH), nano-SiO₂ enhances the colloidal stability, rhamnolipid reduces the surface tension, and deionized water serves as a solvent;

[0039] After the pretreatment of each batch of raw materials, the humic acid content is detected, and the allowable fluctuation is ±2%. If the humic acid-organic acid composite powder cakes, it needs to be re-ball milled to a particle size <50 μm. First, the humic acid composite powder and nano-SiO₂ dry powder are mixed and ball milled at 300 rpm for 30 min, then deionized water is added, and ultrasonic treatment is carried out at 40 kHz for 30 min to form a uniform colloid. Rhamnolipid is added and stirred at 500 rpm for 20 min until completely dissolved. Finally, it is adjusted to pH 7.0 ± 0.5 with 0.1 mol / L NaOH to avoid strong acidity from damaging the soil structure, and the eluent is obtained. The eluent can be stored sealed at 4 °C for 6 months, and the activity retention rate is >90%. Random samples are taken from each batch for elution efficiency testing;

[0040] The elution test process is as follows:

[0041] Weigh 5.00 g of soil into a centrifuge tube;

[0042] Add the eluent according to the set conditions;

[0043] Oscillate at 25 °C and 180 rpm → Centrifuge (4000 rpm × 10 min) → Filter the filtrate through a 0.45 μm membrane and determine the Cd concentration in the filtrate by AAS;

[0044] Calculate the removal rate: (C d : Cd concentration in the filtrate; V: Volume of the eluent; W: Mass of the soil; C t : Total Cd content in the soil).

[0045] When applied in the field, the dosage is 1.0 - 1.5 L of the eluent / kg of soil (calculated based on a 20-cm plough layer with a bulk density of 1.2 g / cm 3 ), and the application method is high-pressure rotary jetting (pressure 0.8 MPa, nozzle spacing 30 cm), with elution carried out 2 times at an interval of 24 h.

[0046] The following further illustrates the rapid elution and removal and repair material for heavy metal cadmium in this paddy field through specific test cases:

[0047] Case 1: Laboratory test, for the preparation and performance verification of the eluent

[0048] 1. Test purpose: To verify the removal efficiency of the eluent for cadmium-contaminated soil, and to optimize the eluent ratio and action conditions.

[0049] 2. Materials and methods:

[0050] The contaminated soil was collected from a certain paddy field in Pengzhou, Chengdu (pH 6.8, total Cd 2.3 mg / kg, DTPA-extractable Cd 0.85 mg / kg); raw materials for the eluent: rice straw (humic acid content 21%), edible mushroom residues.

[0051] Key equipment: Constant temperature shaking incubator (THZ-98A), Fourier transform infrared spectrometer (FTIR, Nicolet iS50).

[0052] 3. Test design:

[0053] A three-factor and three-level orthogonal test (L9(3 3 )) was adopted:

[0054] Factor Level 1 Level 2 Level 3 Eluent concentration (g / L) 5 10 15 Liquid-solid ratio (mL / g) 5:1 10:1 15:1 Oscillation time (h) 2 4 6

[0055] Operation steps:

[0056] Preparation of the eluent: The straw was crushed to 1 mm and fermented under aerobic conditions (55 °C × 7 d) + anaerobic conditions (35 °C × 14 d);

[0057] Extraction with 0.1 mol / L NaOH → Activation with 0.5 mol / L HCl → Ultrafiltration and concentration to a solid content of 15%;

[0058] Elution test: Weigh 5.00 g of soil into a centrifuge tube, add the eluent according to the set conditions, shake at 25 °C and 180 rpm → centrifuge (4000 rpm × 10 min) → filter the filtrate through a 0.45-μm membrane, and measure the Cd concentration in the filtrate by AAS to calculate the removal rate: Calculate the removal rate: (C d : Cd concentration in the filtrate; V: volume of the eluent; W: soil mass; C t : total Cd content in the soil).

[0059] 4. Result analysis:

[0060] Eluent concentration: 10 g / L, liquid-solid ratio: 0:1, oscillation time: 4 h, removal rate: 78.6%.

[0061] Characterization analysis

[0062] FTIR spectrum: The characteristic peaks of the eluent are significant at 3400 cm-1 (-OH), 1720 cm-1 (C=O), and 1600 cm-1 (aromatic C=C), confirming the presence of active functional groups.

[0063] SEM-EDS: The intensity of the Cd characteristic peak (L series line 3.13 keV) on the surface of soil particles after elution decreases by 60%.

[0064] Case 2: Pilot-scale-up and optimization of equipment operation parameters

[0065] 1. Test platform: Mobile elution workstation (processing capacity 500 kg / h), equipped with a spiral mixer, high-pressure rotary jet system (working pressure 0.5 - 1.2 MPa), and eluent recovery tank.

[0066] 2. Test design:

[0067] Optimized by Box-Behnken response surface method:

[0068] Variable Low level High level Leaching pressure (MPa) 0.6 1.0 Leaching times 1 3 Leaching interval (h) 12 36

[0069] 3. Key data:

[0070] Parameter optimization results:

[0071] Optimal conditions: Pressure 0.8 MPa, elution 2 times, interval 24 h, actual removal rate 72.3% (92% of the laboratory value)

[0072] Regeneration performance of eluent:

[0073] Number of cycles Cd interception rate Retention rate of eluent activity 1 96.2％ 100％ 3 89.7％ 85％ 5 82.1％ 73％

[0074] Energy consumption analysis:

[0075] Energy consumption per ton of soil treatment: 18.5 kW·h (42% lower than traditional chemical elution).

[0076] Case 3: Field verification

[0077] 1. Test overview

[0078] Location: Longxing Town, Chongzhou, Chengdu.

[0079] Area: 1.2 mu, divided into 4 treatment groups (control group: clear water; experimental group 1: 0.8 L / kg; experimental group 2: 1.2 L / kg; experimental group 3: 1.6 L / kg).

[0080] Rice variety: Chuanyou 6203 (low cadmium accumulation type).

[0081] 2. Monitoring indicators and methods

[0082] Index Detection method Frequency Available Cd in soil DTPA extraction - AAS method (GB / T 23739) 30 days before and after leaching Cd in rice grains Microwave digestion - ICP-MS (GB5009.268) Maturity stage Soil microbial biomass carbon <![CDATA[Chloroform fumigation-K2SO4 extraction method]]> Once a month

[0083] 3. Key results

[0084] (1) Cadmium removal effect:

[0085]

[0086]

[0087] (2) Soil improvement effect:

[0088] Organic matter content: increased from 2.1% to 3.0% (treatment of experimental group 2).

[0089] Microbial diversity index: increased from 5.2 to 6.7.

[0090] (3) Crop response

[0091] Rice yield: the yield of experimental group 2 increased by 8.7%.

[0092] Root activity: increased by 35%.

[0093] 4. Experimental quality control

[0094] (1) Data reliability:

[0095] Three parallel samples were set for all detection indicators, and the relative standard deviation (RSD) < 5%.

[0096] The detection system was calibrated using a reference material (GBW07408 soil standard sample).

[0097] (2) Environmental monitoring:

[0098] Leakage monitoring of leaching solution: Three monitoring wells were arranged downstream of the experimental area (Cd concentration < 0.005 mg / L).

[0099] Soil structure assessment: The stability of soil aggregates (MWD value) after leaching was maintained above 1.2 mm.

[0100] 5. Conclusion

[0101] This series of experiments confirmed that:

[0102] (1) The rice straw-based eluent can achieve a Cd removal rate of over 75% under the conditions of a liquid-solid ratio of 10:1 and a concentration of 10 g / L.

[0103] (2) The operating parameters of the pilot-scale equipment need to control the pressure at 0.8 MPa and conduct two elution times to ensure the engineering effect.

[0104] (3) In field application, a dosage of 1.2 L / kg can not only ensure food safety (grain Cd < 0.2 mg / kg) but also improve soil fertility.

[0105] As mentioned above, it is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a repair material for rapid elution removal of heavy metal cadmium in rice fields, characterized in that: The following steps are involved: S1. Raw material screening: rice straw and edible fungus residue are selected as raw materials, wherein the humic acid content of the rice straw is 18-22%, and the cellulose / lignin ratio is 4:1; the edible fungus residue contains ≥15% extracellular polysaccharide, 22-25% humic acid content, and the cellulose / lignin ratio is 2:1; S2, raw material pretreatment: add the raw material into a hammer crusher and crush it to 0.5-2mm, with a specific surface area of ​​≥2.5㎡ / g, centrifuge the mushroom residue raw material to dehydrate it to a moisture content of less than 60%, add the mushroom residue into a high-pressure steam sterilizer, steam sterilize it at 120-122℃ for 20min, use a spray humidification system to spray humidify the rice straw raw material to a moisture content of 40-45%, and use a double-screw conical mixer to mix the straw raw material: mushroom residue = 7:3; S3, fermentation process: the mixed raw materials are inoculated with white rot fungi for aerobic fermentation, the inoculation amount is 5%, the fermentation is carried out for 7 days at a temperature of 53-57°C and an aeration rate of 0.6 L / min·kg, and the compost is turned once every 24 hours until the laccase activity of the target product lignin degrading enzyme is ≥50 U / g; Inoculate acid-producing bacteria for anaerobic fermentation at an inoculation rate of 3% in a closed environment at a temperature of 34-36°C and an ORP of less than -200mV for 14 days until the volatile fatty acids in the target product short-chain fatty acids are ≥30mg / g, and the fermented material is dried at 60°C to a moisture content of less than 10%; S4, gradient chemical extraction: alkaline extraction: the raw material is placed in a 0.1 mol / L NaOH solution with a solid-liquid ratio of 1:10, shaken at 60°C for 2h, and the supernatant is collected by centrifugation to obtain macromolecular humic acid; Acidic activation: the raw material is placed in a 0.5 mol / L HCl solution with a solid-liquid ratio of 1:5, left to stand at room temperature for 1 hour, and the supernatant is collected by centrifugation to obtain a small molecule organic acid; Separation and purification: The two extracts were combined, filtered through a 0.45 μm filter membrane, and then concentrated to a solid content of 15% using a ceramic membrane ultrafiltration system; The concentrated extract was heated at -50°C. Freeze drying under 0.1 mbar conditions to obtain humic acid-organic acid composite powder; S5. Preparation of eluent: The eluent includes 25% humic acid-organic acid composite powder, 0.8% nano-SiO2, 2% rhamnose and 72.2% deionized water. The humic acid composite powder is first mixed with nano-SiO2 dry powder, ball-milled for 30 minutes, and then deionized water is added. The mixture is ultrasonically treated at 40kHz for 30 minutes to form a uniform colloid. Rhamnolipid is added and stirred until completely dissolved. Finally, the pH is adjusted to 7.0±0.5 with 0.1mol / L NaOH to obtain the eluent.

2. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S1, the mesh size of the hammer crusher is 1 mm.

3. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S3, pH, volatile fatty acid concentration and laccase activity were measured every 24 hours.

4. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S2, stones and plastic impurities in the rice straw and edible fungus residue are manually removed before crushing, and during the crushing process of the hammer crusher, a cyclone separator is used to remove dust.

5. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S2, the diameter of the atomized water droplets of the spray humidification system is less than 50 μm, and the spraying is evenly performed three times. If the edible fungus residue is dried at 70° C. using a drum dryer.

6. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S2, after the raw materials are pretreated, they are stored in breathable woven bags, with a single bag weight of ≤20kg, and stored at a temperature of ≤25°C and a humidity of <60%. During the storage process, an exhaust system is used for ventilation.

7. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S5, each batch is randomly sampled for elution efficiency test.

8. The method for preparing a repair material for rapid elution removal of heavy metal cadmium in paddy fields according to claim 1, characterized in that: In S5, if the humic acid-organic acid composite powder is agglomerated, it needs to be re-milled to a particle size of <50 μm. The eluent can be sealed and stored at 4° C. for 6 months.

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