Method for safely producing rice in cadmium-polluted soil

Abstract

The invention discloses a method for safely producing rice in cadmium-contaminated soil, which comprises the following steps: adding a soil conditioner into the cadmium-contaminated soil for treatment, and planting rice after treatment is completed, the soil conditioner at least comprises a humic acid loaded nano zero-valent iron material, and the humic acid loaded nano zero-valent iron material is provided with a humic acid-based carrier and a nano zero-valent iron material loaded on the humic acid-based carrier. According to the method for safely producing the rice in the cadmium-polluted soil, the effective cadmium content of the polluted farmland soil can be effectively reduced, the rice yield is increased, meanwhile, the cadmium content in rice grains is reduced, and an effective solution is provided for agricultural sustainable development.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal polluted farmland soil remediation, and in particular to a method for safely producing rice in cadmium polluted soil. Background Art

[0002] Rice is an important food crop in my country, and heavy metal pollution in farmland soil can seriously affect its yield and quality. Among them, cadmium, as one of the main heavy metal pollutants in farmland soil, is extremely active in migration and transformation in the farmland soil-plant system, which not only seriously affects the soil structure and function, but also can be enriched in food crops such as rice and wheat, and act on the human liver, kidneys and locomotor system through the food chain, posing a potential threat to human health. Therefore, improving the farmland soil environment and ensuring food safety production is not only one of the important directions for the development of environmental science, but also an important demand for improving the safety of the agricultural ecological environment.

[0003] In recent years, the development of nanotechnology has provided new opportunities for the rapid and green remediation of polluted farmland soil. Among them, nano zero-valent iron has shown good application potential in solving the problem of heavy metal pollution in soil due to its advantages such as large specific surface area, high surface activity and strong reduction activity. On the one hand, nano zero-valent iron can reduce the bioavailability of heavy metal pollutants such as chromium, lead and cadmium in the soil through passivation, weaken the migration of toxic substances into the food chain, and play a core role in the remediation of heavy metal contaminated soil. On the other hand, nano zero-valent iron can promote the formation of iron film on the root surface of rice and limit the migration of cadmium into the plant. It is worth noting that nano zero-valent iron, as a potential nano fertilizer, can promote rice tillering, starch and other nutrient synthesis, thereby increasing rice yield. Humic acid, as a natural organic polymer, contains a large number of active functional groups, has the characteristics of wide sources and low environmental risks, and has been successfully used in the modification process of various iron-based nanomaterials including nano zero-valent iron and ferrous sulfide. The dispersibility, stability and migration ability of humic acid-modified iron-based nanomaterials in porous media have been significantly improved, showing good application prospects in the remediation of heavy metal-contaminated farmland soil. However, due to the influence of van der Waals forces, high surface energy and magnetic effects, humic acid-modified iron-based nanomaterials added to the environment are prone to agglomeration or oxidation, which seriously limits their promotion and application in the actual soil pollution remediation. Therefore, developing a new method for safely producing rice in cadmium-contaminated soil is the key to achieving the safe utilization of cadmium-contaminated soil. Summary of the invention

[0004] The purpose of the present invention is to provide a method for safely producing rice in cadmium-contaminated soil, which can significantly reduce the effective cadmium content in the soil, effectively reduce the cadmium content in rice, increase rice yield, and achieve safe utilization of cadmium-contaminated soil.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: A method for safely producing rice in cadmium-contaminated soil comprises: adding a soil conditioner to the cadmium-contaminated soil for treatment, and planting rice after the treatment is completed; the soil conditioner comprises at least a humic acid-loaded nanometer zero-valent iron material, and the humic acid-loaded nanometer zero-valent iron material comprises a humic acid-based carrier and a nanometer zero-valent iron material loaded on the humic acid-based carrier.

[0006] Preferably, the humic acid-based carrier includes humic acid and / or humic acid derivatives, and the humic acid derivatives have sulfur-containing groups and phenol groups. Humic acid has the ability to complex and exchange with cations, and can form complexes with metal ions or undergo surface adsorption. Humic acid derivatives can not only improve the hydrophilicity of humic acid, enhance the complexation of humic acid with metal ions, and weaken the migration of heavy metals to the food chain by introducing sulfur-containing groups and phenol groups, but also effectively provide more active groups to improve the loading capacity of the humic acid-based carrier.

[0007] More preferably, the humic acid derivative is derived from humic acid, formaldehyde-sodium bisulfite adduct, and a phenol derivative, and the phenol derivative includes resorcinol and epichlorohydrin.

[0008] More preferably, in the preparation of the humic acid derivative, the humic acid is first reacted with the formaldehyde-sodium bisulfite adduct by heating in a water bath, and then reacted with resorcinol and epichlorohydrin to obtain the humic acid derivative.

[0009] More preferably, in the preparation of the humic acid derivative, the liquid-solid ratio of humic acid to sodium hydroxide solution is 1 g:5-10 mL, and the concentration of the sodium hydroxide solution is 0.2-1.0 mol / L.

[0010] More preferably, in the preparation of the humic acid derivative, the weight ratio of humic acid to formaldehyde-sodium bisulphite adduct is 1:1.5-2.0.

[0011] More preferably, in the preparation of the humic acid derivative, the weight ratio of humic acid to the phenol derivative is 1:0.2-1.

[0012] More preferably, in the preparation of the humic acid derivative, the weight ratio of resorcinol to epichlorohydrin is 1:0.2-1.

[0013] More preferably, in the preparation of the humic acid derivative, the water bath heating reaction temperature is 60-90° C. and the time is 30-90 min.

[0014] More preferably, the preparation method of the humic acid derivative is specifically, The humic acid is dissolved in a sodium hydroxide solution with a concentration of 0.2-1.0 mol / L, the liquid-solid ratio of the humic acid to the sodium hydroxide solution is 1 g: 5-10 mL, formaldehyde-sodium bisulphite adduct is added, the weight ratio of the humic acid to the formaldehyde-sodium bisulphite adduct is 1: 1.5-2.0, the mixture is evenly mixed and heated in a water bath at 60-90° C. for 30-90 min, the reaction solution is cooled to 25° C. after the reaction is completed, a phenol derivative is added, the weight ratio of the humic acid to the phenol derivative is 1: 0.2-1, the phenol derivative includes resorcinol and epichlorohydrin, the weight ratio of the resorcinol to the epichlorohydrin is 1: 0.2-1, the mixture is stirred at room temperature for 1-2 days, the reactant is centrifuged, the solid precipitate is retained and washed with anhydrous ethanol for 3-5 times, and vacuum dried to obtain a humic acid carrier.

[0015] Preferably, in the preparation of the humic acid-supported nano zero-valent iron material, the humic acid-based carrier and ferrous sulfate heptahydrate are mixed, and a sodium borohydride solution is added dropwise to react while nitrogen is introduced to obtain the humic acid-supported nano zero-valent iron material.

[0016] More preferably, in the preparation of the humic acid-loaded nano zero-valent iron material, the weight ratio of the humic acid-based carrier to ferrous sulfate heptahydrate is 1:1.0-1.5.

[0017] More preferably, in the preparation of the humic acid-loaded nano zero-valent iron material, the nitrogen is introduced for 20-60 minutes.

[0018] More preferably, in the preparation of the humic acid-loaded nano zero-valent iron material, the liquid-to-solid ratio of the humic acid-based carrier and the sodium borohydride solution is 1 g:50-150 mL, and the concentration of the sodium borohydride solution is 0.2-1.0 mol / L.

[0019] More preferably, the preparation method of humic acid-loaded nano zero-valent iron material is specifically as follows: The humic acid carrier and ferrous sulfate heptahydrate are mixed evenly, the weight ratio of the humic acid carrier and ferrous sulfate heptahydrate is 1:1.0-1.5, deionized water is added, the weight ratio of the humic acid carrier and ferrous sulfate heptahydrate mixture to deionized water is 1:100-150mL, the mixture is stirred for 9-15h, nitrogen is introduced for 20-60min, and then sodium borohydride solution is added dropwise under nitrogen atmosphere, the concentration of the sodium borohydride solution is 0.2-1.0mol / L, and the liquid-solid ratio of the humic acid carrier and the sodium borohydride solution is 1g:50-150mL. After continuing to stir for 30-90min, the reaction solution is centrifuged, the solid precipitate is retained and washed with anhydrous ethanol for 3-5 times, and vacuum dried to obtain the humic acid-loaded nano zero-valent iron material.

[0020] Preferably, the weight ratio of the soil conditioner to the cadmium-contaminated soil is 1:3-4kg.

[0021] Preferably, the duration of treatment is at least one week.

[0022] More preferably, the method for safely producing rice in cadmium-contaminated soil comprises: The soil conditioner is evenly dispersed in the cadmium-contaminated soil for treatment, and the weight ratio of the soil conditioner to the cadmium-contaminated soil is 1:3-4kg. Rice is planted after one week of treatment; the soil conditioner is prepared by mixing humic acid-loaded nano zero-valent iron material and sodium lactobionate, and the weight ratio of humic acid-loaded nano zero-valent iron material and sodium lactobionate is 1:0.2-1. The addition of sodium lactobionate in the preparation method can not only increase the content of soil organic matter and organic carbon, and enrich the nutrients in the soil; but also can improve the chelating ability of humic acid-loaded nano zero-valent iron material with metals, realize the rapid and efficient adsorption of heavy metal cadmium in the soil, and inhibit the absorption of heavy metals in the soil by rice roots, thereby effectively reducing the cadmium content of rice grains and increasing rice yield.

[0023] The invention also discloses a humic acid-loaded nanometer zero-valent iron material.

[0024] The invention also discloses the use of a humic acid-loaded nanometer zero-valent iron material in repairing cadmium-contaminated soil.

[0025] The present invention uses a soil conditioner to treat heavy metal contaminated soil, so it has the following beneficial effects: the soil conditioner of the present invention includes humic acid-loaded nano zero-valent iron material and sodium lactobionate, and the soil conditioner can not only reduce the bioavailability of heavy metal pollutants in the soil through passivation, weaken the migration of toxic substances to the food chain, and achieve safe utilization of heavy metal contaminated soil; but also promote rice tillering, starch and other nutrient synthesis to increase rice yield. Therefore, the present invention provides a method for safely producing rice in heavy metal contaminated soil with better performance. The present invention uses formaldehyde-sodium bisulfite adduct and phenol derivative to modify the humic acid carrier, so it has the following beneficial effects: the humic acid derivative prepared by the present invention has better hydrophilicity, contains more active groups and a larger specific surface area, which can not only improve the complexing ability of humic acid with heavy metals, but also enhance the adsorption effect of humic acid on heavy metals in the soil; but also give the humic acid carrier a stronger loading capacity. Therefore, the present invention provides a humic acid carrier with better adsorption effect and loading capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the infrared spectrum of the humic acid carrier obtained in Example 2. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0028] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0029] Embodiment 1: S1: A method for preparing humic acid-loaded nano zero-valent iron, comprising: 3 g of humic acid and 3 g of ferrous sulfate heptahydrate were added to 250 mL of deionized water. After nitrogen was introduced for 30 min, 300 mL of sodium borohydride solution was added dropwise under nitrogen atmosphere. The concentration of the sodium borohydride solution was 0.6 mol / L. After stirring for 1 h, the reaction solution was centrifuged and the solid precipitate was retained and washed with anhydrous ethanol for 4 times. It was then vacuum dried for 12 h to obtain humic acid-loaded nano zero-valent iron material.

[0030] S2: Treatment methods for cadmium-contaminated soil include: 3g of humic acid-loaded nano zero-valent iron material was evenly dispersed in 3.5kg of cadmium-contaminated soil, and rice crops were planted one week after treatment.

[0031] Embodiment 2: S1: A method for preparing a humic acid carrier, comprising: 3 g of humic acid was dissolved in 1.0 mol / L sodium hydroxide solution with a mass of 15 mL. 5 g of formaldehyde-sodium bisulfite adduct was added, mixed evenly, and heated in a water bath at 79 °C for 62 min. After the reaction, the reaction solution was cooled to 25 °C, 5 g of resorcinol and 5 g of epichlorohydrin were added, and stirred at room temperature for 2 d. The reactants were centrifuged, the solid precipitate was retained and washed 4 times with anhydrous ethanol, and vacuum dried to obtain a humic acid carrier.

[0032] S2: A method for preparing humic acid-loaded nano zero-valent iron, comprising: 3 g of humic acid carrier and 3 g of ferrous sulfate heptahydrate were added to 250 mL of deionized water. The humic acid carrier was prepared in step S1 of this embodiment. After nitrogen was introduced for 30 min, 300 mL of sodium borohydride solution was added dropwise under nitrogen atmosphere. The concentration of the sodium borohydride solution was 0.6 mol / L. After stirring for 1 h, the reaction solution was centrifuged, the solid precipitate was retained and washed with anhydrous ethanol for 4 times, and vacuum dried for 12 h to obtain humic acid-loaded nano zero-valent iron material.

[0033] S3: Treatment methods for cadmium-contaminated soil include: 3g of humic acid-loaded nano zero-valent iron material was evenly dispersed in 3.5kg of cadmium-contaminated soil, and rice crops were planted one week after treatment.

[0034] Embodiment 3: S1: The preparation method of humic acid carrier is the same as that of Example 2.

[0035] S2: A method for preparing humic acid-supported nano zero-valent iron, wherein the humic acid-supported nano zero-valent iron material is obtained under the same conditions as in Example 2 except that the amount of the humic acid carrier used is changed to 1 g.

[0036] S3: Method for treating cadmium-contaminated soil, same as in Example 2.

[0037] Embodiment 4: S1: A method for preparing a humic acid carrier, wherein a humic acid carrier is obtained under the same conditions as in Example 2, except that the amount of formaldehyde-sodium bisulfite adduct used is changed to 3 g.

[0038] S2: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 2.

[0039] S3: Method for treating cadmium-contaminated soil, same as in Example 2.

[0040] Embodiment 5: S1: A method for preparing a humic acid carrier, wherein a humic acid carrier is obtained under the same conditions as in Example 2, except that the amounts of epichlorohydrin and resorcinol used are changed to 3 g.

[0041] S2: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 2.

[0042] S3: Method for treating cadmium-contaminated soil, same as in Example 2.

[0043] Embodiment 6: S1: The preparation method of humic acid carrier is the same as that of Example 2.

[0044] S2: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 2.

[0045] S3: Treatment methods for cadmium-contaminated soil include: 3g of humic acid-loaded nano zero-valent iron material and 1.5g of sodium lactobionate were evenly dispersed in 3.5kg of cadmium-contaminated soil, and rice crops were planted one week after the treatment.

[0046] Embodiment 7: S1: The preparation method of humic acid carrier is the same as that of Example 2.

[0047] S2: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 2.

[0048] S3: A method for treating cadmium-contaminated soil, wherein a humic acid carrier is obtained under the same conditions as in Example 6 except that the amount of sodium lactobionate used is changed to 0.5 g.

[0049] Comparative Example 1: S1: A method for preparing a humic acid carrier, except that no formaldehyde-sodium bisulphite adduct is added, other conditions are the same as those in Example 2.

[0050] S2: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 2.

[0051] S3: Method for treating cadmium-contaminated soil, same as in Example 2.

[0052] Comparative Example 2: S1: A method for preparing a humic acid carrier, except that resorcinol and epichlorohydrin are not added, and other conditions are the same as those in Example 2.

[0053] S2: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 2.

[0054] S3: Method for treating cadmium-contaminated soil, same as in Example 2.

[0055] Comparative Example 3: S1: The preparation method of humic acid-loaded nano zero-valent iron is the same as that in Example 1.

[0056] S2: Method for treating cadmium-contaminated soil, same as Example 6.

[0057] Experimental Example 1: 1. Material Characterization The infrared spectra of the samples were measured by Fourier transform infrared spectrometer using KBr pellet method at wavenumbers of 500-4000 cm -1 The range is measured with a resolution of 0.06 cm -1 , scanned 32 times.

[0058] Figure 1 This is the infrared spectrum of the humic acid carrier obtained in Example 2, 3450cm -1 The absorption peaks of OH and NH appear near 2900cm -1 and 2830cm -1 The absorption peak of CH appears near 1690 cm -1 There is a C=O absorption peak near 1630cm -1 The absorption peak of C=C appears near 1390cm -1 The absorption peak of CO appears near 1190cm -1 、1068cm -1 and 680cm-1 The absorption peak of sulfonic group appears near 1030cm -1 A COC absorption peak appears nearby.

[0059] 2. Determination of cadmium content in rice grains The rice grains planted in Examples 1-7 and Comparative Examples 1-3 were harvested at 140 d. The method for determining the cadmium content in the grains was based on the national standard "National Food Safety Standard Determination of Cadmium in Food" (GB 5009.15-2023). The mature grains were freeze-dried, shelled, and ground. 0.5 g of the grains were weighed into a digestion tube, 5 mL of nitric acid solution and 2 mL of hydrogen peroxide solution were added, and digested using a microwave digester. After removing the acid and fixing the volume, the cadmium content was determined using inductively coupled plasma mass spectrometry. The determination results are shown in Table 1.

[0060] Table 1 Cadmium content in rice grains

[0061] It can be seen from Table 1 that: Compared with Example 1 of the present invention and Example 2, the cadmium content of the rice grains obtained in Example 2 is lower than that in Example 1, because in the preparation of the humic acid carrier, Example 2 uses formaldehyde-sodium bisulphite adduct and phenol derivatives, while Example 1 does not use them; compared with Comparative Examples 1-2, the cadmium content of the rice grains obtained in Example 2 is lower than that in Comparative Examples 1-2, because in the preparation of the humic acid carrier, Example 2 uses formaldehyde-sodium bisulphite adduct and phenol derivatives in combination, while Comparative Example 1 uses only formaldehyde-sodium bisulphite adduct, and Comparative Example 2 uses only phenol derivatives; compared with Examples 4-5 of the present invention, the cadmium content of the rice grains obtained in Example 2 is lower than that in Examples 4-5, because in the preparation of the humic acid carrier, the amount of formaldehyde-sodium bisulphite adduct and phenol derivative used is different. This indicates that the humic acid derivatives prepared by the present invention can effectively reduce the cadmium content in rice grains, and compared with the use of formaldehyde-sodium bisulphite adducts or phenol derivatives alone, the synergistic use of formaldehyde-sodium bisulphite adducts and phenol derivatives has the best enrichment effect in reducing the cadmium content in rice grains.

[0062] Compared with Example 2 of the present invention, Example 3 shows that the cadmium content of the rice grains obtained in Example 2 is lower than that in Example 3, because in the preparation of the humic acid-loaded nano zero-valent iron material, the amount of the humic acid carrier used in Example 2 and Example 3 is different. This shows that the use of the humic acid carrier and ferrous sulfate heptahydrate in a weight ratio of 1:1.0-1.5 has the best effect of reducing the cadmium content of rice grains.

[0063] Compared with Example 2, Example 6 of the present invention has a lower cadmium content in the rice grains than Example 2, because in the planting process, Example 6 adds sodium lactobionate and humic acid derivatives for synergistic use; compared with Comparative Example 3, Example 6 of the present invention has a lower cadmium content in the rice grains than Comparative Example 3, because in the planting process, Comparative Example 3 only uses sodium lactobionate and does not use humic acid derivatives; compared with Example 7 of the present invention, Example 6 has a lower cadmium content in the rice grains than Example 6, because in the planting, the amount of sodium lactobionate used in Example 6 and Example 7 is different. This shows that the humic acid-loaded nano zero-valent iron material prepared from humic acid derivatives synergistically acts with sodium lactobionate on cadmium-contaminated soil, which can further reduce the cadmium enrichment content of rice grains and achieve safe utilization of cadmium-contaminated soil.

[0064] 3. Determination of rice grain quality The rice planted in Examples 1-7 and Comparative Examples 1-3 were harvested at 140 days, and the rice grain weights were recorded. The measurement results are shown in Table 2.

[0065] Table 2 Rice grain quality

[0066] It can be seen from Table 2 that: Compared with Example 1 and Example 2 of the present invention, the rice grain quality of Example 2 is higher than that of Example 1, because in the preparation of the humic acid carrier, Example 2 uses formaldehyde-sodium bisulphite adduct and phenol derivatives, while Example 1 does not use them; compared with Comparative Examples 1-2, the rice grain quality of Example 2 is higher than that of Comparative Examples 1-2, because in the preparation of the humic acid carrier, Example 2 uses formaldehyde-sodium bisulphite adduct and phenol derivatives in combination, while Comparative Example 1 uses only formaldehyde-sodium bisulphite adduct, and Comparative Example 2 uses only phenol derivatives; compared with Examples 4-5 of the present invention, the rice grain quality of Example 2 is higher than that of Examples 4-5, because in the preparation of the humic acid carrier, the amount of formaldehyde-sodium bisulphite adduct and phenol derivative used is different. This shows that the humic acid derivatives prepared by the present invention can effectively improve the quality of rice grains, and compared with the use of formaldehyde-sodium bisulphite adducts or phenol derivatives alone, the synergistic use of formaldehyde-sodium bisulphite adducts and phenol derivatives has the best effect on improving the quality of rice grains.

[0067] Compared with Example 2 of the present invention, Example 3 shows that the rice grain quality of Example 2 is higher than that of Example 3 because the amount of humic acid carrier used in Example 2 and Example 3 is different in the preparation of humic acid-loaded nano zero-valent iron material. This shows that the use of humic acid carrier and ferrous sulfate heptahydrate in a weight ratio of 1:1.0-1.5 has the best effect of improving the quality of rice grains.

[0068] Compared with Example 2, Example 6 of the present invention has a higher quality of rice grains than Example 2 and Comparative Example 3, because in the planting process, Example 6 adds sodium lactobionate and humic acid derivatives for synergistic use; compared with Comparative Example 3, Example 6 of the present invention has a higher quality of rice grains than Comparative Example 3, because in the planting process, Comparative Example 3 only uses sodium lactobionate and does not use humic acid derivatives; compared with Example 7 of the present invention, Example 6 has a higher quality of rice grains than Example 6, because in the planting, the amount of sodium lactobionate used in Example 6 and Example 7 is different. This shows that the humic acid-loaded nano zero-valent iron material prepared from humic acid derivatives synergistically acts with sodium lactobionate on cadmium-contaminated soil, which can further improve the quality of rice grains and achieve safe utilization of cadmium-contaminated soil.

[0069] The conventional operations in the operating steps of the present invention are well known to those skilled in the art and will not be described in detail here.

[0070] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for safely producing rice in cadmium-contaminated soil, comprising: A soil conditioner is added to cadmium-contaminated soil for treatment, and rice is planted after the treatment is completed; the soil conditioner at least includes a humic acid-loaded nano zero-valent iron material, and the humic acid-loaded nano zero-valent iron material has a humic acid-based carrier and a nano zero-valent iron material loaded on the humic acid-based carrier.

2. A method for safely producing rice in cadmium-contaminated soil according to claim 1, characterized in that: The humic acid-based carrier includes humic acid and / or a humic acid derivative, wherein the humic acid derivative has a sulfur-containing group and a phenol group.

3. The method for safely producing rice in cadmium-contaminated soil according to claim 2, characterized in that: The humic acid derivative is obtained by deriving humic acid, formaldehyde-sodium bisulfite adduct and phenol derivative, and the phenol derivative includes resorcinol and epichlorohydrin.

4. The method for safely producing rice in cadmium-contaminated soil according to claim 2, characterized in that: In the preparation of the humic acid derivative, humic acid is firstly reacted with formaldehyde-sodium bisulfite adduct by heating in a water bath, and then reacted with resorcinol and epichlorohydrin to obtain the humic acid derivative.

5. The method for safely producing rice in cadmium-contaminated soil according to claim 1, characterized in that: In the preparation of the humic acid-loaded nano zero-valent iron material, a humic acid-based carrier and ferrous sulfate heptahydrate are mixed, and a sodium borohydride solution is added dropwise to react while nitrogen is introduced to obtain the humic acid-loaded nano zero-valent iron material.

6. A method for safely producing rice in cadmium-contaminated soil according to claim 5, characterized in that: The weight ratio of the humic acid-based carrier to ferrous sulfate heptahydrate is 1:1.0-1.

5.

7. The method for safely producing rice in cadmium-contaminated soil according to claim 1, characterized in that: The weight ratio of the soil conditioner to the cadmium-contaminated soil is 1g:3.0-4.0kg.

8. The method for safely producing rice in cadmium-contaminated soil according to claim 1, characterized in that: The treatment period is at least one week.

9. The humic acid-loaded nano zero-valent iron material as claimed in claim 5.

10. Use of the humic acid-loaded nano zero-valent iron material according to claim 9 in remediating cadmium-contaminated soil.

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