Composite reinforcing material for soil phytoremediation and preparation and use thereof

Abstract

The application belongs to the field of heavy metal soil remediation, and specifically discloses a plant heavy metal extraction composite reinforcing material, which comprises modified kaolin, iron-based MOF material and polysaccharide polymer in a weight ratio of 1-10:1-10:1-10; the modified kaolin is a material obtained by treating kaolin after calcination with a phosphoric acid source; the iron-based MOF material is an iron metal organic framework material obtained by coordination reaction of a Fe ion source and a ligand; and the polysaccharide polymer is at least one polysaccharide in starch and cellulose and a polysaccharide polymer obtained by carboxylation and / or amidation modification treatment of the polysaccharide. The application also comprises a method for plant reinforcement remediation by using the reinforcing material. The reinforcing material and plant remediation are combined, and synergy can be achieved, so that excellent soil remediation effect can be obtained.

Description

Technical fields:

[0001] This invention belongs to the field of phytoremediation of heavy metal contaminated soil, specifically relating to a composite material for enhancing phytoremediation and a method for synergistic remediation with plants. Background technology:

[0002] With the development and utilization of non-ferrous metal mines, large amounts of heavy metals enter farmland soil through dry and wet deposition, causing a series of environmental pollution problems. Due to the biotoxicity, persistence, and non-degradability of heavy metals, soil contaminated with heavy metals loses much of its utilization value and poses a serious threat to the ecological environment and human health.

[0003] Currently, phytoremediation technology is the most widely used in the remediation of heavy metal pollution. It is a remediation technology that utilizes hyperaccumulating plants to extract and absorb heavy metals from contaminated soil. This technology has the advantages of being green, environmentally friendly, and low-cost. However, it has some limitations, the most prominent being its long remediation cycle, the potential for heavy metal infiltration leading to incomplete remediation, and the risk of secondary pollution. It fails to meet the technical requirements of the current severe heavy metal pollution situation. Some researchers have proposed using multiple extractive plants in synergistic remediation techniques to improve remediation efficiency and shorten the cycle. While this has addressed the long remediation cycle to some extent, it has not fundamentally eliminated the key risks of heavy metal infiltration, incomplete remediation, and secondary pollution. Therefore, the current limitation of phytoremediation technology lies in how to fundamentally solve the key problem of secondary pollution caused by incomplete heavy metal remediation. Summary of the Invention

[0004] To address the problems of low phytoremediation rates, long remediation cycles, and incomplete remediation in existing phytoremediation methods for heavy metal contaminated soil, the primary objective of this invention is to provide a phytoremediation composite enhancement material for heavy metal extraction. This material aims to improve the accumulation of heavy metals, thereby enhancing the extraction capacity of plants, reducing the infiltration of heavy metals, and improving the remediation effect and efficiency.

[0005] The second objective of this invention is to provide a method for preparing the aforementioned plant heavy metal extraction composite reinforcement material and its application in combined plant-based soil remediation.

[0006] To address the issues of unsatisfactory heavy metal accumulation rates and efficiency in existing phytoremediation methods for heavy metal contaminated soils, this invention provides a phytoremediation composite enhancement material for heavy metal extraction, comprising modified kaolin, iron-based MOF material, and polysaccharide polymer in a weight ratio of 1-10:1-10:1-10.

[0007] The modified kaolin is a material obtained by calcining kaolin and then treating it with a phosphate source;

[0008] The iron-based MOF material is an iron metal-organic framework material obtained by coordination reaction of Fe ion source and ligand;

[0009] The polysaccharide polymer is at least one polysaccharide from starch or cellulose, or a polysaccharide polymer modified by carboxylation and / or amidation.

[0010] This invention has discovered that the combination of the aforementioned components and proportions can unexpectedly achieve synergy, which can facilitate the accumulation of heavy metals in heavy metal-contaminated soil, thereby improving the accumulation efficiency and effectiveness of phytoremediation and reducing heavy metal infiltration.

[0011] The modified kaolin, iron-based MOF material, and polysaccharide polymer described in this invention, along with the combined control of their proportions, are key to synergistically improving soil heavy metal enrichment and thereby enhancing the efficiency and effectiveness of phytoremediation.

[0012] In this invention, kaolin is used and modified under the aforementioned conditions, which can unexpectedly combine with other components and proportions to synergistically enhance the efficiency and effectiveness of phytoremediation.

[0013] In this invention, the preparation steps of the modified kaolin are as follows: kaolin is calcined, then the calcined material is soaked in an aqueous solution containing a phosphoric acid source, followed by solid-liquid separation and drying to obtain the modified kaolin.

[0014] Preferably, during the preparation stage of modified kaolin, the calcination atmosphere is at least one of nitrogen, argon, and air;

[0015] Preferably, the roasting temperature is 200–400°C;

[0016] Preferably, the roasting time is 1 to 3 hours;

[0017] Preferably, the phosphoric acid source is a compound that can ionize into phosphate ions in water, preferably at least one of phosphoric acid, water-soluble phosphate, water-soluble hydrogen phosphate, and water-soluble dihydrogen phosphate, and more preferably at least one of phosphoric acid, sodium phosphate, disodium hydrogen phosphate, and disodium hydrogen phosphate.

[0018] Preferably, the concentration of the solute in the aqueous solution of the phosphoric acid source is 5-20 wt%.

[0019] Preferably, the weight ratio of kaolin to phosphate source is 100:1 to 5;

[0020] Preferably, the soaking time is more than 1 hour, and more preferably 5 to 20 hours.

[0021] This study also found that using iron-based MOFs helps to synergistically enhance the efficiency and effectiveness of heavy metal enrichment in plants in conjunction with modified kaolin and polysaccharide polymers.

[0022] In this invention, the Fe ion source is a water-soluble compound that can provide ferrous ions and / or ferric ions, preferably at least one of iron sulfate, chloride, nitrate, and acetate.

[0023] Preferably, the ligand is at least one selected from pyromellitic acid, terephthalic acid, phthalic acid, and isophthalic acid;

[0024] The molar ratio of Fe ion source to ligand can be confirmed based on the theoretical coordination reaction mechanism.

[0025] Preferably, the solvent for the coordination reaction is water or a mixture of water and organic solvents;

[0026] Preferably, the organic solvent is a water-miscible solvent, and is preferably at least one of C1-C4 alcohols, acetone, and THF;

[0027] Preferably, the temperature of the coordination reaction is above 100°C, and more preferably 140–180°C;

[0028] Preferably, the coordination reaction takes 2 to 24 hours, and more preferably 10 to 16 hours.

[0029] For example, an exemplary iron-based MOF material of the present invention includes the following steps: a coordination reaction is carried out in an aqueous solution containing a divalent iron source, a trivalent iron source and trimesic acid in a molar ratio of 1:1:2 to 2.5 at a temperature of 140 to 180°C, followed by solid-liquid separation, washing and drying to obtain the iron-based MOF material.

[0030] In this invention, the polysaccharide polymer is a modified polysaccharide polymer that is bonded and modified with at least one of carboxymethyl starch and carboxymethyl cellulose and a polycarboxyl compound.

[0031] Preferably, the polysaccharide polymer is a modified product of carboxymethyl starch and ethylenediaminetetraacetic acid.

[0032] Preferably, the weight ratio of carboxymethyl starch to ethylenediaminetetraacetic acid is 1 to 20:1, more preferably 5 to 15:1;

[0033] Preferably, the temperature during the modification stage is, for example, 50–90°C;

[0034] Preferably, the modification time is 1 to 5 hours;

[0035] Preferably, the modification reaction is followed by acid washing.

[0036] In this invention, the combination of modified kaolin, iron-based MOF material and polysaccharide polymer components, along with the combined control of component ratios, is conducive to synergistically enhancing the efficiency and effectiveness of phytoremediation.

[0037] Preferably, the weight ratio of modified kaolin, iron-based MOF material, and polysaccharide polymer is 1–6:1–6:1–6; more preferably, it is 3–6:1–3:1–3; and most preferably, it is 5–6:2–3:1–2. Studies have found that further combining the above-mentioned proportions with the above-mentioned components can achieve even better plant enhancement effects.

[0038] This invention also provides a method for preparing the plant heavy metal extraction composite reinforcement material, which obtains modified kaolin, iron-based MOF material and polysaccharide polymer; then, the materials are compounded in the required proportions to obtain the final product.

[0039] The present invention also provides a phytoremediation method for heavy metal contaminated soil, wherein the phytoremediation method comprises applying the phytohemagglutination composite material to the heavy metal contaminated soil to be treated, followed by phytoremediation.

[0040] The present invention has found that, thanks to the use of the aforementioned reinforcing material, it can effectively accumulate heavy metals, which is beneficial to enhancing the plant's repair efficiency and effectiveness.

[0041] In this invention, the application rate of the plant-based heavy metal extraction composite reinforcement material can be adjusted according to the soil type and the heavy metal pollution content; for example, the application rate should not be less than 50 g / m³. 3 Considering processing costs, a further preferred value is 50–500 g / m³. 3 Further preferred is 100–300 g / m³ 3 A further preferred value is 150–250 g / m³. 3 The optimal value is 175–225 g / m³. 3 At the optimal dosage, it can further synergistically improve the phytoremediation and enhancement effects.

[0042] Preferably, the plant-based heavy metal extraction composite reinforcement material is sown onto the heavy metal contaminated soil to be treated, followed by tilling, and then phytoremediation is carried out.

[0043] In this invention, there are no special requirements for the type of soil contaminated with heavy metals. For example, it can be soil contaminated with at least one of the elements commonly found in the industry: cadmium, arsenic, lead, zinc, nickel, and copper.

[0044] The plant types used in the phytoremediation stage of this invention can be adjusted as needed. Preferably, at least one of Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus is used.

[0045] Further optimization involves intercropping two plants among Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus; the most preferred optimization involves intercropping four plants among Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus. This invention has found that, based on the aforementioned reinforcing material, combined with the selected plants and the intercropping method, a synergistic effect can be achieved, further enhancing the efficiency and effectiveness of phytoremediation.

[0046] In this invention, the phytoremediation method and cultivation method can be conventional.

[0047] In this invention, the repair cycle can be less than 4 months, for example, it can be 2 to 3.5 months.

[0048] Beneficial effects

[0049] This invention provides a novel plant-based heavy metal extraction composite enhancement material with controlled composition and proportions. It can efficiently and selectively adsorb heavy metal ions, increasing the concentration of heavy metals in the rhizosphere soil. This not only improves plant extraction efficiency but also fundamentally eliminates the source of heavy metal infiltration. Compared with traditional single-crop or intercropping phytoremediation techniques, this technology can stably improve plant extraction efficiency, shorten the remediation cycle, and reduce the concentration of infiltrated heavy metal ions.

[0050] Furthermore, when using the aforementioned remediation agent, combining it with phytoremediation methods, especially with the four intercropping remediation methods of Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus, can further synergistically improve the heavy metal remediation effect. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the intercropping process in Example 1; Detailed Implementation

[0052] The experimental field was located in a cadmium and arsenic-contaminated farmland area in a city in Hunan Province. The cadmium concentration in the upper soil layer (0-5cm) was 3.26 mg / kg and the arsenic concentration was 428.52 mg / kg, while the cadmium concentration in the lower soil layer (5-15cm) was 4.78 mg / kg and the arsenic concentration was 93.29 mg / kg.

[0053] The specific implementation method is as follows:

[0054] 1. Four potted plants, namely Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus, were cultivated in a greenhouse in a pollution-free area, with a growth cycle of 3 months.

[0055] 2. Component A: Modified kaolin. As a typical example, the modified kaolin used in the following cases is obtained using the following process:

[0056] Sufficient kaolin was crushed to -10 mesh using a jaw crusher, and then ground to -100 mesh using a ceramic ball mill. The fine kaolin was placed in a muffle furnace and calcined in air at 300±20℃ for 2 hours. After cooling to room temperature, it was soaked in a 10% sodium dihydrogen phosphate aqueous solution (the weight ratio of kaolin to phosphate source was 100:2~3) at room temperature for 12 hours, then filtered and dried to obtain modified kaolin, which was stored for later use.

[0057] 3. Component B: Iron-based MOF composite material. As a typical example, the modified kaolin used in the following cases was obtained using the following process:

[0058] FeSO4·7H2O, FeCl3·6H2O and trimesic acid (molar ratio 1:1:2) were mixed in ultrapure water (the iron concentration in the initial solution was 0.5M). The mixture was transferred to a hydrothermal reactor and reacted at 150℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, washed 3-5 times with deionized water, and then washed 3-5 times with anhydrous ethanol. The mixture was then dried in a drying oven at 50℃. The product was stored for later use.

[0059] 4. Component B: Starch-based gel resin: As a typical example, the modified kaolin used in the following cases was obtained using the following process:

[0060] Toluene was added to a mixture of carboxymethyl starch and ethylenediaminetetraacetic acid (weight ratio 10:1), and the mixture was stirred and heated for 2 hours (85°C). After all the toluene was evaporated, the mixture was heated for another 0.5 hours. After cooling to room temperature, the mixture was washed with 5% dilute hydrochloric acid, and then the water in the system was removed by extraction with ethanol. The product was then stored for later use.

[0061] 5. Using a vertical mixer, mix components A, B, and C thoroughly according to different formulation ratios (1-6:1-6:1-6) to obtain the reinforced material (also known as a composite material, where the components refer to the weight ratio).

[0062] 6. Press Figure 1 The intercropping layout (Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus) involved transplanting potted plants grown in the laboratory to the experimental farmland contaminated with heavy metals. The four plant species were planted in separate 0.5m wide beds with a planting density of 10 x 10cm. Each experimental group had a planting area of ​​2m x 2.5m = 5m². 2 The phytoremediation cycle is 3 months.

[0063] Use a rotary tiller to apply the reinforcing material to a depth of 15-2cm and mix it thoroughly with the soil. The application rate is 0-500g / m². 3 .

[0064] 7. After the restoration period ends, 16 sampling points are taken from each experimental field according to the “X” sampling method. The upper soil (0-5cm), lower soil (5-15cm), and plant samples are taken from each sampling point.

[0065] 8. Analyze the heavy metal content of the soil samples. The total heavy metal content in the soil was determined according to the standard "Determination of 12 Metallic Elements in Soil and Sediments - Aqua Regulator Extraction-Inductively Coupled Plasma Mass Spectrometry" (HJ 803-2016). Measure 8 ml of aqua regia into a 50 ml polytetrafluoroethylene crucible, add 3 small glass beads, cover, and heat on a hot plate until it just boils, allowing the aqua regia vapor to permeate the inner wall of the crucible for about 30 minutes. After cooling, discard the aqua regia solution, wash the inner wall of the crucible and the lid with deionized water, and let it dry. Weigh 0.1 g of soil sample that has passed through a 0.15 mm sieve and place it in the prepared crucible, add 6 ml of aqua regia solution, and cover. Heat the aqua regia on a hot plate and keep it at a gentle boil for 2 hours. After digestion, cool to room temperature, filter the extract and collect it in a 50 ml volumetric flask. Clean the inner wall and lid of the crucible three times with 1% nitric acid solution, filter the washings together and collect them in the volumetric flask, make up to volume, filter with a 0.22 μm microporous membrane, and determine the heavy metal concentration using ICP-MS.

[0066] 9. To analyze the heavy metal content of plant samples, weigh 0.04 g of plant sample into a polytetrafluoroethylene crucible, add 6 ml of hydrochloric acid and 2 ml of nitric acid, and heat at a moderate temperature on a hot plate in a fume hood, controlling the temperature of the hot plate at 150°C. When about 3 ml remains after evaporation, switch to low-temperature digestion, open the lid, and digest to remove silica. Shake the crucible frequently to remove white fumes and make the solution clear, with no residue remaining in the crucible. Remove the crucible and cool it. Transfer all contents to a 50 ml volumetric flask, and wash the inner wall of the crucible and the lid three times with 1% nitric acid solution. Filter the washing liquid together and collect it in the volumetric flask. Make up to volume, filter with a 0.22 μm microporous membrane, and determine the heavy metal concentration using ICP-MS. The extraction efficiency E of plants for heavy metals is calculated according to formula (1):

[0067]

[0068] m Plant It refers to the amount of heavy metals in plants, M Plant It is the biomass of plants.

[0069] Example 1

[0070] No composite materials were added. The planting layout consisted of four intercropping species. The experimental results were as follows:

[0071]

[0072]

[0073] The extraction efficiencies of Lantana for Cd and As were 3.09 μg / g and 216.51 μg / g, respectively; those of Cyperus rotundus for Cd and As were 7.55 μg / g and 179.01 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 4.29 μg / g and 167.22 μg / g, respectively; and those of Aster tataricus for Cd and As were 4.15 μg / g and 189.23 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.2738 mg / kg and 28.3340 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.8163 mg / kg and 85.1642 mg / kg, respectively.

[0074] Part 1: Screening of Composite Material Additive Amounts (Examples 2-7)

[0075] Example 2

[0076] The composite material consists of modified kaolin, iron-based MOF material, and starch-based gel resin in a weight ratio of 1:1:1, with a composite material content of 50 g / m³. 2 The planting layout involved intercropping four plant species, and the experimental results were as follows:

[0077]

[0078] The extraction efficiencies of Lantana for Cd and As were 5.59 μg / g and 377.29 μg / g, respectively; those of Cyperus rotundus for Cd and As were 9.83 μg / g and 253.40 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 7.10 μg / g and 237.67 μg / g, respectively; and those of Aster tataricus for Cd and As were 6.43 μg / g and 251.19 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1280 mg / kg and 13.7193 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1568 mg / kg and 16.3764 mg / kg, respectively.

[0079] Example 3

[0080] Compared to Example 2, the only difference is that the amount of composite material used is changed to 100 g / m³. 2 The planting layout involved intercropping four plant species, and the experimental results were as follows:

[0081]

[0082] The extraction efficiencies of Lantana for Cd and As were 5.91 μg / g and 405.72 μg / g, respectively; those of Cyperus rotundus for Cd and As were 10.58 μg / g and 288.13 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 7.97 μg / g and 287.66 μg / g, respectively; and those of Aster tataricus for Cd and As were 7.22 μg / g and 297.34 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1237 mg / kg and 13.2869 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1537 mg / kg and 15.8819 mg / kg, respectively.

[0083] Example 4

[0084] Compared to Example 2, the only difference is that the amount of composite material used is changed to 200 g / m³. 2 The planting layout involved intercropping four plant species, and the experimental results were as follows:

[0085]

[0086] The extraction efficiencies of Lantana for Cd and As were 6.15 μg / g and 426.33 μg / g, respectively; those of Cyperus rotundus for Cd and As were 11.10 μg / g and 310.09 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 8.65 μg / g and 325.46 μg / g, respectively; and those of Aster tataricus for Cd and As were 7.65 μg / g and 310.16 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1196 mg / kg and 12.9276 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1499 mg / kg and 15.4508 mg / kg, respectively.

[0087] Example 5

[0088] Compared to Example 2, the only difference is that the amount of composite material used is changed to 300 g / m³. 2 The planting layout involved intercropping four plant species, and the experimental results were as follows:

[0089]

[0090] The extraction efficiencies of Lantana camara for Cd and As were 6.09 μg / g and 396.47 μg / g, respectively; those of Cyperus rotundus were 10.72 μg / g and 334.37 μg / g, respectively; those of Phytolacca acinosa were 8.31 μg / g and 283.90 μg / g, respectively; and those of Aster tataricus were 7.38 μg / g and 279.09 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1220 mg / kg and 13.1984 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1522 mg / kg and 15.7932 mg / kg, respectively.

[0091] Example 6

[0092] Compared to Example 2, the only difference is that the amount of composite material used is changed to 400 g / m³. 2 The planting layout involved intercropping four plant species, and the experimental results were as follows:

[0093]

[0094]

[0095] The extraction efficiencies of Lantana for Cd and As were 5.86 μg / g and 361.08 μg / g, respectively; those of Cyperus rotundus for Cd and As were 10.64 μg / g and 320.66 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 8.17 μg / g and 257.45 μg / g, respectively; and those of Aster tataricus for Cd and As were 7.21 μg / g and 266.20 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1238 mg / kg and 13.3408 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1541 mg / kg and 15.9164 mg / kg, respectively.

[0096] Example 7

[0097] Compared to Example 2, the only difference is that the amount of composite material used is changed to 500 g / m³. 2 The planting layout involved intercropping four plant species, and the experimental results were as follows:

[0098]

[0099] The extraction efficiencies of Lantana camara for Cd and As were 5.61 μg / g and 349.63 μg / g, respectively; those of Cyperus rotundus were 10.47 μg / g and 306.14 μg / g, respectively; those of Phytolacca acinosa were 8.06 μg / g and 233.85 μg / g, respectively; and those of Aster tataricus were 7.10 μg / g and 244.32 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1257 mg / kg and 13.6021 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1559 mg / kg and 15.9936 mg / kg, respectively.

[0100] Part Two: Screening of Composite Material Composition Ratios (Examples 8-13)

[0101] Example 8

[0102] Compared to Example 4, the only difference was that the formulation ratio was changed to 10 parts modified kaolin, 30 parts iron-based MOF material, and 60 parts starch-based gel resin. The planting layout was four plant species intercropped. The experimental results obtained were as follows:

[0103]

[0104] The extraction efficiencies of Lantana for Cd and As were 5.73 μg / g and 387.52 μg / g, respectively; those of Cyperus rotundus for Cd and As were 10.16 μg / g and 275.83 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 8.19 μg / g and 306.05 μg / g, respectively; and those of Aster tataricus for Cd and As were 7.17 μg / g and 277.82 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1241 mg / kg and 12.9976 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1545 mg / kg and 15.5772 mg / kg, respectively.

[0105] Example 9

[0106] Compared to Example 4, the only difference was that the formulation ratio was changed to 10 parts modified kaolin, 60 parts iron-based MOF material, and 30 parts starch-based gel resin. The planting layout was four plant species intercropped. The experimental results obtained were as follows:

[0107]

[0108] The extraction efficiencies of Lantana camara for Cd and As were 5.42 μg / g and 377.10 μg / g, respectively; those of Cyperus rotundus for Cd and As were 9.21 μg / g and 261.44 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 7.81 μg / g and 291.44 μg / g, respectively; and those of Aster tataricus for Cd and As were 6.55 μg / g and 263.21 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1275 mg / kg and 13.0815 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1561 mg / kg and 15.5796 mg / kg, respectively.

[0109] Example 10

[0110] Compared to Example 4, the only difference was that the formulation ratio was changed to 30 parts modified kaolin, 10 parts iron-based MOF material, and 60 parts starch-based gel resin. The planting layout was four plant species intercropped. The experimental results obtained were as follows:

[0111]

[0112] The extraction efficiencies of Lantana for Cd and As were 6.26 μg / g and 441.97 μg / g, respectively; those of Cyperus rotundus for Cd and As were 11.44 μg / g and 331.30 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 9.19 μg / g and 339.77 μg / g, respectively; and those of Aster tataricus for Cd and As were 7.77 μg / g and 321.03 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1172 mg / kg and 12.8160 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1473 mg / kg and 15.4260 mg / kg, respectively.

[0113] Example 11

[0114] Compared to Example 4, the only difference was that the formulation ratio was changed to 30 parts modified kaolin, 60 parts iron-based MOF material, and 10 parts starch-based gel resin. The planting layout was four plant species intercropped. The experimental results obtained were as follows:

[0115]

[0116] The extraction efficiencies of Lantana for Cd and As were 5.87 μg / g and 403.69 μg / g, respectively; those of Cyperus rotundus were 10.72 μg / g and 298.06 μg / g, respectively; those of Phytolacca acinosa were 8.33 μg / g and 311.78 μg / g, respectively; and those of Aster tataricus were 7.32 μg / g and 296.65 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1224 mg / kg and 12.9543 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1530 mg / kg and 15.4941 mg / kg, respectively.

[0117] Example 12

[0118] Compared to Example 4, the only difference was that the formulation ratio was changed to 60 parts modified kaolin, 10 parts iron-based MOF material, and 30 parts starch-based gel resin. The planting layout was four plant species intercropped. The experimental results obtained were as follows:

[0119]

[0120] The extraction efficiencies of Lantana for Cd and As were 6.72 μg / g and 456.12 μg / g, respectively; those of Cyperus rotundus for Cd and As were 11.56 μg / g and 352.17 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 9.36 μg / g and 354.69 μg / g, respectively; and those of Aster tataricus for Cd and As were 8.03 μg / g and 330.74 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1156 mg / kg and 12.7021 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1459 mg / kg and 15.3721 mg / kg, respectively.

[0121] Example 13

[0122] Compared to Example 4, the only difference was that the formulation ratio was changed to 60 parts modified kaolin, 30 parts iron-based MOF material, and 10 parts starch-based gel resin. The planting layout was four plant species intercropped. The experimental results obtained were as follows:

[0123]

[0124] The extraction efficiencies of Lantana for Cd and As were 6.93 μg / g and 489.73 μg / g, respectively; those of Cyperus rotundus for Cd and As were 11.75 μg / g and 368.29 μg / g, respectively; those of Phytolacca acinosa for Cd and As were 9.60 μg / g and 361.47 μg / g, respectively; and those of Aster tataricus for Cd and As were 8.27 μg / g and 337.13 μg / g, respectively. The Cd and As heavy metal content in the upper soil layer was 0.1128 mg / kg and 12.6164 mg / kg, respectively, while the Cd and As heavy metal content in the lower soil layer was 0.1432 mg / kg and 15.1526 mg / kg, respectively.

[0125] Part Three: Screening of Phytoremediation Methods

[0126] Example 14

[0127] Compared with Example 13, the only difference is that the planting layout was changed to monoculture of Lantana camara, and the experimental results obtained are as follows:

[0128]

[0129] The extraction efficiencies of Lantana for Cd and As were 5.21 μg / g and 319.43 μg / g, respectively. The heavy metal contents of Cd and As in the upper soil layer were 0.2147 mg / kg and 20.3154 mg / kg, respectively, while those in the lower soil layer were 0.2659 mg / kg and 24.7318 mg / kg, respectively.

[0130] Example 15

[0131] Compared with Example 13, the only difference is that the planting layout was changed to monoculture of Cyperus rotundus, and the experimental results obtained are as follows:

[0132]

[0133] The extraction efficiencies of Cyperus rotundus for Cd and As were 8.96 μg / g and 219.78 μg / g, respectively. The Cd and As heavy metal contents in the upper soil layer were 0.1752 mg / kg and 21.6819 mg / kg, respectively, while those in the lower soil layer were 0.2471 mg / kg and 26.3025 mg / kg, respectively.

[0134] Example 16

[0135] Compared to Example 13, the only difference is that the planting layout was changed to a single vertical planting of Phytolacca acinosa, and the experimental results obtained are as follows:

[0136]

[0137]

[0138] The extraction efficiencies of vertically arranged Phytolacca acinosa for Cd and As were 6.03 μg / g and 203.79 μg / g, respectively. The heavy metal contents of Cd and As in the upper soil were 0.1873 mg / kg and 22.3747 mg / kg, respectively, while those in the lower soil were 0.2493 mg / kg and 27.8120 mg / kg, respectively.

[0139] Example 17

[0140] Compared with Example 13, the only difference is that the planting layout was changed to a single planting of *Aster tataricus*. The experimental results obtained are as follows:

[0141]

[0142] The extraction efficiencies of Aster tataricus for Cd and As were 5.35 μg / g and 216.70 μg / g, respectively. The heavy metal contents of Cd and As in the upper soil were 0.1925 mg / kg and 22.5460 mg / kg, respectively, while those in the lower soil were 0.2487 mg / kg and 26.4935 mg / kg, respectively.

[0143] Comparative Example 1

[0144] Compared to Example 13, the only difference is that a certain component is missing or replaced in the composite material, while the total amount of composite material remains unchanged. The experimental groups are as follows:

[0145] A: Modified kaolin is missing from the composite material;

[0146] B: In the composite material, the modified kaolin is replaced in an equal amount with the unmodified kaolin.

[0147] C: In the composite material, modified montmorillonite is used to replace modified kaolinite. That is, in the modification stage, montmorillonite is used to replace the kaolinite for subsequent modification treatment, and the modification conditions remain unchanged.

[0148] D: Iron-based MOF materials are lacking in composite materials;

[0149] E: The composite material lacks starch-based gel resin;

[0150] The experimental results obtained are as follows:

[0151]

[0152]

[0153] In Comparative Example 1, the AE group showed worse results than in Example 13, indicating that the absence or replacement of a certain component in the composite material would reduce the repair effect.

[0154] Based on the results of Examples 1-17, the order from best to worst is as follows: Example 4 > Example 5 > Example 6 > Example 3 > Example 7 > Example 2 > Example 1, Example 13 > Example 12 > Example 10 > Example 11 > Example 8 > Example 9, Example 15 > Example 14 > Example 16 > Example 17.

[0155] 1. In comparative examples 1-7, the amount of composite material used was 200-300 g / m³. 2 The best results are achieved at this time;

[0156] 2. Comparing Examples 4 and 8-13, when the modified kaolin, iron-based MOF material, and starch-based gel resin in the reinforcing material are 30-60 parts, a good synergistic effect can be obtained. In particular, the effect is best when the formula ratio is 60 parts modified kaolin, 30 parts iron-based MOF material, and 10 parts starch-based gel resin.

[0157] 3. A comparison of Examples 1 and Examples 14-17 shows that the use of reinforcing materials can enhance the repair effect of the corresponding plants on heavy metals. Further comparison of Examples 13 and Examples 14-17 shows that the effect of using four kinds of extraction plants is significantly improved, and the repair effect is better than that of four single plants.

[0158] 4. The formula ratio is 60 parts modified kaolin, 30 parts iron-based MOF material, and 10 parts starch-based gel resin. The composite material dosage is 200 g / m³. 2 This is the preferred remediation technology solution of the present invention. The optimal ratio and dosage of composite materials, as well as the synergistic effect of intercropping technology, are key to improving the effect of phytoremediation.

Claims

1. A plant-based heavy metal extraction composite reinforcement material, characterized in that, Including modified kaolin, iron-based MOF materials and polysaccharide polymers in a weight ratio of 1~10:1~10:1~10; The modified kaolin is a material obtained by calcining kaolin and then treating it with a phosphate source; The steps are as follows: kaolin is calcined, then the calcined material is soaked in an aqueous solution containing a phosphoric acid source, followed by solid-liquid separation and drying to obtain the modified kaolin; wherein, the calcination temperature is 200~400℃; the phosphoric acid source is at least one of phosphoric acid, water-soluble phosphate, water-soluble hydrogen phosphate, and water-soluble dihydrogen phosphate. The iron-based MOF material is an iron metal-organic framework material obtained by coordination reaction of Fe ion source and ligand; wherein, the Fe ion source is a water-soluble compound that can provide ferrous ions and / or ferric ions, and the ligand is at least one of trimesic acid, terephthalic acid, phthalic acid, and isophthalic acid. The polysaccharide polymer is a modified product of carboxymethyl starch and ethylenediaminetetraacetic acid.

2. The plant-based heavy metal extraction composite reinforcement material as described in claim 1, characterized in that, During the preparation stage of modified kaolin, the calcination atmosphere is at least one of nitrogen, argon, and air; The roasting time is 1 to 3 hours.

3. The plant-based heavy metal extraction composite reinforcement material as described in claim 1, characterized in that, The phosphoric acid source is at least one of phosphoric acid, sodium phosphate, disodium hydrogen phosphate, and disodium hydrogen phosphate. The concentration of the solute in the aqueous solution of the phosphoric acid source is 5-20 wt%. The weight ratio of kaolin to phosphate source is 100:1~5; Soaking time should be more than 1 hour.

4. The plant-based heavy metal extraction composite reinforcement material as described in claim 3, characterized in that, Soaking time is 5-20 hours.

5. The plant-based heavy metal extraction composite reinforcement material as described in claim 1, characterized in that, The Fe ion source is at least one of iron sulfate, chloride, nitrate, and acetate. The solvent for the coordination reaction is water or a mixture of water and organic solvents; The organic solvent is a solvent that is miscible with water; The coordination reaction is carried out at a temperature above 100°C; The coordination reaction takes 2 to 24 hours.

6. The plant-based heavy metal extraction composite reinforcement material as described in claim 5, characterized in that, The organic solvent is at least one of C1-C4 alcohols, acetone, and THF; The coordination reaction is carried out at a temperature of 140~180℃; The coordination reaction takes 10 to 16 hours.

7. The plant-based heavy metal extraction composite reinforcement material as described in claim 1, characterized in that, An aqueous solution containing a divalent iron source, a trivalent iron source, and trimesic acid in a molar ratio of 1:1:2~2.5 was subjected to a coordination reaction at a temperature of 140~180℃, followed by solid-liquid separation, washing, and drying to obtain the iron-based MOF material.

8. The plant-based heavy metal extraction composite reinforcement material as described in claim 1, characterized in that, The weight ratio of carboxymethyl starch to ethylenediaminetetraacetic acid is 1~20:

1.

9. The plant-based heavy metal extraction composite reinforcement material as described in claim 8, characterized in that, The weight ratio of carboxymethyl starch to ethylenediaminetetraacetic acid is 5~15:

1.

10. The plant-based heavy metal extraction composite reinforcement material as described in claim 1, characterized in that, The temperature during the modification stage is 50~90℃; The modification time is 1-5 hours; After modification, it is subjected to acid washing.

11. The plant-based heavy metal extraction composite reinforcement material according to any one of claims 1 to 10, characterized in that, The weight ratio of modified kaolin, iron-based MOF material and polysaccharide polymer is 1~6:1~6:1~6.

12. The plant heavy metal extraction composite reinforcement material as claimed in claim 11, characterized in that, The weight ratio of modified kaolin, iron-based MOF material and polysaccharide polymer is 3~6:1~3:1~3.

13. The plant heavy metal extraction composite reinforcement material as described in claim 12, characterized in that, The weight ratio of modified kaolin, iron-based MOF material and polysaccharide polymer is 5~6:2~3:1~2.

14. A method for preparing a plant-based heavy metal extraction composite reinforcement material according to any one of claims 1 to 13, characterized in that, Modified kaolin, iron-based MOF materials, and polysaccharide polymers are obtained; then they are compounded in the required proportions to obtain the final product.

15. A phytoremediation method for heavy metal contaminated soil, characterized in that, The plant-based heavy metal extraction composite reinforcement material according to any one of claims 1 to 13 is applied to the heavy metal contaminated soil to be treated, followed by phytoremediation.

16. The phytoremediation method for heavy metal contaminated soil as described in claim 15, characterized in that, The application rate of the plant heavy metal extraction composite reinforcement material shall not be less than 50 g / m³. 3 .

17. The phytoremediation method for heavy metal contaminated soil as described in claim 16, characterized in that, The application rate of the plant heavy metal extraction composite reinforcement material is 50~500g / m³. 3 .

18. The phytoremediation method for heavy metal contaminated soil as described in claim 17, characterized in that, The application rate of the plant heavy metal extraction composite reinforcement material is 100~300 g / m³. 3 .

19. The phytoremediation method for heavy metal contaminated soil as described in claim 18, characterized in that, The application rate of the plant heavy metal extraction composite reinforcement material is 150~250g / m³. 3 .

20. The phytoremediation method for heavy metal contaminated soil as described in claim 19, characterized in that, The application rate of the plant-based heavy metal extraction composite reinforcement material is 175~225 g / m³. 3 .

21. The phytoremediation method for heavy metal contaminated soil as described in claim 15, characterized in that, The aforementioned plant-based heavy metal extraction composite reinforcement material was spread on the heavy metal-contaminated soil to be treated, followed by tilling and then phytoremediation.

22. The phytoremediation method for heavy metal contaminated soil as described in any one of claims 15-21, characterized in that, The heavy metal contaminated soil mentioned above is soil contaminated with at least one of the elements selected from cadmium, arsenic, lead, zinc, nickel, and copper.

23. The phytoremediation method for heavy metal contaminated soil as described in any one of claims 15-21, characterized in that, The plant types used in the phytoremediation phase are at least one of Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus.

24. The phytoremediation method for heavy metal contaminated soil as described in claim 23, characterized in that, The phytoremediation method involves intercropping two of the following plants: Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus.

25. The phytoremediation method for heavy metal contaminated soil as described in claim 24, characterized in that, The phytoremediation methods include four intercropping methods: Lantana camara, Cyperus rotundus, Phytolacca acinosa, and Aster tataricus.

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