A method for inhibiting the absorption of fluoranthene by plants based on nano zero-valent iron dispersion technology

Abstract

The application discloses a method for controlling and inhibiting plant absorption of fluoranthene based on nano zero-valent iron dispersion technology. The method comprises the following steps: preparing an nZVI dispersion liquid by taking IGEPAL CA-720 as a dispersant, spraying the tomato planted in the fluoranthene contaminated soil through the leaf surface, spraying once every 3 days, spraying 5 times in total, and keeping the soil water content as 60% of the maximum field water holding capacity during the cultivation. By optimizing the dispersion effect of nZVI, the application significantly relieves the inhibition of fluoranthene on plant growth, and reduces the accumulation amount of fluoranthene in the plant body, and the bioconcentration factor (BCF) and the transfer factor (TF) are reduced by 38.9% and 46.1% respectively. The method is simple in operation, friendly to the environment, and can effectively control and inhibit the accumulation of fluoranthene in the plant body, thereby providing technical support for safe production of crops in contaminated soil.

Description

Technical Field

[0001] This invention belongs to the field of environmental remediation and agricultural safety technology, and relates to nano-zero valent iron dispersion and its application in alleviating plant growth inhibition and pollutant accumulation in fluoranthene-contaminated soil. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs), as a class of persistent organic pollutants with carcinogenic, mutagenic, and teratogenic effects, are easily absorbed into the food chain by plants in soil, posing a serious threat to agricultural product safety and human health. Fluoranthracene, a typical tetracyclic PAH, is highly hydrophobic and bioaccumulative, easily absorbed by crop roots and translocated to the aboveground parts in contaminated soil, making it one of the key pollutants requiring control in farmland ecosystems.

[0003] Nano-zero valent iron (nZVI) shows potential in controlling the uptake of organic pollutants by plants due to its large specific surface area and strong reducing properties. It can reduce the bioavailability of pollutants in soil through surface adsorption and redox reactions, or form a physical barrier on the plant surface to block the absorption pathway. However, the tendency of nZVI to aggregate leads to poor dispersibility and low efficiency. Undispersed nZVI tends to form large particles (often exceeding 500 nm in diameter), which not only reduces the contact area with pollutants but may also lose its inhibitory activity due to the sedimentation of aggregates, severely limiting its practical application.

[0004] To address the aggregation problem of nZVI, existing technologies often employ surfactant-assisted dispersion, but their effectiveness is significantly influenced by the type and concentration of the dispersant. For example, nonionic surfactants are considered the preferred type due to their high stability and minimal impact from environmental pH; however, different nonionic surfactants (such as Brij-35 and HPCD) can exhibit dispersion effects on nZVI that vary by more than 30%, and some dispersants may even promote the absorption of pollutants by plants through solubilization, posing a secondary risk.

[0005] Currently, key bottlenecks remain in nZVI dispersion technology for controlling crop uptake of fluorescein in contaminated soils: firstly, there is a lack of highly specific and efficient dispersants, making it difficult to ensure control efficacy while improving nZVI dispersibility; secondly, the dispersion process is not integrated with crop management methods such as foliar spraying, failing to specifically reduce the translocation of fluorescein to edible parts. Therefore, developing a technology that can efficiently disperse nZVI and precisely control plant uptake of fluorescein is of great significance for the safe production of crops in contaminated farmland. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned shortcomings of the prior art by providing a nano-zero-valent iron dispersion.

[0007] Another object of the present invention is to provide a method for preparing a nano-zero valent iron dispersion.

[0008] Another object of the present invention is to provide the application of the nano-zero valent iron dispersion.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A nano-zero valent iron dispersion is prepared by dispersing nano-zero valent iron in 0.5 g / L-1 g / L IGEPAL® CA-720 as a dispersant, resulting in a nano-zero valent iron concentration of 0.2-1 g / L.

[0011] As a preferred embodiment of the present invention, the concentration of IGEPAL® CA-720 is 0.5 g / L.

[0012] As a preferred embodiment of the present invention, the concentration of nano-zero valent iron is 0.5 g / L.

[0013] The preparation method of the nano-zero-valent iron dispersion of the present invention includes the following steps:

[0014] (1) Prepare IGEPAL® CA-720 solution using deoxygenated deionized water;

[0015] (2) Add nano-zero valent iron to the IGEPA® CA-720 solution in step (1), and after mechanical stirring and ultrasonic dispersion treatment, finally adjust the pH to 7.0±0.2 to obtain the nano-zero valent iron dispersion.

[0016] As a preferred embodiment of the present invention, the mechanical stirring and ultrasonic dispersion treatment is first performed by mechanical stirring at 500 rpm - 700 rpm for 10-30 min, followed by pulse treatment with a 200W-400W ultrasonic cell disruptor for 10-15 min, with a 30-second working time and a 10-second interval. The pH is then adjusted to 7.0 ± 0.2 with 0.1 mol / L HCl or NaOH, and stirring is continued for 10 min.

[0017] As a further preferred embodiment of the present invention, the mechanical stirring and ultrasonic dispersion treatment is carried out under nitrogen protection throughout the process. First, the mechanical stirring is performed at 600 rpm for 20 min, followed by pulse treatment with a 300W ultrasonic cell disruptor for 10 min. The process involves 30 s of operation followed by a 10 s interval, and the pH is adjusted to 7.0 ± 0.2 with 0.1 mol / L HCl or NaOH. Stirring is then continued for another 10 min.

[0018] The application of the aforementioned nano-zero-valent iron dispersion in alleviating plant growth inhibition and / or reducing pollutant accumulation in plants in soil contaminated with fluorescein.

[0019] The application of the aforementioned nano-zero-valent iron dispersion in the preparation of products that alleviate plant growth inhibition and / or reduce the accumulation of pollutants in plants in soil contaminated with fluorescein.

[0020] A method to alleviate plant growth inhibition and / or reduce pollutant accumulation in plants in fluoranthene-contaminated soil involves foliar spraying of crops grown in fluoranthene-contaminated soil every 3 days for a total of 5 times, while maintaining soil moisture content at 60% of field capacity during cultivation.

[0021] As a preferred embodiment of the present invention, the crop is tomato.

[0022] Beneficial effects:

[0023] The IGEPAAL® CA-720 dispersant screened in this invention can significantly improve the aggregation problem of nZVI and enhance its retention and action efficiency on plant surfaces.

[0024] Foliar spraying is a simple application method. Through multiple sprays, the physical barrier effect of nZVI and its ability to promote plant detoxification and metabolism can be used to alleviate the toxicity of fluorescein. It can effectively alleviate the inhibition of plant growth by fluorescein, while reducing the absorption and accumulation of fluorescein by plants and reducing food chain risks.

[0025] The dispersant and nZVI are environmentally friendly, produce no secondary pollution, and are suitable for in-situ remediation of fluorescein contamination in farmland. Attached Figure Description

[0026] Figure 1. nZVI particle size distribution of different dispersants

[0027] Figure 2. Particle size distribution of nZVI at different concentrations of IGEPAL® CA-720

[0028] Figure 3 Changes in plant height, root length, and aboveground and belowground biomass under different treatments. CK: Tomatoes grown in uncontaminated soil; T: Tomatoes grown in 100 mg / kg fluoranthene-contaminated soil; Tn1: Tomatoes grown in 100 mg / kg fluoranthene-contaminated soil and sprayed with 0.1 g / L nano-zero-valent iron; Tn2: Tomatoes grown in 100 mg / kg fluoranthene-contaminated soil and sprayed with 0.2 g / L nano-zero-valent iron; Tn3: Tomatoes grown in 100 mg / kg fluoranthene-contaminated soil and sprayed with 0.5 g / L nano-zero-valent iron; Tn4: Tomatoes grown in 100 mg / kg fluoranthene-contaminated soil and sprayed with 1 g / L nano-zero-valent iron. Detailed Implementation

[0029] The present invention will be further illustrated by the following examples. The nZVI powder (50-200nm) used was purchased from Beijing Fulangshi Company; Brij-35 (polyoxyethylene lauryl ether), HPCD (hydroxypropyl-β-cyclodextrin) and APG (alkyl glycoside) were purchased from Sinopharm Chemical Reagent Co., Ltd.; IGEPAL® CA-720 (polyoxyethylene alkylphenol ether) (purity ≥98%) was purchased from Sigma Chemical Reagent Co., Ltd.; and Fluoranthene (purity ≥98%) was purchased from Sigma Chemical Reagent Co., Ltd.

[0030] Example 1: Effect of different dispersants on the dispersion of nano-zero valent iron (nZVI)

[0031] Nano-zero valent iron (nZVI) powder with a particle size of 50-200 nm was selected, and four dispersants (Brij-35, HPCD, APG, and IGEPAL® CA-720) were used to prepare dispersions at a concentration of 0.5 g / L to obtain optimized nZVI dispersion. The physicochemical characteristics and stability data of the dispersants are shown in Tables 1 and 2.

[0032] To pretreat nZVI powder, 10 mg of nZVI was weighed and placed in a 250 mL four-necked flask. Four dispersants were used for treatment: 1) Brij-35 (0.5 g / L); 2) APG (0.5 g / L); 3) HPCD (0.5 g / L); 4) IGEPAL® CA-720 (0.5 g / L). 100 mL of deoxygenated deionized water (boiled for 15 min and then purged with nitrogen for 30 min) was added to each treatment to achieve a final nZVI concentration of 0.1 g / L.

[0033] The entire experimental procedure was conducted under nitrogen protection (flow rate 100 mL / min): First, the cells were mechanically stirred at 600 rpm for 20 min, then pulsed with a 300W ultrasonic cell disruptor for 10 min (30 s operation, 10 s interval). The pH was adjusted to 7.0 ± 0.2 with 0.1 mol / L HCl or NaOH, and stirring continued for another 10 min. The dispersion was transferred to 100 mL stoppered centrifuge tubes and incubated in the dark at 25°C. Samples were taken for analysis after 24 h.

[0034] As shown in Tables 1 and 2, the nZVI dispersion effect treated with IGEPA® CA-720 was the best: the smallest average particle size (150±8 nm), the lowest PDI (0.25±0.03), the largest absolute value of Zeta potential (-26.8±0.9 mV), and the highest total iron retention rate after 24 h (92.5±1.8%), which was significantly better than other dispersants (p<0.05). Figure 1 shows that its particle size distribution peak was the narrowest and shifted to the left, indicating the lowest degree of aggregation. This is consistent with the mechanism by which IGEPA® CA-720 inhibits nZVI aggregation through strong steric hindrance.

[0035] Table 1 Physicochemical properties of different dispersants

[0036]

[0037] Table 2. Total iron retention rate after 24 hours with different dispersants.

[0038]

[0039] Example 2: Effect of different concentrations of IGEPAL® CA-720 on the dispersion of nZVI

[0040] Based on IGEPAL® CA-720 as the optimal dispersant in Example 1, nano-zero valent iron (nZVI) powder with a particle size of 50-200 nm was selected, and IGEPA® CA-720 concentration gradients (0.1, 0.2, 0.3, 0.5, 0.8, 1 g / L) were set to explore its optimizing effect on nZVI dispersion. The physicochemical characteristics and stability data of different concentrations of IGEPA® CA-720 are shown in Tables 3 and 4.

[0041] Pretreatment of nZVI powder: Weigh 10 mg of nZVI into a 250 mL four-necked flask and prepare six dispersant concentrations: 1) 0.1 g / L IGEPAL® CA-720; 2) 0.2 g / L IGEPAL® CA-720; 3) 0.3 g / L IGEPAL® CA-720; 4) 0.5 g / L IGEPAL® CA-720; 5) 0.8 g / L IGEPAL® CA-720; 6) 1.0 g / L IGEPAL® CA-720. The remaining steps are the same as in Example 1.

[0042] In this embodiment, the optimal dispersion of nZVI was achieved using 0.5 g / L IGEPAL® CA-720. Tables 3 and 4 show that the dispersion effect exhibits an "optimization followed by a decrease" trend with increasing concentration: at 0.5 g / L, the average particle size of nZVI is the smallest (150 ± 15 nm), the PDI is the lowest (0.25 ± 0.01), the absolute value of the Zeta potential is the largest (-26.8 ± 0.9 mV), and the total iron retention rate after 24 h reaches 92 ± 2.5%. When the concentration increases to 0.8 g / L and 1 g / L, the particle size slightly increases (190 ± 16 nm, 220 ± 18 nm, respectively), and the retention rate decreases, indicating that excessive dispersant forms micelles leading to slight agglomeration. Figure 2 shows that the particle size distribution peak is narrowest at 0.5 g / L, further confirming that this concentration is optimal.

[0043] Table 3 Physicochemical properties of IGEPAL® CA-720 at different concentrations

[0044]

[0045] Table 4. Total iron retention rate after 24 hours at different concentrations of IGEPAL® CA-720

[0046]

[0047] Example 3: Effects of different concentrations of nZVI on tomato growth in fluoranthene-contaminated soil

[0048] Based on the determination of 0.5 g / L of IGEPA® CA-720 as the optimal dispersant and concentration in Examples 1 and 2, nZVI dispersions with nZVI concentrations of 0.1 g / L, 0.1 g / L, 0.2 g / L, 0.5 g / L, and 1 g / L were prepared according to the method in Example 1.

[0049] Preparation of contaminated soil: Fluoranthracene was dissolved in acetone and mixed into the soil at a concentration of 100 mg / kg, and aged for 30 days. Five treatment groups were set up. CK: Uncontaminated soil, foliar sprayed with deionized water; T: Fluoranthracene-contaminated soil (100 mg / kg), foliar sprayed with deionized water; Tn1: Contaminated soil + sprayed with 0.1 g / L nZVI; Tn2: Contaminated soil + sprayed with 0.2 g / L nZVI; Tn3: Contaminated soil + sprayed with 0.5 g / L nZVI; Tn4: Contaminated soil + sprayed with 1 g / L nZVI. Tomato seedlings were transplanted 30 days after transplanting, with three replicates per group. Spraying began on the 7th day after transplanting, once every 3 days for a total of 5 times, with 10 mL sprayed per plant each time. During the cultivation period, the soil moisture content was maintained at 60% of the field capacity. Plant samples were collected after 40 days of cultivation.

[0050] As shown in Figure 3, fluorescein pollution significantly inhibited tomato growth: compared with the control (CK), the plant height in group T decreased by 37.1%, root length decreased by 50.0%, and aboveground / underground biomass decreased by 50.4% and 60.5%, respectively (p<0.05). After spraying nZVI, the growth indicators showed a "first increase and then decrease" trend with concentration, among which the Tn3 treatment (0.5 g / L nZVI) had the best effect: plant height and root length increased by 36.4% and 66.7% respectively compared with group T, and aboveground / underground biomass increased by 61.3% and 100.0% respectively, close to the CK level, indicating that this concentration can effectively alleviate fluorescein toxicity.

[0051] Example 4: Effect of nZVI spraying on fluoranthene accumulation in tomatoes in fluoranthene-contaminated soil

[0052] Three treatment groups (CK, T, and Tn3 (0.5 g / L nZVI)) were selected. The methods for preparing contaminated soil and cultivating plants were the same as in Example 3. Table 5 shows that the Tn3 treatment significantly reduced fluorescein accumulation: the fluorescein content in the aboveground parts decreased by 63.5% compared to the T group, and by 49.5% in the underground parts; BCF and TF decreased by 38.9% and 46.1% respectively compared to the T group (p<0.05). This effect stems from two aspects: firstly, the dispersed nZVI forms a physical barrier on the leaf surface, blocking the absorption pathway of fluorescein through stomata; secondly, it promotes the oxidative metabolism of fluorescein within the plant, reducing its translocation to edible parts.

[0053] Table 5. Changes in fluorescein content, BCF, and TF in the aboveground and underground parts of plants under different treatments.

[0054]

[0055] Note: CK: Tomatoes grown in uncontaminated soil; T: Tomatoes grown in fluoranthene-contaminated soil (100 mg / kg); Tn3: Tomatoes grown in fluoranthene-contaminated soil (100 mg / kg) and sprayed with 0.5 g / L nano-zero valent iron.

Claims

1. The application of nano-zero-valent iron dispersion in alleviating tomato growth inhibition and / or reducing the accumulation of fluorescein pollutants in tomatoes in soil contaminated with fluorescein, characterized in that, The nano-zero valent iron dispersion is prepared by dispersing nano-zero valent iron in 0.5 g / L-1 g / L IGEPAL® CA-720 as a dispersant, resulting in a nano-zero valent iron concentration of 0.2-1 g / L.

2. The application according to claim 1, characterized in that, The concentration of IGEPAL® CA-720 is 0.5 g / L.

3. The application according to claim 1, characterized in that, The concentration of nano-zero valent iron is 0.5 g / L.

4. The application according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Prepare IGEPAL® CA-720 solution using deoxygenated deionized water; (2) Add nano-zero valent iron to the IGEPA® CA-720 solution in step (1), and after mechanical stirring and ultrasonic dispersion treatment, finally adjust the pH to 7.0±0.2 to obtain the nano-zero valent iron dispersion.

5. The application according to claim 4, characterized in that, The mechanical stirring and ultrasonic dispersion treatment is first performed by mechanical stirring at 500 rpm - 700 rpm for 10-30 min, followed by pulse treatment with a 200W-400W ultrasonic cell disruptor for 10-15 min, with a 30-second working time and a 10-second interval. The pH is then adjusted to 7.0 ± 0.2 with 0.1 mol / L HCl or NaOH, and stirring is continued for 10 min.

6. The application according to claim 5, characterized in that, The mechanical stirring and ultrasonic dispersion process is carried out under nitrogen protection. First, the mechanical stirring is carried out at 600 rpm for 20 min, then pulsed with a 300W ultrasonic cell disruptor for 10 min, working for 30 s, with a 10 s interval. The pH is adjusted to 7.0±0.2 with 0.1 mol / L HCl or NaOH, and stirring is continued for 10 min.

7. The application of nano-zero-valent iron dispersion in the preparation of products that alleviate tomato growth inhibition and / or reduce the accumulation of fluorescein pollutants in tomatoes from fluorescein-contaminated soil, characterized in that... The nano-zero valent iron dispersion is prepared by dispersing nano-zero valent iron in 0.5 g / L-1 g / L IGEPAL® CA-720 as a dispersant, resulting in a nano-zero valent iron concentration of 0.2-1 g / L.

8. The application according to claim 7, characterized in that, The concentration of IGEPAL® CA-720 is 0.5 g / L.

9. The application according to claim 7, characterized in that, The concentration of nano-zero valent iron is 0.5 g / L.

10. A method for controlling the absorption of fluorene by tomatoes based on nano-zero-valent iron dispersion technology, characterized in that, Tomatoes grown in fluorescein-contaminated soil were treated by foliar spraying with a nano-zero-valent iron dispersion. The spraying was done every 3 days for a total of 5 times. During the cultivation period, the soil moisture content was maintained at 60% of the field capacity. The nano-zero-valent iron dispersion was prepared by dispersing nano-zero-valent iron in 0.5 g / L-1 g / L IGEPAL® CA-720 as a dispersant.

11. The method according to claim 10, characterized in that, The concentration of IGEPAL® CA-720 is 0.5 g / L.

12. The method according to claim 10, characterized in that, The concentration of nano-zero valent iron is 0.5 g / L.

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