Preparation and application of an environmentally friendly metal chelator modified by ethylenediamine and lignin

Abstract

The application discloses a kind of environment-friendly ethylenediamine modified lignin metal chelator and its application.The application is prepared with natural renewable, biodegradable lignin as base material, and is grafted with ethylenediamine by mannich reaction to obtain environment-friendly ethylenediamine modified lignin;Then ethylenediamine modified lignin is chelated with metal ions to obtain ethylenediamine modified lignin metal chelator.The ethylenediamine modified lignin metal chelator can promote rice root cell proliferation, promote rice growth, and its effect of increasing rice root length, root weight, seedling length and seedling weight is better than that of ethylenediamine modified lignin, and has good application prospect in agricultural field.

Description

Technical Field

[0001] This invention relates to the field of agricultural functional materials technology, specifically to the preparation and application of an environmentally friendly ethylenediamine-modified lignin-based metal chelating agent. Background Technology

[0002] Lignin is the most abundant naturally occurring aromatic polymer in nature, with wide availability and biodegradability. Currently, over 95% of industrial lignin comes from black liquor in papermaking, with a global annual production exceeding 30 million tons. However, in existing technologies, the vast majority of black liquor lignin is directly burned to recover chemicals and energy, with less than 5% used to produce low-value-added products (such as dispersants or binders). This method of utilization not only wastes valuable aromatic resources, but its incomplete combustion may also cause environmental problems.

[0003] Lignin is a complex three-dimensional amorphous polymer composed of three phenylpropane units randomly linked by ether bonds and carbon-carbon bonds. Its structure contains various functional groups such as phenolic hydroxyl groups, alcoholic hydroxyl groups, methoxy groups, and carboxyl groups, endowing it with biological activities such as ultraviolet absorption, antioxidant activity, and antibacterial activity. Advances in modern analytical techniques and materials science have provided new opportunities for in-depth analysis of the structure-activity relationship of lignin and for expanding its application potential. Through appropriate pretreatment and fractional separation, the high-value utilization of each component can be achieved.

[0004] In agriculture, the long-term excessive application of traditional chemical fertilizers has caused numerous problems. With an average fertilizer utilization rate of less than 40%, a large amount of nutrients (especially nitrogen) are lost through volatilization, runoff, or leaching, resulting not only in resource waste but also in soil acidification, compaction, and damage to soil aggregate structure. This leads to the gradual depletion of micronutrients in the soil, ultimately affecting crop quality and posing a risk of agricultural non-point source pollution. Lignin, as a natural biomass resource, possesses non-toxic and biodegradable characteristics. Its macromolecular structure endows it with a certain slow-release potential, theoretically improving fertilizer utilization through slow decomposition. However, unmodified lignin has poor water solubility and mainly contains carbon, hydrogen, oxygen, and nitrogen, with extremely low levels of other nutrients, making direct application insufficient to meet crop growth needs. Therefore, chemical or biological modification is used to introduce active groups, improving its water solubility and complexing ability, thereby increasing its nutrient content (e.g., nitrogen). Furthermore, in agricultural production, trace elements such as iron, zinc, and copper are key nutrients for regulating plant growth and ensuring crop physiological metabolism. By chelating these trace elements with modified lignin, a slow-release effect is achieved, which can alleviate the effects of soil fixation and low plant absorption and utilization caused by traditional inorganic metal salt fertilizers, without causing soil and water pollution. This strategy not only provides a feasible path for the resource utilization of lignin-based waste, but also provides new material support for the transformation of my country's agriculture towards green and efficient directions.

[0005] Therefore, combining the structural characteristics of lignin with the modern agricultural demand for green fertilizers, developing novel lignin-modified materials as crop growth promoters holds significant application potential. These materials can alleviate the deficiency of micronutrients in the soil, promote plant absorption of nitrogen and other organic matter, and solve the problem of lignin-based waste disposal, achieving resource recycling and supporting the green and efficient development of agriculture in my country. Summary of the Invention

[0006] The purpose of this invention is to provide an environmentally friendly ethylenediamine-modified lignin-based metal chelating agent and its preparation method, as well as the use of the ethylenediamine-modified lignin-based metal chelating agent in promoting root cell proliferation and / or promoting plant growth.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] On one hand, the present invention provides a method for preparing an ethylenediamine-modified lignin-based metal chelating agent, comprising the following steps:

[0009] (1) Disperse sulfate lignin in 1,4-dioxane, add sodium hydroxide solution to dissolve it completely; then add ethylenediamine and formaldehyde in sequence, and stir the reaction in a constant temperature oil bath; after the reaction is completed, dialysis the reaction solution to purify it, freeze dry it to obtain aminated lignin;

[0010] (2) Disperse the aminated lignin obtained in step (1) in ultrapure water, add metal ion salt and mix well, stir at room temperature to carry out coordination reaction, dialysis the reaction solution for purification, freeze dry to obtain ethylenediamine modified lignin-based metal chelating agent.

[0011] Preferably, in step (1), the mass ratio of sulfate lignin, ethylenediamine, and formaldehyde is 1:(1~10):(1~10).

[0012] Preferably, in step (1), the temperature of the constant temperature oil bath is 60~100℃; the stirring rate of the stirring reaction is 200~500 rpm, and the reaction time is 4~12 h.

[0013] Preferably, in step (2), the mass ratio of the aminated lignin to the metal ion salt is 1:(20~30).

[0014] Preferably, in step (2), the coordination reaction takes 24 to 48 hours.

[0015] Preferably, in step (2), the metal ion salt is selected from at least one of FeCl3, CuCl2, MgCl2, ZnCl2, and CaCl2.

[0016] On the other hand, the present invention also provides an ethylenediamine-modified lignin-based metal chelating agent prepared according to the above preparation method.

[0017] On the other hand, the present invention also provides the use of the above-mentioned ethylenediamine modified lignin-based metal chelating agent in promoting plant root cell proliferation and / or promoting plant growth.

[0018] Preferably, the promotion of plant growth manifests as at least one of promoting root development and increasing plant biomass.

[0019] Preferably, promoting root development includes increasing root length and root weight.

[0020] Preferably, the promotion of increased plant biomass includes increasing seedling length and seedling weight.

[0021] Preferably, the plant is rice.

[0022] The present invention has the following beneficial effects:

[0023] The ethylenediamine-modified lignin-based metal chelating agent (L-EDA10 / Fe) prepared in this invention can promote the proliferation of rice root cells and promote rice growth. Its effects on increasing rice root length, root weight, seedling length, and seedling weight are superior to those of ethylenediamine-modified lignin (L-EDA10), showing promising application prospects in the agricultural field. This invention not only effectively alleviates the environmental burden caused by lignin accumulation and reduces pollution from incineration, but also reduces the dependence of agricultural inputs on non-renewable petrochemical resources, providing a new technical path for developing low-cost, environmentally friendly green agricultural materials. Attached Figure Description

[0024] Figure 1 Infrared spectrum of ethylenediamine-modified lignin.

[0025] Figure 2 X-ray photoelectron spectroscopy of ethylenediamine-modified lignin.

[0026] Figure 3 The effects of ethylenediamine-modified lignin and iron-chelated ethylenediamine-modified lignin on rice growth.

[0027] Figure 4 Effects of ethylenediamine-modified lignin and iron-chelated ethylenediamine-modified lignin on the proliferation of rice root cells. Detailed Implementation

[0028] The following examples are further illustrations of the present invention, but not limitations thereof. Specific experimental conditions and methods are not specified in the following examples, and the techniques used are generally conventional methods well known to those skilled in the art.

[0029] Example 1: Preparation of ethylenediamine-modified lignin

[0030] 1 g of sulfate lignin was dissolved in 10 mL of 1,4-dioxane, and then 0.5 mL of NaOH (1 mol / L) was added to completely dissolve the lignin. Then, ethylenediamine and formaldehyde solutions were slowly added sequentially and mixed thoroughly. The ratio of lignin to ethylenediamine to formaldehyde was 1:10:10. The mixture was transferred to a round-bottom flask and reacted in a sealed oil bath at 80℃ for 6 h with stirring at 300 rpm. After the reaction, the resulting solution was transferred to a dialysis bag (3500 Da) and dialyzed for 72 h, changing the water frequently to remove impurities. Finally, the dialysate was lyophilized to obtain ethylenediamine-modified lignin (L-EDA10). Fourier transform infrared spectroscopy was performed on the obtained L-EDA10. Figure 1 ) and X-ray photoelectron spectroscopy (XPS) analysis Figure 2 The results showed that ethylenediamine was successfully grafted onto sulfate lignin.

[0031] Example 2: Effects of ethylenediamine-modified lignin and iron-chelated ethylenediamine-modified lignin on promoting rice growth.

[0032] 0.3 g of the ethylenediamine-modified lignin (L-EDA10) prepared in Example 1 was weighed and dispersed in 30 mL of ultrapure water. Then, 6 g of anhydrous ferric chloride was added. After stirring at room temperature for 24 h, the resulting reaction solution was transferred to a 3500 Da dialysis bag for dialysis for 72 h. The water was changed frequently to remove free impurities. After freeze-drying, iron-chelated ethylenediamine-modified lignin (L-EDA10 / Fe) was obtained.

[0033] Rice seeds were soaked in tap water for 24 hours and cultured under constant temperature and light until new shoots appeared. Seeds with similar germination patterns were selected for later use. Next, hydroponic nutrient solutions of different concentrations were prepared. 0.1 g of ethylenediamine-modified lignin (L-EDA10) and iron-chelated ethylenediamine-modified lignin (L-EDA10 / Fe) were dissolved in 1 L of tap water to obtain nutrient solutions with a mass concentration of 0.01%. Tap water was used as the control group. The nutrient solutions were then added to hydroponic containers, and the selected germinated seeds were inoculated into the containers, with 12 replicates per sample. The containers were placed in a light incubator with the following parameters: constant temperature 30℃, alternating light and dark cycles of 4 hours and 4 hours. 20 mL of nutrient solution was added every two days. After 14 days, the root length, seedling length, root weight, and seedling weight of each rice plant were measured and recorded. Figure 3 ).from Figure 3 It can be seen that, compared with the control group, the addition of ethylenediamine-modified lignin (L-EDA10) increased the root length, seedling length, root weight, and seedling weight of rice. Furthermore, the growth-promoting effect was further enhanced after chelating iron ions.

[0034] Example 3: Ethylenediamine-modified lignin and iron-chelated ethylenediamine-modified lignin promote rice root cell proliferation.

[0035] Rice seeds were soaked in tap water for 24 hours, then cultured under constant temperature and light until new shoots appeared. Seeds with similar germination patterns were selected. Next, a hydroponic nutrient solution was prepared by dissolving 0.1 g of ethylenediamine-modified lignin (L-EDA10) and iron-chelated ethylenediamine-modified lignin (L-EDA10 / Fe) in 1 L of tap water to obtain a nutrient solution with a mass concentration of 0.01%. A tap water control group was also included. The nutrient solution was then added to the hydroponic container, and the selected germinated seeds were inoculated into the container, with 12 replicates per sample. The container was then placed in a light incubator with the following parameters: constant temperature 30℃, alternating light and dark cycles of 4 hours and 4 hours. 20 mL of nutrient solution was added every two days. Samples were then collected on days 1 and 7, and root sections were cut for EdU staining (a two-step process of labeling proliferating cells using S-phase DNA incorporation and copper-catalyzed click chemistry; only cells synthesizing DNA (S-phase proliferation) will show staining), and the results were recorded using an upright fluorescence microscope. Figure 4 As shown, on day 1 of culture, all groups showed strong fluorescence signals, indicating that the cells were in an active proliferation state. However, by day 7, only the L-Urea10 / Fe treatment group maintained significant fluorescence intensity, while the fluorescence signals of the other groups were significantly weakened, indicating that the number of cells in the proliferation phase in the L-Urea10 / Fe treatment group was greater than that in the other groups.

[0036] The above detailed description is a specific description of the embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the patent scope of this case.

Claims

1. A method for preparing an ethylenediamine-modified lignin-based metal chelating agent, characterized in that, Includes the following steps: (1) Disperse sulfate lignin in 1,4-dioxane, add sodium hydroxide solution to dissolve it completely; then add ethylenediamine and formaldehyde in sequence, and stir the reaction in a constant temperature oil bath; after the reaction is completed, dialysis the reaction solution to purify it, freeze dry it to obtain aminated lignin; (2) Disperse the aminated lignin obtained in step (1) in ultrapure water, add metal ion salt and mix well, stir at room temperature to carry out coordination reaction, dialysis the reaction solution for purification, freeze dry to obtain ethylenediamine modified lignin-based metal chelating agent.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of sulfate lignin, ethylenediamine, and formaldehyde is 1:(1~10):(1~10).

3. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the constant temperature oil bath is 60~100℃; the stirring rate of the stirring reaction is 200~500 rpm, and the reaction time is 4~12 h.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the aminated lignin to the metal ion salt is 1:(20~30).

5. The preparation method according to claim 1, characterized in that, In step (2), the coordination reaction takes 24 to 48 hours.

6. The preparation method according to claim 1, characterized in that, In step (2), the metal ion salt is selected from at least one of FeCl3, CuCl2, MgCl2, ZnCl2, and CaCl2.

7. The ethylenediamine-modified lignin-based metal chelating agent prepared by the preparation method according to any one of claims 1-6.

8. Use of the ethylenediamine-modified lignin-based metal chelating agent according to claim 7 in promoting root cell proliferation and / or promoting plant growth.

9. The use according to claim 8, characterized in that, The promotion of plant growth is manifested in at least one of promoting root development and increasing plant biomass.

10. The use according to claim 8, characterized in that, The plant in question is rice.

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