A soil-improving, water-retaining, and fertilizing coating material, as well as its preparation method and application

Abstract

The present invention discloses a coating material for improving soil, retaining water and increasing fertilizer, as well as its preparation method and application. In view of the poor water and fertilizer retention capacity and loose structure of sandy soil in desertified areas, nanoclay acidified with hydrochloric acid and citrus peel extract are self-assembled to obtain a coating liquid, which is then ionically cross-linked to obtain an excellent fertilizer. The enhancement effect of the coating material on plant growth promotion in desertified areas is comprehensively evaluated through tests such as texture, controlled release, water retention, and potted plant experiments; and the potential impact of the coating material on the human body and the environment is comprehensively judged through cytotoxicity tests, life cycle assessments, and soil biodegradation experiments. The new citrus peel extract-nanoclay coating material prepared by the method of the present invention overcomes the application limitations of traditional coated fertilizers, can effectively reduce the transportation loss of urea fertilizer, improve the release efficiency of urea, increase the water retention and structural stability of the soil, and promote the growth of plants in harsh environmental areas such as desertification.

Description

Technical Field

[0001] The present invention relates to the technical field of soil and water conservation and desertification prevention and control, and more particularly to a soil-improving, water-retaining, and fertilizing coating material, and a preparation method and application thereof. Background Art

[0002] Desertification is a type of land degradation that occurs in arid, semi-arid, and sub-humid regions and is influenced by multiple factors. Desertification-affected areas often experience soil erosion, decreased fertility, and a decline in land productivity, or even permanent loss, severely impacting human survival and sustainable socioeconomic development. The most cost-effective and long-lasting measure to combat desertification is vegetation restoration. However, the loose soil structure and dry, infertile soils in desertified areas restrict vegetation restoration and plant production in the region. Particularly under the influence of global warming and extreme climate change, drought conditions further exacerbate the soil degradation process, leading to a loose soil structure, reduced water holding capacity, and decreased fertility, resulting in a serious ecological and agricultural crisis. Therefore, there is an urgent need to develop a material that can both improve soil quality and retain moisture and increase nutrients to address the impact of desertification on vegetation restoration and plant production.

[0003] At present, most traditional coated fertilizers are aimed at the problem of soil infertility in non-extreme environments. Their functions are relatively simple and they are difficult to cope with the complex and diverse challenges such as loose soil and water deficiency caused by drought in desertified areas. Therefore, there is an urgent need to design a multifunctional coating material specifically for desertified areas with harsh environments, which can connect various functions and meet the requirements of soil nutrient input, improve water retention capacity and regulate soil structure. In addition, the environment in desertified areas is relatively fragile, so the green and degradable characteristics of the coating material are also particularly important. In summary, it is of great significance to develop a green and degradable soil-improving, water-retaining and fertilizing coating material suitable for desertified areas and its preparation method. Summary of the Invention

[0004] In view of this, the present invention targets the special environmental conditions and soil conditions in desertified areas, overcomes the application limitations of traditional single-function coated fertilizers, and develops a coating material suitable for improving soil, retaining water, and increasing fertilizer in desertified areas. The coating material is used to coat urea to reduce transportation losses of urea fertilizer, improve the release efficiency of urea, increase the water retention and structural stability of the soil, and ultimately promote the growth of plants in harsh environmental areas such as desertification.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] First, the present invention provides a method for preparing a soil-improving, water-retaining, and fertilizing coating material, comprising the following steps:

[0007] (1) placing the nanoclay in dilute hydrochloric acid for acidification and modification, then deacidifying, and ultrasonically dispersing the deacidified modified nanoclay in deionized water to obtain a nanoclay suspension;

[0008] (2) The citrus peel extract is mixed with the nanoclay suspension under stirring conditions for self-assembly and cross-linking to obtain a citrus peel extract-nanoclay coating material.

[0009] Preferably, the concentration of the dilute hydrochloric acid in step (1) is ≥3M, the material-liquid ratio is 1 / 300-1 / 200 g / mL, the ultrasonic power is 200-500 W, and the ultrasonic dispersion time is 0.5-1 h.

[0010] Preferably, the deacidification is specifically:

[0011] Centrifuge at 4000-6000rpm for 15-30min, take the precipitate and add deionized water. The material-liquid ratio of precipitate to water is 1 / 500g / mL. Repeat the operation. Take the supernatant and add a small amount of silver nitrate to it. Observe whether there is precipitation. If there is no precipitation, the deacidification is completed.

[0012] Preferably, the mass ratio is citrus peel extract: nanoclay = 100: (20-100).

[0013] The preparation method of the citrus peel extract comprises the following steps:

[0014] The dried citrus peel powder was passed through a 100-mesh sieve, the collected powder was dispersed in deionized water, and enzymatically hydrolyzed with pectinesterase at 35-50°C for 50-90 min. The mass ratio of enzyme to citrus peel powder was 5-30*10. -6 After enzymatic hydrolysis, the pH value of the suspension is adjusted to 2 with 2M hydrochloric acid solution, and then stirred at 500 rpm in a water bath of 70-90°C for 2-5 hours. After centrifugation, the precipitate is discarded, and then 40-60% by volume of anhydrous ethanol and 1-3% by volume of hydrochloric acid are added thereto, stirred evenly, allowed to stand for 2-6 hours, and then centrifuged to obtain the precipitate, washed with deionized water, and then centrifuged to obtain the precipitate, and then anhydrous ethanol is added to precipitate for 12 hours. Finally, the precipitate is centrifuged and the extract is dried in a freeze dryer for later use.

[0015] In addition, the present invention also provides a citrus peel extract-nanoclay coating material prepared by the method described in the above technical solution.

[0016] In addition, the present invention also provides a method for preparing fertilizer using the citrus peel extract-nanoclay coating material prepared by the method described in the above technical solution or the citrus peel extract-nanoclay coating material, that is, the citrus peel extract-nanoclay coating material is coated on the surface of urea particles, and then cross-linked and solidified using a calcium ion solution. Based on the total mass of the coated fertilizer, the urea content is 45-65%, and the rest is the coating mass.

[0017] The calcium solution comprises 20-30% anhydrous ethanol (v / v), 10-20% glycerol (v / v) and 2-5% calcium chloride (w / v), with the balance being deionized water;

[0018] The cross-linking process is as follows: at 20-30° C., the urea particles coated with the coating liquid are placed in a calcium ion cross-linking liquid for cross-linking for 5-10 seconds, then rinsed with anhydrous ethanol, and then dried to set, which is repeated 3 times.

[0019] The present invention also provides a fertilizer prepared by the method and application of the fertilizer in improving soil in desertified areas. The application amount of the fertilizer is 10-40 kg / mu.

[0020] Specifically, in terms of extending the release time of urea, it can be extended from 0.5h to 15d, which can ultimately effectively improve the release efficiency of urea; in terms of improving the water retention function, the water retention can be extended from 8d to 13d.

[0021] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a soil-improving, water-retaining, and fertilizing coating material and its preparation method and application, which have the following beneficial effects:

[0022] This coating material can effectively improve the mechanical strength of urea by up to 251%, ultimately reducing urea transportation losses. It can also extend the urea release time from 0.5 hours to 15 days, effectively improving urea release efficiency. It also provides water retention, extending the time from 8 days to 13 days, ultimately improving soil water retention. After degradation, the coating material can improve soil quality by increasing the carbon, nitrogen, and hydrogen content in the soil and promoting the formation of micro-soil aggregates, ultimately improving sandy soil quality. The coating material is non-toxic and harmless during application, and its degradation products pose no potential threat to the environment and can also improve soil quality.

[0023] In summary, the new green and degradable citrus peel extract-nanoclay coating prepared by the above method improves the transportability and release performance of urea, and improves soil quality including water retention, thereby overcoming the application limitations of traditional coated fertilizers and providing effective protection for the growth of plants in soil-degraded areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 The present invention is a flow chart for the preparation of citrus peel extract-nanoclay coating material and fertilizer;

[0026] Figure 2 Mechanical strength of fertilizers prepared for each example;

[0027] Figure 3 The controlled release properties of the fertilizers prepared in each embodiment;

[0028] Figure 4 The water retention properties of the fertilizers prepared in each embodiment;

[0029] Figure 5 The soil improvement function of the fertilizer prepared in Example 3;

[0030] Figure 6 Potted plant experiments of the fertilizers prepared in Example 1 and Example 3;

[0031] Figure 7 Cytotoxicity testing and life cycle assessment of the fertilizer prepared in Example 3;

[0032] Figure 8 These are digital photos and scanning electron microscope images of the fertilizer degradation experiment prepared in Example 3. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] As attached Figure 1 As shown, the preparation method of the soil-improving, water-retaining and fertilizing coating material comprises the following steps:

[0035] First prepare the citrus peel extract:

[0036] The dried citrus peel powder was passed through a 100 mesh sieve, the collected powder was dispersed in deionized water, and enzymatically hydrolyzed with pectinesterase at 35-50°C for 50-90 min. The mass ratio of enzyme to citrus peel powder was 5-30*10.-6 After enzymatic hydrolysis, the pH value of the suspension is adjusted to 2 with 2M hydrochloric acid solution, and then stirred at 500 rpm in a water bath of 70-90°C for 2-5 hours. After centrifugation, the precipitate is discarded, and then 40-60% by volume of anhydrous ethanol and 1-3% by volume of hydrochloric acid are added thereto, stirred evenly, allowed to stand for 2-6 hours, and then centrifuged to obtain the precipitate, washed with deionized water, and then centrifuged to obtain the precipitate, and then anhydrous ethanol is added to precipitate for 12 hours. Finally, the precipitate is centrifuged and the extract is dried in a freeze dryer for later use.

[0037] Then prepare the coating material and fertilizer:

[0038] (1) The nanoclay is placed in dilute hydrochloric acid with a concentration of ≥3M for acidification and modification, and then deacidification is performed by centrifuging at 4000-6000 rpm for 15-30 min, taking the precipitate and adding deionized water, with the precipitate to water ratio being 1 / 500 g / mL, repeating the operation, taking the supernatant and adding a small amount of silver nitrate thereto, and observing whether there is precipitation. If there is no precipitation, the deacidification is completed; the modified nanoclay after deacidification is ultrasonically dispersed in deionized water at 200-500 W for 0.5-1 h to obtain a nanoclay suspension;

[0039] (2) blending the citrus peel extract with the nanoclay suspension under stirring conditions, and stirring with a magnetic stirrer for 6-10 hours, so that the extract and the nanoclay spontaneously assemble through hydrogen bonds, van der Waals forces and hydrophobic interactions to obtain a citrus peel extract-nanoclay coating material, wherein the ratio of the citrus peel extract to the nanoclay is 100:(20-100) by mass;

[0040] The citrus peel extract-nanoclay coating material is coated on the surface of urea particles, and then cross-linked and consolidated using a calcium ion solution, wherein the calcium solution includes 20-30% anhydrous ethanol (v / v), 10-20% glycerol (v / v) and 2-5% calcium chloride (w / v), with the balance being deionized water;

[0041] The cross-linking process is as follows: at 20-30°C, the urea particles coated with the coating solution are placed in a calcium ion cross-linking solution for 5-10 seconds, then rinsed with anhydrous ethanol, and then dried to set, and repeated three times;

[0042] The mass ratio of the coating material to the urea particles is (35-55): (45-65).

[0043] The technical solution of the present invention will be implemented and its effect will be verified using specific embodiments below.

[0044] Example 1

[0045] The above scheme was adopted, but the mass ratio of orange peel extract to nanoclay was 100:0, that is, the urea particles were coated with orange peel extract.

[0046] Example 2

[0047] Using the above scheme, the mass ratio of orange peel extract to nanoclay is 100:(20-30).

[0048] Example 3

[0049] Using the above scheme, the mass ratio of orange peel extract to nanoclay is 100:(40-60).

[0050] Example 4

[0051] Using the above scheme, the mass ratio of orange peel extract to nanoclay is 100:(70-80).

[0052] Example 5

[0053] Using the above scheme, the mass ratio of citrus peel extract to nanoclay is 100:100.

[0054] Experimental example

[0055] The product performance of Examples 1-5 was measured as follows:

[0056] First, to determine the mechanical strength of the coated fertilizer, we used a TA.XTC-20 texture analyzer (Baosheng Industrial Development Co., Ltd., Shanghai, China) equipped with a cylindrical probe with a diameter of 10.0 mm. The test results are shown in the attached figure. Figure 2 shown.

[0057] Then, 2g of coated fertilizer was placed in a nylon mesh and mixed with 400g of dry soil, and placed in a 1L container. The soil moisture content was maintained at 50% of the field capacity. After incubation at room temperature for 12h, 1d, 2d, 3d, 5d, 10d, 15d, and 20d, the nitrogen concentration of the soil samples was determined by the Kjeldahl method. The results are shown in the attached figure. Figure 3 shown.

[0058] Finally, 1g of the coating material was thoroughly mixed with 100g of dry soil in a beaker. 10mL of water was then added and weighed. A second beaker containing the same soil but without the coating served as a control. The soil was weighed daily until the mass remained constant. Water retention was estimated using the following formula:

[0059] Water retention rate (%) = (M i -M) / (M0-M)×100%

[0060] Where M is the total weight of the beaker, dry soil, and coating before adding water; M0 is the total weight of the beaker, soil, and coating after adding water; the total weight of the test sample (M i), weigh and record the changes every day, the results are as shown in the attached Figure 4 shown.

[0061] By the attached Figure 2-4 It can be seen that the fertilizers prepared by using Examples 1-5 of the present invention have more excellent performance.

[0062] A soil planting experiment was conducted using the fertilizer prepared in Example 1 or Example 3, with no fertilizer applied as the control group. The specific process is as follows:

[0063] First, 150 g of soil was placed in a plastic pot, and then uncoated urea (control group), pure citrus extract-coated urea (Example 1), and citrus peel extract-nanoclay coated urea (Example 3) were placed in the pot and mixed with the soil. Then, the soaked wheat seeds were placed in the pot, covered with a thin layer of soil (50 g), and the water content of the system was adjusted to maintain it at 50% of the field water holding capacity. The wheat seedlings were continuously cultured and observed for 15 days, and the wheat growth indicators finally determined included: shoot length and root length, leaf width, fresh weight and dry weight. The results are as follows: Figure 6 shown.

[0064] During the planting experiment, soil samples near the degradation site were dried at 60°C and then subjected to elemental analysis (Elementar, UNICUBE, Germany) to determine the N, C, H, and S contents in the soil. Soil samples where no coating degradation occurred were tested as controls. The results are shown in the attached figure. Figure 5 shown.

[0065] The cell counting kit-8 (CCK-8) was used to detect the changes in cell viability of GES-1 cells co-cultured with the coating material samples for 1 day, 2 days and 3 days to evaluate the safety of the coating material on the cells. GES-1 cells (iCell Bioscience Inc.) were cultured in a constant temperature incubator (5% CO2, 37°C) and sterilized on both sides of the coating with ultraviolet irradiation for 30 minutes. Then, complete culture medium with a concentration of 2 mg / mL was added, ultrasonically shaken for 20 minutes, and the supernatant was taken for later use. Working solutions of other concentrations were diluted with the complete culture medium. The culture medium without the addition of the coating material was used as the blank control group. The concentration of GES-1 cells in the logarithmic growth phase was adjusted, and they were inoculated into 96-well plates and cultured overnight to allow the cells to adhere. The cells were then placed in an incubator at 37°C and 5% CO2 for 1 day, 2 days and 3 days. The culture medium was removed and the wells were rinsed with PBS. 10% CCK-8 medium was added at a volume of 150 μL / well, and the cells were cultured for 2 hours under the same conditions as above. Then 100 μL of medium was drawn from each well and placed in a 96-well plate. Subsequently, the absorbance value at a wavelength of 450 nm was detected using an enzyme marker and photographed using a confocal laser scanning microscope (CLSM). The results are shown in Figure 2. Figure 7 shown.

[0066] The coated urea, along with citrus peel extract-nanoclay coating materials and petroleum-based films (represented by polyvinyl chloride) of the same size (approximately 5×5×0.030 cm), were placed in soil (approximately 5 cm deep) to evaluate their biodegradability. After 45 days, the remaining coating materials and films were removed, washed, and completely dried at room temperature. Subsequently, the degraded samples were photographed and observed. The results are shown in the attached figure. Figure 8 shown.

[0067] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0068] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a soil-improving, water-retaining, and fertilizing coating material, characterized in that: The following steps are involved: (1) The nanoclay is placed in dilute hydrochloric acid for acidification and modification, and then deacidified. The deacidified modified nanoclay is ultrasonically dispersed in deionized water to obtain a nanoclay suspension; (2) blending the citrus peel extract with the nanoclay suspension under stirring conditions to perform self-assembly and cross-linking to obtain a citrus peel extract-nanoclay coating material; The preparation method of the citrus peel extract comprises the following steps: The dried citrus peel powder was passed through a 100-mesh sieve, the collected powder was dispersed in deionized water, and enzymatically hydrolyzed with pectinesterase at 35-50°C for 50-90 min. The mass ratio of enzyme to citrus peel powder was 5-30*10 -6 After enzymatic hydrolysis, the pH value of the suspension was adjusted to 2 with 2 M hydrochloric acid solution, and then stirred at 500 rpm in a water bath at 70-90°C for 2-5 hours. After centrifugation, the precipitate was discarded, and 40-60% by volume of anhydrous ethanol and 1-3% by volume of hydrochloric acid were added thereto, stirred evenly, and allowed to stand for 2-6 hours. The precipitate was obtained by centrifugation, washed with deionized water, and then centrifuged to obtain the precipitate. Anhydrous ethanol was then added for precipitation for 12 hours. Finally, the precipitate was obtained by centrifugation, and the extract was dried in a freeze dryer for later use.

2. The method for preparing a soil-improving, water-retaining, and fertilizing coating material according to claim 1, wherein: In step (1), the concentration of dilute hydrochloric acid is ≥3M, the material-liquid ratio is 1 / 300-1 / 200 g / mL, the ultrasonic power is 200-500W, and the ultrasonic dispersion time is 0.5-1h.

3. The method for preparing a soil-improving, water-retaining, and fertilizing coating material according to claim 1, wherein: The deacidification is specifically: Centrifuge at 4000-6000 rpm for 15-30 min, take the precipitate and add deionized water. The material-liquid ratio of precipitate to water is 1 / 500 g / mL. Repeat the operation. Take the supernatant and add a small amount of silver nitrate to it. Observe whether there is precipitation. If there is no precipitation, the deacidification is complete.

4. The method for preparing a soil-improving, water-retaining, and fertilizing coating material according to claim 1, wherein: In terms of mass ratio, citrus peel extract: nanoclay = 100: (20-100).

5. A citrus peel extract-nanoclay coating material prepared by the method according to any one of claims 1 to 4.

6. A method for preparing a fertilizer using the citrus peel extract-nanoclay coating material prepared by the method according to any one of claims 1 to 4 or the citrus peel extract-nanoclay coating material according to claim 5, characterized in that: The citrus peel extract-nanoclay coating material is coated on the surface of urea particles, and then cross-linked and solidified using a calcium ion solution. Based on the total mass of the coated fertilizer, the urea content is 45-65%, and the rest is the coating mass.

7. The method according to claim 6, characterized in that The calcium ion solution comprises 20-30% anhydrous ethanol (v / v), 10-20% glycerol (v / v) and 2-5% calcium chloride (w / v), with the balance being deionized water; The cross-linking process is as follows: at 20-30° C., the urea particles coated with the coating liquid are placed in a calcium ion cross-linking liquid for cross-linking for 5-10 seconds, then rinsed with anhydrous ethanol, and then dried to set, which is repeated 3 times.

8. A fertilizer prepared by the method according to claims 6-7.

9. Use of the fertilizer according to claim 8 in improving soil in desertified areas.

10. The use according to claim 8, characterized in that The application amount of the fertilizer is 10-40 kg / mu.

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