Soil-improving, water-retaining and fertility-increasing coating material as well as preparation method and application thereof

Abstract

The invention discloses a soil-improving, water-retaining and fertility-increasing coating material as well as a preparation method and application thereof, aiming at the obstacle attributes that sandy soil in a desertification region is poor in water-retaining and fertilizer-retaining capacity and loose in structure, hydrochloric acid acidified nano clay and a citrus peel extract are self-assembled to obtain a coating liquid, and then ionic crosslinking is performed to obtain an excellent fertilizer. The gain effect of the coating material on the growth promoting effect of plants in the desertification region is comprehensively evaluated through tests such as texture, controlled release, water retention and potting experiments; the potential influence of the coating material on the human body and the environment is comprehensively judged through a cytotoxicity test, life cycle evaluation and a soil biodegradation experiment. The novel citrus peel extract-nano clay coating material prepared by the method provided by the invention overcomes the application limitation of traditional coated fertilizers, and can effectively reduce the transportation loss of urea fertilizers, improve the release efficiency of urea, increase the water-retaining property and structural stability of soil and promote the growth of plants in regions with severe environments such as desertification.

Description

Technical Field

[0001] The invention relates to the technical field of soil and water conservation and desertification prevention and control, and more specifically 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 semi-humid areas and is affected by a variety of factors. Desertification areas often experience soil loss, decreased fertility, decreased or permanent loss of land productivity, which seriously affects human survival and development and the sustainable development of the social economy. The most economical, effective and lasting measure to prevent and control desertification is to restore vegetation. However, the loose soil structure and dry and barren soil in desertified areas restrict vegetation restoration and plant production in the area. Especially under the influence of global warming and extreme climate change, climate drought has further aggravated the soil degradation process, resulting in loose soil structure, reduced water holding capacity and decreased fertility, causing serious ecological environment and agricultural production crises. Therefore, it is urgent to develop a material that can not only improve soil, but also retain water and increase nutrients in order to cope with the impact of desertification on vegetation restoration and plant production.

[0003] At present, most of the traditional coated fertilizers are aimed at the problem of soil infertility in non-extreme environments. Their functions are relatively single and it is 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, 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 improvement, water retention and fertility coating material suitable for desertified areas and its preparation method. Summary of the invention

[0004] In view of this, the present invention overcomes the application limitations of traditional single-function coated fertilizers in response to the special environmental conditions and soil conditions in desertified areas, 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 the transportation loss 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 solution:

[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 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, 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 200-500 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 solid-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, and deacidification is completed when there is no precipitation.

[0012] Preferably, by mass ratio, 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 pectin esterase was used for enzymolysis 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 a 2M hydrochloric acid solution, and then stirred at 500 rpm in a 70-90°C water bath 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, centrifuged to obtain the precipitate, washed with deionized water, centrifuged again to obtain the precipitate, and then anhydrous ethanol is added to precipitate for 12 hours. Finally, the precipitate is centrifuged to obtain the precipitate, 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 scheme 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 consolidated with 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), and the balance is 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 solutions that, compared with the prior art, the present invention discloses a soil-improving, water-retaining, and fertilization-increasing coating material and a preparation method and application thereof, which have the following beneficial effects:

[0022] The coating material can effectively improve the mechanical strength of urea, up to 251%, and ultimately reduce the transportation loss of urea. The use of the coating material can extend the release time of urea from 0.5h to 15d, and ultimately effectively improve the release efficiency of urea, and can provide a water retention function, which can be extended from 8d to 13d, and ultimately improve the water retention performance of the soil; after degradation, the coating material can play a certain role in soil improvement, increase the content of carbon, nitrogen and hydrogen elements in the soil, promote the formation of micro-soil aggregates, and ultimately improve the quality of sandy soil. That is, the coating material is non-toxic and harmless during the application process, and the degradation products after degradation not only do not pose a potential threat to the environment, but also can 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 performance, 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying 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 for each example;

[0028] Figure 4 The water retention performance of the fertilizer prepared for 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 technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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 pectin esterase was used for enzymolysis 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 a 2M hydrochloric acid solution, and then stirred at 500 rpm in a 70-90°C water bath 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, centrifuged to obtain the precipitate, washed with deionized water, centrifuged again to obtain the precipitate, and then anhydrous ethanol is added to precipitate for 12 hours. Finally, the precipitate is centrifuged to obtain the precipitate, and the extract is dried in a freeze dryer for later use.

[0037] Then prepare the coating material and fertilizer:

[0038] (1) placing the nanoclay in dilute hydrochloric acid with a concentration of ≥3M for acidification and modification, and then deacidification, that is, centrifuging at 4000-6000rpm for 15-30min, taking the precipitate and adding deionized water, the solid-liquid ratio of the precipitate to water is 1 / 500g / mL, repeating the operation, taking the supernatant and adding a small amount of silver nitrate thereto, observing whether there is precipitation, and deacidification is completed when there is no precipitation; the modified nanoclay after deacidification is ultrasonically dispersed in deionized water at 200-500W for 0.5-1h 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 are spontaneously assembled 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), and the balance is 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 cross-linking for 5-10 seconds, then rinsed with anhydrous ethanol, and then dried to fix the shape, and repeated 3 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 verified by using specific embodiments below.

[0044] Example 1

[0045] The above scheme is adopted, but the mass ratio of orange peel extract: nanoclay = 100:0, that is, the urea particles are 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 determined 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 for mechanical strength measurement. The 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 water holding 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 mixed thoroughly with 100g of dry soil and placed in a beaker, then 10mL of water was added and weighed. Another beaker containing the same soil but without the coating was used as a control. The weight was weighed once a day until the mass was constant. The water retention rate was evaluated 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 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 content in the soil. Soil samples without coating degradation 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 to 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 light for 30 minutes, then added to a complete medium with a concentration of 2 mg / mL, ultrasonically shaken for 20 minutes, and the supernatant was taken for use. Working solutions of other concentrations were diluted from the complete medium. The culture medium without the addition of the coating material was used as a blank control group. The concentration of GES-1 cells in the logarithmic growth phase was adjusted, inoculated into a 96-well plate, and cultured overnight to allow the cells to adhere to the wall. 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 150 μL / well, and the cells were cultured for 2 hours under the same conditions as above, and 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 a laser confocal scanning microscope (CLSM) was used to take pictures. The results are shown in Figure 2. Figure 7 shown.

[0066] Coated urea and citrus peel extract-nanoclay coating materials and petroleum-based films (represented by polyvinyl chloride) of the same size (about 5×5×0.030 cm) were placed in soil (about 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 enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be 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 will not be limited to the embodiments shown herein, but rather 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) placing 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; (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.

2. The method for preparing a soil-improving, water-retaining and fertilizing coating material according to claim 1, characterized in that: 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 200-500 W, and the ultrasonic dispersion time is 0.5-1 h.

3. The method for preparing a soil-improving, water-retaining and fertilizing coating material according to claim 1, characterized in that: The deacidification is specifically: Centrifuge at 4000-6000rpm for 15-30min, take the precipitate and add deionized water, the solid-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, and deacidification is completed when there is no precipitation.

4. The method for preparing a soil-improving, water-retaining and fertilizing coating material according to claim 1, characterized in that: 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 fertilizer using the citrus peel extract-nano clay coating material prepared by the method according to any one of claims 1 to 4 or the citrus peel extract-nano clay 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 coating quality.

7. The method according to claim 6, characterized in that The calcium solution comprises 20-30% anhydrous ethanol (v / v), 10-20% glycerol (v / v) and 2-5% calcium chloride (w / v), and the balance is 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 of 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 10-40kg / mu.

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