Soil remediation agent for acidified soil improvement and preparation method of soil remediation agent

Abstract

The invention relates to the technical field of soil improvement, and discloses a soil remediation agent for acidified soil improvement and a preparation method thereof, the soil remediation agent comprises the following raw materials: functionalized sodium alginate microspheres, an improving agent, an organic fertilizer, eggshell powder, straw powder and plant ash; the functionalized sodium alginate microspheres can adsorb activated heavy metal ions in the acidified soil, and are chelated with the heavy metal ions to form a chelate, so that the heavy metal ions are fixed, and the heavy metal ions are prevented from entering crops; the improving agent can play a role in soil for a long time, on one hand, the improving agent and the functional sodium alginate microspheres cooperate to adsorb heavy metal ions in the soil, on the other hand, nutrient elements can be provided, growth and development of crops are promoted, the soil structure is improved, the soil bulk density is reduced, and the problem of soil hardening is solved. Wide application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement, and in particular to a soil repair agent for improving acidified soil and a preparation method thereof. Background Art

[0002] Soil is the foundation of agriculture, which is related to the growth and development of crops and agricultural production. The state of soil affects the yield and quality of crops and is related to food security. Soil also plays an important role in the ecological environment, which can alleviate climate change and maintain ecological balance. With the continuous development and utilization of soil, soil degradation has become more and more serious. Soil acidification is a manifestation of soil degradation, which not only causes the decline of soil fertility, but also affects the growth of crops, resulting in a reduction in grain production and restricting the sustainable development of agriculture. Soil acidification reduces the pH value of the soil, making the heavy metal ions such as chromium, cadmium and copper, which were originally in a stable state, active, causing the activation of heavy metal ions. After the activated heavy metal ions are absorbed by crops, they will accumulate in the body of crops, resulting in heavy metal residues in crops, which endangers the health of animals and humans through the food chain. In addition, soil acidification will cause the normal aggregate structure of the soil to be destroyed, resulting in soil compaction. Soil compaction will increase the soil bulk density, reduce air permeability and water permeability, affect the growth and development of crops, and lead to reduced yields. Therefore, it is necessary to manufacture a repair agent to solve the problem of excessive heavy metal ion content in acidified soil and compaction of acidified soil.

[0003] The patent with application number CN202010160897.X discloses a preparation method of an acidic soil remediation agent, the prepared soil remediation agent and its application. The soil remediation agent includes the following raw materials: red mud, attapulgite, chitosan and acetic acid. The prepared soil remediation agent utilizes the strong alkalinity of red mud to repair acidic soil, and adds attapulgite with bonding properties to control the release of red mud at different pH values ​​through the synergistic effect of attapulgite, red mud and chitosan. It has the advantages of being environmentally friendly and easy to use. However, the patent does not take into account the problems of excessive heavy metal ion content after soil acidification and soil compaction after soil acidification. Therefore, the present invention provides a soil remediation agent for acidified soil improvement, which solves the problems of excessive heavy metal content and soil compaction after soil acidification, and has broad application prospects. Summary of the invention

[0004] The purpose of the present invention is to provide a soil remediation agent for improving acidified soil and a method for preparing the same, which solves the following technical problems:

[0005] (1) Solved the problem of excessive heavy metal ion content in acidified soil;

[0006] (2) Solved the problem of soil compaction caused by acidification.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A soil repair agent for improving acidified soil, comprising the following raw materials in parts by weight: 40-60 parts of functionalized sodium alginate microspheres, 30-50 parts of improver, 30-40 parts of organic fertilizer, 20-30 parts of eggshell powder, 10-15 parts of straw powder, and 10-15 parts of wood ash.

[0009] Furthermore, the preparation method of the functionalized sodium alginate microspheres comprises the following steps:

[0010] Step A, adding sodium alginate to deionized water, stirring to dissolve, adding calcium chloride aqueous solution dropwise, curing for 8-10 hours, separating after centrifugation, washing, and drying at 45-55° C. for 1-3 hours to obtain sodium alginate microspheres;

[0011] Step B, adding sodium alginate microspheres to deionized water, stirring evenly, introducing nitrogen, adding chloroacetaldehyde and an acid binding agent, heating to 60-80° C., reacting for 6-8 hours, filtering, washing, and drying to obtain modified sodium alginate microspheres;

[0012] Step C, adding the modified sodium alginate microspheres to deionized water, stirring evenly, introducing nitrogen, adding 8-aminoquinoline, adjusting the pH to 4.5-5.5, maintaining the water bath temperature at 50-55° C., reacting for 3-5 hours, filtering, and drying to obtain functionalized sodium alginate microspheres.

[0013] By adopting the above technical scheme, sodium alginate can form sodium alginate microspheres under the action of calcium chloride, and under the action of an acid-binding agent, a large number of active hydroxyl groups on the surface of the sodium alginate microspheres can undergo a substitution reaction with the chlorine substituents in the chloroacetaldehyde structure to obtain modified sodium alginate microspheres with aldehyde groups, and the aldehyde groups in the modified sodium alginate microspheres can undergo a Schiff base reaction with the amino groups in the 8-aminoquinoline structure to obtain functionalized sodium alginate microspheres.

[0014] Furthermore, in step A, the mass fraction of calcium chloride is 2.5-3.5%.

[0015] Furthermore, in step B, the acid binding agent is triethylamine or pyridine.

[0016] Furthermore, the preparation method of the improving agent comprises the following steps:

[0017] S1. Grind the diatomaceous earth thoroughly through a 100-300 mesh sieve, acidify it, add it to ethyl acetate, disperse it evenly, introduce nitrogen, add diphenylmethane diisocyanate and dibutyltin dilaurate, reflux for 6-8 hours, centrifuge and wash, disperse the product in deionized water, stir it at 85-95° C. for 10-12 hours, filter and dry it to obtain modified diatomaceous earth;

[0018] S2. Add the modified diatomaceous earth to deionized water, disperse it evenly, then add phosphate buffer and carboxymethyl hydroxypropyl guar gum, stir for 4-6 hours, let it stand for 0.5-1.5 hours, filter and dry to obtain an improving agent.

[0019] By adopting the above technical scheme, the acidified diatomite has higher porosity, larger specific surface area and stronger adsorption capacity, more silanol groups are exposed on the surface of the diatomite, and under the action of dibutyltin dilaurate, the silanol groups on the surface of the diatomite can react with the isocyanate groups in the diphenylmethane diisocyanate structure to obtain modified diatomite with isocyanate groups. The isocyanate groups are positively charged after hydrolysis and can self-assemble with negatively charged carboxymethyl hydroxypropyl guar gum through electrostatic adsorption to form a coating structure, thereby achieving the sustained release effect of phosphate and preparing an improving agent.

[0020] Furthermore, in S1, the acidification method is to add diatomaceous earth to sulfuric acid, acid-leach for 2-4 hours, filter, wash, dry, add to a heating furnace, and calcine at 450-550° C. for 1-3 hours.

[0021] Furthermore, in S1, the mass ratio of the acidified diatomaceous earth to diphenylmethane diisocyanate is 1:5-5.5.

[0022] Furthermore, the organic fertilizer is cake fertilizer or animal manure.

[0023] A method for manufacturing a soil remediation agent for improving acidified soil is as follows:

[0024] Add organic fertilizer, eggshell powder, straw powder and wood ash into the mixer, set the speed to 200-300r / min, mix and stir for 20-40min, add functionalized sodium alginate microspheres and improver into the mixer, set the speed to 20-50r / min, mix and stir for 15-30min, discharge and granulate to obtain soil remediation agent.

[0025] Beneficial effects of the present invention:

[0026] (1) The functionalized sodium alginate microspheres prepared by the present invention have a quinoline structure. Quinoline can chelate with heavy metal ions and adsorb heavy metal ions in the soil. Sodium alginate is an anionic polysaccharide and can use static electricity to adsorb heavy metal ions in the soil. Through the grafting of sodium alginate microspheres with quinoline, the functionalized sodium alginate microspheres have carboxyl-type, Schiff base-type and quinoline-type metal chelating groups, which increase the adsorption sites of heavy metal ions, can fix heavy metal ions, form stable chelates, and prevent heavy metal ions from entering crops and affecting human health through the food chain.

[0027] (2) The improver prepared by the present invention has the advantages that diatomaceous earth itself is light and porous and can reduce the soil bulk density when added to the soil. After acidification, the diatomaceous earth has the advantages of high porosity, large specific surface area and strong adsorption capacity, and is used to adsorb phosphate. The diatomaceous earth is modified and self-assembled with guar gum by electrostatic adsorption to achieve the slow release effect of phosphate. Phosphate can act on the soil for a long time, avoiding excessive addition at one time to aggravate soil acidification. On the one hand, phosphate can form phosphate precipitation with heavy metal ions in the soil, and produce a synergistic adsorption effect of heavy metal ions with functionalized sodium alginate microspheres. On the other hand, phosphate can provide nutrients, promote the growth and development of crops, improve soil structure, and promote the recovery and improvement of soil fertility. Therefore, the improver can improve the stability of the soil, promote the formation of aggregate structure, reduce the soil bulk density, and effectively solve the problem of soil compaction.

[0028] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0030] Figure 1 This is the infrared spectrum of the functionalized sodium alginate microspheres prepared in the example;

[0031] Figure 2 This is the infrared spectrum of the modified diatomaceous earth prepared in the example. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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.

[0033] Example 1

[0034] 1. Preparation of functionalized sodium alginate microspheres

[0035] Step A, adding 3.2 g of sodium alginate into deionized water, stirring to dissolve, then dropping 3% calcium chloride aqueous solution, solidifying for 9 hours, centrifuging, separating, washing, and drying at 50° C. for 2 hours to obtain sodium alginate microspheres;

[0036] Step B, adding 2.8 g of sodium alginate microspheres to deionized water, stirring evenly, introducing nitrogen, adding 1.2 g of chloroacetaldehyde and 0.6 g of triethylamine, heating to 70° C., reacting for 6 h, filtering, washing, and drying to obtain modified sodium alginate microspheres;

[0037] Step C, add 2.5 g of modified sodium alginate microspheres to deionized water, stir evenly, introduce nitrogen, add 0.8 g of 8-aminoquine, adjust the pH to 5, maintain the water bath temperature at 55°C, react for 4 h, filter and dry to obtain functionalized sodium alginate microspheres.

[0038] The samples were prepared by potassium bromide tableting method, and the functionalized sodium alginate microspheres were tested by infrared spectrometer. Figure 1 As shown, the spectral wavenumber test range is 4000cm -1 -500cm -1 , the analysis shows that in the infrared spectrum of functionalized sodium alginate microspheres, 3012cm -1 The absorption peak of the carbon-hydrogen bond in the benzene ring appeared at 1638 cm -1 The absorption peak of carboxyl group appeared at 1614 cm -1 The absorption peak of the carbon-nitrogen double bond in Schiff base appeared at 827 cm -1 and 758cm -1 The absorption peak of the carbon-hydrogen bond of the quinoline ring appears.

[0039] 2. Preparation of Improver

[0040] S1. Grind 3.5 g of diatomaceous earth thoroughly and pass it through a 200-mesh sieve. Add it to 72% sulfuric acid and acid-soak it for 3 hours. After filtering, washing and drying, add it to a heating furnace and calcine it at 500°C for 2 hours to obtain acidified diatomaceous earth.

[0041] S2, add 3g of acidified diatomaceous earth to ethyl acetate, disperse evenly, introduce nitrogen, add 15g of diphenylmethane diisocyanate and 4g of dibutyltin dilaurate, reflux for 8h, centrifuge and wash, disperse the product in deionized water, stir at 90°C for 10h, filter and dry to obtain modified diatomaceous earth;

[0042] The potassium bromide tablet method was used to prepare the sample, and the modified diatomite was tested by infrared spectroscopy. Figure 2 As shown, the spectral wavenumber test range is 4000cm -1 -500cm -1 , analysis shows that in the infrared spectrum of modified diatomite, 3433cm -1 The absorption peak of hydroxyl group appeared at 2280cm -1 The absorption peak of isocyanate group appeared at 1540 cm -1 The absorption peak of nitrogen hydrogen bond in carbamate appeared at 1090 cm -1 The absorption peak of silicon-oxygen bond appears at

[0043] S3. Add 2.5 g of modified diatomaceous earth into deionized water, disperse evenly, then add 0.5 g of phosphate buffer and 2.5 g of carboxymethyl hydroxypropyl guar gum, stir for 6 h, let stand for 1 h, filter and dry to obtain an improving agent.

[0044] 3. Manufacturing of soil remediation agents

[0045] Add 30g cake fertilizer, 20g eggshell powder, 10g straw powder and 10g wood ash into a mixer, set the speed to 200r / min, mix and stir for 20min, then add 40g functionalized sodium alginate microspheres and 30g improver into the mixer, set the speed to 20r / min, mix and stir for 15min, discharge and granulate to obtain a soil remediation agent.

[0046] Example 2

[0047] Manufacturing of soil remediation agents

[0048] 35g of cake fertilizer, 25g of eggshell powder, 12g of straw powder and 12g of wood ash were added to a mixer, the speed was set to 250r / min, and mixed and stirred for 30min. Then, 50g of the functionalized sodium alginate microspheres prepared in Example 1 and 40g of the improver prepared in Example 1 were added to the mixer, the speed was set to 35r / min, mixed and stirred for 20min, discharged, granulated, and a soil remediation agent was obtained.

[0049] Example 3

[0050] Manufacturing of soil remediation agents

[0051] 40g of cake fertilizer, 30g of eggshell powder, 15g of straw powder and 15g of wood ash were added to a mixer, the speed was set to 300r / min, and mixed and stirred for 40min. Then, 60g of the functionalized sodium alginate microspheres prepared in Example 1 and 50g of the improver prepared in Example 1 were added to the mixer, the speed was set to 50r / min, and mixed and stirred for 30min, discharged, and granulated to obtain a soil remediation agent.

[0052] Comparative Example 1

[0053] Manufacturing of soil remediation agents

[0054] 35g of cake fertilizer, 25g of eggshell powder, 12g of straw powder and 12g of wood ash were added to a mixer, the speed was set to 250r / min, and mixed and stirred for 30min. Then, 50g of the functionalized sodium alginate microspheres prepared in Example 1 and 40g of the acidified diatomaceous earth prepared in Example 1 were added to the mixer, the speed was set to 35r / min, mixed and stirred for 20min, discharged, granulated, and a soil remediation agent was obtained.

[0055] Comparative Example 2

[0056] Manufacturing of soil remediation agents

[0057] 35 g of cake fertilizer, 25 g of eggshell powder, 12 g of straw powder and 12 g of wood ash were added to a mixer, the speed was set to 250 r / min, and mixed and stirred for 30 min. Then, 50 g of the functionalized sodium alginate microspheres prepared in Example 1 were added to the mixer, the speed was set to 35 r / min, and mixed and stirred for 20 min. The material was discharged and granulated to obtain a soil remediation agent.

[0058] Comparative Example 3

[0059] Manufacturing of soil remediation agents

[0060] 35g of cake fertilizer, 25g of eggshell powder, 12g of straw powder and 12g of wood ash were added to a mixer, the speed was set to 250r / min, and mixed and stirred for 30min. Then, 40g of the improver prepared in Example 1 was added to the mixer, the speed was set to 35r / min, and mixed and stirred for 20min. The material was discharged and granulated to obtain a soil remediation agent.

[0061] Detection

[0062] Test soil treatment: Take out the 15cm topsoil from the acidified soil farmland, remove the debris in the soil, air-dry and crush, pass through a 2mm pore size sieve, and fully stir and mix the sieved soil to obtain the test soil. Divide the test soil into several portions, each weighing 500g.

[0063] a. Take 6 portions of test soil and add them to deionized water respectively, and divide them into 6 experimental groups. Add 3g of soil remediation agent prepared by Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 to each experimental group respectively, mix them evenly, shake them in a shaking box for 12 hours, let them stand for 2 hours, take the supernatant, and use a soil pH tester to measure the initial pH of the test soil without adding the soil remediation agent, as well as the soil pH value after adding the soil remediation agent for 10 days and 30 days. The results are shown in Table 1;

[0064] Table 1 - Soil pH

[0065] initial 10 days 30 days Example 1 4.83 5.57 6.35 Example 2 4.83 5.62 6.42 Example 3 4.83 5.60 6.39 Comparative Example 1 4.83 5.51 6.32 Comparative Example 2 4.83 5.49 6.31 Comparative Example 3 4.83 5.48 6.28

[0066] It can be seen from Table 1 that the soil remediation agents prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 have obvious effects and can neutralize acidified soil and increase the pH value of the soil.

[0067] b. Add the test soil into deionized water to prepare 1200 mL of a mixture with a solid content of 100 g / L. Add 3 mL of 1 mol / L hydrochloric acid to the mixture. After stirring for 1 hour, the heavy metal ion content is tested as C1. Divide it into 6 experimental groups, add 1 g of the soil remediation agent prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 respectively, stir evenly, let stand for 5 days, take the supernatant, test the heavy metal ion content as C2, and calculate the adsorption rate according to the formula = [(C1-C2) / C1] × 100%. The results are shown in Table 2:

[0068] Table 2 - Heavy metal ion adsorption rate

[0069]

[0070]

[0071] As can be seen from Table 2, the soil remediation agents manufactured by Examples 1 to 3 of the present invention have the function of adsorbing and chelating heavy metal ions. Comparative Example 1 adds functionalized sodium alginate microspheres and acidified diatomaceous earth, and the improver cannot be used to slowly release phosphate and heavy metal ions to form phosphate precipitation, but the acidified diatomaceous earth has a certain ability to adsorb heavy metal ions; Comparative Example 2 adds functionalized sodium alginate microspheres, and the carboxyl group, Schiff base group, and quinoline group in the structure of the functionalized sodium alginate microspheres can be used to chelate heavy metal ions, but no improver is added; Comparative Example 3 adds an improver, and the improver can slowly release phosphate to achieve the effect of fixing heavy metal ions, but no functionalized sodium alginate microspheres are added.

[0072] c. Take 6 portions of test soil and divide them into 6 experimental groups. Add 5g of soil remediation agent prepared by Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 respectively. Test the soil bulk density according to NY / T 1121.4-2006 standard. The results are shown in Table 3:

[0073] Table 3 - Soil Bulk Density

[0074]

[0075]

[0076] As can be seen from Table 3, the soil remediation agents prepared in Examples 1 to 3 have obvious effects on soil compaction, and the soil bulk density is lower than that of the comparative example. The addition of acidified diatomaceous earth in Comparative Example 1 can reduce the soil bulk density, but the effect is limited. Comparative Example 2 does not add an improver, and it is impossible to use guar gum to coat diatomaceous earth phosphate to continuously improve the soil structure and reduce the soil bulk density.

[0077] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A soil remediation agent for improving acidified soil, characterized in that: The soil remediation agent comprises the following raw materials in parts by weight: 40-60 parts of functionalized sodium alginate microspheres, 30-50 parts of improver, 30-40 parts of organic fertilizer, 20-30 parts of eggshell powder, 10-15 parts of straw powder, and 10-15 parts of wood ash.

2. A soil remediation agent for improving acidified soil according to claim 1, characterized in that: The preparation method of the functionalized sodium alginate microspheres comprises the following steps: Step A, adding sodium alginate to deionized water, stirring to dissolve, adding calcium chloride aqueous solution dropwise, curing for 8-10 hours, separating after centrifugation, washing, and drying at 45-55° C. for 1-3 hours to obtain sodium alginate microspheres; Step B, adding sodium alginate microspheres to deionized water, stirring evenly, introducing nitrogen, adding chloroacetaldehyde and an acid binding agent, heating to 60-80° C., reacting for 6-8 hours, filtering, washing, and drying to obtain modified sodium alginate microspheres; Step C, adding the modified sodium alginate microspheres to deionized water, stirring evenly, introducing nitrogen, adding 8-aminoquinoline, adjusting the pH to 4.5-5.5, maintaining the water bath temperature at 50-55° C., reacting for 3-5 hours, filtering, and drying to obtain functionalized sodium alginate microspheres.

3. A soil remediation agent for improving acidified soil according to claim 2, characterized in that: In step A, the mass fraction of calcium chloride is 2.5-3.5%.

4. The soil remediation agent for improving acidified soil according to claim 2, characterized in that: In step B, the acid binding agent is triethylamine or pyridine.

5. The soil remediation agent for improving acidified soil according to claim 1, characterized in that: The preparation method of the improving agent comprises the following steps: S1. Grind the diatomaceous earth thoroughly through a 100-300 mesh sieve, acidify it, add it to ethyl acetate, disperse it evenly, introduce nitrogen, add diphenylmethane diisocyanate and dibutyltin dilaurate, reflux for 6-8 hours, centrifuge and wash, disperse the product in deionized water, stir it at 85-95° C. for 10-12 hours, filter and dry it to obtain modified diatomaceous earth; S2. Add the modified diatomaceous earth to deionized water, disperse it evenly, then add phosphate buffer and carboxymethyl hydroxypropyl guar gum, stir for 4-6 hours, let it stand for 0.5-1.5 hours, filter and dry to obtain an improving agent.

6. The soil remediation agent for improving acidified soil according to claim 5, characterized in that: In S1, the acidification method is to add diatomaceous earth to sulfuric acid, acid-leach for 2-4 hours, filter, wash, dry, add to a heating furnace, and calcine at 450-550° C. for 1-3 hours.

7. The soil remediation agent for improving acidified soil according to claim 5, characterized in that: In S1, the mass ratio of the acidified diatomaceous earth to diphenylmethane diisocyanate is 1:5-5.

5.

8. The soil remediation agent for improving acidified soil according to claim 1, characterized in that: The organic fertilizer is cake fertilizer or animal manure.

9. A method for producing a soil remediation agent for improving acidified soil according to claim 1, characterized in that: The manufacturing method is as follows: Add organic fertilizer, eggshell powder, straw powder and wood ash into the mixer, set the speed to 200-300r / min, mix and stir for 20-40min, add functionalized sodium alginate microspheres and improver into the mixer, set the speed to 20-50r / min, mix and stir for 15-30min, discharge and granulate to obtain soil remediation agent.

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