Composite conditioner for treating sulfate type saline-alkali soil and application of composite conditioner

Abstract

The invention relates to the technical field of saline-alkali soil improvement, in particular to a compound conditioner for treating sulfate type saline-alkali soil and application of the compound conditioner. The compound conditioner is formed by compounding hydrotalcite, acidic zeolite and humic acid; wherein the hydrotalcite is nitrate intercalated MgAl-LDH or MgFe-LDH, and the molar ratio of divalent metal ions to trivalent metal ions of the hydrotalcite is (2: 1)-(4: 1); the acidic zeolite is clinoptilolite treated by a nitric acid solution; the humic acid is mineral source humic acid, and the purity of the humic acid is greater than 80%. The compound conditioner disclosed by the invention can mineralize Na < + > and SO4 < 2-> which are too high in content in saline-alkali soil, reduce the salt content and pH and prevent plants from osmotic stress and alkaline toxicity; the content of nitrate nitrogen and organic matters in soil is increased, and nutrient substances are provided for plants; the soil structure is improved, the water-retaining property and the air permeability are enhanced, the soil bulk density is reduced, and plant germination and root growth are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of saline-alkali land improvement, and particularly relates to a composite conditioner for treating sulfate-type saline-alkali land and its application. Background Art

[0002] The soluble salt content in saline-alkali land is high and the pH is alkaline, which will cause serious osmotic stress to plants, inhibit the absorption of water and nutrient elements by plants, and ultimately cause plant death and food production reduction. Sulfate-type saline-alkali land is a common type of saline-alkali land. It not only has extremely low organic matter content and available nitrogen, phosphorus and potassium content, making it difficult to provide sufficient nutrient elements to plants, but also has small aggregate particle size, strong dispersibility, easy loss of water and nutrients, and poor air and water permeability, seriously affecting the root respiration and growth of plants.

[0003] Currently, the main improvement methods for saline-alkali soil can be divided into three categories: physical improvement, chemical improvement and biological improvement. Physical improvement methods generally include land ploughing, soil replacement, drip irrigation leaching and subsurface pipe drainage, etc. However, physical improvement methods are often affected and restricted by the shortage of fresh water resources, large project volume, high cost and possible secondary salinization, etc., and are difficult to be applied on a large scale. Biological improvement methods mainly include two types. One is to cultivate and plant salt-tolerant crops so that they can grow normally in saline-alkali land; the other is to plant halophilic plants (such as Suaeda glauca, Atriplex patens, Salsola passerina, etc.) or beneficial microorganisms to absorb the salts in the soil and improve the soil aggregate structure and the availability of nutrient elements. The above two biological improvement methods have disadvantages such as long treatment cycle, high technical threshold and narrow application range (plants and microorganisms are difficult to survive in severely saline-alkali land). Chemical improvement is to add substances such as desulfurized gypsum, sulfuric acid, organic fertilizer and biochar to saline-alkali soil to improve the soil salt composition and structure, reduce the soil alkalinity and increase the nutrient content. Among them, gypsum-like substances can provide a large amount of Ca 2+ to release the Na + adsorbed on the soil colloid through competitive adsorption, making it easier to leach and remove the excessive Na + . And substances such as sulfuric acid and sulfur have strong acidity, which can reduce the soil pH through acid-base neutralization and provide nutrients such as nitrogen and sulfur to the soil. In addition, a large number of organic molecules will be produced after the decomposition of organic matter (such as biochar, humic acid and manure, etc.), which can significantly improve the soil colloid properties and enhance the air permeability and water and fertilizer retention capacity of the soil. The problems faced by chemical improvement methods include poor long-term effectiveness, single improvement effect and easy secondary pollution, etc.

[0004] Zeolite belongs to aluminosilicate minerals and has a special pore structure and cage-like space. Because the AlO4 tetrahedron in zeolite carries a negative charge, it requires metal cations outside the framework (such as K + , Na + , Ca2+ , Mg 2+ etc.) to maintain charge balance, which endows it with good cation exchange capacity. Zeolite resources in China are abundant. More than 400 ore deposits have been discovered so far, with reserves exceeding 4 billion tons, ranking first in the world and distributed throughout the country. Among them, Shanxi, Inner Mongolia and Hebei have the richest reserves, accounting for more than 45% of the total reserves. Zeolite has strong water retention capacity, which can reduce water use under drought conditions and maintain soil moisture. The zeolite pores contain abundant exchangeable cations, which can not only slowly release nutrient elements for the soil but also adsorb and limit certain specific cations, having the effect of conditioning the soil element composition and improving fertilizer utilization rate. Finally, its unique physical and chemical properties can also improve the soil aggregate composition, increase soil air permeability and water permeability, which is beneficial to heavy clay or sandy soil.

[0005] Layered double hydroxides (LDHs), also known as hydrotalcite, are a class of typical layered minerals. The characteristics of low cost, easy synthesis and high biocompatibility of LDHs enable LDHs to have the potential for large-scale application in soil treatment; secondly, the unique host-guest structure of LDHs and the multiple interaction forces existing between them endow it with ultra-high stability and ultra-low K sp , which can stably confine anions to achieve an ultra-stable mineralization effect; finally, the composition of the lamellar metal cations and the types of interlayer anions of LDHs can be adjusted, and customized improvement methods can be provided for different types of working conditions.

[0006] At present, hydrotalcite has shown great application potential in the fields of water body and soil pollution remediation respectively, but there is no research on its direct application in the field of saline-alkali soil improvement. Therefore, by utilizing the ultra-stable mineralization advantage of hydrotalcite and the functions of zeolite and humic acid in the field of soil improvement, an efficient, low-cost and pollution-free improvement method for sulfate-type saline-alkali land can be developed. Summary of the Invention

[0007] To solve the above problems, the present invention provides a composite conditioner for treating sulfate-type saline-alkali land and its application.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A composite conditioner for the treatment of sulfate saline-alkali land, which is composed of hydrotalcite, acid zeolite and humic acid; wherein, the hydrotalcite is nitrate intercalated MgAl-LDH or MgFe-LDH, and the molar ratio of its divalent metal ion to trivalent metal ion is 2:1 to 4:1; the acid zeolite is clinoptilolite treated with nitric acid solution; the humic acid is mineral source humic acid with a purity greater than 80%. During preparation, the acid zeolite, humic acid and hydrotalcite are added to a mixer in proportion and stirred for 1 to 3 hours until evenly mixed, then it is obtained.

[0010] Preferably, the molar ratio of the divalent metal ion to the trivalent metal ion in the hydrotalcite is 2:1.

[0011] In the composite conditioner for the treatment of sulfate saline-alkali land of the present invention, the acid zeolite is obtained by crushing clinoptilolite, screening it through a 200-300 mesh sieve, dispersing it in nitric acid solution, and then stirring, centrifuging, washing and drying. Specifically, it includes the following steps:

[0012] S1. Crush clinoptilolite and screen it through a 200-300 mesh sieve, disperse it in 0.1-0.5 mol / L nitric acid solution according to a mass ratio of 1:5, stir for 2-6 hours, and centrifuge to obtain zeolite treated with nitric acid;

[0013] S2. Disperse the zeolite treated with nitric acid in deionized water according to a mass ratio of 1:5, stir and wash for 20 minutes, then centrifuge and dry at 60°C for 6-12 hours.

[0014] The composite conditioner for the treatment of sulfate saline-alkali land of the present invention is prepared from the following raw materials in parts by weight:

[0015] Hydrotalcite 20-35 parts; acid zeolite 44-64 parts; humic acid 13-27 parts.

[0016] The composite conditioner for the treatment of sulfate saline-alkali land of the present invention can be used for the improvement of sulfate saline-alkali land. During application, add the composite conditioner to the sulfate saline-alkali land to be improved at a dosage of 5-15 kg / m 2 and plow to a depth of 20-30 cm and irrigate.

[0017] The present invention improves the soil by applying a hydrotalcite / acid-modified zeolite / humic acid composite conditioner to sulfate saline-alkali land, and cleverly utilizes the super-stable mineralization characteristics of hydrotalcite and the advantages of zeolite and humic acid in the agricultural field. By using the three in combination, the comprehensive improvement of sulfate saline-alkali land is realized, and it has the following beneficial effects:

[0018] (1) There are abundant H in the pore channels of the acid zeolite of the present invention +, after being applied and entering the soil, it can release H + to neutralize OH in the soil - , reducing the soil alkalinity; at the same time, in order to balance the charge, a large amount of Na present in the soil + will fill into the cation vacancies generated by the release of H from the zeolite + , realizing the restriction of Na + ; secondly, the zeolite has a rich pore structure and a large specific surface area, which can enhance the soil air permeability and water retention capacity, and improve the soil structure.

[0019] (2) The hydrotalcite used in the present invention has ultra-high stability and extremely low K sp , and can super-stably mineralize a large amount of SO4 present in the soil through ion exchange and surface adsorption 2- , reducing the content of SO4 in the soil 2- , and having a stable and long-lasting mineralization effect. And the NO3 released by the hydrotalcite - can be absorbed by plants as nitrate nitrogen fertilizer.

[0020] (3) The humic acid used in the present invention, as an organic macromolecular weak acid, can reduce the soil alkalinity, improve the particle size of soil aggregates and colloidal properties, and enhance the soil organic matter content and water and fertilizer retention capacity.

[0021] (4) The composite conditioner of the present invention is applied to the soil, stirred evenly, and after irrigation, the improvement of sulfate saline-alkali soil can be realized, with convenient operation and high improvement efficiency;

[0022] (5) The composite conditioner of the present invention can achieve the long-term stable mineralization of Na + and SO4 2- , increase the organic matter content, improve the soil structure properties, and realize the comprehensive improvement of sulfate saline-alkali soil.

[0023] In summary, the composite conditioner of the present invention can mineralize the excessively high content of Na + and SO4 2- in saline-alkali soil, reduce the salt content and pH, avoid plants from being subjected to osmotic stress and alkaline toxicity; increase the soil nitrate nitrogen and organic matter content, provide nutrients for plants; improve the soil structure, enhance its water retention and air permeability, reduce the soil bulk density, and be beneficial to plant germination and root growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the XRD pattern of the zeolite before and after acid modification in Example 1 of the present invention.

[0025] Figure 2 is the XRD pattern of the MgAl-LDH used in Example 1 of the present invention.

[0026] ​Figure 3 This is the comparison chart of barley emergence rate in Example 4 of the present invention. Detailed implementation mode

[0027] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made. These all belong to the protection scope of the present invention.

[0028] Aiming at the defects of the existing improvement methods for sulfate saline-alkali soil, based on the characteristics of zeolite and hydrotalcite, the present invention proposes a composite conditioner for sulfate saline-alkali soil treatment based on hydrotalcite, acid-modified zeolite, and humic acid. The composite conditioner is composed of hydrotalcite, acidic zeolite, and humic acid. Among them, hydrotalcite, as a type of anion clay material, is composed of a positively charged main layer board and guest anions, where the binding ability of NO3 - to the layer board is weaker than that of SO4 2- and Cl - . Therefore, when the NO3 - intercalated hydrotalcite is added to the saline-alkali soil, NO3 - can be released, and SO4 2- and Cl - can be mineralized into the interlayer, realizing the mineralization of excessive SO4 2- and Cl - in the sulfate saline-alkali soil, while NO3 - can be absorbed by plants as nitrate nitrogen fertilizer. Secondly, due to the unique host-guest structure of hydrotalcite and the multiple interaction forces existing therein, it has a large lattice energy and an extremely low K sp , which can achieve the ultra-stable mineralization of pollutant ions and avoid secondary pollution caused by the dissolution of pollutant ions. And there are abundant H + in the pores of acidic zeolite. After being applied to the soil, it can release H + to neutralize OH - in the soil and form cation vacancies, thereby generating a driving force to capture Na + , and finally effectively restricting Na + in the soil; Humic acid, as an organic macromolecule weak acid, can significantly increase the organic matter content of the soil and improve the soil aggregate structure and colloid properties.

[0029] The first aspect of the present invention provides a composite conditioner for improving sulfate saline-alkali soil, wherein the composite conditioner is prepared from the following raw materials in parts by weight:

[0030] 20 - 35 parts of hydrotalcite; 44 - 64 parts of acidic zeolite; 13 - 27 parts of humic acid.

[0031] The composite conditioner provided by the present invention can be used to improve sulfate saline - alkali soil. After application, SO4 in the soil 2- is mineralized between and on the surface of the hydrotalcite layer, and Na + is filled into the cation vacancies of the zeolite, and NO3 is released - and H + , reducing the soil pH and salt content, increasing the organic matter content, improving the soil structure, and finally achieving the improvement effect.

[0032] In some embodiments of the present invention, the hydrotalcite is NO3 - intercalated magnesium - aluminum or magnesium - iron hydrotalcite, with a molar ratio M 2+ :M 3+ = 2:1. The acidic zeolite is clinoptilolite modified by nitric acid treatment. The humic acid is mineral - derived humic acid with a purity greater than 80%.

[0033] The second aspect of the present invention provides a method for preparing the acidic zeolite as described above. The method includes: crushing the zeolite through a 200 - 300 - mesh sieve and dispersing it into a nitric acid solution with a concentration range of 0.1 - 0.5 mol / L, stirring for 2 - 6 h, centrifuging, washing, and drying at 60 °C for 6 - 12 h to obtain the acidic zeolite.

[0034] In some embodiments of the present invention, the mass ratio of the zeolite to the nitric acid solution is 1:5.

[0035] In some embodiments of the present invention, the washing process is to disperse the zeolite in deionized water according to a mass ratio of 1:5, stir for 20 minutes, and then centrifuge.

[0036] The third aspect of the present invention provides a method for preparing the composite conditioner for sulfate saline - alkali soil improvement as described above. The method includes: adding the acidic zeolite, humic acid, and hydrotalcite into a mixer, and stirring for 1 - 3 h until uniform to obtain the composite conditioner.

[0037] The fourth aspect of the present invention provides the application of the composite conditioner for sulfate saline - alkali soil improvement according to the first aspect as a soil conditioner in the improvement of sulfate saline - alkali soil: adding the composite conditioner to the sulfate saline - alkali soil to be improved at a dosage of 5 - 15 kg / m 2 , plowing to a depth of 20 - 30 cm and irrigating.

[0038] In the present invention, a hydrotalcite / acidity zeolite / humic acid composite conditioner is used for soil improvement. Acid-modified zeolite can improve the air permeability and water and fertilizer retention capacity of the soil, reduce the soil pH and form cation vacancies, and finally mineralize Na in the soil by filling the vacancies. + When hydrotalcite is added to sulfate-type saline-alkali soil, excessive SO4 in the soil 2- can be stably mineralized in its interlayer, and NO3 is released - which serves as nitrate nitrogen fertilizer to provide nutrients for plants. Humic acid has the application effect of increasing the organic matter content of the soil and improving the soil structure. According to the ultra-stable mineralization characteristics of hydrotalcite and the ortho-charge restriction effect, the stable mineralization of SO4 2- and Na + can be realized respectively, avoiding the disadvantages of large water demand, high cost, easy re-salination and short duration in traditional improvement. Finally, it realizes the reduction of the pH value and salt content of sulfate-type saline-alkali soil, increases the organic matter and nitrate nitrogen fertilizer content, improves the water and fertilizer retention capacity and air permeability of the soil, and realizes the comprehensive improvement of sulfate-type saline-alkali soil.

[0039] The present invention will be described in detail below through examples.

[0040] For those not specifying specific conditions in the following examples and comparative examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial channels.

[0041] Example 1: Preparation of acidity zeolite.

[0042] (1) After crushing the clinoptilolite ore, sieve it to obtain 200-mesh zeolite;

[0043] (2) Take 8 g of 200-mesh zeolite and disperse it in 40 mL of 0.5 mol / L nitric acid solution. After stirring for 3 h, centrifuge to obtain the zeolite treated with nitric acid;

[0044] (3) Disperse the zeolite treated with nitric acid in 40 mL of deionized water and stir and wash for 20 min.

[0045] (4) Centrifuge the washed zeolite and place it in an electrothermal blast drying oven at 60 °C for drying for 6 h to obtain acidity zeolite.

[0046] Example 2: Preparation of acidity zeolite

[0047] (1) After crushing the clinoptilolite ore, sieve it to obtain 200-mesh zeolite;

[0048] (2) Take 5 kg of 200-mesh zeolite and disperse it in 25 L of 0.2 mol / L nitric acid solution. Stir for 3 h and centrifuge to obtain the zeolite treated with nitric acid;

[0049] (3) Disperse the zeolite treated with nitric acid into 25 L of deionized water and stir and wash for 20 min.

[0050] (4) Centrifuge and separate the washed zeolite, and place it in an electrothermal blast drying oven to dry at 60 °C for 10 h to obtain acidic zeolite.

[0051] Example 3: Preparation of acidic zeolite

[0052] (1) After crushing the original clinoptilolite ore, sieve it to obtain 300-mesh zeolite;

[0053] (2) Dissolve 4 kg of 300-mesh zeolite in 20 L of 0.5 mol / L nitric acid solution, stir for 6 h, and centrifuge and separate to obtain the zeolite treated with nitric acid;

[0054] (3) Disperse the zeolite treated with nitric acid into 20 L of deionized water and stir for 20 min.

[0055] (4) Centrifuge and separate the washed zeolite, and place it in an electrothermal blast drying oven to dry at 60 °C for 8 h to obtain acidic zeolite.

[0056] Example 4: Preparation of composite conditioner and its application in improving sulfate saline-alkali soil

[0057] (1) Weigh 6 g of the acidic zeolite obtained in Example 1, 1.5 g of humic acid, and 2.5 kg of magnesium-aluminum hydrotalcite, add them to a mixer, and stir for 2 h to obtain a composite conditioner.

[0058] (2) Add 100 g of sulfate saline-alkali soil and 10 g of the above composite conditioner to a petri dish;

[0059] (3) Mix the sulfate saline-alkali soil and the composite conditioner evenly, add 50 mL of water, and then replenish water in a timely manner for 30 days;

[0060] (4) Take samples on the 30th day to test the soil properties and plant barley.

[0061] Example 5: Preparation of composite conditioner and its application in improving sulfate saline-alkali soil

[0062] (1) Weigh 5 kg of the acidic zeolite obtained in Example 1, 1.25 kg of humic acid, and 2.13 kg of magnesium-aluminum hydrotalcite, add them to a mixer, and stir for 2 h to obtain a composite conditioner.

[0063] (2) Broadcast the above composite conditioner into the sulfate saline-alkali land at an application rate of 8 kg / m 2 ;

[0064] (3) Use a rotary tiller to turn over the topsoil to evenly mix the conditioner, with a tillage depth of 30 cm;

[0065] (4) Irrigate the land according to the local irrigation water volume.

[0066] Example 6: Preparation of a composite conditioner and its application in improving sulfate saline-alkali soil

[0067] (1) Weigh 4 kg of the acidic zeolite obtained in Preparation Example 2, 2.04 kg of humic acid, and 4.50 kg of magnesium-iron hydrotalcite and add them to a mixer. After stirring for 1 h, a composite conditioner is obtained.

[0068] (2) Broadcast the above composite conditioner onto the sulfate saline-alkali land at an application rate of 13.2 kg / m 2 ;

[0069] (3) Use a rotary tiller to turn over the topsoil to evenly mix the conditioner, with a tillage depth of 25 cm;

[0070] (4) Irrigate the land according to the local irrigation water volume.

[0071] Test data:

[0072] Test the improvement effects of the saline-alkali land in Example 1, Example 2, and Example 3. The results are shown in Table 1, Table 2, and Table 3.

[0073] Table 1 Comparison of the properties of the saline-alkali land before and after improvement in Example 1

[0074]

[0075] Table 2 Comparison of the properties of the saline-alkali land before and after improvement in Example 2

[0076]

[0077] Table 3 Comparison of the properties of the saline-alkali land before and after improvement in Example 3

[0078]

[0079] It can be seen from the improvement results that 30 days after applying the conditioner, most of the SO4 in the soil was solidified by the conditioner 2- and Na + , and the contents of Cl - and Ca 2+ also decreased. The soil pH and salt content decreased significantly, and the soil physical and chemical properties were significantly improved. Thus, it can be proved that the composite conditioner and improvement method involved in this patent have excellent improvement effects on sulfate saline-alkali soil.

[0080] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or alterations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A composite conditioner for the treatment of sulfate saline-alkali land, characterized in that: This composite conditioner is composed of hydrotalcite, acidic zeolite and humic acid. Among them, the hydrotalcite is nitrate-intercalated MgAl-LDH or MgFe-LDH, and the molar ratio of its divalent metal ions to trivalent metal ions is 2:1 to 4:

1.

2. The composite conditioner for treating sulfate saline-alkali land according to claim 1, wherein: The molar ratio of divalent metal ions to trivalent metal ions in the hydrotalcite is 2:

1.

3. The composite conditioner for treating sulfate saline-alkali land according to claim 1, characterized in that: The acidic zeolite is obtained by crushing clinoptilolite, screening it through a 200-300 mesh sieve, dispersing it in a nitric acid solution, and then stirring, centrifuging, washing and drying.

4. The composite conditioner for treating sulfate saline-alkali land according to claim 3, characterized in that: The concentration range of the nitric acid solution is 0.1-0.5 mol / L, the mass ratio of zeolite to nitric acid solution is 1:5, and the stirring time is 2-6 h.

5. The composite conditioner for treating sulfate saline-alkali land according to claim 3, characterized in that: The washing process includes dispersing the zeolite in deionized water at a mass ratio of 1:5, stirring for 20 min and then centrifuging.

6. The composite conditioner for treating sulfate saline-alkali land according to claim 3, characterized in that: The drying conditions are: temperature is 60 °C and time is 6-12 h.

7. A composite conditioner for treating sulfate saline-alkali land as described in claim 1, characterized in that: The humic acid is mineral source humic acid with a purity greater than 80%.

8. The composite conditioner for treating sulfate saline-alkali land according to claim 1, characterized in that: This composite conditioner is prepared from the following raw materials in parts by weight: Hydrotalcite 20-35 parts; acidic zeolite 44-64 parts; humic acid 13-27 parts.

9. Use of a composite conditioner for treating sulfate saline-alkali land according to any one of claims 1 to 8, characterized in that: It is used for the improvement of sulfate-type saline-alkali land.

10. The application of a composite conditioner for treating sulfate saline-alkali land as claimed in claim 9, wherein: Add the composite conditioner to the sulfate saline-alkali land to be improved at a dosage of 5 - 15 kg / m 2 , plow to a depth of 20 - 30 cm and irrigate.

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