Soil conditioner and preparation method thereof

Abstract

The invention discloses a soil conditioner and a preparation method thereof, and relates to the field of soil conditioners, in particular to a soil conditioner and a preparation method thereof. The preparation method of the soda saline-alkali soil improver comprises the following steps: 1, taking fulvic acid, anhydrous calcium chloride, anhydrous magnesium chloride and anhydrous aluminum chloride for later use; 2, dissolving fulvic acid in a deionized water solution to prepare a fulvic acid solution, and then adding anhydrous calcium chloride, magnesium chloride and aluminum chloride into the fulvic acid solution; 3, uniformly stirring and mixing; 4, transferring the stirred mixed solution into a hydrothermal reaction kettle, and heating; 5, after the hydrothermal reaction is finished, cooling to room temperature, carrying out suction filtration, and drying filter residues at low temperature; and 6, grinding the dried filter residues to obtain the soda saline-alkali soil improver. The soda saline-alkali soil improver is an acidic Ca, Mg and Al hydrotalcite intercalation material; an anhydrous calcium sulfate phase and a compound (H3O) Al3 (SO4) 2 (OH) 6 phase containing aluminum and sulfate radicals are mainly used; the pH of the soda saline-alkali soil can be improved more quickly.

Description

Technical Field

[0001] The present invention relates to the field of soil conditioners, and particularly to a soil conditioner and a preparation method thereof. Background Art

[0002] The main components of soda saline-alkali soil are sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). Soda saline-alkali soil has the characteristics of high pH, high salt content, high exchangeable sodium, low permeability, and low nutrient availability. These characteristics seriously affect the growth and development of plants. The salinization and alkalization processes of soda saline-alkali soil are closely related, and the soil alkalization layer and high salt-containing layer appear in the same layer of the soil. As an important type of saline-alkali soil, soda saline-alkali soil has the particularity and complexity of high soil exchangeable sodium content and difficult salt leaching.

[0003] At present, the commonly used improvement methods for soda saline-alkali soil mainly include physical improvement, chemical improvement, and bioremediation. However, these methods all have certain limitations in practical applications. Physical improvement mainly combines irrigation and drainage management techniques to ensure that the ion content in the soil or water is within the normal range and does not affect crop growth. This method is often restricted by water resources and has a high cost. The existing chemical improvement method refers to adding some ions with adsorption effects to the soil colloid to change the ion composition in the soil. The conditioner can undergo ion exchange with soil Na + to accelerate salt leaching and reduce Na + thereby improving the physical and chemical properties of the soil and creating a suitable environment for crop growth. Among them, ammonium sulfate, calcium phosphate, gypsum, phosphogypsum, humic acid, citric acid, biochar, etc. have been widely studied and used. However, the use of these conditioners may cause secondary pollution. Bioremediation technologies, such as growing green manure and inoculating microorganisms, are environmentally friendly, but the treatment cycle is long and the effect is unstable.

[0004] Soil conditioners, as a product integrating multiple treatment means, have gradually received attention. Summary of the Invention

[0005] In order to improve soda saline-alkali soil, the present invention provides a new soil conditioner and a preparation method thereof.

[0006] The preparation method of the soda saline-alkali soil conditioner of the present invention:

[0007] Step 1: Weigh 8 parts of fulvic acid, 8 parts of anhydrous calcium chloride, 8 parts of anhydrous magnesium chloride, and 1 part of anhydrous aluminum chloride for standby according to mass parts;

[0008] Step 2: Dissolve the above-mentioned fulvic acid in deionized water solution to form a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride, anhydrous magnesium chloride, and anhydrous aluminum chloride to the fulvic acid solution;

[0009] Step 3: Stir and mix evenly;

[0010] Step 4: Transfer the stirred mixture into a hydrothermal reaction kettle and heat it at 180 ± 5 °C for 20 ± 0.5 h;

[0011] Step 5: After the hydrothermal reaction, cool it to room temperature, perform suction filtration, and dry the filter residue at a low temperature;

[0012] Step 6: Grind the dried filter residue to obtain the soda saline-alkali soil conditioner.

[0013] Further, in Step 2, the mass of the deionized aqueous solution is 30 - 50 times the mass of the fulvic acid.

[0014] Further, in Step 2, the mass of the deionized aqueous solution is 40 times the mass of the fulvic acid.

[0015] Further, in Step 3, the stirring time is 1.5 - 2.5 h.

[0016] Further, in Step 4, the drying temperature of the filter residue is 60 ± 5 °C.

[0017] Further, in Step 4, the drying time of the filter residue is 8 - 12 h.

[0018] The soda saline-alkali soil conditioner of the present invention is the soda saline-alkali soil conditioner prepared by using the method described in any one of the above.

[0019] Further, the soda saline-alkali soil conditioner is a hydrotalcite-like intercalation material (LDHs).

[0020] The present invention prepares the soda saline-alkali soil conditioner of the present invention by hydrothermal reaction of environmentally friendly fulvic acid with metal elements such as Ca, Mg, and Al. The soda saline-alkali soil conditioner of the present invention is an acidic Ca, Mg, Al hydrotalcite-like intercalation material (LDHs). The soda saline-alkali soil conditioner of the present invention mainly consists of anhydrous calcium sulfate phase and a compound containing aluminum and sulfate (H3O)Al3(SO4)2(OH)6 phase. The soda saline-alkali soil conditioner of the present invention is not only green and environmentally friendly, but also can quickly improve the pH of soda saline-alkali soil, providing a new technical path and material selection for saline-alkali soil treatment.

[0021] The preparation method of the present invention is simple. The prepared soda saline-alkali soil conditioner is a hydrotalcite-like intercalation material, which can not only effectively reduce the pH of soda saline-alkali soil, but also improve the soil quality. Due to the special crystal structure of the soda saline-alkali soil conditioner of the present invention, it has a more significant long-term pH reduction effect than other fulvic acid hydrothermal reaction products. The conditioner of the present invention, being a hydrotalcite-like intercalation material, can adsorb heavy metal ions in the soil, thereby further promoting plant growth and having broad application prospects. Description of the Drawings

[0022] Figure 1 SEM image of modifier A in Example 1;

[0023] Figure 2 SEM image of modifier B in Example 1;

[0024] Figure 3 SEM image of modifier C in Example 1;

[0025] Figure 4 SEM image of modifier D in Example 1;

[0026] Figure 5 Specific surface area analysis diagram of each modifier in Example 1;

[0027] Figure 6 Pore size analysis diagram of each modifier in Example 1;

[0028] Figure 7 XRD diagram of each modifier in Example 1;

[0029] Figure 8 CV diagram of electrochemical analysis of each modifier in Example 1;

[0030] Figure 9 EIS diagram of electrochemical analysis of each modifier in Example 1. Detailed implementation manners

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0033] Detailed implementation manner 1: The preparation method of the soda saline-alkali soil modifier in this implementation manner is as follows:

[0034] Step 1: Weigh 8 parts of fulvic acid, 8 parts of anhydrous calcium chloride, 8 parts of anhydrous magnesium chloride, and 1 part of anhydrous aluminum chloride for standby;

[0035] Step 2: Dissolve the above-mentioned fulvic acid in deionized water solution to form a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride, anhydrous magnesium chloride, and anhydrous aluminum chloride to the fulvic acid solution;

[0036] Step 3: Stir and mix evenly;

[0037] Step 4: transfer the stirred mixture into a hydrothermal reactor and heat at 180±5°C for 20±0.5h;

[0038] Step 5: After the hydrothermal reaction is completed, cool to room temperature, filter, and dry the residue at low temperature;

[0039] Step 6: Grind the dried filter residue to obtain a soda saline-alkali soil conditioner.

[0040] Fulvic acid (FA) is a highly active substance extracted from natural humic acid. It mainly comes from minerals such as peat, lignite or weathered coal. It can be extracted by chemical methods; it can also be extracted from sawdust, straw, organic matter, humus or other biomass by biochemical methods, which is called biochemical fulvic acid (BFA).

[0041] Fulvic acid is a gray-black powdery substance soluble in water. It is a natural macromolecular organic substance with a negative charge and weak acidity. It can combine with metal ions to form salts. Due to its complex molecular structure, it contains a variety of functional groups, such as carboxyl, phenolic hydroxyl, etc., which give it good ion exchange capacity and chemical reaction activity.

[0042] This embodiment uses fulvic acid as raw material. The main elements of fulvic acid are carbon, hydrogen, oxygen, nitrogen and sulfur. Fulvic acid contains more active functional groups, and its products are green products in agricultural development, which play a very important role in protecting the environment and protecting human health.

[0043] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the mass of the deionized water solution in step 2 is 30 to 50 times the mass of fulvic acid. The other steps and parameters are the same as those in specific embodiment 1.

[0044] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the mass of the deionized water solution in step 2 is 40 times the mass of fulvic acid. The other steps and parameters are the same as those in specific implementation method 1 or 2.

[0045] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the stirring time in step 3 is 1.5 to 2.5 hours. The other steps and parameters are the same as those of specific embodiments 1 to 3.

[0046] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that the stirring time in step 3 is 2 hours. The other steps and parameters are the same as those of specific implementation methods 1 to 4.

[0047] Specific Embodiment Six: The difference between this embodiment and one of Embodiments One to Five is that: the drying temperature of the filter residue in Step Four is 60 ± 5 °C. Other steps and parameters are the same as those in one of Embodiments One to Five.

[0048] Specific Embodiment Seven: The difference between this embodiment and one of Embodiments One to Six is that: the drying temperature of the filter residue in Step Four is 60 °C. Other steps and parameters are the same as those in one of Embodiments One to Six.

[0049] Specific Embodiment Eight: The difference between this embodiment and one of Embodiments One to Seven is that: the drying time of the filter residue in Step Four is 8 - 12 h. Other steps and parameters are the same as those in one of Embodiments One to Seven.

[0050] Example 1

[0051] In this example, the modifiers with 4 different raw material ratios are all prepared by the preparation method of the soil modifier of the present invention.

[0052] Modifier A: Step One: Weigh 1 part of fulvic acid, 1 part of anhydrous calcium chloride, and 1 part of anhydrous magnesium chloride for standby according to mass parts;

[0053] Step Two: Dissolve the above-mentioned fulvic acid in deionized water solution with a mass 40 times that of the fulvic acid to make a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride and anhydrous magnesium chloride to the fulvic acid solution;

[0054] Step Three: Stir for 2 h to mix evenly;

[0055] Step Four: Transfer the stirred mixture into a hydrothermal reaction kettle and heat it at 180 °C for 20 h;

[0056] Step Five: After the hydrothermal reaction, cool to room temperature, filter by suction, and dry the filter residue at 60 °C for 12 h;

[0057] Step Six: Grind the dried filter residue to obtain Modifier A.

[0058] Modifier B (the soda saline-alkali soil modifier of the present invention): Step One: Weigh 8 parts of fulvic acid, 8 parts of anhydrous calcium chloride, 8 parts of anhydrous magnesium chloride, and 1 part of anhydrous aluminum chloride for standby according to mass parts;

[0059] Step Two: Dissolve the above-mentioned fulvic acid in deionized water solution with a mass 40 times that of the fulvic acid to make a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride, anhydrous magnesium chloride, and anhydrous aluminum chloride to the fulvic acid solution;

[0060] Step Three: Stir for 2 h to mix evenly;

[0061] Step Four: Transfer the stirred mixture into a hydrothermal reaction kettle and heat it at 180 °C for 2 h;

[0062] Step 5: After the hydrothermal reaction, cool to room temperature, perform suction filtration, and dry the filter residue at 60°C for 12 h;

[0063] Step 6: Grind the dried filter residue to obtain the modifier B.

[0064] Modifier C: Step 1: Weigh 4 parts of fulvic acid, 4 parts of anhydrous calcium chloride, 4 parts of anhydrous magnesium chloride, and 1 part of anhydrous aluminum chloride according to mass parts for standby;

[0065] Step 2: Dissolve the above-mentioned fulvic acid in deionized water solution with a mass 40 times that of the fulvic acid to make a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride, anhydrous magnesium chloride, and anhydrous aluminum chloride to the fulvic acid solution;

[0066] Step 3: Stir for 2 h to mix evenly;

[0067] Step 4: Transfer the stirred mixture into a hydrothermal reaction kettle and heat at 180°C for 2 h;

[0068] Step 5: After the hydrothermal reaction, cool to room temperature, perform suction filtration, and dry the filter residue at 60°C for 12 h;

[0069] Step 6: Grind the dried filter residue to obtain the modifier C.

[0070] Modifier D: Step 1: Weigh 2 parts of fulvic acid, 2 parts of anhydrous calcium chloride, 2 parts of anhydrous magnesium chloride, and 1 part of anhydrous aluminum chloride according to mass parts for standby;

[0071] Step 2: Dissolve the above-mentioned fulvic acid in deionized water solution with a mass 40 times that of the fulvic acid to make a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride, anhydrous magnesium chloride, and anhydrous aluminum chloride to the fulvic acid solution;

[0072] Step 3: Stir for 2 h to mix evenly;

[0073] Step 4: Transfer the stirred mixture into a hydrothermal reaction kettle and heat at 180°C for 2 h;

[0074] Step 5: After the hydrothermal reaction, cool to room temperature, perform suction filtration, and dry the filter residue at 60°C for 12 h;

[0075] Step 6: Grind the dried filter residue to obtain the modifier D.

[0076] The modifier A, modifier B, modifier C, and modifier D prepared in this example are all powdery solids.

[0077] Performance experiment:

[0078] Control group: Take 4.0 g of soda saline-alkali soil that has been ground and passed through a 1 mm sieve. Do not add any amendment, vortex for 60 seconds to mix evenly, then add 1.0 ml of deionized water and vortex for another 60 seconds to mix evenly.

[0079] Amendment A group: Take 0.04 g of Amendment A and add it to 3.96 g of soda saline-alkali soil that has been ground and passed through a 1 mm sieve. Vortex for 60 seconds to mix evenly, then add 1.0 ml of deionized water and vortex for another 60 seconds to mix evenly.

[0080] Amendment B group: Take 0.04 g of Amendment B and add it to 3.96 g of soda saline-alkali soil that has been ground and passed through a 1 mm sieve. Vortex for 60 seconds to mix evenly, then add 1.0 ml of deionized water and vortex for another 60 seconds to mix evenly.

[0081] Amendment C group: Take 0.04 g of Amendment C and add it to 3.96 g of soda saline-alkali soil that has been ground and passed through a 1 mm sieve. Vortex for 60 seconds to mix evenly, then add 1.0 ml of deionized water and vortex for another 60 seconds to mix evenly.

[0082] Amendment D group: Take 0.04 g of Amendment D and add it to 3.96 g of soda saline-alkali soil that has been ground and passed through a 1 mm sieve. Vortex for 60 seconds to mix evenly, then add 1.0 ml of deionized water and vortex for another 60 seconds to mix evenly.

[0083] Among them, the soda saline-alkali soil is from the Da'an Alkali Land Ecosystem Experimental Station in China, located in the abdomen of the saline-alkali land in the Songnen Plain. This area is a typical representative region of moderately to severely soda saline-alkali land, and the pH value of the collected soil sample is 9.10.

[0084] After application, let it stand at room temperature. Measure the pH value of the soil samples at 24 h, 7 d, 14 d, 21 d, and 28 d respectively. At the same time, conduct performance tests on the soil amendments.

[0085] Experimental results:

[0086] The pH measurement results of the amendments themselves and the amended soil are shown in Table 1.

[0087] Table 1

[0088]

[0089] It can be seen from the pH measurement values in Table 1 that the amendments prepared from fulvic acid and Ca, Mg, and Al are all acidic, and with the increase of the Al element addition amount, the pH of the material shows an obvious downward trend. The pH of Amendments A to D gradually decreases (from 5.74 to 3.68), mainly because with the increase of the aluminum chloride (AlCl3) addition amount, Al 3+ hydrolyzes strongly in aqueous solution to form aluminum hydroxide and releases a large amount of H +, resulting in an increase in the acidity of the solution. Fulvic acid itself is weakly acidic, while neutral salts (CaCl2, MgCl2) have little effect on pH, but the hydrolysis reaction of AlCl3 dominates the pH change, and the greater its dosage, the higher the concentration of H + , and the more significant the pH drop. The hydrothermal reaction may further promote hydrolysis and exacerbate the acidification trend.

[0090] When soil conditioners A, B, C, and D were applied at an addition amount of 1.0% respectively for 24 hours, the pH of the soda saline-alkali soil decreased by 0.4 - 0.6 units. One week after the application of the materials, the pH value of the soil further decreased, reaching a minimum of 8.21. As time continued to increase, the rate of pH decrease tended to level off without a rebound, proving that this type of soil conditioner can rapidly reduce the pH of soda saline-alkali soil and can well maintain the stability of soil physical and chemical properties.

[0091] To evaluate the advantages of the performance of soil conditioners, it is also necessary to examine the properties of the materials themselves on the premise of ensuring the effect. Therefore, the scanning electron microscope images, specific surface area, X-ray diffraction patterns, and electrochemical related curves of the four conditioners were tested and analyzed.

[0092] From the scanning electron microscope images ( Figures 1 to 4 ) of each conditioner in this example, it can be seen that conditioners A, C, and D are mainly layered spherical structures, and the spheres are connected to each other. Conditioner B shows a layered stacking structure, that is, the layered morphology of hydrotalcite-like. And conditioner B also has the best application effect, which may be related to the high specific surface area, adjustable layer spacing, and ordered pore structure of the LDH material. As shown in the data in Table 2, the specific surface area and total pore volume of conditioner B are significantly higher than those of the other three conditioners, indicating that its pore structure is the most developed and has a high adsorption potential. More notably, conditioner B has the largest pore diameter, with an average pore diameter of 18.41 nm, which is suitable for adsorbing macromolecules or rapid mass transfer, but the proportion of micropores may be low. Conditioner A is dominated by micropores, and the most probable micropore diameter is 2.18 nm (the largest), indicating that its micropore proportion is high and it may be more effective in adsorbing small molecules. D has the smallest pore diameter, with an average pore diameter of only 8.72 nm, which may limit the adsorption of macromolecules, but the micropores are dense and the total pore volume is not significantly reduced.

[0093] The specific surface area and pore diameter of each conditioner in Example 1 of this embodiment are respectively as Figure 5 and Figure 6 shown. From the Figure 5 specific surface area analysis, the adsorption amount in the low-pressure region is contributed by micropores, and materials with a high specific surface area (conditioners B and C) perform better. In the high-pressure region, macropores / mesopores begin to play a role, and the adsorption amount of materials with a large total pore volume (conditioner B) continues to increase. From Figure 6From the analysis of the pore size distribution diagram, it can be seen that the distribution of modifier B shows a peak in the larger pore size region (>10 nm), which is consistent with the average pore size data, indicating that it may contain more mesopores / macropores. The distribution of modifier A has a peak concentrated around 2 - 3 nm, with a very high proportion of micropores but a relatively low total pore volume. The distribution of modifier C is between A and B, with a more balanced pore size distribution. The peak of the distribution of modifier D is around 2.12 nm, but the average pore size is small, indicating that the pore size distribution is concentrated and relatively small.

[0094] Table 2

[0095] Name Specific surface area Total pore volume Average pore diameter Most probable micropore diameter <![CDATA[(m 2 / g)]]> <![CDATA[(cm 3 / g)]]> (nm) (nm) Modifier A 6.0542 0.0155 10.2408 2.1800 Modifier B 20.7335 0.0954 18.4050 2.1000 Modifier C 8.7125 0.0354 16.2525 2.1200 Modifier D 5.9179 0.0129 8.7193 2.1200

[0096] In addition, through X-ray Diffraction (XRD), the crystal structures of each modifier were determined as Figure 7 shown. Through analysis, it was found that the modifiers prepared in this example mainly consist of anhydrous calcium sulfate phase and a compound containing aluminum and sulfate, (H3O)Al3(SO4)2(OH)6 phase. (H3O)Al3(SO4)2(OH)6 is a compound containing aluminum and sulfate, which does not occur naturally and should be prepared by hydrothermal synthesis method.

[0097] As shown by the results of the cyclic voltammetry (CV) diagram ([[]] Figure 8 ), modifiers A and B show higher oxidation-reduction peak current densities at specific potentials, indicating higher catalytic activity, faster reaction rate or larger effective surface area. Modifiers C and D with lower current densities may have lower activity due to slow reaction kinetics or large interfacial resistance. Among them, the CV curve of modifier B has the most symmetric peak shape and the smallest ΔEp, indicating the best reaction reversibility.

[0098] From the electrochemical impedance spectroscopy (EIS) diagram ([[]] Figure 9 ), it can be seen that the semicircle diameter of modifier C is the smallest, indicating the lowest interfacial charge transfer resistance and the fastest electrochemical response; the semicircle diameter of modifier A is larger, which may be due to interfacial passivation or adsorption layer hindering charge transfer; the slope of the low-frequency region of modifier B is the steepest, indicating the smallest diffusion resistance and being suitable for applications requiring fast mass transfer. Through comprehensive analysis, it can be obtained that modifier B has a symmetric peak shape, good reversibility, steep slope, best balance performance and high comprehensive efficiency.

[0099] Through comprehensive analysis, it is considered that the application effect and material properties of modifier B (LDHs) with a layered stacked structure are the best.

Claims

1. A preparation method of a soda saline soil conditioner, characterized in that The preparation method of the soda saline-alkali soil conditioner is as follows: Step 1: Weigh 8 parts of fulvic acid, 8 parts of anhydrous calcium chloride, 8 parts of anhydrous magnesium chloride and 1 part of anhydrous aluminum chloride for standby according to mass parts; Step 2: Dissolve the above-mentioned fulvic acid in deionized water solution to make a fulvic acid solution, and then add the above-mentioned anhydrous calcium chloride, anhydrous magnesium chloride and anhydrous aluminum chloride into the fulvic acid solution; Step 3: Stir and mix evenly; Step 4: Transfer the stirred mixture into a hydrothermal reaction kettle and heat it at 180±5°C for 20±0.5 h; Step 5: After the hydrothermal reaction is completed, cool it to room temperature, filter by suction, and dry the filter residue at low temperature; Step 6: Grind the dried filter residue to obtain the soda saline-alkali soil conditioner.

2. The preparation method of a soda saline soil conditioner according to claim 1, characterized in that In Step 2, the mass of the deionized water solution is 30 to 50 times the mass of the fulvic acid.

3. The preparation method of a soda saline soil conditioner according to claim 1, characterized in that, In Step 3, the stirring time is 1.5 to 2.5 h.

4. The preparation method of a soda saline soil conditioner according to claim 1, characterized in that, In Step 4, the drying temperature of the filter residue is 60±5°C.

5. The preparation method of a soda saline soil conditioner according to claim 4, characterized in that, In Step 4, the drying time of the filter residue is 8 to 12 h.

6. A soda saline soil conditioner, characterized in that, The soda saline-alkali soil conditioner prepared by the method according to any one of claims 1 to 5.

7. The soda saline soil conditioner according to claim 6, wherein, The soda saline-alkali soil conditioner is a hydrotalcite-like intercalation material.

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