Attapulgite / calcium silicate composite material and application thereof in acidic soil remediation

Abstract

The application discloses a palygorskite / calcium silicate composite material. The palygorskite / calcium silicate composite material is composed of calcium silicate and modified palygorskite, wherein the modified palygorskite is palygorskite modified by succinic acid and catechin, and the modified palygorskite is loaded on the surface of the calcium silicate. Compared with the prior art, the application combines the modified palygorskite and the calcium silicate to form a synergistic effect, so that the acid soil can be repaired efficiently, economically and sustainably.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation, specifically relating to an attapulgite / calcium silicate composite material for acidic soil remediation. Background Technology

[0002] Attapulgite (also known as palygorskite) is a hydrous magnesium-aluminate silicate clay mineral with a unique layered crystal structure and rod-shaped and fibrous crystal morphology. Its honeycomb-like pore structure creates a large specific surface area (up to 369 m² / g), exhibiting excellent adsorption performance. In the field of acid soil remediation, attapulgite mainly functions through the following mechanisms: In terms of physicochemical properties, the adsorption mechanism of attapulgite is divided into internal surface adsorption and external surface adsorption. When the diameter of the adsorbed molecule is smaller than the pore diameter of attapulgite (approximately 0.38 × 0.63 nm), the adsorption mechanism is internal surface adsorption; when the molecule diameter is larger than the pore diameter, it functions through colloidal adsorption and ion exchange adsorption on the external surface. The surface charge characteristics of attapulgite are affected by the mineral structure, electrolyte concentration, and solution pH. The hydroxyl group on the R-OH group is amphoteric, acting as both an acid and a base, reacting with H+. + or OH - This process helps regulate soil pH.

[0003] Calcium silicate (CaSiO3) is an alkaline silicate mineral with unique chemical structure and physical properties. In acidic soil remediation, it primarily functions through the following mechanisms: Chemically, calcium silicate produces Ca through hydrolysis. 2+ and OH - It neutralizes soil acidity and increases pH value. Summary of the Invention

[0004] The purpose of this invention is to combine attapulgite and calcium silicate to achieve a synergistic effect, providing an efficient, economical, and sustainable technical solution for the remediation of acidic soils.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An attapulgite / calcium silicate composite material is characterized in that: the attapulgite / calcium silicate composite material is composed of calcium silicate and modified attapulgite, wherein the modified attapulgite is attapulgite modified with succinic acid and catechin, and the modified attapulgite is loaded on the surface of calcium silicate.

[0007] Preferably, the modified attapulgite is prepared by a method comprising the following steps:

[0008] First, thoroughly mix succinic acid with attapulgite that has undergone crystal bundle dissociation, and then add catechin and mix thoroughly.

[0009] Preferably, the amount of succinic acid is 0.5-2 wt% of attapulgite, and the amount of catechin is 1-5 wt% of attapulgite.

[0010] More preferably, succinic acid is dissolved in water before mixing.

[0011] More preferably, the catechins are dissolved in ethanol before mixing.

[0012] More preferably, the particle size of attapulgite is ≥3000 mesh, and the particle size of calcium silicate is 150~300 mesh.

[0013] More preferably, the amount of succinic acid is 1 wt% of attapulgite, and the amount of catechin is 3 wt% of attapulgite.

[0014] Preferably, the step of dissociating attapulgite crystal bundles includes:

[0015] The potassium hydroxide solution is sprayed evenly onto the surface of the attapulgite, and after standing for a certain period of time, it is pressed by rollers.

[0016] More preferably, the concentration of the potassium hydroxide solution is 20-30 wt%, and the amount of potassium hydroxide used is 5-10 wt% of attapulgite.

[0017] More preferably, the settling time is 12 to 24 hours.

[0018] Preferably, the mass ratio of calcium silicate to modified attapulgite is 5:1 to 1:1.

[0019] Preferably, the calcium silicate and the modified attapulgite are mixed in a stirred mill.

[0020] Under the action of a stirred mill, a mechanochemical effect occurs between calcium silicate and modified attapulgite, causing the modified attapulgite to be loaded on the surface of calcium silicate, forming a cockle-like composite powder.

[0021] Application of the above-mentioned attapulgite / calcium silicate composite material in acidic soil remediation.

[0022] An acidic soil remediation agent comprises, as described above, attapulgite / calcium silicate composite material, microbial inoculants, and organic fertilizer, wherein the microbial inoculants include acid-resistant Lactobacillus, Bacillus subtilis, Bacillus megaterium, slow-growing rhizobium WP5, and Rhizocystis heterophylla.

[0023] Preferably, the content of the attapulgite / calcium silicate composite material in the acidic soil remediation agent is above 90 wt%.

[0024] Preferably, the amount of microbial inoculant used is 1-5 wt% of the organic fertilizer.

[0025] More preferably, the mass ratio of acid-resistant Lactobacillus, Bacillus subtilis, Bacillus megaterium, slow-growing rhizobium WP5 and Rhizocystis heterophylla is 3:1:1:5:0.5.

[0026] The preparation method of the above-mentioned acidic soil remediation agent includes:

[0027] Granulation of attapulgite / calcium silicate composite material into particles A;

[0028] Microbial agents and organic fertilizers are mixed and granulated to produce granules B;

[0029] Mix particles A and particles B.

[0030] Preferably, the diameter of particle A is 2-3 mm and the diameter of particle B is 2-3 mm. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0032] Example 1

[0033] 1. Crystal bundle dissociation of attapulgite:

[0034] 1.1. Crush the raw attapulgite ore, air dry it naturally until the moisture content is no more than 5%, and then grind it to 80 mesh, which is recorded as ATP-0.

[0035] 1.2. Under stirring, a 20-30 wt% potassium hydroxide solution is evenly sprayed onto the surface of ATP-0. After mixing, it is allowed to stand for 24 hours, and this is recorded as ATP-1. The amount of potassium hydroxide used is 5-10% of the mass of ATP-0. After this step, the attapulgite crystal bundles can be more easily dissociated under the extrusion of rollers.

[0036] 1.3. ATP-1 is pressed twice on a three-roll mill (220 rpm, roller speed ratio 1:3:9, roller spacing 0.5 mm) to fully dissociate the attapulgite, and this is recorded as ATP-2.

[0037] 2. Modification of attapulgite:

[0038] After ATP-2 is pulverized to a fineness of 3000 mesh or higher, it is added to a high-speed mixer. Then, a 5-10 wt% succinic acid aqueous solution (succinic acid is 1% of the mass of ATP-2) is added. The mixture is stirred at 200 rpm for 20 minutes. Then, a 10-15 wt% catechin ethanol solution (catechin is 3% of the mass of ATP-2) is added. The mixture is stirred at 200 rpm for another 10 minutes to obtain modified attapulgite, denoted as ATP-3.

[0039] 3. Crush calcium silicate to about 200 mesh, then mix it with ATP-3 at a mass ratio of 3:1. Add the mixture to a stirring mill and stir and grind it at 500 rpm for 15 minutes to load ATP-3 onto the surface of calcium silicate, forming a burdock-like composite powder. Finally, granulate the powder to prepare particles with a diameter of 2-3 mm, denoted as ATP-Si.

[0040] Comparative Example 1

[0041] The preparation process is the same as that of ATP-Si in Example 1, except that catechins were not used in the modification of attapulgite.

[0042] Comparative Example 2

[0043] The preparation process is the same as that of ATP-Si in Example 1, except that succinic acid was not used in the modification of attapulgite.

[0044] Comparative Example 3

[0045] The preparation process is the same as that of ATP-Si in Example 1. The only difference is that after calcium silicate and ATP-3 are mixed evenly, they are not added to a stirring mill but are directly granulated to produce particles with a diameter of 2-3 mm.

[0046] Example 3

[0047] Commercially available acid-resistant Lactobacillus, Bacillus subtilis, Bacillus megaterium, slow-growing rhizobium WP5, and Rhizocystis heterophylla were mixed in a mass ratio of 3:1:1:5:0.5. Then, the mixture was added to organic fertilizer (Gansu Juyuanda Biotechnology Co., Ltd., model JYD-2) at 3 wt% of the organic fertilizer mass. After thorough mixing, the mixture was granulated into particles with a diameter of 2-3 mm, denoted as OR-MI.

[0048] The ATP-Si and OR-MI from Example 1 were mixed evenly at a mass ratio of 10:1 and denoted as ASOM.

[0049] Example 4

[0050] The experiment was conducted in an acidic field (soil pH 5.1, active aluminum ion content 0.3 ppm). One mu (approximately 0.067 hectares) of corn was planted in both the experimental and control groups. The remediation agent was applied at a rate of 800 kg / mu (approximately 500 kg / hectare), and other fertilization and field management were carried out as usual. The remediation agents used in each experimental group were the products prepared in Examples 1-3 and Comparative Examples 1-2, respectively. Specific results are shown in Tables 1 and 2.

[0051] Active aluminum ions were determined using microwave digestion-inductively coupled plasma atomic emission spectrometry.

[0052] Fifteen days after applying the remediation agent, the soil pH and active aluminum ion content were measured again.

[0053] Table 1 Soil physicochemical properties and maize yield after application of different remediation agents

[0054]

[0055] Table 2. Effects of combined use of attapulgite / calcium silicate composite material with microbial inoculants / organic fertilizer

[0056]

[0057] in conclusion:

[0058] (1) The comparison between ATP-Si and Comparative Examples 1-2 shows that, compared with attapulgite modified with succinic acid or catechin, attapulgite modified with succinic acid and catechin, when combined with calcium silicate, can significantly improve the remediation effect of acidic soil.

[0059] (2) If ATP-3 and calcium silicate are simply mixed, acidic soil will become alkalized in a short period of time, causing the other extreme damage to the soil, namely, turning it into alkaline soil. The same problem exists when calcium silicate is applied alone. Reducing the amount of remediation agent applied can alleviate this damage, but the effect is short-lived and requires repeated application, which is extremely inconvenient. Compared with simple mixing, after loading ATP-3 onto the surface of calcium silicate to form a cocklebur-like composite powder by mechanochemical method, the release of calcium silicate can be slowed down, avoiding the alkalization damage to acidic soil at high application rates. The effect lasts for a long time, and only one application per year is needed.

[0060] (3) Microbial agents / organic fertilizers have almost no remediation effect on acidic soils, which prevents corn crops from growing. However, when microbial agents / organic fertilizers are combined with ATP-3, they can significantly improve the remediation effect of the attapulgite / calcium silicate composite material of this invention on acidic soils and corn yield.

[0061] Example 5

[0062] Calcium silicate is pulverized to about 200 mesh, then mixed with ATP-3 from Example 1 at a mass ratio of 5:1. The mixture is then added to a stirring mill and stirred and ground at 500 rpm for 15 minutes to load ATP-3 onto the surface of calcium silicate, forming a burdock-like composite powder. Finally, the powder is granulated to prepare particles with a diameter of 2-3 mm.

[0063] Example 6

[0064] 1. After pulverizing ATP-2 from Example 1 to a fineness of 3000 mesh or higher, add it to a high-speed mixer. Then add a 5-10 wt% succinic acid aqueous solution (succinic acid is 1.5% of the mass of ATP-2). Stir at 200 rpm for 20 minutes. Then add a 10-15 wt% catechin ethanol solution (catechin is 4% of the mass of ATP-2) and continue stirring at 200 rpm for 10 minutes to obtain modified attapulgite, denoted as ATP-3-1.

[0065] 2. Crush calcium silicate to about 200 mesh, then mix it with ATP-3-1 at a mass ratio of 3:1. Then add it to a stirring mill and stir and grind at 500 rpm for 15 minutes to load ATP-3-1 onto the surface of calcium silicate, forming a burdock-like composite powder. Finally, granulate the powder to prepare particles with a diameter of 2-3 mm.

[0066] Example 7

[0067] 1. After pulverizing ATP-2 from Example 1 to a fineness of 3000 mesh or higher, add it to a high-speed mixer. Then add a 5-10 wt% succinic acid aqueous solution (succinic acid is 0.5% of the mass of ATP-2). Stir at 200 rpm for 20 minutes. Then add a 10-15 wt% catechin ethanol solution (catechin is 1.5% of the mass of ATP-2) and continue stirring at 200 rpm for 10 minutes to obtain modified attapulgite, denoted as ATP-3-2.

[0068] 2. Crush calcium silicate to about 200 mesh, then mix it with ATP-3-2 at a mass ratio of 1:1. Add the mixture to a stirring mill and stir and grind at 500 rpm for 15 minutes to load ATP-3-2 onto the surface of calcium silicate, forming a burdock-like composite powder. Finally, granulate the powder to prepare particles with a diameter of 2-3 mm.

[0069] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An attapulgite / calcium silicate composite material, characterized in that: The attapulgite / calcium silicate composite material is composed of calcium silicate and modified attapulgite, wherein the modified attapulgite is attapulgite modified with succinic acid and catechin, and the modified attapulgite is loaded on the surface of calcium silicate.

2. The attapulgite / calcium silicate composite material according to claim 1, characterized in that: The modified attapulgite is prepared by a method including the following steps: First, thoroughly mix succinic acid with attapulgite that has undergone crystal bundle dissociation, and then add catechin and mix thoroughly.

3. The attapulgite / calcium silicate composite material according to claim 2, characterized in that: The amount of succinic acid is 0.5-2 wt% of attapulgite, and the amount of catechin is 1-5 wt% of attapulgite. Preferably, the particle size of attapulgite is ≥3000 mesh, and the particle size of calcium silicate is 150-300 mesh.

4. The attapulgite / calcium silicate composite material according to claim 3, characterized in that: The amount of succinic acid used is 1 wt% of attapulgite, and the amount of catechin used is 3 wt% of attapulgite.

5. The attapulgite / calcium silicate composite material according to claim 1, characterized in that: The steps involved in the dissociation of attapulgite crystal bundles include: The potassium hydroxide solution is evenly sprayed onto the surface of the attapulgite, and after standing for a certain period of time, it is pressed by rollers. Preferably, the concentration of the potassium hydroxide solution is 20-30 wt%, and the amount of potassium hydroxide used is 5-10 wt% of attapulgite. Preferably, the settling time is 12 to 24 hours.

6. The attapulgite / calcium silicate composite material according to claim 1, characterized in that: The mass ratio of calcium silicate to modified attapulgite is 5:1 to 1:

1.

7. The attapulgite / calcium silicate composite material according to claim 1, characterized in that: The calcium silicate and the modified attapulgite are mixed in a stirred mill.

8. The application of the attapulgite / calcium silicate composite material according to any one of claims 1 to 7 in the remediation of acidic soil.

9. An acidic soil remediation agent, comprising the attapulgite / calcium silicate composite material as described in any one of claims 1 to 7, a microbial agent, and organic fertilizer, wherein the microbial agent comprises acid-resistant Lactobacillus, Bacillus subtilis, Bacillus megaterium, slow-growing rhizobium WP5, and Rhizocystis heterophylla; preferably, the content of the attapulgite / calcium silicate composite material in the acidic soil remediation agent is above 90 wt%, and the amount of the microbial agent is 1 to 5 wt% of the organic fertilizer; preferably, the mass ratio of acid-resistant Lactobacillus, Bacillus subtilis, Bacillus megaterium, slow-growing rhizobium WP5, and Rhizocystis heterophylla is 3:1:1:5:0.

5.

10. A method for preparing the acidic soil remediation agent according to claim 9, comprising: Granulation of attapulgite / calcium silicate composite material into particles A; Microbial agents and organic fertilizers are mixed and granulated to produce granules B; Mix particles A and particles B; Preferably, the diameter of particle A is 2-3 mm and the diameter of particle B is 2-3 mm.

Images