Preparation method and application of KGA adsorbent

Abstract

The invention discloses a preparation method and application of a KGA adsorbent, and the preparation method of the KGA adsorbent comprises the following steps: carrying out primary ultrasonic uniform stirring on kaolinite and water, standing, and carrying out secondary ultrasonic uniform stirring to obtain a suspension; adding a FeCl3 solution into the suspension, and stirring to obtain a goethite mixed solution; adding a regulator into the goethite mixed solution to regulate the pH to weak acidity, adding a reducing agent to regulate the pH to weak acidity, aging at constant temperature, centrifuging, washing with water, drying and grinding to obtain the KGA adsorbent. The method is low in material cost, environmentally friendly, free of secondary pollution and easy and convenient to operate, and an efficient new way is provided for in-situ remediation of organic pollutants such as glyphosate in soil and sediments. The adsorbent KGA is prepared from goethite and kaolinite, so that efficient, low-consumption and environment-friendly adsorption and degradation of glyphosate are realized. KGA is used as a glyphosate adsorbent. The adsorption capacity is improved to 2.67 times through the synergistic effect of KGA, and the KGA has catalytic activity and provides a better solution for sediment repair.

Description

Technical Field

[0001] This invention belongs to the field of adsorption and purification technology, specifically relating to a method for preparing KGA adsorbent and its application. Background Technology

[0002] Kaolinite is a layered aluminosilicate mineral with the molecular formula Al₂Si₂O₅(OH)₄. It consists of a silicon-oxygen tetrahedral layer and an aluminum-oxygen octahedral layer, exhibiting a stable structure. Its surface functional groups are mainly Si-OH and Al-OH, giving it good hydrophilicity. Its specific surface area is typically 10⁻³⁰ m² / g. 2 With a zeta potential of approximately -20 mV at neutral pH, its adsorption performance mainly relies on electrostatic adsorption, hydrogen bonding, and surface complexation, making it suitable for adsorbing metal cations or some small organic molecules. However, due to its low cation exchange capacity and active site density, its adsorption capacity for anionic pollutants such as glyphosate is limited.

[0003] Kaolinite, a natural layered silicate clay mineral, is widely used in aquatic organic pollutant adsorption research due to its large specific surface area, abundant surface hydroxyl groups, and strong cation exchange capacity. Its mechanism of action mainly relies on the physical retention of organic matter by the interlayer domain, hydrogen bonding between surface hydroxyl groups and pollutants, and the fixation of positively charged pollutant molecules through ion exchange. Existing research shows that kaolinite has good adsorption performance for hydrophobic organic compounds such as phenols and dyes, but its application in the remediation of glyphosate in river sediments has significant limitations. Glyphosate molecules contain phosphate, amino, and carboxylic acid groups. Due to their strong polarity and high water solubility, they are easily competitive with humic acids and metal ions, leading to reduced adsorption efficiency. Furthermore, the electrostatic repulsion between the negative charge on the kaolinite surface and the glyphosate anionic groups further reduces adsorption efficiency. In addition, river sediments are porous and highly heterogeneous, making it difficult for kaolinite to penetrate deep into the pollutant interface due to pore blockage, and it lacks redox active sites, thus failing to effectively degrade adsorbed glyphosate.

[0004] Goethite, due to its high surface hydroxyl activity, variable iron valence state, and specific binding ability with phosphate, is an ideal material for modifying kaolinite. By constructing a goethite-loaded layer on the kaolinite surface in situ, a complex is formed that synergistically enhances the adsorption and degradation of glyphosate. Compared to bioremediation, chemical oxidation techniques, or simple physical mixing, which have weak synergistic effects and are prone to aggregation, this goethite-modified kaolinite complex (KGA) combines environmental compatibility, long-term stability, and low cost. Summary of the Invention

[0005] This invention aims to solve the problem of containing K + The technical problem of glyphosate adsorption and degradation in sediments.

[0006] To solve the above problems, this application provides the following technical solution: A method for preparing a KGA adsorbent includes the following steps: S1. Kaolinite and water are ultrasonically stirred once, allowed to stand, and ultrasonically stirred a second time to obtain a suspension. S2. Add FeCl3 solution to the suspension in step S1 and stir to obtain a goethite mixture; S3. Add a regulator to the goethite mixture in step S2 to adjust the pH to weakly acidic, add a reducing agent, add another regulator to adjust to weakly acidic again, age at constant temperature, centrifuge, wash with water, dry, and grind to obtain KGA adsorbent.

[0007] In step S1, the mass ratio of kaolinite to water is 1:10~12.

[0008] In step S1, the ultrasonic stirring rate is 80-100 rpm and the ultrasonic time is 15-20 min; the settling time is 30-40 min; the ultrasonic stirring rate is 80-100 rpm and the ultrasonic stirring time is 15-20 min.

[0009] In step S2, the mass ratio of suspension to FeCl3 is 1:0.9~1.

[0010] In step S2, the stirring rate is 1600~2000 rpm and the stirring time is 40~60 min.

[0011] In step S3, the pH adjuster is either KOH or NaOH; the pH adjuster concentration is 0.05 mol / L to 1 mol / L, and the pH adjuster used for the first pH adjustment is the same as that used for the second pH adjustment.

[0012] In step S3, the ratio of goethite mixture to reducing agent is 1:0.00198~0.00208 by mass.

[0013] In step S3, the reducing agent is either FeCl2 or FeSO4·7H2O.

[0014] Preferably, in step S3, the pH is adjusted to a slightly acidic pH of 6.20 ± 0.02. Preferably, in step S3, the pH is adjusted to a slightly acidic level of 6.20 ± 0.02. Preferably, in step S3, the constant temperature is 45℃~60℃.

[0015] Preferably, in step S3, the aging time is 6-7 days.

[0016] Preferably, in step S3, the water washing conductivity is less than 6 μS / cm.

[0017] Preferably, in step S3, the particle size after grinding is 0.074 mm ~ 0.154 mm.

[0018] Preferably, in step S3, the product is dried at 35℃~40℃ for 1~2 days.

[0019] The application of the KGA adsorbent prepared by the method in the adsorption of glyphosate.

[0020] The application described above, the method for adsorbing glyphosate with KGA adsorbent also includes the following steps: N1. Dissolve the KGA adsorbent in KCl solution to obtain a KGA extractant solution; N2. Glyphosate is dissolved in the KGA extractant solution from step N1 to obtain a glyphosate mixture; N3. Purge the glyphosate mixture from step N2 with nitrogen, adjust the pH with alkali, and stir and shake at room temperature to obtain the extract.

[0021] Preferably, in step N1, the ratio of KGA adsorbent to KCl solution is 0.4g: 190 ml ~ 210 ml.

[0022] Preferably, in step N1, the concentration of the KCl solution is 0.005~0.05 mol / L.

[0023] Preferably, in step N2, the ratio of glyphosate to KGA extractant solution is 0.06 g to 190 ml to 210 ml.

[0024] Preferably, in step N3, nitrogen purging is performed for 15-20 minutes at a flow rate of 0.05-0.1 L / min.

[0025] Preferably, in step N3, the alkali adjuster is either NaOH or NaHCO3; Preferably, in step N3, the alkali adjuster is 0.01~0.1 mol / L; Preferably, in step N3, the pH is 3.5~5.0.

[0026] Preferably, in step N3, the stirring speed is 150~300 r / min, the shaking time is 12~48 h, and the shaking frequency is 2.5~5.0 Hz.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Kaolinite (KGA) is widely available, inexpensive, and simple to prepare. KGA's adsorption capacity for glyphosate reaches 111.64 mg / g, 2.67 times that of pure kaolinite. Goethite drives the oxidative degradation of glyphosate through catalysis, while the kaolinite carrier enriches pollutants and provides a dispersion interface through its large specific surface area. The two work synergistically to achieve an adsorption-catalysis cycle, significantly improving degradation efficiency. KGA is a natural mineral raw material, non-toxic and harmless, and the degradation process does not produce harmful secondary pollutants.

[0028] 2. KGA exhibits excellent permeability and adsorption-catalytic synergy in the adsorption of glyphosate, blocking glyphosate migration and driving its efficient degradation, reducing the accumulation of harmful intermediate products. KGA is used to in-situ load goethite particles onto the surface of kaolinite via co-precipitation. This invention also relates to the application of KGA in the adsorption and degradation of glyphosate residues, where KGA combines adsorption and catalytic degradation functions, resulting in superior performance.

[0029] 3. Achieving efficient, low-consumption, and environmentally friendly adsorption and degradation of glyphosate using KGA, an adsorbent prepared from goethite and kaolinite. This invention uses KGA as a glyphosate adsorbent, providing a solution for in-situ remediation of glyphosate pollution in complex matrices. The synergistic effect of KGA enhances its adsorption capacity and catalytic activity, offering a superior solution for sediment remediation.

[0030] 4. KGA is prepared by co-precipitation, that is, by introducing Fe into a kaolinite suspension. 3+ / Fe 2+ The pH was adjusted to induce the in-situ formation of goethite particles on the kaolinite surface. The KGA composite material combines the advantages of both methods, exhibiting a significant synergistic effect. Because the goethite particles are dispersed and loaded on the kaolinite surface, the material has a stronger adsorption capacity for anionic pollutants such as glyphosate and also possesses a certain catalytic decomposition ability. This material has a stable structure, strong reactivity, and superior adsorption performance compared to single-phase materials. The specific surface area of ​​goethite-modified kaolinite is significantly increased, and the Zeta potential changes from negative to positive, greatly enhancing its adsorption capacity for glyphosate. See SEM images of KGA for reference. Figure 2 b. Attached Figure Description

[0031] Figure 1 XRD patterns of KAO, GOE, KGA, and KGM.

[0032] Figure 2 a is the SEM image of KGM; Figure 2 b is the SEM image of KGA. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments. The following examples do not limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0034] Unless otherwise specified, the following implementation examples are as follows: Figure 1 KAO is kaolinite, with the molecular formula Al2Si2O5(OH)4. GOE is goethite; KGA is a goethite-kaolinite complex; KGM is a goethite-kaolinite mixture.

[0035] 1 ml of water = 1 g of water.

[0036] Adsorption capacity is measured in mg / g; the mass of glyphosate adsorbed per gram of adsorbent (mg).

[0037] Example 1 The preparation method of KGA adsorbent includes the following steps: S1. Mix kaolinite and water thoroughly, sonicate once, let stand, and sonicate a second time to obtain a suspension; In step S1, take 8.9 g of kaolinite powder, add 100 ml of distilled water, and sonicate at 80 rpm for 15 min. Allow to stand for 30 min to hydrate, and sonicate again at 80 rpm for 15 min.

[0038] S2. Add FeCl3 solution to the suspension in step S1 and stir to obtain a goethite mixture; In step S2, the mass ratio of suspension to FeCl3 is 1:0.918. Under magnetic stirring, the stirring rate is 1800 rpm and the stirring time is 50 min. 100 ml of 1 mol / L FeCl3 solution is added to the suspension.

[0039] S3. Add a regulator to the goethite mixture in step S2 to adjust the pH to weakly acidic, add FeCl2 as a reducing agent, add another regulator to adjust to weakly acidic again, age at constant temperature, centrifuge, wash with water, dry, and grind to obtain KGA adsorbent.

[0040] In step S3, 6 mol / L KOH solution was added dropwise to adjust the pH to 6.20 ± 0.02 for the first time, with FeCl2 as the reducing agent. Then, 0.77 g of FeCl2 was added, and 6 mol / L KOH solution was added dropwise to adjust the pH to 6.20 ± 0.02 for the second time. The constant temperature was 55℃. The aging time was 6 days. The conductivity after water washing was less than 6 μS / cm. The particle size after milling was 0.154 mm. The KGA adsorbent was obtained by drying at 40℃ for 1 day.

[0041] The operation method for adsorbing glyphosate with KGA adsorbent also includes the following steps: N1. Dissolve 0.4g KGA in 200ml of 0.01mol / L KCl solution to obtain KGA extractant; N2. Dissolve 0.06g of glyphosate in KGA extractant to obtain a glyphosate mixture; N3. Pass the glyphosate mixture from step N2 through a purge nitrogen gas, then add alkali to adjust the pH, and stir and shake at room temperature to obtain the extract.

[0042] In step N3, nitrogen was purged for 20 minutes at a flow rate of 0.1 L / min. The alkaline adjuster was NaOH; pH=3.5.

[0043] In step N3, the room temperature was 25°C, the rotation speed was 250 r / min, the shaking was carried out for 24 h, and the shaking frequency was 4.2 Hz.

[0044] Then, centrifuge at 25℃ and 10000 r / min for 10 min, filter and dispense into centrifuge tubes using a 0.45 μm nylon membrane, take the supernatant, and determine the glyphosate concentration using the ninhydrin colorimetric method.

[0045] The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0046] KGA adsorption capacity: 111.64 mg / g.

[0047] Example 2 Compared with Example 1, the difference is that the reducing agent FeCl2 in step S3 is replaced by FeSO4·7H2O, and the alkali adjuster in step N3 of the KGA adsorbent adsorption of glyphosate is NaOH adjusted to pH=5.0. Other operating conditions are the same.

[0048] The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0049] KGA adsorption capacity: 101.49 mg / g.

[0050] Example 3 The difference compared to Example 1 lies in the preparation method of the KGA adsorbent: In step S3, the particle size after grinding is 0.074 mm. Other operating conditions are the same.

[0051] The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0052] KGA adsorption capacity: 113.38 mg / g.

[0053] Example 4 Compared with Example 3, the difference is that in step N3, the pH was adjusted to 5.0 using NaHCO3, while other operating conditions remained the same.

[0054] The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0055] KGA adsorption capacity: 103.72 mg / g.

[0056] Comparative Example 1 The preparation method of KGM adsorbent includes the following steps: Take 10g of goethite and 10g of kaolinite mineral powder samples into a 1 L plastic beaker, add 500 ml of ultrapure water, stir evenly, and then ultrasonically disperse for 60 min. At room temperature, magnetically stir for 2 days to obtain KGM adsorbent.

[0057] Similarly, the conductivity of the suspension after washing with water was less than 6 μS / cm. The particle size after milling was 0.154 mm. After drying at 40℃ for 1 day, KGM adsorbent was obtained.

[0058] The operation method for adsorbing glyphosate with KGM adsorbent also includes the following steps: N1. Dissolve 0.4g KGM in 200ml of 0.01 mol / L KCl solution to obtain KGM extractant; N2. Dissolve 0.06g of glyphosate in KGM extractant to obtain a glyphosate mixture; N3. Purge the glyphosate mixture from step N2 with nitrogen gas, then add alkali to adjust the pH, and stir and shake at room temperature to obtain the extract.

[0059] In step N3, nitrogen was purged for 20 minutes at a flow rate of 0.1 L / min. The alkaline adjuster was NaOH; pH=3.5.

[0060] In step N3, the room temperature was 25°C, the rotation speed was 250 r / min, the shaking was carried out for 24 h, and the shaking frequency was 4.2 Hz.

[0061] Then, centrifuge at 25℃ and 10000 r / min for 10 min, filter and dispense into centrifuge tubes using a 0.45 μm nylon membrane, take the supernatant, and determine the glyphosate concentration using the ninhydrin colorimetric method.

[0062] The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0063] KGM adsorption capacity: 87.76 mg / g.

[0064] See Figure 2 a. SEM image of KGM; KGM is prepared by physically mixing goethite and kaolinite in a specific ratio, without forming an interfacial composite structure. Its performance is a weighted sum of the two, with no significant improvement in specific surface area and adsorption capacity. Due to the lack of coating or embedding, goethite tends to agglomerate in the mixed system, affecting system stability. Therefore, its performance in treating complex pollutants such as glyphosate is inferior to that of composite materials. KGA has significantly better adsorption performance than KGM, mainly because goethite particles in KGA are uniformly dispersed on the kaolinite surface, forming a synergistic adsorption and catalytic degradation effect, while goethite particles in KGM tend to agglomerate, resulting in limited adsorption performance and catalytic ability.

[0065] Comparative Example 2 GOE is goethite; The operation method for adsorbing glyphosate with GOE monomer adsorbent also includes the following steps: N1. Dissolve 0.4g of GOE in 200ml of 0.01mol / L KCl solution to obtain GOE extractant; N2. Dissolve 0.06g of glyphosate in GOE extractant to obtain a glyphosate mixture; N3. Purge the glyphosate mixture from step N2 with nitrogen gas, then add alkali to adjust the pH, and stir and shake at room temperature to obtain the extract.

[0066] In step N3, nitrogen was purged for 20 minutes at a flow rate of 0.1 L / min. The alkaline adjuster was NaOH; pH=3.5.

[0067] In step N3, the room temperature was 25°C, the rotation speed was 250 r / min, the shaking was carried out for 24 h, and the shaking frequency was 4.2 Hz.

[0068] Then, centrifuge at 25℃ and 10000 r / min for 10 min, filter and dispense into centrifuge tubes using a 0.45 μm nylon membrane, take the supernatant, and determine the glyphosate concentration using the ninhydrin colorimetric method.

[0069] The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0070] The GOE monomer adsorption capacity was 77.692 mg / g.

[0071] Comparative Example 3 KAO is kaolinite, the difference is... N1 and 0.4 g KAO were dissolved in 200 ml of 0.01 mol / L KCl solution to obtain KAO extractant; The operation method for adsorbing glyphosate with KAO adsorbent is exactly the same as that in Comparative Example 2. The amount of glyphosate adsorbed was calculated based on the difference in glyphosate concentration before and after adsorption. The experiment was repeated three times and the average value was taken.

[0072] The KAO adsorption capacity was 41.773 mg / g.

Claims

1. A method for preparing a KGA adsorbent, characterized in that, Includes the following steps: S1. Kaolinite and water are ultrasonically stirred once, allowed to stand, and ultrasonically stirred a second time to obtain a suspension. S2. Add FeCl3 solution to the suspension in step S1 and stir to obtain a goethite mixture; S3. Add a regulator to the goethite mixture in step S2 to adjust the pH to weakly acidic, add a reducing agent, add another regulator to adjust to weakly acidic again, age at constant temperature, centrifuge, wash with water, dry, and grind to obtain KGA adsorbent.

2. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S1, the mass ratio of kaolinite to water is 1:10~12.

3. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S1, the ultrasonic stirring rate is 80-100 rpm and the ultrasonic time is 15-20 min; the settling time is 30-40 min; the ultrasonic stirring rate is 80-100 rpm and the ultrasonic stirring time is 15-20 min.

4. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S2, the mass ratio of suspension to FeCl3 is 1:0.9~1.

5. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S2, the stirring rate is 1600~2000 rpm and the stirring time is 40~60 min.

6. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S3, the pH adjuster is either KOH or NaOH; the pH adjuster concentration is 0.05 mol / L to 1 mol / L, and the pH adjuster used for the first pH adjustment is the same as that used for the second pH adjustment.

7. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S3, the ratio of goethite mixture to reducing agent is 1:0.00198~0.00208 by mass.

8. The method for preparing a KGA adsorbent according to claim 1, characterized in that, In step S3, the reducing agent is either FeCl2 or FeSO4·7H2O.

9. The application of the KGA adsorbent prepared by the method according to any one of claims 1 to 8 in the adsorption of glyphosate.

10. The application according to claim 9, characterized in that, The operation method for adsorbing glyphosate with KGA adsorbent also includes the following steps: N1. Dissolve the KGA adsorbent in KCl solution to obtain a KGA extractant solution; N2. Glyphosate is dissolved in the KGA extractant solution from step N1 to obtain a glyphosate mixture; N3. Purge the glyphosate mixture from step N2 with nitrogen, adjust the pH with alkali, and stir and shake at room temperature to obtain the extract.

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