Humus-like substance intercalated modified attapulgite, its preparation method and application

Abstract

The present application belongs to the technical field of environmental heavy metal pollution treatment, and discloses a kind of humus-like substance intercalation modified attapulgite and its preparation method and application.The method introduces humus-like substance organic precursor into the interlayer domain of attapulgite by combining the way of "wet immersion + in-situ polycondensation", and generates humus-like substance in-situ by polyphenol-maillard reaction, to realize the successful loading of humus-like substance on the outer surface and interlayer domain of attapulgite.Compared with the traditional method, the present application solves the problems of insufficient organic loading and poor stability, and significantly improves the adsorption performance of the material to heavy metal ions (such as Cd(II)).The prepared modified material has excellent adsorption performance, structural stability and green environmental protection characteristics, and is suitable for treating cadmium ion pollution in water and stabilizing cadmium ions in soil, providing a new idea for the development of new environmental remediation materials.

Description

Technical Field

[0001] This invention relates to the field of environmental heavy metal pollution control technology, specifically to a humus-like material intercalation modified attapulgite soil, its preparation method, and its application. Background Technology

[0002] Excessive cadmium emissions during smelting operations, pesticide and fertilizer use, and mine drainage can lead to excessive Cd(II) levels in soil and water, threatening ecosystem balance and posing serious health risks. Therefore, developing practical and cost-effective adsorbent materials to improve the remediation efficiency of cadmium-contaminated soil and water is of significant practical importance.

[0003] Attapulgite is a natural clay mineral that, due to its large specific surface area, moderate cation exchange capacity, and surface-active hydroxyl groups, can serve as a natural adsorbent and fixative for heavy metals in soil. However, its adsorption efficiency for Cd(II) is relatively limited, making it difficult to meet the high-efficiency requirements for cadmium pollution remediation in practical applications. Modification is an effective way to further enhance the adsorption capacity of attapulgite.

[0004] Traditional methods for modifying attapulgite typically involve mechanically mixing organic matter with attapulgite, allowing the organic matter to be physically adsorbed onto the mineral surface via electrostatic interactions. However, this method has significant drawbacks: firstly, the bond strength between organic matter and minerals is weak, relying solely on weak electrostatic interactions, making it prone to detachment under acidic or slightly high-temperature conditions, resulting in poor material stability, poor adsorption performance, and short service life; secondly, due to the large hydrodynamic radius of organic matter and the small interlayer spacing of minerals, organic matter struggles to penetrate the interlayer domains of minerals, remaining only on their outer surfaces, limiting the loading capacity and hindering the improvement of adsorption performance. Summary of the Invention

[0005] To address the problems existing in current attapulgite modification methods, this invention proposes an innovative method combining wet impregnation and in-situ condensation polymerization for preparing attapulgite modified with humic substances through intercalation. This method enables humic substances to chemically bond on the surface and in the interlayer domains of attapulgite, forming a robust intercalation structure. Compared to traditional modification methods, this invention not only significantly improves the loading strength of organic matter but also effectively solves the problem of easy detachment of the loading material due to physical adsorption, greatly enhancing the adsorption performance of attapulgite for Cd(II) ions, thus providing a more reliable method for the efficient remediation of cadmium pollution.

[0006] The preparation process of this invention is based on the polyphenol-Maillard reaction mechanism. By introducing organic precursors of humic substances (such as reducing sugars, amino acids, and polyphenolic compounds) into the interlayer domains of attapulgite, humic substances are generated in situ via a polyphenol-Maillard reaction. In this process, reducing sugars provide reducing power, amino acids provide amino and carboxyl groups, and polyphenolic compounds provide phenolic hydroxyl groups; these three components work synergistically to generate complex condensation products. These products, through further polymerization and cross-linking, ultimately form humic substances that are firmly bonded to the surface and interlayer domains of attapulgite. During adsorption, the aromatic structures and functional groups (such as hydroxyl and carboxyl groups) in the humic substances undergo complexation reactions with Cd(II) ions, forming stable chemical bonds. Simultaneously, the ion exchange characteristics and surface coordination of attapulgite further enhance its adsorption capacity for Cd(II) ions.

[0007] This invention also studies the adsorption effect of humic substance-modified attapulgite on Cd(II) in water, aiming to apply it to the field of efficient treatment of Cd(II) polluted wastewater.

[0008] Another object of the present invention is to provide attapulgite-modified humus-like material intercalation prepared by the above preparation method.

[0009] Another object of the present invention is to provide the application of humus-like material intercalation-modified attapulgite.

[0010] This invention is achieved through the following technical solution:

[0011] A method for preparing attapulgite soil modified by humus intercalation includes the following steps:

[0012] (1) Add reducing sugars, amino acids and polyphenols to water and stir until completely dissolved to obtain a mixed solution;

[0013] (2) Add attapulgite to the mixed solution obtained in step (1), sonicate, react at a constant temperature, and obtain a suspension;

[0014] (3) Perform solid-liquid separation on the suspension obtained in step (2) and dry the solid phase to obtain the final product.

[0015] Preferably, the reducing sugars include, but are not limited to, glucose, fructose, maltose, etc.; the amino acids include, but are not limited to, glycine, alanine, lysine, arginine, etc.; and the polyphenolic compounds include, but are not limited to, catechol, hydroquinone, gallic acid, protocatechuic acid, etc.

[0016] Since the principle of synthesizing humic substances is based on the polyphenol-Maillard theory, this reaction mechanism is based on polyphenols, amino acids, and reducing sugars as organic precursors for humic substances, which are then generated in situ through a polyphenol-Maillard reaction. Therefore, the above-mentioned modifiers should consist of reducing sugars, amino acids, and polyphenolic compounds; all three are indispensable.

[0017] Preferably, glucose, glycine, and catechol are selected as precursors, for the following reasons:

[0018] Glucose, as a simple reducing sugar, contains multiple hydroxyl groups (-OH), which can participate in condensation reactions to form complex polymers. In humic synthesis, the hydroxyl groups of glucose can undergo dehydration condensation with other compounds to form a stable carbon skeleton.

[0019] Glycine, as the simplest amino acid, contains an amino group (-NH2) and a carboxyl group (-COOH). These functional groups can participate in condensation reactions, form peptide bonds, or cross-link with other organic compounds, thereby increasing the complexity and stability of the synthesized products.

[0020] Catechol is an aromatic compound containing a phenolic hydroxyl group (-OH). Its aromatic ring structure and phenolic hydroxyl group give it high reactivity. The phenolic hydroxyl group of catechol can participate in oxidation reactions to form quinone intermediates, which can then undergo condensation reactions with other organic compounds to form humic substances with aromatic structures.

[0021] Preferably, in the mixed solution of step (1), the concentration of reducing sugars is 0.025-0.1 mol / L, more preferably 0.05 mol / L; the amount of reducing sugars added directly affects the synthesis reaction of humic substances, which serves as a carbon source. The range of 0.025-0.1 mol / L ensures that there is sufficient carbon source in the reaction system to participate in the condensation reaction and form a stable humic substance structure. 0.05 mol / L is considered the optimal addition amount because it can ensure a high yield of humic substances while avoiding side reactions caused by excessive reducing sugars.

[0022] Preferably, in step (1), the concentration of amino acids is 0.025-0.3 mol / L, more preferably 0.15 mol / L; the concentration of polyphenols is 0.025-0.3 mol / L, more preferably 0.15 mol / L; wherein the molar ratio of amino acids to polyphenols is preferably 5:1 (0.25 mol / L: 0.05 mol / L), 3:1 (0.15 mol / L: 0.05 mol / L), 1:1 (0.05 mol / L: 0.05 mol / L), 1:3 (0.05 mol / L: 0.15 mol / L) and 1:5 (0.05 mol / L: 0.25 mol / L), and more preferably 3:1 (0.15 mol / L: 0.05 mol / L).

[0023] This is because amino acids provide amino and carboxyl groups, while polyphenols provide phenolic hydroxyl groups. A 3:1 molar ratio allows these functional groups to complement each other well in the reaction, promoting the condensation reaction. Too high (e.g., 1:5): When the proportion of polyphenols is too high, the oxidation reaction of phenolic hydroxyl groups may be too vigorous, resulting in too many quinone intermediates, which in turn inhibits the condensation reaction with amino acids. This will result in a lower molecular weight of the synthesized humic substance and a decrease in adsorption performance. Too low (e.g., 5:1): When the proportion of amino acids is too high, the reactivity of amino and carboxyl groups may not be fully utilized, resulting in insufficient aromaticity of the humic substance and a reduction in adsorption sites. In addition, an excessively high proportion of amino acids may also increase the synthesis cost. Preferably, in step (1), the water is deionized water; the amount of deionized water added is 200 mL;

[0024] Preferably, in step (2), the ultrasonic treatment conditions are: time of 5-20 min, preferably 8-12 min, for example 10 min; ultrasonic power of 200-300 W, preferably 230-250 W, for example 240 W. Studies have shown that an ultrasonic time of 5-20 minutes can ensure sufficient contact and dispersion between organic matter and attapulgite. For example, 10 minutes of ultrasonic treatment can avoid energy waste and potential damage to the molecular structure of organic matter caused by excessively long ultrasonic time, while also ensuring sufficient contact and dispersion between organic matter and attapulgite. A power range of 200-300 W can provide sufficient energy to promote the intercalation reaction between organic matter and attapulgite, while avoiding local overheating or damage to the organic matter structure that may be caused by excessively high power. For example, 240 W can improve energy utilization efficiency while ensuring reaction efficiency, making it easier for organic molecules to enter the interlayer of attapulgite and form a stable intercalation structure.

[0025] Preferably, in step (2), the isothermal reaction is carried out in an isothermal shaker, and the isothermal reaction conditions are: 40-50℃, reaction time 8-12 days, preferably maintaining the temperature at 45℃ for 10 days; this is because 40-50℃ is considered the optimal temperature range for humus formation during composting, and the temperature conditions are set accordingly. The 8-12 day reaction time ensures that the humus-like synthesis reaction proceeds fully.

[0026] Preferably, in step (3), the drying is performed by vacuum freeze drying for 72±5h.

[0027] The attapulgite-modified material prepared by the above preparation method is a humus-like material intercalation modification.

[0028] Application of attapulgite modified with humic substances in the treatment of Cd(II) pollution in the environment.

[0029] Preferably, the environment includes Cd(II) contaminated industrial wastewater, industrial solid waste, and contaminated soil.

[0030] Furthermore, this invention also provides a method for treating Cd(II)-contaminated wastewater using humus-like intercalation modified attapulgite, comprising the following steps:

[0031] Attapulgite modified with humic substances was added to wastewater containing Cd(II) and allowed to react fully to remove Cd(II) from the water.

[0032] Preferably, stirring or shaking can be performed to ensure sufficient contact between Cd(II) and the adsorbent.

[0033] Preferably, based on a comprehensive consideration of adsorption efficiency, economy and environmental impact, the dosage of humic substance intercalation modified attapulgite is 0.5 to 2.5 g / L; in order to effectively improve the adsorption performance of Cd(II) ions, while avoiding the increased cost and environmental risks caused by excessive use, it is further preferred to be 2.0 g / L.

[0034] Preferably, since the adsorption equilibrium time of attapulgite material is relatively short, the adsorption time for sufficient contact reaction is 10 to 120 minutes; considering adsorption efficiency and economy, adsorption equilibrium is reached in 60 minutes, and 60 minutes is further preferred.

[0035] The beneficial effects of this invention are as follows:

[0036] (1) This invention addresses the problems of poor stability and short service life in existing organic modification methods for attapulgite. It employs an innovative method combining wet impregnation and in-situ polycondensation to prepare attapulgite modified with humic substances through intercalation. These humic substances are chemically adsorbed onto the surface and interlayers of the attapulgite, forming a stable intercalation structure through strong chemical bonds. This structure not only significantly enhances the adsorption capacity of attapulgite for Cd(II) ions and improves adsorption efficiency, but also maintains good stability under acidic or slightly high-temperature conditions, extending the material's service life. Furthermore, it effectively solves the problem of insufficient organic loading in traditional methods, significantly improving the material's adsorption performance.

[0037] The core innovation of this invention lies in the application of in-situ intercalation technology. Compared with traditional physical adsorption methods, in-situ intercalation fixes humic-like substances into the interlayer of attapulgite through chemical bonding, forming a stable intercalation structure, which significantly improves the loading strength and avoids the problem of easy detachment of the load. Furthermore, by optimizing reaction conditions (such as temperature, pH value, and the use of catalysts), this invention achieves efficient synthesis of humic-like substances, further improving the adsorption performance of modified attapulgite. This technology not only improves the loading strength but also enhances the adsorption capacity for Cd(II) ions through chemically bonded humic-like substances, while also aligning with the development concept of green chemistry.

[0038] (2) The treatment process of the present invention involves adding the modified material to the wastewater, which does not require special equipment or complicated operations and is simple to operate;

[0039] (3) The raw materials used in the method of the present invention are widely available, low in cost, and environmentally friendly, which is in line with the concept of green chemistry, and there is no secondary pollution, thus having significant economic and environmental benefits;

[0040] (4) By optimizing the preparation process and adsorption conditions, the modified attapulgite is not only suitable for treating industrial wastewater contaminated with Cd(II), but also for treating polluted soil and industrial solid waste. This invention provides new ideas for the development and application of new environmental materials and shows broad application prospects. Attached Figure Description

[0041] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0042] Figure 1 This describes the effect of the modified material in Example 1 on the adsorption effect of Cd(II) under different glycine and catechin dosage ratios;

[0043] Figure 2 This describes the effect of the modified material in Example 2 on the adsorption effect of Cd(II) under different dosages;

[0044] Figure 3 This is the effect of the modified material in Example 3 on the adsorption effect of Cd(II) at different adsorption times. Detailed Implementation

[0045] To more clearly illustrate the purpose, technical solution, and advantages of this invention, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments. The drawings illustrate only exemplary embodiments of the invention and are not intended to limit its implementation. This invention can be implemented in various forms, and its design concept and core technology are not limited to the embodiments shown in the drawings. These embodiments are provided to facilitate understanding of the principles, structure, and function of this invention by those skilled in the art, thereby enabling them to better master and apply its technical solutions. The terminology used in this specification is only for describing specific embodiments and does not constitute a limitation of the invention.

[0046] Example 1: Preparation of modified materials

[0047] The specific steps for preparing humus-like intercalated modified attapulgite are as follows:

[0048] (1) Add a certain amount of glucose, glycine and catechin to a wide-mouth conical flask, add a certain amount of deionized water, and stir until completely dissolved to form a mixed solution;

[0049] (2) Add 4g of attapulgite to the solution obtained in step (1), sonicate for 10min, and then place the mixture in a constant temperature shaker to maintain the temperature at 45°C for 10 days.

[0050] (3) The suspension of the humic material intercalation modified attapulgite obtained in step (2) is subjected to solid-liquid separation. The obtained solid phase is then vacuum freeze-dried for 72 hours to obtain the modified material, which is then stored in a vacuum dryer.

[0051] Among them, the optimal ratio of glycine and catechin was selected in the experiment:

[0052] The material preparation process is basically the same as above, except that in step (1), the amount of glucose added is 0.1 mol, and the molar ratio of glycine to catechol is 5:1 (0.05 mol: 0.01 mol), 3:1 (0.03 mol: 0.01 mol), 1:1 (0.01 mol: 0.01 mol), 1:3 (0.01 mol: 0.03 mol) and 1:5 (0.01 mol: 0.05 mol), with the preferred molar ratio being 3:1 (0.03 mol: 0.01 mol).

[0053] In addition, a comparative experiment was set up, which was conducted on attapulgite soil that had not been modified in step (1), and the rest was the same as steps (2) and (3) above.

[0054] The prepared materials were subjected to the following application tests:

[0055] An initial cadmium concentration of 200 mg / L was prepared, and the initial pH was adjusted to 7. 0.03 g of the different modified materials prepared above were added to 20 mL of Cd(II) solution. The solution was subjected to shaking reduction and adsorption at 25 °C and 200 r / min for 1440 min. After filtration through a 0.22 μm filter membrane, the cadmium concentration in the filtrate was detected by atomic absorption spectrophotometry (GB 7475-87) for the determination of copper, zinc, lead and cadmium in water. The Cd(II) reduction and adsorption capacity of different modified materials was calculated.

[0056] The results are as follows Figure 1 As shown, the modified material with a glycine to catechin ratio of 3:1 exhibited the best adsorption effect, with a maximum reduction adsorption capacity of 54.47 mg / g. In contrast, the maximum adsorption capacities of the modified material with glycine to catechin ratios of 5:1, 1:1, 1:3, 1:5, and the unmodified attapulgite were 51.5, 47.52, 33.74, 26.85, and 1.54 mg / g, respectively. The adsorption capacity of the modified material was significantly greater than that of the unmodified attapulgite.

[0057] This embodiment illustrates that the modified material has a better adsorption effect on Cd(II) in water, which provides a basis for its practical application in treating wastewater containing Cd(II) pollution.

[0058] Example 2: Effect of different dosages on adsorption efficiency

[0059] The modified material with a glycine to catechin ratio of 3:1 from Example 1 was selected. Different masses (0.01, 0.02, 0.03, 0.04, 0.05 g) were accurately weighed and added to 20 mL of a Cd(II) solution with a pH of 7 and a concentration of 200 mg / L, so that the dosage of the modified material was 0.5, 1.0, 1.5, 2.0, and 2.5 g / L, respectively. The remaining operation procedures and detection methods were the same as the application test method of Example 1.

[0060] The adsorption capacity of the modified material under different dosage conditions is as follows: Figure 2 As shown in the figure. Experimental results show that when the dosage of modified material is 0.5, 1.0, 1.5, 2.0, and 2.5 g / L, the adsorption amounts are 13.82, 20.19, 43.85, 54.47, and 45.52 mg / g, respectively. That is, when the dosage of modified material is 2.0 g / L, the adsorption amount is the highest, at 54.47 mg / g.

[0061] This embodiment illustrates that the addition of modified materials provides a foundation for the rapid and efficient treatment of wastewater containing Cd(II) pollution.

[0062] Example 3: Effect of different reaction times on adsorption efficiency

[0063] The modified material with a glycine and catechin addition ratio of 3:1 was selected from Example 1. The modified material was accurately weighed into 20 mL of a Cd(II) solution with a pH of 7 and a concentration of 200 mg / L. The experiment was carried out at room temperature. The supernatant was taken at different time periods (5, 10, 15, 30, 45, 60, 90, 120 min) to determine the Cd(II) concentration. The operation procedure and detection method were the same as the application test method in Example 1.

[0064] from Figure 3 As can be seen, the adsorption amounts at different time points (5, 10, 15, 30, 45, 60, 90, and 120 min) were 34.62, 41.51, 47.72, 50.82, 52.34, 53.56, 54.01, and 54.30 mg / g, respectively. This indicates that adsorption reached equilibrium after 60 min.

[0065] This embodiment demonstrates that the modified material exhibits good treatment effects when remediating wastewater containing Cd(II) pollution of different concentrations, providing a technical guarantee for its rapid and efficient treatment of heavy metal pollution in water.

[0066] Example 4: Comparison of different modified materials

[0067] Using the same application testing method as in Example 1, the maximum adsorption capacity of attapulgite modified by different methods was measured, and the results are shown in the table below:

[0068] Table 1. Comparison of maximum adsorption capacity of different attapulgite soil modifiers

[0069]

[0070] Literature 1: Cadmium adsorption onto aluminum hydroxide-modified attapulgiteprepared with basic aluminum acetate. Zhang Q, Chu R, Wei Y, et al. Scientific Reports, 14: 31428, 2024.

[0071] Document 2: Removal of Cd(II) and Pb(II) from aqueous solution by modifiedattapulgite clay. Huang R, Lin Q, Zhong Q, et al. Arabian Journal ofChemistry, 13: 4994-5008, 2020.

[0072] Document 3: Study of adsorption property and mechanism of lead(II) andcadmium(II) onto sulfhydryl modified attapulgite. Fu C, Zhu X, Dong X, et al. Arabian Journal of Chemistry, 14: 102960, 2021.

[0073] As can be seen from the above comparative experiments, compared with methods such as aluminum hydroxide modification, mercapto modification, high-temperature calcination, and hydrothermal loading of MgO, the present invention significantly enhances the adsorption capacity of attapulgite for Cd(II) ions and improves the adsorption efficiency by intercalating attapulgite with humic substances.

[0074] Finally, it is important to emphasize that the embodiments provided herein are only a portion of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on this invention without inventive effort should fall within the scope of protection of this invention.

Claims

1. A method for preparing attapulgite soil modified by humus-like intercalation, characterized in that: Includes the following steps: (1) Add reducing sugars, amino acids and polyphenols to water and stir until completely dissolved to obtain a mixed solution; (2) Add attapulgite to the mixed solution obtained in step (1), sonicate, react at a constant temperature, and obtain a suspension; (3) Perform solid-liquid separation on the suspension obtained in step (2), and dry the solid phase to obtain the final product; Wherein, the reducing sugars are selected from glucose, fructose, and maltose; the amino acids are selected from glycine, alanine, lysine, and arginine; and the polyphenolic compounds are selected from catechol, hydroquinone, gallic acid, and protocatechuic acid. In step (1), the concentration of reducing sugars in the mixed solution is 0.025-0.1 mol / L; the concentration of amino acids is 0.025-0.3 mol / L; and the concentration of polyphenols is 0.025-0.3 mol / L.

2. The preparation method according to claim 1, characterized in that: The molar ratio of amino acids to polyphenolic compounds is 5:1, 3:1, 1:1, 1:3, or 1:

5.

3. The preparation method according to claim 1, characterized in that: The concentration of reducing sugars was 0.05 mol / L; the concentration of amino acids was 0.15 mol / L; and the concentration of polyphenols was 0.15 mol / L.

4. The preparation method according to claim 1, characterized in that: In step (2), the ultrasonic treatment conditions are: ultrasonic time is 5-20 min; ultrasonic power is 200-300 W.

5. The preparation method according to claim 1, characterized in that: In step (2), the isothermal reaction is carried out in an isothermal shaker, and the isothermal reaction conditions are: 40-50℃, reaction time 8-12 days.

6. The preparation method according to claim 1, characterized in that: In step (3), drying is performed by vacuum freeze drying for 72±5h.

7. Humus-like intercalation modified attapulgite prepared by any one of the preparation methods of claims 1-6.

8. The application of the humus-like material intercalation modified attapulgite soil according to claim 7, characterized in that, It is applied to the treatment of divalent Cd ion pollution in the environment; the environment includes industrial wastewater, industrial solid waste and contaminated soil contaminated with divalent Cd ions.

9. The application according to claim 8, characterized in that: The method for treating wastewater containing divalent Cd ions is as follows: add attapulgite-modified clay with humic substances to the wastewater containing divalent Cd ions and allow it to fully react.

10. The application according to claim 9, characterized in that: The dosage of humus-like intercalation modified attapulgite soil is 0.5-2.5 g / L.

11. The application according to claim 9, characterized in that: The reaction time for full contact is 10-120 minutes.

Images