A modified bentonite antibiotic adsorbent and a method for preparing the same

Abstract

The application relates to the technical field of environmental adsorption materials, and discloses a modified bentonite antibiotic adsorbent and a preparation method thereof.The adsorbent is composed of polycarboxyl bentonite and acid-modified polyethylene glycol, multiple adsorption mechanisms such as hydrogen bonding, complexation, electrostatic interaction and pi-pi stacking are constructed, through the synergistic effect of multiple functional groups, the adsorbent shows strong adsorption capacity for a wide spectrum of antibiotics with different molecular structures and electrical properties, the defect of narrow adsorption spectrum of single material is overcome, through the ultrasonic blending and drying process, the flexible chain segments of the acid-modified polyethylene glycol can be effectively intercalated in the lamellar structure and pores of the polycarboxyl bentonite, not only the interlayer spacing can be further expanded to expose more internal sites, but also the interface bonding force of the two phases can be enhanced through the intermolecular interaction, the components can be prevented from separating in the use process, and the adsorption effect is ensured.

Description

Technical Field

[0001] This invention relates to the field of environmental adsorption materials technology, specifically to a modified bentonite antibiotic adsorbent and its preparation method. Background Technology

[0002] In recent years, with the development of aquaculture and the widespread use of medicine, antibiotic residues and pollution in environmental water bodies have become a major threat to the environment and health. Commonly used antibiotics such as tetracyclines, sulfonamides, and fluoroquinolones are difficult to remove effectively by traditional wastewater treatment processes. After entering the water environment, they can induce antibiotic resistance genes, posing a serious threat to the ecological environment and human health. Adsorption is considered a very promising deep removal technology because it is simple to operate, relatively inexpensive, and does not produce secondary pollution. Its core lies in how to develop efficient and stable adsorbents.

[0003] Patent announcement CN118616015B discloses an adsorbent, its preparation method, and its application. This adsorbent comprises bio-diatoms and diatomite nanoparticles. The surface of the bio-diatoms is in-situ loaded with diatomite nanoparticles. The bio-diatoms exhibit biocapture and adsorption of nano-clay minerals, allowing the diatomite nanoparticles to be uniformly loaded onto surface organic active sites, thus forming a diatomite nanoparticle film in situ on the diatom surface. This adsorbent effectively preserves the macroporous structure of the diatoms while constructing a multi-level pore structure of mesoporous and microporous structures, exhibiting a large adsorption capacity. The adsorbent prepared by this patent is particularly effective in removing tetracycline antibiotics, showing broad application prospects in the adsorption and pollution control of tetracycline antibiotics. However, although this patent boasts a large adsorption capacity, fast adsorption rate, structural stability, and regenerability, its narrow adsorption spectrum limits its application scenarios. In water bodies where multiple antibiotics coexist, it needs to be combined with other adsorbents for use, which presents significant limitations. Summary of the Invention

[0004] The purpose of this invention is to provide a modified bentonite antibiotic adsorbent and its preparation method, which solves the problems of narrow adsorption spectrum, limited adsorption capacity and rate, poor structural stability and regenerability of adsorbent materials, especially clay mineral-based materials, used for antibiotic removal in water treatment in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A modified bentonite antibiotic adsorbent is composed of polycarboxylated bentonite and acid-modified polyethylene glycol. The polycarboxylated bentonite is prepared by reacting epoxy-functionalized bentonite with pyromellitic dianhydride. The epoxy-functionalized bentonite is prepared by surface modification of bentonite with 3-glycidyl etheroxypropyltriethoxysilane. The acid-modified polyethylene glycol is prepared by reacting sulfonic acid-modified polyethylene glycol with 2-carboxyethylphenylphosphonic acid. The sulfonic acid-modified polyethylene glycol is prepared by reacting polyethylene glycol diglycidyl ether with aminosulfonic acid.

[0007] Furthermore, the mass ratio of the polycarboxylated bentonite to the acid-modified polyethylene glycol is 1-3:1.

[0008] Furthermore, the preparation method of the polycarboxylated bentonite includes the following steps:

[0009] S1: Place 3-glycidyl etheroxypropyltriethoxysilane in anhydrous ethanol, add acetic acid solution to adjust pH, stir magnetically for 1-1.5 h, add bentonite, ultrasonically disperse for 10-15 min, heat to 65-70℃, stir for 6-8 h, filter, wash, and dry to obtain epoxy-functionalized bentonite.

[0010] S2: Place the epoxy-functionalized bentonite in dimethyl sulfoxide, ultrasonically disperse for 15-20 min, introduce nitrogen gas, add pyromellitic dianhydride and catalyst, heat to 80-90℃ and react for 8-10 h, cool to room temperature, filter, wash and dry to obtain polycarboxylated bentonite.

[0011] Through the above technical solution, 3-glycidyl etheroxypropyltriethoxysilane is hydrolyzed to form silanol, which reacts with the hydroxyl groups on the surface of bentonite to modify the surface and obtain epoxy-functionalized bentonite. Then, under the action of a catalyst, the epoxy groups on the surface of epoxy-functionalized bentonite react with the anhydride groups in the pyromellitic dianhydride structure to obtain polycarboxylated bentonite.

[0012] Furthermore, in step S1, adjusting the pH by adding acetic acid solution specifically involves adding acetic acid with a concentration of 1-2 mol / L to adjust the pH to 4-5.

[0013] Furthermore, in step S2, the catalyst is triethylamine.

[0014] Furthermore, the method for preparing the acid-modified polyethylene glycol includes the following steps:

[0015] SS1: Polyethylene glycol diglycidyl ether and aminosulfonic acid were placed in dimethyl sulfoxide, nitrogen gas was introduced, and the temperature was raised to 80-85℃ for 4-6 hours. After cooling, the mixture was transferred to ice-cold ether, the precipitate was collected, washed and dried to obtain sulfonic acid modified polyethylene glycol.

[0016] SS2: Sulfonic acid-modified polyethylene glycol was placed in N,N-dimethylformamide, and 2-carboxyethylphenylphosphine and p-toluenesulfonic acid were added. The mixture was heated and reacted. The product was collected by vacuum distillation to obtain acid-modified polyethylene glycol.

[0017] Through the above technical solution, the epoxy group in the polyethylene glycol diglycidyl ether structure undergoes a ring-opening reaction with the amino group in the aminosulfonic acid structure to obtain sulfonic acid modified polyethylene glycol. Then, under the action of p-toluenesulfonic acid, the hydroxyl group in the sulfonic acid modified polyethylene glycol structure undergoes an esterification reaction with the carboxyl group in the 2-carboxyethylphenylphosphine acid structure to obtain acid modified polyethylene glycol.

[0018] Furthermore, in step SS1, the number-average molecular weight of the polyethylene glycol diglycidyl ether is 300-2000.

[0019] Furthermore, in step SS2, the temperature of the heating reaction is 90-100℃, and the time is 6-8h.

[0020] A method for preparing a modified bentonite antibiotic adsorbent includes the following steps:

[0021] Step 1: Mix polycarboxylated bentonite with acid-modified polyethylene glycol and place it in anhydrous ethanol. After ultrasonic treatment for 20-30 minutes, a suspension is formed.

[0022] Step 2: Stir and evaporate the suspension at 60-65℃ until it becomes a paste, then vacuum dry it at 80-90℃ for 12-15 hours, and finally grind it through a 100-200 mesh sieve to obtain the adsorbent.

[0023] The beneficial effects of this invention are:

[0024] 1. Based on bentonite, abundant carboxyl groups are introduced on its surface. As polar functional groups, they can form strong hydrogen bonds, complexation, and π-π electron stacking with amino and carbonyl groups in antibiotic molecules such as tetracyclines and fluoroquinolones, providing a large number of adsorption sites. At the same time, through the reaction of diacid anhydrides with multiple epoxy groups, a cross-linked network can be formed on the bentonite surface and between layers, which effectively improves the stability of the adsorption material and facilitates recycling.

[0025] 2. Through the stepwise reaction of polyethylene glycol diglycidyl ether with aminosulfonic acid and 2-carboxyethylphenylphosphonic acid, sulfonic acid and phosphonic acid groups are introduced into the flexible polymer chain segments. These two strong acidic groups can ionize over a wide pH range, giving the adsorbent a strong negative charge, enabling it to react with positively charged antibiotics in water, such as sulfonamides and aminoglycosides. This effectively compensates for the deficiency of bentonite, which mainly relies on hydrogen bonding. At the same time, using polyethylene glycol as the polymer chain segment, it has good hydrophilicity and flexibility, which can improve the dispersibility of the complex in water and make it easier for antibiotic molecules to diffuse to the adsorption sites, effectively accelerating the adsorption rate.

[0026] 3. By combining polycarboxylated bentonite with acid-modified polyethylene glycol, a multi-adsorption mechanism combining hydrogen bonding, complexation, electrostatic interaction, and π-π stacking was constructed. Through the synergistic effect of multiple functional groups, this adsorbent exhibits strong adsorption capacity for broad-spectrum antibiotics with different molecular structures and electrical properties, overcoming the narrow adsorption spectrum of single materials. Through ultrasonic blending and drying processes, the flexible segments of acid-modified polyethylene glycol can be effectively intercalated into the layered structure and pores of polycarboxylated bentonite. This not only further expands the interlayer spacing and exposes more internal sites, but also enhances the interfacial bonding force between the two phases through intermolecular interactions, preventing component separation during use and ensuring adsorption efficiency.

[0027] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating the preparation process of a modified bentonite antibiotic adsorbent according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The preparation methods of polycarboxylated bentonite and acid-modified polyethylene glycol in the following embodiments and comparative examples of the present invention are as follows:

[0032] I. Preparation of Polycarboxylated Bentonite

[0033] S1: 1.6 g of 3-glycidyl etheroxypropyltriethoxysilane was placed in 100 ml of anhydrous ethanol, and the pH was adjusted to 4 by adding 1 mol / L acetic acid solution. After magnetic stirring for 1 h, 5 g of bentonite was added, ultrasonically dispersed for 10 min, heated to 65 °C, stirred for 6 h, filtered, washed, and dried to obtain epoxy-functionalized bentonite.

[0034] S2: 6.5g of epoxy-functionalized bentonite was placed in 120ml of dimethyl sulfoxide and ultrasonically dispersed for 15min. Nitrogen gas was introduced, and 3g of pyromellitic dianhydride and 0.06g of triethylamine were added. The mixture was heated to 80℃ and reacted for 8h. After cooling to room temperature, it was filtered, washed, and dried to obtain polycarboxylated bentonite.

[0035] II. Preparation of Acid-Modified Polyethylene Glycol

[0036] SS1: 6g of polyethylene glycol diglycidyl ether and 3.5g of aminosulfonic acid were placed in 80ml of dimethyl sulfoxide, nitrogen gas was introduced, the temperature was raised to 80℃ and reacted for 4h. After cooling, the mixture was transferred to 400ml of ice-cold ether, the precipitate was collected, washed and dried to obtain sulfonic acid modified polyethylene glycol.

[0037] SS2: 6.6g of sulfonic acid modified polyethylene glycol was placed in 100ml of N,N-dimethylformamide, 8.5g of 2-carboxyethylphenylphosphonic acid and 0.2g of p-toluenesulfonic acid were added, the mixture was heated to 90℃ and reacted for 6h, and the product was collected by vacuum distillation to obtain acid-modified polyethylene glycol.

[0038] Example 1

[0039] Preparation of adsorbent

[0040] Step 1: Mix 45 parts of polycarboxylated bentonite with 45 parts of acid-modified polyethylene glycol and place the mixture in 100 parts of anhydrous ethanol. After ultrasonic treatment for 20 minutes, a suspension is formed.

[0041] Step 2: Stir and evaporate the suspension at 60°C until it becomes a paste, then vacuum dry it at 80°C for 12 hours, and finally grind it through a 100-mesh sieve to obtain the adsorbent.

[0042] Example 2

[0043] Preparation of adsorbent

[0044] Step 1: Mix 60 parts of polycarboxylated bentonite with 30 parts of acid-modified polyethylene glycol and place the mixture in 120 parts of anhydrous ethanol. After ultrasonic treatment for 25 minutes, a suspension is formed.

[0045] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0046] Example 3

[0047] Preparation of adsorbent

[0048] Step 1: Mix 90 parts of polycarboxylated bentonite with 30 parts of acid-modified polyethylene glycol and place the mixture in 150 parts of anhydrous ethanol. After ultrasonic treatment for 30 minutes, a suspension is formed.

[0049] Step 2: Stir and evaporate the suspension at 65°C until it becomes a paste, then vacuum dry it at 90°C for 15 hours, and finally grind it through a 200-mesh sieve to obtain the adsorbent.

[0050] Comparative Example 1

[0051] Preparation of adsorbent

[0052] Step 1: Mix 90 parts of acid-modified polyethylene glycol and place it in 120 parts of anhydrous ethanol. After ultrasonic treatment for 25 minutes, a suspension is formed.

[0053] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0054] Comparative Example 2

[0055] Preparation of adsorbent

[0056] Step 1: Mix 90 parts of polycarboxylated bentonite and place it in 120 parts of anhydrous ethanol. After ultrasonic treatment for 25 minutes, a suspension is formed.

[0057] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0058] Comparative Example 3

[0059] Preparation of adsorbent

[0060] Step 1: Mix 60 parts of epoxy-functionalized bentonite with 30 parts of acid-modified polyethylene glycol and place the mixture in 120 parts of anhydrous ethanol. After ultrasonic treatment for 25 minutes, a suspension is formed.

[0061] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0062] Comparative Example 4

[0063] Preparation of adsorbent

[0064] Step 1: Mix 60 parts bentonite with 30 parts acid-modified polyethylene glycol and place the mixture in 120 parts anhydrous ethanol. After ultrasonic treatment for 25 minutes, a suspension is formed.

[0065] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0066] Comparative Example 5

[0067] Preparation of adsorbent

[0068] Step 1: Mix 60 parts of polycarboxylated bentonite with 30 parts of sulfonic acid modified polyethylene glycol and place the mixture in 120 parts of anhydrous ethanol. After ultrasonic treatment for 25 minutes, a suspension is formed.

[0069] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0070] Comparative Example 6

[0071] Preparation of adsorbent

[0072] Step 1: Mix 60 parts of polycarboxylated bentonite with 30 parts of polyethylene glycol diglycidyl ether and place the mixture in 120 parts of anhydrous ethanol. Sonicate the mixture for 25 minutes to form a suspension.

[0073] Step 2: Stir and evaporate the suspension at 63°C until it becomes a paste, then vacuum dry it at 85°C for 13 hours, and finally grind it through a 150-mesh sieve to obtain the adsorbent.

[0074] Performance testing

[0075] Single simulated wastewater solutions of tetracycline and sulfamethoxazole were prepared with an initial concentration C0 = 100 mg / L and pH = 7. The adsorbents prepared in Examples 1-3 and Comparative Examples 1-6 were used as samples. 50 mg of each sample was added to 100 ml of the above single simulated wastewater solutions, and the mixture was shaken at a constant temperature of 25°C. Samples were taken at different time points (5 min, 10 min, 20 min, 30 min, 60 min, 120 min, 180 min, 300 min, and 480 min), filtered through a 0.45 μm membrane, and the concentration C0 was determined using a UV spectrophotometer. t Calculate the adsorption amount q t (mg / g) = (C0-C) t )×V / m;

[0076] With the adsorbent dosage fixed at 0.5 g / L, the initial antibiotic concentrations were varied (20 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 300 mg / L), and the mixture was shaken at 25 °C until adsorption equilibrium was reached (24 h). The equilibrium concentration C was then measured. e Calculate the equilibrium adsorption amount q e The data were fitted using Langmuir and Freundlich models.

[0077] The pH values ​​of tetracycline and sulfamethoxazole (100 mg / L) were adjusted to (3, 5, 7, 9, 11) with 0.1 mol / L hydrochloric acid or sodium hydroxide. After adsorption equilibrium was reached by adding 0.5 g / L of adsorbent, the adsorption capacity was measured.

[0078] Prepare a mixed solution of tetracycline and sulfamethoxazole at 50 mg / L each, add adsorbent (0.5 g / L), and after adsorption equilibrium is reached, measure the remaining concentration of each component and calculate the adsorption capacity.

[0079] The saturated adsorbent was collected by filtration and then mixed with 0.1 mol / L sodium hydroxide and 20% ethanol in equal volume ratio to form a mixed solution. The solution was shaken and desorbed for 2 hours. After washing until neutral, the solution was dried. This adsorption-desorption cycle was repeated 5 times, and the adsorption capacity was recorded each time. Specific results are shown in the table below.

[0080] <![CDATA[BET specific surface area (m 2 / g)]]> <![CDATA[Equilibrium adsorption capacity of tetracycline q e (mg / g)]]> <![CDATA[Equilibrium adsorption capacity q of sulfamethoxazole e (mg / g)]]> Tetracycline adsorption capacity in the mixed solution (mg / g) Adsorption capacity of sulfamethoxazole in the mixed solution (mg / g) Tetracycline capacity retention rate after 5 cycles / % Example 1 163 288 203 215 185 90 Example 2 178 328 192 258 175 93 Example 3 188 305 158 234 140 95 Comparative Example 1 ＜30 105 225 78 190 76 Comparative Example 2 204 278 72 125 40 90 Comparative Example 3 160 185 148 138 125 83 Comparative Example 4 141 98 135 85 110 80 Comparative Example 5 168 295 168 208 150 88 Comparative Example 6 179 260 48 115 30 90

[0081] As shown in the table above, the composite adsorbents of Examples 1-3 of this invention exhibit high equilibrium adsorption capacities for both tetracycline and sulfamethoxazole, demonstrating superior overall performance compared to the comparative examples and single-component materials. The materials in these examples demonstrate a clear multi-mechanism synergistic effect: the polycarboxylated bentonite primarily provides hydrogen bonds and π-π interactions, responsible for the efficient adsorption of tetracycline; the sulfonic acid and phosphonic acid groups of the acid-modified polyethylene glycol contribute strong electrostatic and coordination interactions, dominating the adsorption of sulfamethoxazole. The composite adsorbents maintain high adsorption capacity even in mixed competitive adsorption, and the adsorption retention rate is over 90% after 5 cycles, proving its structural stability, broad-spectrum efficiency, and solving the problems of narrow adsorption spectra and poor stability associated with single materials.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0083] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A modified bentonite antibiotic adsorbent, characterized in that, It is composed of polycarboxylated bentonite and acid-modified polyethylene glycol; the polycarboxylated bentonite is prepared by reacting epoxy-functionalized bentonite with pyromellitic dianhydride; the epoxy-functionalized bentonite is prepared by surface modification of bentonite with 3-glycidyl etheroxypropyltriethoxysilane; the acid-modified polyethylene glycol is prepared by reacting sulfonic acid-modified polyethylene glycol with 2-carboxyethylphenylphosphine; the sulfonic acid-modified polyethylene glycol is prepared by reacting polyethylene glycol diglycidyl ether with aminosulfonic acid.

2. The modified bentonite antibiotic adsorbent according to claim 1, characterized in that, The mass ratio of the polycarboxylated bentonite to the acid-modified polyethylene glycol is 1-3:

1.

3. The modified bentonite antibiotic adsorbent according to claim 1, characterized in that, The preparation method of the polycarboxylated bentonite includes the following steps: S1: Place 3-glycidyl etheroxypropyltriethoxysilane in anhydrous ethanol, add acetic acid solution to adjust pH, stir magnetically for 1-1.5 h, add bentonite, ultrasonically disperse for 10-15 min, heat to 65-70℃, stir for 6-8 h, filter, wash, and dry to obtain epoxy-functionalized bentonite. S2: Place the epoxy-functionalized bentonite in dimethyl sulfoxide, ultrasonically disperse for 15-20 min, introduce nitrogen gas, add pyromellitic dianhydride and catalyst, heat to 80-90℃ and react for 8-10 h, cool to room temperature, filter, wash and dry to obtain polycarboxylated bentonite.

4. The modified bentonite antibiotic adsorbent according to claim 3, characterized in that, In step S1, adjusting the pH by adding acetic acid solution specifically involves adding acetic acid with a concentration of 1-2 mol / L to adjust the pH to 4-5.

5. The modified bentonite antibiotic adsorbent according to claim 3, characterized in that, In step S2, the catalyst is triethylamine.

6. The modified bentonite antibiotic adsorbent according to claim 1, characterized in that, The method for preparing the acid-modified polyethylene glycol includes the following steps: SS1: Polyethylene glycol diglycidyl ether and aminosulfonic acid were placed in dimethyl sulfoxide, nitrogen gas was introduced, and the temperature was raised to 80-85℃ for 4-6 hours. After cooling, the mixture was transferred to ice-cold ether, the precipitate was collected, washed and dried to obtain sulfonic acid modified polyethylene glycol. SS2: Sulfonic acid-modified polyethylene glycol was placed in N,N-dimethylformamide, and 2-carboxyethylphenylphosphine and p-toluenesulfonic acid were added. The mixture was heated and reacted. The product was collected by vacuum distillation to obtain acid-modified polyethylene glycol.

7. The modified bentonite antibiotic adsorbent according to claim 6, characterized in that, In step SS1, the number-average molecular weight of the polyethylene glycol diglycidyl ether is 300-2000.

8. The modified bentonite antibiotic adsorbent according to claim 6, characterized in that, In step SS2, the temperature of the heating reaction is 90-100℃, and the time is 6-8h.

9. A method for preparing the modified bentonite antibiotic adsorbent as described in claim 1, characterized in that, Includes the following steps: Step 1: Mix polycarboxylated bentonite with acid-modified polyethylene glycol and place it in anhydrous ethanol. After ultrasonic treatment for 20-30 minutes, a suspension is formed. Step 2: Stir and evaporate the suspension at 60-65℃ until it becomes a paste, then vacuum dry it at 80-90℃ for 12-15 hours, and finally grind it through a 100-200 mesh sieve to obtain the adsorbent.

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