Pond bottom mud biochar capable of adsorbing ciprofloxacin pollutants and preparation method of pond bottom mud biochar

Abstract

The invention relates to the technical field of inorganic porous materials, and discloses pond bottom mud biochar capable of adsorbing ciprofloxacin pollutants and a preparation method of the pond bottom mud biochar capable of adsorbing ciprofloxacin pollutants, and the preparation method of the pond bottom mud biochar capable of adsorbing ciprofloxacin pollutants comprises the following steps: taking pond bottom mud, drying and grinding to obtain a biochar precursor; heating and carbonizing the biochar precursor to obtain biochar; the biochar is soaked in a strong alkali solution to be heated and activated, and the pond sediment biochar capable of adsorbing ciprofloxacin pollutants is obtained. According to the method, the pond bottom mud biochar is activated by adopting the strong alkali solution, so that the pore structure of the biochar is effectively etched and amplified, and the specific surface area and surface active sites of the biochar are greatly increased. Compared with unmodified biochar, the modified material has the advantage that the adsorption capacity and the removal rate of CIP are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of inorganic porous materials technology, and more specifically, to a pond bottom sediment biochar capable of adsorbing ciprofloxacin pollutants and its preparation method. Background Technology

[0002] Pond aquaculture is a major mode of freshwater fisheries, generating substantial amounts of aquatic products but also producing large quantities of aquaculture sediment and wastewater. These wastes often contain high concentrations of antibiotic residues, with ciprofloxacin (CIP), a commonly used fluoroquinolone antibiotic, being a typical pollutant in aquaculture environments due to its widespread use in controlling bacterial diseases. Persistent CIP residues can not only induce the generation and spread of resistance genes in aquatic environments but also pose a potential risk to ecosystems. Therefore, developing efficient, economical, and environmentally friendly technologies to remove CIP from aquaculture wastewater has become an urgent issue for the sustainable development of aquaculture.

[0003] Currently, methods for treating CIP-containing wastewater mainly include advanced oxidation, membrane separation, coagulation sedimentation, and adsorption. Among these, adsorption has attracted much attention due to its simple operation and relatively low cost. Biochar, as a carbon-rich material produced by biomass pyrolysis, possesses advantages such as large specific surface area, abundant pore structure, and tunable surface functional groups, and is considered a highly promising adsorbent. Existing research has utilized crop straw, wood, sludge, and other raw materials to prepare biochar for the adsorption of pollutants in water bodies.

[0004] However, existing technologies still have several limitations: First, there is insufficient research on coupled technologies specifically designed for the resource utilization of aquaculture waste and the simultaneous treatment of pollutants. The direct use of pond sediment, a major form of solid waste, to prepare functional materials for treating aquaculture wastewater, thus achieving a closed-loop treatment approach of "treating waste with waste," has not yet been fully explored and practiced. Second, conventional biochar often has limited adsorption capacity and selectivity for specific antibiotics such as CIP, and the adsorption performance of unmodified raw biochar is insufficient to meet the requirements for efficient removal. Third, simple physical adsorption merely transfers pollutants from the water body to the solid phase, leading to secondary disposal issues after adsorption saturation. This fails to fully utilize the potential of biochar as a microbial carrier to achieve synergistic removal of pollutants through adsorption and biodegradation.

[0005] Therefore, there is an urgent need for an innovative method that can simultaneously solve the problems of aquaculture sediment disposal and aquaculture wastewater purification. This invention aims to provide a biochar prepared and functionalized from pond sediment through a specific process. This material can not only efficiently adsorb CIP, but also synergistically enhance the degradation process with functional microorganisms, providing an economical, efficient, and sustainable technical solution for antibiotic pollution control in aquaculture environments. Summary of the Invention

[0006] In view of this, the present invention proposes a pond bottom sediment biochar capable of adsorbing ciprofloxacin pollutants and its preparation method, aiming to solve the problems of limited adsorption capacity and low selectivity of conventional biochar for ciprofloxacin in the current technology.

[0007] This invention proposes a method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants, comprising the following steps: 1) Take pond bottom mud, dry it, and grind it to obtain biochar precursor; 2) Biochar is obtained by heating and carbonizing the biochar precursor; 3) The biochar was impregnated in a strong alkaline solution and heated to activate it, thus obtaining pond bottom biochar that can adsorb ciprofloxacin pollutants.

[0008] Preferably, the particle size of the biochar precursor in step 1) is >300 mesh.

[0009] Preferably, the heating and carbonization temperature in step 2) is 600~800℃, and the time is 1.5~3h; The heating and carbonization is carried out under an inert atmosphere; The heating rate for carbonization is 8~20℃ / min.

[0010] Preferably, the concentration of the strong alkali solution in step 3) is 80~120g / L; The mass-to-volume ratio of the strong alkaline solution to the pond bottom biochar is 5-20g:100mL; The strong base includes one or more of KOH, NaOH, Ca(OH)2 and Ba(OH)2.

[0011] Preferably, the heating activation in step 3) is ultrasound-assisted activation; The power of ultrasound is 300~500W.

[0012] Preferably, the heating activation temperature in step 3) is 80~100℃ and the time is 20~40min.

[0013] This invention provides a pond bottom biochar that can adsorb ciprofloxacin pollutants, prepared by the above preparation method.

[0014] This invention also provides an application of the above-mentioned pond sediment biochar capable of adsorbing ciprofloxacin pollutants in the treatment of ciprofloxacin-containing wastewater, the application method of which is as follows: Adding pond bottom biochar, which can adsorb ciprofloxacin pollutants, to wastewater containing ciprofloxacin adsorbs ciprofloxacin pollutants.

[0015] Preferably, the pH value of the ciprofloxacin-containing wastewater is >7.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention innovatively uses pond bottom mud, a waste generated during aquaculture, as the sole raw material, and transforms it into a high-value-added adsorbent material through carbonization and modification. This not only provides an efficient and economical way to utilize the large amount of accumulated aquaculture bottom mud and reduces the cost of solid waste disposal, but also realizes the construction of a closed loop of "pollutant treatment of pollutants" within the aquaculture system, significantly improving the sustainability and environmental benefits of the entire industrial chain.

[0017] (2) This invention activates pond bottom biochar with a strong alkaline solution, effectively etching and expanding the pore structure of the biochar, significantly increasing its specific surface area and surface active sites. Compared with unmodified biochar, the modified material shows a significant improvement in adsorption capacity and removal rate for CIP. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 Scanning electron microscope (SEM) images of pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3; Figure 1 Image (a) in the image is a microscopic morphology diagram of BC600. Figure 1 (b) in the figure is a microscopic morphology diagram of BC700. Figure 1 (c) in the figure is a microscopic morphology diagram of BC800. Figure 1 (d) in the figure is a microscopic morphology diagram of KBC600; Figure 2 Infrared spectra of BC600, BC700, and BC800; Figure 3 The infrared spectrum of KBC600; Figure 4 The adsorption kinetics fitting curve for BC600; Figure 5 The adsorption kinetics fitting curve for KBC600 is shown. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0020] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention proposes a method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants, comprising the following steps: 1) Take pond bottom mud, dry it, and grind it to obtain biochar precursor; 2) Biochar is obtained by heating and carbonizing the biochar precursor; 3) The biochar was impregnated in a strong alkaline solution and heated to activate it, thus obtaining pond bottom biochar that can adsorb ciprofloxacin pollutants.

[0025] In this invention, the particle size of the biochar precursor described in step 1) is >300 mesh. Drying the pond sediment and grinding it through a 300-mesh sieve yields a biochar precursor with uniform particle size. Uniform particle size increases the contact area between the sediment and heat during subsequent carbonization, ensuring a uniform carbonization reaction and avoiding insufficient or excessive carbonization in certain areas. This lays the foundation for preparing biochar with a well-developed pore structure and stable adsorption performance.

[0026] In this invention, the heating and carbonization temperature in step 2) is 600~800℃, preferably 630~780℃, more preferably 650~750℃, and even more preferably 680~720℃; the time is 1.5~3h, preferably 2~2.5h, and even more preferably 2h. A carbonization time of 2h ensures that the organic matter in the sediment is fully decomposed and completely carbonized, forming a stable carbon skeleton structure. At the same time, it avoids insufficient carbonization (insufficient adsorption sites) due to too short a time or increased energy consumption and collapse of the biochar structure due to too long a time.

[0027] In this invention, the heating and carbonization is carried out under an inert atmosphere, which includes one or more of nitrogen, helium, neon, and argon. The inert atmosphere isolates oxygen, preventing the biochar from being oxidized and burned during the high-temperature carbonization process, effectively preserving the carbon content and pore structure of the biochar, and maintaining its adsorption performance.

[0028] In this invention, the heating rate for carbonization is 8~20℃ / min, preferably 8~15℃ / min, more preferably 8~12℃ / min, and even more preferably 10℃ / min. This heating rate avoids excessively rapid heating that could lead to thermal stress concentration inside the sediment, causing pore collapse, while ensuring a stable carbonization process and promoting uniform development of biochar pores.

[0029] In this invention, the concentration of the strong alkali solution in step 3) is 80~120g / L, preferably 85~115g / L, more preferably 90~110g / L, and even more preferably 100g / L.

[0030] In this invention, the mass-to-volume ratio of the strong alkaline solution to the pond bottom biochar is 5-20 g: 100 mL, preferably 8-18 g: 100 mL, more preferably 10-16 g: 100 mL, and even more preferably 12-15 g: 100 mL.

[0031] In this invention, the strong alkali includes one or more of KOH, NaOH, Ca(OH)2 and Ba(OH)2, preferably KOH.

[0032] In this invention, the heating activation in step 3) is ultrasonic-assisted activation. The ultrasonic power is 300-500W, preferably 330-480W, more preferably 350-450W, and even more preferably 500W. Ultrasonic vibration can accelerate the diffusion and penetration of KOH solution on the surface of biochar, promote the modification reaction rate, shorten the activation time, and make the modification more uniform, further increasing the specific surface area and pore volume of biochar.

[0033] In this invention, the heating activation temperature in step 3) is 80~100℃, preferably 85~95℃, more preferably 88~92℃, and even more preferably 90℃; the time is 20~40min, preferably 23~38min, more preferably 25~35min, and even more preferably 30min.

[0034] In this invention, after the heating activation in step 3) is completed, the biochar-strong alkali solution system is placed in the dark and dry conditions for standing for 4 to 8 hours, preferably 6 hours.

[0035] This invention provides a pond bottom biochar that can adsorb ciprofloxacin pollutants, prepared by the above preparation method.

[0036] This invention also provides an application of the above-mentioned pond sediment biochar capable of adsorbing ciprofloxacin pollutants in the treatment of ciprofloxacin-containing wastewater, the application method of which is as follows: Adding pond bottom biochar, which can adsorb ciprofloxacin pollutants, to wastewater containing ciprofloxacin adsorbs ciprofloxacin pollutants.

[0037] In this invention, the pH value of the ciprofloxacin-containing wastewater is >7.

[0038] The pond sediment used in the following examples was collected from the bottom 10cm of the tilapia pond at Nanjing Agricultural University's Wuxi Fisheries Institute. The collection time was May 6, 2023.

[0039] Example 1 (1) After the pond bottom mud is naturally air-dried, it is transferred to an oven and dried at 75°C until the quality is constant; After the dried pond bottom mud is ground, it is passed through a 300-mesh stainless steel sieve for later use.

[0040] (2) The pond bottom mud treated in step (1) is heated in a tube furnace under nitrogen flow. The nitrogen flow rate is 350 mL / min, and the temperature is increased to 600℃ at a rate of 10℃ / min. The temperature is then maintained for 2 hours. The resulting biochar is denoted as BC600.

[0041] (3) Mix 5g of biochar BC600 with 100mL of KOH solution with a concentration of 100g / L and sonicate at 90℃ for 30min with an ultrasonic power of 300W. Then let it stand in the dark and dry for 6h to obtain modified biochar.

[0042] (4) The modified biochar was filtered, washed with sterile water until neutral, and dried to constant weight to obtain pond bottom biochar that can adsorb ciprofloxacin pollutants, denoted as KBC600.

[0043] Example 2 The only difference from Example 1 is that the heating temperature in step (2) is 700°C, the resulting biochar is denoted as BC700, and the resulting modified biochar is denoted as KBC700.

[0044] Example 3 The only difference from Example 1 is that the heating temperature in step (2) is 800°C, the resulting biochar is denoted as BC800, and the resulting modified biochar is denoted as KBC800.

[0045] Example 4 (1) After the pond bottom mud is naturally air-dried, it is transferred to an oven and dried at 75°C until the quality is constant. After the dried pond bottom mud is ground, it is passed through a 300-mesh stainless steel mesh screen for later use.

[0046] (2) The pond bottom mud treated in step (1) is heated in a tube furnace under an argon flow. The argon flow rate is 350 mL / min, and the temperature is raised to 700℃ at a rate of 12℃ / min. The temperature is then maintained for 2 hours to obtain pond bottom mud biochar.

[0047] (3) Mix 12g of pond bottom biochar with 100mL of 95g / L NaOH solution, sonicate at 90℃ for 30min with ultrasonic power of 400W, and then let stand in the dark and dry for 6h to obtain modified biochar.

[0048] (4) The modified biochar was filtered, washed with sterile water until neutral, and dried to constant weight to obtain pond bottom biochar that can adsorb ciprofloxacin pollutants.

[0049] Example 5 (1) After the pond bottom mud is naturally air-dried, it is transferred to an oven and dried at 75°C until the quality is constant. After the dried pond bottom mud is ground, it is passed through a 300-mesh stainless steel mesh screen for later use.

[0050] (2) The pond bottom mud treated in step (1) was heated in a tube furnace under a mixed gas flow of nitrogen and helium (volume ratio 1:1). The mixed gas flow rate was 350 mL / min, and the temperature was raised to 720℃ at a rate of 8℃ / min. The temperature was then maintained for 2.2 h to obtain pond bottom mud biochar.

[0051] (3) Mix 15g of pond bottom biochar with 100mL of KOH-NaOH mixed solution with a concentration of 105g / L (mass ratio 3:1), sonicate at 92℃ for 35min with ultrasonic power of 500W, and then let stand in the dark and dry for 6h to obtain modified biochar.

[0052] (4) The modified biochar was filtered, washed with sterile water until neutral, and dried to constant weight to obtain pond bottom biochar that can adsorb ciprofloxacin pollutants.

[0053] Example 6 (1) After the pond bottom mud is naturally air-dried, it is transferred to an oven and dried at 75°C until the quality is constant. After the dried pond bottom mud is ground, it is passed through a 300-mesh stainless steel mesh screen for later use.

[0054] (2) The pond bottom mud treated in step (1) is heated in a tube furnace under a neon gas flow. The neon gas flow rate is 350 mL / min, and the temperature is raised to 650℃ at a rate of 15℃ / min. After holding at the temperature for 2.5h, pond bottom mud biochar is obtained.

[0055] (3) Mix 10g of pond bottom biochar with 100mL of KOH-Ca(OH)2 mixed solution with a concentration of 90g / L (mass ratio 4:1), sonicate at 88℃ for 28min with ultrasonic power of 350W, and then let stand in the dark and dry for 6h to obtain modified biochar.

[0056] (4) The modified biochar was filtered, washed with sterile water until neutral, and dried to constant weight to obtain pond bottom biochar that can adsorb ciprofloxacin pollutants.

[0057] 1. The pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3 were characterized.

[0058] The microstructure of the pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3 was characterized using scanning electron microscopy. The results are as follows: Figure 1 As shown. Figure 1 Image (a) in the image is a microscopic morphology diagram of BC600. Figure 1 (b) in the figure is a microscopic morphology diagram of BC700. Figure 1 (c) in the figure is a microscopic morphology diagram of BC800. Figure 1 (d) in the figure is a microscopic morphology diagram of KBC600.

[0059] As can be seen from the figure, all samples have relatively smooth and intact surfaces. Comparing biochar BC600 (pyrolysis temperature 600℃), biochar BC700 (pyrolysis temperature 700℃), and biochar BC800 (pyrolysis temperature 800℃), it can be seen that the higher temperature reduces porosity and narrower pore openings, limiting adsorption sites and reducing adsorption efficiency. In contrast, KBC600, after being modified with KOH, has increased surface roughness, smaller pores, and deeper cracks, thereby enhancing the specific surface area and overall adsorption efficiency.

[0060] The pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3 were characterized using Fourier transform infrared spectroscopy. The results are as follows: Figure 2 , Figure 3 As shown. Figure 2 Infrared spectra of BC600, BC700, and BC800; Figure 3 The image shows the infrared spectrum of KBC600. It can be seen from the figure that after modification, the absorption peaks of most functional groups decreased or disappeared. The surface KOH reacted with the C structure and hydroxyl groups of biochar, altering the surface functional groups. The hydroxyl content in KBC600 was significantly reduced, and the CH absorption peak was at 2961 cm⁻¹. -1 It splits at 1093cm -1 and 1026cm -1 The increase in peak values ​​indicates a significant change in the structure of biochar, which is related to the improved CIP adsorption effect.

[0061] The surface elemental composition of BC600 and KBC600 is shown in Table 1.

[0062] Table 1 Surface element content of BC600 and KBC600

[0063] As can be seen from the data in Table 1, KOH modification caused significant changes in the carbon and oxygen elemental composition and carbon-oxygen ratio; the lower O / C and N+O / C values ​​indicate a reduction in oxygen-containing functional groups, an increase in aromaticity and hydrophobicity, and an improvement in adsorption performance.

[0064] The surface characteristic parameters of the pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3 are shown in Table 2.

[0065] Table 2 Surface characteristic parameters of various biochars

[0066] 2. The adsorption performance of ciprofloxacin on the pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3 was tested.

[0067] A. Detect the adsorption capacity of ciprofloxacin on the pond sediment biochar and modified pond sediment biochar prepared in Examples 1-3.

[0068] Take 0.25g each of BC600, KBC600, BC700, KBC700, BC800 and KBC800, add them to 50mL of ciprofloxacin solution with a concentration of 0.001mg / L, and incubate for 1h on a shaker at 25℃ and 190r / min.

[0069] After the culture was completed, the solution was filtered through a 0.22 μm filter membrane, and the concentration of residual ciprofloxacin in the solution was measured. The adsorption capacity of each biochar was calculated, and the measurement results are shown in Table 3.

[0070] Table 3 Adsorption capacity of various biochars for ciprofloxacin

[0071] B. Adsorption kinetics of biochar BC600 and modified biochar KBC600.

[0072] A flask containing 10 mg / L CIP solution was placed on a shaker (25℃, 190 r / min). BC600 and KBC600 were added at an addition ratio of 1 g / L. The remaining CIP concentration was measured at 3, 10, 30, 60, 120, 180, 300, 480, 600, 720, 1080, and 1440 minutes. Based on the measurement results, an adsorption kinetic fitting curve was obtained, as shown below. Figure 4 , Figure 5 As shown.

[0073] 3. The modified biochar KBC600 prepared in Example 1 was used for the treatment of aquaculture wastewater.

[0074] Wastewater from tilapia ponds at Wuxi Fisheries College of Nanjing Agricultural University was used. Modified biochar KBC600 was added to the wastewater at a dosage of 1 g / L. The removal rate of ciprofloxacin reached 47.77% within 1 hour. The concentration of ciprofloxacin in the wastewater and the physicochemical indicators of the water quality are shown in Table 4.

[0075] Table 4. Ciprofloxacin and Physicochemical Indicators in Tilapia Farming Pond Wastewater

[0076] Note: Chlorophyll a is measured in μg / L, pH is dimensionless, and other units are measured in mg / L.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants, characterized in that, Includes the following steps: 1) Take pond bottom mud, dry it, and grind it to obtain biochar precursor; 2) Biochar is obtained by heating and carbonizing the biochar precursor; 3) The biochar was impregnated in a strong alkaline solution and heated to activate it, thus obtaining pond bottom biochar that can adsorb ciprofloxacin pollutants.

2. The method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants according to claim 1, characterized in that, The particle size of the biochar precursor mentioned in step 1) is >300 mesh.

3. The method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants according to claim 2, characterized in that, The heating and carbonization temperature described in step 2) is 600~800℃, and the time is 1.5~3h; The heating and carbonization is carried out under an inert atmosphere; The heating rate for carbonization is 8~20℃ / min.

4. The method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants according to claim 3, characterized in that, The concentration of the strong alkali solution mentioned in step 3) is 80~120g / L; The mass-to-volume ratio of the strong alkaline solution to the pond bottom biochar is 5-20g:100mL; The strong base includes one or more of KOH, NaOH, Ca(OH)2 and Ba(OH)2.

5. The method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants according to claim 4, characterized in that, The heating activation described in step 3) is ultrasonic-assisted activation; The power of ultrasound is 300~500W.

6. A method for preparing pond sediment biochar capable of adsorbing ciprofloxacin pollutants according to claim 4 or 5, characterized in that, The heating activation temperature in step 3) is 80~100℃, and the time is 20~40min.

7. The pond sediment biochar capable of adsorbing ciprofloxacin pollutants prepared by the method of any one of claims 1 to 6.

8. The application of the pond sediment biochar capable of adsorbing ciprofloxacin pollutants as described in claim 7 in the treatment of ciprofloxacin-containing wastewater, characterized in that, The application method is as follows: Adding pond bottom biochar, which can adsorb ciprofloxacin pollutants, to wastewater containing ciprofloxacin adsorbs ciprofloxacin pollutants.

9. The application of pond bottom sediment biochar according to claim 8 in the treatment of ciprofloxacin-containing wastewater, characterized in that, The pH value of the ciprofloxacin-containing wastewater is >7.

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