Preparation method and application of a waste shrimp shell-based biochar material

Abstract

The application discloses a preparation method and application of a biochar material based on waste shrimp shells, and belongs to the fields of environmental functional materials and water treatment. The method is characterized in that waste shrimp shells are used as raw materials, and the biochar material is prepared through high-temperature pyrolysis and acid washing purification. The method effectively removes inorganic ash (mainly calcium carbonate) in the shrimp shell biochar by precisely controlling the pyrolysis temperature (600-900 DEG C) and combining with acid washing treatment, significantly improves the specific surface area and pore structure of the shrimp shell biochar, exposes rich carbon skeletons and surface oxygen-containing functional groups, and the prepared biochar material can be used for degrading antibiotics in wastewater. The biochar material activates peracetic acid (PAA) as a catalyst to generate active oxygen species including singlet oxygen, and rapidly degrades the antibiotics in water. The application realizes high-value utilization of waste shrimp shells, provides a new water treatment material which is low in cost, friendly to the environment and excellent in catalytic performance, and has a wide application prospect in the field of antibiotic wastewater deep treatment.

Description

Technical Field

[0001] This invention relates to the fields of environmental functional materials and water treatment, specifically to a method for preparing and applying biochar material based on waste shrimp shells. Background Technology

[0002] The extensive use and discharge of antibiotics pose a serious threat to the aquatic ecosystem and human health. Sulfamethoxazole (SMX), a typical sulfonamide antibiotic, is frequently detected in the environment. Its chemical properties are stable, making it difficult to remove effectively by traditional biological treatment methods. Therefore, it is urgent to develop efficient and economical advanced treatment technologies for antibiotic wastewater.

[0003] Advanced oxidation technologies based on peracetic acid (PAA) have attracted widespread attention in recent years due to their advantages such as high oxidation potential, few reaction byproducts, and wide applicable pH range. PAA can be activated by various catalysts (such as transition metal ions, metal oxides, and carbon materials) to generate highly reactive species such as hydroxyl radicals (·OH), organic radicals (RO·), and singlet oxygen (¹O2), thereby achieving efficient degradation of organic pollutants. However, homogeneous metal ion catalysts are prone to loss and secondary pollution. Traditional carbon-based catalysts (such as graphene and carbon nanotubes) are expensive to prepare, which limits their large-scale application.

[0004] Biochar, as a carbon-rich material prepared by pyrolysis of agricultural or fishery waste, has advantages such as low cost, large specific surface area, and abundant surface functional groups. Waste shrimp shells contain a large amount of calcium carbonate and organic matter, making them an ideal precursor for biochar preparation. However, the surface of shrimp shell biochar obtained by direct pyrolysis is often covered by ash (mainly CaCO3), which blocks the pores and severely inhibits the exposure of its catalytic active sites and mass transfer efficiency.

[0005] In existing technologies, although there are reports of using shrimp shells to prepare biochar, these methods only employ high-temperature pyrolysis or simple acid washing alone, without combining high-temperature pyrolysis carbonization with acid washing purification processes. This fails to effectively remove ash, or the preparation methods do not fully explore and utilize the potential of biochar to activate PAA. Therefore, how to effectively remove ash and regulate the physicochemical structure of biochar through a post-treatment strategy that combines high-temperature pyrolysis and acid washing purification to obtain efficient and stable PAA activation materials is a key technical challenge for realizing the resource utilization of waste shrimp shells and the efficient treatment of antibiotic wastewater. Summary of the Invention

[0006] The purpose of this invention is to provide a biochar material with high porosity, a pure carbon framework, and abundant surface active sites, as well as a method for preparing the same. This method employs a series of strategies involving "high-temperature pyrolysis-acid washing purification" to efficiently activate PAA (acid-based antibiotics) in the prepared biochar material and rapidly degrade antibiotics in water. Specifically, the method includes the following steps: (1) The pretreated waste shrimp shells are pyrolyzed at high temperature under inert gas protection to carbonize the organic matter and obtain primary biochar, while the calcium in it is mainly in the form of calcium carbonate.

[0007] (2) Weigh a certain amount of the primary biochar from step (1) and acid wash it with acid solution to selectively remove inorganic ash such as calcium carbonate.

[0008] (3) Wash the acid-washed biochar in step (2) until it is neutral and then dry it to obtain the biochar material based on waste shrimp shells.

[0009] Preferably, the waste shrimp shells in step (1) need to be pre-treated, i.e., washed, dried and crushed.

[0010] Preferably, the inert gas in step (1) is nitrogen, the shrimp shell powder is placed in a ceramic boat, and the pyrolysis is carried out in a tube furnace. The high-temperature pyrolysis temperature is 600~900℃, the heating rate is 5~10℃ / min, and the pyrolysis time is 1~3 hours.

[0011] Preferably, the acid washing in step (2) uses HCl with a concentration of 0.5~2mol / L, the acid washing time is 2~6 hours, the mixture is stirred at room temperature, and the solid-liquid ratio of the nascent biochar to HCl is 1g:50mL~5g:250mL.

[0012] Preferably, the mixture after acid washing in step (3) is separated by vacuum filtration, washed with pure water, and dried in an oven at 60°C to constant weight.

[0013] Another objective of this invention is to provide the application of the waste shrimp shell biochar material prepared by the method in the degradation of antibiotics in wastewater. The self-assembled biochar material is added to wastewater containing antibiotics, and then peracetic acid (PAA) solution is added and stirred at room temperature.

[0014] Preferably, the pH of the reaction system is 3-9, the initial concentration of the antibiotic (such as SMX) is 5-10 mg / L, the amount of biochar material added is 0.05-0.5 g / L, the amount of peracetic acid added is 0.2-1.0 mmol / L, and the reaction time is 30-60 min.

[0015] Preferably, the antibiotic includes one or more of sulfamethoxazole (SMX), sulfadiazine (SDZ), tetracycline (TC), and ciprofloxacin (CIP).

[0016] The beneficial effects of this invention are: (1) This invention uses waste shrimp shells as raw materials, which not only solves the problem of waste disposal and realizes "waste treatment" and resource utilization, but also greatly reduces the preparation cost of catalyst.

[0017] (2) The two-step preparation process of the present invention, namely pyrolysis-acid washing, is simple to operate and easy to scale up for production; the acid washing reagent used is a common chemical and can be neutralized and treated, so the environmental risk is controllable.

[0018] (3) The biochar material prepared by the present invention effectively removes ash by acid washing, and the specific surface area and pore volume are significantly increased. In addition, the acid washing process also "unlocks" the pores blocked by ash and exposes more carbon edge defect sites and oxygen-containing functional groups (such as -OH, C=O, CO). Experiments show that compared with un-acid-washed biochar, the acid-washed material has an efficiency of about 13 times higher in degrading SMX.

[0019] (4) The biochar material prepared in this invention, as a heterogeneous catalyst, has carbon defect sites and oxygen-containing functional groups (such as -OH, C=O, CO) on its surface that can synergistically activate peracetic acid (PAA) molecules. During the activation process, the peroxy bond (-OO-) of PAA breaks under the action of the active sites on the biochar surface. On the one hand, it generates a variety of reactive oxygen free radicals, including hydroxyl free radicals (·OH) and acetoxy free radicals (CH3C(O)O·), through the free radical pathway. These free radicals can non-selectively attack antibiotic molecules, achieving rapid oxidative degradation. On the other hand, the surface of the biochar... It can also convert PAA into singlet oxygen (¹O2) through a non-radical pathway. ¹O2, as an electrophilic active species, can selectively and efficiently degrade electron-rich organic pollutants. The synergistic effect of the free radical and non-radical pathways enables the biochar material of this invention to efficiently break the peroxy bond of PAA, achieving rapid and deep degradation of antibiotics such as SMX. At the same time, it effectively overcomes the defect of the single free radical pathway being easily interfered with by the water matrix (such as natural organic matter and inorganic anions), and can still maintain excellent catalytic activity and stability in complex aquatic environments, achieving rapid and efficient degradation of antibiotics such as SMX.

[0020] (5) The biochar material prepared by the present invention can maintain high catalytic activity in a wide pH range (pH=3~9), and shows good degradation effect in different water bodies (such as tap water and lake water), and has the potential for reusability. Attached Figure Description

[0021] Figure 1 SEM images of the shrimp shell biochar of the present invention prepared at 600℃ (before and after acid washing): (a) SEM image of the biochar before acid washing at 600℃, (b) SEM image of the biochar after acid washing at 600℃.

[0022] Figure 2SEM images of the shrimp shell biochar of the present invention prepared at 700℃ (before and after acid washing): (a) SEM image of the biochar before acid washing at 700℃, (b) SEM image of the biochar after acid washing at 700℃.

[0023] Figure 3 SEM images of the shrimp shell biochar of the present invention (before and after acid washing) prepared at 800℃: (a) SEM image of the biochar before acid washing at 800℃, (b) SEM image of the biochar after acid washing at 800℃.

[0024] Figure 4 SEM images of the shrimp shell biochar of the present invention prepared at 900℃ (before and after acid washing): (a) SEM image of the biochar before acid washing at 900℃, (b) SEM image of the biochar after acid washing at 900℃.

[0025] Figure 5 The XRD patterns of the shrimp shell biochar of the present invention before and after acid washing at different preparation temperatures (600~900℃) are compared.

[0026] Figure 6 The Fourier transform infrared (FTIR) spectrum of shrimp shell biochar A-BC700 (prepared at 700℃) in Example 2 of this invention is shown, comparing the changes in functional groups on the sample surface before and after acid washing.

[0027] Figure 7 The graph shows the degradation performance of sulfamethoxazole by activated PAA (800℃ acid-washed sample) from shrimp shell biochar A-BC800 in Example 3 of this invention under different pH conditions.

[0028] Figure 8 This is a graph showing the effect of shrimp shell biochar A-BC800 (800℃ acid-washed sample) in Example 3 of the present invention on the degradation of sulfamethoxazole through multiple cycles under the same conditions.

[0029] Figure 9 The degradation performance of the catalysts for sulfamethoxazole before and after acid washing at different temperatures (600~900℃) is shown in the figure.

[0030] Figure 10 The graph shows the degradation performance of shrimp shell biochar A-BC800 (800℃ acid-washed sample) on sulfamethoxazole (SMX) under different water conditions in Example 3 of this invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the contents described herein.

[0032] Example 1 The specific steps for preparing A-BC600 shrimp shell (South American shrimp) biochar material are as follows: (1) Wash the waste shrimp shells with tap water, rinse them three times with deionized water, dry them in a 60℃ oven for 12 hours, crush the dried shrimp shells with a crusher and pass them through a 100-mesh sieve.

[0033] (2) Weigh 10g of the above shrimp shell powder into a porcelain boat and place it in a tube furnace; under N2 atmosphere protection, heat it to 600℃ at a heating rate of 10℃ / min and keep it at this temperature for 2 hours; after natural cooling, take out the black solid and obtain the primary biochar at different temperatures, which is denoted as U-BC600.

[0034] (3) Weigh 1g of U-BC600 primary biochar and place it in 50mL of 1mol / L HCl solution. Stir magnetically and acid wash for 4 hours at room temperature.

[0035] (4) After acid washing, the solid was separated by filtration and washed with a large amount of ultrapure water until the pH of the filtrate was 7. The washed solid was placed in a 60°C oven and dried for 12 hours to obtain shrimp shell biochar material, denoted as A-BC600.

[0036] like Figure 1 As shown in b, the surface deposits of the sample pickled at 600℃ were effectively removed, exposing a honeycomb porous structure with a relatively uniform pore size distribution, exhibiting a clearer and more open pore structure.

[0037] like Figure 5 As shown, the strong diffraction peaks at 23.5° and 29.4° of the un-acid-washed sample (U-BC600) belong to calcite-type calcium carbonate, while the calcium carbonate diffraction peaks of the acid-washed sample (A-BC600) are significantly weakened.

[0038] like Figure 6 As shown, the un-acid-washed catalyst at approximately 3500 cm⁻¹ -1 A broad but weak absorption peak appears nearby, attributed to the OH stretching vibration (possibly from adsorbed water); approximately 1700 cm⁻¹ -1 The nearby peak (C=O) indicates the presence of a carbonyl group, such as a carboxyl, aldehyde, or ketone group; approximately 1420 cm⁻¹ -1 875cm -1 and 712cm -1 The presence of distinct absorption peaks at these locations is typical of calcite-type calcium carbonate (CaCO3) (corresponding to CO antisymmetric stretching and contraction, CO32-, and CO32-, respectively). 2- Out-of-plane bending and in-plane bending vibrations.

[0039] The characteristic peak of calcium carbonate in the catalyst after acid washing (approximately 1420 cm⁻¹) -1 875cm -1 712cm -1The presence of almost completely dissolved CO and COC in the acid-washed material (A-CB600) confirms that acid washing effectively removed the inorganic calcium components. After acid washing, CO and COC exhibited weak absorption bumps, and the total amount of oxygen-containing groups was higher. No CO3 was observed. 2- It has no C=O peak, retains a large amount of organic oxygen-containing skeleton through low-temperature pyrolysis, introduces hydroxyl / ether bonds through acid washing and oxidation, has well-developed pores, and strong scattering.

[0040] The biochar material A-BC600 prepared in this embodiment was subjected to performance testing for degrading SMX. The specific steps are as follows: (1) Prepare 50 mL of SMX simulated wastewater with a concentration of 10 mg / L in a beaker, add 5 mg of A-BC600 catalyst (the solid-liquid ratio of A-BC600 catalyst to simulated wastewater is 0.1 g / L), and then add 122 μL of PAA solution to make the initial concentration of the mixed solution 0.4 mmol / L.

[0041] (2) Place the beaker in a constant temperature shaker and shake the reaction at 25℃ and 400rpm. Take 1mL of sample at the preset time points (0min, 1min, 3min, 5min, 10min, 20min, 25min, 30min). Immediately after taking the sample, add 20uL of sodium thiosulfate solution to terminate the reaction. After filtering through a 0.22μm filter membrane, determine the remaining SMX concentration by high performance liquid chromatography (HPLC).

[0042] like Figure 9 As shown in the figure, the degradation performance test of the catalyst prepared in Example 1 showed that the degradation effect of the A-BC600 catalyst was significantly better than that of the blank control group without catalyst. After 30 minutes, the residual pollutant concentration ratio C / CO of the blank group remained above 0.85, and the pollutants hardly degraded. However, the C / CO of the A-BC600 catalyst system was only 0.20 after 30 minutes, and the pollutant removal rate reached 80%, proving that the acid-washed 600℃ biochar catalyst has excellent pollutant catalytic degradation ability.

[0043] Example 2 The specific steps for preparing A-BC700 shrimp shell (South American shrimp) biochar material are as follows: (1) Wash the waste shrimp shells with tap water, rinse them three times with deionized water, dry them in a 60℃ oven for 12 hours, crush the dried shrimp shells with a crusher and pass them through a 100-mesh sieve.

[0044] (2) Weigh 10g of the above shrimp shell powder into a porcelain boat, place it in a tube furnace, and heat it to 700℃ at a heating rate of 10℃ / min under N2 atmosphere protection, and keep it at this temperature for 2 hours; after natural cooling, take out the black solid and obtain the primary biochar at different temperatures, which is denoted as U-BC700.

[0045] (3) Weigh 1g of U-BC700 primary biochar and place it in 50mL of 1mol / L HCl solution. Stir magnetically and acid wash for 4 hours at room temperature.

[0046] (4) After acid washing, the solid was separated by filtration and washed with a large amount of ultrapure water until the pH of the filtrate was 7. The washed solid was placed in a 60°C oven and dried for 12 hours to obtain shrimp shell biochar material, denoted as A-BC700.

[0047] like Figure 2 As shown in the figure, compared with the un-acid-washed sample, the acid-washed sample (A-BC700) exhibits a clearer and more open pore structure. The surface deposits of A-BC700 were effectively removed, exposing the honeycomb porous structure.

[0048] like Figure 5 As shown, the strong diffraction peaks at 23.5° and 29.4° of the un-acid-washed sample (U-CB700) belong to calcite-type calcium carbonate, while the calcium carbonate diffraction peaks of the acid-washed sample (A-CB700) are significantly weakened.

[0049] like Figure 6 As shown in the figure, the un-acid-washed U-BC700 sample at 1420 cm⁻¹... -1 875cm -1 712cm -1 A strong characteristic absorption peak of calcium carbonate is present at 1700 cm⁻¹. -1 There is a distinct C=O carbonyl stretching vibration peak nearby, at 3500 cm⁻¹. -1 The broad OH absorption peak at 1700 cm⁻¹ is due to adsorbed water; the characteristic peak of calcium carbonate in the A-BC700 sample completely disappeared after acid washing, confirming that the calcium ash was completely dissolved; the sample after acid washing... -1 The C=O peak essentially disappears, appearing only at 1050~1200 cm⁻¹. -1 The range retains weak CO and COC ether / hydroxyl absorption signals; compared with the 600℃ acid-washed sample, the absorption intensity of oxygen-containing functional groups of the 700℃ acid-washed carbon is slightly reduced, and the baseline tilt is somewhat mitigated, indicating that the heating causes some oxygen-containing groups to be thermally desorbed, and the degree of aromatization of the carbon skeleton is improved.

[0050] The biochar material A-BC700 prepared in this embodiment was subjected to performance testing for degrading SMX. The specific steps are as follows: (1) Prepare 50 mL of SMX simulated wastewater with a concentration of 10 mg / L in a beaker, add 5 mg of A-BC700 catalyst (the solid-liquid ratio of A-BC700 catalyst to simulated wastewater is 0.1 g / L), and then add 122 μL of PAA solution to make the initial concentration of the mixed solution 0.4 mmol / L.

[0051] (2) Place the beaker in a constant temperature shaker and shake the reaction at 25℃ and 400rpm. Take 1mL of sample at the preset time points (0min, 1min, 3min, 5min, 10min, 20min, 25min, 30min). Immediately after taking the sample, add 20uL of sodium thiosulfate solution to terminate the reaction. After filtering through a 0.22μm filter membrane, determine the remaining SMX concentration by high performance liquid chromatography (HPLC).

[0052] like Figure 9 As shown in the figure, the degradation performance test of the catalyst prepared in Example 2 showed that, compared with the blank group without catalyst, the degradation effect of the A-BC700 catalyst was much better than that of the blank control group, and the catalytic activity was higher than that of A-BC600. The pollutant residue in the blank group exceeded 85% after 30 minutes, while the C / CO of A-BC700 was as low as 0.14 after 30 minutes of reaction, and the pollutant removal rate reached 86%, further improving the catalytic degradation ability.

[0053] Example 3 The specific steps for preparing A-BC800 shrimp shell (South American shrimp) biochar material are as follows: (1) Wash the waste shrimp shells with tap water, rinse them three times with deionized water, dry them in a 60℃ oven for 12 hours, crush the dried shrimp shells with a crusher and pass them through a 100-mesh sieve.

[0054] (2) Weigh 10g of the above shrimp shell powder into a porcelain boat, place it in a tube furnace, and heat it to 800℃ at a heating rate of 10℃ / min under N2 atmosphere protection, and keep it at this temperature for 2 hours; after natural cooling, take out the black solid and obtain the primary biochar at different temperatures, which is denoted as U-BC800.

[0055] (3) Weigh 1g of U-BC800 primary biochar and place it in 50mL of 1mol / L HCl solution. Stir magnetically and acid wash for 4 hours at room temperature.

[0056] (4) After acid washing, the solid was separated by filtration and washed with a large amount of ultrapure water until the pH of the filtrate was 7. The washed solid was placed in a 60°C oven and dried for 12 hours to obtain shrimp shell biochar material, denoted as A-BC800.

[0057] like Figure 3As shown in the figure, compared with the un-acidified sample, the acid-washed sample (A-BC800) exhibits a clearer and more open pore structure.

[0058] like Figure 5 As shown, the strong diffraction peaks at 23.5° and 29.4° of the un-acid-washed sample (U-CB800) belong to calcite-type calcium carbonate. When the temperature is increased to 800℃, characteristic peaks of calcium oxide appear. After acid washing (A-BC800), the diffraction peaks of calcium carbonate and calcium oxide are significantly weakened or disappear.

[0059] like Figure 6 As shown in the figure, the un-acid-washed U-BC800 exhibits characteristic peaks of both calcium carbonate and calcium oxide inorganic minerals, with a peak at 1700 cm⁻¹. -1 The carbonyl peak intensity further decreased; after acid washing, all characteristic peaks of inorganic minerals in the A-BC800 series disappeared, and there was no obvious C=O absorption signal at 1050 cm⁻¹. -1 ~1200cm -1 The absorption peak intensities of CO and COC continued to decrease compared to A-BC700, and the spectral baseline tended to be flat. After the pyrolysis temperature was increased to 800℃, oxygen-containing functional groups such as hydroxyl groups and ether bonds on the surface of biochar continued to decompose thermally, the regularity of the carbon skeleton was further improved, and the infrared light scattering effect was weakened.

[0060] The biochar material A-BC800 prepared in this embodiment was subjected to performance testing for degrading SMX. The specific steps are as follows: (1) Prepare 50 mL of SMX simulated wastewater with a concentration of 10 mg / L in a beaker, add 5 mg of A-BC800 catalyst (the solid-liquid ratio of A-BC800 catalyst to simulated wastewater is 0.1 g / L), and then add 122 μL of PAA solution to make the initial concentration of the mixed solution 0.4 mmol / L.

[0061] (2) Place the beaker in a constant temperature shaker and shake the reaction at 25℃ and 400 rpm. Take 1 mL of sample at preset time points (0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 25 min, 30 min). Immediately after taking the sample, add 20 μL of sodium thiosulfate solution to terminate the reaction. After filtering through a 0.22 μm filter membrane, determine the concentration of the remaining SMX by high performance liquid chromatography (HPLC).

[0062] like Figure 7 As shown in the figure, the A-BC800 catalyst exhibits high degradation efficiency under a wide range of pH water conditions and has good pH adaptability.

[0063] like Figure 8As shown in the figure, after five cycles, the A-BC800 catalyst still maintains high degradation performance, demonstrating excellent structural stability and catalytic activity stability. This stability is mainly due to the abundant mesopores and macropores of the biochar support acting as "traffic channels," ensuring that the reactants (PAA and SMX) can effectively contact the active sites deep within the pores and continue to function. The acid washing process effectively removes easily soluble ash such as calcium carbonate, further enhancing the purity and stability of the carbon skeleton. This gives the catalyst a stable structure and cycle life, verifying its stability and application value in a practical reprocessing system.

[0064] like Figure 9 As shown in the figure, the degradation performance of the catalyst prepared in Example 3 was tested. Compared with the blank group without catalyst, the degradation effect of the A-BC800 catalyst was much better than that of the blank control group, making it the sample with the best catalytic activity in this group. In the blank group, the pollutants were hardly degraded after 30 minutes, while the C / CO of A-BC800 dropped to below 0.02 after about 10 minutes, and the pollutants were basically completely removed after 30 minutes, showing the best catalytic degradation performance.

[0065] like Figure 10 As shown in the figure, the A-BC800 catalyst exhibits good degradation performance in a variety of real-world aquatic environments and has broad application potential.

[0066] Example 4 The specific steps for preparing A-BC900 shrimp shell (South American shrimp) biochar material are as follows: (1) Wash the waste shrimp shells with tap water, rinse them three times with deionized water, dry them in a 60℃ oven for 12 hours, crush the dried shrimp shells with a crusher and pass them through a 100-mesh sieve.

[0067] (2) Weigh 10g of the above shrimp shell powder into a porcelain boat, place it in a tube furnace, and heat it to 900℃ at a heating rate of 10℃ / min under N2 atmosphere protection, and keep it at this temperature for 2 hours; after natural cooling, take out the black solid and obtain the primary biochar at different temperatures, which is denoted as U-BC900.

[0068] (3) Weigh 1g of U-BC900 primary biochar and place it in 50mL of 1mol / L HCl solution. Stir magnetically and acid wash for 4 hours at room temperature.

[0069] (4) After acid washing, the solid was separated by filtration and washed with a large amount of ultrapure water until the pH of the filtrate was 7. The washed solid was placed in a 60°C oven and dried for 12 hours to obtain shrimp shell biochar material, denoted as A-BC900.

[0070] like Figure 4 As shown in the figure, compared with the un-acid-washed sample, the acid-washed sample (A-BC900) exhibits a clearer and more open pore structure; among them, the pores of A-BC800 and A-BC900 are more developed, forming a three-dimensional interconnected mesoporous-macroporous network.

[0071] like Figure 5 As shown, the strong diffraction peaks at 23.5° and 29.4° of the un-acid-washed sample (U-BC900) belong to calcite-type calcium carbonate, and as the temperature increases to 900°C, characteristic peaks of calcium oxide appear. After acid washing, the diffraction peaks of calcium carbonate and calcium oxide in all samples (A-BC600~A-BC900) are significantly weakened or disappear, with only a broad diffuse peak remaining near 23°, corresponding to the (002) diffraction of amorphous carbon. This proves that acid washing successfully removed inorganic calcium and obtained a high-purity carbon skeleton.

[0072] like Figure 6 As shown in the figure, the characteristic peaks of un-acid-washed U-BC900 calcium carbonate are weakened, while the diffraction peaks of calcium oxide are significantly enhanced, with a peak at 1700 cm⁻¹. -1 The carbonyl absorption peak almost disappeared; after acid washing, no inorganic mineral characteristic peaks were observed in A-BC900, and the peak at 1050 cm⁻¹ was also absent. -1 ~1200cm -1 Only very weak CO and COC absorption protrusions exist in the interval, making it the sample with the lowest content of oxygen-containing functional groups among the four groups of acid-washed samples; high-temperature pyrolysis at 900℃ significantly removes oxygen-containing functional groups from the surface of biochar, resulting in a highly aromatic carbon skeleton, a smooth and flat infrared spectrum baseline, and the baseline drift caused by pore scattering is basically eliminated.

[0073] The biochar material A-BC900 prepared in this embodiment was subjected to performance testing for degrading SMX. The specific steps are as follows: (1) Prepare 50 mL of SMX simulated wastewater with a concentration of 10 mg / L in a beaker, add 5 mg of A-BC900 catalyst (the solid-liquid ratio of A-BC900 catalyst to simulated wastewater is 0.1 g / L), and then add 122 μL of PAA solution to make the initial concentration of the mixed solution 0.4 mmol / L.

[0074] (2) Place the beaker in a constant temperature shaker and shake the reaction at 25℃ and 400 rpm. Take 1 mL of sample at preset time points (0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 25 min, 30 min). Immediately after taking the sample, add 20 μL of sodium thiosulfate solution to terminate the reaction. After filtering through a 0.22 μm filter membrane, determine the concentration of the remaining SMX by high performance liquid chromatography (HPLC).

[0075] like Figure 9As shown in the figure, the degradation performance test of the A-BC900 catalyst prepared in Example 4 showed that, compared with the blank control group without catalyst, the degradation effect of the A-BC900 catalyst was far superior. In the blank control group, the pollutant residue was higher than 85% after 30 minutes, with almost no self-degradation. In contrast, the A-BC900 catalyst showed that the pollutants were almost completely degraded after 5 minutes of reaction and maintained a very low residue concentration after 30 minutes, demonstrating extremely strong catalytic degradation ability. The eight catalysts prepared in this invention were tested for degradation performance under the same degradation conditions. Compared with the blank control group without catalyst, all showed improved degradation effects. Among them, the degradation effects of catalysts A-BC600 to A-BC900 were significantly improved, with the catalyst prepared by A-BC900 showing the best effect.

[0076] Example 5 (1) Wash the waste shrimp shells (South American shrimp) with tap water, rinse them three times with deionized water, dry them in a 60℃ oven for 12 hours, crush the dried shrimp shells with a crusher and pass them through a 100-mesh sieve.

[0077] (2) Weigh 10g of the above shrimp shell powder into a porcelain boat, place it in a tube furnace, and heat it to 900℃ at a heating rate of 10℃ / min under N2 atmosphere protection, and keep it at this temperature for 2 hours; after natural cooling, take out the black solid to obtain primary biochar.

[0078] (3) Weigh 5g of the above primary biochar and place it in 250mL of HCl solution with a concentration of 2mol / L. Stir magnetically and acid wash for 4 hours at room temperature (the solid-liquid ratio of primary biochar to HCl is 5g:250mL, which is 1g:50mL).

[0079] (4) After acid washing, the solid was separated by filtration and washed with a large amount of ultrapure water until the pH of the filtrate was 7. The washed solid was placed in a 60°C oven and dried for 12 hours to obtain shrimp shell biochar material.

[0080] The biochar material prepared in this embodiment was subjected to performance testing for SMX degradation. The specific steps are as follows: Prepare 50 mL of SMX simulated wastewater with a concentration of 5 mg / L, add 25 mg of the biochar catalyst prepared in this example, and then add PAA solution to make the initial concentration 0.4 mmol / L. Stir the reaction at room temperature for 30-60 min.

[0081] The results show that the biochar material prepared in this embodiment can effectively activate PAA and achieve rapid degradation of SMX, verifying the feasibility of the technical solution of the present invention under acid washing conditions with a high solid-liquid ratio.

[0082] Example 6 (1) Wash the waste shrimp shells (South American shrimp) with tap water, rinse them three times with deionized water, dry them in a 60℃ oven for 12 hours, crush the dried shrimp shells with a crusher and pass them through a 100-mesh sieve.

[0083] (2) Weigh 10g of the above shrimp shell powder into a porcelain boat, place it in a tube furnace, and heat it to 900℃ at a heating rate of 10℃ / min under N2 atmosphere protection, and keep it at this temperature for 2 hours; after natural cooling, take out the black solid to obtain primary biochar.

[0084] (3) Weigh 3g of the above primary biochar and place it in 150mL of 0.5mol / L HCl solution. Stir magnetically and acid wash for 4 hours at room temperature (the solid-liquid ratio of primary biochar to HCl is 3g:150mL, which is 1g:50mL, and the acid concentration is 0.5mol / L).

[0085] (4) After acid washing, the solid was separated by filtration and washed with a large amount of ultrapure water until the pH of the filtrate was 7. The washed solid was placed in a 60°C oven and dried for 12 hours to obtain shrimp shell biochar material.

[0086] The biochar material prepared in this embodiment was subjected to performance testing for SMX degradation. The specific steps are as follows: Prepare 50 mL of SMX simulated wastewater with a concentration of 7 mg / L, add 12.5 mg of the biochar catalyst prepared in this example, and then add PAA solution to make the initial concentration 0.4 mmol / L. Stir the reaction at room temperature for 30-60 min.

[0087] The results show that the biochar material prepared in this embodiment can still maintain good catalytic activity under different acid washing conditions and degradation parameters, further proving the applicability and stability of the technical solution of the present invention within a wide parameter range.

[0088] Comparative Example 1 The preparation method of shrimp shell (South American shrimp) biochar material without acid washing is basically the same as that of Example 4, except that step (3) is not performed, and the other steps are the same as those of Example 4.

[0089] The performance of unwashed biochar U-BC900 prepared in Comparative Example 1 and A-BC900 prepared in Example 4 in degrading SMX was compared according to the above performance testing methods. Figure 9As shown, the degradation effect of un-acid-washed U-BC900 on SMX within a 30-minute reaction time was extremely limited, with the pollutant residue rate still above 85%. In contrast, acid-washed A-BC900 achieved near-complete degradation of the pollutants within 5 minutes. This indicates that acid washing has a decisive impact on the catalytic activity of shrimp shell biochar: the surface of un-acid-washed shrimp shell biochar is covered with a large amount of calcium carbonate ash, resulting in severe pore blockage and the inability to expose active sites, leading to extremely poor catalytic performance. Acid washing effectively removes the ash, opens up the pore structure, and exposes abundant carbon skeletons and oxygen-containing active sites, thereby significantly improving the catalytic degradation efficiency. The huge performance difference before and after acid washing fully demonstrates the necessity and effectiveness of the "high-temperature pyrolysis-acid washing purification" combined strategy of this invention.

[0090] Comparative Example 2 The preparation method of waste crab shell biochar material in Comparative Example 2 is basically the same as that in Example 4, except that the waste shrimp shells in step (1) are replaced with waste crab shells. All other steps are the same as in Example 4.

[0091] The performance of waste crab shell biochar material prepared in Comparative Example 2 and waste shrimp shell biochar material A-BC900 prepared in Example 4 in degrading SMX was compared. Under the same degradation test conditions, the degradation efficiency of waste crab shell biochar material for SMX was significantly lower than that of waste shrimp shell biochar material A-BC900. The reason for this is that although shrimp shells and crab shells are both crustacean wastes, their microstructures are significantly different. Shrimp shells have a more loose, layered, porous hierarchical structure, and the arrangement of their organic matter and calcium carbonate is more conducive to the formation and development of pores during pyrolysis. In contrast, crab shells have a denser structure, and the pore structure formed after pyrolysis is relatively limited. More importantly, shrimp shell biochar can retain more surface oxygen-containing functional groups (such as hydroxyl and carboxyl groups) and carbon edge defect sites after pyrolysis. These active sites are key to activating PAA and generating singlet oxygen, while the active site density of crab shell biochar is significantly lower. Therefore, waste shrimp shells are a better precursor material for preparing highly efficient PAA-activated biochar catalysts.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing biochar material based on waste shrimp shells, characterized in that, The preparation of the biochar material includes the following steps: (1) The waste shrimp shells were pyrolyzed at high temperature under inert gas protection to obtain primary biochar; (2) Weigh a certain amount of the primary biochar from step (1) and wash it with acid solution to remove the inorganic ash. (3) Wash the acid-washed biochar in step (2) until it is neutral and then dry it to obtain the biochar material based on waste shrimp shells.

2. The method for preparing biochar material based on waste shrimp shells according to claim 1, characterized in that: The waste shrimp shells in step (1) need to be pre-treated, namely, washed, dried and crushed.

3. The method for preparing biochar material based on waste shrimp shells according to claim 1, characterized in that: In step (1), the inert gas is nitrogen. The high-temperature pyrolysis is carried out in a tube furnace. The pyrolysis temperature is 600~900℃, the heating rate is 5~10℃ / min, and the pyrolysis time is 1~3 hours.

4. The method for preparing biochar material based on waste shrimp shells according to claim 1, characterized in that: In step (2), HCl is used for pickling. The concentration is 0.5~2 mol / L and the pickling time is 2~6 hours. Stirring is carried out at room temperature. The solid-liquid ratio of the primary biochar to HCl is 1g:50mL~5g:250mL.

5. The method for preparing biochar material based on waste shrimp shells according to claim 1, characterized in that: In step (3), the washing is done with pure water, followed by filtration and drying at a temperature of 50~80℃.

6. The biochar material made from waste shrimp shells is prepared by the method according to any one of claims 1 to 5.

7. The application of the waste shrimp shell biochar material according to claim 6 in the degradation of antibiotics, characterized in that: The waste shrimp shell biochar material, when used in combination with peracetic acid, rapidly degrades antibiotics in water.

8. The application of the waste shrimp shell biochar material according to claim 7 in the degradation of antibiotics, characterized in that: The self-assembled biochar material was added to wastewater containing antibiotics, followed by the addition of peracetic acid solution. The reaction was carried out under stirring at room temperature. The pH of the reaction system was 3-9, the initial concentration of antibiotics was 5-10 mg / L, the dosage of biochar material was 0.05-0.5 g / L, the dosage of peracetic acid was 0.2-1.0 mmol / L, and the reaction time was 30-60 min.

9. The application of the waste shrimp shell biochar material according to claim 8 in the degradation of antibiotics, characterized in that: The antibiotics include one or more of sulfamethoxazole, sulfadiazine, tetracycline, and ciprofloxacin.

Images