A kind of biological carbon prepared by using seawater shrimp culture solid waste and its method and application

Abstract

The present application relates to the technical field of biochar, in particular to a kind of biochar prepared by seawater shrimp culture solid waste and method and application thereof.The specific is that seawater shrimp culture solid waste and seawater shrimp shell are mixed according to the mass ratio of 2-4:1, after mixing, the material obtained by limiting oxygen pyrolysis at 700-900 DEG C is biochar (BC);Or, the product after pyrolysis is mixed to be biochar.The biochar obtained by the present application has better specific surface area, pore size volume, more pollutant adsorption sites, and shows higher adsorption performance on water eutrophication pollutants and enrofloxacin and other antibiotics.

Description

Technical Field

[0001] This invention relates to the field of biochar technology, specifically to a biochar prepared from solid waste from marine shrimp farming, its method, and its application. Background Technology

[0002] Over the past few decades, the global aquaculture industry has experienced rapid development, with aquaculture production increasing by over 600% from 1990 to 2018. According to the Fisheries Statistical Yearbook, my country's crustacean aquaculture production in 2022 reached 6.8484 million tons, of which marine aquaculture production of Litopenaeus vannamei reached 1.3403 million tons, a year-on-year increase of 5.23%, reflecting continuously increasing demand. High-density land-based aquaculture models such as pond farming or recirculating aquaculture systems often generate large amounts of residual feed and waste while achieving high yields. According to the latest national pollution source census, aquaculture pollution emissions account for only 6.35% of total agricultural non-point source pollution emissions, with chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, and total phosphorus reaching 6.66 million tons, 2.23 million tons, 9.91 million tons, and 1.61 million tons, respectively. Improper treatment of these solid wastes could further lead to water quality deterioration in aquaculture, the occurrence of aquatic diseases, and environmental pollution.

[0003] In mariculture systems, wastewater carries large amounts of particulate matter, nitrogen, phosphorus, and other nutrients, making it a key indicator for national and local aquaculture wastewater discharge standards and environmental inspections. Limited options exist for treating residual salt-containing bait waste from mariculture systems, resulting in low reuse rates for this solid waste. Therefore, to address these issues, it is necessary to find green, environmentally friendly, and economical treatment methods for managing and utilizing uneaten feed and excrement generated in mariculture, achieving resource utilization of uneaten feed and excrement, and promoting the green and sustainable development of mariculture. Summary of the Invention

[0004] The purpose of this invention is to provide a biochar prepared from solid waste from marine shrimp farming, its method, and its application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing biochar from marine shrimp farming solid waste involves mixing shrimp excrement and shrimp shells in a mass ratio of 2-4:1, followed by pyrolysis at 700-900℃ under limited oxygen conditions to obtain biochar (BC).

[0007] The mixture of the pyrolysis products is biochar.

[0008] The solid waste from marine shrimp farming consists of residual feed and / or marine shrimp feces that have been air-dried or oven-dried; impurities are removed and the waste is then crushed or pulverized separately for later use.

[0009] Furthermore, the collected uneaten feed, feces, and shrimp shells are air-dried naturally or dried in an electric oven at 70°C for 48 hours until there is no obvious moisture loss. Then, impurities are removed, and the mixture is ground into powder using a ball mill or pulverizer and passed through a 2mm sieve. The pulverized and sieved shrimp feces powder and shrimp shell powder are then processed.

[0010] After the solid waste from marine shrimp farming and the shrimp shells are mixed, N2 is introduced at a rate of 50-60 ml / min to provide an oxygen-limited environment during the oxygen-limited pyrolysis. At the same time, the temperature is raised to 700℃-900℃ at a rate of 14-16℃ / min for pyrolysis and carbonization for 110-130 min. After cooling to room temperature, the biochar (BC) is obtained.

[0011] The composite biochar is obtained by mixing two or more groups of biochar prepared by the above method.

[0012] The above-mentioned solid waste from marine shrimp farming is the feces of Litopenaeus vannamei; the shrimp shells of marine shrimp are the shells of Litopenaeus vannamei.

[0013] A preparation method described above yields biochar prepared from marine shrimp aquaculture solid waste, and the biochar (BC) prepared by the method has a large specific surface area and is porous.

[0014] An application of biochar prepared from marine shrimp farming solid waste, wherein the biochar is used as an adsorbent for nutrients in marine aquaculture tailwater or antibiotics in the environment.

[0015] A composite biochar is obtained by mixing two or more groups of biochar prepared according to the method described above.

[0016] To elaborate further,

[0017] 1) Mix marine shrimp farming solid waste and marine shrimp shells at a mass ratio of 4:1, and then perform lower oxygen pyrolysis at 900℃ to obtain biochar for later use;

[0018] 2) Mix marine shrimp farming solid waste and marine shrimp shells at a mass ratio of 2:1, and then perform lower oxygen pyrolysis at 700℃ to obtain biochar for later use;

[0019] 3) Mix the biochar obtained in step 2) with the biochar obtained in step 1) at a mass ratio of 2:1 to obtain composite biochar.

[0020] An application of the aforementioned composite biochar, wherein the composite biochar is used as an adsorbent for nutrients in marine aquaculture tailwater or for antibiotics in the environment.

[0021] The above adsorption process involves adding the biochar or composite biochar to the seawater aquaculture wastewater to be treated, aerating for 30 minutes, settling for 60 minutes, and then filtering and collecting the precipitate; wherein the amount of biochar or composite biochar added is 5 g / L of wastewater.

[0022] Advantages of this invention:

[0023] The raw materials for the biochar of this invention are the uneaten feed, feces, and shells of Litopenaeus vannamei. The crude protein content of the uneaten feed and feces is 24.39±1.50%, and the crude protein content of the shells is 21.75±0.03%. The crude protein content of the uneaten feed and shells of Litopenaeus vannamei is higher than that of the uneaten feed and feces of the marine fish sole (17.10±0.23%), and much higher than that of crop straw (corn straw 9.3%, rice straw 3.2%, wheat straw 2.6%). The higher the crude protein content in the raw materials of biochar, the greater the aromaticity of the prepared biochar and the more types of aromatic functional groups it possesses, which can improve the chemical adsorption effect of biochar on pollutants.

[0024] The biochar prepared by this invention contains abundant organic matter, which is beneficial for the retention of these oxygen-rich functional groups on the surface of solid waste-derived biochar. This results in a larger specific surface area of ​​the obtained biochar, providing more adsorption sites for pollutants and greatly improving adsorption performance. At 25℃, the composite BC group effectively adsorbs NH4+. + -N (20.32%), NO2 - -N (19.00%), NO3 - -N (10.37%), PO4 3 -P (73.63%) and enrofloxacin (65.21%) showed the most stable adsorption effects, and also provided an effective way to utilize solid waste from marine shrimp farming. Attached Figure Description

[0025] Figure 1 The electron micrographs of different biochars obtained in the embodiments of the present invention are shown in the following figures: ac represents BC700℃-a, BC700℃-b, and BC700℃-c; df represents BC900℃-a, BC900℃-b, and BC900℃-c; and h represents composite BC1.

[0026] Figure 2 The functional group distribution diagrams of different biochars provided in the embodiments of the present invention are shown below. Among them, a is the functional group distribution diagram of BC700℃-a, BC700℃-b, BC700℃-c and composite BC1, and b is the functional group distribution diagram of BC900℃-a, BC900℃-b, BC900℃-c and composite BC1. The addition of shrimp shells increases the variety of oxygen-containing functional groups in biochar. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Unless otherwise specified, the experimental methods in the following embodiments are conventional descriptions.

[0028] The biochar obtained by this invention has superior specific surface area, pore volume, and more pollutant adsorption sites, and exhibits high adsorption performance for eutrophic pollutants in water bodies and antibiotics such as enrofloxacin.

[0029] The raw materials used in the following examples were collected from a marine shrimp farm in Shandong Province, China. The main aquatic species farmed at this farm is the Pacific white shrimp.

[0030] Example 1

[0031] Collection and drying: Dry the uneaten feed, feces and shrimp shells at 70℃ for 48 hours until there is no obvious moisture.

[0032] Crushing: Remove stone chips and debris, then crush using a ball mill or high-speed pulverizer, and pass through a 2mm standard sieve.

[0033] Mixing: Mix the above powder with shrimp feces: shrimp shells (mass ratio) of 1:0 (a), 4:1 (b), or 2:1 (c).

[0034] Pyrolysis: The above-mentioned uniformly mixed samples were placed in a quartz boat and placed in a tube furnace, through which N2 was passed at a rate of 50 ml / min. The initial temperature was 25℃, the heating rate was 15℃ / min, and the temperature was increased to 700℃ or 900℃ for 2 hours for carbonization. The obtained biochar was cooled to room temperature, and the biochar (BC) samples prepared under different conditions were taken out and stored in a sealed desiccator for later use.

[0035] The different samples mentioned above are labeled as BC700℃-a, BC700℃-b, BC700℃-c; BC900℃-a, BC900℃-b, BC900℃-c.

[0036] Meanwhile, BC700℃-b and BC900℃-a biochars were mixed at a mass ratio of 2:1 to obtain composite biochar (BC1).

[0037] The biochar obtained above was subjected to scanning electron microscopy (SEM, see [link]). Figure 1 Functional group distribution diagram (see) Figure 2 pH, ash, specific surface area (BET) analysis, and elemental analysis (see Tables 1 and 2).

[0038] Depend on Figure 1-2 As shown in Table 1, the physicochemical properties of biochar indicate that at the same pyrolysis temperature, the specific surface area and pore size of biochar gradually increase with the addition of shrimp shells. However, at a pyrolysis temperature of 900℃, the addition of shrimp shells reduces the specific surface area of ​​the biochar. Combined with scanning electron microscopy (SEM) images, it was found that BC900℃-c may exhibit structural collapse, thus reducing its specific surface area. BC900℃-b has the largest specific surface area (59.77 m²). 2 / g), the composite BC1 also showed superior results in the physicochemical properties of biochar. On the other hand, the ash content of biochar was positively correlated with the change in pyrolysis temperature (Table 1), and the ash content of biochar gradually increased with the addition of shrimp shells. Figure 2 As can be seen, Figure a shows the functional group distribution of biochar from BC700℃-a, BC700℃-b, BC700℃-c, and composite BC1, ranging from 1471 to 7731 cm⁻¹. -1 At the point where shrimp shells are added, the peak intensity of functional groups increases, and new peak values ​​appear, indicating that the addition of shrimp shells increases the variety of functional groups in biochar, specifically in the range of 1430–1750 cm⁻¹. -1 The peak at this point corresponds to C=O stretching. 1250~1250cm -1 The peak at 1080–1100 cm⁻¹ is caused by the bending vibrations of -OH or OH groups on the surface of biochar. -1 The more prominent spectral peaks nearby are characteristic absorption peaks of the lactone group, resulting from the stretching vibrations of COC and COH. In the adsorption reaction, COC is considered the π-electron acceptor. The peaks are located in the 500–800 cm⁻¹ range. -1 The absorption peaks exhibited by the CH stretching vibration, primarily due to the aromatication of aromatic hydrogens and carbon structures. Therefore, this biochar provides more adsorption sites for aromatic π-π structures and the conjugation of pp with enrofloxacin. The results indicate that the biochar contains a large number of aromatic compounds. Hydrogen bond stretching vibrations, coprecipitation, π electron acceptors, aromatic π-π structures, and pp conjugation all facilitate the binding of N, P nutrients, and enrofloxacin antibiotics to the surface of this biochar. When the pyrolysis temperatures were 500℃ and 700℃, the addition of shrimp shells increased the variety and number of functional groups in the biochar. The shrimp shells, being composed of chitosan, increase the number of oxygen-containing functional groups on the biochar surface. As shown in Table 2, at the same pyrolysis temperature, the N, C, H, and S elements in the biochar gradually decreased with the addition of shrimp shells. BC700℃-a and BC900℃-a had lower H / C ratios, higher polarity, and were rich in aromatic functional groups. At the same pyrolysis temperature, with the addition of shrimp shells, the O content, O / C and (O+N) / C of biochar increased, indicating that the types of oxygen-containing functional groups in biochar increased, while the hydrophilicity and polarity of biochar were enhanced.

[0039] Table 1 Physicochemical properties of biochar derived from solid waste from marine shrimp farming

[0040]

[0041] Table 2 Elemental Analysis of Biochar Derived from Solid Waste in Marine Shrimp Farming

[0042]

[0043] Application Example 1: Adsorption Effects of Different Biochars on Common Pollutants in Water Bodies

[0044] The different biochars obtained above, BC700℃-a, BC700℃-b, BC700℃-c, BC900℃-a, BC900℃-b, and BC900℃-c, were compounded with BC1; and NH4 was applied to them respectively. + -N, NO2 - -N, NO3 - -N,PO4 3 -P and enrofloxacin are adsorbed.

[0045] Specifically:

[0046] Ammonium chloride (NH4Cl), potassium nitrate (KNO3), sodium nitrite (NaNO2), potassium dihydrogen phosphate (KH2PO4), and enrofloxacin antibiotic were used to prepare NH4Cl. + -N, NO2 - -N, NO3 - -N,PO4 3 -P and enrofloxacin. NH4 + NO3 - NO2 - PO4 3- The initial concentrations of biochar and enrofloxacin were 30, 20, 20, 30, and 31.92 mg / L, respectively. Each of the above biochars (0.15 g) was added to 30 ml of NH4. + NO3 - NO2 - PO4 3— In an enrofloxacin solution, the mixture was shaken at 150 rpm at 25°C for 4 h until apparent equilibrium was reached. Afterward, the mixture was centrifuged, the supernatant was collected, and filtered through a 0.45 μm membrane. NH4 + -N, NO3 - -N, NO2 - -N,PO4 3The contents of -P and enrofloxacin sample solutions in the filtrate were determined by Nessler's reagent colorimetry, ultraviolet spectrophotometry, naphthylethylenediamine hydrochloride spectrophotometry, ammonium molybdate spectrophotometry, and ultraviolet spectrophotometry, respectively. All experiments were repeated three times, and the average values ​​were recorded. The contents of each ion were calculated based on the corresponding standard curves.

[0047]

[0048] Where C0 is the initial concentration (mg / L), C t This represents the final concentration (mg / L).

[0049] Table 3. Effects of biochar derived from marine shrimp farming solid waste on NH4+ + -N NO2 - -N NO3 - -NPO4 3 -P and enrofloxacin removal rate

[0050]

[0051] As shown in Table 3, biochar has a negative charge on its surface, which promotes the absorption of NH4+. + Adsorption of -N, BC 700℃-c (46.26%) for NH4 + -N removal rate was the highest, with BC900℃-b (9.41%) achieving the best removal rate for NH4+. + -N removal rate was the worst; at the same pyrolysis temperature, the addition of shrimp shells could reduce NH4+. + The removal rate of NO3- increased. BC900℃-b (16.99%) showed a significant improvement in NO3- removal efficiency. - The highest removal rate of NO3- was achieved at BC700℃-c (-25.41%). - -N removal rate was the worst. BC at 700℃-C (26.27%) showed the worst removal rate for NO2. - -N removal rate was the best; BC900℃-b (-2.57%) showed the best removal rate for NO2. - -N had the worst removal rate. BC at 700℃-C (94.82%) showed the best removal rate for PO4. 3- -P has the highest removal rate; adding shrimp shells can increase PO4. 3- -P removal rate. Increased temperature improves the removal of enrofloxacin by biochar; BC700℃-C (72.32%) showed the highest removal rate of enrofloxacin, followed by BC900℃.

[0052] -c (51.05%) showed the lowest removal rate of enrofloxacin. Compared to other biochar derived from marine aquaculture solid waste, this biochar utilizes the chitosan component of shrimp shells. With the addition of shrimp shells, the specific surface area and pore size of the biochar relatively increase, and the types of oxygen-containing functional groups on the biochar surface increase, thus increasing the adsorption sites for pollutants and enhancing the physical and chemical adsorption of pollutants. This includes strengthening electrostatic adsorption, pore size adsorption, PP, π-π, and p-π conjugation. Therefore, the composite BC1, compared to marine fish solid waste-derived biochar, exhibits the best removal rate of NH4+. + The removal rate of -N increased by 42.30%, and the removal rate of NO2 increased by 42.30%. - The removal rate of -N increased by 41.51%.

[0053] The results of the combined biochar removal rate showed that single-group biochar had no removal effect on a certain pollutant, while the composite BC1 showed relatively stable removal effects on eutrophic substances and antibiotics.

[0054] In summary, this invention utilizes biochar prepared from solid waste from marine shrimp farming to explore its feasibility in wastewater treatment. Based on its physicochemical properties and adsorption test results, the addition of shrimp shells increases the specific surface area, total pore volume, pore size, oxygen content, and the variety of oxygen-containing functional groups in the biochar. Specifically, the composite BC1 enhances the adsorption of NH4+. + -N (20.32%), NO2 - -N (19.00%), NO3 - -N (10.37%), PO4 3 -P (73.63%) and enrofloxacin (65.21%) showed the most stable adsorption effects. Therefore, the composite biochar (composite BC1) effectively adsorbed NH4+ in water. + -N, NO2 - -N, NO3 - -N,PO4 3 Pollutants such as -P and enrofloxacin have good adsorption capacity and can be used for the treatment of aquaculture wastewater. Therefore, processing uneaten shrimp feces and shrimp shells into biochar may be an effective and environmentally friendly option for wastewater treatment, providing a new approach for the resource utilization of solid waste from marine aquaculture.

Claims

1. A composite biochar, characterized in that: 1) Mix marine shrimp farming solid waste and marine shrimp shells at a mass ratio of 4:1, and then perform lower oxygen pyrolysis at 900 °C to obtain biochar for later use; 2) Mix marine shrimp farming solid waste and marine shrimp shells at a mass ratio of 2:1, and then perform lower oxygen pyrolysis at 700 ℃ to obtain biochar for later use; 3) Mix the biochar obtained in step 2) with the biochar obtained in step 1) at a mass ratio of 2:1 to obtain composite biochar.

2. The composite biochar according to claim 1, characterized in that: After mixing marine shrimp farming solid waste and marine shrimp shells, N2 is introduced at a rate of 50-60 ml / min to provide an oxygen-limited environment during the oxygen-limited pyrolysis. At the same time, the temperature is increased to 700 ℃ or 900 ℃ at a rate of 14-16 ℃ / min for pyrolysis carbonization for 110-130 min. After cooling to room temperature, the biochar is obtained.

3. An application of the composite biochar according to claim 1, characterized in that: The composite biochar is used as an adsorbent for nutrients in marine aquaculture tailwater or for antibiotics in the environment.

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