Preparation method of fish pond filtering composite carbon material and fish pond filtering composite carbon material

Abstract

The application belongs to the technical field of fish pond filtering materials, and discloses a preparation method of fish pond filtering composite carbon material and the fish pond filtering composite carbon material. The preparation method of the fish pond filtering composite carbon material comprises the following steps: 1) mixing powders including modified bentonite, biomass powder, diatomite, pore-forming agent and photocatalyst with a binder solution, and performing kneading and extrusion molding treatment to obtain a green body; 2) drying the green body, and performing multi-stage programmed temperature rising carbonization under an inert atmosphere to obtain a porous carbon ceramic framework loaded with photocatalyst after cooling; and 3) immersing the porous carbon ceramic framework in a graphene oxide dispersion solution, and performing reduction and solidification treatment to obtain the fish pond filtering composite carbon material. The preparation temperature is relatively low, and the fish pond filtering composite carbon material has a developed macropore-mesopore-micropore hierarchical pore structure, and can simultaneously realize efficient physical adsorption, photocatalytic degradation and microbial biofilm formation functions.

Description

Technical Field

[0001] This invention relates to the technical field of fish pond filtration materials, and more specifically, to a method for preparing fish pond filtration composite carbon materials and the fish pond filtration composite carbon materials themselves. Background Technology

[0002] Water is essential for the survival of humans, animals, and plants. With the continuous improvement of people's living standards, the demand for ornamental fish farming and aquaculture is gradually increasing, bringing with it a series of water quality problems during the farming process. For example, after prolonged use, aquaculture water may develop a fishy or other unpleasant odor, easily leading to the growth of harmful algae and deterioration of the living environment. In particular, excessive levels of ammonia nitrogen, nitrite nitrogen, and chemical oxygen demand (COD) in aquaculture wastewater pose a serious threat to the health of aquatic organisms.

[0003] Currently, the most common fish pond filtration materials on the market can be divided into two categories:

[0004] The first type is traditional ceramic filter media, mostly prepared by mixing clay and pore-forming agents and then calcining at high temperatures in air. This type of filter media has the following significant drawbacks: First, its preparation typically requires temperatures above 1000℃ to ensure sufficient mechanical strength, resulting in high energy consumption; second, its pore structure is often relatively simple, lacking effective micropore distribution, and its surface biocompatibility is poor, making rapid biofilm formation difficult; third, this type of filter media mainly relies on physical interception, making it difficult to simultaneously remove suspended particulate matter and efficiently degrade ammonia nitrogen and nitrite nitrogen in water. In practical use, it often needs to be used in conjunction with other filter media, leading to high maintenance costs.

[0005] The second type is activated carbon filter material. Although it has a well-developed microporous structure and can exert a good purification effect through physical adsorption in the short term, its defects are also obvious: the content of macropores inside activated carbon is very small, which cannot provide enough internal space for the attachment and reproduction of beneficial bacteria such as nitrifying bacteria, resulting in weak biodegradation ability; in addition, simple adsorption is easy to reach saturation, and once saturated, it loses its purification ability or even causes secondary pollution, resulting in a short service life. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing a fishpond filter composite carbon material with a relatively low preparation temperature and a well-developed macroporous-mesoporous-microporous hierarchical pore structure, which can simultaneously achieve efficient physical adsorption, photocatalytic degradation, and microbial biofilm formation. The technical solution is as follows:

[0007] The preparation method of composite carbon material for fish pond filtration includes the following steps:

[0008] 1) A mixed powder comprising modified bentonite, biomass powder, diatomaceous earth, pore-forming agent and photocatalyst is kneaded and extruded with a binder solution to obtain a green body;

[0009] 2) After drying the green body, it is subjected to multi-stage temperature-increasing carbonization under an inert atmosphere, and after cooling, a porous carbon ceramic skeleton loaded with photocatalyst is obtained.

[0010] 3) The porous carbon ceramic skeleton is impregnated in graphene oxide dispersion, and after reduction and curing treatment, the fish pond filter composite carbon material is obtained.

[0011] As a further improvement to the above preparation method: the mixed powder in step 1) comprises, by weight, 65-75 parts modified bentonite, 55-65 parts biomass powder, 15-20 parts diatomaceous earth, 8-12 parts pore-forming agent, and 2-6 parts photocatalyst; wherein the interlayer spacing of the modified bentonite is ≥1.5 nanometers, and the modified bentonite is obtained by sequentially modifying sodium-based bentonite with acid and Fe... 3+ The modified product is obtained as follows: the pore-forming agent is expanded polystyrene particles with a particle size of 0.3-0.5 mm.

[0012] As a further improvement to the above preparation method: the biomass powder is bamboo powder or distiller's grains powder; the biomass powder undergoes chemical activation and modification treatment before use: the biomass powder is immersed in a mixed modification solution containing zinc chloride and ferric chloride for 1-3 hours, and then dried for later use; the molar ratio of zinc chloride to ferric chloride in the mixed modification solution is 1:(0.5-1); the liquid-solid ratio of the mixed modification solution to the biomass powder is 20-30 mL / g.

[0013] As a further improvement to the above preparation method: the photocatalyst is at least one of nano-titanium dioxide, bismuth ferrite, graphitic carbon nitride or its precursor; the photocatalyst is pre-dispersed in ethanol or water to form a suspension with a concentration of 0.5-2 mg / mL before use, and then sprayed into the mixed powder.

[0014] As a further improvement to the above preparation method: the binder solution in step 1) is a 1.5-3wt% sodium alginate aqueous solution. 35-45 parts of sodium alginate aqueous solution are added for every 100 parts of mixed powder. During the kneading process, a calcium chloride solution with a mass concentration of 1-3wt% is sprayed in to induce in-situ gelation and cross-linking until the material exhibits a viscoelastic state that cannot be broken apart by hand.

[0015] As a further improvement to the above preparation method: the drying method described in step 2) is freeze drying: the extruded preform is pre-frozen at -10°C to -30°C for 2-5 hours, and then freeze-dried at a vacuum of less than 10 Pascals for 24-48 hours.

[0016] As a further improvement to the above preparation method: the multi-stage programmed heating carbonization in step 2) is specifically as follows: under a nitrogen atmosphere, the temperature is increased to 550-650℃ at a heating rate of 2-5℃ / min and held for 1.5-2.5 hours; then the temperature is increased to 750-850℃ and held for 3-6 hours, and finally the furnace is naturally cooled.

[0017] As a further improvement to the above preparation method: the reduction and curing treatment in step 3) adopts a solvothermal grafting method: the porous carbon ceramic skeleton is placed in a mixed dispersion containing graphene oxide and ethylenediamine, and reacted in a high-pressure reactor at 140-180℃ for 3-6 hours. After the reaction, the solid is taken out, washed and dried to obtain the fish pond filter composite carbon material; the mixed dispersion is prepared by adding 0.5-1 mL of ethylenediamine to every 100 mL of graphene oxide dispersion with a concentration of 0.1-0.3 wt%; the liquid-solid ratio of the mixed dispersion to the porous carbon ceramic skeleton is 10-20 mL / g.

[0018] As a further improvement to the above preparation method: the reduction curing treatment in step 3) adopts the ultraviolet curing method: the porous carbon ceramic skeleton impregnated with 0.4-0.6wt% graphene oxide is taken out and placed under an ultraviolet lamp with a wavelength of 254 nm or 365 nm for irradiation for 0.5-2 minutes to obtain the fish pond filter composite carbon material.

[0019] The composite carbon material for fish pond filtration is prepared by the above-mentioned preparation method.

[0020] The preparation method of the fish pond filtration composite carbon material of the present invention and the advantages of the fish pond filtration composite carbon material are as follows:

[0021] (1) This invention uses biomass as a carbon source skeleton, combined with modified bentonite and pore-forming agent. Compared with traditional ceramic filter materials that require high-temperature calcination above 1000℃, this invention can be calcined and formed at a lower temperature, which significantly reduces production energy consumption and cost.

[0022] (2) This invention utilizes the natural vascular bundle structure of biomass in combination with a pore-forming agent to successfully construct a three-dimensional hierarchical pore structure with interconnected macropores, mesopores and micropores. Among them, macropores provide sufficient space for attachment and reproduction of microorganisms such as nitrifying bacteria, which is conducive to rapid biofilm formation. Mesopores and micropores provide a huge specific surface area, which greatly enhances the physical adsorption capacity for ammonia nitrogen, nitrite nitrogen and odor molecules in water.

[0023] (3) The photocatalyst introduced in this invention can generate highly oxidizing free radicals under light (or weak light) conditions, which can actively degrade recalcitrant organic pollutants in water, destroy algal cell walls, and kill pathogens, thus overcoming the shortcomings of traditional carbon materials that can only physically adsorb pollutants and cannot completely eliminate them.

[0024] (4) The reduced graphene oxide introduced in this invention has a unique two-dimensional planar structure. Its surface π-π conjugated system can efficiently adsorb and enrich aromatic compounds and other organic molecules in water, "capture" low-concentration pollutants and enrich them near the catalytic active site, providing a high concentration of reaction substrate for subsequent photocatalytic degradation.

[0025] (5) The main function of reduced graphene oxide is to have a good inhibitory effect on pathogens at low concentrations, while nitrifying bacteria can be effectively protected by the extracellular polymers secreted by their biofilms, which act as a "protective gel". In addition, as an excellent electron acceptor and conductive "highway", reduced graphene oxide can quickly transfer photogenerated electrons generated by the photocatalyst and effectively inhibit the recombination of photogenerated electron-hole pairs, thereby significantly improving the quantum efficiency and photocatalytic reaction rate. This synergistic mechanism realizes the cycle of "adsorption enrichment-in-situ degradation-regeneration", solves the problem of secondary pollution after adsorption saturation, and significantly extends the service life of the filter material.

[0026] (6) This invention further enhances the removal effect of composite carbon materials on heavy metal ions and positively charged pollutants by modifying the interlayer cation exchange capacity of bentonite, while improving the mechanical strength and water resistance of composite carbon materials, making them less prone to pulverization and disintegration under long-term water flow.

[0027] In summary, the composite carbon material for fishpond filtration prepared by this invention integrates physical adsorption, microbial degradation, and photocatalytic oxidation, overcoming the shortcomings of existing filter materials such as simple pore structure, limited functionality, high energy consumption, and short lifespan. It not only possesses high strength, high specific surface area, and excellent self-cleaning ability, but also promotes the stable growth of beneficial bacterial communities due to its good surface biocompatibility, thereby constructing a stable micro-ecological cycle system in the fishpond water. This material can efficiently remove pollutants from the water, effectively maintaining water clarity while significantly reducing the frequency of water changes. It is a green, environmentally friendly, highly efficient, and energy-saving new water treatment material with good practicality.

[0028] The embodiments of the invention provided in this specification will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the embodiments of the invention provided in this specification will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention provided in this specification. Attached Figure Description

[0029] The accompanying drawings, which form part of the embodiments of the invention provided in this specification, are used to aid in understanding the embodiments of the invention provided in this specification. The content provided in the drawings and the related descriptions in the embodiments of the invention provided in this specification can be used to explain the embodiments of the invention provided in this specification, but do not constitute an undue limitation on the embodiments of the invention provided in this specification. In the drawings:

[0030] Figure 1 This is a photograph of the composite carbon material used for fish pond filtration in Example 1.

[0031] Figure 2 This is a pore size distribution diagram of the composite carbon material used for fish pond filtration in Example 1.

[0032] Figure 3 This is a schematic diagram of the dynamic experimental apparatus of the present invention. Detailed Implementation

[0033] The embodiments of the invention provided in this specification will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. Before describing the embodiments of the invention provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that:

[0034] The technical solutions and features provided in the embodiments of the invention provided in this specification, including the following description, can be combined with each other without conflict.

[0035] Furthermore, the embodiments of the inventions provided in this specification mentioned below are generally only a portion of the embodiments of the inventions provided in this specification, and not all of them. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the inventions provided in this specification without creative effort should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0036] Regarding the terminology and units in the embodiments of the invention provided in this specification: The terms "comprising," "including," "having," and any variations thereof in the description, claims, and related parts of the embodiments of the invention provided in this specification are intended to cover non-exclusive inclusion. Furthermore, other relevant terms and units in the embodiments of the invention provided in this specification can be reasonably interpreted based on the relevant content of the embodiments of the invention provided in this specification.

[0037] Example 1

[0038] The preparation method of the fishpond filter composite carbon material in this embodiment includes the following steps:

[0039] 1) Using bamboo powder that has passed through a 100-mesh sieve as biomass powder, a mixed modification solution with a molar ratio of zinc chloride to ferric chloride of 1:0.8 was used. The bamboo powder was soaked in the mixed modification solution for 2 hours with a liquid-to-solid ratio of 25 mL / g. After soaking, the bamboo powder was filtered, dried and set aside for later use.

[0040] By weight, take 72 parts of modified bentonite (interlayer spacing > 1.5 nm), 60 parts of bamboo powder that has passed through a 100-mesh sieve, 18 parts of diatomaceous earth, 10 parts of expanded polystyrene particles (particle size 0.3-0.5 mm), and 4 parts of nano titanium dioxide (anatase type, particle size 30 nm, pre-dispersed in ethanol, concentration 1 mg / mL), and mix them in a kneader at a speed of 45 rpm for 20 minutes.

[0041] Add 1.5-3wt% sodium alginate aqueous solution as a binder according to the ratio of 37.5 parts sodium alginate aqueous solution to every 100 parts of mixed powder, and spray in 2% calcium chloride solution to initiate gelation. Knead until the material is in a viscoelastic state that cannot be broken by hand; then extrude and cut into blanks.

[0042] 2) The green body was pre-frozen at -20℃ for 4 hours, and then freeze-dried at a vacuum of less than 10 Pascals for 36 hours. The dried green body was placed in a tube furnace and protected with nitrogen. The temperature was first increased to 600℃ at a rate of 3℃ / min and held for 2 hours, and then increased to 800℃ and held for 4 hours. The porous carbon ceramic skeleton was obtained by cooling in the furnace.

[0043] 3) Prepare a 0.5 wt% graphene oxide dispersion (dispersant is water), immerse the porous carbon ceramic skeleton in it for 5 minutes, take it out and drain it; then place it under a 254 nm wavelength ultraviolet lamp for 1 minute to reduce graphene oxide and solidify it with the help of photocatalysis to obtain fish pond filter composite carbon material.

[0044] Example 2

[0045] Compared with Example 1, the difference in the preparation method of the fish pond filter composite carbon material in this example is that the biomass raw material powder is distiller's grains powder.

[0046] Example 3

[0047] Compared with Example 1, the preparation method of the fish pond filter composite carbon material in this example is different in that: 3) a mixed dispersion is prepared by adding 0.8 mL of ethylenediamine to every 100 mL of graphene oxide dispersion with a concentration of 0.2 wt%. The porous carbon ceramic skeleton is placed in the mixed dispersion according to a liquid-to-solid ratio of 10-20 mL / g between the mixed dispersion and the porous carbon ceramic skeleton. The mixture is then reacted in a high-pressure reactor at 160°C for 4 hours. After the reaction is completed, the solid is removed, washed, and dried to obtain the fish pond filter composite carbon material.

[0048] Compare with Example 1

[0049] Compared with Example 1, the difference in the preparation method of the fish pond filter composite carbon material in this example is that step 3 is not performed.

[0050] Compare with Example 2

[0051] Compared with Example 1, the preparation method of the fish pond filter composite carbon material in this example is different in that it does not contain a photocatalyst.

[0052] Compare with Example 3

[0053] Compared with Example 1, the difference in the preparation method of the fish pond filter composite carbon material in this example is that it does not contain biomass powder.

[0054] Compare with Example 4

[0055] Compared with Example 1, the difference in the preparation method of the fish pond filter composite carbon material in this example is that pure water is used instead of sodium alginate aqueous solution and calcium chloride solution.

[0056] Compare with Example 5

[0057] Compared with Example 1, the difference in the preparation method of the fish pond filter composite carbon material in this example is that the green body is dried and shaped at 60°C.

[0058] The properties of the materials obtained in the above embodiments and comparative examples were then tested, and the test results are shown in Tables 1 and 2. The bamboo charcoal was obtained by holding bamboo blocks at 600°C for 2 hours under nitrogen protection.

[0059] As shown in Table 1, the fishpond filter composite carbon materials of Examples 1-3 all exhibited excellent performance. Among them, compared with the UV curing of Example 1, Example 3, through in-situ growth of reduced graphene oxide using a solvothermal grafting method, achieved a more thorough reduction, which enhanced the bonding force between the reduced graphene oxide and the porous carbon ceramic framework, thereby improving adsorption performance. Furthermore, ethylenediamine is not only a reducing agent but also a nitrogen dopant, giving the carbon material better biocompatibility and wettability (facilitating biofilm formation), while also providing more defect sites on the surface (facilitating adsorption).

[0060] As can be seen from Examples 1-3 and Comparative Example 1, although the 24-hour bacterial film coverage of the carbon material loaded with reduced graphene oxide decreased, the antibacterial rate was significantly improved. This also proves that reduced graphene oxide brings excellent antibacterial effect to carbon materials.

[0061] Based on Examples 1-3 and Comparative Example 2, it can be seen that although Comparative Example 2 also has a high porosity and specific surface area, its total nitrogen removal effect and antibacterial rate are significantly inferior to those of Examples 1-3, indicating that nano-titanium dioxide plays a key synergistic role in material preparation and performance.

[0062] Based on Examples 1-3 and Comparative Example 3, it can be seen that the specific surface area of ​​the carbon material in Comparative Example 3 is less than 1 m². 2 / g, while the present invention, by adding biomass raw materials and expanded polystyrene particles, makes the carbon material have higher porosity and bioload, and the removal effect of ammonia nitrogen and nitrate is also better.

[0063] Comparative examples 4-5 illustrate that the gelation of sodium alginate aqueous solution and calcium chloride solution, along with freeze-drying, helps to form a more uniform and abundant pore structure, thereby improving various properties.

[0064] Table 1

[0065]

[0066] Table 2

[0067]

[0068] Figure 1 This is a photograph of the composite carbon material used for fish pond filtration in Example 1. Figure 2 This is a pore size distribution diagram of the composite carbon material used for fish pond filtration in Example 1. Figure 1 As shown, carbon materials possess a uniform and abundant macroporous structure. For example... Figure 2 As shown, the interior of the carbon material is mainly composed of mesopores, supplemented by micropores. Macropores provide flow channels, mesopores mainly serve as living spaces for microorganisms, and micropores adsorb and slowly release nutrients. The resulting rich pore structure can significantly improve the adhesion effect of microorganisms.

[0069] The modified bentonite prepared in the above preparation method is as follows: sodium-based bentonite is mixed with 2 mol / L hydrochloric acid solution at a solid-liquid ratio of 1 g: 10 mL, and stirred and acidified at 70 °C for 2 hours. After washing and drying, acidified clay is obtained. Subsequently, the acidified clay is dispersed in water, and ferric chloride is added (the amount added is such that Fe...). 3+ Modified bentonite is obtained by reacting the soil with a load of 3-5% of its weight in water at 60℃ for 6 hours, followed by washing and drying.

[0070] The performance testing methods described above are as follows:

[0071] Figure 3 This is a schematic diagram of the dynamic experimental apparatus of the present invention. Figure 3 As shown, river water taken from a river in Sansheng Township, Chengdu City, was used as the experimental raw water. Each type of activated carbon material was added to the corresponding filter box (filling volume of 0.98L). The dynamic experimental conditions were as follows: total water volume of 7L, containing 0.7mL of commercially available liquid nitrifying bacteria; aeration to maintain dissolved oxygen >5mg / L; total nitrogen of 3.14mg / L; ammonia nitrogen of 0.38mg / L; nitrate of 11.9mg / L; and nitrite of 0.063mg / L; flow rate of 1.1L / min; residence time of 37s; circulation cycle of 6.36 minutes; and total operating time of 30 days.

[0072] Test method for bacterial film coverage: The coverage of the bacterial film on the solid surface is directly observed using an optical microscope. The coverage area of ​​the bacterial film is measured using image analysis software, and then the bacterial film coverage rate is calculated. The bacterial film coverage rate is calculated according to the formula: "Bacterial film coverage rate (%) = (Bacterial film coverage area / Total visible area) × 100%".

[0073] The material used for testing microbial load was an immobilized body that had been left to stand for a period of time after the initial dynamic experiment. The surface microorganisms on this immobilized body may be fewer than those on fresh immobilized bodies, but this does not affect the validity of this validation experiment. The specific steps include:

[0074] (1) Prepare LB medium (10g peptone, 5g yeast extract, 10g NaCl, bring to 1L, pH 7.0), select P2 single colony and inoculate it into 500mL medium, culture at 30℃ and 150rpm for 24h, collect the bacterial suspension and centrifuge at 6000rpm for 5 minutes, discard the supernatant, resuspend with sterile physiological saline and wash the bacterial cells 3 times to prepare a bacterial suspension; put 1g of pretreated packing into a flask containing 100mL of bacterial suspension, shake at 30℃ and 150rpm for 24h to carry out biofilm formation, take it out and gently rinse with sterile physiological saline to remove free bacteria that are not firmly adsorbed on the surface.

[0075] (3) Place 1g of immobilized packing material in a container containing 99mL of sterile phosphate buffer (PBS) and a small amount of sterile glass beads. First, perform ultrasonic cleaning for 2-3 minutes, then vortex vigorously for 5-10 minutes to allow the biofilm in the pores of the packing material to be fully detached and dispersed, thus obtaining a 1:100 concentration stock solution. Take 1mL of the stock solution and add it to a test tube containing 9mL of sterile diluent and mix well to obtain a 1:1000 diluent. Follow this step to perform 10-fold serial dilutions to prepare multiple gradient sample homogenates.

[0076] (4) Select three suitable dilution gradients. Take 0.1 mL of each gradient and spread it evenly on LB solid plates (or take 1 mL and use the pour plate method, ensuring that the agar temperature is cooled to about 45℃). Make three parallel plates for each gradient. After the plates are dried or solidified, turn them over and place them in a 30℃ constant temperature incubator for 48 hours (keeping the temperature consistent with the film culture). Finally, select plates with colony counts between 30 and 300 and count them. Take the average value to calculate the microbial load per gram of packing material.

[0077] The antibacterial rate was tested using the constant-vibration method, specifically as follows: Composite carbon material was cut into 3mm diameter particles, and a certain mass of sample was weighed and sterilized. A glass group was used as a blank control group, with the same treatment conditions as the filter material. A Staphylococcus aureus suspension of a certain concentration was prepared using sterile physiological saline. A certain amount of bacterial suspension was added to the conical flask containing the sterilized composite carbon material and the blank control, followed by a certain amount of sterile nutrient broth. The flasks were then fixed on a constant-temperature shaking bed and reacted at 37℃ and 150rpm for 24 hours. After the reaction, 1mL of bacterial suspension was taken from each flask and diluted to an appropriate multiple with sterile physiological saline. 0.1mL of each suspension was spread onto nutrient agar plates, and after incubation at 37℃ for a certain time, the colony counts of the sample group and the control group were recorded, denoted as A and B. The antibacterial rate was calculated according to "antibacterial rate (%) = [(AB / A)] × 100%".

[0078] The testing method for the biofilm formation cycle is the water quality index detection method, which specifically includes the following steps:

[0079] Prepare simulated wastewater (using ammonium chloride as the sole nitrogen source, with an initial ammonia nitrogen concentration set at 30-50 mg / L, and adding appropriate amounts of glucose, potassium dihydrogen phosphate, and trace elements to meet the growth requirements of microorganisms). Add carbon material to the reactor at a filling ratio of 20%, inoculate with nitrifying bacteria solution, and start operation under conditions of 30℃, dissolved oxygen 2-4 mg / L, and fixed hydraulic retention time. Each operation cycle is 24 hours. At the end of the cycle, discharge the supernatant and replenish with an equal amount of fresh simulated wastewater.

[0080] Starting from day 1 of inoculation, influent and effluent water samples were taken at regular intervals each day. After filtration through a 0.45μm filter membrane, the ammonia nitrogen concentration was determined using Nessler's reagent spectrophotometry. The ammonia nitrogen removal rate for each day was calculated, and a curve showing the change in removal rate over time was plotted. Simultaneously, every 3-5 days, a portion of the carbon material was randomly taken from the reactor, and the viable bacteria count (i.e., microbial load) on a unit mass of packing material was determined using the aforementioned gradient dilution plating method.

[0081] Continuous monitoring continued until the ammonia nitrogen removal rate remained stable above 80% for 5-7 consecutive days with fluctuations of less than 5%, while the microbial load on the packing surface no longer increased significantly and remained at 10. 6 -10 7When the concentration is above CFU / g, the biofilm formation process can be considered complete. The number of days required from the start of inoculation to reaching this stable state is the biofilm formation cycle under this condition.

[0082] Specific surface area and pore size distribution were measured using a high-performance specific surface area and micropore analyzer (model BSD-PM2-1) and the BET method (Brunauer-Emmett-Teller Theory). Porosity was measured using the Archimedes drainage method.

[0083] The embodiments of the invention provided in this specification have been described above. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. All other preferred embodiments and implementations obtained by those skilled in the art based on the above description of the embodiments of the invention provided in this specification without inventive effort should fall within the protection scope of the embodiments of the invention provided in this specification.

Claims

1. A method for preparing composite carbon material for fish pond filtration, characterized in that, Includes the following steps: 1) A mixed powder comprising modified bentonite, biomass powder, diatomaceous earth, pore-forming agent, and photocatalyst is kneaded and extruded with a binder solution to obtain a green body; the biomass powder undergoes chemical activation modification treatment before use: the biomass powder is immersed in a mixed modification solution containing zinc chloride and ferric chloride, and dried after immersion; the binder solution is an aqueous solution of sodium alginate, and calcium chloride solution is sprayed in during the kneading process to initiate in-situ gelation and cross-linking until the material exhibits a viscoelastic state that cannot be broken apart by hand; 2) After drying the green body, it is subjected to multi-stage programmed heating carbonization under an inert atmosphere, and after cooling, a porous carbon ceramic skeleton loaded with photocatalyst is obtained; the drying method is freeze drying. 3) The porous carbon ceramic skeleton is immersed in a graphene oxide dispersion and then subjected to reduction and curing treatment to obtain the fish pond filter composite carbon material. The reduction and curing treatment adopts a solvothermal grafting method: the porous carbon ceramic skeleton is placed in a mixed dispersion containing graphene oxide and ethylenediamine, and reacted in a high-pressure reactor. After the reaction is completed, the solid is taken out, washed and dried to obtain the fish pond filter composite carbon material.

2. The preparation method according to claim 1, characterized in that: The mixed powder mentioned in step 1) comprises, by weight, 65-75 parts modified bentonite, 55-65 parts biomass powder, 15-20 parts diatomaceous earth, 8-12 parts pore-forming agent, and 2-6 parts photocatalyst; wherein the interlayer spacing of the modified bentonite is ≥1.5 nanometers, and the modified bentonite is formed by sequentially modifying sodium-based bentonite with acid and Fe... 3+ The modified product is obtained as follows: the pore-forming agent is expanded polystyrene particles with a particle size of 0.3-0.5 mm.

3. The preparation method according to claim 2, characterized in that: The biomass powder is bamboo powder or distiller's grains powder; the biomass powder is soaked in a mixed modification solution for 1-3 hours; the molar ratio of zinc chloride to ferric chloride in the mixed modification solution is 1:(0.5-1); the liquid-solid ratio of the mixed modification solution to the biomass powder is 20-30 mL / g.

4. The preparation method according to claim 2, characterized in that: The photocatalyst is at least one of nano-titanium dioxide, bismuth ferrite, graphitic carbon nitride or its precursor; the photocatalyst is pre-dispersed in ethanol or water to form a suspension with a concentration of 0.5-2 mg / mL before use, and then sprayed into the mixed powder.

5. The preparation method according to claim 2, characterized in that: The binder solution mentioned in step 1) is a 1.5-3wt% sodium alginate aqueous solution. 35-45 parts of sodium alginate aqueous solution are added for every 100 parts of mixed powder. During the kneading process, a calcium chloride solution with a mass concentration of 1-3wt% is sprayed in to initiate in-situ gelation and cross-linking until the material exhibits a viscoelastic state that cannot be broken apart by hand.

6. The preparation method according to claim 1, characterized in that: The freeze-drying described in step 2) is as follows: the extruded preform is pre-frozen at -10°C to -30°C for 2-5 hours, and then freeze-dried at a vacuum of less than 10 Pascals for 24-48 hours.

7. The preparation method according to claim 1, characterized in that: The multi-stage programmed heating carbonization described in step 2) is as follows: under a nitrogen atmosphere, the temperature is increased to 550-650℃ at a heating rate of 2-5℃ / min and held for 1.5-2.5 hours; then the temperature is increased to 750-850℃ and held for 3-6 hours, and finally the furnace is allowed to cool naturally.

8. The preparation method according to claim 1, characterized in that: In step 3), the reaction is carried out in a high-pressure reactor at 140-180℃ for 3-6 hours; the mixed dispersion is prepared by adding 0.5-1 mL of ethylenediamine to every 100 mL of graphene oxide dispersion with a concentration of 0.1-0.3 wt%; the liquid-solid ratio of the mixed dispersion to the porous carbon ceramic skeleton is 10-20 mL / g.

9. A composite carbon material for fish pond filtration, characterized in that: It is prepared by the preparation method according to any one of claims 1-8.

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