A method for preparing a magnetic carbon-based functional material by using algal residue, the magnetic carbon-based functional material and application

Abstract

The application discloses a kind of methods for preparing magnetic carbon-based functional materials using algal residue, magnetic carbon-based functional materials and applications, belong to new material technical field and energy saving and environmental protection technical field.The algal residue is impregnated with sodium hydroxide in the method, and then treated by metal salt impregnation, high-temperature anaerobic activation, washing and drying to obtain the magnetic carbon-based functional materials.The method has the characteristics of simple production process, easy-to-obtain raw materials and high product solid-liquid efficiency.The method realizes the resource utilization of algal residue, and the prepared new material can be widely applied to the field of environmental protection, especially the field of water treatment and tetracycline degradation technology, and has good economic and social benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a magnetic carbon-based functional material from algal residue, the magnetic carbon-based functional material and application, and belongs to the technical field of new materials and the technical field of energy saving and environmental protection. BACKGROUND

[0002] China is a large country in the production and use of chemical fertilizers. A large amount of nitrogen and phosphorus nutrients is lost with water in the production and use of chemical fertilizers, causing water eutrophication and a large amount of algal residue waste. Because the algal residue has a high water content and contains harmful substances such as microcystin, it is extremely easy to rot and deteriorate, which not only wastes resources but also pollutes the environment. At present, the main methods for treating algal residue are incineration and landfill, but the traditional disposal method of algal residue not only has a very high cost but also may cause waste of resources.

[0003] Some methods for resource utilization of algal residue have been developed, such as:

[0004] The patent application file with Chinese patent application number 202111510772.6 and publication date of December 10, 2021 discloses a preparation method of graphene oxide based on high-salt spirulina residue and its application. The method uses high-temperature tube furnace pyrolysis of high-salt algal residue, and the pyrolysis process is divided into two steps, pre-carbonization and high-temperature pyrolysis. Then the prepared algal residue biochar is oxidized to algal residue graphene oxide by using the improved Hummers method, and the application of the algal residue graphene oxide in catalytic degradation of refractory organic pollutants. However, this method requires the addition of a large amount of inorganic salt and strong oxidizing agent for multiple oxidations, which has harsh conditions, high energy consumption, high cost, and is easy to cause environmental pollution. Moreover, the prepared graphene oxide is difficult to recycle, causing resource waste. The patent application file with Chinese patent application number 202111113702.7 and publication date of September 23, 2021 discloses a processing method for comprehensive utilization of microalgae residue. The method pyrolyzes microalgae residue in a protective gas atmosphere to obtain high-temperature oil gas and biochar. The biochar is mixed with an activator and then activated to obtain a nitrogen-doped carbon-based material. The high-temperature oil gas is separated to obtain biogas and an oil-water mixture. The oil-water mixture is separated to obtain bio-oil and reaction water, realizing effective comprehensive utilization of microalgae residue. However, this method requires the addition of a large amount of dichloromethane and methanol, which are volatile extractants, and has high environmental risk. The yield of the obtained carbon-based material is low, and the carbon-based material yield is not further developed and utilized. In addition, the patent application file with Chinese patent application number 201810408892.7 and publication date of April 27, 2018 discloses an algal residue biochar and its preparation method and application. The method grinds the algal residue and then sieves it. Then the algal residue is pyrolyzed in a high-temperature tube furnace. The pyrolysis environment is nitrogen atmosphere, and the pyrolysis temperature is 400-1000°C. The algal residue biochar is obtained after sieving. The required preparation temperature of this method is high, and the energy consumption of the preparation process is huge. Moreover, a large amount of persulfate is required for the treatment of sulfamethoxazole, and the treatment efficiency is low.

[0005] The above-mentioned scheme discloses the preparation of carbon-based functional materials from algal residue and its application. However, there are problems such as huge energy consumption in the preparation process, high environmental risk, high cost, difficulty in recycling, low efficiency in degrading organic pollutants, and the like. Moreover, the separation of the prepared algal residue carbon-based functional materials from liquid phase is an important factor affecting the practical application, and the preparation method and application conditions are greatly limited.

[0006] In addition, as a broad-spectrum antibiotic, tetracycline antibiotics have become the most widely used class of antibiotics in the world due to their strong antibacterial properties and low price. According to statistics, the total amount of antibiotics consumed by the European Union is about 5×106 kg per year, of which tetracycline antibiotics account for as high as 2.3×106 kg per year. 6kg; in the United States, tetracycline antibiotics accounted for 15.8% of the entire antibiotic market share; China is a big country in the production, sales and use of tetracycline antibiotics, with annual export volume of 1.34 x 10 7 kg, tetracycline antibiotics are most widely used in human disease control and livestock breeding Tetracycline antibiotics mainly include tetracycline hydrochloride, oxytetracycline, chlortetracycline, etc. They are all derivatives of hydrogenated tetracene, so their chemical structures are very similar. And the tetracycline hydrochloride with the most basic compound, because it is a broad-spectrum bacteriostatic agent produced by actinomycetes, has very excellent inhibitory effect on many microorganisms such as gram-negative bacteria, mycoplasma and chlamydia, so it can play a very important role in the prevention and treatment of livestock-related diseases. Tetracycline antibiotics have the characteristics of broad-spectrum, low toxicity, low price, etc., which can be used not only for the treatment and prevention of bacterial infections in livestock and poultry, but also as growth promoters to improve the production performance of livestock and poultry. However, tetracycline antibiotics also have the characteristics of high stability, low degradability, high lipophilicity, etc., which makes them difficult to be decomposed or adsorbed in the environment, easy to migrate and accumulate, and cause long-term potential harm to the environment.

[0007] Tetracycline hydrochloride is the most commonly used one among tetracycline antibiotics, and also the one detected most in livestock and poultry breeding wastewater. Tetracycline hydrochloride is very stable in structure and difficult to be absorbed by animal gastrointestinal tract, about 70% to 80% of which will be excreted out of the body in the form of parent compound, and it is not easy to be biodegraded in the environment. The content of tetracycline hydrochloride in feces can reach hundreds of milligrams per kilogram, and with the application of feces as fertilizer or direct discharge into water bodies, tetracycline hydrochloride will enter the soil and water environment and migrate and transform therein. Most of the untreated excreta will enter water bodies and soil, directly causing pollution to water and soil resources, making the residual drugs in the soil easy to be washed into water bodies or sink into the sediment for storage and enrichment. The residual amount of tetracycline hydrochloride in soil and water can reach several micrograms per liter to several milligrams per kilogram, far exceeding the internationally recognized safe concentration (0.1 μg / L). Tetracycline hydrochloride in the environment not only has toxic effects on non-target microorganisms, but also induces bacteria to develop drug resistance and spreads drug resistance to other bacteria through gene horizontal transfer. This will cause the failure of commonly used antibacterial drugs for humans and animals, increase the difficulty and cost of treating infectious diseases, and even threaten the life safety of humans and animals.

[0008] Because tetracycline hydrochloride is inherently biotoxic, microbial activity is easily inhibited during biological treatment, making traditional biological methods less than ideal for treating tetracycline hydrochloride in water. Ultimately, the majority of tetracycline hydrochloride is released into the aquatic environment as the parent compound. The effectiveness of adsorption methods for treating tetracycline hydrochloride depends not only on the adsorbed tetracycline and the adsorbent material but also on naturally dissolved organic matter present in any natural water. The presence of other organic matter directly competes with tetracycline hydrochloride for available adsorption surface / sites on the adsorbent. Traditional adsorbents suffer from drawbacks such as high preparation costs and difficult regeneration. Membrane separation methods (reverse osmosis, nanofiltration, ultrafiltration, etc.) can effectively reduce high levels of dissolved salts, but they have limitations in removing organic compounds such as tetracycline hydrochloride, and excessively high concentrations of these compounds can lead to membrane structure deterioration or fouling. Backhaus et al. used long-term bioluminescence inhibition experiments with Vibrio fischeri to study 21 commonly used antibiotics, including tetracycline hydrochloride and penicillin. The results showed that tetracycline hydrochloride was the most toxic of all the tested antibiotics and was very difficult to degrade. Therefore, the effective degradation of tetracycline hydrochloride residues in wastewater has attracted widespread attention from the environmental science community.

[0009] Therefore, if a method can be developed to effectively degrade tetracycline antibiotics in wastewater using algal residue, it will have a significant impact on the resource utilization and environmental protection of algal residue. Summary of the Invention

[0010] 1. The problem to be solved

[0011] To address at least one of the aforementioned problems, this invention provides a method for preparing magnetic carbon-based functional materials using algal residue, the magnetic carbon-based functional materials themselves, and their applications, thereby achieving the resource utilization of algal residue and the degradation of tetracycline antibiotics. This method has the advantages of simple operation and readily available raw materials. The magnetic carbon-based functional materials prepared using this method have the characteristics of good solid-liquid separation effect, high adsorption capacity for high-concentration tetracycline antibiotic pollutants, high catalytic degradation efficiency, and reusability.

[0012] 2. Technical Solution

[0013] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0014] The first objective of this invention is to provide a method for preparing magnetic carbon-based functional materials using algal residue, the specific steps of which are as follows:

[0015] (1) Pre-treat the algal residue to obtain dried algal residue powder;

[0016] (2) The dried algal residue powder obtained in step (1) is mixed with a metal salt solution and impregnated. The impregnated powder is then used for the next step of processing.

[0017] (3) drying the obtained algal residue powder;

[0018] (4) using the algal residue powder obtained in step (3) to obtain a solid by dry pyrolysis, and taking out the solid after cooling to room temperature;

[0019] (5) obtaining the algal residue carbon-based functional material by washing and drying the solid obtained in step (4);

[0020] (6) mixing the algal residue carbon-based functional material obtained in step (5) with Fe3O4, and grinding in a ball mill to obtain the magnetic algal residue carbon-based functional material.

[0021] In an embodiment, the pretreatment in step (1) refers to washing, drying and crushing the algal residue, and then treating the algal residue powder with a sodium hydroxide solution by ultrasonic and immersion, and then washing and drying the algal residue powder with distilled water. Further, the treatment with the sodium hydroxide solution is specifically as follows: taking 100 g of the dried and sieved algal residue powder according to a solid-liquid ratio of 1:2 to 1:10, adding a sodium hydroxide solution with a mass concentration of 5% to 20%, and then ultrasonic treating for 5 to 15 min, and then immersing at room temperature for 2 to 12 h.

[0022] In an embodiment, the algal residue in step (1) is most of the existing algal residues, and preferably one of the microalgal residue of the phylum Cyanophyta, the phylum Chlorophyta, the phylum Chrysophyta and the phylum Rhodophyta.

[0023] In an embodiment, the metal salt solution in step (2) is a ferric chloride solution or a magnesium chloride solution or a zinc chloride solution or a cobalt chloride solution or a potassium permanganate solution, and preferably the metal salt solution is a magnesium chloride solution or a cobalt chloride solution or a potassium permanganate solution.

[0024] In an embodiment, the mass concentration of the metal salt solution in step (2) is 5% to 30%.

[0025] In an embodiment, the mixing and immersion in step (2) refers to immersing the algal residue in the metal salt solution at a ratio of 0.003 to 0.007 moL of the metal salt solution per gram of the algal residue, and the immersion temperature is controlled at 15 to 35°C, and the immersion time is 20 to 30 h to ensure sufficient immersion.

[0026] In an embodiment, the mixing and immersion in step (2) refers to immersing the algal residue in 0.005 moL of the metal salt solution per gram of the algal residue, i.e. mixing 200 g of the algal residue with 1 moL of the metal salt solution, and the immersion temperature is controlled at 15 to 35°C, and the immersion time is 24 h to ensure sufficient immersion.

[0027] In an embodiment, the drying in step (3) refers to discarding the residual liquid after the immersion treatment, and drying the algal residue to a water content of not more than 10%. A higher water content is not conducive to the dry pyrolysis.

[0028] In one embodiment, the dry pyrolysis method in step (4) involves placing algal residue powder in a tube furnace, heating it to 400-800°C at a rate of 15-30°C / min under an anaerobic atmosphere provided by a protective gas, maintaining the temperature for 2-4 hours, and then cooling it to room temperature before removing it.

[0029] In one embodiment, the pyrolysis preparation temperature in step (4) is 500–700°C.

[0030] In one embodiment, the preparation time in step (4) is 2 hours.

[0031] In one embodiment, the protective gas in step (4) is nitrogen or carbon dioxide.

[0032] In one embodiment, the flow rate of the protective gas in step (4) is 50 to 150 mL / min.

[0033] In one embodiment, the cleaning in step (5) is performed by using an anhydrous alcohol solution at a solid-liquid ratio of 1:5 to 1:10. Further, the anhydrous alcohol solution is anhydrous methanol or anhydrous ethanol solution.

[0034] In one embodiment, the drying in step (5) is carried out at 40-80°C.

[0035] In one embodiment, step (6) involves mixing algal residue carbon-based functional materials with Fe3O4 at a mass ratio of 1:10, placing the mixture in a ball mill, and operating it in air at a speed of 150-300 rpm for 2-12 hours, alternating between forward and reverse operation every 10-60 minutes.

[0036] The second objective of this invention is to provide a magnetic carbon-based functional material obtained by the method described above for preparing magnetic carbon-based functional materials using algal residue.

[0037] A third objective of this invention is to provide an application of the aforementioned magnetic carbon-based functional material in the degradation of tetracycline.

[0038] Advantages and effects of the present invention:

[0039] (1) The method of preparing magnetic carbon-based functional materials by extracting waste residue from algal residue in eutrophic water bodies of the present invention uses algal residue as raw material, wherein the algal residue includes most of the existing microalgae such as cyanobacteria, green algae, golden algae and red algae. It has low cost and can realize the resource-based disposal of algal residue, solve the problem of low added value in the process of algal residue resource utilization, and has good economic value and practicality.

[0040] (2) The method for preparing the magnetic carbon-based functional material by using the eutrophication algal residue of a water body according to the application has a simple production process and is suitable for factory large-scale production; the algal residue has high organic matter content and is rich in nutrients such as carbon, nitrogen, phosphorus and potassium, thereby providing a good substrate for preparing the carbon-based functional material.

[0041] (3) The method for preparing the magnetic carbon-based functional material by using the eutrophication algal residue of a water body according to the application has the algal residue pretreated by metal salt impregnation, and the magnetic carbon-based functional material is prepared by combining a dry pyrolysis method and a high-energy ball milling method, which is of great significance for expanding the source of magnetic adsorption / catalytic materials. The high-energy ball milling method is used to prepare the magnetic carbon-based functional material, which can increase the performance of the carbon-based functional material and magnetize the carbon-based functional material. In addition, no additional chemical reagent needs to be added in the preparation process of the magnetic carbon-based functional material, and the operation is convenient. In the application process, the magnetic carbon-based functional material can be directly separated from a liquid by an external magnetic field, and recycled.

[0042] (4) The algal residue is mixed with a sodium hydroxide solution, and then ultrasonic and impregnation pretreatment are performed to remove oily substances in the algal residue, thereby providing a strong guarantee for the preparation of the magnetic carbon-based functional material.

[0043] (5) The moisture content of the dried algal residue is controlled to be not more than 10%. When the moisture content is greater than 10%, the algal residue is not fully activated, thereby affecting the generation rate of the carbon-based functional material.

[0044] (6) The magnetic carbon-based functional material can be applied to the control of heavy metal and antibiotic contaminated water bodies, effectively reduces the concentration of heavy metals and high-concentration antibiotic pollutants of 50 mg / L in the water body, and the removal rate of tetracycline hydrochloride can be up to 94.2%, which is suitable for large-scale application. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The flow chart of the method for preparing the magnetic carbon-based functional material by using the algal residue according to the application;

[0046] Figure 2 The scanning electron microscope image of the magnetic carbon-based functional material prepared in Example 1 of the application, magnified 5000 times;

[0047] Figure 3 The scanning electron microscope image of the magnetic carbon-based functional material prepared in Example 2 of the application, magnified 5000 times;

[0048] Figure 4 The scanning electron microscope image of the magnetic carbon-based functional material prepared in Example 3 of the application, magnified 5000 times;

[0049] Figure 5 The X-ray diffraction spectrum of the magnetic carbon-based functional material prepared in Example 1, Example 2 and Example 3 of the application.

[0050] Figure 6 The magnetic carbon-based functional materials prepared in Examples 1, 2, and 3 of this invention exhibit the effect of degrading tetracycline hydrochloride at different reaction times (min); wherein KMnO4-SRBC, MgCl2-SRBC, and CoCl2-SRBC are the magnetic carbon-based functional materials prepared in Examples 1, 2, and 3, respectively. Detailed Implementation

[0051] The present invention will be further described below with reference to specific embodiments.

[0052] Example 1: A method for preparing magnetic carbon-based functional materials using algal residue

[0053] like Figure 1 The flowchart shown below details the specific steps:

[0054] (1) After washing and drying, the algal residue is crushed to 80 mesh. Take 100g of powder, add 200mL of sodium hydroxide solution with a mass concentration of 20% to the algal residue powder, stir thoroughly, sonicate for 15min, and then soak at room temperature for 12h to remove the oily substances in the algal residue. After discarding the residual liquid, dry for later use.

[0055] (2) Impregnate the dried algal residue powder with 0.005 mol of modified compound potassium permanganate per gram of biomass, i.e., mix 200g of algal residue with 1 mol of potassium permanganate solution; specifically, add potassium permanganate solution (controlled at a concentration of 5-30%, such as 10%) to the algal residue powder and mix thoroughly, then impregnate at 25°C for 24h, stirring thoroughly during the impregnation process, and use the impregnated powder for the next step of processing;

[0056] (3) After the soaking treatment is completed, discard the residual liquid and dry the algae residue to a moisture content of 5%;

[0057] (4) Place the above powder in a tube furnace, with a nitrogen flow rate of 50 mL / min, a furnace temperature of 500℃, a heating rate of 20℃ / min, hold for 2 hours, and remove after natural cooling to room temperature.

[0058] (5) The solid obtained from the above treatment is washed three times with anhydrous ethanol solution at a solid-liquid ratio of 1:5 and then dried at 75°C to obtain manganese-modified algal residue carbon-based functional material.

[0059] (6) The obtained algal residue carbon-based functional material is mixed with Fe3O4 at a mass ratio of 1:10, placed in a ball mill, and operated in air at a speed of 150-300 rpm for 2-12 hours, alternating between forward and reverse operation every 10-60 minutes to obtain magnetic algal residue carbon-based functional material.

[0060] Figure 2 This is a scanning electron microscope image of the magnetic carbon-based functional material prepared in this embodiment, magnified 5000 times.

[0061] The performance of the magnetic carbon-based functional material obtained in this embodiment was tested. Specifically, a certain amount of tetracycline hydrochloride was prepared into a tetracycline hydrochloride solution with a mass concentration of 50 mg / L. 0.5 g / L of potassium persulfate and 0.5 g / L of algal residue magnetic carbon-based functional material were added to the tetracycline hydrochloride solution, and the mixture was shaken at 25°C and 150 rpm / min for 3 hours to achieve equilibrium. The centrifuge tube was placed above a magnet, and the supernatant was collected after 30 seconds. The magnetic separation effect between the solid and liquid was good. The concentration of tetracycline hydrochloride in the supernatant was determined by high-performance liquid chromatography (HPLC). Figure 6 As shown, with the increase of time, the removal rate of tetracycline hydrochloride by the magnetic carbon-based functional material prepared in this embodiment gradually increases until the removal rate reaches 92.9% at 180 min.

[0062] In this embodiment, the catalytic reaction was also carried out under the same conditions at a concentration of 20 mg / L tetracycline hydrochloride. The results showed that the reaction rate was particularly fast, and tetracycline hydrochloride could not be detected when the catalyst was added immediately (the whole time was within 1 minute).

[0063] Example 2: A method for preparing magnetic carbon-based functional materials using algal residue

[0064] like Figure 1 The flowchart shown below details the specific steps:

[0065] (1) After washing and drying, the algal residue is crushed to 80 mesh. Take 100g of powder, add 200mL of sodium hydroxide solution with a mass concentration of 20% to the algal residue powder, stir thoroughly, sonicate for 15min, and then soak at room temperature for 12h to remove the oily substances in the algal residue. After discarding the residual liquid, dry for later use.

[0066] (2) The dried algal residue powder was impregnated with 0.005 mol of modified magnesium chloride per gram of biomass, i.e., 200 g of algal residue was mixed with 1 mol of magnesium chloride solution; magnesium chloride solution was added to the algal residue powder and mixed thoroughly, and then impregnated at 25°C for 24 h. The mixture was stirred thoroughly during the impregnation process and then used for the next step of processing.

[0067] (3) After the soaking treatment is completed, discard the residual liquid and dry the algae residue to a moisture content of 5%;

[0068] (4) Place the above powder in a tube furnace, with a nitrogen flow rate of 50 mL / min, a furnace temperature of 500℃, a heating rate of 20℃ / min, hold for 2 hours, and remove after natural cooling to room temperature.

[0069] (5) The solid obtained by the above treatment is washed with anhydrous ethanol solution at a solid-liquid ratio of 1:5 for three times, and then dried at 75°C to obtain a magnesium-modified algal residue carbon-based functional material;

[0070] (6) The obtained algal residue carbon-based functional material is mixed with Fe3O4 at a mass ratio of 1:10, and then placed in a ball mill, which is operated at a speed of 150-300 rpm in air for 2-12 h, and is alternately operated in positive and reverse directions every 10-60 min to obtain a magnetic algal residue carbon-based functional material.

[0071] Figure 3 A scanning electron microscope image of the magnetic carbon-based functional material obtained in this example is shown in FIG. 5.

[0072] The performance of the magnetic carbon-based functional material obtained in this example is detected. A certain amount of tetracycline hydrochloride is configured into a tetracycline hydrochloride solution with a mass concentration of 50 mg / L. 0.5 g / L of potassium persulfate and 0.5 g / L of the algal residue magnetic carbon-based functional material are added to the tetracycline hydrochloride solution. The solution is shaken and balanced at 25°C and a speed of 150 rpm / min for 3 h. The centrifuge tube is placed above a magnet, and the supernatant is taken after 30 s. The magnetic separation effect of the solid-liquid is good. The concentration of tetracycline hydrochloride in the supernatant is determined by high performance liquid chromatography. As shown in FIG. 6, the removal rate of the magnetic carbon-based functional material prepared in this example for tetracycline hydrochloride gradually increases with time, and the removal rate reaches 94.2% at 180 min. Figure 6

[0073] This example also carries out catalytic reaction under the same conditions at a tetracycline hydrochloride concentration of 20 mg / L. The results show that the reaction speed is particularly fast, and tetracycline hydrochloride cannot be detected after the catalyst is put in and detected immediately (within 1 min).

[0074] Example 3: A method for preparing a magnetic carbon-based functional material using algal residue

[0075] As shown in the flow chart of FIG. 7, the specific steps are as follows: Figure 1

[0076] (1) The algal residue is washed, dried, and then pulverized to 80 mesh. 100 g of the powder is taken, 200 mL of a sodium hydroxide solution with a mass concentration of 20% is added to the algal residue powder, and then the mixture is stirred thoroughly and ultrasonically treated for 15 min. Subsequently, the mixture is immersed at room temperature for 12 h to remove oily substances in the algal residue. After the residual liquid is discarded, the mixture is dried for use;

[0077] ​​(2) The ratio of 0.005 moL modified compound cobalt chloride per gram of biomass after drying is impregnated, that is, 200 g of algal residue is mixed with 1 moL of cobalt chloride solution; after adding the cobalt chloride solution to the algal residue powder and thoroughly mixing, impregnation is carried out at 25°C for 24 h, with thorough stirring during the impregnation process; after impregnation, it is used for the next step of treatment;

[0078] (3) After the impregnation treatment is completed, the residual liquid is discarded, and the algal residue is dried to a moisture content of 5%;

[0079] (4) The above powder is placed in a tube furnace, the nitrogen flow rate is 50 mL / min, the furnace temperature is set to 500°C, the heating rate is 20°C / min, and the temperature is maintained for 2 h; after natural cooling to room temperature, it is taken out;

[0080] (5) The solid obtained by the above treatment is washed with anhydrous ethanol solution at a solid-liquid ratio of 1:5 for three times, and then dried at 75°C to obtain cobalt-modified algal residue carbon-based functional material;

[0081] (6) The obtained algal residue carbon-based functional material is mixed with Fe3O4 at a mass ratio of 1:10, placed in a ball mill, and operated in air at a speed of 150-300 rpm for 2-12 h, with positive and negative alternating operation every 10-60 min, to obtain a magnetic algal residue carbon-based functional material.

[0082] Figure 4 A scanning electron microscope image of the magnetic carbon-based functional material prepared in this example is shown, magnified 5000 times.

[0083] The performance of the magnetic carbon-based functional material obtained in this example was detected. A certain amount of tetracycline hydrochloride was prepared into a tetracycline hydrochloride solution with a mass concentration of 50 mg / L. 0.5 g / L of potassium persulfate and 0.5 g / L of algal residue magnetic carbon-based functional material were added to the tetracycline hydrochloride solution, and the mixture was shaken at 25°C and 150 rpm / min for 3 h. The centrifuge tube was placed above the magnet, and the supernatant was taken after 30 s. The magnetic separation effect of the solid-liquid was good. The concentration of tetracycline hydrochloride in the supernatant was determined by high performance liquid chromatography, as shown in Figure 6 As shown, the removal rate of tetracycline hydrochloride by the magnetic carbon-based functional material prepared in this example gradually increased with time, and reached 93.5% at 180 min.

[0084] This example also carried out catalytic reaction under the same conditions at a tetracycline hydrochloride concentration of 20 mg / L. The results showed that the reaction speed was particularly fast, and tetracycline hydrochloride could not be detected immediately after the catalyst was added (within 1 min).

[0085] Comparative Example 1: Effect of preparation temperature on the magnetic carbon-based functional material

[0086] Except for changing the preparation temperature, other experimental steps are consistent with Example 1, and the magnetic carbon-based material is prepared.

[0087] The magnetic carbon-based functional material prepared in this example is detected for performance according to the performance detection method of Example 1, and the results are shown in Table 1. The optimal preparation temperature is 500-700℃.

[0088] Table 1

[0089] Preparation temperature (°C) Removal rate of tetracycline hydrochloride 400 84.3％ 500 (Example 1) 92.9％ 600 93.4％ 700 92.1％ 800 86.7％

[0090] Comparative Example 2: Effect of pyrolysis preparation time on the prepared magnetic carbon-based functional material

[0091] Except for changing the pyrolysis preparation time, other experimental steps are consistent with Example 1, and the magnetic carbon-based material is prepared.

[0092] The magnetic carbon-based functional material prepared in this example is detected for performance according to the performance detection method of Example 1, and the results are shown in Table 2. The effect is not obviously improved by continuing to increase the pyrolysis preparation time after 2h, so the pyrolysis preparation time of 2h is selected.

[0093] Table 2

[0094] Pyrolysis preparation time (h) Removal rate of tetracycline hydrochloride 1 84.3％ 2 (Example 1) 92.9％ 3 93.7％ 4 94.1％ 5 94.6％

[0095] Comparative Example 3: Effect of modification using different metal salt solutions on the prepared magnetic carbon-based functional material

[0096] Except for using different metal salt solutions for modification, other experimental steps are consistent with Example 1, and the magnetic carbon-based material is prepared.

[0097] The magnetic carbon-based functional material prepared in this example is detected for performance according to the performance detection method of Example 1, and the results are shown in Table 3. The effects of using potassium permanganate solution, magnesium chloride solution, and cobalt chloride solution are better.

[0098] Table 3

[0099] Metal salt solution Removal rate of tetracycline hydrochloride Potassium permanganate solution (Example 1) 92.9％ Magnesium chloride solution (Example 2) 94.2％ Cobalt chloride solution (Example 3) 93.5％ Without modification 56.7％ Ferric chloride solution 84.8％ Zinc chloride solution 82.4％ AlCl3 (aluminum chloride solution) 32.1％

[0100] Comparative Example 4:

[0101] In the treatment of algal residue, sodium hydroxide solution is not used, and other steps are consistent with Example 1, and the magnetic carbon-based material is prepared.

[0102] The magnetic carbon-based functional material prepared in this example is detected for performance according to the performance detection method of Example 1, and the removal rate of tetracycline hydrochloride is 77.9%, which is not good.

[0103] Although the present application has been disclosed in its preferred embodiments with reference to the accompanying drawings, it is not intended to limit the present application thereto, and various modifications and alterations can be made thereto by those skilled in the art without departing from the spirit and scope of the present application, and the scope of protection of the present application should be defined by the appended claims.

Claims

1. A method for preparing magnetic carbon-based functional materials using algal residue, characterized in that, The method comprises the following steps: (1) using sodium hydroxide solution to pretreat the algal residue to obtain dried algal residue powder; wherein the sodium hydroxide solution treatment is as follows: taking 100 g of sieved algal residue powder with dry weight, adding sodium hydroxide solution with mass concentration of 5-20%, and then ultrasonicating for 5-15 min, and then immersing at room temperature for 2-12 h, with solid-liquid ratio of 1:2-1:10; (2) mixing and immersing the dried algal residue powder obtained in step (1) with metal salt solution, and then using the immersed product for the next step; wherein the metal salt solution is magnesium chloride solution or cobalt chloride solution or potassium permanganate solution; (3) drying the obtained algal residue; (4) using dry pyrolysis method to obtain solid from the algal residue powder obtained in step (3), and then taking out after cooling to room temperature; wherein the dry pyrolysis method is as follows: placing the algal residue powder in a tube furnace, and then heating to 500-700 ℃ at a heating rate of 15-30 ℃ / min under anaerobic atmosphere provided by protective gas, and then keeping for 2-4 h; (5) washing and drying the solid obtained in step (4) to obtain algal residue carbon-based functional material; (6) mixing the algal residue carbon-based functional material obtained in step (5) with Fe3O4, and then grinding in a ball mill to obtain magnetic algal residue carbon-based functional material.

2. The method of claim 1, wherein, The step (1) pretreatment refers to washing, drying, and then crushing the algal residue, and then sieving through 20-80 mesh screen, and then ultrasonicating and immersing in sodium hydroxide solution, and then washing with distilled water and drying.

3. The method of claim 1, wherein, The drying in step (3) refers to discarding the residual liquid after the end of the immersion treatment, and then drying the algal residue to a water content of not more than 10%.

4. The method of claim 1, wherein, The pyrolysis preparation time of the dry pyrolysis method is 2 h.

5. The method of claim 1, wherein, The protective gas is nitrogen or carbon dioxide, and the gas flow rate of the protective gas is 50-150 mL / min.

6. The method of claim 1, wherein, The washing in step (5) is washing with anhydrous alcohol solution at a solid-liquid ratio of 1:5-1:10, and further, the anhydrous alcohol solution is anhydrous methanol or anhydrous ethanol solution.

7. A magnetic carbon-based functional material, characterized by, The magnetic carbon-based functional material is obtained by the method for preparing the magnetic carbon-based functional material from algal residue according to any one of claims 1-6.

8. Use of the magnetic carbon-based functional material according to claim 7 in degrading tetracycline.

Images