Method for removing algae by activating persulfate with suspended three-dimensional biochar composite material

Abstract

The application discloses a method for removing algae by activating persulfate with a suspended three-dimensional biochar composite material, which is a method for degrading and treating algae by activating persulfate with a suspended three-dimensional biochar composite material as a catalyst, wherein the suspended three-dimensional biochar composite material comprises melamine foam and biochar, and the biochar is loaded on the melamine foam by being wrapped with an adhesive. In the application, the suspended three-dimensional biochar composite material can be suspended in water, thus being in good contact with persulfate and being capable of quickly generating active oxygen species with high activity, the active oxygen species attack algae cells, and then degrade intracellular organic matter, thereby achieving effective inactivation of algae. The method has the advantages of simple process, convenient operation, low cost, high treatment efficiency, wide application range, high reusability, green environmental protection, and clean and pollution-free, is a method that can be widely adopted and can efficiently remove algae, and has high application value and commercial value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of advanced oxidation treatment in contaminated environment, and relates to a method for removing algae, in particular to a method for removing algae by activating persulfate with a suspended three-dimensional biochar composite material. BACKGROUND

[0002] Due to climate change and water body eutrophication, algal blooms have broken out and become more serious and frequent worldwide, which seriously threatens water ecological system and drinking water safety. The toxic metabolites, taste, odor, etc. produced by blue-green algae blooms pose great challenges to drinking water treatment and even harm human health and ecosystems. Among them, Microcystis aeruginosa is one of the main blue-green algae in freshwater ecosystems and is the main cause of blue-green algae blooms. Due to the electrostatic repulsion and steric hindrance effect of blue-green algae, it is difficult to effectively remove algae cells in traditional water treatment processes. Chemical oxidation can change the surface charge of blue-green algae and effectively remove algae cells, but may cause serious secondary pollution. Therefore, it is crucial to develop efficient and practical algal bloom control technology.

[0003] In wastewater treatment, advanced oxidation technology has been widely concerned since its inception. Advanced oxidation technology can degrade trace, persistent and non-biodegradable organic pollutants into smaller molecules or even completely mineralize in a short time. The key to the degradation of organic pollutants by advanced oxidation technology is oxidant, mainly ozone, persulfate, hydrogen peroxide and ferrate, among which, hydrogen peroxide and persulfate are the most widely used and studied. Fenton system based on hydrogen peroxide is widely used, but Fenton reaction needs acidic conditions, and needs to add chemicals to adjust pH, which produces a large amount of iron sludge. Persulfate-based advanced oxidation technology (SR-AOP) is effective in a wider pH range, has a higher oxidation-reduction potential (2.5-3.1V), and produces a higher mineralization rate. Therefore, the advanced oxidation system constructed with persulfate as oxidant is increasingly valued by people.

[0004] In the advanced oxidation system constructed by using persulfate as oxidant, the traditional methods for activating persulfate mainly include heating, ultrasonic, ultraviolet irradiation and adding transition metal, but the activation effect of these methods on persulfate is limited. In recent years, new carbon materials such as graphene and biochar can replace transition metals to catalyze persulfate to produce reactive oxygen species (ROS). Biochar has been widely used to activate persulfate due to its wide source, simple preparation, economic availability, rich surface functional groups, high specific surface area and developed pore structure. However, as a powder material, biochar is easy to agglomerate and settle in water, and the contact time with harmful pollutants is limited, resulting in poor treatment effect and low treatment efficiency, and it is difficult to recycle and easy to cause secondary pollution. In order to overcome the above problems, researchers have loaded biochar and other powder materials on carrier materials, which not only can reduce the agglomeration of powder materials, but also can realize recycling. Loading biochar on the surface of three-dimensional composite material is a promising solution. Among three-dimensional skeleton materials, sponge is a potential choice due to its high porosity, low density, low cost and high stability. However, in existing loaded biochar materials, biochar is difficult to be stably loaded on the carrier, and still has the defect of poor stability, resulting in that biochar is easy to separate from the carrier or disintegrate during use, at this time the performance of the loaded biochar material is poor, and the separated or disintegrated biochar is also easy to enter the water body again and cause secondary pollution. For example, when biochar foam obtained by soaking melamine foam into biochar dispersion and drying is used as an adsorbent to adsorb organic pollutants in water, biochar is easy to separate from the melamine foam, resulting in poor adsorption performance of the biochar foam and easy to cause secondary pollution. In addition, the existing superhydrophobic / superoleophobic loaded biochar materials are usually hydrophobic and light in weight, and are easy to float on the water surface, so it is difficult to effectively improve the contact probability of the materials with hydrophilic substances in aqueous solution, resulting in that it is still difficult to effectively remove pollutants in water, especially pollutants suspended in water. In addition, the preparation method of the existing loaded biochar material still has the defects of complex process and high price. Therefore, it is of great significance to obtain a suspended three-dimensional biochar composite material with high stability, high catalytic efficiency, good recycling property, low cost and environmental friendliness, and a preparation method with simple process, easy operation and mild reaction conditions, for improving the activation effect of biochar material on persulfate and effectively treating water environment. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method for removing algae by using a suspended three-dimensional biochar composite material to activate persulfate, which has the advantages of simple process, easy operation, low cost, high treatment efficiency, wide application range, high reuse rate, green environmental protection and clean pollution-free.

[0006] To solve the above technical problems, the application adopts the following technical solutions.

[0007] A method for removing algae by activating persulfate with a suspended three-dimensional biochar composite material, which degrades and processes algae by activating persulfate with a suspended three-dimensional biochar composite material as a catalyst; the suspended three-dimensional biochar composite material comprises melamine foam and biochar, and the biochar is loaded on the melamine foam by being wrapped with an adhesive.

[0008] The method is further improved, and the mass ratio of the melamine foam to the biochar is 9:5-40; the mass ratio of the biochar to the adhesive is 0.25-4:1.

[0009] The method is further improved, and the biochar is shrimp shell biochar powder and / or sludge biochar powder; the mesh number of the biochar is 80-100; and the adhesive is at least one of polyvinyl alcohol, polyvinylidene fluoride, polyvinylpyrrolidone, polydopamine and octadecylamine.

[0010] The method is further improved, and the specific surface area of the suspended three-dimensional biochar composite material is 90m 2 / g-270m 2 / g; and the pore volume of the suspended three-dimensional biochar composite material is 0.19m 3 / g-0.43m 3 / g.

[0011] The method is further improved, and the preparation method of the suspended three-dimensional biochar composite material comprises the following steps:

[0012] S1, mixing biochar and an adhesive solution, stirring to obtain a biochar dispersion;

[0013] S2, soaking melamine foam into the biochar dispersion, ultrasonic dispersion and drying to obtain melamine foam loaded with biochar;

[0014] S3, calcining the melamine foam loaded with biochar to obtain a suspended three-dimensional biochar composite material.

[0015] In step S1, the mass ratio of the biochar to the adhesive in the adhesive solution is 0.5-4:1.

[0016] In step S1, the biochar further comprises the following treatment before use: grinding the biochar and passing through a screen with a mesh number of 80-100 to obtain biochar powder.

[0017] In a further improvement to the above method, in step S1, the adhesive solution is prepared by the following method: mixing the adhesive with water and stirring for 2 to 4 hours at a temperature of 80℃ to 95℃ and a rotation speed of 300 r / min to 500 r / min to obtain the adhesive solution.

[0018] In a further improvement to the above method, in step S2, the mass ratio of melamine foam to biochar is 9:5 to 40.

[0019] In a further improvement to the above method, step S2 further includes the following treatment of the melamine foam before use: washing the melamine foam alternately with water and ethanol 3 to 5 times each, and drying it at 60°C for 1 to 3 hours.

[0020] In a further improvement to the above method, in step S1, the stirring speed is 300 r / min to 500 r / min; and the stirring time is 20 min to 60 min.

[0021] In a further improvement to the above method, in step S2, the ultrasonic dispersion time is 20 min to 60 min; the drying temperature is 60℃ to 80℃; and the drying time is 6 h to 12 h.

[0022] In a further improvement to the above method, in step S3, the calcination is carried out under an inert atmosphere; the inert atmosphere is nitrogen; the heating rate during the calcination process is 5℃ / min to 12℃ / min; the calcination temperature is 200℃ to 400℃; and the calcination time is 1h to 4h.

[0023] A further improvement to the above method is that the method utilizes suspended three-dimensional biochar composite material to activate persulfate to remove algae from water, including the following treatment: mixing the suspended three-dimensional biochar composite material with algae-containing water, adding persulfate to carry out an oxidation reaction, and completing the removal of algae from the water.

[0024] In a further improvement to the above method, the mass-to-volume ratio of the suspended three-dimensional biochar composite material to algae-containing water is 0.8g~0.9g∶80mL.

[0025] In a further improvement to the above method, the algae in the algae-containing water body is Microcystis aeruginosa; the absorbance of the algae-containing water body is 0.100–0.400; and the pH value of the algae-containing water body is 5–9.

[0026] In a further improvement to the above method, the initial concentration of persulfate in the oxidation reaction system is controlled to be 0.5 mM to 5 mM; the persulfate is sodium persulfate.

[0027] In a further improvement to the above method, the oxidation reaction is carried out at a rotation speed of 100 r / min to 300 r / min; the temperature of the oxidation reaction is 10℃ to 35℃; and the time of the oxidation reaction is 50 min to 380 min.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] (1) This invention provides a method for removing algae by activating persulfate using a suspended three-dimensional biochar composite material. By using the suspended three-dimensional biochar composite material to activate persulfate, algae can be effectively inactivated. Specifically, compared with conventional supported biochar, the suspended three-dimensional biochar composite material used in this invention uses melamine foam as a carrier skeleton, which has advantages such as three-dimensional (3D) structure, high porosity, high nitrogen content, excellent elasticity, light weight, and low density. Therefore, loading biochar onto melamine foam can not only effectively avoid biochar agglomeration, thus still having rich pore structure and excellent catalytic performance, but also the resulting composite material is light in weight and low in density, and can be suspended in water. More importantly, the adhesive effect of the binder can more stably load biochar onto melamine foam. The resulting composite material has excellent stability, can avoid the harm of biochar powder materials to the ecological environment, and has no secondary pollution. In addition, by loading biochar onto melamine foam, The amine foam also facilitates the separation and recycling of composite materials, improving their reusability. Therefore, the suspended three-dimensional biochar composite material of this invention possesses advantages such as high stability, high catalytic efficiency, good recyclability, low cost, and environmental friendliness. It is a novel carbon material with excellent performance. Furthermore, when this suspended three-dimensional biochar composite material is used as a catalyst to activate persulfate, it can remain suspended in water, thus enabling better contact with persulfate and rapid generation of highly active reactive oxygen species. These reactive oxygen species attack algal cells, thereby degrading intracellular organic matter and effectively inactivating algae. This method is characterized by simple process, convenient operation, low cost, high treatment efficiency, wide application range, high reusability, green environmental protection, and cleanliness. It is a widely applicable and efficient method for removing algae, possessing high application and commercial value. It can be widely used to remove pollutants in the environment (such as Microcystis aeruginosa), which is of great significance for expanding the application range of biochar.

[0030] (2) In the suspended three-dimensional biochar composite material used in this invention, by optimizing the mass ratio of biochar to polyvinyl alcohol to 0.25 to 4:1, more biochar can be loaded onto melamine foam while effectively improving the stability of the composite material. This further improves the catalytic performance of the composite material while ensuring that it has the advantages of being lightweight, having low density, and being able to suspend in water. This is because: if there is too much biochar, it will lead to poor catalytic performance and a large amount of detachment, while if there is too little biochar, it will lead to the binder clogging the pores of the biochar and poor catalytic effect. At the same time, by optimizing the amount of polyvinyl alcohol, the mass and density of the composite material can also be controlled, so that it can be better suspended in the water near the water surface.

[0031] (3) In the suspended three-dimensional biochar composite material used in this invention, the biochar used is shrimp shell biochar powder and / or sludge biochar powder. These biochars have abundant surface functional groups, high specific surface area and well-developed pore structure, good adsorption and catalytic effects, and no secondary pollution. At the same time, these biochars are made from biomass through calcination, which has the advantages of wide raw material sources, low cost, simple process, convenient operation and large-scale production, which is conducive to the large-scale utilization of suspended three-dimensional biochar composite materials.

[0032] (4) In the preparation method of the suspended three-dimensional biochar composite material adopted in this invention, biochar is first mixed with an adhesive solution to form a biochar dispersion. Then, melamine foam is immersed in the biochar dispersion and ultrasonically dispersed. Utilizing the adhesive effect, the biochar is uniformly loaded onto the melamine foam. Finally, the melamine foam loaded with biochar is calcined. During the calcination process, the melamine foam loaded with biochar is activated by low-temperature pyrolysis. While ensuring the mechanical stability of the composite material, the pore blockage of the biochar by the adhesive can be cleared, allowing the composite material to maintain a high specific surface area and a rich pore structure similar to that of biochar powder. This is beneficial to improving the catalytic performance of the composite material. Thus, a suspended three-dimensional biochar composite material with high stability, excellent catalytic performance, and environmental friendliness is prepared. At the same time, the preparation method of this invention has the advantages of simple process, readily available raw materials, and low cost. It is environmentally friendly, does not produce toxic or harmful byproducts, is suitable for large-scale preparation, and meets the needs of actual production.

[0033] (5) In the preparation method of the suspended three-dimensional biochar composite material adopted in this invention, by optimizing the calcination conditions, such as the heating rate during the calcination process being 5℃ / min~12℃ / min, the calcination temperature being 200℃~400℃, and the calcination time being 1h~4h, the porosity and active sites of the biochar in the composite material can be further improved under the premise of ensuring stable biochar loading, so that the composite material retains the stability of mechanical properties while having better catalytic performance. Attached Figure Description

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0035] Figure 1 This is a scanning electron microscope image of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of the present invention.

[0036] Figure 2 This is the energy spectrum of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of the present invention.

[0037] Figure 3 This is a nitrogen adsorption-desorption curve of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of the present invention.

[0038] Figure 4 This is a pore size distribution diagram of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of the present invention.

[0039] Figure 5 This is a graph showing the degradation efficiency of chlorophyll by different suspended 3D biochar composite materials (A1, A2, A3, A4, A5, A7) in Example 1 of the present invention.

[0040] Figure 6 The image shows the inactivation effect of the suspended three-dimensional biochar composite material (A1) on Microcystis aeruginosa under different sodium persulfate dosage conditions in Example 2 of this invention.

[0041] Figure 7 The graph shows the degradation effect of the suspended three-dimensional biochar composite material (A1) on chlorophyll under different pH conditions in Example 3 of the present invention.

[0042] Figure 8 The image shows the removal effect of the suspended three-dimensional biochar composite material (A1) on algae in different water bodies in Example 4 of this invention. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available. Unless otherwise specified, the pH value of the algae solution is 7.

[0044] Example 1

[0045] A method for removing algae using suspended three-dimensional biochar composite material to activate sodium persulfate, specifically involving the activation of sodium persulfate by suspended three-dimensional biochar composite material to remove algae from water, comprising the following steps:

[0046] Two pieces each of the suspended three-dimensional biochar composite materials (A1, A2, A3, A4, A5, A7), totaling 0.84 g, were added to 80 mL of Microcystis aeruginosa solution (concentration 3.7*10⁻⁶) with an absorbance of 0.200. 6 In a solution containing 1 mM sodium persulfate (μL), the mixture was shaken at 25°C and 150 rpm for 30 min to reach adsorption equilibrium. Then, 0.01924 g of sodium persulfate (PDS) was added to the solution (the initial concentration of sodium persulfate in the system was 1 mM), and the oxidation reaction was carried out at 150 rpm for 340 minutes to complete the removal of Microcystis aeruginosa from the water.

[0047] Blank group: Take 80 mL of Microcystis aeruginosa solution with an absorbance of 0.200 (concentration 3.7*10⁻⁶). 6 (Units / L), without adding any catalyst material or PDS, all other conditions are the same.

[0048] In this embodiment, the suspended three-dimensional biochar composite material (A1) used comprises melamine foam and biochar, with the biochar encapsulated and loaded onto the melamine foam by polyvinyl alcohol. The mass ratio of melamine foam to biochar in this suspended three-dimensional biochar composite material (A1) is 9:10, and the mass ratio of biochar to polyvinyl alcohol is 1:1. The biochar is shrimp shell biochar powder. The specific surface area of ​​this suspended three-dimensional biochar composite material is 264.4 m². 2 / g, pore volume is 0.43m 3 / g. This suspended three-dimensional biochar composite material is prepared by calcining melamine foam as the carrier skeleton of biochar under the action of polyvinyl alcohol.

[0049] In this embodiment, the preparation method of the suspended three-dimensional biochar composite material (A1) includes the following steps:

[0050] (1) Melamine sponge treatment:

[0051] Melamine sponge was cut into 2cm×2cm×0.5cm cubes, weighing 0.0150g. It was washed three times each with ethanol and ultrapure water, and then dried in an oven at 60℃ (drying time can be 1h to 3h, such as 2h) to obtain melamine foam.

[0052] (2) Loading of biochar

[0053] 1g of polyvinyl alcohol was added to 50mL of ultrapure water and heated in a water bath at 90℃ for 1h with stirring to completely dissolve the polyvinyl alcohol in the water, thus obtaining a polyvinyl alcohol solution. 1g of ground shrimp shell biochar powder was added to the polyvinyl alcohol solution and stirred for 30min. Then, 0.0150g of lumpy melamine sponge (melamine foam) was added and sonicated for 30min. After removal, it was dried in an oven at 60℃ for 12h to obtain melamine foam loaded with biochar.

[0054] In this embodiment, the method for preparing shrimp shell biochar includes the following steps:

[0055] After washing the shrimp shells, they were dried at 105℃, pulverized, and sieved to obtain biomass powder. The temperature was raised to 800℃ under anaerobic conditions for calcination. The calcined biochar powder was then washed with 1M HCl for 12 hours, collected, and dried to obtain shrimp shell biochar.

[0056] (3) Activation of suspended three-dimensional biochar composite materials

[0057] The melamine foam loaded with biochar obtained in step (2) was placed in a tube furnace, nitrogen gas was introduced, the temperature was raised at a rate of 5℃ / min, and it was calcined at 300℃ for two hours. Through low-temperature pyrolysis activation, the pore blockage was reduced and the catalytic performance of the material was improved. After natural cooling, a suspended three-dimensional biochar composite material was obtained, which was numbered A1.

[0058] In this embodiment, the suspended three-dimensional biochar composite material (A2) used is basically the same as the suspended three-dimensional biochar composite material (A1), except that the mass ratio of biochar to polyvinyl alcohol in the suspended three-dimensional biochar composite material (A2) is 2:1.

[0059] In this embodiment, the suspended three-dimensional biochar composite material (A2) is prepared in the same way as the suspended three-dimensional biochar composite material (A1), except that the amount of shrimp shell biochar powder used in step (2) of the suspended three-dimensional biochar composite material (A2) is 2g, and the calcination temperature in step (3) is 400℃.

[0060] In this embodiment, the suspended three-dimensional biochar composite material (A3) used is basically the same as the suspended three-dimensional biochar composite material (A1), except that the mass ratio of biochar to polyvinyl alcohol in the suspended three-dimensional biochar composite material (A3) is 2:1.

[0061] In this embodiment, the preparation method of the suspended three-dimensional biochar composite material (A3) is basically the same as that of the suspended three-dimensional biochar composite material (A1), except that the amount of shrimp shell biochar powder used in step (2) of the suspended three-dimensional biochar composite material (A3) is 2g.

[0062] In this embodiment, the suspended three-dimensional biochar composite material (A4) used is basically the same as the suspended three-dimensional biochar composite material (A1), except that the mass ratio of biochar to polyvinyl alcohol in the suspended three-dimensional biochar composite material (A4) is 2:1.

[0063] In this embodiment, the preparation method of the suspended three-dimensional biochar composite material (A4) is basically the same as that of the suspended three-dimensional biochar composite material (A1), except that the amount of shrimp shell biochar powder used in step (2) of the suspended three-dimensional biochar composite material (A4) is 2g, and the calcination temperature in step (3) is 200℃.

[0064] The suspended three-dimensional biochar composite material prepared in Example 4 is designated as A4.

[0065] In this embodiment, the suspended three-dimensional biochar composite material (A5) used is basically the same as the suspended three-dimensional biochar composite material (A1), except that the mass ratio of biochar to polyvinyl alcohol in the suspended three-dimensional biochar composite material (A5) is 2:1.

[0066] In this embodiment, the preparation method of the suspended three-dimensional biochar composite material (A5) is basically the same as that of the suspended three-dimensional biochar composite material (A1), except that the amount of biochar used in step (2) of the suspended three-dimensional biochar composite material (A5) is 2g, and it is not calcined at 300℃, that is, step (3) is omitted.

[0067] In this embodiment, the suspended three-dimensional biochar composite material (A6) used is basically the same as the suspended three-dimensional biochar composite material (A1), except that the suspended three-dimensional biochar composite material (A6) is not calcined at 300°C, i.e. step (3) is omitted.

[0068] In this embodiment, the suspended three-dimensional biochar composite material (A7) used is basically the same as the suspended three-dimensional biochar composite material (A1), except that the mass ratio of biochar to polyvinyl alcohol in the suspended three-dimensional biochar composite material (A7) is 1.5:1.

[0069] In this embodiment, the preparation method of the suspended three-dimensional biochar composite material (A7) is basically the same as that of the suspended three-dimensional biochar composite material (A1), except that the mass of biochar in step (2) of the suspended three-dimensional biochar composite material (A7) is 1.5g.

[0070] Figure 1 This is a scanning electron microscope (SEM) image of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention. From...Figure 1 It can be seen that the suspended three-dimensional biochar composite material maintains a porous, three-dimensional structure, with porous biochar encapsulated by polyvinyl alcohol and loaded onto a melamine sponge skeleton.

[0071] Figure 2 This is the energy dispersive spectroscopy (EDS) spectrum of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention. From... Figure 2 It can be seen that the suspended three-dimensional biochar composite material (A1) mainly contains C, N and O elements, among which the nitrogen content is significantly increased and higher than the oxygen content, which indicates that the biochar was successfully loaded onto the melamine sponge carrier skeleton.

[0072] Figure 3 This is a nitrogen adsorption-desorption curve of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention. Figure 3 It can be seen that the nitrogen adsorption capacity of the suspended three-dimensional biochar composite material is lower than that of shrimp shell biochar, and the nitrogen adsorption capacity of the material increases significantly after activation. This is because thermal activation reduces the blockage of the pore structure by polyvinyl alcohol and increases its pore structure.

[0073] Figure 4 This is a pore size distribution diagram of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention. From... Figure 4 It can be seen that the pore sizes of the suspended three-dimensional biochar composite materials A1 and A6 of the present invention are similar to those of shrimp shell biochar, but A1 has fewer micropores, while A6 is between A1 and shrimp shell biochar. This is consistent with the results of the nitrogen adsorption-desorption diagram.

[0074] Five mL samples were taken at 0 min and 30 min during the adsorption reaction, and at 10 min, 40 min, 100 min, 220 min, and 340 min during the oxidative degradation reaction. The samples were centrifuged to achieve solid-liquid separation. The supernatant was discarded, and 95% ethanol was added. The samples were then allowed to stand in the dark for 24 h. The chlorophyll concentration change was measured using a UV-Vis spectrophotometer to obtain the chlorophyll degradation efficiency of different materials on *Microcystis aeruginosa*. The results are shown below. Figure 5 As shown.

[0075] Figure 5 This is a graph showing the chlorophyll degradation efficiency of different suspended 3D biochar composite materials (A1, A2, A3, A4, A5, A7) in Example 1 of the present invention. From... Figure 5It can be seen from the adsorption effect in the first 30 minutes that the chlorophyll removal rate of powdered shrimp shell biochar reached 76.7%, indicating that powdered biochar has a significant adsorption effect. In contrast, the three-dimensional biochar composite material (A5) prepared in Comparative Example 1 had the worst adsorption effect, with a chlorophyll removal rate of only 4.6%. Moreover, after catalytic oxidation reaction for 340 minutes, the chlorophyll concentration decreased to 40.1%, indicating that the chlorophyll removal effect of the unactivated A5 was poor. In this invention, when the activation temperature is 200℃, the chlorophyll A removal efficiency of the suspended three-dimensional biochar composite material (A4) for Microcystis aeruginosa increases from 4.6% to 34.0% in the first 30 minutes of adsorption, and reaches 77.7% after adding sodium persulfate for 340 minutes; when the activation temperature increases from 200℃ to 300℃, the chlorophyll A removal efficiency of the suspended three-dimensional biochar composite material (A3) for Microcystis aeruginosa increases to 27.4% in the first 30 minutes of adsorption, and reaches 98.0% after adding PDS for 220 minutes; when the activation temperature further increases to 400℃, the chlorophyll A removal efficiency of the suspended three-dimensional biochar composite material (A2) for Microcystis aeruginosa decreases to 5.0% in the first 30 minutes of adsorption, and reaches 92.5% after adding sodium persulfate for 340 minutes. Therefore, the chlorophyll removal efficiency of suspended three-dimensional biochar composites (A2, A3, A4, A5) prepared at different temperatures varies considerably. The chlorophyll removal efficiency initially increases and then decreases with increasing activation temperature. This is because as the activation temperature rises, the porosity of the biochar in the composite increases, and more active sites are exposed. However, further increases in activation temperature lead to biochar shedding. Thus, the catalytic degradation effect of the composite material significantly increases after activation, indicating that the activated suspended three-dimensional biochar composite material can significantly improve its algae removal efficiency. In summary, temperatures between 200℃ and 400℃ are favorable for obtaining suspended three-dimensional biochar composites with excellent catalytic performance. In particular, the suspended three-dimensional biochar composite material (A3) with an activation temperature of 300℃ exhibits superior catalytic performance and a stable composite structure, significantly improving the chlorophyll removal efficiency.

[0076] To obtain more stable suspended three-dimensional biochar composites, further studies were conducted on the removal effects of different proportions of suspended three-dimensional biochar composites (A1, A3, A7) on chlorophyll A. Figure 5It can be seen that the suspended three-dimensional biochar composite material (A1) of Example 1 of the present invention has good catalytic effect and stable mechanical properties. The chlorophyll removal rate was 4% in the first 30 minutes, 89.1% after 100 minutes of reaction with PDS, and 100% after 340 minutes of reaction with PDS. This indicates that A1 not only has stable mechanical properties but also excellent catalytic effect. When the ratio of biochar to polyvinyl alcohol increases, the adsorption effect of the suspended three-dimensional biochar composite material on *Microcystis aeruginosa* gradually improves. This is because more biochar provides more active sites, promoting the adsorption and removal of *Microcystis aeruginosa* in the first 30 minutes and further improving the catalytic degradation efficiency of chlorophyll. In this invention, when the mass ratio of biochar to polyvinyl alcohol increased from 1:1 to 1.5:1, the chlorophyll A removal efficiency of the suspended three-dimensional biochar composite material for Microcystis aeruginosa (A7) increased from 4% to 13.8% in the first 30 minutes of adsorption. After adding PDS for 100 minutes, the chlorophyll removal rate was 89.3%. When the mass ratio of biochar to polyvinyl alcohol increased from 1:1 to 2:1, the chlorophyll A removal efficiency of the suspended three-dimensional biochar composite material (A3) for Microcystis aeruginosa further increased to 27.4% in the first 30 minutes of adsorption. After adding PDS for 100 minutes, the chlorophyll concentration was 5.3% (at which point the chlorophyll removal rate was 94.7%). After reacting with PDS for 340 minutes, the chlorophyll removal rate was 100%. This indicates that increasing the proportion of biochar is more beneficial for chlorophyll removal. It can be seen that different suspended three-dimensional biochar composite materials (A1, A3, A7) can effectively remove Microcystis aeruginosa from water, indicating that the suspended three-dimensional biochar composite material of the present invention has excellent catalytic performance.

[0077] In summary, the suspended three-dimensional biochar composite material of the present invention not only has stable mechanical properties but also excellent catalytic properties, and can effectively remove Microcystis aeruginosa from wastewater.

[0078] Example 2

[0079] A method for removing algae using suspended three-dimensional biochar composite material to activate sodium persulfate, specifically involving the activation of sodium persulfate by suspended three-dimensional biochar composite material to remove algae from water, comprising the following steps:

[0080] Five portions (two pieces per portion) of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention were obtained, with each pair weighing 0.840 g. These were then added to 80 mL of a Microcystis aeruginosa solution (concentration 3.7*10⁻⁶) with an absorbance of 0.200. 6The microcystis aeruginosa algae solution was prepared by adding different masses of sodium persulfate to the solution, resulting in initial concentrations of sodium persulfate of 0.5 mM, 0.75 mM, 1 mM, 1.25 mM, and 1.5 mM, respectively. The oxidation reaction was carried out at 25 °C and 150 r / min for 250 minutes. After the reaction was completed, the suspended three-dimensional biochar composite material was directly recovered, thus completing the process of inactivating microcystis aeruginosa.

[0081] During the reaction, 5 mL samples were taken at specific time points (0 min, 10 min, 40 min, 70 min, 130 min, and 250 min). The samples were centrifuged to achieve solid-liquid separation. The supernatant was discarded, and 95% ethanol was added. The mixture was then allowed to stand in the dark for 24 h. The chlorophyll concentration change was measured using a UV-Vis spectrophotometer to obtain the chlorophyll degradation efficiency of the suspended three-dimensional biochar composite material on *Microcystis aeruginosa* under different sodium persulfate dosages. The results are as follows: Figure 6 As shown.

[0082] Figure 6 This image shows the inactivation effect of the suspended three-dimensional biochar composite material (A1) on Microcystis aeruginosa under different sodium persulfate dosages in Example 2 of this invention. Figure 6 It can be seen that PS concentrations within the range of 0.5mM to 1.5mM exhibit efficient chlorophyll degradation, with a sodium persulfate concentration of 1mM showing the best effect. As the sodium persulfate concentration increases from 0.5mM to 1mM, the chlorophyll degradation effect gradually increases, indicating that increasing the amount of sodium persulfate promotes the generation of more reactive oxygen species. However, as the sodium persulfate concentration continues to increase, the chlorophyll degradation effect decreases, but a relatively high degradation rate is still maintained. This is because the increased amount of oxidant generates more reactive oxygen species, but the sulfate anions can produce a self-quenching effect with free radicals, reducing the inactivation effect. Therefore, considering both improved efficiency and cost savings, a sodium persulfate concentration of 1mM yields the best chlorophyll degradation effect.

[0083] Example 3

[0084] A method for removing algae using suspended three-dimensional biochar composite material to activate sodium persulfate, specifically involving the activation of sodium persulfate by suspended three-dimensional biochar composite material to remove algae from water, comprising the following steps:

[0085] Five portions (two pieces per portion) of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention were obtained, with each pair weighing 0.840 g. They were added to 80 mL of Microcystis aeruginosa solution with pH values ​​of 5, 6, 7, 8, and 9 and absorbance of 0.200, respectively. Then, 0.01924 g of sodium persulfate (1 mM) was added, and the oxidation reaction was carried out at 25 °C and 150 r / min for 250 minutes. After the reaction was completed, the suspended three-dimensional biochar composite material was directly recovered, thus completing the process of inactivating Microcystis aeruginosa.

[0086] During the reaction, 5 mL samples were taken at specific time points (0, 10 min, 40 min, 70 min, 130 min, and 250 min). The samples were centrifuged to achieve solid-liquid separation. The supernatant was discarded, and 95% ethanol was added. The mixture was then allowed to stand in the dark for 24 h. The chlorophyll concentration change was measured using a UV-Vis spectrophotometer to obtain the chlorophyll degradation efficiency of the suspended three-dimensional biochar composite material on *Microcystis aeruginosa* under different pH conditions. The results are as follows: Figure 7 As shown.

[0087] Figure 7 This image shows the degradation effect of the suspended three-dimensional biochar composite material (A1) on chlorophyll under different pH conditions in Example 3 of this invention. Figure 7 It can be seen that the suspended three-dimensional biochar composite material (A1) exhibits significant chlorophyll degradation within a pH range of 5-9, indicating its effectiveness over a wide pH range, which is of great significance for practical applications. The chlorophyll degradation effect is best under neutral conditions, possibly because H+ is higher under acidic conditions. + Biochar reacts with free radicals, and at higher pH levels, the negatively charged surface of biochar may increase the repulsive force with algal cells, reducing the chlorophyll degradation effect. Therefore, the composite material of this invention exhibits significant chlorophyll degradation within a pH range of 5-9, demonstrating broad applicability.

[0088] Example 4

[0089] A method for removing algae using suspended three-dimensional biochar composite material to activate sodium persulfate, specifically involving the activation of sodium persulfate by suspended three-dimensional biochar composite material to remove algae from water, comprising the following steps:

[0090] Two portions (two pieces per portion) of the suspended three-dimensional biochar composite material (A1) prepared in Example 1 of this invention were obtained, with each pair weighing 0.840 g. They were added to 80 mL of Xiangjiang River water and Taozi Lake water containing Microcystis aeruginosa, respectively, with an absorbance of 0.200. Then, 0.01924 g of sodium persulfate (5 mM) was added, and the oxidation reaction was carried out at 25 °C and 150 r / min for 370 minutes. After the reaction was completed, the suspended three-dimensional biochar composite material was directly recovered, thus completing the process of inactivating Microcystis aeruginosa.

[0091] During the reaction, 5 mL samples were taken at specific time points (0, 10 min, 40 min, 70 min, 130 min, 250 min, and 370 min). The samples were centrifuged to achieve solid-liquid separation. The supernatant was discarded, and 95% ethanol was added. The mixture was then allowed to stand in the dark for 24 h. The chlorophyll concentration change was measured using a UV-Vis spectrophotometer to obtain the chlorophyll degradation efficiency of the suspended three-dimensional biochar composite material on *Microcystis aeruginosa* in different water bodies. The results are as follows: Figure 8 As shown.

[0092] Figure 8 This image shows the removal effect of the suspended three-dimensional biochar composite material (A1) on algae in different water bodies in Example 4 of this invention. Figure 8 It can be seen that when using the suspended three-dimensional biochar composite material (A1) to remove algae from different water bodies, the chlorophyll removal efficiency in Xiangjiang River and Taozi Lake reached 85.5% and 88.9% (370 min) respectively when the sodium persulfate concentration was 5 mM. This is because the actual water bodies contain a large number of impurities that consume the reactive oxygen species in the water. Therefore, it can be seen that the suspended three-dimensional biochar composite material (A1) of this invention has wide applicability and is suitable for removing chlorophyll from various water bodies, with great potential for practical application.

[0093] In summary, the suspended three-dimensional biochar composite material of this invention has advantages such as high stability, high catalytic efficiency, good recyclability, low cost, and environmental friendliness. It is a novel Fenton-like material with excellent catalytic performance. When this suspended three-dimensional biochar composite material is used as a catalyst to activate persulfate, it can be suspended in water, thus enabling better contact with persulfate and rapid generation of highly active reactive oxygen species. These reactive oxygen species attack algal cells, thereby degrading intracellular organic matter and effectively inactivating algae. It features simple process, convenient operation, low cost, high treatment efficiency, wide application range, high reusability, green environmental protection, and clean and pollution-free operation. It is a widely applicable and efficient method for removing algae, with high application and commercial value. It can be widely used to remove pollutants in the environment (such as Microcystis aeruginosa), which is of great significance for expanding the application range of biochar.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for activating persulfate to remove algae using a suspended three-dimensional biochar composite material, characterized in that, The method uses a suspended three-dimensional biochar composite material as a catalyst to activate persulfate for algae degradation, including the following treatment: mixing the suspended three-dimensional biochar composite material with algae-containing water, adding persulfate for oxidation reaction, and completing the removal of algae from the water; the suspended three-dimensional biochar composite material includes melamine foam and biochar, wherein the biochar is coated and loaded onto the melamine foam with an adhesive; the preparation method of the suspended three-dimensional biochar composite material includes the following steps: S1. The biochar and the binder solution are mixed and stirred to obtain a biochar dispersion; the mass ratio of biochar to binder is 0.25 to 4:1; the binder is at least one of polyvinyl alcohol, polyvinylidene fluoride, polyvinylpyrrolidone, polydopamine, and octadecylamine. S2. Melamine foam is immersed in biochar dispersion, ultrasonically dispersed, and dried to obtain melamine foam loaded with biochar; the mass ratio of melamine foam to biochar is 9:5 to 40. S3. Calcining melamine foam loaded with biochar to obtain a suspended three-dimensional biochar composite material; the calcination is carried out under an inert atmosphere; the inert atmosphere is nitrogen; the heating rate during the calcination process is 5 ℃ / min~12 ℃ / min; the calcination temperature is 200 ℃~400 ℃; the calcination time is 1 h~4 h.

2. The method according to claim 1, characterized in that, The biochar is shrimp shell biochar powder and / or sludge biochar powder; the mesh size of the biochar is 80-100 mesh; the specific surface area of ​​the suspended three-dimensional biochar composite material is 90 m². 2 / g~270 m 2 / g.

3. The method according to claim 2, characterized in that, In step S1, the biochar is further processed before use as follows: the biochar is ground and passed through a sieve with a mesh size of 80-100 mesh to obtain biochar powder; the adhesive solution is prepared by the following method: the adhesive is mixed with water and stirred for 2-4 hours at a temperature of 80℃-95℃ and a rotation speed of 300 r / min-500 r / min to obtain the adhesive solution. In step S2, the melamine foam is further treated as follows before use: the melamine foam is washed alternately with water and ethanol, 3 to 5 times each, and then dried at 60 ℃ for 1 to 3 hours.

4. The method according to claim 3, characterized in that, In step S1, the stirring speed is 300 r / min to 500 r / min; the stirring time is 20 min to 60 min. In step S2, the ultrasonic dispersion time is 20 min to 60 min; the drying temperature is 60℃ to 80℃; and the drying time is 6 h to 12 h.

5. The method according to any one of claims 1 to 4, characterized in that, The mass-to-volume ratio of the suspended three-dimensional biochar composite material to algae-containing water is 0.8g~0.9g∶80mL.

6. The method according to claim 5, characterized in that, The algae in the algae-containing water body is Microcystis aeruginosa; the absorbance of the algae-containing water body is 0.100–0.400; and the pH value of the algae-containing water body is 5–9.

7. The method according to claim 6, characterized in that, In the oxidation reaction system, the initial concentration of persulfate is controlled to be 0.5 mM to 5 mM; the persulfate is sodium persulfate.

8. The method according to claim 7, characterized in that, The oxidation reaction is carried out at a rotation speed of 100 r / min to 300 r / min; the oxidation reaction temperature is 10 ℃ to 35 ℃; and the oxidation reaction time is 50 min to 380 min.

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