Biodegradable floating algicide and preparation method thereof

Abstract

The invention discloses a biodegradable floating algicide which comprises agar, quaternary ammonium salt, L-lysine, a phosphorus removal agent and pigment. According to the algicide disclosed by the invention, quaternary ammonium salt and L-lysine are used as main algicide active components, and metal hydroxide or / and metal oxide are / is added as a phosphorus absorption component. The algicide is prepared through a mechanical foaming technology, is light and loose in texture, can expand after absorbing water, and permanently floats on the surface of a water body. Due to the characteristics, the algae removal efficiency is remarkably improved, so that the aim of efficiently removing algae is fulfilled.

Description

Technical Field

[0001] The invention relates to the technical field of algaecides, and in particular to a floating degradable algaecide. Background Art

[0002] Under the combined influence of human activities and global warming, cyanobacteria blooms have occurred frequently in recent years. Cyanobacteria blooms can cause blockages in water supply systems, odor in water bodies, fish deaths, and degradation of aquatic vegetation, destroying the stability of aquatic ecosystems and affecting their service functions. In addition, algal toxins released after the death of cyanobacterial cells have hepatotoxic, neurotoxic and carcinogenic hazards, posing a serious threat to drinking water safety. Therefore, adopting effective cyanobacteria control technology is the key to preventing and controlling cyanobacteria blooms.

[0003] In practical applications, the commonly used algae control technologies mainly include mechanical salvage, addition of chemical agents, and introduction of allelopathic aquatic plants to inhibit algae. Physical salvage can quickly remove a certain amount of cyanobacteria on the surface of the water body, but for water bodies that have formed algae blooms, this method is time-consuming, inefficient, and costly, and cannot achieve the purpose of long-term algae control. Subsequent algae water treatment still requires a lot of cost. Using allelopathic substances secreted by allelopathic aquatic plants to inhibit algae growth has the advantages of good effect, natural and easy-to-obtain materials, and not easy to cause secondary pollution. However, this technology takes a long time to treat, and the plants have high requirements for the growth environment. It is only suitable for small water bodies and is difficult to promote and apply. Compared with the above two technologies, the use of chemical algaecides to disinfect cyanobacteria has become a common technology for emergency treatment of cyanobacteria blooms because of its low cost, fast speed, and significant effect. However, after the chemical agent is directly added to the water body, it is easy to diffuse with the water flow and be quickly diluted, and the efficacy is short-lived; at the same time, excessive local concentration of the agent may also harm other aquatic organisms and cause ecological damage. Therefore, in order to improve the algae control efficiency and sustainability of chemical algaecides, the development of carrier algaecides has become an important approach.

[0004] The slow-release or controlled-release mechanism of carrier algaecides gradually releases algaecidal active substances into the water body, thereby improving the utilization efficiency of the active substances and prolonging the duration of their algaecidal effect, while effectively avoiding the problem of excessive concentration of active substances in local areas. Carriers of natural origin have good environmental compatibility and natural degradation capabilities, avoiding the recycling and treatment steps after use. Currently commonly used natural source carriers (such as chitosan, sodium alginate, biochar, vermiculite, diatomaceous earth, etc.) are mostly suspended in water and are prone to agglomeration and precipitation during actual use. Because cyanobacteria have a pseudo-cavity structure, in order to carry out photosynthesis, they usually float on the surface of the water body to grow and reproduce. Traditional carrier algaecides are difficult to effectively contact with them, resulting in a decrease in algaecidal efficiency. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and provide a floating degradable algaecide. The algaecide uses quaternary ammonium salt and L-lysine as the main algaecidal active ingredients, and adds metal hydroxide or metal oxide as a phosphorus absorbing component. The algaecide is prepared by mechanical foaming technology, has a light and loose texture, can expand after absorbing water, and floats on the surface of the water body for a long time. These characteristics significantly improve the algaecidal efficiency, thereby achieving the purpose of efficient algae removal.

[0006] To achieve the above object, the technical solution of the present invention is to design a biodegradable floating algaecide, which includes agar, quaternary ammonium salt, L-lysine, a phosphorus remover and a pigment.

[0007] Further, it comprises, by weight, 20-200 parts of agar, 1-10 parts of quaternary ammonium salt, 0.5-5 parts of L-lysine, 2-15 parts of phosphorus removal agent and 0-5 parts of pigment; In the algaecide, the weight proportion of the quaternary ammonium salt is greater than the weight proportion of L-lysine, and the weight ratio of the quaternary ammonium salt to the L-lysine is 2-7: 1. Specifically, the weight ratio of the quaternary ammonium salt to the L-lysine can be 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, and any value within the range of any two of the above values.

[0008] Preferably, by weight, it comprises 30-80 parts of agar, 3-8 parts of quaternary ammonium salt, 0.5-3 parts of L-lysine, 2-10 parts of phosphorus removal agent and 2-4 parts of pigment; In the algaecide, the weight proportion of the quaternary ammonium salt is greater than the weight proportion of L-lysine, and the weight ratio of the quaternary ammonium salt to the L-lysine is 4-6:1.

[0009] Preferably, by weight, it comprises 50 parts of agar, 5 parts of quaternary ammonium salt, 1 part of L-lysine, 6 parts of phosphorus remover and 3.5 parts of pigment.

[0010] Furthermore, the weight ratio of the quaternary ammonium salt to L-lysine is 5:1.

[0011] Furthermore, the quaternary ammonium salt is selected from one or more of dodecyldimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium bromide, didecyldimethylammonium bromide, and polydimethyldiallylammonium chloride.

[0012] Furthermore, the dephosphorization agent is at least one or more of metal hydroxides or metal oxides, and the dephosphorization agent includes one or more of zirconium oxide, aluminum oxide, manganese oxide, zirconium hydroxide, lanthanum hydroxide, iron hydroxide, and cerium hydroxide.

[0013] Furthermore, water is added to the agar and heated to melt it, and then quaternary ammonium salt, L-lysine and phosphorus remover are added, and pigment is added after stirring and mixing, and then stirred and foamed during cooling, and finally low-temperature drying is performed to obtain a lightweight flaky floating algaecide.

[0014] A method for preparing a biodegradable floating algaecide, the preparation steps of which are as follows: S1. Add agar to tap water and heat until the agar is completely melted; S2. Add quaternary ammonium salt, L-lysine and phosphorus removal agent, stir and mix, and then add pigment and mix; S3. During the cooling process of the mixture, stirring and foaming is performed to form a fluffy foam mixture; S4. After low-temperature drying, a lightweight flaky floating algaecide is obtained.

[0015] Furthermore, in step S1, the mass fraction of agar is 20-200 parts, and the mass fraction of water is 1000-10000 parts; In step S2, the mixed solution is stirred at 70-100° C. in a water bath to accelerate dissolution; In step S3, the stirring and foaming conditions are: stirring at a speed of 800-1200 rpm for 10-20 minutes; In step S4, the low-temperature drying condition is: drying at 60-80° C. for 12-24 hours.

[0016] A biodegradable floating algaecide can be applied to water bodies containing blooms of cyanobacteria.

[0017] A biodegradable floating algaecide is suitable for various water bodies containing water bloom blue algae such as lakes, reservoirs, rivers, ponds and aquaculture water bodies. The dosage of the algaecide is 0.01-0.50 g / L.

[0018] The design of this algaecide combines multiple biochemical action mechanisms of quaternary ammonium cationic surfactants, L-lysine and metal (hydroxide) oxides to achieve efficient and sustained algaecide effects through synergistic effects.

[0019] First, quaternary ammonium salt cationic surfactants, with their lower critical micelle concentration and excellent interfacial activity, show better wettability, solubilization, foaming and inactivation than traditional surfactants. This component can effectively reduce the surface tension between the solid-liquid-gas interface, thereby enhancing the interaction between the algaecide and the cyanobacterial cells, and further combine with the negatively charged groups of the cyanobacterial cells through electrical neutralization, destroying their outer colloid barrier, penetrating the cell wall and destroying the cell membrane structure, causing the leakage of cell contents and ultimately inducing cell death. L-lysine, as an anti-algae active ingredient, significantly reduces the activity of intracellular ATPase by inhibiting the absorption of calcium, magnesium and other ions by cyanobacterial cells, hindering the phosphate cycle pathway, blocking the cell ATP uptake pathway, and inhibiting the synthesis of new cell walls and related enzymatic reactions. This process directly affects the photosynthesis of cyanobacteria, causing a sharp drop in its photosynthetic efficiency, and ultimately leading to cell lysis and death. The deep interference of L-lysine with the physiological metabolic process of algae further accelerates the extinction of cyanobacteria and prevents their regeneration.

[0020] In addition, the addition of metal hydroxides and / or metal oxides to the algaecide plays an important adsorption role, especially the efficient capture of phosphate ions released when cyanobacteria cells decompose. Phosphorus is a key nutrient element for the growth and reproduction of cyanobacteria. Through the adsorption of metal hydroxides and / or metal oxides, phosphate in the water body is effectively removed, the nutrient supply chain of cyanobacteria is cut off, and its further reproduction is inhibited from the root. This not only improves the immediate effect of the algaecide, but also ensures the long-term control of cyanobacteria and effectively prevents secondary outbreaks. Through the synergistic effect of quaternary ammonium salts, L-lysine, metal hydroxides and / or metal oxides, the algaecide can quickly kill cyanobacterial cells in a short period of time, while blocking their regeneration pathways, and achieve long-term algae control effects by adsorbing key nutrients in the water body. This multifunctional design not only enhances the overall efficiency of algae control, but also has ecological safety and reduces chemical residues in the environment.

[0021] The present invention adopts agar as a carrier matrix. Agar is a natural polysaccharide extracted from seaweed and is composed of neutral agarose, acid agarose and acid galactose. In an aqueous solution, agar begins to dissolve above 90°C and begins to solidify when cooled to below 45°C. The gelation process of agar involves cross-linked self-assembly between agarose molecules, and a semi-flexible filled hydrogel with a three-dimensional porous structure can be formed through hydrogen bonding. In order to further improve the floating performance of the agar carrier, a mechanical foaming process is adopted to prepare the algaecide. The mixed solution of the algaecidal active component and agar is subjected to strong mechanical stirring during the cooling and heating process, so that air is drawn into the solution to form a uniform foam. In this process, the quaternary ammonium salt type cationic surfactant as the algaecidal active component, as a key foaming agent, interacts with gas and liquid through its hydrophilic and hydrophobic groups, forms a monomolecular film on the surface of the bubble, reduces the gas-liquid surface tension, ensures that the bubble is stable and stable during the solidification process, and prevents the foam structure from collapsing. The solidified agar carrier has a uniformly distributed porous foam structure, in which the algaecidal active components are uniformly embedded, and the metal hydroxide particles are firmly wrapped, effectively preventing them from falling off and losing during use, thereby improving the stability of the algaecide.

[0022] The advantages and beneficial effects of the present invention are: 1. The floating biodegradable algaecide has algaecidal active components including quaternary ammonium salt and L-lysine, which work synergistically through different chemical pathways. Quaternary ammonium salt destroys the algae cell membrane, while L-lysine interferes with the metabolic activities of the algae, thereby achieving a rapid and effective algaecidal effect. At the same time, the added metal (hydr) oxide has a high phosphate adsorption capacity, which can capture the phosphate released when the cyanobacteria cells decompose, block the nutrient supply of the cyanobacteria, inhibit the reproduction of cyanobacteria from the root, and effectively achieve long-term control.

[0023] 2. The floating biodegradable algaecide uses agar as a carrier, has good biodegradability, and can be gradually degraded in the natural environment to avoid long-term impact on the ecosystem. The algaecide absorbs water and swells, and can float on the water surface for a long time. It can cover a large area of ​​algae without additional floating devices, increase the contact area between the algaecide and algae cells, and thus improve the algaecide efficiency. This floating characteristic not only simplifies the application method, but also ensures that the algaecide is evenly distributed on the water surface, maximizing its algaecide effect.

[0024] 3. The floating biodegradable algaecide has a simple preparation process, easy-to-obtain raw materials and low cost. Since the amount of algaecidal active components used is small, it can effectively control algae while not causing significant toxic effects on other aquatic plants and animals in the water body, and has good ecological safety.

[0025] 4. The algaecide of the present invention has a rapid algae killing effect, is biodegradable, easy to use, and avoids the secondary pollution problem that may be caused by traditional chemical algaecides. It is suitable for the prevention and control of cyanobacteria in various types of water bodies (lakes, ponds, reservoirs, etc.) and is an efficient, safe and sustainable water purification material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a physical picture of the floating biodegradable algaecide.

[0027] Figure 2 An image of a floating biodegradable algaecide floating on the water surface.

[0028] Figure 3 The algaecidal effect of different doses of algaecides on Microcystis aeruginosa.

[0029] Figure 4 The algaecide effect of different dosages of algaecides on cyanobacteria in actual water bodies. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0031] The sources of raw materials used in the following examples are as follows: Agar was purchased from Kangbaisi Biotechnology Co., Ltd. Edible pigment (green) was purchased from Shanghai Dyestuff Research Institute Co., Ltd.; Other raw materials were of domestic analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd.

[0032] 1. Implementation Example 1 The raw material ratios of a biodegradable floating algaecide are as follows by weight: Tap water 2000 copies Agar 50 servings Dodecyl dimethyl benzyl ammonium chloride 5 servings L-Lysine 1 serving Zirconium Hydroxide 6 servings Pigment (green) 3.5 servings The preparation method comprises the following steps: S1. Add agar to tap water and heat until agar is completely melted; S2. Add quaternary ammonium salt, zirconium hydroxide and L-lysine, place the mixed solution in a water bath at 80°C, stir at 500 rpm, and then add pigment (green) and mix evenly; S3. During the cooling process of the mixed solution, the claw-type stirring head of the stirrer is placed below the liquid level of the mixed solution and stirred at 1200rpm to form a fluffy foam mixture; S4. Spread the foam mixture on the mold (size: 20cm 35cm2cm), dried at 65℃ for 15 h. Get a lightweight floating algaecide in flake form, cut into 0.5cm*0.5cm in size, and can be directly added into algae-containing water when in use.

[0033] (II) Comparative Example Comparative Example 1 A biodegradable floating algaecide, which is different from Example 1 in that the added amount of dodecyl dimethyl benzyl ammonium chloride is 6 parts, and the added amount of L-lysine is 0 parts.

[0034] Comparative Example 2 A biodegradable floating algaecide, which is different from Example 1 in that the amount of L-lysine added is 6 parts, and the amount of dodecyl dimethyl benzyl ammonium chloride added is 0 parts.

[0035] Comparative Example 3 A biodegradable floating algaecide, which is different from Example 1 in that L-lysine and dodecyl dimethyl benzyl ammonium chloride are not added, and the added amount of zirconium hydroxide is 12 parts.

[0036] Comparative Example 4 A biodegradable floating algaecide, which is different from Example 1 in that the added amount of dodecyl dimethyl benzyl ammonium chloride is 1 part and the added amount of L-lysine is 5 parts.

[0037] Comparative Example 5 A biodegradable floating algaecide, which is different from Example 1 in that the added amount of dodecyl dimethyl benzyl ammonium chloride is 3 parts and the added amount of L-lysine is 3 parts.

[0038] Comparative Example 6 A biodegradable floating algaecide, which is different from Example 1 in that the added amount of dodecyl dimethyl benzyl ammonium chloride is 4 parts and the added amount of L-lysine is 2 parts.

[0039] Comparative Example 7 A biodegradable floating algaecide, which differs from Example 1 in that the added amount of dodecyl dimethyl benzyl ammonium chloride is 21 / 4 parts, and the added amount of L-lysine is 3 / 4 parts.

[0040] Comparative Example 8 A biodegradable floating algaecide, which differs from Example 1 in that the added amount of dodecyl dimethyl benzyl ammonium chloride is 16 / 3 parts, and the added amount of L-lysine is 2 / 3 parts.

[0041] (III) Performance testing (1) Performance test 1 Microcystis aeruginosa was selected as the target algae species for inactivation. Microcystis aeruginosa was inoculated with BG11 culture medium in a sterile environment and cultured in a light incubator at a temperature of 25°C, a light-dark ratio of 12 h:12 h, a light intensity of 2000 Lux, and a relative humidity of 75%. The culture was continued until the logarithmic growth phase. Microcystis aeruginosa in the logarithmic growth phase was selected, and the initial algae density was 2*10 6 cells / mL, set up a blank control group and three experimental groups, the dosage of algaecide in the three experimental groups was 0.05, 0.1, and 0.2 g / L, and the control group and the experimental group were set up three times in parallel. Samples were taken at 0, 12, 24, 36, 48, 60, and 72 hours to measure the chlorophyll a concentration of the algae solution.

[0042] The chlorophyll a concentration of the algae solution was determined by the following method: After the algae solution is mixed evenly, it is filtered with a cellulose acetate filter (0.45 μm). After the filter membrane is cut into pieces, it is placed in a tissue grinder, and a small amount of magnesium carbonate powder and 2 mL of 90% acetone are added. After sufficient grinding, chlorophyll a is extracted, and the extract is fixed to 10 mL with 90% acetone. The above extract is centrifuged at 4000 rpm and the supernatant is taken. The 90% acetone solution is used as a blank control, and the absorbance A of the extract is measured at 750, 663, 645, and 630 nm, respectively.

[0043] Chlorophyll a concentration was calculated according to the following formula: Where, —chlorophyll a concentration, μg / L; A750, A663, A645, A630—absorbance values ​​of the extract at wavelengths of 750nm, 663nm, 645nm, and 630nm; V1—volume of the extract after constant volume, mL; V2—volume of filtrated solution, L; L—optical path of cuvette, cm.

[0044] After measuring chlorophyll a, the algaecide killing rate is calculated according to the following formula: Where, IR is the mortality rate of Microcystis aeruginosa, %; C0 is the concentration of chlorophyll a at time 0, μg / L; C t is the concentration of chlorophyll a after t hours, μg / L.

[0045] Figure 3The algaecide effect of the floating biodegradable algaecide provided in Example 1 of the present invention is shown. It can be seen from the figure that when the dosage of the algaecide is 0.05 g / L, most of the Microcystis aeruginosa die within 48 hours, and when the dosage of the algaecide reaches 0.1 g / L and 0.2 g / L, the mortality rate of Microcystis aeruginosa within 48 hours is close to 100%, while in the control group without adding the algaecide, there is no death of Microcystis aeruginosa.

[0046] (2) Performance Test 2 Microcystis aeruginosa was selected as the target algae species for inactivation, and the initial algae density was 2*10 6 cells / mL, the algaecides prepared in Example 1 and Comparative Examples 1-8 were added to the algae solution at 0.1 g / L. After 60 hours, the performance test results of the algaecides were as follows: sample Algaecide rate (%) Example 1 99.8 Comparative Example 1 72.1 Comparative Example 2 75.9 Comparative Example 3 38.8 Comparative Example 4 82.1 Comparative Example 5 91.7 Comparative Example 6 97.9 Comparative Example 7 96.4 Comparative Example 8 89.7 Combining Example 1 with Comparative Examples 1-8, it can be seen that the killing rates of Comparative Examples 1-8 on Microcystis aeruginosa are reduced.

[0047] In Comparative Example 1, the algaecide contains only quaternary ammonium salt as an active ingredient, and mainly relies on its physical destruction of the cell membrane and cell wall of cyanobacteria. Although quaternary ammonium salt can quickly kill cyanobacteria in the early stage, this physical destruction is relatively short-lived and depends on direct contact with cyanobacterial cells. Over time, cells that are not completely destroyed may gradually restore some functions through metabolic repair mechanisms, resulting in a weakened algaecidal effect. In addition, a single physical destruction cannot continuously inhibit the growth and reproduction of cyanobacteria, thereby reducing the inactivation efficiency over a long period of time.

[0048] In Comparative Example 2, the algaecide contains only L-lysine as an active ingredient, and no quaternary ammonium surfactant is added. L-lysine inhibits the growth of cyanobacteria by interfering with their metabolic activities, but this process is usually gradual, especially when external conditions allow cyanobacteria to regulate metabolism. Since the effect of L-lysine does not occur immediately, it takes a long time to significantly reduce the metabolic capacity of cyanobacteria. At the same time, cyanobacteria have strong physiological adaptability and may maintain short-term survival by slowing down growth, reducing photosynthesis or utilizing stored nutrients under metabolic interference. Therefore, although L-lysine can inhibit the metabolic function of cyanobacteria to a certain extent, the algaecidal effect is relatively slow within 60 hours, and the inactivation efficiency is reduced.

[0049] In addition, in combination with Example 1 and Comparative Examples 4-8, it can be seen that in the algaecide, when the weight proportion of the quaternary ammonium salt is greater than the weight proportion of L-lysine, and the weight ratio of the quaternary ammonium salt to L-lysine is 2-7:1, the algaecide has the best algaecide rate, especially when the weight ratio of the quaternary ammonium salt to L-lysine is 5:1, the effect is best.

[0050] Therefore, based on the synergistic effect of L-lysine and quaternary ammonium salt, the algaecide proposed by the present invention can destroy cyanobacteria from both physiological and structural aspects. Quaternary ammonium salt quickly destroys the cell wall and cell membrane of cyanobacteria, and L-lysine interferes with its metabolism and reproduction, forming a double inhibition, thereby significantly enhancing the algaecide effect and prolonging the sustained action time of the algaecide.

[0051] (3) Performance test 3 The preparation steps of the floating biodegradable algaecide are the same as those in Example 1.

[0052] The prepared algaecide was added to algae-containing water samples collected from lakes, and a blank control group and three experimental groups were set up. The algaecide dosages of the three experimental groups were 0.05, 0.1, and 0.2 g / L, respectively. Three parallels were set for both the control group and the experimental group. The chlorophyll a concentration of the algae solution was measured at 0, 12, 24, 36, 48, 60, and 72 hours.

[0053] Figure 4 The floating biodegradable algaecide provided by the embodiment of the present invention has an algaecidal effect on cyanobacteria in actual water bodies. It can be seen from the figure that when the dosage of the algaecide is 0.05 g / L, about 65% of the cyanobacteria die within 72 hours, and when the dosage of the algaecide reaches 0.1 g / L and 0.2 g / L, the mortality rate of Microcystis aeruginosa is close to 100% within 72 hours, while in the control group without adding the algaecide, the cyanobacteria did not die.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A biodegradable floating algaecide, characterized in that: It includes agar, quaternary ammonium salt, L-lysine, phosphorus remover and pigment.

2. The biodegradable floating algaecide according to claim 1, characterized in that: In parts by weight, it comprises 20-200 parts of agar, 1-10 parts of quaternary ammonium salt, 0.5-5 parts of L-lysine, 2-15 parts of phosphorus removal agent and 0-5 parts of pigment; In the algaecide, the weight proportion of the quaternary ammonium salt is greater than the weight proportion of L-lysine, and the weight ratio of the quaternary ammonium salt to the L-lysine is 2-7:

1.

3. The biodegradable floating algaecide according to claim 2, characterized in that: The weight ratio of the quaternary ammonium salt to L-lysine is 5:

1.

4. The biodegradable floating algaecide according to claim 2, characterized in that: The quaternary ammonium salt is selected from one or more of dodecyldimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium bromide, didecyldimethylammonium bromide and polydimethyldiallylammonium chloride.

5. The biodegradable floating algaecide according to claim 1, characterized in that: The dephosphorization agent is at least one or more of metal hydroxides and / or metal oxides, and the dephosphorization agent includes one or more of zirconium oxide, aluminum oxide, manganese oxide, zirconium hydroxide, lanthanum hydroxide, iron hydroxide, and cerium hydroxide.

6. The biodegradable floating algaecide according to claim 1, characterized in that: Water is added to agar and heated to melt it, and then quaternary ammonium salt, L-lysine and phosphorus remover are added, and pigment is added after stirring and mixing. Then, the mixture is stirred and foamed during cooling, and finally low-temperature drying is performed to obtain a lightweight flaky floating algaecide.

7. A method for preparing a biodegradable floating algaecide according to any one of claims 1 to 6, characterized in that: The preparation steps are as follows: S1. Add agar to tap water and heat until the agar is completely melted; S2. Add quaternary ammonium salt, L-lysine and phosphorus removal agent, stir and mix, and then add pigment and mix; S3. During the cooling process of the mixture, mechanical stirring and foaming are performed to form a fluffy foam mixture; S4. After low-temperature drying, a lightweight flaky floating algaecide is obtained.

8. The method for preparing a biodegradable floating algaecide according to claim 7, characterized in that: In step S1, the mass fraction of agar is 20-200 parts, and the mass fraction of water is 1000-10000 parts; In step S2, the mixed solution is stirred at 70-100° C. in a water bath to accelerate dissolution; In step S3, the stirring and foaming conditions are: stirring at a speed of 800-1200 rpm for 10-20 minutes; In step S4, the low-temperature drying condition is: drying at 60-80° C. for 12-24 hours.

9. A biodegradable floating algaecide as claimed in any one of claims 1 to 8, which can be applied to water bodies containing blue-green algae blooms.

10. A biodegradable floating algaecide as claimed in any one of claims 1 to 8, suitable for use in lakes, reservoirs, rivers, ponds and aquaculture water bodies containing aquatic blue algae, wherein the dosage of the algaecide is 0.01-0.50 g / L.

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