A polyaluminum chloride-based algaecide and its preparation method

Abstract

The invention discloses a polyaluminum chloride-based algaecide and a preparation method thereof. The polyaluminum chloride-based algaecide comprises the following raw materials: 10-15 parts of sodium bicarbonate, 15-20 parts of quaternized chitosan, 2-3 parts of basic sodium aluminum carbonate, 10-15 parts of polyaluminum chloride, 5-8 parts of hydrated calcium chloroaluminate, 30-40 parts of red algae biochar, and 40-50 parts of anhydrous ethanol. The polyaluminum chloride-based algaecide prepared by the invention has high algae removal efficiency, fast flocculation and sedimentation speed, is iron-free, has low residual aluminum content, and can achieve a phosphorus removal effect. Sodium bicarbonate generates carbon dioxide at the bottom of the water, which drives the quaternized chitosan to dissolve in the water and disperse with bubbles, thereby increasing the particle collision degree in the water body and eliminating the need for manual stirring. The quaternized chitosan can be adsorbed and combined with negatively charged algae such as cyanobacteria in the water body, precipitated from the water, and adsorbed with the polyaluminum chloride to form flocs, thereby achieving the purpose of algae removal.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and relates to the technical field of algaecides, and particularly relates to a polyaluminum chloride-based algaecide and a preparation method thereof. Background Art

[0002] The outbreak of harmful algal blooms is an important manifestation and the most direct consequence of eutrophication of water bodies. During this period, water microorganisms and algae will multiply rapidly and in large numbers, forming aggregates visible to the naked eye, which will directly lead to increased water turbidity, decreased dissolved oxygen content, and the extinction of large numbers of aquatic plants and animals, affecting the utilization of water resources.

[0003] Currently, the main methods used for algae removal include physical, chemical, biological, and flocculation. Flocculation is widely used for large-scale algae removal, offering a rapid, cost-effective, and effective treatment of waters experiencing severe cyanobacterial blooms. The principle of flocculation is to neutralize or alter the electron layer on the surface of the algae cells by using flocculants or by directly modifying the environmental conditions surrounding them, disrupting their stable double electron layer suspension system. This allows the algae to be adsorbed by the flocculant and form flocs.

[0004] Flocculants are water treatment agents that react with colloids or suspended particles in water to produce flocculent precipitation. They can be categorized by chemical composition into three main groups: organic, inorganic, and composite flocculants. Their primary mechanisms of action include double electron layer compression, charge neutralization, adsorption bridging, and net capture and sweeping. Polyaluminum chloride (PAC), primarily composed of aluminum oxide, is a cationic inorganic polymer flocculant with a polyhydroxyl, multinuclear complex. It can efficiently neutralize the negative charge on the surface of cyanobacteria, promoting cell aggregation. It has a high degree of charge neutralization and bridging effects on colloids and particulate matter in water, effectively promoting the flocculation and removal of cyanobacteria.

[0005] Patent CN106186231A discloses an algaecide coagulant, its preparation and algae removal method, which uses a compound of four components: quartz sand powder, aluminum chloride, polyaluminum chloride and polyaluminum ferric chloride, reducing the amount of coagulant used by 20% to 60%, significantly reducing water treatment costs and heavy metal pollution; however, the algaecide is simply a simple mixture of the four components. In actual application, the four components are dispersed with each other and have a low mutual coordination effect. In addition, manual stirring of the water body is required to achieve the flocculation and algae removal effect. The application scenarios are limited, the algae removal efficiency is low, and the algae removal agent contains iron ions, which makes the risk of residual iron ions in the treated water body too high, posing a potential risk to human health.

[0006] Therefore, there is no polyaluminum chloride-based algaecide that does not require manual assistance, has high algae removal efficiency, fast flocculation and sedimentation speed, and low aluminum residue to meet the algae removal needs in the corresponding fields. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems of the above-mentioned background technology and to provide a polyaluminum chloride-based algaecide and a preparation method thereof.

[0008] The present invention aims to solve the following technical problems:

[0009] 1. How to make the algaecide achieve high algae removal rate without manual assistance;

[0010] 2. How to use the ingredients of the algaecide itself to increase the flocculation speed of the algaecide, thereby reducing the substances in the algaecide that assist the algaecide in flocculation and precipitation;

[0011] 3. How to remove phosphorus while removing blue algae, and at the same time, reduce the residual aluminum content after algae removal.

[0012] The purpose of the present invention can be achieved through the following technical solutions:

[0013] A polyaluminum chloride-based algaecide, comprising the following raw materials: 10-15 parts of sodium bicarbonate, 15-20 parts of quaternized chitosan, 2-3 parts of basic sodium aluminum carbonate, 10-15 parts of polyaluminum chloride, 5-8 parts of hydrated calcium chloroaluminate, 30-40 parts of red algae biochar, and 40-50 parts of anhydrous ethanol;

[0014] The preparation method of polyaluminium chloride-based algaecide comprises the following steps:

[0015] The quaternized chitosan is added to anhydrous ethanol, stirred and dissolved, and then sodium bicarbonate is added. The anhydrous ethanol is heated while stirring to completely evaporate the anhydrous ethanol. The obtained solid is crushed and sieved to obtain chitosan-coated sodium bicarbonate.

[0016] Add polyaluminium chloride into water, stir and dissolve to obtain polyaluminium chloride solution, then add basic sodium aluminium carbonate and continue stirring. After basic sodium aluminium carbonate is completely dissolved, continue stirring for 30-50 minutes, then dry and crush to obtain high basicity polyaluminium chloride;

[0017] The chitosan-coated sodium bicarbonate, high-basicity aluminum chloride, hydrated calcium chloroaluminate and red algae biochar are uniformly mixed and granulated to obtain a polyaluminum chloride-based algaecide.

[0018] Furthermore, the preparation method of quaternized chitosan is:

[0019] Chitosan was dissolved in a 2% acetic acid aqueous solution, 1 mol / L NaOH solution was added dropwise, the pH value was adjusted to 9, the solution was allowed to settle, and then stirred at room temperature for 12 hours for alkalization; the precipitate was washed with distilled water until neutral, mixed with isopropyl alcohol, vigorously stirred at 50°C for 1 hour, and slowly heated to 75°C; 2,3-epoxypropyltrimethylammonium chloride was dissolved in isopropyl alcohol and added dropwise to the isopropyl alcohol solution, and the reaction was continued with stirring for 8 hours; the product was precipitated and washed with anhydrous ethanol, dried, and then ground to obtain quaternized chitosan.

[0020] Furthermore, the ratio of chitosan, 2% acetic acid solution, isopropyl alcohol, and 2,3-epoxypropyltrimethylammonium chloride is 1.5 g:75 mL:50 mL:3 g.

[0021] Further, the preparation method of basic sodium aluminum carbonate is:

[0022] Anhydrous sodium carbonate and aluminum chloride hexahydrate are mixed in a molar ratio of 1.8-2, surfactant OP is added in a ratio of 10 mL / mol, the mixture is ground for 50-60 minutes, and the mixture is placed at room temperature for 48-72 hours. After washing with distilled water and anhydrous ethanol, the mixture is dried at 100-110°C for 2.5-3 hours to obtain basic sodium aluminum carbonate.

[0023] Further, the preparation method of calcium chloroaluminate hydrate is:

[0024] The lime emulsion and polyaluminium chloride solution were stirred at room temperature at a molar ratio of Ca / Al of 2:1. After being stirred evenly, the mixture was allowed to stand for 24-36 hours, filtered, washed with deionized water, dried, and ground through a 100-mesh sieve to obtain hydrated calcium chloroaluminate.

[0025] Furthermore, the preparation method of red algae biochar is:

[0026] The red algae extract is dried after removing impurities, and after being completely dried, it is ground into powder, heated to 400-500° C. at a rate of 10° C. / min under flowing carbon dioxide gas, and then taken out and ground to obtain red algae biochar.

[0027] Beneficial effects of the present invention:

[0028] (1) The polyaluminum chloride-based algaecide prepared by the present invention has high algae removal efficiency, fast flocculation and sedimentation speed, fast algae removal speed, does not contain iron elements, has low residual aluminum content, and can achieve the effect of phosphorus removal at the same time; sodium bicarbonate generates carbon dioxide at the bottom of the water, driving the quaternized chitosan to dissolve in the water and disperse with the bubbles, increasing the particle collision degree in the water body, and no manual stirring is required; the quaternized chitosan can be adsorbed and combined with negatively charged algae such as cyanobacteria in the water body, and precipitated from the water, adsorbed with polyaluminum chloride, forming flocs, thereby achieving the purpose of algae removal;

[0029] (2) The present invention wraps quaternized chitosan on the surface of sodium bicarbonate, prolongs the time for sodium bicarbonate to release carbon dioxide in water, increases the time for carbon dioxide to move in water, thereby increasing the probability of chitosan contacting cyanobacteria and polyaluminum chloride in water, and improving the algae removal efficiency;

[0030] (3) The present invention increases the basicity of polyaluminium chloride by adding basic aluminium carbonate to polyaluminium chloride, thereby increasing the molecular polymerization degree, accelerating the precipitation speed, achieving a good precipitation effect and reducing the amount of residual aluminium. The present invention also adds hydrated calcium chloroaluminate, which dissolves in water and ionizes Ca 2+ , and Al(OH) 3， It not only enhances the adsorption of algae, but also helps flocculation and precipitation in water bodies, and can also adsorb heavy metal ions in water bodies; the ionized Ca 2+ It not only helps the electron transfer in the water and accelerates the adsorption, but also forms calcium carbonate precipitation with carbonate ions in the water. Calcium carbonate increases the collision between particles and provides condensation nuclei for suspended particles such as algae cells in the water, making it easier to form flocs and increasing the density of the flocs, thereby accelerating the sedimentation rate.

[0031] (4) The present invention increases the weight of the polyaluminum chloride-based algaecide by adding red algae biochar, accelerates the sedimentation rate of the polyaluminum chloride-based algaecide, and at the same time, the red algae biochar can also adsorb phosphorus in the water body and activate aluminum ions, so that the aluminum ions react with phosphate to form precipitation, thereby achieving the effect of removing phosphorus from the water body; red algae are rich in Ca 2+ It is also easy to combine with carbonate ions dissolved in water by carbon dioxide to form calcium carbonate precipitates, providing condensation nuclei for polyaluminum chloride, so that the flocs after adsorbing algae can be quickly precipitated, thereby improving the efficiency of algae removal. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1

[0034] A polyaluminum chloride-based algaecide is composed of the following raw materials, measured in parts by weight: 10 parts of sodium bicarbonate, 15 parts of quaternized chitosan, 2 parts of basic sodium aluminum carbonate, 10 parts of polyaluminum chloride, 5 parts of hydrated calcium chloroaluminate, 30 parts of red algae biochar, and 40 parts of anhydrous ethanol.

[0035] The preparation steps of polyaluminium chloride-based algaecide are:

[0036] The quaternized chitosan is added to anhydrous ethanol, stirred and dissolved, and then sodium bicarbonate is added. The anhydrous ethanol is heated while stirring to completely evaporate the anhydrous ethanol. The obtained solid is crushed and sieved to obtain chitosan-coated sodium bicarbonate.

[0037] Sodium bicarbonate can release carbon dioxide in water, which will partially dissolve and increase the H + The concentration of quaternized chitosan can be better dissolved in water. Under the action of carbon dioxide bubbles, quaternized chitosan can increase the collision degree with other particles in water, thereby improving the algae removal efficiency. The sodium bicarbonate wrapped by chitosan can delay the release of carbon dioxide by sodium bicarbonate, so that sodium bicarbonate will not start to release carbon dioxide until it sinks to the bottom of the water, thereby increasing the collision degree of particles in the water and improving the algae removal efficiency.

[0038] Add polyaluminium chloride into water, stir and dissolve to obtain polyaluminium chloride solution, then add basic sodium aluminium carbonate and continue stirring. After basic sodium aluminium carbonate is completely dissolved, continue stirring for 30 minutes, then dry and crush to obtain high basicity polyaluminium chloride;

[0039] Sodium aluminum carbonate can increase the basicity of polyaluminum chloride. Polyaluminum chloride with high basicity forms alum flowers quickly, has large alum flowers, and precipitates quickly. It also has low residual aluminum content, increases the molecular polymerization degree, and reduces the amount of algaecide added.

[0040] The chitosan-coated sodium bicarbonate, high-basicity aluminum chloride, hydrated calcium chloroaluminate and red algae biochar are uniformly mixed and granulated to obtain a polyaluminum chloride-based algaecide.

[0041] Red algae biochar not only has a large specific surface area and pore volume, can be used as an adsorbent to remove phosphorus in water, but also can activate aluminum ions, so that aluminum ions react with phosphate to form precipitation, thereby achieving the effect of removing phosphorus in water. In addition, red algae are rich in Ca 2+ It is also easy to combine with carbonate ions dissolved in water by carbon dioxide to form calcium carbonate precipitation, which provides condensation nuclei for polyaluminum chloride, allowing the flocs after adsorbing algae to precipitate quickly and improve the algae removal efficiency; red algae biochar can also increase the weight of polyaluminum chloride-based algaecide, allowing it to quickly reach the bottom of the water body;

[0042] The preparation method of basic sodium aluminum carbonate is as follows:

[0043] Anhydrous sodium carbonate and aluminum chloride hexahydrate were mixed at a molar ratio of 1.8, and surfactant OP was added at a ratio of 10 mL / mol. The mixture was ground for 50 min, allowed to stand at room temperature for 48 h, washed with distilled water and anhydrous ethanol, and dried at 100°C for 2.5 h to obtain basic sodium aluminum carbonate.

[0044] The preparation method of calcium chloroaluminate hydrate is:

[0045] The lime emulsion and polyaluminium chloride solution were stirred at room temperature in a ratio of Ca / Al of 2:1, stirred evenly and then allowed to stand for 24 hours, filtered, washed with deionized water, dried, and ground through a 100-mesh sieve to obtain hydrated calcium chloroaluminate;

[0046] Calcium chloroaluminate hydrate dissolves in water and releases Ca 2+ , and Al(OH) 3， It not only enhances the adsorption of algae, but also helps flocculation and precipitation in water bodies, and can also adsorb heavy metal ions in water bodies; the ionized Ca 2+ It not only helps the electron transfer in the water and accelerates the adsorption, but also forms calcium carbonate precipitation with carbonate ions in the water. Calcium carbonate increases the collision between particles and provides condensation nuclei for suspended particles such as algae cells in the water, making it easier to form flocs and increasing the density of flocs, thereby enhancing sedimentation performance and improving algae removal efficiency.

[0047] The preparation method of quaternized chitosan is as follows:

[0048] Chitosan was dissolved in a 2% aqueous acetic acid solution, and a 1 mol / L NaOH solution was added dropwise. The pH was adjusted to 9, and the mixture was allowed to settle. The mixture was then stirred at room temperature for 12 hours to alkalize. The precipitate was washed with distilled water until neutral, mixed with isopropyl alcohol, and vigorously stirred at 50°C for 1 hour before slowly heating to 75°C. 2,3-Epoxypropyltrimethylammonium chloride was dissolved in isopropyl alcohol and added dropwise to the isopropyl alcohol solution. The reaction was stirred continuously for 8 hours. The product was precipitated and washed with anhydrous ethanol, dried, and then ground to obtain quaternized chitosan.

[0049] The ratio of chitosan, 2% acetic acid solution, isopropyl alcohol, and 2,3-epoxypropyltrimethylammonium chloride is 1.5 g:75 mL:50 mL:3 g;

[0050] After modification, the amino groups in the chitosan molecule can be dissolved in water and carry a positive charge in water, which can adsorb negatively charged algae and neutralize the charge, allowing the chitosan to precipitate again in the water. The hydrophobic groups of chitosan are adsorbed on the surface of carbon dioxide bubbles under the action of hydrophobic force, increasing the collision probability between chitosan and polyaluminium chloride, causing the chitosan to actively adsorb, flocculate and precipitate with polyaluminium chloride.

[0051] The preparation method of red algae biochar is as follows:

[0052] The red algae extract is dried after removing impurities, and after being completely dried, is ground into powder, heated to 400°C at a rate of 10°C / min under flowing carbon dioxide gas, and then taken out and ground to obtain red algae biochar;

[0053] Example 2

[0054] A polyaluminum chloride-based algaecide is composed of the following raw materials, calculated by weight: 12 parts of sodium bicarbonate, 17 parts of quaternized chitosan, 2.5 parts of basic sodium aluminum carbonate, 102 parts of polyaluminum chloride, 6.5 parts of hydrated calcium chloroaluminate, 35 parts of red algae biochar, and 45 parts of anhydrous ethanol.

[0055] The preparation steps of polyaluminium chloride-based algaecide are:

[0056] The quaternized chitosan is added to anhydrous ethanol, stirred and dissolved, and then sodium bicarbonate is added. The anhydrous ethanol is heated while stirring to completely evaporate the anhydrous ethanol. The obtained solid is crushed and sieved to obtain chitosan-coated sodium bicarbonate.

[0057] Add polyaluminium chloride into water, stir and dissolve to obtain polyaluminium chloride solution, then add basic sodium aluminium carbonate and continue stirring. After basic sodium aluminium carbonate is completely dissolved, continue stirring for 40 minutes, then dry and crush to obtain high basicity polyaluminium chloride;

[0058] The chitosan-coated sodium bicarbonate, high-basicity aluminum chloride, hydrated calcium chloroaluminate and red algae biochar are uniformly mixed and granulated to obtain a polyaluminum chloride-based algaecide.

[0059] The preparation method of basic sodium aluminum carbonate is as follows:

[0060] Anhydrous sodium carbonate and aluminum chloride hexahydrate were mixed at a molar ratio of 1.9, and surfactant OP was added at a ratio of 10 mL / mol. The mixture was ground for 55 minutes, allowed to stand at room temperature for 60 hours, washed with distilled water and anhydrous ethanol, and dried at 105°C for 2.8 hours to obtain basic sodium aluminum carbonate.

[0061] The preparation method of calcium chloroaluminate hydrate is:

[0062] Lime emulsion and polyaluminium chloride solution were stirred at room temperature in a ratio of Ca / Al of 2:1, stirred evenly and then allowed to stand for 30 hours, filtered, washed with deionized water, dried, and ground through a 100-mesh sieve to obtain calcium chloroaluminate hydrate;

[0063] The preparation method of quaternized chitosan is as follows:

[0064] Chitosan was dissolved in a 2% aqueous acetic acid solution, and a 1 mol / L NaOH solution was added dropwise. The pH was adjusted to 9, and the mixture was allowed to settle. The mixture was then stirred at room temperature for 12 hours to alkalize. The precipitate was washed with distilled water until neutral, mixed with isopropyl alcohol, and vigorously stirred at 50°C for 1 hour before slowly heating to 75°C. 2,3-Epoxypropyltrimethylammonium chloride was dissolved in isopropyl alcohol and added dropwise to the isopropyl alcohol solution. The reaction was stirred continuously for 8 hours. The product was precipitated and washed with anhydrous ethanol, dried, and then ground to obtain quaternized chitosan.

[0065] The ratio of chitosan, 2% acetic acid solution, isopropyl alcohol, and 2,3-epoxypropyltrimethylammonium chloride is 1.5 g:75 mL:50 mL:3 g;

[0066] The preparation method of red algae biochar is as follows:

[0067] The red algae extract is dried after removing impurities, and after being completely dried, is ground into powder, heated to 450°C at a rate of 10°C / min under flowing carbon dioxide gas, and then taken out and ground to obtain red algae biochar;

[0068] Example 3

[0069] A polyaluminum chloride-based algaecide is composed of the following raw materials, measured in parts by weight: 15 parts of sodium bicarbonate, 20 parts of quaternized chitosan, 3 parts of basic sodium aluminum carbonate, 15 parts of polyaluminum chloride, 8 parts of hydrated calcium chloroaluminate, 40 parts of red algae biochar, and 50 parts of anhydrous ethanol.

[0070] The preparation steps of polyaluminium chloride-based algaecide are:

[0071] The quaternized chitosan is added to anhydrous ethanol, stirred and dissolved, and then sodium bicarbonate is added. The anhydrous ethanol is heated while stirring to completely evaporate the anhydrous ethanol. The obtained solid is crushed and sieved to obtain chitosan-coated sodium bicarbonate.

[0072] Add polyaluminium chloride into water, stir and dissolve to obtain polyaluminium chloride solution, then add basic sodium aluminium carbonate and continue stirring. After basic sodium aluminium carbonate is completely dissolved, continue stirring for 50 minutes, then dry and crush to obtain high basicity polyaluminium chloride;

[0073] The chitosan-coated sodium bicarbonate, high-basicity aluminum chloride, hydrated calcium chloroaluminate and red algae biochar are uniformly mixed and granulated to obtain a polyaluminum chloride-based algaecide.

[0074] The preparation method of basic sodium aluminum carbonate is as follows:

[0075] Anhydrous sodium carbonate and aluminum chloride hexahydrate were mixed in a molar ratio of 2, surfactant OP was added at a ratio of 10 mL / mol, ground for 60 min, left at room temperature for 72 h, washed with distilled water and anhydrous ethanol, and dried at 110 ° C for 3 h to obtain basic sodium aluminum carbonate;

[0076] The preparation method of calcium chloroaluminate hydrate is:

[0077] Lime emulsion and polyaluminium chloride solution were stirred at room temperature in a ratio of Ca / Al of 2:1, stirred evenly and then allowed to stand for 36 hours, filtered, washed with deionized water, dried, and ground through a 100-mesh sieve to obtain calcium chloroaluminate hydrate;

[0078] The preparation method of quaternized chitosan is as follows:

[0079] Chitosan was dissolved in a 2% aqueous acetic acid solution, and a 1 mol / L NaOH solution was added dropwise. The pH was adjusted to 9, and the mixture was allowed to settle. The mixture was then stirred at room temperature for 12 hours to alkalize. The precipitate was washed with distilled water until neutral, mixed with isopropyl alcohol, and vigorously stirred at 50°C for 1 hour before slowly heating to 75°C. 2,3-Epoxypropyltrimethylammonium chloride was dissolved in isopropyl alcohol and added dropwise to the isopropyl alcohol solution. The reaction was stirred continuously for 8 hours. The product was precipitated and washed with anhydrous ethanol, dried, and then ground to obtain quaternized chitosan.

[0080] The ratio of chitosan, 2% acetic acid solution, isopropyl alcohol, and 2,3-epoxypropyltrimethylammonium chloride is 1.5 g:75 mL:50 mL:3 g;

[0081] The preparation method of red algae biochar is as follows:

[0082] The red algae extract is dried after removing impurities, and after being completely dried, is ground into powder, heated to 500°C at a rate of 10°C / min under flowing carbon dioxide gas, and then taken out and ground to obtain red algae biochar;

[0083] The polyaluminum chloride-based algaecide prepared in Examples 1-3 was tested for algae removal rate and phosphorus removal rate. The test results are shown in Table 1 below. The detection method is as follows: 100 L of water containing algae to be treated was added with 50 g of the polyaluminum chloride-based algaecide in Examples 1-3, and the mixture was allowed to stand for 2 h and 24 h. The absorbance of the algae in the water was measured using a spectrophotometer at an absorption wavelength of 646 nm, with deionized water as a blank control sample and a cuvette size of 20 mm, thereby obtaining the algae removal rate; and the phosphorus concentration in the supernatant was measured using an inductively coupled plasma emission spectrometer to obtain the phosphorus removal rate.

[0084] Table 1

[0085] Example 1 Example 2 Example 3 2h algae removal rate / % 98.7 98.9 98.5 2h dephosphorization rate / % 75.4 76.8 77.3 24h algae removal rate / % 99.3 99.2 99.1 24h phosphorus removal rate / % 79.2 79.5 79.8

[0086] As can be seen from the data in Table 1, the polyaluminum chloride-based algaecide prepared by the present invention has an algae removal rate of more than 98% after 2 hours of algae removal, with a fast algae removal speed and good algae removal effect; the 2-hour phosphorus removal rate also reaches more than 75%, reducing the phosphorus content in the water body and greatly reducing the possibility of re-outbreak of algal blooms; the algae removal rate reaches more than 99% after 24 hours, and the phosphorus removal rate reaches more than 79%, with high algae removal efficiency and good phosphorus removal effect.

[0087] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A polyaluminium chloride-based algaecide, characterized in that: The raw materials are prepared from the following components in parts by weight: 10-15 parts of sodium bicarbonate, 15-20 parts of quaternized chitosan, 2-3 parts of basic sodium aluminum carbonate, 10-15 parts of polyaluminum chloride, 5-8 parts of hydrated calcium chloroaluminate, 30-40 parts of red algae biochar, and 40-50 parts of anhydrous ethanol; The polyaluminium chloride-based algaecide is prepared by the following steps: The quaternized chitosan is added to anhydrous ethanol, stirred and dissolved, and then sodium bicarbonate is added. The anhydrous ethanol is heated while stirring to completely evaporate the anhydrous ethanol. The obtained solid is crushed and sieved to obtain chitosan-coated sodium bicarbonate. Add polyaluminium chloride into water, stir and dissolve to obtain polyaluminium chloride solution, then add basic sodium aluminium carbonate and continue stirring. After basic sodium aluminium carbonate is completely dissolved, continue stirring for 30-50 minutes, then dry and crush to obtain high basicity polyaluminium chloride; The chitosan-coated sodium bicarbonate, high-basicity aluminum chloride, hydrated calcium chloroaluminate and red algae biochar are uniformly mixed and granulated to obtain a polyaluminum chloride-based algaecide.

2. A polyaluminum chloride-based algaecide according to claim 1, characterized in that: The preparation method of the quaternized chitosan is: Chitosan was dissolved in a 2% acetic acid aqueous solution, and a 1 mol / L NaOH solution was added dropwise to adjust the pH to 9 to precipitate it, which was then stirred and alkalized at room temperature for 12 hours. The precipitate was washed with distilled water until neutral, mixed with isopropanol, vigorously stirred at 50°C for 1 hour, and slowly heated to 75°C. 2,3-Epoxypropyltrimethylammonium chloride was dissolved in isopropanol and added dropwise to the isopropanol solution, and the reaction was continued with stirring for 8 hours. The product was precipitated and washed with anhydrous ethanol, dried, and then ground to obtain quaternized chitosan.

3. A polyaluminum chloride-based algaecide according to claim 2, characterized in that: The ratio of the chitosan, 2% acetic acid solution, isopropyl alcohol, and 2,3-epoxypropyltrimethylammonium chloride is 1.5 g:75 mL:50 mL:3 g.

4. A polyaluminum chloride-based algaecide according to claim 1, characterized in that: The preparation method of basic sodium aluminum carbonate is as follows: Anhydrous sodium carbonate and aluminum chloride hexahydrate are mixed in a molar ratio of 1.8-2, surfactant OP is added in a ratio of 10 mL / mol, the mixture is ground for 50-60 minutes, and the mixture is placed at room temperature for 48-72 hours. After washing with distilled water and anhydrous ethanol, the mixture is dried at 100-110° C. for 2.5-3 hours to obtain basic sodium aluminum carbonate.

5. A polyaluminum chloride-based algaecide according to claim 1, characterized in that: The preparation method of the hydrated calcium chloroaluminate is: The lime emulsion and polyaluminium chloride solution were stirred at room temperature in a molar ratio of Ca / Al of 2:

1. After being stirred evenly, they were allowed to stand for 24-36 hours, filtered, washed with deionized water, dried, and ground through a 100-mesh sieve to obtain hydrated calcium chloroaluminate.

6. A polyaluminum chloride-based algaecide according to claim 1, characterized in that: The preparation method of the red algae biochar is: The red algae extract is dried after removing impurities, and after being completely dried, it is ground into powder, heated to 400-500° C. at a rate of 10° C. / min under flowing carbon dioxide gas, and then taken out and ground to obtain red algae biochar.

7. A method for preparing a polyaluminum chloride-based algaecide, characterized in that: Prepared by the following steps: The quaternized chitosan is added to anhydrous ethanol, stirred and dissolved, and then sodium bicarbonate is added. The anhydrous ethanol is heated while stirring to completely evaporate the anhydrous ethanol. The obtained solid is crushed and sieved to obtain chitosan-coated sodium bicarbonate. Add polyaluminium chloride into water, stir and dissolve to obtain polyaluminium chloride solution, then add basic sodium aluminium carbonate and continue stirring. After basic sodium aluminium carbonate is completely dissolved, continue stirring for 30-50 minutes, then dry and crush to obtain high basicity polyaluminium chloride; The chitosan-coated sodium bicarbonate, high-basicity aluminum chloride, hydrated calcium chloroaluminate and red algae biochar are uniformly mixed and granulated to obtain a polyaluminum chloride-based algaecide.