A recyclable water treatment agent based on polyaluminum chloride and its preparation method

Abstract

The present invention relates to a recyclable water treatment agent based on polyaluminum chloride and a preparation method thereof, belonging to the technical field of sewage treatment. The recyclable water treatment agent uses hollow and porous magnetic iron oxide as a carrier, and uses di-n-butylamine and 3-chloropropyltrimethoxysilane to replace and make a surface treatment agent, which is loaded onto the surface of the carrier through a coupling effect. Utilize the tertiary amine structure in the surface treatment agent molecule to coordinate with aluminum chloride, and in-situ form polyaluminum chloride on the surface under alkaline heat reflux conditions. During the polymerization process, a quaternary ammonium structure is formed by bromoethanol and tertiary amine. The hollow and porous carrier enables it to have good suspension and dispersion ability in sewage. The surface quaternary ammonium structure and polyaluminum chloride form a charge neutralization-flocculation dual mechanism to achieve efficient and deep purification. At the same time, it can be quickly separated and recovered through an external magnetic field to achieve the efficient recovery of polyaluminum chloride.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a recyclable water treatment agent based on polyaluminum chloride and a preparation method thereof. Background Art

[0002] As a traditional inorganic polymer flocculant, polyaluminum chloride (PAC) is widely used due to its low cost and wide applicability. However, it has problems such as slow sedimentation rate, difficulty in recycling, and easy residue.

[0003] In recent years, magnetic water treatment agents have become a research hotspot due to their characteristics of being quickly separated and recycled through an external magnetic field. In the prior art, PAC is often loaded on the surface of a magnetic carrier (such as magnetite) to improve its recyclability. However, such technologies still have the following problems: traditional magnetic carriers are mostly solid or dense structures, resulting in poor suspension of the material in sewage, limited contact area with pollutants, and affecting the flocculation efficiency; the manufacturing cost of ultra-fine carriers (such as nanomaterials) is relatively high, and the recovery and separation are difficult; PAC and the magnetic carrier are mostly combined through physical adsorption, and are easily detached due to hydraulic scouring or pH value changes, resulting in a decline in the performance of repeated use; which seriously restricts the development of recyclable water treatment agents. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background art, the purpose of the present invention is to provide a recyclable water treatment agent based on polyaluminum chloride and a preparation method thereof.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of a recyclable water treatment agent based on polyaluminum chloride specifically includes the following steps:

[0007] Step S1: Premix dibutylamine, 3-chloropropyltrimethoxysilane and anhydrous toluene under a dry atmosphere, add potassium hydroxide and mix, heat to 80 - 100 °C and stir for reaction for 1.6 - 2.2 h, filter after cooling, and then distill off toluene under reduced pressure to obtain a surface treatment agent;

[0008] Step S2: Premix the surface treatment agent and an ethanol aqueous solution, adjust the pH value to 4 with acetic acid and stir for hydrolysis for 1 - 1.5 h, add a magnetic carrier and disperse it by ultrasonic wave, stir for coupling for 12 h, filter and wash the filter cake to obtain a modified carrier;

[0009] Step S3: Mix aluminum chloride hexahydrate, bromoethanol and methanol, add the modified carrier and stir for dispersion, heat to 60 - 70 °C for reflux, slowly add an aqueous sodium hydroxide solution and stir for reaction for 6 - 8 h, cool, filter and dry to obtain a recyclable water treatment agent.

[0010] In the above step S1, the feeding ratio of di-n-butylamine, 3-chloropropyltrimethoxysilane, potassium hydroxide and anhydrous toluene is 0.1 mol: 0.1 mol: 2.5 - 4 g: 70 - 100 mL. The substitution reaction of 3-chloropropyltrimethoxysilane and di-n-butylamine forms a tertiary amine compound.

[0011] In the above step S2, the feeding ratio of the magnetic carrier, the surface treatment agent and the ethanol aqueous solution is 50 g: 3.6 - 4.8 g: 130 - 180 mL. The volume fraction of the ethanol aqueous solution is 30 - 40%. The surface treatment agent hydrolyzes in the acidic ethanol aqueous solution and then is coupled and loaded with the magnetic carrier.

[0012] In the above step S3, the feeding ratio of the modified carrier, aluminum chloride hexahydrate, sodium hydroxide, bromoethanol and methanol is 10 g: 8.5 - 10.2 g: 2.6 - 3.3 g: 20 - 25 mL: 150 - 200 mL. The mass fraction of the sodium hydroxide aqueous solution is 8 - 10%. The tertiary amine organic structure grafted on the surface of the modified carrier forms a coordination interaction with aluminum chloride, enriching aluminum chloride near the surface of the modified carrier. Under the condition of thermal reflux, sodium hydroxide promotes the in-situ polymerization and loading of aluminum chloride on the surface of the modified carrier. At the same time, it promotes the quaternization of the tertiary amine structure by bromoethanol, forming quaternary positive charges on the surface of the composite structure.

[0013] The magnetic carrier is prepared by the following steps:

[0014] Step A1: Dissolve ferric chloride hexahydrate, ferrous sulfate heptahydrate and polyvinylpyrrolidone in deionized water, add polystyrene microspheres and stir to disperse. Adjust the pH value of the dispersion to 10 with ammonia water. Increase the pressure of the reaction system to 2 - 3 bar, raise the temperature to 120 - 130 °C and react for 4.5 - 6 h. After cooling, filter. Bake and dry the filter cake at 200 °C to obtain a composite precursor.

[0015] Step A2: Immerse the composite precursor in dichloromethane, stir for 24 h, dissolve and remove the polystyrene microspheres, filter and dry to obtain the magnetic carrier.

[0016] In the above step A1, the feeding ratio of ferric chloride hexahydrate, ferrous sulfate heptahydrate, polystyrene microspheres, polyvinylpyrrolidone and deionized water is 0.2 mol: 0.1 mmol: 4.5 - 5.8 g: 5 - 7 g: 350 - 400 mL. Under hydrothermal conditions, ferric chloride hexahydrate and ferrous sulfate heptahydrate form magnetite particles adsorbed on the surface of the polystyrene microspheres.

[0017] In the above step A1, the average particle size of the polystyrene microspheres is 15 - 30 μm. The polystyrene microspheres with this particle size are used as templates, and the prepared magnetic carrier maintains a high specific surface area and is conducive to magnetic recovery.

[0018] The beneficial effects of the present invention:

[0019] The recyclable water treatment agent of the present invention uses hollow and porous magnetic iron tetroxide as a carrier, and is made into a surface treatment agent by substituting di-n-butylamine and 3-chloropropyltrimethoxysilane. It is loaded onto the surface of the carrier through a coupling effect. Utilize the tertiary amine structure in the surface treatment agent molecule to coordinate with aluminum chloride. Under the condition of alkaline heat reflux, polyaluminum chloride is formed in situ on the surface. And during the polymerization process, a quaternary ammonium structure is formed by bromoethanol and tertiary amine. Compared with the existing magnetic-loaded polyaluminum chloride water treatment agent, the hollow and porous carrier has good suspension and dispersion ability in sewage, fully contacts with the sewage, and is beneficial to flocculation and impurity removal; the surface quaternary ammonium structure increases the initial surface positive charge density, quickly neutralizes the negatively charged particles in the sewage, breaks the colloidal stability, and forms a charge neutralization-flocculation dual mechanism with polyaluminum chloride, shortens the floc formation time, improves the purification speed, and increases the purification depth; in addition, the coordination effect of the surface treatment agent enables polyaluminum chloride to be effectively anchored to the carrier. Coupled with its hollow and large-particle-size structure, it can be quickly separated and recovered by an external magnetic field, realizing the efficient recovery of polyaluminum chloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0021] Figure 1 It is a graph showing the change of turbidity over time during the sewage treatment process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0023] Example 1, Preparation of a recyclable water treatment agent based on polyaluminum chloride, the specific implementation process is as follows:

[0024] (1) Preparation of the magnetic carrier

[0025] Step A1: Dissolve ferric chloride hexahydrate, ferrous sulfate heptahydrate and polyvinylpyrrolidone in deionized water. Add polystyrene microspheres and disperse them by high-speed stirring at 600 rpm. Add industrial ammonia water to adjust the pH value of the dispersion to 10. Introduce compressed air to increase the pressure to 3 bar and heat to 130 °C for reaction for 4.5 h. Among them, the feeding ratio of ferric chloride hexahydrate, ferrous sulfate heptahydrate, polystyrene microspheres, polyvinylpyrrolidone and deionized water is 0.2 mol: 0.1 mmol: 5.8 g: 7 g: 400 mL. The polystyrene microspheres are of the PS030000 type raw material with an average particle size of 30 μm. After cooling, filter, and bake the filter cake at 200 °C for 3 h to obtain a composite precursor.

[0026] Step A2: Immerse the composite precursor in dichloromethane and stir at 60 rpm for 24 h. Filter and dry to obtain a magnetic support.

[0027] (2) Preparation of recyclable water treatment agent

[0028] Step S1: Premix dibutylamine, 3-chloropropyltrimethoxysilane and anhydrous toluene in a dry atmosphere. Add potassium hydroxide and mix. Heat to 100 °C and stir for reaction for 1.6 h. Among them, the feeding ratio of dibutylamine, 3-chloropropyltrimethoxysilane, potassium hydroxide and anhydrous toluene is 0.1 mol: 0.1 mol: 4 g: 100 mL. After cooling, filter, and then distill off toluene under reduced pressure to obtain a surface treatment agent.

[0029] Step S2: Prepare an ethanol aqueous solution with a volume fraction of 30%. Premix the surface treatment agent and the ethanol aqueous solution, adjust the pH value to 4 with acetic acid and stir for hydrolysis for 1 h. Add the magnetic support and disperse it by ultrasonic wave, and then stir for coupling for 12 h. Among them, the feeding ratio of the magnetic support, the surface treatment agent and the ethanol aqueous solution is 50 g: 3.6 g: 180 mL. Finally, filter and wash the filter cake to obtain a modified support.

[0030] Step S3: Mix aluminum chloride hexahydrate, bromoethanol and methanol. Add the modified support and disperse it by stirring. Heat to 70 °C for reflux, and slowly add a 10% sodium hydroxide aqueous solution and stir for reaction for 6 h. Among them, the feeding ratio of the modified support, aluminum chloride hexahydrate, sodium hydroxide, bromoethanol and methanol is 10 g: 8.5 g: 3.3 g: 25 mL: 200 mL. Cool, filter and dry to obtain a recyclable water treatment agent.

[0031] Example 2, preparation of a recyclable water treatment agent based on polyaluminum chloride, the specific implementation process is as follows:

[0032] (1) Preparation of magnetic support

[0033] Step A1: Dissolve ferric chloride hexahydrate, ferrous sulfate heptahydrate, and polyvinylpyrrolidone in deionized water. Add polystyrene microspheres and disperse them by high-speed stirring at 600 rpm. Add industrial ammonia water to adjust the pH value of the dispersion to 10. Increase the pressure to 2.5 bar by introducing compressed air and heat to 130 °C for reaction for 5 h. Among them, the feeding ratio of ferric chloride hexahydrate, ferrous sulfate heptahydrate, polystyrene microspheres, polyvinylpyrrolidone, and deionized water is 0.2 mol: 0.1 mmol: 5.5 g: 7 g: 400 mL. The polystyrene microspheres are of the PS030000 type raw material with an average particle size of 30 μm. After cooling, filter, and bake the filter cake at 200 °C for 3 h to obtain a composite precursor.

[0034] Step A2: Immerse the composite precursor in dichloromethane and stir at 60 rpm for 24 h. Filter and dry to obtain a magnetic support.

[0035] (2) Preparation of recyclable water treatment agent

[0036] Step S1: Premix dibutylamine, 3-chloropropyltrimethoxysilane, and anhydrous toluene in a dry atmosphere. Add potassium hydroxide and mix. Heat to 100 °C and stir for reaction for 1.8 h. Among them, the feeding ratio of dibutylamine, 3-chloropropyltrimethoxysilane, potassium hydroxide, and anhydrous toluene is 0.1 mol: 0.1 mol: 3.5 g: 100 mL. After cooling, filter, and then remove toluene by vacuum distillation to obtain a surface treatment agent.

[0037] Step S2: Prepare an ethanol aqueous solution with a volume fraction of 30%. Premix the surface treatment agent and the ethanol aqueous solution, adjust the pH value to 4 with acetic acid and stir for hydrolysis for 1.2 h. Add the magnetic support and disperse it by ultrasonic wave, and then stir for coupling for 12 h. Among them, the feeding ratio of the magnetic support, the surface treatment agent, and the ethanol aqueous solution is 50 g: 3.9 g: 180 mL. Finally, filter and wash the filter cake to obtain a modified support.

[0038] Step S3: Mix aluminum chloride hexahydrate, bromoethanol, and methanol. Add the modified support and disperse it. Heat to 70 °C for reflux, and slowly add a 10% sodium hydroxide aqueous solution and stir for reaction for 6.3 h. Among them, the feeding ratio of the modified support, aluminum chloride hexahydrate, sodium hydroxide, bromoethanol, and methanol is 10 g: 9 g: 3.3 g: 25 mL: 200 mL. Cool, filter, and dry to obtain a recyclable water treatment agent.

[0039] Example 3, preparation of a recyclable water treatment agent based on polyaluminum chloride, the specific implementation process is as follows:

[0040] (1) Preparation of magnetic support

[0041] Step A1: Dissolve ferric chloride hexahydrate, ferrous sulfate heptahydrate, and polyvinylpyrrolidone in deionized water. Add polystyrene microspheres and disperse them by high-speed stirring at 600 rpm. Add industrial ammonia water to adjust the pH value of the dispersion to 10. Increase the pressure to 2 bar by introducing compressed air and raise the temperature to 120 °C for reaction for 6 h. Among them, the feeding ratio of ferric chloride hexahydrate, ferrous sulfate heptahydrate, polystyrene microspheres, polyvinylpyrrolidone, and deionized water is 0.2 mol: 0.1 mmol: 4.5 g: 5 g: 350 mL. The polystyrene microspheres are of the PS015000 type raw material with an average particle size of 15 μm. After cooling, filter, and bake the filter cake at 200 °C for 3 h to obtain a composite precursor.

[0042] Step A2: Immerse the composite precursor in dichloromethane and stir at 60 rpm for 24 h. Filter and dry to obtain a magnetic carrier.

[0043] (2) Preparation of recyclable water treatment agent

[0044] Step S1: Premix dibutylamine, 3-chloropropyltrimethoxysilane, and anhydrous toluene in a dry atmosphere. Add potassium hydroxide and mix. Heat to 80 °C and stir for reaction for 2.2 h. Among them, the feeding ratio of dibutylamine, 3-chloropropyltrimethoxysilane, potassium hydroxide, and anhydrous toluene is 0.1 mol: 0.1 mol: 2.5 g: 70 mL. After cooling, filter, and then remove toluene by vacuum distillation to obtain a surface treatment agent.

[0045] Step S2: Prepare an ethanol aqueous solution with a volume fraction of 40%. Premix the surface treatment agent and the ethanol aqueous solution. Adjust the pH value to 4 with acetic acid and stir for hydrolysis for 1.5 h. Add the magnetic carrier and disperse it by ultrasonic wave, and then stir for coupling for 12 h. Among them, the feeding ratio of the magnetic carrier, the surface treatment agent, and the ethanol aqueous solution is 50 g: 4.8 g: 130 mL. Finally, filter and wash the filter cake to obtain a modified carrier.

[0046] Step S3: Mix aluminum chloride hexahydrate, bromoethanol, and methanol. Add the modified carrier and disperse it by stirring. Raise the temperature to 60 °C for reflux, and slowly add an 8% sodium hydroxide aqueous solution and stir for reaction for 8 h. Among them, the feeding ratio of the modified carrier, aluminum chloride hexahydrate, sodium hydroxide, bromoethanol, and methanol is 10 g: 10.2 g: 2.6 g: 20 mL: 150 mL. After cooling, filter and dry to obtain a recyclable water treatment agent.

[0047] Example 4, prepare a recyclable water treatment agent based on polyaluminum chloride. The specific implementation process is as follows:

[0048] (1) Preparation of magnetic carrier

[0049] Step A1: Dissolve ferric chloride hexahydrate, ferrous sulfate heptahydrate and polyvinylpyrrolidone in deionized water. Add polystyrene microspheres and disperse them by high-speed stirring at 600 rpm. Add industrial ammonia water to adjust the pH value of the dispersion to 10. Introduce compressed air to increase the pressure to 2.5 bar and heat up to 125 °C for reaction for 5.5 h. Among them, the feeding ratio of ferric chloride hexahydrate, ferrous sulfate heptahydrate, polystyrene microspheres, polyvinylpyrrolidone and deionized water is 0.2 mol: 0.1 mmol: 4.8 g: 6 g: 380 mL. The polystyrene microspheres are of the PS015000 type raw material with an average particle size of 15 μm. After cooling, filter, and bake the filter cake at 200 °C for 3 h to obtain a composite precursor.

[0050] Step A2: Immerse the composite precursor in dichloromethane and stir at 60 rpm for 24 h, filter and dry to obtain a magnetic carrier.

[0051] (2) Preparation of recyclable water treatment agent

[0052] Step S1: Premix dibutylamine, 3-chloropropyltrimethoxysilane and anhydrous toluene under a dry atmosphere, add potassium hydroxide and mix. Heat to 90 °C and stir for reaction for 1.8 h. Among them, the feeding ratio of dibutylamine, 3-chloropropyltrimethoxysilane, potassium hydroxide and anhydrous toluene is 0.1 mol: 0.1 mol: 3.2 g: 90 mL. After cooling, filter, and then remove toluene by vacuum distillation to obtain a surface treatment agent.

[0053] Step S2: Prepare an ethanol aqueous solution with a volume fraction of 40%. Premix the surface treatment agent and the ethanol aqueous solution, adjust the pH value to 4 with acetic acid and stir for hydrolysis for 1.3 h. Add the magnetic carrier and disperse it by ultrasonic wave, and then stir for coupling for 12 h. Among them, the feeding ratio of the magnetic carrier, the surface treatment agent and the ethanol aqueous solution is 50 g: 4.4 g: 160 mL. Finally, filter and wash the filter cake to obtain a modified carrier.

[0054] Step S3: Mix aluminum chloride hexahydrate, bromoethanol and methanol, add the modified carrier and stir for dispersion. Heat up to 65 °C for reflux, and slowly add an 8% sodium hydroxide aqueous solution and stir for reaction for 7.5 h. Among them, the feeding ratio of the modified carrier, aluminum chloride hexahydrate, sodium hydroxide, bromoethanol and methanol is 10 g: 9.8 g: 3 g: 25 mL: 180 mL. After cooling, filter and dry to obtain a recyclable water treatment agent.

[0055] Comparative example 1: Use the industrial grade polyaluminum chloride of Ningbo Shunfan Water Purifying Agent Co., Ltd.

[0056] Comparative example 2: Refer to the prior art and prepare a magnetic water treatment agent by the sol-gel method. Specifically:

[0057] Take nano-ferroferric oxide and disperse it ultrasonically in distilled water. Add sodium carboxymethylcellulose and stir to dissolve to prepare a dispersion. Then dissolve polyaluminum chloride in deionized water, heat it to 45 °C, stir at 300 rpm, and slowly add the dispersion and mix. After that, let it stand for 24 h. Among them, the feeding ratio of nano-ferroferric oxide, polyaluminum chloride, sodium carboxymethylcellulose, distilled water and deionized water is 10 g: 3.5 g: 1.8 g: 50 mL: 30 mL. Then remove the supernatant, dry the substrate, grind and crush it to obtain the magnetic water treatment agent of ferroferric oxide / polyaluminum chloride.

[0058] Take samples from the water treatment agent prepared as above and conduct sewage purification tests and water treatment agent recovery rate tests respectively. Specifically:

[0059] Sewage purification test: Select mining sewage as the purification object, set up a sedimentation platform with a diameter of 20 cm and a depth of 50 cm, add a water purification agent to the sewage according to the aluminum ion content of 15 mg / kg, stir for 10 min, and let it stand to detect the turbidity of the sewage. The specific turbidity changes are as Figure 1 shown;

[0060] Recovery rate test: After removing the supernatant from the sewage purified for 24 h, use an electromagnet with a magnetic field strength of 0.5 T to adsorb the bottom flocs repeatedly three times. Take the adsorbed flocs and dissolve them with nitric acid, detect the aluminum ion content, and calculate the recovery rate = amount of adsorbed aluminum ions / amount of added aluminum ions × 100%. The specific test results are shown in Table 1:

[0061] Table 1

[0062]

[0063] Combined with Figure 1 and the data in Table 1, it can be seen that the water treatment agent prepared in the example has a high degree of sewage purification, and the purification cycle is almost completed in 10 min, showing excellent and efficient water purification ability, and the magnetic adsorption recovery rate reaches more than 80%, realizing effective recovery.

[0064] In the description of the specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0065] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A preparation method of a recyclable water treatment agent based on polyaluminum chloride, characterized in that, It includes the following steps: Step S1: Premix dibutylamine, 3-chloropropyltrimethoxysilane and anhydrous toluene in a dry atmosphere, add potassium hydroxide and mix, heat to 80 - 100 °C and stir for reaction for 1.6 - 2.2 h to prepare a surface treatment agent; Step S2: Premix the surface treatment agent and an ethanol aqueous solution, adjust the pH value to 4 with acetic acid and stir for hydrolysis for 1 - 1.5 h, add a magnetic carrier and disperse it by ultrasonic wave, and stir for coupling for 12 h to prepare a modified carrier; Step S3: Mix aluminum chloride hexahydrate, bromoethanol and methanol, add the modified carrier and stir for dispersion, heat to 60 - 70 °C for reflux, slowly add an aqueous sodium hydroxide solution and stir for reaction for 6 - 8 h to prepare a recyclable water treatment agent.

2. The preparation method of a recyclable water treatment agent based on polyaluminum chloride according to claim 1, characterized in that, The feeding ratio of dibutylamine, 3-chloropropyltrimethoxysilane, potassium hydroxide and anhydrous toluene is 0.1 mol: 0.1 mol: 2.5 - 4 g: 70 - 100 mL.

3. The preparation method of a recyclable water treatment agent based on polyaluminum chloride according to claim 2, characterized in that, The feeding ratio of the magnetic carrier, the surface treatment agent and the ethanol aqueous solution is 50 g: 3.6 - 4.8 g: 130 - 180 mL, and the volume fraction of the ethanol aqueous solution is 30 - 40%.

4. The preparation method of a recyclable water treatment agent based on polyaluminum chloride according to claim 3, characterized in that, The feeding ratio of the modified carrier, aluminum chloride hexahydrate, sodium hydroxide, bromoethanol and methanol is 10 g: 8.5 - 10.2 g: 2.6 - 3.3 g: 20 - 25 mL: 150 - 200 mL.

5. The preparation method of a recyclable water treatment agent based on polyaluminum chloride according to claim 1, characterized in that, The magnetic carrier is prepared by the following steps: Step A1: Dissolve ferric chloride hexahydrate, ferrous sulfate heptahydrate and polyvinylpyrrolidone in deionized water, add polystyrene microspheres and stir for dispersion, adjust the pH value of the dispersion to 10 with ammonia water, pressurize the reaction system to 2 - 3 bar, heat to 120 - 130 °C and react for 4.5 - 6 h, filter after cooling, and bake the filter cake at 200 °C for drying to obtain a composite precursor; Step A2: Immerse the composite precursor in dichloromethane and stir for 24 h, filter and dry to obtain a magnetic carrier.

6. The preparation method of a recyclable water treatment agent based on polyaluminum chloride according to claim 5, characterized in that, The feeding ratio of ferric chloride hexahydrate, ferrous sulfate heptahydrate, polystyrene microspheres, polyvinylpyrrolidone and deionized water is 0.2 mol: 0.1 mmol: 4.5 - 5.8 g: 5 - 7 g: 350 - 400 mL.

7. The preparation method of a recyclable water treatment agent based on polyaluminum chloride according to claim 6, characterized in that, The average particle size of the polystyrene microspheres is 15 - 30 μm.

8. A recyclable water treatment agent based on polyaluminum chloride, characterized in that, Prepared by the method according to any one of claims 1 - 7.

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