Inorganic high molecular water purifying agent and its preparation method

Abstract

The application relates to the technical field of water purifying agents, and particularly discloses an inorganic high-molecular water purifying agent and a preparation method thereof. The inorganic high-molecular water purifying agent is prepared from the following raw materials in parts by weight: modified polyaluminum chloride 60-80 parts, polyaluminum ferric silicate 10-30 parts, lanthanum-cerium co-doped mesoporous carriers 10-20 parts, nano-hydroxyapatite 1-5 parts and magnesium-aluminum hydrotalcite 8-12 parts. The water purifying agent can be widely applied to scenes such as deep phosphorus removal of sewage and coagulation and purification of industrial wastewater. Compared with traditional polyaluminum chloride, the phosphorus removal efficiency of the water purifying agent is significantly improved, the mud yield per unit of phosphorus removal is greatly reduced, the floc is compact and easy to settle, and the water quality adaptability is strong.

Description

Technical Field

[0001] This application relates to the field of water purification agent technology, and more specifically, to an inorganic polymer water purification agent and its preparation method. Background Technology

[0002] In the field of water treatment and purification, coagulation and sedimentation processes, with their simple process flow, low treatment cost, and wide applicability, have always been the core treatment unit in drinking water purification, urban sewage treatment, and industrial wastewater treatment. The performance of water purification agents directly determines the treatment efficiency and operating cost of the coagulation process. Water purification agents can be divided into two main categories according to their molecular structure and mechanism of action: small-molecule coagulants and high-molecular-weight flocculants. Among them, inorganic high-molecular-weight water purification agents possess multiple mechanisms of action, including charge neutralization, adsorption bridging, and net-sweeping. Compared with traditional small-molecule aluminum and iron salt agents, they have significant advantages such as rapid floc formation, superior sedimentation performance, and a wide pH adaptability range, making them the mainstream products in the water treatment agent market. Polyaluminum chloride, as the largest-volume and most widely used representative category of inorganic high-molecular-weight water purification agents, has a wide range of raw material sources, mature production processes, and balanced comprehensive water purification performance. It is widely used in various water treatment scenarios such as turbidity removal, phosphorus removal, decolorization, and suspended solids removal.

[0003] In related technologies, such as the patent document with publication number CN118062968B, a polyaluminum chloride (PAC) water purification composite material and its preparation method are disclosed. This PAC water purification composite material is made from the following raw materials in parts by weight: 60-80 parts of inorganic polymeric coagulant, 20-40 parts of organic polymeric coagulant, and 5-20 parts of surface-loaded metal single-atom antibacterial and algaecidal synergist. The inorganic polymeric coagulant is PAC or PAC combined with at least one of polyaluminum sulfate, polytitanium aluminum chloride, or polyaluminum ferric chloride. The organic polymeric coagulant is at least one of activated silicic acid, polyepoxychloropropaneamine, cationic polyacrylamide, anionic polyacrylamide, sodium carboxymethyl cellulose, or polyvinylpyridine. The above technical solution, through the synergistic compounding of inorganic and organic polymers and the introduction of functional synergistic components, effectively improves the overall water purification effect of the agent, while also endowing the product with additional antibacterial and algaecidal functions, enriching the application scenarios of PAC water purification agents.

[0004] However, in the actual engineering application of deep phosphorus removal in urban wastewater, with the increasing standards for total phosphorus emissions, the industry has found that the use of polyaluminum chloride (PAC) water treatment agents still suffers from technical shortcomings in achieving both high-efficiency phosphorus removal and sludge reduction. On the one hand, PAC's phosphorus removal relies on the chemical reaction between aluminum ions and phosphate ions to form aluminum phosphate precipitates. To ensure that the total phosphorus in the effluent consistently meets the standards, excessive dosage of the agent is often required. The large amount of redundant aluminum salt hydrolyzes to form aluminum hydroxide precipitates, directly leading to a significant increase in sludge production and a substantial increase in sludge dewatering and end-of-pipe disposal costs. On the other hand, existing compound water treatment agents are mostly physical mixing systems, lacking synergistic effects of chemical bonding between components. The flocs generated by phosphorus removal have a loose structure and high water content, resulting in poor settling and dewatering performance, thus failing to achieve good phosphorus removal effects and failing to simultaneously meet the development needs of the water treatment industry for improving standards and efficiency while reducing costs and sludge. Summary of the Invention

[0005] In order to efficiently remove phosphorus while reducing sludge production, this application provides an inorganic polymer water purification agent and its preparation method.

[0006] This application provides an inorganic polymer water purification agent, which adopts the following technical solution: An inorganic polymer water purification agent comprises the following raw materials in parts by weight: Modified polyaluminum chloride 60-80 parts; 10-30 parts of polyaluminum iron silicate; 10-20 parts of lanthanum-cerium co-doped mesoporous support; 1-5 parts of nano-hydroxycalcium phosphate; 8-12 parts of magnesium aluminum hydrotalcite.

[0007] By adopting the above technical solution, firstly, modified polyaluminum chloride is the core functional component of this application. Unlike ordinary polyaluminum chloride, the modified polyaluminum chloride of this application introduces rare earth ions (lanthanum and cerium) during the alkalization reaction, allowing these rare earth ions to embed into Al through hydroxyl bridges. 13 In the terminal sites of polynuclear hydroxyl complexes. This structural feature brings about a profound change in the phosphorus removal mechanism: embedding Al 13 La of the skeleton 3+ and Ce 3+ Rare earth phosphates have a much stronger chemical affinity for phosphate ions than for aluminum ions, and their solubility is extremely low, allowing the phosphorus removal reaction to preferentially occur and proceed more thoroughly at rare earth sites. More importantly, this "functional zoning" strategy enables Al... 13 The aluminum sites in the species are partially freed from the phosphorus removal reaction, and can focus on performing the flocculation function of charge neutralization and adsorption bridging. This avoids the drawback of excessive addition of aluminum ions in traditional polyaluminum chloride, which leads to vacuolization and the generation of a large amount of aluminum hydroxide precipitate when aluminum ions simultaneously undertake the dual tasks of phosphorus removal and flocculation. This curbs the excessive generation of sludge from the chemical source.

[0008] Secondly, the lanthanum-cerium co-doped mesoporous support and nano-hydroxycalcium phosphate form a highly efficient "enrichment-crystallization" synergistic phosphorus removal system. The mesoporous support SBA-15 possesses a regular and ordered pore structure and a large specific surface area, enabling it to physically adsorb and electrostatically enrich low concentrations of phosphate in water. This "captures" and enriches scattered phosphate ions around the support pores, increasing the probability of collisions between rare earth ions and phosphate. Simultaneously, nano-hydroxycalcium phosphate acts as a seed inducing agent, providing a readily available heterogeneous nucleation interface for the rare earth phosphate precipitates generated during the phosphorus removal reaction. This guides their growth into highly crystalline, dense phosphate crystals, rather than loose, amorphous gel-like precipitates. This crystalline phosphorus removal product has high density and a compact structure, allowing for rapid separation during subsequent sedimentation. This not only improves phosphorus removal efficiency but also significantly reduces the water content and volume of the flocs.

[0009] Furthermore, polyaluminum ferric silicate and magnesium aluminum hydrotalcite contributed synergistic effects from two dimensions: floc structure optimization and assisted phosphorus removal, respectively. Polyaluminum ferric silicate, with its long-chain silicate framework, adsorbs, bridges, and sweeps away fine particles generated during phosphorus removal, while its rigid inorganic framework structure imparts higher floc density and shear resistance. Magnesium aluminum hydrotalcite, utilizing its interlayer anion exchange capacity, supplements the chemical removal of residual phosphate in the water, and its weak alkalinity buffers the system pH, creating a suitable chemical environment for the coagulation reaction. The five components are not simply a physical mixture, but rather form a synergistic system with complementary functions and mutually reinforcing structures through chemical bonding and electrostatic interactions between their respective active sites during water treatment. Ultimately, this achieves a significant reduction in sludge production while ensuring stable total phosphorus levels in the effluent.

[0010] Optionally, the modified polyaluminum chloride is prepared by the following method: First, calcium aluminate powder is added to the aluminum chloride solution to carry out an alkalization reaction. The reaction temperature is controlled at 60-90℃, and the reaction is stirred for 20-40 minutes. Then, rare earth salt solution is added, and the reaction is stirred for another 20-30 minutes. Then, calcium aluminate powder is added a second time, and the mixture is aged at 50-80℃ for 5-10 hours to obtain modified polyaluminum chloride sol. The modified polyaluminum chloride sol is then dried to obtain modified polyaluminum chloride.

[0011] By adopting the above technical solution, the first addition of calcium aluminate powder causes aluminum ions to undergo hydrolysis and polymerization to generate Al. 13 After the polynuclear hydroxy complex intermediate, a rare earth salt solution is added midway through the polymerization reaction and the reaction is stirred for a sufficient time to allow La to... 3+ and Ce 3+ In Al 13Before the species is fully formed, it competitively inserts itself into its terminal group site through hydroxyl bridging. Subsequently, a second addition of calcium aluminate powder further promotes the polymerization reaction towards completion, firmly "anchoring" rare earth ions to Al. 13 Within the framework, this in-situ chemical bonding method ensures the stable immobilization and uniform distribution of rare earth ions in polyaluminum chloride. Compared with simple physical mixing, the utilization efficiency and stability of rare earth active sites are greatly improved, guaranteeing the product's long-lasting and efficient phosphorus removal performance in actual water treatment.

[0012] Optionally, the mass concentration of the aluminum chloride solution is 8%-15%; the mass of the calcium aluminate powder added for the first time is 4%-8% of the mass of the aluminum chloride solution; and the mass of the calcium aluminate powder added for the second time is 6%-10% of the mass of the aluminum chloride solution.

[0013] Optionally, the rare earth salts in the rare earth salt solution include lanthanum nitrate and cerium nitrate, the mass concentration of the rare earth salt solution is 5%-15%, and the amount of rare earth salt solution added is 10%-20% of the mass of the aluminum chloride solution.

[0014] By employing the above technical solution, a mixed solution of lanthanum nitrate and cerium nitrate is used as a rare earth modifier, leveraging the synergistic effect of these two rare earth elements to achieve superior phosphorus removal performance. Lanthanum has the strongest known affinity for phosphate and is the primary element for deep phosphorus removal, while cerium, due to its variable valence state, can convert some organic phosphorus and polyphosphate forms into orthophosphates through oxidation during coagulation, expanding the substrate range for phosphorus removal and allowing lanthanum's phosphorus removal efficiency to be fully utilized. Lanthanum-cerium composite intercalation into Al 13 The multi-hydroxy complexes formed after the skeleton have better surface charge density and phosphate recognition ability than polyaluminum chloride modified with single rare earth elements.

[0015] Optionally, the lanthanum-cerium co-doped mesoporous support is prepared by the following method: Molecular sieve SBA-15 was mixed with aqueous solutions of lanthanum salt and cerium salt, and impregnated at 20-30℃ for 6-24h. After filtration and separation, the resulting solid was dried at 80-120℃ for 4-12h and then calcined at 500-700℃ for 2-6h to obtain a lanthanum-cerium co-doped mesoporous support.

[0016] By employing the above technical solution and using SBA-15 molecular sieve as the carrier for lanthanum-cerium composite oxides, its well-ordered mesoporous channel structure achieves high dispersion and stable loading of rare earth active components. During impregnation and calcination, lanthanum and cerium are anchored to the inner wall of the carrier channels in the form of composite oxide nanoparticles, effectively preventing the agglomeration and deactivation of rare earth components. This allows the carrier to continuously and stably release or expose active rare earth sites on its surface after being added to water. This integrated "slow-release-enrichment" carrier design significantly improves the atomic utilization rate of rare earth elements, resulting in a significant increase in phosphorus removal efficiency per unit mass of water purification agent. This reduces the total amount of reagent required to achieve the same phosphorus removal effect, indirectly reducing sludge production.

[0017] Optionally, the lanthanum salt aqueous solution is an aqueous solution of lanthanum chloride, and the cerium salt aqueous solution is an aqueous solution of cerium chloride.

[0018] Optionally, the mass concentration of the lanthanum salt aqueous solution is 3%-10%; the mass concentration of the cerium salt aqueous solution is 2%-6%; and the mass ratio of the molecular sieve SBA-15, the lanthanum salt aqueous solution, and the cerium salt aqueous solution is 1:(2-6):(1-4).

[0019] Optionally, the raw materials may also include 1-3 parts of cationic polyacrylamide.

[0020] By adopting the above technical solution, adding cationic polyacrylamide as an organic coagulant aid, its long-chain molecular structure can exert an adsorption and bridging effect on the fine flocs formed after the action of inorganic water purification agents, further linking the small-sized flocs into larger and denser flocs, thus accelerating the sedimentation and separation process.

[0021] Optionally, the average particle size of the magnesium-aluminum hydrotalcite is 10-100 μm.

[0022] This application also provides a method for preparing an inorganic polymer water purification agent, using the following technical solution: A method for preparing an inorganic polymer water purification agent includes the following steps: Modified polyaluminum chloride, polyaluminum iron silicate, lanthanum-cerium co-doped mesoporous carrier, nano-hydroxycalcium phosphate, magnesium aluminum hydrotalcite, and optional cationic polyacrylamide are mixed according to the stated weight proportions. Deionized water is added to adjust the solid content to 15%-30%. The mixture is stirred and homogenized at 35-60℃ for 1-3 hours at a stirring rate of 200-600 rpm. Then, it is spray-dried at an inlet air temperature of 180-250℃ and an outlet air temperature of 85-110℃ until the moisture content is ≤3%, thus obtaining the inorganic polymer water purification agent.

[0023] By employing the above technical solution, modified polyaluminum chloride sol is mixed and homogenized with other solid components under suitable solid content, temperature, and stirring conditions. This allows the components to fully contact and form a uniformly dispersed system in a liquid environment, followed by rapid dehydration and shaping via spray drying. During the mixing process, the silicate skeleton of polyaluminum silicate iron can partially chemically bond with the aluminum hydroxyl groups on the surface of modified polyaluminum chloride through hydroxyl condensation, forming interfacial bonds between components rather than loose stacking. This chemical bonding enhances the structural strength of the flocculants in the final product during use. The rapid dehydration characteristic of the spray drying process maximizes the preservation of the original chemical state of the active sites of each component, ensuring that the powder product can quickly restore its water purification activity upon reconstitution, achieving complete transfer of product performance and stable application effects.

[0024] In summary, this application has the following beneficial effects: 1. This application uses modified polyaluminum chloride as the core water purification component. During the alkalization synthesis of polyaluminum chloride, a mixed rare earth salt solution of lanthanum and cerium is introduced into the polymerization reaction, allowing rare earth ions to be chemically bonded into Al via hydroxyl bridges. 13 The terminal active sites of the polynuclear hydroxy complex backbone form rare earth-Al composite polynuclear hydroxy complexes, rather than simple physical mixing or surface adhesion. Therefore, rare earth ions are firmly anchored to Al. 13 The skeleton surface is uniformly distributed and will not easily detach or become inactive when applied in water. La embedded with the skeleton end bases 3+ and Ce 3+ Due to its much stronger chemical affinity for phosphate than for aluminum ions, in Al 13 The framework surface forms highly active phosphorus removal sites that preferentially capture phosphate ions, causing the phosphorus removal reaction to mainly occur at rare earth sites rather than at aluminum-consuming sites. 13 The aluminum sites in the species, originally used for flocculation, are partially freed from the task of phosphorus removal and can focus on the flocculation function of charge neutralization and adsorption bridging. This spatial separation and synergistic division of labor for phosphorus removal and flocculation on the same particle allows modified polyaluminum chloride to achieve deep phosphorus removal at a low dosage. This fundamentally avoids the problem of excessive addition of traditional polyaluminum chloride, which leads to the hydrolysis of large amounts of aluminum salts and the formation of aluminum hydroxide precipitates due to aluminum ions simultaneously undertaking the dual tasks of phosphorus removal and flocculation. Thus, while ensuring that the total phosphorus in the effluent consistently meets the standards, sludge production is significantly reduced from the chemical source.

[0025] 2. In this application, a lanthanum-cerium co-doped mesoporous support and nano-hydroxycalcium phosphate are preferably used to form a synergistic enrichment-crystallization system for phosphorus removal products. Polyaluminum iron silicate is also used to reinforce the flocculent structure. Because the mesoporous support SBA-15 has a regular and ordered pore structure and a large specific surface area, it can physically adsorb and electrostatically enrich low concentrations of phosphate in water, capturing and enriching phosphate ions scattered in the water around the support pores. This effectively increases the probability of collision between rare earth ion active sites and phosphate ions and the driving force of the phosphorus removal reaction. Simultaneously, nano-hydroxycalcium phosphate acts as a seed inducing agent to provide the rare earth phosphate precipitate generated during the phosphorus removal reaction. The readily available heterogeneous nucleation interface guides the phosphorus removal products to grow in a crystalline form rather than forming a loose, amorphous gel-like precipitate. This results in the phosphorus removal products having higher density and lower water content. Meanwhile, polyaluminum ferric silicate, with its long-chain silicate skeleton, plays an adsorption, bridging, and sweeping role on the fine crystalline particles generated by phosphorus removal, organizing them into dense flocs supported by a rigid silicate skeleton. This makes the floc structure dense, with strong shear resistance and significantly reduced water content. Therefore, more thorough solid-liquid separation can be achieved in the sedimentation and separation stage, greatly reducing the amount of solids entering the subsequent sludge dewatering system. The sludge dewatering performance and treatment efficiency are significantly improved.

[0026] 3. This application further improves the phosphorus removal-flocculation-sedimentation functional chain of the water purification agent by combining magnesium aluminum hydrotalcite with the optional component cationic polyacrylamide. Because magnesium aluminum hydrotalcite has the typical structural characteristics of layered bimetallic hydroxides, its interlayer anions can undergo anion exchange reactions with residual phosphate ions in the water. After the modified polyaluminum chloride and lanthanum-cerium co-doped mesoporous carrier complete the main phosphorus removal task, it provides supplementary chemical phosphorus removal assurance, ensuring that the total phosphorus in the effluent can stably meet the stringent discharge standards under various water quality fluctuation conditions. Meanwhile, its own weak alkalinity can act as a pH buffer during coagulation, creating a stable and suitable chemical environment for the coagulation reaction of various inorganic components. Cationic polyacrylamide, as an organic polymeric coagulant aid, has a long-chain molecular structure that can adsorb and bridge the fine flocs formed after the action of inorganic water purification agents, further linking small flocs into larger and denser flocs, accelerating the sedimentation and separation process. Furthermore, its positive charge characteristics are well-compatible with the positive charges carried by the inorganic components in the system, preventing premature flocculation or poor compatibility. The above-mentioned auxiliary components and the main phosphorus removal components form a complete synergistic system with complementary functions and time-matched steps, ensuring a tight and smooth connection between the phosphorus removal reaction, floc growth, and solid-liquid separation stages, jointly guaranteeing the simultaneous achievement of the dual goals of stable total phosphorus levels in the effluent and a significant reduction in sludge production. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments.

[0028] The raw materials used in the preparation examples, embodiments, and comparative examples of this application were all commercially available. The information of the main raw material manufacturers is as follows: Aluminum chloride was purchased from Zibo Yundi Chemical Co., Ltd., Shandong Province; calcium aluminate powder was purchased from Henan Huaxin New Materials Co., Ltd.; lanthanum nitrate, cerium nitrate, lanthanum chloride, and cerium chloride were all purchased from Shandong Desheng New Materials Co., Ltd.; molecular sieve SBA-15 was purchased from Hubei Zhonglong Kangsheng Fine Chemical Co., Ltd.; polyaluminum iron silicate was purchased from Henan Zhengyuan Chemical Co., Ltd.; nano-hydroxycalcium phosphate was purchased from Shandong Duoju Chemical Co., Ltd.; magnesium aluminum hydrotalcite was purchased from Shandong Daike Biotechnology Co., Ltd., with product number 11097-59-9.

[0029] Preparation example of modified polyaluminum chloride Preparation Example 1 Modified polyaluminum chloride was prepared by the following method: Take an 8% aluminum chloride solution and add 4% (by mass) of calcium aluminate powder to it for the first alkalization reaction. Control the reaction temperature at 60℃ and stir for 40 min. Then add 10% (by mass) of rare earth salt solution with a concentration of 5% (by mass) of aluminum chloride solution. The solutes in the rare earth salt solution include lanthanum nitrate and cerium nitrate. Continue stirring for 30 min. Then add 6% (by mass) of calcium aluminate powder to the aluminum chloride solution for the second time. Aging treatment is carried out at 50℃ for 10 h to obtain modified polyaluminum chloride sol. The modified polyaluminum chloride sol is dried to obtain modified polyaluminum chloride.

[0030] Preparation Example 2 Modified polyaluminum chloride was prepared by the following method: An 11% aluminum chloride solution was taken, and 6% (by mass) of calcium aluminate powder was added to it for the first alkalization reaction. The reaction temperature was controlled at 75℃, and the reaction was stirred for 30 minutes. Then, a 10% (by mass) rare earth salt solution was added, which contained lanthanum nitrate and cerium nitrate as solutes. The reaction was stirred for another 25 minutes. Then, 8% (by mass) of calcium aluminate powder was added for the second time. The mixture was aged at 65℃ for 7.5 hours to obtain modified polyaluminum chloride sol. The modified polyaluminum chloride sol was dried to obtain modified polyaluminum chloride.

[0031] Preparation Example 3 Modified polyaluminum chloride was prepared by the following method: Take an aluminum chloride solution with a mass concentration of 15%, and add calcium aluminate powder accounting for 8% of the mass of the aluminum chloride solution to it for the first alkalization reaction. Control the reaction temperature at 90℃ and stir for 20 min. Then add a rare earth salt solution accounting for 20% of the mass of the aluminum chloride solution with a mass concentration of 15%. The solutes in the rare earth salt solution include lanthanum nitrate and cerium nitrate. Continue stirring for 20 min. Then add calcium aluminate powder accounting for 10% of the mass of the aluminum chloride solution for the second time. Aging treatment is carried out at 80℃ for 5 h to obtain modified polyaluminum chloride sol. The modified polyaluminum chloride sol is dried to obtain modified polyaluminum chloride.

[0032] Preparation example of lanthanum-cerium co-doped mesoporous support Preparation Example 4 Lanthanum-cerium co-doped mesoporous supports were prepared using the following method: Molecular sieve SBA-15 was mixed with lanthanum salt aqueous solution and cerium salt aqueous solution at a mass ratio of 1:2:1. The lanthanum salt aqueous solution was a 3% lanthanum chloride aqueous solution and the cerium salt aqueous solution was a 2% cerium chloride aqueous solution. After impregnation at 20℃ for 24h, the mixture was filtered and separated. The resulting solid was dried at 80℃ for 12h and then calcined at 500℃ for 6h to obtain a lanthanum-cerium co-doped mesoporous support.

[0033] Preparation Example 5 Lanthanum-cerium co-doped mesoporous supports were prepared using the following method: Molecular sieve SBA-15 was mixed with lanthanum salt aqueous solution and cerium salt aqueous solution at a mass ratio of 1:4:2.5. The lanthanum salt aqueous solution was a 6% lanthanum chloride aqueous solution and the cerium salt aqueous solution was a 4% cerium chloride aqueous solution. After impregnation at 25°C for 15 h, the mixture was filtered and separated. The resulting solid was dried at 100°C for 8 h and then calcined at 600°C for 4 h to obtain a lanthanum-cerium co-doped mesoporous support.

[0034] Preparation Example 6 Lanthanum-cerium co-doped mesoporous supports were prepared using the following method: Molecular sieve SBA-15 was mixed with lanthanum salt aqueous solution and cerium salt aqueous solution at a mass ratio of 1:6:4. The lanthanum salt aqueous solution was a 10% lanthanum chloride aqueous solution and the cerium salt aqueous solution was a 6% cerium chloride aqueous solution. After impregnation at 30℃ for 6 hours, the mixture was filtered and separated. The resulting solid was dried at 120℃ for 4 hours and then calcined at 700℃ for 2 hours to obtain a lanthanum-cerium co-doped mesoporous support.

[0035] Example Example 1 An inorganic polymer water purification agent, the raw material components and formulations of which are shown in Table 1, wherein the modified polyaluminum chloride is the modified polyaluminum chloride prepared in Preparation Example 1, the lanthanum-cerium co-doped mesoporous support is the lanthanum-cerium co-doped mesoporous support prepared in Preparation Example 4, the magnesium aluminum hydrotalcite has an average particle size of 10 μm, and the nano-hydroxycalcium phosphate has an average particle size of 100 nm.

[0036] A method for preparing an inorganic polymer water purification agent includes the following steps: Modified polyaluminum chloride, polyaluminum iron silicate, lanthanum-cerium co-doped mesoporous carrier, nano-hydroxycalcium phosphate, and magnesium aluminum hydrotalcite were mixed by weight, and deionized water was added to adjust the solid content to 15%. The mixture was stirred and homogenized at 35°C for 1 hour at a stirring rate of 200 rpm. Then, it was spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 85°C until the moisture content was ≤3%, thus obtaining the inorganic polymer water purification agent.

[0037] Example 2 An inorganic polymer water purification agent, the raw material components and formulations of which are shown in Table 1, wherein the modified polyaluminum chloride is the modified polyaluminum chloride prepared in Preparation Example 2, the lanthanum-cerium co-doped mesoporous support is the lanthanum-cerium co-doped mesoporous support prepared in Preparation Example 5, the magnesium aluminum hydrotalcite has an average particle size of 50 μm, and the nano-hydroxycalcium phosphate has an average particle size of 100 nm.

[0038] A method for preparing an inorganic polymer water purification agent includes the following steps: Modified polyaluminum chloride, polyaluminum iron silicate, lanthanum-cerium co-doped mesoporous carrier, nano-hydroxycalcium phosphate, and magnesium aluminum hydrotalcite were mixed by weight, and deionized water was added to adjust the solid content to 22%. The mixture was stirred and homogenized at 50°C for 2 hours at a stirring rate of 400 rpm. Then, it was spray-dried at an inlet air temperature of 220°C and an outlet air temperature of 100°C until the moisture content was ≤3%, thus obtaining the inorganic polymer water purification agent.

[0039] Example 3 An inorganic polymer water purification agent, the raw material components and formulations of which are shown in Table 1, wherein the modified polyaluminum chloride is the modified polyaluminum chloride prepared in Preparation Example 3, the lanthanum-cerium co-doped mesoporous support is the lanthanum-cerium co-doped mesoporous support prepared in Preparation Example 6, the magnesium aluminum hydrotalcite has an average particle size of 100 μm, and the nano-hydroxycalcium phosphate has an average particle size of 100 nm.

[0040] A method for preparing an inorganic polymer water purification agent includes the following steps: Modified polyaluminum chloride, polyaluminum iron silicate, lanthanum-cerium co-doped mesoporous carrier, nano-hydroxycalcium phosphate, and magnesium aluminum hydrotalcite were mixed by weight, and deionized water was added to adjust the solid content to 30%. The mixture was stirred and homogenized at 60°C for 3 hours at a stirring rate of 600 rpm. Then, it was spray-dried at an inlet air temperature of 250°C and an outlet air temperature of 110°C until the moisture content was ≤3%, thus obtaining the inorganic polymer water purification agent.

[0041] Table 1. Raw material components and proportions (g) of the water purification agents in Examples 1-3

[0042] Example 4 An inorganic polymer water purification agent, which differs from Example 3 in that the modified polyaluminum chloride in this example is the modified polyaluminum chloride prepared in Preparation Example 2.

[0043] Example 5 An inorganic polymer water purification agent, which differs from Example 3 in that the lanthanum-cerium co-doped mesoporous carrier in this example is the lanthanum-cerium co-doped mesoporous carrier prepared in Preparation Example 5.

[0044] Example 6 An inorganic polymer water purification agent, which differs from Example 3 in that 1g of cationic polyacrylamide is added to the raw materials in this example.

[0045] Example 7 An inorganic polymer water purification agent, which differs from Example 3 in that 2g of cationic polyacrylamide is added to the raw materials in this example.

[0046] Example 8 An inorganic polymer water purification agent, which differs from Example 3 in that 3g of cationic polyacrylamide is added to the raw materials in this example.

[0047] Comparative Example Comparative Example 1 The water purification agent was prepared according to Example 1 in the patent document with announcement number CN118062968B and titled "A Polyaluminum Chloride Water Purification Composite Material and Its Preparation Method".

[0048] Comparative Example 2 An inorganic polymer water purification agent, which differs from Example 7 in that an equal amount of polyaluminum chloride is used in this comparative example instead of modified polyaluminum chloride and lanthanum-cerium co-doped mesoporous carrier.

[0049] Comparative Example 3 An inorganic polymer water purification agent, which differs from Example 7 in that an equal amount of polyaluminum chloride is used instead of modified polyaluminum chloride in this comparative example.

[0050] Comparative Example 4 An inorganic polymer water purification agent, which differs from Example 7 in that no lanthanum-cerium co-doped mesoporous carrier is added in this comparative example, and polyaluminum iron silicate is used instead.

[0051] Performance testing 1. Test water The water quality parameters were as follows: initial total phosphorus concentration 2.5 mg / L, mainly orthophosphate with a small amount of polyphosphate, initial turbidity 50 NTU, pH value 7.2 ± 0.2, and water temperature 25℃.

[0052] 2. Testing equipment and reagents Six-piece programmable coagulation test stirrer, UV-Vis spectrophotometer, portable turbidimeter, electric thermostatic drying oven, analytical balance, 0.45μm aqueous filter membrane, ammonium molybdate spectrophotometric reagent for total phosphorus detection.

[0053] 3. Detection Method (1) Coagulation test method: Take 1L of test water and put it in a beaker. Add a quantitative amount of water purification agent sample, start the six-unit stirrer, and set the stirring program: 300r / min fast stirring for 1min, 150r / min medium speed stirring for 5min, 50r / min slow speed stirring for 10min. After stopping the stirring, let it stand for 30min to settle. Take the supernatant at 2cm below the liquid surface for water quality testing. At the same time, collect all the settled sludge for sludge performance testing.

[0054] (2) Total phosphorus removal rate and total phosphorus in effluent: The total phosphorus concentration in the supernatant was determined by the ammonium molybdate spectrophotometric method of GB11893-89 Water Quality Determination of Total Phosphorus. The total phosphorus removal rate was calculated. The total phosphorus removal rate is equal to the ratio of the difference between the initial total phosphorus concentration and the effluent total phosphorus concentration to the initial total phosphorus concentration multiplied by 100%.

[0055] (3) Dosage to meet standards: Gradually adjust the dosage of the reagent and record the lowest dosage when the total phosphorus in the effluent reaches a stable level of 0.3 mg / L. The unit is mg / L, which is used to characterize the phosphorus removal efficiency.

[0056] (4) Unit phosphorus removal sludge production: Based on the dry sludge mass and total phosphorus removal, calculate the dry sludge mass produced for every 1 kg of total phosphorus removed, in units of kg / kg, to directly characterize the sludge production level.

[0057] (5) Turbidity removal rate: The turbidity of the supernatant was detected by a portable turbidity meter, the turbidity removal rate was calculated, and the performance of conventional coagulation was verified.

[0058] 4. Test Results As shown in Table 2.

[0059] Table 2 Detection Results

[0060] Overall, the inorganic polymeric water purification agent prepared in this application significantly outperforms existing comparative technologies in both phosphorus removal efficiency and sludge production control, effectively overcoming the core deficiency of traditional polyaluminum chloride water purification agents in achieving both high-efficiency phosphorus removal and sludge reduction. Taking Example 8, which exhibits the best comprehensive performance, as an example, compared with Comparative Example 1, which represents existing compound water purification technology, the dosage required to stably achieve a total phosphorus concentration of 0.3 mg / L in the effluent decreased from 65 mg / L to 36 mg / L, a reduction of 44.6%, and the sludge production per unit of phosphorus removal decreased from 2.87 kg / kg to 1.74 kg / kg, a reduction of 39.4%. Compared with Comparative Example 2, which uses a common polyaluminum chloride system, the dosage required to meet the standard decreased by 55%, and the sludge production per unit of phosphorus removal decreased by 46.3%. At the same time, both the total phosphorus removal rate and turbidity removal rate remained high, truly achieving the dual goals of deep phosphorus removal and source sludge reduction.

[0061] The significant improvement in phosphorus removal performance stems primarily from the synergistic effect of the functional zoning design of rare-earth-modified polyaluminum chloride (PAC) and the enrichment enhancement effect of the mesoporous carrier. Comparing the performance differences between Comparative Example 3 and the Example, it can be seen that replacing ordinary PAC with lanthanum-cerium in-situ embedded modified PAC significantly reduces the required dosage and significantly improves the total phosphorus removal rate. This is because rare-earth ions are anchored to Al through hydroxyl bridges. 13 The framework end groups form dedicated, highly active phosphorus removal sites. The extremely low solubility product of rare earth phosphates makes the phosphorus removal reaction more thorough. Simultaneously, the phosphorus removal and flocculation functions are spatially separated at the molecular level, allowing aluminum sites to focus on charge neutralization and bridging flocculation, avoiding the ineffective consumption of aluminum ions and significantly improving the effective utilization rate of metal ions. Comparison of Comparative Example 4 and the Example shows that the phosphorus removal efficiency significantly declines after the absence of the lanthanum-cerium co-doped mesoporous support. This verifies that the enrichment effect of mesoporous channels on low-concentration phosphate ions can increase the collision probability between active sites and phosphate ions. Combined with the oxidative conversion effect of cerium on polyphosphates, this further broadens the phosphorus removal substrate range, jointly ensuring deep phosphorus removal effects at low dosages.

[0062] The reduction in sludge production and the optimization of sludge dewatering performance stem from a dual mechanism of source reduction and crystallization densification. Existing technologies often require excessive dosage of reagents to ensure phosphorus removal meets standards. The large amount of redundant aluminum salt hydrolyzes to generate amorphous aluminum hydroxide gel, which is the core reason for high sludge production, high water content, and difficult disposal. This application significantly improves the effective utilization rate of reagents through a functional zoning mechanism, avoiding ineffective hydrolysis products caused by excessive dosage, and directly reducing sludge production at the source of the chemical reaction. Simultaneously, nano-hydroxycalcium phosphate acts as a seed crystal inducer, guiding rare earth phosphates to grow in an orderly crystalline form, replacing the loose, amorphous gel-like sedimentation in traditional processes. Combined with the rigid silicate skeleton of polyaluminum ferric silicate providing structural support for the flocs, stable water passages are retained within the flocs, significantly reducing interstitial water content. Data shows that the unit phosphorus removal sludge production in all embodiments of this application is generally reduced by more than 30% compared to the comparative examples, with simultaneous improvement in floc settling and dewatering performance, effectively reducing the cost of subsequent sludge disposal and the risk of secondary pollution.

[0063] The synergistic effect of the auxiliary components further improves the overall performance and operational stability of the product without weakening the basic efficiency of traditional coagulation. Magnesium aluminum hydrotalcite replenishes and removes residual phosphate in the water through interlayer anion exchange, while its weak alkalinity buffers pH fluctuations during coagulation, ensuring the main reaction remains in a suitable chemical environment, making phosphorus removal more resistant to water quality fluctuations. Examples 6 to 8, which introduce cationic polyacrylamide, show a further reduction in the dosage and sludge production per unit area compared to Example 3, while simultaneously increasing turbidity removal rate. This verifies the adsorption and bridging effect of organic coagulants on fine flocs, accelerating floc growth and solid-liquid separation. Furthermore, the turbidity removal rate in all examples remains above 95%, with the best reaching 98.3%, indicating that this solution, while enhancing phosphorus removal and sludge reduction, does not sacrifice the basic performance of traditional coagulation and turbidity removal. Instead, it achieves a comprehensive improvement in overall water purification efficiency through the complementary functions of multiple components.

[0064] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An inorganic polymer water purification agent, characterized in that, The raw materials include the following parts by weight: Modified polyaluminum chloride 60-80 parts; polyaluminum iron silicate 10-30 parts; lanthanum-cerium co-doped mesoporous carrier 10-20 parts; nano-hydroxycalcium phosphate 1-5 parts; magnesium aluminum hydrotalcite 8-12 parts. Modified polyaluminum chloride is prepared by the following method: First, calcium aluminate powder is added to an aluminum chloride solution to initiate an alkalization reaction, causing the aluminum ions to hydrolyze and polymerize. The reaction temperature is controlled at 60-90℃, and the reaction is stirred for 20-40 minutes. Then, a rare earth salt solution is added, and the reaction is continued with stirring for another 20-30 minutes. Next, calcium aluminate powder is added a second time to further promote the polymerization reaction towards completion. The mixture is then aged at 50-80℃ for 5-10 hours to obtain modified polyaluminum chloride sol. The modified polyaluminum chloride sol is then dried to obtain modified polyaluminum chloride. The mass concentration of the aluminum chloride solution is 8%-15%, the mass of the calcium aluminate powder added in the first step is 4%-8% of the mass of the aluminum chloride solution, and the mass of the calcium aluminate powder added in the second step is 6%-10% of the mass of the aluminum chloride solution. The lanthanum-cerium co-doped mesoporous support was prepared by the following method: molecular sieve SBA-15 was mixed with lanthanum salt aqueous solution and cerium salt aqueous solution, impregnated at 20-30℃ for 6-24h, and then filtered and separated. The resulting solid was dried at 80-120℃ for 4-12h and then calcined at 500-700℃ for 2-6h to obtain the lanthanum-cerium co-doped mesoporous support. The mass concentration of lanthanum salt aqueous solution was 3%-10%, the mass concentration of cerium salt aqueous solution was 2%-6%, and the mass ratio of molecular sieve SBA-15, lanthanum salt aqueous solution and cerium salt aqueous solution was 1:(2-6):(1-4).

2. The inorganic polymer water purification agent according to claim 1, characterized in that, The rare earth salts in the rare earth salt solution include lanthanum nitrate and cerium nitrate, the mass concentration of the rare earth salt solution is 5%-15%, and the amount of rare earth salt solution added is 10%-20% of the mass of the aluminum chloride solution.

3. The inorganic polymer water purification agent according to claim 1, characterized in that, The lanthanum salt aqueous solution is an aqueous solution of lanthanum chloride, and the cerium salt aqueous solution is an aqueous solution of cerium chloride.

4. The inorganic polymer water purification agent according to claim 1, characterized in that, The raw materials also include 1-3 parts of cationic polyacrylamide.

5. The inorganic polymer water purification agent according to claim 1, characterized in that, The average particle size of the magnesium-aluminum hydrotalcite is 10-100 μm.

6. A method for preparing an inorganic polymeric water purification agent according to any one of claims 1-5, characterized in that, Includes the following steps: Modified polyaluminum chloride, polyaluminum iron silicate, lanthanum-cerium co-doped mesoporous carrier, nano-hydroxycalcium phosphate, magnesium aluminum hydrotalcite, and optional cationic polyacrylamide are mixed according to the stated weight proportions. Deionized water is added to adjust the solid content to 15%-30%. The mixture is stirred and homogenized at 35-60℃ for 1-3 hours at a stirring rate of 200-600 rpm. Then, it is spray-dried at an inlet air temperature of 180-250℃ and an outlet air temperature of 85-110℃ until the moisture content is ≤3%, thus obtaining the inorganic polymer water purification agent.

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