Enhanced metal matrix composite water purifier and method for preparing the same

Abstract

The application discloses an enhanced metal base composite water purifying agent and a preparation method thereof, and belongs to the technical field of water purifying agent preparation, and is used for solving the technical problem that flocculation capacity and stability of the composite water purifying agent in the prior art need to be further improved, and specifically comprises the following steps: preparing a water purifying agent skeleton dispersion liquid by using chitosan and sodium alginate; the application is a porous skeleton of chitosan-sodium alginate, loads a polyphenol-metal complex, is crosslinked by Ca 2+ Cross-linking reinforced structure, and is coated by SiO2 to improve acid and alkali resistance and stability, and finally introduces PAC to realize rapid flocculation; in the preparation process, pH control and stepwise drop are used, so that the organic skeleton, the metal complex and the inorganic coating layer are fully combined; the obtained composite water purifying agent can efficiently remove phosphorus, chromium and suspended solids in water, and exhibits significant synergistic purification effect and storage stability.

Description

Technical Field

[0001] This invention relates to the field of water purification agent preparation technology, specifically to an enhanced metal-based composite water purification agent and its preparation method. Background Technology

[0002] The development of metal-based water purifiers in terms of flocculation capacity and storage stability has been a gradual process. Early single-metal salt water purifiers, such as aluminum sulfate and ferric chloride, could produce flocs relatively quickly, but their structure was loose, settling was slow, and they were sensitive to changes in water temperature. Later, prepolymerized products such as polyaluminum chloride, by controlling the degree of polymerization and molecular structure, made the flocs denser, enhanced their adsorption and bridging capabilities, and made the flocculation effect more stable in low-temperature water. Subsequently, multi-metal composite water purifiers emerged, with the synergistic effect of metal ions such as aluminum and iron significantly improving flocculation strength and applicability. At the same time, storage stability has also been continuously improved. From being easily affected by temperature and developing precipitation or clumping in the early stages, to optimizing the degree of hydrolysis and adding stabilizing components, they have achieved high-temperature non-decomposition and low-temperature non-freezing, allowing the products to maintain good performance during long-term storage and transportation. Thus, metal-based water purifiers have become more efficient and reliable in practical applications.

[0003] Currently, the application of commonly used water purification agents in complex water quality conditions still has certain limitations:

[0004] In terms of flocculation performance, most rely on the flocculation mechanism of single inorganic salt or simple organic modification. When the turbidity of the water is low, the temperature is low, or the content of dissolved organic matter is high, the floc formation rate is significantly reduced. The generated flocs have small particle size, loose structure, insufficient density, slow settling speed, and are prone to producing fine suspended solids residue, resulting in unstable control of effluent turbidity.

[0005] In terms of storage stability, some water purification agents are prone to component stratification, hydrolytic inactivation, or moisture absorption and clumping during long-term storage and transportation. Especially in environments with high humidity or large temperature differences, both physical form and chemical activity may decline, resulting in decreased dosing performance and poor batch-to-batch stability.

[0006] In terms of removing specific pollutants, traditional water purification agents have limited removal rates for anionic dissolved pollutants such as phosphate and chromate. Due to insufficient number of active sites and a single binding mode, they are easily affected by pH changes and coexisting ions. Their complexing, precipitation, or adsorption effects are unstable, making it difficult to maintain high removal efficiency over a wide range of water chemistry conditions.

[0007] Therefore, a solution is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide an enhanced metal-based composite water purifier and its preparation method, which solves the technical problem that the flocculation ability and stability of composite water purifiers in the prior art need to be further improved.

[0009] The objective of this invention can be achieved through the following technical solution: a method for preparing an enhanced metal-based composite water purifier, comprising the following steps:

[0010] S1. Using chitosan and sodium alginate as raw materials, a water purification agent skeleton dispersion is obtained by complexation under acidic conditions through electrostatic interaction.

[0011] S2. Using mixed iron salts and tannic acid as raw materials, a polyphenol pre-complexed metal salt matrix dispersion was prepared by utilizing the coordination complexation reaction between polyphenolic compounds and polyvalent metal ions.

[0012] S3. Based on the synergistic effect between the polysaccharide backbone and the polyphenol-multimetal complex, a water purification agent precursor was prepared by mixing and reacting the water purification agent backbone dispersion and the polyphenol complexed metal salt matrix dispersion.

[0013] S4. Based on the multi-level structure construction strategy of "organic framework-multi-metal complex-inorganic crosslinking agent-inorganic coating layer", calcium chloride and sodium silicate are used to micro-encapsulate the water purification agent precursor to obtain a composite water purification agent dispersion.

[0014] S5. By utilizing the multiple interactions between the polynuclear aluminum hydroxy complex in PAC and the composite framework and surface active sites, the composite water purification agent dispersion is micro-crosslinked and then dried to obtain the composite water purification agent.

[0015] Further, in step S1, the preparation method of the water purification agent skeleton dispersion is as follows: deionized water and acetic acid are added to the reaction vessel, stirred at room temperature for 2-3 minutes, chitosan is added to the reaction vessel, stirred at room temperature for 20-30 minutes, sodium alginate is added to the reaction vessel, stirred at room temperature for 10-15 minutes, and then the reaction solution is passed through a 200-mesh sieve to obtain the water purification agent skeleton dispersion. The ratio of deionized water, acetic acid, chitosan and sodium alginate is 250mL:4-5mL:3-4g:1g.

[0016] The technical approach for preparing the water purification agent skeleton dispersion is as follows: using chitosan and sodium alginate as composite skeleton materials, and utilizing acid solubility and electrostatic complexation mechanism between polysaccharides to construct a stable polymer dispersion system.

[0017] Chitosan is a cationic natural polysaccharide containing amino groups. It is poorly soluble under neutral or alkaline conditions, but in the presence of acetic acid, its amino group (-NH2) is protonated to -NH3. +Intermolecular hydrogen bonds and crystalline regions are effectively disrupted, transforming the solution into a cationic solution with highly dispersed molecular chains. Meanwhile, sodium alginate is an anionic polysaccharide, and its main chain contains carboxyl groups (-COO-). - The cationic chitosan carries a negative charge in the aqueous phase. When added to a dissolved chitosan solution, the cationic chitosan segments and the anionic sodium alginate segments complex through electrostatic interaction, accompanied by chain entanglement and hydrogen bonding, forming a complex polysaccharide framework with a certain spatial network structure. This framework system is in a stable colloidal dispersion state in the aqueous phase, which can provide a large specific surface area and uniform reaction sites, which is beneficial to the uniform loading and fixation of subsequent inorganic flocculants, thereby preparing a water purification agent framework dispersion.

[0018] Further, in step S2, the preparation method of the polyphenol pre-complexed metal salt matrix dispersion is as follows: deionized water and ferric chloride hexahydrate are added to the reaction vessel, stirred at room temperature for 8-10 min, tannic acid is added to the reaction vessel, stirred at room temperature for 15-20 min, and then manganese chloride tetrahydrate and magnesium chloride hexahydrate are added to the reaction vessel. During the stirring process, the pH of the reaction system is adjusted to 3-4, and after stirring for 5-8 min, it is passed through a 100-mesh sieve to obtain the polyphenol pre-complexed metal salt matrix dispersion. The amounts of deionized water, ferric chloride hexahydrate, tannic acid, manganese chloride tetrahydrate and magnesium chloride hexahydrate are 360 ​​mL: 45-50 g: 3-4 g: 1 g: 0.5 g.

[0019] The technical approach for preparing polyphenol pre-complexed metal salt matrix dispersions is as follows: by utilizing the coordination complexation reaction between polyphenolic compounds and multivalent metal ions, a metal-organic complex matrix with stability and reactivity is constructed under aqueous conditions.

[0020] First, ferric chloride hexahydrate is dissolved in deionized water to form Fe. 3+ Hydrated ionic solution, Fe 3+ It possesses strong Lewis acidity and can coordinate with the phenolic hydroxyl groups in polyphenol molecules to form a stable chelate structure. When tannic acid is added to the system, its polyphenolic hydroxyl groups react with Fe... 3+ Coordination occurs, forming Fe-O bonded polyphenol-metal complexes. This process not only stabilizes Fe... 3+ The dispersion state in the aqueous phase also endows the system with strong surface activity and functionalization sites;

[0021] After forming a preliminary Fe-TA complex network, manganese chloride tetrahydrate and magnesium chloride hexahydrate, Mn were introduced. 2+ With Mg 2+As an auxiliary cation, it can bind to some phenolic hydroxyl groups of tannic acid or residual coordination sites of the Fe-TA complex network, further enhancing the structural stability and multi-metal properties of the complex network. In this process, adjusting the pH of the reaction system to 3-4 helps prevent the metal ions from undergoing hydroxide precipitation, while maintaining the polyphenolic hydroxyl groups in a suitable dissociation-coordination state, thereby improving the complexation efficiency and dispersion uniformity. Finally, the obtained system is a multi-metal-polyphenol complex colloidal dispersion with uniform particle size and good stability. This dispersion not only has a high specific surface area and uniform metal distribution, but also provides a chemical basis for subsequent complexation with polysaccharide skeletons and loading of active components of water purification agents.

[0022] Further, in step S3, the preparation method of the water purification agent precursor is as follows: the water purification agent skeleton dispersion is added to the reaction vessel and stirred. After adjusting the pH of the reaction system to 6.2-6.6 with sodium bicarbonate, the polyphenol pre-complexed metal salt matrix dispersion is added dropwise to the reaction vessel. During the dropwise addition process of 40-45 min, the pH of the reaction system is adjusted to 6.2-6.6. After the dropwise addition is completed, stirring is stopped and the mixture is allowed to mature at room temperature for 20-30 min to obtain the water purification agent precursor. The ratio of the water purification agent skeleton dispersion to the polyphenol pre-complexed metal salt matrix dispersion is 1 mL: 1.0-1.2 mL.

[0023] The technical approach for preparing water purification agent precursors is as follows: This step is based on the synergistic effect between the polysaccharide backbone and the polyphenol-polymetallic complex to construct a water purification agent precursor with a stable structure and multiple functional sites.

[0024] The water purification agent's framework dispersion is primarily composed of a chitosan-sodium alginate composite polysaccharide network. Its surface is rich in active groups such as hydroxyl (-OH), amino (-NH2), and carboxyl (-COOH) groups, enabling it to bind with metal ions or organic complexes through hydrogen bonding, electrostatic adsorption, and coordination. During the reaction, sodium bicarbonate is first used to slowly adjust the pH to 6.2-6.6, ensuring that some amino and carboxyl groups on the framework polysaccharide molecules are in a suitable dissociated state. This provides an optimal chemical environment for the subsequent complexation reaction. Simultaneously, this pH range maintains the structural stability of the polyphenol-multimetal complex, preventing Fe... 3+ Mn 2+ Mg 2+ Hydrolysis precipitation of metal ions;

[0025] When the polyphenol pre-complexed metal salt matrix dispersion is added dropwise to the framework dispersion, the polyphenolic hydroxyl groups of the tannic acid-metal complex bind to the hydroxyl, amino, and carboxyl groups of the framework polysaccharide at multiple sites, including hydrogen bonding, coordination chelation, and electrostatic interaction. Under slow dropwise addition and constant pH control, this process promotes the uniform dispersion and firm binding of the complex in the framework network, forming a spatially interpenetrating organic-inorganic composite structure. After maturation at room temperature, it can further promote molecular rearrangement and network stabilization between the framework and the complex, ultimately yielding a water purification agent precursor with uniform structure, strong binding, and multifunctional adsorption and flocculation activities. This precursor combines the mechanical stability of the framework with the chemical activity of the polyphenol-multi-metal complex, providing a material basis for multi-dimensional synergistic effects in subsequent water purification applications.

[0026] Furthermore, in step S4, the preparation method of the composite water purification agent dispersion includes the following steps:

[0027] A1. Add the water purification agent precursor to the reaction vessel and stir. After stirring at room temperature for 4-5 minutes, add calcium chloride dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.5-7.2 during the dropwise addition process of 5-10 minutes. After the dropwise addition is completed, continue stirring for 20-30 minutes to obtain the composite water purification agent preform dispersion.

[0028] A2. Add the composite water purification agent dispersion to the reaction vessel and stir. After stirring at room temperature for 4-5 minutes, add sodium silicate dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.2-6.6 during the dropwise addition process of 10-15 minutes. After the dropwise addition is completed, let it stand for 20-30 minutes to obtain the composite water purification agent dispersion.

[0029] The technical approach for preparing composite water purification agent dispersion is as follows: the preparation of composite water purification agent dispersion relies on a multi-level structural construction strategy of "organic framework-multi-metal complex-inorganic crosslinking agent-inorganic coating layer", which aims to endow the material with higher mechanical strength, stability and composite purification function;

[0030] In step A1, the water purification agent precursor is reacted with a calcium chloride dispersion, utilizing Ca... 2+ It undergoes ionic cross-linking with the carboxyl (-COOH), hydroxyl (-OH) groups, and residual coordination sites of polyphenol-metal complexes in the backbone, Ca 2+ The introduction of [a specific ingredient] can significantly enhance the spatial cross-linking density of the organic-inorganic composite network, thereby improving the mechanical strength and swelling resistance of the material. Simultaneously, controlling the reaction pH within the range of 6.5-7.2 contributes to [the improvement of] Ca [a specific chemical]. 2+ By fully combining with the coordinating groups and avoiding the precipitation of metal ions caused by excessive alkalinity, and after appropriate aging, a dense and highly stable composite water purification agent dispersion is generated.

[0031] In step A2, the composite water purification agent dispersion is reacted with a sodium silicate dispersion. Na2SiO3 is partially hydrolyzed under weakly acidic to near-neutral conditions to generate SiO2·nH2O colloidal particles. These silica particles can deposit and coat the surface of the composite water purification agent particles, forming an inorganic silicon oxide protective film. On the one hand, this coating layer improves the chemical stability and acid and alkali resistance of the material; on the other hand, the silicon oxide framework surface contains a large number of hydroxyl groups, which can provide additional active sites for subsequent adsorption-flocculation-synergistic purification reactions. The final composite water purification agent dispersion has a multi-layered composite structure: an internal highly cross-linked organic-metal complex network, and an external dense silicon oxide film, possessing high strength, excellent stability, and multifunctional purification activity, making it suitable for the purification of various complex water qualities.

[0032] Furthermore, in step A1, the ratio of the water purification agent precursor to the calcium chloride dispersion is 5 mL:1 mL, wherein the calcium chloride dispersion is obtained by mixing calcium chloride and deionized water at a ratio of 4 g:100 mL; in step A2, the ratio of the composite water purification agent preform dispersion to the sodium silicate dispersion is 6 mL:1 mL, wherein the sodium silicate dispersion is obtained by mixing sodium silicate and deionized water at a ratio of 1-2 g:100 mL.

[0033] Furthermore, in step S5, the preparation method of the composite water purification agent includes the following steps:

[0034] B1. Add the composite water purification agent dispersion to the reaction vessel and stir. After stirring at room temperature for 10-12 minutes, add polyaluminum chloride to the reaction vessel and adjust the pH of the reaction system to 6.4-6.6. Continue stirring at room temperature for 20-30 minutes and then pass it through a 100-mesh sieve to obtain the composite water purification agent precursor.

[0035] B2. Add the composite water purification agent precursor to the reactor, adjust the pH of the reaction system to 5.0-5.5, and after the sedimentation is complete, filter the filter cake by suction filtration. Spread the filter cake evenly on the surface of the vacuum belt drying tray to dry. After drying, grind it through the upper 20-mesh sieve and the lower 60-mesh sieve to obtain the composite water purification agent.

[0036] The technical approach to preparing composite water purification agents is as follows: The preparation of composite water purification agents is based on the process of "functional enhancement - solid-liquid separation - structural shaping". By introducing efficient inorganic flocculants and precise drying - powder shaping steps, the materials are endowed with higher water purification reactivity and ease of use.

[0037] In step B1, the composite water purification agent dispersion is mixed with polyaluminum chloride (PAC). The polynuclear aluminum hydroxy complex in PAC can interact with the composite framework and surface active sites in multiple ways:

[0038] Electrostatic neutralization: High-valence aluminum ions in aluminum hydroxide ions react with negatively charged groups (-COO) on the material surface. - -OH - This combination reduces the colloidal stability of the system;

[0039] Bridging adsorption: PAC can form "aluminum oxide-hydroxyl" bridges between particles, promoting particle aggregation;

[0040] Surface composite: The hydroxyl aluminum deposition layer formed by PAC can increase the positive charge and the number of reactive sites on the material surface;

[0041] The pH of this reaction is controlled at 6.4-6.6, which ensures that the aluminum hydroxide complex of PAC is in a stable and active state and avoids its conversion into insoluble Al(OH)3 precipitate. After stirring and sieving, a composite water purification agent precursor with uniform particle size is obtained.

[0042] In step B2, the precursor is adjusted to pH 5.0-5.5, causing the residual aluminum hydroxide to partially hydrolyze and precipitate, solidifying on the material surface. Simultaneously, this promotes further cross-linking of metal ions and organic groups within the material, thereby enhancing structural stability. After static settling, the solid is collected by filtration and then efficiently removed from the water in a vacuum belt drying pan to prevent thermal degradation of the organic framework and polyphenol-metal complex. Finally, after grinding and double-layer sieving, a composite water purification agent with suitable particle size, sufficient exposure of active sites, and stable reactivity is obtained. This finished product exhibits high reactivity, good mechanical strength, and a highly adaptable particle size distribution, making it suitable for rapid flocculation and sedimentation treatment of different types of water bodies.

[0043] Furthermore, in step B1, the ratio of the composite water purification agent dispersion to polyaluminum chloride is 700mL:5-6g; in step B2, the filter cake is spread out to a thickness of 5-8mm, the parameters of the vacuum belt drying tray are 60-70℃, the air pressure is -0.08MPa, the drying time is 2-3h, and the turning interval is 1h.

[0044] The present invention also proposes an enhanced metal-based composite water purifier, which is prepared by the above-mentioned preparation method of an enhanced metal-based composite water purifier.

[0045] The present invention has the following beneficial effects:

[0046] 1. This invention utilizes organic ligands to form a stable organometallic framework with polyvalent metal ions, providing a large number of uniformly distributed coordination and adsorption sites, laying the foundation for subsequent reactions. Subsequently, metal crosslinking enhances the spatial stability of the framework, making the active sites less prone to loss under conditions such as agitation and water flow impact. The silica coating layer further improves the structure's acid and alkali resistance and chemical stability, and increases the number of surface hydroxyl groups, which facilitates hydrogen bonding and electrostatic interactions with suspended particles and dissolved organic matter in water. At the same time, the introduction of polyaluminum chloride (PAC) provides strong charge neutralization and bridging adsorption capabilities, which can quickly break down colloidal particles and promote their aggregation into large and dense flocs. Finally, the framework provides a stable carrier, the silica layer increases adsorption force, and PAC accelerates floc formation, enabling the adsorption, bridging, and sedimentation processes to be completed in a shorter time after addition, thereby significantly improving the flocculation performance of the composite water purification agent.

[0047] 2. This invention uses an organic-metal framework as the main structure, which has high strength and high stability, effectively fixing the active components and preventing decomposition or failure due to temperature and humidity fluctuations. Secondly, the introduction of the silicon-oxygen coating layer gives the material high chemical inertness, effectively isolating moisture and carbon dioxide in the air, reducing the occurrence of moisture absorption and acidification reactions. At the same time, its surface hydroxyl structure can remain stable while maintaining activity. Thirdly, the cross-linking of multivalent metal ions enhances the compactness and stability of the internal structure of the particles, reducing the risk of mechanical pulverization and structural loosening during storage and transportation. Finally, through the synergistic effect of the above multiple protection mechanisms, the product can still maintain good physical form and flocculation performance for a long time under storage conditions with high humidity and large temperature differences, ensuring that the activity does not decrease when opened for use.

[0048] 3. The polyphenolic functional groups introduced into the organic-metal complex framework of the composite water purifier prepared by this invention can form stable complexes with phosphate ions through hydrogen bonding and coordination bonds. Simultaneously, the abundant hydroxyl sites on the framework surface can undergo electrostatic adsorption and coordination exchange with chromate ions; secondly, Ca... 2+ Crosslinking not only improves the stability of the skeleton but also allows it to undergo precipitation reactions with phosphate ions, achieving efficient removal. At the same time, the SiO2 coating layer formed by the hydrolysis of sodium silicate increases the number of surface active sites and improves the acid and alkali resistance of the material, enabling adsorption and precipitation to occur over a wide pH range. Furthermore, polyaluminum chloride provides a large number of aluminum hydroxyl species, which can rapidly flocculate suspended matter through electrostatic neutralization and bridging, while forming precipitates with phosphate ions and aluminum hydroxyl-chromium complexes with chromate ions, thereby significantly improving removal efficiency. Ultimately, through the synergy of multiple chemical reaction mechanisms and physical flocculation mechanisms, this water purification agent can simultaneously achieve efficient removal of phosphorus and chromium and rapid reduction of water turbidity in practical applications. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In this application, the polyaluminum chloride used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number A822730; the sodium alginate used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number S817374; the chitosan used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number C804729; the tannic acid used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number T818845; and the sodium silicate used was purchased from Shanghai Maclean Biotechnology Co., Ltd., with item number S871945.

[0051] Example 1

[0052] This embodiment provides a method for preparing an enhanced metal-based composite water purification agent, including the following steps:

[0053] Step 1: Preparation of water purification agent skeleton dispersion

[0054] Weigh out 250.0 mL of deionized water and 4.0 mL of acetic acid and add them to the reaction vessel. After stirring at room temperature for 2 min, add 3.0 g of chitosan to the reaction vessel and stir at room temperature for 20 min. Then add 1.0 g of sodium alginate to the reaction vessel and stir at room temperature for 10 min. Finally, pass the reaction solution through a 200-mesh sieve to obtain the water purification agent skeleton dispersion.

[0055] Step 2: Preparation of polyphenol pre-complexed metal salt matrix dispersion

[0056] Weigh out 360.0 mL of deionized water and 45.0 g of ferric chloride hexahydrate and add them to the reaction vessel. Stir at room temperature for 8 min, then add 3.0 g of tannic acid to the reaction vessel. Stir at room temperature for 15 min, then add 1.0 g of manganese chloride tetrahydrate and 0.5 g of magnesium chloride hexahydrate to the reaction vessel. Adjust the pH of the reaction system to 3 while stirring. Continue stirring for 5 min and then pass the mixture through a 100-mesh sieve to obtain a polyphenol pre-complexed metal salt matrix dispersion.

[0057] Step 3: Preparation of water purification agent precursor

[0058] Weigh 250.0 mL of the water purification agent skeleton dispersion and add it to the reaction vessel. After adjusting the pH of the reaction system to 6.2 with sodium bicarbonate, add 250.0 mL of the polyphenol pre-complexed metal salt matrix dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.2 during the 40 min dropwise addition. After the addition is complete, stop stirring and let it mature at room temperature for 20 min to obtain the water purification agent precursor.

[0059] Step 4: Preparation of composite water purification agent dispersion

[0060] Weigh out 4.0 g of calcium chloride and mix it with 100.0 mL of deionized water to obtain a calcium chloride dispersion.

[0061] Weigh out 500.0 mL of the composite water purification agent precursor and add it to the reaction vessel. Stir at room temperature for 4 min, then add 100.0 mL of calcium chloride dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.5 during the 5 min dropwise addition. After the dropwise addition is complete, continue stirring for 20 min to obtain the composite water purification agent preform dispersion.

[0062] Weigh out 1.0 g of sodium silicate and mix it with 100.0 mL of deionized water to obtain a sodium silicate dispersion;

[0063] Weigh out 600.0 mL of the composite water purification agent dispersion and add it to the reaction vessel. Stir at room temperature for 4 min, then add 100.0 mL of sodium silicate dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.2 during the 10 min dropwise addition. After the addition is complete, let it stand for 20 min to obtain the composite water purification agent dispersion.

[0064] Step 5: Preparation of composite water purification agent

[0065] Weigh 700.0 mL of the composite water purification agent dispersion and add it to the reaction vessel. Stir for 10 min at room temperature, then add polyaluminum chloride to the reaction vessel and adjust the pH of the reaction system to 6.4. Continue stirring at room temperature for 20 min and then pass it through a 100-mesh sieve to obtain the composite water purification agent precursor.

[0066] Weigh 700.0 mL of the composite water purification agent precursor and add it to the reaction vessel. Adjust the pH of the reaction system to 5.0. After settling, filter the filter cake and spread it evenly on the surface of a vacuum belt drying tray to dry. The thickness of the cake should be 5 mm. The parameters of the vacuum belt drying tray are 60℃, air pressure -0.08 MPa, drying time 2 h, and turning interval 1 h. After drying, grind the cake through a 20-mesh sieve on the top layer and a 60-mesh sieve on the bottom layer to obtain the composite water purification agent.

[0067] Example 2

[0068] This embodiment provides a method for preparing an enhanced metal-based composite water purification agent, including the following steps:

[0069] Step 1: Preparation of water purification agent skeleton dispersion

[0070] Weigh out 250.0 mL of deionized water and 5.0 mL of acetic acid and add them to the reaction vessel. After stirring at room temperature for 3 min, add 4.0 g of chitosan to the reaction vessel and stir at room temperature for 30 min. Then add 1 g of sodium alginate to the reaction vessel and stir at room temperature for 15 min. Finally, pass the reaction solution through a 200-mesh sieve to obtain the water purification agent skeleton dispersion.

[0071] Step 2: Preparation of polyphenol pre-complexed metal salt matrix dispersion

[0072] Weigh out 360.0 mL of deionized water and 50.0 g of ferric chloride hexahydrate and add them to the reaction vessel. Stir at room temperature for 10 min, then add 4.0 g of tannic acid to the reaction vessel. Stir at room temperature for 20 min, then add 1.0 g of manganese chloride tetrahydrate and 0.5 g of magnesium chloride hexahydrate to the reaction vessel. Adjust the pH of the reaction system to 4 while stirring. Continue stirring for 8 min and then pass the mixture through a 100-mesh sieve to obtain a polyphenol pre-complexed metal salt matrix dispersion.

[0073] Step 3: Preparation of water purification agent precursor

[0074] Weigh 250.0 mL of the water purification agent skeleton dispersion and add it to the reaction vessel. After adjusting the pH of the reaction system to 6.6 with sodium bicarbonate, add 250.0 mL of the polyphenol pre-complexed metal salt matrix dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.6 during the dropwise addition process of 45 min. After the dropwise addition is completed, stop stirring and mature at room temperature for 30 min to obtain the water purification agent precursor.

[0075] Step 4: Preparation of composite water purification agent dispersion

[0076] Weigh out 4.0 g of calcium chloride and mix it with 100.0 mL of deionized water to obtain a calcium chloride dispersion.

[0077] Weigh out 500.0 mL of water purification agent precursor and add it to the reaction vessel. Stir at room temperature for 5 min, then add 100.0 mL of calcium chloride dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 7.2 during the 10 min dropwise addition. After the addition is complete, continue stirring for 30 min to obtain the composite water purification agent preform dispersion.

[0078] Weigh out 2.0 g of sodium silicate and mix it with 100.0 mL of deionized water to obtain a sodium silicate dispersion;

[0079] Weigh 600.0 mL of the composite water purification agent dispersion and add it to the reaction vessel. Stir for 5 min at room temperature, then add 100.0 mL of sodium silicate dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.6 during the 15 min dropwise addition. After the addition is complete, let it stand for 30 min to obtain the composite water purification agent dispersion.

[0080] Step 5: Preparation of composite water purification agent

[0081] Weigh 700.0 mL of the composite water purification agent dispersion and add it to the reaction vessel. Stir for 12 min at room temperature, then add polyaluminum chloride to the reaction vessel and adjust the pH of the reaction system to 6.6. Continue stirring at room temperature for 30 min and then pass it through a 100-mesh sieve to obtain the composite water purification agent precursor.

[0082] Weigh 700.0 mL of the composite water purification agent precursor and add it to the reaction vessel. Adjust the pH of the reaction system to 5.5. After settling, filter the filter cake and spread it evenly on the surface of a vacuum belt drying tray to dry. The thickness of the cake should be 8 mm. The parameters of the vacuum belt drying tray are 70℃, air pressure -0.08 MPa, drying time 3 h, and turning interval 1 h. After drying, grind the cake through a 20-mesh sieve on the top layer and a 60-mesh sieve on the bottom layer to obtain the composite water purification agent.

[0083] Example 3

[0084] This embodiment provides a method for preparing an enhanced metal-based composite water purification agent, including the following steps:

[0085] Step 1: Preparation of water purification agent skeleton dispersion

[0086] Weigh out 250.0 mL of deionized water and 4.5 mL of acetic acid and add them to the reaction vessel. After stirring at room temperature for 3 min, add 3.6 g of chitosan to the reaction vessel and stir at room temperature for 24 min. Then add 1.0 g of sodium alginate to the reaction vessel and stir at room temperature for 12 min. Finally, pass the reaction solution through a 200-mesh sieve to obtain the water purification agent skeleton dispersion.

[0087] Step 2: Preparation of polyphenol pre-complexed metal salt matrix dispersion

[0088] Weigh out 360.0 mL of deionized water and 48.0 g of ferric chloride hexahydrate and add them to the reaction vessel. Stir at room temperature for 9 min, then add 3.6 g of tannic acid to the reaction vessel. Stir at room temperature for 18 min, then add 1.0 g of manganese chloride tetrahydrate and 0.5 g of magnesium chloride hexahydrate to the reaction vessel. Adjust the pH of the reaction system to 4 while stirring. Continue stirring for 6 min and then pass the mixture through a 100-mesh sieve to obtain a polyphenol pre-complexed metal salt matrix dispersion.

[0089] Step 3: Preparation of water purification agent precursor

[0090] Weigh 250.0 mL of the water purification agent skeleton dispersion and add it to the reaction vessel. After adjusting the pH of the reaction system to 6.4 with sodium bicarbonate, add 250.0 mL of the polyphenol pre-complexed metal salt matrix dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.4 during the dropwise addition process of 42 min. After the dropwise addition is completed, stop stirring and mature at room temperature for 25 min to obtain the water purification agent precursor.

[0091] Step 4: Preparation of composite water purification agent dispersion

[0092] Weigh out 4.0 g of calcium chloride and mix it with 100.0 mL of deionized water to obtain a calcium chloride dispersion.

[0093] Weigh out 500.0 mL of water purification agent precursor and add it to the reaction vessel. Stir for 5 min at room temperature, then add 100.0 mL of calcium chloride dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.8 during the 8 min dropwise addition. After the addition is complete, continue stirring for 25 min to obtain the composite water purification agent preform dispersion.

[0094] Weigh out 1.6g of sodium silicate and mix it with 100.0mL of deionized water to obtain a sodium silicate dispersion;

[0095] Weigh out 600.0 mL of the composite water purification agent dispersion and add it to the reaction vessel. Stir for 5 min at room temperature, then add 100.0 mL of sodium silicate dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.4 during the 12 min dropwise addition. After the addition is complete, let it stand for 24 min to obtain the composite water purification agent dispersion.

[0096] Step 5: Preparation of composite water purification agent

[0097] Weigh 700.0 mL of the composite water purification agent dispersion and add it to the reaction vessel. Stir for 12 min at room temperature, then add polyaluminum chloride to the reaction vessel and adjust the pH of the reaction system to 6.5. Continue stirring at room temperature for 25 min and then pass it through a 100-mesh sieve to obtain the composite water purification agent precursor.

[0098] Weigh 700.0 mL of the composite water purification agent precursor and add it to the reaction vessel. Adjust the pH of the reaction system to 5.4. After settling, filter the filter cake and spread it evenly on the surface of a vacuum belt drying tray to dry. The thickness of the cake should be 6 mm. The parameters of the vacuum belt drying tray are 65℃, air pressure -0.08 MPa, drying time 3 h, and turning interval 1 h. After drying, grind the cake through a 20-mesh sieve on the top layer and a 60-mesh sieve on the bottom layer to obtain the composite water purification agent.

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 3 is that the step of preparing the composite water purifier precursor is omitted in step five. Instead, a composite water purifier dispersion is used to replace the composite water purifier precursor in the process of preparing the composite water purifier.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 3 is that the step of preparing the composite water purification agent preform dispersion is omitted in step four. Instead, a water purification agent precursor is used to replace the composite water purification agent preform dispersion in the process of preparing the composite water purification agent dispersion.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 3 is that the step of preparing the composite water purification agent dispersion is omitted in step four, and the composite water purification agent preform dispersion is used to replace the composite water purification agent dispersion in an equal amount in step five.

[0105] Performance testing:

[0106] The turbidity reduction rate and settling time reduction rate of the composite water purification agents prepared in Examples 1-3 and Comparative Examples 1-3 were tested in accordance with the standard T / CECS10356-2024 "Flocculants for Wastewater Treatment of Washed Sand and Gravel Aggregates".

[0107] The stability of the composite water purification agents prepared in Examples 1-3 and Comparative Examples 1-3 was evaluated in accordance with the standard YS / T 802-2012 "Flocculants for Alumina Production".

[0108] The total phosphorus and total chromium content of the wastewater discharged from the wastewater treatment plant after purification by the composite water purification agents prepared in Examples 1-3 and Comparative Examples 1-3 were compared with the standard GB 18918-2002 "Discharge Standard of Pollutants for Urban Wastewater Treatment Plants". The specific data are shown in Table 1.

[0109] Table 1 - Performance Test Data for Each Sample

[0110]

[0111]

[0112] Data Analysis:

[0113] Comparative analysis of the data in Table 1 reveals that, compared to flocculation without flocculant, the composite water purifier prepared in this invention exhibits a 99% reduction in turbidity, an 88% reduction in settling time, and can be stably stored for 16 months, while the total phosphorus content of the purified wastewater is 0.1 mg·L⁻¹. -1 The total chromium content is 0.05 mg·L. -1 All data points are better than the comparative data, indicating that:

[0114] Comparative Example 1 eliminated the use of polyaluminum chloride (PAC). Without PAC, the electrostatic repulsion of colloidal particles in the water was not effectively weakened, and particles still struggled to bond firmly after collisions. This resulted in a reduction in the number and size of initial flocs. Due to the slower aggregation rate, the formed flocs were loose and insufficiently dense, leading to a significant decrease in settling velocity during sedimentation. This prolonged the residence time of suspended solids in the water and reduced solid-liquid separation efficiency. Simultaneously, the reduced specific surface area of ​​particles decreased the number of pollutant adsorption sites, significantly decreasing the removal rates of total phosphorus, total chromium, and other indicators in the water. Furthermore, incomplete sedimentation allowed residual suspended particles to enter subsequent treatment stages, increasing the operational burden and potentially increasing the risk of effluent turbidity. Ultimately, this manifested as insufficient flocculation power, decreased sedimentation performance, and an overall weakened purification effect.

[0115] Comparative Example 2: Cancel Ca 2+ After cross-linking, the amount of calcium phosphate precipitate formed in the system is significantly reduced, limiting the decrease in total phosphorus concentration. Simultaneously, the floc skeleton lacks multi-point support, resulting in a loose overall structure and low mechanical strength. Under the impact of water flow, it easily breaks into fine particles. These particles settle slowly, with some remaining suspended in the water, leading to decreased solid-liquid separation efficiency and reduced water transparency. Furthermore, the broken fine particles are easily resuspended and enter subsequent treatment stages, increasing the burden on the filtration system and raising the risk of clogging. Ultimately, due to the weakening of both chemical removal and physical sedimentation, the purification effect is significantly lower than that for calcium-containing systems. 2+ Crosslinking treatment system;

[0116] Comparative Example 3 eliminated the SiO2 coating layer, which made the product prone to moisture absorption and clumping during storage, resulting in decreased particle dispersibility, slower dissolution rate and uneven release of activity during addition. Some active components gradually became ineffective during storage, leading to short-term treatment effects similar to the example after preparation, but the removal efficiency significantly decreased over time. Insufficient dissolution of clumped particles also affected the formation rate and stability of flocs, increased fluctuations in sedimentation performance, and even batch-to-batch differences during long-term storage, increasing the uncertainty of the operation process. Ultimately, the initial effect was acceptable, but the stability was poor, the effective use period was short, and it was difficult to maintain continuous high-efficiency purification.

[0117] In conclusion, this scheme uses chitosan-sodium alginate complex polysaccharide as an organic porous framework, combined with a polyphenol-multimetal complex matrix and Ca... 2+ Ion crosslinking, SiO2 inorganic coating, and PAC high-efficiency flocculant construct a multi-level synergistic water purification system; the framework structure provides a stable carrier and abundant active sites, polyphenol-metal complexes endow the material with multifunctional adsorption and chemical binding capabilities, and Ca... 2+Crosslinking significantly enhances structural density and mechanical strength; the SiO2 coating improves acid and alkali resistance and long-term stability, and increases surface hydroxyl groups for further reaction; the introduction of PAC enables rapid charge neutralization and bridging adsorption at the application end, accelerating floc formation and sedimentation. The components complement each other in terms of structural support, chemical complexation, mechanical strengthening and interfacial reaction, enabling the water purifier to remove phosphorus, chromium and suspended particles while having comprehensive advantages such as rapid reaction and long-term stability, significantly improving the purification efficiency and reliability of complex water quality.

[0118] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing an enhanced metal-based composite water purifier, characterized in that, Includes the following steps: S1. Using chitosan and sodium alginate as raw materials, a water purification agent skeleton dispersion is obtained by complexation under acidic conditions through electrostatic interaction. S2. Using mixed iron salts and tannic acid as raw materials, a polyphenol pre-complexed metal salt matrix dispersion was prepared by utilizing the coordination complexation reaction between polyphenolic compounds and polyvalent metal ions. S3. Based on the synergistic effect between the polysaccharide backbone and the polyphenol-multimetal complex, a water purification agent precursor was prepared by mixing and reacting the water purification agent backbone dispersion and the polyphenol complexed metal salt matrix dispersion. S4. Based on the multi-level structure construction strategy of "organic framework-polymetallic complex-inorganic crosslinking agent-inorganic coating layer", calcium chloride and sodium silicate are used to micro-encapsulate the water purification agent precursor to obtain a composite water purification agent dispersion. S5. By utilizing the multiple interactions between the polynuclear aluminum hydroxy complex in PAC and the composite framework and surface active sites, the composite water purification agent dispersion is micro-crosslinked and then dried to obtain the composite water purification agent. The preparation method of the polyphenol pre-complexed metal salt matrix dispersion is as follows: deionized water and ferric chloride hexahydrate are added to the reaction vessel, stirred at room temperature for 8-10 min, tannic acid is added to the reaction vessel, stirred at room temperature for 15-20 min, and then manganese chloride tetrahydrate and magnesium chloride hexahydrate are added to the reaction vessel. During the stirring process, the pH of the reaction system is adjusted to 3-4, and after stirring for 5-8 min, it is passed through a 100-mesh sieve to obtain the polyphenol pre-complexed metal salt matrix dispersion. The preparation method of the water purification agent precursor is as follows: the water purification agent skeleton dispersion is added to the reaction vessel and stirred. After adjusting the pH of the reaction system to 6.2-6.6 with sodium bicarbonate, the polyphenol pre-complexed metal salt matrix dispersion is added dropwise to the reaction vessel. During the dropwise addition process of 40-45 min, the pH of the reaction system is adjusted to 6.2-6.

6. After the dropwise addition is completed, stirring is stopped and the mixture is allowed to mature at room temperature for 20-30 min to obtain the water purification agent precursor. The preparation method of the composite water purification agent dispersion includes the following steps: A1. Add the water purification agent precursor to the reaction vessel and stir. After stirring at room temperature for 4-5 minutes, add calcium chloride dispersion dropwise to the reaction vessel. Adjust the pH of the reaction system to 6.5-7.2 during the dropwise addition process of 5-10 minutes. After the dropwise addition is completed, continue stirring for 20-30 minutes to obtain the composite water purification agent preform dispersion. A2. Add the composite water purification agent preform dispersion to the reaction vessel and stir. After stirring at room temperature for 4-5 minutes, add sodium silicate dispersion dropwise to the reaction vessel. During the dropwise addition process of 10-15 minutes, adjust the pH of the reaction system to 6.2-6.

6. After the dropwise addition is completed, let it stand for 20-30 minutes to obtain the composite water purification agent dispersion.

2. The preparation method of the enhanced metal-based composite water purifier according to claim 1, characterized in that, In step S1, the preparation method of the water purification agent skeleton dispersion is as follows: deionized water and acetic acid are added to the reaction vessel, stirred at room temperature for 2-3 minutes, chitosan is added to the reaction vessel, stirred at room temperature for 20-30 minutes, sodium alginate is added to the reaction vessel, stirred at room temperature for 10-15 minutes, and then the reaction solution is passed through a 200-mesh sieve to obtain the water purification agent skeleton dispersion. The ratio of deionized water, acetic acid, chitosan and sodium alginate is 250mL:4-5mL:3-4g:1g.

3. The preparation method of the enhanced metal-based composite water purifier according to claim 1, characterized in that, In the preparation of the polyphenol pre-complexed metal salt matrix dispersion, the amounts of deionized water, ferric chloride hexahydrate, tannic acid, manganese chloride tetrahydrate and magnesium chloride hexahydrate are 360mL:45-50g:3-4g:1g:0.5g.

4. The preparation method of the enhanced metal-based composite water purifier according to claim 1, characterized in that, In the process of preparing the water purification agent precursor, the ratio of the water purification agent skeleton dispersion to the polyphenol pre-complexed metal salt matrix dispersion is 1 mL: 1.0-1.2 mL.

5. The preparation method of the enhanced metal-based composite water purifier according to claim 1, characterized in that, In step A1, the ratio of the water purification agent precursor to the calcium chloride dispersion is 5 mL:1 mL, wherein the calcium chloride dispersion is obtained by mixing calcium chloride and deionized water at a ratio of 4 g:100 mL; in step A2, the ratio of the composite water purification agent preform dispersion to the sodium silicate dispersion is 6 mL:1 mL, wherein the sodium silicate dispersion is obtained by mixing sodium silicate and deionized water at a ratio of 1-2 g:100 mL.

6. The preparation method of the enhanced metal-based composite water purifier according to claim 1, characterized in that, In step S5, the preparation method of the composite water purification agent includes the following steps: B1. Add the composite water purification agent dispersion to the reaction vessel and stir. After stirring at room temperature for 10-12 minutes, add polyaluminum chloride to the reaction vessel and adjust the pH of the reaction system to 6.4-6.

6. Continue stirring at room temperature for 20-30 minutes and then pass it through a 100-mesh sieve to obtain the composite water purification agent precursor. B2. Add the composite water purification agent precursor to the reactor, adjust the pH of the reaction system to 5.0-5.5, and after the sedimentation is complete, filter the filter cake by suction filtration. Spread the filter cake evenly on the surface of the vacuum belt drying tray to dry. After drying, grind it through the upper 20-mesh sieve and the lower 60-mesh sieve to obtain the composite water purification agent.

7. The preparation method of the enhanced metal-based composite water purifier according to claim 6, characterized in that, In step B1, the ratio of the composite water purification agent dispersion to polyaluminum chloride is 700mL:5-6g; in step B2, the filter cake is spread out to a thickness of 5-8mm, the parameters of the vacuum belt drying tray are 60-70℃, the air pressure is -0.08MPa, the drying time is 2-3h, and the turning interval is 1h.

8. An enhanced metal-based composite water purifier, characterized in that, The enhanced metal-based composite water purifier is prepared using the preparation method of the enhanced metal-based composite water purifier as described in any one of claims 1-7.

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