Modified polyaluminum chloride with high phosphorus removal performance as well as preparation method and application of modified polyaluminum chloride

Abstract

The invention provides modified polyaluminum chloride with high phosphorus removal performance and a preparation method and application thereof, and belongs to the technical field of modified polyaluminum chloride. The preparation method comprises the following steps: firstly, reacting aluminum chloride, zirconium oxychloride and an alkaline regulator in a water phase to prepare an aluminum-zirconium complex mother solution, then adding a polyhexamethylene biguanide solution into the aluminum-zirconium complex mother solution, and realizing effective compounding of organic long-chain molecules and inorganic complexes under the actions of static electricity, coordination, hydrogen bonds and the like; finally, mannitol serving as a polyhydric alcohol stabilizer is introduced into the organic-inorganic composite system, and premature polymerization and precipitation of the product are inhibited by means of the chelation of mannitol on a metal center and the steric hindrance effect of mannitol on molecules; according to the invention, the complexation of zirconium ions and strong current neutralization of polyhexamethylene biguanide form synergy, the removal efficiency of phosphate is improved, the formed flocculating constituent is more compact and has high settling velocity, and the application range of the product under complex water quality conditions is widened.

Description

Technical Field

[0001] This invention belongs to the field of modified polyaluminum chloride technology, and relates to a modified polyaluminum chloride with high phosphorus removal performance, its preparation method and application. Background Technology

[0002] Eutrophication is becoming an increasingly prominent problem in water bodies, one of the main contributing factors being the presence of excessive phosphorus in industrial and domestic wastewater. Currently, chemical coagulation is one of the most widely used and cost-effective technologies for treating phosphorus-containing wastewater. By adding chemical coagulants, pollutants such as phosphates in the water become unstable and aggregate, forming flocs that are then separated. Among numerous inorganic polymeric coagulants, polyaluminum chloride (PAC) has gained widespread application due to its advantages over traditional aluminum salt coagulants, such as lower dosage and a wider applicable pH range.

[0003] However, traditional polyaluminum chloride is still insufficient in removing phosphorus from high-concentration phosphorus-containing wastewater. Furthermore, the coagulation effect is significantly affected under complex water quality conditions such as low temperature and low turbidity. In low temperature or weakly alkaline environments, high-valence aluminum hydroxyl complexes are difficult to form rapidly, leading to the attenuation of charge neutralization and netting effects, making it difficult to achieve the goal of deep phosphorus removal. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a modified polyaluminum chloride with high phosphorus removal performance, its preparation method, and its applications. This application first prepares a polyaluminum chloride zirconium mother liquor by controlling pH and constant-temperature aging; subsequently, the mother liquor is purified and subjected to an organic-inorganic composite reaction with polyhexamethylene biguanide; finally, mannitol is added to the system for stabilization. This invention improves the phosphorus removal efficiency and flocculation performance of the product through the synergistic effect of zirconium ions and the organic polymer polyhexamethylene biguanide, and broadens its application range under complex water quality conditions such as low temperature and low turbidity.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing modified polyaluminum chloride with high phosphorus removal performance, the method comprising:

[0007] Step (1): Add aluminum chloride, zirconium oxychloride, and spherical calcium carbonate to deionized water to obtain the first reaction solution. Add sodium carbonate solution to adjust the pH of the first reaction solution and then age it at a constant temperature to obtain the second reaction solution.

[0008] Step (2): After cooling the second reaction solution, filter it, add polyhexamethylene biguanide solution to the obtained filtrate and stir at a constant temperature to obtain the third reaction solution;

[0009] Step (3): Add mannitol to the third reaction solution and disperse it evenly to obtain the treatment solution. Add deionized water, stir, and filter to obtain modified polyaluminum chloride with high phosphorus removal performance.

[0010] As a preferred technical solution of the present invention, in step (1), the molar ratio of aluminum chloride to zirconium oxychloride is 1:(0.04-0.06), for example, it can be 1:0.04, 1:0.042, 1:0.044, 1:0.046, 1:0.048, 1:0.050, 1:0.052, 1:0.054, 1:0.056, 1:0.058 or 1:0.06, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0011] In some optional embodiments, the mass ratio of aluminum chloride to spherical calcium carbonate is 1:(0.08-0.12), for example, it can be 1:0.08, 1:0.084, 1:0.088, 1:0.092, 1:0.096, 1:0.100, 1:0.104, 1:0.108, 1:0.112, 1:0.116 or 1:0.12, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0012] In some optional embodiments, the concentration of aluminum chloride in the first reaction solution is 2-3M, for example, it can be 2.0M, 2.1M, 2.2M, 2.3M, 2.4M, 2.5M, 2.6M, 2.7M, 2.8M, 2.9M or 3.0M, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0013] In some alternative embodiments, the concentration of the sodium carbonate solution is 2.5-3.5M, for example, it can be 2.5M, 2.6M, 2.7M, 2.8M, 2.9M, 3.0M, 3.1M, 3.2M, 3.3M, 3.4M or 3.5M, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0014] In some alternative embodiments, the pH of the first reaction solution is adjusted to 3.8-4.0, for example, it can be 3.80, 3.82, 3.84, 3.86, 3.88, 3.90, 3.92, 3.94, 3.96, 3.98 or 4.00, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0015] In some optional embodiments, the isothermal aging temperature is 60-70°C, for example, it can be... Or 70℃, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0016] In some optional embodiments, the isothermal aging time is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0017] As a preferred technical solution of the present invention, in step (2), the second reaction solution is cooled to a temperature For example, it can be 30℃, 30.5℃, 31℃, 31.5℃, 32℃, 32.5℃, 33℃, 33.5℃, 34℃, 34.5℃ or 35℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] In some optional embodiments, the concentration of the polyhexamethylene biguanide solution is 0.5-1.0 wt%, for example, it may be 0.50 wt%, 0.55 wt%, 0.60 wt%, 0.65 wt%, 0.70 wt%, 0.75 wt%, 0.80 wt%, 0.85 wt%, 0.90 wt%, 0.95 wt%, or 1.00 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] In some optional embodiments, the amount of polyhexamethylene biguanide added is 3-5 wt% of the mass of the second reaction solution, for example, it can be 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4.0 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt%, or 5.0 wt%, but is not limited to the values ​​listed, and other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the temperature of the stirring reaction is 45-55°C, for example, it can be... Or 55℃, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0021] In some optional embodiments, the stirring reaction time is 60-70 min, for example, 60 min, 61 min, 62 min, 63 min, 64 min, 65 min, 66 min, 67 min, 68 min, 69 min or 70 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] As a preferred technical solution of the present invention, in step (3), the amount of mannitol added is 3-4% of the mass of the third reaction solution, for example, it can be 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9% or 4.0%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the modified polyaluminum chloride contains ≥10% alumina by mass.

[0024] Secondly, the present invention provides a modified polyaluminum chloride with high phosphorus removal performance.

[0025] In conventional polyaluminum chloride, the aluminum-oxygen nuclei mainly rely on charge neutralization and entrapment to remove suspended solids, while their complexation effect on phosphate is weak, and the particles are dense, the dissolution rate is slow, and the amount of sludge generated is large. This application addresses these shortcomings by modifying the polyaluminum chloride.

[0026] First, zirconium oxychloride is introduced simultaneously during the aluminum hydrolysis-condensation stage. Utilizing the high Lewis acidity of zirconium atoms and their stronger affinity for phosphate, a hybrid nucleus containing Al-O-Zr bonds is generated. The d-orbitals of zirconium can form stable coordinate bonds with the non-bonding electron pairs of phosphate, thus enabling the flocculant to rely not only on electrostatic adsorption. Simultaneously, the high valence state of zirconium increases the positive charge density of the entire nucleus, facilitating rapid charge neutralization and primary floc adhesion. During the inorganic polymerization stage, aluminum and zirconium undergo hydrolysis, constructing polynuclear hydroxyl complexes through hydroxyl and oxygen bridges. The phosphorus removal function of these complexes stems from two pathways: first, the densely distributed positive charge on their surface electrostatically attracts negatively charged phosphate ions in the water, enriching them on the complex surface; second, the active hydroxyl groups or aqueous ligands on the complex surface can form coordinate bonds with phosphate, thereby fixing the phosphate in the form of chemical precipitation. Meanwhile, high-valent cationic complexes, as coagulants, effectively reduce the negative charge on the surface of colloidal particles in water through charge neutralization, eliminate electrostatic repulsion between particles, and promote the instability and aggregation of tiny particles into micro-flocs.

[0027] Secondly, spherical calcium carbonate is used as an alkalizing agent with a controllable reaction rate. Its uniform spherical shape and specific surface area allow for slow and uniform dissolution under stirring, thereby steadily increasing the pH of the system. Compared to the rapid addition of strong bases (such as sodium hydroxide), this mild alkalization method avoids aluminum hydroxide precipitation caused by excessively high local pH, which is beneficial for guiding aluminum ions to generate more polymeric forms with high charge and excellent flocculation properties, thus optimizing the final structure and properties of the polymer.

[0028] This application introduces polyhexamethylene biguanide (PHBQ), achieving rapid coating through hydrogen bonding and electrostatic interactions between the polyguanidine cation and the polyaluminum-zirconium core surface. The guanidine group has the ability to form double hydrogen bonds and ion pairs with phosphate groups, synergistically enhancing phosphorus removal with the zirconium-oxygen site. PHBQ is an organic polymer containing repeating guanidine units in its main chain. In aqueous solution, these guanidine units are protonated, giving PHBQ the characteristics of a cationic polyelectrolyte. When mixed with positively charged aluminum-zirconium complexes, they associate through electrostatic interactions, hydrogen bonds, and coordination. The nitrogen atoms on the PHBQ molecular chain possess lone pairs of electrons, acting as Lewis bases and coordinating with Lewis acid sites (i.e., coordinate-unsaturated metal centers) on the surface of the aluminum-zirconium complex. Simultaneously, hydrogen atoms on the organic polymer can form hydrogen bond networks with hydroxyl groups or aqueous ligands on the surface of the inorganic complex. In terms of coagulation, the long-chain structure of polyhexamethylene biguanide simultaneously adsorbs multiple micro-flocs formed by charge neutralization, resulting in larger and more compact macro-flocs that accelerate the settling process. Regarding phosphorus removal, the positive charge carried by polyhexamethylene biguanide superimposed on the inorganic core further enhances the electrostatic capture capacity of the entire composite system for phosphate ions. Simultaneously, the guanidine group's positive charge remains stable over a wide pH range, compensating for the decrease in aluminum core charge density when alkalinity is insufficient, ensuring the flocs remain dense and possess a high settling velocity. The coating is achieved through physical adsorption rather than free radical polymerization, avoiding guanidine group degradation under high temperature or oxidative conditions, thus reducing energy consumption and the risk of side reactions.

[0029] In the final product formulation stage, mannitol is added as a complexing stabilizer. Mannitol is a polyol with multiple hydroxyl groups in its molecular structure, allowing it to act as a polydentate ligand. It coordinates with the metal centers on the surface of the aluminum-zirconium complex to form chelates, inhibiting further polymerization between the complexes. Furthermore, the mannitol molecules grafted onto the surface of the inorganic complexes exert a steric hindrance effect due to their own spatial volume. This effect physically hinders the approach and aggregation of the polynuclear complex particles, preventing sedimentation or gelation of the product during storage. Subsequently, deionized water is added to adjust to the target concentration, and the mixture is filtered to obtain a homogeneous, clear, and stable high-performance liquid flocculant. This liquid form eliminates the complex dissolution process of solid products, allowing for direct addition and use, resulting in a faster response and more convenient operation.

[0030] Thirdly, the present invention provides a modified polyaluminum chloride with high phosphorus removal performance for use in wastewater treatment.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This application utilizes zirconium oxychloride added during the aluminum hydrolysis-polymerization process to enable zirconium to embed into the polyaluminum core, forming Al-O-Zr bonds. Zirconium provides stable chemical phosphorus-trapping sites due to its high Lewis acidity and d-orbital coordination ability, while its high valence state increases the positive charge of the nucleus, thereby simultaneously enhancing phosphorus removal capacity and charge neutralization-flocculation rate.

[0033] In this application, polyhexamethylene biguanide (PHBQ) coats an aluminum-zirconium core via electrostatic and hydrogen bonding. The long-chain structure of PHBQ simultaneously adsorbs multiple micro-flocs formed by charge neutralization, accelerating the sedimentation process of the flocs. At the same time, the positive charge carried by PHBQ itself is superimposed on the inorganic core, further enhancing the electrostatic capture ability of phosphate ions. Its stable positive charge can maintain the density and rapid sedimentation of the flocs at low temperature or low alkali. The coating process does not require high-temperature polymerization, avoiding guanidine degradation and reducing energy consumption.

[0034] This application prepares a stable and homogeneous liquid product, with mannitol added as a complexing stabilizer to further prevent polymerization and sedimentation. The liquid product eliminates the need for dissolving solid flocculants, allowing for direct addition. The active components disperse instantly in water and exert their effects, resulting in a faster response. Due to the optimized polymer morphology and the synergistic effect of multiple phosphorus removal mechanisms, higher phosphorus removal efficiency can be achieved with lower dosages. Detailed Implementation

[0035] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0036] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0037] Example 1

[0038] This embodiment provides a modified polyaluminum chloride with high phosphorus removal performance and its preparation method. The preparation method of the modified polyaluminum chloride with high phosphorus removal performance specifically includes the following steps:

[0039] Step (1): Add aluminum chloride, zirconium oxychloride, and spherical calcium carbonate to deionized water to obtain the first reaction solution, wherein the molar ratio of aluminum chloride to zirconium oxychloride is 1:0.055, the mass ratio of aluminum chloride to spherical calcium carbonate is 1:0.12, and the concentration of aluminum chloride in the first reaction solution is 2.7M; add sodium carbonate solution with a concentration of 3.2M to adjust the pH of the first reaction solution to 3.9, and then age it at a constant temperature of 60℃ for 2.0h to obtain the second reaction solution;

[0040] Step (2): After cooling the second reaction solution to 34°C, filter it. Add polyhexamethylene biguanide solution to the obtained filtrate and stir the mixture at a constant temperature of 48°C for 68 min to obtain the third reaction solution. The concentration of the polyhexamethylene biguanide solution is 0.65 wt%, and the amount of polyhexamethylene biguanide added is 4.2 wt% of the mass of the second reaction solution.

[0041] Step (3): Add mannitol to the third reaction solution and disperse it evenly to obtain a treatment solution. The amount of mannitol added is 3% of the mass of the third reaction solution. After adding deionized water and stirring thoroughly, filter to obtain modified polyaluminum chloride with high phosphorus removal performance. The mass fraction of alumina in the modified polyaluminum chloride is ≥10%.

[0042] Example 2

[0043] This embodiment provides a modified polyaluminum chloride with high phosphorus removal performance and its preparation method. The preparation method of the modified polyaluminum chloride with high phosphorus removal performance specifically includes the following steps:

[0044] Step (1): Add aluminum chloride, zirconium oxychloride, and spherical calcium carbonate to deionized water to obtain the first reaction solution, wherein the molar ratio of aluminum chloride to zirconium oxychloride is 1:0.04, the mass ratio of aluminum chloride to spherical calcium carbonate is 1:0.10, and the concentration of aluminum chloride in the first reaction solution is 2M; add a 3.5M sodium carbonate solution to adjust the pH of the first reaction solution to 3.8 and then keep it at a constant temperature. The second reaction solution was obtained after aging for 3 hours.

[0045] Step (2): After cooling the second reaction solution to 30°C, filter it. Add polyhexamethylene biguanide solution to the obtained filtrate, and stir the mixture at a constant temperature of 50°C for 70 min to obtain the third reaction solution. The concentration of the polyhexamethylene biguanide solution is 1 wt%, and the amount of polyhexamethylene biguanide added is 3 wt% of the mass of the second reaction solution.

[0046] Step (3): Add mannitol to the third reaction solution and disperse it evenly to obtain a treatment solution, wherein the amount of mannitol added is 4% of the mass of the third reaction solution; add deionized water, stir thoroughly, and filter to obtain modified polyaluminum chloride with high phosphorus removal performance, wherein the mass fraction of alumina in the modified polyaluminum chloride is ≥10%.

[0047] Example 3

[0048] This embodiment provides a modified polyaluminum chloride with high phosphorus removal performance and its preparation method. The preparation method of the modified polyaluminum chloride with high phosphorus removal performance specifically includes the following steps:

[0049] Step (1): Add aluminum chloride, zirconium oxychloride, and spherical calcium carbonate to deionized water to obtain the first reaction solution, wherein the molar ratio of aluminum chloride to zirconium oxychloride is 1:0.06, the mass ratio of aluminum chloride to spherical calcium carbonate is 1:0.08, and the concentration of aluminum chloride in the first reaction solution is 3M; add a 2.5M sodium carbonate solution to adjust the pH of the first reaction solution to 4.0 and then keep it at a constant temperature. The second reaction solution was obtained after aging for 2.2 hours.

[0050] Step (2): After cooling the second reaction solution to 35°C, filter it. Add polyhexamethylene biguanide solution to the obtained filtrate, and stir the mixture at a constant temperature of 45°C for 60 min to obtain the third reaction solution. The concentration of the polyhexamethylene biguanide solution is 0.5 wt%, and the amount of polyhexamethylene biguanide added is 5 wt% of the mass of the second reaction solution.

[0051] Step (3): Add mannitol to the third reaction solution and disperse it evenly to obtain a treatment solution, wherein the amount of mannitol added is 3.6% of the mass of the third reaction solution; add deionized water, stir thoroughly, and filter to obtain modified polyaluminum chloride with high phosphorus removal performance, wherein the mass fraction of alumina in the modified polyaluminum chloride is ≥10%.

[0052] Example 4

[0053] This embodiment provides a modified polyaluminum chloride with high phosphorus removal performance and its preparation method. The preparation method of the modified polyaluminum chloride with high phosphorus removal performance specifically includes the following steps:

[0054] Step (1): Add aluminum chloride, zirconium oxychloride, and spherical calcium carbonate to deionized water to obtain the first reaction solution, wherein the molar ratio of aluminum chloride to zirconium oxychloride is 1:0.05, the mass ratio of aluminum chloride to spherical calcium carbonate is 1:0.11, and the concentration of aluminum chloride in the first reaction solution is 2.3M; add sodium carbonate solution with a concentration of 2.9M to adjust the pH of the first reaction solution to 3.95, and then age it at a constant temperature of 67℃ for 2.7h to obtain the second reaction solution;

[0055] Step (2): After cooling the second reaction solution to 31°C, filter it. Add polyhexamethylene biguanide solution to the obtained filtrate, and stir the mixture at a constant temperature of 55°C for 65 min to obtain the third reaction solution. The concentration of the polyhexamethylene biguanide solution is 0.8 wt%, and the amount of polyhexamethylene biguanide added is 3.6 wt% of the mass of the second reaction solution.

[0056] Step (3): Add mannitol to the third reaction solution and disperse it evenly to obtain a treatment solution, wherein the amount of mannitol added is 3.3% of the mass of the third reaction solution; add deionized water, stir thoroughly, and filter to obtain modified polyaluminum chloride with high phosphorus removal performance, wherein the mass fraction of alumina in the modified polyaluminum chloride is ≥10%.

[0057] Comparative Example 1

[0058] This comparative example provides a modified polyaluminum chloride with high phosphorus removal performance. The difference from Example 1 is that zirconium oxychloride is not added in step (1), while other operating steps and process parameters are exactly the same as in Example 1.

[0059] Comparative Example 2

[0060] This comparative example provides a modified polyaluminum chloride with high phosphorus removal performance. The difference from Example 1 is that in step (2), polyhexamethylene biguanide solution is not added. Other operating steps and process parameters are exactly the same as in Example 1.

[0061] Comparative Example 3

[0062] This comparative example provides a modified polyaluminum chloride with high phosphorus removal performance. The difference from Example 1 is that in step (1), spherical calcium carbonate is not added, and sodium hydroxide solution of the same concentration is used. Other operating steps and process parameters are exactly the same as in Example 1.

[0063] The modified polyaluminum chloride with high phosphorus removal performance in Examples 1-4 and Comparative Examples 1-3 was subjected to performance testing, and the specific process is as follows:

[0064] Phosphorus removal efficiency test: Prepare a phosphate standard water sample of known concentration and add it to the sample. Perform rapid stirring, slow stirring, and static sedimentation sequentially. Take the supernatant and measure its total phosphorus concentration using spectrophotometry. Calculate the phosphorus removal efficiency: Phosphorus removal efficiency = (phosphate standard water sample phosphorus concentration - supernatant phosphorus concentration) / phosphate standard water sample phosphorus concentration × 100%;

[0065] Flocculation performance test: Prepare a standard water sample of kaolin (or humic acid) with known turbidity and add it to the sample. Perform rapid stirring, slow stirring, and static sedimentation sequentially. Take the supernatant and measure its turbidity using a turbidimeter. Calculate the turbidity removal rate: Turbidity removal rate = (turbidity of kaolin (or humic acid) standard water sample - turbidity of supernatant) / turbidity of kaolin (or humic acid) standard water sample × 100%;

[0066] The test results are shown in Table 1.

[0067] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-3

[0068]

[0069] The test results from Example 1 and Comparative Example 1 show that omitting the addition of zirconium oxychloride resulted in the failure to form the crucial Al-O-Zr hybrid core structure. The lack of high-affinity chemilinkage sites provided by zirconium atoms led to a decrease in phosphorus removal efficiency; simultaneously, the contribution of zirconium's high valence state to increasing the overall positive charge density of the polymer also disappeared, resulting in a weakened ability to neutralize negatively charged colloids and organic matter in water, thus reducing its flocculation performance.

[0070] The test results of Example 1 and Comparative Example 2 show that omitting the introduction of polyhexamethylene biguanide and relying solely on the chemical coordination of zirconium sites weakens the phosphorus capture ability, thus reducing the phosphorus removal efficiency. At the same time, the lack of the long-chain structure of polyhexamethylene biguanide can simultaneously adsorb multiple micro-flocs formed by charge neutralization, accelerating the sedimentation of the flocs, thereby leading to a decrease in flocculation performance.

[0071] The test results of Example 1 and Comparative Example 3 show that when spherical calcium carbonate is omitted and rapid alkalization is carried out using only sodium hydroxide solution, the local pH in the reaction system becomes too high due to the rapid addition of alkali, resulting in the formation of a large amount of low-activity amorphous aluminum hydroxide precipitate. Therefore, its phosphorus removal efficiency and flocculation performance both decrease.

[0072] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing modified polyaluminum chloride with high phosphorus removal performance, characterized in that, The preparation method includes: Step (1): Add aluminum chloride, zirconium oxychloride, and spherical calcium carbonate to deionized water to obtain the first reaction solution. Add sodium carbonate solution to adjust the pH of the first reaction solution and then age it at a constant temperature to obtain the second reaction solution. Step (2): After cooling the second reaction solution, filter it, add polyhexamethylene biguanide solution to the obtained filtrate and stir at a constant temperature to obtain the third reaction solution; Step (3): Add mannitol to the third reaction solution and disperse it evenly to obtain the treatment solution. Add deionized water, stir, and filter to obtain modified polyaluminum chloride with high phosphorus removal performance.

2. The method for preparing modified polyaluminum chloride with high phosphorus removal performance according to claim 1, characterized in that, In step (1): the molar ratio of aluminum chloride to zirconium oxychloride is 1:(0.04-0.06).

3. The method for preparing modified polyaluminum chloride with high phosphorus removal performance according to claim 1, characterized in that, In step (1): the mass ratio of aluminum chloride to spherical calcium carbonate is 1:(0.08-0.12).

4. The method for preparing modified polyaluminum chloride with high phosphorus removal performance according to claim 1, characterized in that, In step (1): the sodium carbonate solution is used to adjust the pH of the first reaction solution to 3.8-4.

0.

5. The method for preparing modified polyaluminum chloride with high phosphorus removal performance according to claim 1, characterized in that, In step (2): the amount of polyhexamethylene biguanide added is 3-5 wt% of the mass of the second reaction solution.

6. The method for preparing modified polyaluminum chloride with high phosphorus removal performance according to claim 1, characterized in that, In step (3): the amount of mannitol added is 3-4% of the mass of the third reaction solution.

7. The method for preparing modified polyaluminum chloride with high phosphorus removal performance according to claim 1, characterized in that, In step (3): the mass fraction of alumina in the modified polyaluminum chloride is ≥10%.

8. A modified polyaluminum chloride with high phosphorus removal performance, characterized in that, The modified polyaluminum chloride with high phosphorus removal performance is prepared according to any one of claims 1-7.

9. The application of a modified polyaluminum chloride with high phosphorus removal performance prepared by a method according to any one of claims 1-7 in wastewater treatment.

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