A high polymerization degree water treatment agent for treating eutrophication reservoir water, a preparation method and application thereof

Abstract

The application discloses a high-polymerization-degree water treatment agent for treating eutrophication reservoir water and a preparation method and application thereof, and relates to the field of drinking water treatment. The preparation method comprises the following steps: firstly, pre-polymerization of aluminum oxide, iron oxide and phosphorus pentoxide in a high-temperature molten state to obtain a pre-polymer, and then, the final agent is prepared through the steps of acid dissolution, pH adjustment, mixing with polyacrylamide and an auxiliary flocculant, and aging. Through the unique process, the prepared agent has the characteristics of high polymerization degree, and the key index, i.e., the content of active aluminum (Ala) component (determined by using the Ferron timed complexing colorimetric method) is less than or equal to 10%. The agent is specially used for treating reservoir raw water caused by water quality fluctuation due to algal reproduction, microbial activity and water depth change, can significantly improve the removal efficiency of algae and turbidity, and fundamentally and effectively controls the residual aluminum content in the effluent, thereby guaranteeing the safety of drinking water.

Description

Technical Field

[0001] This application relates to the field of drinking water treatment, and more specifically, to a high degree of polymerization water treatment agent for treating eutrophic reservoir water, its preparation method, and its application. Background Technology

[0002] Water treatment technology is a crucial link in ensuring drinking water safety and preventing water pollution. Coagulation and sedimentation are core steps in drinking water treatment processes, and their effectiveness directly impacts the quality of the effluent from subsequent treatment processes. Currently, the water treatment industry commonly uses traditional inorganic coagulants, such as aluminum sulfate, polyaluminum chloride (PAC), and polyaluminum ferric chloride (PAFC).

[0003] Currently, the industrial production of polyaluminum ferric chloride (PAFC) mainly adopts an aqueous phase synthesis route, which involves dissolving and polymerizing aluminum- and iron-containing raw materials (such as bauxite and calcium aluminate powder) in hydrochloric acid or other acidic solutions. While this aqueous phase method is simple and low-cost, its inherent chemical properties lead to the following significant defects in the final product:

[0004] (1) Limited degree of polymerization and unstable morphology: The hydroxyl bridging reaction in an aqueous environment is a reversible equilibrium process, making it difficult to generate truly high molecular weight polymers. The obtained PAFC products generally have a low degree of polymerization, short molecular chains, and are rich in a large amount of monomeric or oligomeric aluminum (i.e., active aluminum Ala). This low degree of polymerization morphology has poor chemical stability and is considered a "quasi-stable state".

[0005] (2) Easily changeable form and prone to "free": When this low-polymerization-degree PAFC is added to eutrophic reservoir water with complex water quality conditions (such as pH and temperature fluctuations), its inherently unstable form is very prone to depolymerization or transformation. The original polymerized form will "free" back to the simple monomer or oligomer form, and its charge neutralization and bridging ability will decrease sharply. In order to maintain the coagulation effect, the operator has to increase the dosage, which directly leads to the uncontrolled increase of the concentration of free and monomeric aluminum in the water.

[0006] (3) It is not conducive to the precise control of residual aluminum: Due to the "easily free" characteristics of the above-mentioned forms, the residual aluminum content of traditional PAFC agents produced by the aqueous phase method is difficult to predict and effectively control after addition. The aluminum content in the effluent varies greatly with the fluctuation of the raw water quality. Especially when dealing with water sources with high algae and high organic matter, the risk of residual aluminum exceeding the standard is extremely high, which seriously threatens the safety of drinking water.

[0007] Existing technologies (such as CN104891628A) attempt to physically compound PAFC produced by this aqueous phase method with components such as polyacrylamide. However, this is merely an external "repair" and does not solve the fundamental problem of PAFC's unstable molecular structure and easy free flow. Just like using a chain that is inherently weak, no matter how much external reinforcement is applied, it will still easily break under critical stress.

[0008] Therefore, there is an urgent need in this field for a water treatment agent that can be innovated at the molecular structure level to prepare a water treatment agent with high polymerization degree and stable chemical form, thereby fundamentally overcoming the defects of existing technologies and achieving stable and precise control of the residual aluminum content in the effluent purified under complex water quality conditions. Summary of the Invention

[0009] To address the aforementioned problems, this application provides a high-polymerization-degree water treatment agent for treating eutrophic reservoir water, as well as its preparation method and the agent itself.

[0010] This application provides the following technical solution:

[0011] In a first aspect, this application provides a method for preparing a high-polymerization water treatment agent for treating eutrophic reservoir water. The water treatment agent, as determined by the Ferron time-by-time complexation colorimetric method, has an active aluminum (Ala) component content of ≤10%.

[0012] The preparation method includes:

[0013] Aluminum oxide, iron oxide, and phosphorus pentoxide are mixed in a molar ratio of 1-2:1:1-2 and subjected to a prepolymerization reaction in a high-temperature molten state to obtain a prepolymer. The prepolymer is dissolved in water, and the pH is adjusted to 3.0-4.0 with hydrochloric acid to obtain a stable solution containing modified polyaluminum ferric chloride.

[0014] Polyacrylamide and auxiliary flocculant are added sequentially to the stabilized solution, and the mixture is stirred at 40-60°C. The mixed solution is then aged at 50-60°C for 8-12 hours to obtain the water treatment agent.

[0015] Furthermore, in the above prepolymerization reaction, the reaction temperature in the high-temperature molten state is 900℃-1000℃, and the reaction time is 2-3 hours.

[0016] Furthermore, the mass ratio of the modified polyaluminum ferric chloride to the polyacrylamide is 50-60:0.1-0.5.

[0017] Furthermore, the aforementioned auxiliary flocculant is selected from calcium salts or magnesium salts, and the mass ratio of the modified polyaluminum ferric chloride to the auxiliary flocculant is 50-60:2-5.

[0018] Furthermore, the above preparation method also includes adding a photocatalytic material to the mixed solution before aging.

[0019] Furthermore, the photocatalytic material is TiO2, and the mass ratio of the photocatalytic material to the modified polyaluminum ferric chloride is 1-3:50-60.

[0020] Secondly, this application also provides a high degree of polymerization water treatment agent for treating eutrophic reservoir water, which is prepared by the above-mentioned preparation method; the water treatment agent is determined by Ferron time-by-time complexation colorimetry to have an active aluminum (Ala) component content of ≤10%.

[0021] Furthermore, the raw materials of the above-mentioned water treatment agent, by weight percentage, include:

[0022] Modified polyaluminum ferric chloride, content 50-60 wt%;

[0023] Polyacrylamide, content 0.1-0.5 wt%;

[0024] Auxiliary flocculant, content 2-5 wt%;

[0025] The remainder is water;

[0026] The modified polyaluminum ferric chloride is obtained by prepolymerizing aluminum oxide and iron oxide in a molten state to obtain a prepolymer, dissolving the prepolymer in water, and adjusting the pH to 3.0-4.0 with hydrochloric acid.

[0027] Thirdly, this application provides an application of the above-mentioned water treatment agent in the drinking water purification process, which is used to treat reservoir raw water whose water quality fluctuates due to algal growth and / or changes in water intake depth, so as to control the residual aluminum content in the effluent.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. This application utilizes the prepolymerization of aluminum oxide and iron oxide in a high-temperature molten state to generate a polymer precursor with a stable three-dimensional network structure. This process is an irreversible solid-phase reaction, fundamentally avoiding the reversible equilibrium limitations of aqueous methods, resulting in modified PAFCs with extremely high polymerization degree and stable morphology. This structure exhibits strong resistance to interference during water treatment and is not prone to depolymerization, laying the molecular foundation for the stable efficacy of the entire reagent.

[0030] 2. In traditional PAFCs, the high content of active aluminum monomers (Ala content greater than 30%) is the main reason for excessive residual aluminum in the effluent. This application utilizes a stable polymer formed through high-temperature prepolymerization, which primarily transforms into polymeric aluminum (Alb) and gelled aluminum (Alc) during subsequent acid dissolution, significantly reducing the formation of easily residual monomeric aluminum (Ala). This effectively controls the aluminum content in the effluent from the source. Therefore, this application significantly reduces the content of active aluminum (Ala).

[0031] 3. Traditional PAFCs pose a high safety risk when treating reservoir water with fluctuating quality, as the residual aluminum content varies drastically with operating conditions. In contrast, this application, due to the stable form of the reagent and extremely low Ala content, exhibits stable coagulation performance under different water intake depths, temperatures, and algal loads, avoiding uncontrolled aluminum content caused by fluctuations in reagent efficacy and providing reliable protection for the biosafety of drinking water.

[0032] 4. In this solution, stable modified PAFC first achieves efficient charge neutralization and initial flocculation; polyacrylamide (PAM) then bridges and strengthens the microflocculations at an optimized ratio; auxiliary flocculants (calcium / magnesium salts) further compress the double layer and provide a sedimentation framework. These three components form a functional relay of "destabilization-bridging-sedimentation promotion," resulting in dense, large flocs with rapid settling speeds, thus significantly improving the removal efficiency of turbidity, algae, and organic matter, while reducing reagent usage and the burden on subsequent treatment. Furthermore, its highly stable molecular structure allows for a wider tolerance range to changes in raw water pH and temperature, making it particularly suitable for the complex and demanding application scenario of "reservoir raw water with fluctuating water quality due to algal growth and / or changes in intake depth," demonstrating excellent adaptability to various operating conditions.

[0033] 5. In the optimized technical solution, by adding photocatalytic materials (such as TiO2) and combining them with the coagulation process, persistent organic pollutants such as microcystin that are difficult to remove by conventional processes can be effectively degraded under ultraviolet irradiation, realizing the integration of "coagulation sedimentation" and "deep oxidation" and improving the overall safety of the effluent. Attached Figure Description

[0034] Figure 1 This is a flowchart of the method provided in this application. Detailed Implementation

[0035] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0037] Example 1

[0038] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which includes the following steps:

[0039] (1) Aluminum oxide, iron oxide and phosphorus pentoxide were mixed at a molar ratio of 1.5:1:1 and prepolymerized at 950°C in a molten state for 2 hours to obtain a prepolymer.

[0040] (2) Dissolve the prepolymer in water and adjust the pH to 3.0-4.0 with hydrochloric acid to obtain a stable solution containing 55wt% modified polyaluminum ferric chloride;

[0041] (3) Add polyacrylamide (0.3wt%) and auxiliary flocculant CaCl2 (3.5wt%) to the stable solution in sequence, and stir and mix at 55°C;

[0042] (4) The mixed solution is aged at 55°C for 10 hours to obtain the water treatment agent.

[0043] Example 2

[0044] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Example 1 in step (1):

[0045] Aluminum oxide, iron oxide, and phosphorus pentoxide were mixed in a molar ratio of 2:1:1 and subjected to a prepolymerization reaction at 980°C in a molten state for 2 hours to obtain a prepolymer.

[0046] Example 3

[0047] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Example 1 in step (1):

[0048] Aluminum oxide, iron oxide, and phosphorus pentoxide were mixed in a 1:1:1 molar ratio and subjected to a prepolymerization reaction at 930°C in a molten state for 2 hours to obtain a prepolymer.

[0049] Example 4

[0050] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Example 1 in step (4):

[0051] The mixed solution was aged at 50°C for 12 hours to obtain the water treatment agent.

[0052] Example 5

[0053] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Example 1 in step (4):

[0054] The mixed solution was aged at 60°C for 8 hours to obtain the water treatment agent.

[0055] Example 6

[0056] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Example 1 in step (3):

[0057] Polyacrylamide (0.3 wt%) and auxiliary flocculant MgCl2 (3.5 wt%) were added sequentially to the stable solution and stirred at 60°C.

[0058] Example 7

[0059] This embodiment provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Example 1 in that it further includes a step of adding a photocatalytic material:

[0060] (3) Add polyacrylamide (0.3wt%), auxiliary flocculant CaCl2 (3.5wt%) and photocatalytic material TiO2 (2.0wt%) to the stable solution in sequence, and stir and mix at 40-60℃.

[0061] Examples 8-10

[0062] This set of embodiments provides a high degree of polymerization water treatment agent, the preparation method of which differs from that of Embodiment 1 in the mixing ratio of materials, as shown in Table 1.

[0063] Table 1.

[0064] Modified PAFC (wt%) Polyacrylamide (wt%) Auxiliary flocculant (wt%) Photocatalytic materials (wt%) water Example 1 55 0.3 3.5 / margin Example 7 55 0.3 3.5 2.0 margin Example 8 60 0.1 2 / margin Example 9 50 0.5 5 1.0 margin Example 10 53 0.2 2.5 3.0 margin

[0065] Comparative Example 1

[0066] This comparative example provides a water treatment agent, which is formed by compounding commercially available polyaluminum ferric chloride (synthesized by aqueous phase method, 55wt%) with polyacrylamide (0.3wt%), CaCl2 (3.5wt%) and water.

[0067] Comparative Example 2

[0068] This comparative example provides a water treatment agent whose raw materials and component ratios are the same as those in Comparative Example 1, except that the preparation method is as follows:

[0069] Commercially available polyaluminum ferric chloride is dissolved in water to form a stable solution;

[0070] Polyacrylamide and auxiliary flocculant CaCl2 were added sequentially to a stable solution and stirred at 60°C. The mixed solution was then aged at 55°C for 10 hours to obtain the water treatment agent.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 1 is that the maturation process in step (4) is missing: that is, no maturation is performed after step (3) is completed.

[0073] Performance testing

[0074] Determination of active aluminum (Ala) content:

[0075] The active aluminum (Ala) content in the water treatment agents provided in the examples and comparative examples was determined using the Ferron time-wise complexometric colorimetric method. The specific method is as follows:

[0076] Ferron reagent, hydroxylamine hydrochloride (as an antioxidant), and acetate-sodium acetate buffer were mixed in a certain proportion to control the pH value of the reaction system, thus obtaining Ferron buffer solution.

[0077] The water treatment agent samples provided in the examples and comparative examples were diluted to appropriate concentrations.

[0078] The diluted sample was quickly added to the Ferron buffer, mixed thoroughly, and the timing was started immediately.

[0079] Using a UV-Vis spectrophotometer, the absorbance of the reaction solution was measured continuously or intermittently at a specific wavelength of 370 nm for 1 minute, 2 minutes, 5 minutes, 10 minutes... up to 120 minutes.

[0080] A kinetic curve was obtained by plotting absorbance against time. By extrapolation and curve fitting, the absorbance values ​​at 1 minute and 120 minutes were calculated, corresponding to the contents of Ala and (Ala+Alb), respectively, thus allowing the percentage distribution of the three forms, Ala, Alb, and Alc, to be calculated.

[0081] The results are shown in Table 2:

[0082] Table 2.

[0083] Ala (%) Alb (%) Alc (%) Example 1 8.5 86.1 5.4 Example 2 9.2 83.2 7.6 Example 3 9.4 80.2 10.4 Example 7 8.7 86.3 5.0 Comparative Example 1 36.2 48.5 15.3 Comparative Example 2 32.5 49.6 17.9 Comparative Example 3 18.9 75.6 4.5

[0084] As shown in Table 2, the water treatment agents prepared using the high-temperature melt prepolymerization process in the embodiments of this application have an active aluminum content of less than 10%, with Example 1 being the best. In contrast, Comparative Examples 1 and 2, which use PAFC synthesized via the traditional aqueous phase method as raw material, have an active aluminum content greater than 30% in their final products, which is detrimental to aluminum content control. This demonstrates that the high-temperature melt prepolymerization process of this application can significantly improve the degree of polymerization and stability of the agent. In Comparative Example 3, because no curing process was performed during the synthesis of the water treatment agent, the active aluminum content in the final product increased. This is mainly because the curing process promotes the conversion of active aluminum into moderately polymerized aluminum, thereby making the modified PAFC structure more stable.

[0085] II. Water Treatment Application Examples

[0086] The water treatment agents provided in Examples 1 and 7, and Comparative Examples 1-3, were used to treat eutrophic reservoir water. 1. Preparation of experimental water samples: Eutrophic reservoir water was selected during the high-temperature period of summer. The reservoir water conditions are shown in Table 3.

[0087] Table 3.

[0088] Turbidity algae concentration COD pH Reservoir water samples 18 NTU 28μg / L 6.0 mg / L 8.2

[0089] Note: Algal concentration is characterized by chlorophyll a concentration, and the main algae contained is Microcystis aeruginosa.

[0090] 2. Experimental Methods

[0091] The water sample from the reservoir was placed in a beaker, and the water treatment agents provided in Examples 1, 7, and Comparative Examples 1-3 were added at a dosage of 10 mg / L. The mixture was stirred rapidly at 300 rpm for 2 minutes, followed by slow stirring at 40 rpm for 15 minutes, and then allowed to settle for 30 minutes under UV irradiation throughout. Finally, the supernatant was collected and various indicators were tested. The results are shown in Table 4.

[0092] 3. Experimental Results

[0093] Table 4.

[0094] detection indicators Residual aluminum (mg / L) Turbidity removal rate (%) Algae removal rate (%) COD removal rate (%) Overall observation Example 1 0.08 97.4 91.8 56.3 Large and dense flocs with fast settling speed Example 7 0.07 98.2 97.5 58.5 Large and dense flocs with fast settling speed Comparative Example 1 0.18 88 78.5 42.5 The flocs are small, loose, and settle slowly. Comparative Example 2 0.16 90.2 84.3 48.3 The flocs are small, loose, and settle slowly. Comparative Example 3 0.12 92.6 88.6 53.4 The flocs are small, loose, and settle slowly.

[0095] As shown in Table 4, for eutrophic reservoir water during the high-temperature period in summer, the water treatment agents provided in Examples 1 and 7 of this application can stably control the residual aluminum in the effluent within the safe limit of 0.1 mg / L, while the residual aluminum in Comparative Examples 1 and 2 (using conventional PAFC) exceeds the standard. The treatment results of Comparative Example 3 still fail to meet the safety limits. Meanwhile, the water treatment agents in Examples 1 and 7 show significantly better removal rates for turbidity, algae, and organic matter than the comparative examples. Furthermore, because TiO2 was added as a photocatalyst in Example 7, under the same conditions, its treatment results for reservoir water samples are superior to Example 1, especially in significantly improving the removal rate of algae. These specific embodiments are merely explanations of this application and are not intended to limit it. Those skilled in the art can make modifications to these embodiments without contributing any inventive step after reading this specification, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a high-polymerization degree water treatment agent for treating eutrophic reservoir water, characterized in that, The water treatment agent, as determined by the Ferron time-by-time complexation colorimetric method, has an active aluminum (Ala) component content of ≤10%. The preparation method includes: Aluminum oxide, iron oxide, and phosphorus pentoxide are mixed in a molar ratio of 1-2:1:1-2 and subjected to a prepolymerization reaction in a high-temperature molten state at a reaction temperature of 900℃-1000℃ for 1-3 hours to obtain a prepolymer. The prepolymer is then dissolved in water, and the pH is adjusted to 3.0-4.0 with hydrochloric acid to obtain a stable solution containing modified polyaluminum ferric chloride. Polyacrylamide and auxiliary flocculant are added sequentially to the stabilized solution, and the mixture is stirred at 40-60°C. The mixed solution is then aged at 50-60°C for 8-12 hours to obtain the water treatment agent.

2. The method for preparing the high-polymerization degree water treatment agent according to claim 1, characterized in that, The mass ratio of the modified polyaluminum ferric chloride to the polyacrylamide is 50-60:0.1-0.

5.

3. The method for preparing the high-polymerization degree water treatment agent according to claim 1, characterized in that, The auxiliary flocculant is selected from calcium salts or magnesium salts, and the mass ratio of the modified polyaluminum ferric chloride to the auxiliary flocculant is 50-60:2-5.

4. The method for preparing the high-polymerization-degree water treatment agent according to claim 1, characterized in that, It also includes adding a photocatalytic material to the mixed solution before aging.

5. The method for preparing the high-polymerization-degree water treatment agent according to claim 4, characterized in that, The photocatalytic material is TiO2, and the mass ratio of the photocatalytic material to the modified polyaluminum ferric chloride is 1-3:50-60.

6. A high-polymerization water treatment agent for treating eutrophic reservoir water, characterized in that, The water treatment agent is prepared by the preparation method according to any one of claims 1-5; the water treatment agent is determined by Ferron time-by-time complexation colorimetry to have an active aluminum (Ala) component content ≤10%.

7. The high-polymerization-degree water treatment agent for treating eutrophic reservoir water according to claim 6, characterized in that, The raw materials of the water treatment agent, by weight percentage, include: Modified polyaluminum ferric chloride, content 50-60 wt%; Polyacrylamide, content 0.1-0.5 wt%; Auxiliary flocculant, content 2-5 wt%; The remainder is water; The modified polyaluminum ferric chloride is obtained by mixing aluminum oxide, iron oxide and phosphorus pentoxide in a molar ratio of 1-2:1:1-2 and carrying out a prepolymerization reaction in a high-temperature molten state at a reaction temperature of 900℃-1000℃ for 1-3 hours. After obtaining the prepolymer, the prepolymer is dissolved in water, and the pH is adjusted to 3.0-4.0 with hydrochloric acid to obtain the modified polyaluminum ferric chloride.

8. The application of a water treatment agent as described in claim 6 or 7 in the drinking water purification process, characterized in that, It is used to treat reservoir raw water whose water quality fluctuates due to algal growth and / or changes in water intake depth, in order to control the residual aluminum content in the effluent.

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