Magnetite flocculants, methods of making and using the same

Abstract

The application discloses a magnetite flocculant and a preparation method and application thereof, and the preparation method comprises the following steps: mixing ferrous salt and iron salt in water to obtain a first mixed solution; mixing the first mixed solution with triphosphate to obtain a second mixed solution, and adjusting the pH of the second mixed solution to 8-11 to obtain a third mixed solution containing iron ion coprecipitate; and allowing the third mixed solution to undergo hydrothermal reaction at 60-120 DEG C for 2-6 hours to obtain the magnetite flocculant. Thus, the particle size and morphology of the magnetite flocculant are precisely controlled, the dispersibility of the magnetite flocculant is remarkably improved, the particle agglomeration phenomenon is effectively inhibited, the magnetite flocculant can maintain good stability and suspensibility in the aqueous solution, and the magnetite flocculant is convenient for fully contacting with pollutants. Moreover, the synthesis process does not need to frequently monitor and adjust the pH value of the reaction system, the operation process is simplified, the production cost is reduced, and the feasibility of industrial production is improved.

Description

Technical Field

[0001] This application relates to the field of water treatment technology, specifically to magnetite flocculants, their preparation methods, and applications. Background Technology

[0002] Magnetite, due to its excellent magnetic properties, chemical stability, and surface activity, is widely used as a magnetic flocculant in water treatment. Traditional magnetite flocculants are mostly prepared through co-precipitation and hydrothermal methods, but these methods suffer from problems such as uneven particle size, uncontrollable morphology, and a limited number of surface active sites, resulting in low adsorption efficiency for pollutants, poor magnetic separation effects, and difficulty in reuse. Existing methods for preparing magnetite flocculants, such as the mechanochemical action combining ball milling and acid-modified surface treatment, can improve the surface activity and adsorption capacity of magnetite powder, but they fail to effectively solve the problems of particle agglomeration and slow sedimentation. Furthermore, traditional preparation techniques often rely on surfactants or complex modification processes to improve performance, which not only increases production costs but may also introduce the risk of secondary pollution. Some methods synthesize magnetic flocculants by recovering flocs, achieving magnetic recovery of the flocs, but still have shortcomings in controlling magnetite crystal growth, particle size, and dispersibility. Therefore, the preparation methods of magnetite flocculants still need further improvement.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0004] In a first aspect of this application, a method for preparing a magnetite flocculant is provided, comprising:

[0005] Ferrous salt and ferric salt are mixed in water to obtain the first mixture;

[0006] The first mixture is mixed with tripolyphosphate to obtain a second mixture, and the pH of the second mixture is adjusted to 8-11 to obtain a third mixture containing iron ion coprecipitates;

[0007] The third mixture is subjected to hydrothermal reaction at 60℃~120℃ for 2h~6h to obtain magnetite flocculant.

[0008] This application prepares a magnetite flocculant using the above method. The addition of tripolyphosphate enables precise control of the particle size and morphology of the magnetite flocculant, significantly improving its dispersibility, effectively inhibiting particle aggregation, and maintaining good stability and suspension in aqueous solution, facilitating sufficient contact with pollutants. Furthermore, the synthesis process eliminates the need for frequent monitoring and adjustment of the pH value of the reaction system, simplifying the operation, reducing production costs, and enhancing the feasibility of industrial production.

[0009] In addition, the preparation method described above according to this application may also have the following additional technical features:

[0010] In some embodiments of this application, the tripolyphosphate includes at least one of sodium tripolyphosphate, potassium tripolyphosphate, and ammonium tripolyphosphate. Therefore, the material is widely available, which is beneficial for improving the dispersibility and surface activity of the magnetite flocculant, thereby increasing the flocculation efficiency of the magnetite flocculant.

[0011] In some embodiments of this application, the molar ratio of the tripolyphosphate to the molar ratio of iron ions in the first mixture is (5-20):100. This facilitates a more complete reaction between the tripolyphosphate and iron ions, reducing raw material waste.

[0012] In some embodiments of this application, the ferrous salt includes at least one selected from FeCl2, FeSO4, and Fe(NO3)2. Therefore, a wide range of ferrous salts can be selected, and the addition of ferrous salts helps to form magnetite, thereby improving the adsorption and flocculation efficiency of magnetite flocculants for pollutants.

[0013] In some embodiments of this application, the iron salt includes at least one selected from FeCl3, Fe2(SO4)3, and Fe(NO3)3. Therefore, a wide range of iron salts can be selected, and the addition of iron salts helps to form magnetite, thereby improving the adsorption and flocculation efficiency of magnetite flocculants for pollutants.

[0014] In some embodiments of this application, an alkaline solution is added to adjust the pH of the second mixture to 8-11. The alkaline solution includes at least one of ammonia, sodium hydroxide solution, and potassium hydroxide solution. This allows for the wide availability of materials, which is beneficial for precipitating iron ions and accelerating the nucleation and growth reactions of magnetite crystals.

[0015] In some embodiments of this application, the molar ratio of the ferrous salt to the ferric salt is 1:(2-3). This facilitates the formation of magnetite with an ideal chemical composition, thereby improving the flocculation efficiency of the magnetite flocculant.

[0016] In some embodiments of this application, the concentration of iron ions in the first mixture is 0.1 mol / L to 1 mol / L. This is beneficial for promoting the formation of a complete spinel structure (FeO) in magnetite crystals, enhancing the intrinsic magnetism of the material, and simultaneously enabling iron ions to form a stable complex system with tripolyphosphate.

[0017] In some embodiments of this application, the second mixture is stirred at a temperature of 30°C to 60°C and at a stirring speed of 400 rpm to 600 rpm. This facilitates more uniform mixing and improves the reaction rate and stability.

[0018] In a second aspect of this application, a magnetite flocculant is provided, which is prepared using the method described in the first aspect of this application. Therefore, this magnetite flocculant possesses a uniform nanoscale particle size distribution, high specific surface area, and abundant surface-active groups, while optimizing the charge distribution on the magnetite surface, significantly improving the adsorption and flocculation efficiency for suspended solids, heavy metal ions, and organic pollutants in water.

[0019] In some embodiments of this application, the specific surface area of ​​the magnetite flocculant is 50 m². 2 / g~150m 2 / g. Therefore, this magnetite flocculant can provide more active sites for pollutants, which is beneficial for enhancing adsorption capacity.

[0020] In some embodiments of this application, the particle size of the magnetite flocculant is 20 nm to 100 nm. This is beneficial for improving the dispersibility of the magnetite flocculant.

[0021] In some embodiments of this application, the standard deviation of the particle size distribution of the magnetite flocculant is ≤15nm. Therefore, the magnetite flocculant has a more uniform particle size distribution, which improves the collision efficiency with pollutants, helps to form larger and more stable flocs, and accelerates the sedimentation process.

[0022] In some embodiments of this application, the surface Zeta potential of the magnetite flocculant is -20mV to -40mV. This is beneficial for optimizing the surface charge characteristics of the magnetite flocculant, enhancing its electrostatic attraction to pollutant particles with opposite charges, and thus improving flocculation efficiency.

[0023] In a third aspect, this application proposes the application of the magnetite flocculant described in the second aspect in water treatment. Therefore, this magnetite flocculant has broad application prospects in fields such as industrial wastewater treatment and drinking water purification. Attached Figure Description

[0024] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0025] Figure 1 This is a photograph of the appearance of the magnetite flocculant prepared in Example 1 of this application;

[0026] Figure 2 These are the XRD patterns of the magnetite flocculants prepared in Examples 1 and 2 of this application;

[0027] Figure 3 This is a scanning electron microscope (SEM) image of the magnetite flocculant prepared in Example 3 of this application;

[0028] Figure 4 This is a transmission electron microscope (TEM) image of the magnetite flocculant prepared in Example 4 of this application;

[0029] Figure 5 This is a STEM-EDS image of the magnetite flocculant prepared in Example 5 of this application;

[0030] Figure 6 This is a VSM diagram of the magnetite flocculant prepared in Examples 1 and 2 of this application;

[0031] Figure 7 This is an XPS image of the magnetite flocculant prepared in Example 3 of this application;

[0032] Figure 8 This is the FTIR image of the magnetite flocculant prepared in Example 3 of this application;

[0033] Figure 9 This is a Raman diagram of the magnetite flocculant prepared in Example 3 of this application;

[0034] Figure 10 This is a scanning electron microscope (SEM) image of the magnetite flocculant prepared in Comparative Example 1 of this application. Detailed Implementation

[0035] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0036] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0037] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0038] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0039] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0041] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0042] In this application, the order in which the steps are written does not imply a strict execution order and does not limit the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] Related technologies optimize magnetite performance by adding regulators, but technical bottlenecks remain in achieving precise particle size control, morphology control, and efficient recycling. For example, it is difficult to simultaneously control the uniform growth of magnetite particles within the 20nm–100nm range, and there is a lack of effective means to regulate their surface active groups, resulting in limited removal efficiency for suspended solids, heavy metal ions, and organic pollutants in water. Furthermore, traditional magnetic flocculants are prone to magnetic attenuation and decreased adsorption performance after repeated use, failing to meet the demands for efficient and environmentally friendly flocculants in industrial wastewater and drinking water purification. Preparing Fe3O4 particles with controllable size and morphology, surface-loaded with special functional groups (such as -OH groups), and possessing good magnetic properties (high magnetization and low coercivity) is key to enhancing magnetic flocculation water treatment technology.

[0044] In this application, by introducing tripolyphosphate as a bifunctional regulator into the magnetite synthesis system, and utilizing the directional regulation of iron ion hydrolysis and crystal growth by tripolyphosphate under co-precipitation reaction conditions, precise control of magnetite particle morphology and size is achieved. Simultaneously, the addition of tripolyphosphate significantly improves the dispersibility of the magnetite flocculant, effectively inhibiting particle agglomeration and maintaining good stability and suspension in aqueous solution, facilitating sufficient contact with pollutants. Furthermore, through the electrostatic adsorption and steric hindrance effect of tripolyphosphate, the prepared magnetite flocculant possesses a uniform nanoscale particle size distribution, high specific surface area, and abundant surface-active groups, while optimizing the charge distribution on the magnetite surface, significantly improving the adsorption and flocculation efficiency for suspended solids, heavy metal ions, and organic pollutants in water.

[0045] In a first aspect of this application, a method for preparing a magnetite flocculant is provided, comprising:

[0046] S1: Mix ferrous salt and ferric salt in water to obtain the first mixture.

[0047] In some embodiments of this application, the ferrous salt includes at least one selected from FeCl2, FeSO4, and Fe(NO3)2. Therefore, a wide range of ferrous salts can be selected, and the addition of ferrous salts helps to form magnetite, thereby improving the adsorption and flocculation efficiency of magnetite flocculants for pollutants.

[0048] In some embodiments of this application, the iron salt includes at least one selected from FeCl3, Fe2(SO4)3, and Fe(NO3)3. Therefore, a wide range of iron salts can be selected, and the addition of iron salts helps to form magnetite, thereby improving the adsorption and flocculation efficiency of magnetite flocculants for pollutants.

[0049] In some embodiments of this application, the molar ratio of ferrous salt to ferric salt is 1:(2-3), for example, 1:2, 1:2.5, or 1:3. This facilitates the formation of magnetite with an ideal chemical composition, thereby improving the flocculation efficiency of the magnetite flocculant.

[0050] In some embodiments of this application, the concentration of iron ions in the first mixture is 0.1 mol / L to 1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, or 1 mol / L. An iron ion concentration within the above range is beneficial for promoting the formation of a complete spinel structure (FeO) in magnetite crystals, enhancing the intrinsic magnetism of the material, and simultaneously enabling iron ions to form a stable complex system with tripolyphosphate.

[0051] S2: Mix the first mixture with tripolyphosphate to obtain the second mixture, and adjust the pH of the second mixture to 8-11 to obtain the third mixture containing iron ion coprecipitate.

[0052] As an example, tripolyphosphate can be added to the first mixture, and after stirring continuously for 30 minutes, an alkaline solution can be added dropwise to adjust the pH to 8-11 to accelerate the nucleation and growth reaction of magnetite crystals, so as to obtain a third mixture containing iron ion coprecipitates.

[0053] In some embodiments of this application, the tripolyphosphate includes at least one of sodium tripolyphosphate, potassium tripolyphosphate, and ammonium tripolyphosphate. Therefore, the material is widely available, which is beneficial for improving the dispersibility and surface activity of the magnetite flocculant, thereby increasing the flocculation efficiency of the magnetite flocculant.

[0054] In some embodiments of this application, the molar ratio of tripolyphosphate to iron ions in the first mixture is (5-20):100, for example, 5:100, 10:100, 15:100, or 20:100. This facilitates a more complete reaction between the tripolyphosphate and iron ions, reducing raw material waste.

[0055] In some embodiments of this application, an alkaline solution is added to adjust the pH of the second mixture to 8-11 (e.g., 8, 9, 10, or 11). The alkaline solution includes at least one of ammonia, sodium hydroxide solution, and potassium hydroxide solution. This allows for the wide availability of materials, which is beneficial for precipitating iron ions and triggering the nucleation and growth reactions of magnetite crystals.

[0056] In some embodiments of this application, the second mixture is stirred at a temperature of 30°C to 60°C (e.g., 30°C, 40°C, 50°C, or 60°C) and a stirring rate of 400 rpm to 600 rpm (e.g., 400 rpm, 500 rpm, or 600 rpm). This facilitates more uniform mixing and improves the reaction rate and stability.

[0057] S3: Allow the third mixture to undergo a hydrothermal reaction at 60℃~120℃ (e.g., 60℃, 80℃, 100℃ or 120℃) for 2h~6h (e.g., 2h, 3h, 4h, 5h or 6h) to obtain magnetite flocculant.

[0058] In this step, the growth process of magnetite crystals can be precisely controlled by adjusting the temperature and time of the hydrothermal reaction.

[0059] In some embodiments of this application, the reactants obtained from the hydrothermal reaction may also be subjected to centrifugation, washing, and drying processes to separate and purify the magnetite flocculant.

[0060] This application prepares magnetite flocculant using the above method. The addition of tripolyphosphate enables precise control of the particle size and morphology of the magnetite flocculant, significantly improving its dispersibility, effectively inhibiting particle aggregation, and maintaining good stability and suspension in aqueous solution, facilitating full contact with pollutants. Furthermore, the synthesis process eliminates the need for frequent monitoring and adjustment of the pH value of the reaction system, simplifying the operation, reducing production costs, and enhancing the feasibility of industrial production.

[0061] In a second aspect of this application, a magnetite flocculant is provided, which is prepared using the method described in the first aspect of this application. This magnetite flocculant possesses a uniform nanoscale particle size distribution, high specific surface area, and abundant surface-active groups, while also optimizing the charge distribution on the magnetite surface, significantly improving the adsorption and flocculation efficiency for suspended solids, heavy metal ions, and organic pollutants in water.

[0062] In some embodiments of this application, the specific surface area of ​​the magnetite flocculant is 50 m². 2 / g~150m 2 / g, for example, can be 50m 2 / g、70m 2 / g、90m2 / g、110m 2 / g、130m 2 / g or 150m 2 / g, etc. Specific surface area refers to the total surface area per unit mass of magnetite flocculant, which can be measured by BET. Within the above-mentioned specific surface area range, magnetite flocculants possess a greater number of active sites, which is beneficial for enhancing adsorption capacity.

[0063] In some embodiments of this application, the particle size of the magnetite flocculant is 20 nm to 100 nm, for example, it can be 20 nm, 40 nm, 60 nm, 80 nm or 100 nm. This is beneficial to improving the dispersibility of the magnetite flocculant.

[0064] In some embodiments of this application, the standard deviation of the particle size distribution of the magnetite flocculant is ≤15nm, for example, it can be 1nm, 3nm, 5nm, 7nm, 9nm, 11nm, 13nm, or 15nm. The standard deviation of the particle size distribution measures the dispersion of the magnetite flocculant particle size; the smaller the standard deviation, the more concentrated the distribution and the better the uniformity. When the standard deviation of the particle size distribution is within the above range, the magnetite flocculant has a more uniform particle size distribution, which can improve the collision efficiency with pollutants, help form larger and more stable flocs, and accelerate the sedimentation process.

[0065] In some embodiments of this application, the surface Zeta potential of the magnetite flocculant is -20mV to -40mV, for example, it can be -20mV, -25mV, -30mV, -35mV, or -40mV. This is beneficial for optimizing the surface charge characteristics of the magnetite flocculant, enhancing its electrostatic attraction to oppositely charged pollutant particles, and thus improving flocculation efficiency.

[0066] The magnetite flocculant prepared in this application has at least the following beneficial effects:

[0067] (1) Precise controllability: The preparation process is simplified, avoiding the fine pH control and complex modification steps in traditional methods. The reaction conditions are mild and the reaction time is short, reducing production difficulty and energy consumption, which is conducive to large-scale industrial production. Breaking through the limitations of traditional methods, the particle size and morphology of magnetite flocculant particles can be precisely controlled through the electrostatic adsorption and steric hindrance effect of tripolyphosphate. The particle size distribution standard deviation is small and the particle size uniformity is high, which can effectively enhance the adsorption specificity for different pollutants.

[0068] (2) High surface activity: Tripolyphosphate regulation makes the surface of magnetite flocculant rich in -OH and PO4. 3- It has active groups and a higher specific surface area than traditional flocculants.

[0069] (3) Excellent magnetic properties and recyclability: It can be used multiple times when the applied magnetic field strength is ≥0.1T, which helps to solve the problem of poor cycle stability of traditional magnetic flocculants.

[0070] (4) Environmentally friendly: No additional polluting additives are introduced. Tripolyphosphate can participate in the reaction to form a functional structure, reducing the risk of secondary pollution and conforming to the concept of green chemistry.

[0071] (5) Low cost: Raw materials are widely available and inexpensive, and the preparation process is simple, reducing raw material costs and production equipment requirements, thus enhancing the product's market competitiveness. The method for controllable synthesis of magnetite flocculants using tripolyphosphate provided in this application, compared to traditional methods, eliminates the need for complex surfactants and modification processes. High-performance magnetite flocculants can be prepared through simple raw material ratios and reaction condition control. The preparation process of magnetite flocculants is green and efficient, requiring no additional surfactants or template agents, reducing chemical residues and potential environmental hazards.

[0072] (6) Easy to recycle: Utilizing the inherent magnetism of magnetite and the complexing ability of tripolyphosphate, the magnetite flocculant can be quickly separated, recycled and reused through an external magnetic field.

[0073] In a third aspect, this application discloses the application of the magnetite flocculant of the second aspect in water treatment. Therefore, this magnetite flocculant has broad application prospects in fields such as industrial wastewater treatment and drinking water purification.

[0074] In some specific applications, magnetite flocculant is added to the water to be treated at a concentration of 50 mg / L to 200 mg / L, and the mixture is stirred at a speed of 100 rpm to 300 rpm for 10 min to 30 min. The flocs are then rapidly separated by an external magnetic field. The water to be treated includes wastewater containing suspended solids, wastewater containing heavy metal ions, or wastewater containing organic pollutants.

[0075] In some embodiments of this application, the organic pollutants include humic acid, methyl orange, or tetracycline, and the heavy metal ions include Pb. 2+ Cu 2+ or Cd 2+ The concentrations of pollutants in the treated water are all lower than the national emission standards. (Specific implementation method)

[0076] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0077] Example 1

[0078] (1) Weigh 0.05 mol of FeCl2·4H2O and 0.1 mol of FeCl3·6H2O, dissolve them in 500 mL of deionized water to form a mixed solution with a total iron ion concentration of 0.3 mol / L (FeCl2·4H2O). 2+ with Fe 3+ The molar ratio is 1:2;

[0079] (2) Add 5.7g of sodium tripolyphosphate (accounting for 5% of the total iron ion molar amount) under magnetic stirring at 40℃ and continue stirring for 30min;

[0080] (3) Add 25% ammonia water to adjust the pH to 9. After a black precipitate is formed, transfer it to a 1L hydrothermal reactor and react at 100℃ for 4 hours.

[0081] (4) Centrifuge (8000 rpm, 10 min), wash three times each with deionized water and ethanol, and vacuum dry at 60℃ for 12 h to obtain spherical magnetite flocculant powder.

[0082] Test data:

[0083] SEM showed that the average particle size was 45 nm and the standard deviation of the particle size distribution was 12 nm.

[0084] BET has a specific surface area of ​​110m². 2 / g, surface-active groups -OH and PO4 3- The proportion is 85%;

[0085] For Pb 2+ The removal rate of (50 mg / L) was 96.2%, and the magnetic separation time was 3 min.

[0086] Example 2

[0087] (1) Weigh 0.08 mol of FeSO4·7H2O and 0.12 mol of Fe2(SO4)3·9H2O, dissolve them in 800 mL of deionized water to form a mixed solution with a total iron ion concentration of 0.25 mol / L (Fe 2+ with Fe 3+ The molar ratio is 2:3;

[0088] (2) Add 16.5g of potassium tripolyphosphate (accounting for 10% of the total iron ion molar amount) under magnetic stirring at 50℃ and continue stirring for 40min;

[0089] (3) Add sodium hydroxide solution to adjust the pH to 10. After a black precipitate is formed, transfer it to a 1L hydrothermal reactor and react at 120℃ for 6 hours.

[0090] (4) Centrifuge (8000 rpm, 10 min), wash three times each with deionized water and ethanol, and vacuum dry at 60℃ for 12 h to obtain rod-shaped magnetite flocculant powder.

[0091] Test data:

[0092] TEM showed that the rod-shaped particles had an aspect ratio of 3:1 and an average particle size of 60 nm.

[0093] The zeta potential is -35mV, and the adsorption capacity for humic acid (100mg / L) is 220mg / g.

[0094] After 10 cycles of use, the removal efficiency decreases by 8.5%.

[0095] Example 3

[0096] (1) Weigh out 0.06 mol of Fe(NO3)2·6H2O and 0.12 mol of Fe(NO3)3·9H2O, dissolve them in 600 mL of deionized water to form a mixed solution with a total iron ion concentration of 0.3 mol / L (Fe 2+ with Fe 3+ The molar ratio is 1:2;

[0097] (2) Add 18.2g of ammonium tripolyphosphate (accounting for 15% of the total iron ion molar amount) under magnetic stirring at 30℃ and continue stirring for 25min;

[0098] (3) Add potassium hydroxide solution to adjust the pH to 8.5. After a black precipitate is formed, transfer it to a 1L hydrothermal reactor and react at 80℃ for 3 hours.

[0099] (4) Centrifuge (8000 rpm, 10 min), wash three times each with deionized water and ethanol, and vacuum dry at 60℃ for 12 h to obtain flake magnetite flocculant powder.

[0100] Test data:

[0101] SEM showed that the sheet thickness was 20 nm and the lateral dimension was 80 nm to 100 nm.

[0102] Specific surface area is 135m² 2 / g, the removal rate of methyl orange (80mg / L) was 97.8%;

[0103] Magnetic response rate: The sedimentation rate was 98.3% after 5 minutes in a 0.1T magnetic field.

[0104] Example 4

[0105] (1) Weigh out 0.33 mol of FeCl2·4H2O and 0.66 mol of FeCl3·6H2O, dissolve them in 1 L of deionized water to form a mixed solution with a total iron ion concentration of 0.99 mol / L (FeCl2·4H2O). 2+ with Fe 3+ The molar ratio is 1:2;

[0106] (2) Add 38.5g of sodium tripolyphosphate (accounting for 12% of the total iron ion molar amount) under magnetic stirring at 60℃ and continue stirring for 30min;

[0107] (3) Add 25% ammonia water to adjust the pH to 9.5. After a black precipitate is formed, transfer it to a 1.5L hydrothermal reactor and react at 90℃ for 5 hours.

[0108] (4) Centrifuge (8000 rpm, 10 min), wash three times each with deionized water and ethanol, and vacuum dry at 60℃ for 12 h to obtain spherical magnetite flocculant powder.

[0109] Test data:

[0110] The particle size distribution is 20 nm to 80 nm, and the standard deviation of the particle size distribution is 15 nm.

[0111] For Cd 2+ The removal rate of (30 mg / L) was 95.5%, and the efficiency did not decrease significantly after 5 cycles.

[0112] Example 5

[0113] (1) Weigh out 0.033 mol of FeSO4·7H2O and 0.066 mol of Fe2(SO4)3·9H2O, dissolve them in 1 L of deionized water to form a mixed solution with a total iron ion concentration of 0.099 mol / L (Fe 2+ with Fe 3+ The molar ratio is 1:2;

[0114] (2) Add 5.2g of sodium tripolyphosphate (accounting for 20% of the total iron ion molar amount) under magnetic stirring at 45℃ and continue stirring for 45min;

[0115] (3) Add sodium hydroxide solution to adjust the pH to 11. After a black precipitate is formed, transfer it to a 1.5L hydrothermal reactor and react at 60℃ for 2 hours.

[0116] (4) Centrifuge (8000 rpm, 10 min), wash three times each with deionized water and ethanol, and vacuum dry at 60℃ for 12 h to obtain spherical magnetite flocculant powder.

[0117] Test data:

[0118] The average particle size is 35 nm, and the specific surface area is 150 m². 2 / g;

[0119] The removal rate of tetracycline (60 mg / L) was 94.3%, and the turbidity of the supernatant after magnetic separation was <5 NTU.

[0120] Example 6

[0121] The difference from Example 1 is as follows:

[0122] (3) Add 25% ammonia solution to adjust the pH to 8;

[0123] (4) Obtain spheroidal magnetite flocculant powder.

[0124] Test data:

[0125] SEM showed that the particle edges were slightly irregular, with an average particle size of 55 nm.

[0126] The zeta potential is -28mV, and the removal rate of suspended solids (kaolin) is 96.5%.

[0127] Example 7

[0128] The difference from Example 2 is as follows:

[0129] (3) The hydrothermal reaction was carried out at 120℃ for 6 hours;

[0130] (4) Rod-shaped magnetite flocculant particles were obtained.

[0131] Test data:

[0132] TEM showed that the length of the rod-shaped particles increased to 80 nm, the aspect ratio was 4:1, and the specific surface area was 95 m². 2 / g;

[0133] For Cu 2+ The removal rate of (40 mg / L) was 96.0%, and the efficiency was 91.2% after 10 cycles.

[0134] Example 8

[0135] The difference from Example 1 is as follows:

[0136] (2) Replace sodium tripolyphosphate with an equal molar amount of potassium tripolyphosphate.

[0137] Test data:

[0138] The particle size distribution is 40nm to 60nm, and the surface potential is -32mV;

[0139] The adsorption capacity for humic acid is 210 mg / g, and the magnetic separation rate is increased by 10%.

[0140] Comparative Example 1

[0141] The difference from Example 1 is that sodium tripolyphosphate was not added.

[0142] Test data:

[0143] from Figure 10 As can be seen, the SEM image of Comparative Example 1 shows obvious particle agglomeration, with an average particle size of 65 nm and a standard deviation of particle size distribution of 20 nm.

[0144] BET has a specific surface area of ​​80m². 2 / g, with -OH groups accounting for only 70% of the surface-active groups;

[0145] For Pb 2 The removal rate of + (50 mg / L) was 82.0%, and the magnetic separation time was 8 min.

[0146] 1. Characterization and results of magnetite flocculant powder:

[0147] (1) From Figure 1 The appearance of the magnetite flocculant in Example 1 can be observed directly. The particles are uniformly dispersed and there is no obvious agglomeration, showing good physical state and morphological characteristics.

[0148] (2) XRD characterization was performed using a Bruker D8 X-ray diffractometer (Germany). Figure 2 It can be seen that the magnetite flocculant prepared in this application has good crystallinity and obvious crystal structure characteristics, which are highly consistent with the crystal structure of standard magnetite. This indicates that the addition of tripolyphosphate did not change the basic crystal structure of magnetite. At the same time, the spectrum shows that there are no impurity peaks in the sample, indicating that the product has high purity and is a single compound.

[0149] (3) Morphological characterization was performed using a Hitachi SU8010 scanning electron microscope (Japan). Figure 3 It can be seen that, under the regulation of tripolyphosphate, the prepared magnetite flocculant exhibits a uniform spherical morphology with a particle size distribution of about 50 nm, and the particles are well dispersed with no obvious agglomeration, which directly demonstrates the advantages of this application in the precise control of magnetite morphology and particle size.

[0150] (4) Morphological characterization was performed using a JEM-2100F transmission electron microscope from Japan. Figure 4The microstructure of magnetite particles is clearly visible, with clear and regular lattice fringes indicating excellent crystallinity. Simultaneously, a tripolyphosphate layer adsorbed on the particle surface is observed, confirming the complex interaction mechanism between tripolyphosphate and magnetite. This structure lays the foundation for its high adsorption performance. The magnetite flocculant particles are regular in shape and uniform in size, exhibiting excellent dispersibility and no obvious agglomeration. This indicates that tripolyphosphate plays a crucial role in regulating the growth of magnetite crystals, resulting in flocculant particles with good dispersibility, which is beneficial for improving flocculation efficiency.

[0151] (5) From Figure 5 As can be seen, Fe is uniformly distributed in the magnetite flocculant, indicating that the addition of tripolyphosphate did not affect the uniformity of iron distribution in the magnetite crystals. Furthermore, the distribution of other elements (such as O) is observed to be essentially consistent with that of Fe, further confirming the uniform chemical composition of the magnetite flocculant and ensuring its stability and reliability in water treatment processes.

[0152] (6) From Figure 6 As can be seen, magnetite flocculant exhibits good magnetic responsiveness and high saturation magnetization, indicating its rapid response and effective magnetic separation in a magnetic field. This is crucial for the recovery and reuse of magnetite flocculant, significantly reducing water treatment costs and improving economic efficiency.

[0153] (7) XPS characterization was performed using a Kratos Axis Ultra DLD X-ray photoelectron spectroscopy system (UK). Figure 7 It can be seen that the Fe element on the surface of the magnetite flocculant mainly exists in the form of Fe(II) and Fe(III), and the ratio of the two is moderate, which is consistent with the ideal chemical composition of magnetite (Fe). 2+ Fe 3+ =1:2). This indicates that the addition of tripolyphosphate did not change the basic chemical composition of magnetite, but rather helped to improve its adsorption and flocculation efficiency for pollutants.

[0154] (8) FTIR spectra were acquired using a Nicolet iS50 Fourier transform infrared spectrometer from Nicolet Corporation, USA. Figure 8 As can be seen, the magnetite flocculant exhibits a characteristic absorption peak at a specific wavenumber, with the peak around 570 cm⁻¹. -1 The absorption peak at [location] corresponds to the stretching vibration of the Fe-O bond, indicating the presence of stable Fe-O bonds in the magnetite crystal structure. Furthermore, characteristic absorption peaks of tripolyphosphate (such as those at approximately 1080 cm⁻¹) can also be observed. -1The presence of the PO stretching vibration peak at [location missing] confirms that tripolyphosphate successfully participated in the synthesis of magnetite and formed a stable complex with it. This combination not only helps regulate the growth of magnetite crystals but also enhances the surface charge properties of the magnetite flocculant, thereby improving its adsorption capacity for pollutants.

[0155] (9) Raman spectra were acquired using a Renishaw inVia Reflex confocal laser Raman spectrometer. Figure 9 As can be seen, the magnetite flocculant exhibits Raman active vibrational modes at specific wavenumbers, further confirming that its crystal structure is consistent with that of magnetite. Simultaneously, Raman spectroscopy can also provide information about the Fe-O octahedral structure within the crystal, indicating that the addition of tripolyphosphate did not disrupt the basic structural units of magnetite. Instead, through interaction with the magnetite surface, it optimized crystal growth and surface properties, providing strong structural support for the high performance of the magnetite flocculant.

[0156] 2. Performance tests and results of magnetite flocculant powder:

[0157] (1) Treatment of heavy metal-containing wastewater using magnetite flocculant:

[0158] (a) Take Pb-containing 2+ 1L of wastewater with a concentration of 50mg / L was treated with 100mg / L of the magnetite flocculant prepared in Example 1.

[0159] (ii) Stir at 200 rpm for 20 min, then apply a 0.1 T magnetic field for 5 min;

[0160] (III) Detection of Pb in the supernatant 2+ With a concentration of 1.2 mg / L, the removal rate is 97.6%, which is 15% higher than that of traditional magnetic flocculants, and no pre-adjustment of wastewater pH is required.

[0161] (2) Treatment of organic pollutant wastewater using magnetite flocculant:

[0162] (i) 1L of wastewater containing methyl orange (100mg / L) was treated with 150mg / L of magnetite flocculant prepared in Example 2.

[0163] (ii) Stir at 300 rpm for 15 min, and detect the absorbance of the supernatant after magnetic separation;

[0164] (III) The removal rate is 98.1%, the effluent color is less than 10 times, and the adsorption efficiency for anionic dyes is 20% higher than that of traditional materials, which is attributed to the surface -PO4 3- Electrostatic attraction of radicals.

[0165] (3) Cyclic use performance test:

[0166] (a) Take the magnetite flocculant prepared in Example 3 and repeatedly treat Cd-containing materials. 2+ Wastewater (30mg / L) 10 times;

[0167] (ii) After each treatment, magnetic separation is performed, followed by washing with ethanol and drying at 50°C for reuse.

[0168] (iii) The removal rate of the 10th treatment was 91.5%, and the attenuation rate was 8.5%, which is significantly better than traditional materials (attenuation rate >30%).

[0169] (4) Synergistic removal effect of different pollutants:

[0170] (I) Simulating complex wastewater (Pb) 2+ 30 mg / L + humic acid 80 mg / L + suspended solids 200 mg / L);

[0171] (ii) Add 200 mg / L of the magnetite flocculant prepared in Example 5, stir at 150 rpm for 30 min, and perform magnetic separation;

[0172] (III) Detection Results: Pb 2+ The concentration was 0.8 mg / L, the residual humic acid concentration was 6.5 mg / L, and the turbidity of suspended solids was 3 NTU, all of which met the national emission standards. This achieved the simultaneous and efficient removal of heavy metals, organic matter, and suspended solids, breaking through the limitations of traditional flocculants in treating single pollutants.

[0173] In summary, the above embodiments successfully prepared spherical, rod-shaped, and sheet-shaped nano-magnetite flocculants by adjusting parameters such as the amount of tripolyphosphate, reaction pH, and hydrothermal temperature. The particle size is controllable within the range of 20nm to 100nm, with a high specific surface area, a removal rate of ≥95% for various pollutants, and a decay rate of ≤10% after 10 cycles. Compared with traditional methods, this application does not require complex surface modification. Through the dual-function regulation of tripolyphosphate (crystal growth control + surface activity optimization), it achieves precise control of the performance of magnetite flocculants, which has significant advantages such as simple process, low cost, and environmental friendliness, and is easy to realize industrial production.

[0174] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing magnetite flocculant, characterized in that, include: Ferrous salt and ferric salt are mixed in water to obtain the first mixture; The first mixture is mixed with tripolyphosphate to obtain a second mixture, and the pH of the second mixture is adjusted to 8-11 to obtain a third mixture containing iron ion coprecipitates; The third mixture is subjected to hydrothermal reaction at 60℃~120℃ for 2h~6h to obtain magnetite flocculant.

2. The method according to claim 1, characterized in that, The tripolyphosphate includes at least one of sodium tripolyphosphate, potassium tripolyphosphate, and ammonium tripolyphosphate.

3. The method according to claim 1 or 2, characterized in that, The molar ratio of the tripolyphosphate to the molar ratio of iron ions in the first mixture is (5-20):

100.

4. The method according to claim 1 or 2, characterized in that, The ferrous salt includes at least one of FeCl2, FeSO4, and Fe(NO3)2; and / or The iron salt includes at least one of FeCl3, Fe2(SO4)3, and Fe(NO3)3; and / or An alkaline solution is added to adjust the pH of the second mixture to 8-11. The alkaline solution includes at least one of ammonia, sodium hydroxide solution, and potassium hydroxide solution.

5. The method according to claim 1 or 2, characterized in that, At least one of the following conditions must be met: The molar ratio of the ferrous salt to the ferric salt is 1:(2-3); The concentration of iron ions in the first mixture is 0.1 mol / L to 1 mol / L; The second mixture is stirred at a temperature of 30°C to 60°C and at a speed of 400 rpm to 600 rpm.

6. A magnetite flocculant, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

7. The magnetite flocculant according to claim 6, characterized in that, The specific surface area of ​​the magnetite flocculant is 50 m². 2 / g~150m 2 / g.

8. The magnetite flocculant according to claim 6 or 7, characterized in that, The particle size of the magnetite flocculant is 20nm to 100nm.

9. The magnetite flocculant according to claim 6 or 7, characterized in that, The standard deviation of the particle size distribution of the magnetite flocculant is ≤15 nm; and / or The surface zeta potential of the magnetite flocculant is -20mV to -40mV.

10. The application of the magnetite flocculant according to any one of claims 6 to 9 in water treatment.

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