Cu-mn double-doped iron-based flocculant, and preparation method and application thereof

Abstract

This invention provides a Cu-Mn dual-doped iron-based flocculant, its preparation method, and its application, belonging to the field of flocculation treatment technology for dyeing and printing wastewater. This invention introduces copper and manganese into the flocculant, and in subsequent applications, it is combined with hydrogen peroxide to generate a high concentration of hydroxyl radicals on or around the flocculant surface, forming a Fenton-like flocculation synergistic system. This simultaneously achieves the oxidative degradation of recalcitrant organic matter and the efficient flocculation and sedimentation of colloidal suspended solids, resulting in excellent wastewater treatment performance. When using the flocculant prepared according to this invention to treat dyeing and printing wastewater, the COD removal rate is above 86%, and the decolorization rate is above 88%.

Description

Technical Field

[0001] This invention belongs to the field of flocculation treatment technology for dyeing and printing wastewater, specifically relating to a Cu-Mn dual-doped iron-based flocculant, its preparation method, and its application. Background Technology

[0002] With the continuous development of the textile industry, the treatment of dyeing and printing wastewater has gradually become a significant challenge for the environmental protection industry. Dyeing and printing wastewater is a general term for wastewater generated during the pretreatment, dyeing, printing, and finishing processes of textile fibers such as cotton, linen, silk, wool, and chemical fibers. It is a typical industrial wastewater in the textile industry characterized by high pollutant concentrations, deep colors, complex compositions, and difficulty in degradation. Currently, pretreatment + biological treatment + advanced treatment is a commonly used and mature treatment route for dyeing and printing wastewater in industry.

[0003] In the treatment of dyeing and printing wastewater, flocculants are mainly used after the pretreatment screen or equalization tank, and before biological treatment. While biological treatment is effective at removing easily degradable organic matter and has low operating costs, it is less effective against pigments, recalcitrant dyes, and highly salty and toxic pollutants, and has weak resistance to shock treatment. Therefore, it is necessary to arrange flocculation treatment before biological treatment to remove most of the color, solids, colloids, and some COD, reducing the biotoxicity of the wastewater and thus improving the treatment efficiency of biological treatment. In addition, flocculants can also be used in the advanced treatment stage, generally before the end of biological treatment and before discharge or reuse, mainly for further decolorization and removal of residual COD to meet effluent or reuse requirements.

[0004] In the treatment of dyeing and printing wastewater, commonly used flocculants are mainly inorganic polymers such as polyferric sulfate and polyaluminum chloride. They primarily rely on charge neutralization, adsorption bridging, and trapping to remove colloidal and suspended pollutants. However, their effectiveness in removing water-soluble dyes and recalcitrant organic matter is limited, and they face significant bottlenecks in decolorization and COD removal. Furthermore, with increasingly stringent national and industry standards and requirements, ordinary flocculants are finding it increasingly difficult to meet expectations. In such cases, treatment plants may choose to oxidize the wastewater before flocculation to reduce the difficulty of treating some recalcitrant pollutants, but this approach generally leads to a significant increase in treatment costs. Therefore, improving the performance of flocculants is an important research direction. While existing technologies have improved the stability and adsorption capacity of flocculants, they all suffer from the limitation of "flocculation only, without oxidation," resulting in poor removal of highly water-soluble dye molecules from dyeing and printing wastewater and limited decolorization capabilities. Therefore, preparing high-performance flocculants for the flocculation treatment of dyeing and printing wastewater while effectively controlling costs remains a key technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a Cu-Mn dual-doped iron-based flocculant, its preparation method, and its application. The flocculant prepared by this invention is low-cost and exhibits better COD removal and decolorization rates when treating dyeing and printing wastewater.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a Cu-Mn dual-doped iron-based flocculant, comprising the following steps: (1) Mix the complexing agent, water and pH adjuster to obtain a complexing agent solution; (2) The complexing agent solution obtained in step (1) is mixed with copper sulfate and manganese sulfate to carry out a pre-complexation reaction to obtain a pre-complex solution; (3) The pre-complex solution obtained in step (2) is mixed with ferrous sulfate and hydrogen peroxide and subjected to polynuclear coordination and complexation polymerization reaction and then matured to obtain Cu-Mn doped iron-based flocculant.

[0007] Preferably, the complexing agent in step (1) includes citric acid or oxalic acid; the pH value of the complexing agent solution is 4.5~5.0.

[0008] Preferably, the ratio of the amount of complexing agent in step (1) to the total amount of copper sulfate, manganese sulfate and ferrous sulfate in step (2) and step (3) is (1~5):100.

[0009] Preferably, the molar ratio of copper sulfate, manganese sulfate in step (2) to ferrous sulfate in step (3) is (0.01~0.05):(0.03~0.08):1.

[0010] Preferably, the pre-complexation reaction time in step (2) is 5 to 30 minutes.

[0011] Preferably, in step (3), the molar ratio of hydrogen peroxide to ferrous sulfate in the hydrogen peroxide solution is (0.2~0.6):1.

[0012] Preferably, the maturation time in step (3) is 30~90 min.

[0013] The present invention also provides a Cu-Mn dual-doped iron-based flocculant prepared by the preparation method described in the above technical solution.

[0014] The present invention also provides the application of the Cu-Mn dual-doped iron-based flocculant described in the above technical solution in wastewater treatment.

[0015] Preferably, the application includes: mixing the wastewater to be treated with Cu-Mn doped iron-based flocculant and hydrogen peroxide, and then treating it to obtain treated water.

[0016] This invention provides a method for preparing a Cu-Mn dual-doped iron-based flocculant, comprising the following steps: (1) mixing a complexing agent, water, and a pH adjuster to obtain a complexing agent solution; (2) mixing the complexing agent solution obtained in step (1) with copper sulfate and manganese sulfate to perform a pre-complexation reaction to obtain a pre-complex solution; (3) mixing the pre-complex solution obtained in step (2) with ferrous sulfate and hydrogen peroxide to perform a polynuclear coordination and complexation polymerization reaction, followed by aging to obtain a Cu-Mn dual-doped iron-based flocculant. This invention first mixes the complexing agent solution with copper sulfate and manganese sulfate to allow Cu... 2+ Mn 2+ A stable small-molecule metal-complexing agent complex is formed by pre-complexing with a complexing agent. Then, ferrous sulfate and hydrogen peroxide are added, with hydrogen peroxide acting as an oxidant to simultaneously induce polynuclear coordination and complexation polymerization, generating a network chelate structure similar to Fe-Cit-Cu-Cit-Mn-Cit-Fe. After aging, a complexed Cu-Mn dual-doped iron-based flocculant is obtained. This invention, by introducing copper and manganese into the flocculant, and in conjunction with hydrogen peroxide during subsequent application, can generate a high concentration of hydroxyl radicals on or around the flocculant surface, forming a Fenton-like flocculation synergistic system. This simultaneously achieves the oxidative degradation of recalcitrant organic matter and the efficient flocculation and sedimentation of colloidal suspended solids, resulting in excellent wastewater treatment performance. The results of the examples show that when using the flocculant prepared according to this invention to treat dyeing and printing wastewater, the COD removal rate is above 86%, and the decolorization rate is above 88%. Attached Figure Description

[0017] Figure 1 This is a reaction mechanism diagram of the preparation process of the Cu-Mn dual-doped iron-based flocculant of the present invention; Figure 2 The graph shows the COD removal rate of dyeing and printing wastewater by flocculants in Examples 1-3 and ordinary polyferric sulfate flocculant. Figure 3 The graph shows the decolorization rate of dyeing and printing wastewater by flocculants in Examples 1-3 and ordinary polyferric sulfate flocculant. Detailed Implementation

[0018] This invention provides a method for preparing a Cu-Mn dual-doped iron-based flocculant, comprising the following steps: (1) Mix the complexing agent, water and pH adjuster to obtain a complexing agent solution; (2) The complexing agent solution obtained in step (1) is mixed with copper sulfate and manganese sulfate to carry out a pre-complexation reaction to obtain a pre-complex solution; (3) The pre-complex solution obtained in step (2) is mixed with ferrous sulfate and hydrogen peroxide and subjected to polynuclear coordination and complexation polymerization reaction and then matured to obtain Cu-Mn doped iron-based flocculant.

[0019] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.

[0020] The present invention mixes a complexing agent, water and a pH adjuster to obtain a complexing agent solution.

[0021] In this invention, the complexing agent preferably includes citric acid or oxalic acid, more preferably citric acid. The citric acid used in this invention has a multidentate coordination structure, which easily forms a network flocculation structure, and its coordination strength is moderate, preventing the locking of metal ions and thus avoiding subsequent inhibition of Fenton-like processes.

[0022] As one implementation method, the water can be deionized water.

[0023] This invention does not impose a specific limit on the amount of water used, as long as the complexing agent is fully dissolved and the subsequent reaction can proceed sufficiently. As one embodiment, the mass ratio of the complexing agent to water can be 1:10.

[0024] In one embodiment, the pH adjuster can be an aqueous solution of sodium hydroxide. This invention does not impose any particular limitation on the concentration and amount of the pH adjuster; a sodium hydroxide aqueous solution of conventional concentration used in the art can be employed, ensuring that the pH of the complexing agent solution is within the required range.

[0025] In this invention, the pH value of the complexing agent solution is preferably 4.5 to 5.0. By limiting the pH value of the complexing agent solution to the above range, this invention enables the complexing agent to have better metal complexing ability.

[0026] As one embodiment, the mixing of the complexing agent, water, and pH adjuster can be performed by mixing the complexing agent and water, and then adding the pH adjuster. As another embodiment, the mixing can be carried out under conditions of a 35°C water bath and stirring. This invention does not impose any particular limitation on the stirring method and rate; any technical solution well-known to those skilled in the art can be used.

[0027] After obtaining the complexing agent solution, the present invention mixes the complexing agent solution with copper sulfate and manganese sulfate to carry out a pre-complexation reaction to obtain a pre-complex solution.

[0028] In one embodiment, the copper sulfate can be CuSO4·5H2O; the manganese sulfate can be MnSO4·H2O. This invention uses copper sulfate and manganese sulfate, and the subsequent ferrous salt is also ferrous sulfate. The entire system is a sulfate system, avoiding contamination from other types of salts, such as hydrochloride which introduces Cl-. - Cl -It is an OH quencher, which directly consumes the hydroxyl radicals generated in the system, leading to a decrease in oxidation efficiency, and chloride salts will increase the Cl- content in the effluent. - Concentration (printing and dyeing wastewater generally contains Cl) - (Emission limits). This invention incorporates manganese sulfate and copper sulfate to form a Cu-Mn dual-doped structure. During application, during hydrogen peroxide activation, Cu... 2+ Reduced to Cu + Mn 3+ It can quickly convert Cu + Oxidation and regeneration into Cu 2+ It is reduced to Mn 2+ Mn 2+ It can also be reacted with hydrogen peroxide / Fe 3+ Rapid oxidation to Mn 3+ This completes the valence cycle. Compared to other metals, it has better effects, such as Ce, which is a rare earth metal and expensive, CO, which is a carcinogenic heavy metal, and Al, which has no catalytic activity.

[0029] As one embodiment, the mixing of the complexing agent solution with copper sulfate and manganese sulfate can be carried out by adding copper sulfate and manganese sulfate sequentially to the complexing agent solution; the mixing can be carried out under the conditions of a 35°C water bath and stirring.

[0030] In this invention, the pre-complexation reaction time is preferably 5-30 min, more preferably 10 min; the pre-complexation reaction is preferably carried out under 35°C water bath and stirring conditions. As one embodiment, the stirring rate can be 300 rpm.

[0031] This invention first adds copper sulfate and manganese sulfate for pre-complexation and controls the time, enabling Cu to... 2+ Mn 2+ It fully pre-complexes with the complexing agent to form a stable small-molecule metal-complexing agent complex, thus avoiding subsequent hydrolysis of metal ions.

[0032] After obtaining the pre-complex solution, the present invention mixes the pre-complex solution with ferrous sulfate and hydrogen peroxide to carry out a polynuclear coordination and complexation polymerization reaction and then matures it to obtain a Cu-Mn dual-doped iron-based flocculant.

[0033] In one embodiment, the ferrous sulfate can be FeSO4·7H2O. This invention uses ferrous sulfate because other ferrous salts, such as ferrous carbonate and ferrous hydroxide, have poor solubility in weakly acidic aqueous solutions and cannot release free ferrous ions. Ferrous salts containing strong coordinating anions will compete with the complexing agent for coordination, leading to uncontrollable polymerization. Furthermore, their anions are consistent with those of copper sulfate and manganese sulfate, avoiding the introduction of impurities.

[0034] In this invention, the preferred molar ratio of the complexing agent to the total molar ratio of copper sulfate, manganese sulfate, and ferrous sulfate is (1~5):100, more preferably 3:100; the preferred molar ratio of copper sulfate, manganese sulfate, and ferrous sulfate is (0.01~0.05):(0.03~0.08):1, more preferably (0.03~0.05):(0.03~0.05):1, and even more preferably 0.03:0.05:1; the preferred molar ratio of hydrogen peroxide in the hydrogen peroxide solution to ferrous sulfate is (0.2~0.6):1, more preferably 0.5:1. By controlling the proportions of each raw material within the above ranges, this invention can further improve the flocculant's effect on wastewater treatment.

[0035] As one embodiment, the mixing of the pre-complex solution with ferrous sulfate and hydrogen peroxide can be as follows: ferrous sulfate is added to the pre-complex solution and stirred until completely dissolved. The mixture is then stirred for 15 minutes, maintaining the pH of the system at 4.5-5.0 during stirring. A portion of hydrogen peroxide is then added dropwise. After the addition is complete, the mixture is stirred for 5 minutes, adjusting the pH to 4.5-5.0. The remaining hydrogen peroxide is then added dropwise, maintaining the pH of the system stable during the addition. After the addition is complete, stirring continues for 30 minutes. As another embodiment, the concentration of the hydrogen peroxide can be 30 wt%; the portion of hydrogen peroxide can be 60 wt% of the total mass of hydrogen peroxide; the hydrogen peroxide is added dropwise while simultaneously undergoing ultrasonication and stirring; the ultrasonic frequency can be 40 kHz and the power can be 80 W; the stirring rate can be 150-300 rpm; the dropwise addition rate can be 0.4 mL / min; and the mixing can be carried out under a 35°C water bath. This invention uses a two-stage addition of hydrogen peroxide to avoid excessively high local concentrations, which could lead to excessively high local temperatures and the decomposition of hydrogen peroxide into oxygen, thus improving polymerization uniformity. In this invention, polynuclear coordination and complexation polymerization reactions occur during the mixing process, and ultrasound can enhance the micro-dispersion of metal ions during the mixing process.

[0036] As one implementation method, the curing can be carried out under conditions of a 50°C water bath and static standing; the curing time can be 30~90 minutes, or even 60 minutes.

[0037] As one implementation method, after the aging process is completed, the product can be cooled to room temperature, aged in a sealed, light-protected environment for 12 hours, and filtered through slow quantitative filter paper to obtain a Cu-Mn dual-doped iron-based flocculant.

[0038] This invention involves adding copper sulfate and manganese sulfate to a complexing agent solution under weakly acidic conditions for pre-complexation, forming a stable small-molecule metal-complexing agent complex. Ferrous sulfate is then added, and hydrogen peroxide is added dropwise in a gradient under stirring and ultrasonic conditions to initiate coordination and copolymerization reactions. After aging and filtration to remove impurities, a Cu-Mn dual-doped iron-based flocculant is obtained. This flocculant overcomes the limitations of traditional modified PFS (polysaccharide-free ferrous sulfate) which only flocculates without oxidation, achieving synergistic effects of advanced oxidation and flocculation. This results in more thorough decolorization and more significant COD removal from dyeing and printing wastewater. By introducing copper and manganese into the flocculant, and adding a small amount of hydrogen peroxide during application, this invention simultaneously provides in-situ oxidation and flocculation functions, forming a Fenton-like synergistic system. This system simultaneously achieves the oxidative degradation of recalcitrant organic matter and the efficient flocculation and sedimentation of colloidal suspensions.

[0039] The preferred reaction mechanism in the preparation process of the Cu-Mn dual-doped iron-based flocculant of this invention is as follows: Figure 1 As shown.

[0040] Compared with traditional flocculants, the flocculant prepared in this invention has the following advantages and beneficial effects: (1) Strong decolorization ability: Dyeing and printing wastewater generally contains a large amount of dyes and color. Traditional flocculants such as PFS can only remove colloidal dyes and suspended dyes by flocculation. For water-soluble reactive dyes and acid dyes, they can only rely on adsorption capacity, resulting in a low decolorization rate. However, the present invention adds a trace amount of H2O2, which can generate an in-situ Fenton-like reaction, producing ·OH on the surface of the flocs, oxidizing and destroying the dye conjugated system, and can also efficiently decolorize water-soluble dyes.

[0041] (2) Good floc strength and settling performance: Traditional PFS flocs are relatively light, fragile and easy to float, resulting in poor sludge-water separation. The Cu-Mn double-doped iron-based flocculant prepared in this invention has Fe-O-Cu and Fe-O-Mn oxygen bridge embedded structures, making the flocs denser, stronger and faster settling. The advantages can be specifically manifested in the lower load of the sedimentation tank, less sludge and lower water content (the three-dimensional network polymer structure of citric acid bridges enhances the adsorption bridging ability, copper and manganese oxidation breaks the hydration film, forming more compact flocs, and the strong oxidizing property of Fenton-like particles can achieve complete mineralization of organic pollutants and reduce the amount of sludge).

[0042] (3) Higher stability for dyeing and printing wastewater with higher salinity and toxicity: Dyeing and printing wastewater generally contains salt, surfactants and some residual oxidants. Traditional flocculants are easily interfered with and their charge neutralization capacity decreases. However, this invention has a double insurance of flocculation and oxidation. Fenton-like oxidation can destroy interfering substances, and then flocculation is carried out for subsequent treatment. Higher stability enhances the anti-interference ability and makes the effect more stable under water quality fluctuations (the anti-hydrolysis skeleton constructed by citric acid multidentate chelation can effectively inhibit the hydrolysis and dissolution of metal ions, as well as the closed-loop electron circulation system formed by copper and manganese bimetals, so as to continuously regenerate the active sites and reduce irreversible deactivation).

[0043] The present invention also provides a Cu-Mn dual-doped iron-based flocculant prepared by the preparation method described in the above technical solution.

[0044] The present invention also provides the application of the Cu-Mn dual-doped iron-based flocculant described in the above technical solution in wastewater treatment.

[0045] In this invention, the preferred application includes: mixing the wastewater to be treated with Cu-Mn doped iron-based flocculant and hydrogen peroxide, and then treating it to obtain treated water.

[0046] In this invention, the pH value of the water to be treated is preferably 6~7; the mass ratio of the Cu-Mn dual-doped iron-based flocculant to the volume ratio of the wastewater to be treated is preferably (100~300) mg:1L; and the mass ratio of hydrogen peroxide to iron in the Cu-Mn dual-doped iron-based flocculant is preferably (0.1~3):10.

[0047] As one implementation method, the treatment can be as follows: after adding Cu-Mn dual-doped iron-based flocculant and hydrogen peroxide to the wastewater to be treated, stir at 300 rpm for 1 min, then stir at 50 rpm for 15 min, and finally let it stand to settle for 30 min.

[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0049] Example 1 A method for preparing a Cu-Mn dual-doped iron-based flocculant is as follows: (1) Under the conditions of a water bath at 35℃, take a certain amount of deionized water, add citric acid (the mass ratio of citric acid to deionized water is 1:10), stir until completely dissolved, and adjust the pH of the system to 4.5~5.0 with dilute NaOH aqueous solution to obtain citric acid solution; (2) Under the conditions of a water bath at 35°C, CuSO4·5H2O and MnSO4·H2O were added sequentially to the citric acid solution obtained in step (1), and the mixture was stirred at 300 rpm for 10 min to obtain a pre-complex solution. (3) Under a water bath at 35℃, add FeSO4·7H2O (the molar ratio of CuSO4·5H2O, MnSO4·H2O and FeSO4·7H2O is 0.03:0.05:1, and the molar ratio of citric acid to the total molar ratio of CuSO4·5H2O, MnSO4·H2O and FeSO4·7H2O is 3:100) to the pre-complex solution obtained in step (2), stir until completely dissolved, maintain the pH value of the system at 4.5~5.0, continue stirring at 300rpm for 15min, and then add a portion of hydrogen peroxide (concentration of 30wt%, total mass of hydrogen peroxide 60wt%, dropping rate 0.4%). After the addition of hydrogen peroxide (mL / min) was completed, the mixture was stirred for 5 min, and the pH value was adjusted to 4.5~5.0. Then, the remaining hydrogen peroxide was added dropwise (the ratio of the total amount of hydrogen peroxide in the hydrogen peroxide to the amount of FeSO4·7H2O was 0.5:1). During the addition process, the pH value of the system was kept stable. Ultrasonication and stirring were performed simultaneously during the addition process. The ultrasonic frequency was 40kHz and the power was 80W. The stirring rate was 150rpm. After the addition was completed, stirring was continued for 30 min. Then, the mixture was allowed to stand and mature for 60 min under a 50℃ water bath. After cooling to room temperature, it was sealed and aged in the dark for 12 h. Finally, it was filtered using slow quantitative filter paper to obtain a reddish-brown viscous Cu-Mn dual-doped iron-based flocculant.

[0050] Example 2 The molar ratio of CuSO4·5H2O, MnSO4·H2O and FeSO4·7H2O in Example 1 was replaced with 0.05:0.03:1, and everything else was the same as in Example 1.

[0051] Example 3 The molar ratio of CuSO4·5H2O, MnSO4·H2O and FeSO4·7H2O in Example 1 was replaced with 0.04:0.04:1, and everything else was the same as in Example 1.

[0052] The flocculants prepared in Examples 1-3 and ordinary polyferric sulfate were used for flocculation treatment of dyeing and printing wastewater, respectively. Examples 1-3 and Comparative Example 1 all included H2O2, while Comparative Example 2 used polyferric sulfate without H2O2. The initial COD of the dyeing and printing wastewater was 450 mg / L, and the color was 550 Pt-Co°. 500 mL of dyeing and printing wastewater was taken, and the pH was adjusted to 7.0. The flocculant dosage was 200 mg / L, and the H2O2 dosage was 1 / 10 of the iron mass. After adding the flocculant and hydrogen peroxide, the mixture was stirred at 300 rpm for 1 min, then at 50 rpm for 15 min, and finally allowed to settle for 30 min. The supernatant was then used for COD and color determination, and the results are shown in Table 1. Figures 2-3 As shown.

[0053] Table 1. Treatment effects of flocculants in Examples 1-3 and ordinary polyferric sulfate flocculant on dyeing and printing wastewater.

[0054] The comparison results in Table 1 show that the iron-based flocculants prepared in Examples 1, 2, and 3 have advantages over ordinary flocculants in flocculation treatment of dyeing and printing wastewater. In addition, the flocculant prepared in Example 1 is more effective than that in Examples 2 and 3, indicating that the preparation ratio in Example 1 is optimal.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a Cu-Mn dual-doped iron-based flocculant, comprising the following steps: (1) Mix the complexing agent, water and pH adjuster to obtain a complexing agent solution; (2) The complexing agent solution obtained in step (1) is mixed with copper sulfate and manganese sulfate to carry out a pre-complexation reaction to obtain a pre-complex solution; (3) The pre-complex solution obtained in step (2) is mixed with ferrous sulfate and hydrogen peroxide and subjected to polynuclear coordination and complexation polymerization reaction and then matured to obtain Cu-Mn doped iron-based flocculant.

2. The preparation method according to claim 1, characterized in that, The complexing agent in step (1) includes citric acid or oxalic acid; the pH value of the complexing agent solution is 4.5~5.

0.

3. The preparation method according to claim 1, characterized in that, The ratio of the amount of complexing agent in step (1) to the total amount of copper sulfate, manganese sulfate and ferrous sulfate in step (2) and step (3) is (1~5):

100.

4. The preparation method according to claim 1, characterized in that, The molar ratio of copper sulfate, manganese sulfate in step (2) to ferrous sulfate in step (3) is (0.01~0.05):(0.03~0.08):

1.

5. The preparation method according to claim 1, characterized in that, The pre-complexation reaction time in step (2) is 5~30 min.

6. The preparation method according to claim 1, characterized in that, In step (3), the molar ratio of hydrogen peroxide to ferrous sulfate in the hydrogen peroxide solution is (0.2~0.6):

1.

7. The preparation method according to claim 1, characterized in that, The maturation time in step (3) is 30~90 minutes.

8. The Cu-Mn dual-doped iron-based flocculant prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the Cu-Mn dual-doped iron-based flocculant of claim 8 in wastewater treatment.

10. The application according to claim 9, characterized in that, The application includes: mixing the wastewater to be treated with Cu-Mn doped iron-based flocculant and hydrogen peroxide, and then treating it to obtain treated water.

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