Method for treating comprehensive wastewater through combination of potassium ferrate and oxidation
By combining catalytic oxidation and photocatalysis of Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet materials, the high reagent cost and complex operation problems of potassium ferrate combined with Fenton process were solved, and efficient treatment of complex wastewater and resource recovery were achieved, thereby improving the adaptability and sustainability of wastewater treatment.
Patent Information
- Application Number
- CN202510733701.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-04
- Publication Date
- 2025-10-28
AI Technical Summary
Existing potassium ferrate and Fenton oxidation treatment processes suffer from high reagent costs, complex operation, and difficulty in treating high-concentration complex wastewater. Furthermore, traditional carrier fly ash-loaded potassium ferrate is prone to loss, leading to decreased activity and making it difficult to effectively treat comprehensive wastewater containing heavy metals and suspended solids.
Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet materials are used to achieve wastewater pretreatment, catalytic oxidation and material regeneration through a combination of catalytic oxidation and photocatalysis. The multilayer structure and sulfonic acid groups of the nanosheets are used to promote the activation of potassium persulfate, forming a self-sustaining catalytic cycle that is suitable for efficient wastewater treatment under a wide spectrum of pH conditions.
It achieves efficient removal and resource recovery of comprehensive wastewater, reduces the cost of chemicals, improves wastewater treatment efficiency, and the nanomaterials can be recycled, which solves the shortcomings of traditional processes and has strong adaptability.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of industrial wastewater treatment technology, and particularly relates to a method for treating integrated wastewater by combined oxidation with potassium ferrate. Background Technology
[0002] Currently, industries such as chemical, printing and dyeing, pharmaceutical, electroplating, papermaking, and leather processing discharge large amounts of wastewater during production and domestic wastewater treatment. This wastewater has a complex composition and may contain recalcitrant organic matter (such as tar and fragrance additives), heavy metals (such as chromium, nickel, and cadmium), toxic compounds (such as cyanide and sulfides), high concentrations of suspended solids (such as 2000-4000 mg / L in leather wastewater), and high chemical oxygen demand (COD) (such as thousands to tens of thousands of mg / L in papermaking wastewater), making it difficult to treat.
[0003] Combined wastewater is typically treated using a combination of processes, integrating physicochemical and biological methods. Physicochemical methods include advanced oxidation, membrane separation, and adsorption / coagulation, while biological treatment methods include activated sludge processes and anaerobic / aerobic combinations.
[0004] In chemical water treatment, potassium ferrate, Fenton's reagent, and potassium peroxymonosulfate are commonly used as strong oxidants. Combining two oxidants can combine the advantages of two oxidation technologies and improve wastewater treatment efficiency through synergistic effects. However, there are also some drawbacks. For example, the conventional Fenton / potassium peroxymonosulfate combined process requires high dosage throughout the process without staged control, and is prone to generating excessive sludge when treating high-concentration wastewater. Another example is the potassium ferrate combined with Fenton oxidation process. Although it can achieve efficient wastewater treatment by combining the broad-spectrum oxidizing power of potassium ferrate and the deep treatment capability of Fenton, it requires staged acid adjustment. Potassium ferrate requires neutral / weakly acidic conditions, while the Fenton reaction requires strong acidity (pH 3-5), which increases the cost of reagents and the complexity of operation.
[0005] Patent CN 115215481 A discloses a method for treating industrial phosphorus-containing pharmaceutical wastewater, which involves combined treatment of wastewater through a potassium ferrate complex supported on fly ash and Fenton oxidation. However, the fly ash used as a carrier in this method has limited surface functional groups, resulting in low potassium ferrate loading and easy loss, leading to a decline in activity over long-term operation. The entire process requires staged acid adjustment, especially since the Fenton reaction requires strongly acidic conditions (pH 3-5), and the Fe produced by Fenton oxidation... 3+ It forms mixed precipitates with phosphates in wastewater, increasing sludge volume and making it difficult to utilize phosphorus as a resource. Furthermore, it focuses on phosphorus-containing pharmaceutical wastewater and is not effective in treating comprehensive wastewater containing heavy metals, suspended solids, and complex organic matter, resulting in poor adaptability to comprehensive wastewater. Summary of the Invention
[0006] In view of this, the present invention provides a method for treating complex wastewater by combined oxidation with potassium ferrate. This method achieves efficient removal and resource recovery of multiple pollutants in the complex wastewater, and has the characteristics of high treatment efficiency, good selectivity and recyclability, providing a new solution for the treatment of complex industrial wastewater.
[0007] To achieve the above objectives, the present invention employs the following technical solution:
[0008] A method for treating combined wastewater by potassium ferrate oxidation includes the following steps:
[0009] (1) Start-up of wastewater pretreatment and treatment system:
[0010] Constructing Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet materials;
[0011] The wastewater is subjected to full index testing. Based on the test results, the pH of the wastewater is adjusted to 6.0-7.5. Then, large impurities in the wastewater are removed by filtration through a bar screen, and large suspended solids are removed by filtration through a 100-mesh screen.
[0012] The processing system employs a sequencing batch reactor (SBR) equipped with online pH / ORP monitoring, mechanical stirring, and a visible light source; Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are added to the sequencing batch reactor (SBR);
[0013] (2) Catalytic oxidation:
[0014] Start mechanical stirring and visible light source, add a portion of potassium permonosulfate (PMS), control the stirring speed to 150 rpm, catalytic oxidation treatment for 30 min, then add the remaining potassium permonosulfate (PMS), catalytic oxidation treatment for 30-60 min, and track the changes of key parameters through online monitoring of pH / ORP during the catalytic oxidation reaction;
[0015] (3) Solid-liquid separation and material regeneration:
[0016] After the reaction is complete, Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are rapidly separated by an external magnetic field. The supernatant is filtered through a 0.45μm membrane and discharged or reused after meeting the standards.
[0017] The separated Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets were washed sequentially with 0.1M NaOH solution, 0.1M H2SO4 solution and deionized water, and finally regenerated by vacuum drying at 60℃ for 2 h.
[0018] Furthermore, in some preferred embodiments of the present invention, in step (1), the full index detection includes the detection of COD, BOD5, total phosphorus (TP), total nitrogen (TN), pH, conductivity, suspended solids (SS) and the concentration of characteristic pollutants.
[0019] Furthermore, in some preferred embodiments of the present invention, in step (1), the wavelength of the visible light source is 420-550 nm and the light intensity is 50 mW / cm². 2 .
[0020] Furthermore, in some preferred embodiments of the present invention, in step (1), the preparation method of the Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets includes:
[0021] S1: 1.0 g FeSO4·7H2O and 2.7 g FeCl3·6H2O were dissolved in 80 mL ethylene glycol to form a precursor solution with an iron ion concentration of 0.1 M. Then, 3.6 g anhydrous sodium acetate (NaAc) and 1.0 g polyethylene glycol 4000 were added, and the mixture was magnetically stirred for 30 min until completely dissolved. The mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, sealed, and reacted at 200 °C for 10 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was separated by an external magnetic field, washed three times with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain black Fe3O4 powder with a particle size of 50 nm. The obtained Fe3O4 was dispersed in 0.1 M sodium citrate solution, ultrasonicated for 1 h, and freeze-dried to obtain carboxylated Fe3O4 nanoparticles.
[0022] S2: 0.5 g of carboxylated Fe3O4 nanoparticles were dispersed in a mixed solvent of 40 mL acetonitrile and 10 mL deionized water, and sonicated for 30 min to form a uniform suspension. 1.0 mmol of template molecule, 4.0 mmol of 4-vinylpyridine (4-VP) and 0.2 g of 4,4'-azobis(4-cyanopentanoic acid) (Azo-CA) were added, and the mixture was stirred in an ice bath under nitrogen protection for 1 h to allow for complete pre-assembly. Subsequently, 20 mmol of ethylene glycol dimethacrylate (EGDMA) and 0.1 g of azobisisobutyronitrile (AIBN) were added, and the mixture was heated to 60 °C and thermally polymerized under a nitrogen atmosphere for 24 h. After the reaction was completed, the product was collected by magnetic separation, and the template molecule was removed by Soxhlet extraction with a methanol / acetic acid solution with a volume ratio of 9:1 for 48 h. The product was then washed with methanol until neutral and dried under vacuum to obtain Fe3O4@MIP-Azo.
[0023] S3: 0.3g Fe3O4@MIP-Azo was dispersed in 50mL of 4M NaOH solution cooled in an ice bath. 20mL of aqueous solution containing 0.5g KMnO4 was slowly added dropwise, and the temperature was controlled below 10℃. The mixture was stirred for 6h. The product was separated by a magnetic field, washed with pre-cooled 3M NaOH and anhydrous ethanol, and vacuum dried to obtain the Fe3O4@MIP-Azo@K2FeO4 intermediate.
[0024] S4: Dissolve 0.1 g of 4,4'-azodiphenylamine-2,2'-disulfonic acid in 20 mL of borate buffer at pH 9, add 0.01 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 0.005 g of N-hydroxysuccinimide (NHS), activate for 30 min, then add Fe3O4@MIP-Azo@K2FeO4 intermediate, stir and react for 12 h in the dark, after the reaction is complete, magnetically separate, wash alternately with water and ethanol, and dry under vacuum at 40 °C to obtain the product Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets.
[0025] Preferably, in S2, the template molecule is at least one of ciprofloxacin, glyphosate, Reactive Brilliant Blue molecule, and dichromate ion.
[0026] Furthermore, in some preferred embodiments of the present invention, in step (1), the dosage of the Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets is 1.5 g / L.
[0027] Furthermore, in some preferred embodiments of the present invention, in step (1), for wastewater containing characteristic pollutants, the ionic strength of the wastewater is adjusted to 0.01-0.1M NaCl and the temperature is adjusted to 25-40℃.
[0028] Furthermore, in some preferred embodiments of the present invention, in step (2), the total amount of potassium persulfate added is in a molar ratio of COD:PMS = 1:1.2, and the amount of potassium persulfate added for the first time is in a molar ratio of COD:PMS = 1:0.6.
[0029] Furthermore, in some preferred embodiments of the present invention, in step (3), the applied magnetic field strength is 0.3-0.5T and the processing time is 5-10min.
[0030] Beneficial technical effects of the present invention:
[0031] 1. The method for treating comprehensive wastewater by combined potassium ferrate oxidation of the present invention achieves a balance between selective adsorption and broad-spectrum oxidation. Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are used to target and enrich characteristic pollutants, while potassium persulfate and K2FeO4 achieve full-spectrum oxidation. In the wastewater pretreatment and system startup phase, the wastewater undergoes comprehensive index detection and characteristic analysis and pretreatment to ensure optimal performance of subsequent oxidation processes. In the catalytic oxidation reaction phase, SBR is coupled with photocatalysis, Fenton-like oxidation, and direct oxidation to enhance mass transfer efficiency. Under photocatalysis, K2FeO4 on the surface of the Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets first decomposes to produce FeO4. 2- With the addition of ·OH, the initial ORP value rises rapidly, while the sulfonic acid groups of Azo-SO3 promote the activation of PMS to generate SO4· - Fe3O4 core Fe 2+ / Fe 3+ The cycle further sustains the free radical chain reaction, forming a self-sustaining catalytic cycle; the COD removal rate can reach 70-80% within the first 30 minutes, then the rate gradually slows down, and a total reaction time of 60-90 minutes is sufficient to achieve a COD removal rate of over 95%. For phosphorus-containing organic matter, PO4 is released during the oxidation process. 3- It will react with Fe on the material surface 3+ FePO4 precipitate is formed, achieving simultaneous removal and recovery of phosphorus and reducing the load on subsequent treatments. For recalcitrant components, a staged oxidation strategy is adopted. First, a lower dose of oxidant is used to improve the biodegradability of the wastewater, and then the remaining oxidant is added for deep mineralization, which saves on reagent costs and improves the COD removal rate of high-concentration wastewater. In the solid-liquid separation and material regeneration stage, Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets can be rapidly separated by an external magnetic field. After post-treatment, the material is regenerated for recycling, solving the problem of nanomaterial recycling and improving the sustainability of the process.
[0032] 2. The Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets used in this invention have a multi-layered core-shell structure, forming a four-in-one platform for recognition, enrichment, controlled oxidation, and separation. Traditional MIP materials are only used for adsorption, while this material achieves highly efficient PMS activation (increasing the rate constant by 3-5 times) through the sulfonic acid groups of Azo-SO3, and through the Fe3O4... 2+ / Fe 3+ The cycle sustains the free radical chain reaction, forming a self-sustaining catalytic cycle. The magnetic Fe3O4 core not only provides separation, but its surface Fe... 2+ / Fe 3+ Redox pairs can efficiently activate persulfate to produce SO4·- Free radicals, and simultaneously promote the formation of ·OH. Electron transfer channels exist at the interface between Fe3O4 and K2FeO4, Fe... 3+ It can accept electrons generated from the decomposition of K2FeO4, significantly delaying the self-decomposition of potassium ferrate and extending its half-life. The molecularly imprinted layer endows the material with selective recognition capabilities, reducing the consumption of ineffective reagents through selective oxidation and avoiding the generation of toxic intermediates through excessive oxidation. Its three-dimensional cavity structure is complementary to the size and functional groups of target pollutants (such as organophosphorus molecules), achieving an adsorption capacity 3-5 times that of ordinary adsorbents. The photoresponsive characteristics of the azobenzene (Azo) bridging structure further enhance the controllability of catalytic oxidation. Under visible light irradiation, the Azo groups undergo cis-trans isomerization, causing polymer chain segment movement, which both promotes the transport of pollutants to active sites and releases degraded products to prevent blockage of active sites. The introduction of Azo-SO3 solves the key problem of pH limitation in traditional Fenton systems. The sulfonic acid group functions through two mechanisms: first, it acts as a proton carrier to maintain a slightly acidic environment on the material surface, enabling the reaction to proceed efficiently across a broad pH range (3-9); second, SO3... - with Fe 3+ By forming a complex, the formation of iron sludge is inhibited, reducing the amount of sludge by more than 60%. This design eliminates the need for frequent pH adjustments in the wastewater, significantly reducing operating costs. Detailed Implementation
[0033] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.
[0034] The method for treating integrated wastewater by potassium ferrate combined oxidation provided by the present invention includes three stages: wastewater pretreatment and treatment system startup, catalytic oxidation, and solid-liquid separation and material regeneration.
[0035] In the wastewater pretreatment and treatment system start-up phase, it is necessary to pre-construct and synthesize Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet materials, including Fe3O4 nanoparticle preparation, grafting of molecularly imprinted polymer (MIP-Azo), K2FeO4 loading, and Azo-SO3 modification. The Fe3O4 nanoparticles are prepared using a modified solvothermal method to ensure monodispersity and high magnetic responsiveness. The molecularly imprinted layer is constructed using surface imprinting technology. Potassium ferrate loading is achieved through in-situ oxidation precipitation, and Azo-SO3 modification is accomplished via a coupling reaction.
[0036] Preparation of Fe3O4 nanoparticles: 1.0 g FeSO4·7H2O and 2.7 g FeCl3·6H2O were dissolved in 80 mL ethylene glycol to form a precursor solution with an iron ion concentration of 0.1 M. Subsequently, 3.6 g anhydrous sodium acetate (NaAc) and 1.0 g polyethylene glycol 4000 were added, and the mixture was magnetically stirred for 30 min until completely dissolved. The mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, sealed, and reacted at 200 °C for 10 h. After the reaction, the mixture was naturally cooled to room temperature. The product was separated by an external magnetic field, washed three times with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain black Fe3O4 powder with a particle size of 50 nm. The obtained Fe3O4 was dispersed in 0.1 M sodium citrate solution, ultrasonicated for 1 h, and freeze-dried to obtain carboxylated Fe3O4 nanoparticles.
[0037] Grafting of molecularly imprinted polymer (MIP-Azo): 0.5 g of carboxylated Fe3O4 nanoparticles were dispersed in a mixed solvent of 40 mL acetonitrile and 10 mL deionized water, and sonicated for 30 min to form a homogeneous suspension. 1.0 mmol of template molecule, 4.0 mmol of 4-vinylpyridine (4-VP), and 0.2 g of 4,4'-azobis(4-cyanopentanoic acid) (Azo-CA) were added, and the mixture was stirred in an ice bath under nitrogen protection for 1 h to allow for complete pre-assembly. Subsequently, 20 mmol of ethylene glycol dimethacrylate (EGDMA) and 0.1 g of azobisisobutyronitrile (AIBN) were added, and the mixture was heated to 60 °C and thermally polymerized under a nitrogen atmosphere for 24 h. After the reaction was completed, the product was collected by magnetic separation, and the template molecule was removed by Soxhlet extraction with a methanol / acetic acid solution at a volume ratio of 9:1 for 48 h. The product was then washed with methanol until neutral and dried under vacuum to obtain Fe3O4@MIP-Azo.
[0038] K2FeO4 loading and Azo-SO3 modification: 0.3 g Fe3O4@MIP-Azo was dispersed in 50 mL of 4M NaOH solution cooled in an ice bath. 20 mL of aqueous solution containing 0.5 g KMnO4 was slowly added dropwise, maintaining the temperature below 10 °C. The reaction was stirred for 6 h. The product was separated by a magnetic field, washed with pre-cooled 3M NaOH and anhydrous ethanol, and vacuum dried to obtain the Fe3O4@MIP-Azo@K2FeO4 intermediate. 0.1 g 4,4'-azodiphenylamine-2,2'-disulfonic acid was dissolved in 20 mL of borate buffer at pH 9. 0.01 g 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 0.005 g... N-hydroxysuccinimide (NHS) was activated for 30 min, and then Fe3O4@MIP-Azo@K2FeO4 intermediate was added. The reaction was stirred for 12 h under light-protected conditions. After the reaction was completed, the nanosheets were magnetically separated, washed alternately with water and ethanol, and dried under vacuum at 40 °C to obtain the product Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets.
[0039] The Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets were chemically characterized, and the results are shown in the table below.
[0040]
[0041] During the wastewater pretreatment and treatment system startup phase, characteristic analysis and pretreatment of the comprehensive wastewater are required before treatment to ensure optimal performance of subsequent oxidation processes. Specifically, the comprehensive wastewater undergoes comprehensive testing for COD, BOD5, total phosphorus (TP), total nitrogen (TN), pH, conductivity, suspended solids (SS), and concentrations of characteristic pollutants. Based on the test results, the wastewater pH is adjusted to 6.0-7.5. Large impurities such as plastics and fibers are then removed through a bar screen, followed by filtration through a 100-mesh sieve to remove large suspended solids. The treatment system employs a sequencing batch reactor (SBR) with an effective volume of 1 m³. 3 It is equipped with online pH / ORP monitoring, adjustable mechanical stirring speed of 50-200 rpm, and light intensity of 50 mW / cm² with wavelength of 420-550 nm. 2 Visible light source; Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets were added to a sequencing batch reactor (SBR) at a dosage of 1.5 g / L. For wastewater containing characteristic pollutants, the ionic strength of the wastewater was adjusted to 0.01-0.1 M NaCl and the temperature to 25-40 °C to optimize the adsorption selectivity.
[0042] In the catalytic oxidation stage, mechanical stirring and a visible light source are activated. Potassium persulfate (PMS) is added at a COD:PMS molar ratio of 1:0.6, with the stirring speed controlled at 150 rpm. Catalytic oxidation is carried out for 30 minutes, followed by the addition of the remaining potassium persulfate (PMS) and catalytic oxidation for another 30-60 minutes. During the catalytic oxidation reaction, changes in key parameters are tracked online via pH / ORP monitoring. pH, ORP, and dissolved oxygen (DO) are recorded every 5 minutes, and COD and characteristic pollutant concentrations are sampled every 15 minutes. The total amount of potassium persulfate added is calculated based on a COD:PMS molar ratio of 1:1.2. The catalytic oxidation stage employs a multi-mode coupling mechanism combining SBR, photocatalysis, Fenton-like oxidation, and direct oxidation. By using a staged oxidant addition method, reagent costs can be saved by 15-20%, making it particularly suitable for high-concentration wastewater with COD > 3000 mg / L.
[0043] In the solid-liquid separation and material regeneration stage, Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are rapidly separated by applying an external magnetic field of 0.3-0.5T for 5-10 minutes. The supernatant is filtered through a 0.45μm membrane and discharged or reused after meeting the standards. The separated Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are washed sequentially with 0.1M NaOH solution, 0.1M H2SO4 solution and deionized water, and finally regenerated by vacuum drying at 60℃ for 2 hours.
[0044] Example 1:
[0045] Ciprofloxacin was selected as the template molecule, and the nanosheets of this embodiment were prepared according to the above-described Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet preparation method; the pharmaceutical wastewater was treated according to the above-described method of potassium ferrate combined oxidation treatment of comprehensive wastewater.
[0046] Example 2:
[0047] Glyphosate was selected as the template molecule, and the nanosheets of this embodiment were prepared according to the above-described Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet preparation method; the pesticide wastewater was treated according to the above-described method of potassium ferrate combined oxidation treatment of comprehensive wastewater.
[0048] Example 3:
[0049] The nanosheets of this embodiment were prepared by using active brilliant blue molecules as template molecules according to the above-described method for preparing Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets; and the dyeing and printing wastewater was treated according to the above-described method for treating comprehensive wastewater by potassium ferrate combined oxidation.
[0050] Example 4:
[0051] Using dichromate ions as template molecules, the nanosheets of this embodiment were prepared according to the above-described Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet preparation method; the electroplating wastewater was treated according to the above-described method of potassium ferrate combined oxidation treatment of comprehensive wastewater.
[0052] Test example:
[0053] Different types of integrated wastewater were treated using the methods described in Examples 1-4. During the treatment process, the COD value, TP, and concentration of characteristic pollutants before and after treatment were measured, and the corresponding TP removal rate and characteristic pollutant removal rate were statistically analyzed. The treatment results are shown in the table below.
[0054]
[0055]
[0056] The method in Example 1 of this invention achieves a COD removal rate of 96.1% after treating pharmaceutical wastewater, while the traditional Fenton oxidation method achieves a COD removal rate of 85-90% and generates a large amount of iron sludge. The method in Example 2 of this invention achieves a glyphosate degradation rate of 98.5% after treating pesticide wastewater, while the traditional TiO2 / UV photocatalytic method achieves a glyphosate degradation rate of 80-85% and requires 2-4 hours. This is because the Azo-SO3 modification in this invention enhances the photoresponsiveness, and combined with K2FeO4 oxidation, forms multiple active free radicals (·OH, SO4·). - The method in Example 3 of this invention achieves a COD removal rate of 95.9% for dyeing and printing wastewater, while the traditional biological treatment + ozone oxidation method achieves a COD removal rate of 90-93%. In comparison, this invention uses a molecularly imprinted layer (MIP) to selectively adsorb dye molecules, improving local oxidation efficiency, producing no biological sludge, and recovering phosphorus (FePO4 precipitate). The method in Example 4 of this invention achieves a Cr(VI) removal rate of 99.8% for electroplating wastewater, with no secondary pollution. The strong reducing property of Fe3O4@K2FeO4 transforms Cr(VI) into Cr(III) and forms a stable precipitate. In contrast, the traditional chemical precipitation + adsorption method achieves a Cr(VI) removal rate of 85-90%, producing chromium-containing sludge that requires special treatment.
[0057] To further investigate the regeneration performance of the Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet catalyst material, the method in Example 1 of the test case was subjected to 10 cycles. After 10 cycles, the COD removal rate was found to be above 92% of the initial value, and the saturation magnetization loss was <5%, indicating that it has good structural stability and good cycle stability.
[0058] Using the method in Example 2, approximately 0.3 kg of dry weight of FePO4 precipitate (containing P2O5≈30%) was generated from the treatment of 1 ton of pesticide wastewater (COD=1500mg / L). The phosphorus resource recovery rate was >90%, and the purity of the phosphorus recovered in the form of FePO4 was over 85%, which can be directly used for phosphate fertilizer production.
[0059] The above description is merely a preferred embodiment of the present invention, and while it is detailed and specific, it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the principles of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.
Claims
1. A method for treating combined wastewater by potassium ferrate oxidation, characterized in that, The following steps are involved: (1) Start-up of wastewater pretreatment and treatment system: Constructing Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheet materials; The wastewater is subjected to full index testing. Based on the test results, the pH of the wastewater is adjusted to 6.0-7.
5. Then, large impurities in the wastewater are removed by filtration through a bar screen, and large suspended solids are removed by filtration through a 100-mesh screen. The processing system employs a sequencing batch reactor (SBR) equipped with online pH / ORP monitoring, mechanical stirring, and a visible light source; Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are added to the sequencing batch reactor (SBR); (2) Catalytic oxidation: Start mechanical stirring and visible light source, add a portion of potassium permonosulfate (PMS), control the stirring speed to 150 rpm, catalytic oxidation treatment for 30 min, then add the remaining potassium permonosulfate (PMS), catalytic oxidation treatment for 30-60 min, and track the changes of key parameters through online monitoring of pH / ORP during the catalytic oxidation reaction; (3) Solid-liquid separation and material regeneration: After the reaction is complete, Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets are rapidly separated by an external magnetic field. The supernatant is filtered through a 0.45μm membrane and discharged or reused after meeting the standards. The separated Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets were washed sequentially with 0.1M NaOH solution, 0.1M H2SO4 solution and deionized water, and finally regenerated by vacuum drying at 60℃ for 2 h.
2. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that: In step (1), the full index detection includes the detection of COD, BOD5, total phosphorus (TP), total nitrogen (TN), pH, conductivity, suspended solids (SS) and the concentration of characteristic pollutants.
3. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that: In step (1), the wavelength of the visible light source is 420-550 nm and the light intensity is 50 mW / cm². 2 .
4. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that, In step (1), the preparation method of the Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets includes: S1: 1.0 g FeSO4·7H2O and 2.7 g FeCl3·6H2O were dissolved in 80 mL ethylene glycol to form a precursor solution with an iron ion concentration of 0.1 M. Then, 3.6 g anhydrous sodium acetate (NaAc) and 1.0 g polyethylene glycol 4000 were added, and the mixture was magnetically stirred for 30 min until completely dissolved. The mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, sealed, and reacted at 200 °C for 10 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was separated by an external magnetic field, washed three times with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven at 60 °C for 12 h to obtain black Fe3O4 powder with a particle size of 50 nm. The obtained Fe3O4 was dispersed in 0.1 M sodium citrate solution, ultrasonicated for 1 h, and freeze-dried to obtain carboxylated Fe3O4 nanoparticles. S2: 0.5 g of carboxylated Fe3O4 nanoparticles were dispersed in a mixed solvent of 40 mL acetonitrile and 10 mL deionized water, and sonicated for 30 min to form a uniform suspension. 1.0 mmol template molecule, 4.0 mmol 4-vinylpyridine (4-VP) and 0.2 g 4,4'-azobis(4-cyanopentanoic acid) (Azo-CA) were added, and the mixture was stirred in an ice bath under nitrogen protection for 1 h to allow for complete pre-assembly. Subsequently, 20 mmol ethylene glycol dimethacrylate (EGDMA) and 0.1 g azobisisobutyronitrile (AIBN) were added, and the mixture was heated to 60 °C and thermally polymerized under a nitrogen atmosphere for 24 h. After the reaction was completed, the product was collected by magnetic separation, and the template molecule was removed by Soxhlet extraction with a methanol / acetic acid solution with a volume ratio of 9:1 for 48 h. The product was then washed with methanol until neutral and dried under vacuum to obtain Fe3O4@MIP-Azo. S3: 0.3g Fe3O4@MIP-Azo was dispersed in 50mL of 4M NaOH solution cooled in an ice bath. 20mL of aqueous solution containing 0.5g KMnO4 was slowly added dropwise, and the temperature was controlled below 10℃. The mixture was stirred for 6h. The product was separated by a magnetic field, washed with pre-cooled 3M NaOH and anhydrous ethanol, and vacuum dried to obtain the Fe3O4@MIP-Azo@K2FeO4 intermediate. S4: Dissolve 0.1 g of 4,4'-azodiphenylamine-2,2'-disulfonic acid in 20 mL of borate buffer at pH 9, add 0.01 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 0.005 g of N-hydroxysuccinimide (NHS), activate for 30 min, then add Fe3O4@MIP-Azo@K2FeO4 intermediate, stir and react for 12 h in the dark, after the reaction is complete, magnetically separate, wash alternately with water and ethanol, and dry under vacuum at 40 °C to obtain the product Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets.
5. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 4, characterized in that: In S2, the template molecule is at least one of ciprofloxacin, glyphosate, Reactive Brilliant Blue molecule, and dichromate ion.
6. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that: In step (1), the dosage of Fe3O4@MIP-Azo@K2FeO4:Azo-SO3 nanosheets is 1.5 g / L.
7. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that: In step (1), for wastewater containing characteristic pollutants, the ionic strength of the wastewater is adjusted to 0.01-0.1M NaCl and the temperature is adjusted to 25-40℃.
8. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that: In step (2), the total amount of potassium persulfate added is based on a molar ratio of COD:PMS = 1:1.2, and the amount of potassium persulfate added for the first time is based on a molar ratio of COD:PMS = 1:0.
6.
9. The method for treating comprehensive wastewater by combined oxidation with potassium ferrate according to claim 1, characterized in that: In step (3), the external magnetic field strength is 0.3-0.5T and the processing time is 5-10min.