Magnetic coagulation-photocatalysis integrated sewage treatment method

Abstract

The invention belongs to the technical field of sewage treatment. The invention provides a magnetic coagulation-photocatalysis integrated sewage treatment method which comprises the following steps: adding a coagulant and magnetic particles into sewage, and carrying out magnetic coagulation reaction to obtain a mixed solution containing magnetic floc; introducing the mixed solution containing the magnetic floc into a magnetic separation zone, and applying a magnetic field to settle the magnetic floc to obtain a supernatant; introducing the supernate into a photocatalytic reaction area, and carrying out photocatalytic oxidation degradation on the organic pollutants under the action of a light source; eluting and regenerating the magnetic flocs, recovering the magnetic particles, and discharging or recycling the treated water after the treated water is detected to reach the standard. According to the sewage treatment method disclosed by the invention, efficient coagulation and magnetic separation are realized by constructing magnetic particles with core-shell structures, and the removal rate of organic pollutants such as dyes, antibiotics and hormones is remarkably increased by combining a photocatalytic oxidation technology. In addition, the method is high in integration level, small in occupied area, low in energy consumption and convenient for automatic continuous operation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for integrated magnetic coagulation-photocatalysis treatment of wastewater. Background Technology

[0002] With the acceleration of industrialization and urbanization, the types of organic pollutants in wastewater are becoming increasingly complex, commonly including dyes, antibiotics, and hormones. These pollutants are generally characterized by high concentrations, stable structures, reluctance to degrade, and high toxicity. Direct discharge without effective treatment will seriously threaten aquatic ecosystems and human health. Therefore, developing efficient, economical, and sustainable wastewater treatment processes is crucial for promoting the regeneration and recycling of polluted water resources and alleviating environmental pressures and water scarcity.

[0003] Coagulation and sedimentation, a common method in wastewater treatment, is mainly used to remove suspended particulate matter and colloids from wastewater. However, this method has limited ability to remove dissolved organic pollutants, especially in treating high-color, high-chemical-oxygen-demand (COD), and recalcitrant organic pollutants. Furthermore, the flocs produced by ordinary coagulants have slow settling rates, require large footprints, and have low efficiency in subsequent solid-liquid separation. For example, patent number 201910668948.7, entitled "An Invention Patent on a Super-Efficient Separation System and Method Based on Magnetic Coagulation Sedimentation and Activated Carbon Adsorption," discloses a combined magnetic coagulation sedimentation-activated carbon adsorption treatment method. Although this technology enhances the sedimentation process through magnetic flocculants, it still has significant shortcomings in removing highly stable organic pollutants (such as antibiotics), and the adsorbent is prone to saturation and failure, resulting in short operating cycles and high maintenance costs.

[0004] To improve the removal efficiency of organic pollutants, photocatalytic oxidation technology has been widely studied and applied in advanced wastewater treatment. This method utilizes photocatalytic materials, such as titanium dioxide, bismuth metavanadate, and zinc oxide, which can generate reactive oxygen species (e.g., ·OH, ·O2) under ultraviolet or visible light irradiation. - Photocatalysis can efficiently decompose various recalcitrant organic pollutants, offering advantages such as mild reaction conditions, thorough degradation, and no secondary pollution. However, photocatalysis technology still faces the following challenges in practical engineering applications: 1. The small particle size of photocatalysts makes them difficult to recover from the effluent, easily causing secondary pollution; 2. Some catalysts only respond in the ultraviolet band, resulting in low visible light utilization efficiency; 3. High turbidity or the presence of a large amount of particulate matter in the influent hinders light penetration, significantly reducing reaction efficiency. Therefore, there is an urgent need for an integrated wastewater treatment method that can synergistically remove particulate matter and organic pollutants, combining high efficiency and recyclability to meet the treatment needs of complex wastewater and reduce operating costs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for integrated magnetic coagulation and photocatalysis to treat wastewater, addressing the shortcomings of existing technologies.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for integrated magnetic coagulation and photocatalysis treatment of wastewater, comprising the following steps:

[0008] 1) Add coagulant and magnetic particles to wastewater to carry out magnetic coagulation reaction and obtain a mixed liquid containing magnetic flocs;

[0009] 2) The mixture containing magnetic flocs is introduced into the magnetic separation zone, and a magnetic field is applied to cause the magnetic flocs to settle, thus obtaining the supernatant;

[0010] 3) The supernatant is introduced into the photocatalytic reaction zone for photocatalytic oxidation and degradation of organic pollutants under the action of a light source;

[0011] 4) The magnetic flocs obtained from sedimentation are washed and regenerated, and the recovered magnetic particles are recycled for use in step 1). The treated water is discharged or reused after passing the test.

[0012] Preferably, the coagulant in step 1) is one or more of polyaluminum chloride, polyferric sulfate, polyacrylamide, and polyaluminum ferric silicate.

[0013] The mass of the coagulant is 0.1% to 0.3% of the wastewater mass.

[0014] Preferably, the magnetic particles in step 1) are core-shell structured magnetic particles, which consist of a magnetic core layer and a functional shell layer.

[0015] The magnetic core layer is iron(II,III) oxide, and the functional shell layer is doped and modified titanium dioxide, with the doping element being Fe, Ce, Zn, N, or S.

[0016] Preferably, the core-shell structured magnetic particles have a particle size of 80–120 nm and the functional shell has a thickness of 10–20 nm.

[0017] Preferably, the concentration of the magnetic particles added in step 1) is 100-150 mg / L based on the volume of wastewater.

[0018] Preferably, the photocatalytic reaction zone in step 3) contains a photocatalytic material, which is one or more of bismuth metavanadate, zinc oxide, and graphitic carbon nitride.

[0019] The concentration of the photocatalytic material added, based on the volume of wastewater, is 0.1–0.5 g / L.

[0020] Preferably, the light source in step 3) is ultraviolet light and / or visible light, with the wavelength of ultraviolet light being 360-380nm and the wavelength of visible light being 420-480nm.

[0021] Preferably, the organic pollutant in step 3) is one or more of the following: dye pollutants, antibiotic pollutants, and hormone pollutants.

[0022] Preferably, the elution and regeneration method in step 4) is a combination of ultrasonic vibration and chemical elution.

[0023] Preferably, the magnetic separation zone in step 2) and the photocatalytic reaction zone in step 3) are located in an integrated processing device, wherein the magnetic separation zone is located upstream and the photocatalytic reaction zone is located downstream.

[0024] The integrated processing device includes a continuous flow channel, a magnetic separation zone, and a photocatalytic reaction zone.

[0025] The beneficial effects of this invention include the following:

[0026] 1) This invention combines magnetic coagulation with photocatalytic oxidation. The former efficiently removes particulate matter and colloidal pollutants from wastewater, while the latter can further degrade dissolved organic pollutants (such as dyes, antibiotics and hormones), thereby improving the overall treatment effect.

[0027] 2) The Fe3O4@doped modified TiO2 core-shell structure magnetic particles used in this invention have both excellent magnetic responsiveness and visible light catalytic activity. They can form stable flocs in the magnetic coagulation reaction, and can promote the degradation of organic pollutants under light irradiation. They are also easy to magnetically separate and recover, thus realizing the recycling of materials.

[0028] 3) The wastewater treatment method of the present invention has a removal rate of more than 80% for typical pollutants, including 94.4%, 92.5% and 95.0% for acid red dye, tetracycline and estradiol, respectively, a COD removal rate of 86.7% and a turbidity reduction to 5 NTU, which is significantly better than the existing comparative process.

[0029] 4) This invention integrates the magnetic separation zone and the photocatalytic reaction zone into the same integrated processing device, which has a compact structure, small footprint, and can realize continuous flow processing and automated operation, reducing manual intervention and equipment energy consumption.

[0030] 5) The wastewater treatment method of the present invention is applicable to the treatment of various types of high-color, high-COD, and difficult-to-degrade organic wastewater such as dye wastewater, pharmaceutical wastewater, and hormone wastewater, and has broad application prospects in the field of deep treatment of industrial wastewater and urban sewage. Attached Figure Description

[0031] Figure 1This is a process flow diagram of the integrated magnetic coagulation-photocatalysis wastewater treatment of the present invention;

[0032] Figure 2 This is a schematic diagram of the integrated processing device of the present invention;

[0033] Figure 3 This is a schematic diagram of the core-shell structured magnetic particles of the present invention. Detailed Implementation

[0034] This invention provides a method for integrated magnetic coagulation and photocatalysis treatment of wastewater, comprising the following steps:

[0035] 1) Add coagulant and magnetic particles to wastewater to carry out magnetic coagulation reaction and obtain a mixed liquid containing magnetic flocs;

[0036] 2) The mixture containing magnetic flocs is introduced into the magnetic separation zone, and a magnetic field is applied to cause the magnetic flocs to settle, thus obtaining the supernatant;

[0037] 3) The supernatant is introduced into the photocatalytic reaction zone for photocatalytic oxidation and degradation of organic pollutants under the action of a light source;

[0038] 4) The magnetic flocs obtained from sedimentation are washed and regenerated, and the recovered magnetic particles are recycled for use in step 1). The treated water is discharged or reused after passing the test.

[0039] In this invention, the coagulant in step 1) is preferably one or more of polyaluminum chloride, polyferric sulfate, polyacrylamide, and polyaluminum ferric silicate;

[0040] The mass of the coagulant is preferably 0.1-0.3% of the wastewater mass, more preferably 0.15-0.25%, and even more preferably 0.2%.

[0041] In this invention, the magnetic particles in step 1) are preferably core-shell structured magnetic particles, which are preferably composed of a magnetic core layer and a functional shell layer.

[0042] The magnetic core layer is preferably iron(II,III) oxide, and the functional shell layer is preferably doped and modified titanium dioxide. The doping element is preferably Fe, Ce, Zn, N or S.

[0043] In this invention, the method for preparing the core-shell structured magnetic particles preferably includes the following steps:

[0044] S1. Synthesis of magnetic core layers

[0045] FeCl3·6H2O and FeCl2·4H2O were dissolved in water, and ammonia was added to adjust the pH of the solution. Then, the reaction was carried out at a certain temperature to obtain a black precipitate.

[0046] S2. Preparation of functional shell precursor sol

[0047] After dissolving tetrabutyl titanate in anhydrous ethanol, dopant precursor and water were added, and then the pH value was adjusted with nitric acid solution to obtain doped modified titanium dioxide precursor sol.

[0048] S3. Formation of precursors for core-shell structured particles

[0049] The black precipitate was dispersed in a doped and modified titanium dioxide precursor sol, and then ultrasonically dispersed under ultrasonic conditions. The mixture was then heated and dried to obtain a precursor of core-shell structured particles.

[0050] S4. Calcination treatment

[0051] The precursor of the core-shell structured particles was calcined to obtain Fe3O4@doped modified TiO2 core-shell structured magnetic particles.

[0052] In this invention, the molar ratio of FeCl3·6H2O and FeCl2·4H2O in step S1 is preferably 2:1.

[0053] In this invention, the concentration of ammonia in step S1 is preferably 8-10 mol / L, more preferably 8.5-9.5 mol / L, and even more preferably 9 mol / L.

[0054] In this invention, the pH value of the solution adjusted by adding ammonia in step S1 is preferably adjusted to 9-10, and more preferably 10.

[0055] In this invention, the specific temperature mentioned in step S1 is preferably 70-90°C, more preferably 75-85°C, and even more preferably 80°C.

[0056] In this invention, the reaction time in step S1 is preferably 0.5 to 1.5 h, more preferably 0.8 to 1.2 h, and even more preferably 1 h.

[0057] In this invention, the black precipitate in step S1 is Fe3O4 nanoparticles. Preferably, the black precipitate is washed sequentially with deionized water and anhydrous ethanol, and then the washed black precipitate is dried.

[0058] The number of washes is preferably 2 to 4 times, and more preferably 3 times;

[0059] The drying temperature is preferably 50-70°C, more preferably 55-65°C, and even more preferably 60°C. The drying time is preferably 6-10 hours, more preferably 7-9 hours, and even more preferably 8 hours.

[0060] In this invention, the mass-to-volume ratio of tetrabutyl titanate and anhydrous ethanol in step S2 is preferably 1 mmol: 20-40 mL, more preferably 1 mmol: 25-35 mL, and even more preferably 1 mmol: 30 mL.

[0061] In this invention, the dopant precursor in step S2 is preferably Fe(NO3)3, Ce(NO3)3, Zn(NO3)2, thiourea, or urea.

[0062] In this invention, the molar mass ratio of tetrabutyl titanate, dopant precursor and water in step S2 is preferably 1:0.01-0.1:2-4, more preferably 1:0.05-0.08:2.5-3.5, and even more preferably 1:0.06:3.

[0063] In this invention, the concentration of the nitric acid solution in step S2 is preferably 0.1 to 0.5 mol / L, more preferably 0.2 to 0.4 mol / L, and even more preferably 0.3 mol / L.

[0064] In this invention, step S2, which involves adjusting the pH value with nitric acid solution, is preferably adjusted to a pH value of 3 to 4, and more preferably 3.

[0065] In this invention, the mass-to-volume ratio of the black precipitate and the doped modified titanium dioxide precursor sol in step S3 is preferably 1g:20-40mL, more preferably 1g:25-35mL, and even more preferably 1g:30mL.

[0066] In this invention, the power of the ultrasound in step S3 is preferably 100-300W, more preferably 150-250W, and even more preferably 200W; the time for ultrasound dispersion is preferably 20-40min, more preferably 25-35min, and even more preferably 30min.

[0067] In this invention, the heating and drying temperature in step S3 is preferably 70-90°C, more preferably 75-85°C, and even more preferably 80°C; the heating and drying time is preferably 10-14 hours, more preferably 11-13 hours, and even more preferably 12 hours.

[0068] In this invention, the calcination temperature in step S4 is preferably 450-550°C, more preferably 480-520°C, and even more preferably 500°C; the calcination time is preferably 1-3 hours, more preferably 1.5-2.5 hours, and even more preferably 2 hours; and the calcination is preferably carried out under an inert atmosphere.

[0069] In this invention, the particle size of the core-shell structured magnetic particles is preferably 80-120 nm, more preferably 90-110 nm, and even more preferably 100 nm; the thickness of the functional shell is preferably 10-20 nm, more preferably 14-16 nm, and even more preferably 15 nm.

[0070] In this invention, the concentration of the magnetic particles added in step 1) is preferably 100-150 mg / L based on the volume of wastewater, more preferably 120-140 mg / L, and even more preferably 130 mg / L.

[0071] In this invention, the strength of the magnetic field in step 2) is preferably 0.2 to 0.8 T, more preferably 0.4 to 0.6 T, and even more preferably 0.5 T; the magnetic field is a constant magnetic field set perpendicular to the flow direction of the mixture.

[0072] In this invention, the photocatalytic reaction zone described in step 3) preferably contains a photocatalytic material, and the photocatalytic material is preferably one or more of bismuth metavanadate, zinc oxide, and graphitic carbon nitride.

[0073] The concentration of the photocatalytic material, based on the volume of wastewater, is preferably 0.1–0.5 g / L, more preferably 0.2–0.4 g / L, and even more preferably 0.3 g / L.

[0074] In this invention, the light source in step 3) is preferably ultraviolet light and / or visible light. The wavelength of the ultraviolet light is preferably 360-380nm, more preferably 365-375nm, and even more preferably 370nm. The wavelength of the visible light is preferably 420-480nm, more preferably 440-460nm, and even more preferably 450nm.

[0075] In this invention, the organic pollutant in step 3) is preferably one or more of dye pollutants, antibiotic pollutants, and hormone pollutants.

[0076] In this invention, the elution and regeneration method in step 4) is preferably a method of ultrasonic vibration combined with chemical elution.

[0077] In this invention, the preferred specific operation of the elution and regeneration in step 4) is to add the settled magnetic flocs to the chemical eluent and then treat them with an ultrasonic water bath.

[0078] In this invention, the chemical eluent is preferably a dilute hydrochloric acid or hydrogen peroxide solution, and the concentration of the chemical eluent is preferably 0.01-0.05 mol / L, more preferably 0.02-0.04 mol / L, and even more preferably 0.03 mol / L.

[0079] In this invention, the frequency of the ultrasound is preferably 30-50 kHz, more preferably 35-45 kHz, and even more preferably 40 kHz; the power of the ultrasound is preferably 150-200 W, more preferably 160-180 W, and even more preferably 170 W; the temperature of the ultrasound is preferably 20-30 °C, more preferably 25 °C; and the duration of the ultrasound is preferably 10-30 min, more preferably 15-25 min, and even more preferably 20 min.

[0080] In this invention, the ultrasonic oscillation can effectively destroy the magnetic floc structure and improve the desorption efficiency of surface pollutants; the chemical eluent can remove organic residues, coagulants or other impurities adsorbed on the surface of magnetic particles, thereby restoring the surface activity and dispersibility of the magnetic particles.

[0081] In this invention, after the elution in step 4), the magnetic particles are collected by magnetic separation and washed multiple times with deionized water until the washing solution is close to neutral. The resulting magnetic particles can be directly returned to step 1) to continue to be used in the magnetic coagulation reaction, thus achieving recycling.

[0082] In this invention, the treated water in step 4) meets the standard of "Water Quality for Urban Wastewater Reuse for Miscellaneous Uses" (GB / T 18920-2002), and is suitable for municipal miscellaneous use scenarios such as toilet flushing, road watering, and greening water use, thereby realizing the recycling of water resources.

[0083] In this invention, the magnetic separation zone in step 2) and the photocatalytic reaction zone in step 3) are located in an integrated processing device, wherein the magnetic separation zone is located upstream and the photocatalytic reaction zone is located downstream;

[0084] The integrated processing device preferably includes a continuous flow channel, a magnetic separation zone, and a photocatalytic reaction zone.

[0085] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0086] (I) The preparation method of the core-shell structured magnetic particles used in the examples and comparative examples is as follows:

[0087] 1. Preparation of Fe3O4@Ce-TiO2 core-shell structured magnetic particles

[0088] 5.4 g FeCl3·6H2O and 2 g FeCl2·4H2O were dissolved in 100 mL of deionized water to form a clear yellow solution. Then, under magnetic stirring (400 r / min), 9 mol / L ammonia solution was slowly added dropwise to adjust the pH of the solution to 10. The mixture was heated to 80 °C and reacted at a constant temperature for 1 h to obtain a black precipitate. The black precipitate was washed three times each with deionized water and anhydrous ethanol, and dried at 60 °C for 8 h for later use.

[0089] 1 mmol of tetrabutyl titanate was dissolved in 30 mL of anhydrous ethanol, and then 0.06 mmol of Ce(NO3)3 and 3 mmol of deionized water were added. Then, 0.3 mol / L nitric acid solution was added dropwise to adjust the pH of the mixture to 3, thus obtaining Ce-TiO2 precursor sol.

[0090] 1g of black precipitate was dispersed in 30mL of Ce-TiO2 precursor sol, and then ultrasonically dispersed for 30min under ultrasonic power of 200W. The mixture was then heated and dried at 80℃ for 12h to obtain Fe3O4@Ce-TiO2 core-shell structured particle precursor.

[0091] Fe3O4@Ce-TiO2 core-shell structured particle precursors were calcined in a tube furnace filled with nitrogen at 500℃ for 2 hours to obtain Fe3O4@Ce-TiO2 core-shell structured magnetic particles.

[0092] 2. Preparation of Fe3O4@Fe-TiO2 core-shell structured magnetic particles

[0093] The preparation of Fe3O4@Ce-TiO2 core-shell magnetic particles is the same, except that 0.06 mmol Ce(NO3)3 is replaced with 0.06 mmol Fe(NO3)3.

[0094] 3. Preparation of Fe3O4@Zn-TiO2 core-shell structured magnetic particles

[0095] 5.4 g FeCl3·6H2O and 2 g FeCl2·4H2O were dissolved in 100 mL of deionized water to form a clear yellow solution. Then, under magnetic stirring (600 r / min), 8 mol / L ammonia solution was slowly added dropwise to adjust the pH of the solution to 9. The mixture was heated to 70 °C and reacted at a constant temperature for 1.5 h to obtain a black precipitate. The black precipitate was washed four times each with deionized water and anhydrous ethanol, and dried at 50 °C for 10 h for later use.

[0096] Dissolve 1 mmol of tetrabutyl titanate in 25 mL of anhydrous ethanol, then add 0.05 mmol of Zn(NO3)2 and 2.5 mmol of deionized water, and then add 0.1 mol / L nitric acid solution to adjust the pH of the mixture to 3 to obtain Zn-TiO2 precursor sol.

[0097] 1g of black precipitate was dispersed in 20mL of Zn-TiO2 precursor sol, and then ultrasonically dispersed for 40min under ultrasonic power of 100W. The mixture was then heated and dried at 70℃ for 14h to obtain Fe3O4@Zn-TiO2 core-shell structured particle precursor.

[0098] Fe3O4@Zn-TiO2 core-shell structured particle precursors were calcined in a tube furnace filled with nitrogen at 450℃ for 3 hours to obtain Fe3O4@Zn-TiO2 core-shell structured magnetic particles.

[0099] 4. Preparation of Fe3O4@N-TiO2 core-shell structured magnetic particles

[0100] The preparation of Fe3O4@Zn-TiO2 core-shell magnetic particles is the same, except that 0.05 mmol Zn(NO3)2 is replaced with 0.05 mmol urea.

[0101] 5. Preparation of Fe3O4@S-TiO2 core-shell structured magnetic particles

[0102] 5.4 g FeCl3·6H2O and 2 g FeCl2·4H2O were dissolved in 100 mL of deionized water to form a clear yellow solution. Then, under magnetic stirring (500 r / min), 10 mol / L ammonia solution was slowly added dropwise to adjust the pH of the solution to 10. The mixture was heated to 90 °C and reacted at a constant temperature for 0.5 h to obtain a black precipitate. The black precipitate was washed three times each with deionized water and anhydrous ethanol, and dried at 70 °C for 6 h for later use.

[0103] 1 mmol of tetrabutyl titanate was dissolved in 35 mL of anhydrous ethanol, 0.08 mmol of thiourea and 4 mmol of deionized water were added, and then 0.5 mol / L nitric acid solution was added dropwise to adjust the pH of the mixture to 4, thus obtaining the S-TiO2 precursor sol.

[0104] 1g of black precipitate was dispersed in 40mL of S-TiO2 precursor sol, and then ultrasonically dispersed for 20min under ultrasonic power of 300W. The mixture was then heated and dried at 90℃ for 10h to obtain Fe3O4@S-TiO2 core-shell structured particle precursor.

[0105] Fe3O4@S-TiO2 core-shell structured particle precursors were calcined in a tube furnace filled with nitrogen at a temperature of 550℃ for 1 h to obtain Fe3O4@S-TiO2 core-shell structured magnetic particles.

[0106] (II) The organic pollutants added to the simulated wastewater used in the examples and comparative examples and their concentrations are as follows: Acid Red dye: 50 mg / L; Tetracycline: 20 mg / L; Estradiol: 10 μg / L;

[0107] The overall properties of the simulated wastewater are as follows: Chemical oxygen demand (COD): 300 mg / L; Turbidity: 120 NTU.

[0108] (III) The detection methods for various pollutants in the effluent or supernatant samples of the examples and comparative examples are as follows:

[0109] 1. The concentration of Acid Red dye was determined by ultraviolet-visible spectrophotometry, referring to the HJ 970-2018 standard, by measuring the absorbance at the characteristic absorption wavelength (approximately 510 nm) and using a standard curve.

[0110] 2. Tetracycline: After acidifying the sample to pH 3.0 with 0.1 mol / L hydrochloric acid, solid-phase extraction (SPE) was used for enrichment and purification. An Oasis HLB SPE column (200 mg, 6 mL) was used. The SPE column pretreatment sequence was 5 mL methanol and 5 mL ultrapure water. The acidified water sample was added to the column, followed by elution with 5 mL of a 95:5 methanol / ammonia solution (1 mol / L). The eluent was concentrated to approximately 1 mL by nitrogen blowing and then brought to a final volume of 1 mL with methanol-water (1:1). Concentrated samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS / MS). Chromatographic separation was performed using a C18 column (2.1 mm × 100 mm, 3.5 μm). Mobile phase A was 0.1% formic acid aqueous solution, and mobile phase B was 0.1% formic acid acetonitrile. Gradient elution was used, with mobile phase B increasing from 30% to 90% in the first 0-6 min and maintaining 90% for 6-8 min. The flow rate was 0.3 mL / min, and the injection volume was 10 μL. Mass spectrometry was performed in positive ion electrospray ionization mode, and tetracycline target compounds were detected using multiple reaction monitoring (MRM). A standard curve was established using standard solutions, and quantitative analysis was performed based on the peak area of ​​the sample response to calculate the actual concentration of tetracycline in water.

[0111] 3. The detection method for estradiol is the same as that for tetracycline, except that the mass spectrometry uses electrospray negative ion mode;

[0112] 4. COD was determined according to the "HJ 828-2017 Determination of Chemical Oxygen Demand in Water - Dichromate Method";

[0113] 5. Turbidity shall be determined in accordance with GB / T 13200-1991 Determination of Turbidity in Water.

[0114] Example 1

[0115] Polyaluminum chloride and Fe3O4@Ce-TiO2 core-shell magnetic particles (particle size 100 nm, Ce-TiO2 shell thickness 20 nm) were added to wastewater. The mass of polyaluminum chloride was 0.2% of the wastewater mass, and the concentration of Fe3O4@Ce-TiO2 core-shell magnetic particles was 120 mg / L based on wastewater volume. The mixture was first stirred rapidly for 2 min (300 r / min), then slowly stirred for 10 min (100 r / min) to obtain a mixed liquid containing magnetic flocs. The mixed liquid containing magnetic flocs was introduced into a magnetic separation zone, and a vertical magnetic field of 0.5 T was applied. After settling for 10 min, magnetic flocs and supernatant were obtained.

[0116] The supernatant was introduced into the photocatalytic reaction zone, which contained bismuth metavanadate. The concentration of bismuth metavanadate was 0.3 g / L based on the volume of wastewater. The bismuth metavanadate was dispersed in the photocatalytic reaction zone in powder form and kept in uniform suspension by a built-in circulation pump. Then, the organic pollutants were degraded under ultraviolet light with a wavelength of 370 nm for 60 min.

[0117] The magnetic flocs obtained from sedimentation were added to dilute hydrochloric acid with a concentration of 0.03 mol / L, and then treated with an ultrasonic water bath at a frequency of 40 kHz, a power of 180 W, a temperature of 25 ℃, and a duration of 20 min. The magnetic particles were then collected by magnetic separation and washed multiple times with deionized water until the washing solution was nearly neutral. The obtained magnetic particles can be reused in magnetic coagulation reactions, achieving recycling. The treated water is discharged or reused after passing the tests.

[0118] The effluent from this embodiment was tested, and the test results are shown in Table 1.

[0119] Table 1. Removal effect of pollutants in wastewater in Example 1

[0120] Pollution indicators initial concentration Concentration after treatment Removal rate Acid Red Dye 50mg / L 3.1 mg / L 93.8％ tetracycline 20mg / L 1.8 mg / L 91.0％ estradiol 10 μg / L 0.7 μg / L 93.0％ COD 300mg / L 44mg / L 85.3％ Turbidity 120NTU 5NTU 95.8％

[0121] Example 2

[0122] Polyferric sulfate and Fe3O4@Fe-TiO2 core-shell magnetic particles (particle size 80 nm, Fe-TiO2 shell thickness 10 nm) were added to wastewater. The mass of polyferric sulfate was 0.1% of the wastewater mass, and the concentration of Fe3O4@Fe-TiO2 core-shell magnetic particles was 100 mg / L based on wastewater volume. The mixture was first stirred rapidly for 3 min (400 r / min), then slowly stirred for 12 min (80 r / min) to obtain a mixed liquid containing magnetic flocs. The mixed liquid containing magnetic flocs was introduced into a magnetic separation zone, and a vertical magnetic field of 0.4 T was applied. After settling for 8 min, magnetic flocs and supernatant were obtained.

[0123] The supernatant was introduced into the photocatalytic reaction zone, which contained zinc oxide. The concentration of zinc oxide added was 0.5 g / L based on the volume of wastewater. The zinc oxide was dispersed in the photocatalytic reaction zone in powder form and kept in uniform suspension by an internal circulation pump. Then, the organic pollutants were degraded under visible light at a wavelength of 420 nm for 50 min.

[0124] The magnetic flocs obtained from sedimentation were added to a 0.04 mol / L hydrogen peroxide solution and then treated with an ultrasonic water bath at a frequency of 30 kHz, a power of 150 W, a temperature of 20 °C, and a duration of 30 min. The magnetic particles were then collected by magnetic separation and washed repeatedly with deionized water until the washing solution was nearly neutral. The obtained magnetic particles can be reused in magnetic coagulation reactions, achieving recycling. The treated water is discharged or reused after passing the tests.

[0125] The effluent from this embodiment was tested, and the test results are shown in Table 2.

[0126] Table 2. Removal effect of pollutants in wastewater in Example 2

[0127] Pollution indicators initial concentration Concentration after treatment Removal rate Acid Red Dye 50mg / L 3.2 mg / L 93.6％ tetracycline 20mg / L 1.6 mg / L 92.0％ estradiol 10 μg / L 0.8 μg / L 92.0％ COD 300mg / L 46mg / L 84.7％ Turbidity 120NTU 8NTU 93.3％

[0128] Example 3

[0129] Polyacrylamide and Fe3O4@Zn-TiO2 core-shell magnetic particles (particle size 120 nm, Zn-TiO2 shell thickness 15 nm) were added to wastewater. The mass of polyacrylamide was 0.3% of the wastewater mass, and the concentration of Fe3O4@Zn-TiO2 core-shell magnetic particles was 150 mg / L based on wastewater volume. The mixture was first rapidly stirred for 4 min (450 r / min), then slowly stirred for 15 min (120 r / min) to obtain a mixed liquid containing magnetic flocs. The mixed liquid containing magnetic flocs was introduced into a magnetic separation zone, and a vertical magnetic field of 0.8 T was applied. After settling for 6 min, magnetic flocs and supernatant were obtained.

[0130] The supernatant was introduced into the photocatalytic reaction zone, which contained graphitic carbon nitride. The concentration of graphitic carbon nitride, based on the volume of wastewater, was 0.1 g / L. The graphitic carbon nitride was dispersed in the photocatalytic reaction zone in powder form and kept in uniform suspension by an internal circulation pump. Then, the organic pollutants were degraded under ultraviolet light with a wavelength of 380 nm for 55 min.

[0131] The magnetic flocs obtained from sedimentation were added to dilute hydrochloric acid with a concentration of 0.05 mol / L, and then treated with an ultrasonic water bath at a frequency of 50 kHz, a power of 200 W, a temperature of 30 ℃, and a duration of 10 min. The magnetic particles were then collected by magnetic separation and washed repeatedly with deionized water until the washing solution was nearly neutral. The obtained magnetic particles can be reused in magnetic coagulation reactions, achieving recycling. The treated water is discharged or reused after passing the tests.

[0132] The effluent from this embodiment was tested, and the test results are shown in Table 3.

[0133] Table 3. Removal effect of pollutants in wastewater in Example 3

[0134]

[0135]

[0136] Example 4

[0137] Polyaluminum silicate iron and Fe3O4@N-TiO2 core-shell magnetic particles (particle size of core-shell magnetic particles is 80 nm, and thickness of N-TiO2 shell is 18 nm) were added to the wastewater. The mass of polyaluminum silicate iron was 0.15% of the wastewater mass, and the concentration of Fe3O4@N-TiO2 core-shell magnetic particles was 110 mg / L based on wastewater volume. The mixture was first stirred rapidly for 3 min (speed 500 r / min), and then slowly stirred for 10 min (speed 100 r / min) to obtain a mixed liquid containing magnetic flocs. The mixed liquid containing magnetic flocs was introduced into a magnetic separation zone, and a vertical magnetic field of strength 0.6 T was applied. After settling for 7 min, magnetic flocs and supernatant were obtained.

[0138] The supernatant was introduced into the photocatalytic reaction zone, which contained graphitic carbon nitride. The concentration of graphitic carbon nitride, based on the volume of wastewater, was 0.4 g / L. The graphitic carbon nitride was dispersed in the photocatalytic reaction zone in powder form and kept in uniform suspension by an internal circulation pump. Then, the organic pollutants were degraded under ultraviolet light with a wavelength of 360 nm for 50 min.

[0139] The magnetic flocs obtained from sedimentation were added to a 0.03 mol / L hydrogen peroxide solution and then treated with an ultrasonic water bath at a frequency of 35 kHz, a power of 160 W, a temperature of 25 °C, and a duration of 14 min. The magnetic particles were then collected by magnetic separation and washed repeatedly with deionized water until the washing solution was nearly neutral. The obtained magnetic particles can be reused in magnetic coagulation reactions, achieving recycling. The treated water is discharged or reused after passing testing.

[0140] The effluent from this embodiment was tested, and the test results are shown in Table 4.

[0141] Table 4. Removal effect of pollutants in wastewater in Example 4

[0142]

[0143]

[0144] Example 5

[0145] Polyacrylamide and Fe3O4@S-TiO2 core-shell magnetic particles (particle size 110 nm, S-TiO2 shell thickness 16 nm) were added to wastewater. The mass of polyacrylamide was 0.25% of the wastewater mass, and the concentration of Fe3O4@S-TiO2 core-shell magnetic particles was 130 mg / L based on wastewater volume. The mixture was first rapidly stirred for 4 min (500 r / min), then slowly stirred for 15 min (120 r / min) to obtain a mixed liquid containing magnetic flocs. The mixed liquid containing magnetic flocs was introduced into a magnetic separation zone, a vertical magnetic field of 0.4 T was applied, and the mixture was allowed to settle for 8 min to obtain magnetic flocs and supernatant.

[0146] The supernatant was introduced into the photocatalytic reaction zone, which contained zinc oxide. The concentration of zinc oxide added was 0.35 g / L based on the volume of wastewater. The zinc oxide was dispersed in the photocatalytic reaction zone in powder form and kept in uniform suspension by an internal circulation pump. Then, the organic pollutants were degraded under visible light at a wavelength of 480 nm for 50 min.

[0147] The magnetic flocs obtained from sedimentation were added to a 0.01 mol / L hydrogen peroxide solution and then treated with an ultrasonic water bath at a frequency of 40 kHz, a power of 200 W, a temperature of 25 ℃, and a duration of 10 min. The magnetic particles were then collected by magnetic separation and washed repeatedly with deionized water until the washing solution was nearly neutral. The obtained magnetic particles can be reused in magnetic coagulation reactions, achieving recycling. The treated water is discharged or reused after passing the tests.

[0148] The effluent from this embodiment was tested, and the test results are shown in Table 5.

[0149] Table 5. Removal effect of pollutants in wastewater in Example 5

[0150] Pollution indicators initial concentration Concentration after treatment Removal rate Acid Red Dye 50mg / L 2.8 mg / L 94.4％ tetracycline 20mg / L 1.5 mg / L 92.5％ estradiol 10 μg / L 0.5 μg / L 95.0％ COD 300mg / L 41mg / L 86.3％ Turbidity 120NTU 6NTU 95.0％

[0151] Comparative Example 1

[0152] It is basically the same as Example 1, except that the Fe3O4@Ce-TiO2 core-shell structured magnetic particles of Example 1 are omitted, magnetic separation is not performed, and natural sedimentation is used.

[0153] The effluent from this comparative example was tested, and the test results are shown in Table 6.

[0154] Table 6. Removal efficiency of pollutants in wastewater from Comparative Example 1

[0155] Pollution indicators initial concentration Concentration after treatment Removal rate Acid Red Dye 50mg / L 16.5 mg / L 67.0％ tetracycline 20mg / L 8.2 mg / L 59.0％ estradiol 10 μg / L 3.5 μg / L 65.0％ COD 300mg / L 103mg / L 65.7％ Turbidity 120NTU 49NTU 59.2％

[0156] Comparative Example 2

[0157] The results were basically the same as in Example 1, except that the photocatalytic reaction in Example 1 was omitted and the supernatant was directly tested. The results are shown in Table 7.

[0158] Table 7. Removal efficiency of pollutants in wastewater from Comparative Example 2

[0159] Pollution indicators initial concentration Concentration after treatment Removal rate Acid Red Dye 50mg / L 20.0 mg / L 60.0％ tetracycline 20mg / L 8.4 mg / L 58.0％ estradiol 10 μg / L 4.5 μg / L 55.0％ COD 300mg / L 165mg / L 45.0％ Turbidity 120NTU 6NTU 95.0％

[0160] Comparative Example 3

[0161] The results are basically the same as in Example 1, except that the Fe3O4@Ce-TiO2 core-shell magnetic particles in Example 1 are replaced with undoped modified Fe3O4@TiO2 core-shell magnetic particles.

[0162] The effluent from this comparative example was tested, and the test results are shown in Table 8.

[0163] Table 8. Removal efficiency of pollutants in wastewater from Comparative Example 3

[0164]

[0165]

[0166] Comparative Example 4

[0167] The method is basically the same as in Example 1, except that the Fe3O4@Ce-TiO2 core-shell structure magnetic particles in Example 1 are replaced with Fe3O4 magnetic particles.

[0168] The effluent from this comparative example was tested, and the test results are shown in Table 9.

[0169] Table 9. Removal efficiency of pollutants in wastewater from Comparative Example 4

[0170] Pollution indicators initial concentration Concentration after treatment Removal rate Acid Red Dye 50mg / L 22.5 mg / L 55.0％ tetracycline 20mg / L 10.4 mg / L 48.0％ estradiol 10 μg / L 5.6 μg / L 44.0％ COD 300mg / L 125mg / L 58.3％ Turbidity 120NTU 6NTU 95.0％

[0171] As can be seen from the experimental data in Tables 1 to 9, the magnetic coagulation-photocatalysis integrated treatment method adopted in this invention exhibits excellent performance in the removal of various organic pollutants (such as acid red dye, tetracycline, estradiol), as well as COD and turbidity. In particular, it can still achieve efficient synergistic removal even when the pollutant concentration is high and the types are complex.

[0172] In Comparative Example 1, magnetic particles and magnetic separation were not used; instead, natural sedimentation was employed. The pollutant removal rate was generally below 70%, indicating that the traditional coagulation sedimentation method is difficult to effectively remove dissolved organic pollutants and has low solid-liquid separation efficiency.

[0173] Comparative Example 2 omitted the photocatalytic reaction step. Although it achieved better control of turbidity (95%), the removal rate of recalcitrant organic pollutants such as tetracycline and estradiol decreased significantly to 55-60%, indicating that photocatalysis plays a key role in the deep removal of organic matter.

[0174] Comparative Example 3 used undoped modified Fe3O4@TiO2 core-shell magnetic particles. Although the pollutant removal rate was slightly better than that of single coagulation, it was still significantly lower than that of the doped modified Fe3O4@Ce-TiO2 core-shell magnetic particles in this invention, which verifies the enhancing effect of doping elements on the photocatalytic activity of TiO2.

[0175] Comparative Example 4 further removed the functional shell and used only Fe3O4 magnetic particles, resulting in the lowest removal rate (only 48% for tetracycline and only 44% for estradiol), indicating that the magnetic core lacks photocatalytic function and cannot effectively degrade dissolved organic pollutants.

[0176] In summary, this invention, by constructing doped and modified Fe3O4@TiO2 core-shell structure magnetic particles and combining magnetic coagulation to enhance sedimentation with photocatalytic high-efficiency oxidation, exhibits a synergistic effect in removing color, antibiotics, hormones, and COD, significantly outperforming various control group treatment methods. This verifies its applicability and advanced nature in practical complex wastewater treatment.

[0177] 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 integrated magnetic coagulation-photocatalysis treatment of wastewater, characterized in that, It includes the following steps: 1) Add coagulant and magnetic particles to wastewater to carry out magnetic coagulation reaction and obtain a mixed liquid containing magnetic flocs; 2) The mixture containing magnetic flocs is introduced into the magnetic separation zone, and a magnetic field is applied to cause the magnetic flocs to settle, thus obtaining the supernatant; 3) The supernatant is introduced into the photocatalytic reaction zone for photocatalytic oxidation and degradation of organic pollutants under the action of a light source; 4) The magnetic flocs obtained from sedimentation are washed and regenerated, and the recovered magnetic particles are recycled for use in step 1). The treated water is discharged or reused after passing the test.

2. The method for treating wastewater according to claim 1, characterized in that, The coagulant in step 1) is one or more of polyaluminum chloride, polyferric sulfate, polyacrylamide, and polyaluminum ferric silicate; The mass of the coagulant is 0.1% to 0.3% of the wastewater mass.

3. The method for treating wastewater according to claim 1 or 2, characterized in that, Step 1) The magnetic particles are core-shell structured magnetic particles, which consist of a magnetic core layer and a functional shell layer; The magnetic core layer is iron(II,III) oxide, and the functional shell layer is doped and modified titanium dioxide, with the doping element being Fe, Ce, Zn, N, or S.

4. The method for treating wastewater according to claim 3, characterized in that, The core-shell structured magnetic particles have a particle size of 80–120 nm and a functional shell thickness of 10–20 nm.

5. The method for treating wastewater according to claim 4, characterized in that, The concentration of the magnetic particles added in step 1) is 100-150 mg / L based on the volume of wastewater.

6. The method for treating wastewater according to claim 4 or 5, characterized in that, Step 3) The photocatalytic reaction zone contains a photocatalytic material, which is one or more of bismuth metavanadate, zinc oxide and graphitic carbon nitride. The concentration of the photocatalytic material added, based on the volume of wastewater, is 0.1–0.5 g / L.

7. The method for treating wastewater according to claim 6, characterized in that, Step 3) The light source is ultraviolet light and / or visible light, with the wavelength of ultraviolet light being 360-380nm and the wavelength of visible light being 420-480nm.

8. The method for treating wastewater according to claim 7, characterized in that, Step 3) The organic pollutant is one or more of the following: dye pollutants, antibiotic pollutants, and hormone pollutants.

9. The method for treating wastewater according to claim 8, characterized in that, Step 4) describes a elution and regeneration method that combines ultrasonic oscillation with chemical elution.

10. The method for treating wastewater according to claim 8 or 9, characterized in that, The magnetic separation zone in step 2) and the photocatalytic reaction zone in step 3) are located in an integrated processing device, wherein the magnetic separation zone is located upstream and the photocatalytic reaction zone is located downstream; The integrated processing device includes a continuous flow channel, a magnetic separation zone, and a photocatalytic reaction zone.

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