High-flocculation sewage treatment method

Abstract

The invention relates to a high-flocculation sewage treatment method which comprises the following steps: S1, carrying out preliminary pretreatment on raw water; s2, adding a modified flocculant into the sewage; s3, adjusting the pH value of the sewage to 4.5 to 6.5; s4, stirring for 5 minutes at the speed of 200 to 300 rpm, and then stirring for 5 minutes at the speed of 50 to 80 rpm; s5, executing the step S4 at the same time: applying a 0.1-0.3 T magnetic field with a period of 15 seconds in the horizontal direction to the sewage, and applying a vertical constant 0.1-0.3 T magnetic field at the same time; the preparation process of the modified flocculant comprises the following steps: surface modification of Fe3O4NPs, preparation of an SPI solution, preparation of an SPI-Fe3O4 composite solution, and ultraviolet radiation modification. Based on reasonable cooperation of the preparation process, the sulfate adsorption effect and the suspended matter adsorption effect are improved in a breakthrough mode, and an efficient flocculation-deep deodorization-efficient separation three-in-one sewage treatment system is constructed.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a sewage treatment method with high flocculation. Background Art

[0002] In the field of sewage treatment, the conventional treatment process usually includes key steps such as pretreatment, flocculation, sedimentation, and advanced treatment. Among them, the flocculation process is the core link for removing suspended solids in sewage by adding flocculants to the sewage to destabilize and agglomerate the suspended solids in the water into larger flocs. For secondary municipal sewage, aquaculture sewage, and printing sewage, the efficiency of the flocculation process directly determines the subsequent sedimentation separation efficiency and the effluent water quality compliance rate. However, with the increasingly strict sewage discharge standards, traditional flocculation technologies face multiple technical bottlenecks, especially in the treatment of sulfate-containing wastewater, it is difficult to achieve a balance between efficient purification and resource utilization.

[0003] In the prior art, aluminum salt-based flocculants represented by polyaluminum chloride (PAC) are widely used. There are the following problems when using PAC for flocculation:

[0004] Slow sedimentation rate: The flocs formed by PAC have low density and loose structure, and it takes 1 - 2 hours to reach the discharge standard under natural sedimentation conditions. Moreover, they are easily disturbed by water flow, resulting in floc breakage and backmixing, and it is difficult to meet the high-load sewage treatment requirements;

[0005] Lack of sulfate capture ability: PAC has no adsorption or chemical precipitation effect on soluble inorganic salts such as sulfate (SO42-), resulting in the often excessive sulfate concentration in the effluent, which not only causes the risk of salinization of the receiving water body, but also causes malodorous pollution due to the production of hydrogen sulfide (H2S) by the metabolism of sulfate-reducing bacteria (SRB). Summary of the Invention

[0006] The present invention provides a sewage treatment method with high flocculation, which can achieve rapid sedimentation while improving the flocculation effect.

[0007] The technical solution adopted by the present invention:

[0008] A sewage treatment method with high flocculation includes the following steps:

[0009] S1. Conduct preliminary pretreatment on the raw water to remove large particle debris and suspended solids in the sewage;

[0010] S2. Add a modified flocculant to the sewage;

[0011] S3. Adjust the pH of the sewage to 4.5 - 6.5;

[0012] S4. Stir rapidly at 200 - 300 rpm for 5 minutes, and then stir slowly at 50 - 80 rpm for 5 minutes;

[0013] S5. While performing step S4, apply an alternating magnetic field with a horizontal period of 15 seconds and a magnitude of 0.1 - 0.3 T to the sewage, and simultaneously apply a vertical constant magnetic field of 0.1 - 0.3 T.

[0014] The preparation process of the modified flocculant includes surface modification of Fe3O4 NPs, preparation of SPI solution, preparation of SPI - Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection, and drying.

[0015] Further, the method for surface modification of Fe3O4 NPs is as follows: Mix 1 part of 1.2% w / v sodium citrate solution with 1 part of 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4 NPs to 20 - 30 parts of the mixed solution by weight. Perform ultrasonic treatment in an ice bath, treat at 40 - 50 kHz for 30 minutes, extract and separate the modified Fe3O4 NPs with a strong magnet, wash them 3 times with deionized water and 2 times with ethanol in sequence, and vacuum dry at 50 - 55 °C for 12 hours.

[0016] Further, the method for preparing the SPI solution is as follows: Mix 5 - 7 parts of SPI with 100 parts of deionized water by weight. Adjust the pH of the solution to 7 - 8 with 1M NaOH. Stir at a high speed of 500 - 600 rpm in a constant temperature water bath at 53 - 57 °C for 10 minutes, then reduce the speed to 300 - 350 rpm and stir for 50 minutes, and then centrifuge at 3900 - 4000 rpm for 10 minutes to obtain the SPI solution.

[0017] Further, the method for preparing the SPI - Fe3O4 composite solution is as follows: Add 1 part of the modified Fe3O4 NPs to 8 - 10 parts of the SPI solution by weight. Perform ultrasonic treatment in an ice bath at 40 - 50 kHz for 25 minutes. Add glutaraldehyde and stir at 500 - 600 rpm for 10 minutes, then add genipin and continue stirring for 50 minutes. Glutaraldehyde is 1% of the mass of SPI, and genipin is 0.3% of the mass of SPI. Stir at 300 - 350 rpm at 53 - 57 °C for 30 minutes to obtain the mixed solution A.

[0018] Further, add 0.25 part of zirconium - loaded aminated mesoporous silica to 30 - 35 parts of the mixed solution A by weight, stir at 400 - 600 rpm for 1 hour, and maintain the temperature at 23 - 27 °C to obtain the mixed solution B.

[0019] The preparation process of the zirconium-loaded aminated mesoporous silica is as follows: according to the solid-liquid weight ratio of 1:20, the aminated mesoporous silica is impregnated in a zirconium oxychloride precursor solution with a concentration of 0.15 - 0.25 mol / L; ultrasonic treatment is carried out at 55 - 65 °C for 40 minutes with a frequency of 45 kHz, and then the mixture is kept standing and reacting at a constant temperature of 75 - 85 °C for 6 hours, and the pH of the system is maintained at 8.0 - 8.5 during the reaction process; after the reaction is completed, the solid is separated by centrifugation, and the separated solid is washed with deionized water for more than 5 times; the washed product is dried at 75 - 85 °C for 12 hours, and then calcined at 480 - 520 °C for 3 hours with a heating rate of 4 - 6 °C / min.

[0020] Further, the particle size of the loaded amino-functionalized mesoporous silica is 100 - 200 nm, and the pore diameter is 10 - 40 nm.

[0021] Further, the ultraviolet irradiation modification method is as follows: transfer the mixed solution B into a quartz container that can transmit ultraviolet light, use an ultraviolet lamp with a wavelength of 254 nm and a power of 35 W, keep the distance from the liquid surface at 10 cm, and continuously irradiate for 2 hours. During the irradiation process, maintain magnetic stirring at 550 - 650 rpm to obtain the mixed solution C.

[0022] Further, the magnetic collection and drying method is as follows: stir the mixed solution C with a strong magnet, lift the strong magnet and collect the adsorbed substances, repeat the operation until there are no adsorbed substances on the strong magnet, wash with deionized water 5 times and ethanol 5 times in sequence, and freeze-dry at a temperature below -45 °C until the moisture content is below 3%.

[0023] Further, the raw water is one of municipal secondary sewage, aquaculture sewage, and printing sewage. In step S5, after the stirring is completed, a vertical constant magnetic field of 0.4 T is applied to accelerate flocculation precipitation.

[0024] Further, the core particle size of Fe3O4 NPs is 6 - 10 nm.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. Through the cooperation of stepwise stirring and alternating magnetic field, the modified flocculant can be quickly mixed with sewage, which is beneficial to improving the flocculation effect. Based on the self-weight of the modified flocculant and the aggregation of flocculent masses, the flocculent masses have a small buoyancy in the sewage. Coupled with the application of a vertical constant magnetic field, the flocculation precipitation time can be greatly improved. Due to the reasonable cooperation of the preparation process, the present invention has a breakthrough improvement in both the adsorption effects of sulfates and suspended solids. The present invention constructs a three-in-one sewage treatment system of "efficient flocculation - deep deodorization - efficient separation".

[0027] 2. Through the three - level strengthening mechanism of "magnetic core - induced assembly - protein cross - linking and curing - mesoporous silica framework support", the flocculant aggregates have both high mechanical strength, high pollutant adsorption capacity and excellent sedimentation performance. They can still maintain structural stability under complex water quality conditions, and the floc recovery rate is high. Detailed implementation manners

[0028] To better understand the technical content of the present invention, specific embodiments are provided below.

[0029] Embodiment 1

[0030] A high - flocculation sewage treatment method includes the following steps:

[0031] S1. Conduct preliminary pretreatment on the raw water to remove large - particle debris and suspended solids in the sewage;

[0032] S2. Add a modified flocculant to the sewage;

[0033] S3. Adjust the pH of the sewage to 4.5;

[0034] S4. Stir rapidly at 200 rpm for 5 minutes, and then stir slowly at 50 rpm for 5 minutes;

[0035] S5. While performing step S4, perform: Apply an alternating magnetic field of 0.1 T with a horizontal period of 15 s to the sewage, and at the same time apply a vertical constant magnetic field of 0.1 T;

[0036] The preparation process of the modified flocculant includes surface modification of Fe3O4 NPs, preparation of SPI solution, preparation of SPI - Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection and drying.

[0037] Through the modified flocculant under suitable acidity and alkalinity, combined with mechanical stirring and alternating electromagnetic synergy, the flow rate of the flocculant in the sewage can be greatly improved, enabling the modified flocculant to fully exert its flocculation effect. Applying a vertical constant magnetic field while stirring makes the flocculant aggregates tend to move downward, which can greatly improve the precipitation speed.

[0038] Preferably, the surface modification method of Fe3O4 NPs is as follows: Mix 1 part of 1.2% w / v sodium citrate solution with 1 part of 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4 NPs to 20 parts of the mixed solution by weight, and perform ultrasonic treatment in an ice bath, treating at 40 kHz for 30 minutes. Extract and separate the modified Fe3O4 NPs with a strong magnet, wash them 3 times with deionized water and 2 times with ethanol in sequence, and vacuum - dry at 50 °C for 12 hours.

[0039] After modification by the appropriate process, the balance among the dispersibility, adsorption capacity and magnetic responsiveness of Fe3O4 NPs provides a basis for constructing an efficient magnetic flocculant.

[0040] Preferably, the preparation method of the SPI solution is as follows: 5 parts by weight of SPI are mixed with 100 parts of deionized water, and the pH of the solution is adjusted to 7 with 1M NaOH, providing an ideal chemical environment for the full dissolution and stability of SPI. It is stirred at a high speed of 500 rpm in a constant temperature water bath at 53 °C for 10 minutes, effectively promoting the rapid dispersion and preliminary hydration of SPI. Then it is cooled to 300 rpm and stirred for 50 minutes, enabling the SPI molecules to be more fully and evenly hydrated and unfolded, further enhancing the uniformity and stability of the solution. Then it is centrifuged at 3900 rpm for 10 minutes, effectively removing insoluble impurities and undissolved particles in the solution, and finally obtaining a clear, transparent and excellent-performance SPI solution, laying a solid foundation for subsequent processing and application.

[0041] Preferably, the preparation method of the SPI-Fe3O4 composite liquid is as follows: 1 part by weight of modified Fe3O4 NPs is added to 8 parts of the SPI solution, and ultrasonic treatment is carried out in an ice bath at 40 kHz for 25 minutes, which is beneficial to improving the monodispersion of modified Fe3O4 NPs in the SPI solution. Glutaraldehyde is added and stirred at 500 rpm for 10 minutes, and genipin is added and stirred continuously for 50 minutes. Glutaraldehyde is 1% of the mass of SPI and genipin is 0.3% of the mass of SPI. It is stirred at 300 rpm at 53 °C for 30 minutes to obtain solution A. Through the step-by-step strengthening of the double cross-linking agent, a dense "protein-magnetic core" network is formed after the modification of SPI-Fe3O4 NPs, greatly improving the adsorption capacity of pollutants and the mechanical strength of flocs, and greatly improving the flocculation effect and sedimentation rate.

[0042] Preferably, 0.25 part of zirconium-loaded aminated mesoporous silica is added to 30 parts by weight of the mixed solution A.

[0043] It is stirred at 400 rpm for 1 hour while maintaining the temperature at 23 °C to obtain the mixed solution B;

[0044] The preparation process of the zirconium-loaded aminated mesoporous silica is as follows: According to the solid-liquid weight ratio of 1:20, the aminated mesoporous silica is impregnated in a 0.15 mol / L zirconium oxychloride precursor solution; ultrasonic treatment is carried out at 55 °C for 40 minutes with a frequency of 45 kHz, and then it is kept standing and reacting at 75 °C for 6 hours, and the pH of the system is maintained at 8.0 - 8.5 during the reaction process; after the reaction is completed, the solid is separated by centrifugation, and the separated solid is washed with deionized water more than 5 times; the washed product is dried at 75 °C for 12 hours, and then calcined at 480 °C for 3 hours with a heating rate of 4 °C / min.

[0045] This preparation process significantly improves the material's adsorption performance for sulfate and suspended matter and process applicability by optimizing the synthesis conditions of zirconium-loaded aminated mesoporous silica: a reasonable solid-liquid ratio impregnation method combined with ultrasound-assisted penetration is used to ensure uniform dispersion and deep loading of the zirconium oxychloride precursor within the pores of aminated mesoporous silica; the synergistic coordination of zirconium species and amino sites is achieved, while the integrity of the mesoporous structure is improved. Zirconium-loaded aminated mesoporous silica is suitable for deep adsorption treatment of complex water conditions.

[0046] Preferably, the supported aminated mesoporous silica has a particle size of 100 nm and a pore size of 10 nm.

[0047] Preferably, the ultraviolet irradiation modification method is to transfer the mixed solution B into a quartz container that is transparent to ultraviolet light, use an ultraviolet lamp with a wavelength of 254nm and a power of 35W, 10cm away from the liquid surface, and continuously irradiate for 2 hours, maintaining magnetic stirring at 550rpm during the irradiation process to obtain a mixed solution C.

[0048] The above process uses UV irradiation with specific parameters to continuously treat the mixed solution B, and is supplemented by high-speed magnetic stirring, and successfully uses UV light to initiate crosslinking and grafting between the surface of zirconium-loaded amino-modified mesoporous silica and SPI-Fe3O4NPs. This combined process synergistically optimizes the interface bonding and compatibility of the nanocomposite material, and can also give the final product better stability, mechanical properties, reactivity and load capacity through photochemical modification.

[0049] Preferably, the magnetic collection and drying method is to use a strong magnet to stir the mixed solution C, lift the strong magnet and collect the adsorbent, repeat the operation until there is no adsorbent on the strong magnet, wash it with deionized water 5 times and ethanol 5 times in sequence, and freeze-dry it below -45°C to a moisture content of less than 3%.

[0050] The above process can efficiently extract high-purity modified flocculant.

[0051] Preferably, the raw water is one of municipal secondary sewage, aquaculture sewage and printing sewage. In step S5, after stirring, a vertical constant 0.4T magnetic field is applied to accelerate flocculation and sedimentation.

[0052] Preferably, the core particle size of Fe3O4NPs is 6-10nm.

[0053] Embodiment 2

[0054] A high flocculation sewage treatment method comprises the following steps:

[0055] S1. Preliminary pretreatment of raw water to remove large particles and suspended matter in sewage;

[0056] S2. Add a modified flocculant to the sewage;

[0057] S3. Adjust the pH of the sewage to 6.5;

[0058] S4. Stir rapidly at 300 rpm for 5 minutes, and then stir slowly at 80 rpm for 5 minutes;

[0059] S5. While performing step S4, the following operations are carried out simultaneously: Apply an alternating magnetic field of 0.3 T with a horizontal period of 15 seconds to the sewage, and at the same time apply a vertical constant magnetic field of 0.3 T;

[0060] The preparation process of the modified flocculant includes surface modification of Fe3O4 NPs, preparation of SPI solution, preparation of SPI-Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection and drying.

[0061] Preferably, the method for surface modification of Fe3O4 NPs is as follows: Mix 1 part of 1.2% w / v sodium citrate solution with 1 part of 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4 NPs by weight to 30 parts of the mixed solution, and perform ultrasonic treatment in an ice bath at 50 kHz for 30 minutes. Extract and separate the modified Fe3O4 NPs with a strong magnet, wash them 3 times with deionized water and 2 times with ethanol in sequence, and dry them in a vacuum at 55 °C for 12 hours.

[0062] Preferably, the method for preparing the SPI solution is as follows: Mix 7 parts of SPI with 100 parts of deionized water by weight, adjust the pH of the solution to 8 with 1 M NaOH, stir at a high speed of 600 rpm in a constant temperature water bath at 57 °C for 10 minutes, then reduce the speed to 350 rpm and stir for 50 minutes, and then centrifuge at 4000 rpm for 10 minutes to obtain the SPI solution.

[0063] Preferably, the method for preparing the SPI-Fe3O4 composite solution is as follows: Add 1 part of modified Fe3O4 NPs by weight to 10 parts of the SPI solution, perform ultrasonic treatment in an ice bath at 50 kHz for 25 minutes, add glutaraldehyde and stir at 600 rpm for 10 minutes, add genipin and continue stirring for 50 minutes. Glutaraldehyde is 1% of the mass of SPI, and genipin is 0.3% of the mass of SPI. Stir at 300 rpm - 350 rpm at 57 °C for 30 minutes to obtain solution A.

[0064] Preferably, add 0.25 part of zirconium-loaded aminated mesoporous silica to 35 parts of the mixed solution A by weight, stir at 600 rpm for 1 hour, and keep the temperature at 27 °C to obtain the mixed solution B;

[0065] The preparation process of the zirconium-loaded aminated mesoporous silica is as follows: The aminated mesoporous silica is impregnated in a zirconium oxychloride precursor solution with a concentration of 0.25 mol / L according to a solid-liquid weight ratio of 1:20; ultrasonically treated at 65 °C for 40 minutes with a frequency of 45 kHz, and then kept standing and reacting at a constant temperature of 85 °C for 6 hours. During the reaction process, the pH of the system is maintained at 8.0 - 8.5; after the reaction, the solid is separated by centrifugation, and the separated solid is washed with deionized water more than 5 times; the washed product is dried at 85 °C for 12 hours, and then calcined at 520 °C for 3 hours with a heating rate of 6 °C / min.

[0066] Preferably, the particle size of the loaded aminated mesoporous silica is 200 nm, and the pore diameter is 40 nm.

[0067] Preferably, the ultraviolet irradiation modification method is as follows: Transfer the mixed solution B into a quartz container that can transmit ultraviolet light, and use an ultraviolet lamp with a wavelength of 254 nm and a power of 35 W, at a distance of 10 cm from the liquid surface, and irradiate continuously for 2 hours. During the irradiation process, maintain magnetic stirring at 650 rpm to obtain the mixed solution C.

[0068] Preferably, the magnetic collection and drying method is as follows: Stir the mixed solution C with a strong magnet, lift the strong magnet and collect the adsorbed substances, and repeat the operation until there are no adsorbed substances on the strong magnet. Wash it with deionized water 5 times and ethanol 5 times in sequence, and freeze-dry at a temperature below -45 °C until the moisture content is below 3%.

[0069] Preferably, the raw water is one of municipal secondary sewage, aquaculture sewage, and printing sewage. In step S5, after the stirring is completed, apply a vertical constant magnetic field of 0.4 T to accelerate flocculation precipitation.

[0070] Preferably, the core particle size of Fe3O4 NPs is 6 - 10 nm.

[0071] Example Three

[0072] A sewage treatment method with high flocculation includes the following steps,

[0073] S1. Conduct preliminary pretreatment on the raw water to remove large particle debris and suspended solids in the sewage;

[0074] S2. Add a modified flocculant to the sewage;

[0075] S3. Adjust the pH of the sewage to 5.5;

[0076] S4. Stir rapidly at 250 rpm for 5 minutes, and then stir slowly at 65 rpm for 5 minutes;

[0077] S5. While performing step S4, perform the following operations: Apply an alternating magnetic field of 0.2 T with a horizontal direction period of 15 seconds to the sewage, and at the same time apply a vertical constant magnetic field of 0.2 T;

[0078] The preparation process of the modified flocculant includes surface modification of Fe3O4 NPs, preparation of SPI solution, preparation of SPI-Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection and drying.

[0079] Preferably, the method for surface modification of Fe3O4 NPs is as follows: Mix 1 part of 1.2% w / v sodium citrate solution with 1 part of 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4 NPs by weight to 25 parts of the mixed solution. Ultrasonically treat under ice bath, treat at 45 kHz for 30 minutes, extract and separate the modified Fe3O4 NPs with a strong magnet, wash 3 times with deionized water and 2 times with ethanol in sequence, and vacuum dry at 45 °C for 12 hours.

[0080] Preferably, the method for preparing the SPI solution is as follows: Mix 6 parts of SPI with 100 parts of deionized water by weight, adjust the pH of the solution to 7.5 with 1M NaOH, stir at a high speed of 550 rpm in a constant temperature water bath at 55 °C for 10 minutes, then reduce the speed to 330 rpm and stir for 50 minutes, and then centrifuge at 3950 rpm for 10 minutes to obtain the SPI solution.

[0081] Preferably, the method for preparing the SPI-Fe3O4 composite solution is as follows: Add 1 part of modified Fe3O4 NPs by weight to 9 parts of SPI solution, ultrasonically treat under ice bath at 45 kHz for 25 minutes, add glutaraldehyde and stir at 550 rpm for 10 minutes, add genipin and continue to stir for 50 minutes. Glutaraldehyde is 1% of the mass of SPI and genipin is 0.3% of the mass of SPI. Stir at 325 rpm at 55 °C for 30 minutes to obtain the mixed solution A.

[0082] Preferably, add 0.25 part of zirconium-loaded aminated mesoporous silica to 33 parts of the mixed solution A by weight, stir at 500 rpm for 1 hour, and keep the temperature at 25 °C to obtain the mixed solution B;

[0083] The preparation process of the zirconium-loaded aminated mesoporous silica is as follows: Immerse the aminated mesoporous silica in a 0.2 mol / L zirconium oxychloride precursor solution according to the solid-liquid weight ratio of 1:20; ultrasonically treat at 60 °C for 40 minutes with a frequency of 45 kHz, and then keep it standing and reacting at a constant temperature of 75 - 85 °C for 6 hours, maintaining the system pH = 8.0 - 8.5 during the reaction; after the reaction, centrifuge to separate the solid, wash the separated solid with deionized water more than 5 times; dry the washed product at 80 °C for 12 hours, then calcine at 500 °C for 3 hours with a heating rate of 5 °C / min.

[0084] Preferably, the particle size of the loaded aminated mesoporous silica is 150 nm and the pore diameter is 20 nm.

[0085] Preferably, the ultraviolet irradiation modification method is to transfer the mixed solution B into a quartz container that can transmit ultraviolet light, and use an ultraviolet lamp with a wavelength of 254 nm and a power of 35 W. Keep the distance from the liquid surface at 10 cm and irradiate continuously for 2 hours. During the irradiation process, maintain magnetic stirring at 600 rpm to obtain the mixed solution C.

[0086] Preferably, the magnetic collection and drying method is to stir the mixed solution C with a strong magnet, lift the strong magnet and collect the adsorbed substances, and repeat the operation until there are no adsorbed substances on the strong magnet. Wash it 5 times with deionized water and 5 times with ethanol in sequence, and freeze-dry it at a temperature below -45°C until the water content is below 3%.

[0087] Preferably, the raw water is one of municipal secondary sewage, aquaculture sewage, and printing sewage. In step S5, after the stirring is completed, apply a vertical constant magnetic field of 0.4 T to accelerate flocculation precipitation.

[0088] Preferably, the core particle size of Fe3O4NPs is 6 - 10 nm.

[0089] Comparative Example 1

[0090] Directly use PAC as the flocculant.

[0091] A high-flocculation sewage treatment method includes the following steps:

[0092] S1. Conduct preliminary pretreatment on the raw water to remove large particle debris and suspended solids in the sewage;

[0093] S2. Add PAC to the sewage, and the dosage is 25 mg / L;

[0094] S3. Adjust the pH of the sewage to 6.5;

[0095] S4. Stir rapidly at 200 rpm for 5 minutes, and then stir slowly at 50 rpm for 10 minutes;

[0096] S5. While performing step S4, perform the following operations: Apply an alternating magnetic field of 0.1 T with a horizontal direction period of 15 seconds to the sewage, and at the same time apply a vertical constant magnetic field of 0.1 T. After the stirring is completed, apply a vertical constant magnetic field of 0.4 T to accelerate flocculation precipitation.

[0097] Comparative Example 2

[0098] Directly use Fe3O4NPs as the flocculant.

[0099] A high-flocculation sewage treatment method includes the following steps:

[0100] S1. Conduct preliminary pretreatment on the raw water to remove large particle debris and suspended solids in the sewage;

[0101] S2. Add Fe3O4 NPs to the sewage;

[0102] S3. Adjust the pH of the sewage to 4.5;

[0103] S4. Stir rapidly at 200 rpm for 5 minutes, and then stir slowly at 50 rpm for 5 minutes;

[0104] S5. While performing step S4, perform the following: Apply an alternating magnetic field of 0.1 T with a horizontal period of 15 seconds to the sewage, and at the same time apply a vertical constant magnetic field of 0.1 T. After the stirring is completed, apply a vertical constant magnetic field of 0.4 T to accelerate flocculation precipitation

[0105] Preferably, the core particle size of Fe3O4 NPs is 6 - 10 nm.

[0106] Comparative Example 3

[0107] The difference from Example 1 is that the treatment steps for removal are as follows:

[0108] The surface modification method of the Fe3O4 NPs is as follows: Mix 1 part of a 1.2% w / v sodium citrate solution with 1 part of a 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4 NPs to 20 parts of the mixed solution by weight. Perform ultrasonic treatment in an ice bath, treat at 40 kHz for 30 minutes, extract and separate the modified Fe3O4 NPs with a strong magnet, wash 3 times with deionized water and 2 times with ethanol in sequence, and dry in vacuum at 50 °C for 12 hours.

[0109] The implementation plan is as follows:

[0110] A sewage treatment method with high flocculation, including the following steps,

[0111] S1. Perform preliminary pretreatment on the raw water to remove large particulate impurities and suspended solids in the sewage;

[0112] S2. Add a modified flocculant to the sewage;

[0113] S3. Adjust the pH of the sewage to 4.5;

[0114] S4. Stir rapidly at 200 rpm for 5 minutes, and then stir slowly at 50 rpm for 5 minutes;

[0115] S5. While performing step S4, perform the following: Apply an alternating magnetic field of 0.1 T with a horizontal period of 15 seconds to the sewage, and at the same time apply a vertical constant magnetic field of 0.1 T;

[0116] The preparation process of the modified flocculant includes the surface modification of Fe3O4 NPs, the preparation of SPI solution, the preparation of SPI-Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection and drying.

[0117] Preferably, the preparation method of the SPI solution is as follows: 5 parts by weight of SPI are mixed with 100 parts of deionized water, the pH of the solution is adjusted to 7 with 1M NaOH, and it is stirred at a high speed of 500 rpm in a constant temperature water bath at 53 °C for 10 minutes, then the stirring speed is reduced to 300 rpm and stirred for 50 minutes, and then centrifuged at 3900 rpm for 10 minutes.

[0118] Preferably, the preparation method of the SPI-Fe3O4 composite solution is as follows: 1 part by weight of Fe3O4 NPs is added to 8 parts of the SPI solution, and it is ultrasonically treated in an ice bath at 40 kHz for 25 minutes, then stirred at 500 rpm for 10 minutes after adding glutaraldehyde, and genipin is added and stirred continuously for 50 minutes. The glutaraldehyde is 1% of the mass of SPI, and genipin is 0.3% of the mass of SPI, and it is stirred at 300 rpm at 53 °C for 30 minutes to obtain solution A.

[0119] Preferably, 0.25 part by weight of zirconium-loaded aminated mesoporous silica is added to 30 parts of the mixed solution A, and it is stirred at 400 rpm for 1 hour while maintaining the temperature at 23 °C to obtain the mixed solution B;

[0120] The preparation process of the zirconium-loaded aminated mesoporous silica is as follows: According to the solid-liquid weight ratio of 1:20, the aminated mesoporous silica is impregnated in a 0.15 mol / L zirconium oxychloride precursor solution; ultrasonically treated at 55 °C for 40 minutes with a frequency of 45 kHz, and then kept standing and reacting at a constant temperature of 75 °C for 6 hours, and the pH of the system is maintained at 8.0 - 8.5 during the reaction; after the reaction, the solid is separated by centrifugation, and the separated solid is washed with deionized water more than 5 times; the washed product is dried at 75 °C for 12 hours, and then calcined at 480 °C for 3 hours with a heating rate of 4 °C / min.

[0121] Preferably, the particle size of the loaded aminated mesoporous silica is 100 nm, and the pore diameter is 10 nm.

[0122] Preferably, the ultraviolet irradiation modification method is as follows: The mixed solution B is transferred to a quartz container permeable to ultraviolet light, and an ultraviolet lamp with a wavelength of 254 nm and a power of 35 W is used, and the distance from the liquid surface is 10 cm, and it is irradiated continuously for 2 hours. During the irradiation process, magnetic stirring is maintained at 550 rpm to obtain the mixed solution C.

[0123] Preferably, the magnetic collection and drying method is as follows: The mixed solution C is stirred with a strong magnet, the strong magnet is lifted and the adsorbed substances are collected, and the operation is repeated until there is no adsorbed substance on the strong magnet. It is washed 5 times with deionized water and 5 times with ethanol in sequence, and freeze-dried at -45 °C or below until the moisture content is below 3%.

[0124] Preferably, the raw water is one of municipal secondary sewage, aquaculture sewage and printing sewage. In step S5, after the stirring is completed, a vertical constant magnetic field of 0.4 T is applied to accelerate flocculation and precipitation.

[0125] Preferably, the core particle size of Fe3O4 NPs is 6-10 nm.

[0126] Comparative Example 4

[0127] The difference from Example 1 is that the removal treatment steps are as follows: Add 0.25 parts of zirconium-loaded aminated mesoporous silica to 30 parts of mixed solution A by weight, stir at 400 rpm for 1 hour, keep the temperature at 23 °C, and obtain mixed solution B;

[0128] The preparation process of the zirconium-loaded aminated mesoporous silica is as follows: Immerse the aminated mesoporous silica in a 0.15 mol / L zirconium oxychloride precursor solution according to a solid-liquid weight ratio of 1:20; Ultrasonically treat for 40 minutes at 55 °C, with a frequency of 45 kHz, and then keep it standing and reacting at a constant temperature of 75 °C for 6 hours. During the reaction process, maintain the system pH = 8.0-8.5; After the reaction, centrifuge to separate the solid, and wash the separated solid with deionized water more than 5 times; The washed product is dried at 75 °C for 12 hours, and then calcined at 480 °C for 3 hours, with a heating rate of 4 °C / min.

[0129] The particle size of the loaded aminated mesoporous silica is 100 nm, and the pore diameter is 10 nm.

[0130] The ultraviolet irradiation modification method is as follows: Transfer mixed solution B to a quartz container that transmits ultraviolet light, use an ultraviolet lamp with a wavelength of 254 nm and a power of 35 W, keep a distance of 10 cm from the liquid surface, and irradiate continuously for 2 hours. During the irradiation process, maintain magnetic stirring at 550 rpm to obtain mixed solution C.

[0131] This example is as follows:

[0132] A sewage treatment method with high flocculation includes the following steps,

[0133] S1. Conduct preliminary pretreatment on the raw water to remove large particulate impurities and suspended solids in the sewage;

[0134] S2. Add a modified flocculant to the sewage;

[0135] S3. Adjust the pH of the sewage to 4.5;

[0136] S4. Stir rapidly at 200 rpm for 5 minutes, and then stir slowly at 50 rpm for 5 minutes;

[0137] S5. While performing step S4, perform the following: Apply an alternating magnetic field of 0.1 T with a horizontal direction period of 15 seconds to the sewage, and at the same time apply a vertical constant magnetic field of 0.1 T;

[0138] The preparation process of the modified flocculant includes surface modification of Fe3O4 NPs, preparation of SPI solution, preparation of SPI-Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection and drying.

[0139] Preferably, the method for surface modification of Fe3O4 NPs is as follows: Mix 1 part of 1.2% w / v sodium citrate solution with 1 part of 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4 NPs to 20 parts of the mixed solution by weight. Perform ultrasonic treatment in an ice bath, treat at 40 kHz for 30 minutes, extract and separate the modified Fe3O4 NPs with a strong magnet, wash them 3 times with deionized water and 2 times with ethanol in sequence, and dry them in vacuum at 50 °C for 12 hours.

[0140] Preferably, the method for preparing the SPI solution is as follows: Mix 5 parts of SPI with 100 parts of deionized water by weight, adjust the pH of the solution to 7 with 1M NaOH, stir at a high speed of 500 rpm in a constant temperature water bath at 53 °C for 10 minutes, then reduce the speed to 300 rpm and stir for 50 minutes, and then centrifuge at 3900 rpm for 10 minutes.

[0141] Preferably, the method for preparing the SPI-Fe3O4 composite solution is as follows: Add 1 part of Fe3O4 NPs to 8 parts of the SPI solution by weight, perform ultrasonic treatment in an ice bath at 40 kHz for 25 minutes, add glutaraldehyde and stir at 500 rpm for 10 minutes, add genipin and continue stirring for 50 minutes. Glutaraldehyde is 1% of the mass of SPI, and genipin is 0.3% of the mass of SPI. Stir at 300 rpm at 53 °C for 30 minutes to obtain solution A.

[0142] Preferably, the method for magnetic collection and drying is to stir the mixed solution A with a strong magnet, lift the strong magnet and collect the adsorbed substances, repeat the operation until there is no adsorbed substance on the strong magnet, wash it 5 times with deionized water and 5 times with ethanol in sequence, and freeze-dry at -45 °C or below until the moisture content is below 3%.

[0143] Preferably, the raw water is one of municipal secondary sewage, aquaculture sewage and printing sewage. In step S5, after the stirring is completed, apply a vertical constant magnetic field of 0.4 T to accelerate flocculation precipitation.

[0144] Preferably, the core particle size of Fe3O4 NPs is 6 - 10 nm.

[0145] Test Example

[0146] Perform preliminary pretreatment on secondary municipal sewage. After removing large particulate impurities and suspended solids in the sewage, put the treated administrative sewage into the flocculation container in equal amounts (water depth 1 m). Use Examples 1, 2, and 3, and Comparative Examples 1, 2, 3, and 4 to conduct parallel tests on the sewage. The modified flocculant is put in at 25 mg / L. Monitor the SS (suspended solid concentration mg / L) and sulfate content (mg / L) at 20 cm from the bottom of the water for 1 hour. And after the stirring is completed, when starting to continuously apply a vertical constant magnetic field, start timing the precipitation time. The precipitation time is the duration from the start of precipitation to the minimum value of the monitored indicators.

[0147] The test results are as follows:

[0148] Detection Index SS (mg / L) Sulfate Content (mg / L) Precipitation Duration Before Treatment 85.6 81.3 None Comparative Example 1 12.1 80.2 29 Comparative Example 2 83.2 78.1 5 Comparative Example 3 36.1 32.5 9 Comparative Example 4 45.8 52.1 6 Example 1 3.3 3.4 4 Example 2 3.2 3.6 4 Example 3 2.5 2.3 3

[0149] Based on the result table, in Comparative Example 1, traditional PAC is used as the flocculant to treat the sewage in equal amounts (25 mg / L). Its precipitation duration is longer than that of Examples 1 to 3, its flocculation effect is worse than that of Examples 1 to 3, and it does not have the function of adsorbing sulfates.

[0150] In Comparative Example 2, Fe3O4 NPs are directly used as the flocculant to treat the sewage. It can be concluded that the values of each index of the sewage before treatment have a small decrease. Therefore, using Fe3O4 NPs directly as the flocculant has a poor flocculation effect. However, due to the poor adsorption effect of Fe3O4 NPs and its small volume, the buoyancy received is small, resulting in a fast precipitation speed under the action of magnetic force.

[0151] The difference between Comparative Example 3 and Example 1 is that the surface modification of Fe3O4 NPs is removed, resulting in the inability to achieve the balance between the dispersibility, adsorption capacity, and magnetic responsiveness of Fe3O4 NPs, causing the subsequent treatment process effect to be significantly underutilized. It can be seen that although the flocculation and adsorption capacities for sulfates and suspended solids have been significantly improved, compared with Example 1, the effect is significantly worse. Its overall flocculation effect cannot be fully exerted. And due to the poor synergistic effect of its overall process treatment, the flocculated mass is relatively loose, resulting in a large buoyancy received and a low precipitation speed, and a long precipitation time.

[0152] The difference between Comparative Example 4 and Example 1 is that the grafting step of zirconium-loaded amino-functionalized mesoporous silica is removed. It can be seen that although the flocculation and adsorption capacities for sulfates and suspended solids have been significantly improved, compared with Example 1, the effect is significantly worse. And compared with Comparative Example 3, the precipitation time is shorter, and the flocculation effect and the effect of adsorbing sulfates are worse than those of Comparative Example 3.

[0153] It can be concluded that based on the reasonable and complete preparation process in mutual coordination, for Examples 1 to 3, whether it is the effect of adsorbing sulfates and suspended solids, there is a breakthrough improvement compared with the comparative examples. And the precipitation duration of Example 3 is the shortest, and its flocculation effect and the effect of adsorbing sulfates are the most prominent.

[0154] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A sewage treatment method with high flocculation, characterized in that: It includes the following steps: S1. Conduct preliminary pretreatment on the raw water to remove large particulate impurities and suspended solids in the sewage; S2. Add a modified flocculant to the sewage; S3. Adjust the pH of the sewage to 4.5 - 6.5; S4. Stir rapidly at 200 - 300 rpm for 5 minutes, and then stir slowly at 50 - 80 rpm for 5 minutes; S5. While performing step S4, perform: Apply an alternating magnetic field of 0.1 - 0.3 T with a horizontal period of 15 seconds to the sewage, and simultaneously apply a vertical constant magnetic field of 0.1 - 0.3 T; The preparation process of the modified flocculant includes surface modification of Fe3O4NPs, preparation of SPI solution, preparation of SPI - Fe3O4 composite solution, ultraviolet irradiation modification, magnetic collection, and drying.

2. A high - flocculation sewage treatment method according to claim 1, wherein: The method for surface modification of Fe3O4NPs is: Mix 1 part of 1.2% w / v sodium citrate solution with 1 part of 0.5% w / v polyethyleneimine solution by volume. Add 1 part of Fe3O4NPs to 20 - 30 parts of the mixed solution by weight. Perform ultrasonic treatment in an ice bath, treat at 40 - 50 kHz for 30 minutes, extract and separate the modified Fe3O4NPs with a strong magnet, wash 3 times with deionized water and 2 times with ethanol in sequence, and vacuum - dry at 50 - 55 °C for 12 hours.

3. A high - flocculation sewage treatment method according to claim 2, wherein: The method for preparing the SPI solution is: Mix 5 - 7 parts of SPI with 100 parts of deionized water by weight, adjust the pH of the solution to 7 - 8 with 1M NaOH, stir at a high speed of 500 - 600 rpm in a constant - temperature water bath at 53 - 57 °C for 10 minutes, then reduce the speed to 300 - 350 rpm and stir for 50 minutes, and then centrifuge at 3900 - 4000 rpm for 10 minutes to obtain the SPI solution.

4. A high - flocculation sewage treatment method according to claim 3, wherein: The method for preparing the SPI - Fe3O4 composite solution is: Add 1 part of modified Fe3O4NPs to 8 - 10 parts of the SPI solution by weight. Perform ultrasonic treatment in an ice bath, 40 - 50 kHz, for 25 minutes. Add glutaraldehyde and stir at 500 - 600 rpm for 10 minutes, then add genipin and continue stirring for 50 minutes. Glutaraldehyde is 1% of the mass of SPI and genipin is 0.3% of the mass of SPI. Stir at 300 - 350 rpm at 53 - 57 °C for 30 minutes to obtain the mixed solution A.

5. The high-flocculation sewage treatment method according to claim 4, characterized in that: Add 0.25 part of zirconium - loaded aminated mesoporous silica to 30 - 35 parts of the mixed solution A by weight, stir at 400 - 600 rpm for 1 hour, and keep the temperature at 23 - 27 °C to obtain the mixed solution B; The preparation process of the zirconium - loaded aminated mesoporous silica is: Immerse the aminated mesoporous silica in a zirconium oxychloride precursor solution with a solid - liquid weight ratio of 1:20 at 0.15 - 0.25 mol / L. Ultrasonic treatment was carried out at 55 - 65 °C for 40 minutes with a frequency of 45 kHz, and then the reaction was allowed to stand at a constant temperature of 75 - 85 °C for 6 hours while maintaining the pH of the system at 8.0 - 8.5 during the reaction; after the reaction, the solid was separated by centrifugation and the separated solid was washed with deionized water more than 5 times; the washed product was dried at 75 - 85 °C for 12 hours and then calcined at 480 - 520 °C for 3 hours with a heating rate of 4 - 6 °C / min.

6. The high-flocculation sewage treatment method according to claim 5, wherein: The particle size of the supported aminated mesoporous silica is 100 - 200 nm and the pore size is 10 - 40 nm.

7. A high flocculation sewage treatment method according to claim 5, characterized in that: The ultraviolet irradiation modification method is to transfer the mixed solution B into a quartz container that transmits ultraviolet light, and use an ultraviolet lamp with a wavelength of 254 nm and a power of 35 W, at a distance of 10 cm from the liquid surface, and continuously irradiate for 2 hours. During the irradiation process, magnetic stirring is maintained at 550 - 650 rpm to obtain the mixed solution C.

8. A sewage treatment method with high flocculation according to claim 7, characterized in that: The magnetic collection and drying method is to stir the mixed solution C with a strong magnet, lift the strong magnet and collect the adsorbed substances, and repeat the operation until there are no adsorbed substances on the strong magnet. Wash it 5 times with deionized water and 5 times with ethanol in sequence, and freeze-dry at a temperature below -45 °C until the water content is below 3%.

9. A sewage treatment method with high flocculation according to any one of claims 1 to 8, characterized in that: The raw water is one of municipal secondary sewage, aquaculture sewage and printing sewage. In step S5, after the stirring is completed, a vertical constant magnetic field of 0.4 T is applied to accelerate flocculation precipitation.

10. A high-flocculation sewage treatment method according to any one of claims 1 to 8, characterized in that: The core particle size of the Fe3O4 NPs is 6 - 10 nm.