Efficient water treatment method based on magnetic separation fly ash

Abstract

According to the efficient water treatment method based on the magnetic separation fly ash, magnetic seeds rich in Fe3O4, SiO2 and Al2O3 are obtained by controlling the rotating speed and the magnetic field intensity of a magnetic separation device according to the magnetic characteristic of the fly ash, the magnetic seeds are applied to water pollution aerobic treatment, and the water treatment effect and the magnetic seed recovery rate are remarkably improved. According to the method, the problems of low sludge recovery efficiency, high cost, insufficient resource utilization and the like in an existing water treatment technology are well solved, fly ash magnetic seeds with different contents of Fe3O4, SiO2 and Al2O3 can be obtained by accurately adjusting spiral magnetic separation process parameters, different water treatment requirements are met, and the magnetic seed recovery rate is optimized.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a system and method for efficiently recovering bacterial colony-containing sludge in a water treatment process by using spiral magnetic separation fly ash as magnetic seed. Background Art

[0002] In the prior art, the recovery and treatment of bacterial colony-containing sludge generated during water treatment has always been a technical problem. Traditional methods such as sedimentation and filtration have problems such as low treatment efficiency, high cost, and difficulty in sludge recovery. In recent years, some patents have proposed the use of magnetic materials as magnetic seeds for sludge recovery, but there are defects such as high material cost, limited sources, or unstable magnetism.

[0003] For example, patent CN101362641A discloses a method for treating sewage using magnetic particles, but the magnetic particles used in this method are expensive and difficult to obtain, which limits their wide application. Another example is patent CN102897793A, which proposes a method for treating sewage using magnetic biochar. Although biochar has certain adsorption properties, its preparation process is complicated and its magnetism is unstable, resulting in unstable treatment effects. Another example is patent CN105152689A, which introduces a method for sludge recovery using magnetite powder as a magnetic seed. However, magnetite powder resources are limited, the cost is high, and the recovery rate is difficult to reach an ideal level.

[0004] Fly ash is a solid waste from coal-fired power plants, which contains a large amount of iron oxides (such as Fe 3 O 4 ), silicon oxide (SiO 2 ) and aluminum oxide (Al 2 O 3 ), which has potential recycling value. Through the spiral magnetic separation process, high Fe 3 O 4 The fly ash with high content and micron particle size has high specific surface area, which is beneficial to improve the water treatment effect. Therefore, the use of spiral magnetic separation fly ash as magnetic seed for magnetic recovery of bacterial sludge in water treatment is not only low-cost and widely available, but also can effectively improve water treatment efficiency and realize resource recycling. Summary of the invention

[0005] In view of the above technical problems existing in the prior art, the purpose of the present invention is to provide an efficient water treatment method based on magnetic separation of fly ash. The present invention is an innovative and efficient water treatment magnetic recovery method, in particular, using spiral magnetic separation technology to screen out Fe-rich fly ash from the fly ash. 3 O 4 、SiO 2 and Al 2 O 3The method of the present invention can not only efficiently recover the bacterial colony-containing sludge generated in the water treatment process, but also effectively recover the bacterial colony-containing sludge through the SiO 2 and Al 2 O 3 The synergistic effect significantly improves the water treatment effect.

[0006] The technical solution adopted by the present invention is as follows:

[0007] An efficient water treatment method based on magnetic separation fly ash comprises the following steps:

[0008] 1) Use a spiral magnetic separator to magnetically separate fly ash, adjust the magnetic separation speed and magnetic field strength, and screen out Fe-rich particles from the fly ash. 3 O 4 、SiO 2 and Al 2 O 3 Magnetic species;

[0009] 2) The wastewater contaminated with ammonia nitrogen is passed into a water treatment reaction tank containing aerobic sludge for aerobic treatment, and the magnetic seeds described in step 1) are added into the water treatment reaction tank, stirred, and exposed to air to allow the magnetic seeds to react with pollutants in the water body, remove COD and ammonia nitrogen in the water body and reduce turbidity, and finally the magnetic seeds in the water body are magnetically recovered.

[0010] Furthermore, in step 1), the magnetic separation speed is 30-120 rpm, the magnetic field strength is 0.1-0.6 T, and among the magnetic species screened in step 1), Fe 3 O 4 The content of SiO is above 30%. 2 and Al 2 O 3 The total content of the two is between 25% and 55%, and the rest are other impurities, and the impurity content is not higher than 15%.

[0011] Furthermore, in step 1), the magnetic separation speed is 60-80 rpm, the magnetic field strength is 0.3-0.4 T, and among the magnetic species screened in step 1), Fe 3 O 4 The content is 50%-60%, SiO 2 and Al 2 O 3 The total content of the two is between 25% and 35%, and the rest are other impurities, and the impurity content is not higher than 15%.

[0012] Further, in step 1), the fly ash mainly comprises the following components by weight: 45-50% SiO 2 、30-35%Al 2 O 34.5-5.5%Fe 3 O 4 , 5-8% CaO, 0.5-2% TiO 2 , 0.5-1.0% MgO, the remainder is impurities.

[0013] Furthermore, in step 2), the stirring speed is 50-100 rpm, the inoculation amount of sludge in the water body in the water treatment reaction tank is 5-15 vol.%, the water temperature in the water treatment reaction tank is controlled at 20-30°C, and the hydraulic retention time HRT is 1-2 hours.

[0014] Furthermore, in step 2), the concentration of the magnetic seed added to the water in the water treatment reaction tank is 50-150 ppm.

[0015] Furthermore, after step 2), the ammonia nitrogen removal rate of the water body treated is ≥80%, and the turbidity reduction rate is ≥95%.

[0016] Furthermore, the recovery rate of the magnetic seeds is at least 96%.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) Efficient recovery: Utilizing Fe in fly ash 3 O 4 The magnetic properties of the magnetic field can achieve efficient recovery of bacterial colony-containing sludge, with the magnetic seed recovery rate maintained at at least 96%, significantly improving water treatment efficiency.

[0019] 2) Improvement effect: SiO in fly ash 2 and Al 2 O 3 It helps to improve the water treatment effect, specifically by improving technical indicators such as COD removal rate ≥ 90%, ammonia nitrogen removal rate ≥ 80%, and turbidity reduction rate ≥ 95%.

[0020] 3) Resource recycling: realize the resource utilization of fly ash, reduce environmental pollution and reduce water treatment costs;

[0021] 4) Strong flexibility: There will be a lot of entrainment in the fly ash magnetic separation material because magnetic components such as Fe 3 O 4 With other components such as SiO 2 and Al 2 O 3 There is a close connection (for example, forming a glassy body or mixing into a mass), so the magnetically selected Fe 3 O 4 Will come with a higher proportion of SiO 2 and Al 2 O 3The present invention can obtain different Fe 3 O 4 、SiO 2 、Al 2 O 3 The fly ash magnetic seeds with high content can meet different water treatment needs and optimize the magnetic seeds recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of fly ash raw material;

[0023] Figure 2 is the XRD pattern of fly ash sample;

[0024] Figure 3 VSM curve of fly ash sample. DETAILED DESCRIPTION

[0025] The present invention Figure 1 , Figure 2 and Figure 3 The scanning electron microscope (SEM) images, X-ray diffraction (XRD) images and vibrating sample magnetometer (VSM) curves of the fly ash samples are shown, which reveal the microstructure, phase composition and magnetic properties of the fly ash samples respectively.

[0026] pass Figure 1 From the SEM image, we can directly observe the microscopic morphology of the fly ash sample. Fly ash particles are usually irregular in shape and size, and may have tiny particles or pores attached to the surface.

[0027] Figure 2 The XRD pattern is used to analyze the phase composition of fly ash samples. By comparing the standard spectrum, we can determine whether the fly ash contains Fe 2 O 3 , Fe 3 O 4 、SiO 2 、Al 2 O 3 And other main components, and understand their crystallinity and relative content.

[0028] Figure 3 The VSM curve is used to characterize the magnetic properties of fly ash samples. By measuring the magnetization intensity of the sample under different magnetic field strengths, its hysteresis loop can be obtained, so as to understand the magnetic parameters of fly ash such as saturation magnetization intensity, residual magnetization intensity and coercive force. The figure shows that fly ash has a certain degree of magnetism and therefore contains a certain amount of magnetic substances. However, the magnetism is relatively weak, indicating that the content of magnetic substances is relatively small.

[0029] The fly ash sample used in the embodiment of the present invention mainly includes the following components by weight: 48.21% SiO 2 、33.18%Al 2 O 3 、4.8%Fe 3 O 4 , 5.68% CaO, 1.61% TiO 2 , 0.75% MgO, the rest is impurities.

[0030] In the embodiment of the present invention, when the magnetic seeds are added to the water body containing bacterial colony sludge for aerobic treatment, the initial parameters of the water body containing bacterial colony sludge are: COD about 400 mg / L; ammonia nitrogen 80 mg / L; turbidity 200 NTU.

[0031] Embodiment 1:

[0032] The speed of the spiral magnetic separator was set to 60 rpm, and the magnetic field strength was precisely controlled at 0.6 T by adjusting the magnetic circuit structure. Then, the fly ash raw material was fed into the spiral magnetic separator. The raw material was evenly distributed and moved slowly under the action of the screw conveyor, and was also affected by the strong magnetic field generated by the internal magnetic circuit. Through this magnetic separation process, the component Fe 3 O 4 Content 40%, SiO 2 Content 35%, Al 2 O 3 The content of magnetic seeds is 20% and other impurities are 5%. Next, these magnetic seeds are put into the water treatment reaction tank and fully mixed with the water body containing bacterial colony sludge for aerobic treatment. The sludge inoculation amount in the water body is 10vol.%, and the stirring speed is 60rpm. The concentration of magnetic seeds in the water body is 100ppm. Air is exposed to the water body at a rate of 5L / min at room temperature of 20-30℃, and the hydraulic retention time HRT is 2h. Under this reaction condition, the magnetic seeds effectively adsorb and precipitate the pollutants in the water body, achieving a significant water treatment effect of 89% COD removal rate, 80% ammonia nitrogen removal rate, and 95% turbidity reduction rate. Finally, the magnetic seeds in the treated sludge are separated and recovered by an efficient magnetic separation and recovery system, with a recovery rate of up to 96.5%.

[0033] Table 1

[0034]

[0035] Embodiment 2:

[0036] The operating parameters of the magnetic separation equipment were adjusted to ensure that the rotation speed was maintained at 60 rpm and the magnetic field strength was 0.5 T. Subsequently, the raw materials containing various components were fed into the magnetic separation equipment. Under the rotation of the equipment and the action of the magnetic field, the raw materials underwent an efficient separation process. In this process, the Fe-rich 3 O 3 、SiO 2 and Al 2 O 3 The magnetic species were effectively separated and their components were Fe 3 O 4 Content 45%, SiO 2 Content 30%, Al 2 O 3 The content is 18%, and other impurities account for 7%. Next, the separated magnetic seeds are put into the water body to be treated. The experimental conditions of aerobic treatment are the same as those in Example 1. The magnetic seeds, with their unique physical and chemical properties, quickly adsorb and precipitate pollutants in the water body. After a period of reaction, the test results show that the COD removal rate of the water body reached 87%, the ammonia nitrogen removal rate reached 83%, and the turbidity reduction rate was as high as 96.5%, which significantly improved the water quality. Finally, the magnetic seeds in the water body are recovered through efficient magnetic separation and recovery technology, with a recovery rate of up to 97%.

[0037] Table 2

[0038]

[0039] Embodiment 3:

[0040] The operating conditions of the magnetic separator were optimized, the rotation speed was maintained at 60 rpm, and the magnetic field strength was ensured to be stable at 0.1 T. 3 O 4 、SiO 2 、Al 2 O 3 The raw materials with other impurities are sent to the magnetic separator. Under the combined effect of high-speed rotation and strong magnetic field, the components are effectively separated. The magnetic species separated are composed of Fe 3 O 4 Content 50%, SiO 2 Content 25%, Al 2 O 3The content of the magnetic seeds is 15%, and the rest is 10% impurities. Next, these magnetic seeds are put into the water body containing pollutants, and the pollutants in the water body are deeply treated by using their adsorption and coagulation characteristics. The experimental conditions of aerobic treatment are the same as those in Example 1. After testing, the COD removal rate of the treated water body is as high as 69%, the ammonia nitrogen removal rate is 86%, and the turbidity reduction rate is as high as 98%, which significantly improves the water quality. Finally, the magnetic seeds in the water body are recovered by efficient magnetic recovery technology, and the recovery rate is as high as 97.5%.

[0041] Table 3

[0042]

[0043] Embodiment 4:

[0044] The operating parameters of the magnetic separation equipment were adjusted to maintain the rotation speed at 60 rpm and adjust the magnetic field strength to 0.3 T to adapt to the specific raw material composition and processing requirements of this embodiment. 3 O 4 、SiO 2 、Al 2 O 3 The raw materials with other impurities are sent to the magnetic separation equipment. Under the condition of slow rotation speed and moderate magnetic field strength, the components in the raw materials are separated more finely. The separated magnetic species has the composition of Fe 3 O 4 Content up to 55%, SiO 2 The content is 20%, Al 2 O 3 The content is 12%, and the rest is 13% impurities. These magnetic seeds are then put into the water to be treated, and the pollutants in the water are deeply removed by using their efficient adsorption and purification capabilities. The experimental conditions of aerobic treatment are the same as those in Example 1. The treatment results show that the COD removal rate of the water body reached 58%, the ammonia nitrogen removal rate reached 88%, and the turbidity reduction rate was as high as 98.5%, and the water quality was significantly improved. Finally, through the optimized magnetic seed recovery process, the efficient recovery of magnetic seeds was achieved, with a recovery rate of up to 98%.

[0045] Table 4

[0046]

[0047] Embodiment 5:

[0048] In order to verify the effect of high magnetic field strength on magnetic separation, the speed of the magnetic separation equipment was first maintained at 60 rpm and the magnetic field strength was adjusted to 0.4 T. Subsequently, the raw materials were fed into the magnetic separation equipment. 3 O4 Content 60%, SiO 2 Content 18%, Al 2 O 3 Content 10%, and 12% other impurities. Next, these high Fe 3 O 4 The magnetic seeds with a content of 100 μg / cm2 were put into water bodies containing high concentrations of pollutants to evaluate their water treatment performance. The experimental conditions for aerobic treatment were the same as those in Example 1. The results showed that the COD removal rate of the water body reached 46%, the ammonia nitrogen removal rate reached 90%, and the turbidity reduction rate was as high as 99%, which fully proved that the high Fe 3 O 4 The excellent performance of the content magnetic seeds in water treatment. Finally, through the optimized recovery process, the magnetic seeds in the water body were efficiently recovered, with a recovery rate of up to 98.5%.

[0049] Table 5

[0050]

[0051] It can be seen from the experimental results of Examples 1 to 5 that the magnetic field strength is crucial to the selection of magnetic species. When the magnetic field strength increases, the ferroferric oxide content of the magnetic species increases first and then decreases, and different magnetic species have a relatively large impact on the sewage treatment effect.

[0052] Embodiment 6:

[0053] In order to explore the boundary conditions of the magnetic separation process, the rotation speed was set to an extremely low value of 30 rpm, and the magnetic field strength was adjusted to 0.4 T accordingly. Under the conditions of low rotation speed and weak magnetic field strength, the components in the raw material underwent a relatively gentle separation process. 3 O 4 Content 30%, SiO 2 Content 40%, Al 2 O 3 The magnetic seeds were then used to treat water containing pollutants to evaluate their performance in low Fe 3 O 4 The water treatment efficiency under low Fe content, the experimental conditions of aerobic treatment are the same as those in Example 1. The results show that the COD removal rate in the water body reached 94%, the ammonia nitrogen removal rate was 78%, and the turbidity reduction rate was 94%, indicating that even at low Fe 3 O 4 At this concentration, the magnetic seeds still have a certain purification ability. Finally, through a carefully designed recovery process, the magnetic seeds in the water were effectively recovered, with a recovery rate of 96%.

[0054] Table 6

[0055]

[0056] Embodiment 7:

[0057] The operating parameters of the magnetic separation equipment were set to a rotation speed of 120 rpm and a magnetic field strength of 0.4 T to explore the magnetic separation effect under this combination. Under the action of moderate rotation speed and magnetic field strength, the components in the raw material were effectively and stably separated. Among the separated magnetic species, Fe 3 O 4 Content 52%, SiO 2 Content 23%, Al 2 O 3 The content is 16%, and 9% of other impurities. These magnetic seeds were further used to treat water bodies containing various pollutants to evaluate their purification efficiency. The experimental conditions for aerobic treatment were the same as those in Example 1. The experimental results showed that the COD removal rate of the water body treated with magnetic seeds reached 63%, the ammonia nitrogen removal rate reached 85.5%, and the turbidity reduction rate was as high as 97.5%, which fully demonstrated the high efficiency of magnetic seeds in water treatment.

[0058] Finally, through the optimized magnetic seed recovery process, efficient recovery of magnetic seeds was achieved, with a recovery rate of up to 97.8%.

[0059]

[0060] Embodiment 8:

[0061] The operating parameters of the magnetic separation equipment were set to a rotation speed of 10 rpm and a magnetic field strength of 0.4 T to explore the magnetic separation effect under this combination. Under the action of moderate rotation speed and magnetic field strength, the components in the raw material were effectively and stably separated. Among the separated magnetic species, Fe 3 O 4 Content 12%, SiO 2 Content 49%, Al 2 O 3 Content 33%, and 6% other impurities. These magnetic seeds were further used to treat water bodies containing various pollutants to evaluate their purification efficiency. The experimental conditions for aerobic treatment were the same as in Example 1. The experimental results showed that the COD removal rate of the water body treated with magnetic seeds reached 98%, the ammonia nitrogen removal rate reached 64%, and the turbidity reduction rate was as high as 87%, which fully demonstrated the high efficiency of magnetic seeds in water treatment. Finally, through the optimized magnetic seed recovery process, the efficient recovery of magnetic seeds was achieved, with a recovery rate of up to 38%.

[0062] Table 8

[0063]

[0064] It can be seen from the experimental results of Examples 5 to 8 that the magnetic field speed is also crucial to the selection of magnetic species. When the magnetic field speed increases, the ferroferric oxide content of the magnetic species first increases and then decreases, and different magnetic species have a relatively large impact on the sewage treatment effect.

[0065] It can be seen from the experimental results of Examples 1 to 6 that when the magnetic separation speed is 60 rpm and the magnetic field strength is 0.3-0.4 T, the selected magnetic species has the best application effect.

[0066] The main components of the magnetic seed after the fly ash is magnetically separated are ferroferric oxide, silicon oxide and aluminum oxide. In the process of water pollution treatment, ferroferric oxide contains divalent ferrous ions and trivalent ferric ions, which provide iron elements for functional microorganisms, promote nitrification and denitrification, thereby significantly improving the ammonia nitrogen removal rate, significantly reducing turbidity, and improving the magnetic seed recovery rate. In the coagulation and sedimentation process of water treatment, the magnetic seed material contains Al 2 O 3 、SiO 2 There is no negative impact. When pH is adjusted appropriately, some Al 2 O 3 、SiO 2 It can be transformed into ion form, adsorb and decompose organic matter, and reduce COD concentration.

[0067] Embodiment 9:

[0068] The fly ash without magnetic separation is directly used to treat water bodies containing various pollutants to compare and evaluate its purification efficiency. The chemical composition of fly ash is complex, and the content from high to low includes: 48.21% SiO 2 、33.18%Al 2 O 3 , 4.8% iron oxide, 5.68% CaO, 1.61% TiO 2 , 0.75% MgO, the remainder is impurities. The experimental conditions of aerobic treatment in Example 9 are the same as those in Example 1. The experimental results show that the COD removal rate of the water body treated with magnetic seeds is 99%, the ammonia nitrogen removal rate is 9.6%, and the turbidity does not decrease at all, but increases. After the recovery process, the magnetic seeds only achieve 7.8% recovery.

[0069] Table 9

[0070]

[0071] Embodiment 10:

[0072] Commercial Fe 3 O 4The experimental conditions of aerobic treatment in Example 10 are the same as those in Example 1. The experimental results show that the COD removal rate of the water body after magnetic seed treatment is only 4%, the ammonia nitrogen removal rate is 92%, the turbidity reduction rate is 99%, and the magnetic seed recovery rate is 98.60%.

[0073] Comparative Example 5, Example 10 uses high purity Fe 3 O 4 In terms of treatment effect, the ammonia nitrogen removal rate in Example 10 was slightly increased, the turbidity reduction rate and the magnetic seed recovery rate were almost equivalent, but the COD removal rate was greatly reduced. This shows that the comprehensive treatment effect of magnetic separation fly ash in Example 5 is significantly better than that of commercial Fe 3 O 4 Powder, showing significant beneficial effects.

[0074] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An efficient water treatment method based on magnetic separation fly ash, characterized in that The following steps are involved: 1) Use a spiral magnetic separator to magnetically separate fly ash, adjust the magnetic separation speed and magnetic field strength, and screen out magnetic species rich in Fe3O4, SiO2 and Al2O3 from the fly ash; 2) The wastewater contaminated with ammonia nitrogen is passed into a water treatment reaction tank containing aerobic sludge for aerobic treatment, and the magnetic seeds described in step 1) are added into the water treatment reaction tank, stirred, and exposed to air to allow the magnetic seeds to react with pollutants in the water body, remove COD and ammonia nitrogen in the water body and reduce turbidity, and finally the magnetic seeds in the water body are magnetically recovered.

2. A high-efficiency water treatment method based on magnetic separation fly ash as claimed in claim 1, characterized in that In step 1), the magnetic separation speed is 30-120 rpm, the magnetic field strength is 0.1-0.6 T, and in the magnetic species screened in step 1), the content of Fe3O4 is above 30%, the total content of SiO2 and Al2O3 is between 25% and 55%, and the rest are other impurities, and the impurity content is not higher than 15%.

3. The high-efficiency water treatment method based on magnetic separation fly ash according to claim 1, characterized in that In step 1), the magnetic separation speed is 60-80rpm, the magnetic field strength is 0.3-0.4T, and in the magnetic seeds screened in step 1), the content of Fe3O4 is 50%-60%, the total content of SiO2 and Al2O3 is 25%-35%, and the rest is other impurities, and the impurity content is not higher than 15%.

4. The high-efficiency water treatment method based on magnetic separation fly ash according to claim 1, characterized in that In step 1), the fly ash mainly includes the following components by weight: 45-50% SiO2, 30-35% Al2O3, 4.5-5.5% Fe3O4, 5-8% CaO, 0.5-2% TiO2, 0.5-1.0% MgO, and the remainder is impurities.

5. The high-efficiency water treatment method based on magnetic separation fly ash according to claim 1, characterized in that In step 2), the stirring speed is 50-100 rpm, the inoculation amount of sludge in the water body in the water treatment reaction tank is 5-15 vol.%, the water temperature in the water treatment reaction tank is controlled at 20-30°C, and the hydraulic retention time HRT is 1-2 hours.

6. The high-efficiency water treatment method based on magnetic separation fly ash according to claim 1, characterized in that Step 2) The concentration of the medium magnetic seed added to the water in the water treatment reaction tank is 50-150ppm.

7. The high-efficiency water treatment method based on magnetic separation fly ash according to claim 1, characterized in that Step 2) After treatment, the ammonia nitrogen removal rate of the water body is ≥80%, and the turbidity reduction rate is ≥95%.

8. The high-efficiency water treatment method based on magnetic separation fly ash according to claim 1, characterized in that The recovery rate of the magnetic seeds is at least 96%.

Images