A micro-bubble adsorption phosphorus removal material for sewage treatment, a phosphorus removal method and application

Abstract

The application discloses a kind of micro-bubble adsorption phosphorus removal materials for sewage treatment, phosphorus removal method and application, belong to sewage treatment technical field, with straw fiber as matrix, nanometer ferroferric oxide is loaded by hydrothermal synthesis and is obtained fiber composite powder;Lanthanum MOF is synthesized in situ on the surface of fiber composite powder, and lanthanum MOF loaded fiber composite powder is obtained, and then hydrophobic modification is carried out to obtain the micro-bubble adsorption phosphorus removal materials for sewage treatment;The micro-bubble adsorption phosphorus removal materials for sewage treatment can significantly enhance the adsorption capacity and phosphorus selectivity of ferroferric oxide and lanthanum MOF, the hydrophobic layer can adapt to micro-bubble technology, and the in-situ loading and coordination anchoring of each component ensure the stability of the material structure, reduce the loss of components in the recycling process, and finally achieve efficient and stable micro-bubble adsorption phosphorus removal effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a micro-bubble adsorption phosphorus removal material for sewage treatment, a phosphorus removal method and application. BACKGROUND

[0002] Rural domestic sewage often presents the characteristics of low carbon-nitrogen ratio, large fluctuation of water quality and quantity, and rich pathogenic microorganisms such as Escherichia coli. With the improvement of ecological environmental protection standards, if such sewage is directly discharged without treatment, it will not only destroy the water ecology, cause the eutrophication of rivers and lakes to cause blue-green algae blooms, but also pollute groundwater, affect the safety of farmland irrigation, and threaten the quality of agricultural products and human health, and at the same time, waste the recoverable water, nitrogen and phosphorus resources in the sewage.

[0003] Under this background, the nano micro-bubble technology has become a key direction for strengthening the treatment effect of rural domestic sewage due to its unique advantages. The nano micro-bubbles (diameter < 1 pm) are generated by special devices, and compared with traditional bubbles, they have a large specific surface area, and the oxygen mass transfer coefficient is increased by 2-5 times, which can accurately supply oxygen for biological reaction, and the hydroxyl radicals generated when the bubbles break down can also simultaneously degrade refractory organic matter and inactivate pathogenic microorganisms. In the phosphorus removal link, a specific adsorption phosphorus removal material is usually needed to further strengthen the phosphorus removal and recovery efficiency. Commonly used materials mainly include natural mineral materials, industrial by-product based materials and artificial synthetic materials. Through the combination of micro-bubbles and these adsorption materials, the contact efficiency of the materials and phosphorus can be improved by utilizing the mass transfer advantage of micro-bubbles, and the phosphorus removal effect can be strengthened by the targeting action of the adsorption materials.

[0004] Chinese patent application with publication number CN108262029A discloses a preparation method of an organic-inorganic composite modified straw phosphorus removal adsorption material. The organic-inorganic composite modified straw phosphorus removal adsorption material is prepared by taking crop straw as raw material and taking cheap and non-toxic organic acid and calcium salt as modifier. The method is simple and green, but the active site density of the calcium salt is low, and it is easy to form competitive precipitation with interfering ions such as sulfate and carbonate in sewage. When applied in the nano micro-bubble technology for rural sewage treatment, the adsorption phosphorus removal stability is poor, and the recycling effect is not good. SUMMARY

[0005] The purpose of the present application is to provide a micro-bubble adsorption phosphorus removal material for sewage treatment, a phosphorus removal method and application. The straw fiber is used as the matrix, the phosphorus adsorption capacity and selectivity are enhanced by the synergistic effect of ferroferric oxide and lanthanum MOF, the component loss in recycling is reduced by combining with the hydrophobic modified micro-bubble technology, and finally the efficient and stable micro-bubble adsorption phosphorus removal effect is realized.

[0006] The purpose of the present application can be realized by the following technical solutions:

[0007] A micro-bubble adsorption phosphorus removal material for sewage treatment is prepared by the following steps:

[0008] Step one: taking straw fiber as a matrix, hydrothermally synthesizing and loading nano-Fe3O4 to obtain fiber composite powder.

[0009] Step two: in-situ synthesizing lanthanum MOF on the surface of the fiber composite powder to obtain lanthanum MOF loaded fiber composite powder, and then performing hydrophobic modification to obtain the micro-bubble adsorption phosphorus removal material for sewage treatment.

[0010] The straw fiber is any one of corn straw fiber, rice straw fiber and wheat straw fiber.

[0011] Further, the specific preparation process of the fiber composite powder is as follows:

[0012] The straw fiber is added into ethylene glycol, and ultrasonic stirring is performed for 15-30 min, then iron salt hydrate, sodium acetate and ethylenediamine are added, and stirring is continued for 1.5-2.5 h, then it is transferred to a reaction kettle, and reaction is performed at 160-170 ℃ for 8-10 h, then filtration is performed, the filter cake is washed with ethanol and deionized water alternately for 3-5 times, and drying is performed at 60-70 ℃ for 12-14 h to obtain the fiber composite powder.

[0013] Further, the amount ratio of the straw fiber, ethylene glycol, iron salt hydrate, sodium acetate and ethylenediamine is 6-10 g: 150-250 mL: 3-5 g: 9-12 g: 30-35 mL.

[0014] Further, the iron salt hydrate is any one of ferric chloride hexahydrate and nitric acid iron nine hydrate.

[0015] Further, the specific preparation process of the lanthanum MOF loaded fiber composite powder is as follows:

[0016] The fiber composite powder is added into N,N dimethylformamide, stirring is performed for 5-10 min, then lanthanum nitrate is added, and ultrasonic is performed for 20-30 min to obtain solution A; benzimidazole is added into N,N dimethylformamide, and stirring is performed for 10-20 min to obtain solution B; solution A and solution B are transferred into a three-necked flask, and stirring is performed in a 50-60 ℃ oil bath for 18-24 h, then filtration is performed, the filter cake is washed with dimethylformamide solution and ethanol for 3-5 times, and drying is performed to obtain the lanthanum MOF loaded fiber composite powder.

[0017] Further, the amount ratio of the fiber composite powder, N,N dimethylformamide and lanthanum nitrate is 0.65-12 g: 250-500 mL: 3-5 g.

[0018] Further, the amount ratio of benzimidazole and N,N dimethylformamide is 8-15 g: 250-500 mL.

[0019] Further, the volume ratio of solution A and solution B is 1:1.

[0020] Further, the specific preparation process of the micro-bubble adsorption phosphorus removal material for sewage treatment is as follows:

[0021] The lanthanum MOF loaded fiber composite powder is added into a 2wt% hydrophobic modifier methanol solution, stirred for 4-5h, filtered, the filter cake is washed with ethanol for 3-5 times, and vacuum dried at 60-70℃ for 8-10h to obtain the micro-bubble adsorption phosphorus removal material for sewage treatment.

[0022] Further, the dosage ratio of the lanthanum MOF loaded fiber composite powder and the 2wt% hydrophobic modifier methanol solution is 2-3g:200-250mL.

[0023] Further, the hydrophobic modifier is any one of 1-dodecyl mercaptan and 1-hexadecyl mercaptan.

[0024] A phosphorus removal method, comprising the following steps:

[0025] The micro-bubble adsorption phosphorus removal material for sewage treatment and water are prepared into a suspension, which is added into a flocculation zone of a micro-nano air flotation device, introduced into a nano micro-bubble reaction tank, 50-200nm particle size ozone micro-bubbles are generated by using a jet type nano micro-bubble generator, continuous stirring and scum removal are performed, and the phosphorus content in the reaction tank is monitored online, and when the phosphorus content is less than the discharge limit value, the phosphorus removal method is completed.

[0026] The beneficial effects of the present application are:

[0027] 1. The present application realizes the micro-bubble adsorption phosphorus removal material for sewage treatment through multi-step functionalization design, in-situ growth of loaded ferroferric oxide nanoparticles and lanthanum MOF on straw fiber, and then hydrophobic modification by 1-dodecyl mercaptan.

[0028] 2. The fiber composite powder in the present application uses straw fiber as a carrier, loads ferroferric oxide nanoparticles through in-situ growth, provides basic adsorption active sites for phosphorus, and endows the material with strong magnetism, which makes rapid magnetic separation and recycling of the material after adsorption possible.

[0029] 3、The lanthanum MOF loaded fiber composite powder in the application constructs a "double active center" synergistic system with ferroferric oxide by growing porous crystalline lanthanum MOF in situ on the surface of the fiber composite powder, and the lanthanum MOF specifically binds phosphate ions through coordination action by virtue of the super-high specific surface area and rich ion sites, breaks through the adsorption capacity and selectivity bottleneck of a single active center, and the ferroferric oxide plays an auxiliary role to accelerate the diffusion of phosphorus ions to the lanthanum MOF channel and improve the adsorption kinetics performance. The multi-level channels of the two form a complementary structure, which not only ensures smooth ion diffusion, but also maximizes the effective adsorption sites; at the same time, the surface-exposed ion sites can be coordinated and combined with the mercapto group of 1-dodecyl mercaptan, laying a key foundation for subsequent construction of a hydrophobic layer and synergistic action with micro-bubbles. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the application will be clearly and completely described below in conjunction with the embodiments in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0031] Embodiment 1: A micro-bubble adsorption phosphorus removal material for sewage treatment is prepared by the following steps:

[0032] S1: 6g of straw fiber passing through an 80-mesh sieve is added to 150mL of ethylene glycol, ultrasonic stirring is performed for 15min, then 3g of iron chloride hexahydrate, 9g of sodium acetate and 30mL of ethylenediamine are added, stirring is continued for 1.5h, then it is transferred to a reaction kettle, reaction is performed at 160℃ for 8h, filtration is performed, the filter cake is washed with ethanol and deionized water alternately for 3 times, and drying is performed at 60℃ for 12h to obtain a fiber composite powder.

[0033] The straw fiber is used as a carrier, and ferroferric oxide nanoparticles are grown and loaded in situ on the surface of the straw fiber, and the phosphorus removal efficiency is high.

[0034] S2: 0.65g of the fiber composite powder is added to 250mL of N,N dimethylformamide, stirring is performed for 5min, then 3g of lanthanum nitrate is added, ultrasonic stirring is performed for 20min to obtain solution A; 8g of benzimidazole is added to 250mL of N,N dimethylformamide, stirring is performed for 10min to obtain solution B; 250mL of solution A and 250mL of solution B are transferred to a three-necked flask, stirring is performed in a 50℃ oil bath for 18h, filtration is performed, the filter cake is washed with a dimethylformamide solution and ethanol for 3 times, and drying is performed to obtain a lanthanum MOF loaded fiber composite powder.

[0035] In-situ growth and loading of lanthanum MOF with porous crystal structure on the surface of fiber composite powder; the high specific surface area of lanthanum MOF endows the material with high adsorption capacity and selectivity, and forms a "double active center" with ferroferric oxide to synergistically remove phosphorus.

[0036] S3: 2g of lanthanum MOF loaded fiber composite powder is added into 200mL of 2wt% 1-dodecyl mercaptan methanol solution, stirred for 4h, filtered, the filter cake is washed with ethanol for 3 times, and vacuum dried at 60℃ for 8h to obtain a micro-bubble adsorption and phosphorus removal material for wastewater treatment.

[0037] 1-dodecyl mercaptan forms a weak coordination bond with lanthanum ions and iron ions on the surface of lanthanum MOF loaded fiber composite powder through thiol group, and is anchored on the surface of the material, and the long chain of dodecyl group is arranged outward to form a hydrophobic layer, thereby enhancing the hydrophobicity of the material.

[0038] Example 2: The present embodiment provides a preparation method of a micro-bubble adsorption and phosphorus removal material for wastewater treatment, which is different from example 1 in that nine water ferric nitrate is used instead of six water ferric chloride in step S1, and a micro-bubble adsorption and phosphorus removal material for wastewater treatment is prepared.

[0039] Example 3: The present embodiment provides a preparation method of a micro-bubble adsorption and phosphorus removal material for wastewater treatment, which is different from example 1 in that the amount ratio of the straw fiber, ethylene glycol, six water ferric chloride, sodium acetate and ethylenediamine in step S1 is 10g:250mL:5g:12g:35mL.

[0040] Example 4: The present embodiment provides a preparation method of a micro-bubble adsorption and phosphorus removal material for wastewater treatment, which is different from example 1 in that the amount ratio of the fiber composite powder, N,N dimethylformamide and lanthanum nitrate in step S2 is 12g:500mL:5g; and the amount ratio of the benzimidazole and N,N dimethylformamide is 15g:500mL.

[0041] Example 5: The present embodiment provides a preparation method of a micro-bubble adsorption and phosphorus removal material for wastewater treatment, which is different from example 1 in that 1-hexadecyl mercaptan is used instead of 1-dodecyl mercaptan in step S3, and a micro-bubble adsorption and phosphorus removal material for wastewater treatment is prepared.

[0042] Application example: the micro-bubble adsorption and phosphorus removal material for wastewater treatment and water are prepared into a suspension liquid with a concentration of 8wt%, which is added into the flocculation zone of a micro-nano air flotation device, introduced into a nano micro-bubble reaction tank, and 50-200nm particle size micro-bubbles are generated by using a jet type nano micro-bubble generator, and the material is continuously stirred at 800rpm. The hydrophobic surface of the material will combine with the micro-bubbles to form a low-density copolymer and quickly float up, and the scum is removed by a scum remover, so that efficient wastewater treatment can be achieved.

[0043] The raw materials used in the examples 1-5 are commercially available, wherein the straw fiber is any one of corn straw fiber, rice straw fiber and wheat straw fiber; and the micro-bubble adsorption phosphorus removal material for sewage treatment in the application examples is prepared by the preparation method in the examples 1-5.

[0044] Comparative example 1: The difference from example 1 is that the straw fiber is used to replace the fiber composite powder in step S2 without step S1, and the rest of the steps remain unchanged to prepare the micro-bubble adsorption phosphorus removal material for sewage treatment.

[0045] Comparative example 2: The difference from example 1 is that the fiber composite powder in step S1 is used to replace the lanthanum MOF loaded fiber composite powder in step S3 without step S2, and the rest of the steps remain unchanged to prepare the micro-bubble adsorption phosphorus removal material for sewage treatment.

[0046] Comparative example 3: The difference from example 1 is that the rest of the steps remain unchanged without step S3 to prepare the micro-bubble adsorption phosphorus removal material for sewage treatment.

[0047] The micro-bubble adsorption phosphorus removal materials prepared in the examples 1-5 and comparative examples 1-3 are tested for the following performances,

[0048] Adsorption capacity: According to GB11893-1989, ammonium molybdate spectrophotometric method for determination of total phosphorus in water. The micro-bubble adsorption phosphorus removal material for sewage treatment is added into the sewage pool at a dosage of 5 g / L, the initial concentration of phosphate in the potassium dihydrogen phosphate solution is 120 mg / L, the adsorption and phosphorus removal are carried out in the ozone nanometer micro-bubble pool, the adsorption time is 24 h, the adsorption temperature is 25℃, and after the adsorption is completed, the concentration of the solution after adsorption Ce is measured. The adsorption capacity of the adsorption and phosphorus removal material is calculated by the formula q (mg / g) = V*(C0-Ce) / m, wherein C0 and Ce are the initial concentration and the equilibrium concentration of phosphate in the solution (mg / L), respectively; V is the volume of the adsorption solution (L); and m is the mass of the adsorption material (g).

[0049] First phosphorus removal rate and phosphorus removal rate after 20 cycles: The TP content of the water before and after treatment is detected, and the removal rate is calculated; the material after adsorption saturation is desorbed by oscillating in 0.1 mol / L NaOH solution for 30 min, washed with water to neutral, dried and repeated for adsorption experiment, and the phosphorus removal rate is recorded every time, and finally the phosphorus removal rate after the 20th cycle is compared.

[0050] Hydrophobic performance test: water contact angle measurement is carried out by sitting drop method mode, and the instrument automatically obtains the contact angle value of the sample; wherein the injection liquid is distilled water, and the injection volume is 4 μL.

[0051] The results are shown in Table 1:

[0052] Table 1 Test results of adsorption phosphorus removal material performance

[0053] Item Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 First phosphorus removal rate / % 99.5 98.6 97.3 98.7 97.8 83.7 68.8 75.3 Phosphorus removal rate after 20 cycles / % 88.3 87.4 86.9 87.5 86.3 38.6 53.5 48.7 Adsorption capacity / mg / g 128.6 127.9 128.2 127.3 127.8 98.7 65.6 118.3 Water contact angle / ° 156 155 149 152 150 143 147 86

[0054] As can be seen from Table 1, the micro-bubble adsorption phosphorus removal material for sewage treatment prepared in Examples 1-5 is obviously superior to Comparative Examples 1-3.

[0055] In Comparative Example 1, the phosphorus removal rate significantly decreased after 20 cycles, which may be that the straw fiber surface is not loaded with ferroferric oxide nanoparticles, the straw fiber itself is porous and loose, and the mechanical strength is low, the pores of the ferroferric oxide nanoparticles are missing the filling and rigid support effect, and under the action of stirring and oscillation, filtration and extrusion, and alkali erosion, the structure is easy to collapse, in addition, the magnetic assistance of ferroferric oxide improves the separation efficiency of the micro-bubble adsorption phosphorus removal material.

[0056] In Comparative Example 2, the first phosphorus removal rate and adsorption capacity significantly decreased, which may be that the fiber composite powder surface is not loaded with lanthanum MOF, and only relies on the ferroferric oxide nanoparticles in the fiber composite powder, the phosphorus removal effect is poor; the lanthanum MOF can specifically bind phosphate ions through coordination due to its ultra-high specific surface area and rich ion sites, and the lack of which leads to a significant decrease in the maximum adsorption capacity.

[0057] In Comparative Example 3, the contact angle significantly decreased, which may be that the hydrophobic modification of 1-dodecanethiol is missing, the material surface is exposed to the polar crystal surface of lanthanum MOF, the surface hydroxyl of ferroferric oxide and the hydrophilic groups of the residual straw fiber, these hydrophilic groups will produce strong hydrogen bond or electrostatic interaction with water molecules, resulting in water spreading easily on the material surface, finally showing a significant decrease in contact angle, which cannot meet the hydrophobicity requirement of adapting to the synergistic effect of micro-bubbles.

[0058] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and modifications can be made to these embodiments without departing from the principles and spirits of the present application.

Claims

1. A microbubble adsorption phosphorus removal material for wastewater treatment, characterized in that, Prepared by the following steps: Step 1: Using straw fiber as the matrix, nano-iron oxide is hydrothermally synthesized and loaded to obtain fiber composite powder; Step 2: In-situ synthesis of lanthanum MOF on the surface of fiber composite powder to obtain lanthanum MOF-supported fiber composite powder, followed by hydrophobic modification to obtain microbubble adsorption phosphorus removal material for wastewater treatment. The specific preparation process of the lanthanum MOF-supported fiber composite powder is as follows: The fiber composite powder was added to N,N-dimethylformamide and stirred for 5-10 min. Then, lanthanum nitrate was added and sonicated for 20-30 min to obtain solution A. Benzimidazole was added to N,N-dimethylformamide and stirred for 10-20 min to obtain solution B. Solutions A and B were transferred to a three-necked flask and stirred at 50-60℃ for 18-24 h. The mixture was filtered, and the filter cake was washed and dried to obtain lanthanum MOF-supported fiber composite powder. The hydrophobic modification method of the lanthanum MOF-supported fiber composite powder is as follows: Lanthanum MOF-supported fiber composite powder was added to a methanol solution containing 2 wt% hydrophobic modifier, stirred for 4-5 hours, filtered, and the filter cake was washed and dried to obtain a microbubble adsorption phosphorus removal material for wastewater treatment. The hydrophobic modifier is either 1-dodecyl mercaptan or 1-hexadecyl mercaptan.

2. The microbubble adsorption phosphorus removal material for wastewater treatment according to claim 1, characterized in that, The specific preparation process of the fiber composite powder is as follows: Straw fibers are added to ethylene glycol and ultrasonically stirred for 15-30 minutes. Then, iron hydrate, sodium acetate, and ethylenediamine are added and stirred for another 1.5-2.5 hours. The mixture is then transferred to a reaction vessel and reacted at 160-170°C for 8-10 hours. After filtration, the filter cake is washed and dried to obtain fiber composite powder.

3. The microbubble adsorption phosphorus removal material for wastewater treatment according to claim 2, characterized in that, The ratio of straw fiber, ethylene glycol, iron salt hydrate, sodium acetate and ethylenediamine is 6-10g: 150-250mL: 3-5g: 9-12g: 30-35mL; The iron salt hydrate is either ferric chloride hexahydrate or ferric nitrate nonahydrate.

4. The microbubble adsorption phosphorus removal material for wastewater treatment according to claim 1, characterized in that, The ratio of the fiber composite powder, N,N-dimethylformamide, and lanthanum nitrate is 0.65-12g:250-500mL:3-5g; the ratio of the benzimidazole and N,N-dimethylformamide is 8-15g:250-500mL; and the volume ratio of solution A to solution B is 1:

1.

5. The microbubble adsorption phosphorus removal material for wastewater treatment according to claim 1, characterized in that, The ratio of the lanthanum MOF-supported fiber composite powder to a methanol solution containing 2 wt% hydrophobic modifier is 2-3 g: 200-250 mL.

6. The application of a microbubble adsorption phosphorus removal material for wastewater treatment as described in any one of claims 1-5 in the removal of phosphorus from rural domestic wastewater.

7. A phosphorus removal method, characterized in that, Includes the following steps: Wastewater treatment microbubble adsorption phosphorus removal material and water are mixed to form a suspension, which is then added to the flocculation zone of the micro-nano air flotation device and introduced into the nano-microbubble reaction tank. An ozone microbubble with a particle size of 50-200nm is generated by a jet-type nano-microbubble generator, and the mixture is continuously stirred and the scum is scraped off. The microbubble adsorption phosphorus removal material for wastewater treatment is any one of the microbubble adsorption phosphorus removal materials for wastewater treatment according to claims 1-5.