Super-hydrophobic magnetic biochar demulsification degreaser, preparation method and application

Abstract

The invention discloses a super-hydrophobic magnetic biochar demulsification degreaser, a preparation method and application, the preparation method comprises the following steps: firstly, preparing biochar from biomass, then loading magnetic nano ferroferric oxide on the surface of the biochar to obtain a magnetic biochar material, and finally, carrying out hydrophobic modification on the magnetic biochar material through n-dodecanethiol to obtain the super-hydrophobic magnetic biochar demulsification degreaser. The magnetic demulsification degreasing agent is prepared. The preparation method is used for reducing the preparation cost of the demulsifier for emulsifying the oily wastewater, improving the oil removal effect and facilitating recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a super-hydrophobic magnetic biochar demulsifier and oil remover, a preparation method and an application thereof. Background Art

[0002] With the development of industrial production, the metal processing, grain and oil, and leather processing industries, among others, generate large quantities of emulsified oily wastewater. When the floating oil in this emulsified oily wastewater enters the water, it easily spreads and forms an oil film. This oil film on the water surface deprives the water of oxygen, easily leading to hypoxia. The oil and its decomposition products in this emulsified oily wastewater contain a variety of toxic substances. These toxic substances are absorbed and accumulated by organisms in water or soil, causing distortion and entering the human body through the food chain, endangering human health.

[0003] Most emulsified oily wastewater requires primary treatment with chemical demulsification and oil removal before it can enter subsequent treatment processes. However, demulsifiers for emulsified oily wastewater currently suffer from high preparation costs, unsatisfactory oil removal results, and poor recyclability. Summary of the Invention

[0004] The present invention aims to provide a super-hydrophobic magnetic biochar demulsifier and oil remover, a preparation method and an application thereof, so as to reduce the preparation cost of the demulsifier for emulsified oily wastewater, improve the oil removal effect and facilitate recovery.

[0005] In order to solve the above technical problems, the specific scheme adopted by the present invention is: a method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover, firstly, biochar is prepared from biomass, then magnetic nano-ferroferric oxide is loaded on the surface of the biochar to obtain a magnetic biochar material, and finally the magnetic biochar material is hydrophobically modified by n-dodecanethiol to prepare a magnetic demulsifier and oil remover.

[0006] Preferably, the biomass is mugwort, loofah or corn cob.

[0007] Preferably, the method for preparing biochar from biomass is as follows: first, the biomass is freeze-dried in a vacuum, and then pyrolyzed at a high temperature to obtain the biochar.

[0008] Preferably, the operating conditions of vacuum freeze drying are: vacuum degree 10 Pa, drying time 12-20 hours; the operating conditions of high temperature pyrolysis are: heating to 700-900°C at a rate of 4-7°C / min and then keeping warm for 1.8-2.2 hours.

[0009] Preferably, the method for loading magnetic nano-ferroferric oxide on the surface of biochar to obtain a magnetic biochar material is as follows: adding biochar to an ethylene glycol solution, then adding ferric chloride hexahydrate and anhydrous sodium acetate in sequence, mixing thoroughly, adding polyethylene glycol, and after sufficient mixing again, transferring the solution into a high-temperature reactor and maintaining a constant temperature at 150-250°C for 4-6 hours, cooling, washing, and then drying to obtain a magnetic biochar material.

[0010] Preferably, the mass ratio of biochar to ethylene glycol is 1:(50-100), the mass ratio of biochar to ferric chloride hexahydrate is 1:(2-4), the mass ratio of biochar to anhydrous sodium acetate is 1:(5-10), and the mass ratio of biochar to polyethylene glycol is 1:(0.5-1).

[0011] Preferably, the method for hydrophobically modifying the magnetic biochar material with n-dodecyl mercaptan is as follows: adding the magnetic biochar material to an ethanol solution, adding n-dodecyl mercaptan through an automatic dropwise stirring device, and reacting for 3-6 hours to complete the hydrophobic modification.

[0012] Preferably, the mass ratio of the magnetic biochar material to n-dodecanethiol is 1:(3-6).

[0013] A super-hydrophobic magnetic biochar demulsification and oil removal agent is prepared by any one of the above-mentioned preparation methods of the super-hydrophobic magnetic biochar demulsification and oil removal agent.

[0014] Application of a super-hydrophobic magnetic biochar demulsifier and oil remover in sewage and industrial wastewater treatment.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The super-hydrophobic magnetic biochar material prepared in this invention has high demulsification efficiency and excellent oil removal performance for emulsified oil wastewater. Its porous surface structure and super-hydrophobic properties preferentially adsorb oil droplets and puncture the interfacial membrane of the emulsified oil droplets, significantly improving demulsification and oil removal performance. Demulsification efficiency can reach over 90%. The magnetic biochar demulsifier prepared in this invention outperforms commercial demulsifiers (brand: Liliqing, available online).

[0017] 2. The present invention uses biomass as a natural material, which achieves low-cost preparation and waste recycling, and the biomass resource source is extensive, with the advantages of being environmentally friendly, low-cost, easy to prepare, and reducing the secondary pollution of water quality after the use of the agent. In addition, the surface of the biomass has a unique porous structure and a variety of chemical compositions, which can be retained and fully utilized during the carbonization process. In a preferred embodiment of the present invention, a method of combining vacuum freeze drying and high-temperature pyrolysis is used to convert biomass into biochar. Freeze drying directly removes water through ice crystal sublimation, avoiding the biomass shrinkage and pore collapse caused by traditional hot air drying, retaining more volatiles and organic matter, providing more precursors for subsequent pyrolysis, improving the output rate of biochar, and effectively reducing the cost of the material. The uniform structure after freeze drying allows the volatiles to escape through the preset pores during pyrolysis, reducing the pore wall melting caused by local high pressure, forming more developed mesopores and micropores, which can increase the porosity and specific surface area of ​​the biochar, help the material migrate to the oil-water interface, and enhance the demulsification effect.

[0018] 3. The present invention uniformly loads magnetic nano-ferroferric tetroxide on the surface of biochar, that is, it is possible to recycle the demulsifier by adsorption of magnetic substances, thereby improving the recyclability of the material. In a preferred embodiment of the present invention, magnetic nano-ferroferric tetroxide is uniformly loaded on the surface of biochar by a solvent thermal synthesis method. Compared with traditional hydrolysis or high-temperature solid-phase methods, the solvent thermal reaction is carried out in an autoclave. Under high temperature conditions, the dielectric constant and ion product of the polyethylene glycol solvent increase, promoting the rapid dissolution of the precursor and forming a high supersaturation, driving uniform nucleation, reducing the difference in crystal nucleus size, and being able to produce a material with small particle size, narrow particle size distribution range, good crystallization and good dispersibility. The specific surface area of ​​small-sized particles is large, which can provide more adsorption sites and efficiently capture oil molecules through van der Waals forces and hydrophobic effects.

[0019] 4. The present invention constructs micro-nano structure by surface grafting of n-dodecanethiol, and the magnetic demulsification and oil removal biochar material prepared has recyclable, hydrophobic property, oil-water selectivity and interface destruction effect. N-dodecanethiol shows excellent hydrophobicity due to the non-polar structure of long carbon chain, the polarity of thiol group, the ordered arrangement of surface molecules, can improve the hydrophobic property and interfacial activity of magnetic biochar, contribute to material breaking oil-water interface stability, promote oil-water separation. In addition, the automatic dripping stirring reaction device used by the present invention can control the hydrophobic long-chain structure of different contents of uniform load on the surface of magnetic biochar, contribute to the synthesis of various types of super-hydrophobic magnetic biochar demulsifiers, for processing different types of emulsified oil wastewater. Hydrophobic modification method can react at room temperature, and the reaction time is short, and easy to operate, thereby simplifying production technology and reducing production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1Effects of the super-hydrophobic magnetic biochar demulsifier and oil remover prepared in preferred embodiment 3 of the present invention on the transmittance and separation efficiency during the treatment of emulsified oil wastewater under different conditions; (a) is the dosage, (b) is the salinity, (c) is the pH value, and (d) is the Zeta point before and after demulsification;

[0021] Figure 2 Schematic diagram of the hysteresis loop of the super-hydrophobic magnetic biochar demulsifier and oil remover prepared in preferred embodiments 3, 4, and 5 of the present invention;

[0022] Figure 3 SEM images (ac) and EDS mapping diagram (d) of preferred embodiment 5 of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is described below through 5 embodiments:

[0024] Example 1

[0025] This embodiment provides a method for preparing a magnetic biochar demulsifier and oil remover, comprising the following steps:

[0026] In the first step, loofah sponge (SG) was washed with anhydrous ethanol and deionized water three times and then freeze-dried in vacuum for 12 h.

[0027] In the second step, the material obtained in the first step was crushed and sieved with a 60-mesh sieve. Then, the material was placed in a tube furnace, heated to 700°C at a rate of 5°C / min, and kept at this temperature for 2 hours. After cooling to room temperature, the material was taken out and bagged to obtain carbonized loofah.

[0028] In the third step, 2.0 g of the material obtained in the second step was added to 80 mL of ethylene glycol solution. Then, 3.0 g of ferric chloride hexahydrate crystals and 7.0 g of anhydrous sodium acetate were added, followed by thorough stirring using a magnetic heating stirrer. Once the solution was thoroughly mixed, 1.0 g of polyethylene glycol was added and stirring continued for 2 hours. After stirring, the solution was transferred to a high-temperature reactor and maintained at 200°C for 6 hours. After cooling, it was rinsed three times with 50% ethanol and three times with deionized water to retain the magnetic material. The rinsed magnetic material was placed in a vacuum drying oven for 12 hours to produce magnetic biochar CSG1.

[0029] The vacuum freeze-drying process helps increase the porosity and specific surface area of ​​the material. The addition of polyethylene glycol during the reaction of loading magnetic nano-ferroferric oxide can enhance the material's magnetic properties, thereby enhancing its recyclability.

[0030] Example 2

[0031] The preparation method of this embodiment is basically the same as that of Example 1, except that the vacuum freeze-drying time in the first step of Example 1 is extended to 18 hours, and the carbonization temperature in the second step is increased to 800°C.

[0032] Comparative Example 1

[0033] The preparation method of this comparative example is basically the same as that of Example 2, except that the freeze-drying process in the first step of Example 2 is omitted.

[0034] Example 3

[0035] The preparation method of this embodiment comprises the following steps:

[0036] In the first step, the Artemisia selengensis was washed with anhydrous ethanol and deionized water three times and then freeze-dried in vacuum for 18 h.

[0037] The second step is to crush and sieve with a 60-mesh sieve. The material is placed in a tube furnace, heated to 900°C at a rate of 5°C / min, and kept at this temperature for 2 hours. After cooling to room temperature, it is taken out and bagged to obtain carbonized Artemisia selengensis.

[0038] In the third step, 2.0 g of the material obtained in the second step was added to 80 mL of ethylene glycol solution. Then, 3.0 g of hexahydrate, ferric chloride crystals, and 7.0 g of anhydrous sodium acetate were added, followed by thorough stirring using a magnetic heating stirrer. Once the solution was thoroughly mixed, 1.0 g of polyethylene glycol was added and stirring continued for 2 hours. After stirring, the solution was transferred to a high-temperature reactor and maintained at 200°C for 6 hours. After cooling, it was rinsed three times with 50% ethanol and then with deionized water to retain the magnetic material. The rinsed magnetic material was placed in a vacuum drying oven for 12 hours to produce magnetic biochar.

[0039] In the fourth step, the product obtained in the third step was added to 50 mL of ethanol solution and ultrasonically treated for 30 minutes to fully disperse it in the solution. Subsequently, an automatic dripping and stirring reaction apparatus was set at a speed of 500 rpm and a flow rate of 0.1 mL / min. The dripping needle was inserted 1.0 cm above the reaction liquid surface through the PTFE tube, and 5.0 mL of n-dodecanethiol was slowly added. The reaction was allowed to react at room temperature for 5 hours to complete the hydrophobic modification.

[0040] In the fifth step, the magnetic material in the solution obtained in the fourth step was collected using a magnet and washed several times with ethanol. Finally, the product was freeze-dried for 12 hours to obtain a magnetic demulsifier and oil remover SCMH.

[0041] Example 4

[0042] In the first step, corn cobs (YM) were washed three times with anhydrous ethanol and deionized water and freeze-dried in vacuum for 18 h.

[0043] The second step is to crush and sieve the material with a 60-mesh sieve. The material is placed in a tube furnace and heated to 900°C at a rate of 5°C / min and kept at this temperature for 2 hours. After cooling to room temperature, the material is taken out and bagged to obtain carbonized corn cobs.

[0044] In the third step, 2.0 g of the material obtained in the second step was added to 80 mL of ethylene glycol solution. Then, 4.0 g of hexahydrate, ferric chloride crystals, and 8.0 g of anhydrous sodium acetate were added, followed by thorough stirring using a magnetic heating stirrer. Once the solution was thoroughly mixed, 1.0 g of polyethylene glycol was added and stirring continued for 2 hours. After stirring, the solution was transferred to a high-temperature reactor and maintained at 200°C for 6 hours. After cooling, it was rinsed three times with 50% ethanol and then with deionized water to retain the magnetic material. The rinsed magnetic material was placed in a vacuum drying oven for 12 hours to produce magnetic biochar.

[0045] In the fourth step, the product obtained in the third step was added to 50 mL of ethanol solution and ultrasonically treated for 30 minutes to fully disperse it in the solution. Subsequently, an automatic dripping and stirring reaction apparatus was set at a speed of 500 rpm and a flow rate of 0.1 mL / min. The dripping needle was inserted 1.0 cm above the reaction liquid surface through the PTFE tube, and 7.0 mL of n-dodecanethiol was slowly added. The reaction was allowed to react at room temperature for 5 hours to complete the hydrophobic modification.

[0046] In the fifth step, the magnetic material in the solution obtained in the fourth step was collected using a magnet and washed several times with ethanol. Finally, the product was freeze-dried for 12 hours to obtain the magnetic demulsifier and oil remover SCYM1.

[0047] Example 5

[0048] In the first step, corn cobs (YM) were washed three times with anhydrous ethanol and deionized water and freeze-dried in vacuum for 18 h.

[0049] The second step is to crush and sieve the material with a 60-mesh sieve. The material is placed in a tube furnace and heated to 900°C at a rate of 5°C / min and kept at this temperature for 2 hours. After cooling to room temperature, the material is taken out and bagged to obtain carbonized corn cobs.

[0050] In the third step, 2.0 g of the material obtained in the second step was added to 100 mL of ethylene glycol solution. Then, 5.0 g of hexahydrate, ferric chloride crystals, and 10.0 g of anhydrous sodium acetate were added, followed by thorough stirring using a magnetic heating stirrer. Once the solution was thoroughly mixed, 1.0 g of polyethylene glycol was added and stirring continued for 2 hours. After stirring, the solution was transferred to a high-temperature reactor and maintained at 200°C for 6 hours. After cooling, it was rinsed three times with 50% ethanol and then with deionized water to retain the magnetic material. The rinsed magnetic material was placed in a vacuum drying oven for 12 hours to produce magnetic biochar.

[0051] In the fourth step, the product obtained in the third step was added to 50 mL of ethanol solution and ultrasonically treated for 30 minutes to fully disperse it in the solution. Subsequently, an automatic dripping and stirring reaction apparatus was set at a speed of 500 rpm and a flow rate of 0.1 mL / min. The dripping needle was inserted 1.0 cm above the reaction liquid surface through the PTFE tube, and 7.0 mL of n-dodecanethiol was slowly added. The reaction was allowed to react at room temperature for 5 hours to complete the hydrophobic modification.

[0052] In the fifth step, the magnetic material in the solution obtained in the fourth step was collected using a magnet and washed several times with ethanol. Finally, the product was freeze-dried for 12 hours to obtain the magnetic demulsifier and oil remover SCYM2.

[0053] In order to verify the performance of the magnetic biochar demulsifier and oil remover prepared by the present invention, the present invention conducted the following performance tests:

[0054] 1. Characterization test of magnetic biochar demulsifier and oil remover

[0055] The yield, porosity, and specific surface area of ​​magnetic biochar were compared between Example 1, Example 2, and Comparative Example 1, as shown in Table 1. The yield of biochar increased with increasing vacuum freeze-drying time. The porosity and specific surface area of ​​the magnetic biochar surface increased with increasing high-temperature pyrolysis temperature. In Comparative Example 1, where the magnetic biochar material was prepared solely through high-temperature pyrolysis, the specific surface area, total pore volume, and average adsorption pore size test results were all poor. This result indicates that the freeze-dried biomass has a more porous structure.

[0056] 2. Demulsification and oil removal performance test

[0057] Demulsification tests were conducted using the bottle test method at room temperature. A certain mass of magnetic material was added to an oil-in-water emulsion. The sample was placed in an air oscillator and evenly shaken at 140 r / min for 30 minutes to disperse the material. The sample was then allowed to stand for 90 minutes, and an external magnetic field was applied to remove the emulsified oil droplets. The demulsification effect was evaluated by measuring the absorbance and transmittance of the separated crude oil. The water quality was analyzed using the UV spectrophotometric method approved by the Ministry of Ecology and Environment of the People's Republic of China (Trial) PetroChina (HJ970-2018).

[0058] The effects of the products of Examples 3, 4, and 5 were compared with those of Examples 1 and 2, and a commercially available magnetic demulsifier (brand: Liliqing, purchased online), as shown in Table 2. The results show that the oil removal effects of the products of Examples 3, 4, and 5 after superhydrophobic modification are significantly better than those of the other products.

[0059] 3. Comparison of the removal effect of the product SCMH of Example 3 of the magnetic demulsification and oil removal material on emulsified oil under different conditions. The effects of different dosages, salinity and pH values ​​on the emulsified oil removal rate are shown in the figure. Figure 1 As shown. Experiments show that SCMH is salt-tolerant and can be applied to emulsified oily wastewater in a wide pH range. At a pH of 4.0 and a dosage of 600 mg / L, the transmittance and demulsification efficiency of SCMH are 85.95% and 96.1%, respectively. There are chemical adsorption and electrostatic interactions between SCMH and oil droplets. When SCMH is added to emulsified oily wastewater, its high interfacial activity enables it to be quickly adsorbed at the oil-water interface. The reduction in interfacial tension is conducive to breaking the interfacial film, thereby achieving more efficient oil-water separation.

[0060] 4. The surface morphology and particle size distribution of magnetic biochar in Example 5 were compared with those in Example 4 and Example 3. Since the amount of hexahydrate and ferric chloride crystals, anhydrous sodium acetate and polyethylene glycol was increased in the hydrothermal negative magnetic reaction in Example 5, the magnetic loading of the product SCYM2 in Example 5 was increased. Figure 2 As shown in the figure, the saturation magnetization intensity of the product of Example 5 is higher than that of the products of Example 3 and Example 4. Figure 3 Scanning electron microscopy results show that the surface of SCYM2, product from Example 5, is uniformly loaded with nano-Fe₃O₄. The superior removal rate of Example 5 compared to Example 4 in Table 2 suggests that Example 5 possesses a higher magnetic loading. This high Fe₃O₄ loading likely enhances the material's magnetic responsiveness, allowing for faster magnetic separation of adsorbed oil, enhancing oil removal effectiveness.

Claims

1. A method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover, characterized in that: First, biochar is prepared from biomass, and then magnetic nano-ferroferric oxide is loaded on the surface of the biochar to obtain a magnetic biochar material. Finally, the magnetic biochar material is hydrophobically modified by n-dodecanethiol to prepare a magnetic demulsifier and oil remover.

2. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 1, wherein: The biomass is mugwort, loofah or corn cob.

3. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 1, wherein: The method for preparing biochar from biomass is as follows: first, the biomass is freeze-dried in a vacuum, and then pyrolyzed at high temperature to obtain biochar.

4. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 3, wherein: The operating conditions of vacuum freeze drying are: vacuum degree 10Pa, drying time 12-20h; the operating conditions of high temperature pyrolysis are: heating to 700-900°C at a rate of 4-7°C / min and keeping warm for 1.8-2.2h.

5. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 1, wherein: The method for loading magnetic nano-ferroferric oxide on the surface of biochar to obtain magnetic biochar material is as follows: biochar is added to ethylene glycol solution, and then ferric chloride hexahydrate and anhydrous sodium acetate are added in sequence, and polyethylene glycol is added after thorough mixing. After thorough mixing again, the solution is transferred to a high-temperature reactor and maintained at a constant temperature of 150-250°C for 4-6 hours, cooled, washed and dried to obtain the magnetic biochar material.

6. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 5, wherein: The mass ratio of biochar to ethylene glycol is 1:(50-100), the mass ratio of biochar to ferric chloride hexahydrate is 1:(2-4), the mass ratio of biochar to anhydrous sodium acetate is 1:(5-10), and the mass ratio of biochar to polyethylene glycol is 1:(0.5-1).

7. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 1, wherein: The method for hydrophobically modifying the magnetic biochar material with n-dodecanethiol is as follows: adding the magnetic biochar material to an ethanol solution, adding n-dodecanethiol through an automatic dropwise stirring device, and reacting for 3-6 hours to complete the hydrophobic modification.

8. The method for preparing a super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 7, wherein: The mass ratio of magnetic biochar material to n-dodecyl mercaptan is 1:(3-6).

9. A super-hydrophobic magnetic biochar demulsifier and oil remover, characterized by: The invention is prepared by the preparation method of a super-hydrophobic magnetic biochar demulsifier and oil remover according to any one of claims 1 to 8.

10. Use of the super-hydrophobic magnetic biochar demulsifier and oil remover according to claim 9 in the field of sewage and industrial wastewater treatment.

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