A demulsifier for tar ammonia water and a preparation method thereof

Abstract

The application discloses a demulsifier for tar ammonia water and a preparation method thereof. The preparation method of the demulsifier for tar ammonia water comprises the following steps: step (1), FeCl3.6H2O and FeCl2.4H2O are added into a solvent, modified carbon black is added after stirring, ultrasonic treatment is conducted, ammonia water is added to adjust pH under stirring, separation, washing, and finally drying to constant weight to obtain magnetic carbon black; step (2), modified magnetic carbon black is prepared; step (3), carboxylated cyclodextrin, modified magnetic carbon black and a catalyst are added into water, stirring and reaction are conducted, separation, washing, and then drying to constant weight are conducted, and the demulsifier for tar ammonia water is obtained. The demulsifier with magnetism is prepared through modified carbon black, the demulsification capacity of the demulsifier is improved through synergistic effect of multiple groups, the prepared magnetic demulsifier can be reused, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a demulsifier for tar ammonia water and a preparation method thereof. BACKGROUND

[0002] The oil content of organic wastewater formed in the pyrolysis process of coal can generally reach 500-5000 mg / L, and if the oil content is not reduced through pretreatment, the natural environment will be damaged, and the activity of microorganisms will be seriously inhibited in biochemical treatment.

[0003] A large amount of ammonia water is formed in the initial cooling process of coke oven gas, most of which is used as circulating ammonia water, and the part that is discharged in excess is called residual ammonia water. The residual ammonia water contains harmful impurities such as coal tar, phenol, ammonia and cyanide, and is the main source of coking industrial wastewater. There is a phenomenon of partial emulsification of tar and ammonia water in coking enterprises, which causes tar to be difficult to dehydrate, and the tray of the ammonia stripping tower to be blocked and cleaned frequently, so a demulsifier is needed for demulsification.

[0004] The demulsifiers for tar ammonia water in the prior art are mostly used at 60-80 DEG C, and have poor demulsification performance at room temperature, and are not easy to recycle, so there is an urgent need to develop a demulsifier with good demulsification efficiency at room temperature and easy to recycle. SUMMARY

[0005] The purpose of the present application is to provide a demulsifier for tar ammonia water and a preparation method thereof, which solves the technical problems of low demulsification efficiency, difficulty in recycling and difficulty in demulsification at room temperature of the demulsifiers in the prior art.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] The present application provides a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0008] Step (1) FeCl3·6H2O and FeCl2·4H2O are added to a solvent, modified carbon black is added after stirring, ultrasonic treatment is performed, then ammonia water is added to adjust the pH while stirring, separation, washing, and finally drying to constant weight to obtain magnetic carbon black;

[0009] Step (2) The magnetic carbon black is added to diphenyl ether, ultrasonic treatment is performed to obtain a suspension, octadecyl phosphoric acid is added to the suspension, heating is performed, then natural cooling to room temperature is performed, separation, washing, and finally drying to constant weight to obtain modified magnetic carbon black;

[0010] The structural formula of the modified magnetic carbon black is as follows:

[0011] ;

[0012] In the above process, the hydroxyl groups on the surface of the magnetic carbon black are condensed with octadecyl phosphoric acid to obtain modified magnetic carbon black.

[0013] In step (3), the carboxylated cyclodextrin, the modified magnetic carbon black and the catalyst are added to water, and after stirring and reaction, the product is separated, washed and dried to constant weight to obtain a demulsifier for tar ammonia water.

[0014] In the above process, the amino groups on the surface of the modified magnetic carbon black are dehydrated and condensed with the carboxyl groups of the carboxylated cyclodextrin to form a demulsifier grafted with cyclodextrin.

[0015] Preferably, in step (1), the solvent includes at least one of ethanol and ethylene glycol; the amount ratio of FeCl3·6H2O, FeCl2·4H2O, solvent, modified carbon black is (28-56) g:(12-24) g:(1.2-2.4) mL:(12-24) g; the ultrasonic treatment conditions are that the ultrasonic treatment frequency is 20-100 KHz and the ultrasonic treatment time is 15-25 min; the stirring speed is 500-700 rpm; the mass fraction of ammonia water is 5-10 wt%; the pH value is adjusted to 8.5-9.5; the separation method is to use a magnet to assist in separating the solid; the washing method is to wash the solid with water for 3-5 times; and the drying temperature is 70-90℃.

[0016] Preferably, in step (2), the amount ratio of the magnetic carbon black, diphenyl ether and octadecyl phosphoric acid is (15-30) g:(0.8-1.3) L:(2-4) g; the ultrasonic treatment conditions are that the ultrasonic treatment frequency is 20-100 KHz and the ultrasonic treatment time is 10-15 min; the heating conditions are that the heating temperature is 70-90℃ and the heating time is 1-3 h; the separation method is to use a magnet to assist in separating the solid; the washing method is to wash the solid with ethanol and deionized water for 3-5 times in turn; and the drying temperature is 50-70℃.

[0017] Preferably, in step (3), the catalyst includes at least one of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N,N'-dicyclohexyl carbodiimide; the amount ratio of the carboxylated cyclodextrin, the modified magnetic carbon black, the catalyst and water is (0.5-1) g:(15-30) g:(2-5) g:(100-200) mL; the stirring reaction time is 12-24 h; the separation method is to use a magnet to assist in separating the solid; the washing method is to wash the solid with ethanol and deionized water for 3-5 times in turn; and the drying temperature is 50-70℃.

[0018] Preferably, the preparation method of the modified carbon black comprises the following steps:

[0019] Mixing 20-40 g of carbon black and 20-40 g of polyethylene imine to obtain a suspension, stirring and treating the suspension in an ultrasonic field under the condition of a power of 250 W, a frequency of 40 KHz and a temperature of 50-70 DEG C for 6-10 h, then filtering with a 0.22 mu m polytetrafluoroethylene membrane and washing with water for 3-5 times, and finally freeze-drying at (-30)-(-20) DEG C for 24-72 h to obtain the modified carbon black.

[0020] The structural formula of the modified carbon black is as follows:

[0021]

[0022] In the above process, the carbon black is an intrinsic free radical scavenger, and the carbon black is used to capture macromolecular free radicals generated in the ultrasonic process of the polymer solution polyethylene imine.

[0023] Preferably, the preparation method of the carboxylated cyclodextrin comprises the following steps:

[0024] Mixing 2-4 g of beta-cyclodextrin, 1.8-3.6 g of NaOH and 7-15 mL of water, stirring and treating for 10-20 min, then adding 2.5-5 mL of 10-20 wt% 3-chloropropionic acid aqueous solution, reacting at 80-100 DEG C for 1-2 h, cooling to room temperature, then adding 50-80 mL of methanol to obtain a precipitate, filtering, washing the filter residue with 70-90 v / v% ethanol aqueous solution for 4-6 times, and drying to constant weight to obtain the carboxylated cyclodextrin.

[0025] The demulsifier for tar ammonia water is prepared by using the preparation method of the demulsifier for tar ammonia water.

[0026] As described above, due to the adoption of the technical solutions, the present application has the following beneficial effects:

[0027] 1. In the present application, the polyethylene imine is used to modify the nano carbon black through the ultrasonic process, and the hydrophobic group is introduced by grafting octadecyl phosphorus; the introduction of the polyethylene imine can impart the nano carbon black with certain amphiphilicity and positive charge through the action of -NH2, and the synergistic effect of the pi-pi interaction and the electrostatic attraction causes demulsification; the introduction of the octadecyl phosphorus increases the adsorption capacity of the oil in the wastewater, which is beneficial to the coalescence of the oil droplets; the cyclodextrin also has amphiphilicity, which is helpful to the uniform dispersion of the demulsifier particles at the oil-water interface; the synergistic effect of the multiple groups on the demulsifier promotes the demulsification of the tar ammonia water, and after 30 min of demulsification at room temperature, the transmittance of the water phase (TSW) is 86.5%, and the corresponding demulsification rate can reach 99.75%.

[0028] ​2. The demulsifier prepared by the application has certain amphiphilicity and good interfacial activity, and the demulsifier is used in ultra-low dosage to decompose tar ammonia water, so that oil and water are separated, thereby realizing excellent demulsification efficiency. First, electrostatic interaction occurs between the demulsifier and oil droplets or surfactants, the charge balance in the emulsion is destroyed, and demulsification is realized. After an external magnetic field is applied, the residual demulsifier and microdroplets are separated from the water phase by magnetic force, so that the water phase is more clear and transparent. The application of an external magnetic field can accelerate the contact between the magnetic demulsifier particles and the oil droplets, and increase the possibility of mutual contact and merging of the micro oil droplets into large oil droplets, thereby accelerating the demulsification rate of the emulsion. The magnetic demulsifier can be reused for more than 10 times and still has good demulsification efficiency, which is green and environmentally friendly.

[0029] 3. The demulsifier for tar ammonia water prepared by the application can realize tar ammonia water demulsification at a temperature range of 10-90 DEG C, the demulsification temperature range is wider, and the problem of tar ammonia water demulsification at room temperature is solved, thereby improving the utilization range of the demulsifier. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0031] Figure 1 is a preparation process flow chart of the demulsifier for tar ammonia water of the present application;

[0032] Figure 2 is a demulsification effect line graph of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] The substances and sources involved in the following examples and comparative examples are shown in Table 1:

[0035] Table 1

[0036] ;

[0037] Example 1: The present embodiment discloses a preparation method of carboxylated cyclodextrin, comprising the following steps:

[0038] Mixing 3 g of β-cyclodextrin, 2.4 g of NaOH and 11 mL of water, stirring for 15 min, then adding 3.8 mL of 15 wt% 3-chloropropionic acid aqueous solution, reacting at 90°C for 1.5 h, after cooling to room temperature, adding 65 mL of methanol to obtain a precipitate, filtering, washing the filter residue with 80 v / v% ethanol aqueous solution for 5 times, and drying to constant weight to obtain carboxylated cyclodextrin.

[0039] Example 2: This example discloses a preparation method of modified carbon black, comprising the following steps:

[0040] Mixing 30 g of carbon black and 30 g of polyethyleneimine to obtain a suspension, stirring the suspension in an ultrasonic field at a power of 250 W, a frequency of 40 KHz and a temperature of 60°C for 8 h, then filtering with a 0.22 μm polytetrafluoroethylene membrane and washing with water for 4 times, and finally freeze-drying at -25°C for 48 h to obtain modified carbon black.

[0041] Example 3: Referring to Figure 1 This example discloses a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0042] Step (1): adding 42 g of FeCl3·6H2O and 18 g of FeCl2·4H2O into 1.8 mL of ethylene glycol, stirring, then adding 18 g of modified carbon black prepared in Example 2, ultrasonic treating at a frequency of 60 KHz for 20 min, then stirring at a speed of 600 rpm while adding 7.5 wt% ammonia water to adjust the pH to 9, using a magnet to assist in separating the solid, washing the solid with water for 4 times, and finally drying at 80°C to constant weight to obtain magnetic carbon black;

[0043] Step (2): adding 23 g of magnetic carbon black into 1.1 L of diphenyl ether, ultrasonic treating at a frequency of 60 KHz for 12 min to obtain a suspension, adding 3 g of octadecyl phosphoric acid into the suspension, heating at 80°C for 2 h, naturally cooling to room temperature, then using a magnet to assist in separating the solid, washing the solid with ethanol and deionized water for 4 times, and finally drying at 60°C to constant weight to obtain modified magnetic carbon black; Step (3): adding 0.75 g of carboxylated cyclodextrin prepared in Example 1, 23 g of modified magnetic carbon black and 2.5 g of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride into 150 mL of water, stirring for 18 h, using a magnet to assist in separating the solid, washing the solid with ethanol and deionized water for 4 times, and then drying at 60°C to constant weight to obtain a demulsifier for tar ammonia water.

[0044] Example 4: Referring to Figure 1 This example discloses a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0045] Step (1) 28 g of FeCl3-6H2O and 24 g of FeCl2-4H2O were added to 2.4 mL of ethanol, after stirring, 24 g of modified carbon black prepared in Example 2 was added, ultrasonic treatment was carried out at a frequency of 20 KHz for 25 min, then 10 wt% ammonia water was added to adjust the pH to 8.5 while stirring at a speed of 500 rpm, magnetic separation was assisted, and the solid was washed with water for 3 times, finally dried at 90 °C to constant weight, to obtain magnetic carbon black;

[0046] Step (2) 30 g of magnetic carbon black was added to 0.8 L of diphenyl ether, ultrasonic treatment was carried out at a frequency of 100 KHz for 10 min to obtain a suspension, 4 g of octadecyl phosphoric acid was added to the suspension, and then heated at 70 °C for 3 h, and then naturally cooled to room temperature, then the solid was separated by magnetic assistance, and the solid was washed with ethanol and deionized water for 3 times, finally dried at 70 °C to constant weight, to obtain modified magnetic carbon black; Step (3) 0.5 g of carboxylated cyclodextrin prepared in Example 1, 30 g of modified magnetic carbon black, and 2 g of N,N'-dicyclohexyl carbodiimide were added to 100 mL of water, after stirring for 24 h, the solid was separated by magnetic assistance, and the solid was washed with ethanol and deionized water for 5 times, then dried at 70 °C to constant weight, to obtain a demulsifier for tar ammonia water.

[0047] Example 5: Referring to Figure 1 As shown in the figure, the embodiment discloses a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0048] Step (1) 56 g of FeCl3-6H2O and 12 g of FeCl2-4H2O were added to 1.2 mL of ethylene glycol, after stirring, 12 g of modified carbon black prepared in Example 2 was added, ultrasonic treatment was carried out at a frequency of 100 KHz for 15 min, then 5 wt% ammonia water was added to adjust the pH to 9.5 while stirring at a speed of 700 rpm, magnetic separation was assisted, and the solid was washed with water for 5 times, finally dried at 70 °C to constant weight, to obtain magnetic carbon black;

[0049] Step (2) 15 g of magnetic carbon black was added into 1.3 L of diphenyl ether, and a suspension was obtained by ultrasonic treatment at a frequency of 20 KHz for 15 min. 2 g of octadecyl phosphoric acid was added into the suspension, and the mixture was heated at 90 °C for 1 h. The mixture was naturally cooled to room temperature, and then the solid was separated by a magnet. The solid was washed with ethanol and deionized water for 3 times, respectively. Finally, the solid was dried at 50 °C until a constant weight was obtained to obtain the modified magnetic carbon black. Step (3) 1 g of carboxylated cyclodextrin prepared in Example 1, 15 g of the modified magnetic carbon black, and 2 g of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride were added into 200 mL of water. After stirring for 12 h, the solid was separated by a magnet. The solid was washed with ethanol and deionized water for 3 times, respectively. Then, the solid was dried at 50 °C until a constant weight was obtained to obtain the demulsifier for tar ammonia water.

[0050] Example 6: Referring to Figure 1 As shown in the figure, the embodiment discloses a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0051] Step (1) 30 g of FeCl3·6H2O and 20 g of FeCl2·4H2O were added into 1.5 mL of ethanol. After stirring, 15 g of the modified carbon black prepared in Example 2 was added. The mixture was ultrasonically treated at a frequency of 90 KHz for 16 min. Then, 9 wt% of ammonia water was added to adjust the pH to 8.5 while stirring at a speed of 650 rpm. The solid was separated by a magnet and washed with water for 3 times. Finally, the solid was dried at 70 °C until a constant weight was obtained to obtain the magnetic carbon black.

[0052] Step (2) 18 g of the magnetic carbon black was added into 1.2 L of diphenyl ether, and a suspension was obtained by ultrasonic treatment at a frequency of 40 KHz for 15 min. 3.2 g of octadecyl phosphoric acid was added into the suspension, and the mixture was heated at 75 °C for 1.2 h. The mixture was naturally cooled to room temperature, and then the solid was separated by a magnet. The solid was washed with ethanol and deionized water for 3 times, respectively. Finally, the solid was dried at 62 °C until a constant weight was obtained to obtain the modified magnetic carbon black. Step (3) 0.9 g of carboxylated cyclodextrin prepared in Example 1, 18 g of the modified magnetic carbon black, and 2.5 g of N,N'-dicyclohexyl carbodiimide were added into 180 mL of water. After stirring for 21 h, the solid was separated by a magnet. The solid was washed with ethanol and deionized water for 5 times, respectively. Then, the solid was dried at 60 °C until a constant weight was obtained to obtain the demulsifier for tar ammonia water.

[0053] Example 7: Referring to Figure 1 As shown in the figure, the embodiment discloses a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0054] Step (1) 30 g FeCl3-6H2O, 22 g FeCl2-4H2O were added into 2.1 mL ethanol, after stirring, 22 g modified carbon black prepared in Example 2 was added, ultrasonic treatment was carried out at 30 KHz frequency for 24 min, then 6 wt% ammonia water was added to adjust pH to 9.5 while stirring at 550 rpm, the solid was separated with the aid of a magnet, and the solid was washed with water for 3 times, finally dried at 88 °C to constant weight to obtain magnetic carbon black;

[0055] Step (2) 23 g magnetic carbon black was added into 0.9 L diphenyl ether, ultrasonic treatment was carried out at 45 KHz frequency for 12 min to obtain a suspension, 2.4 g octadecyl phosphoric acid was added into the suspension, then heated at 75 °C for 1.5 h, naturally cooled to room temperature, then the solid was separated with the aid of a magnet, the solid was washed with ethanol and deionized water for 4 times, finally dried at 65 °C to constant weight to obtain modified magnetic carbon black; Step (3) 0.85 g carboxylated cyclodextrin prepared in Example 1, 20 g modified magnetic carbon black, 3.5 g 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride were added into 180 mL water, after stirring for 14 h, the solid was separated with the aid of a magnet, the solid was washed with ethanol and deionized water for 5 times, then dried at 55 °C to constant weight to obtain a demulsifier for tar ammonia water.

[0056] Example 8: refer to Figure 1 As shown in the figure, the embodiment discloses a preparation method of a demulsifier for tar ammonia water, comprising the following steps:

[0057] Step (1) 50 g FeCl3-6H2O, 19 g FeCl2-4H2O were added into 2.3 mL ethylene glycol, after stirring, 16 g modified carbon black prepared in Example 2 was added, ultrasonic treatment was carried out at 55 KHz frequency for 17 min, then 6 wt% ammonia water was added to adjust pH to 9 while stirring at 580 rpm, the solid was separated with the aid of a magnet, and the solid was washed with water for 4 times, finally dried at 85 °C to constant weight to obtain magnetic carbon black;

[0058] Step (2) 17 g of magnetic carbon black was added into 1.2 L of diphenyl ether, and a suspension was obtained by ultrasonic treatment for 14 min at a frequency of 40 KHz, 2.2 g of octadecyl phosphoric acid was added into the suspension, and then the mixture was heated at 77 °C for 3 h, and then naturally cooled to room temperature, then the solid was separated by a magnet, and then the solid was washed with ethanol and deionized water for 3 times, and finally dried at 70 °C until the weight was constant, to obtain the modified magnetic carbon black; Step (3) 1 g of the carboxylated cyclodextrin prepared in Example 1, 15 g of the modified magnetic carbon black, and 4.5 g of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride were added into 110 mL of water, and then the solid was separated by a magnet after stirring for 15 h, and then the solid was washed with ethanol and deionized water for 5 times, and then dried at 60 °C until the weight was constant, to obtain the demulsifier for tar ammonia water.

[0059] Comparative Example 1: Compared with Example 3, in the preparation of the demulsifier for tar ammonia water, the magnetic carbon black was not modified by octadecyl phosphoric acid in Comparative Example 1, that is, the modified magnetic carbon black in Step (3) was replaced by the magnetic carbon black prepared in Step (1), and other conditions were unchanged.

[0060] Comparative Example 2: Compared with Example 3, in the preparation of the demulsifier for tar ammonia water, the carbon black was not modified by polyethyleneimine in Comparative Example 2, and other conditions were unchanged.

[0061] Comparative Example 3: Compared with Example 3, in the preparation of the demulsifier for tar ammonia water, the carboxylated cyclodextrin was not added in Comparative Example 3, that is, Step (3) was not performed, and other conditions were unchanged.

[0062] Experimental Example: The content of each component in the original tar ammonia water was as follows: oil 18.1 mg / L, total phenol 262.67 mg / L, CODcr392.51 mg / L, and NH3-N 141.26 mg / L.

[0063] The demulsifiers of Examples 3-8 and Comparative Examples 1-3 were respectively used to treat the original tar ammonia water, and the specific conditions were as follows:

[0064] Under normal temperature conditions, 1 L of tar ammonia water was respectively taken into a beaker, and then 45 mg, 50 mg, 55 mg, 60 mg, 65 mg, 70 mg, 75 mg, and 80 mg of the demulsifier prepared in Example 3 was respectively added, and then the mixture was stirred uniformly, and then was left to stand for 30 min, and then the supernatant was respectively taken for analysis, and the groups were represented as A, B, C, D, E, F, G, and H, and the removal rates of each component in the original tar ammonia water were analyzed, and the test results were shown in Table 2.

[0065] Table 2

[0066] ;

[0067] Under normal temperature condition, 1L of tar ammonia water was measured in a beaker, 60mg of demulsifier prepared by example 3-8 and comparative example 1-3 was added respectively, stirred uniformly, and placed for 30min, the groups are represented as a, b, c, d, e, f, g, h, j, the demulsification rate of the original tar ammonia water and the transmittance after demulsification were tested, and the test results are shown in table 3, Figure 2

[0068] Table 3

[0069]

[0070] From the test results of table 2 and table 3, it can be seen that the demulsifier prepared by example 3 of the present application has good demulsification efficiency. From the comparison of comparative example 1 and example 3, it can be seen that the modification of magnetic carbon black with octadecyl phosphoric acid in the present application can improve the demulsification effect of the demulsifier; from the comparison of comparative example 2 and example 3, it can be seen that the modification of carbon black with polyethylene imine in the present application can improve the demulsification effect of the demulsifier; from the comparison of comparative example 3 and example 3, it can be seen that the addition of carboxylated cyclodextrin in the present application can improve the demulsification rate of the demulsifier.

[0071] The above description is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

[0072] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details, and the present application is not limited to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present application. The embodiments are selected and described in the present specification in order to better explain the principles and practical application of the present application, so that the skilled person in the art can well understand and use the present application. The present application is limited by the claims and the whole scope and equivalents thereof.​​

Claims

1. A method for preparing a demulsifier for tar ammonia water, characterized by, The method comprises the following steps: Step (1): FeCl3·6H2O and FeCl2·4H2O are added into a solvent, and then modified carbon black is added after stirring, and the mixture is ultrasonically treated, and then ammonia water is added to adjust pH value while stirring, and then the mixture is separated, washed, and finally dried to constant weight to obtain magnetic carbon black; Step (2): the magnetic carbon black is added into diphenyl ether, and the mixture is ultrasonically treated to obtain a suspension, and then octadecyl phosphoric acid is added into the suspension, and then the mixture is heated and naturally cooled to room temperature, and then the mixture is separated, washed, and finally dried to constant weight to obtain modified magnetic carbon black; Step (3): carboxylated cyclodextrin, modified magnetic carbon black and a catalyst are added into water, and then the mixture is stirred and reacted, and then the mixture is separated, washed, and finally dried to constant weight to obtain a demulsifier for tar ammonia water; The method for preparing the modified carbon black comprises the following steps: 20-40 g of carbon black and 20-40 g of polyethyleneimine are mixed to obtain a suspension, and then the suspension is stirred and treated in an ultrasonic field under the conditions of a power of 250 W, a frequency of 40 KHz and a temperature of 50-70 ℃ for 6-10 h, and then the suspension is filtered through a 0.22 μm polytetrafluoroethylene membrane and washed with water for 3-5 times, and finally the suspension is freeze-dried at (-30)-(-20) ℃ for 24-72 h to obtain the modified carbon black.

2. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, In the step (1), the solvent comprises at least one of ethanol and ethylene glycol; and the use amount ratio of FeCl3·6H2O, FeCl2·4H2O, the solvent and the modified carbon black is (28-56) g:(12-24) g:(1.2-2.4) mL:(12-24) g.

3. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, In the step (1), the ultrasonic treatment conditions are that the ultrasonic treatment frequency is 20-100 KHz and the ultrasonic treatment time is 15-25 min; the stirring speed is 500-700 rpm; the mass fraction of the ammonia water is 5-10 wt%; the pH value is adjusted to 8.5-9.5; the separation method is that the solid is separated by using a magnet; the washing method is that the solid is washed with water for 3-5 times; and the drying temperature is 70-90 ℃.

4. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, In the step (2), the use amount ratio of the magnetic carbon black, diphenyl ether and octadecyl phosphoric acid is (15-30) g:(0.8-1.3) L:(2-4) g.

5. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, In the step (2), the ultrasonic treatment conditions are that the ultrasonic treatment frequency is 20-100 KHz and the ultrasonic treatment time is 10-15 min; the heating conditions are that the heating temperature is 70-90 ℃ and the heating time is 1-3 h; the separation method is that the solid is separated by using a magnet; the washing method is that the solid is washed with ethanol and deionized water for 3-5 times in sequence; and the drying temperature is 50-70 ℃.

6. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, In the step (3), the catalyst comprises at least one of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N,N'-dicyclohexyl carbodiimide; and the use amount ratio of the carboxylated cyclodextrin, the modified magnetic carbon black, the catalyst and water is (0.5-1) g:(15-30) g:(2-5) g:(100-200) mL.

7. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, The stirring reaction time in the step (3) is 12-24 h; the separation method is to separate the solid with the aid of a magnet; the washing method is to wash the solid with ethanol and deionized water for 3-5 times successively; and the drying temperature is 50-70 ℃.

8. The method for preparing a demulsifier for tar ammonia water according to claim 1, characterized by, The preparation method of the carboxylated cyclodextrin comprises the following steps: 2-4 g of β-cyclodextrin, 1.8-3.6 g of NaOH and 7-15 mL of water are mixed, stirred and treated for 10-20 min, then 2.5-5 mL of 10-20 wt% 3-chloropropionic acid aqueous solution is added, and then the mixture is reacted at 80-100 ℃ for 1-2 h; after being cooled to room temperature, 50-80 mL of methanol is added to obtain a precipitate, the precipitate is filtered, the filter residue is washed with 70-90 v / v% ethanol aqueous solution for 4-6 times, and then dried to constant weight to obtain the carboxylated cyclodextrin.

9. A demulsifier for tar ammonia water prepared by the method according to any one of claims 1-8.

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