Preparation method and application of CN@rGO / RCH high-efficiency catalyst

Abstract

The application belongs to the technical field of composite materials, and relates to a preparation method of a kind of red mud reinforced anaerobic digestion biogas residue biochar loaded coating reduced graphene oxide layer carbon nitride (CN@rGO / RCH) high-efficiency catalyst, which comprises: CN and GO are fully stirred and ultrasonically dispersed in deionized water, and the solid-liquid mixture is hydrothermally reacted at 160-200 DEG C for 12-24 hours to obtain CN@GO; CN@GO and RCH are fully mixed and dispersed in deionized water, and are placed in a gas bath constant-temperature oscillation box for ultrasonic oscillation; after centrifugal drying, pyrolysis is carried out at 700-900 DEG C in an inert gas for 2-4 hours, and after cooling to room temperature, the catalyst is obtained. The prepared catalyst is applied to activate persulfate to degrade tetracycline in water. The preparation process is simple, controllable and environmentally friendly, and by loading and coating carbon nitride with reduced graphene oxide layer after anaerobic high-temperature pyrolysis and hydrochloric acid modification of red mud reinforced anaerobic digestion biogas residue, the environmental hazard solid waste produced by anaerobic digestion is recycled and reused, and the purpose of rapidly degrading tetracycline in water is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials and relates to a biochar catalyst, and in particular to a preparation method and application of a high-efficiency catalyst of red mud enhanced anaerobic digestion of biogas residue biochar loaded with reduced graphene oxide layer-coated carbon nitride (CN@rGO / RCH). Background Art

[0002] Red mud, produced during the alumina refining process, is bauxite slag rich in metallic minerals. Due to its toxicity, strong alkalinity, complex composition, and high production volume, it is considered a hazardous industrial waste. Using red mud to pretreat food waste can improve its biodegradability while alleviating acid inhibition during anaerobic digestion, thereby enhancing the performance and stability of the anaerobic digestion system. However, anaerobic digestion residues mixed with red mud constitute a new type of hazardous solid waste, potentially posing a more serious threat to the ecological environment. Therefore, the disposal of these new types of biogas residues urgently needs to be addressed.

[0003] At present, antibiotics have been widely used in medicine and animal husbandry, not only to protect the health of humans and livestock, but also to promote the growth and development of livestock by adding them to feed. Organisms can only effectively utilize 10% to 20% of antibiotics, and the remaining antibiotics enter the water environment through animal feces and other pathways, causing antibiotic pollution in water bodies. my country's antibiotic use ranks among the highest in the world, and tetracycline (TC) is a broad-spectrum antibiotic with a structure containing a tetracene basic skeleton, ranking first in production and use. Tetracycline has the characteristics of long retention time and wide range of spread. It is very easy to enrich in water bodies and soil, which will pose a serious threat to the ecological environment and human health. Therefore, it is of great significance to seek economical, efficient and sustainable TC treatment methods and technologies.

[0004] Biochar produced from biogas residue from red mud-enhanced anaerobic digestion exhibits a well-developed pore structure, large surface area, and rich functional groups. Biogas residue biochar produced through simple pyrolysis exhibits excellent persulfate activation, demonstrating promising application potential. In particular, the use of red mud as a metal source can further enhance the performance of biochar.

[0005] Based on this, the present invention discloses a high-value-added recycling method for red mud-enhanced anaerobic digestion residue, namely, the residue is made into a new biochar catalyst through pyrolysis and hydrochloric acid modification, and then peroxydisulfate (PDS) is activated to degrade TC, thereby realizing environmentally friendly back-end treatment of red mud-enhanced anaerobic digestion residue and efficient degradation of TC in water. Summary of the Invention

[0006] In view of the problem that the traditional disposal method of red mud reinforced anaerobic digestion biogas residue utilization is easy to cause environmental pollution, the application discloses a preparation method of CN@rGO / RCH high-efficiency catalyst.

[0007] Technical scheme

[0008] A preparation method of CN@rGO / RCH high-efficiency catalyst, comprising the following steps:

[0009] a) carbon nitride (CN) and graphene oxide (GO) are fully stirred and ultrasonically dispersed in deionized water, and the solid-liquid mixture is hydrothermally reacted at 160-200 DEG C for 12-24 hours, preferably hydrothermally reacted at 180 DEG C for 20 hours; the obtained solid is centrifuged and dried to obtain carbon nitride coated with graphene oxide (CN@GO), wherein the material ratio of CN, GO and deionized water is 0.1-0.3g:0.02-0.1g:40-70mL, preferably 0.1g:0.02g:50mL;

[0010] b) carbon nitride coated with graphene oxide (CN@GO) and red mud reinforced anaerobic digestion biogas residue biochar (RCH) modified by hydrochloric acid are fully mixed and dispersed in deionized water, and are placed in a gas bath constant temperature oscillation box for oscillation for 1-3 hours and ultrasonic for 0.5-1.5 hours, preferably oscillation for 3 hours and ultrasonic for 1 hour; the oscillation box temperature is 25+ / -1 DEG C, wherein the material ratio of CN@GO, RCH and deionized water is 0.02-0.1g:0.05-0.2g:40-70mL, preferably 0.02-0.1g:0.1g:50mL;

[0011] 0.2g:40-70mL, preferably 0.02-0.1g:0.1g:50mL;

[0012] c) after the mixture is centrifuged and dried, pyrolysis is carried out in inert gas at 700-900 DEG C for 2-4 hours, preferably at 700 DEG C for 2 hours, and the heating rate is 5 DEG C / min; after cooling to room temperature, CN@rGO / RCH is obtained.

[0013] In the preferred disclosure of the application, in step a), the carbon nitride (CN) is prepared in a conventional method, for example, 7.5g of urea is placed in a crucible, calcined at 520 DEG C for 4 hours with a heating rate of 2 DEG C / min, and naturally cooled to room temperature.

[0014] In the preferred disclosure of the application, in step a), the graphene oxide (GO) is few-layer graphene oxide.

[0015] In the preferred disclosure of the application, in step b), the particle size of the red mud reinforced anaerobic digestion biogas residue biochar (RCH) modified by hydrochloric acid is 200-250 meshes, and the preparation method is as follows:

[0016] 1) adding 1-10% by weight of red mud, preferably 5%, to organic waste, setting the temperature to 35-55° C. and the SRT to 22-50 d, to perform high-solid anaerobic digestion, drying the biogas residue obtained after the anaerobic digestion reaction at 80° C. overnight, cooling to room temperature, and then grinding and sieving to obtain 200-250 mesh red mud enhanced anaerobic digestion residue powder;

[0017] 2) pyrolyzing the red mud enhanced anaerobic digestion residue powder in an inert gas at 600-900° C. for 1-3 hours, preferably at 700° C. for 2 hours, at a heating rate of 5° C. / min, and cooling to room temperature to obtain red mud enhanced anaerobic digestion residue biochar powder (RC);

[0018] 3) The RC powder is placed in 1.2-3.6 wt.% hydrochloric acid and shaken for 30-90 min, preferably 1.8 wt.% hydrochloric acid for 30 min, with an shaking rate of 200 rpm, and the powder is collected and washed with deionized water until the pH of the filtrate is neutral. After drying again, it is ground and sieved to obtain 200-250 mesh hydrochloric acid-modified red mud enhanced anaerobic digestion residue biochar (RCH).

[0019] In a preferred embodiment of the present invention, in step 1), the solid content of the high-solid anaerobic digestion system is 8-20%.

[0020] In a preferred embodiment of the present invention, in step 2), the inert gas is nitrogen.

[0021] In a preferred embodiment of the present invention, in step 3), the concentration of the RC powder after soaking in hydrochloric acid is 4 g / L.

[0022] In a preferred embodiment of the present invention, in step c), the inert gas is nitrogen.

[0023] The material prepared according to the method of the present invention has sludge biochar as the base, and irregular particles formed by surface deposition of red mud and inorganic substances in the sludge and flaky reduced graphene oxide-coated carbon nitride are unevenly distributed on the base, and the material as a whole has a fluffy porous structure.

[0024] The present invention prepares biochar by strengthening anaerobic digestion of biogas residue raw materials through high-temperature pyrolysis of red mud in an anaerobic environment. The hydrochloric acid impregnation activation method is used to effectively increase the specific surface area of ​​the material and efficiently elute the ash contained therein. It also successfully loads a reduced graphene oxide layer coated with carbon nitride to produce a CN@rGO / RCH high-efficiency catalyst.

[0025] Another object of the present invention is to apply the prepared CN@rGO / RCH efficient catalyst to the degradation of antibiotics, especially to activate persulfate to degrade tetracycline (TC) in water.

[0026] The laboratory simulation test of removing TC in water by persulfate oxidation is as follows:

[0027] At room temperature, 100 mL of a conical flask is used as a reaction flask; 15 mg of CN@rGO / RCH catalyst is added to the TC solution (50 mL, 20 mg / L), and after adding peroxydisulfate (PDS), it is placed in a gas bath constant temperature oscillator at a rotation speed of 200 rpm; during the reaction, 3 mL of solution is taken every hour, the catalyst is filtered through a 0.22 μm filter membrane, and the absorbance is measured by a UV-1801 ultraviolet-visible spectrophotometer.

[0028] The removal rate of TC is calculated according to the following formula:

[0029] R(%)=(1-C / C0)×100%=(1-A / A0)×100%

[0030] In the formula, R, C, C0, A, and A0 represent the removal rate of TC, the TC concentration at the time of sampling, the initial TC concentration, the absorbance of the water sample at the time of sampling, and the initial absorbance of the water sample, respectively.

[0031] The reagents used in the application are commercially available and are of analytical purity.

[0032] Advantages

[0033] The preparation process of the application is simple, controllable and environmentally friendly, and the catalyst / PDS system can achieve efficient degradation of TC in water. Through anaerobic high-temperature pyrolysis of red mud enhanced anaerobic digestion of biogas residues and loading and coating of reduced graphene oxide layer carbon nitride after hydrochloric acid modification, the environmental hazardous solid waste produced by anaerobic digestion is recycled and reused, achieving the purpose of hazardous waste resource utilization and rapid degradation of TC in water. The results of the experiment show that the catalyst / PDS system can remove about 90% of TC in 20 min, providing reliable theoretical and practical support for practical application. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The scanning electron microscope photos of CN@rGO / RCH prepared in Example 3 (left: 20000x, right: 10000x);

[0035] Figure 2 The removal rate of the catalyst / PDS system on tetracycline, wherein the tetracycline solution concentration is 20 mg / L, the tetracycline solution volume is 50 mL, and the PDS addition concentration is 0.5 mM. DETAILED DESCRIPTION

[0036] The present technology will be described in detail below with reference to examples so that those skilled in the art can better understand the present technology, but the present technology is not limited to the following examples.

[0037] The red mud reinforced anaerobic digestion residue used in the examples is obtained by adding 5% red mud by mass to organic waste, carrying out high solid anaerobic digestion at a solid content of 10 w.t.% at a temperature of 35-55°C and an SRT of 22-50d.

[0038] Example 1

[0039] A preparation method of a CN@rGO / RCH high-efficiency catalyst, comprising the following steps:

[0040] a) The red mud reinforced anaerobic digestion residue is placed in an 80°C oven and dried overnight, and after cooling to room temperature, it is ground and sieved to obtain 200-250 mesh red mud reinforced anaerobic digestion residue powder;

[0041] b) The red mud reinforced anaerobic digestion residue powder is pyrolyzed in an inert gas at 700°C for 2h, with a heating rate of 5°C / min, and after cooling to room temperature, red mud reinforced anaerobic digestion residue biochar powder is obtained;

[0042] c) 0.2g of the powder obtained in step b) is soaked in 50mL of 1.8wt.% hydrochloric acid for 30min, with a shaker speed of 200rpm;

[0043] d) The powder obtained in step c) is collected, washed several times with deionized water until the filtrate pH is neutral, and then dried and sieved to obtain 200-250 mesh hydrochloric acid modified red mud reinforced anaerobic digestion residue biochar (RCH);

[0044] e) 7.5g of urea is placed in several crucibles and calcined at a high temperature using a muffle furnace, with a calcination time of 4h, a calcination temperature of 520°C, and a heating rate of 2°C / min. Carbon nitride (CN) is obtained after cooling;

[0045] f) 0.1g of CN and graphene oxide (GO) are mixed in a mass ratio of 1:0.2 in several 100mL beakers containing 50mL of deionized water, and then the solid-liquid mixture is transferred to a 100mL reaction kettle for hydrothermal reaction, with a hydrothermal temperature of 180°C and a hydrothermal time of 20h. After hydrothermal reaction, the obtained solid is centrifuged and dried to obtain graphene oxide coated carbon nitride (CN@GO);

[0046] g) mixing the CN@GO obtained in step f) and the RCH obtained in step d) at a mass ratio of 0.2:1 in several 150 mL conical flasks to which 50 mL of deionized water was added, and then placing the conical flasks in an air bath constant temperature shaker for 3 h and ultrasonicating for 1 h, with the shaker temperature at 25±1°C and the rotation speed at 200 rpm;

[0047] h) The mixture obtained in step g) was centrifugally dried, pyrolyzed at 700° C. for 2 h in an inert gas atmosphere at a heating rate of 5° C. / min, and cooled to room temperature to obtain CN@rGO / RCH.

[0048] The removal rate of tetracycline by the high-efficiency catalyst prepared in Example 1, CN@rGO / RCH / PDS system, is as follows: Figure 2 As shown in the figure, when the dosage of biochar catalyst is 0.3 g / L and the dosage of PDS is 0.5 mM, the average removal rate of tetracycline can reach about 90%.

[0049] Example 2

[0050] A method for preparing a CN@rGO / RCH high-efficiency catalyst comprises the following steps:

[0051] a) drying the biogas residue from the enhanced anaerobic digestion of red mud in an oven at 80° C. overnight, cooling it to room temperature, and then grinding and sieving it to obtain a 200-250 mesh red mud enhanced anaerobic digestion biogas residue powder;

[0052] b) pyrolyzing the red mud enhanced anaerobic digestion residue powder in an inert gas at 700° C. for 2 h at a heating rate of 5° C. / min, and cooling to room temperature to obtain the red mud enhanced anaerobic digestion residue biochar powder;

[0053] c) 0.2 g of the powder obtained in step b) was placed in 50 mL of 1.8 wt.% hydrochloric acid and shaken for 30 minutes at a shaker speed of 200 rpm;

[0054] d) collecting the powder obtained in step c), washing the powder with deionized water several times until the pH of the filtrate is neutral, drying it again, grinding and sieving it to obtain 200-250 mesh hydrochloric acid modified red mud enhanced anaerobic digestion residue biochar (RCH);

[0055] e) placing 7.5 g of urea in several crucibles and calcining them at high temperature in a muffle furnace for 4 h at a temperature of 520° C. at a heating rate of 2° C. / min, and cooling the mixture to obtain carbon nitride (CN);

[0056] f) 0.1 g of CN and graphene oxide (GO) were added to several 100 mL beakers with 50 mL of deionized water in a mass ratio of 1:0.2, stirred thoroughly for 3 h, and ultrasonicated for 1 h. The solid-liquid mixture was then transferred to a 100 mL reactor for hydrothermal reaction at 180°C for 20 h. After the hydrothermal reaction, the resulting solid was centrifuged and dried to obtain graphene oxide-coated carbon nitride (CN@GO).

[0057] g) mixing the CN@GO obtained in step f) and the RCH obtained in step d) at a mass ratio of 0.5:1 in several 150 mL conical flasks to which 50 mL of deionized water was added, and then placing the conical flasks in an air bath constant temperature shaker for 3 h and ultrasonicating for 1 h, with the shaker temperature at 25±1°C and the rotation speed at 200 rpm;

[0058] h) The mixture obtained in step g) was centrifugally dried, pyrolyzed at 700° C. for 2 h in an inert gas atmosphere at a heating rate of 5° C. / min, and cooled to room temperature to obtain CN@rGO / RCH.

[0059] The removal rate of tetracycline by the high-efficiency catalyst prepared in Example 2, CN@rGO / RCH / PDS system, is as follows: Figure 2 As shown in the figure, when the dosage of biochar catalyst is 0.3 g / L and the dosage of PDS is 0.5 mM, the removal rate of tetracycline can reach an average of more than 85%.

[0060] Example 3

[0061] A method for preparing a CN@rGO / RCH high-efficiency catalyst comprises the following steps:

[0062] a) drying the biogas residue from the enhanced anaerobic digestion of red mud in an oven at 80° C. overnight, cooling it to room temperature, and then grinding and sieving it to obtain a 200-250 mesh red mud enhanced anaerobic digestion biogas residue powder;

[0063] b) pyrolyzing the red mud enhanced anaerobic digestion residue powder in an inert gas at 700° C. for 2 h at a heating rate of 5° C. / min, and cooling to room temperature to obtain the red mud enhanced anaerobic digestion residue biochar powder;

[0064] c) 0.2 g of the powder obtained in step b) was placed in 50 mL of 1.8 wt.% hydrochloric acid and shaken for 30 minutes at a shaker speed of 200 rpm;

[0065] d) collecting the powder obtained in step c), washing the powder with deionized water several times until the pH of the filtrate is neutral, drying it again, grinding and sieving it to obtain 200-250 mesh hydrochloric acid modified red mud enhanced anaerobic digestion residue biochar (RCH);

[0066] e) placing 7.5 g of urea in several crucibles and calcining them at high temperature in a muffle furnace for 4 h at a temperature of 520° C. at a heating rate of 2° C. / min, and cooling the mixture to obtain carbon nitride (CN);

[0067] f) 0.1 g of CN and graphene oxide (GO) were added to several 100 mL beakers with 50 mL of deionized water in a mass ratio of 1:0.2, stirred thoroughly for 3 h, and ultrasonicated for 1 h. The solid-liquid mixture was then transferred to a 100 mL reactor for hydrothermal reaction at 180°C for 20 h. After the hydrothermal reaction, the resulting solid was centrifuged and dried to obtain graphene oxide-coated carbon nitride (CN@GO).

[0068] g) mixing the CN@GO obtained in step f) and the RCH obtained in step d) in a mass ratio of 1:1 in several 150 mL conical flasks to which 50 mL of deionized water was added, and then placing the conical flasks in an air bath constant temperature shaker for 3 h and ultrasonicating for 1 h, with the shaker temperature at 25±1°C and the rotation speed at 200 rpm;

[0069] h) The mixture obtained in step g) was centrifugally dried, pyrolyzed at 700° C. for 2 h in an inert gas atmosphere at a heating rate of 5° C. / min, and cooled to room temperature to obtain CN@rGO / RCH.

[0070] The removal rate of tetracycline by the high-efficiency catalyst prepared in Example 3, CN@rGO / RCH / PDS system, is as follows: Figure 2 As shown in the figure, when the dosage of biochar catalyst is 0.3 g / L and the dosage of PDS is 0.5 mM, the average removal rate of tetracycline can reach about 90%.

[0071] As attached Figure 1 As shown, inorganic substances from red mud and sludge form irregular particles through surface deposition, which increases the roughness of the biochar surface. At the same time, the carbon nitride coated with flaky reduced graphene oxide is tightly combined with the biochar substrate, and the catalyst as a whole has a fluffy porous structure.

[0072] Example 4

[0073] A method for preparing a CN@rGO / RCH high-efficiency catalyst comprises the following steps:

[0074] a) drying the biogas residue from the enhanced anaerobic digestion of red mud in an oven at 80° C. overnight, cooling it to room temperature, and then grinding and sieving it to obtain a 200-250 mesh red mud enhanced anaerobic digestion biogas residue powder;

[0075] b) pyrolyzing the red mud enhanced anaerobic digestion residue powder in an inert gas at 700° C. for 2 h at a heating rate of 5° C. / min, and cooling to room temperature to obtain the red mud enhanced anaerobic digestion residue biochar powder;

[0076] c) 0.2 g of the powder obtained in step b) was placed in 50 mL of 1.8 wt.% hydrochloric acid and shaken for 30 minutes at a shaker speed of 200 rpm;

[0077] d) collecting the powder obtained in step c), washing the powder with deionized water several times until the pH of the filtrate is neutral, drying it again, grinding and sieving it to obtain 200-250 mesh hydrochloric acid modified red mud enhanced anaerobic digestion residue biochar (RCH);

[0078] e) placing 7.5 g of urea in several crucibles and calcining them at high temperature in a muffle furnace for 4 h at a temperature of 520° C. at a heating rate of 2° C. / min, and cooling the mixture to obtain carbon nitride (CN);

[0079] f) 0.1 g of CN and graphene oxide (GO) were added to several 100 mL beakers with 50 mL of deionized water in a mass ratio of 1:0.5, stirred thoroughly for 3 h, and ultrasonicated for 1 h. The solid-liquid mixture was then transferred to a 100 mL reactor for hydrothermal reaction at 180°C for 20 h. After the hydrothermal reaction, the resulting solid was centrifuged and dried to obtain graphene oxide-coated carbon nitride (CN@GO).

[0080] g) mixing the CN@GO obtained in step f) and the RCH obtained in step d) at a mass ratio of 0.2:1 in several 150 mL conical flasks to which 50 mL of deionized water was added, and then placing the conical flasks in an air bath constant temperature shaker for 3 h and ultrasonicating for 1 h, with the shaker temperature at 25±1°C and the rotation speed at 200 rpm;

[0081] h) The mixture obtained in step g) was centrifugally dried, pyrolyzed at 700° C. for 2 h in an inert gas atmosphere at a heating rate of 5° C. / min, and cooled to room temperature to obtain CN@rGO / RCH.

[0082] The removal rate of tetracycline by the high-efficiency catalyst prepared in Example 4, CN@rGO / RCH / PDS system, is as follows: Figure 2 As shown in the figure, when the dosage of biochar catalyst is 0.3 g / L and the dosage of PDS is 0.5 mM, the average removal rate of tetracycline can reach about 90%.

[0083] Example 5

[0084] A method for preparing a CN@rGO / RCH high-efficiency catalyst comprises the following steps:

[0085] a) drying the biogas residue from the enhanced anaerobic digestion of red mud in an oven at 80° C. overnight, cooling it to room temperature, and then grinding and sieving it to obtain a 200-250 mesh red mud enhanced anaerobic digestion biogas residue powder;

[0086] b) The red mud reinforced anaerobic digestion biogas residue powder was pyrolyzed in inert gas at 700℃ for 2h with a heating rate of 5℃ / min, and the red mud reinforced anaerobic digestion biogas residue biochar powder was obtained after cooling to room temperature;

[0087] c) 0.2g of the powder obtained in step b) was immersed in 50mL of 1.8wt.% hydrochloric acid and oscillated for 30min at a speed of 200rpm;

[0088] d) The powder obtained in step c) was collected, washed with deionized water until the filtrate was neutral, and then dried and sieved to obtain 200-250 mesh hydrochloric acid modified red mud reinforced anaerobic digestion biogas residue biochar (RCH);

[0089] e) 7.5g of urea was placed in several crucibles and calcined at a high temperature using a muffle furnace, the calcination time was 4h, the calcination temperature was 520℃, the heating rate was 2℃ / min, and carbon nitride (CN) was obtained after cooling;

[0090] f) 0.1g of CN and graphene oxide (GO) were mixed in a mass ratio of 1:1 in several 100mL beakers containing 50mL of deionized water, and then the solid-liquid mixture was transferred to a 100mL reaction kettle for hydrothermal reaction, the hydrothermal temperature was 180℃, the hydrothermal time was 20h, and the obtained solid was centrifuged and dried to obtain graphene oxide coated carbon nitride (CN@GO);

[0091] g) The CN@GO obtained in step f) and the RCH obtained in step d) were mixed in a mass ratio of 0.2:1 in several 150mL conical flasks containing 50mL of deionized water, and then the conical flasks were placed in a gas bath constant temperature oscillator for oscillation for 3h and ultrasonic for 1h, the temperature of the oscillator was 25±1℃, and the speed was 200rpm;

[0092] h) The mixture obtained in step g) was centrifuged and dried, and then pyrolyzed in inert gas at 700℃ for 2h with a heating rate of 5℃ / min, and CN@rGO / RCH was obtained after cooling to room temperature.

[0093] The removal rate of tetracycline by the high-efficiency catalyst prepared in Example 5, CN@rGO / RCH / PDS system, was as shown in Figure 2 When the dosage of the biochar catalyst was 0.3g / L and the dosage of PDS was 0.5mM, the removal rate of tetracycline could reach more than 90% on average.

[0094] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a CN@rGO / RCH high-efficiency catalyst, characterized in that: The steps include: a) Carbon nitride (CN) and graphene oxide (GO) are fully stirred and ultrasonically dispersed in deionized water. The solid-liquid mixture is hydrothermally reacted at 160-200°C for 12-24 hours. The resulting solid is centrifuged and dried to obtain graphene oxide-coated carbon nitride (CN@GO). The ratio of CN to GO to deionized water is 0.1-0.3 g: 0.02-0.1 g: 40-70 mL. b) CN@GO and biochar (RCH) from red mud enhanced anaerobic digestion modified with hydrochloric acid were thoroughly mixed and dispersed in deionized water. The mixture was then placed in an air bath constant temperature oscillating box for 1-3 hours and ultrasonicated for 0.5-1.5 hours. The oscillating box temperature was 25±1°C. The material ratio of CN@GO, RCH, and deionized water was 0.02-0.1g: 0.05-0.2g: 40-70mL. The hydrochloric acid modified red mud enhanced anaerobic digestion residue biochar RCH has a particle size of 200 to 250 meshes, and its preparation method is as follows: 1) Adding 1-10% by weight of red mud to organic waste, setting the temperature to 35-55°C and the SRT to 22-50 days, and performing high-solid anaerobic digestion. The biogas residue obtained after the anaerobic digestion reaction is dried at 80°C overnight, cooled to room temperature, and then ground and sieved to obtain 200-250 mesh red mud enhanced anaerobic digestion residue powder; 2) The red mud enhanced anaerobic digestion residue powder was pyrolyzed in an inert gas at 600-900°C for 1-3 hours at a heating rate of 5°C / min, and then cooled to room temperature to obtain the red mud enhanced anaerobic digestion residue biochar powder RC; 3) The RC powder was immersed in 1.2-3.6 wt% hydrochloric acid and shaken for 30-90 min at a shaking rate of 200 rpm. The powder was collected and washed with deionized water until the pH of the filtrate was neutral. The powder was dried again and then ground and sieved to obtain 200-250 mesh hydrochloric acid modified red mud enhanced anaerobic digestion residue biochar RCH; c) After centrifugal drying, the mixture was heated to 700-900 °C in an inert gas and pyrolyzed for 2-4 h at a heating rate of 5 °C / min. After cooling to room temperature, CN@rGO / RCH was obtained.

2. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step a), the solid-liquid mixture is hydrothermally reacted at 180° C. for 20 h.

3. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step a), the material ratio of CN, GO and deionized water is 0.1 g:0.02 g:50 mL.

4. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step b), the CN@GO and the hydrochloric acid-modified red mud enhanced anaerobic digestion residue biochar RCH are fully mixed and dispersed in deionized water, and placed in an air bath constant temperature oscillation box for 3 hours and ultrasonication for 1 hour.

5. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step b), the material ratio of CN@GO, RCH and deionized water is 0.02-0.1 g:0.1 g:50 mL.

6. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step 1), 5% by mass of red mud is added to the organic waste.

7. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step 2), the red mud enhanced anaerobic digestion residue powder is placed in an inert gas at 700°C for pyrolysis for 2 hours.

8. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step 3), the RC powder was immersed in 1.8 wt % hydrochloric acid and shaken for 30 min.

9. The method for preparing the CN@rGO / RCH high-efficiency catalyst according to claim 1, characterized in that: In step c), the mixture is centrifugally dried and then pyrolyzed in an inert gas at 700° C. for 2 h.

10. The CN@rGO / RCH high-efficiency catalyst prepared according to any one of claims 1 to 9, characterized in that: The catalyst is based on biogas residue biochar. Irregular particles formed by surface deposition of inorganic substances in red mud and biogas residue and carbon nitride coated with flaky reduced graphene oxide are unevenly distributed on the substrate, and the overall material has a fluffy porous structure.

11. A use of the CN@rGO / RCH high-efficiency catalyst as claimed in claim 10, characterized in that: The catalyst is applied to degrade antibiotics.

12. The use of the CN@rGO / RCH high-efficiency catalyst according to claim 11, characterized in that: The catalyst is used to activate persulfate to degrade tetracycline in water.

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