Carbon-based material based on sludge biomass and application thereof

Abstract

The invention provides a method for preparing a carbon-based material from sludge-based biomass and application of the carbon-based material. The preparation method of the carbon-based material comprises the following steps: preparing an intermediate through a hydrothermal reaction, and mixing and calcining the intermediate and an organic matter containing a nitrogen element to obtain the carbon-based material which can be used as a catalyst and the like. According to the method, no metal pollutants are introduced, and the energy consumption is low. The carbon-based catalyst prepared through treatment has a very good removal effect on pollutants in sewage treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of sludge treatment, and in particular relates to a method for preparing carbon-based materials from sludge-based biomass and application thereof. Background Art

[0002] Sludge is a semi-solid or solid substance produced during sewage treatment, excluding screens, scum and grit. With the gradual improvement of sewage treatment facilities, sewage is centrally treated, and the amount of sludge produced has exceeded 6.6×10 -7 t, and it is still increasing year by year. Therefore, it is urgent to develop a treatment method to realize the resource utilization and high value utilization of sludge.

[0003] Sludge-based biomass refers to sludge containing rich biomass, which is rich in organic matter and does not contain quartz sand or sediment. A common form is activated sludge. Activated sludge is a general term for microbial communities and the organic and inorganic substances they are attached to. Generally, it can be divided into aerobic sludge and anaerobic sludge. The carbon-based materials made from these sludges have a high specific surface area and rich functional groups, which can be used as adsorbents, and the adjustable electronic structure makes it widely used in battery energy storage, sewage deep treatment and other fields. Among them, in the preparation technology of sludge as a precursor of Fenton-like materials, hydrothermal reaction, pyrolysis and / or introduction of metals are usually used to improve material performance, but there are still defects, such as metal leaching during application, which will cause secondary pollution; there are also attempts to add compounds containing oxygen or nitrogen functional groups to improve catalytic performance, but not all such compounds are useful, and the timing of addition is often with sludge. The mechanism of sludge modification is complex and unclear. For example, the mechanism of persulfate activation with biochar has free radical pathways and non-free radical pathways. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a new method for preparing carbon-based materials from sludge-based biomass and its application. The method does not introduce metal salts and is environmentally friendly. The carbon-based materials prepared by the method have a very good removal effect on pollutants in sewage treatment.

[0005] The present invention is achieved through the following technical solutions. The present invention discloses a method for preparing a carbon-based material, comprising the following steps:

[0006] (2) converting the sludge into an intermediate through hydrothermal carbonization reaction;

[0007] (3) calcining the intermediate obtained in step (2) and a nitrogen-containing organic matter in an inert atmosphere to obtain a nitrogen-doped carbon-based material.

[0008] The preparation of carbon-based materials mainly utilizes biomass from sludge, so the embodiment of the present invention is also called sludge-based biomass to prepare carbon-based materials. The raw materials can be pretreated before the reaction. For example, before the hydrothermal reaction, the sludge is washed to remove inorganic impurities such as metal ions. For example, after the hydrothermal reaction, the product is washed to remove metal ions and the like to obtain a clean intermediate. After calcination, acid washing can also be used to remove metal elements or oxides, and further washing with water and ethanol can be performed. As an example, the present invention discloses a method for preparing carbon-based materials from sludge-based biomass, which includes the following steps:

[0009] (1) Sludge pretreatment: The sludge-based biomass is washed with water and centrifuged to obtain a uniform solid;

[0010] (2) hydrothermal reaction: transferring the solid obtained in step (1) to a reactor for hydrothermal carbonization reaction; cooling the reaction product to room temperature, centrifuging, washing, and drying to obtain an intermediate;

[0011] (3) The intermediate obtained in step (2) is uniformly mixed with an organic substance containing nitrogen, and then calcined. The material obtained after calcination is sequentially acid-washed, water-washed, and alcohol-washed to obtain a carbon-based material.

[0012] The sludge-based biomass can be activated sludge, such as anaerobic granular sludge, aerobic granular sludge, floc activated sludge, algae granular sludge, and can be the activated sludge discharged from the secondary sedimentation tank (or sedimentation area) in the activated sludge system, specifically from a municipal domestic sewage treatment plant, a tannery sewage treatment plant, a garbage leachate sewage treatment plant or activated sludge cultured in a laboratory.

[0013] Furthermore, the water in step (1) can be replaced by an acid solution or an alkaline solution; the concentration of the acid solution or the alkaline solution can be 0.1 mol·L -1 ~0.5mol·L -1 .

[0014] Preferably, the activated sludge and the solution in step (1) can be mixed thoroughly by mechanical stirring, magnetic stirring, shaking, ultrasound or the like.

[0015] Furthermore, the content of the solid added to the reaction kettle in step (2) in the reaction system is 1wt% to 70wt%, such as 20-40wt%, and the pH of the initial mixture in the reaction system can be 3 to 11.

[0016] Furthermore, the temperature of the hydrothermal carbonization reaction in step (2) is 160-300° C., such as 200-250° C.; independently, optionally, the reaction time is 2-8 h.

[0017] Preferably, in step (2), the reaction product is washed with water or ethanol respectively.

[0018] Furthermore, the drying treatment in step (2) can be water bath heating drying, oil bath heating drying, oven direct drying, freeze drying, and the drying time is 6-24h (dried until the sample mass no longer decreases).

[0019] Furthermore, the nitrogen-containing organic matter in step (3) can be melamine, dicyandiamide, urea, dopamine, ethylenediaminetetraacetic acid, etc.

[0020] Furthermore, the mass ratio of the intermediate to the nitrogen-containing organic matter is 1:2-10, such as 1:2-5.

[0021] Furthermore, the mixing method of the intermediate and the nitrogen-containing organic matter in step (3) includes mechanical stirring, impregnation, ball milling and the like.

[0022] Furthermore, the calcination temperature in step (3) is 450-1000°C, such as 600-800°C, preferably 600-700°C; independently optionally, the calcination time is 1-5h.

[0023] Furthermore, the calcination process adopts a gradient heating process with a heating rate of 1 to 10°C min -1 , preferably 5 to 10 °C·min -1 .

[0024] Preferably, during the calcination process, the temperature is from 2 to 10 °C min -1 The heating rate is increased to 600-800℃ and calcined for 1.5-3.0h, and the temperature is naturally lowered after calcination.

[0025] Furthermore, the pickling solution in step (3) may be a solution of hydrochloric acid, sulfuric acid, etc., and the concentration may be 0.1 mol·L -1 ~0.5mol·L -1 .

[0026] On the other hand, the present invention also provides the application of the carbon-based material prepared as above:

[0027] 1) Application in sewage treatment, the obtained carbon-based materials can efficiently remove pollutants;

[0028] 2) Activated persulfate, such as peroxymonosulfate

[0029] 3) Adsorb heavy metals or organic pollutants, such as bisphenol A.

[0030] The present invention has the following positive beneficial effects

[0031] (1) The carbon-based material prepared by hydrothermal carbonization-pyrolysis in the present invention can be used in a Fenton-like system to achieve deep removal of pollutants. Biochar obtained after sludge carbonization can be used as a catalyst precursor. By doping with heteroatoms, its reactive sites are increased, thereby improving the catalytic performance. Therefore, this idea can realize the transformation of sludge into a Fenton-like catalyst, and realize the resource utilization and high-value application of sludge;

[0032] (2) The present invention provides a metal-free catalyst: Although transition metals have a strong activation effect on oxidants such as PMS (permonosulfate), the leaching of metal ions will cause secondary pollution to the environment and bring safety hazards. In response to this problem, metal-free carbon-based materials have better countermeasures, which can activate oxidants through their surface functional groups and defects;

[0033] (3) The present invention provides a non-radical pollutant degradation pathway. Compared with the traditional free radical pathway, the non-radical pathway has a longer half-life and a wider pH tolerance range, and is more selective for pollutants in water rich in anions and natural organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the SEM image of the hydrothermal carbon intermediate;

[0035] Figure 2 The removal effect of bisphenol A by catalysts obtained by different treatments;

[0036] Figure 3 The removal effect of bisphenol A on carbon-based materials prepared with different nitrogen-containing organic matter addition ratios at 700°C;

[0037] Figure 4 The removal effect of bisphenol A by carbon-based materials prepared at different calcination temperatures;

[0038] Figure 5 The removal effect of bisphenol A by carbon-based materials prepared from sludge from different sources;

[0039] Figure 6 The adsorption and removal effect of bisphenol A on carbon-based materials prepared from sludge from different sources;

[0040] Figure 7 This is the adsorption effect of Example 12 on heavy metals;

[0041] Figure 8 This is the removal effect of bisphenol A in Example 12 under a high-salt environment. DETAILED DESCRIPTION

[0042] The present invention is described in more detail below through specific embodiments to facilitate understanding of the present invention, but is not intended to limit the scope of protection of the present invention. The raw materials used in each preparation are aerobic granular sludge.

[0043] Comparative Example 1

[0044] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0045] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0046] Then, the hydrothermal carbonization reaction was carried out at 220 °C for 4 h;

[0047] After the reaction is completed, the product is cooled to room temperature and then centrifuged, washed with water and ethanol until the effluent is clear, and dried in a forced air dryer for 12 hours to obtain a hydrothermal carbon intermediate.

[0048] Comparative Example 2

[0049] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0050] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0051] Then, the hydrothermal carbonization reaction was carried out at 220 °C for 4 h;

[0052] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and dried in a blast dryer for 12 hours to obtain an intermediate;

[0053] (3) The intermediate obtained in step (2) was heated at 5°C min -1 The heating rate was raised to 800℃ and calcined for 2h. The calcination was protected by N2 atmosphere and 0.5mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0054] Example 1

[0055] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0056] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0057] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0058] Then, the hydrothermal carbonization reaction was carried out at 220 °C for 4 h;

[0059] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and dried in a blast dryer for 12 hours to obtain an intermediate;

[0060] (3) The intermediate obtained in step (2) is impregnated and mixed with melamine in a mass ratio of 1:3, dried, ground and mixed evenly, and then heated at 5°C min -1 The heating rate was raised to 800℃ and calcined for 2h. The calcination was protected by N2 atmosphere and 0.5mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0061] Example 2

[0062] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0063] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0064] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 20 wt %;

[0065] Then the hydrothermal carbonization reaction was carried out at 220 °C for 8 h;

[0066] After the reaction is completed, the product is cooled to room temperature and then centrifuged, washed with water and ethanol until the effluent is clear, and dried in a blast dryer for 24 hours to obtain an intermediate;

[0067] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:2, dried and ground, and then heated at 5°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0068] Example 3

[0069] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0070] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0071] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0072] Then, the hydrothermal carbonization reaction was carried out at 220 °C for 4 h;

[0073] After the reaction was completed, the product was cooled to room temperature and centrifuged, washed with water and ethanol until the effluent was clear, and freeze-dried for 6 hours to obtain an intermediate;

[0074] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:3, dried and ground, and then heated at 10°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0075] Example 4

[0076] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0077] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0078] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0079] Then, the hydrothermal carbonization reaction was carried out at 220 °C for 4 h;

[0080] After the reaction was completed, the product was cooled to room temperature and centrifuged, washed with water and ethanol until the effluent was clear, and freeze-dried for 12 h to obtain an intermediate;

[0081] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:4, dried and ground, and then heated at 10°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0082] Example 5

[0083] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0084] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0085] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0086] Then, the hydrothermal carbonization reaction was carried out at 220 °C for 4 h;

[0087] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 20 hours to obtain an intermediate;

[0088] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:5, dried and ground, and then heated at 5°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0089] Example 6

[0090] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0091] (1) Sludge pretreatment: Take the activated sludge cultured in the laboratory, wash it with water, and centrifuge it to obtain a uniform precipitate;

[0092] (2) hydrothermal reaction: transferring the precipitate obtained in step (1) into a reaction kettle and mixing it with water, wherein the content of the precipitate is 30 wt %;

[0093] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 8 h;

[0094] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 20 h to obtain an intermediate;

[0095] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:4, dried and ground, and then heated at 10°C min -1 The temperature was raised to 600 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere protection. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0096] The carbon-based material prepared under this condition can degrade 45%, 64% and 77% of bisphenol A in 10min, 20min and 30min respectively (see the test below for specific reaction conditions).

[0097] Example 7

[0098] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0099] (1) Sludge pretreatment: Take the activated sludge cultured in the laboratory, wash it with water, and centrifuge it to obtain a uniform precipitate;

[0100] (2) hydrothermal reaction: transferring the precipitate obtained in step (1) into a reaction kettle and mixing it with water, wherein the content of the precipitate is 30 wt %;

[0101] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 8 h;

[0102] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 20 h to obtain an intermediate;

[0103] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:3, dried and ground, and then heated at 10°C min -1 The temperature was raised to 600 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere protection. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0104] Example 8

[0105] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0106] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0107] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0108] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 6 h;

[0109] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 10 h to obtain an intermediate;

[0110] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:3, dried and ground, and then heated at 5°C min-1 The heating rate was raised to 800℃ and calcined for 2h. The calcination was protected by N2 atmosphere and 0.5mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0111] Example 9

[0112] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0113] (1) Sludge pretreatment: The activated sludge cultured in the laboratory was washed with deionized water and centrifuged to obtain uniform solids;

[0114] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0115] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 6 h;

[0116] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 10 h to obtain an intermediate;

[0117] (3) The intermediate obtained in step (2) is impregnated and mixed with dicyandiamide in a mass ratio of 1:3, dried and ground, and then heated at 5°C min -1 The heating rate was raised to 800℃ and calcined for 2h. The calcination was protected by N2 atmosphere and 0.5mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0118] Example 10

[0119] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0120] (1) Sludge pretreatment: Take the activated sludge from a municipal sewage treatment plant, wash it with deionized water, and centrifuge it to obtain a uniform solid;

[0121] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 40 wt %;

[0122] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 6 h;

[0123] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 10 h to obtain an intermediate;

[0124] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:3, dried and ground, and then heated at 5°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0125] Embodiment 11

[0126] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0127] (1) Sludge pretreatment: Take the activated sludge from a leather wastewater treatment plant, wash it with deionized water, and centrifuge it to obtain a uniform solid;

[0128] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 40 wt %;

[0129] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 6 h;

[0130] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 10 h to obtain an intermediate;

[0131] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:3, dried and ground, and then heated at 5°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0132] Example 12

[0133] A method for preparing carbon-based materials from sludge-based biomass, the method comprising the following steps:

[0134] (1) Sludge pretreatment: Take the activated sludge from a landfill leachate sewage treatment plant, wash it with deionized water, and centrifuge it to obtain a uniform solid;

[0135] (2) hydrothermal reaction: the solid obtained in step (1) is transferred to a reaction kettle and uniformly mixed with water, wherein the solid content is 30 wt %;

[0136] Then, the hydrothermal carbonization reaction was carried out at 200 °C for 6 h;

[0137] After the reaction is completed, the product is cooled to room temperature and centrifuged, washed with water and ethanol until the effluent is clear, and treated in a blast dryer for 10 h to obtain an intermediate;

[0138] (3) The intermediate obtained in step (2) is impregnated and mixed with urea in a mass ratio of 1:3, dried and ground, and then heated at 5°C min -1 The temperature was raised to 700 °C and calcined for 2 h. The calcination was carried out under N2 atmosphere. 0.5 mol·L -1 The calcined material is pickled with hydrochloric acid, and then washed with water and alcohol to obtain a carbon-based material.

[0139] Detection test:

[0140] 1. The morphology of the intermediate prepared in the hydrothermal reaction process of the above example was observed. Figure 1 The petal-like morphology of the hydrothermal carbon intermediate was observed by SEM, indicating that the hydrothermal reaction was successfully carried out, providing a larger specific surface area for biochar, providing more active sites for the preparation of carbon-based materials, and providing a basis for the excellent performance of carbon-based materials.

[0141] It was also found that two broad carbon peaks were observed in the XRD spectra of the carbon-based materials obtained in each embodiment and Comparative Example 2, and no metal-related peaks were found, indicating that the materials did not contain metals and metal oxides.

[0142] 2. Removal of bisphenol A:

[0143] The conditions in each removal test were the same, and the PMS (peroxymonosulfate) concentration was 1 mol·L -1 , bisphenol A concentration is 0.1 mol·L -1 , the amount of catalyst-carbon-based material is 0.5g·L -1 .

[0144] The removal of bisphenol A by the carbon-based materials prepared in Comparative Examples 1 and 2 and Examples 1, 8 and 9 is as follows: Figure 2 shown.

[0145] The removal of bisphenol A by the carbon-based materials prepared in Examples 2 to 5 is as follows: Figure 3 shown.

[0146] The removal of bisphenol A by the carbon-based materials prepared in Examples 3, 7 and 8 is as follows: Figure 4 The removal of bisphenol A by the carbon-based materials prepared in Examples 3 and 10 to 12 is shown in Figure 5 shown.

[0147] 3. Catalytic mechanism:

[0148] Adding a free radical quencher to the reaction system did not inhibit the degradation of bisphenol A, indicating that free radicals may not participate in the reaction; further using the free radical scavenger DMPO through electron paramagnetic resonance detection, no free radical signal was observed, indicating that free radicals were not generated. On the contrary, using TEMP as a scavenger for electron paramagnetic resonance detection, singlet oxygen signals were observed, and obvious current signals were observed through salt bridge experiments, indicating that the system degrades pollutants through non-free radical pathways.

[0149] It was further found that the carbon-based material prepared by this method also has a good effect on the removal of pollutants in a high-salt environment. Example 12 The removal effect of bisphenol A in the presence of 50 mM anions is as follows Figure 8 Other conditions of the reaction system: PMS (peroxymonosulfate) concentration is 1 mol·L -1 , bisphenol A concentration is 0.1 mol·L -1 , the amount of catalyst-carbon-based material is 0.5g·L -1 .

[0150] 4. Adsorption test:

[0151] The adsorption of bisphenol A by the carbon-based materials prepared in Examples 3 and 10 to 12 is as follows: Figure 6 As shown. Reaction system conditions: Bisphenol A concentration is 0.1 mol·L -1 , the amount of carbon-based material is 0.5 g·L -1 .

[0152] Example 12 The adsorption of heavy metals is as follows Figure 7 Reaction system conditions: prepare a series of heavy metal solutions with different concentrations, the volume is 50mL, the amount of carbon-based material is 20mg, and the adsorption time is 24h.

Claims

1. A method for preparing a carbon-based material, comprising the following steps: (2) Converting sludge-based biomass into intermediates through hydrothermal carbonization reaction; (3) calcining the intermediate obtained in step (2) and a nitrogen-containing organic matter in an inert atmosphere, and acid-washing the material obtained after calcination to obtain a nitrogen-doped carbon-based material.

2. The method according to claim 1, characterized in that: The nitrogen-containing organic matter is selected from melamine, dicyandiamide, urea, dopamine, ethylenediaminetetraacetic acid or a combination thereof; the mass ratio of the intermediate to the nitrogen-containing organic matter can be 1:2-10, such as 1:2-5.

3. The method according to claim 1, characterized in that: The calcination temperature is 450-1000° C., preferably 600-800° C., such as 600-700° C.; the calcination time can be 1-5 h, such as 2 h.

4. The method according to claim 1, characterized in that: The calcination process adopts gradient heating, and the heating rate is 1-10℃·min -1 , preferably 5~10℃·min -1 .

5. The method according to claim 1, characterized in that: The temperature of the hydrothermal carbonization reaction is 160-300° C., such as 200-250° C.; the reaction time can be 2-8 h.

6. The method according to claim 1, characterized in that: The acid used for pickling is hydrochloric acid or sulfuric acid, and the concentration can be 0.1 mol·L -1 ~ 0.5 mol·L -1 .

7. The method according to claim 1, characterized in that: The sludge-based biomass is activated sludge, which may be aerobic granular sludge, anaerobic granular sludge, floc activated sludge, or bacteria-algae granular sludge.

8. A carbon-based material obtainable by the method of any preceding claim.

9. Use of the carbon-based material according to claim 7 in sewage treatment.

10. The use according to claim 8, characterized in that: The use comprises activating a persulfate, such as a peroxymonosulfate.

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