Biological activated carbon for removing tetracycline from wastewater and wastewater purification method

Abstract

The invention discloses biological activated carbon for removing tetracycline from wastewater and a wastewater purification method. The preparation of the biological activated carbon is safer and more environment-friendly, and the biological activated carbon has excellent adsorption performance on tetracycline. The biological activated carbon is bamboo-based activated carbon prepared by performing steam thermal activation on bamboo-based biological carbon; the specific surface area SBET is 1100-1300 m < 2 > / g, the micropore specific surface area Smon is 1080-1200 m < 2 > / g, the outer surface area Sext is 60-70 m < 2 > / g, the total pore volume Vtotal is 0.78-1 cm < 3 > / g, and the average pore diameter Dave is 2.7-3.1 nm; the Fourier transform infrared spectroscopy FTIR analysis result shows that an absorption peak appears in the wave number range of 3200-3600 cm <-1 >, which corresponds to the stretching vibration of hydroxyl; the photoelectron spectroscopy XPS analysis result shows that the relative content of the pi-pi * characteristic peak is 5.7-7%. The bamboo-based activated carbon has excellent adsorption performance on tetracycline.

Description

Technical Field

[0001] The invention relates to the technical field of removing tetracycline (TC) from wastewater by adsorption, and in particular to biological activated carbon for removing tetracycline from wastewater and a wastewater purification method. Background Art

[0002] The rapid development of industry and the widespread use of various drugs have led to the emergence of emerging contaminants (ECs). As a type of ECs, tetracycline (TC) is often detected in wastewater due to its stable structure and strong resistance to degradation. How to remove tetracycline from wastewater is a difficult problem that cannot be ignored. At present, a variety of purification methods such as adsorption, advanced oxidation, membrane filtration, and biodegradation have been applied to remove tetracycline. Among them, adsorption is considered to be an effective tetracycline removal technology due to its advantages such as convenient operation, wide range of application, and relatively simple regeneration. Low-cost adsorption is the current development trend.

[0003] In the past decade, biochar has become a promising low-cost adsorbent due to its excellent physical and chemical properties and its compliance with the concept of green environmental protection. Common raw material sources of biochar include straw, corn straw, waste black fungus residue, bamboo, etc. Compared with other biochars, bamboo-based biochar (BC) has attracted much attention due to its high carbon content and low ash content. Generally speaking, bamboo-based biochar prepared by conventional pyrolysis has a small specific surface area and pore structure, so its adsorption capacity for tetracycline is limited. In order to further improve the adsorption capacity for tetracycline, bamboo-based biochar can be activated to prepare bamboo-based activated carbon (BAC).

[0004] At present, the preparation method of bamboo-based activated carbon mainly uses KOH, H3PO4, ZnCl2 and other reagents for chemical activation based on bamboo-based biochar, but these methods have the disadvantages of strong corrosion, serious environmental pollution, and cumbersome subsequent treatment steps. In addition, in-depth research on the adsorption mechanism of bamboo-based activated carbon on tetracycline is also very rare. Summary of the invention

[0005] The purpose of the present invention is to provide a biological activated carbon for removing tetracycline from wastewater and a wastewater purification method. The preparation of the biological activated carbon is safer and more environmentally friendly, and has excellent adsorption performance for tetracycline.

[0006] In the first aspect, a bio-activated carbon for removing tetracycline from wastewater is provided, which is a bamboo-based activated carbon prepared by steam thermal activation of bamboo-based bio-char; the specific surface area S BET 1100-1300m2 / g, micropore specific surface area S micro 1080-1200m 2 / g, external surface area S ext 60-70m 2 / g, total pore volume V total 0.78-1cm 3 / g, average pore size D ave The Fourier transform infrared spectrum FTIR analysis results show that the -1 There is an absorption peak in the wavenumber range, which corresponds to the stretching vibration of the hydroxyl group; the XPS analysis results show that π-π * The relative content of the characteristic peak is 5.7-7%.

[0007] In a second aspect, a wastewater purification method is provided for removing tetracycline from pretreated wastewater, wherein the wastewater is purified using a fixed bed reactor having a fixed bed layer composed of an adsorbent, wherein the adsorbent is composed of the biological activated carbon for removing tetracycline from wastewater of the first aspect.

[0008] The biological activated carbon used for removing tetracycline from wastewater is prepared by steam thermal activation of bamboo-based biochar, and the preparation process is safer and more environmentally friendly.

[0009] The research on which the present invention is based found that the main adsorption mechanisms of bamboo-based activated carbon for tetracycline are pore filling (the process of tetracycline molecules entering and occupying the pore space on the surface and inside of bamboo-based activated carbon), π-π interaction (non-covalent attraction between two or more π systems, usually aromatic rings) and hydrogen bonding (hydrogen bonds formed between certain functional groups in tetracycline molecules and oxygen-containing functional groups on the surface of bamboo-based activated carbon). The technical means adopted in the technical scheme of the above-mentioned biological activated carbon of the present invention correspond to the above-mentioned three adsorption mechanisms respectively, which can make bamboo-based activated carbon have excellent adsorption performance for tetracycline.

[0010] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings constituting a part of this specification are used to assist the understanding of the present invention. The contents provided in the drawings and the related descriptions in this specification can be used to explain the present invention, but do not constitute improper limitations on the present invention.

[0012] Figure 1This is a scanning electron microscope comparison image of sample BC and sample BAC-700 in the experimental example of the specific implementation method of the present invention.

[0013] Figure 2 This is the N2 adsorption-desorption isotherm curve of each sample in the experimental example of the specific implementation method of the specification of the present invention. In this figure, the Relative pressure (P / Po) on the horizontal axis refers to the relative pressure, that is, the ratio of the gas partial pressure (P) to the saturated vapor pressure (Po); the Adsorbed capacity (ml / g) on ​​the vertical axis refers to the adsorption amount, the unit is milliliter per gram (ml / g), which indicates the volume of gas that can be adsorbed per gram of adsorbent.

[0014] Figure 3 The following is a Fourier transform infrared spectrum (FTIR) of each sample in the experimental example of the specific implementation method of the present invention. In this figure, the horizontal axis Wave number (cm -1 ) refers to wave number, and the vertical axis Transmittance (%) is transmittance, which indicates the percentage of infrared light intensity passing through the sample to the incident light intensity.

[0015] Figure 4 This is an X-ray photoelectron spectrum (XPS) diagram of each sample in the experimental example of the specific implementation method of the specification of the present invention. In this figure, each row represents a sample, from top to bottom are BC (including spectrum a, spectrum b, spectrum c), BAC-500 (including spectrum d, spectrum e, spectrum f), BAC-700 (spectrum g, spectrum h, spectrum i) and BAC-900 (including spectrum j, spectrum k, spectrum l); the left column is the full spectrum (Survey spectrum), the middle column is the C1s (1s orbit of carbon element) fine spectrum, and the right column is the O1s (1s orbit of oxygen element) fine spectrum. The horizontal axis is the binding energy (eV), the vertical axis is the signal intensity (au), and the peaks in the figure represent carbon and oxygen in different chemical states.

[0016] Figure 5 This is a relationship diagram between the dosage of each sample and the tetracycline removal rate in the experimental examples of the specific implementation mode of the present invention. In this figure, the horizontal axis is the dosage of the sample (g / L), and the vertical axis is the TC removal rate (%).

[0017] Figure 6 This is a comparison chart of the TC adsorption capacity of each sample in the experimental example of the specific implementation method of the invention specification. In this figure, the horizontal axis is different samples, and the vertical axis is the adsorption capacity (mg / g), which represents the mass of TC adsorbed per gram of sample. DETAILED DESCRIPTION

[0018] The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that: The technical solutions and technical features provided in each section, including the following description, can be combined with each other without conflict. In addition, where possible, these technical solutions, technical features and related combinations can be assigned specific technical themes and protected by relevant patents.

[0019] The embodiments of the present invention involved in the following description are generally only a part of the embodiments rather than all the embodiments. Based on these embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of patent protection.

[0020] Bamboo-based biochar (BC) has attracted much attention due to its high carbon content and low ash content. Generally speaking, bamboo-based biochar prepared by conventional pyrolysis has a small specific surface area and pore structure, so its adsorption capacity for tetracycline is limited. In order to further improve the adsorption capacity for tetracycline, bamboo-based biochar can be activated to prepare bamboo-based activated carbon (BAC). However, the current preparation method of bamboo-based activated carbon mainly uses KOH, H3PO4, ZnCl2 and other reagents for chemical activation on the basis of bamboo-based biochar, but these methods have the disadvantages of strong corrosiveness, serious environmental pollution, and cumbersome subsequent treatment steps. In addition, in-depth research on the adsorption mechanism of bamboo-based activated carbon on tetracycline is also very rare.

[0021] Based on the above situation, the inventors adopted the basic scheme of preparing bamboo-based activated carbon by steam thermal activation of bamboo-based biochar, so as to make the preparation of bamboo-based activated carbon safer and more environmentally friendly; in addition, in order to deeply study the adsorption mechanism of bamboo-based activated carbon on tetracycline, a specific preparation process of bamboo-based activated carbon was designed, and the relevant properties of the prepared bamboo-based activated carbon were tested, and finally the biological activated carbon for removing tetracycline from wastewater of the present invention was obtained; on the basis of the above-mentioned biological activated carbon, a wastewater purification method based on the biological activated carbon was further studied to remove tetracycline from pretreated wastewater.

[0022] Below, the specific preparation process of bamboo-based activated carbon, the characterization of bamboo-based activated carbon, the adsorption performance of bamboo-based activated carbon on tetracycline, the adsorption mechanism of bamboo-based activated carbon on tetracycline, and the wastewater purification method will be described. It should be pointed out that in the following content, BC represents bamboo-based biochar, BAC represents bamboo-based activated carbon, and TC represents tetracycline.

[0023] 1. The specific preparation process of bamboo-based activated carbon.

[0024] 1.1 Preparation of BC.

[0025] The bamboo is first washed, dried and ground to obtain bamboo powder, and then the bamboo powder is mixed with tar in a mass ratio of 1:0.2-1:0.5, and then heated at a temperature of 500-700°C and 0.05-0.2m 3 / h nitrogen flow rate for carbonization for 0.5-2 hours to obtain bamboo-based biochar.

[0026] The preparation process of the above BC mainly has the following characteristics: First, bamboo powder and tar are mixed in a mass ratio of 1:0.2-1:0.5. In this way, tar can be used as an additional carbon source to increase the carbon content of the final product; a reasonable ratio range of bamboo powder to tar ensures sufficient carbon source supplementation without masking the characteristics of the bamboo itself; tar may form a new carbon structure during pyrolysis, affecting the porosity and specific surface area of ​​the final product; tar can act as a binder to help bamboo powder particles better combine during carbonization; tar contains various organic compounds, which will form new surface functional groups during carbonization. Second, the carbonization conditions are a temperature of 500-700°C and a pressure of 0.05-0.2m 3 / h nitrogen flow rate for 0.5-2 hours. 500-700℃ is a relatively moderate carbonization temperature, which is enough to cause the decomposition of organic matter, but not too high to cause excessive structural collapse. The relatively short carbonization time is aimed at retaining certain functional groups. The use of inert gas (nitrogen) to create an oxygen-free environment and a lower nitrogen flow rate can control the reaction rate and prevent excessive loss of volatile substances.

[0027] 1.2 Preparation of BAC.

[0028] The bamboo-based biochar is heated to the set activation temperature at a heating rate of 3-7°C / min under a mixed flow of nitrogen and steam, and then kept warm for 1.5-3h. The flow rate of the nitrogen is 0.05-0.2m 3 / h, and the flow rate of the steam is 0.1-0.5kg / h.

[0029] The preparation process of the above BAC should have the following characteristics: First, heating at a heating rate of 3-7°C / min. Slow heating helps to uniformly activate and reduce the thermal stress of the product. It can form a more stable pore structure. Second, after heating to the set activation temperature, keep it warm for 1.5-3h. Sufficient insulation time ensures that the activation reaction is fully carried out to form a stable pore structure and surface functional groups. Third, a dual activation environment of nitrogen and steam. Nitrogen provides an inert atmosphere to prevent excessive oxidation; steam acts as an activator to promote pore formation and expansion.

[0030] 1.3 Experimental example.

[0031] Bamboo from Yibin, Sichuan Province, China was used to prepare several BACs using the following complete preparation process, labeled BAC-500, BAC-700, and BAC-900. Sufficient quantities of each BAC should be available for subsequent testing.

[0032] Complete preparation process: Bamboo is repeatedly washed with distilled water to remove attached dirt, then dried, ground and sieved through a 40-50 mesh sieve to obtain bamboo powder. Bamboo powder is mixed with tar in a mass ratio of 1:0.35 and heated at a temperature of 600°C and 0.1 m 3 h -1 Carbonization was performed for 1 hour under a nitrogen flow rate of 0.1 m / s to obtain BC (sample labeled as BC). BC was heated to different activation temperatures (500°C, 700°C, and 900°C) at a heating rate of 5°C / min under nitrogen and steam flow and kept at this temperature for 2 hours. The nitrogen flow rate was 0.1 m / s. 3 / h, the flow rate of steam is 0.35kg / h. Finally, the product is sieved through a 100-150 mesh sieve to obtain BAC-500, BAC-700 and BAC-900.

[0033] BAC-500 is a sample obtained when the activation temperature is 500°C; BAC-700 is a sample obtained when the activation temperature is 700°C; and BAC-900 is a sample obtained when the activation temperature is 900°C.

[0034] 2. Characterization of bamboo-based activated carbon.

[0035] BC, BAC-500, BAC-700 and BAC-900 were characterized, and the physicochemical properties of these samples were analyzed. The pore parameters were measured using a surface area and porosity analyzer (ASAP 2020, Micromeritics Instrument Corporation, USA). The pore size distribution was determined by the Horvath-Kawazoe (HK) method. The morphology of the materials was analyzed using an electron microscope (Eindhoven, the Netherlands). Fourier transform infrared spectroscopy (FTIR) (Spectrum One, PerkinElmer, USA) and X-ray photoelectron spectroscopy (XPS) (KAlpha, Thermo Scientific, USA) were used to analyze the changes in the chemical groups and elemental composition of the materials. The pH drift method was used to determine the zero charge point (pHpzc) value using a pH meter.

[0036] 2.1 Pore structures of BC and BAC.

[0037] See Table 1. In Table 1, S BETRefers to specific surface area; S micro Refers to the micropore specific surface area; S ext Refers to the external surface area; V total Refers to total pore volume; D ave Refers to the average pore diameter.

[0038] Table 1: Pore structure and surface properties of BC and BAC

[0039] As shown in Table 1, as the activation temperature increases from 500°C to 700°C, the specific surface area (S BET ), total pore volume (V tota ) and average pore size (D ave ) have increased. This phenomenon indicates that high temperature promotes the formation of micropores, making BAC have a rich pore structure, thus providing more abundant adsorption sites for TC. Scanning electron microscopy also shows (see Figure 1 ), BAC-700 has a richer pore structure than BC. However, when the temperature is further increased to 900℃, the V total and D ave The sharp drop indicates that the carbon structure melts and collapses due to high temperatures. Figure 2 As shown in Figure 2, at different activation temperatures, BAC exhibited type IV isotherms and H3 hysteresis loops, and the D ave The diameter of BAC is between 2 and 3 nm, indicating that BAC has a typical mesoporous structure. In addition, when P / P0 is less than 0.5, the N2 adsorption curve overlaps with the desorption curve, which is due to the presence of a large number of microporous structures in BAC. Therefore, 700 °C is an ideal activation temperature.

[0040] 2.2 Fourier transform infrared spectroscopy (FTIR) analysis of BC and BAC.

[0041] See also Figure 3 , all BACs are between 3200-3600cm -1 There are peaks near 1589cm-1, which corresponds to the OH stretching vibration, which can form hydrogen bonds with the oxygen-containing functional groups on the TC surface, thereby removing TC. Compared with BC, the C=O / C=C (1589cm-1) related to aromatic compounds in BAC -1 ) and OCO (1021cm -1 ) peak intensity increases, indicating that the increase in activation temperature promotes the formation of aromatic structures. In particular, the aromatic structure of BAC-700 is the most obvious. The aromatic structure on BAC can provide π electrons and bind to TC through π-π interactions.

[0042] 2.3 X-ray photoelectron spectroscopy (XPS) analysis of BC and BAC.

[0043] See Table 2. Table 2 shows the X-ray photoelectron spectroscopy (XPS) analysis results of different samples, including Figure 4 The element surface composition calculated based on the peak area is shown in the figure. Among them: Bond attribution lists the chemical bonds or functional groups corresponding to different peaks in the C1s spectrum and O1s spectrum; Binding energy: The binding energy corresponding to each peak, the unit is electron volt (eV).

[0044] Table 2: BC and BAC binding energies (eV) and elemental surface compositions (%).

[0045] like Figure 2 As shown in Table 2, 284.8ev and 534.4ev correspond to C1s and O1s, respectively. The C1s data spectrum includes CC / CH (284.8ev), C=O (287.6ev), OCO (286.1ev) and OC=O (288.0ev). The O1s spectrum has peaks at 531.6ev and 532.6ev, indicating the presence of C=O and CO, respectively. In particular, BAC-700 exhibits significant π-π * (293.5eV). According to Table 2, π-π * The relative content of the characteristic peak is 6.37%.

[0046] 3. Adsorption performance of bamboo-based activated carbon on tetracycline.

[0047] refer to Figure 5-Figure 6 As shown, the adsorption capacity of BAC-700 can reach 70 mg / g, which is significantly higher than that of BC, BAC-500 and BAC-900.

[0048] In addition, the adsorption performance of BAC-700 at different times was also studied. The rapid adsorption rate of TC within 100 minutes indicated that rapid adsorption occurred in the early stage of adsorption. In the early stage of adsorption, there were many active sites on BAC-700, and a large amount of TC in the solution formed a strong adsorption driving force, which quickly combined with the active sites of BAC-700, and the adsorption amount increased significantly. With the increase of contact time, the number of adsorption sites combined with TC gradually decreased, and the adsorption efficiency of TC gradually decreased until the adsorption equilibrium was reached. At the same time, the adsorption amount of TC within 100 minutes accounted for 65-70% of the entire adsorption process, indicating that BAC-700 can adsorb TC quickly and efficiently.

[0049] 4. Adsorption mechanism of tetracycline by bamboo-based activated carbon.

[0050] In aqueous solution systems, the pollutant adsorption capacity is usually positively correlated with the iodine adsorption value of the adsorbent. However, the inventors found that the correlation between the BAC iodine value and the TC adsorption capacity was not obvious (R2=0.6531). Further research on the correlation between BAC and other iodine values ​​and TC adsorption capacity also showed that there was no significant correlation (R2=0.6218). Therefore, the iodine value is not the main indicator of the excellent adsorption performance of biomass activated carbon. In addition, the isoelectric point (pHpzc) was determined. In the pH range of 2-4.9, the surfaces of TC and BAC-700 were positively charged, indicating that electrostatic interaction is not the main adsorption mechanism.

[0051] The study found that the correlation coefficients R2 between the O / C and H / C of BAC and the TC adsorption capacity were 0.8064 and 0.7545, respectively, and these two indicators were negatively correlated with the TC adsorption capacity. This is mainly because the lower the O / C and H / C, the higher the aromaticity of BAC, resulting in an increase in the benzene ring structure. It can act as a π electron donor, while the large number of -OH functional groups in the TC molecule can act as a π electron acceptor, both of which enhance the TC adsorption capacity through π-π interactions.

[0052] The pore structure of BAC is also an important factor leading to TC removal. BET , S micro and V total There is a significant positive correlation between the adsorption capacity of TC and the R2 is between 0.828 and 0.965. total and S micro The R2 of BAC is more significant, indicating that pore filling controls the adsorption capacity of TC, and micropores play an important role in this process. Correspondingly, the molecular size of TC is 1.23nm*0.84nm*0.67nm, indicating that the pore size of BAC is sufficient for TC to penetrate, so the adsorption behavior of TC is regulated by the pore filling effect.

[0053] In summary, the main adsorption mechanisms of BAC for TC are pore filling, π-π interaction and hydrogen bonding. BAC-700 corresponds to the above three adsorption mechanisms, which enables bamboo-based activated carbon to have excellent adsorption performance for tetracycline.

[0054] Here, considering reasonable errors and possible adjustments, the bamboo-based activated carbon of BAC-700 can be characterized as follows: specific surface area S BET 1100-1300m 2 / g, micropore specific surface area S micro 1080-1200m 2 / g, external surface area S ext 60-70m 2 / g, total pore volume V total0.78-1cm 3 / g, average pore size D ave The results of Fourier transform infrared spectroscopy showed that the wavelength of the -1 The absorption peak appears in the wavenumber range, corresponding to the stretching vibration of the hydroxyl group; the X-ray photoelectron spectroscopy analysis results show π-π * The relative content of the characteristic peaks is 5.7-7%. In the C1s spectrum, the relative content of CC / CH bonds is 70-75%, the relative content of OCO bonds is 5-8%, and the relative content of C=O bonds is 6-8%. The relative content of C=O bonds in the O1s spectrum is 2-4%, and the relative content of C–O bonds is 3-5%.

[0055] 5. Wastewater purification methods.

[0056] Based on BAC-700, the present invention also provides a wastewater purification method for removing tetracycline from pretreated wastewater, wherein the method uses a fixed bed reactor having a fixed bed layer composed of an adsorbent to purify the wastewater, wherein the adsorbent is composed of BAC-700.

[0057] In order to better understand and predict the working process of the above-mentioned fixed bed reactor and provide a basis for the engineering design of the fixed bed reactor, the inventors also compared and analyzed different breakthrough curve models during the working process of the fixed bed reactor. The results showed that the Log-Bohart-Adams model can effectively fit the asymmetric breakthrough curve. The Log-Bohart-Adams model is one of the commonly used mathematical models in the fixed bed adsorption process and is a logarithmically corrected version of the classic Bohart-Adams model. Therefore, it is recommended that the fixed bed reactor be designed according to the Log-Bohart-Adams model.

[0058] In addition, experiments have found that when the adsorbent is saturated with tetracycline, ethanol and / or hydrogen peroxide can be used as a regeneration liquid to perform in-situ washing and regeneration of the adsorbent, and the regeneration effect is good (after multiple regenerations, the adsorbent can still maintain 70% of its adsorption capacity).

[0059] The study believes that the significant regeneration effect of ethanol is due to its ability to physically displace and dissolve TC, thereby regenerating the fixed bed layer. Unlike ethanol displacement desorption, the ideal regeneration effect of H2O2 is due to the acidic functional groups on the surface of BAC-700 reacting with H2O2 to produce ·OH, catalytically degrading TC and achieving regeneration.

[0060] In the above wastewater purification method, the preferred goal of the pretreatment is to make the total dissolved solids TDS of the wastewater not exceed 500 mg / L, the total organic carbon TOC not exceed 5 mg / L, and the pH is controlled within the range of 6.5-7.5. By controlling the total dissolved solids (TDS), total organic carbon (TOC) and pH value, the pretreatment not only optimizes the wastewater conditions to improve the adsorption efficiency of tetracycline by biological activated carbon, but also helps to extend the service life of the adsorbent and equipment. Pretreatment reduces the interference of other pollutants on the adsorption process, making the adsorption process more stable and predictable, and also facilitates the subsequent adsorbent regeneration operation.

[0061] A variety of pretreatment methods can be used to reduce the total dissolved solids (TDS), total organic carbon (TOC) and adjust the pH value in wastewater. These methods include but are not limited to: using membrane separation technologies such as reverse osmosis or electrodialysis to remove dissolved solids; using activated carbon adsorption or advanced oxidation treatment to reduce the organic content; adjusting the pH value by adding chemical reagents or using ion exchange technology. In addition, comprehensive treatment methods such as coagulation-sedimentation and multi-stage filtration systems can also be considered to achieve multiple treatment goals at the same time. The specific pretreatment scheme needs to be selected and combined according to factors such as the initial characteristics of the wastewater, treatment goals, economic costs and subsequent treatment requirements to achieve the best treatment effect.

[0062] The above is a description of the relevant contents of the present invention. A person skilled in the art will be able to implement the present invention based on these descriptions. Based on the above contents of this specification, all other embodiments obtained by a person skilled in the art without making any creative work shall fall within the scope of patent protection.

Claims

1. Biological activated carbon for removing tetracycline from wastewater, characterized in that: It is a bamboo-based activated carbon prepared by steam thermal activation of bamboo-based biochar; its specific surface area S BET 1100-1300m 2 / g, micropore specific surface area S micro 1080-1200m 2 / g, external surface area S ext 60-70m 2 / g, total pore volume V total 0.78-1cm 3 / g, average pore size D ave The Fourier transform infrared spectrum FTIR analysis results show that the -1 Absorption peaks appear in the wavenumber range, corresponding to the stretching vibration of hydroxyl groups; The results of X-ray photoelectron spectroscopy XPS analysis showed that π-π * The relative content of the characteristic peak is 5.7-7%.

2. The biological activated carbon for removing tetracycline from wastewater as claimed in claim 1, characterized in that: The results of X-ray photoelectron spectroscopy XPS analysis showed that in the C1s spectrum, the relative content of CC / CH bonds was 70-75%, the relative content of OCO bonds was 5-8%, and the relative content of C=O bonds was 6-8%. In the O1s spectrum, the relative content of C=O bonds was 2-4%, and the relative content of C–O bonds was 3-5%.

3. The biological activated carbon for removing tetracycline from wastewater as claimed in claim 2, characterized in that: The bamboo raw materials used in the preparation process of the bamboo-based biochar are taken from Yibin City, Sichuan Province, China.

4. The biological activated carbon for removing tetracycline from wastewater as claimed in claim 2, characterized in that: The bamboo-based biochar is prepared by the following method: firstly, bamboo is washed, dried and then ground to obtain bamboo powder, then the bamboo powder is mixed with tar in a mass ratio of 1:0.2-1:0.5, and then heated at a temperature of 500-700°C and a temperature of 0.05-0.2 m 3 / h nitrogen flow rate for carbonization for 0.5-2 hours to obtain bamboo-based biochar.

5. The biological activated carbon for removing tetracycline from wastewater as claimed in claim 1, characterized in that: The steam thermal activation process is as follows: the bamboo-based biochar is heated to a set activation temperature at a heating rate of 3-7°C / min under a nitrogen and steam mixed flow, and then kept warm for 1.5-3h. The nitrogen flow rate is 0.05-0.2m 3 / h, the flow rate of the steam is 0.1-0.5kg / h, and the activation temperature is 650-750°C.

6. The biological activated carbon for removing tetracycline from wastewater as claimed in claim 5, characterized in that: The activation temperature is 700°C.

7. A wastewater purification method for removing tetracycline from pretreated wastewater, characterized in that: A fixed bed reactor having a fixed bed layer composed of an adsorbent is used for wastewater purification, wherein the adsorbent is composed of the biological activated carbon for removing tetracycline from wastewater as described in any one of claims 1 to 6.

8. The wastewater purification method according to claim 7, characterized in that: The fixed bed reactor was designed according to the Log-Bohart-Adams model.

9. The wastewater purification method according to claim 7, characterized in that: When the adsorbent is saturated with tetracycline, the adsorbent is regenerated by in-situ washing using a regeneration liquid; the regeneration liquid is ethanol and / or hydrogen peroxide.

10. The wastewater purification method according to claim 7, characterized in that: The pretreatment can make the total dissolved solids TDS of the wastewater not exceed 500 mg / L, the total organic carbon TOC not exceed 5 mg / L, and the pH value be controlled within the range of 6.5-7.5.

Images