CN114560542A - Method for preparing in-situ iron-loaded biochar based on thermal cracking of magnetic coagulation algae-containing flocs and application of method - Google Patents

Method for preparing in-situ iron-loaded biochar based on thermal cracking of magnetic coagulation algae-containing flocs and application of method Download PDF

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CN114560542A
CN114560542A CN202210189725.4A CN202210189725A CN114560542A CN 114560542 A CN114560542 A CN 114560542A CN 202210189725 A CN202210189725 A CN 202210189725A CN 114560542 A CN114560542 A CN 114560542A
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algae
thermal cracking
biochar
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water
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CN114560542B (en
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马江雅
李砂
夏玮
聂勇
孔艳丽
张会文
丁磊
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Anhui University of Technology AHUT
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Abstract

The invention relates to the technical field of water treatment, in particular to a method for preparing in-situ iron-loaded biochar based on thermal cracking of magnetic coagulation algae-containing flocs and application thereof, wherein the method comprises the steps of treating algae-containing water by using a covalent bond magnetic coagulant, drying, grinding and sieving the collected algae-containing flocs, then carrying out impregnation modification in an activating agent, carrying out suction filtration and drying to constant weight; after sieving, putting the flocs into a tube furnace, and carrying out N treatment at 400-800 DEG C2Thermally cracking the algae-containing flocs in the atmosphere to prepare in-situ iron-carrying blue algae biochar; the prepared biochar is washed by deionized water and dried to obtain the in-situ iron-loaded blue-green algae biochar, the in-situ iron-loaded blue-green algae biochar prepared by the method has the adsorption capacity, the catalytic capacity and the magnetic separation capacity, the operation method is simple and economic to prepare and has good performance, a new method is provided for recycling algae-containing sludge, the problem of secondary pollution of coagulation floc sludge is solved, and the method is an important way for realizing resource circulation.

Description

Method for preparing in-situ iron-loaded biochar based on thermal cracking of magnetic coagulation algae-containing flocs and application of method
Technical Field
The invention relates to the technical field of water treatment, in particular to a method for preparing in-situ iron-loaded biochar based on thermal cracking of magnetic coagulation algae-containing flocs and application thereof.
Background
With the development of agriculture and technology in China, a large amount of nitrogen, phosphorus and organic matters are discharged into rivers and lakes, so that the phenomenon of water bloom caused by excessive propagation of blue algae in water is caused. The blue algae bloom phenomenon damages the ecological environment balance and seriously influences the sanitary safety of drinking water. The current treatment method of algae-containing water comprises the following steps: chemical methods, physical methods and biological methods, wherein chemical algae removal is the most common algae removal method, and has the advantages of rapidness, simplicity, energy conservation and low cost, coagulation sedimentation is a common method, although the coagulation process is simple compared with mechanical fishing operation, the coagulation process faces a problem of floc sludge generated after coagulation treatment, and the current floc sludge treatment methods are as follows: land burial, sanitary landfill, land utilization, ocean abandonment, comprehensive utilization and the like, but the sludge recycling cost is higher, the utilization rate of recycled products is low, and the resource process is hindered. Therefore, the recycling treatment of the algae sludge is a big problem in the environmental field. The organic matter content of the blue algae sludge is very rich, wherein the blue algae is used as an excellent biomass raw material and contains a large amount of protein, saccharides and the like, and simultaneously the cellulose and hemicellulose content is very high; the sludge is enriched in suspended impurities, organic matters, residual coagulant and the like in the sewage body, and the problem to be solved is to reasonably utilize the algae sludge in a recycling manner. Chinese invention patent ZL201811373068.9 discloses a normal temperature pretreatment-hydrothermal carbonization method for preparing magnetic algae-based biochar, which comprises the steps of adding ferric salt and alkali into algae sludge, obtaining the magnetic algae-based biochar through hydrothermal reaction, and the preparation process does not need drying pretreatment, can efficiently treat high-concentration algae-rich water and algae mud/algae residue with high water content, and accords with the low-carbon concept of algae resource utilization. However, the algae sludge of the method comes from algae mud, air-float algae residue, artificial salvage or mechanical algae removal in a sedimentation tank of a water treatment plant, the methods consume a large amount of manpower and material resources and high electric energy, and simultaneously, the method adopts a hydrothermal carbonization method to prepare the biochar with far lower aromatizing degree and stability than high-temperature cracking.
Biochar is produced by pyrolyzing biomass at high temperature (usually under oxygen deficiency or extremely low oxygen content)<700 ℃) to produce a family of insoluble, stable, highly aromatic, carbon-rich solids. The biochar surface has rich functional groups, can be used as a carrier of Fenton-like catalysis, even as a direct catalyst, and participates in the activation process of hydrogen peroxide, persulfate, peracetic acid and the like, so that free radicals with super-oxidizing capability are generated, and persistent organic matters in a water environment can be treatedThe substance is rapidly and effectively degraded. Chinese patent ZL201910694622.1 discloses a modified blue algae biochar composite material and application thereof in treating electroplating wastewater, wherein Taihu blue algae is mixed with KOH and ZnCl2And KHPO4One of the two is mixed and pyrolyzed to obtain biochar, and then the biochar is soaked in an iron-containing solution, and the prepared biochar has the capabilities of adsorbing and catalyzing Fenton-like substances. However, the method carries iron in a mode of ectopic iron-forming.
Therefore, there is a need to prepare a material with high aromatizing degree by using blue algae sludge, develop the material into a functional material with catalytic activity, and apply the functional material to organic wastewater treatment.
In view of the above-mentioned drawbacks, the inventors of the present invention have finally obtained the present invention through a long period of research and practice.
Disclosure of Invention
The invention aims to solve the problem of how to prepare a material with high aromatizing degree by using blue algae sludge, develop the material into a functional material with catalytic activity and apply the functional material to organic wastewater treatment, and provides a method for preparing in-situ iron-loaded biochar based on the thermal cracking of magnetic coagulation algae-containing floc and application thereof.
In order to realize the aim, the invention discloses a method for preparing in-situ iron-loaded biochar based on thermal cracking of magnetic coagulation algae-containing floc, which comprises the following steps:
s1: treating algae-containing water by using a covalent bond magnetic coagulant, collecting algae-containing flocs and drying the flocs;
s2: grinding the dried floc obtained in the step S1, sieving, and soaking in an activator solution;
s3: filtering and drying the floc impregnated in the step S2, and then carrying out thermal cracking treatment in an inert atmosphere;
s4: and (5) washing and centrifuging the sample subjected to the thermal cracking treatment in the step S3, collecting a solid part, and drying to obtain the in-situ iron-carrying blue algae biochar composite material.
The preparation method of the covalent bond magnetic coagulant in the step S1 comprises the following steps:
s11: 4.0g of magnetic Fe3O4The nanoparticles were added to 320mLAdding water ethanol and 80mL deionized water solution, performing ultrasonic treatment for 20min, adding 18mL 25% -28% ammonia water, and continuing ultrasonic treatment for 10min after ensuring that the pH is more than 9 to obtain alkaline Fe3O4Dispersing liquid, namely placing the dispersing liquid in a water bath kettle, keeping the temperature at 40 ℃, then dropwise adding 4mL of ethyl orthosilicate, electrically stirring for 6 hours at 400r/min, and washing for 3-5 times by using absolute ethyl alcohol and deionized water;
s12: adding 200mL of absolute ethyl alcohol into the solution washed in the step S11, placing the solution in a water bath kettle at 40 ℃, dropwise adding 4mL of gamma-aminopropyltriethoxysilane, electrically stirring the solution at 400rpm for 6 hours, and washing the solution for 3 to 5 times by using the absolute ethyl alcohol and deionized water;
s13: adding 6g of acrylamide and 3g of cationic monomer into 15mL of deionized water, magnetically stirring until the acrylamide and the cationic monomer are dissolved at 400r/min, adding the dissolved solution into the solution washed in the step S12, adding 300mL of deionized water, uniformly stirring, placing the solution in a water bath kettle, keeping the temperature at 35 ℃, dropwise adding 3.0g of ammonium persulfate into 40mL of deionized water by using a peristaltic pump, electrically stirring for 24 hours at 350r/min, and washing for 3-5 times by using absolute ethyl alcohol and deionized water to obtain the covalent bond magnetic flocculant.
The concentration of the covalent bond magnetic coagulant used in the step S1 is 25 g/L-327 g/L, the adding amount is 25mL, and the coagulation conditions are as follows: the fast stirring speed is 350r/min, the fast stirring time is 10min, the slow stirring speed is 50r/min, the slow stirring time is 15min, the settling time is 30min, the algae used in the algae-containing water is Microcystis aeruginosa FACHB-905, the algae-containing water is cultured to the logarithmic growth phase under the conditions of 2000ulx, 25 ℃ and the light-dark ratio of 12: 12, the absorbance of the original simulated algae-containing water at 686nm in the coagulation is 0.270-0.300, the drying temperature is 60-80 ℃, and the drying time is 12-24 h.
The activating agent in the step S2 is NaOH or H3PO4Wherein the concentration of NaOH is 2mol/L, H3PO4The concentration is 2mol/L, and the dipping time is 6-10 h.
The inert atmosphere in the step S3 is N2The flow rate of inert gas is 50-100 mL/min, the thermal cracking is divided into two stages, the thermal cracking temperature of the first stage is 30-300 ℃, the thermal cracking time is 40min, and the thermal cracking temperature of the second stage isThe temperature is 300-800 ℃, and the thermal cracking time is 10-50 min.
The step S4 is to wash with deionized water for 3-5 times, wherein the centrifugal speed is 5000r/min, the time is 5-10 min, the drying temperature is 60-80 ℃, and the time is 12-24 h.
The invention also discloses the in-situ iron-loaded biochar prepared by the preparation method and application of the in-situ iron-loaded biochar in treating tetracycline wastewater, and the method comprises the following steps:
(1) adding the in-situ iron-carrying cyanobacteria biochar into tetracycline wastewater, adjusting the pH to 3-11, and placing the system in a constant-temperature shaking table at 25-50 ℃;
(2) and (3) after the system in the step (1) is adsorbed and balanced, adding hydrogen peroxide to carry out Fenton-like oxidation reaction.
The dosage of the original iron-carrying blue algae biochar in the step (1) is 0.05-1.0 g/L, the concentration of the tetracycline waste water is 10-100 mg/L, and the pH is adjusted by adding hydrogen chloride and sodium hydroxide.
In the step (2), the adsorption equilibrium time is 30-60 min, the mass fraction of hydrogen peroxide is 30%, the adding amount is 10-200 mg/L, and the Fenton-like reaction time is 4-6 h; after the reaction is finished, the biochar is easily separated from the water under the action of a magnetic field, and the magnetic separation effect is good
Figure BDA0003524832840000031
The reaction mechanism of the invention is shown in the figure, and is realized by Fe2+Reacts with hydrogen peroxide to generate hydroxyl free radicals, attacks the target pollutant tetracycline to decompose the target pollutant tetracycline, and finally converts the target pollutant tetracycline into CO2And H2O, wherein the hydroxyl radical is generated, is shown as follows.
Fe2++H2O2→Fe3++·OH+OH-
Fe3++H2O2→Fe2++·HO2+H+
Nano Fe3O4SiO for granules2Coating, accommodatingRice Fe3O4The particles have small particle size and large surface free energy, are not easy to disperse in water, and utilize SiO2The coating can improve the dispersibility and the oxidation resistance, the number of hydroxyl groups on the surface of the coating is small, organic materials are not easy to graft, the used raw materials are collected by a covalent bond magnetic coagulant, and the raw materials have Fe3O4The secondary modification is not needed, and the preparation process is simplified; secondary roasting is not needed, and energy is saved; the prepared biochar material has magnetism, and can be easily magnetically separated in water treatment; while Fe3O4Containing Fe2+And Fe3+Fe which can accelerate2+And Fe3+And circulating and shortening the reaction time.
Compared with the prior art, the invention has the beneficial effects that:
1. the algae-containing floc has rich biomass, and can be optimized by activating agent
Aiming at water eutrophication, the invention collects the flocculate after coagulating sedimentation by utilizing the electric neutralization and net-catching rolling sweeping action of the biomass rich in blue algae and the covalent bond magnetic coagulant, and then utilizes NaOH or H3PO4The in-situ iron-carrying blue algae biochar composite material is prepared by modification, and has rich specific surface area and functional groups;
2. the iron of the blue algae biochar comes from raw materials and has wide application
The raw material of the blue algae biochar prepared by the invention contains SiO2Encapsulated Fe3O4The core-shell structure not only avoids the oxidation of ferrous iron at high temperature, but also is easier to load iron compared with the traditional iron loading mode. The biochar prepared by the method is applied to water treatment, has good adsorption performance, can effectively adsorb organic pollutants and metal ions, and can be used as a Fenton-like catalytic carrier to catalyze the capability of hydrogen peroxide to generate free radicals;
3. the algae-containing floc has rich nitrogen-containing functional groups, and provides the most direct ammonification mode for thermal cracking of the biochar
The covalent bond magnetic coagulant consists of acrylamide and cationThe algae flocs collected by the coagulant have nitrogen-containing functional groups, can provide active sites, and improve the content of heavy metals and organic compounds CO2And heavy metal capture capacity, and the direct thermal cracking of the nitrogen-rich biochar is the most ideal amination mode.
Drawings
FIG. 1 shows examples 1 and 2, H3PO4XRD of the in-situ iron-carrying blue algae biochar obtained by modification and NaOH modification;
FIG. 2 is a graph comparing the effects of the biochar composite prepared in examples 1 and 2 activating hydrogen peroxide for fenton-like treatment and treatment of tetracycline wastewater;
FIG. 3 shows the removal rate of algae and UV of the covalent bond magnetic coagulant prepared in example 1 and example 2 at different dosage for treating algae-containing water254A removal rate map;
FIG. 4 is a graph comparing the adsorption removal effect of the biochar composite prepared in example 1 and example 2 on tetracycline waste water;
Detailed Description
The above and further features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.
Example 1
The embodiment provides a method for preparing in-situ iron-carrying cyanobacteria biochar based on thermal cracking of magnetic coagulation algae-containing flocs, which comprises the following steps:
step 1: treating algae-containing water by using a covalent bond magnetic coagulant, collecting flocs after the coagulation hydraulic condition is that the fast stirring speed is 350r/min, the fast stirring time is 10min, the slow stirring speed is 50r/min, the slow stirring time is 15min and the settling time is 30min, and drying at the temperature of 80 ℃ for 24 h;
and 2, step: taking a certain amount of 5.0g of flocs in H with the concentration of 2.0mol/L3PO4Soaking the solution for 8h, filtering, drying, grinding, and sieving with 80 mesh sieve to obtain algae-containing floc powder;
and step 3: putting the powder containing the algae flocs into a square boat, then putting the boat into a tube furnace, and continuously introducing N2Lower heating, firstThe thermal cracking temperature of each stage is 30-300 ℃, and the thermal cracking time is 40 min; the second stage thermal cracking temperature is 300-600 ℃, the thermal cracking time is 30min, then the temperature is kept at 600 ℃ for 1h, N2The flow rate is 50mL/min, and then the mixture is naturally cooled to the room temperature;
and 4, step 4: and (3) washing the biochar prepared by the thermal cracking for 5 times by using deionized water, centrifuging, collecting the solid part, and drying at the drying temperature of 70 ℃ for 24 hours to obtain the in-situ iron-loaded blue algae biochar material.
Example 2
The embodiment provides a method for preparing in-situ iron-carrying cyanobacteria biochar based on thermal cracking of magnetic coagulation algae-containing flocs, which comprises the following steps:
step 1: treating algae-containing water by using a covalent bond magnetic coagulant, collecting flocs after the coagulation hydraulic power condition is that the fast stirring speed is 350r/min, the fast stirring time is 10min, the slow stirring speed is 50r/min, the slow stirring time is 15min and the settling time is 30min, and drying at the temperature of 80 ℃ for 24 h;
step 2: soaking a certain amount of 5.0g floc in 2.0mol/L NaOH solution for 8h, filtering, drying, grinding, and sieving with 80 mesh sieve to obtain algae-containing floc powder;
and step 3: putting the powder containing the algae flocs into a square boat, then putting the boat into a tube furnace, and continuously introducing N2Heating the mixture at the temperature of 30-300 ℃ in the first stage for 40 min; the second stage thermal cracking temperature is 300-600 ℃, the thermal cracking time is 30min, then the temperature is kept at 600 ℃ for 1h, N2The flow rate is 50mL/min, and then the mixture is naturally cooled to the room temperature;
and 4, step 4: and (3) washing the biochar prepared by the thermal cracking for 5 times by using deionized water, centrifuging, collecting the solid part, and drying at the drying temperature of 70 ℃ for 24 hours to obtain the in-situ iron-loaded blue algae biochar material.
The covalent bond magnetic coagulant can effectively remove algae in water, as shown in figure 3, when algae-containing water with the absorbance of 0.270-0.300 is treated, the algae can be effectively removed, and when the addition amount is 5mg/L, the removal effect reaches 100%, so that the covalent bond magnetic coagulant can effectively remove the algaeA cell. Then preparing the biochar by collecting algae-containing flocs and thermally initiating. The in-situ iron-carrying cyanobacteria biochar prepared in the embodiment 1 and the embodiment 2 is characterized, and the detection results are shown in the table 1 and the figure 1: table 1 shows the specific surface area and pore volume of the in-situ iron-loaded cyanobacteria charcoal material prepared in this example, and the specific surface area of the in-situ iron-loaded cyanobacteria charcoal after alkali modification is greatly reduced, mainly due to the surface morphology collapse caused by the corrosion effect of alkali, resulting in the reduction of the average pore diameter. FIG. 1 is an XRD spectrum of the blue algae charcoal material carrying iron in situ prepared in the embodiment, and 2 theta in FIG. 1 is 29.9 degrees, 35.2 degrees, 42.6 degrees, 53.0 degrees, 56.7 degrees and 62.4 degrees which are attributed to Fe3O4The hexahedral cubic phases of (220), (311), (400), (422), (511), and (440) of (f), demonstrate the presence of iron oxide.
Table 1 example 1 and example 2H3PO4The specific surface area and the pore volume of the in-situ iron-carrying blue-green algae biochar obtained by modification and NaOH modification
Figure BDA0003524832840000061
Example 3
The embodiment provides an application of the prepared in-situ iron-loaded biochar in treatment of tetracycline wastewater, which comprises the following steps:
step 1: adding 0.02g of in-situ iron-carrying cyanobacteria charcoal into 200mL of tetracycline wastewater, and placing the system in a constant-temperature shaking table with the temperature of 25 ℃ and the rotating speed of 200rpm for reaction for 30 min;
step 2: and (3) after the system adsorption in the step (1) is balanced, adding 30mg/L hydrogen peroxide to carry out Fenton-like oxidation reaction.
The adsorption effect of the biochar for treating tetracycline wastewater is shown in fig. 4, and the removal effect is poor. After the system is adsorbed and balanced, adding hydrogen peroxide to carry out Fenton-like oxidation reaction, as shown in figure 3, adding the hydrogen peroxide into Fe2+Hydroxyl free radicals generated under the catalytic action have no selective attack on pollutants, and the removal rate of tetracycline is obviously improved.
The foregoing is merely a preferred embodiment of the invention, which is intended to be illustrative and not limiting. It will be understood by those skilled in the art that various changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. A method for preparing in-situ iron-carrying cyanobacteria biochar based on thermal cracking of magnetic coagulation algae-containing flocs is characterized by comprising the following steps:
s1: treating algae-containing water by using a covalent bond magnetic coagulant, collecting algae-containing flocs and drying the flocs;
s2: grinding the dried floc obtained in the step S1, sieving, and soaking in an activator solution;
s3: filtering and drying the floc impregnated in the step S2, and then carrying out thermal cracking treatment in an inert atmosphere;
s4: and (5) washing and centrifuging the sample subjected to the thermal cracking treatment in the step S3, collecting a solid part, and drying to obtain the in-situ iron-carrying blue algae biochar composite material.
2. The method for preparing the in-situ iron-carrying cyanobacteria biochar based on the thermal cracking of the magnetic coagulation algae-containing flocs as claimed in claim 1, wherein the preparation method of the covalent bond magnetic coagulant in the step S1 comprises the following steps:
s11: 4.0g of magnetic Fe3O4Adding the nano particles into 320mL of absolute ethyl alcohol and 80mL of deionized water solution, carrying out ultrasonic treatment for 20min, adding 18mL of 25% -28% ammonia water, and continuing the ultrasonic treatment for 10min after ensuring that the pH value is more than 9 to obtain the alkaline Fe3O4Dispersing liquid, namely placing the dispersing liquid in a water bath kettle, keeping the temperature at 40 ℃, then dropwise adding 4mL of ethyl orthosilicate, electrically stirring for 6 hours at 400r/min, and washing for 3-5 times by using absolute ethyl alcohol and deionized water;
s12: adding 200mL of absolute ethyl alcohol into the solution washed in the step S11, placing the solution in a water bath kettle at 40 ℃, dropwise adding 4mL of gamma-aminopropyltriethoxysilane, electrically stirring the solution at 400rpm for 6 hours, and washing the solution for 3 to 5 times by using the absolute ethyl alcohol and deionized water;
s13: adding 6g of acrylamide and 3g of cationic monomer into 15mL of deionized water, magnetically stirring until the acrylamide and the cationic monomer are dissolved at 400r/min, adding the dissolved solution into the solution washed in the step S12, adding 300mL of deionized water, uniformly stirring, placing the solution in a water bath kettle, keeping the temperature at 35 ℃, dropwise adding 3.0g of ammonium persulfate into 40mL of deionized water by using a peristaltic pump, electrically stirring for 24 hours at 350r/min, and washing for 3-5 times by using absolute ethyl alcohol and deionized water to obtain the covalent bond magnetic flocculant.
3. The method for preparing the in-situ iron-loaded cyanobacteria biochar based on the thermal cracking of the magnetic coagulation algae-containing flocs as claimed in claim 1, wherein the concentration of the covalent bond magnetic coagulant used in the step S1 is 25 g/L-327 g/L, the dosage is 25mL, and the coagulation conditions are as follows: the fast stirring speed is 350r/min, the fast stirring time is 10min, the slow stirring speed is 50r/min, the slow stirring time is 15min, the settling time is 30min, the algae used in the algae-containing water is Microcystis aeruginosa FACHB-905, the algae-containing water is cultured to the logarithmic growth phase under the conditions of 2000ulx, 25 ℃ and the light-dark ratio of 12: 12, the absorbance of the original simulated algae-containing water at 686nm in the coagulation is 0.270-0.300, the drying temperature is 60-80 ℃, and the drying time is 12-24 h.
4. The method for preparing in-situ iron-loaded cyanobacteria biochar based on thermal cracking of magnetic coagulation algae-containing flocs as claimed in claim 1, wherein the activating agent in step S2 is NaOH or H3PO4Wherein the concentration of NaOH is 2mol/L, H3PO4The concentration is 2mol/L, and the dipping time is 6-10 h.
5. The method for preparing in-situ iron-bearing cyanobacteria biochar based on thermal cracking of magnetic coagulation algae-containing flocs as claimed in claim 1, wherein the inert atmosphere in step S3 is N2The flow rate of the inert gas is 50-100 mL/min, the thermal cracking is divided into two stages, the thermal cracking temperature of the first stage is 30-300 ℃, the thermal cracking time is 40min, the thermal cracking temperature of the second stage is 300-800 ℃, and the thermal cracking time is 10-50 min.
6. The method for preparing in-situ iron-loaded cyanobacteria biochar based on the thermal cracking of magnetic coagulation algae-containing flocs as claimed in claim 1, wherein the step S4 is washing with deionized water for 3-5 times, the centrifugal rotation speed is 5000r/min, the time is 5-10 min, the drying temperature is 60-80 ℃, and the time is 12-24 h.
7. The in-situ iron-carrying cyanobacteria biochar prepared by the preparation method of any one of claims 1 to 6.
8. The application of the in-situ iron-carrying cyanobacteria biochar in the treatment of tetracycline wastewater as claimed in claim 7, characterized by comprising the following steps:
(1) adding the in-situ iron-carrying cyanobacteria biochar into tetracycline wastewater, adjusting the pH to 3-11, and placing the system in a constant-temperature shaking table at 25-50 ℃;
(2) and (3) after the system in the step (1) is adsorbed and balanced, adding hydrogen peroxide to carry out Fenton-like oxidation reaction.
9. The application of the in-situ iron-bearing cyanobacteria biochar in the treatment of tetracycline waste water as claimed in claim 8, wherein in the step (1), the dosage of the in-situ iron-bearing cyanobacteria biochar is 0.05 g/L-1.0 g/L, the concentration of the tetracycline waste water is 10 mg/L-100 mg/L, and the pH is adjusted by adding hydrogen chloride and sodium hydroxide.
10. The application of the in-situ iron-carrying cyanobacteria biochar in the treatment of tetracycline wastewater as claimed in claim 8, wherein in the step (2), the adsorption balance time is 30-60 min, the mass fraction of hydrogen peroxide is 30%, the adding amount is 10-200 mg/L, and the Fenton-like reaction time is 4-6 h.
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