CN106179372B - A kind of C@Fe based on biomass porous carbon3O4The Preparation method and use of@Bi composite photo-catalyst - Google Patents

Abstract

The present invention provides a kind of C@Fe based on biomass porous carbon₃O₄The Preparation method and use of@Bi composite photo-catalyst, includes the following steps: the preparation of step 1, porous carbon；The preparation of porous carbon after step 2, modification；Step 3, C@Fe₃O₄The preparation of@Bi composite photo-catalyst.C@Fe prepared by the present invention₃O₄The separation and recovery of@Bi composite photo-catalyst is more convenient, efficient；The C@Fe₃O₄@Bi composite photo-catalyst has preferable photocatalytic activity and stability, while using biomass corncob as carbon source, realizing waste and rationally utilizing, and saves resource.

Description

A preparation method of C@Fe3O4@Bi composite photocatalyst based on biomass porous carbon Law and use

technical field

The invention belongs to the technical field of environmental material preparation, and in particular relates to a preparation method and application of a C@Fe ₃ O ₄ @Bi composite photocatalyst based on biomass porous carbon.

Background technique

Environmental pollution is an urgent problem in today's society, among which air pollution and water pollution are closely related to our lives. Antibiotics are a class of drugs used to treat various non-viral infections. They are often used to suppress and kill various germs in medicine. However, due to the factors of antibiotics themselves, they cannot be completely absorbed in humans or animals, so a large number of antibiotics It is discharged into the environment as metabolites or even in its original state, causing pollution to the water environment. Many experts and scholars use physical, chemical and biological methods to remove and solve the above problems, but these methods are inefficient and easy to cause secondary pollution. Therefore, people have discovered a new treatment technology - photocatalysis, photocatalysis technology Solar energy is usually used as the light source, the cost is low, and the antibiotics in the environment can be degraded into inorganic substances such as carbon dioxide and water through photocatalytic technology, so it is an ideal green technology. Among many photocatalysts, titanium dioxide (TiO ₂ ) is widely used due to its relatively low price, stable and non-toxic chemical properties, etc., but its wide band gap, relatively narrow range of light absorption, and low utilization rate of solar energy lead to the Bismuth-based photocatalysts have attracted extensive attention due to their high photocatalytic activity.

Bi is a semi-metallic material with both metallic and non-metallic properties. Semi-metallic Bi has the advantages of highly anisotropic Fermi surface, small effective electron mass, low carrier density and long free path, etc. Make semimetal Bi a research hotspot (J. Zhao, QFHan, JWZhu, XDWu, X.Wang, Synthesis of Bi nanowire networks and their superior photocatalytic activity for Cr(VI) reduction, Nanoscale, 6(2014) 10062-10070), At the same time, the semimetallic Bi has a small band gap energy and can be used as a direct plasmonic photocatalyst (F.Dong, T.Xiong, YJSun, ZW Zhao, Y.Zhou, X.Feng, ZBWu, A semimetal bismuthelement as a direct plasmonic photocatalyst, Chem.Commun, 50(2014) 10386-10389), applied to photocatalytic technology. However, the semimetallic Bi has a weak adsorption capacity for pollutants. In order to improve the adsorption capacity, biochar (corn cob) was introduced in this paper to treat it as a porous carbon material. The porous carbon material has a large specific surface, and its unique porous structure not only increases the utilization rate of light energy, but also increases the adsorption of pollutants. Combining biochar (corn cob) with semimetallic Bi as a carrier material can adsorb pollutants around semiconductor particles, increasing the local concentration to speed up the reaction rate, thereby further improving the photocatalytic efficiency. In addition, considering the economic cost, we choose magnetic material (Fe ₃ O ₄ ) to compound with semimetal Bi and porous carbon material prepared from corncobs. The composite photocatalyst prepared by the present invention has good magnetic separation properties Greatly improve the recycling cost and secondary utilization rate.

Contents of the invention

In this paper, a high-temperature calcination method was used as the preparation method to prepare a preparation method based on biomass porous carbon C@Fe ₃ O ₄ @Bi composite photocatalyst, which can degrade tetracycline in environmental wastewater very well, and has the advantages of simple synthesis and high degradation rate. high feature.

Technical scheme of the present invention is:

A preparation method of C@Fe ₃ O ₄ @Bi composite photocatalyst based on biomass porous carbon, comprising the following steps:

Step 1. Preparation of porous carbon: first, wash the corn cob three times with deionized water, dry it after removing surface impurities, place the dried corn cob in a tube furnace, and calcinate it under _N2 atmosphere, and wait for the reaction to complete After cooling down to room temperature, it was taken out to obtain product A;

Weigh an appropriate amount of KOH, add an appropriate amount of deionized water to obtain a KOH solution, add the product A to the KOH solution, stir, and then filter the obtained material into an oven for drying, and record it as product B;

The product B is placed in a tube furnace and calcined under _N2 atmosphere. After the reaction is completed and the temperature is lowered to room temperature, it is taken out and washed with deionized water. The obtained sample is porous carbon (C);

Step 2. Preparation of the modified porous carbon: immerse the porous carbon obtained in step 1 in HNO ₃ , and perform a constant temperature water bath reaction under magnetic stirring. After the reaction is completed, the solid mixture is suction filtered and washed until the washing liquid is neutral. , put into a vacuum oven and dry, and the obtained sample is a modified porous carbon;

Step 3. Preparation of C@Fe ₃ O ₄ @Bi composite photocatalyst: add the modified porous carbon prepared in step 2 to ethylene glycol, mix well, then add bismuth nitrate pentahydrate, and ultrasonically mix, Carry out magnetic stirring subsequently, add ferric nitrate nonahydrate after stirring, continue to stir, and stir, obtain mixture D, put into oven and dry _; Calcination, the final sample is C@Fe ₃ O ₄ @Bi composite photocatalyst.

In step 1, the heating rate when calcining the corn cob is 4-6°C/min, the calcining temperature is 400-500°C, and the calcining time is 20-60min.

In step 1, the concentration of the KOH solution is 1 mol/L, and the mass ratio of the mass of KOH to the substance A obtained in step 1 is 1:2.5˜1:3.5.

In step 1, the heating rate when calcining the product B is 4°C-6°C/min, the calcining temperature is 600-800°C, and the calcining time is 50-120min.

In step 2, the concentration of HNO ₃ is 63wt.%, the reaction temperature in the constant temperature water bath is 80° C. during magnetic stirring, and the reaction time in the constant temperature water bath is 3 hours.

In step 3, the magnetic stirring time is 1 h.

In step 3, when preparing mixture D, the amount ratio of the modified porous carbon, bismuth nitrate pentahydrate, iron nitrate nonahydrate and ethylene glycol used is 0.3g:1.44g-3.36g:0.8g:20mL.

In step 3, the heating rate of the calcination is 4°C-6°C/min, the calcination temperature is 300-600°C, and the calcination time is 1-3h.

In steps 1-3, the drying temperature is 60°C.

The C@Fe ₃ O ₄ @Bi composite photocatalyst prepared by the method is used for photocatalytic degradation of tetracycline.

Beneficial effect:

The separation and recovery of the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared by the present invention is more convenient and efficient; the C@Fe ₃ O ₄ @Bi composite photocatalyst has good photocatalytic activity and stability, and at the same time The material corn cob is used as a carbon source, which realizes the rational utilization of waste and saves resources.

Description of drawings

Figure 1: XRD pattern of the C@Fe ₃ O ₄ @Bi composite photocatalyst in Example 1, where a is the C@Fe ₃ O ₄ prepared when the amount of bismuth nitrate pentahydrate was 1.44g in Example 9 @Bi composite photocatalyst; b is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 9 when the addition of bismuth nitrate pentahydrate is 1.92 g; c is the C@Fe ₃ O prepared in Example 1 ₄ @Bi composite photocatalyst; e is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the addition of bismuth nitrate pentahydrate in Example 9 is 2.88g; The C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the addition of bismuth was 3.36g, where the gray circle represents the XRD peak of Fe ₃ O ₄ ;

Figure 2: The XPS spectrum of the sample, where a is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 1, and bd is the high-resolution XPS spectrum of Bi 4f, Fe 2p and C 1s respectively;

Figure 3: SEM and TEM images of different samples, wherein a is the SEM image of the porous carbon prepared in Example 1; b and its illustration are the TEM images of the porous carbon prepared in Example 1; c and e are prepared in Example 1 The SEM image of the C@Fe ₃ O ₄ @Bi composite photocatalyst; d, f are the TEM images of the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 1;

Fig. 4: is the specific surface area diagram of the porous carbon prepared in Example 1, and the illustration is the pore size distribution diagram of the porous carbon prepared in Example 1;

Figure 5: DRS diagrams of different synthesized samples, where a is the single Bi photocatalyst prepared in Example 10, and b is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 1;

Figure 6: The adsorption diagrams of different synthetic samples, where a is the porous carbon prepared in Example 1; b is the C@Fe ₃ O ₄ @Bi prepared in Example 9 when the amount of bismuth nitrate pentahydrate was 1.44g Composite photocatalyst; c is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the addition of bismuth nitrate pentahydrate in Example 9 is 2.4g; d is the addition of bismuth nitrate pentahydrate in Example 9 is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared at 1.92g; e is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the amount of bismuth nitrate pentahydrate was 2.88g in Example 9; f is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the addition amount of bismuth nitrate pentahydrate is 3.36g in Example 9; g is the simple Bi photocatalyst prepared in Example 10;

Figure 7: The photodegradation of tetracycline under visible light for samples with different calcination temperatures, where a is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 12 when the calcination temperature is 400°C; b is the example The C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in 1; c is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 12 when the calcination temperature was 600°C;

Figure 8: The photodegradation of tetracycline by different samples under visible light, where a is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the amount of bismuth nitrate pentahydrate was 3.36g in Example 9; b is The C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the amount of bismuth nitrate pentahydrate was 1.92g in Example 9; c is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 1; d It is the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the addition of bismuth nitrate pentahydrate is 2.88g in Example 9; e is prepared when the addition of bismuth nitrate pentahydrate is 1.44g in Example 9 C@Fe ₃ O ₄ @Bi composite photocatalyst; f is the Bi photocatalyst prepared in Example 10;

Figure 9: Photocatalytic degradation of tetracycline by the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 1 after adding different capture agents, where TEOA is triethanolamine; BQ is p-benzoquinone; TEA is tert-butanol;

Figure 10: Photocatalytic effect diagram of 5 cycles of photocatalytic degradation of tetracycline solution by the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in Example 1.

Detailed ways

The present invention will be further described below in conjunction with specific embodiment:

Photocatalytic activity evaluation: carried out in D1 photochemical reaction instrument (purchased from Yangzhou University Teaching Instrument Factory), 100mL 20mg/L tetracycline simulated wastewater was added to the reaction bottle, then magnetons and 0.1g photocatalyst were added, and the visible light power supply was turned on Perform dynamic adsorption with the aeration device, and start an external super constant temperature water bath to control the temperature of the reaction system at 30°C. After the adsorption equilibrium was reached, light reaction was carried out, samples were taken every 10 minutes, centrifuged, and the concentration of tetracycline in the supernatant was measured, and the degradation effect of tetracycline was judged by C/C ₀ . Among them, _C0 is the concentration of tetracycline after adsorption equilibrium, and C is the concentration of tetracycline at the reaction time T.

Example 1:

(1) Preparation of porous carbon: firstly, the corncobs were washed three times with deionized water, and then dried after removing the surface impurities. The dried corncobs were placed in a tube furnace and heated at a heating rate of 5 °C/min. Calcined at 450° C. for 30 minutes under N ₂ atmosphere, and took it out after the reaction was completed and cooled down to room temperature. Weigh an appropriate amount of KOH, add deionized water to make KOH into a solution with a concentration of 1mol/L, add the carbonized substance into the KOH solution, make the mass ratio of KOH to the carbonized substance 1:3.5, and stir for 30 minutes , then filtered and dried in an oven. Then the dried material was placed in a tube furnace, and calcined at 750°C for 90 minutes at a heating rate of 5°C/min in an _N2 atmosphere. After the reaction was completed and the temperature was lowered to room temperature, it was taken out and rinsed with deionized water several times. After washing, the resulting sample is porous carbon.

(2) Modification of porous carbon: Measure an appropriate amount of 63wt.% HNO ₃ , then add the above porous carbon, immerse the porous carbon in nitric acid, and heat and stir in a water bath at 80° C., then filter the mixture and Wash until the solution is neutral, put it into a vacuum oven and dry, and the obtained sample is a modified porous carbon.

(3) Preparation of C@Fe ₃ O ₄ @Bi composite photocatalyst: Add 0.3g of modified porous carbon into 20ml of ethylene glycol, stir evenly, then add 2.4g of bismuth nitrate pentahydrate, mix well by ultrasonic, then Perform magnetic stirring, add 0.8 g of ferric nitrate nonahydrate after the stirring is completed, continue to stir, and after the stirring is completed, put the mixture into an oven and dry it in an oven at 80°C. Finally, the dried mixture was placed in a tube furnace and calcined at 500 °C for 2 h at a heating rate of 5 °C/min in an N ₂ atmosphere, and the final sample was the C@Fe ₃ O ₄ @Bi composite photocatalyst .

(4) Take 0.1g of the sample in (2) to conduct a photocatalytic degradation test in a photochemical reaction instrument. The experimental results are analyzed by an ultraviolet spectrophotometer, and the photodegradation of tetracycline by the C@Fe ₃ O ₄ @Bi composite photocatalyst is measured. The effect is obvious, indicating that the C@Fe ₃ O ₄ @Bi composite photocatalyst has strong photocatalytic activity.

Example 2:

Carry out the same steps as the preparation process of Example 1, except that the temperature of the tube furnace in step (1) is set to 400°C and 500°C to prepare different carbonized carbon materials, and then synthesize C@Fe ₃ O ₄ @Bi composite light catalyst.

Example 3:

Carry out the same steps as the preparation process in Example 1, except that the calcination time of the tube furnace in step (1) is set to 20min and 60min to prepare different carbonized carbon materials, and then synthesize C@Fe ₃ O ₄ @Bi composite photocatalyst .

Example 4:

Carry out the same steps as the preparation process of Example 1, except that in step (1), the heating rate of the tube furnace is 4°C/min and 6°C/min, respectively, to prepare different carbonized carbon materials, and then synthesize C@Fe ₃ O ₄ @Bi composite photocatalyst.

Example 5:

Carry out the same steps as in the preparation process of Example 1, except that the mass ratios of KOH and carbonized substances in step (2) are 1:2.5 and 1:3, respectively, and then synthesize C@Fe ₃ O ₄ @Bi composite photocatalyst .

Embodiment 6:

Follow the same steps of the preparation process in Example 1, except that the temperature of the tube furnace in step (3) is set to 600°C and 800°C to prepare different porous carbon samples, and then synthesize C@Fe ₃ O ₄ @Bi composite photocatalyst .

Embodiment 7:

The same steps were carried out in the preparation process of Example 1, except that the time of the tube furnace in step (3) was set to 50 min and 120 min to prepare different porous carbon samples, and then synthesize C@Fe ₃ O ₄ @Bi composite photocatalyst.

Embodiment 8:

Carry out the same steps as the preparation process in Example 1, except that the heating rate of the tube furnace in step (3) is 4°C/min and 6°C/min, respectively, to prepare different porous carbon samples, and then synthesize C@Fe ₃ O ₄ @Bi composite photocatalyst.

Embodiment 9:

Carry out the same steps as the preparation process of Example 1, the difference is that in step (5) the amount of bismuth nitrate pentahydrate added is 1.44 g, 1.92 g, 2.88 g and 3.36 g to prepare different C@Fe ₃ O ₄ @Bi The composite photocatalyst was used to investigate the effect of the addition amount of bismuth nitrate pentahydrate on the photocatalytic activity of C@Fe ₃ O ₄ @Bi composite photocatalyst.

Figure 1 and Figure 2 prove that the samples prepared in this application are indeed C@Fe ₃ O ₄ @Bi composite photocatalysts. It can be seen from Figure 5 that the Bi photocatalyst has a strong absorption near the ultraviolet region and the visible region at a wavelength of about 350nm, indicating that the Bi photocatalyst can respond to both ultraviolet and visible light, and the C@Fe ₃ O ₄ @Bi composite photocatalyst has strong absorption in the visible region. Under visible light irradiation, the effect of different additions of bismuth nitrate pentahydrate on the degradation of C@Fe ₃ O ₄ @Bi composite photocatalyst is shown in Figure 8. When the addition of bismuth nitrate pentahydrate was 2.4g, the prepared The samples have better photocatalytic degradation properties of tetracycline. When the addition amount of bismuth nitrate pentahydrate was 1.44g, 1.92g, 2.88g and 3.36g, the prepared samples showed better activity. When the amount of bismuth nitrate pentahydrate added is less than 2.4g, with the increase of the added amount of bismuth nitrate pentahydrate, the photocatalytic activity of the C@Fe ₃ O ₄ @Bi composite photocatalyst increases gradually, when the addition of bismuth nitrate pentahydrate When the amount is greater than 2.4g, the photocatalytic activity of the C@Fe ₃ O ₄ @Bi composite photocatalyst gradually decreases with the increase of the added amount of bismuth nitrate pentahydrate. Considering the photocatalytic activity of the sample, the pentahydrate selected in this application The C@Fe ₃ O ₄ @Bi composite photocatalyst was prepared when the addition amount of bismuth nitrate was 2.4g.

Example 10:

Carry out the same steps of the preparation process in Example 1, except that the modified porous carbon and ferric nitrate nonahydrate are not added in step (5) to prepare the Bi photocatalyst, and investigate the photocatalytic activity of the single substance Bi photocatalyst, the result is shown in Figure 8 As shown, the photocatalytic activity of the pure Bi photocatalyst is low, while the photocatalytic activity of the composite C@Fe ₃ O ₄ @Bi composite photocatalyst increases, indicating that the composite system is beneficial to the improvement of the catalytic degradation performance of the photocatalyst.

Example 11:

The same steps of the preparation process in Example 1 were carried out, except that the heating rate of the tube furnace in step (5) was 4°C/min and 6°C/min, respectively, to prepare different C@Fe ₃ O ₄ @Bi composite photocatalysts.

Example 12:

Carry out the same steps as the preparation process of Example 1, except that the temperature of the tube furnace in step (5) is set to 300°C, 400°C and 600°C respectively to prepare different C@Fe ₃ O ₄ @Bi composite photocatalysts, the results As shown in Figure 7, the degraded activity of the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the calcination temperature was 500°C was the highest, and the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared when the calcination temperature was 600°C The photocatalytic degradation activity is lower than that of the composite photocatalyst prepared when the calcination temperature is 400°C. Considering the activity of the sample, the rational utilization and economic value of the reactants, this application selects the calcination temperature as 500°C to prepare C@Fe ₃ O ₄ @Bi composite photocatalyst.

Example 13:

According to the step (4) in Example 1, the photochemical stability of the C@Fe ₃ O ₄ @Bi composite photocatalyst was investigated for 5 cycles of photocatalytic degradation of tetracycline antibiotic wastewater. The results are shown in Figure 10, and it can be seen from Figure 10 that 5 After the second cycle, the photocatalytic activity of the C@Fe ₃ O ₄ @Bi composite photocatalyst did not decrease significantly, indicating that the C@Fe ₃ O ₄ @Bi composite photocatalyst prepared in this application has good photochemical stability and can secondary recycling.

Figure 1 shows the XRD patterns of different C@Fe ₃ O ₄ @Bi composite photocatalysts. It can be seen from the figure that the diffraction peaks of the prepared composite photocatalysts are 2θ=22.6°, 27.2°, 38.1°, 39.7° and 48.8 °Corresponding to the (003), (012), (104), (110) and (202) crystal planes of Bi (JCPDS No.44-1246) in the standard card library, the gray circles in the figure represent Fe ₃ O ₄ The diffraction peaks indicate that the C@Fe ₃ O ₄ @Bi composite photocatalyst was successfully synthesized by a one-step calcination method. It can be seen from the figure that the addition amount of bismuth nitrate pentahydrate has no effect on the diffraction peaks of the C@Fe ₃ O ₄ @Bi composite photocatalyst. No miscellaneous peaks were found in the figure, indicating that the C@Fe ₃ O ₄ @Bi composite photocatalyst has a high purity.

Figure 2 is the XPS spectrum of the sample. Figure a is the XPS chart of the C@Fe ₃ O ₄ @Bi composite photocatalyst. From the figure, it can be concluded that the synthesized composite photocatalyst contains elements such as C, O, Fe and Bi. It shows that the composite photocatalyst was successfully synthesized, and the high-magnification XPS images of Bi 4f, Fe 2p and C 1s are shown in Figures b, c and d, respectively. The peaks at 159.1eV and 164.4eV correspond to Bi 4f spin-orbit splitting peaks, that is, Bi 4f7/2 and 5/2, corresponding to Bi-O bonds, which mainly originate from some oxidized by air on the surface of the composite photocatalyst. substances, while two shoulder peaks of 157.1eV and 162.5eV appeared on the low binding energy side of Bi 4f 7/2 and 5/2, which mainly correspond to metal Bi. The Fe 2p peak in Figure c indicates that the composite photocatalyst synthesized Containing Fe ₃ O ₄ , the binding energies of the two peaks of C1s in Figure d are 284.5eV and 288.9eV, corresponding to sp2-C and C=O bonds.

Figure 3 is the SEM and TEM images of different samples. It can be seen from the pictures a and b that the porous carbon based on biomass corncobs has been successfully prepared, combined with the specific surface data of different samples (Figure 4), the porous carbon The pore size is mainly about 2nm.

Figure 4 is the adsorption-desorption curve of porous carbon, and the inset is the pore size distribution. It can be seen from the figure that this isotherm is a combination of type I (typical microporous carbon atoms) and type IV (characteristics of mesoporous materials) , which indicates the existence of a large number of micropores and mesopores, which is consistent with the TEM results. The specific surface area of the porous carbon prepared by this application reaches 893.4m ³ g ^-1 , and the specific surface area decreases to 58.92m ³ g ^-1 after compounding. This further demonstrates that the C@Fe ₃ O ₄ @Bi composite photocatalyst was successfully synthesized.

Figure 6 shows the adsorption diagrams of different synthesized samples. It can be seen from the figure that the adsorption of porous carbon is better, and the adsorption of pure elemental Bi photocatalyst is poor, and the adsorption capacity is small. When the Bi photocatalyst was combined with C@Fe ₃ O ₄ , the adsorption of the composite photocatalyst was improved, and with the increase of the amount of bismuth nitrate pentahydrate, the adsorption capacity of the composite photocatalyst decreased gradually.

Figure 9 is the photocatalytic degradation of tetracycline by C@Fe ₃ O ₄ @Bi composite photocatalyst after adding different capture agents. It can be seen from the figure that compared with no capture agent, after adding different capture agents, The performance of photodegradation of tetracycline decreased, indicating that in this application, hydroxyl radicals, holes and superoxide radicals are all active species in the process of photocatalytic degradation of tetracycline. The activity of the composite photocatalyst can be suppressed to the greatest extent after adding the triethanolamine scavenger, which indicates that holes are the main active species in the photocatalyst degradation process of tetracycline in the composite photocatalyst prepared in this application.

Claims (9)

1. a kind of C@Fe based on biomass porous carbon₃O₄The preparation method of@Bi composite photo-catalyst, which is characterized in that including such as Lower step:

The preparation of step 1, porous carbon: corncob is washed with deionized three times first, dries, will dry after removing surface impurity Corncob after dry is placed in tube furnace, in N₂It is calcined under atmosphere, taking-up is cooled to room temperature to the end of reacting, obtain product A；

KOH is weighed, deionized water is added, obtains KOH solution, product A is added in KOH solution, stirs, is then filtered Obtained material is put into baking oven and dries, and is denoted as product B；

Product B is placed in tube furnace, in N₂It is calcined under atmosphere, taking-up is cooled to room temperature to the end of reacting, uses deionized water Washing, resulting sample is porous carbon；

The preparation of porous carbon after step 2, modification: the porous carbon that step 1 is obtained is immersed in HNO₃In, it is carried out under magnetic agitation Water bath with thermostatic control reaction, solid mixture after completion of the reaction filtered and washed, until cleaning solution is in neutrality, is put into vacuum baking It is dried in case, gained sample is the porous carbon after modification；

Step 3, C@Fe₃O₄The preparation of@Bi composite photo-catalyst: the porous carbon after modification obtained in step 2 is added to second two It in alcohol, mixes, five nitric hydrate bismuths is then added, ultrasound mixes, and then carries out magnetic agitation, and nine hydrations are added after stirring Ferric nitrate continues to stir, and stirring terminates, and obtains mixture D, is put into baking oven and dries；When preparing mixture D, used Modification after porous carbon, five nitric hydrate bismuths, Fe(NO3)39H2O and ethylene glycol amount ratio be 0.3 g:1.44 g ~ 3.36 g:0.8 g:20mL；The mixture D of drying is placed in tube furnace, in N₂It is calcined under atmosphere, last gained sample is C@Fe₃O₄@Bi composite photo-catalyst.

2. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 1, heating rate when calcining corncob is 4 ~ 6 DEG C/min, and calcination temperature is 400 ~ 500 DEG C, Calcination time is 20 ~ 60min.

3. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 1, the concentration of KOH solution is 1 mol/L, the quality of KOH and the matter of the resulting product A of step 1 Amount is than being 1:2.5 ~ 1:3.5.

4. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 1, heating rate when calcined product B is 4 DEG C ~ 6 DEG C/min, and calcination temperature is 600 ~ 800 DEG C, Calcination time is 50 ~ 120 min.

5. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 2, the HNO₃Concentration be 63 wt.%, water bath with thermostatic control reaction temperature is 80 when magnetic agitation DEG C, the water bath with thermostatic control reaction time is 3h.

6. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 3, the magnetic agitation time is 1h.

7. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 3, the heating rate of the calcining is 4 DEG C ~ 6 DEG C/min, and calcination temperature is 300 ~ 600 DEG C, is forged The burning time is 1 ~ 3h.

8. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that in step 1 ~ 3, the drying temperature is 60 DEG C.

9. a kind of C@Fe based on biomass porous carbon according to claim 1₃O₄The preparation side of@Bi composite photo-catalyst Method, which is characterized in that the C@Fe of the method preparation₃O₄@Bi composite photo-catalyst is used for photocatalytic degradation tetracycline.