Method for adsorbing tetracycline in water body by using magnetic charcoal loaded graphite phase carbon nitride

Abstract

The invention relates to a method for adsorbing tetracycline in a water body by using magnetic biochar loaded graphite phase carbon nitride, which comprises the following steps: by taking agricultural waste corn straw as a precursor, loading magnetic iron and graphite phase carbon nitride through hydrothermal reaction, and calcining to prepare a FeBC / g-C3N4 (short for FeBC / g-CN) biochar composite material, so as to efficiently adsorb tetracycline pollutants in the water body; and the adsorption rate to 25 mg / L of tetracycline within 10 minutes reaches 91.4%. The material synthesis method is simple, the stability is good, tetracycline pollutants cannot be dissociated and released under long-time adsorption, the problems that a traditional biochar technology is low in adsorption efficiency, pollutants are prone to dissociation and the like are solved, and the material has good application prospects in the field of antibiotic pollutant treatment.

Description

Technical Field

[0001] The invention relates to the technical field of functional composite materials, and in particular to a method for preparing a magnetic biochar-loaded graphite-phase carbon nitride adsorption material and a tetracycline adsorption application thereof. Background Art

[0002] Methods for removing antibiotics from water include advanced oxidation, adsorption, membrane technology and coagulation / flocculation. Adsorption is a very effective technology for removing and treating pollutants. Due to its advantages such as simple operation, low cost and high efficiency, it has received great attention. In recent years, the use of biomass to prepare cheap biochar has become an important treatment method for antibiotic adsorption in water. However, due to the characteristics of the raw materials themselves and some by-products produced during the pyrolysis process during the preparation of biochar, the number and types of pore structure and surface functional groups of biochar are relatively small. In addition, since the surface of biochar is mainly composed of negatively charged functional groups, the adsorption effect on anions is poor. There are also problems such as saturated adsorption and easy dissociation of pollutants in the treatment of antibiotic pollution such as tetracycline. In order to solve the problems existing in biochar obtained by traditional pyrolysis and further enhance its functions, it is an urgent problem to develop a biochar adsorption material that can efficiently adsorb antibiotics and has a simple preparation method. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for adsorbing tetracycline in water by using magnetic biochar loaded with graphite phase carbon nitride in view of the above shortcomings.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A method for adsorbing tetracycline in water by using magnetic biochar loaded with graphite phase carbon nitride, comprising the following steps:

[0006] Step 1, washing corn stalks with deionized water, drying, crushing and sieving to obtain stalk powder;

[0007] Step 2, preparation of graphite phase carbon nitride: place urea in a quartz crucible with a lid and heat to 550°C, keep the constant temperature for 2 hours, cool and collect to obtain g-C3N4;

[0008] Step 3, mixing corn stalk powder, FeSO4·7H2O and g-C3N4 in a mass ratio of (1.2-1.5): 1:1, and drying to obtain a solid powder;

[0009] Step 4, calcining the solid powder obtained in the previous step at 700° C. to obtain a biochar adsorption material;

[0010] Step 5: Disperse the biochar adsorption material obtained in the previous step into the aqueous solution containing tetracycline to be treated, and the amount of biochar adsorption material added is 0.5 g / L.

[0011] Furthermore, the step 2 specifically includes the following steps:

[0012] FeSO4·7H2O and corn straw powder are added to deionized water and mixed and stirred evenly. After magnetic stirring at room temperature for more than 12 hours, the prepared g-C3N4 is added and stirred evenly. After continuing magnetic stirring at room temperature for more than 12 hours, the solid powder is obtained after drying and sieving, and the mass ratio of the corn straw, FeSO4·7H2O and g-C3N4 is 1.5:1:1.

[0013] Furthermore, the step 4 is specifically as follows: placing the solid powder obtained in the previous step in a covered quartz crucible and calcining it at 700° C. in a muffle furnace for 4 hours, cooling it to room temperature after the reaction is completed, washing the obtained product three times by centrifugation with deionized water and ethanol, and obtaining the biochar adsorption material after drying.

[0014] The beneficial effects of the present invention are:

[0015] The magnetic biochar loaded graphite phase carbon nitride (FeBC / g-CN) adsorption material obtained by the present invention can efficiently adsorb tetracycline in wastewater with high adsorption efficiency. The adsorption rate of FeBC / g-CN for 25 mg / L tetracycline reaches 91.4% within 10 minutes, and long-term adsorption for 24 hours will not dissociate and release antibiotic pollutants. The operation is simple and the adsorbent has good stability. The addition of magnetic iron and graphite phase carbon nitride increases the pore volume and dispersion of the biochar material, exposes more adsorption sites, and achieves efficient adsorption of tetracycline in the water environment. At the same time, the material preparation method is simple and easy to prepare, the raw materials are cheap and easy to obtain, and the practical application range is wide. And it has been proved by experiments ( Figure 1 Figure A), the adsorption rate of the prepared FeBC / g-CN composite material was significantly improved compared with the biochar BC monomer and magnetic biochar FeBC at 10 min of reaction, increasing from 49% and 20.9% to 91.4%, and the adsorption performance increased by nearly 4 times and 1.8 times, respectively. Figure 1 As shown in Figure B, the adsorption rate of the FeBC / g-CN composite material for other antibiotics (SEM, CAP, ENR, NFX) reached 80% after 10 minutes of reaction, and it also has good adsorption performance for other types of antibiotics.

[0016] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1Figure A is a test diagram of the adsorption performance of tetracycline by BC, FeBC and FeBC / g-CN, and Figure B is a test diagram of the universal adsorption performance of antibiotics by FeBC / g-CN;

[0018] Figure 2 The AC images in the middle are the SEM scanning electron micrographs of BC, FeBC and FeBC / g-CN at 1.3K times, and the EF images are the SEM scanning electron micrographs of BC, FeBC and FeBC / g-CN at 4.5K times;

[0019] Figure 3 Figure A is the pore size distribution diagram of the adsorption-desorption curves of BC, FeBC and FeBC / g-CN, and Figure B is the Fourier infrared spectrum diagram;

[0020] Figure 4 The tetracycline adsorption performance test diagram of FeBC / g-CN material prepared with different mass ratios of FeSO4·7H2O and g-C3N4. DETAILED DESCRIPTION

[0021] The following examples are provided for a better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are purchased from conventional biochemical reagent stores unless otherwise specified.

[0022] The method of magnetic biochar loaded graphite phase carbon nitride (FeBC / g-CN) adsorption material includes the following steps:

[0023] Step 1, washing the corn stalks with deionized water, drying, crushing and sieving to obtain corn stalk powder;

[0024] Step 2, preparation of graphite phase carbon nitride: place urea in a quartz crucible with a lid and heat to 550°C, keep the constant temperature for 2 hours, cool and collect to obtain g-C3N4;

[0025] Step 3: 0.76 g FeSO4·7H2O and 10 g corn straw powder were added to 50 mL deionized water and dissolved uniformly, and then magnetically stirred at constant temperature for 12 h. Then, g-C3N4 solution (0.76 g g-C3N4 was added to 20 ml deionized water, and ultrasonic dispersion and stirring were performed for 5 min) was added and magnetically stirred at constant temperature for 12 h, and then placed in a vacuum dryer at 80 ° C for 12 h to collect the light brown biomass powder.

[0026] Step 4: The collected light brown biomass powder is placed in a covered quartz crucible and calcined at 700°C in a muffle furnace for 4 hours. After the reaction is completed, it is cooled to room temperature. The obtained product is washed three times by centrifugation with deionized water and ethanol, and finally vacuum dried at 60°C overnight to obtain the final product FeBC / g-CN. The mass ratio of FeBC / g-CN, FeSO4 and g-C3N4 is 1:1.

[0027] Tetracycline adsorption method: Weigh 0.5g / L FeBC / g-CN adsorption material and disperse it into a reactor containing 100mL tetracycline solution (25mg / L TCH) and stir it with magnetic stirring. The reaction temperature is 25℃. Take out the reaction solution at regular intervals, centrifuge it and filter it with a 0.22μm filter membrane, and finally measure its absorbance with a UV spectrophotometer.

[0028] We conducted universal tests on the adsorption performance of BC, FeBC, and FeBC / g-CN materials for tetracycline and other antibiotics, using 25 mg / L antibiotics (TCH, SEM, CAP, ENR, and NFX) as target pollutants. Figure 1 Figures A and B in the middle are the adsorption performance curves of the target pollutant TCH adsorbed by BC, FeBC and FeBC / g-CN material samples for 2 hours and the universal adsorption performance curves of other antibiotics (SEM, CAP, ENR, NFX) adsorbed by FeBC / g-CN materials. Compared with BC and FeBC monomers, the adsorption rate of FeBC / g-CN composite materials was significantly improved at 10 minutes, and the adsorption performance increased by nearly 4 times and 1.8 times, respectively, from 20.9% and 49% to 91.4%, respectively, and the adsorption performance was significantly improved. Figure 1 As shown in Figure B, the FeBC / g-CN composite material also has a good adsorption effect on other antibiotic pollutants. The adsorption rate can reach 80% after 10 minutes of reaction, and it also has good adsorption capacity for other antibiotic pollutants.

[0029] Figure 2 A and E, B and F, C and G are SEM scanning electron microscope images of original corn straw (BC), ferromagnetic corn straw (FeBC) and magnetic graphite phase carbon nitride biochar material (FeBC / g-CN) prepared by the present invention at 1.3K and 4.5K times respectively. It can be seen from the figure that the surface of the original corn straw biochar (BC) is relatively smooth, and the surface of the ferromagnetic modified corn straw biochar (FeBC) presents spherical protrusions, which are attached magnetic iron and easy to agglomerate; after the introduction of graphite phase carbon nitride into the prepared magnetic graphite phase carbon nitride biochar material (FeBC / g-CN), the magnetic iron agglomeration protrusions are destroyed, presenting a lamellar flocculent structure, increasing more adsorption sites, thereby improving the adsorption performance.

[0030] Figure 3The BET adsorption-desorption curve pore size distribution diagram (A) of the original corn straw (BC), ferromagnetic corn straw (FeBC) and the magnetic graphite phase carbon nitride biochar material (FeBC / g-CN) prepared by the present invention. As shown in the figure, all three materials show a type IV curve with an H3 hysteresis loop, and the main pores are mainly micro-mesopores. The modification increases the pore volume of the biochar material and the volume of mesopores and large pores. The Fourier transform infrared spectrum diagram in Figure B shows that the loading of magnetic iron and graphite phase carbon nitride in biochar enhances the characteristic peaks of functional groups and at 611.7-555.9cm -1 A new characteristic peak of iron-oxygen bond appears at 810 cm -1 The corresponding peak is the out-of-plane bending vibration characteristic peak of the g-C3N4 triazine ring, which enriches the functional group structure of the biochar surface and significantly improves the adsorption performance of tetracycline in water.

[0031] like Figure 4 As shown in the figure, the adsorption and removal effects of tetracycline at different FeSO4·7H2O and g-C3N4 mass ratios were 49%, 12%, 35%, 44% and 91% at 10 min, respectively. The magnetic graphite phase carbon nitride biochar material (FeBC / g-CN) prepared at a mass ratio of 1:1 had the best adsorption effect on tetracycline in the solution, with a short reaction time and high efficiency. The adsorption effect of tetracycline at a doping ratio of 1:1 was significantly better than that of other doping ratios. The reason is that the magnetic iron attached to the surface of biochar to form spherical protrusions, and the g-C3N4 doping dispersed the spherical protrusions and presented a lamellar flocculent structure. Excessive incorporation of magnetic iron or g-C3N4 will agglomerate on the surface of biochar, occupy the contact sites on the surface of biochar, and thus affect the adsorption capacity of the biochar surface for tetracycline.

[0032] The above is an example of the best implementation of the present invention, and the parts not described in detail are common knowledge of ordinary technicians in the field. The protection scope of the present invention shall be based on the content of the claims, and any equivalent transformation based on the technical enlightenment of the present invention is also within the protection scope of the present invention.

Claims

1. A method for adsorbing tetracycline in water using magnetic biochar loaded with graphite phase carbon nitride, characterized in that: The following steps are involved: Step 1, washing corn stalks with deionized water, drying, crushing and sieving to obtain stalk powder; Step 2, preparation of graphite phase carbon nitride: place urea in a quartz crucible with a lid and heat to 550°C, keep the constant temperature for 2 hours, cool and collect to obtain g-C3N4; Step 3, mixing corn stalk powder, FeSO4·7H2O and g-C3N4 in a mass ratio of (1.2-1.5): 1:1, and drying to obtain a solid powder; Step 4, calcining the solid powder obtained in the previous step at 700° C. to obtain a biochar adsorption material; Step 5: Disperse the biochar adsorption material obtained in the previous step into the aqueous solution containing tetracycline to be treated, and the amount of biochar adsorption material added is 0.5 g / L.

2. The method for adsorbing tetracycline in water by using magnetic biochar loaded with graphite phase carbon nitride according to claim 1, characterized in that: The step 2 specifically includes the following steps: FeSO4·7H2O and corn straw powder are added to deionized water and mixed and stirred evenly. After magnetic stirring at room temperature for more than 12 hours, the prepared g-C3N4 is added and stirred evenly. After continuing magnetic stirring at room temperature for more than 12 hours, the solid powder is obtained after drying and sieving, and the mass ratio of the corn straw, FeSO4·7H2O and g-C3N4 is 1.5:1:

1.

3. The method for adsorbing tetracycline in water by using magnetic biochar loaded with graphite phase carbon nitride according to claim 2, characterized in that: Specifically, step 4 includes placing the solid powder obtained in the previous step in a covered quartz crucible and calcining it at 700° C. in a muffle furnace for 4 hours. After the reaction is completed, the mixture is cooled to room temperature. The obtained product is centrifugally washed three times with deionized water and ethanol, and dried to obtain a biochar adsorption material.

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