Preparation method and application of ferroboron co-modified magnetic biochar

Abstract

The invention discloses a preparation method and application of ferroboron co-modified magnetic biochar, and relates to the technical field of water body pollution remediation functional materials. The invention aims to solve the problem that the existing adsorption material has a poor adsorption effect on PNP pollutants. The method comprises the following steps: dissolving boric acid into deionized water to obtain a solution a; adding biomass into the solution a, and fully stirring to obtain a solution b; drying the solution b to obtain a mixture c; mixing potassium ferrate with the mixture c obtained in the step S3, grinding and sieving to obtain a mixture d; the mixture d is heated to 690-700 DEG C and calcined for 1.8-2 h; after calcining is finished, cooling, grinding, washing to be neutral, and finally drying and sieving to obtain the ferroboron co-modified magnetic biochar. The preparation method and application of the ferroboron co-modified magnetic biochar can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water pollution remediation functional materials, in particular to a preparation method and application of boron-iron co-modified magnetic biochar. BACKGROUND

[0002] With the growth of population and economic development, nitrophenols produced in the fields of printing and dyeing, petroleum chemical industry, medicine, etc. gradually enter the environment and form new pollution. p-nitrophenol (PNP) is a widely used chemical and medical intermediate. Therefore, it exists in many industrial products such as pesticides, fertilizers and paints, and is inevitably discharged into the natural environment with wastewater, solid pollutants, etc. during many industrial and agricultural production processes, and has an impact on the environment and human health. Because of its certain biological toxicity, p-nitrophenol has been listed as a "priority control pollutant".

[0003] In recent years, significant progress has been made in the research of environmental remediation technology for organic pollutants. Microbial degradation, soil leaching, chemical oxidation and adsorption removal have been developed. Compared with other technologies, adsorption method has become one of the most potential remediation technologies due to its simple operation, high treatment efficiency, wide application scene and controllable cost. As a typical carbon-based adsorption material, biochar (BC) has excellent performance in the field of organic pollutant adsorption due to its highly developed pore structure, significant surface area and highly aromatic carbon-rich microporous characteristics. However, the adsorption capacity of traditional biochar for PNP and other organic pollutants is usually difficult to meet the actual remediation needs, and it is urgent to improve its adsorption capacity through material modification. SUMMARY

[0004] The purpose of the present application is to solve the problem of poor adsorption effect of existing adsorption materials on PNP pollutants, and to provide a preparation method and application of boron-iron co-modified magnetic biochar.

[0005] The preparation method of boron-iron co-modified magnetic biochar is carried out according to the following steps:

[0006] Step S1:

[0007] Dissolve boric acid in deionized water to obtain solution a;

[0008] Step S2:

[0009] Add biomass to solution a obtained in step S1, and after sufficient stirring, obtain solution b;

[0010] Step S3:

[0011] Dry solution b obtained in step S2 to obtain mixture c;

[0012] Step S4:

[0013] Mixing the potassium ferrate with the mixture c obtained in step S3, grinding and sieving to obtain mixture d;

[0014] Step S5:

[0015] Heating the mixture d obtained in step S4 to 690~700℃, and calcining at 690~700℃ for 1.8~2 h; after calcination, cooling, grinding, washing to neutral, and finally drying and sieving, the boron-iron co-modified magnetic biochar is obtained;

[0016] The mass ratio of the boric acid, biomass and potassium ferrate is 9:6:2.4.

[0017] The application of the boron-iron co-modified magnetic biochar, and the application of the boron-iron co-modified magnetic biochar in adsorbing p-nitrophenol.

[0018] The beneficial effects of the present application are:

[0019] The present application synthesizes a boron-iron co-modified magnetic biochar material (Fe@BBC) to repair PNP pollution, and has the advantages of low raw material cost, good repair effect, green environmental protection, etc. Its main action mechanism includes: (1) Fe@BBC adsorbs PNP through π-π electron donor-acceptor (EDA) interaction and hydrophobic adsorption; (2) The boron and hydroxyl, carboxyl and other functional groups on the surface of Fe@BBC provide more binding sites for PNP, and through strong host-guest interaction, non-covalent bonds are formed to selectively bind and fix PNP; (3) The biochar in Fe@BBC and the zero-valent iron contained therein can provide a large number of electrons to promote the reduction reaction of PNP; the boron doped in the material can produce defects to cause local strain to promote the direct transfer process of electrons, further promoting the reduction of PNP; the magnetism imparted by the iron oxide produced by iron doping enables the material to be recycled and reused, reducing the use cost. Therefore, the Fe@BBC material prepared by the present application can realize efficient removal of PNP, and promotes the development and application of organic pollutant repair agents.

[0020] The boron doping in the application can produce local strain defects to improve the surface chemical properties of the biochar, so as to increase the binding sites of the biochar to organic matters. Therefore, the boron doping is beneficial to improve the adsorption of the material to PNP. In addition, the decomposition of potassium ferrate at 700 DEG C can produce zero-valent iron (ZVI) and a series of magnetic iron oxides such as magnetite (Fe3O4) and maghemite (Fe2O3). The addition of potassium ferrate in the process of calcining the biochar can make the generated biochar have both reducing property and magnetism. On the one hand, the local strain of the material surface produced by introducing boron atoms can improve the electron transfer efficiency of the iron-carbon interface and enhance the reduction degradation capacity. Meanwhile, the adsorbent with magnetism can be recycled through an external magnetic field, which can not only efficiently remove the organic pollutants in the environment, but also greatly improve the reusability of the adsorbent.

[0021] The application discloses a preparation method and application of boron-iron co-modified magnetic biochar. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A scanning electron microscope image showing the surface morphology of the boron-iron co-modified magnetic biochar in Example 1;

[0023] Figure 2 A surface carbon element distribution graph of the boron-iron co-modified magnetic biochar in Example 1;

[0024] Figure 3 A surface oxygen element distribution graph of the boron-iron co-modified magnetic biochar in Example 1;

[0025] Figure 4 A surface boron element distribution graph of the boron-iron co-modified magnetic biochar in Example 1;

[0026] Figure 5 A surface iron element distribution graph of the boron-iron co-modified magnetic biochar in Example 1;

[0027] Figure 6 A Fourier transform infrared spectrum of the boron-iron co-modified magnetic biochar in Example 1;

[0028] Figure 7 An X-ray photoelectron spectrum of the boron-iron co-modified magnetic biochar in Example 1;

[0029] Figure 8 A Zeta potential graph of the boron-iron co-modified magnetic biochar in Example 1;

[0030] Figure 9 A pH influence experiment graph of the boron-iron co-modified magnetic biochar in Example 1 to adsorb PNP, wherein represents 50 mg / L, represents 100 mg / L, and represents 150 mg / L;

[0031] Figure 10 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0032] Figure 11 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0033] Figure 12 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0034] Figure 13 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0035] Figure 14 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0036] Figure 15 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0037] Figure 16 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0038] Figure 17 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP;

[0039] Figure 18 Figure 1 represents the kinetic experiment of PNP adsorption on boron-iron co-modified magnetic biochar in Example 1, 1 represents the kinetic Avrami model fitting PNP, 2 represents the kinetic second-order model fitting PNP, 3 represents the kinetic first-order model fitting PNP. DETAILED DESCRIPTION

[0040] Detailed implementation one: the preparation method of boron-iron co-modified magnetic biochar in this embodiment is carried out according to the following steps:

[0041] Step S1:

[0042] Dissolve boric acid into deionized water to obtain solution a;

[0043] Step S2:

[0044] Add biomass into solution a obtained in step S1, and after sufficient stirring, obtain solution b;

[0045] Step S3:

[0046] Dry solution b obtained in step S2 to obtain mixture c;

[0047] Step S4:

[0048] Mix potassium ferrate with mixture c obtained in step S3, grind and sieve to obtain mixture d;

[0049] Step S5:

[0050] Heat mixture d obtained in step S4 to 690-700℃, and calcine at a temperature of 690-700℃ for 1.8-2 h; after calcination, cool, grind, wash to neutral, and finally dry and sieve to obtain boron-iron co-modified magnetic biochar;

[0051] The mass ratio of boric acid, biomass and potassium ferrate is 9:6:2.4.

[0052] Specific implementation method two: the difference between this implementation method and specific implementation method one is that the mass of boric acid to the volume of deionized water in step S1 is (8.5-9) g:(100-120) mL.

[0053] The other steps are the same as specific implementation method one.

[0054] Specific implementation method three: the difference between this implementation method and specific implementation method one or two is that the biomass in step S2 is walnut shell powder.

[0055] The other steps are the same as specific implementation method one or two.

[0056] Specific implementation method four: the difference between this implementation method and one of specific implementation methods one to three is that a magnetic stirrer is used for stirring in step S2, and the stirring time is 10-12 h.

[0057] The other steps are the same as specific implementation methods one to three.

[0058] Specific implementation method five: the difference between this implementation method and one of specific implementation methods one to four is that solution b is poured into an evaporating dish and then placed in an oven at 60-80℃ for drying in step S3.

[0059] Other steps are the same as Embodiment 1-4.

[0060] Embodiment 6: The difference between this embodiment and one of Embodiments 1-5 is that in step S4, the mixture is sieved through a 100 mesh sieve.

[0061] Other steps are the same as Embodiments 1-5.

[0062] Embodiment 7: The difference between this embodiment and one of Embodiments 1-6 is that in step S5, the mixture d is placed in a tube furnace for calcination.

[0063] Other steps are the same as Embodiments 1-6.

[0064] Embodiment 8: The difference between this embodiment and one of Embodiments 1-7 is that in step S5, drying is performed in an oven at 60-80°C.

[0065] Other steps are the same as Embodiments 1-7.

[0066] Embodiment 9: The difference between this embodiment and one of Embodiments 1-8 is that in step S5, the mixture is sieved through a 100 mesh sieve after grinding.

[0067] Other steps are the same as Embodiments 1-8.

[0068] Embodiment 10: Application of the boron-iron co-modified magnetic biochar, the application of the boron-iron co-modified magnetic biochar in adsorbing p-nitrophenol.

[0069] The beneficial effects of the present application are verified by the following examples:

[0070] Example 1: Preparation method of boron-iron co-modified magnetic biochar, which is carried out according to the following steps:

[0071] Step S1:

[0072] Dissolve 9 g of boric acid into 100 mL of deionized water to obtain solution a;

[0073] Step S2:

[0074] Add 6 g of walnut shell powder to solution a, and stir using a magnetic stirrer for 12 h to obtain solution b;

[0075] Step S3:

[0076] Pour solution b into several evaporating dishes, and then place them in an oven at 80°C for complete drying to obtain mixture c;

[0077] Step S4:

[0078] 2.4 g of potassium ferrate was mixed with mixture c, and after grinding, a 100-mesh sieve was obtained, mixture d;

[0079] Step S5:

[0080] Mixture d was placed in a tube furnace and heated to 700°C, and calcined at a temperature of 700°C for 2 h to produce boron-containing biochar and decompose potassium ferrate to generate ZVI and magnetic iron oxides; after natural cooling, the sample was ground, then washed with deionized water until the washing liquid was neutral, the sample was collected and completely dried in an oven at 80°C, and then sieved through a 100-mesh sieve to obtain boron-iron co-modified magnetic biochar Fe@BBC.

[0081] The boron-iron co-modified magnetic biochar material prepared in this example was subjected to pH influence, kinetics, isotherm and cyclic regeneration experiments, and the specific conclusions are as follows:

[0082] 1. Characterization of boron-iron co-modified magnetic biochar (scanning electron microscope and element mapping, Fourier transform infrared spectroscopy, X-ray crystal diffraction, isoelectric point determination):

[0083] The boron-iron co-modified magnetic biochar was observed and the surface elements were determined by field emission scanning electron microscope (model: SU8020).

[0084] Figure 1 The scanning electron microscope image showing the surface morphology of the boron-iron co-modified magnetic biochar in Example 1, Figure 2 The surface carbon element distribution map of the boron-iron co-modified magnetic biochar in Example 1, Figure 3 The surface oxygen element distribution map of the boron-iron co-modified magnetic biochar in Example 1, Figure 4 The surface boron element distribution map of the boron-iron co-modified magnetic biochar in Example 1, Figure 5 The surface iron element distribution map of the boron-iron co-modified magnetic biochar in Example 1.

[0085] As shown in Figure 1 , a large number of blocky and clumpy structures can be clearly observed on the surface of the boron-iron co-modified magnetic biochar, which represents the presence of B and ZVI. At the same time, from Figures 2-5 the element mapping map, it can be further observed that the boron-iron co-modified magnetic biochar contains B and Fe components.

[0086] The surface functional groups of the boron-iron co-modified magnetic biochar were determined by Fourier transform infrared spectroscopy (model: Nicolet 6700).

[0087] Figure 6 The Fourier transform infrared spectrum of the boron-iron co-modified magnetic biochar in Example 1 is shown in Figure 6As shown, 576 cm -1 The peak at 1157 cm⁻¹ corresponds to Fe-O, indicating that ZVI was successfully loaded onto the biochar. The peak at 1157 cm⁻¹ corresponds to Fe-O, indicating that ZVI was successfully loaded onto the biochar. -1 The peak at 3420 cm⁻¹ represents the tensile vibrations of BO and BC; -1 The peak at the position is -OH, which proves the successful synthesis of the material.

[0088] The crystal structure of boron-iron co-modified magnetic biochar was analyzed using an X-ray diffractometer (model: Mini Flex 600).

[0089] Figure 7 The X-ray photoelectron spectrum of the boron-iron co-modified magnetic biochar in Example 1 is shown; Figure 7 As shown, 24.4 o and 27.3 o The peak is related to the amorphous graphitic carbon structure. At 44.7... o and 64.7 o Characteristic peaks related to ZVI were detected at [location], corresponding to the (110) and (200) crystal planes, respectively, indicating that ZVI was actually formed during calcination. 25.1 o 32.3 o and 34.4 o The peaks at the location are related to B2O3, and the detection of these peaks further proves the successful synthesis of the material.

[0090] The isoelectric point (pH) of the boron-iron co-modified magnetic biochar was determined using a Zeta potential analyzer (model: Zetasizer Nano ZS). pzc ).

[0091] Figure 8 This represents the Zeta potential diagram of the boron-iron co-modified magnetic biochar in Example 1; (The diagram is from...) Figure 8 It can be seen that the isoelectric point (pH) of Fe@BBC pzc The measured value was 2.3, indicating that the material exhibits pH-dependent charge reversal characteristics. The surface is positively charged when the solution pH is < 2.3, and becomes negatively charged when the pH is > 2.3. This electrical characteristic directly affects its electrostatic interaction with PNP molecules, exhibiting repulsive or attractive forces at different pH levels, thus influencing its adsorption performance.

[0092] 2. pH:

[0093] The experimental procedure was as follows: the initial pH of the solution was adjusted with 1 M HCl or NaOH, and the pH range of PNP was set to 2.0-10.0. The concentration of PNP adsorbed by Fe@BBC was set to 50-150 mg / L at 25℃.

[0094] Figure 9Figure 1 shows the graph of the pH effect experiment of the boron-iron co-modified magnetic biochar adsorbing PNP in Example 1, ■ represents 50 mg / L, · represents 100 mg / L, and ▲ represents 150 mg / L. As shown in Figure 9 the adsorption capacity of the adsorbent for PNP is low when the solution pH is 2.0, and the adsorption capacity of the adsorbent for PNP is significantly improved when the pH increases to 6.0. When the solution pH continues to increase to 8.0, the adsorption effect of Fe@BBC on PNP is almost not affected by the solution pH. The reason for this phenomenon is that at low pH, PNP mainly exists in the form of molecules, which is not conducive to adsorption; at high pH, PNP exists in the form of ions, which is easily attracted by the solution and the surface charge of the material, which is conducive to adsorption; with the further increase of pH, PNP is dissociated into anions, and Fe@BBC is negatively charged under high pH conditions, which hinders the adsorption process to a certain extent.

[0095] 3. Kinetics:

[0096] The adsorption process is: in 1-160 min, the PNP pollution liquid with a concentration of 100 mg / L at 25°C, the dosage of Fe@BBC is 0.5 g / L.

[0097] Figure 10 Figure 2 shows the graph of the kinetics experiment of the boron-iron co-modified magnetic biochar adsorbing PNP in Example 1, 1 represents the Avrami model fitting PNP, 2 represents the second-order model fitting PNP, and 3 represents the first-order model fitting PNP. As shown in Figure 10 the adsorption amount of Fe@BBC for PNP increases rapidly with time in the first 20 min of the adsorption process, and reaches adsorption equilibrium around 30 min. In addition, Fe@BBC quickly adsorbs PNP in the first 10 min, and basically reaches adsorption equilibrium around 20 min. The reason for this phenomenon may be that in the early stage of adsorption, there are enough adsorption sites exposed to the pollution liquid, resulting in rapid improvement of adsorption efficiency, and with the increase of the contact time of pollutants and adsorbent, the adsorption sites on the surface of the material are gradually occupied, resulting in a decrease in adsorption efficiency, and finally reaching adsorption equilibrium. The optimal fitting of the Avrami model (R²=0.99, SD=4.37) shows that the adsorption is dominated by chemical action, the kinetic mode is regulated by active site distribution, and there is a multiple adsorption effect.

[0098] 4. Isotherm:

[0099] The isotherm conditions PNP solution concentration range: 10-300 mg / L, Fe@BBC dosage is 0.5 g / L; 0.05 g of material is added to 100 mL of different concentrations of pollutant solution, and the adsorption is carried out in a shaker at pH 6, temperatures of 25, 35 and 45 ℃ respectively, for 120 min.

[0100] Figure 11 The isotherm experiment graph of the boron-iron co-modified magnetic biochar adsorbing PNP in Example 1 is shown, where ■ represents 25℃, · represents 35℃, and ▲ represents 45℃, 1 represents Sips model fitting at 25℃, 2 represents Langmuir model fitting at 25℃, 3 represents Freundlich model fitting at 25℃, 4 represents Sips model fitting at 45℃, 5 represents Langmuir model fitting at 45℃, 6 represents Freundlich model fitting at 45℃, 7 represents Sips model fitting at 30℃, 8 represents Langmuir model fitting at 30℃, and 9 represents Freundlich model fitting at 30℃.

[0101] Figure 11 As shown, under the driving of the concentration gradient, the adsorption of the material to PNP gradually increases with the increase of the initial concentration, and the increasing PNP content also causes fierce competition of the pollutant for the limited active sites, resulting in slow increase of PNP absorption until adsorption equilibrium is reached. In addition, the adsorption amount of Fe@BBC to PNP gradually increases at 25-45 ℃, indicating that the passivation process of Fe@BBC to PNP has endothermic characteristics, and the maximum adsorption amount reaches 322.22 mg / g.

[0102] The results show that the Sips model has a higher R 2 and a lower SD (R²=1.00, SD=3.19), which can accurately describe the adsorption process of PNP on Fe@BBC, indicating that the non-homogeneous adsorption is the main adsorption form of Fe@BBC for removing PNP.

[0103] 5. Circulation regeneration experiment:

[0104] Experimental conditions: Fe@BBC is placed in a 100 mg / L PNP contaminated solution and shaken for 120 min. Then the material is taken out, ethanol is used as eluent to remove the adsorbed PNP of the material, the soaking time is 120 min, then the adsorbent is taken out and washed several times with deionized water until the washing liquid is neutral. The adsorbent is placed in a 60℃ oven for drying, taken out, ground and sieved, and the above adsorption and elution process is repeated, a total of 4 cycles, to investigate the repeated regeneration performance of Fe@BBC.

[0105] Figure 12This diagram shows the adsorption cycle experiment of PNP on boron-iron co-modified magnetic biochar in Example 1; as shown. Figure 12 As shown, after four consecutive adsorption-desorption processes, the desorption efficiency of Fe@BBC for PNP still reached 61.98% of the initial amount. Furthermore, after four cycles, the adsorption capacity of Fe@BBC for PNP still reached 97.41 mg / g. In conclusion, Fe@BBC is relatively stable during adsorption-desorption processes and exhibits reliable reusability.

[0106] 6. XPS Analysis:

[0107] Figure 13 This shows the total XPS spectra of PNP before and after adsorption by the boron-iron co-modified magnetic biochar in Example 1. Figure 14 The image shows the XPS N1s spectra of PNP adsorption after adsorption by the boron-iron co-modified magnetic biochar in Example 1. Figure 13 As shown, peaks for C 1s, B 1s, O 1s, and Fe 2p were detected on Fe@BBC, indicating that boronic acid successfully modified BC and loaded ZVI. Furthermore, as... Figure 14 As shown, the appearance of the new N 1s peak indicates that Fe@BBC adsorbs PNP. Specifically, the N 1s peaks at 399.61 eV and 405.65 eV are related to tertiary nitrogen, which refers to the N-C3 / C-NH- functional group, proving that carbon-containing functional groups are involved in the removal of PNP.

[0108] Figure 15 This shows the XPS C1s spectra of PNP before and after adsorption by the boron-iron co-modified magnetic biochar in Example 1. Figure 16 The image shows the XPS O1s spectra before and after the adsorption of PNP by the boron-iron co-modified magnetic biochar in Example 1. Figure 15 As shown, after PNP removal, the peak values ​​corresponding to the CC / C=C, CO, and C=O groups on Fe@BBC were located at 284.67 eV, 286.24 eV, and 288.81 eV, respectively, and significantly shifted to 284.61, 285.84, and 287.16 eV. This shift indicates that C and O-containing groups play a crucial role in the PNP removal process. Furthermore, as... Figure 16 As shown, after binding with PNP, the area of ​​the FeO peak at 530.27 eV in the O 1s spectrum increased from 2.16% to 19.84%, which may be due to the formation of a surface complex.

[0109] Figure 17 This shows the XPS B1s spectra of PNP before and after adsorption by the boron-iron co-modified magnetic biochar in Example 1. Figure 18The image shows the XPS Fe 2p spectra before and after the adsorption of PNP by the boron-iron co-modified magnetic biochar in Example 1. Figure 17 As shown, two peaks representing B(II) and B(III) can be found at 189.35 and 192.94 eV, respectively, in the B 1s spectrum. These two peaks mainly originate from boric acid modification, and this precise detection further improves the success rate of modification. The shift in peak position after PNP adsorption indicates that the boron-containing groups are related to the process of PNP removal by Fe@BBC. Furthermore, as... Figure 18 As shown, Fe(II) and Fe were detected at 711.23, 719.00, 725.76, and 723.49 eV, respectively. 0 The presence of FeOOH and Fe(III) peaks, to some extent, demonstrates the involvement of Fe in the PNP adsorption process.

[0110] Mechanism conclusion of this embodiment:

[0111] (1) The graphene-like aromatic structure of Fe@BBC has a π-π bond covalent electron adsorption effect on PNP;

[0112] (2) Fe@BBC has a negative potential at higher pH and has an electrostatic attraction to ionized PNP;

[0113] (3) The zero-valent iron contained in Fe@BBC has a certain reducing effect on PNP;

[0114] (4) The functional groups introduced on the surface participate in the adsorption process of PNP.

Claims

1. A method for preparing boron-iron co-modified magnetic biochar, characterized in that: The preparation method is carried out according to the following steps: Step S1: Boric acid was dissolved in deionized water to obtain solution a; Step S2: Biomass is added to solution a obtained in step S1, and after thorough stirring, solution b is obtained; Step S3: The solution b obtained in step S2 is dried to obtain mixture c; Step S4: Potassium ferrate is mixed with mixture c obtained in step S3, ground, and sieved to obtain mixture d; Step S5: The mixture d obtained in step S4 is heated to 690~700℃ and calcined at 690~700℃ for 1.8~2h; after calcination, it is cooled, ground, washed until neutral, dried and sieved to obtain boron-iron co-modified magnetic biochar. The mass ratio of boric acid, biomass and potassium ferrate is 9:6:2.

4.

2. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: The ratio of the mass of boric acid to the volume of deionized water in step S1 is (8.5~9) g : (100~120) mL.

3. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: The biomass mentioned in step S2 is walnut shell powder.

4. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: In step S2, a magnetic stirrer is used for stirring for 10-12 hours.

5. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: In step S3, solution b is poured into an evaporating dish and then placed in an oven at 60~80℃ for drying.

6. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: After grinding in step S4, the material is passed through a 100-mesh sieve.

7. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: In step S5, the mixture d is placed in a tube furnace for calcination.

8. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: In step S5, the product is dried in an oven at 60~80℃.

9. The method for preparing boron-iron co-modified magnetic biochar according to claim 1, characterized in that: After grinding in step S5, the material is passed through a 100-mesh sieve.

10. The application of the boron-iron co-modified magnetic biochar prepared by the method according to any one of claims 1-9, characterized in that: The application of the boron-iron co-modified magnetic biochar in the adsorption of p-nitrophenol.

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