Preparation method and application of biochar composite material

Abstract

The invention provides a preparation method and application of a biochar composite material, and relates to the technical field of water treatment.The preparation method comprises the following steps that S1, hydrothermal biochar is prepared, specifically, pine needle powder and distilled water are mixed and subjected to a hydrothermal reaction, and the hydrothermal biochar is obtained; s2, preparation of porous biochar: mixing the hydrothermal biochar and KHCO according to a weight ratio of 1: 4, performing ball milling, and heating to obtain the porous biochar; s3, synthesis of Fe3Co-coated BC: C800 is immersed in a Co / Fe nitrate ethanol solution, a reaction is performed to generate a Fe3Co alloy, the Fe3Co alloy is synchronously loaded on C800, and Fe3Co-coated BC is obtained; according to the preparation method, agricultural and forestry waste pine needles are selected to construct a carbon layer structure with a large number of pores, Fe3Co alloy is loaded to enhance the catalytic activity of PMS, and the pine needle derived biochar loaded Fe3Co alloy catalyst with efficient catalytic performance, namely the biochar composite material (Fe3Co-BC), is constructed for the first time.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and specifically to a preparation method and application of a biochar composite material. Background Art

[0002] With the advancement of the industrialization process, the discharge of industrial wastewater is increasing day by day. The wide demand and use of BPA (bisphenol A) have led to its continuous release into water bodies through various means such as industrial wastewater discharge, landfill leachate leakage, and leaching of waste materials. As an endocrine disrupting compound, even at low exposure levels, the release of BPA can cause damage to the health of humans and other organisms. It is very necessary to carry out research on the removal of BPA in the water environment, but the symmetrical structure of the double benzene rings of BPA determines its high stability in aqueous solutions, which poses higher requirements for advanced water treatment processes.

[0003] In the prior art, for the removal of BPA in industrial wastewater, it mainly relies on traditional water treatment processes such as coagulation sedimentation and filtration. However, with the increasingly strict environmental protection requirements and the increasing complexity of the components of industrial wastewater, processes such as coagulation sedimentation and filtration are difficult to meet the requirements of efficient and environmentally friendly treatment. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a preparation method of a biochar composite material, including the following steps: S1. Preparation of hydrothermal biochar: Mix pine needle powder with distilled water and carry out hydrothermal reaction at 180 °C for 12 hours to obtain hydrothermal biochar (HB); S2. Preparation of porous biochar: Mix hydrothermal biochar (HB) and KHCO3 in a weight ratio of 1:3 - 5 (preferably 1:4), ball mill for 30 minutes, and then heat to 800 °C at a heating rate of 5 °C / min in a nitrogen environment and hold for 2 hours to obtain porous biochar (C800); S3. Synthesis of Fe3Co@BC: Immerse C800 in a Co / Fe nitrate ethanol solution, dry and then pyrolyze for 2 hours, and react to generate Fe3Co alloy and simultaneously load it on C800, namely Fe3Co@BC.

[0005] Furthermore, the Co / Fe nitrate ethanol solution is an ethanol solution (molar ratio) containing Co(NO3)2·6H2O and Fe(NO3)3·9H2O in a ratio of 1:3.

[0006] Furthermore, the mass ratio of the Fe3Co alloy to the porous biochar (C800) is 1:2.

[0007] Further, in step S3, after drying, it is heated to 700 °C at a heating rate of 5 °C / min under a nitrogen atmosphere and pyrolyzed for 2 hours.

[0008] Further, the specific surface area of the Fe3Co@BC is 1218.08 m² / g, the average pore diameter is 7.34 nm, and the Fe3Co alloy particles are uniformly loaded on the porous biochar.

[0009] On the other hand, the present invention provides an application of a preparation method of a biochar composite material.

[0010] Further, the application method is as follows: Step 1: Add Fe3Co@BC and persulfate into the water body containing organic pollutants. The dosage of Fe3Co@BC is 0.2 g / L, and the dosage of persulfate is 0.2 g / L. Step 2: React for 5 minutes at a temperature of 25 °C.

[0011] Further, the organic pollutants include BPA (bisphenol A), basic blue, malachite green, tetracycline hydrochloride, and oxytetracycline hydrochloride.

[0012] Further, the organic pollutant is BPA. The degradation rate of BPA exceeds 99% within 5 minutes, and the removal rate of bisphenol A (BPA) is still higher than 87% after 8 hours of dynamic circulation.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention uses the advanced oxidation process (AOPs) to treat organic pollutants. This method can mineralize or decompose most of the organic substances. Compared with hydroxyl radicals and superoxide radicals, the sulfate radicals generated by activating persulfate (PMS) have a stronger redox potential and can be applied to more complex organic pollutant degradation systems. As an AOP catalyst for driving PMS, the FeCo alloy still has broad research prospects. The large specific surface area and high porosity of biomass carbon are conducive to the adsorption of PMS and pollutants. At the same time, uniform loading of metals and highly dispersed active species can be achieved.

[0014] 2. The present invention selects pine needles, an agricultural and forestry waste, to construct a carbon layer structure with a large number of pores and loads the Fe3Co alloy to enhance the catalytic activity of PMS. For the first time, a pine needle-derived biochar-supported Fe3Co alloy catalyst with high catalytic performance, namely the biochar composite material (Fe3Co@BC), is constructed. For the first time, the Fe3Co@BC catalyst is used to activate PMS to achieve a super-high degradation efficiency of BPA in a short time.

[0015] 3. The present invention constructs a pine needle-derived biochar-supported Fe3Co alloy catalyst (0.5Fe3Co@BC) for the first time. The loading of the Fe3Co alloy optimizes the charge distribution, endowing 0.5Fe3Co@BC with high catalytic performance. Eventually, an ultra-high degradation rate of 99.36% is achieved at 5 min. EPR and electrochemical experiments confirm that the loaded Fe3Co alloy improves the electron transfer efficiency, thereby enhancing the ability to activate PMS and the degradation efficiency of BPA; the removal rate of BPA remains higher than 87% during the 8-hour dynamic cycle; in addition, 0.5Fe3Co@BC also exhibits good degradation performance towards antibiotics and dyes. The catalytic degradation of BPA is a process involving the combined action of free radicals and non-free radicals, and O2• − plays a dominant role in the degradation of bisphenol A.

[0016] 4. The present invention uses the biomass waste pine needles as the carbon source, and constructs a loose and porous carbon layer (C800) structure through KHCO3 activation, which has a high specific surface area of 1616.9 m 2 g −1 . This provides conditions for the highly dispersed Fe3Co alloy and the rapid adsorption and in-situ degradation of BPA. The present invention has particularly important significance for the development and utilization of waste biomass resources and the field of environmental governance, and conforms to the concept of green sustainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a summary diagram of the experimental results of BPA degradation efficiency under different conditions; Figure 1 a is the BPA removal efficiency of different systems within 5 minutes; 1b is the initial concentration of BPA, 1c is the dosage of PMS, 1d is the dosage of the catalyst, 1e is the pH value, and 1f is the effect of temperature on the BPA degradation efficiency.

[0018] Figure 2 is the pseudo-first-order kinetic equation for the degradation of BPA by different materials activating PMS.

[0019] Figure 3 is the pseudo-first-order kinetic constant k for the degradation of BPA at different temperatures.

[0020] Figure 4 is a key experimental data diagram for the adsorption and quantitative analysis of BPA; Figure 4 a is the standard curve of the BPA solution; 4b is the adsorption isotherm of 0.5Fe3Co@BC.

[0021] Figure 5 is the thermodynamic behavior of 0.5Fe3Co@BC adsorbing BPA; Figure 5 a is the effect of temperature on the adsorption of BPA by 0.5Fe3Co@BC, and 5b is the thermodynamic fitting curve of 0.5Fe3Co@BC.

[0022] Figure 6 are the microscopic morphology and structure characterization of the 0.5Fe3Co@BC catalyst; 6a and 6b are the SEM images of 0.5Fe3Co@BC; 6c is the TEM image of 0.5Fe3Co@BC; 6d is the HRTEM image of 0.5Fe3Co@BC; 6e is the SAED pattern of 0.5Fe3Co@BC; 6f is the EDS image of 0.5Fe3Co@BC.

[0023] Figure 7 is the comprehensive characterization diagram for the phase structure, chemical bond, and pore characteristics analysis of different samples; Figure 7 a is the XRD image of different samples, 7b is the Raman image of different samples, 7c is the N2 adsorption - desorption graph and pore size distribution of HB, 7d is the N2 adsorption - desorption graph and pore size distribution of C800; 7e is the N2 adsorption - desorption graph and pore size distribution of 0.5Fe3Co@BC.

[0024] Figure 8 is the pseudo - first - order kinetic constant k for BPA degradation after adding different anions and HA.

[0025] Figure 9 is the comprehensive performance evaluation of the 0.5Fe3Co@BC material in practical environmental applications; Figure 9 a is the influence of different inorganic ions and hyaluronic acid on BPA degradation; 9b is the reusability of 0.5Fe3Co@BC; 9c is the degradation efficiency of BPA in different environments; 9d is the removal efficiency of 0.5Fe3Co@BC for antibiotics and dyes.

[0026] Figure 10 is the dynamic circulation device.

[0027] Figure 11 is the degradation of other organic pollutants by 0.5Fe3Co@BC + PMS; 11a is Basic Blue, 11b is Malachite Green, 11c is Tetracycline Hydrochloride; 11d is Oxytetracycline Hydrochloride.

[0028] Figure 12 is the SEM image of 0.5Fe3Co@BC after use.

[0029] Figure 13 are the XRD images of 0.5Fe3Co@BC before and after use.

[0030] Figure 14 is the identification and mechanism study of reactive free radicals during the degradation of BPA by the 0.5Fe3Co@BC / PMS system; Figure 14a shows the effects of different radical scavengers on the degradation efficiency of BPA; 14b shows the EPR spectra of DMPO trapping •OH and SO4•⁻; 14c shows the EPR spectra of DMPO trapping O2•⁻; 14d shows the EPR spectra of TEMP trapping ¹O2.

[0031] Figure 15 It is a test result diagram for the electrochemical performance and composition analysis of the 0.5Fe3Co@BC composite material; Figure 15 a is the CV diagram of the catalyst; 15b is the electrochemical impedance spectra of different materials; 15c is the XPS survey spectra of 0.5Fe3Co@BC before and after use; 15d is the high-resolution XPS spectra of Co 2p and the change in valence state ratio before and after use; 15e is the high-resolution XPS spectra of Fe 2p and the change in valence state ratio before and after use.

[0032] Figure 16 They are the possible degradation pathways and intermediate products of BPA.

[0033] Figure 17 It is the TOC removal rate. Detailed implementation methods

[0034] Example 1 Preparation of super-porous carbon material (C800) Put 5.00 grams of pine needle powder and 50 milliliters of distilled water into a polytetrafluoroethylene reactor, react at 180 °C for 12 hours to obtain hydrothermal biochar (HB), and then dry it to constant weight in an oven at 80 °C. Mix HB and KHCO3 in a weight ratio of 1:4, and then ball mill for 30 minutes. Heat the mixture in a tube furnace at 800 °C in a nitrogen environment for 2 hours, with a heating rate of 5 °C min -1 . After grinding in an agate mortar, rinse the sample with 1 M KOH for 1 hour and then with 2 M HCl for 1 hour. Finally, filter and dry in a vacuum oven at 80 °C for 24 hours to obtain porous biochar, denoted as C800.

[0035] Example 2 Preparation of Fe3Co alloy catalyst supported on porous carbon layer (0.5Fe3Co@BC) Dissolve 0.058 g of Co(NO3)2∙6H2O and 0.240 g of Fe(NO3)3∙9H2O in 10 mL of ethanol to form a metal nitrate mixture. Add C800 to 35 mL of ethanol and disperse it under ultrasonic conditions for 30 min to form a homogeneous solution. Then, slowly add the metal nitrate mixture to the C800 suspension under magnetic stirring at 80 °C and heat for 1 hour to evaporate the ethanol. Dry the obtained solid in a vacuum oven at 80 °C for 4 hours. Subsequently, heat the obtained solid mixture in a tube furnace in an N2 atmosphere at 5 °C min-1 The heating rate was pyrolyzed at 700 °C for 2 h. The prepared material was designated as Fe3Co@BC. Using the same synthesis method, a series of materials with different loading ratios were prepared by adjusting the mass of added pine needle biochar. The mass ratios of the total mass of cobalt and iron to the mass of C800 were 2:1, 1:1, and 1:2, namely 0.298 g of Co(NO3)2·6H2O, Fe(NO3)3·9H2O (molar ratio 1:3) and 0.149 g of C800, 0.149 g of Co(NO3)2·6H2O, Fe(NO3)3·9H2O (molar ratio 1:3) and 0.149 g of C800, 0.149 g of Co(NO3)2·6H2O and Fe(NO3)3·9H2O (molar ratio 1:3) and 0.298 g of C800, and the corresponding catalysts 2Fe3Co@BC, 1Fe3Co@BC, 0.5Fe3Co@BC were prepared.

[0036] Example 3 Determination of the optimal composite ratio of carbon material / Fe3Co alloy The degradation rates of 2Fe3Co@BC, 1Fe3Co@BC, and 0.5Fe3Co@BC at 5 min were 92.80%, 95.66%, and 99.36% respectively. The doping amount of pine needle biochar in the catalyst was proportional to the degradation efficiency of BPA. The leaching amounts of cobalt (Co) and iron (Fe) ions are shown in Table 1. To balance the ion leaching amount and BPA degradation efficiency, 0.5Fe3Co@BC was selected as the optimal catalyst.

[0037] Table 1 Leaching amounts of cobalt (Co) and iron (Fe) ions in different catalysts

[0038] Example 4 Degradation ability of 0.5Fe3Co@BC for BPA under different conditions At 25 °C, a catalyst (20 mg) was added to 100 mL of 20 mg / L BPA solution under magnetic stirring, and then PMS (20 mg) was added. Next, 1.5 mL of the supernatant was taken and immediately filtered through a 0.22 µm nylon filter head, and then mixed with 0.15 mL of methanol to detect the BPA content. C800, 2Fe3Co@BC, 1Fe3Co@BC, and 0.5Fe3Co@BC were added to the water body containing BPA together with peroxymonosulfate (PMS), and the reaction was carried out for 5 minutes. The degradation efficiency of BPA was calculated. The formula for calculating the BPA degradation efficiency: BPA degradation rate = (1 - C / C0) × 100%, where C is the content of BPA after degradation and C0 is the initial content of BPA. The results are shown in Figure 1 , Figure 1a is the BPA removal efficiency of different systems within 5 minutes; the effects of the initial concentration of BPA 1b, the dosage of PMS 1c, the dosage of catalyst 1d, the pH value 1e, and the temperature f on the BPA degradation efficiency.

[0039] From Figure 1 As can be seen from a, the BPA degradation efficiency achieved by using PMS alone within 5 min is 5.15%; the degradation rate of BPA by activating PMS with C800 is 61.68% at five minutes. The degradation rates of 2Fe3Co@BC, 1Fe3Co@BC, and 0.5Fe3Co@BC at 5 min are 92.80%, 95.66%, and 99.36% respectively. The doping amount of pine needle biochar in the catalyst is proportional to the BPA degradation efficiency. The pore structure of 0.5Fe3Co@BC will expose more metal sites and expand the adsorption space, while promoting the exposure of active species to BPA molecules. Therefore, the unique porous biochar-wrapped alloy structure triggers a rapid adsorption-degradation coupling process, resulting in the efficient removal of BPA.

[0040] Figure 1 b, Figure 1 c, and Figure 1 d show the effects of the initial BPA concentration, the dosage of PMS, and the dosage of catalyst on the BPA degradation performance. Figure 1 In b, as the initial BPA concentration increases from 10 mg / L to 40 mg / L, the BPA degradation efficiency decreases. Figure 1 In c, as the dosage of PMS increases, the BPA degradation efficiency increases. In particular, for the systems of 0.40 and 0.50 g / L, complete removal of BPA is achieved within 5 min. By increasing the amount of PMS, the concentration of reactive free radicals in the reaction system increases, and the effective and rapid degradation of BPA can be achieved. Figure 1 In d, the dosage of catalyst is positively correlated with the BPA degradation reaction rate. As the dosage of catalyst (10 - 50 mg) increases, the BPA degradation rate accelerates.

[0041] This experiment also studied the effect of the initial pH value ( Figure 1 e) on the decomposition of BPA. During the BPA degradation process, the pH value of the solution remains the same as the initial value. The degradation rate of BPA continuously increases as the pH increases from 3.08 to 9.14, and BPA is completely degraded within 5 minutes at pH 9.14. In weakly acidic and weakly alkaline environments, there are relatively few reactive oxygen species that self-annihilate and react with H + However, a large number of reactive oxygen species participate in the degradation reaction of pollutants, increasing the degradation rate of pollutants.

[0042] Figure 1f shows that the degradation rate is positively correlated with the reaction temperature. For the degradation reaction at 45 °C, the degradation rate of BPA can reach 99.66% at 5 min. Further, complete degradation of BPA can be achieved at 4 min under 55 °C. Meanwhile, at 55 °C, the self-decomposition rates of BPA and PMS are only 8.01% and 9.13% at 5 min. High temperature can accelerate the collision frequency among PMS, pollutants and catalysts, thus accelerating the reaction.

[0043] Figure 2 shows the kinetic curves related to BPA degradation. It can be seen from the figure that the degradation of BPA conforms to the pseudo-first-order kinetic equation.

[0044] Figure 3 is the pseudo-first-order kinetic constant (k) for BPA degradation at different temperatures. It can be known from Figure 3 that the kinetic constant of BPA degradation increases from 0.80421 to 1.35343 min -1 as the temperature rises from 25 °C to 55 °C. With the increase of temperature, the k value gradually increases, indicating that the activation of PMS is an endothermic process.

[0045] Example 5 Adsorption efficiency of 0.5Fe3Co@BC for BPA The adsorption isotherm of 0.5Fe3Co@BC for BPA is as Figure 4 shown. The test results show that the maximum adsorption capacity of 0.5Fe3Co@BC is 255.15 mg / g.

[0046] At different BPA concentrations, 20 mg of the catalyst was added to 100 ml of BPA solution (acetonitrile / water, 1 / 4, v / v) and shaken at a constant temperature of 150 rpm. After reaching the adsorption equilibrium, the mixture was filtered through a 0.22-μm filter, and then the concentration of BPA was detected by high-performance liquid chromatography at 278 nm. As Figure 5 shown, the adsorption capacity of the catalyst increases with the increase of temperature. The temperature at which 0.5Fe3Co@BC reaches the adsorption equilibrium is 55 °C.

[0047] Example 6 Characterization of 0.5Fe3Co@BC catalyst The microstructural results of the prepared materials were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as shown in Figure 6 .

[0048] As Figure 6 shown in a, numerous micropores were observed on the surface of 0.5Fe3Co@BC. This is due to the porous structure of C800, which is convenient for subsequent loading of metal elements. In the high-magnification SEM image ( Figure 6As can be seen from b), 0.5Fe3Co@BC retains the advantage of the highly porous structure of the precursor, and the surface of the material presents an irregular pore morphology. TEM was introduced to observe the fine structure of 0.5Fe3Co@BC. The Fe3Co nanoparticles have a spherical-like structure and are relatively evenly anchored on the biochar, as Figure 6 shown in c. In the HRTEM image of 0.5Fe3Co@BC shown in Figure 6 d, lattice fringes of 0.2030 and 0.1438 nm corresponding to the (111) and (220) crystal planes of Fe3Co were observed respectively, which further indicates that the Fe3Co alloy was successfully loaded onto the pine needle biochar. And the radii of the polycrystalline diffraction rings were observed to correspond to the interplanar spacings of the (111) and (220) crystal planes of Fe3Co, as Figure 6 shown in e. EDS mapping was used to detect the surface elements to further determine the composition of the sample. The results show that the C, N, O, Fe, and Co elements in 0.5Fe3Co@BC are evenly and continuously distributed in the prepared catalyst, as Figure 6 shown in f.

[0049] The crystal structure and morphology of the prepared samples were characterized by X-ray diffraction (XRD), as Figure 7 shown in a. All the diffraction peaks of the 2Fe3Co@BC, 1Fe3Co@BC, and 0.5Fe3Co@BC samples with different loading ratios obtained match perfectly with the diffraction peaks of Fe3Co (JCPDS card number 97-015-5843). This indicates that Fe3Co was successfully attached to the carbon material, and at the same time, the high crystallinity of Fe3Co is not affected by the addition amount of pine needle biochar.

[0050] To further verify the XRD results, Raman spectroscopy analysis was performed on the materials Figure 7 shown in b. The ID / IG values of C800, 2Fe3Co@BC, 1Fe3Co@BC, and 0.5Fe3Co@BC are 0.98, 0.93, 0.96, and 0.97 respectively. The ID / IG value of C800 is the largest, indicating that the carbon atoms are in a disordered state. The pore structure and pore size distribution characteristics of the catalyst were studied. As Figure 7 shown in c, according to the classification of the International Union of Pure and Applied Chemistry (IUPAC), the N2 adsorption-desorption curve of HB conforms to the type-IV isotherm and has an H3-type hysteresis loop (at P / P0 = 0.56 - 0.99). C800 shows a significantly increased specific surface area (1616.9 m 2 g −1 ), and the KHCO3 activation increased the specific surface area by about 185 times. After activation, the average pore size decreased from 14.75 nm to 4.18 nm, as Figure 7 shown in d, further confirming the extremely high micropore content of C800.Figure 7 Figure d-7e shows that the N2 adsorption / desorption isotherms of both C800 and 0.5Fe3Co@BC are of type Ⅳ, and the H4-type hysteresis loops are all in the range of 0.5 - 0.99, which means they have a porous structure with abundant micropores and mesopores. Table 2 shows the specific surface area and pore volume and pore size distribution of Fe3Co@BC catalysts with different composite ratios. All materials have a good mesoporous structure (the average pore diameter of mesopores is 2 - 50 nm). Compared with C800, the specific surface area of 0.5Fe3Co@BC decreases to 1218.08 m 2 g −1 . The average pore diameter of 0.5Fe3Co@BC increases to 7.34 nm.

[0051] Table 2 Specific surface area and pore size of HB, C800, 2Fe3Co@BC, 1Fe3Co@BC and 0.5Fe3Co@BC

[0053] By adding several anions and organic compounds (including Cl - , SO4 2- , HCO3 - , H2PO4 - , CO3 2- , NO3 - and HA) that are universal in real life to the solution, the applicability of the 0.5Fe3Co@BC catalyst was verified. According to Figure 8 For the pseudo-first-order kinetic constants of BPA degradation in the presence of Cl - , SO4 2- , HCO3 - , H2PO4 - , CO3 2- , NO3 - and HA.

[0054] The experimental procedure was the same as in Example 4, and different anions were added to evaluate their effects on BPA degradation. As Figure 9 shown in a, SO4 2- and NO3 - only slightly reduced the degradation efficiency; the presence of CO3 2− and HA significantly reduced the overall effectiveness of degradation. It is worth noting that the presence of Cl - instead accelerated the degradation rate, and chloride ions had an obvious positive effect. Similarly, H2PO4 - also showed a positive effect on the degradation of BPA.

[0055] Reusability is also an important consideration criterion for catalysts. While injecting BPA and PMS solutions simultaneously with a circulating water multi-purpose vacuum pump, the column was filled with 0.5Fe3Co@BC material. After continuous operation for 8 h, the instantaneous effluent was taken to detect the BPA concentration to verify the stability of the material. The device is as Figure 10 . As Figure 9 shown in b, although the degradation rate decreased during the 8-hour dynamic cycle, the removal rate of BPA was always higher than 87%, demonstrating that the 0.5Fe3Co@BC catalyst has ideal recycling performance.

[0056] To evaluate the application of the catalyst in real water samples, river water from the Xiaohei River and lake water from the Manduhai Park in Hohhot, Inner Mongolia were taken to prepare a 20 mg / L BPA solution for degradation. 83.64% and 93.65% of BPA in Manduhai Lake water and Xiaohei River water were degraded respectively, as Figure 9 shown in c. The organic matter and ions present in the Xiaohei River water hindered the degradation of BPA by the catalyst. The more obvious decrease in the BPA removal rate in lake water may be due to the presence of a certain amount of natural organic matter in the water sample, which will compete with BPA for adsorption sites and thus inhibit the degradation of BPA by 0.5Fe3Co@BC.

[0057] As Figure 9 shown in d, the removal rates of basic blue 1, malachite green, oxytetracycline hydrochloride and tetracycline hydrochloride by 0.5Fe3Co@BC were 92.92% (24 min), 88.90% (24 min), 83.26% (14 min) and 90.10% (10 min) respectively. It can be seen that 0.5Fe3Co@BC can effectively degrade a variety of dyes and antibiotics by catalytically activating PMS. On the basis of PMS activation, the catalytic degradation ability of the material for basic blue 1, malachite green, tetracycline hydrochloride and oxytetracycline hydrochloride was tested ( Figure 11 ). The results showed that 0.5Fe3Co@BC has equally good catalytic activity for basic blue, malachite green, tetracycline hydrochloride and oxytetracycline hydrochloride.

[0058] Example 7 Stability of 0.5Fe3Co@BC Furthermore, the surface morphology of 0.5Fe3Co@BC after use was tested, and there was no obvious change in the structure of the material after use ( Figure 12 ). Figure 13 is the XRD pattern of 0.5Fe3Co@BC before and after degrading BPA. There was no obvious change in the diffraction peaks before and after the reaction, indicating that the crystal structure of the prepared material is relatively stable.

[0059] Example 8 Identification of reactive oxygen species in the 0.5Fe3Co@BC+PMS system The experimental procedure was the same as that in Example 4, and different radical scavengers were added to evaluate their effects on the degradation of BPA. As Figure 14 shown in a, the order of inhibitory performance on BPA degradation was: p-BQ >> L-histidine > KI > MeOH > DMSO > TBA. When p-BQ was added to the system, the removal rate of BPA decreased to 95.40% at 5 min. Since p-BQ had the strongest inhibitory effect on BPA degradation, it indicated that O2• − dominated in the reaction system. In the presence of L-histidine, it was noted that the overall trend of the BPA degradation reaction decreased. The final degradation rate of BPA decreased to 97.57%. This indicated that 1 O2 also played a role in the degradation process of BPA. The performance of adding KI confirmed the generation of radicals on the catalyst surface, and the degradation of BPA by 0.5Fe3Co@BC+PMS was a heterogeneous catalytic process. The addition of external MeOH indicated that 0.5Fe3Co@BC could activate PMS to generate OH• and SO4• − . After the addition of TBA, the effect on the BPA degradation process was very weak, indicating that OH• played a minor role in the reaction system. The two conditions of adding external MeOH and adding external TBA together indicated that OH• and SO4• − played a role in BPA degradation, and the contribution of SO4• − was greater. These results showed that in the 0.5Fe3Co@BC+PMS+BPA system, the reactive species including 1O2, SO4• − and OH• were the oxidative species for degrading BPA, while O2• − played a major role in the degradation of BPA.

[0060] EPR experiments were carried out using 5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) as a spin trap agent ( Figure 14 b, 14c). The characteristic signals of DMPO-OH• (1:2:2:1, quartet) and DMPO-SO4•− (sextet) were detected in the 0.5Fe3Co@BC+PMS, C800+PMS systems and in PMS alone. These results indicated the rapid formation of OH• and SO4• − . When only PMS was added (0 min), no characteristic peak of DMPO-O2• − was produced. This indicated that PMS self-decomposition did not generate O2• − . The characteristic signals of O2• − were detected in the 0.5Fe3Co@BC+PMS and C800+PMS systems, proving that 0.5Fe3Co@BC and C800 could activate PMS to generate O2• −. The above results prove that the activation of PMS by 0.5Fe3Co@BC generates higher concentrations of O2• − , OH• and SO4• − than that by C800. Figure 14 In d, 2,2,6,6-tetramethyl-4-piperidone (TEMP) was used as the 1 spin-trapping agent for O2 in the EPR experiment. At 2.5 min after adding PMS and 0.5Fe3Co@BC or C800, typical characteristic peaks (1:1:1) of O2 could be observed in both the 0.5Fe3Co@BC+PMS and C800+PMS systems. This indicates that both Fe3Co@BC and C800 can activate PMS to generate 1 O2. Since the characteristic peak signal intensity of O2 generated by the activation of PMS by Fe3Co@BC is stronger, it is confirmed that the Fe3Co@BC composite material generates a higher concentration of free radicals than the C800 carbon material. As mentioned above, both the activated pine needle biochar and the loaded Fe3Co can effectively activate PMS. 1 1 1 1

[0061] Example 9 Contribution of Each Component of 0.5Fe3Co@BC to the Activation of PMS Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the charge transfer among the catalyst, PMS, and BPA. 0.5Fe3Co@BC showed a larger redox potential ( Figure 15 a) in the CV curve, which corresponds to the electron gain behavior of PMS. A stronger current response means that 0.5Fe3Co@BC has a faster kinetic reaction rate and stronger catalytic ability than C800. Cyclic voltammetry confirmed the cyclic stability of the electron transfer of the catalytic material. Similarly, 0.5Fe3Co@BC had a smaller circle diameter in the EIS diagram (15b), showing a higher electron transfer rate. 0.5Fe3Co@BC has a stronger ability to activate PMS than C800. The above results indicate that after the combination of C800 and Fe3Co, the electron transfer ability of the catalyst is enhanced, which is beneficial to the activation of PMS. The electrochemical test results show that the prepared catalyst has good electron transfer performance and redox behavior.

[0062] The elemental changes in 0.5Fe3Co@BC before and after the degradation reaction were analyzed by XPS. Figure 15 The full-range spectrum in c shows the characteristic peaks of Fe, Co, C, N, and O elements, confirming that there is no obvious change in the elemental composition of the catalyst before and after use. Co 0Located at 777.60 eV, Co(II) is located at 781.93 eV and 796.89 eV respectively, Co(III) is located at 779.71 eV and 794.64 eV respectively, and their satellite peaks are located at 785.17 eV and 800.12 eV. After the reaction, Co 0 content decreased from 8.64% to 3.00%, Co(II) content decreased from 35.87% to 25.86%, and at the same time, the proportion of Co(III) increased from 22.76% to 25.28% (Figure 15d). Fe 0 is located at 707.03 eV, Fe(II) is located at 714.17 eV and 726.62 eV respectively, Fe(III) is located at 710.85 eV and 723.24 eV respectively, and their satellite peaks are located at 728.39 eV and 730.20 eV. After the reaction, Fe 0 content decreased from 8.30% to 1.66%, and at the same time, Fe(II) content increased from 29.16% to 31.27%, and the proportion of Fe(III) increased from 38.07% to 46.00% ( Figure 15 e). After the reaction, the contents of metallic Fe and metallic Co decreased significantly, indicating that the Fe3Co alloy participated in the PMS activation reaction and played an important role in the degradation of BPA.

[0063] The relative contents of C, N, O, Fe and Co before and after the reaction are shown in Table 3.

[0064] Table 3 XPS element contents of different samples

[0065] Example 10 Degradation pathway of BPA The degradation intermediates of BPA were determined by high performance liquid chromatography-mass spectrometry. The BPA degradation pathway was inferred based on the intermediates, and its structural formula was deduced according to the m / z values of the fragment ions. Thirteen intermediates were generated from BPA, such as Figure 16As shown in the figure. BPA is converted to 3 - hexen - 1 - ol through two pathways. The first process is as follows: First, the C - C bond connecting the two benzene rings in the BPA molecule breaks, forming 1 - (4 - hydroxyphenyl)ethanol (N4); then, the hydroxyl group is oxidized to a carbonyl group, forming p - hydroxyacetophenone (N5); finally, N5 loses the hydroxyl group to form acetophenone (N6). The second process is as follows: First, the BPA molecule loses two phenolic hydroxyl groups, forming 2,2 - diphenylpropane (N2); then N2 loses two methyl groups, forming diphenylmethanol (N3); N3 generates a monocyclic aromatic hydrocarbon (N7) by opening the right ring and then undergoing electronic rearrangement; finally, it is further converted to aliphatic compounds (N8, N9) through a ring - opening reaction. After being converted to 3 - hexen - 1 - ol (N10) through the above two pathways, it then turns into 2 - hexanone (N11), 2 - pentanol (N12), sec - butanol (N13), and finally forms butane (N14), and is ultimately mineralized into carbon dioxide and water. Table 4 describes the mass spectra of BPA and 13 intermediates.

[0066] Table 4 Mass Spectra of BPA and 13 Intermediates

[0067] The mineralization degree of BPA in the 0.5Fe3Co@BC + PMS system was reflected by the total organic carbon (TOC) removal rate. From Figure 17 It can be seen that the TOC removal rate is positively correlated with the doping amount of C800. The TOC removal rates of 2Fe3Co@BC and 1Fe3Co@BC are 48.36% and 53.73% respectively. The TOC removal rate of 0.5Fe3Co@BC reached 61.05%.

[0068] In summary, the present invention first constructs a pine needle - derived biochar - supported Fe3Co alloy catalyst (0.5Fe3Co@BC). The loading of the Fe3Co alloy optimizes the charge distribution, enabling 0.5Fe3Co@BC to have high - efficient catalytic performance, and finally achieving an ultra - high degradation rate of 99.36% at 5 min. EPR and electrochemical experiments confirm that the loading of the Fe3Co alloy improves the electron transfer efficiency, thereby enhancing the ability to activate PMS and the degradation efficiency of BPA. The removal rate of BPA is always higher than 87% during the 8 - hour dynamic cycle. In addition, 0.5Fe3Co@BC also exhibits good degradation performance for antibiotics and dyes. The catalytic degradation of BPA is a process involving the combined action of free radicals and non - free radicals. O2• − plays a dominant role in the degradation of BPA. The possible pathways and intermediates of BPA degradation are systematically proposed. Finally, the mechanism of 0.5Fe3Co@BC activating PMS to degrade BPA is proposed. This research can provide a new idea for designing Fe3Co alloy catalysts to activate peroxymonosulfate to efficiently and rapidly degrade organic pollutants.

Claims

1. A preparation method of a biochar composite material, characterized in that, It includes the following steps: S1. Hydrothermal biochar preparation: Mix pine needle powder with distilled water, and conduct hydrothermal reaction at 180 °C for 12 hours to obtain hydrothermal biochar; S2. Porous biochar preparation: Mix the hydrothermal biochar with KHCO3 at a weight ratio of 1:3 - 5, ball mill for 30 minutes, then heat it to 800 °C at a heating rate of 5 °C / min in a nitrogen environment and keep it for 2 hours to obtain porous biochar; S3. Fe3Co@BC synthesis: Immerse the porous biochar in a Co / Fe nitrate ethanol solution, dry it and then pyrolyze for 2 hours. The reaction generates Fe3Co alloy and synchronously loads it on the porous biochar, namely Fe3Co@BC.

2. The preparation method of a biochar composite material according to claim 1, characterized in that, The Co / Fe nitrate ethanol solution is an ethanol solution with a molar ratio of Co(NO3)2·6H2O to Fe(NO3)3·9H2O of 1:

3.

3. The preparation method of a biochar composite material according to claim 1, characterized in that, The mass ratio of the Fe3Co alloy to the porous biochar is 1:

2.

4. The preparation method of a biochar composite material according to claim 1, characterized in that, In step S3, after drying, heat it to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and pyrolyze for 2 hours.

5. Application of the preparation method of a biochar composite material according to any one of claims 1 - 4.

6. Use of the preparation method of a biochar composite material according to claim 5, characterized in that, The application method is as follows: Step 1. Add Fe3Co@BC and persulfate into the water body containing organic pollutants. The dosage of Fe3Co@BC is 0.2 g / L, and the dosage of persulfate is 0.2 g / L; Step 2. React at 25 °C for 5 minutes.

7. Use of the preparation method of a biochar composite material according to claim 6, characterized in that, The organic pollutants include bisphenol A, basic blue, malachite green, tetracycline hydrochloride or oxytetracycline hydrochloride.

8. Use of the preparation method of a biochar composite material according to claim 7, characterized in that, The organic pollutant is bisphenol A.

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