Application of activated persulfate by biomass direct-fired power plant endogenous magnetic bottom slag in degradation of sulfamethoxazole pollutants

Abstract

The present application relates to solid waste resource processing technical field, specifically to a kind of application of activating persulfate degradation sulfamethoxazole pollutants by biomass direct-fired power plant endogenic magnetic bottom slag.The present application is screened after cooling the bottom slag generated by the combustion of biomass direct-fired power plant grate furnace, and the bottom slag with particle size between 0.1-0.45 mm is collected.The bottom slag contains endogenic magnetite composition, which can realize the green activation of persulfate (PMS), and is used for the degradation and removal of common organic pollutants sulfamethoxazole (SMX) in water.The adsorption rate of bottom slag to SMX is less than 2%;compared with using PMS alone, the degradation rate of SMX can be significantly improved from 51% to more than 95% by adding the above particle size bottom slag.In the interference of water anions (SO4 2‑ , HCO3 ‑ , NO3 ‑ and Cl ‑ ), bottom slag can maintain more than 90% SMX removal.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and in particular, it relates to the application of activated persulfate degradation of sulfamethoxazole pollutants in endogenous magnetic bottom slag of a biomass direct-fired power plant. Background Technology

[0002] Biomass power generation technology is receiving increasing attention. Grate combustion is the mainstream combustion method for direct combustion power generation of agricultural and forestry biomass, primarily using rice and wheat straw and tree branches. These agricultural wastes generate a large amount of ash and slag during direct combustion, including fly ash and bottom ash. Most of the ash particles generated by grate combustion are deposited on the grate, forming bottom ash, which accounts for 85% of the total ash and slag. Therefore, a large amount of bottom ash solid waste urgently needs resource treatment.

[0003] Currently, the main methods for disposing of biomass ash are landfill and resource utilization. Landfilling is simple to operate but consumes a large amount of land resources. Resource utilization includes applications such as roadbeds, cement additives, and soil conditioners. Existing resource utilization methods fail to fully utilize the porous structure and multi-element enrichment characteristics of biomass ash, leading to resource waste. Therefore, there is an urgent need for a method to achieve high-value-added resource utilization of biomass direct-fired power plant ash. Summary of the Invention

[0004] To address the above technical problems, this invention provides a method for applying persulfate to degrade sulfamethoxazole pollutants using endogenous magnetic bottom ash activated in biomass direct-fired power plants. This invention uses the simply pretreated bottom ash as a catalyst for the persulfate (PMS) degradation of sulfamethoxazole (SMX). The bottom ash, rich in magnetite components primarily composed of natural Fe3O4, efficiently activates the PMS, generating various active oxygen species to degrade the organic pollutant SMX. Since the catalyst is derived from naturally magnetic bottom ash, it does not produce secondary pollutants, representing a green and environmentally friendly innovative treatment method.

[0005] The objective of this invention can be achieved through the following technical steps:

[0006] An application of activated persulfate in the endogenous magnetic bottom ash of a biomass direct-fired power plant to degrade sulfamethoxazole pollutants, using it as a catalyst.

[0007] Furthermore, the application involves washing, removing impurities, drying, and grinding the bottom ash from a biomass direct-fired power plant, and then adding it sequentially with persulfate to wastewater containing sulfamethoxazole, and reacting under stirring.

[0008] Furthermore, the specific operations of washing, removing impurities, drying, and grinding are as follows: First, the bottom slag is washed with tap water until the supernatant is transparent, then washed with deionized water and ultrasonicated until the supernatant is transparent. Then, it is placed in an oven and dried to constant weight. The visible impurities are then selected out, and then crushed using a crusher to collect the bottom slag with a particle size of 0.1 mm to 0.45 mm.

[0009] Furthermore, the biomass source of the bottom ash is herbaceous or woody clean biomass fuel, including agricultural and forestry waste such as corn stalks, wheat stalks, rice stalks, cotton stalks, bagasse, rice husks, peanut shells, and sawdust, but excluding activated sludge, municipal solid waste, and domestic garbage; the collected combustion ash is bottom ash, excluding fly ash.

[0010] Furthermore, the bottom slag has an iron content of 1.0-3.0 wt% and an iron oxide content of 1.5-6.5 wt%, of which the Fe3O4 content is 0.45-2.0 wt%.

[0011] Furthermore, in the aforementioned application, the initial concentration of SMX in the wastewater is 1-15 mg / L; and / or

[0012] The final concentration of PMS added to the wastewater is 0.5-4 mM, preferably 1 mM; and / or

[0013] The bottom residue dosage is 10-60 g / L, preferably 40 g / L, that is, 2 g of bottom residue is added for every 50 mL of reaction solution.

[0014] In this invention, bottom ash can effectively activate PMS, generating reactive oxygen species such as hydroxyl radicals, sulfate radicals, singlet oxygen, and high-valent iron oxides. This is because the iron in the bottom ash precursor crops can be absorbed by the soil, and iron-containing substances are introduced during biomass collection and equipment wear. These iron-containing substances are calcined at high temperatures of 550-900℃ in a grate furnace, where the elemental iron is converted into iron oxides in the bottom ash. At the same time, the incompletely burned carbon in the bottom ash may promote the partial conversion of Fe2O3 into Fe3O4, resulting in the presence of multivalent iron oxides in the bottom ash, thus possessing potential catalytic activity.

[0015] This invention addresses the problem of large-scale generation of bottom slag and the failure of existing treatment and disposal technologies to fully utilize its high metal content and other characteristics for resource utilization. It proposes a resource utilization method that uses a simple pretreatment process to activate PMS as a catalyst for SMX degradation. Compared with existing technologies, the advantages and beneficial effects include:

[0016] (1) Make full use of the iron oxides contained in the bottom ash of biomass direct combustion power plants, especially the active component of magnetite with Fe3O4 as the main component, to achieve high utilization rate and high added value of magnetic bottom ash.

[0017] (2) Innovatively explore the structural and compositional advantages of bottom slag. The silicon oxides and aluminum oxides in the bottom slag serve as a material framework, dispersing active components such as magnetite within them. This avoids the problem of pure Fe3O4 particle accumulation and increases the number of active reaction sites, thereby effectively improving the activation efficiency of the bottom slag for PMS. Simultaneously, the abundant Fe, Al, Mn, Cu, and other metallic components in the bottom slag possess synergistic potential, capable of stimulating various active oxygen species such as hydroxyl groups, sulfate radicals, singlet oxygen, and high-valence iron oxides, thereby specifically degrading and removing organic pollutants.

[0018] (3) The pretreatment process is simple and the technical requirements are low. The overall application method is simple and the cost is low, which has good economic benefits and industrial application prospects.

[0019] (4) The bottom ash of biomass direct combustion power plants has extremely low heavy metal content and no secondary pollution during use. It is a green, environmentally friendly, efficient and energy-saving resource utilization method. Attached Figure Description

[0020] Figure 1 This is a diagram of the pretreated bottom slag material in Example 1;

[0021] Figure 2 The figure shows the SEM analysis results of the pretreated bottom slag in Example 1. In the figure, (a) is the appearance morphology and (b) is the distribution of various elements on the surface of the bottom slag.

[0022] Figure 3 XRD analysis of the pretreated bottom slag in Example 1;

[0023] Figure 4 XPS analysis of the pretreated bottom slag in Example 1;

[0024] Figure 5 The effect of the initial SMX concentration on the degradation effect in Example 1;

[0025] Figure 6 The effect of bottom residue dosage on degradation effect in Example 1;

[0026] Figure 7 The effect of PMS dosage on degradation effect in Example 1;

[0027] Figure 8 The effect of initial solution pH on degradation efficiency in Example 1;

[0028] Figure 9 This illustrates the effect of the presence of the four anions in Example 1 on the degradation effect.

[0029] Figure 10 The results of hysteresis loop measurements for MBA, BA, and NMBA in Example 2;

[0030] Figure 11 The effects of Fe3O4, MBA, BA and NMBA in the catalytic experiments in Example 2 are shown respectively;

[0031] Figure 12 This is the SMX removal effect on simulated actual wastewater in Example 3;

[0032] Figure 13 This is the SMX removal effect on actual wastewater in Example 4;

[0033] Figure 14 The catalytic performance of the initial bottom ash and the bottom ash after four cycles of recycling is evaluated. Detailed Implementation

[0034] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0035] The bottom ash is the bottom ash produced by a direct combustion power plant of agricultural and forestry biomass. The source of agricultural and forestry biomass is clean biomass fuel of herbaceous or woody type, including agricultural and forestry waste such as corn stalks, wheat stalks, rice stalks, cotton stalks, sugarcane bagasse, rice husks, peanut shells, and sawdust. The collected combustion ash of agricultural and forestry biomass is the bottom ash, excluding fly ash.

[0036] In the following examples, the bottom residue was taken from a biomass direct combustion power plant in Anhui Province (the main biomass sources are rice and wheat straw, as well as waste wood). X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma atomic emission spectrometry (ICP) were performed on the bottom residue samples, and the results are shown in Tables 1 and 2 below.

[0037] Table 1. XRF composition analysis of bottom ash from agricultural and forestry biomass direct-fired power plants (wt%)

[0038]

[0039] Table 2. ICP analysis (wt%) of major metallic elements in the bottom ash from agricultural and forestry biomass direct-fired power plants.

[0040]

[0041] The analysis results in Tables 1 and 2 show that the main components of the bottom ash from direct-fired agricultural and forestry biomass power plants are inorganic components such as SiO2, Al2O3, CaO, MgO, K2O, and Fe2O3. The iron oxide content is 5.62%, and the total iron content is 2.43%, providing a good foundation for PMS activation. Furthermore, the heavy metal content in the bottom ash from direct-fired agricultural and forestry biomass power plants is extremely low, and will not cause secondary pollution or harm to the environment.

[0042] Example 1

[0043] This embodiment provides a method for using magnetic bottom ash from a biomass direct-fired power plant as a catalyst to activate PMS for the degradation of organic pollutants SMX, including the following steps:

[0044] (1) Pretreatment of bottom slag: The raw material was washed several times with tap water until the supernatant was clear. Then it was washed with deionized water and sonicated for 10 minutes, repeated three times. The filtered solid was then placed in an oven and dried at 60°C to constant weight. After drying, visible impurities such as obvious yellow bricks, white quartz sand, branches, and iron nails were manually removed. The large-diameter ash slag was then crushed using a crusher and passed through 40-mesh and 150-mesh sieves. Ash slag BA with a particle size between 0.1 mm and 0.45 mm was collected for experiments. The collected ash slag had a slight metallic luster, was gray in color, and consisted of irregular spherical and fragmented particles (see Figure 1 Store in a cool, dry place away from light for later use. The SEM, XRD, and XPS results are shown below. Figures 2-4 As shown, the results indicate that C, O, Si, Fe, and other elements are distributed on its surface. X-ray diffraction (XRD) analysis confirmed the presence of iron oxides in the bottom slag, including Fe2O3 and Fe3O4. X-ray photoelectron spectroscopy (XPS) analysis further confirmed the presence of these elements. Figure 4 In the figure above, the bottom slag is after pretreatment, and the bottom slag is after catalytic reaction for 2 hours as described in (2). Before the catalytic reaction, the proportion of divalent iron in the bottom slag was 7.74%, and the proportion of trivalent iron was 92.26%. It was calculated that Fe3O4 accounted for 30.52% of iron oxides. After the catalytic reaction, the proportion of divalent iron and trivalent iron changed, which confirmed that iron participated in the reaction and that there was mutual conversion between different valence states.

[0045] (2) Experimental procedure for catalytic reaction: Weigh 2g of pretreated bottom residue into a 150mL beaker, then measure 50mL of 5mg / L initial sulfamethoxazole SMX solution, stir magnetically at 200rpm, and add 0.5mL of 100mM PMS stock solution (final concentration 1mM). React at room temperature for 2h. The addition of PMS is marked as the start of the reaction. At 15, 30, 60, 90, and 120min, respectively, take 1mL of the reaction solution, filter it through a 0.22μm PTFE membrane, and then immediately add 0.5mL of the filtrate to a brown vial containing 0.5mL of Na2S2O3 solution for quenching.

[0046] (3) Sample concentration determination: The concentration of SMX in the filtrate obtained after quenching was determined by ultra-high performance liquid chromatography (UPLC). Each experiment was performed in parallel at least twice, and the parameters are shown in Table 3.

[0047] Table 3 UPLC Parameter Conditions

[0048]

[0049] (4) Data processing and effect evaluation: The corresponding SMX concentration is calculated using the sample peak area obtained in (3), and the removal rate, mean, and error bars are calculated. Finally, a dotted line graph is drawn.

[0050] (5) To evaluate the effect of initial SMX concentration on pollutant degradation efficiency, SMX solutions with concentration gradients of 1-15 mg / L were prepared using a 100 mg / L SMX stock solution. The above experiments were conducted with initial SMX concentrations of 1, 2, 10, and 15 mg / L. The results are shown in [Figure number missing]. Figure 5 The bottom sludge / PMS system achieved a removal rate of over 90% for SMX at different concentrations, reaching 100% removal within 15 minutes when the initial SMX concentration was ≤2 mg / L. For initial concentrations of 5 and 10 mg / L, a high removal rate of 95% was achieved after 120 minutes. Overall, the SMX removal rate decreased with increasing initial concentration. This invention uses a higher SMX concentration of 5 mg / L (higher than the environmental concentration) for batch experiments to expand its environmental applicability.

[0051] (6) To evaluate the effect of bottom slag dosage on pollutant degradation efficiency, the pretreated bottom slag mass was changed to 0, 0.5, 1, 1.5, and 3 g for the above experiments. The results are shown in […]. Figure 6 Without the addition of bottom slag, the degradation rate of SMX by PMS was only 51% after 120 minutes. The addition of bottom slag significantly improved the degradation rate, and it increased with the increase of bottom slag dosage. When 2g of bottom slag was added, the degradation rate was 94.8% after 120 minutes, and when 3g was added, the degradation rate was 98.8%. Considering the time cost of bottom slag pretreatment, this invention selected a dosage of 2g for batch experiments.

[0052] (7) To evaluate the effect of PMS dosage on pollutant degradation efficiency, the above experiment was conducted with final PMS concentrations of 0, 0.5, 2, and 4 mM. The results are shown in […]. Figure 7 Without PMS, the removal of SMX from the bottom sludge was considered to be due to adsorption, with a removal rate of only 1.7%. As the PMS concentration increased, the SMX removal rate gradually increased, achieving 100% removal when the PMS dosage exceeded 2 mM. To avoid excessive PMS in the environment, this invention used a dosage of 1 mM for subsequent batch experiments.

[0053] (8) To evaluate the effect of the initial pH of the solution on the degradation efficiency of pollutants, after adding PMS in step (2), sulfuric acid or sodium hydroxide aqueous solution was added to adjust the pH of the system to 3, 5, 7, 9, and 11 respectively before conducting the above experiments. The results are shown in […]. Figure 8(The control group is the group without additional pH adjustment). Overall, the SMX removal rate increases as the pH decreases. Without pH adjustment, the overall SMX removal rate is 95%. At pH=3, the SMX removal rate increases to 98%, and at pH=11, the removal rate is also as high as 96%, confirming the wide pH applicability and catalytic stability of this invention. When the initial pH is 6.87, the bottom residue / PMS system achieves a 95% SMX degradation rate. Given the high removal rate and to avoid introducing other ions to interfere with the experiment, this invention does not adjust the pH and uses the initial pH for batch experiments.

[0054] (9) This invention also evaluated the effects of common anions on the removal of SMX from the bottom sludge / PMS system. After adding PMS in step (2), different concentrations of sulfate ions, bicarbonate ions, nitrate ions, and chloride ions were added respectively before the above experiments were conducted (added in the form of Na2SO4, NaHCO3, NaNO3, and NaCl, respectively). The results are shown in […]. Figure 9 Even with four common anions present at concentrations of 5-50 mM, the bottom sludge / PMS system still achieved a SMX removal rate exceeding 90%, demonstrating its strong resistance to ion interference. This is especially true in the presence of HCO3-. - and Cl - In the presence of these conditions, the removal efficiency is further improved, demonstrating the wide applicability of this method and its high potential for application in real water treatment processes.

[0055] The above batch experiments verified that, under the experimental conditions of room temperature and without adjusting the initial pH, the removal rate of SMX is approximately 95%.

[0056] Example 2

[0057] To fully utilize the active components of natural magnetite in the bottom ash, this invention employs a two-step dry-wet magnetic separation method to extract purer, stronger, and more representative magnetic bottom ash for catalytic experiments, verifying its effectiveness. The specific operating steps are as follows:

[0058] (1) Two-step dry-wet magnetic separation experiment: Weigh 10g of the bottom residue BA, which has been pretreated according to step (1) in Example 1, into a 1L beaker, add 500mL of deionized water, and stir with a glass rod to fully disperse the bottom residue in the water to form a suspension. Then, place a strong magnet (magnetic flux of 1 Tesla) wrapped in plastic film into the suspension and stir vigorously for 2 minutes. Then, rinse the strongly magnetic bottom residue adsorbed on the magnet with deionized water into another clean beaker. Repeat this step until no more strongly magnetic bottom residue adheres to the magnet. The collected strongly magnetic bottom residue is recorded as MBA-1, and the bottom residue remaining in the original beaker is recorded as NMBA. After filtering MBA-1 and NMBA with a 0.45μm filter membrane, they are placed in a 60℃ oven and dried to constant weight. The dried MBA-1 was then subjected to dry magnetic separation: MBA-1 was thinly spread on aluminum foil and manually swept across it with a magnet (magnetic flux of 0.6 Tesla) wrapped in a plastic film. The strongly magnetic residue adsorbed by the magnet was collected. This step was repeated until no more strongly magnetic residue adhered to the magnet. The purer and more representative strongly magnetic residue collected was designated as MBA.

[0059] (2) Catalytic experiments and data analysis were then carried out in accordance with steps (2)-(4) in Example 1.

[0060] Magnetic hysteresis loops were measured for MBA, NMBA, and BA of the simple pretreated bottom slag. The results are as follows: Figure 10 As shown, the magnetic saturation intensities of MBA, NMBA, and BA are 1.92, 0.16, and 0.94 emu / g, respectively. The magnetic saturation intensity of MBA is higher than that of BA and NMBA, which to some extent indicates that the content of magnetite components in each part decreases.

[0061] MBA, NMBA, and BA (basic pretreated residue) were subjected to catalytic experiments according to step (2) of Example 1. The results of the catalytic experiments are as follows: Figure 11 As shown, MBA outperforms simple pretreated bottom sludge BA (control group) and is superior to NMBA. The removal rates of SMX by the three combined with PMS are 96.4%, 94.8%, and 85.2%, respectively. In future practical applications of this method, magnetic separation of the bottom sludge can be considered to concentrate the effective components and more efficiently activate PMS for pollutant degradation.

[0062] In addition, to compare the catalytic effect of pure nano-Fe3O4 with the bottom slag used, in this example, nano-Fe3O4 with the same iron content (i.e., 1.344 g / L) was introduced according to the Fe content of 2.43% determined by ICP and the catalytic experiment was carried out according to step (2) of Example 1. The results are as follows. Figure 11As shown, the removal rate of SMX by the pure Fe3O4-activated PMS was only 66.8%. This is because the silicon oxides and aluminum oxides in the bottom slag used in this invention serve as the material framework, dispersing naturally occurring active components such as magnetite within them. This avoids the problem of pure Fe3O4 particle accumulation and increases the number of active reaction sites, thereby effectively improving the activation efficiency of the bottom slag for PMS. Simultaneously, the abundant Fe, Al, Mn, Cu, and other metallic components in the bottom slag have synergistic potential, which can stimulate various reactive oxygen species such as hydroxyl groups, sulfate radicals, singlet oxygen, and high-valence iron oxides, thereby better activating PMS to degrade and remove organic pollutants.

[0063] Example 3

[0064] To verify the application potential of bottom sediment in actual water bodies, this embodiment uses laboratory deionized water as a control and selects three typical actual water bodies (tap water, pond water, and river water) to prepare SMX simulated wastewater for catalytic degradation experiments. Specific information about the water samples is shown in Table 4.

[0065] Table 4. Water quality characteristics of three actual water bodies

[0066]

[0067] After collecting water samples from three locations, large particulate impurities and suspended solids were removed by filtration using a 0.22 μm filter membrane. Then, 47.5 mL of the filtrate was placed in a 150 mL beaker, and 2.5 mL of SMX stock solution with a concentration of 100 mg / L was added to prepare simulated actual wastewater with an initial SMX concentration of 5 mg / L. Catalytic experiments and data analysis were then conducted according to steps (2)-(4) in Example 1.

[0068] The results of the catalytic experiment are as follows Figure 12 As shown, bottom sediment can efficiently activate PMS to remove SMX from three simulated real wastewaters, with removal rates of 94.3% for tap water, 92.8% for pond water, and 91.3% for river water, demonstrating the broad application potential of bottom sediment in actual sewage treatment and natural water body restoration.

[0069] Example 4

[0070] To verify the removal effect of bottom-sludge activated PMS on SMX in actual wastewater, this embodiment sampled water from the inlet of two wastewater treatment plants in Shandong Province and conducted catalytic degradation experiments using real wastewater. The specific steps are as follows:

[0071] (1) Pretreatment of water samples: about 500 mL of water samples were collected from the inlets of sewage treatment plant 1 and sewage treatment plant 2 respectively, and filtered with a 0.22 μm filter membrane to remove large particulate impurities and suspended solids for later use.

[0072] (2) Catalytic degradation experiment: Take 50 mL of the filtered water sample from (1) into a 150 mL beaker, add 2 g of bottom residue and 1 mM PMS in sequence, and start the reaction. In the other control experiment, no bottom residue was added, and only 1 mM PMS was added to the water sample as a control. At 1, 5, 10, and 15 min of reaction, 1 mL of reaction solution was taken, filtered through a 0.22 μm PTFE membrane, and 0.5 mL of the filtrate was immediately added to a brown sample vial containing 0.5 mL of Na2S2O3 solution for quenching. Then, the SMX concentration was determined and the data were analyzed according to steps (3)-(4) in Example 1. The experimental results are as follows. Figure 13 As shown.

[0073] Testing revealed that the initial SMX concentrations in the influent samples from Wastewater Treatment Plant 1 and Wastewater Treatment Plant 2 were 294.1 ng / L and 362.9 ng / L, respectively. PMS activated with bottom sludge achieved 100% efficient removal within 15 minutes. Furthermore, without the addition of ash in the catalytic experiment, the removal rates of SMX from the two samples by PMS after 15 minutes of reaction were only 78.3% and 73.9%, respectively. This demonstrates the superior performance of bottom-sludge-activated PMS in rapidly and efficiently removing SMX from actual wastewater, providing an efficient and economical solution for practical wastewater treatment.

[0074] Example 5

[0075] To verify the circulation stability of the bottom ash, this embodiment conducted a bottom ash recycling experiment. The specific operating steps are as follows:

[0076] (1) Recovery and cleaning of bottom residue: The reaction liquid that underwent step (2) in Example 1 was collected and filtered using a 0.45 μm filter membrane. The filtered solid was washed three times with deionized water and ethanol, and centrifuged and separated into solid and liquid after each wash. The collected solid was then dried in an oven at 60 °C and used as a new catalyst.

[0077] (2) Cyclic catalysis experiment: The catalysis experiment and data analysis were repeated according to steps (2)-(4) in Example 1. The entire cyclic experiment was carried out four times.

[0078] Experimental results are as follows Figure 14 As shown, after four cycles, the removal rate of SMX by bottom slag activated PMS decreased, but the removal rate of SMX was still as high as 77% in the fourth cycle, which is higher than the efficiency of SMX removal by adding PMS alone (51%). This shows that bottom slag has good stability and durability as a catalyst during use. It can still have high catalytic activity after multiple cycles, which has significant practical value and application prospects.

[0079] The embodiments provided in this invention are intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the basic principles and general practices described herein can be applied to other embodiments without inventive effort. Therefore, the scope of protection of this invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the principles disclosed herein without departing from the scope of this invention should be within the scope of protection of this invention.

Claims

1. The application of bottom ash from a direct-fired power plant of agricultural and forestry biomass as a catalyst in the activation of persulfate degradation of sulfamethoxazole pollutants, wherein the agricultural and forestry biomass is a herbaceous or woody clean biomass fuel, including corn stalks, wheat stalks, rice stalks, cotton stalks, bagasse, rice husks, peanut shells, and sawdust, and the combustion ash of the agricultural and forestry biomass is bottom ash, excluding fly ash; characterized in that, First, the bottom slag is washed with tap water until the supernatant is clear, then washed with deionized water and sonicated until the supernatant is clear. Then, it is placed in an oven and dried to constant weight. Visible impurities are then removed. The bottom slag with a particle size of 0.1 mm to 0.45 mm is then crushed using a crusher. Next, the bottom slag with a particle size of 0.1 mm to 0.45 mm and persulfate are added to wastewater containing sulfamethoxazole and reacted under stirring. The bottom slag contains 1.0-3.0 wt% iron, 1.5-6.5 wt% iron oxide, and 0.45-2.0 wt% Fe3O4; the initial concentration of sulfamethoxazole in the wastewater is 1-15 mg / L, and the final concentration of persulfate added to the wastewater is 0.5-4 mM; the dosage of the bottom slag is 10-60 g / L.

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