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

Abstract

The invention relates to the technical field of solid waste resourceful treatment, in particular to application of endogenous magnetic bottom slag activated persulfate in a biomass direct-fired power plant to degradation of sulfamethoxazole pollutants. According to the method, the bottom slag generated by combustion of the grate furnace of the biomass direct-fired power plant is screened after being cooled, and the bottom slag with the particle size ranging from 0.1 mm to 0.45 mm is collected. Bottom slag contains endogenous magnetite components, green activation of peroxymonosulfate (PMS) can be achieved, and the method is used for degrading and removing common organic pollutant sulfamethoxazole (SMX) in water. The adsorption rate of the bottom slag to SMX is less than 2%; compared with single use of PMS, the degradation rate of SMX can be obviously increased from 51% to 95% or above by adding the bottom slag with the particle size. Under the interference of water anions (SO4 < 2->, HCO3 <->, NO3 <-> and Cl <->), more than 90% of SMX in the bottom slag can be removed.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource treatment, in particular to an application of persulfate activated by magnetic bottom slag generated in a biomass direct-fired power plant to degrade sulfamethoxazole pollutants. Background Art

[0002] Biomass power generation technology is gaining increasing attention. Grate incineration is the mainstream method for direct combustion of agricultural and forestry biomass for power generation, primarily using rice and wheat straw and tree branches. The direct combustion of these crop wastes produces large amounts of ash, including fly ash and bottom ash. Most of the ash particles generated by grate incineration are deposited on the grate, forming bottom ash, which accounts for 85% of the total ash volume. Consequently, this significant amount of bottom ash solid waste urgently requires resource management.

[0003] Currently, the main disposal methods for bottom ash are landfill and resource utilization. Landfill is simple to operate, but it consumes a large amount of land resources. Resource utilization options include using it for roadbeds, cement additives, and soil conditioners. Existing resource utilization methods fail to fully utilize the porous structure and multi-element enrichment properties of bottom ash, resulting in resource waste. Therefore, a method for realizing high-value-added resource utilization of bottom ash from biomass direct-fired power plants is urgently needed. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides an application method for activating persulfate to degrade sulfamethoxazole pollutants using endogenous magnetic bottom ash from biomass direct-fired power plants. The present invention uses the bottom ash after simple pretreatment as a catalyst for the degradation of sulfamethoxazole (SMX) by persulfate (PMS). The bottom ash is rich in magnetite components mainly composed of natural Fe3O4 and efficiently activates PMS to produce a variety of active oxygen species to degrade the organic pollutant SMX. The catalyst is derived from naturally magnetic bottom ash and does not produce secondary pollutants. It is an innovative and green treatment method.

[0005] The purpose of the present invention can be achieved by the following technical steps:

[0006] The invention discloses an application of persulfate as a catalyst to activate magnetic bottom slag generated in a biomass direct-fired power plant to degrade sulfamethoxazole pollutants.

[0007] Furthermore, the application is: after washing, removing impurities, drying and grinding the bottom ash of the biomass direct-fired power plant, it is successively added with peroxymonosulfate into the wastewater containing sulfamethoxazole, and the mixture is reacted under stirring.

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

[0009] Furthermore, the biomass source of the bottom residue is herbaceous or woody clean biomass fuel, including corn straw, wheat straw, rice straw, cotton stalks, sugarcane bagasse, rice husks, peanut shells, wood chips and other agricultural and forestry wastes, excluding activated sludge, municipal solid waste, and domestic garbage; the collected combustion ash is bottom residue, excluding fly ash.

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

[0011] Furthermore, in the 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 amount of bottom slag added is 10-60 g / L, preferably 40 g / L, that is, 2 g of bottom slag is added to every 50 mL of reaction solution.

[0014] In the present invention, bottom ash effectively activates PMS, generating reactive oxygen species such as hydroxyl radicals, sulfate radicals, singlet oxygen, and high-valent iron oxides. This is due to the iron absorption of the soil by crops used as precursors to the bottom ash, as well as the introduction of iron-containing materials during biomass collection and equipment wear. These iron-containing materials are calcined at high temperatures of 550-900°C in the grate furnace, converting the elemental iron in the bottom ash into iron oxides. Furthermore, 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, which possess potential catalytic activity.

[0015] The present invention addresses the current problem of large amounts of bottom ash generated and the inability of existing treatment and disposal technologies to fully utilize its high metal content and other characteristics for resource utilization. A simple pretreatment is used to activate the bottom ash as a catalyst for the PMS degradation SMX experiment. Compared with the existing technology, this resource utilization treatment method has the following advantages and beneficial effects:

[0016] (1) Highly utilize the iron oxides contained in the bottom ash of biomass direct-fired power plants, especially the active component of magnetite mainly composed of Fe3O4, to achieve high utilization rate and high added value of magnetic bottom ash;

[0017] (2) Innovatively explore the advantages of the structure and composition of bottom ash. The silicon oxide and aluminum oxide in the bottom ash serve as the material skeleton, dispersing active ingredients such as magnetite in it, which not only avoids the problem of pure Fe3O4 particle accumulation, but also increases the active sites of the reaction, thereby effectively improving the activation efficiency of the bottom ash for PMS. At the same time, the rich metal components such as Fe, Al, Mn, Cu in the bottom ash have the potential for synergistic effects, which can stimulate a variety of active oxygen species such as hydroxyl, sulfate radicals, singlet oxygen and high-valent iron oxides, thereby specifically degrading and removing organic pollutants;

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

[0019] (4) The heavy metal content in the bottom ash of biomass direct-fired power plants is extremely low, and there is no secondary pollution during use. It is a green, environmentally friendly, and energy-efficient resource utilization method. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0022] Figure 3 This is the XRD analysis of the bottom slag after pretreatment in Example 1;

[0023] Figure 4 This is the XPS analysis of the bottom slag after pretreatment in Example 1;

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

[0025] Figure 6 The effect of the amount of bottom slag added on the degradation effect in Example 1;

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

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

[0028] Figure 9 The effects of the four anions on the degradation effect when they exist in Example 1 are shown below:

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

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

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

[0032] Figure 13 The SMX removal effect on actual wastewater in Example 4;

[0033] Figure 14 The catalytic performance of the initial bottom slag and the bottom slag after four cycles of use. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is specifically and detailed below in conjunction with the embodiments of the present invention and the accompanying drawings.

[0035] The bottom ash is the bottom ash produced by agricultural and forestry biomass direct-fired power plants. The source of agricultural and forestry biomass is herbaceous or woody clean biomass fuel, including corn straw, wheat straw, rice straw, cotton stalks, sugarcane bagasse, rice husks, peanut shells, wood chips and other agricultural and forestry wastes; the collected combustion ash of agricultural and forestry biomass is the bottom ash, and does not include fly ash.

[0036] In the following examples, the raw material bottom ash was taken from a biomass direct-fired power plant in Anhui Province (the main biomass sources were rice, wheat straw, and waste wood); the bottom ash samples were subjected to X-ray fluorescence spectroscopy (XRF) analysis and inductively coupled plasma spectroscopy (ICP) analysis, 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 of main metal elements in bottom ash of agricultural and forestry biomass direct-fired power plants (wt%)

[0040]

[0041] The analysis results in Tables 1 and 2 show that the main components of bottom ash from agricultural and forestry biomass direct-fired 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 bottom ash from agricultural and forestry biomass direct-fired power plants is extremely low, causing no secondary pollution or harm to the environment.

[0042] Example 1

[0043] This embodiment provides a biomass direct-fired power plant magnetic bottom ash as a catalyst for activating PMS to degrade the organic pollutant SMX, including the following steps:

[0044] (1) Pretreatment of bottom slag: Wash the raw material with tap water several times until the supernatant is transparent. Then wash with deionized water and ultrasonicate for 10 minutes, repeat three times, then put the filtered solid into an oven and dry it at 60°C to constant weight. After drying, manually pick out the obvious yellow bricks, white quartz sand, branches, nails and other impurities visible to the naked eye. Then use a crusher to crush the large-particle ash, and then pass it through 40 mesh and 150 mesh sieves, and collect ash BA with a particle size between the two, that is, 0.1mm to 0.45mm, for experiments. The collected ash has a slight metallic luster, is gray, and has the morphology of irregular spherical and fragmented particles (see Figure 1 ), stored in a dark and dry place for future use. The SEM, XRD and XPS results are shown in Figure 2-Figure 4 As shown in the figure, the results show that the surface of the slag contains C, O, Si, Fe and other elements. After X-ray diffraction (XRD) analysis, the bottom slag was confirmed to contain iron oxides, including Fe2O3 and Fe3O4. After X-ray photoelectron spectroscopy (XPS) analysis ( Figure 4 In the figure, the upper figure shows the bottom slag after pretreatment, and the lower figure shows the bottom slag after 2 hours of catalytic reaction (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%. From this, it was calculated that Fe3O4 accounted for 30.52% of the iron oxides. After the catalytic reaction, the proportion of divalent iron and trivalent iron changed, confirming that iron participated in the reaction and that there was mutual conversion between different valence states.

[0045] (2) Experimental procedure for the catalytic reaction: Weigh 2 g of pretreated residue into a 150 mL beaker, then measure 50 mL of the initial 5 mg / L sulfamethoxazole (SMX) solution, stir magnetically at 200 rpm, and add 0.5 mL of 100 mM PMS stock solution (final concentration 1 mM). The mixture is allowed to react at room temperature for 2 h. The reaction begins when PMS is added. 1 mL of the reaction solution is drawn at 15, 30, 60, 90, and 120 min, filtered through a 0.22 μm PTFE membrane, and 0.5 mL of the filtrate is immediately added to a brown injection vial containing 0.5 mL of Na2S2O3 solution for quenching.

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

[0047] Table 3UPLC parameter conditions

[0048]

[0049] (4) Data processing and effect evaluation: The corresponding SMX concentration was calculated using the sample peak area obtained in (3), and the removal rate, mean, and error bar were calculated, and finally a dot-line graph was drawn.

[0050] (5) In order to evaluate the effect of the initial concentration of SMX on the degradation efficiency of pollutants, SMX solutions with a concentration gradient of 1-15 mg / L were prepared using a 100 mg / L SMX mother solution. The above test was carried out with different initial concentrations of SMX, namely 1, 2, 10, and 15 mg / L. The results are shown in Figure 5 The bottom slag / PMS system achieved a removal rate of over 90% for SMX at various concentrations. When the initial SMX concentration was ≤2 mg / L, 100% removal was achieved within 15 minutes. For initial concentrations of 5 and 10 mg / L, 95% efficient removal was achieved within 120 minutes. Overall, the SMX removal rate decreased with increasing initial concentrations. The present invention conducted batch experiments using an SMX concentration of 5 mg / L, which is higher than the environmental concentration, to expand its environmental applicability.

[0051] (6) In order to evaluate the effect of the amount of bottom slag added on the pollutant degradation efficiency, the above test was carried out with different weights of the pretreated bottom slag at 0, 0.5, 1, 1.5 and 3 g. The results are shown in the figure. Figure 6 When no bottom ash was added, the degradation rate of SMX by PMS was only 51% after 120 minutes. The addition of bottom ash significantly improved the degradation rate, and it increased with the increase of the amount of bottom ash added. When 2g of bottom ash 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 the early treatment of bottom ash, the present invention selected a dosage of 2g for batch experiments;

[0052] (7) In order to evaluate the effect of PMS dosage on pollutant degradation efficiency, the above test was carried out with different PMS final concentrations of 0, 0.5, 2, and 4 mM. The results are shown in the figure. Figure 7 Without PMS, the removal of SMX by the bottom residue was considered to be adsorption, with a rate of only 1.7%. As the PMS concentration increased, the SMX removal rate gradually increased. When the PMS dosage exceeded 2mM, 100% removal was achieved. To avoid excessive PMS in the environment, the present invention selected a 1mM dosage for subsequent batch experiments.

[0053] (8) In order 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, and the above test was carried out. The results are shown in the figure. Figure 8(The control group is the group without additional pH adjustment). Overall, the SMX removal rate increases with decreasing pH. Without adjusting the pH, the overall SMX removal rate is 95%. At pH = 3, the SMX removal rate increases to 98%. At pH = 11, the removal rate is as high as 96%, confirming the wide pH applicability and catalytic stability of the present invention. When the pH is not adjusted, the initial pH is 6.87, and the SMX degradation rate of the bottom slag / PMS system is 95%. In view of the high removal rate and to avoid introducing other ions to interfere with the experiment, the present invention does not adjust the pH and uses the initial pH for batch experiments.

[0054] (9) The present invention also evaluated the effect of common anions on the removal of SMX by the bottom slag / PMS system. After adding PMS in step (2), different concentrations of sulfate ions, bicarbonate ions, nitrate ions, and chloride ions were added and the above test was carried out (added in the form of Na2SO4, NaHCO3, NaNO3, and NaCl, respectively). The results are shown in FIG. Figure 9 , when the four common anions are present at a concentration of 5-50mM, the removal rate of SMX by the bottom slag / PMS system is still higher than 90%, indicating that the system has a strong ability to resist ion interference. - and Cl - In the presence of , the removal efficiency is further improved, further demonstrating the wide applicability of this method and its high potential for application in real water treatment processes.

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

[0056] Example 2

[0057] In order to fully utilize the natural magnetite active components in the bottom slag, the present invention uses a two-step dry-wet magnetic separation method to extract a purer, more magnetic, and more representative magnetic bottom slag for catalytic experiments to verify its effectiveness. The specific operation steps are:

[0058] (1) Two-step dry-wet magnetic separation experiment: Weigh 10g of bottom residue BA that has been simply pretreated according to step (1) in Example 1 into a 1L large 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 put a strong magnet (magnetic flux of 1 Tesla) wrapped in plastic film into the suspension, stir vigorously for 2 minutes, and then rinse the strong magnetic bottom residue adsorbed on the magnet with deionized water into another clean beaker, and repeat this step until there is no strong magnetic bottom residue attached to the magnet. The collected strong magnetic bottom residue is recorded as MBA-1, and the bottom residue remaining in the original beaker is recorded as NMBA. MBA-1 and NMBA are filtered using a 0.45μm filter membrane respectively, and then placed in a 60℃ oven to dry to constant weight. The dried MBA-1 is then subjected to dry magnetic separation: MBA-1 is spread thinly on aluminum foil and manually swept over with a magnet (magnetic flux of 0.6 Tesla) wrapped in plastic film, collecting the strongly magnetic bottom residue attracted by the magnet. This process is repeated until no more strongly magnetic bottom residue remains. The collected, purer and more representative strong magnetic bottom residue is designated as MBA.

[0059] (2) Catalytic experiments and data analysis were then performed according to steps (2) to (4) in Example 1.

[0060] The hysteresis loops of MBA, NMBA and simple pre-treated bottom slag BA were measured. 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 component in each part decreases.

[0061] MBA, NMBA and simple pre-treated bottom slag BA were subjected to catalytic tests according to step (2) of Example 1. The catalytic test results are shown in Figure 2. Figure 11 As shown, MBA outperformed the simple pretreated bottom ash BA (control) and even outperformed NMBA. The three synergistically combined with PMS for SMX removal efficiencies of 96.4%, 94.8%, and 85.2%, respectively. Future practical applications of this method could consider magnetic separation of the bottom ash to concentrate the active ingredients for more efficient PMS activation and pollutant degradation.

[0062] In addition, in order to compare the catalytic effect of pure nano-Fe3O4 with that of the bottom slag used, 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 in this example, and a catalytic experiment was carried out according to step (2) of Example 1. The results are shown in FIG. Figure 11As shown, the SMX removal rate of the introduced pure Fe₃O₄ activated PMS is only 66.8%. This is because the silicon oxide and aluminum oxide in the bottom ash used in the present invention serve as the material framework, dispersing naturally occurring active ingredients such as magnetite within it. This not only avoids the problem of pure Fe₃O₄ particle accumulation, but also increases the number of active sites for the reaction, thereby effectively improving the bottom ash's activation efficiency for PMS. Furthermore, the rich metal components of the bottom ash, such as Fe, Al, Mn, and Cu, have the potential for synergistic effects, stimulating a variety of reactive oxygen species, such as hydroxyl radicals, sulfate radicals, singlet oxygen, and high-valent iron oxides, thereby better activating PMS to degrade and remove organic pollutants.

[0063] Example 3

[0064] To validate the potential of bottom slag in real-world water applications, this example used laboratory deionized water as a control. Three other typical water sources (tap water, pond water, and river water) were also selected to prepare SMX simulated wastewater for catalytic degradation experiments. Detailed 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 the three locations, they were filtered through a 0.22 μm membrane to remove large impurities and suspended solids. 47.5 mL of the filtrate was then placed in a 150 mL beaker and 2.5 mL of a 100 mg / L SMX stock solution was added to create simulated real-world wastewater with an initial SMX concentration of 5 mg / L. Catalytic experiments and data analysis were then performed according to steps (2)-(4) of Example 1.

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

[0069] Example 4

[0070] To verify the removal effect of PMS activated by bottom residue on SMX in actual wastewater, this example collected samples from the water inlets of two sewage treatment plants in Shandong Province and conducted a catalytic degradation experiment using real wastewater. The specific steps were as follows:

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

[0072] (2) Catalytic degradation experiment: Take 50 mL of the filtered water sample in (1) and put it into a 150 mL beaker. Add 2 g of bottom slag and PMS with a final concentration of 1 mM in sequence to start the reaction. In another group of control experiments, no bottom slag was added. Only PMS with a final concentration of 1 mM was added to the water sample as a control. 1 mL of the reaction solution was drawn at 1, 5, 10, and 15 minutes of reaction, respectively, and filtered through a 0.22 μm PTFE filter membrane. Then 0.5 mL was drawn from the filtrate and immediately added to a brown injection vial containing 0.5 mL of Na2S2O3 solution for quenching. Subsequently, the SMX concentration was determined and the data analyzed according to steps (3)-(4) in Example 1. The experimental results are shown as follows: Figure 13 shown.

[0073] Testing revealed initial SMX concentrations of 294.1 ng / L and 362.9 ng / L in the influent samples from Wastewater Treatment Plants 1 and 2, respectively. The PMS, activated with ash, achieved 100% efficient removal within 15 minutes. Meanwhile, without the addition of ash, the PMS removal rates for SMX in the two water samples after 15 minutes were only 78.3% and 73.9%, respectively. This demonstrates the excellent effectiveness of ash-activated PMS in rapidly and efficiently removing SMX from actual wastewater, providing an efficient and cost-effective solution for practical wastewater treatment.

[0074] Example 5

[0075] In order to verify the cyclic stability of bottom ash, this embodiment carried out a bottom ash recycling experiment. The specific operation steps are:

[0076] (1) Recovery and Cleaning of Bottom Residue: The reaction solution treated in step (2) of 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, followed by centrifugation and solid-liquid separation after each wash. The collected solid was then dried in an oven at 60°C and used as a new catalyst.

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

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

[0079] The embodiments provided herein 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 the embodiments and that the basic principles and general implementation measures described herein can be applied to other embodiments without requiring creative effort. Therefore, the scope of protection of the present invention is not limited to the above-described embodiments. Any improvements and modifications made by those skilled in the art based on the principles disclosed herein that do not depart from the scope of the present invention should fall within the scope of protection of the present invention.

Claims

1. The application of magnetic bottom ash generated in a biomass direct-fired power plant as a catalyst in the activation of persulfate to degrade sulfamethoxazole pollutants.

2. The use according to claim 1, characterized in that The application is as follows: after washing, removing impurities, drying and grinding the bottom slag from a biomass direct-fired power plant, the bottom slag and peroxymonosulfate are successively added to wastewater containing sulfamethoxazole, and the mixture is reacted under stirring.

3. The use according to claim 2, characterized in that The specific operations of washing, removing impurities, drying and grinding are as follows: first, the bottom residue is washed with tap water until the supernatant is transparent, then washed with deionized water and ultrasonicated until the supernatant is transparent, then placed in an oven, dried to constant weight, and impurities visible to the naked eye are selected, and then crushed with a crusher to collect bottom residue with a particle size of 0.1 mm to 0.45 mm.

4. The use according to claim 2, characterized in that The biomass source of the bottom slag is herbaceous or woody clean biomass fuel.

5. The use according to claim 2, characterized in that The bottom ash has an iron content of 1.0-3.0 wt%, an iron oxide content of 1.5-6.5 wt%, and a Fe3O4 content of 0.45-2.0 wt%.

6. The use according to claim 2, characterized in that In the application, the initial concentration of sulfamethoxazole in the wastewater is 1-15 mg / L; and / or The final concentration of peroxymonosulfate added to the wastewater was 0.5-4 mM.

7. The use according to claim 2, characterized in that The amount of bottom slag added in the application is 10-60 g / L.

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