A mixture for activating persulfate to enhance the degradation of sulfamethoxazole in soil, its preparation method and application

Abstract

The present invention discloses a mixture capable of activating persulfate to enhance the degradation of sulfamethoxazole in soil, and a preparation method and application thereof, which relates to the technical field of substances for activating persulfate and their preparation methods and applications. The preparation method includes: crushing straw and passing it through a sieve, heating the powder obtained by the sieve to a constant temperature, and pyrolyzing it at a constant temperature to obtain biochar for standby; secondly, weighing FeS-Fe<supgt;0< / supgt; and biochar powder respectively and putting them into a grinding cup, and zirconia balls are placed in the grinding cup; finally, grinding the mixture in step 2 under the set grinding parameters to obtain a mixture of Fe<supgt;0< / supgt>-FeS and biochar; wherein, the grinding parameters in step 3 are a rotation speed of 300 rpm - 500 rpm, a grinding time of 10 h - 14 h, and changing the ball milling direction every 2 h - 4 h, and the whole grinding process is carried out in an inert atmosphere. The present invention adopts a ball milling method to synthesize a mixture (Fe<supgt;0-FeS@BC), the preparation method is simple, the operability is strong, and the activation performance is high.

Description

Technical Field

[0001] The present invention relates to the technical field of substances for activating persulfate, their preparation methods and applications, and particularly relates to a mixture capable of activating persulfate to enhance the degradation of sulfamethoxazole in soil, its preparation method and application. Background Art

[0002] Antibiotics have broad-spectrum antibacterial ability because they can inhibit the synthesis of bacterial cell walls, interact with cell membranes, and interfere with protein synthesis. In recent decades, they have played an important role in the fields of medicine, animal husbandry, agricultural production, etc. However, the abuse and incomplete metabolism of antibiotics have inevitably led to the entry of antibiotics into the ecological environment, causing surface water, groundwater and soil pollution. Sulfonamides (SAs) are one of the most widely used antibiotics, and sulfamethoxazole (SMX) is a typical sulfonamide compound used in veterinary medicine. In many countries, the detection rate of SMX is still very high and it accumulates in soil for a long time, although its residual rate is relatively low (0 - 10 mg / kg). In addition, the low-concentration bioaccumulation of SMX in soil can also cause serious ecosystem and health risks after long-term exposure, such as inhibiting microbial activities, inducing bacterial resistance, teratogenicity, mutagenicity, carcinogenicity and hormonal abnormalities. Therefore, it is very necessary to conduct comprehensive research considering efficient and economical technologies to repair soil contaminated by antibiotics.

[0003] Persulfate (PS) is one of the most commonly used oxidants in the remediation of organic pollution. Due to its high efficiency and low cost, extensive research has been conducted on its use in removing antibiotic pollutants in water. However, only a few studies have reported its application in degrading organic pollutants in soil. Generally, the self-transformation process of PS is relatively slow, and external activation of PS is required to generate reactive oxygen species (ROS). Previous studies have shown that PS can be activated by various methods to produce ROS, which can effectively degrade organic pollutants, such as thermal activation, ultraviolet activation, ultrasonic activation, alkali activation, microwave activation, carbonaceous material activation, and transition metal activation. However, some of these methods have been proven to be inappropriate for soil remediation. Ultraviolet activation is difficult to penetrate the soil matrix, while thermal activation and ultrasonic activation require a large amount of energy input. In addition, alkali activation requires a large amount of alkaline materials and may damage the soil properties. In contrast, catalyst activation of PS, such as transition metals and eco-friendly carbonaceous materials, is more adaptable in the remediation of soil organic pollution. Recently, composite materials combining transition metals with biochar (BC) have been widely studied for degrading organic pollutants because BC can provide active sites and reduce the aggregation of magnetic particles. Iron-based materials are often used as raw materials due to their low cost and high reactivity. Hussain et al. used biochar to disperse nano zero-valent iron to effectively degrade nonylphenol in aqueous solution. Shan et al. used nZVI-Ni@BC materials and stabilized catalytic persulfate to degrade trichloroethylene in water. However, many studies have shown that due to surface passivation, Fe 0 has a low adaptability for the remediation of organic polluted soil. In addition, Fe 0 is easily oxidized, and this oxidation process consumes a large amount of electrons, which are involved in the activation of persulfuric acid and the removal of pollutants.

[0004] Some studies have shown that iron sulfide (FeS) also has the ability to activate PS and can maintain an appropriate concentration of Fe2+ in the system. However, some disadvantages of FeS in application have been revealed. The aggregation of magnetic particles in the system and its low catalytic activity limit the pollutant degradation rate. Therefore, hybrid materials made of different materials are used as an improved method to overcome these limitations. Previous studies have found that the hybrid material of ZVI and FeS inherits the advantages of FeS and Fe 0 The passivation of Fe 0 is inhibited, and high catalytic activity is shown. However, a decrease in degradation efficiency due to particle aggregation is still found. Because BC has good dispersibility for iron-based materials, Fe 0 、FeS and the heterogeneous combination of BC (Fe 0-FeS@BC) may be a feasible way to repair organically contaminated soil. However, there are few reports on using a mixture of ZVI and FeS as a PS catalyst, and there is no report on the study of removing SMX from soil by combining Fe 0 and FeS with BC. In addition, traditional methods for synthesizing FeS, Fe 0 and BC composites often require complex procedures, may cause secondary pollution, and are costly. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the activation intensity of substances that can activate persulfate to enhance the degradation of sulfamethoxazole in soil is not high, and the preparation method is complex. The purpose is to provide a mixture that can activate persulfate to enhance the degradation of sulfamethoxazole in soil, its preparation method and application to solve the above problems.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present application provides a preparation method for a mixture that can activate persulfate to enhance the degradation of sulfamethoxazole in soil, including the following steps;

[0008] Step 1: Crush the straw and pass it through a filter sieve. After heating the powder obtained from the filter sieve to a constant temperature, pyrolyze it at a constant temperature to obtain biochar for standby;

[0009] Step 2: Weigh FeS-Fe 0 and biochar powder respectively and put them into a grinding cup, and zirconia balls are placed in the grinding cup;

[0010] Step 3: Grind the mixture in Step 2 under the set grinding parameters to obtain a ball-milled mixture of Fe 0 -FeS and biochar;

[0011] Among them, the grinding parameters in Step 3 are a rotation speed of 300 rpm - 500 rpm, a grinding time of 10 h - 14 h, and the ball-milling direction is changed every 2 h - 4 h. The entire grinding process is carried out in an inert atmosphere.

[0012] Furthermore, the aperture of the filter sieve in Step 1 is 0.1 mm - 0.2 mm, the equipment used for heating is a muffle furnace, the heating rate is 7 °C / min - 13 °C / min, and the biochar is obtained by pyrolyzing at 450 °C - 550 °C for 1.5 h - 2.5 h at the heating rate.

[0013] Furthermore, the mass ratio of FeS-Fe 0 and biochar powder in Step 2 is 1:10 - 1:2.5, and the mass ratio of FeS and Fe 0The molar ratio is 0.5:1 - 2:1.

[0014] Furthermore, the particle size of the zirconia balls is 3 mm - 15 mm.

[0015] Furthermore, the particle sizes of the zirconia balls are mainly 15 mm, 5 mm, and 3 mm, and the mass ratio of the zirconia balls of the three particle sizes is 2:5:3.

[0016] Furthermore, in the grinding cup in step 2, the mass ratio of the zirconia balls to the FeS - Fe 0 and biochar powder is 40:1 - 60:1.

[0017] Furthermore, in step 2, the mass ratio of the FeS - Fe 0 and biochar powder is 1:7.5.

[0018] The present invention also provides a mixture capable of activating persulfate to enhance the degradation of sulfamethoxazole in soil, and the mixture is prepared by the above preparation method.

[0019] To achieve the above object, the present application also proposes an application of a mixture capable of activating persulfate to enhance the degradation of sulfamethoxazole in soil, including the following steps:

[0020] S1: Mix the soil and the persulfate solution, and the mass ratio of the soil to the solvent is 1:12 - 1:1;

[0021] S2: Adjust the pH, and then add the mixture and mix, and the mass ratio of the mixture to the soil is 0.005 - 0.01:3.

[0022] Furthermore, in S1, the molar concentration of the persulfate solution is 5 mM - 30 mM, and in S2, the pH is 3 - 9.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) The present application uses the ball milling method to synthesize a mixture of Fe 0 -FeS and biochar (BC) (Fe0 - FeS@BC), and synthesizes a mixture for activating persulfate (PS) through mechanochemical modification by fully rubbing and colliding the material mixture. The preparation method is simple, highly operable, and the obtained mixture has high activation performance;

[0025] (2) Using the mixture of Fe 0 -FeS and biochar prepared in the present application has great potential for soil remediation. At the same time, the Fe 0- The mass ratio of FeS and biochar, the initial pH value during use, the concentration of persulfate, the mass ratio of soil and solvent, Fe 0 - The mixture of FeS and biochar (Fe 0 -FeS@BC) dosage on soil remediation to obtain an efficient solution. Description of the Drawings

[0026] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings. In the drawings:

[0027] Figure 1 is the degradation situation diagram of SMX in the Fe 0 -FeS@BC system and SMX in Fe 0 , FeS, Fe 0 -FeS, blank system respectively;

[0028] Figure 2 is the Fe obtained by the preparation method of Example 3 0 -FeS@BC system and the dynamic change diagram of Fe in Fe 0 , FeS, Fe 0 -FeS system respectively; 2+ of Fe

[0029] Figure 3 is the PS conversion rate diagram in the Fe 0 -FeS@BC system obtained by the preparation method of Example 3;

[0030] Figure 4 is the Fe obtained by the preparation method of Example 3 0 -FeS@BC system in Fe 0 -FeS@BC before use (a) and after use (b) Fe 2p XPS spectra;

[0031] Figure 5 a is the EDS spectrum of S; Figure 5 b is the EDS spectrum of C; Figure 5 c is the EDS spectrum of Fe; Figure 5 d and Figure 5 e are the SEM images of Fe 0 -FeS@BC;

[0032] Figure 6 is the Fe prepared in Examples 1-4 and Comparative Example 10 Schematic diagram of the effect of -FeS@BC on SMX degradation;

[0033] Figure 7 is the Fe prepared in Example 3 0 Schematic diagram of the effect of the dose of -FeS@BC on SMX degradation;

[0034] Figure 8 is the Fe prepared in Example 3 0 Schematic diagram of the effect of different initial pH values selected by -FeS@BC on SMX degradation;

[0035] Figure 9 is the Fe prepared in Example 3 0 Schematic diagram of the effect of -FeS@BC on SMX degradation under different soil-water mass ratio conditions;

[0036] Figure 10 is the Fe prepared in Example 3 0 Schematic diagram of the effect of -FeS@BC on SMX degradation at different PS concentrations;

[0037] Figure 11 is the Fe prepared in Example 3 0 Schematic diagram of the removal effect of -FeS@BC using different types of scavengers on SMX in the soil system;

[0038] Figure 12 is the Fe prepared in Example 3 0 Schematic diagram of the removal effect of -FeS@BC using different types of scavengers on SMX in the water system;

[0039] Figure 13 is the Fe prepared in Example 3 0 Schematic diagram of the removal effect of -FeS@BC using different types of scavengers on SMX in the water + MF system;

[0040] Figure 14 is the Fe prepared in Example 3 0 Schematic diagram of the removal effect of -FeS@BC using different types of scavengers on SMX in the water + HA system;

[0041] Figure 15 is · EPR spectra of OH and SO4 ·- ;

[0042] Figure 16 is 1 EPR spectrum of O2;

[0043] Figure 17 is the EPR spectrum of O2 ·- ;

[0044] Figure 18 is the EPR spectrum of PFR;

[0045] Figure 19 is Fe prepared in Example 3 0 -FeS@BC schematic diagram of the influence of HA on SMX removal during application;

[0046] Figure 20 is Fe prepared in Example 3 0 -FeS@BC in PS / SMX, Fe 3+ / PS / SMX, Fe 3+ / Phen / PS / SM, Fe 3+ / EDTA / PS / SMX system schematic diagram of SMX degradation;

[0047] Figure 21 is SMX in BC / PS / SMX, BC / Fe 3+ / PS / SMX and BC / Fe 3+ / PS / SMX / EDTA system degradation schematic diagram;

[0048] Figure 22 is BC / Fe 3+ / PS / SMX system Fe 2+ concentration change diagram;

[0049] Figure 23 is a schematic diagram of possible degradation pathways of SMX.

[0050] Note: FeS-Fe 0 : mixture of FeS and Fe 0 ; PS: persulfate; BC: biochar; Fe 0 -FeS@BC: ball-milled mixture of FeS, Fe 0 and BC; SOM: soil organic matter; SMX: sulfamethoxazole; PFRs: persistent free radicals; ROS: reactive oxygen species; HA: humic acid; MF: mineral components; EDTA: ethylenediaminetetraacetic acid. Detailed implementation manners

[0051] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0052] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0053] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0054] Research on a mixture capable of activating persulfate to enhance the degradation of sulfamethoxazole in soil, its preparation method and application

[0055] (1) Soil samples

[0056] The soil was taken from within the top 20 cm depth. After removing plant roots and stones, the soil samples were air-dried, ground, passed through a 0.42 mm sieve at 25 °C, and then stored at 6 °C. A total of 20 mg of SMX acetone solution was added to 1 kg of soil and mixed thoroughly. Then the SMX-contaminated soil was placed in a fume hood and left to volatilize naturally for 2 weeks until the acetone had completely volatilized. Finally, the SMX concentration in the soil samples reached 25 mg·kg -1 .

[0057] (2) Synthesis of Fe 0 -FeS@BC

[0058] Comparative Example 1

[0059] A preparation method of a mixture capable of activating persulfate to enhance the degradation of sulfamethoxazole in soil is provided:

[0060] Step 1: Crush corn straw with a crusher, then filter it through a sieve with a pore size of 0.1 mm - 0.2 mm. Heat the filtered powder at a heating rate of 7 °C / min - 13 °C / min to a temperature of 450 °C - 550 °C and pyrolyze for 1.5 h - 2.5 h to obtain biochar for standby;

[0061] Step 2: Mix FeS-Fe 0 and biochar powder in a certain mass ratio of 1:1, accurately weigh and place them in a grinding cup containing zirconia balls, where the molar ratio of FeS and Fe 0 is 0.5:1 - 2:1;

[0062] Step 3: Under the conditions that the ball milling parameters are set to 300 rpm - 500 rpm, the grinding time is 10 h - 14 h, the direction of ball milling is changed every 2 h - 4 h, and nitrogen is purged during the whole grinding process, grind the mixture in Step 2 to obtain a mixture of Fe 0 -FeS and biochar (Fe 0 -FeS@BC);

[0063] Among them, the zirconia balls include zirconia balls with diameters of 15 mm, 5 mm, and 3 mm respectively, and the mass ratio of the zirconia balls of different sizes is 2:5:3. The mass ratio of the zirconia balls to the FeS-Fe 0 and biochar powder is 40:1 - 60:1.

[0064] Example 1

[0065] Provide a preparation method of a mixture that can activate persulfate to enhance the degradation of sulfamethoxazole in soil:

[0066] Step 1: Crush corn straw with a crusher, then filter it through a sieve with a pore size of 0.1 mm - 0.2 mm. Heat the filtered powder to a temperature of 450 °C - 550 °C at a heating rate of 7 °C / min - 13 °C / min, and pyrolyze for 1.5 h - 2.5 h to prepare biochar for standby;

[0067] Step 2: Mix FeS-Fe 0 and biochar powder according to a certain mass ratio of 1:2.5, accurately weigh and put them into a grinding cup containing zirconia balls. Among them, the molar ratio of FeS to Fe 0 is 0.5:1 - 2:1;

[0068] Step 3: Under the conditions that the ball milling parameters are set to 300 rpm - 500 rpm, the grinding time is 10 h - 14 h, the direction of ball milling is changed every 2 h - 4 h, and nitrogen is purged during the whole grinding process, grind the mixture in Step 2 to obtain a mixture of Fe 0 -FeS and biochar (Fe 0 -FeS@BC);

[0069] Among them, the zirconia balls include zirconia balls with diameters of 15 mm, 5 mm, and 3 mm respectively, and the mass ratio of the zirconia balls of different sizes is 2:5:3. The mass ratio of the zirconia balls to the FeS-Fe 0 and biochar powder is 40:1 - 60:1.

[0070] Example 2

[0071] Provide a preparation method of a mixture that can activate persulfate to enhance the degradation of sulfamethoxazole in soil:

[0072] Step 1: Crush corn straw with a crusher, then filter it through a sieve with a pore size of 0.1 mm - 0.2 mm. Heat the filtered powder at a heating rate of 7 °C / min - 13 °C / min to a temperature of 450 °C - 550 °C, and then pyrolyze it for 1.5 h - 2.5 h to prepare biochar for standby;

[0073] Step 2: Mix FeS - Fe 0 and biochar powder in a certain mass ratio of 1:5, accurately weigh and put them into a zirconia ball milling cup. The molar ratio of FeS and Fe 0 is 0.5:1 - 2:1;

[0074] Step 3: Under the conditions that the ball milling parameters are set to 300 rpm - 500 rpm, the milling time is 10 h - 14 h, the ball milling direction is changed every 2 h - 4 h, and nitrogen is purged during the whole milling process, mill the mixture in Step 2 to obtain a mixture of Fe 0 -FeS and biochar (Fe 0 -FeS@BC);

[0075] The zirconia balls include zirconia balls with diameters of 15 mm, 5 mm, and 3 mm respectively. The mass ratio of the corresponding different-sized zirconia balls is 2:5:3, and the mass ratio of the zirconia balls to FeS - Fe0 and biochar powder is 40:1 - 60:1.

[0076] Example 3

[0077] Provide a preparation method of a mixture that can activate persulfate to enhance the degradation of sulfamethoxazole in soil:

[0078] Step 1: Crush corn straw with a crusher, then filter it through a sieve with a pore size of 0.1 mm - 0.2 mm. Heat the filtered powder at a heating rate of 7 °C / min - 13 °C / min to a temperature of 450 °C - 550 °C, and then pyrolyze it for 1.5 h - 2.5 h to prepare biochar for standby;

[0079] Step 2: Mix FeS - Fe 0 and biochar powder in a certain mass ratio of 1:7.5, accurately weigh and put them into a zirconia ball milling cup. The molar ratio of FeS and Fe 0 is 0.5:1 - 2:1;

[0080] Step 3: Under the conditions that the ball milling parameters are set to 300 rpm - 500 rpm, the grinding time is 10 h - 14 h, the ball milling direction is changed every 2 h - 4 h, and nitrogen is purged during the whole grinding process, grind the mixture in Step 2 to obtain a mixture of Fe 0 -FeS and biochar (Fe 0 -FeS@BC);

[0081] Among them, the zirconia balls include zirconia balls with diameters of 15 mm, 5 mm, and 3 mm respectively, and the mass ratio of zirconia balls of different sizes is 2:5:3. The mass ratio of zirconia balls to FeS-Fe 0 and biochar powder is 40:1 - 60:1.

[0082] Example 4

[0083] Provide a preparation method of a mixture that can activate persulfate to enhance the degradation of sulfamethoxazole in soil:

[0084] Step 1: Crush corn straw with a crusher, then filter it through a sieve with a pore size of 0.1 mm - 0.2 mm, and heat the filtered powder to a temperature of 450 °C - 550 °C at a heating rate of 7 °C / min - 13 °C / min, and pyrolyze for 1.5 h - 2.5 h to obtain biochar for standby;

[0085] Step 2: After mixing FeS-Fe 0 and biochar powder according to a certain mass ratio of 1:10, accurately weigh and put them into a grinding cup containing zirconia balls. Among them, the molar ratio of FeS to Fe 0 is 0.5:1 - 2:1;

[0086] Step 3: Under the conditions that the ball milling parameters are set to 300 rpm - 500 rpm, the grinding time is 10 h - 14 h, the ball milling direction is changed every 2 h - 4 h, and nitrogen is purged during the whole grinding process, grind the mixture in Step 2 to obtain a mixture of Fe 0 -FeS and biochar (Fe 0 -FeS@BC);

[0087] Among them, the zirconia balls include zirconia balls with diameters of 15 mm, 5 mm, and 3 mm respectively, and the mass ratio of zirconia balls of different sizes is 2:5:3. The mass ratio of zirconia balls to FeS-Fe 0 and biochar powder is 40:1 - 60:1.

[0088] (3) SMX degradation experiment

[0089] Batch SMX removal experiments were conducted successively in 150 mm conical flasks. Each conical flask contained 3.00 g of contaminated soil and 5 mM PS solution. A certain amount of glass beads was added to enhance the mixing degree of solid particles and the reaction solution. After the soil and solution were thoroughly mixed for 10 min, 0.01 g of Fe 0 -FeS@BC catalyst was added. The conical flasks were sealed with polytetrafluoroethylene films and fixed in a constant temperature water bath oscillation chamber at 25 °C with a rotation speed of 220 r / min for the reaction. Three parallel vials were extracted at predetermined time intervals and 5 mL of MeOH was immediately introduced to stop further reactions. Subsequently, the suspension was centrifuged at 4000 r / min for 2 min using a 50 mL centrifuge tube and the supernatant was sampled. After adding 5 mL of MeOH, the mixture was oscillated at 220 r / min using a water bath for 10 min to extract SMX residues from the precipitated soil. Each extraction procedure was carried out 3 times and the extracts were thoroughly mixed with the supernatant. The samples were filtered through a 0.22 μm nylon syringe filter and the concentration of SMX was determined by high performance liquid chromatography (HPLC) (Agilent 1260, USA). The initial pH values (pH = 3, 5, 7, 9, 11) of each system in the experiment were adjusted with 0.1 M H2SO4 and 0.1 M NaOH. All treatments in the experiment were repeated three times. In addition, an ultra-high performance liquid chromatography mass spectrometer (HPLC-MS) (ZMD triple quadrupole MS - Waters, USA) was applied to determine the possible degradation intermediates of SMX. To evaluate the contribution of ROS to SMX degradation, methanol (MeOH: k · OH =9.7×10 8 M -1 s -1 , k SO4 ·- =2.5×10 7 M -1 s -1 , k 1O2 =3.0×10 3 M -1 s -1 ), tert-butanol (TBA: k · OH =1.9×10 9 M -1 s -1 , k SO4 ·- =7.7×107M -1 s -1 ), benzoquinone (BQ: (k O2 ·- =0.9 - 1.0×10 9 M -1 s-1 ) and furfuryl alcohol (FFA: k 1O2 = 1.2×10 8 M -1 s -1 ) was used as a quencher in this study. Electron paramagnetic resonance (EPR) experiments (EMX-8 / 2.7C, Bruker, Germany) were carried out to further determine the ROS generated in the reaction.

[0090] (4) Results and discussion

[0091] 4.1 Degradation performance of SMX by Fe 0 -FeS@BC / PS / SMX

[0092] The degradation efficiency of SMX in various systems is as Figures 1 - 3 shown. The PS activation ability of commercial Fe 0 is very low, and the degradation rate of SMX is only 48%, while the degradation rate of the PS system is 23%. Similarly, in the FeS / PS system, SMX was only degraded by 42% after 3 h, while the final removal rate of the BC / PS system was close to 53%. The SMX level in the control group did not change after 12 h, indicating that SMX could stably exist in these suspension reaction systems. In addition, it should be noted that the abundant pores of BC can absorb SMX from the system, and this adsorption may lead to the secondary release of SMX during the removal process. To clarify that SMX is decomposed rather than adsorbed in the BC / PS system, a BC / SMX system was constructed for degradation experiments under the same initial conditions. Compared with the control group, no difference in the SMX concentration was found after the reaction.

[0093] Compared with these systems, the residual rate of SMX in the Fe 0 -FeS@BC / PS / SMX system stabilized between 6% and 8% after 1 h. Subsequently, the dynamic changes of Fe 2+ in the reaction system were monitored to further prove the catalytic effect of Fe 0 -FeS@BC. Under the same initial conditions, including SMX concentration, catalyst dosage and PS concentration, compared with other systems, higher Fe 0 levels were obtained in the Fe 2+ -FeS@BC / PS / SMX system (p < 0.05). These results indicate that Fe 0 -FeS@BC is more likely to release Fe 2+ to trigger the degradation of SMX by PS. In addition, the poor catalytic activities of commercial Fe 0 and FeS have been proven in previous studies. Therefore, the degradation efficiency shown by Fe 0 and FeS in this study is reasonable. Generally speaking, these findings indicate that Fe prepared by ball milling0 Fe-S@BC has excellent PS activation ability.

[0094] It should be noted that the aggregation of magnetic particles and the passivation of iron-based materials are important variables that reduce the pollutant removal efficiency. In the soil-water suspension system used in this experiment, these limitations may be exacerbated due to the interference caused by the magnetic components in the soil and the poor dispersion conditions. Nevertheless, in the Fe 0 -FeS@BC / PS / SMX system, Fe 0 -FeS@BC still has good catalytic removal performance, which may be related to the reduced particle size of Fe 0 -FeS@BC and the increased specific surface area through the ball milling process, resulting in an increased contact area between PS and pollutants, which is confirmed in the SEM images of Fe 0 -FeS@BC. In addition, the distribution of Fe 0 and FeS in the pores of BC reduces particle aggregation. Moreover, studies have shown that introducing S during the ball milling process can prevent iron-based materials from becoming passivated. The XPS spectral results of the Fe 0 -FeS@BC material before and after the reaction show that the contents of Fe(0) and Fe(II) in Fe 0 -FeS@BC decrease significantly after the reaction, while the content of Fe(III) increases significantly. In addition, the dynamic change of the S2O8 2- concentration shows the rapid conversion of PS in the Fe 0 -FeS@BC / PS / SMX system. These results indicate that Fe 0 -FeS@BC can overcome partial iron passivation after ball milling and catalyze the reaction by leaching Fe(0) and Fe(II) into the system, thus activating PS. However, in the FeSO4·7H2O / PS / SMX system, the residual rate of SMX reaches 60%, indicating that excessive Fe 2+ cannot accelerate the degradation rate. This is because excessive iron ions can cause a large number of reactive species in a short time, which may lead to the mutual quenching of ROS.

[0095] As Figure 4 shown, the results indicate that the ball milling process of Fe 0 , FeS, and BC endows the mixture with better activation performance compared to the raw materials. Fe 0 -FeS@BC is synthesized through sufficient friction and collision, which helps with fracture, welding, and deformation, thus dispersing Fe 0 and FeS particles into the gaps and surfaces of BC fragments. In addition, Fe 0 , FeS, and BC are successfully combined, manifested as the symmetric distribution of Fe, S, and C after ball milling. As Figure 5 shown, Fe0 The XRD pattern of -FeS@BC further confirmed this combination and showed the formation of new sulfur and iron compounds, indicating that ball milling is not a simple mixing process but involves chemical reactions. In addition, potential recrystallization and chemical reactions during ball milling were documented in previous studies, suggesting that this process is not a simple mixing of raw materials but a process of changing the chemical composition and structure of particles.

[0096] 4.2, Fe 0 Effect of the mass ratio of -FeS to BC

[0097] With the addition of -FeS@BC at different mass ratios (1:1, 1:2.5, 1:5, 1:7.5, and 1:10), as 0 shown, the removal rates of SMX reached 81.47%, 93.01%, 96.54%, 97.15%, and 82.53%, respectively. These results can be attributed to the effective dispersion of BC on Fe Figure 6 -FeS, which effectively inhibited the aggregation of magnetic particles and increased the reactive sites. However, excessive BC may block the reactive sites due to the aggregation of BC flakes. In addition, an excessive BC component means a too low proportion of iron-containing materials, which are considered the main activators, resulting in a decrease in catalytic activity. Fe 0 -FeS@BC with mass ratios of 1:5 and 1:7.5 had comparable activation effects. The 1:7.5 type of Fe 0 -FeS@BC was selected as the optimal mass ratio for further study in this experiment because of its higher BC ratio, which can reduce the secondary soil pollution caused by this remediation process. 0 0

[0098] 4.3, Fe 0 Effect of the dosage of -FeS@BC on the degradation of SMX

[0099] As Figure 7 shown, as the dosage of Fe 0 -FeS@BC increased from 0 mg to 10 mg, the degradation efficiency of SMX increased rapidly. This may be due to the increase in reactive sites caused by a higher dosage of Fe 0 -FeS@BC. However, when the dosage of Fe 0 -FeS@BC exceeded 10 mg, the removal rate of SMX could not be further improved. By increasing the dosage of Fe 0 -FeS@BC, more Fe 2+ may be generated, while too much Fe 2+It will cause the removal of ROS. Persulfate can also react with additional sulfate radicals. In addition, when there is an excessive amount of activator in the soil-water suspension system, Fe 0 -FeS@BC cannot be fully distributed, and part of the Fe 0 -FeS@BC cannot catalyze the reaction. Therefore, in further experiments, 10 mg of activator was used as the ideal dosage.

[0100] 4.4. Influence of Initial pH Value on SMX Degradation

[0101] As Figure 8 shown, due to the large fluctuation range of pH values in actual polluted sites, the inventors also studied the degradation efficiency of SMX at different initial pH values. Except for the treatment at pH = 11, appropriate removal rates (>95%) were obtained in each reaction system (pH = 3 - 9). When the pH value was 3, the degradation rate of SMX increased significantly. This is because in an acidic environment, the rapid corrosion of iron-based materials will accelerate the reaction catalyzed by persulfate, thus rapidly releasing a large amount of Fe 0 and Fe 2+ . The H + generated by the persulfate reaction system may be the reason for the insignificant decrease in the degradation rate when the pH value increased to 9. In addition, the slight decrease in the degradation rate may be related to the decrease in the redox potential of this system. However, when the pH value continuously rose to 11, the degradation efficiency of SMX showed a significant decrease (P < 0.05). Sufficient alkaline conditions will also cause the precipitation of iron ions and the quenching of SO4 ·- and · OH. In addition, Fe 0 can form iron oxide hydrate with water molecules, thus further slowing down the reaction rate.

[0102] 4.5. Influence of PS Solution Concentration on SMX Degradation

[0103] It should be noted that the PS solution here is prepared by mixing PS and a solvent. In the embodiments of the present invention, water is selected as the solvent. As Figure 10 shown, as the concentration of PS increased from 5 mM to 20 mM, the degradation rate of SMX increased significantly from 72.8% to 97.5%. This is because Fe 0The contact between -FeS@BC and PS is closer, and the increase in PS concentration promotes the generation of ROS with oxidation activity, which drives the degradation of SMX. However, when the PS concentration is increased to 30 mM, the degradation efficiency cannot be further improved. Even when the PS concentration is increased to 40 mM, the degradation efficiency of SMX shows a certain decline because excessive PS will generate redundant reactive free radicals, which will quench each other before contacting SMX. In addition, excessive PS can scavenge excessive ROS.

[0104] 4.6. Influence of soil-water ratio on SMX degradation

[0105] As Figure 9 shown, the soil-water ratio is another aspect considered by the inventors. However, compared with other parameters, the influence of the soil-water ratio on SMX degradation is relatively small. The following soil-water ratios were selected in this experiment: 1:0.5, 1:1, 1:3, 1:5, 1:8, 1:12. When the soil-water ratio is greater than 1, the increase in the soil-water ratio has no obvious effect on the degradation efficiency of SMX. These results indicate that the prepared Fe 0 -FeS@BC can be effectively used to purify SMX-polluted environments with soil-water ratios ranging from 1:1 to 1:12.

[0106] 4.7. Roles of various ROS

[0107] In the soil Fe 0 -FeS@BC / SMX / PS system, a selective scavenging test was carried out to explore the contribution of reactive species to SMX degradation. The activation of PS by the carbon-iron composite material in the system may activate PS to form multiple reactive species, including 1 O2, O2 ·- , · OH and SO4 ·- . However, due to the quite different activation potentials determined by the complex natural soil structure, the activation of PS and the formation of ROS in natural soil are quite complex. For example, iron / manganese-containing minerals and SOM may be involved in the generation and transformation of ROS. In the soil Fe 0 -FeS@BC / SMX / PS system, the reaction between BC and PS is considered to be one of the key factors for generating 1 O2, which is usually related to the transformation of O2 ·- .

[0108] As Figures 11 - 14 and Figures 15 - 18 show, the addition of each quenching agent has a certain inhibitory effect on the degradation of SMX. In this regard, it was found that · OH is more effective than SO4 ·-played a more important role in SMX degradation because the addition of TBA (30%) and MeOH (35%) had a considerable inhibitory effect on the removal of SMX. In addition, in the presence of FFA as a scavenger, we observed that 24% of the SMX residues were present in the Fe in the soil 0 -FeS@BC / SMX / PS system, indicating that SMX was not only degraded by free radicals. In addition, with the addition of BQ, the residual rate of SMX increased to 18%. These results together indicate that 1 O2, O2 ·- , · OH and SO4 ·- might coexist in the Fe in the soil 0 -FeS@BC / SMX / PS system and made important contributions to the degradation of SMX. In the EPR experiment, adducts of DMPO-SO4 (1:1:1:1:1:1), DMPO-OH (1:2:2:1), 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) (1:1:1) and DMPO-O2 were observed, which further confirmed that 1 O2, O2 ·- , · OH and SO4 ·- coexisted. However, even when MeOH, TBA, FFA and BQ coexisted in the Fe in the soil 0 -FeS@BC / SMX / PS system, the inventors still observed a 33% removal rate of SMX. This indicates that there may be other ways to remove SMX. According to previous studies, benchmark carbonaceous materials may be attacked or irradiated by ROS, the surface electronic state may be changed, and reactive transferable intermediates (e.g., persistent free radicals (PFRs)) may be induced to form. Therefore, the signal of PFRs was detected using the EPR experiment. An obvious single resonance signal representing PFRs was found in the soil Fe 0 -FeS@BC / SMX / PS system. Generally speaking, these results indicate that: (1) the degradation of SMX involves free radical and non-free radical oxidation processes; (2) various ROS including 1 O2, O2 ·- , · OH and SO4 ·- and PFR coexist in the soil Fe 0 -FeS@BC / SMX / PS system.

[0109] However, these results are inconsistent with the ROS that dominated in the water reaction system recorded in previous studies · OH and SO4 ·- . To clarify Fe 0The sources of reactive species in the -FeS@BC / SMX / PS system were investigated by conducting the same quenching experiments in an aqueous environment to eliminate the interference of soil components. Interestingly, the inhibitory effect of FFA on SMX removal was similar to that in the soil environment (19%), while the inhibitory effects of 1 M MeOH and TBA increased significantly (P < 0.05). Compared with the control group, the removal efficiency of SMX decreased to 52% and 47%. This indicates that · OH and SO4 ·- are the main reactive oxygen species in the water reaction system. Meanwhile, the addition of BQ only reduced the degradation rate of SMX by 7%. Therefore, these results suggest that Fe 0 -FeS@BC / SMX / PS system also coexists with 1 O2, O2 ·- , · OH and SO4 ·- in the aqueous environment, but the dominant ROS must be · OH and SO4 ·- rather than 1 O2 and O2 ·- . In summary, we can speculate that the Fe 0 -FeS@BC catalyst is not the main reason for the different contents of 1 O2, O2 ·- , · OH and SO4 ·- in different environments. It should be noted that the content of SOM in the soil decreased significantly after the reaction, which may be related to the consumption and chain propagation of reactive oxygen species. Based on the differences presented in the soil and aqueous environments, we made the following assumptions: i) · OH and SO4 ·- were significantly consumed by soil SOM compounds; ii) soil components triggered free radical conversion or activated PS to generate 1 O2 and O2 ·- .

[0110] The effects of humic acid (HA) and mineral fractions (MF) on the degradation reaction were preliminarily investigated, where HA was used as a simulated SOM and the MF fraction was obtained by oxidizing the experimental soil at 400 °C for 4 hours. In addition, the selective scavenging experiments conducted in the MF / Fe 0 -FeS@BC / SMX / PS system were the same as those in the soil Fe 0The results of the -FeS@BC / SMX / PS system were almost the same. This indicates that the presence of MF is mainly responsible for the changes in reactive species. Therefore, XRD experiments were conducted on MF before and after the reaction, and obvious changes occurred in the amorphous and crystalline iron oxides in the soil. It shows that Fe-minerals are involved in the activation of PS and the removal of SMX. It has been demonstrated that minerals containing surface Fe(III) can activate PS to generate O2 ·- , which is consistent with the results of XRD and selective scavenging experiments. In addition, in the presence of PS, O2 ·- and Mn minerals containing a large amount of β-manganese dioxide, O2 1 can be generated through multiple reactions. This can also explain the differences in the content of O2 1 in the water and soil environment. Therefore, it can be speculated that with the presence of MF, O2 ·- may transfer to 1 O2.

[0111] Even in the presence or absence of SOM, the final elimination effect of SMX is not very different, but its mechanism may be very different. In particular, SOM in natural soil is more heterogeneous, with a higher proportion of small molecules compared to HA. As Figure 19 shown, as the HA level increases from 1 mM to 5 mM, the inhibitory effect on the SMX degradation efficiency increases. In addition, 1 O2 and O2 ·- may play an important role in the degradation of SMX, while · OH and SO4 ·- removal of SMX is strictly inhibited by 5 mM HA. On the other hand, in natural soil, SOM · can be generated under the induction of SO4 ·- and activate PS to produce 1 O2 and O2 ·- . In addition, the inhibitory effect of BQ may be underestimated because the presence of quinone compounds can catalyze PS and generate semiquinone radicals (SQ-), which is one of SOM · and may lead to an increase in the content of · OH and SO4 ·- . In addition, the cycle of Fe 3+ / Fe 2+ (E(Fe 3+ / Fe 2+ ) = +0.771) may be accelerated by electrons from reducing agents such as O2 ·- (E(O2 ·- / 1 O2) = -0.18V) and SOM · (E(SOM · / SOM) = -1.72 to -1.19 V). It can be concluded that HA and MF significantly affected the formation and production of ROS, while SMX in soil Fe 0 The degradation in the -FeS@BC / SMX / PS system is very complex.

[0112] 4.8, Fe 3+ / Fe 2+ cycle

[0113] such as Figures 20 - 22 shown, the Fe 3+ / Fe 2+ cycle can maintain an appropriate Fe 2+ concentration and accelerate the degradation of pollutants. Fe in soil 0 -FeS@BC / SMX / PS system may have strong reducing conditions. We used 1 mM of FeCl3 to explore the Fe 3+ / Fe 2+ potential cycle in the soil Fe 0 -FeS@BC / SMX / PS system. The results showed a slight increase in the initial degradation stage, while the final degradation rate did not change significantly. Therefore, to further prove that the reduction of Fe 3+ accelerated the reaction, the inventors introduced 1 mM of 1,10-phenanthroline monohydrate (phen) and 1 mM of EDTA into the system, which formed clathrates with Fe 2+ and Fe 3+ respectively ([[]] Figure 21 ). As reported, the complexes of Fe 2+ -phen and Fe 3+ -EDTA are more stable than Fe 2+ -EDTA and Fe 3+ -phen. In this study, the removal of SMX was greatly inhibited by the added phen and EDTA, which further emphasized the key role played by Fe 2+ and Fe 3+ in the Fe 0 -FeS@BC / SMX / PS system. In addition, the inhibition of the degradation efficiency caused by the hindered conversion between Fe 3+ and Fe 2+ further indicated the dynamic cycle between Fe 2+ and Fe 3+ . In Fe 0Similar results were also obtained in the -FeS / SMX / PS / FeCl3 system and the BC / SMX / PS / FeCl3 system. Note that after introducing FeCl3 into the BC / SMX / PS / FeCl3 system, the removal rate of SMX increased significantly. In addition, the presence of Fe 2+ (dissolved and solid Fe 2+ ) was determined. Therefore, it can be concluded that both BC and Fe 0 -FeS@BC and Fe 0 -FeS can provide reduction conditions during the removal of SMX.

[0114] 4.9 Intermediate products and possible degradation pathways of SMX

[0115] LC-Q-TOF-MS / MS (TripleQuand-4500, SCIEX, USA) was used to detect the transformation products (TPs) generated in the soil Fe 0 -FeS@BC / SMX / PS system. Through MS / MS spectra and literature data, 11 intermediate products were identified. With the presence of different ROSs, attacks on amino groups, C═C double bonds, and sulfonamide bonds, oxidation of anilino groups, and cleavage of isoxazole rings may occur in the SMX molecule. As Figure 23 shown, the possible degradation pathway of SMX in the soil Fe 0 -FeS@BC / SMX / PS system. Generally speaking, due to the short reaction time, some TPs that cannot be completely mineralized will be generated during the removal of SMX. However, compared with SMX, the acute and chronic toxicity doses of these TPs have been recorded to be lower in previous studies.

[0116] Overall, PS activated by Fe 0 -FeS@BC has a stronger ability to degrade SMX in soil than Fe 0 , FeS, and BC. In addition, due to the presence of MF and SOM, the removal process of SMX in the soil Fe 0 -FeS@BC / SMX / PS system is quite complex. Multiple ROSs (such as: 1 O2, O2 ·- , · OH, SO4 ·- and PFR) are generated through the interaction with PS and effectively degrade SMX in the soil-water suspension system. In the soil Fe 0 -FeS@BC / SMX / PS system, the transformation from O2 ·- to 1 O2 and · OH, SO4 ·-Consumption is considered to explain the different removal performances in soil-water suspensions. In addition, the reducing conditions prevalent in the soil Fe 0 -FeS@BC / SMX / PS system have a high Fe 3+ / Fe 2+ cycle, leading to the continuous degradation of SMX. These results of this study jointly demonstrate the excellent performance of the Fe 0 -FeS@BC / SMX / PS system in degrading SMX and show great potential for soil remediation.

[0117] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A mixture Fe 0 -FeS@BC is used in the enhanced degradation of sulfamethoxazole in soil by activating persulfate, and is characterized in that It includes the following steps: S1: Mix soil and persulfate solution, and the mass ratio of the solvent of soil to persulfate solution is 1:12 - 1:1; S2: Adjust the pH to 3 - 9, and then add the mixture Fe 0 -FeS@BC mixture. The mass ratio of the mixture Fe 0 -FeS@BC to the soil is (0.005 - 0.01):3; Among them, the mixture Fe 0 - The preparation method of FeS@BC comprises the following steps: Step 1: Crush the straw and pass it through a sieve. After heating the powder obtained by the sieve to a constant temperature, pyrolyze it at a constant temperature to prepare biochar for standby; Step 2: Weigh FeS-Fe 0 and biochar powder separately and put them into a grinding cup, in which zirconia balls are placed; Step 3: Grind the mixture in Step 2 under the set grinding parameters to obtain Fe 0 - The ball-milled mixture of FeS and biochar, Fe 0 -FeS@BC; The grinding parameters in Step 3 are a rotation speed of 300 rpm - 500 rpm, a grinding time of 10 h - 14 h, and change the ball milling direction every 2 h - 4 h. The whole grinding process is carried out in an inert atmosphere; The mass ratio of FeS-Fe described in Step 2 0 and the biochar powder is 1:7.5 - 1:2.5, and the molar ratio of FeS and Fe 0 is 0.5:1 - 2:

1.

2. Application of a mixture Fe 0 -FeS@BC in activating persulfate to enhance the degradation of sulfamethoxazole in soil, characterized in that The molar concentration of the persulfate solution in S1 is 5 mM - 30 mM.

3. Application of a mixture Fe 0 -FeS@BC in activating persulfate to enhance the degradation of sulfamethoxazole in soil, characterized in that In Step 1, the aperture of the sieve is 0.1 mm - 0.2 mm. The equipment used for heating is a muffle furnace, and the heating rate is 7℃ / min - 13℃ / min. Heat to 450℃ - 550℃ at the heating rate and pyrolyze for 1.5 h - 2.5 h to obtain the biochar.

4. Application of a mixture Fe 0 -FeS@BC in activating persulfate to enhance the degradation of sulfamethoxazole in soil, characterized in that The particle size of the zirconia balls is 3 mm - 15 mm.

5. Use of a mixture Fe 0 -FeS@BC in activating persulfate to enhance the degradation of sulfamethoxazole in soil, characterized in that, The particle sizes of the zirconia balls are mainly 15 mm, 5 mm, and 3 mm, and the mass ratio of the three particle sizes of zirconia balls is 2:5:

3.

6. Application of a mixture Fe 0 -FeS@BC in activating persulfate to enhance the degradation of sulfamethoxazole in soil, characterized in that In the grinding cup of Step 2, the mass ratio of zirconia balls to the mixture of FeS-Fe 0 and biochar powder is 40:1 - 60:

1.

7. Use of a mixture Fe 0 -FeS@BC in the enhanced degradation of sulfamethoxazole in soil by activating persulfate, characterized in that The mass ratio of FeS-Fe 0 and the biochar powder described in step 2 is 1:7.5.

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