Preparation method and application of sulfide nano-zero-valent iron doped biochar

Abstract

The present invention belongs to the field of degradation of aromatic hydrocarbon organic matter in saline-alkali environments, and relates to a preparation method and application of sulfide nano-zero-valent iron-doped biochar. The method includes the selection of a carbon-based material modifier, the preparation of a surface chemically modified carbon-based material, and the degradation process of a target pollutant. The preparation steps of the modified carbon-based material are as follows: first, (1) preparing biochar by carbonizing lotus leaf stems and facility agricultural crop straw at high temperature; (2) preparing sulfide nano-zero-valent iron particles by a modified borohydride reduction method under inert atmosphere conditions; and (3) preparing sulfide nano-zero-valent iron-doped biochar particles. The sulfide nano-zero-valent iron-doped biochar particles are subjected to solid-liquid separation, vacuum drying, and high-temperature calcination under a reducing atmosphere to obtain metal-modified biochar nanoparticles. The above-mentioned material is used to activate persulfate to degrade aromatic hydrocarbon organic matter, degrading the target PAHs to generate non-condensed ring organic small molecule compounds. The operation is simple, the strengthening effect is significant, the degradation effect is obvious, and the material is salt-alkali resistant.

Description

Technical Field

[0001] The present invention belongs to the technical field of application of degradation of aromatic hydrocarbon organic matter in saline-alkali environment, and relates to a preparation method of sulfide nano-zero-valent iron doped biochar and its application in degradation of aromatic hydrocarbon organic matter. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Typical coastal areas of river deltas face significant soil salinization, resulting in poor soil quality and low soil usability. With the extraction of oil in these areas, large amounts of organic components such as aromatic hydrocarbons in crude oil enter the soil through migration and transformation, further damaging the soil structure, reducing organic matter content, and diminishing microbial activity. Polycyclic aromatic hydrocarbons (PAHs), the main component of petroleum aromatic hydrocarbons, consist of 2 to 6 fused rings. They are numerous, chemically stable, and have strong teratogenic, carcinogenic, and mutagenic potential. They have been listed as priority pollutants by the U.S. Environmental Protection Agency (EPA) and the European Union (EU).

[0004] In recent years, PAHs pollution control technology has mainly focused on pollution in the industrial field, while there are fewer studies on pollution control in saline-alkali environments. At the same time, due to the lack of experimental support, it is difficult to degrade PAHs into non-condensed ring organic small molecular weight compounds under saline-alkali stress. Therefore, it is particularly important to explore efficient, economical and environmentally friendly remediation technologies. Persulfate, as a new advanced oxidation technology that can produce more active free radicals, has been widely used in the remediation of contaminated sites. Persulfate activated by traditional methods can effectively degrade and even mineralize low-ring hydrocarbon organic pollutants, but for PAHs with stable structures and trace concentration levels, there are problems such as difficulty in ring opening and incomplete degradation. Studies have shown that surface chemically modified carbon-based materials can enhance the adsorption capacity of persulfate for organic pollutants and stimulate them to produce highly oxidizing sulfate radicals (SO4 - ·), promoting the degradation of macromolecular organic compounds such as PAHs into bioavailable small molecules. Therefore, it is feasible to use modified carbon-based materials to activate persulfate to degrade PAHs.

[0005] For example, the paper "Study on Biochar-Loaded Sulfide Nano-Zerovalent Iron Activated Persulfate Degradation of Acid Red GR" investigated using ephedra as a raw material to prepare biochar, which was loaded with sulfide nano-zerovalent iron to activate persulfate degradation of Acid Red GR. However, the inventors discovered that existing biochar materials failed to meet the requirements for complete degradation of trace concentrations of PAHs in saline-alkaline environments. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a method for preparing sulfide nano-zero-valent iron doped biochar suitable for the degradation of aromatic hydrocarbon organic matter-PAHs in saline-alkali environments.

[0007] Due to their poor water solubility, PAHs molecules interact with hydrophobic organic components through large π bonds, resulting in adsorption and reduced bioavailability. Furthermore, the π-π bond interactions between PAHs' aromatic rings enhance their structural stability, limiting the free radical degradation pathway and electron transfer pathway during the degradation process of traditional activated oxidation technologies, making it difficult to degrade PAHs into non-condensed ring organic, low-molecular-weight compounds. Through systematic research and long-term experiments, the present invention discovered that, compared with other plant straws, biochars derived from lotus leaf stems and agricultural crop straw possess microscopic properties such as a rich porous structure and a surface rich in oxygen-containing functional groups. Furthermore, carbon-based materials modified by surface chemical modification can induce the active free radical oxidation degradation pathway of oxidants, meeting the requirements for complete degradation of trace concentrations of PAHs in saline-alkaline environments.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a method for preparing sulfide nano-zero-valent iron-doped biochar, comprising:

[0010] Using lotus leaf stems and facility agricultural crop straw as carbon sources, biochar is obtained by carbonizing at 300-700°C for 180-540 minutes in an inert atmosphere.

[0011] dissolving a borohydride reducing agent and dithionite in water and mixing them uniformly to obtain a first reaction solution;

[0012] Dissolving trivalent iron salt and polyethylene glycol in water, adding the biochar, sonicating for 20 to 40 minutes, stirring and introducing nitrogen gas for 30 to 60 minutes to prepare a second reaction solution;

[0013] Under an inert atmosphere, the first reaction solution was added dropwise to the second reaction solution at a stirring speed of 10 to 20 r / s at a dropping speed of 0.5 to 1.5 mL / s. After the dropwise addition was complete, the solution was sulfurized for 25 to 50 minutes to obtain a third reaction solution.

[0014] The third reaction solution is centrifuged, washed, and the black precipitate is collected and dried to obtain black particles;

[0015] The black particles are placed in a tube furnace, nitrogen is introduced into the tube furnace for 20 to 60 minutes, and calcined at 150 to 250° C. for 120 to 360 minutes under reducing atmosphere conditions to obtain sulfide nano zero-valent iron doped biochar particles (S-NZVI / BC).

[0016] The second aspect of the present invention provides sulfide nano-zero-valent iron-doped biochar prepared by the above method.

[0017] The third aspect of the present invention provides the use of the above-mentioned sulfide nano-zero-valent iron doped biochar in activating persulfate to degrade trace aromatic hydrocarbon organic pollutants in saline-alkali environments.

[0018] Beneficial effects of the present invention

[0019] (1) The present invention overcomes the shortcomings of existing advanced oxidation technologies and provides a S-NZVI / BC nanoparticle with simple operation, cheap raw materials, short synthesis cycle, high reaction active sites and a preparation method thereof. The prepared active components are high and the particle size is small, which has certain industrial value.

[0020] (2) The prepared nanoparticles are coupled with persulfate to be used for the degradation of aromatic organic matter in saline-alkali environments. This is low-cost and can achieve the purpose of ring-opening degradation of PAHs in a short period of time, which is conducive to its application in actual polluted areas.

[0021] (3) The prepared nanoparticle-coupled persulfate system is suitable for the reduction of PAHs under high salinity and alkali stress conditions, and has a certain reference role and breakthrough in the degradation of aromatic hydrocarbons in saline-alkali environments.

[0022] (4) Different from the existing methods, the present invention adopts a two-step reduction method to prepare the biochar nanomaterial doped with sulfide nano-zero-valent iron, which improves the high reduction activity, sulfidation effect and high selectivity of zero-valent iron, and effectively improves the degradation effect of aromatic hydrocarbon organic matter in saline-alkali environment.

[0023] Therefore, the use of the self-made S-NZVI / BC nanoparticles provided by the present invention coupled with persulfate oxidant to degrade PAHs under saline-alkali stress has important application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is a SEM characterization image of the product of Example 1 prepared by the method of the present invention.

[0026] Figure 2This is a water contact angle measurement diagram of the product of Example 1 prepared by the method of the present invention.

[0027] Figure 3 This is a SEM characterization image of the product of Example 2 prepared by the method of the present invention.

[0028] Figure 4 This is a water contact angle measurement diagram of the product of Example 2 prepared by the method of the present invention.

[0029] Figure 5 The unmodified biochars are the products of Comparative Example 1 and Comparative Example 2 prepared by the method of the present invention.

[0030] Figure 6 The unmodified biochars are the products of Comparative Example 3 and Comparative Example 4 prepared by the method of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] A method for preparing sulfide nano-zero-valent iron-doped biochar suitable for the degradation of aromatic hydrocarbon organic matter (PAHs) in saline-alkali environments.

[0033] The method for preparing sulfide nano-zero-valent iron-doped biochar provided by the present invention comprises the following steps:

[0034] Step A, preparing highly carbonized biochar;

[0035] The dried plant straw is placed in an inert atmosphere in a tubular furnace, continuously flowing inert gas for 30 minutes, and calcined at high temperature to produce highly carbonized biochar. The calcination temperature is 300°C to 700°C and the calcination time is 180 to 540 minutes. The carbonized black solid is cooled, ground, and placed in a brown bottle for later use. The highly carbonized biochar has a particle size of 15 to 50 nm and a black powder with a pore size of 1 to 12 nm.

[0036] The plant straw is lotus leaf stem and facility agricultural crop straw, with a size of 0.5 to 1 cm; the biochar sheet is distributed with micropores and mesopores, and has a regular honeycomb multi-level pore structure with uniform pore size, and secondary pores distributed on the inner surface to form a network structure.

[0037] Step B, preparing a first reaction solution;

[0038] Dissolve the borohydride reducing agent and dithionite in 100 mL of deionized water, mix well, and transfer the solution to a constant pressure funnel to prepare a first reaction solution;

[0039] The concentration of the borohydride reducing agent is 0.4-1.6 mol / L, and the concentration of the dithionite is 0.02-0.08 mol / L;

[0040] The borohydride is sodium borohydride or potassium borohydride, and the dithionite is sodium dithionite or potassium dithionite;

[0041] In the first reaction solution, borohydride ions and dithionite undergo redox reaction to generate divalent sulfide salt;

[0042] Step C, preparing a second reaction solution;

[0043] Add trivalent iron salt dissolved in deionized water and polyethylene glycol (PEG), a metal dispersant, to a sealed reaction bottle, add a certain amount of the biochar prepared in step A, sonicate for 20 to 40 minutes, stir, and introduce nitrogen gas for 30 to 60 minutes to prepare a second reaction solution;

[0044] The ferric salt is ferric chloride or ferric nitrate, the concentration of the ferric salt is 0.1-1.6 mol / L, the metal dispersant PEG is 1.0-3.0 g, which is used to prevent the agglomeration of nanoparticles, the mass ratio of the ferric salt to the biochar is 1:1-1:4, the nitrogen purity is 99.99% (nitrogen volume content), and the gas flow rate is 0.005 m 3 / s~0.02m 3 / s;

[0045] Step D, preparing a third reaction solution;

[0046] Under nitrogen ventilation conditions, the stirring speed is 10-20 r / s, and the first reaction liquid is added dropwise to the second reaction liquid at a dropping speed of 0.5-1.5 mL / s. After the dropwise addition is complete, the sulfurization time is continued for 25-50 minutes to obtain a third reaction liquid;

[0047] The molar ratio of borohydride ions to ferric ions is 1:1 to 1:4; the molar ratio of sulfide ions to ferric ions is 1:2.5 to 1:10; the molar ratio of ferric salt to the borohydride and dithionite is 2:4:3;

[0048] In the second reaction liquid, the biochar-loaded nano-zero-valent iron reacts with sulfide salt to generate a black precipitate of sulfonated nano-zero-valent iron doped with biochar;

[0049] After sulfidation, the electron transfer ability of nano-zero-valent iron is improved and the reaction activity is enhanced. Secondly, the sulfur particles will hinder the adsorption sites of H, which helps to improve the degradation activity of nanoparticles.

[0050] Step E: centrifugation to obtain black particles;

[0051] The third reaction solution was centrifuged at a speed of 3600-4000 r / min for 5-15 min, and washed with deionized water and anhydrous ethanol three times respectively to obtain a black precipitate;

[0052] The black precipitate was placed in a vacuum drying oven and heated at a vacuum degree of 1×10 -2 ~1×10 -1 Pa, drying temperature 30 ~ 60 ℃, drying time 48 ~ 72h, the dried black particles are stored in anaerobic sealed bags for future use;

[0053] Step F, obtaining sulfide nano-zero-valent iron-doped biochar particles;

[0054] The dried black particles were placed in a tube furnace, nitrogen was introduced into the furnace for 20 to 60 minutes, and calcined at high temperature in a reducing atmosphere to produce highly reduced sulfided nano-zero-valent iron-doped biochar particles. The sulfided nano-zero-valent iron-doped biochar particles had a particle size of 20 to 80 nm and a water contact angle of 20° to 30°. This yielded sulfided nano-zero-valent iron-doped biochar particles (S-NZVI / BC).

[0055] The reducing atmosphere is hydrogen; the calcination temperature is 150-250° C.; the calcination time is 120-360 min; the particle size is 20-80 nm;

[0056] Step G, S-NZVI / BC nanoparticle degradation application;

[0057] The mass ratio of S-NZVI / BC nanoparticles to persulfate is 1:5 to 1:20; the pH value is 7 to 9, and the salinity is 0.1% to 0.4%; the reaction time is 4 to 72 hours; and the reaction temperature is room temperature.

[0058] The S-NZVI / BC nanoparticles prepared according to the above method and their application in the degradation of PAHs under saline-alkali stress also fall within the scope of protection of the present invention. The S-NZVI / BC nanoparticles have a particle size of 20 to 80 nm and a water contact angle of 20° to 30°, both less than 90°. They are hydrophilic substances and have a better degree of dispersion in the aqueous reaction liquid than hydrophobic substances, which is beneficial to their reactivity with pollutants in the aqueous phase. The S-NZVI / BC nanoparticles are uniform in size, and the particles are connected together to form a chain. The degradation treatment of PAHs under saline-alkali stress may specifically include the following steps: placing the S-NZVI / BC nanoparticles provided by the present invention in a simulated aqueous system contaminated with PAHs to carry out a ring-opening degradation reaction.

[0059] The concentration ratio of the S-NZVI / BC nanoparticles to persulfate is 0.01:1 to 0.04:1; the pH value can be specifically 7 to 9, and the salinity is 0.1% to 0.4%; the concentration of PAHs is 200 to 4000 mg / kg, the reaction time is 4 to 72 hours, and the reaction temperature is room temperature.

[0060] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0061] Table 1 Specifications of raw materials used in Examples and Comparative Examples

[0062]

[0063] Example 1

[0064] (1) Step A, preparing biochar;

[0065] The dried corn straw from the facility agriculture crop was placed in a tubular furnace under nitrogen atmosphere, and inert gas was continuously introduced for 30 minutes. The calcination temperature was set at 600°C and the calcination time was 180 minutes. The carbonized black solid was cooled, ground, and placed in a brown bottle for later use.

[0066] (2) Step B, preparing a first reaction solution;

[0067] Dissolve 0.8 mol of sodium borohydride and 0.06 mol of sodium dithionite in 100 mL of deionized water, mix well, and transfer the solution to a constant pressure funnel to prepare a first reaction solution;

[0068] The first reaction solution is a redox reaction between borohydride ions and dithionite to generate Na2S;

[0069] (3) Step C, preparing a second reaction solution;

[0070] 200 mL of deionized water was added to a sealed reaction bottle, and nitrogen gas was continuously introduced for 40 min. 0.08 mol of FeCl3·6H2O and 2.0 g of polyethylene glycol (PEG) were added to the sealed reaction bottle and mixed evenly with 10 g of biochar. After ultrasonication for 30 min, the mixture was stirred under a nitrogen atmosphere for 30 min to prepare a second reaction solution.

[0071] (4) Step D, preparing a third reaction solution;

[0072] Under nitrogen ventilation conditions, the first reaction solution was added dropwise to the second reaction solution at a stirring speed of 15 r / s and a dropping speed of 1 mL / s. After the dropwise addition was complete, the sulfurization time was continued for 25 to 50 minutes to generate a black precipitate, thereby obtaining a third reaction solution.

[0073] In this reaction, the molar ratio of borohydride ion, ferric ion, and dithionite ion is: n(BH4 - ):n(Fe 3+ ):n(S2O4 2- )=4:2:3;

[0074] (5) Step E, centrifugation to obtain black particles;

[0075] Solid-liquid separation was performed at a centrifugal speed of 3000 r / min for 10 min, and the mixture was washed three times with deionized water and anhydrous ethanol, respectively. The supernatant was discarded, and the black particles obtained by centrifugation were then dried in a vacuum drying oven at 60°C for 48 h to obtain the black particles, which were then stored in anaerobic sealed bags for future use.

[0076] (6) Step F, obtaining sulfide nano-zero-valent iron-doped biochar particles;

[0077] The dried black particles were placed in a tube furnace, nitrogen was introduced into the tube furnace for 30 minutes, and calcined at 180 ° C for 240 minutes under reducing atmosphere to generate highly reduced sulfide nano zero-valent iron doped biochar particles (S-NZVI / BC c-600 );

[0078] (7) Step G, S-NZVI / BC c-600 Nanoparticle degradation effect;

[0079] S-NZVI / BC nanoparticles activated persulfate to degrade 2-ring polycyclic aromatic hydrocarbon naphthalene under saline-alkali stress. The pH of the reaction water phase was 8, the salinity was 0.2%, and S-NZVI / BC c-600 The mass ratio of nanoparticles to persulfate was 1:10. After reacting at room temperature for 72 hours, the mixture was extracted using a C18 extraction cartridge with n-hexane as the extractant. The extract (i.e., the degradation product of the parent pollutant) was tested and analyzed using gas chromatography-mass spectrometry (GC-MS).

[0080] In the present invention, the nano-zero-valent iron is sulfided, and S will hinder the adsorption site of H. The sulfided nano-zero-valent iron helps to improve the electron transfer ability and reaction activity of the nano-zero-valent iron.

[0081] In the present invention, the prepared black particles are calcined at high temperature under a reducing atmosphere, which is beneficial to reducing the metal oxidation rate and improving the reduction performance of the metal.

[0082] The prepared materials were characterized by scanning electron microscopy (SEM). Figure 1 As shown, S-NZVI / BC c-600The particles are uniform in size, connected together, and the overall shape is chain-like. The particle size is 30nm. Fe and S particles are successfully loaded on C. S-NZVI / BC c-600 The ratio of S, Fe and C particles is S:Fe:C=1:8.3:2.5.

[0083] The water contact angle is used to measure the hydrophilicity and hydrophobicity of the particles, which affects the dispersion of the particles in the solution. The water contact angle of the prepared materials is measured, such as Figure 2 As shown, S-NZVI / BC c-600 The water contact angle of the nanoparticles is 29°~30°, which means they are hydrophilic substances. They are better dispersed in the aqueous reaction liquid than hydrophobic substances, which is beneficial to their reactivity with pollutants and water.

[0084] The degradation products of the parent pollutant were tested and analyzed, and the results are shown in Table 2. It can be seen that the parent pollutant could not be detected after the reaction, indicating that the parent pollutant had been completely degraded.

[0085] Table 2 Analysis of PAHs degradation products

[0086]

[0087]

[0088] Example 2

[0089] (1) Step A, preparing biochar;

[0090] The dried lotus leaf stems were placed in a tube furnace under nitrogen atmosphere and inert gas was continuously introduced for 30 min. The calcination temperature was set at 600°C and the calcination time was 180 min. The carbonized black solid was cooled, ground, and placed in a brown bottle for later use.

[0091] (2) Step B, preparing a first reaction solution;

[0092] Dissolve 0.8 mol of sodium borohydride and 0.06 mol of sodium dithionite in 100 mL of deionized water, mix well, and transfer the solution to a constant pressure funnel to prepare a first reaction solution;

[0093] The first reaction solution is a redox reaction between borohydride ions and dithionite to generate Na2S;

[0094] (3) Step C, preparing a second reaction solution;

[0095] 200 mL of deionized water was added to a sealed reaction bottle, and nitrogen gas was continuously introduced for 40 min. 0.08 mol of FeCl3·6H2O and 2.0 g of polyethylene glycol (PEG) were added to the sealed reaction bottle and mixed evenly with 10 g of biochar. After ultrasonication for 30 min, the mixture was stirred under a nitrogen atmosphere for 30 min to prepare a second reaction solution.

[0096] (4) Step D, preparing a third reaction solution;

[0097] Under nitrogen ventilation conditions, the first reaction solution was added dropwise to the second reaction solution at a stirring speed of 15 r / s and a dropping speed of 1 mL / s. After the dropwise addition was complete, the sulfurization time was continued for 25 to 50 minutes to generate a black precipitate, thereby obtaining a third reaction solution.

[0098] In this reaction, the molar ratio of borohydride ion, ferric ion, and dithionite ion is: n(BH4 - ):n(Fe 3+ ):n(S2O4 2- )=4:2:3;

[0099] (5) Step E, centrifugation to obtain black particles;

[0100] Solid-liquid separation was performed at a centrifugal speed of 3000 r / min for 10 min, and the mixture was washed three times with deionized water and anhydrous ethanol, respectively. The supernatant was discarded, and the black particles obtained by centrifugation were then dried in a vacuum drying oven at 60°C for 48 h to obtain the black particles, which were then stored in anaerobic sealed bags for future use.

[0101] (6) Step F, obtaining sulfide nano-zero-valent iron-doped biochar particles;

[0102] The dried black particles were placed in a tube furnace, nitrogen was introduced into the tube furnace for 30 minutes, and calcined at 180 ° C for 240 minutes under reducing atmosphere to generate highly reduced sulfide nano zero-valent iron doped biochar particles (S-NZVI / BC L-600 );

[0103] (7) Step G, S-NZVI / BC L-600 Nanoparticle degradation effect;

[0104] S-NZVI / BC nanoparticles activated persulfate to degrade 2-ring polycyclic aromatic hydrocarbon naphthalene under saline-alkali stress. The pH of the reaction water phase was 8, the salinity was 0.2%, and S-NZVI / BC L-600The mass ratio of nanoparticles to persulfate was 1:10. After reacting at room temperature for 72 hours, the mixture was extracted using a C18 extraction cartridge with n-hexane as the extractant. The extract (i.e., the degradation product of the parent pollutant) was tested and analyzed using gas chromatography-mass spectrometry (GC-MS).

[0105] In the present invention, the nano-zero-valent iron is sulfided, and S will hinder the adsorption site of H. The sulfided nano-zero-valent iron helps to improve the electron transfer ability and reaction activity of the nano-zero-valent iron.

[0106] In the present invention, the prepared black particles are calcined at high temperature under a reducing atmosphere, which is beneficial to reducing the metal oxidation rate and improving the reduction performance of the metal.

[0107] The prepared materials were characterized by scanning electron microscopy (SEM). Figure 3 As shown, S-NZVI / BC L-600 The particles are uniform in size, connected together, and the overall shape is chain-like, with a particle size of 50nm; Fe and S particles are successfully loaded on C, S-NZVI / BC L-600 The ratio of S, Fe and C particles is S:Fe:C=1:5.5:2.

[0108] The water contact angle is used to measure the hydrophilicity and hydrophobicity of the particles, which affects the dispersion of the particles in the solution. The water contact angle of the prepared materials is measured, such as Figure 4 As shown, S-NZVI / BC L-600 The water contact angle of the nanoparticles is 20°~22°, which means they are hydrophilic substances. They are better dispersed in the aqueous reaction liquid than hydrophobic substances, which is beneficial to their reactivity with pollutants and water.

[0109] The degradation products of the parent pollutant were tested and analyzed. No parent pollutant was detected after the reaction, indicating that the parent pollutant had been completely degraded.

[0110] Comparative Example 1

[0111] Preparation of C-BC biochar;

[0112] The dried corn straw from the facility agriculture crop was placed in a tubular furnace under nitrogen atmosphere, and inert gas was continuously introduced for 30 minutes. The calcination temperature was set at 600°C and the calcination time was 180 minutes. The carbonized black solid was cooled, ground, and placed in a brown bottle for later use.

[0113] The prepared materials were characterized by SEM, and the results were as follows Figure 5 As shown in (a), C-BC presents a regular honeycomb multi-level pore structure with uniform pore size, and secondary pores distributed on the inner surface form a network structure, which is conducive to internal diffusion and adsorption.

[0114] Comparative Example 2

[0115] Preparation of L-BC biochar;

[0116] The dried lotus leaf stems were placed in a tube furnace under nitrogen atmosphere and inert gas was continuously introduced for 30 min. The calcination temperature was set at 600°C and the calcination time was 180 min. The carbonized black solid was cooled, ground, and placed in a brown bottle for later use.

[0117] The prepared materials were characterized by SEM, and the results were as follows Figure 5 As shown in (b), the L-BC particle sheets are distributed with micropores and mesopores, presenting a stacked sheet-like porous structure.

[0118] Comparative Example 3

[0119] Preparation of N / C-BC particles;

[0120] (1) Dried corn straw from a facility agricultural crop was placed in a tubular furnace under nitrogen atmosphere, and inert gas was continuously introduced for 30 minutes. The calcination temperature was set at 600°C and the calcination time was 180 minutes. The carbonized black solid was cooled, ground, and placed in a brown bottle for later use to obtain C-BC.

[0121] (2) C-BC was added to a certain amount of ethanol, stirred continuously for 30 minutes, and ultrasonicated for 60 minutes to prepare a suspension. A certain amount of ammonium nitrate was added to the suspension, and the suspension was heated and stirred until the solvent evaporated to obtain a black substance. The black substance was calcined in a tube furnace at 600°C for 90 minutes. After the sample cooled to room temperature, the black powder was ground and stored in a vacuum to obtain N / C-BC particles.

[0122] In this invention, the mass ratio of C-BC to ammonium nitrate is 1:1.

[0123] The prepared materials were characterized by SEM, and the results were as follows Figure 6 As shown in (a), the unmodified surface functional groups are limited in richness, but have the characteristics of adjustable pore structure, easy surface modification, and stable structure. It is modified with N element and presents a uniform and regular honeycomb porous structure. N particles are evenly distributed in the carbon layer outside the pores, and the C:N particle ratio is 2.85:1. High-temperature carbonization is conducive to the generation of nitrogen-rich carbon materials.

[0124] Comparative Example 4

[0125] Preparation of N / L-BC particles;

[0126] (1) The dried lotus leaf stems were placed in a tube furnace under nitrogen atmosphere, and inert gas was continuously introduced for 30 min. The calcination temperature was set at 600°C and the calcination time was 180 min. The carbonized black solid was cooled, ground, and placed in a brown bottle for later use to obtain L-BC.

[0127] (2) L-BC was added to a certain amount of ethanol, stirred continuously for 30 minutes, and ultrasonicated for 60 minutes to form a suspension. A certain amount of ammonium nitrate was added to the suspension, and the mixture was heated and stirred until the solvent evaporated to obtain a black substance. The black substance was then calcined in a tube furnace at 600°C for 90 minutes. After the sample cooled to room temperature, the black powder was ground and stored in a vacuum to produce N / L-BC particles. In this invention, the mass ratio of L-BC to ammonium nitrate was 1:1.

[0128] The prepared materials were characterized by SEM, and the results were as follows Figure 6 As shown in (b), the unmodified surface functional groups have limited richness, but have the characteristics of adjustable pore structure, easy surface modification, and stable structure. It is modified with N element and presents a uniform and regular honeycomb porous structure. N particles are evenly distributed in the carbon layer outside the pores, and the C:N particle ratio is 2.87:1. High-temperature carbonization is conducive to the generation of nitrogen-rich carbon materials.

[0129] GC-MS analysis showed that the S-NZVI / BC in Example 1 C-600 The nanoparticles degrade PAHs. Following the reaction, for the degradation pathway of low-ring PAHs, active free radicals attack the C=C bond in the benzene ring, leading to oxidation, hydroxylation, and ring-opening reactions, ultimately generating monocyclic hydrocarbons and small molecules (Table 2). Compared to other PAH degradation pathways, S-NZVI / BC showed the best degradation performance.

[0130] The selected S-NZVI / BC nanoparticles have low preparation cost and simple operation, which not only saves costs, but also the metal ions produced during the reaction do not cause secondary pollution to the environment, and can achieve safe utilization of the repaired environment.

[0131] Comparative Example 1

[0132] The difference from Example 1 is that Wu et al. (Wu Zhen, Xu Desheng, Wu Hui, et al. Study on the performance of graphite phase g-C3N4 activated persulfate to degrade polycyclic aromatic hydrocarbons in water [J]. Contemporary Chemical Industry, 2022, 51(7): 1590-1592.) used graphite as a carbon source to activate persulfate to degrade trace concentration levels of PAHs in a saline-alkaline environment (pH 9-11, unknown salinity). The test results showed that the degradation time of PAHs (naphthalene) was 30 minutes and tended to degradation equilibrium, and the degradation efficiency was 50-60%.

[0133] Comparative Example 2

[0134] Sulfide nanoscale zero-valent iron-doped biochar prepared in the paper "Persulfate activation by sulfide-modified nanoscale iron supported by biochar (S-nZVI / BC) for degradation of ciprofloxacin" was used to activate persulfate to degrade the aromatic ciprofloxacin at non-trace concentrations in an alkaline environment (pH 8.5, unknown salinity). The test results showed that when the reaction time was 60 minutes, that is, when the reaction approached equilibrium, the degradation rate was less than 40%.

[0135] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing sulfide nano-zero-valent iron doped biochar, characterized in that: include: Using lotus leaf stems and agricultural crop straw as carbon sources, biochar was obtained by carbonizing them at 300-700℃ for 180-540 min in an inert atmosphere. The lotus leaf stems and the facility agriculture crop straws are 0.5 to 1 cm in size; the facility agriculture crop straws are facility agriculture crop corn straws; dissolving a borohydride reducing agent and dithionite in water and mixing them uniformly to obtain a first reaction solution; Dissolving trivalent iron salt and polyethylene glycol in water, adding the biochar, ultrasonicating for 20 to 40 minutes, stirring and introducing nitrogen gas for 30 to 60 minutes to prepare a second reaction solution; Under an inert atmosphere, the first reaction solution is added dropwise to the second reaction solution at a stirring speed of 10 to 20 r / s at a dropping speed of 0.5 to 1.5 mL / s. After the dropwise addition is complete, sulfurization is continued for 25 to 50 minutes to obtain a third reaction solution. The third reaction solution is centrifuged, washed, and the black precipitate is collected and dried to obtain black particles; The molar ratio of the ferric salt to the borohydride and dithionite is 2:4:3; The black particles were placed in a tube furnace, nitrogen was introduced into the tube furnace for 20 to 60 minutes, and the particles were calcined at 150 to 250° C. for 120 to 360 minutes under reducing atmosphere to obtain sulfide nano zero-valent iron doped biochar particles S-NZVI / BC.

2. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, wherein: The trivalent iron salt is ferric chloride or ferric nitrate.

3. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, wherein: The concentration of trivalent iron salt is 0.1~1.6 mol / L.

4. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, wherein: The borohydride is sodium borohydride or potassium borohydride.

5. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, wherein: The concentration of the borohydride reducing agent is 0.4-1.6 mol / L.

6. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, characterized in that: The dithionite is sodium dithionite or potassium dithionite.

7. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, characterized in that ,, the concentration of dithionite is 0.02~0.08 mol / L.

8. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, wherein: The concentration of the polyethylene glycol is 0.5-1.5 g / mL.

9. The method for preparing sulfide nano-zero-valent iron doped biochar according to claim 1, wherein: The reducing atmosphere is hydrogen.

10. Sulfide nano-zero-valent iron-doped biochar prepared by the method according to any one of claims 1 to 9.

11. Use of the sulfide nano-zero-valent iron doped biochar according to claim 10 in activating persulfate to degrade polycyclic aromatic hydrocarbons in saline-alkali environments.

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