Nitrogen / sulfur co-doped charcoal loaded nano zero-valent iron as well as preparation method and application thereof

Abstract

The invention provides nitrogen / sulfur co-doped charcoal loaded nano zero-valent iron as well as a preparation method and application thereof, and relates to the technical field of sewage treatment. The nitrogen / sulfur co-doped biochar loaded nano zero-valent iron is a composite material prepared by taking nitrogen / sulfur co-doped biochar as a carrier material and loading nano zero-valent iron; the nitrogen / sulfur co-doped biochar is prepared from the following raw materials: melamine, diphenyl disulfide and walnut shells. The nitrogen / sulfur co-doped biochar loaded nano zero-valent iron prepared by the invention combines the porous characteristic of biochar and the high reaction activity of nano zero-valent iron, not only has excellent oxidation resistance and corrosion resistance, but also retains good hydrophilicity and magnetism, can efficiently remove antibiotic pollutants in the environment, and has a good application prospect. And actual operation and recycling are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, and a preparation method and application thereof. Background Art

[0002] The CX bond (X=F, Cl or Br) in halogenated antibiotics not only has antibacterial activity, but also has extremely strong chemical stability and can exist in the environment for a long time. This property enables them to sustainably induce the production of new antibiotic resistance genes and resistant bacteria, posing a serious threat to aquatic ecosystems and human health.

[0003] Nano-zero-valent iron (nZVI) has shown significant potential in removing antibiotics due to its high reactivity and easy separation characteristics. However, its high reactivity makes it easy to react with water, forming a Fe oxide passivation layer, which hinders electron transfer and reduces degradation efficiency. To overcome these limitations, researchers have loaded nZVI on materials such as biochar (BC) and activated carbon to enhance stability and dispersibility. Among them, nZVI loaded on BC can improve electron transfer efficiency and active sites, thereby enhancing the adsorption and degradation of antibiotics. BC, as a porous carbon material, is made from pyrolyzed biomass and is considered an ideal adsorbent due to its abundant raw materials and low cost, but its adsorption performance is limited by surface functional groups and porosity. By making nitrogen-sulfur co-doped biochar (NSBC), specific chemical functional groups can be introduced and the material structure can be adjusted to enhance the interaction with pollutants. Nitrogen regulates surface alkalinity and promotes electrostatic interactions, and sulfur doping provides negatively charged functional groups and enhances van der Waals forces, significantly improving the adsorption performance of modified biochar.

[0004] Chinese invention patent CN110586038A discloses a biochar-loaded nano zero-valent iron material and its application. The preparation method of the zero-valent iron material is as follows: 1. The biomass is crushed and subjected to primary chemical modification to obtain modified biomass; 2. In a nitrogen atmosphere, the pyrolysis furnace is first heated to 450-550°C, and then the modified biomass is placed in the pyrolysis furnace for pyrolysis, and then heated to 650-750°C at an average rate of 2-3°C / min to obtain biochar; 3. The biochar is deeply chemically modified to obtain modified biochar; 4. Anhydrous ethanol, ferrous salt, ultrapure water and modified biochar are mixed evenly to obtain a suspension; 5. In a nitrogen atmosphere, a reducing agent is added to the suspension to reduce ferrous ions, and the reaction is carried out for 0.5-1h after the addition is completed to obtain the biomass-loaded nano zero-valent iron material. This patent does not perform nitrogen / sulfur co-doping on biochar, and does not study the application of biochar-loaded nano zero-valent iron materials in the degradation of antibiotics in water bodies.

[0005] The document "Lu Xiuguo, Chen Jing, Guan Wei. Research on the remediation of Cr(VI) contaminated soil by walnut shell biomass loaded with nano-zero-valent iron [J]. Applied Chemical Industry, 2023, 52(6)." Walnut shells were used to load nano-zero-valent iron to prepare a walnut shell biomass loaded with nano-zero-valent iron composite material, which was added to Cr(VI) contaminated soil. The effects of the addition amount, soil-water ratio and time on the remediation effect of Cr(VI) contaminated soil were studied through soil passivation experiments. This document did not conduct nitrogen / sulfur co-doping on walnut shell biochar, and did not study the application of walnut shell biomass loaded with nano-zero-valent iron in the degradation of antibiotics in water bodies.

[0006] In view of this, it is necessary to provide a co-doped nitrogen / sulfur biochar loaded with nano zero-valent iron to improve its ability to remove halogenated antibiotics, enhance the material's antioxidant capacity and extend its service life. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron and a preparation method and application thereof. Nitrogen and sulfur from specific sources are doped into the biochar, which is then loaded with nano zero-valent iron. The obtained product is applied to the removal of antibiotics, which greatly improves the ability of nano zero-valent iron to remove antibiotics in water.

[0008] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention is as follows:

[0009] On the one hand, the present invention provides a nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, wherein the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is a composite material obtained by using nitrogen / sulfur co-doped biochar as a carrier material and loading nano zero-valent iron; the raw materials for preparing the nitrogen / sulfur co-doped biochar include melamine, diphenyl disulfide and walnut shells.

[0010] Preferably, in the raw material for preparing nitrogen / sulfur co-doped biochar, the mass ratio of the total mass of melamine and diphenyl disulfide to the mass ratio of walnut shell is 0.5-2:1.

[0011] Further preferably, in the raw material for preparing nitrogen / sulfur co-doped biochar, the mass ratio of the total mass of melamine and diphenyl disulfide to the mass ratio of walnut shell is 1:1.

[0012] Preferably, in the raw material for preparing nitrogen / sulfur co-doped biochar, the molar ratio of melamine to diphenyl disulfide is 1-2:1.

[0013] Further preferably, in the raw material for preparing nitrogen / sulfur co-doped biochar, the molar ratio of melamine to diphenyl disulfide is 2:1.

[0014] In the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron of the present invention, the biochar used is walnut shell.

[0015] In another aspect, the present invention provides a method for preparing the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, comprising the following steps:

[0016] Step 1: Mix melamine, diphenyl disulfide and walnut shells in N 2 High temperature pyrolysis under atmosphere to prepare nitrogen / sulfur co-doped biochar;

[0017] Step 2: Nitrogen / sulfur co-doping of biochar with FeSO 4 7H 2 O aqueous solution and then mixed with NaBH 4 The solutions are mixed and reacted to obtain nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron.

[0018] Preferably, the preparation method comprises the following steps:

[0019] Step 1: Mix melamine and diphenyl disulfide to obtain a mixture, mix the mixture with walnut shells, and 2 High temperature pyrolysis under atmosphere to prepare nitrogen / sulfur co-doped biochar;

[0020] Step 2: Nitrogen / sulfur co-doping of biochar with FeSO 4 7H 2 O aqueous solution, and then add NaBH 4 solution, and the reaction yielded nitrogen / sulfur co-doped biochar loaded with nano-zero-valent iron.

[0021] More preferably, in step 1, the molar ratio of N to S is 1-2:1.

[0022] Most preferably, in step 1, the molar ratio of N to S is 2:1.

[0023] More preferably, in step 1, the mass ratio of the total mass of melamine and diphenyl disulfide to the mass of walnut shell is 0.5-2:1.

[0024] Most preferably, in step 1, the mass ratio of the total mass of melamine and diphenyl disulfide to the mass of walnut shells is 1:1.

[0025] More preferably, in step 1, the temperature of the high-temperature pyrolysis is 700-850°C, the heating rate of the high-temperature pyrolysis is 5-15°C / min, and the reaction time of the high-temperature pyrolysis is 3-5h.

[0026] Most preferably, in step 1, the temperature of the high-temperature pyrolysis is 800° C., the heating rate of the high-temperature pyrolysis is 10° C. / min, and the reaction time of the high-temperature pyrolysis is 4 hours.

[0027] More preferably, in step 2, the nitrogen / sulfur co-doped biochar and FeSO 4 7H 2 The mass ratio of Fe in O aqueous solution is 21-28:28.

[0028] Most preferably, in step 2, the nitrogen / sulfur co-doped biochar is mixed with FeSO 4 7H 2 The mass ratio of Fe in O aqueous solution is 1:1.

[0029] More preferably, in step 2, the FeSO 4 7H 2 The concentration of O aqueous solution is 5-10g / L.

[0030] Most preferably, in step 2, the FeSO 4 7H 2 The concentration of the O aqueous solution is 5 g / L.

[0031] More preferably, in step 2, the NaBH 4 The concentration of the solution is 0.24-0.3 mol / L.

[0032] Most preferably, in step 2, the NaBH 4 The concentration of the solution is 0.26 mol / L.

[0033] More preferably, in step 2, the FeSO 4 7H 2 O aqueous solution and NaBH 4 The volume ratio of the solution is 0.5-1:1.

[0034] Most preferably, in step 2, the FeSO 4 7H 2 O aqueous solution and NaBH 4 The volume ratio of the solution is 0.8:1.

[0035] Finally, the present invention provides the use of the above nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron in removing antibiotic pollutants.

[0036] The beneficial effects of the present invention are:

[0037] (1) The nitrogen / sulfur co-doped biochar loaded with nano-zero-valent iron prepared by the present invention combines the porous characteristics of modified biochar with the high reactivity of nano-zero-valent iron. It not only has excellent antioxidant and anti-corrosion properties, but also retains good hydrophilicity and magnetism. It can efficiently remove antibiotic pollutants in the environment under ambient conditions and is easy to operate and recycle.

[0038] (2) The present invention significantly improves the dispersibility and stability of nano-zero-valent iron by using nitrogen / sulfur co-doped biochar as a carrier; nitrogen / sulfur co-doped biochar, with its porous structure, wrinkle defects and abundant surface active sites, effectively promotes the uniform distribution of nano-zero-valent iron particles, significantly enhances the exposure of active sites, increases the contact area with antibiotic pollutants and improves the reaction activity, and ultimately significantly improves the removal efficiency of antibiotics.

[0039] (3) NSBC-nZVI has good regeneration and reuse performance, and still has a high antibiotic removal efficiency after multiple uses, significantly reducing long-term operating costs and improving economic feasibility. In addition, NSBC-nZVI can avoid the risk of secondary pollution in the process of treating antibiotic-containing pollutants and shows excellent performance in the treatment of high-concentration antibiotic-contaminated wastewater.

[0040] (4) The present invention provides an efficient and environmentally friendly solution for the removal of antibiotic pollutants, filling the gap in related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The figures are the results of the influence of the materials prepared in Example 1, Example 5, Comparative Examples 1-2 and Comparative Examples 4-10 on the removal of CIP, wherein (a) is the results of the influence of the materials prepared in Example 1 and Comparative Examples 5-6 on the removal of CIP; (b) is the results of the influence of the materials prepared in Example 1, Example 5, Comparative Examples 1-2, Comparative Examples 4 and Comparative Examples 7-10 on the removal of CIP.

[0042] Figure 2 These are SEM images of NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3, wherein (a) is the SEM image of NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3; (b) is the SEM-EDS element mapping image of NSBC-nZVI prepared in Example 1.

[0043] Figure 3These are the XRD diagrams of NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, SBC-nZVI and NBC-nZVI-1 prepared in Examples 1-2 and Comparative Examples 1-4, wherein (a) is the XRD diagram of NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3; (b) is the XRD diagram of NBC-nZVI-1 prepared in Comparative Example 4.

[0044] Figure 4 FTIR graphs of NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3.

[0045] Figure 5 Raman graphs of NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3.

[0046] Figure 6 This is a graph showing the experimental results of CIP degradation by NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, SBC-nZVI, and NBC-nZVI-1 prepared in Examples 1-2 and Comparative Examples 1-4.

[0047] Figure 7 This is a graph showing the experimental results of CIP degradation by NSBC-nZVI prepared in Example 1 under different pH conditions.

[0048] Figure 8 This is a comparison chart of the recycling performance of the NSBC-nZVI material prepared in Example 1. DETAILED DESCRIPTION

[0049] The following non-limiting examples can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. The following content is merely an exemplary description of the scope of the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, which should also fall within the scope of the present invention.

[0050] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those generally understood by those of ordinary skill in the art to which the present invention belongs.

[0051] The present invention is further described below by way of specific examples. The various chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified. Products from different manufacturers have no significant effect on the effect. Unless otherwise specified, it is understood that the reaction is carried out at room temperature.

[0052] Glossary:

[0053] BC: biochar;

[0054] nZVI: nano zero-valent iron;

[0055] BC-nZVI: biochar loaded with nano-zero-valent iron;

[0056] SBC-nZVI: sulfur-doped biochar loaded with nano-zero-valent iron;

[0057] NBC-nZVI: nitrogen-doped biochar loaded with nano-zero-valent iron;

[0058] NSBC-nZVI: Nitrogen / sulfur co-doped biochar loaded with nano-zero-valent iron.

[0059] Source of walnut shell: 200 mesh walnut shell powder from Saihang Environmental Protection Technology Co., Ltd.

[0060] The source of corn straw: 200 mesh corn straw shell powder from Su Rui Agricultural Products Processing Plant.

[0061] Example 1

[0062] A method for preparing nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron comprises the following steps:

[0063] Step 1. Mix 0.85 g of melamine and 2.2 g of diphenyl disulfide evenly, mix the mixture with 3.05 g of walnut shells, place them in a 50 mL crucible, heat to 800 ° C in a tube furnace at a heating rate of 10 ° C / min and maintain for 4 hours to prepare nitrogen / sulfur co-doped biochar (NSBC) powder.

[0064] Step 2: Mix 0.2 g of NSBC and 1 g of FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water was added, and N 2 Stir for 0.5 h under the conditions, stir evenly, add 250 mL, 0.26 mol / L NaBH 4 After the aqueous solution is added dropwise, it is stirred at the same speed for 1 hour to allow it to react fully.

[0065] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, labeled as NSBC-nZVI.

[0066] In the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron obtained in Example 1, the molar ratio of nitrogen to sulfur is 2:1, and the mass ratio of NSBC to Fe is 1:1.

[0067] Example 2

[0068] A method for preparing nitrogen-doped biochar loaded with nano zero-valent iron comprises the following steps:

[0069] Step 1: Mix 0.4 g of melamine and 3 g of walnut shells, place them in a 50 mL crucible, heat them to 800 ° C in a tube furnace at a heating rate of 10 ° C / min and maintain for 4 hours to prepare nitrogen-doped biochar (NBC) powder.

[0070] Step 2: Mix 0.2g NBC and 1g FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water was added, and N 2 Stir for 0.5 h under the conditions, stir evenly, add 250 mL, 0.26 mol / L NaBH 4 After the aqueous solution is added dropwise, it is stirred at the same speed for 1 hour to allow it to react fully.

[0071] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain nitrogen-doped biochar loaded with nano zero-valent iron, labeled as NBC-nZVI.

[0072] In the nitrogen-doped biochar loaded with nano-zero-valent iron obtained in Example 2, the mass ratio of NBC to Fe is 1:1.

[0073] Example 3

[0074] A method for preparing nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron comprises the following steps:

[0075] Step 1: Evenly mix 0.71 g melamine and 2.0 g diphenyl disulfide, mix the mixture with 2.71 g walnut shells, place them in a 50 mL crucible, heat to 700 ° C in a tube furnace at a heating rate of 5 ° C / min and maintain for 5 h to prepare nitrogen / sulfur co-doped biochar (NSBC) powder.

[0076] Step 2: Mix 0.15 g of NSBC and 1 g of FeSO4 7H 2 O was placed in a 1L three-necked flask, 100mL of pure water was added, and N 2 Stir for 3 h under the same conditions, stir evenly, and add 200 mL of 0.24 mol / L NaBH 4 After the aqueous solution is added dropwise, it is stirred at the same speed for 2 hours to allow it to react fully.

[0077] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, labeled as NSBC-nZVI-1.

[0078] In the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron obtained in Example 3, the molar ratio of nitrogen to sulfur is 1.84:1, and the mass ratio of NSBC to Fe is 3:4.

[0079] Example 4

[0080] A method for preparing nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron comprises the following steps:

[0081] Step 1: Evenly mix 0.91 g melamine and 2.5 g diphenyl disulfide, mix the mixture with 3.41 g walnut shells, place them in a 50 mL crucible, heat to 850 ° C in a tube furnace at a heating rate of 15 ° C / min and maintain for 3 h to prepare nitrogen / sulfur co-doped biochar (NSBC) powder.

[0082] Step 2: Mix 0.24 g of NSBC and 1.4 g of FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water solution was added, and N 2 Stir for 2 h under the same conditions, stir evenly, and add 200 mL of 0.3 mol / L NaBH 4 After the aqueous solution is added dropwise, it is stirred at the same speed for 2 hours to allow it to react fully.

[0083] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, labeled as NSBC-nZVI-2.

[0084] In the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron obtained in Example 4, the molar ratio of nitrogen to sulfur is 1.88:1, and the mass ratio of NSBC to Fe is 6:7.

[0085] Example 5

[0086] Compared with Example 1, the total mass of melamine and diphenyl disulfide remains unchanged, the molar ratio of nitrogen to sulfur is changed from 2:1 to 1:1, and the remaining raw materials and preparation process are the same as those in Example 1, and nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is prepared, which is marked as NSBC-nZVI-3.

[0087] Comparative Example 1

[0088] A method for preparing nano zero-valent iron comprises the following steps:

[0089] Step 1: 1g FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water solution was added, and N 2 Stir for 0.5 h under the same conditions, stir evenly, and add 250 mL of NaBH 4 After the addition is complete, the mixed solution is stirred at the same speed for 1 hour to allow it to react fully.

[0090] Step 2: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain nano zero-valent iron, which is marked as nZVI.

[0091] Comparative Example 2

[0092] A method for preparing biochar-loaded nano-zero-valent iron comprises the following steps:

[0093] Step 1: 3 g of walnut shell biomass was placed in a 50 mL crucible, heated to 800 °C in a tube furnace at a heating rate of 10 °C / min and maintained for 4 h to prepare biochar (BC) powder.

[0094] Step 2: Mix 0.2g BC and 1g FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water solution was added, and N 2 Stir for 0.5 h under the same conditions, stir evenly, and add 250 mL of NaBH 4 After the addition is complete, the mixed solution is stirred at the same speed for 1 hour to allow it to react fully.

[0095] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain biochar-loaded nano zero-valent iron, which is labeled as BC-nZVI.

[0096] In the biochar-loaded nano-zero-valent iron obtained in Comparative Example 2, the mass ratio of BC to Fe is 1:1.

[0097] Comparative Example 3

[0098] A method for preparing sulfur-doped biochar loaded with nano zero-valent iron comprises the following steps:

[0099] Step 1: 0.4 g of diphenyl disulfide was mixed with 3 g of walnut shell biomass, placed in a 50 mL crucible, heated to 800 ° C in a tube furnace at a heating rate of 10 ° C / min and maintained for 4 h to prepare sulfur-doped biochar (SBC) powder.

[0100] Step 2: Mix 0.2g of SBC and 1g of FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water solution was added, and N 2 Stir for 0.5 h under the same conditions, stir evenly, and add 250 mL of NaBH 4 After the addition is complete, the mixed solution is stirred at the same speed for 1 hour to allow it to react fully.

[0101] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain sulfur-doped biochar loaded with nano zero-valent iron, labeled as SBC-nZVI.

[0102] In the sulfur-doped biochar loaded with nano zero-valent iron obtained in Comparative Example 3, the mass ratio of SBC to Fe is 1:1.

[0103] Comparative Example 4

[0104] The difference from Example 2 is that the walnut shells in Example 2 are replaced with corn stalks. The specific steps are as follows:

[0105] A method for preparing nitrogen-doped biochar loaded with nano zero-valent iron comprises the following steps:

[0106] Step 1: Mix 0.4 g of melamine with 3 g of corn straw, place them in a 50 mL crucible, heat them to 800 ° C in a tube furnace at a heating rate of 10 ° C / min and maintain for 4 hours to prepare nitrogen-doped biochar (NBC) powder.

[0107] Step 2: Mix 0.2g NBC and 1g FeSO 4 7H 2 O was placed in a 1L three-necked flask, 200mL of pure water was added, and N 2 Stir for 0.5 h under the same conditions, stir evenly, and add 250 mL of NaBH 4 After the addition is complete, the mixed solution is stirred at the same speed for 1 hour to allow it to react fully.

[0108] Step 3: Wash and collect the black solid precipitate in the suspension with anhydrous ethanol and deionized water respectively, and then freeze-dry it under vacuum conditions at -52°C to obtain nitrogen-doped biochar loaded with nano zero-valent iron, labeled as NBC-nZVI-1.

[0109] In the nitrogen-doped biochar loaded with nano-zero-valent iron obtained in Comparative Example 4, the mass ratio of NBC to Fe is 1:1.

[0110] Comparative Example 5

[0111] Different from Example 1, 2.2 g of diphenyl disulfide in Example 1 was replaced with thiourea to prepare nitrogen / sulfur co-doped biochar-loaded nano zero-valent iron, labeled as NSBC-nZVI-4. In the nitrogen / sulfur co-doped biochar-loaded nano zero-valent iron, the molar ratio of nitrogen to sulfur was 2:1.

[0112] Comparative Example 6

[0113] Different from Example 1, 2.2 g of diphenyl disulfide in Example 1 was replaced with sodium dodecyl sulfate to prepare nitrogen / sulfur co-doped biochar-loaded nano zero-valent iron, which was labeled as NSBC-nZVI-5. In the nitrogen / sulfur co-doped biochar-loaded nano zero-valent iron, the molar ratio of nitrogen to sulfur was 2:1.

[0114] Comparative Example 7

[0115] Compared with Example 1, the total mass of melamine and diphenyl disulfide remains unchanged, the molar ratio of nitrogen to sulfur is changed from 2:1 to 1:3, and the remaining raw materials and preparation process are the same as those in Example 1, and nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is prepared, which is marked as NSBC-nZVI-6.

[0116] Comparative Example 8

[0117] Compared with Example 1, the total mass of melamine and diphenyl disulfide remains unchanged, the molar ratio of nitrogen to sulfur is changed from 2:1 to 1:2, and the remaining raw materials and preparation process are the same as those in Example 1, and nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is prepared, which is marked as NSBC-nZVI-7.

[0118] Comparative Example 9

[0119] Compared with Example 1, the total mass of melamine and diphenyl disulfide remains unchanged, the molar ratio of nitrogen to sulfur is changed from 2:1 to 1:1, and the remaining raw materials and preparation process are the same as those in Example 1, and nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is prepared, which is marked as NSBC-nZVI-8.

[0120] Comparative Example 10

[0121] Compared with Example 1, the total mass of melamine and diphenyl disulfide remains unchanged, the molar ratio of nitrogen to sulfur is changed from 2:1 to 3:1, and the remaining raw materials and preparation process are the same as those in Example 1, and nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is prepared, which is labeled as NSBC-nZVI-9.

[0122] Effect detection

[0123] 1. Effects of different sulfur bases and nitrogen / sulfur molar ratios on the removal of ciprofloxacin

[0124] The effects of the materials prepared in Example 1, Example 5, Comparative Examples 1-2 and Comparative Examples 4-10 on the removal of ciprofloxacin (CIP) were analyzed. The results are as follows: Figure 1 The specific analysis process is as follows:

[0125] like Figure 1 As shown in (a), Comparative Example 5, Comparative Example 6, and Example 1 respectively used thiourea, sodium dodecyl sulfate, and diphenyl disulfide as sulfur sources to prepare the materials. The results showed that when diphenyl disulfide was used as the sulfur base, the removal rate of ciprofloxacin by NSBC-nZVI reached 93%. This result shows that diphenyl disulfide plays an important role as a sulfur source in improving the adsorption performance and catalytic activity of the material. On this basis, the performance of NSBC-nZVI was further optimized by changing the molar ratio of nitrogen and sulfur. Under different N / S molar ratios, the surface properties, electron transfer rate, and catalytic removal ability of the material have all changed significantly. By adjusting the ratio of nitrogen and sulfur, efficient removal of different types of pollutants, especially antibiotics such as ciprofloxacin, can be achieved. As Figure 1 As shown in (b), when the molar ratio of nitrogen to sulfur is 2:1, the removal rate of ciprofloxacin is the highest, so subsequent studies are carried out on this basis.

[0126] Figure 1 In the figure, different letters (a, b, c, d, e, f) indicate that the removal rates are significantly different; the same letters indicate that there is no significant difference in the removal rates.

[0127] 2. Scanning electron microscopy analysis

[0128] The NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3 were subjected to scanning electron microscopy (SEM) analysis. The analysis results are shown in FIG. Figure 2 shown.

[0129] like Figure 2As shown in (a), the SEM image shows that nZVI is spherical, and there is obvious agglomeration between particles, which are tightly aggregated to form a chain structure. In contrast, BC-nZVI shows an amorphous, intact honeycomb structure with a large specific surface area, in which nZVI is mainly attached to the surface of biochar. After nitrogen or sulfur modification, BC exhibits a broken honeycomb structure, providing a wider space, which is conducive to the loading of nZVI. After N / S co-doping, the pore structure of BC is significantly improved, and a large number of spherical aggregates are distributed in the particles, and the degree of aggregation between particles is significantly reduced. SEM-EDS elemental mapping analysis ( Figure 2 (b) reveals the uniform distribution of C, N, Fe, O, and S, further demonstrating the successful nitrogen / sulfur co-doping.

[0130] 3. X-ray diffraction analysis

[0131] X-ray diffraction (XRD) analysis was performed on NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, SBC-nZVI, and NBC-nZVI-1 prepared in Examples 1-2 and Comparative Examples 1-4. The analysis results are shown in Figure 3 .

[0132] like Figure 3 As shown, XRD analysis reveals the crystal structure of the material. The small peaks at 2θ = 35.7° and 44.4° in the spectrum are attributed to Fe 2 O 3 and Fe 0 Although Fe 2 O 3 The characteristic diffraction peak of is not significant, indicating that it comes from the partial oxidation of nano-zero-valent iron. This shows that NSBC-nZVI not only promotes Fe 0 The formation of Fe 0 The XRD results preliminarily verified that nZVI was successfully loaded onto NSBC. The same results were obtained when corn stalks were used as the biomass substrate, and the Fe 3 O 4 , which is also due to the oxidation of the material during the preparation process.

[0133] 4. Fourier transform infrared spectroscopy analysis

[0134] Fourier transform infrared spectroscopy (FTIR) analysis was performed on NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3. The analysis results are shown in Figure 4 .

[0135] like Figure 4As shown, nZVI of different substrates is at 3423, 2907, 1639, 1114, 599 cm -1 There is an obvious absorption peak at 3423cm -1 Nearby, the main characteristic absorption peak is OH bond, which may be water adsorbed on the surface of the material; at 2907cm -1 The main characteristic absorption peak is -CH 2 , belonging to the stretching vibration of the C-OH group; at 1639cm -1 Due to the presence of the aromatic ring structure, it appears as the stretching vibration peak of the C=O group; at 1114cm -1 At 599cm, there is an absorption peak caused by the stretching vibration of the carboxyl C-OH bond; -1 The peak of Fe-O stretching vibration is at 1400 nm, indicating that iron is successfully loaded on the carbon surface. The abundant oxygen-containing functional groups (such as hydroxyl and carboxyl) on the surface of NSBC-nZVI can provide effective active sites for electron transfer.

[0136] 5. Raman spectroscopy analysis

[0137] Raman spectroscopy (Raman) analysis was performed on NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, and SBC-nZVI prepared in Examples 1-2 and Comparative Examples 1-3. The analysis results are shown in Figure 5 .

[0138] like Figure 5 As shown in Figure 2, the Raman spectra of different materials show that the surface-loaded BC-nZVI reduces the defect degree of the carbon material, indicating that there are fewer defects on the surface of the material, which may lead to the adsorption sites being covered on the surface of the material. However, the introduction of nitrogen (N) and sulfur (S) significantly increased the degree of defects on the surface of the carbon material, making I D / I G The ratio increases, which may increase the active sites on the material surface, which is beneficial to the loading of nZVI and enhances its interaction with pollutants. The co-doping of nitrogen and sulfur not only promotes electron transfer on the material surface by adjusting the material structure, but also may improve its catalytic performance, further improving the efficiency of the material in the water treatment process.

[0139] 6. Analysis of the ability to degrade antibiotic pollutants

[0140] The NSBC-nZVI, NBC-nZVI, nZVI, BC-nZVI, SBC-nZVI, and NBC-nZVI-1 materials prepared in Examples 1-2 and Comparative Examples 1-4 were applied to the degradation of antibiotic pollutants. The specific application process is as follows: Taking CIP (ciprofloxacin), a representative antibiotic pollutant in water, as the target pollutant, 2 mg of the target catalytic material was added to 40 mL of a 50 mg / L CIP solution. Samples were taken at fixed intervals, filtered through a 0.22 μm filter membrane, collected in a centrifuge tube, and then analyzed by liquid chromatography to detect the residual concentration of CIP.

[0141] Figure 6 The experimental results of CIP degradation by nZVI on different substrates prepared by Examples 1-2 and Comparative Examples 1-4 are shown. The results show that the degradation rates of CIP by NBC-nZVI, NSBC-nZVI, nZVI, BC-nZVI, SBC-nZVI, and NBC-nZVI-1 are 71%, 95%, 40%, 68%, 41%, and 70%, respectively. The removal of CIP by NBC-nZVI and NBC-nZVI-1 was compared, and the degradation rate results showed that when different biomasses were used as nZVI carriers, no significant differences were shown, which may be related to the similarity of their carbonized structures or the distribution of surface functional groups. The result of NSBC-nZVI removing CIP shows that nitrogen / sulfur co-doping significantly improves the degradation efficiency on the surface of nZVI, and the synergistic effect of nitrogen / sulfur plays a key role in the degradation process of CIP. In particular, the degradation rate of NSBC-nZVI is the highest, which may be due to the fact that nitrogen / sulfur co-doping improves the surface activity and electron transfer ability of the material, thereby enhancing its catalytic degradation performance for CIP.

[0142] Figure 7 The effect of the NSBC-nZVI material prepared in Example 1 on the removal of CIP at different pH values ​​is demonstrated. The results show that NSBC-nZVI has a significant removal effect on CIP under acidic and neutral conditions, while under alkaline conditions, the removal effect is significantly inhibited. This may be because in an alkaline environment, the surface of NSBC-nZVI undergoes varying degrees of oxidation, resulting in a reduction in its surface active sites, thereby reducing its ability to catalyze the degradation of CIP. In addition, the pH value has an important influence on the electron transfer ability of nZVI and its interaction with CIP, which may be the main reason for the weakening of its degradation effect under alkaline conditions.

[0143] 7. Recycling performance

[0144] In order to investigate the recycling performance of the material prepared by the present invention, the NSBC-nZVI material prepared in Example 1 was used as an example to carry out a recycling experiment. 2.00 mg NSBC-nZVI was weighed in a 40 mL brown sample bottle lined with PTFE, 50 mg / L CIP solution was added, and the reaction was carried out according to the experimental steps of the degradation ability analysis of antibiotic pollutants, and each treatment was 1 hour. After the reaction was completed, the solution was filtered, rinsed with deionized water and anhydrous methanol 3 times in sequence, and then filtered, and the obtained material was vacuum freeze-dried for 12 hours. After drying, 2.00 mg of the sample was weighed again, and the same experimental steps were repeated to carry out the second and third recycling experiments. The experiments were marked as recovery once, twice, and three times, respectively.

[0145] Figure 8 The recycling performance of the NSBC-nZVI material prepared in Example 1 is demonstrated. In three experiments, the degradation rates of NSBC-nZVI to CIP were 95%, 79% and 63%, respectively. The gradual decrease in its degradation rate to CIP may be related to the consumption of active sites on the surface of the material or slight oxidation, but overall, the NSBC-nZVI material still exhibits strong catalytic stability and durability, and is suitable for long-term use in practical applications.

[0146] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron, characterized in that: The nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron is a composite material obtained by loading nano zero-valent iron with nitrogen / sulfur co-doped biochar as a carrier material; the raw materials for preparing the nitrogen / sulfur co-doped biochar include melamine, diphenyl disulfide and walnut shells.

2. The nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron according to claim 1, characterized in that: In the raw materials for preparing nitrogen / sulfur co-doped biochar, the mass ratio of the total mass of melamine and diphenyl disulfide to walnut shell is 0.5-2:1; preferably, the mass ratio of the total mass of melamine and diphenyl disulfide to walnut shell is 1:

1.

3. The nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron according to claim 1, characterized in that: In the raw material for preparing nitrogen / sulfur co-doped biochar, the molar ratio of melamine to diphenyl disulfide is 1-2:1; preferably, the molar ratio of melamine to diphenyl disulfide is 2:

1.

4. The method for preparing nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Mix melamine, diphenyl disulfide and walnut shells, and pyrolyze them at high temperature under N2 atmosphere to prepare nitrogen / sulfur co-doped biochar; Step 2: Mix the nitrogen / sulfur co-doped biochar with the FeSO4·7H2O aqueous solution, and after continuous stirring, add the NaBH4 solution dropwise to react and obtain the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron.

5. The preparation method according to claim 4, characterized in that: The following steps are involved: Step 1: Evenly mix melamine and diphenyl disulfide to obtain a mixture, mix the mixture with walnut shells, and pyrolyze them at high temperature under a N2 atmosphere to prepare nitrogen / sulfur co-doped biochar; Step 2: Mix the nitrogen / sulfur co-doped biochar with the FeSO4·7H2O aqueous solution, continue stirring and then slowly add the NaBH4 solution to react to obtain the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron.

6. The preparation method according to any one of claims 4 to 5, characterized in that: In step 1, the molar ratio of melamine to diphenyl disulfide is 1-2:1; and the mass ratio of the total mass of melamine and diphenyl disulfide to walnut shell is 0.5-2:

1.

7. The preparation method according to any one of claims 4 to 5, characterized in that: In step 1, the temperature of the high-temperature pyrolysis is 700-850° C., the heating rate of the high-temperature pyrolysis is 5-15° C. / min, and the reaction time of the high-temperature pyrolysis is 3-5 h.

8. The preparation method according to any one of claims 4 to 5, characterized in that: In step 2, the mass ratio of the nitrogen / sulfur co-doped biochar to Fe in the FeSO4·7H2O aqueous solution is 21-28:

28.

9. The preparation method according to any one of claims 4 to 5, characterized in that: In step 2, the concentration of the FeSO4·7H2O aqueous solution is 5-10 g / L; the concentration of the NaBH4 solution is 0.24-0.3 mol / L; the volume ratio of the FeSO4·7H2O aqueous solution to the NaBH4 solution is 0.5-1:

1.

10. Use of the nitrogen / sulfur co-doped biochar loaded with nano zero-valent iron as described in any one of claims 1 to 3 in removing antibiotic pollutants.

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