Nitrobenzene wastewater treatment method based on sulfur-doped activated carbon and nanometer zero-valent iron gradient composite material
By combining sulfur-doped activated carbon@nano-zero-valent iron gradient composite material with pulsed hydrogen peroxide ultrasonic synergistic process, the problems of low efficiency, high cost and large sludge volume in the treatment of nitrobenzene wastewater in traditional methods have been solved, achieving efficient degradation and heavy metal removal.
Patent Information
- Application Number
- CN202511620971.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-07
- Publication Date
- 2026-01-02
AI Technical Summary
Traditional methods are difficult to efficiently degrade nitrobenzene wastewater under neutral pH conditions, and they also suffer from problems such as high reagent costs, large sludge volume, and insufficient removal rate.
By employing sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, combined with pulsed hydrogen peroxide addition and ultrasonic synergistic process, efficient degradation of nitrobenzene and simultaneous removal of heavy metals under neutral pH conditions can be achieved.
Under neutral pH conditions, the nitrobenzene removal rate reached 99.5%, the sludge volume was reduced by 30%, the effluent nitrobenzene concentration was less than 0.2 mg/L, and the total chromium and COD met the standards, thus reducing the cost of acid-base adjustment.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method for treating nitrobenzene wastewater based on sulfur-doped activated carbon@nano-zero-valent iron gradient composite material. Background Technology
[0002] Nitrobenzene is a typical recalcitrant pollutant in wastewater from the chemical and pharmaceutical industries. It is highly toxic and carcinogenic, and its emission concentration must be strictly controlled below 0.5 mg / L (GB 8978-1996). Traditional treatment methods have the following drawbacks: Fenton oxidation has limitations: it requires pH adjustment to 2-4, has high reagent costs, and generates a large amount of iron-containing sludge (0.2-0.3 kg / m³). 3 Hydrogen peroxide has low efficiency: single addition leads to excessively high local concentrations, causing ineffective decomposition; activated carbon adsorption bottleneck: conventional activated carbon-supported nZVI materials are easily passivated under neutral conditions, and the nitrobenzene removal rate is less than 80%. Summary of the Invention
[0003] To address the aforementioned issues, this invention provides a method for treating nitrobenzene wastewater based on sulfur-doped activated carbon@nano-zero-valent iron gradient composite material. This invention achieves efficient degradation of nitrobenzene and simultaneous removal of heavy metals at neutral pH through a combination of sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, pulsed hydrogen peroxide dosing, and ultrasonic synergistic process.
[0004] To achieve the above objectives, the present invention provides the following technical solution:
[0005] This invention provides a method for treating nitrobenzene wastewater based on sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, comprising the following steps:
[0006] Nitrobenzene-containing wastewater was mixed with sulfur-doped activated carbon@nano zero-valent iron gradient composite material, and hydrogen peroxide was added in a pulse. The mixture was then reacted under ultrasound, filtered, and the resulting filtrate was passed through a sulfur-doped activated carbon filter column.
[0007] The conditions for the ultrasound include: a frequency of 30 kHz, a single transducer power of 10–50 W, and a power density of 100 W / m². 3 ;
[0008] The pH value of the nitrobenzene-containing wastewater is 5.0–8.0;
[0009] The amount of sulfur-doped activated carbon@nano-zero-valent iron gradient composite material added is 1-3 g / L;
[0010] The total dosage of hydrogen peroxide is 0.3-1 g / L, added in 3 doses with a 3-minute interval between each dose. The first dose is 40% of the total dosage, the second dose is 40% of the total dosage, and the third dose is 20% of the total dosage.
[0011] The preparation method of the sulfur-doped activated carbon@nano-zero-valent iron gradient composite material includes the following steps:
[0012] 1) Activate coconut shell activated carbon and sulfide it under hydrogen sulfide and nitrogen to obtain sulfides;
[0013] 2) Immerse the sulfide obtained in step 1) in a 0.2 mol / L ferrous sulfate solution for 0.5 h, and then add sodium borohydride to obtain supported activated carbon;
[0014] 3) The loaded activated carbon obtained in step 2) is immersed in a 0.05 mol / L ferrous sulfate solution for 0.2 h to obtain the composite material;
[0015] 4) Dry the composite material obtained in step 3) to obtain sulfur-doped activated carbon@nano-zero-valent iron gradient composite material.
[0016] Furthermore, the ultrasound conditions include: 30 kHz, power density 100 W / m². 3 .
[0017] Furthermore, the reaction conditions include: a time of 45 min and a rotation speed of 250 rpm.
[0018] Furthermore, the pressure filtration is a plate and frame pressure filtration, with a pressure of 1 MPa and a time of 1 hour.
[0019] Furthermore, in step 1), the coconut shell activated carbon has an average particle size of less than 50 μm and an iodine value of greater than 800 mg / g.
[0020] Furthermore, the activation conditions in step 1) include: activation with a 10% nitric acid solution for 2 hours.
[0021] Furthermore, in step 1), the volume ratio of hydrogen sulfide to nitrogen is 1:9; the sulfidation conditions include a temperature of 650°C and a time of 1.5 hours.
[0022] Furthermore, in step 2), the mass ratio of the sulfide to the volume of the ferrous sulfate solution and the sodium borohydride is 1g:10ml:0.2g.
[0023] Furthermore, in step 3), the mass ratio of the loaded activated carbon to the volume ratio of the ferrous sulfate solution is 1g:10ml.
[0024] Furthermore, the drying conditions in step 4) include: drying under vacuum or nitrogen protection conditions, and drying temperature of 80-100°C.
[0025] Beneficial effects:
[0026] Highly efficient degradation: Sulfur doping promotes Fe2+ degradation + / Fe3 + The nitrobenzene removal rate was ≥99.5% (initial concentration 200 mg / L) during the recycling process.
[0027] Sludge reduction: Pulse dosing reduces hydrogen peroxide loss by 30%, and sludge volume is ≤0.08kg / m³. 3 ;
[0028] Wide pH adaptability: Reacts under neutral conditions, saving on acid-base adjustment costs;
[0029] The following standards must be met: nitrobenzene ≤ 0.2 mg / L, total chromium ≤ 0.05 mg / L, and COD ≤ 80 mg / L in the effluent. Detailed Implementation
[0030] This invention provides a method for treating nitrobenzene wastewater based on sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, comprising the following steps:
[0031] Nitrobenzene-containing wastewater was mixed with sulfur-doped activated carbon@nano zero-valent iron gradient composite material, and hydrogen peroxide was added in a pulse. The mixture was then reacted under ultrasound, filtered, and the resulting filtrate was passed through a sulfur-doped activated carbon filter column.
[0032] The conditions for the ultrasound include: a frequency of 30 kHz, a single transducer power of 10–50 W, and a power density of 100 W / m². 3 ;
[0033] The pH value of the nitrobenzene-containing wastewater is 5.0–8.0;
[0034] The amount of sulfur-doped activated carbon@nano-zero-valent iron gradient composite material added is 1-3 g / L;
[0035] The total dosage of hydrogen peroxide is 0.3-1 g / L, added in 3 doses with a 3-minute interval between each dose. The first dose is 40% of the total dosage, the second dose is 40% of the total dosage, and the third dose is 20% of the total dosage.
[0036] The preparation method of the sulfur-doped activated carbon@nano-zero-valent iron gradient composite material includes the following steps:
[0037] 1) Activate coconut shell activated carbon and sulfide it under hydrogen sulfide and nitrogen to obtain sulfides;
[0038] 2) Immerse the sulfide obtained in step 1) in a 0.2 mol / L ferrous sulfate solution for 0.5 h, and then add sodium borohydride to obtain supported activated carbon;
[0039] 3) The loaded activated carbon obtained in step 2) is immersed in a 0.05 mol / L ferrous sulfate solution for 0.2 h to obtain the composite material;
[0040] 4) Dry the composite material obtained in step 3) to obtain sulfur-doped activated carbon@nano-zero-valent iron gradient composite material.
[0041] In this invention, the preferred conditions for the ultrasound include: 30 kHz and a power density of 100 W / m². 3 In this invention, the preferred reaction conditions include: a time of 45 min and a rotation speed of 250 rpm. In this invention, the pressure filtration is preferably a plate and frame filter press with a pressure of 1 MPa and a time of 1 h.
[0042] This invention involves activating coconut shell activated carbon and then sulfiding it under hydrogen sulfide and nitrogen atmosphere to obtain a sulfide. In this invention, the coconut shell activated carbon is preferably prepared with an average particle size of less than 50 μm and an iodine value greater than 800 mg / g. In this invention, the activation conditions preferably include activation with a 10% (w / w) nitric acid solution for 2 hours. In this invention, the volume ratio of hydrogen sulfide to nitrogen is preferably 1:9; the sulfidation conditions preferably include a temperature of 650°C and a time of 1.5 hours. In this invention, the sulfur doping content of the sulfide is 0.8–1.2 wt%, and it is a hierarchical porous activated carbon with micropores of 0.8–1.5 nm and mesopores of 10–30 nm.
[0043] In this invention, the obtained sulfide is immersed in a 0.2 mol / L ferrous sulfate solution, and then sodium borohydride is added to obtain supported activated carbon. In this invention, the mass ratio of the sulfide to the volume of the ferrous sulfate solution and the mass ratio of the sodium borohydride is 1 g:10 ml:0.2 g. This step generates 60–80 nm nano-sized zero-valent iron nanoparticles supported within the mesopores, accounting for 70% (first layer of support).
[0044] In this invention, the obtained supported activated carbon is immersed in a 0.05 mol / L ferrous sulfate solution to obtain a composite material. In this invention, the preferred mass ratio of the supported activated carbon to the ferrous sulfate solution is 1 g:10 ml. This step generates 15-25 nm nano-sized zero-valent iron nanoparticles supported on the microporous surface, accounting for 30% (second layer of support).
[0045] The present invention involves drying the obtained composite material to obtain a sulfur-doped activated carbon@nano-zero-valent iron gradient composite material. In this invention, the drying conditions preferably include drying under vacuum or nitrogen protection at a temperature of 80–100°C. In this invention, the loading of nano-zero-valent iron in the sulfur-doped activated carbon@nano-zero-valent iron gradient composite material is 12–15 wt%, and the BET specific surface area is ≥850 m². 2 / g.
[0046] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0047] Example 1
[0048] A method for preparing a sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, comprising the following steps:
[0049] 1) Activate coconut shell activated carbon with 10% nitric acid solution (mass ratio of coconut shell activated carbon to nitric acid solution is 1:5) for 2 hours, and then sulfide it at 650℃ for 1.5 hours under hydrogen sulfide and nitrogen (volume ratio is 1:9) to obtain sulfide. The sulfur doping content in the sulfide is 1wt%, and it has a hierarchical pore structure with micropores of 0.8-1.5nm and mesopores of 10-30nm.
[0050] Among them, the average particle size of coconut shell activated carbon is less than 50 μm and the iodine value is greater than 800 mg / g;
[0051] 2) The sulfide obtained in step 1) is immersed in a 0.2 mol / L ferrous sulfate solution for 0.5 h, and then sodium borohydride is added to obtain supported activated carbon. In this step, 60-80 nm nano-zero valent iron is generated and supported in the mesopores, accounting for 70%.
[0052] The mass ratio of sulfide to ferrous sulfate solution and sodium borohydride is 1g:10ml:0.2g.
[0053] 3) The loaded activated carbon obtained in step 2) is immersed in a 0.05 mol / L ferrous sulfate solution for 0.2 h to obtain the composite material;
[0054] In this step, the mass ratio of the supported activated carbon to the volume ratio of the ferrous sulfate solution is 1g:10ml. This step generates 15-25nm nano-zero valent iron loaded on the microporous surface, accounting for 30%.
[0055] The composite material obtained in step 3) was dried to obtain a sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, with a nano-zero-valent iron loading of 14 wt% and a BET specific surface area ≥ 850 m². 2 / g, with an average of 892m 2 / g;
[0056] The drying conditions are as follows: drying is carried out under vacuum or nitrogen protection conditions, and the drying temperature is 80-100℃.
[0057] The steps for preparing the sulfur-doped activated carbon@nano-zero-valent iron gradient composite material to treat nitrobenzene wastewater are as follows:
[0058] Nitrobenzene-containing wastewater was mixed with sulfur-doped activated carbon@nano zero-valent iron gradient composite material, and hydrogen peroxide was added by pulse. The mixture was then reacted under ultrasound, filtered by pressure, and the resulting filtrate was passed through a sulfur-doped activated carbon filter column (empty bed contact time 30 min).
[0059] The conditions for ultrasound include: a frequency of 30 kHz, a single transducer power of 10–50 W, and a power density of 100 W / m². 3 ;
[0060] The nitrobenzene-containing wastewater had a pH of 7.8, a nitrobenzene concentration of 185 mg / L, a COD content of 3200 mg / L, and a total chromium content of 0.85 mg / L.
[0061] The addition amount of sulfur-doped activated carbon@nano-zero-valent iron gradient composite material is 1.5 g / L;
[0062] The total dosage of hydrogen peroxide is 0.6 g / L, which is added in 3 doses with an interval of 3 minutes between each dose. The first dose is 40% of the total dosage, the second dose is 40% of the total dosage, and the third dose is 20% of the total dosage.
[0063] The ultrasound conditions are: 30kHz, power density 100W / m². 3 ;
[0064] The reaction conditions were: time 45 min, rotation speed 250 rpm;
[0065] The pressure filtration was performed using a plate and frame filter press at a pressure of 1 MPa for 1 hour. The sulfur-doped activated carbon@nano-zero-valent iron gradient composite material retained ≥80% of its activity after 5 cycles of use.
[0066] Table 1. Material Recycling Processing Data
[0067]
[0068] Note: This experiment mainly tests the effect of multiple material cycles. In actual treatment, an appropriate amount of new material needs to be added to ensure the removal effect.
[0069] GB 13194-91 Determination of nitrobenzene, nitrobenzene, nitrobenzene and dinitrotoluene in water by gas chromatography;
[0070] GB 11914-89 Determination of Chemical Oxygen Demand in Water - Dichromate Method;
[0071] GB 7466-87 Determination of total chromium in water.
[0072] result:
[0073] After filtration, the concentration of nitrobenzene was 0.18 mg / L, COD was 68 mg / L, and total chromium was 0.03 mg / L.
[0074] Sludge volume: 0.07 kg / m³ 3 The processing cost is 22 yuan / ton.
[0075] Comparative Example 1
[0076] Under the same wastewater conditions as Example 1:
[0077] Adjust the pH to 3.0, and add 2.5 g / L H2O2 and 2.0 g / L FeSO4;
[0078] First, the pH of the nitrobenzene wastewater was adjusted to 3.0 using sulfuric acid. Then, ferrous sulfate was added at a rate of 2.0 g / L, and H₂O₂ was slowly added dropwise at a total dosage of 2.5 g / L. The mechanical stirring rate was maintained at 250 rpm throughout the process, which took 1 hour.
[0079] Nitrobenzene concentration: 0.45 mg / L; sludge volume: 0.28 kg / m³ 3 COD 85mg / L, total chromium 0.37mg / L, cost 58 yuan / ton.
[0080] Comparative Example 2 (Unsulfur-doped activated carbon)
[0081] nZVI was supported on ordinary activated carbon.
[0082] The nitrobenzene removal rate is only 82%, requiring secondary treatment;
[0083] Prove that sulfur doping affects Fe 0 It plays a crucial role in protecting the activity of the virus.
[0084] Material preparation method: Nano-iron slurry and activated carbon were thoroughly mixed by mechanical stirring. The mixing time was 1 hour, the mass ratio of activated carbon to nano-iron slurry was 1:1, the solid content of nano-iron slurry was 8%, and the average particle size of nano-iron was 60 nm.
[0085] The nitrobenzene-containing wastewater has a pH of 7.8, a nitrobenzene concentration of 185 mg / L, a COD content of 3200 mg / L, and a total chromium content of 0.85 mg / L.
[0086] Instructions for use: Add the material at 5.25 g / L (consistent with the nano-iron content in the material of Example 1), mix thoroughly, and stir at 250 rpm for 45 minutes. Add hydrogen peroxide slowly in one go at 0.6 g / L.
[0087] After treatment, the concentration of nitrobenzene was 33.2 mg / L, COD was 192 mg / L, and total chromium was 0.22 mg / L.
[0088] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for treating nitrobenzene wastewater based on sulfur-doped activated carbon@nano-zero-valent iron gradient composite material, characterized in that, Includes the following steps: Nitrobenzene-containing wastewater was mixed with sulfur-doped activated carbon@nano zero-valent iron gradient composite material, and hydrogen peroxide was added in a pulse. The mixture was then reacted under ultrasound, filtered, and the resulting filtrate was passed through a sulfur-doped activated carbon filter column. The conditions for the ultrasound include: a frequency of 30 kHz, a single transducer power of 10–50 W, and a power density of 100 W / m². 3 ; The pH value of the nitrobenzene-containing wastewater is 5.0–8.0; The amount of sulfur-doped activated carbon@nano-zero-valent iron gradient composite material added is 1-3 g / L; The total dosage of hydrogen peroxide is 0.3-1 g / L, added in 3 doses with a 3-minute interval between each dose. The first dose is 40% of the total dosage, the second dose is 40% of the total dosage, and the third dose is 20% of the total dosage. The preparation method of the sulfur-doped activated carbon@nano-zero-valent iron gradient composite material includes the following steps: 1) Activate coconut shell activated carbon and sulfide it under hydrogen sulfide and nitrogen to obtain sulfides; 2) Immerse the sulfide obtained in step 1) in a 0.2 mol / L ferrous sulfate solution for 0.5 h, and then add sodium borohydride to obtain supported activated carbon; 3) The loaded activated carbon obtained in step 2) is immersed in a 0.05 mol / L ferrous sulfate solution for 0.2 h to obtain the composite material; 4) Dry the composite material obtained in step 3) to obtain sulfur-doped activated carbon@nano-zero-valent iron gradient composite material.
2. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, The ultrasound conditions include: 30 kHz, power density 100 W / m². 3 .
3. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, The reaction conditions include: a time of 45 min and a rotation speed of 250 rpm.
4. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, The pressure filtration is a plate and frame pressure filtration, with a pressure of 1 MPa and a time of 1 hour.
5. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, The coconut shell activated carbon in step 1) has an average particle size of less than 50 μm and an iodine value of greater than 800 mg / g.
6. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, The activation conditions for step 1) include: activation with a 10% nitric acid solution for 2 hours.
7. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, In step 1), the volume ratio of hydrogen sulfide to nitrogen is 1:9; the sulfidation conditions include a temperature of 650°C and a time of 1.5 hours.
8. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, In step 2), the mass ratio of the sulfide to the volume of the ferrous sulfate solution and the sodium borohydride is 1g:10ml:0.2g.
9. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, In step 3), the mass ratio of the loaded activated carbon to the volume ratio of the ferrous sulfate solution is 1g:10ml.
10. The method for treating nitrobenzene wastewater according to claim 1, characterized in that, The drying conditions in step 4) include: drying under vacuum or nitrogen protection conditions, and drying temperature of 80-100℃.