Modified graphene material and its application in water treatment

Abstract

The application belongs to the technical field of water treatment, and discloses a modified graphene material and application thereof in water treatment. The modified graphene material with excellent electron conduction performance is prepared by modifying graphene with nano-Fe3O4, and is further used for treating sulfonamidomethoxazole production wastewater, so that a good sulfonamidomethoxazole removal effect is achieved. The modified graphene material builds a direct interspecies electron transfer path among microorganisms, greatly improves the metabolic activity of the microorganisms, and has a broad market application prospect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology and relates to a modified graphene material and its application in water treatment. Background Technology

[0002] Sulfamethoxazole (SMX) is an important sulfonamide antibiotic widely used to treat bacterial infections in humans and animals. Due to its molecular polarity and chemical stability, sulfamethoxazole is frequently detected in aquatic environments. Sulfamethoxazole in the aquatic environment may induce the development of resistant bacteria, which can then transfer sulfamethoxazole resistance genes to the host via horizontal gene transfer, posing a potential threat to the effectiveness of sulfamethoxazole treatment.

[0003] Sulfamethoxazole production wastewater is an organic wastewater rich in carbohydrates, sulfates, and antibiotics. Currently, anaerobic digestion technology can use pollutants in wastewater as a nutrient source to achieve co-metabolic degradation of antibiotics and pollutants. This technology has advantages such as low sludge production, low operating costs, high tolerance to organic matter, and good removal efficiency, making it a reliable and effective choice for treating antibiotic-containing production wastewater.

[0004] However, conventional anaerobic digestion treatment has limited effectiveness in removing antibiotics from wastewater, especially sulfonamides. Antibiotics themselves, as well as sulfate reduction products such as hydrogen sulfide, can be toxic to functional microorganisms in sludge. Besides directly inhibiting methanogenic bacteria activity and affecting anaerobic digestion performance, antibiotics can also indirectly reduce the processing capacity of anaerobic digestion systems through the excessive accumulation of volatile fatty acids.

[0005] Existing research has shown that the ability of microorganisms to remove toxic substances increases with their extracellular electron transfer capacity, and the addition of redox media is a relatively simple and efficient means of promoting electron transfer. Carbon-based materials such as graphene, due to their large specific surface area, can provide more reaction sites for the reduction and transformation of antibiotics. However, graphene has drawbacks such as low electrical conductivity, easy aggregation, and few surface functional groups, which limit its ability to purify wastewater containing sulfamethoxazole. Therefore, it is necessary to modify it to reduce or eliminate the above-mentioned defects and further improve the removal efficiency of sulfamethoxazole in wastewater. Summary of the Invention

[0006] To further improve the treatment capacity of anaerobic digestion systems for sulfamethoxazole-containing wastewater, this invention provides a modified graphene material with excellent electronic conductivity and its application in water treatment. The invention provides the following detailed technical solution.

[0007] First, the present invention provides a modified graphene material, wherein the preparation method of the modified graphene material includes:

[0008] 1) Disperse graphene in deionized water and sonicate for 45-60 min to obtain an aqueous dispersion of graphene.

[0009] 2) Add nano-iron oxide powder to the aqueous dispersion of graphene, mix and stir, and then sonicate for 20-30 minutes to obtain a mixture of graphene and nano-iron oxide; in the mixture, the mass ratio of graphene to nano-iron oxide is 1:10-14.

[0010] 3) Transfer the mixture into a flask, evaporate it to dryness in a water bath at 80-95°C, and after natural cooling, place it in a drying oven to dry.

[0011] 4) Place the dried powder obtained in step 3) into a tube furnace, use argon as the carrier gas, heat it to 300°C at a rate of 5°C / min, maintain it for 2 hours and then let it cool naturally to obtain the final product.

[0012] On the other hand, the present invention also provides the application of the above-mentioned modified graphene material in water treatment, wherein the modified graphene material is used for the treatment of sewage containing antibiotics; wherein the antibiotic is sulfamethoxazole.

[0013] The present invention further provides a method for treating wastewater containing sulfamethoxazole. The method involves introducing the modified graphene material described above into a wastewater treatment system to construct an electron transport pathway between microorganisms and sulfamethoxazole, thereby achieving the purification treatment of wastewater containing sulfamethoxazole.

[0014] Furthermore, the above processing methods include:

[0015] 1) Inoculate the anaerobic seed sludge into the expanded granular sludge bed reactor and add sulfate for reduction and acclimatization;

[0016] 2) The wastewater containing sulfamethoxazole is fed into the acclimated expanded granular sludge bed reactor and kept in a continuous influent state.

[0017] 3) Add the modified graphene material to the expanded granular sludge bed reactor.

[0018] Specifically, in step 1), the sulfate is sodium sulfate; the sulfate concentration is 2500 mg / L.

[0019] Alternatively, the above processing methods include:

[0020] 1) Inoculate the anaerobic seed sludge into the expanded granular sludge bed reactor;

[0021] 2) The wastewater containing sulfamethoxazole is fed into the expanded granular sludge bed reactor and kept in a continuous influent state;

[0022] 3) Add the modified graphene material to the expanded granular sludge bed reactor.

[0023] In step 1) of the above two methods, the COD of the wastewater containing sulfamethoxazole is 10000 mg / L.

[0024] In step 2) of the two methods above, the wastewater containing sulfamethoxazole has a residence time of 48 hours in the expanded granular sludge bed reactor, a pH value of 7-8, a reactor temperature of 37±1℃, and a reflux ratio of 1:20.

[0025] In step 3) of the above two methods, the dosage of modified graphene material is 1 g / L.

[0026] Compared with the prior art, the present invention "a modified graphene material and its application in water treatment" has at least the following beneficial effects:

[0027] This invention utilizes redox media, nano-ferric oxide, to modify graphene. The prepared modified graphene is then combined with anaerobic granular sludge, resulting in a larger specific surface area for the granular sludge and providing more reaction sites between electron donors and acceptors attached to the sludge. Under sulfamethoxazole stress, microorganisms secrete more extracellular polymers to resist the toxicity of the antibiotic. Among these, electrochemically active extracellular polymers such as humic and fulvic acids are generated in large quantities, improving the conductivity of the sludge. This reduces the dependence on cytochrome C and conductive fimbriae in the direct interspecies electron transport pathway, thus allowing more energy to be used for the removal of pollutants such as sulfamethoxazole. This invention develops a functional material with high electron transport capacity, providing a practical solution for the treatment of high-concentration sulfamethoxazole production wastewater. Attached Figure Description

[0028] Figure 1 The removal efficiency of sulfamethoxazole (SMX) under different dosages of modified graphene materials was studied.

[0029] Figure 2 The removal efficiency of sulfamethoxazole (SMX) in a sulfate reduction reactor (Rs) and an anaerobic digestion reactor (Ra) under the optimal dosage of modified graphene material.

[0030] Figure 3 SEM-EDS image (a) and elemental analysis diagram (b) of Rs after the addition of modified graphene material.

[0031] Figure 4 SEM-EDS image (a) and elemental analysis diagram (b) of Ra after the addition of modified graphene material.

[0032] Figure 5 The images show SEM images of Rs and Ra before and after the addition of the modified graphene material. Figure 5(a) and (c) in the image are SEM images of Rs before and after the addition of modified graphene material, respectively. Figure 5 (b) and (d) are SEM images of Ra before and after the addition of modified graphene material, respectively.

[0033] Figure 6 The results show the measurement of extracellular polymeric components of anaerobic sludge Rs and Ra. Figure 6 In the text, "SMX=100mg / L" indicates sulfamethoxazole wastewater without the addition of modified graphene material; "SMX=100mg / L+material" indicates sulfamethoxazole wastewater with the addition of modified graphene material.

[0034] Figure 7 Rs and Ra represent the sludge conductivity before and after the addition of modified graphene materials.

[0035] Figure 8 The relative abundance of genes encoding cytochrome C oxidase and conductive fimbriae assembly proteins in Rs and Ra at each stage. Detailed Implementation

[0036] The present invention will now be described in conjunction with embodiments, providing a clear and complete description of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment describes the preparation of modified graphene materials.

[0039] Weigh 100 mg of graphene and place it in a beaker containing deionized water. After stirring, sonicate for 60 min to fully disperse the graphene, obtaining an aqueous dispersion of graphene. Then weigh 1400 mg of nano-ferric oxide and add it to the aqueous dispersion of graphene. Mix and stir, then sonicate for 30 min to obtain a mixture. Transfer the mixture to a flask, evaporate to dryness in an 80°C water bath, and after natural cooling, place it in a drying oven for further drying. Place the dried powder in a tube furnace (Hefei Kejing Materials Technology Co., Ltd., OTF-1200X), use argon as the carrier gas, and heat at a rate of 5°C / min until reaching 300°C, hold for 2 h, then allow to cool naturally to obtain a black powder, which is the modified graphene material.

[0040] Example 2

[0041] This embodiment describes the effect of the dosage of modified graphene material on the removal efficiency of sulfamethoxazole (SMX).

[0042] Five 250mL brown fermentation bottles (named S0, S1, S2, S3, and S4, respectively) were used, each containing 30mL of anaerobic sludge and 170mL of synthetic wastewater. The dosage of modified graphene material in fermentation bottles S1, S2, S3, and S4 was 0.1, 0.5, 1, and 3 g / L, respectively. S0 served as the control group (CK), without the addition of modified graphene material.

[0043] Glucose, ammonium chloride, and potassium dihydrogen phosphate were used as C, N, and P sources, respectively, while sodium sulfate provided SO4. 2- The parameters of the synthetic wastewater are as follows: COD = 5000 mg / L, SO42- 2- =1250mg / L, SMX=50mg / L, C:N:P=200:5:1, and the synthetic wastewater also contains 1mL / L of trace element concentrate.

[0044] The composition of the trace element concentrate is as follows: 0.5 g / L H3BO3, 0.5 g / L ZnCl2, 0.5 g / L (NH4)6Mo7O 24 ·4H2O, 0.5g / L NiCl·6H2O, 0.5g / L AlCl3·6H2O, 0.5g / L CoCl2·6H2O, 0.5g / LCuSO4·5H2O, 1.6g / L FeCl3, 2.7g / L FeCl3·6H2O, 1g / L MnCl2·4H2O, 5g / LMgSO4·7H2O, 5mL / L 37wt% HCl.

[0045] After purging the fermentation flask with nitrogen, it was placed in a constant-temperature shaker and cultured at 37°C and 130 rpm. 2 mL of sample was collected every 24 hours, with the synthetic wastewater replaced after each sampling. The collected samples were filtered through a polyethersulfone membrane (PES membrane, aqueous, 0.22 μm, 13 nm) into HPLC vials. The sulfamethoxazole content was determined using a high-performance liquid chromatograph (LC-20AT, SHIMADZU, Japan). The mobile phase consisted of acetonitrile and an ultrapure aqueous solution containing 0.08% phosphoric acid in a 4:6 ratio, and the detection wavelength was 270 nm.

[0046] Experimental results: Figure 1 The removal efficiency of sulfamethoxazole (SMX) under different dosages of modified graphene materials was studied. Figure 1 As can be seen, compared with the control group ( Figure 1 Compared with the control group (CK), the removal efficiency of sulfamethoxazole (SMX) in each fermentation flask was improved after the addition of modified graphene material. Among them, fermentation flask S3 with an addition dose of 1 g / L reached the maximum removal efficiency of 80.23% on the 6th day, which was 53.72% higher than the control group.

[0047] Example 3

[0048] This embodiment describes the removal efficiency of sulfamethoxazole (SMX) in a sulfate reduction reactor (Rs) and an anaerobic digestion reactor (Ra) under the optimal dosage of modified graphene material (1 g / L).

[0049] Two identical expanded granular sludge blanket (EGSB) reactors were used as the sulfate reduction reactor (Rs) and the anaerobic digestion reactor (Ra), respectively, with a working volume of 1.98 L (total volume 2.18 L). Both reactors were operated at 37 ± 1 °C with a hydraulic retention time of 48 h. After the reactors stabilized (approximately 60 days), sulfamethoxazole (SMX) was introduced, and the SMX concentration was gradually increased from 0 mg / L to 100 mg / L. Based on the optimal dosage of modified graphene obtained in Example 2, 1 g / L of modified graphene was added at a sulfamethoxazole concentration of 100 mg / L, and an equal amount of modified graphene was added after 40 days.

[0050] Glucose, ammonium chloride, and potassium dihydrogen phosphate were used as C, N, and P sources, respectively, while sodium sulfate provided SO4. 2- The contents of various indicators in the synthetic wastewater were COD = 10000 mg / L, SO42- , and SO42- , respectively. 2- =2500 mg / L, C:N:P = 200:5:1, and the synthetic wastewater also contains 1 mL / L of trace element concentrate. The composition of the trace element concentrate and the test conditions for sulfamethoxazole (SMX) are the same as in Example 2.

[0051] Experimental results: Figure 2 The removal efficiency of sulfamethoxazole (SMX) in a sulfate reduction reactor (Rs) and an anaerobic digestion reactor (Ra) was determined under the condition that the dosage of modified graphene material was 1 g / L. Figure 2 As can be seen, at lower SMX concentrations ( Figure 2 The removal efficiencies of both the sulfate reduction reactor (Rs) and the anaerobic digestion reactor (Ra) were significant, but the removal efficiency decreased as the influent sulfamethoxazole (SMX) concentration gradually increased. Figure 2 The removal efficiencies of Rs and Ra decreased significantly when "50" and "100" were added, indicating that Rs and Ra have very limited purification capabilities for high-concentration sulfamethoxazole (SMX) wastewater. Figure 2 After using the "100+ materials" in the design, both reactors showed a significant improvement in the purification efficiency of sulfamethoxazole (SMX) wastewater, outperforming the best removal efficiency of unmodified graphene materials. Figure 2 The "10" in the formula overcomes the defect of SMX's poor removal effect at high concentrations.

[0052] Example 4

[0053] This embodiment describes the analysis of the surface morphology and elemental composition of anaerobic sludge in the sulfate reduction reactor (Rs) and anaerobic digestion reactor (Ra) after the addition of modified graphene materials. The observation was performed using a scanning electron microscope (SEM, TESCAN MIRA LMS, Czech) equipped with energy dispersive spectroscopy (EDS).

[0054] Experimental results: Figure 3 SEM-EDS image (a) and elemental analysis diagram (b) of a sulfate reduction reactor (Rs) after the addition of modified graphene material. Figure 4 SEM-EDS image (a) and elemental analysis diagram (b) of an anaerobic digester (Ra) after the addition of modified graphene material. Figures 3-4 The results show that after adding the modified graphene material, the carbon, iron, and oxygen content on the surface of the sludge in Rs and Ra is relatively high, indicating that the modified graphene material was successfully mixed with the granular sludge.

[0055] Figure 5 The images show SEM images of the sulfate reduction reactor (Rs) and the anaerobic digestion reactor (Ra) before and after the addition of modified graphene material, respectively. Specifically, (a) and (c) are SEM images of Rs before and after the addition of modified graphene material, respectively; and (b) and (d) are SEM images of Ra before and after the addition of modified graphene material, respectively. Figure 5 As can be seen, before the addition of modified graphene, the sludge samples from both reactors had relatively smooth surfaces with significantly fewer bacteria and extracellular flocs. However, after the addition of modified graphene, the sludge samples had relatively rough surfaces, with more rod-shaped and spherical microorganisms and irregular extracellular flocs observed. This result indicates that the introduction of modified graphene gave the anaerobic sludge a larger specific surface area, providing more reaction sites between electron donors and acceptors attached to the modified graphene, thus facilitating interspecies electron transfer.

[0056] Example 5

[0057] This embodiment describes the extracellular polymeric composition and conductivity of Rs and Ra in anaerobic sludge in Example 3.

[0058] The extracellular polymeric components of anaerobic sludge were examined using three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy (F-7000, HITACHI, Japan), and the sludge conductivity was measured using a three-probe conductivity method.

[0059] The results of the measurement of extracellular polymeric components of anaerobic sludge Rs and Ra are as follows: Figure 6 As shown, Figure 6In the text, "SMX = 100 mg / L" indicates sulfamethoxazole wastewater without the addition of modified graphene material; "SMX = 100 mg / L + material" indicates sulfamethoxazole wastewater with the addition of modified graphene material. Figure 6 It can be seen that after the addition of modified graphene material, the fluorescence peaks of all regions of the extracellular polymers in the Rs and Ra anaerobic sludge were enhanced, indicating that under sulfamethoxazole (SMX) stress, the modified graphene material stimulated microorganisms to release more extracellular polymers to resist toxicity. Furthermore, the fluorescence peaks representing substances such as humic acid and fulvic acid were also enhanced, and the electrical conductivity of the sludge was further improved. Figure 7 ).

[0060] Example 6

[0061] This embodiment describes the metagenomic sequencing and analysis of anaerobic sludge Rs and Ra.

[0062] Anaerobic sludge from Rs and Ra was collected and metagenomically sequenced (Majorbio Bio-Pharm Technology Co., Ltd., Shanghai, China). Based on the sequencing data, functional gene prediction analysis was performed on the Majorbio cloud platform (https: / / cloud.majorbio.com).

[0063] Figure 8 The relative abundance of genes encoding cytochrome C oxidase and type IVpilus assembly protein in Rs and Ra at different stages. Figure 8 The results showed that after the addition of modified graphene, the relative abundance of genes encoding cytochrome C and conductive fimbriae assembly proteins in Rs and Ra both decreased. This indicates that the modified graphene promoted the establishment of the direct interspecies electron transport (DIET) pathway and reduced the demand for cytochrome C and conductive fimbriae in DIET, or replaced cytochrome C and conductive fimbriae in the DIET process. This substitution is beneficial to the system because energy metabolism can be effectively used to remove cellular activities such as sulfamethoxazole (SMX).

[0064] In summary, this invention utilizes a redox medium, nano-ferric oxide, to modify graphene, thereby obtaining a modified graphene material. This modified graphene material significantly improves the removal efficiency of sulfamethoxazole (SMX) in both the Rs and Ra systems, with the optimal dosage of the modified graphene material being 1 g / L. This invention is suitable for treating high-concentration sulfamethoxazole (SMX) production wastewater.

[0065] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A method for treating wastewater containing sulfamethoxazole, characterized in that, The method is as follows: Modified graphene material is introduced into a sewage treatment system to construct an electron transport pathway between microorganisms and sulfamethoxazole, thereby achieving the purification treatment of sewage containing sulfamethoxazole. The modified graphene material is prepared by using nano-iron oxide modified graphene, and its preparation method includes: 1) Disperse graphene in deionized water and sonicate for 45-60 min to obtain a graphene aqueous dispersion; 2) Add nano-iron oxide powder to the graphene aqueous dispersion, mix and stir, and then sonicate for 20-30 minutes to obtain a mixture of graphene and nano-iron oxide; in the mixture, the mass ratio of graphene to nano-iron oxide is 1:10-14. 3) Transfer the mixture into a flask, evaporate it to dryness in a water bath at 80~95℃, and after natural cooling, place it in a drying oven to dry. 4) Place the dried powder obtained in step 3) into a tube furnace, use argon as the carrier gas, heat it to 300°C at a rate of 5°C / min and hold for 2 hours, then let it cool naturally to obtain the product; The processing method includes: 1) Anaerobic seed sludge is inoculated into an expanded granular sludge bed reactor, and sulfate is added for reduction and acclimatization; the sulfate is sodium sulfate; the sulfate concentration is 2500 mg / L; 2) The wastewater containing sulfamethoxazole is fed into the acclimated expanded granular sludge bed reactor and kept in a continuous influent state. 3) Add modified graphene material to the expanded granular sludge bed reactor; Alternatively, the processing method includes: 1) Inoculate the anaerobic seed sludge into the expanded granular sludge bed reactor; 2) The wastewater containing sulfamethoxazole is fed into the expanded granular sludge bed reactor and kept in a continuous influent state; 3) Add modified graphene material to the expanded granular sludge bed reactor.

2. The processing method according to claim 1, characterized in that, In step 2) of both treatment methods, the COD of the wastewater containing sulfamethoxazole is 10000 mg / L.

3. The processing method according to claim 1, characterized in that, In step 3) of both treatment methods, the dosage of modified graphene material is 1 g / L.

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