Modified graphene material and application thereof in water treatment

Abstract

The invention belongs to the technical field of water treatment, and discloses a modified graphene material and application thereof in water treatment. Nano ferroferric oxide is adopted to modify graphene, a modified graphene material with excellent electron conduction performance is prepared, the modified graphene material is further applied to treatment of sulfamethoxazole production sewage, and a good sulfamethoxazole removal effect is achieved. According to the modified graphene material, a direct interspecific electron transfer path is constructed among microorganisms, the metabolic activity of the microorganisms is greatly improved, and the modified graphene material has a wide market application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and relates to a modified graphene material and an application thereof in water treatment. Background Art

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

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

[0004] However, conventional anaerobic digestion treatment has limited effect on the removal of antibiotics in sewage, especially for sulfonamide antibiotics. The antibiotics themselves and sulfate reduction products such as hydrogen sulfide may have toxic effects on functional microorganisms in sludge. In addition to directly inhibiting the activity of methanogens, antibiotics can also indirectly lead to a decrease in the treatment capacity of the anaerobic digestion system through excessive accumulation of volatile fatty acids.

[0005] Studies have shown that the ability of microorganisms to remove toxic substances increases with the improvement of extracellular electron transfer capacity, and the addition of redox mediators is a relatively simple and efficient means of promoting electron transfer. Carbon-based materials such as graphene can provide more reaction sites for the reduction and transformation of antibiotics due to their large specific surface area. However, graphene has defects such as low conductivity, easy aggregation, and fewer surface functional groups, which limits its ability to purify wastewater containing sulfamethoxazole. For this reason, it is necessary to modify it to reduce or eliminate the above defects and further improve the removal effect of sulfamethoxazole in wastewater. Summary of the invention

[0006] In order to further improve the treatment capacity of anaerobic digestion system for sulfamethoxazole-containing wastewater, the present invention provides a modified graphene material with excellent electronic conductivity and its application in water treatment. The present invention provides the following detailed technical solutions.

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

[0008] 1) dispersing graphene in deionized water and subjecting the mixture to ultrasonic treatment for 45 to 60 minutes to obtain a graphene aqueous dispersion;

[0009] 2) Adding nano-iron tetroxide powder to the aqueous dispersion of graphene, mixing and stirring, and then ultrasonically treating for 20 to 30 minutes to obtain a mixed solution of graphene and nano-iron tetroxide; in the mixed solution, the mass ratio of graphene to nano-iron tetroxide is 1:10 to 14.

[0010] 3) The mixed solution was transferred into a flask, evaporated to dryness in a water bath at 80-95°C, and dried in a drying oven after natural cooling;

[0011] 4) placing the dried powder obtained in step 3) into a tube furnace, using argon as carrier gas, heating to 300° C. at a rate of 5° C. / min, maintaining for 2 h, and then cooling naturally to obtain the product.

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

[0013] The present invention further provides a method for treating wastewater containing sulfamethoxazole, which comprises adding the modified graphene material into a wastewater treatment system, constructing an electron transmission pathway between microorganisms and sulfamethoxazole, and achieving purification of the wastewater containing sulfamethoxazole.

[0014] Furthermore, the above processing method includes:

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

[0016] 2) passing the wastewater containing sulfamethoxazole into the acclimated expanded granular sludge bed reactor and maintaining a continuous water inflow state;

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

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

[0019] Alternatively, the above processing method includes:

[0020] 1) Inoculating anaerobic seed sludge into an expanded granular sludge bed reactor;

[0021] 2) passing the sewage containing sulfamethoxazole into the expanded granular sludge bed reactor and maintaining a continuous water inflow state;

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

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

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

[0025] In step 3) of the above two methods, the dosage of the 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] The present invention utilizes the redox medium nano-ferroferric oxide to modify graphene, and combines the prepared modified graphene with anaerobic granular sludge, so that the granular sludge obtains a larger specific surface area, providing more reaction sites between the electron donor and the electron acceptor attached to the sludge. Under the stress of sulfamethoxazole, microorganisms secrete more extracellular polymers to resist the toxic invasion of antibiotics. Among them, electrochemically active extracellular polymers such as humic acid and fulvic acid are generated in large quantities, which improves the conductivity of the sludge, which reduces the dependence on cytochrome C and conductive pili in the direct interspecies electron transfer pathway, so that more energy is used for the removal of pollutants such as sulfamethoxazole. The present invention develops a functional material with high electron transfer ability, which provides a practical solution for the treatment of high-concentration sulfamethoxazole production wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the removal effect of sulfamethoxazole (SMX) under different dosage conditions of modified graphene materials.

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

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

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

[0032] Figure 5 SEM images of Rs and Ra before and after the addition of modified graphene material, respectively. Figure 5(a) and (c) 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 measurement results of extracellular polymer components of anaerobic sludge Rs and Ra. Figure 6 In the figure, "SMX=100 mg / L" represents sulfamethoxazole wastewater without adding modified graphene materials; "SMX=100 mg / L+materials" represents sulfamethoxazole wastewater with adding modified graphene materials.

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

[0035] Figure 8 The relative abundance of genes encoding cytochrome c oxidase and conductive pilus assembly proteins in each stage for Rs and Ra. DETAILED DESCRIPTION

[0036] The present invention is explained below in conjunction with the embodiments, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

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

[0039] Weigh 100 mg of graphene, put it into a beaker filled with deionized water, stir and ultrasonically treat for 60 minutes to fully disperse the graphene to obtain an aqueous dispersion of graphene. Then weigh 1400 mg of nano-iron tetroxide, add the aqueous dispersion of graphene, mix and stir and ultrasonically treat for 30 minutes to obtain a mixture. Move the mixture into a flask, evaporate to dryness in a water bath at 80°C, and dry it in a drying oven after natural cooling. The dried powder is placed in a tubular furnace (Hefei Kejing Material Technology Co., Ltd., OTF-1200X), with argon as the carrier gas, and heat up to 300°C at a heating rate of 5°C / min and keep for 2h, then cool naturally to obtain a black powder, which is the modified graphene material.

[0040] Example 2

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

[0042] In five 250 mL brown fermentation bottles (named S0, S1, S2, S3, S4), each bottle contained 30 mL of anaerobic sludge and 170 mL of synthetic wastewater. The dosage of modified graphene material in fermentation bottles S1, S2, S3, S4 was 0.1, 0.5, 1, 3 g / L, respectively, and S0 was used as the control group (CK), and S0 was not added with modified graphene material.

[0043] Glucose, ammonium chloride, and potassium dihydrogen phosphate were used as C, N, and P sources, respectively, and sodium sulfate was used to provide SO 4 2- The indicators of synthetic wastewater are: COD = 5000 mg / L, SO 4 2- =1250mg / L, SMX=50mg / L, C:N:P=200:5:1, the synthetic wastewater also contains 1mL / L of trace element concentrate.

[0044] The composition of the trace element concentrate is as follows: 0.5g / LH 3 BO 3 、0.5g / L ZnCl 2 , 0.5g / L(NH 4 ) 6 Mo 7 O 24 ·4H 2 O, 0.5 g / L NiCl·6H 2 O, 0.5g / L AlCl 3 6H 2 O, 0.5 g / L CoCl 2 6H 2 O, 0.5g / LCuSO 4 ·5H 2 O, 1.6 g / L FeCl 3 、2.7g / L FeCl 3 6H 2 O, 1g / L MnCl 2 ·4H 2 O, 5g / LMgSO 4 7H 2 O, 5 mL / L 37 wt% HCl.

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

[0046] Experimental results: Figure 1 This is the SMX removal effect corresponding to different dosages of modified graphene materials. Figure 1 It can be seen that compared with the control group ( Figure 1 Compared with CK in the fermentation bottle, the removal effect of sulfamethoxazole (SMX) in each fermentation bottle was improved after adding the modified graphene material. Among them, the fermentation bottle S3 with an added dosage of 1 g / L reached the maximum removal efficiency of 80.23% on the 6th day, which was 53.72% higher than that of the control group.

[0047] Example 3

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

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

[0050] Glucose, ammonium chloride, and potassium dihydrogen phosphate were used as C, N, and P sources, respectively, and sodium sulfate was used to provide SO 4 2- The contents of various indicators in synthetic wastewater are COD = 10000 mg / L, SO 4 2- =2500 mg / L, C:N:P=200:5:1, and the synthetic wastewater also contains 1 mL / L of trace element concentrate. The components of the trace element concentrate and the test conditions of sulfamethoxazole (SMX) are the same as those in Example 2.

[0051] Experimental results: Figure 2 The removal efficiency of sulfamethoxazole (SMX) in the sulfate reduction reactor (Rs) and the anaerobic digestion reactor (Ra) under the condition of 1 g / L modified graphene material dosage. Figure 2 As can be seen, when the concentration of SMX is low ( Figure 2 The removal efficiency of sulfate reduction reactor (Rs) and anaerobic digestion reactor (Ra) was significant, but with the increase of influent sulfamethoxazole (SMX) concentration ( Figure 2 The removal efficiency of Rs and Ra decreased significantly, indicating that the purification capacity of Rs and Ra for high-concentration sulfamethoxazole (SMX) wastewater is very limited. Figure 2 After adding the "100+ materials" in the graphene, the purification efficiency of sulfamethoxazole (SMX) wastewater in both reactors was significantly improved, and was better than the best removal efficiency of unmodified graphene materials ( Figure 2 The “10” in the figure overcomes the defect that SMX has poor removal effect at high concentrations.

[0052] Example 4

[0053] This example describes the surface morphology and elemental composition analysis of anaerobic sludge in a sulfate reduction reactor (Rs) and an anaerobic digestion reactor (Ra) after the addition of modified graphene materials, respectively, and observations were 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 the sulfate reduction reactor (Rs) after adding modified graphene material. Figure 4 SEM-EDS image (a) and elemental analysis diagram (b) of the anaerobic digestion reactor (Ra) after adding modified graphene material. Figures 3-4 It was shown that after adding the modified graphene material, the contents of carbon, iron, and oxygen elements on the surface of the sludge of Rs and Ra were higher, indicating that the modified graphene material was successfully mixed with the granular sludge.

[0055] Figure 5 The SEM images of the sulfate reduction reactor (Rs) and the anaerobic digestion reactor (Ra) before and after the addition of the modified graphene material. (a) and (c) are the SEM images of Rs before and after the addition of the modified graphene material, respectively, and (b) and (d) are the SEM images of Ra before and after the addition of the modified graphene material, respectively. Figure 5It can be seen that before the addition of modified graphene materials, the surface of the sludge samples in the two reactors was relatively smooth, with significantly fewer bacteria and extracellular flocs, while the surface of the sludge samples after the addition of modified graphene materials was relatively rough, with more rod-shaped, spherical microorganisms and irregular extracellular flocs observed. This result shows that the intervention of modified graphene materials has enabled anaerobic sludge to obtain a larger specific surface area, providing more reaction sites between electron donors and electron acceptors attached to the modified graphene materials, which is conducive to interspecies electron transfer.

[0056] Example 5

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

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

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

[0060] Example 6

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

[0062] Anaerobic sludge from RS and RA was collected for metagenomic sequencing (Majorbio Bio-Pharm Technology Co., Ltd, Shanghai, China), and functional gene prediction analysis was performed on the Majorbio cloud platform (https: / / cloud.majorbio.com) based on the sequencing data.

[0063] Figure 8The relative abundance changes of genes encoding cytochrome C oxidase and type IV pilus assembly protein in Rs and Ra at different stages. Figure 8 The results showed that after adding modified graphene materials, the relative abundance of genes encoding cytochrome C and conductive pili assembly proteins in Rs and Ra decreased, indicating that modified graphene materials promoted the establishment of the direct interspecies electron transfer (DIET) pathway and alleviated the need for cytochrome C and conductive pili in DIET, or replaced cytochrome C and conductive pili in the DIET process. This replacement is beneficial to the system because energy metabolism can be effectively used for cellular activities such as the removal of sulfamethoxazole (SMX).

[0064] In summary, the present invention uses redox medium nano-ferroferric oxide to modify graphene to obtain modified graphene materials, which can significantly improve the sulfamethoxazole (SMX) removal efficiency of both Rs and Ra systems, and the optimal modified graphene material dosage is 1g / L. The present invention is suitable for treating high-concentration sulfamethoxazole (SMX) production wastewater.

[0065] The embodiments described above are only some embodiments of the present invention, not all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.

Claims

1. A modified graphene material, characterized in that: The modified graphene material is prepared by using nano-ferroferric oxide, and the preparation method includes: 1) dispersing graphene in deionized water and ultrasonically treating for 45 to 60 minutes to obtain a graphene aqueous dispersion; 2) adding nano-iron tetroxide powder to the graphene aqueous dispersion, mixing and stirring, and then ultrasonically treating for 20 to 30 minutes to obtain a mixed solution of graphene and nano-iron tetroxide; in the mixed solution, the mass ratio of graphene to nano-iron tetroxide is 1:10 to 14; 3) The mixed solution was transferred into a flask, evaporated to dryness in a water bath at 80-95°C, and dried in a drying oven after natural cooling; 4) The dried powder obtained in step 3) is placed in a tubular furnace, and argon is used as a carrier gas, and the temperature is raised to 300° C. at a rate of 5° C. / min and maintained for 2 h, and then naturally cooled to obtain the product.

2. The use of the modified graphene material according to claim 1 in water treatment, characterized in that: The modified graphene material is used for treating sewage containing antibiotics; the antibiotic is sulfamethoxazole.

3. A method for treating wastewater containing sulfamethoxazole, characterized in that: The method comprises: putting the modified graphene material according to claim 1 into a sewage treatment system, constructing an electron transmission pathway between microorganisms and sulfamethoxazole, and achieving purification of sewage containing sulfamethoxazole.

4. The processing method according to claim 3, characterized in that: include: 1) Inoculating the anaerobic seed sludge into the expanded granular sludge bed reactor, and adding sulfate for reduction and acclimatization; 2) passing the wastewater containing sulfamethoxazole into the acclimated expanded granular sludge bed reactor and maintaining a continuous water inflow state; 3) Adding the modified graphene material according to claim 1 to an expanded granular sludge bed reactor.

5. The processing method according to claim 4, characterized in that: In step 1), the sulfate is sodium sulfate; and the sulfate concentration is 2500 mg / L.

6. The processing method according to claim 3, characterized in that: include: 1) Inoculating anaerobic seed sludge into an expanded granular sludge bed reactor; 2) passing the sewage containing sulfamethoxazole into the expanded granular sludge bed reactor and maintaining a continuous water inflow state; 3) Adding the modified graphene material according to claim 1 to an expanded granular sludge bed reactor.

7. The processing method according to claim 4 or 6, characterized in that: In step 1), the COD of the sewage containing sulfamethoxazole is 10000 mg / L.

8. The processing method according to claim 4 or 6, characterized in that: In step 2), the residence time of the wastewater containing sulfamethoxazole in the expanded granular sludge bed reactor is 48 hours, the pH value is 7-8, the temperature of the expanded granular sludge bed reactor is 37±1°C, and the reflux ratio is 1:

20.

9. The processing method according to claim 4 or 6, characterized in that: In step 3), the dosage of the modified graphene material is 1 g / L.

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