Microbial electrolytic tank of graphene electrode and river in-situ remediation method of microbial electrolytic tank

Abstract

The invention discloses a microbial electrolysis cell of a graphene electrode and a riverway in-situ remediation method of the microbial electrolysis cell, and belongs to the technical field of biological electrolysis cells. The microbial electrolysis cell is provided with a graphene-coated bimetallic oxide array electrode, a titanium mesh is used as an electrode substrate, an electro-catalytic material is Graphene-coated NiO / ZnO, and the surface of the electrode is of a three-dimensional space structure. The microbial electrolysis cell is applied to in-situ remediation of a water body in a riverway. When the microbial electrolysis cell is used for repairing the river water body, the microbial electrode is beneficial to rapid formation of a biological membrane, and a large number of microorganisms are accumulated on the surface of the electrode in the wastewater treatment process; meanwhile, the graphene and bimetallic coupling electrode reduces the overpotential required by oxidation reduction of pollutants in wastewater. The metabolism of the electroactive microorganisms on the surface of the electrode is promoted by a proper external power supply, so that the overall efficiency of the microbial electrode disclosed by the invention is greatly improved.

Description

Technical Field

[0001] This invention belongs to the technical field of bioelectrolysis cells, and in particular relates to a microbial electrolysis cell with a graphene electrode and its in-situ river remediation method. Background Technology

[0002] With the continuous development of industrialization, water pollution has become increasingly serious. The "2024 China Ecological Environment Status Bulletin" shows that the proportion of surface water sections with excellent or good water quality reached 78.1%, an increase of 3.2 percentage points compared to the same period of the previous year. However, from 2000 to 2017, total wastewater discharge continued to increase, reaching 69.966 billion tons in 2017, an increase of 68.51% compared to 2000. In the wastewater discharge structure, domestic wastewater discharge has exceeded industrial wastewater discharge, which undoubtedly poses a huge challenge to the quality of surface water. In some cities, emissions of total phosphorus, chemical oxygen demand, and permanganate index still exceed standards, making eutrophication of lakes and reservoirs in the basins prominent, and water ecological risks still exist.

[0003] Traditional microbial electrolysis cells (MECs) suffer from numerous performance problems, including low input / output power (including energy density, current density, and coulombic efficiency), poor current-voltage stability, and high energy consumption. The main reason is that the catalyst layer on the electrode is usually coated with powdered catalyst using a polymer binder, which is not conducive to the exposure of electroactive sites, electron transfer, and mass transfer of reactants. Summary of the Invention

[0004] To address the technical problems existing in the background art, the present invention provides a microbial electrolysis cell with graphene electrodes and a method for in-situ river remediation.

[0005] This invention employs the following technical solution: a microbial electrolytic cell with graphene electrodes, wherein the microbial electrolytic cell has a graphene-coated bimetallic oxide array electrode, and its structure is as follows: A titanium mesh was used as the electrode substrate, and the electrocatalytic material was Graphene@NiO / ZnO, with the electrode surface having a three-dimensional spatial structure.

[0006] In a further embodiment, the microbial electrolysis cell further includes a power supply device; the cathode and anode of the bimetallic oxide array electrode are connected by an external circuit wire to form a closed loop with the power supply device.

[0007] In a further embodiment, the fabrication process of the bimetallic oxide array electrode is as follows: Step 1: Electrode substrate pretreatment: A titanium mesh was obtained by etching the surface of a titanium plate as an electrode substrate with dilute nitric acid. Step 2: Fabrication of the bimetallic oxide electrode: Nickel nitrate hexahydrate solution and copper nitrate trihydrate solution were prepared separately to pre-prepare titanium mesh loaded with bimetallic oxides; The titanium mesh loaded with bimetallic oxides was dried and placed in an air atmosphere in a muffle furnace to form a NiO / CuO bimetallic oxide array electrode with titanium mesh as the substrate at high temperature. Step 3: Fabrication of graphene-coated bimetallic oxide array electrodes: A reduced graphene oxide dispersion was prepared. The reduced graphene oxide dispersion and NiO / CuO bimetallic oxide array electrode were placed in a reaction vessel. The reaction vessel was then transferred to an oven and reacted at a predetermined temperature for a predetermined time to obtain a graphene-coated bimetallic oxide array electrode.

[0008] In a further embodiment, the preparation process of the titanium mesh loaded with bimetallic oxide is as follows: Step 201: Add nickel nitrate hexahydrate solution to copper nitrate trihydrate solution at a predetermined rate and stir to obtain mixed solution A; Step 202: Add anhydrous ethanol and sodium dodecylbenzenesulfonate to mixed solution A and stir to obtain mixed solution B. Place mixed solution B and titanium mesh in a reaction vessel. Step 203: Transfer the reaction vessel from step 202 to an oven and react at a specified temperature for a specified time to obtain a titanium mesh loaded with bimetallic oxides.

[0009] In a further embodiment, the high-temperature environment is 520-580℃, and the high-temperature treatment time is 1 hour.

[0010] In a further embodiment, the preparation method of the reduced graphene oxide dispersion is as follows: Graphene oxide powder was added to deionized water and stirred, followed by the addition of sodium borohydride and continued stirring.

[0011] In a further embodiment, the predetermined temperature is 140-160°C and the predetermined duration is 8-12 hours.

[0012] In a further embodiment, the specified temperature in step 203 is 160-200°C, and the specified duration is 10-14 hours.

[0013] The in-situ river remediation method based on the microbial electrolysis cell described above includes the following steps: Determine the river restoration area, and fix the microbial electrolysis cell within the restoration area as required using a fixing device; The current density and remediation time are determined based on the concentration of pollutants in the water. The voltage of the power supply equipment is adjusted based on the current density, and water remediation is achieved by adsorbing microorganisms in the water.

[0014] In a further embodiment, during fixation, the anode is placed on the surface of sediment at the bottom of the water body, and the cathode is placed in the water body.

[0015] The beneficial effects of the present invention are as follows: The microbial electrolytic cell disclosed in this invention has a graphene-coated bimetallic oxide array electrode, which effectively overcomes the polarization phenomenon of metal oxides during electron transfer and greatly improves the cycle stability of MEC.

[0016] Meanwhile, this invention utilizes microwave radiation pyrolysis expansion to rapidly decompose the epoxy and hydroxyl groups on the surface of graphite sheets under microwave radiation power of 800W and radiation time of 10 min, instantly generating significant pyrolysis pressure. After cooling, a layer of porous graphene is coated onto the electrode surface. Compared to traditional lattice graphene, the introduction of porosity produces many unique properties, such as open band gaps, a larger actual specific surface area, and excellent mass transfer capabilities.

[0017] When using a microbial electrolysis cell for river water remediation, the microbial electrode facilitates the rapid formation of biofilm, resulting in a large accumulation of microorganisms on the electrode surface during wastewater treatment. Simultaneously, the graphene and bimetallic coupled electrode described in this invention reduces the overpotential required for the oxidation-reduction of pollutants in the wastewater. In summary, an appropriate external power supply promotes the metabolism of electroactive microorganisms on the electrode surface, significantly improving the overall efficiency of the microbial electrode of this invention. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the microbial electrolysis cell with graphene electrode in Example 1.

[0019] Figure 2 This is a SEM image of the electrode surface of Example 1.

[0020] Figure 3 This is a structural diagram of the microbial electrolysis cell used in river restoration according to Example 2.

[0021] Figure 4 These are physical comparison images of the three sets of comparative examples of Example 2.

[0022] Figure 5 These are water quality change characteristic diagrams for three sets of comparative examples in Example 2.

[0023] Figure 6 This is a water quality change characteristic diagram of river restoration in Example 2.

[0024] Figure 3The labels in the text are: Frame 1, Fixed Column 2, Fixed Anchor 3, External Circuit Wire 4. Detailed Implementation

[0025] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0026] Example 1 A microbial electrolytic cell with graphene electrodes, the microbial electrolytic cell having a graphene-coated bimetallic oxide array electrode, the structure of which can be referenced. Figure 1 The structure of the graphene-coated bimetallic oxide array electrode is as follows: a titanium mesh is used as the electrode substrate, and the electrocatalytic material is Graphene@NiO / ZnO, wherein the electrode surface has a three-dimensional spatial structure.

[0027] The Graphene@NiO / ZnO described in this embodiment is a graphene-coated NiO / ZnO composite structure. It also includes a power supply device; the cathode and anode of the bimetallic oxide array electrode are connected via external circuit wires, forming a closed-loop circuit with the power supply device.

[0028] In a further embodiment, the fabrication process of the bimetallic oxide array electrode is as follows: Step 1: Electrode substrate pretreatment: A titanium mesh was obtained by etching the surface of a titanium plate as the electrode substrate using dilute nitric acid. It should be noted that titanium plates were chosen in this embodiment primarily because titanium exhibits excellent corrosion resistance in wastewater compared to other metals (such as copper and stainless steel); especially during redox reactions at the electrode, when the surrounding pH changes drastically, titanium demonstrates superior electrocatalytic activity under such extreme acid-base conditions.

[0029] Step 2: Fabrication of the bimetallic oxide electrode: Nickel nitrate hexahydrate solution and copper nitrate trihydrate solution were prepared separately to pre-prepare titanium mesh loaded with bimetallic oxides; The titanium mesh loaded with bimetallic oxides was dried and placed in an air atmosphere in a muffle furnace to form a NiO / CuO bimetallic oxide array electrode with titanium mesh as the substrate at high temperature. Step 3: Fabrication of graphene-coated bimetallic oxide array electrodes: A reduced graphene oxide dispersion was prepared. The reduced graphene oxide dispersion and NiO / CuO bimetallic oxide array electrode were placed in a reaction vessel. The reaction vessel was then transferred to an oven and reacted at a predetermined temperature for a predetermined time to obtain a graphene-coated bimetallic oxide array electrode.

[0030] Furthermore, the specific process for the electrode substrate pretreatment described in this embodiment is as follows: The titanium plate is immersed in 20-50% dilute nitric acid for 2-6 hours to etch its surface, cleaning away oil stains while also increasing the surface roughness of the titanium. More preferably, the concentration of dilute nitric acid is 30%, and the immersion time is 4 hours.

[0031] Furthermore, the preparation process of the nickel nitrate hexahydrate solution is as follows: Weigh 0.6-1.5g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and add it to 50-100ml of deionized water and stir for 30-60min. Preferably, weigh 1g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and add it to 70ml of deionized water and stir for 30min.

[0032] The preparation process of copper nitrate trihydrate solution is as follows: Weigh 0.6-1.5g of copper nitrate trihydrate (Cu(NO3)2·3H2O) and add it to 50-100ml of deionized water, stirring for 30-60min. Preferably, weigh 1g of copper nitrate trihydrate (Cu(NO3)2·3H2O) and add it to 70ml of deionized water, stirring for 30min. The preparation of titanium mesh loaded with bimetallic oxides based on nickel nitrate hexahydrate solution and copper nitrate trihydrate solution is as follows: Step 201: Add nickel nitrate hexahydrate solution to copper nitrate trihydrate solution at a predetermined rate (slowly), and stir for 30-60min to obtain mixed solution A; preferably, the stirring time is 30min.

[0033] Step 202: Add 5-15 mL of anhydrous ethanol and 0.1-0.5 g of sodium dodecylbenzenesulfonate to mixed solution A and stir for 30-60 min to obtain mixed solution B. Place mixed solution B and the titanium mesh in a reaction vessel. It should be noted that the reaction vessel currently used is 150-250 ml. Preferably, add 10 mL of anhydrous ethanol and 0.2 g of sodium dodecylbenzenesulfonate to mixed solution A and stir for 60 min to obtain mixed solution B. Place mixed solution B and the titanium mesh in a reaction vessel.

[0034] Step 203: Transfer the reaction vessel from step 202 to an oven and react at a specified temperature for a specified time to obtain a titanium mesh loaded with bimetallic oxide. The specified temperature is 160-200℃, and the specified time is 10-14 hours. Preferably, the specified temperature is 180℃, and the specified time is 12 hours.

[0035] Furthermore, the high-temperature environment in the muffle furnace air atmosphere is 520-580℃, and the high-temperature treatment time is 1 hour. Preferably, the high-temperature environment is 550℃.

[0036] In a further embodiment, the reduced graphene oxide dispersion is prepared by the following method: 2-4 g of graphene oxide powder is added to 100-150 ml of deionized water, stirred for 30-60 min, and then 0.1-0.5 g of sodium borohydride is added and stirred for another 30-60 min. Preferably, 3 g of graphene oxide powder is added to 140 ml of deionized water, stirred for 30 min, and then 0.5 g of sodium borohydride is added and stirred for another 30 min. Therefore, in the process of preparing the graphene-coated bimetallic oxide array electrode, the predetermined temperature is 140-160 °C, and the predetermined time is 8-12 hours. Preferably, the predetermined temperature is 160 °C, and the predetermined time is 10 hours.

[0037] refer to Figure 2 Before treatment, the surface of the titanium mesh used as the electrode substrate is relatively smooth and flat, exhibiting a regular filamentous cross structure. The surface of the titanium wire has almost no obvious attachments or protrusions. This smooth surface results in a relatively small specific surface area, which, from a microscopic perspective, is not conducive to the adhesion of electrocatalytic materials and sufficient contact with external substances (such as pollutants and microorganisms in the water to be treated).

[0038] After treatment, the electrode surface underwent significant changes. A large amount of network-like, interwoven material grew or was loaded onto the electrode surface, forming a complex and rich three-dimensional spatial structure. These structures intertwined with each other, greatly increasing the specific surface area of ​​the electrode.

[0039] As can be seen from the images, these mesh structures are not limited to the two-dimensional plane of the titanium mesh surface, but extend in all directions of space, forming a three-dimensional architecture similar to a porous sponge. This three-dimensional structure can provide more active sites within a limited volume, providing a broad reaction site for electrocatalytic reactions.

[0040] Graphene's excellent flexibility and ductility allow it to spread and connect with each other on the surface of titanium mesh, while NiO and ZnO are attached to the graphene sheets or fill the gaps in the graphene network in the form of nanoparticles or nanosheets, together constructing this unique three-dimensional spatial structure.

[0041] This three-dimensional spatial structure enhances the electrode's adsorption capacity for pollutants in water, allowing pollutant molecules to diffuse more easily into the porous structure inside the electrode, fully contacting and reacting with the electrocatalytic material. On the other hand, for microorganisms in the microbial electrolysis cell, the abundant pores and three-dimensional structure provide more attachment sites and habitat space, which is conducive to the colonization and growth of microorganisms on the electrode surface, thereby promoting the synergistic effect between microorganisms and electrocatalytic reactions and improving the overall treatment efficiency and performance of the microbial electrolysis cell.

[0042] Example 2 Based on the microbial electrolysis cell disclosed in Example 1, this example discloses an in-situ river remediation method, including the following steps: The river restoration area is determined, and the microbial electrolysis cell is fixed in the restoration area as required by the fixing device; for example, when fixing, the anode is placed on the surface of the sediment at the bottom of the water body, and the cathode is placed in the water body.

[0043] The current density and remediation time are determined based on the concentration of pollutants in the water. The voltage of the power supply equipment is adjusted based on the current density, and water remediation is achieved by adsorbing microorganisms in the water. During water remediation, the metabolic level of electroactive microorganisms in the microbial electrolysis cell is closely related to the applied current.

[0044] Based on this, this embodiment provides three comparative examples. The first group serves as a control group, without any microbial electrolysis cell device. The second and third groups are both equipped with the device of this invention. The current density of the second group is 1 A / m. 2 The current density of the third group was set to 3 A / m 2 The results showed that at 3 A / m 2 The pollutant removal efficiency is higher under these conditions. Based on this result, it is recommended to select 3 A / m² for future practical applications. 2 As an external voltage.

[0045] For ease of understanding, the fixing device described in this embodiment includes: a frame, a fixing column, and a fixing anchor. The frame is assembled from galvanized steel pipes and connectors. The bottom of the fixing column is connected to the fixing anchor, which is submerged in the bottom sediment. The positive and negative electrodes are horizontally placed within the fixing frame, connected to the fixing column by sliding sleeves, and can slide up and down along the fixing column, used to treat pollutants in water at different depths.

[0046] Combination Figure 3 To protect the external circuit wires, they can be passed through the frame or fixed column during fixing to reduce water corrosion of the wires.

[0047] Combination Figure 4 In this embodiment, a transparent acrylic container is used, with dimensions of 50cm × 30cm × 30cm and an effective volume of 45L. Both the anode and cathode are placed horizontally, with a distance of approximately 3cm between them.

[0048] Water from a polluted and odorous river was collected into the aforementioned container. Water quality indicators are shown in the table below. According to the "Surface Water Environmental Quality Standard GB3838-2002," the water used in this embodiment is classified as Class V.

[0049] Table 1. Water quality characteristics of water used in Example 1 (mg / L) Figure 3 This embodiment analyzes the effectiveness of wastewater treatment. In the control group, all indicators showed slight decreases, but no significant changes. TN, TP, and NO3... - -N and COD Mn The concentrations decreased by 10%, 10%, 13%, and 4%, respectively. However, the water quality after purification using this invention showed a significant improvement. At 1 A / m 2 Under certain conditions, TN, TP, NO3 - -N and COD Mn They decreased by 21%, 29%, 11%, and 24% respectively; at 3A / m 2 Under certain conditions, TN, TP, NO3 - -N and COD Mn These figures decreased by 43%, 42%, 34%, and 38%, respectively. Specifically, TN, TP, and NO3... - -N and COD Mn These are all water body indicators, namely: total nitrogen, total phosphorus, nitrate nitrogen, and permanganate.

[0050] In another embodiment, the microbial electrolysis cell described in Example 1 is used at 3A / m 2 The current density, and the effect of in-situ remediation of river water quality for 60 days, can be seen from... Figure 5 It can be observed that the concentrations of pollutants in the water body significantly decreased after remediation using this invention, particularly TN, TP, and NO3. - -N, COD Mn The loss on ignition (LOI) and LOI decreased by 70.00%, 62.50%, 44.83%, 47.62%, and 23.33%, respectively. LOI is the loss on ignition of sediments.

Claims

1. A microbial electrolysis cell with a graphene electrode, characterized in that, The microbial electrolysis cell has a graphene-coated bimetallic oxide array electrode, the structure of which is as follows: A titanium mesh was used as the electrode substrate, and the electrocatalytic material was Graphene@NiO / ZnO, with the electrode surface having a three-dimensional spatial structure.

2. The microbial electrolysis cell with a graphene electrode according to claim 1, characterized in that, The microbial electrolysis cell further includes a power supply device; the cathode and anode of the bimetallic oxide array electrode are connected by an external circuit wire to form a closed loop with the power supply device.

3. The microbial electrolysis cell with a graphene electrode according to claim 1, characterized in that, The fabrication process of the bimetallic oxide array electrode is as follows: Step 1: Electrode substrate pretreatment: A titanium mesh was obtained by etching the surface of a titanium plate as an electrode substrate with dilute nitric acid. Step 2: Fabrication of the bimetallic oxide electrode: Nickel nitrate hexahydrate solution and copper nitrate trihydrate solution were prepared separately to pre-prepare titanium mesh loaded with bimetallic oxides; The titanium mesh loaded with bimetallic oxides was dried and placed in an air atmosphere in a muffle furnace to form a NiO / CuO bimetallic oxide array electrode with titanium mesh as the substrate at high temperature. Step 3: Fabrication of graphene-coated bimetallic oxide array electrodes: A reduced graphene oxide dispersion was prepared. The reduced graphene oxide dispersion and NiO / CuO bimetallic oxide array electrode were placed in a reaction vessel. The reaction vessel was then transferred to an oven and reacted at a predetermined temperature for a predetermined time to obtain a graphene-coated bimetallic oxide array electrode.

4. The microbial electrolysis cell with a graphene electrode according to claim 3, characterized in that, The preparation process of the titanium mesh loaded with bimetallic oxide is as follows: Step 201: Add nickel nitrate hexahydrate solution to copper nitrate trihydrate solution at a predetermined rate and stir to obtain mixed solution A; Step 202: Add anhydrous ethanol and sodium dodecylbenzenesulfonate to mixed solution A and stir to obtain mixed solution B. Place mixed solution B and titanium mesh in a reaction vessel. Step 203: Transfer the reaction vessel from step 202 to an oven and react at a specified temperature for a specified time to obtain a titanium mesh loaded with bimetallic oxides.

5. The microbial electrolysis cell with a graphene electrode according to claim 3, characterized in that, The high-temperature environment is 520-580℃, and the high-temperature treatment time is 1 hour.

6. The microbial electrolysis cell with a graphene electrode according to claim 3, characterized in that, The preparation method of the reduced graphene oxide dispersion is as follows: Graphene oxide powder was added to deionized water and stirred, followed by the addition of sodium borohydride and continued stirring.

7. A microbial electrolysis cell with a graphene electrode according to claim 3, characterized in that, The predetermined temperature is 140-160℃, and the predetermined duration is 8-12 hours.

8. A microbial electrolysis cell with a graphene electrode according to claim 4, characterized in that, The specified temperature in step 203 is 160-200℃, and the specified duration is 10-14 hours.

9. A method for in-situ river remediation using a microbial electrolysis cell as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Determine the river restoration area, and fix the microbial electrolysis cell within the restoration area as required using a fixing device; The current density and remediation time are determined based on the concentration of pollutants in the water. The voltage of the power supply equipment is adjusted based on the current density, and water remediation is achieved by adsorbing microorganisms in the water.

10. The method for in-situ river remediation using a microbial electrolysis cell according to claim 9, characterized in that, When fixed, the anode is placed on the surface of the sediment at the bottom of the water body, and the cathode is placed in the water body.

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