Microorganism-based composite electrode and application thereof in purification of AMCs wastewater

Abstract

The invention discloses a microorganism-based composite electrode and application of the microorganism-based composite electrode in purification of AMCs wastewater, and belongs to the technical field of electrochemical water treatment.The microorganism-based composite electrode takes aspergillus niger spores as an active material, Fe3O4 solid powder as a catalytic material and foam metal as a current collector matrix, and the active material and the catalytic material are prepared into the microorganism-based composite electrode. Aspergillus niger spores are wrapped in Fe3O4 solid powder to form an aspergillus niger spore coated Fe3O4 core-shell structure, the aspergillus niger spore coated Fe3O4 core-shell structure is uniformly distributed in a three-dimensional porous structure of foam metal through a binder, and the microorganism-based composite electrode can be used as a cathode for constructing an electro-Fenton-biological adsorption coupling system and can be used for purifying AMCs wastewater. According to the method, an electro-Fenton-biological adsorption coupling technology is utilized, an AMCs complex structure is damaged through electro-Fenton oxidation, heavy metal ions are released, heavy metal ion adsorption is achieved through the biological adsorption effect of aspergillus niger spores, AMCs wastewater can be well degraded, a reaction system is stable, operation is convenient and controllable, follow-up pollution is avoided, and the method has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical water treatment, and in particular is a microbial-based composite electrode and its application in purifying AMCs wastewater. Background Art

[0002] Antibiotic-metal complexes (AMCs) are a new class of complex organic pollutants that are difficult to degrade. They are widely present in various water bodies. After the sewage is treated by the biochemical stage, trace amounts of antibiotics and heavy metals remain. The structure of antibiotics contains ionizable groups (hydroxyl, amino, and carboxyl, etc.) and heteroatoms such as N, O, and S that can form complexes with a variety of heavy metal ions. Therefore, the two can easily form chelates, which in turn cause framework delocalization and reduce the polarity of the entire chelation system, making them generally insoluble or insoluble in water media, and presenting variable forms and structures under different water media conditions. In addition, the affinity between AMCs and bacterial cell membranes enables them to penetrate cells and bioaccumulate, inducing the growth of drug-resistant bacteria and genes, and posing prominent environmental risks.

[0003] At present, the treatment of AMCs mainly adopts the adsorption method. However, the molecular weight becomes larger after the combination of antibiotics and heavy metals, which brings great difficulties to physical adsorption. At the same time, there are many combinations of antibiotics and heavy metals, and the adsorption method is often selective. More importantly, AMCs are not degraded during the adsorption process, thus producing secondary pollutant materials. Advanced oxidation methods can mineralize organic macromolecules, especially the electro-Fenton method, which is driven by electricity and belongs to the "carbon neutral" green water treatment technology system. Its core is that the H2O2 generated on the electrode can indiscriminately attack organic matter to mineralize it.

[0004] Traditional heavy metal treatment methods mainly include chemical treatment, evaporation concentration, reverse osmosis and adsorption. Compared with the above-mentioned methods, which are expensive and prone to secondary pollution, the adsorption method has the advantages of low cost, simplicity and flexibility, especially the biological adsorption method, which is suitable for low-carbon treatment of large-volume low-concentration heavy metal wastewater. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art, provide a microbial-based composite electrode, combine the electro-Fenton method with the biosorption method, utilize the electro-Fenton-biosorption coupling technology, destroy the AMCs complex structure by electro-Fenton oxidation, release heavy metal ions, and then realize the adsorption of heavy metal ions by the biosorption effect of Aspergillus niger spores, which can well degrade AMCs wastewater, has a stable reaction system, is convenient and controllable in operation, does not require the recovery of the catalyst, has no subsequent pollution problems, and has good application prospects.

[0006] In order to solve the above technical problems, the present invention provides a microbial-based composite electrode. The microbial-based composite electrode uses Aspergillus niger spores as electrode active materials, Fe3O4 solid powder as catalytic material, and foam metal as current collector matrix. The Aspergillus niger spores are wrapped in the Fe3O4 solid powder to form an Aspergillus niger spore@Fe3O4 core-shell structure, and the Aspergillus niger spore@Fe3O4 core-shell structure is uniformly distributed in the three-dimensional porous structure of the foam metal through a binder.

[0007] Preferably, the Aspergillus niger spore has a diameter of 2 μm, and the diameter of the ordered pores on the surface is 0 to 4 nm.

[0008] Preferably, the contents of C, N, O and P in the Aspergillus niger spores are 62%, 10.5%, 22.8% and 3% respectively; the Aspergillus niger spores contain oxygen-containing functional groups and CN bonds, and the oxygen-containing functional groups are -OH, -COOH, CO and C=O.

[0009] Preferably, the binder is PTFE, SBR, PAA or CMC.

[0010] Preferably, the foam metal is foam nickel, foam copper or foam iron, and the porosity of the foam metal is 98%.

[0011] The microbial-based composite electrode of the present invention is mainly composed of Aspergillus niger spores, Fe3O4 and foam metal, which are respectively active materials, catalytic materials and current collectors, and the three form a double-interface overall structure due to the presence of a binder, which are the interface between Aspergillus niger spores and Fe3O4, and the interface where Aspergillus niger spores@Fe3O4 are combined with foam metal. Regulating the composition, concentration, action time and mode of the binder can change the structure at the interface, and then regulate the overall structure, thereby improving the performance of the composite electrode and achieving the synergy of activity, conductivity and stability.

[0012] Aspergillus niger spores [A niger strain purchased from the China National Center for the Preservation of Medical Cultures (CMCC) (strain number: Aspergillus niger CMCC98003)] are the reproductive dormant body of the Aspergillus niger fungus. Its natural properties coincide with the cathode structure and components required for efficient H2O2 production. Aspergillus niger spores can produce 60-80% H2O2 at a higher voltage and have 2e-ORR selectivity. In addition, the functional groups and electronegativity on the surface of Aspergillus niger spores enable them to adsorb a variety of heavy metals, especially Cu 2+ The adsorption capacity of the stalks was 12.1 times that of rice straw of the same mass. 2+ 、Cd 2+ , Hg 2+The removal rates of Aspergillus niger spores can reach 96.6%, 99.85% and 99.7% respectively. It can be seen that Aspergillus niger spores combine electrochemical oxygen reduction activity and heavy metal adsorption characteristics and can be used as active materials for constructing electro-Fenton cathode devices.

[0013] The construction of the electro-Fenton cathode device requires not only active materials, but also Fe catalysts and current collectors. The solid Fe3O4 is prepared into a water-based magnetic fluid to wrap the Aspergillus niger spores. It can not only serve as a protective layer to reduce the impact of water, gas and current on the Aspergillus niger spore clusters, but also become a "bond" between the current collector and the Aspergillus niger spores, directing the current to the surface of the Aspergillus niger spores. In addition, the three-dimensional structure of Fe3O4 can also realize Fe 2+ with Fe 3+ The redox of Fe 2+ As an electron donor, it can effectively catalyze the electro-Fenton reaction. In addition, foamed metal (iron, copper, nickel, etc.) materials are ideal current collectors. The resistance of current and electrons in the transmission process is small. Its three-dimensional open structure and porosity not only provide a large specific surface area to increase active sites, but also facilitate the transmission of O2. The present invention composites Aspergillus niger spores, Fe3O4 and foamed metal to construct an Aspergillus niger spore @Fe3O4 / foamed metal composite electrode, regulates the interface structure of the three, strengthens the stability and activity of the Aspergillus niger spore cathode device, and realizes the transition from microstructure regulation to macro application.

[0014] In order to solve the above technical problems, the present invention also provides an application of a microbial-based composite electrode in constructing an electro-Fenton-biosorption coupling system, specifically using the microbial-based composite electrode as the cathode of the electro-Fenton-biosorption coupling system.

[0015] The microbial-based composite electrode serves as the cathode of the electro-Fenton-biosorption coupling system, enabling the electro-Fenton cathode to have both the ability to produce H2O2 and adsorb heavy metals, achieving a leap from microscopic material control to macroscopic application stability.

[0016] In order to solve the above technical problems, the present invention also provides the application of an electro-Fenton-biosorption coupling system in purifying AMCs wastewater, wherein the antibiotics are mainly tetracyclines (chlortetracycline, oxytetracycline, tetracycline), sulfonamides (sulfamethoxazole, sulfapyridine, thiamphenicol), macrolides (erythromycin, roxithromycin), quinolones (ciprofloxacin, ofloxacin, norfloxacin) and chloramphenicol (thiamphenicol), etc.; the heavy metals are mainly Cu, Zn, Pb, Cd, Ni, Hg, etc.

[0017] The macroscopic process of removing AMCs from wastewater by the electro-Fenton-biosorption coupling system is that after AMCs transfer from infinity to the surface of the microbial-based composite electrode of the electro-Fenton-biosorption coupling system, H2O2 is first produced in situ by the electrode to oxidatively destroy the AMCs complex structure on the electrode surface and release heavy metal ions; then the electrode uses its own biosorption property to capture free heavy metal ions and achieve heavy metal ion adsorption. The former process involves the electrochemical cathode oxygen reduction process of the microbial-based composite electrode material, and the latter involves the microbial adsorption of heavy metal ions. The synergy of composite cathode activity, conductivity and stability is achieved through the interface structure regulation among Aspergillus niger spores, Fe3O4 and foam metal.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] 1. The present invention improves the 2e-ORR selectivity and electrostatic attraction coordination complexation by regulating the electronegativity, oxygen-containing functional groups and pore size of Aspergillus niger spores, that is, the "trinity" regulation of electrons, molecules and nano-microscales, thereby improving the H2O2 yield and adsorption performance;

[0020] 2. By constructing a microbial-based composite electrode of Aspergillus niger spores @Fe3O4 / foam metal, the structure of the interface between Aspergillus niger spores @Fe3O4 and foam metal is regulated to achieve coordinated control of stability, activity and conductivity from microscopic materials to macroscopic electrode devices;

[0021] 3. Through the structural regulation of Aspergillus niger spores and the interface structure regulation of Aspergillus niger spores@Fe3O4 / foam metal, based on the principle of "structure-activity relationship", the application of electro-Fenton-biosorption coupling technology is strengthened, and finally the enhanced degradation of AMCs is achieved. The reaction system is stable, the operation is convenient and controllable, there is no need for catalyst recovery, and there is no subsequent pollution problem, which has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a diagram of the structure of microbial-based composite electrode;

[0023] Figure 2 It is a test chart of the properties of Aspergillus niger spores and their oxygen reduction activity and heavy metal adsorption capacity;

[0024] Figure 3 It is the chemical process of removing AMCs from wastewater by electro-Fenton-biosorption coupling system;

[0025] Figure 4 It is the process of treating AMCs wastewater by electro-Fenton-biosorption coupling system. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0027] Embodiment 1

[0028] The present embodiment provides a microbial-based composite electrode, wherein the microbial-based composite electrode uses Aspergillus niger spores as electrode active materials, Fe3O4 solid powder as catalytic material, and foam metal as current collector matrix, wherein the Aspergillus niger spores are wrapped in the Fe3O4 solid powder to form an Aspergillus niger spore@Fe3O4 core-shell structure, and the Aspergillus niger spore@Fe3O4 core-shell structure is uniformly distributed in the three-dimensional porous structure of the foam metal through a binder, such as Figure 1 shown.

[0029] Aspergillus niger spores are organic materials with regular morphology (2 μm diameter spheres) and large specific surface area in nature. The diameter of the micropores on their surface is 0 to 4 nm ( Figure 2 (a)), the surface contains a large number of oxygen-containing functional groups such as -OH, -COOH, CO, C=O and CN bonds ( Figure 2 (b) shows that the contents of C, N, O, and P in Aspergillus niger spores are 62%, 10.5%, 22.8%, and 3%, respectively, which can effectively achieve self-doping of elements with high N content ( Figure 2 (c)). In addition, the process of the 2-electron ORR reaction is that O2 is transferred from infinity to the electrode surface, and H2O2 is generated after electron gain and loss. This requires the strengthening of two processes: one is the mass transfer process of oxygen, and the other is the process of 2-electron gain and loss. The micropores on the surface of Aspergillus niger spores can effectively strengthen the oxygen transfer. At the same time, the spores are doped with heteroatoms (N, P, etc.) and have oxygen-containing functional groups, which can effectively strengthen the process of double electron gain and loss. Therefore, Aspergillus niger spores are an excellent 2-electron ORR electrode active material. Aspergillus niger spores can produce 60-80% H2O2 ( Figure 2 (d) shows that the ORR process is more inclined to 2e-ORR ( Figure 2 In addition, the functional groups and electronegativity on the surface of Aspergillus niger spores enable them to adsorb a variety of heavy metals, especially Cu 2+ The adsorption capacity is 12.1 times that of rice straw of equivalent mass ( Figure 2 (f) shows that for an initial concentration of 30 mg / L Pb 2+ 、Cd 2+ , Hg 2+ The removal rates can reach 96.6%, 99.85% and 99.7% respectively. Figure 2 (g)) and has adsorption selectivity ( Figure 2 (h)).

[0030] However, the conductivity of Aspergillus niger spores is poor, which requires a composite current collector to transmit current. The present invention prepares Fe3O4 solid powder into a water-based magnetic fluid to wrap the Aspergillus niger spores, which not only serves as a protective layer to reduce the impact of water, air and current on the Aspergillus niger spore clusters, but also becomes a "bond" between the current collector and the Aspergillus niger spores, directing the current to the spore surface; in addition, the three-dimensional structure of Fe3O4 can also realize Fe 2+ with Fe 3+ The redox of Fe 2+ As an electron donor, it can effectively catalyze the electro-Fenton reaction.

[0031] Preferably, the binder is PTFE, SBR, PAA or CMC.

[0032] The active material, catalytic material and current collector of the microbial-based composite electrode of the present invention form a double-interface overall structure due to the presence of the binder, which are the interface between Aspergillus niger spores and Fe3O4, and the interface between Aspergillus niger spores@Fe3O4 and foam metal. By optimizing the type of binder, molecular order and nano-micro regularity are constructed, the interface structure between Aspergillus niger spores@Fe3O4 and the current collector is regulated, the electron transmission capacity is improved, and the conductivity of the composite electrode is strengthened.

[0033] Preferably, the foam metal is foam nickel, foam copper or foam iron, and the porosity of the foam metal is 98%. Foam metal (iron, copper, nickel, etc.) material is a more ideal current collector, and the resistance of electric current and electrons in the transmission process is small, and its three-dimensional open structure and porosity not only provide a large specific surface area to increase active sites, but also facilitate the transmission of O2. The present invention composites Aspergillus niger spores, Fe3O4 and foam metal to construct Aspergillus niger spores @Fe3O4 / foam metal composite electrodes, regulates the interface structure of the three, strengthens the stability of the Aspergillus niger spore cathode device and the coordination of activity, and realizes the leap from microstructure regulation to macroscopic application.

[0034] The present invention achieves coordinated control of H2O2 yield and heavy metal adsorption efficiency through the "trinity" regulation of the electronic, molecular and nano-micro scales of Aspergillus niger spores. Through the regulation of the interface structure of Aspergillus niger spores @Fe3O4 and foam metal, the coordinated control of stability, activity and conductivity from microscopic materials to macroscopic electrode devices is achieved. By exploring the mechanism of the electro-Fenton-biosorption coupling removal of AMCs by the bulk structure and interface structure of melanin spores, the "structure-activity relationship" is clarified. The above research results will explore the key scientific issues in the regulation of the cathode structure of Aspergillus niger spores to enhance the removal of AMCs from a microscopic perspective, and provide a scientific basis and theoretical foundation for the discovery of new materials, new methods and new technologies for the treatment of AMCs pollution in the environment.

[0035] Embodiment 2

[0036] This embodiment provides an application of a microbial-based composite electrode in constructing an electro-Fenton-biosorption coupling system, specifically using the microbial-based composite electrode as the cathode of the electro-Fenton-biosorption coupling system.

[0037] The microbial-based composite electrode serves as the cathode of the electro-Fenton-biosorption coupling system, enabling the electro-Fenton cathode to have both the ability to produce H2O2 and adsorb heavy metals, achieving a leap from microscopic material control to macroscopic application stability.

[0038] Embodiment 3

[0039] This example briefly describes the application of the electro-Fenton-biosorption coupling system in purifying AMCs wastewater using tetracycline-Cu(II) as an example.

[0040] The wastewater sample containing tetracycline (20 mg / L)-Cu(II) (30 mg / L) prepared in the laboratory was added into the electro-Fenton-biosorption coupling system, and the iron-based electrode was used as the anode and a DC regulated power supply was used to control the current density to 50 mA / cm 2, collected purified samples at different times and filtered with a 0.22μm filter membrane, and the removal rates of antibiotics, total organic carbon (TOC) and heavy metals at different times were determined to explore the quantitative relationship. TOC was determined using a TOC instrument, and tetracycline was analyzed using a high-performance liquid chromatography (HPLC) system. The HPLC system used a BEH C18 column (250mm×4.6mm, 5μm), and the mobile phase was a mixed solution of 75% oxalic acid (0.02M) and 25% acetonitrile, with a flow rate of 1.2mL / min; liquid phase mass spectrometry (LC-MS / MS) was used to analyze the intermediate substances in the degradation process of tetracycline, in which the liquid phase separation system was an Acquity UPLC device (Waters) equipped with a Waters-BEH C18 column (1mm×50mm, 1.7μm). The column temperature was 40℃, the mobile phase was pure acetonitrile: 0.1 formic acid = 30:70, and the flow rate was 0.1ml / min -1 The mass spectrometry conditions were as follows: Xevo TQ-S quadrupole mass spectrometer, EIS source, positive ion mode, firstly positive ion scanning mode according to the inferred substance and then parent ion scanning mode, ion source temperature 150°C, degassing temperature 350°C, capillary voltage 3kV, cone voltage 30V, collision voltage 10eV, degassing rate 650L / hr; heavy metal ions were detected by IPC-MS.

[0041] The experimental results show that the removal rate of tetracycline tends to be stable at about 30 minutes, reaching about 99.7%. The total organic carbon (TOC) removal rate of tetracycline also shows an increasing trend during the degradation process, and the TOC removal rate can reach 83.8% after 30 minutes of reaction. During the degradation and removal of tetracycline, heavy metal ions Cu(II) are released and at the same time are biosorbed by the microbial-based composite electrode. When the tetracycline removal rate tends to be stable, the removal rate of Cu(II) also tends to be stable. At 30 minutes, the removal rate of Cu(II) reaches 92.8% (as shown in Table 1).

[0042] Table 1 Removal rates of antibiotics, total organic carbon (TOC) and heavy metals at different times

[0043] Time (min) Tetracycline removal rate (%) TOC removal rate (%) Cu(II) removal rate (%) 5 62.8 11.8 56.4 10 80.3 40.5 75.9 15 85.7 53.6 83.6 20 95.3 68.5 87.6 25 97.8 79.5 91.6 30 99.7 83.8 92.8

[0044] The macroscopic process of removing AMCs from wastewater by the electro-Fenton-biosorption coupling system of the present invention is that after AMCs are transferred from infinity to the surface of the microbial-based composite electrode of the electro-Fenton-biosorption coupling system, H2O2 is first generated in situ by the electrode to oxidatively destroy the AMCs complex structure on the electrode surface and release heavy metal ions; then the electrode uses its own biosorption performance to capture free heavy metal ions to achieve heavy metal ion adsorption, wherein the former process involves the electrochemical cathode oxygen reduction process of the microbial-based composite electrode material, and the latter involves the microbial adsorption process of heavy metal ions (such as Figure 3 , Figure 4 As shown in the figure, the synergy of composite cathode activity, conductivity and stability is achieved by regulating the interface structure among Aspergillus niger spores, Fe3O4 and foam metal.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. A person skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A microbial-based composite electrode, characterized in that: The microbial-based composite electrode uses Aspergillus niger spores as active materials, Fe3O4 solid powder as catalytic material, and foam metal as current collector matrix. Aspergillus niger spores are wrapped in Fe3O4 solid powder to form an Aspergillus niger spore@Fe3O4 core-shell structure, and the Aspergillus niger spore@Fe3O4 core-shell structure is evenly distributed in the three-dimensional porous structure of the foam metal through a binder.

2. The microbial-based composite electrode according to claim 1, characterized in that: The diameter of the Aspergillus niger spore is 2 μm, and the diameter of the ordered pores on the surface is 0-4 nm.

3. The microbial-based composite electrode according to claim 2, characterized in that: The contents of C, N, O and P in the Aspergillus niger spores are 62%, 10.5%, 22.8% and 3% respectively; the Aspergillus niger spores contain oxygen-containing functional groups and CN bonds.

4. The microbial-based composite electrode according to claim 3, characterized in that: The oxygen-containing functional groups are -OH, -COOH, CO and C=O.

5. The microbial-based composite electrode according to claim 1, characterized in that: The binder is PTFE, SBR, PAA or CMC.

6. The microbial-based composite electrode according to claim 1, characterized in that: The foam metal is foam nickel, foam copper or foam iron.

7. The microbial-based composite electrode according to claim 7, characterized in that: The porosity of the foamed metal is 98%.

8. Use of the microbial-based composite electrode according to any one of claims 1 to 7 in constructing an electro-Fenton-biosorption coupling system, characterized in that: The microbial-based composite electrode is used as the cathode of the electro-Fenton-biosorption coupling system.

9. Use of the electro-Fenton-biosorption coupling system according to claim 8 in purifying AMCs wastewater.

Images