A bioelectrochemical system electrode, its preparation method and application

Abstract

The application discloses a kind of bioelectrochemical system electrode and its preparation method and application, belong to bioelectrochemical reaction technical field.The preparation method provided by the application includes the following steps: carbon nanotube suspension is prepared by dispersing nitric acid soaked modified carbon nanotube in polyethyleneimine solution;Foamed titanium plate is used as cathode, and is placed in the carbon nanotube suspension and electrophoretic deposition is carried out, and after washing, drying, it is soaked in sodium dodecyl sulfate solution, and is obtained after drying.The preparation process of the bioelectrochemical system electrode of the application is simple and fast, the bioelectrochemical system electrode prepared has good microorganism affinity and hydrophilicity, and has high COD (chemical oxygen demand) and ammonia nitrogen degradation efficiency in bioelectrochemical degradation of low concentration wastewater, has good running stability, excellent corrosion resistance and excellent application performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-electrochemical reaction, and particularly relates to a bio-electrochemical system electrode and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in the background of the present application is only intended to increase the understanding of the overall background of the present application and should not necessarily be regarded as acknowledging or implicitly suggesting that this information constitutes prior art known to those of ordinary skill in the art.

[0003] Electrodes are the key part of the structure and function of bio-electrochemical systems (BES) and can effectively promote the electron transfer of bacteria. Anodes provide a place for electrochemically active microbial metabolism and reduce the cathode potential through anodic reactions, which indirectly affects the degradation efficiency of pollutants. In addition, cathode materials can also provide anaerobic electron acceptors for the system, oxidize organic pollutants in wastewater, and promote the metabolic rate of anaerobic bacteria. Like anodes, electroactive bacteria (EAB) on cathodes can also be used to reduce refractory pollutants and catalyze energy conversion. In general, the redox reactions on the electrode depend largely on the characteristics of the electrode material used. In the past few decades, common electrodes are mostly made of carbon-based materials, such as carbon brushes, carbon cloth, carbon fiber felt, and graphite particles. These materials have the characteristics of large specific surface area, non-corrosion, good biocompatibility, and good stability. However, the electrical conductivity of carbon-based materials is only 3×10 4 ~1×10 5 S / m, which is much lower than that of most metal-based electrodes. However, metals can be corroded in long-term use, and metal-based materials exhibit poorer biocompatibility than carbon-based materials, and the adhesion of microorganisms to metals is smaller than that to carbon materials.

[0004] Therefore, how to provide a bio-electrochemical electrode with good biocompatibility, corrosion resistance, high electrical conductivity, and high pollutant degradation efficiency is a technical problem to be solved. SUMMARY

[0005] Therefore, the present application provides a bio-electrochemical system electrode and a preparation method and application thereof, which solves the problems of low electrical conductivity of traditional carbon-based material electrodes, poor biocompatibility and poor corrosion resistance of metal-based material electrodes.

[0006] In a first aspect, the present application provides a preparation method of a bio-electrochemical system electrode, comprising the following steps:

[0007] The carbon nanotube suspension is prepared by dispersing the nitric acid immersion modified carbon nanotubes in a polyethyleneimine solution; a titanium foam plate is used as a cathode and is placed in the carbon nanotube suspension for electrophoretic deposition, and then is washed with water, dried, immersed in a sodium dodecyl sulfate solution, and dried to obtain the product.

[0008] Preferably, the preparation method of the nitric acid immersion modified carbon nanotubes comprises the following steps: immersing carbon nanotubes in a concentrated nitric acid solution for 20-30 hours, then washing with water until neutral, and then drying.

[0009] Preferably, the ratio of the amount of the nitric acid immersion modified carbon nanotubes to the amount of the polyethyleneimine solution is 1g:(800-1200)mL; the solvent of the polyethyleneimine solution is water, and the concentration of the polyethyleneimine solution is 3-10wt%.

[0010] Preferably, the voltage of the electrophoretic deposition is 25-35V, and the electrophoretic deposition time is 1-3min.

[0011] Preferably, the solvent of the sodium dodecyl sulfate solution is water, and the concentration of the sodium dodecyl sulfate solution is 0.5-2wt%; the immersion time in the sodium dodecyl sulfate solution is 20-30h.

[0012] In a second aspect, the present application provides a bioelectrochemical system electrode prepared by the above preparation method.

[0013] In a third aspect, the present application provides an application of the above bioelectrochemical system electrode in biodegradation of low-concentration wastewater.

[0014] Preferably, the COD concentration of the low-concentration wastewater is 200-400mg / L, the NH4 + -N concentration is 10-20mg / L.

[0015] Preferably, the application is that the above bioelectrochemical system electrode is used as a cathode and an anode of a bioelectrochemical reactor, then electroactive bacteria are cultivated on the surfaces of the cathode and the anode, and then a voltage between the cathode and the anode is controlled to be 0.2-2V to perform a bioelectrochemical aerobic reaction.

[0016] Preferably, the aeration flow rate of the bioelectrochemical aerobic reaction is 80-150mL / min.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] (1) The preparation process of the bioelectrochemical system electrode of the present application is simple and fast, and can uniformly deposit carbon nanotubes on the surface of the bioelectrochemical system electrode, and the prepared bioelectrochemical system electrode has good biophilicity and hydrophilicity, which is conducive to the growth of electroactive bacteria and the subsequent degradation process of low-concentration wastewater.

[0019] (2) The prepared bio-electrochemical system electrode has good application stability and corrosion resistance, and has high COD (chemical oxygen demand) and ammonia nitrogen degradation efficiency in the bio-electrochemical degradation of low-concentration wastewater, and excellent application performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings constituting a part of the specification of the present application are used to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute improper limitation on the present application. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0021] Figure 1 is the COD concentration change diagram (a) and NH4 + -N concentration change diagram (b) of the bio-electrochemical system electrode of the present application Comparative Examples 1-4 in 12h low-concentration wastewater.

[0022] Figure 2 is the CV (a) and EIS (b) analysis diagram of the bio-electrochemical system electrode of the present application Example 1, Comparative Examples 1-4. DETAILED DESCRIPTION

[0023] It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0024] The present application provides a preparation method of a bio-electrochemical system electrode, comprising the following steps:

[0025] The modified carbon nanotubes soaked in nitric acid are dispersed in a polyethyleneimine solution to prepare a carbon nanotube suspension; a foamed titanium plate is used as a cathode and is placed in the carbon nanotube suspension for electrophoretic deposition, and after water washing and drying, it is soaked in a sodium dodecyl sulfate solution and dried to obtain.

[0026] The foamed titanium plate is used as a substrate, which has a large specific surface area on one hand, promotes the adhesion of microorganisms thereon, and is conducive to improving the rate of bio-electrochemical degradation of pollutants; on the other hand, compared with other metals, it has better corrosion resistance and can stably play a role in the process of bio-electrochemical degradation, and has a longer service life. The carbon nanotubes are deposited on the surface of the foamed titanium layer, which can effectively improve the conductivity of the electrode, and at the same time, the carbon nanotubes can also promote the O +The carbon nanotubes can be used for the reduction production of H2O2, thereby promoting the degradation of pollutants. In addition, the electrode surface after modification of the carbon nanotubes presents a three-dimensional open network framework structure and a relatively smooth surface, thereby providing a larger surface area and more active sites for the growth of microorganisms.

[0027] In the present application, the preparation method of the nitric acid immersion modified carbon nanotubes comprises the following steps: immersing the carbon nanotubes in a concentrated nitric acid solution for 20-30 hours, then washing with water until neutral, and then drying. Through the oxidation modification of the concentrated nitric acid, polar groups such as hydroxyl and carboxyl are introduced on the surface of the carbon nanotubes, which is beneficial to the uniform dispersion of the carbon nanotubes in the polyethyleneimine solution and can promote the interaction between the carbon nanotubes and the foam titanium, thereby increasing the stability of the electrophoretic deposition layer.

[0028] In the present application, the dosage ratio of the nitric acid immersion modified carbon nanotubes to the polyethyleneimine solution is 1g:(800-1200)mL, and more preferably 1g:(900-1100)mL. The solvent of the polyethyleneimine solution is water, and the purity of the water is not specially limited in the present application, and distilled water, deionized water, ultrapure water, etc. can be used. The concentration of the polyethyleneimine solution is 3-10wt%. The polyethyleneimine has polar groups (amino groups) and hydrophobic groups (vinyl groups), and the amino groups on the polyethyleneimine can interact with the nitric acid immersion modified carbon nanotubes through hydrogen bonds. Moreover, the polyethyleneimine has a positive charge, and can also interact with the carbon nanotubes through electrostatic attraction, thereby effectively dispersing the carbon nanotubes and facilitating the uniform deposition of the carbon nanotubes on the foam titanium plate.

[0029] The method for dispersing is not specially limited in the present application, and for example, stirring or ultrasonic dispersion, etc. can be used, and the present application preferably uses ultrasonic dispersion. The process of ultrasonic dispersion is not specially limited in the present application, as long as a carbon nanotube suspension with good dispersibility can be obtained.

[0030] In the present application, the voltage of the electrophoretic deposition is 25-35V, and the electrophoretic deposition time is 1-3min.

[0031] The anode material for electrophoretic deposition is not specially limited in the present application, and the anode commonly used by those skilled in the art can be used. The anode material for electrophoretic deposition is preferably a foam titanium plate, and after the electrophoretic deposition is completed, the cathode and the anode can be interchanged, and then the foam titanium plate originally used as the anode can be electrodeposited.

[0032] In the present application, the solvent of the sodium dodecyl sulfate solution is water, and the concentration is 0.5-2wt%. The time for immersion in the sodium dodecyl sulfate solution is 20-30h. The immersion modification in the sodium dodecyl sulfate solution can further improve the hydrophilicity and biocompatibility of the electrode.

[0033] The application further provides the bioelectrochemical system electrode prepared by the preparation method.

[0034] The application further provides application of the bioelectrochemical system electrode in biodegradation of low-concentration wastewater.

[0035] In the application, the COD concentration of the low-concentration wastewater is 200-400 mg / L, the NH4 + The low-concentration wastewater is generally wastewater after sewage treatment, and the COD content and ammonia nitrogen content are low. The high-level oxidation method such as Fenton, ozone oxidation and filtration is often difficult to effectively reduce the COD content and ammonia nitrogen content, and has low efficiency and high cost. However, the bioelectrochemical method of the application can effectively degrade the low-concentration wastewater in combination with the bioelectrochemical system electrode prepared above, and has low cost and high degradation efficiency.

[0036] In the application, the application is that the bioelectrochemical system electrode is used as cathode and anode of a bioelectrochemical reactor, then electroactive bacteria are cultivated on the surfaces of the cathode and the anode, and then the voltage between the cathode and the anode is controlled to be 0.2-2 V to perform bioelectrochemical aerobic reaction.

[0037] The application does not specially limit the structure of the bioelectrochemical reactor, and a bioelectrochemical reactor commonly used in the art can be used. The application does not specially limit the method for cultivating electroactive bacteria on the surfaces of the cathode and the anode, and a method for cultivating electroactive bacteria commonly known in the art can be used.

[0038] In the application, the aeration flow of the bioelectrochemical aerobic reaction is 80-150 mL / min, and more preferably 90-120 mL / min. Under the aeration condition, better pollutant degradation performance can be achieved.

[0039] The technical scheme of the application is further described below in combination with specific examples. The low-concentration wastewater in the following examples is prepared according to the following conditions (per liter): 300 mg COD (CH3COONa), 45 mg NH4 + -N (NH4Cl), 4 mg PO4 3--P(KH2PO4) and 1 mL of trace element solution. Trace elements (per liter): 2.0 mg biotin, 2.0 mg folic acid, 10.0 mg pyridoxine, 5.0 mg thiamine hydrochloride, 5.0 mg riboflavin, 5.0 mg nicotinic acid, 5.0 mg DL-calcium pantothenate, 0.1 mg vitamin B12, 5.0 mg p-aminobenzoic acid, 5.0 mg lipoic acid. The COD value of the artificial low-concentration wastewater prepared by actual measurement is 300 mg / L, and the ammonia nitrogen content (NH4 + -N) is 16 mg / L.

[0040] Example 1

[0041] The present embodiment provides a preparation method of a bioelectrochemical system electrode.

[0042] (1) The carbon nanotubes were soaked in concentrated nitric acid solution for 24 h, then rinsed with distilled water continuously until the pH value was greater than 6, and impurities were removed. Then the CNTs were dried in an oven at 80°C, then ground uniformly, 1 g of carbon nanotubes was dispersed in 1000 mL of 4 wt% polyethyleneimine aqueous solution, and ultrasonic dispersion was performed for 30 min to obtain a carbon nanotube suspension.

[0043] (2) Two pieces of 6 cm x 2 cm titanium foam plates were used as the cathode and anode for electrophoretic deposition, and were placed in 200 mL of the carbon nanotube suspension, and a constant voltage of 30 V was applied between the cathode and anode for electrophoretic deposition for 2 minutes; then the cathode and anode titanium foam plates were exchanged, and a constant voltage of 30 V was continuously applied for electrophoretic deposition for 2 minutes.

[0044] (3) After the electrophoretic deposition was completed, the electrode surface was rinsed with distilled water, and dried to stabilize the structure.

[0045] (4) The dried electrode was soaked in a 1 wt% sodium dodecyl sulfate solution for 24 h to increase the hydrophilicity of the electrode, and then dried at 70°C.

[0046] Comparative Example 1

[0047] Compared with Example 1, the difference is that the titanium foam plate in Example 1 is replaced by a foam iron plate in the present comparative example.

[0048] Comparative Example 2

[0049] Compared with Example 1, the difference is that the titanium foam plate in Example 1 is replaced by a foam copper plate in the present comparative example.

[0050] Comparative Example 3

[0051] Compared with Example 1, the difference is that the titanium foam plate in Example 1 is replaced by a foam nickel plate in the present comparative example.

[0052] Comparative Example 4

[0053] Compared with Example 1, the difference is that the foam titanium plate is replaced by the foam stainless steel plate in this comparative example.

[0054] Application Examples

[0055] The bioelectrochemical system electrodes from Example 1 and Comparative Examples 1-4 were used as the cathode and anode of a bioelectrochemical reactor (BES), respectively. Aerobic sludge and water were added to the bioelectrochemical reactor and electroactivated at a voltage of 0.5V for 15 days. The reactor was then cleaned to retain the electroactive microorganisms on the electrode surfaces. Low-concentration wastewater was then added to the reactor, and a bioelectrochemical aerobic reaction was carried out at a voltage of 0.5V and an aeration rate of 100mL / min. The low-concentration wastewater was sampled and tested at different time points.

[0056] 1. COD concentration changes and NH4 + -N concentration changes

[0057] Example 1, Comparative Examples 1 to 4 of the bioelectrochemical system electrodes BES reactor in low-concentration wastewater within 12 hours COD concentration changes and NH4 + -N concentration changes as Figure 1 As shown in Table 1. Figure 1 As can be seen from Table 1, the metal type of the electrode will have a great influence on the degradation effect of the bioelectrochemical aerobic degradation of pollutants. The Fe electrode modified BES reactor group of Comparative Example 1 and the Ti electrode modified BES reactor group of Example 1 have the best COD degradation effect, with the lowest COD concentrations of 18.37±1.15 mg / L and 20.87±2.45 mg / L, respectively, and the COD removal efficiency of 93.87±0.32% and 93.04±0.82%, respectively. Then the stainless steel electrode (SS) modified BES reactor group of Comparative Example 4, the Ni electrode modified BES reactor group of Comparative Example 3 and the Cu electrode modified BES reactor group of Comparative Example 2 are followed. NH4 + -N concentration changes and COD concentration changes in a similar pattern, 12h, NH4 + The order of -N removal rate is: Fe>Ti>stainless steel>Ni>Cu.

[0058] Table 1 COD and NH4 of electrode modified BES reactor group for 12 h + -N removal rate and corrosion degree

[0059]

[0060] The inventors found that although the Fe electrode has the highest COD and NH4 +-N removal rate, but its corrosion degree is also the highest, as shown in Table 1, and there are obvious signs of oxidation and shedding, so it cannot be used in the long-term bioelectrochemical degradation of low-concentration wastewater. The titanium electrode of Example 1 shows good COD and NH4 + -N removal rate and operation stability, COD and NH4 in 15h + The -N removal rate is higher than 98%, and the corrosion degree is low, which can be applied to the efficient degradation of low-concentration wastewater for a long time.

[0061] 2. BES electrochemical analysis

[0062] The different metal electrodes modified by CNT in Example 1 and Comparative Examples 1 to 4 will affect the metabolism of electroactive microorganisms in the BES system. This effect can be determined by CV and EIS. Figure 2 a) and EIS( Figure 2 b) Analysis in the figure can show the enrichment of electroactive microorganisms in the BES system. Compared with other modified electrodes, the metal iron modified electrode has the lowest resistance of 82.36Ω (Table 2). In addition, the enhancement of CV behavior indicates that the biochemical performance is significantly enhanced, which can be attributed to the reduction of electrode resistance and the ability of the electrode material to interact with microbial cytochromes, thereby facilitating electron transfer. The high specific surface area and ordered porous structure of the carbon nanotube modified electrode can promote efficient mass transfer, thereby improving microbial adhesion and substrate flux, and improving overall performance. Except for the metal nickel and metal titanium modified electrodes, the other modified bioelectrodes did not show obvious reduction peaks. These values ​​may be related to important mediators, such as C-type cytochromes, OmcA and MtrC mediators, which play a vital role in promoting electron transfer. Analysis of the CV curves of the bioelectrodes showed that the anode of the metal titanium reactor had a higher response current (-1.686mA) at a larger potential, showing higher electroactivity ( Figure 2 a), while the electroactivity of stainless steel, nickel and copper anodes differed little at relative potentials.

[0063] Table 2 Electrochemical parameters of cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS) during repeated cycles

[0064]

[0065] EIS equivalent circuit analysis was performed in the BES reactor, including solution internal resistance, charge transfer resistance, Warburg impedance and capacitance (Table 2). s The range is 17.41-62.37Ω, and the charge transfer resistance R ctThe range is 82.36-669Ω. According to the EIS data, the solution resistance and electrode resistance in the reactor both show a positive correlation with the degradation effect, which indicates that the coupling degradation effect between the biofilm on the surface of the bioelectrode in the bioelectrochemical system and the different modified metal electrodes in each reactor is quite different. In terms of each reactor, the charge transfer resistance of the metal iron (82.36Ω), metal titanium (138.2Ω), stainless steel (182.6Ω), and metal nickel (265.6Ω) electrode reactors is significantly lower. This means that the electroactive microorganisms are better enriched in the BES reactor, and the internal resistance of the bulk solution will also be affected by the microorganism community on the surface of the bioelectrode and reduced. In the metal copper electrode reactor, the charge transfer resistance is 669Ω, which is higher than that in other reactors. High charge transfer resistance means that there is a higher obstacle to electron transfer in the bioelectrode, which is also consistent with the highest COD, NH4 + -N concentration.

[0066] The carbon material has biocompatibility, and the biofilm can promote the microorganisms to adhere to the surface of the bioelectrode more effectively during the culture, and enhance the electron transfer capacity of the bioelectrochemical system for deep degradation of pollutants. Together with the microorganisms involved, the overall efficiency of the BES system depends on several factors, including the physical and chemical properties of the electrode material. The selection of the electrode material plays a crucial role in the performance of the BES, because the electrode determines the type and rate of electrochemical reactions that occur in the system. The results show that the lower the internal resistance and charge transfer resistance of each reactor, the higher the pollutant degradation efficiency.

[0067] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Application of a bioelectrochemical system electrode in bioelectrochemical degradation of low-concentration wastewater, characterized in that: The applications are: The electrodes of the bioelectrochemical system are used as the cathode and anode of the bioelectrochemical reactor, and electroactive bacteria are cultured on the surfaces of the cathode and anode. Then, the voltage between the cathode and anode is controlled to be 0.2~2V to carry out the bioelectrochemical aerobic reaction. The preparation method of the bioelectrochemical system electrode is as follows: The modified carbon nanotubes soaked in nitric acid are dispersed in a polyethyleneimine solution to prepare a carbon nanotube suspension; two titanium foam plates are used as cathode and anode for electrophoretic deposition and placed in the carbon nanotube suspension for electrophoretic deposition; the cathode and anode titanium foam plates are then swapped and placed in the carbon nanotube suspension for electrophoretic deposition; the plates are washed with water, dried, and then immersed in a sodium dodecyl sulfate solution and dried; The COD concentration of the low-concentration wastewater is 200~400 mg / L, NH4 + -N concentration is 10~20 mg / L.

2. The use according to claim 1, characterized in that The method for preparing carbon nanotubes modified by nitric acid immersion comprises the following steps: immersing the carbon nanotubes in a concentrated nitric acid solution for 20 to 30 hours, then washing with water until neutral, and then drying.

3. The use according to claim 1, characterized in that The ratio of the carbon nanotubes modified by nitric acid soaking to the polyethyleneimine solution is 1 g: (800-1200) mL; the solvent of the polyethyleneimine solution is water, and the concentration of the polyethyleneimine solution is 3-10 wt %.

4. The use according to claim 1, wherein The voltage of the electrophoretic deposition is 25-35 V, and the electrophoretic deposition time is 1-3 min.

5. The use according to claim 1, characterized in that The solvent of the sodium lauryl sulfate solution is water, and the concentration is 0.5-2 wt %; the time of immersing in the sodium lauryl sulfate solution is 20-30 hours.

6. The use according to claim 1, wherein The aeration flow rate of the bioelectrochemical aerobic reaction is 80-150 mL / min.

Images