Preparation method of a bimetallic single-atom catalytic cathode Ce&Co / CN and coupled microbial fuel cell

Abstract

The present invention provides a preparation method of a bimetallic single-atom catalytic cathode Ce&Co / CN and a coupled microbial fuel cell; the system inlet water is saline wastewater, and the wastewater flows into the reactor from the bottom water inlet through a peristaltic pump, and then flows out after passing through the microbial anode chamber and the upper cathode chamber; a carbon rod is used as the conductive medium of the anode; the wastewater overflows from the cathode area for effluent collection, and the cathode material is in contact with both oxygen-containing air and wastewater, reducing the demand for aeration, being able to meet the oxygen demand required for the cathode reaction while saving aeration energy; by utilizing the ability of microorganisms to convert wastewater pollutants and generate electricity, combined with the photoelectric response and catalytic ability of the cathode nanocatalyst, energy-saving and efficient treatment of pollutants in industrial wastewater is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment and energy utilization in water pollution control, and relates to the preparation of an efficient Ce&Co / CN modified cathode, as well as an energy-saving system for photoelectrocatalytic synergistic treatment of high-salt wastewater by coupling a composite electrode with microbial electricity generation, with remarkable treatment effects. While treating industrial wastewater, it can generate energy, and the system operation cost is relatively low, providing important reference value for the further development of low-carbon and efficient wastewater treatment technologies. Background Art

[0002] As a kind of refractory wastewater, saline wastewater not only contains a large amount of substances that are difficult to be degraded by microorganisms, but also contains a high content of salts that have strong limitations on biological treatment. Generally speaking, saline wastewater refers to wastewater containing organic substances and dissolved solids with a mass fraction of not less than 3.5%, and has the characteristics of being difficult to treat, high system operation cost, and poor biodegradability.

[0003] A microbial fuel cell combines wastewater treatment and microbial electricity generation. Using electrogenic microorganisms to oxidize organic pollutants and generate electrons, and continuously transporting the electrons to the aerobic region of the cathode for an oxygen reduction reaction to generate current, realizing the recovery and utilization of energy in wastewater organic matter. It is a typical bioelectrochemical system. Compared with traditional sewage biological treatment technologies and traditional fuel cells, it can not only degrade organic wastes in water bodies, but also has certain energy generation benefits, and has the advantages of simple operation, low operation requirements, mild conditions, recyclability, environmental cleanliness and friendliness, etc., and has broad R & D potential. However, there are still problems such as large battery internal resistance, small output power, low Coulomb efficiency and poor effluent water quality.

[0004] Based on existing research, by degrading pollutants through the catalytic reaction of a modified cathode and improving the biodegradability of wastewater, and then applying it to a microbial fuel cell system to improve the treatment effect, it can generate energy and reduce the operation cost, and at the same time no secondary pollution is generated. It is a low-carbon and green method for treating refractory wastewater with great technical and economic advantages. Summary of the Invention

[0005] The present invention couples a photoelectrocatalysis system with a microbial fuel cell power generation system, and successfully constructs a photoelectrocatalytic coupling microbial power generation system (PEC-MFC) for modular low-carbon energy-saving and efficient treatment of industrial wastewater, which does not require aeration and can be adjusted according to the actual wastewater situation. An air cathode is formed at the water-air interface layer of the cathode, reducing the demand for aeration, saving aeration energy consumption and reducing operating costs. Utilizing the ability of microorganisms to transform wastewater pollutants and generate electricity, combined with the photoelectric response and catalytic ability of the cathode nanocatalyst, it realizes the efficient treatment of industrial wastewater, improves the power generation ability of the system, saves treatment costs and aeration energy consumption, and solves the problems of traditional processes for treating industrial wastewater, such as the large amount of chemical reagents used, long operating processes, high equipment costs, large floor area, and high energy consumption.

[0006] The technical solution of the present invention:

[0007] A preparation method of a bimetallic single-atom catalytic cathode Ce&Co / CN is as follows:

[0008] (1) Dissolve urea and cerium and cobalt ion salts in sufficient deionized water and mix evenly, where the molar ratio of cerium ion salt to urea is 1:1×10 5 ~1:3, and the molar ratio of cobalt ion salt to urea is 3:1×10 5 ~1:1000. The obtained solid after drying is calcined at 500 - 530 °C for 2.5 - 4 h, and after cooling, it is ground to obtain catalyst powder for standby.

[0009] (2) Take a dry PVDF binder and dissolve it in DMF solution in small amounts and multiple times, continuously stirring during the period until it is completely dissolved, and drying until a viscous solution coating is obtained.

[0010] (3) After the conductive material is washed and dried; the catalyst powder obtained in step (1) and the viscous solution coating obtained in step (2) are mixed and stirred until dissolved, and evenly coated on the surface of the conductive material, and then dried to obtain a cathode composite electrode.

[0011] Further, in the step (1), the drying temperature is 80 - 100 °C, and the drying time is 12 - 24 h;

[0012] Further, in the step (1), the calcination heating rate is set to 5.0 - 5.2 °C / min;

[0013] Further, in the step (2), the concentration of the PVDF binder in the DMF solution is 3 - 5 g / L;

[0014] Further, in the step (2), it is dried at 80 - 100 °C for 15 - 20 min;

[0015] Further, in the step (3), the conductive material can be a copper sheet, a stainless steel mesh, a carbon fiber cloth, etc.;

[0016] Further, in the step (3), the mass ratio of the catalyst powder in the step (1) to the viscous solution coating obtained in the step (2) is 10:3 to 2:1;

[0017] A coupled biofuel cell system constructed by using a single-atom catalytic cathode Ce&Co / CN specifically includes:

[0018] The coupled biofuel cell system has an up-and-down structure, and the operation mode of the saline wastewater is from bottom to top; the anode chamber of the coupled biofuel cell system is located at the lower part, and the anode chamber is filled with activated carbon particles loaded with Shewanella electrogenic bacteria, and the bottom uses an aeration head to disperse the influent; one end of the anode material is connected to a wire and led out, and is externally connected in series with a resistor, an ammeter and a cathode material in sequence, and a voltmeter is connected in parallel, and the power generation of the anode organisms is continuously monitored in real time by detecting the current situation; the cathode chamber is located at the upper part, and the cathode chamber is filled with the saline wastewater flowing out of the anode chamber, and the cathode is in contact with both air and saline wastewater and is irradiated with light, and the cathode material is externally connected to a wire to introduce the electrons generated by the anode into the cathode chamber; the pretreated saline wastewater continuously enters the bottom of the anode chamber through a flow regulating device for the influent, flows through the anaerobic biological part and enters the cathode chamber, and finally the treated effluent overflows from the overflow device at the upper part of the cathode chamber and is collected.

[0019] The filling rate of the activated carbon particles is 85% - 95%.

[0020] The anode conductive material can be an inert conductive material such as a carbon rod, and the cathode material is the above-mentioned single-atom catalytic cathode Ce&Co / CN.

[0021] The saline wastewater is obtained by diluting 30% high-salt organic amine wastewater by 40 - 60 times to reduce the biological treatment pressure.

[0022] The ratio of the anode chamber to the cathode chamber can be adjusted according to the actual wastewater treatment situation.

[0023] The industrial wastewater treated by the photo-electrocatalytic coupled microbial fuel cell is saline wastewater, and the residence time is set to 8 - 12 h.

[0024] The wastewater is introduced into the system through a buffer aeration head, which can homogenize the influent and reduce the impact of the influent on the system at the same time.

[0025] Except for the parts in contact with the biological anode and the parts connected to the wires, the anode conductive material is treated with waterproof and anti-electricity measures to improve the electron transfer efficiency, such as using waterproof tape to wrap and cover the conductive material.

[0026] The cathode material can be in contact with oxygen-containing air and wastewater simultaneously, eliminating the need for aeration operation and reducing the operating cost.

[0027] Advantages of the present invention:

[0028] (1) A bimetal-doped single-atom catalytic material is prepared, with the metal components uniformly dispersed and anchored, having high catalytic ability;

[0029] (2) On the premise of meeting energy conservation and production capacity, the construction mode of the reactor is improved, achieving good results and providing ideas for the technical coupling treatment of high-salt wastewater.

[0030] (3) Using the bimetal single-atom catalytic material to couple bioelectrochemistry for multi-stage combined treatment of actual wastewater has the characteristics of being clean, efficient, and economical; Description of the Drawings

[0031] Figure 1 It is a schematic diagram of a photoelectrocatalytic coupling microbial fuel cell system (PEC-MFC) device.

[0032] Figure 2 It is the cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS) of a bimetal-doped Ce&Co / g-C3N4 single-atom catalytic electrode. Among them, (a) is the cyclic voltammogram of the catalytic electrode; (b) is the electrochemical impedance spectrum of the catalytic electrode.

[0033] Figure 3 It is the stability data of total organic carbon (TOC) and total nitrogen (TN) of the first-stage effluent of the system. Among them, (a) is the TOC stability diagram of the first-stage effluent of PEC-MFC, with the ordinate being the total organic carbon concentration (mg / L); (b) is the TN stability diagram of the first-stage effluent of EC-MFC, with the ordinate being the total nitrogen concentration (mg / L). The abscissa is the operating time (h) in both cases, and the cathode loading material is Ce&Co / g-C3N4.

[0034] Figure 4 It is the stability data of chemical oxygen demand (COD), total organic carbon (TOC), and total nitrogen (TN) of the second-stage effluent of PEC-MFC. Among them, (a) is the COD stability diagram of the second-stage effluent of PEC-MFC, with the ordinate being the biochemical oxygen demand concentration (mg / L); (b) is the TOC stability diagram of the second-stage effluent of EC-MFC, with the ordinate being the total oxygen demand concentration (mg / L). (c) is the TN stability diagram of the second-stage effluent of EC-MFC, with the ordinate being the total nitrogen concentration (mg / L). The abscissa is the operating time (h) in all cases, and the cathode loading material is Ce&Co / g-C3N4.

[0035] Figure 5It is the ultraviolet full-spectrum scan of the secondary effluent of the PEC-MFC system, with Ce&Co / g-C3N4 as the cathode loading material; the abscissa is the scanning wavelength (nm), and the ordinate is the absorbance (Abs).

[0036] In the figure: 1 water tank; 2 water inlet pipe; 3 peristaltic pump; 4 bottom water inlet; 5 aeration head; 6 anode area; 7 cathode area; 8 cathode; 9 anode conductive material; 10 overflow effluent; 11 wire; 12 external resistor; 13 ammeter; 14 effluent collection container. Specific implementation mode

[0037] The following further illustrates the specific implementation mode of the present invention in combination with the technical solution and the drawings, which does not limit the protection scope of the present invention.

[0038] As Figure 1 shown, the present invention provides a photo-electrocatalytic coupled microbial fuel cell system for treating industrial wastewater. This coupled system has the following modular characteristics, and its treatment design composition includes:

[0039] The reservoir 1 is used to store wastewater; the peristaltic pump 3 pumps the wastewater into the bottom water inlet 4 of the photo-electrocatalytic coupled microbial fuel cell reactor of the treatment system through the lower water inlet pipe 2, and the aeration head 5 evenly and disperses the inlet water, and the wastewater flow rate is controlled by adjusting the peristaltic pump 2.

[0040] The wastewater flows from the bottom water inlet 4 and the aeration head 5 into the anode area 6 filled with activated carbon loaded with Shewanella electrogenic bacteria. After being treated in the anode area 6, it flows into the cathode area 7 and contacts the cathode 8 loaded with the catalytic material.

[0041] The anode area 6 is led out by using the anode conductive material 9 wrapped with water-insulating tape to collect and conduct electrons, and is connected to the cathode 8 through the wire 11, and a 10-10000Ω adjustable external resistor 12 and an ammeter 13 are connected to monitor the microbial electricity generation situation. The top cathode area overflows with water, which is collected by the effluent collection container 14.

[0042] Preparation of the biological anode: Adsorb Shewanella electrogenic bacteria on granular activated carbon. The Shewanella electrogenic bacteria are a mixed bacteria cultured and domesticated from the bottom mud of the Yellow Sea water area of Dalian Xinghai Square. When the stable electricity generation potential of the bacteria measured by a 232-type reference electrode is greater than 0.06V, it can be put into use.

[0043] Example 1

[0044] Combined with Figure 1 , first place the high-salt wastewater diluted 50 times in the reservoir 1, and it flows into the bottom water inlet 4 of the photo-electrocatalytic coupled microbial fuel cell reactor through the water inlet pipe 2. The wastewater flow rate is controlled by the peristaltic pump 3 at a certain position of the water inlet pipe 2, so that the wastewater residence time in the reactor is 8h.

[0045] The wastewater flows into the anode region 6 filled with activated carbon loaded with Shewanella electrogenic bacteria through the bottom water inlet 4 and the aeration head 5 in a dispersed manner. After being treated by the microorganisms in the anode region 6, it flows into the cathode region 7 and contacts the cathode 8, and the wastewater overflows from the upper part of the cathode region 7 and flows out.

[0046] The anode region is filled with activated carbon loaded with microorganisms, and the external conduction of the anode conductive material 9 is set. The cathode part of the electrode is a photoelectrode cathode. A 230V, 50W halogen lamp is set as the visible light source at 10 cm above the reactor.

[0047] Synthesis of Ce&Co / g-C3N4: Take 60 g of urea, 0.5 mM of cerium nitrate, and 0.15 mM of cobalt nitrate (the molar ratios of cerium ion salt to urea and cobalt ion salt to urea are 1:2000 and 3:2×10 4 ) in a 100 ml beaker and stir until dissolved. Dry it in a blast drying oven at 80 °C for 24 h until completely crystallized. Transfer it to a crucible, place it in a muffle furnace, heat it to 520 °C at a heating rate of 5.2 °C / min, keep it at a constant temperature and calcine for 4 h, cool it to room temperature, and grind it to obtain the doped catalyst, which is denoted as Ce&Co / CN.

[0048] Ce&Co / g-C3N4 cathode modification: Use a copper sheet as the electrode carrier, ultrasonically treat it in absolute ethanol and deionized water for 30 minutes, and then dry it at 60 °C. Take 20 mg of PVDF binder and dry it at 80 °C for 15 min. Then dissolve it in 5 mL of DMF solution in small amounts and multiple times, continuously stir it with a glass rod during this period. After complete dissolution, dry it at 80 °C for 20 min to obtain a relatively viscous PVDF binder. Pour 50 mg of the catalytic material into the binder and evenly coat it on the copper sheet electrode carrier (the size of the electrode carrier is controlled to be 5 cm×5 cm, and the actual coating area is 4 cm×5 cm).

[0049] Furthermore, in the steps of preparing the above cathode modification material, the manufacturer of the DMF solution is Shanghai Hushi Laboratory Equipment Co., Ltd.

[0050] Example 2

[0051] Combined with Figure 1 , adopt Figure 1 The PEC-MFC device method in is used to construct a primary reactor to treat high-salt wastewater diluted 50 times. The residence time of the reaction system is 8 h. Samples are taken to detect two data of TOC and TN respectively, and TOC stability curves and TN stability curves are made, as shown in (a) and (b) in Figure 3 respectively;

[0052] Example 3

[0053] Combined with Figure 1, using Figure 1 The PEC-MFC device method in is used to construct a two-stage reactor to treat high-salt wastewater diluted 50 times. The residence time of the reaction system is 8 h for both. Samples are taken to detect three data items of COD, TOC, and TN respectively, and COD stability curves, TOC stability curves, and TN stability curves are made, as shown in Figure 4 the (a), (b), and (c) in;

[0054] Example 4

[0055] Combined with Figure 1 , using Figure 1 the PEC-MFC device in to treat high-salt wastewater diluted 50 times, and the ultraviolet full-spectrum scanning of the secondary effluent of the reactor is carried out to check the change of organic matter in the effluent, as shown in Figure 5 .

Claims

1. A coupled biological fuel cell system, characterized in that, The cathode material of the coupled microbial fuel cell system is a bimetal-doped single-atom catalytic cathode Ce&Co / CN. The coupled microbial fuel cell system specifically includes: The coupled microbial fuel cell system has an up-and-down structure, and the operation mode of the saline wastewater is from bottom to top. The anode chamber of the coupled microbial fuel cell system is located at the lower part, and the anode chamber is filled with activated carbon particles loaded with Shewanella electrogenic bacteria. An aeration head is used at the bottom to disperse the influent. One end of the anode material is connected to a wire and led out externally, and a resistor, an ammeter, and the cathode material are connected in series in sequence, and a voltmeter is connected in parallel. The electricity generation of the anode organisms is continuously monitored in real time by detecting the current situation. The cathode chamber is located at the upper part. The cathode chamber is filled with the saline wastewater flowing out of the anode chamber. The cathode is in contact with both air and the saline wastewater and is irradiated with light. The cathode material is connected to a wire to introduce the electrons generated by the anode into the cathode chamber. The pretreated saline wastewater continuously enters the bottom of the anode chamber through the influent flow regulating device, flows through the anaerobic biological part and enters the cathode chamber, and finally the treated effluent overflows from the overflow device at the upper part of the cathode chamber and is collected. The preparation method of the bimetal single-atom catalytic cathode Ce&Co / CN is specifically as follows: Step (1): Co-dissolve urea and cerium and cobalt ion salts in sufficient deionized water and mix evenly, where the molar ratio of cerium ion salt to urea is 1:1×10 5 ~1:3, and the molar ratio of cobalt ion salt to urea is 3:1×10 5 ~1:1000. The obtained solid after drying is calcined, calcined at 500-530 °C for 2.5-4 h, and ground after cooling to obtain catalyst powder for standby; Step (2): Take the dried PVDF binder and dissolve it in the DMF solution in small amounts and multiple times. During this period, continuously stir until it is completely dissolved, and dry it until a viscous solution coating is obtained. Step (3): After the conductive material is cleaned and dried, the catalyst powder obtained in step (1) and the viscous solution coating obtained in step (2) are mixed and stirred until dissolved, and evenly coated on the surface of the conductive material, and then dried to obtain the cathode composite electrode.

2. The coupled biological fuel cell system according to claim 1, characterized in that, In step (1), the drying temperature is 80~100 °C, and the drying time is 12~24 h; the calcination heating rate is set to 5.0~5.2 °C / min.

3. The coupled biological fuel cell system according to claim 1, wherein, In step (2), the concentration of the PVDF binder in the DMF solution is 3~5 g / L.

4. A coupled biological fuel cell system according to claim 1, wherein In step (2), it is dried at 80~100 °C for 15~20 min.

5. A coupled biological fuel cell system according to claim 1, wherein In step (3), the conductive material can be a copper sheet, a stainless steel mesh, or a carbon fiber cloth.

6. The coupled biological fuel cell system according to claim 1, characterized in that, In step (3), the mass ratio of the catalyst powder in step (1) to the viscous solution coating obtained in step (2) is 10:3~2:

1.

7. A coupled microbial fuel cell system according to claim 1, wherein The filling rate of the activated carbon particles is 85%~95%. The anode material is a carbon rod. The saline wastewater is obtained by diluting 30% high-salt organic amine wastewater by 40-60 times to reduce the biological treatment pressure.

8. A coupled biological fuel cell system according to claim 1, characterized in that, The ratio of the anode chamber to the cathode chamber can be adjusted according to the actual wastewater treatment situation. The residence time of the saline wastewater is set to 8~12 h.

9. A coupled microbial fuel cell system according to claim 1, wherein Except for the parts in contact with the biological anode and the parts connected to the wire, the anode material is treated for waterproof and anti-electricity.

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