Low-cost metal modified electrode material, preparation method and application

Abstract

The invention provides a low-cost metal modified electrode material, a preparation method and application, solves the problems that a carbon nitride material is difficult to recover and poor in sustainability, and improves the photoelectrocatalysis capability of an active carbon material. Further constructing a packed bed cathode coupled microbial fuel cell system; the treated industrial wastewater is high-salt coking wastewater from Anshan steel, a PEC-MFC system filled with electrogenesis microorganisms is used for realizing wastewater recycling and harmlessness, and energy-saving, high-efficiency and one-step treatment of the industrial wastewater is completed.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment and energy utilization in water pollution control, and involves the preparation of a low-cost Ce&Co / CN modified cathode activated carbon granular material and the construction of a filled cathode, as well as an energy-saving system for photoelectric catalytic synergistic treatment of high-salt industrial wastewater coupled with microbial electricity production. The system has low cost and significant water treatment effect, and can achieve energy recovery while treating industrial wastewater in one step, providing an important reference for further developing low-carbon and high-efficiency wastewater treatment technology. Background Art

[0002] Coking wastewater is a typical industrial wastewater. Aromatic and heterocyclic species are widely present in the pollutant spectrum, and it also contains high salt content that has a strong impact on biological treatment. Microorganisms have poor adaptability to wastewater, and it is difficult to achieve good treatment results with biological treatment alone. Advanced oxidation technology (AOPs) is usually required to enhance the removal of refractory substances, but this further increases water treatment costs and energy consumption.

[0003] Combining micro-wastewater treatment with microbial electricity generation, with electricity-generating microorganisms as the medium, while oxidizing and treating organic pollutants, electrons are continuously transported to the cathode aerobic area through an external circuit to undergo oxygen reduction reactions and generate current, thus realizing the recycling of energy in wastewater organic matter. This is a typical bioelectrochemical system. Compared with traditional sewage biological treatment technology and traditional fuel cells, this can not only degrade organic waste in water bodies, but also has certain production efficiency benefits, and has the advantages of simple operation, low operating requirements, mild conditions, recyclability, and clean and friendly environment, and has broad research and development potential.

[0004] Based on the existing research, a simple and low-cost carbon nitride-modified granular activated carbon cathode material was synthesized, which solved the prominent problems of carbon nitride materials being difficult to recycle and poor in sustainability. Then, it was applied in the form of a cathode packed bed in a microbial fuel cell system, which can increase production and reduce operating costs, while generating no secondary pollution. It is a low-carbon, green and technically and economically advantageous method for treating difficult-to-degrade wastewater. Summary of the invention

[0005] The present invention couples photoelectrocatalysis with a microbial fuel cell electricity generation system, uses a low-content, low-cost dopant-modified activated carbon material to form a filled cathode chamber, and couples it with an anode biological chamber to build a modular low-carbon, energy-saving and efficient treatment of industrial wastewater with a photoelectrocatalytic coupled microbial electricity generation system (PEC-MFC) that does not require aeration and is reliably driven by solar energy. The air cathode is formed on the cathode water-air interface layer to reduce the demand for aeration, save part of the aeration energy consumption and reduce the operating cost. In the laboratory, this dual-chamber single reactor coupling system was simply multiplied and amplified, and industrial wastewater was treated in multiple lines to reduce the impact on organisms and improve the treatment efficiency. The ability of microorganisms to transform wastewater pollutants and generate electricity is used to achieve efficient and integrated treatment of industrial wastewater, which not only saves treatment costs and energy consumption, but also solves the problems of traditional processes for treating industrial wastewater, which require a large amount of chemical reagents, occupy a large area, have multiple operating processes, and consume a lot of energy.

[0006] The technical solution of the present invention:

[0007] A method for preparing a low-cost metal-modified electrode, the steps are as follows:

[0008] (1) The granular activated carbon is ultrasonically washed with water until no carbon powder falls off, then immersed in alcohol or industrial alcohol to remove surface organic matter, drained, washed with water, and dried overnight to obtain an AC carrier.

[0009] (2) Co(NO3)2 and Ce(NO3)2 were added into deionized water, followed by melamine as a nitrogen source, and stirred to obtain a homogeneous solution;

[0010] (3) Take the AC carrier obtained in step (1), mix it with the homogeneous solution obtained in step (2) by using an equal volume immersion method, ultrasonically treat it, and then dry it in a forced air drying oven. The obtained dry particles are calcined in a muffle furnace at an annealing temperature of 400-430° C. for 2.5-4 h to obtain the final bimetallic carbon nitride modified filled catalytic cathode, named Co&Ce-g-C3N4 / AC material.

[0011] In the step (1), the diameter of the granular activated carbon is d=1.1-1.7 mm;

[0012] In the step (1), the soaking time is 10 to 30 minutes;

[0013] In the step (1), the volume fraction of alcohol or industrial alcohol is 65-95%;

[0014] In the step (2), the total mass fraction of the metal salt in the homogeneous solution is 2.5 to 5.0 wt %;

[0015] In the step (2), the molar ratio of the cerium salt to the cobalt salt is 1:1*10 5 ~1:3;

[0016] In the step (2), the mass fraction of melamine in the homogeneous solution is 1.5 to 3.0 wt %;

[0017] In the step (3), the ultrasonic treatment time is 20 to 30 minutes;

[0018] In the step (3), the drying temperature is 70 to 100° C. and the drying time is 2 to 6 hours;

[0019] In the step (3), the calcination heating rate is set to 4.8-5.2°C / min.

[0020] A coupled microbial fuel cell, specifically comprising:

[0021] The coupled microbial fuel cell has an overall upper and lower structure, and the operation mode of saline wastewater is bottom-in and top-out; the anode chamber 11 of the coupled microbial fuel cell is located at the bottom, and the anode chamber 11 is filled with activated carbon particles loaded with Shewanella electrogenic bacteria, and the aeration head 12 is used to disperse the water at the bottom of the anode chamber 11; one end of the anode conductive material 7 is connected to the wire 4 and then externally connected to the external resistor 5, the ammeter 6 and the cathode conductive material 7 in series in sequence, and the voltmeter is connected in parallel, and the power generation of the anode organism is continuously monitored in real time by detecting the current and voltage; the cathode chamber 9 is located at the top, and the cathode chamber 9 is filled with saline wastewater flowing out of the anode chamber 11. The above-mentioned Co&Ce-g-C3N4 / AC with integrated catalytic and adsorption effects is loaded in a transparent and permeable cathode container 8, which is convenient for replacement and adjustment in the experiment. The anode chamber 11 and the cathode chamber 9 are separated by a partition 10.

[0022] The cathode is in contact with the air and the saline wastewater at the same time and can be exposed to light. The cathode material Co&Ce-g-C3N4 / AC external wire 4 introduces the electrons generated by the anode into the cathode chamber 9; the pretreated saline wastewater continuously enters the bottom of the anode chamber 11 through the water inlet flow regulating device, flows through the biological anaerobic part and enters the cathode chamber 9, and finally the treated effluent flows out from the overflow device at the top of the cathode chamber 9 and is collected.

[0023] Preferably, a single reactor uses a cylindrical container as the main body, and the volume can be changed according to the actual wastewater treatment needs.

[0024] The domestication of electricity-producing microorganisms is carried out by inoculating the electricity-producing strain of Shewanella into an incubator with appropriate temperature and culture medium, and adding an appropriate amount of the wastewater as a nutrient source to the incubator when the microbial condition is stable. During this period, the wastewater concentration is continuously increased to domesticate the microorganisms until the organisms can adapt to the original wastewater environment. During this period, an ammeter and a voltmeter are used to monitor the growth of the microorganisms.

[0025] The activated carbon particles in the anode chamber 11 have a sheet diameter of d=35-65 mm, a thickness of δ=15-25 mm, and a filling rate of 85%-95%;

[0026] The conductive material 7 of the anode and cathode is an inert conductive material such as a carbon rod;

[0027] The volume ratio of the anode chamber 11 to the cathode chamber 9 is 6:1 to 1:1, which can be adjusted according to the actual wastewater treatment conditions;

[0028] The partition 10 is supported by a porous foam plate with the same diameter as the reactor, and the porous foam plate is wrapped with filter cloth gauze to intercept the detached biofilm, thereby enhancing the metabolism and water purification function of the anode microorganisms;

[0029] The conductive materials 7 of the cathode and anode are all treated with waterproof, insulating and anti-electrical treatment except for the part in contact with the bioanode and the part connected with the wire 4 to improve the efficiency of electron transmission, for example, by wrapping and covering the conductive materials with waterproof tape;

[0030] The cathode container 8 comprises a water-permeable flexible filter screen with a pore size d < 1 mm and a rigid shell;

[0031] The wastewater used to acclimate the microorganisms is obtained by diluting 15% high-salt coking wastewater, and the microorganisms are acclimatized step by step until the organisms adapt to the wastewater.

[0032] Beneficial effects of the present invention:

[0033] (1) Metal carbon nitride-doped activated carbon catalytic materials were prepared, in which the metal components were evenly dispersed and anchored, improving the shortcomings of carbon nitride materials that are easy to lose and difficult to apply, and having higher catalytic ability;

[0034] (2) Under the premise of meeting low cost and production capacity, the MFC reactor was structurally optimized and modularly designed, achieving good treatment effects. By coupling bioelectrochemical and electrocatalytic advanced oxidation methods, it provided applicable new technologies for energy-saving and efficient wastewater treatment (including high-salt coking wastewater, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the photoelectrocatalytic coupled microbial fuel cell system (EC-MFC) device. The photoelectrocatalytic coupled microbial fuel cell system (PEC-MFC) system adds light conditions to the former.

[0036] Figure 2 The cyclic voltammetry curve CV and photocurrent response IT experimental results of the metal-doped carbon nitride filled electrode. Among them, (a) is the cyclic voltammetry curve of the catalytic cathode; (b) is the photocurrent response diagram of the catalytic cathode.

[0037] Figure 3 The experimental results of preparing hydrogen peroxide by electrochemical oxygen reduction. (a) and (b) are the production and yield of H2O2 under the conditions of no light and 0.4V external voltage when using different cathode filling materials and electrolyte combinations; (c) and (d) are the production and yield of H2O2 under the conditions of external light source and 0.4V external voltage when using different cathode filling materials and electrolyte combinations.

[0038] Figure 4 The stability data of total organic carbon (TOC) and total nitrogen (TN) in the effluent of the EC-MFC system. (a) is the TOC stability diagram of the first-stage effluent of the EC-MFC, and the ordinate is the total organic carbon concentration (mg / L); (b) is the TN stability diagram of the first-stage effluent of the EC-MFC, and the ordinate is the total nitrogen concentration (mg / L). The horizontal axes are all running time (h), and the following cathode filling materials are all Ce&Co-g-C3N4 / AC.

[0039] Figure 5 The stability data of total organic carbon (TOC) and total nitrogen (TN) in the first and second effluents of the PEC-MFC system. (a) is the TOC stability diagram of the first effluent of the PEC-MFC, with the ordinate being the total organic carbon concentration (mg / L); (b) is the TN stability diagram of the first effluent of the PEC-MFC, with the ordinate being the total nitrogen concentration (mg / L). The abscissas are all the operation time (h).

[0040] Figure 6 UV for the inlet, primary and secondary effluent of the PEC-MFC system 254 Situation and UV full spectrum scanning diagram, where (a) is UV 254 (b) is the full spectrum scanning result. The horizontal axis is the scanning wavelength (nm) and the vertical axis is the absorbance (Abs).

[0041] In the figure: 1 water reservoir; 2 water inlet pipe; 3 peristaltic pump; 4 wire; 5 external resistor; 6 ammeter; 7 conductive material; 8 cathode container; 9 cathode chamber; 10 partition; 11 anode chamber; 12 aeration head; 13 bottom water inlet; 14 outlet water collection container. DETAILED DESCRIPTION

[0042] The following is a further description of the specific implementation of the present invention in combination with the technical scheme and the accompanying drawings, which is not intended to limit the protection scope of the present invention.

[0043] Example 1

[0044] like Figure 1As shown, the present invention provides a photoelectrocatalytic coupled MFC system for treating high-salinity industrial wastewater. The coupled system uses a filled cathode and a modular design, and its design composition includes:

[0045] The water reservoir 1 is used to store wastewater; the peristaltic pump 3 pumps the wastewater into the bottom water inlet 13 of the treatment system through the lower water inlet pipe 2, and the aeration head 12 evenly and disperses the water inlet, and the wastewater flow rate is controlled by adjusting the peristaltic pump 3.

[0046] Wastewater flows into the anode chamber 11 filled with activated carbon particles loaded with Shewanella exoelectrogenic bacteria (sheet diameter d = 40-60 mm, thickness δ = 20-25 mm, filling rate 90%) from the bottom water inlet 13 and the aeration head 12. After biological treatment, it passes through the middle partition 10 (made of porous foam board and wrapped with inorganic filter cloth) to intercept microorganisms and then flows into the cathode chamber 9, contacting the cathode container 8 filled with cathode conductive material.

[0047] The anode chamber 11 is led out with a conductive material 7 (carbon rod) wrapped with a waterproof tape to collect and conduct electrons, and is connected to the cathode container 8 (flexible filter, pore size d = 0.8mm) filled with Co&Ce-g-C3N4 / AC material through a wire 4 and a conductive material 7, and is connected to a 10-10000Ω adjustable external resistor 5 and an ammeter 6 to monitor the electricity production of microorganisms. The top cathode area overflows water and is collected by the water collection container 14. The volume ratio of the anode chamber 11 to the cathode chamber 9 is 4:1.

[0048] Preparation of biological anode: The anode microorganisms containing Shewanella exoelectrogenic bacteria are adsorbed on granular activated carbon. The mixed bacteria containing Shewanella exoelectrogenic bacteria are obtained by culturing and domesticating the bottom mud in the Xinghai waters of the Yellow Sea and Heishijiao in Dalian. The bacteria can be put into use after the stable electrogenic potential is measured by a 232 reference electrode and is greater than 0.1V.

[0049] Example 2

[0050] Pretreatment of granular carbon (AC) carrier: A sufficient amount of granular activated carbon (diameter d = 1.2 ~ 1.5mm) was ultrasonically washed with water until no carbon powder fell off, and the washed activated carbon was soaked in industrial alcohol (75% by volume) to remove organic matter adhering to the surface, kept for 20min and then drained, and the residual alcohol was washed away with deionized water, and dried at 70°C overnight to obtain an AC carrier.

[0051] Loading of Co&Ce-C3N4: 0.596g Co(NO3)2 and 2.92g Ce(NO3)2 were added to 100mL deionized water, followed by melamine and stirring to obtain a homogeneous solution, the mass fraction of melamine in the homogeneous solution was 2wt%, 70g activated carbon was mixed by equal volume immersion method and ultrasonically treated for 30min, and then dried in a 70℃ forced air drying oven for 2h. The dried particles were further heated to 400℃ in a muffle furnace at a heating rate of 5℃ / min, and annealed for 2h to obtain the final product, named Co&Ce-g-C3N4 / AC, as a cathode filling material.

[0052] Continuous cyclic voltammetry (CV) and photocurrent (IT) tests were performed in a standard three-electrode system using an electrochemical workstation (CHI660E, CHInstruments, China). In the CV test, the working electrode was a glassy carbon electrode, the counter electrode was a Pt electrode, the reference electrode was an Ag / AgCl electrode, the electrolyte solution was 5mM K3Fe(CN)6 and 0.1M KCl, and the scan rate was 100mVs-1. In the IT test, the working electrode was conductive glass, the counter electrode and reference electrode were the same as above, and 0.5mol / L Na2SO4 solution was used as the electrolyte.

[0053] The working electrode preparation process is as follows: 5 mg of the powdered Co&Ce-g-C3N4 / AC prepared in this example, 10 μL of 5% Nafion reagent and 200 μL of deionized water are weighed and placed in a 2 mL sample tube. After complete ultrasonic dispersion, 20 μL of the suspension is evenly dripped on the glassy carbon electrode and conductive glass (ITO, the dripping area is controlled to be 1 cm 2 ) and tested after drying at room temperature. The CV and IT test results are shown in Figure 2 (a) and (b) in .

[0054] The experiment of preparing hydrogen peroxide by electrochemical oxygen reduction was carried out using a double-chamber electrolytic cell, which was composed of an acrylic plate and a water-proof rubber gasket, and an ion exchange membrane was placed between the two electrolytic chambers. The anode was a carbon rod, and the anode electrolyte was a 0.5M Na2SO4 solution. The cathode used a filled electrode, that is, a porous plastic container was used to load the cathode filler and a carbon rod was used to lead it out. The cathode filler was AC or the Co&Ce-g-C3N4 / AC material prepared in this embodiment (abbreviated as CAC in the figure), and the cathode electrolyte was Na2SO4 or 20 times diluted high-salt coking wastewater. Using CAC+Na2SO 4、 CAC+diluted wastewater, AC+Na2SO4 and AC+diluted wastewater were used to carry out continuous ORR experiments for 2 h in the built reactor. A 0.4 V applied voltage was applied between the positive and negative electrodes and samples were taken at intervals of 30 min to monitor the production and yield of hydrogen peroxide. Figure 3 (a) and (b) in .

[0055] Furthermore, based on the above reactor, the cathode was subjected to illumination conditions, and other conditions remained unchanged, and the production and yield of H2O2 under different cathode electrolyte and cathode filling material combinations were tested, such as Figure 3 (c) and (d) in .

[0056] Combination Figure 1 , using the battery system of Example 1, high-salt coking wastewater raw water (COD=2000.0 mg / L, TOC=457.6 mg / L, TN=108.9 mg / L, salinity of 14.9%) was placed in a reservoir 1 and pumped into the bottom water inlet 13 of the electrocatalytic coupled microbial fuel cell (EC-PEC) reactor through a water inlet pipe 2. The wastewater flow rate was controlled by a peristaltic pump 3 to keep the wastewater residence time (HRT) in the reactor at 8 h.

[0057] The wastewater flows into the anode chamber 11 filled with activated carbon loaded with Shewanella exoelectrogenic bacteria through the bottom water inlet 13 and the aeration head 12. After biological treatment, the wastewater flows into the cathode chamber 9 after the microorganisms are intercepted by the middle partition 10 and contacts with the Co&Ce-g-C3N4 / AC material loaded in the cathode container 8.

[0058] Take out water and test TOC and TN data respectively to form TOC stability curve and TN stability curve, such as Figure 4 (a) and (b) in .

[0059] Example 3

[0060] Combination Figure 1 , a secondary reactor was constructed in the manner of Example 1 to treat the original coking wastewater. The secondary reactor was constructed by connecting two batteries described in Example 1 in series, and the wastewater was treated in the two-stage reactor in sequence. The primary and secondary HRTs of the reaction system were set to 8h and 12h, respectively. A 230V, 50W halogen lamp was set 10cm above the reactor as a visible light source, and PMS (concentration 0.5mM) was applied to the cathode chamber. The rest of the construction was the same as in Example 2. After stabilization, the water was taken out to test the TOC and TN data respectively, and the TOC stability curve and TN stability curve were formed, as shown in Figure 5 (a) and (b) in ;

[0061] Furthermore, UV was performed on the system inlet water, primary outlet water and secondary outlet water respectively. 254 and UV full spectrum scanning test to observe the degradation of pollutants, such as Figure 6 (a) and (b) in .

Claims

1. A method for preparing a low-cost metal-modified electrode material, characterized in that: Here are the steps: (1) The granular activated carbon is ultrasonically washed with water until no carbon powder falls off, then immersed in alcohol or industrial alcohol to remove surface organic matter, drained, washed with water, and dried overnight to obtain an AC carrier; (2) Co(NO3)2 and Ce(NO3)2 were added into deionized water, followed by melamine as a nitrogen source, and stirred to obtain a homogeneous solution; (3) Take the AC carrier obtained in step (1), mix it with the homogeneous solution obtained in step (2) by using an equal volume immersion method, ultrasonically treat it, and then dry it in a forced air drying oven. The obtained dry particles are calcined in a muffle furnace at an annealing temperature of 400-430° C. for 2.5-4 h to obtain the final bimetallic carbon nitride modified filled catalytic cathode, named Co&Ce-g-C3N4 / AC material.

2. The method for preparing a low-cost metal-modified electrode material according to claim 1, characterized in that: In the step (1), the diameter of the granular activated carbon is d=1.1-1.7 mm; the soaking time is 10-30 min; and the volume fraction of the alcohol or industrial alcohol is 65-95%.

3. The method for preparing a low-cost metal-modified electrode material according to claim 1, characterized in that: In the step (2), the total mass fraction of the metal salt in the homogeneous solution is 2.5-5.0wt%; the molar ratio of the cerium salt to the cobalt salt is 1:1*10 5 ~1:

3.

4. The method for preparing a low-cost metal-modified electrode material according to claim 1, characterized in that: In the step (2), the mass fraction of melamine in the homogeneous solution is 1.5-3.0 wt%.

5. The method for preparing a low-cost metal-modified electrode material according to claim 1, characterized in that: In the step (3), the ultrasonic treatment time is 20 to 30 minutes; the drying temperature is 70 to 100° C., and the drying time is 2 to 6 hours; and the calcination heating rate is set to 4.8 to 5.2° C. / min.

6. A low-cost metal-modified electrode prepared by the method for preparing a low-cost metal-modified electrode material according to any one of claims 1 to 5.

7. A coupled microbial fuel cell, characterized in that: Specifically include: The coupled microbial fuel cell has an upper and lower structure as a whole, and the operation mode of saline wastewater is bottom-in and top-out; the anode chamber (11) of the coupled microbial fuel cell is located at the bottom, and the anode chamber (11) is filled with activated carbon particles loaded with Shewanella electrogenic bacteria, and the bottom of the anode chamber (11) is used to disperse the water; one end of the conductive material (7) of the anode is connected to the wire (4) and then externally connected to an external resistor (5), an ammeter (6) and a cathode conductive material (7) connected in series in sequence, and a voltmeter is connected in parallel, and the power generation of the anode organism is continuously monitored in real time by detecting the current and voltage conditions; the cathode chamber (9) is located at the upper part, and the cathode chamber (9) is filled with saline wastewater flowing out of the anode chamber (11), and a transparent and water-permeable cathode container (8) is used to load Co&Ce-g-C3N4 / AC prepared by any preparation method described in any one of claims 1 to 5 with integrated catalytic and adsorption effects, so as to facilitate replacement and adjustment in the experiment; the anode chamber (11) and the cathode chamber (9) are separated by a partition (10); The cathode is in contact with air and saline wastewater at the same time and can be irradiated with light. The cathode material Co&Ce-g-C3N4 / AC is connected to an external wire (4) to introduce electrons generated by the anode into the cathode chamber (9). The pretreated saline wastewater continuously enters the bottom of the anode chamber (11) through a water inlet flow regulating device, flows through the biological anaerobic part and enters the cathode chamber (9), and finally the treated effluent flows out from the overflow device at the top of the cathode chamber (9) and is collected.

8. A coupled microbial fuel cell according to claim 7, characterized in that: The active carbon particles in the anode chamber (11) have a layer diameter d of 35 to 65 mm, a thickness δ of 15 to 25 mm, and a filling rate of 85% to 95%. The conductive materials (7) of the anode and cathode are inert conductive materials such as carbon rods. The volume ratio of the anode chamber (11) to the cathode chamber (9) is 6:1 to 1:1, which can be adjusted according to actual wastewater treatment conditions.

9. A coupled microbial fuel cell according to claim 7, characterized in that: The partition (10) is supported by a porous foam board having the same diameter as the reactor, and the porous foam board is wrapped with filter cloth gauze to intercept the detached biofilm, thereby enhancing the metabolism and water purification function of the anode microorganisms; the conductive materials (7) of the cathode and anode are all waterproofed, insulated and anti-electrical except for the part in contact with the biological anode and the part connected with the wire (4).

10. A coupled microbial fuel cell according to claim 7, characterized in that: The cathode container (8) comprises a water-permeable flexible filter screen with a pore size d < 1 mm and a rigid shell.

Images