CN115072838A - Novel method for generating electricity by treating landfill leachate mixed shale gas flowback wastewater through single-chamber microbial fuel cell - Google Patents

Abstract

A new method for treating old landfill leachate mixed shale gas flowback wastewater by using a single-chamber microbial fuel cell belongs to the technical field of organic wastewater treatment. The invention firstly constructs a single-chamber Microbial Fuel Cell (MFC), prepares different materials as an anode catalyst, utilizes anaerobic activated sludge obtained by culturing aerobic activated sludge of a sewage treatment plant as an anode solution, adds nutrient solution and stabilizes for a plurality of weeks, then replaces an anode chamber anaerobic sludge matrix with mixed wastewater of aged landfill leachate and shale gas flowback wastewater, operates the MFC at room temperature and constant pressure, can remove organic pollutants and ammonia nitrogen in the mixed wastewater, and can recover electric energy. The method has the advantages of simple equipment, convenient operation, energy conservation and no secondary pollution. The catalyst at the anode is H-Co ₃ O ₄ Under the condition of/Y, the maximum power density of the MFC system reaches 1179mW/m ² The maximum output voltage is 448mV, the COD removal rate can reach 27.05 percent, and the ammonia nitrogen removal rate can reach 47.88 percent.

Description

A single-chamber microbial fuel cell for waste treatment of landfill leachate mixed with shale gas A New Approach to Hydropower

technical field

The invention relates to a new method for processing old landfill leachate mixed with shale gas flowback wastewater to generate electricity by a single-chamber microbial fuel cell, and belongs to the technical field of organic wastewater treatment.

Background technique

With the rapid development of society and the over-exploitation and utilization of resources, environmental safety issues are particularly prominent in our country and even in the world. Wastewater treatment has become a key part of current environmental safety issues. Among them, the old landfill leachate brought by the landfill treatment usually pollutes the soil, groundwater, surface drinking water sources and the surrounding environment; in the process of hydraulic fracturing and exploitation of shale gas, a large amount of shale gas will be returned. Wastewater is characterized by high salt, complex composition and environmental toxicity. Old landfill leachate and shale gas flowback wastewater are organic wastewater with complex components and difficult to treat. Finding a more efficient treatment of these two wastewaters and realizing resource utilization has become an important issue of environmental safety. At present, the treatment methods for landfill leachate include anaerobic biochemical treatment, membrane treatment, chemical oxidation, etc.; the main methods for treating shale gas flowback wastewater include natural evaporation, filtration, and ozone oxidation. For example, in the 15th issue of "Science and Technology Information" in 2010, "Removal of refractory substances in old landfill leachate by coagulation-precipitation method" (Comparative Document 1), the pollution removal effect of coagulation and sedimentation method on old landfill leachate was studied. The results show that polyaluminum chloride (PAC) has the best effect on the pollution removal of old landfill leachate, but in general, the coagulation and sedimentation method has limited removal effect of pollutants in old leachate, and there are the following problems: (1 ) The technological process is more complicated; (2) The processing cost is relatively high; (3) The utilization rate of resource utilization is not high.

The development trend of the treatment of refractory high-concentration organic wastewater is gradually taking biotechnology as the mainstream. Among them, microbial fuel cells can convert the chemical energy of organic matter into electrical energy through microbial catalytic reaction, and can generate electrical energy while degrading organic matter in wastewater. Compared with traditional methods, the microbial fuel cell system is cost-effective and environmentally friendly, and also realizes the resource utilization of wastewater. For example, "Water Research" Vol. 147 in 2018 "Simultaneous removal of organic matter and iron from hydraulic fracturing flowback water throughsulfur cycling in a microbial fuel cell" (Comparative Document 2), microorganisms using sulfur as the circulating medium and NaCl as the catholyte Fuel cell, multi-batch processing of simulated fracturing flowback fluid, the COD value of waste fluid is reduced from 1348±112m/L to 200-300mg/L, and the power density is 2667±529mW/ ^m3 . But the shortcomings of this method are: (1) the suspended solids in the wastewater need to be pre-treated, and the process is cumbersome; (2) the catholyte has the risk of secondary pollution, and needs to be desalinated after the battery is running; ( 3) Compared with the actual wastewater, the simulated shale gas flowback wastewater has a single composition and a low concentration of organic carbon, so it has little reference value in practical application.

At present, there is no relevant report on using a single-chamber microbial fuel cell to treat old landfill leachate mixed with shale gas flowback wastewater. The present invention adopts a single-chamber air cathode microbial fuel cell to prepare a hydrofluoric acid modified anode catalyst H-Co ₃ O ₄ /Y, taking the mixed wastewater of old landfill leachate and shale gas flowback wastewater as the treatment object, achieving high-efficiency power generation and a certain pollutant removal effect, which has a good application prospect.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a new method for treating old landfill leachate mixed with shale gas backflow wastewater by MFC technology with low cost and environmental protection, so that the wastewater can be effectively degraded, and at the same time, the biomass energy in the wastewater can be converted for bioelectricity.

The method for treating old landfill leachate mixed with shale gas flowback wastewater proposed by the present invention is as follows:

(1) Preparation of anode catalyst H-Co ₃ O ₄ /Y

称取相应质量的NaY分子筛，加入到溶液A中，磁力搅拌2h后，转移到100mL反应釜中，在120℃条件下水热反应12h，反应结束取出冷却至室温，过滤，滤饼用蒸馏水抽滤洗涤后，置于烘箱中干燥，研磨后放入马弗炉中，350℃下焙烧2h，升温速率为5℃/min，冷却到室温后，取出样品再次研磨，即得Co₃O₄/Y；Co₃O₄的制备则不加入NaY分子筛，其余步骤与Co₃O₄/Y制备一致；将制备的Co₃O₄/Y加入到10％HF溶液中，磁力搅拌12h后，离心洗涤，移入烘箱中60℃下干燥、研磨，即制到H-Co₃O₄/Y。Weigh 0.73g cobalt nitrate hexahydrate, 1.5g urea, 0.37g ammonium fluoride, dissolve in 50mL distilled water to obtain solution A; according to the theoretical loading of Co ₃ O ₄ is

Weigh the corresponding NaY molecular sieve, add it to solution A, stir magnetically for 2h, transfer it to a 100mL reaction kettle, conduct hydrothermal reaction at 120°C for 12h, take out and cool to room temperature after the reaction, filter, and filter the filter cake with distilled water After washing, put it in an oven to dry, grind it, put it in a muffle furnace, calcine it at 350°C for 2 hours, with a heating rate of 5°C/min, after cooling to room temperature, take out the sample and grind it again to obtain Co ₃ O ₄ /Y ; The preparation of Co ₃ O ₄ does not add NaY molecular sieve, and the remaining steps are consistent with the preparation of Co ₃ O ₄ /Y; the prepared Co ₃ O ₄ /Y is added to 10% HF solution, and after magnetic stirring for 12h, centrifugal washing, Move it into an oven to dry at 60°C and grind it to prepare H-Co ₃ O ₄ /Y.

(2) Construction of a single-chamber microbial fuel cell

A single-chamber microbial fuel cell (MFC) device was constructed using plexiglass. The device is shown in Figure 1. The device is a three-stage design, and one side of the cathode is a central circular hollow design, so that the air cathode can fully contact the air; It is a cylindrical hollow design to hold liquid; the other side is solid, and the interior of the chamber can be observed; each section is connected by a hollow rubber pad in the middle, which plays the role of airtight and waterproof. The titanium wire of cm is connected to the external circuit, the external resistance is 1000Ω, and the MFC voltage data is collected with a parallel data acquisition instrument.

(3) Start-up of single-chamber microbial fuel cell

The microbial fuel cell was started using the cultured anaerobic sludge as the substrate in the anode compartment. The reactor adopts the intermittent operation mode; after three cycles of operation, the MFC output voltage can remain stable for a long time, and the maximum output voltage of each cycle is close to the MFC start-up.

(4) Running a microbial fuel cell based on aged landfill leachate mixed with shale gas flowback wastewater

Replace the anode chamber anaerobic sludge matrix with a mixed waste liquid of aged landfill leachate and shale gas flowback wastewater, with a mixed volume ratio of 2:1, run the MFC at room temperature and constant pressure, and record its output using a data collector Voltage. The COD and ammonia nitrogen concentrations of the mixed wastewater were measured before and after the operation.

[The beneficial effects of the above-mentioned technical solutions of the present invention are as follows]:

First, the present invention does not require pre-treatment of wastewater, but directly treats old landfill leachate mixed with shale gas flowback wastewater, which is better than that in Reference 2; the present invention can generate electricity while removing pollutants in wastewater , realizing the resource utilization of waste water, which is better than the reference document 1.

Second, the simulated shale gas flowback wastewater used in Comparative Document 2 has low practical value, while the actual wastewater used in the present invention has better application prospects.

Third, the H-Co ₃ O ₄ /Y anode catalyst can significantly enhance the power generation performance of the single-chamber MFC system and maintain a good pollutant removal effect.

Description of drawings:

Figure 1 is a schematic diagram of a single-chamber microbial fuel cell device, in the figure: 1. Anode, 2. Anode chamber, 3. Cathode, 4. Conductor, 5. Resistance box;

Fig. 2 is the curve of the output voltage of the single-chamber MFC with different anode catalysts as a function of time;

Figure 3 shows the power density curves of single-chamber MFCs with different anode catalysts.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

A single-chamber microbial fuel cell treatment method for landfill leachate mixed with shale gas flowback wastewater to generate electricity, the specific steps are as follows:

(1) Preparation of anode catalyst H-Co ₃ O ₄ /Y

Weigh 0.73g of cobalt nitrate hexahydrate, 1.5g of urea, and 0.37g of ammonium fluoride, dissolve them in 50mL of distilled water to obtain solution A; according to the theoretical loading of Co ₃ O ₄ is 30%, weigh NaY molecular sieve of corresponding quality and add it to the solution. In solution A, after magnetic stirring for 2 hours, it was transferred to a 100 mL reaction kettle, and hydrothermally reacted at 120 °C for 12 hours. After the reaction was completed, it was taken out, cooled to room temperature, filtered, and the filter cake was washed with distilled water by suction filtration, dried in an oven, and ground. Then put it into a muffle furnace, calcined at 350 °C for 2 hours, the heating rate is 5 °C/min, and after cooling to room temperature, take out the sample and grind it again to obtain Co ₃ O ₄ /Y; the preparation of Co ₃ O ₄ does not add NaY molecular sieve, the remaining steps are the same as the preparation of Co ₃ O ₄ /Y; the prepared Co ₃ O ₄ /Y was added to 10% HF solution, magnetically stirred for 12 h, washed by centrifugation, moved to an oven at 60°C for drying and grinding, That is, it is prepared to H-Co ₃ O ₄ /Y.

(2) Electrode pretreatment method

Cut the carbon cloth, the size of the anode carbon cloth is 1 × 2cm, and the size of the cathode carbon cloth is 5 × 5cm; immerse the cut carbon cloth in absolute ethanol, ultrasonically clean it for 15 minutes, and then soak it for 30 minutes. Rinse carefully with deionized water; 3) Mix 10% nitric acid solution and 10% sulfuric acid solution according to the volume ratio of 3:1, then immerse the carbon cloth in it, ultrasonically clean it for 15 minutes, and then Soak for 5 hours, rinse carefully with deionized water after soaking; then immerse the carbon cloth in deionized water, ultrasonically clean for 15 minutes, then soak for 30 minutes, and finally carefully clean the carbon cloth with deionized water; Put it into an oven at 60°C for drying, then place it in a muffle furnace, and calcinate at 300°C for 4 hours at a heating rate of 5°C/min.

(3) Fabrication of air cathode

Measure 1 mL of deionized water and 1 mL of 60% polytetrafluoroethylene emulsion (PTFE), add them to a 10 mL small beaker, weigh 30 mg of carbon black, add it to the small beaker in small amounts and several times, and stir evenly to obtain suspension A; Gently brush Suspension A onto a 5×5cm carbon cloth, leave it to air dry for 2 hours, and then place it in a muffle furnace for calcination at 370°C for 25 minutes. , evenly coat a layer of 60% PTFE, dry until the PTFE turns white, calcinate at 370 ° C for 12 minutes, continue to coat a layer of PTFE after the carbon cloth is cooled, calcine, and brush a total of 4 layers; Pipette 400 μL of Nafion solution, 200 μL of isopropanol, and 200 μL of deionized water with a gun, add them to a 10-mL small beaker, and weigh 40 mg of 20% platinum-carbon powder. After ultrasonication for 10 minutes, brush them onto the other side of the carbon cloth, and place them to air dry for 24 hours.

(4) Production of anode

Weigh 2 mg of the prepared H-Co ₃ O ₄ /Y catalyst into a 10 mL small beaker, and then pipette 200 μL absolute ethanol, 100 μL ethylene glycol, and 10 μL Nafion solution into the small beaker, and place it in the small beaker. Ultrasonic in the ultrasonic cleaner for 30min to make it evenly mixed, remove the above suspension with a pipette, and evenly drop it on a 1×2cm carbon cloth, and finally dry it for later use.

(5) Construction of single-chamber microbial fuel cell

The peripheral length, width, and height of the single-chamber MFC are 8.5, 8.5, and 8 cm, respectively. The cavity is cylindrical with a bottom diameter of 4 cm and a height of 4 cm. The effective volume is 50 mL. The material of the entire device is plexiglass. One side is a central circular hollow design, so that the air cathode can fully contact the air; the chamber section is a cylindrical hollow design to hold the liquid; the other side is solid, and the interior of the chamber can be observed; It is connected with a hollowed-out rubber pad in the middle, which plays the role of airtightness and waterproofing; there are small holes on the top, which are used to place the cathode and anode wires and add liquid, etc.; place the anode carbon cloth loaded with the prepared catalyst in turn, and the platinum carbon catalyst loaded. Air cathode, cathode and anode are connected to the external circuit with 0.5cm titanium wire, the external resistance is 1000Ω, and the data acquisition instrument is connected in parallel to collect voltage data.

(6) Start-up of single-chamber microbial fuel cell

The phosphate buffer solution and the cultured activated anaerobic sludge were mixed at a volume ratio of 1:1 as the anolyte, and then 1.6g/L of sodium acetate, 0.05g/L of ammonium chloride, and 12.5mL/L of ammonium chloride were added. Trace metal solution and 5mL/L vitamin solution are used to maintain the growth of microorganisms in the anolyte, wherein the trace metal solution is composed of 6.15g/L magnesium sulfate, 0.5g/L manganese sulfate, 1g/L chlorinated It is composed of sodium and 0.1g/L ferrous sulfate, and the vitamin liquid is composed of 2mg/L bioacid, 2mg/L folic acid, 10mg/L vitamin B6 and 5mg/L riboflavin; The data acquisition instrument records the voltage data of the MFC; when the voltage data drops rapidly, it indicates that the nutrients in the MFC are exhausted and need to be re-added. After several voltage cycles, if the output voltage can be at a higher voltage If it is stable for a long time and the maximum stable voltage in each cycle is close, it indicates that the MFC is successfully started and the biofilm on the electrode material is mature.

(7) Running a microbial fuel cell based on aged landfill leachate mixed with shale gas flowback wastewater

Replace the anode chamber anaerobic sludge matrix with a mixed waste liquid of aged landfill leachate and shale gas flowback wastewater, with a mixed volume ratio of 2:1, run the MFC at room temperature and constant pressure, and record its output using a data collector voltage, and the COD and ammonia nitrogen concentrations of the mixed wastewater were measured before and after the operation.

Example 2

A single-chamber microbial fuel cell treatment method for landfill leachate mixed with shale gas flowback wastewater to generate electricity, the specific steps are as follows:

(1) Preparation of anode catalyst

Same as step (1) in Example 1.

(2) Electrode pretreatment

With step (2) in embodiment 1.

(3) Production of cathode

Same as step (3) in Example 1.

(4) Production of anode

Weigh 2 mg of the prepared Co ₃ O ₄ /Y catalyst into a 10 mL small beaker, pipette 200 μL of absolute ethanol, 100 μL of ethylene glycol, and 10 μL of Nafion solution into the small beaker, and place it in an ultrasonic cleaner. Sonicate for 30 min to make it evenly mixed, then use a pipette to remove the above suspension, and evenly drop it on a 1×2 cm carbon cloth, and finally dry it for later use.

(5) Construction of single-chamber microbial fuel cell

With step (5) in embodiment 1.

(6) Start-up of single-chamber microbial fuel cell

With step (6) in embodiment 1.

(7) Running a microbial fuel cell based on aged landfill leachate mixed with shale gas flowback wastewater

Same as step (7) in Example 1.

Example 3

A single-chamber microbial fuel cell treatment method for landfill leachate mixed with shale gas flowback wastewater to generate electricity, the specific steps are as follows:

(1) Preparation of anode catalyst

Same as step (1) in Example 1.

(2) Electrode pretreatment

With step (2) in embodiment 1.

(3) Production of cathode

Same as step (3) in Example 1.

(4) Production of anode

Weigh 2 mg of the prepared Co ₃ O ₄ catalyst into a 10 mL small beaker, then pipette 200 μL of absolute ethanol, 100 μL of ethylene glycol, and 10 μL of Nafion solution into the small beaker, and place it in an ultrasonic cleaner. Sonicate for 30 min to make it evenly mixed, use a pipette to remove the above suspension, and evenly drop it on a 1×2 cm carbon cloth, and finally dry it for later use.

(5) Construction of single-chamber microbial fuel cell

With step (5) in embodiment 1.

(6) Start-up of single-chamber microbial fuel cell

With step (6) in embodiment 1.

(7) Running a microbial fuel cell based on aged landfill leachate mixed with shale gas flowback wastewater

Same as step (7) in Example 1.

Example 4

A single-chamber microbial fuel cell treatment method for landfill leachate mixed with shale gas flowback wastewater to generate electricity, the specific steps are as follows:

(1) Preparation of anode catalyst

Same as step (1) in Example 1.

(2) Electrode pretreatment

With step (2) in embodiment 1.

(3) Production of cathode

Same as step (3) in Example 1.

(4) Production of anode

In this example, the anode adopts pretreated carbon cloth, and no catalyst is dripped.

(5) Construction of single-chamber microbial fuel cell

With step (5) in embodiment 1.

(6) Start-up of single-chamber microbial fuel cell

With step (6) in embodiment 1.

(7) Running a microbial fuel cell based on aged landfill leachate mixed with shale gas flowback wastewater

Same as step (7) in Example 1.

Experimental results

Example 1 is a suitable method for single-chamber microbial fuel cells to process old landfill leachate mixed with shale gas flowback wastewater to generate electricity.

The MFC system was started and operated under different anode catalyst conditions, and its output voltage versus time curve is shown in Figure 2. Under the condition that the anode catalyst is H-Co ₃ O ₄ /Y, the maximum stable output voltage of the battery is 448mV; the maximum The power density is up to 1179mW/m ² (Figure 3). It shows that the anode catalyst has a great influence on the power generation performance of MFC. The H-Co ₃ O ₄ /Y anode catalyst can accelerate the transfer rate of anode ions, reduce the anode ohmic loss, reduce the activation loss and mass transfer loss, thereby enhancing the microbial fuel The power generation performance of the battery system.

The test shows that when the anode catalysts are blank, Co ₃ O ₄ , Co ₃ O ₄ /Y and H-Co ₃ O ₄ /Y, the COD removal rates of the mixed waste liquid in the MFC system are 22.64%, 27.93% and 24.58%, respectively. % and 27.05%; ammonia nitrogen removal rates were 43.62%, 49.43%, 48.46% and 47.88%, respectively. It shows that the constructed single-chamber microbial fuel cell has a certain removal effect on pollutants in old landfill leachate mixed with shale gas flowback wastewater, and the H-Co ₃ O ₄ /Y anode catalyst can greatly improve the power generation performance of MFC .

Claims (2)

1. a method for single-chamber microbial fuel cell processing landfill leachate mixed shale gas flowback wastewater to generate electricity, is characterized in that comprising the following steps: (1) Preparation of anode catalyst H-Co ₃ O ₄ /Y Weigh 0.73g of cobalt nitrate hexahydrate, 1.5g of urea, and 0.37g of ammonium fluoride, dissolve them in 50mL of distilled water to obtain solution A; according to the theoretical loading of Co ₃ O ₄ is 30%, weigh NaY molecular sieve of corresponding quality and add it to the solution. In solution A, after magnetic stirring for 2 hours, it was transferred to a 100 mL reaction kettle, and hydrothermally reacted at 120 °C for 12 hours. After the reaction was completed, it was taken out, cooled to room temperature, filtered, and the filter cake was washed with distilled water by suction filtration, dried in an oven, and ground. Then put it into a muffle furnace, calcined at 350 °C for 2 hours, the heating rate is 5 °C/min, and after cooling to room temperature, take out the sample and grind it again to obtain Co ₃ O ₄ /Y; the preparation of Co ₃ O ₄ does not add NaY molecular sieve, the remaining steps are the same as the preparation of Co ₃ O ₄ /Y; the prepared Co ₃ O ₄ /Y was added to 10% HF solution, magnetically stirred for 12 h, washed by centrifugation, moved to an oven at 60°C for drying and grinding, That is, it is prepared to H-Co ₃ O ₄ /Y; (2) Construction and start-up of single-chamber microbial fuel cell H-Co ₃ O ₄ /Y, Co ₃ O ₄ /Y, Co ₃ O ₄ catalysts were drop-coated on 1×2 cm carbon cloth and carbon cloth as anode, and organic glass was used to construct a single-chamber microbial fuel cell device. The schematic diagram of the device is shown in the figure below. As shown in Figure 1, the device is a three-stage design. One side of the cathode is a central circular hollow design, so that the air cathode can fully contact the air; the chamber section is a cylindrical hollow design to hold the liquid; the other side is solid , you can observe the inside of the chamber; each section is connected with a hollow rubber pad in the middle, which plays the role of airtight and waterproof. The cathode and anode are connected to the external circuit with 0.5cm titanium wire. The data acquisition instrument collects MFC voltage data; Using the cultured anaerobic sludge as the substrate of the anode chamber, the microbial fuel cell is started, and the reactor adopts the intermittent operation mode; after three cycles of operation, the MFC output voltage can remain stable for a long time, and the maximum value of each cycle When the output voltage is close, the MFC starts to complete; (4) Running a microbial fuel cell based on aged landfill leachate mixed with shale gas flowback wastewater The anode chamber anaerobic sludge substrate was replaced with a mixed waste liquid of aged landfill leachate and shale gas flowback wastewater with a mixed volume ratio of 2:1. The MFC was run at room temperature and constant pressure, and the data acquisition instrument was used to record its Output voltage; COD and ammonia nitrogen concentrations of mixed wastewater were measured before and after operation. 2. The single-chamber microbial fuel cell method according to claim 1 for treating old landfill leachate mixed with shale gas to discharge wastewater, is characterized in that in step 1, firstly adopt hydrothermal-roasting method to prepare Co ₃ O ₄ / Y, and then treated with 10% HF solution to obtain H-Co ₃ O ₄ /Y, which was used as the anode catalyst of single-chamber MFC.

Images