CN105140551B - A Coupling System of PANI/BiVO4 Composite Photocatalyst and Microbial Fuel Cell - Google Patents

Abstract

The invention provides a PANI/BiVO ₄ composite photocatalyst and microbial fuel cell coupling system, which belongs to the technical field of sewage treatment and energy recovery and utilization. The microbial fuel cell degrades organic matter while generating electric energy, and is combined with the PANI/BiVO ₄ composite photocatalytic cathode Constitute PANI/BiVO ₄ photocatalytic and microbial fuel cell coupling system, the degradation rate of Rhodamine B within 2 hours can reach 84%, and the degradation efficiency of Rhodamine B can reach 94% in 30 minutes under acidic condition pH=3 coupling system; The degradation rate of rhodamine B under no light conditions was 62%. The coupling system of PANI/BiVO ₄ composite photocatalyst and microbial fuel cell was suitable for treating organic wastewater and inorganic ammonia nitrogen wastewater, and the removal rate of ammonia nitrogen was 74%. The catalytic performance of PANI/BiVO ₄ composite catalyst is stable.

Description

A Coupling System of PANI/BiVO4 Composite Photocatalyst and Microbial Fuel Cell

technical field

The invention belongs to the technical field of sewage treatment and energy recovery and utilization. In a microbial fuel cell system, organic matter in sewage is used as fuel to generate electric energy while degrading organic matter; combined with photocatalyst, light energy is used to further increase pollutant removal efficiency. Increase energy output.

Background technique

Microbial Fuel Cell (MFC) is the product of the combination of microbial technology and battery technology. It uses the metabolites of microorganisms as the active substance of the electrode, which causes the potential shift of the electrode, increases the potential difference, and thus obtains electrical energy. chemical energy directly into electrical energy. It has the advantages of high efficiency, environmental protection and cleanliness. However, because the research of MFC is still in its infancy, the cost of electrode materials and catalysts is high, and the battery capacity is generally low, which is not enough for external output. Due to the limited biomass retention, the effluent quality is poor, and further sewage treatment is required.

Photocatalytic reaction is one of the methods of material conversion by using light energy. When the photocatalyst is excited by light greater than its band gap energy, it can generate highly active photogenerated hole/electron pairs to degrade pollutants in organic wastewater. However, the current research has proved that it has the problems of low photon quantum efficiency and photoactivity, and how to improve the photocatalytic efficiency has become an urgent problem to be solved. At present, _TiO2 is mostly used to prepare catalysts, which require ultraviolet irradiation or are prone to photocorrosion. As a new type of visible light catalyst, BiVO ₄ has excellent characteristics such as non-toxicity, small Eg, stability, good weather resistance and good environment. Therefore, coupling the two, constructing a photocatalyst/microbial fuel cell coupling system, and introducing solar energy into the microbial fuel cell system can realize the combination of solar energy and microbial fuel cell two clean energy sources. At the same time, it can effectively improve the power generation rate of microbial fuel cells and the removal rate of pollutants. It is a new type of microbial fuel cells with great research value.

Anhuai Lu et al. coupled microbial fuel cells with TiO ₂ photocatalysts, the maximum power density reached 12.03W/m ³ , and the open circuit voltage was 519mV. _TiO2 as a cathode improves the electron transfer efficiency of the cathode and improves the quantum conversion efficiency. However, the degradation rate of pollutants was not reported. (Energy Fuels 2010, 24, 1184–1190: DOI: 10.1021/ef901053j)

The PANI/BiVO ₄ composite photocatalyst and microbial fuel cell coupling system can excite the electron-hole pairs of the photocatalyst, realize the separation of electrons and holes, and thus achieve the degradation effect on wastewater. The degradation effect of the coupling system on rhodamine B is 50% higher than the photocatalytic effect, and the highest degradation efficiency is 94% (within 30min). At the same time, the coupling system of PANI/BiVO ₄ composite photocatalyst and microbial fuel cell also has a degradation rate of 74% for inorganic ammonia nitrogen wastewater.

Contents of the invention

The purpose of the present invention is to provide a PANI/BiVO ₄ composite photocatalyst and microbial fuel cell coupling system, which solves the problems of high catalyst cost, instability and low pollutant removal rate.

The technical scheme of the present invention is: a kind of PANI/BiVO Composite photocatalyst and microbial fuel cell coupling system, the steps are as follows:

1) Preparation of BiVO ₄ catalyst: According to the molar ratio of BiNO ₃ and HNO ₃ of 1:32, dissolve BiNO ₃ 5H ₂ O in 4mol L ^-1 HNO ₃ solution to obtain a mixed solution A, according to the molar ratio of NH ₄ VO ₃ and NaOH Dissolve NH ₄ VO ₃ in 4mol _L ^-1 NaOH solution at a ratio of 1:32 to obtain mixed solution B; The molar ratio is 1, stir for 0.5h, mix the above two mixed solutions according to the molar ratio of BiNO ₃ 5H ₂ O and NH ₄ VO ₃ 1:1, adjust the pH value to 5, and stir for 0.5h to obtain a mixed solution C; Solution C is placed in a reaction kettle, hydrothermally synthesized at 120°C-200°C, cooled to room temperature, the product is washed with deionized water and absolute ethanol to remove the residual liquid, and dried to obtain BiVO ₄ catalyst powder. Grind evenly and set aside;

2) Preparation of PANI/BiVO ₄ composite photocatalyst: Add different proportions of PANI to the mixed solution C obtained in step 1), continue to stir for 0.5 hours to prepare a precursor solution, and synthesize PANI/BiVO ₄ composite photocatalyst in situ by hydrothermal; electrode assembly Preparation: Dissolve the PANI/BiVO ₄ composite photocatalyst in acidic silica sol according to the dispersion amount of 25% based on SiO ₂ , stir and ultrasonically disperse it fully, and evenly coat it on the stainless steel mesh electrode to prepare the electrode assembly;

3) Photocatalytic reactor: immerse the reaction electrode in the simulated wastewater Rhodamine B, place the halogen lamp directly above the liquid surface of Rhodamine B, inject the aeration head at the bottom for aeration; photocatalytic reactor operation: regular sampling , measure its absorbance with an ultraviolet-visible spectrophotometer, and analyze the change of rhodamine B concentration;

4) MFC coupled reactor: a double-chamber reactor is used, carbon particles are placed in the anode chamber, and the anode is an anaerobic environment; rhodamine B or ammonia nitrogen simulated wastewater is placed in the cathode chamber, and aeration is provided at the bottom of the cathode chamber; the anode chamber and The cathode chamber is separated by a proton exchange membrane, and the light source can be placed outside the cathode chamber; the carbon particles placed in the anode chamber are used to inoculate the electrogenic Shewanella bacteria; MFC reactor operation: the cathode adopts stainless steel mesh to load PANI/BiVO ₄ composite photocatalyst, the anode Use carbon rod electrodes, connect resistors, connect circuits with copper wires, and regularly sample and analyze changes in rhodamine B concentration.

The effect and benefit of the present invention is that the combination of MFC and novel PANI/BiVO ₄ composite photocatalyst can realize the combination of solar energy and microbial fuel cell, two clean energy sources, while effectively improving the microbial fuel cell's electricity production rate and the removal rate of pollutants, Improve catalyst efficiency and stability.

Description of drawings

Fig. 1 Effect diagram of degradation of rhodamine B by PANI/BiVO ₄ composite photocatalyst and microbial fuel cell coupling system.

In the figure: the abscissa represents time, the unit is min, the ordinate represents C _t /C ₀ , squares, dots, and triangles respectively represent the effect of BiVO ₄ on photocatalytic degradation of pollutants, the effect of BiVO ₄ on the degradation of pollutants in a coupled system, PANI/BiVO ₄ (5%) Composite catalyst degrades pollutants in the coupling system; it shows that the photocatalyst coupling MFC system has a significant degradation effect on rhodamine B. The BiVO ₄ coupled MFC system improved the photocatalytic degradation effect by 48% compared with BiVO ₄ . And doping BiVO ₄ with PANI can inhibit the recombination of photogenerated electrons and holes, significantly improve the photocatalytic activity of BiVO ₄ , and the degradation effect of rhodamine B on the coupling system for 2 hours can reach 84%.

Figure 2 Comparison of photocatalytic reaction and MFC coupling system (no light) degradation effect.

In the figure: the abscissa represents time, the unit is min, the ordinate represents C _t /C ₀ , squares and dots represent the photocatalytic effect of BiVO ₄ and the degradation effect of BiVO ₄ and MFC coupling system (without light).

Fig. 3 Effect diagram of PANI/BiVO ₄ and MFC coupled system for degrading NH ₄ ⁺ wastewater.

In the figure: the abscissa represents time, the unit is min, the ordinate represents C _t /C ₀ , squares, dots, and triangles respectively represent the initial concentration of NH ₄ ⁺ 30mg/L, 50mg/L, and 100mg/L. From the figure, we can get The out-coupling system also has a strong degradation ability for inorganic wastewater, and its degradation rate for 30mg/L NH ₄ ⁺ wastewater is 73%, and NO ₃ ^- and NO ₂ ^- were not detected in the experiment, which shows that the coupling system has a strong ability to degrade NH ₄ + ⁺ The degradation of waste water is relatively complete without intermediate products.

detailed description

The specific embodiments of the present invention will be described in detail below in conjunction with the technical solutions and accompanying drawings.

Example 1

Preparation of BiVO ₄ catalyst: Dissolve 1.225g BiNO ₃ 5H ₂ O and 0.25g NH ₄ VO ₃ (molar ratio 1:1) in 4mol L ^-1 HNO ₃ and NaOH solutions, and then add 0.1g The surfactant CTAB was stirred for 0.5 h each, then the above two solutions were mixed, the pH value was adjusted to 5, and then stirred for 0.5 h to prepare the precursor solution. Pour the precursor solution into the reaction kettle, hydrothermally synthesize at 120°C for two hours, cool down to room temperature, wash the product three times with deionized water and absolute ethanol, and then dry at 100°C. The obtained powder is carefully ground with a mortar and evenly prepared for later use;

Preparation of PANI/BiVO ₄ composite photocatalyst: 1.225g BiNO ₃ 5H ₂ O and 0.25g NH ₄ VO ₃ (molar ratio 1:1) were dissolved in 4mol L ^-1 HNO ₃ and NaOH solutions respectively, and then respectively added to Add surfactant CTAB to it, stir each for 0.5h, then mix the above two solutions, adjust the pH value to 5, add 0.008g, 0.04g, 0.08PANI, (PANI content 1%, 5%, 10 %), and then stirred for 0.5h to prepare the precursor solution. Pour the precursor solution into the reaction kettle, hydrothermally synthesize at 120°C for two hours, cool down to room temperature, wash the product three times with deionized water and absolute ethanol, and then dry at 100°C. The obtained powder is carefully ground with a mortar and evenly prepared for later use;

Thin film catalyst loading: acidic silica sol is used as the dispersant of the catalyst, and the catalyst is coated on the square stainless steel mesh. The specific operation is as follows: First, cut the 500-mesh square eye plain stainless steel wire mesh into 2cm*3cm, soak it in ethanol, and dry it for later use. Secondly, to prepare acidic silica sol, take a certain amount of absolute ethanol into a beaker, add TEOS, slowly add a mixture of concentrated hydrochloric acid and deionized water to it, and stir for 30 minutes, in which TEOS, absolute ethanol, deionized water and hydrochloric acid The molar ratio is 1:7.6:25:0.28. Disperse the catalyst in the silica sol, ultrasonically, and evenly coat it on the stainless steel mesh.

Photocatalytic reaction: prepare 10mg/L rhodamine B solution, take 100ml of the solution and place it in a 150ml beaker, place the catalyst electrode above in the rhodamine B solution with alligator clips. Place a 50-watt halogen lamp directly above the liquid surface, 10cm away from the liquid surface. Put an aeration device in the reactor, the aeration rate is 1.5m ³ /h. Samples were taken every 15 minutes after the start of the reaction, and the change in absorbance was measured at 553 nm with an ultraviolet-visible spectrophotometer to analyze the change in the concentration of rhodamine B. The reaction time was 2 hours. In the same way, the effect of photocatalytic degradation of rhodamine B on different PANI-loaded catalysts was tested.

Example 2

MFC coupling device: The reaction adopts a double-chamber microbial fuel cell reactor, and the anode chamber is an anaerobic area, in which Shewanella is inoculated. Rhodamine B solution is placed in the cathode chamber, and an aeration device is provided at the bottom. The anode chamber and the cathode chamber are separated by a proton exchange membrane to exchange protons.

MFC degradation reaction: place 60g of carbon particles loaded with microorganisms in the anode chamber, and add 150ml of nutrient solution. Add 200ml of 10mg/L rhodamine B solution in the cathode compartment. The carbon rod is the anode, the stainless steel net carrying the catalyst is the cathode, and the 500Ω resistor is connected with a wire to communicate with the circuit. Place a 50W halogen lamp outside the cathode chamber, facing the photocatalyst. At the beginning of the reaction, samples were taken every 15 minutes to measure the absorbance, and the reaction was carried out for 2 hours.

From the comparison of the photocatalytic effect of BiVO ₄ and the degradation effect of the MFC coupling system in Figure 2, we can conclude that the MFC coupling system can stimulate the electronic transition of the catalyst and promote the separation of electrons and holes under no light conditions. And the excitation effect of the coupled MFC system on the catalyst is 37% higher than that of visible light excitation. It shows that the coupling system of photocatalyst and MFC has strong degradation ability, and it is a very promising technology for degrading pollutants.

Claims (2)

1. a kind of PANI/BiVO₄Composite photo-catalyst and microbiological fuel cell coupled system, it is characterised in that step is as follows：

1)BiVO₄It is prepared by catalyst precursor：According to BiNO₃With HNO₃Mol ratio is 1：32 by BiNO₃·5H₂O is dissolved in 4mol L^-1 HNO₃Mixed solution A is obtained in solution, according to NH₄VO₃It is 1 with NaOH mol ratios：32 by NH₄VO₃It is dissolved in 4mol L^-1's Mixed solution B is obtained in NaOH solution；Then 0.1mol/L surfactant is added into above two mixed solution respectively CTAB, CTAB and BiNO₃Mol ratio be 1, stir 0.5h, according to BiNO₃·5H₂O and NH₄VO₃Mol ratio 1:1 by above two Mixed solution is mixed, regulation pH value to 5, is stirred 0.5h, is obtained mixed solution C；

2)PANI/BiVO₄It is prepared by composite photo-catalyst：To step 1) mixed solution C in add different proportion PANI, continue Stirring prepares precursor liquid in 0.5 hour, the mixed solution C for adding PANI is placed in reactor, hydro-thermal under the conditions of 120 DEG C -200 DEG C Synthesis, is down to room temperature, product is washed into residul liquid-removing with deionized water and absolute ethyl alcohol, dries, obtained PANI/BiVO₄It is multiple Closing light catalyst powder is carefully ground uniformly with mortar；It is prepared by electrode assemblie：With SiO₂Meter, will according to 25% dispersion amount PANI/BiVO₄Composite photo-catalyst is dissolved in acidic silicasol, stirring, and ultrasound makes its fully dispersed, is coated uniformly on stainless On steel mesh electrode, electrode assemblie is made；

3) photo catalysis reactor：Electrode assemblie is immersed in simulated wastewater rhodamine B, Halogen lamp LED is placed in rhodamine B liquid level Surface, bottom injection aeration head, is aerated；Photo catalysis reactor is run：Timing sampling, uses spectrophotometry Its absorbance is measured, rhodamine B change in concentration is analyzed；

The PANI/BiVO₄Composite photo-catalyst and microbiological fuel cell coupled system：Using two-compartment reactor, carbon particle is put In in anode chamber, anode is anaerobic environment；Rhodamine B or ammonia nitrogen simulated wastewater are placed in cathode chamber, and cathode chamber bottom is provided with aeration； Anode chamber is separated with cathode chamber by PEM, and light source is placed in outside negative electrode room；It is placed in carbon particle inoculation electricity production in anode chamber uncommon Tile style bacterium；MFC reactors are run：Negative electrode loads PANI/BiVO using stainless (steel) wire₄Composite photocatalyst, anode uses carbon Bar electrode, connects resistance, uses copper cash connection circuit, timing sampling analysis rhodamine B change in concentration.

2. PANI/BiVO according to claim 1₄Composite photo-catalyst and microbiological fuel cell coupled system, its feature It is, negative electrode is not provided with light source outside room.