微生物燃料电池阴极的功能拓展及机理分析

发布时间：2018-05-09 16:31

本文选题：微生物燃料电池 + 废旧锂电池　；参考：《合肥工业大学》2015年博士论文

【摘要】：微生物燃料电池(Microbial Fuel Cell, MFC)是燃料电池中特殊的一类,它利用微生物作为反应主体,将燃料的化学能转换为电能。MFC的优势在于其处理环境废弃物的同时并对其中蕴涵的能源予以回收,从而起到净化环境和生产清洁能源的双重效果。单从产电的角度来看,短时期内MFC无法超越传统的燃料电池的电能输出性能。因此研究者的目光不在仅仅局限于提高电池的产电性能,而如何进一步拓宽MFC处理废弃物的领域,尤其是如何有效利用阴极以提高MFC的整体功能性,从而使MFC的应用范围得到了进一步地拓展。因此,本文以MFC技术为核心,结合电化学、微生物学和水文地质学的多种研究方法,以目前常用的两种典型MFC反应系统作为研究对象,构建了单室和双室2种类型的矩形反应槽,将MFC的阴极还原能力分别应用于废旧锂电池正极材料LiCoO2的还原浸取和对受硝酸盐污染地下水的原位修复,以提高目标污染物的还原效果和MFC的产电性能为目标,对影响MFC的阴极性能因素展开了研究,得出了以下结论：(1)构建了以弱酸中LiCoO2作为化学阴极电子受体的矩形式双室MFC,探讨了MFC阴极浸取还原LiCoO2的可行性,并探讨了MFC阴极浸取还原LiCoO2过程中阴极液pH、阴极液的离子强度、固液比、催化剂CuCl2等因素对MFC的产电性能与LiCoO2浸取效果的影响。实验结果表明：MFC化学阴极还原LiCoO2使得固相中Co(Ⅲ)被浸取还原为液相中Co(Ⅱ)是可行的,且MFC的浸取效果优于单纯弱酸浸取,同时监测到MFC能够持续地输出电压。阴极液pH值对MFC浸取LiCoO2的过程影响显著,pH越低,MFC的产电性能和LiCoO2的浸取效果越明显；随着阴极液中KCl和催化剂CuCl2添加浓度的增加,MFC输出电压和浸取效率也越高,这是由于阴极液的离子强度增大,活化能减少的缘故；固液比S/L的增加,电池输出电压和LiCoO2浸取效率也增大,但是增加的幅度与固液比的增加幅度不成正比；最后对影响MFC阴极输出电压和Co(Ⅱ)浸取效果的因素分析讨论得出阴极液pH值是LiCoO2还原过程中重要影响因素。因此在后续的实验设计中要重点考虑pH对MFC电位和浸取效果的影响。(2)构建了矩形式单槽生物阴极MFC,模拟受硝酸盐污染地下水的流动条件,对MFC进行补水、排水及淋浴实验,得到实验所需的水力学特征系数,即砂槽含水层的孔隙度0.222,持水度0.148以及渗透系数5.13m/d,说明建立的矩形式单槽MFC内水流符合地下水流动的特点。(3)启动了矩形式单槽生物阴极MFC,经过4周期的循环,电池的输出最大电压稳定在500mV左右,整个启动时间大约需要300h。对MFC启动成功后运行一段时间的阴极、阳极与空白电极做扫描电镜分析,阴极和阳极附着的微生物形态不一样,阴极碳布的纤维丝表面覆盖了一层多孔状结构,细菌多附着在孔状结构上,阳极碳布的表面生长了大量的长链状微生物。然而对混菌系统的SEM观察,仅可作为一种辅助手段验证宏观的实验结果。(4)在矩形式单槽生物阴极MFC稳定运行下,研究了影响MFC促进硝酸盐还原的关键影响参数C/N、无机碳源NaHCO3以及水力停留时间HRT对MFC的产电性能和硝酸盐降解效果的影响。实验结果表明：C/N和无机碳源NaHCO3的增加使得MFC的输出电压增加,降解率也增加,亚硝酸盐和氨氮积累效果,有助于MFC电压的输出；两种水力停留时间HRT2.0d和1.0d下,MFC的输出电压和硝酸盐的降解不同,HRT小反而有利于电压输出和硝酸盐的降解。(5)研究了MFC反应槽的水力梯度对MFC产电效果和硝酸盐降解效果的影响。实验结果表明,水力梯度增大,MFC的最大输出电压增大,反应槽的出口水样中NO3--N浓度减小,NO3--N浓度也呈现出上层浓度大,下层浓度小,且按照水流的水平方向,前端浓度大,后端浓度小的时空分布。这说明水力梯度的改变影响了MFC产电性能和硝酸盐的降解效果。这种模拟结果更能表达水力梯度变化时,地下水中硝酸盐的迁移、转化规律。(6)采用循环伏安曲线法扫描分析了阴极、阳极生物膜的电化学行为。结果表明,挂膜的阳极主要发生的是氧化反应,微生物在电极表面发生的催化氧化；挂膜的阴极发生的是还原反应,阴极微生物在电极表面发生的催化还原。反应溶液中空白电极CV曲线上有一对明显的氧化还原电对,推测反应溶液中存在由微生物新陈代谢分泌到细胞外的氧化还原介体,MFC体系中存在电子穿梭传递机制,电子传递的主要任务由电极上的产电微生物完成的。
[Abstract]:Microbial Fuel Cell (MFC) is a special kind of fuel cell. It uses microbes as the main body of reaction. The advantage of converting the chemical energy of fuel into electrical energy.MFC is to deal with environmental waste and recycle the energy contained in it, so as to purify the environment and produce clean energy. In a short period of time, MFC can not exceed the power output performance of traditional fuel cells in the short period of time. Therefore, the researchers' eyes are not only limited to improving the power production performance of the battery, but how to further broaden the field of MFC processing waste, especially how to effectively use the cathode to improve the overall function of the MFC, Thus, the application range of MFC has been further expanded. Therefore, this paper, taking MFC technology as the core, combined with a variety of research methods of electrochemistry, microbiology and hydrogeology, uses two typical typical MFC reaction systems as the research object, and constructs 2 types of rectangular reaction slots in single and double chambers, and the cathodic reduction energy of MFC The force was applied to the reduction leaching of the cathode material LiCoO2 of the waste lithium battery and the in-situ remediation of the contaminated groundwater contaminated by nitrate. In order to improve the reduction effect of the target pollutants and the electricity production performance of the MFC, the factors affecting the performance of the cathode of the MFC were studied. The following conclusions were obtained: (1) the LiCoO2 was constructed in the weak acid. A rectangular double chamber MFC of cathodic electron acceptor is studied. The feasibility of MFC cathodic reduction of LiCoO2 is discussed. The effects of MFC cathode leaching of pH, ionic strength, solid to liquid ratio, and catalyst CuCl2 on MFC in the process of LiCoO2 reduction are discussed. The experimental results show that MFC chemical cathode is used as a chemical cathode. The reduction of LiCoO2 makes the Co (III) in the solid phase reduced to Co (II) in the liquid phase, and the leaching effect of the MFC is better than that of the simple weak acid leaching. At the same time, the MFC can continuously output the voltage. The pH value of the cathode liquid has significant influence on the process of MFC leaching of LiCoO2, the lower the pH, the more obvious the performance of MFC and the LiCoO2 leaching effect; with Yin. The increase in the concentration of KCl and CuCl2 in the solution, the higher the output voltage and the leaching efficiency of MFC, is due to the increase of the ionic strength and the decrease of the activation energy, and the increase of the output voltage and the efficiency of LiCoO2 in the solid to liquid ratio, but the increase is not proportional to the increase in the ratio of solid to liquid. After the analysis of factors affecting the output voltage of MFC cathode and the effect of Co (II) leaching, it is concluded that the pH value of the cathode is an important factor in the process of LiCoO2 reduction. Therefore, the influence of pH on the MFC potential and the leaching effect should be considered in the subsequent experimental design. (2) a moment form single slot Biological Cathode MFC is constructed, and the simulation of the contaminated underground is under the nitrate pollution. The water flow conditions, the MFC water, drainage and shower experiment, get the hydraulic characteristic coefficient of the experiment, that is, the porosity of the aquifer of sand trough 0.222, the water holding degree 0.148 and the permeability coefficient 5.13m/d. It shows that the water flow in the rectangular single slot MFC conforms to the characteristics of the groundwater flow. (3) the moment form single slot Biological Cathode MFC has been started. After 4 cycles of cycle, the maximum output voltage of the battery is stable at about 500mV. The whole startup time requires about 300h. to run the cathode for a period of time after the successful start of the MFC. The anode and the blank electrode are scanned by scanning electron microscope. The microbes attached to the cathode and the anode are different, and the surface of the cathode carbon fabric is covered with a multi hole shape. A large number of long chain microbes have been grown on the surface of the anode carbon cloth. However, the SEM observation of the mixed bacteria system can only be used as a supplementary means to verify the macro experimental results. (4) the key influence of MFC on the reduction of nitrate is studied under the stable operation of the moment form single slot Biological Cathode MFC. The effect of parameter C/N, inorganic carbon source NaHCO3 and hydraulic retention time HRT on the performance of MFC and the effect of nitrate degradation. Experimental results show that the increase of C/N and inorganic carbon source NaHCO3 increase the output voltage of MFC, increase the degradation rate, the effect of nitrite and ammonia nitrogen accumulation, which is helpful to the output of MFC voltage; two kinds of hydraulic retention time. Under HRT2.0d and 1.0d, the output voltage of MFC is different from the degradation of nitrate. HRT is beneficial to the output of voltage and the degradation of nitrate. (5) the effect of the hydraulic gradient on the output of MFC and the effect of nitrate degradation in the MFC reaction tank is studied. The experimental results show that the hydraulic gradient increases, the maximum output voltage of the MFC increases, and the reaction trough is out. The concentration of NO3--N in the saliva sample decreases, and the concentration of NO3--N also shows a large upper layer concentration and lower concentration in the lower layer. In accordance with the horizontal direction of the flow, the concentration of the front end is large and the concentration of the back end is small. This indicates that the change of the hydraulic gradient affects the performance of MFC and the degradation effect of nitrate. This simulation results can express the change of hydraulic gradient more. The migration and transformation of nitrate in the groundwater. (6) the electrochemical behavior of the cathode and the anode biofilm was scanned by cyclic voltammetry. The results showed that the anode of the membrane mainly occurred oxidation, the catalytic oxidation of the microorganism on the surface of the electrode; the cathode of the hanging film was the reduction reaction, the cathode microorganism was in the electricity. Catalytic reduction of polar surfaces. There is a pair of apparent redox electric pairs on the CV curve of the blank electrode in the reaction solution. It is speculated that there is a redox mediator secreted by microorganism metabolism to the extracellular matrix in the reaction solution, and the electron shuttle transmission mechanism exists in the MFC system, and the main task of electronic delivery is the electric microorganism on the electrode. It's done.

【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TM911.45

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