摘要
随着社会的发展和科学技术的进步，能源以及环境问题逐渐成为人类在二十一世纪面临的两大挑战，严重制约着人类的生存和社会的可持续发展。近年来，传统化石能源的大量使用不仅使得化石能源日益枯竭，还严重污染了环境。同时，环境问题特别是水污染问题也变得日益严重，而目前在污水处理行业，以传统的方式处理废水一直处于“高投入，零产出”状态。因此，为保证社会的可持续发展，寻找新型清洁能源和新的污水处理工艺已成为当务之急。在此背景下，微生物燃料电池（Microbial Fuel Cell，MFC）技术应运而生，并逐渐发展起来。MFC 技术采用微生物作为阳极催化剂，将废水中有机物的化学能转化为电能，在处理污水的同时又产生了电能，是一种清洁无污染的可再生能源装置。MFC由于其在处理污水的同时能够产生电能的这一独特优势，因而受到国内外学者们的广泛关注。
然而，目前MFC输出功率较低，产电性能不高的问题成为了其商业化应用的一大瓶颈。在影响MFC产电性能的众多因素中，阳极性能起到了极为重要的作用。本文从工程热物理的角度出发，针对MFC阳极中底物及产物的传质问题，对阳极生物膜内部、阳极微小孔隙内部的H+传输特性以及电池阴阳两极由于H+跨膜传输造成的水传输现象进行研究。分别研究了以碳纸为阳极材料的微生物电化学系统阳极生物膜内部氢离子的传质特性、以石墨棒为电极单元构建的三维阳极石墨棒阵列内部的氢离子传质特性、以碳刷为电极材料构建的双室微生物燃料电池阴阳两极间的水传输特性。本文主要研究成果如下：
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1.微生物电化学系统（BES）阳极生物膜内传质现象的研究
构建了以碳纸为阳极材料的微生物电化学系统，启动完成后对阳极生物膜内的传质现象进行研究。通过对微生物阳极用循环伏安法进行扫描测试、电化学阻抗测试以及生物膜形貌分析，研究了阳极生物膜内部的传质特性。研究结果表明：运用循环伏安法对微生物阳极进行测试时，使用不同的扫速或者同一扫速不同圈数情况下，阳极的循环伏安曲线（CV曲线）各不相同，扫描速度越小，CV曲线中氧化电流到达峰值后下降越严重。无底物条件下，最大峰电流与扫速的平方根成正比；电化学阻抗测试表明微生物阳极的传质内阻远大于欧姆内阻和传荷内阻。
2. 微小孔隙(0.5 mm)内部活性生物膜成膜及pH分布研究
本实验使用石墨棒（直径0.9 mm），POM板，PTFE硬管构建了毫米级别孔隙的三维阳极阵列（10×10），相邻两根石墨棒间距（孔隙大小）为0.5 mm，研究了毫米级别孔隙的三维阳极阵列不同区域的电流分布、内阻分布、pH分布、生物膜
工作思考
氧化底物时的电子传递方式以及生物膜形貌。研究结果表明：三维阳极阵列从外向内，产电电流不断减少；欧姆内阻和传质内阻基本相同，传质内阻逐渐增大；pH值不断降低；活性生物量不断减少。
3. 双室微生物燃料电池阴阳极间水传递特性研究
本节构建了以碳刷为阴阳极材料的双室微生物燃料电池，研究了由于H+跨膜运输导致的“电渗拖拽”作
用对阴阳两极间水传递现象的影响。研究结果表明，双室MFC阴阳两极间的水传输现象与放电电流强度、阴阳两极磷酸缓冲液（PBS）浓度以及质子交换膜厚度密切相关。放电电流越大、阳极PBS溶液浓度相对于阴极PBS溶液浓度越低、质子交换膜厚度越薄，阴阳极间水传输量越大。
关键词：微生物电化学系统、阳极、微小孔隙、传质现象、水传输
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ABSTRACT
With the development of society and the advancement of science and technology, the energy and environmental problems have gradually become two major challenges which mankind facing in the 21st century and verely constrain the survival of mankind and the sustainable development of society. In recent years, the extensive u of traditional fossil fuels has not only depleted fossil fuels but also riously polluted the environment. At the same time, environmental problems, especially water pollution, have also become increasingly rious. At prent, wastewater treatment in the traditional wage treatment industry has always been in a "high-input, zero-output" state. Therefore, in order to ensure the sustainable development of society, it is imperative to find new clean energy sources and new wastewater treatment process. In this context, Microbial Fuel Cell (MFC) technology came into being and gradually developed. MFC us microorganisms as an anode cataly
st to convert the chemical energy of organic matter in waste water into electrical energy, and it produces electrical energy while treating wage, which is a kind of clean and pollution-free renewable energy plant. Due to its unique advantage of being able to generate electric energy while being treated with wage, MFC has drawn wide attention from domestic and foreign scholars.
However, at prent, the problem of low output power of MFC and low power generation performance has become a big bottleneck of its commercial application. Among the many factors that affect MFC power generation performance, the anode performance plays a very important role. In this paper, from the viewpoint of engineering thermophysics, in view of the mass transfer of substrates and products in the MFC anode, the transmission characteristics of H+ in the anode biofilm and anodic micro pores , and the water transmission between anode and cathode caud by the H+ transmembrane are studied. In this paper, the mass transfer characteristics of H+ inside the anode biofilm of a microbial electrochemical system using carbon paper as anode material, and the mass transfer characteristics of H+ inside a three-dimensional anode graphite rod array constructed using a graphite rod as an electrode unit were studied. The water transfer characteristics between the cathode and the anode of a dual-chamber microbial fuel cell constructed using a carbon brush as an electrode material were studied. The main rearch results of this paper are as follows:
1. Mass transfer phenomenon in anodic biofilms in microbial electrochemical system (BES).
A microbial electrochemical system was constructed with carbon paper as the anode material. After the start-up, the mass transfer phenomenon in the anode biofilm was studied. The mass transfer characteristics of the anode biofilm were studied by scanning the microbial anode with cyclic voltammetry(CV curve), electrochemical impedance spectroscopy（EIS curve）, and biofilm morphology. The results show that when using cyclic voltammetry to test the microbial anode, the CV curve of the anode varies with different scan rates or different numbers of turns at the same scaning speed, the smaller the scanning speed, the more vere the oxidation current in the CV curve drops after reaching the peak value. Under substrate-free conditions, the maximum peak current is proportional to the square root of the scan rate; electrochemical impedance analysis tests show that the mass transfer resistance of the microbial anode is much larger than the ohmic resistance and the charge transfer resistance.
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2. Formation of active biofilm and pH distribution studies in micro-pore (0.5 mm)
A three-dimensional stainless steel wire anode array (10×10) of millimeter-level pores was constructed by using graphite rods（diameter is 0.9 mm）, POM plates and PTFE hard tubes,two a
DOS窗口djacent graphite rod spacing (the pore size) is 0.5 mm. The current distribution, internal resistance distribution, pH distribution, electron transfer modes of biofilm oxidation substrates and biofilm morphology were studied in three-dimensional anodes. The results shows: from the outside to the inside, the current of the three-dimensional anode arrays decrea continuously, the ohmic resistance and the mass transfer resistance are basically the same, but the charge transfer resistance increas gradually, the pH value and the the active biomass keeps decreasing, the thickness of biofilm gradually decreas.
3. Water transport characteristics between cathode and anode of dual-chamber microbial fuel cell.
酷炫壁纸In this ction, a dual-chamber microbial fuel cell with carbon brush as anode and cathode material was constructed. The effect of “electro-osmotic drag”due to H+ trans-membrane transport on the water transport phenomena between cathode and anode was studied. The results show that the phenomenon of water transport between the cathode and anode of the dual-chamber MFC is cloly related to the discharge current intensity, the phosphoric acid buffer (PBS) concentration of the cathode and anode, and the thickness of the proton exchange membrane. The larger discharge current intensity, the lower the concentration of the anodic PBS solution relative to the
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concentration of the cathode PBS solution, and the thinner the thickness of the proton exchange membrane, the greater the amount of water transport between the anode and the cathode.
Key words: microbial electrochemical system, anode, micropore, mass transfer
phenomenon, water transport
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