阴极表面修饰和电压调控改善MEC阴极生物膜生长和产甲烷性能的研究

发布时间：2018-03-20 08:12

本文选题：微生物电解池　切入点：产甲烷　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着全球经济的高速发展,能源与环境问题日益严峻,成为影响人类可持续发展的关键。微生物电解池(Microbial electrolysis cell,MEC)可以将生物质能转化为易于储存和利用的甲烷,在降低CO2排放的同时,缓解紧张的能源需求。为了提高MEC的产甲烷性能,本文从外电压和阴极表面性质两个方面入手,研究其对阴极生物膜及产甲烷特性的影响。本文通过单电压运行及转换电压运行两种方式研究外电压对MEC产甲烷性能及生物膜驯化的影响。在外电压恒定不变的运行条件下,相对于0.5 V和0.9 V,0.7V为本体系最佳产甲烷电压,最大电流密度为45.7A/m3,产甲烷速率为0.349 m3/m3·d,能量回收率为82.0%,具有较好的经济性。此时阴极上生物膜厚实,且生物种类以长杆菌为主。以转换电压方式运行MEC时,通过0.5 V和0.9 V之间的电压多次转换后,库仑效率(CE)增加,在0.9 V外电压下,产气中甲烷含量从44.1%增加到93.0%,产甲烷速率从0.25 m3/m3·d增加到0.41 m3/m3·d,增加幅度为64%,产气中氢气含量从50.4%减少到0.20%,表明电压转换法可以提高0.9V时的产甲烷含量。通过SEM观察生物膜,发现电压转换后高低压下适宜生存的产甲烷菌都丰富,生物形态多样性增加。本文随后考察了不同电压运行方式驯化的生物膜特性,包括对高电压的耐受能力和直接CO2产CH4的能力。当外加电压增加到1.2 V时,在0.7 V电压下运行的阴极生物膜适应性更好,产甲烷速率可达1.32 m3/m3·d,同时具有最大的总甲烷回收率和总能量回收率。当以二氧化碳为阴极产甲烷唯一碳源时,发现低电压(0.5V)下运行过的MEC能产生更大的产甲烷速率(0.054m3/m3·d),是相应0.9 VMEC的6倍。表明适宜在低电压下培养直接二氧化碳产甲烷菌,而高电压下是以氢营养型产甲烷菌为主导的产甲烷。本文还研究了高聚物和碳粉修饰对生物阴极性能的影响。在通过少量高聚物聚偏氟乙烯(PVDF)改性后,因PVDF不导电,运行电流略有降低,产甲烷速率亦有所降低,说明PVDF对阴极产甲烷不利,但阴极表面生物的附着情况差异不大。在使用具有导电性的碳粉修饰时发现,活性炭修饰可提高MEC的化学需氧量(COD)去除率和库仑效率,改善运行性能,且甲烷产量增加了 42.9%,总能量回收率提高了 35%。通过电化学分析,推测电极电容及与电容相关的活性表面积可能是影响MEC的电化学性能和产甲烷性能的主要原因。为探究电容的影响,在碳布上负载等量不同结构的碳粉如多壁碳纳米管(MWCNT)和单壁碳纳米角(SWCNH),获得不同电容阴极,比较两组阴极性能,发现SWCNH组在COD去除率、库仑效率和产甲烷量上优于MWCNT组,总能量回收率高60%。表明此时影响MEC性能主要因素是阴极表面结构而并非电容,SWCHN具有较好的生物相容性,产甲烷菌易于在其表面生长,而MWCNT表面不利于附着产甲烷菌。此外,将PVDF应用于微生物燃料电池(Microbial fuel cell,MFC)的空气阴极时,发现PVDF表面修饰可降低催化层催化剂的损失,当修饰量为65μl2%浓度的PVDF时,得到最好的运行稳定性和功率特性,最大功率密度为27.4W/m3。
[Abstract]:With the rapid development of global economy, energy and environment problem is increasingly serious, has become the key to sustainable human development. Microbial electrolysis cell (Microbial electrolysis, cell, MEC) can convert biomass energy for easy storage and use of methane in reducing CO2 emissions at the same time, ease the tension of energy demand. In order to improve methane production performance of MEC this paper, from two aspects of external voltage and the cathode surface properties of cathode on the biofilm and methane production were studied. Through the single voltage operation and voltage conversion operation of two ways to investigate the influence of external voltage on MEC methane production and biofilm domestication. In operation conditions under constant voltage, compared with the 0.5 V and 0.9 V, 0.7V is the best system of methane producing voltage, the maximum current density is 45.7A/m3, the methane production rate was 0.349 m3/m3 - D, the energy recovery rate was 82%, with Good economy. The biofilm on the cathode and thick, species dominated by long bacilli. To convert the voltage mode MEC, the voltage between 0.5 V and 0.9 V after multiple conversions, the coulombic efficiency (CE) increased in 0.9 V voltage, the content of methane gas production increased from 44.1% to 93%, the methane production rate from 0.25 m3/m3 / D increased to 0.41 m3/m3 - D, the rate of increase of 64%, the hydrogen yield were reduced from 50.4% to 0.20%, showed that the methane content increased when the 0.9V voltage conversion method. Through the observation of SEM biofilm, found that the converted voltage high pressure under suitable methanogens the rich biodiversity patterns increase. This paper then examine the characteristics of biofilm acclimated to different voltage operation mode, including the ability of high voltage tolerance and direct CO2 CH4. When the applied voltage is increased to 1.2 V, operating under the voltage of 0.7 V negative A biofilm adaptability better, methane production rate of up to 1.32 m3/m3 - D, and has the largest total methane recovery rate and the total energy recovery rate. When using carbon dioxide as the only carbon source cathode methane (0.5V), low voltage operation of the MEC can produce more methane production rate (0.054m3/m3. D), is 6 times the corresponding 0.9 VMEC. Indicate that direct carbon dioxide methane producing bacteria under low voltage and high voltage is suitable for methane production to Hydrogenotrophic methanogens is dominant. This paper also studies the effect of modification of biological polymers and carbon cathode performance. In by a small amount of polymer polyvinylidene fluoride ethylene (PVDF) modified by PVDF is not conductive, running current decreases slightly, the methane production rate also decreased, indicating that PVDF is unfavorable to the cathode methane, but the biological surface of the cathode attachment. Little difference in the carbon conductive when using modified Found that the modified activated carbon can improve the COD removal rate of MEC (COD) and coulombic efficiency, improve the operating performance, and methane production increased by 42.9%, the total energy recovery rate increased by 35%. by electrochemical analysis, that the capacitance of the electrode and the active surface area and related capacitance may be the main reasons affecting the electrochemical performance of MEC and methane production. For the influence on the capacitance of the equivalent load of different structures such as carbon multi wall carbon nanotubes on carbon cloth (MWCNT) and single wall carbon nano angle (SWCNH), different capacitor cathode, cathode can be compared between the two groups in the SWCNH group, found that the removal rate of COD, the coulombic efficiency and production the amount of methane is better than that of group MWCNT, the total energy recovery rate of high 60%. indicates that the main factor is the influence of the performance of MEC cathode surface structure instead of capacitors, SWCHN has good biocompatibility, easy to methanogenic bacteria in its surface growth, and MWCNT table The surface is not conducive to the attachment of methanogenic bacteria. In addition, PVDF will be used for microbial fuel cell (Microbial fuel, cell, MFC) of the air cathode, found that PVDF surface modification can reduce the loss of the catalyst layer, when the amount of modified 65 l2% concentration of PVDF, running stability and power characteristics of the best, the most the power density is 27.4W/m3.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM911.45

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