【作者】 杜月；

【导师】 冯玉杰；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2015， 博士

【摘要】 随着环境与能源问题日益严重,对清洁、可再生能源的开发和利用逐渐成为研究热点。光催化与微生物燃料电池同属于新兴的能源与环保技术,二者功能相似,同时具有各自的优点与弊端。光催化可以无选择的降解污染物质,但受限于高的空穴/电子复合几率,微生物燃料电池的污染物局限于生物相容性物质,功率输出低,生物阴极的电子传递机制尚不明确。本文围绕生物阴极微生物燃料电池的产电机制与污染物去除效能展开研究,并寻求有效地方式与光催化技术相耦合,使二者扬长避短,提高污染物降解性能,强化系统的产电性能。间歇流运行的生物阴极微生物燃料电池获得的最大功率密度为15.37 W/m3,氨氮硝化率接近100%。电化学性能分析表明生物阴极具有良好的氧气还原催化活性和双电层电容特性。生物阴极的催化反应与微生物的代谢活性之间存在着密切的相互作用,阴极反应依赖于微生物的代谢活性,同时外电路电子可以作为微生物生长代谢的能源,在一定程度上促进阴极硝化反应。生物相分析结果表明,氨氧化菌(Nitrosomonas sp.)和亚硝酸亚氧化菌(Nitrospira sp和Nitrobacter sp.)在硝化型生物阴极中起到重要作用。由于向阴极提供了大量的有机物质,连续流的运行方式提高了生物阴极微生物燃料电池的反硝化效果,从而实现了同步碳氮去除。阴离子交换膜的使用有利于硝酸根向阳极的迁移,TN去除率由49%提高到80%,然而阴离子交换膜容易受到微生物的污染,阴离子的结构复杂,迁移阻力大,造成功率密度降低,不宜作为分隔材料。曝气速率对系统的产能和COD的去除影响不大,但严重制约着硝化效率,曝气速率0.6 L/min是保证氨氮的高硝化率的必要条件。COD/TN同时影响着系统的TN去除和功率输出。COD/TN为26.5时,TN去除率获得最大值(87.2±1.9%),当COD/TN为33.1时,阴极的氧气还原催化活性出现明显下降。本文将生物阴极与光催化阳极耦合构建了生物阴极–光催化燃料电池(BioPEC),同时利用光催化对难降解污染物的快速氧化和生物阴极的廉价、高效与可再生性,Bio-PEC获得的最大功率密度为211.32±3.54 mW/m2,甲基橙降解速率为0.0120 mg/(L·min)。Bio-PEC可以利用各种有机废水进行产电,光催化阳极室废水较高的pH值和厌氧条件有利于提高功率输出,为了保证溶液离子迁移速率,废水的电导率不应低于10~15 mS/cm。为了同时回收光催化产生的电子与微生物氧化产生的电子,本文提出了光催化电池(PEC)与微生物燃料电池的两种耦合方式。在复合阴极耦合模式中,铂碳阴极PEC(Pt/C-PEC)的连接大大降低了铂碳阴极MFC(Pt/C-MFC)的阳极电位,功率密度由780 mW/m2提高到1098 mW/m2。而在复合系统中,Pt/C-PEC回路产生的电流由150μA下降到20μA,甲基橙降解速率由0.0082 min-1下降到0.0007min-1,说明系统通过牺牲Pt/C-PEC的性能提升了Pt/C-MFC的性能。通过将TiO2光催化阳极与微生物阳极共用同一个阴极的连接方式,构建了复合阳极光催化–微生物燃料电池,实现了光能与生物能的同时利用。基于Pt/CPEC与Pt/C-MFC功率输出特性的不同,Pt/C-PEC的连接有效地提高了Pt/CMFC的阴极电位与功率输出。Pt/C-MFC性能的提高以Pt/C-PEC性能的小幅度下降为代价,系统整体性能较单独Pt/C-MFC有明显提高。该种耦合模式还在生物阴极微生物燃料电池中得到验证,可以缓解生物阴极在运行不良情况下产生的电位波动,提高生物阴极的性能。更多还原

【Abstract】 With the emergency of energy crisis and environmental pollution, more and more attention has been paid to the development and application of clean and renewable energy, such as solar energy and bioenergy. Semiconductor-based photocatalysis and photoelectrocatalysis are promising technologies for solar energy extraction and pollutant degradation, which hold the same purpose as microbial fuel cells(MFCs). Biocathode microbial fuel cells are devices that are catalyzed by microorganisms both in anode and cathode for organic pollutant removal and simultaneously electricity production. Biocathodes are alternatives for noble catalysts used in MFCs for its high efficiency, low-cost, reproducibility. However, the electron transfer mechanism of biocathode remains challenge recently; also, the low power output and vulnerability to persistent organics limits the pratical applications of MFCs. Based on the advantages and disadvantages of photocatalysis and MFCs, the present study was carried out on the working mechanism and pollutant removal of biocathodes, and the possible coupling models for these two technologies.The maximum power density of nitrifying biocathode MFCs in batch mode was ca. 15.37 W/m3. Almost 100% of ammonia was oxidized to nitrate in the biocathode. The biocathode showed the similar catalytic activity of oxygen reduction reaction and better electrical double-layer capacitances compared with Pt/C cathodes according to the electrochemical analysis. There was close interaction between cathodic reaction and microbial metabolism evolved in the cathode process. Based on the variation of nitrification and cathodic oxygen reduction activity towards the initial NH4 Cl and Na HCO3 concentrations of biocathode medium, it was shown that the oxygen reduction process, to some extent, relied on the nitrification activity of biocathode; the external electrons from cathode in turn might benefit the nitrifying bacteria selected in MFC habitat by entering the electron transfer chains as energy source. Nitrifiers, including Nitrosomonas sp., Nitrospira sp. and Nitrobacter sp. were detected in all biocathodes that cultured in different conditions, even that were cultured without NH4 Cl in the medium. These findings provided valuable insights into the possible working mechanism of biocathode.Simultaneous carbon and nitrogen removal was achieved in the continuousflow biocathode MFC. Anion exchange membrane(AEM) used as separator facilitated the transmission of NO3-–N from cathode to anode, resulting in the enhancement of denitrification and the TN removal from 49% to 80%. However, the AEM was not an ideal separator for MFCs because of the susceptibility to biofouling and higher internal resistance of anion migration compared with cation exchange membrane(CEM). The aeration rate showed little effect on the COD removal and power generation, but greatly influenced the nitrification process of biocathode. The aeration rate of 0.6 L/min was the requirement for efficient nitrification. The COD/TN ration of the influent both influenced the TN removal and power output. The maximum TN removal ratio(87.2±1.9%) was obtained with COD/TN ration 26.5; while the COD/TN ration increased to 33.1, the cathode performance deteriorated obviously.The biocathode coupled photoelectrochemical cell(Bio-PEC) was constructed for the first time to integrate the advantages of photocatalytic anode and biocathode. The voltages of Bio-PEC was ca. 250~290 m V, the maximum power density 211.32 ±3.54 m W/m2, and the methyl orange decoloration rate 0.0120 mg/(L· min). Various kinds of waste water can be treated by photo-anode for electricity generation. The higher p H value and anaerobic condition of wastewater benefited the power generation. The minimum conductivity of wastewater should be 10~15 m S/cm to avoid high internal resistances for ion migration.Two coupling patterns for PEC and MFC were proposed to harvest the electrons generated by both photocatalysis process and microbial oxidation. In the hybrid-cathode photoelectrochemical-microbial fuel cell(HCPMFC), the power density of Pt/C-MFC increased from 780 to 1098 m W/m2 when the Pt/C-PEC was connected. In contrast, the improvement of Pt/C-MFC accompanied with the performance reduction of Pt/C-PEC. The current of Pt/C-PEC declined from 150 to 20 μA, and the methyl orange decoloration rate decreased from 0.0082 to 0.0007 min-1 when the Pt/C-MFC connected.The hybrid-anode photoelectrochemical-microbial fuel cell(HAPMFC) was also constructed to integrate the application of solar energy and bioenergy by installing Ti O2 photoanode next to bioanode in microbial fuel cell(MFC), which shares the same cathode. The connection of Pt/C-PEC results in the elevation of cathode potentials of Pt/C-MFC based on the differences of power output characteristics of Pt/C-MFC and Pt/C-PEC alone. The maximum power density increased from 987 to 1645 m W/m2 as the Pt/C-PEC connected to external resistor of 1000 ?. The significant enhancement of power production of MFC is accompanied with the decline of PEC in a lower magnitude, yielding overall power output promotion of HAPMFC. The roles of hybridanode approach were also confirmed in the biocathode MFC. The fluctuation of biocathode potential that was running in poor condition was relied with the connection of Bio-PEC in hybrid-anode pattern.更多还原