【作者】 孙健；

【导师】 胡勇有；

【作者基本信息】 华南理工大学 ， 环境工程， 2010， 博士

【摘要】 可更新能源的开发与废水处理是当今世界可续发展的两大命题。微生物燃料电池(Microbial fuel cell，MFc)能从广泛的有机物及有机废水中获取电能，同时完成废水处理，迅速成为新概念废水处理热点。偶氮染料占几工合成染料总量的80％以上，偶氮染料废水的排放不仅影响环境的美观，而且污染水体，毒害水生生物，同时对几类健康造成潜在威胁。偶氮染料废水浓度高、可生化性差，是公认的难处理有机废水。传统的物化法虽然具有较好的处理效果，然而，昂贵的费用、高的能耗与苛刻的反应条件限制了其实际应用。生物法以其廉价、高效与环境友好等众多优势得到普遍应用。生物法处理偶氮染料废水一般是先厌氧生物还原劈裂偶氮键对偶氮染料脱色，然后好氧生物降解偶氮染料脱色产物芳香胺。理论上，MFc阳极产电菌在厌氧条件下降解有机物从中获取电子并将其传递给阳电极同时产电，MFc阴极以氧气作为电子受体，是故MFc理论上能满足偶氮染料废水生物处理所需要的基本条件。而且，最近开发的生物阴极由于其对最终电子受体选择的多样性，使得开发深度降解废水中的多种污染物(有机或无机)的MFc阴极技术成为可能。由此可以认为，MFc在理论上可实现同步处理偶氮染料废水与产电，有望成为一种全新概念的偶氮染料废水处理技术。本研究首先构建了新型空气阴极一单室型MFc，对其同步处理有机废水与产电特性进行了研究并对其性能进行了优化。在此基础上尝试利用优化后的MFc对典型偶氮染料一活性艳红x3B(ABRX3B)与刚果红进行脱色与同步产电。同时，鉴于ABRX3B脱色产物在厌氧的MFc阳极环境下难以矿化，及脱色产物在空气中发生自氧化反应重新生成的有色产物，构建了好氧生物阴极双室型MFc，尝试利用好氧生物阴极对ABRX3B脱色液作进一步处理并实现同步产电。得到如下主要结果与结论：构建了新型空气阴极．单室型MFc，探讨了在阴极对水面应用微滤膜(MFM)与阳极采用多种污泥接种对其同步处理糖果有机废水与产电性能的影响与机理。实验结果表明，MEM能替换质子交换膜(PEM)应用于空气阴极单室型MFc处理实际有机废水。相对于PEM，MFM能显著提升阴极电势，减小MFc内阻，增大输出功率。MFM阴极MFc产生了高于PEM阴极MFc两倍的最大功率密度。相对于无膜阴极，MFM能有效增大MFc的库伦效率，库伦效率由4 170A，增大到5 16％，且未对MFc产电性能产生负面影响。接种污泥多样性对MFc同步处理有机废水与产电性能影响显著。相对于单一的好氧污泥(AEs)、厌氧污泥(ANS)和湿地沉积物(wLs)接种，混合污泥接种能显著改善MFc产电性能，主要表现在减小MFc内阻、提升MFc产电功率和增大MFc库仑效率。ANs wLs接种的MFc的功率密度输出最大。AEs+ANS接种的MFc获得了最大的库仑效率。膜与接种污泥对MFc去除废水c0D的性能影响较小，但c0D去除率均较高，对浓度1000 mg c0D／I．实际糖果废水的c0D去除率均在92~％以上。利用空气阴极单室型MFc能实现同步偶氮染料降解与产电。以葡萄糖为共基质条件下，与传统厌氧反应器相比，MFc能显著加速ABRx3的脱色，48 h后浓度300 mg~。L的ABRx3基本能完全脱色。脱色主要是由厌氧生物还原作用实现，而非菌体的吸附。偶氮键断裂导致ABRx3的脱色，但ABRx3脱色液暴露在空气中易发生自氧化作用，生成棕褐色氧化产物。mc可重复用于ABRx3高效脱色，脱色性能未出现退化。在ABRx3脱色的同时，MFc产生了O 5 v左右的稳定电压输出，重现性好。MFc阳极混合菌能以ABRx3为唯一碳源，从中缓慢获取电子传递给阳极用于产电，但产电效能极低。探索了系统关键运行条件与因素对空气阴极单室型MFc同步脱色ABRx3与产电性能的影响。在限定的时间内，ABRx3浓度增加导致其脱色速率减缓，但对最终脱色率的影响较小。ABRx3初始浓度高达1500 mg／I．时，48 h的脱色率仍能达到77％。当ABRx3初始浓度低于300 mge，L时未对MFc产电性能产生显著影响。随着ABRx3浓度的增高，c0D去除率降低，脱色产物积累，产电抑制明显，但去除染料并重新更换阳极溶液后产电性能可以恢复到初始水平。葡萄糖是实现MFc同步脱色ABRx3与产电的最佳共基质，其次为蔗糖和糖果废水，醋酸钠最差。相对于高电阻，外接低电阻能加速MFc对ABRx3的脱色。悬浮污泥能加速MFc对ABRx3的脱色同时增大电能输出，但ABRx3的脱色与同步产电主要依赖于阳极生物膜细菌。在空气阴极单室型MFc中以葡萄糖为共基质，探讨了典型偶氮染料刚果红与阳极之间的交互作用。实验结果表明，对浓度300 mg／I．刚果红的脱色未导致MFc最大稳定电压的降低，但显著延长了达到最大稳定电压的时间。刚果红脱色与阳极竞争来自共基质葡萄糖的电子，且相对于阳极刚果红脱色更易于获取电子，刚果红脱色优先于产电。利用液质联用技术(Lc．MS)检测了刚果红的降解产物。阳极对刚果红降解生成了五种主要降解产物，主要为苯和萘的衍生物。采用交流阻抗技术(EIs)探明了对应不同浓度刚果红的阳极阻抗变化。不同浓度刚果红对阳极欧姆阻抗(R。h。)的影响很小，而对阳极的极化阻抗(R。)和扩散阻抗(Rd)影响较大。随着刚果红浓度的增加，R。和R表现为先增大后减小。可能的原因为：低浓度刚果红可作为电子介体增强电子由细菌到阳极的传递。但随着浓度的增加，刚果红脱色会加剧消耗来自共基质葡萄糖的电子，导致传递给阳极的电子减少，增大了阳极极化阻抗和基质扩散阻抗。相对于阳极阻抗，阴极阻抗未受显著影响。利用循环伏安法(cv)测定，探明了阳极表面催化氧化还原反应的变化规律。当刚果红初始浓度低于900 mg/L时，阳极的催化电流未受显著影响。长期的刚果红环境导致了阳极表面催化氧化还原位点与阳极生物膜形态发生了变化。采用变性梯度凝胶电泳(DGGE)和基于16S rRNA的指纹序列分忻等分子生物学技术分忻了同步脱色刚果红与产电的MFc阳极微生物多样性。结果表明，无论以葡萄糖为单一基质还是以葡萄糖和刚果红为共基质的MFc阳极生物膜菌均以Proteobteria(变形菌类)为主，且存在典型的隶属于Proteobacteria类的Geobacteraceae属产电菌。与以葡萄糖为单一基质相比，长期的刚果红脱色导致了阳极生物膜菌群组成发生了变化，催生出新的菌种类型，包括隶属于-Proteobacteria类的Azospirllum菌和Methylobacterium菌、隶属于-Proteobacteria类的硫还原菌和其他一些未可培养细菌。推测这些新出现的菌种导致了刚果红脱色与其脱色产物一芳香胺的进一步降解。利用好氧生物阴极双室型MFc实现了对ABRX3脱色液(DL)的进一步降解与同步产电。好氧生物阴极能在12 h内去除DL 24 8％的c0D，去除的这部分c0D主要为苯胺类衍生物，主要由生物降解作用完成。葡萄糖的添加并不能增强好氧生物阴极对DL的c0D的进一步去除。开路与闭路(500 Q)条件下，好氧生物阴极对DL的c0D去除速率相似，表明好氧生物阴极对DL的降解不是电流依赖过程。DL的加入能极大的提升阴极电势，进而改善MFc的整体产电性能。向好氧生物阴极中加入DL使阴极开路电势提高了1 5倍，由此导致了73％的最大稳定电压的增长和．300qlm的最大功率密度的增长。cv表明，DL中包含的ABRX3脱色产物可作为电子介体协助电子由阴极到氧气的传递，加速氧的还原，从而提升阴极电势。好氧生物阴极表面形成了致密与形态一致的生物膜，表面细菌呈聚合态生长，并观察到有类似“纳米线”的细胞结构生成。更多还原

【Abstract】 Sustainable energy production and wastewater treatment are a top priority in the developing global community. Microbial fuel cells (MFCs) can recover renewable energy from waste organic sources and facilitate energy production while simultaneously accomplishing wastewater treatment. It is becoming a rapid evolving field in abroad and be given much attention by researchers as a novel notion for wastewater treatment.Azo compounds constitute the largest group of synthetic dyes (over 80%) and are widespread used in the dye-manufacturing and dye-consuming industries. The discharge of azo dye-containing wastewater represents a serious environmental problem and a public health concern not only because of their intense color, but also because most of them and their breakdown products are toxic or mutagenic to life and resist to further biodegrade. The azo dye-containing wastewaters are among the most recalcitrant wastewaters due to its high content and unbiodegradable nature.The treatment of dye-containing wastewater still presents a technical challenge. Most physicochemical methods can removal dye efficiently but not feasible due to their expensive cost, limited versatility, sensitive to other wastewater constituents. Alternatively, biological treatment may present a less expensive and environment-friendly way to remove dyes from wastewater. The most logical method for removal of azo dyes in biological wastewater treatment systems is based on anaerobic treatment for the reductive cleavage of the azo linkages in the dye in combination with aerobic treatment for further degradation of the products from azo dye cleavage, which are aromatic amines. MFC technologies also involve in anaerobic, but they are very different from traditional anaerobic wastewater treatment systems. In most cases, the bacteria in anode must be grown in an anaerobic environment in order to produce higher power output. It is also an aerobic system, however, because oxygen is used at the cathode and the use of oxygen is not coupled to microbial respiration. Moreover,a novel MFC incorporating a recently developed biocathode was also devoploved. It can be explored for removal pollutants (inorganic or organic) from water phase due to its variety of terminal electron acceptors. For these novel systems, there are many research aspects that remain to be explored. High and direct energy recovery from various readily biodegradeable organic compounds is another benefit of MFC over traditional anaerobic process. MFCs may offer a new technique in enhancing degradation of azo dye while at the same time recoveringelectricity from a readily biodegradable organic carbon source in practical applications.In this study, an air-cathode single-chamber microbial fuel cell was constructed and its performance on simultaneously wastewater treatment and electricity generation was investigated and improved. The MFC with inproved performance was used in consecutive study for simultaneously decolorization of azo dye and production of electricity. Active brilliant red X-3B (ABRX3) and Congo red were selected as model azo dyes. The effects ofdifferent parameters on the decolorization and elceticity generation process were systemic studied. Detailed mechanistic involves in this process was also elucidated. Considering of the low mineralization efficiency of the decolorization products of ABRX3 in the anaerobicbioanode of MFC and re-colored decolorization products due to autoxidiaztion reaction after exposure to air, a novel aerobic biocathode was introduced for further treatment of the decolorization effluent of the ABRX3 from the anode of MFC coupled with electricity generation. The feasibility was demonstrated and underlying mechanism was clarified. The major conclusions are given below:The performance improvement of an air-cathode single-chamber MFC during confectionery wastewater treatment was firstly demonstrated by using a microfiltration membrane (MFM) on water-facing side of the cathode and multiple aerobic sludge (AES), anaerobic sludge (ANS), and wetland sediment (WLS) as anodic inoculums. Batch test results show that the MFC with an MFM resulted in an approximately two-fold increase in maximum power density compared to the MFC with a proton exchange membrane (PEM). The Coulombic efficiency increased from 4.17% to 5.16% in comparison with the membrane-less MFC, without a significant negative effect on power generation and internal resistor. Overall performance of the MFC was also improved by using multiple sludge inoculums in the anode. The MFC inoculated with ANS+WLS produced the greatest maximal power density of 373 mW/m2 with a substantially low internal resistor of 38 . Higher power density with a decreased internal resistor was also achieved in MFC inoculated with AES+ANS and AES+ANS+WLS in comparison with those inoculated with only one sludge. The MFCs inoculated with AES+ANS achieved the highest Coulombic efficiency. Over 92% COD was removed from confectionery wastewater in all tested MFCs, regardless of the membrane or inoculum used.Electricity generation from readily biodegradable organic substrates accompanied bydecolorization of ABRX3, a representative azo dye, was demonstrated and investigated using a microfiltration membrane air-cathode single-chamber MFC. Batch experiment results showed that accelerated decolorization of ABRX3 can be achieved in the MFC as compared to traditional anaerobic bioreactor using glucose as co-substrate. The ABRX3 with an initialconenctration of 300 mg/L was removed almost completely within 48 h. Biodegradation was the dominant mechanism of the ABRX3 decolorization other than the absorption by biomass. Reductive cleavage of–N N– bond resulted in the ABRX3 decolorization but the decolorization liquid of the ABRX3 (DL) from the anode compartment of MFC was soonautoxidized and was re-colored as dark brown color after exposed to air.The MFC can be repeatly used for simultaneously ABRX3 decolorization and electricity generation without performance deterioration. Stable voltage output of around 0.5 V was obsevered accompanied by ABRX3 decolorization. The bacterial consortia in the MFC were capable of utilizing ABRX3 as a sole metabolite to transfer electrons to the anode. However,the voltage developed remarkably lower than the MFCs fed with readily biodegradableorganic carbons, such as glucose.Effect of operation parameters on performance of the air-cathode single-chamber MFC for simultaneously ABRX3 decolorization and electricity generation was investigated. Electricity generation was not significantly affected by the ABRX3 at 300 mg/L, while higher concentrations inhibited electricity generation due to accumulation of decolorization products. However, voltage can be recovered to the original level after replacement with anodic medium not containing ABRX3. Glucose was the optimal co-substrate for ABRX3 decolorization while acetate was the worst one. Confectionery wastewater was also shown to be a good co-substrate for ABRX3 decolorization and a cheap fuel source for electricity generation in the MFC. Low resistor was more favorable for dye decolorization than high resistor. Suspended sludge should be retained in the MFC to achieve accelerated decolorization of ABRX3 and higher power output.The interaction of a representative azo dye - Congo red with anode was investigated in an air-cathode single-chamber MFC using glucose as co-substrate. The maximum voltage output of the MFC was not significantly affected during decolorization of 300 mg/L Congo red, but the time needed to reach the stable voltage plateau was prolonged, indicating that Congo red will compete electrons with anode and Congo red decolorization is prior to the electricity generation in the MFC. Five main degradation products of Congo red were detected in the anode solution and were identified as benzene and naphthalene derivatives by liquid chromatography– mass spectrometry (LC-MS). Decolorization of different concentration of Congo red has negligible effects on the Ohmic resistor (Rohm) of the anode, but the charge-transfer resistor (Rc) and the diffusion resistor (Rd) were significantly influenced. The Rc and Rd firstly decreased then increased with increasing of Congo red concentration, possibly due to the fact that Congo red can be served as electron shuttle for conveniently electrons transfer from bacteria to the anode at low concentration, but results in accelerated consumption of electrons at high concentration. The cathode impedance was totally not affected by the Congo red addition. Addition of Congo red did not result in any noticeable decrease in the peak catalytic current until Congo red concentration up to 900 mg/L. Longterm decolorization of Congo red resulted in the change in the catalytic active site and the bacterial cellular morphology of the anode biofilm.Denaturing gradient gel electrophoresis (DGGE) and 16S-rRNA gene analysis was performed to investigate the bacterial diversity in the MFC used and not used for Congo red decolorization. The results revealed that the anode biofilm of the two MFCs were all dominated by bacteria which were phylogenetically very closely related to Proteobacteria.AS the most representative electrochemically active bacteria, Geobacter-like species were found to be integral members of the bacterial community in the two MFCs. There are some unique bacterial species in the Congo red–fed MFC compared to that in the glucose-fed MFC, mainly including of Azospirillum and Methylobacterium-like species ( -Proteobacteria), sulfate reducing bacteria ( -Proteobacteria) and some uncultured bacterial species. These bacteria may responsible for the effectively Congo red decolorization or further degradation of the decolorization products in the anode of the MFC .A MFC incorporating a recently developed aerobic biocathode was able to further treat the liquid containing decolorization products of ABRX3, a respective azo dye, and also provides increased power production. Batch test results showed that 24.8% of COD was removed from the DL by the biocathode within 12 h. Metabolism-dependent biodegradation of aniline-like compounds might be mainly responsible for the decrease of overall COD. Glucose is not necessary in this process and contributes little to the COD removal of the DL. The similar COD removal rate observed under closed circuit condition (500 ?) and opened circuit condition indicated that the current had an insignificant effect on the degradation of the DL. Addition of the DL to the biocathode resulted in an almost 150% increase in the open cycle potential of the cathode accompanied by a 73% increase in stable voltage output from 0.33 V to 0.57 V and a 300% increase in maximum power density from 50.74 mW/m2 to 213.93 mW/m~2. Cyclic voltammetry indicated that the decolorization products of the ABRX3 contained in the DL play a role as redox mediator for facilitating electron transfer from the cathode to the oxygen. SEM images revealed that a thick, homogeneous bioflim was formed on the surface of the cathode. The bacteria were clustered in aggregates and produced a large number of nanowires-like long thin filaments that connected to different bacteria aggregates.更多还原