【作者】 张慧敏；

【导师】 吴祖成；

【作者基本信息】 浙江大学 ， 环境工程， 2014， 博士

【摘要】 水污染及水资源短缺问题是制约国民经济社会可持续发展的重要因素之一。传统的废水处理高能耗、高成本,致使污水处理厂难以为继、减排效益得不到正常发挥。能源需求增加也加剧了当前的能源危机,节能降耗的污水处理技术势在必行。然而,受水处理工艺的节制,技术提升空间有限。废水中蕴藏能量已有共识,提取能量已引起科学工作者的广泛关注。从废水中直接提取电能而无需给能的处理技术必将成为一个热点课题。本论文通过设计由还原性污染物与氧化性污染物组成的液相污染物电对燃料电池,模拟污染物,典型的选取Ethanol-Cr(Ⅳ)、Phenol-Cr(Ⅳ)、Urea-Cr(Ⅳ)、 NaBH4-Cu(Ⅱ)及NaBH4-Ni(Ⅱ)电对,将蕴含在燃料和氧化剂中的化学能转化为电能的同时直接去除或转化污染物,为实现污染物脱毒与产电共生进行了基础研究。设计了Ethanol-Cr(Ⅵ)电对燃料电池,以中空Pt/C负载催化阳极与碱性乙醇溶液构成阳极体系、以碳纤维布为电极与酸性Cr(Ⅵ)溶液构成阴极体系,组装成Ethanol-Cr(Ⅵ)电对燃料电池。当Cr (Ⅵ)为3.94mM时可产生开路电压1.46V,负载985Ω外电阻后得到0.7V的输出电压,运行54h后Cr(VI)去除率达96%,起始Cr(VI)浓度为8.65mM时最大功率密度为1900mWm-2。当用带苯环的碳氢污染物苯酚为燃料、以Ni/C负载催化阳极代替Pt/C催化阳极时,940mg L-1的苯酚实现98%的去除率,同时300mg L-1Cr(Ⅵ)达到99%的去除。苯酚在阳极发生电氧化转化为无毒的低分子量有机酸,Cr(VI)在阴极电还原为低毒性Cr(Ⅲ)。此时,开路电压为1.2V、功率密度184mWm-2。选择尿素或尿液作为燃料注入电对燃料电池,负载NiCo/C催化剂为阳极,组装的urea/urine-Cr(Ⅵ)电对燃料电池,0.033M燃料、150mg L-1Cr (Ⅵ)的开路电压为1.08V、最大功率密度为220mWm-2，负载985Ω外电阻运行25h后Cr(Ⅵ)去除率99.4%。改用尿液为燃料,其开路电压为0.84V,最大功率密度为90mWm-2,对应Cr(VI)去除率达98.4%。在此基础上,探索了低电位金属离子在电对燃料电池阴极的还原与去除。以尿素、乙醇、葡萄糖、淀粉和硼氢化钠为燃料,铜离子为氧化剂的电对燃料电池产生的开路电压分别为0.58V、0.65V、0.78V、0.65V和1.5V。当燃料为0.2MNaBH4和2M KOH,铜离子浓度为400mg L-1时,可产生1.5V的开路电压,最大功率密度为1000mWm-2。外加985Ω负载后输出电压为0.65V,运行23h后铜离子去除率达99.9%。若将400mg L-1Ni2+注入电对电池的阴极液,开路电压为1.05V、最大功率密度为260mWm-2。电池运行45.7h后,镍离子去除率达54.8%。由此可见,Cr(Ⅵ)、Cu(Ⅱ)、Ni(Ⅱ)与苯酚或尿素组成的电对燃料电池中可实现直接产电,同时污染物得以去除。这一方法可望成为污染物处理的一种新技术。更多还原

【Abstract】 The shortage of water resources and water pollution restrict the sustainable development of economy and society. Current technologies for wastewater treatments are often energy-intensive. Sewage treatment plants usually needed energy input resulting in high operation costs. Increasing energy demand also contributed to the current energy crisis. Low energy-intensive technology of wastewater treatment is imperative. Usually, wastewater contains covert energy. Harvesting those energies directly from wastewater without supplying energy has become a hot research topic.In this paper, coupled redox fuel cell (CRFC) was designed, typically selecting Ethanol-Cr(Ⅵ), Phenol-Cr (Ⅵ), Urea-Cr(Ⅵ), NaBH4-Cu(Ⅱ) and NaBH4-Ni(Ⅱ) redox, to convert chemical energy in fuel and oxidant directly into electricity and simultaneously achieve detoxification of pollutants. The fundamental study on the harvest of electricity and removal of pollutants was conducted.Ethanol-Cr (Ⅵ) CRFC was assembled. The hollow Pt/C coated on the anode and alkaline alcohol solution composed of anode system, with carbon fiber cloth as the electrode and the acidic chromium (Ⅵ) solution as the cathode. When Cr (VI) was set at3.94mM, an open circuit voltage of1.46V and output voltage of0.7V were gained with loading an external resistance of985Ω. At this situation,96%removal of Cr (Ⅵ) was achieved after running54h. When the initial Cr (Ⅵ) concentration was8.65mM,1900mW m-2of a maximum power density can be obtained.When hydrocarbon organic phenol was used as fuel, and Ni/C instead of Pt/C was employed as the anode in the CRFC,98%phenol of940mg L-1anolyte and99%Cr(Ⅵ) of300mg L-1catholyte can be removed. Phenol electro-oxidation occurs at the anode into non-toxic, low molecular weight organic acids. Cr(Ⅵ) transfers to less toxic Cr (Ⅲ) in the cathodic reduction. Open circuit voltage was1.2V with a maximum power density of184mW m-2.0.033M urea or urine as fuel and150mg L-1Cr (Ⅵ) as oxidant, loading NiCo/C catalyst as the anode to assembly an urea/urine-Cr (Ⅵ) cell, the cell can result in the open-circuit voltage of1.08V and the maximum power density of220mW m-2. With 985Ω of load running25h,99.4%removal of Cr (Ⅵ) can be obtained. Use of urine as fuel, the open circuit voltage of0.84V, a maximum power density of90mW m-z corresponding to Cr (Ⅵ) removal of98.4%can be achieved.On this basis, the feasibility of the cathodic reduction and removal in the CRFC was also explored by using the metal ions with the low potentials as oxidants. Urea, ethanol, glucose, starch, and sodium borohydride as the fuel, copper ion as an oxidant, and the open circuit voltage of the fuel cell were0.58V,0.65V,0.78V,0.65V and1.5V, respectively. When the fuel is0.2NaBH4and2M KOH, copper ion concentration is400mg L-1, it can produce an open circuit voltage of1.5V and a maximum power density of1000mW m-2. The initial output voltage is0.65V. After running23h the copper ion removal is99.9%. If400mg L-1Ni2+implantation catholyte of the CRFC, an open circuit voltage of1.05V and a maximum power density of260mW m-2can be harvested. When the cell runs45.7h, the nickel ion removal is54.8%.Thus, Cr(Ⅵ), Cu(Ⅱ), Ni(Ⅱ) with phenol or urea in the CRFC can directly produce electricity, and contaminants can be simultaneously removed. This approach is expected to become a new technology for pollutant treatment.更多还原