面向工业废水处理的催化电极及燃料电池耦合体系

Progress on catalytic electrodes and fuel cell systems for industrial wastewater treatment

随着我国工业化水平的提高,工业废水的高效节能处理成为废水资源化与能源化进程中的重点和难点.工业废水中常含有难降解或有毒的有机污染物,水质复杂、可生化性差,采用传统废水处理技术(生物法、物化法等)难以实现高效处理和达标排放,残留毒物排入水体带来环境生态风险.电化学技术借助电场作用产生强氧化性物质,氧化去除难降解有机污染物,但去除效率较低、能耗及运行成本较高,限制了其在实际废水处理中的应用.高活性催化电极在结构、形貌、组成的优化进展,为构建以难降解污染物为燃料的新型燃料电池及废水处理体系提供了新的可能.本文围绕催化电极及燃料电池废水处理体系,综述了新型电极材料的制备、优化,探讨了基底、活性成分及其负载方式对催化电极和体系性能的影响;归纳了基于光催化燃料电池和微生物燃料电池的污染物催化降解及实际或模拟废水处理体系的研究进展,并对该类耦合体系的规模化应用作了展望.新型催化电极的开发和耦合燃料电池体系的优化设计,有望推动该技术在高效、节能实际(工业)废水处理中的应用.

Industrial wastewater containing dyes,antibiotics,heavy metal ions and other refractory organic pollutants has complicated components and poor biodegradability.Comparing to traditional bio-treatment processes,electrochemical technologies have significant advantage in treating such kinds of wastewater due to the electrochemically generated reactive species.Modifying the electrodes with catalytic components can enhance pollutant removal capacity in electro-catalytic(EC)or photo-electro-catalytic(PEC)integrated systems,but high energy consumption of electricity still restricts their implement.Self-biased fuel cells,including photocatalytic fuel cells(PFCs)and microbial fuel cells(MFCs),are more sustainable in industrial wastewater/pollutants treatment.Highly active catalytic electrodes are essential to promote pollutant removal and energy conservation.This article reviews the recent development of novel catalytic electrodes in preparation,optimization and sustainable application for industrial wastewater treatment.Technical advantages and optimization spaces of fuel-cell integrated systems(based on PFCs and MFCs)are introduced,and their challenges in large-scale application are pointed out.Catalytic electrodes have broader application fields than powder-form catalysts due to the easy-recyclability and the synergy of catalysis and electrochemistry.An ideal catalytic electrode should be conductive,highly(photo-)electro-active,physically and chemically stable,easy to prepare and low-cost.By optimizing the preparation/loading of novel catalytic materials(heterojunctions,single-atom catalysts etc.),various catalytic electrodes,in forms of self-standing(metal-based,carbon-based and others),film/membrane and particles,etc.,can be obtained with extraordinary(photo-)electro-catalytic activity.Innovative design of catalytic electrodes in structure and component may in-situ integrate multiple technologies such as(photo-)electro-catalysis,advanced oxidation processes(AOPs)and membrane filtration,etc.,which provides more possibility for enhancing electrochemical systems.Novel catalytic electrode of low-cost and high efficiency is still desirable for further optimization of integrated electrochemical systems.PFCs convert solar energy into electricity from the wastes(fuels).Various PFCs(single or dual photo-electrode(s))have been developed for the degradation of dyes,antibiotics and other refractory pollutants.The electricity generation of novel PFC has been improved to 1 V(open circuit voltage)or more in some cases.Enhanced pollutant degradation and energy recovery by optimizing the function of electrode and structure of PFCs are still desirable for complex wastewater treatment.By using exoelectrogens,highly-active catalytic electrodes(anode and/or cathode)can be applied in MFC integrated systems to promote the degradation of refractory pollutants.The synergy of bacteria and catalytic electrodes broadens the application of bio-processes in industrial wastewater treatment,and also benefits the energy recovery(electricity,hydrogen,heavy metals,etc.)of systems.Innovative designs of systems are expected to further reduce the operating costs from ion-exchange membrane,light irradiation and aeration.Although pollutant removal and energy conservation of fuel cells can be further improved by integrating AOPs(Fenton process,sulfate or chlorine radical advanced oxidation,etc.)or combining other processes(EC,PEC,desalination,etc.),less chemical consumption and simpler system configuration/operation are the main trends of sustainable and cleaner production.In the future,efforts need to be done for large-scale industrial wastewater treatment by fuel cell systems:(1)Develop novel catalytic electrodes of low-cost with enhanced performance(visible light response)and integrated functions(photoand/or electro-catalysis,filtration,AOPs,etc.).(2)Construct novel integrated fuel cell systems with highly active catalytic electrodes for multiple pollutant control and energy recovery.(3)Optimize large-scale preparation of catalytic electrodes,and simplify the operations of fuel cell systems,for energy-efficient and cost-effective treatment of real industrial wastewater,during long-term run.