基于氯、铁循环阴阳两极耦合同步去除难生物降解有机污染物及硝氮机制：以焦化废水生物处理出水为例

The concentrations of COD and nitrate nitrogen remain high in the effluent of the biologically treated industrial wastewater (such as coking wastewater) that is featured with high concentrations of organic matter and ammonia nitrogen, complex composition, and distinct biological toxicity. The traditional process for further removal of these pollutants usually needs the supplementation of multiple biological and advanced oxidation units, showing the drawback of high engineering and operating costs. Here, we propose to achieve simultaneous removal of biorefractory organic pollutants and NO3--N by a one-step cathode-anode coupled electrochemical process, which is mediated by the active elements like Cl and Fe available in the biologically pretreated coking wastewater. The research will mainly involve the following aspects: exploring the impacts of the selection of electrode material, the pH value, the type of electrolyte (with or without Cl¯) and Fe source and their concentrations, and the extent of applied current and operating time on the degradation of typical organic compounds and nitrate nitrogen; unraveling the mechanism of the enhanced electron utilization efficiency by the cathode-anode coupled electrochemical process; identifying and regulating the key electron transfer pathway that governs the simultaneous carbon and nitrogen removal based on the redox cycle of Cl and Fe; analyzing and evaluating the performance of the electrochemical system towards the treatment of real biologically pretreated coking wastewater in terms of degradation and energy efficiencies. The output of this research project is expected to provide theoretical knowledge for the application of electrochemical technology in the advanced treatment of industrial wastewater and offer technical insights into the design, construction and operation of energy-saving and efficient electrochemical reactors.

浓度（有机物及氨氮）高、成分复杂、生物毒性强的工业废水（如焦化废水）生物处理后出水中仍然含有较高浓度COD和硝氮，传统工艺用于上述污染物进一步削减需要辅以多个生物或高级氧化单元，呈现出工程造价及运行费用高的弊端性。本项目以焦化废水生物处理出水为例，旨在通过原位利用其中的活性元素如氯、铁，构建基于氯、铁循环的阴阳两极耦合电化学反应器实现难降解有机污染物与硝氮同步去除。重点研究电极材料种类、溶液pH、电解质类型（是否含氯）及浓度、铁源种类及浓度、施加电流大小和运行时间长短等参数对典型有机物及硝氮降解的影响规律；明确阴阳两极耦合促进电子利用效率的机制；识别并调控基于氯、铁循环同步除碳脱氮的关键电子转移途径；分析并评价作用于实际焦化废水生物出水处理的电化学系统效能。项目的顺利开展，将为电化学技术应用于实际工业废水生物出水深度处理提供理论支撑，为节能、高效性电化学反应器设计、构筑和运行提供技术借鉴。

通常，工业废水（如焦化废水）生物处理后出水中仍然含有较高浓度COD和硝氮，传统工艺用于上述污染物进一步削减需要辅以多个生物或高级氧化单元，呈现出工程造价及运行费用高的弊端性。本项目以焦化废水生物处理出水为例，构建了阳极氧化−阴极还原耦合系统，利用废水中自有物质（如Cl–、HCO3–）循环促进活性物种ClO•生成，实现了焦化废水生物出水中的生物难降解有机物和硝酸盐同步去除。例如，在37.5 mA cm–2的电流密度下，选择PbO2及Cu-Zn为阳极和阴极，经6小时电解，可从焦化废水生物出水中去除87.8%的COD（起始浓度228 mg L−1）和86.5%的总氮（起始浓度76 mg L−1）。揭示了铁电絮凝与电氧化耦合、H2O2与电产活性氯耦合实现酚类废水中污染物高效去除及氯代副产物削减机制，通过原位光谱/色谱/理论计算，为电化学原位产生活性氯物种转化为Fe(IV)以及1O2提供证据。提出了高反应活性及稳定性电极材料表面改性与合成方法，阐明了金属电极表面自活化/自重构理论及其作用于废水中硝氮定向转化成氨机制。从反应器及阳极材料设计两个层面提出了将HO•转化为氯自由基策略，用以强化氨氮到氮气选择性转化，实现总氮高效去除。项目的顺利开展，为电化学技术应用于实际工业废水生物出水深度处理提供理论支撑，为节能、高效性电极材料及电化学反应器设计、构筑和运行提供技术借鉴。