电化学耦合反渗透膜系统中铵氧化行为对氨氮去除效率提升的机制探讨

Mechanism exploration of ammonium oxidation behaviors for improved ammonia nitrogen removal efficiency in electrochemically coupled reverse osmosis membrane systems

为提高反渗透膜系统对生活污水中氨氮的去除率,设计了一种新颖的电化学耦合反渗透膜系统。与传统反渗透系统相比,该系统通过创新性地将进料隔网和渗透载体进行导电化处理,并分别连接外部电源的负极和正极,施加电压以增强反渗透膜系统对氨氮的去除能力。结果表明,在4 V外加电压下,反渗透膜系统对氨氮的去除率从未施加电压下的94.51%提升到99.91%。这种增强的氨氮去除率不仅得益于反向电场力对铵根离子的拖曳作用,还得益于高电压条件下的铵氧化作用。通过循环伏安曲线、系列电解实验、电子自旋共振以及自由基猝灭实验,证明了该电化学耦合膜系统中的渗透载体RuO_(2)-IrO_(2)阳极在高电压条件下铵氧化反应的发生,其机制为氯介导的间接铵氧化反应,反应路径为断点氯化。同时,在氯介导的间接铵氧化反应过程中,证实了其活性物种为活性氯而非氯自由基。以上研究结果揭示了铵氧化行为对电化学耦合膜系统中氨氮去除升高的关键作用及其作用机制,为未来的污水资源化处理技术提供了新的理论基础。此外,该系统设计简单,易扩展,维护成本低,具有显著的实际应用潜力。

To enhance the removal rate of ammonia nitrogen in domestic wastewater by reverse osmosis(RO)membrane systems,a novel electrochemically coupled RO membrane system was designed.Compared with conventional RO systems,this system featured an innovative conductive treatment of the feed spacer and permeate carrier,which were connected to the negative and positive poles of an external power supply,respectively.The results indicated that with an applied voltage of 4 V,the ammonia nitrogen removal rate in the RO membrane system increased from 94.51%without applied voltage to 99.91%.This enhanced ammonia nitrogen removal rate was attributed not only to the drag force of the reverse electric field on ammonium ions but also to ammonium oxidation behaviors.Through cyclic voltammetry,a series of electrolysis experiments,electron paramagnetic resonance,and radical quenching experiments,ammonium oxidation behavior was demonstrated to occur at the permeate carrier anode under high applied voltages in the electrochemically coupled membrane system.The mechanism was identified as the chlorine-mediated indirect ammonium oxidation reaction with the breakpoint chlorination reaction pathway.Additionally,in the chlorine-mediated indirect ammonium oxidation process,the active species were found to be active chlorine rather than chlorine radicals.These findings revealed the crucial role and mechanism of ammonium oxidation behavior in the enhanced removal rate of ammonia nitrogen in electrochemically coupled RO membrane systems,thereby providing new theoretical foundations for future wastewater resource recovery technologies.Furthermore,this system offers a simple design,exceptional scalability,and low maintenance costs,highlighting its significant potential for practical applications.