自偏压光电法引发氯自由基高效处理氨氮废水并产氢的研究

The large amount of ammonia nitrogen wastewater has been discharged into water body, causing water eutrophication and severe pollution. However, traditional ammonia nitrogen treatment methods have some drawbacks, such as time-consuming, instability and high-cost. Based on the advantage of breakpoint chlorination method in fast and efficient removal of ammonia nitrogen, the project proposed a new concept that using self-bias photoelectric induced chlorine radical instead of hypochlorous acid to oxidize ammonia nitrogen into nitrogen gas for high efficient treatment of ammonia-nitrogen wastewater and simultaneously hydrogen generation. The project will prepare high active, stable and visible light response Fe2TiO5/BiVO4 heterojunction photoanode and high active MoS2 cathode, then combine them with Si PVC to construct a self-bias photoelectrochemical system to treat ammonia nitrogen wastewater. Through exploring the reaction characteristics of chlorine radical and active chlorine on the electrode surface, the project will discover the mechanism of using chlorine radical and active chlorine for the removal of ammonia nitrogen and establish the corresponding adjustment method. The project combines the advantages of both breakpoint chlorination method and photoelectrocatalysis method to develop a fast, high efficient and wide applicable removal of ammonia nitrogen from wastewater. This method only use solar energy and original chlorine in the wastewater to degrade ammonia nitrogen and generate hydrogen without additional chlorine gas and external bias potential.

氨氮废水进入水体会引起水体富营养化，造成严重水污染。常规氨氮生物处理技术存在着处理时间长、运行不稳定、成本高等问题。项目基于折点氯化法脱氮快速高效的特点，提出了利用自偏压光电催化技术引发氯离子形成氯自由基，以氯自由基替代次氯酸，氧化氨氮生成氮气，从而实现氨氮废水的高效处置并获取氢能的思路。项目通过满足氯自由基生成要求的高效、稳定、可见光响应的Fe2TiO5/BiVO4异质结光阳极材料的制备和高活性产氢MoS2阴极材料的制备，并利用PVC硅电极，构建自偏压光电化学体系处理氨氮废水，通过揭示电极表面氯自由基以及活性氯的反应特性及其与电极材料、反应器、反应体系间的关系，阐明氯自由基以及活性氯氧化氨氮脱氮的反应机制，并建立调控方法。本项目充分发挥了折点氯化法和光电催化法的优势，具有氨氮废水处理快速高效适用性广的特点，处理过程中只需提供太阳能，不需外加氯气和外加偏电压，所需氯离子来自废水,且能产氢

含氮废水的污染是水体富营养化的主要因素，是中国水环境保护的关键问题。但是目前脱氮主流技术，如生物法或者物理法还不能实现氨氮的有效脱除，前者的效率低，稳定性差；而后者的成本高，适应性低。自由基催化氧化是处理各类污染物有效的技术，对各类含氮物质降解具有普适性，但由于传统自由基催化（主要为羟基自由基•OH）选择性低，使得氨氮和硝态氮之间发生相互转化，成为了催化脱氮的瓶颈。半导体中产生的强氧化剂(光生空穴)很容易将氯离子(Cl-) 氧化成氯自由基(Cl•)，而它与富电子物质的反应速率(如NH4+)比•OH更快速，且NH4+向氮气的转化率显著提升。本项目发展的高稳定性WO3光阳极，首先构建了光电-氯自由基催化脱氨体系，实验表明氨氮氧化成氮气的选择性可提高到80%。针对剩余的硝态氮，继续开发制备了具有三维结构、可高效催化硝态氮还原为N2的Pd-Cu修饰泡沫Ni 阴极（Pd-Cu/NF）材料，将其与光电-氯自由基体系结合，最终实现了多种组分无机氮废水总氮去除率>98%。此方法独特之处在于，光阳极产生的Cl•将氨氮快速地转化为N2并形成少量硝态氮，而硝态氮被Pd-Cu/NF阴极选择性地还原为N2并形成微量的氨氮，氨氮进而继续被Cl•氧化，进入新的氧化还原反应，最终氨氮被耗竭循环脱除为氮气。该方法为催化完全脱氮提出了新思路，为各类含氮废水处理提供了新的解决方案。. 利用以上体系，研究了各类含氮废水如含氮有机废水，尿液，有机胺，反渗透浓缩液等，都实现了高效脱氮处理。利用此体系，也进一步发展了一种脱氮废水燃料电池，将含氮有机废水中的化学能转化为电能，在有机物降解脱氮的同时实现产电。如对含氮苯酚废水，脱氮率达到了98.7%，苯酚降解率达到了99.1%，并同时产生了1.23mW cm−2的电能。共发表相关SCI论文13篇，授权专利2项。