过氧化氢预氧化零价铁强化还原去除水中Se(VI)机理研究

Advanced treatment of selenium-bearing effluents is in great demand to satisfy the stringent emission standards. It is difficult to remove selenate through adsorption or ion-exchange in the presence of coexisting anions. In contrast, chemical reduction by zero-valent iron (ZVI) is regarded as an effective route to remove selenate from water. However, the passivation of ZVI remarkably limited its application in water treatment processes. In this proposal, ZVI is subjected to pre-oxidation by hydrogen peroxide to be partially converted to reactive species such as ferrous ion and magnetite, which could enhance the reduction of selenate by ZVI by forming a synergistic system to increase the electron efficiency. Our preliminary study showed that superior efficiency of selenate reduction by ZVI was achieved via pre-oxidation using hydrogen peroxide in comparison with that by simultaneous oxidation. The pre-oxidation strategy is efficient and promising in practical application. Therefore, it is important to investigate the underlying mechanism and to develop the regulation principle to tailor the reactivity of the pre-oxidation system. The objectives of this proposal include: (1) to systematically elucidate the relationship between the conditions of the pre-oxidation reaction and the composition of the pre-oxidation products, (2) to explore the reactive species in the pre-oxidation products and the their synergistic mechanism behind the enhanced selenate reduction, and (3) to establish the method to regulate the reactivity of the pre-oxidation system. Thus, this program is believed to provide technological route and theoretical basis for enhanced removal of selenate through reduction by ZVI.

含硒废水需经深度处理以达到严格的排放标准，在大量阴离子共存条件下，Se(VI)难以通过吸附或离子交换去除。零价铁还原除Se(VI)是一种有效的处理方法，但零价铁的钝化失活严重限制了其工程应用。为克服这一瓶颈问题，本项目拟通过过氧化氢预氧化，将部分零价铁转化生成亚铁和四氧化三铁等活性物种，形成多元复合体系协同还原去除水中Se(VI)，从而强化零价铁的反应活性，提高电子效率。预研结果表明过氧化氢预氧化相比于同步氧化更为高效，作为强化零价铁除Se(VI)的新方法具有良好的应用前景，其内在机制与调控方法具有十分重要的基础意义，有待深入研究。本项目拟系统研究过氧化氢预氧化零价铁反应条件与产物体系组成的关系，揭示预氧化产物体系有效活性物种及强化除Se(VI)的协同机制，建立过氧化氢预氧化强化零价铁除Se(VI)的调控方法，为高效强化零价铁还原除Se(VI)提供技术路径和理论依据。

含硒废水需经深度处理以达到严格的排放标准，在大量阴离子共存条件下，Se(VI)难以通过吸附或离子交换去除。零价铁还原除Se(VI)是一种有效的处理方法，但零价铁的钝化失活严重限制了其工程应用。为克服这一瓶颈，项目开发了通过H2O2/HCl快速预氧化腐蚀高效活化零价铁的方法，形成以零价铁、水合氧化铁(HFO)、Fe3O4和Fe2+为主要活性成分的悬浊液态复合试剂，基于该复合试剂发展了高效去除水中Se(VI)的方法；阐明了硫酸盐共存体系下复合试剂中HFO强化预吸附Se(VI)作用是其有效还原Se(VI)以及提高零价铁电子效率的主要原因，Se(VI)的还原主要由具有较强还原活性的表面结合态Fe(II)介导，Se(VI)的去除主要是经由吸附态Se(IV)最终被还原为Se0的过程；考察了预处理反应条件与溶液化学条件对多元复合体系除Se(VI)性能的影响，发展了过氧化氢预腐蚀强化零价铁还原除Se(VI)的调控方法。基于颗粒零价铁填充柱反应器，项目研究了H2O2强化颗粒零价铁固定床中Se(VI)的时间空间演化规律。构建填充柱流动式反应器，探讨了电化学耦合零价铁强化还原的特性与机理。针对悬浊液态试剂不便于储存和运输问题，项目基于H2O2/HCl预氧化腐蚀零价铁的主要固相活性物种，扩展开发了球磨复合铁基固态还原剂的制备和应用方法。为解决零价铁还原Se(VI)耗时长的问题，项目拓展开发了亚硫酸盐/UV/Fe(III)混凝组合工艺除Se(VI)技术，阐述了相关工作机理，该技术处理富含硫酸盐的Se(VI)溶液、含多种共存阴离子的模拟废水和实际冶炼废水，Se(VI)去除速率较H2O2/HCl零价铁法提高6倍以上，实现了从富含硫酸盐的水中高效快速去除硒酸盐。针对硒污染地区水源水中Se(VI)微污染问题，发展了面向固定床反应器的负载型零价铁深度除Se(VI)技术，出水达到饮用水相关标准。本项目为强化零价铁还原及高效除Se(VI)水处理新工艺开发提供理论基础与技术借鉴。.围绕上述研究，本项目在Water Research等SCI期刊发表论文12篇，申请国家发明专利3项（其中已授权2项），培养研究生4名，如期完成了研究目标和各项研究任务，并丰富扩展了相关研究内容。