全天候吸附辅助光催化及光电催化同步氧化NO和Hg净化电厂尾气的关键技术和科学问题研究

Power plants release a great amount of NO and Hg in sweep gas due to combustion of nitrogen or Hg compounds in coals and the direct combination reaction between N2 and O2 in air at high temperature, which may cause severe damage of the ecological banlance, society development and human body health.. The traditional technologies for removing NO and Hg, including adsorption, microbion technology, catalytic reduction, decomposition and oxidation, usually display disadvantages of high cost and secondary pollution. Photocatalytic oxidation of Hg and NO to easily recyclable NO2 and HgO is promising way for cleaning sweep gas owing to the low cost and less secondary pollution. However, some key probplems should be considered. (1) The Hg and NO are very stable against oxidation, especially at very low concentration, leading to poor phtocatalytic efficiencies.(2) The oxidation of Hg results in HgO, which will cover the photocatalysts and thus decrease their activity. (3) The NO oxidation mainly produces NO2. When it is adsorbed in water, NO will be re-produced, which will obviously reduce the photocatalytic efficiency and also cause the secondary pollution in air. (4) In the daytime, the efficiency of using solar lights is very poor. However, in the night, the photocatalysis can not proceed due to the absence of light irradiation. .This proposal addresses the design and application of novel photocatalysts combined with both adsorption and electrocatalysis and new reactors contained both solar batteries and UV lamps for synchronical removal of NO and Hg in sweep gas of power plants. The adsorbent can rapidly fix and enrich NO and Hg from gas, followed by photocatalytic oxidation. The electrophotocatalysis may greatly enhance the pohotocatalytic efficiency even at very low bias voltage (< 0.4 V). Meanwhile, the synchronical Hg and NO oxidation results in Hg(NO3)2, which can be easily recycled by water washing. It can avoid the formation of NO2 ang HgO,and thus may diminish secondary pollution of NO from NO2 adsorption in water and also avoid the photocatalyst deactivation due to HgO coverage. Futhermore, the batteries can transfer the excess solar energy to electricity, which can drive the electrophotocatalysis and also turn on the UV lights for promoting photocatalytic activities by transfering the sunlights into UV lights and also realizing round-the-clock photocatalytic oxidation of NO and Hg by supplying UV light irradiation in night. .This research involves in materials, photocatalysis,and reaction engineering, all of which are covered by Li and Zhang groups. The two groups have been involved in this collaborative effort for about one year. The team effort can push it forward at a level exceeding that possible for group alone.

以净化电厂尾气为目标，设计含吸附剂的光电催化剂和带太阳能电池板及紫外灯的光催化反应器，进行协同光催化同步氧化Hg和NO，着重解决以下问题：(1)通过吸附和光电催化相结合，克服NO和Hg难氧化，提高光催化效率；(2) 同步氧化Hg和NO产生易溶于水的Hg(NO3)2,可避免生成的NO2在被吸收时产生的NO引起二次污染和难溶于水的HgO覆盖光催化剂导致失活；(3)通过太阳能电池板可把过剩光转化为电能，一方面可驱动光电催化，另一方面，可开启紫外灯，把太阳光转化为短波长紫外光源，提高光催化活性，并在夜间提供紫外灯光照，实现全天候光催化。主要研究内容包括新材料设计、结构裁剪和表面化学修饰以及构效关系阐述,光催化反应器设计和多技术匹配优化，NO和Hg同步光催化氧化光生电子和空穴的综合利用、 吸附与光催化以及光电催化的协同效应研究等，期望发展光催化技术和创新光催化理论，为大气污染控制开辟新途径

在自然科学基金（批准号：21237003）的资助下，针对本项目提出全天候吸附辅助光催化或光电催化同步氧化气相NO 和Hg，高效一步法净化电厂尾气，解决当前人们普遍关注的大气污染问题，通过项目组成员的集体努力，申请书中所列研究计划的要点已基本完成。本项目分析了目前光催化处理气相污染物应用中的瓶颈问题，在光（电）催化剂的设计、光催化全天候反应器的开发、光催化理论方面入手，在微观方面制备了多种具有微观光陷阱结构和可见光激发特性的光催化剂，并对其在同步氧化NOx和Hg方面的构效关系进行了研究，解决了同步光催化氧化NO和Hg过程中，光生电子和空穴的协同利用问题，促进烟气中难以脱除的NO和Hg向着易于脱除的NO2和Hg2+转化，在可见光照射下，光电协同催化NO的去除率达80 %以上；在宏观提出了协同效应促进光（电）催化的构思和实施，包括设计了、光催化氧化-还原偶合体系、吸附-光催化复合体系、植物-吸收辅助光催化反应装置、带太阳能电池板的全天候光（电）催化反应器等，并开发了新型高效吸附剂及其喷射技术与装置，对烟气汞脱除效率在85 %以上，并对NOx、SO2均有良好脱除效果，实现多种污染物联合减排。受本项目资助，已发表与本项目相关SCI源论文123篇，IF>5的文章65篇，已申请专利42项，其中授权24项。共培养了10名博士研究生，24名硕士研究生。项目研究过程中项目组成员参加了国内外各种学术会议，并邀请国内外知名专家进行指导，组织课题组成员到国内外知名高校和研究所参观学习，举办了2016光催化中青年学者论坛暨中国感光学会光催化专业委员会会议等。依托本项目，发展了光驱动污染控制催化剂合成方法学与组装生长机理研究、光驱动污染控制催化剂结构组成调控及其促进光利用的研究；光驱动污染控制协同效应及其促进电荷分离的研究，为推动化学、材料和环境学科发展，推广光催化在环境净化中的应用做出了重要贡献，相关研究项目获上海市自然科学奖一等奖。