Photocatalytic Reduction of Nitrate in Water

光催化还原水中的硝酸盐

• 批准号: 1132779
• 负责人: Paul Westerhoff
• 金额: $ 29.8万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1132779&HistoricalAwards=false
• 关键词: Photocatalytic; Reduction; Nitrate; Water

1132779WesterhoffNitrate (NO3-) is one the most prevalent ground-water contaminants in North America and world-wide. It poses a risk to human health and has a large impact on the natural nitrogen cycle. Nitrate is regulated by the USEPA in drinking water because it is a known cause of methemoglobinemia, or ?blue baby? syndrome, and could possibly be a carcinogen or endocrine disruptor. Nitrate is a soluble ion that is difficult to remove by traditional coagulation or adsorption processes. Risks from oxidized pollutants are best mitigated through chemical or biological reduction to innocuous forms (e.g., N2 from NO3-). Photocatalytic reduction has been reported for decades, yet has not been investigated from an engineering approach for nitrate reduction. Research initiated by the discovery of Honda-Fujishima effect for photocatalytic water splitting (e.g., production of hydrogen as a renewable fuel) and subsequent advances in metal loading of semiconductors suggest that nitrate reduction in near neutral pH without addition of sacrificial agents is possible. Furthermore, it now appears possible that photocatalytic NO3- reduction in water could yield innocuous by-products (N2) instead of undesirable by-products that require additional treatment (e.g., ammonia). Photolysis for disinfection is commonplace in the drinking water industry over the past decade and use of light-based technologies for water treatment will continue to evolve because of their effectiveness, small size footprint, ability to operate without wastestreams, etc. Translational research from the fields of chemistry, material science and physics, where reductive photocatalysts are developed for splitting water, is proposed to be applied towards engineered technologies for nitrate removal from water. The PI?s preliminary data demonstrate the feasibility to photocatalytically reduce nitrate and yield gaseous-N by-products. The goal of this project is to explore and optimize the use of photocatalysts as a reductive technology for treating nitrate in drinking water applications. The underlying hypothesis is nitrate can be converted to innocuous aqueous species in drinking water applications using metal-loaded photocatalysts. The primary research objectives will be to: (1) Understand factors and mechanisms affecting NO3- reduction to N2 for different types of photocatalysts; (2) Apply photocatalyst for NO3- reduction in ion exchange brines and local groundwaters; (3) Investigate practical aspects of photoreactor operation (slurry and fixed film photocatalyst reactors) including role of catalyst ?aging? on catalyst performance in reducing NO3- and catalyst recovery; (4) Screen novel photocatalysts for nitrate and other oxo-anion reduction and develop a framework for selecting emerging photocatalysts for reduction of oxidized pollutants. The preferred outcome is to achieve nitrate treatment under ambient conditions (e.g., pH) and without the need of adding an organic hole scavenger.The project focuses on nitrate, the most prevalent groundwater contaminant in the USA and throughout many other parts the world. Managing the nitrogen cycle is one of the National Academy of Engineering Grand Challenges. Nitrate limits the use of the groundwater for potable purposes, and is a major cause of eutrophication in surface waters. The project will provide societal benefits as well as benefits to individual students. The primary intent is to disseminate knowledge and credible data on issues related to nitrate in drinking water and potential strategies to treat the water. Towards this end the team plans to organize sessions at conferences and develop an open-access website related to nitrate occurrence, health risks and treatment. The research will educate PhD students in environmental engineering and serve as a thesis topic for MS students at a non PhD-degree granting institution. The project will serve as a theme for several capstone senior projects, as part of a project oriented learning curriculum. This project also will support Obama Scholars at ASU (first-time underrepresented undergraduate student), such as a female Hispanic sophomore Civil Engineering student who has been instrumental in obtaining preliminary data for this proposal. Student(s) working on this project will participate in an experience in Washington, DC for 2 weeks where they will learn how science becomes policy.

1132779Westerhoff 硝酸盐 (NO3-) 是北美和世界范围内最普遍的地下水污染物之一。 它对人类健康构成风险，并对自然氮循环产生很大影响。 美国环保局对饮用水中的硝酸盐进行监管，因为它是导致高铁血红蛋白血症或“蓝婴”的已知原因。综合征，并且可能是致癌物或内分泌干扰物。 硝酸盐是一种可溶性离子，很难通过传统的混凝或吸附工艺去除。 氧化污染物的风险最好通过化学或生物还原为无害形式（例如，NO3- 中的 N2）来降低。 光催化还原已被报道数十年，但尚未从硝酸盐还原的工程方法进行研究。 由发现光催化水分解的本田-藤岛效应（例如，生产氢气作为可再生燃料）以及随后在半导体金属负载方面取得的进展而发起的研究表明，在接近中性 pH 值的情况下不添加牺牲剂的硝酸盐还原是可能的。 此外，现在看来，光催化还原水中的 NO3 可能会产生无害的副产品 (N2)，而不是需要额外处理的不良副产品（例如氨）。 过去十年来，光解消毒在饮用水行业中很常见，基于光的水处理技术的使用将继续发展，因为其有效性、占地面积小、无需废水流即可运行等。各领域的转化研究化学、材料科学和物理学的交叉学科，其中开发用于分解水的还原光催化剂，建议应用于从水中去除硝酸盐的工程技术。 PI 的初步数据证明了光催化还原硝酸盐并产生气态氮副产品的可行性。 该项目的目标是探索和优化光催化剂的使用，作为处理饮用水应用中硝酸盐的还原技术。 基本假设是，在饮用水应用中，使用负载金属的光催化剂可以将硝酸盐转化为无害的水性物质。 主要研究目标是：（1）了解不同类型光催化剂影响NO3还原为N2的因素和机制； (2)应用光催化剂还原离子交换卤水和当地地下水中的NO3-； (3) 研究光反应器操作（浆料和固定膜光催化剂反应器）的实际问题，包括催化剂老化的作用？催化剂还原NO3-的性能和催化剂回收； （4）筛选用于还原硝酸盐和其他含氧阴离子的新型光催化剂，并开发用于选择用于还原氧化污染物的新兴光催化剂的框架。 首选结果是在环境条件（例如 pH 值）下实现硝酸盐处理，且无需添加有机空穴清除剂。该项目重点关注硝酸盐，这是美国和世界许多其他地区最普遍的地下水污染物。 管理氮循环是美国国家工程院面临的重大挑战之一。 硝酸盐限制了地下水用于饮用水的用途，并且是地表水富营养化的主要原因。 该项目将为社会效益以及学生个人带来好处。 主要目的是传播有关饮用水中硝酸盐问题的知识和可靠数据以及潜在的水处理策略。 为此，该团队计划在会议上组织会议，并开发一个与硝酸盐发生、健康风险和治疗相关的开放访问网站。 该研究将为环境工程博士生提供教育，并作为非博士学位授予机构硕士生的论文主题。 该项目将作为几个顶点高级项目的主题，作为项目导向学习课程的一部分。该项目还将支持亚利桑那州立大学的奥巴马学者（首次代表性不足的本科生），例如一名西班牙裔女二年级土木工程学生，她在获得该提案的初步数据方面发挥了重要作用。 从事该项目的学生将在华盛顿特区参加为期两周的体验，在那里他们将了解科学如何成为政策。