CAREER: Molecular Electrocatalysts and Reactive Separations for Wastewater Nitrogen Refining

氮（N）肥料的利用对于最大化农业和耕作中的作物产量以养活不断增长的世界人口至关重要。不幸的是，农业径流和废水处理厂释放的过量氮（硝酸盐）也导致了广泛的地下水污染和地表水系统中的营养富集，这一过程通常被称为富营养化。在氮有限的地表水系统，包括湖泊，河流和河口，富营养化已被证明会导致水质下降，氧气耗尽，水生生物群的损失，并发生有害藻类水华。这个CAREER项目的总体目标是探索利用电化学精炼从废水中回收硝酸盐，并将其转化为有价值的产品，如氨，这是氮肥的关键成分。为了推进这一目标，主要研究者建议将化学分离（膜）、电催化（硝酸盐还原反应）、工艺建模、技术经济分析（TEA）和生命周期评估（LCA）联合收割机和集成，以设计、开发和优化反应和分离系统，这些系统可以捕获、浓缩硝酸盐并将其从废水源转化为高纯氨。该项目的成功完成将通过产生新的基础知识和技术来促进硝酸盐污染的缓解并实现循环氮经济，从而造福社会。通过教育和培训，包括指导斯坦福大学的一名研究生，将为社会带来更多的好处。全球氮循环的管理被美国国家工程院确定为14大工程挑战之一。电化学精炼已经成为一种有前途的技术，以促进循环氮经济，因为它可以用来调整氧化态，运输，并将氮污染物从废水转化为有价值的产品，与现有的商业技术相比，成本可能更低，化学投入和排放减少。这个CAREER项目将研究废水中硝酸盐的电化学还原，以产生氨，氨是氮肥的关键成分。为了推进这一目标，主要研究者（PI）提出设计，合成，评估和优化一种新的均相分子催化剂[M（DIM）催化剂，其中M是位于二甲基配体（DIM）中心的过渡金属（Co，Fe，Mn，Cu，Ni）]，可以实现快速，选择性，廉价和节能的电化学硝酸盐还原为高纯氨。本研究的具体目标是：1）设计和合成分子M（DIM）催化剂，并阐明其在各种废水基质中的硝酸盐还原机理; 2）设计和工程化萃取系统，以从处理后的废水中分离催化剂及其反应产物（氨）; 3）设计，开发，优化电力驱动的反应和分离系统，这些系统可以集成到废水处理厂中，以回收硝酸盐并将其转化为高浓度的硝酸盐。高纯氨该项目的成功完成有可能通过产生新的基础知识来推动设计和开发更有效和更具成本效益的废水处理工艺和系统，以回收硝酸盐并将其转化为有价值的产品，从而产生变革性影响。为了实施这个职业项目的教育和推广活动，PI建议利用斯坦福大学现有的计划和资源，设计和启动一年一度的湾区电化学（BAE）训练营，以培训早期阶段的研究生电化学方法和循环水处理应用。此外，本发明还提供了一种方法，PI建议：1）制定和实施REU计划，并增加关于社会公平的研讨会，以招募和留住来自代表性不足群体的本科生; 2）设计和组织水-该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识产权进行评估来支持。优点和更广泛的影响审查标准。

The utilization of nitrogen (N) fertilizers has been critical to maximizing crop yields in agriculture and farming to feed a growing world population. Unfortunately, the release of excess N (nitrate) from agricultural runoffs and wastewater treatment plants has also led to widespread groundwater pollution and nutrient enrichment in surface water systems, a process commonly referred to as eutrophication. In nitrogen-limited surface water systems including lakes, rivers, and estuaries, eutrophication has been shown to cause a decrease in water quality, oxygen depletion, a loss of aquatic biota, and the occurrence of harmful algal blooms. The overarching goal of this CAREER project is to explore the utilization of electrochemical refining to recover nitrate from wastewater and convert it into valuable products such as ammonia which is a critical component of N fertilizers. To advance this goal, the Principal Investigator proposes to combine and integrate chemical separations (membranes), electrocatalysis (nitrate reduction reactions), process modeling, technoeconomic analysis (TEA), and life cycle assessment (LCA) to design, develop, and optimize reaction and separation systems that can capture, concentrate, and convert nitrate from wastewater sources to high purity ammonia. The successful completion of this project will benefit society through the generation of new fundamental knowledge and technology to advance the mitigation of nitrate pollution and enable a circular nitrogen economy. Additional benefits to society will be achieved through education and training including the mentoring of one graduate student at Stanford University. The management of the global nitrogen cycle has been identified as one of the 14 Grand Challenges for Engineering by the US National Academy of Engineering. Electrochemical refining has emerged as a promising technology to advance a circular nitrogen economy as it can be utilized to tune the oxidation states, transport, and conversion of nitrogen pollutants from wastewater to valuable products at potentially lower cost with reduced chemical inputs and emissions than existing commercial technologies. This CAREER project will investigate the electrochemical reduction of nitrate from wastewater to produce ammonia, a critical component of nitrogen fertilizers. To advance this goal, the Principal Investigator (PI) proposes to design, synthesize, evaluate, and optimize a new family of homogenous molecular catalysts [M(DIM) catalysts, where M is a transition metal (Co, Fe, Mn, Cu, Ni) at the center of a dimethyl ligand (DIM)] that could enable the rapid, selective, inexpensive, and energy-efficient electrochemical nitrate reduction to high-purity ammonia. The specific objectives of the research are to 1) design and synthesize molecular M(DIM) catalysts and elucidate their mechanisms of nitrate reduction in various wastewater matrices; 2) design and engineer extraction systems to separate the catalysts and their reaction products (ammonia) from treated wastewater; and 3) design, develop, and optimize electrically driven reactive and separation systems that could be integrated into wastewater treatment plants to recover and convert nitrate to high-purity ammonia. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge to advance the design and development of more efficient and cost-effective wastewater treatment processes and systems to recover and convert nitrate to valuable products. To implement the educational and outreach activities of this CAREER project, the PI proposes to leverage existing programs and resources at Stanford University to design and launch an annual Bay Area Electrochemistry (BAE) Bootcamp to train early-stage graduate students on electrochemical methods and circular water treatment applications. In addition, the PI proposes to 1) develop and implement an REU program augmented with seminars on societal equity to recruit and retain undergraduate students from underrepresented groups and 2) design and organize water-related science fair projects to engage and mentor high school students from underrepresented groups.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.