RII Track-4: Superparamagnetic Iron Oxide Nanoparticles as Recoverable Microwave Susceptors for Pre-hydrolysis of Waste Activated Sludge prior to Anaerobic Digestion

在美国，城市污水处理厂每年产生650万公吨的剩余污泥。这些剩余污泥的运输和处置占废水处理总成本的一半，每年超过20亿美元，每年稳定增长1%。稳定废弃污泥的一种常见做法是在处置之前进行厌氧消化（AD）。该技术可以被描述为在没有游离氧的情况下将污泥微生物转化为沼气。AD产生的沼气是一种有价值的绿色燃料，其热值与天然气相当。 此外，消化污泥在AD之后变得更容易运输和处置。尽管有这些环境和经济优势，但AD具有长的反应时间和低的工艺产率。即使在20-30天的停留时间内，污泥分解也不完全，留下35-45%的污泥未消化。该项目利用活性极强、可回收的磁性氧化铁纳米颗粒（或超顺磁性氧化铁纳米颗粒）来提高污泥消化效率，提高工艺的经济效益和环境效益。这个RII Track-4：NSF项目旨在最大限度地减少与剩余污泥管理相关的成本和环境影响。 该奖学金将在耶鲁大学化学与环境工程系进行，并包括对研究生实习生的支持。超顺磁性氧化铁纳米颗粒（SPION）是突破性的纳米材料，在众多行业中具有显着的应用潜力。SPION可以快速有效地响应磁畴，而没有显著的剩磁。此外，它们可以在微波（MW）照射下快速加热。它们的特性使它们成为污泥预处理应用的有前途的候选者。首先，它们有可能结合到污泥絮凝物组件的组件，并提供即时和强烈的MW加热战略细胞或胞外聚合物。MW辐射产生振荡电磁场，导致SPION的电偶极矩和磁矩旋转，产生内部振动，以局部热量的形式耗散能量。其次，由于它们的尺寸（通常为50 nm），SPION具有封装在微小物理域内的自旋电子，该微小物理域内可以响应磁场而没有剩磁（即，显示出顺磁性和铁磁性材料的性质）。因此，SPION没有磁滞的负担，这使得它们即使在复杂的反应器装置中也能有效和快速地从浆料中回收。这项研究的主要优点是，SPION属性可以策略性地调整为上级介电加热和磁反应性，同时保持材料的完整性，以实现重复使用的MW预处理。 通过这个RII Track-4：NSF奖学金，PI旨在开发一种实用技术，将定制和使用SPIONS作为介电和可回收的催化剂，用于MW诱导的废水污泥预水解。首先，PI和一名毕业实习生将学习高级SPION合成的协议。接下来，该团队将专注于至少三种SPION，这些SPION在顺磁能力，MW加热和重复使用的材料完整性方面表现出希望。最后，将优化废水处理工艺，并进行实验以确定水解途径，如温度、水化学、浆料粘度和羟基自由基形成的作用以及其他基本控制措施，以确保数据质量。 该奖学金将在耶鲁大学化学与环境工程系颁发。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Municipal sewage treatment plants generate 6.5 million metric tons of excess sludge every year in the United States. Transportation and disposal of this excess sludge comprise half of the total wastewater treatment cost, exceeding $2 billion per year with a steady 1% annual increase. A common practice to stabilize waste sludge is anaerobic digestion (AD) prior to disposal. This technology can be described as the microbial transformation of sludge into biogas in the absence of free oxygen. The biogas produced from AD is a valuable green fuel, and it has comparable calorific value to natural gas. Furthermore, the digested sludge becomes easier to transport and dispose of after AD. Despite these environmental and economic advantages, AD has long reaction times, and low process yields. Even under 20-30 days of retention, sludge decomposition is incomplete, leaving 35-45% of the sludge undigested. This project utilizes extremely reactive, recoverable magnetic iron oxide nanoparticles (or superparamagnetic iron oxide nanoparticles) to improve the efficiency of sludge digestion and improve the economic and environmental benefits of the process. This RII Track-4:NSF project aims to minimize the costs and environmental impacts associated with excess sewage sludge management. This fellowship will take place at Yale University within the Department of Chemical and Environmental Engineering and involves support for a graduate trainee.Superparamagnetic iron oxide nanoparticles (SPIONs) are ground-breaking nanomaterials with remarkable application potential in a multitude of industries. SPIONs can respond to magnetic domains rapidly and efficiently without significant remanence. In addition, they can heat rapidly under microwave (MW) irradiation. Their properties make them promising candidates for sludge pretreatment applications. First, they have the potential to bind to components of sludge floc assemblies and deliver immediate and intense MW heating strategically to cells or extracellular polymers. MW irradiation creates an oscillating electromagnetic field that causes SPIONs to have both their electrical dipole moments and their magnetic moments rotate, creating internal vibrations that dissipate energy in the form of heat locally. Second, due to their size (typically 50 nm) SPIONs have spin electrons packed within a minuscule physical domain that can respond to the magnetic field without remanence magnetism (i.e., showing properties of both paramagnetic and ferromagnetic materials). Therefore, SPIONs do not have the burden of magnetic hysteresis, which empowers their effective and rapid recovery from slurries even in complicated reactor installations. The key merit of this proposed study is that SPION properties can be strategically tuned for superior dielectric heating and magnetic reactivity while maintaining material integrity to accomplish repeated use for MW pretreatment. Through this RII Track-4:NSF fellowship, the PI aims to develop a practical technology that will tailor and employ SPIONS as dielectric and recoverable susceptors for MW-induced pre-hydrolysis of wastewater sludges. First, the PI and a graduate trainee will learn protocols for advanced SPION synthesis. Next, the team will focus on at least three SPIONs that show promise in terms of paramagnetic abilities, MW heating, and material integrity for repeated use. Finally, the process for wastewater treatment will be optimized, and experiments to identify hydrolysis pathways such as the role of temperature, water chemistry, slurry viscosity and formation of hydroxyl radicals and other basic controls will be conducted to ensure data quality. This fellowship will take place at Yale University within the Department of Chemical and Environmental Engineering.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.