REACTIVE MEMBRANES FOR SIMULTANEOUS SALT REJECTION AND CONTAMINANT TRANSFORMATION

Conventional membrane treatment technologies, such as nanofiltration and reverse osmosis, effectively remove salts and large contaminants. However, they struggle to eliminate small, neutral organic contaminants, such as pharmaceuticals and industrial chemicals, that persist in water sources and pose risks to human health and the environment. Reactive nanofiltration membranes offer a promising solution by integrating chemical reactions into the membrane process, enabling simultaneous contaminant transformation and salt rejection.

Our research group employs both experimental and theoretical approaches to design and optimize catalytic nanofiltration membranes that enhance water purification efficiency. Experimentally, we have developed a novel membrane fabrication method that integrates polymer and complexation chemistry to anchor transition metal catalysts within polymer membranes. These catalysts drive advanced oxidation reactions, effectively breaking down contaminants into non-toxic byproducts. The membrane’s nano-sized pores not only ensure high salt rejection but also prevent secondary contamination from reaction byproducts, such as sulfate, thereby maintaining the safety and purity of treated water. Furthermore, the confined environment within these nanopores enhances catalytic activity, leading to more efficient contaminant degradation. Additionally, the selective rejection of interfering species (e.g., natural organic matter) enables precise contaminant transformation by creating spatial separation between target contaminants and interfering species.

To guide the rational design and operation of reactive nanofiltration membranes, we also employ a mechanistic modeling approach. Our simulations assess the performance of various catalytic membranes under different operating conditions, providing insights into key transport processes and reaction dynamics. Through systematic analysis, we have identified optimal catalyst loading strategies that balance catalytic efficiency while preventing excessive catalyst use. Additionally, we propose performance metrics to comprehensively evaluate membrane effectiveness in terms of contaminant removal, chemical utilization efficiency, and long-term operational stability. Our research also explores different oxidants and catalysts, assessing their ability to generate reactive species tailored for specific water treatment applications.

The development of reactive nanofiltration membranes represents a significant step forward in water purification, offering a dual-function solution that not only removes salts but also actively transforms pollutants. By integrating catalytic reactions within nanofiltration membranes, our work paves the way for more efficient, sustainable, and adaptable water treatment technologies that address emerging water quality challenges. Through our interdisciplinary approach, we aim to advance membrane science and engineering, contributing to cleaner and safer water for communities worldwide.

RESILIENT POLYESTER MEMBRANES FOR HIGH-PERFORMANCE DESALINATION

Reverse osmosis is one of the most widely used technologies for desalination and advanced water purification, relying on thin-film composite membranes to achieve high salt rejection. These membranes are typically made from aromatic polyamide materials, which have been the industry standard for over two decades due to their effective separation performance and relatively high energy efficiency. However, a major drawback of these membranes is their susceptibility to degradation when exposed to chlorine, a disinfectant commonly used in water treatment processes. Chlorine exposure leads to the breakdown of the polyamide selective layer, significantly reducing membrane lifespan and performance. As a result, chlorine must be removed before desalination through chemical dechlorination steps, such as the addition of sodium bisulfite, adding complexity, cost, and maintenance requirements to water treatment operations.

Recent research has explored alternative membrane materials that maintain high desalination performance while offering improved chemical resilience. One promising approach is the development of polyester-based membranes, which provide high water permeability and strong rejection of key contaminants, including sodium chloride and boron. Unlike traditional polyamide membranes, polyester membranes exhibit complete resistance to chlorine-induced degradation, eliminating the need for extensive chlorine pre-treatment. This advancement simplifies desalination processes, reducing operational costs and extending membrane lifespan.

The development of chlorine-resistant membranes represents a significant breakthrough in desalination technology, improving the durability and long-term efficiency of RO systems. By reducing the need for pre-treatment chemicals and maintenance, these innovations could lead to more cost-effective and sustainable water purification methods. As global water scarcity intensifies, the continued advancement of high-performance, chemically resilient membranes will play a crucial role in ensuring a reliable and affordable supply of clean water.

HIGHLY SELECTIVE MEMBRANES FOR PRECISE ION SEPARATION

As global demand for critical metals such as lithium, cobalt, and nickel continues to rise, there is an urgent need for sustainable and efficient separation technologies. Conventional extraction and recycling methods, such as solvent extraction and precipitation, are energy-intensive, chemically demanding, and often environmentally harmful. Membrane-based separation technologies offer a promising alternative, providing enhanced selectivity and energy efficiency. However, the challenge remains in designing membranes capable of distinguishing between chemically similar metal ions with high precision.

Our research focuses on developing advanced membrane materials that leverage the tunability of metal-organic frameworks (MOFs) and principles of coordination chemistry to achieve high selectivity in metal ion separations. MOFs, with their well-defined porosity and customizable chemistry, provide a unique platform for designing membranes with tailored interactions for specific metal ions. By fine-tuning linker chemistry and functional groups, we systematically enhance ion binding affinity and selectivity, addressing a key limitation in current membrane technologies.

Beyond structural modifications, we incorporate coordination chemistry principles to engineer membranes that mimic biological ion channels, where selective binding interactions drive efficient ion transport. By integrating MOFs with functionalized polymeric layers, we create hybrid membranes that combine molecular recognition with precise ion transport mechanisms. This approach significantly enhances ion selectivity and enables separation processes that are more energy-efficient and environmentally sustainable.

The impact of this work extends to resource recovery, clean energy production, and environmental remediation. Developing scalable and selective membrane technologies enhances metal recycling, reducing reliance on primary mining and minimizing environmental damage. By advancing the molecular understanding of ion selectivity, our research provides a foundation for designing next-generation membranes adaptable to critical separations, such as water purification, battery recycling, and industrial wastewater treatment. These innovations support the global shift toward a circular economy and sustainable resource management.

Selected Publications

1. Ma, Wen, Meng Sun, Dahong Huang, Chiheng Chu, Tayler Hedtke, Xiaoxiong Wang, Yumeng Zhao, Jae-Hong Kim, and Menachem Elimelech. “Catalytic membrane with copper single-atom catalysts for effective hydrogen peroxide activation and pollutant destruction.” Environmental Science & Technology 56, no. 12 (2022): 8733-8745. DOI: https://doi.org/10.1021/acs.est.1c08937
2. Yao, Yujian, Pingxia Zhang, Fei Sun, Wen Zhang, Meng Li, Gang Sha, Long Teng et al. “More resilient polyester membranes for high-performance reverse osmosis desalination.” Science 384, no. 6693 (2024): 333-338. DOI: 10.1126/science.adk0632
3. DuChanois, Ryan M., Mohammad Heiranian, Jason Yang, Cassandra J. Porter, Qilin Li, Xuan Zhang, Rafael Verduzco, and Menachem Elimelech. “Designing polymeric membranes with coordination chemistry for high-precision ion separations.” Science Advances 8, no. 9 (2022): eabm9436. DOI: 10.1126/sciadv.abm9436
4. Violet, Camille, Akash Ball, Mohammad Heiranian, Luis Francisco Villalobos, Junwei Zhang, Betul Uralcan, Heather Kulik, Amir Haji-Akbari, and Menachem Elimelech. “Designing membranes with specific binding sites for selective ion separations.” Nature Water2, no. 8 (2024): 706-718. DOI: https://doi.org/10.1038/s44221-024-00279-6