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Chemical and Biomolecular Engineering

Illinois engineers Kwiyong Kim, left, Professor Xiao Su, Johannes Elbert and Paola Baldaguez Medina are part of a team that developed a new polymer electrode device that can capture and destroy PFAS contaminants present in water. Photo by L. Brian Stauffer

Researchers have demonstrated that they can attract, capture and destroy PFAS – a group of federally regulated substances found in everything from nonstick coatings to shampoo and nicknamed “the forever chemicals” due to their persistence in the natural environment.

Using a tunable copolymer electrode, engineers from the University of Illinois at Urbana-Champaign captured and destroyed perfluoroalkyl and polyfluoroalkyl substances present in water using electrochemical reactions. The proof-of-concept study is the first to show that copolymers can drive electrochemical environmental applications, the researchers said.

The results of the study are published in the journal Advanced Functional Materials.

“Exposure to PFAS has gained intense attention recently due to their widespread occurrence in natural bodies of water, contaminated soil and drinking water,” said Xiao Su, a professor of chemical and biomolecular engineering who led the study in collaboration with civil and environmental engineering professors Yujie Men and Roland Cusick.

PFAS are typically present in low concentrations, and devices or methods designed to remove them must be highly selective toward them over other compounds found in natural waters, the researchers said. PFAS are electrically charged, held together by highly stable bonds, and are water-resistant, making them difficult to destroy using traditional waste-disposal methods.

“We have found a way to tune a copolymer electrode to attract and adsorb – or capture – PFAS from water,” Su said. “The process not only removes these dangerous contaminants, but also destroys them simultaneously using electrochemical reactions at the opposite electrode, making the overall system highly energy-efficient.”

To evaluate the method, the team used various water samples that included municipal wastewater, all spiked with either a low or moderate concentration of PFAS.

 “Within three hours of starting the electrochemical adsorption process in the lab, we saw a 93% reduction of PFAS concentration in the low concentration spiked samples and an 82.5% reduction with a moderate concentration spiked samples, which shows the system can be efficient for different contamination contexts – such as in drinking water or even chemical spills,” Su said.

Based on concepts first proposed in Su’s previous work with arsenic removal, the process combines the separation and reaction steps in one device. “This is an example of what we call processes intensification, which we believe is an important approach for addressing environmental concerns related to energy and water,” Su said.

The team plans to continue to work with various emerging contaminants, including endocrine disruptors. “We are also very interested in seeing how these basic copolymer concepts might work outside of environmental systems and help perform challenging chemical separations, such as drug purification in the pharmaceutical industry,” Su said.

Postdoctoral researcher Kwiyong Kim and graduate student Paola Baldaguez Medina are the lead authors of the study. Postdoctoral researchers Johannes Elbert and Emmanuel Kayiwa also contributed to the study.

The U. of I., the National Science Foundation and the Illinois Water Resources Center supported this study.

The paper “Molecular tuning of redox-copolymers for selective electrochemical remediation” is available online and from the U. of I. News Bureau. DOI: 10.1002/adfm.202004635.

Professor Xiao Su has been selected as a 2020 Scialog Fellow AND The ACS Division of Colloid and Surface Chemistry for the 2020 Viktor K. LaMer Award

Congratulations to Professor Xiao Su, who has been selected as a Scialog Fellow to participate in the 2020 Scialog: Negative Emissions Sicence (NES) Initiative, jointly sponsored by Research Corporation for Science Advancement (RCSA) and the Alfred P. Sloan Foundation. 

The Scialog fellowship invites around 50 early career faculty to participate in the initiatives. This year’s negative emissions theme (NES) covers the pressing challenge of rapid-decarbonization of the global economy, and involves a multidisciplinary input from  chemistry, physics, materials science, biology, engineering, and geophysics.

Xiao joined the Illinois faculty in 2019, and has since built an exciting research program on exploring molecular engineering for electrochemical separations and process intensification. His group focuses on understanding the fundamental principles of redox-systems, and discovering new supramolecular interactions for achieving higher molecular selectivity in separation processes. Areas of application include fine chemical purification, water purification, and environmental remediation.

Xiao received his BASc in Chemical Engineering from the University of Waterloo, Canada, and earned his PhD in Chemical Engineering from MIT.

Link to Award: https://rescorp.org/scialog/negative-emissions-science

The ACS Division of Colloid and Surface Chemistry for the 2020 Viktor K. LaMer Award

Professor Xiao Su is also the winner of the 2020 ACS Viktor K. LaMer Award from the Division of Colloid and Surface Chemistry. The ACS LaMer Award recognizes an outstanding PhD thesis accepted by a U.S. or Canadian University during the three year prior the award year.

The official LaMer award lecture will be presented in the 2021 ACS Colloids and Surface Science meeting.

Link to Award Announcement: https://colloids2020.blogs.rice.edu/2020-awards/

It takes a lot of energy to collect, clean and dispose of contaminated water. Some contaminants, like arsenic, occur in low concentrations, calling for even more energy-intensive selective removal processes.

In a new paper, researchers address this water-energy relationship by introducing a device that can purify and remediate arsenic-contaminated water in a single step. Using specialized polymer electrodes, the device can reduce arsenic in water by over 90% while using roughly 10 times less energy than other methods.

The findings of the new study are published in the journal Advanced Materials.

Professor Xiao Su, left, graduate student Stephen Cotty, center, and postdoctoral researcher Kwiyong Kim have developed an energy-efficient device that selectively absorbs a highly toxic form of arsenic in water and converts it into a far less toxic form. Photo by Fred Zwicky.

Arsenic is a naturally occurring element that enters aquifers, streams and lakes when water reacts with arsenic-containing rocks and is considered highly toxic, the researchers said. This is a global issue affecting more than 200 million people in 70 countries.

Not all arsenic is the same, said Xiao Su, a chemical and biomolecular engineering professor at the University of Illinois who directed the study. The most dangerous form of arsenic, known as arsenite, is highly reactive with biological tissues, but converts to a less toxic form, called arsenate, through a simple oxidation reaction.

“We can remove arsenite from water using absorbents, specialized membranes or evaporation, but these are all very energy-intensive processes that ultimately leave behind a lot of toxic waste,” Su said. “By having a device that can capture arsenite with a high selectivity and convert it to a less toxic form, we can reduce the toxicity of the waste while purifying the water.”

The proof-of-concept device works by integrating the contaminant separation and reaction steps within a single unit with an electrocatalytic cell – similar to a battery –using redox-active polymers. When the contaminated water enters the device, the first polymer electrode selectively captures the arsenite and sends it to the other polymer electrode, where it is stripped of two of its electrons – or oxidized – to form arsenate. Pure water then leaves the device, and the arsenate waste is concentrated for further disposal, Su said.

“The process is powered by electrochemical reactions, so the device does not require a lot of electricity to run and allows for the reuse of the electrodes based only on electrochemical potential,” Su said. “Combining the separation and reaction steps into one device is an example of what we call processes intensification, which we believe is an important approach for addressing environmental concerns related to energy and water – in particular, the amount of energy it takes to purify and remediate contaminated water.”

In addition to improved sustainability and energy efficiency, this elctrochemical approach has advantages for field deployment, the researchers said. Users can run the device using solar panels in areas where electricity is scarce – like in parts of rural Bangladesh, a country where over 60% of the population is affected by arsenic-contaminated water, the researchers said.

There are challenges to address before the device is ready for real-world implementation. “We need to increase the stability of the electrodes because this process will need to be cycled many times while running,” Su said. “We’re using very specialized, highly advanced polymer materials for the electrodes. However, we need to make sure we design them to be not only highly selective for arsenic, but also very stable and robust so that they do not need to be replaced constantly. This will require further chemical development to overcome.”

Su also is affliated with the Beckman Institute for Advanced Science and Technology at the U. of. I.

Postdoctoral researcher Kwiyong Kim and graduate student Stephen Cotty, both from the Su group, are the lead authors of the study. Professor Chia-Hung Hou, from the Graduate Institute of Environmental Engineering at the National University of Taiwan, collaborated with the U. of I. on this research.

The National Science Foundation and the U. of I. supported this research.

To reach Xiao Su, call 217-300-0134; email x2su@illinois.edu.

The paper “Asymmetric redox-polymer interfaces for electrochemical reactive separations: Synergistic capture and conversion of arsenic” is available from the U. of I. News Bureau. DOI: 10.1002/adma.201906877

Dr. Xiao Su, assistant professor in Chemical and Biomolecular Engineering, has been awarded a National Science Foundation Early CAREER Award for his work on developing new molecular separation processes for isomer separation.

The NSF’s Early Career Development Program’s CAREER Awards are prestigious and competitive awards given to junior faculty who exemplify the role of teacher-scholar through outstanding research, excellent education, and the integration of education and research within the context of the mission of their respective organizations.

Assistant Professor Xiao Su won an NSF CAREER Award
Assistant Professor Xiao Su

For this project, Su will explore electrochemical approaches to enhancing molecular selectivity in isomeric separations. Selective separation of biologically-active molecules from the liquid-phase can be one of the most expensive steps in pharmaceutical and biochemical manufacturing. Isomers are molecules that have the same atom composition but differ in structural arrangement, and enantiomers are isomers that are non-superimposable mirror images of each other. Isomeric purification can be an extremely difficult separation process.

More than half of drugs currently used in the US and worldwide have been enantiomers, including therapeutics for cancer, AIDS, neurologic diseases, and arthritis. While one enantiomer often provides superior clinical performance, the opposite enantiomer can be potentially toxic. Su seeks to develop new isomeric separation processes based on electrochemically-mediated interactions for more efficient and sustainable purification of small molecules.

“I am truly excited to receive the NSF CAREER award, which will enable new directions in my research group on rational design of electrodes, and enantioselective separations. The project strongly aligns with our vision to bring electrochemical approaches to fine chemical separations, and provides an opportunity to connect fundamental chemistry concepts with chemical engineering applications,” Su said. “I am also very excited to start our proposed outreach activities, through all the educational resources here at Illinois.”

Su’s project is entitled “CAREER: Molecular Design of Electrochemically-Mediated Systems for Isomeric Separations.” The NSF CAREER award will provide five years of support for the project and a number of integrated outreach activities. For outreach, he plans to collaborate with the University of Illinois Center for Innovation in Teaching and Learning and the International Programs in Engineering to develop new programs for improving engineering undergraduate education, strengthening K-12 outreach, and promoting international exchange.

Xiao Su joined the department as an assistant professor in January 2019. He received his PhD in Chemical Engineering from the Massachusetts Institute of Technology in 2017, and conducted his postdoctoral research there. His research group explores the supramolecular engineering of electrochemical interfaces, with a focus on molecularly-selective separations, functional materials discovery and process intensification.

Congratulations, Dr. Su!

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