(4p) Designing Nanoscale Hybrid Materials for Reactive Separation of CO2 and Critical Elements to Build a Sustainable Future | AIChE

(4p) Designing Nanoscale Hybrid Materials for Reactive Separation of CO2 and Critical Elements to Build a Sustainable Future

Research Interests

My research focuses on the fundamental understanding of novel nanoscale hybrid materials in natural and engineered systems and the investigation of reactive separation technologies for sustainable energy and material recovery and utilization pathways. In particular, I work on one of the most difficult challenges faced by humanity, climate change, and seek to improve the overall sustainability of the ways that we harvest and use energy and resources by integrating carbon capture, utilization, and storage (CCUS) schemes with resource recovery from solid wastes. By creating a new circular economy of elements, we will be able to address climate change as well as other environmental impacts caused by both historical and modern societies.

The research program that I will establish focuses on three distinct, but closely related topics aimed at closing the carbon and other elemental cycles targeting sustainable energy and materials. As a ‘platform’ technology, my research will aim to design and synthesize nanoscale hybrid materials for reactive separations, while tuning chemical and structural properties for targeted functionalities. Nanoparticle Organic Hybrid Materials (NOHMs – my Ph.D. research) and Metal-Organic Frameworks (MOFs – my postdoc research) are two great examples of emerging nanoscale materials on which I will focus.

I will develop next-generation nanoscale hybrid materials for the following two grand challenges: CO2 capture and conversion, and recovery of critical elements from natural or waste streams, while focusing on the understanding of their coupled kinetic and transport behaviors. First, I plan to design magnetic MOF/zeolite composite adsorbents to capture CO2 from humid ambient air under cold temperature conditions (unconventional, rarely studied, extreme conditions). The embedded magnetic nanoparticles inside the adsorbents can be heated by applying an alternating current magnetic field. The targeted heat generation via magnetic induction will make the adsorbent heating process isolated and thus it will directly facilitate CO2 desorption, make the process more energy efficient. With unique hybrid adsorbent materials coupled with remote electromagnetic heating, direct air capture (DAC) under extreme conditions will become economically viable. I also plan to encapsulate nanoscale sorbent materials (e.g., NOHMs and MOFs) and catalysts in a single carrier (e.g., particulate systems) for combined CO2 capture and conversion. The unique encapsulation design will allow the delivery of captured CO2 to the catalytic active sites and reduce the overall energetics of CO2 capture and conversion to value-added products.

The second grand challenge on which I would like to focus is the recovery of critical materials (e.g., rare earth elements) from wastes (e.g., alkaline industrial wastes, waste-to-energy ashes, iron and steel slags, electronic wastes including batteries and wind turbines). Unlike conventional mining and separation processes, the recovery of metals and critical elements from these waste streams is greatly challenged by the heterogeneity of the feedstock and competition between metal ions. Thus, I plan to develop a new class of NOHMs, MOF composites, and zeolite composites that can be magnetically separated after capturing the target metals. This technology will eliminate the need for energy-intensive liquid-liquid separation steps and will allow stepwise reactive separation of critical elements in complex solutions.

My Ph.D. research under Prof. Ah-Hyung Alissa Park at Columbia University and my current postdoctoral research under Prof. Christopher W. Jones and Prof. Ryan P. Lively at the Georgia Institute of Technology have ideally positioned me to pursue these research goals. During my Ph.D., I focused on coupled kinetic and mechanistic studies of elemental extraction from silicate minerals and alkaline industrial wastes for CO2 utilization. In this study, I designed a unique internal grinding reactor system to enhance diffusion-limited elemental extraction behaviors. The integration of 29Si MAS NMR and dissolution kinetic studies on silicate minerals and industrial wastes was critical to identify the underlying mechanisms of elemental extraction and reactivity of silicate materials. I also performed research to develop hybrid CO2 capture materials based on encapsulation of highly viscous CO2 capture solvents for direct air capture and point-source CO2 capture. The solvents have been encapsulated by a highly CO2-permeable polymer shell and the capture kinetics were significantly improved by increasing the interfacial area. This research aimed to optimize the encapsulation method for CO2 capture solvents and develop a fundamental understanding of mass transfer and chemical reaction in ternary gas (CO2) – liquid (solvents) – solid (polymer shell) systems.

My current postdoctoral research focuses on the synthesis and characterization of zeolites and amine impregnated hybrid MOF materials for direct air capture. Their CO2 adsorption behaviors, including equilibrium and kinetic CO2 capture experiments, as well as the competitive adsorption of CO2 and moisture, have been investigated under a wide range of temperatures and relative humidities to cover an array of global deployment locations for DAC technologies. These works have expanded my expertise in adsorption and separations processes, as well as MOF synthesis and characterization.

Teaching Interests

I believe that strong fundamentals are the first set of qualifications for chemical engineers to become rational leaders who will contribute to solving future engineering-related challenges in industry and academia. During my graduate and post-graduate training, I have had many opportunities to teach and mentor both undergraduate and graduate students. One of my mentees, who is a female Black student, is currently pursuing her Ph.D. in Chemical Engineering at UC Berkeley, and another undergraduate mentee (another female student) co-authored a referred journal article with me. Teaching someone to critically think about research problems and develop solutions to research challenges was a great experience and I feel passionately about building my career around these activities. I particularly enjoyed mentoring students from varied backgrounds because I often learned from them in the process, as well. I have derived personal satisfaction from mentoring students from disadvantaged or underrepresented groups and seeing their growth as researchers, leaders and people. In addition to teaching experiences as a teaching assistant, my advisor, Prof. Alissa Park, gave me a number of opportunities to give guest lectures in her classes (e.g., Particle Technology). I learned how to prepare lecture materials with insightful points of discussion to encourage class participation and watching students gain the confidence to actively participate in the in-class activities. Both individual mentoring and classroom teaching were very rewarding experiences for me.

Chemical engineers are generally described as ‘problem solvers,’ and engineering-related challenges we will face in the future are highly complex. Thus, engineers should be creative and know how to develop better solutions by collaborating with people from different fields of research. For this reason, problem-solving sessions that encourage students to think on their own and to share their ideas via spontaneous in-class discussions are a major part of my classes. By sharing different creative ideas from each student, the students will uncover varied approaches to the given problem, providing a menu of solutions to the problems they face. Additionally, I frequently use open-ended questions to trigger the scientific curiosity of students and inspire them to think outside the box, providing hopefully unlimited possible solutions to problems. I also emphasize to my students that being able to convey one’s vision to others (communication), valuing the opinions of others (being a good listener), handling conflicts professionally (self-awareness), and stepping up as a leader when it is necessary are important traits of a good engineer and team player.

To effectively teach students the fundamentals of chemical engineering, I will utilize drawings, pictures, or schematic comparisons to convey complex concepts and to motivate and engage them. In addition to learning about the scientific/engineering theory, students must know how the fundamental knowledge they learn during class is applied in practice to build a strong engineering intuition. I, therefore, try to have lab sessions along with normal classes to show them how the theory and equations are utilized in the lab. The hands-on lab session makes students fully understand the scientific theory and its application. Due to my strong background in chemical engineering, I will be able to teach most chemical engineering courses, including Mass Transfer, Thermodynamics, and Chemical Reaction Engineering. I would also like to develop a graduate level class on “Reactive Separations for Sustainable Energy and Materials.”