About

Xiao Su is an Associate Professor in Chemical and Biomolecular Engineering at the University of Illinois, Urbana-Champaign. He obtained his Bachelor in Applied Sciences in Chemical Engineering from the University of Waterloo in 2011 and completed his PhD in Chemical Engineering from MIT in 2017. During his doctoral studies at MIT, he worked under the supervision of Professor T. Alan Hatton from Chemical Engineering and Professor Timothy F. Jamison from Chemistry. His doctoral research focused on electrochemically-mediated water purification, for which he received the MIT Water Innovation Prize and the MassCEC Catalyst Award. Since joining the University of Illinois, Xiao Su has been recognized with several prestigious awards including the NSF CAREER Award (2019), the ACS Victor K. Lamer Award (2020), the ISE-Elsevier Prize for Green Electrochemistry (2021), the ACS Unilever Award (2023), and the AIChE FRI/John G. Kunesh Award (2023). His research focuses on molecular engineering for advanced separations and process intensification.

Research topics

• Chemistry
• Materials science
• Organic chemistry
• Inorganic chemistry
• Chemical engineering
• Combinatorial chemistry
• Nanotechnology
• Physical chemistry
• Metallurgy
• Biochemical engineering
• Process engineering

Selected publications

• Glucose-driven uncoupling of methanogenesis from acidogenesis to generate carboxylates in anaerobic digestion: Insights into microbial dynamics and operational parameters

  Biomass and Bioenergy · 2026-01-21

  articleOpen access

  Anaerobic digestion is a process for resource recovery used to produce biogas. However, research focus has shifted toward producing valuable carboxylates due to low natural gas costs. This study uncoupled methanogenesis from acidogenesis by adding glucose as an external carbon source to maintain low pH and enable stable carboxylate production in bioreactors inoculated with beef cattle waste. The central pattern observed involves glucose utilization converted predominantly to lactate or acetate inhibiting methanogenesis. Shorter retention times (5 vs. 20 days) increased total acid production (53.5 vs. 49.7 g/L), especially lactate and butyrate, while recirculation changed acid profiles toward acetate (about 30–60 % increases). Adjustment of pH from acidic (pH 4.0) to neutral (pH 6.5) enhanced total acid accumulation (up to 58.0 g/L) with acetate as a dominant product, whereas lactate production significantly decreased by about 80 %. Chemical oxygen demand analysis also showed improved carbon conversion with recirculation and pH adjustment, which highlights their role in enhancing carboxylate yields. Microbial community analysis revealed Bacillota (49.4–63.8 %) – Bacilli (33.9–64.7 %) – Bacillus (4.3–35.8 %) as the predominant taxa. Lactic acid bacteria played an important role in early lactate production. Methanogens were detected early, indicating successful inhibition of methanogenesis in later phases. Network analysis further identified Clostridia and Dysgonomonas as major contributors to acetate production and linked Lactiplantibacillus to lactate accumulation. These findings highlight operational parameters in carboxylate profiles and microbial dynamics during anaerobic fermentation with glucose as an external carbon source. We suggest that this mechanism would also apply to any other soluble, rapidly fermented carbohydrate substrate source. • This study aims to uncouple methanogenesis and improve carboxylate yields instead. • Shorter retention time increased total acid production, favoring lactate and butyrate. • Recirculation shifted acid profiles towards increased acetate production by 30–60 %. • pH from acidic to neutral enhanced total acid accumulation with increased acetate and decreased lactate. • Network analysis identified Clostridia and Dysgonomonas as key acetate producers, linking Lactiplantibacillus to lactate.

  PublisherDOI

• Challenges and Opportunities in PFAS Waste Management for Semiconductor Manufacturing

  Environmental Science & Technology · 2026-01-14 · 2 citations

  articleSenior authorCorresponding

  Semiconductor manufacturing is rapidly expanding alongside tightening environmental regulations and increasing public concern around per- and polyfluoroalkyl substances (PFAS). Because of their unique chemical properties, PFAS are used across numerous processes in semiconductor manufacturing. Given process complexity and lengthy development timelines for alternatives, eliminating PFAS use in this industry is not currently feasible. Developing practical technologies for PFAS waste management is therefore critical but uniquely challenging in semiconductor manufacturing due to the nature of waste streams (parts-per-billion PFAS concentrations, complex backgrounds including hundreds of chemicals, prevalence of ultrashort PFAS, total stream volumes up to 35,000 m3 per day per facility, and distribution across gas, liquid, and solid phases) and significant constraints on space and systems redesign. This review describes recent developments and key questions that must be addressed to develop impactful and commercially viable detection and abatement methods for PFAS waste management in semiconductor manufacturing. Integrating these technologies into compact, high-performance systems and testing them under realistic conditions (complex PFAS mixtures, high fluoride/ionic strength, pH 6–11, low contact time, process variability) through industrial collaborations is essential for scalable, cost-effective solutions. Research addressing semiconductor industry-specific PFAS waste is essential to enable environmental compliance while supporting the continued growth of semiconductor manufacturing.

  PublisherDOI

• Selective Recovery of Cerium over Lanthanum Using Alternating Current Electro-Precipitation for Sustainable Rare Earth Elements Separation

  ECS Meeting Abstracts · 2025-07-11

  articleSenior author

  Rare earth elements (REEs), particularly cerium (Ce) and lanthanum (La), play a critical role in modern technologies but face significant supply challenges due to limited resources and increasing demand. Traditional separation technologies, such as liquid-liquid extraction and ion exchange, often struggle with low selectivity and high waste generation. In this study, we developed a novel alternating current (AC) electro-precipitation strategy to selectively recover cerium from lanthanum in multicomponent waste streams. By leveraging the redox activity of Ce and the distinct solubility differences between Ce and La oxides, our approach enables efficient separation while minimizing chemical consumption. The proposed electrochemical system uses alternating anodic and cathodic currents to selectively deposit CeO₂, a stable and insoluble tetravalent oxide, while facilitating the dissolution of La hydroxides. Optimization of key parameters, such as current density, frequency, and solution pH, allowed for the selective recovery of Ce with a purity exceeding 90%. Further validation was achieved using iron slag leachates as a real-world feedstock, where Ce recovery reached up to 88% after pH adjustment. The system also demonstrated practical applicability in terms of energy and cost analysis, offering a sustainable and scalable solution for REE recycling. This work highlights the potential of AC-driven electro-precipitation for addressing the challenges of REE separation and recycling, paving the way for sustainable supply chain solutions.

  PublisherDOI

• Developing Equivalent Circuit Models to Understanding of the Impact of Fabrication on Performance of Capacitive Deionization System with Ferrocene Coated Electrodes

  ECS Meeting Abstracts · 2025-11-24

  article

  Polyvinyl ferrocene (PVF) is a polymer with high selectivity for valuable materials such as gold and rhenium as well as aqueous pollutants such as arsenic and phosphate. Capacitive deionization (CDI) systems incorporating PVF have demonstrated significant capacitance and metal selectivity. According to technoeconomic analysis (TEA) calculations, selectivity, capacitance, and longevity are essential for high-performance electrodes, requiring balanced optimization across all three aspects. However, the longevity and total electrode capacitance of PVF-coated electrodes remain critical challenges to practical applications, and the mechanisms underlying capacitance decay require further investigation. In this study, an equivalent circuit model was developed to characterize faradiac and electric double layer (EDL) contributions to capacitance and analyze the decay of capacitance and Faradaic behavior during extended cycling tests. The model incorporates both resistive and capacitive components of carbon-based EDL systems alongside Faradaic charge-transfer elements for the ferrocene coatings. The Faradaic current component was simulated with Nernst equation and charge balance principles. Calibration was achieved using experimental data from electrodes with different PVF-activated carbon (AC) coating ratios. Electrodes were prepared by applying PVF:AC slurries (ratios of 1:2 and 1:20) onto carbon paper substrates. PVF:AC electrodes were also coated with deacetylated Chitosan (CS) to evaluate the potential for aminated biopolymers to mitigate PVF loss and extend electrode lifetime. SEM imaging confirmed slurry adhesion to the substrate and revealed PVF overloading in the 1:2 ratio coating. The hybrid EDL-faradiac equivalent circuit could be accurately calibrated to all electrode fabrication and operation conditions (R² > 0.999). Calibrating EDL and faradaic contributions to current revealed that electrode composition significantly affected the distribution of EDL and faradaic capacitance. For the PVF:AC = 1:2 electrode, the mass of AC, which contributed to the double-layer capacity, is similar to PVF, where the mass contributions of PVF and AC were comparable, the electrochemical (Faradaic) capacity dominated, with a double-layer to Faradaic capacity ratio of approximately 1:1.5. In contrast, the PVF:AC = 1:20 electrode exhibited a strongly EDL-dominated behavior, with a ratio of approximately 6.1:1, indicating the dominant role of double-layer storage in anion adsorption. Equivalent circuit modeling also enabled quantification of active PVF surface loading changes across cycles. Calibrated declines in ferrocene surface loading concentrations aligned with the capacitance decay observed experimentally. Notably, the model indicated that incorporating chitosan effectively prevents PVF loss during charge-discharge cycles. For the PVF:CNT = 1:20 electrode, chitosan coated AC:PVF electrodes had significantly higher capacitance retention than non-coated electrodes, increasing from 51.0% without CS treatment to 88.4% with CS treatment after 2,000 cycles. However, for the redox-dominant PVF:AC = 1:2 electrode, CS had limited benefit for electrode duration, with retention values of 32.7% (with CS) and 29.5% (without CS). Furthermore, the CS-treated PVF:AC = 1:20 electrode preserved 43.5% of its electrochemical capacity and 86.4% of its EDL capacity after 2,000 cycles, compared to just 2.3% and 65.1%, respectively, for PVF:AC = 1:20 electrode without CS treatment. This study demonstrates the value of equivalent circuit modeling in understanding electrochemical processes and optimizing electrode fabrication and performance. These findings provide critical insights for designing more durable and efficient PVF-based electrodes in CDI systems, paving the way for broader applications in resource recovery and water treatment.

  PublisherDOI

• Redox-Active Crown Ether Copolymer for Selective Lithium Recovery from Spent Lithium-Ion Batteries

  ACS Energy Letters · 2025-09-01 · 2 citations

  articleSenior authorCorresponding

  The increasing demand for lithium, alongside concerns over resource scarcity and supply chain risks, has driven the need for alternative lithium sources, particularly from spent lithium-ion batteries (LIBs). Here, we introduce a redox-active crown ether copolymer designed for highly selective and electrochemically reversible lithium recovery from organic LIB leachates. A lithium-selective moiety, (12-crown-4)methyl methacrylate (12C4MA), is combined with a redox-active moiety, ferrocenylpropyl methacrylamide (FPMAm), into a redox copolymer electrosorbent to replace acid-based regeneration with electrostatic repulsion. The redox response enhances lithium ingress into the polymer, doubling lithium uptake (0.58 molLi/molCrE) and enabling electrochemical regeneration upon the FPMAm oxidation. Our system exhibits exclusive lithium uptake, even in complex leachates containing competing metals (e.g., iron, nickel, and cobalt) and organic degradants. Techno-economic analysis highlights high energy efficiency and competitive lithium pricing to the market value (∼$12.7 per kgLi). Overall, our work demonstrates a scalable, electrified adsorbent platform for sustainable and chemical-free critical metal recovery.

  PublisherDOI

• <i>(Invited)</i> Modular Electrochemical Separations for Scalable Critical Element Recovery

  ECS Meeting Abstracts · 2025-11-24

  article1st authorCorresponding

  Separation processes are critical to mining and mineral processing, through the concentration and purification of valuable elements. Maximizing metal recovery while reducing water and chemical usage are central goals within a range of mining contexts, especially within the context of in-situ resource utilization related to space applications. Electrochemical approaches provide a pathway sustainable mining through renewable-electron driven metal recovery. Molecular selectivity is a central challenge for separation processes in mining, requiring detailed fundamental understanding and control of complex interfacial and colloidal interactions at multiple scales. To overcome these limitations, we pursue the molecular design of electrochemically-responsive interfaces for the selective recovery of critical elements. We explore these tunable electrosorbent platforms for the recovery of transition metal oxyanions, noble metals, and rare-earth elements, and discuss electrochemical engineering pathways for scalable and modular deployment. Finally, we present a perspective in which electrochemical purification processes can synergistically integrate within a sustainable mining framework, by coupling with upstream ore extraction, beneficiation, and sustainable hydrometallurgical techniques. On the long-term, we expect these advances in molecular separations to be directly relevant in space engineering.

  PublisherDOI

• MoO3--assisted MXene-derived TiO2/C-graphene composite structure for high-capacitance electrode materials of ionic liquid-based supercapacitors

  Journal of Energy Storage · 2025-08-15 · 3 citations

  article
  PublisherDOI

• Molecular Design of Highly-Nitrate Selective Electrosorbents by Controlling Polymer Solvation Properties

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  Selective capture of nitrate is a critical process for water purification and resource circularity. 1 The major challenge of developing selective adsorbent and membrane materials towards nitrate has arisen from similar physical properties between nitrate and competing anions such as chloride. 2 Redox active polymers with nitrogen-containing functional groups such as polyaniline (PANI) have shown promising nitrate adsorption capacities (1.13 mmol/g polymer ) but with limited nitrate selectivity (α NO3/Cl = 3.2). 3 To extend beyond the nitrate selectivity of the conventional redox polymers, we propose a novel material design to separate nitrate based on their solvation properties. In this work, we design functional polyaniline redox-polymers as highly selective electrosorbents towards nitrate by controlling the polymer surface hydrophobicity through synthetic functionalization. We elucidated the mechanisms behind the exceptional nitrate selectivity through a combination of ab initio molecular dynamics (AIMD) and in-situ electrochemical quartz crystal microbalance (EQCM) studies. The hydrophobicity of the alkylated PANIs reduces chloride binding, thus enhancing electrosorptive selectivity towards nitrate. Through technoeconomic analysis (TEA), we report a 50% lower estimated nitrate removal costs using PNMA electrode compared to the scenario using non-functional PANI due to enhancement of selectivity and uptake, and a corresponding decrease in energy consumption per nitrate ion removed. Cho, K.-H.; Chen, C.-Y.; Aguda, A.; Fournier, M. J.; Su, X., Toward sustainable electrochemically mediated separations driven by renewable energy. Joule 2024 . Tsai, S.-W.; Wu, M.-C.; Ng, H. Y.; Hou, C.-H., Advancing the Electrosorption Selectivity of Nitrate Through Fine-Tuning Hydrophobic Ammonium Functional Groups in Anion Exchange Membranes for Membrane Capacitive Deionization. ACS ES&amp;T Water 2024, 4 (12), 5598-5607. Kim, K.; Zagalskaya, A.; Ng, J. L.; Hong, J.; Alexandrov, V.; Pham, T. A.; Su, X., Coupling nitrate capture with ammonia production through bifunctional redox-electrodes. Nature Communications 2023, 14 (1).

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• Tailoring Selectivity in Redox-Copolymers for the Electrochemical Recovery of Platinum Group Metals from Complex Feedstocks

  Environmental Science & Technology · 2025-07-29

  articleSenior authorCorresponding

  Platinum group metals (PGMs) are essential for growing energy applications, and with declining ore grades and the complexity of feedstocks, efficient separation processes for PGM recovery and purification are needed. Redox-copolymer electrosorbents were developed for the selective recovery of PGM chloroanions from ores processed via flotation and leaching, as well as catalytic converters. An electrosorbent integrating a ferrocene redox moiety and a metal-affinity ligand achieved a separation factor >20 between palladium and platinum. Electrochemically assisted regeneration enhanced the release efficiency by >90% compared to a solely pH-driven ligand deprotonation. Thus, the combination of electrochemical stimulus with pH swings can reduce the overall load of chemical input when compared to a solely chemical regeneration. The redox-copolymer retained 90% of uptake capacity after over 300 cycles and demonstrated improved stability over the redox-homopolymer. Unlike processes that may require pH adjustment or alkaline precipitation, our approach achieves PGM uptake directly from highly acidic (pH ∼1) leachates from both ores and catalytic converters in the presence of excess transition metals and competing inorganic ions in solutions. A technoeconomic analysis demonstrated that Pt recovery becomes economically viable after only nine regeneration cycles, highlighting the cost-efficiency of the process. This work highlights redox-copolymers as a promising platform for metal recovery from complex feedstocks, with tunable selectivity, robustness, and regeneration.

  PublisherDOI

• <i>(Invited)</i> Neutron Reflectivity Studies of Fluoride Extraction and Separation from Aqueous Media Using Electrochemically Switched Polyaniline Films

  ECS Meeting Abstracts · 2025-11-24

  article

  Remediation strategies providing clean water for human consumption are a global challenge [1]. Industrial activity and agricultural practices are common sources of contaminants [2], but naturally occurring species can also be present at toxic levels, as exemplified by fluoride under certain geological conditions. The beneficial dental health effects of low levels of fluoride (0.5-1.0 mg/L.) are widely appreciated, but excessive amounts (&gt; 1.50 mg/L) are hazardous to health [3]. Fluoride analysis using ion selective electrodes is well established [4], but sustainable separation technologies are less well developed [5]. This presentation focuses on the latter aspect through electrochemically switched ion-exchange at polyaniline films. Previous studies involved use of the EQCM to study the total fluoride uptake of polymer and copolymer films derived from aniline and substituted derivatives [6]. Coulometric assays of film redox switching in monomer-free electrolyte provided the number of potential sites for fluoride interaction. Correlation with the corresponding film mass changes provided total solvent population changes. Co-monomer feedstock was found to have a significant influence on film absolute solvent population and redox-driven solvent population change [6]. It also affects the ease of fluoride uptake/release and, under certain conditions, can result in fluoride ion trapping. To extend the insights from the EQCM studies, we have undertaken neutron reflectivity (NR) measurements on electrodeposited polyaniline films exposed to aqueous electrolyte solutions, with a focus on fluoride-containing media. The strategy is to complement spatially integrated population data (for polymer, ions and solvent) from EQCM nanogravimetry with spatially resolved population data from NR. Species selectivity is provided by isotopic substitution, via (i) measurements on hydrogenous and deuterated polymer films, derived from h -aniline and d 5 -aniline, respectively, and (ii) exposure of both film types to H 2 O and D 2 O electrolyte solutions. From the above experiments, we report data for polyaniline films equilibrated in fully reduced and oxidised states when exposed to aqueous acid solution and neutral sodium fluoride solution. These static data are complemented by slow scan potentiodynamic measurements during film redox state switching. The potentiodynamic NR data will be correlated with the analogous EQCM data, for which temporal resolution is more straightforward but at the cost of no spatial resolution. For the first time, we also report progress on open circuit (no ion-exchange) isotopically labelled solvent displacement (H 2 O for D 2 O and vice versa ) using an HPLC pump system. Combination of the NR and EQCM data will be discussed in pursuit of design criteria for a sustainable electrochemically-controlled ion-exchange system suitable for fluoride extraction from natural waters. References [1] https://sdgs.un.org/goals/goal6 [2] P. Srimuk, X. Su, J. Yoon, D. Aurbach, V. Presser, Nature Reviews Materials, 5 (2020), 517. [3] WHO report WHO/CED/PHE/EPE/19.4.5 (2019). [4] G.A. Crespo, Electrochimica Acta, 245 (2017) 1023. [5] X. Su, Current Opinion in Colloid &amp; Interface Science 46 (2020) 77. [6] A. Unal, A.R. Hillman, K.S. Ryder, S. Cihangir, J. Electrochem. Soc. 168 (2021) 022502.

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Recent grants

• CAREER: Molecular Design of Electrochemically-Mediated Systems for Isomeric Separations

  NSF · $523k · 2020–2025

• Faradaic electrochemically-mediated processes for micropollutant remediation

  NSF · $360k · 2019–2022

Frequent coauthors

• T. Alan Hatton

  Massachusetts Institute of Technology

  32 shared

• Johannes Elbert

  University of Illinois Urbana-Champaign

  27 shared

• Nayeong Kim

  19 shared

• Kwiyong Kim

  Ulsan National Institute of Science and Technology

  14 shared

• Stephen Cotty

  University of Illinois Urbana-Champaign

  13 shared

• Raylin Chen

  University of Illinois Urbana-Champaign

  13 shared

• Jemin Jeon

  13 shared

• Jin Soo Kang

  Massachusetts Institute of Technology

  12 shared

Labs

• Su Research GroupPI

Education

• Ph.D., Chemical Engineering

  University of Illinois Urbana-Champaign

  2005

• M.S., Chemical Engineering

  University of Illinois Urbana-Champaign

  2002

• B.S., Chemical Engineering

  University of Science and Technology of China

  1999

Awards & honors

• ACS Analytical Division Satinder Ahuja Award in Separation S…
• DOE Early Career Award (2024)
• AIChE Separations Division FRI/John G. Kunesh Award (2023)
• Unilever Award Recipient (2023)
• Center for Advanced Study, Fellow (2022)