Research

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We apply modern chemical research tools and techniques to develop more sustainable technologies for environmental and energy applications. We are currently developing technologies that employ innovative catalytic, hydrothermal, and photochemical processes to purify water, produce bio-renewable energy and chemicals, and recover valuable resources from waste streams. Prof. Strathmann, with more than 20 years of research experience, leads the research group’s efforts.

Current research projects include:

  • Developing innovative technologies to remediate groundwater contaminated by persistent and toxic fluorochemicals (e.g., PFOS, PFOA)
  • Valorizing waste streams through integrated biochemical-hydrothermal-catalytic conversion processes that produce liquid fuels, valuable industrial chemicals, and fertilizer
  • Advancing heterogeneous catalytic technologies for reduction of toxic oxyanion groundwater contaminants (e.g., nitrate and perchlorate)
  • Developing models that can be integrated into biorefinery systems optimization platforms to reduce production costs and life cycle environmental impacts of algae biofuels
  • Identifying the dominant mechanisms controlling the transformation of organic micropollutants of emerging concern (e.g., pharmaceuticals, flame retardants) in reclaimed wastewater systems

Innovative technologies for remediation of groundwater contaminated by toxic fluorochemicals

afff1Recent analyses show widespread occurrence of perfluoro and polyfluoroalkyl substances (PFAS) like PFOS and PFOA in drinking water sources throughout the country at levels exceeding the EPA’s lifetime health advisory levels. The contaminants result from use in consumer and industrial products, including aqueous film-forming foams (AFFF) used for fire suppression. These chemicals are highly recalcitrant, with no evidence of natural abiotic or biological degradation pathways. While the conventional technology for treating water contaminated by perfluorochemicals is activated carbon adsorption, this approach is inefficient and costly due to rapid breakthrough of shorter chain analogues from adsorber beds. In addition, activated carbon adsorption only acts to separate the contaminants from water, and the used carbon material requires disposal or further treatment.

afff2Our group has been conducting research on the application of innovative technologies for treating perfluorochemicals that leads to both their removal and destruction. Laboratory and field investigations are underway to study hybrid technologies that combine advanced separations processes (e.g., nanofiltration,  ion exchange) with photochemical treatment of the perfluorinated chemicals in the resulting concentrate streams. Destruction of PFASs can enable recycling of concentrates and lower costs and life cycle environmental impacts of treatment technology. Another new project is examining the application of hydrothermal treatment to destroy PFASs in site investigation-derived wastes (IDWs).  Application of high resolution mass spectrometry methods enables us to track fluorochemicals degradation within complex contaminant mixtures during treatment. The influence of groundwater geochemistry and structure-reactivity analyses are being coupled to develop process models, and laboratory experiments are being used to inform the design of a pilot-scale treatment system that will be deployed for field demonstration. The research is currently supported by the Department of Defense’s Strategic Environmental Research and Development Program (SERDP), the Air Force Civil Engineering Center (AFCEC), and the National Science Foundation’s Environmental Chemical Sciences Program. Collaborators include Chris Higgins (CSM), Chris Bellona (CSM), Charles Schaefer (CDM Smith), Shubham Vyas (CSM), Harold Wright (Carollo Engineers), Rula Deeb (Geosyntec Consultants), Lee Ferguson (Duke), and Ana Urtiaga (Univ. Cantabria, Spain).

Article on the cover of the Denver Post (Oct 27, 2016) describing the project and it’s contribution to addressing groundwater contamination in Colorado Springs area.

Press release about our project funded by the Air Force Civil Engineering Center.

Check out the following recent publications in this area:

  • J. Liu, D. Van Hoomissen, T. Liu, A. Maizel, X. Huo, S. Fernández, C. Ren, X. Xiao, Y. Fang, C. Schaefer, C. Higgins, S. Vyas, and T.J. Strathmann. (2018). Reductive Defluorination of Branched Per- and Polyfluoroalkyl Substances with Cobalt Complex Catalysts. Environmental Science & Technology Letters. 5, 289-294. 10.1021/acs.estlett.8b00122.
  • C.E. Schaefer, C. Andaya, A. Burant, C.W. Condee, A. Urtiaga, T.J. Strathmann, and C.P. Higgins. (2017). Electrochemical Treatment of Perfluorooctanoic acid and Perfluorooctane Sulfonate: Insights into Mechanisms and Application to Groundwater Treatment. Chemical Engineering Journal. 317, 424-432. http://dx.doi.org/10.1016/j.cej.2017.02.107

Integrated biochemical-hydrothermal-catalytic pathways for valorizing waste streamsmosesgc

Population growth and economic development are generating increased demand for new sources of energy and chemical precursors, while simultaneously producing growing quantities of waste. Concurrently, there is growing agreement that waste streams should be viewed as valuable resources rather than economic burdens. While anaerobic digestion technologies are mature and widely adopted for energy recovery from waste organic materials, the biogas product has low value in comparison to liquid fuels and higher value organic chemicals that can be produced from the same waste streams using alternative biochemical, thermochemical, and catalytic processes.

ht-catalysisOur group is working with collaborators at the National Renewable Energy Lab (NREL) to develop integrated pathways for optimizing valorization of wastewater. Our major approach applies hydrothermal and catalytic processing steps to convert tailored wastewater biosolids (e.g., lipid-rich algae, polyhydroxyalkanoate-rich microbial biomass) and waste-derived lipids (e.g., sewer trap grease) to liquid hydrocarbon fuels and other high value industrial chemicals (e.g., nylon precursor). Processing biosolids and waste lipids in their native wet state eliminates energy intensive drying steps and chemical-intensive extraction steps required of more conventional processing routes. Currently, we are working with collaborators in the ReNUWIt Research Center to evaluate the application of hydrothermal liquefaction/gasification to convert algal biomass harvested from wastewater treatment processes to liquid and gaseous fuels. We are also developing sequential hydrothermal + vapor-phase catalysis to fractionate, depolymerize, and chemically upgrade wastewater biosolids into high purity gasoline-range hydrocarbon fuels. This work is supported by the National Science Foundation’s Engineering Research Center for Re-inventing the Nation’s Urban Water Infrastructure (ReNUWIt) and the NSF CBET environmental engineering and environmental sustainability programs.  Collaborators include Jeremy Guest and B.K. Sharma (Univ. Illinois), Derek Vardon (NREL), Will Tarpeh and Kara Nelson (UC Berkeley), and Nirmala Khandan (New Mexico State).

Check out the following recent publications in this area:

  • D. Kim, D.R. Vardon, D. Murali, B.K. Sharma, and T.J. Strathmann. (2016). Valorization of Waste Lipids through Hydrothermal Catalytic Conversion to Liquid Hydrocarbon Fuels with In Situ Hydrogen Production. ACS Sustainable Chemistry and Engineering. 4, 1775-1784. http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.5b01768
  • J.G. Linger, D.R. Vardon, M.T. Guarnieri, E.M. Karp, G.B. Hunsinger, M.A. Franden, C.W. Johnson, T.J. Strathmann, P.T. Pienkos, G.T. Beckham. (2014). Lignin Valorization through Integrated Biological Funneling and Chemical Catalysis. Proceedings of the National Academy of Sciences. 111, 12013-12018. http://dx.doi.org/10.1073/pnas.1410657111

 


Heterogeneous catalytic technologies for reduction of oxyanion water pollutants

perchlorate-mechanismOxyanion contaminants, including nitrate (NO3), nitrite (NO2), perchlorate (ClO4), chromate (CrO42-), and bromate (BrO3), are among the most ubiquitous contaminants in aquatic environments, resulting from overuse of fertilizer, improper disposal of rocket fuel, industrial discharges, and even drinking water disinfection processes. Oxyanions are especially difficult to treat with conventional water and wastewater treatment processes because of their highly oxidized nature and poor removal during clarification processes.

syntheticcatalystOur team has been investigating the use of supported metal catalysts (e.g., Pd, Rh, Ru) for promoting reductive transformation of the oxyanions into inert byproducts like N2, Cl, and Br using H2 gas a reducing agent. Economic and life cycle analyses indicate that these processes can be competitive with current technologies if certain materials development benchmarks that we are working on can be met. Current efforts include development of hybrid treatment systems that couple catalysts with ion exchange processes. Ion exchange is effective for removing oxyanions from water, but concentrated waste brines are generated during regeneration of the spent resins; treatment of the waste brines by catalytic reduction can enable reuse of the brines, cutting both costs and effluent discharges of pollutants. We are also focusing on preparation of catalysts that substitute lower cost metals (e.g., Ni, Ru) in place of the Pd-based materials.Active nanoparticle structures can be tuned and functionalized to enhance reactivity and shift product selectivity. This work is currently supported by the National Science Foundation. Collaborators include Charlie Werth (University of Texas at Austin), Shubham Vyas (CSM), and Jinyong Liu (Univ. California Riverside).

Check out the following recent publications in this area:

  • X. Huo, J. Liu, T.J. Strathmann (2018). Ruthenium Catalysts for the Reduction of N-Nitrosamine Water Contaminants. Environmental Science & Technology. 52, 4235-4243. 10.1021/acs.est.7b05834
  • X. Huo, D.J. Van Hoomissen, J. Liu, S. Vyas, and T.J. Strathmann (2017). Hydrogenation of Aqueous Nitrate and Nitrite with Ruthenium Catalysts. Applied Catalysis B: Environmental. 211, 188-198. https://doi.org/10.1016/j.apcatb.2017.04.045
  • A.M. Bergquist, M. Bertoch, G. Gildert, T.J. Strathmann, and C.J. Werth. (2017). Catalytic Denitrification in a Trickle Bed Reactor: Ion Exchange Waste Brine Treatment. Journal of the American Water Works Association. 109, 5, E129-E143. http://dx.doi.org/10.5942/jawwa.2017.109.0055

 


Models for optimizing costs and life cycle impacts during algal biofuel production

model4Development of financially viable algal biorefineries has been limited, in part, to a lack of quantitative models linking design decisions in upstream cultivation to downstream processing needs and outcomes. Hydrothermal processing of algal biomass in its native wet state has also emerged as a promising pathway algal biofuel production. Our group is working with collaborators at the University of Illinois and the National Renewable Energy Lab (NREL) to formulate predictive models linking hydrothermal liquefaction product yields and characteristics directly to biochemical composition of algal biomass feedstocks (i.e., lipid, protein, and carbohydrate content). Our approach builds upon the concept of biochemical component additivity. Further, we are integrating this modeling approach for hydrothermal liquefaction with upstream microalgae cultivation models through a techno-economic analysis framework to provide system-scale optimization across the value chain of microalgae to fuel. This work is currently supported by the National Science Foundation through their CBET environmental engineering and environmental sustainability programs and the ReNUWIt Engineering Research Center. Collaborators include Jeremy Guest and B.K. Sharma (Univ. Illinois), Philip Pienkos, Ryan Davis, Tao Dong, and Lieve Laurens (NREL).

Check out the following recent publications in this area of our work:

  • Y. Li, S. Leow, A.C. Fedders, B.K. Sharma, J.S. Guest, and T.J. Strathmann (2017). Quantitative Multiphase Model for Hydrothermal Liquefaction of Algal Biomass. Green Chemistry19, 1163-1174. http://dx.doi.org/10.1039/C6GC03294J
  • S. Leow, J.R. Witter, D.R. Vardon, B.K. Sharma, J.S. Guest, and T.J. Strathmann. (2015). Prediction of Microalgae Hydrothermal Liquefaction Products from Feedstock Biochemical Composition. Green Chemistry. 17, 3584-3599. http://dx.doi.org/10.1039/C5GC00574D [ISI-IF = 6.828]

 


Degradation of organic micropollutants in reclaimed wastewater applications

usda1Our team is also actively studying the processes and mechanisms that control the fate and persistence of organic micropollutants of emerging concern (e.g., pharmaceuticals, flame retardants, antibiotics) present in reclaimed wastewater. Growing scarcity of water supplies, particularly in the southwestern United State, is leading more utilities to implement wastewater reclamation projects, often using reclaimed water for irrigation of food crops and turf. Better understanding of the abiotic and biological processes that contribute to degradation of trace organic micropollutants in soil and aquatic systems is needed to develop more accurate risk assessment models for the application of reclaimed wastewater. Our group is specifically focusing on studying the influence of anaerobic soil redox conditions on rates and pathways of organic micropollutant degradation. Sensitive and high resolution mass spectrometry methods are being used to monitor a suite of trace organic pollutants and identify major transformation products. In addition, we are studying the role that soil minerals play in promoting degradation of selected chemicals of concern. We have found that common soil minerals (e.g., iron oxides) can catalyze the rapid transformation of otherwise recalcitrant chemicals. At the usda2same time, our collaborators are studying the microbiome involved in degradation of important micropollutants in soil systems. This work is currently supported by USDA’s NIFA Program. Collaborators include Alison Cupples (Michigan State).

Check out the following recent publications in this area of our work:

  • Y. Fang, E. Kim, T.J. Strathmann. (2018). Mineral- and base-catalyzed hydrolysis of organophosphate flame retardants – A potential major fate-controlling sink in soil and aquatic environments. Environmental Science & Technology. 52, 1997-2006. 10.1021/acs.est.7b05911
  • J.-R. Thelusmond, E. Kawka, T.J. Strathmann, and A.M. Cupples. (2018) Diclofenac, Carbamazepine and Triclocarban Biodegradation in Agricultural Soils and the Microorganisms and Metabolic Pathways Affected. Science of the Total Environment. 640-641, 1393-1410. 10.1016/j.scitotenv.2018.05.403
  • J.R. Thelusmond, T.J. Strathmann, and A.M. Cupples. (2016). The Identification of Carbamazepine Biodegrading Phylotypes and Phylotypes Sensitive to Carbamazepine Exposure in Two Soil Microbial Communities. Science of the Total Environment. 571, 1241-52. http://dx.doi.org/10.1016/j.scitotenv.2016.07.154 [ISI-IF = 3.967]