Research Project Full Title: Non-Precious Metal Substitution into Hydrogenation Metal Alloy Catalyst Deposited onto Redoc Active Supports for Facile Nitrate Destruction in Drinking Water
Principal Investigator(s): Charles Werth, Simon Humphrey, Graeme Henkelman
Researcher(s): Jacob Troutman, Chenxu Yan
Sponsor(s): National Science Foundation
Full Abstract: Overview: Hydrogenation catalysts are a critical component of modern life. They convert oil into gasoline, breakdown biomass intermediates into biofuel, create fertilizer from air, and aid in the synthesis of life-saving pharmaceuticals. However, they are surprisingly not used in drinking water treatment. Instead, we rely on decades-old technologies that reliably produce safe drinking water, but are expensive and have large negative environmental footprints. A prime example is ion exchange (IX) for oxyanion removal. It simply transfers this pollutant from water to another phase, and results in a concentrated waste stream that is disposed of in sewers, evaporation ponds, and coastal waters. The primary goal of the proposed work is to advance the science of supported metal-alloy catalyst activity and stability for disruptive treatment of the ubiquitous water pollutant and oxyanion nitrate (NO3-). The specific objectives are to (1) create new metal alloy nanoparticle catalysts with markedly higher catalytic activity for NO3- reduction, (2) identify electronically active supports that enhance catalytic activity and stability of alloy metal nanoparticles (MNPs) for water treatment, and (3) evaluate the environmental impacts and costs of the new catalysts using life cycle assessment, with a focus on ammonia (NH4+) recovery for agriculture reuse. To address the objectives, a suite of platinum group metal (PGM)-based alloy NPs with lattice substituted semi- and non-precious metal atoms (e.g., copper) will be synthesized using a novel microwave-assisted method, supported on a series of redox active supports, and characterized using advanced microscopic/spectroscopic techniques. The new catalysts will be evaluated without/with amended indium (In) for NO3- and nitrite (NO2-) reduction kinetics, and selectivity for NH4+. The results will be compared to catalyst properties, and interpreted with density functional theory calculations, to probe controlling mechanisms. Long-term catalyst stability will be evaluated under realistic water treatment conditions, and the results used to perform economic and environmental life cycle assessments.
Intellectual merits. The primary goal is to develop entirely new and never-before synthesized supported-alloy NP catalyst materials that will transform the state-of-practice with respect to water treatment. The current go-to removal technology for NO3- and NO2- in water is ion exchange (IX), which only transfers the pollutants from one phase to another and imparts high economic and environmental costs for regeneration. The new class of alloy MNPs will substitute non- and semi-precious metals into PGM lattices, and their activity and stability will be enhanced by anchoring to redox active supports. This would substantially decrease both their cost and environmental impacts. Additional intellectual merits include: gaining new fundamental knowledge regarding the effects upon overall catalytic activity when hydrogenation-inactive metals are incorporated into the lattice of platinum group metal nanocrystals; gaining a clearer fundamental understanding of the influence of redox active supports on alloy MNP activity and stability; and gaining a quantitative assessment of the effects of new supported-metal alloys on cost and sustainability of catalytic treatment systems for pollutants in drinking water.
Broader Impacts. This work will improve the economics and safety of NO3-/NO2- treatment in impacted water, and lead to a transformation in the water/wastewater industry for removing this high priority pollutant. This work will support one PhD student for three years, and an additional PhD student for one semester. The primary PhD student will participate in an NSF NRT INFEWS training program. Undergraduates will be recruited to work on the project from the Texas Research EXperience (TREX) Program, which targets students from underrepresented groups, and from the Graduates Linked with Undergraduates in Engineering (GLUE) program, which targets 2nd year female undergraduate students and provides them with a large support network and enrichment activities. The PIs will expand an NSF undergraduate international exchange program that was started in Chemistry by co-PI Humphrey to Civil Engineering. Students in this program will also be recruited to the project. The primary PhD student will mentor the undergraduate students. K-12 outreach efforts will involve preparing a water treatment interactive exhibit for ExploreUT, dubbed The Biggest Open House in Texas, and developing interactive water-treatment learning modules for elementary school summer camps in Austin and delivering them over each summer of the grant.