THWRC Awarded Proposal 515UTA0053H

Project Number:       515UTA0053H

Title:                           Tailoring the Structure of Hydrogenation Catalysts to Transform the Economic and

                                      Environmental Sustainability of Nitrate Removal from Drinking Water

Lead PI:                     Charles Werth

Awarded Amount:    $50,000

ABSTRACT

Nitrate is the world’s most widespread groundwater contaminant, and is common in shallow aquifers located under agriculturally intense areas of land.  Nitrate is regulated because it causes methemoglobinemia in infants, and coverts in vivo to carcinogenic N-nitroso compounds.  The go-to technology for nitrate removal is ion exchange (IX).  It is efficient at nitrate removal from drinking water, but comes with a steep financial and environmental cost, primarily due to the large amounts of salt required for IX resin regeneration.  Alternative technologies are reverse osmosis and two emerging options: biological treatment and catalytic reduction.  Reverse osmosis is cost prohibitive for nitrate removal unless it is coupled with desalination.  Biological treatment is financially competitive, but concerns regarding turbidity, introducing pathogens, and erratic performance under varying conditions limit application.  Catalytic reduction of nitrate has emerged as a promising option, but greater catalyst activity is need to lower costs.

The primary goal of the proposed work is to develop an entirely new class of catalysts with sufficient nitrate reduction activity and selectivity to reduce current metal costs and environmental impacts for catalytic treatment by at least a factor of ten.  The specific objectives of the proposed work are the following: (1) To synthesize a new class of noble metal-based alloys with markedly higher activity for nitrate reduction per unit cost, (2) To evaluate the role of inexpensive but active catalyst supports on activity enhancement, (3) To determine the role of catalyst structure on selectivity for the end product N2, and (4) To evaluate the costs and environmental impacts of the new catalysts in cooperation with Calgon Carbon using cost and life cycle assessment. 

Our research methodology involves synthesis and characterization of individual and alloy metal nanoparticle catalysts, loading of these catalysts onto inert and redox active supports, testing of the catalysts for nitrate reduction activity and selectivity for the dinitrogen end product, and cost and environmental life cycle estimates of field reactors based on the improved catalysts. A suite of Pd- and Rh- based alloy nanoparticle catalysts will be synthesized using a novel microwave-assisted method recently developed by our collaborator, Dr. Simon Humphrey in chemistry.  The catalyst will be characterized for shape and size using transmission electron microscopy, metal content using ICP-MS, and dispersion onto supports using CO chemisorption.  Nitrate reduction activity and selectivity for dinitrogen in water will be evaluated in batch reactors sparged with hydrogen (electron donor) and maintained at a constant pH.  Financial and life cycle costs of integrating the improved catalysts into a field scale reactor will be evaluated with our partners Johnson Matthey and Calgon Carbon using the SimaPro software.

Our expected results are expressed by the following hypotheses: i) Pd and Rh-based alloys doped with Ag will show higher activity than pure Pd and Rh on a total metal basis for nitrate reduction, ii) active metal oxide supports will alter electronic properties of Pd and enhance catalytic activity, especially at Pd-metal oxide interfaces, and iii) greater catalyst activity and lower requirements for Pd/Rh metal will improve the cost and sustainability of nitrate treatment.  The total cost of the project is $50,000 over two years.  This will primarily be used to support a graduate research assistant, undergraduates, and some research supplies.