PIs : Werth, Charles J. / Jawahar Hussaini, Syed Mubeen
Nitrate is the world's most ubiquitous groundwater pollutant, and its management is recognized as one of the Grand Challenges by the National Academy of Engineering. Catalytic treatment has emerged as a more sustainable option for nitrate removal from drinking water, but its implementation has been stymied by a lack of scientific knowledge and innovation in new materials that directly address challenges in reactor performance and scale-up. Specifically, nitrate treatment in scalable reactors is limited by hydrogen delivery to reactive catalysts sites. The PIs propose a high risk/high reward approach that is based on generating adsorbed atomic hydrogen in situ via electroactive catalyst supports. The overriding hypothesis is that atomic hydrogen can be electrolytically generated at the same (or directly adjacent to) site where nitrate reduction occurs, and this generation can be balanced with nitrate reduction to eliminate hydrogen mass transfer limitations, optimize hydrogen use, minimize energy consumption, and recover value-added resources, ammonium and chlorine. The specific objectives of the proposed work are: 1) To identify the fundamental bulk material and surface chemical properties responsible for the synthesis of carbon-based catalyst supports with high-electrical conductivity, metal dispersion, water permeability, and strength. 2) To elucidate reaction mechanisms and kinetics of coupled electrolytic hydrogen generation and nitrate reduction processes in batch and flow-through reactors, and to identify the fundamental properties of new catalytic materials that optimize these processes. 3) To evaluate the economic and environmental sustainability of a hybrid ion exchange - electrochemical reactor for nitrate removal from drinking water.
The proposed approach involves novel synthesis and electro/catalytic experiments that aim to elucidate structure/property correlations, reaction mechanisms, and optimal reactor conditions for efficient nitrate removal coupled with ammonia recovery from simulated drinking water, and an economic and environmental life cycle analyses of the technology coupled to ion exchange waste brine treatment and reuse that will serve as feedback for process optimization. Potential scientific advancements include: (i) foundational insights and structure-activity relationships to guide synthesis of new cathodic materials that efficiently generate hydrogen and reduce nitrate at catalytically reactive sites; (ii) the design of a novel electrolytic- based reactor that integrates these robust cathodic materials into a packed-bed flow system; (iii) integrated resource recovery of agriculturally valuable ammonium, as well as chlorine for catalyst fouling mitigation and water disinfection; and (iv) the development and dissemination of an integrated model that allows scale up for a cost and environmental impact assessment for new technology development. Proposed educational, outreach and engagement activities include using UT Austin's engineering open houses to expose junior high and high school students to engineering design for water treatment the development of a new teaching modules and dissemination to water utilities through an industry collaborator.
