Mechanistic Studies of Water Disinfectants on Iron Interfaces

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Kathryn Perrine and her students will study fundamental chemical interactions between chloramine, a compound used for water disinfection, with iron, iron oxide, and iron carbonate surfaces. Disinfectants are used to treat pathogens in distribution water lines, but also react with natural organic matter to produce undesired byproducts that can make their way into ground water. (Mono)chloramine is a preferred oxidizing disinfectant since it produces fewer byproducts than other chlorine-containing disinfectants.

Iron, iron oxide, and iron carbonate surfaces are ubiquitous in the environment and present as minerals and iron-containing distribution lines. The surface adsorption mechanism and deactivation of chloramine on iron interfaces is not well understood. This project will investigate the surface chemical reaction and decomposition mechanisms of chloramine on well-defined interfaces.

These studies have the potential to advance our understanding of oxidation mechanisms in complex mixtures in aqueous systems that impact the effect of contaminants in water quality. Undergraduate students will experience summer research internships and precollege outreach activities. Students in grades 6-12 will participate in inquiry-based labs that will be developed as part of Michigan Tech’s summer youth programs.

These activities will focus on aqueous surface chemistry and corrosion, effects of pH on metal dissolution, and surface reactions at the liquid/solid interface.

The key objectives will be addressed on the kinetic adsorption and decomposition mechanism of chloramine on iron interfaces at the gas/solid interface on well-defined single crystal surfaces. The influence of the iron surface sites and hydroxyl sites from water and H2 dissociation will promote or block the chloramine reaction and decomposition pathways.

The adsorption of chloramine on iron at the liquid/solid interface will be measured using the PI’s new in situ polarized modulated infrared reflection absorption spectroscopy (PM-IRRAS) method at the air/liquid/solid interface to connect the surface mechanism under pristine conditions with realistic reactions in the condensed phase. Using novel surface analysis techniques that measure reactions at the gas/solid and liquid/solid interface, the research being conducted under this award, has the potential to impact areas across disciplines focusing on water resources and their purification, with societal implications associated with water sourcing, maintenance and management.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.