Synthetic Manganese Oxides for Oxidative and Catalytic Removal of Contaminants of Emerging Concern

Case Western Reserve University, Cleveland OH

Investigators

Abstract

This award is supported by the Environmental Chemical Sciences Program of the Division of Chemistry. Professors Huichun Zhang and Daniel Lacks of Case Western Reserve University and their students study the reactions of manganese oxide (MnOx) with emerging contaminants (ECs). There is a large variety of emerging contaminants - compounds that are increasing in our streams, rivers, lakes and oceans due to human inputs into wastewater streams. Contaminants of emerging concern include pharmaceutical and personal care products, fire retardants, and pesticides. Research is needed to determine if these compounds are harmful to human, animal and/or plant life. Conventional water treatment processes were not designed to remove ECs and their removal efficiencies are often insufficient. Among advanced treatment technologies, the use of MnOx is promising because these compounds are natural oxidants. Numerous synthetic MnOx are highly useful in applications such as energy production and chemical synthesis. Only a small subset of naturally abundant MnOx compounds have been examined for their reactivity in breaking down ECs. This project examines the reactivity of a variety of synthetic MnOx compounds in removing ECs. The results of this research may enable more cost-effective water treatment technologies targeting ECs removal at contaminated sites. The research efforts are coupled with an educational and outreach plan designed to involve underrepresented graduate, undergraduate, and high school students in research. Project findings are integrated into the undergraduate and graduate curriculum, and broadly disseminated to communities with diverse backgrounds, including professionals as well as the general public. This research has important implications for safe-guarding human, animal and plant life and health. This research employs a multi-faceted approach combining experimental and computational tools to investigate oxidation of ECs either directly by MnOx or catalytically using permanganate with MnOx. A range of MnOx are first synthesized to have different structures, Mn oxidation states, porosity, and dopants. Then, a variety of MnOx properties are characterized experimentally, including morphological, structural, surface, electrochemical, compositional, and thermodynamic properties. Some of these compounds are designed theoretically. Based on the observed reactivity of MnOx as either an oxidant or a catalyst, quantitative structure-activity relationships are developed as a function of MnOx properties. Finally, MnOx reaction mechanisms are elucidated using multipronged approaches. These include examining the role of Mn(III) species, lattice oxygen, Mn-O bond, and Lewis acid sites, and conducting kinetic modeling. 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.