Collaborative Research: Effects of Structural Impurities on the Reactivity and Transformation of Lower Valent Manganese Oxides

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The Environmental Chemical Science Program in the Chemistry Division supports this project by Professors Bojeong Kim and Elizabeth B. Cerkez at Temple University and Professor Evert J. Elzinga at Rutgers University-Newark. The team investigates the effects of metal impurities on the structure, reactivity, and stability of manganese (Mn) oxides. Natural Mn oxides typically contain a range of impurities, but the impact of these impurities on the chemical reactions and mineral transformations are unknown. Mn oxides have important applications in industry, such as in batteries, energy storage devices, and sensors. There are potential industrial uses of minerals whose properties could be changed by including metal impurities. This project engages graduate and undergraduate students at both Temple and Rutgers Universities. The team makes presentations to retirement communities in the Philadelphia area, which brings new and interesting science to an often-overlooked demographic group. This project examines hausmannite and manganite, the most widely distributed Mn(II/III) oxides in the environment. The research team examines how and to what extent metal impurities alter the minerals’ structure, reactivity, and stability. They also examine the potential release of foreign metals during various reactions. Hausmannite and manganite substituted with varying trace metal types (divalent-only Ni and Zn versus redox-active Co) and concentrations (1 and 2 wt%) are measured for As(III) oxidizing ability and transition metal solubility to quantify the substitution effects. The mineralogical transformation kinetics in substituted minerals are also compared with pristine minerals. A variety of state-of-the-art analytical techniques are employed to characterize the coordination chemistry and valence of metal substituents, probe interfacial redox chemistry, and identify transformation products. The project provides mechanistic insights into the effects of metal impurities on the structure, reactivity, and stability of Mn minerals. The project further highlights the role of the lower valent Mn oxides in the geochemical cycling of Mn, trace metals, and metalloids in natural environments.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.