WELCOME

1. WELCOME Manganese and the Environment Allison Mentor: Dr. Tratnyek Frontline Mentor: Jim Nurmi

2. Reduced Forms of Manganese • Manganese Metal (Mn0) • Atomic Number 25 • Second most abundant transition metal in the Earth’s crust. • Physical and chemical properties similar to iron metal. • Aq Manganese (Mn2+) • Bioavailable form of manganese. • Found in soils, sediments, and natural waters. • Occurs as a cation in solution. http://en.wikipedia.org/wiki/Manganese Photo from Wendy Smythe

3. Oxidized Forms of Manganese • Manganese Dioxide (MnO2) • Plays a key role in the biogeochemical cycles of metals and organic carbon. • Can degrade pollutants through oxidation. • Used as a cathode in dry cells and batteries. • Permanganate (MnO4-) • Powerful oxidizer used for water treatment. • Violet color http://en.wikipedia.org/wiki/Manganese_dioxide www.liboxgoa.com/potassium%20permanganate.html

4. Areas of Manganese Research • Naturally abundant • Bacteria can oxidize Mn(II) in natural aqueous environments • Soil and sediment remediation • Metal removal and recovery • Environmental impact • Overexposure can lead to permanent, neurodegenerative damage, with symptoms of Parkinson’s disease • Accumulate charges at the electrode/electrolyte interface. • Power supply • Naturally abundant • Influences the transport of contaminants and • nutrients in the environment • Stores energy by accumulation of charges at the electrode/electrolyte interface • Power supply for electronic products • Bacteria can oxidize Mn(II) in natural aqueous environments • Soil and sediment remediation • Metal removal and recovery

5. Purpose: Capacitance of Biogenic Manganese Compare the electrical potential of synthetic MnO2 and biogenic manganese oxides by fabricating electrodes and measuring current vs. potential by cyclic voltammetry.

6. Electrochemical Setup • Potentiostat • Glassy carbon rotating disk electrode • Ag/AgCl reference electrode • Platinum wire counter electrode • Na2SO4 electrolyte solution

7. Source of Materials • Self Made • Precipitate KMnO4 and polyethelyne glycol • Adapted from Ragupathy, P., et al, “Remarkable Capacity Retention of Nanostructured Manganese Oxide upon Cycling as an Electrode Material for Supercapacitor” • Manufactured • Mn2O3 from Fisher Scientific • Biogenic manganese from P. Putida GB-1

8. Comparison of Methods: Mao’s Method • Ethanol • 5 wt % Nafion solution • MnO2 particles iAdapted Mao, L., et al. “Electrochemical Characterization of Catalytic Activities of Manganese Oxides to Oxygen Reduction in Alkaline Aqueous Solution.” Journal of The Electrochemical Society, 149 (2002): 504-507.

9. Comparison of Methods: Liu’s Method • MnO2 • Acetylene black • Polyvinylidene fluoride (PVDF) • N-methyl-2-pyrrolidone (NMP) iiAdapted from Liu, E., et al. “Potentiodynamical deposition of nanosized manganese oxides as high capacitance electrochemical capacitors.” Journal of Materials Science: Materials in Electronics 18 (2007): 1179–1182.

10. Method Experimentation Results • Liu’s Method is used in because of better electrode coverage • Electrode tip must be heated in so MnO2 slurry adheres to electrode

11. Results Fig. 1a Cyclic voltammetry, Various types of manganese on electrode surface Fig. 1b Differential CV, ΔI vs. Potential Manganese

12. Conclusions • Reproducible electrochemical results • CVs of synthetic manganese oxides and biogenic manganese produce different results, which demonstrates that they have different electrochemical characteristics. • Larger capacitance differences are observed at intermediate potentials

13. Thank you Dr. Paul Tratnyek, Dr. Jim Nurmi, Karen Wenger, Dr. Antonio Baptista, Elizabeth Woody, CMOP, and the Apprenticeships in Science and Engineering program for making my internship possible.