2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 5. Marquis Intl. Symp. / New and Advanced Materials and Technologies
| Editors: | Kongoli F, Marquis F, Chikhradze N |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 590 pages |
| ISBN: | 978-1-987820-69-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Effect of Crystal Structure in Manganese Dioxide for Water Purification
Hideki Koyanaka1;1FORWARD SCIENCE LABORATORY LTD., Oita, Japan;
Type of Paper: Regular
Id Paper: 291
Topic: 43
Abstract:
Manganese dioxide (MnO2) crystallizes into various phases including α-type (hollandite; tetragonal), β-type (pyrolusite; rutile), λ-type (spinel; cubic), ε-type (hexagonal), r-type (ramsdellite; orthorhombic), and γ-type (nsutite; r-type containing β, and ε-types as the intergrowths in the structure), etc. The crystal structures of manganese dioxide all contain a fundamental building block of MnO6 octahedron. And the block of MnO6 queues up in various arrays to construct the different crystal structures described above. However, the oxygen array of the crystal lattice usually features other octahedral and tetrahedral sites that may accommodate Mn and other cations via subtle distortion/tilting of the MnO6 octahedra and/or formation of oxygen defects. This variation of crystal structure gives rise to a variety of very intriguing physical and chemical functions. Thus, many functions have been studying for such applications as battery materials, ion-exchangers, heavy-metals adsorbents, sensor electrolytes, catalysis of the oxygen evolution core in chloroplasts, etc. Almost all these functions relate to the protonations in MnO2 based on the interactions with water. The protonation capabilities of MnO2 strongly depend on the difference in crystal structures. A key factor in useful protonations is a strong hydrogen-bonding between protons and oxygen-pairs in the crystal structures, in order to provide such important basic properties as proton conduction, proton storage, and water oxidation. In this report, the experimental results using different MnO2 crystal structures for removing such toxic materials as tritium, cadmium, and arsenic from water are discussed.