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Mineral Products and Characteristics of Phase Transformation after Hydrothermal Treatment according to the Synthetic Method and Cation Combination during Birnessite Synthesis
버네사이트 합성 시 합성 방법 및 양이온 조건에 따른 생성 광물 및 열수처리 후 상전이 특성
Econ. Environ. Geol. 2019 Dec;52(6):509-17
Published online December 31, 2019;  https://doi.org/10.9719/EEG.2019.52.6.509
Copyright © 2019 the Korean society of economic and environmental gelology.

Soyoung Min and Yeongkyoo Kim*
민소영 · 김영규*

School of Earth System Sciences, Kyungpook National University, Daegu 41566, Korea
경북대학교 지구시스템과학부
Received August 12, 2019; Revised August 29, 2019; Accepted November 28, 2019.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
The birnessite (7Å manganate, δ-MnO2) which is a manganese oxide and comprises manganese nodules, is a major manganese mineral on the earth surface and a precursor in the synthesis of todorokite. In this study birnessite was synthesized by three different methods: Feng et al. (2004) and Luo et al. (1998) based on redox reaction and Ma et al. (1999) based on reduction reaction. 12 birnessite samples were synthesized by different combinations of Na+ and K+ cations based on the base (OH-) and permanganate (MnO4-) reagents in the synthesis. The mineral compositions of synthesized birnessite were identified by XRD, and the two cation ratio in the mineral was measured by ICP. The products obtained after hydrothermal treatment of Mg-buserite, by the precursor of birnessite, was examined by XRD, and then phase transition to todorokite and their characteristics were compared. Our results show that the byproducts and the characteristics of phase transition by each synthetic method have different trends. Hausmannite (γ-Mn3O4) and feitknechtite (β-MnOOH) were formed by both methods in the redox reaction mechanism. By Feng et al. (2004)'s method, manganite (γ-MnOOH) phase only appeared when cation was predominantly Na+. Two birnessite samples synthesized by redox reaction mechanism showed phase transition to todorokite (10Å manganate, OMS-1) when both NaOH and KMnO4 were used together. However, single-phase birnessite was formed by Ma et al. (1999)'s method, and phase transition was confirmed only for the sample when the cation was only composed of Na+.
Keywords : manganese oxide, birnessite, todorokite, phase transition, mineral synthesis

 

December 2019, 52 (6)