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EFFECTS OF REACTION CONDITIONS ON THE FORMATION OF TODOROKITE AT ATMOSPHERIC PRESSURE

¹ College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
² Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

^* E-mail address of corresponding author: tanwf{at}mail.hzau.edu.cn

Todorokite is a common Mn oxide (with a tunnel structure) in the Earth surface environment, and can be obtained by hydrothermal treatment or refluxing process from precursor buserite with a layered structure. Several chemical reaction conditions for the phase transformation from Na-buserite to todorokite at atmospheric pressure were investigated, including temperature, pH, crystallinity of precursor Na-buserite, the amount of the interlayer Mg²⁺ of the Mg-buserite and clay minerals. The results showed that the conversion rate and crystallinity of todorokite decreased with falling temperature, and Mg-buserite could not be completely transformed to todorokite at lower temperatures (40°C). The poorly crystalline Na-buserite could be converted into todorokite more easily than highly crystalline Na-buserite. Todorokite can be prepared at pH 5–9, but the rate of conversion and crystallinity of todorokite did vary with pH in the order: neutral alkali > acidic. The conversion rate of todorokite decreased with decreasing interlayer Mg²⁺ content of the Mg-buserite. The presence of montmorillonite or goethite slowed the formation reaction of todorokite in the refluxing process, and the reaction time was prolonged when the amounts of those minerals were increased.

Key Words: Birnessite • Clay Mineral • Mn Oxide • Todorokite • Transformation

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				H. Cui, X. Liu, W. Tan, X. Feng, F. Liu, and H. D. Ruan INFLUENCE OF Mn(III) AVAILABILITY ON THE PHASE TRANSFORMATION FROM LAYERED BUSERITE TO TUNNEL-STRUCTURED TODOROKITE Clays and Clay Minerals, August 1, 2008; 56(4): 397 - 403. [Abstract] [Full Text] [PDF]