Cui,H., Liu,X., Tan,W., Feng,X., Liu,F. and Ruan,H.D.(2008): Influence of Mn(III) availability on the phase transformation from layered buserite to tunnel-structured todorokite. Clays and Clay Minerals, 56(4), 397-403.

『層状ブセライトからトンネル構造轟石への相変化における3価のマンガンの有効性の影響』


Abstract
 Todorokite is a common Mn oxide mineral in terrestrial and ocean-floor environments, and it is commonly synthesized from layered Na-buserite. Pyrophosphate, which is known to form strong complexes with Mn(III) at a pH range of 1-8, was added to a suspension of Na-buserite in order to sequester the available Mn(III) in Na-buserite. No Mn(III)-pyrophosphate complex was formed in solution at pH 10, and the treated Na-buserites were concerted completely to todorokite. Significant transformation reductions were observed when Na-buserite was treated with pyrophosphate solution at pH 7. The presence of Mn(III) within the MnO6 octahedral sheets of Na-buserite is critical for the transformation from layered buserite to tunnel-structured todorokite at atmospheric pressure. At lower pH, two effects are combined to reduce the amount of Mn(III) in the layers: (1) the complexing power of pyrophosphate is increased; and (2) the transformation from Na-buserite to H-birnessite, which is concomitant with the migration of Mn(III) from layers to the interlayer, and the partial disproportionation of Mn(III). The results showed that Mn(III) played a key role in the transformation of layered Na-buserite to tunnel-structures todorokite at atmospheric pressure.

Key Words: Buserite; Mn oxide; Todorokite; Transformation; Refluxing.』

Introduction
Experimental
 Preparation of Na-buserite
 Treatments of Na-buserite using Na4P2O7 solutions
 Ion-exchange of Na-buserite and subsequent conversion to todorokite
 Methods of analysis
  Measure of Mn(III)-pyrophosphate complex
  X-ray diffraction analysis
  Transmission electron microscopy measurement
Results
 Effect of pH in Na4P2O7 solutions on the phase transformation from Na-buserite to todorokite
 Effect of Na4P2O7 concentration at pH 7 on the phase transformation from Na-buserite to todorokite
 Effect of Na4P2O7 treatment time on phase transformation from Na-buserite to todorokite
 Effect of reflux time on the phase transformation from Na-buserite to todorokite
Discussion and conclusions
Acknowledgments
References



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