Hostname: page-component-7dd5485656-c8zdz Total loading time: 0 Render date: 2025-10-31T09:01:44.110Z Has data issue: false hasContentIssue false
  • English
  • Français

Transformation of Synthetic Birnessite to Cryptomelane: An Electron Microscopic Study

Published online by Cambridge University Press:  02 April 2024

Cy-Chain Chen ,
D. C. Golden  and
J. B. Dixon
Cy-Chain Chen
Affiliation:
Department of Soil & Crop Sciences, Texas A&M University, College Station, Texas 77843
D. C. Golden
Affiliation:
Department of Soil & Crop Sciences, Texas A&M University, College Station, Texas 77843
J. B. Dixon
Affiliation:
Department of Soil & Crop Sciences, Texas A&M University, College Station, Texas 77843
Get access Rights & Permissions [Opens in a new window]

Abstract

Na-saturated bimessite was synthesized by oxidizing an alkaline MnCl2 solution with gaseous O2. Transmission electron microscopy (TEM) showed no morphological change upon K-saturation of the bimessite, but selected-area diffraction (SAD) revealed structural disorder. Stepwise heating of the K-birnessite to 800°C yielded cryptomelane, as indicated by X-ray powder diffraction (XRD). Various degrees of transformation to the final cryptomelane product were observed by TEM and SAD, but not by XRD. Unaltered bimessite formed chiefly as thin, platy crystals of apparent hexagonal outline. The cryptomelane crystals that formed by heating the K-saturated bimessite were acicular. Bimessite crystals, partially transformed to cryptomelane and displaying non-integral diffraction spots, formed plates having linear striations and rods twinned at 60° to each other. These intermediate products commonly retained some of the original hexagonal appearance of the parent bimessite. Structural disorder was detected in the partially transformed crystals by SAD. TEM revealed 6.8- and 4.8-Å spacings of the (110) and (200) planes of cryptomelane, respectively. The basal planes of bimessite layers (001) appeared to correspond topotactically to the (110) plane of cryptomelane during these transformations.

Keywords

BimessiteCryptomelaneSelected area diffractionStructural disorderSynthesisThermal treatmentTransmission electron diffraction

Information

Type
Research Article
Information
Clays and Clay Minerals , Volume 34 , Issue 5 , October 1986 , pp. 565 - 571
Copyright
Copyright © 1986, The Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Article purchase

Temporarily unavailable

References

Arrhenius, G. O. and Tsai, A. G., 1981 Structural, phase transformation and prebiotic catalysis in marine manganese minerals: Scripps Inst. Ocean., La Jolla, California SIO Ref. Series 81 1–19.Google Scholar
Dixon, J. B., Golden, D. C., Uzochukwu, G. A., Chen, C. C., Hayes, M. H. B. and Herbillon, A., 1986 Soil manganese oxides Soil Colloids, Structures, and Associations in Soil Aggregates Ghent, Belgium NATO Workshop (in press).Google Scholar
Faulring, G. M., Zwicker, W. K. and Forgeng, W. D., 1960 Thermal transformations and properties of cryptomelane Amer. Minerai. 45 946–959.Google Scholar
Giovanoli, R., Varentsov, I. M. and Grasselly, G., 1980 On natural and synthetic manganese nodules Geology and Geochemistry of Manganese, Vol. 1 Budapest Hungarian Acad. Sci. 160–202.Google Scholar
Golden, D. C., Chen, C. C. and Dixon, J. B., 1986 Synthesis of todorokite Science 231 717–719.10.1126/science.231.4739.717CrossRefGoogle ScholarPubMed
Golden, D. C., Dixon, J. B. and Chen, C. C., 1986 Ionexchange, thermal transformation, and oxidizing properties of bimessite Clays & Clay Minerals 34 511–520.10.1346/CCMN.1986.0340503CrossRefGoogle Scholar
Post, J. E., Von Dreele, R. B. and Buseck, P. R., 1982 Symmetry and cation displacements in hollandite: structure refinements of hollandite, cryptomelane, and priderite Acta Crystallogr. B38 1056–1065.10.1107/S0567740882004968CrossRefGoogle Scholar
Turner, S. and Buseck, P. R., 1981 Todorokite: a new family of naturally occurring manganese oxides Science 212 1024–1027.10.1126/science.212.4498.1024CrossRefGoogle Scholar