Factors governing formation of todorokite at atmospheric pressure

摘要

Todorokite commonly occurs in Earth surface environments. The factors governing formation of todorokite, such as reaction temperature, metal ions, dissolved O_2 and pH, were investigated in this paper. Results showed that the forming rate of todorokite and its crystallinity decreased with falling reaction temperature, and the effect of temperature was more significant than that of other parameters. Nature of metal ions in the interlayer of buserite precursor and the structure of the buserite precursor obviously affected buserite transformation into todorokite. Weak bonding between the metal ions and MnO_6 layer of buserite was favorable to todorokite formation. The rate of todorokite formation was promoted at a lower temperature with appropriate bubbling of O_2. The pH in the system slightly influenced the todorokite formation, and todorokite could also be formed in a weak alkali medium or in a slightly acidic medium. Aged buserite precursor more easily form todorokite than the unaged one.