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Dissolution and phase transformation processes of hausmannite in acidic

  • [设施]:北京正负电子对撞机
  • [期刊/会议名称]:Chemical Geology
  • [摘要]:Hausmannite is the most widely distributed spinel-structured manganese oxide in soils and sediments. The transformation of this metastable manganese oxide to Mn(IV) oxides with higher adsorption capacity has attracted much research interest, while the transformation mechanisms and influencing factors still remain largely unknown, especially under acidic condition. In this work, the transformation processes of hausmannite at different pH values and the influence of cations were studied. Results indicated that hausmannite was transformed into manganite at pH 5.0–9.0. The dissolution of hausmannite was initiated and promoted by protons (≤ 7.0), and the decrease of pH accelerated its conversion to Mn(IV) oxides. The tunnel-structured Mn(IV) oxide was generated via two steps during the dissolution process of hausmannite at pH ≤ 3.0. Hausmannite was disproportionated to δ-MnO2 at first, which was then transformed to nsutite in the presence of Na+ and H+ through the transfer of electrons from adsorbed Mn(II) to structural Mn(IV). The disproportionation of hausmannite to δ-MnO2 was not affected by other cations, while the presence of K+ promoted the further transformation of δ-MnO2 to cryptomelane. The structural rearrangement process of δ-MnO2 was the rate-determining step for the formation of final products. This work expands the understanding of the formation, transformation and geochemical processes of manganese oxides in supergene environments.
  • [发表日期]:2018
  • [第一作者]:罗瑶
  • [第一作者单位]:华中农业大学
  • [通讯作者]:邱国红
  • [通讯作者单位]:华中农业大学
  • [论文类型]:0
  • [期刊分类]:SCI2区
  • [学科分类]:环境科学_生态学
  • [影响因子]:3.570
  • [关键词]:Hausmannite; Disproportionation; Transformation; Birnessite; Nsutite; Cryptomelane
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