水钠锰矿的光化学形成和转变：阳离子对微观形貌和晶体结构的影响,Environmental Science & Technology

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水钠锰矿的光化学形成和转变：阳离子对微观形貌和晶体结构的影响
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2018-06-04 , DOI: 10.1021/acs.est.7b06592
Tengfei Zhang ₁ , Lihu Liu ₁ , Wenfeng Tan ₁ , Steven L. Suib ₂ , Guohong Qiu ₁ , Fan Liu ₁

Affiliation

锰氧化物是在土壤和沉积物中具有出色的氧化和吸附活性的重要成分，它会影响自然环境中养分和污染物的运输和命运。在这项工作中，在硝酸盐的存在下，在太阳辐射下，通过Mn ²⁺_水溶液的光催化氧化形成水钠锰矿。研究了层间阳离子（Na ⁺，Mg ²⁺和K ⁺）的浓度和种类对水钠锰矿晶体结构和微观形貌的影响。进一步研究了吸附的Mn ²⁺和pH在光合水钠锰矿转化中的作用。结果表明，Mn ²⁺_aq由超氧自由基氧化成水钠锰矿（O ₂^{• -}）从光解产生的NO ₃^-紫外光照射下。水钠锰矿的粒径和厚度随阳离子浓度的增加而减小。在K ⁺的存在下，水钠锰矿显示出板状形态，而当使用Na ⁺或Mg ²⁺时，其显示出皱巴巴的片状形态。水钠锰矿的不同微观形貌可归因于中间层中阳离子的位置。吸附Mn ²⁺高pH值有助于将水钠锰矿还原为低价锰氧化物，包括方锰矿，辉锰矿和锰矿。这项研究表明，层间阳离子和Mn ²⁺在水环境中水钠锰矿的光化学形成和转化中起重要作用。

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Photochemical Formation and Transformation of Birnessite: Effects of Cations on Micromorphology and Crystal Structure

As important components with excellent oxidation and adsorption activity in soils and sediments, manganese oxides affect the transportation and fate of nutrients and pollutants in natural environments. In this work, birnessite was formed by photocatalytic oxidation of Mn²⁺_aq in the presence of nitrate under solar irradiation. The effects of concentrations and species of interlayer cations (Na⁺, Mg²⁺, and K⁺) on birnessite crystal structure and micromorphology were investigated. The roles of adsorbed Mn²⁺ and pH in the transformation of the photosynthetic birnessite were further studied. The results indicated that Mn²⁺_aq was oxidized to birnessite by superoxide radicals (O₂^•–) generated from the photolysis of NO₃^– under UV irradiation. The particle size and thickness of birnessite decreased with increasing cation concentration. The birnessite showed a plate-like morphology in the presence of K⁺, while exhibited a rumpled sheet-like morphology when Na⁺ or Mg²⁺ was used. The different micromorphologies of birnessites could be ascribed to the position of cations in the interlayer. The adsorbed Mn²⁺ and high pH facilitated the reduction of birnessite to low-valence manganese oxides including hausmannite, feitknechtite, and manganite. This study suggests that interlayer cations and Mn²⁺ play essential roles in the photochemical formation and transformation of birnessite in aqueous environments.

更新日期：2018-06-04

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