BACKGROUND Although most reported biogenic Mn oxides are hexagonal birnessites, other types of biogenic Mn oxides also commonly occur in the environment. However, sorption characteristics and underlying mechanisms of the adsorption of heavy-metal ions on these biogenic Mn oxides are still rarely addressed. In this study, the sorption mechanisms of Cu(II) on a low valence biogenic Mn oxide, poorly crystallized bixbyite-like Mn2O3 (α-Mn2O3), were investigated. RESULTS The maximum adsorption capacity of Cu(II) onto this biogenic Mn oxide at pH 6.00 was 796 mmol/kg (0.45 mol Cu mol(-1) Mn). The complex structure of adsorbed Cu(II) was constrained using Cu extended X-ray absorption fine structure (EXAFS) analysis, combined with structural parameters of the biogenic Mn oxide with alternately arranged regular and distorted MnO6 octahedra obtained through multiple-FEFF fitting of Mn EXAFS data. The sorbed Cu(II) was found to coordinate with the biogenic Mn oxide particle edges as inner-sphere complexes. At a relatively low Cu(2+) loading (233 mmol/kg, pH 6.00), Cu(II) adsorbed onto the biogenic Mn oxide with two types of coordinated complexes, i.e., (1) coordinated with one regular/distorted MnO6 octahedron as a monodentate-mononuclear complex and (2) with two adjacent MnO6 octahedra as a bidentate-binuclear complex. While, at a relatively high Cu(2+) loading (787 mmol/kg, pH 6.00), only one type of coordinated complex was constrained, the adsorbed Cu(II) coordinated with one regular/distorted MnO6 octahedron as a monodentate-mononuclear complex. CONCLUSIONS This research extends further insight into the bacterial Mn(II) oxidation in the environment and serves as a good reference for understanding the interactions between metal ions and biogenic low valence Mn oxides, which are still poorly explored either theoretically or practically.

中文翻译：

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Cu（2+）在土壤中分离到的芽孢杆菌CUA产生的生物型方铁矿状Mn2O3的吸收机理。

背景技术尽管大多数报道的生物锰氧化物是六角形的水钠锰矿，但是其他类型的生物锰氧化物也通常在环境中出现。然而，这些生物锰氧化物上的重金属离子的吸附特性和潜在机理仍很少得到解决。在这项研究中，研究了Cu（II）在低价生物成因的氧化锰，结晶度较弱的方铁矿状Mn2O3（α-Mn2O3）上的吸附机理。结果在pH 6.00时，该生物氧化锰对Cu（II）的最大吸附容量为796 mmol / kg（0.45 mol Cu mol（-1）Mn）。使用Cu扩展X射线吸收精细结构（EXAFS）分析限制了吸附的Cu（II）的复杂结构，通过对锰EXAFS数据进行多次FEFF拟合，获得了生物成因的Mn氧化物的结构参数，具有交替排列的规则和变形的MnO6八面体。发现吸附的Cu（II）与生物锰氧化物颗粒边缘协调为内球络合物。在相对较低的Cu（2+）负载（233 mmol / kg，pH 6.00）下，Cu（II）通过两种配位配合物吸附到生物锰氧化物上，即（1）与一个规则/扭曲的MnO6八面体配位（2）带有两个相邻的MnO6八面体作为双齿-双核复合物。在较高的Cu（2+）负载（787 mmol / kg，pH 6.00）下，仅约束了一种配位配合物，吸附的Cu（II）与一种规则/扭曲的MnO6八面体配位为单齿-单核。复杂的。