Biogenic manganese oxides (BMOs) formed in a culture of the Mn(II)-oxidizing fungus Acremonium strictum strain KR21-2 are known to retain enzymatic Mn(II) oxidation activity. Consequently, these are increasingly attracting attention as a substrate for eliminating toxic elements from contaminated wastewaters. In this study, we examined the Ba²⁺ sequestration potential of enzymatically active BMOs with and without exogenous Mn²⁺. The BMOs readily oxidized exogenous Mn²⁺ to produce another BMO phase, and subsequently sequestered Ba²⁺ at a pH of 7.0, with irreversible Ba²⁺ sequestration as the dominant pathway. Extended X-ray absorption fine structure spectroscopy and X-ray diffraction analyses demonstrated alteration from turbostratic to tightly stacked birnessite through possible Ba²⁺ incorporation into the interlayer. The irreversible sequestration of Sr²⁺, Ca²⁺, and Mg²⁺ was insignificant, and the turbostratic birnessite structure was preserved. Results from competitive sequestration experiments revealed that the BMOs favored Ba²⁺ over Sr²⁺, Ca²⁺, and Mg²⁺. These results explain the preferential accumulation of Ba²⁺ in natural Mn oxide phases produced by microbes under circumneutral environmental conditions. These findings highlight the potential for applying enzymatically active BMOs for eliminating Ba²⁺ from contaminated wastewaters.

中文翻译：

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通过不可逆生物氧化锰螯合优先消除Ba2 +

已知在氧化Mn（II）的真菌（Acremoniumstrictum）菌株KR21-2的培养物中形成的生物锰氧化物（BMO）保留了酶促Mn（II）的氧化活性。因此，这些作为从受污染的废水中消除有毒元素的基质越来越受到关注。在这项研究中，我们检查了有和没有外源Mn ²⁺的酶活性BMO的Ba ²⁺螯合潜力。BMO容易氧化外源Mn ²⁺以产生另一个BMO相，随后在pH值为7.0的条件下与不可逆Ba ²⁺螯合Ba ²⁺。隔离是主要途径。扩展的X射线吸收精细结构光谱学和X射线衍射分析表明，可能通过将Ba ²⁺掺入中间层，从透水层变为紧密堆积的水钠锰矿。Sr 2 ⁺，Ca ²⁺和Mg ²⁺的不可逆螯合作用微不足道，并且保留了层状水钠锰矿结构。竞争性螯合实验的结果表明，BMO比Ba ²⁺胜于Sr 2 ⁺，Ca ²⁺和Mg ²⁺。这些结果说明了Ba ²⁺的优先积累在周围环境条件下由微生物产生的天然锰氧化物相中。这些发现凸显了应用酶活性BMO消除污染废水中Ba ²⁺的潜力。