Abstract Trace metal structural impurities are common in Mn (II/III) oxides, yet their effects on the oxides' reactivity and stability have not been experimentally assessed. The present investigation quantifies such effects for the first time by measuring the extent of mineral dissolution of pristine and Ni-substituted hausmannite (MnIIMnIII2O4) (at 1 and 2 wt% Ni) in 8-h batch reactions at pH 5 with/without arsenite (As(III)). Ni substitution occurred at Mn(III) octahedral sites, causing noticeable structural modification in lattice parameters with a decrease in Jahn-Teller distortion, particularly at 2 wt%. In both acidic and reductive dissolution (with As(III)), the Ni-substituted hausmannite exhibited enhanced Mn release relative to the pristine mineral, with concurrent release of structural Ni increasing with substitution percentage. When As(V) release was normalized by surface area, Ni-substituted hausmannite showed a higher As(III) oxidation percentage than the pristine phase. Further, higher ratios of Mn(II):As(V) were observed in Ni-substituted hausmannite. As K-edge X-ray absorption spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy analyses indicated that As(III) oxidation lead to the formation of binuclear bidentate As(V) surface complexes. Enhanced reactivity of Ni-substituted hausmannite may be attributed to lowered mineral stability, which promotes accelerated mineral dissolution and increased structural Mn release, resulting in formation/exposure of highly reactive sites. Thus, structural impurities dictate the properties, reactivity, and stability of the Mn(II/III) oxides, affecting the level of dissolution and the extent of redox reactions, which together impact the fate and cycling of transition metals and metalloids in surface environments.

中文翻译：

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Ni 掺入对磷锰矿 (Mn3O4) 反应性和稳定性的影响：对 Mn、Ni 和 As 溶解度和循环的环境影响

摘要 痕量金属结构杂质在 Mn (II/III) 氧化物中很常见，但尚未通过实验评估它们对氧化物反应性和稳定性的影响。本研究首次通过测量原始和 Ni 取代的锝锰矿 (MnIIMnIII2O4)（Ni 含量为 1 和 2 重量％）在 8 小时间歇反应中，在有/没有亚砷酸盐的情况下，对这种影响进行量化。作为（III））。Ni 取代发生在 Mn(III) 八面体位点，导致晶格参数的显着结构改变，Jahn-Teller 畸变减少，特别是在 2 wt% 时。在酸性溶解和还原溶解（含 As(III)）中，Ni 取代的 hausmannite 表现出相对于原始矿物的 Mn 释放增强，同时结构 Ni 的释放随着取代百分比的增加而增加。当 As(V) 释放按表面积归一化时，Ni 取代的 hausmannite 显示出比原始相更高的 As(III) 氧化百分比。此外，在 Ni 取代的黑锰矿中观察到更高的 Mn(II):As(V) 比率。由于 K 边 X 射线吸收光谱和衰减全反射-傅立叶变换红外光谱分析表明 As(III) 氧化导致双核双齿 As(V) 表面复合物的形成。Ni 取代的锰铁矿的反应性增强可能归因于降低的矿物稳定性，这促进了矿物溶解加速和结构 Mn 释放增加，导致高反应性位点的形成/暴露。因此，结构杂质决定了 Mn(II/III) 氧化物的性质、反应性和稳定性，