Effects of structural cobalt on the stability and reactivity of hausmannite and manganite: Cobalt coordination chemistry and arsenite oxidation
Effects of structural cobalt on the stability and reactivity of hausmannite and manganite: Cobalt coordination chemistry and arsenite oxidation
复制标题
DOI：
10.1016/j.chemgeo.2021.120453
复制
发表时间：
2021-11
期刊：
影响因子：
3.9
通讯作者：
Boyoung Song;Elizabeth B. Cerkez;E. Elzinga;Bojeong Kim
中科院分区：
文献类型：
--
作者：
Boyoung Song;Elizabeth B. Cerkez;E. Elzinga;Bojeong Kim
黑锰矿和锰氧化物，最丰富的锰（II/III）的氧化物在环境中，通常含有钴（Co）作为结构杂质，但钴取代的锰（II/III）氧化物的结构，稳定性和反应性的影响还没有实验评估。使用原始和钴取代矿物与不同的钴负载量（1和2重量%），本研究观察到的结构特性的变化，以及这些矿物的稳定性和反应性对酸性和还原性溶解与亚砷酸盐（As（III））。钴取代黑锰矿的晶格参数和矿物的表面积产生显着的变化，而锰氧化物提出很少或没有钴取代的影响。在这两种矿物中，Mn和Co的释放加速还原溶解，虽然超过85%的钴仍然在矿物结构。只有黑锰矿显示随着Co取代的增加，As（III）向As（V）的氧化增加，其中化学计量的[Mn（II）]水与[As（V）]水的比率为/接近2。X-射线吸收光谱分析表明，钴（II）和钴（III）在四面体和八面体网站，分别与结构钴（II）在黑锰矿占主导地位的共存。唯一的占位钴（II）在八面体网站锰氧化物出现诱导的平均锰氧化态的变化。在矿物表面上观察到多个砷酸盐表面络合物，其中双齿双核模式是主要物种。因此，Co取代改变了溶解条件下的Mn（II/III）氧化物的稳定性和反应性，虽然程度不同的Co配位化学，价态和矿物结构中的数量。
Hausmannite and manganite, the most abundant Mn(II/III) oxides in the environment, commonly contain cobalt (Co) as a structural impurity, yet the effects of Co substitution on the structure, stability, and reactivity of Mn(II/III) oxides have not been experimentally assessed. Using pristine and Co-substituted minerals with varying Co loadings (1 and 2 wt%), the present study observed changes in the structural properties, as well as stability and reactivity of these minerals toward acidic and reductive dissolution with arsenite (As(III)). Cobalt substitution in hausmannite produced significant changes in the lattice parameters and surface areas of the mineral, while manganite presented little to no Co substitution effects. In both minerals, Mn and Co release was accelerated in reductive dissolution, although more than 85% of the Co remained in the mineral structure. Only hausmannite showed increased oxidation of As(III) to As(V) with increased Co substitution, where the stoichiometric [Mn(II)]aqto [As(V)]aqratio was at/close to 2. X-ray absorption spectroscopy analysis indicated the co-presence of Co(II) and Co(III) at tetrahedral and octahedral sites, respectively, with structural Co(II) dominating in hausmannite. The sole occupancy of Co(II) at octahedral sites in manganite appeared to induce changes in the average Mn oxidation state. Multiple surface complexes of arsenate were observed on the mineral surfaces, with the bidentate binuclear mode being the major species. Thus, Co substitution altered the stability and reactivity of the Mn(II/III) oxides under dissolution conditions, although the extent varied by the Co coordination chemistry, valence, and quantity in the mineral structures.