The Key Laboratory of Water and Sediment Sciences, College of Environmental Sciences and Engineering, Peking University, Beijing100871, China.
State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing210023, China.
Environ Sci Technol. 2023 Feb 21;57(7):3002-3011. doi: 10.1021/acs.est.2c08179. Epub 2023 Feb 6.
Magnetite (Mt) has long been regarded as a stable phase with a low reactivity toward dissolved sulfide, but natural Mt with varying stoichiometries (the structural Fe(II)/Fe(III) ratio, ) might exhibit distinct reactivities in sulfidation. How Mt stoichiometry affects its sulfidation processes and products remains unknown. Here, we demonstrate that is a master variable controlling the rates and extents of sulfide oxidation by magnetite nanoparticles (11 ± 2 nm). At pH = 7.0-8.0 and the initial Fe/S molar ratio of 10-50, the partially oxidized magnetite ( = 0.19-0.43) can oxidize dissolved sulfide to elemental sulfur (S), but only surface adsorption of sulfide, without interfacial electron transfer (IET), occurs on the nearly stoichiometric magnetite ( = 0.47). The higher initial rate and extent of sulfide oxidation and S production are observed with the more oxidized magnetite that has the higher electron-accepting capability from surface-complexed sulfide (S(-II)). The FeS clusters formed from magnetite sulfidation can be oxidized by the most oxidized magnetite with = 0.19 but not by other magnetite particles. A linear relationship between the Gibbs free energy of reaction and the surface area-normalized initial rate of sulfide oxidation is observed in all experiments under the different conditions, suggesting the S(-II)-magnetite IET dominates magnetite sulfidation at high Fe/S molar ratios and near-neutral pH.
磁铁矿 (Mt) 长期以来被认为是一种对溶解态硫化物具有低反应性的稳定相，但具有不同化学计量比（结构 Fe(II)/Fe(III) 比， ）的天然 Mt 可能在硫化过程中表现出不同的反应性。Mt 的化学计量比如何影响其硫化过程和产物尚不清楚。在这里，我们证明 是控制磁铁矿纳米颗粒（11 ± 2 nm）硫化速率和程度的主要变量。在 pH = 7.0-8.0 和初始 Fe/S 摩尔比为 10-50 时，部分氧化的磁铁矿（ = 0.19-0.43）可以将溶解态的硫化物氧化为元素硫（S），但只有表面吸附的硫化物发生在几乎化学计量的磁铁矿（ = 0.47）上，而没有界面电子转移（IET）。在具有更高电子接受能力的表面络合硫化物 (S(-II)) 的更氧化的磁铁矿上，观察到更高的初始硫化物氧化和 S 生成速率和程度。磁铁矿硫化形成的 FeS 簇可以被氧化，但不是其他磁铁矿颗粒氧化。在所有实验中，在不同条件下，反应吉布斯自由能与硫化物氧化初始速率的表面积归一化之间都存在线性关系，表明在高 Fe/S 摩尔比和近中性 pH 条件下，S(-II)-磁铁矿 IET 主导磁铁矿硫化作用。
