Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China; University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, China.
Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China.
Chemosphere. 2019 May;222:422-430. doi: 10.1016/j.chemosphere.2019.01.157. Epub 2019 Jan 28.
The adsorption behavior of thioarsenite (TAs) on the surface of hematite (α-FeO) is unknown at present. In the present study, we have investigated the transformation and reactions of TAs [monothioarsenite (MTAs) and dithioarsneite (DTAs)] on the surface of α-FeO in the presence of sulfide at S/As = 1 and 3 by X-ray absorption spectroscopy (XAS) and Raman spectroscopy. The adsorption envelopes reveal that the adsorption of TAs on α-FeO is significantly less than that of arsenite (As) in the pH range from 7 to 11 with the initial As concentration of 25 mg L. However, at the initial As concentration of 135 mg L, the uptake of TAs by α-FeO is higher at pH 7 but lower at pH 8-11 than that of As. The adsorption isotherms show that the adsorption of As on α-FeO is largely inhibited by the presence of aqueous sulfide at pH 7 with low As equilibrium concentration (<40 mg L). Whereas the uptake of As by α-FeO is highly elevated compared with the value predicted by Langmuir model at pH 7 with high As equilibrium concentration (>40 mg L), implying the formation of As-bearing (surface) precipitate. The As and S K-edge XAS as well as Raman spectroscopy confirm the formation of As sulfide precipitate on the surface of α-FeO in MTAs system. It is worth to note that the oxidation of (thio)As occurs on the surface of α-FeO in DTAs system under strictly anaerobic conditions. These results shed new light on the understanding of the interfacial behavior of As and point to the potential implication in immobilization and removal of arsenic in sulfidic environment.
目前，关于亚碲酸根（TAs）在赤铁矿（α-FeO）表面的吸附行为尚不清楚。在本研究中，我们通过 X 射线吸收光谱（XAS）和拉曼光谱研究了在 S/As=1 和 3 的条件下，硫化物存在时，MTAs 和 DTAs 在α-FeO 表面的转化和反应。吸附包络表明，在 pH 值为 7 到 11 的范围内，初始 As 浓度为 25 mg/L 时，TAs 在α-FeO 上的吸附量明显小于亚砷酸盐（As）。然而，在初始 As 浓度为 135 mg/L 时，pH 值为 7 时 TAs 在α-FeO 上的吸附量高于 pH 值为 8-11 时的 As，而在 pH 值为 7 时，低 As 平衡浓度（<40 mg/L）下，水溶液中的硫化物会极大地抑制 As 在α-FeO 上的吸附。然而，在 pH 值为 7 且 As 平衡浓度较高（>40 mg/L）时，α-FeO 对 As 的吸附量与 Langmuir 模型预测值相比有显著提高，这意味着形成了含 As 的（表面）沉淀物。As 和 S K 边 XAS 以及拉曼光谱证实了在 MTAs 体系中，α-FeO 表面形成了 As 硫化物沉淀物。值得注意的是，在严格厌氧条件下，DTAs 体系中（硫代）As 在α-FeO 表面发生氧化。这些结果为理解 As 的界面行为提供了新的认识，并指出了在硫化环境中固定和去除砷的潜在意义。
