Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing, 100039, China.
Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
Water Res. 2021 Apr 15;194:116917. doi: 10.1016/j.watres.2021.116917. Epub 2021 Feb 10.
Arsenopyrite is a common metal sulfide mineral and weathers readily in the open environment, releases As, and pollutes the surrounding environment. Humic acid (HA) is ubiquitous in soils, sediments and waters, and contains various functional groups and complex with arsenic, iron and other metal ions that affect the weathering behavior of arsenopyrite. Because As, iron, and HA are redox-active compounds, electrochemical techniques, including polarization curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), were used to fundamentally investigate the weathering process and mechanism of arsenopyrite over a wide range of environmental relevant conditions. Polarization curves showed higher HA concentrations (0-1000 mg•L), higher temperatures (5-35°C) or acidities (pH 1.0-7.0) promoted arsenopyrite weathering; there was a linear relationship between the corrosion current density (i), temperature (T) and acidity (pH): i = -3691.2/T + 13.942 and i = -0.2445pH + 2.2125, respectively. Arsenopyrite weathering readily occurred in the presence of HA as confirmed by its activation energy of 24.1 kJ•mol, and EIS measurements confirmed that the kinetics were controlled by surface reaction as confirmed by decreased double layer resistance. CV and surface characterization (FTIR and XPS) showed that arsenopyrite initially oxidized to S, As(III) and Fe, then S and Fe were ultimately converted into SO and Fe, while As(III) oxidized to As(V). Furthermore, the carboxyl (-COOH) and phenolic (-OH) of HA could bind with As(III)/(V) and Fe via a ligand exchange mechanism forming As(III)/(V)-HA and As(III)/(V)-Fe-HA complexes that hinders the formation of FeAsO and decreases the bioavailability of As. Findings gained from this study are valuable for the understanding of the fate and transport of As in acidic conditions, and have powerful implications for the remediation and management of As-bearing sites affected by mining activities.
砷黝铜矿是一种常见的金属硫化物矿物，在开放环境中容易风化，释放砷并污染周围环境。腐殖酸（HA）在土壤、沉积物和水中普遍存在，含有各种官能团，并与砷、铁和其他金属离子络合，影响砷黝铜矿的风化行为。由于砷、铁和 HA 是氧化还原活性化合物，因此采用电化学技术，包括极化曲线、电化学阻抗谱（EIS）和循环伏安法（CV），在广泛的环境相关条件下从根本上研究了砷黝铜矿的风化过程和机制。极化曲线表明，较高的 HA 浓度（0-1000mg•L）、较高的温度（5-35°C）或酸度（pH 1.0-7.0）促进了砷黝铜矿的风化；腐蚀电流密度（i）与温度（T）和酸度（pH）之间存在线性关系：i=-3691.2/T+13.942 和 i=-0.2445pH+2.2125。HA 的存在促进了砷黝铜矿的风化，其活化能为 24.1kJ•mol。EIS 测量结果证实，动力学受表面反应控制，双电层电阻降低。CV 和表面特性（FTIR 和 XPS）表明，砷黝铜矿首先氧化为 S、As（III）和 Fe，然后 S 和 Fe 最终转化为 SO 和 Fe，而 As（III）氧化为 As（V）。此外，腐殖酸（HA）的羧基（-COOH）和酚基（-OH）可通过配体交换机制与 As（III）/（V）和 Fe 结合，形成 As（III）/（V）-HA 和 As（III）/（V）-Fe-HA 配合物，从而阻碍 FeAsO 的形成并降低 As 的生物利用度。本研究的结果对于了解酸性条件下 As 的归宿和迁移具有重要意义，并且对受采矿活动影响的含 As 场地的修复和管理具有重要意义。
