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.
Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, NSW 2007, Australia.
J Hazard Mater. 2023 Jun 5;451:131145. doi: 10.1016/j.jhazmat.2023.131145. Epub 2023 Mar 5.
Pyrite is the most common metal sulfide mineral in the crust and readily weathers under natural circumstances to release H to acidify surrounding groundwater and soil, resulting in heavy metal ions in the surrounding environment (e.g., meadow and saline soils). Meadow and saline soils are two common, widely distributed alkaline soils and can affect pyrite weathering. Currently, the weathering behaviors of pyrite in saline and meadow soil solutions have not been systematically studied. Electrochemistry coupled with surface analysis methods were employed to study pyrite weathering behaviors in simulated saline and meadow soil solutions in this work. Experimental results suggest that saline soil and higher temperatures increase pyrite weathering rates due to the lower resistance and greater capacitance. Surface reactions and diffusion control the weathering kinetics, and the activation energies for the simulated meadow and saline soil solutions are 27.1 and 15.8 kJ mol, respectively. In-depth investigations reveal that pyrite is initially oxidized to Fe(OH) and S, and Fe(OH) further transforms into goethite γ-FeOOH and hematite α-FeO, while S ultimately converts into sulfate. When these iron compounds enter alkaline soils, the alkalinity of soil changes, and iron (hydr)oxides effectively reduce the bioavailability of heavy metals and benefit alkaline soils. Meanwhile, weathering of natural pyrite ores containing toxic elements (such as Cr, As, and Cd) makes these elements bioavailable and potentially degrades the surrounding environment.
黄铁矿是地壳中最常见的金属硫化物矿物，在自然条件下很容易风化，释放出 H 来酸化周围的地下水和土壤，导致周围环境中重金属离子（如草地和盐渍土壤）的存在。草地和盐渍土壤是两种常见的、广泛分布的碱性土壤，会影响黄铁矿的风化。目前，尚未系统研究黄铁矿在盐渍和草地土壤溶液中的风化行为。本工作采用电化学与表面分析方法研究了模拟盐渍和草地土壤溶液中黄铁矿的风化行为。实验结果表明，由于较低的电阻和较大的电容，盐渍土壤和较高的温度会增加黄铁矿的风化速率。表面反应和扩散控制风化动力学，模拟草地和盐渍土壤溶液的活化能分别为 27.1 和 15.8 kJ/mol。深入研究表明，黄铁矿首先被氧化为 Fe(OH)和 S，Fe(OH)进一步转化为针铁矿 γ-FeOOH 和赤铁矿 α-FeO，而 S 最终转化为硫酸盐。当这些铁化合物进入碱性土壤时，土壤的碱度会发生变化，铁（氢）氧化物有效降低了重金属的生物有效性，有利于碱性土壤。同时，含有有毒元素（如 Cr、As 和 Cd）的天然黄铁矿矿石的风化会使这些元素具有生物有效性，从而可能破坏周围环境。
