重金属在黄铁矿中的相态及其释放的分级提取和漫反射红外光谱分析

以分级提取-电感耦合等离子体质谱考察了黄铁矿中重金属的相态分布。结果表明,黄铁矿中的重金属以Pb为主,总量达830mg/kg,并且酸可交换态Pb主要存在于碳酸盐相中或直接以PbS形式存在,这部分Pb达56.9%;易还原态Pb主要存在于铁氧化物相中,为29.7%;可氧化态和残余态Pb存在于硫化物相和硅酸盐相中,分别为3.5%和9.9%。黄铁矿在自然条件下以Pb释放为主,Cr和Cd的释放也不容忽视。漫反射红外光谱表征发现,黄铁矿在表面氧化过程中,其表面羟基增强,表明存在表面溶解及表面酸化现象。进一步的机理探讨认为,重金属在黄铁矿表面存在一种“溶解-吸附”平衡,这一平衡由黄铁矿表面氧化和碳酸盐中和作用共同控制,并决定重金属的释放及迁移。

Phase Distribution and Release of Heavy Metal in Pyrite Using Sequential Extraction Procedure and Diffuse Reflectance Fourier Transform Infrared Spectroscopy

Phase distributions of heavy metals in pyrite were analyzed by inductively coupled plasma mass spectrum with sequential extraction procedure. The result showed that Pb was the main heavy metal in pyrite and its total content was 830 mg/kg. Pb of exchangeable state by acid existed mostly in galena (PbS) or carbonate phase of pyrite and this proportion was 56.9%, Pb of reducible state existed in iron oxides by 29.7% in proportion, Pb of oxidable and residual state existed in sulfide and silicate by 3.5% and 9.9%, respectively. The release of Pb in pyrite was primary, but the release of Cr and Cd should not be neglected. The surface reaction in pyrite was investigated by the diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and it was found that the surface hydroxyls in pyrite were strengthened in the process of surface oxidation; moreover, the surface dissolution and surface acidification were existed. A release mechanism of heavy metal was proposed that the dissolution-adsorption equilibrium occurred, and further the equilibrium was under the control of both surface oxidation in pyrite and neutralization reaction by carbonate, and finally induced heavy metal release and migration.