Liu Hong-fang, Qian Tian-wei, Zhang Min-gang
Guang Pu Xue Yu Guang Pu Fen Xi. 2015 Feb;35(2):543-6.
Selenium (Se) is an elementary trace nutrient element for human but there is a very narrow range between deficit and toxic levels. Furthermore, excessive intake of Selenium is harmful for human. The product species of selenite which was removal by pyrite particles was studied in the present research In the experiments, the pyrite particles were prepared by the wet ball mill method, and surface analyses of pyrite before and after contact with Se(IV) were conducted using X-ray photoelectron spectroscopy (XPS). Besides, the prepared pyrite samples were also characterized using both X-ray diffraction (XRD) and scanning electron microscope (SEM). X-ray diffraction analysis indicated that the purity of the prepared pyrite particles was above 97%, and the characteristic diffraction peaks of the particles well matched with that of FeS2 crystalline. Scanning electron microscope determination showed the shape of the particles was approximate ball and the size was range from 80 to 180 nm. And thus the pyrite particles prepared by the wet ball mill method had less particle size, larger specific surface area and higher reactive ability. The batch experiments exhibited the pyrite particles were able to remove 95% of Se(IV) (20 mg x L(-1)) from water within 12 hours. And the kinetic tests indicated reaction process between pyrite and Se(IV) fits a pseudo-first order kinetic model, which gives a pseudo-first order rate constant(kobs) of 0.26 h(-1). XPS analyses were using the XPSPEAK program which has a Gaussian Lorentzian function. The results clearly displays that Se(IV) prefer to react with the surface-bound S2(2-) rather than reacted with the surface-bound Fe2+ of pyrite particles. From XPS graph, it can be seen that the binding energy of sulfur element and iron element composed of pyrite shifted to the left a little, which means expensive state of sulfur element and iron element appeared on the pyrite surface. Analysis of the oxidation state of Se on the surface of pyrite particles by X-ray photoelectron spectra showed evidence for the reduction of Se(VI) to insoluble element Se(0) species. Besides, a spot of Se(IV) was existence on the surface of pyrite particles. The calculation results displayed that zero-valent selenium was dominarnt. At that, redox reaction was the main process when removal of Se( IVN)in aqueous environment with pyrite, along with sorption reaction at the same time. The results of removal of Se(IV) in groundwater using pyrite offer important theoretical value and practical significance.
硒（Se）是人体必需的微量营养元素，但缺乏与中毒水平之间的范围非常窄。此外，过量摄入硒对人体有害。本研究对黄铁矿颗粒去除亚硒酸盐的产物种类进行了研究。实验中，采用湿式球磨法制备黄铁矿颗粒，并利用X射线光电子能谱（XPS）对其与Se(IV)接触前后进行表面分析。此外，还使用X射线衍射（XRD）和扫描电子显微镜（SEM）对制备的黄铁矿样品进行了表征。X射线衍射分析表明，制备的黄铁矿颗粒纯度在97%以上，颗粒的特征衍射峰与FeS₂晶体的特征衍射峰匹配良好。扫描电子显微镜测定表明，颗粒形状近似球形，尺寸范围为80至180nm。因此，湿式球磨法制备的黄铁矿颗粒粒径较小，比表面积较大，反应活性较高。批次实验表明，黄铁矿颗粒能够在12小时内从水中去除95%的Se(IV)（20mg·L⁻¹）。动力学测试表明，黄铁矿与Se(IV)之间的反应过程符合准一级动力学模型，准一级速率常数（kobs）为0.26h⁻¹。XPS分析使用具有高斯洛伦兹函数的XPSPEAK程序。结果清楚地表明，Se(IV)更倾向于与表面结合的S₂²⁻反应，而不是与黄铁矿颗粒表面结合的Fe²⁺反应。从XPS图谱可以看出，黄铁矿中硫元素和铁元素的结合能略有左移，这意味着黄铁矿表面出现了高价态的硫元素和铁元素。通过X射线光电子能谱分析黄铁矿颗粒表面硒的氧化态，结果表明Se(VI)被还原为不溶性元素Se(0)物种。此外，黄铁矿颗粒表面存在少量的Se(IV)。计算结果表明零价硒占主导。此时，在水环境中用黄铁矿去除Se(IV)时，氧化还原反应是主要过程，同时伴有吸附反应。利用黄铁矿去除地下水中Se(IV)的研究结果具有重要的理论价值和实际意义。
