基于XPS对硫铁矿去除SeO2-3的机理研究

硒是动植物及人体生长必需的十五种微量元素之一，具有清除体内自由基、抗氧化、增强免疫力等功能，但其安全剂量的范围却很窄。利用扫描电子显微镜（SEM）和X射线衍射仪（XRD）对湿法球磨制备的硫铁矿形貌进行了表征。SEM观测发现加乙醇助磨后的硫铁矿为粒径大小较均匀的球形颗粒团聚体，粒径范围在17～200 nm之间，平均粒径138 nm。XRD衍射图谱中的特征峰与FeS₂衍射图谱中各峰位置基本一致，因此判定硫铁矿中主要化学组分为FeS₂，且图谱中基本没有杂峰，表明制备过程中并未混入杂质，样品纯度较高。实验结果表明，该法制备的硫铁矿具有颗粒粒径小、比表面积大、反应活性高等优点。研究中利用X射线光电子能谱仪（XPS）对硫铁矿去除水体中SeO2-₃的机理进行了研究。研究结果表明, （1）在较为广泛的实验pH范围（pH 2.2～11.5），硫铁矿均能有效去除水体中SeO2-₃，去除效率（除pH值7.8以外）均达到90%以上；（2）硫铁矿与SeO2-₃发生反应后，其主要组成元素的XPS特征峰结合能有所减小，表明硫铁矿表面发生了一定化学变化；（3）酸碱环境下硫铁矿去除SeO2-₃的机理不完全相同，酸性环境下，硫铁矿对SeO2-₃的去除是单纯的氧化还原过程，即硫铁矿中被酸活化的S2-₂将SeO2-₃还原为单质Se(0)，并且酸性越强，SeO2-₃去除效果越好；碱性环境下，SeO2-₃的去除过程中氧化还原与络合反应并存，硫铁矿表面有络合态Fe(OH)SeO₃和单质Se(0)两种存在形态，且碱性越强，络合态Fe(OH)SeO₃含量越高。以上研究结果为硫铁矿去除固定水体和土壤中以SeO2-₃为代表的可变价金属阴离子提供重要理论依据和应用基础。

Research of the Removal of SeO32-With Pyrite Based on XPS

Selenium is one of the 15 essential trace elements necessary for the growth of animals,plants,and humans.It has the functions of scavenging free radicals,anti-oxidation and enhancing immunity,etc.,but its safe dosage range is very narrow.The pyrite’s morphology prepared by wet ball milling was characterized by scanning electron microscope(SEM)and X-ray diffraction(XRD).SEM observations were found that the pyrite after the addition of ethanol was a spherical particle agglomerate with a relatively uniform particle size,ranging from 17 to 200 nm,with an average particle size of 138 nm.The characteristic peaks in the XRD diffraction pattern are the same as the positions of the peaks in the FeS₂ diffraction pattern.Therefore,it is determined that the main chemical component in pyrite is FeS2,and there are no impurity peaks in the pattern,indicating that no impurities were mixed in the process of preparation.The sample purity is high.The experimental results show that this method’s pyrite has the advantages of small particle size,large specific surface area,and high reaction activity.In the research,X-ray photoelectron spectroscopy(XPS)was used to study the mechanism of removing Se(Ⅳ)by pyrite.The research results show that(1)In a relatively wide experimental pH range(pH 2.2~11.5),pyrite can effectively remove SeO₃^2-and the removal efficiency(except pH 7.8)is above 90%;(2)After the reaction of pyrite with SeO₃^2-,the characteristic peaks of its main constituent elements appeared the left shift indicated that a certain chemical change had taken place on the surface of the pyrite;(3)The mechanism of removal of SeO₃^2-with pyrite in an acid-base environment is a little different.In an acidic environment,the removal of SeO₃^2-by pyrite is a simple redox process.That is,S22-activated by the acid in pyrite reduces Se(Ⅳ)to Se(0),and the stronger the acidity,the better the removal effect of SeO₃^2-;in the alkaline environment,the oxidation-reduction and complexation reactions coexist during the removal of SeO₃^2-,and the surface of pyrite has complexed Fe(OH)SeO3 and elemental Se(0)exist in two forms,and the stronger the basicity,the more the content of complexed Fe(OH)SeO3.The above research results provide an important theoretical basis and application basis for removing variable valence metal anions represented by SeO₃^2-from water and soil by pyrite.