含氧溶液中毒砂氧化溶解的XAFS研究

毒砂的氧化溶解是环境As污染的重要来源之一。本研究对毒砂的氧化反应过程及产物进行了研究。考察了不同参数:pH、溶解氧(Dissolved Oxygen,DO)对毒砂氧化反应的影响,利用X射线吸收精细结构(X-ray Absorption Fine Structure,XAFS)分析了毒砂氧化过程中As的形态转化。XAFS光谱学数据表明,pH=4时,毒砂发生较强的氧化反应,释放的As(V)被氧化过程中形成的铁氧化物吸附;pH=7时,毒砂氧化释放的As(III)被铁氧化物吸附,表面存在少量的类似雄黄(As S)的物质;而pH=9时,毒砂几乎不发生氧化,表面只存在少量的硫代亚砷。结果表明,pH是影响毒砂氧化的重要因素。中碱性条件下,毒砂氧化反应释放出的Fe快速形成了Fe的氧化物沉淀,包裹在毒砂的表面,阻碍毒砂继续氧化。

XAFS study on oxidation dissolution of arsenopyrite in O2-bearing solution

Background:One of the most important pollution sources of arsenic is the oxidation dissolution of arsenopyrite in oxygen-bearing solution.Purpose:This work investigated the oxidation process and product of arsenopyrite in O2-bearing solution using batch experiment.Methods:The influences of pH and dissolved oxygen (DO) on the oxidation dynamics of arsenopyrite are investigated. Besides that we also analyze the transformation of arsenic in the process of the oxidation of arsenopyrite using X-ray Absorption Fine Structure (XAFS).Results:XAFS spectroscopy data shows that, at pH=4, the oxidation of arsenopyrite is intensive and the released As(Ⅴ) would be absorbed by iron oxide formed in the process of oxidation; at pH=7, the released As(Ⅲ) would be absorbed by iron oxide and a few realgar analogues appear in the surface of arsenopyrite; at pH=9, the oxidation of arsenopyrite almost does not occur, but only a small amount of thioarsenates exhibit in the surface of arsenopyrite.Conclusion:The pH is the most important parameter controlling the oxidation of arsenopyrite. The oxidation of arsenopyrite is inhibited in neutral and alkaline conditions, due to the formation of Fe oxides on the surface of arsenopyrite quickly.