锑矿冶炼区土壤/水界面锑吸附过程中三价锑的氧化行为与关键影响因素

Antimony (Sb) and its compounds are considered to be hazardous to human health or even carcinogenic. Sb is a redox-sensitive element, making its mobility directly susceptible to changes in the soil redox state. Sb occurs in Earth’s surface as two inorganic species, Sb(OH)3 and Sb(OH)6-. Sb(III) is more toxic than Sb(V). The solubility and mobility of Sb(V) are greater than those of Sb(III). Behavior of Sb in the environment depends to a great extent on its oxidation state. .Mineral-water interfaces not only bind metal ions but also can accelerate oxidation reactions. The presence of these materials in soils may play a detoxifying role for soil- adsorbed Sb. Thus, knowledge about the oxidation of Sb(III) to Sb(V) in the environment is important for risk assessment. Furthermore, antimony oxidation processes take place during adsorption. However, up to now, laboratory-based quantitative studies on co-oxidation and sorption of antimony on natural sorbents are still few. The environmental behaviors of Sb may vary greatly among different types of soils, which is also not well understood at the present time. .China has the most abundant Sb resources in the world. The local environments near Sb mining and smelting areas were seriously contaminated. Antimony pollution is one of the typical environmental issues in China, which has been typically detected around smelter. Previous studies showed that most antimony was emitted as Sb(III) from smelting operations and deposited in the surface soils as the same form. However, in soils it is generally believed that antimony is exists mainly as Sb(V). Some studies found that more than 70% of Sb(III) in soils will be oxidated to Sb(V) within 2 days. However, the process of Sb(III) oxidation on soils is not clear: it is unknown whether the Sb (V) remains adsorbed to the soil surface or is mobilised and released from soil surface. .In this study, the kinetics of sorption and behavior of Sb(III) oxidation will be investigated in different soils (cultivated land, forest land, and uncultivated land) from an antimony smelting area. Considering the related geological background, the experimental research will be performed as a function of pH. In addition, it will also study the effects of soil organic matter (SOM) on sorption and oxidation behavior by treating the soil to remove the SOM fraction. Sorption kinetics and adsorption isotherms studies will gain insight into the overall sorption behavior by using batch experiments, and will reveal sorption processes of Sb at the soil-water interfaces. Adsorption and oxidation kinetics studies will obtain a time-resolved kinetic behavior by using stirred-flow method, and will realize behavior of Sb(III) oxidation during the rapid adsorption processes. The results of this study will deeply characterize behaviors of Sb environmental geochemistry at the soil surfaces, and improve risk assessments about the mobility of Sb in related antimony smelting areas..

我国是锑储量大国，全球近90%的锑产自我国。锑矿冶炼活动已造成冶炼区周围土壤高度富集Sb，成为我国特有的土壤环境问题之一。土壤中Sb的毒性与归趋取决于Sb的吸附过程与形态，而探明Sb(Ⅲ)的氧化行为则是认识土壤Sb吸附过程的关键所在。本项目结合我国主要锑矿冶炼区高Sb和弱碱性土壤环境的特点，分别对研究区三种土壤（耕地、林地、荒地）开展不同因素（pH、有机质）影响下的相关实验：用Batch方法研究土壤Sb吸附的特征与过程，阐明土壤/水界面Sb吸附的环境地球化学行为与关键影响因素；用Stirred-flow方法研究Sb(Ⅲ)的氧化反应过程，揭示土壤/水界面Sb吸附过程中Sb(Ⅲ)的氧化行为及其关键影响因素。研究成果为深入认识Sb在土壤/水界面的环境地球化学行为和正确评价锑矿冶炼区土壤中Sb的危害性提供科学依据。