Fe0-As(III)/As(V)-H2O体系中砷的可控还原机制及产物稳定性研究

还原是Fe0-As(III)/As(V)-H2O体系中砷的化学行为之一，但由于以往单质砷的生成量较低，使得该体系砷的还原行为长期被忽视。申请者前期研究发现，在改变反应方式或调控零价铁对砷的吸附行为后，可明显强化砷的还原，甚至获得纯的单质砷。针对Fe0-As(III)/As(V)-H2O体系砷还原机制未知、细颗粒单质砷环境稳定性不明的问题，基于Fe-As界面结构热力学的第一性原理，本项目通过绘制界面结构稳定性热力学相图，结合电化学研究方法，揭示砷的可控还原机理；进一步查明环境条件、介质类型以及溶液组分等因素对砷还原行为的影响规律，获得单质砷高选择性还原制取的调控机制。基于此，定量评价所得单质砷的生物可利用性、环境稳定性和潜在生态风险，解明产物成分-结构-稳定性的内在机制。通过本研究可完善和丰富零价铁除砷的基础理论，实现单质砷的可控制备，达到脱砷与固砷的双重功效，为“砷害”治理提供新的思路。

The reduction of arsenic is one of important behaviors in the system of Fe0-As(III)/As(V)-H2O. Due to the low production of arsenic element, the study on reductive behavior of arsenic in the system of Fe0-As(III)/As(V)-H2O has always been ignored. Our preliminary study found that reduction of arsenic by Fe0 was obviously strengthened after controlling the behavior of arsenic adsorption or changing reaction way, and even single arsenic element with high purity was obtained. Base on the first-principles calculation of the interface structure for Fe-As, the thermodynamic stability phase diagram of the interface structure for Fe-As was given, the mechanism of arsenic reduction was revealed by means of electrochemistry method in this project. Furthermore, the effects of environment, medium and solution composition on reductive behavior of arsenic in the system is systematically investigated via characterization on shape and structure of reductive product. The controllable reductive mechanism of arsenic element was also revealed. Based on the results, the bioavailability, solubility stability, environmental stabilization and potential ecological risk of reductive arsenic products in the system are quantitatively evaluated, and the mechanism of the chemical composition, structure and stabilization for the reductive products was also clarified. This study is expected to solve the key issue on controllable reduction of arsenic in the Fe0-As(III)/As(V)-H2O system and to enrich and perfect the theoretical system of arsenic removal with Fe0, which provides a new idea for the treatment of arsenic pollution with Fe0 system.