天然铁硫酸盐次生矿物晶相结构耦合锑环境行为机制研究

Antimony pollution prevention and control in water environment is an important task in the 13th five-year plan for ecological and environmental protection. It has been reported that iron-based adsorbents can effectively remove antimony, while they possess some limits such as high costs and low removal efficiency. Our previous study showed that the natural iron sulfate secondary minerals formed in the coal mine acid wastewater owned high efficiency of removing antimony from waters. However, little is known about the environmental behavior characteristics of migration, transformation, immobilization and release of antimony under the action of natural iron sulfate secondary minerals, especially the mechanisms of coupling process between the crystal structures of these secondary minerals and the environmental behaviors of antimony. Here in this project, we will collect the natural iron sulfate secondary minerals from the abandoned coal mine and employ multiple surface analysis techniques to investigate the laws of coupling process between the crystal structure of these secondary minerals and the immobilization of antimony, and then determine the factors that influence the antimony removal efficiency. We also aim to clarify the characteristics of coupling process between the interfacial reactions of these secondary minerals and the release/re-immobilization of antimony as well as the critical factors. The outcomes of this project are expected to reveal the geochemical process mechanism of antimony migration, transformation, immobilization and release, and then provide plenty of basic data, theoretical guidance, and technical support for the application of natural iron sulfate antimony secondary minerals in the treatment of antimony contaminated water.

水环境锑污染防控是“十三五”生态环境保护规划的重要任务。研究证实含铁吸附材料能有效去除锑，但现有含铁吸附材料存在经济成本和除锑效率的局限性。我们前期发现煤矿酸性废水中天然铁硫酸盐次生矿物具有高效去除水体中锑的特性，但迄今针对天然铁硫酸盐次生矿物作用下水体中锑的迁移、转化、固定和释放的行为特征，尤其是该类次生矿物晶相结构和锑环境行为间的耦合作用过程机制，仍缺乏清晰认识。基于此，本项目以废弃煤矿AMD中不同形成阶段的天然铁硫酸盐次生矿物为研究对象，基于多种现代表面分析技术，深入研究该类次生矿物的晶相结构与锑固定行为间的耦合作用过程规律，明确锑去除的主控因子，阐明该类次生矿物表面过程耦合锑释放/再固定行为的过程特征及主导因素，精细刻画锑迁移、转化、固定、释放等地球化学过程机制，为天然铁硫酸盐次生矿物应用于水体锑污染治理提供基础数据支撑和理论指导。

本项目针对我国水体锑污染问题，通过模拟实验和现代科学技术手段，重点研究了不同环境因子影响下天然铁硫酸盐次生矿物对水体中锑的迁移、转化、固定和释放的行为特征，尤其是该类次生矿物晶相结构和锑环境行为间的耦合作用过程，为天然多组分次生矿物应用于水体锑污染治理提供基础数据支撑和理论指导，取得以下研究成果：.（1）系统研究了三种不同形成阶段的天然铁硫酸盐次生矿物（成熟态m-SIM、过渡态t-SIM和新生态n-SIM）对锑/砷的吸附行为，阐明了不同环境因子作用下天然铁硫酸盐次生矿物对锑/砷的吸附性能，明确了锑/砷去除的最佳环境条件，揭示了其对锑/砷的去除作用机制。.（2）研究弱酸性环境中天然多组分次生铁矿物的晶相结构与锑固定行为间的耦合作用过程。通过对比实验，阐明了天然多组分次生铁矿物的晶相转变与其Sb(V)吸附行为的作用关系。结合X射线荧光光谱分析结果，天然多组分次生铁矿物对Sb(V)的吸附并不是该矿物中各单组分次生铁矿物对Sb(V)的吸附作用的简单加和，而是存在一定的相互促进作用。.（3）研究了水体中的DOM对天然多组分次生铁矿物吸附去除Sb(V)的效果及Sb(V)在次生铁矿物中的稳定性。发现腐殖酸对天然多组分次生铁矿物吸附Sb(V)存在显著抑制作用，且这种抑制作用随着HA浓度升高而增强；高浓度富里酸轻微抑制天然多组分次生铁矿物对Sb(V)的吸附，L-色氨酸对Sb(V)吸附存在一定程度的促进作用。此外，高浓度DOM存在的环境中，Sb(V)在天然多组分次生铁矿物中的稳定性不同于三种单组分次生铁矿物。.（4）初步开展了Fe(II)-天然多组分次生铁矿物-厌氧状态下锑的环境行为特征研究。研究发现，随着pH增加，Fe(II)对天然多组分次生铁矿物的相转变影响加剧，且与Fe(II)浓度成反比。在酸性环境中，Fe(II)的共存有利于吸附在天然多组分次生铁矿物中Sb(V)的稳定性。并研究了该过程的作用机制。