含砷尾矿中砷(As)及伴生元素铊(Tl)等毒性元素易向周边水和土壤介质中迁移,揭示尾矿中毒性元素的矿相特征及其释放机制具有重要意义。本研究以某雄黄矿区含砷尾矿为研究对象,结合化学分析、矿物学表征等手段,通过静态浸出实验探究含砷尾矿中As和Tl的矿相特征及其释放机制。研究结果表明,含砷尾矿中As和Tl的环境行为明显受到其矿相特征及赋存形态影响。矿物学分析结果显示尾矿中As的主要矿物相为砷铂矿和砷铁矿,矿物解离度表明砷矿物处于风化状态,As释放风险较高;而Tl则以伴生元素形式存在于Ca、Mn和Mg等矿物相中,这些矿物的沉淀溶解控制着尾矿中Tl的释放。尾矿中As主要以铁锰氧化物结合态和有机结合态存在,Tl主要以铁锰氧化物结合态和残渣态存在。酸性浸出条件下金属的活性态比例增高,可交换态As由0.29%上升至1.67%,可交换态Tl从5.46%升高至8.67%;尾矿中As释放加强而Tl受到抑制,表明尾矿中As与Tl释放存在竞争关系。As的浸出符合双常数模型,为多因素控制的物理和化学过程;Tl的浸出符合抛物线扩散模型,由结构掺入和表面吸附等扩散机制控制。本研究明确了含砷尾矿As和Tl的释放特性、化学形态转变及矿物相特征,为含砷尾矿中As和Tl污染风险控制提供了科学依据。

Arsenic (As) and associated thallium (Tl) can be released from As-bearing tailings and enter the surface water and soil environment. It is of great importance to understand the mineralogy and release characteristics of the toxic elements in tailings. In this study, the ore phases and their release mechanisms of As and Tl in As-bearing tailings from a realgar mining area are studied using batch leaching tests combined chemical analysis and mineral phases analysis. The results showed that the release of As and Tl was affected by the phases and speciation of the elements. The main As phases in the tailings were sperrylite and angelellite and they were prone to As release due to weathering. Thallium, as accompanying element, was associated with phases composed of Ca, Mn, Mg minerals, and the release of Tl was controlled by the precipitation and dissolution of these minerals. In the tailings, As mainly bounded to Fe-Mn oxides and organic materials, whilst Tl mainly bounded to Fe-Mn oxides and residual materials. The exchangeable fraction of As increased from 0.29% (before leaching) to 1.67% (after acid leaching); while for Tl it increased from 5.46% to 8.67%. The release of As was enhanced while Tl was inhibited under acidic conditions, which suggested the release of As and Tl in tailings was competitive. The leaching behavior of As conformed to the two-constant equation, indicating the leaching of As was a physiochemical process controlled by many factors. The leaching of Tl, which conformed to a parabolic diffusion equation, was mainly controlled by diffusion mechanisms such as structural incorporation and surface adsorption. In this study, the release characteristics, speciation and mineralogy of As and Tl in As-bearing tailings were clarified, which provided an essential reference of the pollution risk control for As and Tl in As-bearing tailings.