典型汞尾矿汞的释放特征——以万山岩屋坪尾矿库为例

Investigating mercury release characteristics from typical mercury tailings:a case study of Wanshan Yanyaping Tailings depot

为研究汞尾矿中汞的释放特征,以我国典型汞矿区——万山岩屋坪尾矿库为研究对象,采用静态浸泡和动态淋溶方法,结合试验前后尾矿的矿物组成、汞赋存形态占比及释放动力学,共同探究汞在尾矿中的释放特征。研究结果显示:在静态浸泡中,pH值为4.5,固液比(g∶mL)为1∶10条件下汞释放质量浓度最大,静态浸泡后尾矿物相组成减少,碳酸盐结合态汞和离子交换态汞占比降低。在动态淋溶中,降雨pH值为4.5,降雨强度为2.616 mL/min条件下释放的汞质量浓度最大,动态淋溶后各物相组成减少,残渣态汞、碳酸盐结合态汞和离子交换态汞占比降低。释放动力学拟合结果表明,汞的释放过程符合二级动力学模型。研究为汞矿区尾矿中汞的释放及矿区的潜在污染防治等环境问题提供了理论支撑及科学依据。

Utilizing Wanshan Yanwuping Tailings reservoir,a representative mercury mining site in China,as the focal point of this study,both static and dynamic leaching experiments were conducted to explore the characteristics of mercury release from the tailings.This comprehensive analysis involved assessing the mineral compositions of the tailings before and after the experiments,evaluating the distribution patterns of mercury accumulation,and studying the release kinetics.The study revealed several key findings:The tailings from Wanshan Yanwuping Tailings reservoir exhibited a weakly alkaline nature;predominant heavy metals within the tailings included Mn,Hg,and Zn,while the mineral composition primarily comprised SiO 2,CaMg(CO 3)2,and other non-metallic minerals;in static leaching experiments,the highest concentration of released mercury occurred at a pH of 4.5 and a solid-liquid ratio(g:mL)of 1:10,moreover,the composition of the tailings decreased following static leaching;the proportion of mercury in the carbonate-bound and ion-exchange states decreased,while the proportion of mercury among heavy metals was lower compared to mercury in the carbonate-bound and ion-exchange states.After static leaching,there was a decrease in the mineral phase composition of the tailings,along with a reduction in the proportions of carbonate-bound mercury and ion-exchanged mercury.This led to an increased risk of mercury release and transport.During dynamic leaching,the highest concentration of mercury was released under rainfall conditions with a pH of 4.5 and an intensity of 2.616 mL/min.Following dynamic leaching,there was a decrease in phase composition,accompanied by reductions in the proportions of mercury in the residual state,carbonate-bound state,and ion-exchange state.Consequently,the risks associated with the release and migration of heavy-metal mercury were heightened.The results of the release kinetic fitting revealed that the Hg release process conforms to the proposed second-level kinetic model.This suggests that the release of Hg from tailings under simulated rainfall leaching is not simply a diffusion process,but likely involves particle diffusion,surface adsorption-desorption at the solid-liquid interface,and liquid-membrane diffusion.These findings underscore the complexity of the physicochemical processes involved,which are controlled by a variety of diffusion mechanisms.This study contributes theoretical support and a scientific basis for understanding Hg release from tailings in Hg mines,as well as for addressing potential pollution prevention and control measures and other environmental concerns.