Investigating mercury release characteristics from typical mercury tailings:a case study of Wanshan Yanyaping Tailings depot
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 SiO2,CaMg(CO3)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.
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