The mercury sulfidation experiments were conducted in the pH range from 1 to 13. The results show that Hg（II） reacted with equimolar S（ II ） has the lowest remained Hg（II ） concentration （9.7 μg/L） at pH 1.0 ...The mercury sulfidation experiments were conducted in the pH range from 1 to 13. The results show that Hg（II） reacted with equimolar S（ II ） has the lowest remained Hg（II ） concentration （9.7 μg/L） at pH 1.0 and the highest remained concentration （940.8μg/L） at pH 13.0. Meanwhile, the changes of pH values were monitored exactly, which reveal that solution pH values change when mixing the same pH value solutions of HgCI2 and Na2S. In order to explain the phenomena and determine the reaction paths of Hg（II） reacting with S（ II ） in the solution, the concerned thermodynamics was studied. Species of S（ II ）-H2O system and Hg（II）-H2O system at different pH values were calculated, and then the species distribution diagrams of S（II）-H2O system, Hg（ II ）-H2O system and Hg（ II ）-Cl-OH--H20 system were drawn. Combining the experimental data and thermodynamic calculation, the mechanism of Hg（II） reacting with S（II） was deduced. The results indicate that different species of S（ II ） and Hg（II） have the diverse reaction paths to form HgS precipitate at different pH values and the standard Gibbs free energies change （△tGm^⊙） of those equations are also calculated, which can provide a guidance for mercury-containing wastewater treatment with Na2S.展开更多
When a liquid is supercooled,its structural equilibration timeτeqincreases sharply approaching the glass transition temperature Tg,below which it is kinetically arrested in the out of equilibrium glassy state.Upon an...When a liquid is supercooled,its structural equilibration timeτeqincreases sharply approaching the glass transition temperature Tg,below which it is kinetically arrested in the out of equilibrium glassy state.Upon annealing below Tg,such glassy state relaxes toward the equilibrium state.There is growing evidence that such relaxation process is quite complex,influenced by the complexity of the potential energy landscape.Here we report the observation of a hierarchical aging pathway in the process of the glass-to-supercooled liquid transition in various molecular glass forming systems.Differential scanning calorimetry reveals that the glassy state upon annealing below Tgfirstly enters a transient metastable supercooled liquid state with slightly higher enthalpies than that of the equilibrium supercooled liquid state when extrapolated to below Tg.This observation is also confirmed by structural measurements via Raman scattering.The dynamics of the transient metastable-to-stable supercooled liquid transition exhibits characteristics of thermodynamic transition at spinodal temperature Tspslightly above Tg,leading to anomalous behaviors such as the appearance of a transition-like behavior in the plot of fragility measurements.These observations imply that the free energy landscape of the supercooled liquid develops complexity with qualitative changes approaching Tgand could have strong influence on the process of the glass transition.展开更多
基金Project(50925417) supported by China National Funds for Distinguished Young ScientistsProject(50830301) supported by the Key Project of the National Natural Science Foundation of China+2 种基金Project(308019) supported by the Key Science and Technical Project of Ministry of Science and Technology of ChinaProject(2007BAC25B01) supported by the National Key Project of Science and Technical Supporting Programs Funded by Ministry of Science and Technology of China during the 11th Five-Year PlanProject(08JJ3020) supported by the Natural Science Foundation of Hunan Province, China
文摘The mercury sulfidation experiments were conducted in the pH range from 1 to 13. The results show that Hg（II） reacted with equimolar S（ II ） has the lowest remained Hg（II ） concentration （9.7 μg/L） at pH 1.0 and the highest remained concentration （940.8μg/L） at pH 13.0. Meanwhile, the changes of pH values were monitored exactly, which reveal that solution pH values change when mixing the same pH value solutions of HgCI2 and Na2S. In order to explain the phenomena and determine the reaction paths of Hg（II） reacting with S（ II ） in the solution, the concerned thermodynamics was studied. Species of S（ II ）-H2O system and Hg（II）-H2O system at different pH values were calculated, and then the species distribution diagrams of S（II）-H2O system, Hg（ II ）-H2O system and Hg（ II ）-Cl-OH--H20 system were drawn. Combining the experimental data and thermodynamic calculation, the mechanism of Hg（II） reacting with S（II） was deduced. The results indicate that different species of S（ II ） and Hg（II） have the diverse reaction paths to form HgS precipitate at different pH values and the standard Gibbs free energies change （△tGm^⊙） of those equations are also calculated, which can provide a guidance for mercury-containing wastewater treatment with Na2S.
基金supported by the National Basic Research Program of China (2015CB856801)
文摘When a liquid is supercooled,its structural equilibration timeτeqincreases sharply approaching the glass transition temperature Tg,below which it is kinetically arrested in the out of equilibrium glassy state.Upon annealing below Tg,such glassy state relaxes toward the equilibrium state.There is growing evidence that such relaxation process is quite complex,influenced by the complexity of the potential energy landscape.Here we report the observation of a hierarchical aging pathway in the process of the glass-to-supercooled liquid transition in various molecular glass forming systems.Differential scanning calorimetry reveals that the glassy state upon annealing below Tgfirstly enters a transient metastable supercooled liquid state with slightly higher enthalpies than that of the equilibrium supercooled liquid state when extrapolated to below Tg.This observation is also confirmed by structural measurements via Raman scattering.The dynamics of the transient metastable-to-stable supercooled liquid transition exhibits characteristics of thermodynamic transition at spinodal temperature Tspslightly above Tg,leading to anomalous behaviors such as the appearance of a transition-like behavior in the plot of fragility measurements.These observations imply that the free energy landscape of the supercooled liquid develops complexity with qualitative changes approaching Tgand could have strong influence on the process of the glass transition.
