This paper describes new experimental results on mlneral-water reaction kinetics obtained in plug-flow systems at high temperatures and pressures. As an example, the rates of reaction between calcite, fluorite, albite...This paper describes new experimental results on mlneral-water reaction kinetics obtained in plug-flow systems at high temperatures and pressures. As an example, the rates of reaction between calcite, fluorite, albite and water in the continuous flowing system have been measured in three separate studies. All experiments are carried out by suspending a sample bag in the plug-flow vessel, by pumping water at carefully controlled rates through the vessel, and by collecting and analyzing the reacted solution. In addition, the reaction mechanisms of fluorite and albite in a packed bed reactor have been studied with the aid of an axial dispersion model. The main factors controlling the effective dissolution rate with respect to temperature, solvent flow rate, and chemistry of the input solutions have been evaluated. It is also found that a non-steady state process is, in some cases, still observed, even under conditions where steady state conditions should have been attained. These results provide展开更多
The sorption of cadmium(Cd) is one of the most important chemical processes in soil, affecting its fate and mobility in both soil and water and ultimately controlling its bioavailability. In order to fundamentally und...The sorption of cadmium(Cd) is one of the most important chemical processes in soil, affecting its fate and mobility in both soil and water and ultimately controlling its bioavailability. In order to fundamentally understand the sorption/desorption of Cd in soil systems, X-ray absorption fine structure spectroscopy(XAFS) has been applied in numerous studies to provide molecular-level information that can be used to characterize the surface adsorption and precipitation reactions that Cd can undergo. This information greatly improves our current knowledge of the possible chemical reactions of Cd in soil. This paper critically reviews the mechanisms of Cd sorption/desorption at the mineral-water interface based on XAFS studies performed over the past twenty years. An introduction to the basic concepts of sorption processes is provided, followed by a detailed interpretation of XAFS theory and experimental data collection and processing,ending finally with a discussion of the atomic/molecular-scale Cd sorption mechanisms that occur at the soil mineral-water interface. Particular emphasis is placed on literature that discusses Cd adsorption and speciation when associated with iron, manganese, and aluminum oxides and aluminosilicate minerals.Multiple sorption mechanisms by which Cd is sorbed by these minerals have been found, spanning from outer-sphere to inner-sphere to surface precipitation,depending on mineral type, surface loading, and pH. In addition, the application of complementary techniques(e.g.,113 Cd nuclear magnetic resonance(NMR) and molecular dynamics simulation) for probing Cd sorption mechanisms is discussed. This review can help to develop appropriate strategies for the environmental remediation of Cd-contaminated soils.展开更多
基金Project supported by the National Natural Science Foundation of China and N.S.F. of the U.S.A. and Shell Companies Foundation.
文摘This paper describes new experimental results on mlneral-water reaction kinetics obtained in plug-flow systems at high temperatures and pressures. As an example, the rates of reaction between calcite, fluorite, albite and water in the continuous flowing system have been measured in three separate studies. All experiments are carried out by suspending a sample bag in the plug-flow vessel, by pumping water at carefully controlled rates through the vessel, and by collecting and analyzing the reacted solution. In addition, the reaction mechanisms of fluorite and albite in a packed bed reactor have been studied with the aid of an axial dispersion model. The main factors controlling the effective dissolution rate with respect to temperature, solvent flow rate, and chemistry of the input solutions have been evaluated. It is also found that a non-steady state process is, in some cases, still observed, even under conditions where steady state conditions should have been attained. These results provide
基金funded by the National Natural Science Foundation of China (Nos. 41722303, 41977267, and 41473084)the National Key R&D Program of China (No. 2017YFD0800303)+1 种基金the financial support of the Opening Fund of State Key Laboratory of Environmental Geochemistry (No. SKLEG2019712)the National 1 000 Youth Talent Program of China。
文摘The sorption of cadmium(Cd) is one of the most important chemical processes in soil, affecting its fate and mobility in both soil and water and ultimately controlling its bioavailability. In order to fundamentally understand the sorption/desorption of Cd in soil systems, X-ray absorption fine structure spectroscopy(XAFS) has been applied in numerous studies to provide molecular-level information that can be used to characterize the surface adsorption and precipitation reactions that Cd can undergo. This information greatly improves our current knowledge of the possible chemical reactions of Cd in soil. This paper critically reviews the mechanisms of Cd sorption/desorption at the mineral-water interface based on XAFS studies performed over the past twenty years. An introduction to the basic concepts of sorption processes is provided, followed by a detailed interpretation of XAFS theory and experimental data collection and processing,ending finally with a discussion of the atomic/molecular-scale Cd sorption mechanisms that occur at the soil mineral-water interface. Particular emphasis is placed on literature that discusses Cd adsorption and speciation when associated with iron, manganese, and aluminum oxides and aluminosilicate minerals.Multiple sorption mechanisms by which Cd is sorbed by these minerals have been found, spanning from outer-sphere to inner-sphere to surface precipitation,depending on mineral type, surface loading, and pH. In addition, the application of complementary techniques(e.g.,113 Cd nuclear magnetic resonance(NMR) and molecular dynamics simulation) for probing Cd sorption mechanisms is discussed. This review can help to develop appropriate strategies for the environmental remediation of Cd-contaminated soils.
