Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe...Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.展开更多
The degradation behavior of ethyl xanthate(EX) salt was the most widely used collector in sulfide mineral flotation and emission of flotation tailings with residual EX was harmful to environment. In this work, hydroge...The degradation behavior of ethyl xanthate(EX) salt was the most widely used collector in sulfide mineral flotation and emission of flotation tailings with residual EX was harmful to environment. In this work, hydrogen peroxide(H2O2) was investigated by UV-visible spectroscopy(UV/Vis) at different p H values from 3 to 12. For p H value from 5 to 12, EX was oxidized into ethyl per xanthate(EPX) by H2O2. Then EPX was further oxidized into thiosulfate(TS) salt rather than ethyl thiocarbonate(ETC) and this step was the reaction-limited step. Then depending on p H values, TS was degraded into sulphate and carbonate salts(p H>7) or elemental sulfur(p H<7). The kinetics data show that the degradation rate of EX increases with increasing the H2O2 concentration and is independent on the p H values. Without H2O2, EX is hydrolyzed to carbon disulfide fast at p H value <3.0, but the reaction of hydrolysis is undetectable at p H value >3.0 during test time.展开更多
基金Project supported by the Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,China
文摘Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.
基金Project(2013AA064102)supported by the National High Technology Research and Development Program of ChinaProject(B14034)supported by the Program of Introducing Talents of Discipline to Universities,ChinaProject supported by the 2011 Collaborative Innovation Center for Clean and Efficient utilization of Strategic Metal Mineral Resources,China
文摘The degradation behavior of ethyl xanthate(EX) salt was the most widely used collector in sulfide mineral flotation and emission of flotation tailings with residual EX was harmful to environment. In this work, hydrogen peroxide(H2O2) was investigated by UV-visible spectroscopy(UV/Vis) at different p H values from 3 to 12. For p H value from 5 to 12, EX was oxidized into ethyl per xanthate(EPX) by H2O2. Then EPX was further oxidized into thiosulfate(TS) salt rather than ethyl thiocarbonate(ETC) and this step was the reaction-limited step. Then depending on p H values, TS was degraded into sulphate and carbonate salts(p H>7) or elemental sulfur(p H<7). The kinetics data show that the degradation rate of EX increases with increasing the H2O2 concentration and is independent on the p H values. Without H2O2, EX is hydrolyzed to carbon disulfide fast at p H value <3.0, but the reaction of hydrolysis is undetectable at p H value >3.0 during test time.
