The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm...The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm） and the concentration of ammonium chloride （3.5-5.5 mol/L） on leaching rate of zinc were studied. The results show that decreasing the particle size of zinc silicate and increasing the leaching temperature and concentration of ammonium chloride can obviously enhance the leaching rate of zinc. Among the kinetic models of the porous solids tested, the grain model with porous diffusion control can well describe the zinc leaching kinetics. The apparent activation energy of the leaching reaction is 161.26 kJ/mol and the reaction order with respect to ammonium chloride is 3.5.展开更多
Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to ...Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to assess the effect of particle size,sulfuric acid concentration,pressure,reaction time and temperature on the extraction of zinc and the dissolution of silica.Under the optimum conditions employed,up to 99.25% of zinc extraction and 0.20% silica dissolution are obtained.The main minerals in leaching residue are quartz and small amounts of undissolved oxide minerals of iron,lead and aluminum are associated with quartz.展开更多
Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precur...Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.展开更多
Nanocomposites of ZnO encapsulated in mesoporous silica were prepared by wetness impregnation and calcination. The samples were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption...Nanocomposites of ZnO encapsulated in mesoporous silica were prepared by wetness impregnation and calcination. The samples were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption isotherms, and X-ray photoelectron spectroscopy. The effects of ZnO content and thermal treatment on the existing form of ZnO as well as phase transformation were investigated. ZnO exists stably in the form of non-crystalline phase or cluster when crystallite size is small. With increasing ZnO content, as the size of ZnO reaches a critical size of crystalline phase, the non-crystalline ZnO or cluster transforms structurally to crystalline ZnO with low energy state. Besides, Zn2Si04 was obtained by solid-state reaction between ZnO and rnesoporous silica. The mesoporous silica acts as not only a reactant but also a diffusion barrier which inhibits the phase transformation from ^-Zn2Si04 to ^-Zn2Si04. The formation temperature of Zn2Si04 is lower than that of conventional solid-state reaction because of the unique structure of mesoporous silica.展开更多
基金Project(2014CB643404)supported by the National Basic Research Program of ChinaProject(51374254)supported by the National Natural Science Foundation of China
文摘The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm） and the concentration of ammonium chloride （3.5-5.5 mol/L） on leaching rate of zinc were studied. The results show that decreasing the particle size of zinc silicate and increasing the leaching temperature and concentration of ammonium chloride can obviously enhance the leaching rate of zinc. Among the kinetic models of the porous solids tested, the grain model with porous diffusion control can well describe the zinc leaching kinetics. The apparent activation energy of the leaching reaction is 161.26 kJ/mol and the reaction order with respect to ammonium chloride is 3.5.
基金Project(2007CB613605) supported by the National Basic Research Program of China
文摘Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to assess the effect of particle size,sulfuric acid concentration,pressure,reaction time and temperature on the extraction of zinc and the dissolution of silica.Under the optimum conditions employed,up to 99.25% of zinc extraction and 0.20% silica dissolution are obtained.The main minerals in leaching residue are quartz and small amounts of undissolved oxide minerals of iron,lead and aluminum are associated with quartz.
文摘Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.
基金supported by the National Natural Science Foundation of China under Grant No. 51202103the China Postdoctoral Science Foundation under Grant No. 2012M510789+1 种基金the Natural Science Foundation of Inner Mongolia Autonomous Region under Grant No. 2011BS0804the Program of Higher-level Talents of Inner Mongolia University under Grant No. Z20100123
文摘Nanocomposites of ZnO encapsulated in mesoporous silica were prepared by wetness impregnation and calcination. The samples were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption isotherms, and X-ray photoelectron spectroscopy. The effects of ZnO content and thermal treatment on the existing form of ZnO as well as phase transformation were investigated. ZnO exists stably in the form of non-crystalline phase or cluster when crystallite size is small. With increasing ZnO content, as the size of ZnO reaches a critical size of crystalline phase, the non-crystalline ZnO or cluster transforms structurally to crystalline ZnO with low energy state. Besides, Zn2Si04 was obtained by solid-state reaction between ZnO and rnesoporous silica. The mesoporous silica acts as not only a reactant but also a diffusion barrier which inhibits the phase transformation from ^-Zn2Si04 to ^-Zn2Si04. The formation temperature of Zn2Si04 is lower than that of conventional solid-state reaction because of the unique structure of mesoporous silica.
