Palygorskite clays sampled from palygorskite clay deposits in Jiangsu and Anhui provinces were investigated by transmission electron microscopy (TEM). Many intergrowth phenomena of special ultra-microstructure between...Palygorskite clays sampled from palygorskite clay deposits in Jiangsu and Anhui provinces were investigated by transmission electron microscopy (TEM). Many intergrowth phenomena of special ultra-microstructure between smectite and palygorskite were found. The ultra-microstructure indicates that palygorsite fiberrous crystals grow along (001) of primary smectite through structural transformation and decomposition of the primary smectite. According to field investigation and X-ray diffraction (XRD) analyses, the transformation mechanism and process can be described as: formation of smectite from basalt weathering deposited in localiza- tion basin; evaporation of lake water in aridity environment causing pH increase and concentra- tion of magnesium ion in interstice water of sediment smectite in the lake basin. Under alkaline conditions, magnesium ion occupied interlayer positions of the smectite. Because of the misfit between magnesium octahedral sheet and smectite layer, magnesium ion interaction with smec- tite layers caused the smectite to transform into palygorskite, and resulted in the formation of smectite and palygorskite complex particulates, and even smaller secondary smectite crystal plates. The transformation of smectite structure resulted in the formation of nanometer minerals with large specific surface area and excellent property of physics and chemistry in smec- tite-palygorskite mixing clay. The results from TEM investigation are important for understanding properties of palygorskite clay and application.展开更多
矿石的检测是矿山企业采矿生产的重要工作,它既可以帮助分析指导采矿生产,又是后续选矿(冶炼)生产配比的组织保障。但是由于矿石的特殊性以及现场环境工况的复杂性,传统的矿石品位检测方法难以在无损检测的前提下准确的判断品位。X射线...矿石的检测是矿山企业采矿生产的重要工作,它既可以帮助分析指导采矿生产,又是后续选矿(冶炼)生产配比的组织保障。但是由于矿石的特殊性以及现场环境工况的复杂性,传统的矿石品位检测方法难以在无损检测的前提下准确的判断品位。X射线透射法已经成熟应用于安检、医疗领域中进行物质识别,本文将此方法改进引入矿石品位检测中,通过感知器算法形成分类曲线,依据分类曲线统计 K 值,进而判断矿石品位。这种方法立足于大量实验数据,判断结果和实际相符程度高,并且实现无损检测。展开更多
The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the ...The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the core-shell interface. The chemical compositions and the fine structure of nZVI are characterized with a combination of spherical aberration corrected scanning transmission electron microscopy(Cs-STEM), X-ray energy-dispersive spectroscopy(XEDS), electron energy loss spectroscopy(EELS), and high-resolution X-ray photoelectron spectroscopy(HR-XPS). Atomically resolved EELS at the oxygen K-edge unfolds that the Fe species in nZVI are well stratified from Fe(Ⅲ) oxides in the outermost periphery to a mixed Fe(Ⅲ)/Fe(Ⅱ) interlayer, then Fe(Ⅱ) oxide and the pure Fe(0) phase. Reactions between As(Ⅴ)and nZVI suggest that a well-structured local redox gradient exists within the shell layer, which serves as a thermodynamically favorable conduit for electron transfer from the iron core to the surface-bound As(Ⅴ). HR-XPS with ion sputtering shows that arsenic species shift from As(Ⅴ), As(Ⅲ)/As(Ⅴ) to As(Ⅴ)/As(Ⅲ)/As(0) from the iron oxide shell–water interface to the Fe(0) core. Results reinforce previous work on the efficacy of nZVI for removing and remediating arsenic while the analytical TEM methods are also applicable to the study of environmental interfaces and surface chemistry.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40072017).
文摘Palygorskite clays sampled from palygorskite clay deposits in Jiangsu and Anhui provinces were investigated by transmission electron microscopy (TEM). Many intergrowth phenomena of special ultra-microstructure between smectite and palygorskite were found. The ultra-microstructure indicates that palygorsite fiberrous crystals grow along (001) of primary smectite through structural transformation and decomposition of the primary smectite. According to field investigation and X-ray diffraction (XRD) analyses, the transformation mechanism and process can be described as: formation of smectite from basalt weathering deposited in localiza- tion basin; evaporation of lake water in aridity environment causing pH increase and concentra- tion of magnesium ion in interstice water of sediment smectite in the lake basin. Under alkaline conditions, magnesium ion occupied interlayer positions of the smectite. Because of the misfit between magnesium octahedral sheet and smectite layer, magnesium ion interaction with smec- tite layers caused the smectite to transform into palygorskite, and resulted in the formation of smectite and palygorskite complex particulates, and even smaller secondary smectite crystal plates. The transformation of smectite structure resulted in the formation of nanometer minerals with large specific surface area and excellent property of physics and chemistry in smec- tite-palygorskite mixing clay. The results from TEM investigation are important for understanding properties of palygorskite clay and application.
文摘矿石的检测是矿山企业采矿生产的重要工作,它既可以帮助分析指导采矿生产,又是后续选矿(冶炼)生产配比的组织保障。但是由于矿石的特殊性以及现场环境工况的复杂性,传统的矿石品位检测方法难以在无损检测的前提下准确的判断品位。X射线透射法已经成熟应用于安检、医疗领域中进行物质识别,本文将此方法改进引入矿石品位检测中,通过感知器算法形成分类曲线,依据分类曲线统计 K 值,进而判断矿石品位。这种方法立足于大量实验数据,判断结果和实际相符程度高,并且实现无损检测。
基金the National Natural Science Foundation of China(11475127,51578396,41673096,and 41772243)National Postdoctoral Program for Innovative Talents(BX201700172)
文摘The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the core-shell interface. The chemical compositions and the fine structure of nZVI are characterized with a combination of spherical aberration corrected scanning transmission electron microscopy(Cs-STEM), X-ray energy-dispersive spectroscopy(XEDS), electron energy loss spectroscopy(EELS), and high-resolution X-ray photoelectron spectroscopy(HR-XPS). Atomically resolved EELS at the oxygen K-edge unfolds that the Fe species in nZVI are well stratified from Fe(Ⅲ) oxides in the outermost periphery to a mixed Fe(Ⅲ)/Fe(Ⅱ) interlayer, then Fe(Ⅱ) oxide and the pure Fe(0) phase. Reactions between As(Ⅴ)and nZVI suggest that a well-structured local redox gradient exists within the shell layer, which serves as a thermodynamically favorable conduit for electron transfer from the iron core to the surface-bound As(Ⅴ). HR-XPS with ion sputtering shows that arsenic species shift from As(Ⅴ), As(Ⅲ)/As(Ⅴ) to As(Ⅴ)/As(Ⅲ)/As(0) from the iron oxide shell–water interface to the Fe(0) core. Results reinforce previous work on the efficacy of nZVI for removing and remediating arsenic while the analytical TEM methods are also applicable to the study of environmental interfaces and surface chemistry.
