Transport behavior of humic acid-modified nano-hydroxyapatite in saturated packed column: effects of Cu, ionic strength, and ionic composition

The surfaces of nano-hydroxyapatite (nHAP) used for contaminated soil and groundwater remediation may be modified to render nHAP highly mobile in the subsurface. Humic acid (HA) is widely used to modify and stabilize colloid suspensions. In this work, column experiments were conducted to determine the effects of contaminant (e.g., Cu) concentration, ionic strength (IS), and ion composition (IC) on the transport behavior of HA-modified nHAP in saturated packed columns. IS and nature of the cation had strong effects on the deposition of nHAP, and the effect was greater for divalent than for monovalent cations. Divalent cations have a greater capacity to screen the surface charge of nHAP, and Ca(2+) bridges the HA-modified nHAP colloidal particles, which causes greater deposition. Moreover, Cu(2+) had a greater effect on the transport behavior than Ca(2+) due to their strong exchange with Ca(2+) of nHAP and its surface complexation with nHAP. The relative travel distance L(T), of the injected HA-modified nHAP colloids, ranges from less than one to several meters at varying Cu concentrations, ISs, and ICs in saturated packed columns. The results are crucial to evaluate the efficacy of nHAP on the remediation of contaminated soil and groundwater environments.     

Aggregation of reduced graphene oxide and its nanohybrids with magnetite and elemental silver under environmentally relevant conditions

Journal of Nanoparticle Research - Utilizing solar energy for hydrogen evolution is a great challenge for its insufficient visible-light power conversion. In this paper, we report a facile...     

纳米TiO_2微胶粒的光化反应制备机理及量子尺寸效应

研究了由水相Ｔｉ３＋制备纳米极ＴｉＯ２微胶粒的光化反应机理及反应动力学，给出反应速率方程，讨论了ＴｉＯ２微胶粒的量子尺寸效应，经电镜测试ＴｉＯ２粒子的直径为１５～２５ｎｍ，反应过程中由气相色谱仪监测生成物Ｈ２。     

Kinetics and equilibria of the chromatographic separation of maltose and trehalose

Trehalose, a nonreducing disaccharide, has been extensively applied to food, cosmetics, and pharmaceutical goods. The resultant solution of trehalose prepared by enzymatic methods includes high amounts of maltose. However, it is quite difficult to separate maltose and trehalose on an industrial scale because of their similar properties. In this paper, a high‐performance resin was selected as a stationary phase to separate trehalose and maltose, and the resolution of these sugars was 0.59. The potential of a cation exchange resin was investigated as the stationary phase in separating trehalose and maltose using deionized water as the mobile phase. Based on the equilibrium dispersive model, the axial dispersion coefficients and overall mass transfer coefficients of maltose and trehalose were determined by moment analysis at two different temperatures, 50 and 70°C. Other parameters, including the column void and the adsorption isotherms, were also determined and applied to simulate the elution curves of trehalose and maltose. The simulated results matched the experimental data, validating the parameters. The optimized parameters are critical to the chromatographic separation of trehalose and maltose on an industrial scale.     

纳米TiO2微胶粒的光化应制备机理及量子尺寸效应

研究了由水相Ｔｉ＾３＋制备纳米极Ｔｉ＾Ｏ２微胶粒的光化反应机理及反应动力学，给出反应速率方程。讨论了ＴｉＯ２微胶粒的量子尺寸效应，经电镜测试ＴｉＯ２粒子的直径为１５－２５ｎｍ。反应过程中由气相色谱仪监测生成物Ｈ２。