Bioremediation of uranium from waste effluents using novel biosorbents: a review

Journal of Radioanalytical and Nuclear Chemistry - Several treatments for the removal of toxic heavy metals like uranium from wastewater have been developed, but none of them are sufficiently...     

Influence of substitution on dielectric and impedance spectroscopy of Sr1 − xBi2 + yNb2O9 ferroelectric ceramics synthesized by chemical route

Nanocrystalline powders of Sr_1 − xBi_2 + yNb₂O₉ (SBN, x = 0.0, 0.1, 0.2, 0.3, and 0.4; y = 0, 0.066, 0.133, 0.200, and 0.266) were prepared by aqueous solution method using water-soluble Sr-EDTA, Bi-EDTA and Nb-tartarate as the starting materials. XRD showed that the samples were free from fluorite or pyrochlore phase within heat-treatment temperature from 550 to 600 °C. Average crystallite size and particle diameter were observed to be between 10 and 25 nm, which were analyzed through XRD and TEM, respectively. Bi-substitution has substantially improved the sinterability of SBN and enabled to achieve high density (96%), which was otherwise difficult in the case of pure SBN. The dielectric properties of SBN ceramics were significantly enhanced by the partial replacement of Sr²⁺ ions by the trivalent bismuth ions. The complex impedance diagrams of Bi-substituted SBN, x = 0.4 ceramics exhibited only one semicircle indicating a significant contribution from the grains. In contrast, the impedance plots for pure and other substituted SBN ceramics show an additional low-frequency semicircle, which was attributed to the blocker size effects. The dielectric behavior of pure and Bi-substituted SBN ceramics was rationalized using the impedance and modulus data.     

A novel synthesis of FeNbO<Subscript>4</Subscript> nanorod by hydrothermal process

This study reports a facile, gram-scale synthesis of FeNbO₄ nanorods via hydrothermal route, using iron nitrate [Fe(NO₃)₃] and niobium tartarate (Nb tartarate) in presence of potassium peroxosulfate. The formation of single phase, polycrystalline orthorhombic structure of FeNbO₄ was confirmed by the careful analysis of the X-ray diffraction (XRD) pattern. The average crystallite size, calculated using a few XRD peaks, was found to be 12.8 nm. As indicated by transmission electron microscopy (TEM) and field emission scanning electron microscopy, the average length and diameter of the rods were found to be only 25 × 7 nm and 47 × 14 nm, respectively. The selected area electron diffraction and high-resolution transmission electron microscopy (HRTEM) data of the single rod implied that FeNbO₄ nanorods were polycrystalline in nature and grew up along the c-axis. HRTEM also revealed that the fringes are equidistant with a lattice separation of 0.91 Ǻ, which corresponded to the (111) plane of the FeNbO₄ crystal. Elemental composition of the nanorods was confirmed using electron dispersive X-ray spectroscopy analysis while binding state of the surface was intervened through X-ray photoelectron spectroscopy. Mechanistic investigations suggested that potassium peroxosulfate played a crucial role in the unidirectional growth of particles. The synthetic method is simple, amenable to scale up and contributes a new tool box for the development of FeNbO₄-based one-dimensional (1D) structures that appears to be more promising for a myriad of applications, compared to their 3D counterparts.