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In this paper, TEM-EDX, FTIR, XPS, PIXE, and EPBS were employed to identify the uranium biosorption behavior and the potential mechanism on cells of Geotrichum sp. dwc-1, isolated from soils. These results displayed that the biosorption behavior was greatly dependent on pH and uranium was absorbed by bounding to amino, phosphate as well as carboxyl functional groups. Uranium biosorption behavior on Geotrichum sp. dwc-1 involves bioaccumulation, electrostatic interaction and ion exchange process. This work throws further light on potential fungal roles these mechanisms for elemental recovery and bioremediation. [ABSTRACT FROM AUTHOR]

Three types of graphene sheets (GS) were decorated by chemical oxidation, electrolysis and ball-milling, respectively. These oxidized samples were characterized using SEM, XRD, Raman, FT-IR and XPS, and then were employed to enrich U(VI) from aqueous solutions as a function of pH, contact time and initial concentration of U(VI). These results displayed that the quantities and types of oxygen-functional groups were extremely different through these methods, which highly determined the adsorption capacity of graphene oxide to uranium. This work may provide some helpful information to optimize these fabrication processes and improve the adsorption ability of GS to uranium. [ABSTRACT FROM AUTHOR]

Novel graphene oxide -carbon nanotubes (GO-CNTs) hybrid aerogels were fabricated via a freeze-drying method using aqueous solutions of GO and CNTs. The resulting aerogels were characterized by scanning electron microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy and thermal gravity analysis. The three-dimensional GO-CNTs aerogels were used to remove uranium(VI) from aqueous solutions. The results showed that GO-CNTs aerogels had high removal ability to uranium(VI) and could be a promising sorbent for many environment applications. [ABSTRACT FROM AUTHOR]

The extraction kinetics of uranium(VI) and thorium(IV) with Tri-iso-amyl phosphate (TiAP) from nitric acid medium has been investigated using a Lewis Cell. Especially, dependences of the extraction rate on stirring speed, temperature, interfacial area were firstly measured to elucidate the extraction kinetics regimes. The experimental results demonstrated that extraction kinetic of U(VI) is governed by chemical reactions at interface with an activation energy, E, of 43.41 kJ/mol, while the rate of Th(IV) extraction is proved to be intermediate controlled, of which the E is 23.20 kJ/mol. Reaction orders with respect to the influencing parameters of the extraction rate are determined, and the rate equations of U(VI) and Th(IV) at 293 K have been proposed as respectively. [ABSTRACT FROM AUTHOR]

The extraction behavior of U(VI) and Th(IV) with tri-isoamyl phosphate-kerosene (TiAP-KO) from nitric acid medium was investigated in detail using the batch extraction method as a function of aqueous-phase acidity, TiAP concentration and temperature, then the thermodynamic parameters associated with the extraction were derived by the second-law method. It could be noted that the distribution ratios of U(VI) or Th(IV) increased with increasing HNO concentration until 6 or 5 M from 0.1 M. However, a good separation factor ( D/ D) of 88.25 was achieved at 6 M HNO, and the stripping of U(VI) from TiAP-KO with deionized water or diluted nitric acid was easier than that of Th(IV). The probable extracted species were deduced by log D-log c plot at different temperatures as UO(NO)·(TiAP) and Th(NO)·(TiAP), respectively. Additionally, △ H, △ G and △ S for the extraction of U(VI) and Th(IV) revealed that the extraction of U(VI) by TiAP was an exothermic process and was counteracted by entropy change, while the extraction of Th(IV) was an endothermic process and was driven by entropy change. [ABSTRACT FROM AUTHOR]