Superparamagnetic polyvinylpyrrolidone/chitosan/Fe3O4 electrospun nanofibers as effective U(VI) adsorbents

Magnetoactive electrospun fibrous membranes consisting of polyvinylpyrrolidone (PVP), chitosan (CS) and pre-fabricated, double-layer oleic acid-coated magnetite nanoparticles (OA.OA.Fe₃O₄) were fabricated and evaluated as new adsorbent materials for the removal and recovery of uranium (U(VI)) from aqueous solutions. The adsorption has been investigated by batch-type experiments and the solid material has been characterized by X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy/energy dispersive X-ray analysis (TEM/EDX) and vibration sample magnetometry (VSM) measurements prior and after uranium adsorption. The experimental adsorption data were found to be well fitted with the Langmuir isotherm and the pseudo-second order kinetic model. The results indicate that PVP/CS/OA.OA.Fe₃O₄ fibrous adsorbents exhibit good adsorption properties towards U(VI) in aqueous solutions, achieving a q_max value of 0.77 mol kg⁻¹ (183.3 mg g⁻¹) at pH 6.0. The experiments regarding the regeneration and reuse of the magnetoactive adsorbents were carried out using Na₂CO₃, at pH ~11. After four cycles, the percentage relative adsorption remained stable (~100%) whereas the desorption percentage decreased from 31.9% to 21.0%. Generally, the presented results demonstrate that the incorporation of the Fe₃O₄ NPs has a positive effect on the adsorption efficiency of U(VI) from aquatic environments.     

Synthesis and antifungal activity of reduced graphene oxide nanosheets

Reduced graphene oxide (rGO) nanosheets were produced using a modified Hummers method. Antifungal activity of rGO nanosheets was tested against three fungi i.e., Aspergillus niger (A. niger), Aspergillus oryzae (A. oryzae) and Fusarium oxysporum (F. oxysporum). The rGO inhibits the mycelial growth of the fungi and it is believed that this is due to its sharp edges. The half maximal inhibitory concentration (IC₅₀), a measure of the effectiveness of the rGO in inhibiting the fungi, was investigated. IC₅₀ values of the rGO against F. oxysporum, A. niger, and A. oryzae are 50, 100, and 100 μg ml^?1, respectively.     

When users become sensors: can we trust their readings?

Smart sensor network arises as a new generation of sensor networks, where a crowd of possibly anonymous volunteers are involved in the tasks of collecting data from the surrounding environment and providing it to the community. In this paper, we analyze one of the main questions, often forgotten, in these scenarios: whether or not we can trust the sensor readings provided by the individuals engaged in the sensor network. We introduce a data reliability architecture capable of filtering and validating sensor readings in an open environment, where not all users are equally honest. Simulations based on a real world smart sensor application allow us to make a first analysis of the proposed architecture's performance and the variables that have a significant impact on this performance. Copyright © 2013 John Wiley & Sons, Ltd.