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Gheju M.,Polytechnic University of Timisoara | Balcu I.,Romanian National Institute for Research and Development in Electrochemistry and Condensed Matter
Journal of Hazardous Materials | Year: 2011

This work presents investigations on the total removal of chromium from Cr(VI) aqueous solutions by reduction with scrap iron and subsequent precipitation of the resulted cations with NaOH. The process was detrimentally affected by a compactly passivation film occurred at scrap iron surface, mainly composed of Cr(III) and Fe(III). Maximum removal efficiency of the Cr(total) and Fe(total) achieved in the clarifier under circumneutral and alkaline (pH 9.1) conditions was 98.5% and 100%, respectively. The optimum precipitation pH range which resulted from this study is 7.6-8.0. Fe(total) and Cr(total) were almost entirely removed in the clarifier as Fe(III) and Cr(III) species; however, after Cr(VI) breakthrough in column effluent, chromium was partially removed in the clarifier also as Cr(VI), by coprecipitation with cationic species. As long the column effluent was free of Cr(VI), the average Cr(total) removal efficiency of the packed column and clarifier was 10.8% and 78.8%, respectively. Our results clearly indicated that Cr(VI) contaminated wastewater can be successfully treated by combining reduction with scrap iron and chemical precipitation with NaOH. © 2011 Elsevier B.V.

Herklotz A.,Oak Ridge National Laboratory | Rus S.F.,Romanian National Institute for Research and Development in Electrochemistry and Condensed Matter | Ward T.Z.,Oak Ridge National Laboratory
Nano Letters | Year: 2016

The optical band gap of the prototypical semiconducting oxide SnO2 is shown to be continuously controlled through single axis lattice expansion of nanometric films induced by low-energy helium implantation. While traditional epitaxy-induced strain results in Poisson driven multidirectional lattice changes shown to only allow discrete increases in bandgap, we find that a downward shift in the band gap can be linearly dictated as a function of out-of-plane lattice expansion. Our experimental observations closely match density functional theory that demonstrates that uniaxial strain provides a fundamentally different effect on the band structure than traditional epitaxy-induced multiaxes strain effects. Charge density calculations further support these findings and provide evidence that uniaxial strain can be used to drive orbital hybridization inaccessible with traditional strain engineering techniques. © 2016 American Chemical Society.

Ercuta A.,West University of Timisoara | Chirita M.,Romanian National Institute for Research and Development in Electrochemistry and Condensed Matter
Journal of Crystal Growth | Year: 2013

Porous crystals of magnetite and vacancy-ordered maghemite, rhombohedron-shaped, reaching 150 μm in size, and having remarkably large specific surface area (88.55 m2/g for magnetite, 40.14 m 2/g for maghemite) were obtained via topotactical conversion, starting from hydrothermally grown siderite single crystals. The increase in density (from 3.9 g/cm3 for siderite to 5.24 g/cm3 for magnetite and 4.9 g/cm3 for maghemite) caused quasi-ordered internal pores-grains pattern, with mesocrystalline appearance. The X-ray Line-Profile Fitting-based microstructure analysis gave 64±6 nm and 84±8 nm for the average inner grains size in magnetite and maghemite. Structure and phase content analysis indicated high purity and crystallinity. Magnetic measurements indicated saturation magnetization (92.1 emu/g for magnetite and 85.5 emu/g for maghemite) approaching the upper limits reported for the pure bulk oxides. © 2013 Elsevier B.V.

Gheju M.,Polytechnic University of Timisoara | Balcu I.,Romanian National Institute for Research and Development in Electrochemistry and Condensed Matter
Journal of Hazardous Materials | Year: 2010

Hexavalent chromium reduction with scrap iron has the advantage that two wastes are treated simultaneously. The reduction of hexavalent chromium by scrap iron was investigated in continuous system, using as reducing agent the following scrap iron shapes and sizes: (1) spiral fibers, (2) shavings, and (3) powder. The shape and size of scrap iron were found to have a significant influence on chromium and iron species concentration in column effluent, on column effluent pH and on Cr(VI) reduction mechanism. While for large scrap iron particles (spiral fibers) homogeneous reduction is the dominant Cr(VI) reduction process, for small scrap iron particles (powder) heterogeneous reduction appears to be the dominant reaction contributing to Cr(VI) reduction. All three shapes and sizes investigated in this work have both advantages and disadvantages. If found in sufficient quantities, scrap iron powder seem to be the optimum shape and size for the continuous reduction of Cr(VI), due to the following advantages: (1) the greatest reduction capacity, (2) the most important pH increase in column effluent (up to 6.3), (3) no chromium was detected in the column effluent during the first 60. h of the experiment, and (4) the lowest steady-state Cr(VI) concentration observed in column effluent (3.7. mg/L). But, despite of a lower reduction capacity in comparison with powder particles, spiral fibers and shavings have the advantage to result in large quantities from the mechanic processing of steel. © 2010 Elsevier B.V.

Zamfir A.D.,West University of Timisoara | Zamfir A.D.,Romanian National Institute for Research and Development in Electrochemistry and Condensed Matter
Advances in Experimental Medicine and Biology | Year: 2014

Gangliosides, sialylated glycosphingolipids, are particularly enriched in mammalian central nervous system where their expression is cell type-specifi c and changes particularly during brain development, maturation, aging, and diseases. For this reason, gangliosides are important diagnostic markers for various brain ailments, including primary and secondary brain tumors and neurodegenerative diseases. Among all biochemical and biophysical methods employed so far for ganglioside analysis, mass spectrometry (MS) emerged as one of the most reliable due to the sensitivity, accuracy, and speed of analysis as well as the possibility to characterize in details the molecular structure of the identifi ed biomarkers. This chapter presents signifi cant achievements of MS with either electrospray (ESI), chip-based ESI, or matrix-assisted laser desorption/ionization (MALDI) in the analysis of gangliosides in normal and diseased human brain. Specifi cally, the chapter assesses the MS contribution in determination of topospecifi city, fi logenetic, and brain development stage dependence of ganglioside composition and structure as well as in discovery of ganglioside markers in neurodegenerative/ neurodevelopmental conditions, primary and secondary brain tumors. The highlighted accomplishments in characterization of novel structures associated to severe brain pathologies show that MS has real perspectives to become a routine method for early diagnosis and therapy based on this biomolecule class. © 2014, Springer International Publishing Switzerland.

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