Implementing magnetically-active Sn-based nanocomposites in hexavalent chromium removal from drinking water.

A novel nanocomposite consisting of FeO-loaded tin oxyhydroxy-chloride is demonstrated as an efficient adsorbent for the removal of hexavalent chromium in compliance to the new drinking water regulation. This study introduces a continuous-flow production of the nanocomposite through the separate synthesis of (i) 40 nm FeO nanoparticles and (ii) multilayered spherical arrangements of a tin hydroxy-chloride identified as abhurite, before the application of a wet-blending process. The homogeneous distribution of FeO nanoparticles on the abhurite's morphology, features nanocomposite with magnetic response whereas the 10 % loaded nanocomposite preserves a Cr(VI) uptake capacity of 7.

Se(IV)/Se(VI) adsorption mechanisms on natural and on Ca-modified zeolite for Mediterranean soils amended with the modified zeolite: prospects for agronomic applications.

In the present study, the ability of a modified CaCl zeolite (Ca-Z) to both increase Se(IV) availability and restrict Se(VI) mobility in soils is examined. As it was resulted from batch experiments and verified by X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies, higher amounts of both Se species adsorbed on Ca-Z compared to natural zeolite (Z-N) forming outer-sphere complexes while the oxidation state did not alter during agitation of samples. Thereafter, Ca-Z was incorporated in six Greek soils, divided into acid and alkaline, at a 20% (w/w) rate and a series of equilibrium batch experiments were performed with soils alone and soils-Ca-Z mixtures to investigate sorption and desorption processes and mechanisms.

Probing the structural role of Cr in stabilized tannery wastes with X-ray absorption fine structure spectroscopy.

The effective stabilization of tannery sludge wastes is explored using X-Ray Absorption Fine Structure (XAFS) spectroscopies. Solidification of the Cr-rich waste was realized via vitrification of the incinerated sludge with silica and flux agents. It is demonstrated that the effective reduction of Cr(VI) and the structural role of Cr are strongly modulated by the chemical composition of the waste.

Crystalline and amorphous calcium carbonate as structural components of the Calappa granulata exoskeleton.

The exoskeleton of crustaceans consists of chitin biopolymers where the embedded inorganic biominerals, mainly CaCO, affect strongly its mechanical properties. Raman and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies and Transmission Electron Microscopy (TEM) are applied to investigate the CaCO structure in various parts of the Calappa granulata crab exoskeleton. The shape of the main Raman peak of CaCO reveals the presence of two phases which are identified as calcite and amorphous calcium carbonate (ACC).

Enhanced thermal conductivity in percolating nanocomposites: a molecular dynamics investigation.

In this work we present a molecular dynamics investigation of thermal transport in a silica-gallium nitride nanocomposite. A surprising enhancement of the thermal conductivity for crystalline volume fractions larger than 5% is found, which cannot be predicted by an effective medium approach, not even including percolation effects, the model systematically leading to an underestimation of the effective thermal conductivity. The behavior can instead be reproduced if an effective volume fraction twice larger than the real one is assumed, which translates into a percolation effect surprisingly stronger than the usual one.

Natural radioactivity studies in a paleontology site and paleoclimate interpretation of the last 8 Mya.

Fossil bones and sediments from different horizons of the Upper Miocene paleontological site of Platania, Drama-Greece were studied using U, U, Th series and K measurements obtained by γ-spectroscopy. Additionally, SEM and XRF analysis was applied to bone and sediment samples while a lithological analysis of the sediments was also carried out. The Ra/U ratios in the fossilization layers are attributed to the U depletion from the sediment and its incorporation into the fossils.

High pressure Raman study of type-I collagen.

The high pressure response of type-I collagen from bovine Achilles tendon is investigated with micro-Raman spectroscopy. Fluorinert™ and methanol-ethanol mixtures were used as pressure transmitting media (PTM) in a diamond anvil cell. The Raman spectrum of collagen is dominated by three bands centred at approximately 1450, 1660 and 2930 cm , attributed to C-H deformation, C=O stretching of the peptide bond (amide-I band) and C-H stretching modes respectively.

Optimization of tetravalent manganese feroxyhyte's negative charge density: A high-performing mercury adsorbent from drinking water.

This study demonstrates an optimization procedure for the development of an Hg-specified adsorbent able to comply with the regulation limit for drinking water of 1μg/L. On this purpose, the synthesis of Mn(IV)-feroxyhyte was modified to achieve high negative charge density by combining alkaline and extreme oxidizing conditions. In particular, precipitation of FeSO at pH9 and excess of KMnO follows a very fast nucleation step providing a product with very small nanocrystal size (1-2nm), high specific surface area (300m/g) and maximum negative charge density (1.

Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite.

Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples.

Monitoring the role of Mn and Fe in the As-removal efficiency of tetravalent manganese feroxyhyte nanoparticles from drinking water: An X-ray absorption spectroscopy study.

The implementation of amorphous tetravalent manganese feroxyhyte (TMFx) nanoparticles, prepared via co-precipitation synthesis, as an efficient As(V)-removal material is investigated using X-ray absorption fine structure (XAFS) spectroscopy at the Fe-, Mn- and As-K-edges. The optimum synthesis conditions and chemical composition of the TMFx adsorbent were determined by the degree of polymerization in the adsorbents' microstructure. Under synthesis into mildly acidic conditions, the change in the polymerization of the metal-oxyhydroxyl chains (metal=Fe, Mn) provides more adsorption sites at edges and corner sites in the bonding environment of Fe and Mn, respectively, thereby enhancing As uptake.

Detailed spectroscopic study of the role of Br and Sr in coloured parts of the Callinectes sapidus crab claw.

The exoskeleton of crustaceans consists mainly of calcium carbonate (CaCO3) minerals and in many cases exhibits vivid colouration due to the presence of proteins rich in carotenoid chromophores. The exposure of aquatic animals in sea water results often in the incorporation of trace elements in their exoskeleton. The bonding configuration of Br and Sr trace elements in regions with different staining (white, orange and blue) of the exoskeleton of the Callinectes sapidus in crab claw are systematically investigated by a number of complementary spectroscopic techniques, including X-ray absorption fine structure spectroscopy (EXAFS), X-ray fluorescence, Raman and visible light reflectivity spectroscopies.

Sn(II) oxy-hydroxides as potential adsorbents for Cr(VI)-uptake from drinking water: An X-ray absorption study.

The feasibility of implementing a Sn(II) oxy-hydroxide (Sn6O4(OH)4) for the reduction and adsorption of Cr(VI) in drinking water treatment was investigated using XAFS spectroscopies at the Cr-K-edge. The analysis of the Cr-K-edge XANES and EXAFS spectra verified the effective use of Sn6O4(OH)4 for successful Cr(VI) removal. Adsorption isotherms, as well as dynamic Rapid Small Scale Test (RSSCT) in NSF water matrix showed that Sn6O4(OH)4 can decrease Cr(VI) concentration below the upcoming regulation limit of 10μg/L for drinking water.

An X-ray absorption study of synthesis- and As adsorption-induced microstructural modifications in Fe oxy-hydroxides.

Synthetic adsorbents based on Fe oxy-hydroxides (FeOOH) prepared under a wide range of pH-values via intense oxidation conditions of FeSO4 as well as the As(III) and As(V) adsorption mechanism are investigated using X-ray absorption fine structure (XAFS) spectroscopies at the Fe- and As-K-edges. Synthesis in an alkaline environment promotes the face-connectivity of the Fe(O,OH)6 chains at the expense of edge- and corner-sharing linkage, which is consistent with the lower surface charge density and in turn with the lower arsenic adsorption capacity. Microstructural changes are also detected after As(V) adsorption onto FeOOH synthesized at pH 5.

Composition and hydrophilicity control of Mn-doped ferrite (MnxFe3-xO4) nanoparticles induced by polyol differentiation.

Manganese doped ferrite (MnxFe3-xO4) nanoparticles with x = 0.29-0.77 were prepared under solvothermal conditions in the presence solely of a polyol using the trivalent manganese and iron acetylacetonates as precursors.

Reducing the inversion degree of MnFe2O4 nanoparticles through synthesis to enhance magnetization: evaluation of their (1)H NMR relaxation and heating efficiency.

Manganese ferrite (MnFe2O4) nanoparticles of identical size (9 nm) and with different inversion degrees were synthesized under solvothermal conditions as a candidate theranostic system. In this facile approach, a long-chain amine, oleylamine, was utilized as a reducing and surface-functionalizing agent. The synthesized nanoparticles were shown to have a cubic-spinel structure as characterized by TEM and XRD patterns.

A XAFS study of plain and composite iron(III) and chromium(III) hydroxides.

Reduction of hexavalent Cr(VI) to the trivalent state is the common strategy for remediation of Cr(VI) contaminated waters and soils. In the presence of Fe the resulting compounds are usually mixed Fe(III)-Cr(III) phases, while, under iron-free conditions, reduction leads to formation of plain Cr(III) hydroxides. Environmental stability of these compounds depends on their structure and is important to understand how different precipitation conditions affect the local atomic order of resulting compounds and thus their long term stability.

Study of fossil bones by synchrotron radiation micro-spectroscopic techniques and scanning electron microscopy.

Earlymost Villafranchian fossil bones of an artiodactyl and a perissodactyl from the Milia excavation site in Grevena, Greece, were studied in order to evaluate diagenetic effects. Optical microscopy revealed the different bone types (fibro-lamellar and Haversian, respectively) of the two fragments and their good preservation state. The spatial distribution of bone apatite and soil-originating elements was studied using micro-X-ray fluorescence (µ-XRF) mapping and scanning electron microscopy.

A novel approach for arsenic adsorbents regeneration using MgO.

An integrated procedure for the regeneration of iron oxy-hydroxide arsenic adsorbents by granulated MgO is proposed in this study. A continuous recirculation configuration, with a NaOH solution flowing sequentially through the saturated adsorbent (leaching step) and the MgO (adsorption step) column beds, was optimized by utilizing the high arsenic adsorption efficiency of MgO at strong alkaline environments. Experimental results indicated that the total amount of leached arsenic was captured by MgO whereas the regenerated iron oxy-hydroxide recovered around 80% of its removal capacity upon reuse.

Tetravalent manganese feroxyhyte: a novel nanoadsorbent equally selective for As(III) and As(V) removal from drinking water.

The development of a single-phase Fe/Mn oxy-hydroxide (δ-Fe0.76Mn0.24OOH), highly efficient at adsorbing both As(III) and As(V), is reported.

Application of conventional and microbeam synchrotron radiation x-ray fluorescence and absorption for the characterization of human nails.

The synchrotron radiation based spectroscopies X-ray fluorescence and X-ray absorption fine structure are used to detect illness-related changes in the elemental distribution and bonding environment of metals in human nails. The effective atomic number of a collection of nails is determined using two methods, the X-ray transmittance and the scattering method, and is found equal to 7.5 +/- 0.

Local bonding geometry of oxygen implanted in GaN: a depth-dependent study.

The bonding environment of oxygen implanted in GaN is studied using near edge X-ray absorption fine structure spectroscopy at the O-K-edge. The 70 keV oxygen ions form a 200 nm-thick subsurface layer that is highly defective or amorphous depending on the implantation fluence which ranges from 1 x 10(15) cm-2 to 1 x 10(17) cm(-2). The information depth of the fluorescence photons varies from 50 to 63 nm, depending on the angle of incidence.

On the distribution and bonding environment of Zn and Fe in glasses containing electric arc furnace dust: a mu-XAFS and mu-XRF study.

We apply synchrotron radiation assisted X-ray fluorescence (SR-XRF), SR-XRF mapping as well as micro- and conventional X-ray absorption fine structure (mu-XAFS and XAFS) spectroscopies in order to study the bonding environment of Fe and Zn in vitrified samples that contain electric arc furnace dust from metal processing industries. The samples are studied in the as-cast state as well as after annealing at 900 degrees C. The SR-XRF results demonstrate that annealing does not induce any significant changes in the distribution of either Fe or Zn, in both the as-cast and annealed glasses.