Determination of trace levels of dissolved vanadium in seawater by use of synthetic complexing agents and inductively coupled plasma-atomic emission spectroscopy (ICP-AES)

In the determination of traces of dissolved vanadium in complex matrices such as seawater, separation and enrichment from the matrix is of special importance. A wide variety of methods has been proposed for preconcentration, depending to the nature of samples and the methods to be used for measurement. Among these methods separation techniques based on sorption on to chelating resins seem convenient, rapid, and capable of achieving a high concentration factor. The methods proposed in this paper are based on the transformation of all dissolved vanadium species in seawater into organic complexes by use of synthetic complexing agents such as dithizone, luminol, or 8-hydroxyquinoline; the resulting vanadium-organic complexes were sorbed on to a C(18) column at a flow rate of 5 mL min(-1). The vanadium sorbed on the C(18) columns was then stripped by use of nitric acid (2 mol L(-1)) and analysed by inductively coupled plasma-atomic emission spectroscopy, ICP-AES. This method was optimised and use of other chelating resins, such as chelamine, chelex-100, and immobilised 8-hydroxyquinoline and was compared by passing seawater samples directly over the resins. The experimental conditions (pH, acid used for elution, and contact time between the liquid sample and the resin) were optimised. The results were compared for all the resins used and were indicative of excellent and coherent reproducibility.     

Mn doped ZnO nanostructured thin films prepared by ultrasonic spray pyrolysis method

Mn-doped ZnO thin films with different percentage of Mn content (0, 1, 3 and 5 at.%) and substrate temperature of 350 °C, were deposited by a simple ultrasonic spray pyrolysis method under atmospheric pressure. We have studied the structural and optical properties by using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and ultra-violet visible near infrared (UV–Vis-NIR) spectroscopy. The lattice parameters calculated for the Mn-doped ZnO from XRD pattern were found to be slightly larger than those of the undoped ZnO, which indicate substitution of Mn in ZnO lattice. Compared with the Raman spectra for ZnO pure films, the Mn-doping effect on the spectra is revealed by the presence of additional peak around 524 cm⁻¹ due to Mn incorporation. With increasing Mn doping the optical band gap increases indicating the Burstein–Moss effect.     

Facile synthesis of Cu-LDH with different Cu/Al molar ratios: application as antibacterial inhibitors

Research on Chemical Intermediates - A range of Cu-LDHs has been synthesized by co-precipitation using metal nitrate precursors and sodium carbonate under varying molar ratios Cu/Al...     

Synthesis and Characterization of Bis‐quinazolines from Linear Tetra‐amines Involving 2‐(Aminomethyl)benzenamine with Aldehydes

Three tetra‐amine compounds 2‐((2‐(2‐aminobenzylamino)ethylamino)methyl)benzenamine ( L1 ), 2‐((3‐(2‐aminobenzylamino)propylamino)methyl)benzenamine ( L2 ), and 2‐((4‐(2‐aminobenzylamino)butylamino)methyl)benzenamine ( L3 ) were synthesized and then their reaction with 2‐hydroxybenzaldehyde, 2‐nitrobenzaldehyde, and 2‐hydroxy‐3‐methoxybenzaldehyde were investigated. Treatment of L1 , L2 , and L3 with the former aldehydes gave derivatives of quinazolines in a good yield. The products have been studied with IR, ¹H NMR, ¹³C NMR, COSY, HMQC, and microanalysis.     

Enhancement of Congo red dye removal efficiency using Mg-Fe-layered double hydroxide

Research on Chemical Intermediates - In this study, Mg-Fe(II)-Al-layered double hydroxide with different molar ratios Fe/Al (Mg0.80-Fe0.14-Al0.06-LDHs and Mg0.80-Fe0.20-Al0.00-LDHs) was prepared...     

Determination of trace metal complexes by natural organic and inorganic ligands in coastal seawater.

It is well-documented that organic compounds form strong complexes with most metals in aquatic systems, and that seawater is a complex medium which contains a large variety of organic and inorganic ligands, including colloidal matter. We suggest that most trace metals are complexed in seawater and that some inorganic metals complexes are either labile or not stable. In contrast, metal-organic complexes are often stable and need various and specific treatments to be dissociated. In this paper we try to illustrate a good tendency of some trace metals to be complexed by organic ligands in seawater. A solid-phase extraction method was applied using a C18 column as a resin that is able to separate metals complexed by neutral organic ligands, and the chelamine resin to separate metal species that are present as labile inorganic complexes. The determination of total dissolved metal concentrations was achieved by formatting a metal-8-hydroxyquinoline complex, followed by adsorption on C18 columns and ICP-AES analysis.     

A percolation approach to study the high electric field effect on electrical conductivity of insulating polymer

The effect of percolation threshold on the behaviour of electrical conductivity at high electric field of insulating polymers has been briefly investigated in literature. Sometimes the dead ends links are not taken into account in the study of the electric field effect on the electrical properties. In this work, we present a theoretical framework and Monte Carlo simulation of the behaviour of the electric conductivity at high electric field based on the percolation theory using the traps energies levels which are distributed according to distribution law (uniform, Gaussian, and power-law). When a solid insulating material is subjected to a high electric field, and during trapping mechanism the dead ends of traps affect with decreasing the electric conductivity according to the traps energies levels, the correlation length of the clusters, the length of the dead ends, and the concentration of the accessible positions for the electrons. A reasonably good agreement is obtained between simulation results and the theoretical framework.     

Distribution coefficient and redox behaviour of uranium in Authie Bay (northern France)

Some mechanistic aspects associated with uranium release/immobilization and sedimentation in Authie Bay are presented in the present work. For this purpose, U contents in estuarine oxic waters, porewaters and sediment solids are determined. These analytical data allow us to appraise the partitioning of this metal between the liquid phase and the particulate matter/sedimentary material by calculating its distribution coefficient. Our findings further reveal that the distribution coefficient varies significantly with depth probably in response to the microbial activities in these sediments. This is confirmed by our studies on the geochemical behaviour of Fe and Mn in Authie Bay sediments. Finally, studies on the thermodynamic characteristics of sedimentary U in Authie Bay are undertaken in order to select possible U water–mineral equilibria that could involve in this environment, and to help define conditions of sedimentary U bioreduction.     

Low-temperature growth of nanocrystalline silicon films prepared by RF magnetron sputtering: Structural and optical studies

In order to contribute to the understanding of the optoelectronics properties of hydrogenated nanocrystalline silicon films, a detailed study has been conducted. Structural analysis (infrared absorption and Raman scattering spectroscopy), combined with optical measurements spectroscopy (optical transmission, photothermal deflection spectroscopy and photoconductivity) were used to characterize the films. The samples were elaborated by radio-frequency magnetron sputtering of crystalline silicon target, under a hydrogen (70%) and Argon (30%) gas mixture, at three different total pressures (2, 3 and 4 Pa) and varying substrate temperature (100, 150 and 200 °C). The results clearly indicate that the films deposited at 2 Pa are amorphous, while for 3 and 4 Pa nanocrystalline structures are observed. These results are discussed in the framework of the existing models.     

PGAA metals analysis in tailings in Zaida abandoned mine,high Moulouya,Morocco

The basin of Moulouya Oued is a region where mining industry has been developed early in the 20th century. As a consequence, residues generated from past mining activities over the years have been dumped as piles of tailings. Zaïda is one of the most affected region in this basin because of lead mine exploitation for long time. The aim of this study is to determine the amount of trace elements and the contamination of the river sediments. Analysis of collected samples has been achieved using the prompt gamma activation analysis method. The samples, in form of powders, were enclosed in Teflon sheets. The spectra were analyzed using HYPERMET PC software and the chemical composition is calculated using an Excel-macro that provides the concentrations as molar and weight percentages, as well as the corresponding masses of the oxides. The validation of the analytical method is demonstrated with the analysis of a reference material. The results show that the distribution of the studied metals (Pb, Zn, Cu, Cd, Cr Ni, and As) in the basin is dependent on location with a very significant contamination by Pb, Zn, Cu, Cd, Cr, and Ni close to the lead mine sites.