Adsorptive removal of thiazine dyes from aqueous solutions by oil shale and its oil processing residues: Characterization, equilibrium, kinetics and modeling studies

Adsorption characteristics of oil shale (OS) and its pyrolysis byproducts for cationic thiazine dyes were investigated using thionine (TH), toluidine blue (TB) and methylene blue (MB)

The removal of radioactive strontium ions from aqueous solutions by isotopic exchange using strontium decavanadates and corresponding mixed oxides

Two types of strontium decavanadate samples (A and B) were synthesized conductometrically in different pH ranges of 6.7-5.6 and 4.2-3.5, respectively. The samples were used as isotope exchangers after heat treatment at 333, 378 and 573 K for the removal of Sr-90 radionuclide from the aqueous solution which is one of the most important fission products of uranium. The content of crystalline water in the exchangers was determined by thermo-gravimetric analysis (TGA). They were characterized using the X-ray diffraction (XRD), diffuse reflectance infrared Fourier-transforms (DRIFT) and the energy dispersive spectral (EDS) analysis. The SEM micrographs showed that sample A dried at 333 K has an urchin-like structure but it decomposes as annealed at 573 K. Sample B dried at 333 K is composed of quadrangular-prism like micro-rods but nano-sized platelets also formed at 573 K. The time-dependent studies conducted at three different molar ratios of strontium ions in the exchanger to the solution showed that Sr2+ ions completely exchanged at the ratio of 3.5 and 2.0 for the samples A and B annealed at 573 K, respectively. The kinetic data were analyzed using McKay, Nernst Planck, and Paterson's models and correlated to structural characteristics of the exchangers. The Sr-removal capacities of the exchangers evaluated by applying the Langmuir isotherm model increased with the annealing temperature. The results revealed that radioactive Sr2+ ions can be selectively removed by the exchangers annealed at 573 K from real wastewater because the exchange fractions are not significantly affected by the pH changes and the common coexisting cations

Sensitive determination and electro-oxidative polymerization of azodyes on a carbon paste electrode modified with bentonite

A new composite carbon paste electrode incorporating bentonite (BentMCPE) was developed and used for extremely sensitive determination and electro-oxidative polymerization of azodyes using cyclic voltammetry. Lanaset Red 2B (LR2B) was selected as a model molecule for optimization of operational parameters such as amount of modifier, the pH of buffer medium, scan rate and dye concentration. Performance analyses showed that BentMCPE allows determination of LR2B, Acid Blue 113 (AB113) and Acid Yellow 17 (AY17) dyes as low as (6-8) x 10(-10) mol/L at pH 5.5. The peak intensities increased with the repetitive scans due to electrocatalytic anodic polymerization of the dyes. The results of multiple scans in single binary and ternary dye solutions showed that all of the dyes whether hydroxyl substituted (LR2B and AY17) or not (AB113) can be polymerized on the BentMCPE surface. Two possible electro-polymerization pathways were proposed by assuming formation of different radical intermediates produced from azo/hydrazone tautomers of the dyes. A comparison of FT-IR spectra recorded after the first and tenth repetitive scans confirmed that the electro-polymerization process proceeds by head to tail interactions of the radicals with dye monomers deposited on the electrode surface. (C) 2015 Elsevier B.V. All rights reserved

Concentration-Polarization-Induced Precipitation and Ionic Current Oscillations with Tunable Frequency

At the nanoscale, charges present at the surfaces of liquid–solid interfaces greatly influence the properties of ions and molecules present in the solution, and can lead to nanoscale effects such as ion selectivity, ion current rectification, and modulation of local ionic concentrations. Concentration polarization is another nanoscale phenomenon whereby ion concentrations are enriched at one opening of an ion-selective nanopore and depleted at the other. We show that when a nanopore is in contact with a weakly soluble salt present at a concentration below its solubility product, concentration polarization can lead to locally enhanced ionic concentrations and precipitation of the salt. Formed precipitates partially or fully occlude the nanopore’s opening as indicated by a measured transient decrease of the nanopore’s conductance. We have identified experimental conditions at which the locally created precipitate is either pushed through or dissolved, clearing the pore entrance and allowing the precipitation reaction to occur again. The dynamic process of precipitate formation and dissolution is observed as ion current fluctuations and oscillations with frequencies reaching 200 Hz. The frequency of the system operation exceeds other nanopore-based oscillators by 2 orders of magnitude, which we believe stems from the 30 nm length of the pores examined here, versus ∼10 μm long pores reported before

Photocatalytic efficiency of titania nonylphenol ethoxylate composite thin films under solar irradiation

Photocatalytic efficiency of titania thin-films on ITO synthesized in the presence of nonylphenol-surfactants containing different numbers of ethoxylate-units was investigated under solar-irradiation. A colorless transparent titania-gel formed in the non-aqueous medium in the presence of nonylphenol-10-ethoxylates while milky white opaque gel was observed with nonylphenol-35-ethoxylates. They were coated on ITO plate by dipping method and calcined at 350, 500 and 700 degrees C. The XRD, IRRAS, EDS, SEM and AFM analyses revealed that different composite nanostructures are formed by calcinations of Ti-nonylphenol-35-ethoxylates at 350 and 500 degrees C. The photocatalytic-efficiencies of the composite films are better than the other titania nanostructures. Transparency and band-gap energy evaluated from transmittance measurements demonstrated that visible-light responsive Ti-nonylphenol-35-ethoxylates composites are more efficient catalysts than UV-absorbable Ti-nonylphenol-b0-ethoxylates films. The photocatalytic degradation rate of the methylene-blue on the catalysts was calculated using the Langmuir-Hinshelwood equation and its modified form derived in this study by considering intensity changes in solar light. The dye degradation efficiency of the Ti-nonylphenol-ethoxylate films changes in the 58-74% range after 2 h of irradiation in 0.02 mM MB solution. The solution completely decolorized after 8 h of irradiation on the TiNP-35 catalysts calcined at 350 degrees C

Synthesis, Electrochemistry, DFT Calculations, Antimicrobial Properties and X-ray Crystal Structures of Some NH- and/or S- Substituted-1,4-quinones

The NH-, NH-,S- substituted-1,4-naphthoquinones and NH-, Ssubstituted-1,4-benzoquinones have been synthesized from the reaction between quinones (2,3-Dibromo-1,4-naphthoquinone or p-benzoquinone) and different amines. The structures of the compounds have been confirmed using FTIR, UV-Vis, H-1-NMR, C-13-NMR, mass MS(ESI) spectrometry and cyclic voltammetry (CV). The ground state energies of the molecules have been estimated using B3LYP functional with different basis sets based on time dependent density functional theory (TD-DFT). The theoretical Delta E-gap values obtained from TD-DFT calculations have been compared with UV visible spectroscopy results. Antibacterial and antifungal activities of the synthesized compounds have been evaluated against Escherichia coli, Staphylococcus aureus and Microsporum canis, Trichophyton mentagrophytes, respectively. Two representative crystal structures of quinone derivatives, 2-(4-Fluorophenylamino)-3-bro-monaphthalene-1,4-dione and 2-(3,5-Dimethylphenylthio)cyclo-hexa-2,5-diene-1,4-dione, are reported with CCDC 1811265 and CCDC 1811263, respectively

A square-pyramidal iron(III) complex obtained from 2-hydroxy-benzophenone-S-allyl-thiosemicarbazone: synthesis, characterization, electrochemistry, quantum chemical studies and antioxidant capability

2-Hydroxybenzophenone-S-allyl-thiosemicarbazone and 3-allyl-salicylaldehyde were condensed by template effect of iron(III) ion to yield the N2O2 type-chelate complex. The S-allyl-thiosemicarbazone (1) and the iron(III) complex (2) were characterized by elemental analysis, magnetic measurements, electronic, infrared, Raman and H-1-NMR spectra, and also single-crystal X-ray diffraction technique. Electrochemical characterization of the iron(III) complex was carried out by using cyclic voltammetry. The complex gives a metal based one electron reversible Fe-III/Fe-II reduction and, S-allyl-thiosemicarbazone-based oxidation and reduction reactions. The reduction potentials of the S-allyl-thiosemicarbazone and the complex are calculated in terms of Gibbs free energy change of the redox reaction at the theory level of UwB97XD/LANL2DZ/PCM. The optimized geometries and vibrational frequencies of the compounds were calculated using the DFT/UwB97XD method with the 6-31 G(d,p) basis set and compared to experimental data. TD-DFT was employed to examine the electronic transitions of the complex and to conduct the NBO charges at the same level. For the compounds, in vitro total antioxidant capacity (as TEAC coefficient) and scavenging activity of reactive oxygen species (ROS) which are hydroxyl radical (center dot OH), superoxide anion radical (center dot O-2-), and hydrogen peroxide (H2O2) have been determined by using spectroscopic methods

Gating of Hydrophobic Nanopores with Large Anions

Understanding ion transport in nanoporous materials is critical to a wide variety of energy and environmental technologies, ranging from ion-selective membranes, drug delivery, and biosensing, to ion batteries and supercapacitors. While nanoscale transport is often described by continuum models that rely on a point charge description for ions and a homogeneous dielectric medium for the solvent, here, we show that transport of aqueous solutions at a hydrophobic interface can be highly dependent on the size and hydration strength of the solvated ions. Specifically, measurements of ion current through single silicon nitride nanopores that contain a hydrophobic-hydrophilic junction show that transport properties are dependent not only on applied voltage but also on the type of anion. We find that in Cl- containing solutions the nanopores only conducted ionic current above a negative voltage threshold. On the other hand, introduction of large polarizable anions, such as Br- and I-, facilitated the pore wetting, making the pore conductive at all examined voltages. Molecular dynamics simulations revealed that the large anions, Br- and I-, have a weaker solvation shell compared to that of Cl- and consequently were prone to migrate from the aqueous solution to the hydrophobic surface, leading to the anion accumulation responsible for pore wetting. The results are essential for designing nanoporous systems that are selective to ions of the same charge, for realization of ion-induced wetting in hydrophobic pores, as well as for a fundamental understanding on the role of ion hydration shell on the properties of solid/liquid interfaces

A genetic probe into the ancient and medieval history of Southern Europe and West Asia

Literary and archaeological sources have preserved a rich history of Southern Europe and West Asia since the Bronze Age that can be complemented by genetics. Mycenaean period elites in Greece did not differ from the general population and included both people with some steppe ancestry and others, like the Griffin Warrior, without it. Similarly, people in the central area of the Urartian Kingdom around Lake Van lacked the steppe ancestry characteristic of the kingdom’s northern provinces. Anatolia exhibited extraordinary continuity down to the Roman and Byzantine periods, with its people serving as the demographic core of much of the Roman Empire, including the city of Rome itself. During medieval times, migrations associated with Slavic and Turkic speakers profoundly affected the region