Kinetics of zero-valent iron reductive transformation of the anthraquinone dye Reactive Blue 4

The effect of operational conditions and initial dye concentration on the reductive transformation (decolorization) of the textile dye Reactive Blue 4 (RB4) using zero-valent iron (ZVI) filings was evaluated in batch assays. The decolorization rate increased with decreasing pH and increasing temperature, mixing intensity, and addition of salt (100 g L⁻¹ NaCl) and base (3 g L⁻¹ Na₂CO₃ and 1 g L⁻¹ NaOH), conditions typical of textile reactive dyebaths. ZVI RB4 decolorization kinetics at a single initial dye concentration were evaluated using a pseudo first-order model. Under dyebath conditions and at an initial RB4 concentration of 1000 mg L⁻¹, the pseudo first-order rate constant (k_obs) was 0.029 ± 0.006 h⁻¹, corresponding to a half-life of 24.2 h and a ZVI surface area-normalized rate constant (k_SA) of 2.9 × 10⁻⁴ L m⁻² h⁻¹. However, as the initial dye concentration increased, the k_obs decreased, suggesting saturation of ZVI surface reactive sites. Non-linear regression of initial decolorization rate values as a function of initial dye concentration, based on a reactive sites saturation model, resulted in a maximum decolorization rate (V_m) of 720 ± 88 mg L⁻¹ h⁻¹ and a half-saturation constant (K) of 1299 ± 273 mg L⁻¹. Decolorization of RB4 via a reductive transformation, which was essentially irreversible (2–5% re-oxidation), is believed to be the dominant decolorization mechanism. However, some degree of RB4 irreversible sorption cannot be completely discounted. The results of this study show that ZVI treatment is a promising technology for the decolorization of commercial, anthraquinone-bearing, spent reactive dyebaths.     

Meteorological variations of PM2.5/PM10 concentrations and particle-associated polycyclic aromatic hydrocarbons in the atmospheric environment of Zonguldak, Turkey

Airborne particulate matter (PM_2.5 and PM₁₀) concentrations were measured in Zonguldak, Turkey from January to December 2007, using dichotomous Partisol 2025 sampler. Collected particulate matter was analyzed for 14 selected polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography with fluorescence detection (HPLC-FL). The seasonal variations of PM_2.5 and PM₁₀ concentrations were investigated together with their relationships with meteorological parameters. The maximum daily concentrations of PM_2.5 and PM₁₀ reached 83.3 μg m⁻³ and 116.7 μg m⁻³ in winter, whereas in summer, they reached 32.4 μg m⁻³ and 66.7 μg m⁻³, respectively. Total concentration of PM₁₀-associated PAHs reached 492.4 ng m⁻³ in winter and 26.0 ng m⁻³ in summer times. The multiple regression analysis was performed to predict total PM_2.5- and PM₁₀-associated PAHs and benzo(a)pyrene-equivalent (BaPE) concentrations with respect to meteorological parameters and particulate mass concentrations with the determination coefficients (R²) of 0.811, 0.805 and 0.778, respectively. The measured mean values of concentrations of total PM_2.5- and PM₁₀-associated PAHs were found to be 88.4 ng m⁻³ and 93.7 ng m⁻³ while their predicted mean values were found to be 92.5 ng m⁻³ and 98.2 ng m⁻³, respectively. In addition, observed and predicted mean concentration values of PM_2.5-BaPE were found to be 14.1 ng m⁻³ and 14.6 ng m⁻³. The close annual mean concentrations of measured and predicted total particulate related PAHs imply that the models can be reliably used for future predictions of particulate related PAHs in urban atmospheres especially where fossil fuels are mainly used for heating.     

Electrochemical codeposition of magnesium and nickel alloy for hydrogen storage

Magnesium and nickel alloy was prepared electrochemically in dimethylsulfoxide (DMSO) solution. Its structure, composition and property for hydrogen storage were studied by SEM, ICP, XRD, and charge and discharge test. It is found that codeposition of magnesium and nickel can take place at the potentials from −2.0 to −3.2 V (vs. Ag/Ag⁺) in 0.15 M LiClO₄ + DMSO solution containing MgCl₂ and NiCl₂. The surface morphology and the hydrogen storage capacity of the prepared alloy are influenced by the deposition potential. The alloy prepared at −2.4 V (vs. Ag/Ag⁺) is mainly composed of Mg₂Ni phase and shows its best electrochemical capacity of 361.8 mAh g⁻¹, corresponding to a hydrogen storage capacity of 1.35 wt.%.     

Sorption behavior of nano-TiO2 for the removal of selenium ions from aqueous solution

Titanium dioxide nanoparticles were employed for the sorption of selenium ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption was found to be fast, and to reach equilibrium basically within 5.0 min. The sorption has been optimized with respect to the pH, maximum sorption has been achieved from solution of pH 2–6. Sorbed Se(IV) and Se(VI) were desorbed with 2.0 mL 0.1 mol L⁻¹ NaOH. The kinetics and thermodynamics of the sorption of Se(IV) onto Nano-TiO₂ have been studied. The kinetic experimental data properly correlate with the second-order kinetic model (k₂ = 0.69 g mg⁻¹ min⁻¹, 293 K). The overall rate process appears to be influenced by both boundary layer diffusion and intraparticle diffusion. The sorption data could be well interpreted by the Langmuir sorption isotherm. The mean energy of adsorption (14.46 kJ mol⁻¹) was calculated from the Dubinin–Radushkevich (D–R) adsorption isotherm at room temperature. The thermodynamic parameters for the sorption were also determined, and the ΔH⁰ and ΔG⁰ values indicate exothermic behavior.     

Surface and grain-boundary energies as well as surface mass transport in polycrystalline CeO2

The multiphase equilibration technique for the determination of the equilibrium angles that develop at the interphase boundaries of a solid–liquid–vapor system, has been used to calculate the surface and interfacial energies in polycrystalline CeO₂ and CeO₂/Cu system in argon atmosphere at the temperature range 1473–1773 K. Linear temperature functions were obtained by extrapolation, for the surface energy γ_sv (J/m²) = 2.465–0.563 × 10⁻³ T and the grain-boundary energy γ_ss (J/m²) = 1.687–0.391 × 10⁻³ T of the ceramic, as well as for the interfacial energy γ_sl (J/m²) = 2.623–1.389 × 10⁻³(T −1356 K) of the CeO₂/Cu system. Grain-boundary grooving studied on polished surfaces of CeO₂ annealed in argon atmosphere at the same temperature range has shown that surface diffusion was the dominant mechanism for the mass transport. The surface diffusion coefficient can be expressed according to the equation D_s (m²/s) = 3.82 × 10⁻⁴ exp(−308,250/RT).     

Electrochemical reclamation of silver from silver-plating wastewater using static cylinder electrodes and a pulsed electric field

Silver was reclaimed from silver-plating wastewater by using a pulsed electric field (PEF) combined with static cylinder electrodes (SCE). The conditions that produced the maximal silver recovery rate (RR_Ag) (99%) were as follows: average retention time of 10 min, interelectrode gap of 50 mm, solution pH of 9.0, temperature of 45 °C, initial Ag(I) concentration of 1000 mg L⁻¹, PEF pulse frequency of 1200 Hz, current density of 5.0 A m⁻² and a pulse duty cycle of 60%. Compared with the conventional direct current (DC) technology, the PEF process exhibited improvements in the silver recovery rate (RR_Ag), total energy consumption (TEC) and physical properties of the silver deposits, especially for low Ag(I) concentrations, for example, from 500 to 1000 mg L⁻¹. For an initial Ag(I) concentration of 500 mg L⁻¹, the PEF process produced an RR_Ag of up to 99%, and the TEC was 4.56 kWh (kg Ag)⁻¹. In comparison, the RR_Ag and TEC were 90% and 5.66 kWh (kg Ag)⁻¹, respectively, in the DC process. The results of SEM observation and XRD analysis indicated that the silver deposits formed by the PEF process were smaller, denser, and of a higher purity than those produced by the DC process. Therefore, the presented method was effective for reclaiming silver from silver-plating wastewater.     

Rib waveguides based on Zn-substituted LiNbO3 films grown by liquid phase epitaxy

The fabrication of epitaxially grown Zn-substituted LiNbO₃ (Zn:LiNbO₃) waveguide films and rib waveguides is reported and detailed investigations about microstructure, morphology and optical waveguide properties are provided. Zn:LiNbO₃ films were grown on congruent X-cut LiNbO₃ substrates by a modified liquid phase epitaxy in solid–liquid coexisting solutions. The homogeneously Zn-substituted films exhibit high crystalline perfection and extremely flat surfaces with averaged surface roughness of rms = 0.2–0.3 nm. At the film/substrate interface a Zn-containing transient layer has been observed, which allows the growth of elastically strained Zn:LiNbO₃ film lattices. X-ray diffraction reciprocal-space measurements prove the pseudomorphic film growth. The refractive index difference between substrate and film depends on the zinc substitution content, which increase with rising growth temperatures. For films with 5.3 mol% Zn (Δn_o ≈ +5 × 10⁻³) only ordinary ray propagation was observed, while for films with 7.5 mol% Zn (Δn_o ≈ +8 × 10⁻³, Δn_e ≈ +5 × 10⁻³) both modes, TM and TE propagate. Stress-induced refractive index changes are in the order of Δn ≈ 10⁻⁴. In rib waveguide microstructures singlemode propagation with nearly symmetrical field distribution has been observed. To demonstrate the potential of the proton exchange-assisted dry-etching technique interferometer microstructures were fabricated.     

Preparation, characterization and applications of novel iminodiacetic polyurethane foam (IDA-PUF) for determination and removal of some alkali metal ions from water

The new type of ion chelating resin (IDA-PUF) has iminodiacetic group that was prepared from polyurethane foam (PUF) by the reaction between primary amine of PUF and monochloro-acetic acid. The IDA-PUF was characterized using infrared spectra, elemental and thermal analysis. The exchange properties and chromatographic behaviour of the new chelating resin were investigated for removal of some alkali metal ions (lithium, sodium and potassium) using batch and column processes. The maximum distribution coefficient (K_D) of trace alkali metal ions was in the pH range of 8–10. The kinetics of sorption of the alkali metal ions was found to be fast with average values of half-life of sorption (t_1/2) of 4.93 min. The values of ΔG, ΔS and ΔH were −3.86 kJ mol⁻¹, 57.73 J mol⁻¹ K⁻¹ and 14.41 kJ mol⁻¹, respectively, which reflects the spontaneous and endothermic nature of ion exchanger process. The average sorption capacity of IDA-PUF is 4.8 mmol/g for alkali metal ions, enrichment factors ≈40 and the recovery 95–100% were also achieved with average value of RSD% = 1.67. The proposed method has been successfully applied to preconcentrate, determinate and remove the alkali metal ions from different samples of water.     

Interactive behavior of caffeine at a platinum electrode surface

Interactive behavior of caffeine at a charged platinum/solution interface was investigated in a wide temperature range, from 295 to 333 K, in a phosphate buffer solution pH 7.0. It was shown that the amount of adsorbed caffeine (surface concentration) is directly proportional to the measured adsorption surface charge density resulting from caffeine oxidation to theophilline. At low temperatures, a monolayer of caffeine molecules laying in a flat orientation on the Pt surface is adsorbed, while at higher temperatures, conformational changes occur, resulting in tilting of the adsorbed molecules to allow for higher surface concentrations to be achieved. A highly negative Gibbs energy of adsorption, ranging from −51.1 kJ mol⁻¹ at 295 K to −60.6 kJ mol⁻¹ at 333 K, demonstrated a high affinity of caffeine for the Pt surface. Although the adsorption process was found to be endothermic (ΔH_ADS = 20 kJ mol⁻¹), it was determined that a large positive change in the adsorption entropy (TΔS_ADS = 75 ± 3 kJ mol⁻¹) represents the driving force for the strong interaction of caffeine with Pt.     

Deformability enhancement in ultra-fine grained, Ar-contained W compacts by TiC additions up to 1.1%

Nano-sized Ar bubbles give negative influence on the fracture resistance and occurrence of superplasticity in ultra-fine grained (UFG) W–TiC compacts. In order to enhance deformability in UFG, Ar-contained W–TiC compacts, effects of TiC addition on the high-temperature deformation behavior were examined. W–TiC compacts with TiC additions of 0, 0.25, 0.5, 0.8 and 1.1 wt% were fabricated by mechanical alloying in a purified Ar atmosphere and hot isostatic pressing. Tensile tests were conducted at 1673–1973 K (0.45–0.54 T_m, T_m: melting point of W) at initial strain rates from 5 × 10⁻⁵ to 5 × 10⁻³ s⁻¹. It is found that as TiC addition increases, the elongation to fracture significantly increases, e.g., from 3 to 7% for W–0 and 0.25TiC/Ar to above 160% for W–1.1TiC/Ar when tested at 1873 and 1973 K at 5 × 10⁻⁴ s⁻¹. The flow stress takes a peak at 0.25%TiC and decreases to a nearly constant level at 0.5–1.1%TiC. The ranges of the strain rate sensitivity of flow stress, m, and the activation energy for deformation, Q, with TiC additions are 0.17–0.30 and 310–600 kJ/mol, respectively. The observed effects of the TiC additions on the tensile properties are discussed.     

Microstructures and thermoelectric properties of p-type pseudo-binary AgxBi0.5Sb1.5−xTe3 (x = 0.05–0.4) alloys prepared by cold pressing

The p-type pseudo-binary Ag_xBi_0.5Sb_1.5−xTe₃ (x = 0.05–0.4) alloys were prepared by cold pressing. The thermal conductivities (κ) were calculated from the values of heat capacities, densities and thermal diffusivities measured, and range approximately from 0.66 to 0.56 (W K^− 1 m^− 1) for the Ag_xBi_0.5Sb_1.5−xTe₃ alloy with molar fraction x being 0.4. Combining with the electrical properties obtained in the previous study, the maximum dimensionless figure of merit ZT of 1.1 was obtained at the temperature of 558 K.     

Thermophysical Property Measurements of Liquid and Supercooled Iridium by Containerless Methods

Thermophysical properties of equilibrium and supercooled liquid iridium were measured using noncontact diagnostic techniques in an electrostatic levitator. Over the 2300–3000 K temperature range, the density can be expressed as ρ (T)=19.5×10³ − 0.85(T− T_m) (kg·m⁻³) with T_m=2719 K. The volume expansion coefficient is given by 4.4 × 10⁻⁵ K⁻¹. In addition, the surface tension can be expressed as γ (T)=2.23 × 10³ − 0.17(T−T_m)(10⁻³N·m⁻¹) over the 2373–2833 K span and the viscosity as η(T)=1.85 exp [3.0× 10⁴/(RT)](10⁻³Pa·s) over the same temperature range.     

Bacterial biosurfactant in enhancing solubility and metabolism of petroleum hydrocarbons

Biosurfactant can make hydrocarbon complexes more mobile with the potential use in oil recovery, pumping of crude oil and in bioremediation of crude oil contaminant. In the investigation, bacterial isolates capable of utilizing poly-cyclic aromatic hydrocarbons like phenanthrene, pyrene and fluorene were used. A gradual decrease of the supplemented hydrocarbons in the culture medium was observed with corresponding increase in bacterial biomass and protein. The medium having the combined application of fluorine and phenanthrene caused better biosurfactant production (0.45 g l⁻¹) and (0.38 g l⁻¹) by Pseudomonas aeruginosa strains MTCC7815 and MTCC7814. The biosurfactant from MTCC7815 (41.0 μg ml⁻¹) and MTCC7812 (26 μg ml⁻¹) exhibited higher solubilization of pyrene; whereas, MTCC8165 caused higher solubilization of phenanthrene; and that of MTCC7812 (24.45 μg ml⁻¹) and MTCC8163 (24.49 μg ml⁻¹) caused more solubilzation of fluorene. Higher solubilization of pyrene and fluorene by the biosurfactant of MTCC7815 and MTCC7812, respectively enhanced their metabolism causing sustained growth. Biosurfactants were found to be lipopeptide and protein–starch–lipid complex in nature and they could reduce the surface tension of pure water (72 mN m⁻¹) to 35 mN m⁻¹. The critical micelle concentration (CMC) was also lower than the chemical surfactant sodium dodecyl sulphate (SDS). They differed in quantity and structure. The predominant rhamnolipids present in biosurfactants were Rha–C₈–C₁₀ and Rha–C₁₀–C₈.     

Synthesis of layered Li1.2+x[Ni0.25Mn0.75]0.8−xO2 materials (0 ≤ x ≤ 4/55) via a new simple microwave heating method and their electrochemical properties

Li_1.2+x[Ni_0.25Mn_0.75]_0.8−xO₂ (0 ≤ x ≤ 4/55) was prepared by a new simple microwave heating method and the effect of extra Li⁺ content on electrochemistry of Li_1.2Ni_0.2Mn_0.6O₂ (x = 0) was firstly revealed. X-ray diffraction identified that they had layered α-NaFeO₂ structure (space group R-3m). Linear variation of lattice constant as a function of x value supported the formation of solid solution, that is, extra Li⁺ is possibly incorporated in structure of layered Li_1.2Ni_0.2Mn_0.6O₂ (x = 0), accompanying oxidization of Ni²⁺ to Ni³⁺ to form Li_1.2+x[Ni_0.25Mn_0.75]_0.8−xO₂ (0 ≤ x ≤ 4/55). This was confirmed by X-ray photoelectron spectroscopy that Ni³⁺ appeared and increased in content with increasing x value. Charge–discharge tests showed that Li_1.2+x[Ni_0.25Mn_0.75]_0.8−xO₂ (0 ≤ x ≤ 4/55) truly displayed different electrochemical properties (different initial charge–discharge plots, capacities and cycleability). Li_1.2Ni_0.2Mn_0.6O₂ (x = 0) in this work delivered the highest discharge capacity of 219 mAh g⁻¹ between 4.8 and 2.0 V. Increasing Li content (x value in Li_1.2+x[Ni_0.25Mn_0.75]_0.8−xO₂) reduced charge–discharge capacities, but significantly enhancing cycleability.     

Irradiation induced effects on Ni3N/Si bilayer system

The irradiation effect in Ni₃N/Si bilayers induced by 100 MeV Au ions at fluence 1.5 × 10¹⁴ ions/cm² was investigated at room temperature. Grazing incidence X-ray diffraction determined the formation of Ni₂Si and Si₃N₄ phases at the interface. The roughness of the thin film was measured by atomic force microscopy. X-ray reflectivity was used to measure the thickness of thin films. X-ray photoelectron spectroscopy has provided the elemental binding energy of Ni₃N thin films. It was observed that after irradiation (Ni 2p_3/2) peak shifted towards a lower binding energy. Optical properties of nickel nitride films, which were deposited onto Si (100) by ion beam sputtering at vacuum 1.2 × 10⁻⁴ torr, were examined using Au ions. In-situ I–V measurements on Ni₃N/Si samples were also undertaken at room temperature which showed that there is an increase in current after irradiation.     

Electrical and optical properties of 12CaO·7Al2O3 electride doped indium tin oxide thin film deposited by RF magnetron co-sputtering

12CaO·7Al₂O₃ electride (C12A7:e⁻) doped indium tin oxide (ITO) (ITO:C12A7:e⁻) thin films were fabricated on a glass substrate by an RF magnetron co-sputtering system with increasing number of C12A7:e⁻ chips (from 1 to 7) and at various oxygen partial pressure ratios. The optical transmittance of the ITO:C12A7:e⁻ thin film was higher than 70% in the visible wavelength region. In the electrical properties of the thin film, a decrease of the carrier concentration from 2.6 × 10²⁰ cm^− 3 to 2.1 × 10¹⁸ cm^− 3 and increase of the resistivity from 1.4 × 10^− 3 Ω cm to 4.1 × 10^− 1 Ω cm were observed with increasing number of C12A7:e⁻ chips and oxygen partial pressure ratios. It was also observed that the Hall mobility was decreased from 17.27 cm²·V^− 1·s^− 1 to 5.13 cm²·V^− 1·s^− 1. The work function of the ITO thin film was reduced by doping it with C12A7:e⁻.     

Effect of the adsorbate (Bromacil) equilibrium concentration in water on its adsorption on powdered activated carbon. Part 1. Equilibrium parameters

This study was carried out to investigate the adsorption equilibrium and kinetics of a pesticide of the uracil group on powdered activated carbon (PAC). The experiments were conducted at a wide range of initial pesticide concentrations (5 μg L⁻¹ to 500 μg L⁻¹ at pH 7.8), corresponding to equilibrium concentrations of less than 0.1 μg L⁻¹ for the weakest, which is compatible with the tolerance limits of drinking water. Such a very broad range of initial solute concentrations resulting powdered activated carbon (PAC) concentrations (0.1–5 mg L⁻¹) is the main particularity of our study. The application of several monosolute equilibrium models (two, three or more parameters) has generally shown that Bromacil adsorption is probably effective on two types of sites. High reactivity sites (K_L  10³ L mg⁻¹) which are 10–20 less present in a carbon surface than lower reactivity sites (K_L  10 L mg⁻¹), according to the q_m values calculated by two- or three-parameter models. The maximum capacity of the studied powdered activated carbon (PAC), corresponding to monolayer adsorption, compared to the Bromacil molecule surface, would be between 170 mg g⁻¹ and 190 mg g⁻¹. This theoretical value is very close to the experimental q_m values obtained when using linearized forms of Langmuir, Tóth and Fritz–Schluender models.     

Photoluminescence and electrochemistry behavior of well-dispersible poly-N-[5-(8-quinolinol)ylmethyl]aniline/nano-TiO2 composite

Well-dispersible poly-N-[5-(8-quinolinol)ylmethyl]aniline/nano-TiO₂ composite was synthesized by the surface modification of nano-TiO₂ particles using poly-N-[5-(8-quinolinol)ylmethyl] (PANQ), and it was characterized by Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, thermogravimetric analysis and scanning electron microscope, as well as conductivity and cyclic voltammogram were given. The conductivity of this composite was 2.1 × 10⁻² S cm⁻¹ at 25 °C, and showed good redox reversibility. It was easy to cast a transparent conducting film with photoluminescent property.     

Structural analysis of Sm doped nanocrystalline Mg–Cd ferrites prepared by oxalate co-precipitation method

The structural properties of polycrystalline Sm³⁺ doped Mg_1 − xCd_x Fe₂O₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) have been investigated by oxalate co-precipitation method from high purity sulphates. The samples were sintered at 1050 °C for a duration of 5 h. The X-ray diffraction measurements confirmed the formation of a cubic spinel structure. The different parameters like lattice constant, X-ray density, physical density, porosity, crystallite size, site radii and bond length on tetrahedral and octahedral sites have been calculated. The lattice constant increases with an increase in Cd²⁺ content and shows non linear behavior. The crystallite size was calculated using Scherrer formula and varies from 28.69 to 32.05 nm. Physical densities were obtained by Archimedes principle. The surface morphology studied by scanning electron microscope shows that the grain size of the samples increases with an increase in Cd²⁺ content. The IR spectra show two strong absorption bands around 5.87 × 10⁴ m^− 1 and 4.27 × 10⁴ m^− 1 on the tetrahedral and octahedral sites respectively. IR spectra also show that Sm³⁺ occupies the octahedral B-site.     

Impedance spectroscopy measurements of charge carrier mobility in 4,4'-N,N'-dicarbazole-biphenyl thin films doped with tris(2-phenylpyridine) iridium

The charge carrier mobility of green phosphorescent emissive layers, tris(2-phenylpyridine) iridium [Ir(ppy)₃]-doped 4,4'-N,N'-dicarbazole-biphenyl (CBP) thin films, has been determined using impedance spectroscopy (IS) measurements. The theoretical basis of mobility measurement by IS rests on a theory for single-injection space-charge limited current. The hole mobilities of the Ir(ppy)₃-doped CBP thin films were measured to be 10^− 10–10^− 8 cm²V^− 1 s^− 1 in the 2–7 wt.% Ir(ppy)₃-doped CBP from the frequency dependence of both conductance and capacitance. These hole mobility values are much lower than those of the undoped CBP thin films (~ 10^− 3 cm²V^− 1 s^− 1) because the Ir(ppy)₃ molecules act as trapping centers in the CBP host matrix. These mobility measurements in the Ir(ppy)₃-doped CBP thin films provide insight into the hole injection process.