Novel two-ply composite membranes of chitosan and sodium alginate for the pervaporation dehydration of isopropanol and ethanol

Novel two-ply dense composite membranes were prepared using successive castings of sodium alginate and chitosan solutions for the pervaporation dehydration of isopropanol and ethanol. Preparation and operating parameters namely polymer types facing to the feed stream, NaOH treatment for the regeneration of chitosan, and crosslinking system types were investigated using the factorial design method. It was shown that these parameters were all critical to the performance of the membrane in the form of the main and interaction effects. The pervaporation performance of the two-ply membrane with its sodium alginate layer facing the feed side and crosslinked or insolubilized in sulfuric acid solution was compared with the pure sodium alginate and the chitosan membranes in terms of the flux and separation factors. It was shown that although its flux was lower than that of the pure sodium alginate and chitosan membranes, the separation factors at various alcohol concentrations were in between values for the two pure membranes. For the dehydration of 90 wt% isopropanol–water mixtures the performance of the two-ply membrane which was moderately crosslinked in formaldehyde was found to match the high performance of the pure sodium alginate membrane. This two-ply membrane had fluxes of 70 g/m² h at 95% EtOH, 554 g/m² h at 90% PrOH and separation factors of 1110 at 95% EtOH, 2010 at 90% PrOH and its mechanical properties were better than that of the pure sodium alginate membrane.     

A competitive transport across polymeric membranes. Study of complexation and separation of ions

The removal and separation of Cu(II), Zn(II) and Ni(II) from nitrate aqueous solutions were studied by competitive transport across cellulose triacetate plasticized membranes modified with polyelectrolytes: polyethyleneimine (PEI) and polyethyleneglycol (PEG). Competitive transport of trace ions from aqueous solutions across polymer inclusion membranes containing a mixture of the three polymers (cellulose triacetate as the support) and tris(2-ethylhexyl-phosphate) (TEHP) as the plasticizer provide the selectivity order: Cu(II) > Ni(II) > Zn(II). A long-term transport experiment was carried out to demonstrate the durability of polymer inclusion membranes. A separation of bivalents cations (Cu²⁺, Ni²⁺, Zn²⁺) and monovalent cations (K⁺ and Na⁺) is achieved.     

The investigations on K and L X-ray fluorescence parameters of gold compounds

The study aimed to determine the chemical effects on the K and L X-ray intensity ratios and the K and L X-ray production cross sections for gold compounds. The K shell fluorescence yields and L shell average yields were also investigated. The samples were excited by 59.5 keV γ-rays from an ²⁴¹Am annular radioactive source and 123.6 keV γ-rays from a ⁵⁷Co annular radioactive source. K and L X-rays emitted from samples were counted by an Ultra-LEGe detector with a resolution of 0.150 keV at 5.9 keV. The experimental values were compared with theoretical, the semi-empirical and other experimental values.     

An insight to the filtration mechanism of Pb(II) at the surface of a clay ceramic membrane through its preconcentration at the surface of a graphite/clay composite working electrode

The use of cyclic voltammetry (CV) and linear scan anodic stripping voltammetry (LSASV) to predict the selectivity of microfiltration ceramic membranes made from a lump of local clay towards Pb(II) ions filtration is described. The membranes were characterized by different techniques followed by CV analysis of the Fe(CN)₆^3-/Fe(CN)₆^4- redox couple and Pb(II) on bare graphite, raw clay, and clay-modified carbon paste electrode (clay-modified CPE). The effect of clay loading in the range of 1–10 % (w/w) on the electrodes is studied, where an enhanced peak current is observed for 5 % w/w clay. Moreover, a decrease in the peak current can be seen for bare graphite electrodes, suggesting that the clay mineral had played a substantial role in the sieving of heavy metal ions through the ceramic membrane. The electroactive surface area of 5% w/w raw clay towards Fe(II) ions was found to be in the order of 3.07 × 10^-2 cm² and higher than 5% w/w clay sintered to 1000 °C and bare graphite. CV analysis shows that both, 5 % w/w raw clay and 5 % w/w clay sintered to 1000 °C exhibited high peak currents towards Pb(II) ions. The mobility of the Pb(II) ions is found to increase when 5% w/w clay sintered to 1000 °C is utilized as membrane/electrode, leading to an increase in the amount of reduced Pb(II) ions on the surfaces of the clay membranes/electrodes. The study suggests successful filtration of Pb(II) ions through the proposed membrane/electrode and a much better accumulation than Fe(II) at the surface of the membrane/electrode before being subjected to filtration.     

Vibrational spectra,conformational equilibria,ab initio calculations and vibrational assignments of ethylmethylfluorosilane

The infrared spectra of ethylmethylfluorosilane (CH₃SiHFCH₂CH₃) have been recorded as a vapour, liquid and solid at 78 K in the 4000–50 cm⁻¹ range and isolated in an argon matrix at ca. 5 K. Infrared spectra of two different solid phases were obtained after annealing to temperatures of 120 and 130 K, and recooling to 78 K. Although the IR spectra were quite similar in the MIR region, certain differences were noted in the FIR region below 400 cm⁻¹. The most stable conformer MeMe was present after annealing to 130 K, but three bands belonging to MeH were detected after annealing to 120 K. Various infrared bands changed intensity when the argon matrix was annealed to temperatures between 20 and 35 K, and some of these were related to changes in the conformational abundance.Raman spectra of the liquid were recorded at room temperature and at various temperatures between 295 and 153 K. Spectra of an amorphous and annealed solid were recorded at 78 K. In the variable temperature Raman spectra, various bands changed in intensity and were interpreted in terms of conformational equilibria between the three possible conformers. Complete assignments were made for all the bands of the most stable conformer MeMe. From various bands assigned to the three conformers, the conformational enthalpy difference ΔH from MeMe to the intermediate energy conformer MeH was found to be 0.5 kJ mol⁻¹ and to the highest conformer MeF was 0.7 kJ mol⁻¹. At ambient temperature this leads to 39% MeMe, 32% MeH and 29% of the MeF conformer in the liquid.Ab initio calculations in the RHF, MP2, DFT approximations and very accurate G2 calculations were carried out. With one exception, the MeMe conformer had the lowest enthalpy in all these calculations, the MeH had the intermediate and the MeF the highest enthalpy, and the calculations were in good agreement with the measurements.     

Evolution of microstructure and crack pattern in NiO thin films under 200 MeV Au ion irradiation

NiO thin films grown on Si (100) substrate by electron beam evaporation method and sintered at 700 °C were irradiated with 200 MeV Au¹⁵⁺ ions. The fcc structure of the sintered films was retained up to the highest fluence (1×10¹³ ions cm^?2) of irradiation. However the microstructure of the pristine film underwent a considerable modification with increasing ion fluence. 200 MeV Au ion irradiation led to compressive stress generation in NiO medium. The diameter of the stressed region created by 200 MeV Au ions along the ion path was estimated from the variation of stress with ion fluence and found to be ～11.6 nm. The film surface started cracking when irradiated at and above the fluence of 3×10¹² ions cm^?2. Ratio of the fractal dimension of the cracked surface obtained at 200 MeV and 120 MeV (Mallick et al., 2010a) Au ions was compared with the ratio of the radii of ion tracks calculated based on Coulomb explosion and thermal spike models. This comparison indicated applicability of thermal spike model for crack formation.     

Albumin separation with Cibacron Blue carrying macroporous chitosan and chitin affinity membranes

Cibacron Blue F3GA, Procion Red HE-3B and Procion Blue MX-R were immobilized on macroporous chitosan and chitin membranes with concentrations as high as 10–200 μmol/ml membrane. These dyed membranes were chemically and mechanically stable, could be reproducibly prepared, and operated at high flow rates. Human serum albumin (HSA) and bovine serum albumin (BSA) were selected as model proteins, and their adsorption on and desorption from the dyed chitosan membranes investigated. The Cibacron Blue F3GA membranes had a higher protein adsorption capacity, much greater for HSA than BSA, than the other dyed membranes. About 8.4 mg HSA/ml membrane were adsorbed at saturation by Cibacron Blue F3GA–chitosan membranes from a 0.05 M Tris–HCl/0.05 M NaCl, pH 8 solution. The chitin membranes had a lower dye content and hence a lower protein adsorption capacity than the chitosan membranes. The effects of important operation parameters (flow rate, protein concentration and loading) were also investigated. Cibacron Blue F3GA–chitosan membranes were employed for the separation of HSA from human plasma and high purity HSA thus obtained. This suggests that these membranes could be used for large-scale plasma fractionation.     

Structural modifications of swift heavy ion irradiated PEN probed by optical and thermal measurements

The effects of swift heavy ion irradiation on the structural characteristics of Polyethylene naphthalate (PEN) were studied. Samples were irradiated in vacuum at room temperature by lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver (120 MeV) ions with the fluence in the range of 1×10¹¹–3×10¹²  ions cm⁻². Ion induced changes were analyzed using X-ray diffraction (XRD), Fourier transform infra red (FT-IR), UV–visible spectroscopy, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Cross-linking was observed at lower doses resulting in modification of structural properties, however higher doses lead to the degradation of the investigated polymeric samples.     

Observed bands in Raman and infrared spectra of 1,3-dioxolane and their assignments

We present a Raman study of liquid and polycrystalline dioxolane, together with data for a solid dioxolane/argon film. Observed bands are assigned to the bent conformer on the basis of ab initio calculated vibrations, accompanied with potential energy distribution. Two internal modes were calculated at 658 and 720 cm⁻¹ for the bent form. These were observed at 665 and 722 cm⁻¹ in liquid, and split into four bands (at 694, 697, 725, and 728 cm⁻¹) in the crystal at 10 K. In the solid dioxolane/argon film an additional band appears at 705 cm⁻¹ (between the bands at 675 and 726 cm⁻¹). A search for an additional dioxolane conformer trapped in argon was undertaken by performing molecular dynamics simulations of dioxolane/argon solid film and averaging overall molecular conformations. The resulting conformation did not correspond to an energy minimum, but indicated that changes of only a few degrees in dihedral angles could shift ring deformation and OCO bending modes for more than 10 cm⁻¹. Differential scanning calorimetric measurements gave evidence of solidification upon cooling at 146 K, and two phase changes on heating (one at 158.3 K, and a melting transition at 180.3 K). Further study is required on the hysteresis effect in the temperature behavior of dioxolane, and on the nature of the intermediate solid phase.     

Heavy metals and color retention by a synthesized inorganic membrane

In this study, a new type of a double-layer ceramic membrane was used for the filtration of wastewater. The synthesized membrane consists of a macroporous substrate (with pore size of about 0.1 μm) prepared following the colloid filtration technique and a thin film functional layer (with pore size of about 10 nm) carried out according to the sol–gel preparation method.The ceramic membranes were tested for the removal of cadmium, zinc, Methylene Blue and Malachite Green from water under a pressure of 5 bar and a treatment time of 2 h. Liquid filtration and flow tests through these membranes resulted in a rejection rate of 100% for Methylene Blue and Malachite Green. This paper also presents the ability of the tubular membrane prepared to separate heavy metals (cadmium and zinc) from their synthetic aqueous solutions. The influence of the applied pressure, feed solute concentration, feed pH on the rejection of cadmium and zinc ions was studied. Retention rates of cadmium and zinc ions of 100% were observed for an initial feed concentration of 10⁻⁴ mol/L.     

Consideration on excitation mechanisms in a high-power two-jet plasma

The study of excitation mechanisms in the region before the jet confluence of a high-power two-jet plasma used for analysis of different powders has been undertaken. Distribution of excited levels of Fe atoms and ions according to the Boltzmann population was found. Measuring Fe atomic and ionic excitation temperatures showed their considerable difference (≈ 2000–2500 K). The effect of argon on line intensities of a wide range of elements was investigated by the experiment with argon covering. A negligible effect of argon covering on line intensities of atoms with ionization energy of < 8 eV allows one to assume their predominant excitation by electron impact. The argon participation in excitation of atoms having ionization energy of > 8 eV was revealed. This is likely to be due to Penning ionization by metastable argon followed by ion recombination with an electron and stepwise de-excitations. A more pronounced effect of argon covering was observed for ionic lines of investigated elements with total excitation energy ranging from 11 to 21 eV. Penning ionization followed by electron impact is believed to be a probable mechanism for ion excitation. The contribution of metastable argon to excitation processes results in departure from local thermodynamic equilibrium and different atomic and ionic excitation temperatures.     

Characterization of the water-insoluble pyrolytic cellulose from cellulose pyrolysis oil

Water-insoluble pyrolytic cellulose with similar appearance to pyrolytic lignin was found in cellulose fast pyrolysis oil. The influence of pyrolysis temperature on pyrolytic cellulose was studied in a temperature range of 300–600 °C. The yield of the pyrolytic cellulose increased with temperature rising. The pyrolytic cellulose was characterized by various methods. The molecular weight distribution of pyrolytic cellulose was analyzed by gel permeation chromatography (GPC). Four molecular weight ranges were observed, and the M_w of the pyrolytic cellulose varied from 3.4 × 10³ to 1.93 × 10⁵ g/mol. According to the elemental analysis (EA), the pyrolytic cellulose possessed higher carbon content and lower oxygen content than cellulose. Thermogravimetric analysis (TGA) indicated that the pyrolytic cellulose underwent thermo-degradation at 127–800 °C and three mass loss peaks were observed. Detected by the pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), the main pyrolysis products of the pyrolytic cellulose included saccharides, ketones, acids, furans and others. Fourier transforms infrared spectroscopy (FTIR) also demonstrated that the pyrolytic cellulose had peaks assigned to CO stretching and glycosidic bond, which agreed well with the Py-GC/MS results. The pyrolytic cellulose could be a mixture of saccharides, ketones, and their derivatives.     

Enhanced performance of an anode-supported YSZ thin electrolyte fuel cell with a laser-deposited Sm0.2Ce0.8O1.9 interlayer

A power density of over 1.4 W cm^?2 at 0.7 V was achieved at 750 °C for an anode-supported YSZ thin electrolyte fuel cell with a dense Sm_0.2Ce_0.8O_1.9 (SDC) interlayer fabricated by pulsed laser deposition, while the cell with a conventional porous SDC interlayer exhibited only 0.8 W cm^?2 at this voltage. The dense SDC interlayer significantly reduced the ohmic resistance of the fuel cell. For example, at 750 °C, the ohmic resistance of the fuel cell with a dense SDC interlayer was 0.08 Ω cm²; while that of the cell with a porous SDC interlayer fabricated by conventional screen-printing was 0.16 Ω cm². The pronounced reduction in ohmic resistance might be due to the fully dense structure and thus improved electrical conductivity of the SDC interlayer, increased contact area at the interface between the dense SDC interlayer and the YSZ electrolyte, and suppressed Zr migration into the SDC interlayer.     

Effect of swift heavy ion irradiation on ethylene–chlorotrifluoroethylene copolymer

The swift heavy irradiation induced changes taking place in ethylene–chlorotrifluoroethylene (E–CTFE) copolymer films were investigated in correlation with the applied doses. Samples were irradiated in vacuum at room temperature by lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver (120 MeV) ions with the fluence in the range of 1×10¹¹–3×10¹² ions cm^?2. Structural and thermal properties of the irradiated as well as pristine E–CTFE films were studied using FTIR, UV–visible, TGA, DSC and XRD techniques. Swift heavy ion irradiation was found to induce changes in E–CTFE depending upon the applied doses.     

Thermodynamics of the Cu(II) adsorption on thin vanillin-modified chitosan membranes

In this work, low-density vanillin-modified thin chitosan membranes were synthesized and characterized. The membranes were utilized as adsorbent for the removal of Cu(II) from aqueous solutions. The experimental data obtained in batch experiments at different temperatures were fitted to the Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model. The adsorption equilibrium data fitted well with the Langmuir model (average R² > 0.99). Interactions thermodynamic parameters (Δ_intH, Δ_intG, and Δ_intS), as well as the interaction thermal effects (Q_int) were determined from T = (298 to 333) K. The thermodynamic parameters, the Dubinin–Radushkevick equation and the comparative values of Δ_intH for some Cu(II)–adsorbent interactions suggested that the adsorption of Cu(II) ions to vanillin-chitosan membranes show average results for both the diffusional (endothermic) and chemical bonding (exothermic) processes in relation to the temperature range studied.     

Studies on polypyrrole modified nafion membrane for vanadium redox flow battery

In order to prevent the vanadium crossover and preferential water transfer in all-vanadium redox flow battery (VRFB), three methods – electrolyte soaking, oxidation polymerisation and Electrodeposition, were used to modify Nafion 117 membranes using pyrrole. The surface of the modified membranes was uniform and even, and the membranes were characterised in terms of morphology, membrane area resistance, vanadium permeability and water transfer property. The properties of all the modified membranes were improved greatly. The membranes modified by Electrodeposition showed a best combination of the membrane resistance, vanadium permeability and water transfer property, the experimental results showed that the V(IV) ion permeability of polypyrrole modified Nafion membranes by Electrodeposition at the conditions of 0.025 mA cm⁻² and 0 ^°C for 60 min reduced more than 5 times from 2.87 × 10⁻⁶ cm² min⁻¹ to 5.0 × 10⁻⁷cm² min⁻¹, and the water transfer property decreased more than 3 times from 0.72 ml/72 h cm² to 0.22 ml/72 h cm². All above properties made the modified Nafion membranes more applicative in the VRFB system. This paper also reported other methods for Nafion membrane modification and the influences of the deposition conditions on the properties of the membrane selectivity and water transfer.     

Radiotracer and analytical evidences proving the reduction of ClO4− ions at the cobalt/electrolyte solution interface

The occurrence of the reduction of ClO₄⁻ ions in the course of the dissolution (corrosion) of Co was indicated through the study of the adsorption of radio labelled (³⁶Cl) Cl⁻ ions. A detailed analytical study determining the Co²⁺ and Cl⁻ content of the solution phase furnished firm evidences that under suitable chosen experimental conditions the 4Co + ClO₄⁻ + 8H⁺=4Co²⁺ + Cl⁻ + 4H₂O reaction could be as important as the Co + 2H⁺=Co²⁺ + H₂ reaction considered in the literature as the only reaction path.     

Effect of aging on UF membranes by a streaming potential (SP) method

In this paper we have determined, by a streaming potential (SP) method, the isoelectric point (IEP) of a new cellulose membrane, the regenerated cellulose material. This membrane is more hydrophilic than the classical cellulose acetate material and less sensitive to protein adsorption, with an IEP of 3.4.Furthermore, we have validated an SP method as a new method to control aging of porous membranes. We validate the SP technique on a surface of 30 cm² for a membrane with a molecular weight cut-off of 10 kDa.In this new field of research where nondestructive techniques are not many, we have shown, for the first time, the efficiency of coupling permeability and SP measurements to control aging of mesoporous polymer membranes.     

Proton (3 MeV) and copper (120 MeV) ion irradiation effects in low-density polyethylene (LDPE)

Low-density polyethylene (LDPE) was irradiated with proton (3 MeV) and copper (120 MeV) ions to analyze the induced modifications with respect to optical and structural properties. In the present investigation, the fluence for proton irradiation was varied up to 2×10¹⁵ protons cm⁻², while that for copper beam was kept in the range of 1×10¹ to 1×10¹³ ions cm⁻² to study the swift heavy ion-induced modifications in LDPE. Ultraviolet–visible (UV–vis), FTIR and X-ray diffraction (XRD) techniques were utilized to study the induced changes. The analysis of UV–vis absorption studies reveals that there is decrease of optical energy gap up to 43% on proton irradiation (at 2×10¹⁵ ions cm⁻²), whereas the copper beam (at 1×10¹³ ions cm⁻²) leads to a decrease of 51%. FTIR analysis indicated the presence of unsaturations due to vinyl end groups in the irradiated sample. The formation of OH and CO groups has also been observed. XRD analysis revealed that the semi-crystalline LDPE losses its crystallinity on swift ion irradiation. It was found that the proton beam (2×10¹⁵ ions cm⁻²) decreased the crystallite size by 23% whereas this decrease is of 31% in case of the copper ion-irradiated LDPE at 1×10¹³ ions cm⁻².     

Stability and performance of porous silica–zirconia composite membranes for pervaporation of aqueous organic solutions

Porous silica–zirconia membranes were fabricated by the sol–gel techniques to study their stability against water and the pervaporation performance of aqueous solutions of organic solvents. Zirconia (10–70 mol%) was added to silica to obtain silica–zirconia composite membranes by firing at 400–500 °C for pervaporation tests with organic solvent/water mixtures, such as iso-propyl alcohol (IPA)/water and tetrahydrofuran (THF)/water mixtures at their normal boiling points.The membrane coatings have been done effectively by the hot-coating methods proposed previously. Boiling water treatments introduced in the coating processes have made the membranes quite stable even in the high water concentration region of aqueous organic solutions at their normal boiling points. Zirconia contents larger than about 40 mol% have made the silica–zirconia membranes quite stable. The membranes of zirconia contents less than about 30 mol% were found not stable in a dilute aqueous solution of IPA. The membranes fabricated by the conventional dip-coating methods with slow drying were not stable against water because of the probable segregation of silica and/or silica-rich phases during drying.The membranes fired at lower temperature (400 °C) gave a higher water flux of around 500 mol m⁻² h⁻¹ (9 kg m⁻² h⁻¹) with a separation factor larger than 1500 at 10 wt.% of water in the boiling feed of IPA/water mixture, for example.