Surfactant immobilized interlayer species bonded to montmorillonite as recyclable adsorbent for lead ions

Removal of lead ( Pb2+ ) ions from aqueous solution by adsorption onto surfactant-immobilized interlayer species bonded to montmorillonite clay (SIIS-clay) was investigated. Surfactant-immobilized interlayer chromate bound to clay (SIICr-clay) was prepared by treatment of montmorillonite clay with hexadecyltrimethylammonium (HDTMA) bromide followed by chromate adsorption at the intergallery framework of the clay. Experiments were carried out as a function of solution pH, solute concentration, and temperature (5-45 degrees C). The Dubinin-Kaganer-Radushkevich (DKR) model was adopted to describe the single-solute adsorption isotherms. Adsorption energy for lead ions on SIICr-clay computed from the DKR equation shows that a precipitation mechanism was operative. The thermodynamic parameters ( Delta G 0, Delta H 0, and Delta S 0) for lead ion adsorption on SIICr-clay were also determined from the temperature dependence. The kinetics of metal ion adsorption was examined and the first-order rate constant was finally evaluated. Adsorbed lead ions could be recovered completely on leaching with the disodium salt of ethylenediamine tetraacetic acid (EDTA) solution and the adsorbent was found to readsorb lead ions repeatedly after leaching. Thus, surfactant-modified smectite clays offer an effective method for designing a recyclable adsorbent for lead ions.     

Effect of microwave radiation on hydroxy propyl methyl cellulose polymer films and HPMC/poly(vinylpyrrolidone) polymer blend films using the wide-angle X-ray technique

The changes in the microstructural parameters of microwave-irradiated hydroxy propyl methyl cellulose (HPMC) and HPMC/PVP (poly(vinylpyrrolidone)) blend films have been studied using the Wide Angle X-Ray Scattering Technique (WAXS) method. The crystal imperfection parameters, such as lattice strain (g%), the average number of unit cells ? N ? counted in a direction perpendicular to Bragg's plane (hkl), spacing of (hkl planes dhkl, crystallite size ? Ds ?, distortion width, standard deviation, stacking faults, twin faults, were computed by the whole pattern fitting method. The obtained results were quantified in terms of the radiation dosage given to the samples. X-ray analysis reveals that there is a decrease in the crystallite size with the increase in the radiation dosage. Fourier transform Infra-Red (FTIR) analysis has been also carried out for both the unirradiated and irradiated films to study the effect of microwave radiation on HPMC and HPMC/PVP polymer blend films. The scanning electron microscope study is also carried out to know the surface morphology of these blend films.     

Vanadium pentoxide nanobelts: One pot synthesis and its lithium storage behavior

In this paper, we report a synthesis, characterization and electrochemical properties of V₂O₅ nanobelts. V₂O₅ nanobelts have been prepared via hydrothermal treatment of commercial V₂O₅ in acidic (HCl/H₂SO₄) medium at relatively low temperature (160 °C). The hydrothermally derived products have been characterized by powder X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), Raman spectroscopy, X‐ray photo electron spectroscopy (XPS), UV‐Vis spectroscopy, Scanning/Transmission electron microscopy (SEM/TEM). XRD pattern of V₂O₅ nanobelts show an orthorhombic phase. From the FTIR spectrum, the peak observed at 1018 cm⁻¹ is characteristic of the stretching vibration mode of the terminal vanadyl, V = O. The UV‐Vis absorption spectrum of V₂O₅ nanobelts show maximum absorbance at 430 nm, which was blue‐shifted compared to that of bulk V₂O₅. TEM micrographs reveal that the products consist of nanobelts of 40‐200 nm in thickness and several tens of micrometers in length. The electrochemical analysis shows an initial discharge capacity of 360 mAh g⁻¹ and its almost stabilized capacity is reached to 250 mAh g⁻¹ after 55 cycles. A probable reaction mechanism for the formation of orthorhombic V₂O₅ nanobelts is proposed.     

A simple spectrophotometric method for the determination of phosphate in soil, detergents, water, bone and food samples through the formation of phosphomolybdate complex followed by its reduction with thiourea

A simple spectrophotometric method is developed here for the determination of phosphate present in the samples of soil, detergents, water, bone and food based on the formation of phosphomolybdate complex with the added molybdate followed by the reduction of the complex with thiourea in aqueous sulfuric acid medium. The system obeys Beer's law at 840 nm in the phosphate concentration range, 0.5-10.0 μg/ml. Molar absorptivity, correlation coefficient and Sandell's sensitivity values are found to be 1.712 mol(-1) cm(-1), 0.9769 and 0.0555 μg cm(-2) respectively. For a comparison of the results determined from the developed method, phosphate present in the same set of samples is determined separately following an official method. The results of the developed method are agreeing well with those of the official phosphomolybdate method.     

Structural,thermal, and electrical studies of sodium iodide (NaI)-doped hydroxypropyl methylcellulose (HPMC) polymer electrolyte films

Solid polymer electrolyte films based on hydroxypropyl methylcellulose (HPMC) complexed with sodium iodide (NaI) were prepared using solution cast method. The dissolution of the salt into the polymer host and the structural properties of pure and complexed HPMC polymer electrolyte films were confirmed by X-ray diffraction (XRD) studies. XRD results revealed that the amorphous domains of HPMC polymer matrix were increased with increase in NaI salt concentration. The degree of crystallinity was found to be high in pure HPMC samples. The thermal properties were studied using differential scanning calorimetry (DSC). DSC results revealed that the presence of NaI in the polymer matrix increases the melting temperature; however, it is observed that fusion heat is high for pure HPMC films. The variation of film morphology was examined by scanning electron microscopy. Fourier transform infrared spectral studies revealed vibrational changes that occurred due to the effect of dopant salt in the polymer. Direct current conductivity was measured in the temperature range of 313–383 K. The magnitude of electrical conductivity was found to increase with the increase in salt and temperature concentration. The data on the activation energy regions (regions I and II) indicated the dominance of ion-type charge transport in these polymer electrolyte films. The composition HPMC:NaI (5:4) is found to exhibit the least crystallinity and the highest conductivity.     

Simple spectrophotometric method for the determination of sulfur dioxide by its decolorizing effect on the peroxovanadate complex

A simple, rapid, and economical spectrophotometric method is developed for the determination of sulfur dioxide in sugar and air samples. The developed method is based on a red-brown peroxovanadate complex (λ_max = 470 nm) produced in 2 M sulfuric acid when ammonium metavanadate is treated with hydrogen peroxide. Under fixed concentrations of hydrogen peroxide and ammonium metavanadate, when sodium metabisulfite (Na₂S₂O₅ = 2SO₂) is added, it preferentially reacts with hydrogen peroxide producing sulfuric acid, and the unreacted hydrogen peroxide then reacts with ammonium metavanadate; therefore, the concentration of sulfur dioxide is directly proportional to a decrease in the concentration of the peroxovanadate complex. The stoichiometric ratio between hydrogen peroxide and ammonium metavanadate as well as the stability constant of the complex are determined by the modified Job’s method and the respective values are found to be 1: 1 and 2.5 × 10⁴ mol⁻¹ L, respectively. The system obeys Lambert-Beer’s law in the concentration range 3.57–64.26 ppm of sulfur dioxide. The molar absorptivity, correlation coefficient, and Sandell’s sensitivity values are found to be 0.649 × 10³ L mol⁻¹ cm⁻¹, 0.9908, and 0.1972 μg cm⁻², respectively. The method is applied to the determination of sulfur dioxide present in commercial sugars and air samples. The results obtained are reproducible with a standard deviation of 0.02–0.05. For method validation, sulfur dioxide is also determined separately following the AOAC method for an air sample and the ICUMSA method for commercial sugars. The results obtained by the developed and official methods are in good agreement. The text was submitted by the authors in English.     

Effects of CdCl2 concentration on the structural,thermal and ionic conductivity properties of HPMC polymer electrolyte films

Ionics - The present study illustrates cadmium chloride (CdCl2)-doped hydroxypropyl methylcellulose (HPMC) polymer electrolyte films. Solution cast method is employed to prepare polymer electrolyte...     

A simple and rapid spectrophotometric method for the determination of nitrite by its decolorizing effect on peroxovanadate complex

A rapid, simple, and most economical spectrophotometric method was proposed for the determination of nitrite in various water samples, soil samples, and roots of leguminous plants. The method is based on decolorizing effect of nitrite on complex formed between hydrogen peroxide and vanadate in acidic medium. The decolorization of that complex by nitrite was exploited to monitor the reaction spectrophotometrically at 470 nm.The method was optimized for effect of concentrations of ammonium metavanadate, hydrogen peroxide, various acids, concentrations of sulphuric acid, order of reagents addition and color stability. The color of the complex was found to be stable for about 2 days, and the stability constant of the complex was also calculated by modified Job's method. The linearity range of the calibration graph was over 6.67-66.7 microg ml(-1) of nitrite with molar absorptivity, 0.276 x 10(3) mol(-1) l cm(-1) and Sandell's sensitivity, 0.1667 microg cm(-2). The method was applied successfully for the determination of nitrite in soil samples, various wastewater samples and roots of leguminous plants.