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31.
A novel cation exchanger (TFS-CE) having carboxylate functionality was prepared through graft copolymerization of hydroxyethylmethacrylate onto tamarind fruit shell (TFS) in the presence of N,N′-methylenebisacrylamide as a cross-linking agent using K2S2O8/Na2S2O3 initiator system, followed by functionalisation. The TFS-CE was used for the removal of Cu(II) from aqueous solutions. At fixed solid/solution ratio the various factors affecting adsorption such as pH, initial concentration, contact time, and temperature were investigated. Kinetic experiments showed that the amount of Cu(II) adsorbed increased with increase in Cu(II) concentration and equilibrium was attained at 1 h. The kinetics of adsorption follows pseudo-second-order model and the rate constant increases with increase in temperature indicating endothermic nature of adsorption. The Arrhenius and Eyring equations were used to obtain the kinetic parameters such as activation energy (Ea) and enthalpy (ΔH#), entropy (ΔS#) and free energy (ΔG#) of activation for the adsorption process. The value of Ea for adsorption was found to be 10.84 kJ · mol?1 and the adsorption involves diffusion controlled process. The equilibrium data were well fitted to the Langmuir isotherm. The maximum adsorption capacity for Cu(II) was 64 · 10 mg · g?1 at T = 303 K. The thermodynamic parameters such as changes in free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were derived to predict the nature of adsorption process. The isosteric heat of adsorption increases with increase in surface loading indicating some lateral interactions between the adsorbed metal ions. 相似文献
32.
Mahanta D Madras G Radhakrishnan S Patil S 《The journal of physical chemistry. B》2008,112(33):10153-10157
A method for the removal of anionic (sulfonated) dyes from aqueous dye solutions using the chemical interaction of dye molecules with polyaniline is reported. Polyaniline (PANI) emeraldine salt was synthesized by chemical oxidation. Sulfonated dyes undergo chemical interactions with the charged backbone of PANI, leading to significant adsorption of the dyes. This phenomenon of selective adsorption of the dyes by PANI is reported for the first time and promises a green method for removal of sulfonated organics from wastewater. The experimental observations from UV-vis spectroscopy, X-ray diffraction, and conductivity measurements rule out the possibility of secondary doping of polyaniline salt by sulfonated dye molecules. A possible mechanism for the chemical interaction between the polymer and the sulfonated dye molecules is proposed. The kinetic parameters for the adsorption of sulfonated dyes on PANI are also reported. 相似文献
33.
Subramanian NH Manigandan P Wille A Radhakrishnan G 《Journal of chromatographic science》2011,49(8):603-609
This work describes a new method for the determination of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in water matrices by suppressed conductivity detection. Separation was achieved by isocratic elution on a reversed-phase column thermostated at 45°C using an aqueous mobile phase containing boric acid and acetonitrile. The PFOA and PFOS content in the water matrix were quantified by a pre-concentration technique. For the concentration range of 1 to 15 ng/mL and 2 to 30 ng/mL, the linear calibration curve for PFOA and PFOS yielded coefficients of determination (R(2)) of 0.9995 and 0.9985, respectively. The relative standard deviations were smaller than 1.5% for PFOA and PFOS. The retention-time precision of four consecutive 12 h injections was smaller than 0.641% and 0.818%, respectively. The presence of common divalent cations, such as calcium, magnesium, and iron in water matrices impairs PFOS recovery. This drawback was overcome by applying inline matrix elimination method. The optimized method was successfully applied for drinking water, ground water, and seawater samples. 相似文献
34.
Nanocrystalline tungsten oxides (WO3−δ) are currently receiving a lot of attention because of their interesting electrical, magnetic, optical and mechanical properties. In this report, we present the synthesis of PEG assisted tungsten oxide (WO3) nanoparticles by simple household microwave irradiation (2.45 GHz) method. The samples were characterized using powder X-ray diffraction (XRD), thermal analysis (TG/DTA), transmission electron microscopy (TEM), UV-visible diffusion reflectance spectroscopy (UV-VIS-DRS), cyclic voltammetry and electrochemical impedance spectroscopy. Powder XRD results revealed that both the samples prepared with and without surfactant crystallize in the orthorhombic structure corresponding to WO3·H2O phase. Subsequent annealing under identical conditions (600 °C/air/6 h) led to significantly different products i.e. monoclinic W17O47 from surfactant free sample and orthorhombic WO3 from PEG assisted sample. Blue emission was observed through UV-VIS-DRS with blue shift and the band gap energy was estimated as 2.7 and 3.28 eV for PEG assisted as prepared (WO3·H2O) and annealed samples (WO3) respectively. Electrochemical measurements have been performed on all the samples deposited on the surface of glassy carbon (GC) electrode which showed high sensitivity and good selectivity for PEG assisted sample (WO3·H2O) for the direct detection of l-dopa. 相似文献
35.
Herein we describe an efficient one pot strategy toward highly functionalized isoquinolone fused azabicycles having great synthetic potential via C–H activation of N-pivaloyloxy benzamides under very mild conditions. The reaction is accomplished at room temperature within one hour in good to excellent yields and is found to be compatible with a range of diazabicyclic olefins and benzamides. The present strategy offers an easy route for the synthesis of biologically relevant compounds which possess multiple points for divergent synthesis. N–N bond cleavage of synthesized compounds may enable their significant role as effective precursors for the preparation of diaminocyclopentane fused isoquinolones. 相似文献
36.
Titanium‐Catalyzed Hydroalumination of Conjugated Dienes: Access to Fulvene‐Derived Allylaluminium Reagents and Their Diastereoselective Reactions with Carbonyl Compounds 下载免费PDF全文
Dr. Jomy Joseph Dr. Florian Jaroschik Dr. Dominique Harakat Dr. K. V. Radhakrishnan Dr. Jean‐Luc Vasse Prof. Jan Szymoniak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5433-5438
The described titanium‐catalyzed hydroalumination of conjugated dienes opens up a new way to allylaluminium reagents. The reaction is carried out by using diisobutylaluminium hydride (DIBAL‐H) and a catalytic amount of [Cp2TiCl2] (Cp=cyclopentadienyl). When applied to mono‐ and disubstitued pentafulvenes, this reaction proceeds in a highly endocyclic manner. The formed allylaluminium compounds react regio‐ and stereoselectively with both aldehydes and ketones to afford homoallylic alcohols that are suitable synthons for functionalized cyclopentanones. An extension of this methodology to simple dienes was also investigated. In the proposed mechanism, the initially formed bimetallic species (Ti/Al) are involved in the two possible catalytic cycles with a direct hydroalumination or/and a hydrotitanation followed by a titanium to aluminium transmetallation. 相似文献
37.
N. T. Madhu P. K. Radhakrishnan W. Linert 《Journal of Thermal Analysis and Calorimetry》2006,84(3):607-611
The
phenomenological, kinetic and mechanistic aspects of the nitrate, chloride,
bromide and iodide complexes of nickel(II) with1,2-(diimino-4’-antipyrinyl)ethane
(GA) have been studied by TG and DTG techniques. The kinetic parameters like
activation energy, pre-exponential factor and entropy of activation were computed.
The rate controlling process in all stages of decomposition is random nucleation
with one nucleus on each particle (Mampel model). 相似文献
38.
John Kallikat Augustine Veeramani Vairaperumal Sharmila Narasimhan Padma Alagarsamy Anbarasi Radhakrishnan 《Tetrahedron》2009,65(48):9989-1409
Propylphosphonic anhydride (T3P®) has been demonstrated to be an efficient and mild reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles from carboxylic acids. 相似文献
39.
Joseph LK Dayas KR Damodar S Krishnan B Krishnankutty K Nampoori VP Radhakrishnan P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(4):1281-1285
The laser-induced luminescence studies of the rare earth titanates (R2Ti2O7) (R=La, Nd and Gd) using 355 nm radiation from an Nd:YAG laser are presented. These samples with submicron or nanometer size are prepared by the self-propagating high temperature synthesis (SHS) method and there is no known fluorescence shown by these rare earths in the visible region. Hence, the luminescence transitions shown by the La2Ti2O7 near 610 nm and Gd2Ti2O7 near 767 nm are quite interesting. Though La3+ ions with no 4f electrons have no electronic energy levels that can induce excitation and luminescence processes in the visible region, the presence of the Ti3+ ions leads to luminescence in this region. 相似文献
40.
Hui Yee Yeong Brigitte Voit Yang Li Fritz E. Kühn Narayanan Radhakrishnan 《Macromolecular Symposia》2011,308(1):35-42
Summary: Polyisobutylene is an industrially important polymer which is conventionally prepared by polymerization at temperatures below 0 °C. The application of solvent ligated metal complexes associated with weakly coordinating counteranions (WCAs), however, allows the room temperature (30 °C) polymerization of isobutylene resulting in highly reactive polyisobutylene (HR-PIB) containing a high content of terminal double bonds. Recently described complexes include manganese (II), copper(II), molybdenum(III) and zink(II) complexes which were coordinated octahedrally with the boron and alumina based WCAs, each with its own advantages and traits. 相似文献