S. Ananda

Photocatalytic degradation of rhodamine B dye using hydrothermally synthesized ZnO

The sunlight mediated photocatalytic degradation of rhodamine B (RB) dye was studied using hydrothermally prepared ZnO (T = 150°C andP ∼ 20–30 bars). Zinc chloride was used as the starting material along with sodium hydroxide as a solvent in the hydrothermal synthesis of ZnO. Different durations were tried to obtain pure ZnO phase, which was later confirmed through powder X-ray diffraction. The photocatalytic behaviour of the prepared ZnO was tested through the degradation of RB. The disappearance of organic molecules follows first-order kinetics. The effect of various parameters such as initial dye concentration, catalyst loading, pH of the medium, temperature of the dye solution, on the photo degradation of RB were investigated. The thermodynamic parameters of the photodegradation of RB, like energy of activation, enthalpy of activation, entropy of activation and free energy of activation revealed the efficiency of the process. An actual textile effluent containing RB as a major constituent along with other dyes and dyeing auxiliaries was treated using hydrothermally synthesized ZnO and the reduction in the chemical oxygen demand (COD) of the treated effluent revealed a complete destruction of the organic molecules along with colour removal.

Oxidation of dimethylsulphoxide by sodium m-bromobenzene- sulphonamide: A kinetic and mechanistic study

Abstract The kinetics of oxidation of dimethylsulphoxide (DMSO) by sodium N-bromobenzenesulphonamide or bromamine-B (BAB) has been studied in HClO4, HCl and NaOH media, at 35°C, with OsO4 as a catalyst in the latter medium. In acid medium, the rate shows a first order dependence on [BAB] and second order in [H+], but Is Independent of substrate concentration. Alkali retards the reaction (Inverse first order) and the rate is independent of oxidant concentration, but shows fractional order in [DMSO] and depends on (0sO4]2. The solvent isotope effect was studied by using D2O. Activation parameters have also been determined. Mechanisms proposed and the derived rate laws are consistent with the observed kinetics.

Photocatalytic treatment of municipal wastewater using modified neodymium doped TiO2 hybrid nanoparticles.

Photocatalytic degradation of municipal wastewater was investigated using reagent grade TiO2 and modified neodymium doped TiO2 hybrid nanoparticles. For the first time, surface modification of Nd3 + doped TiO2 hybrid nanoparticles were carried out with n-butylamine as surface modifier under mild hydrothermal conditions. The modified nanoparticles obtained were characterized by Powder XRD, FTIR, DLS, TEM, BET surface area, zeta potential and UV-Vis Spectroscopy. The characterization results indicated better morphology, particle size distribution and low agglomeration of the nanoparticles synthesized. It was found that photodegradation of wastewater using surface modified neodymium doped TiO2 nanoparticles was more compared to pure TiO2, which can be attributed to the doping and modification with n-butylamine.

In situ surface modification of molybdenum‐doped organic–inorganic hybrid TiO2 nanoparticles under hydrothermal conditions and treatment of pharmaceutical effluent

Molybdenum‐doped TiO2 organic–inorganic hybrid nanoparticles were synthesized under mild hydrothermal conditions by in situ surface modification using n‐butylamine. This was carried out at 150°C at autogeneous pressure over 18 h. n‐Butylamine was selected as a surfactant since it produced nanoparticles of the desired size and shape. The products were characterized using powder X‐ray diffraction, Fourier transform infrared spectrometry, dynamic light‐scattering spectroscopy, UV–Vis spectroscopy and transmission electron microscopy. Chemical oxygen demand was estimated in order to determine the photodegradation efficiency of the molybdenum‐doped TiO2 hybrid nanoparticles in the treatment of pharmaceutical effluents. It was found that molybdenum‐doped TiO2 hybrid nanoparticles showed higher photocatalytic efficiency than untreated TiO2 nanoparticles.

Palladium(II)‐Catalyzed Oxidation of Primary Amines by Bromamine‐T in Alkaline Medium: A Kinetic and Mechanistic Study

Oxidations of n‐propyl, n‐butyl and n‐hexylamines by bromamine‐T (BAT), catalyzed by Pd(II), in alkaline medium have been kinetically studied at 30 °C. The reaction rate shows a first‐order dependence on [BAT], a fractional‐order dependence each on [NaOH] and [Pd(II)], and an inverse fractional‐order dependence on [Cl–]. The reaction rate is independent of [amine]. The addition of the reduction product of BAT, p‐toluenesulfonamide, and the variation of dielectric constant of the solvent have no effect on the rate. The catalytic constants were calculated at different temperatures. Activation parameters were evaluated.

Palladium(II)-phenothiazine complexes: synthesis and characterization

Abstract Palladium(II) chloride or nitrate complexes of phenothiazine and its derivatives have been prepared. The new complexes were characterized by their elemental analyses, molar conductivity, magnetic susceptibility and spectroscopic data. The molecular formulae of the complexes were found to be: [C12H9NS)2PdCl2]·H2O where C12H9NS = phenothiazine (PTZ); [C12H8ClNS)2PdCl2] where C12H8ClNS = 2-chlorophenothiazine (CPTZ); [(C21H27N2S2)Pd2Cl5].2H2O where (C21H27N2S2)+ = protonated thioridazine (TRH+); and [(C17H21N2S)2Pd2Cl5]NO3 where (C17H21N2S)+ = protonated promethazine (PMH+). The PM complex behaves as an electrolyte whereas the other complexes act as nonelectrolytes in solution. All the complexes are diamagnetic species. Tentative structures have been proposed.

Ruthenium(III) Catalyzed Oxidation of Aliphatic Primary Amines by Bromamine-T in Hydrochloric Acid Medium: A Kinetic Study

Abstract The kinetics of the ruthenium(III) catalyzed oxidation of the aliphatic primary amines n-propylamine, n-butylamine and isoamylamine, by sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) in HCl medium has been studied in the temperature range 298–313 K. The reaction rate shows a first-order dependence each on BAT, amine, and ruthenium(III). The reaction also shows an inverse fractional- and inverse first-order dependence on acid at low and high [HCl] ranges, respectively. Added halide ions and p-toluenesulfonamide (reduction product of BAT), and variation of ionic strength of the solvent medium have no effect on the rate. The activation parameters have been evaluated. Mechanisms consistent with the kinetic data have been proposed. The protonation constant of monobromamine-T has been evaluated to be 29 ± 2. A Taft LFE relationship is observed for the ruthenium(III) catalyzed reaction with ρ∗ = −4.6 indicating that the electron donating groups enhance the reaction rate. An isokinetic relation...

Photocatalytic degradation of textile effluent using hydrothermally synthesised titania supported molybdenum oxide photocatalyst

Abstract The photocatalytic degradation of textile effluent using hydrothermally synthesised titania supported molybdenum oxide photocatalyst at 200°C with an autogenous pressure and experimental duration of 24 h has been reported. A control over the particle size, morphology and crystallinity of the photocatalyst has been studied with respect to the experimental parameters such as nutrient composition, solvent, pH, experimental duration, temperature and pressure. The products synthesised were characterised using XRD, SEM, FTIR, etc. The photodegradation of textile effluent using these composite was investigated under both solar and ultraviolet irradiation. The degradation of textile effluent was checked by the following parameters: chemical oxygen demand (COD), percentage transmission (%T), irradiation time and duration. The preliminary results are highly encouraging and further work is being carried out for the use of these photocatalytic compounds for other organic decomposition.

Hydrothermal coating of ZnO onto calcium alumino silicate beads and their application in photodegradation of amaranth dye

Abstract Hydrothermal coating of ZnO nanoparticles onto the surface of calcium alumino silicate beads was carried out under hydrothermal conditions (T, 220°C; P, 300 psi; duration, 12 h). The reagent grade ZnO and calcium alumino silicate beads (0·5–1·0 mm in diameter, specially prepared as supporting material for ZnO) were used as starting materials along with 1M NaOH as a mineraliser leading to the formation of a new class of photocatalytic material. The effect of the hydrothermal experimental parameters on the coating of ZnO nanoparticles, and the grain morphology, etc. was investigated and thus obtained ZnO coated calcium alumino silicate beads were characterised using X-ray diffraction, SEM, Fourier transform infrared and positron annihilation spectroscopy. Sunlight and ultraviolet light mediated photocatalytic degradation of amaranth dye was studied using hydrothermally prepared ZnO coated calcium alumino silicate beads. The effect of various parameters such as initial dye concentration, catalytic loading, pH of the medium, time duration and light source on the photodegradation of amaranth dye was investigated. Silk industrial effluents containing amaranth dye as a major constituent along with other dyes and dyeing auxiliaries were treated using ZnO coated calcium alumino silicate beads.

Oxidation of aliphatic ketones by bromamine-b: a kinetic study

Abstract The kinetics of oxidation of propan-2-one, boutan-2-one, pentan-2-one, pentan-3-one and 4-methyl pentan-2-one by sodium N-bromobenzenesulphonamide or bromamine-B (BAB) in perchloric acid madium was studied at 30°C. The rate shows a first order dependence each on [ ketone ] and [ H+ ] and is independent of [ oxidant ]. Variation of ionic strength of medium and addition of the reaction product benzenesulphonamide have no effect on tha rate and the dielectric effect is positive. The proposed mechanism involves acid catalysed enolisation of ketone in the rate limiting step followed by a fast interaction with the oxidant. This is supported by the magnitude of inverse solvent isotope effect of 1.62± 0.01 observed in D2O medium. Activation parameters Ea, ΔH†, ΔS‡, ΔG‡ and log A have been calculated by studying the reaction at different temperatures (293–309 K).