The kinetics of Hg(II)-catalyzed reaction between hexacyanoferrate(II) and nitroso-R-salt has been followed spectrophotometrically by monitoring the increase in absorbance at 720 nm, the λ max of green complex, [Fe(CN) 5 N-R-salt] 3− as a function of pH, ionic strength, temperature, concentration of reactants, and the catalyst. In this reaction, the coordinated cyanide ion in hexacyanoferrate(II) gets replaced by incoming N-R-salt under the following specified reaction conditions: temperature = 25 ± 0.1 • C, pH = 6.5 ± 0.2, and I = 0.1 M (KNO 3 ). The stoichiometry of the complex has been established as 1:1 by mole ratio method. The rate of catalyzed reaction is slow at low pH values and then increases with pH and attains a maximum value between 6.5 and 6.7. The rate finally falls again at higher pH values due to nonavailability of [H + ] ions needed to regenerate the catalytic species. The rate of reaction increases initially with [N-R-salt] and attains a maximum value and then levels off at higher [N-R-salt]. The rate of reaction shows a variable order dependence in [Fe(CN) 6 4− ] ranging from unity at lower concentration to 0.1 at higher concentrations. The effect of [Hg 2+ ] on the reaction rate shows a complex behavior and the same has been explained in detail. The activation parameters for the catalyzed reactions have been evaluated. A most plausible mechanistic scheme has been proposed based on the experimental observations. C 2005 Wiley Periodicals, Inc. Int J Chem Kinet

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In this study, Coconut Coir Pith was used to prepare a low cost bio adsorbent through chemical modification. The effect of adsorbent dosage, contact time, initial metal-ion concentration, pH and temperature on the adsorption of nickel onto chemically modified coconut coir pith was investigated. The maximum removal was observed at pH 6.0 and adsorbent dose 2.0 g/L for initial metal-ions concentration 50 mg/L. Study of temperature effect proved that the process is endothermic. Langmuir and Freundlich isotherm models were used for equilibrium adsorption data. Langmuir isotherm proved to be a better fit. Pseudo first order and pseudo second order kinetic models were applied to analyze the kinetic mechanism of adsorption. The values of Gibbs free energy ΔG°, Enthalpy ΔH° and Entropy ΔS° was calculated by the thermodynamic studies.

For the very first time, a detailed kinetic study for the preparation of silver nanoparticles (silver NPs) by neuroleptic agent gabapentin (GBP) in the absence of a stabilizer has been reported in this investigation. This paper is devoted to the preparation of silver nanoparticles by a chemical reduction method in which gabapentin acts as both a reductant and a stabilizer, and AgNO3 is used as a source of Ag+ ions and NaOH for maintaining the alkaline medium. A UV–visible spectrophotometer is used to monitor the progress of the reaction kinetics in an aqueous medium by changing the concentration of different variables such as AgNO3, NaOH, and gabapentin at 40 °C. It is found that the reaction rate follows a pseudo-first-order reaction. The thermodynamic activation parameters were also studied at five different temperatures (303, 308, 313, 318, and 323 K) and used in the support of the proposed mechanistic scheme for the formation of silver nanoparticles. The prepared silver nanoparticles were characterized using different techniques: UV–visible spectrophotometry, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The average particle size was observed in the range of 5–45 nm.