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Abstract  

In this present work, the kinetic reaction constants including the forward (kf, Cs adsorption onto granite) and backward (kb, Cs desorption from granite) rate constants of Cs on granite were determined by fitting the experimental data from both adsorption and desorption experiments with a pseudo first-order reaction model. In the case of Cs adsorption, both forward and backward rate constants are consistent with one another as Cs loading less than 0.1 mM. In contrast, both forward and backward reaction constants from desorption experiment dramatically increase as the Cs loading increases. Rearrangement of these desorption data by linearization technique, a notable instantaneous desorption process appears, which profoundly influences the determination of the rate constants. Based on our fitting results, the rate constants including both forward and backward reactions determined from Cs adsorption onto granite are much suitable to represent the adsorption behavior, in which the recommended values are of 0.42 and 0.03 h−1, respectively.

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Abstract  

In this study, a high catalytic activity of palladium nanoparticles immobilized on alumina (Al2O3) is reported for the industrially important reduction of aromatic nitro compounds to amino compounds. The palladium nanoparticles were immobilized on alumina by a simple physical precipitation method. The synthesis of palladium nanoparticles was done in ethylene glycol without using any external stabilizing agent. The composite particles exhibited good colloidal stability. The catalytic activity is investigated qualitatively by high performance liquid chromatography (HPLC) and quantitatively by photometrically monitoring the reduction of p-nitrophenol by an excess of sodium borohydride (NaBH4) in the presence of nanocomposites. The kinetic data could be explained by the assumption of pseudo first-order reaction with respect to p-nitrophenol.

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slow decomposition of MB. After that, the reaction follows the pseudo first-order rete law, the equation for the pseudo first-order reaction could be given by Eq. 15 under the consideration of the induction period [ 30 ]. where C t denotes the

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catalytic activity. The conversion of phenol on Co-300 only reached 54% after 7 h. Usually, it has been reported that pseudo first-order reaction kinetics was used to describe the reaction rate of HDO reactions [ 2 , 4 ]. The relationship between the

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transformation of phenol was described by pseudo first-order reaction kinetics. The relationship between the conversion ( x ) and the rate constant ( k , mL g −1 s −1 ) could be described as ln(1 − x ) = kC cat t , where t was the reaction time and C cat

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Abstract  

Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide consecration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order.

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Abstract  

A small ultraviolet-visible absorption spectrometer which uses fibre optic coupled immersion probes has been incorporated into a laboratory scale reaction calorimeter. The combined instrument has been tried out using the hydrolysis of acetic anhydride as a test reaction. With the calorimeter operating in the isoperibolic mode good agreement is found for the pseudo-first order reaction rate constant as determined from spectroscopic and calorimetric measurements. Experiments have been made in order to follow the reaction indirectly using optical pH measurements with acid-base indicators. The possibility of determining the temperature dependence of the rate constant in a single experiment has also been investigated.

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Abstract  

Electrospray ionization mass spectrometry (ESI-MS) was used for the study of cyclization of organic chelating compounds (chelators). Four chelating compounds were studed: Symmetrical ethylenediaminediacetic acid (s-EDDA), Unsymmetrical ethylenediaminediacetic acid (u-EDDA), N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA), and N-(2-hydroxyethyl)iminodiacetic acid (HEIDA). The chelators were cyclized with treatments of acids and heating. The open and cyclized form of the chelators were semi-quantified by both positive and negative ion modes ESI-MS. The kinetics of chelator cyclization was studied as a function of reaction temperature and the pH of the matrix. The cyclization of s-EDDA was found to be a pseudo-first order reaction in s-EDDA and overall second order. The cyclizations of HEIDA and HEDTA are reversible reactions. Higher temperature and lower pH favors cyclization.

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Abstract  

The effects of absorbed doses, initial pH and 1-naphthol concentration onto its radiolysis in aqueous sulphuric and hydrochloric acids by gamma rays from 60Co were investigated. Under the experimental conditions, 1-naphthol degradation yields increased with increasing the absorbed doses (0.3–3.0 kGy) and with decreasing the initial 1-naphthol concentration (20–1 ppm). It was found out that the hydrated electrons did not play any significant roles in 1-naphthol radiolysis, as the degradation yields were higher at pH0 ~ 0.46 compared to those at pH0 ~ 2.0–5.0. The corresponding radiolytic yields G(−1-naphthol) were (6.13 ± 1.00)) × 10−2 and (5.11 ± 0.22) × 10−2 μmol/J in sulphuric acids, (15.61 ± 3.85) × 10−2 and (4.76 ± 0.48) × 10−2 μmol/J in hydrochloric acids. 1-Naphthol degradation rates could be described by the kinetic equations of pseudo-first-order reactions. An empirical relation between the observed reaction constants k D and the initial 1-naphthol concentrations was established, enabling to predict the absorbed doses required for a given treatment efficiency. Three products of 1-naphthol degradation were revealed using an HPLC/UV procedure.

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Abstract

In this study, UV/oxidant and UV/TiO2/oxidant systems were employed to treat textile wastewater. The parent compound was C.I. reactive red 198 (RR198). The selected oxidants were H2O2, Na2S2O8, NaBrO3, and NaIO4. The effects of oxidant dosage (1–24 mM), wavelength of UV (254 and 365 nm) and radical scavenger addition (C2H5OH) were determined in UV/oxidant systems. The experimental results revealed that all oxidants effectively decolorized RR198 under 254 nm irradiation; however, only Na2S2O8 and NaIO4 can decolorize RR198 under 365 nm irradiation. The decolorization rates fit a pseudo-first order reaction model. Under 254 nm irradiation and 6 mM oxidant addition, the decolorization rate constants (k) of H2O2, Na2S2O8, NaBrO3, and NaIO4 for RR198 were 10.24, 17.93, 13.37, and 11.90 h−1. Under 365 nm irradiation, 1 g/L TiO2 and 1 mM NaIO4 addition, the k values of the UV/TiO2, UV/NaIO4, and UV/TiO2/NaIO4 systems were 0.50, 0.52, and 11.67 h−1. The inhibition of RR198 decolorization by the addition ethanol indicates that the primary decolorization pathway involves hydroxyl radicals in UV/H2O2 and UV/Na2S2O8 systems, and that oxidation by other radicals is probably important in UV/NaBrO3 and UV/NaIO4 systems.

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