Oxidative Decolorisation of Eriochrome Black T with Chloramine-T: Kinetic, Mechanistic, and Spectrophotometric Approaches

The kinetics and mechanism of oxidative decolorisation of Eriochrome Black T (EBT) with sodium N-chloro-p-toluenesulfonamide or Chloramine-T (CAT), catalysed by osmium tetroxide [Os(VIII)] in alkaline medium and uncatalysed in acid medium, have been spectrophotometrically investigated at 303 K. The reaction exhibited a first-order dependence of rate on [CAT]0 and [EBT]0 in both media, and also with respect to [H+]. The order with respect to [OH-] and [Os(VIII)] was fractional. Activation parameters were deduced. It was observed that the uncatalysed decolorisation reaction was ca. eightfold faster in acid medium in comparison with alkaline medium, while the Os(VIII)-catalysed reaction was ca. sevenfold faster than the uncatalysed reaction. Mechanisms and rate laws were determined. The chemical oxygen demand of Eriochrome Black T dye was also determined. Importantly, the developed oxidative decolorisation method is simple, efficient, inexpensive, requires less time, and is environmentally benign. Hence, it can be adapted for treating Eriochrome Black T present in industrial and laboratory wastewater

Oxidation of mephenesin and guaifenesin with chloramine-B in hydrochloric acid medium: Design of kinetic model

339-345Kinetics of oxidation of mephenesin and guaifenesin by sodium N-chlorobenzenesulfonamide (CAB) have been investigated in HCl medium at 303 K. The oxidation behaviour is similar for both the substrates. The rate shows a first order dependence on both [CAB]₀ and [HCl], and is fractional in [substrate]₀. The orders individually in [H⁺] and [Cl⁻] are fractional. The variation of ionic strength and addition of the reduction product, benzenesulfonamide, has no significant effect on the reaction rate. The solvent isotope effect has been studied using D₂O, and the oxidation products have been identified. Composite activation parameters for the reaction have been determined from Arrhenius plots. Michaelis-Menten type of kinetics is observed and activation parameters for the rate limiting steps have also been computed. The proposed mechanism assumes the simultaneous catalysis by H⁺ and Cl⁻ ions. The reaction is found to be moderately faster in guaifenesin in comparison with mephenesin, which may be attributed to the involvement of methoxy and methyl groups of the substrate. The observed results have been explained by a plausible mechanism and the related rate law has been proposed

Oxidative decolorization of methyl red dye with chloramine-T ─ Kinetic and mechanistic chemistry

416-422<span style="font-size:9.0pt;mso-bidi-font-size: 12.0pt" lang="EN-GB">A simple and expeditious oxidative decolorization technique has been developed for the removal of Methyl Red dye (MR; C.I. Acid Red 2) present in the wastewater. The kinetic and mechanistic aspects of the present redox system have also been investigated. Kinetics and oxidative decolorization of MR dye with sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in HClO4 medium at 303 K has been investigated spectrophotometrically at λmax 524 nm. The reaction shows a first-order dependence of rate each on [CAT]o and [MR]o. The reaction is catalyzed by [HClO4] and the order with respect to [H+] is found to be fractional (0.75). Activation parameters have been evaluated. The oxidation products of MR dye are identified as N-(4-dimethylamino-phenyl)-hydroxylamine and 4-nitroso-benzoic acid by GC-MS analysis. The observed results have been explained by a plausible mechanism and the related rate law is deduced. Further, the present redox system can be adopted for treating MR dye present in industrial effluents with suitable modifications to reduce the toxicity caused by MR dye. </span

Oxidative Cleavage of &#x3b2;-Lactam Ring of Cephalosporins with Chloramine-T in Alkaline Medium: A Kinetic, Mechanistic, and Reactivity Study

Cephalosporins are β-​lactam antibiotics, and the important drugs of this group are cephalexin, cefadroxil and cephradine. In the present research, the kinetics and mechanism of oxidn. of cephalexin (CEX)​, cefadroxil (CFL)​, and cephradine (CPD) with chloramine-​T (CAT) in alk. medium were investigated at 301 K. All the three oxidn. reactions follow identical kinetics with a first-​order dependence each on [CAT]​o and [substrate]​o. The reaction is catalyzed by hydroxide ions, and the order is found to be fractional. The dielec. effect is neg. Proton inventory studies in H2O-​D2O mixts. with CEX as a probe have been made. Activation parameters and reaction consts. have been evaluated. Oxidn. products were identified by mass spectral anal. An isokinetic relation was obsd. with β = 378 K, indicating that enthalpy factors control the rate. The rate increases in the following order: CPD > CFL > CEX. The proposed mechanism and the derived rate law are consistent with the obsd. kinetics

Use of Cu(II) catalyst assisted oxidative decolorization of dye by chlorinating species in water: A kinetic and mechanistic study with acid red1 dye

A quick and easy decolorization method has been created in the current study to get rid of the Acid Red 1 (AR1) dye from the wastewater. At 298 K, the kinetics of oxidative decolorization of AR1 dye with Chloramine-B (CAB) in NaOH medium, catalyzed by copper(II) sulphate, have been examined spectrophotometrically (λmax = 506nm). The experimental rate laws found are as follows: d[CAB]/dt = k [CAB]0 [AR1]0 [Cu(II)]x / [OH−]y in an alkaline medium, where x and y are less than unity.Under ideal experimental conditions, 90% dye decolorization is achieved in 30 minutes using concentrations of 0.003M [CAB], 0.0003M [AR1], 0.003M [Cu(II), and 0.003M [OH−].In the current kinetic redox system, the Cu(II) catalyst showed to be an effective homogeneous catalyst. The 4-acetamido-5,6-dioxo-5,6-dihydro naphthalene-2-sulphonic acid is identified as the oxidation product using mass spectrum analysis. The FTIR spectra show the absence of N=N stretching bands at 1489 cm−1 which confirms the oxidative breakdown of the azo group, a fundamental chromophore responsible for color, which induces toxicity in the waste water. The decolorization reaction catalyzed by Cu(II) is approximately six times faster than the uncatalyzed reaction. The catalytic constant (Kc) is calculated at various temperatures, and activation parameters for copper(II) are also evaluated. The observed results are explained by plausible mechanisms, and relative rate laws has been deduced. Chemical oxygen demand (COD) has been significantly reduced by the oxidative decolorization process. Phytotoxicity tests revealed that the treated dye sample is less toxic than the untreated dye sample. An economic analysis is carried out. Notably, with appropriate modifications, the developed oxidative decolorization technique is expected to benefit in the removal of AR1 dye present from industrial wastewater

Recent advances in the development of high efficiency quantum dot sensitized solar cells (QDSSCs): A review

Quantum dots play an important role in third-generation photovoltaics. The key focus on quantum dots is due to their cost effect, capacity to work in diffused light, ease of fabrication, light weight, and flexibility which pique curiosity to further research. The incorporation of quantum dots into photovoltaics results in theoretically high thermodynamic conversion efficiencies of up to 40%, but in practise, the efficiencies are lower than those of dye-sensitized solar cells. Recent developments of different components like photoanode, quantum dot sensitizer, electrolyte, and counter electrode were discussed in detail. It was observed that by changing the synthesis methods, the adhesion properties might vary, which leads to enhancing the photovoltaic properties such as power conversion efficiency (PCE), open circuit voltage (Voc), short circuit current (Jsc), and fill factor (FF). The first report on the efficiency of Quantum Dot Sensitized Solar Cells (QDSSCs) was 0.12%. As of today, the efficiency is reported as 18.1 %, and further, the researchers are working to improve the efficiency of QDSSCs