Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric acid media have been investigated using conventional spectrophotometric technique. In both acidic media, the reactions manifested first order kineticsin [permanganate] and less than unit order each in [reductants] and [acid]. Increasing ionic strength had no effect on the oxidation rates. Oxidation rates of fluorenes in perchloric acid were higher than those in sulfuric acid and the order of the oxidation rates was: Fl > Fl-I > Fl-Br > Fl-Cl. Final oxidation products were identified by GC/MS and FT-IR analyses in all cases as 9H-fluorenone derivatives. Reaction constants as well as activation parameters of the second order rate constants were also evaluated

Kinetics of hexacyanoferrate (III) (HCF) oxidation of fluorene (Fl) in organic alkaline medium has been studied by spectrophotometric technique at a constant ionic strength of 0.15 mol dm-3 and at a temperature of 25°C. The reaction showed a first order kinetics with respect to [HCF] and fractional-first order dependences on both [Fl] and [OH- ]. The oxidation rate was increased with the increase in the ionic strength of the reaction medium. The oxidation mechanism was suggested which involves formation of a 1:1 intermediate complex between fluorene and HCF species in a pre-equilibrium step. The final oxidation product of fluorene was identified by spectroscopic and chemical tools as 9H-fluorenone. The appropriate rate law expression was deduced and the reaction constants involved in the mechanism were evaluated. The activation parameters of the rate constant of the slow step along with the thermodynamic quantities of the equilibrium constants were evaluated and discussed.

The electrochemical behavior of nickel, Inconel 600, Incoloy 800 and 316 stainless steel electrodes in different concentration of NaOH solution was investigated using the cyclic voltammetry technique (CV). All the curves in the anodic branch of the CV are characterized by anodic dissolution peak (A), passive region (B), anodic dissolution peak (C) before oxygen evolution. In the case of the cathodic branch of CV there is one reduction peak (D) in case of Ni electrode but there are two reduction peaks (D and E) in case of the three alloys used. All these peaks are explicated. The effect of chloride ion as a pitting agent on the cyclic voltammetry and the potentiodynamic anodic polarization of Ni ,Inconel 600, Incoloy 800 and 316 SS electrodes in NaOH solution was investigated. As the concentrations of the chloride ions increase the change of the amount of the anodic charge Δqa increases and the values of the pitting corrosion potential are shifted to the more negative direction indicating the breakdown of passivity and the imitation of the pitting corrosion. At one and the same Cl- ion concentration, the resistance to the pitting attack decreases in the following order: 316SS > Inconel 600 > Incoloy 800> 316 SS. This order depends on the chemical composition of these alloys.

The inhibiting power of three synthesized amino acids based-surfactant molecules, namely, sodium N-dodecyl asparagines (AS), sodium N-dodecylhistidine (HS) and sodium N-dodecyltryptophan (TS) on the dissolution of carbon steel was inspected in 0.5 M NaCl and 05 M NaOH solutions at 25 °C. The methods employed in this work were weight-loss (WL), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The chemical structures of the synthesized surfactants were confirmed by FT-IR and 1 HNMR. The inhibition efficiencies were found to increase as the surfactants concentrations increase, while decreasing with increasing the concentration of the corrosive media (NaCl & NaOH) and temperature. Results obtained from the different techniques revealed that the inhibition efficiency of the compound TS was higher than those of both AS and HS. The inhibition efficiencies of the synthesized surfactants were declined in terms of strong adsorption of surfactants on the surface of carbon steel and forming a protective film and such adsorption was found to obey Langmuir isotherm. Both thermodynamic and kinetic parameters were evaluated which support the mechanism of physical adsorption of the inhibitors. The tested surfactants were found to act as mixed-type inhibitors with anodic predominance. The surface morphology of the carbon steel surface was examined by scanning electron microscopy (SEM). The inhibitory mechanism of carbon steel corrosion was suggested. Results obtained from all employed methods are consistent with each other

Three amino acids based-surfactants, namely, sodium N-dodecyl asparagines (AS), sodium N-dodecyl histidine (HS) and sodium N-dodecyl tryptophan (TS) were synthesized and were investigated as corrosion inhibitors for mild steel (ST-37-2) in 0.5 M HCl at 25 oC. The methods employed in this work were weight-loss (WL), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The useful surface active properties of the synthesized surfactants were also evaluated. The inhibition efficiencies were found to increase with the inhibitor concentration, while decrease with increasing the concentration of hydrochloric acid and temperature. Results obtained from the different techniques revealed that the inhibition efficiency increases in the following sequence: AS < HS < TS. The high inhibition efficiencies of the synthesized surfactants were declined in terms of strong adsorption of the surfactant molecules on mild steel surface and forming a protective film separating the steel surface from the corrosive acid medium. The adsorption operation was found to obey Langmuir isotherm. Thermodynamic and kinetic parameters were evaluated by adsorption theory and kinetic equations which support the mechanism of physical adsorption of the inhibitors. The polarization measurements showed that the tested surfactant molecules act as mixed-type inhibitors with anodic predominance. The mechanism of inhibition of mild steel corrosion was also suggested. Results obtained from all employed methods are consistent with each others.

The inhibition of corrosion of mild steel in HCl in the presence of vanillin (van) coexisting with some amino acids, i.e., valine (val), cysteine (cys), methylcysteine hydrochloride (m-cys) and methionine (meth) are compared. The possible synergistic inhibition of the corrosion by these amino acids using vanillin are also examined. It has been found that the inhibition efficiency of the studied amino acids in HCl is arranged as follows; meth < m-cys < cys < val. In the presence of vanillin, the inhibition efficiencies are arranged as follows; m-cys < val < meth < cys. This arrangement of the inhibition efficiency is explained based on the possible synergistic adsorption of the studied amino acids with the pre-adsorbed chloride ions.

Oxidation of tryptophan (Trp) by potassium permanganate in acid, neutral and alkaline media led to the formation of the corresponding aldehyde (indole-3-acetaldehyde), ammonia and carbon dioxide. The oxidation kinetics was studied by a spectrophotometric technique at fixed ionic strengths and at 25 o C. All the reactions showed a first order dependence on [MnO4 - ] and fractional-first order kinetics in [Trp]. Fractional-second order kinetics in [H+ ] and fractional-first order dependence with respect to [OH- ] were revealed in acid and alkaline media, respectively. An increase in the ionic strength in alkaline medium increased the oxidation rate of tryptophan, whereas it had a negligible effect on the oxidation rate in acid medium. Plausible oxidation mechanisms in all media were suggested and the rate-laws expressions were derived. Furthermore, the reactions constants included in the various steps of the suggested mechanisms were evaluated.

The kinetics of platinum(IV) oxidation of cadaverine (CAD) in perchloric acid medium was studied at a constant ionic strength of 2.0 mol dm-3 and at 25°C. The oxidation reaction was followed spectrophotometrically. The reaction exhibited a first order kinetics in [PtIV] and less than unit order dependences with respect to [CAD] and [H+ ]. Increasing ionic strength and dielectric constant decreased the oxidation rate. The final oxidation products of cadaverine were identified as 5-aminopentanal and ammonia. The oxidation mechanism was proposed and the appropriate rate-law expression was deduced. The activation parameters of the second order rate constant were evaluated and discussed.

Sodium N-dodecyl arginine surfactant (sodium 2-(dodecylamino)-5-guanidinopentanoate) was synthesized and examined as an inhibitor for the corrosion of Sabic iron in acidic (HCl), neutral (NaCl) and alkaline (NaOH) media using different techniques, namely, weight-loss (WL), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). Increasing the concentrations of the acidic, neutral and alkaline media increased the corrosion rates of Sabic iron and increased the corrosion rate in the order: HCl >> NaCl > NaOH. It was found that the inhibition efficiency of the inhibitor increased with the concentration of the inhibitor while decrease with raising temperature. The results indicate that the inhibition efficiency of the inhibitor increased in the studied media in the sequence: HCl > NaCl > NaOH. The high inhibition efficiency of arginine surfactant inhibitor was interpreted on the basis of strong adsorption of the inhibitor molecules on the surface of Sabic iron and forming a protective film. The adsorption was found to obey Langmuir adsorption isotherm. The evaluated thermodynamic and kinetic parameters support the mechanism of physical adsorption of the inhibitor. The results obtained from all used techniques are in a good agreement with each others.

This paper describes a novel method for the removal of potassium tellurite (TeIV), a toxic tellurium (IV) compound, via its bioreduction using the drug flucloxacillin (Flx) in an aqueous sulfuric acid solution. The kinetics of the bioreduction process were monitored using UV–Vis absorption spectra at an ionic strength of 2.0 mol dm−3 and 298 K. The reaction between TeIV and Flx was set at a 1:1 stoichiometry. The reduction reaction followed first-order kinetics for [Flx] and fractional-first-order kinetics for [TeIV] and [H+]. The effects of ionic strength and relative permittivity of the reaction medium were also explored. Supplementation with divalent transition metal ions enhanced the reduction rate. The reaction products were identified, in order of their stoichiometric results, spot tests and FT-IR spectra as 3-(2-chloro-6-fluorophenyl)-5-methylisoxazol-4-carbocylic acid, 5,5-dimethyl-thiazolidine-2,4-dicarboxlic acid, ammonium ion, carbon dioxide and elemental tellurium (Te0 ). The reaction rate dependence on temperature was studied, and the activation and thermodynamic parameters were assessed and discussed. The derived rate-law expression was found to be in excellent accordance with the acquired investigational outcomes. A conceivable reaction mechanism has been provided, which includes a reaction between the protonated flucloxacillin (Flx+) and tellurous acid (H2TeO3) as the essential reactive species, resulting in the construction of an intermediate complex. Such complex decays in the rate-determining step to yield the final reaction products.