Some fatty acid oxadiazoles for corrosion inhibition of mild steel in HCl

576-583Inhibition effect of some fatty acid oxadiazoles on the corrosion of mild steel (MS) in aqueous solution containing 1 N HCl was investigated by weight loss, potentiodynamic polarization technique, electrochemical impedance spectroscopy and scanning electron microscopy. The adsorption of these compounds was found to obey Langmuir adsorption isotherm. Various thermodynamic parameters were calculated to investigate the mechanism of corrosion inhibition. The effect of inhibitor concentration, solution temperature, immersion time and acid concentration on the corrosion of mild steel has also been investigated by weight loss technique. Scanning electron microscopy (SEM) is used to examine the surface morphology of the mild steel samples both in absence and presence of inhibitor at optimum concentration. Potentiodynamic polarization data showed that the compounds studied are cathodic type inhibitors in the acid solution. Electrochemical impedance spectroscopy was also used to investigate the mechanism of the corrosion inhibition

Kinetics and mechanism of base-catalysed hydrolysis of L-asparagine and its copper(II} complex

737-739Kinetic studies on hydrolysis of L-asparagine and Cu(II)-L-asparagine complex have, been carried out in sodium hydroxide solution (0.1-2.5 mol dm-3). The pseudo-first order rate constants follow the general relationship: kobs = k0[OH-] where k0 is an empirical constant

Synthesis and characterization of a Hg(II) selective II-butyl acetate cerium(IV) phosphate as a new intercalated fibrous ion exchanger: Effect of surfactants on the adsorption behaviour

1856-1860n-butyl acetate Ce(IV) phosphate, a new Hg(II) selective, intercalated fibrous ion exchanger, has been synthesized and characterized by its ion exchange properties, thermal stability and adsorption behaviour for metal ions, X-ray, IR, TGA/DTA and SEM studies. Effect of surfactants on the adsorption behaviour of the material has also been studied. The exchanger has been found to be selective for Hg(II), hence, it can be utilized for the separation of this metal ion from other heavy metals from aqueous media. Studies on the effect of surfactants on the adsorption behaviour of this material show that for heavy metals ion, the adsorption increases with the concentration of anionic surfactants up to the CMC value and then decreases. But, for cationic, surfactants, the reverse is true. For non-ionic surfactant, adsorption remains constant up to the CMC value and then increases. For alkaline earths, the exchanger shows the same trend as above for cationic and non-ionic surfactants. However, for anionic surfactants, it is constant throughout the whole concentration range

Kinetics and mechanism of alkaline hydrolysis of urea and sodium cyanate

1116-1119The kinetics of hydrolysis of urea has been studied in 0.5 to 3.0 mol dm- 3 sodium hydroxide solution at different temperatures. Urea hydrolysis follows an irreversible first order consecutive reaction path: The variation of k1obs with [alkali] is linear at [OH-]=5.0 to 1.5 mol dm-3, thereafter a sharp increase in the reaction rate is observed for first step hydrolysis of urea. The second step rate constant (k2obs) is found to be independent of [alkali]. Hydrolysis of urea in alkaline medium follows an elimination-addition mechanism. The reaction does not proceed through the formation and decomposition of tetrahedral intermediate. Sodium cyanate hydrolysis obeys an irreversible pseudo-first order kinetics. [OH-] has no significant effect on the rate constants. The following rate equations have been derived for the two step hydrolysis of urea. On the basis of observed data, probable mechanisms have been proposed.<br

Kinetics and mechanism of alkaline hydrolysis of urea and sodium cyanate

1116-1119The kinetics of hydrolysis of urea has been studied in 0.5 to 3.0 mol dm- 3 sodium hydroxide solution at different temperatures. Urea hydrolysis follows an irreversible first order consecutive reaction path: The variation of k1obs with [alkali] is linear at [OH-]=5.0 to 1.5 mol dm-3, thereafter a sharp increase in the reaction rate is observed for first step hydrolysis of urea. The second step rate constant (k2obs) is found to be independent of [alkali]. Hydrolysis of urea in alkaline medium follows an elimination-addition mechanism. The reaction does not proceed through the formation and decomposition of tetrahedral intermediate. Sodium cyanate hydrolysis obeys an irreversible pseudo-first order kinetics. [OH-] has no significant effect on the rate constants. The following rate equations have been derived for the two step hydrolysis of urea. On the basis of observed data, probable mechanisms have been proposed.<br