New coordination polymers. III: Oxidation of poly(vinyl alcohol) by permanganate ion in alkaline solutions. Kinetics and mechanism of formation of intermediate complex with a spectrophotometric detection of manganate(vi) transient species
ABSTRACT The kinetics of formation of the [PVA. MnVIO] intermediate complex have been measured by the conventional spectrophotometric technique. The rate of formation of the complex was found to be given by the expression d[Complex]/dt = k1[MnO-4][PVA−]. The results showed that the rate of formation is dependent on the base concentration. A first-order reaction in permanganate and fractional order with respect to the poly(vinyl alcohol) (PVA) concentration were observed. The activation parameters have been evaluated and a tentative reaction mechanism has been suggested.
Separation Science and Technology 02/2010; 45(2):212-220. · 1.09 Impact Factor
Article: Removal and adsorption characteristics of polyvinyl alcohol from aqueous solutions using electrocoagulation.[show abstract] [hide abstract]
ABSTRACT: The study was to investigate the performance of electrocoagulation (EC) for the efficient removal of polyvinyl alcohol (PVA) from aqueous solutions. Several parameters were evaluated to characterize the PVA removal efficiency, such as various electrode pairs, current densities, supporting electrolytes, temperatures, and initial electrolyte concentrations. The effects of the current density, supporting electrolyte, and temperature on the electrical energy consumption were also investigated. The experimental results indicate that a Fe/Al electrode pair is the optimum choice out of four different electrode pair combinations. The optimum current density, supporting electrolyte concentration, and temperature were found to be 5 mA cm(-2), 0.008 N NaCl, and 298 K, respectively. The PVA removal efficiency decreased with increasing in the initial concentrations. The kinetic studies indicated that the EC process was best described using pseudo-second-order kinetics. The experimental data were also compared to different adsorption isotherm models in order to describe the EC process. The adsorption of PVA was best fitted by the Langmuir adsorption isotherm model. Thermodynamic parameters such as the Gibbs free energy, enthalpy, and entropy indicated that the adsorption of PVA on metal hydroxides was feasible, spontaneous and endothermic in the temperature range of 288-318 K.Journal of hazardous materials 05/2010; 177(1-3):842-50. · 4.14 Impact Factor
Article: MnO2 nanostructures of different morphologies from amino acids-MnO4- reactions in aqueous solutions.[show abstract] [hide abstract]
ABSTRACT: In this paper, we describe a simple method for the synthesis of MnO(2) nanostructures (quantum dots) by permanganate oxidations of methionine and cysteine. Upon addition of permanganate to a solution of reductant (methionine and/or cysteine), yellow-brown color species appears within the time of mixing which was stable for several weeks. The UV-vis spectroscopy and transmission electron microscopy (TEM) techniques were used to characterize the nature of color formed. TEM images show that the MnO(2) sol consists of aggregated spherical nonoparticles (size in the range ca<or=7 nm) of various forms. In addition, we observed the different morphologies of the MnO(2) nanostructures (MnO(2) nanoparticles, nanosheet, and fiber-like aggregated nanostructures) under different experimental conditions. The effect of various parameters, such as [H(+)], [MnO(4)(-)], and [reductants] was also investigated.Colloids and surfaces. B, Biointerfaces 11/2010; 81(1):381-4. · 2.60 Impact Factor