K. Muraleedharan

Thermal decomposition kinetics of 2-furaldehyde thiosemicarbazone complexes of cadmium(II) and mercury(II)

Abstract Complexes of cadmium(II) and mercury(II) with 2-furaldehyde thiosemicarbazone have been subjected to non-isothermal kinetic investigation in air using TG, DTG and DTA techniques. The kinetic parameters for both stages of decomposition of these complexes were evaluated by the weighted least-squares approach, using the Coats- Redfern, Freeman-Carroll and Horowitz- Metzger methods. The values of kinetic parameters obtained by the three methods are in good agreement.

Kinetics of thermal decomposition of sulphate-doped potassium metaperiodate

Abstract The effect of sulphate dopant on the thermal decomposition kinetics of potassium metaperiodate (KIO 4 ) has been studied by isothermal thermogravimetric analysis in the temperature range 580–600 K. Doping enhances the decomposition rate and the effect increases linearly with increasing dopant concentration. The decomposition process was found to the best described by the Prout-Tompkins equation. The activation energies (E) for pure and 1 × 10 −4 , 1 × 10 −3 , 1 × 10 −2 and 1 × 10 −1 mol% sulphate-doped KIO 4 are, respectively, 239.7, 229.2, 218.4, 212.5 and 209.5 kJ mol −1 . Doping did not affect the E values significantly.

Effects of dopants on the isothermal decomposition kinetics of potassium metaperiodate

The isothermal decomposition and kinetics of potassium metaperiod- ate (KIO4) were studied by thermogravimetry as a function of the concentration of dopants. The thermal decomposition of KIO4 proceeds mainly through two stages: an acceleration period up to α = 0.50 and a decay stage. The thermal decomposition data for both doped and untreated KIO4 were found to be best described by the Prout-Tompkins Equation. The α-t data of doped and un- treated samples of KIO4 were subjected to isoconversional studies for the de- termination of the activation energy values. The isoconversional studies of the isothermal decomposition of untreated and doped samples of KIO4 indicated that the thermal decomposition of KIO4 proceeds through a single kinetic mo- del, the Prout-Tompkins model, throughout the entire range of conversion, as opposed to earlier observations.

A computational investigation on the structure, global parameters and antioxidant capacity of a polyphenol, Gallic acid

A computational DFT-B3LYP structural analysis of a poly phenol, Gallic acid (GA) has been performed by using 6-311++ G (df, p) basis set. The GA is a relatively stable molecule with considerable radical scavenging capacity. It is a well known antioxidant. The NBO analysis shows that the aromatic system is delocalized. The results reveal that the most stable radical is formed at O3-atom upon scavenging the free radicals. Global descriptive parameters show that GA acts as an acceptor center in charge transfer complex formation which is supported by ESP and contour diagrams and also by Qmax value. The GA is a good antioxidant and it can be better understood by HAT and TMC mechanisms as it has low BDE, ΔHacidity and ΔGacidity values. The ΔBDE and ΔAIP values also confirm that the antioxidant capacity of GA can be explained through HAT rather than the SET-PT mechanism.

Flexible chitosan-nano ZnO antimicrobial pouches as a new material for extending the shelf life of raw meat

As a breakthrough to open up the industrial use of novel environmentally benign packaging material, we propose the first report on portable chitosan-ZnO nano-composite pouches that will serve as elite entrants in smart packaging. A facile, one pot procedure was adopted for the preparation of the C-ZnC films. In order to tune the property of C-ZnC films, four different composite films were prepared by varying the concentration of ZnO. The prepared films were found to be much superior when compared to bare chitosan and other conventional films. Two bacterial strains that commonly contaminate in packed meat were selected as target microbes to elucidate the antimicrobial activity of the prepared C-ZnO film. Detailed investigations revealed that the antimicrobial efficiency is linearly related to the amount of ZnO nano-particles in the composite. The C-2 films exhibited excellent antimicrobial activity and was fabricated into packaging pouches for raw meat. The prepared pouches showed significant action against the microbes in raw meat owing to its complete inhibition of microbial growth on the sixth day of storage at 4°C. The C-2 pouches stand as a top-notch material when compared to polyethylene bag in extending the shelf life of raw meat.

Thermal decomposition kinetics of zirconyl oxalate, zirconyl oxalic acid and ammonium zirconyl oxalate

Abstract The thermal decomposition studies of zirconyl oxalate (ZO), Zirconyl oxalic acid (HZO) and ammonium zirconyl oxalate (NZO) have been earned out in air by TG, DTG and DTA techniques. The kinetic parameters (non-isothermal method) for their main oxalate decomposition step have been evaluated using the method suggested by Horowitz and Metzger. The results indicate that the values of E and A for the main oxalate decomposition step of these compounds are in the order ZO ≈ HZO

Thermal decomposition kinetics of thiophene-2-carboxaldehyde thiosemicarbazone complexes of nickel(II) and palladium(II)

The thermal analysis of Ni(II) and Pd(II) complexes with thiophene-2-carboxaldehyde thiosemicarbazone have been studied using TG technique. Their decompositions are subjected to critical evaluation using the equations of Coats-Redfern, Horowitz-Metzger and modified Horowitz-Metzger and the kinetic parameters (non-isothermal method) have been evaluated for each step of decomposition by the method of weighted least-squares.ZusammenfassungMittels TG wurde die Thermoanalyse der Komplexe aus Ni(II) und Pd(II) mit Thiophen-2-carboxaldehyd-thiosemicarbazon untersucht. Ihre Zersetzung wurde mittels der Gleichungen von Coats-Redfern, Horowitz-Metzger und einer modifizierten Horowitz-Metzger-Gleichung einer kritischen Auswertung unterzogen. Die kinetischen Parameter (nichtisotherme Methode) wurden für jeden Zersetzungsschritt mittels der Methode gewichteter Quadratsummen geschätzt.

Evaluation of kinetic parameters for the thermal decomposition of piperonaldehyde tfflosemicarbazone complexes of cobalt(II) and zinc(II) halides

Abstract The thermal decomposition of piperonaldehyde (3,4-methylenedioxybenzaldehyde) thiosemicarbazone complexes of Co(II) and Zn(II) halides has been studied thermogravimetrically in air (non-isothermal method). Reaction order n , apparent activation energy E ★ , the pre-exponential factor A and entropy of activation Δ S ★ were computed by the weighted least squares method using the Coats-Redfem and Horowitz-Metzger equations. The values of E ★ , A and Δ S ★ obtained by the two different methods agree well. The mechanism for the decomposition follows the Mampel model equation, i.e. -ln(l-α) for g(α), and the rate-controlling process is random nucleation with the formation of a nucleus on every particle.

One-pot synthesis of poly vinyl alcohol (PVA) supported silver nanoparticles and its efficiency in catalytic reduction of methylene blue

Abstract Stable silver nanoparticles were synthesized using polyvinyl alcohol (PVA) as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer matrix. The successful incorporation of silver nanoparticles in a PVA matrix was confirmed by UV–Visible spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. The synthesized silver nanoparticles were characterized by a peak at 426 nm in the UV–Vis spectrum. TEM studies showed the formation of spherical shaped silver nanoparticles of 10–13 nm, following the reduction by UV irradiation. Catalytic properties were studied by means of UV-Visible spectroscopic analysis. The synthesized silver nanoparticles exhibited good catalytic properties in the reduction of methylene blue.

Numerical data for the evaluation of kinetic parameters of solid state decompositions by the non-isothermal method

Abstract Determination of the kinetic parameters of the thermal decomposition of solids usually requires a knowledge of the function g (α), describing the mechanism of decomposition. An effective and fast method is described for the determination of kinetic parameters from a single non-isothermal curve. Numerical data in the form of a ready reference table are given from which the kinetic parameters can be obtained once the correct form of g (α) has been established.