S. Ahmad Nabavi-Amri

In this research, the acid-base properties of two glycosilated flavanones namely naringoside and hesperidin were thermodynamically studied using spectrophotometric and potentiometric techniques at various temperatures (293.15–313.15) K. Because of very low solubility of these flavanones in aqueous solution, the protonation constants were obtained in ethanol-water mixtures (60–90% v/v) containing 0.10 mol dm− 3 tetra-n-butylammonium perchlorate (TBAP) as supporting electrolyte for naringoside and DMSO-water mixed solvents (50–95% v/v) containing 0.10 mol dm− 3 NaCl for hesperidin. Data process for the calculation of the protonation constants was done using the computer program STAR. The thermodynamic quantities (ΔG°, ΔH°, and ΔS°) of the protonation process were obtained by means of modified van't Hoff equation. It was found that the acid dissociation reaction is exothermic and the entropic contribution is low for both the flavanones. Finally, the influence of solute-solvent interactions on the protonation equilibria in various temperatures was modelled using Kamlet, Abboud and Taft (KAT) solvatochromic parameters and Hildebrand's solubility index. © 2017

Nano-structural particles of silica were synthesized from low-cost rice husk by acid leaching and further annealing at different temperatures. The surface of the nanoparticles was then functionalized using amino-silane to improve their adsorption properties. The structure of the nano-absorbent was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA). The efficiency of the formed absorbent for the adsorption of quercetin, a plant flavonoid with potent antioxidant activity, was examined in different compositions of water-ethanol mixture (0-100% by v/v). In the batch experiments, the effect of variation of initial concentration of quercetin, pH of solution, and solvent composition was explored on the adsorption behavior. The equilibrium adsorption data were better represented by the Freundlich isotherm model rather than the Langmuir model. In addition, the optimum conditions for quercetin adsorption were achieved at alkaline pH ranges. Furthermore, a significant relationship was found between the adsorption capacity and the extent of preferential solvation of quercetin by ethanol in the binary mixture. Modeling the rate of adsorption was done through different kinetic equations. The results indicated that the adsorption kinetics was well described by the pseudo-second-order model. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

The aging properties of bitumen evaluated by means of Fourier transform Infrared spectroscopy. The effect of sodium borohydride as a reducing agent on the chemical structure of bitumen in aging process was studied. The bitumen was aged by means of the rolling thin film oven test then pressure aging vessel. Reduced modified bitumen were resistant to the formation of carbonyl and sulfoxide groups nearly unchanged, indicating the improvement of aging resistance of bitumen by the reduction process. As well as physical properties tests (penetration and softening point) of bitumen showed the more resistance of reduced modified bitumen against aging. © 2015 Taylor and Francis Group, LLC.