Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin-Raduskevich (D-R) isotherms. The mean sorption energy (E) of copper sorption onto silica gel was calculated from D-R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.     

Toward the understanding of the metabolism of levodopa I. DFT investigation of the equilibrium geometries, Acid-base properties and levodopa-water complexes

Levodopa (LD) is used to increase dopamine level for treating Parkinson's disease. The major metabolism of LD to produce dopamine is decarboxylation. In order to understand the metabolism of LD; the electronic structure of levodopa was investigated at the Density Functional DFT/B3LYP level of theory using the 6-311+G** basis set, in the gas phase and in solution. LD is not planar, with the amino acid side chain acting as a free rotator around several single bonds. The potential energy surface is broad and flat. Full geometry optimization enabled locating and identifying the global minimum on this Potential energy surface (PES). All possible protonation/deprotonation forms of LD were examined and analyzed. Protonation/deprotonation is local in nature, i.e., is not transmitted through the molecular framework. The isogyric protonation/deprotonation reactions seem to involve two subsequent steps: First, deprotonation, then rearrangement to form H-bonded structures, which is the origin of the extra stability of the deprotonated forms. Natural bond orbital (NBO) analysis of LD and its deprotonated forms reveals detailed information of bonding characteristics and interactions across the molecular framework. The effect of deprotonation on the donor-acceptor interaction across the molecular framework and within the two subsystems has also been examined. Attempts to mimic the complex formation of LD with water have been performed.     

Effect of Steam Baking on Acrylamide Formation and Browning Kinetics of Cookies

Abstract: Effects of baking method and temperature on surface browning and acrylamide concentration of cookies were investigated. Cookies were baked in natural and forced convection and steam‐assisted hybrid ovens at 165, 180, and 195 °C and at different times. For all oven types, the acrlyamide concentration and surface color of cookies increased with increasing baking temperature. Significant correlation was observed between acrylamide formation and browning index, BI, which was calculated from Hunter L, a, and b color values, and it showed that the BI may be considered as a reliable indicator of acrylamide concentration in cookies. Acrylamide formation and browning index in cookies were considered as the first‐order reaction kinetics and the reaction rate constants, k, were in the range of 0.023 to 0.077 (min^?1) and 0.019 to 0.063 (min^?1), respectively. The effect of baking temperature on surface color and acrylamide concentration followed the Arrhenius type of equation, with activation energies for acrylamide concentration as 6.87 to 27.84 kJ/mol; for BI value as 19.54 to 35.36 kJ/mol, for all oven types. Steam‐assisted baking resulted in lower acrylamide concentration at 165 °C baking temperature and lower surface color for all temperatures. Steam‐assisted baking is recommended as a healthy way of cooking providing the reduction of harmful compounds such as acrylamide for bakery goods, at a minimal level, while keeping the physical quality. Practical Application: The kinetics of acrylamide formation and browning of cookies will possibly allow definition of optimum baking temperatures and times at convectional and steam‐assisted baking ovens. The kinetic model can be used by developing baking programs that can automatically control especially a new home‐scale steam‐assisted hybrid oven producing healthy products, for the use of domestic consumers.     

Mathematical Modeling of Particle Segregation During Centrifugal Casting of Metal Matrix Composites

When a metal matrix composite undergoes centrifugal casting, the velocity, deceleration, displacement, and segregation of its particles are modeled according to changes in the centrifugal radius, as well as by variations in the molten metal viscosity as the temperature decreases during the cooling process. A cast aluminum alloy A356 reinforced by 10 V% of silicon carbide particles (SiC), with a median diameter of 12 μm, was used to conduct the experiments, and a mathematical modeling showed that the particles’ volume fraction on the outer casting face varied according to whether the viscosity of the liquid metal used was constant or variable. If variations in viscosity during the cooling process are taken into account, then the volume fraction of the particles for a given time of centrifugation changes on the outer casting face, while it increases if the viscosity was constant. Modeling the particle segregation with variable viscosity produces results that are closer to those obtained with experiments than is the case when a constant viscosity is used. In fact, the higher the initial pouring and mold temperatures, the higher the effect of the viscosity variation on particle segregation.     

The underpotential deposition of Bi2Te3−ySey thin films by an electrochemical co-deposition method

Bi₂Te_3−ySe_y thin films were grown on Au(1 1 1) substrates using an electrochemical co-deposition method at 25 °C. The appropriate co-deposition potentials based on the underpotential deposition (upd) potentials of Bi, Te and Se have been determined by the cyclic voltammetric studies. The films were grown from an electrolyte of 2.5 mM Bi(NO₃)₃, 2 mM TeO₂, and 0.3 mM SeO₂ in 0.1 M HNO₃ at a potential of −0.02 V vs. Ag|AgCl (3 M NaCl). X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were employed to characterize the thin films. XRD and EDS results revealed that the films are single phase with approximate composition of Bi₂Te_2.7Se_0.3. SEM studies showed that the films are homogeneous and have micronsized granular crystallites.     

Degradation of thermomechanical performance and lifetime estimation of multilayer greenhouse polyethylene films under simulated climatic conditions

The main objective of this work is to investigate the impact of degradation of low‐density polyethylene multilayer films, used as greenhouses covers, under some desert simulated climatic conditions on their mechanical behavior, thermal stability and lifetime. The climatic conditions considered are temperature, ultraviolet (UV) radiation, and humidity which are the most detrimental factors in the ageing of the polymeric greenhouses covers. At the molecular level, the combined effects of these environmental conditions cause oxidation and severe structural modifications of the polymer which are the main mechanism of degradation. In this work, multilayer polyethylene films with 180 μm overall thickness are artificially aged at different twelve combined climatic conditions of temperature, UV radiation and humidity. Deferential scanning calorimetry (DSC) analyses and mechanical tests were carried out to characterize the material and evaluate the degradation level of the thermal, physicochemical, and mechanical properties of the films. The results revealed that, the investigated broad range of climatic conditions have remarkable deteriorative impact on the performance of the film and its functionality; the highest degradation rate was under the combined effect of UV radiation and temperature ageing condition. The correlation between the created modifications in the material structure and the degradation level of cover properties and its lifetime is discussed. POLYM. ENG. SCI., 55:287–298, 2015. © 2014 Society of Plastics Engineers     

Innovative Carbon Dioxide‐Capturing Organic Solvent: Reaction Mechanism and Kinetics

The reaction rates of CO₂ with an innovative CO₂‐capturing organic solvent (CO₂COS), consisting of blends of 2‐tert‐butyl‐1,1,3,3‐tetramethylguanidine (BTMG) and 1‐propanol, were obtained as function of BTMG concentration and temperature. A stopped‐flow apparatus with conductivity detection was used. The reaction was modeled by means of a modified termolecular reaction mechanism which resulted in a second‐order rate constant, and activation energies were calculated for a defined temperature range. Quantum chemical calculations at the B3LYP/6‐31G(d) level also produced the activation energy of this reaction system which strongly supports the experimental findings.     

Physicochemical and Radiation Hazardous Properties of Scale TENORM Waste: Evaluation by Different Analytical Techniques

The scale material in TENORM waste from petroleum industry was characterized using nuclear and non-nuclear techniques. The scale TENORM samples were collected from the Ras Shukeir area on the west bank of the Suez Gulf in Egypt during gas and oil production. These scales represent the TENORM deposits formed in the pipelines and removed during the periodical maintenance. X-ray fluorescence analysis showed that the main elements in all investigated fractions were Si, Fe, Mg, Ca, Sr, and Ba in addition to traces of some heavy elements, e.g. Pb, Cr, and Zn. The radioactivity concentrations of natural radionuclides ²²⁶Ra, ²³²Th, and ⁴⁰K in seven particle size fractions were found to be in the range from 14.1 ± 0.4 to 28.9 ± 0.9, from 5.0 ± 0.2 to 9.5 ± 0.4, and from 0.25 ± 0.02 to 0.43 ± 0.02 kBq kg^–1, respectively. The radiation hazard parameters were calculated. The values obtained are much greater than the accepted values. The results were compared to the values reported for other countries.     

Atmospheric dispersion modeling of CO<Subscript>2</Subscript> emissions from a cement plant’s sources

The study aims to estimate a cement plant’s carbon dioxide (CO₂) concentrations from individual sources as well as combined emissions from all the sources. Four main CO₂ emission sources were considered: process from the calcination of limestone, the combustion of fossil fuel in the kilns, the power plant, and the dump trucks used for raw material transportation. An integrated modeling system comprised of the California PUFF and Weather Research and Forecasting was applied. The power plant and the stacks of three kilns were modeled as point sources, whereas the vehicular emissions were treated as a line source. In the first part of the study, modeling of the cement plant’s individual sources was carried out to predict CO₂ at each receptor of the domain. In the second part, the CO₂ concentrations of combined emissions from all of the plant’s sources were predicted. Individual modeling of each of the plant’s CO₂ emission sources showed that the highest CO₂ at each receptor of the domain resulted from the calcination process. In the case of combined modeling of all the cement plant’s sources, the predicted peak concentrations of CO₂ were 357.19 and 36.11 mg/m³ for one-hour and 24-hour averaging periods, respectively.