VOLUME 37, NO2, APR-2015

Initially Approximated Quasi Equilibrium Manifold

Most commonly, kinetics model reduction techniques are based on exploiting time scale separation into fast and slow reaction processes. Then, a researcher approximates the system dynamically with dimension reduction for slow ones eliminating the fast modes. The main idea behind the construction of the lower dimension manifold is based on finding its initial approximation using Quasi Equilibrium Manifold (QEM). Here, we provide an efficient numerical method, which allow us to calculate low dimensional manifolds of chemical reaction systems. This computation technique is not restricted to our specific complex problem, but it can also be applied to other reacting flows or dynamic systems provided with the condition that a large number of extra (decaying) components can be eliminated from the system. Through computational approach, we approximate low dimensional manifold for a mechanism of six chemical species to simplify complex chemical kinetics. A reduced descriptive form of slow invariant manifold is obtained from dissipative system. This method is applicable for higher dimensions and is applied over an oxidation of CO/Pt.read more

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Muhammad Shahzad, Hina Arif, Muhammad Gulistan and Muhammad Sajid

Polymer Coated MWCNT/Terpolymer Composites: Spectral, Thermal and Electrical Properties

The terpolymer-1 was prepared from radicalic polymerization of (E)-4-[3-(benzofuran-2-yl)-3-oxoprop-1-enyl] phenyl acrylate (BPCA), 2-hydroxyethyl methacrylate (HEMA) and N-isopropylacrylamide (NIPA). The terpolymer-2 was prepared using 2-Acrylamidoglycolic acid mono hydrate (AMGA) instead of HEMA. The oxidized multi-walled carbon nanotube (MWNT-COOH) and thyonylchloride (SOCl2) was used in preparing of carbonyl chloride-functionalized carbon nanotube (MWNT-COCl). MWNT-COCl was coated separately by terpolymer-1 and terpolymer-2, heating at 120 oC for 6 h. Spectral and thermal properties, the photo-crosslinking behaviors and dielectrical and electrical properties of the terpolymers and the composites were investigated. The composite-1 exhibits a double emission wavelength at 325 nm and at 680 nm for an excitation wavelength of 530 nm. In the photo-crosslinking studies of terpolymer 1, immediately after each irradiation time intervals, the absorbance change at 345 nm was monitored. Dielectric constant is not change noticeably with temperature for nonpolar polymers whereas dielectric constant increases with temperature for strong polar polymers.read more

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Demet Coşkun, Mehmet Fatih Coşkun and Mehmet Coşkun

The Melting Behavior and Thermal Stability of Green Poly(L-lactic acid) with N, N, N, N'-Tetra(benzoyl) Ethylene Diamine Tetraacetic Acid Dihydrazide

The thermal properties of green poly(L-lactic acid) (PLLA) with N, N, N, N'-tetra(benzoyl) ethylene diamine tetraacetic acid dihydrazide (NA) at different conditions were investigated. The melting behavior of PLLA/NA sample after isothermal crystallization at 100 °C showed that the low-temperature melting peak shifted to high temperature with increasing of crystallization time. However, the high-temperature melting peak did not show any change. Meantime, the melting enthalpy of cold crystallization was higher than that of hot crystallization, and the difference between cold crystallization and hot crystallization increased from 0.31 J/g to 0.89 J/g with increasing of crystallization time. Heating or cooling rate affected the melting behavior of PLLA, the low-temperature and high-temperature melting peak shifted to low temperature with increasing of rate, and the ratio of melting peak area between low-temperature melting peak and high-temperature melting peak decreased. Thermal stability of PLLA/NA indicated that PLLA/NA only exhibited one decomposition stage as decomposition of PLLA.read more

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Yanhua Cai, Qiang Xu, Liping Ren and Lisha Zhao

Effect of Microwave Heating on the Leaching of Lateritic Nickel Ore in Perchloric Acid

In this study, the leaching conditions of Sivrihisar (Adatepe) limonite type lateritic ore in acidic medium were investigated. Leaching experiments were carried out using conventional and microwave-assisted method. The effects of stirring speed, leaching temperature, perchloric acid concentration, solid/liquid ratio and particle size on conventional leaching were determined. Microwave-assisted leaching was carried out by using the optimum results of the conventional leaching. The pre-heating process was applied on different microwave powers (0, 90, 180, 360 and 600 W) and pre-processing time (0, 1, 3, 5, 7, 10, 15 and 20 min). These experimental results demonstrated that acid leaching was a convenient method for Ni extraction from lateritic ore. The higher dissolution and the higher Ni recoveries in the microwave-assisted leaching process were obtained in less leach time.read more

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Tevfik Agacayak and Merve Koseler

Studies of Dispersed Phase Size in a Helical Tube Reactor with a Liquid-liquid Heterogeneous System

The size of the dispersed phase was a key variable of the liquid-liquid heterogeneous flow system. In this work, the Sauter mean diameter (SMD) of the dispersed phase in a novel helical tube reactor (HTR) was evaluated by using a castor oil-water system. Experimental results showed that the SMD decreased with the increased Reynolds number and volumetric flowrate ratio of water to oil. The SMD in the HTR with vertical charging was smaller ion between calculated and experimental data was within ±20% than that with parallel charging. A dimensionless correlation of SMD in the HTR was proposed and the deviation between calculated and experimental data was within ±20%.read more

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Guang-Wen Chu, Hai-Kui Zou, Xiao Yu, Yong Luo, Jing Zhou, Moses Arowo and Jian-Feng Chen

Synthesis, Physico-Chemical Characterization, Antibacterial and Antifungal Activities Studies of a New Schiff Base Ligand and its Transition Metal Complexes

The complexes of Co(II), Cu(II) and Zn(II) with the Schiff base 2-[(E)-{[4-(4-aminophenoxy)phenyl]imino}methyl]-6-ethoxyphenol (LH) have been synthesized and their structure have been elucidated on the basis of elemental analyses, IR, 1H- and 13C-NMR spectra, electronic spectra, magnetic susceptibility measurements and thermogravimetric analyses (TGA). Mononuclear complexes with a metal:ligand ratio of 1:1 have been prepared with Co+2 and Zn+2 salts, whereas the copper(II) complex is dinuclear which have a metal:ligand ratio of 2:1. According to the results, it is suggested that the ligand is coordinated to each metal atom by the phenolic oxygen and the azomethine nitrogen atoms. The synthesized compounds were tested for antimicrobial activity against in vitro antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium) and antifungal activities (Candida globrata and Candida tropicalis) by the minimum inhibitory concentration (MIC) method. All of the selected compounds showed weak antimicrobial activity against test microorganisms (256-1024 μg/mL).read more

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Hakan Şahal, Erdal Canpolat, Mehmet Kaya and Nazan Kara

Application of Graphene as a Sorbent for the Preconcentration and Determination of Trace Amounts of Mercury in Water Samples by Hydride Generation Atomic Fluorescence Spectrometry

The potential of graphene as a solid-phase extraction adsorbent for the separation and preconcentration of mercury (Hg) was investigated. Hg2+ was found to be quantitatively adsorbed onto graphene within pH 6.0-8.0, and then completely eluted with 4.0 mL of nitric acid/methanol (1:1, v/v) solution at a flow rate of 2.0 mL min−1. A new method using a microcolumn packed with graphene as a sorbent was developed for the preconcentration of trace amount of Hg2+ prior to its determination by hydride generation atomic fluorescence spectrometry. Under the optimum experimental conditions, the detection limit of this method for Hg2+ was 5.0 ng L−1, with an enrichment factor of 15.0, and the relative standard deviation was 3.5% at the 1.0 μg L−1 Hg2+ level. The method was then applied for the determination of trace amount of Hg2+ in water samples with satisfactory results.read more

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Hai Yan Liu, Xu Feng Meng, Chao Li, An Qiang Jia, Jing Ci Li and Jing Jun Ma

Optimization and Modeling of Process Variables of Biodiesel Production from Marula Oil using Response Surface Methodology

This paper presents an optimization study in the production of biodiesel production from Marula oil. The study was carried out using a central composite design of experiments under response surface methodology. A mathematical model was developed to correlate the transesterification process variables to biodiesel yield. The transesterification reaction variables were methanol to oil ratio, x1 (10-50 wt %), reaction time, x2 (30-90 min), reaction temperature, x3 (30-90 °C) stirring speed, x4 (100-400 rpm) and amount of catalyst, x5 (0.5-1.5 g). The optimum conditions for the production of the biodiesel were found to be: methanol to oil ratio (29.43 wt %), reaction time (59.17 minutes), reaction temperature (58.80°C), stirring speed (325 rpm) and amount of catalyst (1.02 g). The optimum yield of biodiesel that can be produced was 95 %. The results revealed that the crucial fuel properties of the biodiesel produced at the optimum conditions met the ASTM biodiesel specifications.read more

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Christopher C Enweremadu and Hilary L Rutto

Evaluation of Efficacy of Advanced Oxidation Processes Fenton, Fenton-like and Photo-Fenton for Removal of Phenol from Aqueous Solutions

Contamination of water, soil and groundwater caused by aromatic compounds induces great concern in most world areas .Among organic pollutants, phenol is mostly considered dangerous due to its high toxicity for human and animal. Advanced oxidation processes (AOPs) is considered as a most efficient method also the best one for purifying organic compounds which are resistant to conventional physical and chemical processes. This experimental study was carried out in laboratory scale. First, a synthetic solution was made of phenol. Then, Fenton, Fenton-like and photo-Fenton processes were applied removing phenol from aquatic solution. The effects of Hydrogen Peroxide concentration, catalyst, pH and time were studied to phenol removal efficiency. Results showed that Photo-Fenton process with removal efficiency (97.5%) is more efficient than Fenton and Fenton-like processes with removal efficiency (78.7% and 82.5% respectively), in pH=3, [H2O2 ]= 3mM, [Fe2+]= 0.1 mM, phenol concentration 100 mg L-1 and time reaction 60 min, the phenol removal was 97.5%.read more

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Mohamadreza Rezaee Mofrad, Maryam Emamgholi Nezhad, Hossein Akbari, Mahmood Atharizade and Mohammad Bagher Miranzadeh

Solid-phase Extraction on Magnetic Multi-walled Carbon Nanotubes Coupled with Flame Atomic Absorption Spectrometry for Determining Lead and Cadmium in Traditional Chinese Medicine

In this study, magnetic carbon nanotubes (MCNTs) were prepared by mixing the magnetic particles and multi-walled carbon nanotubes in dispersed solutions. These MCNTs were used as adsorbents of magnetic solid-phase extraction (MSPE). By coupling MSPE with flame atomic absorption spectrometry, a rapid and sensitive method for analyzing lead and cadmium using ammonium pyrrolidine dithiocarbamate as chelating reagent was established. Under optimal conditions, calibration graphs were linear in the range of 10.0–400.0 μg L-1 and 10.0–300.0 μg L-1 with detection limit of 0.6 μg L-1 and 0.5 μg L-1 for Pb and Cd, respectively. A good relative standard deviation for determining 300.0 μg L-1 of Pb and Cd were 3.8 and 3.4%, respectively. The proposed method was applied to analyze several traditional Chinese medicine samples with satisfactory results.read more

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Gui Fang Qin, Meng Yi Jiang, Hou Shu Mei, Yao Ke Rong and Jing Jun Ma