VOLUME 41, NO2, APR-2019

Thermal Properties of Acylated Low Molecular Weight Chitosans

Acylated low molecular weight chitosans (LChA) were prepared from nucleophilic acylation of chitosan using acid anhydrides of short and medium chain length (4 - 10) to study the response of applied heat as a function of acyl chain length. Thermogravimetric analysis (TGA) revealed the decomposition of LChA consisted of glucosamine and acyl-glucosamine units around 141 - 151°C to 400 - 410°C. Both TGA and differential scanning calorimetry (DSC) analyses indicated that the introduction of acyl groups disrupted the hydrogen bonding of chitosan, the effect was more prominent as the degree of substitution and chain length of LChA increased. Grafting of acyl chains lowered the kinematic viscosity of LChA as the disruption of hydrogen bonding led to decreased hydrodynamic volume. Field emission scanning electron micrographs showed that LChA with longer chains having larger particle size due to bigger occupancy volume of acyl chains during spray drying.read more

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Shu Xian Tiew and Misni Misran

Modeling of a Nickel-based Fluidized Bed Membrane Reactor for Steam Methane Reforming Process

Hydrogen being a green fuel is rapidly gaining importance in the energy sector. Steam methane reforming is one of the most industrially important chemical reaction and a key step in the production of high purity hydrogen. Due to inherent deficiencies of conventional reforming reactors, a new concept based on fluidized bed membrane reactor is getting the focus of researchers. In this work, a nickel-based fluidized bed membrane reactor model is developed in the Aspen PLUS® process simulator. A user-defined membrane module is embedded in the Aspen PLUS® through its interface with Microsoft® Excel. Then, a series combination of Gibbs reactors and membrane modules are used to develop a nickel-based fluidized bed membrane reactor. The model developed for nickel-based fluidized bed membrane reactor is compared with palladium-based membrane reactor in terms of methane conversion and hydrogen yield for a given panel of major operating parameters. The simulation results indicated that the model can accurately predict the behavior of a membrane reactor under different operating conditions. In addition, the model can be used to estimate the effective membrane area required for a given rate of hydrogen production.read more

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Mustafa Kamal Pasha, Iftikhar Ahmad, Jawad Mustafa, Manabu Kano

Properties and Characteristic of Amine-Polymer Blend Membrane

Polymer blend technology has earned a significant position in the field of polymer science. Current membrane technology can easily and simply remove and separates carbon dioxide as pressure, temperature, costs, and energy requirements are low. There is also no corrosion problem from the straightforward process of removing CO2 from natural gas, especially in remote or offshore locations that are easily scaled up. However, glassy polymeric membranes suffer from a lack of permeability causing performance degradation and higher selectivity. Nevertheless, amine solutions are capable of purifying naturally acidic gas. Within this framework, the blending of the polysulfone (PSU) glassy polymer with amines such as diethanolamine (DEA), methyl diethanolamine (MDEA), and monoethanolamine (MEA) in a dimethylacetamide solvent, resulted in the development of flat sheet membranes with the desired properties. The findings showed good miscibility between PSU and amines blends, all the original functional groups were shown by FTIR. The synthesized amine polymer blend membrane were found to have homogenous surfaces and a packed bed sphere structure (PBSS) as shown by FESEM images. Furthermore the addition of different amine solution, have increased the size of PBSS due to incorporation of amine molecule into the sphere.read more

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Asim Mushtaq, Hilmi Mukhtar and Azmi Mohd Shariff

Grafting of Chitosan: Structural, Thermal and Antimicrobial Properties

In this study, some new chitosan materials were synthesized by the grafting of chitosan with the monomers such as 1-vinylimidazole (VIM), methacrylamide (MAm) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). First of all, chitosan methacrylate was prepared by esterification of primary -OH group with methacryloyl chloride a 25.13% yield by mole. The monomers were grafted into chitosan methacrylate via free radical polymerization using 2,2'-Azobisisobutyronitrile as an initiator in N,N-dimethylformamide. The graft copolymers were characterized by FT-IR spectra and elemental analysis. Thermal stabilities of the graft copolymers were determined by TGA (thermo gravimetric analysis) method. The synthesized chitosan methacrylate and its graft copolymers were tested for their antimicrobial activity against bacteria and yeast.read more

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Nevin Cankaya

Microwave Absorbing Properties of Polyaniline-NiFe2O4: V composites

In this study, vanadium doped NiFe2O4 was produced by using mixed oxide technique. The NiFe2-xVxO4 composition was synthesized and x was selected as 0.1, 0.2 and 0.3, respectively. The single-phase Ni ferrite was produced after sintering at 1100°C for 4h. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were performed for structural analysis. The results of the structural analysis indicated that the second phase did not form in NiFe2-xVxO4. Additionally, the polyaniline-vanadium doped NiFe2O4 composites were produced by hot pressing using the compositions of NiFe1.9V0.1O4.1, NiFe1.8V0.2O4.2, NiFe1.7V0.3O4.3, and aniline. The weight ratios of vanadium-doped nickel ferrite and aniline were 1:1 and 1:3, respectively. Epoxy resin was used to produce microwave-absorbing composites. The fabricated composites were characterized by using Fourier transform infrared spectroscopy (FTIR). Furthermore, the magnetic properties of the fabricated composites were investigated by using a vibrating sample magnetometer (VSM). The microwave absorbing performances of the polyaniline-NiFe2O4: V composites were investigated by reflectivity in 0–8 GHz, using a two–port vector network analyzer. A minimum of -42.17 dB reflection performance was obtained in 7.02 GHz at the thickness of 2.0 mm. This reflection performance can be modulated simply by controlling the content of polyaniline in the samples for the required frequency bands.read more

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Ethem Ilhan SAHIN and Selcuk PAKER Mesut KARTAL

Study the Effect of Magnetized Water on Some of the Chemical Parameters for EBT Complexes with Some of M2+ Ions

In this paper, the effect of magnetized water on the stability constant Kst, oscillation strength f, molar extinction coefficient εmax and Gibbs free energy ΔG for complexes was investigated. Complexes of Eriochrome black T (EBT) as a ligand with Ca2+, Mn2+, and Zn2+ ions were prepared for this purpos. The stability constant values of the complexes found to be decreased by using magnetic water in their preparation except for EBT-Ca complex. Both Ca2+ and Mn2+ ions showed deviation from Irving-Williams order. The oscillation strength shows the type of spectrum is absorption spectrum for all complexes and in both in magnetized and non-magnetized water. εmax found to be increased by using magnetized water over than non-magnetized water. The stability constants for the complexes calculate analytically by applying jobs method and Yoe and Jones method.read more

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Rawa'a Abass Majeed, Wissam Sallal Ulaiwi, and Mohammed Faiad Naief

Recent Progress in the Application of Ionic Liquids in Electrochemical Oxidation and Reduction

Electrochemical oxidation and reduction, with clean power, are key to energy conversion and storage. For example, electrochemical oxidation is a determining step for fuel cells, combination of electrochemical oxidation and reduction can form a metal-air battery. Electrochemical oxidation and reduction make significant contributions to prepare valuable chemicals directly and improve yield efficiency and reduce the three wastes, which have become one of the green methodologies. Ionic liquids have attracted increasing attentions in the area of electrochemistry due to their significant properties including good chemical and thermal stability, wide liquid temperature range, considerable ionic conductivity, nonflammability, broad electrochemical potential window and tunable solvent properties. Up to now, abundant studies of ionic liquids have reported for their practical applications for electrochemical reactions. This review covers recent studies on the applications of ILs as green and universal replacements for the traditional reagents in electrochemical oxidation and reduction. The adaptabilities of ILs in these reactions are predicted as a solution to the problems of conventional electrochemical processes and to become a powerful method in electrochemical oxidation and reduction.read more

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Nan Yao and Yu Lin Hu

Photometric Study of Oxidation of Ascorbic Acid by Methylene Green in Aqueous Alcoholic System

The photochemical study for oxidation of ascorbic acid with methylene green was studied in aqueous and aqueous methanol, ethanol, and isopropanol at temperature ranges from 303-318 K in acidic medium. The quantum yield of the photochemical oxidation of ascorbic acid with methylene green was determined by irradiation of reaction mixture by monochromatic light of 657 nm and transmitted light was recorded by photocell response as electrical signals on galvanometer. The rate of reaction mixture in terms of quantum yield was determined and found independent of variation in methylene green concentration and had increased with the concentration of ascorbic acid. The effect of dielectric constant was studied by varying the compositions of alcohol and the results obtained revealed that the quantum yield decreased with the decrease of the polarity of system in acidic medium. On the basis of kinetics the reaction follow pseudo first order and mechanism has been proposed. Thermodynamic parameter such as energy of activation (Ea*), change in enthalpy of activation (ΔH*), change in free energy of activation (ΔG*), and change in entropy of activation (ΔS*) were also calculated.read more

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Sameera Razi Khan, Rehana Saeed, Maria Ashfaq, Summyia Masood

Using Heterocycle to Improve the Selectivity of Rhodamine-6G Dye: Synthesis of Pyrrole-Modified Rhodamine-6G and its Recognition to Zn2+

The fluorescent sensor XQN for Zn2+ based on rhodamine-6G have been designed and synthesized. XQN showed fluorescent specific selectivity and high sensitivity for Zn2+ against other metal ions such as Fe3+, Cr3+, Hg2+, Ag+, Ca2+, Cu2+, Pb2+, Cd2+, Ni2+, Co2+ and Mg2+ in CH3CN-PBS(phosphate buffer saline) (10 mM, v/v=7:3, pH = 7.4) solution. The distinct color change and the rapid emergence of fluorescence emission provided naked-eyes detection for Zn2+. The test strip results showed that these sensors could act as a convenient and efficient Zn2+ test kit. The recognition mechanism of the sensor toward Zn2+ was evaluated by IR and the Job’s plots. The detection limits of XQN towards Zn2+ was calculated as 2.39 µM. In addition, XQN-Zn2+ fluorescence lifetime and fluorescence quantum yield were also measured.read more

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Rui Qiao, Hai-Yun Fan, Cui-Bing Bai, Ling Dai, Lin Zhang, Jie Zhang, Shui-Sheng Chen and Hui Miao

Inorganic-Framework Molecularly Imprinted CdS/TiO2 for Selectively Photocatalytic Degradation of Di (2-ethylhexyl) phthalate

In order to improve the photocatalytic efficiency and selectivity of di (2-ethylhexyl) phthalate (DEHP) under solar-driven, the inorganic-framework molecularly imprinted CdS/TiO2, named as MIP-CdS/TiO2, was prepared by using DEHP as template molecule and tetrabutyl titanate as titanium source and functional monomer. The as-prepared MIP-CdS/TiO2 was characterized by scanning electron microscopy (SEM), X-ray energy spectrum (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis Spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectrum (PL). And the specific recognition and photocatalytic selectivity of MIP-CdS/TiO2 to DEHP were investigated. The results show that inorganic-framework molecular imprinting on the surface of CdS/TiO2 can result in existence of specific recognition sites of DEHP, extend and intensify the absorption visible light of CdS/TiO2, inhibit the recombination of the photo-induced electron-holes pairs. MIP-CdS/TiO2 has a specific recognition to DEHP. The binding selectivity coefficients of DEHP relative to its analogues DBP and DMP are 2.78 and 2.60, respectively. Compared with CdS/TiO2, MIP-CdS/TiO2 exhibits higher photocatalytic activity and selectivity for DEHP. Under simulated solar light irradiation, the degradation efficiency of DEHP photocatalyzed by MIP-CdS/TiO2 is 75.5%, which is 1.63 times as high as that of DEHP photocatalyzed by CdS/TiO2.read more

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Fangyan Chen, Yiming Liu, Xi Zhang, Lina He and Yubin Tang