VOLUME 34, NO4, AUG 2012

Characterization of Single and Pairwise No2 Adsorption on the (Mgo)9 and (Cao)9 Clusters

Vibrational spectra have been computed by means of the B3LYP hybrid density functional in order to interpret the experiments [J. Phys. Chem. B 2002, 106, 6358], particularly regarding a transient 1225 cm−1 absorption during accumulation of NO2 in MgO supported BaO. The degree of generality of results is tested by comparing (NO2)x(MO)9 for x=1, 2 and M=Mg, Ca. Finger prints are produced for the single bidentate M2+−[ONO]−−M2+ surface nitrite ion, a novel single monodentate [Oclus−NO2]2− ion, and the chemisorbed nitrite/nitrate ion pair, i.e., M2+ − [ONO]−−M2++ [Oclus−NO2]−. The results suggest the novel monodentate [Oclus− NO2]2− to be responsible for the experimentally observed 1225 cm-1 absorption, being a transient towards surface nitrate rather than nitrite formation. This result is consistent with a mechanistic periodic DFT study concerning the initial loading of NO2 in BaO.read more

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ALI HASSAN BAWA ,FATHI HASSAN BAWA ,

An Alternative Approach to the Heterogeneous Electron Transfer Rate Constant Expression

In the theoretical treatment of heterogeneous electron transfer rate constant, ko, the expression for the rate constant is considered as a composite of two parts: a dynamical pre-exponential one, the other the activation barrier (exponential) part. The pre-exponential part has been treated through several models: the collision frequency, the precursor- equilibrium and the Khan models. In this work, a simple alternative approach based on random walk model is proposed. The advantage of this random walk model is that all the parameters in it are either experimentally measurable or can be easily calculated. The result of calculation shows it to be far superior to collision frequency model, even better than precursor-equilibrium model and comparable to Khan model.read more

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MUHAMMAD ASLAM ,MUHAMMAD. SAMIUDDIN QADRI ,IFTIKHAR AHMAD TAHIRI ,MAHBOOB MOHAMMAD ,

Degradation Study of Reactive Violet 1 by Gamma Radiation

The radiolytic degradation of reactive violet 1 dye in aqueous media as a model system was carried out. The dye solutions (10 to 50 mg/L) were irradiated to the absorbed doses of 2, 5, 10 and 15 kGy using Co-60 gamma radiation source. The change in absorbance, decrease in chemical oxygen demand (COD) and degree of decolouration were investigated in presence of oxygen and hydrogen peroxide. The degraded end products in treated samples were identified using Fourier transform infrared (FTIR) and Gas chromatography- mass spectrometry (GC-MS). Complete decolouration and 80 % COD reduction achieved when dye solutions were exposed to the radiation absorbed dose of 15 kGy. Evaluation of radiolytic end products revealed that dye molecules were completely breakdown into fragments of lower molecular masses.read more

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MAKSHOOF ATHER ,MUNAWAR IQBAL ,MAJID MUNEER ,IJAZ AHMAD BHATTI ,

Effect of Cross Linker Concentration on Swelling Kinetics of a Synthesized Ternary Co-Polymer System

Using equal volumes of three monomers (acrylic acid, vinyl acetate and methyl acrylate), ternary co-polymers were synthesized with different concentrations of cross linker, ethylene glycol dimethacrylate (EGDMA). Benzoylperoxide was used as an initiator (concentration of 1% w/v) for the synthesis of hydrogel systems. A number of experiments were carried out to illustrate the swelling behavior of the gel with different concentrations of cross linker. The analysis of swelling data shows that the swelling phenomena is function of concentration of the cross linker used. Graphical and statistical analysis of diffusion exponents shows that the diffusion mechanism for water penetration into the synthesized gel system is controlled by concentration of the cross linker, i.e. n=noCC, where n is diffusion exponent, no(=0.6548) is pre-exponential factor, CL(= -0.0345) is  cross linker concentration sensitivity coefficient of the gel.read more

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MUHAMMAD ASLAM MALANA ,ZAFAR IQBAL ZAFAR ,RUBAB ZUHRA ,

Bone Mineral Density and the Relationship between Lipid Profile and Bone Mineral Density in the Rats Administered Juniperus Communis Linn.

The aim of the study is to investigate the relationship of Juniperus Communis Lynn. with the bone mineral density in the rats fed with a high cholesterol (1%) diet. Thirty five Wistar albino rats weighed approximately 250-300 were used in this study. The rats are divided in five groups of seven each. Groups I and II were administered 0.5 ml of 0.5% Sodium Carboxy Methyl Cellulose (SCMC), while Groups II, IV and V administered 0.5 ml of juniperus communis linn dissolved in  25, 50, 100 mg/kg. Group I and Group II were fed with normal pellets while the other four groups were fed with pellets containing 1% cholesterol. Levels of lipid profile and High Density Lipoprotein Cholesterol (HDL-C) were defined in all the groups. Furthermore, bone mineral density (B M D) of the animals were obtained with DEXA scanner. BMD values of the rats did not show a different among the groups. Significant negative correlations were determined between BMD measurements and LDL-C levels in all groups connected with dose of Juniperus Communis oil. However, this relationship was not linear.read more

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MEHMET AKDOGAN ,ERSIN USKUN ,MUSTAFA YILDIZ ,YONCA SONMEZ ,

Effect of Support on Hydrogenolysis of Glycerol over Cu Catalysts

Hydrogenolysis of biomass-derived glycerol is an alternative route to produce 1, 2-propanediol. Supported Cu catalysts were prepared by the wetness impregnation method and characterized by N2 adsorption–desorption, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR), temperature programmed desorption of NH3 (NH3-TPD) and temperature programmed reduction (TPR) techniques, and then tested for glycerol hydrogenolysis. It was found that the nature of support significantly affected the performance of the catalysts, revealing a correlation between catalytic activity and total acidity. Compared with ZrO2, SiO2 and HZSM-5, γ-Al2O3 showed superior performance due to its surface properties, and with 20wt% Cu loaded, glycerol conversion and 1, 2-propanediol selectivity reached 85.05% and 85.71% at 513 K and 6 MPa H2, respectively.read more

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JIE ZHOU ,NING ZHAO ,YUHAN SUN ,SHUNLI HAO ,WEI WEI ,FUKUI XIAO ,

Conformation and the Unique H-Bond of 2-(N,N-dimethylamino) Benzoic Acid in Gas Phase

Only a few examples on strong neutral hydrogen bonds are known in the chemical literature. This computational organic chemistry study illustrates that the most stable conformer of the title amino acid in gas phase is (I). The conformational analysis of (I) around the O1-C1 bond leads to destabilizing the structure due to breaking the N H1-O1 hydrogen bond. However, this could not be used to estimate the hydrogen bond strength due to an unexpected interfering destabilizing factor that could not be quantified. Therefore, the hydrogen bond strength was estimated using a simulation model and the second order perturbation analysis. The B3LYP and the MP2 calculations predict the hydrogen bond in the gas phase to be stronger than 10 kcal/mol, which allows classifying it as a strong neutral hydrogen bond. To the best of our knowledge, this is the strongest neutral H-bond encountered that it is not a resonance assisted H-bond (RAHB). From a fundamental point of view, this example is a new addition to the hydrogen bond theory.read more

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IBRAHIM ABDELKARIM MOUSA SARAIREH ,OLUSEUN AKINTOLA ,TAREQ IRSHAIDAT ,

Perchlorate Adsorption by Granular Activated Carbon Modified with Cetyltrimethyl Ammonium Chloride

To improve the adsorption of perchlorate (ClO4-) in contaminated water, granular activated carbon (GAC) was modified with cetyltrimethyl ammonium chloride (CTAC). To investigate the adsorption mechanism of perchlorate the structure of GAC-CTAC was characterized by scanning electron microscopy (SEM) and FTIR spectroscopy. Then the GAC-CTAC was used for the adsorption of perchlorate in water. The effects of the adsorption time, pH, initial ClO4- concentration, and co-existed anions on perchlorate adsorbed by GAC-CTAC were studied. The results show that the GAC-CTAC could absorb perchlorate better in water. The adsorption capacity of perchlorate on GAC-CTAC decreases in the alkaline solution, and increases with increasing the initial concentration. The competitive adsorption exists between co-existed anions and ClO4- on GAC-CTAC. In addition, adsorption of ClO4- on GAC-CTAC fits the Langmuir, Freundlich and Tempkin isothermal models in the range of the experimental concentration. The adsorption process follows pseudo-second order kinetics.read more

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WU CHUN-DU ,ZHENG LU ,ZHOU YANG ,ZHU MING-LONG ,PENG YIN-XIAN ,CAI CUI-YUN ,

Selection of Lixiviant System for the Alkaline in-Situ Leaching of Uranium from an Arkosic Type of Sandstone and Measuring the Dissolution Behaviour of some Metals and Non-Metals

A laboratory simulation study was carried out to check the possibility of alkaline in-situ leaching of uranium from an arkosic type of sandstone recovered from a specific location at a depth of 300-500 m. The ore body was overlaying impervious clay shale below the water table. Different CO3-2 containing soluble salts were tested as complexing agent of the UO+2 ions along with H2O2 as oxidizing agent. The lixiviant system, comprising NH4HCO3 as complexing agent along with H2O2 as oxidizing agent in concentrations of 5 g/L and 0.5 g/L respectively, was found to be the most efficient for the leaching of uranium among the 25 different compositions employed. Along with uranium, the dissolution behaviour of 15 other metals, non-metals and radicals, including eight transition metals, was also observed in the lixiviant employed. These were Na, K, Ca, Mg, Cl, SO4-2, CO3-2, Ti, V, Cr, Mn, Fe, Cu, Zn and Mo.  It was found that the leaching of uranium compared to non-transition metals/radicals followed the trend Cl- > SO4-2 > U > Na+ > K+ > Mg+2 > Ca+2 > CO3-2. The comparison of uranium leaching to the transition metals was in the order U > Cr > Mo > V > Ti > Cu > Zn > Mn > Fe. Physical parameters like pH, oxidation reduction potential (ORP) and conductivity were also measured for the fresh and pregnant lixiviants. It was found that the leaching of uranium is directly related to the concentration of native soluble hexavalent uranium, contact time of the lixiviant and ore and to some extent with the total concentration of uranium as well as the porosity and permeability of the ore.read more

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SYED SAKHAWAT SHAH ,YAHYA KHAN ,MUHAMMAD SIDDIQ ,

Adsorption Kinetics and Isotherms for the Removal of Zinc Ions from Aqueous Solutions by an Ion-Exchange Resin

The capacity of ion exchange resins, Dowex HCR-S, for removal of Zinc from aqueous solution was investigated under different conditions such as initial solution pHs, stirring speeds, temperatures, initial concentrations and resin dosages. Adsorption equilibrium isotherms were analyzed by Langmuir, Freundlich, Temkin, Elovich, Khan, Sips, Toth, Radke-Praunstrzki, Koble-Corrigan, models. Khan model was found to show the best fit for experimental data. The experimental kinetic data were analyzed using the first-order, second-order, Elovich and intra-particle kinetic models and the second-order kinetic model described the ion exchange kinetics accurately for Zn (II) ions. Thermodynamic activation parameters such as ΔG*, ΔS* and ΔH* were also calculated.read more

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SERKAN BAYAR ,BAYBARS ALI FİL ,RECEP BONCUKCUOGLU ,ALPER ERDEM YILMAZ ,