Advances in Physical Chemistry The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Remediation of Rhodamine B Dye from Aqueous Solution Using Casuarina equisetifolia Cone Powder as a Low-Cost Adsorbent Mon, 17 Oct 2016 13:14:45 +0000 The removal of toxic dye rhodamine B (RB) from aqueous solution was achieved by using Casuarina equisetifolia cone (CEC) as an adsorbent. Batch experiment method was used in order to investigate the effects of contact time, pH, temperature, ionic strength, and dye concentration on the adsorption process. Kinetics and isotherm theoretical models were applied on the experimental data and it was found that the pseudo-2nd-order kinetics and the Langmuir isotherm model best fitted into the data. The Langmuir maximum adsorption capacity for CEC was determined as 49.5 mg g−1. The adsorption of RB onto CEC is thermodynamically favourable, feasible, and endothermic in nature. Muhammad Khairud Dahri, Muhammad Raziq Rahimi Kooh, and Linda B. L. Lim Copyright © 2016 Muhammad Khairud Dahri et al. All rights reserved. General Randić, Sum-Connectivity, Hyper-Zagreb and Harmonic Indices, and Harmonic Polynomial of Molecular Graphs Sun, 25 Sep 2016 13:43:12 +0000 We present explicit formula for the general Randić connectivity, general sum-connectivity, Hyper-Zagreb and Harmonic Indices, and Harmonic polynomial of some simple connected molecular graphs. Mohammad Reza Farahani, Wei Gao, M. R. Rajesh Kanna, R. Pradeep Kumar, and Jia-Bao Liu Copyright © 2016 Mohammad Reza Farahani et al. All rights reserved. Removal of Phosphate Using Red Mud: An Environmentally Hazardous Waste By-Product of Alumina Industry Mon, 29 Aug 2016 16:35:46 +0000 The industrial waste, bauxite residue generated in the Bayer chemical process of alumina production, commonly known as red mud (RM) has been used as the adsorbent for selective removal of phosphate in aqueous solutions. RM collected from the storage area of alumina industry was characterized by chemical analysis and physical methods such as BET surface area, Scanning Electron Microscopy (SEM), particle size analysis, and X-ray diffraction (XRD) methods. Among the various red mud samples (0.2–200 μ) studied, the samples treated with 1 M HCl for 2 h were found better for the selective adsorption of phosphate in comparison with untreated and heat treated RM samples. The presence of phosphate in the aqueous samples collected after adsorption studies with red mud was determined by standard spectrophotometric procedure using ammonium molybdate and ascorbic acid in nitrate medium at 880 nm. The studies reported significant adsorption of phosphate on acid treated red mud in comparison with adsorption of phosphate on untreated and heat treated red mud, respectively. The adsorption of phosphate on raw red mud and activated red mud was further investigated with respect to stirring time, pH of the solution, dose of adsorbent, and varying phosphate concentration. Acid treated RM is observed as an efficient and cost-effective adsorbent for selective removal of phosphate in aqueous solutions. Shivkumar S. Prajapati, P. A. Mohamed Najar, and Vijay M. Tangde Copyright © 2016 Shivkumar S. Prajapati et al. All rights reserved. Kinetics and Mechanistic Study of Permanganate Oxidation of Fluorenone Hydrazone in Alkaline Medium Mon, 25 Jul 2016 09:52:01 +0000 The oxidation kinetics of fluorenone hydrazone (FH) using potassium permanganate in alkaline medium were measured at a constant ionic strength of 0.1 mol dm−3 and at 25°C using UV/VIS spectrophotometer. A first-order kinetics has been monitored in the reaction of FH with respect to [permanganate]. Less-than-unit order dependence of the reaction on [FH] and [OH−] was revealed. No pronounced effect on the reaction rate by increasing ionic strength was recorded. Intervention of free radicals was observed in the reaction. The reaction mechanism describing the kinetic results was illustrated which involves formation of 1 : 1 intermediate complex between fluorenone hydrazones and the active species of permanganate. 9H-Fluorenone as the corresponding ketone was found to be the final oxidation product of fluorenone hydrazone as confirmed by GC/MS analysis and FT-IR spectroscopy. The expression rate law for the oxidation reaction was deduced. The reaction constants and mechanism have been evaluated. The activation parameters associated with the rate-limiting step of the reaction, along with the thermodynamic quantities of the equilibrium constants, have been calculated and discussed. Ahmed Fawzy, Saleh A. Ahmed, Ismail I. Althagafi, Moataz H. Morad, and Khalid S. Khairou Copyright © 2016 Ahmed Fawzy et al. All rights reserved. Energy Landscape of Pentapeptides in a Higher-Order Conformational Subspace Mon, 16 May 2016 07:35:06 +0000 The potential energy landscape of pentapeptides was mapped in a collective coordinate principal conformational subspace derived from principal component analysis of a nonredundant representative set of protein structures from the PDB. Three pentapeptide sequences that are known to be distinct in terms of their secondary structure characteristics, (Ala)5, (Gly)5, and Val.Asn.Thr.Phe.Val, were considered. Partitioning the landscapes into different energy valleys allowed for calculation of the relative propensities of the peptide secondary structures in a statistical mechanical framework. The distribution of the observed conformations of pentapeptide data showed good correspondence to the topology of the energy landscape of the (Ala)5 sequence where, in accord with reported trends, the α-helix showed a predominant propensity at 298 K. The topography of the landscapes indicates that the stabilization of the α-helix in the (Ala)5 sequence is enthalpic in nature while entropic factors are important for stabilization of the β-sheet in the Val.Asn.Thr.Phe.Val sequence. The results indicate that local interactions within small pentapeptide segments can lead to conformational preference of one secondary structure over the other where account of conformational entropy is important in order to reveal such preference. The method, therefore, can provide critical structural information for ab initio protein folding methods. Karim M. ElSawy Copyright © 2016 Karim M. ElSawy. All rights reserved. Corrigendum to “(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2-Based Nanomaterials” Thu, 28 Apr 2016 07:26:38 +0000 Radim Beranek Copyright © 2016 Radim Beranek. All rights reserved. Simulation of Ni-MH Batteries via an Equivalent Circuit Model for Energy Storage Applications Wed, 16 Mar 2016 06:32:12 +0000 Impedance measurement was conducted at the entire cell level for studying of the Ni-MH rechargeable batteries. An improved equivalent circuit model considering diffusion process is proposed for simulation of battery impedance data at different charge input levels. The cell capacity decay was diagnosed by analyzing the ohmic resistance, activation resistance, and mass transfer resistance of the Ni-MH cells with degraded capacity. The capacity deterioration of this type, Ni-MH cell, is considered in relation to the change of activation resistance of the nickel positive electrodes. Based on the report and surface analysis obtained from the energy dispersive X-ray spectroscopy, the composition formula of metal-hydride electrodes can be closely documented as the AB5 type alloy and the “A” elements are recognized as lanthanum (La) and cerium (Ce). The capacity decay of the Ni-MH cell is potentially initiated due to starved electrolyte for the electrochemical reaction of active materials inside the Ni-MH battery, and the discharge product of Ni(OH)2 at low state-of-charge level is anticipated to have more impeding effects on electrode kinetic process for higher power output and efficient energy delivery. Ying Zhu, Wenhua H. Zhu, Zenda Davis, and Bruce J. Tatarchuk Copyright © 2016 Ying Zhu et al. All rights reserved. Calculating Heat of Formation Values of Energetic Compounds: A Comparative Study Mon, 14 Mar 2016 09:59:21 +0000 Heat of formation is one of several important parameters used to assess the performance of energetic compounds. We evaluated the ability of six different methods to accurately calculate gas-phase heat of formation () values for a test set of 45 nitrogen-containing energetic compounds. Density functional theory coupled with the use of isodesmic or other balanced equations yielded calculated results in which 82% (37 of 45) of the values were within ±2.0 kcal/mol of the most recently recommended experimental/reference values available. This was compared to a procedure using density functional theory (DFT) coupled with an atom and group contribution method in which 51% (23 of 45) of the values were within ±2.0 kcal/mol of these values. The T1 procedure and Benson’s group additivity method yielded results in which 51% (23 of 45) and 64% (23 of 36) of the values, respectively, were within ±2.0 kcal/mol of these values. We also compared two relatively new semiempirical approaches (PM7 and RM1) with regard to their ability to accurately calculate . Although semiempirical methods continue to improve, they were found to be less accurate than the other approaches for the test set used in this investigation. Michael S. Elioff, Jordan Hoy, and John A. Bumpus Copyright © 2016 Michael S. Elioff et al. All rights reserved. Hydrogen Abstraction from Fluorinated Ethyl Methyl Ether Systems by OH Radicals Wed, 10 Feb 2016 08:39:06 +0000 A systematic computational investigation of hydrogen abstraction by OH from the full series of fluorinated ethyl methyl ethers (EME) containing at least one H and one F, (, ; and not allowed), including 147 reactants and 469 transition states, has been carried out, employing the MP2/6-31G(d) level of theory. Results for optimized geometries, including evidence of intramolecular hydrogen bonding in transition states, and barrier heights are presented. Trends pertaining to the number of fluorines substituted, key bond lengths, barrier heights, and key bond angles were found with good correlations and were investigated. An increase in the number of F increases the barrier height of the reaction. An increase in some parameters such as C–H length of TS, relative change in C–H from reactants to TS, ∠COC of reactants, ∠HOH in the TS, and relative change in ∠HOH between TS and free water bond angle also correlates with increased barrier height. An increase in other parameters like C–H length in the reactants and hydrogen bonding can decrease the barrier height. Curtis W. White and Jaime M. Martell Copyright © 2016 Curtis W. White and Jaime M. Martell. All rights reserved. A Group Theoretical and Quantum Chemical Study of Electronic Absorption and Fluorescence, Vibrational Spectra, and Conformations of Trimethine Cyanine Dye Molecules Mon, 18 Jan 2016 11:55:30 +0000 The energetic structures and conformations of trimethine cyanine dye molecules were investigated. For research, group theoretical and quantum chemical calculation methods were used. The theoretical group analysis of electronic and vibrational structure of molecules was carried out. Also, the energetic structures and conformations of the molecule of this dye were studied. Research shows that the investigated molecule may reside in three different conformational states, one of which is highly symmetric (symmetry ) and the other two with low symmetry. The third conformer is characterized by lowering of binding energy of the electronic system by 0.23 eV, and the long-wavelength absorption band is shifted to lower energies. Also the group theoretical analysis of the trimethine cyanine molecule had allowed systematizing the vibrational and electronic quantum transitions and identifying the bands in the absorption spectra. It is shown that the excitation of the molecule in -state causes trans-cis-isomerization. The presence of the barrier of ~0.1 eV allows the fluorescence process to compete with isomerization process, but isomerization causes a decrease in the fluorescence quantum yield of the dye. Vita Solomko, Petro Kondratenko, and Yuriy Lopatkin Copyright © 2016 Vita Solomko et al. All rights reserved. Decay of Metastable State with Account of Agglomeration and Relaxation Processes Tue, 05 Jan 2016 14:16:18 +0000 Theoretical description of the metastable phase decay kinetics in the presence of specific connections between the embryos of small sizes has been given. The theory of the decay kinetics in the presence of relaxation processes is constructed in analytical manner. The -mers nucleation is investigated and the global kinetics of decay is also constructed in this case analytically. Victor Kurasov Copyright © 2016 Victor Kurasov. All rights reserved. DFT Study of a Novel Organic Film: The Structural versus Magnetic Effects Sun, 29 Nov 2015 13:00:44 +0000 Unsaturated fatty acids have great interest by their activities as industrial materials in novel applications. In the present work, the cis-3-hexenoic acid (HA) adsorbed on the Ni(111) surface was studied by first-principles calculations using the Vienna Ab Initio Simulation Package (VASP). The most stable location for HA is presented on top site of Ni(111), although the energies are very similar for all the adsorption sites. The surface-molecule interaction takes place between the carboxyl group of HA and surrounding Ni atoms. The adsorption is weak and consequently the metal-molecule length is enhanced. The carboxyl group is elongated and weakened after adsorption giving rise to a shift in stretching frequencies. There are notable changes on the magnetic moments values of Ni surface atoms neighboring to the molecule that mainly induced magnetic moments on O and H atoms. Noticeable charge transfer occurs in 3d 4s, p Ni orbitals and 2s C, 2s p O, 1s H orbitals of carboxyl group. The surface presents positive work function changes after adsorption as a consequence of an electron back-donation. During interaction, the significance of the magnetic effects over the structural effects is evidenced. This sets the stage for a future adsorption process improvement based on the modification of the surface magnetic properties. S. Simonetti, A. Juan, G. Brizuela, and S. Ulacco Copyright © 2015 S. Simonetti et al. All rights reserved. Geometry, Energy, and Some Electronic Properties of Carbon Polyprismanes: Ab Initio and Tight-Binding Study Mon, 26 Oct 2015 14:24:12 +0000 We report geometry, energy, and some electronic properties of [n,4]- and [n,5]prismanes (polyprismanes): a special type of carbon nanotubes constructed from dehydrogenated cycloalkane C4- and C5-rings, respectively. Binding energies, interatomic bonds, and the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have been calculated using density functional approach and nonorthogonal tight-binding model for the systems up to thirty layers. It is found that polyprismanes become more thermodynamically stable as their effective length increases. Moreover, they may possess semiconducting properties in the bulk limit. Konstantin P. Katin, Stanislav A. Shostachenko, Alina I. Avkhadieva, and Mikhail M. Maslov Copyright © 2015 Konstantin P. Katin et al. All rights reserved. DFT Study on the Oxidative Addition of 4-Substituted Iodobenzenes on Pd(0)-Phosphine Complexes Sun, 04 Oct 2015 13:06:56 +0000 The oxidative addition of 4-substituted iodobenzenes on Pd(0)-PMe3 complexes has been studied at the BP86 level of theory including dispersion correction and solvation effect, with tetrahydrofuran as solvent. The bisphosphine pathway was found to be barrierless, whereas the monophosphine route is hampered by the high dissociation energy of trimethylphosphine. The reaction free energy of this step shows linear correlation with the Hammett constants of the para substituents with the most electron withdrawing groups being the most exergonic. Tímea R. Kégl, László Kollár, and Tamás Kégl Copyright © 2015 Tímea R. Kégl et al. All rights reserved. Revisiting Oxidative Dehydrogenation of Ethane by W Doping into MoVMn Mixed Oxides at Low Temperature Tue, 27 Jan 2015 09:12:27 +0000 The catalytic performance of MoVMnW mixed oxides was investigated in the oxidative dehydrogenation of ethane at three different reaction temperatures (235, 255, and 275°C) using oxygen as an oxidant. The catalysts were characterized by using X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. The MoVMnW mixed oxide catalyst showed the 70–90% of ethylene selectivity at the reaction temperatures. However, a significant decrease in the selectivity of ethylene was observed by increasing the reaction temperature from 235°C to 275°C. Mohammed H. Al-Hazmi, Taiwo Odedairo, Adel S. Al-Dossari, and YongMan Choi Copyright © 2015 Mohammed H. Al-Hazmi et al. All rights reserved. Preparation of Zirconium Oxide Powder Using Zirconium Carboxylate Precursors Wed, 31 Dec 2014 00:10:16 +0000 Zirconia was prepared at low temperatures (<450°C) using single several source precursors based on zirconium carboxylates where the R groups were systematically varied. The combination of density functional theory (DFT) calculations and extensive characterization of the precursors (i.e., X-ray diffraction, thermal gravimetric analysis, infrared spectroscopy, and scanning electron microscopy) indicated that the carboxylic acid complexes may link the zirconium metal with a cis bidentate configuration. Periodic DFT calculations were performed to examine the interaction between monoclinic ZrO2 and propanoic acid. Dissociative adsorption takes place through the cis bidentate structure with an adsorption energy of −1.43 eV. Calculated vibrational frequencies using the optimized structure are in good agreement with experimental findings. Mohammed H. Al-Hazmi, YongMan Choi, and Allen W. Apblett Copyright © 2014 Mohammed H. Al-Hazmi et al. All rights reserved. Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface Mon, 15 Dec 2014 08:57:29 +0000 Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS. Tien Duc Pham, Motoyoshi Kobayashi, and Yasuhisa Adachi Copyright © 2014 Tien Duc Pham et al. All rights reserved. Evaluation of Density Matrix and Helmholtz Free Energy for Harmonic Oscillator Asymmetric Potential via Feynmans Approach Sun, 02 Nov 2014 08:03:57 +0000 We apply a Feynmans technique for calculation of a canonical density matrix of a single particle under harmonic oscillator asymmetric potential and solving the Bloch equation of the statistical mechanics system. The density matrix and kinetic energy per unit length can be directly evaluated from the solving solutions. From the evaluation, it was found that both of the density matrix and kinetic energy per unit length depended on the parameter of the value of asymmetric potential , the value of axes-shift potential , and temperature (T). Comparison of the Helmholtz free energy was derived by the Feynmans technique and the path-integral method. The results illustrated are slightly different. Piyarut Moonsri and Artit Hutem Copyright © 2014 Piyarut Moonsri and Artit Hutem. All rights reserved. Effect of Concentration on Isomerization of Rhodanine Derivatives of Merocyanine Dyes in Polar Solvents Wed, 27 Aug 2014 12:05:51 +0000 Rhodanine derivatives of merocyanine dyes with residues of 1,3,3-trimethyl-3H-indole and 3-ethylbenzothiazoline have been found to possess two molecular forms in diluted solutions of polar solvents such as dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidinone. The first molecular form was observed to prevail at low concentrations of the dyes, normally up to 10−5 M. The second one prevails at higher concentrations and is displayed through a new band in the electronic absorption spectrum, which is red-shifted with respect to the absorption band of the first form. No similar effect was found for these dyes by use of nonpolar solvents or upon alkyl-substitution of the molecules at nitrogen atom in the rhodanine moiety. We assign the above two forms to different molecular isomers and the analogous spectral changes were shown to take place by light or heat influence which correspond to a typical isomerization effect for the related merocyanine dyes. It is discussed that the isomer transformation is facilitated by the increased mobility of the proton bonded to the nitrogen atom of the rhodanine moiety in the polar environment and the increased amount of dye-dye collisions. O. P. Dimitriev, K. P. Grytsenko, O. I. Tolmachev, Yu. L. Slominskii, M. A. Kudinova, and S. Schrader Copyright © 2014 O. P. Dimitriev et al. All rights reserved. Ruthenium(III) Catalysis in Perborate Oxidation of 5-Oxoacids Sun, 24 Aug 2014 06:23:47 +0000 Ruthenium(III) catalyzes perborate oxidation of substituted 5-oxoacids in acidic solution. The catalyzed oxidation is first order with respect to the oxidant and catalyst. The rate of ruthenium(III) catalyzed oxidation displays the Michaelis-Menten kinetics on the reductant and is independent of [H+] of the medium. Hydrogen peroxide is the reactive species of perborate and the kinetic results reveal formation of ruthenium(III) peroxo species-5-oxoacid complex. Electron-releasing substituents accelerate the reaction rate and electron-withdrawing substituents retard it. The order of reactivity among the studied 5-oxoacids is p-methoxy   p-methyl > p-phenyl > −H > p-chloro > p-bromo > m-nitro. Activation parameters are evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data is proposed and discussed. A suitable rate law is derived based on the mechanism. S. Shree Devi, P. Krishnamoorthy, and B. Muthukumaran Copyright © 2014 S. Shree Devi et al. All rights reserved. Full Kinetics and a Mechanistic Investigation of the Green Protocol for Synthesis of β-Aminoketone in the Presence of Saccharose as a Catalyst by a One-Pot Three-Component Reaction Mon, 16 Jun 2014 00:00:00 +0000 For the first time, in a green protocol, an investigation of the kinetics and mechanism of the reaction between benzaldehyde 1, 4-chloroanilinne 2, and acetophenone 3 compounds in the presence of saccharose as a catalyst was performed for generating β-aminoketone. For determining the kinetic parameters, the reaction was monitored by using the UV/Vis spectrophotometry technique. The second order rate constant () was automatically calculated by the standard equations contained within the program. In the studied temperature range, the second order rate constant (, ) depended on reciprocal temperature that was in good consistent with Arrhenius and Eyring equations, respectively. These data provided the suitable plots for calculating the activation energy and parameters (Ea, , , and ) of the reaction. Furthermore, useful information was obtained from studying the effects of solvent, concentration, and catalyst on the reaction mechanism. The results showed that the first step of the reaction mechanism is a rate determining step (RDS). The obtained experimental data and also the steady state assumption confirmed the proposed mechanism. Sayyed Mostafa Habibi-Khorassani, Malek Taher Maghsoodlou, Mehdi Shahraki, Sadegh Talaie Far, and Mir Rasul Mousavi Copyright © 2014 Sayyed Mostafa Habibi-Khorassani et al. All rights reserved. A Development of Ethanol/Percarbonate Membraneless Fuel Cell Thu, 29 May 2014 08:34:05 +0000 The electrocatalytic oxidation of ethanol on membraneless sodium percarbonate fuel cell using platinum electrodes in alkaline-acidic media is investigated. In this cell, ethanol is used as the fuel and sodium percarbonate is used as an oxidant for the first time in an alkaline-acidic media. Sodium percarbonate generates hydrogen peroxide in aqueous medium. At room temperature, the laminar-flow-based microfluidic membraneless fuel cell can reach a maximum power density of 18.96 mW cm−2 with a fuel mixture flow rate of 0.3 mL min−2. The developed fuel cell features no proton exchange membrane. The simple planar structured membraneless ethanol fuel cell presents with high design flexibility and enables easy integration of the microscale fuel cell into actual microfluidic systems and portable power applications. M. Priya, A. Arun, M. Elumalai, S. Kiruthika, and B. Muthukumaran Copyright © 2014 M. Priya et al. All rights reserved. Equilibrium, Kinetics, and Thermodynamics of the Removal of Nickel(II) from Aqueous Solution Using Cow Hooves Mon, 19 May 2014 07:20:47 +0000 The feasibility of using powdered cow hooves (CH) for removing Ni2+ from aqueous solution was investigated through batch studies. The study was conducted to determine the effect of pH, adsorbent dosage, contact time, adsorbent particle size, and temperature on the adsorption capacity of CH. Equilibrium studies were conducted using initial concentration of Ni2+ ranging from 15 to 100 mgL−1 at 208, 308, and 318 K, respectively. The results of our investigation at room temperature indicated that maximum adsorption of Ni2+ occurred at pH 7 and contact time of 20 minutes. The thermodynamics of the adsorption of Ni2+ onto CH showed that the process was spontaneous and endothermic. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models were used to quantitatively analysed the equilibrium data. The equilibrium data were best fitted by Freundlich isotherm model, while the adsorption kinetics was well described by pseudo-second-order kinetic equation. The mean adsorption energy obtained from the D-R isotherm revealed that the adsorption process was dominated by physical adsorption. Powdered cow hooves could be utilized as a low-cost adsorbent at room temperature under the conditions of pH 7 and a contact time of 20 minutes for the removal of Ni(II) from aqueous solution. I. Osasona, O. O. Ajayi, and A. O. Adebayo Copyright © 2014 I. Osasona et al. All rights reserved. Plasma Formation during Acoustic Cavitation: Toward a New Paradigm for Sonochemistry Sun, 04 May 2014 11:19:23 +0000 The most recent spectroscopic studies of single bubble (SBSL) and multibubble (MBSL) sonoluminescence reveal that the origin of extreme intrabubble conditions is related to nonequilibrium plasma formed inside the collapsing bubbles. Analysis of the relative populations of OH(A2Σ+) vibrational states observed during MBSL in water saturated with noble gases shows that in the presence of argon at low ultrasonic frequency weakly excited plasma is formed. At high-frequency ultrasound the plasma inside the collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. Plasma formation during SBSL was observed in concentrated H2SO4 preequilibrated with Ar. The light emission spectra exhibit the lines from excited Ar atoms and ionized oxygen . Formation of species is inconsistent with any thermal process. Furthermore, the SBSL spectra in H2SO4 show emission lines from Xe+, Kr+, and Ar+ in full agreement with plasma hypothesis. The photons and the “hot” particles generated by cavitation bubbles enable the excitation of nonvolatile species in solutions increasing their chemical reactivity. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble but then diffuse into the liquid phase and react with solution precursors to form a variety of products. Sergey I. Nikitenko Copyright © 2014 Sergey I. Nikitenko. All rights reserved. Sorption of Ammonium Ions onto Natural and Modified Egyptian Kaolinites: Kinetic and Equilibrium Studies Thu, 24 Apr 2014 00:00:00 +0000 Thermally activated, acid-activated, and acid-leached of thermally activated kaolinites were prepared from the Egyptian ore. The physical and chemical properties were studied using N2 sorption at −196°C, FTIR, SEM, and the total surface acidity. The sorption of ions on the investigated sorbents was controlled with the solution pH, sorbent dosage, and initial concentration of solution. Kinetic and equilibrium sorption at 30°C were employed. Four kinetic models were applied to the kinetic sorption data; pseudo-second-order, Elovich, and intraparticle diffusion models fitted well the kinetic data whereas pseudo-first-order model was less applicable. Elovich parameters refer to physical sorption type of on nonuniform sites and the intraparticle diffusion controls the sorption of by kaolinites to a small extent. The equilibrium sorption data followed Langmuir and D-R models; the negative value of indicates a spontaneous sorption and the mean sorption energy obtained shows also physical sorption. The sorption capacities of nonactivated and activated Egyptian kaolinites towards sorption (10.87–45.45 mg·g−1) were good sorbents as compared with those uptaken by other clays reported in the literature and proved to be more active besides being less expensive and highly available. Ola I. El-Shafey, Nady A. Fathy, and Thoria A. El-Nabarawy Copyright © 2014 Ola I. El-Shafey et al. All rights reserved. Dielectric Relaxation Studies of 2-Butoxyethanol with Aniline and Substituted Anilines Using Time Domain Reflectometry Tue, 18 Feb 2014 11:27:01 +0000 The complex dielectric spectra of 2-butoxyethanol with aniline and substituted anilines like aniline, o-chloroaniline, m-chloroaniline, o-anisidine and m-anisidine binary mixtures in the composition of different volumes of percent (0%, 25%, 50%, 75%, and 100%) have been measured as a function of frequency between 10 MHz and 30 GHz at 298.15 K. The dielectric parameters like static dielectric constant and relaxation time have been obtained by using least square fit method. By using these parameters , effective Kirkwood correlation factor , corrective Kirkwood correlation factor , Bruggeman factor , excess dielectric constant , and excess inverse relaxation time values are calculated and discussed to yield information on the dipolar alignment and molecular rotation of the binary liquid mixtures. From all the derived dielectric parameters, molecular interactions are interpreted through hydrogen bonding. P. Jeevanandham, S. Kumar, P. Periyasamy, and A. C. Kumbharkhane Copyright © 2014 P. Jeevanandham et al. All rights reserved. Oxidation of Tetracaine Hydrochloride by Chloramine-B in Acid Medium: Kinetic Modeling Mon, 10 Feb 2014 10:04:44 +0000 Tetracaine hydrochloride (TCH) is one of the potent local anaesthetics. A kinetic study of oxidation of tetracaine hydrochloride by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB) has been carried in HClO4 medium at 303 K. The rate shows first-order dependence on , shows fractional–order dependence on , and is self-governing on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increased the rate. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction was found to be 1 : 5 and the oxidation products were identified by spectral analysis. The conjugate free acid C6H5SO2NHCl of CAB is postulated as the reactive oxidizing species. The observed results have been explained by plausible mechanism and the related rate law has been deduced. Jayachamarajapura Pranesh Shubha and Puttaswamy Copyright © 2014 Jayachamarajapura Pranesh Shubha and Puttaswamy. All rights reserved. Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure Wed, 15 Jan 2014 17:06:56 +0000 Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs) and hydroxy double salts (HDSs) can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release. The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers. The orthoisomer showed a more sustained and complete release as compared to the other isomers. Stephen Majoni and Jeanne M. Hossenlopp Copyright © 2014 Stephen Majoni and Jeanne M. Hossenlopp. All rights reserved. Synthesis and Study of Electrical Properties of SbTeI Thu, 09 Jan 2014 08:54:26 +0000 Needle shaped SbTeI crystals were obtained by solid state reaction. Electrical resistance was measured in the temperature range of 4 K to 550 K. SbTeI shows a metallic behavior from 4 K to 300 K, and at higher temperature (>300 K), it shows semiconducting behavior. Unlike SbSI, this material shows almost zero resistance around 550 K. It shows a piezoelectric behavior with a capacitance of 717 pF and its carrier density and nobilities are found to be 2.12 × 1016 cm−3 and 1.01 cm2/(V·s), respectively. Crystals of SbTeI are characterized by XRD, SEM, and Raman analysis. Electrical activation energy is found to be 0.52 eV. It is suggested that this material may be studied for its application as a superconductor with Tc higher than room temperature. Harish K. Dubey, L. P. Deshmukh, D. E. Kshirsagar, Madhuri Sharon, and Maheshwar Sharon Copyright © 2014 Harish K. Dubey et al. All rights reserved. Solvent Effect on Photoinitiator Reactivity in the Polymerization of 2-Hydroxyethyl Methacrylate Wed, 18 Dec 2013 12:51:01 +0000 Efficacy of photoinitiators such as riboflavin (RF), camphorquinone (CQ), and safranin T (ST) and triethanolamine as a coinitiator has been compared in carrying out the polymerization of 2-hydroxyethyl methacrylate (HEMA) in aqueous and organic solvents. HEMA solutions were polymerized in the presence of RF, CQ, and ST using a low intensity visible radiation source. HEMA was assayed by a UV spectrophotometric method during the initial stages of the reactions (i.e., ~5% change). A comparison of the efficacy of photoinitiators in causing HEMA polymerization showed that RF is more efficient than CQ and ST. The rate of polymerization is directly related to solvent dielectric constant and inversely related to the solvent viscosity. RF is the most efficient photoinitiator in the polymerization of HEMA and the highest rate of reaction occurs in aqueous solutions. A general scheme for the polymerization of HEMA in the presence of photoinitiators is presented. Iqbal Ahmad, Kefi Iqbal, Muhammad Ali Sheraz, Sofia Ahmed, Syed Abid Ali, Sadia Hafeez Kazi, Tania Mirza, Raheela Bano, and Mohammad Aminuddin Copyright © 2013 Iqbal Ahmad et al. All rights reserved.