Estimation of sodium bicarbonate crystal size distributions in a steady-state bubble column reactor

Sodium bicarbonate is a substance which is produced in the middle stages of the soda ash production process. In this precipitation process, carbon dioxide gas is continuously injected into the bubble column reactor, which contains carbonate and bicarbonate solutions. This work deals with the study of the gas?Cliquid mass transfer, coupled with chemical reactions, and the liquid?Csolid mass transfer, coupled with crystallization. In this mathematical model, a mole balance has been instituted on flows and components through the bubble column, which also utilized a nucleation and growth formula for the solid phase and the Danckwerts?? theory for mass transfer between the gas and liquid phases. The mathematical model can predict the effects of several parameters on the sodium bicarbonate crystal size distributions. We computed the mathematical simulation model results with the experimental results of the bubble column reactor of the Shiraz Petrochemical Complex for validating the model and investigated the effects of different parameters on the sodium bicarbonate crystal size distributions.     

New bis[N-(4-pyridyl)-P-Toluene Sulfonamide] Palladium Dichloride a Novel Fluorophore for Determination of Lysine Amino Acid

Here, we are describing the study of the chemiluminescence arising from the reaction of bis (2,4,6-trichlorophenyl) oxalate (TCPO) system with new bis [N-(4-pyridyl)-p-toluene sulfonamide] palladium dichloride (BSPC) as a novel luminescent. The optimum concentrations of all reagents such as sodium salicylate (SS) as catalyst, hydrogen peroxide as oxidizing reagent and the relationships between the chemiluminescence intensity and concentrations of TCPO, SS, hydrogen peroxide and BSPC are reported. After optimization the required reagents, the system were used for determination of amino acid lysine, as an effective and selective quencher in the solution functioning in a Stern–Volmer fashion. This resulted in the development of a facile and highly sensitive chemiluminescence detection scheme for the determination of lysine in biological samples. Ultimately, estimating quenching constant K _q of 4.29?×?10³ M^?1 was successfully carried out. Under the optimal conditions, the evaluated lower and upper detection limits of measurable concentration of lysine are 1.17?×?10^?7 and 3.18?×?10^?4 M, respectively.     

Barium Sulfate Effects on the Electrochemical Behaviors of Nanostructured Lead Dioxide and Commercial Positive Plates of Lead-Acid Batteries

Positive electrode with uniform lead dioxide nanostructures directly synthesized by cyclic voltammetry (CV) method on the lead substrate in 1 M sulfuric acid solution including different concentration of barium sulfate. The effect of potential scan rate, sulfuric acid and barium sulfate concentration were studied on the morphology and particle size of lead dioxide using scanning electron microscopy (SEM) and X-ray diffraction techniques (XRD). The effect of barium sulfate was studied on the CV parameters including anodic peak current (I _p^a), cathodic peak current (I _p^c), anodic peak potential (E _p^a) and cathodic peak potential (E _p^c) during synthesis process. Finally, the effect of barium sulfate on the discharge capacity and cycle life of nanostructured positive electrodes and commercial positive plates was investigated. Both CV and battery test results showed that barium sulfate with concentration of 1 × 10⁻⁵ M can be used as suitable additive for positive paste of lead-acid batteries.     

Low Temperature Hydrothermal Synthesis of MnO<Subscript>2</Subscript> Nanoclusters as Positive Material of RAM Batteries

MnO₂ nanoclusters were synthesized by a low temperature hydrothermal method. In the presented procedure, MnO₂ was precipitated by oxidation of manganese sulfate solution upon addition of ammonium persulfate solution. The synthesized sample was characterized by SEM and XRD. Optimized nanoclusters with needle diameters of 30 nm were synthesized by mixing of manganese sulfate solution (0.8 M) with ammonium persulfate solution (0.7 M) in sulfuric acid media (0.8 M) at constant temperature of 80 °C. Effect of solid state lithium sulfate treatment on the phase composition, particle size and morphology of the obtained MnO₂ nanoclusters was studied at different temperatures. The obtained results showed that lithium salt can changes MnO₂ nanoclusters morphology without any intercalation. Discharge capacity and cycle life of the synthesized MnO₂ nanoclusters as positive materials of RAM battery (Zn–MnO₂ battery), before and after treatment with lithium sulfate were studied. MnO₂ nanopowder showed average discharge capacity of 190 mA.h/g (with respect to MnO₂ weight) during 3 first discharges. Lithium sulfate-treated powder showed higher discharge capacity (160 mA.h/g) and shorter cycle life than the untreated powder.     

Synthesis, Characterization, Crystal and Molecular Structure Analysis of Di-μ-chlorido-bis{[(4-bromobenzoylmethylene) triphenyl-λ5-phosphorane]chloridomercury(II)}

Abstract  

The reaction of phosphorus ylide Ph₃PCHC(O)C6H4–4–Br with HgCl₂ in equimolar ratios using methanol as a solvent is reported. This reaction led to binuclear complex C-Coordination of ylide and trans-like structure of complex [Br–BPPY HgCl₂]₂·2CHCl₃(1) is demonstrated by single crystal X-ray analyses and IR, ¹H and ³¹P NMR spectroscopy. Elemental analyses indicate a 1:1 stoichiometry between the ylide and Hg(II) in the product two Hg atoms are four-coordinate in the form of a tetrahedral. The title molecule [Hg₂Cl₄(C₂₆H₂₉BrOP)₂]·2CHCl₃(1) has a crystallographic inversion centre at the centroid of the four-membered ring formed by the two Hg atoms and two Cl atoms, with one short Hg–Cl(2.393A^°) bond, one Hg–C bond and two asymmetric bridging Hg–Cl (bonds at distances o 2.7345 and 2.2.7090A. The crystal packing is stabilized by C–H…O hydrogen bonds.     

Holographic Dark Energy in a Non-flat Universe with Granda-Oliveros Cut-off

Motivated by Granda and Oliveros (GO) model, we generalize their work to the non-flat case. We obtain the evolution of the dark energy density, the deceleration and the equation of state parameters for the holographic dark energy model in a non-flat universe with GO cut-off. In the limiting case of a flat universe, i.e. k=0, all results given in GO model are obtained.     

Coupled out of plane vibrations of spiral beams for micro-scale applications

An analytical method is proposed to calculate the natural frequencies and the corresponding mode shape functions of an Archimedean spiral beam. The deflection of the beam is due to both bending and torsion, which makes the problem coupled in nature. The governing partial differential equations and the boundary conditions are derived using Hamilton’s principle. Two factors make the vibrations of spirals different from oscillations of constant radius arcs. The first is the presence of terms with derivatives of the radius in the governing equations of spirals and the second is the fact that variations of radius of the beam causes the coefficients of the differential equations to be variable. It is demonstrated, using perturbation techniques that the derivative of the radius terms have negligible effect on structure’s dynamics. The spiral is then approximated with many merging constant-radius curved sections joined together to approximate the slow change of radius along the spiral. The equations of motion are formulated in non-dimensional form and the effect of all the key parameters on natural frequencies is presented. Non-dimensional curves are used to summarize the results for clarity. We also solve the governing equations using Rayleigh’s approximate method. The fundamental frequency results of the exact and Rayleigh’s method are in close agreement. This to some extent verifies the exact solutions. The results show that the vibration of spirals is mostly torsional which complicates using the spiral beam as a host for a sensor or energy harvesting device.     

Electronic properties of bilayer and trilayer graphyne in the presence of electric field

The influence of electric field on the electronic properties of bilayer and trilayer graphyne has been studied using the density functional theory. We have investigated alpha graphyne due to its analogous to graphene. The bilayer and trilayer graphyne with different stacking style configurations have been considered. Our results indicate that the electronic properties of alpha graphyne are insensitive to the number of graphyne layer and configuration. The bilayer and trilayer graphyne are semimetal similar to the monolayer graphyne. It is found that applying a uniform electric field perpendicular to the graphyne sheet changes the electronic properties of AB-stacked bilayer and ABC-stacked trilayer graphyne so that they become semiconductor. The band gaps of the bilayer and trilayer graphyne with these configurations are enhanced by increasing strength of the electric field. Therefore, possibility of controlling the electronic properties of graphyne by applying electric field makes graphyne as a good candidate for next generation nanoelectronic devices.     

Electrochemical Detection of Persulfate at the Modified Glassy Carbon Electrode with Nanocomposite Containing Nano‐Ruthenium Oxide/Thionine and Nano‐Ruthenium Oxide/Celestine Blue

The present study describes the fabrication of a sensitive amperometric sensor for the determination of persulfate. The immobilization surface was prepared by modifying a glassy carbon (GC) electrode with a nanocomposite containing ruthenium oxide (RuOx) nanoparticles and thionine (TH) or celestin blue (CB). The modified electrodes indicated excellent electrocatalytic activity toward persulfate reduction at a potential of +0.1 V. The proposed sensor showed detection limits of 1.46 µM for the GC/RuOx/TH modified electrode and 2.64 µM for the GC/RuOx/CB modified electrode. The sensitivities were obtained as 3 nA µM^?1 at a concentration range of 10 µM to 11 mM for the GC/RuOx/TH modified electrode and 1 nA µM^?1 at a concentration range of 10 µM to 6 mM for the GC/RuOx/CB modified electrodes.     

Tungstate sulfuric acid as an efficient catalyst for the synthesis of benzoxazoles and benzothiazoles under solvent-free conditions

Tungstate sulfuric acid (TSA) has been found to be an efficient and reusable catalyst for the synthesis of benzoxazole and benzothiazole derivatives via reactions of orthoesters with o-aminophenols or o-aminothiophenols in high yields.