Effects of different potential functions on modeling of RO membrane performance by use of an advanced model

Modeling of reverse osmosis membranes is essential for progress in membrane separation technology. Effects of a new potential function on the modified surface force pore flow (MD-SF-PF) model were investigated by Moradi et al. in 2012. The main purpose of this research was to study the effects of other potential functions on the advanced and extended form of the MD-SF-PF model (i.e. the EX-MD-SF-PF model). The results obtained were compared by use of an objective function and by using the root-mean-square deviation. The best potential function was finally selected and a new model was proposed. The complex and nonlinear equations of the EX-MD-SF-PF model were solved by use of advanced numerical methods, for example finite difference and the finite volume. The proposed model, besides enabling excellent prediction of the performance of membranes, for example separation factor, and solvent and pure fluxes, has much better root-mean-square deviation than the EX-MD-SF-PF model. Profiles of potential function against pore radius and pore length were plotted and good trajectories were obtained. Profiles of solute concentration at the beginning, middle, and end of a pore were calculated and compared. The velocity profile of the permeating solvent was calculated and plotted. Most of the experimental data were predicted by use of the model.     

Transesterification of Methylbenzoate with Alcohols Catalyzed by Natural Phosphate

Transesterification of methylbenzoate with various alcohols was catalyzed by natural phosphate with or without solvent in heterogeneous media. The molar ratio of alcohol/ester, solvent effect, and weight of catalyst effect have been studied. We have found that the nature of alcohol and the reaction temperature play an important role in the transesterification process. The catalyst can be regenerated and reused without lost of activity.     

Generalizing the polymerization conditions for the production of monodisperse polymeric particles via dispersion polymerization

In this study, the preparation of various methacrylic particles with monodisperse size via dispersion polymerization in polar media was discussed. The effect of various polymerization conditions such as polarity of the medium, monomer, stabilizer, and initiator concentration, polymerization temperature, and initiator type on the size and size distribution of these particles was evaluated. The experimental results showed that, with a decrease in the difference between medium solubility parameter (MSP) and polymer solubility parameter (PSP), stabilizer concentration and with an increase in monomer content size of the particles increased and size distribution of them became broader. The obtained results showed that the particle size and size distribution of various polymers were different functions of initiator concentration. It means that, for the production of monodisperse particles, specific amount of initiator is needed for each type of the polymers. Moreover, it was observed that the size and size distribution of the particles with higher polarity were more sensitive to changing the polarity of the medium, and the size distribution of the particles with lower glass transition temperature (T _g) is more sensitive to changing the stabilizer concentration which is because of less stability of them. Furthermore, to our surprise, the obtained results showed that, in MSP-PSP of 18.5 MPa^0.5, size and size distribution of all types of the particles became equivalent.     

Solid Phase Extraction of Uranium by Naphthalene‐Methyltrioctylammonium Chloride and Arsenazo(III) Adsorbent and Subsequent Spectrophotometric Determination

A simple and effective method has been presented for the preconcentration of uranium by solid phase extraction. For this purpose arsenazo(III) supported on naphthalene‐methyltrioctylammonium chloride was used as an adsorbent and uranium solution at pH 3.5 with flow rate of 1 mL·min⁻¹ was passed through the column. Therefore, uranium‐arsenazo(III) complex was formed onto column. Uranium was quantitatively eluted with 5 mL of a 0.1% ammonium tetraphenylborate and determined by spectrophotometric method at 652 nm. Several parameters such as pH, amount of reagents, sample volume, etc. were investigated. The effect of diverse ions on the preconcentration has also been studied and the optimized conditions developed have been utilized for the trace determination of uranium. A preconcentration factor of 100 was achieved. The relative standard deviation (N=8) was 0.5% for 3 ng· mL⁻¹ of uranium. The three sigma detection limit (36) was 0.045 ng·mL⁻¹     

Density of the Extremal Solutions for a Class of Second Order Boundary Value Problem

In this paper, we prove a theorem on the existence of extremal solutions to a second-order differential inclusion with boundary conditions, governed by the subdifferential of a convex function. We also show that the extremal solutions set is dense in the solutions set of the original problem.     

Cadmium and lead ions can be removed simultaneously from a binary aqueous solution by the sono-sorption method

This paper presents the effect of ultrasound on the simultaneous removal of Cd²⁺ and Pb²⁺ ions from a binary aqueous solution in the presence of natural sorbent (sono-sorption method). The obtained results compare with the results of control method which was achieved in the absence of ultrasound. The experiments under sonication were carried out by 20 kHz apparatus. The effect of different parameters such as the amount of sorbent, contact time, temperature, and specially the competitive sorption of ions were considered for both methods. It is found that the sorption efficiency of Cd²⁺ was decreased in the presence of Pb²⁺. But, the presence of Cd²⁺ had a negligible effect on the removal of Pb²⁺. The results show that in the binary solution, the removal efficiency was higher in the presence of ultrasound than the control method. Both ions in binary solution can be removed to near completion with ultrasound. Two different multi-component isotherm equations based on the Langmuir isotherm were applied on the studied system to predict the sorption behavior of the components.     

Preparation and application of triphenyl(propyl-3-hydrogen sulfate)phosphonium bromide as new efficient ionic liquid catalyst for synthesis of 5-arylidene barbituric acids and pyrano[2,3-d]pyrimidine derivatives

Research on Chemical Intermediates - We report synthesis of triphenyl(propyl-3-hydrogen sulfate)phosphonium bromide ([TPPHSP]Br) as a reusable green Brønsted-acidic ionic liquid catalyst and...     

L-Fourier multipliers for the Dunkl operator on the real line

We consider Fourier multipliers for L^p associated with the Dunkl operator on and establish a version of Hörmander's multiplier theorem. In applying this version, we come up with some results regarding the oscillating multipliers, partial sum operators and generalized Bessel potentials.     

A concise synthesis of (+)-SCH 351448

[structure: see text] We describe a highly convergent synthetic approach to the natural product (+)-SCH 351448 (1)-a hexane-soluble heptacoordinate monosodium salt of a C(2)-symmetrical macrocyclic dilactone. Our approach implements a photochemical acylation as the key step to combine two nearly identical but orthogonal C1-C29 fragments, followed by a base-induced intramolecular acylation and deprotection to yield the natural product.     

Determination of the Vapor Pressure Curve of a Liquid in the Presence of a Nonvolatile Solute

We present a modification of the data analysis for the classical physical chemistry experiment Determination of Enthalpy of Vaporization by the Boiling-Point Method. The vapor pressures of solutions of both ionic and molecular compounds are determined at different temperatures. In this experiment we show that the enthalpy of vaporization change is dependent on the type and amount of nonvolatile solute present. Sets of data collected for different concentrations of sodium chloride, urea, and sucrose solutions are analyzed in order to determine H_vap and S_vap for pure water and for solutions of ionic and molecular solutes.Students perform the data analysis taking into consideration the activity coefficient for the solution and the mole fraction of the solvent. Simultaneous data analysis is introduced and results are used to explain the meaning of the physical parameters determined using this method of data analysis.