Composite of conducting polyaniline-isobutylated urea formaldehyde: Preparation and characterization

Composite of conductive polyaniline-isobutylated urea formaldehyde have been prepared by chemical oxidative emulsion polymerization of aniline in the presence of isobutylated urea formaldehyde resin (BUFR) in toluene-water solvents at room temperature. The mass loading of polyaniline was controlled by varying the BUFR/aniline charging ratio as well as oxidant (ammonium persulfate)/aniline molar ratio. Some factors capable of affecting the yield and conductivity of composite, such as amount of the oxidant, type of the dispersants (span-80 and span-20), and amount of resin and organic acid (para-toluene sulfonic acid) were investigated. The prepared composites were characterized by FTIR spectroscopy and scanning electron microscopy (SEM).     

Multiobjective optimization scheme for industrial synthesis gas sweetening plant in GTL process

In industrial amine plants the optimized operating conditions are obtained from the conclusion of occurred events and challenges that are normal in the working units. For the sake of reducing the costs, time consuming, and preventing unsuitable accidents, the optimization could be performed by a computer program. In this paper, simulation and parameter analysis of amine plant is performed at first. The optimization of this unit is studied using Non-Dominated Sorting Genetic Algorithm-II in order to produce sweet gas with CO 2 mole percentage less than 2.0% and H 2 S concentration less than 10 ppm for application in Fischer-Tropsch synthesis. The simulation of the plant in HYSYS v.3.1 software has been linked with MATLAB code for real-parameter NSGA-II to simulate and optimize the amine process. Three scenarios are selected to cover the effect of (DEA/MDEA) mass composition percent ratio at amine solution on objective functions. Results show that sour gas temperature and pressure of 33.98 ? C and 14.96 bar, DEA/CO 2 molar flow ratio of 12.58, regeneration gas temperature and pressure of 94.92 ? C and 3.0 bar, regenerator pressure of 1.53 bar, and ratio of DEA/MDEA = 20%/10% are the best values for minimizing plant energy consumption, amine circulation rate, and carbon dioxide recovery.     

Electrochemical and chemical synthesis of nanostructure copoly(aniline-o-anisidine-o-toluidine) and study of its electrochemical behavior in organic sulfonic acid media

Terpolymerization of aniline, o-anisidine and o-toluidine was carried out by electrochemical and interfacial chemical polymerization. All homopolymers and terpolymer thin films have been synthesized through electropolymerization at room temperature in aqueous solutions containing 0.5 M of organic sulfonic acid, such as p-toluene sulfonic acid, methane sulfonic acid, sulfosalicylic acid, dodecylbenzene sulfonic acid, and 0.1 M of aniline, o-anisidine and o-toluidine monomers, using cyclic voltammetry method, applying a sequential linear potential scan at a rate of 25 mV s^?1 between ?0.1 and 0.9 V. The electrochemical terpolymerization has been performed at various mole ratios of monomers. Nanoparticles obtained from conjugation of homo- and terpolymer with organic sulfonic acids, were prepared by a chemical oxidation via interfacial chemical polymerization. SEM micrographs, FTIR spectra and conductivity measurements using four-probe method were applied for the characterization of the products. Terpolymer was characterized by higher conductivity than poly-o-toluidine and lesser than polyaniline and poly-o-anisidine. The solubility of terpolymers was dependent on the monomers mole ratio.     

Comparison of dispersive liquid–liquid microextraction and hollow fiber liquid–liquid–liquid microextraction for the determination of fentanyl,alfentanil, and sufentanil in water and biological fluids by high-performance liquid chromatography

Dispersive liquid–liquid microextraction (DLLME) and hollow fiber liquid–liquid–liquid microextraction (HF-LLLME) combined with HPLC–DAD have been applied for the determination of three narcotic drugs (alfentanil, fentanyl, and sufentanil) in biological samples (human plasma and urine). Different DLLME parameters influencing the extraction efficiency such as type and volume of the extraction solvent and the disperser solvent, concentration of NaOH, and salt addition were investigated. In the HF-LLLME, the effects of important parameters including organic solvent type, concentration of NaOH as donor solution, concentration of H₂SO₄ as acceptor phase, salt addition, stirring rate, temperature, and extraction time were investigated and optimized. The results showed that both extraction methods exhibited good linearity, precision, enrichment factor, and detection limit. Under optimal condition, the limits of detection ranged from 0.4 to 1.9 μg/L and from 1.1 to 2.3 μg/L for DLLME and HF-LLLME, respectively. For DLLME, the intra- and inter-day precisions were 1.7–6.4% and 14.2–15.9%, respectively; and for HF-LLLME were 0.7–5.2% and 3.3–10.1%, respectively. The enrichment factors were from 275 to 325 and 190 to 237 for DLLME and HF-LLLME, respectively. The applicability of the proposed methods was investigated by analyzing biological samples. For analysis of human plasma and urine samples, HF-LLLME showed higher precision, more effective sample clean-up, higher extraction efficiency, lower organic solvent consumption than DLLME.     

Cross-linking mechanisms of arginine and lysine with α,β-dicarbonyl compounds in aqueous solution

Cross-linking in proteins by α,β-dicarbonyl compounds is one of the most damaging consequences of reactive carbonyl species in vivo and in foodstuffs. In this article we investigate computationally the cross-linking of glyoxal and methylglyoxal with lysine and arginine residues using density functional theory and the wB97XD dispersion-corrected functional. Five pathways, A-E, have been characterized. In pathways A and B, the reaction proceeds via formation of the Schiff base, aldimine, followed by addition of arginine. In contrast, in pathways C-E, direct addition of arginine to the dicarbonyl compounds occurs first, leading to a dihydroxyimidazolidine intermediate, which then reacts with lysine after dehydration and proton transfer reactions. The results reveal that pathways A, C, and E are competitive whereas reactions via pathways B and D are much less favorable. Inclusion of up to five explicit water molecules in the proton transfer and dehydration steps is found to lower the energy barriers in the feasible pathways by about 5-20 kcal/mol. Comparison of the mechanisms of methylglyoxal-derived imidazolium cross-linking (MODIC) and glyoxal-derived imidazolium cross-linking (GODIC) shows that the activation barriers are lower for GODIC than MODIC, in agreement with experimental observations.     

Diffusion of magnetic nanoparticles in a multi-site injection process within a biological tissue during magnetic fluid hyperthermia using lattice Boltzmann method

In this study the lattice Boltzmann model (LBM) has been used to simulate diffusion of magnetic nanoparticles (MNPs) injected at multiple sites inside a biological tissue during magnetic fluid hyperthermia (MFH). To validate the numerical results, diffusion in infinite one and two dimensional domains have been compared with the analytical solutions. Agreement were excellent. Also diffusion of a water based nanofluid containing magnetite MNPs (ferrofluid) for mono and multi-site injection in the tissue has been studied. Moreover, the effects of ferrofluid injection volume as well as infusion flow rate of ferrofluid on the distribution of MNPs have been investigated.     

Fresnel biprism as a 1D refractive axicon

Fresnel biprism is a one dimensional refractive element that has a lateral linear phase. Having been considered this element as a refractive axicon, its focal depth was evaluated theoretically and experimentally by means of Fresnel–Kirchhoff integral. It is shown that its focal length is a function of its refractive index and its apex angle. Experimental results are in very good agreement with theoretical work.     

Synthesis and activity measurement of some water-gas shift reaction catalysts

The effect of calcination temperature on the activity and some properties of low temperature water gas shift reaction catalysts has been investigated. The activities of catalysts have been determined using a fixed bed catalytic reactor. The following results may be deduced from the present study. 1. The catalysts' total surface area decreased with increasing calcination temperature, presumably due to the partial sintering of the catalysts particles. 2. The presence of an amorphous CuO phase within the structure of some catalysts may be related to the desirable conditions prevailing during synthesis of the latter. 3. Observation of a similar trend between the increase in copper crystallite particle size and enhancement of catalyst activities with increasing calcination temperature demonstrates the important contribution made by the copper crystallite phase to the overall activities of water gas shift reaction catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Transition metal complexes of furfural and benzil schiff bases derived from S-benzyldithiocarbazate

New nickel(II), copper(II), cobalt(III) and rohdium(III) complexes of two Schiff base ligands formed by condensation of furfural and benzil with S-benzyldithiocarbazate have been synthesized and characterized by elemental analysis and magnetic and spectroscopic measurements. The nickel(II) complexes, Ni(NS)₂ and Ni(ONS)₂ (NS and ONS stand for the uninegatively charged furfural and benzil Schiff bases, respectively) are square-planar and octahedral, respectively. The Cu(NS)Cl complex is paramagnetic with a magnetic moment fo 1.73 B.M. A halogen-bridged dimeric structure is proposed for this complex. The copper(II) complex, Cu(ONS)Cl is diamagnetic, suggesting strong antiferromagnetic interactions between a pair of copper(II) ions in a thiolo sulphur-bridged dimeric or polymeric structure. Cobalt(II) ions are oxidized in the presence of the Schiff bases with the concomitant formation of cobalt(III) complexes of empirical formulae, Co(NS)₃, Co(ONS)₂ClO₄ and Co(ONS)₂Cl, respectively, which are spin-paired and octahedral. The rhodium(III) complex of the furfural Schiff base, Rh(NS)₂Cl is tentatively assigned a halogen-bridged dimeric structre.