Scientia Iranica
Volume:25 Issue: 6, Nov - Dec 2018

In this work Fe3O4@SiO2 core-shell nanoparticles functionalized with 2-mercaptobenzothiazole as a magnetic nanosorbent was utilized for the simultaneous extraction of trace amounts of cadmium(II), copper(II), nickel(II), zinc(II) and lead(II) ions. A Box–Behnken design was applied with several variables for optimization of the extraction and elution steps. In the selected conditions, it was observed that limits of detection were 0.14 ng mL−1 for Cd(II), 0.24 ng mL−1 for Cu(II), 0.30 ng mL−1 for Ni(II), 0.27 ng mL−1 for Zn(II) and 0.53 ng mL−1 for Pb(II) and the maximum sorption capacity of this suggested magnetic nanosorbent was 168, 138, 104, 120, and 220 mg g−1 for Cd(II), Cu(II), Ni(II), Zn(II) and Pb(II), respectively. Finally, the suggested procedure was applied for determination of target metal ions at trace levels in different water samples, sugar, edible salts and various vegetables (lettuce, broccoli, and tomato) samples with satisfactory results.

An efficient synthesis of 4,4'-(phenylmethylene)bis(1H-pyrazol-5-ol)-3-carboxylates is achieved by one pot pseudo five-component reaction of phenylhydrazine, acetylenedicarboxylates and aromatic aldehydes in the presence of nano-NiZr4(PO4)6 at 60°C in water. Nano-NiZr4(PO4)6 has been characterized by powder X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Use of simple and readily available starting materials, excellent yields in short times, reusability of the catalyst, little catalyst loading and simple operational procedures are some of the important features of this protocol.

In this research article, ionic liquid modified SBA-15 mesoporous material (SBA-IL) as a recyclable, heterogeneous catalyst efficiently catalyzed the synthesis of pyranonaphthoquinone-fused spirooxindoles through the one-pot three-component reaction of isatin derivatives, activated methylene reagents, and 2-hydroxy-1,4-naphthoquinone. The reactions were performed under microwave irradiation and solvent-free conditions. The synthesized SBA-IL was characterized by SEM, FT-IR, nitrogen adsorption-desorption, and thermogravimetric analyses. Excellent chemical yields, short reaction times, mild reaction condition, easy workup procedures and reusability of catalyst are noteworthy advantages of this protocol.

Fully substituents new pyrazolo[3,4-d]pyrimidines were synthesized. The synthesis starts with cyanomethylphenylketone that reacts with phenyl hydrazine to give the corresponding aminopyrazole. The latter undergoes a cyclocondensation with an N,N'-bis(arylmethylidene)arylmethane yielding the final product. Both synthetic steps are high-yielding (the overall yields between 65-78%). The newly synthesized compounds were characterized by 1H NMR, 13C NMR and elemental analysis

Nα-protected ureidopeptides were synthesized efficiently using Bromodimethylsulfonium bromide mediated Curtius rearrangement through the in-situ generation of carboxylated sulfonium intermediate. Conversion of carboxylic acids to ureidopeptides in good yield was obtained in one-pot under mild reaction conditions, through a simple workup. To check the binding modes and binding affinity of urea functional group with target protein, the synthesized compounds were subjected to docking studies. Docking scores confirm that the molecules Boc-Leu-ψ[NHCONH]-Ala-OMe and Leu-ψ[NHCONH]-Ala-OMe have least energy and good agreement with the results of antibacterial studies against Escherichia coli, Staphylococcus aureus and Pseudomonas aeroginosa with respect to Streptomycin sulphate as a standard. The synthesized compounds were well characterized by IR, 1H NMR, 13C NMR and mass spectral studies.

An efficient synthesis of benzopyranophenazines has been presented by one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes and malononitrile with graphene oxide dichlorotriazine (GO-DCT) as an efficient nanocatalyst under microwave irradiation in ethanol. The catalyst has been characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Atomic force microscopy (AFM) and scanning electron microscopy (SEM). Atom economy, experimental simplicity, wide range of products, low amount of catalyst loading, the reusability of the catalyst, excellent yields in short reaction times and applying the microwave methodology as an efficient and green method are some of the substantial features of this method.

Different concentrations (100%, 90% and 80%) of extracting solvent methanol were used to determine antioxidant capacities of seven pigmented rice cultivars bran on the basis of phytochemicals and other antioxidants. TPCs of red colored bran (Zag, Kaw quder, Shel kew) were highest in 100% methanol and that of black pigmented (Samarkand), lightly blackish (Kaw kareed) and brown (Gull zag, Teli zag) were highest in 80% and 90% methanol. The higher flavonoid contents in non-pigmented Gull zag and Teli zag were due to luteolin-7-O-glucoside, quercetinhexoside, apigenin-7-O-glucoside, quercetin-3-O-galactoside, apigenin and (epi)catechin rather than anthocyanins in pigmented rice. Higher anthocyanin contents of extracts in lower methanol concentration was due to higher percentage of Cyanidin-3-O-rutinoside, Pelargonidin-3-O-diglucoside, cyanidin-3-O-galactoside. The antioxidant activity had shown a similar trend in which the pigmented cultivars showed higher antioxidant activity in 100% methanol except red colored She lkew having higher value in 90% methanol, while among the light colored brown rice bran, Kaw kareed showed higher activities in 80% methanol and Teli zag in 90% methanol.

Cuo/WO3/TiO2 photocatalyst was prepared applying the sol-gel combustion method. It was characterized by X-ray fluorescence spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, porosimetry, and scanning electron microscopy techniques. The activity of CuO/WO3/TiO2 was investigated for the photocatalytic degradation of phenol wastewater. Operating conditions of batch experiments such as initial concentration of phenol, photocatalyst dose, amount of H2O2, and pH were optimized. Rate constants of the pseudo first order reaction for several photocatalysts were determined (TiO2: 0.0054 min-1, WO3/TiO2: 0.0071 min-1, CuO/TiO2: 0.0118 min-1, CuO/WO3/TiO2: 0.0621 min-1). The CuO/WO3/TiO2 had the best performance, and its rate constant was 11.5 times greater than TiO2. The CuO/WO3/TiO2 activity under sun light was considerable. The activity of CuO/WO3/TiO2 for 4-chlorophenol, and 3-phenyl-1-propanol degradation was also successful.

In this study, multiwall carbon nanotubes (MWCNTs) were chemically oxidized (OMWCNTs) and functionalized with ethylenediamine (EDAMWCNTs) and diethylenetriamine (DETAMWCNTs) as amine precursors. The electrocatalysts were prepared through deposition of Pt nanoparticles on the functionalized MWCNTs by polyol method. The average size of Pt nanoparticles was found to lie between 4 and 5 nm. Cyclic Voltammetry (CV), Rotating Disk Electrode (RDE), Electrochemical Impedance Spectroscopy (EIS), and Chronoamperometry (CA) were employed to evaluate the electrochemical properties of the electrocatalysts. The Electrochemical active surface area (EASA), number of electron transferred (n), and onset potential for EDAMWCNTs and DETAMWCNTs were found to be about 32.2 and 45.8 (m2/g Pt), 4.03 and 4.10 (electron per oxygen molecule), and 0.986 and 0.997 (V vs RHE), respectively. However, in the case of Pt-OMWCNTs the above mentioned electrochemical characteristics were calculated to be 24.2 (m2/g Pt), 3.34 (electron per oxygen molecule), and 0.824 (V vs RHE), respectively. Moreover, EIS and CA indicate that introducing amine functional groups lead to less electron transfer resistance and better electrocatalytic activity and stability during oxygen reduction. The results show that the higher number of nitrogen atoms within the amine functional groups the more enhanced electrocatalytic performance of Pt nanoparticles in ORR.

The present investigation highlighted the methane adsorption on synthesized activated carbons (ACs) based upon hydrothermally treated cellulose and lignin followed by a chemical activation utilizing the ZnCl 2 as an activating agent. The influence of effective parameters such as; hydrothermal pretreatment, precursor type, carbonization temperature, and impregnation ratio upon the textural properties of synthesized materials as well as adsorption capacities of methane examined. Thermal stability and decomposition procedures of cellulose and lignin determined through the TGA technique while all prepared ACs characterized via the N2 adsorption-desorption analysis utilizing the BET-BJH surface area measurement and field emission scanning electron microscopy (FESEM). FTIR spectra of the prepared species were obtained in order to investigate the existing functional groups and consider effects of the added activating agent upon them. Amongst all prepared materials, the AC produced through hydrothermally treated cellulose impregnated with ZnCl 2 possessing a ratio of 1 and carbonized at 600˚C revealed improved surface and textural properties enhancing the methane storage. Furthermore, hydrothermal pretreatment provided micropore diameters ranging from 1.8-2.2nm. These resulted in 6.42mmol/g of methane adsorbed at 298K and 3.65MPa. In order to systematically understand behaviors of adsorbents for the process at hand several kinetic and isotherm models understudied.

This work presents a new GA-Fuzzy method to model dynamic behavior of a process, based on Recurrent Fuzzy modeling through Mamdani approach whose inference system is optimized by Genetic Algorithms. By using the Mamdani approach, the proposed method surmounts the need to solve various types of mathematical equations governing the dynamic behavior of the process.
The proposed method consists of two steps; i) constructing a startup version of the model, ii) optimizing the shape of membership functions of the fuzzy sets corresponding to the variables exist in the fuzzy model, along with the production rules constituting the inference such that the obtained fuzzy model can predict the dynamic behavior of the process fairly accurately.
The proposed method is used to predict the dynamic behavior of the reaction section of the Tennessee Eastman (TE) benchmark. The overall accuracy of the obtained results compared to their corresponding counterparts in TE benchmark. The mean absolute percentage error (MAPE) of the key process variables which are temperature, pressure, and level of the reactor, and the reactor cooling water outlet temperature were calculated as 1.17%, 0.38%, 1.5%, and 1.57%, respectively, showing high prediction capability of the proposed method.

In this study, application of ultrasound wave for permeability enhancement of reservoir rocks was experimentally examined. In this regards, a specific core holder apparatus was designed with the ability of in-situ exposure of ultrasound to the plug at high-pressure condition, which is a better representative of ultrasound application in real wellbores. The effect of ultrasound power and exposure time as well as probe-plug distance on permeability stimulation was evaluated. The results showed that ultrasound could stimulate the permeability of asphaltene-damaged rocks, in which its efficiency is significant in sandstone rock. Analysis of asphaltene content in the output fluid showed that, as the result of ultrasound exposure, 84% of deposited asphaltenes in the sandstone plug was removed, which is corresponding to 67% of permeability recovery. It was also found that the stimulated permeability increases with increasing exposure time and power while decreases with increasing probe-plug distance, however an optimum value for exposure time and power, after which the permeability recovery is not significantly enhanced, was observed. Analysis of experiments also showed that probe-plug distance has the most prominent effect on recovery of damaged permeability in comparison to ultrasound time and power.

Controlling the looper height and strip tension is important in hot strip mills, because these variables affect both the strip quality and strip threading. Many researchers have proposed and applied a variety of control schemes for this problem, but the increasingly strict market demand for strip quality requires further improvements. This paper describes a multivariable active disturbance rejection control (MADRC) strategy that realizes the decoupling control of a hydraulic looper multivariable system. Simulation experiments for a traditional proportion- integration (PI) controller and the proposed MADRC controller were conducted using MATLAB/Simulink software. The simulation results show that the proposed MADRC ensures good robustness and adaptability under modeling uncertainty and external disturbance .It is concluded that the designed MADRC controller produces better dynamic performance than the traditional PI controller, and the proposed looper control system is effective and practical.