Scientia Iranica
Volume:25 Issue: 3, May - June 2018

In this study, the adsorption of methylene blue (MB) dye has been studied with modified Fe-MOF-5 and MOF-5, synthesized at room temperature by direct mixing approach. The morphology and physicochemical properties of prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The removal rate of Fe-MOF-5 was considerably greater MOF-5 which shows the adsorption performance of MOF-5 can be improved through the modification. The influences of various parameters on the adsorption interaction of the prepared compounds were considered in pH value, contact time, temperature, adsorbent dosage and concentration of MB. Consequently, the adsorption kinetics, thermodynamics and isotherms were consistently explored. To predict the adsorption isotherms and to specify the characteristic parameters for process design, four isotherm models such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) were applied. The experimental isotherm data were found to fit the Langmuir model properly. Additionally, adsorption kinetic data were tested using pseudo-first-order, pseudo-second-order and Elovich model and were found to be fitted into pseudo-second-order model. The thermodynamic parameters illustrated that the adsorption was a spontaneous and endothermic process.

he reaction of the functionalized mesoporous SBA-15 in absolute ethanol with copper(II) acetate afforded a novel CuII-Schiff base/SBA-15 catalyst. The compound CuII-Schiff base/SBA-15 was characterized by IR spectroscopy, small-angle X-ray diffraction (SAX), energy dispersive X-ray Analysis (EDXS), X-ray absorption near edge structure (XANES), scanning electron microscope (SEM), transmission electron microscope (TEM) and N2 adsorption/desorption studies. Further, we tested the catalytic activity of this well-defined material in three-component copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions to obtain 1,4-disubstituted-1,2,3-triazoles in good to excellent yields from an organic halide, sodium azide and alkyne in water as a green solvent. More importantly, the catalyst can be recovered and reused efficiently up to five consecutive cycles with negligible loss of catalytic activity.

Nano kaolin-SO3H as a new reusable and green heterogeneous catalyst was prepared by reaction of kaolin nanoparticles with chlorosulfonic acid. This new type of solid acid which contains the properties of a Lewis acid (Al3) and a Brønsted acid (SO3H group), was characterized by FT-IR, XRD, SEM, TEM, XRF, EDS and TGA. Nano kaolin-SO3H was used as a recoverable acidic heterogeneous catalyst for one-pot synthesis of 2,4,5-trisubstituted imidazoles via three component condensation of 1,2-diketones, various aromatic aldehydes and ammonium acetate. Short reaction time, simple work-up, high yields, solvent-free conditions and environmental friendly catalyst are some advantages of this protocol.

The structural and conformational behavior of gemcitabine (2’, 2’-difluoro cytidine) was investigated by advanced NMR experiments and computational quantum mechanical method (DFT) using potential energy scanning (PES) in gas and solution phases at polarizable continuum model (PCM). Three stable conformers (G1, G2 and G3) were predicted from minimum points in potential energy diagram. In order to measure coupling constant values, a set of 2D spectra (H-H COSY, H-C HMQC and H-C HMBC) were analyzed. Optimized structures and spin-spin coupling constant calculations in gas and solution phases were performed by B3LYP/6-311(d,p) method. Both energy and NMR parameters showed that G1-form is more stable than other conformers. For coupling constant analysis, Karplus equations for 1JC-H, 2JC-H, and 3JC-Hwere derived. Also, solvent effect investigation performed and results showed both inter- and intra-molecular interactions affect stability of G1 conformer.

This research for the first time addressed to prepare nanocatalysts of Cu and Cu/Zn supported on alumina using microemulsion route. To do this, stable colloidal systems of Cu and Zn nanoparticles were firstly prepared in a W/O microemulsion system. The formulated microemulsions were formed from copper nitrate and zinc nitrate as source of metals, cyclohexane as oil phase and AOT as anionic surfactant. To confirm the formation of Cu and Zn colloidal systems after reduction of ions, dynamic light scattering (DLS) method has been used. From the DLS results, it was found that the nanoparticles average size for colloidal suspension system was about 2 nm. Finally, γ-Al2O3 was added to the colloidal systems to make the Cu/Al2O3 or Cu-Zn/Al2O3 nanocatalysts. The resulted nanocatalysts were characterized by FE-SEM and XRD techniques. The prepared nanocatalysts were tested for hydrogenation reaction of an unsaturated aldehyde in a batch reactor and mild condition.

Ethylene propylene diene monomer (EPDM) rubber has been widely used in the various outdoor and industrial applications. However, in order to improve its adhesion properties it needs some surface modification. Mediated electrochemical oxidation by Ag (II) was thus employed to evaluate the feasibility of EPDM surface modification. The electrochemical behavior of Ag (I) /Ag (II) redox couple was initially studied at different temperatures in an electro-membrane cell using IrO2/Ta2O5anode. The reversibility of the redox reaction improved at low temperatures. The apparent rate constant for Ag (I) oxidation (k1) at 3 kA m-2 was (s-1).
The surface chemistry, morphology and wettability of the activated EPDM rubber by Ag (II) were then analyzed and the modified EPDM surface showed a significant decrease in the water contact angle resulting in an increase in the surface free energy and improved wettability. ATR analysis revealed presence of oxygen-containing polar groups on the modified rubber surface. SEM results showed that the short treatment time at room temperature only changed the morphology of the rubber surface, which is attributed to the etching of the outermost surface.

This research focuses on loading of curcumin (Cur) anticancer drug onto nanocarriers, based on graphene oxide (GO), and improvement of loading efficiency. Surface of synthesized GO was modified by citric acid (CA) and functionalized by folic acid (FA) as a targeting agent. The functionalized GO by CA (CGO) and FA (GO-FA) were analyzed by Fourier transform infrared (FTIR). Furthermore FA was conjugated to the composite of CGO to prepare stabilized and targeted GO. The CGO-FA composite was characterized by FTIR and scanning electron microscopy (SEM) analysis. Thereafter, Cur as hydrophobic drug was loaded onto GO, CGO, GO-FA, and CGO-FA. Loaded Cur onto GO was characterized by SEM, FTIR and UV-Vis spectrophotometry. To increase the loading efficiency of Cur, the effects of water and ethanol as solvents and the weight ratios of initial Cur to GO (Cur/GO) were evaluated on the loading efficiency by response surface methodology. Comparing the loaded drug efficiencies onto different carriers demonstrated maximum loading onto CGO compared with the other carriers at optimal conditions. The optimized condition was concluded at 25.6% water in solution and 1.66 ratio of Cur/GO to achieve 112.5% loading efficiency and 13.5 ratio of loading efficiency/weight of initial Cur, respectively.

The sol-gel method was used to synthesize zero-valent iron/titanium dioxide supported on activated carbon (Fe0/TiO2/AC) Adsorbent and the adsorbents were comprehensively characterized by XRF, XRD, FT-IR, BET, FE-SEM and EDX analysis. The batch experiments were performed to evaluate the effect of adsorbent type, pH of solution, pollutant initial concentration and contact time on the 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption efficiency. The equilibrium experiments revealed that the Langmuir isotherm was good fitted to the adsorption equilibrium data, whereas; the adsorption kinetic experiments indicated that the adsorption procedure was excellent described through a pseudo-first-order kinetic model. The obtained maximum adsorption capacities from Langmuir isotherms of 86.5, 87.5, 86,57 and 88.76 mg/g were achieved for activated carbon (AC), zero-valent iron/activated carbon (Fe0/AC), titanium dioxide/activated carbon (TiO2/AC) and Fe0/TiO2/AC at the 2,4-D initial concentration of 90 mg/L, pH=4 and 25 ℃, respectively.

The leaching behavior of an Iranian copper oxide ore in sulphuric acid was investigated in detail to evaluate the influence of various factors, to optimize the dissolution conditions and to determine the kinetics of the leaching. The results indicated that the increase in the leaching time and temperature enhanced the leaching rate of copper. The leaching rate increased up to a certain value with increasing the agitation rate, acid concentration and liquid/solid ratio and with further increment reduced. Agitaion rate had the most influence on the dissolution of copper. The 3D response surface graphs confirmed the interactive effects of sulphuric acid concentration, agitation speed, and liquid/solid ratio with temperature. About 91% copper content was leached at~13% sulphuric acid concentration, stirring rate of 600 rpm, liquid/solid ratio of 10 mL/g and 50 °C after 80 min leaching. The dissolution kinetics was examined according to heterogeneous models. The shrinking core model assuming rate control by diffusion through the product layer was found appropriate to describe the dissolution of copper in sulphuric acid solution. The activation energy was obtained to be 26.699 kJ/mol and equation representing the leaching kinetics of copper based on diffusion-controlled model was found to be 1-3(1-x)2/3(1-x) = 161.97×exp(-26.699×103/8.314×T)×t.

The non-oxidative aromatization of methane was studied over M-Zn/HZSM-5 (M=La, Co, Pd, and Pt) catalysts using propane as a co-reactant. The catalysts were characterized by BET, SEM, NH3-TPD and XRD techniques. Catalytic tests were performed in a fixed-bed reactor at 823 K, using a mixture of methane, propane, and nitrogen with ratio of 6/1/1.3, respectively. Propane conversion was above50% and remained stable in the first 12 hours on stream; however, the methane conversion rapidly dropped from a high of about 10% to zero within 4 hours, implying the absence of a stoichiometric reaction between the reactants. Both zinc and the second metal (M) had a beneficial effect on aromatic selectivity and Pt-Zn/HZSM-5 exhibited the highest aromatic yields and catalyst stability. The results of the present study showed that co-feeding of methane with propane cannot successfully induce methane to participate in aromatization reactions.

The extruded alumina was prepared via extrusion of a paste which contains boehmie, δ-alumina, polyethylene glycol 400 as an additive and nitric acid as a peptizing agent. Porosity and crushing strength of the samples were carried out by means of N2 adsorption-desorption isotherm and mechanical strength instrument respectively. The calcined extruded alumina has the specific surface area of 168-240 m2/g, pore volume 0.37-0.5 cm3/g and pore diameter 8.2-8.8 nm. More than 36% of pore volume belonged to the pore diameters larger than 10 nm. The lateral crushing strength was found to be 232-476 N/cm2. The highest crushing strength of prepared samples was 30% higher than those reported in the literature. Addition of aluminum nitrate to the paste increased 50%in the lateral crushing strengthso it reached the value of622 N/cm2. This was mainly due to the binder functionality of aluminum nitrate which led to stronger connections between the particles. The extruded alumina did not show any deformation when introduce to the impregnation solution. This extruded alumina can be used as the catalyst support.