جستجوی مقالات مرتبط با کلیدواژه « روی اکسید » در نشریات گروه « شیمی »

Ever-increasing exploitation of tetracycline antibiotics (TCs) for controlling infectious diseases in humans and animals, and other applications of TCs in other industries, such as veterinary medicine and aquaculture have made our environment especially the aquatic medium contaminated. As a result, many bacteria have become resistant to this class of antibiotics in which this resistivity has made treating humans with TCs antibiotics problematic. Adsorption is a popular method used for removing TCs from aqueous solution due to its ease of operation and at the same time being economically and timely efficient. Researchers have been applying graphene oxide as an adsorbent since 2012 due to its interesting properties, specifically higher hydrophilicity in compared to graphene. Since then and by employing surface modification techniques on graphene, graphene oxide, and reduced graphene oxide, scientists have been attempting to study the removal efficiency of TCs from aqueous solution through studying adsorption isotherm and adsorption kinetics. In addition, studies have been conducted to optimize the condition of the experiment, such as pH, contact time, dosage of adsorbent, initial concentration of TCs solution and ionic strength. Herein, by introducing the mathematical models related to the adsorption process, articles of the past 12 years about using nano-adsorbents based on graphene and its derivatives for TCs removal have been reviewed.

In this research, the activity and potential energy effect of ring pressure in simple 10-7 membered cycloalkynes in reaction with nitrile oxides, nitrile sulfides and triazoles have been studied by DFT method. Structural properties, thermodynamic and kinetic data such as reaction free energy changes (ΔrG), transition state free energy changes (ΔG*) and reaction rate constants (k) were obtained at 298 K temperature and the effect of substitution groups (R) in dipoles (R- CNO, R-CNS, R-N3) have been investigated on the reaction rate. The results show that by reducing the size of the ring and the bending of the triple bond and as a result of increasing the potential energy of the ring pressure in cycloalkynes, ΔG* of the zygotic ring reaction decreases. Also, the rate constants and free energy changes of the reactions increase with the reduction of the ring size.

In this paper, Mn2+-doped iron oxide nanoparticles/reduced graphene oxide (Mn-IONs@RGO) nanocomposite are fabricated through an electrochemical synthesis procedure for the first time. The electrosynthesis procedure is based on the electrochemical growth of IONs onto the RGO plates electrophoretically deposited on the cathode electrode. X-ray diffraction pattern of the prepared nanocomposite revealed its magnetite crystal structure. For the prepared Mn-IONs@RGO nanocomposite, particle morphology of IONs, Mn2+ cations doping in their crystal structure and presence of reduced GO plates were confirmed through FE-SEM observations, EDS as well as FT-IR analyses. Mn-IONs showed spherical particles with 20-25 nm in size and elemental composition of 71.36 wt% iron, 7.71 wt% manganese and 20.93 wt% oxygen. It was also found that 59.15 wt% iron, 8.42 wt% manganese, 23.67 wt% oxygen and 8.76 wt% carbon are presents within the composition of the synthesized Mn-IONs@RGO sample. The presence of Mn and C in the composition Mn-IONs@RGO revealed doping of IONs with Mn2+ cations and formation of Mn-IONs particles onto RGO layers through electrochemical deposition route. The superparamagnetic nature of the fabricated nanocomposite was confirmed through M-H curve and magnetic data obtained by vibrating sample magnetometer (VSM) analysis. The Mn-IONs@RGO nanocomposite showed magnetic properties of Ms=31.86 emu g–1, Mr=0.07 emu g–1 and Hci=2.29 G.

In this study, the synthesis and characterization of Sr-Ce-ZnO/HAp nanocomposite in the degradation of rhodamine B under visible light was investigated. Structure of Sr-Ce-ZnO/HAp nanocomposite identified by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy diffraction (EDX) spectroscopy (visible-spectrophotometer) UV-Vis and adsorption/desorption porosimetry were confirmed by BET analysis. Evaluations showed that adopted with metal cations and the presence of hydroxyapatite reduced energy gap, increased surface area, increased adsorption and decreased electron-hole recombination. As a result, it significantly increases the photocatalytic activity of Sr-Ce-ZnO/HAp nanocomposite compared to other prepared nanoparticles. The results also showed that more than 91% of rhodamine B was removed within 90 minutes after the start of the reaction. The first-order reaction constant and the rate constant of 0.023 min-1 were obtained.

Graphene oxide functionalized by pyrimidinium hydrogen sulfate ([email protected]) is an efficient and environmentally benign catalyst for the synthesis of bis-coumarins. At first, graphene oxide was prepared according to a modified Hummers method from the oxidation of graphite using violent oxidants such as concentrated sulfuric acid, sodium nitrate, potassium permanganate, and Hydrogen peroxide. It was subsequently modified by 2-aminopyrimidine through amide formation and then treated with sulfuric acid to reach the catalyst as pyrimidinium hydrogen sulfate ([email protected]). The catalyst was characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and FTIR spectroscopy. The synthesis of bis-coumarins was implemented through a one-pot process using no solvent by the reaction of 4-hydroxycoumarin and functionalized benzaldehydes. The scope and limitations of the procedure were examined using aromatic aldehydes with various functional groups. The functional groups had no significant effect on the product yields. The catalyst exhibited efficient properties such as simple work-up, no byproducts, sustainability, nonmetal and safe components, stability under reaction conditions, and recoverability. The synthetic route shows significant properties including sustainable, simple work-up, solvent-free condition, short reaction times, and no by-product.

In recent years, graphene oxide has become one of the most attractive materials for design and manufacturing of membranes used in water treatment processes. Because graphene oxide shows unique properties, such as a high surface area, good mechanical properties, simple synthesis techniques, presence of various functional groups on its surface and the possibility of surface modification. Various methods have been proposed for preparing graphene oxide membranes, each of which has its own advantages and disadvantages. On the other hand, it is possible to control and adjust the functions and performance of these separation membranes by making changes in the synthesis process or by modifying graphene oxide itself. Here, Firstly, the various common methods for preparing separation membranes based on graphene oxide will be discussed. Then, methods of controlling and adjusting the performance of these membranes to attain more favorable conditions for water treatment processes will be developed.

Silver-iron oxide binary nanocomposites have attracted great attentions due to hybrid unique properties of silver (Ag) and iron oxide (Fe3O4) nanoparticles such as magnetic, optical and antimicrobial properties. Catalytic degradation of organic pollutants, electrochemical sensor and targeted antimicrobial agents are some potential applications of Ag/Fe3O4 nanocomposites. In this study, Ag/Fe3O4 nanocomposites were synthesized using starch as a stabilizer and linker between Ag and Fe3O4 nanoparticles. Their antibacterial and antibiofilm activities against E. coli, P. aeruginosa and S. aureus were evaluated and compared with Ag nanoparticles. The 15–20 nm Ag-nanoparticles adhered as single particles to the agglomerations of 2-10 nm Fe3O4 nanoparticles. MIC and MBEC of the nanocomposites, depending on cell types and producing conditions, were 2-14 ppm and 20-30 ppm, respectively. In the presence of nanocomposites at a half of MIC concentration, Lag phase of growth curve of E. coli and P. aeruginosa increased about 8h and 5h, respectively. Bare Fe3O4 nanoparticles have no significant effect on growth curve of gram positive and negative bacteria, while Ag/Fe3O4 nanocomposites showed more antibacterial activity against gram negative bacteria than Ag nanoparticles. Antibiofilm activity of Ag/Fe3O4 nanocomposites against P. aeruginosa and Methicillin-resistant S. aureus was significantly more than Ag nanoparticles. Unlike Ag nanoparticles, Ag/Fe3O4 nanocomposites at a MBEC concentration inhibited the increase of biofilm biomass. Amount of starch acted an important role on the nanocomposite antibacterial activity. Evaluation of bacterial death time exhibited that Ag nanoparticles killed tested gram- positive and negative species faster than Ag/Fe3O4 nanocomposites that may be attributed to involvement of Ag nanoparticles in the starch matrix and Fe3O4 agglomerations and subsequently, slow release of Ag ions.

The aim of this experimental study is to investigate the thermal and hydrodynamic performance of graphene oxide and alumina nanofluids with two types of nanoparticle shapes in a plate heat exchanger. The nanofluids with a weight fraction of 0.1% were prepared by dispersing nanoparticles in pure water via a probe ultrasonic apparatus and a vigorous mechanical mixer. Then, the thermo-physical properties of the nanofluids including thermal conductivity and viscosity were analyzed and compared. For the thermal test, a heating system including a brazed plate exchanger equipped with two pumps, two flowmeters, four thermometers, two storage tanks, and insulated steel tubes was set up. The flow rate of hot fluid (pure water) was fixed and the nanofluid was used as cold fluid to cool the hot fluid at flowrates of 1.5, 2, 2.5, 3, and 3.5 L/min. Thermal and hydrodynamic performance was investigated by calculating heat transfer rate, Nusselt number, friction coefficient, pressure drop, pumping power, and finally the performance coefficient criterion (the ratio of heat transfer obtained to pumping power consumed). In comparison with water, the highest enhancement in heat transfer was obtained at the lowest flow rate of graphene oxide and alumina nanofluids to the extent of 46% and 18 %, respectively. This study showed that the maximum performance index was related to the graphene oxide nanofluid at flowrates less than 2.5 L/min, while at flowrates higher than 2.5 L/min, the performance index of graphene oxide nanofluid showed a significant drop and was lower than alumina nanofluid.

In the present study, with the knowledge of the properties and advantages of various nano-porous materials, nanoparticles of manganese oxide (II) were exchanged on the zeolite-Y surface (covalent bond) and its structure was characterized by using various techniques such as FT-IR, XRD, BET, FESEM, and EDX analyses. In the following, the manganese oxide/zeolite (MnO2@zeolite-Y) as a green active nanocatalyst for the synthesis of ethyl 2-((1H-benzo[d]imidazole-2-ylamine)(ariyl)methylthio) acetate were used via a one-pot multicomponent reaction of aryl aldehydes, 2-amino benzimidazole, and ethyl 2-mercaptoacetate in a water-ethanol solvent and room temperature. This catalytic method has many advantages, such as the use of non-toxic, low-cost, available, and recyclable acidic nanocatalyst (Lewis), the short reaction time, the ease of separating pure products, the use of green solvents, and mild conditions. The present method also promises that in the future it can be used as a convenient synthetic route for the preparation of new sulfur-bearing peptide derivatives based on 2-amino benzimidazole core under moderate conditions.

Graphene Oxide (GO) 2D (two-dimensional) material, comprised of sp2 hybridized carbon atoms and has properties and applications in various fields such as medical, environmental, and other industries. The present study aims to synthesize GO using four different methods and characterize them by FT-IR, CHN, XRD, Raman, SEM, and EDS techniques. Finally, evaluated their antibacterial activities of them. For this purpose to synthesize GO, four methods of modified Marcano (KMnO4, H2SO4/H3PO4), Hummers methods (KMnO4, NaNO3, H2SO4), modified Hummers (KMnO4, H2SO4) and the Brodie method (KMnO4, H2SO4, HNO3) were compared. As well as, the antibacterial activities of all four methods were evaluated for gram-positive (S. aureus and M. luteus) and gram-negative (E. coli and V. harveyi) bacteria by disk diffusion method. The results of this research showed that Marcano’s method excluding the NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9:1 mixture of H2SO4/H3PO4 improves the efficiency of the oxidation process. Marcano’s method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers’ method or two methods with additional KMnO4. The average size of the synthesis of GO with Marcano’s method was estimated by the Debye-Scherrer equation as around 19.7 nm. The results of this research showed that synthesized GO with four different methods did not have any antibacterial activities.

In this study, the hydrodynamic behavior of a conical fluid bed containing hydrophilic titanium oxide P25 nanoparticles and the formation of agglomerates were investigated. The particles with an initial diameter of 21 nm were fluidized by nitrogen and airflow at different superficial gas velocities. The size of the agglomerates during fluidization was determined by laser imaging and microscope electron diffraction (SEM) in the range of 40- 250 μm. According to laser images, the average size of agglomerates fluidized by nitrogen gas and airflow was 112 and 131 μm, respectively, while the average size of the complex agglomerates at the end of fluidization with nitrogen gas and airflow were 75 and 95 μm, respectively. The dynamical analysis of the bed showed that the size of the final agglomerates is highly dependent on the fluidization time. Due to the strong attractive forces between the nanoparticles, the size of the primary agglomerates was in the range of approximately 220-120 μm, which, with the continuation of fluidization, was broken down into smaller particles in the range of 145-100 μm. Young's modulus was calculated by fitting the displacement curve obtained from atomic force microscopy to 144 kPa, which corresponded to the Hertz model (141 kPa). The results indicated that increasing the gas velocity and applying airflow can partly increase the mean sphericity of particles (0.82-0.86). According to the experiments, fluidization time had a significant effect on the reduction of particle sphericity (0.58-0.75), which was affected by the failure of large agglomerates with sharp edges. The results showed that the initial agglomerates were fragile and have porosity above 80%, whereas the ultimate porosity was less than 50% with a relatively smooth surface. Unlike particle fluidization in cylindrical fluidized beds, the results of this study can help reduce particle agglomeration and achieve uniform particle size distribution.

Na[Ln(edta)(H2O)n] (Ln = Dy, Ho, Yb and Er, n = 1-3) complexes were synthesized using lanthanide salts and Na4(edta). The synthesized lanthanide complexes were characterized using different techniques including elemental analysis, UV-Vis, FT-IR and fluorescence spectroscopy. Their structures were also optimized using DFT method. Then, the complexes were refluxed in the presence of a mixture of Al(OH)3 and H3BO3 for 24 h. The reaction mixture was then calcined at 400°C for 5 h. The obtained powder as a new phosphorescent pigment was dispersed in water and acrylicpolyurethane resin, and new phosphorescent pigments were finally prepared by adding different percentages of lanthanide oxides to the original pigment. The prepared phosphorescent pigments were investigated using XRD, XRF, and solid state phosphorescence spectroscopy.

A simple and selective method for the preconcentration of Fe(III) and Zn ions prior to flame atomic absorption spectrometric (FAAS) determinations using a column packed with nano graphene oxide (GO) as a solid-phase extractant has been presented in this manuscript. The method is based on the sorption of mentioned ions on synthesized GO with use of Methyl-2-(4-methoxy-benzoyl)-3- (4-methoxyphenyl)-3-oxopropanoylcarbamate) as chelating agent. Some effective parameters on the extraction and complex formation were selected and optimized. Under the optimized conditions (pH 9, flow rate 9 mL min−1), metal ions were retained on the column, then quantitatively eluted by 5 mL 3.0 mol L−1 HNO3 solution. The preconcentration factor was calculated as 240. The detection limits for the understudy analyte ions were found in the range of 0.22 ng mL-1 to 0.28 ng mL-1 (for Fe3+ and Zn2+, respectively). The column packed with GO was good enough for metal ions separation in matrixes containing alkali, alkaline earth, transition and heavy metal ions. This method was also used to determine the recovery rate of the studied ions in real samples.

The purpose of this study was to investigate the effect of the addition of nanofluids consisting of nanoparticles of magnesium oxide and polyacrylamide polymer on the drag reduction in the turbulent flow of water in a rough horizontal pipeline. For this purpose, three effective parameters of the process (nanoparticle concentration, surfactant concentration, and Reynolds number) in each pipeline were investigated and optimized by the surface response method. The highest rate of drag reduction was calculated by a numerical optimization method of 82%. The model adequacy was investigated using ANOVA analysis. Given the high values of the coefficient of determination and the adjusted coefficient of determination, it was determined that the data are well described by the second-order empirical model.

In this study, Ag, Ce codoped ZnO/polyaniline nanocomposites were synthesized as photocatalysts for the simultaneous degradation of organic pollutants para nitrophenol and methylene blue under UV light. XRD, FESEM, and UV-Vis analyzes were used to determine the physical, chemical, and optical properties of the synthesized samples. Photocatalytic experiments showed better performance of Ag-Ce-ZnO/PANI nanocomposite compared to other samples. The results showed that after 60 minutes, about 88% of methylene blue and 56% of para nitrophenol were degraded by this nanocomposite. The good photocatalytic performance of Ag-Ce-ZnO/PANI nanocomposites can be attributed to the reduction of electron-hole recombination, increased electrical conductivity, and increased adsorption. The stable and efficient photocatalytic activity of the prepared nanocomposite identifies it as an effective photocatalyst in the degradation of organic pollutants solely or simultaneously.

With the development of technology, and the expansion of using industrial paints, environmental pollution has become a general crisis today. Among the various methods, photocatalysis has attracted attention, because it is a simple, low-cost, and effective method for removing organic contaminants. Photocatalysis based on nanocomposites is an effective way of removal of industrial contamination. In this study, graphene oxide, and graphene oxide-silica/magnetite nanocomposites, were synthesized with three different weight ratios of magnetite. After structural characterization (XRD, UV-vis, VSM, FTIR, FESEM, EDS, TEM), their performance as an effective adsorbent, evaluated for removing methylene blue dye from aqueous solutions. The results indicate that graphene oxide-silica/magnetite (1:3) shows the highest degradation rate, about 94.95% compared to (1:2) and (1:1) samples with 92.52% and 88.46%, respectively. Therefore, by increasing the amount of magnetite, degradation percentage and photocatalysis efficiency increase.

In this study, graphene oxide immobilized on chitosan contains cobalt ferrite (CoFe2O4@CS@GO) as a new recyclable magnetic nabnocatalyst was used in the synthesis of bis(aminopyrimidine) derivatives by the reaction of aromatic aldehydes and 6-aminouracil in ethanol with good to excellent yields under reflux conditions. The CoFe2O4@CS@GO catalyst can be easily recovered by magnetic separation and used several times without significantly reducing its catalytic activity. The catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDs) and vibrating sample magnetometer (VSM).The high efficiency of the products and easy separation of the nanocatalyst from the products with external permanent magnet are some advantages of this method. Products were identified by the comparison of their physical properties and spectra data, with those reported for authentic samples.

In this study a graphene oxide nanoparticles were synthesized based on the temperature-sensitive absorbent to selectively absorb diazinon from aqueous solutions. Infrared spectroscopy (FTIR), morphology (SEM) and thermal balance analysis (TGA) techniques were used to detect nanosorbent functional groups. Using these techniques, it was observed that the amine functional group was formed on the surface of the nanosorbent.To find the optimal removal conditions, the effect of effective parameters such as pH, temperature, adsorbent amount, initial analyte concentration and contact time were tested. The concentration of residual diazinon in aqueous solution was measured by Uv-Vis spectrophotometry. The synthesized nanosorbent can be used 7 times repeatedly to extract diazinon. Also, studies on absorption isotherms have shown that diazinon uptake follows the Langmuir equation. The application of synthesized nanosorbents in real samples indicates the high efficiency of this adsorbent in the selective removal and extraction of diazinon from aqueous environment.

In this investigation, a novel nano-adsorbent based on magnetic graphene oxide nanocomposite was used for dispersive solid-phase microextraction (D-SPME) of melamine in environmental water samples. The m@GO-RAFT agents were synthesized by surface modification of Fe3O4 nanoparticles with graphene oxide via surface reversible addition-fragmentation chain transfer (RAFT) copolymerization, as characterized by electron microscopy (SEM and TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). Several parameters affecting extraction performance, including the extraction solvent, amount of nano-adsorbent, contact time and back-extraction time, and sample pH were evaluated and optimized. Under the optimum conditions, analytical figures of merit such as linearity, limit of detection (LOD) and limit of quantitation (LOQ) were found to be 0.03–100 µg/L, 0.011 µg/L, and 0.027 µg/L, respectively.