جستجوی مقالات مرتبط با کلیدواژه « روی اکسید » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

In this study, photocatalytic ozonation process was used to remove Acid Blue 113 dye from the dye solution. The catalyst applied in the process was the three-component nanocomposite Fe2O3/MgO/MoS2, which was synthesized by hydrothermal method for the first time and then identified by various methods. To analyze and optimize the parameters of the photocatalytic ozonation process, response surface methodology (RSM) was employed using the Box-Benken design. The results show that time, pH, and amount of the catalyst are the parameters that influence dye removal. The optimal conditions for these variables to remove dye solution with a concentration of 25 mg/l include pH 2.27, 8.6 mg of the catalyst, ozone flow of 0.2 mg/l.h in 26 min. Under these conditions, the proposed process removed 99.3 % of the dye. In addition, the nanocatalyst showed high reusability and stability (92 %) after eight consecutive use cycles. According to the results, the synthesized nanocomposite can be used in the catalytic ozonation process to treat industrial dye-containing effluents.

In this research, zinc oxide (ZnO) nanorods were grown by chemical bath deposition method on two types of electrospun polyacrylonitrile (PAN) nanofibers for photocatalytic decomposition of methyl orange dye. Various structures of ZnO were investigated to achieve the maximum rate of photocatalytic degradation by adjusting the growth variables of nanorods, including growth time, concentration of growth solution, and growth substrate, using the design of Expert (DOE) technique. The X-ray diffraction (XRD) pattern of the sample confirmed the wurtzite crystal structure, and diffuse reflectance spectroscopy (DRS) analysis showed an energy gap of 3.2 eV for ZnO. Also, the optimized sample with a growth time of 10 hours and a concentration of 62.5 mM of zinc nitrate and hexamethylenetetramine (HMTA) showed a decomposition rate constant (k) of 0.0038 min-1</sup>. Flexibility, quick and convenient recovery of photocatalyst from treated wastewater, and easy and cheap synthesis method promise the operational applications of the synthesized samples.

Hypothesis:

 Carbxylated graghene oxide nanosheets were synthesized and the nanosheets were applied to the surface modification of the polyethersulfonebased nanofiltration membranes for water treatment.

Different concentrations of the synthesized carboxylated graphene oxide nanosheets were used as the surface modifiers to prepare the PES/PEI c-GO nanofiltration membranes. The prepared membranes were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), 3D surface images (AFM) and X-ray diffraction (EDX) spectroscopy. The permeability and the separation performance of the constructed membranes were evalueted by the water contact angle, water content, the flow of pure water and the rejection of sodium sulfate salt and heavy metals.

the FTIR analysis showed the formation of favorable bonds in the synthesized carboxylated graphene oxide nanosheets and the fabricated membranes. The membrane surface modification by c-GO nanosheets led to a decrease in membrane roughness and the contact angle decreased from 75° for the neat membrane to 36° for M1 at 0.001 g of carboxylated graphene oxide nanosheets. Moreover, the water content increased and M2 showed the highest water content. The highest pure water flux was obtained at 13.065 L/m2.h for the constructed M2 membrane containing 0.01 g of carboxylated graphene oxide nanosheets. In addition, the highest rejection of sodium sulfate salt (Na2SO4) was observed 67.5 % for the M3 membrane containing 0.1 g of c-GO nanosheets and the highest rejection of copper nitrate (Cu(NO3)2) was obtained 87.21% for the M1 membrane containing 0.001 g of c-GO nanosheets. Furthermore the obtained results indicated the improvement of the anti-fouling properties of the modified membranes containing carboxylated graphene oxide nanosheets compared to the base membrane.

Research subject: In situ synthesis of nanoparticles due to greater impact on production mechanisms (such as reducing oil viscosity), uniform distribution of nanoparticles in reservoir fluids, no reduction in formation permeability due to no injection of nanofluids into the reservoir and also economic efficiency is more importance than other nanoparticle synthesis methods which are used in enhanced oil recovery (EOR) processes.
Research approach: In this study, the effect of in-situ synthesized of cerium oxide (CeO2) nanoparticles at low temperature on the oil recovery factor was investigated. For this purpose, water was considered as the based fluid for dispersion of synthesized nanoparticles. Also, in order to study the effect of nanoparticles concentration in the base fluid on the final oil recovery factor, several nanofluids were prepared at different concentrations of 0.01, 0.1, 0.25 and 0.5 wt.%. Finally, the prepared nanofluids were injected at the injection rate of 0.07 ml/h up to 1 PV into the micromodel and the amount of produced oil and the movement of the injected fluid in the porous medium were analyzed.
Main

The results showed that the synthesized CeO2 nanoparticles in this study have appropriate performance to improve the oil recovery factor. The presence of small amounts of these nanoparticles (concentration of 0.01 wt. %), causes a significant increment in oil recovery factor (about 7%) compared to water injection alone. Also, the oil extraction coefficient increased by increasing the concentration of nanoparticles in the base fluid. So that for nanofluids with concentrations of 0.01, 0.1, 0.25 and 0.5 wt.%, the oil recovery factor were 25%, 38%, 43% and 45%, respectively. However, by increasing the concentration of nanoparticles in the base fluid, from an optimal amount onwards, the probability of particle deposition in the micromodel increased, the effect of nanoparticles on changing the hydrodynamic properties of the injected fluid and oil production mechanisms decreased.

In this research, the efficiency of the photocatalytic process of zinc oxide nanoparticles in removing Basic Red 46 azo dye from the aqueous solution has been investigated in a batch system, exposed to UV light with a power of 15 W. Also, the number of samples and data analysis were predicted using design expert software. According to the results, with increasing the initial concentration of the dye solution, the percentage of photocatalytic degradation decreases, and with enhancing the catalyst concentration to an optimal value equal to 1 g/L, the removal efficiency of the dye increases. In addition, the percentage of dye removal is directly related to the duration of radiation. According to the analysis of the results in the design expert software, the maximum removal of the Basic Red 46 azo dye was obtained at pH =11 and the contaminant concentration was 45 mg/L with an amount of 0.61 g/L of zinc oxide as catalyst in 86 minutes.

Hypothesis:

Ultrafiltration (UF) membranes play a vital role in chemical processes through the separation of high molecular weight compounds, but suffer from a fouling phenomenon in which materials precipitate or adhere on the membrane surface; since the UF membrane feed is susceptible to the growth of microorganisms, biofouling can occur more often, which reduces the membrane performance. Some methods have been suggested to overcome the biofouling phenomenon which one of the best methods is the application of nanoparticles in the membrane.

ZnO and CuO nanoparticles and ZnO/CuO nanocomposite at three different concentrations (1, 3 and 5% by weights) were used to improve the antibacterial properties of PVC membrane. First, nanoparticles were synthesized through co-precipitation method and characterized by XRD and FTIR analyses. Then, the mixed matrix membranes were prepared and their properties were investigated in terms of permeation flux, porosity and contact angle. 

To study the antibacterial properties of the fabricated membranes, the disk diffusion method using Escherichia coli as gram-negative model was applied. The membrane containing 5% (by weight) ZnO with clear zone diameter equal to 9 mm and the membranes containing 3% (by weight) ZnO and 5% (by weight) CuO with clear zone diameter equal to 8.1 mm showed the best antibacterial activities. The results showed that the synthesized nanoparticles can improve the characteristics of the PVC membranes such as hydrophilicity (reducing contact angle from 86.28° to 67.55°) and impart antibacterial activities in the membranes. This method can be utilized to reduce the biofouling of membranes in the separation processes.

Thermoset nanocomposites, due to their strength and special physical and mechanical properties compared to metal materials, are widely used in the manufacture of household appliances, electrical appliances, coatings and sports equipment, and sanitary wares. The thermal properties of epoxy nanocomposites depend on the adhesion between the nanoparticles and matrix. Also, designing high quality and efficient epoxy nanocomposites with suitable physical and mechanical properties requires understanding the phenomena that occur during the curing reaction. The reaction of epoxy resin and curing agent as well as the study of curing kinetics play an important role in controlling the deformation of the structure and physical and mechanical properties of the composites. Investigating the dispersion of nanoparticles and selecting the appropriate mixing method can improve the curing reaction or crosslinking of epoxy nanocomposites. It can also prevent the agglomeration of nanoparticles, that affect thermal reactions. Modified iron oxide nanoparticles reduce the reaction activation energy and the curing time. Reaction time and temperature are two important factors for evaluating chemical curing reactions. Modeling analysis of curing kinetics of epoxy nanocomposites is a solution to overcome the problems of thermal reactions that occur during the curing reactions. In this paper, the curing kinetics modeling of epoxy nanocomposites and the effect of adding modified and unmodified iron oxide nanoparticles on the amount of activation energy, curing index, and rheological, mechanical and thermal properties are introduced.

Unsaturated polyester resin has many applications in composite industry. In thick part items made with this resin, a lot of heat is released in a short time during curing, on the other hand, the low heat transfer coefficient of this resin increases the temperature in the center of the part to 200°C. In thick parts, the large temperature difference between the center and walls of the sample causes internal stresses, so the addition of particles with high thermal conductivity can help to eliminate this defect. Therefore, in this research, graphene oxide particles have been used to improve the properties of unsaturated polyester resin.

In this study, graphene oxide and modified graphene oxide were used to improve the thermal conductivity and dynamic properties of unsaturated polyester resin. The effect of adding graphene oxide and modified graphene oxide particles on thermal conductivity and dynamic properties of the resin by amounts of 0.05 and 0.3% (wt) of the particles was studied by a thermal conductivity measuring device for solids and DMA test.

The results showed that silane modifier can cause strong covalent bonds between the particles and resin and change the thermal conductivity coefficient and dynamic properties. Addition of 0.05% by weight of graphene oxide to the resin increased the storage modulus in the glass region by 10%. Adding the same amount of modified graphene oxide increased the storage modulus by 36%. Silane modifier improved the dispersion of graphene oxide particles in the resin, and created stronger interactions between the particles and the resin network, so significantly increased the resin storage modulus. Better particle dispersion in the resin can increase the surface heat resistance of the particles. Therefore, the thermal conductivity is reduced compared to the thermal conductivity of unmodified graphene oxide.

N owadays, with population growth, the demand for fresh water is rising rapidly.Development of membrane based systems such as reverse osmosis, nanofilteration,ultrafilteration, and microfilteration is important strategy to reduce water scarcity.Improving performance, life time and other properties of membranes are always importantissues to reduce cost and energy consumption of membrane based-water treatment systemand should be considered to develop membrane technologies. Recently, graphene oxidehas attracted great attention to modify relevant membranes and manufacture novelnanocomposite membranes. Graphene oxide has unique structure and properties and can beproduce at commercial scale with low cost. Functional groups of graphene oxide includinghydroxyl, epoxy and carboxyl lead to strong interaction with polymeric matrix. Usinggraphene oxide in surface and matrix of polymer can improve mechanical strength, thermalstability, hydrophilicity and antifouling of polymeric membrane and subsequently improvemembrane flux and performance in desalination process. In this review, the processes formodifying of membrane surface and synthesizing of nanocomposite membrane usinggraphene oxide have been evaluated. The mechanism of graphene oxide influence onmembrane porosity, structure, characteristics and performance has been also discussed.

Hypothesis:

 Nowadays, nanofiltration membranes are used extensively in desalination and water treatment, but some major drawbacks in the desalination such as low flux and rejection should be handled through application of modified nanomaterials. A number of research works have been done in this field but the importance of the subject makes more studies in this field indispensable.

Thin film nanocomposite membranes containing titanium oxide nanotubes and modified titanium oxide nanotubes were evaluated in this study which after synthesis of the nanotubes, their inner surface was modified and after synthesizing the membranes, the membranes’ water permeability and rejection of the monovalent and divalent ions were measured. Furthermore, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) tests were used to study the neat and modified nanotubes. Field emission scanning electron microscopy (FE-SEM) analysis was used to study the morphology and structure of these thin film membranes.

The performance of polyamide thin film membranes was evaluated by pure water permeation test, contact angle test, permeation flux of the feed and rejection of sodium and copper ions. Due to the hydrophilicity of the nanotubes and formation of small pore on the membrane surface, the maximum pure water flux (26.5 L/m2h) was obtained for the membrane containing 0.05% (wt) unmodified nanotube; an increase of 73.2% compared to its neat membrane. Due to the reduced diameter of the modified nanotubes and providing sufficient energy barrier for the salts to be rejected, the maximum sodium ion rejection (93.11%) was obtained for the membrane containing 0.2% (wt) modified nanotubes.

 Graphene oxide (GO) modified with a double bond-containing chemical was used in the preparation of polystyrene composites by combination of “grafting through” and reversible addition-fragmentation chain-transfer (RAFT) polymerization methods. The main objectives were (1) application of two reaction sites for in situ grafting of polystyrene chains from the GO surface, (2) increasing of grafting density in the polymerization process by grafting through two different sites and (3) evaluation of styrene RAFT polymerization in two different grafting densities and various GO contents.

After modification of GO with ethylenediamine (EDA) using nucleophilic ring opening reaction that is resulted in amine-functionalized GO (GOA), coupling reaction was conducted between the GOA and (3-methacryloxypropyl) dimethylchlorosilane (MCS) to obtain GOOHD layers with different modifier contents. Then, grafting through RAFT polymerization method was utilized for preparation of polystyrene composites.

X-ray photoelectron spectroscopy shows successful modification of the GO layers with EDA and MCS. Molecular bonding characterization was performed by Fourier transform infrared spectroscopy for the neat and modified GO. Variations in electron conjugation were studied by Raman spectroscopy. Molecular weight and polydispersity index of the free and anchored polystyrene chains were calculated from the size exclusion chromatography. By using thermogravimetric analysis, thermal properties and grafting ratios of the modifiers and polystyrene chains were studied. Grafting ratio of the modifiers was 12.9% and 7.5% for the modified GO layers with high and low grafting densities, respectively. Morphology of the GO layers was investigated through transmission and scanning electron microscopy. Oxidation changed the flat and smooth graphite to wrinkled layers, and grafting polystyrene chains resulted in turbid layers.

 Graphene oxide (GO) as an important nanoparticle having unique characteristics and the ability to improve physical and mechanical properties of different biopolymers has been taken into consideration during the last decade.  Thus, in this study, graphene oxide was used for the modification of polymeric films based on chitosan (CS)/gelatin (GL)/polyvinyl alcohol (PVA).

Two series of films with different composition ratios were prepared by solution casting method. Graphene oxide at different concentrations (0, 0.2, 0.4 and 0.8 wt%) was added to the solutions to investigate the effect of PVA and GO amounts on the physical and mechanical properties of the films. The synthesized films were investigated by tensile, swelling, water vapor transmission rate (WVTR), antibacterial and scanning electron microscopy (SEM) tests.

The tensile results showed that the graphene oxide improved the mechanical properties such as tensile modulus and strength, while decreased the elongation-at-break of the prepared samples. The increase in the PVA content of the films led to lower mechanical properties in films. The results of swelling tests at three different (neutral, acidic, and basic) media showed that the PVA led to the decrement of swelling, and higher amounts of GO resulted in a considerable decrease in degree of swelling of the films. The WVTR results showed that the changing in film composition did not considerably change the WVTR of the films, while the GO resulted in a decrease in WVTR of the samples. The antibacterial results showed that adding PVA did not affect the inhibition zone diameter, meanwhile the addition of graphene oxide led to an increase of the inhibition zone diameter. The SEM results showed a uniform distribution of GO nanoparticles within the polymeric films which was due to the compatibility of GO with polymeric matrix.

 Polyglycidyl nitrate (PGN) is used in the manufacture of propellant elastomers due to its properties such as highly energetic composition, high density, high oxygen balance, high explosion enthalpy and suitable compatibility with other components. In addition to its desirable properties, this polymer has disadvantages such as high glass transition temperature, poor mechanical properties, and low content of total solid. Also, its elastomer can undergo decuring process. To remedy these disadvantages, its copolymers are prepared using polymers with optimal thermal and mechanical properties.

In this research an energetic polypropylene glycol/polyglycidyl nitrate/polypropylene glycol (PPG/PGN/PPG) triblock copolymer was synthesized for the first time by cationic ring-opening polymerization of propylene oxide and PGN as macroinitiator, in the presence of boron trifluoride etherate (BF3.OEt2) as the catalyst. The effect of temperature and catalyst content on molecular weight and reaction yield was investigated. The obtained product was characterized by FTIR, GPC, and 1H and 13C NMR spectroscopy. Also, the thermal properties of the copolymer were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

The results showed that by increasing the temperature from 0 to 15°C, the conversion and yield increased. On the other hand, due to the low boiling point of propylene oxide (34°C) and the exothermic reaction, it is impossible to increase the reaction temperature above 15°C. By increasing the catalyst content from 0.2% to 1% by weight of the initiator, the polymer molecular weight increased and the highest yield was achieved in presence of 1% by weight of the catalyst, but by increasing the catalyst content from 1 to 1.5 weight percent, yield and molecular weight have decreased due to the development of adverse reactions. Studies by TGA and DSC showed an increase in thermal stability and a decrease in glass transition temperature of the copolymer compared to PGN.

 The basic limitation of biopolymers compared to the petroleum-based polymers is their weak physical and mechanical properties. In recent years, efforts have been made to properly incorporate nanoparticles into the polymer to reduce the limitation of their use in the packaging industry by partially improving the physical and mechanical properties of these films. This study aimed to incorporate zinc oxide nanoparticles into gelatin-biopolymer-based nanocomposite films, in order to improve their physical, mechanical and thermal properties.

Gelatin-based nanocomposite films were prepared by adding different amounts of zinc oxide nanoparticles (0, 0.5, 1.5 and 3%) using the so-called casting method. By performing several tests, different properties of the manufactured nanocomposite films including thickness, density, water vapor permeability, mechanical properties, degree of transparency, color properties and finally, their biodegradability were investigated.

the results showed that increasing the concentration of zinc oxide nanoparticles increased the tensile strength and decreased the elongation-at-break of this biofilm. The results of physical tests showed that increase in nanoparticles concentration reduced the permeability to water vapor from 0.76 to 0.48. Incorporating zinc oxide nanoparticles affected the transparency of the biofilms i.e. their transparency reduced by increasing nanoparticles concentration. By adding nanoparticles to gelatin-based films, thermal properties including glass transition temperature and melting temperature increased. Also, the thermal stability of the biofilms increased from 533.38°C (0.5% nanoparticles) to 559.53°C (1.5% nanoparticles). The results of biodegradability in soil and light showed that with increasing the concentration of nanoparticles, the biodegradability was reduced. This is mainly due to the addition of nanoparticles, which results in a greater bond strength between the components, and consequently the delay in biodegradation.

The effective supportation of nano particles specialty metal oxide on the surface of different catalyst supports including organic, inorganic or organic-inorganic catalyst supports is a suitable method for improvement of nano particle properties and increasing of catalysts yield. In the paper, spherical α-Fe2O3 nanoparticles were supported on the surface of inorganic silica as a catalyst support, using solid-state dispersion (SSD) method. All products were characterized by using XRF, FTIR, SEM, XRD and BET surface area. The results indicated that the supported nanocatalyst (α-Fe2O3 /Silica) successfully was prepared. By using XRD analysis and
Warren-Averbach method average size of spherical α-Fe2O3 NPs supported by SSD method were measured 27.50 nm. The nanocatalyst presented in this study can be applied in the different areas such as catalytic and photocatalytic reactions.

Dextrin-g-polypyrrole/graphene oxides (PDGP/GO) nanocomposite was synthesized using in-situ polymerization and direct blending of PDGP and graphene oxide nanoparticles. The products were named nanocomposite 1 and nanocomposite 2, respectively. The prepared nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology and structure of nanocomposites were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The performance of the synthesized nanocomposites in removing Pb (II) and methylene blue dye from aqueous solutions was evaluated. The effect of pH, adsorbent dosage, contact time and contaminant concentration on Pb (II) and methylene blue uptake capacity was studied. On the other hand, the percentage removal of Pb (II) metal ion by nanocomposite 2 (96%) was higher than that of nanocomposite 1 (88%). The optimum condition for effective removal of methylene blue dye by nanocomposite 1 (94%) and nanocomposite 2 (98%) could be obtained at pH 8, nanocomposite dosage of 100 mg, contact time of 60 min and methylene blue concentration of 80 mg/L. Langmuir and Freundlich isotherm models, pseudo-first-order and pseudo-second-order kinetics equations and thermodynamic models were used to determine the mechanism of Pb (II) and methylene blue adsorption on the nanocomposite 2. The results showed that the Langmuir isotherm, pseudo-first-order kinetic and spontaneous adsorption were suitable models for Pb (II) sorption on nanocomposite 2, while the Freundlich isotherm, pseudo-second-order kinetic and spontaneous adsorption were suitable models for methylene blue dye removal. Therefore, the PDGP/GO nanocomposite prepared by direct blending could be considered as a promising adsorbent for Pb (II) and methylene blue removal from aqueous solutions.

In this study, TiO2/Fe2O3/zeolite as catalyst was synthesized by co-precipitation method. Synthesized catalyst was characterized by XRD, XRF, FT-IR and FE-SEM analysis. XRD and FT-IR analysis confirmed the presence of TiO2 and Fe2O3 on the zeolite surface. FE-SEM photographs indicated that TiO2 and Fe2O3 nanoparticles deposited on zeolite surface and the size of nanophotocatalyst was approximately 45nm. The investigation of the synthesized catalyst was performed for metronidazole removal from contaminated water and results were analyzed by response surface methodology (RSM). Results indicated that at optimal conditions containing of metronidazole concentration (100mg/L), pH (4), radiation time (90min), nanophotocatalyst concentration (1g/L) and hydrogen peroxide concentration (50mg/L), the contaminant degradation efficiency was about 70%.

This study explored the impact of kinetic relations and operating conditions on the dissolution rate of titanium slug to production of TiO2 powders in the size distribution of 50-100 nm. To reach powder with 98% purity, dried and grinned titanium slag in the size distribution of 45-160 μm react with sulfuric acid based on sulphate process. The effect of operating parameters such as acid concentration, digestion temperature, digestion time, and initial particle size of dried slag is studied. By optimizing the digestion factors in dissolution process, and using sonochemical technique in dissolution reactions, the maximum extraction efficiency of TiO2 and maximum weight fraction of removed iron is obtained. Regression analysis showed that that results of shrinking core theory including control diffusion and especially control chemical reaction model applied in this study is in agreement with the experimental data. Based on the kinetic studies, the activation energy of dissolution process is determined to 38.12 kJ.mol-1 and the reaction order was assumed to be first order mechanism with respect to acid concentrations.