نشریه شیمی و مهندسی شیمی ایران
سال سی و پنجم شماره 4 (پیاپی 82، زمستان 1395)

In this work, the performance of Ti-phosphate-supported vanadium (v) oxide catalyst in The reaction of phthalic anhydride production by selective catalytic oxidation of o-xylene was investigated. Four catalyst samples with the active phase of 2, 7, 12 and 15 wt% were made in order to investigate the effect of vanadium loading.To determine the characteristics of samples, a number of experiments such as BET, XRD, SEM, NH3-TPD, and TGA were done. Moreover, the reactor test was carried out in order to evaluate activity and selectivity to phthalic anhydride. According to XRD patterns before the reaction, titania was observed in the anatase phase which was the desirable phase for the reaction of o-xylene oxidation to phthalic anhydride. With increasing vanadium loading, the number of acidic sites on catalyst surface decreases. In addition, the catalytic activity and selectivity to phthalic anhydride were improved. At high values of vanadium, the effect of active phase loading on the catalytic performance decreased due to the formation of V2O5 on the catalyst surface. 15V-Tip sample had the most selectivity to phthalic anhydride with values of 37% at the temperature of 450oC.

Linear monoterpenes are a group of terpenes which have been studied in this research. Geraniol, myrcene, neural, and geranial are considered as linear monoterpenes. The boron nitride fullerene-like is B12N12. First, the quantum calculation has been done on the linear monoterpenes. Next, the kind of absorption of monoterpenes on B12N12 has been examined. Calculations have been done by density functional theory method with B3LYP/6-31G* using the Gaussian software. To find the highest interaction energy between monoterpenes and B12N12, the structure of several complexes has been studied. Absolute energy, absorption energy, gap energy, highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy have been calculated for interaction between linear monoterpenes and boron nitride nanoparticle. The result shows that geraniol monoterpene has the highest interaction to boron nitride, B12N12.

One of the major concerns of industrial toxic heavy metals such as boron in wastewater petrochemical industry. In this study, a comparison between natural and modified clinoptilolite with sulfuric acid as a low-cost adsorbent to remove boron from aqueous solutions has been made. The results show that the modified clinoptilolite more willing to absorb boron compared to the unmodified clinoptilolite. In addition, parameters such as initial concentration of boron, sorbent particle size, pH, adsorbent dosage and direct contact with the absorber and the absorption solution containing boron contaminants effectively. The optimum amount of boron absorbed by the modified clinoptilolite at pH=8 was obtained. The balance between absorbent and adsorbent contact time of 240 minutes and 480 g/L of the adsorbent optimal amount of clinoptilolite modified to obtain maximum absorption efficiency was appropriate. Removal of boron by clinoptilolite modified in optimal conditions %92/35. So Clinoptilolite modified with sulfuric acid has a high potential for use in industrial wastewater treatment plants. Also included Langmuir isotherm between the three models, Freundlich and Dubinin-Radushkevich boron model Freundlich adsorption on clinoptilolite modified sorbent well described. Boron adsorption kinetics models on absorbent natural clinoptilolite and clinoptilolite modified based on kinetic models Lagergren and Ho and colleagues and particle diffusion model was investigated and that the pseudo-second model more consistent with the experimental data and as a kinetic model of this process was introduced.

In this research, the superabsorbent hydrogel based on natural xanthan gum was synthesized using acrylic acid as a monomer, ammonium persulfate as initiator and magnetic iron oxide nanoparticles as a cross-linking agent. The synthesized hydrogel was evaluated by infrared spectroscopy and scanning electron microscopy. All variables affecting the swelling capacity of the hydrogel including the concentration of cross-linking agent, initiator, and monomer to xanthan weight ratio were optimized. The absorption of the optimized sample was 330 g/g. For examining the quality of the synthesized hydrogel, the absorption of the sample in different salt solutions and its swelling behavior in different pH values were measured. The optimized sample showed minimal changes in pH values from 5-11. Furthermore, in order to study the drug delivery, Diclofenac Sodium was used in two acidic and alkaline buffer environments. Within first 5 hours, the initial drug was released from the optimized sample at pH=8.

In this research, we report the significant conductivity enhancement of the PEDOT:PSS through adding different amounts of various nanoparticle into PEDOT:PSS aqueous solutions was synthesized in laboratory research. The synthesized PEDOT:PSS in laboratory scale demonstrated good conductivity and transparency of the surface. To evaluate the conductivity was studied silver nanoparticles as doping and these nanoparticles were used in conductivity final tests. Also, ionic liquid was used for study the polymer conductivity, 2-methylimidazolium chloride. The mechanism for this conductivity enhancement of optical and electrical was studied through various chemical and physical characterizations. The minimum of resistance (488 Ω) and maximum of conductivity was reached at about 5wt.% of 2-methylimidazolium chloride into the solution was synthesized in laboratory research. Appears to conductivity enhancement observed in this study is mainly due to the effect of nanoparticles and ionic liquids on the electrical and optical properties and conformational change of PEDOT chains, and hence weaken the electrostatic interactions between PEDOT cationic chains and PSS anionic chains. These resulted in the creation of a better conduction pathway among PEDOT:PSS particles, attributed to the improvement of conductivity. The electrical changes may be made to consider of polymers in applications such as organic light-emitting diodes and solar cells.

In this research, the effects of the presence of additives such as sodium dodecyl sulfate (as a surfactant) and sodium carbonate (as acid acceptor) on the top layer characteristics and gas separation properties of composite membranes, prepared by an interfacial polymerization method, were studied ATR-FTIR and SEM techniques showed the important role of the additives on the structural density and thickness of the top layer. As a result, the top layer of the prepared sample in the presence of both additives was the densest and the thickest while that of the sample prepared in the absence of both additives was the thinnest one. Furthermore, based on the AFM results, the composite membrane prepared in the presence of just sodium carbonate presented the roughest (Rmax = 520 nm) and that prepared in the presence of both additives shows the smoothest (Rmax = 148 nm) surface. Investigation of the gas permeances of membranes shows that the membrane with top layer prepared in the presence of just sodium carbonate has the highest CO2 permeance (25.2 GPU), due to its thin and rough top layer. Moreover, the highest CO2/CH4 selectivity (58) was obtained by the composite membrane prepared in the presence of both additives. On the other hand, the highest CO2/N2 and CO2/O2 selectivities (63 and 54, respectively) were achieved through the utilization of the composite membrane prepared in the presence of just sodium dodecyl sulfate.

Chamomile has used in pharmaceutical, food and cosmetic industry since ancient times. The purpose of Chamomile extract concentration by using the nanofiltration membranes methods is to achieve a way that will be more easy automation, more simple, cheaper, higher Efficiency, less cost, better selection, Scale and shorter process time and the better exploitation condition. Chamomile extract concentration by using the nanofiltration membranes method was investigated in variable pressure and variable flow velocity. by Improvement in Membrane parameters especially pressure and flow velocity and removing the fouling on the membrane surface, we are able to decrease the rejection efficiency and increase the flux. Effect of pressure range 6 - 8 bar was investigated when the liquid extract was passing. According to the flux curves over time, the flux was reduced from 21/6-14-4 L/m².h to 7/8-6/2 L/m².h. When the pressure was constant (7 bars) and velocity was10-20m/s the flux decreased from 72-14/4 L/m².h to 9-7/8 L/m².h, as well as the concentration of Apigenin active ingredient was reduced from 27/46 ppm to 10/13 ppm. At pressure range 6 - 8 (bar) and constant value of flow velocity(10m/s) concentration decreased from 30/ 70 to 9/86 (ppm).Concentration and flux reduction and rejection efficiency increasing that observed in images that had been taken from the surface of the nanofiltration membranes a result of creating of fouling and concentration polarization phenomenon during the process time.

Over decades, micro and nanoparticles were developed as biodegradable carrier or scaffolds to deliver and control a release of various therapeutic agents like drugs, proteins, cells, and genes. In the present study, production of chitosan microparticles and simultaneously, loading retinoic acid in the microspheres using coaxial electrospray method was statistically evaluated by response surface methodology. The results showed that the particle size and the morphology of produced microspheres may be controlled by changing some experimental conditions like the concentration of chitosan (X1), flow rate of the retinoic acid stream (X2), chitosan to the retinoic acid ratio (X3), and intensity of the electrical force (X4). The optimized condition to achieve a lowest particles size and narrow size distribution was found at 3%w/v chitosan, 0.1 mL/h flow rate of retinoic acid, the ratio of chitosan to retinoic acid equal to 6, and under a voltage of 10.7 kV. The stability of the produced microspheres chitosan in nutrient broth was studied for 10 days. The acceptable stability of the microspheres may allow them to be studied in vivo.

Coupling of a local triplet silylene with a local triplet nitrene with the same spin electrons through an acetylene linkage gives a new brand of high spin quintet intermediates of (nitrenoethynyl)halosilylene (X-C-CºC-N, where X® H, F, Cl, Br), which are rather experimentally hard to find. Placing the same linkage between the local closed-shell singlet silylene (s2p0) and the local triplet nitrene (p1p1) gives triplet minima which are 44-61 kcal/mol more stable than their corresponding quintets. The singlet states are approached through connecting triplet states of silylene and nitrene with the opposite spin electrons. Triplet states identified as ground states, while all singlet, triplet, and quintet states of (nitrenoethynyl)halosilylene species are minimal in their corresponding potential energy surface (PES). Our results are compared at B3LYP, MP2, MP4(SDTQ) levels using 6-311** basis set.

Acid gases removal such as carbon dioxide from gas streams is a major problem in industrial. The existence of this gas causes to different problems. The aim of this work is to find solvents that have more performance for CO2 absorption. Henry’s law constant of CO2 in some solvents have been calculated by using a model that is constructed from Quantities Structure-Property Relationship (QSPR) method. Firstly, solvent molecules are optimized based on Density Functional Theory (DFT) method at the level of B3LYP and 6-11 G (d,p) basis set in Gaussian software and then molecular descriptors are calculated by Dragon. The capability of the model with two simple molecular descriptors including a number of hydroxyl functional group (n-ROH) and Balaban centric index (BAC) is examined by Leave-One-Out Cross Validation (LOO-CV) method.The coefficient of determination (R[2) value and Average Relative Deviation percent (ARD%) for this model are 0.95 and less than 7%, respectively. Results show high accuracy of the model and good agreement with experimental values in literature.

By use of experimental data, gathered from a pilot-scale rotary drum, which was made from transparent plastic materials, an improved model was developed for describing the steady state bed depth profile of material flow in a rotary drum. The structure of the improved model is based on the existing steady state model with four added parameters. Development of the improved model includes two stages. At the first stage, the boundary condition of the original model is corrected by use of the experimental data gathered from the bed depth of materials at the discharge cross section with Support Vector Regression (SVR) method. Then, the parameters of the improved model were calculated, using the bed depth of materials at various locations along the drum with the Genetic Algorithm (GA) method. Image processing techniques were used for measurement of the bed depth at different locations along the drum. The improved model was determined to have better fitness at all the ranges of operating and design parameters, particularly, at high values of the slope of drum and low values of rotational speed as well as the discharge end region, where the original model is not working well. The Mean Square Errors (MSE) of the original and the improved models were 0.122 and 0.014, respectively.

Efficient use of water resources due to the high cost of water supply resulting from population increases and the warming of the earth is necessary. The researchers of environment believe that shutting the water off behind dams will decrease water level and also causing droughts.In this study, using the CFD method, surface evaporation of Amirkabir Dam as a case study during one aqueous year was studied. For modeling, heat, and mass transfer equations, Navies-Stokes equation and VOF model are used. Data from the model were compared with experimental results. So results confirmed that the proposed model is overlap. Also, temperature profile and mass transfer rate of water level were evaluated. The results of the simulation show that surface evaporation is effective factors for reducing the height and water level behind dams

In this study, the heat transfer and fluid flow, water-Al2O3nanofluid in a microchannel, two-dimensional rectangular in volume fractions 2%, 4%, 6% and 8% nanoparticles and Reynolds number from 10 to 50 using Computational Fluid Dynamics (CFD) has been investigated. The governing equations of continuity and momentum and thermal are solved by finite element method and by applying boundary conditions by using COMSOL Multiphysics 5.0 software. Simulation results have shown, the local Nusselt number water-Al2O3nanofluid in Reynolds number 6.9 and volume fractions 5% is a good agreement with experimental data. Increasing the Reynolds number leads to increases fluid velocity and increase the density of streamlines in the edge of the baffle and the creation of larger vortex flow that increases the heat transfer coefficient. By increasing the number of baffles leads to the formation of the recirculation zone, which increased outlet temperatures due to better heat exchange fluid to the walls of the microchannel. So that the output of fluid temperature in Reynolds number 40 in the microchannel six baffle and in the microchannel one baffle is 322.35 K and 314.9 K, respectively. By increasing the height of baffle, increase recirculation zone and then increase the heat transfer coefficient. In six baffle microchannel for Reynolds number 50, the value of pressure drop and the nusselt number is found to be 15 and 28 higher when compared with that Reynolds number in 10, respectively. But also the average output temperature is increased by increasing nanoparticle volume fractions and viscosity affected by size zone. For one baffle microchannel by rising nanoparticle volume fractions from 0.02 to 0.1, the temperature (K) enhancing 0.56 % percent. But the effect of the distance between the baffles, the average temperature of the microchannel output is low.

The deterioration of ancient porous materials due to the dehydration and crystallization of water-soluble salts is a well-known phenomenon. Salt crystallization is an important factor in the deterioration of ancient ceramics and will almost always cause some degree of damage, ranging from exfoliation of the glaze to complete disintegration of the body. To avoid any ultimate damage of aggressive salts, it is very important the essential desalination process be accomplished within a short period of time because of the direct contact of the historical porous material with water. Since EC is proportional to the concentration of ions, therefore desalination process can be monitored by EC readings. In this paper, it was documented that Electrical Conductivity (EC) is an accurate, reliable, fast and simple method for monitoring of salt extraction during desalination process. To validate this method, 52 experimental runs, designed by Response Surface Methodology (RSM) have been performed. RSM is carried out by Minitab software, version 16. Independent parameters in this research are firing temperature, immersing time, agitation rate, type, and concentration of surfactant. Calcium ion was selected as an indicator of soluble salts and measured through Atomic Absorption Spectroscopy (AAS). Electrical conductivity and calcium ion concentration are measured as desirable responses. The correlation between Ca2 concentration and EC readings was also investigated. Pearson correlation between EC and extracted Ca2 is .923 with p-value = 0.000 and linear function between these parameters are observed with approximately 96% goodness of the fit. Therefore, EC is introduced as a suitable indicator for monitoring of salt removal efficiency in the immersing system method. This monitoring method is recommended for determining the end point of desalination process especially in archaeological sites and restoration workshops where a reliable, and fast method is most desirable.

In this study, we investigated the antibacterial properties of silver nanocomposites in standard and flame-retardant expandable polystyrenes (EPS). To prepare the silver-polystyrene nanocomposite, we solved polymers separately in a solvent before adding nanoparticles into the solution. For both of EPS samples, three different gelatin yellowish solutions of silver nanoparticles in polystyrene were synthesized at 12.5, 25 and 37.5 µg/cm3. TEM and XRD imaging showed that the silver nanoparticles were about 20 nm in diameter. Additionally, SEM imaging was used for the investigation of silver nanoparticles distribution and also morphology of the nanocomposite cross sections. Samples were laid on polymeric nanocomposite disks to study the antimicrobial properties of them in the presence of gram-negative E. coli ATCC 25922 bacteria and gram-positive Staphylococcus aureus ATCC 6538 bacteria through the standardized single disk. Our comparative study showed that flame-retardant expandable polystyrene-silver nanocomposite does not have any antimicrobial property against these bacteria, while standard expandable polystyrene-silver nanoparticle has some antibacterial potential on Staphylococcus aureus ATCC 6538 which was dependent on concentration levels of the silver nanoparticles. Results of this work could be justified based on the roles of silver nanoparticle concentrations, impurities in polystyrenes and structure of the microorganisms. This research may be considered as a base for investigations on antimicrobial properties of polystyrene nanocomposites as well as vast industrial and healthcare applications of them in the future.