دکتر علیرضا سلیمانی نظر

The adsorption of methylparaben (MP) on Calgon carbon (F400) and Norit-type granular activated carbons (GACs) from aqueous solutions was examined. The influence of humic acid (HA) on adsorption of MP under different pH conditions was evaluated. The adsorption isotherm results are well described by Freundlich model. The MP adsorption capacity on F400 and Norit GACs was found to be of 150 mg/g. In the presence of 2.357 mg/L HA total organic carbon (TOC), the maximum MP adsorption capacity on F400 GAC at pH 7 was increased to 2.2 folds. The Norit-type GAC had a comparatively higher uptake capacity of MP than F400 GAC. The key mechanism for MP adsorption onto the F400 GAC was through the hydrogen interaction between –OH functional group of the MP molecules. The MP adsorption capacity on Norit GAC was increased from 5 to 100 mg/g at pH 7.

In photocatalytic microreactors the catalyst layer is obtained by integration of nanostructure films of semiconductors. One of these nanostructures that have a good photocatalytic activity is ZnO nanowires. The photocatalytic degradation of methylene blue in a continuous flow microreactor with ZnO nanowires deposited film is simulated. A finite element model is developed using COMSOL Multiphysics version 5.3 software to simulate the microreactor performance. The kinetic law of the photocatalytic reaction is assumed to be Langmuir–Hinshelwood. The kinetic constants kLHa and K are determined 1.43×10-7 mol/m2s and 7.5 m3/mol, respectively. The percent of average absolute deviation of the model in predicting the methylene blue outlet concentration obtained about 0.12% mol/m3. The model showed a very good agreement with the published experimental data. The effect of microreactor depth, methylene blue inlet concentration and flow rate on the methylene blue degradation is also investigated. The simulation results showed that the microreactor with shorter depth and lower values of inlet concentration and flow rate has higher efficiency. Thiele modulus and Damköhler number are both estimated lower than 1. It indicates that the photocatalytic reactions occur without internal and bulk mass transfer limitations.

A three-dimensional (3D) simulation of four photocatalytic microreactors is performed using mass and momentum balance equations. The simulated results are validated with the available experimental data for the photocatalytic removal of methylene blue (MB) in two microcapillaries as well as dimethylformamide (DMF) and salicylic acid (SA) in two microchannels. In the surface layers of the microreactor, a photo removal reaction takes place, and the kinetic rates are described by the Langmuir-Hinshelwood (L-H) model. The Damköhler number for these microreactors is less than one, which indicates that the mass transfer rate is limited by the reaction rate. The numerical study and kinetic constants determination are carried out by using computational fluid dynamic techniques. The 3D modelpredictionsare ingood agreementwith the availableexperimental data sets. The results of the parametric study show that by increasing the microreactor length from 50 to 90mm, the removal efficiency improves from 76% to 93%. Moreover, the removal rate is increased by about 40% by reducing the microchannel depth from 500 to 100 .

A novel polymeric nanocomposite pour point depressant (PPD), based on polymethyl methacrylate (PMMA) and montmorillonite (MMT) clay, was synthesized and characterized. For a comprehensive comparison, the influence of neat polymethyl methacrylate (PMMA) and PMMA/clay nanocomposite on reducing pour point, gelation point, apparent viscosity, and yield stress of a model waxy crude oil was investigated, followed by evaluation of their performances precisely. The rheometry test results showed that the addition of 400 ppm of PPMA and 800 ppm of PMMA/clay nanocomposite to waxy crude oil reduced the pour point from 13˚C (for untreated sample) to 0 and -3 ˚C, respectively. Thus, the addition of PMMA/clay nanocomposite to waxy crude oil resulted in a 120% reduction in the pour point.

The influences of several operating factors on the viscosity of the Isfahan refinery waxy crude oil sample are studied through conducting some rheological shear rotational tests. The Taguchi design method is adopted to determine the impact of factors such as shear rate, temperature, cooling rate, wax content, and asphaltene content on the viscosity of the waxy crude oil. The results show that temperature with a contribution of 53.61% is the most influential factor. The wax content, shear rate, and asphaltene content have a contribution of 20.86, 14.75, and 3.11% respectively. The cooling rate does not have a statistically significant effect on the viscosity. The results of the rheological oscillatory tests confirm that the temperature and wax content change the viscoelastic properties of the waxy crude oil completely. An increase in the wax content from 12 to 22 wt.% raises the wax appearance temperature (WAT) from 19.1 to 34.9 °C and improves the gel point from 13 to 34.1 °C. By decreasing the temperature or increasing wax content, the viscoelastic nature of the oil sample changes from a viscoelastic fluid to a viscoelastic solid.

In this study, the thermal characteristics of turbulent nanofluid flow in a helical tube in the tube heat exchanger (HTTHE) were assessed numerically through computational fluid dynamics (CFD) simulation. The findings of both the turbulent models: realizable k-epsion (k-ε) and re-normalisation group (RNG) k-epsilon were compared. The temperature distribution contours show that realizable and RNG k-ε models, together with the swirl dominated flow are of more uniform temperature distributions. The proper prediction of two layer theory leads to having a uniform temperature distribution and proper dimensionless wall distance (Y+). The turbulent flow and heat transfer of two nanofluids (SiO2, Al2O3) and base fluid with respect to swirl dominated flow was simulated through the RNG model. The effects of the concentration of nanoparticles on heat transfer characteristics in HTTHE and two turbulent models were analyzed in a comprehensive manner. It is concluded that up to 1% concentration of SiO2 and 1% concentration of Al2O3, similar heat transfer characteristics are observed. Comparison between the CFD results with the predicted values for friction factor coefficient (f) and Nusselt number (Nu) calculated through experimental correlations indicate the maximum errors of 6.56% and 0.27%, 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.

To assess the effect of micro-organisms on the reduction of wax appearance temperature (WAT) of waxy crude oil, some appropriate strains were obtained from contaminated samples exposed to hydrocarbon compounds for a long time. By conducting some screening tests, four strains were chosen and aerated in a bioreactor; they were then grown in some hydrocarbon environments in order to produce biological inhibitors. The ability of the biological inhibitors in wax deposition prevention or reduction of WAT is assessed. The WAT is determined by means of the optical absorption spectroscopy method. The absorption plots show that biological compounds are highly effective in reducing WAT; however, different strains are not of the same efficiency. In some cases, the efficiency of biological inhibitors is more than chemical inhibitors. The optimization experiments were run with the objective of achieving the maximum WAT reduction through the Taguchi design method, and the optimum cultivation condition was identified. According to the analysis of variance, pH with a contribution of 49.63% is the most influential factor on the cultivation of the most efficient micro-organisms. The factors of temperature, the inoculation fluid, and nitrogen concentrations are ranked after pH with the contributions of 32.39, 7.92, and 1.39% respectively.

In this paper, the potentials of using particles, especially nanoparticles, in enhanced oil recovery is investigated. The effect of different nanoparticles on wettability alteration, which is an important method to increase oil recovery from oil-wet reservoirs, is reviewed. The effect of different kinds of particles, namely solid inorganic particles, hydrophilic or hydrophobic nanoparticles, and amphiphilic nanohybrids on emulsion formation (which is cited as a contributing factor in crude oil recovery) and emulsion stability is described. The potential of nanohybrids for simultaneously acting as emulsion stabilizers and transporters for catalytic species of in situ reactions in reservoirs is also reviewed. Finally, the application of nanoparticles in core flooding experiments is classified based on the dominant mechanism which causes an increase in oil recovery from cores. However, the preparation of homogeneous suspensions of nanoparticles is a technical challenge when using nanoparticles in enhanced oil recovery (EOR).
Future researches need to focus on finding out the proper functionalities of nanoparticles to improve their stability under harsh conditions of reservoirs.

An electrochemical analysis on a single channel PEM fuel cell was carried out by Computational Fuel Cell Dynamics (CFCD). The objective was to assess the latest developments regarding the effects of change in the current collector materials, porosity of electrodes and gas diffusion layer on the fuel cell power density. Graphite, as the most applicable current collector material, was applied followed by Aluminum and Titanium. It was found that titanium enhances the performance of the fuel cell as compared to the graphite and aluminum. Other results obtained were: the total porosity of electrode's layers does not have a significant effect on power density. At higher porosity of gas diffusion layer at voltages higher than 0.5 is favorable in gas diffusion, which leads to better performance. A numerical model, based on the assessment of basic best practice guidelines for CFCD, was developed that led to reasonably good agreement with the experimental results.

The heat transfer for a non-Newtonian power-law fluid over a moving surface is investigated by applying a uniform suction/injection velocity profile. The flow is influenced by internal heat generation/absorption. The energy equation is solved at constant surface temperature condition. The Merk-Chao series is applied to obtain a set of ODEs instead of a complicated PDE. The converted ordinary differential equations are solved numerically, adopting the fourth order Runge–Kutta method coupled with the shooting technique. The effects of the fluid type, suction/injection and heat source/sink parameters on heat-transfer are discussed. It is observed that thermal boundary layers for pseudo plastic fluids are thicker than that of the dilatants. There exists a direct relation between dimensionless temperature and the injection parameter or the heat generation parameter rise. Injection of a fluid to the surface generates more flow penetration into the fluid, which causes an increase in the thermal boundary layer and the temperature.

The use of nanoparticles, including metal oxide surfaces, as asphaltene adsorbents is a potential method of removing and/or upgrading asphaltenes. The adsorption of two asphaltene types, extracted from two types of Iranian crude oil, onto nanoparticles (TiO2, SiO2, and Al2O3) are assessed and the thermal behavior of the adsorbed asphaltenes is examined under an oxidizing atmosphere through thermogravimetric and differential scanning calorimetry (TG/DSC) analyses. The extracted asphaltenes are characterized through the X-ray diffraction technique, and adsorption isotherms are measured through UV-Vis spectrophotometry of the asphaltene-toluene model solutions. The isotherm data of all the nanoparticles are adequately fitted by the Langmuir model, indicating that asphaltenes form monolayer coverage on solids surface sites. The adsorption capacities of asphaltenes onto the metal oxides follow the order of Al2O3> TiO2> SiO2. The results indicate that asphaltene with high aromaticity has more adsorption affinity, indicating the effect of the chemical structural of the asphaltenes. The results of asphaltene oxidation tests reveal that the presence of nanoparticles leads to a decrease in oxidation temperature (~100 °C) and activation energy. The effects of nanoparticles on asphaltene oxidation are catalytic.

The convective heat transfer and pressure drop of water based Al2O3 nanofluid in a horizontal tube subject to constant wall temperature condition is investigated by computational fluid dynamic (CFD) method. The Al2O3 nanofluid at five volume concentration of 0.1, 0.5, 1.0, 1.5 and 2 % are applied as a non Newtonian power law and Newtonian fluid with experimentally measured properties of density, viscosity, thermal conductivity and specific heat capacity. The power law fluid determines the heat transfer coefficient and pressure drop better than that of the Newtonian fluid. The experimentally measured viscosity is used as consistency index and the flow behavior index (n) is computed in various Reynolds number and nanoparticle concentrations in order to minimize the difference between the experimental and computational results. It is revealed that n is a function of nanoparticle concentration and independent of nanofluid velocity and Al2O3 nanofluid behaves as a shear thickening fluid for n>1. Both the experimental and computational results show an increase in the heat transfer coefficient and pressure drop with an increase in the nanofluid concentration. By using the experimental data a correlation for the average Nusselt number estimation based on the dimensionless number (Re and Pr) and nanoparticles concentration (φ) is obtained. The results of this correlation introduce a 1.162 % average absolute deviation.

In this study, the performance of advanced oxidation process using titanium and iron oxides based on the natural zeolite (clinoptilolite) as nano photocatalyst was studied and the effects of various factors on the furfural degradation such as pH, dosage of catalyst, initial concentration of furfural and contact time were examined. The co-precipitation method was applied for the synthesis of nano photocatalyst. The SEM and XRD analyses showed a uniform distribution of titanium dioxide and iron nanoparticles on the zeolite.The furfural degradation could successfully happen at neutral to alkaline solutions. Moreover, increasing the amount of catalyst does not have significant effects on the degradation efficiency. By enhancement of the initial concentration of furfural, the rate of degradation decreases. The maximum efficiency of 98% could be achieved within 120 minutes.

The effects of water/oil volume ratio, type and concentration of demulsifier, water salinity and mixing speed on the average water droplets size in water-oil emulsion are evaluated at different times through NMR measurements.The type and concentration of demulsifier have the greatest effects on the average droplet size with 38% and 31.5%, respectively. The water/oil volume ratio, water salinity and mixing speed are significant factors with 13.1%, 7.5% and 5.71%, respectively. The commercial demulsifier Break 6754 has the greater influenceon the average droplet size compared to the acrylic acid. The water droplets size increases upon increasing the concentration of demulsifier, the water volume ratio and the salinity of water and decreases upon increasing the mixing speed.

The interaction between the ions and the charge of membranes can affect the efficiency of pollutant removal. The present study investigated the removal efficiency of hexavalent chromium and nitrate ions from both actual and synthetic contaminated water via two different commercial spiral wound polyamide nanofilters. In addition, the interaction of ions under different experimental conditions was investigated by using a Box-Behnken design (BBD). The Box–Behnken design optimized the contributing factors which included pH (5-9), the initial concentration of Cr (VI) (0.05-5 mg/L) and the initial concentration of nitrate (40-160 mg/L). The maximum removal efficiency of both Cr (VI) and nitrate was achieved at a pH of 9.0, as 99 % and 90 % for the Iranian nanofilter (NF-I) and 98 % and 82 % for the Korean nanofilter (NF-K), respectively. The results also indicated that as the initial concentration of Cr (VI) increased, the removal efficiency was enhanced while the removal efficiency of nitrate decreased according to the pH. However, by increasing the initial concentration of nitrate, the removal efficiency of both the Cr (VI) and nitrate increased. For actual water samples at an optimum pressure of 0.6 Mpa (NF-K) and 0.8 Mpa (NF-I), the removal efficiency of Cr(VI) and nitrate obtained was 95% and 76 % for the NF-K and 97 % and 86 % for the NF-I, respectively.

The Taguchi design of experiments (DOE) approach is adopted here to evaluate the impact of effective factors such as nanoparticles type, nanoparticles to model solution mass ratio, asphaltene structure, and temperature on asphaltene adsorption equilibrium. Herein, the toluene asphaltene solution model is applied. Three commercially nanoparticles (SiO2, Al2O3, and TiO2) are used. Asphaltene characterizations are carried out by X-ray diffraction (XRD) analysis. It is found that the nanoparticle type and asphaltene structure with a respective influence of 48.5% and 3.11% have the maximum and minimum contribution on the amount of adsorbed asphaltene at the selected levels respectively. Aluminum oxide nanoparticle has the maximum and silicon oxide nanoparticle shows the minimum adsorption. The temperature has no statistical significance. Asphaltenes with higher aromaticity have more tendencies for adsorption on nanoparticles.

An aquaculture system can be a potentially significant source of antibacterial compounds and ammonia in an aquatic environment. In this study, the removal of total ammonia nitrogen and florfenicol antibiotic from synthetic aqueous wastewater was assessed by applying a commercial TFC (thin film composite) polyamide nanofilter. The effects of pH (6.5-8.5), pressure (4-10 bar), concentration of total ammonia nitrogen (1-9 mg/L), and florfenicol (0.2-5 mg/L) on the removal efficiency of the nanofilter were studied at a constant 70% recovery rate. It was found that by increasing the pH within the range of 6.5 to 8.5, it enhanced the removal efficiency by up to 98% and 100% for total ammonia nitrogen and florfenicol, respectively. With an increase in pressure from 4 to 7 bar, the removal percentage increased and then, it decreased from 7 to 10 bar. The interactions factors did not have significant effects on the both pollutants removal efficiencies. To obtain optimal removal efficiencies, an experimental design and statistical analysis via the response surface method were adopted.

The efficiency of diazinon (as insecticides) and nitrate (related to nitrogen fertilizer) removal from contaminated water is investigated through NF membrane technique. The effects of nitrate concentration (40-160 mg/l), diazinon concentration (10-1000 µg/l) and pH (5-9) on the efficiency of a commercial polyamide nanofilter membrane at a constant pressure of (800 KPa) are investigated. The response surface method (Box-Behenken design) is applied in design of experiment. As the diazinon concentration and pH are enhanced, the contaminant removal efficiency increases from 85% to 90%; while nitrate concentration has an opposite effect (removal efficiency reduces about 10%). The regression models obtained for nitrate and diazinon rejection show good fitting to the experimental results (r-squared equal to 94% and 98%, respectively). The models are able to predict the evolution of diazinon and nitrate as a function of concentration and pH at a constant pressure.

Monte Carlo simulation is adopted to study the aggregation of asphaltene phenomenon in crude oil. Simulation is accomplished by applying two different potential functions to allow for asphaltene-asphaltene, asphaltene- resin and resin-resin interactions to take place. Asphaltene molecule is considered as a flat molecule, consisting of seven spheres. Resin molecule is considered to be a single sphere and the other hydrocarbons molecules contained in crude oil are modeled as a continuum media. The effect of media on intermolecular interactions is described by definition of a parameter that is composed of two dielectric and Hamaker constants. The effects of asphaltene concentration, temperature and solvent type on the aggregation of asphaltene molecules are investigated by applying both of the potential functions. The predicted results are compared.