Sharif Digital Repository

For many years the model of a dynamic adsorption layer (DAL) is well established as explanation for the behavior of rising bubbles in surfactant solutions. This model explains the velocity profile and the evolution of the shape of a rising bubble based on the hypothesis of the balance between the drag force and the structure of the adsorbed layer governed by Marangoni convection. However, direct measurements of interfacial properties of the bubble during rising are a real challenge. Here we present a new experimental protocol called "bubble in flow field" suitable for direct measurements of dynamic interfacial properties of a bubble surface using the capillary pressure tensiometry under... 

A high silica CHA-type membrane was synthesized by the in-situ crystallization method on a disk like α-alumina porous support to separate both acid (H2S, CO2) gases from methane. The membrane showed a permeance of 3.39×10-8mol/m2sPa for pure CO2with CO2/CH4 ideal selectivity of 21.6 at 303K and 100kPa pressure difference across the membrane. The membrane was also tested with N2 and O2 pure gases indicating a small O2/N2 selectivity of 1.2-1.4, which shows that this type of membrane is not suitable for O2/N2 separation. The membrane performance was also analyzed by binary (CO2-CH4) and ternary (H2S-CO2-CH4) gas mixtures, with compositions near the real sour natural gas (CO2: 2.13mol%, H2S:... 

We present fabrication, characterization, and experimental results describing electrical actuation and readout of the mechanical vibratory response of electrospun ZnO nanofibers. For a fiber with an approximate radius of 200 nm and a length of 70 ìm, a resonance frequency around 3.62 MHz with a quality factor (Q) of about 235 in air at ambient conditions is observed. It is shown that the measured frequency of the resonance is consistent with results from finite element simulations. Also, the measurements were performed in an enclosed chamber with controlled levels of ethanol vapor. The adsorption of ethanol causes a shift in the resonance frequency of the fibers, which can be related to the... 

In this work, asphaltene adsorption in a sandstone core sample under dynamic conditions and during miscible CO2 injection was studied using live oil sample which is close to real conditions in petroleum reservoirs. In order to investigate of damage in sandstone core sample by the deposited material such as asphaltene, the morphology analysis of sandstone core sample using scanning electron microscopic method was studied. Also analyses of the adsorbed material in sandstone core sample by Soxhlet extraction using an azeotrope mixture and with SARA method were performed. The experimental results show that by increasing the flow rate of injected CO2, the amount of asphaltene in retained material... 

In the present work, adsorption of hydrogen molecules over a metal organic framework (MOF-5) has been investigated by using first principles density functional theory (DFT). Different strategies have been applied for improving hydrogen storage, i.e. metal doping, boron substitution and functionalization. The metal atoms used for enhancing hydrogen adsorption include Li, Ca and Sc. It is found that the binding energy between these metal atoms and MOF is not enough to prevent clustering. Therefore a number of carbon atoms are substituted by boron atoms and it is indicated that boron substitution enhances the binding energies, significantly. Also the results reveal that boron substituted MOF... 

In this work, a new model based on multilayer kinetic adsorption mechanism has been proposed to account asphaltene adsorption in porous media under dynamic condition and the model was verified using experimental data obtained in this work and also with those reported in the literature. In the proposed model two steps are considered for asphaltene adsorption. The first step is taken as adsorption of asphaltenes on the surface of the porous media and the second step is taken as adsorption of asphaltenes on the asphaltenes already adsorbed on the porous media. The Crank-Nicholson method, central difference in space and trapezoidal rule in time, giving second order convergence in time was... 

We outline a comprehensive numerical procedure for modeling of species transport and surface reaction kinetics in electrokinetically actuated microfluidic devices of rectangular cross section. Our results confirm the findings of previous simplified approaches that a concentration wave is created for sufficiently long microreactors. An analytical solution, developed for the wave propagation speed, shows that, when normalizing with the fluid mean velocity, it becomes a function of three parameters comprising the channel aspect ratio, the relative adsorption capacity, and the kinetic equilibrium constant. Our studies also reveal that the reactor geometry idealized as a slit, instead of a... 

This paper presents a state of the art review of adsorption models for a new plant-based surfactant adsorption onto sandstone minerals. The adsorption data at both kinetic and equilibrium modes were obtained from batch experiments. Four adsorption kinetic models, five two-parameter, and six three-parameter equilibrium models were used for interpretation of the obtained data. Among the two and three-parameter isotherm models applied, the Jovanovic and the Khan isotherms showed the best fit, respectively. And the pseudo-second order model presented a better fit than other kinetic models. Finally, a computer-based modeling approach was developed and used for predicting the kinetics of... 

GAC has been modified by loading of potassium nickel hexacyanoferrate (KNiCF) as a new adsorbent for cesium adsorption. The potassium nickel hexacyanoferrate-loaded granular activated carbon (KNiCF-GAC) was characterized using powder x-ray diffraction (XRD) and nitrogen adsorption-desorption isotherm data, infrared spectroscopy, and its cesium adsorption performance in aqueous solution was investigated. The effect of the various parameters such as initial pH value of the solution, contact time, temperature, and initial concentration of the cesium ion on the adsorption efficiencies of KNiCF-GAC have been studied systematically by batch experiments. The adsorption isotherm of KNiCF-GAC was... 

In past decades, many attempts have been made to use water-soluble polymers as a mobility control agent to improve sweep efficiency of enhanced oil recovery processes. However, sensitivity of the thickening behavior of these polymers to some harsh conditions, such as high salinity, has cast serious doubt on their applicability in reservoir conditions. By expansion of nanotechnology, scientists discovered that nanoparticles can be utilized as thickening and rheology control agents in many polymer solutions. In this study, hydrophilic fumed silica is added to hydrolyzed polyacrylamide and sulfonated polyacrylamide solutions. The effect of the addition of nano silica on the thickening and... 

A new photocatalyst (Ag-S/PEG/TiO2) was synthesized by adding polyethylene glycol (PEG) to an efficient Ag-S/TiO2 photocatalyst, to obtain a photocatalyst that is highly active under visible light. In addition to Ag-S/PEG/TiO2, Ag-S/TiO2 and pure TiO2 were prepared to compare their properties and activities. Specifically, the morphologies and microstructures of the nanophotocatalysts were characterized by means of powder X-ray diffraction (XRD), N2 adsorption-desorption measurements, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy,... 

Although CO2 injection significantly increases the amount of oil recovered, it can cause asphaltene deposition in oil reservoirs. Asphaltene deposition leads to formation damage, in which treatment is a costly and problematic operation. In this work, impact of asphaltene precipitation and deposition during CO2 injection are investigated for recombined oil both in sandstone and carbonate core samples through dynamic flow experiments. Injection of oil and CO2 was performed simultaneously. Then, pressure drops along the core were recorded continuously to estimate permeability reductions during the experiments. Online viscosity of injected fluid was measured by a designed capillary viscometer.... 

During any microbial enhanced oil recovery process, both cells and the metabolic products of bacteria govern the tertiary oil recovery efficiency. However, very accurate examination is needed to find the functionality of these tiny creatures at different reservoir conditions. In this regard, the effect of cell structure on ultimate microbial recovery efficiency which is the most dominant mechanism based on the microorganism types (gram-negative or gram-positive) was systematically investigated. At the first stage, possible different active mechanisms using Bacillus stearothermophilus SUCPM#14 strain were tested using specially designed injection protocol, in situ and ex situ core flooding... 

The rising velocity of air bubbles in surfactant solutions is a sensitive measure for the formation of a dynamic adsorption layer (DAL) at the bubble surface. Due to a certain surface coverage by adsorbed species the bubble surface starts to become immobilized and the rising velocity is retarded. There is a large difference in the retardation effect in presence of the protein β-lactoglobulin (BLG) alone and its mixed solutions with surfactants. In presence of added surfactants BLG forms complexes, which adsorb and retard the bubble rising velocity according to their respective surface activity and adsorption kinetics. While the nonionic surfactant C12DMPO does not show significant increase... 

A novel organic-inorganic hybrid heterogeneous catalyst system was obtained from the reaction of the molybdenum(VI) complex of salicylidene 2-picoloyl hydrazone with mesoporous silica containing 3-chloropropyl groups prepared by a direct synthetic approach involving hydrolysis and co-condensation of tetraethylorthosilicate (TEOS) and 3-chloropropyltrimethoxysilane in the presence of the triblock copolymer P123 as template under acidic conditions. Characterization of the functionalized materials by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), N2 adsorption/desorption, FT-IR and UV-Vis spectroscopy, and thermogravimetric... 

Among the asphaltene flow assurance issues, the most major concern because of asphaltene is its potential to deposit in reservoir, well tubing, flow lines, separators, and other systems along production lines causing significant production losses. Hence, the focus of this study is to understand the depositional tendency of asphaltene using quartz crystal microbalance with dissipation (QCM-D) measurements. The results are presented in two consecutive papers, with this paper (part 1) dealing with model oil systems. The depositing environment is varied by changing the system temperature, asphaltene polydispersity, solvent (asphaltene stability), depositing surface, and flow rate. This paper... 

An extracting medium based on chitosan-polypyrrole (CS-PPy) magnetic nanocomposite was synthesized by chemical polymerization of pyrrole at the presence of chitosan magnetic nanoparticles (CS-MNPs) for micro-solid phase extraction. In this work, magnetic nanoparticles, the modified CS-MNPs and different types of CS-PPy magnetic nanocomposites were synthesized. Extraction efficiency of the CS-PPy magnetic nanocomposite was compared with the CS-MNPs and Fe3O4 nanoparticles for the determination of naproxen in aqueous samples, via quantification by spectrofluorimetry. The scanning electron microscopy images obtained from all the prepared nanocomposites revealed that the CS-PPy magnetic... 

The inflow pattern of liquid into a droplet is studied experimentally using a surface active dye and compared with results of CFD simulations. The results show visual agreement between experiments and simulations. The CFD simulations show also good agreement with the surface tension measured by drop profile analysis tensiometry (PAT). The inflow of the surfactant induces a Marangoni instability caused by the local arrival of the surfactant at the drop surface. The onset of this Marangoni instability observed experimentally has a delay of about 10. s when compared with the simulation results. Different scenarios are discussed, including a boundary layer barrier, a kinetic-controlled... 

The effect of pulse reverse current (PRC) method on Ni-Mo coatings electroplated from chloride solution was investigated by various plating parameters such as plating duration, the anodic duty cycle, the anodic current density and the cathodic current density. By increasing the anodic duty cycle and anodic current density, the Mo content of coatings reached 68wt.% and 78wt.%, respectively at cathodic current densities of 500 and 300mAcm-2. The Mo content of coatings increases by the preferential dissolution of Ni on the anodic pulse and also by the replenishment of Mo complexes in the diffusion layer near the substrate surface during the anodic pulse. In comparison with the direct current... 

Continuous adsorption in stirred reactors in the form of carbon in pulp (CIP) and resin in pulp (RIP) is an established process for the extraction of gold and uranium. Under the circumstance of intraparticle diffusion resistance, CIP and RIP have been accurately modeled by the Boyd's series (reversible adsorption) and shrinking core model (irreversible adsorption). The present study, in its first part, introduces an analytical formula that most closely approximates both models. Using such formula, the study addresses a basic algorithm for optimization of single-stage continuous adsorption systems through linking of the major process variables. Furthermore, this study is devoted to developing...