Sharif Digital Repository

Petroleum monoaromatics including benzene, toluene, ethylbenzene, and xylenes (BTEX) are among the notorious volatile organic compounds that contaminate water and soil. In this study, a surfactant- modified natural zeolite and its relevant granulated nanozeolites were evaluated as potential adsorbents for removal of petroleum monoaromatics from aqueous solutions. All experiments performed in batch mode at constant temperature of 20°C and pH of 6.8 for 48 h. The results revealed that the amount of BTEX uptake on granulated zeolites nanoparticles were remarkably higher than the parent micron size natural zeolite (in the order of four times). The isotherms data were analyzed using five models... 

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

Microfluidic-based concentration gradient generators (CGGs) have a number of applications in chemical, biological and pharmaceutical studies. Thus, precise design of the microfluidic system is crucial to maintaining the desired concentration gradient in microchannels. One of the design considerations is the length of microchannels in the structure of a CGG. A CGG with a short length fails to provide the complete diffusive mixing, while the size of the microchip would unfavorably increase by incorporating a long CGG. Considering a CGG as a tree-like structure consisting of T-shaped micromixers, the mixing process of the species at a straight microchannel has been solved analytically. Herein,... 

The effects of H2O/SiO2, TMAOH/SiO2, Na/(Na+K), and SiO2/Al2O3 ratios in the parent gels on the crystallization of nanoparticles of T-type zeolites were studied. A Taguchi orthogonal experimental design with the above-mentioned parameters (each at three levels) was used to optimize the experiment parameters by the analysis of variances (ANOVA). Applying the Taguchi method significantly reduced the time and cost required for optimization. The synthesized products were characterized by X-ray diffraction and scanning electron microscopy. As a result of the Taguchi analysis, H2O/SiO2 and TMAOH/SiO2 were the most influencing parameters for the synthesis of zeolite T. © 2009 WILEY-VCH Verlag GmbH... 

In this paper, the effects of two methods of iridium impregnation into HZSM-5 on catalyst stability, selectivity for propylene and byproducts in the conversion of methanol to propylene (MTP) were investigated in a continuous flow isotherm fixed-bed reactor. XRD, BET surface area, NH 3-TPD and ICP-AES analytical techniques were applied to define the physical and chemical characteristics of zeolites. The reaction was conducted at 480°C and 1 bar with WHSV = 1 h -1, and with an equal weight percent of methanol and water in the feed. The results revealed that iridium impregnation into HZSM-5 powder led to enhanced propylene selectivity (8%) and catalyst stability while iridium impregnation into... 

Polymerase Chain Reaction (PCR) is an important and prevalent technique in biotechnology because of its crucial role in cloning DNA fragments and diagnostic applications. In the present study, a high-throughput two-phase PCR device is designed and fabricated which utilizes a serpentine microchannel together with a spiral structure. The former is for the droplet-generation and mixing and the latter is for the thermal cycling process. Moreover, the effect of diamond nanoparticles (diamondNP) on the performance of PCR is also investigated while using commercial PCR devices and the fabricated PCR device designed in this study. Using numerical simulation, it is shown that within the simple and... 

The liquid-phase dehydration of methanol to dimethyl ether was investigated over various materials including synthetic zeolites, namely, ZSM-5, Y, Mordenite, Ferrierite and Beta as well as silica and alumina. The key characters investigated were the Si/Al ratio and cation exchange. The results showed that the Mordenite zeolite exchanged with H+ exhibited the highest activity in dehydration of methanol. After finding the most active catalyst, the Mordenite zeolite was modified with Cu, Zn, Ni, Al, Zr, Mg and Na via wet-impregnation method to further improve its selectivity, and characterized by AAS, XRD, NH3-TPD, NH3-FT-IR and BET surface area techniques. It was found that these materials... 

An acid treatment of the cordierite monolith followed by coating of the CNT onto it by means of catalytic decomposition of methane was performed. The resulting material utilized as the support for the CoMo catalyst. The characterization outcomes showed that the CNTs were distributed uniformly on the surface of the monolith leading to a high BET surface area and relatively good adhered mesoporous layer of CNTs. Moreover, the catalytic activity of the resulting catalysts determined in an HDS reaction of naphtha. It was concluded that the activity of the CoMo catalyst over the CNT coated monolithic support (FACNT) was higher than that of the CoMo deposited onto the acid-treated monolith and... 

The objective of this study was to evaluate the effects of P 2O5 particle size distribution on the crystalline phases and microstructure of lithium disilicate glass-ceramics derived from the TiO2-ZrO2-Li2O-CaO-Al2O 3-SiO2 system for dentistry applications. The samples were made via fusion and casting procedure. Crystallisation as well as the morphology and microstructure of the samples were investigated using X-ray diffraction, differential scanning calorimetric and scanning electron microscopy. The results showed that the crystallisation of the samples occurred in the range of 500-650°C. The main crystalline phase was lithium disilicate (Li2Si2O5) along with Lithium metasilicate (Li2SiO3),... 

The separation of xylene isomers is an important application in separation processes that is based on their adsorption properties on different adsorbents. In this work, the Price and Danner method was employed with a neural network to investigate the adsorption behavior of binary systems of p-xylene/m-xylene, p-diethyl benzene/m-xylene, and p-diethyl benzene/p-xylene and the ternary system of p-diethyl benzene/m-xylene/p-xylene at 130 and 175°C. The Redlich-Kister, Wilson, and NRTL models were used to determine the activity coefficients in the adsorbed phase. Comparison with experimental data from the literature indicated that the proposed thermodynamic model would best determine surface... 

Rocks and rock-like materials frequently fail under compression due to the initiation, propagation and coalescence of the pre-existing microcracks. The mechanism of microcrack coalescence process in rock-like materials is experimentally and numerically investigated. The experimental study involves some uniaxial compression tests on rock-like specimens specially prepared from portland pozzolana cement, mica sheets and water. The microcrack coalescence is studied by scanning electron microscopy on some of the prepared thin specimens. It is assumed that the mica sheets play the role of microcracks within the specimens. Some analytical and numerical studies are also carried out to simulate the... 

The present work aims to fabricate cordierite/BZBS glass (Bi2O3-ZnO-B2O3-SiO2) composites through one-step heat treatment. Cordierite was synthesized from a solid-state reaction of aluminum hydroxide, magnesium hydroxide, and silica gel. BZBS glass was obtained through the classic melt quenching technique. Milled cordierite powder was mixed with different volume fractions of glass powders and heat treated at 950 °C. Considering the densification behavior along with the microwave dielectric features, two composites (C70G30 and C60G40) were chosen for further examination. These composites were separately heat treated at different temperatures from 650 up to 900 °C, then characterized due to... 

Inertial particle focusing as a powerful passive method is widely used in diagnostic test devices. It is common to use a curved channel in this approach to achieve particle focusing through balancing of the secondary flow drag force and the inertial lift force. Here, we present a focusing device on a disk based on the interaction of secondary flow drag force, inertial lift force, and centrifugal forces to focus particles. By choosing a channel whose cross section has a low aspect ratio, the mixing effect of the secondary flow becomes negligible. To calculate inertial lift force, which is exerted on the particle from the fluid, the interaction between the fluid and particle is investigated... 

Polyethylene/clay nanocomposites (PECNC) were synthesized via in situ Ziegler-Natta catalyst polymerization. Activated catalyst for polymerization of ethylene monomer has been prepared at first by supporting of the cocatalyst on the montmorillonite (MMT) smectite type clay and then active complex for polymerization formed by reaction of TiCl4 and aluminum oxide compound on the clay. Acid wash treatment has been used for increasing hydroxyl group and porosity of the clay and subsequently activity of the catalyst. The nano- structure of composites was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Obtained results show that silica layers of the mineral clay... 

In this work, cristobalite crystallization and its effects on mechanical and chemical behaviour of injection moulded silica-based ceramic cores were investigated. In order to simulate casting process condition, the sintered samples at 1220 °C were also heated up to 1430 °C. Flexural strength test was carried out on both sintered and heat treated samples. Chemical resistance of the cores was evaluated by leaching the samples inside 43. wt% KOH solution at its boiling point. Phase evolution and microstructure were investigated by thermal analyses (DTA and DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). Results showed that cristobalite was... 

The objective of the present work is development of joint approximate diagonalization of eigenmatrices (JADE) as a member of independent component analysis (ICA) family, for the analysis of gas chromatography-mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS) data to address incomplete separation problem occurred during the analysis of complex sample matrices. In this regard, simulated GC–MS and GC × GC–MS data sets with different number of components, different degree of overlap and noise were evaluated. In the case of simultaneous analysis of multiple samples, column-wise augmentation for GC–MS and column-wise super-augmentation... 

Due to the increasingly serious environmental problems presented by waste tires, the feasibility of using elastic and flexible tire-rubber particles as aggregate in concrete is investigated in this study. Tire-rubber particles composed of tire chips, crumb rubber, and a combination of tire chips and crumb rubber, were used to replace mineral aggregates in concrete. These particles were used to replace 12.5%, 25%, 37.5%, and 50% of the total mineral aggregate's volume in concrete. Cylindrical shape concrete specimens 15 cm in diameter and 30 cm in height were fabricated and cured. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete.... 

The use of a draft tube fluidized bed bioreactor (DTFBB) has been successfully demonstrated for the bioleaching of a chalcopyrite concentrate (Mousavi, et. al., 2005). In the present paper this technique was used for the bioleaching of zinc from a sphalerite bearing low-grade ore. A strain of the thermophilic bacterium, Sulfobacillus, has been isolated from the Kooshk lead and zinc mine near the city of Yazd (Iran) and is tested at temperatures 47 °C-72 °C. This is compared to leaching with a strain of the mesophile Acidithiobacillus ferrooxidans, which has been adapted to the high levels of zinc and the presence of the low-grade ore, and which was tested at temperatures 18 °C-42 °C. The... 

The deactivation of solid acid catalysts in liquid phase alkylation of isobutane with 2-butene was investigated. Since under liquid phase conditions the alkylation reaction is severely diffusion limited, effects of diffusion on the rate of reaction and deactivation pathways were considered. In the present work, an attempt has been made to implement more appropriate assumptions in order to properly model catalyst deactivation in a mixed reactor. Accordingly, spatial variation of diffusivity in the pores of the catalyst was considered as a function of time on stream. The effect of the pore mouth plugging was also investigated and it was found that this phenomenon had a pronounced effect on the...